The male and female are of nearly the same size, and so like in appearance that the sex cannot be distinguished with certainty by any external character. The comb and wattles of the male are sometimes conspicuously larger than those Of the female, but this difference is not regular. Although the voices of the male and female are different, the difference is not easily described, nor is it readily detected except by people who are familiar with the birds, and whose ears are trained to distinguish the different notes. Both sexes make a rapid, sharp, clattering sound, and also a shrill cry of two notes. The cry of the male is harsher and has a more aggressive tone; that of the female has a somewhat plaintive sound, which some people describe as like the words "come back, come back." The name "guinea" comes from the country of Guinea in Africa, from which the birds were introduced into America and Western Europe. The male guinea fowl is called a guinea cock; the female, a guinea hen; the young, guinea chickens. =Origin.= The guinea fowl is a native of Africa. It is said that there are about a dozen similar species on that continent. This species is abundant there in both the wild and the domesticated state, and also in a half-wild state. It was probably brought into partial domestication at a very early date, for it was known to the ancient Greeks and Romans, as well as to the early civilized nations of Northern Africa. It may have been distributed through Western Europe by the Romans. According to one account, some English monks had guineas in the thirteenth century. It is likely that they were rare in Europe at that time and soon disappeared, for the modern Europeans had never seen them until they were taken to Europe from the West Indies, where, it is said, they had been brought by slave ships from Africa. There is a tradition that the first guineas in America were brought direct from Africa with the first cargo of slaves from that continent. In the West Indies and in South America the guinea, after its introduction, ran wild. The natural color of the species is a bluish-gray with many small, round white spots on each feather. On the flight feathers of the wings these spots are so placed that they form irregular bars. [Illustration: Fig. 165. White guinea fowls]