Proceedings of the Royal Society. 277 
A Paper on the Generation of Fishes, by Dr. hPa Prevost, was 
read. 
The principal object of this paper was to describe the devolope- 
ment of the foetus of the bull’s-head, or miller’s-thumb (cotus 
gobio). » 
The testicles are composed of a congeries of small canals, ter- 
minated at the upper part by ceca, and containing the semen, 
which they discharge into a common canal opening into the meatus, 
by which the urine is discharged. Under the microscope the semen 
appears composed of globules and animalcules. The eggs of the 
female are emitted covered with mucus, which swells up when it 
absorbs water. The yolk is enveloped in a fine membrane, ad- 
hering to which is a white granulated cicatricula, not visible be- 
fore foecundation. 
The description of the developement of the foetus given by the 
author is not intelligible without the annexed plate. 
The Society then adjourned over one Thursday, to meet again on 
Thursday, June 17; 
at which meeting Lovell Edgeworth, Esq., was admitted a Fellow; 
and the following papers were read: 
On the Action of finely-divided Platinum on Gaseous Mixtures, and 
its application to their Analysis, By W. Henry, M.D., F.R.S, 
In the first section of this paper the author described the action 
of finely-divided platinum, at common temperatures, on mixtures 
of hydrogen and olefiant gas with oxygen; of hydrogen and 
carburetted hydrogen with oxygen; of hydrogen and carbonic 
oxide with oxygen; of hydrogen and cyanogen with oxygen; of 
carbonic oxide and carburetted hydrogen with oxygen; of hydro- 
gen, carburetted hydrogen, and carbonic oxide with oxygen; and 
of the same with the addition of olefiant gas. From the experi- 
ments detailed under these several heads, it appears that when the 
compound combustible gases mixed with each other, with hydrogen, 
and with oxygen are exposed to platinum balls or sponge, the 
seyeral gases are not acted upon with equal facility, but that, next 
