NATURE 



[Stl'TEMEER 15, 19 10 



LETTERS TO THE EDITOR. 

 [Zhe Editor does not hold himselj responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part 0/ NATURE. 

 No notice is taken of anonymous communications.] 



Lord Morton's Quagga H>brid and Oiigin of Dun 

 Horses. 



Will you allow me to suggest that some of the data 

 which speculators upon the antecedents and the history o( 

 the horse have made much use of arc not too trustvvorihy? 



First, I would suggest that there is doubt whether Lord 

 Morton's famous quagga hybrid is a hybrid at all. 

 Agassi's portrait of it and ot its sire and dam are to be 

 seen in the museum of the Royal College of Surgeons in 

 London. According to the portrait, the hybrid was a bay 

 with black " points," the blackness mounting just to the 

 pastern joint, as it does in many bays. 



Chestnut has been shown to be recessive to all other 

 colours; and a chestnut never has black "points." Prof. 

 Cossar Ewart tells us that " in their body colour none " of 

 his hybrids took after their sire, the Burchell zebra, a 

 close relation to the quagga. Now, in Lord Morton's 

 case, we have a chestnut mare producing a bay, a colour 

 she certainly does not contain. Is that possible? 



Again, we have a chestnut and a quagga, whose legs 

 were white, or, at any rate, a dirty white, producing a foal 

 with black " points." Is that also possible? Unfor- 

 tunately, there is one disturbing element in what has just 

 been put forward ; but it is not serious. I understand that 

 Agassi may have painted the " hybrid " from a drawing, 

 not from the life. But in a case so critical, and with Lord 

 Morton at least to keep him right, it is scarcely possible he 

 could have given the " hybrid " a colour and " points " it 

 did not possess. 



Ne.xt, I would suggest that the dun colour in horses is 

 not a reversion. In view of the fact that one of our 

 greatest men believed in the dun reversion, and also that 

 it led him and others to argue the primitive horse to be 

 dun and striped, my suggestion may be held to be very 

 ■presumptive. All the same, it must be made. 



In April last, the Royal Dublin Society published a paper 

 for me on " The Inheritance of Coat Colour in Horses," 

 in which it was pointed out somewhat tentatively, because 

 the evidence then at command was small, that dun is 

 dominant to chestnut, black, bay, and brown, and recessive 

 to grey ; while its relation to roan was not clear. Since 

 that time a considerable body of further evidernce has been 

 got, and it all confirms the original conclusion. Accord- 

 ingly, a dun foal cannot be got unless one of its parents is 

 either a dun or a grey or a dun roan. Greys are, therefore, 

 the only colour that could throw dun " reversions." 



My chief purpose in asking you to publish this letter is 

 to beg for evidence on the points at issue from anyone 

 who would be good enough to send it. What is wanted is 

 evidence — 



(r) As to the body colours and leg markings of hybrids 

 between zebras (especially Burchell zebras) and chestnut 

 horses, and 



(2) -As to the parentage of dun horses. 



Perhaps it may be well to say that, if there is difficulty 

 In distinguishing bays, duns, and chestnuts, the following 

 can usually be relied upon : — Unless white " stockings " 

 intervene, bays and duns have always black " points." In 

 bays the colour of the nostril patch is nearly always lighter 

 than that of the face, but in duns there is no distinct 

 break between the colours of the nostril patch and the face. 

 Chestnuts have not black " points "; their legs are coloured 

 like their bodies. James Wilson. 



Royal College of Science, Dublin. 



Prof. W'ilson thinks the " bay " filly which Lord 

 Morton says he obtained by crossing a chestnut mare with 

 a quagga was not- a hybrid, because he assumes that a 

 chestnut does not contain a bay colour, and that the off- 



NO. 2133, VOL. 84] 



spring of a white-legged quagga and a chestnut mare 

 would not be likely to have black " points." Prof. Wilson 

 also thinks " that the dun colour in horses is not a 

 reversion," and that the primitive horse was not, as 

 Darwin and others believed, " dun and striped." 



The prevailing colour of all the wild Equidae now living 

 in Asia is dun, and the wild horse I^Equus przcwalskii) 

 has dark points and usually a light muzzle. .•\s crosses 

 between varieties of Burchell zebras with white " points," 

 and crosses between zebras and ponies have, usually, 

 dark patches at the fetlocks, and as the body colour of 

 zebra-horse hybrids is usually yellow, rufous, or leather- 

 dun, it may be assumed that the renrote ancestors of the 

 modern zebras only differed in their coat colour from 

 Prejvalsky's horse in being more richly striped. 



The drawing of Lord Morton's filly by .\gass^ might 

 be said to represent a bay or a bay-dun — that the filly 

 was a bay-dun rather than a bay may be inferred from 

 Lord Morton saying that in her colour, as well as in her 

 form, the hybrid filly afforded " very decided evidence of 

 her mixed origin." A light chestnut Iceland pony mare 

 in my stud produced a bay-dun with dark " points " to a 

 yellow-dun Prejvalsky stallion, and a richly striped yellow- 

 dun Highland mare produced first a dark bay with dark 

 " points " and then a light bay (also with dark " points ") 

 to a chestnut thoroughbred (Diplomat). I am hence not 

 surprised that Lord Morton's chestnut .Arab produced a 

 filly of a bay or bay-dun colour to a quagga. 



it has hitherto, so far as I know, not been pointed out 

 that there are two kinds of duns, viz. : — (t) duns without 

 either a dorsal band, shoulder or leg stripes, and (2) duns 

 with a dorsal band and, as a rule, more or less distinct 

 bars on the legs — sometimes also with zebra-like markings 

 on the face, neck, shoulders, and trunk, and spots on the 

 hind quarters. Duns without stripes of any kind are now 

 and again obtained when a grey is bred with a black or 

 with a bay. The dun colour in these unstriped horses is 

 apparently not a reversion. Moreover, the offspring of 

 two unstriped yellow-duns may be bay or brown. 



Yellow-duns with a dorsal band and at least vestiges 

 of leg bars are, in all probability, either the descendants 

 of a long line of dun ancestors or are reversions. Owing 

 to the elimination of duns by breeders — the Arabs thought 

 duns only fit for Jews to ride — there probably does not 

 exist to-day a yellow-dun thoroughbred, but now and 

 again one sees a well-bred yellow-dun hunter with distinct 

 leg bars — a descendant, perhaps, of the dun mare or the 

 dun Arab which figure amongst the ancestors of Touch- 

 stone. 



That dun is latent in some bays and blacks was proved 

 recently by a black Shetland mare from Unst producing 

 to a bay .Arab (Insaf), with a dorsal band and leg bars 

 a richly striped yellow-dun. There are striped white, 

 yellow, leather, and mouse duns. I have obtained a 

 striped white dun from a r-ed-roan .Arab mare and a yellow- 

 dun Norse stallion ; a striped yellows-dun from a bay 

 Sumatra stallion and a mouse-dun Shetland-Welsh mare ; 

 a striped leather-dun from a yellow-dun Highland stallion 

 and a chestnut Shetland-.-\rab mare ; and a mouse-dun 

 from a yellow-dun Highland stallion and a black Highland 

 mare. 



My crossing experiments do not support the view that 

 chestnut never contains bay or that yellow-dun is always 

 dominant with chestnut, bay, brown, and black — they on 

 the whole support the view that characters are " patent " 

 or " latent " rather than, as Mendelians say, " present " 

 or " absent." 



As to the colour of hybrids between a Burchell zebra 

 and chestnut mares, I have little to say. .A chestnut polo- 

 pony mare produced three hybrids. In the first two 

 (twins) the body colour at bir-th w'as of a rufous tint, and 

 the stripes of a faint reddish-brow^n colour. When full 

 grown, the body colour was of a leather-dun hue, the 

 stripes being a slightly darker shade of the same colour. 

 In the third hybrid the body colour, golden-dun at birth, 

 was eventually a dark yellow-dun. The stripes in this 

 third hybrid are of a brow^n colour, arid extremely well 

 marked on the neck and limbs. Dark-brown patches at 

 the fetlocks represent black " points." 



J. C. Ewart. 



