269 



Further Remarks on the Histology of Sponges. 

 By B. W. Priest. 



(Read March 25th, 1881.) 



Since bringing my paper on Sponges before you, I have sought all 

 the information I could in the time on the matter of the Burrowing 

 Sponges, and still hold to the same opinion that I had then, that a 

 certain class of Sponges are capable of burrowing or boring cavities 

 in hard and soft substances. 



I certainly cannot see why, because the Cliona and others of that 

 class occupy the cavities made by Annelids or Molluscs, that they 

 should not be capable of burrowing for themselves. No doubt in 

 perforating the shells in which they are found they avail themselves 

 of ready-made spaces and cavities, and spread out and line them, and 

 so in that case take a more or less massive form which they are 

 known to do, Carter. and others describing Cliona celata in a form, 

 where it does not burrow, but occurs massive. 



Carter, in describing Cliona corallinoides in the Annals of Natural 

 History for 1871, states 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 Melohesia lichenoides, which goes on grow- 

 ing (that is, spreading in all directions), while Cliona, every here and 

 there, makes holes through this crust or thalloid frond for its pore- 

 area or vents as required. Still quoting Carter, he goes on to sa y, 

 " Of course, therefore, these * holes ' are occupied by a longer or 

 shorter cylindrical prolongation of the Sponge in proportion to the 

 thickness of the crust, which thus presents as many heads, so that 

 when the shell is dissolved off by acid the heads project here and 

 there above the general surface of the Sponge." 



Again, my friend Mr. Hillier, of Ramsgate, in a letter to me on 

 the subject, states that Cliona celata burrows in the hard limestone of 

 which the pier is partly built, and that it sends up its oscula right 

 through any other Sponge which may be growing over the stone ; 

 — in fact liking to get freely at the water, and that it is on that 

 account it is never found inside, but outside, the harbour. 



