ON GENERATION. 225 



a certain time, they continue barren. This is also the case with 

 eggs, some of which, though they may have been conceived 

 in consequence of intercourse, still remain unprolific unless per- 

 fected by repeated and con tinned connections. Whence it happens 

 that some eggs are more speedily changed by incubation than 

 others, exhibiting traces of the foetus from the third day; others 

 again, either become spoiled, or suffer transformation into the 

 foetus more slowly, exhibiting no indications of the future chick 

 even up to the seventh day, as shall be made to appear by and 

 by, in speaking of the generation of the chick from the egg. 



Thus far have we discoursed of the uterus of the fowl, and 

 its function ; of the production of the hen's egg, and of its dif- 

 ferences and peculiarities, from immediate observation; and 

 from the instances quoted, conclusions may be drawn with 

 reference to other oviparous animals. 



We have now to pursue the history of the generation and 

 formation of the foetus from the egg. For indeed, as I have 

 said above, the entire contemplation of the family of birds is 

 comprehended in these two propositions : how is an egg engen- 

 dered of a male and female ; and by what process do males and 

 females proceed from eggs ? the circle by which, under favour 

 of nature, their kinds are continued to eternity. 



EXERCISE THE FOUBTEENTH. 



Of the production of the chick from the egg of the hen. 



Of the growth and generation of the hen's egg enough has 

 already been said; and we have now to lay before the reader our 

 observations on the procreation of the chick from the egg, a 

 duty which is equally difficult, and profitable, and pleasant. 

 For in general the first processes of nature lie hid, as it were, 

 in the depths of night, and by reason of their subtlety escape 

 the keenest reason no less than the most piercing eye. 



Nor in truth is it a much less arduous business to investigate 

 the intimate mysteries and obscure beginnings of generation 

 than to seek to discover the frame of the world at large, and 

 the manner of its creation. The eternity of things is connected 



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