VARIATION AND HEREDITY 137 



of inheritance. In illustration we 

 may refer to hybrid trout, half-bred sheep, 

 and mulattoes. 



APPLICATION TO EVOLUTION THEORY. 

 Like Weismannism, which has for one of its 

 foundations the idea of germinal continuity, 

 JVIendelism conceives of the hereditary rela- 

 tjnn in-thfr .strirt p^n g ^ i.e. not as between the 

 bodies of parent and offspring, buL Between 

 the pflrmtal and tfre fj^aJ! 



Like Weismannism, which has for another 

 of its foundations the idea of determinants 

 or representative particles constituting the 

 mosaic of inheritance, Mendelism regards the 

 organism as built jy oTajEimber oFdefinite, 

 separably' 'heritable' characters. 



Mendelism has thrown light on at least 

 certain kinds of variation, those which are 

 due to the addition or omission of one or more 

 definite elements. As Bateson puts it: 

 "With the development of the inquiry it has 

 become clear that vitiation, in so far as it 

 consists in the omission of elementary fac- 

 tors, is the 



he white sweet pea 

 in the variation by which one of the colour- 

 factors was dropped out. Such variation is 

 not, as it was formerly supposed that all 

 variation must be, a progress from a lower 

 degree of complexity to a higher, but the 



