President's Address. 145 



been referred to, the question was asked, Can we by the 

 theory of natural selection satisfactorily account for the 

 evolution of the Proboscidea — for the development of the 

 trunk, the lengthening and subsequent shortening of the 

 mandible, and the remarkable modifications of the teeth and 

 cranium. 



Before considering this question, it may be as well to 

 point out that we are still lamentably ignorant of the causes 

 of variation, without which natural selection is powerless 

 to effect changes in even the simplest organisms. 



Not only must it be admitted that we know surprisingly 

 little of the causes of variation, but we must also admit that 

 there is little chance of the mystery of variation being solved. 

 Variation may be said to be the inheritance of the ages. 

 It is an attribute of protoplasm as inscrutable as life itself, 

 a force which responds to various kinds of stimuli, and hence 

 to a certain extent under control, but withal a force we can 

 neither create nor destroy. 



Taking variation for granted, let us now inquire how 

 far the theory of natural selection accounts for the making 

 of the elephant. 



At the outset, it is well to remember that Darwin did not 

 regard natural selection as the sole factor in organic evolu- 

 tion. " I am convinced," he said, " that natural selection has 

 been the main, but not the exclusive means of modification." 

 Wallace, the joint discoverer of the doctrine, has, however, 

 again and again stated that he believes natural selection has 

 been and is the sole cause of organic evolution ; that by 

 natural selection, and natural selection alone, we can account 

 for the disappearance of some forms and the gradual modi- 

 fication of others; 



If Wallace is right in his contention, then the last word 

 has been said as to the general method of evolution ; but 

 if Darwin was right in believing natural selection was one 

 of several factors, that it was in itself unable to effect all the 

 wonderful changes in organic nature, it behoves us to find 

 out, if possible, the other factors. That there is much to be 

 said for Wallace's view may be inferred from the fact that 

 the only serious criticism of natural selection has consisted 



