In fact, every real process has a character of its own: a something which distinguishes it from any other, despite of general resemblances up to a certain point.
Petrifaction, then, being assumed, as an operation which has really taken place after one way or another, it falls next to be considered, what was the original nature of these fossils? I mean the objects which we find thus preserved in our seaside pebbles. What was the department in Creation to which they belonged? Was it animal or vegetable before it thus became altogether mineral?
For myself, I will at once say that I have no doubt it was animal; but not an animal of a very high order. The specimens which I now possess, and which are all of them chosen, some of them rare, I should assign to such creatures as the “zoophytes” or “polyps,” both radiated and globular. And I know of nothing, among many hundreds of specimens gathered from a dozen different beaches, which presents the evidence of having belonged to vegetable organization, with the exception of sundry varieties of petrified wood, which speak for themselves, and could not be mistaken by anybody.
I will now state two or three reasons, which to my own mind are conclusive, for the above decision.
In the first place, then, the structures here perpetuated in stone are of great delicacy, and they have been immersed in ancient seas, as is testified by the localities in which they are obtained. Now vegetable structure as fine as this, if immersed long enough for any such change to come in question, must have utterly perished by maceration, and then the petrifaction could not have taken place. I know that part of the stem (and I think fruit) of one species of “conifer” has been found in the Isle of Wight in the condition of a fossil; but this belonged to a hardy class of plants, and the lobes or plates which composed its bark and husk are themselves highly siliceous, to say nothing of the presence of iron in the rind of most of these stems. So that the process would be a long one, and the fibrous material of the tree would stand it well. But in these pebbles some of the threads or tubes run from the size of small twine to that of the rays in a spider’s web; and no vegetable substance with which I am acquainted, excepting the filaments of “asbestos” (which is a vegetating mineral) in rock-crystal, could abide and retain its form, so as to allow of the changes by infiltration or otherwise which have passed upon the original structure.
If it be said in reply to this, that we have the exquisitely delicate “dendritic” markings, as of leaves and filaments of shrubs or sea-weed, in the heart of the white chalcedony “mocha-stones” from the East, the answer is evident: these are not really vegetable traces, but only resemble such in their configuration and colours. They are simply shoots and ramifications of a metal,—as iron or manganese. Those in the “weed-agate” of India, which exactly resemble sprays of fine sea-weed, are produced by “delessite.”
Indeed, it is both diverting and instructive to observe how Nature permits, and even seems to abound in, curious coincidences and striking resemblances between things of entirely diverse character. The dried polyp, called “encrinoid echinoderm,” bears a wonderful likeness to one species of Indian corn. (See the plate at p. 137 of Mr. Rymer Jones’s beautiful work on “The Animal Kingdom.”) And the other day, when I was enjoying a leisure hour in the British Museum, I suddenly remarked that the “carapace” (back-shell) of the splendid fossil specimen of the “Holoptychius nobilissimus” in one of the cases might serve for a sketch of the back of a capercailzie, where the grey and purple feathers overlap one another. Yet here is no real connection whatever. Only Dame Nature had gone to play.
Secondly. The preservation of these “polyp” forms, in the manner in which they have been preserved, seems to me to be due to a feature or circumstance which is strictly animal and not vegetable. I refer to the fact of the creature, while it was alive, inhabiting a house, a house built by himself, or emanating from his own substance. For, just as we could know but little of the existence or habits of “shell-fish,” were it not for their shells, so I think we may assume that the choanite must, when alive, have dwelt in a tough, horny “coperculum,” answering to the shape of his body and the number of his “polyps” (if he was a compound creature), because otherwise he would have been like a jelly-fish or naked slug, and his “polypary” could not have been preserved in a stony fossil. Of course, whatever was merely flesh, or adipose matter, has long since perished; but the house or shell in which it whilome dwelt remains. Thus, the “echinus” built himself a dome, such a residence as a hedgehog would require to live comfortably in, and through the various orifices of which his spines could be protruded at pleasure. The “ammonite,” being shaped like a snake, preferred living in a shell of that form, where the creature when coiled up was safe. The “alcyonite” had a more exquisite taste in house-building, answering, we may be sure, to the complex and beautiful structure with which the great Creator had endowed him. His home was a palace, containing long galleries and secret doors and wheel-windows; and here some of the delicate tubes are fringed at their extremities like the petals of a flower.