The face and carriage of many animals cannot express feelings as in the human, though it is not unreasonable to assume that animals may indicate feelings by expression understood by their mates, though not understood or even noticed by man. When they can express it in a human way their feelings may be read. The dejection of nostalgia is especially shown by anthropoid apes. Gorillas have been noted for it from the earliest writers. The orang is prone to it, shows it by his attitude and expression, and sometimes dies of it. It is stated in _A Handbook of the Management of Animals in Captivity in Lower Bengal_, p. 130, that elephants have been observed to shed tears abundantly if forced to leave their old home and surroundings. How much other animals who cannot express homesickness may feel it, and how often it is a cause of unhappiness, depression and predisposition to disease, it is impossible to say. Most wild animals in captivity are sterile. The reason is not known. It shows the profound effect of captivity. It would be difficult to determine whether the sterility of a mating is the fault of the male or the female. There is no apparent rule for sterility. Some families are always sterile in captivity, others are fertile, even with very unfavorable surroundings. The deer, horses, hippopotamuses, pigs, goats, sheep and oxen, are good breeders; while antelopes, rhinoceroses, giraffes, elephants, are poor breeders. Some members of a family may be good, others poor. The lion and puma breed fairly well; the tiger, leopard and jaguar, very poorly. Bears breed well, but the mother usually destroys her young. We cannot mate wild animals and birds simply by putting males and females together in the same cage. Domestic mammals and birds usually mate under such conditions, but wild ones often refuse. Many mammals and probably all birds that are not polyandrous or polygamous reserve the right to select their mates, and if the sexes are put together by man they may view each other with indifference or with animosity. There are many males and females of the same species of mammals at the Zoological Garden that will not consent to live together. A male monkey in a cage with several females will very often select one female for his mate and will have nothing to do with the others. Among monkeys fertility varies greatly. It is not practical to determine the ratio among the various kinds, as some kinds are much commoner in zoological collections than others. I think that in general the Old World monkeys (_Cercopithecidæ_) are better breeders in captivity than those of the New World (_Cebidæ_). The anthropoid apes are very poor breeders indeed; of the many gibbons, orangs, and chimpanzees, that for years have been captive in Europe and America, it is probable that only the chimpanzee has bred, and that very rarely.