100 



Chapter V. 



Hatcliing of Insect Eggs 



The contents of an egg principally consist of nutri- 

 ment adapted to the different parts of the germ 

 which it contains — the yolk for nourishing; the soft 

 parts; tiie white, for the blood and other fluids; and 

 the shell, for the bones. In the case of insects, as 

 well as of birds, fishes, and reptiles, the embryo is 

 placed in the most advantageous j-osition for par- 

 taking of the repast, — namely, in a particular corner 

 where it may breathe fresh air always communicated 

 to the chamber of the egg by ventilatory passages in 

 the shell ; if these be shut up, by covering the egg 

 with grease, varnish, or chalk, it is suffocated and 

 dies. In the case of birds, according to Malpighi 

 and the older physiologists*, the rudiment of the 

 chick, while still a minute point, is lodged on the 

 film that envelopes the yolk, near the centre of the 

 egg ; and, — as the floating wick of a mariner's lamp 

 is constantly preserved upon a level u ith the surface 

 by the mobility of the slings and the weight of the 

 oil-vessel tending downwards, however the ship move, 

 — there is an ingenious natural mechanism, which 

 prevents the embryo chick from being upset when 

 the egg is stirred. The yolk is sustained by two 

 membranous ribbons, visible at the aperture of the 

 egg, and fastening it on each side to the common 

 membrane glued to the shell. These suspensory 

 bands being fixed above the centre of the yolk, of 



* M;ilpi<;lii, (ie(Uo iiicuUato; Lceuweiihoeck, Epist. phys. xl. ; 

 a«)d Hiuvey, in Willughhy's Ornilliol. c. ill. 



