on embryos obviously indicate that the initial formation 

 of all animals takes place in general in the same order; but 

 in this case each of them varies infinitely in the details and 

 stages of his development. Each animal exists separately from 

 all other animals yet represents a link of the unbroken chain 

 of all creatures" (p. 160). 



Yakushkin compared the regularity of development of the 

 chick in its egg and the human fetus in the uterus, with the 

 idea, which was circulating at the beginning of the nineteenth 

 century, of the successive formation in man of features 

 characteristic of lower animal forms. That the character of 

 Yakushkin 's argument had a historical and not a Naturphilo- 

 sophical point of view is clear. He accepted the idea of 

 recapitulation of the physical organization of thinking as 

 a function of the brain, and talked about the gradual 

 development of this function in animals. Affirmation of the 

 gradual development of intellectual activities in the animal 

 world, based on comparative embryology, led Yakushkin to the 

 recognition of the primacy of matter over the soul, i.e. it 

 revealed to him the basic scientific materialistic solution 

 of the main question of philosophy. This ideology permeated his 

 embryological ideas: to explain the phenomena of development 

 he did not need the assistance of any special power or any 

 unified world power, but would refer only to the material 

 properties of the growing embryo and the effect of physical 

 factors of the surrounding environment. 



Evidence of the continuing struggle of the progressive 

 (Ed. : materialistic, positivistic) ideology with idealism is 

 found in a paper by that courageous nature investigator, the 

 materialist Iustin Evdokimovich Diadkovskii (1784 - 1841) .68 

 Professor of Moscow University and the Moscow Medical-Surgical 



68. The significance of the work of Diadkovskii for the history 

 of Russian philosophy and science was elucidated recently 

 in an interesting small monograph by S. P. Mikulinskii, 

 "I. E. Diadkovskii (1748 - 1841) : Ideology and Common 

 Biological Views," Mosc. Obshch. Isp. Prir. (1951), 117 pp., 

 and also in S. L. Sobol ' , "I. E. Diadkovskii — A Russian 

 Materialist-Biologist at the Beginning of the 19th Century," 

 TRUGY UN-TA 1ST. ESTESTV. , V (1953), pp. 145 - 156. 



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