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
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
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
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
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
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. 61°. 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
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 striæ, 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
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
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
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
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 palæontological 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
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,
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
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
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."
INDEX
A.
Acacia, wide range of in Australia, [185]
Acacia heterophylla, and Acacia koa, [443]
Acæna in California, [527]
Accipiter hawaii, [314]
Achatinellinæ, average range of, [317]
Ægialitis sanctæ-helenæ, [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]
Alectorænas 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, palæontological 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]
Amphisbænidæ, [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]
Angræcum 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 Palæozoic 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]
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]
orchideæ 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 compositæ of the Galapagos, [288]
on the compositæ of St. Helena, [307]
on the Mascarene compositæ, [445]
on Sandwich Island compositæ, [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]
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]
wingless, of New Zealand, [476]
Blackburn, Mr. T., on the beetles of the Sandwich Islands, [318]
Blakiston and Pryer on birds of Japan, [396]
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]
Bovidæ, [29]
Brady, Mr. H. B., on habitat of globigerinæ, [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 Hepaticæ 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]
Cæcilia, species of, in the Seychelles, [432]
wide distribution of, [432]
Cæciliadæ, [28]
Callithea Leprieuri, distribution of, [18]
Callithea sapphira, [18]
Camels as destroyers of vegetation, [296]
former wide distribution of, [421]
Campanula vidalii, [261]
Carabus, numerous species of, [42]
Carboniferous boulder-beds, [201]
warm Arctic climate, [201]
Carnivora in Madagascar, [417]
Carpenter, Dr., on habitat of globigerinæ, [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]
Cebibæ, 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]
Centetidæ, [27]
Centetidæ, formerly inhabited Europe, [420]
Central America, mixed fauna of, [53]
Ceratodus, or mud-fish, [69]
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]
Chrysochloridæ, [29]
Cicindela, [17]
Cicindelidæ common to South America and Madagascar, [28]
Clay, red, of Bermuda, [265]
Climate, astronomical causes of changes of, [126]
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 Palæozoic 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]
Compositæ 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]
Cossonidæ, 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]
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 Palæozoic 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]
Dendrœca, [19]
D. cœrulea, [19]
D. discolor, [19]
D. dominica, [19]
Dendrœca coronata, variation of, [58]
Dendrophidæ, [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]
Dididæ, 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]
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]
Dryiophidæ, [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]
Echimyidæ, [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 schœniclus, 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]
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]
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. lanceolatus, [22]
G. bispecularis, [22]
G. sinensis, [22]
G. taivanus, [22]
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]
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]
Globigerinæ, 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 Achatinellinæ, [318]
Günther, 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]
Hepaticæ, 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]
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]
Icteridæ, [50]
Iguanidæ, [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]
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]
Leguminosæ, 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]
Lepidosternidæ, [27]
Limestone as indicating change of sea and land, [84]
Limnæa involuta, [356]
Linaria purpurea, on railway bank, [514]
Liopelma hochstetteri, in New Zealand, [483]
Liotrichidæ, [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]
Lobeliaceæ, 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 Palæarctic 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]
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]
Megalæmidæ, [27]
Meleagris, [50]
Melilotus vulgaris, on railway banks, [513]
Meliphagidæ, [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 hepaticæ, [365], [368]
on temporary appearance of plants, [513]
Mniotiltidæ, 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]
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]
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]
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]
Nordenskjöld, 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]
Octodontidæ, [27]
Œnanthe fluviatilis, [361]
Œninghen, Miocene flora of, [183]
Œnothera 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]
Orchideæ, 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]
Palæarctic Region, limits of, [39]
characteristic features of, [41]
Palæozoic 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, Palæarctic, [42]
Parus ater, [19]
P. britannicus, [321]
P. camtschatkensis, [19]
P. cinctus, [20]
P. cœruleus, [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. teneriffæ, [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]
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]
Pœcilozonites, 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]
Pteroptochidæ, [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]
Rhodolæna altivola in Madagascar, [440]
Rhus toxicodendron in Bermuda, [272]
Ridgway, Mr., on birds of Galapagos, [281]
River-channels, buried, [336]
Roches moutonnées, [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]
Scotophilus tuberculatus in New Zealand, [474]
Scrophularincæ, 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]
summary of conclusions on the rate of formation of the, [221]
Seebohm, Mr., on Parus palustris, [65]
on Emberiza schœniclus, [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, Palæarctic, [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]
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 hepaticæ, [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]
Striæ flammea, range of, [15]
Struthiones, [30]
Struthious birds of New Zealand as indicating past changes, [478]
Stylidium, wide range of, [185]
Submerged forests, [334]
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]
Sylviadæ, overlapping genera of, [29]
T.
Talpidæ, a Palæarctic 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 Palæarctic 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]
Tragulidæ, [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 fuscescens, variation of, [58], [59]
Tylor, A., on estimating the rate of denudation, [214]
Tyrannidæ, an American family, [50]
U.
Uraniidæ, [28]
Uropeltidæ, [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]
Vireonidæ, an American family, [49]
W.
Wallich, Dr., on habitat of globigerinæ, [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]
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
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 Palæontology, 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 Palæarctic 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 Palæarctic Region has been furnished me by Mr. G. A. Boulenger, of the British Museum:—
| Snakes. | Frogs and Toads. |
| Achalinus—China, Japan. Cœlopeltis—S. Eur., N. Af., S.W. Asia. Macroprotodon—S. Eur., N. Af. Taphrometopon—Cent. Asia. | Pelobates—Eur., S.W. Asia. Pelodytes—W. Europe. Discoglossus—S. Eur., N.W. Af. Bombinator—Eur., Temp. Asia. Alytus—Cent. and W. Eur. |
| Lizards. | Newts. |
| Phrynocephalus—Cent. and S.W. Asia. Anguis—Europe, W. Asia. Blanus—S.W. Eur., N.W. Africa, S.W. Asia. Trogonophis—N.W. Africa. Lacerta—Eur., Temp. Asia, N. Africa (one sp. in W. Af.). Psammodromus—S.W. Eur., N.W. Africa. Algiroides—S. Eur. | Salamandra—Eur., N. Af., S.W. Asia. Chioglossa—Spain and Portugal. Salamandrina—Italy. Pachytriton—East Thibet. Hynobius—China and Japan. Geomolge—E. Manchuria. Onychodactylus—Japan. Salamandrella—Siberia. Ranidens—Siberia. Batrachyperus—East Thibet. 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. schœniclus, 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 Globigerinæ 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 Globigerinæ "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, Folkestone. | White Chalk, 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 débris | 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 débris, 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 débris 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 débris. 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 débris 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 Primæval 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 Archæology" 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 -128° F. instead of -239° F. If this corrected amount were used in our calculations, the January temperature of England during the glacial epoch would come out 17° 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. Nordenskjöld'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. Szabó 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 Palæozoic, 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 27° and 30° S. Lat.; since the Andes, which in 32° S. Lat. reach 23,300 feet high, and in 28° 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-aërial 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):—
| Latitude. | Present Temperature. | Miocene Temperature. | Difference. | |
| 1. Switzerland | 47°.00 | 53°.6 F | 69°.8 F | 16°.2 F |
| 2. Dantzig | 54°.21 | 45°.7 ,, | 62°.6 ,, | 16°.9 ,, |
| 3. Iceland | 65°.30 | 35°.6 ,, | 48°.2 ,, | 12°.6 ,, |
| 4. Mackenzie River | 65°.00 | 19°.4 ,, | 48°.2 ,, | 28°.8 ,, |
| 5. Disco (Greenland) | 70°.00 | 19°.6 ,, | 55°.6 ,, | 36°.0 ,, |
| 6. Spitzbergen | 78°.00 | 16°.5 ,, | 51°.8 ,, | 35°.3 ,, |
| 7. Grinnell Land | 81°.44 | 1°.7 ,, | 42°.3 ,, | 44°.0 ,, |
It is interesting to note that Iceland, which is now exposed to the full influence of the Gulf Stream, was only 12°.6 F. warmer in Miocene times, while Mackenzie River, now totally removed from its influence was 28° 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 80° 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 Palæozoic 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 Palæozoic 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 51½ 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-aërial, 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-aërial 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 Palæozoic 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 édition de la Carte Géologique 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.
[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. Acæna, 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 Débris 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. schivelyæ 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. Günther, 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.
| Carabidæ. Feronia calathoides. ,, insularis. ,, galapagoensis. Amblygnathus obscuricornis. Solenophorus galapagoensis. Notaphus galapagoensis. Dytiscidæ. Eunectes occidentalis. Acilius incisus. Copelatus galapagoensis. Palpicornes. Tropisternus lateralis. Philhydrus sp. Staphylinidæ. Creophilus villosus. Necrophaga. Acribis serrativentris. Phalacrus darwinii. Dermestes vulpinus. Malacoderms. Ablechrus darwinii. Corynetes rufipes. Bostrichus unciniatus. Tetrapriocerca sp. Lamellicornes. Copris lugubris. Oryctes galapagoensis. |
Elateridæ. Physorhinus galapagoensis Heteromera. Allecula n. s. Stomion helopoides. ,, lævigatum. Ammophorus obscurus. ,, cooksoni. ,, bifoveatus. Pedonœces galapagoensis. ,, pubescens. Phaleria manicata. Curculionidæ. Otiorhynchus cuneiformis. Anchonus galapagoensis. Longicornia. Mallodou sp. Eburia amabilis. Anthribidæ. Ormiscus variegatus. Phytophaga. Diabrotica limbata. Docema galapagoensis. Longitarsus lunatus. Securipalpes. Scymuns 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 34° 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 Sanctæ Helenæ, 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 Compositæ."—Journal of the Linnean Society, Vol. XIII. p. 563 (1873).
[124] The Melhaniæ 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 Achitinellidæ."
[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 Compositæ are mostly shrubs, while several are trees reaching twenty or thirty feet in height. The numerous Lobeliaceæ, 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 Primulaceæ—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. Günther, 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 hepaticæ, 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 40° in America and 50° 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 hepaticæ 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 Timeliidæ; Tricophoropsis and Oreoctistes among the Brachypodidæ; Chlamydochœra among the Campophagidæ.
[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. ,, cagos. Peculiar species. 14. ,, concinnus. Peculiar. Mindanao and Basilan. 15. Phlæomys cummingi. Peculiar genus. 16. Mus ephippium. 17. ,, everetti. Peculiar species. Insectivora. 18. Crocidura luzoniensis. Peculiar species. 19. ,, 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. ,, rufus. Peculiar species. 33. Hipposideros diadema. 34. ,, pygmæus. Peculiar species. 35. ,, larvatus. 36. ,, obscurus. Peculiar species. 37. ,, coronatus. Peculiar species. 38. ,, bicolor. 39. Megaderma spasma. 40. Vesperugo pachypus. 41. ,, tenuis. 42. ,, abramus. 43. Nycticejus kuhlii. 44. Vespertilio macrotarsus. Peculiar species. 45. ,, capaccinii. 46. Harpiocephalus cyclotis. 47. Kerivoula hardwickii. 48. ,, 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 Viverridæ," 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 Arctogæa. 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 faunæ 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. Palæornis wardi. Columbæ. Alectorænas 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 Réunion, 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 à 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 essayé, mais sans succcès, d'y transporter des grenouilles qui mangent les œufs 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 Encyclopædia Britannica, ninth edition, vol. iii., p. 732; and that on "The Extinct Birds of Rodriguez," by Dr. A. Günther 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. Günther.
[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 (Bixaceæ) | 1 sp., a shrub, Maur., Rod., Sey., also Madagascar. |
| Medusagyne (Ternströmiaceæ) | 1 sp., a shrub, Seychelles. |
| Astiria (Sterculiaceæ) | 1 sp., a shrub, Mauritius. |
| Quivisia (Meliaceæ) | 3 sp., shrubs, Mauritius (2 sp.), Rodriguez (1 sp.), also Bourbon. |
| Cossignya (Sapindaceæ) | 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 (Leguminosæ) | 1 sp., a shrub, Mauritius, also Madagascar. |
| Roussea (Saxifragaceæ) | 1 sp., a climbing shrub, Mauritius and Bourbon. |
| Tetrataxis (Lythraceæ) | 1 sp., a shrub, Mauritius. |
| Psiloxylon ,, | 1 sp., a shrub, Mauritius and Bourbon. |
| Mathurina (Turneraceæ) | 1 sp., a shrub, Rodriguez. |
| Fœtidia (Myrtaceæ) | 1 sp., a tree, Mauritius. |
| Danais (Rubiaceæ) | 4 sp., climbing shrubs, Maur. (1 sp.), Rodr. (1 sp.), also Bourbon and Madagascar. |
| Fernelia (Rubiaceæ) | 1 sp., a shrub, Mauritius and Rodriguez. |
| Pyrostria ,, | 6 sp., shrubs, Mauritius (3 sp.), also Bourbon and Madagascar. |
| Scyphochlamys (Rubiaceæ) | 1 sp., a shrub, Rodriguez. |
| Myonima ,, | 3 sp., shrubs, Mauritius, also Bourbon. |
| Cylindrocline (Compositæ) | 1 sp., a shrub, Mauritius. |
| Monarrhenus ,, | 2 sp., shrubs, Mauritius, also Bourbon and Madagascar. |
| Faujasia (Compositæ) | 3 sp., shrubs, Mauritius, also Bourbon and Madagascar. |
| Heterochænia (Campanulaceæ) | 1 sp., a shrub, Mauritius, also Bourbon. |
| Tanulepis (Asclepiadaceæ) | 1 sp., a climber, Rodriguez. |
| Decanema ,, | 1 sp., a climber, Mauritius, also Madagascar. |
| Nicodemia (Loganiaceæ) | 2 sp., shrubs, Mauritius (1 sp.), also Comoro Islands and Madagascar. |
| Bryodes (Scrophulariaceæ) | 1 sp., herb, Mauritius. |
| Radamæa ,, | 2 sp., herb, Seychelles (1 sp.), and Madagascar. |
| Colea (Bignoniaceæ) | 10 sp., Mauritius (1 sp.), Seychelles (1 sp.), also Bourbon and Madagascar. (Shrubs, trees, or climbers.) |
| Obetia (Urticaceæ) | 2 sp., shrubs, Mauritius, Seychelles, and Madagascar. |
| Bosquiea (Moreæ) | 3 sp., trees, Seychelles (1 sp.), also Madagascar. |
| Monimia (Monimiaceæ) | 3 sp., trees, Mauritius (2 sp.), also Bourbon. |
| Cynorchis (Orchideæ) | 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 (Liliaceæ) | 3 sp., shrubs (succulent), Mauritius, also Bourbon. |
| Lodoicea (Palmæ) | 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. |
| Acanthophænix ,, | 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.
| Families of Malayan Birds not found in islands East of Celebes. | Families of Moluccan Birds not found in islands West of Celebes. |
| Troglodytidæ. Sittidæ. Paridæ. Liotrichidæ. Phyllornithidæ. Eurylæmidæ. Picidæ. Indicatoridæ. Megalænidæ. Trogonidæ. Phasianidæ. |
Paradiseidæ. Meliphagidæ. Cacatuidæ. Platycercidæ. Trichoglossidæ. Nestoridæ. |
[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 Struthionidæ," 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 12b. 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 Geckonidæ: Nephrurus, Rhynchœdura, Heteronota, Diplodactylus, Œdura. Family Pygopodidæ (peculiar): Pygopus, Cryptodelma, Delma, Pletholax, Aprasia. Family Agamidæ: Chelosania, Amphibolurus, Tympanocryptis, Diporophora, Chlamydosaurus, Moloch, Oreodeira. Family Scincidæ: Egerina, Trachysaurus, Hemisphænodon. 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 Leguminosæ in Oceanic Islands, due probably to their usually dry and heavy seeds, not adapted to any of the forms of aërial 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 Leguminosæ 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 Müeller'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 20° S. Lat. as against temperate Africa and Europe up to 47°—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 Müeller'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. Ipomœa. 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 Œnothera 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 (Géographie Botanique Raisonnée) 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 Palæozamia, 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.