346 ON GENERATION. 



miracles; and the parts are commenced, not by change of 

 place, but by alteration in softness, hardness, temperature, and 

 the other differences observed in similar parts, these being now 

 actually made, which had before existed only potentially." 



This is, in nearly so many words, the opinion of Aristotle, 

 which supposes that the foetus is formed from the seed by mo- 

 tion, although it is not at present in communication with the 

 foetus, but simply has been so at a former time : his reasonings 

 are, indeed, ingenious, and carefully put together, and from 

 what we see in the order of the generation of parts, not im- 

 probable. For the heart, with the channel of the veins, is 

 first noticed as an animate principle, in which motion and 

 sense reside ; or, as it were, an emancipated son, and a genital 

 part, whence the order of the members is delineated, whence 

 all things pertaining to the completion of the animal are dis- 

 posed, and which has all the attributes bestowed upon it by 

 Aristotle. 



But it seems impossible, that the heart should be formed in 

 the egg by the seed of the male, when that seed neither exists 

 in the egg, nor touches it, nor ever has touched it ; because the 

 seed does not enter the uterus where the egg is, (as is allowed by 

 Fabricius,) nor is in any way attracted by it ; nay, even the 

 maternal blood is not in the egg, nor any other prepared mat- 

 ter, out of which the seed of the male may form this genital 

 part, the author of all the others. For it is not immediately 

 after coition, while the seed still remains within the body, and is 

 in communication, that any part of the chick exists in the egg, 

 but after many days, when incubation has taken place. More- 

 over, in fishes, when the geniture of the male does nothing 

 but touch the eggs externally, and does not enter into them, 

 it is not likely that it performs any more ample functions 

 when the agency is external, than does the seed of the cock in 

 the already formed eggs of the hen. Besides, since immedi- 

 ately after coition no trace of the egg as yet exists, but it is 

 afterwards generated by the hen herself (I am speaking of the 

 prolific egg) ; when now the seed of the cock is departed and 

 vanished, there is no probability that the foetus is formed in 

 that egg by the aforesaid seed, through means of one or any 

 number of successive motions. 



Nor indeed does the difference between prolific and unpro- 



