iO 



JVA TURE 



[May 1 6, 1901 



(as Sitiurnia carpini and Orgyia aniiqua) accept the first 

 male that arrives, while those of others (as Charaeas 

 graminis) allow a period of competitive courtship ; and, 

 further, that as a rule moths with bright colours belong — 

 or at a former period did belong — to the latter group 

 rather than to the former. 



Plate's own view as to female choice is that it is 

 exercised only as between pairing and not pairing. 

 There is, he thinks, plenty of evidence as to success or 

 failure of incitements employed by the male, but little or 

 none of choice by the female between individual suitors. 

 The distinction seems rather delicate. A would-be 

 pairer may fail from want of sufficient power to charm the 

 female ; but rejection implies choice, and if competitive 

 incitement does take place, as Plate seems to allow, 

 whether simultaneously or successively, how does this 

 differ from sexual selection in Darwin's sense? 



On the subject of " sports," the author is no doubt 

 right in contending that they have little or no bearing on 

 the question of species-formation. But before unre- 

 servedly asserting that they must tend to be swamped 

 by intercrossing with the parent species, he would have 

 done well to examine the evidence brought forward by 

 Standfuss and others in support of the position that the 

 crossing of an aberration with the parent form may 

 often result, not in the production of intermediate types, 

 but in the sharp cleavage of the offspring into two groups, 

 each resembling one of the parents and not the other. 

 If these observations and experiments are to be relied on, 

 they imply the theoretical possibility of a sport, sup- 

 posing it to be selected, eventually displacing the parent 

 form ; and, indeed, there is little doubt that under 

 domestication something very much like this has actually 

 occurred. 



The treatment of adaptation is in many respects ex- 

 cellent. Kallima, the well-known Indian genus of leaf- 

 like butterflies, is once more brought to the front and 

 used as a conclusive instance of selection, furnishing also 

 a good redicctio ad absiiydiDii of the " photographic " 

 theory. But the author introduces a needless confusion 

 by his method of handling the subject of "direct" and 

 " indirect " adaptation. The former, he says, is repudiated 

 by the "School of so-called Neo-Darwinians," of whom 

 he specifies Weismann, Wallace and Spengel. It is 

 certainly repudiated by them in the sense that they see 

 no evidence for the " transmission of modifications due to 

 individual plasticity," to use Lloyd Morgan's expression. 

 But a distinction much more in accordance with the facts 

 is that between " variable" and " invariable "adaptations. 

 In the former are included such cases of individual 

 assimilation in colour to surrounding conditions as have 

 been principally made known, in the instance of eater- 

 pillars and chrysalises, by the labours of a " Neo- 

 Darwinian." These adaptations are apparently "direct " 

 in the sense that they mark a reaction of the individual to 

 its own environment, but not in the sense that they are 

 in any way actually produced by that environment. In 

 common with all other cases of adaptation, whether 

 variable or invariable, they are ultimately the result of a 

 process of selection. The sensitive species is selected, 

 not because it is green or because it is brown, but because 

 in response to the appropriate conditions it is capable of 

 becoming either one or the other. Plate's inclusion of 

 NO. 1646, VOL. 64] 



Haeckel, Lloyd Morgan, Osborn and Henslow in the 

 same category of believers in " direct adaptation," to- 

 gether with his criticism of Baldwin on an earlier page, 

 serves to show that he has imperfectly grasped the point 

 at issue. What we hold to be the true doctrine has been 

 excellently expressed by Spengel in a passage quoted by 

 Plate with disapproval (p. 141). 



Though we have felt bound to express dissent on many 

 points, we must not be taken as undervaluing Plate's 

 labours. On the contrary, we have formed a high opinion 

 of his knowledge, industry and argumentative power. As 

 a champion of the indispensability of natural selection he 

 has done excellent service, and it is only to be regretted 

 that in adopting this illuminating principle he has failed 

 to set himself free from the bonds of what seems to us a 

 fanciful and unnecessary adjunct. F. A. D. 



A TEXT-BOOK OF ELECTRICITY. 

 DeschanePs Natural Philosophy. III. Electricity. By 

 J. D. Everett. Pp. xii -I- 358. (London : Blackieand 

 Son, Ltd., 1 90 1.) 



PROF. EVERETT'S " Deschanel ' is too well known 

 to need commendation, and the new edition which is 

 now before us has the many merits of its predecessors. 

 The account it gives of fundamental electrical phenomena 

 IS admirable, the descriptions of apparatus are clear and 

 good, though at times slightly too concise, the printing is 

 well arranged and accurate, and the illustrations are 

 excellent. In places, it is true, we recognise old friends 

 which have done duty somewhat too often. 



At the same time, the task just now of writing a really 

 satisfactory text-book of electricity is a most difficult one, 

 and Prof. Everett's success is not complete. 



" The work," he says in his preface, " is in the main 

 new. Electrical theory has been revolutionised during 

 the past few years ; and great need exists for a text-book 

 which shall present the subject in its present shape 

 as a clear and connected whole without demanding on 

 the part of the reader an exceptional amount of mathe- 

 matical knowledge. This is the want which I have en- 

 deavoured to supply." 



"The work is /« the main new." Prof. Everett has 

 hampered himself in his attempt to give a modern theory 

 of electricity by retaining even that part of the old which 

 he has kept ; the result is somewhat of a patchwork. 

 Thus, Maxwell's conceptions with regard to electric 

 action in dielectrics are introduced as "a new chapter in 

 electrostatics." What was wanted was not an additional 

 chapter in an old book, but an elementary account of the 

 fundamental phenomena of electrostatics, given in the 

 language of Maxwell's theory. 



The book commences with electrostatics, and of neces- 

 sity the language used at first is that of the theory of 

 action at a distance. A charged body attracts light 

 bodies and repels other bodies similarly charged ; the 

 action of a gold leaf electroscope depends on the repul- 

 sion between the like charges of the leaves ; the electro- 

 phorus is described as a means of obtaining electricity in 

 small quantities, but no explanation is given in §30 of 

 its action. 



The idea of electric potential is introduced in chapter 

 vi., the first of the chapters in large type. These, it is 



