Among several acidic glycan components found in Hemicentrotus embryos, the "F"- and "S"-components were specifically affected by treatment with Li+ and Zn2+ , respectively. The amount of the "F"-component in Li+ -treated embryos was about 60% that in normal embryos. This fact was in accordance with the reduced alcian blue staining of the surfaces in Li+ -treated embryos. Moreover, the "F"-component in Li+ -treated embryos appeared to be composed of two subcomponents, while in normal and Zn2+ -treated embryos it appeared to be single. The "S"-component in Zn2+ -treated embryos was about 8% that in normal embryos. According to histochemistry with a lectin probe, it was found that UEA-I was much more strongly associated with a hyaline layer in Li+ -treated than in normal and Zn2+ -treated embryos. Li+ -treated embryos developed into exogastrulas, which were divided by a constriction into two parts; an animal half which stained intensely with alcian blue, and a vegetal half which stained poorly. On the other hand, Zn2+ -treated embryos remained as permanent blastulas. Considering the above, it is suggested that change in the acidic glycan pattern leads to alterations in the morphogenesis of sea urchin embryos.