Abstract: 1. In agreement with the observations of earlier workers the writer has found that the carpospores of Nemalion helminthoides (Valley) Bate. v. vermiculare (Sur.) Tseng (materials obtained along the coast of Tsingtao) give rise to prostrate filaments which are uniseriate and branched, each cell with a single stellate chromatophore. 2. Algologists generally believe that, in Nemalion, the erect fronds are emerged directly from prostrate filaments grown from carpospores. In contrast to this assumption, the writer repeatedly found that the erect fronds of N. helminthoides var. vermiculare were able to reappear in nature where the prostrate filaments (and any other algal inhabitant) had been exterminated previously by treating with lime-water in early spring. This finding strongly indicates that these erect fronds were not formed directly from the prostrate filaments arising from carpospores of the previous year. 3. The prostrate filaments (arising from carpospores), either cultivated in the laboratory or found in the field, produce monospores from early spring to early summer. The sporangia are either sessile or unicellularly stalked, growing on the cells of the middle parts of the filaments. They germinate again into protrate filamentous systems which are morphologically extremely similar to those grown from carpospores. This prostrate system is evidently an important (if not the only) source from which the erect fronds of Nemalion arise. 4. Since the early spring of 1960, the writer has periodically sought for the monospores from the following materials gathered in nature: 1) prostrate filaments; 2) juvenile erect thalli free from bases and prostrate filaments. It is found that only the prostrate filaments are capable of producing monospores. 5. On several occasions the writer observed that the prostrate filaments originating from the monospores aggregated in such a manner as to indicate possibilities of giving rise to erect fronds. However, more careful observations are needed to arrive at a definite conclusion.