May lo, 1894 J 



NA TURE 



29 



selection will not, in most cases, make much difference in the 

 maintenance of such adjustment. Obviously this ground of 

 objection to the theory of the cessation of selection opens up a 

 much larger question than can here be dealt with, viz. the ad- 

 justing or eliminating value of the presence of selection. But 

 if Prof. Weldon will read what I wrote last year in the Con- 

 temporary Review, during the Spencer- VVeismann controversy, 

 he will find that in this matter I am quite on the side of Mr. 

 Bateson and himself. It has always been my endeavour to 

 argue that the ultra-Darwinian school of Wallace and Weismann 

 are pushing deductive speculation much too far in maintaining 

 "The All-Sufficiencyof Natural .Selection." I shall never believe 

 — any more than Darwin believed — that what I have called 

 "selection value " is unlimited. But this is not incompatible 

 with the belief that in whatever degree natural selection may 

 have been instrumental in the construction of an adjustment, 

 in some degree must its subsequent cessation tend to the 

 degeneration of this adjustment, especially where complicity as 

 distinguished from size is concerned, as stated in my last letter. 

 Summing up his objections to the doctrine of Panmixia, 

 Prof. Weldon says they are two : " First, it is based on the as- 

 sumption that selection, when acting on a species, must of 

 necessity change the mean character of the species — an assump- 

 tion incompatible with the maintenance of a species in a constant 

 condition." This refers to the paragraph of his letter which, as 

 already stated, I do not understand. The doctrine of Panmi.xia, 

 as far as we are now concerned with it, does not refer to 

 "species," but to specific characters, i.e. structures, organs, 

 instincts, &c. Again, the doctrine, even with regard to specific 

 characters, makes no " assumption " touching the presence of 

 "selection acting on a species" — least of all that iwz^i presence 

 will not maintain the species in a constant condition. On the 

 contrary, the very essence of the doctrine is, that it is \.\\t presence 

 of selection which tnaintains the constancy of a species (or specific 

 character), and therefore that it is the cessation of selection which 

 »(;»«/j the constancy by withdrawal of the maintaining influence. 

 Hence, I do not understand Prof. Weldon's first objection. 

 His second is, "that in the only case which has been 

 experimentallv investigated, the condition said to result 

 from a condition of Panmixia does not, in fact, occur." 

 This one case, he explains, is: — "Mr. Galton has shown 

 that civilised Englishmen are themselves in a condition of Pan- 

 mixia, at least with respect to several characters, especially 

 stature and the colour of the eyes. Now the mean stature of 

 I Englishmen is known to be increasing, and there is no evidence 

 lof the disappearance of coloured eyes." But, as regards stature, 

 lit can scarcely be mainlamed that there is not some cause <it 

 ^work to account for the increase ; yet, unless this is maintained, 

 |the case is clearly irrelevant. Again, the colour of the eyes of 

 [Our mixed population cannot have had more than thirty or 

 forty generations svherein to be affected by Panmixia, and there- 

 Tore the most ardent supporters of this doctrine would scarcely 

 [expect any result to be yet appreciable in the case of so pro- 

 nounced a racial character. Surely a better "case" is the one 

 which I have already given in the most ancient and the most 

 Irapidly-breeding of our domesticated animals. It was the 

 .facts observed in this "case" which first suggested tome the 

 •doctrine of Panmixia, and so led me to question the inherited 

 leffects of disuse. Similarly, a year later, Mr, Galton, in his 

 !" Theory of Heredity " (which anticipated by about ten years 

 all the fundamental parts of Weismann's), wrote of P.anmixia 

 thus : — " A special cause may be assigned for the effects of dis- 

 luse in causing hereditary atrophy of the disused parts. It has 

 already been shown that all exceptionally developed organs 

 tend to deteriorate ; consequently those that are not protected 

 by heredity will dwindle. The level of muscular efficiency in 

 Ihe wing of a strongly-Hying bird is like the level of water in 

 ^he leaky vessel of a Danaid, only secured to the race by con- 

 stant effort, so to speak ; let the effort be relaxed ever so little, 

 hnd the level immediately falls. . . . That this is a universal 

 [endency among races in a state of nature, is proved by the fact 

 ihat existing races are only kept at their present level by the 



severe action of selection." Gkorge J. Rum.a.nes. 



Oxford, May 5. 

 P.S. — I gladly accept the verbal correction in Prof. Weldon's 



hird paragraph. 



Physiological Psychology and Psychophysics. 

 Owing to my bookseller's habit of forwarding N/VTURic in 

 nonthly batches, I have only just seen the remarks appended to 



NO. 1280, VOL. 50] 



my letter in the issue of March X 5. I think that the termino- 

 logical question is sufficiently important to warrant a reply to 

 these. 



(1) I do not, of course, "subsume" psychophysics to 

 physiological psychology. The latter, I stated, is both wider 

 and narrower than experimental psychology ; and wider, because 

 it includes the consideration of certain (" the most important ") 

 psychological problems — not of ail such problems. (Kor this 

 view of physiological psychology, f/". Wundt, "Physiological 

 Psychology," fourth edition, I. p. 9.) 



(2) Fechner, " the coiner of the word," defines psychophysics 

 as " eine exacte Lehre von den functionellen oder Abhangig- 

 keitsbeziehungen zwischen Korper und Seele, allgemeiner 

 zwischen Korp-rlichen undgeisligen, physi^cher und psychischer 

 Welt." {cf. " Psychophysik," second edition, I. p. 8.) What my 

 critic says on this head is, therefore, incorrect. 



(3) In th-? most widespread and important school of experi- 

 mental psychology existing to-day — that of Wundt — there is 

 agreement upon definitions. And even if my critic's remarks 

 were true, it would not follow that a number of wrongs made a 

 right. 



(4) I might, in my last letter, have adverted upon the term, 

 psyiho-physiological. I did not understand what it exactly 

 meant. In NATttRE of March 29, Prof. LI. Morgan defines 

 it (p. 504) as the equivalent of Fechner's internal psychophysics. 

 {op. cit. p. 10). In this sense it is not wanted ; the phrases 

 "external" and "internal psychophysics" are in use. (It 

 might, however, be used to signify that part of physiology which 

 has a conscious correlate. ) 



(5) My critic triumphantly adduces "reaction-limes" as a 

 subject treated of in the University College course. That course, 

 i.e. deals with one conscious element, and with <;«?type (action) 

 o( one of the two modes of conscious combination (association : 

 fusion is left out of account). Prof. Munsterberg (Preface to 

 Psycliological Lahoratjry of Haward University) speaks of " the 

 error, which is so prevalent, that experimental psychology is 

 confined to the study of sensations and simple reaction-times." 



(6) I am sorry that Dr. Hill's name should have been men- 

 tioned. I should not think of offering any opinion upon his 

 work. I know no more of it than do the other readers of 

 Nature. If he sees these remarks, I hope he will believe that 

 my original criticism was meant to be quite impersonal. 



(7) "By far the larger part of the really fruitful work [in 

 psycho-physiology] " says my critic, " . . . . has been done in 

 the investigation of the senses." If he means by psycho- 

 physiology what Prof LI. Morgan does, I must disagree with 

 him. To substantiate either view would need an article. As 

 he writes not as a working psychophysicist (else he would have 

 been acquainted with Fechner's Psychophysik), I think that the 

 onus proliandi lies with him. 



(8) As to Prof. LI. .Morgan's paper on " the scope of psycho- 

 physiology [= internal psycophysic-i]," I must plead guilty to 

 finding the writer's eclecticism somewhat unintelligible, and his 

 whole treatment a little general and superficial. 



(9) A very interesting minor question is that of the relation 

 of Wundt's physiology psychology to Fechner's internal psycho- 

 physics. {cf. Kuipe, Arch. f. Geschichte du Philosopliie, 1892, 

 pp. 183-4.) 



Cornell University, April l6. E. B. TiTCHENER. 



It seems hardly profitable to carry on a discussion with Dr. 

 Titchener at intervals of more than a month. I readily confess 

 that through an error of memory, for it is a good while since I 

 read the " Elemente der Psychophysik," I misrepresented 

 Fechner's use of the term psychophysics. The fact, however, 

 that he recognised an "outer psychophysics," and the further 

 fact that, as he shows ("Elemente," i. p. u), nearly the whole 

 of his inquiry has to do with establishing the relation of external 

 stimuli to psychic phenomena, show that the error I fell 

 into was not altogether unnatural. Are not the inquiries of 

 Weber, Fechner, and their successors still brought under the 

 head of psychophysics by those who reject Fechner's peculiar 

 " psycho- physical " interpretation of the results? And do not 

 nine students out of ten, who are not themselves "working 

 psycho-physicists," associate the term "psychophysics" with 

 these important lines of inquiry ? If so, I would contend that 

 there is room for a reconsideration of the terminology of the 

 subject. The retention of Fechner's " outer psychophysics " 

 seems confusing if, as I understand Dr. Titchener to say, 

 "psychophysics ' has properly to do with the correlation 



