109 



ACCOUNT OF BRITISH SPONGES. 



formed between the period of its being quitte4 

 by one inhabitant, and the possession of another ; 

 for the hermit-crab is continually changing its 

 abode, in order to accommodate its cell to its 

 growth. 



In every instance where a crab has been found 

 to inhabit such a shell, the sponge has invariably 

 spread within the aperture, and frequently a con- 

 siderable extension of the lip to the shell, is pro- 

 duced by the sponge. 



This species of sponge is found on several parts of 

 our coast, which makes me suspect that it has been 

 confounded with tomentosa, as it does not appear 

 to have been described. It is not uncommon in 

 the estuary of Kingsb ridge, and is frequently 

 taken by the dredgers, 



Spongia suberia, differs from t anient osa as much 

 in its habits as in its texture : it never appears to 

 attach itself to any fixed body ; no part of its 

 surface ever indicates such an attachment ; and 

 consequently, we may conclude it is not sessile^ 

 but independent. It is ponderous (comparatively 

 speaking) even when dry ; it has no visible pores 

 to the naked eye even in fractured parts ; and its 

 surface is regularly smooth without any little in- 

 dentations or inequalities, and is hard to the 

 touch. 



The tomentosa, on the contrary, is always affix- 

 ed by its surface, is not very fine in its internal 

 texture, is extremely light, brittle, and soft, ^nd 

 its surface full of small inequalities. 



