A Year at the Shore

by Philip Henry Gosse

We have a pretty attractive little Cynthia in our dredging,—the Currant Squirter.[152] It is not uncommon in deep water off this coast, and in Weymouth Bay; frequently occurring in family groups crowded together on old shells. Generally there is one of superior dimensions to the rest, the venerable parent of the colony; and, surrounding him, others of varying size, and (doubtless) age, down to very minute infants. The full size is about that of half a small cherry; but it is more usual to see them not exceeding that of half a red currant. These comparisons will also give a fair idea of their shape and colour, especially in a state of contraction, as when lifted from the water: for they are little hemispheres of a brilliant, scarcely pellucid, crimson hue, seated on the shell by the whole broad base. Under water, and at ease, the form becomes more conical, rising into a point; whence, in full expansion, the two siphons protrude, slightly divergent, and the one a little superior to the other, each opening by a distinctly quadrangular orifice.

FOUR-ANGLED SQUIRTER.

Contrasting with this neat and pretty little family, we have here another species of the genus, the Four-angled Squirter.[153] You would hardly suppose this to be an animal at all, if uninitiated; but might readily pass it over as a rude stone, or a bit of wood roughly bruised and worn by the waves beating it among the rocks, so uncouth and coarse and shapeless it is. It forms a great mass, some two inches high, rudely four-sided, of a dull yellowish-olive hue, rising into two blunt eminences, which individually retain the quadrangular shape, and in activity open by symmetrically quadrangular orifices. It is a sluggish, unattractive lump of flesh, somewhat between leather and jelly in texture, coarsely pellucid, but not transparent, and its exterior is usually distinguished by various extraneous matters imbedded in the test, as well as by forests of tangled zoophytes which creep over it and root in it as on the rock. The surface itself, moreover, is much corrugated by an irregular network of depressions, marking off angular warty areas.

On the other hand, the little Currant is a pleasing inhabitant of the aquarium. Of manners, to be sure, it has not much, good or bad, but the form and colour are agreeable; as is also the effect produced by the grouping of the brilliant drops of jelly. Little of change takes place, beyond the occasional contraction and reprotrusion of the orifices; but sometimes you may see, as I have seen, at certain times, the laying of eggs by this species, which is an interesting phenomenon. These are perfectly globular, about the size of small shot or pins’ heads, of a rich scarlet-crimson hue: they are deposited in a singular manner. The oviduct does not extend to the exterior of the body, but discharges the eggs into a large cavity formed by the mouth, of which the discharging siphon is the outlet. From this orifice, then, they are expelled, shot out perpendicularly with considerable force, so that they describe arched courses through the water, like bombs shot from a mortar, rising to a height ten times that of the animal. I have observed a dozen or more eggs thus discharged in quick succession, which then fall to the bottom around the parent, destined to constitute one of those family groups in which we usually find the species.

I have not been successful in rearing these eggs to maturity. The development of the Tunicata has, however, been observed by various naturalists, and by none more thoroughly than by the late Sir John Dalyell, whose elaborate and costly works, profusely illustrated, are such a mine of information respecting the lower forms of marine life.

TRANSFORMATIONS.

The young escapes from the egg in a form as unlike the parent as can be imagined. It is a flat ovate body with a long flat tail, altogether presenting a curious resemblance to the tadpole of a frog. In this condition I have found the larva of the Clavelina, and have followed it to the development of the Ascidia form. By means of the rapid vibrations of the powerful tail, the little tadpole swims for short distances through the water, with more effort than effect. After a while, it rests; swims again, and again rests; till at last it moves no more. A coloured eye-speck is visible on the surface, destined to be absorbed; the tail is beginning to disappear (in some cases it is separated by a spontaneous constriction at its junction with the body, in others it appears to be gradually absorbed); one or more warts are seen budding from the opposite extremity of the body. These last secrete a cement by which the animal is finally attached to its support, shell, stone, or sea-weed, either growing out into creeping and adherent root-threads, or enlarging into a broad base, from which the body begins to grow upward. After a while the two orifices are formed; first within, on the mantle, before the exterior test is pierced; then the internal organs, the gill-sac, and the pulsating heart, if it be one of the transparent species, become recognisable; the single eye-speck, a temporary organ, pales and disappears; and the permanent circles of visual organs are formed around the siphonal orifices. And thus the Ascidian is developed.

BOTRYLLI.

The genera Ascidia and Cynthia consist of isolated distinct individuals; the Clavelina and the Perophora exist in the form of groups, composed of distinct individuals associated by a common branching root-thread, whence they irregularly bud forth. There are, however, other genera, in which the compound life is more prominently manifest, the individual being recognisable only by carefully dissecting it out from the common mass. To this form belong many gelatinous masses which occur on our rocky coasts; one in particular,[154] conspicuous for its rich scarlet and orange colours, which forms irregular pear-shaped lumps, that hang from low-lying ledges, and that look not unlike strawberries. This is extremely abundant. More attractive still are the Botrylli,[155] which doubtless many persons have gazed on with admiration, wondering what they can be,—animal, vegetable, or what. They look as if small quantities of jelly had been spilt, sometimes on a stone, sometimes on the broad leaf of a tangle, sometimes on a shrubby sea-weed, entangling the twigs and leaves in the gelatinous mass. When we look closely at such an object, we see that it is studded with little starry systems of oblong specks, of some bright colour contrasting with the ground-tint;—perhaps the stars are bright orange on a warm brown, or pale straw-colour on a chocolate ground, or green on an iron-grey. The stars vary in outline, often being angular, often oval, or circular: they vary, too, in dimensions, and in number of the constituent specks; some may be a sixth of an inch in diameter, and contain a dozen or more; others may be less than half that size, and have no more than two or three; or even a single speck may be seen here and there, which has not yet begun to develop the starry form.