294 APPENDIX II 



Although we cannot be certain that we have seen the 

 nuclei of the large pigment cells as shown in the dia- 

 gram (Fig. 23, p. 139), we concluded that there must be 

 such nuclei, and that the pigment masses were real cells 

 and not syncytia. We were chiefly led to this conclusion 

 by noticing the long regular lines of granules running down 

 the nerves towards the optic ganglion, as shown in the 

 diagram. It seemed to us that these rows of single 

 granules would not be so straight and even, unless enclosed 

 within a long pseudopodium-like process of the pigment 

 cells. Were the granules semi-independent cells, their 

 arrangement could hardly be so straight and regular. We 



Fig. 65. — Pigment granules (? cells) from the eye of Apus, X ca. 3000, showing a 

 stainable nucleus, surrounded by a thin crust of brown pigment, ihe whole 

 enclosed within a hyaline substance. 



were further induced to take this view from finding that, in 

 some specimens, the pigment in the unpaired " eye " was 

 composed of similar eye-pigment granules, also arranged in 

 long pseudopodium-like strands. In most of the specimens 

 examined, the pigment in the unpaired " eye " was similar 

 to that in the pigment cells of the rest of the body, i.e. it 

 was in the form of very minute olive green granules. Tlie 

 occasional finding of eye-pigment in the unpaired " eye " 

 was especially interesting in reference to the origin we 

 attributed to that organ out of an anterior pair of 

 Annelidan eyes. 



Around the paired eyes, the green pigment reaches up to 

 their very rim, and indeed stretches over the outer edges of 



