Abstract: Researches with aquatic organisms under space conditions became more and more important.The development towards the cotrolled ecological life supported systems(CELSS)requires understaning of embryogenesis,ecophysiology and ecology in general.Loacha small animal,adaptable to environment,and its development rapid,providing the possibility of having all the developmental prcess during the relative short times of space flight.Therefore,it hbeen regarded as a biological system by which we could better undstand the developmental principles.Its embryonic development hbeen described detailedly.