The present work was undertaken to know the range of tolerable salinity of ambryvs and fries of Hypophthalmiehthys molitrix. Errtbryos and fries were raised in solution of different degzees of salinity(1/5, 1/7, 1/10,1/15，1/20, 1/25，1/35 M NaCl in ordinary fresh water with negligeable salt vontent). The PH value of the culture medium was found to be about 6.7 and the water temperature was maintained at about 20-24℃. The results of the expeziments are the fpllowing; 1.The percentage of hatched embryos as well as that of survived fries, was found inversely proportional to the salt concentration of the culture medium; the higher the salinity, the less the percentage of hatched embryos and of survived fries,and vice versa. 2.The rate of hatching was also found varied inversely with the salt concentration of the culture medium; the higher the salinity, the longer the time for hatching, and vice versa. 3, The highest percentage v# hatching (96%) of the expanding blastula was found in a medium containing 1/25M. sodium ehlaride,but the embryo of muscular responae stage was found reaching the same high level of hatchahility (99%)in a medium containing 1/7M NaCI. Similarly, while fries of 24 hours after hatching were found developed normally (100%) for 72 hours in a medium of 1/15M NaCl; fries of 48 hours after hatching were found adapted well to a higher degree of salt concentrativp (1/10 M) for the same interval. The results mentioned above coincide with what Олифан has found in other species of Cyprinidae (1941, 1945). 4.Fries of Hypophthalmiehthys molitrix are found in large quantities in Yang Tae Kiang and Si Kiang in China during the natural breeding season, but in Tsien Tang been an unsettled problem as to where the fries of those rivers have gene and it seems clear new that most of tha embryos and fries may have been carried into the sea where they are killed by the higher salinity of the watex before they can swim at will.