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Choice exerted by the female Length of courtship Unpaired birds Mental qualities and taste for the beautiful Preference or antipathy shewn by the female for particular males Variability of birds Variations sometimes abrupt Laws of variation Formation of ocelli Gradations of character Case of Peacock, Argus pheasant, and Urosticte.
If we admit the principle of gradual evolution, there must formerly have existed many species which presented every successive step between the wonderfully elongated tail-coverts of the peacock and the short tail- coverts of all ordinary birds; and again between the magnificent ocelli of the former, and the simpler ocelli or mere coloured spots on other birds; and so with all the other characters of the peacock.
This latter is provided above with two slender six-jointed antennae, two very large faceted eyes at the side, and three ocelli forming a triangle. The last four segments, of decreasing breadth, are retractile beneath the carapax, as is also the broad plume that terminates them, and which is formed of three short, transparent, and elegantly ciliated bristles.
Nevertheless they are not illuminated from strictly the same point as they ought to be; for the white marks on the ocelli of the feathers which are held almost horizontally, are placed rather too much towards the further end; that is, they are not sufficiently lateral.
Thwaites states that there is a smaller tank leech of an olive-green colour, with some indistinct longitudinal striæ on the upper surface; the crenated margin of a pale yellowish-green; ocelli as in the paddi-field leech; length, one inch at rest, three inches when extended. Mr. E.L. LAYARD informs us, Mag. Nat.
On the pupa are four quite distinct conical tubercles forming a transverse line just in front of the ocelli; and there are also two larger, longer tubercles, on the outer side of each of which, an ocellus is situated. Search was made on July 16th, where the ground was hard as stone for six inches in depth, below which the soil was soft and fine, and over twenty cells were dug out.
The Saturniidae include some of the most beautiful of all moths, their wings being decorated, as in our British Emperor moth, with fine ocelli; and Mr. 'Proc Ent. It is a singular fact that no British moths which are brilliantly coloured, and, as far as I can discover, hardly any foreign species, differ much in colour according to sex; though this is the case with many brilliant butterflies.
Circular spots are sometimes surrounded by one or more differently shaded zones, and are thus converted into ocelli. Nor need much be said on the wonderful difference between the sexes of many birds. The common peacock offers a striking instance.
Male moths mate with females of their kind distinctly different from them in colour, and male butterflies pair with albinos of their species, when these differ widely from the usual colouring. A few moths are also provided with small simple eyes called ocelli; these are placed on top of the head and are so covered with down they cannot be distinguished save by experts.
Thus the several species of Polyplectron manifestly make a graduated approach to the peacock in the length of their tail-coverts, in the zoning of the ocelli, and in some other characters. Part of a tail-covert of Polyplectron chinquis, with the two ocelli of natural size. Hence I concluded that the early progenitors of the peacock could not have resembled a Polyplectron.
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