212 Marx I sahelle Steele 



cells shown in /. It frequently happens that not all of the tissues 

 included in what may be regarded as a single pigment region are 

 pigmented (Fig. 73). The unpigmented tissues, shown in the 

 area represented in this figure, contain but few recognizable 

 nuclei. Here and there are cells that show a few pigment granules 

 and occasionally small groups of such cells. These facts together 

 with the general appearance of the tissue suggest that eventually 

 the entire area might have become packed with pigment. 



Figs. 29, 32, 44 represent eve stumps of Palaemonetes that show 

 somewhat different tvpes of these abnormal pigment formations. 

 Fig. 32 presents a rather unusual tvpe. Externallv the pigment 

 appears as thicklv scattered granules instead of a dense black 

 mass as in most cases. Sections of this stump show a small quan- 

 tity of new tissue Iving at the distal end and alongside the nerve 

 stump. The cells composing the new tissue are closelv packed, 

 large, granular, and their nuclei do not take up iron haematoxylin 

 at all. Along the side of the eve stump a number of small pigment 

 cysts appear but for the most part the cells of the new tissue are 

 not yet denselv pigmented. Manv of them, however, show 

 numerous pigment granules. This particular specimen shows 

 less of the connective tissue-like, fibrous network than is usually 

 found in the pigment areas. Apparently this stump shows an 

 earlv stage in abnormal pigment secretion. The other two cases 

 figured show dense masses of pigment. Fig. 44 presents a single 

 compact mass. In each case sections show the pigment arranged 

 in the characteristic cvsts, such as are seen in Fig. 73. 



One additional fact of interest is shown in Fig. 44. The pig- 

 ment cvsts in this case do not lie whollv above and distal to the 

 remains of the optic ganglion but are embedded in the end of the 

 optic stump. Apparentlv the upper part of the ganglion stump 

 has degenerated and given place to the pigment. This is not an 

 unique instance as several other stumps have presented a similar 

 phenomenon. There was one case in particular in which there 

 were several small pigment cysts embedded in different portions of 

 the remains of the optic ganglion. The ganglion, in this case had 

 almost entirely degenerated, apparentlv. This animal had been 

 preserved in alcohol, however, and it was consequently impossible 



