Omphalos: An Attempt to Untie the Geological Knot

by Philip Henry Gosse

Enclosed in the clear purplish-grey jelly, in the midst of scattered lighter specks, we see several star-like figures of bright hues, in which yellow and red are predominant; the symmetrical arrangement of which pleases the eye, and reminds us of some ornamental pattern designed by human art. Each star is composed of several (three, seven, ten or more) pear-shaped animals, with their smaller ends meeting in the centre around a common orifice, from which a current of water is discharged.

Now this assemblage of animals bears evidence of progressive development. Some time ago a tiny egg was discharged from a parent Botryllus, which presently produced a little active tadpole-like larva, called a "spinule." This swam actively by means of its wriggling tail; but at length it settled head downward on this piece of sea-weed. Immediately the head adhered, by an effused cement, to its support; the tail now gradually disappeared; and the round head, in the midst of a mass of jelly-like cement, began to display two orifices on its surface. It soon assumed a pear-like shape, and thus the first Botryllus was formed.

From the side of this "pear," another was developed by gemmation, and a third on the opposite side; the smaller ends of all were in contact, and the orifices of these extremities began to merge into one; while the large ends diverged. A fourth and a fifth "pear" were successively produced in the same mode, until a star or "system" was formed. Meanwhile the surrounding mass of living jelly had been commensurately enlarging, and a new Botryllus, separate from the other star, had been produced in the jelly, which was the commencing point of a second system; and thus, by degrees, the compound mass of systems has grown to its present state of development.

BOTRYLLUS.
a, portion of one system and of a mass, on Phyllophora rubens; b, an egg c, spinule; d, the same, attached; e, the tail absorbed; f, the young Botryllus. All magnified.

This process has been one of time: the adhesion of the "spinule" took place in about sixteen hours after its escape from the egg. The appearance of the two orifices was when the little animal was four days old; and by the end of a week a second "pear" had budded. The attainment of the present condition may have occupied about six months.

Nay; time has been no element in this development; it is prochronic development; it is the development of creation, not of nature.

Behold that ruffling of the smooth surface of the water; it is caused evidently by the forcible ejection of a current from some source a little way beneath the surface. Yes, it proceeds from the orifice in this mass of calcareous grit; where the protruding pipe of shell indicates the snug fortress of a Clavagella. I will carefully break away a little of the soft stone, and we shall see the curious structure more clearly. Ha! I have split off a piece which nicely exposes the whole burrow, without having materially injured the creature or his shell.

You see it is a bivalve Mollusk with one valve firmly imbedded and cemented into the stony wall of its chamber. But the hinder end of this valve is continued into a shelly tube, intended to protect the siphons, which is carried through the gallery forming the entrance into the chamber, and opens by a wide orifice in the free water outside. It is to this tube that I call your attention.