318 
IOWA ACADEMY OF SCIENCE 
Quantitative differences appear in the amount of pigment in the hair, 
intense and dilute conditions being readily recognizable. The effects 
of age and sun are quite noticeable also, fading usually being produced, 
in some cases the black hair losing its; black pigment almost entirely 
and giving the rusty black so common in Percherons and general work 
horses. 
THE INHERITANCE OF THE RED PIGMENT. 
Hurst and Bunsow have shown that chestnut breeds true. The figures 
in the table, taken from various sources,* show that out of 1,610 matings 
all but 16 are chestnut. This is a deviation from a pure recessive of l% r 
but since it has been shown that the average stud book contains 2% 
of errors, this 1% may be readily credited to that. It will be noticed 
that the variates are 6 bays and 10 blacks. Bay is the common color 
of a colt at birth and a rusty black is nearly as frequent. Since many 
colts are recorded at from one to three months of age and since the 
natal coat is not shed usually until the foal is twelve weeks old, errors 
here are not unexpected. > 
The black pigment seems more complicated in nature. 406 individuals 
show it to 41 without when black is mated to black and 200 bear it to 
108 without when black is mated to chestnut. Since most of the indi- 
viduals in the black by black matings are from the Percheron breed in 
which there are a large number of homozygous blacks the small ratio 
of chestnut segregation is not surprising. The 15 bays from the black 
by black mating are unexpected. Eleven of these came from Sturte- 
vant ’s records. He offers the possibility of error explaining it on the 
ground of error in the natal coat, on the difficulty in distinguishing dark 
browns from blacks in the parents and by other means. These seem 
sufficient to the writer to permit disregarding them since he found none 
in his studies on actual individuals, (some 100 in number). Sturtevant 
and the other investigators are disturbed by the high per cent of bays 
from the black by chestnut matings, but this is probably due to the idea 
of hay held by them. It fits the writer’s hypothesis perfectly. The 
factors so far considered may be lettered as Sturtevant has done, C for 
the chestnut ground pigment and H for the black pigment, (Hurst’s 
factor) . 
♦The Government Gray Draft Horse Experiment at Ames, pedigree and original 
animal study by the writer, Sturtevant’s, Wilson’s and Anderson’s papers principally, 
with isolated cases from the agricultural press. 
