THE "HERTWIG EFFECT" IN TELEOST DEVELOPMENT

1. Mature sperm of Fundulus heteroclitus were exposed to ionizing radiations from Cs.-137 at the rate of 5000 r/min., for doses ranging from 5000 r to 150,000 r, and were then used to fertilize normal eggs of the same species. Control eggs from the same batch were inseminated with unirradiated sperm from the same source.2. While variations in normal fertilizability of the control eggs do occur, associated with the season and breeding activity, in every case some eggs were fertilized and developed following insemination with sperm which had been exposed to every dose level. This was not mere activation since cleavages followed.3. The presence of irradiated (sperm) chromatin had no effect on the time or nature of the early cleavages. The initial adverse effects were noted at the time of gastrulation.4. Exposures of sperm to 500 r had no apparent effect on the development of eggs, while exposures to 5000 r caused high mortality and morbidity, and above 5000 r (to the sperm) the effect of ionizing radiations ...