200 GENETICS 



vironment, as in the case of animals set free after hav- 

 ing been in captivity, and sometimes to hybridization, 

 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, i 

 To quote Davenport: "There is nothing more mys- 

 terious about reversion, from the modern standpoint, 

 than about forming a word from the proper combina- 

 tion of letters." 



4. THE ART AND SCIENCE or BREEDING 



The art of breeding animals and plants has been 

 practiced from very early times while the science of 

 maintaining old types and initiating new ones is of 

 comparatively recent origin. 



Some of the methods that have been employed with 

 varying degrees of success are: 



A. Mass selection; 



B. Pedigree breeding ; 



C. Inbreeding; 



D. Hybridization; 



E. Genotypic selection. 



A. MASS SELECTION 



The natural thing to do in the maintenance or im- 

 provement of cultivated plants and domestic animals is 

 to select seeds from the best looking plants and to 



