216 GENERATION 



It may also be observed, that at no period coidd I observe a mem- 

 brana pupillaris. 



The little horny knob * at the end of the beak with which it breaks 

 the shell when arrived at the full time and makes its escape, is also 

 gradually forming into a more regular and determined point, the pro- 

 gress of which is seen from the first figure to the sixth. 



When very young we may observe two oviducts, one on each side ; 

 they would appear to be behind the kidneys at their first formation, 

 but become more and more forwards as the chick grows, and before 

 hatching the right seems to decay, 



There are two kinds of down on the chick, one long, which comes 

 first, about two or three days before hatching ; a second, or fine down, 

 forms at the roots of the other. It is probably the long down that 

 comes off with the feather. 



The chick some time before birth has a kind of mixed action of life, 

 for it breathes, and we can hear it pip and chirp in the egg ; and we 

 find that the adidt circulation through and out of the heart is formed 

 before birth: yet it is receiving its nourishment from the remaining 

 slime. 



Vivification of the Embryo. 



For this purpose a heat is always necessary equal to the heat of the 

 parent animal. In the human female and in the hen, the heat of the 

 body [is higher than that of the surroimding atmosphere, and therefore 

 in the one, vivification goes on in the uterus, in the other, under the 

 belly of the parent. But in] the turtle, fish, &c, where the heat of 

 the animal [is the same as the atmosphere, the ova are left to incubate 

 at a distance from the parent]. 



Where the natural heat of the animal is the same with, or very 

 nearly that of the atmosphere, the parent is not solicitous about its ova, 

 as, for example, in fishes, in the turtle [Chelone], [in many] insects,°&c. 



Generation of the EeP. 



The natural history of the mode of propagation in the common eel 

 [Anguilla latirostris, Yarrell] has, I believe, never yet been described; 

 and this has probably in some degree arisen from a dissimilarity 

 between their [generative] parts and [those of] fish in common, so as 

 not to enable one to reason from analogy ; and, as the mode of propa- 

 gation in animals can only be known when that operation is going on 



1 [Physiological Catalogue, vol. v. plate 76, figs. 17, 18 b. Hunt. Preps. Nos. 3457, 

 3159.] 



- [Hunt. Preps. Nos. 2660 {Conger vulgaris), 3202 {Anguilla latirostris).'] 



