Part 13

Still, however, the question of organization remains. Did these ancient Placoid fishes stand high or low in the scale? According to the poet, “What can we reason but from what we know?” We are acquainted with the Placoid fishes of the present time; and from these only, taking analogy as our guide, can we form any judgment regarding the rank and standing of their predecessors, the Placoids of the geologic periods. But the consideration of this question, as it is specially one on which the later assertors of the development hypothesis concentrate themselves, I must, to secure the space necessary for its discussion, defer till my next chapter. Meanwhile, I am conscious I owe an apology to the reader for what he must deem tedious minuteness of description, and a too prolix amplitude of statement. It is only by representing things as they actually are, and in the true order of their occurrence, that the effect of the partially selected facts and exaggerated descriptions of the Lamarckian can be adequately met. True, the disadvantages of the more sober mode are unavoidably great. He who feels himself at liberty to arrange his collected shells, corals, and fish-bones, into artistically designed figures, and to select only the pretty ones, will be of course able to make of them a much finer show than he who is necessitated to represent them in the order and numerical proportions in which they occur on some pebbly beach washed by the sea. And such is the advantage, in a literary point of view, of the ingenious theorist, who, in making figures of his geological facts, takes no more of them than suits his purpose, over the man who has to communicate the facts as he finds them. But the homelier mode is the true one. “Could we obtain,” says a distinguished metaphysician, “a distinct and full history of all that has passed in the mind of a child, from the beginning of life and sensation till it grows up to the use of reason,—how its infant faculties began to work, and how they brought forth and ripened all the various notions, opinions, and sentiments which we find in ourselves when we come to be capable of reflection,—this would be a treasure of natural history which would probably give more light into the human faculties than all the systems of philosophers about them since the beginning of the world. But it is in vain,” he adds, “to wish for what nature has not put within the reach of our power.” In like manner, could we obtain, it may be remarked, a full and distinct account of a single class of the animal kingdom, from its first appearance till the present time, “this would be a treasure of natural history which would cast more light” on the origin of living existences, and the true economy of creation, than all the theories of all the philosophers “since the beginning of the world.” And in order to approximate to such a history as nearly as possible,—and it does seem possible to approximate near enough to substantiate the true readings of the volume, and to correct the false ones,—it is necessary that the real vestiges of creation should be carefully investigated, and their order of succession ascertained.

HIGH STANDING OF THE PLACOIDS.—OBJECTIONS CONSIDERED.

We have seen that some of the Silurian Placoids were large of size: the question still remains, Were they high in intelligence and organization?

The Edinburgh Reviewer, in contending with the author of the “Vestiges,” replies in the affirmative, by claiming for them the first place among fishes. “Taking into account,” he says, “the brain and the whole nervous, circulating, and generative systems, they stand at the highest point of a natural ascending scale.” They are fishes, he again remarks, that rank among “the very highest types of their class.”

“The fishes of this early age, and of all other ages previous to the Chalk,” says his antagonist, in reply, “are, for the most part, cartilaginous. The cartilaginous fishes—Chondropterygii of Cuvier—are placed by that naturalist as a second series in his descending scale; being, however, he says, ‘in some measure parallel to the first.’ How far this is different from their being the highest types of the fish class, need not be largely insisted upon. Linnæus, again, was so impressed by the low characters of many of this order, that he actually ranked them with worms. Some of the cartilaginous fishes, nevertheless, have certain peculiar features of organization, chiefly connected with reproduction, in which they excel other fish; but such features are partly partaken of by families in inferior sub-kingdoms, showing that they cannot truly be regarded as marks of grade in their own class. When we look to the great fundamental characters particularly to the framework for the attachment of the muscles, what do we find?—why, that of these Placoids,—‘the highest types of their class,’—it is barely possible to establish their being vertebrata at all, the back-bone having generally been too slight for preservation, although the vertebral columns of later fossil fishes are as entire as those of any other animals. In many of them traces can be observed of the muscles having been attached to the external plates, strikingly indicating their low grade as vertebrate animals. The Edinburgh Reviewer ‘highest types of their class’ are in reality a separate series of that class, generally inferior, taking the leading features of organization of structure as a criterion, but when details of organization are regarded, stretching farther, both downward and upward, than the other series; so that, looking at one extremity, we are as much entitled to call them the lowest, as the Reviewer, looking at another extremity, is to call them the ‘highest of their class.’ Of the general inferiority there can be no room for doubt. Their cartilaginous structure is, in the first place, analogous to the embryonic state of vertebrated animals in general. The maxillary and intermaxillary bones are in them rudimental. Their tails are finned on the under side only,—an admitted feature of the salmon in an embryonic stage; and the mouth is placed on the under side of the head,—also a mean and embryonic feature of structure. These characters are essential and important, whatever the Edinburgh Reviewer may say to the contrary; they are the characters which, above all, I am chiefly concerned in looking to, for they are features of embryonic progress, and embryonic progress is the grand key to the theory of development.”

Such is the ingenious piece of special pleading which this most popular of the Lamarckians directs against the standing and organization of the earlier fishes. Let us examine it somewhat in detail, and see whether the slight admixture of truth which it contains serves to do aught more than to render current, like the gilding of a counterfeit guinea spread over the base metal, the amount of error which lies beneath. I know not a better example than that which it furnishes, of the entanglement and perplexity which the meshes of an artificial classification, when converted, in argumentative processes, into symbols and abstractions, are sure to involve subjects simple enough in themselves.

Fishes, according to the classification of a preponderating majority of the ichthyologists that have flourished from the earliest times down to those of Agassiz, have been divided into two great series, the Ordinary or osseous, and the Chondropterygii or cartilaginous. And these two divisions of the class, instead of being ranged consecutively in a continuous line, the one in advance of the other, have been ranged in two parallel lines, the one directly abreast of the other. There is this further peculiarity in the arrangement, that the line of the cartilaginous series, from the circumstance that some of its families rise higher and some sink lower in the scale than any of the ordinary fishes, outflanks the array of the osseous series at both ends. The front which it presents contains fewer genera and species than that of the osseous division; but, like the front of an army drawn out in single file, it extends along a greater length of ground. And to this long-fronted series of the cartilaginous, or, according to Cuvier, chondropterygian fishes, the Placoid families of Agassiz belong,—among the rest, the Placoids of the Silurian formations, Upper and Lower. But though all the Placoids of this latter naturalist be cartilaginous fishes, all cartilaginous fishes are not Placoids. The Sturionidæ are cartilaginous, and are, as such, ranked by Cuvier among the Chondropterygii, whereas Agassiz places them in his Ganoid order. Many of the extinct fishes, too, such as the Acanthodei, Dipteridæ, Cephalaspidæ, were, as we have seen, cartilaginous in their internal framework, and yet true Ganoids notwithstanding. The principle of Agassiz’s classification wholly differs from that of Cuvier and the older ichthyologists; for it is a classification founded, not on the character of the internal but on that of the cuticular or dermal skeleton. And while to the geologist it possesses great and obvious advantages over every other,—for of the earlier fishes very little more than the cuticular skeleton survives,—it has this further recommendation to the naturalist, that, (in so far at least as its author has been true to his own principles,) instead of anomalously uniting the highest and lowest specimens of their class,—the fishes that most nearly approximate to the reptiles on the one hand, and the fishes that sink furthest towards the worms on the other,—it gathers into one consistent order all the individuals of the higher type, distinguished above their fellows by their development of brain, the extensive range of their instincts, and the perfection of their generative systems. Further, the history of animal existences, as recorded in the sedimentary rocks of our planet, reads a recommendation of this scheme of classification which it extends to no other. We find that in the progress of creation the fishes began to be by groupes and septs, arranged according to the principle on which it erects its orders. The Placoids came first, the Ganoids succeeded them, and the Ctenoids and Cycloids brought up the rear. The march has been marshalled according to an appointed programme, the order of which it is peculiarly the merit of Agassiz to have ascertained.

Now, may I request the reader to mark, in the first place that what we have specially to deal with at the present stage of the argument are the Placoid fishes of the Silurian formations, Upper and Lower. May I ask him to take note, in the second, that the long-fronted chondropterygian series of Cuvier, though it includes, as has already been said, the Placoid order of Agassiz,—just as the red-blooded division of animals includes the bimana and quadrumana,—is no more to be regarded as identical with the Placoids, than the red-blooded animals are to be regarded as identical with the apes or with the human family. It simply includes them in the character of one of the three great divisions into which it has been separated,—the division ranged, if I may so express myself, on the extreme right of the line; its middle portion, or main body, being composed of the Sturiones, a family on the general level of the osseous fishes; while, ranged on the extreme left, we find the low division of the Suctorii, i. e. Cyclostomi, or Lampreys. But with the middle and lower divisions we have at present nothing to do; for of neither of them, whether Sturiones or Suctorii, does the Silurian System exhibit a trace. Further be it remarked, that the scheme of classification which gives an abstract standing to the Chondropterygii, is in itself merely a certain perception of resemblance which existed in certain minds, having cartilage for its general idea; just as another certain perception of resemblance in one other certain mind had cuticular skeleton for its general idea, and as yet another perception of resemblance in yet other certain minds had red blood for its general idea. As shown by the disparities which obtain among the section which the scheme serves to separate from the others, it no more determines rank or standing than that greatly more ancient scheme of classification into “ring-streaked and spotted,” which served to distinguish the flocks of the patriarch Jacob from those of Laban his father-in-law, but which did not distinguish goats from sheep, nor sheep from cattle.

The effect of introducing, after this manner, generalizations made altogether irrespective of rank, and avowedly without reference to it, into what are inherently and specifically questions of rank, admits of a simple illustration.

Let us suppose that it was not with the standing of the Silurian Placoids that we had to deal, but with that of the mammals of the recent period, including the quadrumana, and even the bimana, and that we had ventured to describe them, in the words of the Edinburgh Reviewer, as “the very highest types of their class.” What would be thought of the reasoner who, in challenging the justice of the estimate, would argue that these creatures, men as well as monkeys, belonged simply to that division of red-blooded animals which includes, with the bimana and quadrumana, the frog, the gudgeon, and the earthworm?—a division, he might add, “which, when details of organization are regarded, stretches farther, both downward and upward,” than that division of the white-blooded animals to which the crab, the spider, the cuttle-fish, and the dragon fly belong; “so that, looking at one extremity, any one is as much entitled to call the red-blooded animals the lowest division, as any other, looking at another extremity, is to call them the highest division, of animals.” What, it might well be asked in reply, has the earthworm, with its red-blood to do in a question respecting the place and standing of the bimana? Or what, in the parallel case, have the Suctorii—the worms of Linnæus—to do in a question respecting the place and standing of the real Placoids? True it is that, according to one principle of classification, now grown somewhat obsolete, men and earthworms are equally red-blooded animals; true it is that, according to another principle of classification, the Placoids of Agassiz and the cartilaginous worms of Linnæus are equally Chondropterygii. The bimana and the earthworm have their red blood in common; the glutinous hag and the true Placoids have as certainly their internal cartilage in common; and if the fact of the red blood of the worm lowers in no degree the rank of the bimana, then, on the same principle, the fact of the internal cartilage of the glutinous hag cannot possibly detract from the standing of the true Placoid. In both cases they are creatures that entirely differ,—the earthworms from the bimana, and the cartilaginous worms from the Placoids; and the classification which tags them together, whether it be that of Aristotle or that of Cuvier, cannot be converted into a sort of minus quantity, of force enough to detract from the value and standing of the bimana in the one case, or of the true Placoids in the other. It is in no degree derogatory to the human family that earthworms possess red blood; it is in no degree derogatory to the true Placoids that the Suctorii possess cartilaginous skeletons.

Let the reader now mark the use which has been made, by the author of the “Vestiges,” of the name and authority of Linnæus. “Linnæus,” he states, “was so impressed by the low character of many of this order, (the Chondropterygii,) that he actually ranked them with worms.” Now, what is the fact here? Simply that Linnæus had no such general order as the Chondropterygii in his eye at all. Though chiefly remarkable as a naturalist for the artificialness of his classifications, his estimate of the cartilaginous fishes was remarkable—though carried too far in its extremes, and in some degree founded in error—for an opposite quality. It was an estimate formed, in the main, on a natural basis. Instead of taking their cartilaginous skeleton into account, he looked chiefly at their standing as animals; and, struck with that extent of front which they present, and with both their superiority on the extreme right, and their inferiority on the extreme left, to the ordinary fishes, he erected them into two separate orders, the one lower and the other higher than the members of the osseous line. And so far was he from regarding the true Placoids—those Chondropterygii which to an internal skeleton of cartilage add external plates, points, or spines of bone—as low in the scale, that he actually raised them above fishes altogether, by erecting them into an order of reptiles,—the older Amphibia Nantes. Surely, if the name of Linnæus was to be introduced into this controversy at all, it ought to have been in connection with this special fact; seeing that the point to be determined in the question under discussion is simply the place and standing of that very order which the naturalist rated so high,—not the place and standing of the order which he degraded. It so happens that there is one of the Chondropterygii which, so far from being a true Placoid, does not possess a single osseous plate, point, or spine: it is a worm like creature, without eyes, without movable jaws, without vertebral joints, without scales, always enveloped in slime, and greatly abhorred by our Scotch boatmen of the Moray Frith, who hold that it burrows, like the grave-worm, in the decaying bodies of the dead. And this creature, “the glutinous hag,” or, according to north-country fishermen, the “ramper-eel,” or “poison-ramper,” was regarded by Linnæus as belonging, not to the class of fishes, but to the Vermes. Now, this is the special fact with which, in the development controversy, the author of the “Vestiges” connects the name of the Swedish naturalist! All the fish of the Silurian System belonged to that true Placoid order which Linnæus, impressed by its high standing, erected into an order, not of worms, but of reptiles. He elevated A, the true Placoid, while he degraded B, the glutinous hag. But it was necessary to the argument of the author of the “Vestiges” that the earliest existing fish should be represented as fish low in the scale; and so he has cited the name and authority of Linnæus in its bearing against the glutinous hag B, as if it had borne against the standing of the true Placoid A. The Patagonians are the tallest and bulkiest men in the world, whereas their neighbors, the Fuegians are a slim and diminutive race. And if, in some controversy raised regarding the real size of the more gigantic tribe, they were to be described as the “very tallest types of their class,” any statement in reply, to the effect that some trustworthy voyager had examined certain races of the extreme south of America, and had found that they were both short and thin, would be neither relevant in its facts nor legitimate in its bearing. But if the controversialist who thus strove to strengthen his case by the voyager’s authority, was at the same time fully aware that the voyager had seen not only the diminutive Fuegians, but also the gigantic Patagonians, and that he had described these last as very gigantic indeed, the introduction of the statement regarding the smaller race, when he wholly sank the statement regarding the larger, would be not merely very irrelevant in the circumstances, but also very unfair. Such, however, is the style of statement to which the author of the “Vestiges” has (I trust inadvertently) resorted in this controversy.

It is not uninstructive to mark how slowly and gradually the naturalists have been groping their way to a right classification in the ichthyic department of their science, and how it has been that identical perception of resemblance, having cartilage for its general idea, to which the author of the “Vestiges” attaches so much importance, that has served mainly to retard their progress. Not a few of the more distinguished among their number deemed it too important a distinction to be regarded as merely secondary; and so long as it was retained as a primary characteristic, the fishes failed to range themselves in the natural order;—dissimilar tribes were brought into close neighborhood, while tribes nearly allied were widely separated. It failed, as has been shown, to influence Linnæus; and though he no doubt pressed his peculiar views too far when he degraded the glutinous hag into a worm, and elevated the Sharks and Rays into reptiles, it is certainly worthy of remark, that, in the scheme of classification which is now regarded as the most natural,—that of Professor Muller, modified by Professor Owen,—the ichthyic worms of the Swede are placed in the first and lowest order of fishes,—the Dermopteri,—and the greater part of his ichthyic reptiles, in the eleventh and highest,—the Plagiostomi. Cuvier yielded, as has been shown, to the idea of resemblance founded on the material of the ichthyic framework, and so ranged his fishes into two parallel lines. Professor Oken, after first enunciating as law that “the characteristic organ of fishes is the osseous system,” confessed the “great difficulty” which attaches to the question of skeletal “texture or substance,” and finally gave up the distinction founded on it as obstinately irreducible to the purposes of a natural classification. “The cartilaginous fishes,” he says, “appear to belong to each other, and are also usually arranged together; yet amongst them we find those species, such as the Lampreys, which obviously occupy the lowest grade of all fishes, while the Sharks and Rays remind us of the Reptilia.” And so, sinking the consideration of texture altogether, he placed the family of the Lamprey, including the glutinous hag, at the bottom of the scale, and the Sharks and Rays at the top. Agassiz’s system, peculiarly his own, has had the rare merit, as I have shown, of furnishing a key to the history of the fish in its several dynasties, which we may in vain seek in any other. His divisions,—if, retaining his strongly-marked Placoids and Ganoids, as orders stamped in the mint of nature, we throw his perhaps less obviously divisible Ctenoids and Cycloids into one order,—the corneous or horn-covered,—are scarcely less representative of periods than those great classes of the vertebrata, mammals, birds, reptiles, and fishes, which we find not less regularly ranged in their order of succession in the geologic record than in the “Animal Kingdom” of Cuvier,—a shrewd corroboration, in both cases, I am disposed to think, of the rectitude of the arrangement. What seems to be the special defect of his system is, that having erected his four orders, and then finding a certain number of residuary families that, on his principle of cuticular character, stubbornly refused to fall into any determinate place, he distributed them among the others, with reference chiefly to the totally distinct principle of Cuvier. Thus the Suctorii, soft, smooth, slimy-skinned fishes, that do not possess a single placoid character, and are not true Placoids, he has yet placed in his Placoid order, influenced, apparently, by the “perception of resemblance that has cartilage for its central idea;” and the effect has been a massing into one anomalous and entangled group the fishes of the first period of geologic history, with fishes of which we do not find a trace save in the existing scene of things, and of the highest families of their class with families that occupy the lowest place. But we live in an age in which even the benefactors of the world of mind cannot make false steps with impunity; and so, while Agassiz’s three ichthyic orders will continue to be recognized by the palæontologist as the orders of three great geologic periods, the Suctorii have already been struck from off his higher fishes by the classification of Muller and Owen, and carried to that lowest point in the scale (indicated by Linnæus and Oken) which their inferior standing renders so obviously the natural one. Some of my readers may perhaps remember how finely Bacon, in his “Wisdom of the Ancients,” interprets the old mythologic story of Prometheus. Prometheus, says the philosopher, had conferred inestimable favors on men, by moulding their forms into shape, and bringing them fire from heaven; and yet they complained of him and his teachings to Jupiter. And the god, instead of censuring their ingratitude, was pleased with the complaint, and rewarded them with gifts. In putting nature to the question, it is eminently wholesome to be doubting, cross-examining, complaining; ever demanding of our masters and benefactors the philosophers, that they should reign over us, not arbitrarily and despotically,

“Like the old kings, with high exacting looks, Sceptred and globed,”

but like our modern constitutional monarchs, who govern by law; and, further, that an appeal from their decisions on all subjects within the jurisdiction of Nature should for ever be open to Nature herself. The seeming ingratitude of such a course, if the “complaints” be made in a right spirit and on proper grounds, Jupiter always rewards with gifts.

Let us now see for ourselves, in this spirit, whether there may not be something absolutely derogatory, in the existence of a cartilaginous skeleton, to the creatures possessing it; or whether a deficit of internal bone may not be greatly more than neutralized, as it assuredly must have been in the view of Linnæus, Muller, and Owen, by a larger than ordinary share of a vastly more important substance.

THE PLACOID BRAIN. EMBRYONIC CHARACTERISTICS NOT NECESSARILY OF A LOW ORDER.

That special substance, according to whose mass and degree of development all the creatures of this world take rank in the scale of creation, is not bone, but brain. Were animals to be ranged according to the solidity of their bones, the class of birds would be assigned the first place; the family of the Felidæ, including the tiger and lion, the second; and the other terrestrial carnivora the third. Man and the herbivorous animals, though tolerably low in the scale, would be in advance of at least the reptiles. Most of these, however, would take precedence of the sagacious Delphinidæ; the osseous fishes would come next in order; the true Placoids would follow, succeeded by the Sturiones; and the Suctorii, i. e. Cyclostomi or Lampreys, would bring up the rear. There would be evidently no order here: the utter confusion of such an arrangement, like that of the bits of a dissected map flung carelessly out of its box by a child, would of itself demonstrate the inadequacy and erroneousness of the regulating principle. But how very different the appearance presented, when for solidity of bone we substitute development of brain! Man takes his proper place at the head of creation; the lower mammalia follow,—each species in due order, according to its modicum of intelligence; the birds succeed the mammalia; the reptiles succeed the birds; the fishes succeed the reptiles; next in the long procession come the invertebrate animals; and these, too, take rank, if not according to their development of brain proper, at least according to their development of the substance of brain. The occipital nervous ganglion of the scorpion greatly exceeds in size that of the earthworm; and the occipital nervous ring of the lobster, that of the intestinal Ascaris. At length, when we reach the lowest or acrite division of the animal kingdom, the substance of brain altogether disappears. It has been calculated by naturalists, that in the vertebrata, the brain in the class of fishes bears an average proportion to the spinal cord of about two to one; in the class of reptiles, of about two and a half to one; in the class of birds, of about three to one; in the class of mammals, of about four to one; and in the high-placed, sceptre-bearing human family, a proportion of not less than twenty-three to one. It is palpably according to development of brain, not development of bone, that we are to determine points of precedence among the animals,—a fact of which no one can be more thoroughly aware than the author of the “Vestiges” himself. Of this let me adduce a striking instance, of which I shall make further use anon.

“All life,” says Oken, “is from the sea; none from the continent. Man also is a child of the warm and shallow parts of the sea in the neighborhood of the land.” Such also was the hypothesis of Lamarck and Maillet. In following up the view of his masters, the author of the “Vestiges” fixes on the Delphinidæ as the sea-inhabiting progenitors of the simial family, and, through the simial family, of man For that highest order of the mammalia to which the Simiadæ (monkeys) belong, “there remains,” he says, “a basis in the Delphinidæ, the last and smallest of the cetacean tribes. This affiliation has a special support in the brain of the dolphin family, which is distinctly allowed to be, in proportion to general bulk, the greatest among mammalia next to the orang-outang and man. We learn from Tiedemann, that each of the cerebral hemispheres is composed, as in man and the monkey tribe, of three lobes,—an anterior, a middle, and a posterior; and these hemispheres present much more numerous circumvolutions and grooves than those of any other animal. Here it might be rash to found any thing upon the ancient accounts of the dolphin,—its familiarity with man, and its helping him in shipwreck and various marine disasters; although it is difficult to believe these stories to be altogether without some basis in fact. There is no doubt, however, that the dolphin evinces a predilection for human society, and charms the mariner by the gambols which it performs beside his vessel.”

Here, then, the author of the “Vestiges” palpably founds on a large development of brain in the dolphin, and on the manifestation of a correspondingly high order of instincts,—and this altogether irrespective of the structure or composition of the creature’s internal skeleton. The substance to which he looks as all-important in the case is brain, not bone. For were he to estimate the standing of the dolphin, not by its brain, but by its skeleton, he would have to assign to it a place, not only not in advance of its brethren the mammalia of the sea, but even in the rear of the reptiles of the sea, the marine tortoises, or turtles,—and scarce more than abreast of the osseous fishes. “Fishes,” says Professor Owen, in his “Lectures on the Vertebrate Animals,” “have the least proportion of earthy matter in their bones; birds the largest. The mammalia, especially the active, predatory species, have more earth, or harder bones, than reptiles. In each class, however, there are differences in the density of bone among its several members. For example, in the fresh-water fishes, the bones are lighter, and retain more animal matter, than in those which swim in the denser sea. And in the dolphin, a warm-blooded marine animal, they differ little in this respect from those of the sea-fish.” Such being the fact, it is surely but fair to inquire of the author of the “Vestiges,” why he should determine the rank and standing of the Delphinidæ according to one set of principles, and the rank and standing of the Placoids according to another and entirely different set? If the Delphinidæ are to be placed high in the scale, notwithstanding the softness of their skeletons, simply because their brains are large, why are the Placoids to be placed low in the scale, notwithstanding the largeness of their brains, simply because their skeletons are soft? It is not too much to demand, that on the principle which he himself recognizes as just, he should either degrade the dolphin or elevate the Placoid. For it is altogether inadmissible that he should reason on one set of laws when the exigencies of his hypothesis require that creatures with soft skeletons should be raised in the scale, and on another and entirely different set when its necessities demand that they should be depressed.

But do the Placoids possess in reality a large development of brain? I have examined the brains of almost all the common fish of our coast, both osseous and cartilaginous, not, I fear, with the skill of a Tiedemann, but all the more intelligently in consequence of what Tiedemann had previously done and written: and so I can speak with some little confidence on the subject, so far at least as my modicum of experience, thus acquired, extends. Of all the common fish of the Scottish seas, the spotted or lesser dog-fish bears, in proportion to its size, the largest brain; the gray or picked dog-fish ranks next in its degree of development; the Rays, in their various species, follow after; and the osseous fishes compose at least the great body of the rear; while still further behind, there lags a hapless class—the Suctorii, one of which, the glutinous hag, has scarce any brain, and one, the Amphioxus or lancelet, wants brain altogether. I have compared the brain of the spotted dog-fish with that of a young alligator, and have found that in scarce any perceptible degree was it inferior, in point of bulk, and very slightly indeed in point of organization, to the brain of the reptile. And the instincts of this Placoid family,—one of the truest existing representatives of the Placoids of the Silurian System to which we can appeal,—correspond, we invariably find, with their superior cerebral development. I have seen the common dog-fish, Spinax Acanthias, hovering in packs in the Moray Frith, some one or two fathoms away from the side of the herring boat from which, when the fishermen were engaged in hauling their nets, I have watched them, and have admired the caution which, with all their ferocity of disposition, they rarely failed to manifest;—how they kept aloof from the net, even more warily than the cetacea themselves,—though both dog-fish and cetacea are occasionally entangled;—and how, when a few herrings were shaken loose from the meshes they at once darted upon them, exhibiting for a moment, through the green depths, the pale gleam of their abdomens, as they turned upon their sides to seize the desired morsels,—a motion rendered necessary by the position of the mouth in this family; and how next, their object accomplished, they fell back into their old position, and waited on as before. And I have been assured by intelligent fishermen, that at the deep-sea white-fishing, in which baited hooks, not nets, are employed, the degree of shrewd caution exercised by these creatures seems more extraordinary still. The hatred which the fisher bears to them arises not more from the actual amount of mischief which they do him, than from the circumstance that in most cases they persist in doing it with complete impunity to themselves. I have seen, said an observant Cromarty fisherman to the writer of these chapters, a pack of dog-fish watching beside our boat, as we were hauling our lines, and severing the hooked fish, as they passed them, at a bite, just a little above the vent, so that they themselves escaped the swallowed hook; and I have frequently lost, in this way, no inconsiderable portion of a fishing. I have observed, however, he continued, that when a fresh pack of hungry dog-fish came up, and joined the pack that had been robbing us so coolly, and at their leisure, a sudden rashness would seize the whole,—the united packs would become a mere heedless mob, and, rushing forward, they would swallow our fish entire, and be caught themselves by the score and the hundred. We may see something very similar to this taking place among even the shrewder mammalia. When pig refuses to take his food, his mistress straightway calls upon the cat, and, quickened by the dread of the coming rival, he gobbles up his rations at once. With the comparatively large development of brain, and the corresponding manifestations of instinct, which the true Placoids exhibit, we find other unequivocal marks of a general superiority to their class. In their reproductive organs they rank not with the common fishes, nor even with the lower reptiles, but with the Chelonians and the Sauria. Among the Rays, as among the higher animals, there are individual attachments formed between male and female: their eggs unlike the mere spawn of the osseous fishes, or of even the Batrachians, are, like those of the tortoise and the crocodile, comparatively few in number, and of considerable size: their young, too, like the young of birds and of the higher reptiles, pass through no such metamorphosis as those of the toad and frog, or of the amphibia generally. And some of their number—the common dog-fish for instance—are ovoviviparous, bringing forth their young, like the common viper and the viviparous lizard, alive and fully formed.

“But such features,” says the author of the “Vestiges,” referring chiefly to certain provisions connected with the reproductory system in the Placoids, “are partly partaken of by families in inferior sub-kingdoms, showing that they cannot truly be regarded as marks of grade in their own class.” Nay, single features do here and there occur in the inferior sub-kingdoms, which very nearly resemble single features in the placoid character and organization, which even very nearly resemble single features in the human character and organization; but is there any of the inferior sub-kingdoms in which there occurs such a collocation of features? or does such a collocation occur in any class of animals—setting the Placoids wholly out of view—which is not a high class? Nay, further, does there occur in any of the inferior sub-kingdoms—existing even as a single feature—that most prominent, leading characteristic of this series of fishes,—a large brain?

But is not the “cartilaginous structure” of the Placoids analogous to the embryonic state of vertebrated animals in general? Do not the other placoid peculiarities to which the author of the “Vestiges” refers,—such as the heterocercal or one-sided tail, the position of the mouth on the under side of the head, and the rudimental state of the maxillaries and intermaxillaries,—bear further analogies with the embryonic state of the higher animals? And is not “embryonic progress the grand key to the theory of development?” Let us examine this matter. “These are the characters,” says this ingenious writer, “which, above all, I am chiefly concerned in looking to; for they are features of embryonic progress, and embryonic progress is the grand key to the theory of development.” Bold assertion, certainly; but, then, assertion is not argument! The statement is not a reason for the faith that is in the author of the “Vestiges,” but simply an avowal of it; it is simply a confession, not a defence, of the Lamarckian creed; and, instead of being admitted as embodying a first principle, it must be put stringently to the question, in order to determine whether it contain a principle at all.

In the first place, let us remark, that the cartilaginous structure of the Placoids bears no very striking analogy to the cartilaginous structure of the higher vertebrata in the embryonic state. In the case of the Delphinidæ, with their soft skeletons, the analogy is greatly more close. Bone consists of animal matter, chiefly gelatinous, hardened by a diffusion of inorganic earth. In the bones of young and fœtal mammalia, inhabitants of the land, the gelatinous prevails; in the old and middle-aged there is a preponderance of the earth. Now, in the bones of the dolphin there is comparatively little earth. The analogies of its internal skeleton bear, not on the skeletons of its brethren the mature full-grown mammals of the land, but on the skeletons of their immature or fœtal offspring. But in the case of the true Placoids that analogy is faint indeed. Their skeletons contain true bone;—the vertebral joints of the Sharks and Rays possess each, as has been shown, an osseous nucleus, which retains, when subjected to the heat of a common fire, the complete form of the joint; and their cranial framework has its surface always covered over with hard osseous points. But though their skeletons possess thus their modicum of bone, unlike those of embryonic birds or mammals, they contain, in what is properly their cartilage, no gelatine. The analogy signally fails in the very point in which it has been deemed specially to exist. The cartilage of the Chondropterygii is a substance so essentially different from that of young or embryonic birds and mammals, and so unique in the animal kingdom, that the heated water in which the one readily dissolves has no effect whatever upon the other. It is, however, a curious circumstance, exemplified in some of the Shark family, though it merely serves, in its exceptive character, to establish the general fact, that while the rays of the double fins, which answer to the phalanges, are all formed of this indissoluble cartilage, those rays which constitute their outer framework, with the rays which constitute the framework of all the single fins, are composed of a mucoidal cartilage, which boils into glue. At certain definite lines a change occurs in the texture of the skeleton; and it is certainly suggestive of thought, that the difference of substance which the change involves distinguishes that part of the skeleton which is homologically representative of the skeletons of the higher vertebrata, from that part of it which is peculiar to the creature as a fish, viz. the dorsal and caudal rays, and the extremities of the double fins. These emphatically ichthyic portions of the animal may be dissipated by boiling, whereas what Linnæus would perhaps term its reptilian portion abides the heat without reduction.

But is not the one-sided tail, so characteristic of the sharks, and of almost all the ancient Ganoids, also a characteristic of the young salmon just burst from the egg? Yes, assuredly; and, so far as research on the subject has yet extended, of not only the salmon, but of all the other osseous fishes in their fœtal state. The salmon, on its escape from the egg, is a little monster of about three quarters of an inch in length, with a huge heart-shaped bag, as bulky as all the rest of its body, depending from its abdomen. In this bag provident nature has packed up for it, in lieu of a nurse, food for five weeks; and, moving about every where in its shallow pool, with its provision knapsack slung fast to it, it reminds one disposed to be fanciful, save that its burden is on the wrong side, of Scottish soldiers of the olden time summoned to attend their king in war,—

“Each on his back, a slender store, His forty days’ provision bore, As ancient statutes tell.”

Around that terminal part of the creature’s body traversed by the caudal portion of the vertebral column, which commences in the salmon immediately behind the ventrals, there runs at this period, and for the ensuing five weeks in which it does not feed, a membranous fringe or fin, which exactly resembles that of the tadpole, and which, existing simply as an expansion of the skin, exhibits no mark or rays. In the place of the true caudal fin, however, we may detect with the assistance of a lens, an internal framework with two well-marked lobes, and ascertain, further, that this tail is set on awry,—the effect of a slight upward bend in the creature’s body. And when viewed in a strong light as a transparency, we perceive that the spinal cord takes the same upward bend, and, as in the sturgeon, passes in an exceedingly attenuated form into the upper lobe. What may be regarded as the design of the arrangement is probably to be found in the peculiar form given to the little creature by the protuberan bag in front. A wise instinct teaches it, from the moment of its exclusion from the egg, to avoid its enemies. In the instant the human shadow falls upon its pool, we see it darting into some recess at the side or bottom, with singular alacrity; and in order to enable it to do so, and to steer itself aright,—as, like an ill-trimmed vessel, deep in the water ahead, the balance of its body is imperfect,—there is, if I may so express myself, a heterocercal peculiarity of helm required. It has got an irregularly-developed tail to balance an irregularly-developed body, as skiffs lean on the one beam and full on the other require, in rowing, a cast of the rudder to keep them straight in their course.

Sinking altogether, however, the final cause of the peculiarity, and regarding it simply as a fœtal one, that indicates a certain stage of imperfection in the creature in which it occurs, on what principle, I ask, are we to infer that what is a sign of immaturity in the young of one set of animals, is a mark of inferior organization in the adult forms of another set? The want of eyes in any of the animal families, or the want of organs of progression, or a fixed and sedentary condition, like that of the oyster, are all marks of great inferiority. And yet, if we admit the principle, that what are evidences of immaturity in the young members of one family are signs of inferior organization in the fully-grown members of another, it could easily be shown that eyes and legs are defects, and that the unmoving oyster stands higher in the scale than the ever-restless fish or bird. The immature Tubularia possess locomotive powers, whereas in their fully developed state they remain fixed to one spot in their convoluted tubes. The immature Lepas is furnished with members well adapted for swimming, and with which it swims freely; as it rises towards maturity, these become blighted and weak; and, when fully grown,—fixed by its fleshy pedicle to the rock or floating log to which it attached itself in its transition state,—it is no longer able to swim. The immature Balanus is furnished with two eyes: in its state of maturity these are extinguished, and it passes its period of full development in darkness. Further, it is not generally held that in the human family a white skin is a decided mark of degradation, but rather the reverse; and yet nothing can be more certain than that the Negro fœtus has a white skin. Since eyes, and organs of progression, and a power of moving freely, and a white skin, are mere embryonic peculiarities in the Balanus, the Lepas, the Tubularia, and the Negro, and yet are in themselves, when found in the mature animal, evidences of a high, not of a low standing, on what principle, I ask are we to infer that the peculiarity of a heterocercal tail, embryonic in the salmon, is, when found in the mature Placoid, an evidence, not of a high standing, but of a low? Every true analogy in the case favors an exactly opposite view. In the heterocercal or one-sided tail, the vertebral joints gradually diminish, as in the tails of the Sauria and Ophidia, till they terminate in a point; whereas the homocercal tail common to the osseous fishes exhibits no true analogy with the tails of the higher orders. Its abruptly terminating vertebral column, immensely developed posterior processes, and broadly expanded osseous rays, seem to be simply a few of the many marks of decline and degradation which fishes, the oldest of the vertebrata, exhibit in this late age of the world, and which, in at least the earlier geologic periods, when they were greatly younger as a class, they did not betray.

a. Tail of Spinax Acanthias.