be that their knowledge of distant
objects was mainly gained through sensitiveness to odors.

Of invertebrate land animals the same must be said. The land mollusks
and the great order of insects and other land arthropods only to a minor
extent dwell in the open light. Very many species haunt the
semi-obscurity of trees or groves, hide among the grasses, lurk under
bark, sticks, and stones, or dwell through most of their lives
underground. Hosts of others are nocturnal. To only a small percentage
of insects can sight be of any great utility, while hearing seems also
to be of slight importance. Smell is probably the principal sense
through which these animals gain information of distant objects.

There is existing evidence that the sense of smell in some insects is
remarkably acute. The imprisoned female of certain nocturnal species,
for instance, will attract the males from a comparatively immense
distance, under conditions in which neither sight nor hearing could have
been brought into play. The emission of odors and acute sensibility to
them is the only presumable agency at work in those instances. As
regards the most intelligent of the insects, the ants and the termites,
the former are largely subterranean, the latter not only subterranean,
but blind. In the one case, sight can play only a minor part, in the
other, it plays no part at all. Touch and smell seem to be the dominant
senses in these animals, and the degree of intelligence they display
shows of how high a development these senses are susceptible. Yet the
intelligence arising from them must necessarily be local and limited in
its application; it cannot yield the breadth of information and degree
of mental development possible under the dominance of sight.

In the vertebrates we find a fully developed and broadly capable organ
of vision, and it might be hastily assumed that in those animals sight
is the dominant sense. But there are numerous facts which lead to a
different conclusion. Many of the vertebrates are nocturnal, many dwell
in obscure situations, many in the total darkness of caverns,
underground tunnels and excavations, or the ocean's depths. To all these
sight must be of secondary importance. Hearing also can be of no
superior value, and the dominant sense must be that of smell. In the
bats there would appear to be a remarkably acute power of touch, if we
may judge from the facility with which they can avoid obstacles at full
flight after their