August 31, 1893 J 



NA TURE 



413 



of the Physical Society ; that with a few modifications it could 

 deal with all the more important physical papers annually 

 published in this country ; and that such centralisation is very 

 desirable. Such modifications I beg to suggest are the follow- 

 ing : — (1) Let mathematical papers, i.e., those which consist 

 of problems in mixed mathematics rather than pure physics, be 

 offered to the Pliil. Mag., publishing the conclusions, with 

 a reproduction of any resulting diagram, in brief abstract in the 

 journal. (2) Let papers be invited not only for reading during 

 the winter 'tason, but for publication at intervals throughout 

 the year, whenever enough matter has been collected to fill a 

 number, as is done in many other publications. (3) Let selec- 

 tions be made from these for reading, on the grounds [«] of 

 scientific importance, [/'] suilability for discussion, [c] expeii- 

 mental demonstration. (4) Reprint in abstract, or occasionally 

 in full, papers read before other societies (excepting, of course, 

 the Royal Society). 



I feel that some apology is due for making these suggestions 

 elsewhere than at an annual general meeting of the Physical 

 Society, but the attendance at the meetings is no measure of 

 the important work which this society does in the publication 

 of physical papers, and as these suggestions arise directly out of 

 the discussion which has arisen in your columns, they may per- 

 haps not be out of place there. Ai.EX. P. Tkotter. 



28, Victoria Street, Westminster. 



The Definition of "Heredity." 



When all the world is ringing with the words "heredity" 

 and "inheritance," it is natural to feel some surprise and 

 amazement on hearing from even so high an authority as Dr. 

 Hurst that they are expressive of nothing but the incoherence 

 of ideas emanating from confused brains. Perhaps as a student 

 of Darwinism I may be allowed a little space in your columns 

 to suggest that there is an alternative view to that held by Dr. 

 Hurst. 



His position I understand to be this : No force of any kind 

 except natural selection is at work to preserve the form of 

 organisms from alteration. Does he mean to confine the ap- 

 plication of this statement to organisms existing under stable 

 conditions, or would it have equal force in the piobably 

 numerous cases where temporary changes in circumstances occur ? 

 Now it cannot be denied that there is some factor of consider- 

 able power controlling the variations of species from the normal 

 type ; but that it is a natural selection, as ordinarily understood, 

 seems to me to be at least open to discussion. If, without the 

 action of natural selection all species are liable to react to any 

 change in their environment, there is no reason against and very 

 great probability in favour of many species having been de- 

 stroyed by the advent of new conditions followed by the substi- 

 tution of new forms quite ill-adapted to the old conditions. 

 What would then be likely to happen should the original cir- 

 cumstances return ? Two alternatives are possible under Dr. 

 Hurst's view. Either the form resulting from the first change 

 must be lost, or it must again become modified ; but the chances 

 are infinite against any approximation to the original organism 

 being reached unless there be some tendency towards a return 

 to former types. 



If we adhere to the opinion that "heredity is something 

 more than mere family likeness," and not quite comparable to 

 the " tendency of all weathercocks to point to the south-west," 

 we are at once freed from the difficulty, and can see how a 

 species might outlive many temporary changes in the form of 

 influences 10 which it might be subjected. In order that species 

 may be modified to suit new permanent surroundings it is ob- 

 viously unnecessary that the variations arising among the indi- 

 viduals shall be very frequent, and, when organisation and en- 

 vironment are in agreement, it is equally obvious that the fewer 

 the departures from the normal type the better will it be for the 

 species. If, then, the tendency is strong in all organisms to 

 conform to an ancestral type, whenever there is a merely tem- 

 porary change of environment the chances of some at least of 

 the individuals leaving unmodified descendants, when the old 

 conditions reassert themselves, is vastly increased ; and if mean- 

 while .some other individual families have become somewhat 

 modified, then the number of species in existence may also have 

 been increased. Of course I am supposing that the period 

 during which abnormal conditions of life remain in force shall 

 not extend sufficiently to allow all the unmodified individuals 

 to be eliminated by the action of natural selection. 



If I have been successful in my argument, I think it will be 



NO. 1244, VOL 48] 



clear that the force which I should designate by the term 

 "heredity" cannot be described as a tendency fostered by 

 natural selection ; for, while any influence it may exert antago- 

 nistic to the development and continuance of species will be 

 counteracted by natural selection, the benefits it may confer are 

 almost entirely prospective, and therefore do not fall within the 

 range of the force which tends to preserve favourable variations. 



I conceive that the definition of the word "heredity" should 

 be — the tendency, more or less strong according to the age of 

 the species, to follow certain types, exhibited by all organisms, 

 and that it is no mere abstract idea devoid of objective existence, 

 but a force the importance of which we are not yet able to fully 

 grasp. 



In conclusion I should liketo mention a point with regard to 

 the case of Saturnia which has, I think, been overlooked. What 

 has really been proved is simply the fact that the insect is ex- 

 tremely susceptible to modification by change of food. If some 

 entirely new food-plant, if possible chosen from an entirely dif- 

 ferent order, could be found as a substitute for either species of 

 Inglans, and the result: were carefully watched, the experiment 

 could not fail to be instructive, I will not say conclusive. 



Rochdale, August 19. J. Spencer Smithson, 



Sexual Colouration of Birds. 



The recent controversy in your columns with regard to the 

 non-inheritance of acquired characters opens up the question 

 whether the principle of natural selection operates universally in 

 the animal kingdom, or whether we must involve other causes 

 to supplement it. In Dr. Hurst's letter of August 17 (p. 368) 

 is a sentence which seems to embody what has generally been 

 understood as Darwinism : " If anything has ever been rendered 

 certain in biology by prolonged experiment and observation, it is 

 the fact that specific characters are maintained constant by selec- 

 tion, and that alone." But how does this agree with Dr. 

 Wallace's theory of accessory plumes ? This theory he himself 

 thus expresses ("Darwinism," p. 293): "The fact that they 

 have been developed to such an extent in a few species is an 

 indication of such perfect adaptation to the conditions of exist- 

 ence, such complete success in the battle for life, that there is 

 in the adult male, at all events, a surplus of strength, vitality, 

 and growth-power which is able to expand itself in this way 

 without injury." Here we have two entirely different views of 

 what is meant by the struggle for existence. According to Dr. 

 Hurst it ii incessant ; let its operation cease, and the' characters 

 of the species become speedily obliterated. According to Dr. 

 Wallace a victorious species may leave the arena, arid rest upon 

 its laurels. But if natural selection ceases to work in this field, 

 why not in others? The colours, it is true, may be due merely 

 to waste products turned to account, but the annual growth of 

 the peacock's plumes — often nearly five feet in length — must 

 require a great expenditure of vital (orce. 



In Brown's " Thier-reich" it is stated that even in ordinary 

 cases moulting is not unaccompanied with danger to the bird. 

 And this is not all : the secondary wing feathers of the argus 

 pheasant are developed to such an extent that they are said " al- 

 most entirely to deprive the bird of flight " (" Descent of Man," 

 vol.'ii. p. 97). The theory by which Darwin himself accounted 

 for these phenomena, viz. that the female selected the most 

 brilliantly coloured male as her partner, explained the facts, 

 but failed for want of sufficient evidence that any such selection 

 took place. I cannot think that the two forms of sexual selec- 

 tion, by battle and by female preference, conflict, since the hen 

 bird might well admire the combination of fine plumes and war- 

 like prowess. 



There is, besides, Mr. Stolzmann's theory that it is to the 

 advantage of the species that the number of males should 

 be kept down, since bachelor males persecute the hen bird upon 

 the nest. This assumes what is not well proved, that males 

 largely outnumber females. But a very large proportion of the 

 species in which the cock-bird is highly decorated are poly- 

 gamous, and in these cases the number of males is obviously 

 excessive. Mr. Stolzmann's theory in no way conflicts with 

 Darwin's, but rather supplements it. Moreover, it is hardly 

 •nore than an extension of Dr. Wallace's view that the dullness 

 of the female's plumage is due to her need of protection, which 

 in the case of the male is less necessary. Both Darwin's theory 

 and Mr. Stolzmann's require further evidence, but they each 

 have the merit of suggesting a cause for the constancy of the 

 same plumage through successive generations. 



Scoutie, Lavig, N.B., August 24. F. C. IIeadley. 



