Regeneration in Compound Eyes of Crustacea 2il 



appearance of the pigment outlined in Fig. 72. An examination 

 of Fig. 73 shows that the deposition of pigment appears to begin 

 at several centers. These centers gradually increase in size. 

 There also seems to be a tendency for the several centers to fuse 

 with each other. It is further seen that the pigment cells or 

 masses vary from very large to very small areas. 



A study of depigmented sections suggests that these smaller 

 pigment bodies arise in one of tw^o ways: first, by an out-pocketing 

 of the cytoplasm, which after becoming distended with pigment 

 separates from the parent mass and second, by an unequal division 

 of the cell. It is possible that the latter is the true method for all 

 cases. But it was not possible to determine this point with cer- 

 tainty. When a pigment cell has become gorged with pigment 

 the nucleus is much changed and distorted. And even after the 

 most thorough depigmentation it cannot always be identified. 

 Consequently it may be that the smaller masses, in which no nuclei 

 are visible, are not mere masses of cytoplasm that have been 

 constricted off but are the result of unequal cell division. Fig. 75/ 

 shows a small group of depigmented pigment bodies. In the 

 larger masses nuclei are visible. In the smaller bodies nuclei 

 cannot be determined with certainty. 



The amount of pigment within a cell varies. Some cells contain 

 only a few scattered granules while others are so completely filled 

 that they appear to be black homogeneous masses. In these more 

 densely filled cells the pigment appears to have fused into solid 

 brittle masses that can be crushed like starch grains, g in Fig. 75 

 represents one of these masses after it has been crushed. 



The pigment is dissolved from the sections with the greatest 

 difficulty. Mayer's chlorine method was generally used for this 

 purpose. But in removing the cyst-like depositions of pigment it 

 was found that alternate treatment with the chlorine method and 

 with one-twentieth per cent KOH in 70 per cent alcohol gave 

 equally as good and more rapid results. Even with this treatment 

 twelve to twenty-four hours were required to remove the pigment 

 from sections 6/i thick. Frequently this failed to dissolve the 

 dense pigment masses. In Fig. 75 the dense, crushed pigment 

 mass g lies in the same section with the group of depigmented 



