GBRMWAL SELECTION. i? 



I do not pledge myself, of course, to give an expla- 

 nation of every spot and every line on a wing. The 

 inscription is often a very complicated one, dating 

 from remote and widely separated ages; for every 

 single existing species has inherited the patterns of 

 its ancestral species and that again the patterns of 

 a still older species. Even at its origin, therefore, 

 the wing was far from being a tabula rasa, but was 

 a closely written and fully covered sheet, on which 

 there was no room for new writing until a portion of 

 the old had been effaced. But other parts were pre- 

 served, or only slightly modified, and thus in many 

 cases gradually arose designs of almost undecipherable 

 complexity. 



I should be far from maintaining that the markings 

 arose unconformably to law. Here, as elsewhere, the 

 dominance of law is certain. But I take it, that the 

 laws involved here, that is, the physiological conditions 

 of the variation, are without exception subservient to 

 the ends of a higher power — utility ; and that it is util - 

 ity primarily^that determines the kind of colors, spots, 

 streaks and bands that .shall originate, as also their 

 place and mode of .disposition. The laws come into 

 consideration only to the extent of conditioning the 

 quality of the constructive materials— the variations, 

 out of which selection fashions the designs in ques- 

 tion. And this also is subject to important restric- 

 tions, as will appear in the sequel. 



The meaning of formative laws here is that definite 

 spots on the surfaces of the wings are linked together 

 in such a manner by inner, invisible bonds, as to 

 represent the same spots or streaks, so that we can 

 predict from the appearance of a point at one spot the 

 appearance of another similar point at another, and 



