SOME ASCIDIANS FROM THE ISLE OF WIGHT. 131 



When the test has been removed from the rest of the body, the 

 oral and cloacal siphons are seen to be short (PI. V, fig. 3). The 

 musculature is, as usual, almost confined to the right side of the body ; 

 the fibres are long and delicate. Round each of the siphons a number 

 of delicate fibres form a complete sphincter. 



On the left side, the course of the intestine is visible through the 

 body-wall. The stomach is rounded in form and is situated at some 

 little distance (about one-fifth of the total body-length) from the 

 posterior end of the body. The intestine is narrow and uniform ; its 

 first bend is well in front of the cloacal siphon, its anterior wall being 

 on a level with the ganglion ; the second bend of the intestine is 

 behind the cloacal siphon, its posterior wall being on a level with the 

 opening of the oesophagus into the pharynx ; the rectum is directed 

 obliquely forwards towards the cloaca. 



Upon opening the pharynx from end to end, along the line of 

 the endostyle, the remaining structures can be examined. 



The coronal tentacles are forty or more in number. In an individual 

 possessing forty tentacles, they were of three sizes and regularly 

 arranged — ten long and slender primaries, ten intermediate secondaries, 

 and twenty short tertiaries. 



The prcebranchial zone is studded with microscopic papillae. 



The aperture of the dorsal tubercle is crescentic in the smaller 

 specimens, horse-shoe shaped in the individual represented in fig. 1, 

 the horns not being incurved. 



An epijiharyngeal groove extends along one-third of the distance 

 between the dorsal tubercle and the ganglion, which is situated 

 half-way between the mouth and the cloacal aperture. The ganglion 

 is small, three times as long as broad, and extends over three cf 

 the meshes of the pharyngeal wall, beginning at the fourteenth 

 horizontal bar. The epipharyngeal groove becomes elevated towards 

 its posterior end, and behind it commences the dorsal lamina, which 

 is very narrow, strongly ribbed transversely, and pectinated at its 

 margin. The ribs and teeth of the lamina correspond in number 

 with the horizontal bars of the pharyngeal wall. Occasionally there 

 are minute projections from the edge of the lamina which alternate 

 with the teeth in position. The concave side of the lamina shows a 

 series of weak ridges running towards its edge very obliquely from 

 before backwards. 



