Darwin- Wallace Celebration. 9 



It is the constant search for and detection of these often 

 unexpected differences between very similar creatures, that 

 gives such an intellectual charm and fascination to the mere 

 collection of these insects ; and when, as in the case of 

 Darwin and myself, the collectors were of a speculative turn 

 of mind, they were constantly led to think upon the " why " 

 and the " how " of all this wonderful variety in nature this 

 overwhelming, and, at first sight, purposeless wealth of 

 specific forms among the very humblest forms of life. 



Then, a little later (and with both of us almost accidentally) 

 we became travellers, collectors, and observers, in some of the 

 richest and most interesting portions of the earth ; and we 

 thus had forced upon our attention all the strange phenomena 

 of local and geographical distribution, with the numerous 

 problems to which they give rise. Thenceforward our in- 

 terest in the great mystery of how species came into existence 

 was intensified, and again to use Darwin's expression 

 " haunted " us. 



Finally, both Darwin and myself, at the critical period 

 when our minds were freshly stored with a considerable body 

 of personal observation and reflection bearing upon the 

 problem to be solved, had our attention directed to the system 

 of positive checks as expounded by Malthus in his ' Principles 

 of Population/ The effect of this was analogous to that of 

 friction upon the specially-prepared match, producing that 

 flash of insight which led us immediately to the simple but 

 universal law of the " survival of the fittest," as the long- 

 sought effective cause of the continuous modification and 

 adaptation of living things. 



It is an unimportant detail that Darwin read this book two 

 years after his return from his voyage, while I had read it 

 before I went abroad, and it was a sudden recollection of its 

 teachings that caused the solution to flash upon me. I attach 

 much importance, however, to the large amount of solitude 

 we both enjoyed during our travels, which, at the most 

 impressionable period of our lives, gave us ample time for 

 reflection on the phenomena we were daily observing. 



This view, of the combination of certain mental faculties 



