126 SEXUAL SELECTION: BIRDS. [Part II. 



also noticed a variety ©f the common pigeon with the 

 wing-bars symmetrically zoned with three bright shades, 

 instead of being simply black on a slaty-blue ground, as in 

 the parent-species. 



In many large groups of birds it may be observed 

 that the plumage is differently colored in each species, 

 yet that certain spots, marks, or stripes, though likewise 

 differently colored, are retained by all the species. Anal- 

 ogous cases occur with the breeds of the pigeon, which 

 usually retain the two wing-bars, though they may be 

 colored ;*ed, yellow, white, black, or blue, the rest of the 

 plumage being of some wholly different tint. Here is a 

 more curious case, in which certain marks are retained, 

 though colored in almost an exactly reversed manner to 

 what is natural ; the aboriginal pigeon has a blue tail, 

 with the terminal halves of the outer webs of the two 

 outer tail-feathers white ; now there is a sub-variety hav- 

 ing a white instead of a blue tail, with precisely that 

 small part black which is white in the parent-species. 44 



• 

 Formation and Variability of the Ocelli or Eye-like 



Spots on the Plumage of Birds. — As no ornaments are 

 more beautiful than the ocelli on .the feathers of various 

 birds, on the hairy coats of some mammals, on the scales 

 of reptiles and fishes, on the skin of amphibians, on the 

 wings of many Lepidoptera and other insects, they de- 

 serve to be especially noticed. An ocellus consists of a 

 spot within a ring of another color, like the pupil within 

 the iris, but the central spot is often surrounded by addi- 

 tional concentric zones. The ocelli on the tail-coverts of 

 the peacock offer a familiar example, as well as those on 

 the wings of the peacock-butterfly (Vanessa). Mr. Tri- 

 men has given me a description of a South African moth 



44 Bechstein, ' Naturgeschichte Deutscblauds,' B. iv. 1795, s. 31, ou a 

 lub- variety of the Monck pigeon. 



