It may, however, be said, though I think not with justice, that we ought not to take two species, however closely allied, to illustrate such a point. But very good examples can be found in the same species. A common German butterfly, _Araschnia Levana_, has two distinct varieties, _Levana_ being the winter, and _prorsa_ the summer form; and between these an intermediate form, _porima_, can be bred from the summer form by keeping the pupæ cold. Dr. Weismann, who has largely experimented on this insect, has given accurate illustrations of the varieties. Plate V. is taken from specimens in our possession. In the males of both _Levana_, Fig. 4, and _prorsa_, Fig. 1, the hind-wing has a distinct row of spots, and a less distinct one inside it, and in the females of both these are represented by dark stripes. In _porima_ we get every intermediate form of spots and stripes, both in the male and female, and as these were hatched from the same batch of eggs, or, are brothers and sisters, it is quite impossible to doubt that here, at least, we have an actual proof of the change of spots into stripes. [Illustration: Fig. 1. Part of secondary feather of Argus Pheasant. _a. a._ Elongated spots, incipient ocelli. _b._ Interspaces. _c. c._ Axial line. _d. d._ Double spots, incipient ocelli. _e._ Minute dottings. _f. f._ Shaft. _k. k._ Line of feathering.] [Illustration: Fig. 2. Part of secondary wing feather of Argus Pheasant. _a._ Oval. Axis at right angles. _b._ Round. _c. c._ Shaft. _d._ Imperfect ocellus. _e._ Expansion of stripe. _f._ Interspace. _g._ Stalk. _h._ Edge of feather. _k._ Line of feathering.] [Illustration: Plate V. SEASONAL VARIETIES.] The change of spots more or less irregular into eye-spots, or ocelli, is equally clear; and Darwin's drawing of the wings of _Cyllo leda_[16] illustrates the point well. "In some specimens," he remarks, "large spaces on the upper surfaces of the wings are coloured black, and include irregular white marks; and from this state a complete gradation can be traced into a tolerably perfect ocellus, _and this results from the contraction of the irregular blotches of colour_. In another series of specimens a gradation can be followed from excessively minute white dots, surrounded by a scarcely visible black line, into perfectly symmetrical and larger ocelli." In the words we have put in italics Darwin seems to admit these ocelli to be formed from blotches; and we think those of the Argus pheasant can be equally shown to arise from spots.