I am not going to describe the interesting structure and economy of this atom of life; but merely wish to direct your attention to one point,—the evidence which it affords of the lapse of past time.
Every one of these hundreds of stony cells, together with its living tenant, was normally produced by a process of gemmation; each having budded forth from the side of its predecessor as a knob of clear gelatinous flesh, in the midst of which was developed, first the cell, and then the polypide,—the latter appearing in a rudimentary condition, and gradually acquiring its proper organs, before the orifice of the cell was opened.
I said every one of the cells was thus formed; but I ought to have excepted a single cell, which, though in nowise differing from the rest in form or structure, had a very different origin. This was the primal cell, and its beginning was as follows:
A minute atom of a scarlet hue, and of a semi-elliptical shape, was one day whirling round and round with rapid gyrations in the open sea. It was of soft consistence, covered with strongly vibrating cilia, and furnished with some stouter setæ. After enjoying its motile instincts awhile, it settled down on this pebble, and became stationary. Presently it secreted and deposited calcareous matter around at, like a coating of the thinnest glass, the red parenchyma receding from the hyaline wall towards the centre.
Soon an orifice with thickened edges appeared on the upper side, and minute spines grew from the edges, which quickly lengthened. It was now a Lepralia cell, and now the polypide was developed, and protruded its mouth from the orifice, surrounded by its elegant bell of ciliate tentacles. This solitary cell became the parent of hundreds more, by the gemmative process which I have already described.
But the red swimming atom;—whence came that? Well, it was shot out from the interior of a previous Lepralia, the result not of a gemmative but of a generative act. It originated in another patch similar to the one which incrusts this pebble, and that, in like manner, and by exactly similar stages, looked back to an anterior patch, and so on.
Plausible as this inference is, it is false; for the little aggregation of cells and polypides has been called into existence by the Divine fiat, this very instant.
We are still at the sea-shore. Within the long and narrow crevices into which these low-lying ledges of shale are split, innumerable tufts of sea-weed,—olive, purple, and green,—are perpetually waving in the wash of the sea. On one of these branching shrubs of Phyllophora, there is adhering, apparently cast there by accident, an irregular mass of pellucid jelly. It firmly cleaves to the alga, enclosing the bases of several branches within its firm but gelatinous substance.
This knob of jelly is a compound animal of the genus Botryllus, and it has just been created as we see it. In order to understand its nature, look at it more closely.