116 A Defence of Menders 



there is no purity of germ-cells ? The new conception goes 

 a long way and it may well reach to such facts as these. 



But for the present we will assume that Mendel's 

 principle applies only to certain phenomena of alternative 

 inheritance, which is as far as our warrant yet runs. 



No close student of the recent history of evolutionary 

 thought needs to be told what the attitude of Professor 

 Weldon and his followers has been towards these same 

 disquieting and unwelcome phenomena of alternative 

 inheritance and discontinuity in variation. Holding at 

 first each such fact for suspect, then treating them as rare 

 and negligible occurrences, he and his followers have of 

 late come slowly to accede to the facts of discontinuity a 

 bare and grudging recognition in their scheme of evolution*. 



Therefore on the announcement of that discovery which 

 once and for all ratifies and consolidates the conception of 

 discontinuous variation, and goes far to define that of 

 alternative inheritance, giving a finite body to what before 

 was vague and tentative, it is small wonder if Professor 

 Weldon is disposed to criticism rather than to cordiality. 



We have now seen what is the essence of Mendel's 

 discovery based on a series of experiments of unequalled 

 simplicity which Professor Weldon does not venture to 

 dispute. 



* Bead in this connexion Pearson, K., Grammar of Science, 2nd 

 ed. 1900, pp. 3902. 



Professor Weldon even now opens his essay with the statement 

 or perhaps reminiscence that " it is perfectly possible and indeed 

 probable that the difference between these forms of inheritance 

 [blended, mosaic, and alternative] is only one of degree." This may be 

 true; but reasoning favourable to this proposition could equally be 

 used to prove the difference between mechanical mixture and chemical 

 combination to be a difference of degree. 



