176 ANIMAL LIFE AND HUMAN PEOGEESS 



tration I choose some experiments with poultry carried 

 by the late Major P. G. Baijey and myself. We crossed the 

 Sebright bantam with one of the smaller full-sized breeds, the 

 gold-pencilled Hamburgh. Eoughly speaking, the Hamburgh 

 is about double the weight of the Sebright. The first-cross 



900 1000 iioo 1200 /3oo 



FIG. 8. Diagram showing the experimental results obtained by crossing 

 silver Sebright bantams with a gold -pencilled Hamburgh cock. Since in 

 poultry the hen is always lighter than the cock, the F^ hens have been 

 " weighted," i.e. multiplied by a constant factor (found experimentally), to 

 bring their weights up to those of the corresponding cocks. In the F 2 

 generation the records of the cocks only are shown. A similar result was 

 obtained for the hens. 



birds were intermediate in size, though they approximated 

 more closely to the larger Hamburgh (Fig. 8). Bred 

 together they gave rise to an F 2 generation ranging from 

 birds smaller than the Sebright to birds larger than the Ham- 

 burgh, the majority, as the curve shows, being intermediates of 

 various weights. 



