August 26, 1922] 



NA TURE 



275 



such pels entirely unintelligible, and the experiment 

 illustrating the retention of congo red by a gelatin gel 

 must receive quite another explanation than that given 

 to it. 



The Development of Vertebrates. 



Traiie d'embryologie des vertebres. Par Prof. A. 

 Brachet. Pp. xvi + 602. (Paris: Masson et Cie., 

 1921.) 60 francs net. 



FOR a remarkably clear and well-illustrated 

 account of the development of the vertebrates 

 the student could not do better than turn to this text- 

 book from the pen of the distinguished professor of 

 the University of Brussels. The information given is 

 thoroughly up-to-date, the conclusions for the most 

 part convincingly supported by- an abundance of facts 

 marshalled with great skill. While the author does 

 not hesitate to discuss controversial questions, yet 

 this treatise is strikingly free from prejudice, and none 

 the less interesting because it deals for the most part 

 with matters of. fact. We find none of the fantastic 

 phylogenetic interpretations of developmental stages 

 according to the recapitulation theory which disfigure 

 so many general text-books of embryology. 



Naturally, in a single volume of some 600 pages, 

 the whole range of vertebrate embryology cannot be 

 covered in detail, and it is the early stages and germ- 

 layer formation that receive particular attention. 

 We know of no text-book in French or English with 

 such a lucid account of these complex processes in 

 the vertebrates. By skilful selection and the omission 

 of unimportant detail Prof. Brachet also provides good 

 descriptions of the development of the chief organs. 

 The development of the cranial nerves, for instance, is 

 particularly well presented. 



There are some points on which the author is not 

 convincing, and on which his conclusions might, we 

 think, be revised and modified. In the account of the 

 mesoblastic somites of the head, like so many other 

 embryologists, he uncritically adopts van Wijke's 

 scheme of enumeration, which inevitably leads to 

 confusion in the region of the hyoid arch, instead of 

 Balfour's system. We are unable to understand his 

 reluctance to admit that in vertebrates above Amphi- 

 oxus there are still traces of the formation of mesoderm 

 from enterocoelic pouches, and we consider that he 

 attaches too much importance to what he terms 

 acrogenesis, cephalogenesis and notogenesis, a distinc- 

 tion which seems somewhat artificial and founded on 

 certain specialisations of growth in the embryos of 

 higher forms. Nevertheless, Prof. Brachet's volume is 

 an excellent treatise, and will be heartily welcomed by 

 students and teachers of embryology. 

 NO. 2756, VOL. I IO] 



Our Bookshelf. 



The Principle of Relativity. Original Papers. By 

 A. Einstein and H. Minkowski. Translated into 

 English by M. N. Saha and S. N. Bose. With a 

 Historical Introduction by Prof. P. C. Mahalanobis. 

 Pp. xxiii+ 186. (Calcutta: University of Calcutta, 

 1920.) 



The book under review begins with an interesting 

 historical account of the experiments dealing with the 

 elucidation of the aether-idea in physics, and we are 

 led through the work of Michelson and Morley, Lorentz 

 and others to a brief account of Einstein's theory of 

 relativity and some of the results obtained with its 

 aid. The second section reproduces Einstein's original 

 paper " On the Electrodynamics of Moving Bodies " 

 (Annalen der Physik, 1905), and this is followed by a 

 short note on Albrecht (!) Einstein and the various 

 phases of his scientific activity. The next section on 

 the " Principle of Relativity " is apparently a trans- 

 lation of Minkowski's paper on " The Fundamental 

 Equations for the Electromagnetic Processes in Moving 

 Bodies " (Gbttinger Nachrichten, 1908), though no 

 reference is given, and the title is omitted. An ap- 

 pendix to this is given, and it concludes with the well- 

 known lecture of Minkowski on " Space and Time," 

 delivered to the German Naturforscherversammlung 

 at Cologne (1908), and published in the Physikalische 

 Zeitschrijt (1909) and in " Das Relativitatsprinzip," a 

 collection of papers by Lorentz, Einstein, and Min- 

 kowski (Teubner, 1913). The sixth section of the 

 book consists of Einstein's monumental work on the 

 " General Theory of Relativity and Gravitation " 

 (Annalen der Physik, 1916), and the concluding section 

 brings a number of explanatory notes, mostly mathe- 

 matical, on special points. 



The translation cannot be called a good one. In 

 a work of this kind we expect a fairly literal transla- 

 tion, but in the present book there are numerous errors 

 in translation, and the choice of English equivalents 

 for German words is frequently unfortunate. In 

 many instances the mathematics is faultily- reproduced. 

 The numbering of the pages is not continuous, but 

 recommences at the beginning of section 4, and the 

 omission of the footnotes from the originals is regret- 

 table. Provided it is studied with care, the translation 

 will nevertheless be of service to those who are 

 unfamiliar with German, and wish to grapple with 

 the pioneer works on this subject, some of which are 

 rather inaccessible. 



A Little Book on Water Supply. By Dr. William 

 Garnett. Pp. xv+144. (Cambridge: At the Uni- 

 versity Press, 1922.) 65. 6d. net. 



" This little book when in manuscript was condemned 

 by a very high authority on educational publications, 

 for it did not enable the reader to prepare for any 

 specific examinations." So the preface begins. But 

 was not the verv high authority anxious to be kind ? 

 We, too, are inclined to condemn the little book as 

 an educational work, not because it is useless for 

 examinations, but because it lacks a coherent plan. 



There is no attempt to group the portions of letter- 

 press into chapters. General statements are sand- 



