154 RAYMOND PEARL 



Summary of Fi matings 231 



Matings of the second cross-bred (F2) generation 232 



Matings of Fi cT 576 with Fi females 234 



Matings of Fi cf 577 with Fi females 236 



Matings of Fi cf 576 with Barred Plymouth females. . .' 238 



Matings of Fi c?' 576 with Cornish Indian Game females 239 



Matings of Fi cf 577 with Barred Plymouth females 239 



IVIatings of Fi cf 577 with Cornish Indian Game females 240 



Matings of Barred Plymouth Rock males with Barred Fi females. . . 240 



Matings of Barred Plymouth Rock males with Black Fi females 243 



Matings of Cornish Indian Game males with Black and Barred Fi 



females 246 



Summary and discussion of results 250 



The facts and their interpretation 250 



Possible criticisms 256 



Selection problem 261 



Prepotency 264 



The practical bearing of these results 265 



Literature cited 266 



INTRODUCTION 



During the course of an investigation into the inheritance of 

 fecundity in the domestic fowl, which has now involved thirteen 

 generations and several thousand individuals, and has occupied 

 the major portion of the writer's time during the past five years, 

 two definite and clear-cut results have come to light.- These 

 are: 



First: that the record of egg production or fecundity of a hen 

 is not of itself a criterion of any value whatsoever from which to 

 predict the probable egg production of her female progeny. An 

 analysis of the records of production of large numbers of birds 

 shows beyond any possibility of doubt that, in general, there is no 

 correlation between the egg production of individuals and either 

 their ancestors or their progeny. 



Second: that, notwithstanding the fact just mentioned, fecun- 

 dity is, in some mar ner or other, inherited in the domestic fowl. 

 This must clearly be so, to mention but a single reason, because it 

 has been possible to isolate and propagate from a mixed flock 



- For a complete list to date of the publications, in which the results of the inves- 

 tigation referred to have appeared, see the bibliography at the end of this paper. 

 Throughout this paper numbers in parentheses refer to titles in the bibliography. 



