As a flash of lightning in the duration of the night, so is the life of man in the duration of nature. When one looks out on a storm at night, he sees for an instant the landscape illumined by the lightning-flash. All seems at rest. The branches in the wind, the flying clouds, the falling rain are all motionless in this instantaneous view. The record on the retina takes no account of change, and to the eye the change does not exist. Brief as the lightning-flash in the storm is the life of man compared with the great time-record of life upon earth. To the untrained man who has not learned to read these records, species and types in life are enduring. Thus arose the theory of special creation and permanence of type, a theory which could not persist when the fact of change and the forces causing it came to be studied in detail. But when man came to study the facts of individual variation and to think of their significance, the current of life no longer seemed at rest. Like the flow of a mighty river, never returning, ever sweeping steadily on, is the movement of all life. The changes in human history are only typical of the changes that take place in all living creatures. In fact, human history is only a part of one great life-current, the movement of which is everywhere governed by the same laws, depends on the same forces, and brings about like results. The facts and generalizations of change constitute the subject-matter of evolution. And as the fact of life is a fundamental one, and in some degree modifies all phenomena which it concerns, we have as the central axis of the science in question, the study of organic evolution. In fact, while inorganic evolution, or orderly change in environment, exists, we do not know to what degree the laws and forces of organic evolution can be reduced to the same terms of expression. The theory of the essential and necessary unity of life and non-life, of mind and matter, is still a matter of philosophical speculation only. We can neither prove the truth of Monism, nor understand it; nor is the contrary hypothesis either comprehensible or credible. The fundamental unity of organic evolution and inorganic evolution is yet to be proved, while the laws which govern living matter are certainly in part peculiar to life. For this reason the evolution of astronomy, of dynamic geology, of geography, as well as the purely hypothetical evolution of chemistry, must be separated from life evolution. Cosmic evolution and organic evolution show, or seem to show, some divergence from each other. There are some elements which are not held in common, or which, at least, are not identical when measured in human terms. For the latter, the science of organic evolution, there is therefore certainly need of a distinctive term. This has been lately furnished by Professor Patrick Geddes, who has chosen the term bionomics. Bionomics ([Greek: bios], life; [Greek: nomos], law or custom) is the science which treats of the changes in