154 LIGHT AND THE BEHAVIOR OF ORGANISMS 



to time and bent in various directions, remaining in any 

 given position only a few minutes, so that during the periods 

 in which the foot was fixed, the oral end was directed toward 

 various points of the compass. But it will be seen by refer- 

 ring to the figure that the looping movements were in 

 general directed toward the source of light. The only 

 movements in the opposite direction occurred in specimens 

 Cand E. The former moved in this direction but once, the 

 last looping move it made during the experiment; the latter 

 was not seen in the act of moving. It did however reach 

 the end of the aquarium farthest from the source of light 

 where it came to the surface and remained to the end of 

 the experiment. 



d. Reactions of negative specimens. — At 11.35 a.m., 

 April 17, two specimens were exposed in the small rectangu- 

 lar aquarium to direct sunlight. They became very active 

 at once and bent from side to side, expanding and con- 

 tracting frequently. One changed its position by looping 

 five times in a little more than 15 minutes, the other by 

 looping three times. Both proceeded from the source of 

 light nearly as directly as the positive specimens studied 

 moved toward it. There was no apparent relation between 

 the direction of bending and the source of light, just as 

 was found to be true in positive specimens. The anterior 

 end appeared to be directed toward the source of light as 

 much of the time as away from it, but locomotion occurred 

 only when this end was directed from the light. After 

 having been exposed a little over 15 minutes they lost their 

 attachment to the bottom and became perfectly quiet, 

 apparently having been injured by the intense light. 



As already stated the anterior end of Hydra is successively 

 directed toward various points of the compass. After re- 

 maining in a given position a few minutes the animals usually 

 contract, turn toward one side and expand again. Some- 

 times however they bend and turn so as to change their 

 position without contracting. There is no definite relation 

 between the direction of bending and the source of light. 



