=Reproduction by Budding. Parthenogenesis.= In the animal and vegetable kingdoms the higher organisms become more and more complicated. They are no longer composed of a single cell, but of an increasing number of these cells combined in a whole, of which each part, adapted for a special purpose, is itself formed of cells, differentiated as much by their organic form as by their chemical and physical constitution. In this way, in plants, are formed the leaves, flowers, buds, branches, trunk, bark, etc.; and in animals the skin, intestine, glands, blood, muscles, nerves, brain, sense organs, etc. In spite of the great complication of the divers living multicellular organisms, one often finds among them the power of reproduction by fission or by budding. In certain animals and plants, groups of cells vegetate in buds which separate from the body later on and form a new individual; this occurs among the polypi and plants with bulbs, etc. One can even form a tree by means of a cutting. Ants and bees, which have not been fecundated, are capable of laying eggs which develop by _parthenogenesis_ (virgin parturition) and become complete individuals. But these degenerate and disappear if reproduction by parthenogenesis or budding is continued during several generations. Among the higher animals, the vertebrates and man, there is no reproduction without conjugation; no parthenogenesis or budding. So far as we have studied the question we see in the animal and vegetable kingdoms sexual reproduction, or conjugation, as a _sine qua non_ for the indefinite continuation of life. =The Sexual Glands. The Embryo.= However complicated the organism, it always possesses a special organ, the cells of which, all of the same form, are reserved for the reproduction of the species and especially for conjugation. The cells of these organs, called _sexual glands_, have the power of reproducing themselves so that they reconstruct the whole individual (the type of the species) from which they arose, in an almost identical form, by conjugation (sometimes also, for a certain time, by parthenogenesis) under certain fixed conditions as soon as they leave its body. We can thus say with _Weismann_, speaking philosophically, that these germinal cells continue the life of their parents, so that in reality death only destroys part of the individual, namely, that which has been specially adapted for certain exclusively individual ends. Each individual, therefore, continues to live in his descendants.