Gemmules are formed as a result of the combining of glycoprotein or lipoprotein cells, which are present in the archaeocytes- totipotent cells as a part of the food material, into a cell mass. This cell mass is then surrounded by an amoebocyte, which is a mobile cell. The central mass of the archaeocytes is surrounded by the amoebocytes and a solid thick chitin layer is secreted around it. Sclera oblasts secrete amphidisc spicules in the middle of the internal and external membranes of the cells. This becomes solid and is known as a gemmule.