ABSTRACT
THE thesis that the evolutionary system is such that it is characterized by an inherent tendency to evolve in the direction of greater efficiency does not of course imply that such progressive improvements always occur in every evolutionary sequence. There may be other tendencies also in operation, and in some cases these may be dominant and prevent the improvement
The actual results which evolution has produced are at present usually considered in terms of three categories. For the sake of clarity it may be as well to introduce the actual technical terms which are employed for these. They have been particularly well discussed in a valuable paper by Julian Huxley.1
