

ECTEINASCIDIA AND THE CLAVELINID^E 153 



verse vessels, short tentacular languets, which are, however, 

 merely prolongations of the edge of the membrane (PI. 

 VI, fig. 7) On each side of the dorsal lamina two internal 

 longitudinal bars are absent, but their places are indi- 

 cated by the rows of papilliform connecting ducts (PL VI, 

 fig. 7, c. d') At each side of the endostyle there is a 

 single such row of papilliform connecting ducts, with no 

 corresponding longitudinal bar. 



The Tentacles are very numerous and slender, and are 

 closely placed. There are about 80 altogether, of which 

 40 are very short, and are placed alternately with the 40 

 much larger ones, which, however, are not all of one size, 

 but vary considerably in length (see PL VII., fig. 8), some 

 being twice as large as others. 



The Dorsal Tubercle has a simple elongated, elliptical 

 aperture placed close behind the tentacles (PL VI, fig. 8). 



The Alimentary Canal is placed on the left side of the 

 branchial sac, and there is no distinct abdomen. There 

 is only a single well-marked loop, that between the 

 stomach and intestine, in which the genital organs lie 

 (see PL VI, fig. 9). The oesophagus is short and narrow, 

 and runs posteriorly to the ovate stomach (fig. 9, st.) 

 The intestine runs posteriorly for a short distance from 

 the stomach, and then turns veutrally, and then anteriorly 

 in a wide curve. When it reaches a level in front of the 

 oesophagus it turns dorsally and runs to the dorsal edge 

 of the body, where it turns abruptly forwards to form the 

 rectum running towards the atrial aperture. The rectum 

 thus runs almost exactly at aright angle to the preceding 

 part of the intestine. There is an extremely delicate 

 digestive gland ramifying over the walls of the intestine, 

 with a distinct duct, which leaves the intestine on the 

 inner side of the intestinal loop and after crossing a por- 

 tion of the testis opens into the stomach. 



