Vestiges of the Natural History of Creation (Chapter 14)
by Robert Chambers
Hypothesis of the Development of the Vegetable and
Animal Kingdoms.
t has been already intimated, as a general fact, that there
is an obvious gradation amongst the families of both the vegetable and
animal kingdoms, from the simple lichen and animalcule respectively up to
the highest order of dicotyledonous trees and the mammalia. Confining our
attention, in the meantime, to the animal kingdom—it does not appear
that this gradation passes along one line, on which every form of animal
life can be, as it were, strung; there may be branching or double lines at
some places; or the whole may be in a circle composed of minor circles, as
has been recently suggested. But still it is incontestable that there are
general appearances of a scale beginning with the simple and advancing to
the complicated. The animal kingdom was divided by Cuvier into four
sub-kingdoms, or divisions, and these exhibit an unequivocal gradation in
the order in which they are here enumerated:—Radiata, (polypes, &c.;)
mollusca, (pulpy animals;) articulate, (jointed animals;) vertebrate,
(animals with internal skeleton.) The gradation can, in like manner, be
clearly traced in the classes into which the sub-kingdoms are
Subdivided, as, for instance, when we take those of the vertebrate in this
order—reptiles, fishes, birds, mammals.
While the external forms of all these various animals
are so different, it is very remarkable that the whole are, after all,
variations of a fundamental plan, which can be traced as a basis throughout
the whole, the variations being merely modifications of that plan to suit
the particular conditions in which each particular animal has been designed
to live. Starting from the primeval germ, which, as we have seen, is the
representative of a particular order of full-grown animals, we find all
others to be merely advances from that type, with the extension of
endowments and modification of forms which are required in each particular
case; each form, also, retaining a strong affinity to that which precedes
it, and tending to impress its own features on that which succeeds. This
unity of structure, as it is called, becomes the more remarkable, when we
observe that the organs, while preserving a resemblance, are often put to
different uses. For example: the ribs become, in the serpent, organs of
locomotion, and the snout is extended, in the elephant, into a prehensile
instrument.
It is equally remarkable that analogous purposes are
served in different animals by organs essentially different. Thus, the
mammalia breathe by lungs; the fishes, by gills. These are not
modifications of one organ, but distinct organs. In mammifers, the gills
exist and act at an early stage of the fœtal state, but afterwards go back
and appear no more; while the lungs are developed. In fishes, again, the
gills only are fully developed; while the lung structure either makes no
advance at all, or only appears in the rudimentary form of an air-bladder.
So, also, the baleen of the whale and the teeth of the land mammalia are
different organs. The whale, in embryo, shews the rudiments of teeth; but
these, not being wanted are not developed, and the baleen is brought
forward instead. The land animals, we may also be sure, have the rudiments
of baleen in their organization. In many instances, a particular structure
is found advanced to a certain point in a particular set of animals, (for
instance, feet in the serpent tribe,) although it is not there required in
any degree; but the peculiarity, being carried a little farther forward, is
perhaps useful in the next set of animals in the scale. Such are called
rudimentary organs. With this class of phenomena are to be ranked the
useless mammae of the male human being, and the unrequired process of bone
in the male opossum, which is needed in the female for supporting her
pouch. Such curious features are most conspicuous in animals which form
links between various classes.
As formerly stated, the marsupials, standing at the
bottom of the mammalia, shew their affinity to the oviparous vertebrate, by
the rudiments of two canals passing from near the anus to the external
surfaces of the viscera, which are fully developed in fishes, being
required by them for the respiration of aerated waters, but which are not
needed by the atmosphere-breathing marsupials. We have also the peculiar
form of the sternum and rib-bones of the lizards represented in the
mammalia in certain white cartilaginous lines traceable among their
abdominal muscles. The struphionidæ (birds of the ostrich type) form a
link between birds and mammalia, and in them we find the wings imperfectly
or not at all developed, a diaphragm and urinary sac, (organs wanting in
other birds,) and feathers approaching the nature of hair. Again, the
ornithorynchus belongs to a class at the bottom of the mammalia, and
approximating to birds, and in it behold the bill and web-feet of that
order!
For further illustration, it is obvious that,
various as may be the lengths of the upper part of the vertebral column
in the mammalia, it always consists of the same parts. The giraffe has
in its tall neck the same number of bones with the pig, which scarcely
appears to have a neck at all.[1] Man, again, has
no tail; but the notion of a much-ridiculed philosopher of the last
century is not altogether, as it happens, without foundation, for the
bones of a caudal extremity exist in an undeveloped state in the os
coccygis of the human subject. The limbs of all the vertebrate
animals are, in like manner, on one plan, however various they may
appear. In the hind-leg of a horse, for example, the angle called the
hock is the same part which in us forms the heel; and the horse, and
all other quadrupeds, with almost the solitary exception of the bear,
walk, in reality, upon what answers to the toes of a human being. In
this and many other quadrupeds the fore part of the extremities is
shrunk up in a hoof, as the tail of the human being is shrunk up in the
bony mass at the bottom of the back. The bat, on the other hand, has
these parts largely developed. The membrane, commonly called its wing,
is framed chiefly upon bones answering precisely to those of the human
hand; its extinct congener, the pterodactyle, had the same membrane
extended upon the fore-finger only, which in that animal was prolonged
to an extraordinary extent. In the paddles of the whale and other
animals of its order, we see the same bones as in the more highly
developed extremities of the land mammifers; and even the serpent
tribes, which present no external appearance of such extremities,
possess them in reality, but in an undeveloped or rudimental state.
The same law of development presides over the
vegetable kingdom. Amongst phanerogamous plants, a certain number of
organs appear to be always present, either in a developed or
rudimentary state; and those which are rudimentary can be developed by
cultivation. The flowers which bear stamens on one stalk and pistils on
another, can be caused to produce both, or to become perfect flowers,
by having a sufficiency of nourishment supplied to them. So also, where
a special function is required for particular circumstances, nature has
provided for it, not by a new organ, but by a modification of a common
one, which she has effected in development. Thus, for instance, some
plants destined to live in arid situations, require to have a store of
water which they may slowly absorb. The need is arranged for by a
cup-like expansion round the stalk, in which water remains after a
shower. Now the pitcher, as this is called, is not a new organ,
but simply a metamorphose of a leaf.
These facts clearly shew how all the various organic
forms of our world are bound up in one—how a fundamental unity
pervades and embraces them all, collecting them, from the humblest
lichen up to the highest mammifer, in one system, the whole creation of
which must have depended upon one law or decree of the Almighty, though
it did not all come forth at one time. After what we have seen, the
idea of a separate exertion for each must appear totally inadmissible.
The single fact of abortive or rudimentary organs condemns it; for
these, on such a supposition, could be regarded in no other light than
as blemishes or blunders—the thing of all others most
irreconcilable with that idea of Almighty Perfection which a general
view of nature so irresistibly conveys. On the other hand, when the
organic creation is admitted to have been effected by a general law, we
see nothing in these abortive parts but harmless peculiarities of
development, and interesting evidences of the manner in which the
Divine Author has been pleased to work.
We have yet to advert to the most interesting class
of facts connected with the laws of organic development. It is only in
recent times that physiologists have observed that each animal passes,
in the course of its germinal history, through a series of changes
resembling the permanent forms of the various orders of animals
inferior to it in the scale. Thus, for instance, an insect, standing at
the head of the articulated animals, is, in the larva state, a true
annelid, or worm, the annelida being the lowest in the same class. The
embryo of a crab resembles the perfect animal of the inferior order
myriapoda, and passes through all the forms of transition which
characterize the intermediate tribes of crustacea. The frog, for some
time after its birth, is a fish with external gills, and other organs
fitting it for an aquatic life, all of which are changed as it advances
to maturity, and becomes a land animal. The mammifer only passes
through still more stages, according to its higher place in the scale.
Nor is man himself exempt from this law. His first form is that which
is permanent in the animalcule. His organization gradually passes
through conditions generally resembling a fish, a reptile, a bird, and
the lower mammalia, before it attains its specific maturity. At one of
the last stages of his fœtal career, he exhibits an intermaxillary
bone, which is characteristic of the perfect ape; this is suppressed,
and he may then be said to take leave of the simial type, and become a
true human creature. Even, as we shall see, the varieties of his race
are represented in the progressive development of an individual of the
highest, before we see the adult Caucasian, the highest point yet
attained in the animal scale.
To come to particular points of the organization.
The brain of man, which exceeds that of all other animals in complexity
of organization and fulness of development, is, at one early period,
only "a simple fold of nervous matter, with difficulty distinguishable
into three parts, while a little tail-like prolongation towards the
hinder parts, and which had been the first to appear, is the only
representation of a spinal marrow. Now, in this state it perfectly
resembles the brain of an adult fish, thus assuming in transitu
the form that in the fish is permanent. In a short time, however, the
structure is become more complex, the parts more distinct, the spinal
marrow better marked; it is now the brain of a reptile. The change
continues; by a singular motion, certain parts (corpora
quadragemina) which had hitherto appeared on the upper surface, now
pass towards the lower; the former is their permanent situation in
fishes and reptiles, the latter in birds and mammalia. This is another
advance in the scale, but more remains yet to be done. The complication
of the organ increases; cavities termed ventricles are formed,
which do not exist in fishes, reptiles, or birds; curiously organized
parts, such as the corpora striata, are added; it is now the brain of
the mammalia. Its last and final change alone seems wanting, that which
shall render it the brain of MAN."[2] And this
change in time takes place.
So also with the heart. This organ, in the mammalia,
consists of four cavities, but in the reptiles of only three, and in
fishes of two only, while in the articulated animals it is merely a
prolonged tube. Now in the mammal fœtus, at a certain early stage,
the organ has the form of a prolonged tube; and a human being may be
said to have then the heart of an insect. Subsequently it is shortened
and widened, and becomes divided by a contraction into two parts, a
ventricle and an auricle; it is now the heart of a fish. A subdivision
of the auricle afterwards makes a triple-chambered form, as in the
heart of the reptile tribes; lastly, the ventricle being also
subdivided, it becomes a full mammal heart.
Another illustration here presents itself with the
force of the most powerful and interesting analogy. Some of the
earliest fishes of our globe, those of the Old Red Sandstone, present,
as we have seen, certain peculiarities, as the one-sided tail and an
inferior position of the mouth. No fishes of the present day, in a
mature state, are so characterized; but some, at a certain stage of
their existence, have such peculiarities. It occurred to a geologist to
inquire if the fish which existed before the Old Red Sandstone had any
peculiarities assimilating them to the fœtal condition of existing
fish, and particularly if they were small. The first which occur before
the time of the Old Red Sandstone, are those described by Mr.
Murchison, as belonging to the Upper Ludlow Rocks; they are and
rather small. Still older are those detected by Mr. Philips, in the
Aymestry Limestone, being the most ancient of the class which have as
yet been discovered; these are so extremely minute as only to be
distinguishable by the microscope. Here we apparently have very
clear demonstrations of a parity, or rather identity, of laws presiding
over the development of the animated tribes on the face of the earth,
and that of the individual in embryo.
The tendency of all these illustrations is to make
us look to development as the principle which has been
immediately concerned in the peopling of this globe, a process
extending over a vast space of time, but which is nevertheless
connected in character with the briefer process by which an individual
being is evoked from a simple germ. What mystery is there here—and
how shall I proceed to enunciate the conception which I have ventured
to form of what may prove to be its proper solution! It is an idea by
no means calculated to impress by its greatness, or to puzzle by its
profoundness. It is an idea more marked by simplicity than perhaps any
other of those which have explained the great secrets of nature. But in
this lies, perhaps, one of its strongest claims to the faith of
mankind.
The whole train of animated beings, from the simplest
and oldest up to the highest and most recent, are, then, to be regarded
as a series of advances of the principle of development, which
have depended upon external physical circumstances, to which the
resulting animals are appropriate. I contemplate the whole phenomena as
having been in the first place arranged in the counsels of Divine
Wisdom, to take place, not only upon this sphere, but upon all the
others in space, under necessary modifications, and as being carried
on, from first to last, here and elsewhere, under immediate favour of
the creative will or energy.[3] The nucleated
vesicle, the fundamental form of all organization, we must regard as the
meeting-point between the inorganic and the organic—the end of the
mineral and beginning of the vegetable and animal kingdoms, which thence
start in different directions, but in perfect parallelism and analogy.
We have already seen that this nucleated vesicle is itself a type of
mature and independent being in the infusory animalcules, as well as the
starting point of the fœtal progress of every higher individual in
creation, both animal and vegetable. We have seen that it is a form of
being which electric agency will produce—though not perhaps usher
into full life—in albumen, one of those compound elements of
animal bodies, of which another (urea) has been made by artificial
means. Remembering these things, we are drawn on to the supposition,
that the first step in the creation of life upon this planet was a
chemico-electric operation, by which simple germinal vesicles were
produced. This is so much, but what were the next steps? Let a
common vegetable infusion help us to an answer. There, as we have seen,
simple forms are produced at first, but afterwards they become more
complicated, until at length the life-producing powers of the infusion
are exhausted. Are we to presume that, in this case, the simple
engender the complicated? Undoubtedly, this would not be more wonderful
as a natural process than one which we never think of wondering at,
because familiar to us—namely, that in the gestation of the
mammals, the animalcule-like ovum of a few days is the parent, in a
sense, of the chick-like form of a few weeks, and that in all the
subsequent stages—fish, reptile, &c.—the one may, with
scarcely a metaphor, be said to be the progenitor of the other. I
suggest, then, as an hypothesis already countenanced by much that is
ascertained, and likely to be further sanctioned by much that remains
to be known, that the first step was an advance under favour of
peculiar conditions, from the simplest forms of being, to the next more
complicated, and this through the medium of the ordinary process of
generation.
Unquestionably, what we ordinarily see of nature is
calculated to impress a conviction that each species invariably
produces its like. But I would here call attention to a remarkable
illustration of natural law which has been brought forward by Mr.
Babbage, in his Ninth Bridgewater Treatise. The reader is
requested to suppose himself seated before the calculating machine, and
observing it. It is moved by a weight, and there is a wheel which
revolves through a small angle round its axis, at short intervals,
presenting to his eye successively, a series of numbers engraved on its
divided circumference.
Let the figures thus seen be the series, 1, 2, 3, 4,
5, &c., of natural numbers, each of which exceeds its immediate
antecedent by unity.
"Now, reader," says Mr. Babbage, "let me ask you how
long you will have counted before you are firmly convinced that the
engine has been so adjusted, that it will continue, while its motion is
maintained, to produce the same series of natural numbers? Some minds
are so constituted, that, after passing the first hundred terms, they
will be satisfied that they are acquainted with the law. After seeing
five hundred terms few will doubt, and after the fifty thousandth term
the propensity to believe that the succeeding term will be fifty
thousand and one, will be almost irresistible. That term will be
fifty thousand and one; and the same regular succession will continue;
the five millionth and the fifty millionth term will still appear in
their expected order, and one unbroken chain of natural numbers will
pass before your eyes, from one up to one hundred
million.
"True to the vast induction which has been made, the
next succeeding term will be one hundred million and one; but the next
number presented by the rim of the wheel, instead of being one hundred
million and two, is one hundred million ten thousand and two.
The whole series from the commencement being thus,—
| 1 | |
| 2 | |
| 3 | |
| 4 | |
| 5 | |
| ... | |
| .... | |
| ..... | |
| ...... | |
| 99,999,999 | |
| 100,000,000 | |
| regularly as far as | 100,000,001 | |
| 100,000,002 | the law changes. |
| 100,030,003 | |
| 100,060,004 | |
| 100,100,005 | |
| 100,150,006 | |
| 100,210,007 | |
| 100,280,008 | |
| ... ... ... | |
| ... ... ... | |
"The law which seemed at first to govern this series
failed at the hundred million and second term. This term is larger than we
expected by 10,000. The next term is larger than was anticipated by 30,000,
and the excess of each term above what we had expected forms the following
table:—
| 10,000 |
| 30,000 |
| 60,000 |
| 100,000 |
| 150,000 |
| ... ... |
| ... ... |
being, in fact, the series of triangular numbers,[4] each multiplied by 10,000.
"If we now continue to observe the numbers presented by
the wheel, we shall find, that for a hundred, or even for a thousand terms,
they continue to follow the new law relating to the triangular numbers; but
after watching them for 2761 terms, we find that this law fails in the case
of the 2762d term.
"If we continue to observe, we shall discover another
law then coming into action, which also is dependent, but in a different
manner, on triangular numbers. This will continue through about 1430 terms,
when a new law is again introduced which extends over about 950 terms, and
this, too, like all its predecessors, fails, and gives place to other laws,
which appear at different intervals.
"Now it must be observed that the law that each
number presented by the engine is greater by unity than the preceding
number, which law the observer had deduced from an induction of a
hundred million instances, was not the true law that regulated its
action, and that the occurrence of the number 100,010,002 at the
100,000,002nd term was as necessary a consequence of the original
adjustment, and might have been as fully foreknown at the commencement, as
was the regular succession of any one of the intermediate numbers to its
immediate antecedent. The same remark applies to the next apparent
deviation from the new law, which was founded on an induction of 2761
terms, and also to the succeeding law, with this limitation only—that,
whilst their consecutive introduction at various definite intervals, is a
necessary consequence of the mechanical structure of the engine, our
knowledge of analysis does not enable us to predict the periods themselves
at which the more distant laws will be introduced."
It is not difficult to apply the philosophy of this
passage to the question under consideration. It must be borne in mind that
the gestation of a single organism is the work of but a few days, weeks, or
months; but the gestation (so to speak) of a whole creation is a matter
probably involving enormous spaces of time. Suppose that an ephemeron,
hovering over a pool for its one April day of life, were capable of
observing the fry of the frog in the water below. In its aged afternoon,
having seen no change upon them for such a long time, it would be little
qualified to conceive that the external branchiae of these creatures were
to decay, and be replaced by internal lungs, that feet were to be
developed, the tail erased, and the animal then to become a denizen of the
land. Precisely such may be our difficulty in conceiving that any of the
species which people our earth is capable of advancing by generation to a
higher type of being. During the whole time which we call the historical
era, the limits of species have been, to ordinary observation, rigidly
adhered to. But the historical era is, we know, only a small portion of the
entire age of our globe. We do not know what may have happened during the
ages which preceded its commencement, as we do not know what may happen in
ages yet in the distant future. All, therefore, that we can properly infer
from the apparently invariable production of like by like is, that such is
the ordinary procedure of nature in the time immediately passing before our
eyes. Mr. Babbage's illustration powerfully suggests that this ordinary
procedure may be subordinate to a higher law which only permits it
for a time, and in proper season interrupts and changes it. We shall soon
see some philosophical evidence for this very conclusion.
It has been
seen that, in the reproduction of the higher animals, the new being passes
through stages in which it is successively fish-like and reptile-like. But
the resemblance is not to the adult fish or the adult reptile, but to the
fish and reptile at a certain point in their fœtal progress; this
holds true with regard to the vascular, nervous, and other systems alike.
It may be illustrated by a simple diagram. The fœtus of all the four
classes may be supposed to advance in an identical condition to the point
A. The fish there diverges and passes along a line apart, and peculiar to
itself, to its mature state at F. The reptile, bird, and mammal, go on
together to C, where the reptile diverges in like manner, A and advances by
itself to R. The bird diverges at D, and goes on to B. The mammal then goes
forward in a straight line to the highest point of organization at
M. | |
 |
This diagram shews only the main ramifications; but the
reader must suppose minor ones, representing the subordinate differences of
orders, tribes, families, genera, &c., if he wishes to extend his views to
the whole varieties of being in the animal kingdom. Limiting ourselves at
present to the outline afforded by this diagram, it is apparent that the
only thing required for an advance from one type to another in the
generative process is that, for example, the fish embryo should not diverge
at A, but go on to C before it diverges, in which case the progeny will be,
not a fish, but a reptile. To protract the straightforward part of the
gestation over a small space—and from species to species the space
would be small indeed—is all that is necessary.
This might be done by the force of certain external
conditions operating upon the parturient system. The nature of these
conditions we can only conjecture, for their operation, which in the
geological eras was so powerful, has in its main strength been long
interrupted, and is now perhaps only allowed to work in some of the lowest
departments of the organic world, or under extraordinary casualties in some
of the higher, and to these points the attention of science has as yet been
little directed. But though this knowledge were never to be clearly
attained, it need not much affect the present argument, provided it be
satisfactorily shewn that there must be some such influence within the
range of natural things.
To this conclusion it must be greatly conducive that the
law of organic development is still daily seen at work to certain effects,
only somewhat short of a transition from species to species. Sex we have
seen to be a matter of development. There is an instance, in a humble
department of the animal world, of arrangements being made by the animals
themselves for adjusting this law to the production of a particular sex.
Amongst bees, as amongst several other insect tribes, there is in each
community but one true female, the queen bee, the workers being false
females or neuters; that is to say, sex is carried on in them to a point
where it is attended by sterility. The preparatory states of the queen bee
occupy sixteen days; those of the neuters, twenty; and those of males,
twenty-four. Now it is a fact, settled by innumerable observations and
experiments, that the bees can so modify a worker in the larva state, that,
when it emerges from the pupa, it is found to be a queen or true female.
For this purpose they enlarge its cell, make a pyramidal hollow to allow of
its assuming a vertical instead of a horizontal position, keep it warmer
than other larvæ are kept, and feed it with a peculiar kind of food.
From these simple circumstances, leading to a shortening of the embryotic
condition, results a creature different in form, and also in dispositions,
from what would have otherwise been produced. Some of the organs possessed
by the worker are here altogether wanting.
We have a creature "destined to enjoy love, to burn with
jealousy and anger, to be incited to vengeance, and to pass her time
without labour," instead of one "zealous for the good of the community, a
defender of the public rights, enjoying an immunity from the stimulus of
sexual appetite and the pains of parturition; laborious, industrious,
patient, ingenious, skilful; incessantly engaged in the nurture of the
young, in collecting honey and pollen, in elaborating wax, in constructing
cells and the like!—paying the most respectful and assiduous attention
to objects which, had its ovaries been developed, it would have hated and
pursued with the most vindictive fury till it had destroyed them!"[5] All these changes may be produced by a mere
modification of the embryotic progress, which it is within the power of the
adult animals to effect. But it is important to observe that this
modification is different from working a direct change upon the embryo. It
is not the different food which effects a metamorphosis. All that is done
is merely to accelerate the period of the insect's perfection. By the
arrangements made and the food given, the embryo becomes sooner fit for
being ushered forth in its image or perfect state. Development may be said
to be thus arrested at a particular stage—that early one at which the
female sex is complete. In the other circumstances, it is allowed to go on
four days longer, and a stage is then reached between the two sexes, which
in this species is designed to be the perfect condition of a large portion
of the community. Four days more make it a perfect male. It is at the same
time to be observed that there is, from the period of oviposition, a
destined distinction between the sexes of the young bees. The queen lays
the whole of the eggs which are designed to become workers, before she
begins to lay those which become males. But probably the condition of her
reproductive system governs the matter of sex, for it is remarked that when
her impregnation is delayed beyond the twenty-eighth day of her entire
existence, she lays only eggs which become males.
We have here, it will be admitted, a most remarkable
illustration of the principle of development, although in an operation
limited to the production of sex only. Let it not be said that the
phenomena concerned in the generation of bees may be very different from
those concerned in the reproduction of the higher animals. There is a unity
throughout nature which makes the one case an instructive reflection of the
other.
We shall now see an instance of development operating
within the production of what approaches to the character of variety of
species. It is fully established that a human family, tribe, or nation, is
liable, in the course of generations, to be either advanced from a mean
form to a higher one, or degraded from a higher to a lower, by the
influence of the physical conditions in which it lives. The coarse features,
and other structural peculiarities of the negro race only continue while
these people live amidst the circumstances usually associated with
barbarism. In a more temperate clime, and higher racial state, the face and
figure become greatly refined. The few African nations which possess any
civilization also exhibit forms approaching the European; and when the same
people in the United States of America have enjoyed a within- door life for
several generations, they assimilate to the whites amongst whom they live.
On the other hand, there are authentic instances of a people originally
well-formed and good-looking, being brought, by imperfect diet and a
variety of physical hardships, to a meaner form. It is remarkable that
prominence of the jaws, a recession and diminution of the cranium, and an
elongation and attenuation of the limbs, are peculiarities always produced
by these miserable conditions, for they indicate an unequivocal
retrogression towards the type of the lower animals. Thus we see nature
alike willing to go back and to go forward. Both effects are simply the
result of the operation of the law of development in the generative system.
Give good conditions, it advances; bad ones, it recedes. Now, perhaps, it
is only because there is no longer a possibility, in the higher types of
being, of giving sufficiently favourable conditions to carry on species to
species, that we see the operation of the law so far limited.
Let us trace this law also in the production of certain
classes of monstrosities. A human fœtus is often left with one of the
most important parts of its frame imperfectly developed: the heart, for
instance, goes no farther than the three-chambered form, so that it is the
heart of a reptile. There are even instances of this organ being left in
the two-chambered or fish form. Such defects are the result of nothing more
than a failure of the power of development in the system of the mother,
occasioned by weak health or misery. Here we have apparently a realization
of the converse of those conditions which carry on species to species, so
far, at least, as one organ is concerned. Seeing a complete specific
retrogression in this one point, how easy it is to imagine an access of
favourable conditions sufficient to reverse the phenomenon, and make a fish
mother develop a reptile heart, or a reptile mother develop a mammal one.
It is no great boldness to surmise that a super-adequacy in the measure of
this under-adequacy (and the one thing seems as natural an occurrence as
the other) would suffice in a goose to give its progeny the body of a rat,
and produce the ornithorynchus, or might give the progeny of an
ornithorynchus the mouth and feet of a true rodent, and thus complete at
two stages the passage from the aves to the mammalia.
Perhaps even the transition from species to species does
still take place in some of the obscurer fields of creation, or under
extraordinary casualties, though science professes to have no such facts on
record. It is here to be remarked, that such facts might often happen, and
yet no record be taken of them, for so strong is the prepossession for the
doctrine of invariable like-production, that such circumstances, on
occurring, would be almost sure to be explained away on some other
supposition, or, if presented, would be disbelieved and neglected. Science,
therefore, has no such facts, for the very same reason that some small
sects are said to have no discreditable members—namely, that they do
not receive such persons, and extrude all who begin to verge upon the
character. There are, nevertheless, some facts which have chanced to be
reported without any reference to this hypothesis, and which it seems
extremely difficult to explain satisfactorily upon any other. One of these
has already been mentioned—a progression in the forms of the
animalcules in a vegetable infusion from the simpler to the more
complicated, a sort of microcosm, representing the whole history of the
progress of animal creation as displayed by geology. Another is given in
the history of the Acarus Crossii which may be only the ultimate stage of
a series of similar transformations effected by electric agency in the
solution subjected to it. There is, however, one direct case of a
translation of species, which has been presented with a respectable amount
of authority.[6] It appears that, whenever oats sown
at the usual time are kept cropped down during summer and autumn, and
allowed to remain over the winter, a thin crop of rye is the harvest
presented at the close of the ensuing summer. This experiment has been
tried repeatedly, with but one result; invariably the secale cereale
is the crop reaped where the avena sativa, a recognised different
species, was sown. Now it will not satisfy a strict inquirer to be told
that the seeds of the rye were latent in the ground and only superseded the
dead product of the oats; for if any such fact were in the case, why should
the usurping grain be always rye? Perhaps those curious facts which have
been stated with regard to forests of one kind of trees, when burnt down,
being succeeded (without planting) by other kinds, may yet be found most
explicable, as this is, upon the hypothesis of a progression of species
which takes place under certain favouring conditions, now apparently of
comparatively rare occurrence. The case of the oats is the more valuable,
as bearing upon the suggestion as to a protraction of the gestation at a
particular part of its course. Here, the generative process is, by the
simple mode of cropping down, kept up for a whole year beyond its usual
term. The type is thus allowed to advance, and what was oats becomes
rye.
The idea, then, which I form of the progress of organic
life upon the globe—and the hypothesis is applicable to all similar
theatres of vital being—is, that the simplest and most primitive
type, under a law to which that of like-production is subordinate, gave
birth to the type next above it, that this again produced the next higher,
and so on to the very highest, the stages of advance being in all
cases very small—namely, from one species only to another; so that the
phenomenon has always been of a simple and modest character. Whether the
whole of any species was at once translated forward, or only a few parents
were employed to give birth to the new type, must remain undetermined; but,
supposing that the former was the case, we must presume that the moves
along the line or lines were simultaneous, so that the place vacated by one
species was immediately taken by the next in succession, and so on back to
the first, for the supply of which the foundation of a new germinal
vesicle out of inorganic matter was alone necessary. Thus, the production
of new forms, as shewn in the pages of the geological record, has never
been anything more than a new stage of progress in gestation, an event as
simply natural, and attended as little by any circumstances of a wonderful
or startling kind, as the silent advance of an ordinary mother from one
week to another of her pregnancy. Yet, be it remembered, the whole
phenomena are, in another point of view, wonders of the highest kind, for
in each of them we have to trace the effect of an Almighty Will which had
arranged the whole in such harmony with external physical circumstances,
that both were developed in parallel steps—and probably this
development upon our planet is but a sample of what has taken place,
through the same cause, in all the other countless theatres of being which
are suspended in space.
This may be the proper place at which to introduce the
preceding illustrations in a form calculated to bring them more forcibly
before the mind of the reader. The following table was suggested to me, in
consequence of seeing the scale of animated nature presented in Dr.
Fletcher's Rudiments of Physiology. Taking that scale as its basis, it
shews the wonderful parity observed in the progress of creation, as
presented to our observation in the succession of fossils, and also in the
fœtal progress of one of the principal human organs.[7] This scale, it may be remarked, was not made up with
a view to support such an hypothesis as the present, nor with any apparent
regard to the history of fossils, but merely to express the appearance of
advancement in the orders of the Cuvierian system, assuming, as the
criterion of that advancement, "an increase in the number and extent of the
manifestations of life, or of the relations which an organized being bears
to the external world." Excepting in the relative situation of the annelida
and a few of the mammal orders, the parity is perfect; nor may even these
small discrepancies appear when the order of fossils shall have been
further investigated, or a more correct scale shall have been formed.
Meanwhile, it is a wonderful evidence in favour of our hypothesis, that a
scale formed so arbitrarily should coincide to such a nearness with our
present knowledge of the succession of animal forms upon earth, and also
that both of these series should harmonize so well with the view given by
modern physiologists of the embryotic progress of one of the organs of the
highest order of animals.
 |
|
 |
The reader has seen physical conditions several times
referred to, as to be presumed to have in some way governed the progress
of the development of the zoological circle. This language may seem vague,
and, it may be asked,—can any particular physical condition be adduced
as likely to have affected development? To this it may be answered, that
air and light are probably amongst the principal agencies of this kind
which operated in educing the various forms of being. Light is found to be
essential to the development of the individual embryo. When tadpoles were
placed in a perforated box, and that box sunk in the Seine, light being
the only condition thus abstracted, they grew to a great size in their
original form, but did not pass through the usual metamorphose which brings
them to their mature state as frogs. The proteus, an animal of the frog
kind, inhabiting the subterraneous waters of Carniola, and which never
acquires perfect lungs so as to become a land animal, is presumed to be an
example of arrested development, from the same cause. When, in connexion
with these facts, we learn that human mothers living in dark and close
cells under ground,—that is to say, with an inadequate provision of
air and light,—are found to produce an unusual proportion of defective
children,.[8] We can appreciate the important effects
of both these physical conditions in ordinary reproduction. Now there is
nothing to forbid the supposition that the earth has been at different
stages of its career under different conditions, as to both air and light.
On the contrary, we have seen reason for supposing that the proportion of
carbonic acid gas (the element fatal to animal life) was larger at the time
of the carboniferous formation than it afterwards became. We have also seen
that astronomers regard the zodiacal light as a residuum of matter
enveloping the sun, and which was probably at one time denser than it is
now. Here we have the indications of causes for a progress in the
purification of the atmosphere and in the diffusion of light during the
earlier ages of the earth's history, with which the progress of organic
life may have been conformable. An accession to the proportion of oxygen,
and the effulgence of the central luminary, may have been the immediate
prompting cause of all those advances from species to species which we have
seen, upon other grounds, to be necessarily supposed as having taken place.
And causes of the like nature may well be supposed to operate on other
spheres of being, as well as on this. I do not indeed present these ideas
as furnishing the true explanation of the progress of organic creation,
they are merely thrown out as hints towards the formation of a just
hypothesis, the completion of which is only to be looked for when some
considerable advances shall have been made in the amount and character of
our stock of knowledge.
Early in this century, M. Lamarck, a naturalist of the
highest character, suggested an hypothesis of organic progress which
deservedly incurred much ridicule, although it contained a glimmer of the
truth. He surmised, and endeavoured, with a great deal of ingenuity, to
prove, that one being advanced in the course of generations to another, in
consequence merely of its experience of wants calling for the exercise of
its faculties in a particular direction, by which exercise new developments
of organs took place, ending in variations sufficient to constitute a new
species. Thus he thought that a bird would be driven by necessity to seek
its food in the water, and that, in its efforts to swim, the outstretching
of its claws would lead to the expansion of the intermediate membranes, and
it would thus become web-footed. Now it is possible that wants and the
exercise of faculties have entered in some manner into the production of
the phenomena which we have been considering; but certainly not in the way
suggested by Lamarck, whose whole notion is obviously so inadequate to
account for the rise of the organic kingdoms, that we only can place it
with pity among the follies of the wise. Had the laws of organic
development been known in his time, his theory might have been of a more
imposing kind.
It is upon these that the present hypothesis is mainly
founded. I take existing natural means, and shew them to have been capable
of producing all the existing organisms, with the simple and easily
conceivable aid of a higher generative law, which we perhaps still see
operating upon a limited scale. I also go beyond the French philosopher to
a very important point, the original Divine conception of all the forms of
being which these natural laws were only instruments in working out and
realizing. The actuality of such a conception I hold to be strikingly
demonstrated by the discoveries of Macleay, Vigors, and Swainson, with
respect to the affinities and analogies of animal (and by implication
vegetable) organisms.[9] Such a regularity in the
structure, as we may call it, of the classification of
animals, as is shewn in their systems, is totally irreconcilable with
the idea of form going on to form merely as needs and wishes in the animals
themselves dictated. Had such been the case, all would have been irregular,
as things arbitrary necessarily are. But, lo, the whole plan of being is as
symmetrical as the plan of a house, or the laying out of an old-fashioned
garden! This must needs have been devised and arranged for beforehand. And
what a preconception or forethought have we here! Let us only for a moment
consider how various are the external physical conditions in which animals
live—climate, soil, temperature, land, water, air—the
peculiarities of food, and the various ways in which it is to be sought;
the peculiar circumstances in which the business of reproduction and the
care-taking of the young are to be attended to—all these required to
be taken into account, and thousands of animals were to be formed suitable
in organization and mental character for the concerns they were to have
with these various conditions and circumstances—here a tooth fitted for
crushing nuts; there a claw fitted to serve as a hook for suspension; here
to repress teeth and develop a bony net-work instead; there to arrange for
a bronchial apparatus, to last only for a certain brief time; and all these
animals were to be schemed out, each as a part of a great range, which was
on the whole to be rigidly regular: let us, I say, only consider these
things, and we shall see that the decreeing of laws to bring the whole
about was an act involving such a degree of wisdom and device as we only
can attribute, adoringly, to the one Eternal and Unchangeable. It may be
asked, how does this reflection comport with that timid philosophy which
would have us to draw back from the investigation of God's works, lest the
knowledge of them should make us undervalue his greatness and forget his
paternal character? Does it not rather appear that our ideas of the Deity
can only be worthy of him in the ratio in which we advance in a knowledge
of his works and ways; and that the acquisition of this knowledge is
consequently an available means of our growing in a genuine reverence for
him!
But the idea that any of the lower animals have been
concerned in any way with the origin of man—is not this degrading?
Degrading is a term, expressive of a notion of the human mind, and the
human mind is liable to prejudices which prevent its notions from being
invariably correct. Were we acquainted for the first time with the
circumstances attending the production of an individual of our race, we
might equally think them degrading, and be eager to deny them, and exclude
them from the admitted truths of nature. Knowing this fact familiarly and
beyond contradiction, a healthy and natural mind finds no difficulty in
regarding it complacently. Creative Providence has been pleased to order
that it should be so, and it must therefore be submitted to. Now the idea
as to the progress of organic creation, if we become satisfied of its
truth, ought to be received precisely in this spirit. It has pleased
Providence to arrange that one species should give birth to another, until
the second highest gave birth to man, who is the very highest: be it so,
it is our part to admire and to submit. The very faintest notion of there
being anything ridiculous or degrading in the theory—how absurd does
it appear, when we remember that every individual amongst us actually
passes through the characters of the insect, the fish, and reptile, (to
speak nothing of others,) before he is permitted to breathe the breath of
life! But such notions are mere emanations of false pride and ignorant
prejudice. He who conceives them little reflects that they, in reality,
involve the principle of a contempt for the works and ways of God, For it
may be asked, if He, as appears, has chosen to employ inferior organisms as
a generative medium for the production of higher ones, even including
ourselves, what right have we, his humble creatures, to find fault? There
is, also, in this prejudice, an element of unkindliness towards the lower
animals, which is utterly out of place. These creatures are all of them
part products of the Almighty Conception, as well as ourselves. All of them
display wondrous evidences of his wisdom and benevolence. All of them have
had assigned to them by their Great Father a part in the drama of the
organic world, as well as ourselves. Why should they be held in such
contempt? Let us regard them in a proper spirit, as parts of the grand
plan, instead of contemplating them in the light of frivolous prejudices,
and we shall be altogether at a loss to see how there should be any
degradation in the idea of our race having been genealogically connected
with them.
Notes
Danbenton established the rule, that all the viviparous quadrupeds have seven vertebrae in the neck.
Lord's Popular Physiology. It is to
Tiedemann that we chiefly owe these curious observations; but ground
was first broken in this branch of physiological science by Dr. John
Hunter.
When I formed this idea I was not aware of
one which seems faintly to foreshadow it—namely, Socrates's
doctrine, afterwards dilated on by Plato, that "previous to the
existence of the world, and beyond its present limits, there existed
certain archetypes, the embodiment (if we may use such a word) of
general ideas; and that these archetypes were models, in imitation of
which all particular beings were created."
The numbers 1, 3, 6 10, 15, 21, 28, &c. are
formed by adding the successive terms of the series of natural numbers
thus:
| 1= 1 | |
| 1+2= 3 | |
| 1+2+3= 6 | |
| 1+2+3+4=10 | , &c. |
They are called triangular numbers, because a number of points
corresponding to any term can always be placed in the form of a triangle;
for instance—
| . |
|
.
. . |
|
.
. .
. . . |
|
.
. .
. . .
. . . . |
| 1 |
|
3 |
|
6 |
|
10 |
Kirby and Spence.
See an article by Dr. Weissenborn, in the New
Series of "Magazine of Natural History," vol. i. p. 574.
"It is a fact of the highest
interest and moment that as the brain of every tribe of animals appears to
pass, during its development, in succession through the types of all those
below it, so the brain of man passes through the types of those of every
tribe in the creation. It represents, accordingly, before the second month
of gestation, that of an avertebrated animal; at the second month, that of
an osseous fish; at the third, that of a turtle; at the fourth, that of a
bird; at the fifth, that of one of the rodentia; By the sixth, that of one
of the ruminantia; at the seventh, that of one of the digitigrada; at the
eighth, that of one of the quadrennana; till at length, at the ninth, it
compasses the brain of man! It is hardly necessary to say, that all this is
only an approximation to the truth; since neither is the brain of all
osseous fishes, of all turtles, of all birds, nor of all the species of any
one of the above order of mammals, by any means precisely the same, nor
does the brain of the human fœtus at any time precisely resemble,
perhaps, that of any individual whatever among the lower animate.
Nevertheless, it may be said to represent, at each of the above-mentioned
periods, the aggregate, as it were, of the brains of each of the tribes
stated; consisting as it does, about the second month, chiefly of the
mesial parts of the cerebellum, the corpora quadrigemina, thalami optic),
rudiments of the hemispheres of the cerebrum and corpora striate; and
receiving in succession, at the third, the rudiments of the lobes of the
cerebrom; at the fourth, those of the fornix, corpus callosum, and septum
lucidum; at the fifth, the tubor annulare, and so forth; the posterior
lobes of the cerebrum increasing from before to behind, so as to cover the
thalami optici about the fourth month, the corpora quadrigemina about the
sixth, and the cerebellum about the seventh. This, then, is another example
of an increase in the complexity of an organ succeeding its centralization;
as if Nature, having first piled up her materials in one spot, delighted
afterwards to employ her abundance, not so much in enlarging old parts as
in forming new ones upon the old foundations, and thus adding to the
complexity of a fabric, the rudimental structure of which is in an animals
equally simple."—Fletcher's Rudiments of Physiology.
Some poor people having taken up their abode in
the cells under the fortifications of Lisle, the proportion of defective
infants produced by them became so great, that it was deemed necessary to
issue an order commanding these cells to be shut up.
These affinities and analogies are explained in
the next chapter.
| |
[ Robert Chambers,
Vestiges of the
Natural History of Creation, 1st edition, 1844; James Secord,
ed., Chicago: University of Chicago Press, 1994, pp. 191-235. ]
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