Parental care is rare among the lowest vertebrata. Among fishes the young are generally hatched without the assistance of the parents. There are exceptions to this among the Teleostei, where the male assumes the usual maternal functions of constructing a nest and jealously guarding the ova deposited there by the female. The male of certain species of the Arius, carries the ova in his pharynx. Nearly all of the reptiles, having placed their eggs in a convenient sunny spot, pay no more attention to them. With few exceptions, the relations of the sexes of the lower vertebrata can be described as fickle; they meet in the pairing time, part again, and have little more to do with one another. “The Chelonia form,” says Westermarck, “with regard to their domestic habits, transition to the birds, as they do also from a zoölogical and particularly from an embryological point of view.” He then goes on to show that parental affection in the latter class, not only on the side of the mother but on that of the father, has come to high development. Members of the two sexes aid each other in nest-building, the females bringing the materials and the males doing the work. Other duties which come with the mating season are shared by both, the mother being concerned with incubation and the father aiding her by taking her position when she leaves the nest for intervals, providing her with food which he gathers, and protecting her from dangers. When the breeding season is over and the young have come, a new set of duties is evolved. Young birds are not left alone by their parents, absences being necessitated only by searches for food for all members of the nest. When dangers threaten the nest both father and mother defend it bravely. [Illustration: FAMILY LIFE AMONG BIRDS. GROUP OF AMERICAN EGRET (COURTESY OF MUSEUM OF NATURAL HISTORY, NEW YORK)] All efforts are made to have the young shift for themselves as soon as they have grown strong enough to make it feasible. Independence and self-dependence come only after they are in all ways capable of meeting their needs. On the other hand, there are some species whose young, from the beginning of their ultra-oval existence, require and receive no care from the parents. The duck is one of a species which leaves all parental care to the female. In general it may be said that both parents share the parental duties, the chief duties, such as hatching and rearing of the young, falling to the mother, while the father gathers food and keeps off enemies.[25] The relations of the two sexes are, therefore, very intimate, and association lasts even after the breeding season has passed. And only the birds of the Gallinaceous family are an exception to the rule of making such association permanent once it has been started, death alone ending it.