Part 26

Do you observe these two round fleshy leaves, just peeping from the sandy earth? They are the earliest growths of a plant of Arachis hypogaea. In this case again, to understand the true relations of this organism, we must expose it wholly to view.

Beneath the surface of the earth, then, I find that these seed-leaves are the two halves (cotyledons) of a kind of pea, which was formerly enclosed in a wrinkled skinny pod. But what is most interesting is that the pod is here, the cotyledons shooting out of it. And, attached to one end of the pod, here is a slender stalk, now withered and dry, which projects out of the ground into the air.

Now here we have a beautiful link of connexion with the past. The plant before us does not ripen its seeds, and then drop them to care for themselves, as most plants do. "The young fruit, instead of being placed at the bottom of the calyx, as in other kinds of pulse, is found at the bottom and in the inside of a long slender tube, which looks like a flower-stalk. When the flower has withered, and the young fruit is fertilized, nothing but the bottom of the tube with its contents remains. At this period a small point projects from the summit of the young fruit, and gradually elongates, curving downwards towards the earth. At the same time the stalk of the fruit lengthens, until the small point strikes the earth, into which the now half-grown fruit is speedily forced, and where it finally ripens in what would seem a most unnatural position."

The young plant before us has been this moment created, and created in this incipient stage of growth: and yet there is, even here, an indubitable evidence, so far as physical phenomena can afford it, of a past history. It would be utterly impossible to select any stage in the life of the Earth-pea, which did not connect itself, visibly and palpably, with a previous stage.

Let us return to the shore-loving Mangrove. You object to my assumption that it was created as a tree, with a well-branched stem elevated upon a series of arching roots; and to my deduction of pre-lapsed years for the formation of those roots. Very well. I give it up. You allow that the primitive Mangrove was created in some stage, but you contend for the germ-stage, the simplest condition of the plant, whatever that might be.

Now, where shall we find it? In the first pair of developed leaves? They certainly point back to the cotyledons. To the cotyledons, then, let us look.

Lo! the young plant is germinating before its connexion with the parent is severed. It is the singular habit of this tree, that its seeds are already in a growing condition, while they hang from the twig. Each seed is a long club-shaped body, with a bulbous base and a slender point, more or less produced. While it yet hangs from the branch, the radicle and crown of the root begin to grow, and gradually lengthen, until the tip reaches the soil, which it penetrates and thus roots itself; while those which depend from the higher branches, after growing for a while, drop, and, sticking in the mud, throw out roots from one end, and leaves from the other.

What have you gained, then, in this case, by going back to the germ? The germ as decisively asserts its origination from an already existing organism--the parent tree--as the flourishing tree witnesses its gradual development from a germ. The Mangrove could not by possibility have been created in any stage, consistent with the identity of the species with that which we behold now in the nineteenth century,--that did not show ocular evidence of a previous history;--evidence from the nature of things fallacious.

It would be merely tiresome to go on through the vegetable kingdom. In every plant the simplest condition--viz. that of a spore or seed--depends on some development, or process, or series of processes, that have preceded it. Nor does the lapse of time between the previous process and the apparent result at all destroy their necessary connexion. In the case of the curious Misseltoes, the ovule does not appear till three months after the pollen has been shed; but when it does appear, its existence as an organism capable of developing the characteristic form of its species, is as truly dependent on the previous existence of the pollen, as if not an hour had intervened.

Supposing the essential conditions of vegetable organisms to have been at the first what they are now; in other words, supposing specific identity to have been always maintained,--which I have demanded as a postulate for this argument,--it appears to me demonstrable, that every plant in the world presented at the moment of its creation evidences prochronic development, in nowise to be distinguished from those on which we firmly rely as proving the lapse of time.

But is the case otherwise in the animal world?

We traced back the history of our Medusa through its marvellous series of gemmative developments, till we reached the minute Infusory-like gemmule, which is its simplest form. Now it is quite legitimate to assume that this, and not the pulmonigrade umbrelliform stage, was the one in which the new-created Medusa began existence. Have we, then, got rid of the evidence of past time, which we deduced from the successive changes through which the adult had passed? What is this ciliated planule, and whence comes it? It is the embryo discharged from the fringed ovary of a female Medusa; it has already passed through several changes of colour and form. It is now of a deep yellow colour; it has been violet; it has been colourless: it is now shaped like a dumb-bell; it was a globule; it had been a mulberry-mass. Yet earlier, it had been a component cell of the ovarian band, which divided the generative cavity from that of the stomach, in the parent Medusa.

In like manner the ciliated gemmule from which was formed the "pluteus" of the Urchin, was dependent on the existence of a parent Urchin; the monadiform germ from which was developed the pentacrinus of the Feather-star, was originally hidden in the ovarian tubes of a parent Feather-Star: the infant Serpula that deposited the first atoms of calcareous matter as a commenced tube, had begun its own existence in the body of a parent Serpula.

It is true the evidence of the connexion between the germ and the parent is not in these low forms always patent to the eye; it is physiological. But it is not less conclusive to one who is able to appreciate its force. A physiologist is as sure that every germ, every ovum, in the Invertebrate animals, was produced by an animal of a former generation, as he is of the same fact in a Mammal, where his eye can see the scar of the umbilical cord.

In many instances there is stronger, or rather more obvious and ordinarily appreciable, evidence of the link between the present and the past generation, than the physiological dependence. The world of Insects, which, from its immensity, and from the high organic rank of its members, affords us so exhaustless a mine of economical wonders,--is rich in examples to the point. A few of these I shall cite.

The eggs of many Insects are not dropped anywhere, at random; for, as the newly-born young have limited powers of locomotion, and yet are in general able to subsist only on some particular kind of food, it is necessary that their birth should occur in the immediate proximity of such food: and therefore that the egg should be so placed. Now this circumstance would not be specially noteworthy if the locality selected for the deposition of the egg were the same as that in which the parent insect had been accustomed to find its own private enjoyments: we should reasonably say that the eggs were placed here, because the parents happened to be here. The case, however, is very different.

We never find the egg of the Peacock Butterfly adhering to the leaf of a cabbage, nor that of the Garden White to the leaf of a nettle; but the nettle is invariably selected for the former, and a cruciferous plant for the latter.

Yet there is nothing in the individual wants or likings of the Butterfly, in either case, to account for this. Both the one and the other flutter through the sunny air, alight to drink the water of some slushy pool, rest on the expanding flowers and probe them for nectar, or suck the exuding juices of an over-ripe fruit. But when did you ever see the gorgeous-eyed Peacock feeding on a nettle, or the White on a cabbage? Eagerly as they seek these plants, it is solely for the purpose of depositing their eggs where instinct teaches them their unborn progeny will find suitable food.

Supposing, therefore, we had found the egg of either of these butterflies at the moment of its creation, we should assuredly have found it on the nettle or the cabbage (as the case might be); because to suppose it in any other situation would be equivalent to supposing it so placed as that the end of its creation--the life of the species created--would be ipso facto frustrated. But, finding it so, the question naturally arises,--Why here, and not elsewhere? and the only possible answer, on the ground of phenomena, is, Because the parent chose this situation for it. And thus we are inevitably thrown back to an anterior generation, which is equivalent to past time.

Again, if we had seen the egg of the Nut Weevil (Balaninus nucum) just come from the creative hand of God, we should certainly have found it within the immature soft-shelled hazel-nut, because there alone would the grub when hatched meet with "food convenient for" it. And yet if we had sought (ignorant of the fact of its recent creation) the reason of its being there, our acquaintance with entomology would have pointed to the parent beetle, who, with her jaws placed at the tip of a long slender snout, had bored a tiny hole in the tender shell, and had then projected the egg from her abdomen into the interior.

The eggs of the Oestridae--for example, the Worble of the Ox (Oestrus bovis) or the Bot of the Sheep (Oe. ovis)--would be discovered in no other circumstances than beneath the skin of the former, and at the edge of the nostrils of the latter. For these are the respective situations in which the egg is always deposited, that of the Worble hatching in situ, and forming a superficial abscess in communication with the external air, and that of the Sheep-bot producing a larva which crawls up the nostrils of the poor animal, till it finds a suitable resting-place in the frontal sinuses of the skull. To suppose the egg in any other circumstances than those which I have mentioned, would be to consign it to certain destruction. Yet does not its presence there bear witness to the eclectic care of the parent Gadfly, whose unerring instinct knew how to seek and select the right position?

If you had set yourself to look for the egg of a Pimpla manifestator, a common Cuckoo-fly, where would you have looked for it, but in the fatty tissues of a wild bee's grub, that was lodged in a deep hole in some old post? If you had sought elsewhere, you would surely have been disappointed. And would not its presence there bear testimony to the lengthened ovipositor of the well-known brisk and busy fly, and to its remarkable habits?

The grub of the Pill Chafer or Tumble-dung Beetle (Phanaeus) feeds on the ordure of Mammalia. And, in order that the newly-hatched young may have a copious supply of food at hand, the parent chafer with its jaws detaches a mass of recent ordure, which it then rolls over the ground with its hind feet, until it acquires a globular form, and a coating of earth or sand. An egg is then deposited in the centre of the ball, which is rolled into a hole made in the earth to receive it. The coating of earth drying and hardening, keeps the interior of the mass fresh and moist until the young grub is hatched, when it at once begins to devour its savoury and delicate provision.

It would be vain to search for the egg of a Cynips except within a vegetable gall, or at least within the tissues of a plant that are going to produce one. Take as an example C. quercus, which produces the spongy excrescence well known as the common Oak-apple. The female Gall-fly is furnished with an ovipositor in the shape of a very fine curved needle, with which she punctures the tender bark of an oak shoot, lodging an egg in the perforation. Stimulated by some fluid, probably, which is poured into the wound at the same time, the sap forms a peculiar tissue around the egg, swelling into a large ball, on which the young grub begins to feed eagerly, and in which it finds the only nutriment on which it could subsist.

Now, if we had found the egg of a Gall-fly newly created, we should certainly have found it in a gall; and the gall would have afforded us indubitable evidence of the wounding of the vegetable tissues, and of the organ, secretion, and instinct of the tiny fly by which the process had been effected. The evidence would be irresistible, but of course it would be fallacious.

Let us now look at a few examples in which the egg is found in invariable association not merely with something that the parent has found for it, but with something that has proceeded from her, a part of herself.

Of this nature are the eggs of that beautiful, but most cacodious, lace-winged fly, Chrysopa perla. If you had seen one of these (or more) at the instant of its creation, you would have seen a tiny oval body placed at the extremity of an elastic footstalk half-an-inch in length, and as fine as a hair, standing erect from the surface of a leaf. This thread is composed of a gummy secretion, evolved in a gland attached to the oviduct of the female Lace-fly. When she deposits an egg, she first exudes a drop of this gum on the surface of a leaf, and then, elevating her abdomen, the viscid substance is drawn out in a thread, which presently hardening in the air, the egg is left at the tip of the filament. An experienced entomologist, on seeing this object, would have no hesitation in declaring the origin of the footstalk to be the gum-gland of the female Chrysopa; and yet he would certainly have drawn a false inference in the case that I am supposing.

Many Spiders enclose their eggs in an envelope, the produce of their own bowels. Take an interesting example, as narrated by the eloquent Mr. Kirby. "There is a Spider common under clods of earth (Lycosa saccata), which may at once be distinguished by a white globular silken bag, about the size of a pea, in which she has deposited her eggs, attached to the extremity of her body. Never miser clung to his treasure with more tenacious solicitude than this spider to her bag. Though apparently a considerable incumbrance, she carries it with her everywhere. If you deprive her of it, she makes the most strenuous efforts for its recovery; and no personal danger can force her to quit the precious load. Are her efforts ineffectual? a stupefying melancholy seems to seize her; and, when deprived of this first object of her cares, existence itself appears to have lost its charms. If she succeeds in regaining her bag, or you restore it to her, her actions demonstrate the excess of her joy. She eagerly seizes it, and with the utmost agility runs off with it to a place of security.