Baer's table continues also to the left, where it shows 

 that the ovum is a consequence of the dichotomy of asexual 

 and sexual multiplication, and to the right, where it presents 

 the divergence of the amphibia and mammals according to 

 peculiarities of later development. The text (p. 321 and on 

 (225 ff.)) gives a detailed commentary to this table. One of 

 its main purposes is to show clearly that the embryo in the 

 course of development sometimes does not pass from one main 

 type to another. From the point of view of modern embryology, 

 Baer's scheme could have included a series of corrections, 

 such as that spiral development is inherent not only to 

 molluscs (to the massive type), but also to the annelid worms 

 (representatives of Baer's elongated type), and so on. Baer 

 himself stipulated the imperfection of his scheme, as also all 

 others, but his main idea about the divergent character of 

 development need not fluctuate with particular corrections. 



Baer considered it absolutely natural that the erroneous 

 point of view that transmission to embryonic stages correspond 

 to simply constructed animals had acquired many supporters. 

 Since fish deviate less from the basic type than mammals, it 

 is natural that the embryo of mammals is more similar to fish 

 than the embryo of fish is to mammals. 



To the fifth scholium Baer attached four corollaries, 

 which begin with the wonderful aphorism so frequently cited 

 thereafter: "The history of development is a real light for 

 the study of organic bodies. At each step it finds its 

 application, and all ideas which we have about the reciprocal 

 relations of organic bodies will experience the influence of 

 our knowledge of the history of development" (p. 328 (231)). 



The first corollary is entitled "The application of this 1 _ 

 scholium to the study of arrested development (Hemmungsbildung) ." 

 It begins with the confirmation that arrested development can 

 be understood only by knowing the process of normal development. 

 After that comes a controversy with those authors who considered 

 that arrested development illustrates the repetition of ancestral 



13. (Ed.: "Hemmungsbildung" means structural defects, 

 malformations, or arrested development, but Baer 

 seems to have meant the last.) 



358 



