"Educability" is the quality which distinguishes the brain of increased size. Dogs are more "educable" than rabbits; monkeys more so than dogs; and men more so--vastly more so--than monkeys and apes. The human infant is born with a few inherited mechanisms of "instinct," such as that which causes it to find its mother's nipple and to suck it, and to cling and support its own weight as no full-grown child can do. It is singularly free from any large number of inherited "instincts," and, to its own great advantage, has, during the many years in which it is protected by its parents, to learn everything and to construct new brain mechanisms--the results of "education" of the individual. We here use the word "education" in its proper and widest sense. Thus we get an indication of "the reason why" the modern rhinoceros has a brain eight times as big as the titanotherium's. It is more "educable." The ancestors of our modern armour-plated friend have been surviving and beating their less "educable" brothers and sisters and cousins through a vast geological lapse of time; and the brains of the survivors have always been bigger, and they have become more educable and more educated until the race has culminated in those models of "sweet reasonableness," the modern rhinoceroses! It must be confessed that this character attributed to the rhinoceros is a matter of inference and not of direct observation of that animal when under his native sky. We do not judge the survivor of a fine early Miocene family by the fury and annoyance he shows when shot at, nor by the stolid contempt with which he treats mankind at the Zoo. The same signification--"educability"--attaches to the large brain of the higher apes; and man's still larger brain means still greater educability and resulting reasonableness.