importance to the causes of variation than to any of the other problems considered by Darwin, among which functional activity and external conditions seemed the most powerful. He was thus led to believe that a deeper insight into the phenomena of evolution would ultimately be obtained by pursuing the line of inquiry suggested by Lamarck, than by continually searching for new instances of adaptation to be explained by the Darwinian formula. While in this frame of mind he was "delighted to find" that Weismann had to contend with a formidable opponent in his own country, and concluded that he could not for the present oppose the progress of his views more effectively in England than by publishing a translation of Prof. Eimer's arguments. It had seemed to this author long ago to be of the greatest importance to undertake an investigation of the question whether the modification or variation of the species of animals is not governed by definite laws. The Darwinian theory suggested none. The investigation of the laws of variation included the question of the causes of variation. There was likewise a gap in the Darwinian theory where these should be explained. The principle of utility, the selection of the useful in the struggle for existence, did not explain the first origin of new characters, but only, and that partially, the progress and the gradually effected pre-eminence of those characters. If we could know, the author assumed, all the natural laws which have operated in the evolution, and which operate in the existence of a single animal or a single plant, we should understand the laws of the organic world altogether. Applying this principle, the unreserved study of a single species of animal, the author declares, led him to the discovery of a whole series of laws, which the extension of the investigation to other species showed to hold good generally. This animal was the wall-lizard (Lacerta muralis cœrulea), a species of remarkable variability, with which he became acquainted on the rocks of Capri. The result of his researches, which were extended to various classes of animals, "was the recognition of the dominion of laws in the process of variation, not only of the lizard, but also in the most diverse tribes of the animal kingdom; these laws holding firstly in the variations of marking, previously regarded as quite indifferent, unimportant, or fortuitous, but also applying to other characters. I was able to demonstrate that variation everywhere takes place in quite definite directions which are few in number, and I was able on the basis of my observations to put forward the view that the causes which lead to the formation of new characters in organisms, and in the last result to their evolution, consist essentially in the chemicophysiological interaction between the material composition of the body and external influences. Finally, I succeeded, through the facts I established, in referring the separation into species, . . . in connection with the rest of my views, to natural causes." Previously to presenting these results in the present volume, a brief review is given of the newest theories concerning evolution. The translator has endeavored to make his work sufficiently English to be readable, and to preserve the full force and exact significance of Prof. Eimer's expression.
A Short Course of Experiments in Physical Measurement. By Harold Whiting. In Four Parts. Part I: Density, Heat, Light, and Sound. Cambridge: John Wilson & Son. Pp. 278.
The course of laboratory work which this book is to comprise covers the ground of both the "minimum" and the "maximum" requirements in physics for admission to Harvard College, and it is intended also to serve as a preparation for courses in mechanical and electrical engineering in other institutions. Mental training is the chief object aimed at, through the care required, and the practice in inductive and controlled methods secured. The policy of the book is rather "to show how comparatively accurate results may be obtained by rough apparatus, than to explain the use of instruments of precision, which in the hands of a student are apt to give erroneous results." The author states that not so much mathematics is involved in these experiments as would appear from a first glance, because many proofs are given in full here which in most textbooks have been taken for granted. The volume is illustrated with many cuts of apparatus. The second, third, and fourth parts are to contain experiments in other departments of physics.
