ON GENERATION. 277 



of the father, or a mixture of the two ? And here the greatest 

 difficulties are occasioned by those eggs that are produced by 

 the concurrence of animals of different species, as, for example, 

 of the common fowl and pheasant. In such an egg, I ask, is 

 it the vital principle of the father or that of the mother, which 

 inheres ? or is it a mixture of the two ? But how can vital 

 principles be mingled, if the vital principle (as form) be act 

 and substance, which it is, according to Aristotle ? For no one 

 will deny, whatever it be ultimately which in the fruitful egg 

 is the beginning and cause of the effects we witness, that it is 

 a substance susceptible of divers powers, forces, or faculties, and 

 even conditions, virtues, vices, health and sickness. For 

 some eggs are esteemed to be longer, others shorter lived ; some 

 engender chickens endowed with the qualities and health of 

 body that distinguished their parents, others produce young that 

 are predisposed to disease. Nor is it to be said that this is 

 from any fault of the mother, seeing that the diseases of the 

 father or male parent are transferred to the progeny, although 

 he contributes nothing to the matter of the egg; the procreative 

 or plastic force which renders the egg fruitful alone proceeding 

 from the male; none of its parts being contributed by him. 

 For the semen which is emitted by the male during inter- 

 course does by no means enter the uterus of the female, in 

 which the egg is perfected ; nor can it, indeed, (as I first an- 

 nounced, and Fabricius agrees with me,) by any manner or way 

 get into the inner recesses of that organ, much less ascend as 

 high as the ovary, near the waist or middle of the body, so that 

 besides its peculiar virtue it might impart a portion of matter 

 to the numerous ova whose rudiments are there contained. For 

 we know, and are assured by unquestionable experience, that 

 several ova are fecundated by one and the same connexion, 

 not those only that are met with in the uterus and ovary, but 

 those likewise that are in some sort not yet begun, as we shall 

 state by and by, and indeed, as we have already had occasion 

 to assert in our history. 



If, therefore, an egg be rendered fruitful by its proper vital 

 principle, or be endowed with its own inherent fecundating force, 

 whence or whereby either a common fowl, or a hybrid betwixt 

 the fowl and the pheasant is produced, and that either male or 

 female, like the father or the mother, healthy or diseased ; we 



