33S MB. A. hakcoce: on the anatomy 



of what we may now term the oral lamina (the pseudo-gill). All 

 the nerves are given to the walls of the cavity — in other words, to 

 the inner tunic or mantle. The anterior extremity of the ganglion 

 is produced a little, giving an appearauce to the organ as if com- 

 posed of two centres. On the anterior surface of the produced 

 extremity there are three or four imperfectly formed black pig- 

 ment specks, having the appearance of rudimentary eyes, which, 

 however, Professor Huxley considers auditory capsules. 



The " languet," with its ciliated " fossa," is placed just in front 

 of the ganglion, consequently on the same middle ventral line with 

 it and the oral lamina ; it is a long, tapering, conical process, with 

 a longitudinal groove which widens at the base where it joins the 

 fossa, over which it seems to straddle. There can scarcely be any 

 doubt that this is an organ of special sense ; and it would appear 

 probable that its office is to ascertain the quality of the respira- 

 tory currents, and may therefore be olfactory. Thus in function 

 the "languet" would seem to agree with the branchial tubercle so 

 constant in the other Tunicates ; but it is, moreover, homologi- 

 cally speaking, the same organ, as appears demonstrated by its 

 position in relation to the ganglion, the ciliated band, and the 

 pseudo-gill. Like the tubercle, too, it is a production of the lining 

 membrane ; and, as indicated by the longitudinal groove,like it, also, 

 the " languet " is probably formed of two portions or folds of this 

 membrane. It must, therefore, not be confounded, as it frequently 

 has been, with the tentacular iilaments of the oral lamina in Olave- 

 lina, Pyrosoma, and several other simple and compound Ascidians. 



The homologies, however, do not stop here ; the clear anasto- 

 mosing vessels or tubes ramifying over the surface of the intes- 

 tine, described and figured by Prof Huxley*, and supposed to 

 "represent a hepatic organ," or "a sort of rudimentary lacteal 

 system," are, there can be no doubt, the homologue of the rudi- 

 mentary liver before described in Ascidia and in some of the 

 C)Tithiadae ; and, indeed, the structure appears to resemble very 

 closely that of the hepatic organ in Ascidia parallelogramma. The 

 "mass of clear cells," the " elseoblast " of Krohn, according to 

 Huxley, may perhaps prove to be the -same as the well-known 

 cell-structure before described as coating the alimentary tube in 

 the Ascidice ; but this is mere conjecture. 



Thus we see how close the relationship is between Salpa and 

 Ascidia ; with Clavelina, however, the connexion is still more in- 

 timate. This is undoubtedly a near ally ; it is only necessary to 

 * Op. cit. p. 570, 



