CHANGES IN SUSCEPTIBILITY OF DROSOPHILA EGGS TO ALPHA PARTICLES

Abstract

1. Changes in the susceptibility of Drosophila eggs to different kinds of radiation have been followed during early development. 2. It was found that the eggs become more susceptible to alpha particles during cleavage and blastulation and more resistant during organogenesis, the point of maximum sensitivity being reached at or just after the beginning of gastrulation. 3. A comparison of these findings with those obtained for 200 kv. X-rays showed that the eggs were most resistant to the X-rays when they were most susceptible to the alpha particles. 4. Further experiments with 40 kv. X-rays and gamma rays indicated that the organisms were consistent in their responses to radiation capable of penetrating uniformly to all parts. 5. It appears, therefore, that the difference in response to alpha particles was due mainly to two factors: (a) the short penetration range of the radiation into protoplasm, and (b) the movement of the active cells into and out of its range.