264 APPLICATION OF BREEDING PRINCIPLES 



the creaminess, but the large deposit of fat under the skin gives 

 the white plumage a yellowish tinge. 



It is also caused in many cases by the " burning " of the white 

 plumage during the summer when the birds are exposed continu- 

 ously to the rays of the sun. Most of the noted breeders of exhi- 

 bition white birds keep them confined practically all the time, 

 letting them out only toward night. 



Soil Effects on Plumage and Shank. The presence of certain 

 alkalies in the soil may make it almost impossible to secure the 

 greatest degree of color in plumage and shanks. In certain sections 

 it is impossible to get and keep the clear yellow shank, owing to the 

 presence of alkalies in the soil. Certain highly colored soils, of 

 a clay or shale nature, are a great hindrance to the breeder by 

 compelling him to confine his birds. (For further discussions on 

 breeding for color see references, page 265.) 



Breeding Fallacies. There are two alleged facts in breeding 

 which should be explained. 



The influence of a previous sire or impregnation on the charac- 

 ter of subsequent chicks. In the case of fowls, even after a cock 

 bird has been removed from the pen he may become the parent 

 of chicks hatched from eggs subsequently laid by these hens, for 

 the sperm continues active within the hen for from ten days to 

 two weeks. But if, after the eggs laid have ceased to be fertile, 

 a new cock be added, different from the first, there is no proof 

 of any influence of the previous male bird. Experiments by Waite 

 show that at least three weeks must elapse before one can be sure 

 that the effect of a previous mating has ceased. 



Another alleged effect is that of imagination upon the subse- 

 quent progeny. For example, there is no ground for believing 

 that, if two pens of birds, one black and the other white, run side 

 by side, any splashing or mixing shown in the progeny is due to 

 the effect of sight or imagination. A more sane hypothesis would 

 be that the opposing cock bird jumped the fence and fertilized 

 the eggs. 



REVIEW. 



1. Name four objects toward which all poultry breeding of a commercial 



nature is tending. 



2. What are the commercial possibilities of crossbreeding? 



3. Define "grading up," and state its commercial possibilities. 



4. Define "inbreeding," and name three ways in which it is possible to 



inbreed. 



5. What can you say of the prepotency of in-bred progeny? 



