( Ixxi ) 



by this agency when of any advantage to the possessor. The 

 survival of the fittest is utilitarianism i)i crcfhis."* 



In endeavouring to interpret specific characters from the 

 utilitarian point of view we have therefore to consider not 

 only the possibility of direct, but likewise the possibility of 

 indirect utility. If the direct and obvious utility of every diag- 

 nostic character be insisted upon as an essential condition of 

 the theory of natural selection, then we are imposing upon that 

 theory a burden which its founders did not and do not sanc- 

 tion. If in the name of that theory we are told that all the 

 trivial differences of colour, pattern, marking, etc., with 

 which entomological systematists have made us so abun-> 

 dantly familiar, must be assigned a direct use in the 

 economy of the species, then it appears to me that we are 

 pushing Mr. Darwin's teaching beyond its legitimate limits, 

 and I for one should candidly confess that the theory had 

 broken down. I should be among the first to admit that 

 such a strain could not be borne by the doctrine, and that 

 an implicit faith in the direct adaptational value of every 

 detail would transcend the limits of legitimate scientific 

 faith. But it cannot fairly be urged that either Darwin 

 or Wallace have nan-owed us down to this restricted 

 view. The tenour of their teaching is simply to urge 

 caution before deciding that such or such a character is not 

 of adaptational value, a caution which has surely acquired 

 greater and greater significance with the progress of dis- 

 covery since the promulgation of the theory. Of all classes 

 of the animal kingdom, insects have furnished the most 

 numerous and the most striking examples of the adaptational 

 value of characters which, but for the light of the doctrine, 

 would be absolutely devoid of meaning.f 



* " Trans. Essex Field Club," Vol. III., p. 81. 



+ A most remarkable contribution to tliis phase of evolutional biology has 

 recently been furnished by Mr, Walter Garstang withiespect to Crustacea. 

 See his paper " On the Functions of certain Diagnostic Characters of 

 Decapod Crustacea," read at the last Liverpool Meeting of the British Asso- 

 ciation ; also "Contributions to Marine Bionomics; the Habits and 

 Eespiratory Mechanism of Corystes cassivelaunua," " Journ. Marine Biol. 

 Assoc," Vol IV., p. 223. Mr. Garstang informs me that a more complete 

 paper is in i curse of preparation. 



