April 2, 1908J 



NA TURE 



509 



LETTERS TO THE EDITOR. 



[The Editor does not bold himself responsible for opinions 

 expressed by his correspondents. Neither can he t4ndertake 

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

 manuscripts intended for this or any other part of Nature. 

 No notice is taUen of anonymous communications.] 



Mendelian Characters among Shorthorns. 



I iiA\'E just come upon a phenomenon which, ahhough 

 it may be interesting to naturalists, may be alarming to 

 breeders of Shorthorn cattle. It is that the roan Shorthorn 

 is a hybrid, and must remain so for ever. 



The data on which this statement is based are to be 

 found in a paper on the inheritance of coat-colour in 

 cattle, by Miss A. Harrington and Prof. Karl Pearson, 

 published in Biometrika- 'or March, 1906. 



For the purposes o their paper these authors, having 

 examined in the Shorthorn Herd-book the pedigrees of 

 more than 2000 calves, noted the colours of these and 

 iheir parents, and analysed and tabulated the figures 

 found. They divided trie sires and dams according to the 

 colours under which they are registered, and then made 

 an analysis of the colours of the calves produced. There 

 are five different colours registered, viz. red, red and 

 little white, red and white, roan, and white. A sire of 

 any one of these colours may be bred with a dam of 

 any one of them. Miss Barrington and Prof. Pearson 

 made an analysis of the colours of the calves produced 

 by bulls of all the five colours when bred with cows of 

 every one of the same five colours. For instance, they 

 found that by mating 514 roan bulls with 514 roan cow's 

 there had been produced eighty-six red calves, thirty-one 

 red with little white calves, thirty-five red and white 

 calves, 278 roan calves, and eighty-four white calves. 



These cases at a first glance give rise to no Mendelian 

 suggestion. No more does the full collection of cases. 

 Miss Barrington and Prof. Pearson failed to find in them 

 ;uiy .Mendelian indications. 



iSut if we consider the nature and history of the Short- 

 horn breed the Mendelian characters come out. The 

 Shorthorn is a composite breed. A hundred and fifty 

 years ago it consisted of at least three, and possibly four, 

 different strains. The chief ancestry came from the Low 

 Countries. They were red-and-white fleclccd cattle — flcck- 

 I'ieh. In Durham and Yorkshire they wedged themselves 

 in between the original British black cattle in the north 

 and the Anglo-.Saxon red cattle in the south. They also 

 possibly reached westwards to the Longhorns. The ."Xnglo- 

 Saxon red cattle were probably the purest. The northern 

 black cattle and the western Longhorns were not pure. 

 Thev were intermixed with white cattle — cattle which had 

 been introduced originally by the Romans. It was 

 impossible for the recently introduced flecked cattle not to 

 become mi.xed with black blood in the north, with white 

 blood in the north and west, and with red blood in the 

 south. Breeders, however, did not like the black blood, 

 and it was soon bred out. The white was retained, but, 

 so far as I know, it is difficult to say how much Anglo- 

 Saxon red blood was retained. It is on that ground any 

 uncertainty-arises. But, if red blood was retained, it was 

 nearly related to the red and white blood introduced from 

 the Continent. 



If we look upon the .Anglo-Saxon red cattle and the 

 Low Country red-and-white cattle as being of one race, 

 then, since the black blood was bred out, the Shorthorn 

 is a combination of two races. If we look upon these 

 red and red-and-white cattle as different races, then the 

 Shorthorn is a combination of three. 



I tried to find Mendflian characters among the cases 

 collected by Miss Barrington and Prof. Pearson by 

 assuming the Shorthorn to be a three-fold combination, 

 hut unsuccessfully. Then Prof. Arthur Thomson's account 

 of the blue Andalusian fowl in his newly published 

 " Heredity " suggested the idea that the red, red and 

 little white, and red-and-white Shorthorns might be taken 

 as one race. Are not these Shorthorns splashed reds just 

 as one of the blue Andalusian parents is " splashed 

 white "? The Shorthorn, then, becomes a composite breed 

 with one parent white and the other splashed red. 



NO. 2005, VOL. 77I 



.'\ssuming this to be so, then the Mendelian characters 

 of the Shorthorn come out. There are one or two small 

 discrepancies, but they can be explained. It is sometimes 

 difficult to say whether a calf is red-and-white or roan. 

 Thus all that are labelled red and white may not be 

 really red and white, and all that are labelled roan may 

 not be really roan. Among Shorthorn breeders white 

 calves are not desirable. Cases of false registration and 

 the substitution of another calf for a white — that is, giving 

 a red or a roan calf a white calf's pedigree — have not been 

 unknown. Thus some red or roan calves may not be the 

 progeny of the parents attributed to them. For the same 

 reason that white calves are undesirable, a good many 

 white calves are not registered at all. Thus the real 

 numbers of white calves born are greater than the numbers 

 registered, and the number of matings recorded is less 

 than it ought to be through matings that produced white 

 calves being unrecorded. For the reason that white calves 

 are not wanted, a white bull and a white cow are very 

 seldom mated. T'^us very few such matings are registered. 



Assuming the .horthorn to be a combination of two 

 races, a red and white, then, according to the Mendelian 

 formulae as exe plified by the blue Andalusian fowl, we 

 ought to get tl - following results : — 



(i) Red crossed by red should give red calves. 



(2) White crossed by white should give white calves. 



{3) Red crossed by white should give roans. 



(4) Roans inbred should give reds, whites, and roans 

 in the proportion of i, i, 2. 



(5) Roans crossed by reds should give roans and reds in 

 equal proportions. 



(6) Roans crossed by w^hites should give roans and 

 whites in equal proportions. 



This, giving heed to the expected exceptions as 

 indicated above, is what we find, viz. : — 



Red Roan White 



438 Reds crossed by reds give ... 413 ... 25 ... u 



3 Whites crossed by whites give o ... o ... 3 



71 Reds crossed by white give... 3 ... 68 ... o 



514 Roans crossed by roans give ... 152 ... 278 ... 84 



456 Roans crossed by reds give ... 226 ... 230 ... o 



23 Roans crossed by whites give... o ... 14 ... 9 



For the breeder of Shorthorns this means that, if he 



wishes to avoid white calves, he is limited to three crosses, 



viz. red with red, red with roan, and red with white. He 



gets whites when whites are bred together, when whites 



are bred with roans, or when roans are bred together. 



James Wilson. 

 Royal College of Science, Dublin, March 19. 



The Nature of 7 and X-Rays. 



In a letter to Nature of January 23 (p. 270) Prof. Bragg 

 mentions the results of some experiments on y rays from 

 which he concludes that the ether pulse theory of 7 rays 

 is not tenable, but which support his theory that the 

 7 rays consist of neutral pairs revolving in a plane con- 

 taining their direction of translation. From the close 

 resemblance of X-rays to 7 rays he assumes that they 

 also consist of neutral pairs. His reasoning seems to be 

 that if the 7 rays are ether pulses only, they should pro- 

 duce in any substance which they strike secondary kathode 

 rays which come off equally in all directions, and if they 

 do not the ether pulse theory cannot be correct. 



Prof. Bragg's e.xperiments show that the secondary 

 kathode rays coming from the side of a substance on which 

 the 7 rays fall differ in the amount of ionisation they 

 produce from those coming from the side from which the 

 7 rays emerge. Also that the "emergence" kathode rays 

 from a substance of low atomic weight are greater than 

 those from a substance of higher atomic weight, while 

 with the " incidence " kathode rays the substance of high 

 atomic weight gives off more than the substance of lower. 



I have been working for some time upon the secondary 

 kathode rays produced by X-rays with a form of apparatus 

 which can be easily adapted for a repetition, with X-rays, 

 of Prof. Bragg's experiments with 7 rays (see .imer. Jour. 

 Sci., October, 1907, p. 285). I have therefore tried to 



