MENDEL'S LIFE AND WORK 31 



Another group of variation plienomena which 

 has been very much illuminated hj the work 

 clone on Mendelian lines is that due to the 

 influence of the character-factors upon one another 

 when combined in the same individual. The 

 simplest case is that where one character of a 

 pair is completely dominant to the other, as in 

 all of Mendel's pea experiments. But it often 

 happens that the two characters associated in a 

 hybrid act upon one another in various degrees, 

 so that either a more or less intermediate type 

 is produced, or an entirely novel character appears. 

 But even more important than this action of one 

 character of each pair upon the other in the 

 body of the hybrid has been the discovery that 

 the characters bel^ging to different pairs may 

 profoundly affect one another when occurring in 

 the same organism, and that what are apparently 

 quite new forms or, it may be, reversions to old 

 forms arise in this way. One general outcome 

 of Mendel's Law, and of the work done in connec- 

 tion therewith, has thus been the demonstration of 

 the subordinate and accidental character of many 

 of the phenomena of variation, the importance of 

 the really fundamental variations in the germ-plasm 

 being consequently brought into even greater 

 prominence than before. 



The other direction in which Mendel's work on 

 Heredity has had a most important though indirect 

 influence, is in connection with the problem of 

 Evolution. The Darwinian conception of Natural 



c 



