124 JOURNAL OF THE [May, 



mainly the life-history of the sponge of commerce, describing its 

 development both from the egg and from the bud. He concluded 

 his Address with a notice of Cliona, or the boring-sponge, and 

 of the harm done by it to the oyster. He gave it as his opinion 

 that the embryology of sponges ranks them with the Metazoa. 

 His observations form the second article in this Number of the 

 Journal. 



Discussion elicited the following matter : — 



Mr. J. D. Hyatt : " The boring-sponge attacks shells and 

 limestones. It sends out into them roots, or arms, which, 

 through ramification, become smaller and smaller, like the 

 mycelium of a fungus. The borings in even very hard marble 

 reach sometimes a depth of more than two inches, and at 

 their extremities they are microscopic. 



" I have discovered no evidence that the health of the oyster 

 is impaired by the boring of the sponge. The sponge does not 

 feed upon the oyster. It has been observed in aquaria to attach 

 itself quite as readily to a vacant as to an occupied shell. When 

 its arms have penetrated to the inner surface of the shell of a 

 living oyster, the mantle of the mollusk, becoming irritated by 

 their presence, checks and, I think, stops the intruders by de- 

 positing at once an extraordinary quantity of nacre at the points 

 of intrusion. You see as a result small elevations at those points. 

 The shell may, at the same time, have become so far honey- 

 combed in other directions that it can be easily crushed by the 

 hand." 



Prof. Rice : " The sponge does not, it is true, seek the oyster; 

 yet the oyster is liable to perish in consequence of the disinte- 

 gration of its shell by the borings of the sponge. This liability 

 occurs in those cases in which the borings have weakened the 

 innermost plate to such a degree that the part to which the 

 adductor muscle is attached gives way under the traction of the 

 muscle. The valves are then forced open by the tension of the 

 ligament, and the oyster is left defenceless against its enemies. 



"I have seen shells in which the borings seemed to penetrate, 

 not only the nacreous lining proper, but also layer after layer of 

 material which the oyster had deposited for the obvious purpose 

 of protecting itself against the encroachments of the sponge." 



