272 ON GENERATION. 



in the same way as the seeds of plants are justly entitled their 

 eggs, not only as being the matter or that from which, but the 

 efficient or that by which the pullet is engendered. In which 

 finally no part of the future offspring exists de facto, but in 

 which all parts inhere in potentia. 



The seed, properly so called, differs however from the geni- 

 ture, which by Aristotle is defined to be ' ' that which, proceeding 

 from the generator, is the cause, that which first obtains the 

 principle of generation; in those, to wit, whom nature destined 

 to copulate. But the seed is that which proceeds from these 

 two in their connection : and such is the seed of all vegetables, 

 and of some animals, in which the sexes are not distinct; like 

 that which is first produced by male and female commingled, 

 a kind of promiscuous conception, or animal; for this already 

 possesses what is required of both." 



The egg consequently is a natural body endowed with animal 

 virtues, viz. principles of motion and rest, of transmutation and 

 conservation ; it is, moreover, a body which, under favorable 

 circumstances, has the capacity to pass into an animal form ; 

 heavy bodies indeed do not sink more naturally, nor light ones 

 float, when they are unimpeded, than do seeds and eggs in virtue 

 of their inherent capacity become changed into vegetables and 

 animals. So that the seed and the egg are alike the fruit and 

 final result of the things of which they are the beginning and 

 efficient cause. 



For a single pullet there is a single egg; and so Aristotle 1 

 says : " from one seed one body is engendered ; for example, 

 from a single grain of wheat one plant ; from a single egg one 

 animal; for a twin-egg is, in fact, two eggs." 



And Fabricius 2 with truth observes : " The egg is not only 

 an exposed uterus, and place of generation, but that also on 

 which the whole reproduction of the pullet depends, and which 

 the egg achieves as agent, as matter, as instrument, as seat, and 

 all else, if more there be, that is needful to generation." He 

 shows it to be an organ because it consists of several parts, and 

 this, from the statement of Galen, who will have the very es- 

 sence of an organ to be that " it consist of several parts, all of 



1 Gen. Anim. lib. i, cap. 20. 2 Loc. cit. p. 47. 



