Between one of the elliptic ornaments and a perfect ball-and-socket
ocellus, the gradation is so perfect that it is scarcely possible to
decide when the latter term ought to be used. The passage from the one
into the other is effected by the elongation and greater curvature in
opposite directions of the lower black mark (b, Fig. 59), and more
especially of the upper one (c), together with the contraction of the
elongated sub-triangular or narrow mark (d), so that at last these
three marks become confluent, forming an irregular elliptic ring. This
ring is gradually rendered more and more circular and regular,
increasing at the same time in diameter. I have here given a drawing
(Fig. 60) of the natural size of an ocellus not as yet quite perfect.
The lower part of the black ring is much more curved than is the lower
mark in the elliptic ornament (b, Fig. 59). The upper part of the ring
consists of two or three separate portions; and there is only a trace
of the thickening of the portion which forms the black mark above the
white shade. This white shade itself is not as yet much concentrated;
and beneath it the surface is brighter coloured than in a perfect
ball-and-socket ocellus. Even in the most perfect ocelli traces of the
junction of three or four elongated black marks, by which the ring has
been formed, may often be detected. The irregular sub-triangular or
narrow mark (d, Fig. 59), manifestly forms, by its contraction and
equalisation, the thickened portion of the ring above the white shade
on a perfect ball-and-socket ocellus. The lower part of the ring is
invariably a little thicker than the other parts (Fig. 57), and this
follows from the lower black mark of the elliptic ornament (b, Fig. 59)
having originally been thicker than the upper mark (c). Every step can
be followed in the process of confluence and modification; and the
black ring which surrounds the ball of the ocellus is unquestionably
formed by the union and modification of the three black marks, b, c, d,
of the elliptic ornament. The irregular zigzag black marks between the
successive ocelli (Fig. 57) are plainly due to the breaking up of the
somewhat more regular but similar marks between the elliptic ornaments.
The successive steps in the shading of the ball-and-socket ocelli can
be followed out with equal clearness. The brown, orange, and
pale-leadened narrow zones, which border the lower black mark of the
elliptic ornament, can be seen gradually to become more and more
softened and shaded into each other, with the upper lighter part
towards the left-hand corner rendered still lighter, so as to become
almost white, and at the same time more contracted. But even in the
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