the theory of the stability of the types as species, 

 proclaiming the study of their development."** 



An identical opinion about the significance of Wolff's 

 investigations was stated by Ya. A. Barzenkov in a 

 posthumously published outline of the history of comparative 

 anatomy. ^ On characterizing the theory of "evolution" of 

 Haller and Bonnet and the study connected with it about 

 "inserting of the embryos," Barzenkov wrote: "From this theory, 

 by the way, one sequence developed which is very important 

 for the theoretical natural sciences: the stability, and 

 the invariability of the types." (p. 96) "As a very young 

 man, Wolff ... came to the belief that this theory is not 

 possible." (p. 97) Proving the falseness of preformation and 

 turning instead to the principle of epigenesis, Wolff 

 consequently disproved also the idea of the stability of 

 types. The quotations from Wolff's manuscripts which were 

 recently published by B. E. Raikov undoubtedly indicate that 

 he was sure of the support for the changeability of the types 

 and, therefore, can be truly considered one of the predeces- 

 sors of Lamarck and Darwin. 



Giving credit to Wolff's efforts to proving epigenesis, 

 his idea about the origin of the parts of the embryo from 

 folds having the form of plates or leaves must be noted in 

 particular, because this observation influenced Pander and 

 Baer. 



The previously discussed list of Wolff's works 

 undoubtedly indicates that he actually had seen these 

 structures and called them leaves or membranes. It is 

 possible also to give another example, from which it can 

 be concluded that he had seen not only layers in the embryo 

 itself, but that he also recognized that by their means the 

 embryo and all the remaining blastodisc are united into 

 a single unity. Describing the structure of the "cardiac 

 fossa" which represents, according to Wolff's description, 



8. F. Engels, Old introduction to DIALECTICS OF MATURE 

 (STAROE VVEDENIE K DIALEKTIKE PRIRODY) , K. MARX 

 AND F. ENGELS. SOCH., v. xiv, p. 483. 



9. Readings of Ya. A. Barzenkov about comparative anatomy. 

 Uch. Zap. Mosk. un-ta, vyp. 4, 1884, p. 242. 



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