Regeneration in Compound Eyes of Crustacea 215 



relatively large amount of new tissue was regenerated by this eye, 

 and sections show that normal regeneration had begun (Figs. 68, 

 69). A new hypodermis was completely differentiated and on one 

 side the differentiation of ommatidia was taking place (Fig. 69). 

 The greater part of the new tissue was made up, however, of cells 

 of a character known to be abnormal. The hypodermal cells are 

 practically the only cells that appear normal. With the exception 

 of a small area on one side almost the whole of the interior is filled 

 with rounded cells containing polymorphic nuclei. Fig. 71 

 represents a part of Fig. 70 more highly magnified and showing the 

 structure in greater detail. A comparison of these two figures 

 with the series shown in Fig. 75 cannot fail to show a striking 

 similarity. 



Altogether there is strong evidence that the failure of the old 

 retinulae to disintegrate completely is the immediate cause of 

 abnormal pigment deposition, in many cases at least. Further, 

 there is some evidence that regenerating retinulae may sometimes 

 become involved in the abnormal secretion of pigment. Group 

 ^, Fig. 75, represents a probable case of this sort. The group was 

 taken from the regenerating part of the eye in a region where there 

 is positive evidence that some normal regeneration is taking place. 

 A few of the cells in the group still show but few pigment granules 

 and show elongated nuclei, characteristic of regenerating retinulae 

 (Fig. 75J, ret. 72.) 



The appearance of the network of tissue with which many of 

 these pigment nodules are associated still remains to be accounted 

 for. Evidences which point to the origin of this are not so numer- 

 ous as are the evidences that the old retinulae form the centers for 

 the pigment secretion. In some cases these pigment nodules are 

 found embedded in the hypodermis of the eye stalk, in other cases 

 in the membrane surrounding the optic ganglion. In such 

 instances it seems probable that the fibrous network supporting 

 these nodules is due to the hypertrophy of the normal tissue 

 immediately surrounding the pigment deposits. In those cases, 

 however, where a great mass of this fibrous network developed it 

 seems to have had a different origin. There are three particularly 

 striking instances of the unusual development of this abnormal 



