Variation and Heredity 285 



25 per cent recessive egg-cells; while the remaining 50 per 

 cent of each kind would meet each other. Or, as Mendel 

 showed by the following scheme : — 



Pollen-cells A A a a 



1 X \ 



Egg-cells A A a a 



Or more simply by this scheme : — 



Mendel's results have received confirmation by a number of 

 more recent workers, and while in some cases the results 

 appear to be complicated by other factors, yet there can 

 remain little doubt that Mendel has discovered one of the 

 fundamental laws of heredity. 



It has been found that there are some cases in which the 

 sort of inheritance postulated by Mendel's law does not seem 

 to hold, and, in fact, Mendel himself spoke of such cases. 

 He found that some kinds of hybrids do not break up in 

 later generations into the parent forms. He also points out 

 that in cases of discontinuity the variations in each character 

 must be separately regarded. In most experiments in cross- 

 ing, forms are chosen which differ from each other in a 

 multitude of characters, some of which are continuous and 

 others discontinuous, some capable of blending with their 

 contraries while others are not. The observer in attempting 

 to discover any regularity is confused by the complications 

 thus introduced. Mendel's law could only appear in such 

 cases by the use of an overwhelming number of examples 

 which are beyond the possibilities of experiment. 1 



Let us now examine the bearing of these discoveries on 



1 This statement is largely taken from Bateson's book. 



