REVIEWS 723 



be made economical. Ozone treatment is rather too diffusely discussed in a 

 chapter of twenty-nine pages, whilst chlorine is imperfectly dealt with on three 

 pages (198-200), with a short reference on p. 47. Household purification has 

 only three and a half pages of text, in a chapter containing a good description of 

 water-softening machines, including Dr. Ganz's " Permutit" process. 



A review of bacterial and chemical testing is given in Chap. X. (pp. 260-285) 

 and Chap. XI. describes conductivity tests, standards of purity and microscopical 

 examination. Chaps. XII. and XIII., on the problems of distribution, treat ably 

 on lead and iron corrosion and solvency, on " Water Hammer " and enter briefly 

 also into special questions of public health and water supply. But we meet with 

 a surprising sentence on p. 348 : " To the oft-discussed question whether sewage- 

 polluted water is able to cause typhoid in the absence of the specific germ of the 

 disease, the majority of bacteriologists would probably answer that it is not." 

 In other places the wording is not happy — e.g. " the seeds of bodily ailments " 

 (p. i), "general tone is under par" (p. 3), "beyond the demesne (domain.?) of 

 agricultural activity" (p. 8), "traces of the bacillus" (p. 24), "they merit no ban 

 on hygienic grounds" (p. 14), "the consumers of the metropolitan area" (p. 27), 

 " iron is taken up by water with more or less reluctance " (p. 330), " the activity 

 is in full swing" (p. 86). "Water undertakers" (pp. 5, 13, 18, etc.) is inelegant, 

 " farmsteading " is ugly, "defilement" is continually repeated (pp. xiii, 8, 11, 13, 

 14, 15, 22 and others). We have also too much repetition in the matter and such 

 redundancy as "wells in districts adjacent to the metropolis," instead of "wells 

 near London." "Terrain" (pp. 18, 146) is hardly an English word. In the 

 eighteen pages of description of plankton (pp. 293-310) much irrelevant material 

 is introduced : the figures are excellent but of course can only cover a small 

 portion of the ground. The bibliography repeats the names of works two or 

 three times. Of misprints, there are " prfeerence " (p. 3), "Palasozic" (p. 11), 

 " infectionskh " (p. 17) ; in fig. 84 two of the reference letters are omitted. Titles 

 of periodicals might have been much abbreviated. The test on p. 24 is inexcusably 

 dangerous, so is the suggestion (p. 42) to anticipate development of algae in deep 

 well waters by adding copper sulphate. It is rather unfortunate to mention 

 Cladothrix as connected with iron difficulties when a footnote says that it thrives 

 in iron-free water (p. 332). 



These minor points of criticism derogate very little from the great utility of 

 this work and can be easily amended in the new edition which will probably be 

 demanded early. Useful tables relating to water filtration and distribution and 

 a good index terminate a volume which is full of practical experience. 



Samuel Rideal. 



An Introduction to Zoology. By Robert W. Hegner. [Pp. xii -f- 350 ; 

 161 figs.] (New York: The Macmillan Company, 1910. Price 8^. net.) 



There are evidences that the teaching of zoology at the present time is under- 

 going many changes and Dr. Hegner's text-book is a striking instance of 

 departure from the older school. The author claims no originality for his work ; 

 nevertheless it must be accorded him, as he has certainly struck off from the 

 beaten track and leads his readers into many fascinating and intensely interesting 

 byways of zoological science. 



The title is somewhat misleading, as the subject is practically confined to 

 invertebrate zoology. 



Commencing with a general introduction on the phenomena of life, the author 



