288 



Mendelism. 



[JULY, 



determinant. Similarly, black is apparently dominant to red 

 in the Angus and Galloway breeds of cattle, while in other 

 breeds, if both black and red are present, we get the brindled 

 marking. 



In stating the method in which new combinations are pro- 

 duced, it has been said that the offspring of the first crosses, 

 if sufficiently numerous, will include the desired result. The 

 proviso must not be lost sight of, for it points to the most 

 formidable obstacle in the way of researches into the laws 

 of heredity in domestic animals. If we set out to modify 

 two characters of an animal, it can be shown that there is 

 only one chance in sixteen that the second generation will 

 contain what we want; if we wish a new combination of three 

 characters, the chances are one in sixty-four ; each additional 

 factor multiplies the chances against by four. Next, we have 

 the complexity resulting from the separation of the sexes 

 in animals. It will be readily understood why plants provide 

 the best material for such researches ; by self-fertilising a 

 plant, we can ensure that both the male and the female 

 elements are of the same constitution, both visually and 

 latently, and the breeding of the large numbers required 

 presents no great difficulty. But all these obstacles to the 

 application of the new methods to the larger animals appear 

 insignificant when it is pointed out that the territory so far 

 explored by the followers of Mendel is really, from an 

 economic point of view, a very limited one. For the laws 

 of inheritance of such indefinite characters as size, shape, 

 fertility, vigour, are still unknown. If, for example, we select 

 such an important problem as the combining in one breed 

 of a high standard of beef and milk production, the indefinite- 

 ness which characterises these points, as contrasted with, say, 

 horns and no horns, renders the application of Mendelian 

 methods to the problem almost inconceivable, not to speak 

 of the impossibility of testing males for milk-producing 

 capacity. 



The Mendelian does not depreciate the value of the time- 

 honoured method of selection in attacking such problems; 

 he only hopes to discover the laws which govern the varia- 

 tions which the breeder has hitherto left very largely to 

 chance; moreover, he suspects that the improvement in any 



