Inheritance of Characteristics in Domestic Fowl

by Charles Benedict Davenport

Both parents with right lop.
Pen No.	No. of mother.	No. of father.	Offspring.
			Right.	Left.
817	6188	3900	7	8
817	6406	3900	12	17
831	1011	4213	7	16
831	3040	4213	13	10
831	4219	4213	4	21
831	6602	4213	6	15
833	1310	4222	4	7
833	4361	4222	6	4
833	7519	4222	2	4
904	4714	7870	6	7
			67	109
Both parents with left lop.
841	3867	3890	3	9
841	4663	3890	9	7
903	9824	8463	6	5
			18	21
Mother left lop, father right.
831	1980	4213	9	17
904	3901	7840	4	3
904	7645	7840	6	3
			19	23
Mother left lop, father right.
903	3946	8463	2	0
903	4079	8463	7	2
903	4082	8463	11	6
			20	8
Summary.
Parents		Offspring.
		Total.	Right.	Left.
			P. ct.	P. ct.
Both with right lop		176	38	62
Both with left lop		39	46	54
Mother left lop, father right		42	45	55
Mother right lop, father left		28	71	29

From table 56 it appears, summing all cases, that there are more left-lopping offspring than right-lopping as 161 to 124 or as 56.5 per cent to 43.5 per cent and that this excess holds whether both parents are right-lopping, or both left-lopping, or the mother left and the father right. Only in the case when the mother is right-lopping is there a majority of offspring of the same sort, but here the numbers are too inconsiderable to carry much weight. Although there is not clear evidence of any sort of inheritance, it is probable that the position of the lop is not determined by a single factor, but by a complex of factors.

The conclusion that right and left conditions are not simple, alternative qualities accords with the results obtained by others. Thus Larrabee (1906) finds that the dimorphism of the optic chiasma of fishes (in some cases the right optic nerve being dorsal and in others the left) is not at all inherited, but in each generation the result is strictly due to chance. This is, perhaps, the same as my conclusion that the hereditary factors are complex. Lutz (1908) finds that in the mode of clasping the hands interdigitally the right thumb is uppermost in 73 per cent of the offspring when both parents clasp with right thumb uppermost, but in only 42 per cent of the offspring when both parents clasp with left thumb uppermost. The mode of clasping is inherited, but not in simple Mendelian fashion.

CHAPTER X.
PLUMAGE COLOR.

A. THE GAMETIC COMPOSITION OF THE VARIOUS RACES.

Plumage color, like hair color, varies greatly among domesticated animals. This diversity is, no doubt, in part due to the striking nature of color variations, but chiefly to the fact that the requisite variations are afforded in abundance. The principal color varieties, in poultry as in other domesticated animals, are melanism, xanthism, and albinism. In addition, poultry show the dominant white, or "gray" white, first recognized in poultry by Bateson and Saunders (1902), which is also found in many mammals, as, for instance, in goats, sheep, and cattle. Besides these uniform colors, we find numerous special feather-patterns, such as lacing (or edging of the feather), barring, penciling, and spangling. Also, there are special patterns in the plumage as a whole, such as wing-bar, hackle, saddle, breast, and top of head (crest). Now, all of these color characters are inherited each in its own definite fashion.

In studying the color varieties of poultry we must first of all, as in flower color (Correns, 1902), mice (Cuénot, 1903), guinea-pigs and rabbits (Castle), various plants and animals (Bateson and his pupils), recognize the existence of certain "factors." In poultry the factors that I have determined are as follows:

• C, the color factor, absence of which results in albinism.
• J, the Jungle-fowl pattern and coloration.
• N (nigrum), the supermelanic factor.
• X, the superxanthic or "buff" factor.
• W, the graying (white) factor.

We have now to consider how these factors are combined in birds of the different races.