Pternis lunulata Temminck et Schlegel is a well known Scorpaenoid fish by its beautiful coloration and poisonous spines. It is widely distributed in tropical Pacific extending to southern Japan. The authors carried out artificial insemination of this fish on August 28, 1954, at Tamanoura Cho, Goto Islands, Nagasaki Prefecture, Kyushu, and observed the egg development and hatched larvae. The ovary of this fish was composed of two egg masses, one of which consisted of fully matured eggs inbedded in a gelatinous substance, the other was of immature eggs without gelatinous substance and situated inner part of the former. It seemed to us that the matured egg mass would be spawned, as some previous authors reported, in a pair of egg balloons. The presence of the immature egg mass, seemed to denote the repeated spawning by the same female in one season. The egg and the gelatinous substance are colorless, transparent and bouyant. The shape of the egg is almost spherical, measuring 0.81~0.83 mm in diameter, with a single oil globule measuring 0.16~0.17 mm in diameter. The hatching took place in 24 hours at the water temperature 27~30℃, when the entire egg was still without pigment. The newly hatched larva was 1.52~1.58 mm in total length with the myotomes 11+16=27 (vertebral number of this fish is 9+15=24) (Fig. 1, g). Two days after hatching the larva attained 2.3~2.5 mm in total length, when the first appearance of the melanophores was observed on the eyes and middle of the tail (Fig. 1, i). In 4 days the yolk and oil globule were entirely consumed but the length of the larva did not change. The pectoral fins were well developed, fan like in shape. marginally pigmented by the melanophores. Number of myotomes was 8+18=26 (Fig. 1, j). The larva 12 hours or more after hatching showed peculiar deformation as is shown in Fig. 1, h, when preserved in 10 % formalin solution.