Longevity -- Modifications not necessarily simultaneous -- Modificationsapparently of no direct service -- Progressive development -- Characters ofsmall functional importance, the most constant -- Supposed incompetence ofnatural selection to account for the incipient stages of useful structures-- Causes which interfere with the acquisition through natural selection ofuseful structures -- Gradations of structure with changed functions --Widely different organs in members of the same class, developed from oneand the same source -- Reasons for disbelieving in great and abruptmodifications.

I will devote this chapter to the consideration of various miscellaneousobjections which have been advanced against my views, as some of theprevious discussions may thus be made clearer; but it would be useless todiscuss all of them, as many have been made by writers who have not takenthe trouble to understand the subject. Thus a distinguished Germannaturalist has asserted that the weakest part of my theory is, that Iconsider all organic beings as imperfect: what I have really said is, thatall are not as perfect as they might have been in relation to theirconditions; and this is shown to be the case by so many native forms inmany quarters of the world having yielded their places to intrudingforeigners. Nor can organic beings, even if they were at any one timeperfectly adapted to their conditions of life, have remained so, when theirconditions changed, unless they themselves likewise changed; and no onewill dispute that the physical conditions of each country, as well as thenumber 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 believesin natural selection "must arrange his genealogical tree" in such a mannerthat all the descendants have longer lives than their progenitors! Cannotour critics conceive that a biennial plant or one of the lower animalsmight range into a cold climate and perish there every winter; and yet,owing to advantages gained through natural selection, survive from year toyear by means of its seeds or ova? Mr. E. Ray Lankester has recentlydiscussed this subject, and he concludes, as far as its extreme complexityallows him to form a judgment, that longevity is generally related to thestandard of each species in the scale of organisation, as well as to theamount of expenditure in reproduction and in general activity. And theseconditions have, it is probable, been largely determined through naturalselection.

It has been argued that, as none of the animals and plants of Egypt, ofwhich we know anything, have changed during the last three or four thousandyears, so probably have none in any part of the world. But, as Mr. G.H.Lewes has remarked, this line of argument proves too much, for the ancientdomestic races figured on the Egyptian monuments, or embalmed, are closelysimilar or even identical with those now living; yet all naturalists admitthat such races have been produced through the modification of theiroriginal types. The many animals which have remained unchanged since thecommencement of the glacial period, would have been an incomparablystronger case, for these have been exposed to great changes of climate andhave migrated over great distances; whereas, in Egypt, during the lastseveral thousand years, the conditions of life, as far as we know, haveremained absolutely uniform. The fact of little or no modification havingbeen effected since the glacial period, would have been of some availagainst those who believe in an innate and necessary law of development,but is powerless against the doctrine of natural selection or the survivalof the fittest, which implies that when variations or individualdifferences of a beneficial nature happen to arise, these will bepreserved; but this will be effected only under certain favourablecircumstances.

The celebrated palaeontologist, Bronn, at the close of his Germantranslation of this work, asks how, on the principle of natural selection,can a variety live side by side with the parent species? If both havebecome fitted for slightly different habits of life or conditions, theymight live together; and if we lay on one side polymorphic species, inwhich the variability seems to be of a peculiar nature, and all meretemporary variations, such as size, albinism, etc., the more permanentvarieties are generally found, as far as I can discover, inhabitingdistinct stations, such as high land or low land, 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.

Bronn also insists that distinct species never differ from each other insingle characters, but in many parts; and he asks, how it always comes thatmany parts of the organisation should have been modified at the same timethrough variation and natural selection? But there is no necessity forsupposing that all the parts of any being have been simultaneouslymodified. The most striking modifications, excellently adapted for somepurpose, might, as was formerly remarked, be acquired by successivevariations, if slight, first in one part and then in another; and as theywould be transmitted all together, they would appear to us as if they hadbeen simultaneously developed. The best answer, however, to the aboveobjection is afforded by those domestic races which have been modified,chiefly through man's power of selection, for some special purpose. Lookat the race and dray-horse, or at the greyhound and mastiff. Their wholeframes, and even their mental characteristics, have been modified; but ifwe could trace each step in the history of their transformation--and thelatter steps can be traced--we should not see great and simultaneouschanges, but first one part and then another slightly modified andimproved. Even when selection has been applied by man to some onecharacter alone--of which our cultivated plants offer the best instances--it will invariably be found that although this one part, whether it be theflower, fruit, or leaves, has been greatly changed, almost all the otherparts have been slightly modified. This may be attributed partly to theprinciple of correlated growth, and partly to so-called spontaneousvariation.

A much more serious objection has been urged by Bronn, and recently byBroca, namely, that many characters appear to be of no service whatever totheir possessors, and therefore cannot have been influenced through naturalselection. Bronn adduces the length of the ears and tails in the differentspecies of hares and mice--the complex folds of enamel in the teeth of manyanimals, and a multitude of analogous cases. With respect to plants, thissubject has been discussed by Nageli in an admirable essay. He admits thatnatural selection has effected much, but he insists that the families ofplants differ chiefly from each other in morphological characters, whichappear to be quite unimportant for the welfare of the species. Heconsequently believes in an innate tendency towards progressive and moreperfect development. He specifies the arrangement of the cells in thetissues, and of the leaves on the axis, as cases in which natural selectioncould not have acted. To these may be added the numerical divisions in theparts 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 thefirst place, to be extremely cautious in pretending to decide whatstructures now are, or have formerly been, of use to each species. In thesecond place, it should always be borne in mind that when one part ismodified, so will be other parts, through certain dimly seen causes, suchas an 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 casesof correlation, which we do not in the least understand. These agenciesmay be all grouped together, for the sake of brevity, under the expressionof the laws of growth. In the third place, we have to allow for the directand definite action of changed conditions of life, and for so-calledspontaneous variations, in which the nature of the conditions apparentlyplays a quite subordinate part. Bud-variations, such as the appearance ofa moss-rose on a common rose, or of a nectarine on a peach-tree, offer goodinstances of spontaneous variations; but even in these cases, if we bear inmind the power of a minute drop of poison in producing complex galls, weought not to feel too sure that the above variations are not the effect ofsome local change in the nature of the sap, due to some change in theconditions. There must be some efficient cause for each slight individualdifference, as well as for more strongly marked variations whichoccasionally arise; and if the unknown cause were to act persistently, itis almost certain that all the individuals of the species would besimilarly modified.

In the earlier editions of this work I underrated, as it now seemsprobable, the frequency and importance of modifications due to spontaneousvariability. But it is impossible to attribute to this cause theinnumerable structures which are so well adapted to the habits of life ofeach species. I can no more believe in this than that the well-adaptedform of a race-horse or greyhound, which before the principle of selectionby man was well understood, excited so much surprise in the minds of theolder naturalists, can thus be explained.

It may be worth while to illustrate some of the foregoing remarks. Withrespect to the assumed inutility of various parts and organs, it is hardlynecessary to observe that even in the higher and best-known animals manystructures exist, which are so highly developed that no one doubts thatthey are of importance, yet their use has not been, or has only recentlybeen, ascertained. As Bronn gives the length of the ears and tail in theseveral species of mice as instances, though trifling ones, of differencesin structure which can be of no special use, I may mention that, accordingto Dr. Schobl, the external ears of the common mouse are supplied in anextraordinary manner with nerves, so that they no doubt serve as tactileorgans; hence the length of the ears can hardly be quite unimportant. Weshall, also, presently see that the tail is a highly useful prehensileorgan to some of the species; and its use would be much influence by itslength.

With respect to plants, to which on account of Nageli's essay I shallconfine myself in the following remarks, it will be admitted that theflowers of the orchids present a multitude of curious structures, which afew years ago would have been considered as mere morphological differenceswithout any special function; but they are now known to be of the highestimportance for the fertilisation of the species through the aid of insects,and have probably been gained through natural selection. No one untillately would have imagined that in dimorphic and trimorphic plants thedifferent lengths of the stamens and pistils, and their arrangement, couldhave 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 othersthey are suspended; and within the same ovarium of some few plants, oneovule holds the former and a second ovule the latter position. Thesepositions seem at first purely morphological, or of no physiologicalsignification; but Dr. Hooker informs me that within the same ovarium theupper ovules alone in some cases, and in others the lower ones alone arefertilised; and he suggests that this probably depends on the direction inwhich the pollen-tubes enter the ovarium. If so, the position of theovules, even when one is erect and the other suspended within the sameovarium, would follow the selection of any slight deviations in positionwhich favoured their fertilisation, and the production of seed.

Several plants belonging to distinct orders habitually produce flowers oftwo kinds--the one open, of the ordinary structure, the other closed andimperfect. These two kinds of flowers sometimes differ wonderfully instructure, yet may be seen to graduate into each other on the same plant. The ordinary and open flowers can be intercrossed; and the benefits whichcertainly are derived from this process are thus secured. The closed andimperfect flowers are, however, manifestly of high importance, as theyyield with the utmost safety a large stock of seed, with the expenditure ofwonderfully little pollen. The two kinds of flowers often differ much, asjust stated, in structure. The petals in the imperfect flowers almostalways consist of mere rudiments, and the pollen-grains are reduced indiameter. In Ononis columnae five of the alternate stamens arerudimentary; and in some species of Viola three stamens are in this state,two retaining their proper function, but being of very small size. In sixout of thirty of the closed flowers in an Indian violet (name unknown, forthe plants have never produced with me perfect flowers), the sepals arereduced from the normal number of five to three. In one section of theMalpighiaceae the closed flowers, according to A. de Jussieu, are stillfurther modified, for the five stamens which stand opposite to the sepalsare all aborted, a sixth stamen standing opposite to a petal being alonedeveloped; and this stamen is not present in the ordinary flowers of thisspecies; the style is aborted; and the ovaria are reduced from three totwo. Now although natural selection may well have had the power to preventsome of the flowers from expanding, and to reduce the amount of pollen,when rendered by the closure of the flowers superfluous, yet hardly any ofthe above special modifications can have been thus determined, but musthave followed from the laws of growth, including the functional inactivityof parts, during the progress of the reduction of the pollen and theclosure of the flowers.

It is so necessary to appreciate the important effects of the laws ofgrowth, that I will give some additional cases of another kind, namely ofdifferences in the same part or organ, due to differences in relativeposition on the same plant. In the Spanish chestnut, and in certain fir-trees, the angles of divergence of the leaves differ, according to Schacht,in the nearly horizontal and in the upright branches. In the common rueand some other plants, one flower, usually the central or terminal one,opens first, and has five sepals and petals, and five divisions to theovarium; while all the other flowers on the plant are tetramerous. In theBritish Adoxa the uppermost flower generally has two calyx-lobes with theother organs tetramerous, while the surrounding flowers generally havethree calyx-lobes with the other organs pentamerous. In many Compositaeand Umbelliferae (and in some other plants) the circumferential flowershave their corollas much more developed than those of the centre; and thisseems often connected with the abortion of the reproductive organs. It isa more curious fact, previously referred to, that the achenes or seeds ofthe circumference and centre sometimes differ greatly in form, colour andother characters. In Carthamus and some other Compositae the centralachenes alone are furnished with a pappus; and in Hyoseris the same headyields achenes of three different forms. In certain Umbelliferae theexterior seeds, according to Tausch, are orthospermous, and the central onecoelospermous, and this is a character which was considered by De Candolleto be in other species of the highest systematic importance. ProfessorBraun mentions a Fumariaceous genus, in which the flowers in the lower partof the spike bear oval, ribbed, one-seeded nutlets; and in the upper partof the spike, lanceolate, two-valved and two-seeded siliques. In theseseveral cases, with the exception of that 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, oronly in a quite subordinate manner. All these modifications follow fromthe relative position and inter-action of the parts; and it can hardly bedoubted that if all the flowers and leaves on the same plant had beensubjected to the same external and internal condition, as are the flowersand leaves in certain positions, all would have been modified in the samemanner.

In numerous other cases we find modifications of structure, which areconsidered by botanists to be generally of a highly important nature,affecting only some of the flowers on the same plant, or occurring ondistinct plants, which grow close together under the same conditions. Asthese variations seem of no special use to the plants, they cannot havebeen influenced by natural selection. Of their cause we are quiteignorant; we cannot even attribute them, as in the last class of cases, toany proximate agency, such as relative position. I will give only a fewinstances. It is so common to observe on the same plant, flowersindifferently tetramerous, pentamerous, etc., that I need not giveexamples; but as numerical variations are comparatively rare when the partsare few, I may mention that, according to De Candolle, the flowers ofPapaver bracteatum offer either two sepals with four petals (which is thecommon type with poppies), or three sepals with six petals. The manner inwhich the petals are folded in the bud is in most groups a very constantmorphological character; but Professor Asa Gray states that with somespecies of Mimulus, the aestivation is almost as frequently that of theRhinanthideae as of the Antirrhinideae, to which latter tribe the genusbelongs. Aug. St. Hilaire gives the following cases: the genusZanthoxylon belongs to a division of the Rutaceae with a single ovary, butin some species flowers may be found on the same plant, and even in thesame panicle, with either one or two ovaries. In Helianthemum the capsulehas been described as unilocular or tri-locular; and in H. mutabile, "Unelame PLUS OU MOINS LARGE, s'etend entre le pericarpe et le placenta." Inthe flowers of Saponaria officinalis Dr. Masters has observed instances ofboth marginal and free central placentation. Lastly, St. Hilaire foundtowards the southern extreme of the range of Gomphia oleaeformis two formswhich he did not at first doubt were distinct species, but he subsequentlysaw them growing on the same bush; and he then adds, "Voila donc dans unmeme individu des loges et un style qui se rattachent tantot a un axeverticale et tantot a un gynobase."

We thus see that with plants many morphological changes may be attributedto the laws of growth and the inter-action of parts, independently ofnatural selection. But with respect to Nageli's doctrine of an innatetendency towards perfection or progressive development, can it be said inthe case of these strongly pronounced variations, that the plants have beencaught in the act of progressing towards a higher state of development? Onthe contrary, I should infer from the mere fact of the parts in questiondiffering or varying greatly on the same plant, that such modificationswere of extremely small importance to the plants themselves, of whateverimportance they may generally be to us for our classifications. Theacquisition of a useless part can hardly be said to raise an organism inthe natural scale; and in the case of the imperfect, closed flowers, abovedescribed, if any new principle has to be invoked, it must be one ofretrogression rather than of progression; and so it must be with manyparasitic and degraded animals. We are ignorant of the exciting cause ofthe above specified modifications; but if the unknown cause were to actalmost uniformly for a length of time, we may infer that the result wouldbe almost uniform; and in this case all the individuals of the specieswould be modified in the same manner.

>From the fact of the above characters being unimportant for the welfare ofthe species, any slight variations which occurred in them would not havebeen accumulated and augmented through natural selection. A structurewhich has been developed through long-continued selection, when it ceasesto be of service to a species, generally becomes variable, as we see withrudimentary organs; for it will no longer be regulated by this same powerof selection. But when, from the nature of the organism and of theconditions, modifications have been induced which are unimportant for thewelfare 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 numberof mammals, birds, or reptiles, whether they were clothed 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 usas of high systematic importance, and consequently is often assumed to beof high vital importance to the species. Thus, as I am inclined tobelieve, morphological differences, which we consider as important--such asthe arrangement of the leaves, the divisions of the flower or of theovarium, the position of the ovules, etc., first appeared in many cases asfluctuating variations, which sooner or later became constant through thenature of the organism and of the surrounding conditions, as well asthrough the intercrossing of distinct individuals, but not through naturalselection; for as these morphological characters do not affect the welfareof the species, any slight deviations in them could not have been governedor accumulated through this latter agency. It is a strange result which wethus arrive at, namely, that characters of slight vital importance to thespecies, are the most important to the systematist; but, as we shallhereafter 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 aninnate tendency towards progressive development, yet this necessarilyfollows, as I have attempted to show in the fourth chapter, through thecontinued action of natural selection. For the best definition which hasever been given of a high standard of organisation, is the degree to whichthe parts have been specialised or differentiated; and natural selectiontends towards this end, inasmuch as the parts are thus enabled to performtheir functions more efficiently.

A distinguished zoologist, Mr. St. George Mivart, has recently collectedall the objections which have ever been advanced by myself and othersagainst the theory of natural selection, as propounded by Mr. Wallace andmyself, and has illustrated them with admirable art and force. When thusmarshalled, they make a formidable array; and as it forms no part of Mr.Mivart's plan to give the various facts and considerations opposed to hisconclusions, no slight effort of reason and memory is left to the reader,who may wish to weigh the evidence on both sides. When discussing specialcases, Mr. Mivart passes over the effects of the increased use and disuseof parts, which I have always maintained to be highly important, and havetreated in my "Variation under Domestication" at greater length than, as Ibelieve, any other writer. He likewise often assumes that I attributenothing to variation, independently of natural selection, whereas in thework just referred to I have collected a greater number of well-establishedcases than can be found in any other work known to me. My judgment may notbe trustworthy, but after reading with care Mr. Mivart's book, andcomparing each section with what I have said on the same head, I neverbefore felt so strongly convinced of the general truth of the conclusionshere arrived at, subject, of course, in so intricate a subject, to muchpartial error.

All Mr. Mivart's objections will be, or have been, considered in thepresent volume. The one new point which appears to have struck manyreaders is, "That natural selection is incompetent to account for theincipient stages of useful structures." This subject is intimatelyconnected with that of the gradation of the characters, often accompaniedby a change of function, for instance, the conversion of a swim-bladderinto lungs, points which were discussed in the last chapter under twoheadings. Nevertheless, I will here consider in some detail several of thecases advanced by Mr. Mivart, selecting those which are the mostillustrative, as want of space prevents me from considering all.

The giraffe, by its lofty stature, much elongated neck, fore legs, head andtongue, has its whole frame beautifully adapted for browsing on the higherbranches of trees. It can thus obtain food beyond the reach of the otherUngulata or hoofed animals inhabiting the same country; and this must be agreat advantage to it during dearths. The Niata cattle in South Americashow us how small a difference in structure may make, during such periods,a great difference in preserving an animal's life. These cattle can browseas well as others on grass, but from the projection of the lower jaw theycannot, during the often recurrent droughts, browse on the twigs of trees,reeds, etc., to which food the common cattle and horses are then driven; sothat at these times the Niatas perish, if not fed by their owners. Beforecoming to Mr. Mivart's objections, it may be well to explain once again hownatural selection will act in all ordinary cases. Man has modified some ofhis animals, without necessarily having attended to special points ofstructure, by simply preserving and breeding from the fleetest individuals,as with the race-horse and greyhound, or as with the game-cock, by breedingfrom the victorious birds. So under nature with the nascent giraffe, theindividuals which were the highest browsers and were able during dearths toreach 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. Thatthe individuals of the same species often differ slightly in the relativelengths of all their parts may be seen in many works of natural history, inwhich careful measurements are given. These slight proportionaldifferences, due to the laws of growth and variation, are not of theslightest use or importance to most species. But it will have beenotherwise with the nascent giraffe, considering its probable habits oflife; for those individuals which had some one part or several parts oftheir bodies rather more elongated than usual, would generally havesurvived. These will have intercrossed and left offspring, eitherinheriting the same bodily peculiarities, or with a tendency to vary againin the same manner; while the individuals less favoured in the samerespects will have been the most liable to perish.

We here see that there is no need to separate single pairs, as man does,when he methodically improves a breed: natural selection will preserve andthus separate all the superior individuals, allowing them freely tointercross, and will destroy all the inferior individuals. By this processlong-continued, which exactly corresponds with what I have calledunconscious selection by man, combined, no doubt, in a most importantmanner with the inherited effects of the increased use of parts, it seemsto me almost certain that an ordinary hoofed quadruped might be convertedinto a giraffe.

To this conclusion Mr. Mivart brings forward two objections. One is thatthe increased size of the body would obviously require an increased supplyof food, and he considers it as "very problematical whether thedisadvantages thence arising would not, in times of scarcity, more thancounterbalance the advantages." But as the giraffe does actually exist inlarge numbers in Africa, and as some of the largest antelopes in the world,taller than an ox, abound there, why should we doubt that, as far as sizeis concerned, intermediate gradations could formerly have existed there,subjected as now to severe dearths. Assuredly the being able to reach, ateach stage of increased size, to a supply of food, left untouched by theother hoofed quadrupeds of the country, would have been of some advantageto the nascent giraffe. Nor must we overlook the fact, that increased bulkwould act as a protection against almost all beasts of prey excepting thelion; and against this animal, its tall neck--and the taller the better--would, as Mr. Chauncey Wright has remarked, serve as a watch-tower. It isfrom this cause, as Sir S. Baker remarks, that no animal is more difficultto stalk than the giraffe. This animal also uses its long neck as a meansof offence or defence, by violently swinging its head armed with stump-likehorns. The preservation of each species can rarely be determined by anyone advantage, but by the union of all, great and small.

Mr. Mivart then asks (and this is his second objection), if naturalselection be so potent, and if high browsing be so great an advantage, whyhas not any other hoofed quadruped acquired a long neck and lofty stature,besides the giraffe, and, in a lesser degree, the camel, guanaco andmacrauchenia? Or, again, why has not any member of the group acquired along proboscis? With respect to South Africa, which was formerly inhabitedby numerous herds of the giraffe, the answer is not difficult, and can bestbe given by an illustration. In every meadow in England, in which treesgrow, we see the lower branches trimmed or planed to an exact level by thebrowsing of the horses or cattle; and what advantage would it be, forinstance, to sheep, if kept there, to acquire slightly longer necks? Inevery district some one kind of animal will almost certainly be able tobrowse higher than the others; and it is almost equally certain that thisone kind alone could have its neck elongated for this purpose, throughnatural selection and the effects of increased use. In South Africa thecompetition for browsing on the higher branches of the acacias and othertrees must be between giraffe and giraffe, and not with the other ungulateanimals.

Why, in other quarters of the world, various animals belonging to this sameorder have not acquired either an elongated neck or a proboscis, cannot bedistinctly answered; but it is as unreasonable to expect a distinct answerto such a question as why some event in the history of mankind did notoccur in one country while it did in another. We are ignorant with respectto the conditions which determine the numbers and range of each species,and we cannot even conjecture what changes of structure would be favourableto its increase in some new country. We can, however, see in a generalmanner that various causes might have interfered with the development of along 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 supportsingularly few large quadrupeds, for instance South America, though it isso luxuriant, while South Africa abounds with them to an unparalleleddegree. Why this should be so we do not know; nor why the later tertiaryperiods should have been much more favourable for their existence than thepresent time. Whatever the causes may have been, we can see that certaindistricts and times would have been much more favourable than others forthe development of so large a quadruped as the giraffe.

In order that an animal should acquire some structure specially and largelydeveloped, it is almost indispensable that several other parts should bemodified and coadapted. Although every part of the body varies slightly,it does not follow that the necessary parts should always vary in the rightdirection and to the right degree. With the different species of ourdomesticated animals we know that the parts vary in a different manner anddegree, and that some species are much more variable than others. Even ifthe fitting variations did arise, it does not follow that natural selectionwould be able to act on them and produce a structure which apparently wouldbe beneficial to the species. For instance, if the number of individualsexisting in a country is determined chiefly through destruction by beastsof prey--by external or internal parasites, etc.--as seems often to be thecase, then natural selection will be able to do little, or will be greatlyretarded, in modifying any particular structure for obtaining food. Lastly, natural selection is a slow process, and the same favourableconditions must long endure in order that any marked effect should thus beproduced. Except by assigning such general and vague reasons, we cannotexplain why, in many quarters of the world, hoofed quadrupeds have notacquired much elongated necks or other means for browsing on the higherbranches of trees.

Objections of the same nature as the foregoing have been advanced by manywriters. In each case various causes, besides the general ones justindicated, have probably interfered with the acquisition through naturalselection of structures, which it is thought would be beneficial to certainspecies. One writer asks, why has not the ostrich acquired the power offlight? But a moment's reflection will show what an enormous supply offood would be necessary to give to this bird of the desert force to moveits huge body through the air. Oceanic islands are inhabited by bats andseals, but by no terrestrial mammals; yet as some of these bats arepeculiar species, they must have long inhabited their present homes. Therefore Sir C. Lyell asks, and assigns certain reasons in answer, whyhave not seals and bats given birth on such islands to forms fitted to liveon the land? But seals would necessarily be first converted intoterrestrial carnivorous animals of considerable size, and bats intoterrestrial insectivorous animals; for the former there would be no prey;for the bats ground-insects would serve as food, but these would already belargely preyed on by the reptiles or birds, which first colonise and aboundon most oceanic islands. Gradations of structure, with each stagebeneficial to a changing species, will be favoured only under certainpeculiar conditions. A strictly terrestrial animal, by occasionallyhunting for food in shallow water, then in streams or lakes, might at lastbe converted into an animal so thoroughly aquatic as to brave the openocean. But seals would not find on oceanic islands the conditionsfavourable to their gradual reconversion into a terrestrial form. Bats, asformerly shown, probably acquired their wings by at first gliding throughthe air from tree to tree, like the so-called flying squirrels, for thesake of escaping from their enemies, or for avoiding falls; but when thepower of true flight had once been acquired, it would never be reconvertedback, at least for the above purposes, into the less efficient power ofgliding through the air. Bats, might, indeed, like many birds, have hadtheir wings greatly reduced in size, or completely lost, through disuse;but in this case it would be necessary that they should first have acquiredthe power of running quickly on the ground, by the aid of their hind legsalone, so as to compete with birds or other ground animals; and for such achange a bat seems singularly ill-fitted. These conjectural remarks havebeen made merely to show that a transition of structure, with each stepbeneficial, is a highly complex affair; and that there is nothing strangein a transition not having occurred in any particular case.

Lastly, more than one writer has asked why have some animals had theirmental powers more highly developed than others, as such development wouldbe advantageous to all? Why have not apes acquired the intellectual powersof man? Various causes could be assigned; but as they are conjectural, andtheir relative probability cannot be weighed, it would be useless to givethem. A definite answer to the latter question ought not to be expected,seeing that no one can solve the simpler problem, why, of two races ofsavages, one has risen higher in the scale of civilisation than the other;and this apparently implies increased brain power.

We will return to Mr. Mivart's other objections. Insects often resemblefor the sake of protection various objects, such as green or decayedleaves, dead twigs, bits of lichen, flowers, spines, excrement of birds,and living insects; but to this latter point I shall hereafter recur. Theresemblance is often wonderfully close, and is not confined to colour, butextends to form, and even to the manner in which the insects holdthemselves. The caterpillars which project motionless like dead twigs fromthe bushes on which they feed, offer an excellent instance of a resemblanceof this kind. The cases of the imitation of such objects as the excrementof birds, are rare and exceptional. On this head, Mr. Mivart remarks, "As,according to Mr. Darwin's theory, there is a constant tendency toindefinite variation, and as the minute incipient variations will be in ALLDIRECTIONS, they must tend to neutralize each other, and at first to formsuch unstable modifications that it is difficult, if not impossible, to seehow such indefinite oscillations of infinitesimal beginnings can ever buildup a sufficiently appreciable resemblance to a leaf, bamboo, or otherobject, for natural selection to seize upon and perpetuate."

But in all the foregoing cases the insects in their original state no doubtpresented some rude and accidental resemblance to an object commonly foundin the stations frequented by them. Nor is this at all improbable,considering the almost infinite number of surrounding objects and thediversity in form and colour of the hosts of insects which exist. As somerude resemblance is necessary for the first start, we can understand how itis that the larger and higher animals do not (with the exception, as far asI know, of one fish) resemble for the sake of protection special objects,but only the surface which commonly surrounds them, and this chiefly incolour. Assuming that an insect originally happened to resemble in somedegree a dead twig or a decayed leaf, and that it varied slightly in manyways, then all the variations which rendered the insect at all more likeany such object, and thus favoured its escape, would be preserved, whileother variations would be neglected and ultimately lost; or, if theyrendered the insect at all less like the imitated object, they would beeliminated. There would indeed be force in Mr. Mivart's objection, if wewere to attempt to account for the above resemblances, independently ofnatural selection, through mere fluctuating variability; but as the casestands there is none.

Nor can I see any force in Mr. Mivart's difficulty with respect to "thelast touches of perfection in the mimicry;" as in the case given by Mr.Wallace, of a walking-stick insect (Ceroxylus laceratus), which resembles"a stick grown over by a creeping moss or jungermannia." So close was thisresemblance, that a native Dyak maintained that the foliaceous excrescenceswere really moss. Insects are preyed on by birds and other enemies whosesight is probably sharper than ours, and every grade in resemblance whichaided an insect to escape notice or detection, would tend towards itspreservation; and the more perfect the resemblance so much the better forthe insect. Considering the nature of the differences between the speciesin the group which includes the above Ceroxylus, there is nothingimprobable in this insect having varied in the irregularities on itssurface, and in these having become more or less green-coloured; for inevery group the characters which differ in the several species are the mostapt to vary, while the generic characters, or those common to all thespecies, are the most constant.

The Greenland whale is one of the most wonderful animals in the world, andthe baleen, or whalebone, one of its greatest peculiarities. The baleenconsists of a row, on each side of the upper jaw, of about 300 plates orlaminae, which stand close together transversely to the longer axis of themouth. Within the main row there are some subsidiary rows. Theextremities and inner margins of all the plates are frayed into stiffbristles, which clothe the whole gigantic palate, and serve to strain orsift the water, and thus to secure the minute prey on which these greatanimals subsist. The middle and longest lamina in the Greenland whale isten, twelve, or even fifteen feet in length; but in the different speciesof Cetaceans there are gradations in length; the middle lamina being in onespecies, according to Scoresby, four feet, in another three, in anothereighteen inches, and in the Balaenoptera rostrata only about nine inches inlength. The quality of the whalebone also differs in the differentspecies.

With respect to the baleen, Mr. Mivart remarks that if it "had onceattained such a size and development as to be at all useful, then itspreservation and augmentation within serviceable limits would be promotedby natural selection alone. But how to obtain the beginning of such usefuldevelopment?" In answer, it may be asked, why should not the earlyprogenitors of the whales with baleen have possessed a mouth constructedsomething like the lamellated beak of a duck? Ducks, like whales, subsistby sifting the mud and water; and the family has sometimes been calledCriblatores, or sifters. I hope that I may not be misconstrued into sayingthat the progenitors of whales did actually possess mouths lamellated likethe beak of a duck. I wish only to show that this is not incredible, andthat the immense plates of baleen in the Greenland whale might have beendeveloped from such lamellae by finely graduated steps, each of service toits possessor.

The beak of a shoveller-duck (Spatula clypeata) is a more beautiful andcomplex structure than the mouth of a whale. The upper mandible isfurnished on each side (in the specimen examined by me) with a row or combformed of 188 thin, elastic lamellae, obliquely bevelled so as to bepointed, and placed transversely to the longer axis of the mouth. Theyarise from the palate, and are attached by flexible membrane to the sidesof the mandible. Those standing towards the middle are the longest, beingabout one-third of an inch in length, and they project fourteen one-hundredths of an inch beneath the edge. At their bases there is a shortsubsidiary row of obliquely transverse lamellae. In these several respectsthey resemble the plates of baleen in the mouth of a whale. But towardsthe extremity of the beak they differ much, as they project inward, insteadof straight downward. The entire head of the shoveller, thoughincomparably less bulky, is about one-eighteenth of the length of the headof a moderately large Balaenoptera rostrata, in which species the baleen isonly nine inches long; so that if we were to make the head of the shovelleras long as that of the Balaenoptera, the lamellae would be six inches inlength, that is, two-thirds of the length of the baleen in this species ofwhale. The lower mandible of the shoveller-duck is furnished with lamellaeof equal length with these above, but finer; and in being thus furnished itdiffers conspicuously from the lower jaw of a whale, which is destitute ofbaleen. On the other hand, the extremities of these lower lamellae arefrayed into fine bristly points, so that they thus curiously resemble theplates of baleen. In the genus Prion, a member of the distinct family ofthe Petrels, the upper mandible alone is furnished with lamellae, which arewell developed and project beneath the margin; so that the beak of thisbird resembles in this respect the mouth of a whale.

>From the highly developed structure of the shoveller'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 isconcerned, through the beak of the Merganetta armata, and in some respectsthrough that of the Aix sponsa, to the beak of the common duck. In thislatter species the lamellae are much coarser than in the shoveller, and arefirmly attached to the sides of the mandible; they are only about fifty innumber on each side, and do not project at all beneath the margin. Theyare square-topped, and are edged with translucent, hardish tissue, as iffor crushing food. The edges of the lower mandible are crossed by numerousfine ridges, which project very little. Although the beak is thus veryinferior as a sifter to that of a shoveller, yet this bird, as every oneknows, constantly uses it for this purpose. There are other species, as Ihear from Mr. Salvin, in which the lamellae are considerably less developedthan in the common duck; but I do not know whether they use their beaks forsifting the water.

Turning to another group of the same family. In the Egyptian goose(Chenalopex) the beak closely resembles that of the common duck; but thelamellae are not so numerous, nor so distinct from each other, nor do theyproject 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 thecorners." Its chief food, however, is grass, which it crops like thecommon goose. In this latter bird the lamellae of the upper mandible aremuch coarser than in the common duck, almost confluent, about twenty-sevenin number on each side, and terminating upward in teeth-like knobs. Thepalate is also covered with hard rounded knobs. The edges of the lowermandible are serrated with teeth much more prominent, coarser and sharperthan in the duck. The common goose does not sift the water, but uses itsbeak exclusively for tearing or cutting herbage, for which purpose it is sowell 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 thelamellae are less developed than in the common goose.

We thus see that a member of the duck family, with a beak constructed likethat of a common goose and adapted solely for grazing, or even a memberwith a beak having less well-developed lamellae, might be converted bysmall changes into a species like the Egyptian goose--this into one likethe common duck--and, lastly, into one like the shoveller, provided with abeak almost exclusively adapted for sifting the water; for this bird couldhardly use any part of its beak, except the hooked tip, for seizing ortearing solid food. The beak of a goose, as I may add, might also beconverted by small changes into one provided with prominent, recurvedteeth, like those of the Merganser (a member of the same family), servingfor the widely different purpose of securing live fish.

Returning to the whales. The Hyperoodon bidens is destitute of true teethin an efficient condition, but its palate is roughened, according toLacepede, with small unequal, hard points of horn. There is, therefore,nothing improbable in supposing that some early Cetacean form was providedwith similar points of horn on the palate, but rather more regularlyplaced, and which, like the knobs on the beak of the goose, aided it inseizing or tearing its food. If so, it will hardly be denied that thepoints might have been converted through variation and natural selectioninto lamellae as well-developed as those of the Egyptian goose, in whichcase they would have been used both for seizing objects and for sifting thewater; then into lamellae like those of the domestic duck; and so onward,until they became as well constructed as those of the shoveller, in whichcase they would have served exclusively as a sifting apparatus. From thisstage, in which the lamellae would be two-thirds of the length of theplates of baleen in the Balaenoptera rostrata, gradations, which may beobserved in still-existing Cetaceans, lead us onward to the enormous platesof baleen in the Greenland whale. Nor is there the least reason to doubtthat each step in this scale might have been as serviceable to certainancient Cetaceans, with the functions of the parts slowly changing duringthe progress of development, as are the gradations in the beaks of thedifferent existing members of the duck-family. We should bear in mind thateach species of duck is subjected to a severe struggle for existence, andthat the structure of every part of its frame must be well adapted to itsconditions of life.

The Pleuronectidae, or Flat-fish, are remarkable for their asymmetricalbodies. They rest on one side--in the greater number of species on theleft, but in some on the right side; and occasionally reversed adultspecimens occur. The lower, or resting-surface, resembles at first sightthe ventral surface of an ordinary fish; it is of a white colour, lessdeveloped in many ways than the upper side, with the lateral fins often ofsmaller size. But the eyes offer the most remarkable peculiarity; for theyare both placed on the upper side of the head. During early youth,however, they stand opposite to each other, and the whole body is thensymmetrical, with both sides equally coloured. Soon the eye proper to thelower side begins to glide slowly round the head to the upper side; butdoes not pass right through the skull, as was formerly thought to be thecase. It is obvious that unless the lower eye did thus travel round, itcould not be used by the fish while lying in its habitual position on oneside. The lower eye would, also, have been liable to be abraded by thesandy bottom. That the Pleuronectidae are admirably adapted by theirflattened and asymmetrical structure for their habits of life, is manifestfrom several species, such as soles, flounders, etc., being extremelycommon. The chief advantages thus gained seem to be protection from theirenemies, and facility for feeding on the ground. The different members,however, of the family present, as Schiodte remarks, "a long series offorms exhibiting a gradual transition from Hippoglossus pinguis, which doesnot in any considerable degree alter the shape in which it leaves the ovum,to the soles, which are entirely thrown to one side."

Mr. Mivart has taken up this case, and remarks that a sudden spontaneoustransformation in the position of the eyes is hardly conceivable, in whichI quite agree with him. He then adds: "If the transit was gradual, thenhow such transit of one eye a minute fraction of the journey towards theother side of the head could benefit the individual is, indeed, far fromclear. It seems, even, that such an incipient transformation must ratherhave been injurious." But he might have found an answer to this objectionin the excellent observations published in 1867 by Malm. ThePleuronectidae, while very young and still symmetrical, with their eyesstanding on opposite sides of the head, cannot long retain a verticalposition, owing to the excessive depth of their bodies, the small size oftheir lateral fins, and to their being destitute of a swim-bladder. Hence,soon growing tired, they fall to the bottom on one side. While thus atrest they often twist, as Malm observed, the lower eye upward, to see abovethem; and they do this so vigorously that the eye is pressed hard againstthe upper part of the orbit. The forehead between the eyes consequentlybecomes, as could be plainly seen, temporarily contracted in breadth. Onone occasion Malm saw a young fish raise and depress the lower eye throughan angular distance of about seventy degrees.

We should remember that the skull at this early age is cartilaginous andflexible, so that it readily yields to muscular action. It is also knownwith the higher animals, even after early youth, that the skull yields andis altered in shape, if the skin or muscles be permanently contractedthrough disease or some accident. With long-eared rabbits, if one earflops forward and downward, its weight drags forward all the bones of theskull on the same side, of which I have given a figure. Malm states thatthe newly-hatched young of perches, salmon, and several other symmetricalfishes, have the habit of occasionally resting on one side at the bottom;and he has observed that they often then strain their lower eyes so as tolook upward; and their skulls are thus rendered rather crooked. Thesefishes, however, are soon able to hold themselves in a vertical position,and no permanent effect is thus produced. With the Pleuronectidae, on theother hand, the older they grow the more habitually they rest on one side,owing to the increasing flatness of their bodies, and a permanent effect isthus produced on the form of the head, and on the position of the eyes. Judging from analogy, the tendency to distortion would no doubt beincreased through the principle of inheritance. Schiodte believes, inopposition to some other naturalists, that the Pleuronectidae are not quitesymmetrical even in the embryo; and if this be so, we could understand howit is that certain species, while young, habitually fall over and rest onthe left side, and other species on the right side. Malm adds, inconfirmation of the above view, that the adult Trachypterus arcticus, whichis not a member of the Pleuronectidae, rests on its left side at thebottom, and swims diagonally through the water; and in this fish, the twosides of the head are said to be somewhat dissimilar. Our great authorityon Fishes, Dr. Gunther, concludes his abstract of Malm's paper, byremarking that "the author gives a very simple explanation of the abnormalcondition of the Pleuronectoids."

We thus see that the first stages of the transit of the eye from one sideof the head to the other, which Mr. Mivart considers would be injurious,may be attributed to the habit, no doubt beneficial to the individual andto the species, of endeavouring to look upward with both eyes, whileresting on one side at the bottom. We may also attribute to the inheritedeffects of use the fact of the mouth in several kinds of flat-fish beingbent towards the lower surface, with the jaw bones stronger and moreeffective on this, the eyeless side of the head, than on the other, for thesake, as Dr. Traquair supposes, of feeding with ease on the ground. Disuse, on the other hand, will account for the less developed condition ofthe whole inferior half of the body, including the lateral fins; thoughYarrel thinks that the reduced size of these fins is advantageous to thefish, as "there is so much less room for their action than with the largerfins above." Perhaps the lesser number of teeth in the proportion of fourto seven in the upper halves of the two jaws of the plaice, to twenty-fiveto thirty in the lower halves, may likewise be accounted for by disuse. >From the colourless state of the ventral surface of most fishes and of manyother animals, we may reasonably suppose that the absence of colour inflat-fish on the side, whether it be the right or left, which is under-most, is due to the exclusion of light. But it cannot be supposed that thepeculiar speckled appearance of the upper side of the sole, so like thesandy bed of the sea, or the power in some species, as recently shown byPouchet, of changing their colour in accordance with the surroundingsurface, or the presence of bony tubercles on the upper side of the turbot,are due to the action of the light. Here natural selection has probablycome into play, as well as in adapting the general shape of the body ofthese fishes, and many other peculiarities, to their habits of life. Weshould keep in mind, as I have before insisted, that the inherited effectsof the increased use of parts, and perhaps of their disuse, will bestrengthened by natural selection. For all spontaneous variations in theright direction will thus be preserved; as will those individuals whichinherit in the highest degree the effects of the increased and beneficialuse of any part. How much to attribute in each particular case to theeffects of use, and how much to natural selection, it seems impossible todecide.

I may give another instance of a structure which apparently owes its originexclusively to use or habit. The extremity of the tail in some Americanmonkeys has been converted into a wonderfully perfect prehensile organ, andserves as a fifth hand. A reviewer, who agrees with Mr. Mivart in everydetail, remarks on this structure: "It is impossible to believe that inany number of ages the first slight incipient tendency to grasp couldpreserve the lives of the individuals possessing it, or favour their chanceof having and of rearing offspring." But there is no necessity for anysuch belief. Habit, and this almost implies that some benefit great orsmall is thus derived, would in all probability suffice for the work. Brehm saw the young of an African monkey (Cercopithecus) clinging to theunder surface of their mother by their hands, and at the same time theyhooked their little tails round that of their mother. Professor Henslowkept in confinement some harvest mice (Mus messorius) which do not possessa structurally prehensive tail; but he frequently observed that they curledtheir tails round the branches of a bush placed in the cage, and thus aidedthemselves in climbing. I have received an analogous account from Dr.Gunther, who has seen a mouse thus suspend itself. If the harvest mousehad been more strictly arboreal, it would perhaps have had its tailrendered structurally prehensile, as is the case with some members of thesame order. Why Cercopithecus, considering its habits while young, has notbecome thus provided, it would be difficult to say. It is, however,possible that the long tail of this monkey may be of more service to it asa balancing organ in making its prodigious leaps, than as a prehensileorgan.

The mammary glands are common to the whole class of mammals, and areindispensable for their existence; they must, therefore, have beendeveloped at an extremely remote period, and we can know nothing positivelyabout their manner of development. Mr. Mivart asks: "Is it conceivablethat the young of any animal was ever saved from destruction byaccidentally sucking a drop of scarcely nutritious fluid from anaccidentally hypertrophied cutaneous gland of its mother? And even if onewas so, what chance was there of the perpetuation of such a variation?" But the case is not here put fairly. It is admitted by most evolutioniststhat mammals are descended from a marsupial form; and if so, the mammaryglands will have been at first developed within the marsupial sack. In thecase of the fish (Hippocampus) the eggs are hatched, and the young arereared for a time, within a sack of this nature; and an Americannaturalist, Mr. Lockwood, believes from what he has seen of the developmentof the young, that they are nourished by a secretion from the cutaneousglands of the sack. Now, with the early progenitors of mammals, almostbefore they deserved to be thus designated, is it not at least possiblethat the young might have been similarly nourished? And in this case, theindividuals which secreted a fluid, in some degree or manner the mostnutritious, so as to partake of the nature of milk, would in the long runhave reared a larger number of well-nourished offspring, than would theindividuals which secreted a poorer fluid; and thus the cutaneous glands,which are the homologues of the mammary glands, would have been improved orrendered more effective. It accords with the widely extended principle ofspecialisation, that the glands over a certain space of the sack shouldhave become more highly developed than the remainder; and they would thenhave formed a breast, but at first without a nipple, as we see in theOrnithorhyncus, at the base of the mammalian series. Through what agencythe glands over a certain space became more highly specialised than theothers, I will not pretend to decide, whether in part through compensationof growth, the effects of use, or of natural selection.

The development of the mammary glands would have been of no service, andcould not have been affected through natural selection, unless the young atthe same time were able to partake of the secretion. There is no greaterdifficulty in understanding how young mammals have instinctively learned tosuck the breast, than in understanding how unhatched chickens have learnedto break the egg-shell by tapping against it with their specially adaptedbeaks; or how a few hours after leaving the shell they have learned to pickup grains of food. In such cases the most probable solution seems to be,that the habit was at first acquired by practice at a more advanced age,and afterwards transmitted to the offspring at an earlier age. But theyoung kangaroo is said not to suck, only to cling to the nipple of itsmother, who has the power of injecting milk into the mouth of her helpless,half-formed offspring. On this head Mr. Mivart remarks: "Did no specialprovision exist, the young one must infallibly be choked by the intrusionof the milk into the wind-pipe. But there IS a special provision. Thelarynx is so elongated that it rises up into the posterior end of the nasalpassage, and is thus enabled to give free entrance to the air for thelungs, while the milk passes harmlessly on each side of this elongatedlarynx, and so safely attains the gullet behind it." Mr. Mivart then askshow did natural selection remove in the adult kangaroo (and in most othermammals, on the assumption that they are descended from a marsupial form),"this at least perfectly innocent and harmless structure?" It may besuggested in answer that the voice, which is certainly of high importanceto many animals, could hardly have been used with full force as long as thelarynx entered the nasal passage; and Professor Flower has suggested to methat this structure would have greatly interfered with an animal swallowingsolid food.

We will now turn for a short space to the lower divisions of the animalkingdom. The Echinodermata (star-fishes, sea-urchins, etc.) are furnishedwith remarkable organs, called pedicellariae, which consist, when welldeveloped, of a tridactyle forceps--that is, of one formed of threeserrated arms, neatly fitting together and placed on the summit of aflexible stem, moved by muscles. These forceps can seize firmly hold ofany object; and Alexander Agassiz has seen an Echinus or sea-urchin rapidlypassing particles of excrement from forceps to forceps down certain linesof its body, in order that its shell should not be fouled. But there is nodoubt that besides removing dirt of all kinds, they subserve otherfunctions; and one of these apparently is defence.

With respect to these organs, Mr. Mivart, as on so many previous occasions,asks: "What would be the utility of the FIRST RUDIMENTARY BEGINNINGS ofsuch structures, and how could such insipient buddings have ever preservedthe life of a single Echinus?" He adds, "not even the SUDDEN developmentof the snapping action would have been beneficial without the freelymovable stalk, nor could the latter have been efficient without thesnapping jaws, yet no minute, nearly indefinite variations couldsimultaneously evolve these complex co-ordinations of structure; to denythis seems to do no less than to affirm a startling paradox." Paradoxicalas this may appear to Mr. Mivart, tridactyle forcepses, immovably fixed atthe base, but capable of a snapping action, certainly exist on some star-fishes; and this is intelligible if they serve, at least in part, as ameans of defence. Mr. Agassiz, to whose great kindness I am indebted formuch information on the subject, informs me that there are other star-fishes, in which one of the three arms of the forceps is reduced to asupport for the other two; and again, other genera in which the third armis completely lost. In Echinoneus, the shell is described by M. Perrier asbearing two kinds of pedicellariae, one resembling those of Echinus, andthe other those of Spatangus; and such cases are always interesting asaffording the means of apparently sudden transitions, through the abortionof one of the two states of an organ.

With respect to the steps by which these curious organs have been evolved,Mr. Agassiz infers from his own researches and those of Mr. Muller, thatboth in star-fishes and sea-urchins the pedicellariae must undoubtedly belooked at as modified spines. This may be inferred from their manner ofdevelopment in the individual, as well as from a long and perfect series ofgradations in different species and genera, from simple granules toordinary spines, to perfect tridactyle pedicellariae. The gradationextends even to the manner in which ordinary spines and the pedicellariae,with their supporting calcareous rods, are articulated to the shell. Incertain genera of star-fishes, "the very combinations needed to show thatthe pedicellariae are only modified branching spines" may be found. Thuswe have fixed spines, with three equi-distant, serrated, movable branches,articulated to near their bases; and higher up, on the same spine, threeother movable branches. Now when the latter arise from the summit of aspine they form, in fact, a rude tridactyle pedicellariae, and such may beseen on the same spine together with the three lower branches. In thiscase the identity in nature between the arms of the pedicellariae and themovable branches of a spine, is unmistakable. It is generally admittedthat the ordinary spines serve as a protection; and if so, there can be noreason to doubt that those furnished with serrated and movable brancheslikewise serve for the same purpose; and they would thus serve still moreeffectively as soon as by meeting together they acted as a prehensile orsnapping apparatus. Thus every gradation, from an ordinary fixed spine toa fixed pedicellariae, would be of service.

In certain genera of star-fishes these organs, instead of being fixed orborne on an immovable support, are placed on the summit of a flexible andmuscular, though short, stem; and in this case they probably subserve someadditional function besides defence. In the sea-urchins the steps can befollowed by which a fixed spine becomes articulated to the shell, and isthus rendered movable. I wish I had space here to give a fuller abstractof Mr. Agassiz's interesting observations on the development of thepedicellariae. All possible gradations, as he adds, may likewise be foundbetween the pedicellariae of the star-fishes and the hooks of theOphiurians, another group of the Echinodermata; and again between thepedicellariae of sea-urchins and the anchors of the Holothuriae, alsobelonging to the same great class.

Certain compound animals, or zoophytes, as they have been termed, namelythe Polyzoa, are provided with curious organs called avicularia. Thesediffer much in structure in the different species. In their most perfectcondition they curiously resemble the head and beak of a vulture inminiature, seated on a neck and capable of movement, as is likewise thelower jaw or mandible. In one species observed by me, all the aviculariaon the same branch often moved simultaneously backwards and forwards, withthe lower jaw widely open, through an angle of about 90 degrees, in thecourse of five seconds; and their movement caused the whole polyzoary totremble. When the jaws are touched with a needle they seize it so firmlythat the branch can thus be shaken.

Mr. Mivart adduces this case, chiefly on account of the supposed difficultyof organs, namely the avicularia of the Polyzoa and the pedicellariae ofthe Echinodermata, which he considers as "essentially similar," having beendeveloped through natural selection in widely distinct divisions of theanimal kingdom. But, as far as structure is concerned, I can see nosimilarity between tridactyle pedicellariae and avicularia. The latterresembles somewhat more closely the chelae or pincers of Crustaceans; andMr. Mivart might have adduced with equal appropriateness this resemblanceas a special difficulty, or even their resemblance to the head and beak ofa bird. The avicularia are believed by Mr. Busk, Dr. Smitt and Dr.Nitsche--naturalists who have carefully studied this group--to behomologous with the zooids and their cells which compose the zoophyte, themovable lip or lid of the cell corresponding with the lower and movablemandible of the avicularium. Mr. Busk, however, does not know of anygradations now existing between a zooid and an avicularium. It istherefore impossible to conjecture by what serviceable gradations the onecould have been converted into the other, but it by no means follows fromthis that such gradations have not existed.

As the chelae of Crustaceans resemble in some degree the avicularia ofPolyzoa, both serving as pincers, it may be worth while to show that withthe former a long series of serviceable gradations still exists. In thefirst and simplest stage, the terminal segment of a limb shuts down eitheron the square summit of the broad penultimate segment, or against one wholeside, and is thus enabled to catch hold of an object, but the limb stillserves as an organ of locomotion. We next find one corner of the broadpenultimate segment slightly prominent, sometimes furnished with irregularteeth, and against these the terminal segment shuts down. By an increasein the size of this projection, with its shape, as well as that of theterminal segment, slightly modified and improved, the pincers are renderedmore and more perfect, until we have at last an instrument as efficient asthe chelae of a lobster. And all these gradations can be actually traced.

Besides the avicularia, the polyzoa possess curious organs calledvibracula. These generally consist of long bristles, capable of movementand easily excited. In one species examined by me the vibracula wereslightly curved and serrated along the outer margin, and all of them on thesame polyzoary often moved simultaneously; so that, acting like long oars,they swept a branch rapidly across the object-glass of my microscope. Whena branch was placed on its face, the vibracula became entangled, and theymade violent efforts to free themselves. They are supposed to serve as adefence, and may be seen, as Mr. Busk remarks, "to sweep slowly andcarefully over the surface of the polyzoary, removing what might be noxiousto the delicate inhabitants of the cells when their tentacula areprotruded." The avicularia, like the vibracula, probably serve fordefence, but they also catch and kill small living animals, which, it isbelieved, are afterwards swept by the currents within reach of thetentacula of the zooids. Some species are provided with avicularia andvibracula, some with avicularia alone and a few with vibracula alone.

It is not easy to imagine two objects more widely different in appearancethan a bristle or vibraculum, and an avicularium like the head of a bird;yet they are almost certainly homologous and have been developed from thesame common source, namely a zooid with its cell. Hence, we can understandhow it is that these organs graduate in some cases, as I am informed by Mr.Busk, into each other. Thus, with the avicularia of several species ofLepralia, the movable mandible is so much produced and is so like a bristlethat the presence of the upper or fixed beak alone serves to determine itsavicularian nature. The vibracula may have been directly developed fromthe lips of the cells, without having passed through the avicularian stage;but it seems more probable that they have passed through this stage, asduring the early stages of the transformation, the other parts of the cell,with the included zooid, could hardly have disappeared at once. In manycases the vibracula have a grooved support at the base, which seems torepresent the fixed beak; though this support in some species is quiteabsent. This view of the development of the vibracula, if trustworthy, isinteresting; for supposing that all the species provided with aviculariahad become extinct, no one with the most vivid imagination would ever havethought that the vibracula had originally existed as part of an organ,resembling a bird's head, or an irregular box or hood. It is interestingto see two such widely different organs developed from a common origin; andas the movable lip of the cell serves as a protection to the zooid, thereis no difficulty in believing that all the gradations, by which the lipbecame converted first into the lower mandible of an avicularium, and theninto an elongated bristle, likewise served as a protection in differentways and under different circumstances.

In the vegetable kingdom Mr. Mivart only alludes to two cases, namely thestructure of the flowers of orchids, and the movements of climbing plants. With respect to the former, he says: "The explanation of their ORIGIN isdeemed thoroughly unsatisfactory--utterly insufficient to explain theincipient, infinitesimal beginnings of structures which are of utility onlywhen they are considerably developed." As I have fully treated thissubject in another work, I will here give only a few details on one aloneof the most striking peculiarities of the flowers of orchids, namely, theirpollinia. A pollinium, when highly developed, consists of a mass ofpollen-grains, affixed to an elastic foot-stalk or caudicle, and this to alittle mass of extremely viscid matter. The pollinia are by this meanstransported by insects from one flower to the stigma of another. In someorchids there is no caudicle to the pollen-masses, and the grains aremerely tied together by fine threads; but as these are not confined toorchids, they need not here be considered; yet I may mention that at thebase of the orchidaceous series, in Cypripedium, we can see how the threadswere probably first developed. In other orchids the threads cohere at oneend of the pollen-masses; and this forms the first or nascent trace of acaudicle. That this is the origin of the caudicle, even when ofconsiderable length and highly developed, we have good evidence in theaborted pollen-grains which can sometimes be detected embedded within thecentral and solid parts.

With respect to the second chief peculiarity, namely, the little mass ofviscid matter attached to the end of the caudicle, a long series ofgradations can be specified, each of plain service to the plant. In mostflowers belonging to other orders the stigma secretes a little viscidmatter. Now, in certain orchids similar viscid matter is secreted, but inmuch larger quantities by one alone of the three stigmas; and this stigma,perhaps in consequence of the copious secretion, is rendered sterile. Whenan insect visits a flower of this kind, it rubs off some of the viscidmatter, and thus at the same time drags away some of the pollen-grains. >From this simple condition, which differs but little from that of amultitude of common flowers, there are endless gradations--to species inwhich the pollen-mass terminates in a very short, free caudicle--to othersin which the caudicle becomes firmly attached to the viscid matter, withthe sterile stigma itself much modified. In this latter case we have apollinium in its most highly developed and perfect condition. He who willcarefully examine the flowers of orchids for himself will not deny theexistence of the above series of gradations--from a mass of pollen-grainsmerely tied together by threads, with the stigma differing but little fromthat of the ordinary flowers, to a highly complex pollinium, admirablyadapted for transportal by insects; nor will he deny that all thegradations in the several species are admirably adapted in relation to thegeneral structure of each flower for its fertilisation by differentinsects. In this, and in almost every other case, the enquiry may bepushed further backwards; and it may be asked how did the stigma of anordinary flower become viscid, but as we do not know the full history ofany one group of beings, it is as useless to ask, as it is hopeless toattempt answering, such questions.

We will now turn to climbing plants. These can be arranged in a longseries, from those which simply twine round a support, to those which Ihave called leaf-climbers, and to those provided with tendrils. In thesetwo latter classes the stems have generally, but not always, lost the powerof twining, though they retain the power of revolving, which the tendrilslikewise possess. The gradations from leaf-climbers to tendril bearers arewonderfully close, and certain plants may be differently placed in eitherclass. But in ascending the series from simple twiners to leaf-climbers,an important quality is added, namely sensitiveness to a touch, by whichmeans the foot-stalks of the leaves or flowers, or these modified andconverted into tendrils, are excited to bend round and clasp the touchingobject. He who will read my memoir on these plants will, I think, admitthat all the many gradations in function and structure between simpletwiners and tendril-bearers are in each case beneficial in a high degree tothe species. For instance, it is clearly a great advantage to a twiningplant to become a leaf-climber; and it is probable that every twiner whichpossessed leaves with long foot-stalks would have been developed into aleaf-climber, if the foot-stalks had possessed in any slight degree therequisite sensitiveness to a touch.

As twining is the simplest means of ascending a support, and forms thebasis of our series, it may naturally be asked how did plants acquire thispower in an incipient degree, afterwards to be improved and increasedthrough natural selection. The power of twining depends, firstly, on thestems while young being extremely flexible (but this is a character commonto many plants which are not climbers); and, secondly, on their continuallybending to all points of the compass, one after the other in succession, inthe same order. By this movement the stems are inclined to all sides, andare made to move round and round. As soon as the lower part of a stemstrikes against any object and is stopped, the upper part still goes onbending and revolving, and thus necessarily twines round and up thesupport. The revolving movement ceases after the early growth of eachshoot. As in many widely separated families of plants, single species andsingle genera possess the power of revolving, and have thus become twiners,they must have independently acquired it, and cannot have inherited it froma common progenitor. Hence, I was led to predict that some slight tendencyto a movement of this kind would be found to be far from uncommon withplants which did not climb; and that this had afforded the basis fornatural selection to work on and improve. When I made this prediction, Iknew of only one imperfect case, namely, of the young flower-peduncles of aMaurandia which revolved slightly and irregularly, like the stems oftwining plants, but without making any use of this habit. Soon afterwardsFritz Muller discovered that the young stems of an Alisma and of a Linum--plants which do not climb and are widely separated in the natural system--revolved plainly, though irregularly, and he states that he has reason tosuspect that this occurs with some other plants. These slight movementsappear to be of no service to the plants in question; anyhow, they are notof the least use in the way of climbing, which is the point that concernsus. Nevertheless we can see that if the stems of these plants had beenflexible, and if under the conditions to which they are exposed it hadprofited them to ascend to a height, then the habit of slightly andirregularly revolving might have been increased and utilised throughnatural selection, until they had become converted into well-developedtwining species.

With respect to the sensitiveness of the foot-stalks of the leaves andflowers, and of tendrils, nearly the same remarks are applicable as in thecase of the revolving movements of twining plants. As a vast number ofspecies, belonging to widely distinct groups, are endowed with this kind ofsensitiveness, it ought to be found in a nascent condition in many plantswhich have not become climbers. This is the case: I observed that theyoung flower-peduncles of the above Maurandia curved themselves a littletowards the side which was touched. Morren found in several species ofOxalis that the leaves and their foot-stalks moved, especially afterexposure to a hot sun, when they were gently and repeatedly touched, orwhen the plant was shaken. I repeated these observations on some otherspecies of Oxalis with the same result; in some of them the movement wasdistinct, but was best seen in the young leaves; in others it was extremelyslight. It is a more important fact that according to the high authorityof Hofmeister, the young shoots and leaves of all plants move after beingshaken; and with climbing plants it is, as we know, only during the earlystages of growth that the foot-stalks and tendrils are sensitive.

It is scarcely possible that the above slight movements, due to a touch orshake, in the young and growing organs of plants, can be of any functionalimportance to them. But plants possess, in obedience to various stimuli,powers of movement, which are of manifest importance to them; for instance,towards and more rarely from the light--in opposition to, and more rarelyin the direction of, the attraction of gravity. When the nerves andmuscles of an animal are excited by galvanism or by the absorption ofstrychnine, the consequent movements may be called an incidental result,for the nerves and muscles have not been rendered specially sensitive tothese stimuli. So with plants it appears that, from having the power ofmovement in obedience to certain stimuli, they are excited in an incidentalmanner by a touch, or by being shaken. Hence there is no great difficultyin admitting that in the case of leaf-climbers and tendril-bearers, it isthis tendency which has been taken advantage of and increased throughnatural selection. It is, however, probable, from reasons which I haveassigned in my memoir, that this will have occurred only with plants whichhad already acquired the power of revolving, and had thus become twiners.

I have already endeavoured to explain how plants became twiners, namely, bythe increase of a tendency to slight and irregular revolving movements,which were at first of no use to them; this movement, as well as that dueto a touch or shake, being the incidental result of the power of moving,gained for other and beneficial purposes. Whether, during the gradualdevelopment of climbing plants, natural selection has been aided by theinherited effects of use, I will not pretend to decide; but we know thatcertain periodical movements, for instance the so-called sleep of plants,are governed by habit.

I have now considered enough, perhaps more than enough, of the cases,selected with care by a skilful naturalist, to prove that natural selectionis incompetent to account for the incipient stages of useful structures;and I have shown, as I hope, that there is no great difficulty on thishead. A good opportunity has thus been afforded for enlarging a little ongradations of structure, often associated with strange functions--animportant subject, which was not treated at sufficient length in the formereditions of this work. I will now briefly recapitulate the foregoingcases.

With the giraffe, the continued preservation of the individuals of someextinct high-reaching ruminant, which had the longest necks, legs, etc.,and could browse a little above the average height, and the continueddestruction of those which could not browse so high, would have sufficedfor the production of this remarkable quadruped; but the prolonged use ofall the parts, together with inheritance, will have aided in an importantmanner in their co-ordination. With the many insects which imitate variousobjects, there is no improbability in the belief that an accidentalresemblance to some common object was in each case the foundation for thework of natural selection, since perfected through the occasional preservation of slight variations which made the resemblance at all closer;and this will have been carried on as long as the insect continued to vary,and as long as a more and more perfect resemblance led to its escape fromsharp-sighted enemies. In certain species of whales there is a tendency tothe formation of irregular little points of horn on the palate; and itseems to be quite within the scope of natural selection to preserve allfavourable variations, until the points were converted, first intolamellated knobs or teeth, like those on the beak of a goose--then intoshort lamellae, like those of the domestic ducks--and then into lamellae,as perfect as those of the shoveller-duck--and finally into the giganticplates of baleen, as in the mouth of the Greenland whale. In the family ofthe ducks, the lamellae are first used as teeth, then partly as teeth andpartly as a sifting apparatus, and at last almost exclusively for thislatter purpose.

With such structures as the above lamellae of horn or whalebone, habit oruse can have done little or nothing, as far as we can judge, towards theirdevelopment. On the other hand, the transportal of the lower eye of aflat-fish to the upper side of the head, and the formation of a prehensiletail, may be attributed almost wholly to continued use, together withinheritance. With respect to the mammae of the higher animals, the mostprobable conjecture is that primordially the cutaneous glands over thewhole surface of a marsupial sack secreted a nutritious fluid; and thatthese glands were improved in function through natural selection, andconcentrated into a confined area, in which case they would have formed amamma. There is no more difficulty in understanding how the branchedspines of some ancient Echinoderm, which served as a defence, becamedeveloped through natural selection into tridactyle pedicellariae, than inunderstanding the development of the pincers of crustaceans, throughslight, serviceable modifications in the ultimate and penultimate segmentsof a limb, which was at first used solely for locomotion. In theavicularia and vibracula of the Polyzoa we have organs widely different inappearance developed from the same source; and with the vibracula we canunderstand how the successive gradations might have been of service. Withthe pollinia of orchids, the threads which originally served to tietogether the pollen-grains, can be traced cohering into caudicles; and thesteps can likewise be followed by which viscid matter, such as thatsecreted by the stigmas of ordinary flowers, and still subserving nearlybut not quite the same purpose, became attached to the free ends of thecaudicles--all these gradations being of manifest benefit to the plants inquestion. With respect to climbing plants, I need not repeat what has beenso lately said.

It has often been asked, if natural selection be so potent, why has notthis or that structure been gained by certain species, to which it wouldapparently have been advantageous? But it is unreasonable to expect aprecise answer to such questions, considering our ignorance of the pasthistory of each species, and of the conditions which at the present daydetermine its numbers and range. In most cases only general reasons, butin some few cases special reasons, can be assigned. Thus to adapt aspecies to new habits of life, many co-ordinated modifications are almostindispensable, and it may often have happened that the requisite parts didnot vary in the right manner or to the right degree. Many species musthave been prevented from increasing in numbers through destructiveagencies, which stood in no relation to certain structures, which weimagine would have been gained through natural selection from appearing tous advantageous to the species. In this case, as the struggle for life didnot depend on such structures, they could not have been acquired throughnatural selection. In many cases complex and long-enduring conditions,often of a peculiar nature, are necessary for the development of astructure; and the requisite conditions may seldom have concurred. Thebelief that any given structure, which we think, often erroneously, wouldhave been beneficial to a species, would have been gained under allcircumstances through natural selection, is opposed to what we canunderstand of its manner of action. Mr. Mivart does not deny that naturalselection has effected something; but he considers it as "demonstrablyinsufficient" to account for the phenomena which I explain by its agency. His chief arguments have now been considered, and the others will hereafterbe considered. They seem to me to partake little of the character ofdemonstration, and to have little weight in comparison with those in favourof the power of natural selection, aided by the other agencies oftenspecified. I am bound to add, that some of the facts and arguments hereused by me, have been advanced for the same purpose in an able articlelately published in the "Medico-Chirurgical Review."

At the present day almost all naturalists admit evolution under some form.Mr. Mivart believes that species change through "an internal force ortendency," about which it is not pretended that anything is known. Thatspecies have a capacity for change will be admitted by all evolutionists;but there is no need, as it seems to me, to invoke any internal forcebeyond the tendency to ordinary variability, which through the aid ofselection, by man has given rise to many well-adapted domestic races, andwhich, through the aid of natural selection, would equally well give riseby graduated steps to natural races or species. The final result willgenerally have been, as already explained, an advance, but in some fewcases a retrogression, in organisation.

Mr. Mivart is further inclined to believe, and some naturalists agree withhim, that new species manifest themselves "with suddenness and bymodifications appearing at once." For instance, he supposes that thedifferences between the extinct three-toed Hipparion and the horse arosesuddenly. He thinks it difficult to believe that the wing of a bird "wasdeveloped in any other way than by a comparatively sudden modification of amarked and important kind;" and apparently he would extend the same view tothe wings of bats and pterodactyles. This conclusion, which implies greatbreaks or discontinuity in the series, appears to me improbable in thehighest degree.

Everyone who believes in slow and gradual evolution, will of course admitthat specific changes may have been as abrupt and as great as any singlevariation which we meet with under nature, or even under domestication. But as species are more variable when domesticated or cultivated than undertheir natural conditions, it is not probable that such great and abruptvariations have often occurred under nature, as are known occasionally toarise under domestication. Of these latter variations several may beattributed to reversion; and the characters which thus reappear were, it isprobable, in many cases at first gained in a gradual manner. A stillgreater number must be called monstrosities, such as six-fingered men,porcupine men, Ancon sheep, Niata cattle, etc.; and as they are widelydifferent in character from natural species, they throw very little lighton our subject. Excluding such cases of abrupt variations, the few whichremain would at best constitute, if found in a state of nature, doubtfulspecies, closely related to their parental types.

My reasons for doubting whether natural species have changed as abruptly ashave occasionally domestic races, and for entirely disbelieving that theyhave changed in the wonderful manner indicated by Mr. Mivart, are asfollows. According to our experience, abrupt and strongly markedvariations occur in our domesticated productions, singly and at rather longintervals of time. If such occurred under nature, they would be liable, asformerly explained, to be lost by accidental causes of destruction and bysubsequent intercrossing; and so it is known to be under domestication,unless abrupt variations of this kind are specially preserved and separatedby the care of man. Hence, in order that a new species should suddenlyappear in the manner supposed by Mr. Mivart, it is almost necessary tobelieve, in opposition to all analogy, that several wonderfully changedindividuals appeared simultaneously within the same district. Thisdifficulty, as in the case of unconscious selection by man, is avoided onthe theory of gradual evolution, through the preservation of a large numberof individuals, which varied more or less in any favourable direction, andof the destruction of a large number which varied in an opposite manner.

That many species have been evolved in an extremely gradual manner, therecan hardly be a doubt. The species and even the genera of many largenatural families are so closely allied together that it is difficult todistinguish not a few of them. On every continent, in proceeding fromnorth to south, from lowland to upland, etc., we meet with a host ofclosely related or representative species; as we likewise do on certaindistinct continents, which we have reason to believe were formerlyconnected. But in making these and the following remarks, I am compelledto allude to subjects hereafter to be discussed. Look at the many outlyingislands round a continent, and see how many of their inhabitants can beraised only to the rank of doubtful species. So it is if we look to pasttimes, and compare the species which have just passed away with those stillliving within the same areas; or if we compare the fossil species embeddedin the sub-stages of the same geological formation. It is indeed manifestthat multitudes of species are related in the closest manner to otherspecies that still exist, or have lately existed; and it will hardly bemaintained that such species have been developed in an abrupt or suddenmanner. Nor should it be forgotten, when we look to the special parts ofallied species, instead of to distinct species, that numerous andwonderfully fine gradations can be traced, connecting together widelydifferent structures.

Many large groups of facts are intelligible only on the principle thatspecies have been evolved by very small steps. For instance, the fact thatthe species included in the larger genera are more closely related to eachother, and present a greater number of varieties than do the species in thesmaller genera. The former are also grouped in little clusters, likevarieties round species; and they present other analogies with varieties,as was shown in our second chapter. On this same principle we canunderstand how it is that specific characters are more variable thangeneric characters; and how the parts which are developed in anextraordinary degree or manner are more variable than other parts of thesame species. Many analogous facts, all pointing in the same direction,could be added.

Although very many species have almost certainly been produced by steps notgreater than those separating fine varieties; yet it may be maintained thatsome have been developed in a different and abrupt manner. Such anadmission, however, ought not to be made without strong evidence beingassigned. The vague and in some respects false analogies, as they havebeen shown to be by Mr. Chauncey Wright, which have been advanced in favourof this view, such as the sudden crystallisation of inorganic substances,or the falling of a facetted spheroid from one facet to another, hardlydeserve consideration. One class of facts, however, namely, the suddenappearance of new and distinct forms of life in our geological formationssupports at first sight the belief in abrupt development. But the value ofthis evidence depends entirely on the perfection of the geological record,in relation to periods remote in the history of the world. If the recordis as fragmentary as many geologists strenuously assert, there is nothingstrange in new forms appearing as if suddenly developed.

Unless we admit transformations as prodigious as those advocated by Mr.Mivart, such as the sudden development of the wings of birds or bats, orthe sudden conversion of a Hipparion into a horse, hardly any light isthrown by the belief in abrupt modifications on the deficiency ofconnecting links in our geological formations. But against the belief insuch abrupt changes, embryology enters a strong protest. It is notoriousthat the wings of birds and bats, and the legs of horses or otherquadrupeds, are undistinguishable at an early embryonic period, and thatthey become differentiated by insensibly fine steps. Embryologicalresemblances of all kinds can be accounted for, as we shall hereafter see,by the progenitors of our existing species having varied after early youth,and having transmitted their newly-acquired characters to their offspring,at a corresponding age. The embryo is thus left almost unaffected, andserves as a record of the past condition of the species. Hence it is thatexisting species during the early stages of their development so oftenresemble ancient and extinct forms belonging to the same class. On thisview of the meaning of embryological resemblances, and indeed on any view,it is incredible that an animal should have undergone such momentous andabrupt transformations as those above indicated, and yet should not beareven a trace in its embryonic condition of any sudden modification, everydetail in its structure being developed by insensibly fine steps.

He who believes that some ancient form was transformed suddenly through aninternal force or tendency into, for instance, one furnished with wings,will be almost compelled to assume, in opposition to all analogy, that manyindividuals varied simultaneously. It cannot be denied that such abruptand great changes of structure are widely different from those which mostspecies apparently have undergone. He will further be compelled to believethat many structures beautifully adapted to all the other parts of the samecreature and to the surrounding conditions, have been suddenly produced;and of such complex and wonderful co-adaptations, he will not be able toassign a shadow of an explanation. He will be forced to admit that thesegreat and sudden transformations have left no trace of their action on theembryo. To admit all this is, as it seems to me, to enter into the realmsof miracle, and to leave those of science.