NA TURE 



241 



THURSDAY, JULY 16, 1908. 



EXPERIMENTAL ENTOMOLOGY. 



ExpcrimcnIcUe Entomologische Studien vom pliysik- 

 aliscli-chcmisclicii Staiidpunkt aus. By Prof. P. 

 Bachmetjew. Zweiter Band; mit 25 Tafeln. Pp. 

 xvi + 944+cviii. (Sophia : Staatsdruckerei, 1907.) 



ALTHOUGH it is well known that many excellent 

 observers have of late years devoted their atten- 

 tion to experimental work of which insects are the 

 subject, it is probable that few students of entomoIoi;y 

 have realised hitherto how large is (he mass of 

 material that has now been accumulated in this de- 

 partment of research. The present work is somewhat 

 of a revelation. Its tale of nearly a thousand pages 

 consists almost entirely of a condensed account of 

 the investigations conducted by various experimenters 

 on the influence of external factors on the phenomena 

 of insect life. Even so, the list is not quite complete, 

 for, though the author, working under many diffi- 

 culties, has displayed an amount of industry in col- 

 lecting his material that is really astonishing, we 

 could yet name more than one memoir bearing on 

 the subject that seems to have escaped his vigilance. 

 We note, for example, the omission of any reference 

 to the striking experiments of Mr. G. A. K. Marshall 

 on South African Lepidoptera. Nevertheless, the com- 

 pilation has, on the whole, been admirably executed, 

 and Prof. Bachmetjew's bulky volume will be indis- 

 pensable to those workers in the subject who wish 

 to have the results of nearly all previous investigations 

 in a readily accessible form. The amount of labour 

 saved to his colleagues in entomology by the author's 

 determination to record every relevant fact hitherto 

 ascertained by experiment is quite incalculable. 



The work is divided into two parts, the first dealing 

 with the actual results obtained by various investi- 

 gators, the second giving the theoretical conclusions 

 considered by these and other authorities to be war- 

 ranted by the experiments in question. As might be 

 expected, these speculative opinions are of very un- 

 equal value, and it is to be observed that the author 

 makes little or no attempt to decide between them 

 when they are contradictory, or to condemn them 

 when erroneous. He has rather set before himself 

 the task of recording without distinction, not only 

 every fact relating to his subject, but also every 

 conclusion at any time, suggested, whether the latter 

 be good or bad. His own views, save on a few 

 points, are not much in evidence. It is clear from this 

 that the book has serious limitations; these, how- 

 ever, do not prevent it from being extremely useful 

 within the scope allowed it by its author. The in- 

 sects dealt with naturally belong almost entirely to 

 the order of Lepidoptera. 



The effects of the various external factors are con- 

 sidered in their relation to the time occupied in 

 development, to the size and form of the perfect 

 insect, and to its ultimate colouring and pattern. 

 Under each of these main heads the influence is con- 

 sidered of cliinate, moisture, temperature, light," the 

 colouring of the surroundings, food, including 

 NO. 2020, VOL. 78] 



chemical food-material artificially employed, elec- 

 tricity, magnetism, friction, artificial constriction, 

 pressure, gravitation, and other factors. 



The author defers to a future treatise the questions 

 of seasonal dimorphism, protective resemblance, 

 mimicry, and parthenogenesis. The omission of these 

 subjects, especially of the first three, marks a further 

 limitation of an important character, for they often 

 have a special bearing on the interpretation of such 

 facts as are here recorded. Indeed, inasmuch as an 

 appreciation of the significance of the changes induced 

 by the operation of e.xternal factors is often entirely 

 dependent on a knowledge of the insect in question 

 in its relation to seasonal, mimetic, and cryptic con- 

 ditions, the present treatise, useful as it is, can only 

 be considered as a partial introduction to the theory 

 of the subject. 



The book is fitly dedicated to Dr. Max Standfuss, of 

 Zurich, whose experiments, conducted on a very lar-jc 

 scale, have, perhaps, done more than those of any 

 other investigator to establish our knowledge of the 

 effects of temperature applied during the immature 

 stages on the form and colouring of the perfect in- 

 sect. His experiments in hybridisation, although car- 

 ried out before attention had been generally directed 

 to the epoch-making work of Mendel, are also very 

 worthy of note. Next to Standfuss's experiments, 

 perhaps the most important work of this nature is 

 that conducted through many years by Mr. F. Merri- 

 field at Brighton, and we are glad to see that due 

 prominence is given to his admirable investigations 

 in Prof. Bachmetjew's pages. Among other work 

 carried out by English experimenters is that of Prof. 

 Poulton, which also comes in for appreciative notice, 

 but here we cannot fail to observe the somewhat un- 

 fortunate effect of the author's determination to re- 

 serve the question of protective coloration for future 

 treatment. Much of the significance of Poulton 's re- 

 sults on the effect of surrounding objects on the 

 colouring of larvse and pupae is thus for present pur- 

 poses lost. It is from their bearing on evolutionary 

 problems that data of this kind derive their highest 

 interest, and we must once more remark on the op- 

 portunities thus missed by the author. We may hope, 

 however, that the omission is only of a temporary 

 character, and that we shall yet see a treatise from 

 his hand which will throw fresh light on many ques- 

 tions of primary importance in the study of evolution. 



The plates consist for the most part of graphic 

 representations of the statistical results furnished by 

 the tables in the body of the work. They are useful 

 as exhibiting series of facts in a form which by most 

 people is more easily appreciated than a bare 

 numerical statement. 



It will have been gathered from the foregoing re- 

 marks that. Prof. Bachmetjew's volume is mainly 

 designed as a work of reference. In accordance with 

 this plan, the literature of the subject has been very 

 carefully catalogued, and the bibliography, which 

 occupies seventy-seven pages at the end of the book, 

 besides occasional lists given in the text, is of a very 

 full description. It is true that there are omissions, 

 but these do not appear to be numerous. 



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