Observations were made in Senegal between 1997−1998 on the length of embryonic development in Octopus vulgaris. The data were from eggs which had been laid by two females in the open sea and fourteen females in concrete tanks. The observations in natural surroundings are the first concerning this species. Hatching occurred after 15−42 d at 27 °C, 29−49 d at 22−23 °C, 57−65 d at 21 °C and 80−87 d at 17 °C. These values are higher than the few data previously recorded in European aquariums, particularly for temperatures under 20 °C.