264 ON GENERATION. 



Breaking the shell, and regarding the position of the chick, I 

 found both the remains of the albumen and the two portions 

 of the vitellus (which we have said are divided by the colli- 

 quation induced by the gentle heat), possessing the consis- 

 tency, colour, taste, and other qualities which distinguish the 

 yelks of unincubated eggs similarly boiled. I have, therefore, 

 frequently asked myself how it came to pass that unprolific eggs 

 set under a hen are made to putrefy and become offensive by 

 the same extraneous heat which produces no such effect upon 

 prolific eggs, both of the fluids of which remain sweet and un- 

 changed, although they have an embryo in the midst of them, 

 (and this even containing some small quantity of excrementitious 

 matter within it,) so that did any one eat the yelk of such an 

 egg in the dark, he would not distinguish it from that of a fresh 

 egg which had never been sat upon. 



EXERCISE THE TWENTY-THIRD. 



Of the exclusion of the chick, or the birth from the egg. 



The egg is, as we have said, a kind of exposed uterus, and 

 place in which the embryo is fashioned : for it performs the 

 office of the uterus and enfolds the chick until the due time of its 

 exclusion arrives, when the creature is born perfect. Oviparous 

 animals consequently are not distinguished from viviparous by 

 the circumstance of the one bringing forth their young alive, 

 and the other not doing so ; for the chick not only lives and 

 moves within the egg, but even breathes and chirps whilst there ; 

 and, when it escapes from the shell, enjoys a more perfect ex- 

 istence than the foetus of animals in general. Oviparous and 

 viviparous animals rather differ in their modes of bringing 

 forth ; the uterus or place in which the embryo is formed being 

 within the animal in viviparous tribes, where it is cherished 

 and brought to maturity, whilst in oviparous tribes the uterus, 

 or egg, is exposed or without the animal, which, nevertheless, 

 by sitting on it does not cherish it less truly than if it were still 

 contained within the body. 



