150 BRITISH TUNICATA. 



Ascidia ; but in Glavelina there are no longitudinal 

 cords to interrupt their continuity. 



The anterior cord in connexion with the upper ex- 

 tremity of the endostyle is well developed ; but the 

 posterior cord has disappeared, for the lower end of 

 the endostyle reaches the margin of the oral orifice, 

 and thus the space it usually occupies is obliterated. 

 The branchial tubercle is small and circular, but more 

 respecting it could not be determined. 



The oral lamina, as above stated, is replaced in 

 Clavelina by a longitudinal series of large filamentous 

 processes, tapering to points, and with their bases 

 widened transversely and united to the transverse 

 branchial membrane ; there are as many processes as 

 laminae, namely fourteen or fifteen. 



There are two circles of simple tentacular filaments 

 a little within the entrance of the inhalant tube, one a 

 short way above the other. In the upper circle the 

 tentacles are small and more numerous than those of 

 the lower circle, in which there are about six which 

 are very superior in size to the others. 



The endostyle is largely developed, extending the 

 whole length of the branchial sac, and being united 

 below to the margin of the mouth. It is of an opaque 

 yellow colour, is firm, and wider than usual, the margin 

 of the groove being thrown more backwards. It is 

 composed of three members, a broad central plate-like 

 rod, and two narrow lateral rods, the free margins of 

 which are delicate and membranous. The central rod 

 exhibits a median line as if it were composed of two 

 longitudinal elements . 



The heart lies at the left side of the intestinal loop ; 

 and, according to Milne Edwards, is lodged within a 

 delicate pericardium. It is tubular and is bent upon 

 itself. The branchial suspenders are as well developed 

 and as numerous as usual. 



The mouth is a large rounded orifice opening into 

 the bottom of the branchial sac at an angle inclined 

 backwards. From this point the oesophagus descends 



