2 THE VOYAGE OF H.M.S. CHALLENGER. 



Subgenus Carijoa, F. Miiller. 



Carijoa, F. Miiller, Arcliiv f. Naturgesch., Jahrg. xxxiii. p. 330, 1867. 



Telesto (Carijoa) trichostemma (Dana) (PI. III. figs, la, lb; PI. V. fig. 1; PI. VI. figs. 



1,2). 



Telesto (Carijoa) trichostemma, Chall. Report, Alcyonaria, Zool. Chall. Exp., part lxiv. p. 264. 

 Gorgonia trichostemma, Dana, Zooph., p. 665. 



The description of this interesting species was given in the former report upon the 

 Alcyonaria of the Challenger collection. This, after further research, I would now 

 complete, and elucidate by means of several illustrations. 



The most striking characteristic of the species is the peculiar construction of a kind 

 of inner skeleton, such as is commonly to be met with in Tubipora. The spicules 

 surrounding the elongated digestive cavities of the primary and secondary axial polyps 

 lie in such intimate contact with one another that, in the older parts of the colony, they 

 form a continuous calcareous cylinder. Towards the base this is further strengthened by 

 the horny substance secreted between the spicules. 



If this calcareous tube be isolated by maceration, or by treatment with caustic potash, 

 it persists as a connected structure, composed of a very fine, almost sponge-like, calcareous 

 substance having the form of the polyps. Its outer wall is marked with eight furrows, 

 between which arise an equal number of longitudinal ribs. The associated tubes of the 

 axial polyps of the second order are short, and seated upon the main axis like the calyces 

 of a Madrepore. The cavity does not communicate with that of the main tube, but is 

 separated from it by a delicate spongy calcareous lamella. In transverse sections of the 

 older primary polyps of the stem, eight slightly-developed mesenteric folds may be seen 

 to project into the cavity of the tube ; their mesoderm contains no spicules ; the inner wall 

 is covered with a cylindrical epithelium, which, on certain parts of the preserved specimen, 

 may be still seen to be equipped with cilia. To the outside of this follows a thin 

 structureless mesodermic layer, which becomes thicker at a mesenteric fold into which 

 it enters. Further to the outside is the zone of spicules. These are arranged, in part, 

 longitudinally, in part towards the periphery ; together they form a network. They 

 do not, however, fuse together, but are only interlocked by their spines. 



In this way they build up a connected whole, which, when isolated, forms a tube. 

 The spicules are thickest in the inner layer, being quite loose towards the outside. The 

 ectoderm is only distinguishable in a few places, when it appears as a layer of cylindrical 

 cells. For the most part it has been destroyed and penetrated by the tissue of a siliceous 

 sponge, which covers the whole colony, even spreading itself over the smaller secondary 

 polyps. In the lower portion it develops in considerable thickness, and deforms, in a 

 remarkable manner, the habit of the whole colony, so that the lateral polyps look as if 

 they were pressed against the stem. 



