United States or Tunisia ? Vote for the TOP Country of the Week !
A broken or interrupted range may often be accounted for by the extinction of the species in the intermediate regions. It cannot be denied that we are as yet very ignorant as to the full extent of the various climatical and geographical changes which have affected the earth during modern periods; and such changes will often have facilitated migration.
Three times a day, Quonab rubbed that blackened ankle. The grease saved the skin from injury, and in a week Rolf had thrown his crutches away. The month of May was nearly gone; June was at hand; that is, the spring was over. In all ages, man has had the impulse, if not the habit, of spring migration. Yielding to it he either migrated or made some radical change in his life.
So a general migration begins toward that place; that is, all the animals begin to travel to that place with their families. These animals may start from different places a hundred miles apart, and yet after a few days they will get to that same Water Hole.
The different destiny of these stocks has been wonderful indeed. Of those who went west, we have only to enumerate the names under which they appear in history Celts, Greeks, Romans, Teutons, Slavonians to see and to know at once that the stream of this migration has borne on its waves all that has become most precious to man.
The relation between the power and extent of migration in certain species, either at the present or at some former period, and the existence at remote points of the world of closely allied species, is shown in another and more general way. Mr. Gould remarked to me long ago, that in those genera of birds which range over the world, many of the species have very wide ranges.
The Gallic migration undoubtedly passed by like a torrent with irresistible rapidity: how then is it possible to suppose that Melpum resisted them for two centuries, or that they conquered it and yet did not disturb the Etruscans for two hundred years? It would be absurd to believe it, merely to save an uncritical expression of Livy.
When the population of one settlement became too thick, they were seized by an irresistible impulse to "follow the migration," as the expression went. The easy independence of the first hunter-agriculturalist was upset by the advance of immigration. His range was curtailed, his freedom limited. His very breath seems to have become difficult.
The strongest apparent exception to this latter rule, is that of the so-called "colonies" of M. Barrande, which intrude for a period in the midst of an older formation, and then allow the pre-existing fauna to reappear; but Lyell's explanation, namely, that it is a case of temporary migration from a distinct geographical province, seems to me satisfactory.
Yet, as we have reason to believe that some species have retained the same specific form for very long periods, enormously long as measured by years, too much stress ought not to be laid on the occasional wide diffusion of the same species; for during very long periods of time there will always have been a good chance for wide migration by many means.
The day fixed for our final migration to "Lake Laicomo," at length arrived, and taking a farewell for "the season," of our deserted tenement at Castle-hill, we set out for the cabin, to spend our first night there. It was not without some feelings of regret that we left a spot now become so familiar, to bury ourselves in the woods out of sight of the sea.
Word Of The Day