Page:The common shells of the sea-shore (IA commonshellsofse00wood 0).pdf/13

Rh examples is that which is given in the illustration (Plate I., fig. 1), and it is technically named Botryllus polycyclus. Both of these terms are of Greek origin, and are peculiarly appropriate; the first signifying a bunch of grapes, and the other being formed of two words which signify "many-circled."

This species is easily recognisable by its form, although it varies in colour, being sometimes blue and sometimes purple. As may be seen by reference to the illustration, the individuals are united by a jelly-like substance, which forms a thin, semi-transparent crust upon the sea-weed or other object on which it rests. These beautiful star-like objects are common on nearly every part of our coast, and may venerally be found on the great tangle-weeds, over the fronds of which they form masses of several inches in diameter.

At fig. 3 of the same plate is drawn another species, in order to show a different method of uniting the individuals. In the previous species the individuals are set upon a common gelatinous incrustation, but in the they are at some distance from each other, and united by a delicate thread, which is, in fact, a modification of the "tunic" common to all the individuals. Though a very small species, it is rather pretty, the individuals being transparent as jelly, and dotted with orange and brown, and the uniting thread being pure lustrous white. Delicate as is this thread, the blood circulates through it, so that the nourishment which is taken by any individual is equally beneficial to the whole community.

When taken, they should be at once placed in a shallow vessel of sea-water, and left in perfect quietude for some little time, in order that the systematic contraction and extension of the central orifice may be noted.

We now come to a more advanced and more interesting group of these semi-molluscs, called the : Their name is very appropriate, for they look