Comparing observed results in the distribution of colors in the F2 generation with expectation, it is seen that the proportions are close, and this closeness of observation with expectation is evidence for the correctness of the hypothesis.

The hypothesis may be further tested in later generations by breeding together the different sorts of individuals obtained in F2. In pursuance of such a test I mated various pure black hens with pure black cocks and those of F1, and, as was to have been expected, obtained families of different sorts, simply because even pure blacks have differing gametic constitutions. Thus in pen 824 I mated an extracted black cock with 3 black hens. All were apparently of the zygotic constitution C2J2Nn, forming gametes CJN and CJn. Mated together these should give the three black combinations C2J2N2, C2J2Nn, C2J2nN, to one Game, C2J2n2. Actually there were obtained 64 black and 23 Game, 66 to 22 being expectation. In another pen (pen 804) an F1 cock was mated to various black F2 hens. The families fall into 2 classes. The cock, of course, produced gametes CJN, CJn, cJN, cJn. With four females like him (Nos. 3902, 3908, 5431, 6043) I got: black 40, white 13, Game 14; expected, black 38, white 17, Game 13. Three females (Nos. 4715, 4716, 5099) evidently produced gametes CJN, CJn. Expectation is that blacks and Games shall be produced in the proportions of 3 to 1. Actually 30:14 were obtained where 33:11 was expected. All of these results accord closely with the hypothesis.

The whites obtained in F2 are of 3 types, but in all alike the color factor is missing. Hence it can not reappear in the offspring, and, consequently, no colored offspring are to be expected. But, first, it must be stated that the extracted whites of the F2 generation are not always of a pure white. Indeed, the parent Silkies are in some cases not perfectly white, but show traces of "smoke." There are different degrees of albinism; the coloring enzyme may be absent to small traces. This variability in degree of albinism is familiar to all students of albinism in man. My breeding of extracted whites was done in pen 817 and consisted of a pure white cock (No. 3900) and 2 hens. Of these 1 (No. 6046) was pure white and produced in a total of 15 only white offspring, but among those that were described as unhatched I have recorded traces of pigment in 24 per cent of the cases. The second hen (No. 3899) had black flecks in the white plumage. She had 20 offspring, of which 2 (unhatched) are recorded as having N down, 2 as "blue," and 3 others show traces of black pigment. Thus, 7 birds in 20, or 35 per cent of all, show more or less black, even as the albinic mother does. On the whole, however, omitting from present consideration the phenomenon of incomplete albinism, we may say that 2 pure albino parents produce only albinic offspring, while imperfectly albinic parents produce some imperfectly albinic offspring.

2. SILKIE × WHITE LEGHORN.

By hypothesis this cross is between cJnwx and CJNWx. The first generation should give the zygotic formula CcJ2NnWwx2, or, more simply, CcJ2NnWw. This formula resembles closely that of the White Leghorn, except that the coloring and graying factors and that for supermelanism are all heterozygous and hence diluted; only the Jungle coloration remains unchanged. Actually, the first generation yielded a lot of white birds like the Leghorn, but with this difference, that, as the males became mature, they gained red on the wing-bar and to a slight extent on the lacing of the saddle. The females gained a faint blush of red on the breast. Thus red appeared, in small amount, in just those places in the respective sexes which are red in the Jungle-fowl. The explanation of its appearance that I have to suggest is that, both on account of the diluting of the supermelanic coat and of the graying factor, the red of the undiluted underlying Jungle coloration is revealed.

Since the hybrids are heterozygous in respect to 3 pairs of characters, when segregation occurs each parent produces 8 kinds of gametes, as follows: CJNW, CJNw, CJnW, CJnw, cJNW, cJNw, cJnW, cJnw. When both parents produce these 8 kinds of gametes we may expect, in 64 offspring, the proportions of the several types shown in table 59.

Table 59.—Probable frequency in 64 progeny.

Zygotic formula. White. White + red. Game. Black.
C2J2N2W21.........
C2J2N2Ww2.........
C2J2N2w2.........1
C2J2NnW22.........
C2J2NnWw...4......
C2J2Nnw2......2...
C2J2n2W21.........
C2J2n2Ww...2......
C2J2n2w2......1...
CcJ2N2W22.........
CcJ2N2Ww 4.........
CcJ2N2w2.........2
CcJ2NnW24.........
CcJ2NnWw...8......
CcJ2Nnw2......4...
CcJ2n2W22.........
CcJ2n2Ww...4......
CcJ2n2w2......2...
c2J2—16.........
Total (64)341893

While, if the progeny were all to survive to maturity, we might expect to get the proportions of white and of white-and-red progeny called for, yet, since the red color appears in most cases at an age after the chicks are described, it will be necessary in comparing experience with calculation to combine the first two classes as whites. We then find the proportions given in table 60.