12 Biogenetic Law of Recapitulation 
fluous and functionless from the first.””! 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 biogenctic 
law. 
Also Delage draws attention to the fact that all those 
structures which disappear during the progress of 
development must nevertheless have their significance.? 
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.” * 
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 cther 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 
*Wilhelm Roux: Der Kampf der Teile im Organismus. Leipzig, 
Engelmann, 1881. P. 59. 
*Delage: L’hérédité et les grands problémes de la biologie 
générale. Paris, Schleicher, 1903. P. 176. 
Oscar Hertwig: Die Zelle und die Gewebe. Zweites Buch. 
Jena, Fischer, 1808. P. 232. 
