PORIFERA OF THE L.M.B.C. DISTRICT. 229 



(Ira ciUata, which was attached to the surface of the 

 Stelletta. The prionorrhabds are arranged radiately, the 

 ideal centre of the circle lying inside the Sycandra. But 

 only this one small portion of the Stelletta, opposite to 

 which the Si/candra is situated, shows those spicules. 



As this special kind of spicule has never before been 

 described in Stelletta colling si, nor in any other sponge, the 

 question arises whether my specimen is identical at all 

 with St. coU'nu/si or whether the spicules are present in all 

 specimens of St. collingsi and have been overlooked by 

 former investigators, or lastly, whether they are a special 

 acquirement which may become developed in the sponge 

 under certain conditions. I am inclined to accept the last 

 of the three views. I have mentioned already that the pri- 

 onorrhabds were found only in a certain portion of Stelletta^ 

 and I believe that they have been acquired by the sponge 

 under the special abnormal conditions to protect itself 

 against the encroaching foreign body, a calcareous sponge. 

 As in my specimen they are very localized, it is quite 

 possible that they have been overlooked by other workers. 



I collected several specimens of Stelletta collingsi at Puffin 

 Island, in one of the caves on the north end of the island, 

 in April, 1889. One specimen had been found there already, 

 in June, 1888. The colour of the living specimen is 

 greyish-white. 

 Padhymatisma johnstonia, Bowerbank. 



The colour of this species is known to be subject to 

 great variation. Bowerbank* states — *' Littoral specimens, 

 light to dark slate-grey. Deep sea specimens, pink or 

 red." And Sollasf says — " Slate-grey on the portion ex- 

 posed to the light, almost white beneath ; specimens from 



* Bowerbank, " British Spongiadae," vol. ii., p. 51. 



t SoUas, "Report on the Tetractinellida, " collected by H.M.S. "Chal- 

 lenger," p. 243, 



