80 INHERITANCE IN POULTRY. 



The result of the breeding experiments described herein bears upon this 

 discussion. No other group, I imagine, exhibits so many characteristics as 

 poultry ; of the comb alone there are half a dozen forms. The forms of 

 feathers and their color patterns are numerous. These forms are sharply 

 marked off from one another for the most part ; moreover, when two char- 

 acteristics are crossed the result is rarely a blend. This was a great surprise 

 to me, as I had anticipated that blends would be the rule ; and, overwhelmed 

 by the facts, I embraced at once the theory of immutable characteristics. 



That there are unit characters in poultry can not be doubted. When single 

 and V comb are crossed and progeny obtained all w r ith a Y comb, how con- 

 vincingly do the second hybrids reproduce the single comb in some individuals 

 and the V comb in others ! Though the cerebral hernia and its associated 

 great crest may disappear in the first generation of hybrids, how beautifully 

 do they reappear in one-fourth of the offspring of such hybrids ! How in- 

 structive is it to see perfectly plain feathered offspring arising from a frizzled 

 pair, or in a Black Minorca X Dark Brahma white-laced hackles appearing 

 in an otherwise dead- black plumage ! Truly we may hope, as in chemistry, 

 to make various kinds of molecules by the proper admixture of our atoms 

 the characteristics. Even in man such non-blending characteristics are evi- 

 dent. One of the most famous is the Hapsburg lip or chin, which from the 

 fifteenth century has persisted to the present day despite infusion of new 

 blood during fifteen generations.* Another striking case is that of Irypo- 

 phalangia in man, described by Farabee (1905). In the four or five gener- 

 ations studied, there has, he states, "never been a single instance of partial 

 inheritance, but in all cases all extremities have been affected in precisely 

 the same way." 



While admitting, thus, the reality of unit characters, the further study of 

 the evidence of hybridization in poultry has led me away from the conception 

 that they are rigid and immutable as atoms are, which may be combined 

 and recombined in various way and always come out of the process in their 

 pristine purity. This is by no means the case. Very frequently, if not 

 always, the character that has been once crossed has been affected by its 

 opposite with which it was mated and whose place it has taken in the hybrid. 

 It rnay be extracted therefrom to use in a new combination, but it will be 

 found to be altered. This we have seen to be true for almost every char- 

 acteristic sufficiently studied for the comb form, the nostril form, cerebral 

 hernia, crest, muff, tail length, vulture hock, foot- feathering, foot color, ear- 

 lobe, and both general and special plumage color. Everywhere unit char- 

 acters are changed by hybridizing. 



How does this fact bear on the rival theories of evolution ? It has an im- 

 portant bearing on them. It is not in accord with the statements of de Vries 



* Cf. F. A. Woods, 1902-03. 



