No. 581] 



IXIIEIUTAXCE OF FKCUXDITY 



307 



This material will be published as opportunity offers. 



It is the purpose of the present paper to record certain 

 facts which are pertinent to a general consideration of 

 the problem of inheritance of fecundity, but at the same 

 time do not fall in the direct line of the experimental 

 inquiry. They are matters, in other words, which are 

 essentially by-products of the investigation but still have 

 a more or less important bearing on the interpretation, 

 in a broad sense, of the whole. 



I. The Seasonal Distribution of a Flock Egg Produc- 

 tion UNDER A MENDELIAN SYSTEM OF BREEDING AS 

 COMPARED WITH SlMPLE MASS SELECTION 



The mean egg production per bird in the different 

 months of the laying year has been given by Pearl and 

 Surface 3 in an earlier paper. Those results are based on 

 the weighted mean production of the flocks of Barred 

 Plymouth Rocks at the Maine Agricultural Experiment 

 Station during the ten years that a system of mass-selec- 

 tion was followed in breeding for egg production. 



It is an obvious deduction from the results of the Men- 

 delian experiments recorded in the earlier papers already 

 referred to, that by their application it should be possible 

 to modify the average production of a flock over a rather 

 wide range, the modification being of a fixed and perma- 

 nent character under any definite conditions of environ- 

 ment and breeding. To many practical poultrymen the 

 only test of the validity of the conclusions reached which 

 has any significance, is that of average flock production. 

 It is obvious that from a technically critical point of view 

 such a test has, of itself, relatively small value in helping 

 to judge of the correctness of a Mendelian interpretation. 

 At the same time it is clear that if one takes a flock of 

 poultry of mixed genetic constitution in respect of fecun- 

 dity and aims to preserve in his breeding only animals 

 carrying both the factors L, and L 2 necessary for high 



3 Pearl, R., and Surface, F. M., "A Biometrical Study of Egg Production 

 in the Domestic Fowl." II. Seasonal Distribution of Egg Production," 

 U. S. Dept. of Agr., B. A. I. Bull. 110, Pt. II, pp. 81-170, 1911. 



