embryo, i.e. development of yolk (ovum) and semen; 

 3) processes occurring during copulation, i.e. the influence 

 of sperm upon the yolk, and finally 4) formation of the 

 additional parts of the ovum — albumin, membranes and ovum 

 cocoons . 



Only after this it is possible to begin the study of 

 embryonic development, which Warnek divided into two periods. 

 The first period includes the development of the fertilized 

 ovum, i.e. the process of division and preparation of the 

 development of organs, and the second, the period of develop- 

 ment of all systems of organs of the developing animal. 



In his investigations Warnek proceeded from the following 

 situations established by the embryologists: 1) for the 

 transformation of yolk into an embryo fertilization is 

 absolutely necessary; 2) this last consists of the material 

 influence of semen on the yolk; 3) this influence takes place 

 only in an infinitely small space, therefore the spermatozoa 

 of the semen must come in direct contact with the mass of 

 yolk; 4) the result of fertilization is the formation of the 

 elementary organs of the embryo (cells); 5] the cells acquire 

 different forms, grouped in complicated organs of the embryo, 

 and thus form its body. 



Warnek expressed regret that embryologists could not 

 completely solve the following important questions related 

 to the development of animals: 1) how the yolk, i.e. substance 

 of the ovum is transformed into tissue of the embryo; 2) how 

 its transformation at the time of development occurs; 3) in 

 what does the secret influence of the semen on the yolk 

 consist. 



The first question Warnek considered to be solvable, 

 and he expressed the hope that in a short while the other 

 two questions would also be explained. 



The solution of the principal questions of embryology, 

 in Warnek' s opinion, could take place on the basis of the 

 following presentations: 



The cause of the phenomena conditioning the beginning 

 and the subsequent development of the embryo is 

 ordinarily attributed to the vital power, which 



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