INHERITANCE OF WINTER EGG PRODUCTION 109 



In 1917 he ^Yas bred again for the same purpose as in 1915, but 

 this time was mated to other birds also. The resuhs for 1917 

 are in striking contrast to those of 1915, although the records 

 of the new mates are only slightly better than the old. How- 

 ever, if the two years are combined, the actual ratio is 12 high: 

 14 mediocre: 11 zero, which may represent a theoretical ratio of 

 13.75 high: 18.50 mediocre: 4.75 zero. 



Cornish male by Rhode Island Red female cross 



The detailed data of this cross are given in table 8. The 

 results of this experiment are of prime importance for theories 

 of the inheritance of winter egg production, because it demon- 

 strates, in the Rhode Island Red breed at least, that high pro- 

 duction descends from mother to daughter. It is important to 

 realize that the Cornish stock used in our experiments was ob- 

 tained from the same source as Pearl's. Further, our data on 

 the Cornish are in good agreement with the numerical results 

 obtained by him (Pearl, '12). It is Uke^\ise of importance to 

 note that the Cornish females bred to the same male as the 

 Rhode Island Red females give a strikingl}^ different result. If we 

 attempt to reduce these data to the form of Pearl's theory, we at 

 once become involved in difficulties. In the first place, no high 

 producers at all are to be expected, yet we find that twenty- 

 eight of the thirty-one individuals are high producers."* 



While the average winter egg production (49.2 eggs) of the 

 cross-bred pullets is not equal to that of their mothers (71.6 

 eggs), it is nearly equal to that (52.5 eggs) of the mother's 

 families, i.e., the mothers and their sisters. The average pro- 

 duction of the mother's families seems a fairer basis for com- 

 parison, as the mothers were a group of indi\dduals with 

 production much above the average, and regression would cer- 

 tainly be expected. The average hatching date of the five 

 mothers is April 16; of their famihes, May 2; and of the cross 

 breeds, April 19. The differences in time of hatching may 



* Unless otherwise indicated, a high producer is a bird that lays 30 or more 

 eggs before March 1 of her pullet j^ear. 



