62 MASS. EXPERIMENT STATION BULLETIN 428 



of 79 females, actually disclosed four broody individuals — a result which would be 

 expected to occur onl}- when breeding females are not fully tested for deferred 

 broodiness and when breeding males are inadequately progeny tested. The 

 1944 generation includes 67 females now being tested. 



Effectiveness of Selective Breeding to Reduce Mortality. (Regional Poultr\- 

 Research Laboratory and Departments of Veterinary Science and Poultry Hus- 

 bandry, Massachusetts Agricultural Experiment Station cooperating.) Results 

 of this project for eight generations hatched from' 1935 to 1942 were published 

 in Bulletin 420. 



To produce the generations hatched in 1943, 1944, and 1945, the plan of breed- 

 ing has been changed. A low mortality line has been reproduced from yearling 

 males and females within the line so that inbreeding has been necessary. A high 

 mortality line has been reproduced from young males and females within the 

 line and inbreeding has been practiced. The sole basis of selection in both lines 

 has been the mortality rate. Results thus far suggest that selective breeding 

 may be effective in producing two lines that differ significantly in mortality 

 rates to the age of 18 months. 



Genetic Laws Governing the Inheritance of High Fecundity in Domestic 

 Fowl. (F. A. Hays and Ruby Sanborn.) In Bulletin 423 it was shown that at 

 least sixteen different factors may affect egg production. These factors are in 

 part environmental, but probably in greater part are governed b>' inheritance. 

 Among the most important new characters are spring, summer, and fall inten- 

 sity-. Of considerable importance also are spring and summer pause duration. 

 Special attention is now being given to the inheritance phase of spring, summer, 

 and fall intensity. 



The primary sex ratio in chickens has been studied for the first time and evi- 

 dence of a 50-50 sex ratio reported. 



A line of birds carrying only autosomal gene E' for early sexual maturity has 

 been developed. Such females attain sexual maturity at from 190 to 200 days 

 of age. When sex-linked gene E was present with gene E', the mean age at sexual 

 maturity was reduced to 170-175 days. When neither gene for early sexual 

 maturity was present, the age at sexual maturity ranged from 200 to 300 days. 



A Study of Fertility Cycles in Males. (F. A. Hays.) Results reported for the 

 hatching season of 1944 suggest that sex hormones may have some value in stim- 

 ulating males that are at least 36 months old to active spermatogenesis. They 

 had no value for younger males. This test was repeated in 1945 using a higher 

 dosage of sex hormone and more artificial illumination. Results were entirely 

 negative in this second test and fertility stood at the same level in hormone- 

 treated, artifically lighted, and control pens. 



A Genetic Analysis of Rhode Island Red Color. (F. A. Hays.) Colorimetric 

 studies on feather pigment from three generations indicate that dense pigmenta- 

 tion in darker colored birds is due to several recessive genes. Further study is 

 being' given to this phase of the problem. 



Secondary and Adult Sex Ratio in Relation to Hatchability. (F. A. Hays.) 

 High and low hatchability lines were started in the spring of 1945. A complete 

 record of sex is being secured on all dead embryos from the ninth day on and upon 

 all chicks up to the adult stage of sexual maturity. 



A Study of Egg Characters of the Domestic Fowl. (F. P. Jeffrey.) Nine hundred 

 and si.xteen pedigreed R. I. Red pullets from 161 dams and 22 sires have been 

 classified as to egg weight, degree of shell color, egg shape, percentage egg shell. 



