Many species of protozoa become inanimate, enclosing themselves in protective shell_like coverings, often sphere_shaped, called cysts, when conditions are not favorable. Some protozoa may stay encysted for months, even years, and still remain viable, returning to 磍ife?when conditions improve. These cysts, about 50 microns in diameter, are those of Blepharisma, the same species you see swimming about.