RAPID FEATHERING IN RHODE ISLAND REDS 5 



The head and the back tracts were slowest in developing feathers; the abdomen, 

 neck, and thigh regions were also rather slow in developing; and the shoulder, 

 breast, and tail developed feathers rather early. Males feathered more slowly 

 than females, and there was a significant difference in age when feather growth 

 started between lines 1 and 2. 



When the age at which feathering was complete in the different feather tracts 

 is considered, it will be noted that head, leg, and abdomen were slowest to com- 

 plete feather development; the back, tail, and breast were next in order; and the 

 shoulder and thigh regions completed feather development rather early. In 

 almost all tracts studied, the males of line 2 were slower than those of line 1. 

 Females in the two lines did not differ greatly in time required for complete 

 feather development in the different feather tracts. This is in line with the previ- 

 ous observation that feathering phenotypes are difficult to distinguish in females. 



Percentage of Chicks Completely Feathered in the Different 

 Tracts at Eight Weeks of Age 



It is desirable to learn something about stages of feather growth in the differ- 

 ent tracts at the age of 8 weeks. Since selective breeding had just begun when 

 these observations were made, it is self-evident that the fast and slow lines would 

 be less diverse than in later generations. 



Table 3 indicates that both lines were rather poorly feathered at 8 weeks of 

 age when the experiment began. In line 1 only 9.91 percent of the males had 

 complete back feathering, while in line 2 the percentage was even less, 2.94 

 percent. 



Table 3. — Percentage of Chicks Completely Feathered in the 

 Different Tracts at 8 Weeks of Age. 1934-1935. 



In the females, the percentages were 72.41 and 41.67 respectively for lines 1 and 

 2. These data indicate that at the beginning of the experiment both lines in- 

 cluded some rapid-feathering birds. 



Relation Between Feathering at Twelve Days and Back Feathering 



at Eight Weeks 



Records on tail development at 12 days and on feathering over the back at 8 

 weeks were taken on all chicks in the control group and in lines 1 and 2 for the 

 generations hatched in 1938 and 1939. It seemed particularly desirable to study 

 the relation between the sex-linked recessive gene si which produces tail growth 

 during the second week and the presence or absence of back feathering at 8 

 weeks of age. Since there is a sex-dimorphism, the sexes were considered sep- 

 arately. The chicks were classified as either rapid or slow feathering at 12 days 



