THE BOOK OF POULTRY. 



the breeder to predict the results of certain 

 matings, just as the chemist predicts the result of 

 placing two substances together. Genetics may 

 not for some time reduce the science of breeding 

 to the exactness of chemistry ; possibly with 

 living organisms the exactness of physical science 

 is unattainable ; still Genetics will throw a great 

 deal of light upon the work of breeding and will 

 point the way to a high degree of exactitude. 



iVIendelism is the name applied to the 

 methods which Gregor Mendel used in his 

 e.xperiments on heredity and varia- 

 What is tion. These methods have been re- 



Mendelism ? vived during the last ten years by the 

 pioneers of Genetics. Mendel's man- 

 ner of experimenting affords a practical means 

 of tackling the problems of heredity, for it 

 enables us to trace the history of any character or 

 characters through one or more generations. So 

 far Mendelian experiments have been concerned 

 with cross-breeding. At first we may be in- 

 clined to doubt how far the results so established 

 will help the breeder of pure stock. But cross- 

 breeding has been resorted to because it was 

 easier to perceive the course of heredity by 

 crossing specimens with characteristics markedly 

 different, such as tall or short peas, rose or 

 single comb in fowls, etc. Tlie knowledge of 

 heredity so gained will prove of value to the 

 breeder of pure stock in many ways, for it will 

 inlorm him of the methods used, and will put at 

 his disposal means of testing the breeding value 

 of his stock, and will also open up ways of 

 strengthening and perfecting his pure bred 

 animals and birds. A caution must, however, 

 be entered here as to the possibilities of Men- 

 delism for the fancier, at any rate for the 

 present. Professor Bateson says, " applied to 

 the business of breeding winners in established 

 breeds the principles of Mendelism cannot 

 materially help, for almost always the points 

 which tell are too fine to be dealt with in our 

 analysis. The principles aheady ascertained 

 will be found of practical assistance in the 

 formation of new breeds, and may save many 

 mistakes and waste of time. Indirectly, how- 

 ever, as Mendelian methods familiarise the pro- 

 cesses of heredity, so far they will assist the 

 breeder in his work." 



There are certain lessons taught by the 

 facts already learned from Mendelism which are 

 of great use to the breeder and which he should 

 apply in his own work. First of all, the value 

 of breeding from known individuals has been 

 thoroughly established. To succeed on Men- 

 delian lines the breeding must be done with 

 individuals. It is not possible to establish any 

 facts by breeding indiscriminately from a pen 



of birds. Trap nesting had undoubtedly in the 

 past brought this home to the average breeder, 

 but not with the same force as Genetics has. 

 The fact that trap nests have been in more or 

 less general use is evidence that the fancy as a 

 whole was learning from other sources this 

 lesson of breeding from individuals. This prac- 

 tice, established first, probably, for utilitarian 

 purposes, has been justified by Mendelian ex- 

 periments, which have shown that the trap nest 

 is as valuable to the fancier as to the utility man. 

 Many a fancier can point to individual birds as 

 the sire or dam of their noted winners. Men- 

 delism, then, teaches the breeder that he must 

 breed from individuals, and that he ought to 

 know the progeny of every one of his stock 

 birds. With this knowledge he will be able to 

 discard the wasters, and to mate up for next 

 year's breeding, with an accuracy approaching 

 almost to mathematical e.xactness. 



The breeding value of a bird does not 

 depend so much upon outward appearances as 

 upon pedigree in the Mendelian 

 Breeding sense. The idea of pedigree gener- 



Value ally accepted is that of stock, being 



bred in one way for a number of 

 generations. Mendelism teaches us to look 

 upon pedigree in the light of the nature of the 

 factors contained in the germ-cells of the in- 

 dividual birds. If those factors are the ones 

 required, then the pedigree is satisfactory ; if 

 those factors consist of any not required, if there 

 are too few, or some which inhibit the action of 

 the rest, then the pedigree is not satisfactory. 

 Mendelism has shown that a satisfactory con- 

 dition is independent of the number of genera- 

 tions for which the strain has been bred ; it is 

 possible to attain it in the second. The points 

 upon which the excellence of a show bird depends 

 are often', as will be shown later on, probably 

 " fluctuations " {i.e. non-transmissible variations), 

 and for these reasons a very perfect exhibition 

 specimen may not be a first-class breeder. An 

 ordinary specimen of the same strain will prob- 

 ably do quite as well in the breeding pen, and 

 so the fancier would be well advised to buy the 

 ordinary bird at a moderate sum rather than the 

 prize-winner at a long price. Mendelism thus 

 enables a breeder to place a correct value on 

 pedigree. 



In mating up pens the general advice given 

 is that no two birds which have the same faults 

 should be mated together, but that when one 

 has a prominent fault the mate should be strong 

 on that point. This general advice is un- 

 doubtedly good and sound, and Mendelism 

 explains how and why it works, and further it 

 shows us how to utilise birds in future breeding 



