Regeneration in Co)n pound Eyes of Crustacea 209 



of faintly staining nuclei. These tissues resemble very closely the 

 depigmented tissues of the abnormal pigment masses. This 

 resemblance suggests that possibly the two abnormal appearances 

 have had a common origin. 



A case partially resembling the one just described was observed 

 in a green shrimp, Palaemonetes viridis. The original injury 

 consisted in the removal of a small part of the top of the eye. The 

 eye was operated upon August i. On the ninth of the same month 

 the animal moulted and was preserved. Figs. 17 and 18 represent 

 dorsal and ventral views of the injured eye. The dorsal surface of 

 the whole eye is shown in Fig. 17. Fig. 18 represents the distal 

 end of the eye from the ventral side and under greater magnifica- 

 tion. A pigmented mass similar in general outline to the retinular 

 area in the normal eye is visible through the transparent outer 

 tissues. Distal to the pigmented portion is a considerable area of 

 transparent tissue with flecks of pigment scattered through it. 



The distal contour of the eye is irregular because of a swelling or 

 protuberance similar to the one on the hermit crab's eye previously 

 described. This eye also shows an unusual development of new 

 tissue considering the time in which it was produced. 



Sections of this eye show that the optic ganglion had not been 

 injured, that not all of the ommatidia had been removed and that 

 a considerable part of the old pigment remained. The ommatidia 

 that were left have almost completely degenerated, however, and 

 the whole distal portion of the stump is filled with a comphcated 

 network of faintly staining cells. There is also absolutely no 

 regularity in cellular arrangement, as is seen in normally regener- 

 ating eyes. For the most part the nuclei are scarcely distinguish- 

 able from the cell-body. Although here and there are scattered 

 nuclei which stain more deeply. There are evidences in some 

 cases that these are nuclei of disintegrating ommatidial structures. 

 Some sections show remains of old cones associated with the 

 darkly staining nuclei. Comparison of others of these deeply 

 staining nuclei with the nuclei of partially depigmented cells 

 shows a similarity between the two which suggests that the former 

 belong to cells in which pigment secretion has lately begun. 



It is evident that most of the pigment masses present are the 



