Mr. H. J. Carter on Parasites of the Spongida. 171 



tortuous, branched, tubular filament which sooner or later 

 infests almost every hard marine organization, both kerataceous 

 and calcareous. How far it may occur after death I am not 

 able to state ; but it is present in the fibre of Aplysina capensis, 

 Cart. MS. ('Annals,' 1875, vol. xvi. p. 192)— that is, a red- 

 dish, purple, massive hircinoid psendoceratinal sponge from 

 Algoa Bay, which, from the presence of the sarcode, appears to 

 have been living when taken up for preservation. 



Thus Dr. BoAverbank's genera respectively, viz. ^'Sternma- 

 tumema " and " Aidiskia " were founded on the presence of 

 a parasite, and that following, viz. " Cartilospongia " [ih. p. 

 408, pi. xiv. figs, 6-8), upon the structure of a compressed, 

 circular, cake-shaped piece of bone ! Curiously enough, in 

 examining Dr. Bowerbank's collection, the identical bone has 

 come before me, which appears to be the body of a foetal 

 whale's vertebra, bearing the exact dimensions and descriptive 

 characters given by Dr. Bowerbank {I. c). At first sight it 

 is very much like the skeleton of a sponge of this shape ; but 

 the odour evolved by making a vertical section of it through 

 the short axis, and the microscopic examination, place beyond 

 a doubt its true nature. As Dr. Bowerbank was a good 

 observer, his description and illustrations are valuable from 

 their correctness ; but his inference was incorrect. 



FoEEiGN Objects. 



Although these, being without life before they were taken 

 up by the sponge, cannot be considered parasites, yet there 

 is one which so frequently occurs in the Psammonemata, 

 so like a mineral product, and often so abundantly, that it 

 demands a passing observation here. I allude to a little prism 

 of calcite banded occasionally with yellow, brown, red, or 

 amethystine colours, separately or more or less united in the 

 same prism. It occurs in these sponges generally^ but most 

 plentifully in the Arenosa from Port Jackson ; and hence I 

 thought at first that it must come from some mineral source 

 there ; however, one day finding groups of these prisms in situ 

 in a large specimen of an Esperia from Southern Australia, 

 which had also enclosed some bivalve shells like Crenatula 

 phasianoptera^ I was led to compare them with the structure 

 of the latter, and immediately saw that, everywhere, their 

 source must be from the disintegration of thin shells like this, 

 which are made up of similar prisms, coloured in accordance 

 with the shells from which they are derived. 



