IOWA ACADEMY OP SCIENCE 
319 
BAYS AND BROWNS. 
Bay and brown are distinguished with difficulty by each of the inves- 
tigators and by most practical men. On. this account the writer has made 
no attempt to separate them but has lumped such records together. 
Bay is a restriction factor, which will be called B, that limits the 
development of the black pigment to the eye, mane, tail, skin, lower limbs 
and the extremities in general. It can operate only in the presence of 
factor H, black pigment. Brown probably differs from bay in having 
the dapple pattern combined with the restriction factor B. This’ per- 
mits some black to appear where the dapples are located and gives a 
darker appearance. This idea would suit the microscopic as well as 
visual evidence since brown differs from bay in the presence of black 
hairs. Most writers have considered brown dominant to bay, a condi- 
tion which would suit the above theory since the dappling pattern is 
apparently dominant. 
Bay to bay gives 5,723 bay, 274 black and 672 chestnut. This varies 
quite a little from the expected 9 :3 :4 ratio. However, the bays are very 
largely, (all but about 500), from the American Saddle Horse and 
Standard Bred records, and bay has been the dominating color among 
them for seventy-five years. The deficiency in blacks may be accounted 
for by their lack of popularity. Bay to black and to chestnut give 
qualitatively similar results as would be expected, but there is a lower 
percentage of bays and a higher percentage of blacks in one case and 
chestnuts in the other than w T ould be expected. 
The high per cent of bays in the offspring of blacks to chestnuts has 
been non-conformable to previous theories. The restriction factor B 
does not appear except in the presence of H, black pigment. Theoreti- 
cally three-fourths of the chestnuts ought to carry this restriction fac- 
tor, so that the mating of these to blacks should always supply bays. 
Prom this standpoint there is a deficiency rather than an excess of bays. 
THE DUNS. 
Duns are little known. Their numbers are few and they may be 
grouped into at least three kinds. The ordinary buckskin with black 
extremities is probably a dilute bay, the yellowish dun a dilute chestnut 
and the cream colored with light mane and tail, a dilute sorrel with 
the yellow extremities, factor M, 
Since the records do not separate them they will not be dealt with 
further. Factor I, the dilution factor, is probably epistatic to all but 
gray and roan. 
