444 



NATURE 



[June i, 191 i 



not of a tlioroughly convincing nature, all the more 

 so, seeing that the work is primarily intended for the 

 layman, who has not the means of sifting out such 

 matter and putting the correct interpretation upon it. 

 Thus in dealing with Malta fever, in a few short 

 sentences he would lead the reader to infer that mos- 

 quitoes often serve as the " inoculating^ " agents, 

 and unfortunately leaves one entirely in the dark as 

 to the true cause of the spread of this disease. 



Many of the photographic illustrations which 

 accompany this work are very good ; indeed, more 

 especially so are those representative of the various 

 developmental stages of the mosquitoes; we do not 

 agree with the author's statement, however, that 

 all his pictures show " the insects, not as we think 

 they should be, but as they actually are," because 

 both colour values and general morphological char- 

 acters are in many instances entirely wanting, and 

 the resulting print is nothing more than a silhouette. 

 Moreover, the photographs of both museum and 

 microscopical preparations show a marked absence 

 of care and neatness in the display of the various 

 organs, and such figures as these stand out in marked 

 contrast to those of Manson, Kellog, Nuttall, and 

 others. We would point out also that Figs. 76 and 

 77 represent a female and male mosquito respectively, 

 and not the reverse order, as stated by the author. 

 Ochromy'ia anthropophaga (p. 49) should read Auch- 

 mcrvmyia luteola. The latter, not the former, is the 

 parent of the congo-floor maggot. 



This work is furnished with an extensive and use- 

 ful bibliography occupying forty-seven pages, to which 

 annotations are appended. 



SYSTEMATICS. 

 Die taxonomischcn Grenzen der Art und ihrer Uiitcr- 

 abtcilungen. Versuche einer genauen Definition 

 der untersten systetnatischen Kategorien. By 

 Andreas Semenov-Tian-Shansky. Pp. 24. (Ber- 

 lin : R. Friedlaender and Son, 19 10.) Price 2s. 

 THIS is the German translation of a pamphlet 

 which appeared first in Russian. It deals on 

 a wide basis with the definition of the term species 

 and the lower categories in classification. The author 

 —whose title, "Tian-Shansky," reminds us of. his 

 exploration of the Tian-shan or Celestial Mountains in 

 Central Asia — pleads for uniformity of terminology 

 in the various branches of botany and zoology, and 

 then proceeds to examine critically the opinions of 

 various botanists and zoologists on the criteria of 

 species and its several component varieties. The 

 large experience gained by Semenov from his many 

 years' study of insects, especially Coleoptera, and his 

 acquaintance with at least an essential portion of the 

 literature bearing on the subject, enable him to sub- 

 stantiate his criticisms by illustrations drawn from 

 his own knowledge and to adduce corroborative 

 evidence from the writings of other authors. The 

 co-existent species are defined by the author as units 

 which are morphologically and psycho-physiologically 

 separated from each other. The units thus isolated 

 do not fuse, although very occasional intercrossing 

 NO. 2170, VOL. 86] 



may occur. The individuals belonging to a species 

 may all be practically alike, or they may form various 

 kinds of varieties. Semenov defines four principal 

 categories of modifications within a species : — 



1. .Subspecies or geographical race (subspecid 

 the most important subdivision of a species, inasmut ii 

 as it represents a phylogenetic stage one degree 

 below the complete separation from the parent stock. 



2. Nation (natio) is a term proposed by Semenov 

 for local varieties which are subdivisions of a sub- 

 species, each natio occupying only a comparatively 

 small definite portion of the whole area of the sub- 

 species. 



3. -Morph (morpha) is adopted for the non-geo- 

 graphical varieties which are produced 1 ' rrii,n 

 of the seasons, the soil or the food. 



4. Aberration {abcrratio) is employed for purtly in- 

 dividual deviations from the normal type. 



It appears to us so very difficult and often impos- 

 sible to draw in nature a distinction between sub- 

 species and nation ( = sub-subspecies) that in many 

 cases the employment of one or the other term will 

 entirely depend on the personal opinion of an author. 

 The Greek term morpha does not appeal to us as a 

 happy choice, and will hardly recommend itself to 

 systematists generally, who are used to the Latin 

 term forma, often employed with a convenient qualify- 

 ing addition, such as /. temp., for the seasonal form. 



The pamphlet is a lucid interpretation of the dis- 

 tinguished author's view, and will be read with great 

 profit by all who are interested in the philosophical 

 aspect of systematics. K. J. 



COORDINATE GEOMETRY. 

 An Elementary Treatise on Coordinate Geometry of 

 Three Dimensions. By R. J. T. Bell. Pp. 

 xvi + 355. (London: Macmillan and Co., Ltd., 

 1910.) Price JOS. net. 



THE substance of this volume has formed the 

 material of a course of lectures delivered for 

 some years past to undergraduates in Glasgow. Its 

 object is to provide the student, whose bent is towards 

 applied mathematics, with as complete an exposition 

 of the subject as he will require, and at the same 

 time to act as an introduction to those who intend 

 to proceed to a more exhaustive study of differential 

 geometry and the theory of surfaces. Its scope is 

 best indicated by a brief enumeration of the headings 

 of the chapters : — coordinates, direction ratios, the 

 plane and straight line, change of axes, the sphere, 

 the cone, the conicoids, axes of sections, generating 

 lines, confocals, the general equation of the second 

 degree, systems of conicoids, conoids and general 

 surfaces, curves in space, ruled surfaces, curvature, 

 geodesies. It will be noted that there is no mention 

 of homogeneous and tangential coordinates. The 

 author has excluded these on the ground that the 

 student has already acquired a knowledge of the 

 general principles involved from his work in plane 

 geometry. The same consideration has led him to 

 exclude any section on dualitv or reciprocation. Some 

 teachers will regret this omission, as the student is 



