ON GENERATION. 357 



(aiiima) to the egg, and that combined from the souls of the 

 parents, these being occasionally of different species, the horse 

 and the ass, the common fowl and the pheasant, for example, 

 this vital principle not being a mixture but only an union ; and 

 allow the pullet to be produced in the manner of the seeds of 

 plants, by the same efficient principle by which the perfect 

 animal is afterwards preserved through the rest of its life, so 

 that it would be absurd to say that the ftetus grew by one 

 vital principle without the uterus or ovum, and by another 

 within the uterus or ovum did we grant all this, I say 

 (although it is invalid and undeserving faith), our history of 

 generation from the egg, nevertheless, upsets the foundations 

 of the doctrine, and shows it to be entirely false ; namely, that 

 the egg is produced from the semen of the cock and hen, or 

 that any seminal fluid from either one or other is carried to 

 the uterus, or that the embryo or any particle of it is fashioned 

 from any seminal fluid transported to the uterus, or that the 

 semen galli, as efficient cause and plastic agent, is anywhere 

 stored up or reserved within the body of the hen to serve when 

 attracted into the uterus, as the matter and nourishment 

 whence the foetus which it has produced should continue to 

 grow. The conditions are wanting which he himself admits, 

 after Aristotle, to be necessary, viz., that the embryo be consti- 

 tuted by that which is actual and preexists, and the chick by 

 that which is present and exists in the place where the chick 

 is first formed- and increases ; further, that it be produced by 

 that which is accomplished immediately and conjunctly, and is 

 the same by which the chick is preserved and grows through 

 the whole of its life. For the semen galli (and whether it is 

 viewed as animate or inanimate is of no moment) is nowise 

 present and conjunct either in the egg or in the uterus; neither 

 in the matter from which the chick is fashioned, nor yet in the 

 chick itself already begun, and as contributing either to its 

 formation or perfection. 



He dreams, too, when he seeks illustrations of his opinions 

 on an animated semen from such instances as the seeds of 

 plants and acorns; because he does not perceive the differ- 

 ence alleged by Aristotle 1 between the " geniture" admitted in 



1 De Gener. Anim. lib. il, cap. 1. 



