364 TOILERS IN THE SEA. 



shells may be determined with the greatest con- 

 fidence. 1 



Much more recently, H. J. Carter says of a species 

 of Clwna, that not only does it excavate shells, but 

 the sandstone rock, too, of the same locality where 

 it shelters itself, under the florid expansions of the 

 Nullipores. And in 1881 Mr. B. W. Priest, who had 

 previously held an opposite view, frankly declared 

 that " he had come to the conclusion that no known 

 worm could bore in the manner indicated, where the 

 ramifications are very numerous, and in some cases 

 very fine, and most of them more or less filled up 

 with the sponge or its remains." And further, " I 

 still hold to the same opinion, that a certain class of 

 sponges are capable of burrowing or boring cavities 

 in hard and soft substances." 2 



Having given a summary of opinion on the boring 

 capacity of these sponges, we must candidly admit 

 that they have not remained unchallenged, and that 

 there have been, and still are, excellent observers who 

 do not consider that the burrowing can be accom- 

 plished by the sponge. Foremost amongst these was 

 the late Dr. Bowerbank, who says, " Some naturalists 

 have promulgated the idea that this sponge has the 



1 " On the Excavating Powers of Sponges," by A. Hancock,, 

 in "Annals of Natural History," vol. iii. (1849), P- 3 21 - 

 - "Journal of Quekett Microscopical Club," vol. vi. p. 269. 



