--This volume must be approached with liberality of spirit. If the reader must assume a pro- fessionally defensive attitude, with one hand raised to' set off the whole critical battery of his reference shelves, he may perhaps riddle the book at a hundred points, not one of which is likely to be vital. At the same time he may prove himself merely stiff-necked before some of the richest chapters of constructive criticism which have been printed in re- cent years. Perhaps the chief trouble is that Rensch falls between two stools. He disclaims the intention of scholarly completeness, yet falls short of the ease and continuity of the scientific essay. Where he might follow the graceful sequences of Dar- 'winian exposition, or the sincere sim- plicity of a Julian Huxley, he retains the jolting, subdivided, ugliness of the techni- cal paper of the day, though without its pretense to mechanical completeness. From an elaborate review and analysis of the geographic principle in modern sys- tematics Rensch passes with almost naive directness to the problem of the origin of species and the evidence for the direct influence of environmental changes, nor- mally unaided by mutation, selection, or the indefinite factors of "orthogenesis." The heart of the matter lies in the seventh chapter, which examines, and often,--perhaps suspiciously often,--sus- tains, such laws and such suggestions as serve to coordinate racial and enviren- mental gradations. The total' is impos- ing, and while it goes without saying that such an exposition, confined within 185 pages of text, can in strictness hardly win more than the verdict of "not proven," the array of evidence presented on such matters as progressive variation in size, proportion, and melanin quantity or quality, physiologic factors, sexual affinity and its relation to morphology, the relationships of laboratory and field genetics, and the histological basis of nany phenomena, is sufficient to keep a good company of field, museum, and li- brary naturalists employed for a genera- tion, testing and checking one plausible and constructive hypothesis after another. There is a suggestion that certain American sources have been treated rather casually. Those who are familiar with the array of modern critical para- phernalia which Dr. Linsdale has brought to bear on his races of Passerella will be amused to see his paper dismissed as "depending wholly on direct measure- ments, with no ratios." F. B. Sumner, who is drawn upon more extensively than any other American or Englishman, with J. A. Allen a close second, is apt to be "swallowed whole" with little regard even for his own reservations, as is the case with his experiments on temperature and hair-weight in mice. As may be inferred, the vast majority of sources, outside Rensch's personal investigation in Europe and the East Indies, are German. Two hundred and forty-eight titles are brought into play and assembled at last in an excellent bibliography of cited works. On page 116 a section heading has been omitted. On page 82 the word "rassen" appears to have been used in- adverntly in place of "arten."---T. T. McCARE, Februj 7, 1930.