12 Biogenetic Law of Recapitulation 



fluous and functionless from the first." l Development 

 of this sort, proceeding toward its goal not by the direct 

 line but by byways and often backwards, would be incom- 

 prehensible were it not for the fundamental biogenetic 

 law. 



Also Delage draws attention to the fact that all those 

 structures which disappear during the progress of 

 development must nevertheless have their significance. 2 



Similarly Oscar Hertwig notes expressly that there 

 exist many embryonal organs "which never come into a 

 position to perform the function which they have once 

 performed during the course of phylogeny." 3 



We must then regard this fundamental biogenetic law 

 as true. We can even suppose it to be a close approxima- 

 tion, that ontogeny represents phylogeny exactly. 



It is true that during the first ontogenetic stages 

 phylogeny is only epitomized, but this becomes steadily 

 less true the farther development proceeds, and during the 

 later stages ontogeny can be regarded as an almost exact 

 repetition of all the corresponding phylogenetic stages. 



The human embryo, on account of the more numerous 

 and careful researches of which it has been the object, 

 serves better than any other to illustrate this almost exact 

 phylogenetic repetition in the later stages. Its develop- 

 ment demonstrates even to the smallest details how the 

 embryo passes through the whole series of forms of the 

 pithecanthropoids, its immediate ancestors. Thus for 

 example the articulations of the leg in man show during 



1 Wilhelm Roux: Der Kampf der Teile im Organismus. Leipzig, 

 Engelmann, 1881. P. 59. 



2 Delage: L'heredite et les grands problemes de la biologic 

 generate. Paris, Schleicher, 1903. P. 176. 



'Oscar Hertwig: Die Zelle und die Gewebe. Zwcites Buch. 

 Jena, Fischer, 1898. P. 232. 



