Sporocysts are elongated sacs that produce either more sporocyst or rediae. It develops within the germinal cells of the sporocyst or redia. Energy is needed to develop into a sporocyst. The sporozoites are placed parallel along the long axis of the sporocyst. The mother sporocyst produces many daughter sporocysts. The miracidium grows into the sporocyst stage. This stage is known as the sporocyst. Within the visceral mass of Dreissena, the miracidium transforms into a mother (primary) sporocyst. Each daughter sporocyst forms new larvae called cercariae. Here, it undergoes metamorphosis into a sporocyst. The insectivorous birds are attracted to the pulsating of the metacercariae in the sporocyst. Inside the snail, the miracidium sheds its epithelium, and develops into a mother sporocyst. One mother sporocyst produces half a million cercariae. This name is based on the bi-valve sporocyst morphology which some Goussians display. The sporocyst gives rise to small larvae called rediae.