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
produce offspring which will breed with either parent stock; and tame
dogs in different quarters of the world, although all of them fertile
inter se, are in many cases obviously blood kin to the neighboring
wild, wolf-like or jackal-like creatures which are specifically, and
possibly even generically, distinct from one another. The big red wolf
of the South American plains is not closely related to the northern
wolves; and it was to me unexpected to find it interbreeding with