

chairman's address. 503 



ono of the provided stallions out of an indifferent country mare. It had been 

 kept as an unusually good-looking colt, and was now travelling the country as 

 a breeding stallion, under the highest auspices. I thought to myself that if 

 such a practice is sanctioned by breeding acumen and common-sense, Science 

 is not after all so very ambitious if she aspires to do rather better. The breeder 

 has continually to remind himself that it is not what the animal or plant looks 

 that matters, but what it is. Analysis has taught us to realise, first, that each 

 animal and plant is a double structure, and next that the appearance may show 

 only half its composition. 



With respect to the inheritance of many physiological qualities of divers 

 kinds we have made at least a beginning of knowledge, but there is one class 

 of phenomena as yet almost untouched. This is the miscellaneous group of 

 attributes which are usually measured in terms of size, fertility, yield, and the 

 like. This group of characters has more than common significance to the prac- 

 tical man. Analysis of them can nevertheless only become possible when pure 

 science has progressed far beyond the point yet reached. 



I know few lines of pure research more attractive and at the same time more 

 likely to lead to economic results than an investigation of the nature of varia- 

 tion in size of the whole organism or of its parts. By what factors is it caused ? 

 By what steps does it proceed ? By what limitations is it beset ? In illustra- 

 tion of the application of these questions I may refer to a variety of topics 

 that have been lately brought to my notice. In the case of merino sheep I 

 have been asked by an Australian breeder whether it is possible to combine 

 the optimum length of wool with the optimum fineness and the right degree 

 of crimping. I have to reply that absolutely nothing is yet known for certain 

 as to the physiological factors determining the length or the fineness of wool. 

 The crimping of the fibres is an expression of the fact that each particular hair is 

 curved, and if free and untwisted would form a corkscrew spiral, but as to 

 the genetics of curly hair even in man very little is yet known. But leaving the 

 question of curl on one side, we have in regard to the length and fineness of 

 wool a problem which genetic experiment ought to be able to solve. Note that 

 in it, as in almost all problems of the 'yield' of any product of farm or garden, 

 two distinct elements are concerned — the one is size and the other is number. The 

 length of the hair is determined by the rate of excretion and length of the period 

 of activity of the hair follicles, but the fineness is determined by the number of 

 follicles in unit area. Now analogy is never a safe guide, but I think if we 

 had before us the results of really critical experiments on the genetics of sizo 

 and number of multiple organs in any animal or even any plant, we might not 

 wholly be at a loss in dealing with this important problem. 



A somewhat similar question comes from South Africa. Is it possible to 

 combine the qualities of a strain of ostriches which has extra long plumes with 

 those of another strain which has its plumes extra lustrous? I have not been 

 able fully to satisfy myself upon what the lustre depends, but I incline to think 

 it is an expression of fineness of fibre, which again is probably a consequence 

 of the smallness and increased number of the excreting cells, somewhat as the 

 fineness of wool is a consequence of the increased number and smallness of the 

 excreting follicles. 



Again the question arises in regard to flax, how should a strain be bred 

 which shall combine the maximum length with maximum fineness of lib'-o.' 

 The element of number comes in here, not merely with regard to the number 

 of fibres in a stem but also in two other considerations, first, that the plant 

 should not tiller at the base, and, secondly, that the decussation of the flower- 

 ing branches should be postponed to the highest possible level. 



Now in this problem of the flax, and not impossibly in the others I have 

 named, we have questions which can in all likelihood be solved in a form which 

 will be of general, if not of universal, application to a host of other cognate 

 questions. By good luck the required type of flax may be struck at once, 

 in which case it may be fixed by ordinary Mendelian analysis, but if the 

 problem is investigated by accurate methods on a large scale, the results may 

 show the way into some of those general problems of size and number which make 

 a great part of the fundamental mystery of growth. 



I see no reason why these things should remain inscrutable. There is indeed 



1911. Q q 



