MOLLUSCA. 149 
_on land; for this purpose the ova are enclosed in chambers 
of a particular kind.” The assertion here made, and found- 
ed on a prioré considerations, that the shell is not formed 
until after the egg is hatched, is opposed by every observa- 
tion which we have been able to make on the subject; and 
what is more surprising, it is at variance with his own ob- 
servations on the garden snail, the very example produced 
in its confirmation. The eggs of a snail, laid on the 5th of 
August 1773, were hatched on the 20th of that month, 
and their condition at this time distinctly stated. “On the 
20th,” he says, “the young were hatched, and the shell 
completely formed.” It is much more becoming in a phi- 
losopher to observe how nature operates, than to pronounce 
what she must do. 
OrprerR ]._— TERRESTRIAL. 
The animals of this order reside constantly on the land. 
When by accident they fall into the water, they appear to 
be incapable of using their foot as a sucker or as a fin, and 
die after a few writhings. The species in general prefer 
moist places, and are seldom very active in dry weather. 
After a shower they speedily leave their hiding places, and 
at this time they may be readily collected. The eggs are 
hatched on land. 
ist Subdivision. 
Cloak and foot parallel, and containing the viscera between 
them. 
In this group are included those animals denominated 
slugs in this country. They possess four retractile tenta- 
cula, of unequal length, though in some cases one pair is 
