In systematic zoology and comparative anatomy, the attempts 

 to establish theoretical ideas depended not on arbitrary 

 a priori assumptions, but on critical comparisons of strictly 

 tested facts, performed by Lamarck and Geoff roy Saint-Hilaire 

 from the beginning of the nineteenth century. In embryology, 

 Baer solved this problem by achieving unsurpassed results. 

 It is not accidental, therefore, that as a subtitle to UBER 

 ENTWICKLUNGSGESCHICHTE he put the words "Observations 

 and Reflections." In his book, Baer applied the richest 

 empirical material, obtained by thorough observations, to 

 his theoretical discussions, and thus suggested how inves- 

 tigators could delve into other aspects of biology. 



In order to be convinced without doubt as to the 

 correctness of the judgments of Baer and his work, it is 

 necessary to have sufficient detail of his scientific heritage, 

 The following chapters, 17 through 23, contain the actual 

 contents of Baer's embryological and teratological works, 

 and his most important theoretical general conclusions. The 

 last chapter, 24, devoted to Baer considers his ideology. 



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