SOME ASCIDIANS FROM THE ISLE OF WIGHT. 143 



direction on the right side, almost entirely overgrown by small algre, 

 and extensive colonies of the Polyzoon Alcyonidium mytili and some 

 Didemnids. Here and there on the right surface a few minute 

 tubercles may be detected. Oral aperture on the right side, sub- 

 terminal, not prominent, bounded by nine lips ; cloacal aperture on 

 the right side near the dorsal edge, very slightly nearer the anterior 

 than the posterior end of the body, bounded by six lips. 



Upon removal of the test the rest of the body is seen to be of 

 a yellowish colour, the musculature being of a rather deeper amber- 

 colour. The oral and cloacal siphons are tubular but short. The oral 

 siphon terminates in nine sub-triangular lips, which are rather 

 prominent, with rounded apices and with a spoon-shaped concavity on 

 their external surfaces. The edge of the siphon is bounded by a thin 

 red line which is discontinuous towards the tips of most of the lips. 

 A small red ocellus is found behind the red line between each pair of 

 lobes, and the surface of the siphon is slightly sprinkled with red dots. 

 The cloacal siphon terminates in six lobes, bounded similarly by a 

 thin red line, but without ocelli. It is directed straight towards its 

 external orifice. 



Musculature coarse and strong, the fibres amber- coloured. 



Viscera disposed as usual in the species, the posterior border of the 

 stomach being nearly ^ inch from the posterior end of the body ; the 

 anterior wall of the intestine at its first bend is on a level with the 

 ganglion ; the posterior wall at its second bend is on a level with 

 the opening of the oesophagus into the pharynx. 



Renal vesicles large, forming a soft yellowish coating over the 

 stomach and intestine ; concretions showing as a small brown spot in 

 each vesicle, when looked at with a lens, but resolving themselves 

 in each case into a compact mass of several concretions, of different 

 sizes and of a yellowish-brown colour, when examined under a low 

 power of the microscope (cf. Roule). 



Tentacles about thirty in number, short, of unequal sizes, irregularly 

 arranged. 



Prcebranchial zone studded with microscopic papillae arranged more 

 or less regularly in longitudinal rows. 



Dorsal tubercle longer than broad, presenting two apertures, one 

 behind the other. The anterior is crescentic, with the horns produced 



