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filled with that fluid. This trough exists in the horsemen land-crabs, but it is smaller, and a spongy mass furnishes the requisite moisture. The gills of the land-crabs, in other respects, do not differ from those of the tribe in general. God, when he formed these animals, would not separate them from their kind by a different mode of respiration, but by this compensating contrivance he fitted them for the circumstances in which he decreed to place them, and for a long sojourn out of the water.
What is the great object of this law of the Creator, that impels them to seek, in many cases, a mountain retreat, at a distance from the ocean, which forms the liquid atmosphere fitted to the great body of the Crustaceans, has not hitherto, for want of sufficient and accurate details of their history, been made fully obvious. When insects leave the waters to become denizens of the earth and air, the object appears evidently an increase of food, not only for terrestrial animals, whether moving on the one or in the other, but to multiply even that of the inhabitants of the waters. When the day-flies burst in such myriads from the banks of rivers which they inhabited in their first state, the fishes are all in motion, and often jump from the water to catch the living flakes that are every moment descending. When in the water, or under it, these animals and the mayflies are defended, or concealed from the fishes, and therefore are not so easy to come at; but now is their harvest, and when they drop their eggs, they fall towards the stream, and it is deemed a shower of manna.
The same object brings the several kinds of land-crabs at stated times to sea, to deposit their eggs where their young may reach a certain maturity, if not undergo a metamorphosis ; probably at this period there is an assemblage of aquatic devourers of Crustaceans, to share in the expected harvest. And during the route of the myriads that thus migrate to the sea, beasts and birds, and man himself, all partake of the feast thus provided for them.
If we give this subject of the migration of animals due consideration, and reflect what would be the consequence if no animals ever changed their quarters, we shall find abundant reason for thankfulness to the Almighty Father of the universe, for the care he has taken of his whole family, and of his creature man in particular, consulting not only his sustentation and the gratification of his palate by multiplying and varying his food, but also that of his other senses, by the beauty, motions, and music of the animals that are his summer or winter visiters : did the nightingale forsake our groves, the swallow our houses and gardens, the cod-fish, mackarel, salmon, and herring our seas, and all the other animals that occasionally visit us their several haunts, how vast would be the abstraction from the pleasure and comfort of our lives.
By means of these migrations, the profits and enjoyments derivable from the animal creation are also more equally divided, at one season visiting the south, and enlivening their winter, and at another adding to the vernal and summer delights of the inhabitant of the less genial regions of the north, and making up to him for the privations of winter. Had the Creator so willed, all these animals might have been organized so as not to require a warmer or a colder climate for the breeding or rearing of their young: but his will was, that some of his best gifts should thus oscillate, as it were, between two points, that the benefit they conferred might be more widely distributed, and not become the sole property of the inhabitants of one climate : thus the swallow gladdens the sight both of the Briton and the African ; and the herring visits the coasts, and the salmon the rivers of every region of the globe. What can more strongly mark design, and the intention of an all-powerful, all-wise, and beneficent Being, than that such a variety of animals should be so organized and circumstanced as to be directed annually, by some pressing want, to seek distant climates, and, after a certain period, to return again to their
former quarters; and that this instinct should be productive of so much good to mankind, and, at the same time, be necessary, under its present circumstances, for the preservation or propagation of the species of these several animals.
There is another view that may be taken of this subject, equally shewing the attention of the Almighty Father to the wants of every description of his creatures. The migrating tribes of almost every kind are attended by numerous bands of predaceous animals, which, as well as man, partake in the general harvest ; the bears, wolves, foxes, dogs, and, in tropical countries, other beasts of prey, hang on the flanks of the bands of emigrators, and capture and devour the stragglers. The vultures, and other carnivorous birds, follow and share in the spoil: and the emigrating fishes are attended by whole tribes of predaceous birds and fishes, which thin their numbers before they are taken by the nets of the fisherman.
I am next to say something on the local distribution of animals. By their local distribution, I mean their station in any given country. Under this head they may be divided into terrestrial, amphibious, and aquatic.
The local distribution of terrestrial animals is
very diversified. Some inhabit the loftiest mountains, here the eagle builds its aërie, and the condor deposits its eggs on the bare rock; and here the chamois? often laughs at the efforts of the hunter, astonishing him by the ease with which it scours over the rocks, or with which it ascends or descends the most inaccessible precipices.
Some animals, that in high latitudes are found in the plains, in a warmer atmosphere seek the mountains. Of this description is the beautiful Apollo butterfly,' which, in Sweden is very common in the country and gardens about Upsal, while in France it is found only on mountains between three and four thousand feet above the level of the sea. I received very fine specimens collected by a friend in the Pyrenees. The common viper* also, which in northern Europe is found in the plains, in southern is found only on Alpine or Subalpine mountains.
It has been observed by an ingenious and learned writer, that the terrestrial globe seems to be formed of two immense mountains, set base to base at the equator, and that upon each of these hemispheres the vegetables and animals are generally placed in parallel zones, according
1 Surcorhamphus Gryphus. 3 Parnassius Apollo.
Antilope Rupicapra. 4 Coluber berus.