While in the Clavellinidæ the animals are connected by creeping tubular prolongations of the common tunic through which the blood circulates, the Botrylli form translucent jelly-like masses of various hues of orange, yellow, purple, blue, grey, and green; sometimes nearly uniform in tint, sometimes beautifully variegated, and very frequently pencilled as if with stars of gorgeous device; now encrusting the surface of the rock, now descending from it in icicle-like projections. They are also frequently attached to the broad-leaved fuci, investing the stalks, or clothing with a glairy coat the expanse of the fronds. "In examining their bodies," says the distinguished naturalist previously quoted, "we find that it is not a single animal which is before us, but a commonwealth of beings bound together by common and vital ties. Each star is a family, each group of stars a community. Individuals are linked together in systems, systems combined into masses. Few bodies among the forms of animal life exhibit such exquisite figures as those which we see displayed in the combinations of these compound Ascidians." In the genus Diazona, which has its chief seat in the Mediterranean, the animals, which are very prominent and arranged in concentric circles, form a single system expanded into a disc like that of a flower or of an Actinia. The anal orifices, it will be seen, are situated close to the branchial apertures at the free end of the single animals, while in the Botrylli they open into a central excretory cavity. [Illustration: A single individual of Pyrosoma giganteum, cut out of the common test and magnified. _a._ Branchial or external orifice. _b._ Anal or internal orifice. _d._ Stomach. _e._ Liver. _f._ Branchiæ. ] In the Pyrosomes we find large colonies of small individuals aggregated in the form of a cylinder open at one end. Their mouths or anterior extremities are situated on the exterior of this hollow body, which they bristle with large and longish tubercles (_a_), whilst the opposite or anal orifices (_b_) open into the cavity of the cylinder, whose smooth wall they perforate with numerous small holes. By a simultaneous action the central cavity is either narrowed or enlarged, and by this means the strange social republic glides slowly through the waters. The Pyrosomes inhabit the Mediterranean and the warmer parts of the ocean. In the former at times their abundance is a source of great annoyance to the fishermen, sometimes even completely clogging their nets, and on the high seas they are not seldom met with in almost incredible profusion. Their delicate and transparent forms, their elegant tints, and their unrivalled phosphorescence render them objects of admiration to the voyager, and entitle them to rank amongst the most resplendent living gems of the ocean. [Illustration: Salpa maxima.