A Preliminary Study on the Embryonic Development of R.plicatula

The present paper deals with the embryonic development of R. plicatula which is androgynism. The fertlized eggs of R. plicatula were obtained in viro fertilization. The whole process of embryonid development lasts for 327 h at the water temperature of (25±1) ℃ and is made up of six stage, all of which are merogesis stage. Blastula stage. gastrula stage. trochelminth larva. taking shape stage of larva and hatching stage of larva. The times of trochelminth larva stage and of the formation stage of young spiral shell accounts for 73.3 percent of the whole process of embryonic development. The embryonic length increase by 6.4 times during the embryonic development. Trochelminth larva doesn't produce apparent preoral ciliary apparatus. postoral ciliary apparatus and apical plate. The ciliates are equally distributed over the surface of embryo.