MOLLUSC A. 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 priori 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- 



ORDER I 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, 



1st 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 



