January 12, 1905] 



NA TURE 



243 



the literature of the subject. We do not find any re- 

 ference to the underlying assumption which has up to 

 the present been unearthed in every attempt to treat the 

 problem mathematically. But this is hardly a point on 

 which anyone but a specialist could be expected to 

 light, and the majority of specialists make the assump- 

 tion without knowing it {pace Burbury's criticisms). 



The last chapter but one deals with the development 

 of mathematical thought. We have selected for 

 special examination the portions dealing with Cantor's 

 researches on the transfinite and the continuum, and 

 we find the subject treated in such a way as to pre- 

 sent a clear and definite picture to one who has not 

 specialised in this difiicult branch of mathematical 

 thought. The last chapter contains a retrospect and 

 prospect. 



We must not omit to mention what is, perhaps, as 

 important a feature as any, namely, the footnotes, 

 which occupy a considerable proportion of the whole 

 book, and constitute a kind of historic encyclopjedia. 



We do not believe in filling reviews with lists of mis- 

 prints, but the "Racket" (index, p. 800) may per- 

 haps better describe Stephenson's locomotive than its 

 correctly spelt name. A more serious defect is that 

 these two large and bulky volumes have been issued 

 with the pages uncut, and readers have to waste much 

 time in doing what is the proper work of the guillotine 

 before they can begin the book. This want of thought 

 on the part of the publisher (on his own head be it — 

 i.e., the guillotine) constitutes a serious obstacle to the 

 attempts made by scientific workers of the present day 

 in endeavouring to cope with the ever-increasing mass 

 of literature that accumulates before them. 



G. H. Bryan. 



THE PROBLEMS OF VARIATION. 

 I'ariation in Animals and Plants. By H. M. Vernon, 

 M.D. The International Scientific Series. Pp. ix + 

 415. (London : Kegan Paul and Co., Ltd., 1903.) 

 Price 55. 



I^HIS little book meets a real want. The frequent 

 discussions of recent years upon the problems of 

 evolution have been followed with much interest by 

 an increasing number of readers and listeners, with 

 the desire but often the inability to understand. 

 .\ very large amount of interest and stimulus has been 

 excited by such questions as acquired characters and 

 their transmission or non-transmission by heredity, 

 the continuity of the germ-plasm, physiological selec- 

 tion, continuous or discontinuous evolution, De Vries's 

 experiments and views on mutation, the Mendelian 

 hypothesis as opposed to that of Galton and the bear- 

 ing of the great array of facts, the fruits of observ- 

 ation and experiment conducted by those who take 

 opposite sides in the controversy. The present writer 

 has often been surprised at the keenness of the interest 

 which can coexist with an almost complete lack of 

 knowledge of the essential details, and he feels that 

 the present work provides precisely the information 

 that is required — a clear, accurate, and dispassionate 

 statement, not too long or too detailed, of researches 

 and reasoning upon problems connected with variation. 

 NO. 1837, VOL. 71] 



The notable success of Section D during the late 

 meeting of the British .Association at Cambridge 

 provides an excellent illustration of the wide and deep 

 interest excited, at the present moment, by the last 

 of the subjects mentioned above, and was in itself in 

 some measure an answer to the complaint in the presi- 

 dential address that insufficient attention was paid 

 to the re-discovered discoveries of Mendel. The sub- 

 ject was new to probably a large proportion of the 

 audience : those among them who had taken the 

 opportunity of reading the fourth and fifth chapters 

 (on blastogenic variation) of this work must have felt 

 that they were thoroughly prepared to follow the dis- 

 cussion in all its detail. 



The book is divided into three parts, of which the 

 first, dealing with the facts of variation, contains- 

 three chapters, on the measurement of variation, 

 dimorphism and discontinuous variation, and corre- 

 lated variation respectively; the second, the causes of 

 variation, includes two chapters on blastogenic vari- 

 ations, one on certain laws of variation, and four re- 

 spectively treating of the effects of temperature and 

 light, moisture and salinity, food and products of meta- 

 bolism, and conditions of life in general; the third, 

 variation in its relation to evolution, is considered in 

 chapters on the action of natural selection on variation, 

 and on adaptive variations. 



The author wisely uses the word " hybridisation " 

 very prominently in his account of Mendel's researches 

 and conclusions. In the comparison between the 

 Galtonian and Mendelian views of heredity an im- 

 portant difference is sometimes lost sight of — the pre- 

 sent writer does not remember hearing it expressly 

 mentioned, although it was certainly implied, at Cam- 

 bridge. The former view is, at any rate chiefly, built 

 upon the results of interbreeding between individuals 

 separated by ordinary differences, the latter upon inter- 

 breeding between individuals separated by differences 

 comparatively large. " Ordinary " differences are the 

 points of distinction — generally small, mainly differ- 

 ences of degree — by which we discriminate between 

 the individuals of a species forming a single compact 

 mass, or if the species be broken up into two or more 

 masses — then between the individuals within each of 

 them. The larger differences alluded to are the 

 points of distinction — generally large, frequently 

 differences of kind — between the individuals of one 

 mass (" species," " race," or " breed ") and those of 

 another, or between the ordinary individuals of a 

 mass and those sudden large departures from its type 

 which are apt to appear spontaneously in its midst. 

 Even when breeds or races are distinguished by a test 

 apparently so superficial and unimportant as colour, 

 we are probably often confronted by the mere outward 

 sign of inward and important distinction. 



If the Mendelian view should hereafter be estab- 

 lished beyond the possibility of doubt, there will still 

 remain the interesting question of the part it has 

 played in evolution. This is very largely the attempt 

 to decide whether Darwin's earlier or later views were 

 correct, whether evolution proceeds from the selection 

 of large variations, "as when man selects," or from 

 the selection of ordinary individual differences as-- 



