No. COO] PIEBALD BATS AND MULTIPLE FACTOBS 



73:; 



minal fluctuations, one would have difficulty in accounting 

 for the above facts. If these various selected generations 

 differ in the number of multiple factors they bear, one 

 can easily understand that the reason that practically no 

 modification is apparent when the third generation is 

 crossed, is that the number of plus factors in this genera- 

 tion and in the wild are not very different; in the fifth 

 and sixth generations there may be a few more plus fac- 

 tors than in the wild, and in the tenth generation there 

 are several more. 



13. The early generations of the plus race, although 

 only very slightly lowered by crosses with wild, are strik- 

 ingly lowered by crosses with Irish. In a cross in which 

 the hooded parent came from the second generation, the 

 lowering was .83 ; when the hooded parent crossed came 

 from the third generation, the lowering was 1.65. Now 

 how may this fact be interpreted? If the change in the 

 means following a cross be assumed to be due to the ac- 

 tion of different numbers of factors in the races crossed, 

 it is clear that this particular wild is more like the plus 

 race in regard to its factors than is the particular Irish 

 race. In other words the wild race seems to have more 

 plus factors than the Irish race. When early generations 

 of the plus race are crossed with wild there is hardly any 

 change in the averages of the F 2 hoodeds, because there 

 are about the same plus factors in the wild as in these 

 early generations of the plus race. When these same 

 generations of the plus race are crossed with Irish there 

 is a considerable decrease in the averages because there 

 are fewer plus factors in the Irish than in the early gen- 

 erations of the plus race. Now if the germ plasms of the 

 wild and Irish differ in regard to the number of accessory 

 factors, and if the germ plasms of the plus and minus 

 races differ in this same regard, comparisons of all the 

 crosses between these races should show the following 

 results: crosses between wild and minus should give 

 greater modifications in F 2 than crosses between wild and 

 plus; crosses between Irish and minus should modify the 



