454 THE EVOLUTION OF MAN. 



and, in many respects, very pleasant dualistic theory of the 

 mind, as being wholly untenable, because irreconcilable 

 with genetic facts, then the opposite monistic view alone 

 remains to us, according to which the human mind, like 

 that of any other animal, is a function of the central nervous 

 system, with which it has developed in inseparable con- 

 nection. Ontogenetically, we see this in every child ; 

 phylogenetically, we must assert it in accordance with the 

 fundamental law of Biogeny. In every human embryo 

 the medullary tube develops from the skin-sensory layer, 

 and from the anterior part of that tube the five brain- 

 bladders of Skulled Animals (Craniota), and from these 

 the mammalian brain (at first with the characteristics of 

 the lower, then with those of the higher Mammals). 

 Just as this entire ontogenetic process is but a short repro • 

 duction, occasioned by Heredity, of the same process in the 

 Phylogeny of Vertebrates, so also the wonderful mental 

 activity of the human race has gradually developed, step 

 by step, in the course of many thousands of years, from tht^ 

 less perfect mental activity of the lower Vertebrates. And 

 the evolution of the mind in each child is only a brief 

 reproduction of that long phylogenetic process. 



The extraordinary and important bearing of Anthro- 

 pogeny on Philosophy, in the light of the fundamental prin- 

 ciple of Biogeny, now becomes apparent. The speculative 

 philosophers who will take possession of the facts of On- 

 togeny and explain them phylogenetically (according to that 

 law), will introduce a greater advance in the history of 

 Philosophy than has been made by the greatest thinkers of 

 all previous centuries. Undoubtedly every clear and logical 

 thinker must draw from the facts of Comparative Anatomy 



