556 



for the district under consideration, the author gives figures and 

 descriptions of the known species that have not so far been taken 

 there. At first sight we are rather inclined to think that Dr. 

 Penard has gone a little too far perhaps in the splitting up of 

 species, but in all cases he backs up his opinion with weighty 

 arguments drawn from his own careful observations. 



While not aspiring to rank with Leidy so far as illustrations go, 

 the book contains useful figures of all the species, and at the end 

 (p. 702) there is a very interesting full-page illustration showing 

 one species of every genus drawn to a uniform scale of three 

 hundred diameters. Included in the book are a series of valuable 

 ^'Notes'' on such subjects as the methods of collection and study 

 of Fresh-water Rhizopods, their shells, protoplasm, nuclei, para- 

 sites, geographical distribution, reproduction, vitality, and even 

 psychology. There is also a good list of the literature of the 

 subject. We heartily congratulate Dr. Penard on the appearance 

 of this most useful book, and we hope it will be the means of 

 stirring up renewed interest in a group of organisms which 

 deserves very much more consideration than it usually receives. 



D. J. S. 



The Pole of Diffusion and Osmotic Pressure in Plants. By 

 B. E. Livingston. 9 x 5| in., xiii. + 149 pp. Decennial 

 Publications of the University of Chicago, Second Series, 

 Vol. YIII. Chicago, 1903: University Press. Price, 

 $1.50 net. 



This volume consists of two distinct parts. The first, under 

 the head " Physical Conditions," deals with elementary physical 

 facts and theories relating to the subjects treated of in the 

 second part, and might well serve as an introduction to a work 

 on physical chemistry. The matter is clearly expressed, but the 

 reader who lacks the knowledge which this part gives cannot be 

 the same as he who would be interested in the subsequent pages. 

 Should the student of osmotic pressure be required to pay for an 

 elementary part which he will not need ? The writer states in 

 the preface : " It has been difiicult for the student of physiology, 

 who is not at the same time versed in physical chemistry, to 

 obtain the information required for the prosecution of the work 



