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VII. NEW BOOKS. Studies in General Physiology. By JAQUES LOEB. 2 vols. Pp. 782. The Decennial Publications of the University of Chicago, sec. series, vol. xv. 1905. Ix these two volumes Prof. Loeb has brought together thirty-eight sleeted papers previously published in various periodicals, mostly German. The volumes thus contain the most important contributions to general physiology of this very original worker. " A single leading idea permeates all the papers of this collection, namely, that it is possible to get the life-phenomena under our control, and that such a control and lothing else is the aim of biology." Comparative physiology has been for some decades unduly neglected by almost all the leading physiologists, who have concentrated their attention upon human physiology and have kept in view chiefly its relations to human pathology and medicine rather than the general problems of biology. Prof. Loeb's brilliant experimental researches in comparative physiology are therefore specially valuable at this time, because they are awakening a widespread interest in the more general problems. The most important papers of this collection deal fith three topics: (1) the tropisms of animals, (2) heteromorphosis, (3) fertilisation of egg-cells. The papers of the last group report experiments which Prof. Loeb succeeded in inducing development of the un- fertilised eggs of sea-urchins and worms up to an advanced stage by means of chemical and physical treatment. The most interesting fact about these experiments is that their success seems to prove the reality the author's insight into some of the chemical and physical conditions }f growth, because it was achieved not merely empirically, but by the aid )f theoretical considerations. The same is true, in much smaller degree, the experiments of the second group. These consisted mainly of very simple manipulations by means of which the author succeeded in in- ducing worms and sea-anemones and other such creatures to develop lew heads or mouths or tails in various unusual positions. The author inclined to regard the constancy with which any such result follows the appropriate treatment as evidence of a long step made towards the lechanical explanation of life-phenomena and as a heavy blow to neo- ritalism. But to me at least the experiments seem to render any con- 3eption of the morphogenetic forces less, rather than more, possible. So long as each organ is believed to develop only in its appropriate relations with the rest of the organs of the body one can imagine a certain segregation of particles of like functions (call them gemmules or by any Dther of the many new names for this old conception) and reciprocal leterminations of neighbouring groups. But if, as these experiments seem to indicate, every part is capable of developing any kind of structure and undertaking any kind of function if only subjected to the appropriate stimuli, these vaguely helpful conceptions must be rejected, id we stand more helpless than ever before the mysteries of growth,