Principles of Heredity 115 



Every case therefore which obeys the Mendelian principle 

 is in direct contradiction to the proposition to which Pro- 

 fessor Weldon's school is committed, and it is natural that 

 he should be disposed to consider the Mendelian principle 

 as applying especially to "alternative" inheritance, while 

 the law of Galton and Pearson is to include the phenomenon 

 of blended inheritance. The latter, he tells us, is "the 

 most usual case," a view which, if supported by evidence, 

 might not be without value. 



It is difficult to blame those who on first acquaintance 

 concluded Mendel's principle can have no strict application 

 save to alternative inheritance. Whatever blame there is 

 in this I share with Professor Weldon and those whom he 

 follows. Mendel's own cases were almost all alternative ; 

 also the fact of dominance is very dazzling at first. But 

 that was two years ago, and when one begins to see clearly 

 again, it does not look so certain that the real essence of 

 Mendel's discovery, the purity of germ-cells in respect of 

 certain characters, may not apply also to some phenomena 

 of blended inheritance. The analysis of this possibility 

 would take us to too great length, but I commend to those 

 who are more familiar with statistical method, the consider- 

 tion of this question : whether dominance being absent, 

 indefinite, or suppressed, the phenomena of heritages 

 completely blended in the zygote, may not be produced 

 by gametes presenting Mendelian purity of characters. 

 A brief discussion of this possibility is given in the 

 Introduction, p. 31. 



Very careful inquiry would be needed before such a 



possibility could be negatived. For example, we know 



that the Laws based on Ancestry can apply to alternative 



inheritance ; witness the case of the Basset-hounds. Here 



' there is no simple Mendelian dominance ; but are we sure 



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