GENERATION OF ANIMALS, IV. iv. 



perceived from what has just been said ; a discus- 

 sion of these matters is also to be found in the 

 Problems." 



This, then, may be taken as the way in which we 

 deal with this subject. 



With regard to the redundance of parts which (c) Reason 

 occurs contrary to Nature, the cause of this is the *^****- 

 same as that of the production of twins, since the 

 cause occurs right back in the fetations, whenever 

 more material gets " set " than the nature of the part 

 requires : the result then is that the embrvo has 

 some part larger than the others, e.g., a finger or a 

 hand or a foot, or some other extremity or Hmb ; 

 or, if the fetation has been split up, several come 

 to be formed — ^just as eddies are formed in rivers ; 

 here too, if the fluid which is being carried along and 

 is in movement meets with any resistance, two self- 

 contained eddies are formed out of the original one, 

 both of which have the same movement.^ What 

 happei^s in the case of the fetations is on the same 

 lines. The normal part and the redundant one are 

 usually attached quite close to one another, although 

 sometimes they are farther away because of the 

 movement which arises in the fetation, and above 

 all because (a) the excess of material recurs again 

 at the place from which it was originally drawn off, 

 and (6) the form which it has is derived from the 

 part where it developed as a redundancy.*^ 



Some creatures develop in such a way that they 

 have two generative organs [one male, the other 

 female]. Always, when this redundancy happens, 

 one of the two is operative and the other inoperative, 



it goes back to where it came from, viz., X ; thus a Y is 

 formed at X. 



441 



