GENERATION OF ANIMALS, i: xii. 



cannot provide, being easily injured and cold. The 

 testicles, however, are inside in some animals but 

 outside in others : since, however, they also need 

 shelter and covering to keep them safe and to secure 

 concoction for the semen (for if they have been 

 exposed to cold and rendered stiff they cannot be 

 drawn up and emit the semen), those animals 

 whose testes are in the open have a covering of skin 

 over them known as the scrotum ; while those animals 

 the nature of whose skin is so hard that it is not 

 amenable to this arrangement, and cannot be used 

 for a WTapping and is not soft or Uke ordinary skin 

 (e.g., animals whose skin is like that of fish, and those 

 whose skin is made of horny scales) — they must of 

 necessity have their testes inside. On this account 

 the dolphins and those cetacea which possess testes 

 have them inside ; so do those horny-scaled animals 

 which are o\-iparous and four-footed. Birds, too, have 

 hard skin, which will not accommodate itself to the 

 size of the testes and make a wrapping for them, and 

 this makes another reason why in all these cases the 

 testes are inside in addition to the reasons (previously 

 mentioned") due to the necessary exigencies of 

 copulation. And for this selfsame reason the testes 

 are also inside in the elephant and in the hedgehog ; 

 the skin of these two animals, as of the others, is not 

 well adapted for having the protective part separate. 

 ''[Contrary positions of the uterus are found in those 

 animals which are internally vi\iparous and in those 

 which are externally oviparous ; and again in some 

 of the latter class it is placed low down, in others by 

 the diaphragm, as for instance in fishes on the one 



* The following paragraph is simply a hash-up of parts of 

 the preceding chapters. 



37 



