No. 48.— 1897.] on Wallace's theory. 



87 



shell are attended with variations in the other parts of the 

 animal or not ? 



In the genus Plotheia, surely careful collecting and 

 breeding of the larvae would show whether the different 

 species interbreed or not, and by collecting the Munias of 

 the Andamans and Nicobars, and attempting to interbreed 

 them together, or with our Ceylon species, similar facts 

 might be ascertained. 



When I first became acquainted with Darwin's " Origin 

 of Species " I lived in a house surrounded with large 

 grounds, with several hothouses, where the cultivation of 

 domestic varieties of plants was an object lesson on 

 Darwin's works, and no more thorough convert to Darwinism 

 than myself ever existed ; but when I came to study in the 

 British Museum and saw species from all parts of the 

 world, the theory seemed to me by no means satisfactory, 

 and when in Ceylon I saw our extraordinarily varied 

 Phasmidce, all living side by side in the same woods under 

 precisely similar conditions of life, I ceased to have any 

 faith in Natural Selection as the true cause for the origin of 

 species. 



My error arose from the idea that variations must be 

 useful, whereas we cannot attach any idea of utility to the 

 variations which I have exhibited to-night. It is only when 

 the slowly changing environment gives a better chance of 

 survival to one or more of these varieties over the other 

 that Natural Selection comes into play. 



I do not know exactly what interpretation to place on 

 Professor Wallace's dictum, that " only useful variations are 

 preserved." If this applies to the whole animal, of course 

 in the long run this must be the case : only the fittest survive 

 — but if to particular structures, it seems to me to run 

 counter to the theory. 



In tracing the supposed line of descent, the preservation 

 of useless or merely ornamental characters seems to me to 

 afford a most important guide. 



