Young mussels instead of glochidia were observed to be discharged by gravid individuals of Anodonla bigbba(Heude) in April and May of 1993. Among the shells of the young mussel，a stout，triangular shell of glochidium and its hooks at the far end of the ventral margin were in evidence. Loops of newly grown shell were found to be around the glochidial shell，and a ciliated foot，anterior and posterior abductors，gill rudiments，and anus could also be recognized. The young mussels were kept alive in laboratory for 39 days，indicating that they had the ability to live independantly. It is made clear by the study that the glochidia of this mussel species has undergone the metamorphosis inside the maternal marsupia. It is the first time to find in China a naiad species metamorphosing without parasitism，a significant fact for studying the evolution of Chinese unionid and its phylogenetic relationships with world freshwater mussels. Furthermore，in view of the differences of adult shell and life history between Anodonla bigbibba (Heude) and Anodonta woodiana (Lea)，the name of A·bigbbba given by Heude should be recovered.