In this connexion Poulton has brought forward interesting facts showing that the mimics of one model, belonging to different genera, often secure the same effect in quite different ways. Thus the glass-like transparency of the wings in the Heliconiidæ of the genus _Methona_ depends on a considerable reduction of the size of the scales, which ordinarily cover both sides of the wing as thickly as the tiles on a roof, and produce the colour. In another quite similar species, also transparent-winged, the Danaid _Ituna ilione_, the transparency is due to the absence of most of the scales, and in a third mimic, _Castnia linus_, var. _heliconoides_, the scales are not altered either in size or number, but have become absolutely unpigmented and transparent. In a fourth mimic, a Pierid, _Dismorphia crise_, the scales have not decreased in number, but have become quite minute, while in a fifth case, the nocturnal _Hyelosia heliconoides_ Swains., the same thing has happened as in _Castnia_, but the scales are also fewer in number. Thus in each of the mimics the changes which have taken place in the scales are quite different, but they bring about the same effect, the glass-like transparency of the wings, on which the resemblance to the model depends: what we have before us is, therefore, not a similarity of variation, but only an appearance of similarity in external features. In the face of such facts there can be no further question of the often repeated objection, that the resemblance of model and copy depend on the similarity of external influences upon species living in the same latitude, even if that were not already sufficiently refuted by the frequent restriction of the mimicry to the female. And that mimicry should be a mere matter of chance is negatived even by the single fact that model and copy always live in the same area, and that the local varieties of the model are faithfully followed by the mimic. An interesting example of this is furnished by _Elymnias undularis_, already mentioned, for in this case the female (Pl. II, Fig. 23) mimics the brown-yellow _Danais plexippus_ (Pl. II, Fig. 22), not wherever _E. undularis_ occurs, but only in Ceylon and British India. In Burmah, where another Danaid, _D. hegesippus_, is common, it mimics that; and in Malacca it does not copy a Danaid at all, but resembles the male of its own species, which in India is very different from it, since there the female mimics one of the blue iridescent Euplœæ (Pl. III, Fig. 24). It cannot therefore be a matter of 'chance,' and we should have to give up all attempt at a scientific interpretation if we were not prepared to accept that of natural selection. Even the interference of a purposeful Power can hardly be seriously considered in this case, even by those who are inclined to such a view, for the _gradual_ approximation to the model, which is a matter of course in a process of evolution, could only appear, if referred to the benevolent