556 



NA TURE 



[April 29, 1922 



the most striking fashion how crude and inadequate are 

 the suppositions which we entertained before the world 

 of gametes was revealed. The appearance of the plant 

 tells us httle or nothing of these things. In Mendehsm, 

 we learnt to appreciate the implication of the fact that 

 the organism is a double structure, containing ingredients 

 derived from the mother and from the father respec- 

 tively. We have now to admit the further conception 

 that between the male and female sides of the same 

 plant these ingredients may be quite differently appor- 

 tioned, and that the genetical composition of each may 

 be so distinct that the systematist might without 

 extravagance recognise them as distinct specifically. 

 If then our plant may by appropriate treatment be 

 made to give off two distinct forms, why is not that 

 phenomenon a true instance of Darwin's origin of 

 species ? In Darwin's time it must have been ac- 

 claimed as supplying all and more than he ever 

 hoped to see. We know that that is not the true 

 interpretation for that which comes out is no new 

 creation. 



Only those who are keeping up with these new 

 developments can appreciate fully their vast signifi- 

 cance or anticipate the next step. That is the province 

 of the geneticist. Nevertheless, I am convinced that 

 biology would gain greatly by some co-operation among 

 workers in the several branches. I had expected that 

 genetics would provide at once common ground for the 

 systematist and the laboratory worker. This hope has 

 been disappointed. Each still keeps apart. System- 

 atic literature grows precisely as if the genetical dis- 

 coveries had never been made, and the geneticists more 

 and more withdraw each into his special " claim " — a 

 most lamentable result. Both are to blame. If we 

 cannot persuade the systematists to come to us, at 

 least we can go to them. They too have built up a vast 

 edifice of knowledge which they are willing to share 

 with us, and which we greatly need. They too have 

 never lost that longing for the truth about evolution 

 which to men of my date is the salt of biology, the 

 impulse which made us biologists. It is from them 

 that the raw materials for our researches are to be 

 drawn, which alone can give catholicity and breadth to 

 our studies. We and the systematists have to devise a 

 common language. 



Both we and the systematists have everything to 

 gain by a closer alliance. Of course we must specialise, 

 but I suggest to educationists that, in biology at least, 

 specialisation begins too early. In England certainly, 

 harm is done by a system of examinations discouraging 

 to that taste for field natural history and collecting, 

 spontaneous in so many young people. How it may be 

 on this side, I cannot say, but with us attainments of 

 that kind are seldom rewarded, and are too often 

 despised as trivial in comparison with the stereotyped 

 biology which can be learned from text-books. Never- 

 theless, given the aptitude, a very wide acquaintance 

 with nature and the diversity of living things may be 

 acquired before the age at which more intensive study 

 must be begun, and is the best preparation for research 

 in any of the branches of biology. 



The separation between the laboratory men and the 

 systematists already imperils the work, I might almost 

 say the sanity, of both. The systematists will feel the 

 ground fall from beneath their feet, when they learn 

 and realise what genetics has accomplished, and we, 

 close students of specially chosen examples, may find 

 our eyes dazzled and blinded when we look up from our 

 work-tables to contemplate the brilliant vision of the 

 natural world in its boundless complexity. 



I have put before you very frankly the considerations 

 which have made us agnostic as to the actual mode and 

 processes of evolution. When such confessions are 

 made the enemies of science see their chance. If we 

 cannot declare here and now how species arose, they 

 will obligingly offer us the solutions with which obscur- 

 antism is satisfied. Let us then proclaim in precise 

 and unmistakable language that our faith in evolution 

 is unshaken. Every available line of argument con- 

 verges on this inevitable conclusion. The obscurantist 

 has nothing to suggest which is worth a moment's 

 attention. The difficulties which weigh upon the pro- 

 fessional biologist need not trouble the layman. Our 

 doubts are not as to the reality or truth of evolution, 

 but as to the origin of species, a technical, almost 

 domestic, problem. Any day that mystery may be 

 solved. The discoveries of the last twenty-five years 

 enable us for the first time to discuss these questions 

 intelligently and on a basis of fact. That synthesis will 

 follow on an analysis, we do not and cannot doubt. 



Alternating-Current Mineral Separation,^ 



By Prof. S. J. Truscott, Imperial College (Royal School of Mines), South Kensington. 



INVESTIGATION of the possible use of alternating 

 i current in magnetic separation, either in the 

 direction of obtaining a rotary field by polyphase 

 currents, or otherwise, has hitherto not resulted in 

 any useful discovery. Recently, however, Mr. W. M. 

 Mordey, past president of the Institution of Electrical 

 Engineers, by arranging poles energised by two-phase 

 currents to follow one another across the stream, has 

 succeeded in driving iron minerals and iron compounds 

 in that direction. This effect is not one of ordinary 

 magnetic attraction and repulsion, but apparently a 

 display of " hysteretic repulsion," a repulsion conse- 

 quent upon the magnetism residual after each alterna- 



' W. M. Mordey, Transactions South African Institute of Electrical 

 Engineers, December 1921. 



NO. 2739, VOL. 109] 



tion, and made continuous by the moving field 

 contributed by polyphase current. 



A laminated alternating-current magnet behaves 

 towards magnetite or iron-filings much like a direct- 

 current magnet, in that tufts of these materials form 

 at the poles, from which lines of force radiate. 

 On the other hand, towards such a feebly magnetic 

 mineral as haematite no attraction appears to be 

 exercised but a decided repulsion is witnessed, for 

 example, when a dish containing powdered haematite 

 is laid upon an upturned pole. This repulsion is con- 

 tinuous when the dish spans a number of poles and 

 these are energised by polyphase current. Similar 

 repulsion of magnetite occurs at a lower excitation or 

 when the dish is lifted sensibly off the poles. 



