Kitabı oku: «Omphalos: An Attempt to Untie the Geological Knot», sayfa 12

It is impossible to read this description without being reminded of the manner in which the bean or other leguminous seed links itself with a former generation by means of the dehiscent legume, itself a production of the parent plant. And the same reasoning applies to this case, as to the other; – the egg, if the Blatta was created in that stage, would triumphantly show in the pod with which it was covered, a record of past processes.

So, once more, with the immense tribes of solitary Bees, Wasps, and Spheges. I shall mention but one example, from my own experience. It is the Dirt Dauber (Pelopœus flavipes) of North America. The female of this elegant fly, when about to lay her eggs, builds up a tubular nest of cells with fine mud, which she makes by mingling and kneading road-dust with her saliva. Each tube consists of several cells, separated by transverse partitions of the mortar; and in each, before she closes it up, she lays a single egg, which she then covers with spiders which are to constitute the food of the grub when hatched, and to last it during the whole period of its larval growth. Dead spiders would not do, for their bodies would either dry up, or become putrescent long before the young grub could devour them. On the other hand, if a number of these fierce and carnivorous creatures were immured, in health, they would soon destroy one another. To obviate this, the parent-fly ingeniously stings every spider just sufficiently to paralyse, without killing it. Thus nearly a score of living spiders are packed away in a cell scarcely larger than a lady's thimble; and thus they remain fresh and succulent food for the larva, not only till it is ready to begin its eating task, but even to the close of its repast.

I think this a particularly instructive example. The Pelopœus was indubitably created; for it exists. As indubitably it was created in some stage of its cyclical life-history. If as an imago, then I press the argument from the necessity of its previous metamorphoses. If as a pupa, or a larva, or an egg, each of these conditions of life was entirely passed as an inmate of the mud-walled cottage; which, cottage was built and stocked with food by the industry and skill of the parent-fly. The grub could not have lived without the stored spiders; the spiders could not have been stored (normally) without the agency of the fly.

In some other instances the connexion between germ and parent is patent to the eye. The beautiful Star-fish, Cribella, passes through all its infant metamorphoses, changing from an ovum to an Infusory, thence to a Pluteus (or what is analogous to it), thence to a Star-fish, all in the marsupium provided for the occasion, by the drawing together of the arms of the patient mother. The female Brachionus carries its deposited eggs attached to the hinder part of its body; and thus we can trace, through their transparent coats, the gradual development of the organs of the embryo, – the coloured eye, the rotatory cilia, the complex mastax, – and even detect the vigorous movements of these and other parts, while yet carried hither and thither by the parent.

But further, in the class from which I have taken this last illustration – that of the Rotifera – there are examples of viviparous genera; and these, because of the perfect transparency of all the integuments, are peculiarly instructive and germane to my argument.

In Rotifer macrurus the ovary with its germinal vesicles is distinctly seen occupying one side of the animal. From this one of the vesicles enlarges, until it becomes a long-oval translucent sac, nearly filling the whole left side of the visceral cavity. A kind of spasmodic movement is suddenly observed in this oblong ovum, and instantly we see, in its place, a well-developed living young; as distinctly visible as if it were excluded. It lies in a bent position, with its foot upturned; is nearly half the length of the parent; is furnished with a proboscis, with a pair of crimson eyes, with ciliary wheels, with a mastax whose toothed hemispheres frequently work vigorously, and with all the viscera proper to the species.

In the beautiful, comparatively large, and economically singular genus, Asplanchna, the same process of development can be watched with perfect facility through every stage.

In the body of the female parent, as transparent as the clearest glass, the band-like ovary is seen floating in the visceral cavity, with several ova in various degrees of advancement. We trace one of these till it becomes a manifestly living young in the ovisac, lying along at the bottom of the parental cavity, more than one-third of whose volume is occupied by it: – supposing it to be a female infant. All its organs, – the eyes, the jaws, the stomach, the pancreatic glands, the ovary with its nuclei, the muscles, the rotatory cilia, &c. can be traced with the utmost distinctness long before birth, and its motions are strong and voluntary.

Neither in this case, nor in that of Rotifer, does the young animal pass through any metamorphosis; the unborn young has the full development of the parent, in every respect but size. In each case, the visible life-history of the individual commences not at birth, but at a period long antecedent, if indeed it can be said to commence at all, where we see it gradually developed from a nucleus, which was an integral part of the parental ovary, even before that parent's birth.

In the case of the amusing little Water-fleas (Daphnia), we have another example of viviparous generation, which, owing to the same cause as in the Rotifera, – the transparency of the integument, can be followed through all its stages by the eye of the observer. The eggs of this little Crustacean are deposited in a special chamber within the valves of the parent, where they are hatched. The young remain in their receptacle for a period, which varies according to the temperature, but long enough for them to undergo important changes in structure, and to pass their first moult.⁹⁶

Here, again, it is impossible to select a condition which does not take hold of a pre-existence; for the youngest independent stage is dependent on earlier stages; and these are passed in visible connexion with the parent.

It is true there is in this genus, another mode of reproduction, by means of eggs which are thrown off enveloped in an organic covering, called the ephippium. If this condition be selected for the argument of my supposed opponent, I reply that it amounts to nearly the same thing; only the case will then come into the category of those animals whose earliest stages are protected by coverings formed from the body of the parent, – like the Hypogymna, and the Cockroach, already alluded to.

Where then, in these species, can we possibly select a stage of life, which is not inseparably and even visibly connected with a previous stage?

If we come to the vertebrate creatures, the argument becomes assuredly not less convincing. The formidable Shark, which we considered as a well-toothed adult ready for slaughter, let us suppose to have been created in the harmlessness of infancy. It is a slender thing, some ten or twelve inches long, bent upon itself, inclosing in the ring thus made, the vitellus or yelk-bag, the contents of which are in process of being absorbed into the abdomen. But the whole, – Shark, yelk-bag, and all – is imprisoned in a brown horny capsule, that looks like a pillow-case, with long tapes appended to the four corners.

This very peculiar protecting capsule points clearly to a peculiar structure in the parent. The embryo was not inclosed in the pillow-case, at its first formation; but, in the course of its descent from the ovary through the oviduct, it had to pass a region of the latter, where was a thick glandular mass, – the nidamental gland, – whose office it was to secrete a dense layer of albumen, with which, the embryo became invested. This substance took the form of the flattened purse, or pillow-case, with produced angles, above described, and on its exclusion from the duct assumed a very tough horny consistence, and a dark mahogany colour.

The comparative anatomist would, therefore, without the least hesitation, refer the origin of the investing capsule to the nidamental glands of the female Shark; but supposing the embryo to be but just created, his physiological science would only lead him to a false conclusion.

If the Tree-frog afforded us evidence of pre-existent time, in the metamorphosis which it must naturally have experienced from the tadpole to the reptilian condition, what shall we say to that strange and uncouth member of the same class, – the Surinam Toad (Pipa)? Little would be gained by selecting the germ-stage, as the presumed epoch of creation in this case; for, according to the extraordinary economy of this genus, the male acts as midwife, and the female as wet-nurse, to the hopeful progeny.

"As fast as the female deposits her eggs, the male who attends her arranges them on her broad back, to the number of fifty or upwards. The contact of these eggs with the skin appears to produce a sort of inflammation; the skin of the back swells, and becomes covered with pits or cells, which enclose each a single egg, the surface of the back resembling the closed cells of a honeycomb. The female now betakes herself to the water; and in these cells the eggs are not only hatched, but the tadpoles undergo their metamorphosis, emerging in a perfect condition, though very small, after a lapse of eighty-two days from the time in which the eggs were placed in their respective pits."

To a tyro in animal physiology it might seem that the smooth rounded egg of a bird or a lizard, presents an example of an organism in the simplest possible condition, and in a stage which, if any can be, is independent of anything that went before.

But is it so? Let us see. Here is the egg of the common Fowl. I take it in my hand, and perceive nothing but an uniform, smooth, hard, white surface. This I break, and find that it is a thin layer of calcareous substance, which, on microscopical examination, proves to be composed of minute polygonal particles, so agglutinated as to leave open spaces in the interstices of their contiguous angles.

Below this calcareous shell I find a membrane (membrana putaminis), which seems, from its thinness in most parts, to be single, but which is separated into two layers at the large end of the egg.

Within this membrane there is another (the chalaza) which, closely enveloping the yelk, passes off from it towards each extremity of the egg in the form of a twisted cord.

Then comes a delicate membrane (memb. vitelli) in close contact with, and enveloping the orange-coloured yelk; which latter carries, on one point of its globular surface, the thin blastoderm, or germinal membrane.

The yelk-globe, fastened by its twisted chalazæ, is suspended in a glairy fluid (albumen), which fills the space between it and the membrana putaminis. This fluid, though apparently homogeneous, is really composed of many layers, and the innermost of these it is which is condensed into the chalaza.

Such, then, is the complex structure of this apparently simple object. What light can it throw on our inquiry?

Each of these component parts bears witness to a succession of past periods. The yelk with its germ was first formed, escaping naked, or clothed only with its own excessively delicate membrane, from its ovisac into the oviduct. Through the course of this tube it now slowly descended, receiving successive investments as it proceeded. The albumen was deposited layer upon layer from the mucous membrane of the upper part of the oviduct; the first depositions condensing into the chalaza. By and by it came down to a region of the oviduct where a tenacious secretion was poured out, which, investing the albumen, soon hardened into a substance resembling thin parchment, and formed the membrana putaminis; two successive layers of this were deposited, between which a bubble of gas, chiefly composed of oxygen generated in the interval, was inclosed. Then it descended still farther, to a part where the lining membrane of the duct was endowed with the power of secreting calcareous matter, which, as above stated, was deposited in a thin layer of polygonal atoms. And now, having received all its components, and having arrived at the orifice of the duct, the egg was laid.

Here, then, there is abundant evidence of successive processes, which must have preceded the existence of this complete and perfect egg. But there is yet one more evidence which I have reserved to the last, because it is peculiarly distinct and palpable, even to the senses.

The chalaza, we see, is twisted at each pole of the yelk-globe, until it resembles a piece of twine: what is the meaning of this? It was, as I observed, deposited as a loosely enveloping membrane in the upper part of the oviduct; the yelk-globe, however, was progressively descending; and, as it descended, it continually revolved upon its axis; by means of which rotation the investing membrane was gathered at each pole into a spirally twisted cord, stretching from the yelk to the ends of the membrana putaminis. Thus it presents us with an unmistakeable record of what took place in the earlier periods of the descent.

We saw distinct traces of the past in the structure of a feather. But the feathers have already begun to develop before the young bird leaves the egg. And the structure of the egg carries us back to the oviduct of the parent-fowl.

At what stage of existence, then, could a bird, by possibility, have been created, which did not present distinct records of prochronic development?

If we come to the Mammalia, the impossibility of finding such a stage becomes only more and more obvious. For it is a law in physiology, that the higher the grade of organization assigned to any being, the more it is assisted in infancy by the parent.

"This law is remarkably exemplified in the class Mammalia, which unquestionably ranks at the head of the animal kingdom, in respect to degree of intelligence and general elevation of structure. It is the universal and most prominent characteristic of this class, that the young are retained within the body of the female parent, until they have made considerable progress in their development; that, whilst there, they derive their support almost immediately from her blood; and that they are afterwards nourished for some time by a secretion which she affords."⁹⁷

The fœtus of the Kangaroo, when expelled from the womb, is scarcely more than an inch in length. Its limbs and its tail are indeed formed, but the imperfect creature has been compared to an earthworm, for the colour and semi-transparency of the integument. In this condition it is unable to find and seize the nipple, and equally unable to draw sustenance therefrom, by its own unaided efforts. The milk is ejected, by the muscular action of the mother, into the throat of the fœtus, and there is a peculiar and beautiful contrivance to obviate the danger of the injected fluid's passing into the trachea instead of the œsophagus.

Yet, from this helpless naked condition to that of the active, well-clothed, experienced young, able to quit the maternal pouch at will, and flee to it for protection, there is a well-understood and perfectly appreciable concatenation of stages, each of which looks back to, and depends on, those previously existing. And, during the whole of these, the mother's presence is necessary to the comfort, and, for the greater part of them, to the very existence of the infant.

Thus, once more, there is no condition of the animal, on which we may fix, as being so simple, as to have no retrospective history.

The umbilical cicatrix I have already alluded to; but I may be permitted to mention it again; because, in all the higher Mammalia, at least, it exists, throughout life, an eloquent witness to the organic connexion of the individual with a mother, and therefore to her pre-existence. If it were legitimate to suppose that the first individual of the species Man was created in the condition answering to that of a new-born infant, there would still be the need of maternal milk for its sustenance, and maternal care for its protection, for a considerable period; while, if we carry on the suggested stage to the period when this provision is no longer indispensable, the development of hair, nails, bones, &c., will have proceeded through many stages. And, in either condition, the navel cord or its cicatrix remains, to testify to something anterior to both.

XII
THE CONCLUSION

"We have no experience in the creation of worlds."

Chalmers.

We have passed, in review before us the whole organic world: and the result is uniform; that no example can be selected from the vast vegetable kingdom, none from the vast animal kingdom, which did not at the instant of its creation present indubitable evidences of a previous history. This is not put forth as a hypothesis, but as a necessity; I do not say that it was probably so, but that it was certainly so; not that it may have been thus, but that it could not have been otherwise.

I do not touch the inorganic world: my acquaintance with chemistry is inadequate for this: perhaps the same law does not extend to the inorganic elements: perhaps their developments, and combinations are not, like the economy of plants and animals, essentially and exclusively cyclical: perhaps carbon and oxygen and hydrogen could be created in conditions, which obviously did not depend on any previously existing conditions. This I do not know: I neither affirm nor deny it. But I think I have demonstrated in these pages, that such a cyclical character does attach to, and is inseparable from, the history of all organic essences; and that creation can be nothing else than a series of irruptions into circles: that, supposing the irruption to have been made at what part of the circle we please, and varying this condition indefinitely at will, – we cannot avoid the conclusion that each organism was from the first marked with the records of a previous being. But since creation and previous history are inconsistent with each other; as the very idea of the creation of an organism excludes the idea of pre-existence of that organism, or of any part of it; it follows, that such records are false, so far as they testify to time; that the developments and processes thus recorded have been produced without time, or are what I have called prochronic.

Nor is this conclusion in the least degree affected by the actual chronology of creation. The phenomena were equally eloquent, and equally false, whether any individual organism were created six thousand years ago, or innumerable ages; whether primitively, or after the successive creations and annihilations of former organisms.

The law of creation supersedes the law of nature; so far, at least, as the organic world is concerned. The law of nature, established by universal experience, is, that its phenomena depend upon certain natural antecedents: the law of creation is, that the same phenomena depend upon no antecedents. The philosopher who should infer the antecedents from the phenomena alone, without having considered the law of creation, would be liable to form totally false conclusions. In order to be secure from error, he must first assure himself that creation is eliminated from the category of facts which he is investigating; and this he could do only when the facts come within the sphere of personal observation, or of historic testimony. Up to such a period of antiquity as is covered by credible history, and within such a field of observation as history may be considered fairly cognisant of, – the inference of physical antecedents from physical phenomena, in the animal or vegetable world, is legitimate and true. But, beyond that period, I cannot safely deduce the same conclusion; because I cannot tell but that at any given moment included in my inquiry, creation may have occurred, and have been the absolute beginning of the circular series.

The question of the actual age of any species, whether plant or animal, is one which cannot be answered, except on historic testimony. The sequence of cause and effect is not adequate to answer it; for a legitimate use of this principle, supposing it the only element of the inquiry, would inevitably lead us to the eternity of all existing organic life.

One of the familiar street-exhibitions in the metropolis is a tiny coach and horses of glittering metal; which, by means of simple machinery, course round and round the margin of a circular table. Let us suppose two youths of philosophical turn to come up during the process. They gaze for a while, and one asks his companion the following question.

"How long do you suppose that coach has been running round?"

"How long! for an indefinite period, for aught I know. I have counted twenty-two turns, and can see no change: nor can I suggest any point where the course could have begun."

Here a shrewd lad, carrying a grocer's basket, breaks in.

"Oh no; there have been only six-and-twenty turns altogether. Four turns had been made when you came up. The whole began by the man taking the carriage out of a box; then he set it down out there, just opposite to us, and gave it a little push with his finger, and it has been running ever since. I saw him do it."

Now perhaps you will say that a glance at the machinery beneath the table would show in a moment how many turns had been made, and how many could be made. Very true: but what if the tramp had locked up his clock-work, and would not let you look at it?

The only evidence worth a rush is that of the lad who saw the whirligig set a-going.

I wish it to be distinctly understood, that I am not proving the exact or approximate antiquity of the globe we inhabit. I am not attempting to show that it has existed for no more than six thousand years. I wish this to be distinctly stated, because I am sure I shall meet with many opponents unfair enough, or illogical enough, to misrepresent or misunderstand my argument, and sound the trumpet of victory, because I cannot demonstrate that. All I set myself to do, is to invalidate the testimony of the witness relied on for the indefinitely remote antiquity; to show that in a very large and important field of nature, evidence exactly analogous to that relied on would inevitably lead to a false conclusion, and must, therefore, be rejected, or received only contingently; received only as indicative of probability, and that only in the absence of any positive witness to the contrary.

Perhaps it may be objected, that there is no sufficient analogy between the phenomena from which the past history of a single organism is inferred, and those from which the past history of a world is inferred. Is there not?

Permit me to repeat an illustration I have already used. The geologist finds a fossil skeleton. His acquaintance with anatomy enables him to pronounce that the objects found are bones. He sees cylinders, condyles, cavities for the marrow, scars of attachment of muscles and tendons, foramina for the passage of nerves and blood-vessels; he finds the internal structure, no less than the form and surface, such as to leave not a doubt that these are real bones. Now universal experience has taught him that bones imply the existence of flesh; that flesh implies blood; that blood implies life; that life implies time. He therefore concludes unhesitatingly, that this skeleton was once alive, and that time passed over it in that living condition.

Is not this process of reasoning exactly parallel to that which he would have pursued if he had examined an animal the moment after its creation, (supposing this fact to be unknown to him,) and by which he would in like manner have inferred past time? And where is the vital difference between the two cases, which would operate to make a conclusion which is manifestly false in the one case, necessarily true in the other?

One of the most eminent of living botanists has set forth in striking terms the parallelism which I am suggesting. Speaking of the shoot as the vegetable individual, and the woody trunk as a kind of ever-accumulating ground, which supports successive generations of shoots, he uses the following comparison.

"The history of the grand development of nature on the surface of our globe presents an analogy, which may perhaps serve to set this relation in a clear light. The successive geological formations superposed during the course of countless ages, present, buried in their depths, the traces of as many formations of the organic world, each of which carpeted the then superior stratum of the earth with a new life, until it found its own grave in the succeeding formation, when a new uprising of organic life took its place. In the same way, the stem of a tree is a multistratified ground, in whose layers the history of earlier growths is legibly preserved. The number of the woody layers indicates the number of the generations which have perished, i. e. the age of the whole tree: a distinct annual ring is the monument of a vigorous season, an indistinct one of a bad season, a sickly one (which is often found among healthy ones) indicates the unhealthiness of the foliage of that particular year. The practised woodman can decipher many facts of the past in the layers of the trunk; e. g. a good season for foliage or for seed, damage by frost or by insects, &c."⁹⁸

In order to perfect the analogy between an organism and the world, so as to show that the law which prevails in the one obtains also in the other, it would be necessary to prove that the development of the physical history of the world is circular, like that already shown to characterise the course of organic nature. And this I cannot prove. But neither, as I think, can the contrary be proved.

The life of the individual consists of a series of processes which are cyclical. In the tree this is shown by the successive growths and deaths of series of leaves: in the animal by the development and exuviation of nails, hair, epidermis, &c.

The life of the species consists of a series of processes which are cyclical. This has been sufficiently illustrated in the preceding pages, in the successive developments and deaths of generations of individuals.

We have reason to believe that species die out, and are replaced by other species, like the individuals which belong to the species, and the organs which belong to the individual. But is the life of the species a circle returning into itself? In other words, if we could take a sufficiently large view of the whole plan of nature, should we discern that the existence of species δ necessarily involved the pre-existence of species γ, and must inevitably be followed by species ε? Should we be able to trace the same sort of relation between the tiger of Bengal and the fossil tiger of the Yorkshire caves, between Elephas Indicus and Elephas primigenius, as subsists between the leaves of 1857 and the leaves of 1856; or between the oak now flourishing in Sherwood Forest and that of Robin Hood's day, from whose acorn it sprang?⁹⁹

I dare not say, we should; though I think it highly probable. But I think you will not dare to say, we should not.¹⁰⁰

It is certain that, when the Omnipotent God proposed to create a given organism, the course of that organism was present to his idea, as an ever revolving circle, without beginning and without end. He created it at some point in the circle, and gave it thus an arbitrary beginning; but one which involved all previous rotations of the circle, though only as ideal, or, in other phrase, prochronic. Is it not possible – I do not ask for more – that, in like manner, the natural course of the world was projected in his idea as a perfect whole, and that He determined to create it at some point of that course, which act, however, should involve previous stages, though only ideal or prochronic?

All naturalists have speculated upon the great plan of Nature; a grand array of organic essences, in which every species should be related in like ratio to its fellow species, by certain affinities, without gaps and without redundancies; the whole constituting a beautiful and perfect unity, a harmonious scheme, worthy of the infinite Mind that conceived it. Such a perfect plan has never been presented by any existing fauna or flora; nor is it made up by uniting the fossil faunas and floras to the recent ones; yet the discovery of the fossil world has made a very signal approach to the filling up of the great outline; and the more minutely this has been investigated, the more have hiatuses been bridged over, which before yawned between species and species, and links of connexion have been supplied which before were lacking.¹⁰¹

It is not necessary, – at least it does not seem so to me, – that all the members of this mighty commonwealth should have an actual, a diachronic existence; anymore than that, in the creation of a man, his fœtal, infantile, and adolescent stages should have an actual, diachronic existence, though these are essential to his normal life-history. Nor would their diachronism be more certainly inferrible from the physical traces of them, in the one case than in the other. In the newly-created Man, the proofs of successive processes requiring time, in the skin, hairs, nails, bones, &c. could in no respect be distinguished from the like proofs in a Man of to-day; yet the developments to which they respectively testify are widely different from each other, so far as regards the element of time. Who will say that the suggestion, that the strata of the surface of the earth, with their fossil floras and faunas, may possibly belong to a prochronic development of the mighty plan of the life-history of this world, – who will dare to say that such a suggestion is a self-evident absurdity? If we had no example of such a procedure, we might be justified in dealing cavalierly with the hypothesis; but it has been shown that, without a solitary exception, the whole of the vast vegetable and animal kingdoms were created, – mark! I do not say may have been, but MUST have been created – on this principle of a prochronic development, with distinctly traceable records. It was the law of organic creation.