116 NATURE STUDY REVIEW [10:3— Mar., 1914 



order to appreciate the very interesting stories that are related. 

 The author is thoroughly familiar with his subject matter, writes 

 in a clear style and presents a mass of facts well organized. The 

 illustrations, of which there are over three hundred, are many of 

 them by Bruce Horsfall, which is a guarantee of their scientific 

 as well as their artistic value. 



In addition to tracing the history of several of the great sub- 

 divisions of the mammals, there are discussions of several general 

 matters. There is a chapter, five, on the geographical develop- 

 ment of the Americas, chapter six is on the geographical dis- 

 tribution of mammals, and chapter seven is on successive mammal- 

 lian faunas. This last chapter of over 90 pages is one that the 

 general reader will appreciate as it gives a very excellent idea of 

 the whole drift of the evolutionary movement in the mammal 

 group. The last chapter, chapter 18, on modes of mammalian 

 evolution, will be read by the general reader and the specialist 

 with equal interest, for it is a statement of conclusions to which 

 the author comes after his extensive study of fossil evidence. 

 He believes that there are many striking instances of parallel 

 development, that new species are usually formed through the 

 similar and simultaneous movement of many individuals, rather 

 than from a single individual or pair, that development has 

 usually been divergent rather than convergent and that it 

 has proceeded by reduction in the number of parts and the enlarg- 

 ment and specialization of those that are left. Finally he thinks 

 that development among the mammals has been a remarkably 

 direct and unswerving process. As to whether the process is a 

 continuous or discontinuous one, he prefers to let specialists in 

 other fields of paleontology decide where the evidence is clearer 

 than it is among the fossil mammals. 



The Infancy of Animals, by W. C. Pycraft, pp. XIV plus 272, 

 Henry Holt & Co. Price $1.75. 



This book is an accumulation of facts related much after the 

 manner of the older natural histories. There is no very marked 

 attempt to discuss theories. At points, one could wish the theoret- 

 ical discussion somewhat amplified, as in the discussion, for 

 instance, of colors and coloration. It is pointed out that longi- 

 tudinal stripes are characteristic of many young and that later 

 these come to be broken up into spots and, by recombination, into 



