207 • 



Thus the D D, or pure seeds of the strain, may be tested 

 out and used to breed true. This resuh reached 1\v Alendel 

 forty years tigo, was further tested and proved recently b;y 

 Dr. Castle in experiments on guinea-pigs or cavies. 



EXPERniEXTS WITH GUINEA PIGS. 



He wanted some rough-coated, "rosetted" albino varieties 

 In order to produce these he commenced with cavies posses- 

 sing rough-pigmentcd or colored coat, and albino smooth coat 

 Observe that the problem was complicated by two alternative 

 characteristics. He had to breed not only for color, as the peas 

 were cultivated, but also for rough or smooth hair in addition. 

 Experiments showed that the rough coat is alternative with, 

 and dominant over, the smooth coat, and also that pigmented 

 or colored coat is dominant over white coat. 



Crossing rough colored or pigmented with smooth albinos, 

 it was found that hybrids were produced all of which exhibited 

 only the dominant characteristics, viz : the rough and colored 

 coat. 



When bred together the above resolve themselves up into 

 nine categories, though the characteristics are not all apparent. 

 In only three out of sixteen offspring: did the hidden or reces- 

 sive characteristic of albino color and smoot coat appear. Tlie 

 result of three to one was therefore demonstrated. The breed- 

 er using Mendel's law would test each rough coated albino 

 for purity, by crossing each with a smooth coated albino, which 

 contained recessive qualities only. The result would be that 

 about one-third of the rough white cavies would produce to 

 this cross only progeny similar to themselves. Others would 

 produce mixed three rough and one smooth albino, and those 

 would be rejected as hybrids. 



By this test the individuals of the dominant character D D 

 may be determined without any recessive character D (T(), 

 (R) D. They are pure and will remain so. 



SEGREGATION AND DOMINANT CHARACTERS. 



From these experiments we have two elements, segregation 

 in breeding, and dominant characteristics. 



The mathematics of segregation is understood from the na- 

 ture of the development of the germ cell, but the cause of the 

 characteristic of dominance is a mystery. It is found to be 

 an important element to be reckoned with. 



SPECIFIC RESULTS.- 



With these applications the law becomes a working rule, 

 and poultry breeders Avith others may intelligently breed in a 



