MAYER: COLOR AXD COLOR-PATTERNS. 189 



(Figs. 20—23) have been introduced merely to give an idea of tlie 

 curiously strict limitations wliich nature has imposed upon the differ- 

 entiation of the color-pattern. Many beautiful effects might have 

 been produced, such for example as that of alternate interspaces 

 showing different colors, but this is not seen in nature. 



It is interesting to recall the fact, that the colors themselves are 

 inij)ure and by no means so brilliant as they, perhaps, might have 

 been, had Xatural Selection been more severe in regard to color. 



There is doubtless some physiological reason why spots almost 

 invariably appear and disappear in the middle of the interspaces^ and 

 when we know more of the anatomical and histological conditions 

 of the wing during the development of the colors, we may be able to 

 discover it. It will be remembered that in the developing pupal 

 wings of Callosamia promethea and Danais plexippus I found that 

 the colors first made their appearance in the interspaces, and finally 

 spread out so as to tinge over the nervures. 



(4) Origin of Color- Variations. There is every reason to 

 believe that all kinds of spots and bands, which are essentially 

 only fused spots, may appear or disappear in any individual 

 specimen without going through a long com-se of Xatural Selection 

 and slow phylogenetic differentiation. Darwin and Trimen ('71) 

 and Bateson ('9-1) have demonstrated that this is true for eye-spots. 

 In the Heliconidae I have found that bands and rows of spots are 

 very variable in different specimens of the same species (see Plate 7, 

 Figs. 84-87). 



There is a large and widely scattered literature recording the 

 appearance and disappearance of colors and markings upon the 

 wings of Lepidoptera. Limits of time and space prohibit my doing 

 justice to it here, but it may be well to call attention to a very few 

 of the more recent papers upon the subject. Many of the color- 

 aberrations recorded in this list of papers may be due to the direct 

 iiiHuence of environmental conditions nj^on the individual, but others 

 are no doubt true sports or, to speak crudely, " congenital " variations, 

 and might under favorable conditions of life become the ancestors 

 of new varieties or species. It seems highly probable that new 

 species often arise from just such sports in the manner so frequently 

 and ably expounded by Bateson. 



