VARIATION AND HEREDITY 141 



For the facts of heredity and variation unite 

 to prove that genetic variation is a phenome- 

 non of individuals. Each new character is 

 formed in some germ-cell of some particular 

 individual, at some point of time." 



The issue at present seems to be this, that 

 there are characters which blend when crossed, 

 and others which segregate when crossed. 

 Patient work is necessary in order to test 

 these two groups and to discover what is 

 the criterion of blending and alternating 

 respectively. In his interesting work on 

 "Hereditary Characters," Dr. Charles E. 

 Walker maintains the thesis that racial 

 characters tend to blend and that individual 

 characters are transmitted in an alternative 

 or Mendelian manner. 



ORIGIN OF VARIATIONS. Since variations 

 form the raw materials of evolution, it would 

 be satisfactory if we could conclude this 

 chapter by stating how they arise. But that 

 is quite impossible at present. We know 

 very little that is certain in regard to the 

 originative factors in evolution. We must 

 still confess, with Darwin : " Our ignorance 

 of the laws of variation is profound." It 

 may be of interest, however, to notice some 

 of the suggestions that have been made in 

 regard to this fascinating problem. 



