Now such examples as this of simultaneous mimicry in several species are of peculiar interest for us when we come to inquire more closely into the process by which the resemblances can be supposed to have been brought about. Take for example the case of _E. undularis_. The male is evidently an unprotected insect in so far as mimicry is concerned, while the female exhibits the general pattern and coloration characteristic of the warningly coloured and presumably distasteful species _D. plexippus_ or _D. chrysippus_. If we are to suppose this to have been brought about by the operation of natural selection it is clear that we must regard the colour and pattern of the male as the original colour and pattern of both sexes. For natural selection cannot be supposed to have operated in causing the male to pass from a protected to an unprotected condition, or even in causing him {68} to change one unprotected condition for another. Probably all adherents of the mimicry theory would be agreed in regarding the male of _Elymnias undularis_ as shewing the ancestral coloration of the species, and in looking upon the female as having been modified to her own advantage in the direction of _D. plexippus_. The question that we have to try to decide is how this has come about--whether by the accumulation of slight variations, or whether by a sudden change or mutation in the pattern and colour of the female by which she came to resemble closely the Danaine. It is clear that if _D. plexippus_ were what it is to-day before the mimetic approach on the part of _E. undularis_ began, small variations in the latter would have been of no service to it. The difference between the two species would have been far too great for individuals exhibiting slight variation in the direction of _D. plexippus_ to stand any chance of being confused with this species. And unless such confusion were possible natural selection could not work. There is, however, an immediate way out of the difficulty. We may suppose that the coloration of the male of the mimic, _E. undularis_, is not only the ancestral colour of its own species but also of the model. _D. plexippus_ on this supposition was very like _E. undularis_, of which both sexes were then similar to what the male is to-day. The pattern is, however, an inconspicuous one, and it can be imagined that it might be to the advantage of _D. plexippus_ to don a brighter garb for the advertisement of its unpleasant qualities. {69} Variations in the direction of a more conspicuous pattern would for that reason tend to be preserved by natural selection, until eventually was evolved through its means the well-marked pattern so characteristic of the model to-day. If in the meantime variations in the same direction occurred among the females of _E. undularis_ these would tend to be preserved through their resemblance to the developing warning pattern of the distasteful Danaine model. The development of model and mimic would proceed