272 J. G. WALLER ON THE BURROWING SPONGE. 



entirely perforated with minute borings about the twentieth of an 

 inch in diameter, wit}] out the slightest vestige of the sponge in 

 any part ; and Dr. Bowerbank has produced such overwhelming 

 testimony that in itself it is sufficient to dispose of this statement. 

 Dr. Bowerbank states that, he has found it in the interior of 

 the shells of Balani, and has also found it filling up excavations 

 made by lithodomus molluscs in the rocks at Tenby. To this, 

 I can add, that I have found it in the empty tubes of the Ser- 

 pula. Dr. Bowerbank further states that " I have in my collec- 

 tion several specimens of large Balani, which I took from the sides 

 of rocks forming the Guliot caves at Sark, which are perforate^, in 

 the usual manner, with numerous sinuous canals, which I found 

 filled with the living a?inelids, the dried remains of which still remain 

 in them, and without the slightest indication of the presence of 

 H. Celata, and I have also found living annelids in the deeply seated 

 portions of the perforations in the limestone boulders of Tenby, 

 beyond the range of the sponge ; so that I think it may be rea- 

 sonably concluded, that the sponge occupies the canals and cavities 

 in shells and stones which have been excavated by other animals, 

 and that they have no power to excavate such residences themselves." 

 (Vide " British Spongiadae, Art. Hymeniacidon Celata.") 



I hold it as impossible for any one, who enters into the study of 

 this sponge with unprejudiced views, to arrive at any other conclu- 

 sion. It is necessary, however, for me briefly to state what means 

 Mr. Hancock has considered the sponge has for the work he attri- 

 butes to it. He says " The excavations are effected by mechanical 

 and not by chemical means. With respect to Cliona, it is well 

 known to possess silicious spicula, some of the points of which 

 penetrate the surface of the animal, and might be supposed capable 

 of reducing the calcareous bodies in which these creatures bury 

 themselves." To my mind this process would be about as effectual 

 as mining the tunnel of Mont Cenis with darning needles. " But," 

 the writer continues, " other and apparently more efficient agents 

 have been discovered covering the surface of the sponge " — and 

 these he minutely describes, and has figured as " certain silicious 

 particles." Now, silicious particles are commonly enough found 

 on the tissues of nearly all sponges. I have a specimen of the 

 genus Chalina, which is rendered quite rigid by the dermis being 

 filled with extraneous grains of sand not in any way united to the 

 fibres of the network. The instance is remarkable, but I look 



