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



" The mesogloea of the mesenteries is strongly constructed, and on it can be 

 recognised well-developed muscle-pennons. The generative organs, borne in the 

 supporting lamina, consisted of ova in the individual which I investigated. The mesen- 

 terial filaments are of the customary structure. 



" The mesenterial arrangement is to be referred to the macrotype. The specimen 

 investigated possessed thirty-six mesenteries, of which five pairs pertained to the dorsal 

 zone, and thirteen pairs to the ventral ; in the latter zone were ranged regularly, on each 

 side of the directives, six pairs, consisting of a macro- and a micro-mesentery. 



" The body- wall is drawn inwards at a right angle ; on the inner side of this 

 region a definite endodermal sphincter may be recognised. The pleatings of the 

 endodermal muscle-lamina are more clearly marked than in Palythoa axinellce ; and 

 produce on the mesogloea prominent antler-like prongs. The accretions are continued 

 on to the inch-awn region of the body-wall, but die out at its lower edge, where the 

 oral disc commences." 



The identity of this animal with Palythoa anguicoma is doubtful, as Norman, who 

 created the species, gave no figure of it. I was influenced by the circumstance that 

 eighteen rough radial furrows are ascribed to this form ; besides which the incrustation 

 on it should be only superficial. 



Palythoa, sp. (?)* 



Habitat. — (a) Station 135 a, off Inaccessible Island, October 16, 1873; 60-90 

 fathoms, (b) Station 135 c, off Nightingale Island, October 17, 1873 ; 100-150 fathoms. 



In the same bottle with Palythoa anguicoma was another species of Palythoa, which 

 recurred in a second tube, the contents of which were dredged a day later than the 

 first, and at a greater depth. The specimens in cmestion could easily be distinguished 

 from individuals of Palythoa anguicoma by containing black particles of hornblende. 

 Erdmann attempts to separate the two species, and gives the following description : — 



" In this species also the larger part of the material consists of individuals torn away 

 from the colony ; one colony, which was undoubtedly not mutilated, was represented by 

 three individuals, ranged behind one another on a ribbon-like ccenenchyme. Externally 

 this species differs from the preceding in colour only, which is in this case a dull grey- 

 brown ; besides this, from the greater firmness and unevenness of the body-wall, it may 

 be recognised that the mass of accretions is greater. The body-wall presents, in contrast 

 to the former species in which the relations are reversed, a considerable zone charged 

 with accretions, opposed to a slightly-developed soft zone of mesogloea. In the latter 

 there passes close under the endoderm a cell-canal, frequently constricted, but rarely 

 interrupted ; external to this follow immediately the accessory deposits, so that of 

 the numerous canals and spaces observed in the preceding species only a few roundish 

 cell-islets are preserved." 



