MENDELISM 33 



normal. Fluctuations are thus repressed as soon 

 as they appear, and it is not easy to comprehend 

 how they could be the foundation for settled 

 changes. 



The Mendelian school of biologists pin their 

 faith to " sports " or mutations. The researches 

 of Mendel showed that these may represent new 

 innate impulses which interbreeding may conceal, 

 but cannot obliterate. Hybrids between the 

 44 sport " and a normal individual may not display 

 the new character. But a proportion of the repro- 

 ductive cells which they produce will contain it, 

 and, if two of the hybrids interbreed (as may 

 happen in the course of a few generations) some 

 of their offspring will possess the new character 

 purely, will display it in their form or colour, and, 

 if they interbreed, will produce offspring in which 

 the new character is fixed. Here, then, is a process 

 by which a new variety of importance may be 

 established, and by which it is established by 

 breeders and nurserymen. Instances of per- 

 sistent, or Mendelian, characters are tallness and 

 dwarfness of habit in plants, the colours of certain 

 flowers, the forms and markings of different 

 breeds of rabbits, fowls and pigeons, the colour 

 of the eyes in mankind. All characters do not, 

 however, appear to be of this class. We know 

 from experience that there are numerous, and 

 very important, peculiarities that do not resist 

 cross-breeding : the characters of both parents 

 are blended in the hybrid offspring of finches and 

 canaries, of dogs and jackals, and of white and 

 coloured races of mankind. But Mendelist ex- 

 perimenters have proved a fact which is of 

 immense importance that the reproductive cells 

 which are produced in large numbers by male and 

 female may differ among themselves, that they 

 may possess different shares of ancestral charac- 



