822 
IOWA ACADEMY OF SCIENCE 
Anther chestnut mare known as the half-hackney bred qualitatively the 
same producing two colts of the first class and one of the second. Four 
chestnut mares with yellow manes mated to three different chestnut 
stallions with yellow manes produced thirteen foals with yellow manes. 
The summary of data on this is appended. 
Chestnut Stallions 
without Yellow Manes 
Chestnut Stallions 
with Yellow Manes 
Chestnut mares with yellow manes 
Chestnut mares without yellow manes 
25 without 6 with 
IT without 8 with 
13 with 
19 without 3 with 
This shows it apparently to be recessive. A cream colored mare with 
light mane and tail produced three dun colts with black extremities when 
crossed to a bay. This would fit the above hypothesis although it throws 
no light on it. 
THE DILUTION FACTOR. 
The dilution factor I is apparently dominant. Mouse is a dilute form 
of black and three, matings of mouse to black have given two mouse- 
colored and one black. The mouse-colored parent of the black was pro- 
duced by a black stallion to a dun mare so was known to be heter- 
ozygous. The table shows that duns mated to other colors have produced 
13 duns to 19 other colors, near enough to expectation in such small 
numbers to account for dilution being a dominant factor. It must be 
remembered that duns are not popular in America at least and hence 
there will probably be a deficiency. Also because of this most duns will 
be heterozygous. 
v SUMMARY. 
* 
The factors so far discussed will account for the following colors, those 
qualitatively alike being grouped together: 
Sorrel-Chestnut-Liver. 
Black-Mouse. 
Bay-Brown-Blood bay-Mahogany bay-Seal Brown. 
Dun-Buekskin-Cream-Isabellme. 
Gray-White. 
Blue roan. 
Roan-Strawberry Roan-Red Roan. 
Piebald-Skewbald-Blaze and white stockings. 
Dappling. 
