154 MAINE AGRICULTURAL EXPERIMENT STATION. I9II. 



asserting that fecundity is not inherited in fowls, and that the 

 present writer's investigations show essentially nothing more 

 than that. It will be the purpose of this paper to present some 

 figures sufficient to indicate with some degree of probability, I 

 think, first that egg production in fowls is inherited, and second 

 that it is probably inherited in accord with the genotype concept, 

 in spite of the fact that we do not and can not here have "pure 

 lines" in the strict sense of Johannsen's definition. In the pres- 

 ent paper, owing to limitations of space, the whole of the data 

 in hand obviously can not be presented. Only a few illustrative 

 cases can be given here. 



Before entering upon the discussion of the evidence it is 

 necessary to call attention to two points. The first is in regard 

 to the unit of measuring egg production used in the work. Kor 

 reasons which have been discussed in detail elsewhere * the unit 

 of study has been taken as the egg production of the bird before 

 March i of her pullet year. This "winter production" is a bet- 

 ter unit for the study of the inheritance of fecundity than any 

 other which can be used practically. All records of production 

 given in this paper are then to be understood as "winter" rec- 

 ords, comprising all eggs laid up to March i of the first year of 

 a bird's life. It may be said that the "normal" mean winter 

 production of Barred Plymouth Rocks (the breed used in this 

 work) is fairly indicated by the 8-year average of the Maine 

 Station flock. This average November i to March i produc- 

 tion is 36.12 eggs.* This figure is based on eight years con- 

 tinuous trapnesting of the flock with which the present work 

 was done, carried out before these investigations were begun. 



In the second place it is desirable to call attention to some of 

 the difficulties which attend an attempt to analyze the inheritance 

 of the character egg production. The most important of these 

 is the fact that this character is not visibly or somatically ex- 

 pressed in the male. A male bird may carry the genes of high 



* Bull. Me. Agr. Exp. Sta., No. 165. U. S. Dept. Agr. Bur. Anim. Ind., 

 Bui. no, Part II. 



* It should be said that up to and including the winter of 1907 only 

 the November i to March i records are available as a "winter" record. 

 Since that time the small number of eggs laid before November i (on 

 the average two or three per bird) are included in the "winter" totals. 

 These, then, give, as stated, the total production up to March i. 



