74 INHERITANCE OF CHARACTERISTICS IN DOMESTIC FOWL. 



is more striking than to see the hens of this F^ generation with evidences 

 of the female Game pattern (plate 6). 



Comparing observed results in the distribution of colors in the F^ 

 generation with expectation, it is seen that the proportions are close, and 

 this closeness of observation with expectation is evidence for the correct- 

 ness of the hj^Dothesis. 



The hypothesis may be further tested in later generations by breeding 

 together the different sorts of individuals obtained in F^. In pursuance 

 of such a test I mated various pure black hens with pure black cocks and 

 those of F and, as was to have been expected, obtained famiUes 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 C^JJSln, 

 forming gametes CJN and CJn. Mated together these should give the 

 three black combinations C^JJSl^, C^J^Nn, C^J^nN, to one Game, C^J^n^. 

 Actually there were obtained 64 black and 23 Game, 66 to 22 being expec- 

 tation. In another pen (pen 804) an F, cock was mated to various black 

 Fj 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 pro- 

 duced 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 F^ are of 3 types, but in all aUke 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 Fj 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. 



