A Defence of Mendel's Principles of Heredity 1 05 



to practical naturalists it was evident from the first that 

 there are great groups of facts which could not on any 

 interpretation be brought within the scope of Galton's 

 Law, and that by no emendation could that Law be 

 extended to reach them. The existence of these phen- 

 omena pointed to a different physiological conception of 

 heredity. Now it is precisely this conception that Mendel's 

 Law enables us to form. Whether the Mendelian principle 

 can be extended so as to include some apparently Galtonian 

 cases is another question, respecting which we have as yet 

 no facts to guide us, but we have certainly no warrant for 

 declaring such an extension to be impossible. 



Whatever answer the future may give to that question, 

 it is clear from this moment that every case which obeys 

 the Mendelian principle is removed finally and irretrievably 

 from the operations of the Law of Ancestral Heredity. 



At this juncture Professor Weldon intervenes as a 

 professed exponent of Mendel's work. It is not perhaps 

 to a devoted partisan of the Law of Ancestral Heredity 

 that we should look for the most appreciative exposition of 

 Mendel, but some bare measure of care and accuracy in 

 representation is demanded no less in justice to fine work, 

 than by the gravity of the issue. 



Professor Weldon's article appears in the current number 

 of Biometrika, Vol. I. Pt. n. which reached me on Saturday, 

 Feb. 8. The paper opens with what purports to be a 

 restatement of Mendel's experiments and results. In this 

 " restatement " a large part of Mendel's experiments 

 perhaps the most significant are not referred to at all. 

 The perfect simplicity and precision of Mendel's own 

 account are destroyed ; with the result that the reader of 

 Professor Weldon's paper, unfamiliar with Mendel's own 

 memoir, can scarcely be blamed if he fail to learn the 



