NO subject is of such perennial interest as evolution, for evolution means the gradual growth of one type of an organism into another as the generations succeed one another. It is quite clear that if the possibility of this kind of growth be conceded for one type of organism it must hold good for all, since all, from the highest to the lowest, exhibit the same essential types of growth and reproduction. Therefore the problem of evolution is the problem of the growth of all animated Nature, of which we ourselves form a part.