In this paper are given some results of observations on the general as well as the breeding habits of Octopus variabilis typicus (Sasaki), carried out in Tyosen (Korea). This octopus lives in the shallow calm water of muddy bottom, burrowing a deep tunnel in which it hides itself. On the western coast of Tyosen it is caught with a kind of spade or a small hand plough, digging the muddy flat at the low tide, chiefly in spring and autumn. The main breeding season is from May to June, sometimes extending to the autumnal months. The number of the ripe ovarian eggs found in one female is about 120-130. The egg is comparatively large and takes an elongated egg-plant form, measuring 21.1-22.1 mm×7.0-7.9 mm in those shortly before hatching. The basal part of the egg-shell is elongated into a filiform stalk of about 9 mm in length, by which the egg is attached to the inner wall of the-tunnel. After spawning the female parent is supposed to guard anxiously over the eggs in the hole, till the young hatches out. The larva just hatched is about 29.0-33.2 mm in total length, and the arms are already very long, showing the formula 1>2>3>4, as in the adult. The organisation of body of the young after hatching is so well developed that it can enter the burrowing life from the beginning. It seems to become mature in two years, and its span of life to be over three years. The size of the adult commonly met with is 400-600 mm in total length, and the largest ones reach over 700 mm.