_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.
[Illustration: Fig. 47.
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.