NATURE 



593 



THURSDAY, JUNE 19, 1913. 



MENDELISM AND STOCK-BREEDING. 

 The Principles of Stock-Breeding. By Prof. James 

 Wilson. Pp. vii+146. (London: Vinton and 

 Co., Ltd., 1912.) Price 55. net. 



IN this volume Prof. Wilson claims "to deal 

 with the problem of stock-breeding- in the 

 light of the Mendelian discovery." The book is 

 addressed to breeders ; for the sake of clearness 

 11 is shorn of many words common to the writings 

 1 >i the modern exponent of this branch of biological 

 science, and it is clearly designed to stimulate the 

 practical breeder to base the conduct of his busi- 

 ness on Mendelian principles. 



A book from the pen of Prof. Wilson is sure 

 to command attention, and in this instance he 

 brings abundant enthusiasm to help him in his 

 task, and is full of hope for the future. We are 

 not convinced, however, of the wisdom of the 

 undertaking; neither scientific enthusiasm nor 

 hope appeals forcibly to the practical man; he 

 requires facts on which to base his work. The 

 author himself demonstrates that very few facts 

 applicable to the breeding of domesticated animals 

 are yet to hand, and it seems to us that the time 

 has not yet come when breeders as a whole 

 can reap substantial benefit from the theorv of 

 Mendel. 



The enthusiastic Mendelian may, perhaps, con- 

 sider that he has effectively disposed of the opinion 

 of many biologists that Mendelism has not yet 

 been proved to be the main road, has merely been 

 shown to be a side track alongside that road which 

 leads to the solution of the mysteries of heredity 

 and variation. But the practical breeder is aware 

 of this scientific scepticism ; he is even more diffi- 

 cult to convince than is the pure theorist, and we 

 doubt if the examples of applied Mendelism which 

 Prof. Wilson gives will serve to stimulate his belief 

 in the practical value of that theory. 



There are three main reasons why the applica- 

 tion of Mendelism to stock-breeding is rendered 

 difficult : time, cost, and trustworthy data. To- 

 day we have a very meagre allowance of data, and 

 the little we have is rarely trustworthy. In order 

 to gain such data many years must pass, and 

 many wealthy breeders must content themselves 

 with the collection of facts which shall be recorded 

 in great detail. This knowledge must be gained 

 by exceedingly careful observation of the results 

 obtained by breeding on a definite plan and on a 

 large scale, and the records must be designed to 

 embrace the conduct of a number of characters 

 which may in themselves be exceedingly difficult to 

 NO. 2277, VOL. 91] 



observe ; and when the facts are known they must 

 be applied. 



The author gives an instance of such application. 

 "Assume," he says lightly, "that sixty-four heifer 

 calves are got, because this is the smallest number 

 that will split into all the possible cases " ; of these, 

 only one can have the characters desired, and these 

 characters can only be fully determined after the 

 animal has grown up. But in order to get such 

 a herd of heifer calves a much larger number must 

 be bred; and suppose this heifer dies before she 

 reaches maturity, or suppose she proves to be 

 sterile ! Is this a problem which is likely to attract 

 any but a very rich and a very large breeder? One 

 may grow wheat on an infinitely larger scale at 

 a nominal cost, but the breeding of stock in suffi- 

 cient numbers is a very different matter, as Ray- 

 mond Pearl's experiments clearly show. It is 

 true the author adds that " In practice such a 

 number need not necessarily be bred, because from 

 a smaller number the desired stock could eventu- 

 ally be raised." But he does not define what he 

 means by "eventually," and it seems that the 

 element of chance must have a large share in the 

 calculation. 



In the early part of the book, Prof. Wilson gives 

 a lucid account of the old theories of stock-breed- 

 ing. We scarcely think, however, that he does full 

 justice to some of the experimental work done 

 in those days, and cannot agree with some of the 

 deductions he draws from his study of the subject ; 

 as, for instance, in the degree of attention paid 

 by the old breeders to the part played by the sire, 

 and, if we understand him aright, in the relation of 

 artificial selection to evolution. 



The chapter on the Mendelian theory and animals 

 is another instance of the author's power of ex- 

 position. In spite of great difficulties, he has 

 surely made this part of his subject clear to his 

 readers. In doing so he has emphasised the fact 

 that when you can apply Mendel's theory to 

 observed phenomena you may thus obtain valu- 

 able knowledge of the forces which act in order 

 to produce those phenomena, and he shows that 

 to this extent you will gain a clearer view of their 

 significance. 



But if this is all the help Mendelism will give 

 to breeders there will undoubtedly be much dis- 

 appointment shown by those who have been led 

 to expect that it will serve as a short cut to the 

 production of improved breeds, and for the modi- 

 fication of special characters ; that it will take the 

 place of those laborious methods of selection hither- 

 to practised by the few successful breeders — who 

 are born with an eye for the detection of minute 

 variations, and can afford to fail many times 

 — and thus put success within the reach of all. 



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