Speciation in Rodents of the Colorado River Drainage

In 1531 the first vague rumors of the existence of a mighty river in the deserts of southwestern North America a fired the imagination of the inhabitants of the New World. Rather than being abated by the passage of time and the in crease of knowledge, this fever of wonder and curiosity has in creased Even the most effete and apathetic modern sophisticate is profoundly stirred by his first glimpse of this marvel, the Colorado River of the West . To the student of nature, the river and its gorges in their colorful setting in the desert fastnesses hold a special significance. Here one feels that the forces of nature have been and still are functioning on such a vast scale and their effects are so dramatically emphasized that this must indeed be an especially appropriate region in which to observe certain natural processes in operation.