90 EXAMINATION OF 



they arrive at the ftate of a chryfalis, which is a 

 perfed egg. Another difference may ftill be re- 

 marked in oviparous animals: The eggs of hens, 

 and other birds, are of all different fizes; but 

 thofe of fifties, frogs, Sec. which lay them before 

 they are perfed:, are all of the fame fize. He 

 indeed obferves, that, in pigeons, which lay two 

 eggs, all the fmall eggs that remain in the ova- 

 rium are of the fame bulk ; and that the two on- 

 ly which are next to be excluded exceed the fize 

 of the reft. The fame thing happens in cartila- 

 ginous fifties, as in the ray, which only brings to 

 maturity two eggs at a time, all the reft being of 

 different fizes, like thofe of the hen. 



He next defcribes anatomically the parts ne- 

 ceflary to generation ; and remarks, that the li- 

 tuation of the anus and vulva in birds differ from 

 thofe of all other animals, the anus being placed 

 before, and the vulva behind *. And, with 

 regard to the cock and all fmall birds, he al- 

 ledges, that they have no proper penis, and that 

 they generate by rubbing, without any intro- 

 miftion. But male-ducks, geefe, and oftriches, 

 are amply provided with this inftrument. 



Hens prod-'.ce eggs without the intervention 

 of the cock; but, though perfed:, they are 

 fewer in number, and unfertile. He credits 

 not the common opinion, that a few days inter- 

 courfe with the cock are fufficient to impregnate 

 all the eggs which a hen will lay during the year; 



but 



* Moft of thefe fa<fls are taken from Ariftotle. 



