NATURAL HISTORY FISH. 24? I 



excluded from the egg, may be considered in 

 the tadpole state as fish ; and you would not 

 find their singular metamorphosis without in- 

 terest. Or I could detail to you the true 

 histories which naturalists have given of the 

 habits of snails and earthworms, and of the 

 sexual relations of these apparently con- 

 temptible animals; but this is too delicate 

 a subject to dwell on. Even the renewing 

 or change of shell in the crawfish, when 

 it falls in its soft state an easy prey to fish, 

 is a curious inquiry not only for the phy- 

 siologist, but likewise for the chemist. On 

 these points, I must request you to refer to 

 writers in Natural History : yet I shall per- 

 form my promise, and say a few words on 

 winged insects, which, in their origin and 

 metamorphosis, offer the most extraordinary 

 known miracles perhaps of terrestrial natures. 

 You must be acquainted with the origin of our 

 common house flies ? 



PHYS. We know, that they spring from 



maggots, and that both the common and blue 



bottle fly deposit their ova in putrid animal 



matter, where the eggs are hatched and pro- 



R 



