OTHER FACTORS OF EVOLUTION 129 



fully sought information, from other authorities, I find these facts 

 confirmed, and that the same applies to Mohammedan children. We 

 are aware that for ages their ancestors have been compelled to 

 memorise long portions of their sacred books, and although 

 occasionally we meet with a child of any nation with a gigantic 

 memory, that differs widely from the case of a people where it has 

 become a general characteristic." 



Another point, depending upon cerebral development in particular 

 directions and its transmission by heredity, is also of much impor- 

 tance. A child usually learns to speak slowly and with much 

 difficulty ; but I have contended elsewhere ' that the child would 

 never be able to speak at all if he had not inherited from very 

 remote ancestors certain nervous mechanisms in the brain upon 

 which this power depends ; and that if the child has to learn to speak 

 this is due to the fact that he begins to try as soon as the appro- 

 priate nerve centres begin to develop. When, in certain cases, the 

 acquirement of speech has not taken place at the usual time, it 

 sometimes happens that years after, on the occurrence of some strong 

 stimulus the previously dumb person begins to talk, without going 

 through the usual process of learning how to do it. Four cases in 

 illustration are cited. One was a patient of my own, one a patient 

 of the late Dr. Wigan, and the other two are matters of ancient 

 history — cases referred to by Herodotus, which, in face of the 

 modern instances, cannot be lightly dismissed. 



Herbert Spencer, as is well known, holds that the inheritance of 

 functionally-caused alterations has come " more to the front as 

 evolution has advanced," and that " it has played the chief part in 

 producing the highest types . . . the action of natural selection 

 being limited to the destruction of those who are constitutionally 

 too feeble to live, even with external aid. . . . Natural selection 

 acts freely in the struggle of one society with another ; yet among 

 the units of each society, its action is so interfered with that 

 there remains no adequate cause for the acquirement of mental 

 superiority by one race over another, except the inheritance of 

 functionally-produced modifications." = 



The question whether Acquired Characters resulting from 

 changes in the External Conditions of Life are inherited or not 

 cannot be profitably discussed without precise references to Weis- 



' " Aphasia and other Speech Defects," 1898, pp. 5-8. 

 " " Biology," I, pp. 553 and 560. 

 9 



