tiveness of the tongue-tip is required | tion, or the preservation of Favored for perfect speech, this use is not suffi- Races in the Struggle for Life." Here ciently important to have been devel- are two figures of speech which conoped by natural selection. spire to produce an impression more or less erroneous. The expression "natural selection" was chosen as serving to indicate some parallelism with artificial selection-the selection exercised by breeders. Now selection connotes How, then, is this remarkable trait of the tongue-tip to be accounted for? Without difficulty, if there is inheritance of acquired characters. For the tongue-tip has, above all other parts of the body, unceasing experiences of volition, and thus gives to the thoughts small irregularities of surface. It is in of readers a wrong bias. Some incontact with the teeth, and either con- crease of this bias is produced by the sciously or unconsciously is continually words in the second title, "favored exploring them. There is hardly a races;" for anything which is favored moment in which impressions of adja- implies the existence of some agent cent but different positions are not be- conferring a favor. I do not mean that ing yielded to it by either the surfaces Mr. Darwin himself failed to recognize of the teeth or their edges; and it is the misleading connotations of his continually being moved about from words, or that he did not avoid being some of them to others. No advantage misled by them. In chapter iv. of the is gained. It is simply that the tongue's "Origin of Species "he says that, conposition renders perpetual exploration sidered literally, "natural selection is a almost inevitable; and by perpetual false term," and that the personificaexploration is developed this unique tion of nature is objectionable; but he power of discrimination. Thus the law holds throughout, from this highest degree of perceptiveness of the tongue-tip to its lowest degree on the back of the trunk; and no other explanation of the facts seems possible. thinks that readers, and those who adopt his views, will soon learn to guard themselves against the wrong implications. Here I venture to think that he was mistaken. For thinking this there is the reason that even his "Yes, there is another explanation," disciple, Mr. Wallace - no, not his disI hear some one say; "they may be ciple, but his co-discoverer, ever to be explained by panmixia." Well, in the honored-has apparently been influfirst place, as the explanation by pan- enced by them. When, for example, in mixia implies that these gradations of combating a view of mine, he says that perceptiveness have been arrived at by" the very thing said to be impossible the dwindling of nervous structures, by variation and natural selection has there lies at the basis of the explanation an unproved and improbable assumption; and, even were there no such difficulty, it may with certainty be denied that panmixia can furnish an explanation. Let us look at its preten been again and again effected by variation and artificial selection; " he seems clearly to imply that the processes are analogous and operate in the same way. Now this is untrue. They are analogous only within certain narrow limits; and, in the great majority of cases, natural selection is utterly incapable of doing that which artificial selection does. To see this it needs only to de-personalize nature, and to remember that, as Mr. Darwin says, nature is "only the aggregate action and product of many natural laws [forces]." Observe its relative shortcomings. Artificial selection can pick out a particular trait, and, regardless of other traits of the individuals displaying it, can increase | which it arises than of other families. it by selective breeding in successive Variations which, though advantageous, generations. For, to the breeder or fail to do this, must disappear again. fancier, it matters little whether such Let us take a case. individuals are otherwise well consti- Keenness of scent in a deer, by givtuted. They may be in this or that ing early notice of approaching eneway so unfit for carrying on the strug-mies, subserves life so greatly that, gle for life, that, were they without other things equal, an individual having human care, they would disappear it in an unusual degree is more likely forthwith. On the other hand, if we than others to survive, and, among deregard nature as that which it is, an scendants, to leave some similarly assemblage of various forces, inorganic endowed or more endowed, who again and organic, some favorable to the transmit the variation with, in some maintenance of life and many at va- cases, increase. Clearly this highly riance with its maintenance-forces useful power may be developed by natwhich operate blindly -we see that ural selection. So also, for like reasons, there is no such selection of this or that may quickness of vision and delicacy trait, but that there is a selection only of hearing. Though it may be reof individuals which are, by the aggre- marked in passing that since this extra gate of their traits, best fitted for living. sense-endowment, serving to give early And here I may note an advantage alarm, profits the herd as a whole, possessed by the expression "survival which takes the alarm from one indiof the fittest;" since this does not tend vidual, selection of it is not so easy, to raise the thought of any one charac- unless it occurs in a conquering stag. ter which, more than others, is to be But now suppose that one member of maintained or increased; but tends the herd-perhaps because of more rather to raise the thought of a general efficient teeth, perhaps by greater musadaptation for all purposes. It implies cularity of stomach, perhaps by secrethe process which nature can alone tion of more appropriate gastric juices carry on the leaving alive of those - is enabled to eat and digest a not which are best able to utilize surround- uncommon plant which the others reing aids to life, and best able to combat fuse. This peculiarity may, if food is or avoid surrounding dangers. And scarce, conduce to better self-maintewhile this phrase covers the great mass nance, and better fostering of young, if of cases in which there are preserved the individual is a hind. But unless well-constituted individuals, it also this plant is abundant, and the advancovers those special cases which are tage consequently great, the advantages suggested by the phrase "natural se- which other members of the herd gain lection," in which individuals succeed from other slight variations may be beyond others in the struggle for life equivalent. This one has unusual agilby the help of particular characters ity and leaps a chasm which others which conduce in important ways to balk at. That one develops longer hair prosperity and multiplication. For now in winter, and resists the cold better. observe the fact which here chiefly Another has a skin less irritated by concerns us, that survival of the fittest flies, and can graze without so much can increase any serviceable trait only interruption. Here is one which has if that trait conduces to prosperity of an unusual power of detecting food the individual, or of posterity, or of under the snow; and there is one both, in an important degree. There which shows extra sagacity in the can be no increase of any structure by choice of a shelter from wind and rain. natural selection unless, amid all the That the variation giving the ability to slightly varying structures constituting eat a plant before unutilized may bethe organism, increase of this particu- come a trait of the herd, and eventually lar one is so advantageous as to cause of a variety, it is needful that the indigreater multiplication of the family invidual in which it occurs shall have Like more descendants, or better descend-| decrease it only in certain cases. ants, or both, than have the various the increase produced by a variation, other individuals severally having their the decrease produced by one must be small superiorities. If these other in- such as will sensibly conduce to preserdividuals severally profit by their small vation and multiplication. It is, for superiorities, and transmit them to instance, conceivable that were the long equally large numbers of offspring, no and massive tail of the kangaroo to increase of the variation in question become useless (say by the forcing of can take place; it must soon be can- the species into a mountainous and celled. Whether in the " Origin of rocky habitat filled with brushwood), a Species " Mr. Darwin has recognized variation which considerably reduced this fact, I do not remember, but he the tail might sensibly profit the indihas certainly done it by implication in vidual in which it occurred; and, in his "Animals and Plants under Do- seasons when food was scarce, might mestication." Speaking of variations cause survival when individuals with in domestic animals, he there says that, large tails died. But the economy of "Any particular variation would gen- nutrition must be considerable before erally be lost by crossing, reversion, any such result could occur. Suppose and the accidental destruction of the that in this new habitat the kangaroo varying individuals, unless carefully had no enemies; and suppose that, preserved by man" (vol. ii. 292). That consequently, quickness of hearing not which survival of the fittest does in cases like the one I have instanced is to keep all faculties up to the mark, by destroying such as have faculties in some respect below the mark; and it can produce development of some one faculty only if that faculty is predominantly important. It seems to me that many naturalists have practically lost sight of this, and assume that natural selection will increase any advantageous trait. Certainly a view now widely accepted assumes as much. being called for, large ears gave no greater advantage than small ones. Would an individual with smaller ears than usual survive and propagate better than other individuals in consequence of the economy of nutrition achieved? To suppose this is to suppose that the saving of a grain or two of protein per day would determine the kangaroo's fate. Long ago I discussed this matter in the "Principles of Biology" (§ 166), taking as an instance the decrease of the jaw implied by the crowding of the teeth, and now proved by measurement to have taken place. Here is the pas The consideration of this view, to which the foregoing paragraph is introductory, may now be entered upon. This view concerns, not direct selec-sage:tion, but what has been called, in quesNo functional superiority possessed by a tionable logic, “reversed selection" small jaw over a large jaw, in civilized life, the selection which effects, not increase can be named as having caused the more of an organ, but decrease of it. For frequent survival of small-jawed individas, under some conditions, it is of ad-uals. The only advantage which smallness vantage to an individual and its descend- of jaw might be supposed to give, is the ants to have some structure of larger advantage of economized nutrition; and size, it may be, under other conditions this could not be great enough to further - namely, when the organ becomes useless of advantage to have it of smaller size; since, even if it is not in the way, its weight and the cost of its nutrition are injurious taxes on the organism. But now comes the truth to be emphasized. Just as direct selection can increase an organ only in certain cases, so can reversed selection The the preservation of men possessing it. decrease of weight in the jaw and cooperative parts that has arisen in the course of many thousands of years, does not amount to more than a few ounces. This decrease has to be divided among the many generations that have lived and died in the interval. Let us admit that the weight of these parts diminished to the extent of an ounce in a single generation (which is a large admission); it still cannot be con- | pear from a species which lives in the tended that the having to carry an ounce dark." Doubtless this is a reasonable less in weight, or the having to keep in repair conclusion. To explain the facts on an ounce less of tissue, could sensibly affect the hypothesis that acquired characters any man's fate. And if it never did this are inheritable seems very difficult. nay, if it did not cause a frequent survival One possible explanation may indeed of small-jawed individuals where large be named. It appears to be a general jawed individuals died, natural selection could neither cause nor aid diminution of law of organization that structures are stable in proportion to their antiquity; the jaw and its appendages. that while organs of relatively modern origin have but a comparatively superficial root in the constitution, and readily disappear if the conditions do not favor their maintenance, organs of ancient origin have deep-seated roots in the constitution, and do not readily disappear. 1 When writing this passage in 1864, I never dreamt that a quarter of a century later, the supposable cause of degeneration here examined and excluded as impossible, would be enunciated as not only a cause, but the cause, and the sole cause. This, however, has hapHaving been early elepened. Weismann's theory of degen- ments in the type, and having continued eration by panmixia, is that when an to be reproduced as parts of it during a organ previously maintained of the period extending throughout many geoneedful size by natural selection, is no logical epochs, they are comparatively longer maintained at that size, because persistent. Now the eye answers to it has become useless (or because a this description as being a very early smaller size is equally useful), it results organ. But waiving possible interprethat among the variations in the size, tations, let us admit that here is a diffiwhich take place from generation to culty - a difficulty like countless others generation, the smaller will be pre- which the phenomena of evolution served continually, and that so the part present, as, for instance, the acquirewill decrease. And this is concluded ment of such a habit as that of the without asking whether the economy in Vanessa larva, hanging itself up by the nutrition achieved by the smaller vari-tail and then changing into a chrysalis ation, will sensibly affect the survival which usurps its place a difficulty of the individual and the multiplication which, along with multitudes, has to of its stirp. To make clear his hypoth- await future solution, if any can be esis, and to prepare the way for criticism, let me quote the example he himself gives when contrasting the alleged efficiency of dwindling by panmixia with the alleged inefficiency of dwindling from disuse. This example is furnished him by the Proteus. Concerning the "blind fish and amphibia "found in dark places, which have but rudimentary eyes "hidden under the skin," he argues that "it is difficult to reconcile the facts of the case with the ordinary theory that the eyes of these animals have simply degenerated through disuse." After giving instances of rapid degeneration of disused organs, he argues that if the effects of disuse are so striking in a single life, we should certainly expect, if such effects can be transmitted, that all traces of an eye would soon disap found. Let it be granted, I say, that here is a serious obstacle in the way of the hypothesis; and now let us turn to the alternative hypothesis, and observe whether it is not met by difficulties which are much more serious. Weismann writes: 1 While the proof of this article is in hand, I learn that the Proteus is not quite blind, and that its eyes have a use. It seems that when the underground streams it inhabits are unusually swollen, some individuals of the species are carried out of the caverns into the open (being then sometimes captured). It is also said that the creature shuns the light; this trait being, I presume, observed when it is in captivity. Now obviously, among individuals carried out into the open, those which remain visible are apt to be carried off by enemies ; whereas, those which, appreciating the difference between light and darkness, shelter themselves in dark places, survive. Hence the tendency of natural selection is to prevent the decrease of the eyes beyond that point at which they can distinguish between light and darkness. Thus the apparent anomaly is explained. t The caverns in Carniola and Carinthia, | of the eye, some larger, some smaller, in which the blind Proteus and so many thau the size previously reached, and other blind animals live, belong geologically that in virtue of the economy, those to the Jurassic formation; and although we do not exactly know when, for example, the Proteus first entered them, the low organization of this amphibian certainly indicates that it has been sheltered there for a very long period of time, and that thousands of generations of this species have succeeded having the smaller will continually survive and propagate, instead of those having the larger. Properly to appreciate this supposition, we must use figures. To give it every advantage we will assume that there have been only two thousand generations, and we will assume that, instead of being reduced to a rudiment, the eye has disappeared altogether. What amounts of variation shall we suppose? If the idea is that the process has operated uniformly on each generation, the implication is that individuals having the eyes 20th less some advantage has been gained by the which demand consideration - namely, the in weight; and this will hardly be conhigher developinent of other organs which tended. Not to put the hypothesis at compensate for the loss of the degenerating this disadvantage, let us then imagine structure, or the increase in size of adjacent that there take place, at long intervals, parts. If these newer developments are of decreasing variations considerable in advantage to the species, they finally come amount-say th, once in a hundred to take the place of the organ which natural selection has failed to preserve at its point of highest perfection.1 one another in the caves. Hence there is no reason to wonder at the extent to which the degeneration of the eye has been already carried in the Proteus, even if we assume that it is merely due to the cessation of the conserving influence of natural selection. But it is unnecessary to depend upon this assumption alone, for when a useless organ degenerates, there are also other factors On these paragraphs let me first remark that one cause is multiplied into two. The cause is stated in the abstract, and it is then re-stated in the concrete, as though it were another cause. generations. This is an interval almost too long to be assumed; but yet if we assume the successive decrements to occur more frequently, and therefore to be smaller, the amount of each becomes too insignificant. If, seeing the small head, we assume that the eyes of the Proteus originally weighed some ten Manifestly, if by decrease of grains each, this would give us, as the the eye an economy of nutriment is amount of the decrement of th, ocachieved, it is implied that the econo- curring once in a hundred generations, mized nutriment is turned to some ad- one grain. Suppose that this eelFantageous purpose or other; and to shaped amphibian, about a foot long Specify that the nutriment is used for and more than half an inch in diamthe further development of compensat- eter, weighs three ounces a very ng organs, simply changes the indefi- moderate estimate. In such case the ate statement of advantage into a decrement would amount to 11th of definite statement of advantage. There the creature's weight; or, for convenare not two causes in operation, though ience, let us say that it amounted to the matter is presented as though there were. But passing over this, let us now represent to ourselves in detail this procwhich Professor Weismann thinks Till, in thousands of generations, effect he observed reduction of the eyes; the process being that at each sucBessive stage in the decrease, there Last take place variations in the size 1 Essays upon Heredity, p. 87. th, which would allow of the eyes being taken at some fourteen grains each. To this extent, then, each oc |