An opportunity was taken to carry out the artificial fertilization and incubation at different temperatures of eggs of the bogue, Boops boops (Linnaeus, 1758) during a cruise on R.V. 'Cirolana' organized by the Fisheries Laboratory, Lowestoft. Adult fish for use in the experiment were obtained by bottom trawling in 165 m depth of water at 43° 44' N02° 44' W on 10 May 1980 between 0449 and 0549 h GMT. The bottom temperature at the trawling position was estimated to be ~ 11 · 8 °C, based on measurements made at nearby stations. Eggs and milt from several males and females were added to a container of sea waterheld at approximately 11 °C; after 1 h the fertilized eggs were transferred as four separate subsamples each of approximately too eggs to clean sea water in the incubation beakers. Thesebeakers were then gradually acclimatized over a period of 2 h to the incubation temperatures of80, 131, 182 and 22·8°C.

At all temperatures mortality was high during early embryonic development. At 228 °C all eggs were dead after 9J h of incubation at which time some of these specimens had formed a blastoderm cap, but with no sign of overgrowth of the yolk. In a few of the eggs held at 80 °C development proceeded normally until immediately before closure of the blastopore (~ 106 h after ferilization) when irregular vacuoles were seen in the area around the blastopore and development was disrupted; after 112 h of incubation all eggs held at 80 °C were dead.