On the Life-History of Acetabularia Calyculus QUOY et GAIMARD

1. Acetabularia Calyculus QUOY et GAIMARD which grows along the coast of Tita Peninsula (Aiti Prefecture) was used of observations. The plant is monoecious. In August, many cysts (gametangia) which are freed from the sporangia of a fertile whorl (umbrella) liberate the gametes without coming to rest. The gamete is pear-shaped or somewhat rectangular in form when viewed along the dorsal direction. 2. After germination the zygote develops into a short thread with no septa. It, however, grows rapidly in the next spring and bears many sterile whorls. In summer, it attains its maximum size becoming an adult bearing an “umbrella” at its apex. The conjugation is seen between the gametes escaped from the plants in culture (f1), and the zygote develops into a plant of the next generation (f2). Next summer, many cysts are formed on the f2-plants, but the further development have not been followed. In my culture, the plant is not encrusted with carbonate of lime and, moreover, the apex of the sporangium is not concave. 3. The development of the sterile hairs is different from that of the fertile branch. The shape of the sterile plant of Ac. Calyculus resembles Batophora Oerstedi. From the standpoints of this resemblance and the lateral position of the sporangia Acetabularia seems to have a nearer relation to Batophora than to Bornetella.