110 EVOLUTION AND MAN S PLACE IN NATURE 



life, that it presents two classes of facts. Can mental 

 phenomena, with all their variations, be traced to the 

 germ-cell ? 



Notwithstanding the large advance in our know 

 ledge of embryonic life, a new and still more difficult 

 problem arises, where, when, and how do mental 

 phenomena appear, in process of development of a 

 human life ? * This problem stands quite apart from 

 the problem of evolution of life, which must be 

 treated at a later stage, when we institute comparisons 

 between animal and human intelligence. The problem 

 now before us is one concerned with the development 

 of each individual life. Attention is concentrated on 

 the appearance of the higher phase of life which is 

 common to our race. Here direct knowledge fails us. 

 We are, therefore, restricted to such inductions as 

 ; may seem warranted by familiar facts of our conscious 

 life. As natural history has modified hypotheses con 

 cerning germ-plasm, so must consciousness of rational 

 life modify the theory concerning heredity. Passing 

 towards a field of conjecture, where we confessedly deal 

 with the unknown, it is essential that we keep fast hold 

 on the terms of our problem. Only thus shall we be 

 warranted in venturing into conjecture, or in cherishing 

 reasonable expectation of the reliability of our results. 



Haeckel s treatment of the subject tends to obscure 

 the problem. He would find the explanation of 

 heredity in periodic wave-generation of the organic 

 molecules/ making the reproductive power the 

 equivalent of the memory. 2 A mechanical hypo 

 thesis does not need memory, and memory at its best 



1 See Professor E. Ray Lankester s Advancement of Science, p. 52. 



2 Gesammelte Populdre Vortrage, ii. p. 70. 



