334 SCIENCE PROGRESS 



object has been to discover what types of structure condition colour obvious to 

 the eye — the problem being one of special interest from the physiological as well 

 as the chemical standpoint. The importation of the all-seeing spectroscope into 

 the discussion makes an already complex problem one of hopeless complexity, as 

 every substance apparently has some absorptive power. Within the visible region, 

 the spectrocope has enabled us to learn little, if anything, more than we have 

 learnt with the aid of our eyes alone as to the " origin of colour " ; at most we have 

 ascertained with its aid that a few substances are visibly coloured, the colour of 

 which had escaped detection owing to the fact that they are but slightly absorptive 

 and had not been examined in sufficient thickness to permit of the eye appreciating 

 their colour. Sufficient for the day is the evil thereof — to many investigators of 

 colour problems ; there is no reason to disturb their simplicity of belief in the 

 human eye, nor to lay superhuman tasks before the contemplation of the student. 



So long as the electron is but " a figment of the physicist's imagination " (p. 545) 

 — it cannot well be claimed that it is more at present, and Dr. Smiles shows a 

 surprising lack of sense of proportion in referring to the atomic theory in similar 

 terms — it were better to refrain from advocating its adaptability to the problems of 

 valency ; the student should not at present be misled into believing that any real 

 progress has been made in applying electronic conceptions to the explanation of 

 chemical phenomena ; he should rather be taught that what has been advanced is 

 but superficial paraphrase of current chemical conceptions and that we are still in 

 a position of " as you were " of knowing nothing of first causes in chemistry. 



Read, mark, learn and inwardly digest — above all, inwardly digest — is the 

 caution to be given to all who would ponder on the interconnexion of structure 

 and properties. The present-day tendency is to bolt food ; we need a return to the 

 chewing habit in science perhaps more than in ordinary life. 



The Mutation Theory. Experiments and Observations on the Origin of Species 

 in the Vegetable Kingdom. By Hugo De Vries, Professor of Botany at 

 Amsterdam. Translated by Prof. J. B. Farmer and A. D. Darbishire. 

 Vol. I. The Origin of Species by Mutation. [Pp. xv + 582.] (London : 

 Kegan Paul, Trench, Triibner & Co., Ltd., 1910. Price iZs. net.) 



It is a satisfaction to have an English translation of the original documents of 

 Prof. De Vries's Muiatiofi Theory, and our feeling of satisfaction is heightened 

 when we find a translation by two experts who have themselves contributed notably 

 to the investigation of evolution-problems. They have not spared pains to give 

 us in pleasant English a reliable version of this great, but somewhat difficult 

 book, and they appear to us to have been singularly successful in their rendering 

 of the original. In fact, we prefer the translation to the original. Any alterations 

 that have been made have been examined and approved by the author. We 

 offer our congratulations and thanks to Messrs. Farmer and Darbishire. To 

 mix little things with great, we cannot say that we admire the contraction " Pro " 

 which occurs in front of Professor Farmer's name on the title-page of the copy 

 sent to us. 



Prof. De Vries's Die Mutationstheorie began to appear in 1900 and it was soon 

 recognised as a landmark. As the translators justly observe, it set forth "a 

 successful attempt to bring the process of specific differentiation within the sphere 

 of experimental inquiry." It need not be said that it is extremely desirable to 

 have a detailed knowledge of a book like this, but we are not prepared to follow 

 the translators' preface in its suggestion that this is a sine qua non for intelligent 



