20:2 



GENERATION. 



These two parts [the yolk and white] are enclosed in a pretty large 

 opake membrane, which is lamellated, for it can be divided and subdi- 

 vided into a number of layers ; but it would seem to be divided into 

 two, the innermost the thinner. At the great end this membrane is 

 separated into two laminae ; the outer, or that next to the shell, con- 

 tinues to Hue the shell ; but the inner passes across, leaving a space 

 between the two of about three-eighths of an inch in diameter, and is 

 concave on that side next to the slime ; though not so much as the 

 outer one on the side next the shell. This space is filled with air. 

 Over the whole is the shell, composed of calcareous earth, about half a 

 line in thickness, the outer surface of which has a vast number of 

 indentations on it, as it were, looking porous. It appears to have no 

 regular construction ; it does not look like crystallization, as in the 

 enamel of the teeth. The colour of the shell in the common fowl is 

 generally white, but in some it is brown, as in the Chittagong fowl. 

 This shell gives the whole a firmness which defends its contents. It 

 certainly admits air to pass both it and the membrane. 



The egg, which is the produce of the female, or of the female parts 

 in the hermaphrodite, is to be considered in two lights. In one it is to 

 be considered as the uterus, and in the other as the breast. The slime 

 is the uterine part, intended for the support of the chick while in its 

 uterus or egg ; and the yolk supports it for some days after being 

 hatched, in place of milk, although for a much shorter time ; so that 

 the oviparous animal collects the whole necessary nourishment, and 

 throws it out at once ; while the viviparous retains the rudiments of 

 the young, and furnishes it nourishment as it is wanted. 



We have reason to suppose that the slime comes nearest to the 

 nature of blood of any animal substance we know ; and we know it is 

 alive, therefore not necessary to undergo any change to have this effect 

 produced ; for it is only the absorption of living parts, therefore is 

 capable of composing the animal without having undergone the act of 

 digestion ; and in this alone it undergoes but little alteration, as it 

 composes the whole parts without much loss ; for an egg, through the 

 whole process of incubation, only loses .... grains 1 , and as that would 

 produce a vacuum somewhere in the egg, — more especially as the parts 

 formed are more solid than the parts which composed them, — therefore 

 it is reasonable to suppose they would occupy a smaller space. But it 

 would appear that the cavity at the thick end of the egg, between the 



1 [According to Dr. Prout, the loss of weight in the egg of the common fowl 

 during incubation, exceeds by about eight times that which the egg sustains by ordi- 

 nary keeping : tlus latter loss is at*tbe rate of about nine grains daily for a certain 

 period.— Phil. Trans. 1822, p. 377.] 



