Abstract: This paper deals with the influence of bromoacetamide on the development of snail eggs,its effect on inducing diapause of snail eggs at different developmental stages (bkstula,gastrula,trochophore and veliger) both at different concentrations of bromoacetamide at the same time and at same concentration at different times.Besides,the oviposition of the snails and the eggs within snails have also been studied.The results are as follows: (1)When the snail eggs were immersed in bromoacetamide at concentrations of 0.034ppm-0.067ppm,deformation of snail eggs appeared from unicelluar to gastrula stages,but it was not observed after the trochophore-veliger stages.When the eggs at different stages were separately immersed in bromoacetamide,they were all found delormed.The molluscicidal concentration for inducing deformation of eggs was higher at the trochophore-veliger and metamophotic stages than that at the blastula and gastula stages (Figs.1-5)(2) After immersed in bromoacetamide solution,the development of the snail eggs were obviously retarded.The effects varied with different concentrations.Within the same exposure time,the higher the bromoacetamide concentration,the higher the diapause rate(3) The longer the immersion time,the lower concentration was needed to delay the development and the lower hatching rate was for the eggs at the same or different str.ges.(4)After treatment with bromoacemide,the average number of eggs laid by a female snail was reduced.(5)By using 3H-labered bromoacetamide,it was found that the radioativity of 3H-labeled bromoacetamide per hundred snail eggs was raised along with the increasing of the molluscicide concentration.It is concluded that direct exposure to low concentration of bromoacetamide could inhibit the development of snail eggs and obviously reduce the hatching rate.Furthermore,the chemical could enter the snail,damage the snail ovary and cause diapause of the snail eggs even though it could not kill the snail directly.It could also reduce the output of snail eggs and delay the reproductive period of the Oncomelania snail.