20 MASS. EXPERIMENT STATION BULLETIN 429 



Table 12. — Relation of Month of Onset and Completion of Wing 



Primary Molt to Egg Production During Biological Year, 



Production Stock Only 



Aug. Sept. Oct. Nov. Dec. Jan. 



Complete Wing Molt 



Onset of wing molt* 



Number of birds 39 18 15 



Average production during 



biological year, eggs 232.8 233.8 248.8 



Completion of wing molt 



Number of birds 1 5 51 64 14 



Average production during 



biological year, eggs 224.0 235.8 224.2 228.5 236.9 



Incomplete Wing Molt 



Onset of wing molt* 



Number of birds 28 31 36 8 



Average production during 



biological year, eggs 229.1 239.5 265.7 240.6 



*Data on the time of onset of wing molt are incomplete because a considerable proportion of 

 the birds began molting before August. 



Inheritance Studies — Results from Breeding Two Lines 



Matings were made over a three-year period beginning in 1941, to study tiie 

 mode of inheritance of time required for molting and date of completion of molt. 

 Line A was selectively bred from females that stopped laying soon after the onset 

 of molt in wing primaries, mated to males that completed their wing molt early 

 in the fall. Line B was selectively bred from females that continued to lay for a 

 considerable period after the onset of molt in wing primaries, mated to males 

 that completed their wing molt late in the fall. The molting behavior of the 

 sons is considered first. 



MOLTING BEHAVIOR OF FATHERS AND SONS 



The time required for molting in the different feather regions and the date of 

 completion are recorded in table 13 by generations. 



In the first generation there is opportunity for a comparison of a father with 

 his two sons in line A. Although the time required for the molting process was 

 highly variable, the sons molted at a more rapid rate than their sire in all regions 

 except thigh, lower leg, and wing primaries. The date on which molting was 

 complete was extremely close in father and sons, except in wing primaries. In 

 wing primaries the sons completed their molt one month later than their sire. 



Line A in the second generation showed little variability between father and 

 sons either in the date that molt was completed in the different feather regions 

 or in the average number of days required for the molt. 



In line B in the second generation, the sire was a slow molting individual. In 

 general, his sons molted more rapidly than their sire, but in wing molt they were 

 slow. The four sons also completed their molt in the different regions at an 

 earlier date than their sire. A comparison of the sons in lines A and B indicates 

 that the males in line B molted their wing primaries more slowly and completed 

 their wing molt at a considerably later date than those of line A. 



Data are very meager for the third generation. In line A molt was completed 

 rather early in most feather regions except the wing primaries, with the average 

 date November 3. 



