1/2 



NATURE 



[October 30, 19 19 



thirdly, because useless publications increase the 

 burden of librarians and scholars. We are far 

 from wishing- to discourage genuine attempts to 

 reproduce Fermat's line of thought. In view of 

 the state of mathematical knowledge 250 years 

 ago, Fermat's proof, assuming it to be correct — 

 a point on which expert opinions differ — is as 

 likely to be discovered by a clever schoolboy of 

 seventeen as by a more highly trained mathe- 

 matician. 



Mr. Cashmore, in the tract before us, presents 

 three distinct "proofs," all erroneous. In I. 

 (p. 14) he states that when 



ax^ + by2 = w", then to = aw^ + hv^^, 

 the letters denoting ordinary integers. A numeri- 

 cal example is enough to show that this is 

 erroneous ; thus 



22+5.12 = 32, 11.23 + 93=53; 



but there are no integral solutions of 



The first of several fallacies in II. occurs on 

 p. 26, and in III. (p. 43) Mr. Cashmore states 

 that when (^" — q")y"-i is divisible by pq, then y 

 is divisible by ^q, it being assumed that p and q 

 are integers with no common factor It is seen 

 that this deduction is erroneous by taking 



W. E. H. B. 



Secrets of Animal Life. By Prof. J. Arthur 

 Thomson. Pp. viii + 324. (London: Andrew 

 Melrose, Ltd., 1919.) Price 75. 6d. net. 

 This is a collection of forty essays, contributed 

 during recent years by Prof. Thomson to the 

 New Statesman, and now collected in a handy 

 and attractive volume. In his own clear and 

 charming style the author seeks " to interest 

 thoughtful readers in the multitudinous problems 

 of animal life," and he wisely enforces the lesson 

 that, in many cases, the solutions of these 

 problems are " secrets " still. Such familiar 

 subjects as the habits of rooks and cuckoos or 

 the " Fall of the Year " are mixed with review- 

 summaries of noteworthy recent zoological 

 literature of general interest such as Watson and 

 Lashley's observations on the "homing" of 

 terns, Emery's researches on the habits of 

 Amazon ants, or Petersen's surveys of the 

 Zostera-beds off the coasts of Denmark. The 

 problems of inheritance and evolution are pro- 

 minent, as might be expected, and from such 

 papers as "With Darwin Forwards " and "The 

 Mendelian Clue," the "thoughtful reader" may 

 gain a clear introductory view of the fields of 

 biological inquiry, as well as guidance in the way 

 of deeper study. Prof. Thomson never misleads 

 those for whom he writes by implying that after 

 reading him they have no more to learn ; his 

 treatment of "The Problem of Cave Blindness," 

 for example, affords a needed corrective to wide- 

 spread dogmatism on a subject that has appealed 

 to popular imagination since the early days of 

 evolutionary biology. G. H. C. 



NO. 2609, VOL. 104] 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself restonsibte for opinions 

 expressed by his correspondents. Neither can he undertake to 

 return, or to correspond with the writers of, rejected manu- 

 scripts intended for this or any other part of nature. No 

 notice is taken of anonymous communications.] 



International Relations in Science. 



I DO not agree with the proposals made by Prof. 

 D'Arcy Thompson in Nature of October 23. I think 

 that the loss our academies and societies move in this 

 matter the better. For my own part I objected alto- 

 gether to the proposal made during the war tO' 

 strike off our records the names of distinguished 

 men of enemy nationality who had been elected 

 " foreign members " before the war. They had not 

 been admitted to any power or rights in consequence 

 of that election, and it was, in my judgment, futile 

 and petty to endeavour to obliterate the record of the 

 honour which had been justly accorded to them. 



As to making overtures to, and the reception of 

 overtures from, the academies of those hostile 

 nationalities with which peace is not yet ratified, it 

 seems to me that our own societies and academies 

 should at present neither offer nor accept any such 

 overtures. They are mere formalities and demonstra- 

 tions without any real significance or value, and 

 must be, and are often designed to be, misleading. 

 On the other hand, I think every individual should 

 act according to his own feeling and judgment, an(J 

 not according to mass sentiment, in regard to entering 

 into friendly relatioos with German men of science. 

 At present I personally could not accept such rela- 

 tions. I wish to reserve all action in the matter until 

 my memory of many things has faded. But I will 

 never wittingly treat even those whom I most dislike 

 with less than justice tempered by generosity. 



E. Ray Lankester. 



The Response of Plants to Wireless Stimulation. 



.\ GROWING plant bends towards light; this is true, 

 not only of the main stem, but also of its branches 

 and attached leaves and leaflets. This movement in 

 response is described as the tropic effect of light. 

 Growth itself is modified by the action of light : 

 two different effects depending on the intensity 

 are produced ; strong stimulus of light causes 

 a diminution of rate of growth, but very feeble 

 stimulus induces an acceleration of growth. The 

 tropic effect is very strong in the ultra-violet region 

 of the spectrum with its extremely short wave-length 

 of light; but the effect declines practically to zero 

 as we move towards the less refrangible rays, the 

 yellow and the red, with their comparatively long 

 wave-length. As we proceed further in the infra-red 

 region we come across the vast range of electric 

 radiation, the wave-lengths of which vary from the 

 shortest wave I have been able to produce (o-6 cm.) 

 to others which may be miles in length. There thus 

 arises the very interesting question whether plants 

 perceive and respond to the long aether-waves, in- 

 cluding those employed in signalling through space. 



At first sight this would appear to be very un- 

 likely, for the most effective rays are in the ultra- 

 violet region with wave-length as short as 20x10-' 

 cm. ; but with electric waves used in wireless ^ sig- 

 nalling we have to deal with waves 50,000,000 times 

 as long. The perceptive power of our retina is con- 

 fined within the very narrow range of a single octave, 

 the wave-lengths of which lie between 70x10-" cm. 

 and 35x10-' cm. It is diflicult to imagine that 

 plants could perceive radiations so widely separated 

 from each other as the visible light and the invisible 

 electric waves. 



But the subject assumes a different aspect when we 



