The drawings are considered to be the most important part 

 of the morphological works. The pictures, reproducing the 

 studied objects as they were seen either with the naked eye 

 or with the aided eye, reveal the level of the technique and 

 the exactness of the observations. The schematic drawings 

 are considered the graphic expressions of the authors' 

 theoretical opinions. Therefore the original drawings speak 

 about the scientific priorities and facilitate the descrip- 

 tion in words of the corresponding discoveries. In reference 

 to this, we must not forget the authors of revisions and 

 educational textbooks; although they occasionally reprint 

 the illustrations of the foreign authors, often they are not 

 a bit better than the drawings of the Russian investigators 

 published earlier. The reprinting of the original drawings 

 of Wolff, Tredern, Boyanus, Pander, Baer, Grube, Nordman, 

 Warnek and Krohn in the present book is to present the level 

 of their morphological investigations, and also to defend 

 the priority of the Russian embryologists . 



The present book was finished in 1950. Its contents, and 

 also the plan for its continuation to subsequent stages 

 of embryology in our country, were reported in the meeting 

 of the sector of the history of biology in the Institute 

 of Natural Science History of the Academy of Science of 

 USSR and in the Academic Council of this Institute. 



The author is deeply grateful to T. D. Detlaf; 

 L. D. Lioznera, S. R. Mikulinsky, S. L. Sobol and 

 G. A. Shmidt, who listened to the reports about the contents 

 of this book or read the manuscript and made critical 

 comments. The author particularly thanks the collective of 

 the library of the Moscow Society of Naturalists, who 

 willingly helped during the search for literary sources and 

 illustrated materials. 



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