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THE AMERICAN NATURALIST [Vol. XLYII 



cent, chestnut, 12 per cent, black, 12 per cent, brown, and 

 52 per cent. bay. Bay to chestnut results in : 34 per cent, 

 chestnut, 4 per cent, black, 3 per cent, brown, and 59 per 

 cent. bay. The behavior of bay with chestnut is just 

 what is to be expected if chestnut is recessive, as it seems 

 to be. But it is in the matings of chestnut with black 

 and brown that the real difficulty is encountered. Why 

 should chestnut and black matings give 40 per cent, bay, 

 and with brown it gives 52 per cent. bay. I must confess 

 that up to this time I have not found an explanation to 

 this. With these exceptions chestnut certainly behaves 

 as a recessive to all other coat colors in horses. 



Another strong evidence of the hypostatic position of 

 chestnut is found in the matings in which it is not in- 

 volved in the color of either the sire or the dam. Black 

 X black matings give 3 per cent, chestnut foals. Black 

 X brown gives 2 per cent, chestnut. Black X bay gives 

 9 per cent, chestnut. Brown X bay gives 7 per cent, 

 chestnut. Brown X brown 2 per cent, chestnut. Bay X 

 bay gives 13 per cent, chestnut. Here are six classes of 

 matings with no external evidence of chestnut in the 

 animals mated, yet regularly there come from them chest- 

 nut foals. This certainly is the way a unit-character 

 should behave, and to behave this way it must be reces- 

 sive. A striking example of the recessive nature of chest- 

 nut is to be found in The Theorist, a chestnut trotting 

 bred stallion. I gave his color pedigree in The Horse- 

 man of December 17, 1912. The three generations im- 

 mediately before him are of solid colors other than chest- 

 nut. The fourth generation has one chestnut individual, 

 and the next generation two. If this is not the behavior 

 of a unit-character I am unable to state how a recessive 

 character should behave. 



There are some stallions that are homozygous for their 

 own colors and are unable to produce even from chestnut 

 mares any chestnut foals. The two trotting stallions are 

 Bingen and Alcyo, who, I have found, do not produce any 

 chestnuts, although each one has had numerous mares 

 who to other stallions do produce chestnut foals. 



Black is dominant to chestnut and hypostatic to brown, 



