450 



NA TURE 



[March 7, 1^95 



But there will commonly be fouad a few individuals which differ 

 so remirkably from their fellows as to catch the eye at once. 

 Such large deviations differ (rom the smaller ones, at least in 

 mc-t casts, by their extreme rarity ; but they have been ex- 

 tensively collecied, and most museums contain numerous 

 examples of il\eir occurrence. Some naluralis's have been led, 

 from the striking characier of such variations, to assume for 

 them a preponderant share in the modification of specific 

 character. These persons assume, if I understand them rightly, 

 that the advantages or disadvantages which accompany the more 

 frequent slight abnormalities are in themselves of necessity 

 slight ; and that the elTect of such slight abnormalities may be 

 neglected, in comparison with the effect produced by the 

 occasional appeatanceofconsiderable deviations from (he normal 

 type. They regard change in specific character as an event 

 which occurs, not slowly and continuously, but occasionally and 

 by steps of considerable magnitude; as a conseciuence of tlie 

 capricious appearance of "sports." 



Without presuming to deny the possible effect of occasional 

 " sports " in exceptional cases, it is the object of the present 

 remarks to discuss the effects of small variations, as it may be 

 deduced from the study of two organs in a single species 



The case chosen is the varia'ion, during growth and in adult 

 life, of two dimensions of female Carcinus nutnas, recently 

 investigated by a Commitiee of the Royal Society ; and what is 

 here said may be considered an appendi.v; to the report of that 

 Committee. 



The questions raised by the Darwinian hypothesis are 

 purely statistical, and the statistical method is the only one at 

 pre.'>ent obvious by which that hypothesis can be experimenially 

 checked. 



In order to estimate the effect of small variations upon the 

 chance of survival, in a given species, it is necessary to measure 

 first, the percentage of young animals exhibiting this variation ; 

 secondly, the percentage of adults in which it is present. If ihe 

 percentage of adulls exhibiting Ihe variation is less than the per- 

 centage of young, then a certain percentage of young animals has 

 either lost the character during growth or has been destroyed. 

 The law of growth having been ascertained, the rate of destruc- 

 tion may be measured ; and in this way an estimate of the 

 advantage or disadvantage of a variation may be obtained. In 

 order to estimate the effect of deviations of one organ upon the 

 rest of the body, it is necessary to measure the average 

 character of the rest of the body in individuals with varjing 

 magnitude of the given organ ; and by the application of Mr. 

 Gallon's method of measuring correlation, a simple estimate of 

 this effect may be obtained. In the same way a measure of the 

 effect of parental abnormality upon abnormality of offspring may 

 be numerically measured by the use of Gallon's correlation 

 function, and such measurements have been made, in the case of 

 human stature, by Mr. Gallon himself. 



It is to be observed that numerical data, of the kind here 

 indicated, contain all the information necessary for a knowledge 

 of the direction and rate of evolution. Knowing that a given 

 deviation from the mean characier is associated with a greater 

 or less percentage death-rale in the animals possessing it, the 

 importance of such a deviation can be estimated wiibout the 

 necessity of inquiring how that increase or decrease in the 

 death-rate is Iruught about, so ibat all ideas of "functional 

 adaptation " become unnecessary. In the same way, a theory 

 of the mechanism of heredity is not necessary in order to measure 

 the abnormality of offspring associated with a given parental 

 abnormality. The importance of such numerical statements, by 

 which the current theories of adaptation, iScc, m.ay be tested, is 

 »trongly urged. 



The report itself describes an attempt lo furnish some 

 of the numcric'l data referred to for two dimensions of the 

 shore crab. The data collected give an approximation to the 

 law of frequency with which deviations from the aver.ige 

 character occur at various ages. The conclusions drawn ate 

 (rt) Iha' there i» a period of growth during whrch the frequency 

 of deviations increases, illu-.traiing Darwin's statement that 

 variations frequently appear late in life ; (h) that in one case 

 the preliminary increase is fidlowcil by a decrease in the fre- 

 quency cf deviations of given magnitude, in the other case it is 

 not ; and that (n, awuming a particular law of growth (which 

 remains, at it admitted, lo be experimentally tolcd), the ob- 

 served phenomena imply a selective destruction in the one case, 

 and not in the other. 



It is not conicnded that the law of frequency at various ages. 



adoplcd in the report, is exact. It is, however, hope! that the 

 approximation is suiliciently exact to give numerical estimates 

 of the quantises measured, which are at least of the same order 

 as the quantities themselves, and for this reason it is hoped 

 that the njethod adopted may prove useful in other cases. 



SCIENCE IN THE MAGAZINES. 



TX the I'ebruary number of the K^rlnighlly, Dr. A. R. 

 Wallace discussed in some detail Mr. Hateson's views on 

 variation in relation to the method of organic evolution. He 

 concludes hisaitack in the current number, and considers Mr. 

 Francis Galton's views, stated in " Natural Inheritance " and 

 in "Thumb an<l Finger Marks." It is held that the methods 

 of organic evolution favoured by Mr. Bateson and Mr. Galton 

 have failed to establish themselves as having any relation to the 

 actual facts of nature. The reason for their failure is stated by 

 Dr. Wallace as follows : — "they have devoted themselves too 

 exclusively to one set of factors, while overl loking others which 

 are boih more general and more fundamental. These are — the 

 enormously rapid multiplication of all organisms during more 

 favourable periods, and the consequent weeding out of all but 

 the fittest in what must be on the whole stationary populations. 

 And, acting in combination with this a;;/;;/.!/ destruction oftlia 

 less tit, is the/.viW;Va/ elimination under recurrent unfavour- 

 able conditions, of such a large proportion of each species as to 

 leave only a small traction — the very elect of the elect — to con- 

 tinue the race. It is only by keeping the tremendous severity 

 of this inevitable and never-ceasing process of selection always 

 present to our minds, and applying it in detail to each suggested 

 new factor in the process of evolution, that we shall be able 

 to determine what part such factors can take in the production 

 of new species. It is because they have not done this, that the 

 two authors, whose works have been here examined, have so 

 completely failed to make any real advance towards a more 

 complete solution of the problem of the Origin of Species than 

 has been reached by Darwin and his successors." 



A story worth repeating here is told by Mr. John Murray, 

 the publisher, in Gooii lV,'>ds. One day Charles Darwin came 

 to see the late Mr. .Murray, and brought with him a MS. As 

 he laid it on the table, he said, " Mr. Murray, here isa book 

 which has cost me many years of hard labour ; the preparation 

 of it has alVorded me the greatest interest, but I can hardly hope 

 that it will prove of any interest lo the general public. Will 

 you bring it out for me, as you have done my other books ? 

 The booli was Darwin's famous work on " Karthworms," which 

 in the course of three months reached a fifth edition. Mr. 

 Murray gives the incident as an illustration of the extreme 

 modesty of a very distinguished man. The same magazine con- 

 tains some stories of snake cannibalism, by Mr. H. Stewart. 

 A very readable story, in which observations of the planet Mars, 

 and projects of signalling to our ruddy brother, arc described, 

 is contributed by Sir. J. Munro to Cassell's Fiimily Magiizii:- 

 Mr. .Munro makes the Martians signal to us by means of ligl ' 

 from various incandescent elements, the natures of which aie 

 detected spectroscopically. lie has a lively imatjination, and 

 is fairly accurate in his astronomical references In the English 

 llltistraleil, we notice another of Mr. Grant .Mien's " Moorland 

 Idylls "^ihis time on butterflies; and also something about lions, 

 by Mr. I'hil Robinson. In \.\Mi Strand Magazint, Mr. J. Holt 

 Schooling gives a number of ingenious diagrams for graphically 

 representing statistics relating lo the population of different 

 countries. I'hcre is also the concluding pait of an article by 

 Mr. W. G. FiizGerald, on " Some Curiosities of Modern Photo- 

 graphy," in which, among other illustrations, occur I'rof. Boys' 

 pictures of moving bullets, and a good reproduction of Dr. 

 Koberls' photograph of the nebula in Andromeda. Another 

 article of interest to photogra|)hcrs appears in Lc Mondt 

 Moderne (or Vehraaiy, under the title " Lcs Mouvcmcnts de 

 I'Ouvricr." A number of excellent reproductions of some of 

 M. Marey's photogiaphs accompany this article. The same 

 magazine contains a description of compressed air systems of 

 tramway traction. 



In addition to the mag.azines menlioncd in the foregoing, the 

 following have been received, but they do not contain any 

 articles of scientific interest : — Conlniiporary, Century, Scrihner, 

 Chaml'trs\ , Longman's, National, Sunday Magaiine, and 

 Humanitarian. 



NO. 1323, VOL. 51] 



