Chapter L: Agassiz (4)

It was small, however, compared with specimens of the _Asterolepis_ found elsewhere. The hyoid plate figured in page 110, (fig. 36,)—a Thurso specimen which I owe to the kindness of Mr. Dick,—measures nearly fourteen inches, and the cranial buckler of the same individual, fifteen one fourth inches, in breadth. The latter, when entire, must have measured twenty-three one half inches in length; and the fish to which it belonged, if formed in the proportions of the _Glyptolepis_, ten feet six inches; and if in those of the _Diplopterus_, from twelve feet five to thirteen feet eight inches in length. Did the shield still exist in its original state as a buckler of tough, enamel-crusted bone, it might be converted into a Highland target, nearly broad enough to cover the ample chest of a Rob Roy or Allan M’Aulay, and strong enough to dash aside the keenest broadsword. Another hyoid plate found by Mr. Dick measures sixteen one half inches in breadth; and a cast in the British Museum, from one of the Russian specimens of Professor Asmus, (fig. 46,) twenty-four inches. The individual to which this last plate belonged must, if built in the shorter proportions, have measured eighteen, and if in the longer, twenty-three feet in length. The two hyoid plates of the specimen of _Holoptychius_ in the British Museum measure but four and a half inches along that transverse line in which the Russian _Asterolepis_ measures two feet, and the largest Thurso specimen sixteen inches and a half. The maxillary bone of a cod-fish two and a half feet from snout to tail measures three inches in length. One of the Russian maxillary bones in the possession of Professor Asmus measures in length twenty-eight inches. And that space circumscribed by the sweep of the lower jaw which it took, in the Russian specimen, a hyoid plate twenty-four inches in breadth to fill, could be filled in the two-and-a-half-feet cod by a plate whose breadth equalled but an inch and a half. Thus, in the not unimportant circumstance of size, the most ancient Ganoids yet known, instead of taking their places, agreeably to the demands of the development hypothesis, among the sprats, sticklebacks, and minnows of their class, took their place among its huge basking sharks, gigantic sturgeons, and bulky sword-fishes. They were giants, not dwarfs.

HYOID PLATE OF RUSSIAN ASTEROLEPIS.

(One twelfth the natural size, linear.)]

But what of their organization? Were they fishes low or high in the scale? On this head we can, of course, determine merely by the analogies which their structure exhibits to that of fishes of the existing period; and these point in three several directions;—in two of the number, directly on genera of the high Ganoid order; and in the third, on the still higher Placoids and Enaliosaurs. No trace of vertebræ has yet been found; and so we infer—lodging, however, a precautionary protest, as the evidence is purely negative, and therefore it some degree inconclusive—that the vertebral column of the _Asterolepis_ was, like that of the sturgeon, cartilaginous. Respecting its external covering, we positively know, as has been already shown, that, like the _Lepidosteus_ of America and the _Polypterus_ of the Nile, it was composed of strong plates and scales of solid bone; and, regarding its dentition, that, as in these last genera, and even more decidedly than in these, it was of the mixed ichthyic-reptilian character,—an outer row of thickly-set fish-teeth being backed by an inner row of thinly-set reptile-teeth. And its form of coprolite indicates the spiral disposition of intestine common to the Rays and Sharks of the existing period, and of the Ichthyosauri of the Secondary ages. Instead of being, as the development hypothesis would require, a fish low in its organization, it seems to have ranged on the level of the highest ichthyic-reptilian families ever called into existence. Had an intelligent being, ignorant of what was going on upon earth during the week of creation, visited Eden on the morning of the sixth day, he would have found in it many of the inferior animals, but no trace of man. Had he returned again in the evening, he would have seen, installed in the office of keepers of the garden, and ruling with no tyrant sway as the humble monarchs of its brute inhabitants, two mature human creatures, perfect in their organization, and arrived at the full stature of their race. The entire evidence regarding them, in the absence of all such information as that imparted to Adam by Milton’s angel, would amount simply to this, that in the morning man _was not_, and that in the evening he _was_. There, of course, could not exist, in the circumstances, a single appearance to sanction the belief that the two human creatures whom he saw walking together among the trees at sunset had been “developed from infusorial points,” not created mature. The evidence would, on the contrary, lie all the other way. And in no degree does the geologic testimony respecting the earliest Ganoids differ from what, in the supposed case, would be the testimony of Eden regarding the earliest men. Up to a certain point in the geologic scale we find that the Ganoids _are not_; and when they at length make their appearance upon the stage, they enter large in their stature and high in their organization.

FISHES OF THE SILURIAN ROCKS—UPPER AND LOWER. THEIR RECENT HISTORY, ORDER, AND SIZE.

But the system of the Old Red Sandstone represents the _second_, not the _first_, great period of the world’s history. There was a preceding period at least equally extended, perhaps greatly more so, represented by the Upper and Lower Silurian formations. And what is the testimony of this morning period of organic existence, in which, so far as can yet be shown, vitality, in the planet which man inhabits, and of whose history or productions he knows anything, was first associated with matter? May not the development hypothesis find a standing in the system representative of this earliest age of creation, which it fails to find in the system of the Old Red Sandstone?

It has been confidently asserted, not merely that it _may_, but that it _does_. Ever since the publication, in 1839, of Sir Roderick Murchison’s great work on the Silurian System, it had been known that the remains of fishes occur in a bed of the “Ludlow Rock,”—one of the most modern deposits of the _Upper_ Silurian division; and subsequent discoveries both in England and America, had shown that even the _base_ of this division has its ichthyic organisms. But for year after year, the lower half of the system,—a division more than three thousand feet in thickness,—had failed, though there were hands and eyes busy among its deposits, to yield any vertebrate remains. During the earlier half of the first great period of organic existence, though the polyparia, radiata, articulata, and mollusca, existed, as their remains testified, by myriads, fish had, it was held, not yet entered upon the scene; and the assertors of the development theory founded largely on the presumed fact of their absence. “It is still customary,” says the author of the “Vestiges of Creation,” in his volume of “Explanations,” “to speak of the earliest fauna as one of an elevated kind. When rigidly examined, it is not found to be so. IN THE FIRST PLACE, IT CONTAINS NO FISH. There were seas supporting crustacean and molluscan life, but _utterly devoid of a class of tenants who seem able to live in every example of that element which supports meaner creatures_. This single fact, that only invertebrated animals now lived, is surely in itself a strong proof that, in the course of nature, _time_ was necessary for the creation of the superior creatures. And if so, it undoubtedly is a powerful evidence of such a theory of development as that which I have presented. If not, let me hear an equally plausible reason for the great and amazing fact, that seas were for numberless ages destitute of fish. I fix my opponents down to the consideration of this fact, so that no diversion respecting high molluscs shall avail them.” And how is this bold challenge to be met?

Most directly, and after a fashion that at once discomfits the challenger.

It might be rationally enough argued in the case, that the author of the “Vestiges” was building greatly more on a piece of purely negative evidence,—the presumed absence of fish from the Lower Silurian formations,—than purely negative evidence is, from its nature as such, suited to bear; that only a very few years had passed since it was known that vertebrate remains occurred in the _Upper_ Silurian, and only a few more since they had been detected in the Old Red Sandstone; nay, that within the present century their frequent occurrence in even the Coal Measures was scarce suspected; and that, as his argument, had it been founded twelve years ago on the supposed absence of fishes from the Upper Silurian, or twenty years ago on the supposed absence of fishes from the Old Red Sandstone, would have been quite as plausible in reference to its negative data then as in reference to its negative data now, so it might now be quite as erroneous as it assuredly would have been then. Or it might be urged, that the fact of the absence of fish from the Lower Silurians, even were it really a fact, would be in no degree less reconcilable with the theory of creation by direct act, than with the hypothesis of gradual development. The fact that Adam did not exist during the first, second, third, fourth, and fifth days of the introductory week of Scripture narrative, furnishes no argument whatever against the fact of his creation on the sixth day. And the remark would of course equally apply to the non-existence of fishes during the Lower Silurian period, had they been really non-existent at the time, and to their sudden appearance in that of the Upper. But the objection admits of a greatly more conclusive answer. “I fix my opponents down,” says the author of the “Vestiges,” “to the consideration of this fact,” _i. e._ that of the absence of fishes from the earliest fossiliferous formations. And I, in turn, fix you down, I reply, to the consideration of the antagonist fact, not negative, but positive, and now, in the course of geological discovery, fully established, that fishes were _not_ absent from the earliest fossiliferous formations. From none of the great geological formations were fishes absent,—not even from the formations of the Cambrian division. “The Lower Silurian,” says Sir Roderick Murchison, in a communication with which, in 1847, he honored the writer of these chapters, “is no longer to be viewed as an invertebrate period; for the _Onchus_ (species not yet decided) has been found in the Llandeilo Flags and in the Lower Silurian rocks of Bala. In one respect I am gratified by the discovery; for the form is so very like that of the _Onchus Murchisoni_ of the Upper Ludlow rock, that it is clear the Silurian system is one great natural-history series, as is proved, indeed, by all its other organic remains.” It may be mentioned further, in addition to this interesting statement, that the Bala spine was detected in its calcareous matrix by the geologists of the Government Survey, and described to Sir Roderick as that of an _Onchus_, by a very competent authority in such matters,—Professor Edward Forbes, and that the annunciation of the existence of spines of fishes in the Llandeilo Flags we owe to one of the most cautious and practised geologists of the present age,—Professor Sedgwick of Cambridge.

So much for the _fact_ of the existence of vertebrata in the Lower Silurian formations, and the _argument_ founded on their presumed absence. Let me now refer—their presence being determined—to the tests of size and organization. Were these Silurian fishes of a bulk so inconsiderable as in any degree to sanction the belief that they had been developed shortly before from microscopic points? Or were they of a structure so low as to render it probable that their development was at the time incomplete? Were they, in other words, the embryos and fœtuses of their class? or did they, on the contrary, rank with the higher and larger fishes of the present time?

It is of importance that not only the direct _bearing_, but also the actual _amount_, of the evidence in this case, should be fairly stated. So far as it extends, the testimony is clear; but it does not extend far. All the vertebrate remains yet detected in the Silurian System, if we except the debris of the Upper Ludlow bone-bed, might be sent through the Post-Office in a box scarcely twice the size of a copy of the “Vestiges.” The naturalist of an exploring party, who, in crossing some unknown lake, had looked down over the side of his canoe, and seen a few fish gliding through the obscure depths of the water, would be but indifferently qualified, from what he had witnessed, to write a history of _all_ its fish. Nor, were the some six or eight individuals of which he had caught a glimpse to be of small size, would it be legitimate for him to infer that only small-sized fish lived in the lake; though, were there to be some two or three large ones among them, he might safely affirm the contrary. Now, the evidence regarding the fishes of the Silurian formation very much resembles what that of the naturalist would be, in the supposed case, regarding the fishes of the unexplored lake; with, however, this difference, that as the deposits of the ancient system in which they occur have been examined for years in various parts of the world, and all its characteristic organisms, save the ichthyic ones, found in great abundance and fine keeping, we may conclude that the fish of the period were comparatively few. The palæontologist, so far as the question of number is involved, is in the circumstances, not of the naturalist who has only once crossed the unknown lake, but of the angler who, day after day, casts his line into some inland sea abounding in shell-fish and crustacea, and, after the lapse of months, can scarce detect a nibble, and, after the lapse of years, can reckon up all the fish which he has caught as considerably under a score. The existence of this great division of the animal kingdom, like that of the earlier reptiles during the Carboniferous period, did not form a prominent characteristic of those ages of the earth’s history in which they began to be.

The earliest discovered vertebral remains of the system—those of the Upper Ludlow rock—were found in digging the foundations of a house at Ludford, on the confines of Shropshire, and submitted, in 1838, by Sir Roderick Murchison to Agassiz, through the late Dr. Malcolmson of Madras. I used at the time to correspond on geological subjects with Dr. Malcolmson,—an accomplished geologist and a good man, too early lost to science and his friends,—and still remember the interest which attached on this occasion to his communication bearing the Paris post-mark, from which I learned for the first time that there existed ichthyic fragments greatly older than even the ichthyolites of the Lower Old Red Sandstone, and which made me acquainted with Agassiz’s earliest formed decision regarding them. Though existing in an exceedingly fragmentary condition,—for the materials of the thin dark-colored layer in which they had lain seemed as if they had been triturated in a mortar,—the ichthyologist succeeded in erecting them into six genera; though it may be very possible,—as some of these were formed for the reception of detached spines, and others for the reception of detached teeth,—that, as in the case of _Dipterus_ and _Asterolepis_, the fragments of but a single genus may have been multiplied into two genera or more. And minute scale-like markings, which mingled with the general mass, and were at first regarded as the impressions of real scales, have been since recognized as of the same character with the scale-like markings of the _Seraphim_ of Forfarshire, a huge crustacean. Even admitting, however, that a set of teeth and spines, with perhaps the shagreen points represented in page 54, fig. 2, _b_, in addition, may have all belonged to but a single species of fish, there seem to be materials enough, among the remains found, for the erection of two species more. And we have evidence that at least two of the three kinds were fishes of the Placoid order, (_Onchus Murchisoni_ and _Onchus tenuistriatus_,) and—as the supposed scales must be given up—no good evidence that the other kind was not. The ichthyic remains of the Silurian System next discovered were first introduced to the notice of geologists by Professor Phillips, at the meeting of the British Association in 1842.[22] They occurred, he stated, in a quarry near Hales End, at the base of the Upper Ludlow rock, immediately over the Aymestry Limestone, and were so exceedingly diminutive, that they appeared to the naked eye as mere discolored spots; but resolved under the microscope into scattered groupes of minute spines, like those of the _Cheiracanthus_, with what seemed to be still more minute _scales_, or, perhaps,—what in such circumstances could scarce be distinguished from scales,—shagreen points of the scale-like type. The next ichthyic organism detected in the Silurian rocks occurred in the Wenlock Limestone, a considerably lower and older deposit, and was first described in the “Edinburgh Review” for 1845 by a vigorous writer and masterly geologist, (generally understood to be Professor Sedgwick of Cambridge,) as “a characteristic portion of a fish undoubtedly belonging to the Cestraciont family of the Placoid order.” In the “American Journal of Science” for 1846, Professor Silliman figured, from a work of the States’ Surveyors, the defensive spine of a Placoid found in the Onondago Limestone of New York,—a rock which occurs near the base of the Upper Silurian System, as developed in the western world;[23] and in the same passage he made reference to a mutilated spine detected in a still lower American deposit,—the Oriskany Sandstone. In the Geological Journal for 1847, it was announced by Professor Sedgwick, that he had found “_defences of fishes_” in the Upper Llandeilo Flags, and by Sir Roderick Murchison, that the “defence of an _Onchus_” had been detected by the geologists of the Government survey, in the Limestone near Bala. Sir Roderick referred in the same number to the remains of a fish found by Professor Phillips in the Wenlock Shale. And such, up to the present time, is the actual _amount_ of the evidence with which we have to deal, and the dates of its piecemeal production. Let us next consider the _order of its occurrence in the geologic scale_.

{ +-----+
{ Upper | | Fish, 1838,
{ Ludlow. | 1 | (Murchison.)
{ | | Fish, 1842,
{ +-----+ (Phillips.)
{ Aymestry | |
{ Limestone. | 2 |
{ +-----+
UPPER SILURIAN ROCKS. { Lower | |
{ Ludlow. | 3 |
{ +-----+
{ Wenlock | | Fish, 1845,
{ Limestone. | 4 | (Sedgwick.)
{ | | Fish, 1846,
{ +-----+ (Silliman.)
{ Wenlock | 5 | Fish, 1847.
{ Shale. | | (Phillips.)
+-----+
-----
{ +-----+
{ Caradoc | |
{ Sandstone, | 6 |
{ &c. | |
LOWER SILURIAN ROCKS. { +-----+
{ Llandeilo | | Fish, 1847,
{ Flags, &c. | 7 | (Sedgwick.)
{ +-----+
-----
{ +-----+
{ Plynlimmon | |
{ Group. | _a_ |
{ +-----+
{ Bala | | Fish, 1847,
CAMBRIAN ROCKS. { Limestone. | _b_ | (Geologists of
{ | | Government
{ +-----+ Survey.)
{ Snowdon | |
{ Group. | _c_ | Fucoids.
{ | |
{ +-----+

The better marked sub-divisions of the Silurian System, as described in the great work specially devoted to it, may be regarded as seven in number. An eight has since been added, by the transference of the Tilestones from the lower part of the Old Red Sandstone group, to the upper part of the Silurian group underneath; but in order the better to show how ichthyic discovery has in its slow course penetrated into the depths, I shall retain the divisions recognized as those of the system when that course began. The highest or most modern Silurian deposit, then, (No. 1 of the accompanying diagram,) is the _Upper_ Ludlow Rock; and it is in the superior strata of this division that the bone-bed discovered in 1838 occurs; while the exceedingly minute vertebrate remains described by Professor Phillips in 1842 occur in its base. The division next in the descending order is the Aymestry Limestone, (No. 2;) the next (No. 3.) the _Lower_ Ludlow rock; then (No. 4.) the Wenlock or Dudley Limestone occurs; and then, last and oldest deposit of the _Upper_ Silurian formation, the Wenlock shale, (No. 5.) It is in the fourth, or Wenlock Limestone division, that the defensive spine described in the “Edinburgh Review” for 1845 as the oldest vertebrate organism known at the time, was found;[24] while the vertebrate organism found by Professor Phillips belongs to the fifth, or base deposit of the Upper Silurian. Further, the American spines of Onondago and Oriskany, described in 1846, occurred in rocks deemed contemporary with those of the Wenlock division. We next cross the line which separates the base of the Upper from the top of the Lower Silurian deposits, and find a great arenaceous formation, (No. 6,) known as the Caradoc Sandstones; while the Llandeilo Flags, (No. 7,) the formation upon which the sandstones rest, compose, according to the sections of Sir Roderick, published in 1839, the lowest deposit of the Lower Silurian rocks. And it is in the upper part of this lowest member of the system that the ichthyic defences, announced in 1847 by Professor Sedgwick, occur. Vertebrate remains have now been detected in the same relative position in the _seventh_ and _most ancient_ member of the system, that they were found to occupy in its _first_ and _most modern_ member ten years ago. But this is not all. Beneath the Lower Silurian division there occur vast fossiliferous deposits, to which the name “Cambrian System” was given, merely provisionally, by Sir Roderick, but which Professor Sedgwick still retains as representative of a distinct geologic period; and it is in these, greatly below the Lower Silurian base line, as drawn in 1839, that the Bala Limestones occur. The Plynlimmon rocks (_a_)—a series of conglomerate, grauwacke, and slate beds, several thousand yards in thickness—intervene between the Llandeilo Flags and the Limestones of Bala, (_b_.) And, of consequence, the defensive spine of the _Onchus_, announced in 1847 as detected in these limestones by the geologists of the Government Survey, must have formed part of a fish that perished many ages ere the oldest of the Lower Silurian formations _began_ to be deposited.

Let us now, after this survey of both the amount of our materials, and the order and time of their occurrence, pass on to the question of size, as already stated. Did the ichthyic remains of the Silurian System, hitherto examined and described, belong to large or to small fishes? The question cannot be altogether so conclusively answered as in the case of those Ganoids of the Lower Old Red Sandstone whose dermal skeletons indicate their original dimensions and form. In fishes of the Placoid order, such as the Sharks and Rays, the dermal skeleton is greatly less continuous and persistent than in such Ganoids as the Dipterians and Cœlacanths; and when their remains occur in the fossil state, we can reason, in most instances, regarding the bulk of the individuals of which they formed part, merely from that of detached teeth or spines, whose proportion to the entire size of the animals that bore them cannot be strictly determined. We can, indeed, do little more than infer, that though a large Placoid may have been armed with but small spines or teeth, a small Placoid could not have borne very large ones. And to this Placoid order all the Silurian fish, from the Aymestry Limestone to the Cambrian deposits of Bala inclusive, unequivocally belong. Nor, as has been already said, is there sufficient evidence to show that any of the ichthyic remains of the Upper Ludlow rocks do _not_ belong to it. It is peculiarly the order of the system. The Ludlow bone-bed contains not only defensive spines, but also teeth, fragments of jaws, and shagreen points; whereas, in all the inferior deposits which yield any trace of the vertebrata, the remains are those of defensive spines exclusively. Let us, then, take the defensive spine as the part on which to found our comparison.

One of the best marked Placoids of the Upper Ludlow bone-bed is that _Onchus Murchisoni_ to which the distinguished geologist whose name it bears refers, in his communication, as so nearly resembling the oldest Placoid yet known,—that of the Bala Limestone. And the living fishes with which the _Onchus Murchisoni_ must be compared, says Agassiz, though “the affinity,” he adds, “may be rather distant,” are those of the genera “_Cestracion_, _Centrina_, and _Spinax_.” I have placed before me a specimen of recent _Spinax_, of a species well known to all my readers on the sea-coast, the _Spinax Acanthias_, or common dog-fish, so little a favorite with our fishermen. It measures exactly two feet three inches in length; and of the defensive spines of its two dorsals,—these spear-like thorns on the creature’s back immediately in advance of the fins, which so frequently wound the fisher’s hand,—the anterior and smaller measures, from base to point, an inch and a half, and the posterior and larger, two inches. I have also placed before me a specimen of _Cestracion Phillippi_, (the Port Jackson Shark,) a fish now recognized as the truest existing analogue of the Silurian Placoids. It measures twenty-two three fourth inches in length, and is furnished, like _Spinax_, with two dorsal spines, of which the anterior and larger measures from base to point one one half inch, and the posterior and smaller, one one fifth inch. But the defensive spine of the _Onchus Murchisoni_, as exhibited in one of the Ludlow specimens, measures, though mutilated at both ends, three inches and five eighth parts in length. Even though existing but as a fragment, it is as such nearly twice the length of the largest spine of the dog-fish, unmutilated and entire, and considerably _more_ than twice the length of the largest spine of the Port Jackson Shark. The spines detected by Professor Phillips, in an inferior stratum of the same upper deposit, were, as has been shown, of microscopic minuteness; and when they seemed to rest on the extreme horizon of ichthyic existence as the most ancient remains of their kind, the author of the “Vestiges” availed himself of the fact. He regarded the little creatures to which they had belonged is the fœtal embryos of their class, or—to employ the language of the Edinburgh Reviewer—as “the tokens of Nature’s first and half-abortive efforts to make fish out of the lower animals.” From the latter editions of his work, the paragraph to which the Reviewer refers has, I find, been expunged; for the horizon has greatly extended, and what seemed to be its line of extreme distance has travelled into the middle of the prospect. But that the passage should have at all existed is a not uninstructive circumstance, and shows how unsafe it is, in more than external nature, to regard the line at which, for the time, the landscape closes, and heaven and earth seem to meet, as in reality the world’s end. The Wenlock spine, though certainly not microscopic, is, I am informed by Sir Philip Egerton, of but small size; whereas the contemporary spine of the Onondago Limestone, though comparatively more a fragment than the spine of the Upper Ludlow _Onchus_,—for it measures only three inches in length,—is at least five times as bulky as the largest spine of _Spinax Acanthias_. Representing one of the massier fishes disporting amid the some four or five small ones, of which in my illustration, the naturalist catches a glimpse in fording the unknown lake, it at least serves to show that all the Silurian ichthyolites must not be described as small, seeing that not only might many of its undetected fish have been large, but that some of those which _have_ been detected were actually so. Another American spine, of nearly the same formation,—for it occurs in a limestone, varying from twenty to seventy feet in thickness, which immediately overlies that of the Onondago deposit, though still more fragmentary than the first, for its length is only two three eighth inches,—maintains throughout a nearly equal thickness,—a circumstance in itself indicative of considerable size; and in positive bulk it almost rivals the Onondago one. Of the Lower Silurian and Bala fishes no descriptions or figures have yet appeared. And such, up to the present time, is the testimony derived from this department of Geology, so far as I have been able to determine it, regarding the size of the ancient Silurian vertebrata. “No organism,” says Professor Oken, “is, nor ever has one been, created, which is not microscopic.” The Professor’s pupils and abettors, the assertors of the development hypothesis, appeal to the geological evidence as altogether on _their_ side in the case; and straightway a few witnesses enter court. But, lo! among the expected dwarfs, there appear individuals of more than the average bulk and stature.

a. _Posterior Spine of Spinax Acanthias._

b. _Fragment of Onondago Spine._

(Natural Size.)]

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.