Regeneration in Compound Eyes of Crustacea 191 



and may be seen in a relatively well defined row (Fig. 68). Soon 

 after the retinular nuclei have been separated from the nuclei at 

 the surface they themselves begin to divide (Fig 68) in a plane at 

 right angles to their plane of original division. These longitudinal 

 divisions may begin before the nuclei have reached their definitive 

 position. This division continues until a band composed of many 

 nuclei has been formed. Figs. 60 and 62 show portions of such 

 bands. 



Here and there single nuclei are found lying much nearer the 

 basement membrane than the retinular band (Figs. 60, 62). 

 These are occasionally seen constricted. It has been impossible 

 to determine with certainty the fate of these scattered nuclei but 

 there are evidences which suggest that they become the nuclei of 

 the accessory pigment cells. 



The retinular nuclei even in the early stages of their migration 

 stain much more deeply than the nuclei at the periphery. But at 

 this stage no definite cytoplasmic outlines can be distinguished. 

 Very faintly staining delicate strands of cytoplasm, however, can 

 be found extending between the retinular nuclei and the periphery. 

 These strands form an intermingled network and with the nuclei lie 

 in a granular substance. Soon after the nuclei have reached their 

 definitive position the cell bodies of the retinulae can be recog- 

 nized. Each nucleus appears surrounded by more or less definite 

 strands of cytoplasm which are radially arranged and extend 

 outward toward the periphery and inward to the basement mem- 

 brane (Figs. 60, 65). These can now be definitely recognized as 

 retinular cells. Usually it is easier to see the proximal than the 

 distal strands for at an early stage these lower processes begin to 

 secrete pigment and are consequently more conspicuous (Fig. 65). 

 At the stage represented by Fig. 62 there is only the merest begin- 

 ning of pigment deposition. The fibers are but little differentiated 

 from their background which still seems to be composed largely of 

 a homogeneous granular material, probably to a great extent 

 coagulated plasma. 



At a stage such as is represented by Figs. 60, 62, in which there 

 is only the merest beginning of pigment secretion delicate cyto- 

 plasmic processes can be traced from the retinular nuclei inward 



