Dec. 6, 1888] 



NATURE 



127 



say I am aware of anything of the kind. The " late Prof. 

 Nageli " may be dead against me possibly ; but I was mt aware 

 that he was dead in any other sen?e. Nor do I see that as he 

 insists (quite correctly as I think) on the inutility of fa'juily 

 ■characters he can afford much comfort to Mr. Romanes, who 

 regards them as (generally adaptive. 



I have devoted a good deal of time to the study of 

 Mr. Romanes's paper published by the Linnean Society. 

 I believe I have stated the conclusions to be drawn from 

 that paper with tolerable accuracy. If I have not done 

 so, I undoubtedly owe him a sincere apology. But I am 

 bound to confess that, the more I study his views, the 

 more I find myself in disagreement with him as to the in- 

 utility of specific characters ; as to the utility and mode of 

 origin of generic characters and those of higher grade ; as to 

 sterility as a primary specific difference ; and as to the value of 

 so-called physiological selection. In all these matters he is, I 

 am satisfied, contradicted by botanical experience. 1 think if 

 he had imita'ed the example of Mr. Darwin, and had carefully 

 collected a large b^dy of evidence on each of these points with 

 a perfectly open mind, he would have found this out for himself. 

 What, however, I view with less patience than his unsustained 

 generalizations, is his persistent attempt to place them on the 

 shoulders of the Darwinian theory. I have reluctantly arrived 

 at the conviction that his only excuse for so doing is that he has 

 fundamentally misunderstood that theory. At any rate, I cannot 

 in any other way account for the strained mterpretation which 

 he has put on passages from Mr. Darwin's writings. I may 

 give, as an example, the passage he quotes "to justify the 

 insinuation " that the " Origin of Species " has been misnamed ; 

 the obvious drift of this does not relate to specific differences 

 at all, but to those which are characteristic of families. It is 

 easy to see, in facr, by a comparison of pp. 170 and 176 of the 

 sixth edition, that the passage cited by Mr. Romanes wa^ inserted 

 by Mr. Darwin to meet the point raised by Nageli to which I 

 have referred above. Certainly I think that no one would have" 

 been more surprised than Mr. Darwin when he wrote the words 

 could he have fore een that they would be used to im]3Ugn the 

 validity of the title of his theory and of his book. Everyone 

 knows that Mr. Darwin was the fairest and most generous- 

 minded of men. He constantly admits ihe possibility of explana- 

 tions to which he really, however, did not attach much import- 

 ance. Such admissions Mr. Romanes appears to me to treat 

 as if wrung from a hostile witness. In my judgment this is 

 entirely to misapprehend their significance or the spirit in which 

 they were made. W. T. Thiselton-Dyer, 



Koyal Gardens, Kew, December I. 



Natural Selection and Useless Structures. 



In his letter on " Mr. Romanes's Paradox " (Nature, Nov- 

 ember I, p. 7), Mr. Thiselton Dyer questions the existence of 

 indifferent or slightly disadvantageous specific characters. That 

 letter referred, in a highly laudatory yet somewhat deprecating 

 manner, to a lately published (Proc. Roy. Soc, No. 269) 

 obituary notice of Mr. Darwin ; and it implied that Mr. G. 

 J. Romanes, from his unfamiliarity with the study of species, did 

 not quite know what he was talking about when he asserted 

 that such indifferent characters do in fact exist. I, who claim 

 to have had some slight experience in the practical discrimina- 

 tion of spe;ies, ask permission to make a few observations in 

 your columns on the subject. 



Everyone would, I supp^se, regard the frequent absence of 

 the toe-nail on the hallux of the orang as an indifferent matter, 

 but I am inclined to consider the feeble development of that 

 digit itself as a slightly di-advantageous one. However that 

 may be, I am strongly of opinion that the abortion of the index 

 in the Potto can never have saved the lives of the earliest in- 

 dividuals so distinguished. I have, as yet, heard no reason 

 assigned for the life-saving action of the thumbless hands of 

 Colobtis and Aides, or of the tail of the one chameleon in which 

 alone (so far as I know) that org.in is not prehensile. The metallic 

 lustre of the peritoneum of some fishes is hard to explain by either 

 "natural" or "sexual" selection; as also are such specific 

 characters as the extension, or non-extension, of the premaxillse 

 to the frontals, or the pattern of the foldings of enamel and 

 cement in various Rodents. The complexity of the teeth of 

 Labyrinthoiion, or the similar multiplicity co-existing in those of 

 Orycteropus and Myliohatis (which can hardly have been derived 

 from a common ancestor, though their resemblance extends even 

 to microscopic structure), are unquestionably good taxidcrmic 



characters ; yet they can hardly have been due to the action of 

 natural selection, as I pointed out in my " Genesis of Species" 

 in 1870. But if such "selection" cannot originate characters 

 which form the diagnosis of a species, then it cannot possibly be 

 the origin of such species. To say that the rudimentary index 

 of the Potto is a character which, though itself useless, has been 

 carried on the back, as it were, of some possible bat unknown 

 useful simultaneous variation which co exists with it or did co-exist 

 with it in som3 unknown ancestor is a purely gratuitous asser- 

 tion. Such assertions are the less warranted because we have 

 evidence that the energy of Nature's destructive forces has 

 been exaggerated. Prof. Dyer tells us that natural selection 

 is a hard taskmaster ; but it is not, I think, so hard a 

 one as some persons suppose. This seems to me clear 

 from such facts as the finding of hares and rabbits in 

 which an incisor tooth has grown so as to complete the 

 circle it always tends to form — a condition which shows a 

 remarkable preservation of life under extremely disadvantageous 

 circumstances. A stoat, three of whose feet had been cut off 

 at different times by traps, has nevertheless (I am informed) 

 lived long enough for its injured limbs to heal so thoroughly 

 that the beast could get a living on its one foot and three 

 stumps. Cases of prolonged life under trying circumstances are 

 not so rare. I recollect the skeleton of a monkey which must 

 have long suffered from acute rheumatism in its native forests. 



Prof. Dyer deprecates the admission, by the author of the 

 obituary notice, that indifferent or slightly disadvantageous 

 characters may be evolved in spile of "natural selection." 

 But the obituary notice admits viitch more than that, since, 

 according to its author, a maintainer of "natural selection " is 

 free to affirm the genesis of specie? by sudden, considerably, 

 definite variations, directly produced by the reaction of the 

 innermost nature of an organism on the stimulus of its environ- 

 menr, according to precise innate laws of its being. This cer- 

 tainly is not "natural selection," as understood and taught by 

 Mr. Darwin, and the inventor of a new term has alone the 

 right to fix what its meaning shall be. 



The statement of ihe obituary notice seems equivalent to an unin- 

 tentional but virtual abandonment of 'natural selection," while 

 still retaining the name — reducing it, in effect, to that merely sub- 

 ordinate role we all admit that it plays. To call such a mode ot 

 origin " origin by natural selection "seems much the same thing as 

 declaring an elaborately prepared theatrical transformation scene 

 to be brought about by the chains and cords which prevent its 

 moving pieces from passing beyond their assigned limits. The 

 true meaning of " natural selection " is frankly declared by that 

 distinguished biologist upon whose shoulders the mantle of the 

 deceased prophet seems to have fallen. Prof. Lankester, in his 

 article "Zoology" (in the last volume of the " Encyclopredia 

 Britannica") has just given a mo>t straightforward, lucid, and 

 forcible representation of Darwinism. Nevertheless, the article 

 (in the same volume) on "V.rlation" by Prof. Geddes, 

 appears to me to be more in harmony with the facts of biology. 

 It is, of course, open to anyone to say : " All species which 

 succeed do so from some cause, and this may be metaphorically 

 said to ' select ' them." Therefore, since all causes are " natural " 

 causes, every species which does succeed must succeed through 

 " natural selection." This is equivalent to saying : " Nature is 

 so conditioned as to produce the results it does produce " — an 

 assertion most true, but somewhat trivial. When a term is so 

 stretched as to mean "anything," it thereby comes to mean 

 " nothing." and its use can serve no purpose save the preserva- 

 tion of a phrase it may be desired, for some reason, not to 

 discard. S r. George Mivart. 



Hurstcote, Chilwonh, Surrey, November 28. 



A Mussel living in the Branchiae of a Crab. 



Late this autumn, while searching for Crustacea at Amroth, 

 in South Wales, I found rather an exceptionally good specimen 

 of the common shore crab {Carcinus vuvnas), which I took 

 back to the hotel to clean and preserve. On removing the 

 carapace, I found a mussel living among the branchiae, and 

 fastened to them by means of its byssus. It was in good con- 

 dition, and measured % of an inch in length. The carapace of 

 the crab measured z\ inches wide by i| inches long. I could 

 find no signs on the exterior of the crab of anything remarkable 

 within, nor was there any damage to the shell, or hole through 

 which the mussel could have passed. It seems that the mussel, 

 while yet minute, or in a larval condition, must have been carried 



