Scores of other beings of still more lowly degree swarmed about us, but as the tide lapped out of our little bayou, the four-eyes again attracted our attention. They began to get restless, swimming back and forth and shuffling over the mud, until at last in desperation at the ebbing of their element, they made a dash to get past us into the open water of the caño. Some dived, but so buoyant are they that they can scarcely stay below a second, and soon popped up on the surface again. Others scrambled, rolled, and squirmed along over the ooze on each side of us, many making good progress and escaping. We caught several and placed them in an aquarium for study. When hard pressed in deep water these curious fish progress by a series of leaps—up on their tail end and down again, up and down again, describing a series of curves and making very fast time. When examined closely we see that these fish have only two eyes, but these are divided in such a way that there appear to be double that number. There are two distinct pupils, one elevated above the head like the eyes of a frog, the other separated by a band of tissue and below the water-line. So when the fish floats in its normal position at the surface the upper pupils, fitted for vision in the air, watch for danger above, while the lower pair keeps a submarine lookout for insect food and aquatic enemies. Monkeys are perfectly at home in this land of branches, the ever-cautious capuchins and now and then a long-limbed spider monkey swinging through the trees with as easy a motion as the flight of a bird. Biggest of all are the great red howlers, who keep to the deeper, more narrow channels, and in the evening and again at dawn send their voices to the farthest limits of the mangroves. They do not howl, they roar, and the sound is perfectly suited to such a wilderness as this. Before the first signs of day light up the east, a low, soft moaning comes through the forest, like the forewarning of a storm through pine trees. This gains in volume and depth until it becomes a roar. It is no wind now, nor like anything one ever hears in the north; it is a deep, grating, rumbling roar—a voice of the tropics; a hint of the long-past ages when speech was yet unformed. We grew to love the rhythm of this wild music, and it will always be for us the memory-awakening sound of the tropical wilderness. The wealth of life in this region was evident when we began to explore a river flowing down from the highlands in the far-distant interior of Venezuela. One could spend a year here and not begin to exhaust the wonders on every hand.