174 EVOLUTION 



A strengthened representative item or deter- 

 minant in the germ-plasm will nourish itself 

 more abundantly than its neighbours. " It 

 may get into a permanent upward movement, 

 and attain a degree from which there is no 

 falling back." On the other hand, a weakened 

 determinant will have less power of attracting 

 nutriment, and will tend to go downhill If 

 it be the determinant of something useful, 

 then the ordinary process of natural selection 

 will eliminate the individual that develops 

 from the impoverished germ-cell; if it bt 

 the determinant of something useless natural 

 selection will not interfere, and the deter- 

 minant will continue getting weaker every 

 generation. 



The theory of germinal selection is, of 

 course, an hypothesis, dealing like Mendel's 

 theory of gametic segregation with the in- 

 visible, but it may be nevertheless useful 

 in enabling us provisionally to formulate a 

 number of very puzzling facts, and in sug- 

 gesting experimental work, on which, even- 

 tually, we must base our conclusions as to 

 these abstruse questions. 



According to Weismann, germinal selection 

 helps us to understand the dwindling away 

 of organs which have sunk below the level 

 touched by ordinary natural selection; the 



