UC-NRLF D3fi - /L A^-~ -> ' Lygaida) " exhibits, in an eminent J degr*ee; the" orclmary" occurrence of an imperfect perfect-state; whilst indi- viduals are occasionally found with fully developed organs of flight*". Lyceus brevipennis, Lat., also ordinarily occurs with abbreviated hemelytra; but it has been found with them perfect by Westwood, as well as with metathoracic wings. None of the above examples however would appear to do more than refer to the alary instability of the Insecta, as a matter of fact ; but this is all for which we are now contending, the preceding chapter having been in part devoted to some of the presumptive causes of it. Whether the specimens of Oncocephalus griseus, to which Spinola called attention, were insular ones, I cannot say ; but he seems to have noted an example in which an opposite phenomenon to those which Mr. Westwood has cited, was displayed, and moreover to have speculated on the conditions producing it, when he suggests : " I/influence du climat septentrional parait avoir arrete le developpe- ment des organes du volf." And, again, when com- menting upon the other tendency in a representative of the Reduviada, he says (' Essai/ p. 96) : " Je pense que la presence des ailes et leur developpement dependent du climat." Whilst treating of two British species of the same family, Mr. Westwood observes : " The Pro- stemma guttula, Fab., and Coranus subapterus, Curt., are interesting on account of their being generally found in * Introduction to the Modern Classification of Insects, ii. p. 480. t Essai, p. 103. , f , c c it ^ : , 102 an undeveloped imago state,, the latter being either entirely apterous or with the fore- wings rudimental, although occasionally to be met with having the fore- wings completely developed*"." The common Phos- phuga atrata of our own country has the organs of flight very rudimentary, and much too small for use : yet the late Mr. Holme of Oxford has mentioned-]-, that he has several times taken it on the wing, during the hot sun- shine. And, concerning the Olisthopus rotundatus, he states J that every specimen which he captured in the Scilly Islands was subapterous. But facts like these are, after all, nothing more than such as we may trace the counterpart of in higher ani- mals than the Insecta. Mr. Gould informs me, that the Swallows of Malta, which have but a comparatively narrow space to cross over, to the African continent, constitute (although specifically identical with them) a distinct race from those of England, all of which, he believes, winter in Morocco. But, what are the differ- ences displayed ? From amongst many minor ones, of a climatal or geographical nature, the most conspicuous is the length of the wings , those which have annually a longer journey to perform having, through a course of ages, acquired, as a race, a superior capacity for flight. And, in answer to a late query on this subject, he adds that all the sylvan birds in Malta, such as the Black- caps, Willow-wrens, &c., though unquestionably of the * Introduction to the Modern Classification of Insects, ii. p. 473. t Trans, of the Ent. Soc. of London, ii. p. 60. % Id. ii. p. 59. 103 / same species as those of Great Britain, exhibit small local characteristics by which they may be immediately distinguished, such as the length of the wings, size of the bills, and tints of the plumage. So that the migra- tory birds generally, which pass to and fro between Europe and Africa in that particular latitude, would appear to form separate races from those which traverse the ocean to our own country; and to be, most of them, remarkable, inter alia, for a slight shortening of their organs of transit. If, however, the members of the insect tribes are capable of but small variation in actual structure, with the exception, in certain instances, of the greater or less development of the wings ; we shall find that their ex- ternal characters are much more prone to instability. There is not an item indeed of all their secondary diagnostics which does not admit of a positive change ; and, though it be only within fixed limits that the several modifications can occur, those boundaries are frequently far apart, and include at times numerous phases within their embrace which have been too often looked upon as specific. Thus, whether we regard their bulk, outline, colour, or sculpture, anything like absolute constancy, under all circumstances and conditions, does not so much as exist ; and we are driven to admit, that the physical influences to which these various creatures are exposed have a very decided power over their general configuration and aspect. It would be needless, however, to attempt to discuss the above details of aberration separately ; because, where any one of them is especially 104 interfered with, it usually happens that the others are more or less involved with them : but we may offer a few desultory remarks, which will tend to show that disturbing agents are apt to mar them both individually and as a whole, and not only so, but to affect them in a permanent manner (as indeed has been already inti- mated), according as similar combinations of them are, from local causes (as it were), selected, to be acted upon. I have stated in the last section of the preceding chapter that insect stature is eminently beneath the control of contingences from without; adducing, amongst other examples, in support of this, the Madeiran Ptinus albopictus, a species which, whilst it averages more than a line in length on the central island of the group, is reduced to less than half that bulk on a small and weather-beaten rock (the Ilheo Chao) at a distance from it. Judging indeed from many hundred specimens of the Ptini which I have submitted to a close comparison, " the most constant of their characters would seem to be outline and sculpture, whilst size and colour are appa- rently the least to be depended upon : so that trifling differences may be of specific indication in the former case, where in the latter much larger ones are worth- less*." I have in fact generally noticed, that size and colour are more peculiarly liable to be affected together. This, however, is nothing more than what we should anticipate, since the same causes which have stunted the * Insecta Maderensia, pp. 260, 261. 105 dimensions, during a long series of ages, of any par- ticular creature, will for the most part be found to have also impaired the brilliancy of its tints. Luxuriance of vegetation and sheltered districts are alike conducive, in the Annulosa, to the development both of the body and its adornment ; or, in other words, where the vege- table creation attains its maximum (which it certainly does not do in situations which are exposed to the irri- tating consequences of a perpetually stormy atmosphere), there the animal world will be usually observed to thrive. There are many insects which appear to have two distinct states, both in magnitude and hue, which we are seldom (in some instances, I believe, never) able to unite by intermediate links, or grades ; and yet which are universally admitted, although found in actually the self-same spots (a fact which prevents their being looked upon as separate, local modifications of a common type), to be mere varieties of each other. They are, however, exceptions to the general rule ; and, although infringing on the strict definition of a " variety," as given at a pre- ceding page*", we nevertheless feel an a priori conviction that they are by no means specifically dissimilar inter se. Such phases, as regards stature, are presented by the Brachinus crepitans and Lamprias chlorocephalus of our own country ; whilst, as regards colour, the Philhydrus melanocephalus, Aphodius plagiatus, and the Psylliodes erythrocephala (constituting in its paler garb the P. ni- * Vide supra, p. 5. F5 106 gricollis, Mshm) may be quoted, as cases in point. Thus, also, in Madeira, the Mycetoporus pronus, Erich., has a large and small form, living in communion, which I have never been able to connect, and yet which are un- questionably identical (differing in no respect except in size) : and so have the Stenus Heeri, Woll., and the Saprinus nitidulus, Fab.* As regards the instability displayed by colour, in the insect tribes, when subjected to the action of certain conditions and influences from without, so much has been said in the fourth section of the preceding chapter, * Although, in our ignorance of their real nature, we cannot cite them as actually analogous to these separate phases in certain members of the Insecta, yet we are forcibly reminded by the latter of the distinct states which many of the Terrestrial Mollusca pre- sent (frequently in equal proportions) in the same localities. Thus, most of the Pupa have at least two abruptly-marked forms, a larger and smaller one. Many of the Helices also exhibit this ten- dency in an eminent degree : I have indeed been shown specimens by Sir Charles Lyell of the Helix hirsuta, Say, from North America, one state of which is considerably more than double the dimensions of the other ; and I believe it is a well-known fact that intermediate links have not yet been observed to connect the extremes. May not therefore the gigantic H. Lowei and Bowdichiana, which are now extinct in the Madeira Islands, have been but forms of the H. Portosanctana and punctulata, respectively, co-existent with them, though more sensitive to the great diminutions of altitude and area which were consequent on the breaking-up of a once con- tinuous land ? If such be the case, however, it is certain that they were far commoner at an early period than their smaller colleagues (which, now, in their proper districts, absolutely teem), seeing that the latter are extremely rare in the fossil deposits, whilst they themselves literally abound. 107 that it is unnecessary to repeat it here. True it is that it was then my sole province to discuss the causes which would appear to regulate, in a large measure, the external aspect of the Annulosa ; yet the existence of inconstancy, in the several organs and characters involved (with which alone we are now concerned), was, by the nature of the case, implied : so that if the disturbing element was de- monstrated, the mere fact that the thing (whatsoever it may have been) was interfered with, was surely proved a fortiori. I there pointed out the great proneness to a change in hue which divers circumstances are apt to induce; and I particularly instanced proximity to the sea-shore, and other saline spots, as well as an attach- ment to calcareous districts, as amongst the most power- ful of the deranging contingences. In case, however, that any further evidence should be looked for, on this immediate subject, I will quote the following, relating to the Bembidium Atlanticum of the Madeira Islands, which was but just touched upon in that chapter, as a concluding example of the general effect of physical agents on the colour of these lower creatures. " Through- out all the Madeiran Coleoptera there is perhaps no insect which displays such an extraordinary range of colouring as the present one does ; and although it is true that the section of Bembidium to which it belongs is essentially a variable one, yet I am not acquainted with any Peryphus in which the paler patches of the elytra are so remarkably unstable, or which appear to be so completely under the control of external circumstances, 108 as are those of the B. Atlanticum : and indeed unless viewed in the mass, we should scarcely be inclined to recognize the same species in the many aspects which it puts on between its extremes. The examination, how- ever, of a very large number of examples, and a careful consideration of the several localities and altitudes in which they were taken, has convinced me that there is unquestionably but a single type of form amongst my entire series, since the whole are so intimately connected, by successive gradations both of outline and colour, that it is perfectly impossible to isolate even a single specimen, or to draw a line of specific demarcation between any two consecutive members of the chain. It will be per- ceived, by a reference to the diagnosis, that the insect in question passes imperceptibly from nearly a pure green, through a well-defined spotted state, into one which has the elytra almost testaceous, the paler portions being at last so largely developed as to become confluent, and almost to cover the entire surface. In Madeira proper the darker varieties would seem to be typical ; whereas in Porto Santo the brightly coloured ones preponderate, and in fact are all but universal. Both extremes do nevertheless occur in both islands, the tendency being merely, in either case, to assume the particular modifi- cation characteristic of the spot*. And so it is with the outline and sculpture (no less than with bulk and hue) : they also are equally liable to disturbance from physical causes, as indeed has been * Insecta Maderensia, p. 78. 109 already insisted upon. Like most of the minutiae of variation, however, to which we have called attention, it is more particularly on islands that this is to be observed, isolation, during an interval sufficiently long, appear- ing to possess some especial control over the external contour and surface of the insect races. Thus, in the Madeiras, for instance, the Caulotropis lucifugus has its prothorax more distinctly punctured, and its elytra more perceptibly striated, in the principal island, than on any of the smaller members of the group ; in Porto Santo, indeed, it is almost free from sculpture of any kind ; whilst its ally, the C. conicollis, apart from being some- what larger, is, on the contrary, both more punctured and striated on the Dezerta Grande than it is in Madeira proper. The Omias Waterhousei, again (in addition to its slightly increased bulk and less shining envelope, in that locality), is more lightly impressed on the Dezerta than it is in Madeira : and, not to mention other differ- ences, the Ellipsodes glabratus is densely beset with most minute granules on that same rock whereas on the mountain slopes of the central mass, it is highly polished and glabrous. The Helops confertus, we have intimated at a previous page, is less coarsely sculptured in the lofty regions of Madeira, than in the lower ones : and the H. futilis has its elytral tubercles apparent in Madeira proper, but evanescent on the Dezerta Grande. The Eurygnathus Latreillei assumes a permanent variety on the Dezerta, the insect having become modified through a long isolation on those weather-beaten heights, 110 where it not only attains a more gigantic stature than in Porto Santo, but is invariably also more parallel and opake, has the sides of its prothorax more recurved, with the punctures towards the lateral angles almost obsolete, and the striae of its elytra somewhat more evidently punctate"*. Such examples, however, might be multiplied ad infi- nitum ; and I will not therefore devote further space to the bringing together of facts which it is hardly possible will be disputed, especially as it has been my wish, in the present chapter, merely to enumerate what the organs and characters principally are which are more peculiarly sensitive to change, throughout the Annulose tribes. This I may venture to hope, though briefly, I have in part done ; and I will consequently pass on to other considerations, which, even if somewhat alien to the im- mediate question of insect instability, should scarcely be altogether omitted in a treatise like this. * Insecta Maderensia, pp. 21, 22. Ill CHAPTER V. GEOLOGICAL REFLECTIONS. WE frequently hear it asserted, that, since the members of the Insecta are so numerous and minute, when com- pared with those of other departments of the organic world, the entomologist, whose province it is to collect and classify them, can have but little time, if he attempt the real advancement of his particular science, for ge- neralizations on a broad scale. Now, whilst there is necessarily some reason in this remark (for the investiga- tion of species is a work of such labour and drudgery that it is apt to monopolize all the leisure hours which the greater number of us are able to command), we should recollect, on the other hand, that the soundest theorists have ever been the most patient and accurate observers ; and have, many of them, spent whole years of their lives as humble students in Nature's domain. We need not be afraid that an occupation amongst what is microscopically small is liable to cramp the mind, and render it unfit for wider processes of induc- tion, since the very opposite of this would seem to come nearer to the truth. The understanding which has been well tutored by a system of close and steady obser- 112 vation, which has been trained to seize upon differences amongst the objects of our common experience, to balance the importance of generic and specific charac- ters, as tested in the acquisitions of our daily walks ; and which has been gradually brightened and matured by the habitual exercise of its judgment on the most trifling phenomena around us, has usually gained strength enough to form conclusions from such data, which will not only stand the test of analysis, but will be free from those eccentricities of genius which too often mar the speculations of less practical naturalists. The mind, moreover, having been chained and fettered for a season to the mere detail of facts, breaks forth, under such cir- cumstances, with all the vigour with which the contempla- tion of truth has gifted it, and takes its flight as it were to a clearer sky; and, though a reaction may at times set in, hurrying it away into regions beyond its sphere, it will assuredly return at length, fraught with the soberness which its vocation has inspired, and commence to build up its hypotheses, step by step, in harmony with the material which it has amassed. Yet though entomologists may be in reality as well qualified as any other natural historians for drawing general conclusions from the result of their researches, it is impossible to conceal the fact, that, as a body, they have not ordinarily done so. Whether this has hap- pened through an accidental disinclination on their part to occupy themselves in such matters, or (which is more probable) from their whole time having been engrossed 113 by the dry routine of their science, I do not pretend to determine : be the solution, however, what it may, the inference is practically the same, that the Annulosa have not hitherto been sufficiently regarded, in the great questions of zoological geography. But especially have they been ignored during that most significant of considerations which has been so ably brought forward of late years by some of our keenest observers, namely, the distribution of animals, as affected by geological changes, on the earth's surface. It would be well if the collector of insects would devote at least a tithe of his energies to the speculative branch of his subject. Certain it is that much would probably be advanced, at first, on slender premises ; and would, as a consequence, fall to the ground, leaving no record behind it. Yet such must inevitably be the case, at the outset, in every region of inquiry ; and we are prepared to expect it. It does not however follow that good would not be developed also ; whilst we are confi- dent of the fact, that unless the trial be made, it cannot possibly arise. No question has ever yet been mooted without beneficial results : it has either been shown to be absurd, and has received its death-blow on the spot, or else truth has been elicited (indirectly perhaps), which has at once shed a new ray of light on some of its obscurest bearings. And so, assuredly, it would be in the present instance. We cannot doubt that there is much to be discovered in the past history of insect dissemination, which would tend, when rightly interpreted, to explain 114 many of the occult phenomena of the present day ; and we may be equally satisfied that this cannot by any possibility be attempted without the assistance of geo- logy. Let us therefore glance hastily at a few of those more undeniable convulsions which we are aware have, at various epochs, taken place ; and endeavour to catch a glimpse of how, in the common course of things, that portion of the insect world would be affected which was exposed to their influence. First and foremost, perhaps, in importance, of all the changes which it is self-evident have happened, may be mentioned subsidence. Including, as it does, both the general lowering of some countries, and the actual isola- tion of others, there are, I believe, no physical crises to which we could point, through the instrumentality of which the very existence of the insect races (not to allude to their diffusion) has been, by the nature of the case, more seriously interfered with. We know that there are certain species of an alpine and boreal cha- racter, which cannot live except in a climate of low tem- perature, guaranteed to them either by elevation in one land, or by a higher latitude in another: and let us picture the consequences of the gradual sinking of a mountain chain, even to a small extent, the summits of which only just afforded the conditions of atmosphere necessary for the continuance of creatures like these. Now this is an example by no means far-fetched, and such as must have occurred in instances innumerable. But, what would be the many results of a diminution in 115 the level of our imaginary range ? It needs no argu- ment to prove, that one at least would be manifest in the total extinction of those forms which could not adapt themselves to the increased heat. Others, which were able with difficulty to endure the alteration, would in all probability, even though they had now emigrated to the loftiest peaks, nourish less vigorously than before ; and it is not unlikely, moreover, that they would become somewhat modified from their normal states, states which, be it recollected (for this is an instructive lesson), would still exist in more northern zones. During my researches in mountain tracts, I have usually remarked, that the highest points of land either teem with life, or else are perfectly barren. My own experience would certainly tend to prove, that, in a general sense, one or the other of these extremes does almost constantly obtain. And, although I would not wish to dogmatize on phgenomena which may in reality be ex- plicable on other hypotheses, it would perhaps be worth while to inquire whether the geological movements of subsidence and elevation will not afford some clew to the right interpretation of them. Be this, however, as it may, I can answer, that in many countries, where there are strong indications of the former, the alpine summits harbour an insect population to a singular extent ; whilst in others, where the latter is as distinctly traceable, the upland ridges are comparatively untenanted. Now we have already shown, that where the gradual lowering of a region has taken place, there will be, of necessity, an 116 undue accumulation of life on its loftiest pinnacles, for, even allowing a certain number of species (which even formerly were only just able to find a sufficient alti- tude for their development) to have perished, we shall have concentrated at that single elevation the residue of all those which have survived from the ancient elevations above it. But, if, on the other hand, an area, already peopled, be in parts greatly upheaved, there will be either a universal dying-out, from the cold, of a large proportion of its inhabitants, or else an instinctive striving amongst them to desert the higher grounds on which they have been lifted up, and to descend to their normal altitudes : in both cases, however, the present summits will display the same feature, namely, utter desolation. Such are a few of the effects which elevation and subsidence, even on a small scale, would seem (when tested by theory and practice) to produce. It yet remains for us to suggest, that the latter, when carried to its maximum, so as to cause the actual separation by the sea of one district from another, is a contingency of immense significance in regulating the distribution of the Annulose tribes. Their outward contour and aspect we have shown in a previous chapter to be very largely beneath the control of isolation, provided a sufficient time can be granted for the change : but their ultimate absence from any particular place, through the impedi- ment which it offers to their migratory progress, we have not yet touched upon. Let us conceive, therefore, 117 an extensive continent ; and, since the insects which at present inhabit our earth must, if the doctrine of specific centres he true, have been originally created in certain definite spots, let us suppose a limited proportion of them to have been first produced upon this tract. Self- dissemination, we will assume, has been going on for centuries : those species which were gifted with quick diffusive powers have become pretty evenly dispersed over its surface ; whilst those of naturally slow or seden- tary habits have peopled, comparatively, but small areas around the respective localities of their birth. Such may have been the case, at some fixed period, amongst the aboriginal beings of any country which we choose to select as an illustration. But there is another element to be considered. If this region be not insular, it will have received colonists from foci of radiation situated beyond its bounds ; and these, therefore, according to their several capabilities for progression, will have, like- wise, in parts, overspread, or tenanted, it. Now it is impossible to cite a more simple example than this. But let us endeavour to realize what would be the neces- sary consequence of the breaking up of such a district as that which we have imagined. If a general sinking should take place, causing its higher points to be alone visible above the ocean, or merely a partial one, so as to admit of the sea encompassing portions of it which would remain unaffected in their altitude; the result practically would be the same, namely, the constitution of a group of islands out of a once continuous land. Then, as regards the 118 animal population of this tract, the main phsenomena are almost self-evident. Should any of its isolated frag- ments chance to contain a portion of one of those limited areas which a species of slow progressive powers had succeeded in colonizing, it would of course harbour (pro- vided that the other portion has disappeared) what would now be denned as endemic. Numbers of these small areas, or, in other words, of the species which had over- spread them, would in all probability be lost for ever ; whilst the occurrence of any of the surviving ones in more than a single island would manifestly depend on the proximity of the islands inter se. Those forms which had diffused themselves over the whole original con- tinent would now be found in all the detachments of the cluster; whilst others, which had wandered over the greater portion of it only, might be traceable perhaps in every island except a few. Such are the primary facts which suggest themselves, whilst discussing the question of isolation as regulating the distribution of the Annulose tribes. Its after effects, on their external configuration and development, we have examined in a preceding chapter of this treatise; and we have also lately intimated what might be a few of the presumptive consequences of a subsidence (in a general sense), apart from the still more important principle of isolation. Before, however, we dismiss these brief and elementary reflexions on the upward and down- ward movements which geology testifies to have occurred, at various epochs, on the earth's surface, I shall per- 119 haps be pardoned if I digress so far from my immediate subject as to trace out some of the actual results of iso- lation in the diffusion of the Insecta (especially recogni- zable in the stoppage of a former migratory progress) in a few of the northern Atlantic groups. I should pre- mise, however, that it is from the Coleoptera alone that I shall attempt to draw my inferences; nevertheless, since that order is more extensive than any of the others, and has moreover been closely investigated in most of those islands, it may possibly afford us data of sufficient comprehensiveness and accuracy for practical purposes. To commence, then, with the Madeiras and Canaries ; the first facts which isolation discloses to us, concerning the statistics of a region which was once continuous throughout that portion of the Atlantic, are the slowness and the direction of the ancient migratory movements. The former of these is rendered evident from the vast number of endemic species which are at present con- tained, not merely in the two groups combined, but in the several islands of which each of them is composed. True it is, that these peculiar forms are, most of them, apterous, and of naturally sluggish self-disseminating powers; yet, still the circumstance remains, that these various creatures had not overrun areas of any extent before the land of passage was destroyed, for otherwise they must have occurred, now, on islands and rocks but slightly removed from each other, which they do not. The latter of the above conclusions, namely, the direction of the migratory current, will become apparent in the 120 sequel. We may premise however, that, so far as the aborigines of this province are concerned, their course will be found, upon the whole, to have been a northerly one. As regards the slowness, and the direction, of the quondam migration (questions which can scarcely be treated apart from each other), some light may be thrown on the subject from considerations like the fol- lowing. The Canaries are the head-quarters of the genus Hegeter ; Teneriffe may indeed be called the land of Hegeters. No less than thirteen or fourteen species have been recorded as indigenous to those islands ; and there can be no reasonable doubt whatsoever that that ancient region (when continuous and entire) was the primaeval centre, or range, of that Heteromerous group. The Hegeters are an apterous race, and of a sedentary temperament ; hence, when the area (whether by general or partial subsidence, it signifies not) was broken up, it is not surprising that those local fragments of it should have become the nucleus of reception, as it were, for the members of that genus. Nevertheless, a few of these many representatives (of more discursive capabilities per- haps than the rest) had found their way, before the period of dissolution, to a isiderable distance from their original haunts. Thus, one of them (the H. late- bricola, Woll.) had arrived at what now constitutes the rocks of the Salvages ; another (the H. elongatus, Oliv.), at least, if not two, had colonized the Madeiras, and is said (though I believe incorrectly) to have even reached 121 the present coast of Portugal. This latter species is clearly of a more adaptive nature than its allies, inas- much as it has, also, naturalized itself (though this may be a more recent, and accidental, circumstance) on the opposite shores of Africa. One thing, however, is at any rate manifest, that the Hegeters attain their maximum in the Canaries, and that a few members only have been sent oif, in a northerly, or north-easterly, direction, from thence. In like manner, the genus Tarphius is distinctively Madeiran. I have detected nearly twenty well-defined species of it in that group; yet, out of so large a number, two only have occurred beyond the central island. Now the Tarphii are, also, wingless ; and crea- tures of very sluggish propensities, scarcely ever stir- ring from the masses of loose rotting timber which they so assimilate in hue, and to the under sides of which they affix themselves, day and night. Although difficult to investigate in their precise economy, it is extremely probable (may I not say, certain ?) that some important and peculiar office is assigned to them in the remote upland districts to which they exclusively belong : and there cannot be any question, to a person who has studied them carefully on the spot, but that the region which they now inhabit is the actual area of their prim- aeval appearance on this earth. Many kindred species may of course have been lost, during those gigantic subsidences which caused the Madeiras to be shaped out, and to tell their tale above the waves as ruins of an G 122 ancient land ; yet our existing cluster of forms could not have wandered far at that early period, from the Serras and ridges of their birth, perhaps not so far indeed (considering the limited bounds within which they are now confined, and that time should in reality have increased their range rather than diminished it) as they have succeeded in doing at the present day. Hence we may reasonably conclude, that Madeira proper is an example of what we have alluded to in a preceding page, namely, of the accidental retention, during a vast downward movement, of a nucleus of small specific areas of colonization, the colonizers of which had not extended elsewhere. But I stated, that two of the above-men- tioned Tarphii have occurred beyond the central mass, It is in Porto Santo that they make their appearance ; nevertheless, since one of them is apparently peculiar to that island, it is only the T. Lowei, Woll. (an insect of a different, and more active, nature than the rest) which has violated that local exclusiveness which would seem to be almost a generic character, as it were, of its allies. That species, however, both in its manners and aspect, recedes materially from the remainder. Although, like them, nocturnal in its habits, it is able to run with con- siderable velocity ; and, instead of attaching itself to the blocks of putrefying wood, which both fall and decay in situ on those elevated tracts, it hides within the bunches of Evernia scopulorum and prunastri which clothe the trunks of living trees, and fill up the crevices of the weather-beaten peaks. Hence, when contrasted with 123 its comrades, we can easily understand how the varied processes of accidental transportation would operate to increase the range of a creature which differs so essen tially, in many respects, from them. It is indeed, not unfrequently, brought down, at the present day, by human agencies from the mountain-slopes ; for, since the cutting of faggots is one of the few sources of live- lihood to a large proportion of the poor of Funchal, numerous insects of subcortical and lichen-infesting tendencies are subject to be naturalized (provided they can adapt themselves to the change) in altitudes lower than their normal ones : so that there are many chances, even a priori, in favour of the T. Lowei having over- spread, whether by natural or artificial means, a wider area than its congeners. I believe that there is no such thing as a Tarphius in the Canarian Group : neverthe- less, singularly enough, a representative, which is more akin to the T. Lowei than to any other hitherto dis- covered (and which was imagined until lately to have been the sole exponent of the genus), namely, the T. gibbulus, Germ., occurs in Sicily. From which data we arrive at this significant fact : that, whilst Madeira proper is, without doubt, the original centre of the Tarphii, two species (one of which is, likewise, Ma- deiran) are found in Porto Santo, to the north-east of it ; whilst a third makes its appearance in an island of the Mediterranean. The genus Acalles presents a nucleus of species in the Canaries, moulded on a very large pattern. A closely G2 124 allied member, the A. Neptunus, Woll. (whicli may per- haps be in reality but an insular modification of the A. argillosus, Schon., from Teneriffe),has been detected on the rocks of the Salvages, to the north of them; whilst on the Dezerta Grande, one of the most southern stations of the Madeiran Group, we have a third, which displays far more in common with the Canarian type than it does with that which obtains in Madeira proper ; which last is gradually, in its turn, merged into the ordinary European form. The genus Pecteropus, Woll., is another instance in point. I possess three or four species from the Grand Canary, Fuertaventura, and Teneriffe ; and I believe it will be found, on inquiry, to attain its maximum in that cluster. Unlike the others, however, which we have just cited, it is powerfully winged -, and we should consequently expect to trace the evidences of its northward progression with comparative perspicuity. Can we therefore do so ? Yes : in Ma- deira proper it has two representatives, and in Porto Santo (to the north of it) one. And so with Xenostron- gylus, Woll. (which is likewise winged), we have two species, at least, in the Canaries ; one in the Madeiras ; and a third, unless I am mistaken, in Sicily. The genus Ditylus is shadowed forth in the Canary Islands by two or three singular representatives of a pallid, testaceous hue ; and, although the group is entirely absent in Ma- deira, a species (the D. fulvus, Woll.) is found on the ' Great Piton ' of the Salvages, so nearly resembling, except in its smaller size, one of those from the Canaries 125 that I think it far from improbable that it is a fixed insular state of that insect. Deucalion, also, may be quoted in support of this twofold hypothesis, of the direction, and the slowness, of the former migratory movements. It is an apterous genus, and of eminently sluggish habits ; and what is the consequence ? we have a very remarkable species (the D. oceanicum, Woll.) on one of the rocks of the Salvages, whilst another (the D. Desertarum, Woll.) has been isolated on the two southernmost islands of the Madeiran Group ; and of so sedentary a nature is this last, that, although physically unimpeded, it has not, even to this day, overrun the diminutive areas on which, when the surrounding region was submerged, it was originally saved from destruction. So strongly indeed was this fact impressed upon me, when I first detected it, that I shall perhaps be excused for recapitulating in extenso the few reflexions which then suggested themselves to my mind. " There is no genus, perhaps, throughout all the Madeiran Coleoptera, more truly indigenous than Deucalion. Confined appa- rently, so far as these islands are concerned, to the remote and almost inaccessible ridges of the two south- ern Dezertas, it would seem to bid defiance to the most enthusiastic adventurer who would scale those dangerous heights. Its excessive rarity, moreover, even when the localities are attained, must ever impart to it a peculiar value in the eyes of a naturalist ; whilst its anomalous structure and sedentary* mode of life give it an addi- * " When we consider indeed the apterous nature of Deucalion, 126 tional interest in connexion with that ancient continent, of which these ocean ruins, on which for so many ages it has been cut off, are the undoubted witnesses. Approxi- mating in affinity to Parmena and Dorcadion, yet pre- senting a modification essentially its own, it becomes doubly important in a geographical point of view ; and it was therefore with the greater pleasure that I lately received a second representative, from the distant rocks of the Salvages, midway between Madeira and the Canaries. Differing widely in specific minutiae, yet agreeing to an identity in everything generic, they offer conjointly the strongest presumptive evidence to the quondam existence of many subsidiary links (long since lost, and radiating in all probability from some interme- diate type) during the period when the whole of these islands were portions, and perhaps very elevated ones, of a vast continuous land. ***** The Deucalion Desertarum is of the utmost rarity, the only two* speci- its subconnate elytra, and its attachment (at any rate in the larva state) to the interior of the stems of particular, local plants, or its retiring propensities within the crevices of rocks; we are at once struck with the conviction, that, during the enormous interval of time which has elapsed since the mighty convulsions which rent asunder these regions terminated, it has probably never removed many yards from the weather-beaten ledges which it now inhabits." * Since the above was published, I have succeeded in detecting one more example, namely (in June 1855) on the summit of the Ilheo Bugio, or Southern Dezerta, within a few yards of the self- same spot where it was found by the Rev. R. T. Lowe in May 1850. Although I searched diligently on the Dezerta Grande, during my late campaign in the Madeira Islands, I was not able (so great is its rarity) to discover farther traces of it on that rock. 127 mens which I have seen having been captured (the first by myself, in 1849 ; and the second by the Rev. R. T. Lowe, in 1850) on the respective summits of the Middle and Southern Dezertas. So local indeed does it seem to be, that it, apparently, has not extended itself even over the Dezerta Grande (where there are no external ob- stacles to bar its progress) ; but retains the very position which in all probability constituted its original centre of dissemination at the remote period of time when this ancient continent received its allotted forms. Judging from the slowness with which creatures of such habits must necessarily, under any circumstances, be diffused, it is at least unlikely that the present one could have circulated far, when the now submerged portions of that region began to give way; and hence it is not impossible that the Southern Dezerta, with the adjacent part (then united to it) of the Central one, may have embraced the whole area of its actual primseval range, the remains of which (though they be now separated by a channel) it still continues to occupy, and from which, even when physically unimpeded, it has never roamed*." Although it is not my province in this volume to draw inferences from data which are not strictly entomologi- cal, I shall perhaps be pardoned for adding a few words on the testimony which the Land Mollusca of the Madeiras would seem to afford, in support of the general slowness of the animal migrations over that primseval continent. The researches of the Rev. R. T. Lowe, and * Insecta Maderensia, p. 435. 128 of myself, on every rock and island of the group, have, it appears, so nearly exhausted the whole number of species which lately remained to be found, that the con- chological statistics are perhaps, at the present time, more accurate than those of any other department of the fauna : and, independently of the modifications which have been manifestly brought about, in some few instances, by isolation, since the periods of subsidence, it is truly singular to remark how every detached portion of the entire cluster harbours real species, which are now pecu- liarly its own. Thus (to select an illustration from amongst the most anomalous of the endemic forms), we have in Madeira proper, Porto Santo, and on the South- ern Dezerta, respectively, true representatives, in the Helix tiarella, coronata, and coronula, which in all probability still occupy the positions (or nearly so) of their original debut upon this earth. Considering the sluggish, or sedentary, nature of the Terrestrial Mollusks, it is extremely likely (nay, almost certain) that many intermediate links, radiating from the same type, were lost for ever, when the gigantic movements which rent this ancient region were in course of operation : so that, if such were in reality the case, we need not be surprised that one at least of this small geographical nucleus should have been preserved on three of the existing islands of the group. That these are actual species (saved alive from their fellows, after the wholesale destructions in this Atlantic province had been completed), and no results of insular development, is demonstrated by the 129 fact that two of them (for the third has apparently become extinct) have not altered one iota since the fossil period, which, in the opinion of Sir Charles Lyell, is anterior to the dissolution of the intermediate land ; whereas, had they been mere modifications of each other, induced by the local conditions and influences to which they have been, through a long series of ages, severally exposed, the difference between their recent contour and that of their fossil homologues would have been doubtless at once conspicuous. I gather, therefore, that like the Tarphii, to which we have lately drawn attention, they are veritable surviving members of an esoteric assemblage which found its birth-place on this post-miocene (?) tract. In a similar manner, the H. undata in Madeira pro- per, the H. Vulcania on the Dezertas, and the H. Porto- sanctana in Porto Santo, are representative species, each occupying the same position, and being equally abundant, on their respective islands : and, although it may be a problem whether the second of these is not an insular modification of the first (or vice versa) yet, with the analogy of the three already mentioned before us, I am inclined a priori to view it as distinct. These, also, occur in a subfossil state ; and no alteration appears to have been brought about, by either circumstances or time. And so it is with numerous others (as the H. latens in Madeira, and the H. obtecta in Porto Santo; the H. squalida in Madeira, and the H. depauperata in Porto Santo; the H. Delphinula in Madeira, and the H. tectiformis in Porto Santo), which are no less repre- G5 130 sentative inter se. From which we are driven to con- clude ; first, that this quondam continent was densely stocked at the beginning with foci of radiation created expressly for itself* ; and, secondly, that the areas which these various creatures had overspread, before the land of passage was broken up, was extremely limited, or, which amounts to the same thing, that their migratory progress was unusually slow. Touching the two-fold question, of the local engage- ment of this Atlantic district with specific centres of diffusion, and the extreme slowness of their diffusive pro- gress, much instruction may be derived from a contem- plation of the conchological statistics. Porto Santo, for instance, is a very small island (not more than seven miles in length), yet the number of endemic species which it includes is so perfectly astounding that it may be appropriately termed a generic area of radiation. * It would seem, when viewed on a broad scale, as if particular districts throughout the world had been made as it were the special fields for the exercise of the creative force, or that, generic areas of radiation were part of the elementary design. Thus, Professor E. Forbes records his belief that most, if not indeed all, of the ter- restrial animals and plants now inhabiting Britain are members of specific centres beyond its bounds, they having migrated to it over a continuous land, before, during, or after the glacial epoch. Hence, since the greater number of them are supposed to have come from the central Germanic plains, we may assume that those plains were one of the primary areas of diffusion for a large mass of created beings. There is good cause for suspecting that the Pyrenean region may have been another ; and certainly all evidence would tend to prove that this vast Atlantic province was, also, well stocked with aboriginal forms. 131 Nor does this primaeval excess of its aboriginal beings strike us more forcibly than does the utter quiescence (if I may so express it) which has been going on amongst them since the remote era of their birth. Although a few have apparently died out* since that epoch, conse- quent perhaps on the change of level and diminished range which took place during the process of subsidence ; we are amazed to find that certain species which are now limited to particular spots (even whilst unopposed by physical barriers) have been absolutely peculiar to them * Assuming the Helix Lowei and Bowdichiana to be gigantic phases of the H. Portosanctana and punctulata, respectively ; four only, namely H. fluctuosa and lapicida, Achatina Eulina, and Cyclo- stoma lucidum (the first three of which are extinct throughout the entire group), seem to have altogether disappeared. Nevertheless, the gradual dying-out, as it were, of species, both here and in Madeira proper, is singularly evident. Thus, in the latter, the Cani- 9al beds show the H. tiarella to have been once most abundant (it literally teems in those calcareous formations). Yet so rare is it in a recent state, that, until the summer of 1855, when it was detected by myself and the Rev. R. T. Lowe in two remote spots along the perpendicular cliffs of the northern coast, it was supposed to have been lost for ages. And the same may be said of its counterpart, the H. coronata, in Porto Santo, which, likewise, swarms in every fossil-bed of that island ; but which was, also, until I met with it, on the 15th of December 1848, adhering to slabs of stone at a con- siderable depth beneath the ground, on the extreme eastern peak (opposite to the Ilheo de Cima), imagined to have long passed away. And so, reasoning from analogy, I think it far from impro- bable that the third representative of this little geographical assem- blage, the H. coronula of the Bugio (which has hitherto only occurred in the mud deposits on the summit of that rock), may be still alive, though perhaps in very small numbers, on some of the inaccessible ridges of those dangerous heights. 132 from the first, or, in other words, that, whilst the fossil deposits extend throughout the lower regions of the island, far and wide, it is only in those respective por- tions of the beds which join on to the present " habitats " that the fossil homologues of several of the species are to be met with. The H. Wollastoni is eminently a case in point. That most interesting of the Madeiran Mol- lusks was first detected by myself on the southern ascent of the Pico de Conseilho, of Porto Santo, April 22, 1849 ; and the subsequent explorations of the Rev. R. T. Lowe, in conjunction with my own, have, I think, satisfactorily proved that it occurs nowhere else except upon that single slope. Throughout the large expanse of calcare- ous incrustations which are spread over the island else- where, and on the adjoining Ilheo de Baixo, all of which teem with shells, I think I may assert, without fear of contradiction, that the H. Wollastoni does not so much as exist. Yet at the Zimbral d'Areia, which the Pico de Conseilho directly overhangs, a rich tract for these fossil remains, as well as in the muddy composition of a cliff near at hand, it literally abounds. In like manner, we might recall many others which are peculiar, recent and fossil \ to the self-same precincts. Such, for example, are the H. calculus and commixta, which swarm on the summit of the Ilheo de Baixo, in both states. The H. attrita, again, is the Pico d'Anna Ferreira modification of the H. polymorpha ; and it is only in the beds towards the base of that mountain that its fossil homologue is found. But what do these facts 133 indicate ? Surely they tell us plainly of what we have already so often insisted upon, namely, the redun- dancy of this once continuous land with specific foci of its own, and the sluggish or sedentary nature of those primaeval radiating forms. We must not however omit to notice, that some few of these endemic Helices appear to have been gifted (as we should a priori anticipate) with more rapid capabi- lities for diffusion than the rest. Thus, the H. erubescens and paupercula seem not only to have colonized the entire province of which the Madeiras are detached frag- ments, but to have even found their way to that distant portion of it which now constitutes the Azores. The H. polymorpha has also penetrated the Madeiran region throughout ; and being, like the H. erubescens, peculiarly sensitive to the action of external influences, we per- ceive, in consequence, that almost every island and rock has now its own especial phasis of it. So greatly indeed is that species beneath the control of local circum- stances, that the very districts of an island as insignifi- cant as Porto Santo have each their separate races to boast of. On the Pico d'Anna Ferreira it assumes a form to which the name of H. attrita has been applied ; when on the Ilheo de Baixo, it is the H. papilio ; at the Zimbra d'Areia, on the Pico de Conseilho, and in the Bibeira da Coxinha, it is the H. pulvinata-, and, in many other situations widely removed inter se, it puts on the shape (variable, both in size and hue) to which the title of H. discina has been given. But, if we leave 134 Porto Santo, and follow this Protean Helix into the other divisions of the group ; we meet with it on the Dezertas as the H. senilis (those moreover from the central island having a much more open umbilicus than is the case in the northern and southern ones), whilst in Madeira proper it constitutes the H. lincta (with an additional pale variety for the calcareous district of Cani9al), and the H. saccharata, from the Sao Lou- renjo promontory. In the same may we might pursue the H. erubescens, and show that in the sylvan regions, and on the low barren Ponta Sao Louren9o of Madeira, on the Pico de Facho of Porto Santo, on the Ilheo Chao, on the Central Dezerta, and on the Bugio (where it at- tains a gigantic size), it has its distinct and permanent phases, the evident results of isolation, and other topo- graphical influences, since the subsidence of the inter- vening tracts. And in like manner, the Clausilia delto- stoma is universal throughout the Madeiran Archipelago, displaying, however, in Porto Santo a fixed and strongly ribbed state, peculiar to that island. Thus, if the examples which we previously cited tend to establish the extreme slowness of the migratory movements of the terrestrial mollusca across this former continent, the present ones (which refer to a few exceptional species of quicker self-diffusive powers) will show, no less than the insects to which I have lately called attention, that where sufficient areas had been overspread (before the periods of subsidence) for the creatures to have 135 reached what now constitute the various islands of the cluster, we at once detect traces of this fact, through their more or less altered aspects, the result of isola- tion, and diminished range, during the enormous in- terval which has elapsed since the successive convulsions which caused the partial destruction of this Atlantic province were brought to a close. To return, however, to the insects, after this long con- chological digression, I need not multiply evidence, in corroboration of my theory. Enough has been said to render intelligible the idea which I wished to convey, concerning the general direction of the migratory current over that ancient tract, and the extreme slowness of its progress, the former of which I consider probable from the north-easterly course in which creatures generi- cally identical were, if we may so express it, "given- off;" whilst the circumstance of their being for the most part specifically dissimilar (or, in other words, of the islands harbouring, many of them, species which are endemic) would seem as it were to establish the latter. We must not however forget, that it is only to the aborigines of this quondam land that the above specula- tions apply. Assuming the region not to have been insular, that is to say, to have been connected, on its outer limits, with a European, or Mediterranean, conti- nent ; it would necessarily follow, that a certain number of colonists must have found their way over its area, and moreover in an opposite direction to the living 136 stream (if we may so call it) which had been long flow- ing in a north-easterly course across its surface. What- ever be the length of the periods, however, during which these counter migrations were going on, I think it sufficient to state that I would refer them to epochs altogether different, so that, accompanied as they may have been by special geological phaenomena, which, if known, would in all probability become at once explana- tory, we should be the less inclined to regard as absurd what might appear at first sight difficult to understand. In the case of the British Isles indeed, no less than five of these distinct migratory eras have been assumed, and specified*, by Professor Edward Forbes; therefore (what- ever value be attached to his able and interesting theory) I do not consider it necessary to apologize for requiring at least two in behalf of this ancient Atlantic province. Not to insist upon those of his faunas and floras which are of a less evident, or more questionable, character, he has at any rate proved, I think, almost to a demon- stration, the westward progress of the great mass of our British animals and plants, over a then unbroken land (the upheaved bed of the glacial sea), from the central Germanic plains; whilst the accurate calculations of the late Mr. Thompson of Belfast, concerning the reptile statistics of Ireland, England, and Belgium, respectively, have succeeded in showing, with much presumptive rea- son, how the formation of St. George's Channel, before * Origin of the Fauna and Flora of the British Isles (in Mem. of the Geol. Survey of Great Britain, vol. i. p. 336, A.D. 1846). 137 that of the German Ocean, interrupted the march of these wanderers to the far West, and debarred an im- mense proportion of them from an entry into Ireland, which would otherwise have colonized that country equally with our own. As regards Professor Forbes' s views of the creation of a vast continent (reaching far into the Atlantic *) at the close of the miocene epoch, through the upheaved bed of a shallow miocene sea, a region moreover of such an extent as to have connected the various island groups between the Fucus bank and the shores of the Old World, not only with each other, but with a Mediterra- nean province, Asturias, and even the south-west of Ireland, I must be content to pass them by, hazarding only a few crude and desultory remarks. So large a question, indeed, cannot be safely handled without a corresponding amount of data, in all departments of natural science, to reason from, which I do not possess: still, if a speculation from entomological premises, per se, be not altogether worthless, I would point to the conclusions (lately adverted to) which my Madeiran researches have forced upon me, concerning the direc- tion of the former insect migrations, inferences which are, from first to last, of necessity erroneous, if the requisite medium for transit (into South-European lati- * " My own belief," says Professor Forbes, " is, that the great belt of gulf-weed, ranging between the 15th and 45th degrees of north latitude, and constant in its place, marks the position of the coast-line of that ancient land." 138 tudes, at all events) be a mere conjecture or romance. Such a notion, however, I would not for a moment entertain, for there is too much direct evidence in support of distinct epochs of diffusion, to allow of any hypothesis, when endeavouring to account for the phenomena which we now behold, to supersede the assumption of a once continuous tract. No matter if we be compelled to suppose, whilst attempting to in- terpret what we see, that the disseminating current has flowed in exactly opposite courses, at different and remote periods, over the surface of that ancient land, seeing that the fact (if such in reality it be) remains untouched, that the land itself is at any rate there. I am not, however, prepared to assert that the opinion at which I had independently arrived, from the insect statistics, does positively require a northerly prolonga- tion of that area beyond the line of the central Mediter- ranean districts ; yet, after making every possible allow- ance for accidental introductions since the subsidences have taken place, there is still left a large residuum which I am convinced can never be explained (unless the doctrine of specific centres be a myth) except through the means of ordinary and regular migration over an unbroken continent. Nevertheless, though I would not presume, from insufficient material, to insist upon an extension of this Atlantic region into higher latitudes than those which I have just referred to, I must express my individual belief that, the more the subject is examined, with reference to the distribution of 139 the Ammlosa, the less will Professor Forbes's idea suffer from the inquiry. In the ' Insecta Maderensia/ I have already thrown out a few scattered hints which bear on this immediate consideration ; and, since no subsequent reason has induced me either to withdraw or modify them (but rather the reverse), I will select the following, extracted from my preface to that work. "Taking a cursory view of the Coleoptera here described, the fauna may perhaps be pronounced as having a greater affinity with that of Sicily than of any other country which has been hitherto properly investi- gated. Apart from the large number of our genera (and even species) which are diffused over more or less of the entire Mediterranean basin, this is especially evinced in some of the most characteristic forms, such as Apotomus, Xenostrongylus, Tarphius, Cholovocera, Holoparamecus, Berginus, Litargus, Thorictus, and Boro- morphus. There is, moreover, strange though it may appear to be, some slight (though decided) collective assimilation with what we observe in the south-western extremity of our own country and of Ireland, nearly all the species which are common to Madeira and the British Isles being found in those particular regions; whilst one point of coincidence at any rate, and of a very remarkable nature, has been fully discussed under Mesites. Whether or not this partial parallelism may be employed to further Professor E. Forbes' s theory of the quondam approximation, by means of a continuous land, of the Kerry and Gallician hills, and of a huge 140 miocene continent extending beyond the Azores, and including all these Atlantic clusters within its embrace, I will not venture to suggest : nevertheless, it is impos- sible to deny that, so far as the Madeiras betoken, everything would go to favour this grand and compre- hensive idea. Partaking in the main of a Mediterranean fauna, the northern tendency of which is in the evident direction of the south-western portions of England and Ireland, and with a profusion of endemic modifications of its own (bearing witness to the engorgement of this ancient tract with centres of radiation created expressly for itself), whilst geology proclaims the fact that subsi- dences on a stupendous scale have taken place, by which means the ocean's groups were constituted; we seem to trace out on every side records of the past, and to catch the glimpses, as it were, of a veritable Atlantis from beneath the waves of time *" * Although, for want of a better name, it may be admissible, when speaking either figuratively or poetically, to allude to this former region (as I have done in the above quotation) under the title of " Atlantis;" yet it seems incredible that certain writers (assuming its quondam existence) should have recently referred to it seriously as the possible " Atlantis of the ancients ! " Consider- ing that there is good reason to believe that all these islands were islands in a miocene sea, and that, if (through a general elevation) they were subsequently connected, the land of passage was broken up long anterior to the appearance of man upon the earth, " the ancients" must have assuredly merited their appellation, if they could have thrown any light on a problem which belongs to an epoch thus remote. Whether the "Atlantis" had any being at all except in the imagination of the Latin poets, or whether (as Lord 141 The Mesites Maderensis, Woll., to which I alluded in the above quotation, is undoubtedly a strong case in point. Although specifically dissimilar from the M. Tardii, its Irish counterpart, it nevertheless approaches it so closely, that it might be literally mistaken, primd facie, for that insect ; and we know that it is one of the plans on which Nature commonly proceeds, that species which are not merely representative of (or analogous to) each other, but which are actual homologues, or allies, should usually emanate at first from foci not far removed inter se ; or, at all events, if distant, connected by an intervening land: in other words, that generic areas, no less than specific centres, of radiation, form a sub- stantial item of the comprehensive scheme on which the system of created things was originally planned. We detect traces of this primary law in each division, or class, of the organic world ; nor is its reality as a law interfered with, through the occasional exceptions which are liable, as in every other instance, to present them- selves. Such deviations are often easily to be accounted for, whether by natural or artificial means ; and do not Bacon has suggested) it was the New World, will probably never now be known ; yet the fact that the Insulce Fortunate of Juba are almost universally identified with the present Canarian Group (as indeed the accurate description of Pliny well nigh demonstrates), and the Purpurarice with the Madeiras, ought at once, apart from geological evidence, to point out the absurdity of the hypothesis, that an Atlantic continent, in the very position which those islands occupy, could have been acknowledged to have any existence by the literature of either Rome or Greece. 142 affect the subject, as a whole. Sometimes indeed they become at once intelligible from the historical records connected with them, proving that human agencies have been at work acting as transporting media, within a period comparatively recent ; whilst at others, the fact of the creature having been endowed with self-diffusive powers to an extravagant degree may succeed equally in rendering the phenomena explicable. But, even where neither of these solutions would seem to suffice, we should still recollect that it is only in the mass that such questions can be pronounced upon; and that, con- sequently, where we are able to discover a rule which is for the most part adhered to, it is more philosophical to conclude that the departures from it are the result of special disturbing causes (whatsoever they may have been), than to permit them to undermine our faith in what would be otherwise universally true. Thus, the botanist tells us of Ixias, Stapelias, Mesembrianthe- mums, Pelargoniums, and Euphorbias, as concentrated in Southern Africa ; of Magnolias in Central America ; of Calceolarias on the Andes; of Myrtles, Banksias, Mimosas, and Eucalypti, in Australia ; and of the Bread-fruit Trees in the South Sea Islands : the orni- thologist points, inter alia, to the Toucons and Hum- ming-Birds from South America and the West Indies ; whilst the student of the higher animals informs us of the Kangaroos (indeed of the whole of the subclass Marsupialia, except the genus Didelphys) as peculiar to Australia and a few islands to the north of it ; of Lemur 143 proper to Madagascar ; of the Sloths, Armadillos, Tree Porcupines, and of Alligators, and of the Platyrrhini (amongst the Monkeys), to South America; and of the Ourangs to the islands of the Indian Archipelago. And so it is with the Insecta; many of the larger groups of which (as Amycterus and Paropsis, in Australia; Pachyrhynchus and Apocyrtus, in the Philippine Islands ; Hipporhinus, Monochelus, Dichelus, and Moluris, in Southern Africa ; Macronota, in Java ; and Naupactus, Hypsonotus, Centrinus, Platyomus, and Cyrtonota, in South America) are confined to countries of propor- tionate magnitude, whilst the smaller ones are more com- monly (as it were) shaped out for special provinces or re- gions, according as local circumstances may require pri- mary adaptations to harmonize with them. Thus, whilst we frequently find an extensive genus diffused over the greater portion of the known world, we perceive that even its structural characteristics are not uniform throughout, but afford fixed geographical modifications (not, in this case, however, the effect of development), which have often, in their turn, obtained the name of ' genera/ and have been described as such. Whether genera, however, or not, they are undeniably small topographical assemblages, satellites around their central types; and they may therefore be safely regarded as genera, if we choose to view them in that light. Of such a nature I have already pointed out* is Saprinus, as compared with Hister ; Atlantis with Laparocerus ; and Oxyomus with * Insecta Maderensia, p. 214. 144 Aphodius; and, I might also add, Mesites with Cos- sonus. I believe indeed that Mesites will be found to attain its maximum on the Pyrenees (I already possess two or three species, in abundance, from that region) ; and, if such should be the case, we shall be able to ap- preciate the significance of two representatives so closely allied as the M. Tardii and Maderensis, one of which has been given off in the direction of Ireland, and the other of the Madeiran Archipelago. But I will not digress further on the subject of this Atlantic province; since, however much I may indivi- dually regard it as a reality of the past (which the Coleopterous statistics have compelled me to do), it must of necessity remain, as heretofore, a matter of much controversy and doubt. I should indeed apologize for having trespassed on the reader's attention, in wandering thus far from the immediate results of subsidences, which I proposed, at the outset of this chapter, to exa- mine, with reference to the impeded diffusion of the Annulose races. Nevertheless, concluding that a prac- tical illustration of the effects of one of those great downward movements to which geology so repeatedly bears witness would not be irrelevant to the assumed consequences which I had previously ventured to define, I have acted on that judgment; and, having finished my task, will now proceed to notice, briefly, a few other considerations which should not be omitted, when inquiring into insect distribution as influenced by geolo- gical phenomena. 145 Next in importance, perhaps, to the elevations and sinkings (traces of one or the other of which are more or less manifest in almost every region of the world), natural barriers may be cited, as presenting, not un- frequently, insurmountable obstacles to the self- dissemi- nation of the insect tribes. By natural barriers, how- ever, I would be understood to imply natural primary barriers, or, in other words, such as have continued as barriers ever since the present animals and plants came into existence upon the earth. For, the ocean (by way of illustration) is a natural barrier ; and yet it is not necessarily a primary one, as may be readily gathered from the above remarks, in which the results of subsi- dences are discussed, subsidences which have had the effect of letting it in over portions of an already tenanted ', and unbroken, continent. Mountain- chains, also, are barriers ; but it may happen that they have not been so from the beginning, as in instances, for example, where they have been gradually upraised during periods geolo- gically recent. But both sea and alpine ranges are barriers, when (as usually happens) they have remained as such since the creation of the several species which now inhabit our globe. Mr. Darwin has acknowledged this distinction, whilst commenting upon the marked divergence of the faunas on the eastern and western slopes of the Cordillera. " This fact," says he, ' ' is in perfect accordance with the geological history of the Andes; for these mountains have existed as a great barrier since the present races of animals have appeared ; H 146 and therefore, unless we suppose the same species to have been created in two different places, we ought not to expect any closer similarity between the organic beings on the opposite sides of the Andes, than on the opposite shores of the ocean. In both cases, we must leave out of the question those kinds which have been able to cross the barrier, whether of solid rock or salt- water*." Conceding, therefore, this distinction between barriers of a primaeval and more recent character, it is not diffi- cult to understand why the opposite sides of an alpine chain, as well as countries separated by the sea, should display different phenomena from each other. On the contrary indeed, if we could feel satisfied that no means of accidental transportation had operated to take them there, and that the animals themselves were incapable of enduring great diversities of temperature, and other con- tingencies ; we should be startled to discover creatures specifically identical in such regions, so long at least as the doctrine of unique centres of radiation formed part of our zoological creed. We must not, however, be too hasty in questioning (if I may be pardoned for the com- pletion of a metaphor of which I thoroughly disapprove) this article of our faith, through the occurrence of simi- lar beings in areas between which there exist barriers, both primary and well-defined; for the methods of diffusion are so complicated and numerous, that, even where human agency (that most important of elements) * Journal of Researches, pp. 326, 327. 147 is not concerned, what at first sight may frequently appear to be impossible becomes clear enough when more critically inquired into. Some species, we know, are gifted with greater powers for horizontal and vertical progression than their comrades, and can (though they are doubtless exceptions to the general rule) pass through extremes of atmosphere sufficient to render even lofty mountain summits no obstacles to them. Others, as the Calosoma Syncophanta of Europe, have been stated to traverse the ocean unhurt* ; and I believe that many do at times accidentally arrive, in a half-drowned state, especially after boisterous weather, across channels of considerable breadth. Mr. Kirby, on examining the marine rejectamenta, during one of these apparent oc- currences, along the Suffolk coast, writes as follows : " Whether the insects I observed upon the beach, wetted by the waves, had flown from our own shores, and, fall- ing into the water, had been brought back by the tide ; or whether they had succeeded in the attempt to pass from the continent to us, by flying as far as they could, * Many of the Calosomata would appear to possess this power of crossing, either by flight or by abandoning themselves to the waves (though more probably by the assistance of both), even ma- rine barriers with impunity. Numerous instances are on record to this effect ; and I am informed by Mr. Darwin that a Calosoma flew on board the ' Beagle,' off the Bay of San Bias, in South America, whilst they were ten miles from shore. It seems likely, therefore, that the occasional occurrence of the C, Syncophanta in our own country, along the southern and eastern coasts, is due to this generic capability, and consequently (as indeed it is usually acknowledged to be), the result of accident, H2 148 and then falling had been brought by the waves, cannot certainly be ascertained; but Kalm's observation in- clines me to the latter opinion*." And Sir Charles Lyell remarks : " Exotic beetles are sometimes thrown on our shore, which revive after being drenched in salt waterf." Nor should we forget that chance agencies of every description, which we are too apt to overlook, are daily at work (and have been so since, at any rate, the last creative epoch) to transport these variously organized beings beyond their original spheres. Sometimes they are carried on, or within, the bodies of larger animals, which is especially the case with the parasitic tribes ; at others on floating trunks of trees, and casual substances of divers kinds, which are able to resist for a definite period the destructive action of an element saturated with salt. Unwilling victims, again, are ever and anon hurried to comparatively distant lands by the very winds that blow ; and not only to distant lands, but over altitudes in which the severity of the cold would quickly annihilate them, were they (as perhaps usually happens) to be deposited there on their headlong and compulsory course. " As almost aD insects are winged J," says Sir Charles Lyell, " they can readily spread them- selves wherever their progress is not opposed by un- * Introduction to Entomology, ii. p. 13. t Principles of Geology, 9th ed. p. 657. J Although this is true on a broad scale, a reference to my ob- servations in a preceding chapter will show, that in some countries, especially islands, the reverse will frequently be found to obtain. 149 congenial climates, or by seas, mountains, and other physical impediments ; and these barriers they can some- times surmount by abandoning themselves to violent gales, which may in a few hours carry them to very con- siderable distances. On the Andes some sphinxes and flies have been observed by Humboldt, at the height of 19,180 feet above the sea, and which appeared to him to have been involuntarily carried into those regions by ascending currents of air*." With respect to the acci- dental conveyance of numerous species across the sea, it is not to the winds alone that we must look for an ex- planation. Large and rapid rivers are liable to inun- date their banks and bring down insects in prodigious masses, which are disgorged into the ocean, and car- ried to a distance from the coast, in proportion to the violence of the ejecting stream. When the body of water is considerable, the sea becomes diluted to an un- usual extent ; and creatures which must have otherwise perished, from the action of the salt, are able to survive for a time, and may be deposited, by means of rapid currents into which they are borne, on neighbouring islands and continents. Even the Hydradephaga are thus occasionally transported ; for Darwin mentions having captured a Colymbetes off Cape S ta Maria (to the north of the Rio de la Plata), when forty-five miles from the shore. And, in his ' Journal of Researches/ he records the following remarkable facts, which bear upon this immediate question. " On another occasion, * Principles of Geology, p. 656. 150 when seventeen miles off Cape Corrientes, I had a net overboard to catch pelagic animals. Upon drawing it up, to my surprise I found a considerable number of beetles in it, and, although in the open sea, they did not appear much injured by the salt water. I lost some of the specimens ; but those which I preserved belonged to the genera Colymbetes, Hydroporus, Hydrobius, Nota- phus, Cynucus, Adimonia, and Scarabaeus. At first I thought that these insects had been blown from the shore ; but upon reflecting that, out of the eight species, four were aquatic (and two partly so) in their habits, it appeared to me most probable that they were floated into the sea by a small stream which drains a lake near Cape Corrientes. On any supposition, it is an inter- esting circumstance to find live insects swimming in the open ocean seventeen miles from the nearest point of land*." Accidental means of dissemination, such as those to vyhich I have just alluded, and others to which we might appeal, will generally account, and with much presump- tive truth, for the many exceptional cases which present themselves, during our investigation into the effects of natural barriers, as visible in the distribution of the Annulose races, on the earth's surface. I say " excep- tional cases," because any one who has laboured practi- cally in mountain tracts cannot have failed to recog- nize the marked difference which is often displayed by the insect population on opposite sides of some alpine * Journal of Researches, p. 159. 151 chain ; whilst he whose lot has been cast amidst island groups, will have become even more conscious than the former of the permanency of those impediments which have been placed (in this instance by the broad arms of the mighty ocean) as checks upon a too rapid system of diffusion. But if the sea and mountain ranges, when of a suffi- cient age in situ, are amongst the most effectual of Nature's barriers against the self-dispersion of the animate tribes ; it follows that, if the two could be (as it were) united, we should have found the greatest ob- stacle which physical conditions can ordinarily present against the wandering capabilities of the latter. The question therefore arises, Is it possible for them to be so joined ? Undoubtedly it is : and hence we arrive at the conclusion, that a mountain island should afford us the minimum of size, as regards the areas its species have overspread, which any country is able to furnish. Madeira is a mountain island, its highest peaks rising, although resting on so small a base, to an alti- tude of more than 6000 feet. Yet it is only partially a case in point; for, although it was a mountain mass, and perhaps a very elevated one, when its endemic beings made their first appearance upon its surface, we have already intimated that it has become isolated since that epoch : so that, whilst one of the natural barriers against dispersion which it involves (namely, mountain ridges) may be considered as primary ; the other (to wit, the sea, as it now obtains) has played, as an agent of 152 obstruction, but a secondary part. Still, there is good reason to believe that the ancient tract of which it is a portion was broken up at a comparatively early date after the creation of those peculiar organic forms which found their birthplace within its bounds ; and that, con- sequently, the latter could not have wandered far (if we except those species on which unusual powers of diffu- sion were bestowed) when the land of passage began to give way. Hence, even the sea, in this particular in- stance, partakes almost of the character (no less than the mountain heights) of an original impediment ; and Madeira therefore may be safely quoted as an example in which two barriers, of a primary nature, are united ; and where, consequently, we may anticipate those ultra phenomena of areal limitation upon which we have been just commenting. But let us now inquire, whether the hypothesis at which we have arrived will stand the test of experience ; for unless it will do so, we might have been spared the labour of propounding it. Madeira is a country com- posed of narrow mountain ridges, which radiate from central crests, and form the lateral boundaries of deep and precipitous ravines. Modifications of this structural type are of course traceable everywhere; the upland tracts are often undulating and broad, and the buttresses which slope towards the sea are sometimes expansive and irregular : yet upon the whole the above description is correct, and we may accept it in a generic sense. Now we may premise that, even to this day, it is an 153 island of floods; therefore, how much more must it have been so when its primaeval forests, in all their splendour, caused an amount of exhalation and moisture of which at present we can have but a remote conception ! Hence, it is hardly to be imagined, that (however limited may have been the naturally acquired areas of those of its inmates which are most sluggish and sedentary) a fusion would not have taken place, in the course of ages, so as to render its modern fauna, in a large measure, homogeneous throughout. Yet, in spite of this esoteric tendency, it is surprising how little amalgamation has been effected amongst the tenants of its several districts. Scarcely a gorge or woodland serra exists within its bounds which does not harbour some species essentially its own; and in many instances the ranges of these creatures are so local or confined, that they might be easily overlooked even in their respective neighbour- hoods. It is certain, however, that the floods (which happen periodically) have done considerable work in naturalizing many of the subalpine forms, which could adapt themselves to the climatal change, in altitudes below their normal ones : and, in the north of the island, where the temperature is cooler than on the opposite side, and where the lofty defiles terminate, even at their lowest outlets, in abrupt precipices along the coast, so that the rejectamenta during the annual rains are brought into direct contact with the shore, this gradual process of deportation is particularly evident, a circumstance to which I have already alluded else- H 5 154 where*. But, after making due allowance for these powerful means of dissemination (which, in the common order of things, must necessarily obtain in mountain islands, as it were, par excellence), the fact still remains, that in the Madeiran Group the acquired areas, even up to the present date, of a vast proportion of the insect inhabitants, are wonderfully circumscribed. The real state of the case, however, would appear to be simply this : that the floods, although they may have tended to diffuse the members of a comparatively uniform alpine fauna in the various clefts or gorges beneath, can have had no power to combine the aborigines of the several gorges themselves ; and, since a large proportion of the endemic species of those islands are (as I have previously stated) apterous, the perpendicular edges of the ravines, which in many instances rise to an elevation of 2000 feet, have acted (and ever will act) as impassable barriers to vast numbers of the insect tribes. With this single example (by way of illustration), which the Madeiras have supplied, I will take my leave of the question of natural barriers, as tending to regulate the topographical diffusion of the Annulosa, feeling that I have already devoted too much time and space to this portion of the subject (if such indeed it be) which I had proposed in the present treatise to discuss. Other barriers might have been adverted to, such as large rivers, extensive deserts, and thickly set forests (espe- cially of pine-trees, which frequently offer a very decided * Insecta Maderensia, p. 81. 155 impediment to insect progress), but they are of secondary importance, when compared with marine and alpine ones ; and their consequences may be, to a certain extent, deduced from the considerations which I have just entered into. My main object has been to draw attention to the fact, that the great obstacles which Nature has placed against the too rapid dispersion of animal life should be more strictly taken into account (as a matter of positive reality) than it is, during our investigations into entomological geography. To be aware that these barriers exist, and yet to feel surprised, especially in a country where the species are principally wingless, that we do not discover indications of a general uniformity in its fauna, involves an absurdity, unless the doctrine of specific centres of creation be a mere coinage of the brain. But, if we believe in that theory (which, until it can be shown to be impossible, I hold that we are a priori bound to do), we must at least act consistently with ourselves, and not anticipate phseno- mena where we have neither reason nor right to look for them. We are too apt to draw a line of imaginary demarca- tion between the sciences, as though each had its own propositions to establish, and nothing more: indeed, some of us would appear to assume (though perhaps tacitly), that what is proved to be true in one depart- ment may be, at least, rendered inconsistent (if not actually negatived) in another. But surely this requires no argument to refute, since a principle which is true. 156 is true under every circumstance and condition; for otherwise, it could be both true and false. We need not therefore be afraid of comparing truth with truth, under whatever shape it may arrive, as though it were possible that either of its phases could ever suffer from the ordeal of a close contact ; since, if they be really true, and free from deception, they must needs go hand in hand, and may become (however opposite they be in their subjects) directly explanatory of each other. The astronomer who is not intimately acquainted with pure mathematical analysis, in its various aspects and bearings, is in fact no astronomer at all. The geologist who would interpret the grand phsenomena of the earth's crust apart from statical and dynamical knowledge, and without the help which the chemist, mineralogist, anatomist, zoologist, and botanist can afford him, stands a fair chance of leaving his problems unsolved ; whilst the students of zoology and botany who would endeavour to understand, and account for, what they see in the animal and vegetable worlds around them, without calling in geology to their aid, must assuredly be pre- pared to fail signally in their attempts. All indeed must work in concert, if the whole is to be advanced, and not only in concert, but as mutually assisting each other. "By the help of truths already known, more may be discovered; for those inferences which arise from the application of general truths to the particular things and cases contained under them, must be just.* " * Religion of Nature Delineated, pp. 73, 74. 157 CHAPTER VI. THE GENERIC THEORY. How glorious to the observant eye is the great system of the organic world, how perfect in each separate part, how complete and harmonious the whole ! The unity of the comprehensive plan, amidst the infinite modifica- tions which it includes, has ever been a theme of admi- ration and delight ; for the mind, which has once caught a glimpse, even in physics, of what it is not possible to disprove, instinctively clings to it, as to a grand material truth. The discovery, at all times, of what we feel to be actually certain is in itself so fascinating, that the very data which it gives us are scarcely more prized than the mere knowledge that we have gained a single additional light to guide us on our forward way : for, since in the inductive sciences we can but climb from step to step, at a slow and even pace, we hail with inward satisfaction whatsoever may tend to lighten our task, and to lead us more quickly onwards (gradually though we must of necessity advance) towards its final accomplishment. But how, it may be asked, is this general harmony of the organic creation to be insisted upon, when beings so extravagant and dissimilar are everywhere to be met 158 with ? Is it possible to recognize anything like a unity of type amongst creatures so differently constructed, and so widely removed from each other in their habits, aspects, functions, and attributes? Such questions as these, however, though they may occasionally perplex the tyro, or amateur, are not likely to be raised by any- one who has mastered the merest alphabet of zoology, and who is aware that the integrity of Nature is some- thing real and positive, as experience indeed is ever tending more and more to corroborate, and by no means the day-dream of an enthusiastic, or fertile, imagination. To trace out the progressive development of animal life, from its humblest phases ; and to mark, as they become visible in the intermediate grades, the first rudiments of organs and instincts which are destined to attain their maximum in the higher ones, embody but a small portion of what it is the naturalist's mission to investi- gate. To him belongs the special privilege of inquiring dogmatically into this structural advancement ; and of suggesting methods of classification which shall accord, in their several component divisions, so far at least as is practicable, with the constitutional change. We should recollect, however, that this system, being based upon truth, must, if it would be consonant throughout, adapt itself to all the various phenomena (in their respective positions, in the scale), from the consideration of which it should be exclusively deduced, or built. To draw broad conclusions of any kind, or to attempt the esta- blishment of propositions and principles, from simple 159 dialectics, without a previous training in the practical bearings of the subject, would be absurd, and almost certain to beget error. "It cannot be that axioms established by means of reasoning [alone] should be of any value for the discovery of new results ; because the subtilty of Nature far exceeds the subtilty of reasoning. But axioms duly and orderly abstracted from parti- culars, in their turn easily point out and mark off new particulars ; and so render the sciences active*." Such were the words of the greatest philosopher which this country has ever produced ; and it would be well, whilst examining the causes of what we see, and endeavouring to obtain some faint and distant notion of the vast scheme of Nature as originally designed, to keep them constantly in view, lest, by trusting to theory only, apart from observation and facts; or by venturing to pervert the latter (instead of being led by them), so as to tally with our preconceived ideas of what ought to be, we miss our road, and become lost in the mazy labyrinth of our own fanciful inventions. With this preliminary stricture on the express duty which devolves upon the naturalist (with whom the phenomena of the organic world principally rest, for interpretation) to make facts, rather than reason and * "Nullo mode fieri potest, ut axiomata per argumentationem constituta ad inventionem novorum operum valeant ; quia subtilitas naturae subtilitatem argumentandi multis partibus superat. Sed axiomata a particularibus rite et ordine abstracta, nova particularia rursus facile indicant et designant; itaque scientias reddunt ac- tivas." Novum. Organum, Aphoris. xxiv. 160 argument, the basis of his various doctrines, at any rate of those in which the critical subject of arrangement is concerned ; I shall perhaps be pardoned, after having been drawn, in the preceding chapters (however involun- tarily), into the question of ' species/ as rigidly denned, if I now offer a few passing remarks on the theory of genera. There can be no doubt that amongst a large class of ordinary observers a clear perception of the generic system, in an abstract sense, does not by any means prevail. What the nature of a genus really is, would appear to have been very commonly overlooked, or per- haps misunderstood, by people of this stamp ; and the consequence has been, that the wildest notions have frequently arisen, even from men of sound specific attainments, as to the claims (for annihilation or re- tention, as ' genera') of certain subsidiary zoological assemblages. The terms ' genus 3 and ' species ' have been conjointly so long associated in our minds with the selfsame things (whatsoever they may be), that they have become almost part and parcel of the objects them- selves; so that the student who does not sufficiently reflect on their true signification, is apt to regard them as of equal importance, or, rather, more often perhaps than otherwise, to make the latter subservient (or inferior) to the former ! This however is, in reality, the very reverse of what should be the case, as a moment's consideration will indeed at once convince us : for what are genera, after all, but dilatations (as it were) along a 161 chain which is itself composed of separate, though dif- ferently shaped, links ? The links (or the actual, inde- pendent bodies which constitute the chain) are the species ; but the knobs, or swellings, which their several forms may tend, by degrees, to establish along its course (through the slight disparity which each of them pre- sents from that which is next in succession to it; and therefore through the gradual manner in which the bulbs, or nodules, may be said, on the whole, to be pro- duced), are the groups into which those species naturally fall. It matters not a straw whether these assemblages be primary, secondary, tertiary, &c., in other words, whether they be departments, families, or genera, as usually understood, the principle is in every instance the same ; the difference being merely relative, and not absolute. Or, if we choose to vary the simile, we may compare the whole system to a cord, upon which beads, of innu- merable sizes, patterns, and colours, have been densely strung. Now, if there were no such things as natural divisions in the organic world, these beads (which repre- sent the separate species) might have been disposed of anyhow, their positions, with respect to each other, would under those circumstances have been of no im- portance. But such is not the case : there is an order and method throughout Nature, which shows that every individual portion of it has been adjusted by the Master's hand, and that nothing has been left to chance. Those beads (to follow up the metaphor) of countless magni- 162 tudes and hues, have had their proper places allotted to them, and moreover with such care and regularity, that a complete plan, or scheme, of distribution is at once conspicuous. Although there are not even two, amongst that enormous multitude, which are precisely alike (for every species, however it may resemble its next ally, has some distinctive feature of its own), we immediately per- ceive that those beads which have most in common, are, as it were, attracted to each other, so as, by their close approximation, or contact, to create excrescences and stripes, of divers kinds, along the entire length of the cord. If we assume now that the red beads have been collected together, to the length (for instance) of a yard, and that within that space a dozen protuberances, of discordant aspects and dimensions, have (by the union of those beads which more nearly simulate each other) been brought about ; we shall have a very fair idea of the ordinary grouping of the animate tribes. The red beads, taken in the mass, may be likened to a perfect ' ' family ;" the differing gibbosities to twelve well -marked "genera," which that family includes; whilst the " species " (the real dramatis persona, of independent existence, which are nevertheless compelled to occupy the situations we have described, thus causing the divi- sions to be mapped out) are here typified, as everywhere, by the several beads themselves. I have not thought it necessary to pursue this reason- ing into higher divisions than " families " but of course it may be extended to any amount, so as to shadow 163 forth, equally, the compartments of primary significance. Nor would I wish to imply, by the above similes, that I regard a lineal method of arrangement as the correct one. Every zoologist is aware, that in Nature such does not exist : but the mode of illustration which I have selected is applicable to all systems alike, so far as the principle is concerned. It will consequently be seen, from what has been said, that the terms " genus " and " species " not only differ very considerably in importance, but in signification also. Whilst the former is merely suggestive of a particular position which a creature occupies in a systematic scale (a position, however, which depends upon the various structural peculiarities which it possesses in common with other beings, which thus more or less resemble it) ; the latter expresses the actual creature itself: so that while one applies to several animals (of distinct natures and origins, though bound together by a certain bond of imitation), the other belongs to a single race alone, which it therefore exclusively indicates. But if such be the case, it will perhaps be asked, Why then insist upon a generic name at all, if the specific one be sufficient to denote all that is required, namely, the animal itself 1 To which, however, we may reply, that the binomial nomen- clature is demanded for two elementary reasons, first, because it is founded upon a natural truth, which (to say the least) it would be unwise to violate ; and, secondly, because it is convenient, both for simplification and analysis. We should assuredly be surprised were a man 164 to object to his surname, as unnecessary, because he has a Christian (or specific*) one which is the exponent of him alone. True it is that his family (or generic) title applies to the rest of his kin also ; but, since there are other people (of other families) who may have the same individual appellation as himself, it is clearly desirable, even as a matter of expediency alone, that patronymic and Christian name should be alike retained. We need not, however, plead expediency, in favour of this accept- ance of what has been so long tested, and shown to be correct ; we appeal to a higher tribunal, that of expe- rience, in proof that it draws its origin from Nature itself, and is implied by the very existence, or reality, of natural groups. The ' Methode Mononomique ' has indeed been attempted f; and it has failed, or at any rate it has shown itself to be inferior, both ideally and in prac- tice, to the plan commonly in use : and if I might be pardoned a passing conjecture on its ultimate success, I should be inclined, since it' is contrary to the canon of the organic world, to regard its case as utterly hopeless. Let us not be unfair, however, towards those who have sought to establish a nomenclature which they conceived would be less open to objections than that which we have been hitherto accustomed to endorse. The notion did, * In selecting this simple method to illustrate the principle of a binomial system of nomenclature, it is scarcely necessary to remind the reader that I do not intend to imply that every man is specifically distinct from his neighbour ! t Considerations sur un Nouveau Systeme de Nomenclature, par C. J. B. Amyot (Rev. ZooL, p. 133, A.D. 1838). 165 at any rate, arise out of an apparent defect in the bino- mial process, for the inconveniences which they com- plained of are real ones ; and, having felt them practi- cally, they aspired to sweep them away by remodelling the whole system afresh. But, had it not been for an evident misconception of the generic theory, in the abstract, the trial would in all probability have never been made ; and we should have been spared the downfall of a contrivance which has had but little to recommend it beyond the ingenuity of its machinery and detail. If we analyse the motives for this experiment, we shall find that it originated from a belief, that genera are either purely imaginary, or else that they must (like species) have a definite and isolated existence. Now both of these conclusions appear to be equally gratuitous and untenable ; and such as a lack of observation could alone beget. Genera are not mere phantoms of the brain (as most naturalists will readily admit) ; but they are, like- wise, by no means abrupt, or well-marked, on their outer limits (except indeed by accident, of which here- after), but merge into each other by gradations, more or less slow and perceptible. Such being the case, we can easily understand why it is that the followers of the ' Methode Mononomique' (who, paralysed by the fact that genera are seldom clearly defined at their extremes, would seem to repudiate them in toto) have rashly regarded the binomial system as intolerable. Finding that it was possible for numerous species, whose structural charac- teristics were less conspicuously pronounced than those 166 of their allies, to be enumerated, and with equal plausi- bility, under two consecutive groups ; they immediately inferred that the groups themselves could not be upheld on account of these connective links : and so it was re- solved (through a new and artificial scheme) to ignore them ; and to fall back upon the creed, that species alone (and not genera) are to be recognized in the organic world. This was but the device, however, at the outset, of a single mind ; and the perverts to it have been but few. It is in direct opposition to the first principles of nomenclature, and sets at defiance a great natural truth. But what, it may be inquired, is this great primary truth which the monomial system tends to violate ? I repeat what I have already stated, that it is the existence of natural assemblages which that scheme would, if it were practicable, discountenance. Order and symmetry, however (which involve classification, or arrangement), are the law of Nature, and it is not possible to set them aside. It matters not if harsh lines of demarcation are undiscernible between the several consecutive groups, the groups themselves must still remain (however equivo- cal it may be where they exactly commence or termi- nate), and cannot be wiped out. To suppose a priori that the allied divisions of the animate creation are per- fectly disconnected inter se, is in fact to break the chain on which the unity of the organic world depends ; whilst to assume that groups cease to be groups when they can be discovered to merge into each other, would no less destroy the harmony of that admirable method, or 167 array, which the naturalist, above all others, delights to contemplate. If things are no longer to be regarded as dissimilar because they unite on their outer limits, differences may be given up, as having no special meaning, and as therefore unworthy of investigation. It requires but a slight insight into the physical universe to be convinced, that nearly everything which we see (and, moreover, without injuring its individual reality] is blended into that to which it is the most akin. Night is distinct from day ; yet, so long as the twilight inter- venes, no man can pronounce where the one ends, and the other begins. Heat is opposed to cold ; yet, if by degrees they be respectively diminished, they will at last amalgamate, in a central temperature. And thus it is with things material. The sea and the land are essen- tially unlike ; yet the precise boundary between the two is never clearly denned, the ebb and flow are constantly going on, and the line of separation is variable. The mountain-range is moulded on a different type to the level country beneath it ; yet the turning-point of them both is, in all instances, on neutral ground. We need not however adduce further evidence in support of this fact, that, throughout the whole of Nature, the general principle of fusion (either absolute or apparent) is most obvious. From first to last, traces of it are everywhere to be detected; not only between clusters, or material combinations, of objects (in which case it is absolute), but even between the objects themselves, under which circumstances, however, it is merely apparent ; for, since 168 they are specifically dissimilar, it can only arise from their near resemblance to each other, and not from their positive coalescence. But, admitting that this universal blending, throughout the animate world, does not inter- fere with the gradual conformation of its several groups, which therefore should be recognized ; we may perhaps be told by the believers in the ' Methode Mononomique/ that they do not intend to ignore the arrangement which Nature has so broadly laid down, but that, on the contrary, they tacitly endorse it, their device having reference to the names only. To this however it will be sufficient to reply, that, if they deem it necessary (of which I am by no means convinced) to accept the natural genera of the organic creation at all, why not acknowledge them ? and how can they be so well acknowledged, either in principle or practice, as through the medium of a binomial nomenclature? Such a system is the only consistent one, on the hypothesis that they do consider them of primary importance; it is more in unison with our notions of what ought to be ; more suggestive of what actually is ; more honest and generous to those who have laboured (as describers), with such care and diligence, before us. It will be perceived, from the above remarks, that, although professedly criticizing the ' Methode Mono- nomique/ into the analysis of which my subject has unintentionally drawn me, it is the absurdity of ob- jecting to genera because they are not rigidly defined throughout, that I have been mainly striving to con- 169 demn. It is indeed well nigh incredible that any such strictures could ever have been advanced; for it must surely have occurred to the most superficial inquirer, that genera, after all, cannot be homogeneous, seeing that they are necessarily composed of detached species, no two of which are precisely similar, even in the few structural details which may have been accidentally chosen for generic diagnostics. How is it possible, therefore, that mere groups, even though they be in accordance with Nature, should be so far isolated and uniform in their character as to occupy an analogous position to that of the absolutely independent species (of distinct origins) which they severally contain ? Taking the preceding considerations into account, the question Avill perhaps arise, How then is a genus to be defined? To which I may reply that, were I asked whether genera had any real existence in the animate world, my answer would be that they undoubtedly have, though not in the sense (which is so commonly supposed) of abrupt and disconnected groups. I con- ceive them to be gradually formed nuclei, through the gathering together of creatures which more or less resemble each other, around a central type : they are the dilatations (to use our late simile) along a chain which is itself composed of separate, though differently shaped links, the links being the actual species them- selves, and the swellings, or nodes, the slowly developed genera into which they naturally fall. When I say 170 ' f slowly developed," my meaning may possibly require some slight comment. It is simply therefore to guard against the fallacy, which I have so often disclaimed, that genera are abruptly (or suddenly) terminated on their outer limits, that the expression has been employed. Though I believe that a series of species, each partially imitating the next in contact with it, is Nature's truest system; yet we must be all of us aware that those species do certainly tend, in the main, to map out assemblages of divers phases and magnitudes, distin- guished by peculiar characteristics which the several members of each squadron have more or less in common. So that it is only in the middle points that these various groups, respectively, attain their maximum, every one of which (by way of illustration) may be described as a concentric bulb, which becomes denser, as it were, in its successive component layers, and more typical, as it approaches its core. If, then, the theory of genera be such as I have endea- voured to expound, it results from what has been said, that every generic type is to be looked for in, or about, the centre of its peculiar group, or at any rate in that region of it which would seem to be the most charac- teristically, or evenly, pronounced. I lay particular stress upon this conclusion, because (if correct) it will somewhat modify the notions which are occasionally entertained upon the subject. A stricture, however, may here be required upon what I have advanced, lest, 171 through using the metaphors which I selected for the elucidation of a principle, it be supposed that I would wish them to apply to the smaller details, likewise, of the problem. If a genus has been portrayed under the similitude of a bulb, or of a nodule (formed by the ap- proximation of beads which more or less resemble each other in their primary aspect), it does not follow that either bulb or nodule are to diminish in a similar ratio towards their respective circumferences, or, which is the same thing, that they are to be symmetrical ; whether spherical, ovoid, or otherwise. The general method of the organic creation is a progressive one; and its suc- cessive types, therefore, will not always be found to radiate equally from their normal foci : so that it is in the direction of the higher (rather than the lower) extre- mities of the assemblages that those foci are usually to be discerned ; and where the groups are large, it is not often difficult to pronounce which of their ends are, as a whole, the more perfectly developed. It will, moreover, be further acknowledged (if my premises are allowed), that, since it is a somewhat central position which the typical member of a genus usually occupies, the diagnostic characters, although (in combination) carried out to the full, are more evenly balanced in a generic type than in any of its associates ; or, in other words, that a species in which any single organ is monstrously enlarged, at the expense of the rest, is seldom typical of the assemblage with which it is placed ; but may be a priori regarded as in all proba- 172 bility a transition form, leading us onwards into some neighbouring group *. I will not, however, venture too closely into this ques- tion in its minor bearings ; suffice it to have demon- strated that, whatever be the rate, law, or direction, of the advancement of the various groups towards a more perfect model ; or in whatsoever position the several types are to be discerned, with respect to their immediate associates, genera cannot be isolated and distinct, but must of necessity merge (each into two or more others) on their outer limits. Hence, if such be the case, as I contend that it usually is (the exceptions to the rule being, as I shall hope shortly to prove, the result of accident, and by no means a part of the original design), it may perhaps be a problem, how far we are justified in rejecting many large and natural assemblages, through the fact that they blend, both at their commencement and termination, imperceptibly, with others, their pre- cise boundaries being dimly defined. That the recognition of genera is necessary, even as a matter of mere convenience, is self-evident; for in many extensive departments they combine with each other so completely at their extremities (although sufficiently well-marked in the mass), that, unless we are prepared * I may add, that this suggestion, as to the evenly balanced state of generic types, is in accordance with the views of Mr. Waterhouse, whose extensive knowledge in the higher departments of zoolo- gical science gives a value to his opinion, especially on questions such as these, which I am glad to have an opportunity of acknow- ledging. 173 to accept them as they are, we must needs repudiate them altogether : under which circumstances, our diffi- culties, both in determination and nomenclature, would be increased tenfold. We should also recollect, that clusters which seem abruptly chalked out whilst our knowledge is imperfect, are very frequently united with others when fresh discoveries are made, and the inter- mediate grades brought to light : so that their apparent isolation may oftentimes arise from our ignorance of the absent links, rather than from the fact itself. It would surely be more desirable, therefore, when viewed even in the light of expediency alone, to submit to the possi- bility of a few neutral species being conceded, with equal reason, to different groups, than to amalgamate the whole, and so lose sight of the general method or arrangement, into which the various creatures do un- questionably (in a broad sense) dispose themselves. If, however, there be any truth in the generic doctrine as above enunciated, the question of convenience may be omitted from our speculations in toto, seeing that all genera (except those whose present abruptness is the effect of accident) fuse into others with which they are in immediate contact : so that in reality, unless we ignore these natural assemblages from first to last, we have no choice left us as regards the equivocal forms ; but must consent to recognize them as of doubtful loca- tion, and as possessing an equal right to be placed in one or the other of two consecutive groups, according 174 to the judgment of the particular naturalist who has to deal with them. But let us glance at the subject through the medium of an example, and endeavour to realize what would be the consequence of that wholesale combination at which we must sooner or latter arrive, if genera are not to be upheld because they slowly merge into each other as we recede from their respective types. The immense de- partment Carabida, of the Coleoptera, is eminently a case in point. In the details of their oral organs the whole of that family display (as I have elsewhere* re- marked) so great a similarity inter se, or rather shade off into each other by such imperceptible gradations, that the tendency which various clusters of them possess to assume modifications of form which attain their max- imum only in successive centres of radiation, must often- times be regarded as generic, if we would not shut our eyes altogether to the natural collective masses into which the numerous species (however gradually) are, in the main, so manifestly distributed. It is possible indeed that, as our knowledge advances and new dis- coveries take place, we shall so far unite many of the consecutive nuclei which are now considered pretty clearly defined, that we shall be driven at last either to accept the Linnsean genera only, or else the entire host of subsidiary ones (albeit perhaps in a secondary sense) which are, one by one, being expunged. And, since * Annals of Nat. Hist. (2nd series), xiv., p. 199. 175 under the former contingency the determination of species would become practically well nigh hopeless, it is far from unlikely that we shall eventually hail the latter as, after all (at any rate to a certain extent), the more con- venient of the two. Look, for instance, at the great genus Pterostichus, which has nearly 200 representatives in Europe alone : true it is that its several sections (Pcecilus, Argutor, Omaseus, Corax, Steropus, Platysma, Cophosus, Pterostichus proper, Abax, Percus, and Molops) , although easily recognized in the mass, do unquestionably blend into each other; yet I believe that it has arisen from a too rigid promulgation of the generic theory that they have not been retained as separate. And this opinion may be rendered somewhat more plausible, from the knowledge that certain of the Pterostichi (the Argutors, for instance) approach so closely, in their trophi, to CalathuSj as to be hardly discernible from it ; which latter genus is scarcely distinguishable (struc- turally) from Pristonychus, a form which, in its turn, leads us on towards another type. Who would have imagined, again, some fifty years ago, that the widely distributed groups, Calosoma and Carabus, were not thoroughly detached inter se ? yet what naturalist now can draw an exact line of demarcation between them ? And so it is with numerous others, which it is needless to recall. The practical inference, however, from the whole, is this : that if genera must be rejected because they are not homogeneous and isolated throughout, the 176 only ones that will remain are those which have become abrupt from causes which are merely accidental. Having now, however, examined the question in its broadest phasis, that is to say, on the supposition that Nature is complete in her several links and parts; I shall perhaps be expected to offer a few passing words on what I have already hinted at, namely, the possi- bility of genera being absolutely well-defined, even on their outer limits, from accident. Briefly, then, it is through the extinction of species that groups may, in some instances, be abruptly expressed: but, as such contingences are at all times liable (whether from natural or artificial causes) to happen; it would be unfair to build up our generic definition from examples which are the exception, and not the rule, and, more than mere " exceptions " (as commonly understood by that term), the result of positive disturbances from without. Yet, that genera thus distinctly bounded, at either end, do actually occur, must be self-evident to any one who has attempted to study the distribution of organic beings with reference to the geological changes which have taken place on the earth's surface ; for it is clear that a vast proportion of the creatures which inhabit our globe came into existence at periods anterior to many of those great convulsions which altered finally the positions of sea and land, apportioning to each the areas which they now embrace : so that, if generic provinces of radiation (no less than specific centres) be 177 more than a fancy or romance, it is certain that nume- rous members of many geographical assemblages must have perished for ever during the gigantic sinkings which have at various epochs been brought about. From which it follows, that those groups, or clusters, of which but few representatives (comparatively] are extant, will be more or less abruptly terminated, according as the original type to which they severally belong was peculiar, and in proportion as the number of its exponents has been reduced. Although there are many means through which species may become annihilated, yet, since the sub- sidence of a tract into the sea involves the maximum of loss which a space of that magnitude can sustain, the above conclusion gives rise to a corollary : that it is in islands that we should mainly look for genera which are to be rigidly pronounced. The question therefore naturally suggests itself, Is this in harmony with what we see; or, in other words, is it consistent with ex- perience, or not? I believe that it is; for I think it will be found, on inquiry, that the greater proportion of those groups which are more especially isolated in their character (I do not say, necessarily, the most anomalous ; though this in some measure follows from the fact of their detachment) are peculiar to countries which are insular. But, however important an element, in the eradica- tion of species, submergence may be; we must not entirely omit to notice other methods also, through the i5 178 medium of which genera may become well-defined. We should recollect that the removal of a very few links from an endemic cluster is sufficient to cause its dis- junction from the type to which it is next akin, and that where the creatures which unite in composing it are of slow diffusive powers, or sedentary habits, the elimina- tion of such links is (through the smallness of the areas which have been overspread) a comparatively easy opera- tion. The accidental introduction of organic beings amongst others to the interests of which they are hostile, may be a powerful means, as Mr. Darwin has suggested, of keeping the latter in check, and of finally destroying them*. The gradual upheaval of a tract which has been well-stored with specific centres of radiation, created expressly for itself, may (through the climatal changes which have been brought about) succeed in extirpating races innumerable, those only surviving which are able to adapt themselves to the altered condi- tions ; and which would now be consequently looked upon as abrupt topographical assemblages. The over- * A familiar example of this disappearance of a creature before the aggressive powers of another, which is either hostile to or stronger than itself, is presented by the Black Rat (Mus rattus) of our own country, which is said to have been extremely abundant formerly, but which is now replaced by the common brown (or " Hano- verian ") one of Northern Europe. The British species, however, although it has become extremely scarce, is not yet quite extermi- nated : it has been recorded (vide ' Zoologist/ 611) in Essex, and in Devonshire (' Zoologist/ 2344) ; and it still swarms on a small rock off Lundy Island, in the Bristol Channel. It is reported, moreover, to have been lately re-introduced at Liverpool. 179 whelming effect of a volcanic eruption, in a region where the aborigines of the soil have not wandered far from their primaeval haunts, may, as Sir Charles Lyell has well remarked, put an end to others, and so effect the separation of their allies from the central stock. And, lastly, the intervention of man, with all the various concomitants which civilization, art, and agriculture bring in his train, is the most irresistible of every agency in the extensive (though often accidental) demo- lition of a greater or less proportion of the animate tribes. The whole of these ultimate assortments, however, are dependent, as it were, for their outline, upon contingency or chance ; and we must not deduce our ideas of genera from the examples which they supply. We should rather reflect, that it is no matter of mere speculation, that many organic links, now absent, have, through the crises and occurrences to which we have just drawn attention, become lost. On the contrary, indeed, we know that, in the common course of things, it must have been so; and therefore we are induced to regard those cases as exceptional, and as in no way expository of Nature's universal scheme. The more we look into the question, whether by the light of analogy or the evidence of facts, the more are we convinced that lines of rigid demarcation (either between genera or species, though especially the former) do not anywhere, except through accident, exist. And hence it is that we ascend, by degrees, to a comprehension of that unity at which I 180 have already glanced ; and are led to believe that, could the entire living panorama, in all its magnificence and breadth, be spread out before our eyes, with its long-lost links (of the past and present epochs) replaced, it would be found, from first to last, to be complete and continuous throughout, a very marvel of perfection, the work of a Master's hand. 181 CHAPTER VII. Deposita sarcina, levior volabo ad ccelum. S. Jerome. HAVING now completed the short task which I had undertaken to perform, I will, in conclusion, offer a few brief comments on the results at which we have arrived, and endeavour to realize to what extent the considera- tion of them is likely to be found useful, during our inquiries into the general subject of entomological geography. Commencing with the thesis, that specific variation, whether as a matter of experience or as probable from analogy, does ipso facto exist; I have endeavoured to maintain that position, by evidence of divers kinds ; and I have sought to strengthen the inferences deduced, by an appeal to some of those external agents and circum- stances which may be reasonably presumed (if not indeed actually demonstrated) to have had a consider- able share in bringing it about. I have also suggested what the principal organs and characters are, in the Insecta, which would appear to be more peculiarly sensitive to the action of local influences; and I have then diverged to the question of topographical distribu- tion, in connection with the geological changes on the earth's surface ; and, lastly, to some practical hints 182 arising out of a proper interpretation of the generic theory. How far I have succeeded in elucidating the several points which I proposed to examine, is a problem which must be solved by others ; meanwhile, if I have failed at times to interpret what seems scarcely to admit of positive proof, I shall at least have had the advantage of propounding the enigmas for discussion, and of so paving the way for future research. We must remember, however, that, where certainty is not to be had, proba- bility must be accepted in its stead ; or, as an old writer has well expressed it : " That we ought to follow pro- bability when certainty leaves us, is plain, because it then becomes the only light and guide that we have. For, unless it is better to wander and fluctuate in abso- lute uncertainty than to follow such a guide ; unless it be reasonable to put out our candle because we have not the light of the sun, it must be reasonable to direct our steps by probability, when we have nothing clearer to walk by *". What my chief aim in the present treatise has been, will be easily perceived, namely, to substantiate, as such, those elements of disturbance (on the outward con- tour of the Annulose tribes) with which the physical world does everywhere abound : and, thereupon, to pro- voke the inquiry, whether entomologists, as a mass, have usually taken them into sufficient account, when de- scribing as " species," from distant quarters of the globe, insects which recede in only minute particulars * Religion of Nature Delineated, p. 103. 183 from their ordinary states. My own impression is, that they have not done so ; and, moreover, that, if they had, our catalogues would have worn a very different appearance to what they now do : for, when once the subject is fairly looked into and analysed, it is impossible not to be convinced, that the primd-facie aspect of these creatures is eminently beneath the control of the several conditions to which they have been long exposed. But let me not be misunderstood in the conclusion which I have been thus compelled to endorse, or be supposed to ignore the fact that truly representative species may frequently occur in countries far removed from each other ; which cannot therefore be regarded as modifica- tions of a common type. I believe, however, that this doctrine of representation, whatever truth it may con- tain, has been too much relied upon ; and that we have been over-ready to take advantage of it (unproved as it is) for the multiplication of our, so called, " specific novelties/' I suspect, indeed, that actual representative species (if they may be thus expressed) are more often to be recognized on the isolated portions of a formerly continuous tract, than in regions which have been widely separated since the last creative epoch ; and that, in the instances where beings of a nearly identical aspect are detected in opposite divisions of the earth, it is more often the case that members of them have been trans- ported at a remote period (either by natural or artificial means) from their primaeval haunts, and have become gradually altered by the circumstances amongst which 184 they have been placed, than that the respective phases were produced in situ on patterns almost coincident. I have before announced my conviction, that generic areas have a real existence in Nature's scheme; and that, consequently, where species which are so intimately allied that they can with difficulty be distinguished, prevail, there is presumptive reason to suspect (until at least the contrary is rendered probable) that the areas which they now colonize were once connected by an intervening land, or, in other words, that the migra- tions of the latter were brought about, through ordinary diffusive powers, from specific centres within a moderate distance of each other. I say "presumptive reason," because there are undoubted exceptions to this law (as to every other), and it can therefore be only judged of on a broad scale. Still, I contend that in a wide sense it holds good ; and that, consequently, if closely related " species " are traceable in countries which geology demonstrates to have been far asunder during the entire interval since the first appearance of the present animals and plants upon our earth, there is at any rate an a priori probability that they are no species at all, but permanent geographical states, which have been slowly matured since their casual introduction beyond their legitimate bounds. If we except those forms which are in reality but modifications, from climatal and other causes (and which have, therefore, been wrongly quoted as distinct) ; I believe that a vast proportion of the species which 185 have been usually considered to be " representative " ones, were members, in the first instance, of the self- same assemblages, which had wandered to a distance from their primteval haunts, and were afterwards, through the submergence of the intervening land, cut off from their allies. I have adduced, in a preceding chapter, some remarkable examples in illustration of this hypothesis, an hypothesis which I believe to be the true clue to a very large item of the " specific representation " theory. A considerable number of the Madeiran Helices may be cited (which I have already done 1 *) as, in the strictest sense, representative of each other, and as therefore specifically distinct : and I may add, that it is to island groups that we must mainly look for this system in its full development. But, apart from the fact that I would not wish to resign in toto the doctrine of (( specific representation," even as frequently understood (that is to say, as recog- nizable in countries which have been altogether dis- connected since the last creative epoch), and therefore, a fortiori j in what I conceive to be its truer meaning ; there is yet another point on which I would desire to be interpreted aright, whilst endeavouring to substantiate the action of local influences on the members of the insect world. It has been my aim, in the preceding pages, to call attention to the importance of external circumstances and conditions in regulating, within defi- nite limits, the outward aspect of the Articulate tribes. * Vide supra, p. 128. 186 I do not, however, assert that every species is liable to be interfered with ab extra ; that is a question which the greater or less susceptibility of the several races, as originally constituted, can alone decide ; still less would I willingly lend a helping hand to that most mischievous of dogmas, that they are //-important in their opera- tion, or, in other words, that they possess within them- selves the inherent power (though it may not invariably be exercised) of shaping out (provided a sufficient time be granted them, and in conjunction with the advancing requirements of the creatures themselves) those perma- nent organic states to which the name of species (in a true sense) is now applied. Such a doctrine is in reality nothing more than the transmutation theory, in all its unvarnished fulness ; and I do not see how it can be for a moment maintained, so long as facts (and not reason- ing only) are to be the basis of our speculations. I repeat, that it is merely within fixed specific bounds that I would advocate a freedom of development, in obedi- ence to influences from without : only I would widen those limits to a much greater extent than has been ordinarily done, so as to let in the controlling prin- ciple of physical agents, as a significant adjunct for our contemplation. It does indeed appear strange that naturalists, who have combined great synthetic qualities with a profound knowledge of minutiae and detail, should ever have upheld so monstrous a doctrine as that of the transmis- sion of one species into another, a doctrine, however, 187 which arises almost spontaneously, if we are to assume that there exists in every race the tendency to an un- limited progressive improvement. There are certainly no observations on record which would, in the smallest degree, countenance such an hypothesis. Many animals and plants, it is true, are capable of considerable modifi- cations and changes, for the better, very much more than is the case with others. But what does this prove, except that their capacity for advancement has a slightly wider compass than that of their allies ? It touches not the fact, that the boundaries of their respective ranges are absolutely and critically denned. It is moreover a singular phenomenon, and one in which the strongest proofs of design (or a primary adjustment of limits with a view to the future) may be discerned, that the mem- bers of the organic creation which display the greatest adaptive powers, are those which were apparently des- tined to become peculiarly attendant upon man. " The best-authenticated examples," says Sir Charles Lyell, "of the extent to which species can be made to vary may be looked for in the history of domesticated animals and cultivated plants. It usually happens that those species which have the greatest pliability of organiza- tion, those which are most capable of accommodating themselves to a great variety of new circumstances, are most serviceable to man. These only can be carried by him into different climates, and can have their pro- perties or instincts variously diversified by differences of nourishment and habits. If the resources of a species 188 be so limited, and its habits and faculties be of such a confined and local character, that it can only flourish in a few particular spots, it can rarely be of great utility. We may consider, therefore, that in the domestication of animals and the cultivation of plants, mankind have first selected those species which have the most flexible frames and constitutions, and have then been engaged for ages in conducting a series of experiments, with much patience and at great cost, to ascertain what may be the greatest possible deviation from a common type which can be elicited in these extreme cases*." The fact, however, that all areas of aberration (how- ever large they may be) are positively circumscribed, need scarcely be appealed to, in exposing the absurdity of the transmutation hypothesis. The whole theory is full of inconsistencies from beginning to end ; and from whatever point we view it, it is equally unsound. How, for instance, can any amount of local influences, or the progressive requirements of the creatures themselves, give rise to the appearance of several well-marked re- presentatives of a genus on the self- same spot,- where the physical conditions for each of them are absolutely the same ? Look, for example, at the Tarphii (to which I have already alluded f) of Madeira : I have detected about eighteen abundantly defined species; and, as stated in a previous chapter, I have but little doubt, from their sedentary habits, and the evident manner in * Principles of Geology, 9th edition, pp. 583, 584. t Vide supra, p. 121. 189 which they are adjusted to the peculiarities of the region in which they obtain, that they are strictly an esoteric assemblage, inhabiting the actual sites (or nearly so) of their original debut upon this earth. Here, then, we have a sufficient length of time for developments to have taken place; they are all exposed to the self-same agencies from without (for they live principally in com- munion) ; yet, though I have examined carefully more than a thousand specimens (a large proportion of them beneath the microscope), I have never discovered a single intermediate link which could be regarded as in a transition state between any of the remainder. But how is this ? Is it possible to account for differences so decided, yet each of such amazing constancy, amongst the several creatures of a central type which have been exposed to identical conditions through, at any rate, generations innumerable? They clearly cannot be ex- plained on the doctrine of transmutation : yet they are no exceptions to the ordinary rule, occupying an ana- logous position to the members of every other endemic group. But I will not occupy more space on the transmuta- tion theory : suffice it to have shown that, in thus con- ceding a legitimate power of self-adaptation, in accord- ance with external circumstances, to the members of the insect world; and in suggesting the inquiry, whether the action of physical influences has been adequately allowed for by entomologists generally (or, in other words, whether the small shades of difference which 190 have often, because permanent, been at once regarded as specific, may not be sometimes rendered intelligible by a knowledge of the localities in which the creatures have been matured), I do not necessarily open the door to the disciples of Lamarck, or infringe upon the strict orthodoxy of our zoological creed. On the contrary, indeed, I believe that the actual reverse is nearer the truth; and, moreover, that those very hyper-accurate definers who recognize a " species" wheresoever the minutest decrepancy is shadowed forth, will be found eventually (however unaware of it themselves) to have been the most determined abettors of that dogma, see- ing that their species, if such they be, do most assuredly pass into each other. We must not, however, omit to notice, briefly, how this perversion of Nature's economy took its rise. It was from the desire, which is almost inherent within us, to account for everything by physical laws ; and to dis- pense with that constant intervention of the direct crea- tive act which the successive races of animals and plants, such as are proved by geology to have made their appear- ance at distinct epochs upon this earth, would seem to require. Or, which amounts to the same thing, it resulted through an endeavour to explain by material processes what is placed beyond their reach. But, if this be the case, it may be reasonably asked, Are mate- rial laws then not to be inquired into, and should the various influences which operate in the organic world around us be debarred from analysis? Unquestion- 191 ably not. Truth is truth, under whatever aspect it may come; and cannot possibly contradict another truth. To exercise our intellectual faculties, by tracing out, through slow, inductive methods, the modus operandi of even a single natural law, is an honourable task ; nor should the apparent smallness of the media which we are at times compelled to employ, render it less so (else would this present treatise, like many others of a kindred stamp, have been best unwritten) : but it is from the conceit that our own imperfect interpretations have left nothing more to be found out, that the great danger is to be anticipated. An effect may be literally dependent upon a certain proximate cause ; and if we be so fortu- nate as to ascertain that cause, we have done something ; but it does not necessarily follow that we have done much. On the contrary, it often happens that, in so doing, we have achieved wonderfully little, seeing that the pro- blem may be self-evident. Behind that " cause," we should recollect, others lie concealed, of a far deeper nature, each depending upon the next in succession to it j until, in the order of causation, we are at length led back, step by step, to the Final One, with which alone the mind can be thoroughly content. " We make dis- covery after discovery," says Dr. Whewell, "in the various regions of science j each, it may be, satisfactory, and in itself complete, but none final. Something always remains undone. The last question answered, the answer suggests still another question. The strain of music from the lyre of Science flows on, rich and 192 sweet, full and harmonious ; but never reaches a close : no cadence is heard with which the intellectual ear can feel satisfied*." As regards that most obscure of questions, what the limits of species really are, observation alone can decide the point. It frequently happens indeed that even observation itself is insufficient to render the lines of demarcation intelligible, therefore, how much more mere dialectics ! To attempt to argue such a subject on abstract principles, would be simply absurd ; for, as Lord Bacon has remarked, " the subtilty of Nature far exceeds the subtilty of reasoning : " but if, by a careful collation of facts, and the sifting of minute particulars gathered from without, the problem be fairly and deli- berately surveyed, the various disturbing elements which the creatures have been severally exposed to having been duly taken into account, the boundaries will not often be difficult to define. Albeit, we must except those races of animals and plants which, through a long course of centuries, have become modified by man, the starting- points of which will perhaps continue to the last shrouded in mystery and doubt. It would be scarcely consistent indeed to weigh tribes which have been thus unnaturally tampered with by the same standard of evidence as we require for those which have remained for ever un- touched and free, especially so, since (as we have already observed) it does absolutely appear, that those species, the external aspects of which have been thus artificially con- * Indications of the Creator (London, 1845), p. 163. 193 trolled, are by constitution more tractile (and possess, therefore, more decided powers for aberration) than the rest. Whether traces of design may be recognized in this circumstance, or whether those forms were originally selected by man on account of their pliability, it is not for me to conjecture ; nevertheless, the first of these in- ferences is the one which J should, myself, be a priori inclined to subscribe to. In examining, however, this enigma, of the limits within which variation is (as such) to be recognized-, it should never be forgotten, that it is possible for those boundaries to be absolutely and critically marked out even where we are not able to discern them : so that the difficulty which a few domesticated creatures of a singu- larly flexible organization present, should not unneces- sarily predispose us to dispute the question in its larger and more general bearings. Nor should we be unmind- ful that (as Sir Charles Lyell has aptly suggested) " some mere varieties present greater differences, inter se, than do many individuals of distinct species " for it is a truth of considerable importance, and one which may help us out of many an apparent dilemma. But, whatever be the several ranges within which the members of the organic creation are free to vary ; we are positively certain that, unless the definition of a species, as involving relationship, be more than a delusion or ro- mance, their circumferences are of necessity real, and must be indicated somewhere, as strictly, moreover, and rigidly, as it is possible for anything in Nature to be 194 chalked out. The whole problem, in that case, does in effect resolve itself to this, Where, and how, are the lines of demarcation to be drawn ? No amount of incon- stancy, provided its limits be fixed, is irreconcilable with the doctrine of specific similitudes. Like the ever- shifting curves which the white foam of the untiring tide describes upon the shore, races may ebb and flow ; but they have their boundaries, in either direction, beyond which they can never pass. And thus in every species we may detect, to a greater or less extent, the emblem of instability and permanence combined : al- though perceived, when inquired into, to be fickle and fluctuating in their component parts, in their general outline they remain steadfast and unaltered, as of old, " Still changing, yet unchanged ; still doom'd to feel Endless mutation, in perpetual rest." INDEX. Aberration, perhaps indicated universally, 16, 17, 18. Aborigines, insect, unimportant for climatal modifications, 25, 26, 27. Acalles, the Canarian type of, apparent on the Salvages and De- zertas, 124. Neptunus, Woll., perhaps a state of A. argillosus, 124. Achatina Eulima, Lowe, its extinction in Porto Santo, 131. Achenium Hartungii, Heer, a form of A. depressum, 65. Acherontia Atropos, Linn., its introduction into Madeira perhaps recent, 74. Adimonia, the capture of, out at sea, 150. Aepus marinus, Strom., pallid hue of, 64. Robinii, Lab., pallid hue of, 64. Agabus bipustulatus, Linn., unaffected by climate, 31. Alligators, their peculiarity to S. America, 143. Alpine species, some peculiarly so, 40. Altitude and latitude, sometimes reciprocal, 35, 114. Amycterus, its concentration in Australia, 143. Amyot, M., his ' Methode Mononomique,' 164. Analogies, Lord Bacon on the importance of, 13 ; why necessary to be studied, 14. Analogy, argument from, 10, 11, 12. Anchomenus marginatus, Linn., slightly modified in Madeira, 38. Andes, dissimilarity of the fauna on the opposite sides of the, 146. Anobium striatum, Oliv., unaffected by climate, 31. Antennae, joints of, said occasionally to vary, 96. Anthicus bimaculatus, Illig., variability of, near the sea, 63. fenestratus, Schmidt, slightly modified in Madeira, 38. humilis, Germ., variability of, in salt places, 63. instabilis, Hoffm., pallid hue of, 64. Anthonomus ater, Mshm, very small in Lundy Island, 58, 73. Aphelocheirus