Hogg, on the Water-Snail. 
91 
Observations on the Development and Growth of the Water- 
Snail {Limneus stagnalis). By Jabez Hogg, M.R.C.S.. &c. 
(Kead March 29th, 1854.) 
In submitting the observations which I have the honour of 
bringing to the notice of the Fellows of the Microscopical 
Society this evening — on the Development and Growth of 
the Water-snail (^Limneus stagnalis) — I do so with considerable 
diffidence. When I first gave the subject my special atten- 
tion, and began to jot down the remarks that occurred to 
me as growing out of my experiences, I was not fully aware 
of the extent to which many able investigators had traversed 
the same ground before me. So far back as 1754, precisely 
a century since, Baker, in his book entitled, ' Employment 
for the Microscope' (p. 325), was the earliest to describe 
" a small water-snail and its spawn, or eggs, fastened in little 
masses, against the sides of the glass," in which he kept 
them. It also engaged the attention of the illustrious 
Swammerdam ; and, more recently, that of Reaumur and 
Dr. Grant. Mr. Bowerbank's very interesting and careful 
observations on the ' Structure of the Shells of Mollusca and 
Conchifera,' and the scientific researches of Dr. Carpenter, 
have thrown great additional light upon this subject. A brief 
record of my own personal investigations, with regard to this 
department of microscopic observation can, therefore, present 
no signal feature of interest beyond that of confirming and 
enforcing the experience of the talented and eminent micro- 
scopists who have preceded me. It is with this view that I 
venture to lay before the Microscopical Society the few 
remarks which I have now the privilege of reading, happy if 
I shall have contributed, in however slight a degree, to add in 
any way to the store of knowledge already accumulated. 
Into a glass vase, where my stock of Chara, Vallisneria, &c., 
is growing, I introduced last Autumn a single Limneus, for 
the purpose of observing its habits ; I was then more espe- 
cially curious to see its mode of creeping along, under the 
surface of the water, by means of its fleshy foot. Upon one 
occasion, as I sat watching the movements of the animal, 
attached as it then was to the side of the vase, near the surface 
of the water, it suddenly became uneasy, moving to and fro, 
and in a short time it began to deposit very slowly, through 
a fissure near its ventral aperture, a small gelatinous sac, 
filled with transparent specks, at the same time firmly gluing 
it to the glass. This sac I examined with a pocket magnify- 
ing-glass, and found it contained fifty-six ova. Each egg was 
VOL. IT. k 
