i66 



SCIENCE 



[Vol. XXI. No. 529 



the discussions by shart historical accounts of the development 

 of our knowledge on the various topics. 



The second part of the book is devoted to the development of 

 special organs, and here the author is more confined to the mam- 

 mals and gives less consideration to the other vertebrates The 

 method of consideration is that of the study of organs according 

 to their origin in the different layers of the body. These are 

 considered, therefore, under four heads. The organs of the 

 endoderm include the alimentary system in general: the organs 

 of the ectoderm include the nervous system; the organs of 

 the middle germ-layer include the muscles, the urinary and 

 sexual organs. Professor Hertwig's views of the body cavity 

 lead him to the formulation of a fourth layer of the vertebrate 

 embryo, which he calls the intermediate layer or mesenchyme, 

 and the last section of the text-book studies the development of 

 the organs from this mesenchyme. These, according to Hert- 

 wig, are the circulatory system and the skeleton. 



The special meritsof this book are the logical treatment and its 

 consideration of the embryological facts as parts of a system. 

 The general method of the treatment of the subject is a compara- 

 tive rather than a physiological one, and the text-book will give 

 the student an insight into comparative anatomy but very little 

 consideration of the physiology of the developing embryo In 

 one of the two sections, it is true, the mechanics of development 

 are considered, but in general, the text-book is a morphological 

 rather than a physiological study. This is, of course, a natural 

 outcome of the line of work in which Professor Hertwig has 

 been so successfully engaged for so many years. 



Not the least valuable part of the book consists in the abundant 

 literature. .Some fifty pages are devoted to giving the titles and 

 references to the most important papers of vertebrate embry- 

 ology. The book has, also, another feature, somewhat rare in 

 German scientific books, but of extreme value to students, in the 

 form of short, logical, but intelligible summaries at the end of 

 every section giving in outline the important conclusions. 



On the whole, the text-book of Professor Hertwig is probably 

 the best general study of vertebrate embryology that has ap- 

 peared in the English language up to the present time, and itcan 

 be most heartily recommended to all interested in these sub- 

 jects. 



Chemical Lecture Experiments. Non-Metallic Elements. By G. 



S. Newth, F.I.C. London and New York, Longmans, Green 



& Co. 333 p. 8°. 

 A BOOK of chemical lecture experiments, carefully classified and 

 systemalicall3' arranged, cannot but be welcome to many. 

 Moreover, a book from a practised hand, such as Mr. G. S. Newth, 

 chemical lecture demonstrator in the Royal College of Science, 

 South Kensington, has a particular value in that its experiments 

 are so given as to be readily repeated and are not, as is often the 

 case, merely a statement of the reaction with a few confusing 

 details. Mr-. Newth has chosen his experiments well and has 

 described them in clear concise language. The book has a two- 

 fold purpose in easing the labors of the lecturer and of the stu- 

 dent alike. For the former it supplies a useful repertoire of lec- 

 ture experiments and will surely be gladly received, removing, as 

 it does entirely, the humdrum search for such examples and re- 

 actions as can be suitably and successfully demonstrated on the 

 lecture table. This, as every lecturer knows, is by no means a 

 small item in the preparation of a lecture, and, moreover, being 

 important, it cannot be carelessly or hastily done. The experi- 

 ment must be quickly and successfully performed or the interest 

 of the student is turned to illy-concealed ridicule, and the lecturer 

 is, so to speak, lost. 



To the student the book appeals in providing a ready reference 

 to serve as a companion in the lecture room, and in supplying 

 the deficiencies of his notes. Indeed, it may in most cases en- 

 tirely relieve him of the necessity of taking notes upon the ex- 

 l^eriments themselves, drawings of the apparatus, etc., and he 

 will thus be enabled to devote his attention to the explanations 



CALENDAR OF SOCIETIES. 

 Anthropological Society, Washington. 



March 14. — Major John W. Powell, A 

 Study in Psychology. 



Geological Society, Washington. 



March 33 —G. K. Gilbert, An Open Fiss- 

 ure; G. P. Merrill, Remarks on the So-Called 

 Onyx Marbles or Travertines; C. D. Wal- 

 cott, The Algonkian Rocks of the Grand 

 Canyon of the Colorado. 



Chemical Society, Washington. 



Feb. 9. — W. H. Krug, A New Method for 

 Estimating Furfurol-Hydrazone ; E. E. 

 Ewelland H. W. Wiley, On Some Products 

 of the Cassava Plant Professor Wiley de- 

 scribes the plant as it occurs in Florida, and 

 says there is every leason to believe that, if 

 the attention of capitalists is called to it, a 

 large quantity of land now covered with 

 pines could be profitably cleared and de- 

 voted to the cultivation of the cassava plant. 

 A minimum average yield is four tons of 

 roots per acre, which may be readily in- 

 creased by proper fertilization to eight or 

 ten tons per acre. Maize could not compete 

 with cassava if the same intelligent cultiva- 

 tion is applied, and there is a prospect that 

 the cassava will eventually take the place 

 of maize in the production of starch, glu- 

 cose, etc. 



March 9.— W. D. Bigelow and K. P. Mc- 

 Elroy, Determination of Lactose in Presence 

 of Invert Sugar and Sucrose. 



Philosophical Society, Washington. 



March 18. — W. H. Holmes, Traces of 

 Glacial Man in the Trenton Gravels; Asaph 

 Hall, The Planet Mars. 



THE RADIOMETER. 



By DANIEL S. TROY. 



This contains a discussion of the reasons 

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Heading Matter Notices. 



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