depends on the presence or absence of three separate factors 

 which act in a Mendehan manner. These factors are : — 1. 

 A fecundity factor (A, a), making for a winter production 

 of less than thirty eggs; 2. a sex-hnked fecundity factor 

 (B,b), also making for a winter egg-production of less than 

 thirty eggs; when these two factors are joined a winter pro- 

 duction of more than thirty eggs occurs; and 3. sex factors 

 of the WZ type of inheritance, the female being heterozy- 

 gous and the male homozygous, and the factor for female - 

 ness being linked with the recession fecundity factor b. 



Pearl's three groups of hens probably represent six 

 genotypes: WBAZbA, WBAZba, forming the high producers 

 of group 1 ; WBaZba, WbAZbA, WbAZba forming group 2, 

 and WbaZba forming group 3. 



The cocks would be divided into two groups represent- 

 ing nine genotypes: WBAWBA, WBAWBa in group 1, 

 from which can be expected high producing daughters; and 

 WBaWBa, WBAWbA, WBAWba, WBaWba, WbAWbA, 

 WbAWba and WbaWba. 



" It is, therefore, no use simply to select hens from moth- 

 ers with high egg production, since the factor which deter- 

 mines this character is transmitted by the mot)ier only to 

 her male offspring." To get a strain of high producers 

 "the father of the selected hens should be the son of a hen 

 with high egg production, and only by mating such cocks 

 with hens which themselves are good layers can a pure strain 

 be built up." 



(See also Babcock and Clausen, pp 560-562 and 585- 

 590, and Wilson pp. 99-103). 



What proofs (besides that mentioned above) can be 

 given for the belief that high fecundity is inherited from 

 the sire ? 



In the cases of Drosophila, man and sheep, it will be 

 observed that the male transmits certain characters to his 

 daughters only, while in the cases of Abraxas and Fowl the 

 female transmits certain characters to her sons only. In 

 the former cases the characters appear in the males and are 

 transmitted by the females That is, if a color-blmd man 

 marries a normal woman the offspring are normal. But if 

 a daughter marries a normal man some of the sons will be 

 color blind. 



If a white-eved male Drosophila is mated to a red-eyed 

 female the offspring are red-eyed. If these are mbred all 

 the F2 daughters are red-eyed, but half the sons are white- 



119 



