These structures are small bone like particles made out of calcium carbonate or silicon dioxide. Their functions are support and protection. Each cell is in direct contact with the water so its excretory and respiratory functions are taken care of individually by each cell. They reproduce through the process of budding where an adult will grow an offspring from it side. Sponges are also know to regenerate lost body parts.
Sexual reproduction is limited.
Structures called gemmules are formed from amebocytes and spicules during environmental stress. Water is taken into the sponge through its many incurrent pores and circulated out through the osculum. Sponges contain the protein spongin which acts as a base for the cells to cling to while forming the animal. The medusa is an umbrella shaped structure with its tentacles near the bottom of the animal. They contain tentacles with special stinging cells called nematocysts.