“In other species the glands are confined to the males, or are more developed than in the females; and they almost always become more active during the rutting season. At this period the glands on the sides of the face of the male elephant enlarge, and emit a secretion having a strong musky odor. The males, and rarely the females, of many kinds of bats have glands and protrudable sacs situated in various parts; and it is believed that these are odoriferous. “The rank effluvium of the male goat is well known, and that of certain male deer is wonderfully strong and persistent. Besides the general odor, permeating the whole body of certain ruminants (for instance, _Bos moschatus_) in the breeding season, many deer, antelopes, sheep, and goats, possess odoriferous glands in various situations, more especially on their faces. The so-called tear-sacs, or suborbital pits, come under this head. These glands secrete a semifluid fetid matter which is sometimes so copious as to stain the whole face, as I have myself seen in an antelope. They are ‘usually larger in the male than in the female, and their development is checked by castration.’ According to Desmarest they are altogether absent in the female of _Antilope subgutturosa_. Hence, there can be no doubt that they stand in close relation with the reproductive functions. They are also sometimes present, and sometimes absent, in nearly allied forms. In the adult male musk-deer (_Moschus moschiferus_), a naked space round the tail is bedewed with an odoriferous fluid, whilst in the adult female and in the male until two years old, this space is covered with hair, and is not odoriferous.” Darwin believes in these cases that the odor serves to attract the females. He admits that here, “active and long-continued use cannot have come into play as in the case of the vocal organs.” He concludes, therefore, that “the odor emitted must be of considerable importance to the male, inasmuch as large and complex glands, furnished with muscles for everting the sac, and for closing or opening the orifice, have in some cases been developed. The development of these organs is intelligible through sexual selection, if the most odoriferous males are the most successful in winning the females, and in leaving offspring to inherit their gradually perfected glands and colors.” There is sometimes a difference in the mammals in the hair of the two sexes both in amount and in color. In some species of goats the males have a beard, in others it is present in both sexes. The bull, but not the cow, has curly hair on the forehead. In some monkeys the beard is confined to the male, as in the orang; in other species it is only larger in the males. “The males of various members of the ox family (Bovidæ), and of certain antelopes, are furnished with a dewlap, or great fold of skin on the neck, which is much less developed in the female.