456 THE BIOCOSMOS HISTORICAL. 



His scientific activity embraced the whole 

 field of Biology, though his work on Plants 

 has been lost. A good deal of his Zoology 

 survives, though in a fragmentary way. He 

 paid much attention to embryology which is 

 usually deemed a very modern science; day 

 by day he observed the evolving chick in the 

 hen's egg, and had his eye generally on the 

 development of animal-life. Thus he pre- 

 enacted an important phase of the modern 

 movement toward Evolution, for the embry- 

 ological researches of Von Baer (first part 

 published in 1828) are decidedly evolutionary 

 before Darwin. But Aristotle had already 

 opened the same field. 



He also paid especial attention to the struc- 

 ture and functions of animals, and he sought 

 to classify them in larger and smaller divis- 

 ions according to their kinship. An extensive 

 and close observation of animals he shows, 

 and some of his statements of fact have been 

 verified quite recently by science. Thus on 

 many sides he radiates germinal thoughts 

 which require ages to unfold and ripen. 



It is evident that he sees the pivotal fact 

 of organic Life to be Generation, a conception 

 which the botany and the zoology of today are 

 beginning to develop fully. Says he: "First 

 study the facts or appearances of animals; 

 then reach down to their causes; but finally 



