366 



NA TURE 



\_Fed. 17, 188; 



LETTERS TO THE EDITOR 



\_7he Editor does not hold himself resfonsiilc for opinions ex- 

 pressed by his correspondents. Neither can he undertakt lo 

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

 scripts. No notice is taken of anonymous communications. 



[ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containing interesting and novel facts. ] 



Mr. Romanes on Physiological Selection 



1 HAVE just seen Mr. Romanes's article in the Nineteen! h 

 'Century, and his letter specially replying to myself in your issue 

 of January 13 (p. 247). I do not propose to continue the dis- 

 cussion, but ask leave to make a few observations on some 

 features of his reply in both the article and the letter. 



On the question of the "inutility of specific characters," he 

 appeals to authority against nie, and especially to Darwin's very 

 cautious remarks, which seem to me to support my view much 

 more than they do those of Mr. Romanes ; but in any case this is 

 a matter in which I decline to accept authority as an infallible 

 guide. The impossibility of proving a negative is proverbial, 

 but my opponent declares that his negative — the uselessness of 

 specific characters — wants no proving, but must be accepted till 

 in every case the affirmative is proved. Here, again, is a canon 

 of criticism the validity of which I wholly deny. 



As to the swamping effects of intercrossing, there is again an 

 appeal to authority, and Mr. Romanes now e.'iplains away (in 

 the Nineteenth Century) what he had said about " simultaneous 

 ■variations," by asking me to show such variations as the occur- 

 a'ence of an incipient spur on a duck's foot or horn on the head of 

 :a racehorse, in the belief, apparently, that these are the class of 

 characters which are distinctive of closely-allied species ! Such 

 a demand, seriously made, appears to me so preposterous as to 

 render further discussion of the matter with such an adversary 

 out of the question. 



The argument to show that the supposed physiological varia- 

 tions would be perpetuated, seems to me as weak and unsatis- 

 factory as ever. Tlie question is really not worth further dis- 

 cussion till the required variations are proved to exist in the 

 requisite abundance and po;sessing the peculiar relations to each 

 other and to the rest of the species which would alone give them 

 any chance of survival. 



I now leave the question, as between myself and Mr. Romanes, 

 to the consideration of those naturalists who may be able to 

 bestow upon it the requi-ite time and attention. 



Alfred R. Wallace 



Washington, U..S.A., January 30 



Instantaneous Shutters 



In reference to tlie interesting'paperby Mr. Malloc'dn Natl; re 

 (February 3, p. 325), I quite agree with him in his condemnatian 

 of a drop-shutter of any form. 



But I would point out a form of shutter that I have myself 

 found of the greatest value — one, namely, working horizontally 

 across the lens. It has the very great advantage in landscape 

 work that it can carry an aperture of this form SJ or any modili- 

 cation thereof, the advantage gained thereby being that the sky 

 receives a far shorter exposure than the foreground, a point of 

 much importance in landscape photography. The '\J piece is 

 loose, and any shajie cut out of black cardboard or paper can 

 be inserted. Of this power I have frequently availed myself 

 when photographing snow-clad mountains. 



The shutter can be made to pass across the lens at any speed, 

 from the most instantaneous flash to slower motions, and it has 

 the further advantage of working immediately behind the lens — 

 the proper place, I think, for a shutter. 



H. Stuart-Wurtlev 



South Kensington Museum, February 4 



Svastika Cross and Sun 



Is there any evidence that the srastiha represents the sun ? 

 and is it not a simple co Jecture? (NATtJitE, February 10, p. 

 345)- 



The svastika r^ is a complex emblem, and there is a possible 

 origin which has not been investigated. It decomposes into 



tno \, and this is a character to be found extensively distributed 

 throughout the syllabic and alphabetic systems. If T. is a 

 symbol for man and fish, it will not be related to sun i nme- 

 di.itely. 



The theory of Mr. Ilaliburton and others, and mythological 

 conformity, give the cross or Tau as naturally derived from the 

 Pleiades, and not fro:n the sun. The cross is also a symbol for 

 the nose in prehistoric sculpture. Hvde Clarke 



32 St. George's Square, S.W., February 12 



\ 



Life-Energy, or the Dynamics of Health and Disease 



Since it is admitted that matter is indestructible, it is obvious 

 that life can be only the manifestation of that energy whic'a is 

 set free by the reduction of compounds embxiying more energy 

 to states of combination which embody less energy. 



Life therefore is the result of the continuous interchange of 

 partners between the compound molecules constituting chemical 

 and organic compounds. 



"In any transformation which takes place -without the appli- 

 cation, or the giving out, of work, the heat developed is the 

 equivalent of the excess of the original over the final potential 

 energy due to the chemical affinities involved ; the final state oj 

 ti'cry combination is that in which the potential energy of chemical 

 affinity is a minimum " (Tail). 



If these words formulate the law which governs those com- 

 binations of elementary substances known as inorganic compounds, 

 how much more must they refer to the combinations of the same 

 elementary substances wliich go to form organic compounds ? 



Life thus becomes an expression for the sum of the difference 

 between the original potential energy of the food and the final 

 potential energy of the excretions. All chan^'e in the configura- 

 tion of matter, whether physical or chemical, must be accom- 

 panied by either the evolution of, or the absorption of, energy. 



Energy, as far as is known, has but one source, the sun. 



Whether that energy act by direct impingement of solar rays 

 producing the ascending scale of effects from genial warmth to 

 fatal sunstroke, or whether it be second-hand, from the decom- 

 position of vegetable matter, or third-hand, from the decomposition 

 of animal substances which obtained it from vegetable substances, 

 its origin is still the same. 



Assuming then the universality of this energy, which shows 

 itself in all the intangible forms of life, and growth, and all 

 organic change, it will be the effort of the writer to adduce evi- 

 dence to prove that much which is still mysterious in both health 

 and disease is due to its subtle action too. 



The vibrations of direct solar energy which fall upon the optic 

 nerve give rise to those molecular disturbances which produce 

 the subjective sensation of light. 



Physical change is thus originated by an immaterial agent. 

 Work is done, and cannot continue to be performed without 

 renewal of the material acted on. 



But when the vibrations of direct solar energy fall upon the 

 tissues of a growing .plant, energy is incorporated into those 

 tissues. This energy so attunes the atomic vibrations in the 

 plant molecules as to bring them into combining harmony with 

 the carbon and hydrogen atoms present in the forms of carbonic 

 acid and water. 



The hydrocarbon compound, starch, is formed, and embodies 

 within itself the energy which made it starch. 



Each molecule of starch maintains its individuality as starch 

 only so long as it retains within itself that solar energy under the 

 influence of which it became starch ; as soon as part of that 

 energy is lost the starch is degraded to its original condition of 

 carbonic acid and water. Yet that energy which works such 

 molecular miracles is sought for among the products of decom- 

 position in the form of heat only, and if not recognisable as such 

 is put out of count in the world's work. 



While it is thus evident that the vegetable kingdom lives a 

 constructive life, storing up energy from an extra-terrestrial 

 source, it is equally demonstrable that the animal kingdom lives 

 a destructive life, unable to add .aught to the sum of energy 

 required for the work of the planet. Consequently an approxi- 

 mate expression for the value of the energy incorporated in the 

 plant may be found in the work done, as a result of its con- 

 sumption, by the animal. 



4500 grains of plant carbon ai'e daily excreted by every 

 average man in the form of carbonic acid. Carbon and oxygen 

 independently embody a greater sum of original energy than is 



