CONCERNING THE BEHAVIOR OF GONIONEMUS. 



BY 



ROBERT M. YERKES. 



{From the Marine Biological Laboratory, Woods Hole, Mass.) 



The courtesy of Mr, Morse in calling my attention to the results 

 of his study of the reactions of Gonionemus and in discussing them 

 with me before their publication has made possible the following 

 prompt explanation, on my part, of the apparent differences in our 

 results. 



Since Mr. Morse told me of the results of his study of the reac- 

 tions of Gonionemus to light I have repeated certain of my earlier 

 experiments and made such additional observations concerning 

 the influence of light as the scarcity of material at the time per- 

 mitted. I wish now to present the results of my recent experi- 

 ments, in connection with my reply to the criticisms of my work. 



As appears from Mr. Morse's paper,^ we disagree concerning 

 the following five points : 



1. That light is an important factor in the determination of the 

 inversion of the bell when the medusa reaches the surface of the 

 water. 



2. That there is at times a temporary gathering in the brighter 

 region when the medusae are exposed to intense light in a vessel of 

 which one portion is shaded. 



3. That sudden decrease in the intensity of illumination tem- 

 porarily inhibits the movement of an active individual. 



4. That intense light may determine the direction of movement. 



5. That the influence of light on active individuals is different 

 from its influence on resting individuals. 



Mr. Morse has contradicted all of the above statements of my 

 papers. 



'Morse. Notes on the Behavior of Gonionemus. Jour. Comp. Neurol. Psychol., Vol. 16, No. 6. 

 1906. 



