This fact is occasionally brought vividly to the mind of an observer when he first passes a Rolls-Royce car in all its glory and magnificence, and then a rough squalid kind of trolly in which the engine-parts of a similar future Rolls-Royce are out for trial. In principle it is not a long step from these illustrations to the diverse environments of animals in which their lot is cast, and their reaction to them as to behaviour and structural change. Some Changes in Habits of Man. There are two current views as to the present erect posture of man, one which traces it to the adoption of a new posture by a pronograde four-footed ancestor, and the other that man’s ancestors were “never typically pronograde with four supporting limbs,” but derived from an arboreal stock in which the forelimbs were mobile rather than stable. Whenever or wherever man became orthograde he opened up for himself and his descendants immense regions of structural and functional change and became increasingly dominant over his environment. Changes in muscles, joints, bones, bursæ, lungs, heart, and vessels occurred through his employing in new modes the muscles, joints, bones, bursæ, lungs, heart and vessels he already possessed, and the resemblance between these structures of man and the great apes has given to the latter the name of anthropoid, and this similarity of structures in the highest Primates has done much to support in the past that Simian origin of man which is at present questioned. The behaviour of the apes and early man were sufficiently alike to lead either to a parallel or genetic similarity. This point is, perhaps, irrelevant in considering the great field for initiative in the formation of new physical characters, and chief among these new reflex-arcs which have built up the marvellous organ of man’s glory and greatness; but no one can dispute the elementary fact that the ancestor of man who adopted terrestrial bipedal locomotion and became orthograde, owed it to his growing brain and the higher integration of his organs for that function. But besides the new posture he had adopted he learned to talk articulately, to make tools, and to use stereoscopic vision. None of these could have been started on the upward way without a long process of trial and error in the course of his total experience and practice of his powers. The results that followed from these three properties of his are inconceivably great, and it is unnecessary to enlarge on such a theme or to add to the number of examples. Leaving, then, the immediate ancestor to work out his own destiny in his new terrestrial home, we must as before proceed backward in the history of animal life in the line of Primate ancestry. Primate Ancestry.