96 INHERITANCE OF CHARACTERISTICS IN DOMESTIC FOWL. 



In 1907 I mated a prevailingly white male of the preceding year, that 

 had red wing-bar, hackle, and breast, with the reddest females and obtained, 

 along with pure whites and blacks and barred birds, these colors combined 

 with red in various degrees, but not clearly in advance of the reddest of 

 1906. In 1908 I mated a white male, having red as in the Game, with my 

 reddest hybrids. Again, white and white-and-buff birds appeared, but they 

 showed no advance, except in one instance, among 138 young. This indi- 

 vidual (No. 7950), derived exclusively from the Black-red Game and White 

 Leghorn on one side and on the other from the White Leghorn-Game Ban- 

 tam cross, had a uniform buff down. Unfortunately the chick quickly died. 



The conclusion is that after three years of selection of the reddest off- 

 spring no appreciable increase of the red was observed except for the 

 remarkable case of one undeveloped chick with completely buff down. This, 

 indeed, looks like a sport, or, perhaps, it is due to unsuspected factors. 

 The experiment will be continued. 



F. NON-INHERITABLE CHARACTERS. 



So well-nigh universal is heredity that it is justifiable to entertain a 

 doubt whether any character may fail of inheritance. So far as my experi- 

 ence goes, non-inheritable characters are such as are weak in ontogeny, 

 so that they may readily fail of development even when conditions are 

 propitious; or else they are so complex so far removed from simple unit- 

 characters that their heritability in accordance with established canons 

 is obscured. The first case is apparently illustrated by the rumpless cock 

 (No. 117) and the wingless fowl; the second case by lop-comb and by right- 

 and-left alternatives in general. 



Apart from the distinct characters that fall under these two categories 

 there are the fluctuating quantitative conditions. These depend for the 

 most part, as already pointed out, on variations in the point at which the 

 ontogeny of a character is stopped; and the stopping-point is, in turn, 

 often, if not usually, determined by external conditions which favor or 

 restrict the ontogeny. Whether or not such quantitative variations are 

 transmitted is still doubtful. Our experiment in increasing quaUties, such 

 as redness in plumage-color, by selection of quantitative fluctuations have 

 not been successful in the sense anticipated; neither have selections of 

 comb, polydactylism, or syndactylism. Recently, prolonged attempts at 

 the Maine Agricultural Experiment Station to increase egg-yield of poultry 

 by selection have been without result. Apparently, within limits, these 

 quantitative variations have so exclusively an ontogenetic signification 

 that they are not reproduced so long, at least, as environmental conditions 

 are not allowed to vary widely. 



The conclusions which others have reached, and upon which de Vries 

 has laid the greatest stress, that quantitative and qualitative characters 

 differ fundamentally in their heritabihty is supported by our experiments. 



