No. 546] MENDELIAN PROPORTIONS 347 



In Table III a few possible matings are shown with 

 the percentage of recessives and the constant ratios 

 which appear in the next generation. It is apparent 

 from examination of the figures that if a disturbance 

 takes place there is often a partial return in the next 

 generation to the original condition. Sometimes this 

 return is complete, as would occur if, beginning with the 

 ratio of 1:2:1, some disturbance should make it 1:1:1. 

 In the next generation there would be a return to the 

 1:2:1 condition. There were 25 per cent, of recessives 

 at the beginning. This became changed to 33.3 per cent, 

 by mutation but returned in the next generation to 25 

 per cent. 



TABLE III 



But there is not always a diminution of this kind. If 

 the original ratio be 4:4:1, which is constant, and this 

 be changed by mutation to 4:6:1, the original 11.1 per 

 cent, of recessives is at first reduced to 9 per cent., only 

 to rise in succeeding generations to 13.2 per cent. It is 

 very easy to overestimate the importance of the tend- 

 ency to return to a stable ratio, since such stable ratios 

 are practically without limit, and instead of returning 

 to the same ratios, it is easily possible to reach stability 

 in a new ratio somewhat different from the original. 

 This may be shown by an example (Table IV). 



