May 31, 1883] 



NATURE 



101 



points save one, which, as he truly observes, is "seemingly 

 capable of settlement by scientific inquiry." This point simply 

 is as to whether variation in plants and animals is promiscuous 

 {not " lawless ") or is restricted to beneficial lines. 



Now with reference to this point, I observed in my first letter 

 (Nature, vol. xxvii. p. 362) that if variation is promiscuous it 

 is only the favourable variations that are able to survive, and 

 hence the sole ground of entertaining natural selection as an 

 agency in the process of evolution ; but that, on the other hand, 

 if it could be shown tint variations always take place ex- 

 clusively ia the directions required for a development of the 

 adaptations, so as to leave no room for the operation of natural 

 selection, then the evidence of design as deduced from the theory 

 of evolution would become comparable with that evidence as 

 deduced from the theory of special creation. But I also pointed 

 out that " the burden of proof lies with the natural theologim to 

 show that there has been some such intelligent guidance of I he 

 variations, not with the evolutionist to show cause why there 

 may not have been such guidance." And now I understand 

 Prof. Gray accepts this as a correct statement of thecase, observ- 

 ing in his last letter that, if variation is promiscuous, "then no 

 doubt the theory of natural selection may be ' the substitute of 

 the theory of special design,' so as to efface that evidence of 

 underlying intelligence which innumerable and otherwise inex- 

 plicable adaptations of means to ends in nature was thought to 

 furnish. If it is not so, then the substitute utterly fails." 



It is most satisfactory to me that the issue has thus been 

 clearly reduced to a simple matter of scienific observation, and 

 I may add that I am much interested to find that a naturalist of 

 such high standing as Prof. Gray still holds to the view that, 

 " so far as observation extends, it does not warrant the supposi- 

 tion of omnifarious and aimless variation." Of course, if I had 

 not believed in "aimless variation" as of universat occurrence 

 in organic nature, I should never have supposed that the theory 

 of evolution by natural selection could in any way touch the 

 theory of special design ; but finding that my fundamental belief 

 in this matter is still op;n to question by so esteemed an authority 

 as Prof. Gray, and observing that we are here upon the ground 

 of a purely scientific question, I should like to say a few words 

 in justification of this belief. 



No one has attended to the subject of variation with a tenth 

 part of the care that was bestowed upon it by Mr. Darwin, and 

 no one has been gifted with abetter judgment in matters of this 

 kind. 1 shall therefore restrict myself to giving a brief outline 

 of hi> matured opinion upon the subject. 



Everywhere he speaks of variation as promiscuous or aimless, 

 but never as " law less," and only under a carefully guarded 

 meaning as accidental. That is to say, he has no doubt that 

 every variation is due to causes, th iugh not of a teleological 

 kind. Of these causes he regards changes of environment as 

 highly important ; but neverlhele-s he is inclined to lay less 

 weight on these "than on a tendency to vary due to causes of 

 which « e are quite ignorant." ' But with reference to variations 

 not taking place exclusively in beneficial lines he says : " As 

 man has domesticated so many animals and plants belonging to 

 widely different classes, and as he certainly did not choose with 

 prophetic instinct those species which would vary most, we may 

 lifer that all natural species, if exposed to analogous conditions, 

 would, on an average, vary to the same degree. . . . We have 

 abundant evidence of the constant occurrence under nature of 

 slight individual differences of the most diversified kinds ; and 

 we are thus led to conclude that species have generally originated 

 by the natural selection of extremely slight differences ; . . . 

 although each modification must have its own exciting cause, 

 and though each is subjected to law, yet we can so rarely trace 

 the precise relation between cau-e and effect, that we are tempted 

 to speak of variations as if they arose spontaneously. We may 

 even call them accidental, but this must be only in the sense in 

 which we say that a fragment of rock dropped from a height 

 owes its shape to accident. ... If an architect were to rear a 

 noble and commodious edifice without the use of cut stone, by 

 selecting from the fragments at the base of a precipice wedge- 

 formed stones for his arches, elongated stones for his lintels, and 

 flat stones for his roof, we should admire his skill and regard 

 him as the paramount power. Now the fragments of stone, 

 though indispensable to the architect, bear to the edifice the same 

 relation which the fluctv.a'ing variations of organic beings bear to 

 the varied and admirable structures ultimately acquired by their 

 modified descendants. . . . The shape of the fragments at the 



* Origin of Species," 6lh edition, p. 107. 



base of our precipice may be called accidental, but this is not 

 strictly correct ; for the shape of each depends on a long 

 sequence of events, all obeying natural laws ; . • . but in regard 

 to the use to which the fragments may bt put, their shape may 

 be strictly said to be accidental. . . . Can it be reasonably 

 maintained that the Creitor intentionally ordered, if we use the 

 word in any ordinary sense, that certain fragments of rock should 

 assume certain shapes, so that the builder might erect his edifice ? 

 If the various laws which have determined the shape of each 

 fragment were not predetermined for the builder's sake, can it 

 be maintained with any greater probability that He specially 

 ordained for the sake of the breeder each of the innumerable 

 variations in our domestic animals and plants ; — many of these 

 variations being of no service to man, and not beneficial, far 

 more often injurious, to the creatures themselves? Did He 

 ordain that the crop and tail-feathers of the pigeon should vary 

 in order that the fancier might make his grotesque pouter and 

 fantail breeds? Did He cause the frame and mental qualities of 

 the dog to vary in order that a breed might be formed of in- 

 domitable ferocity, with jaws fitted to pin down the bull for 

 man's brutal sport ? But if we give up the principle in one case, 

 — if we do not admit that the variations of the primeval dog 

 were intentionally guided in order that the greyhound, for 

 instance, that perfect image of symmetry and vigour, might be 

 formed, — no shadow of reason can be assigned for the belief 

 that variations, alike in nature and the result of the same general 

 laws, which have been the groundwork through natural selection 

 of the formation of the most perfectly adapted animals in the 

 world, man included, were intentionally and specially designed. 

 However much we may wish it, we can hardly follow Prof. Asa 

 Gray in his belief ' that variati in has been led al nig certain 

 beneficial lines,' like a stream 'along definite and useful lines 

 of irrigation.'" ' 



I could give a number of other quotations to the same general 

 effect from the writings of Mr. Darwin, but I think these are 

 enough to show, as I have said, that if there is any evidence of 

 variations being determined in special and beneficial lines, it 

 now lies with the teleologist to adduce such evidence. If this 

 could be done it would be a matter of immense importance, both 

 from a scientific and a speculative point of view, seeing that on 

 the scientific side it would be subversive of the whole theory of 

 natural selection, and on the speculative side would therefore 

 leave us where we were before the publication of the " Origin 

 of Species." But at present the whole weight of such scientific 

 evidence as we have appears ti me unquestionably opposed to 

 Prof. Gray's statement that, "so far as observation extends, it 

 does not warrant the supposition of omnifarious and aimless 

 variation." George J. Romanes 



Carson Footprints 



In Naure (vo 1 . xxvii. p. 57S) wdiich I have just seen, the 

 Duke of Argyll calls your attention to the so-called human foot- 

 prints uncovered in the prison yard at Carson, Nevada. I have 

 carefully examined these tracks, and read a paper on the subject 

 before the California Academy of Science, August 27, 1S82. 

 Unfortunately the Proceedings of the Academy have not yet 

 been published, though copies of the several papers on this sub- 

 ject have been printed and privately distributed. Perhaps a 

 brief account of these tracks will be interesting to your readers. 



The nearly horizontal strata in which they occur consist of 

 beds of sandstone with thin layers of fine shale. The track 

 layer, which is one of these latter, has been uncovered over an 

 are 1 of nearly two acres, and forms the floor of the prison yard, 

 while the stone removed has been used to build the prison. In 

 the course of the excavation a number of fossils have been 

 found, among which the most important are the jaws and teeth 

 of an elephant, probably E. Americanus, and two species of 

 horse, Equus Pacificus and occidentaHs ; some freshwater shells, 

 all of recent species, have also been found. The age of the 

 deposit seems to be that of the " Kquus beds" of American 

 geologists, which by some are put in the uppermost Pliocene, 

 and by others in the lowest Quaternary. It is probably a tran- 

 sition between the two. 



The whole surface of the shale exposed in the prison yard 

 is literally covered with tracks of many kinds, but the mud was 

 so soft when the tracks w ere made that the nature of many of 

 them can only be guessed. Some were probably those of a 

 horse ; some probably of a wolf ; some certainly of a deer ; 



1 " Variations of Animals and Plants under Domestication." Secon 

 edition, vol. ii. pp. 401-2, 410, 416, 426-8. 



