PREFACE. i x 



dependence of the various logical processes. In 

 several instances, particularly those of radicles, 

 climbing plants, and electric organs, the discus- 

 sions have been carried into considerable detail: 

 this has been done for the purpose of show- 

 ing what an actual course of investigation and 

 reasoning is like, how results, whether true or 

 false, are worked out. 



At the same time, no effort has been made to 

 make the treatment of Darwin's method exhaust- 

 ive, nor has any formal explanation of the vari- 

 ous logical processes been made. Those who 

 are likely to read this book are already suffi- 

 ciently familiar with the terminology of logic and 

 the practice of science to understand it easily; 

 and extended explanations would require an ex- 

 cursion into the domain of formal logic, which 

 is not a part of the purpose of the present 

 work. 



Some of the most important processes have 

 been selected, and Darwin's applications of 

 them illustrated, in such a way as to confine 

 the whole discussion within the narrowest pos- 

 sible limits. It is an easy matter to provoke 

 differences of opinion in discussing either the 



