ASCIDIANS 



CHAP. 



Perophora, Wiegmann, with a short compact body and intestine 

 alongside the branchial sac. Clavelina Icpadiformis and Perophora 

 listeri are common British species found at a few fathoms depth 

 off 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 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. 



FIG. 34. A, Hypobythius calycodes, Moseley ; B, Chelyosoma macleayanum, Brod. and 

 Sowb. ; C, Corynascidia suhmi, Herdman ; D, Rhodosoma callense, Lac.-Dtith. 



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

 stigmata straight. Many genera, of which the following are the 

 more important: dona, Fleming, dorsal languets present^ 

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



