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		On the second day after fertilization, the control sample was a normally developing embryo at the archenteron stage. Samples 2, 3, and 4 all looked very similar. They were irregularly dividing, had variances in numbers of cell divisions and shapes of cells, and had no archenterons. The third day observations exhibited controls which were at the pluteus larvae stage. The larvae were normal and mobile. The other three samples all looked similar. They were very irregular and underdeveloped. Sample 2 had an especially large number of dead cells that appeared in clumps. Figure 2. A, C, G, & K are Lytechinus variegatus controls at the following stages after fertilization: A=30 minutes, C=5 hours, G=2 days, and K=3 days. D, H, & L are embryos which have been irradiated just prior to fertilization. Pictures were taken at D=5 hours, H=2 days, and L=3 days. B, E, I, & M are images of embryos which have been irradiated 10 minutes after fertilization. Pictures were taken at B=30 minutes, E=5 hours, I=2 days, and M=3 days. F, J, & N are embryos which have been irradiated 30 minutes after fertilization. Pictures were taken at F=5 hours, J=2 days, and N=3 days.