8o THE FIRST PRINCIPLES OF HEREDITY 



determinants, and it is conceivable that some will get less 

 nourishment, others more. The former accordingly will 

 become weaker, more ineffective, the latter stronger and 

 more powerful. As the determinants determine the quality 

 of the corresponding part of the body (the " determinate "), 

 this determinate in its turn will vary in accordance with its 

 determinant, and be developed in a lesser degree if its de- 

 terminant is weaker, and vice versa. Not only this, but once 

 a determinant has become weak and varied in the minus 

 direction through what was at first a merely accidental 

 change of the food-supply, its assimilative power will 

 become lessened, thus still further adding to the same 

 deteriorating process, until the determinant, and with it its 

 determinate, may completely disappear. On the other hand, 

 determinants varying in the plus direction would, by drawing 

 nourishment more and more towards themselves, become 

 stronger and stronger, and thus lead to a stronger expression 

 of their own determinates. It is by this process, which 

 Weismann has called " Germinal Selection," that he tries 

 to explain the atrophy (dwindling) of organs and their ulti- 

 mate disappearance. As Weismann does not admit the 

 inheritance of acquired characters, according to which the 

 gradual dwindling and ultimate loss of an organ is brought 

 about by the inherited disuse of the organs through suc- 

 cessive generations, he had to find another explanation for 

 these cases, and advanced for this purpose his theory of 

 Germinal Selection. Furthermore, the same theory en- 

 ables him to explain the occurrence of highly-developed 

 traits in civilized man, as the musical faculty, etc., which 

 are not useful in the struggle for existence, and could not 

 therefore have been evolved by the process of Natural 

 Selection. For a discussion of these questions, however, 

 we must refer the reader to the books on Darwinism and 

 Natural Selection. 



