Migration of the RctmnJ Piginent 543 



for examination by being hardened, cut into sections and stained 

 with borax carmine. 



Eyes of the different experiments showed a very perfect series 

 of migration stages both for the proximal and the distal pigment. 

 In the dark series, the proximal pigment was always proximal to 

 the basement membrane. At 10° C. (Fig. 3) it was close against 

 the basement membrane; at 20° C. the distance of its distal mar- 

 gin below this membrane was equal to about one-fifth the length 

 of the rhabdom; at 30° C. (Fig. 4) the distance was two-fifths of 

 the length of the rhabdom. In the light series at 10° C. (Fig. i) 

 there was a strong concentration of the proximal pigment into the 

 ends of the cells just distal to the rhabdom. Only a little pigment 

 could be seen proximal to this. At 20° C. more of the pigment was 

 proximal in position and surrounded the rhabdom. At 30° C. 

 (Fig. 2) the pigment was rather dense around the rhabdom yet 

 not so abundant as at the distal ends of the cells. Both series 

 show that with increasing temperature the proximal pigment 

 moves proximally and with decreasingtemperature it moves distally. 



The distal retinular cells can not be said to show as pronounced 

 a response as the proximal ones did, yet the series was convincing. 

 In all preparations from the light series the distal retinular cells 

 were proximal to the cone; in the dark series they were at least 

 partly surrounding it. At 20° C. in the light the distal pigment 

 was in large part distributed evenly along the cone cells; a small 

 part was collected at the top of the proximal retinular cells. Low 

 temperature increased the effect of the light by massing all of the 

 pigment just above the proximal retinular cells. The high tempera- 

 ture produced an even distribution of the pigment along the cone 

 cells with no proximal accumulation. In the dark condition the 

 distal pigment cells completely covered the cone at high tempera- 

 ture (Fig. 4). Low temperature (Fig. 3) resulted in a proximal 

 migration equal to one-third the length of the cone. In general, 

 increased temperature causes distal, and decreased temperature, 

 proximal migration in distal retinular cells. 



It may be said that in both types of pigment cells in Pal^emonetes 

 the effect of increased temperature is opposite to that of increased 

 light. 



