152 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



distinct papillae which are terminated by the branchial 

 and atrial apertures. The colour is light yellowish grey, 

 and the bodies are almost quite transparent, the viscera 

 showing through distinctly (fig. 2). An ascidiozooid varies 

 from 7 mm. to 2 cm. in length, and from 3 mm. to 6 mm. 

 in greatest breadth. 



The Test is very thin and membranous, and perfectly 

 transparent, and is easily torn off from the mantle. No 

 vessels are present, and no test cells are visible in the 

 transparent homogeneous matrix. 



The Mantle is thin and transparent, but moderately 

 muscular. The siphons are indistinctly lobed at their 

 extremities, and are provided with strong sphincter and 

 radial muscle bands. The muscle bands over the rest of 

 the body are all transverse in direction, and are rather 

 numerous. They are in the main parallel, but branch 

 and re-unite occasionally, so as to form a long-meshed 

 network (PL VI, fig. 4). The small blood spaces in the 

 mantle are all engorged with blood corpuscles, and so 

 become visible as a close network (PI. YI, fig. 5). 



The Branchial Sac is large, and extends nearly to the 

 posterior end of the body. The transverse vessels are 

 wide and are all of the same size (PI. VI, fig. 6). The 

 internal longitudinal bars are not wide. They are joined 

 to the transverse vessels at the angles of the meshes by 

 narrow papilliform connecting ducts which are distinctly 

 wider at their distal ends than where they leave the 

 transverse vessels (fig. 6, c. d.) The meshes are elongated 

 antero-posteriorly, and contain each about four long- 

 narrow elliptical stigmata. The vessels of the branchial 

 sac, like those of the mantle, are for the most part 

 engorged with blood corpuscles. 



The Dorsal Lamina consists of a rather narrow plain 

 membrane from which spring, at the level of the trans- 



