174 
March 27th, 1865. 
John Parry, Esq., in the Chair. 
Exhibitions. 
Sections of various Shells. — Mr. Parry. 
An apparatus for applying pressure to the cover-glasses of 
objects freshly mounted in Canada Balsam. It consisted of 
a dozen small upright pistons placed in a frame, and each 
furnished with a spiral spring coiled around the rod and 
pressing against the upper horizontal bar of the frame. 
Communications. 
Dr. Alcock exhibited a second time his specimens of 
shells of Marine Entomostraca, from the coast of Galway. 
He said that renewed examination of them and the collection 
of many more specimens had strengthened his belief that, 
however numerous their forms, they are entitled to be con- 
sidered as so many distinct species, and he did not think that 
the general arguments used by Prof. Williamson in support 
of an opposite opinion at the meeting of February 20th, had 
any application to their particular case. In the first place it 
was stated that the outer skin or shells of these creatures is 
of less value for distinction than the internal parts ; but Dr. 
Baird had described nine out of his fifteen species from living 
specimens, and yet in these his specific distinctions are 
mainly derived from the shells. Again, we were reminded 
that some of the Entomostraca are known to undergo meta- 
morphoses, and that this might probably be the case with the 
genera Cythere and Cythereis ; but Cypris, which approaches 
very nearly in character to Cythere, does not undergo these 
changes, and might furnish some ground for the supposition 
that these Marine Entomostraca also do not ; but it would 
be sufficient for the present purpose to state that there is no 
