January 30, 1908] 



NA TURE 



293 



thought, and it may be commended to all who desire 

 the welfare of their' country. \\'e hope, however, the 

 education of the future will teach that it is unpardon- 

 able for a book of this kind to be published without 

 an index. 



ScouWng for Boys. A Handbook for Iiislruction in 

 Good Citizenship. By Lieut. -General R. S. S. 

 Baden-Powell, C.B. Parts i. and ii. (London : 

 Horace Cox, 190S.) Price of each part, 4d. net. 

 In an earlier volume, ".Aids to Scouting," Lieut. - 

 General Baden-Powell has shown that the charac- 

 teristics of the good scout are those which distinguish 

 the successful man of science. In his appeal to 

 headmasters in 1901, Prof. Armstrong pointed out 

 how full of good advice in the training of children 

 that book is. The present book, which is to be com- 

 pleted in six parts, two of which have now appeared, 

 also may be recommended as likely to result in the 

 development of faculties of observation, regard for 

 accuracy, conscientiousness, and other desirable 

 cliaracters. 



Photograms of the Year 1907. Text, pp. 48; illus- 

 trations, pp. 112. (London: Dawbarn and Ward, 

 Ltd., 1907.) Price 2s. net. 

 Between the covers of the book we have a collection 

 of reproductions of about 200 different pictures, about 

 one-fourth of which are selections from the exhibi- 

 tions held recently in London, while the remainder 

 serve as examples of the pictorial work of the year, 

 not onlv by home, but by colonial and foreign workers. 

 The pictures are excellently reproduced, on stout 

 paper, and every care seems to have been taken to 

 ensure their being as true as possible to the originals. 

 In the text Mr. H. Snowden Ward gives us an 

 interesting critique of the " Work of the Year," and 

 contributions are included from the pens of various 

 well-known colonial and foreign photographers. 



Those who wish to make themselves acquainted 

 with the main features of last year's work in pictorial 

 photography will find much to interest them in the 

 present issue. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

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

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Stability in Flight. 



Now that two or three people have succeeded, by skilful 

 manipulation, in travelling on a more or less determinate 

 course in the air, it would be well that inventors should 

 turn their thoughts to securing stability in flight without 

 the demand of constant attention on the part of the 

 aeronaut. 



In a note written some years ago on this subject, I 

 said : — " No flying machine will be satisfactory which does 

 not contain some automatic device for securing stability. 

 The principles which must be embodied in such a governor 

 are in themselves simple, and may be realised in many 

 ways. 



■■ The principal axes of the flying machine have to be 

 kept related in a definite way to the direction of the force 

 of gravity and of the accelerations. 



To do this, the action of the governor must depend on 

 the position of the axes of the machine in relation to the 

 direction of two pendulums (or their equivalents), one 

 having a very long and the other a very short period. 

 In this connection, ' long ' and ' short ' have reference 

 to what may be called the rate of instability." (A twenty- 

 second period for the long, and a tenth of a second for 

 the short pendulum, would be the sort of thing required.) 



NO. 1996, VOL. yj] 



The long pendulum presents the greatest practical 

 difiiculties, but they can be met. 



Until something of this kind is done, flying will remain 

 a feat of personal skill. Probably most people could 

 acquire this skill if they could practise when young, but, 

 in learning to fly, any accident generally puts an end to 

 the power of gaining further experience. 



A. Mallock. 



6 Cresswell Gardens, Kensington, S.W. 



The Inheritance of "Acquired" Characters. 



May I have space for a communication dealing, not 

 with Mr. Spicer's letter (p. 247), but with some problems 

 it suggests? 



.•\n individual develops from the germ-cell under the 

 influence of various stimuli, of which the principal are 

 nutriment, use, and injury. Nutriment supplies the 

 material, but not the stimulus, for all growtii. Up to 

 birth, the human being, for example, develops wholly or 

 almost wholly under this stimulus. Subsequently some of 

 his structures continue to develop under it, for instance, 

 his hair, teeth, external ears, and organs of generation, 

 which grow whether or not they be used. But most of 

 his structures now develop mainly, if not solely, under 

 the stimulus of use, for e.\ample, his voluntary muscles, 

 limbs, heart, and brain. Thus if the limb of an infant 

 be paralysed it grows comparatively little, and the muscles 

 atrophy. If the individual be injured, as by a cut, the 

 injury supplies the stimulus for the growth (scar) which 

 repairs the damage. 



Scientific writers are accustomed to divide the characters 

 of a living being into those which are " inborn " or 

 " innate " and those which are '* acquired," and are in 

 the habit of declaring that the former tend to be " in- 

 herited " by offspring, but not the latter. I doubt if any- 

 thing in science has been provocative of more confusion, 

 misunderstanding, and futile controversy than this use of 

 inaccurate terms. All our evidence indicates that the 

 structures of the child are derived, not from the corre- 

 sponding structures of the parent, but wholly from a 

 germ-cell which dwelt as a parasite within the parent. 

 Only in a purely metaphorical sense, then, does the child 

 inherit from the parent. It resembles the parent merely 

 because parent and child are derived from very similar 

 germ-plasms which have been acted on to a very similar 

 extent by very similar stimuli. 



If we analyse the words of biologists carefully, we find 

 that by an inborn character they imply one which has 

 developed under the stimulus of nutriment, and by an 

 acquirement one which has developed under the stimulus 

 of use or injury. When they speak of the " transmission " 

 of an " inborn " character, thev imply that it has developed 

 in bcth parent and child under the stimulus of nutriment; 

 when they speak, as is still sometimes done, of the trans- 

 mission of an acquirement, thev impiv that a character 

 which developed in the parent under the stimulus of use 

 or injury has developed in the child under the stimulus of 

 nutriment. Apart from the immediate effects of injury 

 (e.g. loss of tissue), I thinii it would puzzle anyone to 

 indicate in what respects an " inborn " character is more 

 innate and Inherited than an acquirement. Obviously 

 these vitally useful powers of growing, of developing in 

 certain fixed directions under the stimulus of use and 

 injury are just as truly inborn and rooted in the germ- 

 plasm, just as truly products of evolution, as the power of 

 growing under the stimulus of nutriment. It follows that 

 the so-called acquirements are *' Innate " and " Inherited " 

 In precisely the same sense as the so-called inborn 

 characters. 



It Is true that, since no character can be used or injured 

 until it exists, all structures begin to develop under the 

 stimulus of nutriment, and therefore that all acquirements 

 are modifications of innate characters. But early develop- 

 ment Is no evidence of innateness, and most acquirements, 

 like most of the growth made under the stimulus of 

 nutriment, are nothing other than extensions of growth 

 previously made. It is true also that innate characters 

 arise Inevitably as the child develops, whereas some 

 acqiairements are more or less rare. But this Is only 

 because the stimulus of nutriment Is inevitably received. 



