BREEDING POULTRY FOR EGG PRODUCTION. I4I 



tion cockerels in house No. 2 have a somewhat lower mean 

 winter production than those in No. i house. These were the 

 last two pens to be mated and it was then not possible any- 

 longer to select as many high layers to offset (in the average) 

 the low layers as had been done in mating up the pens in No. 

 I house. 



4. Considering next the females which produced adult 

 daughters, the differences in winter production are much more 

 marked than when all mated females are taken together. The 

 means in this case, however, stand in the same relation to each 

 other as when all females are included. As would be expected 

 the mean production of the mothers of adult daughters is higher 

 than the mean production of all females bred in the same class. 

 This merely means that the better a hen lays the more likely 

 she is to have adult progeny, because she has more chances. 

 The mothers of adult daughters of foreign cockerels have a 

 mean winter production more than i6 eggs higher than that of 

 the mothers of daughters of the two Station males in house No. 

 2. The difference is much smaller between the two sets of 

 mothers in house No. i though there it is probably statistically 

 significant. The females in the out-cross matings which pro- 

 duced adult daughters thus have the higher egg production 

 records. If this factor has any influence at all it would evi- 

 dently act in accord with any beneficial result of the outcross- 

 ing itself to help to produce higher laying in the progeny. 



Let us turn next to the results of the experiment. ' The fre- 

 quency distributions for the winter * and spring (March i to 

 June i) egg production of the daughters of (a) foreign cock- 

 erels, (b) Station cockerels in house No. i and (c) Station cock- 

 erels in house No. 2 are given in Table E. 



The usual biometric constants for these distributions are pre- 

 sented in the following table. 



The means of Table F are shown graphically in fig. yy. 



* Cf. p. 154 infra. 



