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



here they are visible also when covered with soft parts, so that the outer surface of the 

 sponge is distinguished throughout by small conuli 0"2 to 0'33 mm. high, the average 

 distance between them being 1 mm.; but it differs both from Coscinoderma lanuginosum 

 and Coscinoderma confragosum with respect to the character of its surface, which has no 

 special superficial incrustation, the skin not differing from that of Euspongia or 

 Cacosjyongia , and the manner in which the fibres form meshes. As in most other 

 SpongidsB, the meshes are here polygonal, although still formed by fibres all of the same 

 size — on an average 0"042 mm., i.e.. almost three times as thick as those of Coscino- 

 derma confragosum — a new character distinguishing this species both from Coscinoderma 

 lanuginosum and Coscinoderma confragosum. The average size of the meshes is 0"25 mm. 

 In external shape the specimen representing this new species in the Challenger collection 

 is in the form of a crust, but with local thickenings 10 mm. in height. In contrast 

 to the Challenger specimen of Coscinoderma confragosum, which shows a very well 

 developed osculum, no oscula can be discerned on the surface of this specimen. 



Colour. — Soft parts pale greyish, skeletal fibres brownish-yellow. 



Habitat. — On the reefs Honoruru, Sandwich Islands ; depth 40 fathoms. 



Coscinoderma ahum, n. sp. (PL V. figs. 4-6). 



This species is a good species also, provided of course that the genus Coscinoderma 

 be good. The meshes of the skeleton, as in the species just described, are of polygonal 

 outline, but on an average twice as large, the fibres themselves being one and a half 

 times as thick. Unlike all other representatives of the genus hitherto known, the fibres 

 are abundantly charged with foreign enclosures, so that they appear of a rather dirty- 

 white colour. Again, the external appearance of the sponge itself is novel, and is perhaps 

 not devoid of systematic importance. While in the two preceding species we have had to 

 deal with forms either incrusting or massive, Coscinoderma altum is found in the form 

 of a long cylindrical stalk with rounded upper end 230 mm. high and about 18 mm. 

 broad, with denticulated- outer surface, the prominences 075 mm. high and 2 mm. apart 

 being however rather blunt, and the skin itself presents the same appearance as that of 

 Aplysina aerophoba as drawn by F. E. Schulze.^ The specimen contained numerous 

 ]\torul8e, and I make use of this opportunity in order to turn attention to a peculiarit}^ 

 which, in a stUl higher degree, I have very often observed in Cacospongia and JEuspongia, 

 as mentioned in my paper "Ueber die Spermatogenese bei Sycandra raphanus," but which, 

 as far as I am aware, is hitherto uudescribed. I mean the extraordinary growth of the 

 endothelial cells surrounding the growing embryos. They do not differ in size from 

 other parenchyma-cells when young, but as they grow they do not become like the pave- 

 ment-cells, but increase both in area and volume. Again, when surrounding a Morula 



1 Zeitsclir. f. tnss. ZooL, Bd. xxx. pi. xxi. fig. 1, 1878. 



