THE ORIGIN OF ORNAMENTATION. 515 



a veil ; and I believe they can be shown to have arisen in an entirely diff- 

 erent way, by an alteration in the relative position of certain bars and 

 spots common to butterflies of this group. No doubt all other complex 

 ocelli, such as those with spiral annuli, could be shown, upon special study, 

 to have originated in some similar manner. 



After reaching such a stage of complication, and assuming the known 

 tendency to suffusion of markings in butterflies, that is, the blending of 

 neighboring spots, we may easily see that, by the amalgamation of adjoin- 

 ing s[)Ots in different transverse rows, every conceivable pattern can be 

 explained. There is nothing left to consider but the diversity in color 

 itself; and observation shows that although there are prevailing tints as 

 well as prevailing patterns in special groups of butterflies, that neverthe- 

 less these colors are often very pliable ; for instance white, yellow, and 

 orange are readily interchangeable ; and a similar reciprocal relation exists 

 between orange and red, or between certain tones of yellow and brown. 



Again, when we compare individuals of the same s})ecies, especially if 

 of opposite sexes, the great difference between them in the profusion with 

 which scales of metallic blue are sprinkled upon a normal dark ground 

 shows how easily black or dark brown is replaced by metallic bkie ; the 

 latter again is readily interchangeable with metallic green, or with purple 

 or ordinary blue or green. Some instances of this interchangeability are 

 given elsewhere, and it is not therefore worth while to dilate upon it 

 here. It should, however, be stated that the iridescence on the wings of 

 many butterflies is of an entii'ely different nature, being due to a micro- 

 scopic striation of the outer surface of the scales. 



The hypothesis, then, of the origin and development of color-patterns 

 in butterflies which I would maintain is based upon the scale of complica- 

 tion seen in the markings of living Lepidoptera, and the prevalence among 

 them of certain general patterns. According to it, the wings first showed 

 signs of divergence from uniformity by a deepening of the color next the 

 outer margin, which thereafter became separated into distinct transverse 

 bands ; these bands, in breaking up, gave rise to dark-veined or to spotted 

 wings, which served as the basis for all the variegated patterns of the 

 present day, including ocelli, which are only specialized forms of simple 

 interspacial spots. 



This discussion leads naturally to the consideration of the intimate con- 

 nection between the color-patterns and the frame-work of the wings in 

 Lepidoptera; this relation, indeed, must be considered one of the most 

 important features in the topography of the wings, if I may use the 

 expression. It is seen with the first appearance of ornamentation, in the 

 wavy outline of the transverse bands, each wave corresponding to the 

 position of the adjacent veins. It is still more conspicuous when these 

 bands break up into bars or spots. But its full force is shown when the 



