F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

similar means. Out of twenty seeds or animals transported to an island, even if far less well-stocked than Britain, perhaps not more than one would be so well fitted to its new home, as to become naturalised. But this, as it seems to me, is no valid argument against what would be effected by occasional means of transport, during the long lapse of geological time, whilst an island was being upheaved, and before it had become fully stocked with inhabitants. On almost bare land, with few or no

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

difficulties are insuperable; though they often are in this case, and in that of the individuals of the same species, extremely great. As exemplifying the effects of climatal changes on distribution, I have attempted to show how important has been the influence of the modern Glacial period, which I am fully convinced simultaneously affected the whole world, or at least great longitudinal belts. As showing how diversified are the means of occasional transport, I have discussed at some little

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

We can here consider only a few cases. In regard to fish, I believe that the same species never occur in the fresh waters of distant continents. But on the same continent the species often range widely and almost capriciously; for two river-systems will have some fish in common and some different. A few facts seem to favour the possibility of their occasional transport by accidental means; like that of the live fish not rarely dropped by whirlwinds in India, and the vitality of their ova when

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

occasional means of transport having been largely efficient in the long course of time, than with the view of all our oceanic islands having been formerly connected by continuous land with the nearest continent; for on this latter view the migration would probably have been more complete; and if modification [page] 42

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

species on islands and on the mainland, though separated by hundreds of miles of open sea. If the existence of the same species at distant and isolated points of the earth's surface, can in many instances be explained on the view of each species having migrated from a single birthplace; then, considering our ignorance with respect to former climatal and geographical changes and various occasional means of transport, the belief that this has been the universal law, seems to me incomparably the

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

several islands. This difference might indeed have been expected on the view of the islands having been stocked by occasional means of transport—a seed, for instance, of one plant having been brought to one island, and that of another plant, to another island. Hence when in former times an immigrant settled on any one or more of the islands, or when it subsequently spread from one island to another, it would undoubtedly be exposed to different conditions of life in the different islands, for it

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

scarcely any means of transport would carry seeds for very great distances; for seeds do not retain their vitality when exposed for a great length of time to the action of sea-water; nor could they be long carried in the crops or intestines of birds. These means, however, would suffice for occasional transport across tracts of sea some hundred miles in breadth, or from island to island, U [page] 43

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

effects of all the changes of climate and of the level of the land, which have certainly occurred within the recent period, and of other similar changes which may have occurred within the same period; if we remember how profoundly ignorant we are with respect to the many and curious means of occasional transport, a subject which has hardly ever been properly experimented on; if we bear in mind how often a species may have ranged continuously over a wide area, and then have become extinct in

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

batrachians and of terrestrial mammals notwithstanding the presence of a rial bats, the singular proportions of certain orders of plants, herbaceous forms having been developed into trees, c., seem to me to accord better with the view of occasional means of transport having been largely efficient in the long course of time than with the view of all our oceanic islands having been formerly connected by continuous land with the nearest continent; for on this latter view the migration would

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

from this capacity as an almost necessary consequence. We can here consider only a few cases. In regard to fish, I believe that the same species never occur in the fresh waters of distant continents. But on the same continent the species often range widely and almost capriciously; for two river-systems will have some fish in common and some different. A few facts seem to favour the possibility of their occasional transport by accidental means; like that of the live fish not rarely dropped by

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

of difference in the several islands. This difference might indeed have been expected on the view of the islands having been stocked by occasional means of transport a seed, for instance, of one plant having been brought to one island, and that of another plant to another island. Hence, when in former times an immigrant settled on any one or more of the islands, or when it subsequently spread from one island to another, it would undoubtedly be exposed to different conditions of life in the

F387    Book:     Darwin, C. R. 1869. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 5th ed. Tenth thousand.   Text   Image   PDF

strictly correct: the currents of the sea are not accidental nor is the direction of prevalent gales of wind. It should be observed that scarcely any means of transport would carry seeds for very great distances: for seeds do not retain their vitality when exposed for a great length of time to the action of sea-water; nor could they be long carried in the crops or intestines of birds. These means, however, would suffice for occasional transport across tracts of sea some hundred miles in breadth, or

F387    Book:     Darwin, C. R. 1869. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 5th ed. Tenth thousand.   Text   Image   PDF

very ignorant of the full extent of the various climatal and geographical changes which have affected the earth during modern periods; and such changes may obviously have facilitated migration. As an example, I have attempted to show how potent has been the influence of the Glacial period on the distribution of the same and of allied species throughout the world. We are as yet profoundly ignorant of the many occasional means of transport. With respect to distinct species of the same genus

F387    Book:     Darwin, C. R. 1869. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 5th ed. Tenth thousand.   Text   Image   PDF

piles of volcanic matter. I must now say a few words on what are called accidental means, but which more properly should be called occasional means of distribution. I shall here confine myself to plants. In botanical works, this or that plant is stated to be ill adapted for wide dissemination; but for transport across the sea, the greater or less facilities [page] 43

F387    Book:     Darwin, C. R. 1869. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 5th ed. Tenth thousand.   Text   Image   PDF

in space, it certainly is the general rule that the area inhabited by a single species, or by a group of species, is continuous, and the exceptions, which are not rare, may, as I have attempted to show, be accounted for by former migrations under different circumstances, or through occasional means of transport, or by the species having become extinct in the intermediate tracts. Both in time and space, species and groups of species have their points of maximum development. Groups of species

F387    Book:     Darwin, C. R. 1869. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 5th ed. Tenth thousand.   Text   Image   PDF

centre; and I am inclined to look in the southern, as in the northern hemisphere, to a former and warmer period, before the commencement of the Glacial period, when the Antarctic lands, now covered with ice, supported a highly peculiar and isolated flora. It may be suspected that before this flora was exterminated during the last Glacial epoch, a few forms had been already widely dispersed to various points of the southern hemisphere by occasional means of transport, and by the aid, as halting

F387    Book:     Darwin, C. R. 1869. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 5th ed. Tenth thousand.   Text   Image   PDF

our ignorance with respect to former climatal and geographical changes and to the various occasional means of transport, the belief that a single birthplace is the law, seems to me incomparably the safest. In discussing this subject, we shall be enabled at the same time to consider a point equally important for us, namely, whether the several species of a genus, which [page] 43

F391    Book:     Darwin, C. R. 1872. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 6th ed.; with additions and corrections. Eleventh thousand.   Text   Image   PDF

they be long carried in the crops or intestines of birds. These means, however, would suffice for occasional transport across tracts of sea some hundred miles in breadth, or from island to island, or from a continent to a neighbouring island, but not from one distant continent to another. The floras of distant continents would not by such means become mingled; but would remain as distinct as they now are. The currents, from their course, would never bring seeds from North America to Britain

F391    Book:     Darwin, C. R. 1872. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 6th ed.; with additions and corrections. Eleventh thousand.   Text   Image   PDF

opposite hemispheres to mingle, and left some of them stranded on the mountain-summits in all parts of the world. As showing how diversified are the means of occasional transport, I have discussed at some little length the means of dispersal of fresh-water productions. If the difficulties be not insuperable in admitting that in the long course of time all the individuals of the same species, and likewise of the several species belonging to the same genus, have proceeded from some one source; then

F391    Book:     Darwin, C. R. 1872. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 6th ed.; with additions and corrections. Eleventh thousand.   Text   Image   PDF

, which have certainly occurred within the recent period, and of other changes which have probably occurred,—if we remember how ignorant we are with respect to the many curious means of occasional transport,—if we bear in mind, and this is a very important consideration, how often a species may have ranged continuously over a wide area, and then have become extinct in the intermediate tracts,—the difficulty is not insuperable in believing that all the individuals of the same species, wherever found

F391    Book:     Darwin, C. R. 1872. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 6th ed.; with additions and corrections. Eleventh thousand.   Text   Image   PDF

should be called occasional means of distribution. I shall here confine myself to plants. In botanical works, this or that plant is often stated to be ill adapted for wide dissemination; but the greater or less facilities for transport across the sea may be said to be almost wholly unknown. Until I tried, with Mr. Berkeley's aid, a few experiments, it was not even known how far seeds could resist the injurious action of sea-water. To my surprise I found that out of 87 kinds, 64 germinated after an

F391    Book:     Darwin, C. R. 1872. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 6th ed.; with additions and corrections. Eleventh thousand.   Text   Image   PDF

certain groups, but not those of other groups in the same class, having been modified—the absence of certain whole orders, as of batrachians and of terrestrial mammals, notwithstanding the presence of aerial bats,—the singular proportions of certain orders of plants,—herbaceous forms having been developed into trees, c.,—seem to me to accord better with the belief in the efficiency of occasional means of transport, carried on during a long course of time, than with the belief in the former

F391    Book:     Darwin, C. R. 1872. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 6th ed.; with additions and corrections. Eleventh thousand.   Text   Image   PDF

species with which each has to compete, is at least as important, and generally a far more important element of success. Now if we look to the species which inhabit the Galapagos Archipelago and are likewise found in other parts of the world, we find that they differ considerably in the several islands. This difference might indeed have been expected if the islands have been stocked by occasional means of transport—a seed, for instance, of one plant having been brought to one island, and that of

F401    Book:     Darwin, C. R. 1876. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 6th ed., with additions and corrections. [First issue of final definitive text]   Text   Image   PDF

been already widely dispersed to various points of the southern hemisphere by occasional means of transport, and by the aid as haltingplaces, of now sunken islands. Thus the southern shores of America, Australia, and New Zealand, may have become slightly tinted by the same peculiar forms of life. Sir C. Lyell in a striking passage has speculated, in language almost identical with mine, on the effects of great alternations of climate throughout the world on geographical distribution. And we

F401    Book:     Darwin, C. R. 1876. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 6th ed., with additions and corrections. [First issue of final definitive text]   Text   Image   PDF

that we are as yet very ignorant as to the full extent of the various climatal and geographical changes which have affected the earth during modern periods; and such changes will often have facilitated migration. As an example, I have attempted to show how potent has been the influence of the Glacial period on the distribution of the same and of allied species throughout the world. We are as yet profoundly ignorant of the many occasional means of transport. With respect to distinct species of