304 Scientific Proceedings, Royal Dublin Sociebj. 



Dr. Crampe's two conclusions referred to above are : — 



(1) Chestnuts have chestnut foals only, with chestnut roans and 



chestnut greys among them, and 



(2) Blacks have both black and chestnut foals, and also roans and 



greys of these colours. 



When we remember tlie liability of roan and grey to the error of misde- 

 scription, there can be no doubt tliat the first of these conclusions is the same 

 as that arrived at independently by Mr. Hurst twenty years later. The 

 second conclusion, however, points to black being a second dominant to 

 chestnut; and this inference is confirmed by Dr. Walther's data. At 

 Trakehnen the desire arose to have a section of tlie stud consisting of black 

 horses only ; and to accomplish this, the black mares which were already in 

 the stud, no matter how they had been bred, were mated with black sires 

 only. 



The colours from which the black sires and dams had themselves been 

 bred were as follows : — 



These 30 black sires and 174 blaok dams had 574 foals, of which 506 were 

 black and 68 chestnut. Thus black is a simple dominant to chestnut and 

 differs from it in one pair of characters, for, if it differed in more, some other 

 colour or colours would have been produced. 



In Dr. Walther's paper " brown " stands for bay and brown together, and, 

 since the two colours are really one, we may use the same designation in the 

 rest of this paper. 



It is the usual experience that if two conditions differ each from a third 

 in one pair of characters, they differ from each other in two pairs, and the 

 three conditions in question form the second, third, and first or fourth groups 

 of a two-pair set of four groups. Thus brown, black, and chestnut should 

 take the places indicated in the following set : — 



X X X OS 



Y y Y y 



9 : 3:3:1 



? Brown Black Chestnut 



' i'lum tliis it can be infeiied that black is recessive to brown. 



