CHAPTER XXIV

SUMMARY AND CONCLUSION

The Present Volume is the Development and Application of a Theory--Statement of the Biological and Physical Causes of Dispersal--Investigation of the Facts of Dispersal--of the Means of Dispersal--of Geographical Changes Affecting Dispersal--of Climatal Changes Affecting Dispersal--The Glacial Epoch and its Causes--Alleged Ancient Glacial Epochs--Warm Polar Climates and their Causes--Conclusions as to Geological Climates--How far Different from those of Mr. Croll--Supposed Limitations of Geological Time--Time Amply Sufficient both for Geological and Biological Development--Insular Faunas and Floras--The North Atlantic Islands--The Galapagos--St. Helena and the Sandwich Islands--Great Britain as a Recent Continental Island--Borneo and Java--Japan and Formosa--Madagascar as an Ancient Continental Island--Celebes and New Zealand as Anomalous Islands--The Flora of New Zealand and its Origin--The European Element in the South Temperate Floras--Concluding Remarks.

The present volume has gone over a very wide field both of facts and theories, and it will be well to recall these to the reader's attention and point out their connection with each other, in a concluding chapter. I hope to be able to show that, although at first sight somewhat fragmentary and disconnected, this work is really the development of a clear and definite theory, and its application to the solution of a number of biological problems. That theory is, briefly, that the distribution of the various species and groups of living things over the earth's surface, and their aggregation in definite assemblages in certain areas, is the {532} direct result and outcome of a complex set of causes, which may be grouped as "biological" and "physical." The biological causes are mainly of two kinds--firstly, the constant tendency of all organisms to increase in numbers and to occupy a wider area, and their various powers of dispersion and migration through which, when unchecked, they are enabled to spread widely over the globe; and, secondly, those laws of evolution and extinction which determine the manner in which groups of organisms arise and grow, reach their maximum, and then dwindle away, often breaking up into separate portions which long survive in very remote regions. The physical causes are also mainly of two kinds. We have, first, the geographical changes which at one time isolate a whole fauna and flora, at another time lead to their dispersal and intermixture with adjacent faunas and floras--and it was here important to ascertain and define the exact nature and extent of these changes, and to determine the question of the general stability or instability of continents and oceans; in the second place, it was necessary to determine the exact nature, extent and frequency of the changes of climate which have occurred in various parts of the earth,--because such changes are among the most powerful agents in causing the dispersal and extinction of plants and animals. Hence the importance attached to the question of geological climates and their causes, which have been here investigated at some length with the aid of the most recent researches of geologists, physicists, and explorers. These various inquiries led on to an investigation of the mode of formation of stratified deposits, with a view to fix within some limits their probable age; and also to an estimate of the probable rate of development of the organic world; and both these processes are shown to involve, so far as we can judge, periods of time less vast than have generally been thought necessary.

The numerous facts and theories established in the First Part of the work are then applied to explain the phenomena presented by the floras and faunas of the chief islands of the globe, which are classified, in accordance with their physical origin, in three groups or classes, each {533} of which are shown to exhibit certain well-marked biological features.

Having thus shown that the work is a connected whole, founded on the principle of tracing out the more recondite causes of the distribution of organisms, we will briefly indicate the scope and object of the several chapters, by means of which this general conception has been carried out.

Beginning with simple and familiar facts relating to British and European quadrupeds and birds, I have defined and shown the exact character of "areas of distribution," as applied to species, genera, and families, and have illustrated the subject by maps showing the peculiarities of distribution of some well-known groups of birds. Taking then our British mammals and land-birds, I follow them over the whole area they inhabit, and thus obtain a foundation for the establishment of "zoological regions," and a clear insight into their character as distinct from the usual geographical divisions of the globe.

The facts thus far established are then shown to be necessary results of the "law of evolution." The nature and amount of "variation" is exhibited by a number of curious examples; the origin, growth, and decay of species and genera are traced, and all the interesting phenomena of isolated groups and discontinuous generic and specific areas are shown to follow as logical consequences.

The next subject investigated is the means by which the various groups of animals are enabled to overcome the natural barriers which often seem to limit them to very restricted areas, how far those barriers are themselves liable to be altered or abolished, and what is the exact nature and amount of the changes of sea and land which our earth has undergone in past times. This latter part of the inquiry is shown to be the most important as it is the most fundamental; and as it is still a subject of controversy, and many erroneous views prevail in regard to it, it is discussed at some length. Several distinct classes of evidence are adduced to prove that the grand features of our globe--the position of the great oceans {534} and the chief land-areas--have remained, on the whole, unchanged throughout geological time. Our continents are shown to be built up mainly of "shore-deposits"; and even the chalk, which is so often said to be the exact equivalent of the "globigerina ooze" now forming in mid-Atlantic, is shown to be a comparatively shallow-water deposit formed in inland seas, or in the immediate vicinity of land. The general stability of continents has, however, been accompanied by constant changes of form, and insular conditions have prevailed over every part in succession; and the effect of such changes on the distribution of organisms is pointed out.

We then approach the consideration of another set of changes--those of climate--which have probably been agents of the first importance in modifying the specific forms as well as the distribution of animals. Here again we find ourselves in the midst of fierce controversies. The occurrence of a recent glacial epoch of great severity in the northern hemisphere is now universally admitted, but the causes which brought it on are matter of dispute. But unless we can arrive at these causes, as well as at those which produced the equally well demonstrated mild climate in the Arctic regions, we shall be quite unable to determine the nature and amount of the changes of climate which have occurred throughout past ages, and shall thus be left without a most important clue to the explanation of many of the anomalies in the distribution of animals and plants.

I have therefore devoted three chapters to a full investigation of this question. I have first given such a sketch of the most salient facts as to render the phenomena of the glacial epoch clear and intelligible. I then review the various suggested explanations, and, taking up the two which alone seem tenable, I endeavour to determine the true principles of each. While adopting generally Mr. Croll's views as to the causes of the "glacial epoch," I have introduced certain limitations and modifications. I have pointed out, I believe, more clearly than has hitherto been done, the very different effects on climate of water in the liquid and in the solid state; and I have {535} shown, by a variety of evidence, that without high land there can be no permanent snow and ice. From these facts and principles the very important conclusion is reached, that the alternate phases of precession--causing the winter of each hemisphere to be in _aphelion_ and _perihelion_ each 10,500 years--would produce a complete change of climate only where a country was _partially_ snow-clad; while, whenever a large area became almost _wholly_ buried in snow and ice--as was certainly the case with Northern Europe and America during the glacial epoch--then the glacial conditions would be continued and perhaps even intensified when the sun approached nearest to the earth in winter, instead of there being at that time, as Mr. Croll maintains, an almost perpetual spring. This important result is supported by reference to the existing differences between the climates of the northern and southern hemispheres, and by what is known to have occurred during the last glacial epoch; and it is shown to be in complete harmony with the geological evidence as to interglacial mild periods.

Discussing next the evidence for glacial epochs in earlier times, it is shown that Mr. Croll's views are opposed by a vast body of facts, and that the geological evidence leads irresistibly to the conclusion that during a large portion of the Secondary and Tertiary periods, uninterrupted warm climates prevailed in the north temperate zone, and so far ameliorated the climate of the Arctic regions as to admit of the growth of a luxuriant vegetation in the highest latitudes yet explored. The geographical condition of the northern hemisphere at these periods is then investigated, and it is shown to have been probably such as to admit the warm tropical waters freely to penetrate the land, and to reach the Arctic seas by several channels; and, adopting Mr. Croll's calculations as to the enormous quantity of heat that would thus be conveyed northwards, it is maintained that the mild Arctic climates are amply accounted for. With such favourable geographical conditions, it is shown, that changes of excentricity and of the phases of precession would have no other effect than to cause greater differences {536} of temperature between summer and winter; but, wherever there was a considerable extent of very lofty mountains the snow-line would be lowered, and the snow-collecting area being thus largely increased a considerable amount of local glaciation might result. Thus may be explained the presence of enormous ice-borne rocks in Eocene and Miocene times in Central Europe, while at the very same period all the surrounding country enjoyed a tropical or sub-tropical climate.

The general conclusion is thus reached, that geographical conditions are the essential causes of great changes of climate, and that the radically different distribution of land and sea in the northern and southern hemispheres has generally led to great diversity of climate in the Arctic and Antarctic regions. The form and arrangement of the continents is shown to be such as to favour the transfer of warm oceanic currents to the north far in excess of those which move towards the south, and whenever these currents had free passage _through_ the northern land-masses to the polar area, a mild climate must have prevailed over the whole northern hemisphere. It is only in very recent times that the great northern continents have become so completely consolidated as they now are, thus shutting out the warm water from their interiors, and rendering possible a wide-spread and intense glacial epoch. But this great climatal change was actually brought about by the high excentricity which occurred about 200,000 years ago; and it is doubtful if a similar glaciation in equally low latitudes could be produced by means of any such geographical combinations as actually occur, without the concurrence of a high excentricity.

A survey of the present condition of the earth supports this view, for though we have enormous mountain ranges in every latitude, there is no glaciated country south of Greenland in N. Lat. 61deg. But directly we go back a very short period, we find the superficial evidences of glaciation to an enormous extent over three-fourths of the globe. In the Alps and Pyrenees, in the British Isles and Scandinavia, in Spain and the Atlas, in the Caucasus {537} and the Himalayas, in Eastern North America and west of the Rocky Mountains, in the Andes of South Temperate America, in South Africa, and in New Zealand, huge moraines and other unmistakable ice-marks attest the universal descent of the snow-line for several thousand feet below its present level. If we reject the influence of high excentricity as the cause of this almost universal glaciation, we must postulate a general elevation of _all_ these mountains about the same time, geologically speaking--for the general similarity in the state of preservation of the ice-marks and the known activity of denudation as a destroying agent, forbid the idea that they belong to widely separated epochs. It has, indeed, been suggested, that denudation alone has lowered these mountains so much during the post-tertiary epoch, that they were previously of sufficient height to account for the glaciation of all of them; but this hardly needs refutation, for it is clear that denudation could not at the same time have removed some thousands of feet of rock from many hundreds of square miles of lofty snow-collecting plateaus, and yet have left moraines, and blocks, and even glacial striae, undisturbed and uneffaced on the slopes and in the valleys of these same mountains.

The theory of geological climates set forth in this volume, while founded on Mr. Croll's researches, differs from all that have yet been made public, in clearly tracing out the comparative influence of geographical and astronomical revolutions, showing that, while the former have been the chief, if not the exclusive, causes of the long-continued mild climates of the Arctic regions, the concurrence of the latter has been essential to the production of glacial epochs in the temperate zones, as well as of those local glaciations in low latitudes, of which there is such an abundance of evidence.

The next question discussed is that of geological time as bearing on the development of the organic world. The periods of time usually demanded by geologists have been very great, and it was often assumed that there was no occasion to limit them. But the theory of development demands far more; for the earliest fossiliferous rocks {538} prove the existence of many and varied forms of life which require unrecorded ages for their development--ages probably far longer than those which have elapsed from that period to the present day. The physicists, however, deny that any such indefinitely long periods are available. The sun is ever losing heat far more rapidly than it can be renewed from any known or conceivable source. The earth is a cooling body, and must once have been too hot to support life; while the friction of the tides is checking the earth's rotation, and this cannot have gone on indefinitely without making our day much longer than it is. A limit is therefore placed to the age of the habitable earth, and it has been thought that the time so allowed is not sufficient for the long processes of geological change and organic development. It is therefore important to inquire whether these processes are either of them so excessively slow as has been supposed, and I devote a chapter to the inquiry.

Geologists have measured with some accuracy the maximum thickness of all the known sedimentary rocks. The rate of denudation has also been recently measured by a method which, if not precise, at all events gives results of the right order of magnitude and which err on the side of being too slow rather than too fast. If, then, the _maximum_ thickness of the _known_ sedimentary rocks is taken to represent the _average_ thickness of _all_ the sedimentary rocks, and we also know the _amount_ of sediment carried to the sea or lakes, and the _area_ over which that sediment is spread, we have a means of calculating the _time_ required for the building up of all the sedimentary rocks of the geological system. I have here inquired how far the above suppositions are correct, or on which side they probably err; and the conclusion arrived at is, that the time required is very much less than has hitherto been supposed.

Another estimate is afforded by the date of the last glacial epoch if coincident with the last period of high excentricity, while the Alpine glaciation of the Miocene period is assumed to have been caused by the next earlier phase of very high excentricity. Taking these as data, the {539} proportionate change of the species of mollusca affords a means of arriving at the whole lapse of time represented by the fossiliferous rocks; and these two estimates agree in the _order_ of their magnitudes.

It is then argued that the changes of climate every 10,500 years during the numerous periods of high excentricity have acted as a motive power in hastening on both geological and biological change. By raising and lowering the snow-line in all mountain ranges it has caused increased denudation; while the same changes have caused much migration and disturbance in the organic world, and have thus tended to the more rapid modification of species. The present epoch being a period of very low excentricity, the earth is in a phase of _exceptional stability_ both physical and organic; and it is from this period of exceptional stability that our notions of the very slow rate of change have been derived.

The conclusion is, on the whole, that the periods allowed by physicists are not only far in excess of such as are required for geological and organic change, but that they allow ample margin for a lapse of time anterior to the deposit of the earliest fossiliferous rocks several times longer than the time which has elapsed since their deposit to the present day.

Having thus laid the foundation for a scientific interpretation of the phenomena of distribution, we proceed to the Second Part of our work--the discussion of a series of typical Insular Faunas and Floras with a view to explain the interesting phenomena they present. Taking first two North Atlantic groups--the Azores and Bermuda--it is shown how important an agent in the dispersal of most animals and plants is a stormy atmosphere. Although 900 and 700 miles respectively from the nearest continents, their productions are very largely identical with those of Europe and America; and, what is more important, fresh arrivals of birds, insects, and plants, are now taking place almost annually. These islands afford, therefore, test examples of the great dispersive powers of certain groups of organisms, and thus serve as a basis on which to found our explanations of many anomalies of distribution. Passing {540} on to the Galapagos we have a group less distant from a continent and of larger area, yet, owing to special conditions, of which the comparatively stormless equatorial atmosphere is the most important, exhibiting far more speciality in its productions than the more distant Azores. Still, however, its fauna and flora are as unmistakably derived from the American continent as those of the Azores are from the European.

We next take St. Helena and the Sandwich Islands, both wonderfully isolated in the midst of vast oceans, and no longer exhibiting in their productions an exclusive affinity to one continent. Here we have to recognise the results of immense antiquity, and of those changes of geography, of climate, and in the general distribution of organisms which we know have occurred in former geological epochs, and whose causes and consequences we have discussed in the first part of our volume. This concludes our review of the Oceanic Islands.

Coming now to Continental Islands we consider first those of most recent origin and offering the simplest phenomena; and begin with the British Isles as affording the best example of very recent and well known Continental Islands. Reviewing the interesting past history of Britain, we show why it is comparatively poor in species and why this poverty is still greater in Ireland. By a careful examination of its fauna and flora it is then shown that the British Isles are not so completely identical, biologically, with the continent as has been supposed. A considerable amount of speciality is shown to exist, and that this speciality is real and not apparent is supported by the fact, that small outlying islands, such as the Isle of Man, the Shetland Isles, Lundy Island, and the Isle of Wight, all possess certain species or varieties not found elsewhere.

Borneo and Java are next taken, as illustrations of tropical islands which may be not more ancient than Britain, but which, owing to their much larger area, greater distance from the continent, and the extreme richness of the equatorial fauna and flora, possess a large proportion of peculiar species, though these are in general very closely allied to those of the adjacent parts of Asia. The {541} preliminary studies we have made enable us to afford a simpler and more definite interpretation of the peculiar relations of Java to the continent and its differences from Borneo and Sumatra, than was given in my former work (_The Geographical Distribution of Animals_).

Japan and Formosa are next taken, as examples of islands which are decidedly somewhat more ancient than those previously considered, and which present a number of very interesting phenomena, especially in their relations to each other, and to remote rather than to adjacent parts of the Asiatic continent.

We now pass to the group of Ancient Continental Islands, of which Madagascar is the most typical example. It is surrounded by a number of smaller islands which may be termed its satellites since they partake of many of its peculiarities; though some of these--as the Comoros and Seychelles--may be considered continental, while others--as Bourbon, Mauritius, and Rodriguez--are decidedly oceanic. In order to understand the peculiarities of the Madagascar fauna we have to consider the past history of the African and Asiatic continents, which it is shown are such as to account for all the main peculiarities of the fauna of these islands without having recourse to the hypothesis of a now-submerged Lemurian continent. Considerable evidence is further adduced to show that "Lemuria" is a myth, since not only is its existence unnecessary, but it can be proved that it would not explain the actual facts of distribution. The origin of the interesting Mascarene wingless birds is discussed, and the main peculiarities of the remarkable flora of Madagascar and the Mascarene islands pointed out; while it is shown that all these phenomena are to be explained on the general principles of the permanence of the great oceans and the comparatively slight fluctuations of the land area, and by taking account of established palaeontological facts.

There remain two other islands--Celebes and New Zealand--which are classed as "anomalous," the one because it is almost impossible to place it in any of the six zoological regions, or determine whether it has ever been actually joined to a continent--the other because it {542} combines the characteristics of continental and oceanic islands.

The peculiarities of the Celebesian fauna have already been dwelt upon in several previous works, but they are so remarkable and so unique that they cannot be omitted in a treatise on "Insular Faunas"; and here, as in the case of Borneo and Java, fuller consideration and the application of the general principles laid down in our First Part, lead to a solution of the problem at once more simple and more satisfactory than any which have been previously proposed. I now look upon Celebes as an outlying portion of the great Asiatic continent of Miocene times, which either by submergence or some other cause had lost the greater portion of its animal inhabitants, and since then has remained more or less completely isolated from every other land. It has thus preserved a fragment of a very ancient fauna along with a number of later types which have reached it from surrounding islands by the ordinary means of dispersal. This sufficiently explains all the peculiar _affinities_ of its animals, though the peculiar and distinctive _characters_ of some of them remain as mysterious as ever.

New Zealand is shown to be so completely continental in its geological structure, and its numerous wingless birds so clearly imply a former connection with some other land (as do its numerous lizards and its remarkable reptile, the Hatteria), that the total absence of indigenous land-mammalia was hardly to be expected. Some attention is therefore given to the curious animal which has been seen but never captured, and this is shown to be probably identical with an animal referred to by Captain Cook. The more accurate knowledge which has recently been obtained of the sea bottom around New Zealand enables us to determine that the former connection of that island with Australia was towards the north, and this is found to agree well with many of the peculiarities of its fauna.

The flora of New Zealand and that of Australia are now both so well known, and they present so many peculiarities, and relations of so anomalous a character, {543} as to present in Sir Joseph Hooker's opinion an almost insoluble problem. Much additional information on the physical and geological history of these two countries has, however, been obtained since the appearance of Sir Joseph Hooker's works, and I therefore determined to apply to them the same method of discussion and treatment which has been usually successful with similar problems in the case of animals. The fact above noted, that New Zealand was connected with Australia in its northern and tropical portion only, of itself affords a clue to one portion of the specialities of the New Zealand flora--the presence of an unusual number of tropical families and genera, while the temperate forms consist mainly of species either identical with those found in Australia or closely allied to them. But a still more important clue is obtained in the geological structure of Australia itself, which is shown to have been for long periods divided into an eastern and a western island, in the latter of which the highly peculiar flora of temperate Australia was developed. This is found to explain with great exactness the remarkable absence from New Zealand of all the most abundant and characteristic Australian genera, both of plants and of animals, since these existed at that time only in the _western_ island, while New Zealand was in connection with the _eastern_ island alone and with the tropical portion of it. From these geological and physical facts, and the known powers of dispersal of plants, all the main features, and many of the detailed peculiarities of the New Zealand flora are shown necessarily to result.

Our last chapter is devoted to a wider, and if possible more interesting subject--the origin of the European element in the floras of New Zealand and Australia, and also in those of South America and South Africa. This is so especially a botanical question, that it was with some diffidence I entered upon it, yet it arose so naturally from the study of the New Zealand and Australian floras, and seemed to have so much light thrown upon it by our preliminary studies as to changes of climate and the causes which have favoured the distribution of plants, that I felt my work would be incomplete without a consideration of {544} it. The subject will be so fresh in the reader's mind that a complete summary of it is unnecessary. I venture to think, however, that I have shown, not only the several routes by which the northern plants have reached the various southern lands, but have pointed out the special aids to their migration, and the motive power which has urged them on.

In this discussion, if nowhere else, will be found a complete justification of that lengthy investigation of the exact nature of past changes of climate, which to some readers may have seemed unnecessary and unsuited to such a work as the present. Without the clear and definite conclusions arrived at by that discussion, and those equally important views as to the permanence of the great features of the earth's surface, and the wonderful dispersive powers of plants which have been so frequently brought before us in our studies of insular floras, I should not have ventured to attack the wide and difficult problem of the northern element in southern floras.

In concluding a work dealing with subjects which have occupied my attention for many years, I trust that the reader who has followed me throughout will be imbued with the conviction that ever presses upon myself, of the complete interdependence of organic and inorganic nature. Not only does the marvellous structure of each organised being involve the whole past history of the earth, but such apparently unimportant facts as the presence of certain types of plants or animals in one island rather than in another, are now shown to be dependent on the long series of past geological changes--on those marvellous astronomical revolutions which cause a periodic variation of terrestrial climates--on the apparently fortuitous action of storms and currents in the conveyance of germs--and on the endlessly varied actions and reactions of organised beings on each other. And although these various causes are far too complex in their combined action to enable us to follow them out in the case of any one species, yet their broad results are clearly recognisable; and we are thus encouraged to study more completely every detail and {545} every anomaly in the distribution of living things, in the firm conviction that by so doing we shall obtain a fuller and clearer insight into the course of nature, and with increased confidence that the "mighty maze" of Being we see everywhere around us is "not without a plan."

{549}

INDEX

A. Acacia, wide range of in Australia, 185 _Acacia heterophylla_, and _Acacia koa_, 443 Acaena in California, 527 _Accipiter hawaii_, 314 Achatinellinae, average range of, 317 _Aegialitis sanctae-helenae_, 305 Africa, characteristic mammalia of, 416 former isolation of, 418 Africa and Madagascar, relations of, 418 early history of, 419 African highlands as aiding the migration of plants, 524 African reptiles absent from Madagascar, 418 Aggressive power of the Scandinavian flora, 511 Air and water, properties of, in relation to climate, 131 _Alectoraenas pulcherrimus_, 429 Allen, Mr. J. A., on variation, 58 Allied species occupy separate areas, 478 Alpine plants, their advantages as colonisers, 503 Alternations of climate in Switzerland and North America, 121 Alternations of climate, palaeontological evidence of, 119 Amazon, limitation of species by, 18 _Amblyrhynchus cristatus_, 279 American genera of reptiles in Madagascar, 417 Amphibia, dispersal of, 76 of the Seychelles, 432 introduced, of Mauritius, 435 of New Zealand, 483 Amphioxus, 63 Amphisbaenidae, 28 _Amydrus Tristramii_, restricted range of, 16 _Anas Wyvilliana_, 314 Ancient continental islands, 244, 411 Ancient glacial epochs, 169 what evidence of may be expected, 175 Ancient groups in Madagascar, 419 Andersson, N. J., on the flora of the Galapagos, 287 Andes, migration of plants along the, 520 _Angraecum sesquipedale_, 440 Animal life, effects of glacial epoch on, 117 Animal life of Formosa, 401 _Anoa depressicornis_, 456 Antarctic continent as a means of plant-dispersion, 521 Antarctic islands, with perpetual snow, 136 Antelopes, overlapping genera of, 29 Antiquity of Hawaiian fauna and flora, 328 of land-shells, 79 of New Zealand, 526 of plants as affecting their dispersal, 82 _Apera arundinacea_, 503 _Apium graveolens_ in New Zealand, 515 Apteryx, species of, 476 _Arabis hirsuta_ on railway arch, 514 Archaic forms still existing, 229 Arctic and Antarctic regions, contrasts of, 135 Arctic current, effects of a stoppage of, 150 Arctic plants in the southern hemisphere, 509 Arctic regions, mild climates of, 181 recent interglacial mild period in, 182 Arctic warm climates of Secondary and Palaeozoic times, 201 Areas of distribution, 13 separate and overlapping, 17, 28 Ascension, former climate and productions of, 303 Astronomical and geographical causes, comparative effects of, on climate, 207 Astronomical causes of change of climate, 126 of glaciation, 140 Atlantic isles, peculiar mosses of, 368 Atlantosaurus, the largest land-animal, 98 _Atriplex patula_ on a railway bank, 515 Auchenia, 27 Austen, Mr. Godwin, on littoral shells in deep water, 337 Australia, two sets of Northern plants in, 523 South European plants in, 523 Australia and South Africa, supposed connection of, 525 {550} Australian Alps, indications of glaciation in, 163 birds absent from New Zealand, 483 flora, general features of, 491 richest in temperate zone, 491 recent and derivative in the tropics, 492 its south-eastern and south-western divisions, 493 Sir Joseph Hooker on, 494 geological explanation of, 494 its presence in New Zealand, 498 natural orders of, wanting in New Zealand, 490 orchideae in China, 527 genera of plants in India, 524 plants absent from New Zealand, 488, 490 none in north temperate zone, 527 running wild in Neilgherrie mountains, 528 region, definition of, 45 mammals and birds of, 46 seeds scattered in New Zealand, 508 Aylward, Captain, on glaciation of South Africa, 163 Azores, 247 absence from, of large-fruited trees or shrubs, 260 zoological features of, 248 birds of, 249 insects of, 253 beetles of, 253 land-shells of, 256 flora of, 256 Azores and New Zealand, identical plants in both, 512 Azorean bird-fauna, origin of, 250 fauna and flora, deductions from, 261 plants, facilities for the dispersal of, 260

B. _Babirusa alfurus_ in Celebes, 456 Badgers, 41 Bahamas contrasted with Florida, 5 Baker, Mr., on flora of Mauritius and the Seychelles, 441 Bali and Lombok, contrasts of, 4 Banca, peculiar species of, 386 _Barbarea precox_ on railway bank, 514 Barn-owl, wide range of, 15 Baron, Rev. R., on the flora of Madagascar, 441 Barriers to dispersal, 73 Batrachia, 30 Bats in Bermuda, 269 Bears of Europe and America, 14 Beaver of Europe and America, 14 Beetles of the Azores, 253 remote affinities of some of, 255 of the Galapagos, 284 of St. Helena, 298 of the Sandwich Islands, 318 peculiar British species of, 351 Bell-birds, distribution of, 24 Bennett, Mr. Arthur, on peculiar British plants, 360 on the vegetation of railway banks, 514 Bentham, Mr., on the compositae of the Galapagos, 288 on the compositae of St. Helena, 307 on the Mascarene compositae, 445 on Sandwich Island compositae, 325 Bermuda, 262 soundings around, 263 red clay of, 265 zoology of, 266 reptiles of, 266 birds of, 266 insects of, 269 land-mollusca of, 270 flora of, 271 Bermuda and Azores, comparison of bird-faunas of, 268 _Bernicla sandvichensis_, 314 Biological causes which determine distribution, 532 Biological features of Madagascar, 416 Birds as plant-dispersers, 81 as seed-carriers, 81, 258 common to Great Britain and Japan, 396 common to India and Japan, 399 specific range of, 15 range of British, 34 range of East Asian, 38 variation in N. American, 58 dispersal of, 75 of the Azores, 249 of Bermuda, 266 of Bermuda and Azores compared, 268 of the Galapagos, 280 of the Sandwich Islands, 313 peculiar to Britain, 340 of Borneo, 377 of Java, 382 of the Philippines, 388 of Japan, 396 peculiar to Japan, 398 peculiar to Formosa, 404 common to Formosa and India or Malaya, 407 of Madagascar, and their teachings, 422 of Comoro Islands, 429 of the Seychelles, 430 of the Mascarene islands, 436 of islands east and west of Celebes, 454 of Celebes, 458 peculiar to Celebes, 459 Himalayan types of, in Celebes, 462 list of, in Celebes, 466 of New Zealand, 476, 482 wingless, of New Zealand, 476 Blackburn, Mr. T., on the beetles of the Sandwich Islands, 318 Blakiston and Pryer on birds of Japan, 396 {551} Bland, Mr., on land-shells of Bermuda, 270 Blanford, Mr. W. T., on small effect of marine denudation, 225 Blanford, Mr. H. F., on former connection of Africa and India, 426 Blocks, travelled and perched, 109 Blue magpies, range of, 15 Borneo, geology of, 375 mammalia of, 376 birds of, 377 affinities of fauna of, 381 Borneo and Asia, resemblance of, 6 Borneo and Java, 373 Boulder-beds of the carboniferous formation, 201 Boulder clays of east of England, 118 Bovidae, 29 Brady, Mr. H. B., on habitat of globigerinae, 92 Braithwaite, Dr. R., on peculiar British mosses, 365 Britain, probable climate of, with winter in _aphelion_, 156 British birds, range of, 34-38 British Columbia, interglacial warm periods in, 121 British fauna and flora, peculiarities of, 370 British Isles, recent changes in, 332 proofs of former elevation of, 334 submerged forests of, 335 buried river channels of, 336 last union of, with continent, 337 why poor in species, 338 peculiar birds of, 339 fresh-water fishes of, 340 peculiar insects of, 344 peculiar Lepidoptera of, 347 peculiar Coleoptera of, 351 peculiar Trichoptera of, 355 peculiar land and fresh-water shells of, 356 peculiarities of the flora of, 360 peculiar mosses and Hepaticae of, 366 British mammals as indicating a zoological region, 33 Buller, Sir W. L., on the New Zealand rat, 475 Buried river-channels, 336 _Buteo solitarius_, 314 Butterflies of Celebes, peculiar shape of, 463 Butterflies, peculiar British, 347

C. Caddis-flies peculiar to Britain, 355 Caecilia, species of, in the Seychelles, 432 wide distribution of, 432 Caeciliadae, 28 _Callithea Leprieuri_, distribution of, 18 _Callithea sapphira_, 18 Camels as destroyers of vegetation, 296 former wide distribution of, 421 Camelus, 17, 27 _Campanula vidalii_, 261 Canis, 17, 26 Carabus, numerous species of, 42 Carboniferous boulder-beds, 201 warm Arctic climate, 201 Carnivora in Madagascar, 417 Carpenter, Dr., on habitat of globigerinae, 92 Carpenter, Mr. Edward, on Mars and glacial periods, 164 _Carduus marianus_ in New Zealand, 515 _Carpodacus purpureus_ and _P. californicus_, 68 Castor, 17 Casuarina, 185 in India, 527 Cause of extinction, 63 Caves of Glamorganshire, 336 Cebibae, overlapping genera of, 29 Celebes, physical features of, 451 islands around, 452 zoology of, 455 derivation of mammals of, 457 birds of, 458 not a continental island, 461 insect peculiarities of, 462 Himalayan types in, 462 peculiarity of butterflies of, 463 list of land-birds of, 466 Centetidae, 27 Centetidae, formerly inhabited Europe, 420 Central America, mixed fauna of, 53 Ceratodus, or mud-fish, 69 Cervus, 17, 26 Chalk a supposed oceanic formation, 89 Chalk at Oahu, analysis of, 90 Chalk, analysis of, 91 Chalk mollusca indicative of shallow water, 93 Chalk sea, extent of, in Europe, 93 Chalk-formation, land-plants found in, 94 deposited in an inland sea, 93 of Faxoe an ancient coral-reef, 94 modern formation of, 95 supposed oceanic origin of, erroneous, 96 "Challenger" soundings and shore-deposits, 86 "Challenger" ridge in the Atlantic, 101 Chameleons very abundant in Madagascar, 430 Chamois, distribution of, 13 Changes of land and sea, 83 Chasmorhynchus, distribution of, 24 _C. nudicollis_, 24 _C. tricarunculatus_, 24 _C. variegatus_, 24 _C. niveus_, 24 _Chilomenus lunata_, 300 Chinchillas, 26 Chrysochloridae, 29 Cicindela, 17 Cicindelidae common to South America and Madagascar, 28 Clay, red, of Bermuda, 265 Climate, astronomical causes of changes of, 126 {552} properties of snow and ice in relation to, 131 of Britain with winter in _aphelion_, 156 of Tertiary period in Europe and N. America, 178 temperate in Arctic regions, 181 causes of mild Arctic, 190 of Tertiary and Secondary periods, 199, 202 of the Secondary and Palaeozoic epochs, 200 change of, during Tertiary and Secondary Periods, 200 affected by arrangement of the great continents, 205 nature of changes of, caused by high excentricity, 230 exceptional stability of the present, 232 changes of, as affecting migration of plants, 517 Climatal changes, 106 change, its essential principle restated, 158 changes as modifying organisms, 229 Clouds cut off the sun's heat, 145 Coal in Sumatra, 385 Coast line of globe, extent of, 221 Cochoa, distribution of, 25 Cockerell, Mr. Th. D. A., on slugs of Bermuda, 271 on British land and fresh-water shells, 356 Cold alone does not cause glaciation, 135 how it can be stored up, 133 Coleoptera of the Azores, 253 of St. Helena, 298 of the Sandwich Islands, 318 peculiar British species of, 351 Comoro Islands, 428 mammals and birds of, 428 Compositae of the Galapagos, 288 of St. Helena, 307 of the Sandwich Islands, 325 of the Mascarene Islands, 445 species often have restricted ranges, 504 Conclusions on the New Zealand flora, 506 Contemporaneous formation of Lower Greensand and Wealden, 221 Continental conditions throughout geological time, 97-99 changes and animal distribution, 102 extensions will not explain anomalous facts of distribution, 449 Continental islands, 243 of recent origin, 331 general remarks on recent, 408 ancient, 411 Continental period, date of, 337 Continents, movements of, 88 permanence of, 97 general stability of, 101, 103 geological development of, 205 Continuity of land, 74 Continuity of now isolated groups, proof of, 70 Cook, Captain, on a native quadruped in New Zealand, 476 Cope, Professor, on the Bermuda lizard, 266 _Coracias temminckii_, in Celebes, 463 Corvus, 17 Cossonidae, in St. Helena, 299 Cretaceous deposits in North Australia, 493, 496 Cretaceous flora of Greenland, 185 of the United States, 189 Croll, Dr. James, on Antarctic icebergs, 136 on winter temperature of Britain in glacial epoch, 141 on diversion of gulf-stream during the glacial epoch, 143 on loss of heat by clouds and fogs, 145 on geographical causes as affecting climate, 148 on ancient glacial epochs, 170 on universality of glacial markings in Scotland, 174 on mild climates of Arctic regions, 189 on ocean-currents, 190, 204 on age of the earth, 213 on mean thickness of sedimentary rocks, 220 on small amount of marine denudation, 225 on buried river-channels, 336 Ctenodus, 69 Cyanopica, distribution of, 24 _Cyanopica cooki_, restricted range of, 15, 24 _Cyanopica cyanus_, 24 _Cynopithecus nigrescens_, in Celebes, 456

D. Dacelo, 47 Dana on continental upheavals, 88 on chalk in the Sandwich Islands, 90 on elevation of land causing the glacial epoch, 152 on elevation of Western America, 194 on the development of continents, 205 on shore-deposits, 222 on life extermination by cold epochs, 230 Darwin, experiment on _Helix pomatia_, 78 on the permanence of oceans, 100 on cloudy sky of Antarctic regions, 146 on glaciers of the Southern Andes, 147 on geological time, 211 on complex relations of organisms, 226 on oceanic islands, 242 on seeds carried by birds, 257 {553} experiments on seed-dispersal, 258 on natural history of the Keeling Islands, 286 theory of formation of atolls, 397 on cultivated plants not running wild, 507 Dawkins, Professor Boyd, on animal migrations during the glacial epoch, 120 Dawson, Mr. G. M., on alternations of climate in British Columbia, 121 Professor, on Palaeozoic boulder-beds in Nova Scotia, 201 De Candolle on dispersal of seeds, 80 Deep-sea deposits, 219 Deer in Celebes, 456 _Delphinium ajacis_, on a railway bank, 515 _Dendroeca_, 19 _D. coerulea_, 19 _D. discolor_, 19 _D. dominica_, 19 _Dendroeca coronata_, variation of, 58 Dendrophidae, 29 Denudation destroys the evidences of glaciation, 172 Denudation and deposition as a measure of time, 213 Denudation in river basins, measurement of, 215 Denudation, marine as compared with sub-aerial, 225 Deposition of sediments, how to estimate the average, 221 Deserts, cause of high temperature of, 132 Diagram of excentricity and precession, 129 Diagram of excentricity for three million years, 171 Dididae, how exterminated, 436 Didunculus, keeled sternum of, 437 Diospyros, in upper greensand of Greenland, 186 _Diplotaxis muralis_, on railway banks, 513 Dipnoi, discontinuity of, 69 Dipterus, 69 Discontinuity among North American birds, 67 Discontinuity a proof of antiquity, 69 Discontinuous generic areas, 23 Discontinuous areas, 64 why rare, 64 Dispersal of animals, 72 of land animals, how effected, 73, 76 along mountain-chains, 81 of seeds by wind, 80, 257 by birds, 81, 258 by ocean-currents, 81, 258 of Azorean plants, facilities for, 260 Distribution, changes of, shown by extinct animals, 102 how to explain anomalies of, 420 Drontheim mountains, peculiar mosses of, 368 Dobson, Mr., on bats of Japan, 394 on the affinities of _Mystacina tuberculata_, 474 Dodo, the, 436 aborted wings of, 437 Dryiophidae, 28 Dumeril, Professor, on lizards of Bourbon, 435 Duncan, Professor P. M., on ancient sea of central Australia, 496

E. Early history of New Zealand, 484 Earth's age, 210 East Asian birds, range of, 38 East and West Australian floras, geological explanation of, 494 Echidna, 30 Echimyidae, 27 Elevation of North America during glacial period, 154 causing diversion of gulf-stream, 154 Elwes, Mr. H. J., on distribution of Asiatic birds, 380 _Emberiza schoeniclus_, discontinuity of, 66 _E. passerina_, range of, 66 _E. pyrrhulina_, 66 Endemic genera of plants in Mauritius, &c., 443 Endemic genera of plants in New Zealand, 526 English plants in St. Helena, 297 Environment, change of, as modifying organisms, 225 _Eriocaulon septangulare_, 363 Ethiopian Region, definition of, 42 birds of, 43 Ettingshausen, Baron von, on the fossil flora of New Zealand, 499 on Australian plants in England, 518 Eucalyptus, wide range of, in Australia, 185 Eucalyptus and Acacia, why not in New Zealand, 507 Eucalyptus in Eocene of Sheppey, 518 Eupetes, distribution of, 25 Europe, Asia, &c., as zoological terms, 32 European birds, range of, 16 in Bermuda, 269 European occupation, effects of, in St. Helena, 294 European plants in New Zealand, 507 in Chile and Fuegia, 521 Everett, Mr., on Bornean birds, 377 on mammalia of the Philippines, 387 on Philippine birds, 388 on raised coral-reefs in the Philippines, 389 Evolution necessitates continuity, 70 Excentricity and precession, diagram of, 129 Excentricity, variations of, during three million years, 171 Excentricity a test of rival theories of climate, 171 Excentricity, high, its effects on warm and cold climates, 198 Explanation of peculiarities of the fauna of Celebes, 460 {554} Extinct animals showing changes of distribution, 102 Extinct birds of the Mascarene Islands, 436 of New Zealand, 476 Extinction caused by glacial epoch, 122

F. Families, restricted areas of, 29 distribution and antiquity of, 68 Fauna and flora, peculiarities of British, 370 Fauna of Borneo, affinities of, 381 of Java, 382 of Java and Asia compared, 384 Faunas of Hainan, Formosa, and Japan compared, 407 Felis, 17, 26 Ferns, abundance of, in Mascarene flora, 445 Ficus, fossil Arctic, 186 Fire-weed, the, of Tasmania, 513 Fisher, Rev. O., on temperature of space, 131 Fishes, dispersal of, 76 peculiar British, 340 cause of great speciality in, 343 mode of migration of fresh-water, 344 fresh-water, of New Zealand, 484 Floating islands, and the dispersal of animals, 74 Flora of the Azores, 256 of Bermuda, 271 of the Galapagos, 287 of St. Helena, 305 of the Sandwich Islands, 321; peculiar features of, 323 peculiarities of the British, 360 of Madagascar and the Mascarene Islands, 439 of Madagascar and South Africa allied, 445 of New Zealand, 487 very poor, 488 its resemblance to the Australian, 489 its differences from the Australian, 490 origin of Australian element in, 498 tropical character of, explained, 500 summary and conclusion on, 506 Floras of New Zealand and Australia, summary of conclusion as to, 542 Florida and Canada, resemblances of, 5 and Bahamas, contrasts of, 5 Fogs cut off the sun's heat in glaciated countries, 145 Forbes, Mr. D., analysis of chalk, 91 Forbes, Mr. H. O., on plants of the Keeling Islands, 286 Formosa, 400 physical features of, 401 animal life of, 401 list of mammalia of, 402 list of land-birds peculiar to, 404 Forests, submerged, 335 Fowler, Rev. Canon, on peculiar British coleoptera, 346, 351 Freezing water liberates low-grade heat, 145 Fresh-water deposits, extent of, 97 organisms absent in St. Helena, 304 snail peculiar to Ireland, 356 fishes of the Seychelles, 433 Frogs of the Seychelles, 432 of New Zealand, 483 Fuegia, European plants in, 521 _Fulica alai_, 313

G. Galapagos Islands, 275 Galapagos, absence of mammalia and amphibia from, 278 reptiles of, 278 birds of, 280 insects of, 284 land-shells of, 285 flora of, 287 and Azores contrasted, 290 _Galbula cyaneicollis_, distribution of, 18 _rufoviridis_, 18 _viridis_, 18 Galeopithecus, 63 _Gallinula sandvichensis_, 313 Gardner, Mr. J. S., on Tertiary changes of climate, 203 Garrulus, distribution of species of, 20 _Garrulus glandarius_, 21, 23, 65 _G. cervicalis_, 21 _G. krynicki_, 21 _G. atricapillus_, 21 _G. hyrcanus_, 21 _G. brandti_, 21, 23 _G. lanceolatus___, 22 _G. bispecularis_, 22 _G. sinensis_, 22 _G. taivanus_, 22 _G. japonicus_, 22, 65 Geikie, Dr. James, on interglacial deposits, 121 Sir Archibald, on age of buried river-channels, 337 on stratified rocks being found near shores, 87 on formation of chalk in shallow water, 96 on permanence of continents, 104 on variation in rate of denudation, 173 on the rate of denudation, 215 on small amount of marine denudation, 225 Genera, extent of, 17 origin of, 61 rise and decay of, 64 Generic areas, 17 Generic and Family distribution, 25 Genus, defined and illustrated, 17 Geographical change as a cause of glaciation, 148 changes, influence of, on climate, 150, 152 {555} changes, effect of, on Arctic climates, 195 changes of Java and Borneo, 385 changes as modifying organisms, 228 Geological climates and geographical conditions, 204 time, 210 change, probably quicker in remote times, 223 time, value of the estimate of, 224 time, measurement of, 235 changes as aiding the migration of plants, 519 climates as affecting distribution, 534 climates, summary of causes of, 536 time, summary of views on, 539 Geology of Borneo, 375 of Madagascar, 412 of Celebes, 451 of New Zealand, 472 of Australia, 494 _Geomalacus maculcosus_, 356 Glacial climate not local, 113 deposits of Scotland, 112 Glacial epoch, proofs of, 107 effects of, on animal life, 117 alternations of climate during, 118 as causing migration and extinction, 122 causes of, 125 the essentials to the production of, 136 probable date of the, 160 and the climax of continental development, 206 date of last, 233 Glacial phenomena in North America, 116 Glaciation was greatest where rainfall is now greatest, 139 action of meteorological causes on, 142 summary of chief causes of, 144 in Northern Hemisphere, the only efficient cause of, 144 of New Zealand and South Africa, 162 local, due to high excentricity, 207 widespread in recent times, 536 Gleichenia in Greenland, 186 in relation to chalk, 89 Globigerina-ooze, analysis of, 91 Globigerinae, where found, 92 Glyptostrobus, fossil, 186 Goats, destructiveness of, in St. Helena, 295 Godman, Mr., on birds reaching the Azores, 248, 250 Gray, Professor Asa, on extinction of European plants by the glacial epoch, 123 Great Britain and Japan, birds common to, 396 Greene, Dr. J. Reay, on chameleons in Bourbon and Mauritius, 435 Greenland, loss of sun-heat by clouds in, 147 an anomaly in the Northern Hemisphere, 154 Miocene flora of, 183 Cretaceous flora of, 186 flora of ice-surrounded rocks of, 522 Grinnell Land, fossil flora of, 184 Guernsey, peculiar caddis-fly in, 355 Gulick, Rev. J. T., on Achatinellinae, 318 Guenther, Dr., on gigantic tortoises, 279 on peculiar British fishes, 341 on _Urotrichus gibsii_, 394 on lizards in the London Docks, 431 on Indian toads in Mauritius, 438 Guppy, Mr., on chalk of Solomon Islands, 91

H. Haast, Dr., on otter-like mammal in New Zealand, 475 Habitability of globe due to disproportion of land and water, 209 _Haplothorax burchellii_, 299 Hartlaub, Dr., on "Lemuria," 423, 426 _Hatteria punctata_, 483 Haughton, Professor, on heat carried by ocean-currents, 194 comparison of Miocene and existing climates, 197 on geological time, 211, 219 on thickness of sedimentary rocks, 219 Hawaiian fauna and flora, antiquity of, 328 Heat and cold, how dispersed or stored up, 131 Heat required to melt snow, 134 evolved by frozen water, its nature and effects, 145 cut off by cloud and fogs, 145 Hector, Dr., on Triassic and Jurassic flora of New Zealand, 526 Heer, Professor, on chalk sea in Central Europe, 93 Heilprin, Professor, on insects of Bermuda, 269 on land-shells of Bermuda, 270 _Helianthemum Breweri_, 360, 363 Heliodus, an American fossil, 69 Helix, 17 Hemiptera of St. Helena, 303 Hepaticae, peculiar British, 366 non-European genera of, in Britain, 367 Hesperomys, 26 Hesperornis allied to ostriches, 481 _Hieracium iricum_, 362 High land essential to the production of a glacial epoch, 195 Hildebrand, Dr. W., on flora of the Sandwich Islands, 321 Himalayan birds and insects in Celebes, 462 Hippopotamus in Yorkshire as proving a mild climate, 119 Hochstetter on the aquatic mammal of New Zealand, 475 {556} Hooker, Sir Joseph, on the Galapagos flora, 287 on affinities of St. Helena plants, 306 on peculiar British plants, 360, 363 on the flora of New Zealand, 488 on proportion of temperate and tropical Australian floras, 492 on current of vegetation from north to south, 510 on supposed occurrence of Australian plants in England in the Tertiary period, 518 Horne, Mr. John, on ice-sheet covering the Isle of Man, 115 Hull, Professor, on Permian breccias in Ireland indicating ice-action, 201 Humming-birds, restricted ranges of, 16 Hutton, Captain, on struthious birds of New Zealand, 479 Huxley, Professor, on geological time, 211 on European origin of African animals, 419 Hyomoschus, 27 Hyracoidea, restricted range of, 30

I. Ice-action, what evidences of, during the Tertiary period, 178 indications of ancient, 200 Ice-borne rocks, a test of a glacial epoch, 176 in Miocene of N. Italy, 178 in Eocene of Alps, 178 in Eocene of Carpathians and Apennines, 179 absence of, in English and N. American Tertiaries, 180 Ice-cap, why improbable or impossible, 161 Iceland, a continental island, 450 Icteridae, 50 Iguanidae, 50 Indian birds in Formosa, 407 Indian Ocean as a source of heat in Tertiary times, 192 Indian genera of plants in Australia, 492 Indicator, distribution of, 25 Insectivora in Madagascar, 417 Insects, dispersal of, 77 of the Miocene period, 77 restriction of range of, 78 of the Azores, 253 of Bermuda, 269 of the Galapagos, 284 of St. Helena, 298 of the Sandwich Islands, 318 peculiar British, 344 of Celebes, peculiarities of, 462 scarcity of, in New Zealand, 505 Insular faunas, summary of conclusions as to, 539, 542 Interglacial warm periods on the continent and in North America, 121 Interglacial periods and their probable character, 152 Interglacial periods will not occur during an epoch of extreme glaciation, 155 Interglacial climates never very warm, 159 Ireland, poverty of, in reptiles, 339 in plants, 339 peculiar fishes of, 342 plants of, not found in Great Britain, 364 Islands, classification of, 242 importance of, in study of distribution, 241 remote, how stocked with plants and animals, 261 submerged between Madagascar and India, 425 Isle of Wight, peculiar beetle of, 351 _Isatis tinctoria_, on railway bank, 513 Ithaginis, 26

J. Japan, zoological features of, 393 mammalia of, 394 birds of, 396 birds peculiar to, 398 birds in distant areas, 399 Japan and Formosa, 391 Java, fauna of, 382 Asiatic species in, 384 Java and Borneo, past changes of, 385 Jays, distribution of species of, 20 of Europe and Japan, 67 Jeffreys, Dr. Gwyn, on shallow-water mollusca in chalk, 92 on fossil shallow-water shells in deep water, 337 Jones, Mr., on migration of birds to Bermuda, 268 on vegetation of the Bermudas, 272 Juan Fernandez, flora and fauna of, 287 Judd, Prof. J. W., on absence of glaciation in east Europe, 139 on glaciation of the Alps produced by elevation, 179 _Juniperus barbadensis_, 272 Jura, travelled blocks on, 110 Jurassic warm Arctic climate, 202

K. Keeling Islands, animals of, 286 Kirk, Mr. T., on temporary introduced plants, 515 Knowledge of various kinds required for study of geographical distribution, 7, 9

L. _Lagopus scoticus_, 340 Land as a barrier to ocean-currents, 150 {557} Land and sea, changes of, 83 how changes of, affect climate, 148, 150 Land and water, disproportion of, renders globe habitable, 209 Land-birds of Celebes, list of, 466 Land-connection, how far necessary to dispersal of mammals, 73 Land-shells, great antiquity of, 79 universal distribution of, 79 causes favouring the abundance of, 79 of the Azores, 256 of Bermuda, 270 of the Galapagos, 284 of St. Helena, 304 of the Sandwich Islands, 316 of the Seychelles, 434 _Laurus canariensis_, 260 Leguat on animals of Bourbon, 435 on the Solitaire, 436 Leguminosae, abundance of, in Australia, 490 "Lemuria," a supposed submerged continent, 422-426 Lemurs in Madagascar, 416 Lendenfeld, Dr. R. von, on glaciation in the Australian Alps, 163 Leopard, enormous range of, 14 Lepidoptera, list of peculiar British, 347 Lepidosiren, 63 _Lepidosiren paradoxa_ and _L. annectens_, 69 Lepidosternidae, 27 Limestone as indicating change of sea and land, 84 _Limnaea involuta_, 356 _Linaria purpurea_, on railway bank, 514 _Liopelma hochstetteri_, in New Zealand, 483 Liotrichidae, 29 List of the land-birds of Celebes, 466 Lizard peculiar to the Mascarene Islands, 438 Lizards of the Galapagos, 278 local variation of colour of, 431 of New Zealand, 483 Lobeliaceae, abundance of, in the Sandwich Islands, 324 Locality of a species, importance of, 12 _Loddigesia mirabilis_, rarity of, 16 Lord, Mr., on species of Urotrichus, 394 Low-grade and high-grade heat, 145 Lowlands nowhere covered with perpetual snow, 136 Lundy Island, peculiar beetles of, 354 Lyell, Sir Charles, on permanence of continents, 84 on calcareous mud, 90 on the distribution of chalk, 93 on geographical causes as modifying climate, 148 on estimate of geological time, 211, 235 on classification of sedimentary rocks, 217 Lynxes, a Palaearctic group, 41

M. McLachlan, Mr., on peculiar British caddis-flies, 355 Madagascar, physical features of, 412 former condition of, 414 biological features of, 416 mammalia of, 416 reptiles of, 417 relation of, to Africa, 418 early history of, 419 birds of, in relation to "Lemuria," 422 flora of, 439 conclusion on fauna and flora of, 446 great antiquity of, 446 Madagascar and Africa, contrast of, 6 Maillard on animals of Bourbon, 435 Malay Islands, local peculiarities of flora in, 187 past history of, 389 Malayan birds in Formosa, 406 Mammalia of East Asia, range of, 34 of North Africa, range of, 34 Mammalia, dispersal of, 73 of Britain, range of, 33 poverty of, 329 of Borneo, 376 of Java, 382 of the Philippines, 387 of Japan, 393 of Formosa, 402 common to Formosa and India, 403 of Madagascar, 416 of Comoro Islands, 428 of Celebes, 455; whence derived, 457 of New Zealand, 474 Maori legend of origin of the forest-rat, 475 Maoris, their accounts of the moa, 477 Map of the old Rhone glacier, 110 of North and South Polar Regions, 138 of the Azores, 248 of Bermuda, 263 of the Galapagos, 276, 277 of the South Atlantic Ocean, 293 of the Sandwich Islands, 311 of the North Pacific with its submerged banks, 312 of British Isles and the 100-fathom bank, 333 of Borneo and Java, 374 of Japan and Formosa, 392 physical, of Madagascar, 413 of the Madagascar group, 415 of the Indian Ocean, 425 of Celebes, 452 of sea-bottom around New Zealand, 472 of Australia in Cretaceous period, 497 Marcou, Professor Jules, on the Pliocene and glacial epochs, 233 Marmot, range of, 15 Mars as illustrating glacial theories, 164, 168 {558} Mars, no true ice-cap on, 166 Marsupials, range of, 30 Marsh, Prof. O. C., on the Atlantosaurus, 98 on Hesperornis, 481 Marsh, Mr., on camels as desert-makers, 296 Mascarene Islands, 428-445 Mascarene plants, curious relations of, 442 endemic genera of, 443 Mascarene flora, fragmentary character of, 444 abundance of ferns in, 445 Mauritius, Bourbon, and Rodriguez, 434 Measurements of geological time, 233 agreement of various estimates of, 235 concluding remarks on, 236 _Medicago sativa_ in New Zealand, 515 Megalaemidae, 27 Meleagris, 50 _Melilotus vulgaris_, on railway banks, 513 Meliphagidae, 47 Melliss, Mr., on the early history of St. Helena, 295 _Melospiza melodia_, variation of, 58 Merycotherium, 123 Meteorological causes as intensifying glaciation, 142 Migration caused by glacial epoch, 122 of birds to Bermuda, 267 of plants from north to south, 512 of plants and alterations of snow line, 516 of plants due to changes of climate, 517 of plants from north to south, long continued, 518 of plants aided by geological changes, 519 of plants by way of the Andes, 520 of plants by way of Himalayas and South Asia, 523 of plants through Africa, 524 Mild Arctic climates, stratigraphical evidence of, 187 causes of, 190 dependent on geographical changes, 191 effects of high excentricity on, 198 summary of causes of, 537 Miocene Arctic flora, 183 flora of Europe, 123 or Eocene floras, 185 deposits of Java, 385 fauna of Europe and North India, 419 Mississippi, matter carried away by, 172 Mitten, Mr. William, on peculiar British mosses and hepaticae, 365, 368 on temporary appearance of plants, 513 Mniotiltidae, a nearctic group, 49 Mnium, peculiar species of, in the Drontheim mountains, 368 Moas of New Zealand, 476 Mollusca, dispersal of, 78 Monotremata, restricted range of, 30 Moraines, 108 of Ivrea, 116 More, Mr. A. G., on peculiar Irish plants, 364 Morgan, Mr. C. Lloyd, on thickness of formations not affected by denudation, 220 Moseley, Mr. H. N., on seeds carried by birds, 259 on the flora of Bermuda, 272 Mosses, peculiar British, 366 non-European genera of, in Britain, 367 how diffused and why restricted, 368 Mt. St. Elias, why not ice-clad, 154 Mountain chains aiding the dispersal of plants, 81 as aids to migration of plants, 513 Mueller, Baron von, census of Australian plants, 492 _Munia brunneiceps_, in Celebes, 463 Murray, Mr. J., on oceanic deposits, 86 on chalk-like globigerina-ooze, 92 on mean height of continents, 216 on land-area of the globe, 221 Mus, 17, 26 _Mygale pyrenaica_, range of, 15, 24 _M. muscovitica_, 24 _Myialestes helianthea_ in Celebes, 463 _Myrica faya_, 260 Myrsine, fossil in Greenland, 186 _Mytilus edulis_, sub-fossil in Spitzbergen, 182

N. Nares, Capt. Sir G., on snow and ice in high latitudes, 135 on abrupt elevation of Bermuda, 264 Nearctic Region, definition of, 48 mammalia of, 48 birds of, 49 reptiles of, 50 _Nectarinea osea_, restricted range of, 16 Neilgherries, Australian plants naturalized in, 528 Neotropical Region, definition of, 51 low types of, 52 Nevill, Mr. Geoffrey, on land-shells of the Seychelles, 434 on destruction of Seychelles flora, 445 New species, origin of, 56 Newton, Mr. E., on short wings of the Seychelles dove, 437 Newton, Professor, on recently extinct birds, 437 Newts, restricted range of, 30 New Zealand, recent glaciation of, 163 New Zealand, 471 geology of, 472 form of sea-bottom around, 473 zoological character of, 473 mammalia of, 474 {559} wingless birds of, 476 past changes of, 478 winged birds and lower vertebrates of, 482 deductions from peculiarities of fauna of, 484 period of its union with N. Australia, 484 the flora of, 487, 506 origin of Australian element in the flora of, 498 tropical character of flora, 500 tropical genera common to Australia, 501 temperate species common to Australia, 502 route of Arctic plants to, 521 European plants in, 509 endemic genera of plants in, 526 great antiquity of, 526 Nordenskjoeld, Prof., on absence of perpetual snow in N. Asia, 135 on recent milder climate in Spitzbergen, 182 on former Polar climates, 187 on geology of Spitzbergen, 188 North America, glacial phenomena in, 116 interglacial warm periods in, 121 condition of, in Tertiary period, 194 Northern genera of plants in S. temperate America, 521 hemisphere, absence of southern plants from, 527 flora, hardiness of, 528

O. Ocean-currents as carriers of plants, 81 as affecting interglacial periods, 152 as determining climate, 153 effects of, in Tertiary times, 196 Ocean, Darwin on permanence of, 100 Oceanic and continental islands, 242 Oceanic islands a proof of the permanence of oceans, 100 Oceanic islands, 244 --the Azores, 247 general remarks on, 329 Octodontidae, 27 _Oenanthe fluviatilis_, 361 Oeninghen, Miocene flora of, 183 _Oenothera odorata_, on a railway bank, 514 Oliver, Professor, on peculiar Bermudan plants, 272 Operculata, scarcity of, in the Sandwich Islands, 317 _Ophrys apifera_, temporary appearance of, 514 Orchideae, species have restricted ranges, 505 Orchids, abundance of, in Bourbon and Mauritius, 446 why almost universal in the tropics, 446 Orders, distribution of, 30 Organic change dependent on change of conditions, 225, 228 Oriental Region, definition of, 44 mammals and birds of, 44 reptiles of, 45 insects of, 45 Origin of new species, 56, 60 of new genera, 61 of the Galapagos flora, 288 of the beetles of St. Helena, 298 of Australian element in the New Zealand flora, 498 Orkney, peculiar fishes of, 341 Orthonyx not a New Zealand genus, 483 Osprey, wide range of, 15 Ostriches, limitation of, 30 Otter-like mammal in New Zealand, 475 Overlapping and discontinuous areas, 28

P. _Pachyglossa aureolimbata_, in Celebes, 463 Palaearctic Region, limits of, 39 characteristic features of, 41 Palaeozoic formations, depth of, round London, 218 Palm confined to Round Island, 444 Panax, fossil in Greenland, 186 Papilio, 17 Paraguay, no wild horses or cattle in, 226 Parnassius, Palaearctic, 42 _Parus ater_, 19 _P. borealis_, 19, 64 _P. britannicus_, 321 _P. camtschatkensis_, 19 _P. cinctus_, 20 _P. coeruleus_, 20 _P. cyaneus_, 20 _P. cristatus_, 20 _P. ledouci_, 20 _P. lugubris_, 20 _P. major_, 19 _P. palustris_, 19; discontinuous area of, 65 _P. rosea_, 340 _P. teneriffae_, 20 Passeres of the Sandwich Islands, 314 Past changes of New Zealand, 478 Payer, Lieut., on evaporation of ice during the Arctic summer, 140 Peculiar fauna of New Zealand, deductions from, 484 Pengelly, Mr., on submerged forests, 335 _Pennula millei_, in Sandwich Islands, 313 Permanence of continents, summary of evidence for, 103 Permian formation, indications of ice-action in, 200 Perodicticus, a local genus, 26 _Petroselinum segetum_, on railway bank, 514 {560} Philippine Islands, 387 mammalia of, 387 birds of, 388 past history of, 389 _Phyllodactylus galapagensis_, 279 _Phylloscopus borealis_, range of, 15 Physical causes which determine distribution, 533 features of Formosa, 401 Pica, 17 Pickering, Dr., on the flora of the Sandwich Islands, 323 on temperate forms on mountains of the Sandwich Islands, 323 _Pithecia monachus_, distribution of, 18 _P. rufibarbata_, 18 Pitta, distribution of, 25 Plants, dispersal of, 80 seeds of, adapted for dispersal, 80 wide range of species and genera of, 185 poverty of, in Ireland, 339 peculiar British, 359 of Ireland not in Great Britain, 364 cause of their wide diffusion and narrow restriction, 369 easily dispersed often have restricted ranges, 504 how they migrate from north to south, 512 of existing genera throughout the Tertiary period, 520 southern migration of, by way of the Himalayas, 523 southern migration of, through Africa, 524 endemic genera of, in New Zealand, 526 Platypus, 30 _Plestiodon longirostris_ of Bermuda, 266 Po, matter carried away by, 173 Podargus, Australian genus, 47 Poecilozonites, peculiar to Bermuda, 270 _Poinciana regia_ in Madagascar, 440 Populus, fossil in Spitzbergen, 184 Pourtales, Count, on modern formation of chalk, 95 on sedimentary deposits in Gulf of Mexico, 222 Poverty in species of Britain, 338 Precession of Equinoxes, influence of, on climate, 126 Preservation of species, 63 Proboscidea, range of, 30 Proteus, why preserved, 63 Psophia, range of species of, 18 Pteroptochidae, 29 Pyrenean ibex, restricted range of, 15

R. Railways, new plants on, 513 Ramsay, Mr. Wardlaw, on Philippine birds, 388 Professor, on ancient land surfaces, 99 on geological time 212 on thickness of sedimentary rocks, 219 Rat, native, of New Zealand, 475 Rate of organic change usually measured by an incorrect scale, 232 Rats in the Galapagos, 278 Raven, wide range of, 15 Reade, T. Mellard, on changes of sea and land, 84 Recent continental islands, 243, 331 Red clay of Bermuda, 265 Reptiles, dispersal of, 75 of the Galapagos, 278 of the Sandwich Islands, 316 cause of scarcity of, in British Isles, 339 of Madagascar, 417 of the Seychelles, 430 of Mauritius and Round Island, 438 of New Zealand, 483 _Rhodolaena altivola_ in Madagascar, 440 _Rhus toxicodendron_ in Bermuda, 272 Ridgway, Mr., on birds of Galapagos, 281 River-channels, buried, 336 _Roches moutonnees_, 108 Rodents in Madagascar, 417 Round Island, a snake and a palm peculiar to, 438, 444 _Rumex pulcher_ in New Zealand, 515 Rye, Mr. E. C., on peculiar British insects, 345, 351

S. St. Helena, 292 effects of European occupation on the vegetation of, 294 insects of, 298 land-shells of, 304 absence of fresh-water organisms in, 304 native vegetation of, 305 Salvin, Mr., on the birds of the Galapagos, 280 Sandwich Islands, the, 310 zoology of, 313 birds of, 313 reptiles of, 316 land-shells of, 316 insects of, 318 vegetation of, 321 antiquity of fauna and flora of, 328 Sassafras, in Swiss Miocene, 183 Scandinavian flora, aggressive power of, 511 Scientific voyages, comparative results of, 7 Sciurus, 26 Sclater, Mr. P. L., on zoological region, 32, 39 Scotland, glacial deposits of, 112-115 probable rate of denudation in, 173 Miocene flora of, 184 peculiar fishes of, 341 {561} _Scotophilus tuberculatus_ in New Zealand, 474 Scrophularincae, why few species are common to Australia and New Zealand, 505 Sea, depth of, around Madagascar, 414 depth of, around Celebes, 452 Sea-bottom around New Zealand and Australia, 473 Sea-level, changes of, dependent on glaciation, 161 complex effects of glaciation on, 162, 164 rise of, a cause of denudation, 174 Seas, inland, in Tertiary period, 191 Section of sea-bottom near Bermuda, 264 Sedges and grasses common to Australia and New Zealand, 504 Sedimentary rocks, how to estimate thickness of, 217 thinning out of, 217 how formed, 218 thickness of, 217, 221 summary of conclusions on the rate of formation of the, 221 Seebohm, Mr., on _Parus palustris_, 65 on _Emberiza schoeniclus_, 66 on snow in Siberia, 166 on birds of Japan, 396 Seeds, dispersal of, 257 carried by birds, 258 _Senecio australis_, on burnt ground, 513 Sericinus, Palaearctic, 42 Seychelles Archipelago, 429 birds of, 430 reptiles and amphibia of, 430 fresh-water fishes of, 433 land-shells of, 434 Sharp, Dr. D., on beetles of the Sandwich Islands, 319 on peculiar British beetles, 345 Shells, peculiar to Britain, 356 Shetland Isles, peculiar beetle of, 354 Shore deposits, 85, 211 proving the permanence of continents, 97 distance from coast of, 221 _Sialia sialis_, variation of, 58 Siberia, amount of snow and its sudden disappearance in, 166 Silurian boulder-beds, 201 warm Arctic climate, 202 Simiidae, 27 _Sisyrinchium bermudianum_, 272 Skertchley, Mr., on four distinct boulder-clays, 118 on Tertiary deposits in Egypt and Nubia, 191 on climatic stability of present epoch, 233 Slug peculiar to Ireland, 356 Snake peculiar to Round Island, 438 Snakes of the Galapagos, 280 of the Seychelles, 431 Snow and ice, properties of, in relation to climate, 131 Snow, effects of, on climate, 133 Snow, quantity of heat required to melt, 134 often of small amount in high latitudes, 135 never perpetual on lowlands, 136 conditions determining perpetual, 137 maintains cold by reflecting the solar heat, 144 Snow-line, alterations of, causing migration of plants, 516 Sollas, Mr. J. W., on greater intensity of telluric action in past time, 223 South Africa, recent glaciation of, 163 many northern genera of plants in, 524 its supposed connection with Australia, 525 South American plants in New Zealand, 521 South Temperate America, poor in species, 53 climate of, 146 Southern flora, comparative tenderness of, 528 Southern plants, why absent in the Northern Hemisphere, 527 Space, temperature of, 129 Specialisation antagonistic to diffusion of _species_, 505 Species, origin of new, 56 extinction of, 63 rise and decay of, 64 epoch of exceptional stability of, 232 dying out and replacement of, 409 preservation of, in islands, 410 Specific areas, 14; discontinuous, 64 _Spiranthes romanzoviana_, 364 Spitzbergen, Miocene flora of, 184 absence of boulder-beds in, 187 Spruce, Dr. Richard, on the dispersion of hepaticae, 309 Stability of extreme glacial conditions, 159 Stainton, Mr. H. T., on peculiar British moths, 346-350 Stanivoi mountains, why not ice-clad, 154 Starlings, genera of, in New Zealand, 482 _Stellaria media_, temporary appearance of, 515 Sternum, process of abortion of keel of, 437 Stow, Mr. G. W., on glacial phenomena in South Africa, 163 Stratified rocks formed near shores, 85, 87 deposits, how formed, 218 Striated rocks, 107 blocks in the Permian formation, 200 _Striae flammea_, range of, 15 Struthiones, 30 Struthious birds of New Zealand as indicating past changes, 478 Stylidium, wide range of, 185 Submerged forests, 334 {562} Subsidence of isthmus of Panama, 151 Sumatra, geology of, 385 Sweden, two deposits of "till" in, 121 Swimming powers of mammalia, 74 Swinhoe, Mr. Robert, researches in Formosa, 400 Switzerland, interglacial warm periods in, 121 Sylviadae, overlapping genera of, 29

T. Talpidae, a Palaearctic group, 41 Tapirs, distribution of, 25 former wide range of, 393 Tarsius, 63 _Tarsius spectrum_ in Celebes, 456 Tasmania and North Australia, resemblance of, 5 route of Arctic plants to, 520 _Taxodium distichum_ in Spitzbergen, 184 Temperate climates in Arctic regions, 181 Australian genera of plants in New Zealand, 502 Australian species of plants in New Zealand, 502 Temperature, how dependent on sun's distance, 129 of space, 129 Tertiary glacial epochs, evidence against, 179 warm climates, continuous, 187 Test of glaciation at any period, 175 _Testudo abingdonii_, 279 _T. microphyes_, 278 Tetraogallus, distribution of, 24 Thais, a Palaearctic genus, 42 Thomson, Sir William, on age of the earth, 213 Sir Wyville, on organisms in the globigerina-ooze, 89 analysis of globigerina-ooze, 91 _Thryothorus bewickii_, discontinuity of, 68 "Till" of Scotland, 112 several distinct formations of, 121 Tits, distribution of species of, 19 Torreya, fossil in Spitzbergen, 186 Tortoises of the Galapagos, 278 Trade-winds, how modified by a glacial epoch, 142 Tragulidae, 27 Travelled blocks, 109 Tremarctos, an isolated genus, 29 Triassic warm Arctic climate, 200 Tribonyx not a New Zealand genus, 483 Trichoptera peculiar to Britain, 355 Trogons, distribution of, 28 Tropical affinities of New Zealand birds, 483 character of the New Zealand flora, cause of, 500 genera common to New Zealand and Australia, 501 Turdus, 17, 26 _Turdus fuscescens_, variation of, 58, 59 Tylor, A., on estimating the rate of denudation, 214 Tyrannidae, an American family, 50

U. Uraniidae, 28 Uropeltidae, 30 Urotrichus, distribution of, 25 Ursus, 26

V. Variation in animals, 57 amount of, in N. American birds, 58 Vegetation, local peculiarities of, 185 effects of Polar night on, 198 _Vesperugo serotinus_, range of, 14 _Vireo bellii_, supposed discontinuity of, 68 Vireonidae, an American family, 49

W. Wallich, Dr., on habitat of globigerinae, 92 Warren, Mr. W., information on British lepidoptera, 347 Water, properties of, in relation to climate, 131, 133 Waterhouse, Mr., on Galapagos beetles, 284 Wales, peculiar fish of, 341 Warm climates of northern latitudes, long persistence of, 201 Watson, Mr. H. C., on the flora of the Azores, 256 on peculiar British plants, 359 on vegetation of railway banks, 513 Webb, Mr., on comparison of Mars and the Earth, 166 West Australia, rich flora of, 494 former extent and isolation of, 497 West Indies, a Neotropical district, 53 White, Dr. F. Buchanan, on the Hemiptera of St. Helena, 303 Mr. John, on native accounts of the moa, 477 Whitehead, Mr. John, on Bornean birds, 377 Wilson, Mr. Scott B., on birds of the Sandwich Islands, 314 Winged birds of New Zealand, 482 Wingless birds never inhabit continents, 437 their evidence against "Lemuria," 438 of New Zealand, 476 Wings of struthious birds show retrograde development, 437 {563} Winter temperature of Europe and America, 196 Wolf, range of, 14 Wollaston, Mr. T. V., on insular character of St. Helena, 294 on St. Helena shells and insects, 297 Wood, Mr. Searles V., jun., on formation of "till," 114 on alternations of climate, 118 on causes of glacial epochs, 125 conclusive objection to the excentricity theory, 160 on continuous warm Tertiary climates, 180 Woodward, Dr. S. P., on Ammonites living in shallow water, 95 Woodward, Mr., on "Lemuria," 426 Wright, Dr. Percival, on lizards of the Seychelles, 431

Y. Young, Professor J., on contemporaneous formation of deposits, 221 Young Island, lofty Antarctic, 522

Z. Zoology of the Azores, 248 of Bermuda, 262 of the Sandwich Islands, 313 of Borneo, 376 of Madagascar, 416 of islands round Celebes, 453 of Celebes, 455 Zoological and geographical regions compared, 32, 54 Zoological features of Japan, 393 character of New Zealand, 473

THE END

{564}

RICHARD CLAY AND SONS, LIMITED, LONDON AND BUNGAY.

* * * * *

[1] A small number of species belonging to the West Indies are found in the extreme southern portion of the Florida Peninsula.

[2] I cannot avoid here referring to the enormous waste of labour and money with comparatively scanty and unimportant results to natural history of most of the great scientific voyages of the various civilized governments during the present century. All these expeditions combined have done far less than private collectors in making known the products of remote lands and islands. They have brought home fragmentary collections, made in widely scattered localities, and these have been usually described in huge folios or quartos, whose value is often in inverse proportion to their bulk and cost. The same species have been collected again and again, often described several times over under new names, and not unfrequently stated to be from places they never inhabited. The result of this wretched system is that the productions of some of the most frequently visited and most interesting islands on the globe are still very imperfectly known, while their native plants and animals are being yearly exterminated, and this is the case even with countries under the rule or protection of European governments. Such are the Sandwich Islands, Tahiti, the Marquesas, the Philippine Islands, and a host of smaller ones; while Bourbon and Mauritius, St. Helena, and several others, have only been adequately explored after an important portion of their productions has been destroyed by cultivation or the reckless introduction of goats and pigs. The employment in each of our possessions, and those of other European powers, of a resident naturalist at a very small annual expense, would have done more for the advancement of knowledge in this direction than all the expensive expeditions that have again and again circumnavigated the globe.

[3] The general facts of Palaeontology, as bearing on the migrations of animal groups, are summarised in my _Geographical Distribution of Animals_, Vol. I. Chapters VI., VII., and VIII.

[4] Since these lines were written, a fine series of specimens of this rare humming-bird has been obtained from the same locality. (See _Proc. Zool. Soc._ 1881, pp. 827-834.)

[5] Many of these large genera are now subdivided, the divisions being sometimes termed genera, sometimes sub-genera.

[6] The Palaearctic region includes temperate Asia and Europe, as will be explained in the next chapter.

[7] The following list of the genera of reptiles and amphibia peculiar to the Palaearctic Region has been furnished me by Mr. G. A. Boulenger, of the British Museum:--

SNAKES. FROGS AND TOADS.

_Achalinus_--China, Japan. _Pelobates_--Eur., S.W. Asia. _Coelopeltis_--S. Eur., N. Af., _Pelodytes_--W. Europe. S.W. Asia. _Discoglossus_--S. Eur., N.W. Af. _Macroprotodon_--S. Eur., N. Af. _Bombinator_--Eur., Temp. Asia. _Taphrometopon_--Cent. Asia. _Alytus_--Cent. and W. Eur.

LIZARDS. NEWTS.

_Phrynocephalus_--Cent. and S.W. _Salamandra_--Eur., N. Af., S.W. Asia. Asia. _Anguis_--Europe, W. Asia. _Chioglossa_--Spain and Portugal. _Blanus_--S.W. Eur., N.W. Africa, _Salamandrina_--Italy. S.W. Asia. _Pachytriton_--East Thibet. _Trogonophis_--N.W. Africa. _Hynobius_--China and Japan. _Lacerta_--Eur., Temp. Asia, N. _Geomolge_--E. Manchuria. Africa (one sp. in _Onychodactylus_--Japan. W. Af.). _Salamandrella_--Siberia. _Psammodromus_--S.W. Eur., N.W. _Ranidens_--Siberia. Africa. _Batrachyperus_--East Thibet. _Algiroides_--S. Eur. _Myalobatrachus_--China, Japan. _Proteus_--Caverns of S. Austria.

[8] Remains of the dingo have been found fossil in Pleistocene deposits but the antiquity of man in Australia is not known. It is not, however, improbable that it may be as great as in Europe. My friend A. C. Swinton, Esq., while working in the then almost unknown gold-field of Maryborough, Victoria, in January, 1855, found a fragment of a well-formed stone axe resting on the metamorphic schistose bed-rock about five feet beneath the surface. It was overlain by the compact gravel drift called by the miners "cement," and by an included layer of hard iron-stained sandstone. The fragment is about an inch and three-eighths wide and the same length, and is of very hard fine-grained black basalt. One side is ground to a very smooth and regular surface, terminating in a well-formed cutting edge more than an inch long, the return face of the cutting part being about a quarter of an inch wide. The other side is a broken surface. The weapon appears to have been an axe or tomahawk closely resembling that figured at p. 335 of Lumholtz's _Among Cannibals_, from Central Queensland. The fragment was discovered by Mr. Swinton and the late Mr. Mackworth Shore, one of the discoverers of the gold-field, before any rush to it had taken place, and it seems impossible to avoid the conclusion that it was formed prior to the deposit of the gravel drift and iron-stained sandstone under which it lay. This would indicate a great antiquity of man in Australia, and would enable us to account for the fossilised remains of the dingo in Pleistocene deposits as those of an animal introduced by man.

[9] These facts are taken from a memoir on _The Mammals and Winter Birds of Florida_, by J. A. Allen; forming Vol. II., No. 3, of the Bulletin of the Museum of Comparative Zoology at Harvard College, Cambridge, Massachusetts.

[10] The great variation in wild animals is more fully discussed and illustrated in the author's _Darwinism_ (Chapter III.).

[11] See _Ibis_, 1879, p. 32.

[12] In Mr. Seebohm's latest work, _Birds of the Japanese Empire_ (1890), he says, "Examples from North China are indistinguishable from those obtained in Greece" (p. 82).

[13] _Ibis_, 1879, p. 40. In his _Birds of the Japanese Empire_ (1890), Mr. Seebohm classes the Japanese and European forms as _E. schoeniclus_, and thinks that their range is probably continuous across the two continents.

[14] Lyell's _Principles of Geology_, ii., p. 369.

[15] Mr. Darwin found that the large _Helix pomatia_ lived after immersion in sea-water for twenty days. It is hardly likely that this is the extreme limit of their powers of endurance, but even this would allow of their being floated many hundred miles at a stretch, and if we suppose the shell to be partially protected in the crevice of a log of wood, and to be thus out of water in calm weather, the distance might extend to a thousand miles or more. The eggs of fresh-water mollusca, as well as the young animals, are known to attach themselves to the feet of aquatic birds, and this is probably the most efficient cause of their very wide diffusion.

[16] _Principles of Geology_, 11th Ed., Vol. I., p. 258.

[17] On Limestone as an Index of Geological Time.

[18] In his _Preliminary Report on Oceanic Deposit_, Mr. Murray says:--"It has been found that the deposits taking place near continents and islands have received their chief characteristics from the presence of the _debris_ of adjacent lands. In some cases these deposits extend to a distance of over 150 miles from the coast." (_Proceedings of the Royal Society_, Vol. XXIV. p. 519.)

"The materials in suspension appear to be almost entirely deposited within 200 miles of the land." (_Proceedings of the Royal Society of Edinburgh_, 1876-77, p. 253.)

[19] _Geographical Evolution. (Proceedings of the Royal Geographical Society._ 1879, p. 426.)

[20] Professor Dana was, I believe, the first to point out that the regions which, after long undergoing subsidence and accumulating vast piles of sedimentary deposit have been elevated into mountain ranges, thereby become stiff and unyielding, and that the next depression and subsequent upheaval will be situated on one or the other sides of it; and he has shown that, in North America, this is the case with all the mountains of the successive geological formations. Thus, depressions, and elevations of extreme slowness but often of vast amount, have occurred successively in restricted adjacent areas; and the effect has been to bring each portion in succession beneath the ocean but always bordered on one or both sides by the remainder of the continent, from the denudation of which the deposits are formed which, on the subsequent upheaval, become mountain ranges. (_Manual of Geology_, 2nd Ed., p. 751.)

[21] _Nature_, Vol. II., p. 297.

[22] Sir W. Thomson, _Voyage of Challenger_, Vol. II., p. 374.

[23] The following is the analysis of the chalk at Oahu:--

Carbonate of Lime 92.800 per cent. Carbonate of Magnesia 2.385 ,, Alumina 0.250 ,, Oxide of Iron 0.543 ,, Silica 0.750 ,, Phosphoric Acid and Fluorine 2.113 ,, Water and loss 1.148 ,,

This chalk consists simply of comminuted corals and shells of the reef. It has been examined microscopically and found to be destitute of the minute organisms abounding in the chalk of England. (_Geology of the United States Exploring Expedition_, p. 150.) Mr. Guppy also found chalk-like coral limestones containing 95 p.c. of carbonate of lime in the Solomon Islands.

The absence of _Globigerinae_ is a local phenomenon. They are quite absent in the Arafura Sea, and no _Globigerina_-ooze was found in any of the enclosed seas of the Pacific, but with these exceptions the _Globigerinae_ "are really found all over the bottom of the ocean." (Murray on Oceanic Deposits--_Proceedings of Royal Society_, Vol. XXIV., p. 523.)

The above analysis shows a far closer resemblance to chalk than that of the _Globigerina_-ooze of the Atlantic, four specimens of which given by Sir W. Thomson (_Voyage of the Challenger_ Vol. II. Appendix, pp. 374-376, Nos. 9, 10, 11 and 12) from the mid-Atlantic, show the following proportions:--

Carbonate of Lime 43.93 to 79.17 per cent. Carbonate of Magnesia 1.40 to 2.58 ,, Alumina and Oxide of Iron 6.00? to 32.98 ,, Silica 4.60 to 11.23 ,,

In addition to the above there is a quantity of insoluble residue consisting of small particles of sanidine, augite, hornblende, and magnetite, supposed to be the product of volcanic dust or ashes carried either in the air or by ocean currents. This volcanic matter amounts to from 4.60 to 8.33 per cent. of the _Globigerina_-ooze of the mid-Atlantic, where it seems to be always present; and the small proportion of similar matter in true chalk is another proof that its origin is different, and that it was deposited far more rapidly than the oceanic ooze.

The following analysis of chalk by Mr. D. Forbes will show the difference between the two formations:--

Grey Chalk, White Chalk, _Folkestone_. _Shoreham_.

Carbonate of Lime 94.09 98.40 Carbonate of Magnesia 0.31 0.08 Alumina and Phosphoric Acid a trace 0.42 Chloride of Sodium 1.29 -- Insoluble debris 3.61 1.10

(From _Quarterly Journal of the Geological Society_, Vol. XXVII.)

The large proportion of carbonate of lime, and the very small quantity of silica, alumina, and insoluble _debris_, at once distinguish true chalk from the _Globigerina_-ooze of the deep ocean bed.

[24] Notes on Reticularian Rhizopoda; in _Microscopical Journal_, Vol. XIX., New Series, p. 84.

[25] _Proceedings of the Royal Society_, Vol. XXIV. p. 532.

[26] See Presidential Address in Sect. D. of British Association at Plymouth, 1877.

[27] _Geological Magazine_, 1871, p. 426.

[28] In his lecture on _Geographical Evolution_ (which was published after the greater part of this chapter had been written) Sir Archibald Geikie expresses views in complete accordance with those here advocated. He says:--"The next long era, the Cretaceous, was more remarkable for slow accumulation of rock under the sea than for the formation of new land. During that time the Atlantic sent its waters across the whole of Europe and into Asia. But they were probably nowhere more than a few hundred feet deep over the site of our continent, even at their deepest part. Upon their bottom there gathered a vast mass of calcareous mud, composed in great part of foraminifera, corals, echinoderms, and molluscs. Our English chalk, which ranges across the north of France, Belgium, Denmark, and the north of Germany, represents a portion of the deposits of that sea-floor." The weighty authority of the Director-General of the Geological Survey may perhaps cause some geologists to modify their views as to the deep-sea origin of chalk, who would have treated any arguments advanced by myself as not worthy of consideration.

[29] _Introduction and Succession of Vertebrate Life in America_, by Professor O. C. Marsh. Reprinted from the _Popular Science Monthly_, March, April, 1878.

[30] _Physical Geography and Geology of Great Britain_, 5th Ed. p. 61.

[31] Of late it has been the custom to quote the so-called "ridge" down the centre of the Atlantic as indicating an extensive ancient land. Even Professor Judd at one time adopted this view, speaking of the great belt of Tertiary volcanoes "which extended through Greenland, Iceland, the Faroe Islands, the Hebrides, Ireland, Central France, the Iberian Peninsula, the Azores, Madeira, Canaries, Cape de Verde Islands, Ascension, St. Helena, and Tristan d'Acunha, and which constituted as shown by the recent soundings of H.M.S. _Challenger_ a mountain-range, comparable in its extent, elevation, and volcanic character with the Andes of South America" (_Geological Mag._ 1874, p. 71). On examining the diagram of the Atlantic Ocean in the _Challenger Reports_, No. 7, a considerable part of this ridge is found to be more than 1,900 fathoms deep, while the portion called the "Connecting Ridge" seems to be due in part to the deposits carried out by the River Amazon. In the neighbourhood of the Azores, St. Paul's Rocks, Ascension, and Tristan d'Acunha are considerable areas varying from 1,200 to 1,500 fathoms deep, while the rest of the ridge is usually 1,800 or 1,900 fathoms. The shallower water is no doubt due to volcanic upheaval and the accumulation of volcanic ejections, and there may be many other deeply submerged old volcanoes on the ridge; but that it ever formed a chain of mountains "comparable in elevation with the Andes," there seems not a particle of evidence to prove. It is however probable that this ridge indicates the former existence of some considerable Atlantic islands, which may serve to explain the presence of a few identical genera, and even species of plants and insects in Africa and South America, while the main body of the fauna and flora of these two continents remains radically distinct.

In my _Darwinism_ (pp. 344-5) I have given an additional argument founded on the comparative height and area of land with the depth and area of ocean, which seems to me to add considerably to the weight of the evidence here submitted for the permanence of oceanic and continental areas.

[32] In a review of Mr. T. Mellard Reade's _Chemical Denudation and Geological Time_, in _Nature_ (Oct. 2nd, 1879), the writer remarks as follows:--"One of the funny notions of some scientific thinkers meets with no favour from Mr. Reade, whose geological knowledge is practical as well as theoretical. They consider that because the older rocks contain nothing like the present red clays, &c., of the ocean floor, that the oceans have always been in their present positions. Mr. Reade points out that the first proposition is not yet proved, and the distribution of animals and plants and the fact that the bulk of the strata on land are of marine origin are opposed to the hypothesis." We must leave it to our readers to decide whether the "notion" developed in this chapter is "funny," or whether such hasty and superficial arguments as those here quoted from a "practical geologist" have any value as against the different classes of facts, all pointing to an opposite conclusion, which have now been briefly laid before them, supported as they are by the expressed opinion of so weighty an authority as Sir Archibald Geikie, who, in the lecture already quoted says:--"From all this evidence we may legitimately conclude that the present land of the globe, though formed in great measure of marine formations, has never lain under the deep sea; but that its site must always have been near land. Even its thick marine limestones are the deposits of comparatively shallow water."

[33] _Antiquity of Man_, 4th Ed. pp. 340-348.

[34] _The Great Ice Age and its Relation to the Antiquity of Man._ By James Geikie, F.R.S. (Isbister and Co., 1874.)

[35] This view of the formation of "till" is that adopted, by Dr. Geikie, and upheld by almost all the Scotch, Swiss, and Scandinavian geologists. The objection however is made by many eminent English geologists, including the late Mr. Searles V. Wood, Jun., that mud ground off the rocks cannot remain beneath the ice, forming sheets of great thickness, because the glacier cannot at the same time grind down solid rock and yet pass over the surface of soft mud and loose stones. But this difficulty will disappear if we consider the numerous fluctuations in the glacier with increasing size, and the additions it must have been constantly receiving as the ice from one valley after another joined together, and at last produced an ice-sheet covering the whole country. The grinding power is the motion and pressure of the ice, and the pressure will depend on its thickness. Now the points of maximum thickness must have often changed their positions, and the result would be that the matter ground out in one place would be forced into another place where the pressure was less. If there were no lateral escape for the mud, it would necessarily support the ice over it just as a water-bed supports the person lying on it; and when there was little drainage water, and the ice extended, say, twenty miles in every direction from a given part of a valley where the ice was of less than the average thickness, the mud would necessarily accumulate at this part simply because there was no escape for it. Whenever the pressure all round any area was greater than the pressure on that area, the _debris_ of the surrounding parts would be forced into it, and would even raise up the ice to give it room. This is a necessary result of hydrostatic pressure. During this process the superfluous water would no doubt escape through fissures or pores of the ice, and would leave the mud and stones in that excessively compressed and tenacious condition in which the "till" is found. The unequal thickness and pressure of the ice above referred to would be a necessary consequence of the inequalities in the valleys, now narrowing into gorges, now opening out into wide plains, and again narrowed lower down; and it is just in these openings in the valleys that the "till" is said to be found, and also in the lowlands where an ice-sheet must have extended for many miles in every direction. In these lowland valleys the "till" is both thickest and most wide-spread, and this is what we might expect. At first, when the glaciers from the mountains pushed out into these valleys, they would grind out the surface beneath them into hollows, and the drainage-water would carry away the _debris_. But when they spread all over the surface from sea to sea, and there was little or no drainage water compared to the enormous area covered with ice, the great bulk of the _debris_ must have gathered under the ice wherever the pressure was least, and the ice would necessarily rise as it accumulated. Some of the mud would no doubt be forced out along lines of least resistance to the sea, but the friction of the stone-charged "till" would be so enormous that it would be impossible for any large part of it to be disposed of in this way.

[36] That the ice-sheet was continuous from Scotland to Ireland is proved by the glacial phenomena in the Isle of Man, where "till" similar to that in Scotland abounds, and rocks are found in it which must have come from Cumberland and Scotland, as well as from the north of Ireland. This would show that glaciers from each of these districts reached the Isle of Man, where they met and flowed southwards down the Irish Sea. Ice-marks are traced over the tops of the mountains which are nearly 2,000 feet high. (See _A Sketch of the Geology of the Isle of Man_, by John Horne, F.G.S. _Trans. of the Edin. Geol. Soc._ Vol. II. pt. 3, 1874.)

[37] _The Great Ice Age_, p. 177.

[38] These are named, in descending order, Hessle Boulder Clay, Purple Boulder Clay, Chalky Boulder Clay, and Lower Boulder Clay--below which is the Norwich Crag.

[39] "On the Climate of the Post-Glacial Period." _Geological Magazine_, 1872, pp. 158, 160.

[40] _Geological Magazine_, 1876, p. 396.

[41] _Early Man in Britain and his Place in the Tertiary Period_, p. 113.

[42] Heer's _Primaeval World of Switzerland_ Vol. II., pp. 148-168.

[43] Dr. James Geikie in _Geological Magazine_, 1878, p. 77.

[44] This subject is admirably discussed in Professor Asa Gray's Lecture on "Forest Geography and Archaeology" in the _American Journal of Science and Arts_, Vol. XVI. 1878.

[45] In a letter to _Nature_ of October 30th, 1879, the Rev. O. Fisher calls attention to a result arrived at by Pouillet, that the temperature which the surface of the ground would assume if the sun were extinguished would be -128deg F. instead of -239deg F. If this corrected amount were used in our calculations, the January temperature of England during the glacial epoch would come out 17deg F., and this Mr. Fisher thinks not low enough to cause any extreme difference from the present climate. In this opinion, however, I cannot agree with him. On the contrary, it would, I think, be a relief to the theory were the amounts of decrease of temperature in winter and increase in summer rendered more moderate, since according to the usual calculation (which I have adopted) the differences are unnecessarily great. I cannot therefore think that this modification of the temperatures, should it be ultimately proved to be correct (which is altogether denied by Dr. Croll), would be any serious objection to the adoption of Dr. Croll's theory of the Astronomical and Physical causes of the Glacial Epoch.

The reason of the theoretical increase of summer heat being greater than the decrease of winter cold is because we are now nearest the sun in winter and farthest in summer, whereas we calculate the temperatures of the glacial epoch for the phase of precession when the _aphelion_ was in winter. A large part of the increase of temperature would no doubt be used up in melting ice and evaporating water, so that there would be a much less increase of sensible heat; while only a portion of the theoretical lowering of temperature in winter would be actually produced owing to equalising effect of winds and currents, and the storing up of heat by the earth and ocean.

[46] Dr. Croll says this "is one of the most widespread and fundamental errors within the whole range of geological climatology." The temperature of the snow itself is, he says, one of the main factors. (_Climate and Cosmology_, p. 85.) But surely the temperature of the snow must depend on the temperature of the air through which it falls.

[47] In an account of Prof. Nordenskjoeld's recent expedition round the northern coast of Asia, given in _Nature_, November 20th, 1879, we have the following passage, fully supporting the statement in the text. "Along the whole coast, from the White Sea to Behring's Straits, no glacier was seen. During autumn the Siberian coast is nearly free of ice and snow. There are no mountains covered all the year round with snow, although some of them rise to a height of more than 2,000 feet." It must be remembered that the north coast of Eastern Siberia is in the area of supposed greatest winter cold on the globe.

[48] Dr. Croll objects to this argument on the ground that Greenland and the Antarctic continent are probably lowlands or groups of islands. (_Climate and Cosmology_, Chap. V.)

[49] "On the Glacial Epoch," by James Croll. _Geol. Mag._ July, August, 1874.

[50] "The general absence of recent marks of glacial action in Eastern Europe is well known; and the series of changes which have been so well traced and described by Prof. Szabo as occurring in those districts seems to leave no room for those periodical extensions of 'ice-caps' with which some authors in this country have amused themselves and their readers. Mr. Campbell, whose ability to recognise the physical evidence of glaciers will scarcely be questioned, finds quite the same absence of the proof of extensive ice-action in North America, westward of the meridian of Chicago." (Prof. J. W. Judd in _Geol. Mag._ 1876, p. 535.)

The same author notes the diminution of marks of ice-action on going eastward in the Alps; and the Altai Mountains far in Central Asia show no signs of having been largely glaciated. West of the Rocky Mountains, however, in the Sierra Nevada and the coast ranges further north, signs of extensive old glaciers again appear; all which phenomena are strikingly in accordance with the theory here advocated, of the absolute dependence of glaciation on abundant rainfall and elevated snow-condensers and accumulators.

[51] I have somewhat modified this whole passage in the endeavour to represent more accurately the difference between the views of Dr. Croll and Sir Charles Lyell.

[52] For numerous details and illustrations see the paper--"On Ocean Currents in Relation to the Physical Theory of Secular Changes of Climate"--in the _Philosophical Magazine_, 1870.

[53] See _Darwin's Naturalist's Voyage Round the World_, 2nd Edition, pp. 244-251.

[54] The influence of geographical changes on climate is now held by many geologists who oppose what they consider the extravagant hypotheses of Dr. Croll. Thus, Prof. Dana imputes the glacial epoch chiefly, if not wholly, to elevation of the land caused by the lateral pressure due to shrinking of the earth's crust that has caused all other elevations and depressions. He says: "Now, that elevation of the land over the higher latitudes which brought on the glacial era is a natural result of the same agency, and a natural, and almost necessary, counterpart of the coral-island subsidence which must have been then in progress. The accumulating, folding, solidification, and crystallisation of rocks attending all the rock-making and mountain-making through the Palaeozoic, Mesozoic, and Cenozoic eras, had greatly stiffened the crust in these parts; and hence in after times, the continental movements resulting from the lateral pressure necessarily appeared over the more northern portions of the continent, where the accumulations and other changes had been relatively small. To the subsidence which followed the elevation the weight of the ice-cap may have contributed in some small degree. But the great balancing movements of the crust of the continental and oceanic areas then going forward must have had a greatly preponderating effect in the oscillating agency of all time--lateral pressure within the crust." (_American Journal of Science and Arts_, 3rd Series, Vol. IX. p. 318.)

"In the 2nd edition of his _Manual of Geology_, Professor Dana suggests elevation of Arctic lands sufficient to exclude the Gulf Stream, as a source of cold during glacial epochs. This, he thinks, would have made an epoch of cold at any era of the globe. A deep submergence of Behring's Strait, letting in the Pacific warm current to the polar area, would have produced a mild Arctic climate like that of the Miocene period. When the warm current was shut out from the polar area it would yet reach near to it, and bring with it that abundant moisture necessary for glaciation." (_Manual of Geology_, 2nd Edition, pp. 541-755, 756.)

[55] Dana's _Manual of Geology_, 2nd Edition, p. 540.

[56] Dr. Croll says that I here assume an impossible state of things. He maintains "that the change from the distant sun in winter, and near sun in summer to the near sun in winter and distant sun in summer, aided by the change in the physical causes which this would necessarily bring about, would certainly be sufficient to cause the snow and ice to disappear." (_Climate and Cosmology_, p. 106.) But I demur to his "necessarily." It is not the _direct_ effect of the nearer sun in winter that is supposed to melt the snow and ice, but the "physical causes," such as absence of fogs and increase of warm equatorial currents. But the near sun in winter acting on an ice-clad surface would only increase the fogs and snow, while the currents could only change if a large portion of the ice were first melted, in which case they would no doubt be modified so as to cause a further melting of the ice. Dr. Croll says: "The warm and equable conditions of climate which would then prevail, and the enormous quantity of intertropical water carried into the Southern Ocean, would soon produce a melting of the ice." (_Loc. cit._ p. 111.) This seems to me to be assuming the very point at issue. He has himself shown that the presence of large quantities of ice prevents "a warm and equable climate" however great may be the sun-heat; the ice therefore would _not_ be melted, and there would be no increased flow of intertropical water to the Southern Ocean. The ocean currents are mainly due to the difference of temperature of the polar and equatorial areas combined with the peculiar form and position of the continents, and some one or more of these factors must be altered _before_ the ocean currents towards the north pole can be increased. The only factor available is the Antarctic ice, and if this were largely increased, the northward-flowing currents might be so increased as to melt some of the Arctic ice. But the very same argument applies to both poles. Without some geographical change the Antarctic ice could not materially diminish during its winter in _perihelion_, nor increase to any important extent during the opposite phase. We therefore seem to have no available agency by which to get rid of the ice over a glaciated hemisphere, _so long as the geographical conditions remained unchanged and the excentricity continued high_.

[57] In the _Geological Magazine_, April, 1880, Mr. Searles V. Wood adduces what he considers to be the "conclusive objection" to Dr. Croll's excentricity theory, which is, that during the last glacial epoch Europe and North America were glaciated very much in proportion to their respective climates now, which are generally admitted to be due to the distribution of oceanic currents. But Dr. Croll admits his theory "to be baseless unless there was a complete diversion of the warm ocean currents from the hemisphere glaciated," in which case there ought to be no difference in the extent of glaciation in Europe and North America. Whether or not this is a correct statement of Dr. Croll's theory, the above objection certainly does not apply to the views here advocated; but as I also hold the "excentricity theory" in a modified form, it may be as well to show why it does not apply. In the first place I do not believe that the Gulf Stream was "completely diverted" during the glacial epoch, but that it was diminished in force, and (as described at p. 144) _partly_ diverted southward. A portion of its influence would, however, still remain to cause a difference between the climates of the two sides of the Atlantic; and to this must be added two other causes--the far greater penetration of warm sea-water into the European than into the North American continent, and the proximity to America of the enormous ice-producing mass of Greenland. We have thus three distinct causes, all combining to produce a more severe winter climate on the west than on the east of the Atlantic during the glacial epoch, and though the first of these--the Gulf Stream--was not nearly so powerful as it is now, neither is the difference indicated by the ice-extension in the two countries so great as the present difference of winter-temperature, which is the essential point to be considered. The ice-sheet of the United States is usually supposed to have extended about ten, or, at most, twelve, degrees further south than it did in Western Europe, whereas we must go twenty degrees further south in the former country to obtain the same mean winter-temperature we find in the latter, as may be seen by examining any map of winter isothermals. This difference very fairly corresponds to the difference of conditions existing during the glacial epoch and the present time, so far as we are able to estimate them, and it certainly affords no grounds of objection to the theory by which the glaciation is here explained.

[58] Dr. Croll objects to this argument, and adduces the case of Greenland as showing that ice may accumulate far from sea. But the width of Greenland is small compared with that of the supposed Antarctic ice-cap. (_Climate and Cosmology_, p. 78.)

[59] The recent extensive glaciation of New Zealand is generally imputed by the local geologists to a greater elevation of the land; but I cannot help believing that the high phase of excentricity which caused our own glacial epoch was at all events an assisting cause. This is rendered more probable if taken in connection with the following very definite statement of glacial markings in South Africa. Captain Aylward in his _Transvaal of To-day_ (p. 171) says:--"It will be interesting to geologists and others to learn that the entire country, from the summits of the Quathlamba to the junction of the Vaal and Orange rivers, shows marks of having been swept over, and that at no very distant period, by vast masses of ice from east to west. The striations are plainly visible, scarring the older rocks, and marking the hill-sides--getting lower and lower and less visible as, descending from the mountains, the kopjies (small hills) stand wider apart; but wherever the hills narrow towards each other, again showing how the vast ice-fields were checked, thrown up, and raised against their Eastern extremities."

This passage is evidently written by a person familiar with the phenomena of glaciation, and as Captain Aylward's preface is dated from Edinburgh, he has probably seen similar markings in Scotland. The country described consists of the most extensive and lofty plateau in South Africa, rising to a mountain knot with peaks more than 10,000 feet high, thus offering an appropriate area for the condensation of vapour and the accumulation of snow. At present, however, the mountains do not reach the snow-line, and there is no proof that they have been much higher in recent times, since the coast of Natal is now said to be rising. It is evident that no slight elevation would now lead to the accumulation of snow and ice in these mountains, situated as they are between 27deg and 30deg S. Lat.; since the Andes, which in 32deg S. Lat. reach 23,300 feet high, and in 28deg S. Lat. 20,000, with far more extensive plateaus, produce no ice-fields. We cannot, therefore, believe that a few thousand feet of additional elevation, even if it occurred so recently as indicated by the presence of striations, would have produced the remarkable amount of glaciation above described; while from the analogy of the northern hemisphere, we may well believe that it was mainly due to the same high excentricity that led to the glaciation of Western and Central Europe, and Eastern North America.

These observations confirm those of Mr. G. W. Stow, who, in a paper published in the _Quarterly Journal of the Geological Society_ (Vol. XXVII. p. 539), describes similar phenomena in the same mountains, and also mounds and ridges of unstratified clay packed with angular boulders; while further south the Stormberg mountains are said to be similarly glaciated, with immense accumulations of morainic matter in all the valleys. We have here most of the surface phenomena characteristic of a glaciated country, only a few degrees south of the tropic; and taken in connection with the indications of recent glaciation in New Zealand, and those discovered by Dr. R. von Lendenfeld in the Australian Alps between 6,000 and 7,000 feet elevation (_Nature_, Vol. XXXII. p. 69), we can hardly doubt the occurrence of some general and wide-spread cause of glaciation in the southern hemisphere at a period so recent that the superficial phenomena are almost as well preserved as in Europe. Other geologists however deny that there are any distinct indications of glacial action in South Africa; but the recent discovery by Dr. J. W. Gregory, F.G.S., of the former extension of glaciers on Mount Kenya 5,000 feet below their present limits, renders probable the former glaciation of the South African Highlands.

[60] The astronomical facts connected with the motions and appearance of the planet are taken from a paper by Mr. Edward Carpenter, M.A., in the _Geological Magazine_ of March, 1877, entitled, "Evidence Afforded by Mars on the Subject of Glacial Periods," but I arrive at somewhat different conclusions from those of the writer of the paper.

[61] In an article in _Nature_ of Jan. 1, 1880, the Rev. T. W. Webb states that in 1877 the pole of Mars (? the south pole) was, according to Schiaparelli, entirely free of snow. He remarks also on the regular contour of the supposed snows of Mars as offering a great contrast to ours, and also the strongly marked dark border which has often been observed. On the whole Mr. Webb seems to be of opinion that there can be no really close resemblance between the physical condition of the Earth and Mars, and that any arguments founded on such supposed similarity are therefore untrustworthy.

[62] _London, Edinburgh and Dublin Philosophical Magazine_, Vol. XXXVI., pp. 144-150 (1868).

[63] _Climate and Time in their Geological Relations_, p. 341.

[64] _Nature_, Vol. XXI., p. 345, "The Interior of Greenland."

[65] Prof. J. W. Judd says: "In the case of the Alps I know of no glacial phenomena which are not capable of being explained, like those of New Zealand, by a great extension of the area of the tracts above the snow-line which would collect more ample supplies for the glaciers protruded into surrounding plains. And when we survey the grand panoramas of ridges, pinnacles, and peaks produced for the most part by sub-aerial action, we may well be prepared to admit that before the intervening ravines and valleys were excavated, the glaciers shed from the elevated plateaux must have been of vastly greater magnitude than at present." (Contributions to the Study of Volcanoes, _Geological Magazine_, 1876, p. 536.) Professor Judd applies these remarks to the last as well as to previous glacial periods in the Alps; but surely there has been no such extensive alteration and lowering of the surface of the country since the erratic blocks were deposited on the Jura and the great moraines formed in North Italy, as this theory would imply. We can hardly suppose wide areas to have been lowered thousands of feet by denudation, and yet have left other adjacent areas apparently untouched; and it is even very doubtful whether such an extension of the snow-fields would alone suffice for the effects which were certainly produced.

[66] _Geological Magazine_, 1876, p. 392.

[67] Colonel Fielden thinks that these trees have all been brought down by rivers, and have been stranded on shores which have been recently elevated. See _Trans. of Norfolk Nat. Hist. Soc., Vol. III._, 1880.

[68] _Geological Magazine_, 1876, "Geology of Spitzbergen," p. 267.

[69] The preceding account is mostly derived from Professor Heer's great work _Flora Fossilis Arctica_.

[70] _Geological Magazine_, 1875, p. 531.

[71] _Geological Magazine_, 1876, p. 266. In his recent work--_Climate and Cosmology_ (pp. 164, 172)--the late Dr. Croll has appealed to the imperfection of the geological record as a reply to these arguments; in this case, as it appears to me, a very unsuccessful one.

[72] It is interesting to observe that the Cretaceous flora of the United States (that of the Dakota group), indicates a somewhat cooler climate than that of the following Eocene period. Mr. De Rance (in the geological appendix to Capt. Sir G. Nares's _Narrative of a Voyage to the Polar Sea_) remarks as follows: "In the overlying American Eocenes occur types of plants occurring in the European Miocenes and still living, proving the truth of Professor Lesquereux's postulate, that the plant types appear in America a stage in advance of their advent in Europe. These plants point to a far higher mean temperature than those of the Dakota group, to a dense atmosphere of vapour, and a luxuriance of ferns and palms." This is very important as adding further proof to the view that the climates of former periods are not due to any general refrigeration, but to causes which were subject to change and alternation in former ages as now.

[73] Mr. S. B. J. Skertchley informs me that he has himself observed thick Tertiary deposits, consisting of clays and anhydrous gypsum, at Berenice on the borders of Egypt and Nubia, at a height of about 600 feet above the sea-level; but these may have been of fresh-water origin.

[74] By referring to our map of the Indian Ocean showing the submarine banks indicating ancient islands (Chap. XIX.), it will be evident that the south-east trade-winds--then exceptionally powerful--would cause a vast body of water to enter the deep Arabian Sea.

[75] In his recently published _Lectures on Physical Geography_, Professor Haughton calculates, that more than half the solar heat of the torrid zone is carried to the temperate zones by ocean currents. The Gulf Stream itself carries one-twelfth of the total amount, but it is probable that a very small fraction of this quantity of heat reaches the polar seas owing to the wide area over which the current spreads in the North Atlantic. The corresponding stream of the Indian Ocean in Miocene times would have been fully equal to the Gulf Stream in heating power, while, owing to its being so much more concentrated, a large proportion of its heat may have reached the polar area. But the Arctic Ocean occupies less than one-tenth of the area of the tropical seas; so that, whatever proportion of the heat of the tropical zone was conveyed to it, would, by being concentrated into one-tenth of the surface, produce an enormously increased effect. Taking this into consideration, we can hardly doubt that the opening of a sufficient passage from the Indian Ocean to the Arctic seas would produce the effects above indicated.

[76] For an account of the resemblances and differences of the mammalia of the two continents during the Tertiary epoch, see my _Geographical Distribution of Animals_, Vol. I. pp. 140-156.

[77] Professor Haughton has made an elaborate calculation of the difference between existing climates and those of Miocene times, for all the places where a Miocene flora has been discovered, by means of the actual range of corresponding species and genera of plants. Although this method is open to the objection that the ranges of plants and animals are not determined by temperature only, yet the results may be approximately correct, and are very interesting. The following table which summarizes these results is taken from his Lectures on Physical Geography (p. 344):--

_______________________________________________________________________ | | | Present | Miocene | | | |Latitude.|Temperature.|Temperature.|Difference.| |_____________________|_________|____________|____________|___________| | 1. Switzerland | 47d.00 | 53d.6 F | 69d.8 F | 16d.2 F | | 2. Dantzig | 54d.21 | 45d.7 ,, | 62d.6 ,, | 16d.9 ,, | | 3. Iceland | 65d.30 | 35d.6 ,, | 48d.2 ,, | 12d.6 ,, | | 4. Mackenzie River | 65d.00 | 19d.4 ,, | 48d.2 ,, | 28d.8 ,, | | 5. Disco (Greenland)| 70d.00 | 19d.6 ,, | 55d.6 ,, | 36d.0 ,, | | 6. Spitzbergen | 78d.00 | 16d.5 ,, | 51d.8 ,, | 35d.3 ,, | | 7. Grinnell Land | 81d.44 | 1d.7 ,, | 42d.3 ,, | 44d.0 ,, | |_____________________|_________|____________|____________|___________|

It is interesting to note that Iceland, which is now exposed to the full influence of the Gulf Stream, was only 12deg.6 F. warmer in Miocene times, while Mackenzie River, now totally removed from its influence was 28deg warmer. This, as well as, the greater increase of temperature as we go northward and the polar area becomes more limited, is quite in accordance with the view of the causes which brought about the Miocene climate which is here advocated.

[78] The objection has been made, that the long polar night would of itself be fatal to the existence of such a luxuriant vegetation as we know to have existed as far as 80deg N. Lat., and that there must have been some alteration of the position of the pole, or diminution of the obliquity of the ecliptic, to permit such plants as magnolias and large-leaved maples to flourish. But there appears to be really no valid grounds for such an objection. Not only are numbers of Alpine and Arctic evergreens deeply buried in the snow for many months without injury, but a variety of tropical and sub-tropical plants are preserved in the hot-houses of St. Petersburg and other northern cities, which are closely matted during winter, and are thus exposed to as much darkness as the night of the Arctic regions. We have besides no proof that any of the Arctic trees or large shrubs were evergreens, and the darkness would certainly not be prejudical to deciduous plants. With a suitable temperature there is nothing to prevent a luxuriant vegetation up to the pole, and the long continued day is known to be highly favourable to the development of foliage, which in the same species is larger and better developed in Norway than in the south of England.

[79] _Geological Magazine_, 1873, p. 320.

[80] _Geological Magazine_, 1877, p. 137.

[81] _Manual of Geology_, 2nd Ed. p. 525. See also letter in _Nature_, Vol. XXIII. p. 410.

[82] _Nature_, Vol. XVIII. (July, 1878), p. 268.

[83] "On the Comparative Value of certain Geological Ages considered as items of Geological Time." (_Proceedings of the Royal Society_, 1874, p. 334.)

[84] _Trans. Royal Society of Edinburgh_, Vol. XXIII. p. 161. _Quarterly Journal of Science_, 1877. (Croll on the "Probable Origin and Age of the Sun.")

[85] _Philosophical Magazine_, April, 1853.

[86] It has usually been the practice to take the amount of denudation in the Mississippi valley, or one foot in six thousand years, as a measure of the rate of denudation in Europe, from an idea apparently of being on the "safe side," and of not over-estimating the rate of change. But this appears to me a most unphilosophical mode of proceeding and unworthy of scientific inquiry. What should we think of astronomers if they always took the lowest estimates of planetary or stellar distances, instead of the mean results of observation, "in order to be on the safe side!"? As if error in one direction were any worse than error in another. Yet this is what geologists do systematically. Whenever any calculations are made involving the antiquity of man, it is those that give the _lowest_ results that are always taken, for no reason apparently except that there was, for so long a time, a prejudice, both popular and scientific, against the great antiquity of man; and now that a means has been found of measuring the rate of denudation, they take the slowest rate instead of the mean rate, apparently only because there is now a scientific prejudice in favour of extremely slow geological change. I take the mean of the whole; and as this is almost exactly the same as the mean of the three great European rivers--the Rhone, Danube, and Po--I cannot believe that this will not be nearer the truth for Europe than taking one North American river as the standard.

[87] "On the Height of the Land and the Depth of the Ocean," in the _Scottish Geographical Magazine_, 1888.

[88] These figures are merely used to give an idea of the rate at which denudation is actually going on now; but if no elevatory forces were at work, the rate of denudation would certainly diminish as the mountains were lowered and the slope of the ground everywhere rendered flatter. This would follow not only from the diminished power of rain and rivers, but because the climate would become more uniform, the rainfall probably less, and no rocky peaks would be left to be fractured and broken up by the action of frosts. It is certain, however, that no continent has ever remained long subject to the influences of denudation alone, for, as we have seen in our sixth chapter, elevation and depression have always been going on in one part or other of the surface.

[89] The following statement of the depths at which the Palaeozoic formations have been reached in various localities in and round London was given by Mr. H. B. Woodward in his address to the Norwich Geological Society in 1879:--

_Deep Wells through the Tertiary and Cretaceous Formations._

Harwich at 1,022 feet reached Carboniferous Rock. Kentish Town ,, 1,114 ,, ,, Old Red Sandstone. Tottenham Court Road ,, 1,064 ,, ,, Devonian. Blackwall ,, 1,004 ,, ,, Devonian or Old Red Sandstone. Ware ,, 800 ,, ,, Silurian (Wenlock Shale).

We thus find that over a wide area, extending from London to Ware and Harwich, the whole of the formations from the Oolite to the Permian are wanting, the Cretaceous resting on the Carboniferous or older Palaeozoic rocks; and the same deficiency extends across to Belgium, where the Tertiary beds are found resting on Carboniferous at a depth of less than 400 feet.

[90] _Geological Magazine_, Vol. VIII., March, 1871.

[91] Mr. C. Lloyd Morgan has well illustrated this point by comparing the generally tilted-up strata denuded on their edges, to a library in which a fire had acted on the exposed edges of the books, destroying a great mass of literature but leaving a portion of each book in its place, which portion represents the thickness but not the size of the book. (_Geological Magazine_, 1878, p. 161.)

[92] Professor J. Young thinks it highly probable that--"the Lower Greensand is contemporaneous with part of the Chalk, so were parts of the Wealden; nay, even of the Purbeck a portion must have been forming while the Cretaceous sea was gradually deepening southward and westward." Yet these deposits are always arranged successively, and their several thicknesses added together to obtain the total thickness of the formations of the country. (See Presidential Address, Sect. C. British Association, 1876.)

[93] Mr. John Murray in his more careful estimate makes it about 51-1/2 millions.

[94] As by far the larger portion of the denuded matter of the globe passes to the sea through comparatively few great rivers, the deposits must often be confined to very limited areas. Thus the denudation of the vast Mississippi basin must be almost all deposited in a limited portion of the Gulf of Mexico, that of the Nile within a small area of the Eastern Mediterranean, and that of the great rivers of China--the Hoang Ho and Yang-tse-kiang, in a small portion of the Eastern Sea. Enormous lengths of coast, like those of Western America and Eastern Africa, receive very scanty deposits; so that thirty miles in width along the whole of the coasts of the globe will probably give an area greater than that of the area of _average_ deposit, and certainly greater than that of _maximum_ deposit, which is the basis on which I have here made my estimates. In the case of the Mississippi, it is stated by Count Pourtales that along the plateau between the mouth of the river and the southern extremity of Florida for two hundred and fifty miles in width the bottom consists of clay with some sand and but few Rhizopods; but beyond this distance the soundings brought up either Rhizopod shells alone, or these mixed with coral sand, Nullipores, and other calcareous organisms (Dana's _Manual of Geology_, 2nd Ed. p. 671). It is probable, therefore, that a large proportion of the entire mass of sediment brought down by the Mississippi is deposited on the limited area above indicated.

Professor Dana further remarks: "Over interior oceanic basins as well as off a coast in quiet depths, fifteen or twenty fathoms and beyond, the deposits are mostly of fine silt, fitted for making fine argillaceous rocks, as shales or slates. When, however, the depth of the ocean falls off below a hundred fathoms, the deposition of silt in our existing oceans mostly ceases, unless in the case of a great bank along the border of a continent."

[95] From the same data Professor Haughton estimates a minimum of 200 million years for the duration of geological time; but he arrives at this conclusion by supposing the products of denudation to be uniformly spread over the _whole sea-bottom_ instead of over a narrow belt near the coasts, a supposition entirely opposed to all the known facts, and which had been shown by Dr. Croll, five years previously, to be altogether erroneous. (See _Nature_, Vol. XVIII., p. 268, where Professor Haughton's paper is given as read before the Royal Society.)

[96] See _Geological Magazine_ for 1877, p. 1.

[97] In his reply to Sir W. Thomson, Professor Huxley _assumed_ one foot in a thousand years as a not improbable rate of deposition. The above estimate indicates a far higher rate; and this follows from the well-ascertained fact, that the area of deposition is many times smaller than the area of denudation.

[98] Dr. Croll and Sir Archibald Geikie have shown that marine denudation is very small in amount as compared with sub-aerial, since it acts only locally on the _edge_ of the land, whereas the latter acts over every foot of the _surface_. Mr. W. T. Blanford argues that the difference is still greater in tropical than in temperate latitudes, and arrives at the conclusion that--"If over British India the effects of marine to those of fresh-water denudation in removing the rocks of the country be estimated at 1 to 100, I believe that the result of marine action will be greatly overstated" (_Geology and Zoology of Abyssinia_, p. 158, note). Now, as our estimate of the rate of sub-aerial denudation cannot pretend to any precise accuracy, we are justified in neglecting marine denudation altogether, especially as we have no method of estimating it for the whole earth with any approach to correctness.

[99] Agassiz appears to have been the first to suggest that the principal epochs of life extermination were epochs of cold; and Dana thinks that two at least such epochs may be recognised, at the close of the Palaeozoic and of the Cretaceous periods--to which we may add the last glacial epoch.

[100] This view was, I believe, first put forth by myself in a paper read before the Geological Section of the British Association in 1869, and subsequently in an article in _Nature_, Vol. I. p. 454. It was also stated by Mr. S. B. J. Skertchley in his _Physical System of the Universe_, p. 363 (1878); but we both founded it on what I now consider the erroneous doctrine that actual glacial epochs recurred each 10,500 years during periods of high excentricity.

[101] Explication d'une seconde edition de la _Carte Geologique de la Terre_ (1875), p. 64.

[102] For most of the facts as to the zoology and botany of these islands, I am indebted to Mr. Godman's valuable work--_Natural History of the Azores or Western Islands_, by Frederick Du Cane Godman, F.L.S., F.Z.S., &c., London, 1870.

[103] See Chap. V. p. 78.

[104] Some of Mr. Darwin's experiments are very interesting and suggestive. Ripe hazel-nuts sank immediately, but when dried they floated for ninety days, and afterwards germinated. An asparagus-plant with ripe berries, when dried, floated for eighty-five days, and the seeds afterwards germinated. Out of ninety-four dried plants experimented with, eighteen floated for more than a month, and some for three months, and their powers of germination seem never to have been wholly destroyed. Now, as oceanic currents vary from thirty to sixty miles a day, such plants under the most favourable conditions might be carried 90 X 60 = 5,400 miles! But even half of this is ample to enable them to reach any oceanic island, and we must remember that till completely water-logged they might be driven along at a much greater rate by the wind. Mr. Darwin calculates the distance by the average time of flotation to be 924 miles; but in such a case as this we are entitled to take the extreme cases, because such countless thousands of plants and seeds must be carried out to sea annually that the extreme cases in a single experiment with only ninety-four plants, must happen hundreds or thousands of times and with hundreds or thousands of species, naturally, and thus afford ample opportunities for successful migration. (See _Origin of Species_, 6th Edition, p. 325.)

[105] The following remarks, kindly communicated to me by Mr. H. N. Moseley, naturalist to the _Challenger_, throw much light on the agency of birds in the distribution of plants:--"Grisebach (_Veg. der Erde_, Vol. II. p. 496) lays much stress on the wide ranging of the albatross (Diomedea) across the equator from Cape Horn to the Kurile Islands, and thinks that the presence of the same plants in Arctic and Antarctic regions may be accounted for, possibly, by this fact. I was much struck at Marion Island of the Prince Edward group, by observing that the great albatross breeds in the midst of a dense, low herbage, and constructs its nest of a mound of turf and herbage. Some of the indigenous plants, _e.g._ Acaena, have flower-heads which stick like burrs to feathers, &c., and seem specially adapted for transposition by birds. Besides the albatrosses, various species of Procellaria and Puffinus, birds which range over immense distances may, I think, have played a great part in the distribution of plants, and especially account, in some measure, for the otherwise difficult fact (when occurring in the tropics), that widely distant islands have similar mountain plants. The Procellaria and Puffinus in nesting, burrow in the ground, as far as I have seen choosing often places where the vegetation is the thickest. The birds in burrowing get their feathers covered with vegetable mould, which must include spores, and often seeds. In high latitudes the birds often burrow near the sea-level, as at Tristan d'Acunha or Kerguelen's Land, but in the tropics they choose the mountains for their nesting-place (Finsch and Hartlaub, _Orn. der Viti- und Tonga-Inseln_, 1867, Einleitung, p. xviii.). Thus, _Puffinus megasi_ nests at the top of the Korobasa basaga mountain, Viti Levu, fifty miles from the sea. A Procellaria breeds in like manner in the high mountains of Jamaica, I believe at 7,000 feet. Peale describes the same habit of _Procellaria rostrata_ at Tahiti, and I saw the burrows myself amidst a dense growth of fern, &c., at 4,400 feet elevation in that island. Phaethon has a similar habit. It nests at the crater of Kilauea, Hawaii, at 4,000 feet elevation, and also high up in Tahiti. In order to account for the transportation of the plants, it is not of course necessary that the same species of Procellaria or Diomedea should now range between the distant points where the plants occur. The ancestor of the now differing species might have carried the seeds. The range of the genus is sufficient."

[106] _Nature_, Vol. VI. p. 262, "Recent Observations in the Bermudas," by Mr. J. Matthew Jones.

[107] "The late Sir C. Wyville Thomson was of opinion that the 'red earth' which largely forms the soil of Bermuda had an organic origin, as well as the 'red clay' which the _Challenger_ discovered in all the greater depths of the ocean basins. He regarded the red earth and red clay as an ash left behind after the gradual removal of the lime by water charged with carbonic acid. This ash he regarded as a constituent part of the shells of Foraminifera, skeletons of Corals, and Molluscs, [_vide_ _Voyage of the Challenger_, Atlantic, Vol. I. p. 316]. This theory does not seem to be in any way tenable. Analysis of carefully selected shells of Foraminifera, Heteropods, and Pteropods, did not show the slightest trace of alumina, and none has as yet been discovered in coral skeletons. It is most probable that a large part of the clayey matter found in red clay and the red earth of Bermuda is derived from the disintegration of pumice, which is continually found floating on the surface of the sea. [See Murray, "On the Distribution of Volcanic Debris Over the Floor of the Ocean;" _Proc. Roy. Soc. Edin._ Vol. IX. pp. 247-261. 1876-1877.] The naturalists of the _Challenger_ found it among the floating masses of gulf weed, and it is frequently picked up on the reefs of Bermuda and other coral islands. The red earth contains a good many fragments of magnetite, augite, felspar, and glassy fragments, and when a large quantity of the rock of Bermuda is dissolved away with acid, a small number of fragments are also met with. These mineral particles most probably came originally from the pumice which had been cast up on the island for long ages (for it is known that these minerals are present in pumice), although possibly some of them may have come from the volcanic rock, which is believed to form the nucleus of the island." _The Voyage of H.M.S. Challenger_, Narrative of the Cruise, Vol. I. 1885, pp. 141-142.

[108] Four bats occur rarely, two being N. American, and two West Indian Species. _The Bermuda Islands_, by Angelo Heilprin, Philadelphia, 1889.

[109] Fourteen species of Spiders were collected by Prof. A. Heilprin, all American or cosmopolitan species except one, _Lycosa atlantica_, which Dr. Marx of Washington describes as new and as peculiar to the islands. (Heilprin's _The Bermudas_, p. 93.)

[110] Mr. Theo. D. A. Cockerell informs me that there are two slugs in Bermuda of which specimens exist in the British Museum,--_Amalia gagates_ Drap. common in Europe, and _Agriolimax campestris_ of the United States. Both may therefore have been introduced by human agency. Also _Vaginulus Morelete var. schivelyae_ which seems to be a variety of a Mexican species; perhaps imported.

[111] "Notes on the Vegetation of Bermuda," by H. N. Moseley. (_Journal of the Linnean Society_, Vol. XIV., _Botany_, p. 317.)

[112] _Gigantic Land Tortoises Living and Extinct in the Collection of the British Museum._ By A. C. L. G. Guenther, F.R.S. 1877.

[113] The following list of the beetles yet known from the Galapagos shows their scanty proportions and accidental character; the forty species belonging to thirty-three genera and eighteen families. It is taken from Mr. Waterhouse's enumeration in the _Proceedings of the Zoological Society_ for 1877 (p. 81), with a few additions collected by the U. S. Fish Commission Steamer _Albatross_, and published by the U. S. National Museum in 1889.

CARABIDAE. ELATERIDAE. Feronia calathoides. Physorhinus galapagoensis ,, insularis. HETEROMERA. ,, galapagoensis. Allecula n. s. Amblygnathus obscuricornis. Stomion helopoides. Solenophorus galapagoensis. ,, laevigatum. Notaphus galapagoensis. Ammophorus obscurus. DYTISCIDAE. ,, cooksoni. Eunectes occidentalis. ,, bifoveatus. Acilius incisus. Pedonoeces galapagoensis. Copelatus galapagoensis. ,, pubescens. PALPICORNES. Phaleria manicata. Tropisternus lateralis. CURCULIONIDAE. Philhydrus sp. Otiorhynchus cuneiformis. STAPHYLINIDAE. Anchonus galapagoensis. Creophilus villosus. LONGICORNIA. NECROPHAGA. Mallodou sp. Acribis serrativentris. Eburia amabilis. Phalacrus darwinii. ANTHRIBIDAE. Dermestes vulpinus. Ormiscus variegatus. MALACODERMS. PHYTOPHAGA Ablechrus darwinii. Diabrotica limbata. Corynetes rufipes. Docema galapagoensis. Bostrichus unciniatus. Longitarsus lunatus. Tetrapriocerca sp. SECURIPALPES. LAMELLICORNES. Scymuns galapagoensis. Copris lugubris. Oryctes galapagoensis.

[114] Mr. H. O. Forbes, who visited these islands in 1878, increased the number of wild plants to thirty-six, and these belonged to twenty-six natural orders.

[115] Juan Fernandez is a good example of a small island which, with time and favourable conditions, has acquired a tolerably rich and highly peculiar flora and fauna. It is situated in 34deg S. Lat., 400 miles from the coast of Chile, and so far as facilities for the transport of living organisms are concerned is by no means in a favourable position, for the ocean-currents come from the south-west in a direction where there is no land but the Antarctic continent, and the prevalent winds are also westerly. No doubt, however, there are occasional storms, and there may have been intermediate islands, but its chief advantages are its antiquity, its varied surface, and its favourable soil and climate, offering many chances for the preservation and increase of whatever plants and animals have chanced to reach it. The island consists of basalt, greenstone, and other ancient rocks, and though only about twelve miles long its mountains are three thousand feet high. Enjoying a moist and temperate climate it is especially adapted to the growth of ferns, which are very abundant; and as the spores of these plants are as fine as dust, and very easily carried for enormous distances by winds, it is not surprising that there are nearly fifty species on the island, while the remote period when it first received its vegetation may be indicated by the fact that nearly half the species are quite peculiar; while of 102 species of flowering plants seventy are peculiar, and there are ten peculiar genera. The same general character pervades the fauna. For so small an island it is rich, containing four true land-birds, about fifty species of insects, and twenty of land-shells. Almost all these belong to South American genera, and a large proportion are South American species; but several of the insects, half the birds, and the whole of the land-shells are peculiar. This seems to indicate that the means of transmission were formerly greater than they are now, and that in the case of land-shells none have been introduced for so long a period that all have become modified into distinct forms, or have been preserved on the island while they have become extinct on the continent. For a detailed examination of the causes which have led to the modification of the humming birds of Juan Fernandez see the chapter on Humming Birds in the author's _Natural Selection and Tropical Nature_, p. 324; while a general account of the fauna of the island is given in his _Geographical Distribution of Animals_, Vol. II. p. 49.

[116] No additions appear to have been made to this flora down to 1885, when Mr. Hemsley published his _Report on the Present State of our Knowledge of Insular Floras_.

[117] _Journal of the Linnean Society_, Vol. XIII., "Botany," p. 556.

[118] _Geographical Distribution of Animals_, Vol. II. p. 81.

[119] _St. Helena: a Physical, Historical, and Topographical Description of the Island, &c._ By John Charles Melliss, F.G.S., &c. London: 1875.

[120] Mr. Marsh in his interesting work entitled _The Earth as Modified by Human Action_ (p. 51), thus remarks on the effect of browsing quadrupeds in destroying and checking woody vegetation.--"I am convinced that forests would soon cover many parts of the Arabian and African deserts if man and domestic animals, especially the goat and the camel, were banished from them. The hard palate and tongue, and strong teeth and jaws of this latter quadruped enable him to break off and masticate tough and thorny branches as large as the finger. He is particularly fond of the smaller twigs, leaves, and seed-pods of the _Sont_ and other acacias, which, like the American robinia, thrive well on dry and sandy soils, and he spares no tree the branches of which are within his reach, except, if I remember right, the tamarisk that produces manna. Young trees sprout plentifully around the springs and along the winter water-courses of the desert, and these are just the halting stations of the caravans and their routes of travel. In the shade of these trees annual grasses and perennial shrubs shoot up, but are mown down by the hungry cattle of the Bedouin as fast as they grow. A few years of undisturbed vegetation would suffice to cover such points with groves, and these would gradually extend themselves over soils where now scarcely any green thing but the bitter colocynth and the poisonous foxglove is ever seen."

[121] _Coleoptera Sanctae Helenae_, 1877; _Testacea Atlantica_, 1878.

[122] On Petermann's map of Africa, in _Stieler's Hand-Atlas_ (1879), the Island of Ascension is shown as seated on a much larger and shallower submarine bank than St. Helena. The 1,000 fathom line round Ascension encloses an oval space 170 miles long by 70 wide, and even the 300 fathom line, one over 60 miles long; and it is therefore probable that a much larger island once occupied this site. Now Ascension is nearly equidistant between St. Helena and Liberia, and such an island might have served as an intermediate station through which many of the immigrants to St. Helena passed. As the distances are hardly greater than in the case of the Azores, this removes whatever difficulty may have been felt of the possibility of _any_ organisms reaching so remote an island. The present island of Ascension is probably only the summit of a huge volcanic mass, and any remnant of the original fauna and flora it might have preserved may have been destroyed by great volcanic eruptions. Mr. Darwin collected some masses of tufa which were found to be mainly organic, containing, besides remains of fresh-water infusoria, the siliceous tissue of plants! In the light of the great extent of the submarine bank on which the island stands, Mr. Darwin's remark, that--"we may feel sure, that at some former epoch, the climate and productions of Ascension were very different from what they are now,"--has received a striking confirmation. (See _Naturalist's Voyage Round the World_, p. 495.)

[123] "Notes on the Classification, History, and Geographical Distribution of Compositae."--_Journal of the Linnean Society_, Vol. XIII. p. 563 (1873).

[124] The Melhaniae comprise the two finest timber trees of St. Helena, now almost extinct, the redwood and native ebony.

[125] _Journal of the Linnean Society_, 1873, p. 496. "On Diversity of Evolution under one set of External Conditions." _Proceedings of the Zoological Society of London_, 1873, p. 80. "On the Classification of the Achitinellidae."

[126] "Memoirs on the Coleoptera of the Hawaiian Islands." By the Rev. T. Blackburn, B.A., and Dr. D. Sharp. _Scientific Transactions of the Royal Dublin Society._ Vol. III. Series II. 1885.

[127] See Hildebrand's _Flora of the Hawaiian Islands_, Introduction, p. xiv.

[128] _Flora of the Hawaiian Islands_, by W. Hildebrand, M.D., annotated and published after the author's death by W. F. Hildebrand, 1888.

[129] These are obtained from Hildebrand's _Flora_ supplemented by Mr. Bentham's paper in the _Journal of the Linnean Society_.

[130] Among the curious features of the Hawaiian flora is the extraordinary development of what are usually herbaceous plants into shrubs or trees. Three species of Viola are shrubs from three to five feet high. A shrubby Silene is nearly as tall; and an allied endemic genus, Schiedea, has numerous shrubby species. _Geranium arboreum_ is sometimes twelve feet high. The endemic Compositae are mostly shrubs, while several are trees reaching twenty or thirty feet in height. The numerous Lobeliaceae, all endemic, are mostly shrubs or trees, often resembling palms or yuccas in habit, and sometimes twenty-five or thirty feet high. The only native genus of Primulaceae--Lysimachia--consists mainly of shrubs; and even a plantain has a woody stem sometimes six feet high.

[131] _Geological Magazine_, 1870, p. 155.

[132] _Transactions of the Edinburgh Geological Society_, Vol. I. p. 330.

[133] _Quarterly Journal of Geological Society_, 1850, p. 96.

[134] _British Association Report_, Dundee, 1867, p. 431.

[135] The list of names was furnished to me by Dr. Guenther, and I have added the localities from the papers containing the original descriptions, and from Dr. Haughton's _British Freshwater Fishes_.

[136] See "The Virginia Colony of Helix nemoralis," T. D. A. Cockerell, in _The Nautilus_, Vol. III. No. 7, p. 73.

[137] I am indebted to Mr. Mitten for this curious fact.

[138] The following remarks by Dr. Richard Spruce, who has made a special study of mosses and especially of hepaticae, are of interest. "From what precedes, I conclude that no existing agency is capable of transporting the germs of our hepatics of tropical type from the torrid zone to Britain, and I venture to suppose that their existence at Killarney dates from the remote period when the vegetation of the whole northern hemisphere partook of a tropical character. If I am challenged to account for their survival through the last glacial period, I reply that, granting even the existence of a universal ice-cap down to the latitude of 40deg in America and 50deg in Europe, it is not to be assumed that the whole extent, even of land, was _perennially_ entombed 'in thrilling regions of thick-ribbed ice.' Towards the southern margin of the ice the climate was probably very similar to that of Greenland and the northern part of Norway at the present day. The summer sun would have great power, and on the borders of sheltered fjords the frozen snow would disappear completely, if only for a very short period, and I ask only for a month or two, not doubting the capacity of our hepatics to survive in a dormant state under the snow for at least ten months in the year. I have gathered mosses in the Pyrenees where the snow had barely left them on August 2nd; by September 25th they were re-covered with snow, and would not be again uncovered till the following year. The mosses of Killarney might even enjoy a longer summer than this; for the gulf-stream laves both sides of the south-western angle of Ireland, and its tepid waters would exert great melting power on the ice-bound coast, preventing at the same time any formation of ice in the sea itself." This passage is the conclusion of a very interesting discussion on the distribution of hepaticae in a paper on "A New Hepatic from Killarney," in the _Journal of Botany_, vol. 25, (Feb. 1887), pp. 33-82, in which many curious facts are given as to the habits and distribution of these curious and beautiful little plants.

[139] While these pages are passing through the press I am informed by my friend Mr. W. H. Beeby that in the Shetland Isles, where he has been collecting for five summers, he has found several plants new to the British flora, and a few altogether undescribed. Among these latter is a very distinct species of Hieracium (_H. Zetlandicum_), which is quite unknown in Scandinavia, and is almost certainly peculiar to the British Islands. Here we have another proof that entirely new species are still to be discovered in the remoter portions of our country.

[140] In the first edition of this work the numbers were 400 and 340, showing the great increase of our knowledge during the last ten years, chiefly owing to the researches of Mr. A. H. Everett in Sarawak and Mr. John Whitehead in North Borneo and the great mountain Kini Balu.

[141] These are Allocotops, Chlorocharis, Androphilus, and Ptilopyga, among the Timeliidae; Tricophoropsis and Oreoctistes among the Brachypodidae; Chlamydochoera among the Campophagidae.

[142] In a letter from Darwin he says:--"Hooker writes to me, 'Miguel has been telling me that the flora of Sumatra and Borneo are identical, and that of Java quite different.'"

[143] "On the Geology of Sumatra," by M. R. D. M. Verbeck. _Geological Magazine_, 1877.

[144] _Pitta megarhynchus_ (Banca) allied to _P. brachyurus_ (Borneo, Sumatra, Malacca); and _Pitta bangkanus_ (Banca) allied to _P. sordidus_ (Borneo and Sumatra).

[145] The following list of the mammalia of the Philippines and the Sulu Islands has been kindly furnished me by Mr. Everett.

QUADRUMANA.

1. Macacus cynomolgus. 2. Tarsius spectrum.

CARNIVORA.

3. Viverra tangalunga. 4. Paradoxurus philippinensis. Also in Palawan. 5. Felis bengalensis. In Negros Island.

UNGULATA.

6. Bubalus mindorensis. Peculiar species. 7. Cervus philippinus. Peculiar species. 8. " alfredi. Peculiar species. 9. " nigricans. Peculiar species. 10. " pseudaxis. Sulu only. Probably introduced. 11. Sus marchesi. Peculiar species.

RODENTIA.

12. Sciurus philippinensis. Peculiar species. 13. Sciurus cagos. Peculiar species. 14. " concinnus. Peculiar. Mindanao and Basilan. 15. Phlaeomys cummingi. Peculiar genus. 16. Mus ephippium. 17. " everetti. Peculiar species.

INSECTIVORA.

18. Crocidura luzoniensis. Peculiar species. 19. Crocidura edwardsiana. Peculiar species. 20. Dendrogale sp. 21. Galeopithecus philippinensis. Peculiar species.

CHIROPTERA.

22. Pteropus leucopterus. 23. " edulis. 24. " hypomelanus. 25. " jubatus. 26. Xantharpyia amplexicaule. 27. Cynopterus marginatus. 28. " jagorii. Peculiar species. 29. Carponycteris australis. 30. Rhinolophus luctus. 31. " philippinensis. Peculiar species. 32. Rhinolophus rufus. Peculiar species. 33. Hipposideros diadema. 34. " pygmaeus. Peculiar species. 35. Hipposideros larvatus. 36. " obscurus. Peculiar species. 37. Hipposideros coronatus. Peculiar species. 38. Hipposideros bicolor. 39. Megaderma spasma. 40. Vesperugo pachypus. 41. " tenuis. 42. Vesperugo abramus. 43. Nycticejus kuhlii. 44. Vespertilio macrotarsus. Peculiar species. 45. Vespertilio capaccinii. 46. Harpiocephalus cyclotis. 47. Kerivoula hardwickii. 48. Kerivoula pellucida. Peculiar species. 49. " jagorii. Peculiar species. 50. Miniopterus schreibersii. 51. " tristis. Peculiar species. 52. Emballonura monticola. 53. Taphyzous melanopogon. 54. Nyctinomus plicatus.

[146] Extracted from Messrs. Blakiston and Pryer's _Catalogue of Birds of Japan_ (_Ibis_, 1878, p. 209), with Mr. Seebohm's additions and corrections in his _Birds of the Japanese Empire_ 1890. Accidental stragglers are not reckoned as British birds.

[147] Mr. Swinhoe died in October, 1877, at the early age of forty-two. His writings on natural history are chiefly scattered through the volumes of the _Proceedings of the Zoological Society_ and _The Ibis_; the whole being summarised in his _Catalogue of the Mammals of South China and Formosa_ (_P. Z. S._, 1870, p. 615), and his _Catalogue of the Birds of China and its Islands_ (_P. Z. S._, 1871, p. 337).

[148] Captain Blakiston has shown that the northern island--Yezo--is much more temperate and less peculiar in its zoology than the central and southern islands. This is no doubt dependent chiefly on the considerable change of climate that occurs on passing the Tsu-garu strait.

[149] See Dr. J. E. Gray's "Revision of the Viverridae," in _Proc. Zool. Soc._ 1864, p. 507.

[150] Some of the Bats of Madagascar and East Africa are said to have their nearest allies in Australia. (See Dobson in _Nature_, Vol. XXX. p. 575.)

[151] This view was, I believe, first advanced by Professor Huxley in his "Anniversary Address to the Geological Society," in 1870. He says:--"In fact the Miocene mammalian fauna of Europe and the Himalayan regions contain, associated together, the types which are at present separately located in the South African and Indian provinces of Arctogaea. Now there is every reason to believe, on other grounds, that both Hindostan south of the Ganges, and Africa south of the Sahara, were separated by a wide sea from Europe and North Asia during the Middle and Upper Eocene epochs. Hence it becomes highly probable that the well-known similarities, and no less remarkable differences, between the present faunae of India and South Africa have arisen in some such fashion as the following: Some time during the Miocene epoch, the bottom of the nummulitic sea was upheaved and converted into dry land in the direction of a line extending from Abyssinia to the mouth of the Ganges. By this means the Dekkan on the one hand and South Africa on the other, became connected with the Miocene dry land and with one another. The Miocene mammals spread gradually over this intermediate dry land; and if the condition of its eastern and western ends offered as wide contrasts as the valleys of the Ganges and Arabia do now, many forms which made their way into Africa must have been different from those which reached the Dekkan, while others might pass into both these sub-provinces."

This question is fully discussed in my _Geographical Distribution of Animals_ (Vol. I., p. 285), where I expressed views somewhat different from those of Professor Huxley, and made some slight errors which are corrected in the present work. As I did not then refer to Professor Huxley's prior statement of the theory of Miocene immigration into Africa (which I had read but the reference to which I could not recall) I am happy to give his views here.

[152] The total number of Madagascar birds is 238, of which 129 are absolutely peculiar to the island, as are thirty-five of the genera. All the peculiar birds but two are land birds. These are the numbers given in M. Grandidier's great work on Madagascar.

[153] _The Ibis_, 1877, p. 334.

[154] In a paper read before the Geological Society in 1874, Mr. H. F. Blanford, from the similarity of the fossil plants and reptiles, supposed that India and South Africa had been connected by a continent, "and remained so connected with some short intervals from the Permian up to the end of the Miocene period," and Mr. Woodward expressed his satisfaction with "this further evidence derived from the fossil flora of the Mesozoic series of India in corroboration of the former existence of an old submerged continent--Lemuria."

Those who have read the preceding chapters of the present work will not need to have pointed out to them how utterly inconclusive is the fragmentary evidence derived from such remote periods (even if there were no evidence on the other side) as indicating geographical changes. The notion that a similarity in the productions of widely separated continents at any past epoch is only to be explained by the existence of a _direct_ land-connection, is entirely opposed to all that we know of the wide and varying distribution of _all_ types at different periods, as well as to the great powers of dispersal over moderate widths of ocean possessed by all animals except mammalia. It is no less opposed to what is now known of the general permanency of the great continental and oceanic areas; while in this particular case it is totally inconsistent (as has been shown above) with the actual facts of the distribution of animals.

[155] _Geographical Distribution of Animals_, Vol. I., pp. 272-292.

[156] The term "Mascarene" is used here in an extended sense, to include all the islands near Madagascar which resemble it in their animal and vegetable productions.

[157] For the birds of the Comoro Islands see _Proc. Zool. Soc._, 1877, p. 295, and 1879, p. 673.

[158] The following is a list of these peculiar birds. (See the _Ibis_, for 1867, p. 359; and 1879, p. 97.)

PASSERES.

_Ellisia seychelensis._ _Copsychus seychellarum._ _Hypsipetes crassirostris._ _Tchitrea corvina._ _Nectarinia dussumieri._ _Zosterops modesta._ " _semiflava._ _Foudia seychellarum._

PSITTACI.

_Coracopsis barklyi._ _Palaeornis wardi._

COLUMBAE.

_Alectoraenas pulcherrimus._ _Turtur rostratus._

ACCIPITRES.

_Tinnunculus gracilis._

[159] Specimens are recorded from West Africa in the _Proceedings of the Academy of Natural Science_, Philadelphia, 1857, p. 72, while specimens in the Paris Museum were brought by D'Orbigny from S. America. Dr. Wright's specimens from the Seychelles have, as he informs me, been determined to be the same species by Dr. Peters of Berlin.

[160] "Additional Notes on the Land-shells of the Seychelles Islands." By Geoffrey Nevill, C.M.Z.S. _Proc. Zool. Soc._ 1869, p. 61.

[161] In Maillard's _Notes sur l'Isle de Reunion_, a considerable number of mammalia are given as "wild," such as _Lemur mongoz_ and _Centetes setosus_, both Madagascar species, with such undoubtedly introduced animals as a wild cat, a hare, and several rats and mice. He also gives two species of frogs, seven lizards, and two snakes. The latter are both Indian species and certainly imported, as are most probably the frogs. Legouat, who resided some years in the island nearly two centuries ago, and who was a closer observer of nature, mentions numerous birds, large bats, land-tortoises, and lizards, but no other reptiles or venomous animals except scorpions. We may be pretty sure, therefore, that the land-mammalia, snakes, and frogs, now found wild, have all been introduced. Of lizards, on the other hand, there are several species, some peculiar to the island, others common to Africa and the other Mascarene Islands. The following list by Prof. Dumeril is given in Maillard's work:--

_Platydactylus cepedianus._ " _ocellatus._ _Hemidactylus peronii._ " _mutilatus._ _Hemidactylus frenatus._ _Gongylus bojerii._ _Ablepharus peronii._

Four species of chameleon are now recorded from Bourbon and one from Mauritius (J. Reay Greene, M.D., in _Pop. Science Rev._ April, 1880), but as they are not mentioned by the old writers, it is pretty certain that these creatures are recent introductions, and this is the more probable as they are favourite domestic pets.

Darwin informed me that in a work entitled _Voyage a l'Isle de France, par un Officier du Roi_, published in 1770, it is stated that a fresh-water fish had been introduced from Batavia and had multiplied. The writer also says (p. 170): "_On a essaye, mais sans succces, d'y transporter des grenouilles qui mangent les oeufs que les moustigues deposent sur les eaux stagnantes._" It thus appears that there were then no frogs on the island.

[162] That the dodo is really an abortion from a more perfect type, and not a direct development from some lower form of wingless bird, is shown by its possessing a keeled sternum, though the keel is exceedingly reduced, being only three-quarters of an inch deep in a length of seven inches. The most terrestrial pigeon--the Didunculus of the Samoan Islands, has a far deeper and better developed keel, showing that in the case of the dodo the degradation has been extreme. We have also analogous examples in other extinct birds of the same group of islands, such as the flightless Rails--Aphanapteryx of Mauritius and Erythromachus of Rodriguez, as well as the large parrot--Lophopsittacus of Mauritius, and the Night Heron, _Nycticorax megacephala_ of Rodriguez, the last two birds probably having been able to fly a little. The commencement of the same process is to be seen in the peculiar dove of the Seychelles, _Turtur rostratus_, which, as Mr. Edward Newton has shown, has much shorter wings than its close ally, _T. picturatus_, of Madagascar. For a full and interesting account of these and other recently extinct birds see Professor Newton's article on "Fossil Birds" in the _Encyclopaedia Britannica_, ninth edition, vol. iii., p. 732; and that on "The Extinct Birds of Rodriguez," by Dr. A. Guenther and Mr. E. Newton, in the Royal Society's volume on the Transit of Venus Expedition.

[163] See _Ibis_, 1877, p. 334.

[164] A common Indian and Malayan toad (_Bufo melanostictus_) has been introduced into Mauritius and also some European toads, as I am informed by Dr. Guenther.

[165] This brief account of the Madagascar flora has been taken from a very interesting paper by the Rev. Richard Baron, F.L.S., F.G.S., in the _Journal of the Linnean Society_, Vol. XXV., p. 246; where much information is given on the distribution of the flora within the island.

[166] It may be interesting to botanists and to students of geographical distribution to give here an enumeration of the endemic genera of the _Flora of the Mauritius and the Seychelles_, as they are nowhere separately tabulated in that work.

Aphloia (Bixaceae) 1 sp., a shrub, Maur., Rod., Sey., also Madagascar. Medusagyne (Ternstroemiaceae) 1 sp., a shrub, Seychelles. Astiria (Sterculiaceae) 1 sp., a shrub, Mauritius. Quivisia (Meliaceae) 3 sp., shrubs, Mauritius (2 sp.), Rodriguez (1 sp.), also Bourbon. Cossignya (Sapindaceae) 1 sp., a shrub, Mauritius, also Bourbon. Hornea ,, 1 sp., a shrub, Mauritius. Stadtmannia ,, 1 sp., a shrub, Mauritius. Doratoxylon ,, 1 sp., a shrub, Mauritius and Bourbon. Gagnebina (Leguminosae) 1 sp., a shrub, Mauritius, also Madagascar. Roussea (Saxifragaceae) 1 sp., a climbing shrub, Mauritius and Bourbon. Tetrataxis (Lythraceae) 1 sp., a shrub, Mauritius. Psiloxylon ,, 1 sp., a shrub, Mauritius and Bourbon. Mathurina (Turneraceae) 1 sp., a shrub, Rodriguez. Foetidia (Myrtaceae) 1 sp., a tree, Mauritius. Danais (Rubiaceae) 4 sp., climbing shrubs, Maur. (1 sp.), Rodr. (1 sp.), also Bourbon and Madagascar. Fernelia (Rubiaceae) 1 sp., a shrub, Mauritius and Rodriguez. Pyrostria ,, 6 sp., shrubs, Mauritius (3 sp.), also Bourbon and Madagascar. Scyphochlamys (Rubiaceae) 1 sp., a shrub, Rodriguez. Myonima ,, 3 sp., shrubs, Mauritius, also Bourbon. Cylindrocline (Compositae) 1 sp., a shrub, Mauritius. Monarrhenus ,, 2 sp., shrubs, Mauritius, also Bourbon and Madagascar. Faujasia (Compositae) 3 sp., shrubs, Mauritius, also Bourbon and Madagascar. Heterochaenia (Campanulaceae) 1 sp., a shrub, Mauritius, also Bourbon. Tanulepis (Asclepiadaceae) 1 sp., a climber, Rodriguez. Decanema ,, 1 sp., a climber, Mauritius, also Madagascar. Nicodemia (Loganiaceae) 2 sp., shrubs, Mauritius (1 sp.), also Comoro Islands and Madagascar. Bryodes (Scrophulariaceae) 1 sp., herb, Mauritius. Radamaea ,, 2 sp., herb, Seychelles (1 sp.), and Madagascar. Colea (Bignoniaceae) 10 sp., Mauritius (1 sp.), Seychelles (1 sp.), also Bourbon and Madagascar. (Shrubs, trees, or climbers.) Obetia (Urticaceae) 2 sp., shrubs, Mauritius, Seychelles, and Madagascar. Bosquiea (Moreae) 3 sp., trees, Seychelles (1 sp.), also Madagascar. Monimia (Monimiaceae) 3 sp., trees, Mauritius (2 sp.), also Bourbon. Cynorchis (Orchideae) 3 sp., herb, ter., Mauritius. Amphorchis ,, 1 sp., herb, ter., Mauritius, also Bourbon. Arnottia ,, 2 sp., herb, ter., Mauritius, also Bourbon. Aplostellis ,, 1 sp., herb, ter., Mauritius. Cryptopus ,, 1 sp., herb, Epiphyte, Mauritius, also Bourbon and Madagascar. Lomatophyllum (Liliaceae) 3 sp., shrubs (succulent), Mauritius, also Bourbon. Lodoicea (Palmae) 1 sp., tree, Seychelles. Latania ,, 3 sp., trees, Mauritius (2 sp.), Rodriguez, also Bourbon. Hyophorbe ,, 3 sp., trees, Mauritius (2 sp.), Rodriguez, also Bourbon. Dictyosperma ,, 1 sp., tree, Mauritius, Rodriguez, also Bourbon. Acanthophaenix ,, 2 sp., trees, Mauritius, also Bourbon. Deckenia ,, 1 sp., tree, Seychelles. Nephrosperma ,, 1 sp., tree, Seychelles. Roscheria ,, 1 sp., tree, Seychelles. Verschaffeltia ,, 1 sp., tree, Seychelles. Stevensonia ,, 1 sp., tree, Seychelles. Ochropteris (Filices) 1 sp., herb, Mauritius, also Bourbon and Madagascar.

Among the curious features in this list are the great number of endemic shrubs in Mauritius, and the remarkable assemblage of five endemic genera of palms in the Seychelles Islands. We may also notice that one palm (_Latania loddigesii_) is confined to Round Island and two other adjacent islets offering a singular analogy to the peculiar snake also found there.

[167]

_Families of Malayan Birds not found in islands East of Celebes._

Troglodytidae. Sittidae. Paridae. Liotrichidae. Phyllornithidae. Eurylaemidae. Picidae. Indicatoridae. Megalaenidae. Trogonidae. Phasianidae.

_Families of Moluccan Birds not found in islands West of Celebes._

Paradiseidae. Meliphagidae. Cacatuidae. Platycercidae. Trichoglossidae. Nestoridae.

[168] For outline figures of the chief types of these butterflies, see my _Malay Archipelago_, Vol. I. p. 441, or p. 216 of the tenth edition.

[169] Dobson on the Classification of Chiroptera (_Ann. and Mag. of Nat. Hist._ Nov. 1875).

[170] See Buller, "On the New Zealand Rat," _Trans. of the N. Z. Institute_ (1870), Vol. III. p. 1, and Vol. IX. p. 348; and Hutton, "On the Geographical Relations of the New Zealand Fauna," _Trans. N. Z. Instit._ 1872, p. 229.

[171] Hochstetter's _New Zealand_, p. 161, note.

[172] The animal described by Captain Cook as having been seen at Pickersgill Harbour in Dusky Bay (Cook's 2nd Voyage, Vol. I. p. 98) may have been the same creature. He says, "A four-footed animal was seen by three or four of our people, but as no two gave the same description of it, I cannot say what kind it is. All, however, agreed that it was about the size of a cat, with short legs, and of a mouse colour. One of the seamen, and he who had the best view of it, said it had a bushy tail, and was the most like a jackal of any animal he knew." It is suggestive that, so far as the points on which "all agreed"--the size and the dark colour--this description would answer well to the animal so recently seen, while the "short legs" correspond to the otter-like tracks, and the thick tail of an otter-like animal may well have appeared "bushy" when the fur was dry. It has been suggested that it was only one of the native dogs; but as none of those who saw it took it for a dog, and the points on which they all agreed are not dog-like, we can hardly accept this explanation; while the actual existence of an unknown animal in New Zealand of corresponding size and colour is confirmed by this account of a similar animal having been seen about a century ago.

[173] Owen, "On the Genus Dinornis," _Trans. Zool. Soc._ Vol. X. p. 184. Mivart, "On the Axial Skeleton of the Struthionidae," _Trans. Zool. Soc._ Vol. X. p. 51.

[174] The recent existence of the Moa and its having been exterminated by the Maoris appears to be at length set at rest by the statement of Mr. John White, a gentleman who has been collecting materials for a history of the natives for thirty-five years, who has been initiated by their priests into all their mysteries, and is said to "know more about the history, habits, and customs of the Maoris than they do themselves." His information on this subject was obtained from old natives long before the controversy on the subject arose. He says that the histories and songs of the Maoris abound in allusions to the Moa, and that they were able to give full accounts of "its habits, food, the season of the year it was killed, its appearance, strength, and all the numerous ceremonies which were enacted by the natives before they began the hunt, the mode of hunting, how cut up, how cooked, and what wood was used in the cooking, with an account of its nest, and how the nest was made, where it usually lived, &c." Two pages are occupied by these details, but they are only given from memory, and Mr. White promises a full account from his MSS. Many of the details given correspond with facts ascertained from the discovery of native cooking places with Moas' bones; and it seems quite incredible that such an elaborate and detailed account should be all invention. (See _Transactions of the New Zealand Institute_, Vol. VIII. p. 79.)

[175] See fig. in _Trans. of N. Z. Institute_, Vol. III., plate 12_b._ fig. 2.

[176] _Geographical Distribution of Animals_, Vol. I., p. 450.

[177] In my _Geographical Distribution of Animals_ (I. p. 541) I have given two peculiar Australian genera (_Orthonyx_ and _Tribonyx_) as occurring in New Zealand. But the former has been found in New Guinea, while the New Zealand bird is considered to form a distinct genus, _Clitonyx_; and the latter inhabits Tasmania, and was recorded from New Zealand through an error. (See _Ibis_, 1873, p. 427.)

[178] The peculiar genera of Australian lizards according to Boulenger's British Museum Catalogue, are as follows:--Family GECKONIDAE: Nephrurus, Rhynchoedura, Heteronota, Diplodactylus, Oedura. Family PYGOPODIDAE (peculiar): Pygopus, Cryptodelma, Delma, Pletholax, Aprasia. Family AGAMIDAE: Chelosania, Amphibolurus, Tympanocryptis, Diporophora, Chlamydosaurus, Moloch, Oreodeira. Family SCINCIDAE: Egerina, Trachysaurus, Hemisphaenodon. Family doubtful: Ophiopsiseps.

[179] These figures are taken from Mr. G. M. Thomson's address "On the Origin of the New Zealand Flora," _Trans. N. Z. Institute_, XIV. (1881), being the latest that I can obtain. They differ somewhat from those given in the first edition, but not so as to affect the conclusions drawn from them.

[180] This accords with the general scarcity of Leguminosae in Oceanic Islands, due probably to their usually dry and heavy seeds, not adapted to any of the forms of aerial transmission; and it would indicate either that New Zealand was never absolutely united with Australia, or that the union was at a very remote period when Leguminosae were either not differentiated or comparatively rare.

[181] Sir Joseph Hooker informs me that the number of tropical Australian plants discovered within the last twenty years is very great, and that the statement as above made may have to be modified. Looking, however, at the enormous disproportion of the figures given in the "Introductory Essay" in 1859 (2,200 tropical to 5,800 temperate species) it seems hardly possible that a great difference should not still exist, at all events as regards species. In Baron von Mueeller's latest summary of the Australian Flora (_Second Systematic Census of Australian Plants_, 1889), he gives the total species at 8,839, of which 3,560 occur in West Australia, and 3,251 in New South Wales. On counting the species common to these two colonies in fifty pages of the _Census_ taken at random, I find them to be about one-tenth of the total species in both. This would give the number of distinct species in these areas as about 6,130. Adding to these the species peculiar to Victoria and South Australia, we shall have a flora of near 6,500 in the temperate parts of Australia. It is true that West Australia extends far into the tropics, but an overwhelming majority of the species have been discovered in the south-western portion of the colony, while the species that may be exclusively tropical will be more than balanced by those of temperate Queensland, which have not been taken account of, as that colony is half temperate and half tropical. It thus appears probable that full three fourths of the species of Australian plants occur in the temperate regions, and are mainly characteristic of it. Sir Joseph Hooker also doubts the generally greater richness of tropical over temperate floras which I have taken as almost an axiom. He says: "Taking similar areas to Australia in the Western World, _e.g._, tropical Africa north of 20deg S. Lat. as against temperate Africa and Europe up to 47deg--I suspect that the latter would present more genera and species than the former." This, however, appears to me to be hardly a case in point, because Europe is a distinct continent from Africa and has had a very different past history, and it is not a fair comparison to take the tropical area in one continent while the temperate is made up of widely separated areas in two continents. A closer parallel may perhaps be found in equal areas of Brazil and south temperate America, or of Mexico and the Southern United States, in both of which cases I suppose there can be little doubt that the tropical areas are far the richest. Temperate South Africa is, no doubt, always quoted as richer than an equal area of tropical Africa or perhaps than any part of the world of equal extent, but this is admitted to be an exceptional case.

[182] Sir Joseph Hooker thinks that later discoveries in the Australian Alps and other parts of East and South Australia may have greatly modified or perhaps reversed the above estimate, and the figures given in the preceding note indicate that this is so. But still, the small area of South-west Australia will be, proportionally, far the richer of the two. It is much to be desired that the enormous mass of facts contained in Mr. Bentham's _Flora Australiensis_ and Baron von Mueeller's _Census_ should be tabulated and compared by some competent botanist, so as to exhibit the various relations of its wonderful vegetation in the same manner as was done by Sir Joseph Hooker with the materials available twenty-one years ago.

[183] From an examination of the fossil corals of the South-west of Victoria, Professor P. M. Duncan concludes--"that, at the time of the formation of these deposits the central area of Australia was occupied by sea, having open water to the north, with reefs in the neighbourhood of Java." The age of these fossils is not known, but as almost all are extinct species, and some are almost identical with European Pliocene and Miocene species, they are supposed to belong to a corresponding period. (_Journal of Geol. Soc._, 1870.)

[184] "On the Origin of the Fauna and Flora of New Zealand," by Captain F. W. Hutton, in _Annals and Mag. of Nat. Hist._ Fifth series, p. 427 (June, 1884).

[185] To these must now be added the genera Sequoia, Myrica, Aralia, and Acer, described by Baron von Ettingshausen. (_Trans. N.Z. Institute_, xix., p. 449.)

[186] The large collection of fossil plants from the Tertiary beds of New Zealand which have been recently described by Baron von Ettingshausen (_Trans. N. Z. Inst._, vol. xxiii., pp. 237-310), prove that a change in the vegetation has occurred similar to that which has taken place in Eastern Australia, and that the plants of the two countries once resembled each other more than they do now. We have, first, a series of groups now living in Australia, but which have become extinct in New Zealand, as Cassia, Dalbergia, Eucalyptus, Diospyros, Dryandra, Casuarina, and Ficus; and also such northern genera as Acer, Planera, Ulmus, Quercus, Alnus, Myrica, and Sequoia. All these latter, except Ulmus and Planera, have been found also in the Eastern-Australian Tertiaries, and we may therefore consider that at this period the northern temperate element in both floras was identical. If this flora entered both countries from the south, and was really Antarctic, its extinction in New Zealand may have been due to the submergence of the country to the south, and its elevation and extension towards the tropics, admitting of the incursion of the large number of Polynesian and tropical Australian types now found there; while the Australian portion of the same flora may have succumbed at a somewhat later period, when the elevation of the Cretaceous and Tertiary sea united it with Western Australia, and allowed the rich typical Australian flora to overrun the country. Of course we are assuming that the identification of these genera is for the most part correct, though almost entirely founded on leaves only. Fuller knowledge, both of the extinct flora itself and of the geological age of the several deposits, is requisite before any trustworthy explanation of the phenomena can be arrived at.

[187] The following are the tropical genera common to New Zealand and Australia:--

1. _Melicope._ Queensland, Pacific Islands. 2. _Eugenia._ Eastern and Tropical Australia, Asia, and America. 3. _Passiflora._ N.S.W. and Queensland, Tropics of Old World and America. 4. _Myrsine._ Tropical and Temperate Australia, Tropical and Sub-tropical regions. 5. _Sapota._ Australia, Norfolk Islands, Tropics. 6. _Cyathodes._ Australia and Pacific Islands. 7. _Parsonsia._ Tropical Australia and Asia. 8. _Geniostoma._ Queensland, Polynesia, Asia. 9. _Mitrasacme._ Tropical and Temperate Australia, India. 10. _Ipomoea._ Tropical Australia, Tropics. 11. _Mazus._ Temperate Australia, India, China. 12. _Vitex._ Tropical Australia, Tropical and Sub-tropical. 13. _Pisonia._ Tropical Australia, Tropical and Sub-tropical. 14. _Alternanthera._ Tropical Australia, India, and S. America. 15. _Tetranthera._ Tropical Australia, Tropics. 16. _Santalum._ Tropical and Sub-tropical Australia, Pacific, Malay Islands. 17. _Carumbium._ Tropical and Sub-tropical Australia, Pacific Islands. 18. _Elatostemma._ Sub-tropical Australia, Asia, Pacific Islands. 19. _Peperomia._ Tropical and Sub-tropical Australia, Tropics. 20. _Piper._ Tropical and Sub-tropical Australia, Tropics. 21. _Dacrydium._ Tasmania, Malay, and Pacific Islands. 22. _Dammara._ Tropical Australia, Malay, and Pacific Islands. 23. _Dendrobium._ Tropical Australia, Eastern Tropics. 24. _Bolbophyllum._ Tropical and Sub-tropical Australia, Tropics. 25. _Sarcochilus._ Tropical and Sub-tropical Australia, Fiji, and Malay Islands. 26. _Freycinetia._ Tropical Australia, Tropical Asia. 27. _Cordyline._ Tropical Australia, Pacific Islands. 28. _Dianella._ Australia, India, Madagascar, Pacific Islands. 29. _Cyperus._ Australia, Tropical regions mainly. 30. _Fimbristylis._ Tropical Australia, Tropical regions. 31. _Paspalum._ Tropical and Sub-tropical grasses. 32. _Isachne._ Tropical and Sub-tropical grasses. 33. _Sporobolus._ Tropical and Sub-tropical grasses.

[188] Insects are tolerably abundant in the open mountain regions, but very scarce in the forests. Mr. Meyrick says that these are "strangely deficient in insects, the same species occurring throughout the islands;" and Mr. Pascoe remarked that "the forests of New Zealand were the most barren country, entomologically, he had ever visited." (_Proc. Ent. Soc._, 1883. p. xxix.)

[189] Introductory Essay _On the Flora of Australia_, p. 130.

[190] Hooker, _On the Flora of Australia_, p. 95.--H. C. Watson, in Godman's _Azores_, pp. 278-286.

[191] As this is a point of great interest in its bearing on the dispersal of plants by means of mountain ranges, I have endeavoured to obtain a few illustrative facts:--

1. Mr. William Mitten, of Hurstpierpoint, Sussex, informs me that when the London and Brighton railway was in progress in his neighbourhood, _Melilotus vulgaris_ made its appearance on the banks, remained for several years, and then altogether disappeared. Another case is that of _Diplotaxis muralis_, which formerly occurred only near the sea-coast of Sussex, and at Lewes; but since the railway was made has spread along it, and still maintains itself abundantly on the railway banks though rarely found anywhere else.

2. A correspondent in Tasmania informs me that whenever the virgin forest is cleared in that island there invariably comes up a thick crop of a plant locally known as fire-weed--a species of Senecio, probably _S. Australis_. It never grows except where the fire has gone over the ground, and is unknown except in such places. My correspondent adds:--"This autumn I went back about thirty-five miles through a dense forest, along a track marked by some prospectors the year before, and in one spot where they had camped, and the fire had burnt the fallen logs, &c., there was a fine crop of 'fire-weed.' All around for many miles was a forest of the largest trees and dense scrub." Here we have a case in which burnt soil and ashes favour the germination of a particular plant, whose seeds are easily carried by the wind, and it is not difficult to see how this peculiarity might favour the dispersal of the species for enormous distances, by enabling it temporarily to grow and produce seeds on burnt spots.

3. In answer to an inquiry on this subject, Mr. H. C. Watson has been kind enough to send me a detailed account of the progress of vegetation on the railway banks and cuttings about Thames Ditton. This account is written from memory, but as Mr. Watson states that he took a great interest in watching the process year by year, there can be no reason to doubt the accuracy of his memory. I give a few extracts which bear especially on the subject we are discussing.

"One rather remarkable biennial plant appeared early (the second year, as I recollect) and renewed itself either two or three years, namely, _Isatis tinctoria_--a species usually supposed, to be one of our introduced, but pretty well naturalised, plants. The nearest stations then or since known to me for this _Isatis_ are on chalk about Guildford, twenty miles distant. There were two or three plants of it at first, never more than half a dozen. Once since I saw a plant of _Isatis_ on the railway bank near Vauxhall.

"Close by Ditton Station three species appeared which may be called interlopers. The biennial _Barbarea precox_, one of these, is the least remarkable, because it might have come as seed in the earth from some garden, or possibly in the Thames gravel (used as ballast). At first it increased to several plants, then became less numerous, and will soon, in all probability, become extinct, crowded out by other plants. The biennial _Petroselinum segetum_ was at first one very luxuriant plant on the slope of the embankment. It increased by seed into a dozen or a score, and is now nearly if not quite extinct. The third species is _Linaria purpurea_, not strictly a British plant, but one established in some places on old walls. A single root of it appeared on the chalk facing of the embankment by Ditton Station. It has remained there several years and grown into a vigorous specimen. Two or three smaller examples are now seen by it, doubtless sprung from some of the hundreds or thousands of seeds shed by the original one plant. The species is not included in Salmon and Brewer's _Flora of Surrey_.

"The main line of the railway has introduced into Ditton parish the perennial _Arabis hirsuta_, likely to become a permanent inhabitant. The species is found on the chalk and greensand miles away from Thames Ditton; but neither in this parish nor in any adjacent parish, so far as known to myself or to the authors of the flora of the county, does it occur. Some years after the railway was made a single root of this _Arabis_ was observed in the brickwork of an arch by which the railway is carried over a public road. A year or two afterwards there were three or four plants. In some later year I laid some of the ripened seed-pods between the bricks in places where the mortar had partly crumbled out. Now there are several scores of specimens in the brickwork of the arch. It is presumable that the first seed may have been brought from Guildford. But how could it get on to the perpendicular face of the brickwork?

"The Bee Orchis (_Ophrys apifera_), plentiful on some of the chalk lands in Surrey, is not a species of Thames Ditton, or (as I presume) of any adjacent parish. Thus, I was greatly surprised some years back to see about a hundred examples of it in flower in one clayey field either on the outskirts of Thames Ditton or just within the limits of the adjoining parish of Cobham. I had crossed this same field in a former year without observing the Ophrys there. And on finding it in the one field I closely searched the surrounding fields and copses, without finding it anywhere else. Gradually the plants became fewer and fewer in that one field, and some six or eight years after its first discovery there the species had quite disappeared again. I guessed it had been introduced with chalk, but could obtain no evidence to show this."

4. Mr. A. Bennett, of Croydon, has kindly furnished me with some information on the temporary vegetation of the banks and cuttings on the railway from Yarmouth to Caistor in Norfolk, where it passes over extensive sandy Denes with a sparse vegetation. The first year after the railway was made the banks produced abundance of _Oenothera odorata_ and _Delphinium Ajacis_ (the latter only known thirty miles off in cornfields in Cambridgeshire), with _Atriplex patula_ and _A. deltoidea_. Gradually the native sand plants--Carices, Grasses, _Galium verum_, &c., established themselves, and year by year covered more ground till the new introductions almost completely disappeared. The same phenomenon was observed in Cambridgeshire between Chesterton and Newmarket, where, the soil being different, _Stellaria media_ and other annuals appeared in large patches; but these soon gave way to a permanent vegetation of grasses, composites, &c., so that in the third year no _Stellaria_ was to be seen.

5. Mr. T. Kirk (writing in 1878) states that--"in Auckland, where a dense sward of grass is soon formed, single specimens of the European milk Thistle (_Carduus marianus_) have been known for the past fifteen years; but although they seeded freely, the seeds had no opportunity of germinating, so that the thistle did not spread. A remarkable exception to this rule occurred during the formation of the Onehunga railway, where a few seeds fell on disturbed soil, grew up and flowered. The railway works being suspended, the plant increased rapidly, and spread wherever it could find disturbed soil."

Again:--"The fiddle-dock (_Rumex pulcher_) occurs in great abundance on the formation of new streets, &c., but soon becomes comparatively rare. It seems probable that it was one of the earliest plants naturalised here, but that it partially died out, its buried seeds retaining their vitality."

_Medicago sativa_ and _Apium graveolens_, are also noted as escapes from cultivation which maintain themselves for a time but soon die out. (_Transactions of the New Zealand Institute_, Vol. X. p. 367.)

The preceding examples of the _temporary_ establishment of plants on newly exposed soil, often at considerable distances from the localities they usually inhabit, might, no doubt, by further inquiry be greatly multiplied; but, unfortunately, the phenomenon has received little attention, and is not even referred to in the elaborate work of De Candolle (_Geographie Botanique Raisonnee_) in which almost every other aspect of the dispersion and distribution of plants is fully discussed. Enough has been advanced, however, to show that it is of constant occurrence, and from the point of view here advocated it becomes of great importance in explaining the almost world-wide distribution of many common plants of the north temperate zone.

[192] Sir Joseph Hooker informs me that he considers these identifications worthless, and Mr. Bentham has also written very strongly against the value of similar identifications by Heer and Unger. Giving due weight to the opinions of these eminent botanists we must admit that Australian genera have not yet been _demonstrated_ to have existed in Europe during the Tertiary period; but, on the other hand, the evidence that they did so appears to have some weight, on account of the improbability that the numerous resemblances to Australian plants which have been noticed by different observers should _all_ be illusory; while the well established fact of the former wide distribution of many tropical or now restricted types of plants and animals, so frequently illustrated in the present volume, removes the antecedent improbability which is supposed to attach to such identifications. I am myself the more inclined to accept them, because, according to the views here advocated, such migrations must have taken place at remote as well as at recent epochs; and the preservation of some of these types in Australia while they have become extinct in Europe, is exactly paralleled by numerous facts in the distribution of animals which have been already referred to in Chapter XIX., and elsewhere in this volume, and also repeatedly in my larger work.

[193] Out of forty-two genera from the Eocene of Sheppey enumerated by Dr. Ettingshausen in the _Geological Magazine_ for January 1880, only two or three appear to be extinct, while there is a most extraordinary intermixture of tropical and temperate forms--Musa, Nipa, and Victoria, with Corylus, Prunus, Acer, &c. The rich Miocene flora of Switzerland, described by Professor Heer, presents a still larger proportion of living genera.

[194] The recent discovery by Lieutenant Jensen of a rich flora on rocky peaks rising out of the continental ice of Greenland, as well as the abundant vegetation of the highest northern latitudes, renders it possible that even now the Antarctic continent may not be wholly destitute of vegetation, although its climate and physical condition are far less favourable than those of the Arctic lands. (See _Nature_, Vol. XXI. p. 345.)

[195] Dr. Hector notes the occurrence of the genus _Dammara_ in Triassic deposits, while in the Jurassic period New Zealand possessed the genera _Palaeozamia_, _Oleandrium_, _Alethopteris_, _Camptopteris_, _Cycadites_, _Echinostrobus_, &c., all Indian forms of the same age. Neocomian beds contain a true dicotyledonous leaf with _Dammara_ and _Araucaria_. The Cretaceous deposits have produced a rich flora of dicotyledonous plants, many of which are of the same genera as the existing flora; while the Miocene and other Tertiary deposits produce plants almost identical with those now inhabiting the country, together with many North Temperate genera which have since become extinct. (See p. 499, footnote, and _Trans. New Zealand Inst._, Vol. XI. 1879, p. 536.)

[196] The fact stated in the last edition of the _Origin of Species_ (p. 340) on the authority of Sir Joseph Hooker, that Australian plants are rapidly sowing themselves and becoming naturalised on the Neilgherrie mountains in the southern part of the Indian Peninsula, though an exception to the rule of the inability of Australian plants to become naturalised in the Northern Hemisphere, is yet quite in harmony with the hypothesis here advocated. For not only is the climate of the Neilgherries more favourable to Australian plants than any part of the North Temperate zone, but the entire Indian Peninsula has existed for unknown ages as an _island_ and thus possesses the "insular" characteristic of a comparatively poor and less developed flora and fauna as compared with the truly "continental" Malayan and Himalayan regions. Australian plants are thus enabled to compete with those of the Indian Peninsula highlands with a fair chance of success.

* * * * *

Corrections made to printed original.

Page 10. "the general stability of continents": 'sontinents' in original.

Pages 35, 250, 361, 363 "oenanthe" read for "aenanthe" throughout for consistency

Page 50. "some others of the lower animals": 'animials' in original.

Page 82. "transmission along mountain chains": 'mountains chains' in original.

Page 99. "our present land masses": 'massses' in original.

Page 149. "the whole earth should theoretically be": 'thoretically' in original.

Page 200. "the flora and fauna, in the British area": 'Brittish' in original.

Page 234. "the indications of an uninterrupted warm climate": 'indic-tions' on line break in original.

Page 306. "artificially removed by man": 'artifically' in original.

Page 346. "Elachista rufocinerea, the larva of which ...": 'lava' in original.

Page 456. "Cynopithecus nigrescens": 'Cynopitheus' in original.

Footnote 100. "S. B. J. Skertchley": 'S. B. K.' in original. I have left the name as Skertchley as Wallace uses this spelling almost consistently, although Skertchly (as on p. 118) appears to be correct.--Tr.

Footnote 105. "the transportation of the plants": 'transporation' in original.

Footnote 110. "Agriolimax campestris": 'Agriolimaoe' (ligand oe) in original.