METHODS AND RESULTS OF ETHNOLOGY. 253 



changes, must a stock have been isolated from all 

 others for innumerable generations, and have 

 found ample time for the hereditary hardening of 

 its special peculiarities into the enduring charac- 

 ters of a persistent modification. 



Nor, if it be true that the physiological differ- 

 ences of species may be produced by variation and 

 natural selection, as Mr. Darwin supposes, would it 

 be at all astonishing, if, in some of these separated 

 stocks, the process of differentiation should have 

 gone so far as to give rise to the phenomena of 

 hybridity. In the face of the overwhelming 

 evidence in favour of the unity of the origin of 

 mankind afforded by anatomical considerations, 

 satisfactory proof of the existence of any degree of 

 sterility in the unions of members of two of the 

 " persistent modifications " of mankind, might well 

 be appealed to by Mr. Darwin as crucial evidence 

 of the truth of his views regarding the origin of 

 species in general. 



staeles to the existence of the white races within the 

 Tropics. There is, however, this point to be considered, 

 that the fevers to which the white men succumb are 

 probably caused by microbes; and that modern thera- 

 peutic science is daily teaching us more and more about 

 the ways of obtaining immunity from or alleviating these 

 attacks. What would become of black competition if 

 fever "vaccination" proved effectual? — 1894.] 



