chairman's ADMfflSS. 595 



make on a commercial scale, and the gain in yield is striking, the increase 

 ranging as high as 95 per cent. These figures sound extravagant, but from what 

 I have frequently seen in peas and sweet peas, I am prepared for even greater 

 increase. But what is this increase? How much of it is due to change in 

 number of parts, how much to transference of differentiation or liomoeosis, as I 

 have called it — leaf-buds becoming flower-buds, for instance — and how much to 

 actual increase in size of parts ? To answer these questions would be to make 

 an addition to human knowledge of incalculably great significance. 



Then we have the further question, How and why does the increase dis- 

 appear in subsequent generations? The very uniformity of the cross-breds be- 

 tween pure strains must be taken as an indication that the phenomenon is 

 orderly. Its subsidence is probably orderly also. Shull has advocated the most 

 natural view that heterozygosis is the exciting cause, and that with the gradual 

 return to the homozygous state the effects pass off. I quite think this may be 

 a part of the explanation, but I feel difficulties, which need not here be de- 

 tailed, in accepting this as a complete account. Some of the effect we may prob- 

 ably also attribute to the combination of complementary factors; but whether 

 heterozygosis, or complementary action, is at work, our experience of cross- 

 breeding in general makes it practically certain that genetic factors of special 

 classes only can have these properties, and no pains should be spared in identi- 

 fying them. It is not impossible that such identification would throw light on 

 the nature of cell division and of that meristic process by which the repeated 

 organs of living things are constituted, and I have much confidence that in the 

 course of the analysis discoveries will be made bearing directly both on the 

 general theory of heredity and on the practical industry of breeding. 



In the application of science to the arts of agriculture, chemistry, the founda- 

 tion of sciences, very properly and inevitably came first, while breeding re- 

 mained under the unchallenged control of simple common-sense alone. The 

 science of genetics is so young that when we speak of what it also can do we 

 must still for the most part ask for a long credit; but I think that if there is full 

 co-operation between the practical breeder and the scientific experimenter, we 

 shall be able to redeem our bonds at no remotely distant date. In the mys- 

 terious properties of the living bodies of plants and animals there is an engine 

 capable of wonders scarcely yet suspected, waiting only for the constructive 

 government of the human mind. Even in the seemingly rigorous tests and trials 

 which have been applied to living material apparently homogeneous, it is not 

 doubtful that error has often come in by reason of the individual genetic hetero- 

 geneity of the plants and animals chosen. A batch of fruit trees may be all of 

 the same variety, but the stocks on which the variety was grafted have hitherto 

 been almost always seminally distinct individuals, each with ite own powers 

 of luxuriance or restriction, their own root-systems, and properties so diverse 

 that only in experiments on a colossal scale can this diversity be supposed to 

 be levelled down. Even in a closely bred strain of cattle, though all may 

 agree in their ' points,' there may still be great genetic diversity in powers of 

 assimilation and rapidity of attaining maturity, by which irregularities by no 

 means negligible are introduced. The range of powers which organic variation 

 and genetic composition can confer is so vast as to override great dissimilarities 

 in the conditions of cultivation. This truth is familiar to every raiser and 

 grower, who knows it in the form that the first necessity is for him to get the 

 right breed and the right variety for his work. If he has a wheat of poor 

 yield, no amount of attention to cultivation or manuring will give him a good 

 crop. An animal that is a bad doer will remain so in the finest past tire. All 

 praise and gratitude to the student of the conditions of life, for he can do, and 

 has done, much for agriculture, but the breeder can do even more. 



When more than fifteen years ago the proposal to found a school of agri- 

 culture in Cambridge was being debated, much was said of the importance of 

 the chemistry of soils, of researches into the physiological value of food-stuffs, 

 and of other matters then already prominent on the scientific horizon. I re- 

 member then interpolating with an appeal for some study of the physiology 

 of breeding, which I urged should find a place in the curriculum, and I pointed 

 out that the improvement in the strains of plants and animals had done at least 

 as much — more, I really meant — to advance agriculture than had been accom- 

 plished by other means. My advice found little favour, and I was taken to 



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