498 



NATURE 



[January 15, 1920 



small group of men engaged in the industry, and 

 their" jealousies of one another and especially of 

 outsiders. They have endeavoured to keep their 

 secrets as well as their profits. The author says 

 that the story is, for the most part, a chronicle 

 of bitter struggles to maintain a monopoly, even 

 at the cost of ruinous losses, and the stubborn 

 persistence in "obsolete methods." But the 

 chapter on the "latest methods of salt-making" 

 leads us to hope that these times are nowr of little 

 more than historic interest. The book is well 

 illustrated, showing ancient works from old 

 prints, salt-mine interiors, subsidences of land 

 consequent on salt mining, and the most modern 

 apparatus. 



(5) " Industrial Chemistry" is, of course, a 

 much more extensive subject than any of the pre- 

 ceding. Though the price of this volume is less 

 than half that of any of the others, it is not the 

 smallest book, and, bound in a very presentable 

 green cloth, it shows what is possible in book 

 production even in these times. It is difficult to 

 see how anyone could have got more information 

 into the same space than Dr. Ranken has, or to 

 find any section of this wide subject that he has 

 passed over, and yet the volume is a true 

 "people's book," and does not leave any impres- 

 sion of undue condensation. The first chapter, 

 being headed "Catalysis and Catalysts," may tend 

 to repel the non-technical reader, but he has 

 only to pass over the title and all will be well. 

 The honesty of the author is highly commendable 

 when he says that "there are fashions in 

 chemistry as in other lines, and the views con- 

 cerning catalysis held to-day may be absolutely 

 unfashionable to-morrow." This is true of other 

 matters than catalysis. C. J. 



FRESH-WATER BIOLOGY. 

 (i) Fresh-water Biology. By Prof. H. B. Ward 

 and Prof. G. C. Whipple. With the collabora- 

 tion of a Staff of Specialists. Pp. ix-fiiii. 

 (New York : John Wiley and Sons, Inc. ; Lon- 

 don : Chapman and Hall, Ltd., 1918.) Price 

 285. net. 

 (2) Aquatic Microscopy for Beginners ; or, Common 

 Objects from the Ponds and Ditches. By Dr. 

 A. C. Stokes. Fourth edition, revised and en- 

 larged. Pp. ix -f 324. (New York : John Wiley 

 and Sons, Inc. ; London : Chapman and Hall, 

 Ltd., 1918.) Price los. 6d. net. 

 (i) pROFS. WARD AND WHIPPLE and their 

 1 twenty-five collaborators have produced a 

 volume to which students may refer for precise 

 information upon the organisms met with in fresh 

 water in North America. Introductory chapters 

 NO. 2620, VOL. 104] 



deal with general biological factors and methods 

 of collecting. Succeeding chapters, devoted re 

 spectively to single orders or classes, give 

 general account of the occurrence, a brief descrip 

 tlon of the anatomy (including reference to the 

 features used in classification) and of the life- 

 history and biological relations, and, finally, a 

 key to the genera, and in several cases also to 

 the principal species of the group. The informa- 

 tion in the key about any given genus includes 

 not only the diagnostic characters, but also in 

 most cases an illustration and some reference to 

 the frequency, the range, or other data ; thus the 

 whole information "forms a solid panel and 

 appeals promptly and as a whole to the eye and 

 mind of the student." 



Much good work has been put into this book, 

 and especial mention may be made of the excel- 

 lent chapters on Turbellaria, Trematodes and 

 Cestodes, and free-living Nematodes, the last- 

 named noteworthy for the detailed figures. The 

 chapters on Cladocera, Copepoda, Ostracoda, and 

 Mollusca are provided with numerous original 

 illustrations. In the chapter on Rotifers, Prof. 

 H. S. Jennings has given a very useful account' 

 of the biology and structure of these animals, and 

 a survey of the families, pointing out the various 

 modifications from the Notommatoid type from 

 which the author (with Wesenberg-Lund) con- 

 siders the other families to have been derived. 



In addition to the notes on habitat given 

 throughout the book, here and there are short 

 notes on points of special importance connected 

 with the distribution. Two of these may be cited 

 as examples. Reference is made to the finding 

 by Prof. Carman, in September, 1916, of large 

 numbers of the fresh-water medusa Craspedacusta 

 (^Limnocodium) soiverbii in a creek near Frank- 

 fort, Kentucky. This medusa, first found in 1880 

 in the Victoria Regia tank in the Botanic Gardens 

 in Regent's Park, and afterwards in tanks in 

 other gardens in Europe and America, is now 

 recorded for the first time from other than arti- 

 ficial surroundings. Dr. Ortmann, in a short 

 note under Mysis relicta, states that, so far as 

 the North American stock of this species is con- 

 cerned, there is no reason to assume that it is a 

 marine relic ; it may be regarded as an immigrant 

 into the Great Lakes in Glacial times. 



This excellent treatise should greatly stimulate 

 the study of the fresh-water fauna of North 

 America, and will be very helpful for comparative 

 purposes also to workers in this country. 



(2) The author, who modestly styles himself 

 " only a beginner " writing for beginners, has 

 given his descriptions of the microscope and its 

 parts and of aquatic organisms in language as 



