226 ON GENERATION. 



with the reciprocal interchange of generation and decay; and as 

 the sun, now in the east and then in the west, completes the 

 measure of time by his ceaseless revolutions, so are the fleeting 

 things of mortal existence made eternal through incessant 

 change, and kinds and species are perpetuated though indivi- 

 duals die. 



The writers who have treated of this subject have almost all 

 taken different paths; but having their minds preoccupied, they 

 have hitherto gone to work to frame conclusions in consonance 

 with the particular views they had adopted. 



Aristotle, 1 among the ancients, and Hieron. Fabricius of 

 Aquapendente, among the moderns, have written with so much 

 accuracy on the generation and formation of the chick from 

 the egg that little seems left for others to do. Ulyssus Aldro- 

 vandus, 2 nevertheless, described the formation of the chick in 

 ovo; but he appears rather to have gone by the guidance of Aris- 

 totle than to have relied on his own experience. For Volcherus 

 Goiter, living at this time in Bologna, and encouraged, as he 

 tells us, by Aldrovandus, his master, opened incubated eggs 

 every day, and illustrated many points besides those noted by 

 Aldrovandus ; 3 these discoveries, however, could scarcely have 

 remained unknown to Aldrovandus. TEmilius Parisanus, a 

 Venetian physician, having discarded the opinions of others, 

 has also given a new account of the formation of the chick 

 from the egg. 



But since our observations lead us to conclude that many 

 things of great consequence are very different from what they 

 have hitherto been held to be, I shall myself give an account 

 of what goes on in the egg from day to day, and what parts are 

 there transmuted, directing my attention to the first days espe- 

 cially, when all is most obscure and confused, and difficult of 

 observation, and in reference to which writers have more par- 

 ticularly drawn the sword against one another in defence of 

 their several discordant observations, which, in sooth, they 

 accommodate rather to their preconceived opinions respecting 

 the material and efficient cause of animal generation than to 

 simple truth. 



What Aristotle says on the subject of the reproduction of 



1 Hist. Anim. lib. vi, cap. 2, 3. * Ornithol. lib. xiv. 



3 Nobil. Exercit. lib. vi. 



