Abstract:Based on the analysis of Maurolicus muelleri (Gmelin, 1788) larvae and juveniles samples col- lected during the oceanographical expedition cruises which were conducted in central and western tropical Pacific and the Kuroshio extension regions in the East China Sea, from April to June during 1978 to 1986, and combined with the related literature, this paper described the morphological characteristics of the eggs, larvae and juveniles of M. muelleri in detail. It aims to enrich the knowledge on the early life history stage of fishes in China and to provide available information to resolve taxonomic problems of this specie. The egg of the M. muelleri is buoyant, colorless, and spherical in shape. The egg membrane is uniquely sculptured, with the envelope considerably thickened and drawn up into hexagonally arranged points. The diameter of the egg ranges from 1.29 to 1.82 mm. And the inner diameter of the egg envelope ranges from 0.87 to 1.17 mm. The egg has a single oil globule measuring 0.22 to 0.28 mm, and with a narrow perivitelline space. The yolk is coarsely segmented. The pigmentation was lacking on the embryo during the embryogenesis. Prelarva, 2.80 mm in total length (TL): the anus was located just behind the yolk sac, somewhat posteriorly to the middle of the body. The number of the myomeres was 17+16=33. The pigmentation was still lacking on its body. Prelarva, 2.90 mm in TL: the melanophores begin to scatter on the optic vesicle. Postlarva, 5.90 mm in TL: the air-bladder well developed with its upper posterior part scattered with pigment spots. Postlarva, 6.90 mm in TL: 2 BR and 2 IV2 photophores were apparent. Postlarva, 8.20 mm in TL: the black pigment spots on the upper posterior part of the air-bladder were becoming increaseingly pigmented. Otherwise, 3 BR, OP3 and 7 IV2 photophores were apparent. Juvenile, 10.70 mm in TL: a pigment stripe was scattered on central of the ventral sac. The number of BR and IV2 photophores increased; otherwise, 1 ORB photophore was apparent. Juvenile, 14.00 mm in TL: some black star-shaped pigmentation that varied in size were scattered on the dorsal surface of its body from the top of the head to the caudal peduncle. Dense melanophores on the caudal peduncle were observed. The entire ventral sac was scattered with black pigment spots. OP1, OP2, 5 IV1, 5 OA, 4 VAV, 6 AC2 and 6 AC3 photophores were apparent. However, till then the photophores system has not well-developed.