546 



NATURE 



[July i, 1920 



desiccation. They can aestivate for a considerable 

 time. In habit they are largely nocturnal, and 

 are most active on misty nights. They feed mainly 

 on fungi. They mate on the ground, and, though 

 hermaphrodite, one functions as a male and the 

 other as a female. The eggs are laid singly at the 

 base of tufts of grass and beneath the surface. It 

 takes between two and three years for an in- 

 dividual to reach full maturity. 



For experimental purposes a number of Bahama 

 forms were introduced into the Florida Keys, 

 which present a considerable range in climatic 

 factors and vegetation. There is on many of the 

 Keys an indigenous species of Cerion, C. incanum, 

 Binney, but it is not nearly related to any of the 

 forms introduced ; and one of the interesting 

 . results obtained by Dr. Bartsch was that the 

 cross-breeding of the native species with the intro- 

 duced C. viaregis brought about a state of flux. 

 Had the resulted colony been discovered by one 

 who did not know the history, a description would 

 have been given of a very variable species. The 

 inference is that similar complexes of unknown 

 origin are likewise the product of cross-breeding. 

 The case is peculiarly interesting because C. in- 

 canum and C. viaregis are very remotely related. 

 "The fact is, that it is very surprising that 

 organisms presenting such great differences in 

 organisation should be able to cross at all, and it 

 is still more remarkable that they should have 

 produced fertile crosses." The author is inclined 

 to believe that the crossing has an "energising 

 effect " on the new product, but recent work on 

 "hybrid vigour" leads one to think rather that 

 what occurs is a happy pooling of hereditary items 

 which corroborate one another. The general pic- 

 ture the author's results leave in the mind is that 

 species separated for ages might be brought to- 

 gether by changes of level, so that crossing re- 

 sulted. There followed an efflorescence of new- 

 forms which were later subjected to isola- 

 tion on islands and promontories where inbreeding 

 gradually eliminated diverse characters, eventually 

 resulting in the more or less homogeneous ex- 

 pression which now marks in the Bahamas a multi- 

 tude of insulated colonies. 



Space and Time in Contemporary Physics: An 

 Introduction to the Theory of Relativity and 

 Gravitation. By Prof. Moritz Schlick. Ren- 

 dered into English by Henry L. Brose. With 

 an introduction by Prof. F. A. Lindemann. 

 Pp. xi-fSg. (Oxford: At the Clarendon Press, 

 1920.) Price 65. 6d. net. 

 Here is a readable book, excellently translated, 

 for which we have again to thank Mr. H. L. 

 Brose. Though it is called an introduction to the 

 theory of relativity and gravitation, it is more 

 strictly an essay on "The Inseparability of Geo- 

 metry and Physics in Experience," to quote the 

 title of its fifth chapter. The main problem in 

 presenting the work of Einstein to the physicist 

 is to enable him to see how obstinately meta- 

 physical he is. 



"Time and space can be dissociated from 

 NO. 2644, VOL. 105] 



physical things, and events only in abstraction. 

 The combination or oneness of space, time, and 

 things is alone reality ; each by itself is an abstrac- 

 tion." Many will say such statements are meta- 

 physical in nature. In a sense, indeed, any state- 

 ment is metaphysical which is concerned with 

 logic. The real merit of Einstein's theory is that 

 it does not trouble to ask what space and time 

 are, or how far they may be logically separated 

 from things. It does not attempt the separation. 

 It goes straight ahead, keeping them all together 

 until a result is arrived at which may be tested 

 without any doubt or dispute as to its logical 

 meaning, by the only method of exact observation, 

 the perception of complete coincidence. It renders 

 Newton's highly metaphysical definitions of space 

 and time unnecessary ; but while philosophers 

 pause to see how they have to re-model their 

 definitions, the physicist may congratulate him- 

 self that history has again proved that the real 

 advances are made by those who, with open mind, 

 continue in their endeavour to order the direct 

 facts of experience in the most comprehensive 

 manner. 



History of the Great War, based on Official 

 Documents. By Direction of the Historical 

 Section of the Committee of Imperial Defence : 

 Naval Operations. Vol. i. By Sir J. S. 

 Corbett. Pp. xiv + 470 + case of 18 maps. 

 (London: Longmans, Green, and Co., 1920.) 

 Price lys. 6d. net. 



This important volume, the first of a series which 

 is expected to run to four or five volumes, is 

 described on its cover as the "official history of 

 the war." This description is modified within by 

 the explanation that, though it is based on official 

 documents inaccessible to the general public, its 

 views and opinions are those of its author alone, 

 for which the Admiralty accepts no responsibility. 

 This explanation unquestionably diminishes the 

 official nature of the publication ; but, on the other 

 hand, it immensely increases its historic interest 

 and its scientific value. For Sir Julian Corbett 

 is a master of naval lore ; he is deeply versed in 

 the strategy and the tactics of the great captains 

 of the old days. Consequently he has come to 

 the study and interpretation of the masses of in- 

 formation concerning the late war laid before him 

 by the Government with a splendid reserve of 

 knowledge and with a perfected apparatus of 

 criticism, and it is eminently satisfactory to be 

 assured that he has had a perfectly free hand in 

 dealing with his material and in drawing his con- 

 clusions. 



The volume deals in a most illuminating manner 

 and with a wealth of new information with the 

 situation at the outbreak of the war, with the 

 problems which the Navy had to face and solve 

 during the critical months of 1914, and finally 

 with the thrilling battle of the Falkland Islands. 

 We await with eager anticipation the remaining 

 volumes of the series. The maps, it may be 

 added, are of the highest value and importance. 



