168 SCIENCE PROGRESS 



will cover not only that subject in the sense in which it is generally understood, 

 but also that usually designated as General Physiology. The line of demarcation 

 between these two sciences has always been a difficult one to draw, and since they 

 both aim at the investigation and analysis of the phenomena of living beings and 

 the expression of such activities in terms of physics and chemistry, it is wise in 

 such a series of volumes to include both branches of study, which are, after all, 

 fundamentally the same. The editors of the series are Jaques Loeb, T. H. 

 Morgan, and W. J. V. Osterhaut, and these in themselves are sufficient guarantee 

 of the quality of the books to come. This is but the first, and as the list of volumes 

 in preparation, besides those by the editors, includes such names as Conklin, 

 Pearl, and Jennings, the width of its appeal will be manifest. Such a series has 

 long been needed in order that biologists in all countries may be kept in touch with 

 this prolific school of American scientists, and it is assured of a good reception. 



Loeb's own views on what may be called, for lack of better terminology, the 

 mechanistic conception of life, are too well known to be again made the subject of 

 discussion, and it will suffice to say that they are here presented in his usual 

 vigorous manner. Much of the matter in the first chapters, which are introductory, 

 is familiar to followers of Loeb's work ; but its inclusion is necessary for the right 

 appreciation of the discussion. The main part of the book is occupied with the 

 description of new and interesting experiments on the tropisms of the lower 

 animals. Apart from the actual matter contained, which is in itself valuable, 

 there are also described certain experiments and pieces of apparatus that could 

 easily be utilised for demonstrating these reactions in class work. 



The author seeks to show that tropisms are the result of a mass-chemical 

 reaction, and the phenomenon mainly investigated was that of heliotropism. It 

 is claimed that all the numerous reactions obtained in the light experiments of 

 other workers and of the new ones here described are the direct result of the 

 photo-chemical activity of the light. Moreover, the law of Bunsen and Roscoe, 

 that the photo-chemical effect produced is a function of the intensity into the 

 duration of the illumination, is held to be valid in all cases of animal and plant 

 heliotropisms. Several very ingenious experiments were devised to test this 

 claim, and the results in all cases appear to justify the author's assumptions. 



Although heliotropism is the subject most studied, there are other portions 

 dealing with goetropism, chemotropism, thermotropism, stereotropism, etc., and it 

 is interesting to note that the author has found that the same fundamental tropisms 

 are exhibited by sessile animals, e.g. hydrozoa and plants on the one hand, and by 

 motile plants and animals on the other, a point that emphasises very clearly the 

 basic nature of these reactions in living beings. 



Whether one agrees with the author's mechanistic explanation of the behaviour 

 of organisms or not, this is a book that will have to be considered seriously by all 

 workers on the subject. The "vitalist" will find in its pages trenchant criticisms 

 of his attitude that cannot be dismissed by any airy platitudes, since they are 

 supported by a wealth of experimental results. 



The volume is a fascinating and a useful one, and should its successors in the 

 series maintain the standard it has set, they will perform a signal service to 

 biologists the world over. C. H. O'D. 



A Junior Course of Practical Zoology. By A. M. Marshall, M.A., D.Sc, 

 F.R.S., and C. H. HURST, Ph.D. Eighth Edition. Edited by F. W. 

 Gamble, D.Sc, F.R.S. [Pp. xxxvi+515, with 94 figures.] (London: 

 John Murray, 1918. Price 12s. net.) 



It is unnecessary to review a book like " Marshall and Hurst," for it is in the 



