GENERATION OF ANIMALS, I. x.-xi. 



egg : nothing is generated from an imperfect egg. 

 The reason why they do not lay their eggs externally 

 is because thev are by nature cold creatures, not hot, 

 as some persons allege." Anyway, the eggs they XI 

 produce are soft-skinned — because the creatures have 

 so httle heat in them that their natural constitution 

 does not dry oiFthe outermost part of the eggs. Thus 

 the coldness of the creatures is the reason why the 

 eggs they produce are soft-skinned, and the fact that 

 the eggs are soft -skinned is the reason they are not 

 produced externally : if they were, they would come 

 to grief. 



When the animal is formed out of the egg, the 

 process of formation is for the most part the same 

 as for birds : (the eggs) descend, and the young 

 animals are formed close by the pudenda, as occurs 

 also in creatures which are viviparous right from the 

 outset. Another result of this is that in animals such 

 as we are now discussing the uterus differs both from 

 that of the Vivipara and from that of the Ovipara, 

 since they have a share in both these groups ; that 

 is to say, in all the Selachians the uterus is at the same 

 time close by the diaphragm and also extends along 

 do\vnwards. (However, to ascertain the arrange- 

 ment of the uterus of the Selachians and other kinds 

 as well, the Dissections ^ should be inspected and also 

 the Researches '^). Thus the Selachians have their 

 uterus high up because they are oviparous and lay 

 perfected eggs, while they have it low down because 

 they are Niviparous ; thus they have a share in both. 



Animals which are viviparous from the outset '^ all 

 have the uterus low down, since they have no natural 



' H.A. 510 b 5 ff. 

 " See above, 718 b 30. 



SS 



