172 GENETICS IN RELATION TO AGRICULTURE 
tails from the color pattern of the Wild Rock Pigeon from the Shetland 
Islands. 
The data which Darwin presented while giving qualitative evidence 
of recombination of factors do not provide quantitative data on which to 
base a Mendelian analysis. Staples-Browne, however, has presented 
a case which admits of more definite analysis. He crossed a Black- 
barb and a White Fantail and obtained black birds in F;. In Fy», he 
obtained the results which are tabulated in Table XX XI. Cole has pro- 
posed the following factor analysis for the principal colors in pigeons: 
B—a factor epistatic to the series of factors which produce red in 
pigeons, and giving black pigmentation. The allelomorph b then results 
in red pigmentation. 
S—a, factor for extension of pigment which appears to act on B only. 
BS gives black birds, whereas Bs gives birds in which the black pigment 
is aggregated into clumps in the barbules, the so-called blue pigeons. 
T—a factor which gives black tail feathers when B is present. The 
allelomorph 6 under similar conditions gives blue tailed birds. 
W—a series of factors for white pigmentation which Cole designates 
W:1, We, W3, W.. By W, is designated simply an undetermined number 
of these white factors which may affect different portions of the plumage. 
Likewise by w, is designated the recessive allelomorphs of these white 
factors, birds with such a genetic constitution being self-colored. 
Taste XXXI.—F, Resutts From Buack Bars X WuitEe Fantail PIGEONS 
| Black | Bl | | pera 
“jaca Black | Red en Or | Pigmented = 
ars e 5 orth eal eed Little | Much | White 
| | white | white | self 
o Blacks (self)io ge se 2 ocer | 5 | oe 5 i 5 
10 Black (white feathers)..| 10 s 10 a cr 10 
2: Blues (seli)cscpcas aes, 2 2 2, 
2 Blue (white feathers)... . 2 oe 2 2 
5 Red (white feathers).....)  .. 5 ? ? 2 
2 White (black feathers)... 2 s ? 2 2 
2 White (red feathers)......}  .. 2 ie ? 2 
6G Whitex(Self)i.. J. ce scceeces i ? ? ? 6 
Total observed........| 21 7 15 4 ig |) <f-4 4 
DARE SSL! 21 7 14 D4 ? | iy ? ? 
With these factors the Black Barb would be BBSSTTw,w, and the 
White Fantail bbSSuW,W,. The Fi of such a cross, BOSSTtW,w, 
would be black more or less splashed with white as were those obtained 
in the experiment, and in F, a series of forms would be obtained de- 
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