356 Mr* A. Hancock on the Excavating Sponges. 



preliminary to the discussion on the mode by which the excava- 

 tions are effected ; — the principal object of my paper being to 

 show a similarity in this respect between Cliona and the excava- 

 ting Mollusca. 



Dr. Grant, whose opinion I quoted in my paper, and who 

 wrote on the subject many years previous to the appearance of 

 Dr. Nardo' s memoir, seems to be the first to have asserted the pro- 

 bability of Cliona forming its own abode. He says, " It may be 

 questioned whether the sharp siliceous spicula and constant cur- 

 rents of its papillae do not exert some influence in forming or en- 

 larging the habitation of this zoophyte." Mr. Wm. M'Calla, too, 

 was quoted as having stated that Cliona was " very destructive 

 to the shells that came within its reach." And from the fact 

 that M. Duvernoy had named a species terebrans, it was inferred 

 that he also was convinced that these sponges formed the cham- 

 bers they occupy, though I knew no more of what he had written 

 on the subject than appears in the ' Microscopic Journal/ It is 

 therefore pretty evident that I had no pretension to the discovery 

 of the fact that Cliona has the power of burying itself in hard 

 calcareous bodies ; though I foUnd it necessary to put this matter, 

 so far as I was able, beyond a doubt. In this respect the re- 

 searches of Nardo and Michelin are of the greatest value ; for 

 confirmation is still required, as it appears all are not yet satisfied 

 that a sponge can penetrate shell and stone. It would have been 

 well, therefore, if Mr. Morris had given the abstract at greater 

 length. 



It may be questioned, however, how far the Italian naturalist 

 is justified in discarding the name given to these sponges by 

 Dr. Grant, merely because that gentleman did not fully under- 

 stand the nature of the production he described. Were such a 

 principle to be admitted, nomenclature would be for ever fluctua- 

 ting, and hundreds of names used by the early writers might be 

 at once superseded. Dr. Grant's description is excellent, full and 

 clear ; so that even the species may be determined. Why then 

 should he be stripped of the honour of his discovery? Had 

 there been any obscurity, — any difficulty in determining what 

 was meant, then there might have been some plea for adopting 

 the generic appellation of a subsequent observer ; but even Nardo 

 himself does not appear to doubt that his genus is identical with 

 the Cliona of Grant. 



Neither can I at present assent to Mr. Morris's opinion, that 

 my two species C. Fryeri and C. spinosa are identical with Vioa 

 Nardina and V. Michelini. This there is reason to doubt. I 

 have certainly not seen the figures referred to, but the descrip- 

 tions are not full enough for identification ; and indeed, so far 

 as they go, do not very well agree with my species. The charac- 



