208 Scientific Proceedings, Royal Dublin Society. 



tbe recessive with wliich it is accompanied. Grey carrying brown, for 

 instance, should produce no colour lower than brown. 



(4) An impure colour carrying any recessive wlien mated with that 

 recessive sliould produce itself only and that recessive. Grey carrying 

 chestnut, for instance, should produce greys and chestnuts only when mated 

 with chestnuts. 



Perhaps the last of these results brings out the difference between the 

 horse colours and characters of the ordinary nature. Since there are six 

 colours at least, and dominance and reoessiveness exist among them, there 

 ought to be at least three pairs of factors, if the factors were normal. Call 

 them X and .-r, T and y, and Z and z. Chestnut, being the lowest recessive, 

 should carry tlie characters x y z, and grey, being the liighest dominant, as 

 we shall see presently, should carry the factors XY Z. Then impure grej' 

 might have any one of the following constitutions : — 



XX XX X.V XX X.r Xr Xr 

 TY Y// YY Yy YY Yy Yy 

 Zz ZZ ZZ Zz Zz ZZ Zz 



Some of these ought to produce several colours when mated with chestnut 



and, excepting tlie last one, no chestnuts at all. Take the fourth for example. 



XX icx X.V 



Yy X //.'/ should produce Yy, 



Zz zz Zz 



Tlie first of these constitutions would be grey, the other three would each 

 be some other colour, but none of them would be chestnut. This, however, 

 is altogether contrary to experience when grey is mated with chestnut. 



Consider, first, the behaviour of grey, because it is easier to get data 

 regarding that colour than the other two, dun and cream. But grey data 

 must be used with care, for the reason that a grey horse is seldom, if ever, 

 born grey ; and many misdescriptions result thereby which have to be 

 corrected where possible, or allowed for if not corrected. White foals are 

 occasionally born, but the horse that eventually becomes grey is generally 

 born a dull black. Grey hairs usually appear with the casting of the first 

 eoat, most conspicuously about the head. In a year or two the head is 

 distinctly grey and the body well mixed. In seven or eiglit years the body 

 is quite grey, and the legs, which are the last to be affected, sliow clear signs 

 of greyness. Eventually all is grey, and if the horse live long enough, white. 

 But the early stages are not the same in all, for some cast several coats before 

 they are noticed to be grey. Thus many a grey, more especially those that 

 die young or are early found to be of little value, remains in the stud book 



