126 



NATURE 



[July 28, 1923 



account of the subject is correspondingly "alive" 

 and authoritative. 



Among much that calls for comment in this book 

 is a good account of a variety of metal X-ray tubes 

 which have so far been used chiefly in spectrometry. 

 The recent researches which have filled the gap of 

 4 octaves between the former boundaries of the ultra- 

 violet spectrum and the X-ray spectrum receive full 

 attention. 



One of the more recent triumphs of X-rays in the 

 field of atomic physics is the work of the Due de 

 Broglie on the speed of the secondary electrons excited 

 when X-rays fall upon matter. The speed was dis- 

 played by the method of the " magnetic spectrum " ; 

 and using X-rays of a specific wave-lengthy de Broglie 

 was able to show that the secondary electrons arranged 

 themselves into well-defined groups which had been 

 ejected respectively from the K, L, M, etc. rings of 

 the atoms of the material. These results, which 

 receive simple explanation on the quantum theory 

 and that of Bohr, have been confirmed in Great 

 Britain by Whiddington, and widely extended at 

 the Cavendish Laboratory by Ellis, who used radium 

 y-rays of much shorter wave-length than can at present 

 be generated artificially. The present volume contains 

 an interesting account of these enthralling investiga- 

 tions. 



There are many valuable tables of wave-lengths, 

 etc. in the book, and a number of plates showing 

 some fine examples of X-ray emission and absorption 

 spectra. At the end of each chapter there is a good 

 bibliography. In accordance with French custom 

 there is no index, but tradition is scouted by the 

 provision of a serviceable stiff cover, a feature which 

 will make its appeal in other countries. 



G. W. C. Kaye. 



Elementary Zoology. 



Essentials of Zoology for Students of Medicine and First 

 Year Students of Science. By Prof. A. Meek. Pp. 

 xii -1-325. (London: Longmans, Green and Co., 

 1922.) 105. 6d. net. 



THE volume before us, intended for students of 

 medicine and first-year students of science, is 

 written by one who retains his belief in the " type 

 system," and clearly has no sympathy with those who 

 believe that this method of teaching, unless used with 

 great discretion, is liable to do much to kill the student's 

 interest in his subject. 



The book consists of ten chapters, each devoted to 

 one of the more important divisions of the animal 

 kingdom. The qhapter on Protozoa commences with 

 NO. 2804, VOL. 112] 



short descriptions of Amoeba, Paramecium, Vorti- 

 cella, Cercomonas ; these are followed by a section 

 dealing with general considerations such as morpho- 

 logy, physiology, psychology, reproduction, sym- 

 biosis ; and the chapter concludes with an account of 

 important parasitic types — Opalina, Monocystis, Plas- 

 modium, Trypanosoma. The descriptions of the 

 various types are short and concise, but we notice a 

 number of sentences which are liable to mislead the 

 elementary student : such statements as that the 

 trypanosome " progresses by the action of the flagellum 

 which is posterior,'' that the recrudescence of malarial 

 attacks is due to the female gametocyte developing 

 parthenogenetically, that the fully grown " Plas- 

 modium " becomes crescentic, require qualification or 

 emendation. 



The chapter on Ccelenterata deals with Hydra and 

 Obelia, that on Platyhelmia with Distoma and Taenia, 

 that on Mollusca with Anodonta, that on Annelida 

 with Lumbricus and Nereis, that on Crustacea with 

 Nephrops, that on Insecta with Blatta, Anopheles, 

 Culex, and Glossina. We are glad to see our old friend 

 Amphioxus accorded the dignity of a special chapter. 

 The chapter entitled Pisces deals with the skate, and 

 that entitled Amphibia with the frog. This is followed 

 by a chapter on the development of birds and mammals, 

 and the book ends with a chapter on Mammalia, dealing 

 mainly with the rabbit. 



As in the Protozoan chapter, so also in other parts of 

 the book, we notice many statements that might with 

 advantage be emended in a new edition. It is not 

 accurate to say the gastrula is a stage in the develoj)- 

 ment of all the metazoa. It would be wise to use the 

 word solenocyte in the sense defined by its inventor. 

 The expression " schizocoel or mesench^Tne " is liable 

 to lead the careless student to think these terms are 

 synon\Tnous. Such statements as " the myoccel de- 

 velops a sclerotome," " the longitudinal valve [of the 

 frog's conus arteriosus] is disposed in a slightly spiral 

 direction from the right anterior aspect to near the 

 left of the median line posteriorly," " the skeletal 

 muscular system is derived from the . . . myoccel of 

 the ccelomic mesoderm," " species of Rana are used for 

 food . . . and large numbers are employed in zoological 

 and physiological laboratories " (the italics are ours), 

 are, to say the least, awkwardly expressed. 



Such statements as we have quoted indicate that 

 the book would have been the better for more careful 

 revision before going to press. Notwithstanding such 

 blemishes in detail we are of opinion that the book 

 will prove useful to the class of student for whom it is 

 intended. It is illustrated by numerous figures, some- 

 what rough in execution but for the most part clear 

 and intelligible as well as accurate. 



