The oocyst is a spherical structure, 50–60 microns in diameter, that develops from the zygote in a sporozoan life cycle. It is surrounded by a tough cyst to prevent dehydration or other damage during its transit through the life cycle (which may involve separate hosts). In the case of the malarial parasite Plasmodium (see malaria) the oocyst on the outer wall of the mosquito's stomach. The oocyst grows in size and its contents divide repeatedly to form sporozoites, which are released into the body cavity of the mosquito when the oocyst bursts.