sure how the divisions will occur under given conditions, as we are that H 2 -f O will give water. We have to find out both facts experientially to start with, and both are novel then and never so again. However all this may be, Mr. Baldwin's pronunciamento will, in its negative aspects at least, undoubtedly have a salutary influence upon the discussions at present going forward.
It has now been sufficiently illustrated what was meant by saying at the outset that a synthetic era in biology must necessarily involve a measure of philosophy. Biologists find, in bringing together all the lines of evidence bearing upon evolution, the great synthetic hypothesis, that they must define the scope of the principles with which they work, e.g., causation, mechanism, teleology, etc. The problems of heredity, variation, selection, and the like, inevitably involve these categories. Moreover, consciousness must at least be recognized, and so the psychologist is called in and given respectful attention. Mr. Baldwin's book is an admirable example of this convergence of scientific and philosophic interests, and the biologist must acknowledge his obligation for the forceful way in which these matters outside his own sphere have been laid before him.
Of the nineteen chapters in the present volume, eleven are reprints, with more or less of change, from articles previously published. In addition to the seven new chapters, in which the most important material deals with psychology and its relations to biology, including the chapter on genetic modes, Mr. Baldwin submits in appendices a list of admirable discussions upon organic selection and its near relatives by Osborn, Lloyd Morgan, Poulton, Headley, Conn, and himself.
Although the book inevitably suffers somewhat from its mode of construction, it is nevertheless, in the reviewer's opinion, much the most lucid and vigorous of the series to which it belongs. Despite a certain measure of repetition, there are almost none of the annoying cross references to the author's other works of which reviewers of his previous books have so often complained. One may think the argument good, bad, or indifferent; but at all events it is straightforward and ready to rest upon its own merits. The shortcoming which the lay reader most often feels, is the lack of richer illustrative material. In its place one finds a strong disposition to "logical disquisition," as Mr. Baldwin calls it, when criticising Romanes for a similar sin. Such a defect is, perhaps, unavoidable when a scientist steps outside his own specialty, and it should be said in fairness that Mr. Baldwin makes no pretense of biological proficiency. Taken together, Mental Development, Social and Ethical Interpretations, and Development
