THE EVOLUTION OF MAN 



Let us start at once from embryology, which 

 pointed in the right direction in our quest for the 

 preceding stage. 



How is the Gastrula type formed ? Let us sup- 

 pose a typical case in which the Gastrula is still 

 swimming about as a genuine skin-and-stomach 

 larva, a little cylinder with an orifice at one end. 

 This little cylinder arises before our eyes by a 

 very simple process. Its starting point is the 

 fertilized egg. The Gastrula-larva is composed 

 of many little building stones or cells. An adult 

 animal may consist of many millions of cells. 

 But the genuine egg from which the development 

 of the embryo starts, generally, after fertilization, 

 consists of only one cell and never more than 

 one. *Just as surely as every human being comes X 

 from an egg which is attached to the ovarium 

 of the human female and which through contact 

 with the semen of a human male becomes fer- 

 tilized, just so surely this same human being alsox 

 Becomes out of one single cell. 



Now between this single egg cell and the multi- 

 cellular Gastrula stage, we always observe the 

 following process, which occurs with iron con- 

 sistency: The egg splits up into two cells by a 

 process of fission, and two cells become four, 

 eight, etc., until there is finally a lump of many 



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