XIV PREFACE 



to emphasize this fact. To have given pride of place to the verte- 

 brates might have given a more clear-cut picture, and could 

 certainly have provided more abundant and detailed examples; 

 but it would have thrown the intended comparison out of perspec- 

 tive. The search for good examples among invertebrates proved 

 unexpectedly successful. It has been decided, therefore, to 

 publish the book in two parts instead of one ; but the unified plan 

 of relatively simple presentation is being maintained. 



The present part of the book covers only the kinetic and 

 metabolic hormones, their sources, actions and the ways in which 

 their secretion is controlled. The second part* will contain a 

 similar treatment of the morphogenetic hormones, namely those 

 concerned with growth, differentiation and reproduction ; it will 

 also discuss such topics as the relation of the chemical constitution 

 of hormones to the sources from which they are derived and their 

 type of action. A consideration of the distribution of hormones in 

 the animal kingdom may also throw some light on the possible 

 evolution of these chemical activators, as well as suggesting prob- 

 lems for investigation. 



Many of these problems must be apparent to anyone who 

 surveys the field of hormone research; yet it is permissible to 

 assume that few research workers have time to undertake such a 

 survey, as their own work becomes more and more specialized and 

 results in the pubhcation of books that are confined to single 

 classes of animals or single endocrine organs. It is therefore hoped 

 that the present work may be useful to some specialists as well as 

 to the teachers and students for whom it is primarily intended. 



It has clearly not been possible for the writer to review the 

 whole literature of so rapidly expanding a subject; but the main 

 original papers on the kinetic and metabolic hormones of inverte- 

 brates have been covered up to the summer of 1958, while the 

 vertebrate examples have been checked by recent reviews and 

 reports of symposia. The references at the end of each chapter 

 show the sources used, but make no pretence to being complete, 

 though they should provide a useful starting point for anyone 

 wishing to go further. 



* Animal Hormoties, a comparative survey. Part \\. Morphogenetic Hormones ^ 

 in preparation. 



