なみうずむし Dugesia japonica 個体群の生態学的調査

1. The natural population of Dugesia japonica was examined both in a mountain stream at Higo-dani vallay and in a land stream at Shinfukuro-gawa River, Tottori City, during the period from March to December in 1962, at monthly intervals. 2. Seasonal changes in the population of Dngesia japonica were recorded. The population density sharply increases in the period from early March to July, but it decreases in August. However, the dens-ity in each population increases slightly in the period from October to early Nobember. 3. The population density is always large at downstreams ( in the case of Higo-dani valley) or stations at stream center ( in the case of Shin-fukuro-gawa River), whereas the river bed is composed of unsettled stones or pebbles. 4. Seasonal changes in the microdistribution at natural habitat were studied in 4 stations at downstream of Shin-fukuro-gawa River from March to November in 1962. In the period from March to June, flatwo-rms live on each station, but in July and August almost all of the flatworms live on the north side of river and there are none present on the south side whereas the water is shallow. Again in early times of October, they are found out on each station.