INHERITANCE OF FECUNDITY 251 



nish Indian Games; (c) the Fi individuals obtained by reciprocally 

 crossing these two breeds; and {d) the F^ individuals obtained by 

 mating the i^i's inter se and back upon the parent forms in all 

 possible combinations. The fully-pedigreed material made use 

 of in this present paper includes something over a thousand adult 

 females, each of which was trap-nested for at least oiie year, and 

 many for a longer period. This material covers four generations. 

 The birds of the fifth generation have just completed their winter 

 records at the time of writing. Besides this fully pedigreed mate- 

 rial, the collection and study of which has occupied five years 

 there was available as a foundation, without which the results 

 discussed in this page could not have been reached, nine years of 

 continuous trap-nest records for Barred Plymouth Rocks, involv- 

 ing 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 

 paper is based is (a) large in amount, (b) extensive in character, 

 and (c) in quality as accurate as it is humanly possible to get 

 records of the egg production of fowls (Pearl 31). On these 

 accounts the facts presented are worthy of careful consideration, 

 and have a permanent value quite apart from any interpretation 

 which may be put upon them. 



The essential facts brought out in this study of fecundity appear 

 to me 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 completely to produce any steady change in type in the 

 direction" of selection. 



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

 widely distinct and permanent (under ordinary breeding) differ- 

 ences in respect of degree of fecundity between different standard 

 breeds of fowls commonly kept by poultrymen, and (6) a study of 

 pedigree records of poultry at once discovers pedigree lines (in 

 some measure inbred of course) in each of which a definite, parti- 



