206 SALMONIA. 



I EIGHTH DAY. 



of the habits of snails and earthworms, and of the 

 sexual relations of these apparently contemptible 

 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 physiologist, 

 but likewise for the chemist. On these points, I 

 must request you to refer to writers on Natural 

 History : yet I shall perform 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 ? 



PffYS. 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 produce maggots; that after feeding 

 upon the decomposing animal material, they gradually 

 change, gain a hard or horny coat, seem as if entombed, 

 and wait in a kind of apparent death or slumber, till 

 they are mature for a new birth, when they burst 

 their coatings and appear in the character of novel 

 beings fitted to inhabit another element. 



o 



HAL. The history of the birth and metamorphosis 

 of all other winged insects is very similar, but with 

 peculiarities dependent upon their organs, wants, and 



