Cherfas, N. B. - Agricultural Research Organization, Fish and Aquaculture Research Station, Dor, Mobile Post Hof Hacarmel 30820, Israel.  
Kozinsky, O. - Agricultural Research Organization, Fish and Aquaculture Research Station, Dor, Mobile Post Hof Hacarmel 30820, Israel.  
Rothbard, S. - Agricultural Research Organization, Fish and Aquaculture Research Station, Dor, Mobile Post Hof Hacarmel 30820, Israel. 
Hulata, G. - Agricultural Research Organization, Fish and Aquaculture Research Station, Dor, Mobile Post Hof Hacarmel 30820, Israel.

Eggs inseminated with irradiated (by ultraviolet light) or non-irradiated spermatozoa were given temp. shocks of 0°-2°C at 0.5 min intervals for 45-60 min. Cold shocks initiated at 0.5 to 5.0 min after insemination were tested. The highest proportions of diploid gynogenetic and triploid embryos were obtained when the shock was initiated 1-2 min after insemination.