SOME ASCIDIANS FROM THE ISLE OF WIGHT. 137 



position, but it is always nearer the posterior than the anterior end of 

 the body, between half and two-thirds of the way down the dorsal 

 edge. Both apertures are small and inconspicuous ; no ocelli were 

 observed in the living animal. 



The dimensions of the largest specimen are as follows : — 

 Maximum length ... • rf hich 

 „ breadth . . . f „ 



,, thickness . . . £ „ 



The test is firm and cartilaginous, though rather thin ; it is not 

 rough to the touch, but its surface is in reality studded with minute 

 tubercles of bluntly conical form. They are so small that they 

 cannot be readily observed when the test is immersed iu alcohol, but 

 when removed for a moment from the fluid, the presence of minute 

 projections is detected by the broken reflection of light from its upper 

 surface. A portion of the surface of the test is shown on PL VI., 

 fig. 9, considerably magnified. A series of vertical sections through 

 the test shows that the tubercles are quite solid, and that the culs- 

 de-sac of the test-vessels have no connection with them. The greater 

 part of the test is composed of huge "bladder-cells," the largest of 

 which are as large as many of the tubercles on the surface ; they are 

 of spherical or polyhedral form. The superficial tubercles are entirely 

 destitute of bladder-cells. 



The body when deprived of the test is at least twice as long as 

 broad in the majority of the specimens, but in one individual the pro- 

 portion between the two dimensions is slightly less than this. The 

 oral and cloacal siphons are both rather long and tubular, and the 

 cloacal siphon is particularly so (PL VI, fig. 8). 



From the oesophageal opening being situated near the posterior 

 corner of the pharynx, the viscera extend to the posterior end of the 

 body. The stomach is rounded in form and considerably wider than 

 the intestine. The course of the intestine has been sufficiently 

 indicated above. 



The ganglion is remarkably elongated, being six times as long as 

 broad ; it extends from the level of the fifteenth to that of the 

 twenty-first horizontal bar in the specimen shown in figs. 7 and 8. 



The epipharyngeal groove in the same individual is a low furrow, 

 not elevated behind, extending from the dorsal tubercle as far as the 



