45 



our typical fonn AsckUa, of which there are many species 

 ill British seas, widely distributed round our coasts. Two 

 other common British forms, belonging to this family, are 

 Ciona intestinalis, with a very soft, pale-green test and 

 languets in place of a dorsal lamina, and Corella parallelo- 

 gramma, in which the stigmata of the branchial sac are 

 curved to form beautiful spirals. 



Family III. Cynthiid^ : — Solitary fixed Ascidians, 

 usually with leathery test ; branchial and atrial apertures 

 both 4-lobed Branchial sac longitudinally folded; stig- 

 mata straight ; tentacles simple or compound. 



This is the largest family of Simple Ascidians, and 

 contains a number of genera, about six of which are 

 British. Stijela has simple tentacles, and not more than 

 4-folds on each side of the branchial sac. A very common 

 species all round our coasts, between tide marks, is the 

 little red Stijela (or Styelopsis) grossularia. In Cynthia 

 the tentacles are compound, and there are more than 

 4 folds, usually 7 or 8, on each side of the branchial sac. 

 The curious little Forbesella tessellata, from deep water 

 in the Irish Sea, is in some respects intermediate between 

 Styela and Cynthia. 



Family IV. Molgulid^ : — Solitary Ascidians, often 

 not fixed; branchial aperture 6-lobed, atrial 4-lobed. Test 

 usuall}^ encrusted with sand. Branchial sac longitudinally 

 folded ; stigmata more or less curved, usually arranged in 

 spirals; tentacles compound. 



Several species of Molgula, all looking when dredged 

 like little sandy balls, and one of Eugyra (E. glutinans) , 

 are common at a few fathoms depth round most parts of 

 our coasts. 



