VISUAL RECEPTORS AS BIOLOGICAL TRANSDUCERS 



39 



Fig. 4. Schematic drawing of sagital section through Limulus ommatidium. 

 (From Demoll, R., 1917, Die Sinnesorgane der Arthropoden ihr Bau und ihre Func- 

 tionen. Friederick Vieweg & Sohn. Braunschweig). 



Fig. 5. Schematic drawing of transverse section through Limulus eye. (Same 

 source as Fig. 4.) 



the pipette was advanced the response to light was tested after each thrust. 

 After persistent probing a response to light was usually found unless the om- 

 matidium had been damaged, but always in a highly localized region of the 

 ommatidium. If the pipette was moved just a little bit, the response was lost. 



