On the basis of cytological observations on chromosomes of leucocytes, fertilized eggs and early embryonic cells, both male and female crucian carp, Carassius auratus gibelio, caught from Shuangfeng reservoir in Fangzheng County, Heilongjiang Province, were disclosed to be triploid in karyotype and they did reproduce by natural gynogenesis, and so the bisexual phenotype of crucian carp's population in Shuangfeng reservior does not indicate that they would reproduce by amphimixis.Intraspecific and intergeneric crosses with the crucian carp all revealed that heterologous sperm not only gave a gynogenetic stimulus to the ova of crucian carp, but also could produce some effects on characters of the gynogenetic offspring. This gynogenetic phenomenon with biological effects of heterologous sperm is termed "allogynogenesis" in order to distinguish it from the term "gynogenesis". The progeny of crucian carp developed through allogynogenesis is called allogynogenetic crucian carp.The biological effects of the heterologous sperm expressed in allogynogenetic crucian carp are as follows:1. Effect on growth. Heterologous sperm could provide allogynogenetic crucian carp with enhanced growth rates. Compared with gynogenetic crucian carp, the average growth rate of allogynogenetic crucian carp with red carp sperm was 34.7%(12.9—64.4%) faster, and that of another allogynogenetic crucian carp, with red goldfish sperm was 19.3%(15.8—22.5%) faster on the average.2. Affecting sex ratio. Heterologous sperm caused allogynogenetic crucian carp to be consisted of different percentage of male progeny. For example, the percentage of males in progeny of crucian carp (♀×♂) was 18.2%, the percentages of males in progeny of crucian carp (♀) mated with goldfish (Carassius auratus auratus ♂) and red goldfish (C. auratus auratus red variety ♂) were 15.6% and 2.5% (0—3%), respectively, but no male has yet been found in the progeny of crueian carp (♀) mated with red carp (♂).3. Effect on the liver LDH isoenzyme pattern. Compared with crucian carp, the liver LDH isoenzyme pattern of allogynogenetie crucian carp (progeny of crucian carp♀×red carp♂) had a quicker staining reaction and higher relative activity of the second and third groups of the isoenzyme pattern.4. Variation in body colour. In allogynogenedc crucian carp and their backcross generation there were a few individuals with a small piece of red-color epidermis covering about 1—8 scales.