462 'Jourjial of Comparative Neurology and Psychology. 



shadow by the contraction of the tentacles on the portion of the 

 organism which was in the shadow. The effect was a sort of 

 crawling movement. This reaction I saw^ only three times. 



The reasons for certain of the apparent disagreements in the 

 results of Mr. Morse's experiments and my own are my failure to 

 state that the sunlight was not perpendicular to the bottom of the 

 dish, and his failure to take note of the exact form of my statement 

 of results. With the light perpendicular to the bottom of the 

 vessel I obtained the same results as Mr. Morse. There was no 

 evidence of the directive influence of light. There is a flat con- 

 tradiction in our statements, however, so far as the reaction to 

 oblique light is concerned. Possibly this would disappear if the 

 meaning of the term were more fully explained in Mr. Morse's 

 paper. 



Of the fourth paradoxical fact to which attention is called at the 

 beginning of Mr. Morse's paper — namely, that the reactions of 

 active medusae when stimulated by light are different from those of 

 resting individuals under the same conditions of stimulation — I 

 find no further mention. Possibly it was his intention to dispute 

 the statement on the basis of the other facts to which he had called 

 attention. I am unable to see anything paradoxical in the state- 

 ment that the effect of light depends upon the physiological condi- 

 tion of the organism. It would be strange indeed if the active and 

 the quiescent medusa reacted to light in the same manner. 



Finally, Mr. Morse concludes from the results of his study of 

 Gonionemus that the behavior of this organism conforms to the 

 theory of trial and error rather than to the theory of the tropisms 

 proposed by Verworn and Loeb. While partially agreeing with 

 him in this, I still hold that several of the reactions which I have 

 described are in part determined as to the direction of movement 

 by the quality, intensity and location of the stimulus and therefore 

 conform to the theory of the tropisms formulated by Loeb. There 

 is more or less trial in all the reactions of Gonionemus, but I fail to 

 see why trial and error and local action should be mutually exclu- 

 sive. It seems to me that Verworn and Loeb, in connec- 

 tion with the tropism explanation of certain reactions, have laid 

 emphasis upon the definiteness and uniformity of reactions, while 

 Jennings, Holmes and others have laid all stress upon the variable- 

 ness, complexity and modifiability of the same reactions. Both 

 points of view are important, but they supplement rather than 



