152 GENETICS 



due sometimes to the action of a more natural en- 

 vironment, as in the case of animals set free after 

 having been in captivity, and sometimes to hybridi- 

 zation, since there seems to be a general tendency of 

 hybridized organisms to "revert" to ancestral types. 

 It is now known that reversion, like atavism, is 

 simply a case of latent characters becoming apparent 

 according to the Mendelian principle of segregation. 

 To quote Davenport : "There is nothing more mys- 

 terious about reversion* from the modern standpoint, 

 than about forming a word from the proper com- 

 bination of letters." 



4. SOME METHODS OF IMPROVING OLD AND ESTAB- 

 LISHING NEW TYPES 



a. The Method of Hallet 



This method, which was formulated by the English 

 wheat-grower Hallet in 1869, has been in common 

 use for a long time. It consists in placing the organ- 

 isms to be bred in the very best possible environment 

 and then choosing those individuals which make the 

 best showing as the stock from which to breed further, 

 a procedure based upon the deep-seated belief that 

 acquired characters are inherited. 



For example, in a field of wheat, plants near the 

 edge of the field which, from lack of crowding or by 

 reason of proximity to an extra local supply of fer- 

 tilizer or any other favorable environmental factor, 

 make a more vigorous growth than their neighbors, 



