HEREDITY AND MENDEl/s EAW 1 87 



know in a general way that progressive characteristics dominate 

 over the more embryonic ; but we liave to learn the meaning of 

 individual potency and tlie reason why some pairs of character- 

 istics exhibit equipotency or heteropotency and others allelo- 

 potency. As ever in science the formulation of a law only 

 awakens a new series of inquiries. 



DISCUSSION. 

 By W. J. SriLLMAN. 



In listening; to the address of Doctor Davenport, this evening, it has oc- 

 curred to me that I might be able to suggest a possible explanation of one of 

 the characteristics noted in the offspring of the hooded fowl. Professor Bate- 

 son made many experiments with walnut-combed fowls, interbreeding them 

 with a single-comb, finding the walnut-comb to be compounded of the pea- 

 comb and the rose-comb. 



It is possible that the " hood " is composed of two characters intead of be- 

 ing a single element in itself. 



Suppose the hood character to depend upon two factors 7" and /, and that 

 T is much more important than / in producing the character. The allelo- 

 morphic formula of the pure hooded fowl would then be TT, tt ; gametes It 



The formula of fowls with plain heads is 00, 00 ; gametes Oo. The cross 

 is rO, to; gametes Tt, TO, Ot, Oo. 



Fortuitous union of these gametes gives 



If 7" alone is difficult to distinguish from 7"and /together, this would give 

 twelve hoods and four smooth or nearly smooth heads, or three hoods to one 

 smooth head, which agrees with Dr. Davenport's results. But of the smooth 

 heads three-quarters would show the slight tendency to the hooded condition, 

 due to the presence of character /, provided, of course, my suggestion is cor- 

 rect. This explanation is merely an hypothesis and may or may not be correct. 



