334 ON GENERATION. 



One of these ways, viz., when the object is made out of 

 something pre-existing, is exemplified by the formation of a 

 bed out of wood, or a statue from stone ; in which case, the 

 whole material of the future piece of work has already been in 

 existence, before it is finished into form, or any part of the 

 work is yet begun; the second method is, when the material is 

 both made and brought into form at the same time. Just 

 then as the works of art are accomplished in two manners, 

 one, in which the workman cuts the material already prepared, 

 divides it, and rejects what is superfluous, till he leaves it in the 

 desired shape (as is the custom of the statuary) ; the other, as 

 when the potter educes a form out of clay by the addition 

 of parts, or increasing its mass, and giving it a figure, 

 at the same time that he provides the material, which he 

 prepares, adapts, and applies to his work ; (and in this point 

 of view, the form may be said rather to have been made than 

 educed;} so exactly is it with regard to the generation of 

 animals. 



Some, out of a material previously concocted, and that has 

 already attained its bulk, receive their forms and transfigura- 

 tions ; and all their parts are fashioned simultaneously, each 

 with its distinctive characteristic, by the process called meta- 

 morphosis, and in this way a perfect animal is at once born ; on 

 the other hand, there are some in which one part is made before 

 another, and then from the same material, afterwards receive 

 at once nutrition, bulk, and form : that is to say, they have 

 some parts made before, some after others, and these are at the 

 same time increased in size and altered in form. The struc- 

 ture of these animals commences from some one part as its 

 nucleus and origin, by the instrumentality of which the rest 

 of the limbs are joined on, and this we say takes place by the 

 method of epigenesis, namely, by degrees, part after part ; and 

 this is, in preference to the other mode, generation properly 

 so called. 



In the former of the ways mentioned, the generation of 

 insects is effected where by metamorphosis a worm is born 

 from an egg ; or out of a putrescent material, the drying of 

 a moist substance or the moistening of a dry one, rudiments 

 are created, from which, as from a caterpillar grown to its full 

 size, or from an aurelia, springs a butterfly or fly already of a 



