liv THE DARWIN CENTENARY. [Februarys. 



that it is applicable to the behavior of a large number of animals. 

 This principle of "trial and error" is in reality the rejection or 

 elimination of unfit responses during the individual life of an 

 organism, and if a similar principle should be found to be applicable 

 to other physiological processes it would probably explain in equally 

 simple manner many apparently purposive responses which are at 

 present inexplicable. Thus the simple principle of the elimination 

 of the unfit, whether of individuals, or of parts of individuals, or 

 of physiological responses, would offer a possible and natural expla- 

 nation of the almost universal occurrence of fitness in the living 

 world. 



But whether the Darwinian theory is capable of explaining all 

 the fitnesses of organisms or not, it does succeed, as no other theory 

 does, in offering a natural and causal explanation of very many of 

 these wonderful phenomena. The development of particular struc- 

 tures and functions to meet particular conditions of life, such as 

 organs of locomotion, sensation, digestion and reproduction; organs 

 and instincts of protection, offense and defense; and all the multi- 

 tudes of diverse forms and ways in which organisms are fitted to 

 carry on the fundamental properties of life amidst the most varied 

 conditions — these diversities we may reasonably expect a theory of 

 evolution to explain, and it is the crowning glory of Darwin's theory 

 that it is, on the whole, able to explain them. 



IV. 



This is a brief review of Darwin's most important work. Some 

 of his generalizations have been and still are of the greatest impor- 

 tance, others were of less value and have since been abandoned. In 

 this respect his work is not unlike that of other scientists, and yet 

 we all recognize that Darwin occupies a unique position in biology; 

 that indeed he stands almost alone in the greatness of his influence 

 on the world, and that his name can be properly associated only with 

 that of Sir Isaac Newton, by whose side he lies in Westminster 

 Abbey, and with two or three others in the whole history of science. 



What is the secret of the tremendous influence which Darwin 

 has had upon the entire world? He was of course a remarkable 

 man, remarkably well prepared for a supremely great work. Keen 



