The one genus _Hypobythius_, Moseley, contains two stalked deep-water forms found by the "Challenger;" _H. calycodes_ (Fig. 34, A), from the North Pacific, 2900 fathoms, and _H. moseleyi_ from the South Atlantic, 600 fathoms. [Illustration: FIG. 34.—A, _Hypobythius calycodes_, Moseley; B, _Chelyosoma macleayanum_, Brod. and Sowb.; C, _Corynascidia suhmi_, Herdman; D, _Rhodosoma callense_, Lac.-Duth.] SUB-FAM. 2. ASCIDIINAE.—Internal longitudinal bars present; stigmata straight. Many genera, of which the following are the more important:—_Ciona_, Fleming, dorsal languets present; _Ascidia_, Linnaeus (in part _Phallusia_, Savigny), dorsal lamina {73}present (Fig. 15, p. 40); _Rhodosoma_, Ehrenberg, anterior part of test modified to form operculum (Fig. 34, D); _Abyssascidia_, Herdman, intestine on right side of branchial sac. The type genus of this section, _Ascidia_, has been described in detail above (Chapter II. p. 39), and Figs. 15 to 26 illustrate its structure and life-history. There are many species. _Ciona intestinalis_, Linn. (Fig. 40, B), is one of the commonest of British Ascidians, and lives readily in aquaria. SUB-FAM. 3. CORELLINAE.—Stigmata curved and forming spirals (Fig. 35). Three genera:—_Corella_, Alder and Hancock, test gelatinous, body sessile; _Corynascidia_, Herdman, test gelatinous, body pedunculated (Fig. 34, C), a remarkable deep-sea form with very delicate spirally-coiled vessels in the branchial sac (Fig. 35, A), found in the Pacific (2160 faths.) and the Southern Ocean; _Chelyosoma_, Brod. and Sowb., upper part of test modified into horny plates (Fig. 34, B). [Illustration: FIG. 35.—A, branchial sac of _Corynascidia suhmi_, Herdman; B, branchial sac of _Corella japonica_, Herdman. _i.l_, Internal longitudinal bars; _tr_, transverse vessels. (After Herdman.)] _Corella_ contains several British species, one of which, _C. parallelogramma_, O. F. Müll., is one of the commonest and most handsome Ascidians in our coralline zone (about 20 faths.). Through its clear crystalline test the lemon-yellow and carmine pigmentation of the mantle, and even (with a lens) the working of the cilia along the spiral stigmata of the branchial sac (compare Fig. 35, B), can readily be seen. The beating of the heart can be seen just in front of the viscera upon the _right_ side of the branchial sac (compare with _Ascidia_, Fig. 23). In the family Ascidiidae the eggs are minute and contain {74}little or no food-yolk, and the tailed larvae (Figs. 26, 42, A) are of the typical form and structure described in Chapter II.