LIMN^AD^. 
197 
The following Table respecting the eggs of Zm- 
7i(Bad(B is drawn up from M. Bouchard’s observations, 
the first column giving the form of the masses of 
eggs, the second the number of eggs in each mass, 
the third the number of days after they are laid 
before they hatch. 
1. 
2. 
3. 
Limnea auricularia - 
elliptical 
60—100 
15—16 
ovata - 
- 
jj 
60— 80 
peregra 
- 
60— 80 
stagnalis 
- 
100—130 
palustris 
- 
cylindrical 
60— 80 
rmindp, d 
15— 20 
Amphipeplea glutinosa 
- 
X. V/ Vi 
30— 40 
Physa hypnoriim 
- 
round or oval 
3— 12 
16 
fontinalis 
- 
roundish 
3— 12 
16 
Yelletia lacustris 
- 
orbicular 
5— 12 
24—26 
Planorbis contortus - 
- 
6— 8 
10—12 
corneus 
- 
20— 40 
16 
alb us 
- 
)> 
10— 13 
12 
— imbricatus 
- 
3— 6 
10—12 
12 
1 0 1 9 
margin atus 
- 
6 
carinatus - 
- 
6 
nitidus 
" 
4— 8 
10—12 
It had been supposed that the shells of fluviatile 
Mollusca could be distinguished from those of the 
terrestrial kind, by the edge of the mouth of the 
shell never being furnished with a thickened in- 
ternal rib, and not being in the slightest degree 
reflexed, and that the animal never closes it with an 
epiphragm ; however, further examination has shown 
that when the Pond-snails and the Whirl-shells are 
left nearly dry by the evaporation of the water. 
