BREEDING POULTRY FOR EGG PRODUCTION. 1 53 



ing merely a somatic basis. But specifically how far has the* 

 genotype concept any application in case of ' "non-self ed" or- 

 ganisms ? Johannsen in his "Elemente" has thoroughly analyzed 

 Galton's material and shown that it is capable of a satisfactory 

 and reasonable interpretation on the genotype hypothesis, and 

 East and Shull have gone far in the analysis of genotypes in 

 maize. This, however, is only a beginning. There is the great- 

 est need for careful, thorough investigations of the inheritance 

 of characters showing marked fluctuating variation in organisms 

 having the sexes separate. Here lies one of the crucial fields 

 in the study of inheritance to-day. Through the brilliant re- 

 sults in Mendelian 'directions and from the study of really 

 "pure" lines v/e are getting clear-cut ideas as to the inheritance 

 of qualitatively difl'erentiated characters, such as color, pattern 

 and the like, on the one hand, and in regard to the inheritance 

 of quantitative variation in self-fertilized or non-sexually re- 

 producing organisms, on the other hand. But beyond all these 

 lie the difficult cases where in dioecious forms quantitative varia- 

 tions must be dealt with. If these can be cleared up and 

 brought harmoniously into a general scheme or view-point re- 

 garding inheritance, we shall have gone a long way in the solu- 

 tion of this world-old biological problem. 



For some four years past the writer has been engaged in a 

 study of the inheritance of fecundity in the domestic fowl. The 

 problem presented here is an important one from the practical 

 as well as the theoretical standpoint. If definite and sure meth- 

 ods of improving the average egg production of poultry by 

 breeding can be discovered it will mean much to the farmers of 

 the nation. At the same time egg production is a character ad- 

 mirably adapted to furnish definite and crucial data regarding 

 inheritance. Variations in egg production are readily measured, 

 and can be directly expressed in figures. 



The general results of this study of the inheritance of fecun-^ 

 dity may be said, in a word, to be so far as they go in entire 

 accord with the genotype concept, and not to agree at all with 

 the "statistico-ancestral" theory of inheritance. Indeed so ill 

 is the accord here that the chief exponent of the latter doctrine 

 has recently attempted to throw the whole case out of court * by 



* Pearson, K., "Darwinism, Biometry and some Recent Biology, I,' 

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



