Page:Popular Science Monthly Volume 55.djvu/205

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HE present fauna of our planet includes many varieties of mammals and reptiles, and a few kinds of birds, that are found only on certain islands—a fact which seemed rather to justify the once universal belief in the origin of species by separate acts of creation.

A different theory of explanation has, however, been suggested by the discovery of fossil remains, proving the former existence of closely allied forms on continents where their battle for existence had to be fought against beasts of prey and competitors for a limited food supply.

The supposed products of an island genesis by the fiat of supernatural agencies, demanding recognition in mental penance and the payment of tithes, may thus be simply animal Crusoes, favored by the positive or negative advantages of their surroundings.

The dodo, in its struggle for survival, would have had no chance against South American tiger-cats. Not one of the twenty-odd species of Madagascar lemurs could have held its own against the competition of the African daylight monkeys.

Yet there was a time when night apes and large ground birds seem to have had things all their own way, the world over, and Central America may have afforded a chance for existence to several species of reptiles which at present are found only on the West Indian islands.

The Cuban bush tortoise (Eniys nigra) is found only in the forests of Santiago and Puerto Principe, and there only on the south coasts. It is the most sluggish creature of its genus, and does not seem to have had enterprise enough to crawl around the sand belt of Cape Maysi and colonize the jungles of the north side provinces. It is as helpless as a hedgehog, minus its bristles. The darkeys of the Cuban planters crack its armor with home-made hammers, and the tortuga prieta, or prieta, as they call it for short, forms a factor of holiday menus as frequently as 'possum pie in southern Georgia.

Swift-flowing rivers bear it away as they would a floating log, and it is wholly incredible that its ancestors should have crossed the Caribbean Sea in quest of a more congenial home; but it is possible enough that its eggs may have been ferried across on one of the driftwood islands which the Sumasinta River often tears from the coast swamps of southern Mexico and carries into the current of the Gulf Stream. The evolution of the South American giant cats was