Wilson — Polyc/amous Mendelian Factors. 311 



It will be noticed that, when dun is mated with chestnut black and brown, 

 tlie total number of these three colours together is equal to the number of 

 duns, but that no greys are produced. On the oilier hand, when dun and 

 grey are mated, grey foals are produced. Thus dun is dominant to chestnut, 

 black, and brown, and recessive to grey. This finding is confirmed by the fact 

 that seven dun horses were found, none of which had a dun, but each of 

 which had a grey parent. Two were the progeny of grey and grey, three of 

 grey and black, one of grey and bay, and one of grey and brown. And it 

 was confirmed farther by the use of tliree dun sires sent in succession to Clare 

 Island on the coast of Galway by the Irish Congested Districts Board. There 

 were no other sires on the island, and the mares were bays aud browns, with 

 a few blacks and one or two greys and chestnuts. The pi-ogeny of the first two 

 sires were all duns, while the last, which had dun mares to mate witli, got tliree 

 quarters of his foals dun, excepting one grey foal, which was out of a grey 

 mare. 



In the paper of 1912 the position of cream could not be determined 

 further than to say it was recessive to dun aud dominant to chestnut, but 

 Dr. Walther found data which show it to be dominant to black and brown. 

 He found horses which carry what he calls yellow " ground pigment," 

 namely duns and creams, dominant in colour to those carrying red 

 " ground pigment," namely bays and browns and chestnuts. He also found 

 yellow pigmented horses with black " points," namely duns, dominant to 

 similarly pigmented horses without black " points," namely creams. 



Thus we have the series : Chestnut, black, bay and brown, cream, 

 dun, and grey in which each of the colours in the order set down is recessive 

 to all those to the right and each is the result of a single polygamous 

 factor. 



It may be remarked that Dr. Walther's conclusions, if the "absences" 

 be substituted by what they signify, put the six colours in the same series of 

 dominants and recessives. This will be seen if his conclusions are set down 

 in parallel columns: one containing them approximately as expressed, aud 

 the other as altered : — 



As expressed. As altered. 



(1) G-rey is dominant to its (1) Grey is dominant to all 



absence. other colours. 



(2) Yellow ground-pigment is ;2) Dun and cream are domi- 



dominant to red. uant to brown, black, and 



chestnut. 



