INHERITANCE OF FECUNDITY 265 



high genotype with regard to those characters; then it is to be expected, 

 on the hypothesis under consideration, that his progeny will tend on the 

 average to be like himself in performance regardless of what he is mated 

 with, because any female to which he is mated will be either of a high 

 genotype like himself or of a lower one. But if genotypic high perform- 

 •ance is dominant over genotypic lower performance, than all the off- 

 spring in the first generation must approximate to the high condition 

 exemplified in the sire. But this is the very essence of what is called 

 prepotency in actual breeding practice. 



It seems to me that certain of the facts set forth in this paper 

 give strong support to this view. A class 1 B.P.R. cf ( = /L1L2 . 

 /LiLo) will get all high producing daughters (barring physio- 

 logical defects of development) regardless of the females to which 

 he is mated. He will show all the objective phenomena of 'pre- 

 potency.' B.P.R. cf 550 is an example of this. A class 7 B.P.R. 

 male would, in breeders' parlance, be regarded as less prepotent 

 then a class 1 male, but, even so, more prepotent than the general 

 run of the flock. 



The essential point here should not be misunderstood. It is 

 not, of course, contended that simple Mendelian 'dominance' 

 in general, and prepotency are the same thing. More than that 

 is demanded. It is only suggested that a homozygous dominant 

 individual, when high performance is dominant over low, has all 

 the objective characteristics of a prepotent individual in the 

 breeder's sense. 



That this suggestion explains all the facts regarding prepo- 

 tence is by no means asserted. It seems to me, however, that 

 it does furnish the explanation for a part of the phenomena at 

 least, and by so much helps towards a final solution, since it 

 brings us nearer to the kernel of the problem. 



The practical hearing of these results 



To the practical poultryman the data and conclusions of this 

 paper would appear to have some significance. They make it 

 possible to outline a scheme of breeding for increased egg pro- 

 duction which shall be intelligently directed towards the attain- 

 ment of that end. This, however, is not the place to discuss such 

 a scheme. That will be undertaken later in another place. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 13, NO. 2 



