72 THE VOYAGE OF H.M.S. CHALLENCxER. 



spermospores aud not sperm-balls, as I did in the description of Carteriospongia radiata, 

 for they are quite difi'erent in appearance and structure. In Carteriospongia radiata, and 

 in other instances, these formations present an aggregation of cells, if not ripe spermatozoa, 

 these cells being each equivalent to the other, and the whole lying in a capsule formed 

 by numerous pavement cells ; in Verongia the analogous capsule is formed by a single 

 cell, the endothelium is not to be found at all. In one word, the male generative 

 products are quite equivalent to those of Calcarea as I have described them in Sycon 

 raphanus} I must confess I can find no explanation of this ; the matter appeared to me 

 strange even before, when I thought the Calcarea were opposed in this respect to the 

 ivhole group of Silicea. I was thoroughly startled when, hand in hand with indubitable 

 sperm-balls in Carteriospongia as well as in some other Keratosa of the collection, 

 I discerned in my preparations of both species of Verongia the most typical spermo- 

 spores. I was not able to follow out their development, but when ripe they recall so 

 vividly the corresponding formations in Sycon raphanus (with the sole distinction that 

 while in this latter instance the nucleus of the covering cell in quite ripe spermospores is 

 in most cases indistinct, in Verongia I find quite empty capsules, nevertheless, provided 

 with it) that I must identify both these formations ; on the other hand, I have now no 

 doubt that at the development of the sperm-halls no covering cell is formed, that its 

 description by F. E. Schulze^ agrees closely with the reality. I have repeatedly 

 examined Oscarella {Halisarca) and Aplysilla, and was able to follow out the develop- 

 ment of their sperm-balls from tlie first beginning, and I can only affirm the former 

 statements of F. E. Schulze, that we have in these instances to do with real division of 

 the sperm cells, and that there is no covering cell to be discerned. On the whole the 

 enigmatic question requires a special and extensive investigation, the more so that it is 

 not only of spongiological but also of general interest. 



Colour. — External surface black, that of the central cavity and parenchyma grey, 

 skeletal fibres brownish yellow. 



Habitat. — Oft' Barra Grande, September 10, 1874 ; depth, 400 fathoms. 



A perusal of the preceding pages shows that of thirty-four determinable forms brought 

 home by the Challenger Expedition, almost two-thirds (21) have been found to be new, 

 and that only three species [Psammopemma densum, Luffaria variabilis, and Cacospongia 

 collectrix) were obtained from more than one locality. Under such conditions any 

 discussion of the geographical distribution of the Keratosa would be possible only if 

 extended over all the Keratosa hitherto described. It must be said, however, that on 



1 Sitzungsh. Alcad. d. TFiss. JFien, Bd. Ixxxvi., 1882. 

 - Zeitschr.f. wiss. Zool., Bd. xxviii. p, 24, pi. iii. flg. 19. 



