452 'Journal of Comparative Neurology and Psychology. 



observed the process in collecting Gonionemus in the Eel Pond as 

 they came to the surface on being disturbed. It is, therefore, a 

 normal reaction. 



Reactions to Light and to Heat. 



Jennings ('o6) after a resume of the work on the reactions of 

 Gonionemus states that ''in the behavior of Gonionemus with respect 

 to light, there are a number of paradoxical facts." These "para- 

 doxical facts" refer to the reactions which have been described by- 

 previous workers, viz: The medusae collect first in the illumi- 

 nated portion of the jar and later are to be found in the shaded 

 portion. The swimming movements cease as the medusa swims 

 from a region of greater to one of less intensity of illumination and 

 also when it swims in the opposite direction. The reaction to 

 sunlight is a direct response whereby the medusa turns directly 

 toward the shadow and swims into it. Finally, the reactions of a 

 swimming organism are different from those of one at rest. 



The writer has examined these several reactions and finds his 

 results somewhat at variance with those previously described. 

 Thus, about forty medusae were put into a Chester jar, 33 cm. high, 

 and 21 cm. in diameter which was placed in a box lined with black 

 paper so that no light could fall upon the jar except upon one 

 side. The medusae began swimming directly to the surface of the 

 water, inverting and sinking in their usual way. At no time could 

 it be said that the medusae had collected on the illuminated side of 

 the jar. Yerkes obtained the reaction by stirring the water and 

 this was done in the present case, but the result was the same. 

 Sunlight was thrown horizontally through the jar by means of a 

 large mirror and later, sunlight was thrown vertically downward 

 and then vertically upward through the jar, the box being dis- 

 carded for a cylinder of black paper. In no case was there a col- 

 lection of medusae in the illuminated portion of the vessel. 



Attention was then turned to the matter of cessation of move- 

 ments. A glass vessel, 15.5 cm. long, 14 cm. high and 4 cm. deep 

 was covered on three sides with black paper. The fourth side was 

 left uncovered in order to observe the reactions of the medusae, this 

 being done from under a black cover. By removing strips of 

 various widths from the black paper, the light was allowed to 

 enter the vessel in any direction or with any size of beam. It may 



