III ASCIDIAE SIMPLICES—ASCIDIIDAE Whe 
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. £0, B), is one of the commonest of British Ascidians, and 
lives readily in aquaria. 
Sub-Fam. 3. Coreliinae.—Stigmata curved and forming 
spirals (Fig. 35). Three genera :—Corella, Alder and Hancock, 
test gelatinous, body sessile; Corynascidia, Herdman, test 
Fie, 35.—A, branchial sac of Oorynascidia suhnmi, Herdman ; B, branchial sac of 
Corella japonica, Herdman. 7./, Internal longitudinal bars ; ¢7, transverse vessels. 
(After Herdman.) 
gelatinous, body pedunculated (Fig. 54, 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. 54, B). 
Corella contains several British species, one of which, (7 
parallelogramma, O. F. Miill., 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 
