THE DESCENT OF MAN 59 



development, reproduced a number of ancestral 

 forms in succession, and that this constituted a 

 conclusive proof of his descent from beasts. I 

 believe, however, that recent investigations in com- 

 parative morphology and in evolution justify very 

 serious doubts as to the accuracy of the biogenetic 

 principle in general, and especially as to its 

 application to man. 



The first point the accuracy of the biogenetic 

 principle in general has been discussed by Karl 

 Ernst v. Baer, and its true value has been 

 ascertained. 1 



Quite recently it has been critically examined 

 by Oskar Hertwig in his General Biology, and in 

 the last chapter of his Handbook of Compara- 

 tive and Experimental Evolution of Vertebrates. 

 According to the most valuable statements made 

 by Hertwig, the evolution of the individual is not a 

 repetition of that of the race, but, assuming the 

 principle of evolution, we must regard it as a 

 continuation of the development of the race. As 

 this process continues, the corresponding new 

 generation must advance somewhat further than 

 its immediate predecessor ; there is no simple 

 repetition of the evolution of the race. 2 



1 See also J. Reinke, The Laminariacece, and HaecJceVs Biogenetic prin- 

 ciple, Kiel, 1903. 



2 Haeckel himself shows that he recognises this fact, for in the develop- 

 ment of the individual he distinguishes Palingenesis, or repetition of 

 ancestral forms, and Caenogenesis, or new formations. The latter, in fact, 

 so often outweighs the former in importance as to overthrow the 'prin- 



