394 



Prof. W. F. R Weldon. Note on the [Jan. 15, 



Scawen Blunt* for the Kehailan strain of Arabs. The same assertion is 

 also made for the horses called " rote " (? red chestnut) in the Jutland breed 

 by Jensen.f Finally, we have a general statement by Hayes,J applicable to 

 all kiuds of horses, that in the vast majority of cases a foal from a chestnut 

 dam by a chestnut sire is of a chestnut colour. 



The existence of the two kinds of dominants, and the conclusions based 

 thereon have not, so far as I know, been previously recognised. 



Note on the Offspring of llioi^oughbred Chestnut Mares. 

 By W. F. E, Weldon, F.E.S. 



(Received January 15, — Eead January 18, 1906.) 



The colours of English thoroughbred race-horses, as recorded in Weatherby's 

 General Stud-Book, are grouped under the six main categories — Grey, Eoan, 

 Chestnut, Bay, Brown, Black ; but each category includes a considerable 

 range of colour, and intermediates occur with quite sensible frequency. At 

 the meeting of the Eoyal Society, held on December 7 last, the suggestion 

 was made that the relation between the most important colours, Chestnut, 

 Bay, and Brown, might be expressed by a simple Mendelian formula — Bay 

 or Brown being regarded as determined by one Mendelian unit, which was 

 " dominant " to the " recessive " Chestnut. In discussing this suggestion, I 

 made certain statements, which I promised to justify as soon as possible, by 

 offering the data, on which they were based, for publication. The object of 

 the present note is partly to fulfil my promise, and partly to call attention 

 to certain facts which must be considered in the attempt to apply any 

 Mendelian formula whatever to the inheritance of coat colour in race- 

 horses. 



I have taken from Weatherby's Stud-Book a fairly complete record of all 

 the foals produced in England by Chestnut mares during the period (rather 

 more than eight years) covered by vols. 18 and 19. All cases of doubtful 

 paternity have been excluded, and I have not tried to obtain external 

 evidence in the few cases where the colour of sire or of foal is omitted. With 



* ' The Nineteenth Century and After,' 1906, January, p. 63. 



t ' Deut. Pferdezucht.,' I, Hft. 11, 1904. (Original not seen ; abstract in ' J. B. Landw. 

 Pfl. u. Tierziichtung,' 1905, II, p. 273.) 



% 1 Points of the Horse ' (3rd ed.), 1904, p. 326. 



