GENERATION OF ANIMALS, II. v. 



alike in all animals and plants. Why then does this 

 Soul fail to bring the parts to their completion and so 

 produce an animal r Because the parts of an animal 

 are bound to possess sentient Soul, since they are not 

 on a par with those of a plant ; and that is why the 

 male is required to take its share in the business (the 

 male being separate from the female in such animals). 

 The facts bear this out : wind-eggs become fertile 

 if the male treads the female within a certain period. 

 However, the cause of these things >vill be fully deter- 

 mined later on.** 



If there is any class of animal which is female and 

 has no separate male, it is possible that this generates 

 offspring from itself. This has not so far been 

 reUably obsened, it is true, but some instances in the 

 class of fishes give cause to suspect that it may be 

 the case. Thus, of the fish known as erythrinus * 

 not a single male specimen has so far been ob- 

 served, whereas female ones have been, full of 

 fetations.*^ But although with regard to these we 

 have no rehable proof so far, there are also in the 

 class of fishes some which are neither male nor fe- 

 male : e.g., eels,** and one sort of cestreus * which 

 frequents marshland rivers. In all animals, how- 

 ever, where the male and female are separate, 

 the female is unable by itself to generate offspring 



indicate that they are descended from an original deej>- 

 water fish. See additional note, p. 565, 



' This cannot be the grrey midlet {Mugil capita, Cuv.), but 

 is probably a species of Muraena or Gymnotus. In P.A. 

 ti9ti a 5, Aristotle speaks of a cestreus found in the lake at 

 Siphae in Boeotia, on the south coast, near Thespiae (now 

 Tipha). Cf. also the reference at 763 b 1 to Pyrrha, where 

 there was a lagoon which was apparently one of Aristotle's 

 favourite spots for studying animals. 



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