PLYMOUTH ROCK STANDARD AND BREED ROOK 55 



themselves to their surroundings are poor layers as well as poor 

 breeders and show birds. 



From this it may be logically inferred that occasionally a 

 bird reverts to its wild ancestry and is incapable of true domes- 

 tication. 



Mendelism*. Mendelism is a law of inheritance discovered 

 by Gregor Johann Mendel in 1868, and rediscovered by De Vries, 

 Correns and Tschermak in 1900. It is generally considered 

 under three heads : Unit characters, dominance, and segregation. 

 The important feature is the latter that is, the segregation of 

 potential factors in the germ cells of crosses and their chance 

 combination. 



In animal breeding, absolute purity of all inherited factors 

 is difficult to obtain, as the parents even in highly selected stock 

 generally differ in their inheritance. Therefore, segregation and 

 recombination invariably occurs. Hence the necessity for con- 

 stant selection toward a desired end. 



If the breeding of fowls involved simply one, two or a very 

 few characteristics, the application of Mendelian principles would 

 be easily followed and understood, but, as at present practiced, 

 this application in the breeding of standard fowls with their 

 many requirements in shape, color and markings, becomes a 

 difficult problem. 



However, the application of the Mendel law has had little, 

 if any, bearing upon the accomplishments of breeders of stand- 

 ard-bred fowls. It is only within a very few years that Men- 

 delian principles have been studied in this connection, and at the 

 present time only a very few of the more studious and best edu- 

 cated fanciers and breeders are making efforts to apply these 

 principles. 



However, several of the state educational institutions and 

 experiment stations are applying these principles, and closely 

 observing and recording the results. The most important appli- 

 cation is in connection with the inheritance in fecundity, the one 

 feature in breeders that may be accurately stated, possibly accu- 

 rately measured, though even in this case, the influence of loca- 

 tion, environment and climatical changes from season to season, 

 month to month, etc., may, of course, affect the results. 



*For a complete treatise of this subject, the reader should consult 

 some work on "Genetics." 



