THE EVOLUTION OF MAN 



thing which was temporarily feasible and served 

 as a means of adaptation, but was soon dropped, 

 and did not reappear and become typical until the 

 mammals arose. 



Again, in the development of the eggs of the 

 lamprey, we see a sudden flaring up of almost 

 the identical method which has later become typi- 

 cal for the amphibians of the present day. All 

 these things indicate that at this stage we meet 

 once more one of those ancient mixed groups, 

 typical for our line of descent, which contained 

 the historical germs of all higher forms and were, 

 so to say, reservoirs for all the possibilities of 

 subsequent evolution. 



At the same time, we approach at this stage 

 an entirely new and exceedingly significant point 

 of departure, the source of all vertebrates in gen- 

 eral. 



What is the characteristic mark of a verte- 

 brate, including man ? The back bone, that great 

 internal prop of the body. Well, then, we see 

 the back bone growing softer and softer among 

 the Ceratodus class, sturgeons and sharks, and it 

 seems to dissolve more and more the further back 

 we trace it. In the lamprey and finally in Am- 

 phioxus .this backward formation is almost com- 

 pleted. There the proud column has become 



109 



