THE society's NOTE-BOOKS. 205 



conical form resembling the rose of a watering-pot, only that the 

 margin is fringed with a corona of delicate diverging spicules. 

 The tubes are very sensitive to touch and light. They instantly 

 contract and withdraw themselves when exposed to powerful sun- 

 light. Currents of water flow into the poriferous tubes and out of 

 the oscular tubes. In autumn this sponge mass will be found 

 crowded with ciliated embryos, about i/2oth of an inch long, with 

 spicules already developed in them. These Cliones are also found 

 in a fossil state in the shells of the Silurian strata, where we find 

 Belemnites perforated by them in a similar manner to the recent 

 oyster. Miss Henty's slide shows the spicules well with a high 

 power. E. E. Jarrett. 



This slide is a happy variation from the usual run of slides, 

 and Miss Jarrett's note adds greatly to the interest of it. 



The process by which such soft, helpless-looking creatures as 

 these tiny sponges are able to perforate hard shells, and even lime- 

 stone rocks, is so obscure and so difificult of explanation, that some 

 naturalists — and Dr. Bowerbank among them — have been led to 

 deny the possibility of the thing. They hold that these borings 

 are the work of marine annelids, and that the sponges afterwards 

 appropriate them for purposes of protection and concealment, and 

 live there as parasites upon the shell. But the balance of evidence 

 seems to be in favour of the Sponges making the holes as well as 

 living in them. Those who care to go into the subject will find it 

 somewhat fully discussed in Quekett Journal, No. 47, July, 1881. 



J. H. Green. 



Although the question as to whether the sponge does the 

 boring for itself is fully discussed in the number referred to of the 

 Quekett Journal, the matter is not settled. I think there is much 

 probability in the view that the sponge itself excavates the hole it 

 occupies. How it does so is another question which Mr. Waller, 

 the writer in the Quekett Jour 7ial, does not attempt to settle. 



Geo. U. Brown. 



Can the boring be effected by evolution of carbonic acid from 

 the sponge, dissolving away the carbonate of lime of the shell ? 

 Some of the lichens ( Verrucaria) in some such manner sink their 

 shields deeply into the limestone rock on which they grow. 



