15 



which they perforated. " It was jby the 

 whole mantle. The mantle folds out of the 

 lower end of the two valves and encloses 

 them as a finger-glove does the finger. The 

 sides of the mantle are thus pressed against 

 the sides of the crypt, which are worn away 

 as the rock is under the foot of the limpet. 

 The lime ahsorhed hy the mantle is no doubt 

 used in secreting and renewing the valves." 

 He had observed the i)erforations of the 

 univalves by keeping them in sea water and 

 the bivalves by splitting open theii* crypts 

 with a chisel and hammer. 



Ajyril. A paper on Vegetable Physiology was read 

 by Dr. Hallifax. After a general survey of 

 the whole question, Dr. Hallifax remarked 

 that he would confine himself to the general 

 facts of the ascent and diffusion of the sap or 

 nutritive fluid of plants. All were familiar 

 with the ascent of the sap, but when one 

 enquired as to how the ascent was made, 

 gi-eat diversity of opinion was found among 

 the authorities, the main points asserted by 

 all being that most of the fluid was taken up 

 by root absorption, in large quantities and 

 with great force. Some Physiologists ac- 

 counted for the process by what is called 

 endosmose, the delicate cell covering acting 

 as a membrane. The root itself was found 

 to be similar in structure to the stem, a 

 prolongation of which it really was, and 

 consisted of various tissues arranged around 

 the pith. The question then arose, which of 

 these tissues took up sap. Experiments had 

 shewn that the ascent was by means of the 



