THE SHAPES AND SIZES OF ANIMALS 117 



to each of us, that ideas have occurred unex- 

 pectedly on subjects to which we had pre- 

 viously paid but little attention ; ideas, which 

 though recognised at once as crude and disjointed, 

 are yet felt instinctively to contain germs of interest, 

 worthy of future development. Such ideas should 

 not be let slip : it is well to docket them, and 

 without attempting too soon to frame a consistent 

 notion of their real bearing, or of the conclusions 

 to which they may lead, it is well also to keep a 

 look-out for any additional facts or ideas bearing 

 on the subject, to take due note of them, and 

 after a time to turn out one's box, go over one's 

 notes, and take stock of one's material. At this 

 stage conversation and discussion with others will 

 probably afford material assistance : and in bring- 

 ing before you this evening a subject concerning 

 which my state of mind is exactly expressed by 

 saying that I want to find out what I think about 

 it, I believe I am utilising in a very proper and 

 legitimate manner the advantages which such a 

 Society as ours confers upon its members. 



The problem that I desire to deal with, that of 

 the forms and dimensions, or in more popular 

 language, the shapes and sizes of animals, may be 

 stated thus : Is it a mere matter of chance that 

 animals, say butterflies and birds, have certain 

 characteristic shapes ? Clearly it is not altogether 

 so : it is plain to every one that the shapes of 

 animals are correlated with their habits, and that 

 if it were a purely haphazard business there would 

 be no reason why butterflies should so much 



