406 HARRY THOMAS FOLGER. 



after a mechanical shock as well as after sudden illumination, is 

 of value and has been used, as we shall see presently, for a study 

 of the relationship which exists between the reactions caused by 

 mechanical shock and those brought about by light. 



In a study of the influence of light on Amoeba (Folger, '25) 

 the question occurred : since the animal must recover from the 

 effects of a sudden illumination before it will again respond to 

 sudden illumination, must it also recover from the effects of a 

 mechanical shock before it will respond to sudden illumination? 

 The answer was clearly an affirmative one. In many instances the 

 mechanical shock entirely inhibited a response to a sudden in- 

 crease in luminous intensity, when the latter was applied shortly 

 afterward. In these instances, however, the shock was brought 

 about by moving the coverslip with the tip of a lead pencil, a 

 method which, while it did produce undoubted results, is ex- 

 tremely crude. As a better means for controlling mechanical 

 shock has since been used, the experiment dealing with the effect 

 of this stimulus on the response to sudden illumination has been 

 repeated and the results are presented in the following pages. 



Moreover, if a mechanical shock preceding sudden illumination 

 influences the response to the latter, the question also arises, is the 

 reverse true? Does sudden illumination affect the response to 

 mechanical shock? The results of experiments designed to an- 

 swer this question are also set forth in this paper. 



MATERIALS AND METHODS. 



Specimens of Aniceba protcus were used in the experiments, 

 raised in small glass vessels containing a culture solution formed 

 by adding raw hay to distilled water. Large and active individ- 

 uals were selected for experimentation. 



Two sets of apparati were employed, one to bring about sudden 

 illumination, the other to cause a mechanical shock. The latter 

 was obtained by allowing a copper wire, weighing about 300 mg., 

 to drop through a glass tube, 68 cm. in length, which was sup- 

 ported by a stand and clamps in such a manner that the weight 



rapidly and still not have " recovered " from the effects of stimulation as 

 indicated by the fact that it fails to respond to a second exposure to illumi- 

 nation. 



