An Outline of 

 the Theory of Organic Evolution 



With a Description of some of 

 the Phenomena which it explains 



By MAYNARD M. METCALF, Ph.D. 



Professor of Biology in the Woman's College of Baltimore 



SECOND EDITION, REVISED 



Cloth, 8vo f Colored Plates, $2.50 net 



The lectures out of which this book has grown were written for the 

 author's students at the Woman's College of Baltimore, and for others in 

 the college not familiar with biology who had expressed a desire to attend 

 such a course of lectures. The book is, therefore, not intended for biolo- 

 gists, but rather for those who would like a brief introductory outline of 

 this important phase of biological theory. 



It has been the author's endeavor to avoid technicality so far as possible, 

 and present the subject in a way .that will be intelligible to those unfamiliar 

 with biological phenomena. The subject, however, is somewhat intricate, 

 and cannot be presented in so simple a manner as to require no thought 

 on the reader's part; but it is hoped that the interest of the subject will 

 make the few hours spent in the perusal of this book a pleasure rather 

 than a burden. 



In many instances matter that might have been elaborated in the text 

 has been treated in the pictures, which, with their appended explanations, 

 form an essential part of the presentation of the subject. This method of 

 treatment has been chosen both for the sake of the greater vividness thus 

 secured and because it enables the book to be reduced to the limits de- 

 sired. Many of the illustrations have been obtained from books with 

 which the reader may wish later to become familiar. 



THE MACMILLAN COMPANY 



Publishers 64-66 Fifth Avenue New York 



