No. 5S1] 



INHERIT A AY K OV II-' IXI'lTY 



317 



paragraph of the quotation, and I think that the explana- 

 tion of the discrepancy there is contained in the closing 

 words of the paragraph where Mr. Steane says: 



The pullets were . . . inclined to be delicate and more or less under- 

 sized, while the percentage of fertile eggs was lessened. 

 This would indicate that other causes besides the breed- 

 ing operations were working to bring about a poor physio- 

 logical condition of the progeny, which is of course incon- 

 sistent with high productivity. Lowered fertility of eggs 

 is one of the best indicators of reduced vitality which can 

 be found. 



We appear to have, in this case, a rather complete inde- 

 pendent confirmation by a practical poultryman of one of 

 the present writer's chief results in regard to the inher- 

 itance of fecundity. 



III. Summary 

 In this paper it has been shown that : 



1. There is a marked difference in average egg produc- 

 tion per bird of Barred Plymouth Rock pullets of the 

 Maine Station strain at the present time as compared 

 with what obtained during the period of simple mass- 

 selection for this character. 



2. This difference is in the direction of a substantially 

 higher mean production at the present time, when tested 

 on flocks of large size. 



3. The increase in flock average productivity is most 

 pronounced in respect to winter production, which is the 

 laying cycle to which especial attention has been given in 

 the breeding. 



4. The cause of this increase in flock productivity ap- 

 pears, with a degree of probability which is very high and 

 amounts nearly to certainty, to be that the method of 

 breeding the stock now followed is more closely in accord 

 with the mode of inheritance of fecundity than was the 

 simple mass-selection practised in the earlier period. 



5. The result announced in earlier papers that high 

 fecundity is a sex-linked character, for which the female 

 is heterozygous, has been confirmed by practical poultry- 

 men in their breeding operations. 



