OF THREE AUSTRALIAN SPECIES OF TUNICATA. 369 



gently curved, and ornamented with yellow vascular lines. The curvature of these beau- 

 tiful organs is due to the presence of longitudinal muscular fibres on the concave border, 

 having no others to antagonize them on the opposite side. 



The branchial network is minute and regular, and the membrane is thrown into about 

 fourteen longitudinal folds; seven on either side of the body extending between the 

 branchial and oral apertures, and increasing in length from before backwards, in which 

 direction also they gradually become more curved. 



The mouth is small and surrounded by the converging ends of the longitudinal folds of 

 the branchial membrane, leading into a short oesophagus, which curves downwards and 

 backwards to join an elongated stomach, from whose tapering pyloric end the intestine 

 takes a very similar coui-se to that described in the former case, and terminates in the 

 cloacal chamber near the position of the mouth. 



The liver consists of numerous short and compressed glandular sacculi of a rich brownish- 

 red colour, lying on the left side and along the inferior border of the stomach, into which 

 their contents are potired. 



The products of digestion are usually to be seen in the intestine, connected together by 

 a plastic substance, and rolled into a filiform, continuous, and highly convoluted mass, 

 extending from the stomach to the vent. 



The testes and ovaria are identical in character, position and relations with those of the 

 foregoing Ascidian. 



The heart lies on the left side of the body, just below and in front of the corresponding 

 ovarium. It rests on a small brown cylindroid body with rounded extremities, and 

 exhibiting a slight curvature, with its concavity looking upwards and forwards. This 

 body appears to lie loosely in a blood-sinus adapted to receive it, and is chiefly composed 

 of minute cells, cell-nuclei, and an amorphous matter enclosed in a membranous sac, 

 but exhibiting no very definite arrangement. What its real nature is I have not been 

 able to determine, though I am disposed to believe that it may be the representative of 

 the " elceoblast " of the Salpian. 



III. In Shark Bay also, and in about three fathoms water, we obtained another small 

 Ascidian, so nearly aUied to those just described as to merit brief notice here. It is nearly 

 of the same size as the King George's Sound species, but rather more narrowed and pro- 

 duced above, and more rounded at the base. 



The branchial and cloacal openings lie on nearly the same level, at the extremes of the 

 upper border, and are tubular and prominent, though capable of considerable retraction. 



The test is thin, smooth, colourless, and beautifully transparent, so far caUing to mind 

 the pelagic Tunicata generally. It is, however, loosely covered over TNdth the fine sandy 

 particles of the sea-bottom on which it rests, being apparently qmte unattached, though 

 perhaps unable to change its place at wiU. 



The muscular coat and its epithelial covering are also quite transparent and free from 

 pigment. 



The external openings, particularly at their base, are surrounded with radiating and 

 VOL. XXII. 3 c 



