and each of them in large numbers of individuals. The multiple origin has the effect of strengthening the new types. A large part of the mutations, being either injurious or useless, disappear.
This failure may be made a principle. If, in order to secure one good novelty, nature must produce many bad ones at the same time, the possibility of improvements coming by pure chance must be granted at once, and all hypotheses concerning the direct causes of adaptation at once become superfluous.
Accordingly, in this new view of phylogenetic development, aside from its very great technical importance for biology and for all evolutionary doctrine, the reviewer finds much of great philosophical interest, especially as regards the questions of origin and of purpose. In the discussion of practically all questions of origin, there are two typical views which are taken. The one is advanced by the man who emphasizes the necessity of keeping the law of identity intact. Accordingly, for him all change or origin in which something new apparently comes into existence consists at bottom only of changes in the configuration (motion) of a system made up of some kind of elements, which in that way should retain their identity with themselves. If he be a physicist and use differential equations, then these elements are conceived of as mass-points. This type is found to be characterized by the conviction that such a procedure is more logical, and by its insistence on certain principles as self-evident and therefore as necessarily true. However, to hold to be true is not to be true.
The other type of thinker is able to use the same equations without finding it necessary to conceive or image their meaning in any such terms. Physical change for him is not in every case a diminutive cosmical or molar phenomenon, a change of place ; but there are as well changes of state, of qualities, to which the equations are applied, and which are frankly admitted to present something quite new and not deducible from elements of any kind. The conditions in the presence of which the new appears, i.e., the critical point, can be empirically established; or, within certain limits, the degree of change or appearance of something new can be found by experiment to be a function of an independent variable. Thus there is established a purely empirical law of determination. Before, however, such experimentation is made, it is quite impossible to predict either the critical point or the new qualities which shall appear there; and afterward it is equally impossible to deduce these from any elements that might be chosen. There is here no logical determination or necessity, but recognition is frankly made of a de novo origin, of discontinuity, of a
