Between the opposing forces in our small battle-field of the hairy coat there have been waged battles to which those of Mukden, Verdun, the Somme and Arras, are not to be compared in point of time. They are but as one day to a thousand years. On one side of the conflict in our present chosen field the ancient primitive type of the lemur has remained entrenched for some millions of years, until there arose new forces in its descendants on the other side and this changed the war of positions into one of movement. It was indeed “a contemptible little army” which came forward to oppose the ancient barbarian forces of the lemur, long prepared and organised, and these new armies fought under the banner, Habit. In the slowly-formed patterns in many types of mammals we have records of the treaties made after these long struggles and the rectifications of frontier which became necessary. The critic may call these “battles of kites and crows,” and ask What war correspondents were allowed to describe them; but a battle, whether great or small, long or short, is important to the parties concerned, and it is open to us to “reconstruct” the facts of the battle as do the historians on their part, for example, Sir James Ramsay the battle of Agincourt--with tolerable verisimilitude. But in science, especially geological science, the process of reconstruction is much more ambitious and bold than any that is here attempted. Who has not been fascinated, if he has read Sir E. Ray Lankester’s work on Extinct Animals, by the skill and daring with which he conveys to us a vivid idea of the form and mode of life, with scanty data, of the extinct Moa of New Zealand, the great Pterodactyle, Pteranodon, or the Diprotodon of Owen--“the probable appearance in life” of these uncanny but very real inhabitants of the earth in days long past. How skilfully did Owen from a piece of bone seven inches long, sent to him by a gentleman in New Zealand sixty years ago, pronounce it to be a part of the thigh-bone of a bird like an ostrich, and then after a few years had passed, confirmed it by more bones of the skeleton, till the large Moa, extinguished 600 or 700 years ago by the Maoris, lived again before us--an historical personage; or how by the examination of the skull and most of its skeleton the giant marsupial from Australia, Diprotodon, was resuscitated and admired; or again, how from the bones of the arms, shoulder-girdle and fingers was built up the strange body of Pteranodon, the great flying dragon. All of which is the legitimate and approved business of biologists and palæontologists, and this digression is made here to show that my line of treatment of a little subject agrees with that in a greater one; nay, it even proceeds in its explanations of events on the ever valuable principle of Lyell in a still greater one without which to-day geology would be a thing of naught, that is, the principle of _explaining changes in the surface of