PARKEE : EETINAL PIGMENT CELLS OF PALiEMONETES. 



29- 



eyes were in the condition characteristic for the dark, were decapitated ; 

 their right optic stalks were cut off and pat in a light moist chamber, 

 and their left stalks, likewise cut off, were placed, as a check on the 

 results of the experiment, in a dark moist chamber. After an interval 

 of two hours both sets of stalks were hardened and afterwards cut and 

 examined. In a corresponding way optic stalks in the condition charac- 

 teristic for the light were cut off and subjected to the dark. 



The results of these expei'iments are shown in the following tables. 



Four Right Optic Stalks in Darh Condition cut off and placed in the 

 Light two Hours. 



The four left optic stalks cut from the same animals and retained, as 

 a check, in a dark chamber, all presented on examination the condition 

 typical for the dark. 



Four Right Optic Stalks in Light Condition cut off and placed in the 

 Dark two Hours. 



The four left optic stalks cut fi-om the same animals and retained, as 

 a check, in a light chamber, all presented on examination the condition 

 typical for the light. 



It is obvious from these observations that, after the excision of an 

 optic stalk, the photomechanical changes may still take place, if not com- 

 pletely, at least partially, and it might be inferred from this that the 

 brain exerted at least a partial influence over these changes. This con- 

 clusion, however, is invalidated by the fact that in one case recorded in the 



