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 COLOR AND SEX. 45 exact value remains to be determined by closer obser- vation. Color and Sex!^ — It is not possible here to discuss at length the vexed question of sexual coloration. But, as a means of directing observation, I present a synopsis of the principal types of secondary sexual characters, with some of the theories which have been advanced to ac- count for them, SYNOPSIS OP THE SECONDARY SEXUAL CHARACTERS OF BIRDS. Size. I. STRUCTURAL. j Male larger than female (usual). Female larger than male (rare). f p,. j iIale brighter than female. I o 01. ^ x^emale brighter than male (rare). I C Assumption of plumes, ruffs, crests, trains, Plumage. etc.: special modification of wing and tail I Form. feathers. I I a. Worn by male alone. [ yb. Worn by both sexes. ( Sole or greater development in male of brightly col- Of the body. ored bare tracts of skin, combs, wattles, caruncles, ( and other fleshy or horny appendages. Of the feet. Sole or greater development in male of spurs. /vr^i 1-11 ( Male with more highly colored or larger bill than Of the bill, -j f^,j^^^i^_ . - ^ II. FUNCTIONAL. r) •. S P'X male when similar to or brighter than female. i ursuit. ^ j^y female when brighter than male. Display. By male of accessory plumes and other appendages. Battle. By male using spurs, wings, bill, etc. ,,. Vocal, by male and, rarely, female. Music. ^ Mechanical, by male and sometimes female. f Dances, mock fights, aerial evolutions, construction of o. , I bowers, decoration of playgrounds, attitudinizing, ^^rivt strutting, etc. naoits. I ^ -gy j^^jg h^ioxQ the female. [ b. Among the males alone. Sex (D. Appleton & Co.). Wallace, Darwinism (Macinillan Co.).
 * Read Darwin, The Descent of Man and Selection in Relation to