GENERATION OF ANIMALS, I. xxii.-xxiii. 



semen, and in the case of those which do, this semen 

 is not a part of the fetation as it develops. In the 

 same way, nothing passes from the carpenter into the 

 pieces of timber, which are his material, and there is 

 no part of the art of carpentrj' present in the object 

 which is being fashioned : it is the shape and the form 

 which pass from the carpenter, and they come into 

 being by means of the movement in the material. It 

 is his soul, wherein is the " form," and his knowledge, 

 which cause his hands (or some other part of his body) 

 to move in a particular way (different ways for differ- 

 ent products, and always the same way for any one 

 product) ; his hands move his tools and his tools move 

 the material." In a similar way to this, Nature acting 

 in the male of semen-emitting animals uses the semen 

 as a tool, as something that has movement in actu- 

 ality ; just as when objects are being produced by 

 any art the tools are in movement, because the 

 movement which belongs to the art is, in a way, 

 situated in them. Males, then, that emit semen 

 contribute to generation in the manner described. 

 Those which emit no semen, males into which the 

 female inserts one of its parts, may be compared to 

 a craftsman who has his material brought to him. 

 Males of this sort are so weak that Nature is unable 

 to accomplish anything at all through intermediaries : 

 indeed, their movements are only just strong enough 

 when Nature herself sits watching over the business ; 

 the result is that here Nature resembles a modeller 

 in clay rather than a carpenter ; she does not rely 

 upon contact exerted at second hand when fashioning 

 the object which is being given shape, but uses the 

 parts of her o^\■n very self to handle it. 



In all animals which can' move about, male and XXIII 



Conclusion. 



121 



