Reproduction takes place in _S. carteri_ in three distinct ways, two of which may be regarded as normal, while the third is apparently the result of accident. If a healthy sponge is torn into small pieces and these pieces are kept in a bowl of water, little masses of cells congregate at the tips of the radiating fibres of the skeleton and assume a globular form. At first these cells are homogeneous, having clear protoplasm full of minute globules of liquid. The masses differ considerably in size but never exceed a few millimetres in diameter. In about two days differentiation commences among the cells; then spicules are secreted, a central cavity and an external membrane formed, and an aperture, the first osculum, appears in the membrane. In about ten days a complete young sponge is produced, but the details of development have not been worked out. The most common normal form of reproduction is by means of gemmules, which are produced in great numbers towards the end of the cold weather. If small sponges are kept alive in an aquarium even at the beginning of the cold weather, they begin to produce gemmules almost immediately, but these gemmules although otherwise perfect, possess few or no gemmule-spicules. If the sponge becomes desiccated at the end of the cold weather and is protected in a sheltered place, some or all of the gemmules contained in the meshes of its skeleton germinate _in situ_ as soon as the water reaches it again during the "rains." It is by a continuous or rather periodical growth of this kind, reassumed season after season, that large masses of sponge are formed. In such masses it is often possible to distinguish the growth of the several years, but as a rule the layers become more or less intimately fused together, for no limiting membrane separates them. A large proportion of the gemmules are, however, set free and either float on the surface of the water that remains in the ponds or are dried up and carried about by the wind. In these circumstances they do not germinate until the succeeding cold weather, even if circumstances other than temperature are favourable; but as soon as the cold weather commences they begin to produce new sponges with great energy. Sexual reproduction, the second normal form, takes place in _S. carteri_ mainly if not only at the approach of a change of season, that is to say about March, just before the hot weather commences, and about November, just as the average temperature begins to sink to a temperate level. At these seasons healthy sponges may often be found full of eggs and embryos, which lie in the natural cavities of the sponge without protecting membrane.