Letter | Published:

Production of Mutations by Neutrons



IN experiments to determine the possibility of producing mutations by treatment with neutrons, adult males of Drosophila melanogaster were subjected to a neutron bombardment derived from a 485 gm. block of beryllium exposed to the γ-rays from 4 gm. of radium. It is known that beryllium thus exposed produces neutrons of two velocities, the fast ones having an energy of 0·60 million electron-volts and the slow of 0·16 million electron-volts. Fast neutrons were used in one series of experiments, the very slow ones being excluded by means of a cadmium plate. In a second series, the fast neutrons were slowed down by passage through paraffin, so that only slow neutrons were used. In a third series, serving as a control, paraffin was substituted for the beryllium block, so that the flies received no neutrons but did receive the same gamma radiation and secondary radiation from the radium source as in the first two series. In these three series, a thick lead block was used to remove most of the radium γ-radiation. Finally, in a fourth series, serving as a second kind of control, the flies were not irradiated artificially in any way.

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