GENERATION OF ANIMALS, II. vii. 



lation of the rhine and the haios." Also, the origin 

 of the proverb about Libya, to the effect that 

 " Libya is always bringing forth something new," * 

 In said to be that there animals of different species 

 unite, since owing to the fact that as there is very 

 little water they all meet together at the few places 

 where springs are to be found, and so animals of 

 different species unite. 



It is kno\\Ti that with one exception all the animals 

 which are produced as a result of such unions copulate 

 with each other and unite in their turn and are able 

 to produce young of both sexes. Mules are the one 

 exception. They are sterile and do nqt generate 

 either by union with each other or with other animals. 

 It is, of course, a general problem why any particular 

 male or female is sterile : there are men and women 

 who are sterile, and there are instances in the several 

 kinds of animals, e.g., horses and sheep. But with the 

 mules we have a whole race which is sterile. Lea\ing 

 this exception for the moment : elsewhere the causes 

 of steriUty are numerous, (a) Men and women alike 

 are sterile from birth if they are deformed in the 

 regions employed for copulation ; as a result, the 

 men do not grow a beard but remain as eunuchs, 

 while the women do not reach pubertv' ; (6) others 

 become sterile as they advance in age, sometimes 

 (i) because they have put on too much flesh : in men 



Piatt thinks the rhinobates is the angel-fish ; Thompson 

 offers the opinion that it is " probably the modern genus 

 Khinohatus " ; Piatt says " it certainly did not belong to the 

 modern genns of that name." 



* For this proverb and its explanation, <•/. the similar 

 passage H.A. 606 b 19 if. Piatt suggests that a mutilated 

 passage in Hippocrates, tt. aepojv vSarcov tottcov 12 Jin., con- 

 tained a statement on this subject. 



245 



