69<s 



THE AMERICAN NATURALIST 



[Vol. XL VI 



five years, there was available as a foundation, without 

 which the results here discussed could not have been 

 reached, nine years of continuous trap-nest records for 

 Barred Plymouth Eocks, involving thousands of birds, 

 which had been subjected during this long period to mass 

 selection for increased egg production. ■ 



Altogether it may fairly be said that the material on 

 which this work is based is (a) large in amount, (b) ex- 

 tensive in character, and (c) in quality as accurate as it is 

 humanly possible to get records of the egg production of 

 fowls. 2 On these accounts the facts presented seem 

 worthy of careful consideration, and to have a perma- 

 nent value quite apart from any interpretation which 

 may be put upon them. 



The essential facts brought out in this study of fe- 

 cundity appear to be the following: 



1. The record of fecundity of a hen, taken by and of 

 itself alone, gives no definite, reliable indication from 

 which the probable egg production of her daughters may 

 be predicted. Furthermore mass selection on the basis 

 of the fecundity records of females alone, even though 

 long continued and stringent in character, failed com- 

 pletely to produce any steady change in type in the di- 

 rection of selection. 



2. Fecundity must, however, be inherited since (a) 

 there are widely distinct and permanent (under ordi- 

 nary breeding) differences in respect of degree of fe- 

 cundity between different standard breeds of fowls com- 

 mon W kept by poultrymen, and (b) a study of pedigree 

 records of poultry at once discovers pedigree lines (in 

 some measure inbred of course) in each of which a defi- 

 nite, particular degree of fecundity constantly reappears 

 generation after generation, the "line" thus "breeding 

 true" in this particular. With all birds (in which such 

 a phenomenon as that noted under b occurs) kept under 

 the same general environmental conditions such a result 



'Pearl, E., "On the Accuracy of Trap-nest Eecords," Me. Agr. Expt. 

 Sta. Ann. Kept, for 1911, pp. 186-193. 



