To explore the morphological characteristics of , the morphological changes in the embryos and larvae were observed using scanning electron and optical microscope. The results obtained were as follows. (1) The embryonic and larval development of included six stages:cleavage, blastula, gastrula, trochophore, pelagospheric larva, and creeping larva. The cleavage, blastula, gastrula, and trochophore stages occurred within the egg envelope. The egg envelope was discarded when the pelagospheric larva was out of the membrane and did not develop into epidermis. (2) At a water temperature of 30℃-31.5℃, the oosperm began to cleave 30 min after fertilization and the gastrula was formed after 2 h. After 4 h, it developed into trochophore. After 24 h, the larva was out of the envelope and developed to a pelagospheric larva. After 8-9 d, the pelagospheric larva developed into creeping larva. (3) exhibited a typical helical complete cleavage. The trochophore larva could swim by rotating. The surface of the embryo body was covered with cilia, and the front of the body had a bundle of long cilia called apical cilia. The cilia which protruded from the body through the center of the egg envelope can be divided into two types-normal and spoon-shaped cilia. The embryo body formed eyespot, nephridioduct, and other organs. (4) The pelagospheric larva swam rapidly and captured phytoplankton. The anterior ciliary ring was short, and the eyespot and ganglion were on the head. The postoral ciliary ring was long; the cilia were also divided into two kinds (normal and scoop-shaped cilia). With development, the muscle bundles of the body wall continued to become strong and formed the square lattice texture. The stomach gradually moved forward to the head, intestine extended and spiraled, and anus was formed in the anterior end of the body. (5) The creeping larva crawled on the surface of the sediment and devoured gravel. The body surface developed a stratum corneum, and the body wall muscle became strong. Flaky protuberances were formed in the anterior part of the body, which developed into tentacles. The introvert had regularly arranged mastoid; it was convex to the central zone of the body, forming a spherical tail. The retractor muscle, ventral nerve cord, fixing muscles organ, and other tissues were obvious. The study provides morphological details of embryonic and larval development in . Furthermore, it provides a theoretical reference for the procreation regulation and artificial breeding of .