330 Mr. H. J, Carter on the Parasites of the Sponges. 



From the subject of measurements Dr. Gray suddenly di- 

 verges to make the following observation. Again referring to 

 my paper on Trionyx Phayrei, he says, " the sternum is thus 

 described : — ' Seven osseous plates, of which five are visible 

 and granular ;' " and, seizing on the word " seven," he either 

 believes that I was ignorant of the elementary fact of the 

 number of plates that compose the sternum of the tortoise, or 

 twists my words to favour an hypothesis pleasant to himself. 

 He makes the very just supposition that I meant the nine 

 sternal bones : but this quibble is unworthy of Dr. Gray ; for 

 he had only to look at my figure and he would have discovered 

 the explanation of my using the word seven — the transverse 

 suture of the lateral plates being obliterated, the two pairs in 

 this adult specimen being externally resolved into one pair, so 

 that, as I have already observed, only seven distinct osseous 

 plates exist. In describing things as they are, it is quite un- 

 called-for to enter into the first principles of things as they 

 have been. 



I regret having encroached so much on your valuable space, 

 and the wandering character of this note, which has been in- 

 duced, however, by the digressions that distinguish Dr. Gray's 

 article to which this is in reply. 



Calcutta, Sept. 16, 1871. 



XLT. — Parasites of the Sponges. By H. J. Carter, F.E. S. &c. 



My dear Dr. Francis, 



I hope soon to send you an illustrated paper on the Parasites 

 of Sponges, beginning with Dr. Bowerbank's Stematumem'a, 

 Avhich, so far as this author's specimen of " fibro-membranous 

 tissue" goes (Brit. Spong. pi. xii. figs. 256 & 260 ; Annals, 

 1845, vol. xvi. pi. 14. fig. 1) is no more a sponge, or part of 

 one, than his so-called Halyphysema. The latter, as you 

 know, I have long since shown in the ^ Annals ' to be a Fora- 

 minifer, dressing itself out in spicules after the manner of the 

 jackdaw with peacock's feathers, but probably not for the 

 same purpose ; and the fibre of the former, illustrative of the 

 so-called " fibro-membranous tissue " in Stematumenia^ I shall 

 soon show to be an Alga, and probably an Oscillator mm ^ 

 which, from its frequently infesting sponges of difterent kinds 

 in all quarters of the globe, I propose to name " Spongiophaga 

 communis. ^^ 



Schmidt (in 1862, Spong. Adriat,, and especially in 1864, 

 Suppl.), after having given a great deal of attention to these 



