No. 590] FECUNDITY IN THE DOMESTIC FOWL 



95 



character within the race, without crossing, by the above 

 scheme. 



The next step was the definition of the categories of 

 the character winter egg production. From long study 

 of the character I concluded that the natural categories 

 in this strain were (a) zero winter production, (b) winter 

 production between zero and 30 eggs, and (c) a winter 

 production of over 30 eggs. These were chosen as work- 

 ing categories. If any one will turn to p. 719 of Profes- 

 sor Castle's paper and examine Fig. 1, which is there 

 printed, they will find that even he chooses categories of 

 the character with which he is working. Nowhere have 

 these ever been quantitatively defined; nowhere has he 

 ever presented any evidence that the step from his rat 

 grade + 1 (for example) to his grade + 2 represents a 

 more or less inclusive category than a difference in winter 

 production of from to 30 eggs. Professor Castle reads 

 us a beautiful little homily about Mendel's peas. But I 

 am not clear that either Mendel or Castle has shown that 

 the amount of variation within the category " yellow" is 

 less than the amount of variation within my fecundity 

 category of 4 'under 30. ' ' From the only study which has 

 ever been made of the matter, Weldon's, 6 I should cer- 

 tainly conclude that the category ' ' under 30" in winter 

 egg production carries within itself distinctly less varia- 

 tion than the category "yellowness" in peas. Castle's 

 assertion about my fecundity categories ill becomes one 

 whose work in genetics has dealt almost without a single 

 exception with non-quantitatively defined Mendelian cate- 

 gories. Of course, as a matter of fact, he knows, I know, 

 and everybody knows that the variations within the Men- 

 delizing category are of no significance so far as the Men- 

 delian result is concerned. I happen to have observed, 

 for example, that there are at least four genetically dis- 

 tinct rose combs in poultry. Yet they are all rose; any 

 of them crossed with single gives a 3 : 1 ratio in F 2 . 



6 Weldon, W. F. E., "Mendel's Laws of Alternative Inheritance in 

 Peas," Biometrika, Vol. I, pp. 228-265, 1902. 



