Page:Through the Brazilian Wilderness by Theodore Roosevelt (1925).djvu/98

 by flight. It was curious to see one lumbering off at a rocking canter, the big bushy tail held aloft. One, while fighting the dogs, suddenly threw itself on its back, evidently hoping to grasp a dog with its paws; and it now and then reared, in order to strike at its assailants. In one patch of thick jungle we saw a black howler monkey sitting motionless in a tree top. We also saw the swamp-deer, about the size of our blacktail. It is a real swamp animal, for we found it often in the papyrus-swamps, and out in the open marsh, knee-deep in the water, among the aquatic plants.

The tough little horses bore us well through the marsh. Often in crossing bayous and ponds the water rose almost to their backs; but they splashed and waded and if necessary swam through. The dogs were a wild-looking set. Some were of distinctly wolfish appearance. These, we were assured, were descended in part from the big red wolf of the neighborhood, a tall, lank animal, with much smaller teeth than a big northern wolf. The domestic dog is undoubtedly descended from at least a dozen different species of wild dogs, wolves, and jackals, some of them probably belonging to what we style different genera. The degree of fecundity or lack of fecundity between different species varies in extraordinary and inexplicable fashion in different families of mammals. In the horse family, for instance, the species are not fertile inter se; whereas among the oxen, species seemingly at least as widely separated as the horse, ass, and zebra—species such as the domestic ox, bison, yak, and gaur—breed freely together and their offspring are fertile; the lion and tiger also breed together, and pro-