Appendix D 2.

THE ANNULOSE TYPE.

The production of a segmental structure by undulatory movements, suggested in Appendix D, as also in B (first published in 1858) as explaining the vertebral column, has been recently suggested by Prof. Korschelt as the cause of that segmentation of the annulose type which gives the name to it. He espouses a--

“view which is based upon the assumption that at first an unsegmented, elongated ancestral form was produced by terminal growth, whereupon the entire body became separated at once into a large number of segments by a re-arrangement of the individual organs. This assumption is supported by the consideration that with the lateral sinuous movement of the body, and with the rigidity of the tissues caused by increasing differentiation, the formation of alternating regions of greater and less motility was of considerable advantage to the individual, and rendered possible a further elongation of the body. The first cause for the appearance of metameric segmentation would then be sought in the manner of locomotion and in mechanical conditions. However, this latter view is not supported in any way by embryology.” (Embryology of Invertebrates, Part I, pp. 349–50.)

I venture to think the confession that this view “is not supported in any way by embryology” should be joined with the confession that it is at variance with that abstract embryology which comprehends the process of development in general. The assumption that there took place “a re-arrangement of the individual organs” of “an unsegmented, elongated ancestral form,” in such wise that the organs, previously single, presently became multiple, so that instead of one organ of each kind there were substituted many organs of each kind, is inconsistent with the general law of evolution, organic and other--implies not integration but disintegration. Everywhere the advance is from many like parts performing like functions to relatively few unlike parts performing unlike functions. The higher forms of the annulose type itself show this. Compare a myriapod and a crab. In the one we have not only a great number of similar segments bearing similar limbs, but we have in each segment a dilatation of the main blood-vessel--a rudimentary heart--a swollen portion of the nerve cord--a small ganglion--and so on; whereas in the other, besides relatively few segments and few limbs (sundry of them extremely unlike the rest) we have a vascular system concentrated into a central heart with arteries and a concentrated nervous system, such that the great ganglia in the integrated carapace immensely subordinate the ganglia of the remaining segments; and similarly with the other organs. Now unless it be denied that these highest decapods have been evolved from low types akin to myriapods in composition, it must be admitted that the progress has been from a string of many like segments with similar sets of organs to a group of relatively-few unlike segments with dissimilar sets of organs. If so we cannot rationally deny that the progress has been of this nature up from the lowest annelid, instead of having been, as Prof. Korschelt’s hypothesis implies, of opposite nature at the beginning.

In a preceding passage a clear recognition of the normal course of development occurs. In opposing the view set forth in §§ 205–7 of this work, Prof. Korschelt says:--

“It seems scarcely favourable to this theory that the degree of independence which the individual segments present is comparatively slight. The most important organs (nervous system, body musculature, blood-vascular system) show themselves to be single fundaments of the entire body, and are also developed as such even though they also exhibit evidences of metamerism. Even the excretory canals may give up their segmental isolation and become united to one another by means of longitudinal canals.” (Ib. p. 348.)

On turning back to § 206, the reader will, I think, demur to the assertion that the independence is “comparatively slight”; seeing that, as in Ctenodrilus, a single segment sometimes becomes separate and reproduces other segments to form a new series. Instead of admitting that “the most important organs” “show themselves to be single fundaments of the entire body,” it may be held, contrariwise, that their original independence in each segment is masked only to the degree involved by their co-operation as parts of a compound organism. But chiefly I remark that when it is said that “the excretory canals may give up their segmental isolation and become united” by “longitudinal canals,” there is a clear confession that the isolation of these organs was original and their union superinduced--an implication that the course of evolution is as I have described it, and at variance with the course of evolution assumed by Prof. Korschelt.

Yet another incongruity is involved in his interpretation. He writes:--

“Just as in the consideration of the tapeworm chain we were induced by the comparison with unsegmented forms to refer the entire chain to an unsegmented individual, and, on the other hand, to see in the proglottis, not a complete individual, but only the abstricted hinder portion of the body of the Cestode, in the same manner, and with much more reason, we adhere to the individuality of the Annelid body.” (P. 349.)

And then on the preceding page, referring to the composition of the Annelid body, he says:--“The most natural comparisons are those with the tapeworm chain and with the strobila of the Scyphomedusæ.” Now since it is here assumed that the tapeworm and the strobila are analogous in composition, it is implied that the detached proglottis and the detached medusa are analogous; and hence if we are to regard the proglottis as “not a complete individual but only the abstricted hinder portion of the body of the Cestode,” then we must similarly regard the medusa as not a complete individual, but only the abstricted hinder portion of the strobila. This commits us to the strange conclusion that whereas individuality is ascribed to the original simple polyp, and by and by to the partially-segmented strobila, though these are without special senses and with only rudiments of muscular and nervous systems, individuality is denied to the detached medusa, which has organs of sense, a distinct nervo-muscular system and a considerable power of locomotion, as well as a generative system: traits which in other cases characterize developed individuals. Here also, then, there seems to be an inversion of the ordinary conception.

This conception of the proglottis and the medusa is, I see, accepted by some as tenable. But if we accept it we must accept also an analogous conception, which will I think be regarded as untenable. It is that supplied by the Aphides. From an egg proceeds a series of sexless and wingless females, and at the end of the series there come winged males and females with resulting gamic reproduction. If instead of forming a discrete series the imperfect females formed a concrete series, the members of which could individually feed without being detached from one another, as the segments of a tapeworm can, the parallelism would be complete; and then, according to the view in question, we should have to regard the perfect males and females eventually arising, not as individuals but as terminal portions of the series, containing generative products and having wings for the dispersion of them--locomotive egg-bearing segments of the chain. Whoever espouses this view must hold either that the first imperfect female of the series was the individual or that the entire string of them constituted the individual (in conformity with a view once propounded by Prof. Huxley). But he must do more than this. Since the Aphides have descended from some winged species of the order Hemiptera, he must hold that among those remote ancestors each particular fly, male or female, was an individual; but that when abundant food and inert life led to the partheno-genetic habit, and to chains of sexless forms, the males and females eventually produced at the end of each chain, though, like their remote ancestors, possessed of procreative organs and wings, are not individuals.

One of my critics says:--

“You have overstated the case in your favour: the alimentary canal does not, as you suggest, show a segmentation corresponding to that of the other organs in Annelids. Either it is a simple uniform tube, or else its differentiations (pharynx, œsophagus, crop, intestine) are quite independent of the repetition of the somites.”

In presence of statements made in works of authority, this objection greatly surprises me. I meet with the descriptive word “moniliform” applied to the intestine in some Annelids, and then in the Text Book of Claus, translated and edited by Sedgwick, it is said, concerning the alimentary canal in the Annelida:--

“This is followed by the gastric region of the gut, which occupies the greatest portion of the length of the body, and is either regularly constricted in correspondence with the segments, or possesses lateral diverticula.” (P. 365.)

And again on p. 369 it is said:--

“The intestine usually preserves the same structure in its entire length and is divided by regular constrictions into a number of divisions or chambers, which correspond to the segments and dilate again into lateral diverticula and cæca.”

The alimentary canal thus presents the segmental character as clearly as consists with fulfilment of its function. If the successive segments are co-operating units of a compound animal having but one mouth, then, necessarily, the gut cannot be completely cut into parts, each answering to a segment, for there could be, in that case, no passage for the food. If the portion of the intestine belonging to each segment has a conspicuous dilatation, or has a cæcum on each side, it exhibits the segmental character as much as the physical requirements permit. So far from being at variance with the hypothesis, its structure exhibits a verification of it.

The next objection runs as follows:--

“Then, again, the ovaries and testes do not exhibit a corresponding segmentation. When it is allowable to speak of ovary or testis at all as in Lumbricus, we find that in the case of both organs we have at most two pairs.”

It seems to me that the distribution of the generative organs in a comparatively-developed member of the Annelid type, is not the question. We have to ask what it is in undeveloped members of that type. Among them the repetition of generative parts is in some cases just what the theory implies. Thus in Claus I read:--“In the marine Chætopoda, the ova or spermatozoa originate on the body-wall from cells of the peritoneal membrane, either in the anterior segments alone or along the whole length of the body.” So that in these last cases there are, in all the segments, parts from which arise generative products. The fact that these parts are not definite ovaries and testes is irrelevant. Ovaries and testes are developed generative structures, and in the order of evolution are preceded by undeveloped ones; and the fact that these undeveloped ones are found in little-developed members of the type conforms perfectly to the hypothesis. [I may remark in passing that here is a good illustration of that process of evolution which, in the above speculation of Prof. Korschelt, is supposed to be inverted: many dispersed, similar, and indefinite parts, are integrated into a few localized and definite parts.]

In continuation the critic above quoted says:--“My position is that the repetition of segments in an Annelid is a phenomenon of the same nature as the repetition of hairs in a Mammal or of scutes in a Reptile”, and he proceeds to give instances of repetitions of organs in other types, as of the reproductive structures and excretory system in the young Dog-fish or of the ovaries in Amphioxus. These examples do not seem to me relevant. No parallelism exists between the repetition of a particular organ in an animal, and the repetition of an entire cluster of organs constituting a physiological whole. The repetitions of the ovaries in Amphioxus and of the excretory system in a young Dog-fish, occur without threatening to divide into similar parts the entire organism. But the segmental repetitions in an annulose creature implicate the structures at large, and would, if pushed a little further, result in separate creatures. The segment of a low Annelid contains alimentary, vascular, nervous, excretory, reproductive, sensory and locomotive organs--all the organs required for carrying on life, save certain organs of external relation which its position excludes. When there is shown some vertebrate animal, or proto-vertebrate animal, that is divisible into parts each of which is in great measure physiologically independent, I shall feel obliged to abandon my position.

* * * * *

While this appendix is in hand I have received from another expert, whose view is in general agreement with my own, a letter containing the following passage:--

“You will see that Dohrn’s theory was the antithesis of your own view of vertebrate structure, namely that the vertebræ were formed by the segmentation, from mechanical causes of a body originally simple. This view of yours has been confirmed by later researches, which have shown that the most primitive forms allied to the Vertebrates, possessing the essential organs, viz., gill-slits, notochord, and dorsal nerve cord, are not segmented animals, like Annelids and Crustacea, but simple animals, having at most three regions, not exactly corresponding to segments. These primitive unsegmented forms are Ascidian tadpoles, Balanoglossus, and certain other primitive forms. The embryology of Vertebrates also proves that they are originally simple and not segmented animals, especially the fact that there is originally one pronephric duct or primitive kidney.”

Nevertheless there survives a leaning towards the notion of a segmental origin of the Vertebrata. But the repetitions of organs named in support of this notion have, I think, no more relation to the genesis of the vertebrate type than the multiplication of vertebræ in a snake has relation to the genesis of the vertebral column.

APPENDIX E.

THE SHAPES AND ARRANGEMENTS OF FLOWERS.

In Part IV., Chapter X., under the title of “The Shapes of Flowers,” I have, after describing their several kinds of symmetry, as habitually related to their positions, made some remarks by way of interpretation. The truth that flowers exhibit a radial symmetry when they are so placed as to be equally affected all round by incident forces, having been exemplified, and also the truth that they assume a bilateral symmetry when they are so placed that their two sides are conditioned in ways different from the ways in which their upper and lower parts are conditioned; I have gone on to inquire (in § 234) by what causes such modifications of form are produced. I have stated that, originally, I inclined to ascribe them entirely to differences in the relations of the parts to physical forces--light, heat, gravitation, etc.; but that I found sundry facts stood in the way of this interpretation. And I have said that “Mr. Darwin’s investigations into the fertilization of Orchids led me to take into account an unnoticed agency.” Continuing to recognize the physical forces as factors having some influence, I have concluded that the most important factor is the action of insects; which, aiding most the fertilization of those flowers which most facilitate their entrance, produce, in course of generations, a form of flower specially adapted to the special position.

Though still adhering to this interpretation, I have since found reason to think that the original interpretation contains a larger portion of truth than I supposed at the time when I was led thus to revise it. While staying at Mürren, in Switzerland, in 1872, I observed some modifications in a species of Gentian, which proved to me that the action of incident physical forces on flowers is, in some cases, very rapid and decided. The species furnishing this evidence was the Gentiana Asclepiadea; which I found in a copse formed of bushes that were here wide apart and there close together. In some places not near to the bushes, the individuals of the species grew vertically; in other places, partially shaded, their inclined shoots curved in such directions as to get the most light; and in other cases their shoots were led to take directions almost or quite horizontal. That, along with these modifications in the directions of their shoots, there went adjustments in the attitudes of their leaves, was a fact not specially worthy of remark; for plants placed inside the windows of houses habitually show us that leaves quickly bend themselves into attitudes giving them the greatest amounts of light. But the fact which attracted my attention was, that the flowers changed their attitudes in an equally-marked manner. The radial distribution passed into a bilateral distribution with the greatest readiness. Comparison of the annexed figures will show the character of this change.

Figure I. represents part of a vertically-growing shoot. This belonged to an individual growing unimpeded by bushes, and getting light on all sides. Here it is observable that the pairs of leaves, placed alternately in directions transverse to one another--one pair pointing, say, north and south, and the next pair pointing east and west--maintain, taking them in the aggregate, a radial distribution; and it is also observable that the alternate pairs of flowers are similarly arranged.

Figure II. is a sketch from a shoot which leaned towards one side, and of which the higher part, as it bent more and more, got its upper side more and more differently conditioned from its lower side. Here we find that not only the leaves, but also the flowers, have adjusted themselves to the changed conditions. The leaves of the lowest pair hang out in the normal way, on the opposite sides of the axis, so that a plane passing through their surfaces will cut the axis transversely; and their two axillary flower-buds, c and d, are similarly placed on opposite sides of the axis. But at the other part of the shoot, we see both that the leaves have adjusted themselves so that their planes, no longer cutting the axis transversely, keep a fit adjustment with respect to the light; and also that the flowers, no longer on opposite sides of the axis, have bent round to the upper side, as at a and b.

Figure III. shows us this re-arrangement carried still further. The shoot it represents was growing in a direction nearly horizontal, and therefore receiving the light only on one side. And here, besides seeing that the leaves have so adjusted themselves that they all lie in approximately the same plane, which is parallel to the axis instead of transverse to it, we see that the two pairs of flower-buds have both come round to the upper side of the axis. So that in this shoot, the original radial symmetry in the arrangement of leaves and flowers, is completely changed into a bilateral symmetry.

These facts do not, it is true, prove any modification in the forms of the flowers themselves: they only prove modification in the grouping of the flowers. But beyond showing, as they do conclusively, how readily a bilateral arrangement of flowers is producible out of an arrangement that was not bilateral, by the action of light, etc.; they give increased probability to the belief that changes in the shapes of flowers are producible by the same agencies. Doubtless this change in the attitudes of the flower-buds is due to the action of light on their calyces and peduncles more than to its action on their unfolding corollas. But along with an action so decided on the growth of these sheathing and supporting organs containing chlorophyll, it is scarcely probable that there is no action on the growth of the petals, containing other colouring matter; considering that in both cases the development of the colouring matter depends on the action of light, and considering also the effect of light on petals, familiarly shown by their opening and closing. And if even but a small effect is producible on the growth of the corolla, then it is to be expected that light will be an agent in changing the form of the corolla, when the attitude of the flower causes its parts to be differently exposed. For a small effect on the individual flower will become a great effect in the flowers of remote descendants; provided the changed attitudes of the flowers preserve considerable constancy throughout the succession of individuals.

Be this as it may, however, the facts I have here described, which I doubt not other observers have seen paralleled in other plants, are instructive, as showing how quickly certain metamorphoses are produced, and as implying the easy establishment of such metamorphoses as permanent characters in a species, if the modifying conditions become permanent. The changes of arrangement I have pointed out, do not become permanent in this species because its individuals are variously affected by the modifying forces: on some they do not act at all, on some a little, on some much; and even on the same individual the different shoots are quite differently affected. But if the habit of this plant were greatly changed--if, for instance, by spreading into habitats yielding abundant nutriment, the plant became very luxuriant, and, multiplying its branches, grew shrub-like; it is clear that, being shaded by one another, these branches would be habitually circumstanced in a way like that which we here see produces bilateralness in the distribution of the flowers, if not in the flowers themselves; and being thus permanently affected, would become permanently bilateral. Accumulating by inheritance, what is here only an individual peculiarity, would become a peculiarity of the species--a specific character.

APPENDIX F.

PHYSIOLOGICAL (OR CONSTITUTIONAL) UNITS.

There has recently come before me a fact which has a significant bearing on the hypothesis of Constitutional units: serving, indeed, to give an apparently conclusive proof of its truth. Before stating it, however, I may with advantage re-state the several evidences already assigned in support of it.

* * * * *

1. First comes the à priori reason. These units in the germ of an organism which cause development into a special structure, cannot be chemical units--cannot be simply molecules of proteid substance in one or other of its forms; since these are not special to any type of creature but common to all creatures. Nor can they be what we may call morphological units--the cells or protoplasts; because in the early stages of development the cells of one organism are indistinguishable from those of others, and because were cells the units of composition there could be no interpretation of what are called unicellular organisms--nothing to account for the innumerable varieties of them. Hence, of necessity, the structural elements of which each organism is built, being neither proteid molecules nor cells, must be something between them: probably some complex combination of different isomeric forms of proteids.

* * * * *

2. That units of such natures are the essential components of each species of organism, is shown by the fact that in low types of creatures, little differentiated into special tissues, any considerable portion of the body will, when separated, begin to assume the structure proper to the species--a truth recently shown afresh by Prof. T. H. Morgan’s experiments on the regeneration of Planaria maculata (already referred to in § 206) showing that various fragments cut out develop into new individuals, and that when, being too small they die before doing this, there is always an abortive attempt to assume the specific structure.

* * * * *

3. This truth that a portion of undifferentiated tissue, if adequate in quantity, assumes the structure of the type, illustrating as it does the proclivity of the constitutional units towards the structure of the species, allies itself with the phenomena of both agamogenesis and gamogenesis. The first of these shows us how a fissiparously-detached portion of the parental tissue takes on the same form as the parent; and the second shows how those small detached portions distinguished as sperm-cell and germ-cell also, when united and supplied with the needful materials, do the same thing.

* * * * *

4. But the set of phenomena following the union of sperm-cell and germ-cell differ in a certain way from those which follow when a gemma or other unfertilized portion of parental tissue is detached. The incomprehensibleness of this difference as otherwise contemplated, and the partial comprehensibleness of it when joined with the hypothesis of physiological units, furnish a further support for the hypothesis.

The familiar truth learnt by the tyro in algebra that an apparent solution which contains the unknown quantity is no solution, is a truth apt to be overlooked in other spheres than the algebraic. An illustration is supplied by the answer once given in Parliament to the question “What is an Archdeacon?”--“One who discharges archidiaconal functions.” But science as well as daily life furnishes examples. When it is said by Engelmann, Hensen, Hertwig, and Maupas that “the essential end of sexuality is rejuvenescence, that is, the restoration of growth-energy,” we have another instance of an explanation which explains nothing. What is the phenomenon to be explained? That unfolding of an organism from a germ which displays growth-energy. And what is the explanation? The giving of fresh growth-energy. The unknown quantity “growth-energy” is contained in the explanation proposed. There exists no conception of “juvenescence” save that derived from observing developing plants and animals; and if “re” be prefixed, no interpretation is thereby given to the unexplained thing “juvenescence.”

Coleridge somewhere comments on a source of fallacy which he calls the “hypostasis of a relation”--the changing of a relation into a thing. The plumber who tells you that water rises in a pump “by suction” supplies an instance. Having assumed suction to be an agent, he thinks that he understands how the piston does its work. Some of the explanations given of fertilization supply further instances. When it is said that sexual union has for its end “to give increased vigour to all the vital processes,” it is tacitly implied that vigour is a something--a something which can be given. But now, in the first place, it is only by the hypostasis of a relation that we are led to think of vigour as a thing. Vigour is a state--that state of a living body which enables it to give out much motion. What enables it to do this? The presence in it of abundant molecules containing much molecular motion which can be transformed into molar motion: the transformation being effected by the falling of these molecules into their simpler and relatively-inert components, which are thereupon excreted. Energy-containing matter is used up, and more energy or vigour can be given only by supplying more such matter. How then can the union of two nuclei--those of the sperm-cell and germ-cell--give vigour? Only an infinitesimal portion of vigour in the sense above explained exists in either, and the union of them leaves it still infinitesimal. And then, even supposing the vigour to be an entity and to be appreciable in quantity, how could it go on producing that immense combination of physiological actions seen in the unfolding of the germ into an organism? and how could it go on producing the physiological actions of an adult organism during a whole century?

May we not then say that these proposed explanations leave the question where it was--are nominal solutions, not real solutions?

* * * * *

5. But the hypothesis of constitutional units furnishes, if not a satisfactory answer yet, something in the nature of an answer--a true cause; that is to say, a cause actually known to us as operating in other cases. In § 92 it was pointed out that in proportion as units are similar, there may be built up from them an aggregate which is relatively stable, and that along with increasing dissimilarity the stability of the aggregate decreases. It was inferred that if a group of constitutional units belonging to one individual which have become moulded into relatively exact congruity with the organism and with one another by long co-operation, are mingled with some belonging to another individual which, differently circumstanced, has become somewhat different in itself and in its units, then the mass formed by the union of the two groups will be relatively unstable--relatively modifiable by incident forces. Whereas in either organism, no longer perpetually changed in the relations of its parts by growth, there is an approach towards equilibrium between the whole and its components, the components contributed by the two to form a germ, being slightly unlike one another, will not form a group in a state of equilibrium. The group they form will be capable of easy change by incident forces; and they will so be rendered free to follow their proclivities towards the typical form of the species. Inferring this we must also infer that so long as these two sets of slightly different units are not exposed to any constant forces tending to coerce them into the same form, there will continue to exist in the nuclei of all descendant cells this same relative instability and consequent plasticity.

Such evidence as we have verifies this interpretation. There is first the universal fact that development of the germ begins when it is exposed to an incident force--heat--the undulations of which, increasing the oscillations of the mixed units, give them greater freedom to arrange themselves in conformity with their type. We see this alike when spring warmth makes a seed germinate and when the warmth of a sitting hen sets up organization in her eggs. Heat frees the molecules of inorganic matter from local restraints and, as we see in molten metal, lets them yield to other forces; and similarly in this organic matter, the units are made free to follow their proclivities. Then, secondly, there comes the evidence from comparisons between the effects of mixing constitutional units differing in various degrees. Let the cluster of mixed units be derived from animals that are ordinally distinct. Nothing happens. The units each contributes tend to arrange themselves after the parental type. Hence a conflict between the tendencies towards two markedly unlike structures, and no structure arises. Suppose the mixed units come from two kindred species--say horse and ass. The structures which they respectively tend to form, being in their main characters alike, there is such co-operation as produces a working organism but an organism in certain respects imperfect--a mule. Suppose, again, the units come from two varieties of the same species. A perfect organism results, and, as shown by Mr. Darwin when detailing the effects of crossing, an unusually vigorous organism. The units being more unlike than those belonging to the same variety, the instability of the germ-plasm is unusually great, and the transformations which constitute development and action become unusually active. When, as in ordinary cases, the units are supplied by members of the same variety who have not been made very much alike by their antecedents, there follows the usual amount of organic vigour. Coming now to the results of breeding in-and-in--breeding between individuals whose constitutions (i.e. constitutional units) have for generations been growing more alike in the absence of crossing with other stirps--we see that diminution of organic vigour is displayed: there is a decrease in the rate of physiological change. Finally, on coming to a closer relationship, as in marriages between cousins, in whom the constitutional units are more than commonly alike, we see there frequently follows either barrenness or the production of feeble offspring.

All these facts, then, are congruous with the hypothesis that the use of fertilization is the mixing of unlike units, and consequent production of plasticity. Leaving out cases in which the unlikenesses are so great as wholly to prevent co-operation among the units, the degree of vigour, that is, the activity of physiological change, is great where the unlikeness is great and diminishes with the approach towards likeness.

* * * * *

6. The existence of constitutional units seems otherwise necessarily implied. I refer to the fact that no organism is a homogeneous mean between its parents but consists of a mixture of parts, some following one parent and some the other. Among illustrations of this the most conspicuous are those yielded by the variously-mixed colours of hair or feathers. Horses, cattle, dogs, cats, hens, pigeons display these mixtures: colours in one place like the mother and in another place like the father. As the internal organs are invisible, and as visible organs have indefinite shapes and graduate indefinitely into adjacent ones, the mixture of traits is elsewhere less conspicuous; but occasional marked cases (especially in malformations) leave no doubt that it pervades the entire organism.

This peculiarity of transmission seems necessarily to imply that there are distinct units derived from the two parents, and that in the course of development there is more or less segregation of them--those of the one origin predominating so far in some places as to give special likeness to one parent, and those derived from the other doing the like in other places. All which interpretation is impossible unless the hypothesis of constitutional units be admitted.

* * * * *

7. I come at length to the special evidence referred to at the outset. It is evidence of the same nature as that just assigned, but carried to a higher stage. It is furnished not by the segregation of traits derived from two parents of the same variety, but is furnished by the segregation of traits derived from parents of different varieties. In articles on “Bud Variations or Sports” (Gardener’s Chronicle, 1891) Dr. Masters gives various examples of the separation or unmixing of ancestral constitutions. Mr. Noble formed a hybrid between Clematis Jackmani and C. patens. One of these varieties flowers in the autumn on new wood, while the other flowers in the spring on old wood; and the result is that flowers of two kinds, quite unlike, are produced at different parts of the year, and that by pruning so as to cut away one or other set of shoots, the plant may be made to produce exclusively for the time being one or other sort of flower.

“Another very interesting case of unmixing, or, if it be preferred, of partial mixture, is afforded by Neubert’s Berberis. This is a hybrid between the evergreen pinnate-leaved Mahonia and the deciduous simple-leaved Berberis vulgaris, and it bears leaves some of which are intermediate in appearance, while others are much like those of one or other of its parents.

“A not uncommon illustration of a similar kind, is the production of a Peach and a Nectarine on the same branch, and we have just learnt from Canon Ellacombe that some of the Berlin Hellebores show evidence of their hybrid nature by occasionally producing foliage [and flowers?] of the two parents separately from the same root-stock.

“In addition to the cases given above, we may here cite a few more which have come under our notice, such as a Chrysanthemum, half the florets of which are of one colour, half of another. A hybrid Calanthe, showing a similar piebald variation, is shown in Fig. 14. A very curious case was that of the Narcissus received from Mr. Walker, and in which flowers of two distinct varieties sprang from the same bulb. Grapes not uncommonly show their crossed origin by presenting a striped appearance, one stripe being of one colour, one of another, as may also be seen in the Orange, Apple, Lemon, and Currant.”

Thus, however the germ-plasm is constituted its essential components cannot be all alike. Before there can be this dissociation of ancestral characters, there must be in the germ-plasm different elements capable of being dissociated. This single fact seems to compel us to assume constitutional units.

APPENDIX G.

THE INHERITANCE OF FUNCTIONALLY-CAUSED MODIFICATIONS.

In Part II, Chapter X^A, I have confessed that the process by which a structure changed by use or disuse affects the sperm-cells or germ-cells whence arise descendants, is unimaginable: without, however, inferring that therefore such a process does not exist. With others it seems different. Some three years ago the following expression of opinion came to me from a zoological expert:--

“Many zoologists--most of us here at Cambridge--are intensely opposed to the doctrine of the inheritability of acquired variations. Even assuming that the developmental power of a germ is determined by its molecular structure (and I for one would question this--Driesch and his school when they find that they can squeeze a developing egg into all sorts of shapes without altering the final result, that one blastomere in an egg which has divided into 8 is still able to reproduce a whole embryo--question it also), we still fail to conceive any means by which, for instance, a change in the development of a muscle or nerve can effect a corresponding change in that part of the germ which is destined to produce a corresponding part in the descendant.”

Here it will be observed that belief in the inheritance of structural effects wrought by use and disuse, is rejected because of inability “to conceive any means” by which the modifications produced in an organ can effect a correlated modification in the germ of a descendant: failure to conceive is the test. The implication is that some alternative hypothesis is accepted because the correlating of a variation in an organ with a corresponding germ-variation is effected by a means which is conceivable. This is the hypothesis of Weismann. Concerning its conceivability I have, in the chapter just named, already written as follows:--

“If we follow Prof. Weismann we are led into an astounding supposition. He admits that every variable part must have a special determinant, and that this results in the assumption of over two hundred thousand for the four wings of a butterfly. Let us ask what must happen in the case of a peacock’s feather. On looking at the eye near its end, we see that the minute processes on the edge of each lateral thread must have been in some way exactly adjusted, in colour and position, so as to fall into line with the processes on adjacent threads: otherwise the symmetrical arrangement of coloured rings would be impossible. Each of these processes, then, being an independent variable, must have had its particular determinant. Now there are about 300 threads on the shaft of a large feather, and each of them bears on the average 1,600 processes, making for the whole feather 480,000 of these processes. For one feather alone there must have been 480,000 determinants, and for the whole tail many millions. And these, along with the determinants for the detailed parts of all the other feathers, and for the variable components of all organs forming the body at large, must have been contained in the microscopic head of a spermatozoon!” [And each of them must, throughout all the complex developmental processes, have preserved the ability to find its way to the exact place where it was wanted!]

If my Cambridge correspondent is able to conceive this process implied by the hypothesis of Weismann, I can only say that he has an enviable power of imagination.

* * * * *

But now comes the strange fact that an impossibility of thought implied by Weismann’s hypothesis does not cause rejection of it, but yet is urged as a reason for rejecting an alternative hypothesis which does not imply it. One objector cannot conceive that “a change in the development of a muscle or nerve can effect a corresponding change in that part of the germ which is destined to produce a corresponding part in the descendant”; and another objector says it is “very hard to believe” that a functionally-changed organ will so affect spermatozoa and ova that “one particular part of them will be so altered that the organisms which grow up from them will be able to present the same modification on the application of a different stimulus.” It is tacitly assumed by both that, as in the hypothesis of Weismann so in the counter-hypothesis, a particular part of the germ-plasm gives origin to a particular part of the developed organism. But nothing of the kind is implied. The nature of the counter-hypothesis (at any rate as held by me) is entirely misapprehended. Anyone who turns back to the chapters in the first volume where the conception of physiological units (or constitutional units) was set forth, or who re-reads the foregoing appendix, will see that there is altogether excluded any idea of correlation between certain parts of the germ and certain parts of the resulting organism. The units are supposed to be all alike, and during the progressive embryological changes local groups of them are supposed to take on different forms and structures under the combined forces, general and local, brought to bear on them. This conception is necessitated by all the evidence. The fact disclosed by the experiments of Driesch, Wilson, and Chabry, that from fractions of an ovum structures may be obtained like that obtained from the whole ovum, only smaller, necessitates it. The fact that any sufficiently large fragment of a polyp or planarian, no matter from what part of the body taken, will develop into a complete polyp or planarian necessitates it. The fact that from an undifferentiated portion of a plant, even so small as a scale, a complete plant may arise necessitates it. And it is necessitated by the fact that among plants, roots are produced by imbedded shoots and shoots by roots, as well as by the fact that low animals, such as hydroids, if deprived of both head and root, will develop a head from the root part and a root from the head part, if their respective conditions are inverted. All this evidence shows conclusively that the component units of each species, whether existing in the germ or in the developed organism, are, when not yet differentiated by local conditions, all alike, and that the notion of special parts of the germ-plasm correlated with special parts of the resulting organism, is entirely alien to the hypothesis.

“But how do the units of a modified organ affect the units of the germ in such wise that these produce an inherited modification of the organ?” will be asked. This difficulty has been dealt with in §§ 97d, 97e, where the analogy between the social organism and the individual organism has been brought in aid: serving, if not to furnish a conception, yet to furnish an adumbration. Regarding citizens as the units of an unfolding society, say a colony, it was pointed out that the nature they inherit from a mother-society gives them a proclivity towards a society of like structure, the traits of which are progressively assumed as the colony grows sufficiently large to make them possible. At the same time it was pointed out that while the influence of the entire aggregate on the individuals is seen in this forming of them into a society of the inherited type, the influences of local circumstances, and of individuals on one another, in each group, make them differentiate into appropriate social structures, taking on fit occupations and industries: the implication being that in virtue of their inherited natures they all have partial capacities for the various activities they undertake; so that an immigrant clerk sets up a tavern, a compositor takes to carpentering, and a university man rides after cattle or is employed on a sheep farm. Evidence was given in that place, as in the above paragraph, that the constitutional units of an organism similarly have all of them potentialities for taking on this or that structure and mode of action which local conditions determine. It was further argued that as citizens are continually being remoulded by their society into congruity with it, and, if circumstances change them, tend to remould their society; so in the individual organism, there is this reciprocal action of the whole on the units and of the units on the whole. Hence it was inferred that the modified units in any modified part tend to diffuse modifications like their own through the units at large: being aided by the circulation of protoplasm, as suggested in §§ 54d and 97f. And it was urged that, however inconceivably complex such a process may be, yet it seems not incredible when we recognise the probability that an organism is more or less permeable to undulations propagated by its molecules: Rontgen rays giving warrant. If such units throughout the tissues may take in and send out ethereal waves which bring it into rhythmical relations with others of its kind and tend to produce congruity, it becomes, if not conceivable still supposable, that throughout the circulating protoplasm there goes on a continual harmonization of its components--a moulding of each by all and of all by each. Should it be said that such a process is too marvellous to be reasonably assumed, the reply is that it is not more marvellous than heredity itself, which, were it not familiar to us, would be thought incredible.

* * * * *

But as I have said in the place referred to--“At last then we are obliged to admit that the actual organizing process transcends conception. It is not enough to say that we cannot know it; we must say that we cannot even conceive it:” can only conceive the possibility of a suggested interpretation.

Hence we have to rely upon evidences of other kinds. Among these, some which I think dispose absolutely of the fashionable hypothesis while they harmonize with the opposed hypothesis, have now to be named. That their implication should not have been generally recognized would have seemed to me incomprehensible were it not that I have myself only now observed this implication. The facts are these:--

“Verlot mentions a gardener who could distinguish 150 kinds of camellia, when not in flower; and it has been positively asserted that the famous old Dutch florist Voorhelm, who kept above 1,200 varieties of the hyacinth, was hardly ever deceived in knowing each variety by the bulb alone. Hence we must conclude that the bulbs of the hyacinth and the branches and leaves of the camellia, though appearing to an unpractised eye absolutely undistinguishable, yet really differ.” (Darwin, Variation of Animals and Plants, &c., vol. ii, p. 251.)

More recently testimony to like effect has been given by Dr. Maxwell Masters, and has already been quoted by me in a note to § 286 in illustration of another truth. He says concerning such variations:--

“To the untrained eye, the primordial differences noted are often very slight; even the botanist, unless his attention be specially directed to the matter, fails to see minute differences which are perceptible enough to the raiser or his workmen.... These apparently trifling morphological differences are often associated with physiological variations which render some varieties, say of wheat, much better enabled to resist mildew and disease generally than others. Some, again, prove to be better adapted for certain soils or for some climates than others; some are less liable to injury from predatory birds than others, and so on.”

In his Vegetable Teratology, p. 493, Dr. Masters names another fact having a like implication--the fact that among seedling stocks which have not yet flowered, those which will produce double flowers are distinguishable. He says:--

“This separation of the single from the double-flowered plants, M. Chatié tells us is not so difficult as might be supposed. The single stocks, he explains, have deep green leaves (glabrous in certain species), rounded at the top, the heart being in the form of a shuttlecock, and the plant stout and thick-set in its general aspect, while the plants yielding double flowers have very long leaves of a light green colour, hairy and curled at the edges, the heart consisting of whitish leaves, curved so that they enclose it completely.”

What is the general truth implied? Clearly that there exists no such thing as an independent local variation. Some marked change in the form or colour of a flower or a fruit draws attention; and, being a change which interests the florist or gardener, pecuniarily or otherwise, not only draws attention but usually monopolizes attention: the natural impression produced being that this variation stands there by itself--is without relation to variations elsewhere. But now it turns out that there are concomitant variations all over the plant. Even in underground bulbs certain appreciable differences go along with certain conspicuous differences in the flowers. And if along with a striking change in a flower which the florist contemplates, there go changes all over the plant not obvious to careless observers but visible to him, we must infer that there are everywhere minute differences which even the florist cannot perceive: the whole constitution of the plant has diverged in some measure from the constitutions of kindred plants. Every local variation implies a change pervading the entire organism, manifested in concomitant variations everywhere else.

If so, what becomes of the hypothesis of determinants--the hypothesis that there is a special element in the germ-plasm which results in a special local modification in the adult organism? That there are no facts supporting it has been all along manifest; but now it is manifest that the facts directly contradict it.

At the same time it may be remarked that while the facts are wholly incongruous with the hypothesis of determinants and its accompanying elaborate speculation, they are not incongruous with the alternative hypothesis. Impossible though it may be to imagine the natures of those ultimate units peculiar to each species, which have proclivities towards the particular form of organization characterizing it, yet that a change of structure arising in one part of the organism is accompanied by multitudinous changes of structure in other parts of the organism, is not only congruous with the belief that there exist such constitutional units, but yields it distinct support. For if, as above argued, a conspicuous local variation is not the result of any modification of units special to the locality, but is the result of a modification of the units at large, then it must happen that such modification must have its effects on all other parts of the organism; so that there cannot fail to result all those small concomitant variations above indicated.

May we not also say that it becomes less incomprehensible that structural changes caused by use and disuse are inherited? If, as we see, a local variation spontaneously arising is accompanied by multitudinous other local variations, implying a necessary correlation between each local variation and the general constitution of the organism; then it may be argued that if a marked change of function in an organ causes increase or decrease of it, this general correlation implies that there must be a reciprocal reaction between the part and the whole, tending to re-establish their congruity. The constitution at large will in so far be changed, and along with its change will go corresponding changes in the sperm-cells and germ-cells.

* * * * *

Finally let me add, not another argument, but another fact of observation, of the kind which opponents demand, but which, when they are from time to time furnished, are severally pooh-poohed as not enough. Each of them is spoken of as a solitary fact and slighted as inadequate; and when by and by another is named, this is treated in the same way; so that the facts which if brought together would be recognized as sufficient are never brought together. That to which I refer is set forth in a pamphlet by M. Leo Errera, Professor at the University of Brussels, entitled “Hérédite d’un Caractère acquis chez un Champignon pluricellulaire;” being an account of experiments of Dr. Hunger, at the Botanical Institute in Brussels. First enumerating various instances of adaptations to climate, as those of plants which, fitted to northern regions, preserve their constitutional rapidity of growth and seeding when brought south, and do this for several generations, he goes on to detail the culture-experiments of M. Hunger, and sums up the results of these in the following words:--

“On déduit de là que:

“1^o Les conidies d’Aspergillus niger sont adaptées à la concentration du milieu où a vécu l’individu qui les porte; cet effet est encore plus marqué après deux générations passées dans un milieu donné (Expér. I et II);

“2^o II s’agit d’une véritable adaptation et non pas simplement d’un accroissement de vigueur chez les conidies provenant des liquides concentrés, car ces mêmes conidies germent moins rapidement et donnent des plantes moins vigoureuses que les conidies normales lorsqu’on les sème de nouveau sur le milieu-type: en s’adaptant aux liquides concentrés, elles se sont désadaptées du liquide normal (Expér. III);

“3^o Une génération passée sur le liquide normal n’efface pas l’influence d’une ou de deux générations antérieures passées sur une liquide plus concentré (Expér. IV).

“Tous ces résultats concordent: ils montrent une légère, mais incontestable transmission héréditaire de l’adaptation au milieu.”

SUBJECT-INDEX.

(For this Index as it appeared in previous editions the Author is indebted to F. HOWARD COLLINS, Esq., of Edgbaston, Birmingham. It has now been adjusted to suit the present revised and enlarged edition.)

Acacia, foliar organs, =II=, 41, 264.

Acalephæ: environment, =I=, 105; water in, =I=, 173.

Acari: special creation and effects of, =I=, 428; direct transformations, =I=, 706; segmentation, =II=, 111.

Acorus calamus, agamic propagation, =I=, 642.

Acquired characters, inheritance of: functionally-produced modifications in plants and animals, =I=, 307–13, 318, 526, 541, 562, 692–5; =II=, 618–22; conceivability of, on the hypothesis of physiological units, =I=, 368–71, 695; =II=, 618–22; diminution of jaw, =I=, 541–2, 693; current views on, =I=, 559–60; cessation of selection, =I=, 560–3; Eimer’s theory of orthogenesis, =I=, 560; species differentiation, =I=, 573; location of mammalian testes, =I=, 573; tactual perceptiveness, =I=, 602–8, 633, 665, 666, 672–3, 692; blindness of cave-animals, =I=, 612–3, 647–9; co-adaptation of co-operative parts, =I=, 621, 663–5; transmission of disease, =I=, 622–3; hypothesis supported by telegony, =I=, 624–8, 644–6, 649–50; views of Darwin and neo-Darwinists, =I=, 630, 685, 690; why facts in support are meagre, =I=, 632; degradation of little toe, =I=, 652–3, 673; neuter forms of social insects, =I=, 658–9, 663–4, 670, 675; degenerated instinct in ants, =I=, 660–2; rudimentary limbs of whale, =I=, 669, 692; importance of question, =I=, 672, 690; monstrous development of honey-ants, =I=, 683–4; osteology of Punjabis, =I=, 689; summary of evidences in support, =I=, 692–5; genesis of vertebrate skull, =II=, 227; false joints, =II=, 371, 372; conceivability of rival hypotheses, =II=, 618–22; adaptation to environment in Aspergillus, =II=, 623.

Acrogens, the term, =II=, 55–6. (See Archegoniateæ.)

Actinophrys: a primary aggregate, =II=, 76; genesis, =II=, 452.

Actinozoa: multiaxial development, =I=, 166; waste and repair, =I=, 213, 219; differentiation, =I=, 391; parasitism, =I=, 397; integration, =II=, 92; symmetry, =II=, 189, 192; growth and genesis, =II=, 444.

Activity: the principle of, the essential element in Life, =I=, 113, 114, 122; not inherent in living matter, =I=, 120; nutrition and genesis, résumé, =II=, 497–9; and evolution, =II=, 501–4.

Adaptation: general truths, =I=, 227–33, 233–5; botanical, =I=, 227; physiological, =I=, 228–33; psychological, =I=, 229, 230–3; structural, functional, and interdependence, =I=, 235–9, 240–1, 318; social and organic stability, =I=, 240–2; résumé, =I=, 242–3; to varied media, =I=, 479–81, 489, 556; multiplication of effects, =I=, 512–3, 550; direct equilibration, =I=, 522–3; natural selection and equilibration, =I=, 530–5; non-adaptive specific characters, =I=, 565; time required for effecting, =I=, 565–6; an obstacle to re-adaptation, =II=, 11; of skin and skeleton, =II=, 215, 217; outer tissue, =II=, 312–4, 387; skin and mucous membrane differentiation, =II=, 321–2, 389; vascular system, =II=, 343–4; osseous, =II=, 352; muscular, =II=, 368–9, 391; persistence of force and physiological, =II=, 394; of reproductive activity to conditions, =II=, 411–6; vertebræ development, =II=, 563–6. (See also Co-adaptation.)

Africa, effect of climate on inhabitants, =I=, 30.

Agamogenesis: alternation with gamogenesis, =I=, 266–7, 272–3, 284–94, 336, 592; =II=, 415; parallelism in karyokinesis, =I=, 267–8; a process of disintegration, =I=, 276–7; conditions determining its continuance, =I=, 284–94, 295–7, 330; physiological units, =I=, 351; =II=, 613; spontaneous fission, =I=, 582, 584–7, 589–92, 595–6, 599; remarkable extent of, under favourable conditions, =I=, 591–2, 640–1; in Actinozoa, =II=, 92; in Hydrozoa, =II=, 102; in Annelida, =II=, 103; innutrition, =II=, 179–80.

Agaricinæ, =II=, 139, 257.

Agassiz, L. J. R., zoological classification, =I=, 380.

Aggregates, Animal and Plant (see Morphology).

Agility, a vital attribute, =I=, 578.

Agrimony, floral symmetry, =II=, 42, 167, 170.

Air, in vegetal tissues, =II=, 567–8, 583, 591, 593.

“Air plants,” =I=, 208.

Albumen: properties, =I=, 12; Lieberkühn’s formula, =I=, 13; diffusibility, =I=, 19; in organic tissues, =I=, 41.

Alcohols, properties, =I=, 10–12.

Algæ: reproduction, and the dynamic element in life, =I=, 118–9; multicentral development, =I=, 163, 164; axial development, =I=, 165; locomotive powers of minute forms, =I=, 196; uniform tissue and function, =I=, 200, 586; gamogenesis, =I=, 271, 279, 280, 283; =II=, 448, 449, 450; fertility, =I=, 582; =II=, 440, 441; fission, =I=, 584, 585; unicellular forms, =II=, 22; integration in Confervoideæ and Conjugateæ, =II=, 25; pseudo-foliar and axial development, =II=, 28–33, 57; foliar development, =II=, 76, 91; branch symmetry, =II=, 145; cell metamorphoses, =II=, 176; tissue differentiation, =II=, 244, 246, 251, 252, 256, 272, 385–6; adaptation of reproductive activity to conditions, =II=, 289; integration, =II=, 292; indefiniteness, =II=, 295; genesis and development, =II=, 463.

Alimentary canal: metabolic processes and agents, =I=, 68–9, 74; structural traits, =I=, 192; progressive development, =I=, 195; relation to environment, =I=, 196; function, =I=, 205; segmentation in annelids, =II=, 125; differentiation, =II=, 301, 302, 321–2, 323–5, 389; specializations in birds, =II=, 325; in ruminants, =II=, 327–9; differentiation of liver, =II=, 329–33; muscularity, =II=, 364.

Allotropism: of organic constituents, =I=, 4, 9; muscular action, =I=, 59.

Alloys, melting point of, =I=, 339.

Alternation of generations, misleading application of term, =II=, 84. (See Agamogenesis and Gamogenesis.)

Amitosis, occurrence of, in morbid tissues, =I=, 264.

Ammonia: properties, =I=, 7, 9; nerve stimulation, =I=, 55.

Amœba: central development, =I=, 163; a primary aggregate, =II=, 86; symmetry of encysted, =II=, 186; symbiosis, =II=, 400.

Amphibia: classification of, =I=, 392; embryonic respiratory system, =I=, 457; structure and media, =I=, 483; limb locomotion, =II=, 15; segmentation, =II=, 122, 225; outer tissues, =II=, 311; respiration, =II=, 334, 338; Owen on skeleton, =II=, 552, 557, 558.

Amphioxus: separation of segmentation spheres of egg, =I=, 691; embryogeny, =II=, 121; local segmentation, =II=, 125–7, 605; genesis of vertebrate axis, =II=, 213–6, 218, 222; development, =II=, 564.

Amphipnous cuchia, vascular air-sacs, =II=, 337.

Anabas scandens, the climbing fish, =I=, 480, 483.

Anacharis (see Eloidea).

Anæsthetics, diverse effects of, =I=, 55.

Angræcum, assimilative function of root, =II=, 255.

“Animal Spirits,” vitalism and, =I=, 115.

Animals: nutrition and molecular re-arrangement, =I=, 36–7; nitrogenous character, =I=, 39–41; sensible motion, =I=, 57; metabolism, =I=, 62–77; multiplication of energies, =I=, 75; contrasted traits of plants and, =I=, 196; what is an individual? =I=, 246–7; solar influence, =I=, 500, 556; geologic changes affecting, =I=, 501–4, 549, 550, 556; interdependence with plants, =I=, 504–6, 514; =II=, 398–401; complexity of influences affecting, =I=, 506; geographical isolation and origin of species, =I=, 568–9; vital attributes, =I=, 577–9; distribution and antiquity of plant and animal types, =II=, 297; mutual dependence of organisms at large, =II=, 397–408; hypothetical plant-animal type, =II=, 397; progressive increase of size, =II=, 401; laws of multiplication, =II=, 411–6; rhythm in numbers, =II=, 419; law of weights and dimensions, =II=, 434.

Animals, domesticated: variation, =I=, 324, 326, 560, 563, 693; interbreeding, =I=, 345–7, 354; =II=, 615; pure and mixed breeds, =I=, 354, 625.

Annelida: phosphorescence, =I=, 50; axial development, =I=, 165, 166; integration, =I=, 363; larval forms and phylogeny, =I=, 447; =II=, 115; segmental fission, =I=, 588–9; segmentation, =I=, 98–101, 103–4, 602–5; =II=, 107–9, 125–7; lateral gemmation, =II=, 105; embryogeny, =II=, 119; bilateral symmetry, =II=, 197–200; genesis, =II=, 444, 453.

Annulosa: regeneration, =I=, 361–2; distinctive traits, =I=, 392; origin of type, =II=, 98–110, 602–6; unit of composition, =II=, 105; application of term, =II=, 111; vertebrate symmetry compared, =II=, 203–6; segmental differentiation, =II=, 207–9; unintegrated function in Planaria, =II=, 373; development and genesis, =II=, 464; nutrition and genesis, =II=, 490. (See also Annelida and Arthropoda.)

Anthropomorphism, former prevalence of, =I=, 419.

Ants: utilization of aphids, =I=, 660–1; =II=, 403, 405; nest-mates, =II=, 405; castes in social species, =I=, 658–9, 670, 675; loss of self-feeding instinct in Amazons, =I=, 660–1, 663–4; monstrous development of Honey-ants, =I=, 683; bulk and fecundity, =II=, 492. (See also Termites.)

Aphis: individuality, =I=, 249, 250; =II=, 603; parthenogenesis, =I=, 274–5, 289; fertility, =I=, 582, 640–1; =II=, 476, 490; utilized by ants, =I=, 660–1; =II=, 403, 405; over-multiplication checked by lady-bird, =II=, 406.

Aquatic animals, large size attained by, =I=, 156.

Arachnida: avoidance of danger, =I=, 92; oviparous homogenesis, =I=, 271; segmentation, =I=, 469; =II=, 113, 114; integration and homology, =II=, 111, 121; bilateral symmetry, =II=, 198.

Arcella: symmetry, =II=, 186; outer tissue differentiation, =II=, 309.

Archegoniateæ: morphological composition, =II=, 32–5; growth and development, =II=, 50–6; tubular structure, =II=, 58, 62; alternating generation not distinctive, =II=, 84; asymmetry and environment, =II=, 140; integration, =II=, 293, 296; individuation and genesis, =II=, 441, 451, 463.

Archenteron: primitive externality, =II=, 301; formation of cœlom, =II=, 302.

Archiannelida: segmentation, =II=, 125.

Arenicola marina: polytrochal larvæ, =II=, 109.

Arm: embryogeny of human, =I=, 169; vicarious use of, =I=, 209.

Army, morphological analogy, =II=, 6.

Arteries (see Vascular System).

Arthropoda: uniaxial development, =I=, 165; protoplasmic continuity, =I=, 190, 629; excursiveness, =I=, 481; limb locomotion, =II=, 15; integration and homology, =II=, 111–4, 121; bilateral symmetry, =II=, 197–200; genesis, =II=, 445, 453.

Ascidians: multiaxial development, =I=, 165, 166; functional differentiation, =I=, 202; composite individuality of Doliolum, =I=, 247; self-fertilization, =I=, 342; integration, =II=, 94, 96, 97; symmetry, =II=, 194; origin of vertebrate type, =II=, 194, 598, 605.

Ascomycetes, reproduction, =II=, 450.

Assimilation: compared with reasoning, =I=, 81–7; a trait of vitality, =I=, 577.

Asteroidea, radial symmetry, =II=, 196.

Astronomy: growth of celestial bodies, =I=, 135; Schleiden on individuality, =I=, 245; evolution, =I=, 432, 435; classification of stars, =I=, 444; rhythm of, and organic change, =I=, 499–501, 557; law of equilibration, =I=, 519–20; co-operation of structure and function, =II=, 3.

Atavism: occurrence of, =I=, 305–6, 314; digital variation, =I=, 321–3.

Atoms: use of term, =I=, 6, 31; ethereal undulations and oscillations, =I=, 31–5.

Australia: settler’s usages, =I=, 364; ratio of jaw to skull in natives, =I=, 541.

Axillary buds, origin and development, =II=, 65–8.

Axis: “neutral” of mechanics, =II=, 210; genesis of vertebrate, =II=, 212–6, 224–7.

Bacteria: fission, =I=, 270; non-nucleated, =II=, 20; rate of increase, =II=, 443.

Baer, K. E. von: embryological formula, =I=, 171, 172, 451, 453, 461, 466; zoological classification, =I=, 383; on animal transitions, =I=, 480.

Balanophoræ, inner tissue, =II=, 274.

Bark: varied development, =II=, 247–9; physiological differentiation, =II=, 249–50, 258, 386.

Basidiomycetes, reproduction, =II=, 450.

Bat, infertility of, =II=, 473.

Bates, H. W., protective mimicry of butterflies, =I=, 398.

Batrachia (see Amphibia).

Bean, vascular system, =II=, 573, 591.

Beaver, tail and co-adapted structures, =I=, 616.

Bees (see Insects).

Begoniaceæ: multiplication =I=, 224, 317, 442; individuality, =I=, 251; development from scales, =I=, 282; symmetry, =II=, 159, 166; development, =II=, 271.

Berkeley, M. J., indefiniteness of mosses and ferns, =II=, 296.

Bile, arrest of excretion, =I=, 209.

Bilirubin and biliverdine, function of, =II=, 330, 333.

Biology: definition and divisions, =I=, 124–5; organic structural phenomena, =I=, 125–7; also functional, =I=, 127–9; actions and reactions of function and structure, =I=, 129–30; genesis, =I=, 130–1; limited knowledge of, =I=, 131; evolution, =I=, 432, 434; sociological analogies (see Sociology).

Biophors, Weismann’s germ-plasm units (see Weismann).

Birds: flesh-eating and grain-eating contrasted, =I=, 68; growth and expenditure of force, =I=, 142; size of egg and adult, =I=, 144; limitations on flight, =I=, 155; self-mobility, =I=, 175; temperature, =I=, 176; functional and structural differentiation, =I=, 201; food of starving pigeon, =I=, 215; viviparousness, =I=, 271; heredity and pigeon breeding, =I=, 305; atavism in pigeon, =I=, 314; osseous variation in pigeon, =I=, 321; classification, =I=, 392; migrations and change of habits, =I=, 399, 402, 500; distribution in time, =I=, 410; Darwin on petrels, =I=, 455; rudimentary teeth, =I=, 457; vertebræ, =I=, 471; =II=, 564; feather development, =I=, 473; habits of water ouzel, =I=, 485; egg shells and direct equilibration, =I=, 526; bones of waders and direct equilibration, =I=, 527; fertility and nervous development, =I=, 598; cellular continuity, =I=, 629; adaptation of structure to environment, =II=, 12; sexual selection, =II=, 269; wing spurs, =II=, 313; outer tissue differentiation, =II=, 314–5, 387; alimentary canal development, =II=, 325, 327; muscular colour and activity, =II=, 365–9; nutrition, =II=, 433; cost of genesis, =II=, 436; growth and genesis, =II=, 454, 458; heat expenditure and genesis, =II=, 468–9, 474; activity and genesis, =II=, 470–2, 474; contrasted mammalian fertility, =II=, 470; eggs of wild and tame, =II=, 478; fertility of blackbird and linnet compared, =II=, 503; Owen on skeleton of, =II=, 559, 560, 561.

Bischoff, embryogeny of human arm, =I=, 169.

Bison, modifications entailed by increased weight of head, =I=, 512.

Blackbird, contrasted with linnet in development, =II=, 503.

Blainville, de, definition of life, =I=, 79, 93.

Blastosphere, independence of cells in Echinoderm larvæ, =I=, 185.

Blastula, definition of life and formation of, =I=, 112.

Blood: similarity of iron peroxide, =I=, 17; metabolic processes, =I=, 69; segregation of abnormal constituents, =I=, 180; protozoon life of corpuscles, =I=, 186–7; morbid changes, =I=, 221, 701; assimilative power and organic repair, =I=, 221–2; respiratory tissue differentiation, =II=, 310–1; pressure in mammals, =II=, 340. (See also Vascular System.)

Blow-fly, Weismann on nutrition and genesis in, =I=, 678–9.

Boers, Cape, habits and fertility, =II=, 508.

Boismont, A. B. de, on human fertility, =II=, 511.

Bone: growth and function, =I=, 151; adaptability, =I=, 230; =II=, 217–8; function and weight, =I=, 308, 693; mammalian cervical vertebræ, =I=, 394; evolution and vertebral column, =I=, 470–1; partial development, =I=, 473; size of head as influencing, =I=, 512, 536–9; direct equilibration and strength, =I=, 527; natural selection and co-adaptations, =I=, 614–21, 674, 677; rudimentary limbs of whale, =I=, 668, 685, 692; inheritance of acquired modifications in Punjabis, =I=, 689; skull development, =II=, 222; theory of supernumerary, =II=, 223; Cope on origin of vertebrate osseous system, =II=, 225–7; differentiation, =II=, 344–56; false joints, =II=, 370–2; Owen’s theory of vertebrate skeleton, =II=, 548–66.

Book-worm, food of, =I=, 77.

Born, G., experiments on frog larvæ, =I=, 365.

Botany, biological classification, =I=, 124, 125. (See Plants.)

Bothriocephalus, development, =II=, 490.

Botryllidæ: development, =I=, 166; independence of components, =I=, 247; agamogenesis, =I=, 641.

Bower, Prof., on alternation of generations, =II=, 84.

Brachiopoda, rude vascular system, =II=, 340.

Bradbury, J. B., on vaso-dilators, =I=, 55.

Brain: natural selection and mental evolution, =I=, 553; analysis of substance, =I=, 596; weight in higher animals, =I=, 598–9; size in civilized and uncivilized, =II=, 530.

Branches (see Morphology).

Branchiæ (see Respiratory System).

Brass, effect of antimony on, =I=, 121.

Bread, diamagnetism, =I=, 370.

Breeding: heredity, =I=, 304–5; in-and-in, =I=, 344–7, 353; =II=, 615; pure and mixed, =I=, 354, 625.

Bricks, changed equilibrium shown by, =I=, 38, 42.

Brodie, T. G., cell chemistry, =I=, 260.

Brownell, Miss J. L., on birth-rate in United States, =II=, 520.

Brown-Séquard, on inherited epilepsy, =I=, 312, 624.

Bryophyllum, peculiar proliferation, =II=, 295.

Bryophyta, large size attained by some, =I=, 138.

Bryozoa, gemmation, =I=, 588.

Budding (see Gemmation).

Buds: development, =I=, 167–8; theories of heredity and cauline, =I=, 358–9, 360; axillary, =II=, 65–9; effects of nutrition, =II=, 73–4.

Butterfly: protective mimicry, =I=, 398; instance of tame, =I=, 684.

Cabbage, varieties of, =I=, 302.

Cactaceæ: foliar and axial development, =II=, 47–9; differentiation in, =II=, 258, 276, 282; vascular system, =II=, 282; dye permeability and circulation, =II=, 571, 572; wood formation, =II=, 575, 577, 578, 580.

“Callus,” budding from, =I=, 358, 359.

Camel, natural selection and hump of, =I=, 534.

Canadians, French, fertility of, =II=, 509.

Cancer, the definition of life, =I=, 111; œsophageal, =II=, 324; and vascular system, =II=, 343.

Caoutchouc, leaf-structure, =II=, 589.

Capillaries (see Vascular System).

Capillarity, and vegetal vascular system, =II=, 279–80, 286, 568, 570, 585, 587, 592–6.

Carbohydrates: instability, =I=, 10; the term “hydro-carbon,” ib.; molecular changes in, =I=, 42–3; organic transformation, =I=, 43, 48; metabolic processes, =I=, 63–77, 262–3; =II=, 362.

Carbon: properties, =I=, 3–5, 20; compounds, =I=, 6, 7, 9, 10–12, 13, 24–5.

Carbonic acid (carbon dioxide): properties, =I=, 6, 7, 9; in animal and plant functions, =I=, 62, 214; =II=, 398; diffusibility, =II=, 331.

Carbonic oxide, properties, =I=, 6.

Carnivores: nitrogenous food, =I=, 47, 68; katabolic process, =I=, 71; restricted environment, =I=, 396; their beneficial effects on animal life, =II=, 405–6.

Carpenter, W. B.: on functional specialization, =I=, 208; reproduction of seaweed, =I=, 582; vegetal cell multiplication, =I=, 585; structure and multiplication of compound organisms, =I=, 586–9; on fundamental traits of sex, =I=, 595; nutritive system of invertebrates, =I=, 595; Macrocystis, =II=, 450; nutrition and reproductive function, =II=, 460.

Cartilage (see Bone).

Castration, effect of, on growth, =II=, 459.

“Castration parasitaire,” Julin on, =II=, 493–6.

Catalysis, and vital metamorphosis, =I=, 39, 43.

Cattell, McKeen, on tactual perceptiveness, =I=, 666.

Caulerpa, simulation of higher plant-forms, =II=, 22.

Cave-animals, degeneration of eyes, =I=, 309, 612–3, 614, 647–9, 693.

Cell, the: incomprehensibility of forces at work in, =I=, 118; protoplasts and their traits, =I=, 181; the cell-theory, =I=, 184, 252; =II=, 17–21, 85; differentiation, =I=, 188–9, 194; the continuity of protoplasm, =I=, 190–2, 194, 628–30; =II=, 21; its structure, =I=, 253–5; function of centrosome, =I=, 254–5, 257; structure and function of nucleus, =I=, 255–6, 258–9; karyokinesis, =I=, 257–8; function of chromatin, =I=, 259–65; fertilization and function of polar bodies, =I=, 266–8; theories of heredity based on theory, =I=, 356; Weismann’s differentiation into reproductive and somatic, =I=, 622, 628–30, 633–44; nucleus absent or dispersed, =II=, 20, 85; morphological differentiation, =II=, 175–7; animal morphology, =II=, 228–30; morphological summary, =II=, 233; vegetal tissue differentiation, =II=, 249–50, 386; vascular development, =II=, 279–84, 389.

Centipede, bilateral symmetry, =II=, 198–200.

Cephalopoda: bilateral symmetry, =II=, 203; vascular system, =II=, 341.

Cercariæ (see Distoma).

Cereus, tissue differentiation, =II=, 276, 283.

Cesalpino, =I=, 377.

Cestoda (see Entozoa).

Chætopoda, segmentation, =II=, 98, 103, 605.

Chaja, wing spurs, =II=, 313.

Change, and definition of life, =I=, 81–90, 113.

Charles, R. H., on inheritance of acquired modifications in leg-bones of Punjabis, =I=, 689.

Chatié, on single and double stocks, =II=, 622.

Chemistry: properties of organic elements, =I=, 3–5, 20, 22; of diatomic compounds, =I=, 7–10; tri-atomic, =I=, 10–12; poly-atomic, =I=, 12–13, 25; traits of evolution, =I=, 23–4; ethereal undulations and atomic oscillation, =I=, 31–6; chemical affinity and organic change, =I=, 36–7, 38–43; oxidation and generation of heat, =I=, 46–9, 60; generation of nerve force, =I=, 52, 60; metabolism, =I=, 62–77; physiology and organic, =I=, 127; flesh constituents, =I=, 154; composition of organisms and environment, =I=, 173; organic development and differential assimilation, =I=, 179–80; chemical units, =I=, 225; =II=, 612; primitive ideas of elements, =I=, 417; evolution of organic compounds, =I=, 696–701, 703.

Chestnut, leaf symmetry, =II=, 149, 153.

Chiton: simulation of segmentation, =II=, 116, 118; symmetry, =II=, 202.

Chlorophyll: function, =I=, 65; =II=, 263; nutrition and absence of, =II=, 74; constitution, =II=, 262; symbiotic presence in animals, =II=, 400.

Chondracanthus gibbosus, enormous development of reproductive system, =II=, 487.

Chordata, affinities, =I=, 466.

Chromatin (see Cell).

Circle, the, and evolution hypothesis, =I=, 433.

Circulation (see Vascular System).

Cirrhipedia: Darwin on retrograde development, =I=, 458; remarkable transformation in Sacculina, =II=, 494–5.

Civilization, human evolution and genesis, =II=, 529–31.

Cladophora: integration, =II=, 25; axial development, =II=, 28.

Classification: subjective conception, =I=, 78; two purposes of, =I=, 374; a gradual process, =I=, 375; botanical, =I=, 377–80, 389–90; zoological, =I=, 380–9; incomplete equivalence of groups, =I=, 389, 445–6, 448, 555, 572; group attributes, =I=, 390–3; the truths interpreted, =I=, 393–4; ethnologic and linguistic evolution, =I=, 441–6; organic evolution, =I=, 443, 447, 555; differences in kind and degree, =I=, 444–6; antecedent structural similarity, =I=, 447, 448–9; Von Baer’s formula, =I=, 451–4, 555; organic, not uniserial, =II=, 115.

Classification of the Sciences, The, and evolution and dissolution, =II=, 5.

Claus, C, on segmentation in Annelids and Chætopods, =II=, 605.

Clover: flower and axial development, =II=, 45; symmetry, =II=, 152.

Co-adaptation of co-operative parts: principles underlying, =I=, 234–5, 511–3, 514–5; slow operation of the process, =I=, 236; sociological analogy, =I=, 237–40; reversion under original conditions, =I=, 240; the analogy continued, ib.; the case of bison’s head, =I=, 512; natural selection an inadequate explanation, =I=, 535, 614–21, 692; Romanes on “cessation of selection” as effecting, =I=, 560, 561–2; Weismann’s theories, =I=, 560–3, 663–5, 670, 674–5; natural selection and economy of growth, =I=, 562; physiological processes involved, =I=, 566–7; Wallace’s argument from artificial selection, =I=, 615; what are co-operative parts? =I=, 616–7; “intra-selection” examined, =I=, 676–8.

Coal, social effects of supply, =I=, 238–9, 241.

Cocoa-nut, growth and fertility, =II=, 457.

Coccospheres: vital problem presented by protective structures, =I=, 119; imbricated plates, =I=, 182.

Cockroach, ousting of European species, =I=, 399.

Cod: ova of, =II=, 435; growth and fertility, =II=, 454.

Codium: symmetry, =II=, 136; tissue differentiation, =II=, 246.

Cœlenterata: rudimentary contractile organs, =I=, 58; vital changes in polyp, =I=, 95; axial development, =I=, 165, 166; environment and structure, =I=, 173; self-mobility, =I=, 175; =II=, 14, 15; functional differentiation, =I=, 201, 391; inactivity and waste, =I=, 213; reparative power, =I=, 219, 224; individuality, =I=, 246, 247, 250; heterogenesis, =I=, 273, 277, 296; negative disintegration in Hydrozoa, =I=, 276, 587; reproductive tissue, =I=, 281; differentiation in Hydrozoa, =I=, 391; classificatory value, =I=, 446; regeneration of fragments, =II=, 90; integration, =II=, 90, 102, 105, 124; gemmation, =II=, 91; tertiary aggregation, =II=, 92, 95, 124; molluscan affinities, =II=, 115; radial symmetry, =II=, 188; symmetry of compound, =II=, 192–3; segmental differentiation, =II=, 207; physiological differentiation in Hydra and analogy, =II=, 300; ciliation of blastula, =II=, 301; tissue reduplication, =II=, 301–2, 389; outer tissue differentiation, =II=, 309; osmosis in Hydra, =II=, 339; vascular system in Hydra, =II=, 340, 376; functional co-ordination, =II=, 376; symbiosis, =II=, 400; asexual genesis, =II=, 443–4; growth and sexual genesis, =II=, 452; development and genesis, =II=, 462; nutrition and genesis, =II=, 476.

Cœlom, origin and function, =II=, 302–3.

Collins, F. Howard, jaws and teeth of savages and civilized, =I=, 541.

Colloids: T. Graham on, =I=, 15–8; diffusibility, =I=, 18–21; organic, =I=, 21, 25, 26; pliability and elasticity, =I=, 27; capillary affinity, =I=, 28; isomerism, =I=, 59; instability, =I=, 350; molecular mobility and diffusibility, =II=, 331; instability of, and nerve differentiation, =II=, 356–61; and muscular tissue, =II=, 361–4.

Colonies, autogenous development and parallel in heredity, =I=, 366–8; =II=, 620.

Colour: sensation of, =I=, 54; phœnogamic, =II=, 75, 265–6; light and vegetal, =II=, 261–2; floral fertilization, =II=, 267–9; sexual selection, =II=, 269; activity and muscular, =II=, 365–9; physiological units and mixture of, in offspring, =II=, 616, 617.

Commensalism, organic Integration as displayed in, =II=, 402–4.

Compositæ: floral symmetry, =II=, 173.

Condor, weight of, =I=, 155.

Confervoideæ, =I=, 279, 280; =II=, 25, 28, 449. (See Algæ.)

Conjugateæ, =II=, 449. (See Algæ.)

Conjugation, in Algæ, =I=, 279; in Protozoa, =I=, 280; =II=, 452; can fission persist without? =I=, 637; relation to growth, =II=, 449.

Connective tissue, Hertwig’s classification, =I=, 189.

Constitutional units, =I=, 369. (See Physiological Units.)

Consumption, hereditary transmission, =I=, 307.

Co-ordination of actions (see Life).

Cope, E. D., on origin of vertebrate structure, =II=, 225–7.

Cormophyta: slight internal differentiation, =II=, 273; vascular system, =II=, 280.

Corpuscula tactus, their function, =I=, 75.

Correspondence, use of word, =I=, 97. (See Life.)

Cousin-marriages, =I=, 345; =II=, 615.

Cow: what prompts her to mumble a bone? =I=, 120.

Cow-parsnip (see Heracleum).

Crab (see Crustacea).

Creation (see Special creation).

Crinoidea, symmetry, =II=, 195–6.

Crocodile, continuous growth, =I=, 154, 292.

Crookes, Sir W., hypothetical chemical unit “protyle,” =I=, 22, 23.

Cruciferæ, floral symmetry, =II=, 164, 171.

Crustacea: locomotion of lobster, =I=, 175; regeneration of limbs, =I=, 224, 360, 589; =II=, 76; homogenesis, =I=, 271; genesis and nutrition in Daphnidæ, =I=, 290–1; growth and genesis, =I=, 292; degeneration of eye in cave-inhabiting, =I=, 309, 614, 648; hermit-crab parasite, =I=, 397; changes of media, =I=, 401, 481–2; retrograde development in cirripedes, =I=, 458; segmentation, =I=, 468–9; =II=, 114; Darwin on jaws and legs, =I=, 471; survival of cirripedes, =I=, 517; integration and homology, =II=, 111–4, 121, 603; bilateral symmetry, =II=, 198–201; eyes, =II=, 318; dermal structure of hermit-crab, =II=, 322, 387; fertility, =II=, 453; nutrition and genesis in parasitic species, =II=, 487; “castration parasitaire,” =II=, 493–6.

Crystalloids: Prof. Graham on, =I=, 15–8; diffusibility, =I=, 18–21; organic, =I=, 21–2, 26.

Crystals: simulation of life in “storm glass,” =I=, 96; growth, =I=, 135–7, 577; segregation, =I=, 179, 221, 223; equilibration, =I=, 337; physiological units and polarity, =I=, 701–6; time and formation, =II=, 77.

Ctenodrilus, segmental individuality, =II=, 103, 603, 604.

Cube, bilateral symmetry, =II=, 132.

Cunningham, J. T., =I=, vi; =II=, vi; on non-adaptive specific characters, =I=, 565; food of blow-fly larvæ, =I=, 678; arthropod segmentation, =II=, 114; egg-production of Conger, =II=, 425.

Cuttle-fish, Individuality of Hectocotylus, =I=, 250.

Cuvier, zoological classification, =I=, 381.

Cyanogen, properties, =I=, 7, 9.

Cyclichthys, dermal structure, =II=, 306.

Dalyell, Sir J., regeneration in Dasychone, =I=, 361; propagation of Hydra, =II=, 476.

Daphnidæ, heterogenesis and nutrition, =I=, 290–1.

Darwin, C: Origin of Species, =I=, 129; =II=, 528; natural selection and function, =I=, 308–9, 693; atavism, =I=, 314; osseous variations in pigeons, =I=, 321; plant variation and domestication, =I=, 325; “spontaneous variation,” =I=, 328, 697; floral fertilization, =I=, 340; =II=, 168, 267, 407, 608; intercrossing and self-fertilization, =I=, 344, 345; intercrossing =I=, 347, 611, 669; his theory of pangenesis examined, =I=, 356–62, 370, 372; plant-fertilization and distribution, =I=, 397; habits of birds, =I=, 400; distribution and natural barriers, =I=, 402, 476; disappearance and non-reappearance of species, =I=, 406; distribution in time and space, =I=, 410; linguistic classification, =I=, 442; classification of organisms, =I=, 443; classification and descent, =I=, 448; on petrels, =I=, 455; suppression of organs, =I=, 457; development of Cirrhipedia, =I=, 438; jaws and legs of Crustacea, =I=, 471; aborted organs, =I=, 474, 563; relations of species in Galapagos archipelago, =I=, 478; opinions of E. Darwin and Lamarck, =I=, 491; the term “survival of the fittest,” =I=, 530; Indirect equilibration by natural selection, =I=, 530–5; inheritance of acquired characters, =I=, 535–42, 560, 630, 685, 690; Wallace on natural selection in man, =I=, 553; misleading connotations of term “natural selection,” =I=, 609, 695; caste gradations and jaws of driver ants, =I=, 658; attachment of climbing plants, =II=, 276–7; vegetal fructification, =II=, 294; earth-worm, =II=, 402; animal sterility and domestication, =II=, 480, 483; variation in hyacinth and camellia, =II=, 621.

Darwin, Dr. E., modifiability of organisms, =I=, 490, 492–7.

Death: an arrest of vital correspondence, =I=, 102; only limit to vegetal growth, =I=, 153; cessation of co-ordination of actions, =I=, 578, 579; Weismann’s hypothesis, =I=, 636–8; physiological integration, =II=, 374, 392; cause of natural, =II=, 413; relation to births, =II=, 417.

Definiteness: of vital change, =I=, 87–90, 106, 109; developmental, =I=, 178; functional, =I=, 212; segregation of evolution, =I=, 514–6.

Definition, difficulties of, =I=, 78; =II=, 17.

Degeneracy, morphological obscurations due to, =II=, 12, 13.

Dendrobium (see Orchids).

Desmidiaceæ: unicellular, =II=, 21; linear and central aggregation, =II=, 23; natural selection and symmetry, =II=, 134, 133; morphological differentiation, =II=, 177; tissue, =II=, 244; genesis, =II=, 440, 449.

Determinants, Weismann’s germ-plasm units (see Germ-plasm).

Development: an increase of structure, =I=, 162; =II=, 461; primarily central, =I=, 162, 166; uni- and multicentral, =I=, 163–4, 166–7; axial, =I=, 164, 167; uni- and multiaxial, =I=, 165–6; a change to coherent definite heterogeneity, =I=, 167–70, 179; Von Baer’s formula, =I=, 171–2; individual differentiation from environment, =I=, 172–8; cell-formation, =I=, 225; discontinuous, and agamogenesis, =I=, 275; Prof. Huxley’s classification, =I=, 276; sociological parallel to autogenous, =I=, 364–8; =II=, 620; retrograde, =I=, 457–8; inequalities among co-operative parts, =I=, 617; “heterochrony,” =I=, 655; continuous and discontinuous vegetal, =II=, 52; summary of physiological, =II=, 384–90; nutrition and genesis, résumé, =II=, 497–9; evolution, =II=, 501–5; commencement of genesis, =II=, 506; of vertebrate limbs, =II=, 553. (See also Multiplication.)

Development Hypothesis, The, =I=, 417.

Dialects (see Language).

Dialysis, and diffusibillty. =I=, 19, 20.

Diastase, decomposition of, =I=, 38, 40.

Diatomaceæ: tissue, =II=, 244; genesis, =II=, 440, 448.

Diatomic compounds (see Chemistry).

Dicotyledons: growth, =I=, 139, 143; =II=, 63–4, 69–72, 78, 82–3; uniaxial development, =I=, 165; stem and leaf functions, =II=, 257; mechanical stress and wood formation, =II=, 277; growth and genesis, =II=, 451.

Differentiation (see Morphology and Physiology).

Difflugia: primary aggregate, =II=, 86–7; symmetry, =II=, 186; outer tissue differentiation, =II=, 309.

Diffusion, of colloids and crystalloids, =I=, 18–20; =II=, 331.

Digestion: action of nitrogenous compounds, =I=, 69; obesity, =II=, 480–4; fertility, =II=, 514.

Dimorphism: floral, =I=, 534; sexual, in parasites, =I=, 315; social insects (see Insects).

Dinosaurs, size of, =I=, 139.

Diphyes: individuality, =I=, 246; symmetry, =II=, 192.

Disease: segregation of blood constituents, =I=, 179; changes in blood from, =I=, 221, 701; heredity, =I=, 306–7, 312–3, 622–3; belief in supernatural origin, =I=, 419; parasitism and special creation, =I=, 427; morbid products as specific characters, =I=, 567; telegony, =I=, 646; dermal structure, =II=, 306; intestinal muscular hypertrophy, =II=, 325; indigestion and alimentary canal development, =II=, 328; jaundice and bilirubin, =II=, 330; localization of excretion, =II=, 331; membranes in inflammatory, =II=, 343; osseous differentiation in rickets, =II=, 352; fatty degeneration, =II=, 482.

Disintegration, physiological (see Physiology).

Distoma: metagenesis, =I=, 273–4; disintegration of genesis, =I=, 276; cycle of generations, =II=, 489.

Distribution: physical limits, =I=, 396; organic environment, =I=, 396–8; parasitic conditions, =I=, 397–8; simultaneity of agencies affecting, =I=, 398; mutual encroachments of species, =I=, 398–401, 477, 489; facts disproving pre-adaptation to habitats, =I=, 401–3, 411–2; of animals and plants in time, =I=, 404–11, 412; ousting of native species in New Zealand, =I=, 477; local influences, =I=, 477–9, 489; through varied media, =I=, 479–85, 489, 556; past and present organic forms, =I=, 485–9, 556; complex organization and, =II=, 296–7.

Division of labour, physiological (see Labour).

Dog: contrasted lives of tortoise and, =I=, 103, 104; inherited habits, =I=, 309, 573; abnormal digits, =I=, 324; interbreeding of divergent varieties, =I=, 565; decrease of jaw, =I=, 615, 693; telegony, =I=, 645; conditions affecting fertility, =II=, 474, 479.

Dohrn, theory of vertebrate structure, =II=, 606.

Doliolum, combination of individualities, =I=, 247.

Domestication (see Animals).

Doubleday, E., on nutrition of genesis, =II=, 510–2.

Driesch, separation of segmentation spheres of Echinus ovum, =I=, 691; =II=, 618.

Dropsy (see Disease).

Drosera: individuality, =I=, 251; proliferous growth, =II=, 75.

Du Bois-Reymond, E. H., electricity from muscles and nerves, =I=, 50.

Dumas, antithesis of animals and plants, =I=, 62.

Dwarfs, Hindu family of, =I=, 316.

Ear, development of vertebrate, =II=, 318, 320.

Earth, climatic rhythm and organic change, =I=, 499–501, 557.

Earth-worm: bilateral symmetry, =II=, 199, 200; mould production, =II=, 402.

Echinococcus (see Entozoa).

Echinodermata: independence of blastosphere cells, =I=, 185; protoplasmic continuity in embryos, =I=, 190; separation of segmentation spheres of ovum, =I=, 691; =II=, 618; symmetry, =II=, 191, 195–6.

Economy: of growth in natural selection, =I=, 536, 562; a trait of organic evolution, =II=, 501, 504.

Ectoderm: functional differentiation, =I=, 202, 203; functional vicariousness, =I=, 209; reproductive function, =I=, 281.

Effects, Multiplication of: variation, =I=, 329–30, 333; organic evolution, =I=, 511–4, 515, 517, 549, 557; =II=, 405–6; morphological development, =II=, 7–9, 234; physiological differentiation, =II=, 390–1, 392.

Eggs (see Embryology).

Eimer, T., theory of orthogenesis, =I=, 563–4.

Elasmobranchii: protoplasmic continuity, =I=, 629; segmentation, =II=, 126.

Electricity: genesis in organic matter, =I=, 50–2, 60; muscular action, =I=, 59; incomprehensibility, =I=, 121.

Elephant: fertility, =I=, 583, 599; =II=, 459, 506; cerebro-spinal system, =I=, 598, 599.

Elk, Irish, horns and correlated parts, =I=, 537, 674.

Eloidea canadensis: individuality, =I=, 248; enormous agamic multiplication, =I=, 642.

Elongation, and locomotion in animals, =II=, 15.

Embryology: as aiding biology, =I=, 125–6; simulated growth, =I=, 136; initial and final organic bulks, =I=, 143, 158, 161; fœtal flesh constituents, =I=, 154; human arm development, =I=, 169; Von Baer’s formula, =I=, 170–2, 451–4, 466; embryonic heat, =I=, 177; spherical organic form, =I=, 177; unit-life in multicellular organisms, =I=, 185–6; functional differentiation, =I=, 203; individuality, =I=, 246–7; unspecialized reproductive tissue, =I=, 279–83, 317; changes following impregnation, =I=, 283–4; nutrition and vegetal growth, =I=, 285–8, 295–7; and animal growth, =I=, 289–94, 295–7; physiological units and heredity, =I=, 317–9; variation and parental functional condition, =I=, 324; uterine environment, =I=, 327–8; physiological units and variation, =I=, 330–4, 458; fertilized and unfertilized ova, =I=, 340–1; hermaphrodism, =I=, 341–2, 344; sociological parallel, =I=, 366–8; evolution hypothesis, =I=, 434, 436, 453, 454, 555; petrel development, =I=, 455; substitution and suppression of organs, =I=, 456–8, 466, 472–3; structural proclivities of physiological units, =I=, 458; abridgment of stages, =I=, 458–9, 464; disappearance of intermediate forms, =I=, 459–60, 463; pre-adaptation, =I=, 461–3; discrimination of species in early stages, =I=, 461; anomalous persistence of ancestral traits, =I=, 463–5; phylogeny, =I=, 486; egg-shell function, =I=, 527; genesis of grades in social insects, =I=, 654–6, 658–9, 679–80; determination of sex, =I=, 657; order of development qualified by needs, =I=, 679; osteology of Punjabis, =I=, 689; direct transformations and physiological units, =I=, 706; transformation of blastema, =II=, 20; arrest of growth and innutrition, =II=, 73; development of segmented animals, =II=, 100–2, 602; adaptive vertebrate segmentation, =II=, 118–23, 124, 223–4, 605–6; animal cell morphology, =II=, 228; primary differentiations of germinal layers, =II=, 300–2; lung development, =II=, 333–4; mammalian ova-maturation, =II=, 342–3; movements of ova, =II=, 356, 363; modifications in mole, =II=, 391; genesis and nutrition, =II=, 424, 425; fish ova, =II=, 435, 454; cost of genesis, =II=, 435–6; number of birds’ eggs, =II=, 454–6, 478; heat and genesis, =II=, 468, 474; activity and genesis in birds, =II=, 470–2, 474; vertebrate limb development, =II=, 553; ossification in vertebrates, =II=, 556; Owen’s vertebrate theory, =II=, 563; development of vertebræ, =II=, 564. (See also Multiplication.)

Embryology of conceptions, =I=, 451.

Emigrants, type of organization among, =I=, 364; =II=, 620.

Endoderm: functional differentiation, =I=, 202, 203; functional vicariousness, =I=, 209.

Endogen, application of term, =II=, 62, 78, 82. (See Monocotyledons.)

Energy: evolution of, in animals, =I=, 71–7; organic growth and expenditure, =I=, 141; functional transfer, =I=, 201–6; chromatin as the source of, in karyokinesis, =II=, 261–5. (See also Force.)

Entozoa: metagenesis, =I=, 273, 641; self-fertilization, =I=, 342; distribution, =I=, 398; and special creation, =I=, 428; fission in simple types, =I=, 584; nutrition and genesis, =I=, 641; =II=, 488; direct transformation, =I=, 706; integration, =II=, 102; segmentation, =II=, 107, 108; interdependence and organic integration, =II=, 404.

Environment: degree of life and complexity of, =I=, 104–7; relation to organic structure and function, =I=, 172–8; =II=, 12–5; adaptation to varied media an evidence of evolution, =I=, 479–81, 556; influence of solar system, =I=, 500, 556; inherited adaptation to, =II=, 623.

Eolis, branchiæ, =II=, 118.

Epidermis (see Skin).

Epilepsy: definition of life and movements in, =I=, 112; heredity, =I=, 312.

Epithelium: ciliated, =I=, 187; Hertwig’s classification, =I=, 189; reproductive function, =I=, 280; “pavement” and “cylinder,” =II=, 229.

Epizoa: distribution, =I=, 398; special creation and effects of, =I=, 428; interdependence and organic integration, =II=, 404; nutrition and genesis, =II=, 487.

Equilibration: variation and law of, =I=, 326, 334; molecular arrangement, =I=, 337–45; of organic change, =I=, 348, 347, 557; direct and indirect, =I=, 519–22, 573; adaptation by direct, =I=, 522–3, 551, 557; nutrition, defence, and fertilization of plants, =I=, 523–5; direct of animals, =I=, 525–8, 551, 557; natural selection and indirect, =I=, 530–4, 552, 557; of natural selection, =I=, 543–7, 552–3, 557; increasing importance of direct, =I=, 553; of forces acting on species, =I=, 571–2; =II=, 417–20; phenomena not accounted for by, =I=, 573; tissue differentiation, =II=, 245; genesis of nervous system, =II=, 307–8; functional, =II=, 391–4; laws of multiplication, =II=, 411–6; in human and social evolution, =II=, 537. (See also Acquired characters and Natural selection.)

Errera, L., on inherited adaptation to environment in Aspergillus, =II=, 623.

Ethnology: heredity, =I=, 303–4, 310; plasticity of mixed races, =I=, 354; primitive ideas, =I=, 417; evolution and classification, =I=, 441–3, 446; natural selection, =I=, 553.

Euphorbiaceæ: foliar and axial development, =II=, 47–8; physiological differentiation, =II=, 258; dye permeability and circulation, =II=, 571; wood formation, =II=, 575, 577, 578; foliar vascular system, =II=, 589–92, 596.

Evaporation: organic change, =I=, 28; vegetal circulation, =II=, 587.

Evolution: chemical elements and compounds, =I=, 22–4, 67; primordial form of living matter, =I=, 63–4, 181; =II=, 21–2; definitions of life, =I=, 107–10; growth the primary trait of, =I=, 135; comprehends growth and development, =I=, 162; illustrations in development, =I=, 167–70, 178–9; progressive structural differentiation, =I=, 181–4, 192–6, 211–2; life before organization, =I=, 210; heterogeneity of function, =I=, 211; stability of species, =I=, 242, 515, 518; individuality, =I=, 247; cell-organization, =I=, 262; genesis, heredity, and variation resulting from, =I=, 354–5; period required for organic, =I=, 407, 565–6; contrasted with special creation hypothesis, =I=, 415, 431–40; derivation of hypothesis, =I=, 431, 439, 554; increasing belief in, =I=, 431–3, 439; experiences supporting conceivability, =I=, 433–5, 439; direct evidence, =I=, 435–7, 439; malevolence not implied by, =I=, 437–9; evidence from classification, =I=, 443, 444, 449, 466, 555; embryology, =I=, 451–3, 466; substitution and suppression of organs, =I=, 456–8, 466, 472–3; insect segmentation, =I=, 468–9; vertebral column development, =I=, 470–2; rudimentary organs, =I=, 472–5; adaptation to varied media, =I=, 479–85, 556; growth of the theory of organic, =I=, 490–8; instability of the homogeneous, a cause, =I=, 509–11, 516, 550; multiplication of effects, =I=, 511–14, 517–8, 550; =II=, 405; segregation, and heterogeneity and definiteness of, =I=, 514–8, 550; natural selection and general doctrine of, =I=, 543–8, 557; factors tabulated, =I=, 551; inductive evidences summarized, =I=, 555–6; surviving disbelief in France, =I=, 559; current theories of organic, =I=, 559–74; Eimer’s theory of orthogenesis, =I=, 563–4; Gulick on monotypic and polytypic, =I=, 569; phenomena unexplained by theories, =I=, 573–4; inorganic and the System of Philosophy, =I=, 696; “spontaneous generation,” =I=, 696–701, 702; dissolution and problems of morphology, =II=, 4–6; morphology and formula, =II=, 7–9, 231–5; difficulties of definition, =II=, 17; cell-doctrine, =II=, 17–21, 85; unicellular origin of plants, =II=, 21–2; résumé of plant-morphology, =II=, 78–80; origin and differentiation of phænogamic type, =II=, 83; physiological problems, =II=, 239–43; tissue differentiation, =II=, 244–6, 385; integration of organic world, =II=, 396, 406; race and individual multiplication, =II=, 428–30; declining fertility and human, =II=, 431, 529–30; individuation, genesis, and, =II=, 501–5; human life, prospective, =II=, 522–5; forces influencing human, =II=, 525–8; future of population, =II=, 532–7; self-sufficingness of, =II=, 537; vertebral, =II=, 563–6.

Excretion: genesis of organs of, =II=, 303; localization of, =II=, 331–3.

Exogen, application of term, =II=, 82. (See Dicotyledons.)

Expenditure (see Multiplication).

Eye, the: molecular transformations in visual process, =I=, 75–6; progressive development, =I=, 195; =II=, 317–9; waste and repair, =I=, 218; transmitted defects, =I=, 306, 311, 694; degeneration in cave-animals, =I=, 309, 612–3, 614, 647–9, 693; late development in insects, =I=, 658; migration in flat fishes, =II=, 205.

Fabre, J. H., nutrition and sex in Osmia tricornis, =I=, 657.

False joints, =I=, 230; theories of heredity and, =I=, 362, 364; =II=, 371–2.

Fats, the: physical and chemical properties, =I=, 10–12; non-nitrogenous, =I=, 41; action of bile, =II=, 330.

Fatty degeneration, and failing vitality, =I=, 41.

Feathers, development, =I=, 474; =II=, 314–6.

Feet, heredity and size, =I=, 311.

Ferments, changes and nitrogenous character of, =I=, 38.

Ferns: foliar development and nutrition, =II=, 76; inner tissue differentiation, =II=, 273; indefiniteness, =II=, 296; genesis, =II=, 441, 463.

Fertility, the General Law of Animal, =I=, 577–601. (See Multiplication.)

Fertilization: unit-life of generative elements, =I=, 185–6; the function of chromatin, =I=, 260, 263–5; extrusion of polar bodies, =I=, 266–8; nature and functions of generative elements, =I=, 279–83, 317, 334, 342, 593–7; differentiation and variation effected by, =I=, 330–2; the essential object of, =I=, 340–1; =II=, 614–6; hermaphrodism and self-, =I=, 341–2; crossing and its effects, =I=, 343–7; isolation of species in respect of, =I=, 570; floral (see Flowers).

Ficus, foliar structure, =II=, 589, 596.

Fingers: embryogeny of human, =I=, 169; heredity and abnormal, =I=, 305, 314, 321–3; autogenous development of supernumerary, =I=, 363; rudimentary, =I=, 473.

Fishes: sizes of ova and adult, =I=, 143–4; growth of pike, =I=, 154, 292; size and environment, =I=, 156; temperature, =I=, 174; self-mobility, =I=, 175; continuity of blastomeres, =I=, 214; =II=, 327; genesis, =I=, 271; =II=, 435, 436; conditions affecting genesis, =I=, 292–3, 583, 598, 599; =II=, 454; classification, =I=, 392; change of media, =I=, 401, 480; distribution in time, =I=, 408–9; climbing species, =I=, 480, 482; migrations, =I=, 500; dermal structure, =I=, 526; =II=, 305–6, 315, 387; Cunningham on non-adaptive specific characters, =I=, 565; elongation and locomotion, =II=, 15; segmentation, =II=, 122, 225; bilateral symmetry, =II=, 203–5; eyes of Pleuronectidæ, =II=, 205; genesis of vertebrate axis, =II=, 212–6, 218–21, 225; ossification of paleozoic, =II=, 218; respiratory organs, =II=, 334–8; activity and muscular colour, =II=, 365–9; Owen on skeleton, =II=, 552, 557, 558–60, 562, 564.

Fission (see Agamogenesis).

Flint, Austin, on telegony, =I=, 644.

Flounder, symmetry and eyes, =II=, 205.

Flower, Sir W., on ferret, =II=, 480.

Flowers: pollen propulsion in orchids, =I=, 57; nature of reproductive elements, =I=, 283; insect fertilization, =I=, 340, 525; =II=, 168, 174, 267, 407; self- and mutual fertilization, =I=, 342–5, 570; Darwin on homologies, =I=, 472; direct equilibration and fertilization, =I=, 524–5; dimorphism, =I=, 534; foliar homology of petals, =II=, 43–6; symmetry, =II=, 132, 161, 162–4, 170, 174, 608; fertilization and symmetry, =II=, 164–70; clusters and components, =II=, 170–4; nutrition and inflorescence, =II=, 179–80, 541–2, 546–7; tissue differentiation, =II=, 265–9; separation of ancestral traits in hybrids, =II=, 616–7.

Fly, beneficial parasitism, =II=, 406.

Food (see Nutrition).

Food-cavity, genesis and development of, =I=, 188, 195.

Foraminifera: form, =I=, 173; primary aggregate, =II=, 87, 124; progressing integration, =II=, 89–90, 124.

Force: action on like and unlike units, =I=, 5; expenditure and organic growth, =I=, 149–54, 161; functional accumulation, transfer, and expenditure, =I=, 198–9, 201–3, 391; waste and expenditure, =I=, 214–5; distribution during strain, =II=, 209–12. (See also Energy, and Persistence of Force.)

Fossils (see Palæontology).

Foster, Sir M., on storage of glycogen, =I=, 70, 74; Increase of weight in hybernating dormouse, =I=, 214.

Fowls (see Gallinaceæ).

Foxglove: abnormal development, =I=, 287; =II=, 46; floral distribution, =II=, 141; nutrition and growth, =II=, 179.

France: surviving disbelief in organic evolution, =I=, 559; rate of multiplication, =II=, 509, 512.

Frankland, Sir E., on isomerism of protein, =I=, 700.

Fraser, Col. A. T., on family of Hindu dwarfs, =I=, 316.

Fries, E., multiplication of Reticularia, =I=, 582; =II=, 450.

Frog: vitality of detached heart, =I=, 111; of larval fragments, =I=, 365.

Fry, Sir E., on alternation of generations, =II=, 84.

Fuci: cell multiplication, =II=, 27; undifferentiated outer tissue, =II=, 256.

Function: as a basis of classification, =I=, 124–9, 129–31; simultaneous progress of structure and, =I=, 197, 211; divisions of, =I=, 198–200, 391; correlative complexity of structure, =I=, 200, 210–1; progressive differentiations, =I=, 201–4; concomitant integration, =I=, 205–8; specialization and vicariousness, =I=, 208–10; formula of evolution, =I=, 211; diminished ability and overwork, =I=, 215–6; growth and increased, =I=, 228–33, 234–5; interdependence of social and organic, =I=, 237–9, 240–2; structure and heredity, =I=, 306–13, 318–9 (see Acquired Characters); aids natural selection, =I=, 308; organic interdependence, =I=, 318–9; parental condition and variation, =I=, 324, 326; variation and altered, =I=, 325–6, 333–4; as causing variation, =I=, 334–5; effect on physiological units, =I=, 353–4; =II=, 620; zoological classification, =I=, 391–3; multiplication of effects, =I=, 512; law of equilibration, =I=, 519–22, 557; correlation of changes in, =I=, 529; structural effects of changing, =I=, 541–2; structural co-operation, =II=, 3, 217; vicarious vegetal, =II=, 270; vicariousness and specialization, =II=, 293; epidermic structure, =II=, 312–4, 387; structure and muscular, =II=, 369, 391; adaptive bone-structures, =II=, 370–1; equilibration and adaptation, =II=, 392; persistence of force and adaptation, =II=, 394. (See also Physiology.)

Fungi: nitrogenous character, =I=, 40; development, =I=, 163, 164, 165; conjugation, =I=, 279; =II=, 449; fission, =I=, 584, 585; integration, =II=, 24–5, 293; symmetry, =II=, 137–40, 146; puff-ball tissue, =II=, 246, 252, 386; tissue differentiation, =II=, 256; inner tissue, =II=, 279; indefiniteness, =II=, 295; growth and genesis, =II=, 459; nutrition and genesis, =II=, 487.

Gallinaceæ: conditions affecting fertility, =II=, 454–5, 469, 471; masculine traits of old hens, =II=, 495.

Galls: definition of life and, =I=, 111; Hertwig on, =I=, 690.

Galton, F., on variation outside the mean, =I=, 669.

Gamogenesis: homogenesis, =I=, 270, 271, 336; heterogenesis, =I=, 270, 336; independence of offspring, =I=, 278; reproductive tissue, =I=, 279–84; vegetal nutrition, =I=, 285–8, 293; =II=, 39; animal nutrition, =I=, 289–94, 297; when and why does it recur? =I=, 294–7, 336–40; effect on species, =I=, 347–9; leaf formation, =II=, 39; alternating generation in liverworts, =II=, 80–4; molluscan homogenesis, =II=, 116, 117–8; vertebrate, =II=, 118; growth, =II=, 266. (See also Fertilization, and Multiplication.)

Gasteropoda (see Mollusca).

Geddes and Thompson, on the determination of sex, =I=, 657.

Gelatine, nutritive value of, =I=, 77.

Gemmation: and genesis, =I=, 272–6; theories of heredity and, =I=, 361; annulose, =II=, 100–5, 106.

Generalization, impossibility of perfect, =I=, 450.

Generation, and genesis: the words, =I=, 269.

Genesis (see Multiplication).

Gentiana: floral arrangement, =II=, 608–11.

Genus: indefinite value, =I=, 389, 446; instability of homogeneous and heterogeneity of, =I=, 509–11, 515, 517–8, 550, 557.

Geology: growth displayed in, =I=, 135, 136; distribution in time, =I=, 404–11, 412; special creation, =I=, 419, 426; evolution, =I=, 432, 437; record congruous with evolution, =I=, 485–9, 556; organic influence of changes, =I=, 501–3, 549, 550, 557; climatic influence of changes, =I=, 503; time required for organic evolution, =I=, 565–6; rise of insect and plant relations, =II=, 407; human evolution and changes, =II=, 534.

Geometry, evolution illustrated by, =I=, 433–4.

Germ-cell: unspecialized nature, =I=, 279–83, 317; dissimilarity, =I=, 330, 332, 334, 342; equilibrium, =I=, 340. (See also Fertilization.)

Germ-plasm, Weismann’s theory of, =I=, 357–8; inconsistent with plant embryogeny, =I=, 359; regeneration of lost limbs, =I=, 362; variations in peacock’s tail feather, =I=, 372, 695; =II=, 618–9; alleged differentiation of reproductive and somatic cells, =I=, 622, 628–30, 633–44, 646; origin of variations in neuter insects, =I=, 659, 663–5, 671, 675; correlated variations in stag, =I=, 677; insuperable difficulties, =I=, 682; conceivability of hypothesis, =I=, 695; =II=, 619; correlated variations in cultivated plants, =II=, 621–2.

Ghost-theory, Vitalism and, =I=, 114.

Giraffe, co-adaptation of structures, =I=, 615.

Gizzard, development of birds, =II=, 320.

Glass, molecular re-arrangement, =I=, 337, 352, 704.

Glove, strain analogy, =II=, 575.

Glycogen, In animal metabolism, =I=, 70, 72.

Goethe, J. W. von: foliar homology, =II=, 43–4, 543, 544; archetypal hypothesis, =II=, 122; vegetal fructification and nutrition, =II=, 180; theory of supernumerary bones, =II=, 223; on the skull, =II=, 561.

Gold, effect of bismuth on, =I=, 121.

Gorilla, callosities, =II=, 312.

Gould, J., Birds of Australia, =II=, 469.

Gout (see Disease).

Grafting, Born’s experiments with frog larvæ, =I=, 365.

Graham, T., properties of water, =I=, 9; =II=, 359; colloids and crystalloids, =I=, 15–8; =II=, 356; their diffusibility, =I=, 18–20; sapid and insipid substances, =I=, 53.

Graminæ: foliar surfaces, =II=, 61, 263; floral symmetry, =II=, 165; physiological differentiation, =II=, 257.

Graminivores, food contrasted with that of carnivores, =I=, 68.

Grassi, on food habits of Termites, =I=, 686.

Gravity: its ultimate incomprehensibility, =I=, 121; vegetal circulation, =II=, 586. (See also Specific Gravity.)

Gregarina: central development, =I=, 163; primary aggregate, =II=, 87; symmetry, =II=, 186.

Grimaux, on artificial proteids, =I=, 39.

Growth: organic and inorganic, =I=, 135–7; simulation of, =I=, 136; limits to, =I=, 137, 155–7; structural complexity, =I=, 138–40, 145–7, 161; nutrition, =I=, 140, 147–9, 161; expenditure of energy, =I=, 141–3, 161; initial and final bulks, =I=, 143–4, 157–60, 161; final arrest of, =I=, 149–55, 639; where unceasing, =I=, 154; résumé with generalizations, =I=, 161; defined, =I=, 162; =II=, 461; increased function, =I=, 228–33, 234–5; functional interdependence, =I=, 235–9, 240; nutrition and vegetal, =I=, 293, 294–7, 336; =II=, 39; heterogenesis and animal nutrition, =I=, 289–93, 296, 336; homo- and heterogenesis and natural selection, =I=, 294–8; of acrogens, =II=, 56; cylindrical form of vegetal, =II=, 56–64; endogenous, =II=, 60–2, 78; exogenous, =II=, 63–4, 78; plant differentiation, =II=, 129–131; tissue differentiation, =II=, 370; formation of adaptive bone-structures, =II=, 370–2; progressive increase of size with evolution, =II=, 401–2; vegetal, and asexual genesis, =II=, 439–42; animal, and asexual genesis, =II=, 442–5; antagonistic to asexual genesis, =II=, 446; vegetal and sexual genesis, =II=, 448–51; animal and sexual genesis, =II=, 452–6, 495; antagonistic to sexual genesis, =II=, 457–8; nutrition and genesis, résumé, =II=, 497–9; evolution and, =II=, 501–5; commencement of genesis, =II=, 506; fertilization and restoration of growth-energy, =II=, 613.

Gulick, T.: on monotypic and polytypic evolution, =I=, 569; physiological selection, =I=, 569–71.

Gunpowder, nitrogenous instability, =I=, 8, 43.

Gymnotus, electricity of, =I=, 51.

Gyrodactylus elegans, rapid succession of generations, =I=, 641; =II=, 488.

Habit, change of, in plants, =I=, 308.

Hæmal, term applied to female element, =I=, 594–5.

Hairs: non-conductors of heat, =I=, 526; vegetal, and natural selection, =I=, 532; development, =II=, 314–6; tactual organs, =II=, 317.

Hand: embryogeny, =I=, 169; heredity and size of, =I=, 311; distribution of veins, =I=, 364.

Hardy, W. B., =I=, vii; =II=, vi.

Hare: activity and muscular colour, =II=, 365; expenditure and genesis, =II=, 472.

Hart, J. A., on “Parasol” ants, =I=, 687–8.

Havilland, G. D., collection of Termites, =I=, 687.

Haystack, chemical action in, =I=, 74.

Head, structural influence of size, =I=, 512, 537.

Hearing: the sense of, =I=, 54; multiplying agencies, =I=, 75.

Heart (see Vascular System).

Heat: action on di- and tri-atomic compounds, =I=, 7–8, 10–12, 23, 24; on colloids and crystalloids, =I=, 26; organic changes from evaporation, =I=, 29; chemical decomposition by, =I=, 33; organic oxidation, =I=, 46–9, 60; growth and organic, =I=, 152–3; animal, vegetal, and environment, =I=, 174–5, 177; alloy melting points, =I=, 339; organic effects of rhythm in terrestrial, =I=, 498, 557; effect on physiological units, =I=, 705; respiration in fishes, =II=, 337; animal preservation, =II=, 434; vertebrate expenditure and genesis, =II=, 468–9, 474; insect genesis, =II=, 476; seasonal variations and genesis, =II=, 484–5; in germination, =II=, 615.

Hebrew idea of creation, =I=, 421.

Hectocotylus, individuality, =I=, 250.

Hellin, D., on multiparity and twin-births, =II=, 457.

Hen, what prompts her to pick up egg-shell fragments? =I=, 120.

Henslow, Rev. G., inheritance of functionally-produced changes, =I=, 560.

Hepaticæ: Schleiden on, =II=, 51, 52; continuous and discontinuous development, =II=, 52; phyletic homologies, =II=, 80–4; meaning of so-called alternating generation, =II=, 84; vascular system, =II=, 280; genesis and development, =II=, 463.

Heredity: structural modification, =I=, 232; function of cell-nucleus in, =I=, 258–59; general truths, =I=, 301–4; transmission of congenital peculiarities, =I=, 304–7; structure and altered function, =I=, 307–13, 318–9 (see also Acquired Characters); atavism, or recurrence of ancestral traits, =I=, 314; sex limitation, =I=, 314–6; physiological units, résumé, =I=, 350–5; =II=, 612–6; Darwin’s and Weismann’s theories examined, =I=, 356 et seq., 559–61; =II=, 622; true theory must include plants, =I=, 358; inadequacy of theory of physiological units, =I=, 360–1; sociological parallel, =I=, 366–8; natural selection (q. v.), =I=, 545–7, 553, 557; ethnology and natural selection, =I=, 553; unsolved problems, =I=, 573–4; mutilations, =I=, 631; ultimate process incomprehensible, =I=, 695; cell-doctrine, =II=, 19; physiological development, =II=, 242; wood formation, =II=, 287; tissue differentiation, =II=, 304, 312–4; respiratory system, =II=, 311; osseous differentiation, =II=, 351; muscular adaptation, =II=, 367; persistence of force and physiological adaptation, =II=, 394; vegetal vascular system, =II=, 574, 582, 588, 596.

Hermaphrodism, =I=, 340–3.

Hertwig, O.: on Weismann’s germ-plasm theory, =I=, 690; cell characters, =I=, 691; meaning of fertilization, =II=, 613.

Hertwig, R., classification of tissues, =I=, 189.

Heterochrony of development, =I=, 655.

Heterogeneity: in chemical evolution, =I=, 23–4; of vital changes, =I=, 84–90; of development, =I=, 170, 178; functional, =I=, 204–8, 211–2; of organic matter, =I=, 350–5; organic and instability of homogeneous, =I=, 509–11, 517, 549, 557; segregation accompanying, =I=, 514–6, 517–8, 550.

Heterogenesis: occurrence, =I=, 270, 272–5, 336; animal nutrition, =I=, 289–91, 295–7; natural selection, =I=, 295–8; heredity, =I=, 301.

Hindus: food, =I=, 68; dwarf family, =I=, 316.

Histology (see Physiology).

Hofmeister, sporophytic generation of Archegoniates, =II=, 80.

Hollyhock, floral symmetry, =II=, 167, 169, 170.

Homogeneous, instability of the: variation, =I=, 330, 334, 342; evolution, =I=, 509–11, 517, 549, 557; morphological development, =II=, 7–9, 234; direction of vegetal growth, =II=, 181; radial symmetry, =II=, 190; physiological differentiation, =II=, 384, 392.

Homogenesis (see Gamogenesis).

Homology, simulation of, by analogy, =II=, 14.

Hooker, Sir J. D., =I=, ix; European plants in New Zealand, =I=, 477; plant distribution, =I=, 479; adaptation of plants to varied media, =I=, 484; plant growth, =II=, 56; Balanophoræ and Raffiesiaceæ, =II=, 274; structural complexity, =II=, 295, 297; relative antiquity and distribution of plants and animals, =II=, 297; bean vascular system, =II=, 574.

Hooker, Sir W., on fructification in Jungermanniaceæ, =II=, 52.

Horns, natural selection and correlated variation, =I=, 537, 567, 674, 677.

Horse: ancestral types, =I=, 409; fertility, =I=, 598; weight of brain, =I=, 599; quagga markings, =I=, 624, 627.

Husbandry, co-ordination of actions in, =I=, 96, 579.

Hutchinson, Sir J., hereditary syphilis, =I=, 623.

Huxley, T. H., =I=, ix; “continuous” and “discontinuous” development, =I=, 164; classification of development, =I=, 276; hermaphrodism, =I=, 344; zoological classification, =I=, 383; on “Persistent Types,” =I=, 408–9; ancestral equine types, ib.; segmentation of articulates, =I=, 468–9; =II=, 113; agamic multiplication of Aphis and Entozoa, =I=, 640–1; =II=, 476; cell-doctrine, =II=, 21; vertebrate embryo, =II=, 119, 120; molluscan symmetry, =II=, 202; tegumentary organs, =II=, 314, 315; vertebrate sensory organs, =II=, 318, 319; Chondracanthus, =II=, 487; Owen’s vertebrate theory, =II=, 563.

Hyacinth: lateral spike, =II=, 42; symmetry, =II=, 141, 162.

Hybernation, waste and repair in, =I=, 214–5.

Hybrids, separation of ancestral traits in, =II=, 616–7.

Hydro-carbons: properties, =I=, 6–9; the term carbo-hydrates (q. v.), =I=, 10.

Hydrochloric acid, in gastric juice, =I=, 69.

Hydrogen: chemical and physical properties, =I=, 3–5; compounds, =I=, 6, 8, 9, 10–12, 12–13.

Hydrozoa (see Cœlenterata).

Hymenoptera (see Insects).

Hypertrophy (see Disease).

Hypospadias, telegonic transmission, =I=, 646.

Hypostasis of a relation, exemplified in explanations of fertilization, =II=, 613.

Ideas (see Psychology).

Individuality: the botanical, =I=, 244–6; the zoological, =I=, 246–7; the fertilized germ product, =I=, 248–9; definition of life, =I=, 250.

Individuation: and genesis, =I=, 583–4; =II=, 428–30, 499; total cost, =II=, 435–7; genesis and evolution, =II=, 501–5, 529, 530.

Infusoria: functional specialization, =I=, 391; primary aggregate, =II=, 87; asymmetry, =II=, 187, 188; differentiation, =II=, 299, 385; genesis, =II=, 442, 446, 452.

Injuries, repair of animal, =I=, 219, 222–4, 316; =II=, 102, 611.

Insanity, inherited, =I=, 314.

Insects: temperature, =I=, 47, 174; phosphorescence, =I=, 49; self-mobility, =I=, 175; parthenogenesis, =I=, 274–5, 277, 294, 592, 640; growth and reproduction, =I=, 292; species distribution determined by presence of, =I=, 396–7; eyes of cave-inhabiting, =I=, 309, 612–3, 614, 647–9, 693; persistent types, =I=, 408; retrograde development, =I=, 458; segmentation, =I=, 468–9; =II=, 114; aborted organs, =I=, 474; East Indian distribution, =I=, 478; floral fertilization, =I=, 525; =II=, 168–9, 406–7, 608; appliances for cleaning antennæ, =I=, 651; eyes, =I=, 658; =II=, 318; integration and homology, =II=, 111–3, 121; bilateral symmetry, =II=, 198; sexual selection, =II=, 269; eyes, =II=, 318; environment, =II=, 433; cost of genesis, =II=, 436, 437; development and genesis, =II=, 461; nutrition and genesis, =II=, 476, 490–2.

Insects, Social, origin of caste gradations in, =I=, 654–65, 670, 674, 675, 678–84, 686–8.

Instability of the homogeneous (see Homogeneous).

Instinct: organic evolution and co-ordination of, in mason-wasp, =I=, 574; a vital attribute, =I=, 578; loss of self-feeding, in Amazon ants, =I=, 660–1, 663–4.

Integration: in chemical evolution, =I=, 23; morphological composition, =II=, 4–6; arthropod, =II=, 111–4, 121; physiological, in plants, =II=, 292–5, 295–8, 390; of organic world, =II=, 396–408; genesis, =II=, 424, 426–9.

Intelligence, a vital attribute, =I=, 579.

Internodes: varied development, =II=, 45; nutrition and length, =II=, 178–9.

Intestine (see Alimentary Canal).

Intra-selection, Roux’s theory of, =I=, 562, 676–8.

Irish, nutrition and genesis, =II=, 510.

Iron: colloidal form of peroxide, =I=, 17, 20; molecular re-arrangement, =I=, 337, 704; vegetal absorption, =II=, 573.

Iron industry, interdependence of social function, =I=, 237–41.

Isolation, and species differentiation, =I=, 568–9.

Isomerism: of organic constituents, =I=, 4, 9, 25; tri- and poly-atomic compounds, =I=, 11, 13, 25; muscular action, =I=, 59; organic evolution, =I=, 700, 703; differentiation of nerve tissue, =II=, 356–60, 361; of muscular tissue, =II=, 361–4.

Jackson, J. Hughlings, on inheritance of nervous peculiarities, =I=, 313, 694.

Jaundice (see Disease).

Jaws, of uncivilized and civilized, =I=, 541–2, 612, 693.

Johnson, G. Lindsey, on inherited myopia, =I=, 694.

Jones, T. Rymer, on fission, =I=, 585, 590.

Julin, C., on “castration parasitaire” in Crustaceans, =II=, 493–6.

Jungermanniaceæ: morphology, =II=, 33–4; relations of high and low types, =II=, 35, 55; continuous and discontinuous development, =II=, 52–5, 92; tubular structure, =II=, 58, 62; proliferous growth, =II=, 67, 91; colour, =II=, 75, 265; symmetry, =II=, 140; fertility and growth, =II=, 441.

Jussieu, A. de, plant classification, =I=, 378.

Karyokinesis, =I=, 257, 259, 263–5.

Kerner, A., on cauline buds, =I=, 358; plant classification in Natural History of Plants, =I=, 378–9.

Kidd, Benj., his acceptance of Weismannism, =I=, 690.

Kitto, Dr., his visual memory and deafness, =I=, 230.

Klebs, on Hydrodictyon, =I=, 288; Vaucheria, =II=, 84.

Klein, E., multiplication of Bacteria, =II=, 443.

Korschelt, E., annulose segmentation, =II=, 103, 601–3, 605; Arenicola larvæ, =II=, 109.

Labour, physiological division of, =I=, 204, 207, 591; =II=, 373; its meaning and Weismann’s fallacious interpretation, =I=, 634–5.

Lacaze-Duthiers, on origin of annulose type, =II=, 110.

Lamarck: zoological classification, =I=, 382; opinions of E. Darwin and, =I=, 491, 493–7; neo-Darwinists and, =I=, 630–1.

Laminariaceæ: pseudo-foliar and axial development, =II=, 30; tissue, =II=, 247, 256, 272.

Language: and evolution, =I=, 442, 444, 446; perceptiveness of tongue-tip, =I=, 607.

Lankester, Sir E. Ray, absence of nucleus in Archerina, =I=, 183; diversity of Protozoa, ib.; zoological classification, =I=, 387; blindness of cave-animals, =I=, 647–8, 649.

Laugh, definition of life and, =I=, 112.

Laurel, leaves of, =II=, 149, 249.

Leaves: growth of shoot, =I=, 168; development and aggregation, =II=, 37–42, 76; stem-like stalks, =II=, 41; homologies, =II=, 42, 75–7, 83; nutrition and compound, =II=, 42; foliar and axial development, =II=, 46–50, 541–7; “adnate,” =II=, 58; proliferous growth, =II=, 67, 91; nutrition and development, =II=, 76–8; symmetry, and of branches, =II=, 148–50, 151; size and distribution of leaflets, =II=, 152–5; transition from compound to simple, =II=, 155–8; unsymmetrical form, =II=, 158–9; natural selection and distribution, =II=, 179; morphological summary, =II=, 234–5; tissue differentiation, =II=, 247; distribution, =II=, 249; outer tissues of stem and, =II=, 256–9, 270, 386; distribution of stomata, =II=, 260–1; wax deposit on, =II=, 260, 261; light and colour, =II=, 261–2; superficial differentiation, =II=, 263–5, 270, 387; abortive in parasitic plants, =II=, 274; submerged, in aquatic plants, =II=, 274–5; inner tissue differentiation, =II=, 278, 388; vascular tissue differentiation, =II=, 286, 288, 388; dye absorption and circulation, =II=, 570–4, 577; vascular system, =II=, 588–92, 596; arrangement, =II=, 608–11.

Lepidoptera (see Insects).

Lepidosiren: ossification, =II=, 218; respiration, =II=, 338; skeleton, =II=, 553, 555, 560.

Lepidosteus: armour, =I=, 526; air-bladder, =II=, 334.

Leroy-Beaulieu, Pierre, on Australian miners’ usages, =I=, 364.

Lessonia: Hooker on growth, =II=, 56; branch symmetry, =II=, 146.

Lewes, G. H., definition of life, =I=, 80.

Lichens: tissue, =I=, 586; cell multiplication, =II=, 27; Hooker on growth, =II=, 56; tubular structure, =II=, 57; integration, =II=, 293; dual nature, =II=, 399; reproduction, =II=, 450.

Liebig, Baron, nitrogenous food stuffs, =I=, 47–8.

Life: co-ordination of actions, =I=, 79, 89, 577–80; defined by Schelling, =I=, 78, 178; Richeraud, =I=, 79; De Blainville, =I=, 79, 93; Lewes, =I=, 80; definition yielded by contrasting most unlike kinds, =I=, 81–8; changes showing, =I=, 91; vital actions and environment, =I=, 92–3; resulting addition to conception, =I=, 93, 326; Comte’s definition, =I=, 93; correspondence of external and internal relations, =I=, 93–6, 100; =II=, 523; continuous adjustment of such relations, =I=, 99; completeness proportionate to correspondence, =I=, 101–4, 109, 349; length and complexity, =I=, 103; complexity of environment and degree of, =I=, 104–6; definitions of evolution and, =I=, 107–10; deficiencies of formula, =I=, 112–3; activity the essential element, =I=, 113; hypothesis of independent vital principle examined, =I=, 114–7; difficulties of physico-chemical theory, =I=, 117–20; ultimate incomprehensibility, =I=, 120–3, 373; validity of conclusions reached, =I=, 123; is organization produced by? =I=, 197; precedes organization, =I=, 210; definitions of individuality and, =I=, 250; effect of incident forces on, =I=, 348–9, 355; length in individuals and species, =I=, 422; equilibration of, =I=, 547, 557; final formulation of definition, =I=, 580; co-ordination of actions and sexual differentiation, =I=, 593; “absolute” commencement of, =I=, 699, 702; integration and augmentation, =II=, 426; prospective human, =II=, 522–5.

Light: influence on organisms, =I=, 30–6; =II=, 433; nitrogenous plants, =I=, 40; organic phosphorescence, =I=, 49; heliotropism, =I=, 92; =II=, 160; effects on organic matter, =I=, 149; plant adaptation, =I=, 227; rhythmical variation of, and organic life, =I=, 499, 557; vegetal influences, =II=, 130, 131, 147, 149, 158; influence on flowers, =II=, 167–8, 608–11; vegetal tissue differentiation, =II=, 253–5, 258, 259; action on leaves, =II=, 260–4; on plant vascular system, =II=, 288, 297, 586; development of sensory organs, =II=, 320.

Liliaceæ, floral symmetry, =II=, 170.

Lime, leaf forms, =II=, 158, 159.

Lindley, J., plant classification, =I=, 377.

Linnæus, C., classificatory system, =I=, 377, 380.

Linnet, contrasted with blackbird in development, =II=, 503.

Liver: metabolic processes, =I=, 69, 70; vitality of excised, =I=, 111; development, =II=, 329–33.

Liver-fluke (see Distoma).

Liverworts (see Hepaticæ).

Lizard, regeneration of lost tail, =I=, 360.

Locomotion (see Motion).

Logic, reasoning and definition of life, =I=, 81–6.

Logwood, vegetal staining, =II=, 569–74, 577–81, 584.

Longevity, and complexity of life, =I=, 102–3.

Lubbock, Sir J.: on growth and genesis in insects and crustaceans, =I=, 292; aquatic flies, =I=, 400.

Lungs (see Respiratory System).

Lymphatic system: amœboid cells, =I=, 187; structural traits, =I=, 192, 193.

MacBride, E. W., =I=, vi; =II=, vi; zoological phyla, =I=, 386–7; arthropod segmentation, =II=, 114; ctenidia of slug, =II=, 117; conjugation of Paramæcium, =II=, 452.

Macrocystis pyrifera, gigantic seaweed, =I=, 121.

Magenta, vegetal staining, =II=, 569–74, 577–81, 584.

Magnetism: muscular action, =I=, 59; incomprehensibility, =I=, 121.

Maillet, B. de, modifiability of organisms, =I=, 490, 496.

Mammalia: temperature and molecular change, =I=, 30; nutrition and growth, =I=, 141; expenditure of force, =I=, 142, 156; flesh constituents, =I=, 154; temperature, =I=, 174, 177; self-mobility, =I=, 175; functional and structural differentiation, =I=, 201; heart-function, =I=, 206; viviparous homogenesis, =I=, 271; variation and uterine environment, =I=, 327; classification, =I=, 392; cervical vertebræ, =I=, 394; =II=, 564; aquatic types, =I=, 400; fossil remains and rate of evolution, =I=, 407; ancient and modern forms contrasted, =I=, 408–10; embryonic respiratory system, =I=, 456; suppression of teeth, =I=, 457; arrested development, =I=, 473–4; simulated homologies, =I=, 485; natural selection and inactive parts, =I=, 534; re-development of rudimentary organs, =I=, 563; location of testes and current theories, =I=, 573; fertility and development, =I=, 583; =II=, 465; fertility and nervous development, =I=, 598–9; locomotion and elongated form, =II=, 15; symmetry, =II=, 204; tegumentary structure, =II=, 314; circulation, =II=, 340; vascularity and ova-maturation, =II=, 342–3; activity and muscular colour, =II=, 365–9; functional integration, =II=, 375; outer tissue differentiation, =II=, 387; growth and genesis, =II=, 456, 459; comparative fertility, =II=, 465, 470; heat expenditure and genesis, =II=, 467–9; activity and fertility, =II=, 472; nutrition and genesis, =II=, 479–80.

Man: effect of climate on vigour, =I=, 30; flesh and grain eaters compared, =I=, 68; longevity and life, =I=, 103; complex environment, =I=, 105; embryogeny of arm, =I=, 169; fertility and conditions affecting it, =I=, 300, 570, 583; =II=, 484, 506–21; inheritance of functionally-produced changes, =I=, 310–3, 541, 605, 608, 612, 652, 673, 689, 693–4; heredity and sex, =I=, 315–6; function of bilirubin, =I=, 330; cousin-marriages, =I=, 346; =II=, 615; primitive notions, =I=, 417–9; inutility of Appendix vermiformis, =I=, 474; diminution of jaw, =I=, 541, 612, 693; co-ordination of actions greatest in, =I=, 579; fundamental traits of sex, =I=, 594–7; obesity, =I=, 594; substance and weight of brain, =I=, 596, 599; distribution of tactual perceptiveness, =I=, 602–8, 665–6, 672–3, 692; telegony, =I=, 625, 644–5; degradation of little toe, =I=, 652, 673; transmitted osteological peculiarities of Punjabis, =I=, 689; traits of twin-bearing women, =II=, 457; comparative mammalian fertility, =II=, 465; future evolution, =II=, 522–37. (See also Language and Sociology.)

Manatee, nailless paddles, =I=, 473.

Manx cats, =I=, 303.

Marchantiaceæ: symmetry, =II=, 140; outer tissue differentiation, =II=, 252.

Marmot, hybernation and waste, =I=, 214–5.

Marriage (see Multiplication).

Marsh, O. C., on telegony, =I=, 644.

Masters, M. T., on foliar homology, =II=, 46–7; selection of inconspicuous variations in plants, =II=, 298, 621; separation of ancestral constitutions in plant hybrids, =II=, 616; single and double stocks, =II=, 622.

Matter, incomprehensibility of interactions, =I=, 121–2.

Mechanics: transverse strains, =II=, 209–12; genesis of vertebrate axis, =II=, 212–6, 216–8, 224, 225–7; osseous differentiation, =II=, 345–51; disintegrated motion, =II=, 375; analogy from locomotive, =II=, 517–9; future human evolution, =II=, 524; strain and vegetal structure, =II=, 574–88, 592–6.

Medusæ: contractile functions, =I=, 58; =II=, 374; individuality, =I=, 248; heterogenesis, =I=, 273; fertility, =I=, 582; strobilization, =I=, 592; symmetry, =II=, 188–91.

Mehnert, E., on feet of pentadactyle vertebrates, =I=, 461.

Mensel’s salt, temperature and isomerism, =I=, 77.

Metabolism: antithesis between plants and animals, =I=, 62–3; evolution hypothesis and primordial, =I=, 63–4; in plants, =I=, 64–7; animals, =I=, 67–77; nervo-muscular activities, =I=, 71–7; summary, =I=, 77; cell processes, =I=, 261.

Metals: remarkable interactions of some, =I=, 121; melting of alloys, =I=, 339; atomic re-arrangement, =I=, 352.

Metamerism (see Segmentation).

Metazoa: cellular structure, =I=, 184, 194; =II=, 21; subordination of units, =I=, 185–7; general characters of tissues, =I=, 188–9; protoplasmic continuity, =I=, 190–2, 194, 628; genesis of food-cavity and visual organ, =I=, 195; Weismann’s differentiation theory, =I=, 637–43.

Meteorology: non-vital changes shown in, =I=, 82, 84; crystallization of “storm glass,” =I=, 96; special creation, =I=, 419; rhythm in, and organic change, =I=, 499–501, 557; variations due to geologic change, =I=, 503.

Microstomida, segmental reproduction, =II=, 102.

Migration: of animal species, =I=, 396–401, 411; solar influences, =I=, 500; part played by, in organic evolution, =I=, 568; causes of, =II=, 533–4.

Milk, heat and supply of, =II=, 468.

Milne-Edwards, H., “physiological division of labour,” =I=, 204; Weismann’s erroneous application of it, =I=, 634; on ocular structure, =II=, 318.

Mind (see Psychology).

Mitosis (see Karyokinesis).

Mobility, molar and molecular, =I=, 14; environment and self-mobility, =I=, 177.

Mohl, on phænogamic growth, =II=, 82.

Mole, modifications due to habits, =II=, 391.

Molecules: mechanically considered, =I=, 14; stability, =I=, 337–40; nerve differentiation, =II=, 355–61, 379–82.

Mollusca: axial development, =I=, 165; genesis, =I=, 271; =II=, 444; hermaphrodism, =I=, 341; classificatory traits, =I=, 392; distribution in time, =I=, 405, 408, 410, 446–7; trochophore and its relationships, =I=, 447; =II=, 108, 109, 115; development, =I=, 460; amphibious and terrestrial, =I=, 481; indirect equilibration, =I=, 534; secondary aggregation, =II=, 115–7; symmetry, =II=, 201–3; outer tissue, =II=, 310, 387; alimentary system, =II=, 325; vascular system, =II=, 340–1.

Molluscoida, =II=, 598. (See Polyzoa and Tunicata.)

Monocotyledons: growth, =I=, 138, 139, 143; uniaxial development, =I=, 165; cotyledonous germination and endogenous growth, =II=, 59–62, 69–72, 82–3, 181–2; absence of helical phyllotaxy in Ravenala, =II=, 182; surface contrasts, =II=, 257; outer leaf tissue, =II=, 263; wood formation, =II=, 278; growth and genesis, =II=, 451.

Monstrosities, in plants, =II=, 78, 541, 546; vertebrate, =II=, 118.

Morgan, T. H., on regeneration of Planaria, =II=, 102, 611.

Morphology: facts comprised in, =I=, 125–6; morphological units, =I=, 190–2, 225; rudimentary organs, =I=, 472–5, 556; structural and functional co-operation, =II=, 3, 239; integration, =II=, 4–6, 181–96; change of shape, =II=, 6; formula of evolution, =II=, 7–9; as interpreted by phylogeny, =II=, 10–6; evolution and cell-doctrine, =II=, 17–21.

Morphology, Animal: evolution and segmentation of Articulata, =I=, 468–9; vertebral column development, =I=, 470; simulated homologies, =II=, 14–5; primary aggregates, =II=, 85–8, 123–4; secondary, =II=, 88–91, 124; tertiary, =II=, 91–3; integration and independence of individuality, =II=, 93–9, 124; annulose segmentation, =II=, 98–101, 106–10, 125–7, 602–7; progressive annulose integration, =II=, 100–5, 111–5, 121, 124, 223; unintegrated molluscan form, =II=, 115–7; vertebrate segmentation and integration, =II=, 117–23, 124–7, 223–4, 602, 606–7; motion and symmetry, =II=, 183–5; symmetry of primary and secondary aggregates, =II=, 186, 187–91; of compound Cœlenterata, =II=, 192–4; simulation of plant shapes, =II=, 192; symmetry of Polyzoa and Tunicata, =II=, 194; of Platyhelminthes and Echinoderms, =II=, 195–7; of Annulosa, =II=, 197–201; of molluscs, =II=, 201–3; of vertebrates, =II=, 203–6, 208; similarity of animal and plant, =II=, 206; cell-shapes, =II=, 228–30; evolution and generalizations summarized, =II=, 231–5. (See also Structure.)

Morphology, Vegetal: simulated homologies, =II=, 13–4; unicellular plants, =II=, 21; aggregation and integration, =II=, 22–6, 78–9; pseudo-foliar development, =II=, 26–8; pseudo-axial, =II=, 28–9; pseudo-foliar and axial, =II=, 30–2; composition of Archegoniates, =II=, 33–5; leaf development and aggregation, =II=, 37–42, 75–8; foliar homologies, =II=, 42–6, 75–8; foliar and axial development, =II=, 46–50, 541–7; growth and development of Archegoniates, =II=, 50–6; of Phænogams, =II=, 56–64, 78–80; axillary bud development, =II=, 65–9; phænogamic modes of growth, =II=, 69–72; homologies, =II=, 73–5, 80–4; development of foliar into axial organs, =II=, 75–8; résumé, =II=, 78–80; criticisms and replies, =II=, 80–4; can plant shapes be formulated? =II=, 128; growth and differentiation, =II=, 129–31; kinds of symmetry, =II=, 131–3; symmetry of primary aggregates, =II=, 134–7; of secondary, =II=, 137–40; tertiary, =II=, 140–3; symmetry and environing influences, =II=, 143–4; symmetry of branches, =II=, 145–8; leaf and branch symmetry, =II=, 148–50; phænogamic unit homology, =II=, 151; size and distribution of leaflets, =II=, 152–5; transition from compound to simple leaves, =II=, 155–8; unsymmetrical leaf development, =II=, 158–9; differentiation of homologous units, =II=, 159–60; floral symmetry, =II=, 161–74; cell-differentiation and metamorphosis, =II=, 175–7; nutrition and differentiation, =II=, 178; and inflorescence, =II=, 179; helical growth of phænogams, =II=, 180–1; summary of symmetry, =II=, 234; stress and structure, =II=, 275–9, 388. (See also Structure.)

Morton, Lord, quagga-marked foal, =I=, 624.

Moser, impressions produced by light on metals, =I=, 352.

Mosses: varied development, =II=, 501, 52; homologies, =II=, 80, 81; indefiniteness, =II=, 296; multiplication, =II=, 441.

Moth, clothes, food of larva, =I=, 77.

Motion: organic, and environment, =I=, 75–7, 175–8, 196; of animals and waste, =I=, 214, 220; simulation of locomotive structures, =II=, 15.

Motor organs, differentiation of, =I=, 262.

Mountains: climatic effects, =I=, 504; growth of trees on, =II=, 142.

Mouse: fertility of, =II=, 421, 473; tapeworm parasitism, =II=, 490; compared with rat, =II=, 503–4.

Mucor, =II=, 22, 123.

Mucous membrane, differentiation, =II=, 321–2, 389.

Multiplication: decline of fertility with evolution, =I=, 103; =II=, 431; vitalism, =I=, 116; phenomena classified, =I=, 130; the term “genesis,” =I=, 269; processes classified, =I=, 270–6, 336, 583; a process of disintegration, =I=, 276; reproductive tissue in gamogenesis, =I=, 278–84; nutrition and growth, =I=, 285–94, 295–7, 299; natural selection, =I=, 295–8; hermaphrodism, =I=, 340–4; in-and-in breeding, =I=, 344–7; physiological units, =I=, 350–5; law of race-maintenance, =I=, 581; =II=, 420–3, 430; effect of mental application, =I=, 597; =II=, 511–4, 516–9, 530; individuation antagonistic to, =I=, 598–600; =II=, 428–30, 435–7, 499, 501–5; checks put by carnivores on, =II=, 405; four factors in rate of, =II=, 416, 435; destructive and preservative forces, =II=, 417–20; rhythm of species, =II=, 419; nutrition and disintegration of, =II=, 424, 425, 430; integration and genesis, =II=, 426–8; influence of environment, =II=, 432–3; and variations of expenditure, =II=, 433–5; growth and asexual genesis, =II=, 439–46; asexual and sexual distinguished, =II=, 448; sexual genesis and growth, =II=, 448–58, 495; and development, =II=, 461–5; plant expenditure, =II=, 467; animal expenditure, =II=, 468–72; nutrition in plants, =II=, 475, 511; in animals, =II=, 476–84, 511; seasonal variations, =II=, 484–5; nutrition, résumé, =II=, 486, 497–9; nutrition and parasitic, =II=, 486–90; reversion to agamogenesis, =II=, 490–2; human fertility, =II=, 506–10; Doubleday on, =II=, 510–2; civilized and uncivilized, =II=, 514–6; human evolution and decline in, =II=, 529–31; the future of population, =II=, 532–7; equilibration and evolution, =II=, 537.

Muscle: electrical contrasts, =I=, 50; action of, =I=, 59; metabolism, =I=, 70, 71–4; definition of life and actions of, =I=, 112–3; growth and function, =I=, 151, 155; development, =I=, 170; Hertwig’s classification of tissues, =I=, 189; functional differentiation, =I=, 203–4; waste and repair, =I=, 215–7; modifiability and adaptability, =I=, 228–9, 230, 232; correlated variations, =I=, 536–9, 614–21, 676, 693; resistance to strains, =I=, 639; action on bones in Punjabis, =I=, 689; differentiation, =II=, 361–9; activity and colour, =II=, 365–9; integration, =II=, 376, 382; equilibration in action, =II=, 393; activity and fertility in birds, =II=, 470–2; future human evolution, =II=, 523; origin of vertebrate type, =II=, 598–600.

Music: limited adaptability of voice and ear, =I=, 231; inheritance of faculty, =I=, 311–2, 694.

Mutilations, the question of their inheritance, =I=, 631.

Mycetozoa, growth and reproduction, =I=, 298–9.

Myocommata (myotomes), and vertebrate skeleton, =II=, 216, 217–8, 222.

Myopia, inheritance of, =I=, 306, 694.

Myrianida fasciata, =I=, 361; =II=, 445.

Myriapoda: gemmation, =I=, 589; segmentation, =I=, 590; =II=, 113, 114, 601; degenerated eyes of cave-inhabiting, =I=, 649; integration and homology, =II=, 111–4; genesis, =II=, 445.

Myxothallophyta, =I=, 378.

Nails, mammalian, =I=, 473.

Nais: regeneration of detached parts, =I=, 219, 361.

Narcissus, separation of ancestral traits in hybrids, =II=, 617.

Natural selection: structural modification, =I=, 211; in cell processes, =I=, 263–4; multiplication, =I=, 295–8; aided by function, =I=, 308–10; special creation, =I=, 426–7; the term “survival of the fittest,” =I=, 530; indirect equilibration, =I=, 530–5, 552–3, 557, 571; changes unexplained by, =I=, 535–42, 571; =II=, 371; tendency to economy, =I=, 536, 562; decrease of jaw, =I=, 541, 693; general doctrine of evolution, =I=, 543–8, 557; unceasing operation, =I=, 552; human races, =I=, 553; current views, =I=, 559–60; panmixia and cessation of selection, =I=, 560–3; intra-selection, =I=, 562, 676–8; Eimer’s theory of orthogenesis, =I=, 564; Mr. Cunningham’s criticism, =I=, 565–6; location of mammalian testes, =I=, 573; co-ordinated instincts of mason-wasp, =I=, 574; tactual perceptiveness, =I=, 603–8, 633, 646, 665, 671, 672, 692; erroneously identified with artificial selection, =I=, 609, 695; reversed selection, =I=, 611; blindness of cave-animals, =I=, 613, 614, 647–8, 693; co-adaptation of co-operative parts, =I=, 614, 621, 663–5, 670, 674, 675, 689, 692; where operative, =I=, 632; Weismann on conceivability of process, =I=, 651; degeneration of little toe, =I=, 652–3, 673; genesis of caste gradations In social insects, =I=, 654–60, 663, 670, 675, 684; self-feeding instinct in ants, =I=, 660–2, 670; rudimentary organs, =I=, 667–9, 671, 692; horns of stag, =I=, 676–8, 692; musical faculty, =I=, 694; the neo-Darwinian position reviewed, =I=, 694–5; vegetal nutrition, =II=, 51–2; upright vegetal growth, =II=, 56–7; endogenous growth, =II=, 57–8; exogenous, =II=, 64; Navicula symmetry, =II=, 135; foliar, =II=, 158; foliar distribution, =II=, 167, 179; floral fertilization and symmetry, =II=, 168–70, 608–11; helical phænogamic growth, =II=, 181; Echinodermata and bilateral symmetry, =II=, 197; vertebrate structure, =II=, 214–20, 227; phænogamic tissue differentiation, =II=, 248; physiological differentiation, =II=, 252, 256; rootlets of ivy, =II=, 254; stomata and foliar surfaces, =II=, 261, 262; floral fertilization, =II=, 268–9; sexual selection, =II=, 269; vegetal tissue differentiation, =II=, 279; wood formation, =II=, 287–8, 290; animal tissue differentiation, =II=, 304–8; evolution of nervous system, =II=, 307–8; respiratory system, =II=, 311; dermal callosities, =II=, 312–4; sensory organ complexities, =II=, 321; skin and mucous membrane differentiation, =II=, 322; localization of excretion, =II=, 333; respiratory organs of fishes, =II=, 335–8; heart and vascular system, =II=, 341, 344; osseous differentiation, =II=, 355; also muscular, =II=, 363, 368–9; “false joints,” =II=, 371; insect nutrition and genesis, =II=, 499; economics of evolution, =II=, 501–5; author’s enunciation of survival of the fittest in 1852, =II=, 528–9; evils of interference with, in man, =II=, 532–3; vegetal tissue formation, =II=, 582, 594–6; origin of vertebrate type, =II=, 599.

Nature, more complex than supposed, =I=, 252, 450.

Navicula, symmetry, =II=, 134–5.

“Nebular Hypothesis,” =I=, 23.

Negation, inconceivability of, the ultimate test of truth, =I=, 675.

Negroes, telegony In United States, =I=, 644–5.

Nemertidæ: continuing vitality of pilidium, =I=, 250; bilateral symmetry, =II=, 195.

Neo-Darwinists, and Lamarck, =I=, 630; their position reviewed, =I=, 694–5.

Nerves: electrical phenomena, =I=, 51; generation of nerve force, =I=, 52–6, 60; corpuscula tactus, =I=, 75; Hertwig’s classification of tissues, =I=, 189; structural traits, =I=, 192, 193; environment and structure, =I=, 196; differentiation, =I=, 203; =II=, 355–61; vasomotor system, =I=, 206; vicarious function, =I=, 209; activity and waste, =I=, 216; adaptability, =I=, 229, 232, 236; parallelism in cell processes, =I=, 260–2; heredity, =I=, 313; effects of severance, =I=, 349; relative development in men and women, =I=, 594; analysis of brain substance, =I=, 596; individuation and development of, =I=, 598, 599, 600; distribution of tactual perceptiveness, =I=, 603–8, 633, 646, 665–6, 671, 672, 692; alleged costliness of tissue, =I=, 662; instinct degeneration in ants, ib.; “sensation areas,” =I=, 666; segmentation in Annelids, =II=, 125; ectodermal derivation, =II=, 303–4; co-operating factors in evolution of, =II=, 307–8; differentiation from muscle, =II=, 363. (See also Psychology.)

Nervousness, hereditary transmission, =I=, 307.

Neurine, =I=, 594, 597.

Neuter insects (see Insects).

New Zealand: invasion of alien species, =I=, 477; kinship of past and present forms, =I=, 489.

Nitrogen: properties, =I=, 3–5, 20, 24; compounds and their properties, =I=, 6, 8, 9, 12–14, 25–6, 39, 41, 42–3; =II=, 250; organic importance, =I=, 42–3; evolution of heat and oxidation, =I=, 47; violent organic effects of compounds, =I=, 54–5; function in metabolism, =I=, 63–4, 66, 68–76; presence in protoplasm, =I=, 66; action in digestion, =I=, 69; fat accumulation and fertility, =II=, 483.

Nitro-glycerine, violent effects of, =I=, 55, 122.

Notochord: segmentation, =II=, 125, 218–22; formation, =II=, 217–8, 600; in Permian vertebrates, =II=, 225.

Noumenon, life not manifested as, =I=, 580.

Nuclein, =II=, 21.

Nucleus: central development, =I=, 163; in simple organisms, =I=, 183; phenomena exhibited by, =I=, 255–8; current hypotheses of function, =I=, 258–9; properties and function of chromatin, =I=, 259–65; fusion in fertilization, =I=, 283–4; function in unicellular reproduction, =I=, 595–6; absence of, =II=, 20–1; diffused form, =II=, 85; macro- and micronucleus in conjugation, =II=, 452.

Nutrition: organic molecular re-arrangement, =I=, 36; nitrogenous and non-nitrogenous, =I=, 47–8, 68, 71–4, 77; =II=, 362; food assimilation and reasoning, =I=, 81; needful for vital change, =I=, 94; relation to growth, =I=, 140, 143, 144, 147–9, 150, 157, 161; expenditure of energy, =I=, 157, 391; fluid, =I=, 208; vegetal fructification, =I=, 267; =II=, 266; vegetal growth and genesis, =I=, 293, 294–7, 336; animal growth and genesis, =I=, 289–93, 295–7, 336; conditions qualifying antagonism of growth and genesis, =I=, 299; competition among parts of an organism for, =I=, 562, 566, 676; sex differentiation, =I=, 594–5; cell multiplication, =I=, 638; differentiation of neuter insects, =I=, 655–60, 670, 674, 686–8; monstrous ant forms, =I=, 683–4; leaf development, =II=, 39, 42, 73–8; vegetal development, =II=, 51–2, 178, 276; axillary buds, =II=, 65–9, 73–4; effect on animal aggregation, =II=, 93; internodes and inflorescence, =II=, 178–80; helical phænogamic growth, =II=, 181; action of bile, =II=, 330; osseous development, =II=, 349, 353; genesis, =II=, 419, 422, 427, 435–7, 452; parental loss in feeding young, =II=, 424, 429; diverse sources, =II=, 433; Carpenter on reproduction and, =II=, 460; animal development and genesis, =II=, 465; expenditure and genesis, =II=, 468; variations of genesis, =II=, 475–80, 511; obesity and genesis, =II=, 480–4, 511; general doctrine of genesis, =II=, 486; genesis and vegetal parasitism, =II=, 486; also animal, =II=, 487–90, 495; insect genesis, =II=, 490–2; genesis, résumé, =II=, 497–9; and evolution, =II=, 501–4; of blackbird and linnet, =II=, 503; genesis in human race, =II=, 508–10, 514–6; Doubleday on, =II=, 510–2; future human evolution, =II=, 526, 531; floral monstrosities, =II=, 542, 546, 547.

Obesity, nutrition and genesis, =II=, 480–4, 511.

Odoriferous glands, natural selection and, =I=, 534.

Odours: floral fertilization, =II=, 268–9; animal protection, =II=, 434.

Offspring: parental loss entailed by nurture, =II=, 424, 429; influence of age on, =II=, 507.

Oken, L., archetypal hypothesis, =II=, 122; theory of supernumerary bones, =II=, 223; on the skull, =II=, 561.

Oliver, F. W., classification of plants, =I=, 378–9.

Ophryotrocha puerilis, ciliation of segments, =II=, 109.

Orchids: pollen propulsion, =I=, 57; leaf formation in Dendrobium, =II=, 60–1; aërial roots and physiological differentiation, =II=, 255, 257; foliar surface, =II=, 264.

Organic matter: properties of elements, =I=, 3–5, 22; of compounds, =I=, 5–13, 25; molar and molecular mobility, =I=, 12–14; colloid and crystalloid form, =I=, 15–8, 25; their diffusibility, =I=, 18–21, 26; extreme complexity, =I=, 21; laws of evolution and genesis of, =I=, 22–4; modifiability, =I=, 27, 44; capillarity and osmosis, =I=, 28; effects of heat, =I=, 29; of light, =I=, 30–4; nitrogenous, =I=, 39–43; oxidation and evolution of heat, =I=, 46, 60; genesis of electricity, =I=, 50–2, 60; sensible motions in, =I=, 59; transformations and persistence of force, =I=, 61; metabolism, =I=, 62–77; artificial production of compounds, =I=, 64; contrasted with inorganic matter, =I=, 107–8; incomprehensibility of vital changes in, =I=, 122; instability, =I=, 149, 508; phosphorus in cell-organization, =I=, 260–1; heterogeneity, =I=, 350–5; “spontaneous generation” and evolution of, =I=, 696–701; cell-doctrine and evolution of, =II=, 17–21.

Organization (see Structure).

Ormerod, Dr., on sex and nutrition in wasps, =I=, 656.

Orthogenesis, Eimer’s theory of, =I=, 563–4.

Osmosis: organic effects, =I=, 28, 29; in animals, =I=, 58; in vascular system, =II=, 339; in vegetal tissue, =II=, 568, 575, 577, 585, 592–6.

Osteology (see Bone).

Ovum (see Egg and Fertilization).

Owen, Sir R.: metagenesis and parthenogenesis, =I=, 273–4; fossil mammals, =I=, 410; human parasites, =I=, 427; continuous operation of creative power, =I=, 492; fission in Infusoria, =I=, 584, 585, 595–6; parthenogenesis, =I=, 592; theory of vertebrate skeleton, =II=, 123, 548–66; theory of supernumerary bones, =II=, 223; Eschricht on Ascaris, =II=, 488.

Oxalis: radial symmetry, =II=, 152; foliar surface, =II=, 264.

Oxen: comparison with sheep, =I=, 158, 160; cerebro-spinal system, =I=, 508.

Oxidation (see Oxygen).

Oxygen: properties, =I=, 3–5, 20, 22; compounds, =I=, 6–7, 10–13, 22, 24–5; a crystalloid, =I=, 21; combining power and atomic weight, =I=, 33; organic change from, =I=, 37; heat generation, =I=, 46–9; phosphorescence, =I=, 49; nerve force dependent on, =I=, 53; animal metabolism, =I=, 72, 73; necessary to animal life, =I=, 94–5, 577; activity and amount inhaled, =I=, 214.

Packard, A. S., on eyes of cave-animals, =I=, 648–9, 693.

Paget, Sir J., blood changes in small-pox and scarlatina, =I=, 221, 701.

Palæontology: distribution in time, =I=, 404–11, 412; special creation, =I=, 425; congruity with evolution hypothesis, =I=, 485–9, 556; relations of present to extinct species, =II=, 10–11; scarcity of remains, =II=, 34–5; secondary thickening in plants, =II=, 56; Cope on osteology of Permian Vertebrates, =II=, 225–6.

Pangenesis, Darwin’s theory of, =I=, 356, 357, 359, 360, 362, 372.

Panmixia, Weismann’s hypothesis of: Its relation to Romanes’ “cessation of selection,” =I=, 560; alleged selective process denied, =I=, 561–3, 667, 685; distribution of tactual perceptiveness, =I=, 608; rudimentary eyes of cave fauna, =I=, 612–3, 647; Romanes on process, =I=, 649, 667; degeneration of self-feeding instinct In Amazon ants, =I=, 660–2, 670; rudimentary limbs of whale, =I=, 668–9, 685; a pure speculation, =I=, 671; markings on leg-bones of Punjabis, =I=, 689.

Paramœcium: parasite infesting, =I=, 427; reproduction, =II=, 443, 452.

Parasites: sexual dimorphism, =I=, 315; limits to distribution, =I=, 397; special creation and, =I=, 427–9, 438; retrograde development, =I=, 457; =II=, 12; aphis and ant, =I=, 660–1; =II=, 403, 405; as an integrating agency, =II=, 402–4; its comparative recency, =II=, 404; nutrition and genesis in vegetal, =II=, 486; in animal, =II=, 487–90, 493; “castration parasitaire” in crustaceans, =II=, 493–6.

Parasol Ants, origin of classes, =I=, 687–8.

Parthenogenesis: occurrence, =I=, 274–5; alternating with gamogenesis, =I=, 289–91; Owen on, =I=, 592; laws of multiplication, =II=, 415; in articulate animals, =II=, 445.

Pasteur, L., silkworm diseases, =I=, 622–3.

Peacock: theories of heredity and structure of tail feather, =I=, 372–3, 695; =II=, 618–9.

Pear, foreright shoots, =I=, 287.

Peloria: in gloxinia, =II=, 166; phænogams, =II=, 180.

Penguin, dermal structure, =II=, 314.

Pepsin, =I=, 69.

Pericyclic fibres of monocotyledons, =II=, 278.

Peripatus capensis, protoplasmic continuity, =I=, 629.

Peri-visceral sac, function and differentiation, =I=, 391.

Perkin, W. H., =I=, vi.

Persistence of force, corollaries from: properties of compounds, =I=, 3; organic transformation, =I=, 60; growth, =I=, 150; organic energy, =I=, 220; variation, =I=, 335; genesis, heredity, and variation, =I=, 354–5; morphological summary, =II=, 235; vegetal tissue differentiation, =II=, 245; physiological development, =II=, 394.

Petals: foliar homology, =II=, 43–6; “adnate,” =II=, 58.

Petrels, Darwin on, =I=, 455.

Phænogams: production of spermatozoids, =I=, 186; morphological composition, =II=, 37–79; leaf transitions, =II=, 37–42; foliar homologies, =II=, 42–9; origin of type, =II=, 49–84; vertical growth, =II=, 56–64; axillary buds, =II=, 66; cotyledonous germination and endogenous growth, =II=, 69–72; axial homologies, =II=, 73–5; irregular development, =II=, 75–8; degree of composition, =II=, 78; reproductive homology, =II=, 80–4; uni- and multiaxial symmetry, =II=, 141–3; unit of composition, =II=, 151; helical growth, =II=, 181; secondary thickening, =II=, 247; tissue and leaf differentiation, =II=, 247–9, 387; also bark and cambium, =II=, 249–50, 386; also outer tissue, =II=, 252, 256–9, 270, 386–7; wax deposit on leaves, =II=, 260–2; differentiation of inner tissues, =II=, 273–5, 388; vascular system development, =II=, 280–4, 388; integration, =II=, 293–5, 296, 390; insect fertilization, =II=, 407; multiplication, =II=, 441, 442; genesis and growth, =II=, 451, 457; and development, =II=, 464; and nutrition, =II=, 476, 477, 511; substitution of axial for foliar organs, =II=, 541–7.

Phenomenon, life manifested as, =I=, 580.

Philology (see Language).

Phoronis, individuality, =II=, 444.

Phosphorescence, organic, =I=, 49.

Phosphorus: allotropic, =I=, 4; in cell physiology, =I=, 259–62; cerebral activity, =I=, 596–7; organic evolution, =I=, 703.

Photogenes, visibility of, =I=, 218.

Phylogeny: as interpreting morphology, =II=, 10–12; difficulties of affiliation, =II=, 34–5. (See Embryology and Evolution.)

Physiological Units: definition, =I=, 226; genesis, =I=, 280–1, 316; heredity, =I=, 315–9; variation, =I=, 330, 331–2, 333; =II=, 619; stability, =I=, 340; =II=, 614; self-fertilization, =I=, 342–4, 353; interbreeding, =I=, 345, 353; =II=, 615; recapitulation of hypothesis, =I=, 350–5; =II=, 612–7; structural proclivities, =I=, 362, 364, 369–71; =II=, 613, 622; sociological analogy, =I=, 364; =II=, 620; complexity in organized types, =I=, 368–70; re-named “constitutional units,” =I=, 369; telegony, =I=, 650; “mechanical theory,” =I=, 701–6; morphological development, =II=, 7–9; cell-doctrine, =II=, 17–21; development, =II=, 76; “false joints,” =II=, 371–2; dissociation of ancestral traits in hybrids, =II=, 616–7; inheritance of acquired characters, =II=, 618–23.

Physiological division of labour (see Labour).

Physiological Selection, =I=, 569–71.

Physiology: and psychology, =I=, 127; subdivisions, =I=, 128; vicarious function, =I=, 208; primitive interpretations, =I=, 417; multiplication of effects exemplified, =I=, 512; =II=, 390; relations to morphology, =II=, 3, 239–41; evolutionary interpretation of phenomena, =II=, 241–5, 384–95; ultimate inconceivability of processes, =II=, 372; correlated integration and differentiation, =II=, 373.

Physiology, Animal: metabolism, =I=, 67–77; vertebrate internal symmetry, =II=, 108; tissue differentiation in Protozoa, =II=, 299, 385; primary tissue differentiation, =II=, 300–2, 382, 389; natural selection and tissue differentiation, =II=, 304–8; outer tissue in Cœlenterata, =II=, 309–10; respiratory organs, =II=, 310–1, 333–8; differentiation of animal epidermic tissue, =II=, 312–4, 387; development of tegumentary organs, =II=, 314–6; of sensory, =II=, 317–20; inner and outer tissue transition, =II=, 321–2, 389; alimentary canal differentiation, =II=, 323–5; gizzard development in birds, =II=, 325; alimentary canal of ruminants, =II=, 327–9; differentiation of liver, =II=, 329–33; of animal vascular system, =II=, 339–44; of osseous system, =II=, 344–55; of nerve tissue, =II=, 355–61; of muscle, =II=, 361–9; differentiation and integration, =II=, 373–6; in vascular system, =II=, 376–9, 383; in nerves, =II=, 379–82; origin of development, =II=, 384; differentiation and instability of homogeneous, =II=, 384–9, 392; summary of development, =II=, 384–94; multiplication of effects, =II=, 390–1, 392; equilibration, =II=, 391–4. (See also Function.)

Physiology, Plant: metabolism, =I=, 62–7; tissue differentiation in secondary aggregates, =II=, 246, 385; in phænogams, =II=, 247–9, 386; in bark and cambium, =II=, 249–50, 386; in free and fixed surfaces, =II=, 251–6, 270, 386; outer stem and leaf tissue, =II=, 256–9, 270, 386; superficial differentiation in leaves, =II=, 260–4, 270, 387; floral tissue differentiation, =II=, 265–9; outer tissue, résumé, =II=, 270; inner tissue differentiation, =II=, 273–5, 388; supporting tissue, =II=, 275–9, 285–8, 388; vascular system development, =II=, 273–5, 279–84, 285–8, 388; inner tissue, summary, =II=, 288–91, 388; integration, =II=, 292–8; differentiation and instability of homogeneous, =II=, 384–9, 392; multiplication of effects, =II=, 390–1, 392; equilibration, =II=, 391–4; circulation and wood formation, =II=, 564–97; dye permeability, =II=, 569–74, 577–81, 584, 586. (See also Function.)

Pickering, J. W., on artificial proteids, =I=, 39.

Pig: colour of muscles, =I=, 365–6; telegony, =I=, 627; fertility of domestic and wild sow, =II=, 479–80.

Pigeons: food of starving, =I=, 215; heredity and variation, =I=, 305, 321, 615; atavism, =I=, 314; fertility, =II=, 471–2, 478.

Pike, unceasing growth, =I=, 154, 292.

Pique-gouffe, commensal relations with buffalo, =II=, 403.

Plagiochila, evolution of stem, =II=, 62.

Planaria: integration, =II=, 101–2; Morgan on regeneration, =II=, 102, 611; segmentation, =II=, 107; symmetry, =II=, 195; unintegrated function, =II=, 373.

Plants: influence of heat, =I=, 29; effect of solar rays, =I=, 31–6, 500, 557; chemical composition, =I=, 40–1; heat generation, =I=, 47; phosphorescence, =I=, 49; electricity, =I=, 51; sensible motion, =I=, 56–7, 58; metabolism, =I=, 62–7, 70; vital changes, =I=, 86, 87, 91, 94; simulation by crystals, =I=, 96; vital adjustments, =I=, 102; length and complexity of life, =I=, 103–4; biological classification, =I=, 125; growth, =I=, 136, 138, 140, 143, 145–9, 153, 160–1; =II=, 401–2; development, =I=, 163–5, 167–70, 272; weight, temperature, and self-mobility, =I=, 174; function, =I=, 174–8; structure, =I=, 194–6; =II=, 21; animal structure contrasted, =I=, 196; function and structure, =I=, 200; vicarious function, =I=, 208–9; waste and repair, =I=, 213, 220; physiological units, =I=, 225–6, 317, 360; adaptation, =I=, 227; what is an individual? =I=, 244–6, 250–1; genesis, =I=, 270, 271, 272–3, 274, 276–8, 279–85; relation of nutrition to growth and genesis, =I=, 284–9, 294, 295–300, 642; =II=, 39; ovule homologues, =I=, 288; natural selection, =I=, 294–8, 532, 533; =II=, 51; heredity, =I=, 301–4, 308, 358–60; variation, =I=, 320, 323–4, 325–6; fertilization, =I=, 340–5; classification, =I=, 377–80, 389–90; distribution, =I=, 396–400, 401–3, 404–12, 478–9, 556; special creation and parasitism, =I=, 428; evolution hypothesis, =I=, 434, 443, 449–50; rudimentary organs, =I=, 474, 475, 556; varied media, =I=, 484; =II=, 32; alien and native species in New Zealand, =I=, 477; E. Darwin and Lamarck on evolution of, =I=, 490–8; geologic changes affecting, =I=, 501–3, 557; interdependence of animals and, =I=, 504–6, 514; =II=, 398; complexity of influences affecting, =I=, 506; direct equilibration, =I=, 523–5; indirect, =I=, 532, 533; seed distribution, =I=, 546; wood development, =II=, 285–7, 289, 567–97; interdependence, =II=, 402–3, 404; insect relations, =II=, 406–7; adaptation and multiplication, =II=, 411–6; rhythm in numbers, =II=, 419; growth and asexual genesis, =II=, 439–42; growth and sexual genesis, =II=, 448–51; expenditure, =II=, 467; horticulture, nutrition, and genesis, =II=, 477; tree development, =II=, 553; circulation and wood formation, =II=, 567–92; dye permeability and circulation, =II=, 569–74, 577–81, 584, 586; résumé on circulation and wood formation, =II=, 592–7. (See also Multiplication, Morphology, and Physiology.)

Plasmodium, dissolution of, =I=, 185.

Plato, ἰδέα of, =II=, 550.

Platyhelminthes: transverse fission, =II=, 101; segmented and non-segmented types, =II=, 102, 107; symmetry, =II=, 195, 197; multiplication and growth, =II=, 488–9.

Plethora, fertility and, =II=, 480–4, 511.

Pleurococcaceæ, unicellular form, =II=, 21, 134.

Pleuronectidæ: symmetry and location of eyes, =II=, 205; outer tissue, =II=, 387.

Plumatella: metagenesis, =I=, 277; symmetry, =II=, 195.

Podostemaceæ, undeveloped circulatory system, =II=, 274.

Polar bodies, hypothesis concerning extrusion of, =I=, 266–8.

Polarity, organic, of physiological units, =I=, 226, 315, 317, 332, 350–1, 701–6.

Polyatomic compounds (see Chemistry).

Polychætæ, anomalous development in Myrianida, =I=, 361.

Polycytharia, integration, =II=, 90, 124.

Polygastrica, aggregation, =I=, 586.

Polymerism: of compounds, =I=, 9, 11, 25; nerve tissue, =II=, 356.

Polypori, symmetry and environment, =II=, 139.

Polyps (see Cœlenterata).

Polyzoa: size, =I=, 140; multiaxial development, =I=, 165; structural indefiniteness, =I=, 173; functional differentiation, =I=, 202; trochophoral kinship, =I=, 447; integration, =II=, 93–4, 96, 124; symmetry, =II=, 194, 207; vascular system, =II=, 340; gemmation, =II=, 444.

Poor Laws, and natural selection, =II=, 532.

Population, A Theory of, =I=, 265, 577–601; =II=, 411.

Potato: simulated growth, =I=, 136; vicarious function of tuber, =I=, 209; =II=, 255; sub-species, =I=, 302; dye absorption, =II=, 279.

Preservation: fertility and self-, =I=, 581; =II=, 423, 430; nutrition, =II=, 493.

“Progress; its Law and Cause,” theory of species differentiation, =I=, 568.

Projectiles, factors in flight of, =I=, 450–1.

Proteids: metabolic function, =I=, 67, 68, 69, 72, 76; complexity of molecule, =I=, 122.

Protein: evolution, =I=, 23, 24; isomerism, =I=, 700, 703, 704.

Proteus, degeneration of eye, =I=, 613.

Protodrilus, intestine segmentation, =II=, 125.

Protophyta: internal movements, =I=, 56; limit of growth, =I=, 138; development, =I=, 164; structure, =I=, 173, 181–3; self-mobility, =I=, 175; individuality, =I=, 245; multiplication, =I=, 270, 276, 279, 581, 584–5; =II=, 439, 462; genesis and nutrition, =I=, 295; unicellular, =II=, 21; central aggregation, =II=, 24; symmetry, =II=, 134; tissues, =II=, 244, 249; primary differentiation, =II=, 385; primordial type, =II=, 398; symbiosis, =II=, 400.

Protoplasm: self-increasing function of primordial, =I=, 63–4; plant metabolism, =I=, 65–7; complexity, =I=, 122, 253–5; differentiation in simple organisms, =I=, 182–3; continuity and inter-circulation, =I=, 190–2, 371, 629; =II=, 21, 620; “streaming,” =I=, 253; structure, =I=, 253–5. (See also Cell.)

Protozoa: inorganic components, =I=, 17; locomotion, =I=, 58, 175; =II=, 14; vital changes shown by, =I=, 94; limitation of growth, =I=, 138; development, =I=, 164; structure, =I=, 173, 181–3; incipient differentiation, =I=, 198, 391; =II=, 299, 309; multiplication, =I=, 270, 276, 279, 280, 582, 584; =II=, 442, 451–2; genesis and nutrition, =I=, 295; distribution, =I=, 396; parasites infesting, =I=, 427; Weismann’s hypothesis of immortality, =I=, 637; “spontaneous generation,” =I=, 697–701; non-nucleated, =II=, 20; primary aggregate, =II=, 86–7, 124; progressing integration, =II=, 89–91, 124; symmetry, =II=, 186; primordial plant-animal type, =II=, 397–8; symbiosis, =II=, 400.

Protyle, hypothetical chemical unit, =I=, 22, 23.

Pseud-axial development, vegetal, =II=, 28–9, 30.

Pseudo-foliar development, vegetal, =II=, 26–8, 30.

Psychidæ: parthenogenesis, =I=, 275; sexual dimorphism, =I=, 683.

Psychology: reasoning and definition of life, =I=, 81–8; correspondence shown by recognition, =I=, 95; contrasted with physiology, =I=, 127; departments of, =I=, 127–8; vicarious function, =I=, 209; waste and repair in sensory organs, =I=, 217; sensory adaptability, =I=, 229, 231, 232; inheritance of sensory defects, =I=, 306; musical talent, =I=, 311–2; intellectual progress and special creation hypothesis, =I=, 417; special creation a pseud-idea, =I=, 420, 429, 433, 554; legitimacy of evolution hypothesis, =I=, 433–5, 439, 554; embryology of ideas, =I=, 450, 457; persistent formative power unrepresentable, =I=, 492; E. Darwin’s and Lamarck’s theory of desires, =I=, 494; natural selection and brain evolution, =I=, 553; genesis and cerebral activity, =I=, 594; =II=, 512–4, 516–9, 530; heredity and distribution of tactual perceptiveness, =I=, 602–8, 646, 665–6, 672, 692; inconceivability of the negation, =I=, 675; vitiation of evidence, =II=, 88; repetition and perception, =II=, 143; differentiation of sensory organs, =II=, 317–20; differentiation of nerve tissue, =II=, 355–61; functional integration, =II=, 376; also integration, =II=, 380–2; equilibration of nerve discharge, =II=, 393; human fertility and nerve development, =II=, 466, 532; future human evolution, =II=, 523–5, 527; human evolution and genesis, =II=, 529–31; future mental development, =II=, 535; origin of vertebrate type, =II=, 598–600.

Pteridophyta: size attained by, =I=, 138, 139; homologies, =II=, 80–1, 82; frond surface differentiation, =II=, 260.

Pteropoda: bilateral symmetry, =II=, 201; dermal respiration, =II=, 310.

Ptyaline, metabolic function, =I=, 69.

Punjabis, inheritance of acquired osteological peculiarities, =I=, 689.

Pyrosomidæ: phosphorescence, =I=, 47; integration, =I=, 588; =II=, 97.

Quagga, telegonic transmission of markings to offspring of mare, =I=, 624, 627, 646.

Quills, development, =II=, 314–6.

Rabbit: activity and muscle colour, =II=, 365; over-running checked by weasels, =II=, 405; expenditure and genesis, =II=, 472.

Radial, definition, =II=, 148.

Radiolaria: unicentral development, =I=, 163; secondary aggregation, =II=, 88; symmetry, =II=, 187.

Radula, development of roots from leaflets, =II=, 34.

Rafflesiaceæ: homogenesis, =I=, 272; tissue differentiation, =II=, 274; nutrition and genesis, =II=, 486.

Rat (see Rodentia).

Rathke, H., on vertebrate embryo, =II=, 119.

Ray, J., plant classification, =I=, 378.

Reasoning, compared with assimilation, =I=, 81–7.

Recapitulation, embryological, =I=, 453.

Regeneration (see Repair).

Rejuvenescence, and sexual fertilization, =I=, 637; =II=, 613.

Remak, R., vertebrate embryo, =II=, 120.

Repair: continuity of, =I=, 216–9; animal injuries, =I=, 219, 222–4; =II=, 102, 611; deductive interpretation, =I=, 221–2; theories of heredity and regenerative phenomena, =I=, 360–1.

Repetition of like parts, =II=, 126.

Reproduction (see Multiplication).

Reptilia: growth and expenditure of force, =I=, 142; sizes of ova and adult, =I=, 144; longevity of crocodile, =I=, 154; temperature, =I=, 174; waste, =I=, 214; distinctive characters, =I=, 392; distribution in time, =I=, 409, 412; vertebral segmentation, =I=, 470; rudimentary limbs of snakes, =I=, 473; fertility and development, =I=, 583, 598, 599; regeneration, =I=, 589; elongated form, =II=, 15; supernumerary vertebræ, =II=, 123, 564; bilateral symmetry, =II=, 203, 204; Cope on segmentation in extinct, =II=, 225, 226; activity and muscular colour, =II=, 365; functional integration, =II=, 375; outer tissue differentiation, =II=, 387; Owen on skeleton, =II=, 560.

Resistance of media to locomotion, =II=, 15.

Respiratory System: effect of light, =I=, 31; organic re-arrangement, =I=, 37; cutaneous, =I=, 209; air-cells of lungs, =I=, 254; embryonic branchiæ of salamander, =I=, 457; differentiation, =II=, 310–1, 333–8; physiological integration, =II=, 374–5, 382; vascular differentiation and integration, =II=, 377.

Retrograde metamorphoses, in animals, =II=, 12.

Retzius, G., superficial nerve-endings, =I=, 666.

Reversed Selection, =I=, 611, 612.

Rhabdospheres, calcareous armour and dynamic element in life, =I=, 119.

Rhizoids, foliar expansions, =II=, 50.

Rhizopoda: structure, =I=, 173; undifferentiated function, =I=, 200; a primary aggregate, =II=, 86; symmetry, =II=, 186; tissue differentiated, =II=, 299, 385; motion of sarcode, =II=, 356; symbiosis, =II=, 400.

Rhythm: astronomic and organic, =I=, 499, 557; law of equilibration, =I=, 520–1; in multiplication, =II=, 419.

Richeraud, Baron A., definition of life, =I=, 79.

Riley, C. V., on telegony, =I=, 645; Termites, =I=, 680, 681; pouch of Honey-ants, =I=, 684.

Rodentia: incursions, =I=, 399; American types, =I=, 403; fertility and development, =I=, 583, 599.

Rivinus, plant classification, =I=, 377.

Rokitansky, on false joints, =I=, 230.

Romanes, G. J.: on “cessation of selection,” =I=, 560–2; isolation and species differentiation, =I=, 569; “physiological selection,” =I=, 569–71; panmixia, =I=, 649, 667; influence of a previous sire on progeny, =I=, 649.

Röntgen rays, =I=, 121; =II=, 621.

Roots: developed from leaflets, =II=, 34; physiological differentiation, =II=, 253–5, 270; nutrition from leaves, =II=, 274; size and function, =II=, 276.

Rotiferæ: latent vitality of desiccated, =I=, 117; trochopore, =II=, 108, 109; molluscan relationship, =II=, 115; fertility and size, =II=, 453, 459.

Roux, W.: “intra-selection,” =I=, 676; functional adaptation, =II=, 354.

Rudimentary organs: the definition of life and, =I=, 112; natural selection and eyes of cave fauna, =I=, 309, 612–4, 647–9, 693; evolution hypothesis, =I=, 472–5, 556; limbs of whale, =I=, 668–9, 685, 693.

Ruminants, alimentary canal development, =II=, 327–9.

Salamander, embryonic branchiæ, =I=, 457.

Salmonidæ, reproduction and growth, =I=, 291–3; =II=, 454.

Salpidæ: heterogenesis, =I=, 272, 277; integration, =I=, 588; =II=, 97.

Sap (see Vascular system).

Sarcina: central aggregation, =II=, 24; fertility, =II=, 440.

Savage, Dr., on “Heredity and Neurosis,” =I=, 313.

Scenedesmus, individuation, =II=, 24.

Scent: natural selection and keenness of, =I=, 610; floral fertilization, =II=, 268–9; animal protection, =II=, 434.

Schelling, E. W. J. von, definition of life, =I=, 78, 178.

Schleiden, J. M., on individuality, =I=, 245; on liverworts, =II=, 50, 52; algal indefiniteness, =II=, 296.

Science, complex revelations of, =I=, 252, 369, 450.

Scyphomedusæ, strobilization, =II=, 108.

Sea: changes and movements in, =I=, 83; life in, lower than terrestrial, =I=, 104; distribution, =I=, 396, 517; change of media caused by, =I=, 481; geologic influence, =I=, 502.

Seals: nail-bearing toes, =I=, 473; vibrissæ, =II=, 317.

Seasons: reproductive periodicity, =I=, 299; variations of genesis with, =II=, 484–5.

Sedgwick, Adam: on continuity of protoplasm in animals, =I=, 190, 629; =II=, 21; zoological classification, =I=, 387; discrimination of species in embryonic stages, =I=, 461; persistence of ancestral traits, =I=, 463–4; Archiannelidan segmentation, =II=, 109.

Sedgwick, Wm.: heredity and sex, =I=, 305, 314; telegonic transmission of hypospadias, =I=, 646.

Seeds: nitrogenous, =I=, 40; temperature of germinating, =I=, 47; =II=, 615; vitalism and latent vitality of, =I=, 116–7; variation in environment, =I=, 327; natural selection among, =I=, 532.

Segmentation (metameric): special creation hypothesis, =I=, 468–9; Huxley on number of somites in higher articulates, ib.; in annulose animals, =II=, 98–110, 111–5, 601–5; simulated molluscan, =II=, 116; in vertebrates, =II=, 125–7, 225–7, 606–7; in elasmobranchs, =II=, 126.

Segregation: of growth, =I=, 136; of like units, =I=, 179; organic repair, =I=, 221; variation, =I=, 331, 334; heterogeneity, and definiteness of evolution, =I=, 514–6, 517–8; morphological development, =II=, 7–9; physiological units, =II=, 616.

Self-fertilization, animal and vegetal, =I=, 341–4, 353.

Senses, the (see Psychology).

Sex: in Ascidian colonies, =I=, 247; limitation of heredity by, =I=, 314–6; correlated traits, =I=, 371–2, 513; nutrition and determination of, in social insects, =I=, 655–60, 678–84, 686–9; neural and hæmal traits, =I=, 683; differentiation of organs, =II=, 303; castration and growth, =II=, 459; Julin on “castration parasitaire” in crustaceans, =II=, 493–6; the object of fertilization, =II=, 613. (See also Fertilization.)

Sexual Selection (see Natural Selection).

Sharp, D.: on insect somites, =I=, 469; food habits of Termites, =I=, 686–7.

Sheep: contrasted with oxen, =I=, 158, 160; crossing of English and French breeds, =I=, 625; nutrition and genesis, =II=, 480.

Sherrington, Prof., on effects of nerve severance, =I=, 349.

Ship-building, interdependence of social functions, =I=, 237–9, 241.

Shipley, A. E.: segmentation of Microstomida, =II=, 102; Protodrilus, =II=, 125.

Silica, colloid and crystalloid, =I=, 16.

Silicic acid: properties, =I=, 16; isomerism, =I=, 59.

Silicon, allotropic, =I=, 4.

Silkworm disease, =I=, 622–3.

Simulation: of homology by analogy, =II=, 14, 485; of segmented structure by molluscs, =II=, 116.

Siphonophora, specialization of component polyps, =II=, 95.

Sirenia, simulated fish form, =I=, 485.

Size (see Growth).

Skeleton, vertebrate (see Vertebrata).

Skin: respiratory function, =I=, 209; adaptability, =I=, 228; =II=, 312–4, 387; transmitted peculiarities, =I=, 306; Wallace on distribution of sensitiveness, =I=, 646–7; differentiation, =II=, 215, 217, 304–7; tegumentary development, =II=, 314–6, 387; differentiation of sensory organs, =II=, 317–20; and mucous membrane, =II=, 303–4, 321–2, 389.

“Skin friction,” and locomotion of aquatic animals, =I=, 156.

Skull (see Vertebrata).

Sleep, repair favoured by, =I=, 216.

Small-pox, blood changes from, =I=, 221.

Smith, Prof. W., on fertility of diatomaceæ, =II=, 440.

Smith, W. P., on telegony in calves and foals, =I=, 645.

Smith, W. W., on habits of Tetramorium, =I=, 660.

Snakes (see Reptilia).

“Social organism,” author’s essay on, =I=, 363, 676.

Sociology: environment and degree of life, =I=, 105–6; functional differentiation, =I=, 204; division of labour, =I=, 207, 363–4, 367; functional interdependence, =I=, 237–9, 240–2; autogenous development of units in colonies, =I=, 364, 367–8; =II=, 620; belief in social evolution, =I=, 432; natural selection, =I=, 553; =II=, 532; integration and differentiation, =II=, 378–9; effects of population, =II=, 535–6; equilibration, =II=, 537.

Soil, dependence of plant evolution on, =II=, 402.

Solanum jasminoides, organs of attachment, =II=, 276.

Solar system, autogenous development illustrated by distribution of forces in, =I=, 366.

Sole, symmetry and location of eyes, =II=, 205.

Soma-plasm, Weismann’s theory of differentiation from germ-plasm, =I=, 357, 622, 628–30, 633–44.

Somites (see Segmentation).

Special creation: and evolution, =I=, 412, 415, 431; improbabilities, =I=, 418–9, 430, 439, 554; inconceivability, =I=, 420, 429, 431, 554; of individuals and species, =I=, 421–4; the implication of beneficence, =I=, 425–9; summary, =I=, 429, 554; Von Baer’s formula, =I=, 451–6; vertebrate skeleton, =II=, 551, 556, 565.

Species: adaptation and stability, =I=, 242; hereditary transmission, =I=, 301–4; variation in wild and cultivated, =I=, 323–5, 326, 693; gamogenesis and life of, =I=, 347–9; physiological units, =I=, 362, 364, 369–71, 458; =II=, 613; indefiniteness, =I=, 389, 445, 572; special creation, =I=, 422–4; instability of homogeneous, and differentiation of, =I=, 509–11, 515, 517–8, 550, 557; persistence of, =I=, 516, 518; =II=, 10–11; natural selection and equilibration, =I=, 543–8, 553, 557; non-adaptive characters, =I=, 565; morbid products as marks of, =I=, 567; migration and isolation as causes of differentiation, =I=, 568–9; increasing multiformity of aggregate, =II=, 396.

Specific gravity, of organisms and environment, =I=, 174, 177.

Spermatozoa} Sperm-cell } (see Fertilization).

Sphere: tendency of units to form, =I=, 15; the embryonic form, =I=, 177; symmetry, =II=, 131.

Spheroid, symmetry, =II=, 132.

Spiders (see Arachnida).

Spine (see Vertebrata).

Sponge: structure and dynamic element in life, =I=, 119; multicentral development, =I=, 164; units and aggregate, =I=, 185; reproductive tissue, =I=, 283; integration, =I=, 586; =II=, 90, 383; physiological differentiation, =II=, 300, 386; development and genesis, =II=, 463; analogy from, =II=, 576.

Spontaneous generation: and heterogenesis, =I=, 270; and evolution, =I=, 696–701, 703.

Stag, horns and correlated structures, =I=, 567, 670, 676–7, 692.

Stamens, and foliar homology, =II=, 44.

Starches: properties, =I=, 11; transformations, =I=, 66, 68, 69, 70; =II=, 593.

Star-fishes (see Asteroidea).

Statoblasts, of Plumatella, =I=, 277.

Steenstrup, on “Alternate Generation,” =I=, 592.

Sterility (see Multiplication).

Stickleback: ova, =II=, 454; bothriocephalus in, =II=, 490.

Stomach (see Alimentary canal).

Stomata, distribution, =II=, 260–1.

Straight line, and evolution hypothesis, =I=, 433.

Strain: compression and tension of, =I=, 151; =II=, 209–12; relation to mass, =I=, 155–7; vegetal structure, =II=, 574–88, 592–6; origin of vertebrate type, =II=, 600.

Strawberry: multiaxial development, =I=, 166; multiplication, =II=, 441.

Strength, a vital attribute, =I=, 578.

Structure: appliances for generating motion, =I=, 75–7; biological classification, =I=, 125–7, 129; size and organic, =I=, 137; growth and complexity, =I=, 138, 145, 161; relation to environment, =I=, 172–8, 195–6; of unicellular organisms, =I=, 181–3; multicellular, =I=, 183–96; Hertwig’s classification of tissues, =I=, 189; continuity of units, =I=, 190–2; systems of organs, =I=, 192; division into universal and particular, =I=, 193–4; general truths, =I=, 194–5; plant and animal, contrasted, =I=, 195–6; precedence of function or, =I=, 197, 211; correlative complexity of function and, =I=, 200, 211; progressive concomitant differentiation, =I=, 201–4; physiological units, =I=, 225–6, 362, 364, 369–71; =II=, 613; social and organic interdependence, =I=, 235–42; varied by function, =I=, 334, 535; =II=, 217 (see Acquired Characters); zoological classification, =I=, 390–2; equilibration, =I=, 521, 557; progress of, and genesis, =I=, 590–1; =II=, 462; co-operation with function, =II=, 3; evolution and increased, =II=, 4; retrograde metamorphosis, =II=, 12; simulated homologies, =II=, 13–14; earliest organic forms, =II=, 19; cylindrical vegetal, =II=, 57–62; permanence and complexity, =II=, 295, 296; function and epidermic, =II=, 312–4, 387; and muscular, =II=, 369, 391; adaptation and equilibration, =II=, 392; persistence of force and physiological adaptation, =II=, 394; evolution, =II=, 501–4. (See also Morphology.)

Struggle, for nutriment among components of an organism, =I=, 562, 676; for existence (see Natural Selection).

Struthers, Sir J.: on heredity, =I=, 305, 314; digital variation, =I=, 321; rudimentary limbs of whale, =I=, 668.

Strychnine, effects of, =I=, 54, 55.

Sturgeon, size of ova and adult, =I=, 144.

Sugars: properties, =I=, 10–11; transformations, =I=, 38, 40, 66, 69, 70; =II=, 593.

Suicide, hereditary tendency to, =I=, 307.

Sulphur: allotropic, =I=, 4, 59; organic evolution, =I=, 703.

Sun (see Light).

Survival of the Fittest, the expression, =I=, 530, 610. (See Natural Selection.)

Swan, vertebræ of neck, =II=, 123.

Swiftness, a vital attribute, =I=, 578.

Syllis ramosa, lateral branching, =I=, 166, 361; =II=, 105, 108.

Symbiosis, =II=, 399, 400.

Symmetry (see Morphology).

Syphilis, hereditary transmission, =I=, 623.

Tactual, Perceptiveness, heredity and the distribution of, =I=, 602–8, 633, 665, 666, 672, 692.

Tænia (see Entozoa).

Tansley, A. G., =I=, vi; =II=, vi; adaptation of reproductive activity to conditions in Algæ, =I=, 288–9; shapes of Caulerpa, =II=, 22; stem-thickening in extinct Thallophytes, =II=, 56; natural selection and leaf-distribution, =II=, 179.

Tape-worm (see Entozoa).

Taste, dependent on chemical action, =I=, 54.

Teeth: hereditary transmission, =I=, 306; suppression of mammalian, =I=, 457; of uncivilized and civilized, =I=, 541, 693.

Tegumentary organs, origin of, =I=, 314–6.

Telegony, or the Influence of a previous sire on offspring, =I=, 624–7, 644–6, 649–50.

Temperature (see Heat).

Tension (see Strain).

Termites: fertility, =I=, 583; =II=, 493; late development of sexual organs, =I=, 680; nutrition and differentiation of forms, =I=, 681.

Tetramorium, utilization of aphides by, =I=, 660–1.

Thallophyta: size, =I=, 138, 139; low co-ordination of parts, =I=, 164; pseudo-foliar, =II=, 28; “transition place,” =II=, 30; simulation of higher types, =II=, 32; secondary thickening in extinct species, =II=, 56; sexual and asexual genesis, =II=, 84. (See also Algæ.)

Tickling, physiology of, =I=, 76.

Tide (see Sea).

Time, as a factor in growth, =II=, 77.

Tissue, Hertwig’s classification, =I=, 189. (See Physiology.)

Tongue, perceptiveness of tip, =I=, 606–8, 665, 672–3.

Tortoise: contrasted life of dog and, =I=, 103–4; natural selection and carapace, =I=, 534.

“Transcendental Physiology,” =I=, 176.

Tree, as symbolizing phylogeny, =I=, 428, 452–3. (See Plants.)

Trematoda: agamogenesis, =I=, 277; parasitism, =I=, 428; alternate generation, =I=, 592.

Trembley, A., on the polyp, =I=, 223.

Trichinosis, in Germany, =I=, 428.

Trochophore, phyletic relationships shown by, =I=, 447; =II=, 108–9.

Tubicolæ: development, =II=, 100; bilateral symmetry, =II=, 197.

Tunicata: gemmation, =I=, 588; =II=, 445; alternate generation, =I=, 592; integration, =II=, 93–4; tertiary aggregation, =II=, 124; symmetry, =II=, 194–5.

Tunny, size of ova and adult, =I=, 144.

Turbellaria: segmentation, =II=, 102; symbiosis, =II=, 400.

Turnip: chlorophyll in roots, =I=, 209; =II=, 254; vascular system, =II=, 281, 284, 578, 591, 596.

Twins: similarity of, =I=, 324; traits of women bearing, =II=, 457.

“Types, persistent,” Huxley on, =I=, 408.

Ulcer, dermal structure, =II=, 306.

Ultimate Reality, incomprehensibility of, =I=, 120.

Ulva: cell multiplication, =II=, 26; outer tissue, =II=, 256.

Umbelliferæ: floral symmetry, =II=, 171; axial and foliar organs, =II=, 541–6.

United States: cases of telegony, =I=, 644–5; birth-rate, =II=, 520.

Units: differentiation and dissimilarity, =I=, 20; “protyle,” =I=, 22–3; shapes in higher types, =I=, 164; differential assimilation, =I=, 180; primordial organic, =I=, 181; morphological composition, =I=, 184–7, 194, 252; =II=, 5, 7–9, 21, 79, 85–6; segregation and organic repair, =I=, 221–2, 222–6; chemical, morphological, and physiological, =I=, 225–6; =II=, 612; stability, =I=, 339; instability and heterogeneity of organic, =I=, 350; Darwin’s gemmules, =I=, 356–60, 362, 372; Weissmann’s germ-plasm (q. v.) ib.; sociological comparison, =I=, 363–8; specific proclivities in embryogeny, =I=, 458; phænogamic, =II=, 73, 151; annulose, =II=, 105; incident force and homologous, =II=, 159; morphological summary, =II=, 233. (See also Physiological Units.)

“Universal Postulate,” =I=, 675.

Unsymmetrical, definition, =II=, 131.

Urea, muscular energy and excretion, =I=, 72.

Van Beneden, P. J., on Tænia, =II=, 103.

Variation: digital, =I=, 331; effects of parental conditions, =I=, 324; of altered function, =I=, 325, 334, 693; dissimilarity of initial conditions, =I=, 327–32, 333; “spontaneous,” =I=, 328, 513, 697; =II=, 529; persistence of force, =I=, 335; physiological units, =I=, 348–54, 360, 369, 371–3; =II=, 614–7, 622–3; Weismann’s germ-plasm theory, =I=, 357–8, 372–3, 671, 677; =II=, 622; equilibration and vegetal, =I=, 523–5; Weismann’s panmixia theory, =I=, 561–3, 649, 667–9, 671, 685; reproductive organs, =I=, 570; natural selection and concomitant, =I=, 614–21, 653, 664, 674, 692; and disused organs, =I=, 648, 668; plus and minus. =I=, 667, 685; Masters on correlated, in plants, =II=, 298, 621–2; equilibration of favourable, =II=, 394.

Vascular System: effects of vegeto-alkalies, =I=, 55; nutrition, =I=, 146, 148; embryonic development, =I=, 169; structural traits, =I=, 192, 193; function, =I=, 199; of Ascidians. =I=, 202; functional differentiation and integration, =I=, 205–6; organic repair, =I=, 217, 221–2; effect of function, =I=, 229, 234–5, 236; equilibration, =I=, 535; community in compound organisms, =I=, 588; development of vegetal, =II=, 273–5, 279–84, 285–8, 388; differentiation of, summary, =II=, 288–90, 388; differentiation of animal, =II=, 339–44; osseous development, =II=, 347–51; muscularity, =II=, 364; muscular colour, =II=, 365–9; heart-motor apparatus, =II=, 374; differentiation and integration in animal, =II=, 376–9, 383; wood formation, =II=, 567–92; résumé of wood formation, =II=, 592–7.

Vaucheria, reproduction, =I=, 279, 289.

Vegetative System, co-ordination of actions in, =I=, 578.

Vegeto-alkalies, physiological effects of, =I=, 54–5.

Velocity, of moving bodies, =II=, 219–20.

Vertebrata: size, =I=, 139; size at birth and maturity, =I=, 144; axial structure, =I=, 165; embryonic development and self-mobility, =I=, 175; functional differentiation, =I=, 206, 591; reparative power, =I=, 219, 223, 589; homogenesis universal, =I=, 271; distinctive traits, =I=, 392; =II=, 35; distribution in time, =I=, 408; classificatory value, =I=, 446; embryonic mammalian respiratory system, =I=, 456; embryological pre-adaptation, =I=, 461; evolution and vertebral column, =I=, 470; rudimentary organs, =I=, 473; evolution and varied media, =I=, 479–85; size of head and vertebræ, =I=, 512, 537; segregation and evolution of vertebræ, =I=, 515; fertility and development, =I=, 583, 598–9; Weismann on reproductive cells, =I=, 635; limb locomotion, =II=, 15; adaptive segmentation, =II=, 117–23, 125–7, 223, 602, 605–7; supernumerary vertebræ, =II=, 123; bilateral symmetry, =II=, 203–6; internal organic symmetry, =II=, 208; genesis of rudimentary axis, =II=, 212–6; natural selection and genesis of structure, =II=, 216, 227; origin of notochord, =II=, 216–8; spinal segmentation, =II=, 218–22, 224; skull development, =II=, 222, 227; résumé of axis development, =II=, 224; Cope on author’s theory, =II=, 225–7; nerve differentiation, =II=, 304; sensory organs, =II=, 318; air-chambers, =II=, 334; osseous differentiation, =II=, 344–55; activity and muscular colour, =II=, 365–9; heart-motor apparatus, =II=, 374; cost of genesis, =II=, 436; agamogenesis unknown, =II=, 445; growth and genesis, =II=, 454; heat expenditure and genesis, =II=, 468–9, 474; Owen, theory of skeleton, =II=, 548–66; evolution of vertebræ, =II=, 563–6; origin of type, =II=, 598–600.

Vestiges of Creation, =I=, 491.

Vibrissæ, function of, =I=, 75.

Vitalism, hypothesis examined, =I=, 114–7.

Vittadini, C., on silkworm disease, =I=, 622–3.

Viviparons genesis, =I=, 271, 274–5, 278.

Voice, correlated sexual traits, =I=, 371–2.

Volcano, definition of life and, =I=, 85, 89.

Volvocineæ: unicentral development, =I=, 163; individuality, =I=, 245; disintegration of genesis, =I=, 276, 587; spherical aggregation, =II=, 24; symmetry, =II=, 137, 187; fertility, =II=, 441.

Vomiting, alimentary canal development, =II=, 328.

Vorticella: secondary aggregate, =II=, 90; symmetry, =II=, 188.

Wallace, A. R.: “The Origin of the Human Races,” =I=, 553; the expression “Survival of the Fittest,” =I=, 530; his association of natural with artificial selection, =I=, 609; co-adaptation in giraffe, =I=, 615; skin sensitiveness, =I=, 646.

Wasp: co-ordination of instincts in Mason-, =I=, 574, 679–80; genesis of worker, =I=, 654–7.

Waste, animal, =I=, 69, 213–5, 228; relation to activity, =I=, 196, 220–1; in plants, =I=, 213, 220.

Water: properties, =I=, 7, 9; colloidal affinity for, =I=, 28; organic change from, =I=, 29; organic need for, =I=, 147; proportion in mammalian adult and fœtus, =I=, 154; motion through, =I=, 156; organic development and environment, =I=, 173, 177, 479; terrestrial organisms inhabiting, =I=, 400; adaptation of organisms to change of media, =I=, 479–85; vegetal tissue differentiation, =II=, 253; molecular re-arrangement, =II=, 359; colloidal contraction, =II=, 361–2.

Water-weed, American, invasion of, =I=, 399.

Watts, Dr., on The Principles of Biology, =I=, ix.

Wax, foliar deposit, =II=, 260–1.

Weber, on tactual discriminativeness, =I=, 602.

Weight: relation to environment of organic, =I=, 174, 177; varying as cube of dimensions, =I=, 151; =II=, 434, 470.

Weismann, Aug.: reproductive tissue in Medusæ, =I=, 281; in Daphnidæ, =I=, 290; his theory of the differentiated germ-plasm and its fundamental units, =I=, 357, 622–3, 628–30, 633–44, 646; =II=, 618–9, 622; the alleged differentiation and plant-phenomena, =I=, 359–60; and regenerative processes, =I=, 360; false joints, =I=, 362; implied complexity of determinants, =I=, 370; theory inadequate to explain correlation of sexual traits, =I=, 372; and variations in peacock’s tail feather, =I=, 372–3, 695; =II=, 618; his view of natural selection as sole factor in organic evolution, =I=, 559; the doctrine of panmixia, =I=, 561–3, 612, 632, 649, 667–9, 671, 685, 689; arguments against inheritance of acquired characters, =I=, 612–3, 651–65, 669–71; blindness of cave-animals, =I=, 613; current acceptance of his views, =I=, 631, 690; cannot explain the process of natural selection, =I=, 651; the degradation of the little toe in man, =I=, 652, 669, 673; caste gradations of social insects, =I=, 654, 658–65, 670, 675, 678–84, 685; food-seeking instinct in Amazon ants, =I=, 660, 670; the co-adaptation of co-operative parts, =I=, 663–4, 670, 674, 675, 676; tactual discriminativeness, =I=, 665, 672; intra-selection, =I=, 676–8; effect of nutrition on fertility of blow-fly, =I=, 678–9.

Whale: weight of brain, =I=, 599; rudimentary limbs, =I=, 668–9, 685, 693.

Wheat, adaptive variations, =II=, 298.

Whistling, definition of life and, =I=, 112.

White-Cooper, Mr., on inheritance of abnormal vision, =I=, 306.

Willow, nutrition and growth, =I=, 294.

Wilson, E. B.: composition of chromatin, =I=, 260; separation of segmentation spheres of Amphioxus ovum, =I=, 691.

Wind: and vegetal bilateral symmetry, =II=, 142; and inner vegetal tissue differentiation, =II=, 275–9, 285, 288, 388; and proliferation of Bryophyllum, =II=, 295; and vegetal sap movement, =II=, 583, 584, 587; résumé, 592–6.

Wolff, C.: vegetal fructification and nutrition, =I=, 283; =II=, 179–80; vegetal vascular system, =II=, 283.

Women (see Man).

Wood (see Plants).

Yeast: fermentation, =I=, 38; fertility, =I=, 581; =II=, 440; linear aggregation, =I=, 587; =II=, 23.

Zebra marks in horses, =I=, 314.

Zoology, classification, =I=, 124–5, 380–9.

Zoophytes, structural indefiniteness, =I=, 173.

Zoospores, unit-life of, =I=, 185.

Zygote, of conjugating Algæ, =I=, 283.

THE END.

FOOTNOTES:

It seems needful here to say, that allusion is made in this paragraph to a proposition respecting the ultimate natures of Evolution and Dissolution, which is contained in an essay on The Classification of the Sciences, published in March, 1864. When the opportunity comes, I hope to make the definition there arrived at, the basis of a re-organization of the second part of First Principles: giving to that work a higher development, and a greater cohesion, than it at present possesses. [The intention here indicated was duly carried out in 1867.]

Let me here refer those who are interested in this question, to Prof. Huxley’s criticism on the cell-doctrine, published in the Medico-Chirurgical Review in 1853.

A critic who thinks the above statements are “rather misleading” admits that the lowest types of organisms yield them support, saying that “there are certainly masses of protoplasm containing many nuclei, but no trace of cellular structure, in both animals and plants. Such non-cellular masses may exist during development and later become separated up into cells, but there are certain low organisms in which such masses exist in the adult state. They are called by some botanists non-cellular, by others multi-nucleate cells. Clearly the difference lies in the criteria of a cell. There are also some Protozoa, and the Bacteria, in which no nucleus has certainly been demonstrated. But it is usual to consider the bodies of such organisms as cells nevertheless, and it is supposed that such cells represent a stage of development in which the nucleus has not yet been evolved, though the chemical substance ‘nuclein’ has been formed in some of them.”

Perhaps it will be most correct to say that, excluding the minute, non-nucleated organisms, all the higher organisms--Metazoa and Metaphyta--are composed throughout of cells, or of tissues originally cellular, or of materials which have in the course of development been derived from cells. It must, however, be borne in mind that, according to sundry leading biologists, cells in the strict sense are not the immediate products either of the primitive fissions or of subsequent fissions; but that the multiplying so-called cells are nucleated masses of protoplasm which remain connected by strands of protoplasm, and which acquire limiting membranes by a secondary process. So that, in the view of Mr. Adam Sedgwick and others, the substance of an organism is in fact a continuous mass of vacuolated protoplasm.

In further illustration, Mr. Tansley names the fact that in the genus Caulerpa we have extremely complicated forms often of considerable size produced in the same way. The various species simulate very perfectly the members of different groups among the higher plants, such as Horse-tails, Mosses, Cactuses, Conifers and the like.

It may be objected that in Cladophora the separate compartments of the thallus severally contain many nuclei, making it doubtful whether they descend from uni-nucleate cells. If, however, they do not they simply illustrate another form of integration.

The great mass of early ancestral types--plant and animal--consisting of soft tissues, have left no remains whatever, and we have no reason to suppose that those which left remains fell within the direct ancestral lines of any existing forms. Contrariwise, we have reason to suppose that they fell within lines of evolution out of which the lines ending in existing forms diverged. We must therefore infer that the difficulties of affiliation which arise if we contemplate divergent types now existing, would not arise if we had before us all the early intermediate types. The Mammalia differ in sundry respects from all other kinds of Vertebrata--Fishes, Reptiles, Birds; and if the absence of hair, mammæ, and two occipital condyles, in these other vertebrates were taken to imply a fundamental distinction, it might, in the absence of any known fossil links, be inferred that the Mammalia belonged to a separate phylum. But these differences are not held to negative the assumed relationship. Similarly among plants. We must not reject an hypothesis respecting a certain supposed type, because the existing types it must have been akin to present traits which it could not have had. We are justified in assuming, within limits, a hypothetical type, unlike existing types in traits of some importance. Hence results the answer to a criticism passed on the above argument, that it implies relations between the undeveloped and developed forms of the Jungermanniaceæ such as the facts do not show us. This objection is met on remembering that the types in which the supposed transition took place disappeared myriads of years ago.

There is much force in the criticism passed on the above paragraph, and by implication on some preceding paragraphs, that though in plants which tend to produce compound leaves the production is largely dependent on the supply of nutriment, yet the unqualified statement of this relation as a general one, is negatived by the existence of plants which bear only simple leaves, however much high nutrition causes growth. But mostly valid though this objection is, it is probably not universally valid. I am led to say this by what occasionally occurs in flowers. The flowering stem of the Hyacinth is single; but I have seen a cultivated Hyacinth in which one of the flowers had developed into a lateral spike. Still more striking evidence was once supplied to me by Agrimony. All samples of this plant previously seen had single flowering spikes, but some years ago I met with one, extremely luxuriant, in which some flowers of the primitive spike were replaced by lateral spikes; and I am not sure that some of these, again, did not bear lateral spikes. Now if in plants which, in probably millions of cases, have their flowering stems single, excessive nutrition changes certain of their flowers into new spikes, it is a reasonable supposition that in like manner plants which are thought invariably to bear only single leaves, will, under kindred conditions, bear compound leaves.

See British and Foreign Medico-Chirurgical Review for January, 1862.

Schleiden, who chooses to regard as an axis that which Mr. Berkeley, with more obvious truth, calls a mid-rib, says:--“The flat stem of the Liverworts presents many varieties, consisting frequently of one simple layer of thin-walled cells, or it exhibits in its axis the elements of the ordinary stem.” This passage exemplifies the wholly gratuitous hypotheses which men will sometimes espouse, to escape hypotheses they dislike. Schleiden, with the positiveness characteristic of him, asserts the primordial distinction between axial organs and foliar organs. In the higher Archegoniates he sees an undeniable stem. In the lower Archegoniates, clearly allied to them by their fructification, there is no structure having the remotest resemblance to a stem. But to save his hypothesis, Schleiden calls that “a flat stem,” which is obviously a structure in which stem and leaf are not differentiated. He is the more to be blamed for this unphilosophical assumption, since he is merciless in his strictures on the unphilosophical assumptions of other botanists.

To this interpretation it is objected that “the more-developed Jungermanniaceæ” do not appear to have arisen from the lower forms of Jungermanniaceæ--that is to say, from such lower forms as are now existing. It may, however, be contended that this fact does not exclude the interpretation given; since the higher forms may well have been evolved, not from any of the lower forms we now know, but from lower forms which have become extinct. This, indeed, is the implication of the evolutionary process as pointed out in the note to Chap. I. If then we assume some early type of intermediate structure, the explanation may not improbably hold.

I am indebted to Dr. Hooker for pointing out further facts supporting this view. In his Flora Antarctica, he describes the genus Lessonia (see Fig. 37), and especially L. ovata, as having a mode of growth simulating that of the dicotyledonous trees, not only in general form but in internal structure. The tall vertical stem thickens as it grows, by the periodical addition of layers to its periphery. That even Thallophytes should thus, under certain conditions, present a transversely-increasing axis, shows that there is nothing absolutely characteristic of Phanerogams in their habit of stem-thickening. Mr. Tansley gives me further verification by the statement that “it is also now certain that members of the Equisetineæ and Lycopodineæ, as well as some Ferns which flourished in Carboniferous times, had secondary thickening in their stems quite comparable to that of modern Dicotyledonous trees.”

See note at the end of the chapter.

Since this paragraph was put in type [this refers to the first edition], I have observed that in some varieties of Cineraria, as probably in other plants, a single individual furnishes all these forms of leaves--all gradations between unstipulated leaves on long petioles, and leaves that embrace the axis. It may be added that the distribution of these various forms is quite in harmony with the rationale above given.

Since these figures were put on the block, it has occurred to me that the relations would be still clearer, were the primary frond represented as not taking part in these processes of modification, which have been described as giving rise to the erect form; as, indeed, the rooting of its under surface will prevent it from doing in any considerable degree. In such case, each of the Figs. 111 to 117, should have a horizontal rooted frond at its base, homologous with the pro-embryo among Acrogens. This primary frond would then more manifestly stand in the same relation to the rest, as the cotyledon does to the plumule--both by position, and as a supplier of nutriment. Fig. 117a, which I am enabled to add, shows that this would complete the interpretation. Of the dicotyledonous series, it is needful to add no further explanation than that the difference in habit of growth, will permit the second frond to root itself as well as the first; and so to become an additional source of nutriment, similarly circumstanced to the first and equal with it.

How the element of time modifies the result, is shown by the familiar fact that crystals rapidly formed are small, and become relatively large when left to form more slowly. If the quantity of molecules contained in a solution is relatively great, so that the mutual polarities of the molecules crowded together in every place throughout the solution are intense, there arises a crystalline aggregation around local axes; whereas, in proportion as the local action of molecules on one another is rendered less intense by their wider dispersion, they become relatively more subordinate to the forces exerted on them by the larger aggregates of molecules that are at greater distances, and thus are left to arrange themselves round fewer axes into larger crystals.

It is objected that these transformations should be much commoner than they are, were they caused solely by the variations of nutrition described. The reply is that they are comparatively rare in uncultivated plants, where such variations are not frequent. The occurrence of them is chiefly among cultivated plants which, being artificially manured, are specially liable to immense accessions of nutriment, caused now by sudden supplies of fertilizing matters, and now by sudden arrival of the roots at such matters already deposited in the soil. It is to these great changes of nutrition, especially apt to take place in gardens, that these monstrosities are ascribed; and it seems to me that they are as frequent as may be expected.

Since this paragraph was published in 1865, much has been learned concerning cell-structure, as is shown in Chapter VI^A of Part I. While some assert that there exist portions of living protoplasm without nuclei, others assert that a nucleus is in every case present, and that where it does not exist in a definite aggregated form it exists in a dispersed form. As remarked in the chapter named, “the evidence is somewhat strained to justify this dogma.” Words are taken in their non-natural senses, if one which connotes an individualized body is applied to the widely-diffused components of such a body; and this perverting of proper meanings leads to obscuration of what may perhaps be an essential truth. As argued in the chapter named (§§ 74e, 74f), nuclear matter is, as shown by its chemical character, an extremely unstable substance, the molecular changes of which, perpetually going on, initiate shocks, producing changes all around. In the earlier stages of cell-evolution this unstable substance is dispersed throughout the cytoplasm; whereas in the more advanced stages it is gathered together in one mass. If so, instead of saying there is a dispersed nucleus we should say there are the materials of a nucleus not yet integrated.

This statement seems at variance with the figure; but the figure is very inaccurate. Its inaccuracy curiously illustrates the vitiation of evidence. When I saw the drawing on the block, I pointed out to the draughtsman, that he had made the surrounding curves much more obviously related to the contained bodies, than they were in the original (in Dr. Carpenter’s Foraminifera); and having looked on while he in great measure remedied this defect, thought no further care was needed. Now, however, on seeing the figure in the printer’s proof, I find that the engraver, swayed by the same supposition as the draughtsman that such a relation was meant to be shown, has made his lines represent it still more decidedly than those of the draughtsman before they were corrected. Thus, vague linear representations, like vague verbal ones, are apt to grow more definite when repeated. Hypothesis warps perceptions as it warps thoughts.

Though the subdivision into chambers of the shell does not correspond to the subdivision into cell-units it may still be held that since in the solitary types the subdivision of the nucleus is followed by formation of new individuals which separate, and since in the compound types the subdivision of the nucleus is followed by growth and formation of new chambers, the compound type must be regarded as an aggregate of the second order.

A critic says the question is “what are the forces internal or external which produce union or separation.” A proximate reply is--degree of nutrition. As in a plant new individuals or rudiments of them are cast off where nutrition is failing, so in a compound animal. The connecting part dwindles if it ceases to carry nutriment.

It has been pointed out that I have here understated the evidence of physiological integration. An instance of it among Hydrozoa is shown in Fig. 151, but by a strange oversight I have forgotten to name the various cases furnished by the Siphonophora in which the individual polypes of a compound aggregate are greatly specialized in adaptation to different functions.

Recently Mr. T. H. Morgan has made elaborate experiments which show that Planaria Maculata may be cut into many pieces from various parts and of various shapes--even a slice out of the side--and each, if not too small, will produce a perfect animal.

Since this was written in 1865 there has come to light evidence more completely to the point than any at that time known. In the subdivision of Platyhelminthes known as Turbellaria, there are some, the Microstomida which, by a process of segmentation form “chains of 4, then 8, then 16, and sometimes even 32 individuals.” “Each forms a mouth [lateral] and for some time the chain persists, but the individuals ultimately become sexually matured and then separate.” (Shipley, Zoology of the Invertebrata, p. 92.) Here it should be remarked that the lateral mouths enable the members of a string to feed separately, and that nutrition not being interfered with they doubtless gain some advantage by temporary maintenance of their union--probably in creeping.

I find that the reasons for regarding the segment of a Tænia as answering to an individual of the second order of aggregation, are much stronger than I supposed when writing the above. Van Beneden says:--“Le Proglottis (segment) ayant acquis tout son développement, se détache ordinairement de la colonie et continue encore à croître dans l’intestin du même animal; il change même souvent de forme et semble doué d’une nouvelle vie; ses angles s’effacent, tout le corps s’arrondit, et il nage comme une Planaire au milieu des muscosités intestinales.”

Though this was doubtful in 1865 it is no longer doubtful. In an individual Ctenodrilus monostylus, which multiplies by dividing and subdividing itself, “parts arise which are destitute of both head and anus and at times consist of only a single segment.” In another species, C. pardalis, there is separation into many segments; and each segment before separating forms a budding zone out of which other segments are afterwards produced, completing the animal (Korschelt and Heider, Embryology, i, 301–2).

In place of those originally here instanced about which there are disputes, I may give an undoubted one described by McIntosh, the Syllis ramosa, a species of chætopod living in hexactinellid sponges from the Arafura Sea, which branches laterally repeatedly so as to extend in all directions through the canals of the sponge. In most cases the buds terminate in oval segments with two long cirri each. But male and female buds were found, provided each with a head, and containing ovaries and testes. Sometimes these sexual buds had become separate from the branched stock.

The name Annulosa, once used to embrace the Annelida and Arthropoda, has of late ceased to be used. It seems to me better than Appendiculata, both as being more obviously descriptive and as being more exclusive.

The fusion of the segments forming the Arthropod head and the extreme changes, or perhaps in some cases disappearances, of their appendages, put great difficulties in the way of identification; so that there are differences of opinion respecting the number of included segments. Prof. MacBride writes:--“It is highly probable that a primary head (præoral lobe or præstomium) has been derived from annelid ancestors, but the secondary fusion of body-segments with this head, in other words the formation of a secondary head, has gone on independently in the different classes of the phylum Arthropoda, viz., Arachnida, Crustacea, and Tracheata (including Insects and Myriapods). Judged by the number of appendages (which gives an inferior limit) the head of a malacostracous Crustacean consists of præstomium and 8 segments; the head of an insect of præstomium and 4 segments; the head of a Myriapod of præstomium and 3 segments; and the head of an Arachnid of præstomium and 3 segments.” Again, the comment of Mr. J. T. Cunningham is:--“According to Claus and most modern authorities there are only 5 segments in the head of an Arthropod, the eyes not counting as appendages; and further it should be noted that the second pair of antennæ are wanting in Insects.”

Of course difference of opinion respecting the number of somites in the head involves difference of opinion respecting the number constituting the entire body, which, in the higher Arthropods, is said by some to be 19 and by others 20. But those who thus differ in detail, agree in regarding all the segments of head and body as homologous, and this is the essential point with which we are here concerned.

Prof. MacBride corrects this statement by saying that “The ctenidia or gills (which in Mollusca generally are represented only by a single pair) are here represented by a large number of pairs; they do not, however, correspond in either number or position to the shell plates.” It may, I think, be contended that if these had any morphological significance, they would not differ in arrangement from the shell plates, and would not be limited to this special type of Mollusc.

Though it is alleged that at a later stage the posterior part of the skull is formed by fusion of divisions which are assumed to represent vertebræ, yet it is admitted that the anterior part of the skull never shows any signs of such division. Moreover in both parts the bones show no trace of primitive segmentation.

See note at the end of the chapter.

A qualifying fact should be named. When the production of vertebral segments has become constitutionally established, so that there is an innate tendency to form them, there arises a liability to form supernumerary ones; and this, from time to time recurring, may lengthen the series, as in the body of a snake or the neck of a swan. This qualification, however, affects equally the hypothesis of an ideal type and the hypothesis of mechanical genesis.

Here and throughout, the word radial is applied equally to the spiral and the whorled structures. These, as being alike on all sides, are similarly distinguished from arrangements that are alike on two sides only.

It should be added that this change of distribution is not due to change in the relative positions of the insertions of the leaves but to their twistings.

We may note that some of these leaves, as those of the Lime, furnish indications of the ratio which exists between the effects of individual circumstances and those of typical tendencies. On the one hand, the leaves borne by these drooping branches of the Lime are with hardly an exception unsymmetrical more or less decidedly, even in positions where the causes of unsymmetry are not in action: a fact showing us the repetition of the type irrespective of the conditions. On the other hand, the degree of deviation from symmetry is extremely variable, even on the same shoot: a fact proving that the circumstances of the individual leaf are influential in modifying its form. But the most striking evidence of this direct modification is afforded by the suckers of the Lime. Growing, as these do, in approximately upright attitudes, the leaves they bear do not stand to one another in the way above described, and the causes of unsymmetry are not in action; and here, though there is a general leaning to the unsymmetrical form, a large proportion of the leaves become quite symmetrical.

It was by an observation on the forms of leaves, that I was first led to the views set forth in the preceding and succeeding chapters on the morphological differentiation of plants and animals. In the year 1851, during a country ramble in which the structures of plants had been a topic of conversation with a friend--Mr. G. H. Lewes--I happened to pick up the leaf of a buttercup, and, drawing it by its foot-stalk through my fingers so as to thrust together its deeply-cleft divisions, observed that its palmate and almost radial form was changed into a bilateral one; and that were the divisions to grow together in this new position, an ordinary bilateral leaf would result. Joining this observation with the familiar fact that leaves, in common with the larger members of plants, habitually turn themselves to the light, it occurred to me that a natural change in the circumstances of the leaf might readily cause such a modification of form as that which I had produced artificially. If, as they often do with plants, soil and climate were greatly to change the habit of the buttercup, making it branched and shrub-like; and if these palmate leaves were thus much overshadowed by one another; would not the inner segments of the leaves grow towards the periphery of the plant where the light was greatest, and so change the palmate form into a more decidedly bilateral form? Immediately I began to look round for evidence of the relation between the forms of leaves and the general characters of the plants they belong to; and soon found some signs of connexion. Certain anomalies, or seeming anomalies, however, prevented me from then pursuing the inquiry much further. But consideration cleared up these difficulties; and the idea afterwards widened into the general doctrine here elaborated. Occupation with other things prevented me from giving expression to this general doctrine until Jan. 1859; when I published an outline of it in the Medico-Chirugical Review.

It is objected to the above interpretation that “many flowers of sizes intermediate between the Hollyhock and the Agrimony are radially symmetrical and yet grow sideways. I may mention various Liliaceæ, e.g. Chlorophytum, Eucomis, Muscari, Anthericum. Sagittaria, also, has many of its flowers in this position. Further, if the higher insects alight on flowers in a definite way, as they do, the parts of the flower must bear different relations to the visiting insect, however large, so that flowers unvisited ought all to be zygomorphic.” My reply is that in the sense which here concerns us, the different petals of the Hollyhock-flower do not bear different relations to the visiting insect; since, practically, the upper and lateral petals bear no physical relations at all: in so far as the visiting bee is concerned they are non-existent. The argument implies that change in the form of a flower from the radial to the bilateral is likely to take place only when the contact-relations of the petals to the visiting insect, are such as to make some forms facilitate its action more than others; and the large petals of the Hollyhock cannot facilitate its action at all. In respect of the Liliaceæ instanced, it is needful to inquire whether the structures are such that this alleged cause of bilateral symmetry can come into play.

I had intended here to insert a figure exhibiting these differences; but as the Cow-parsnip does not flower till July, and as I can find no drawing of the umbel which adequately represents its details, I am obliged to take another instance.

It has been pointed out to me that “the extreme development of the corolla so often found in the outer flowers or on the outer side of the outer flowers in closely-packed inflorescences, associated as it often is with disappearance of stamens or carpels or both, is usually put down to specialization of these outer flowers for attractive purposes. Since the whole inflorescence is increased in conspicuousness by such a modification, it is supposed that natural selection favoured those plants which sacrificed a portion of their seed-bearing capacity for the supposed greater advantage of securing more insect visits.” But granting this interpretation, it may still be held that increase of attractiveness due to increase of area must be achieved by florets at the periphery, and that their ability to achieve it depends on their having an outer, unoccupied, space which the inner florets have not; so that, though in a more indirect way, their different development is determined by different exposure to conditions.

One of my critics writes:--“This chapter might of course be enormously extended, not only as in the preceding ones by citation of quite similar cases, but by the introduction of fresh groups of cases.”

Natural selection may have operated in establishing a constitutional tendency to other sudden abridgments. Mr. Tansley alleges that this is a part-cause of the varying distribution of leaves. He says:--“I have myself made some observations on the length of internodes in the Beech, and am satisfied that it follows quite other laws, connected with the suitable disposition of the leaves on the branch. Although I have not had the opportunity of following up this line of work so as in any way to generalize the results, I suspect that ‘indirect equilibration’ is a widespread cause of such variation.”

It is but just to the memory of Wolff, here to point out that he was immensely in advance of Goethe in his rationale of these metamorphoses. Whatever greater elaboration Goethe gave to the theory considered as an induction, seems to me more than counter-balanced by the irrationality of his deductive interpretation; which unites mediæval physiology with Platonic philosophy. A dominant idea with him is that leaves exist for the purpose of carrying off crude juices--that “as long as there are crude juices to be carried off, the plant must be provided with organs competent to effect the task”; that while “the less pure fluids are got rid of, purer ones are introduced” and that “if nourishment is withheld, that operation of nature (flowering) is facilitated and hastened; the organs of the nodes (leaves) become more refined in texture, the action of the purified juices becomes stronger, and the transformation of parts having now become possible, takes place without delay.” This being the proximate explanation, the ultimate explanation is, that Nature wishes to form flowers--that when a plant flowers it “attains the end prescribed to it by nature”; and that so “Nature at length attains her object.” Instead of vitiating his induction by a teleology that is as unwarranted in its assigned object as in its assigned means, Wolff ascribes the phenomena to a cause which, whether sufficient or not, is strictly scientific in its character. Variation of nutrition is unquestionably a “true cause” of variation in plant-structure. We have here no imaginary action of a fictitious agency; but an ascertained action of a known agency.

The Natural History Review for July, 1865, contained an article on the doctrine of morphological composition set forth in the foregoing Chaps. I. to III. In this article, which unites exposition and criticism in a way that is unhappily not common with reviewers, it is suggested that the spiral structure may be caused by natural selection. When this article appeared, the foregoing five pages were standing over in type, as surplus from No. 14, issued in June, 1865.

A verifying comment on this paragraph runs as follows:--“In the Hypotricha Infusoria, which creep over solid surfaces, there is a differentiation between ventral and dorsal surface and an approach to bilateral symmetry. The ventral surface is provided with movable cilia, the dorsal with immobile setæ.”

Criticisms on the above passage have shown the need for naming sundry complications. These complications chiefly, if not wholly, arise from changes in modes of life--changes from the locomotive to the stationary, and from the stationary to the locomotive. Referring to my statement that (ignoring the spherical) the radial type is the lowest and must be taken as antecedent to the bilateral type, it is alleged that all existing “radial animals above Protozoa are probably derived from free-swimming, bilaterally-symmetrical animals.” If this is intended to include the planulæ of the hydroid polyps, then it seems rather a straining of the evidence. These locomotive embryos, described as severally having the structure of a gastrula with a closed mouth, can be said to show bilateralness only because the first two tentacles make their appearance on opposite sides of the mouth--a bilateralness which lasts only till two other tentacles make their appearance in a plane at right angles, so giving the radial structure. I think the criticism applies only to cases furnished by Echinoderms. The larvæ of these creatures have bilaterally-symmetrical structures, which they retain as long as they swim about and which such of them as fix themselves lose by becoming similarly related to conditions all round: the radial structure being retained by those types which, becoming subsequently detached, move about miscellaneously. But, as happens in some of the Sea-urchins and still more among the Holothurians, the structure is again made bilaterally-symmetrical by a locomotive life pursued with one end foremost. Should it be contended that the conditions and the forms are reciprocally influential--that either may initiate the other, it still remains unquestionable that ordinarily the conditions are the antecedents, as is so abundantly shown by plants.

Should it be proved that the Ascidian is a degraded vertebrate, then the argument will be strengthened; since loss of bilateral symmetry has gone along with change to asymmetrical conditions.

A critical comment made on this sentence runs as follows:--“The aërial roots of most epiphytic orchids contain chlorophyll in their cortex throughout their length, but the cortex being covered by a ‘velamen’ of air-containing cells which break up and reflect incident light, the green colour is not visible through this opaque coat. When moistened the cells of the velamen take up water and the green colour immediately shows through. Such roots do not however possess stomata. The roots of certain species of Angræcum, however, contain the whole of the assimilating tissue of the plant.”

The current doctrine that chlorophyll is the special substance concerned in vegetal assimilation, either as an agent or as an incidental product, must be taken with considerable qualification. Besides the fact that among the Algæ there are many red and brown kinds which thrive; and besides the fact that among the lower Archegoniates there are species which are purple or chocolate-coloured; there is the fact that Phænogams are not all green. We have the Copper-Beech, we have the black-purple Coleus Verschaffeltii, and we have the red variety of Cabbage, which seems to flourish as well as the other varieties. Chlorophyll, then, must be regarded simply as the most general of the colouring matters found in those parts of plants in which assimilation is being effected by the agency of light. Though it is always present along with the red and brown pigments, yet there is much evidence to show that these are the actual assimilative pigments.

This seems as fit a place as any for noting the fact, that the greater part of what we call beauty in the organic world, is in some way dependent on the sexual relation. It is not only so with the colours and odours of flowers. It is so, too, with the brilliant plumage of birds; and it is probable that the colours of the more conspicuous insects are in part similarly determined. The remarkable circumstance is, that these characteristics, which have originated by furthering the production of the best offspring, while they are naturally those which render the organisms possessing them attractive to one another, directly or indirectly, should also be those which are so generally attractive to us--those without which the fields and woods would lose half their charm. It is interesting, too, to observe how the conception of human beauty is in a considerable degree thus originated. And the trite observation that the element of beauty which grows out of the sexual relation is so predominant in æsthetic products--in music, in the drama, in fiction, in poetry--gains a new meaning when we see how deep down in organic nature this connexion extends.

Students of vegetal physiology, familiar with the controversies respecting sundry points dealt with in this chapter, will probably be surprised to find taken for granted in it, propositions which they have habitually regarded as open to doubt. Hence it seems needful to say that the conclusions here set forth, have resulted from investigations undertaken for the purpose of forming opinions on several unsettled questions which I had to treat, but which I could find in books no adequate data for treating. The details of these investigations, and the entire argument of which this chapter is partly an abstract, will be found in Appendix C.

To this implied inference it is objected that “excess of nutritive material does not necessarily lead to correspondingly increased growth.” My reply is that a concomitant factor is activity of the tissue, and that in its absence growth is not to be expected.

In recent years (since 1890) Prof. Wilhelm Roux, in essays on functional adaptation, has set forth some views akin to the foregoing in respect to the general belief they imply, though differing in respect of the physiological processes he indicates. The following relevant passage has been translated for me from an article of his in the Real-Encyclopädie der gesammten Heilkunde:--“A more complete theory of functional adaptation by the author is founded on the assumption that the ‘functional’ stimulus, or ‘the act of exercising the function’ (in muscles and glands), and especially, in the case of bones, the concussion and tension caused by stress and strain, exert a ‘trophic’ stimulus on the cells, in consequence of which, and along with an increased absorption of nutriment, they grow and eventually increase (or the osteoblasts at the point of greater stimulus form more bone); while, conversely, with continued inactivity, by absence of these stimuli the nourishment of the cell declines so that the waste is insufficiently replaced (or otherwise that the bone-substance gradually loses its power of resistance to the osteoblasts formed as a result of inactivity”).

An outline of the doctrine set forth in the following chapters, was originally published in the Westminster Review for April, 1852, under the title--A Theory of Population deduced from the General Law of Animal Fertility; and was shortly afterwards republished with a prefatory note stating that it must be accepted as a sketch which I hoped at some future time to elaborate. In now revising and completing it, I have omitted a non-essential part of the argument, while I have expanded the remainder by adding to the number of facts put in evidence, by meeting objections which want of space before obliged me to pass over, and by drawing various secondary conclusions. The original paper, with omissions, will be found in Appendix A to Volume I of this work.

I was here thinking only of the cases which are general among insects, but it seems that vertebrate animals, too, furnish cases. Mr. Cunningham writes:--“There is a curious instance of this in the Conger: the female grows to 6 or 7 feet long and a weight of 60 lbs. and upwards and then ceases to feed for 6 months while the eggs develop, and when the eggs are shed dies.”

I say “normal” for the purpose of excluding not only morbid growths but excess of fat.

To meet a possible criticism it should be remarked that this calculation assumes that the power of asexual reproduction is not exhausted by the end of the month. It has been found that “the successive fissions of Paramœcium cannot continue indefinitely. After some hundreds of generations the products of fission are small, have no mouth, and die unless before this they have been allowed to conjugate with individuals of another brood.” It may, however, be fairly taken for granted that “some hundreds of generations” would take longer than a month.

Even this number is far exceeded. Dr. Edward Klein, in a lecture he gave at the Royal Institution on June 2, 1898, asserted that 246 bacteria in a cubic centimetre of nutritive liquid would multiply to 20,000,000 in the course of twenty-four hours: a rate which, at the end of the third day, would give, as the offspring of one individual, 537,367,797,000,000.

It has since been shown that in Myrianida fasciata as many as 29 attached groups exist. See Cambridge Natural History, Vol. II, Worms, Rotifers and Polyzoa, p. 280.

To this passage Prof. MacBride appends the remark:--“This is quite proven now, and the statement as it stands is quite correct; but far better and more minutely worked out cases are to be found amongst the Infusoria. In Paramœcium for example, there are normally present a large macronucleus and a small micronucleus lying alongside of it. When two individuals adhere preparatory to conjugation, the macronucleus breaks up into fragments which are absorbed: the micronucleus--which has some time previously divided into two--begins to break up further and eventually forms eight bodies; all of these except one disappear; this last piece then divides into two; of these two one represents a male genital cell, for it passes over into the body of the other Paramœcium and fuses with one of the two corresponding nuclei there; thus each of the two individuals which adhere fertilizes the other. The two individuals then separate and the nucleus (result of fusion of male and female nuclei) in each divides into four. Of these, two move to one end of the animal and two to the other. The animal then divides into two transversely--each of the products thus having two nuclei which form the micro-and macronucleus of it. Thus it appears that the function of sexual union is simply to give increased vigour to all the vital processes including fission. Since as mentioned above (p. 443) if it is prevented, the products of fission are eventually unable to feed themselves.”

A passage translated for me from the German may be here given in verification. Dr. Dionys Hellin in an essay on the origin of Multiparity and Twin-births, refers to the thesis above set forth, and says that “the fact that it is generally women of small growth who bear twins is in complete agreement with it.” He adds that “Puech is right in his opinion that twin pregnancies are a direct result of relatively large ovaries (i.e., in comparison with the whole body). He has observed that for the same size of body the ovarium of a pluriparous animal is always of greater volume than that of a uniparous animal ... a sow has ovaries as large as a cow’s; but while the latter bears only one calf [at a time], the sow brings forth 6–15 at each litter. Even in animals of the same species but belonging to different races these relations may be verified,” e.g., Barbary sheep and ordinary sheep.

When, after having held for some years the general doctrine elaborated in these chapters, I agreed, early in 1852, to prepare an outline of it for the Westminster Review, I consulted, among other works, the just-issued third edition of Dr. Carpenter’s Principles of Physiology, General and Comparative--seeking in it for facts illustrating the different degrees of fertility of different organisms, I met with a passage, quoted above in § 339, which seemed tacitly to assert that individual aggrandizement is at variance with the propagation of the race; but nowhere found a distinct enunciation of this truth. I did not then read the Chapter entitled “General View of the Functions,” which held out no promise of such evidence as I was looking for. But on since referring to this chapter, I discovered in it the definite statement that--“there is a certain degree of antagonism between the Nutritive and Reproductive functions, the one being executed at the expense of the other. The reproductive apparatus derives the materials of its operations through the nutritive system, and is entirely dependent upon it for the continuance of its function. If, therefore, it be in a state of excessive activity, it will necessarily draw off from the individual fabric some portion of the aliment destined for its maintenance. It may be universally observed that, when the nutritive functions are particularly active in supporting the individual, the reproductive system is in a corresponding degree undeveloped,--and vice versâ.” P. 592.

The climate, the locality, and the kind of food, are of course all factors; and hence, probably, the differences between the statements of different authorities concerning these several cases. Prof. MacBride writes:--

“According to Flower (Mammals, Living and Extinct) the Ferret is a domesticated variety of the common polecat, which has 3 to 8 young. Darwin (Animals and Plants) says that the wild sow often breeds twice a year and produces a litter of 4 to 8, and sometimes even 12. The domestic sow breeds twice and would breed oftener if permitted, and if any good at all produces 8 in litter.”

It is worth while inquiring whether unfitness of the food given to them, is not the chief cause of that sterility which, as Mr. Darwin says, “is the great bar to the domestication of animals.” He remarks that “when animals and plants are removed from their natural conditions, they are extremely liable to have their reproductive systems seriously affected.” Possibly the relative or absolute arrest of genesis, is less due to a direct effect on the reproductive system, than to a changed nutrition of which the reproductive system most clearly shows the results. The matters required for forming an embryo are in a greater proportion nitrogenous than are the matters required for maintaining an adult. Hence, an animal forced to live on insufficiently-nitrogenized food, may have its surplus for reproduction cut off, but still have a sufficiency to keep its own tissues in repair, and appear to be in good health--meanwhile increasing in bulk from excess of the non-nitrogenous matters it eats.

Huxley, Anatomy of Invertebrated Animals, p. 274.

Shipley, Zoology of Invertebrata, p. 112.

I am told that “Wagner, who described the larva, found that it bored into the bark of trees. It attacks also the wheat plant, and is a most destructive parasite.” Apparently this statement is at variance with the foregoing inference. It is clear, however, that since these heaps of nitrogenous refuse in which it has been found are artificial and recent, they cannot be its natural habitats; and it seems not improbable that these larvæ, suddenly supplied with a more nutritive food in unlimited amount, may have as a consequence acquired this habit of agamogenetic multiplication which did not characterize the species under its natural conditions and relatively low nutrition.

This is exactly the reverse of Mr. Doubleday’s doctrine; which is that throughout both the animal and vegetable kingdoms, “over-feeding checks increase; whilst, on the other hand, a limited or deficient nutriment stimulates and adds to it.” Or, as he elsewhere says--“Be the range of the natural power to increase in any species what it may, the plethoric state invariably checks it, and the deplethoric state invariably develops it; and this happens in the exact ratio of the intensity and completeness of each state, until each state be carried so far as to bring about the actual death of the animal or plant itself.”

I have space here only to indicate the misinterpretations on which Mr. Doubleday has based his argument.

In the first place, he has confounded normal plethora with what I have, in § 355, distinguished as abnormal plethora. The cases of infertility accompanying fatness, which he cites in proof that over-feeding checks increase, are not cases of high nutrition properly so-called; but cases of such defective absorption or assimilation as constitutes low nutrition. In Chap. IX, abundant proof was given that a truly plethoric state is an unusually fertile state. It may be added that much of the evidence by which Mr. Doubleday seeks to show that among men, highly-fed classes are infertile classes, may be out-balanced by counter-evidence. Many years ago Mr. G. H. Lewes pointed this out: extracting from a book on the peerage, the names of 16 peers who had, at that time, 186 children; giving an average of 11·6 in a family.

Mr. Doubleday insists much on the support given to his theory by the barrenness of very luxuriant plants, and the fruitfulness produced in plants by depletion. Had he been aware that the change from barrenness to fruitfulness in plants, is a change from agamogenesis to gamogenesis--had it been as well known at the time when he wrote as it is now, that a tree which goes on putting out sexless shoots, is thus producing new individuals; and that when it begins to bear fruit, it simply begins to produce new individuals after another manner--he would have perceived that facts of this class do not tell in his favour.

In the law which Mr. Doubleday alleges, he sees a guarantee for the maintenance of species. He argues that the plethoric state of the individuals constituting any race of organisms, presupposes conditions so favourable to life that the race can be in no danger; and that rapidity of multiplication becomes needless. Conversely, he argues that a deplethoric state implies unfavourable conditions--implies, consequently, unusual mortality; that is--implies a necessity for increased fertility to prevent the race from dying out. It may be readily shown, however, that such an arrangement would be the reverse of self-adjusting. Suppose a species, too numerous for its food, to be in the resulting deplethoric state. It will, according to Mr. Doubleday, become unusually fertile; and the next generation will be more numerous rather than less numerous. For, by the hypothesis, the unusual fertility due to the deplethoric state, is the cause of undue increase of population. But if the next generation is more numerous while the supply of food has not increased in proportion, then this next generation will be in a still more deplethoric state, and will be still more fertile. Thus there will go on an ever-increasing rate of multiplication, and an ever-decreasing share of food, for each person, until the species disappears. Suppose, on the other hand, the members of a species to be in an unusually plethoric state. Their rate of multiplication, ordinarily sufficient to maintain their numbers, will become insufficient to maintain their numbers. In the next generation, therefore, there will be fewer to eat the already abundant food, which becoming relatively still more abundant, will render the fewer members of the species still more plethoric, and still less fertile, than their parents. And the actions and reactions continuing, the species will presently die out from absolute barrenness.

A good deal of this chapter retains its original form; and the above paragraph is reprinted verbatim from the Westminster Review for April, 1852, in which the views developed in the foregoing hundred pages were first sketched out. This paragraph shows how near one may be to a great generalization without seeing it. Though the struggle for life is the alleged motive force; though the process of natural selection is recognized; and though to it is ascribed a share in the evolution of a higher type; yet the conception is not that which Mr. Darwin has worked out with such wonderful skill and knowledge. In the first place, natural selection is here described only as furthering direct adaptation--only as aiding progress by the preservation of individuals in whom functionally-produced modifications have gone on most favourably. In the second place, there is no trace of the idea that natural selection may by co-operation with the cause assigned, or with other causes, produce divergences of structure; and of course, in the absence of this idea, there is no implication that natural selection has anything to do with the origin of species. And in the third place, the all-important factor of variation--“spontaneous,” or incidental as we may otherwise call it--is wholly ignored. Though use and disuse are, I think, much more potent causes of organic modification than Mr. Darwin supposes--though, while pursuing the inquiry in detail, I have been led to believe that direct equilibration has played a more active part even than I had myself at one time thought; yet I hold Mr. Darwin to have shown beyond question, that a great part of the facts--perhaps the greater part--are explicable only as resulting from the survival of individuals which have deviated in some indirectly-caused way from the ancestral type. Thus, the above paragraph contains merely a passing recognition of the selective process; and indicates no suspicion of the enormous range of its effects, or of the conditions under which a large part of its effects are produced.

For the information of those who may wish to examine metamorphoses of these kinds, I may here state that I have found nearly all the examples described, in the neighbourhood of the sea--the last-named, on the shore of Locheil, near Fort William. Whether it is that I have sought more diligently for cases when in such localities, or whether it is that the sea-air favours that excessive nutrition whence these transformations result, I am unable to say.

These two dyes have affinities for different components of the tissues, and may be advantageously used in different cases. Magenta is rapidly taken up by woody matter and other secondary deposits; while logwood colours the cell-membranes, and takes but reluctantly to the substances seized by magenta. By trying both of them on the same structure, we may guard ourselves against any error arising from selective combination.

Those who repeat these experiments must be prepared for great irregularities in the rates of absorption. Succulent structures in general absorb much more slowly than others, and sometimes will scarcely take up the dye at all. The differences between different structures, and the same structure at different times, probably depend on the degrees in which the tissues are charged with liquid and the rates at which they are losing it by evaporation.

It may be added here that, on considering the mechanical actions that must go on, we are enabled in some measure to understand both how such inosculating channels are initiated, and how the structures of their component cells are explicable. What must happen to one of these elongated prosenchyma-cells if, in the course of its development, it is subject to intermittent compressions? Its squeezed-out liquid while partially escaping laterally, will more largely escape upwards and downwards; and while repeated lateral escape will tend to form lateral channels communicating with laterally-adjacent cells, repeated longitudinal escape will tend to form channels communicating with longitudinally-adjacent cells--so producing continuous though irregular longitudinal canals. Meanwhile each cell into and out of which the nutritive liquid is from time to time squeezed through small openings in its walls, cannot thicken internally in an even manner: deposition will be interfered with by the passage of the currents through the pores. The rush to or from each pore will tend to maintain a funnel-shaped depression in the deposit around; and the opening from cell to cell will so acquire just that shape which the microscope shows up--two hollow cones with their apices meeting at the point where the cell-membranes are in contact. Moreover, as confirming this interpretation, it may be remarked that we are thus supplied with a reason for the differences of shape between these passages from one pitted cell to another, and the analogous passages that exist between cells otherwise formed and otherwise conditioned. In the cells of the medulla, and others which are but little exposed to compression, the passages are severally formed more like a tube with two trumpet-mouths, one in each cell. This is just the form which might be expected where the nutritive fluid passes from cell to cell in moderate currents, and not by the violent rushes caused by intermittent pressures. Of course it is not meant that in each individual cell these structures are determined by these mechanical actions. The facts clearly negative any such conclusion, showing us, as they in many cases do, that these structures are assumed in advance of these mechanical actions. The implication is, that such mechanical actions initiated modifications that have, with the aid of natural selection, been accumulated from generation to generation; until, in conformity with ordinary embryological laws, the cells of the parts exposed to such actions assume these special structures irrespective of the actions--the actions, however, still serving to aid and complete the assumption of the inherited type.

Some exceptions to this occur in plants that have retrograded in the character of their tissues towards the simpler vegetal types. Certain very succulent leaves, such as those of Sempervivum, in which the cellular tissue is immensely developed in comparison with the vascular tissue, seem to have resumed to a considerable extent what we must regard as the primitive form of vegetal circulation--simple absorption from cell to cell. These, when they have lost much of their water, will take up the dye to some distance through their general substance, or rather through its interstices, even neglecting the vessels. At other times, in the same leaves, the vessels will become charged while comparatively little absorption takes place through the cellular tissue. Even in these exceptional cases, however, the movement through cellular tissue is nothing like as fast as the movement through vessels.

It seems probable, however, that osmotic distention is here, especially, the more important of the two factors. The rising of the sap in spring may indirectly result, like the sprouting of the seed, from the transformation of starch into sugar. During germination, this change of an oxy-hydro-carbon from an insoluble into a soluble form, leads to rapid endosmose; consequently to great distention of the seed; and therefore to a force which thrusts the contained liquids into the plumule and radicle, and gives them power to displace the soil in their way: it sets up an active internal movement when neither evaporation nor the change which light produces can be operative. And similarly, if, in the spring, the starch stored-up in the roots of a tree passes into the form of sugar, the unusual osmotic absorption that arises will cause an unusual distention--a distention which, being resisted by the tough bark of the roots and stem, will result in a powerful upward thrust of the contained liquid.

Transcriber’s Note:

1. Obvious printers’, spelling and punctuation errors have been silently corrected.

2. Where appropriate, original spelling has been retained.

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