292 RKVISION OF THE MONAXONlD SPONGES,!., 



macerated by means of caustic potash, and which consist of 

 closely packed spicules held together by what appears to be a 

 kind of connective tissue. A skeleton of similar nature, though 

 of very different conformation, is possessed also by Cliona hixonii; 

 but I have so far met with nothing of a like kind in any other 

 of the species of Spirastrella that I have examined, nor has such 

 a skeleton been mentioned by Vosmaer.* It would seem not 

 unlikely, therefore, that .V. australis and S. ramulosa are more 

 closely related to Cliona than to Spirastrella: and the question 

 arises as to what particular features are to be regarded as essen- 

 tially distinguishing the two genera. To this question, I do not 

 think a satisfactory answer can, at present, be given. The dis- 

 tinction recognised by Vosmaer is summed up in his statement 

 that, "whereas the latter (Cliona) begins its post-larval life by 

 boring into calcareous matter, Spirastrella never does so " : but 

 although this may ultimately prove of value as a basis for 

 separating the two genera, the fact remains that the life-history 

 of most of the species included in the genus Sjnrastrella is as yet 

 unknown to us. At present, the practical difficulty which pre-' 

 sents itself is how to determine, in a given case, whether a 

 massive sponge seemingly a Spirastrella has or has not been in 

 early life a boring sponge; and in striking illustration of this, is 

 the fact that Vosmaer himself has confounded with Sjnrastrella 

 ptirpnrea a species that undoubtedly should be referred to 

 Cliona. I refer to Spirastrella, areolata Dendy, which in the 

 areolation of its surface and in its possession of spined microxea 

 (apparently overlooked by Vosmaer) shows so close an analogy 

 with Clio7ia hixonii as to render unquestionable the close re- 

 lationship of the two. There is a number of species also - unre- 

 ferred to by Vosmaer — concerning which it is an entirely open 



* I think it is exceedingly probable, however, that Spirastrella rohasta 

 (Carter) Dendy(14) — which was regarded by Carter as a variety of Spira- 

 strella cimcat7-ix—wi\\ be found to possess an analogous type of skeleton. 

 I have seen only a thin section of this sponge — one presented to the Aus- 

 tralian Museum by Prof. Dendy — and although this is insufficient to pro- 

 vide unmistakable evidence of liie presence of such "fibres," neverthele.ss 

 the structure of the skeleton, as displayed tlieiein, exhibits, on the whole, 

 a marked similarity l(^ that of S. australis. 



