It may be said here that sight only slowly gained dominance in animal life. Though the eye, as an organ of vision, is found at a low level in the animate scale, the indications are that it long played a subordinate part, and has gained its full prominence only in man. During long ages life was confined to the sea, hosts of beings dwelling in the semi-obscurity of the under waters, and great numbers at too great a depth for light to reach them. To vast multitudes of these sight was partly or completely useless. The same may be said of hearing, the under-water habitat being nearly or completely a soundless one. The only one of the higher senses likely to be of general use to these oceanic forms is that of smell, and it may 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.