GENERATION OF ANIMALS, II. viii. 



and the seed of an animal of its own species." Further, 

 Empedocles applies his argument equally to the male 

 and the female. . But, people say, the male mule 

 does generate at the age of seven years ; it is the 

 female which is totally infertile and that is simply 

 because she fails to bring the nourishing of the 

 fetation to its completion (as instances of fetations 

 in mules have been known to occur). 



Still, perhaps an abstract argument might be con- 

 sidered more con\incing than those which we have 

 already mentioned. I call it an abstract one, because 

 in so far as it is a more general argument it is further 

 removed from those principles which belong to this 

 particular subject. It goes somewhat hke this. In 

 the normal course of nature the offspring which a 

 male and a female of the same species produce is a 

 male or female of that same species — for instance, 

 the offspring of a male dog and a female dog is a 

 male dog or a female dog. Two animals which differ 

 in species produce offspring which differs in species ; 

 for instance, a dog differs in species from a hon, and 

 the offspring of a male dog and a female hon is differ- 

 ent in species ; so is the offspring of a male lion and 

 a female dog. This being so, it follows that as both 

 male and female mules are produced, which of course 

 do not differ in species, and as a mule is the offspring 

 produced by a horse and an ass, both of which are 

 different in species from the mule, it is impossible for 

 any offspring to be produced by mules ; the reason 

 being : (a) no offspring of a different species can be 

 produced by them, because the offspring of two 

 animals male and female of the same species belongs 

 itself to that species, nor (6) can a mule be pro- 

 duced, because that is the offspring of a horse and an 



253 



