Abstract: The cytological behavior of sperm was observed after the sperm incorporated intodechorioned eggs of gynogenetic Silver crucian carp(Carassius gibelio)and bisexual fish(Carassius auratus red variety or Cy prinus carpio red variety).In bisexual dechorioned eggsthe sperm nuclei may undergo decondensing and developed into pronuclei.By contrast,although a few heterologous sperm nuclei became to some extent enlarged the pronuclei did notappear all.Furthermore,the established cell-free system from extraction of two types of eggswere employed to incubate the Triton-X100 treated sperm.The sperm nuclei in the two typesof extractions were fully developed, and then became the form of pronucleus,indicating thatthere are some factors responsible for sperm nucleus swelling and male pronucleus formationin gynogenetic Silver crucian carp eggs.However, when heterologous sperm entered intactgynogenetic eggs through micropyle,the nuclear envelope of sperm failed to breakdown dueto the abnormality of relative function in cytoplasm of the egg, and the further developmentwas thus inhibited. The significance of setting-up cell free system lies in that an efficient approach can be established to analyse the molecular mechanism by which the naturalgynogenesis was regulated during fertilization.