Зображення сторінки

the sharpest part of the current he hovered for a moment, and then dashed into the stream. With a good glass I saw him buried deeply in the water, holding his neck well above it. It was evident he had some difficulty in getting out of it again. A few heavy and laborious flaps of his immense and powerful wings lifted him at last, but with empty talons. Very tired apparently, he flew to an adjacent bank of gravel and sat there for some minutes to rest. But his countenance and attitude were that of restlessness, eagerness, and disappointment. He then rose and returned to exactly the same point in the air, and thence made a second plunge. It was beautiful to see his bearing in the stream, with the water breaking against his great brown chest, and his arched neck keeping his snowy head clear of its turbulence. This time the difficulty in emerging was much greater, for his talons were fast in a fine salmon. With a strong effort, however, his pinions again lifted bim and his prey, which it seemed as much as he could do to carry to the same bank of gravel, where the struggles of the fish were soon put an end to by the Eagle's terrific clutches and his powerful beak. This was all honourable work, and although the Osprey was frequently to be seen on the same river, I never observed it to be followed or molested by the Eagle. On another day one of these magnificent birds lighted on a blasted Pine which overhung the river at the height of about 500 feet, and from that elevation he watched one of our party playing a salmon, an operation which he seemed to regard with great curiosity, and probably with some longing to take his part in the sport. The pure white head and the equally pure tail of this fine Eagle, in contrast with the dark chocolate brown of the rest of the plumage, make it one of the handsomest of its tribe.

The Provinces of North America have one great advantage which is not possessed by any part of Europe. They are in unbroken land connection with the Tropics. There is no transverse range of mountain, there is no region of desert sands, no strait even of narrow sea, to impede the most delicate forms of the southern fauna from travelling northwards with the summer sun. It is wonderful how many tender creatures make out their passage to our own shores with the returning spring; but in Britain there are none which come from a farther distance than that limited belt of the African Continent which lies between the Atlas and the Mediterranean. Very many of them pass their winters no farther off than the sunny banks of the Riviera. Last winter I found the olives at Cannes full of Blackcaps and Willow Wrens, while the Whitethroat and the Sardinian Warbler sometimes serenaded us from the roses which climbed around our windows. But no bird from tropical Africa can cross the Desert and the Atlas. These great transverse barriers in the path of migration are barriers not to be overcome. In America, on the other hand, there is no such impediment in the way of an uninterrupted passage from the lowest southern to the highest northern latitudes. The consequence is that even Canada, whose soil is fast bound in ice for some five months of the year, is the resort in summer of a joyous company from

the far south, who find upon their way a perfect continuity in the supply of food, and in their final goal, even amidst a very different vegetation, a summer heat which is fitted for the rearing of their young. It is due to this that the woods of North America are illuminated with the brilliant colouring of not a few species which almost seem to contrast unmaturally with the foliage of Birch and Pine. Foremost among these visitants from the far south I knew that Canada was visited every year by a single species of that wonderful family of birds which is one of the glories of nature—the Humming-birds. It was one of my great expectations in crossing the Atlantic that I might see the Rubythroat (Trochilus colubris). Everywhere I asked about it—whether any had been seen, and if so, where? Everywhere I was told that they were more or less common, but that they had not come that season yet—or that they were only to be seen in the evenings —or that they only come out on very hot days—or that they never came except to honeysuckle in the verandahs. My eye searched in vain round every horse-chestnut tree in blossom, under every “piazza' with baskets of flowers, and over the surface of every wall bedecked with creepers. The Rubythroat, like Wordsworth's Cuckoo, was “still longed for, never seen. At last, in walking one day up the mountain behind Montreal, I leaned over a paling which enclosed the water reservoir of the city. Below me there was a steep bank of grass, facing the south, and rich in the common flowers of such grass in England. Suddenly there emerged from it what first struck me as a very large, but also a very narrowshaped beetle, which flew with the straight, rapid, and steady flight of the larger Coleoptera. As in them, the wings were not distinctly visible, but were represented by a sort of vibratory haze. I was speculating on this extraordinary object, when a clearer light revealed, projecting from the head of my supposed beetle, a long, slender, and curved proboscis or bill. In an instant it was flashed upon me that I was looking for the first time on the flight of a Humming-bird in its wild and native state. I have often read of the insect-like habits and appearance of these birds. But until I saw it I had formed no distinct conception of this curious feature in their appearance. Its flight was not in the least like that of a bird. Nor was its gorgeous but partial brilliancy of colouring on the throat visible to me. The metallic green of the back of this particular species, which was turned towards me, being in shadow, produced a very dark effect upon the eye. But there it was—this gem of creation—this migrant from the far south—this representative of a group of birds whose headquarters are in the dense forests or among the luxuriant blossoms or on the lofty volcanic comes of Tropical America—there it was living and flying among trees which might have been English trees, and over grass which was indistinguishable from English grass. I was not so fortunate as to see one other specimen alive in any part of Canada or the States. I heard

one a few evenings before in his own garden. At another place one had visited that morning some flowers in a window or a verandah. But, strange to say, where one other specimen was seen was near our encampment, thirty miles up the forests of the Restigouche, where there was no garden, not a single cultivated flower, and not even among the woods a single blossoming tree or shrub, except perhaps the mountain ash, the sloe, or the bird cherry. One of our party in search of rare birds saw a strange outline on the topmost twig of a withered Pine, and on shooting it found, by the help of the Indians, that he had killed a 'Rubythroat. It brought home to me how secondary, in the distribution of animals, is the mere effect of climate and of vegetation. This Humming-bird could evidently live quite as well in the woods of Scotland as in the woods of the Restigouche, so far as climate or food are concerned. If the Trochilidæ existed in any part of the Old World, and had an uninterrupted path of migration, we should doubtless have them every summer in England as surely as we have the Swallow, or as Canada has the Rubythroat. But this particular form of bird has been born, or created, or developed in the New World alone; and to that one sole area of distribution it is limited by surrounding oceans.

On the other hand, the ornithologist from Europe recogrises in the birds of North America a great number of species so closely allied to those at home that they have precisely the same habits and the same general aspect. The common Thrush of America (Turdus migratorius), which the first colonists absurdly called the Robin, for no other reason than that it has a russet-coloured breast, is so like our own common Thrush or Blackbird that there is no generic difference whatever. Its alarm-notes combine those of the Fieldfare and the Blackbird. The Bluebird (Sialia sialis) is the real representative of our Robin, though it has not the same habits of familiarity with man. But it is not one or two species merely that exhibit this likeness. There is an obvious cousinship and correspondence between the great bulk of the species which cannot be mistaken, and the closeness of which would be unaccountable if their original centres of origin bad been separated, as the habitats now are, by 3,000 miles of ocean. Naturalists are therefore now coming to trace the cause of this near relationship between the European and the North American fauna to that ancient connection which the two Continents had at the time when the regions, which are now under Arctic conditions, were in the enjoyment of a climate compatible with a rich development of both animal and vegetable life. In that mysterious Miocene age when abundant forests, like the forests of Japan, flourished in Greenland, and in all probability elsewhere within the Arctic Circle, the Old and the New Worlds may have been united, so to speak—as, indeed, they almost now are—in their northern roots. One thing is quite certain, that if the near likeness to each other of different organic forms is

cannot have been created or developed in widely separated portions of the globe, then there must have been at some former time some close connection between Europe and America which does not exist at present. It is to be observed, however, that the impossibility of separate origins for forms alike, or even identical, is a mere assumption which may not be true. Although it figures largely in the theory of development as propounded by Mr. Darwin and by Mr. Wallace, it is no necessary part of the idea of creation by birth or by evolution. . It is an assumption founded on another assumption—namely, that the natural variations of form which occur from time to time (and which are the supposed origin of species) are variations which can never be identical in two separate places; and this assumption rests again upon a third—namely, that varieties are really accidental, and not due to any internal law of growth inherent in all forms of life. But this is an assumption which not only may be, but probably is, contrary to fact. Mr. Darwin has never pretended to account for variations. He assumes that as a matter of fact they do occur, and that once they have occurred, they are preserved or rejected according as they do or do not fit well into surrounding conditions. This may be quite true, and yet it may be equally true that these variations are not accidental, but are determined by a law of which we know nothing, but which is as definite and certain in its operation as the law determining the primary and the derivative forms of crystals. In this case the same or closely similar forms may have arisen at widely different parts of the globe; and the necessity of any geographical connection between land surfaces now widely separated would be either disposed of altogether or would be pushed back to such primordial times as to be incapable of being traced. I am not now propounding this supposition as one which can be verified. It would certainly throw the whole subject of the distribution of species and genera into great confusion. But then it is a kind of confusion which closely corresponds with the apparent confusion which actually prevails in nature. The assumption that identical or almost identical forms cannot arise at any place but one, is an assumption which has a most attractive simplicity about it. It rests, however, upon nothing except upon the doctrine of chances. But if the work of creation and development is not a work subject to chance at all, but has been due to the evolution of germs having potential energies of a fixed and definite kind, then the doctrine of chances does not apply, and would be of little avail against the probability of similar forms appearing in regions very far apart. It is well known that the existing distribution of species is such as to involve the utmost difficulties in applying to it the theory of exclusive centres of creation. These difficulties are so great that to a naturalist so eminent and so competent as Agassiz they seemed insuperable. The counter hypothesis, which I have here suggested, does not exclude the probable effects of external conditions in modifying forms which are nevertheless mainly due of these hypotheses the most probable solution may be found. The birds of North America present some cases of multiplied variety that suit very well the theory which dwells principally on the effect of surrounding conditions. But, on the other hand, there are many cases in which it does not seem to fit the facts at all. The boundless forests of that country, for example, seem admirably adapted to encourage the establishment of variety in such a family as that of the Picidae or Woodpeckers. And accordingly we do find a very large variety of kindred forms, one of them scarcely distinguishable from its cousin in Europe. I saw at least three or four distinct species in the very limited distance I could penetrate into the forests of the Restigouche. But, on the other hand, let us see how the same expectation is disappointed in another remarkable family of birds—the Alcedinidae or Kingfishers. If there is one feature which more than another distinguishes the North American Continent, it is its wealth of waters. Mighty rivers with every degree of rapidity and of stillness, smaller streams in every measure of size, and with every variety of character, lakes in millions which are mere ponds, and lakes so large that the navigator upon them loses sight of land, creeks and lagoons of every shape and form, marshes fringed with wood, and marshes on the bare and open coast—and all this immense variety of aqueous surface swarming with fish, and with crustaceans, and with every form of creature that “inhabiteth the waters under the earth.' Yet, in spite of all this wealth of external conditions, this vast hotbed, as one might have supposed, for the growth of variety in that peculiar family of birds which is specially adapted for the capture of fish, there is but one solitary species—the Belted Kingfisher. If the family were wholly unrepresented upon the American Continent, this absence of variety would be less remarkable. But the stock exists. It has thrown off no varieties—one solitary species fishes in the boundless waters of North America from the Delaware to Baffin's Bay. I may mention here that on examining a nest of this fine bird in a gravel bank on the Restigouche River we found that the eggs were laid not on fish bones, but on the broken shells of Crayfish—which was the first intimation we had of the existence of these fresh water crustaceans in the stream. The truth is that as yet we have made very little way in understanding the Origin of Species. The general idea of origin by descent, or of creation by birth, fits well into many of the facts. But this general conception does not necessitate our acceptance of the particular theory of Mr. Darwin, that variations occur only as it were by accident, or only by small and almost insensible modifications, or that one particular form can only arise at one time and one place. On the contrary, it may be that all variations arise out of a definite and predetermined law, that this law may determine the appearance of the same forms at many places and at different times, and also that such changes are not always gradual or infinitesimally small,

« НазадПродовжити »