STATES OF INSECTS. 87 



acid. 1 he eggs of birds are lined by a fine membrane ; 

 but I have examined several of those of insects, and 

 have been able to discover nothing of the kind in them. 

 I will not, however, affirm that it does not exist, though 

 the shell of the insect egg appears more analogous to the 

 membrane that lines that of the bird than to the outside 

 shell itself. 



Within this integument is included a fluid, on the 

 precise nature of which, except that it is an aqueous 

 whitish fluid, few or no observations have been made, or 

 indeed are practicable ; but it is reasonable to suppose 

 that like the white and yolk of the bird's egg, it serves 

 for the development of the organs of the germe of the 

 future insect. 



But few observations are recorded that relate to the 

 embryo included in the egg. It is stated, that it is in- 

 vested with an extremely fine and delicate pellicle — sup- 

 posed by some analogous to the Chorion and Amnios of 

 the human foetus, though others think the shell of the 

 egg to correspond with the Chorion, and the successive 

 integuments of the larva with the Amnios*. When the 

 egg is first laid, nothing indeed is to be seen in it but the 

 fluid just mentioned ; the first change in this fluid is the 

 appearance of the head of the embryo, more particularly 

 in Coleoptera, of two points, the rudiments of the mandi- 

 bles, and of those apertures into the tracheae which I 

 have called spiracles b ; the little animal we may suppose 



* Compare N. Diet. d'Hist. Nat. xvi. 246. with xx. 352— j but as 

 the Amnios immediately envelops the foetus, the pellicle seems most 

 analogous to it, and the shell to the Chorion. 



b Swamm. Bibl. Nat. ed. Hill, h 133. a. Comp. N. Diet. d'Hist. 

 Nat. xvi. 246. 



