70 



SCIENCE. 



[N. S. Vol. XII. No. 289. 



earlier part of the filtration. In the reviewer's 

 hands this method has yielded even larger 

 errors with water heavily charged with minute 

 flagellates and other motile organisms, when 

 checked by more precise methods of filtration. 

 The greatest escape of organisms occurred, 

 not at the beginning, but toward the close of 

 the period of filtration. The author concludes 

 that the method is precise within 10 per cent., 

 i. e., two examinations of the same sample 

 seldom differ by more than that a,mount. 



A few pages are devoted to a brief discussion 

 of the plankton method in which the Reighard 

 and Birge nets are described though the more 

 generally used Apstein model is not mentioned. 

 The author objects to the standard unit of vol- 

 ume, a cubic meter, adopted by planktologists 

 on the ground that it necessitates the use of 

 large numbers in the case of minute organisms. 

 In plankton work a uniform unit is a necessity 

 and the small unit of the Sedgwick-Eafter 

 method, which he suggests, is equally objec- 

 tionable, as it would frequently necessitate 

 the employment of fractions or decimals, and 

 could not be readily correlated with most avail- 

 able and generally accepted unit for quantita- 

 tive work, viz, the cubic meter. The statement 

 that ' many delicate organisms are crushed upon 

 the net ' in the collection of plankton and that 

 the pumping method conduces to imperfect fil- 

 tration are not borne out by the practical ex- 

 perience of the reviewer. 



The comparative absence of organisms in 

 rain and ground waters and in filter- galleries 

 is noted, and their relative abundance in surface 

 waters is discussed. The general statement is 

 made that standing water contains more organ- 

 isms than running water. "Samples from rivers, 

 unless collected near shore, seldom contain 

 many organisms. Organisms found in streams 

 are largely sedentary forms. Their food-supply 

 is brought to them by the water continually 

 passing. In quiet waters there are found free- 

 swimming forms that must go in search of their 

 food." It is undoubtedly true that there is but 

 little plankton in the small and rapidly flowing 

 streams of New England and in like waters 

 elsewhere ; but in larger streams there is a true 

 plankton, often abundant, and very largely 

 made up of typical plankton organisms, as has 



been shown by investigations of the Elbe, the 

 Oder, the Danube, the Nile, the Illinois and the 

 Mississippi Rivers. The current probably bears 

 some inverse ratio to the number of organisms 

 present in a stream, but the fact of its presence 

 does not necessarily preclude the development 

 of an abundant and typical plankton in river 

 waters, provided time for breeding is afforded. 

 Interesting data concerning the physics of 

 lakes and reservoirs, especially in regard to the 

 seasonal overturning of the water and summer 

 stagnation below the thermocline, are to be found 

 in the chapter on limnology. The organisms 

 which occur in water-supplies are listed with 

 reference to the frequency of their occurrence 

 and their obnoxious qualities. In all 186 gen- 

 era are catalogued of which but 18 are common, 

 and of these at least 10 are troublesome because 

 of their unpleasant effects upon potable waters. 

 The relative frequency of different organisms 

 and the relation of their occurrences to the 

 depth of the pond, to the nature of the bottom, 

 to the color of the water, and to the chemical 

 analysis are discussed in the light of statistics 

 accumulated in the biological examinations of 

 Massachusetts waters. The same data afford a 

 basis for a treatment of the seasonal, horizontal 

 and vertical distribution of organisms in pond 

 and reservoir waters. Technical matters such 

 as the odors of water-supplies, the storage of 

 ground, and of surface-waters, and the growth 

 of organisms in water-pipes receive expert 

 attention. 



A considerable part of the work is given up 

 to a descriptive list of the genera of microscopic 

 organisms which will be of great assistance to 

 the amateur or the beginner. Nineteen well-ex- 

 ecuted half-tone plates will further assist in the 

 identification of the more common organisms. 

 We note the omission of Pleodorina, which occa- 

 sionally becomes a water-pest ; that Spirodela is 

 figured as Lemna; and that Diaptomiis appears on 

 the plate with the ovisac dorsal to the abdomen. 

 The bibliography at the close of the book 

 seems to be very full in the technical pha,ses of 

 the subject of water supplies. On the biolog- 

 ical side it is less satisfactory, the titles by no 

 means representing the best or the latest litera- 

 ture of the subject, a defect easily remedied in 

 a later edition. 



