ON GENERATION. 445 



action, which is the generation of the chick, the chief cause of 

 this is the semen and the chalazse, these two being the prime 

 cause of the generation of the chick, the semen being the effi- 

 cient cause, the chalaza the matter only." Now according to 

 the opinion of Aristotle, it must be allowed that that which 

 generates is included in the egg ; but Fabricius denies that the 

 semen of the cock is contained in the egg. 



Nor does he wander less wide of the mark when he speaks 

 of the chalazae as the matter from which, by the influence of 

 the semen galli, the chick is incorporated. For the chick is 

 not produced either from one or the other, nor yet from both 

 of the chalazse, as we have shown in our history. Neither is 

 the generation of the chick effected by metamorphosis, nor by 

 any new form assumed and division effected in the chalazse, 

 but by epigenesis, in the manner already explained. Nor are 

 the chalazse especially fecundated by the semen of the male 

 bird, but the cicatricula rather, or the part which we have 

 called the eye of the egg, from which, when it enlarges, the 

 colliquament is produced, in and from which, subsequently, 

 the blood, the veins, and the pulsating vesicles proceed, after 

 which the whole body is gradually formed. Moreover, on his 

 own admission, the semen of the cock never enters the uterus 

 of the hen, and yet it fecundates not only the eggs that are 

 already formed, but others that are yet to be produced. 



Fabricius refers the albumen and vitellus to the second ac- 

 tion of the egg, which is the nutrition and growth of the 

 chick. " The vitellus and albumen," he says, l " are in quan- 

 tity commensurate with the perfect performance of this action, 

 and with the due development and growth of the chick. The 

 shell and membranes are therefore the safety of the whole of 

 the egg as well as the security of its action. But the veins 

 and arteries which carry nourishment are organs without which 

 the action of the egg, in other words, the growth and nutrition 

 of the chick, would not take place." It is uncertain, how- 

 ever, whether the umbilical vessels of the embryo or the veins 

 and arteries of the mother, whence the egg is increased, are 

 here to be understood. For a like reason the uterus and in- 

 cubation ought to be referred to this last class of actions, 



1 Op. cit. p. 48. 



