520 MR. TRIMEN ON MIMETIC ANALOGIES AMONG AFRICAN BUTTERFLIES. 



liy wearing the aspect, respectively, of three prevalent species of Danais ; while the 

 Madagascarene Pajnlio Meriones, so closely allied to P. Ilerope as to he regarded hv 

 most authors as merely a local race of the latter, presents but one form of female, not 

 greatly differing from the male. 



Such results as these, confirming and supplementing, as they do, the similar series of 

 facts observed by Mr. Bates in Equatorial America, as well as those tabulated by Mr. 

 Wallace in reference to India and the Malayan archipelago, are of the deepest signi- 

 ficance. Inexplicable as they must ever remain when regarded on the theory of the 

 independent creation of all organic beings precisely as we now behold them, they become 

 clearly intelligible when viewed as the natural consequences of the innate variability of 

 species, and the preservation and development by inheritance, through all time and under 

 all changes of surrounding conditions, of every successive variation advantageous to the 

 organism originating it. In the infinitely complicated "struggle for life," any advan- 

 tage, however slight, inevitably has its effect ; and the individuals possessing it will not 

 only hold their ground to the exclusion of less fortunate competitors, but will transmit 

 the precious quality to some at least of their descendants. The process by which natural 

 selection gradually effects those innumerable protective resemblances of which these 

 mimetic analogies among butterflies form but a small portion, has been so ably traced by 

 distinguished naturalists, that it is unnecessary for me to attempt what could at best be 

 but a repetition of arguments already adduced ; but I may be permitted, in conclusion, 

 to express my conviction of the harmonious relation in which the theory of the muta- 

 bility and gradual origin of species stands in regard to what is now universally admitted 

 respecting inorganic nature. K o one disputes, at the present day, that the crust of the 

 earth has undergone profound changes both structurally and chemically ; but who is 

 now found attempting to account for these mutations on the exploded theory of vast 

 convulsions of nature or general cataclysms ? It is conceded on all hands that the 

 known forces and agencies at work under our eyes are sufficient, in the lapse of ages, to 

 account for all the past changes, however stupendous, of whicli the records remain ; but, 

 with a strange inconsistency, any suggestion of gradual change in the incomparably 

 more plastic and variable organic world is too often rejected with incredulity or disdain ; 

 and many men of science still cling to the theory of successive whosesale destructions 

 and as sudden creations to account for the extinct organisms revealed by palaeontology. 



It may, with confidence, be predicted that the day is not far distant when such dis- 

 cordant views of Nature will be unknown in the scientific world ; for the progress of dis- 

 covery proclaims, with ever-increasing force, that the famous axiom Natura non facit 

 saltum, is a truth of universal application, and that it is as impossible to sever the life of 

 the present from that of the remotest past as to interpose a barrier between the present 

 and the unknown future. 



