PREFACE 



biological ideas be received on terms of equality with those 

 of the other sciences. The biologist believes that he has 

 much to offer, both to man the intelligent being and to 

 man the animal, subject to hunger and disease. He is 

 convinced that even the most intimate problems of exist- 

 ence, those problems w^hich concern man's mental and 

 emotional life, are susceptible of a helpful objective 

 analysis. At the same time, he realizes just how difficult 

 it is for most people to accept the thesis that the complex 

 attributes and the many-sided activities of the human 

 being can be studied as carefully, as precisely, and as 

 impartially as those of any other being about which we 

 wish to learn the truth. It requires some knowledge of 

 what has been accomplished, some familiarity with the 

 methods by which the work is done; and it demands an 

 intellectual independence above the ordinary. 



As a contribution toward a better understanding of the 

 ideals, the methods, and the results of biology, this book 

 is presented. It contains a series of relatively non-technical 

 discussions of the present conditions of several of the more 

 important subdivisions of the subject, emphasizing recent 

 advances and expressing a few conservative predictions as 

 to probable future trends. Those phases of biology which 

 have been — or may be — of especial service to mankind 

 have been stressed, with the hope of enlisting the interest 

 of the general reader and of giving him a clearer and more 

 accurate idea of the problems involved and of the progress 

 in solving them. In one sense, therefore, the authors have 

 endeavored to give a wider publicity to their wares. But 

 there has been no insulting attempt to tell nature stories 

 of the type which appeals to immature minds. It is a serious 

 book intended for people who find satisfaction in the 

 disentanglement of the mysteries of the universe in which 

 they live. 



[viii] 



