A comparative morphological analysis was performed for freshwater and marine sponges belonging to the order Haplosclerida (class Demospongiae, subclass Ceractinomorpha). The analysis was based on the comparison of morphogeneses alternating in the course of sexual and asexual reproduction. The most significant features of ontogenesis in the Haplosclerida compared with those in other representatives of the subclass Ceractinomorpha are (1) the alternating of sexual and asexual (of a gemmulogenesis type) reproduction in the life cycle; (2) the presence of specialized nurse cells in oogenesis and gemmulogenesis; the accumulation of yolk-type inclusions takes place at the expense of these cells; (3) the formation of yolk granules not only during oogenesis, but also in the period of cleavage; (4) sclerocytes that produce larval spicules turn the first differentiated cells of the embryo; (5) the developed larva of haploscleridans is a parenchymula showing a great degree of cytodifferentiation and the presence of both provisory (a flagellated cortical layer, a skeleton, and a spacious cavity lined with pinacocytes) and definitive (choanocyte chambers) organs; and (6) the leading role in morphogeneses during sexual and asexual reproduction is played by nucleolate amebocytes with basophilic cytoplasm (archaeocytes). These are the source of oogonia, gemmules, and nurse cells. They also play an important role in restorative morphogeneses. All these specific features allow ontogenesis in the representatives of the order Haplosclerida to be considered as a particular type of development within the subclass Ceractinomorpha, class Demospongiae.