546 Mr. C. F. M. Swynnerton on 



Summary of the Position as regards Preferences. 



If graded preference is found to be at all general here, 

 it will provide us with a fairly complete and satisfactory 

 explanation — at all events from a purely selectionist point 

 of view — of the coloration of the eggs of birds, and much 

 that has hitherto seemed difficult will be explained. On this 

 account, the possibility is worth considering. 



That there is a basis for possible preference in the varying 

 composition of the contents of different eggs is suggested 

 by their varying taste and consistency. That the former 

 should be in some cases unpleasant to the human palate is 

 highly suggestive, though not conclusive. A consideration 

 of this kind (the "peculiar smelP' of Heliconidse and 

 Euploeinse, and the former's possession of exsertible glands) 

 constituted the whole of the more direct evidence on which 

 Bates founded his theory of mimicry^ now well supported by 

 evidence and widely accepted. But, for eggs, we have in 

 addition the evidence of a number of experiments, apparently 

 reliable so far as they go. Does this evidence represent what 

 occurs amongst egg-eaters generally? 



The critic's position is that, while there is nothing 

 inherently improbable in the idea of preference, he sees no 

 signs of it in nature *. The fairness of this may readily 

 be admitted. But (since uncontrolled acceptances prove 

 nothing) neither has any good evidence as yet been adduced 

 against preference. Proof or disproof remains, therefore, 

 a matter for special observation. 



The Claims, and a Definition. 

 The claims made are worth re-stating briefly to avoid 

 misunderstanding. It is not claimed that some eggs are not 

 eaten. All are eaten, even with eagerness, under certain 

 circumstances, though some are believed to be refused 

 more frequently than others. Nor is it claimed that 

 all egg-eaters necessarily thus discriminate, though, for 

 the support of the theory, it would be necessary for a 



* Rev. F. C. R, Joiu-dain, in a letter (17. iv. '15). 



