72 



ASCIDIANS 



CHAP. 



Perophora, Wiegniann, with a short compact body and intestine 

 alongside the branchial sac. Clavelina lepadifo7'mis and Peropliora 

 listeri are common British species found at a few fathoms depth 

 oiT various parts of our coast. Both occur round the south end 

 of the Isle of Man. In autumn Clavelina accumulates reserve- 

 material in the ectoderm cells of parts of the stolon, which remain 

 when the rest of the colony dies away, and then form new buds 

 in spring. 



Fam. 2. Ascidiidae. — Solitary fixed Ascidians, never forming 

 colonies ; with gelatinous or cartilaginous test ; branchial aperture 

 usually eight-lobed, atrial aperture usually six-lobed ; branchial 

 sac not folded ; internal longitudinal bars usually present ; stig- 

 mata straight or curved ; tentacles simple ; gonads in or around 

 the intestinal loop. This family is divided into three sections : — 



Sub-Fam. 1. Hypobythiinae. — Branchial sac with no internal 

 longitudinal bars, test strengthened with curious symmetrically 

 placed nodules. 



The one genus Hyijolythius, 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, GOO fathoms. 



Fig. 34.— a, Hypdbythius calycodes, Moseley ; B, Chelyosoma mackayanum, Brod. and 

 Sowb. ; C, Corynascidia suhvn, Herdman ; D, Rhodosoma callense, Lac.'-Diith.' 



Sub-Fam. 2. Ascidiinae. — Internal longitudinal bars present; 

 stigmata straight. Many genera, of which the followino- are the 

 more important: — Ciona, Fleming, dorsal languets present; 

 Ascidia, Linnaeus (in part Phallusia, Savigny), dorsal lamina 



