It has not been ever obtained artificially the mature and fertilizable eggs by any predecessors from the ovary of Mytilus edulis. It was successful in obtaining the numerous fertilizable eggs in my experiment, in which the mantle piece was either stimulated by alternative electric current or by bathing it in M/2 KCl solution for longer than 1 minute. At first numerous immature eggs were oozed out of the out end of genital ducts of mantle by its contraction together with the small, cytolysed eggs, follicular epithelium and many granules. The relaxation of mantle began as its contraction ceased, and thus the exudation was stopped gradually. And then the mantle piece began to ooze out numerous maturing and matured eggs after about 30 minutes of stimulation without mingling any other things. The eggs thus obtained were well fertilizable and developed to swimming larvae. Therefore, it is suggested that KCl solution or electric current act as a stimulant to ovary so as to induce eggs to mature.