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THE AMEBIC AN NATURALIST [Vol. XL V 



throw the whole case out of court 3 by 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 pre- 

 sent 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 present 

 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. For reasons which have been dis- 

 cussed in detail elsewhere 4 the unit of study has been 

 taken as the egg production of the bird before March 1 

 of her pullet year. This ' ' winter production" is a better 

 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" records, comprising all eggs laid up to 

 March 1 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 1 to March 1 production 

 is 36.1.2 eggs. 5 This figure is based on eight years con- 

 tinuous trap-nesting of the flock with which the present 



3 Pearson, K., "Darwinism, Biometry and some Eecent Biology, I," 

 Biometrika, Vol. 7, pp. 368-385, 1910. 



* Bull. Me. Agr. Exp. Bta., No. 166. U. S. Dept. Agr. Bur. Anim. Ind., 

 Bui. 110, Part II. 



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

 November 1 to March 1 records are available as a "winter" record. Since 

 that time the small number of eggs laid before November 1 (on the average 

 two or three per bird) are included in the "winter" totals. These, then, 



