. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 274 A. S. PEARSE. surface. The righting reaction is one of the most characteristic activities of this species. If an individual is placed in a flat- bottomed dish containing sea water and held with its ventral side uppermost until the tube-feet have attached themselves (usually about half a minute), it slowly pulls the body over with the tube- feet until the ventral surface is against the bottom of the dish. The tube-feet are helped to perform this righting reaction by the rings of muscular constriction which pass slowly fro
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 274 A. S. PEARSE. surface. The righting reaction is one of the most characteristic activities of this species. If an individual is placed in a flat- bottomed dish containing sea water and held with its ventral side uppermost until the tube-feet have attached themselves (usually about half a minute), it slowly pulls the body over with the tube- feet until the ventral surface is against the bottom of the dish. The tube-feet are helped to perform this righting reaction by the rings of muscular constriction which pass slowly from one end of the body to the other. The direction of the turning is deter- mined by various factors, light being an important one. For ex- ample, when an individual rests on its dorsal surface with the long axis of the body at right angles to the direction of the light, the ventral surface is usually turned away from the light as the body is righted. In order to test the locomotor reactions on an inclined surface four individuals were each given four consecutive trials in the h. I Fig. 5. Diagram showing the position in which individuals were placed in the dish during experiments to test the locomotion on an inclined surface. The arrows represent the direction of the light, a, anterior end ; k, high side of dish ; /, low side of dish ; /, posterior end. bottom of a round glass dish, which measured thirty centimeters in diameter and contained sea water. This dish was placed directly in front of a window which was the only source of light in the room and the bottom was tipped ° from the horizontal at right angles to the direction of the light rays. Animals were placed separately in this dish with the long axis of the body parallel to rays of light (F'g- 5)- They were first given two trials with the bottom of the dish. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these
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