Part 9 (2/2)

Leaving the vegetable kingdom, those organisms which, though beautiful indeed and instructive, are yet inanimate, let us seek others which are endowed with a higher style of life, a life which is distinguished by a measure of consciousness of the exterior world, and a perception of relations to it. Let us look for animals.

We retrace our steps to the verge of the rippling sea, where the belt of umbrageous Mangroves fringes its margin. Beneath the arching roots of these are now reposing in the warm sunlit shallows many creatures which number this as the first day of their existence. It is their natal, or rather (to make a word) their _creatal_ day.

Here is a specimen of the Sea-pen (_Pennatula_), closely resembling a rather thick and fleshy feather, with its quill-end inserted in the tenacious marl which const.i.tutes the floor of the sea along this sh.o.r.e, and with the greater part of its body, including all the pinnated portion, erect, and waving lightly in the gentle swell of the bay. Its central stem is beset on each side with about twenty-five horizontal purple pinnae, and each pinna bears from five to fifteen polypes with eight tentacles each.

Let us wade out to yonder reef. See this great ma.s.s of Millepore, growing in thin irregular perpendicular plates, which join each other at various angles, so as to form a large open honeycomb-like structure, much resembling the second stomach of an ox. It is covered with what appears a thin stratum of fawn-coloured jelly, but this consists of innumerable disks, which protrude from myriads of orifices not larger than those produced by the punctures of a fine needle; as we may discern by touching the soft slimy surface, when the whole retires, and leaves apparent only the white stony surface dotted with numberless holes, within which the disks have disappeared, and whence they will again presently re-appear.

Here too is a ma.s.sive shrub of stone, a n.o.ble example of the Muricated Madrepore. It consists of a great mult.i.tude of short tranches, which are themselves branched and branched again, every part covered with little mammillary warts, and pierced with innumerable holes in which stand radiating plates of the common stone. Out of these plated orifices, especially those towards the tips of the branches, for the older ones are empty and dead, we see perpetually peeping forth, expanding for an instant, and then coyly withdrawing, lovely little green disks, surrounded with thread-like tentacles; and from the extreme end of each branch there protrudes one exactly similar to the rest in all respects, except that it is nearly twice as large. Here then are the living architects; these have secreted within their gelatinous membranes the calcareous atoms, whose aggregate forms the stony shrub before us.

Shall we try to estimate the number of polypes that have been occupied in building this tree? There are about a hundred branches, which, taken one with another, and followed along the sinuous course of their many branchlets, we may estimate to average a continuous length of eight feet each; that is, 800 feet of branch in all. Now we may consider these branches as averaging a thickness of two inches and a half in circ.u.mference, which gives us a surface of 24,000 square inches.

Finally, there are about ten polype-cells in each square inch; and thus there are or have been in this coral-ma.s.s, nearly a quarter of a million of polype inhabitants.

[Ill.u.s.tration: MURICATED MADREPORE.]

But look at this dark crimson edifice of many stories, tier above tier, each horizontal floor of red stone sustained by a mult.i.tude of slender cylindrical pillars. When we look closely at them, we see that the pillars are tubes, perforating one or more of the floors, from the lowest tier to the uppermost.

Have we any clue to the age of these corals, or to that of either of them, supposing we did not know that they have been created to-day? Not definitely, perhaps; but indefinitely we have, certainly. In the case of the Sea-pen, the polypes have all been formed in succession; as also in that of the stony Millepore and Madrepore, with this addition, that every newly formed polype deposited an increase to the stony substance, which thus went on increasing till the great foliated or ramified ma.s.s that we see was formed.[61] And so, with this series of floors and pillars, which is the solid portion of another coral-polype, the Organ-pipe (_Tubipora musica_).

[Ill.u.s.tration: ORGAN-PIPE.]

Every one of these stories has been formed in succession. From the tips of some of the tubes we see protruding an elegant polype of an emerald-green hue, having eight starry tentacles, and giving off from its base an enveloping membrane, which spreads over the rim of the tube and descends on the outside to the floor. By means of this vascular membrane, both tube and floor have been formed. Calcareous particles, deposited, one by one, in its substance, gradually built up the tube of the primary polype, or probably the tubes of the first series, the bas.e.m.e.nt or ground-floor. When these tubes had arrived at a certain height, all simultaneously began to develope the fleshy membrane horizontally, which expanded until that from each touched that from its neighbour, with which it united. Meanwhile the calcareous deposition went on in this horizontal layer, and thus the first floor was made.

Now from the living vascular upper surface of this layer sprang up at certain spots buds,[62] offshoots of the common flesh, which soon rose into columns, and, by a process of calcareous deposition, became tubes with terminal polypes, which in turn spread out a horizontal layer, and thus the second floor was built. Hence a new race of polypes budded, which by and by formed the third floor; and so on in succession, until the series had attained the height which we see.

If we a.s.sume one of these stories to be the growth of a year,[63] we have ocular evidence in this specimen of six years' age, for here are six successive floors. But no: for it was created complete, as we see it, this very hour.

Yonder goes a _Medusa_, pumping its way laboriously, yet not ineffectively, just beneath the surface of the clear wave. It is a great affair, nearly a foot in diameter. Have we, from merely examining its appearance and structure, any criterion by which we can guess whether it has lived an hour, or a year, or ten years? Surely we have; for this ma.s.s of clear jelly is composed, like all other organic bodies, of cells, which have been gradually generated, by nutrition and a.s.similation, from the embryo.[64] This process must have occupied many months, if not several years; but the history of this Medusa did not begin when it took its present umbrella-like form. Shall we trace it back a little farther?

At some time back, then, this creature detached itself as the terminal one of many little saucer-like bodies, which had been for some time previously forming by the gradual constriction of a thick fleshy stem.

Before the constriction began to be visible, this stem was the body of a white Hydraform polype, affixed by its base, and furnished at its free extremity with thirty-two tentacles. It had lived several years in this form, developing many Hydroid polypes, just like itself, by successive gemmations. Before it took this shape, which it a.s.sumed gradually, its tentacles being developed in geometrical progression, 32 from 16, from 8, from 4,--it was a soft ovoid planule clothed with vibratile cilia, which swam freely in the sea, like an _Infusorium_.

Thus the physiologist would confidently a.s.sign to this Medusa an existence of several years, as an independent organism; _nor could his conclusions be controverted_, except by the knowledge of the fact that the Medusa _has been but just now created_.

We pa.s.s on. Here is an _Echinus_. Let it be borne in mind still, that we have, _in idea_, the power of pursuing our researches on each creature at the moment which follows that of its creation; and that, when that actually was is of no consequence to our investigation.

Here then is this new-made _Echinus sphaera_, a somewhat conical globe of three inches diameter, which is covered with a forest of spines, pedicellariae, and suckers, and which glides majestically along, with an even but slow progress, over rock and reef. Its vitals are enclosed in a hollow box of calcareous sh.e.l.l, which is built up of nearly a thousand pieces. This specimen, which is rather below than above the average size, is formed of ten meridional rows of large plates (the interambulacral), and ten of small (the ambulacral). The former series are each composed of thirty-two plates, making in all three hundred and twenty; the latter have just double that number, making six hundred and forty; thus this Urchin's box is built up of nine hundred and sixty plates; every one of which is of definite shape and angle, and fits into the angles of its fellows with the accuracy of the most skilfully constructed cabinet-work.

Now every one of these plates is an eloquent witness to the past life-history of the Sea-urchin. For the reason why the enclosing box is made of so many pieces is, that it might gradually expand and enlarge its capacity with the ever increasing requirements of the soft organs within. Every plate is enveloped by a vascular flesh, from which the calcareous particles are deposited in a constant and perfectly uniform ratio; and thus all the const.i.tuent plates are continually enlarged by additions to both the internal and external surfaces (increasing their strength), and to their sutural margins (increasing their combined capacity), until the adult dimensions are attained.

The size of the new-born Echinus is not nearly equal to that of one of these plates, and the progressive increase of the plates by deposition on their edges has certainly taken several years to accomplish.[65]

The same result is inferrible from the structure of the spines with which every plate is armed. Each of these is a very long cone of calcareous matter, arranged in minute oval chambers, divided by thin gla.s.sy walls, and deposited particle by particle from the thin stratum of living flesh with which each has been invested from its first embryonic development.

But of this _Echinus_, as of the _Medusa_ before, we find a history anterior to either box or spines. Its first appearance in this stage of existence was as a barely-visible circular disk, constructed on the outside of the stomach of a singular transparent organism, much like a Medusa, but of a domular form with four or six legs, stiffened by calcareous rods, and a crowning pinnacle. For some undefined time this gelatinous dome had been gliding with a stately movement through the open sea, before there was the least trace of the disk, which afterwards grew to the _Echinus_. In its earliest condition the dome itself was a soft, spherical, mulberry-like _Infusorium_, covered with vibratile cilia; this altered its form to that of a three-sided pyramid, and this to the vaulted dome.

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