370 NATURE-STUDY REVIEW [12:8— Nov., 1916 



which, instead of dying, the whole organism breaks up or divides into new 

 individuals, which repeat the cycle of growth, development, and reproduction 

 and finally, to those cases in which the whole organism or parts of it appear to 

 grow old, but live on indefinitely." 



One can give in a brief review no notion of the bulk of the 

 material with which the author has worked, or his methods of 

 procedure. His final chapter is on the current theories of explana- 

 tion of the phenomena which he is discussing. His own conclusion 

 is that sensecence and rejuvenscence are both explicable in terms 

 of metabolism. Few American zoologists have put out a greater 

 volume of experimental and observational work than has Dr. 

 Child. Other zoologists will welcome this collection of his major 

 experiments and the discussion of their significance, regardless of 

 whether he thinks the author's conclusions are justifiable or not. 



The Adolescent Period. By Louis Starr. 211 p. P. Blakiston & 

 Son Co. $1.00. 



This book will be welcomed by the high school educator as well as 

 parents who are concerned with children of adolescent age. The 

 first chapter calls attention to the way in which growth occurs, its 

 irregularity, and the conditions of all bodily organs, especially 

 during the pubertal period. Chapter II is a very sane, simple 

 chapter on physical education both for boys and girls. Chapter III 

 discusses the more common disorders of adolescence; Chapter IV 

 the faults and criminal tendencies, and the two other chapters 

 discuss the sexual phases of adolescence. 



The author states that of girls in the upper classes socially, from 

 fifty to sixty per cent, are unhealthy to a greater or less degree. 

 Of these 36 per cent, are anaemic; about the same proportion have 

 constant headaches, and 10 per cent, have curvature of the spine. 

 The percentage of illness for boys during this period is not as great, 

 but is sufficient to make it manifest that few parents or teachers 

 understand the adolescent period. The author's discussion of the 

 whole problem is frank, simple and free from unnecessary scientific 

 technicalities. 



