抄録
1. The Sardine seems to strain plankton, by swimming with opening mouth and further controlling the swimming velocity and the diameter of the mouth, so as to make the velocity of current on the gill-rakers the optimum velocity (about 2-3cm./sec.). Therefore, the feeding velocity of the sardine seems to be proportional to the surface of the gill-rakers, when the plankton dencity in the water is constant.
2. By whether the time, which the gill-rakers require to be closed by plankton, is short or long, the sardine seems to recognize the plankton density in the water where it is feeding, in a short time (about one minute).
3. The secondary concentration for the plankton gathered by the gill-rakers in the oral cavity seems to be performed by “the pharyngeal pockets” and “the pharyngeal rakers”.
