. Carnegie Institution of Washington publication. 76 THE BEHAVIOR OF LOVvER ORGANISMS. animal behavior. straight path to FIG. 25.* course, become in general. In the study here set forth observation was directed primarily to the questions of how certain Rotifera react under the stimulus of the agencies which usually give rise to the so- called tropisms—light, chemicals, heat, elec- tricity, contact, etc.—and to these questions the present account will be devoted. The species whose reactions were exam- ined belong chiefly to the loricate group of free-swimming Rotifera, and include a num- ber of
. Carnegie Institution of Washington publication. 76 THE BEHAVIOR OF LOVvER ORGANISMS. animal behavior. straight path to FIG. 25.* course, become in general. In the study here set forth observation was directed primarily to the questions of how certain Rotifera react under the stimulus of the agencies which usually give rise to the so- called tropisms—light, chemicals, heat, elec- tricity, contact, etc.—and to these questions the present account will be devoted. The species whose reactions were exam- ined belong chiefly to the loricate group of free-swimming Rotifera, and include a num- ber of species of the Rattulidae, several species of Cathypnadae, two or three species of Euch- lanis, Plcesoma lenticulare, Anurtza cochle- aris, and Brachionus pala. These were studied as opportunity offered. In most cases the reactions of any one species were not determined with relation to more than two or three classes of stimuli. The behavior of Anurcea cochlearis was examined most fully. This species will be used as a type in describ- ing the reactions. I have already given a brief account of the general reaction type in certain species of the Rattulidre in my mono- graph of that group (Jennings, 1903). METHOD OF LOCOMOTION. The free-swimming Rotifera progress through the water in the same manner as the ciliate infusoria. The cilia in the Rotifera are limited to the anterior end, as they are in the peritrichous infusoria. It is interesting to note that the same device is adopted in the one group as in the other, to compensate for irregularities in the form of the body, etc., which might result in swerving from the This is by revolution on the long axis, causing the a spiral with a straight axis. In the Infusoria the * FIG. 25.—Spiral path followed in ordinary swimming by Anur&a cochlearis Gosse, showing different positions of body in different parts of the course; a, dorsal surface; i>, left side; c, ventral surface; d, right side. The animal revolves on its long
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