PREFACE'"'-'-.. I-/'.,-". 



The subject matter of general biology, as presented in current 

 text books, is variously interpreted. In some it means an in- 

 troduction to the essential structures and vital manifestations 

 of animals and plants. In others it means the discussion of 

 hypotheses and principles of biology. In others it becomes an 

 encyclopoedia of the facts of physiology, hygiene and ecology. 

 With the first method the course is based largely upon labora- 

 tory work and the principles are illustrated with specific types. 

 The second and third methods are largely didactic and are 

 illustrated by examples taken at random from the entire animal 

 or plant kingdom. 



We believe thoroughly in the type and laboratory method of 

 instruction, and in choosing the types with such care that they 

 serve as points of departure for various lines of development in 

 subsequent course work. The present work is based upon the 

 excellent course outlined in Sedgwick and Wilson's General 

 Biology which occupies so prominent a place in the teaching of 

 American biology, and my only excuse for offering another to 

 the long list of text books is the need, which we have felt at 

 Columbia, of a work along similar lines to cover a course of 

 about thirty class exercises and as many laboratory periods. 



The book is planned somewhat differently from that of 

 Sedgwick and Wilson partly because of the enlarged scope, 

 partly because of the excellent general introductory courses 

 offered in up-to-date secondary schools. Emphasis is laid at 

 the outset on cellular activities, especially on the importance 

 of enzymes in metabolism and development, while animal 

 differentiation for the performance of primary functions of 

 protoplasm is the main theme of the entire course. In the 

 development of this theme organisms of one cell, organisms of 

 tissues, and organisms of organs are taken up in succession. 



ill 



