214 Mary Isabelle Steele 



tion. This shows that in some cases they disintegrate much more 

 rapidly than in others. In some eyes examined twenty-five to 

 thirty-five days after the operation similar rounded cells with 

 polymorphic nuclei are fiDund in numbers, increasing by amitotic 

 division. In still other cases, cells of this character containing 

 pigment granules are found. 



Fig. 75<3, b, c, d, e, f, g represents a series of groups of these 

 rounded cells with polymorphic nuclei. These groups were taken 

 from crayfish, hermit crabs, Crangon and Palaemonetes, represen- 

 ing in all seven species. The first three groups, a, h and c, show 

 the appearance of breaking down retinulae, seventeen hours, 

 thirty-nine hours and sixteen days, respectively, after the injury; 

 d, e and / show the secretion of abnormal pigment as found in 

 eyes ten, twenty-three and sixty-seven days respectively after the 

 injury; / represents a group of depigmented cells that were so filled 

 with pigment that without depigmentation no structures were 

 visible. An examination of this series cannot fail to show the 

 similarity between the breaking down retinulae and the pigment 

 secreting cells. Particularly is this so if it is remembered that, 

 except a and h, no two groups are taken from the same species. 



These facts taken together have suggested that the immediate 

 cause of the pathological pigment secretion is the abnormal 

 activity of old retinulae which have not completely broken down. 

 It has already been mentioned that after an eye has been operated 

 upon the pigment from the injured retinulae frequently becomes 

 greatly scattered among the other tissues. Not only does the 

 retinular pigment become scattered but in some cases the rounded 

 retinular cells, also, are found considerable distances down the 

 stalk and on the side opposite the injury. These instances were 

 observed in eyes examined from fifteen to twenty days after the 

 injury. It seems probable that some of these metamorphosed 

 retinular cells become embedded in other tissues, then later divide 

 amitotically and begin to secrete pigment. The nodules of pig- 

 ment previously described are the result. In some cases the 

 multiplication of these pathological cells takes place rapidly so 

 that large areas are occupied by them. Fig. 70, which is from 

 a section of the eye shown in Fig. 20, represents such a case. A 



