For accompanying with space radiobiological studies,dry eggs of native ,Artemia, were irradiated in the laboratory by 14 Mev fast neutrons and ,60,Co γ-rays, and their development was then followed. Doses of the fast neutrons used were 10,50 100,200,400,600,800 and 1000 Gy, and those of γ-rays were 50,100,500,1000 and 2000 Gy respectively. The irradiated eggs, together with the control, were stored at 4℃ before incubation and observations.,The results are as follows: (1) A significant delay of early development was seen in eggs irradiated by both radiations. (2) The rates of emergence and hatching decreased with the increase of the doses, and went down further after the prolongation of egg-storage at 4℃. (3) The mortality peak of the larvae hatched from irradiated eggs appeared within 2—5 days after hatching, and the RBE's of the fast neutrons, for LD,50, comparing with the γ-rays were found to be 1.80 on the 3 rd day, 2.44 on the 4th day, and 2.27 on the 5th day.