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Professor Child 1 has made a most thoughtful attempt to solve a funda- 

 mental biological problem; for the book contains not only an explanation of 

 the phenomenon of growing old, or senescence, a process of much human 

 interest, but it also contains the foundation of an even more important theory 



inheritance. The great value of the book is due not only to these philosophical 

 t also to the very large amount of original, 

 ; author, as is well known, has 

 been engaged for many years in the experimental study of the general prob- 

 lems of regeneration and morphogenesis in animals; in this treatise he presents 

 not only the more important of the observations he has made but also the 

 general conclusions to which this work has led. The book is full of material 

 of fact, presented in a logical and convincing manner, to support the general 

 theory of the nature of the process of senescence, the nature and extent of 

 rejuvenescence, the significance of sexual reproduction and maturation, and 

 the nature of the processes at work in the phenomena of regeneration, growth, 

 and the determination of form in animals and plants. It thus contains the 

 basis of a new theory of animal and plant forms, and a resulting new theory 

 of the process of inheritance which is to be the subject of a separate treatise, 

 shortly to appear. Not the least valuable feature of the book is that it treats 

 of these general processes as they occur both in plants and animals, and the 

 essential identity of the processes in the two living kingdoms is clearly revealed. 

 Zoology and botany thus mutually illuminate each other, and the conclusions 

 must arouse the keenest interest of both zoologists and botanists. The theories 

 are so far reaching and fundamental that if substantiated they will profoundly 

 alter many prevalent conceptions of biology. The book represents, therefore, 

 one of the most original and important constructive contributions made by 

 an American biologist. 



The thesis of the author is that senescence is a universal attribute of living 

 organisms, plants as well as animals. Where it appears to be absent, as in the 

 infusoria and some plants, this is not due to its actual absence, but to a rejuvenes- 

 cence taking place in more or less irregular rhythms by which the results of 



'Child, C. M., Senescence and rejuvenescence. 8vo. pp. 481. University of 



