722 SCIENCE PROGRESS 



observer. Complications are added through the presence of poisons and through 

 the variations which must occur in the conditions of osmosis in the cells them- 

 selves as they die. The technique is full of sources of error, almost as serious as 

 those involved by the equation upon which it depends and so it is difficult to 

 speculate as to what he really has seen. The combinations of agar, stain and 

 various other substances used by the author are original, though films of agar jelly 

 have been used for ten or fifteen years, polychrome methylene blue has long been 

 a favourite stain for living cells and the effects of poisons and other substances 

 upon living cells have been studied by a large number of men for more than 

 twenty years. While it is of course impossible to state definitely that mitoses 

 have not been produced by Mr. Ross's method, it is extraordinarily improbable 

 that they have. Certainly there is nothing in the book which suggests that he 

 has ever seen a mitotic figure and cytologists will be convinced of the inaccuracy 

 of his observations and his interpretations thereof by his statements that " the 

 Altmann's granules form the chromosomes, the nucleolus the centrosomes and 

 the nucleus forms the spindle " (p. i66), "that the so-called nuclei of leucocytes 

 ought, we think, in reality always to be called the centrosomes and the word 

 nucleus deleted from their morphology" (p. 13). The sub-title of his book in- 

 volves the belief in normal asymetrical mitoses. It is common knowledge that 

 normal mitoses are symetrical. 



Cytologists will not accept his discoveries as easily and carelessly as he 

 attributes opinions to them, for what he states as the generally accepted opinions 

 with regard to mitosis and reduction are at best but a caricature of the truth. 



C. E. W. 



Modern Methods of Water Purification. By John Don, F.I.C., A.M.I.Mech.E., 

 and John Chisholm, A.M.I.Mech.E., engineer and manager of the 

 Airdrie, Coatbridge and District Waterworks. [Pp. xiv + 368 ; 98 illus- 

 trations.] (London: Edward Arnold, 191 1. Price 15^. net.) 



The success of Mr. Don's well-known essay at the Institution of Mechanical 

 Engineers on " The Filtration and Purification of Water Supplies " has led him 

 to bring out, in collaboration with Mr. Chisholm, the present treatise on " the 

 most efficient appliances for the treatment of water, with details of working 

 and costs of construction and management," subjects which are here admirably 

 described and fully illustrated. Particularly interesting also are the sections on 

 the rationale of sand-filtration — Dunbar's theory of absorption or rtrt'sorption, 

 Kemna's (not Ke/itia) and Pennink's views, and the scattered paragraphs on 

 non-submerged filters (pp. 67, yj, 85, etc.). Whilst not disputing the frequent 

 usefulness of the top "filtering skin," the authors point out its many faults as 

 distinguished from the action of the slimy coating on the lower sand grains which 

 entangles organisms. A summary is given of Dr. Houston's researches on the 

 "safety change" of river waters under storage ; and it is remarked that "theoreti- 

 cally the water is stored for about fifteen days at Chelsea and Lambeth and for 

 ninety-five days at Staines ; but it can easily be understood that the water which 

 is brought to the filter-beds may have been impounded for very different periods, 

 according to the exigencies of supply and demand." We must not forget that it 

 was just this urgency of supply that in 1866 caused unpurified water, contaminated 

 with cholera by one immigrant family, to be distributed in East London, 

 occasioning 16,000 cases and 6,000 deaths. The precautions for general efficiency 

 in filtration are dealt with at length in this volume ; but it is recognised that a 

 rapid process for the destruction of pathogenic organisms is safer and can now 



