MOVEMENT TOWARD LIGHT IN COELENTERATES 1 51 



tions represented by dots (a) in the accompanying diagram 

 (Fig. 22). At 12 M. all were still in the positions where 



Fig. 22 



o,y 



Fig. 23 



4:55 P.M. 



■<r- 

 <- 

 <- 



n 



Fig. 24 



Fig. 22. Movement of Hydra viridis in total darkness, a, position at begin- 

 ning of course, 8 a.m., jy; x, position at 8 a.m., j\; o, 9 a.m., I'V; y, 8 a.m., y\. 

 Fig. 23. Movement of the same specimens after exposure to light. 8 to 



11 a.m., j\. Note that they have become much more active. 



Fig. 24. Movement of H. viridis toward source of light, n; intensity 



12 ± ca. m. All the looping movements of each specimen are represented from 

 three o'clock until the close of the experiment. The dots represent points of 

 attachment. The animals extended in various directions from each point but 

 usually traveled only toward source of light. 



they first became attached. They were well expanded and 

 the anterior ends were variously directed. At 2.15 p.m. 

 one had moved about 3 mm., the rest not at all. At 8 a.m. 

 the following morning four had moved to positions desig- 



