i68 MENDELISM CHAP. 



repetition, we may safely ignore telegony as a factor in 

 heredity. 



Heterozygous forms play a greater part in the breeding 

 of animals than of plants, for many of the qualities sought 

 after by the breeder are of this nature. Such is the blue 

 of the Andalusian fowl, and, according to Professor Wil- 

 son, the roan of the Shorthorn is similar, being the hetero- 

 zygous form produced by mating red with white. The 

 characters of certain breeds of canaries and pigeons again 

 appear to depend upon their heterozygous nature. Such 

 forms cannot, of course, ever be bred true, and where sev- 

 eral factors are concerned they may when bred together 

 produce but a small proportion of offspring like them- 

 selves. As soon, however, as their constitution has been 

 analysed and expressed in terms of Mendelian factors, 

 pure strains can be built up which when crossed will give 

 nothing but offspring of the desired heterozygous form. 



The points with which the breeder is concerned are 

 often fine ones, not very evident except to the, practised 

 eye. Between an ordinary Dutch rabbit and a winner, 

 or between the comb of a Hamburgh that is fit to show 

 and one that is not, the differences are not very apparent 

 to the uninitiated. Whether Mendelism will assist the 

 breeder in the production of these finer points is at present 

 doubtful. It may be that these small differences are 

 heritable, such as those that form the basis of Johann- 

 sen's pure lines. In this case the breeder's outlook is 



