ARISTOTLE'S BIOLOGY 



These famous passages may be taken as 

 indicating Aristotle's view of the graded order- 

 ing of life, with reference to the phenomena 

 exhibited by living beings after they are 

 formed. The processes of their generation 

 were likewise graded in accordance with the 

 nature of the animal. This graded change in 

 the manner of generation, more than any other 

 fact, seems to have determined Aristotle's 

 classification of animals. 



Doubtless a similarity in obvious organic 

 structure led men to recognize the larger 

 natural divisions, like birds and fishes. Such 

 generic likenesses, with due account taken of 

 evident as well as more subtle differences, 

 might be followed in forming conceptions of 

 subordinate groups. But to the mind searching 

 for criterions of identity or distinction, nothing 

 is more taking than the ways in which animals 

 reproduce their kind. So felt this profound 

 student of life. Perhaps no other man has ever 

 discovered so many interesting facts touching 

 the production of the young within and without 

 the womb. Of course he stood but at the 

 threshold of embryology. He had no micro- 

 scope. The myriad facts which the studies of 

 the last two centuries have elicited were un- 



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