Mtgratioji of the Retinal Pigment 



541 



rhabdom. In decreasing light the distal pigment cells mvoe 

 distally till they surround the cone and the proximal pigment is 

 carried below the basement membrane. In consequence of the 



-'Cta. 



mm vdpx 



rh6. .nsJ/ 



76.bc 



liqht lO'c. 



"^z:^ 





Hqht Wc. darklO°c. darkSO'c. 



Fig. I Fig. 2 Fig. 3 Fig. 4 



Figs. I to 4 longitudinal sections of theommatidia of Palaemonetes, magnified 200 diameters, show- 

 ing the distribution of the retinal pigment under the following conditions: 



Fig. I, in light and at 10° C. cl. c9n., cone cell; cl. crn., corneal hypodermal cell; cl. dst., distal 

 retinular cell; cl. px., proximal retinular cell; cvn., cone; mb. ha., basement membrane; cta., cuticula; 

 rhb., rhabdom. , 



Fig. 2, in light and at 30° C. 



Fig. 3, in dark and at 10° C. 



Fig. 4, in dark and at 30° C. 



movement of the proximal pigment, the light-colored accessory 

 pigment about the rhabdom is exposed and may serve, as Exner 



