No. 590] FECUNDITY IN THE DOMESTIC FOWL 93 



This of course is the reason for the progeny test. I do 

 not think I am in any sense exaggerating if I say that it is 

 one of the chief results of the Mendelian method of study- 

 ing inheritance to show that in many cases and for many 

 characters it is impossible, in the absence of a progeny 

 test, to be sure of the genetic constitution of the individual 

 from an examination of the soma alone. I fancy that if I 

 cared to be fussily nasty in my controversial methods I 

 could cite page after page from Professor Castle's Men- 

 delian writings where even he, in order to be quite sure 

 about the genetic constitution of an individual, has had to 

 breed it. This is all I mean by the progeny test. Why 

 am I and my fowls held up to scorn and ridicule because 

 I say that it is frequently impossible to tell the genetic 

 constitution of a fowl with respect to fecundity without 

 breeding it 1 Surely fecundity in poultry and coat color 

 in rats only differ in this respect in degree, if they differ 

 at all, not in kind. I think if any one will read pp. 604 and 

 605 of my last Naturalist paper, which is the immediate 

 objective of Professor Castle's attack, he will have to 

 admit that the interpretation which I give of the earlier 

 results is not entirely senseless, and might indeed explain 

 them. In any case, it is in thorough accord, methodolog- 

 ically considered, with the very best current Mendelian 

 usage, including that of Professor Castle himself. 



IV 



This brings us to the most serious phase of Castle's at- 

 tack, namely that in which he denies the validity of my 

 conclusions respecting the inheritance of the character 

 fecundity in fowls. 



On the top of p. 716 he asserts that I "assume'' that 

 two Mendelizing factors are concerned in the inheritance 

 of fecundity, "but without any sufficient published evi- 

 dence for either conclusion. " As I have published 3 many 

 Pages of evidence in demonstration of my conclusions on 

 this point, one can only infer from this statement of 



3 In particular in the Journal of Experimental Zoology, Vol. 13, 1912. 



