To him also was directed an extensive preface describing the 

 history of the book and explaining the principles and 

 terminology employed. In his preface, Baer recalled the 

 happy time of his work with Pander in Dollinger's laboratory 

 in Wiirzburg. 



After his arrival in Konigsburg in 1818, Baer received 

 both the texts (Latin and German) of Pander's dissertation 

 and noted there several conditions which appeared doubtful 

 to him. In particular, he questioned Pander's ideas about 

 "primary folds" and about the formation of the amnion. In 

 the summer of 1819, Baer conducted an independent study of 

 chick development, first with the objective of explaining to 

 himself some obscure areas in Pander's work. He attained 

 the desired clarity only after continuing his work during 

 the next summer; already his investigations yielded so much 

 profound material that he went on with embryological research, 

 extending it from birds to other vertebrates, especially 

 amphibia and mammals. One of the most important conclusions, 

 which, in his words, "penetrated like rays of light," was 

 "the idea that gradually in the embryo the vertebrate type 

 structure develops." This idea was based on the theory of 

 four types, established independently by Baer and by Cuvier. 



His study of chick development led Baer to conclude that 

 the course of embryonic development experiences strict 

 regularity, an idea so simple that it causes surprise that 

 no one had detected it previously. "Now one can be sure," 

 Baer wrote, 



when the course of development appears so simple 

 that all is clear by itself and hardly requires 

 confirmation through investigation. But the 

 story of Columbus* egg is repeated every day, and 

 what matters to me is only once to have placed it 

 in the ring. How slowly one advances to gain 

 knowledge of what is obvious, especially if the 



B. E. Raikov and I. I. Skolov, with the cooperation 

 of Yu. I. Polyanskii and P. G. Svetlov; translation 

 of the second volume, Yu. M. Olenev, I. I. Skolov 

 and B. E. Raikov, with the participation of 

 P. G. Svetlov (90). 



302 



