REPORT ON THE TUNICATA. 123 



The arrangement found in Culeolus wyville-thomsoni is perhaps the most distinct. 

 Here the meshes are much smaller than in any of the other species, and three distinct 

 sizes of transverse vessels are present (fig. 14). In Culeolus murrayi there are two 

 sizes, arranged alternately. In the other four species the transverse vessels are apparently 

 all of equal calibre. 



The number of folds in the branchial sac was only determined in two of the species, 

 Culeolus murrayi and Culeolus wyville-thomsoni, and in both it was six on each side. 

 In the other species there are several folds on each side, probably six also. The 

 simplest form of fold is that seen in Culeolus perlueidus, where it consists merely of one 

 additional bar running parallel with and attached to each internal longitudinal bar on 

 its inner surface. The irregular secondary transverse vessels and fine longitudinal vessels 

 found occasionally in Culeolus recumbens and Culeolus moscleyi are very interesting as 

 showing a tendency towards the formation of stigmata. This process has gone further in 

 Culeolus j>erlucidus, where the fine longitudinal vessels intermediate to the internal 

 longitudinal bars divide the meshes into spaces comparable with true stigmata. 



With regard to the apparent absence of spicules in the branchial sac and endostyle 

 of Culeolus perlueidus, Dr. Theel informs me that in some of the Challenger Holothurids 

 the integument has been entirely, and in others partially, decalcified, in consequence 

 probably of some impurity in the spirit in which they were preserved. Possibly a 

 similar process has occurred in the case of this Ascidian. 



The Endostyle was not examined in Culeolus perlatus. In all the other species, 

 ignoring the absence of spicules in Culeolus perlueidus, this organ is very similar. In 

 Culeolus murrayi, Culeolus ivyville-thomsoni, and Culeolus recumbens the greatest 

 development of spicules is in the outer clear edge, and in the last species they are confined 

 to that locality. In Culeolus moscleyi, however, though present in the clear edge also, 

 they are more plentiful over the central opaque area. 



There is nothing worthy of remark in the languets along the dorsal edge of the 

 branchial sac. 



The Tentacles. — The tentacles are very similar in all the species, and are of the 

 ordinary Cynthiad type. In some of the larger ones, however, especially in Culeolus 

 murrayi, one notices that peculiar puffing out of the lower or branchial membranous 

 surface of the tentacle so characteristic of the organ in the Molgulidse. 1 



In three of the species, Culeolus murrayi, Culeolus wycille-thomsoni, and Culeolus 

 perlatus, the number of tentacles is sixteen, and they are of two sizes, eight of each being 

 arranged alternately. In Culeolus murrayi, in addition to these, there are also a certain 

 number of much smaller ones of various sizes, and having no apparent symmetrical 

 arrangemeut. In Culeolus wyviUe-thomsoni one of the large tentacles situated in the 

 dorsal region is very much larger than any of the others. In Culeolus recumbens the 



1 See H. de Lacaze-Duthiers, Les Ascidies Simples des cotes de France, Arch, de Zool. expex. et g£n., t. vi. p. 477. 

 Paris, 1877. 



(ZOOL. CHALL. ESP.— fAUT xvii. — 1882.) R 17 



