Reproduction occurs asexually by budding and sexually. Development of fertilized eggs takes place within the sponge. The larval stage has outer flagellated cells, often with spicules. The young break out of the parent's mesohyl, and become free swimming larvae, but not for more than two days.
Sponges have different amoeboid cells in the mesohyl. Acheocytes are large cells with large nuclei. These cells are totipotent, meaning they can develop into any cell type. Sclerocytes, also in the mesohyl, accumulate calcium to produce spicules. Three sclerocytes will fuse to form spicules in intercellular spaces.
Development - Life Cycle: indeterminate growth