6 Mr. H. J. Carter on three Pachytragous Sponges 



bullock's liver." Now, assuming, in accordance with Dr. 

 Bowerbank's experience, tliat this is the best way to preserve 

 sponges for description, we can hardly tliink that the colours 

 of the wet were different from those of the dried specimen ; or 

 this would have been noticed. 



Hence, as the species which I have been describing is jet- 

 black when dry, and the body or internal substance inclining, 

 if any thing, to dirty green, while the same colours are pre- 

 sented by the portions which have been preserved in spirit 

 and water, I cannot but infer that at least, as before stated, 

 the black sponge which I have designated by the specific 

 name of " niger " is a variety of Dercitus Bucklandi^ and 

 therefore deserving of this separate denomination. 



But whether the reader chooses to admit this or not, he can 

 hardly fail to see that, ca-t. par.^ there is a vast difference 

 between the description of a sponge from " the life," and that 

 of one wliieli the author has only seen after death. 



It is not difficult to find this sponge, because it docs not gi*ow, 

 like many, on the under surface of the rock, but grows on its 

 sides in deep boAvers, sought for apparently by the sponge 

 for protection from the waves. Then, its black-velvet-looking 

 appearance strikes the eye immediately ; but the difficulty 

 of getting at it, except in a more or less horizontal position, 

 and its toughness and firm adlierence, rendering it neces- 

 sary to take off a portion of the rock on which it grows wnth 

 hammer and chisel to obtain the whole of the specimen, make 

 its collection by no means an easy task for a stiff old collector. 



Perhaps the most remarkable point, after all, about this 

 sponge is the presence of the celluliferous cortical layer and the 

 characters of the cells of which it is composed — since, by their 

 accumulation here, and being scattered through the substance 

 of the sponge, they, although totally different in composition, 

 do occupy a position exactly like that of the globular cr}^stal- 

 loids which form a crust round and are scattered generally 

 through the substance of the Geodidse. But of this more 

 under " General Observations." 



The puckered state of this sponge on the surface, while in 

 situ, seems to arise from contraction occasioned by the falling 

 of the tide, or absence of water, when its substance becomes 

 drawn towards the more prominent points of the rugged por- 

 tion of rock beneath, over which it may be growing. But, 

 whether this explanation be correct or not, the puckered 

 radiating lines from particular points on the surface of the 

 sponge are remarkable. 



It is also worthy of remark that, although the sjionges of 



