Principles of Heredity 177 



on the other but he does not tell us how he proposes to 

 apply them. 



In the cross between the albino and the grey von Fischer 

 tells us that both colours appear in the offspring, but always, 

 without exception or variation, that of the father only, in 

 5847 individuals. 



Surely, the law of ancestry, if he had a moment's 

 confidence in it, might rather have warned Professor 

 Weldon that von Fischer's results were wrong somewhere, 

 of which there cannot be any serious doubt. The precise 

 source of error is not easy to specify, but probably careless- 

 ness and strong preconception of the expected result were 

 largely responsible, though von Fischer says he did all the 

 recording most carefully himself. 



Such then is the evidence resting " on excellent 

 authority": may we some day be privileged to see the 

 "examples which may be doubted"? 



The case of mice, invoked by Professor Weldon, has 

 also been referred to in our Report. Its extraordinary 

 value as illustrating Mendel's principles and the beautiful 

 way in which that case may lead on to extensions of those 

 principles are also there set forth (see the present 

 Introduction, p. 25). Most if not all of such "conflicting" 

 evidence can be reconciled by the steady application of 

 the Mendelian principle that the progeny will be constant 

 when and only when* similar gametes meet in fertilisa- 

 tion, apart from any question of the characters of the 

 parent which produces those gametes. 



* Excluding "false hybridisations." 



12 



