Gynogenetic diploid eggs by inhibiting the second polar body with 6-DMAP in Chlamys farreri were induced by genetically inactivated Crassostrea gigas sperms with ultraviolet.We observed nuclear behaviors of its gynogenetic embryos using fluorescent micro-technique during its early developmental stages.According to cytological observation,the ultraviolet-irradiated sperm nucleus could gently expand once after incorporating into egg and developed into a male pronucleus,but could not form chromosomes and became a dense chromatin body(DCB).DCB was seen either in the region of the furrow or in the cytoplasm of the blastomere,but could not fuse with the female pronucleus.The developmental progress of gynogenetic embryo was seriously delayed,but when added 6-DMAP,comparing with gynogenetic diploid,the developmental progress of gynogenetic diploid embryo was quickened and was also synchronous.In this study, we also reported and analyzed the embryo with complicated ploidy yielded in gynogenetic diploid group,besides gynogenetic diploid,there were hybrid,heterologous triploid,gynogenetic haploid,gynogenetic tetraploid,etc.Cytological evidence of gynogenesis in Chlamys farreri induced by heterologous sperm was demonstrated.