ASCIDIAE SIMPLICES ASCIDIIDAE 



73 



present (Fig. 15, p. 40); Bhodosoma, Ehrenberg, anterior part 

 of test modified to form operculum (Fig. 34, D) ; Ahyssascidia, 

 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. Oiona intestinalis, Linn. 

 (Fig. 40, B), is one of the commonest of British Ascidians, and 

 lives readily in aqutiria. 



Sub-Fam. 3. Corellinae. — Stigmata curved and forming 

 spirals (Fig. 35). Three genera: — Corella, Alder and Hancock, 

 test gelatinous, body sessile ; Corynascidia, Herdman, test 





^^V^ ; U(S 



B 



Fig. 35. — A, branchial sac of Oorynascidia suJiTn-i, Herdman ; B, branchial sac of 

 Om-ella japonica, Herdman. i.l, Internal longitudinal bars ; tr, transverse vessels. 

 (After Herdman.) 



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). 



Corella contains several British species, one of which, C. 

 paralldogramma, 0. F. MlilL, 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)i 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 



