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The effect of two temperatures (14[degrees]C and 18[degrees]C) and incubation systems (artificial versus female care) on the embryonic development of Octopus vulgaris was studied. Octopuses (six females and two males) were captured in the Ria of Vigo (Northwest Spain). Egg batches were divided into two groups: one left with female care, and others were incubated with artificial aeration. The results indicate that the type of incubation did not affect the embryonic development, whereas temperature had a marked effect on it. The duration of embryonic development was 40 days at 18[degrees]C and 67 days at 14[degrees]C. Results suggest that a reduction of around 24 days [degrees][C.sup.-1] can be obtained when O. vulgaris embryos are incubated into the temperature tolerance range of this species. Results showed that temperature modulated in a different form the embryonic development, at least until stage XIII, where embryos at 18[degrees]C showed lower values of eggs and embryo length than embryos at 14[degrees]C. The proportion of arm/total length was 21% higher in embryos at 14[degrees]C compared with 18[degrees]C, suggesting that in the first phases of embryo development, muscle development is favored at low temperature. Results showed that embryos at 14[degrees]C and 18[degrees]C had no differences in two critical processes, that is, nervous system synthesis (measured through eye synthesis) and organogenesis (measured through mantle length). The fact that there were no differences between hatchlings developing from embryos at both experimental temperatures demonstrates that O. vulgaris embryos can be favored if spawn occurs at relatively low temperatures.KEY WORDS: embryonic development, Octopus vulgaris, temperature, paralarvae, INTRODUCTIONThe common octopus Octopus vulgaris (Cuvier, 1797) is the best known of the more than 100 species described (Mangold 1983) and one of the most studied cephalopod from the culture [...]