of Heredity 13 



reality ; though whether some of the cases that depart 

 most widely from it can be brought within the terms of 

 the same principle or not, can only be decided by further 

 experiments. 



One may naturally ask, How can these results be 

 brought into harmony with the facts of hybridisation 

 hitherto known ; and, if all this is true, how is it that 

 others who have carefully studied the phenomena of hy- 

 bridisation have not long ago perceived this law ? The 

 answer to this question is given by Mendel at some length, 

 and it is, I think, satisfactory. He admits from the first 

 that there are undoubtedly cases of hybrids and cross-breds 

 which maintain themselves pure and do not break up. 

 Such examples are plainly outside the scope of his law. 

 Next he points out, what to anyone who has rightly 

 comprehended the nature of discontinuity in variation is 

 well known, that the variations in each character must be 

 separately regarded. In most experiments in crossing, 

 forms are taken which differ from each other in a multi- 

 tude of characters some continuous, others discontinuous, 

 some capable of blending with their contraries, while others 

 are not. The observer on attempting to perceive any 

 regularity is confused by the complications thus intro- 

 duced. Mendel's law, as he fairly says, could only appear 

 in such cases by the use of overwhelming numbers, which 

 are beyond the possibilities of practical experiment. Lastly, 

 no previous observer had applied a strict statistical method. 



Both these answers should be acceptable to those who 

 have studied the facts of variation and have appreciated 

 the nature of Species in the light of those facts. That 

 different species should follow different laws, and that the 

 same law should not apply to all characters alike, is exactly 

 what we have every right to expect. It will also be 



