May 20, 1922] 



NA TURE 



643 



shown as a frontispiece. Teachers will welcome the 

 large collection of examples and revision questions. 



(6) Part I of the " Elements of Natural Science " 

 includes mechanics, chemistry, heat, properties of 

 matter, light, and sound. With part 2 the course is 

 intended to cover the "general science" syllabuses of 

 School Certificate and Army Entrance Examinations. 

 The treatment of the subject-matter, together with 

 the experiments in illustration, should prove success- 

 ful in exciting and maintaining the interest of the 

 student. H. S. A. 



Parasitism and Symbiosis. 



Le Parasitisme et la Symbiose. Par Prof. M. Caullery. 

 {Encyclopedie Scientifique : Bibliotheque de Biologic 

 Generale.) Pp. xiii + 400 + xii. (Paris : Gaston Doin, 

 1922.) 14 francs net. 



FEW zoologists are so well qualified as Prof. 

 Caullery, who is editing the series of works 

 on general biology to which the volume under notice 

 belongs, to survey the range of parasitism and sym- 

 biosis. He is the pupil and successor at the Sorbonne 

 of Alfred Giard, and like him is distinguished by a 

 remarkable versatility, having brilliantly investigated 

 the life histories of parasites belonging to many phyla. 

 In his laboratory, too, there was largely carried out 

 the work of Guyenot on aseptic life, which is funda- 

 mental for future attempts to solve the problems of 

 symbiosis. 



There are good modern treatises on medical para- 

 sitology, but these naturally concern themselves with 

 a much narrower field than that required by the 

 student of general biology for whom this book is 

 designed. Throughout, it is characterised by an admir- 

 able lucidity, and the vast amount of information it 

 contains does not interfere with the well-balanced 

 arrangement. Recent research which has a general 

 bearing on parasitism is presented with great care, 

 and the bibliography is complete and invaluable. 



Commensalism, parasitism, and symbiosis are dealt 

 with successively as related phenomena. The series 

 of more or less modified parasites which exist in many 

 animal groups offer perhaps the most striking illustra- 

 tions which can be given of the reaUty of evolution. 

 Prof. Caullery has treated the groups he knows best 

 in detail from this standpoint. The adaptation of 

 the parasitic isopods (especially Entoniscidae) to their 

 diverse hosts, the evolution of the Rhizocephala in 

 the cirripedes, and the clear series of parasites in the 

 gasteropods are given the attention they deserve. 

 There might also have been included with advantage 

 an account of the passage in the nematodes from 

 forms with a perfect alimentary canal through the 

 NO. 2742, VOL. 109] 



intermediate group of the Mermithidae to those 

 complete parasites which absorb food only through 

 the skin. 



Passing over the very useful chapters on the various 

 types of parasitic life-history, the migrations of " heter- 

 oxenous " forms, and the adaptations for reproduction 

 in parasites, there follows an interesting discussion of 

 specificity of parasites, especially in connection with 

 human interference with the distribution of insects 

 and the parasites they convey. We miss a reference 

 to the very rigid specificity which is stated to exist 

 in the Mallophaga, occurring on birds. Here the 

 association of host and parasite apparently took place 

 at an early stage in the evolution of both groups, and 

 the well-marked systematic relationships of the different 

 Mallophaga actually throw light on those of the bird 

 genera on which they are found. 



In the chapters on symbiosis reviews are given of 

 the large number of cases recently described where 

 unicellular symbiotes are found in different inverte- 

 brate groups, and then of the extraordinary extension 

 of research on these lines by Pierantoni and Portier. 

 The claim of the latter that every living cell contains 

 symbiotic organisms was seriously considered and 

 rejected by a committee of French biologists, but 

 interest in research on symbiosis is still intense in 

 France. F. A. Potts. 



Our Bookshelf. 



Anleitung zur mineralogischen Bodenanalyse. Von Dr. 

 Franz Steinriede. Zweite umgearbeitete und er- 

 weiterte Auflage. Pp. viii + 240. (Leipzig : W. 

 Engelmann, 1921.) 60 marks. 



The original appearance of this book in 1889 marked 

 the first serious attempt to apply petrological methods 

 to the study of the minerals of the soil. During the 

 thirty-two years that have since elapsed, petrological 

 methods have undergone considerable development, 

 while, on the other hand, our knowledge of the soil has 

 similarly been enormously extended. The develop- 

 ment of these two subjects, however, has proceeded 

 mainly on quite separate lines, particularly in this 

 country, where soil investigators have studied chiefly 

 the chemical and biological aspects of soil fertility. 

 That our present methods of examination of soil 

 frequently fail us in accounting for observed differences 

 in fertility is an indication of the need for new methods 

 of attack, among which mineralogical analysis is un- 

 doubtedly of importance. 



The appearance of the new edition of a book by a 

 pioneer in the subject is thus welcome, especially as 

 no similar book exists in this country. The author 

 gives a succinct but adequate account of all the 

 important aspects of the subject, including elutriation 

 and flotation methods of separation, optical and other 

 physical as well as chemical methods of examination. 

 The data for the application of these methods are 

 collected in a series of useful tables, together with a 



