INTRODUCTION. 1 1 



extraordinary stimulus to the students who were 

 trying to find some way of understanding life. 



New Aspects of Biology. These three concep- 

 tions seized hold of the scientific world at periods 

 not very distant from each other, and their influ- 

 ence upon the study of living nature was imme- 

 diate and extraordinary. Living things now came 

 to be looked upon not simply as objects to be 

 catalogued, but as objects which had a history, 

 and a history which was of interest not merely in 

 itself, but as a part of a general plan. They were 

 no longer studied as stationary, but as moving 

 phases of nature. Animals were no longer looked 

 upon simply as beings now existing, but as the 

 results of the action of past forces and as the 

 foundation of a different series of beings in the 

 future. The present existing animals and plants 

 came to be regarded simply as a step in the long 

 history of the universe. It appeared at once that 

 the study of the present forms of life would offer 

 us a means of interpreting the past and perhaps 

 predicting the future. 



In a short time the entire attitude which the 

 student assumed toward living phenomena had 

 changed. Biological science assumed new guises 

 and adopted new methods. Even the problems 

 which it tried to solve were radically changed. 

 Hitherto the attempt had been made to find in- 

 stances of purpose in nature. The marvellous 

 adaptations of living beings to their conditions 

 had long been felt, and the study of the purposes 

 of these adaptations had inspired many a mag- 

 nificent conception. But now the scientist lost 

 sight of the purpose in hunting for the cause. 

 Natural law is blind and can have no purpose. 

 To the scientist, filled with the thought of the 



