 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org, recorded by Chip in Tampa, Florida, on February 28, 2006. The Origin of Species by Means of Natural Selection or the Preservation of Favourite Races in the Struggle for Life. Sixth London Edition by Charles Darwin. Chapter 7. Miscellaneous Objections to the Theory of Natural Selection Longevity. Modifications not necessarily simultaneous. Modifications apparently of no direct service. Progressive development. Characters of small functional importance, the most constant. Supposed incompetence of natural selection to account for the incipient stages of useful structures, causes which interfere with the acquisition through natural selection of useful structures, gradations of structure with changed functions, widely different organs in members of the same class, developed from one and the same source, reasons for disbelieving in great and abrupt modifications. I will devote this chapter to the consideration of various miscellaneous objections which have been advanced against my own views, as some of the previous discussions may thus be made clearer. But it would be useless to discuss all of them, as many have been made by writers who have not taken the trouble to understand the subject. Thus a distinguished German naturalist has asserted that the weakest part of my theory is that I consider all organic beings as imperfect. What I have really said is that all are not as perfect as they might have been in relation to their conditions, and this is shown to be the case by so many native forms in many quarters of the world having yielded their places to intruding foreigners. Nor can organic beings, even if they were at any one time perfectly adapted to their conditions of life, have remained so when their conditions changed, unless they themselves likewise changed, and no one will dispute that the physical conditions of each country, as well as the number and kinds of its inhabitants, have undergone many mutations. A critic has lately insisted with some parade of mathematical accuracy that longevity is a great advantage to all species, so that he who believes in natural selection must arrange his genealogical tree in such a manner that all the descendants have longer lives than their progenitors. Cannot our critics conceive that a biennial plant or one of the lower animals might range into a cold climate and perish there every winter, and yet owing to advantages gained through natural selection, survive from year to year by means of its seeds or ova. Mr. E. Ray Lancaster has recently discussed this subject, and he concludes, as far as its extreme complexity allows him to form a judgment, that longevity is generally related to the standard of each species in the scale of organization, as well as to the amount of expenditure in reproduction and in general activity, and these conditions have, it is probable, been largely determined through natural selection. It has been argued that, as done of the animals and plants of Egypt, of which we know anything, have changed during the last three or four thousand years, so probably have none in any part of the world. But, as Mr. G. H. Lewis has remarked, this line of argument proves too much, for the ancient domestic races figured on the Egyptian monuments or embalmed are closely similar or even identical with those now living, yet all naturalists admit that such races have been produced through the modification of their original types. The many animals which have remained unchanged since the commencement of the glacial period would have been an incomparably stronger case, for these have been exposed to great changes of climate and have migrated over great distances, whereas in Egypt, during the last several thousand years, the conditions of life, as far as we know, have remained absolutely uniform. The fact of little or no modification having been affected since the glacial period would have been of some avail against those who believe in an innate and necessary law of development, but it is powerless against the doctrine of natural selection or the survival of the fittest, which implies that when variations or individual differences of the beneficial nature happen to arise, these will be preserved, but this will be affected only under certain favorable circumstances. The celebrated paleontologist, Braun, at the close of his German translation of this work, asks how, on the principle of natural selection, can a variety live side by side with the parent species? If both have become fitted for slightly different habitats of life or conditions, they might live together, and if we lay on one side polymorphic species, in which the variability seems to be of a peculiar nature, and all mere temporary variations such as size, albinism, etc., the more permanent varieties are generally found, as far as I can discover, inhabiting distinct stations, such as highland or lowland, dry or moist districts. Moreover, in the case of animals which wander much about and cross freely, their varieties seem to be generally confined to distinct regions. Braun also insists that the distinct species never differ from each other in single characters, but in many parts, and he asks how it always comes that many parts of the organization should have been modified at the same time through variation and natural selection. But there is no necessity for supposing that all the parts of any being have been simultaneously modified. The most striking modifications, excellently adapted for some purpose, might as was formerly remarked, be acquired by successive variations, if slight, first in one part and then in another, and as they would be transmitted altogether, they would appear to us as if they had been simultaneously developed. The best answer, however, to the above objection is afforded by those domestic races which have been modified, chiefly through man's power of selection, for some natural purpose. Look at the race and Dre horse, or at the Greyhound and Mastiff, their whole frames and even their mental characteristics have been modified. But if we could trace each step in the history of their transformation and the latter steps can be traced, we should not see great and simultaneous changes, but first one part and then another, slightly modified and improved. Even when selection has been applied by man to some one character alone, of which our cultivated plants offer the best instances, it will invariably be found that although this one part, whether it be flower, fruit or leaves, has been greatly changed, almost all the other parts have been slightly modified. This may be attributed partly to the principle of co-related growth, and partly to so-called spontaneous variation. A much more serious objection has been urged by Bronn and recently by Broca, namely that many characters appear to be of no service whatsoever to their possessors, and therefore cannot have been influenced through natural selection. Bronn adduces the length of the ears and tails of the different species of hairs and mice, the complex folds of enamel in the teeth of many animals, and a multitude of analogous cases. With respect to plants this subject has been discussed by Negaly in an admirable essay. He admits that natural selection has affected much, but he insists that the families of plants differed chiefly from each other in morphological characters, which appear to be quite unimportant for the welfare of the species. He consequently believes in an innate tendency towards progressive and more perfect development. He specifies the arrangement of the cells in the tissues and of the leaves on the axis, as cases in which natural selection could not have acted. To these may be added the numerical divisions in the parts of the flower, the position of the ovules, the shape of the seed, when not of any use for dissemination, etc. There is much force in the above objection. Nevertheless, we ought in the first place to be extremely cautious in pretending to decide what structures now are or have formerly been of use to each species. In the second place it should always be borne in mind that when one part is modified so will be other parts, though certainly dimly seen causes such as increased or diminished flow of nutriment to a part, mutual pressure, an early developed part affecting one subsequently developed, and so forth, as well as through other causes which lead to the many mysterious cases of correlation which we do not in the least understand. These agencies may be all grouped together for the sake of brevity under the expression of the laws of growth. In the third place we have to allow for the direct and definite action of changed conditions of life and for so-called spontaneous variations in which the nature of the conditions apparently plays quite a subordinate part. Bud variations, such as the appearance of a moss rose on a common rose, or of a nectarine on a peach tree, offer good instances of spontaneous variations. But even in these cases, if we bear in mind the power of a minute drop of poison in producing complex gulls, we ought not to feel too sure that the above variations are not the effect of some local change in the nature of the sap. Due to some change in the conditions, there must be some efficient cause for each slight individual difference as well as for the more strongly marked variations which occasionally arise. And if the unknown cause were to act persistently, it is almost certain that all the individuals of the species would be similarly modified. In the earlier editions of this work I underrated, as it now seems probable, the frequency and importance of modifications due to spontaneous variability. But it is impossible to attribute to this cause the innumerable structures which are so well adapted to the habits of life of each species. I can no more believe in this than that the well adapted form of a race-horse or greyhound, which before the principle of selection by man was well understood, excited so much surprise in the minds of older naturalists, can thus be explained. It may be worth while to illustrate some of the foregoing remarks. With respect to the assumed inutility of various plants and organs, it is hardly necessary to observe that even in the higher and best known animals many structures exist which are so highly developed that no one doubts that they are of importance, yet their use has not been or has only recently been ascertained. As Braun gives the length of the ears and tail in the several species of mice as instances, though trifling ones, of differences in structure which can be of no special use, I may mention that, according to Dr. Schoble, the external ears of the common mouse are supplied in an extraordinary manner with nerves, so that they no doubt serve as tactile organs. Hence the length of the ears can hardly be quite unimportant. We shall also presently see that the tail is a highly useful prehensile organ to some of the species, and its use would be much influenced by its length. With respect to plants, to which, on account of Nagli's essay, I shall confine myself in the following remarks, it will be admitted that the flowers of the orchids present a multitude of curious structures which, a few years ago, would have been considered as mere morphological differences without any special function, but are now known to be of the highest importance for the fertilization of the species through the aid of insects, and would probably have been gained through natural selection. No one until lately could have imagined that in dimorphic and trimorphic plants the different lengths of the stamens and pistols and their arrangement could have been of any service, but now we know this to be the case. In certain whole groups of plants the ovules stand erect, and in others they are suspended, and within the same ovarium of some few plants one ovule holds the former, and a second ovule the latter position. These positions seem at first purely morphological, or of no physiological signification, but Dr. Hooker informs me that within the same ovarium the upper ovules alone in some cases, and in others the lower ones alone are fertilized, and he suggests that this probably depends on the direction in which pollen tubes enter the ovarium. If so, the position of the ovules, even when one is erect and the other suspended within the same ovarium, would follow the selection of any slight deviations in position which favored their fertilization and the production of seed. Several plants belonging to distinct orders habitually produce flowers of two kinds, the one open of the ordinary structure, the other closed and imperfect. These two kinds of flowers sometimes differ wonderfully in structure, yet may be seen to graduate into each other on the same plant. The ordinary and open flowers can be intercrossed, and the benefits which certainly are derived from this process are thus secured. The closed and imperfect flowers are, however, manifestly of high importance, as they yield with the utmost safety a large stock of seed, with the expenditure of wonderfully little pollen. The two kinds of flowers often differ much, as just stated in structure. The petals in the imperfect flowers almost always consist of mere rudiments. The pollen grains are reduced in diameter. In Ononis Columne five of the alternative stamens are rudimentary, and in some species of Viola three stamens are in this state, two retaining their proper function, but being of very small size. In six out of thirty of the closed flowers in an Indian violet, name unknown for the plants have never produced with me perfect flowers, the sepals are reduced from the normal number of five to three. In one section of the Malfigassier the closed flowers, according to A. de Jusiot, are still further modified, for the five stamens which stand opposite to the sepals are all aborted. A sixth stamen standing opposite to a petal being alone developed. And this stamen is not present in the ordinary flowers of this species. The style is aborted, and the ovaria are reduced from three to two. Now, although natural selection may well have the power to prevent some of the flowers from expanding, and to reduce the amount of pollen when rendered by the closure of the flowers superfluous, yet hardly any of the above special modifications can have been thus determined, but must have followed from the laws of growth according to the functional inactivity of parts during the progress of the reduction of the pollen and the closure of the flowers. It is so necessary to appreciate the important effects of the laws of growth that I will give some additional cases of another kind, namely of differences in the same part or organ due to differences in relative position on the same plant. In the Spanish chestnut, and in certain fir trees, the angles of divergence of the leaves differ, according to Jusiot, in the nearly horizontal and the upright branches. In the common rue, and some other plants, one flower, usually the central or terminal one opens first, and has five sepals and petals, and five divisions to the ovarian, while all the other flowers on the plant are tetramerous. In the British adoxa, the uppermost flower generally has two calyx lobes, with the other organs tetramerous, while the surrounding flowers generally have three calyx lobes, and the other organs pentamerous. In many composite and umbifilie, and some other plants, the circumferential flowers have their corollas much more developed than those of the center, and this seems often connected with the abortion of the reproductive organs. It is a mere curious fact, previously referred to, that the achines, or seeds of the circumference and center, sometimes differ greatly in form, color, and other characters. In carthomas, and in some other composite, in the central achines alone are furnished with apapus, and in the hierosis the same head yields achines of three different forms. In certain umbifare, the exterior seeds, according to Tauch, are ortho spermus, and the central one, colio spermus, and this is a character which was considered by Dekandel to be in other species of the highest systematic importance. Professor Braun mentions a fumaraceous genus, in which the flowers in the lower part of their spike bear oval, ribbed, or one-seeded nutlets, and in the upper part of the spike, lancelete, two-valve, and two-seeded celics. In these several cases, with the exception of the well-developed ray florets, which are of service in making the flowers conspicuous to insects, natural selection cannot, as far as we can judge, have come into play, or only in a quite subordinate manner. All these modifications follow from the relative position and interaction of the parts, and it can hardly be doubted that if all the flowers and leaves on the same plant had been subjected to the same external and internal condition as are the flowers and leaves in certain positions, all would have been modified in the same manner. In numerous other cases we find modifications of structure which are considered by botanists to be generally of a highly important nature, affecting only some of the flowers of the same plant, or occurring on distinct plants which grow together under the same conditions. As these variations seem of no special use to the plants, they cannot have been influenced by natural selection. Of their cause we are quite ignorant, we cannot even attribute them, as in the last class of cases to any proximate agency, such as relative position. I will give only a few instances. It is so common to observe on the same plant, flowers indifferently tetramorous, pentamorous, etc., that I need not give examples. But as numerical variations are comparatively rare, when the parts are few, I may mention that, according to Dekendol, the flowers of Popavar Bractetum offer either two sepals with four petals, which is the common type with poppies, or three sepals with six petals. The manner in which the petals are folded on the bud is in most groups of very constant morphological character, but Professor Asa Gray states that with some species of mimulus, the estivation is almost as frequently that of the renantidae as of the antirinidae, to which the latter tribe, the genus, belongs. August Saint-Hilaire gives the following cases. The genus Zantaxelon belongs to a division of the rootice with a single ovary, but in some species flowers may be found on the same plant and even in the same panicle with either one or two ovaries. In Hiliantium, the capsule has been described as unilocular or trilocular, and in H. Mutabil, un dame pluie ou malage s'attend entre le pericarp et la placenta. In the flowers of Soparnia officinalis, Dr. Masters has observed instances of both marginal and free central placentation. Lastly, Saint-Hilaire found toward the southern extreme of the range of Gomphia oleiformis, two forms which he did not at first doubt were distinct species, but he subsequently saw them growing on the same bush, and adds, Voilà, donc dans une même individu, des loges et une style qui s'est rachèchement tantôt à son axe venticulé et tantôt à une ginobesse. We thus see that with most plants many morphological changes may be attributed to the laws of growth and the interaction of parts independently of natural selection. But with respect to Nagelli's doctrine of an innate tendency toward perfection or progressive development, can it be said in the case of these strongly pronounced variations that the plants have been caught in the act of progressing toward a higher state of development? On the contrary, I should infer from the mere fact of the parts in question differing or varying greatly on the same plant that such modifications were of extremely small importance to the plants themselves, of whatever importance they may generally be to us for our classifications. The acquisition of a useless part can hardly be said to raise an organism in the natural scale, and in the case of the imperfect closed flowers above described, if any new principle has to be invoked, it must be one of retrogression, rather than of progression, and so it must be with many parasitic and degraded animals. We are ignorant of the exciting cause of the above specified modifications, but if the unknown were to act almost uniformly for a length of time, we may infer that the result would be almost uniform, and in this case all the individuals of the species would be modified in the same manner. From the fact of the above characters being unimportant for the welfare of the species, any slight variations which occurred in them would not have been accumulated and augmented through natural selection. A structure which has been developed through long-continued selection, when it ceases to be of service to a species, generally becomes variable, as we see with rudimentary organs, for it will no longer be regulated by this same power of selection. But when, from the nature of the organism and of the condition, modifications have been induced which are unimportant for the welfare of the species, they may be, and apparently often have been, transmitted in nearly the same state to numerous otherwise modified descendants. It cannot have been of much importance to the greater number of mammals, birds or reptiles, whether they were closed with hair, feathers or scales, yet hair has been transmitted to almost all mammals, feathers to all birds, and scales to all true reptiles. A structure, whatever it may be, which is common to many allied forms, is ranked by us as of high systematic importance, and consequently is often assumed to be of high vital importance to the species. Thus, as I am inclined to believe, morphological differences which we consider as important, such as the arrangement of the leaves, the divisions of the flower, or of the ovarium, the positions of the ovules, etc., first appeared in many cases as fluctuating variations, which sooner or later became constant through the nature of the organism and of the surrounding conditions, as well as through the intercrossing of distinct individuals, but not through natural selection. For as these morphological characters do not affect the welfare of the species, any slight deviations in them would not have been governed or accumulated through this latter agency. It is a strange result which we thus arrive at, namely that characters of slight vital importance to the species are the most important to the systematist, but as we shall here and after see when we treat of the genetic principle of classification, this is by no means so paradoxical as it may at first appear. Although we have no good evidence of the existence in organic beings of an innate tendency towards progressive development, yet this necessarily follows, as I have attempted to show in the fourth chapter, through the continued action of natural selection. For the best definition which has ever been given of a high standard of organization is the degree to which the parts have been specialized or differentiated, and natural selection tends towards this end in as much as the parts are thus enabled to perform their functions more efficiently. A distinguished zoologist, Mr. St. George Minvart, has recently collected all the objections which have ever been advanced by myself and others against the theory of natural selection as propounded by Mr. Wallace and myself, and has illustrated them with admirable art and force. When thus marshaled they make a formidable array, and it forms no part of Mr. Minvart's plan to give the various facets and considerations opposed to its conclusions, no slight effort of reason and memory is left to the reader, who may wish to weigh the evidence on both sides. When discussing special cases, Mr. Minvart passes over the effects of the increased use and disuse of parts, which I have always maintained to be highly important, and have treated my variation under domestication at greater length than, as I believe, any other writer. He likewise often assumes that I attribute nothing to variation, independently of natural selection, whereas in the work just referred to I have collected a greater number of well-established cases than can be found in any other work known to me. My judgment may not be trustworthy, but after reading with care Mr. Minvart's book, and after comparing each section with what I have said on the same head, I never before felt so strongly convinced of the general truth of the conclusions here arrived at, subject, of course, in so intricate a subject, too much, partial error. All Mr. Minvart's objections will be, or have been, considered in the present volume. The one new point which appears to have struck many readers is that natural selection is incompetent to account for the incipient stages of useful structures. This subject is intimately connected with that of the gradation of the characters, often accompanied by a change of function, for instance the conversion of a swim bladder into lungs, points of which were discussed in the last chapter under two headings. Nevertheless I will here consider in some detail several of the causes advanced by Mr. Minvart, selecting those which are the most illustrative, as what of space prevents me from considering all. The giraffe, by its lofty structure, much elongated neck, forelegs, head, and tongue, has its whole frame beautifully adapted for browsing on the higher branches of trees. It can thus obtain food beyond the reach of the other ungulata or hoofed animals inhabiting the same country, and this must be a great advantage to it during dearths. The Neata cattle in South America show us how a small difference in structure may make during such periods a great difference in preserving an animal's life. These cattle can browse as well as others on grass, but from the projection of the lower jaw they cannot, during the often recurrent droughts, browse on the twigs of trees, reeds, etc., to which food the common cattle and horses are often driven, so that at these times the Neatas perish if not well fed by their owners. Before coming to Mr. Minvart's objections, it may be well to explain once again how natural selection will act in all ordinary cases. Man has modified some of his animals without necessarily having attended to special points of structure, but simply preserving and breeding from the fleetist animals, as with the racehorse and the greyhound, or as with the gamecock by breeding from the victorious birds. So under nature, with the Nessian giraffe, the individuals which were the highest browsers and were able during dearths to reach even an inch or two above the others will often have been preserved, for they will have roamed over the whole country in search of food, that the individuals of the same species often differ slightly in the relative lengths of all their parts may be seen in many works of natural history, in which careful measurements are given. These slight proportional differences, due to the laws of growth and variation, are not of the slightest use or importance to most species, but it will have been otherwise with the Nessian giraffe, considering its probable habits of life for those individuals which had some one part or several parts of their bodies, rather more elongated than usual, would generally have survived. These will have intercrossed and left offspring, either inheriting the same bodily peculiarities or with a tendency to vary again in the same manner, while the individuals less favored in the same respects will have been the most liable to perish. We see here that there is no need to separate single pairs, as man does, when he methodically improves a breed. Natural selection will preserve and thus separate all the superior individuals, allowing them freely to intercross and will destroy all the inferior individuals. By this process, long continued, which exactly corresponds to what I have called unconscious selection by man, combined no doubt in a more important manner with the inherited effects of the increased use of parts, it seems to me almost certain that an ordinary hoofed quadruped might be converted into a giraffe. To this conclusion, Mr. Minvar brings forward two objections. One is that the increased size of the body would obviously require an increased supply of food, and he considers it as very problematical whether the disadvantages then arising would not, in times of scarcity, more than counterbalance the advantages. But as the giraffe actually does exist in large numbers in Africa, and as some of the largest antelopes in the world, taller than an ox, around there, why should we doubt that, as far as size is concerned, intermediate gradations could formerly have existed there, subjected, as now, to severe dirts? Assuredly, the being able to reach, at each stage of increased size, to a supply of food left untouched by other hoofed quadrupeds of the country, would have been of some advantage to the nascent giraffe. Nor must we overlook the fact that increasing bulk would act as little protection against almost all beasts of prey, accepting the lion, and against this animal, its tall neck and the taller the better, would, as Mr. Chauncey Wright has remarked, serve as a watchtower. It is from this cause, as Sir S. Baker remarks, that no animal is more difficult to stalk than the giraffe. This animal also uses its long neck, as a means of offense or defense, by violently swinging its head around with stump-like horns. The preservation of each species can rarely be determined by any one advantage, but by the union of all, great and small. Mr. Minvard then asks, and this is his second objection, if natural selection be so potent, and if high browsing be so great an advantage, why has not any other hoofed quadruped acquired a long neck and a lofty stature besides the giraffe, and, to a lesser degree, the camel, guanaco, and macrocinha? Or, again, why has not any member of the group acquired a long proboscis? With respect to South Africa, which was formerly inhabited by numerous herds of the giraffe, the answer is not difficult, and can be best given by an illustration. In every meadow in England in which trees grow, we see the lower branches trimmed or planed to an exact level by the browsing of the horses or cattle, and what advantage would it be, for instance, to sheep, if kept there, to acquire slightly longer necks? In every district some kind of animal will almost certainly be able to browse higher than the others, and it is almost equally certain that this one kind alone could have had its neck elongated for this purpose, through natural selection and the effects of increased use. In South America the competition for browsing on the higher branches of the acacias and other trees must be between giraffe and giraffe, and not with the other ungulate animals. Why, in other quarters of the world, various animals belonging to this same order have not acquired either an elongated neck or a proboscis? Cannot be distinctly answered, but it is as unreasonable to expect a distinct answer to such a question as why some event in the history of mankind did not occur in one country while it did in another. We are ignorant with respect to the conditions which determine the numbers and range of each species, and we cannot even conjecture what changes of structure would be favorable to its increase in some new country. We can, however, see in a general manner that various causes might have interfered with the development of a long neck or proboscis. To reach the foliage at a considerable height without climbing, for which hoofed animals are singularly ill-constructed, implies greatly increased bulk of body, and we know that some areas support singularly few large quadrupeds, for instance South America, though it is so luxuriant, while South Africa abounds with them to an unparalleled degree. Why this should be? So we do not know. Nor why the later tertiary periods should have been so much more favorable for their existence than the present time. Whatever the causes may have been, we can see that certain districts and times would have been much more favorable than others for the development of so large a quadruped as the giraffe. In order that an animal should acquire some structures specially and largely developed, it is almost indispensable that several other parts should be modified and co-adapted. Although every part of the body varies slightly, it does not follow that the necessary parts should always vary in the right direction and to the right degree. With the different species of our domesticated animals, we know that the parts vary in a different manner and degree and that some species are more variable than others. Even if the fitting variations did arise, it does not follow that natural selection would be able to act on them and produce a structure which apparently would be beneficial to the species. For instance, if the number of individuals existing in a country is determined chiefly through destruction by beasts of prey, by external or internal parasites, etc., as seems often to be the case, then natural selection will be able to do little or it will be greatly retarded in modifying any particular structure for obtaining food. Lastly, natural selection is a slow process and the same favorable conditions must long endure in order that any market effect should thus be produced. Except by assigning such general and vague reasons, we cannot explain why, in many quarters of the world, hoofed quadrupeds have not acquired much elongated necks or other means for browsing on higher branches of trees. Objections of the same nature as the foregoing have been advanced by many writers. In each case, various causes, besides the general ones just indicated, have probably interfered with the acquisition through natural selection of structures, which it is thought would be beneficial to certain species. One writer asks, why has not the ostrich acquired the power of flight? But a moment's reflection will show that an enormous supply of food would be necessary to give this bird of the desert force to move its huge body through the air. Oceanic islands are inhabited by bats and seals, but by no terrestrial mammals, yet as some of these bats are peculiar species, they must have long inhabited their present homes. Therefore, Sir C. Lyell asks and assigns through certain reasons in answer, why have not seals and bats given birth on such islands to forms fitted to live on the land? But seals would necessarily be first converted into terrestrial carnivorous animals of considerable size, and bats into terrestrial insectivorous animals. For the former, there would be no prey. For the bats, ground insects would serve as food, but these would already be largely preyed upon by the reptiles or birds, which first colorize and abound on most oceanic islands. Gradations of structure with each stage beneficial to a changing species will be favored only under certain peculiar conditions. A strictly terrestrial animal, by occasionally hunting for food in shallow water than in streams or lakes, might at last be converted into an animal so thoroughly aquatic as to brave the open ocean. But seals would not find on oceanic islands the conditions favorable to their gradual reconversion into a terrestrial form. Bats, as formerly shown, probably acquired their wings by at first gliding through the air from tree to tree, like the so-called flying squirrels, for the sake of escaping from their enemies or for avoiding falls. But when the power of true flight had once been acquired, it would never be reconverted back, at least for the both purposes, into the less efficient power of gliding through the air. Bats might indeed, like many birds, have had their wings greatly reduced in size or completely lost through disuse, but in this case it would be necessary that they should first have acquired the power of running quickly on the ground by the aid of their hind legs alone so as to compete with the birds and other ground animals, and for such a change a bat seems singularly ill-fitted. These conjectural remarks have been made merely to show that a transition of structure with each step beneficial is a highly complex affair, and there is nothing strange in a transition not having occurred in any particular case. Lately more than one writer has asked why have some animals had their mental powers more highly developed than others, as such development would be advantageous to all. Why have not apes acquired the intellectual powers of man? Various causes could be assigned, but as they are conjectural and their relative probability cannot be weighed, it would be useless to give them. A definite answer to the latter question ought not to be expected, seeing that one can solve the simpler problem why of two races of savages has one risen higher in the scale of civilization than the other, and this apparently implies increased brain power. We will return to Mr. Minvart's other objections. Insects often resemble, for the sake of protection, various objects such as green or decayed leaves, dead twigs, bits of lichen, flowers, spines, excrement of birds, and living insects, but to this latter point I shall hereafter recur. The resemblance is often wonderfully close, and is not confined to color, but extends to form and even to the manner in which the insects hold themselves. The caterpillars, which project motionless like dead twigs from the bushes on which they feed, offer an excellent instance of a resemblance of this kind. The cases of this imitation of such objects as the excrement of birds are rare and exceptional. On this head Mr. Minvart remarks, as according to Mr. Darwin's theory, there is a constant tendency to indefinite variation, and as the minute incipient variations will be in all directions, they must tend to neutralize each other, and, at first, to form such unstable modifications that it is difficult, if not impossible, to see how such indefinite oscillations of infinitesimal beginnings can ever build up a sufficiently appreciable resemblance to a leaf, bamboo, or other object for natural selection to seize upon and perpetuate. But in all the foregoing cases the insects in their original state no doubt presented some rude and accidental resemblance to an object commonly found in the stations frequented by them. Nor is this at all improbable considering the almost infinite number of surrounding objects and the diversity in form and color of the hosts of insects which exist. As some rude resemblance is necessary for the first start, we can understand how it is that the larger and higher animals do not, with the exception, as far as I know, of one fish, resemble, for the sake of protection, special objects, but only the surface which commonly surrounds them, and this chiefly in color. Assuming that an insect originally happened to resemble in some degree a dead twig or decayed leaf, and that it varied slightly in many ways, then all the variations which rendered the insect at all more like any such object, and thus favored its escape, would be preserved, while other variations would be neglected and ultimately lost, or if they rendered the insect at all less like the imitated object, they would be eliminated. There would indeed be force in Mr. Minvart's objection if we were to attempt to account for the above resemblances independently of natural selection through mere fluctuating variability, but as the case stands there is none. Nor can I see any force in Mr. Minvart's difficulty with respect to the last touches of perfection in the mimicry, as is the case given by Mr. Wallace, of a walking stick insect, Seroxilus natsaris, which resembles a stick grown over by a creeping moss, or Jungermania. So close was this resemblance that a native dyac maintained that the foliaceous excrescences were really moss. Insects are preyed upon by birds and other enemies whose sight is probably sharper than ours, and every grade in resemblance which added an insect to escape notice or detection would tend toward its preservation, and the more perfect the resemblance, so much the better for the insect. Considering the nature of the differences between the species in the group which includes the above Seroxilus, there is nothing improbable in this insect having varied in the irregularities on its surface, and in these having become more or less green-colored, for in every group the characters which differ in the several species are the most apt to vary, while the genetic characters, or those common to all the species, are the most constant. The Greenland Whale is one of the most wonderful animals in the world, and the baleen, or whalebone, one of its greatest peculiarities. The baleen consists of a row on each side of the upper jaw of about three hundred plates, or laminate, which would stand close together transversely to the longer axis of the mouth. Within the main row there are some subsidiary rows. The extremities and inner margins of all the plates are frayed into stiff bristles which clothe the whole gigantic pallet, and serve to strain or sift the water, and thus to secure the minute prey on which these great animals subsist. The middle and longest lamina in the Greenland Whale is ten, twelve, or even fifteen feet in length, but in the different species' obstetations there are gradations in length. The middle lamina being in one species, according to Scoresby, four feet, in another three, and another eighteen inches, and in the Balanaptura rostara only about nine inches in length. The quality of the whalebone also differs in the different species. With respect to the baleen, Mr. Minvert remarks that if it had once attained such a size and development as to be at all useful, then its preservation and augmentation within serviceable limits would be promoted by natural selection alone. But how to obtain the beginning of such a useful development? In answer it may be asked, why should not the early progenitors of the whales with baleen have possessed a mouth constructed something like the laminated beak of a duck? Ducks, like whales, subsist by sifting the mud and water, and the family has sometimes been called kriblators or sifters. I hope that I may not be misconstrued into saying that the progenitors of whales did actually possess mouths laminated like the beak of a duck. I wish only to show that this is not incredible, and that the immense plates of baleen in the Greenland Whale might have been developed from such lamellae by finely graduated steps, each of service to its possessor. The beak of a shoveler duck, spatula klepeita, is a more beautiful and complex structure than the mouth of the whale. The upper mandible is furnished on one side, in the specimen examined by me, with a row or comb formed of 188 thin elastic lamellae, obliquely beveled so as to be pointed and placed transversely to the longer axis of the mouth. They arise from the pallet and are attached by flexible membrane to the sides of the mandible. Those standing toward the middle are the longest, being about one-third of an inch in length, and they protect fourteen one-hundredths of an inch beneath the edge. At their bases there is a short subsidiary row of obliquely transversed lamellae. In these several respects they resemble the plates of baleen in the mouth of a whale, but towards the extremity of the beak they differ much as they project inward, instead of straight downward. The entire head of the shoveler, though incomparably less bulky, is about one-eighteenth the length of the head of a moderately large baleenoptera rostora, in which species the baleen is only nine inches long, so that if we were to make the head of the shoveler as long as that of the baleenoptera, the lamellae would be six inches in length, that is two-thirds the length of the baleen in this species of whale. The lower mandible of the shoveler duck is furnished with lamellae of equal length with those above, but finer, and in being thus furnished it differs conspicuously from the lower jaw of the whale, which is destitute of baleen. On the other hand the extremities of these lower lamellae are frayed into fine bristly points, so that they thus curiously resemble the plates of baleen. In the genus Pryon, a member of the distinct family of the petrals, the upper mandible alone is furnished with lamellae, which are well developed and project beneath the margins, so that the beak of this bird resembles, in this respect, the mouth of a whale. From the highly developed structure of the shoveler's beak we may proceed, as I have learned from information and specimens sent to me by Mr. Salvin, without any great break as far as fitness for sifting is concerned, through the beak of Meriganta armata, and in some respects through that of the aches sponsor, to the beak of the common duck. In this latter species the lamellae are much coarser than in the shoveler, and are firmly attached to the sides of the mandible. They are only about fifty in number on each side and do not project at all beneath the margin. They are square-tipped and are edged with translucent, hardish tissue, as if for crushing food. The edges of the lower mandible are crossed by numerous fine ridges which project very little, although the beak is thus very inferior as a sifter to that of the shoveler, yet this bird, as everyone knows, constantly uses it for that purpose. There are other species, as I heard from Mr. Salvin, in which the lamellae are considerably less developed than in the common duck, but I do not know whether they use their beaks for sifting the water. Turning to another group in the same family, in the Egyptian goose, Kinolopex, the beak closely resembles that of the modern duck, but the lamellae are not so numerous nor so distinct from each other, nor do they project so much inward, yet this goose, as I am informed by Mr. E Bartlett, uses its bill like a duck by throwing the water out at the corners. Its chief food, however, is grass, which it crops like the common goose. In this latter bird the lamellae of the upper mandible are much coarser than in the common duck, almost confluent, about twenty-seven in number on each side and terminating upward in teeth-like knobs. The palate is also covered with hard rounded knobs. The edges of the lower mandible are serrated with teeth much more prominent, coarser and sharper than in the duck. The common goose does not sift the water, but uses its beak exclusively for tearing or cutting herbage, for which purpose it is so well fitted that it can crop grass closer than almost any other animal. There are other species of geese, as I hear from Mr. Bartlett, in which the lamellae are less developed than in the common goose. We thus see that a member of the duck family, with a beak constructed like that of a common goose and adapted solely for grazing, or even a member with a beak having less well developed lamellae, might be converted by small changes into a species like the Egyptian goose. This into one like the common duck, and lastly into one like the shoveler, provided with a beak almost exclusively adapted for sifting the water, for this bird would hardly use any part of its beak except the hooked tip for seizing or tearing solid food. The beak of a goose, as I may add, might also be converted by small changes into one provided with prominent, recurved teeth, like those of the Mergancer, a member of the same family, serving for the widely different purpose of securing live fish. Returning to the whales, hyperodonbidens is destitute of true teeth in an efficient condition, but its palate is roughened according to Lassipidae with small, unequal hard points of horn. There is therefore nothing improbable in supposing that some early cetacean form was provided with similar points of horn on the palate, but rather more regularly placed and which, like the knobs on the beak of the goose, aided it in seizing or tearing its food. If so, it will hardly be denied that the points might have been converted through variation and natural selection into lamellae as well developed as that of the Egyptian goose, in which case they would have been used both for seizing objects and for sifting the water, then into lamellae like those of the domestic duck, and so onward until they became as well constructed as those of the shoveler, in which case they would have served exclusively as a sifting apparatus. From this stage, in which the lamellae would be two-thirds the length of the plates of baleen in the Belanatra Rostara, gradations which may be observed in still existing cetaceans lead us onward to the enormous plates of baleen in the Greenland Whale, nor is there the least reason to doubt that each step in this scale might have been as serviceable to certain ancient cetaceans with the functions of the parts slowly changing during the progress of development, as are the gradations in the beaks of the differing existing members of the duck family. We should bear in mind that each species of duck is subjected to a severe struggle for existence, and that the structure of every part of its frame must be well adapted to its conditions of life.