July 4, 1889] 



NATURE 



221 



elusions under severe and prolonged tests, such as those 

 attempted in Fritz Miiller's " Fiir Darwin," and in 

 Weismann's study of the markings of Lepidopteran 

 larvse. As Semper pointed out long ago (and too much 

 insistence cannot be laid upon it), the present need is not 

 for fine-spun theory — we have theories galore— but for 

 the judicious compilation of facts selected where the 

 leverage will tell, facts which shall either upset or 

 confirm — it matters not which — the theory of natural 

 selection. 



The book before us must be classed among the 

 speculative works just mentioned ; and the gist of the 

 author's views may be gathered from the following para- 

 graph, written in 1880 (p. 401) : — " Every permanent new 

 form (species or variety) commences with the isolation of 

 individual emigrants, separated for a prolonged period 

 from the habitat of some parent species which is in the 

 stage of variability. The active factors in the process 

 are : (i) adaptation of the immigrant colonists to the exter- 

 nal conditions of the new habitat (nutrition, climate, soil- 

 composition, competition) ; and (2) the impression and 

 development of the individual characteristics of the first 

 colonists upon and in their posterity by reason of the 

 breeding between near kin. This formative process 

 ceases as soon as, owing to rapid multiplication, the 

 levelling and compensating effects of intercrossing make 

 themselves felt, resulting in and niaintaining that uniformity 

 which characterizes every gooa species and permanent 

 variety." Wagner's hypothesis exalts the importance of 

 geographical isolation at the expense of natural selection, 

 and thus approximates, both at starting-point and con- 

 clusion, to Mr. Gulick's recent theory of " divergent evo- 

 lution through cumulative segregation " (Journ. Linnean 

 Soc, vol. XX. p. 189), though in detail the respective 

 courses taken by the two writers are by no means 

 identical.'* 



Consisting of a reprint of articles published between 

 1868-86, mainly in Kosinos, Das Ausland, and \h& Allge- 

 meine Zeituiig, the matter of the book has been long 

 before the public, and its conclusions have been attacked 

 from time to time by Haeckel, Weismann, Oscar Schmidt, 

 and others ; a translation of the first, and perhaps the 

 most important article, has appeared in London (Stan- 

 ford, 1873) : criticism of the theory in this place is therefore 

 unnecessary. The present reprint is edited by Wagner's 

 nephew and namesake, in accordance with a wish ex- 

 pressed some time before his death in 1887, and contains, 

 besides the articles previously published, a biographical 

 sketch by Dr. von Scherzer, and editorial introductions ; 

 while the last 127 pages are devoted to an attempt of the 

 editor to build certain recent discoveries, such as those of 

 the Challenger, into the original structure. It is hardly 

 necessary to say that, being a close-printed German 

 octavo of 667 pages, the book possesses no index. 



Sylvan Folk. By John Watson. (London: T. Fisher 

 Unwin, 1889.) 



Mr. Watson expresses much contempt for what he calls 

 "the dry bones of science." We are not sure that we 

 quite understand what he means by this expression, but 

 It evidently does not imply that he dislikes results ob- 

 tamed by careful and exact observation. In the present 

 little volume he gives ample proof that he often brings 

 hirnself face to face with Nature, and that he knows how 

 to interpret many of the innumerable signs and symbols 

 which are readily misunderstood, or altogether over- 

 looked, by less careful inquirers. Mr. Watson is especially 

 happy in his notes upon the ways of birds ; but he has also 

 interesting chapters on mice, voles, and shrews, on red 

 deer, fallow, and roe, on British seals, on British fur- 

 bearers, and on " Nature by night." There is not much 

 that is absolutely new in any of the information he has 

 brought together ; but his descriptions are so fresh— they 

 suggest so vividly the idea of happy hours spent among 

 attractive scenes in the open air— that they will give 



genuine pleasure to everyone who reads them. The 

 book will be especially interesting to young readers, who 

 will be glad to learn that it depends very much upon 

 themselves, according to Mr. Watson, whether they shall 

 be on terms of intimacy with the wildest woodland 

 creatures. Mr. Watson thinks that the power of attracting 

 wild creatures was once a much more common possession 

 than it is now. 



A Practical Guide to the Climates and Weather of India, 



Ceylon, and Burmah, &^c. By Henry F. Blanford, 



F.R.S. Pp. 369. (London: Macmillan and Co., 1889.) 

 The appearance of this book is very opportune. The 

 Indian Meteorological Office has been in existence for 

 some twenty years, and inasmuch as the region over 

 which its operations extend comprises a very considerable 

 area of the earth's surface, representing climatological 

 conditions of the most varied character, a general resume 

 of the information as to these conditions is one of the 

 most important contributions to climatology that could be 

 made. 



Mr. Blanford has well fulfilled his task. He says his 

 work " is not addressed to meteorologists and physicists, 

 .... but more particularly to agriculturalists, medical 

 officers, engineers, pilots and other seafaring men, and to 

 those others of the general public to whom the weather 

 and the climates of India and of its seas are practical and 

 not scientific objects of interest." 



The book is divided into two parts : (i) the elements of 

 climate and weather ; (2) the climates and weather in 

 relation to health and industry. 



The former is naturally the more technical, while the 

 latter appeals to the general public, as it gives a detailed 

 description of the climates of the principal and most fre- 

 quented hill stations, as well as of the plains, under which 

 latter general head the different provinces or districts 

 receive each a separate notice. 



One section is specially devoted to the storms of the 

 Indian Seas. In their discussion Mr. Blanford is a pro- 

 nounced adherent of the spiral in-draft theory in contra- 

 distinction to the old circular theory and the well-known 

 " eight-point rule." 



About the most valuable chapter is the last, which 

 is mainly occupied with rainfall and evaporation. The 

 questions relating to these are of paramount importance 

 for the bare existence of millions of the population. Such 

 a famine as that of 1834 in the Doab was sufficient to 

 induce the authorities of the day to construct the Ganges 

 Canal, the greatest work of the kind in the world, and 

 one which has in a great measure corrected the injurious 

 effects of irregularity in the rainfall. 



The appendixes give the tabular results of the instru- 

 mental records, which are required to substantiate the 

 general statements contained in the previous pages. 



The work is a most creditable production, and it will 

 long remain the standard authority on any question 

 bearing on the chmate of the Indian Peninsula. 



The Unrivalled Atlas. Enlarged Edition (i 8th). (London 



and Edinburgh : W. and A. K. Johnston, 1889.) 

 A NEW and enlarged edition of this atlas has just been 

 published. The forty maps which it contains are well 

 engraved and especially full of information concerning 

 railway communication, whilst the fact that the index 

 contains 20,000 names of places, with their latitude and 

 longitude, testifies to its completeness. An extension of 

 the atlas has been made by the addition of two classical 

 maps, with an index to them, two physical maps of the 

 British Isles and Europe, and two astronomical plates, 

 each being accompanied with descriptive letterpress. A 

 misleading paragraph occurs in the explanation of tidal 

 action. We read : " The moon exerts a much greater 

 influence on the production of tides than the sun ; for, 

 though its mass is excessively small in proportion, it is 

 four hundred times nearer the earth." The inference that 



