22 The Recapitulation Theory and Human Infancy 



twig representing the species of which it is a member. It must 

 in a general way go through the particular line of forms which 

 preceded it in all past times: there must be what has been aptly 

 called a "recapitulation" of the successive ancestral structures. 

 This, at least, is the conclusion necessitated by the generaliza- 

 tion we are considering under its original crude form." 28 



Thus in any unfolding embryo there are two sets of energies 

 at work, one tending toward the type of the primitive ances- 

 tors, the other toward the evolved terminal type, the inter- 

 mediate structures being influenced by their conflict. Still 

 other factors intervene to affect the character of development. 

 One is economy. A premium is placed upon any animal in a 

 series which can mature at a saving in vital energy. This tends 

 to shorten the process. Economy again explains the entire 

 disappearance of intermediate forms in some cases. Economy 

 explains, once more, "preadaptation," in the earlier preparation 

 of structures and functions of increasing size and importance 

 in the life of the evolving animal. A demand for more time 

 in the upbuilding of increasingly complicated organs may also 

 bring about preadaptations. Finally the lack of uniformity 

 in the decrease and disappearance of organs may be explained 

 in several ways: large organs will suffer more than small ones 

 from the principle of economy; decrease in unused organs may 

 not coincide with the evolution of more important ones; ances- 

 tral features may become embodied as parts of new organs; 

 and some disused organs may entail evil by being in the way 

 of the modes of living. 29 



Spencer's views are interesting in that while they arrive at 

 an acceptance of the chronological idea of recapitulation, they 

 do so by inferences directly from the law of von Baer. But 

 recapitulation is true only to the extent that von Baer's law 

 holds, and Spencer is very well aware of the variations from the 

 law. His statements thus escape the extreme form given to 

 those of Haeckel by the latter's presupposition of a biogenetic 

 fundamental law. Spencer's position is representative of an 

 acceptance of recapitulation more just to the complexities of 

 the facts, and more nearly in accord with the views of Darwin 

 and Muller. 



Loc. tit., p. 453. 



., p. 458, et seq. 



