MAYER: COLOR AND COLOR-PATTERNS. 189 
(Figs. 20-23) have been introduced merely to give an idea of the 
curiously strict limitations which 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 
impure and by no means so brilliant as they, perhaps, might have 
been, had Natural 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 course of Natural Selection 
and slow phylogenetic differentiation. Darwin and Trimen (’71) 
and Bateson (’94) have demonstrated that this is true for eye-spots. 
In the Heliconidae I haye 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 
influence of environmental conditions upon 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, 
