Abstract: An annual life cycle, including 4 developmental stages, is discovered in Anabaenopsis raciborskii Wolosz of the West Lake, Hangzhou. The progress of these developmental stages is influenced by the enviroment. The third stage with heterocysts expressed distinctly as Anabaenopsis raciborskii Wolosz., and the fourth stage was formerly recognized as Raphidiopsis sinensis and R. curvata. It is considered based on these facts that Anabaenopsis raciborskii Wolosz., R. curvata Frit. et Rich. and R. sinensis Jao are different forms at dif-ferent stages of ontogeny, and ought be treated as a single species.

Key words: Heterocyst, Akinate, Anabacnopsis raciborskii, Raphidiopsis curvata, R. sinensis