GENERATION OF ANIMALS, I. viii.-x. 



would have produced increase of size is in them 

 diverted to form seed, (b) Birds, however, and 

 quadrupedal Ovipara lay eggs that are perfect," and 

 these eggs for safety's sake are bound to have a hard 

 skin (while they are still growing, they have a soft 

 skin), and the shell is formed by heat, which evapor- 

 ates the fluid from the earthy substance ; hence the 

 place where this is to be done must of necessity be 

 hot — a condition which is fulfilled by the region round 

 the diaphragm, as the fact that it concocts the food 

 shows. So, if the eggs must of necessity be within 

 the uterus, the uterus must of necessity be alongside 

 the diaphragm in those animals whose eggs are in a 

 perfected condition when laid, while it must be low 

 down in those whose eggs are imperfect when laid ; 

 it will be advantageous so. Further, it is more 

 natural that the uterus should be low down than 

 high up (unless there is some other business of 

 Nature's which prevents it), since its conclusion is 

 down below too ; and where the conclusion is, 

 there also the function is ; thus the uterus is where 

 the function is. 



Similarly, the Vivipara differ from one another. IX 

 Some of them bring forth their young alive not 

 externally only but also within themselves,*' as for 

 instance, human beings, horses, dogs and all haired 

 animals, also such water-animals as dolphins, whales 

 and such cetacea.'' 



Selachia and \ipers, though they bring forth their X 

 young alive externally, first of all produce eggs 

 internally. And the egg they produce is a perfected 

 one, for thus only is an animal generated from the 



* C'f. H.A. 566 b 2, where Aristotle explains this to mean 

 those creatures which have no gills, but a blowhole. 



31 



