No. 2.] COMPOUND EYES OF ANNELIDS. 277 



chia (Fig. 14). These latter nerves, however, are seen to give 

 off branches, at certain places, into the epidermis, and so, if 

 there be an epithelial network of nerves, there may be a con- 

 nection between the eye and the two large trunks. In gold 

 chlorid and other surface preparations, however, I have not been 

 able to find these optic nerves at all, nor to discover any such 

 epithelial nervous system. 



Transverse sections of the eye show its component cells radi- 

 ating out, fan-like, from a central point, so as to present sym- 

 metrical right and left sides, and showing usually several, often 

 a considerable number of the refracting cells distinguishable 

 from the smaller pigment cells by the possession of the periphe- 

 ral, clear inclusion, as well as by the fact that their nuclei are 

 situated centrally as compared with the more peripheral nuclei 

 of the ordinary pigment cell. 



Tangential sections (Figs. 8, 9, 10) taken successively nearer 

 the central part of the eye show the relative positions of the 

 simply pigmented and the refracting cells, as well as the posi- 

 tion of nuclei and the structure of these latter cells at different 

 levels. Just within the cuticle (Fig. 8) the stained inclusions 

 of the refracting cells are surrounded each by the clear part of 

 the base of the cell. Each refracting cell is imbedded in the red 

 pigment, in which are irregularly scattered the nuclei of small 

 pigment cells. The boundaries of the cells are not seen, but 

 some pigment more densely aggregated about the clear cells is 

 probably to be regarded as belonging to the surface of these 

 refracting cells. The refracting cells, traced into sections nearer 

 the central part of the eye (Fig. 9), show as clear, stained areas 

 the peculiar nodulated or roughly lamellated axial part of the 

 cell seen in Fig. 5, between nucleus and inclusion. No nuclei 

 are seen at this level, but large masses of pigment between the 

 above cells. Still farther down (Fig. 10), sections show the 

 nuclei of the refracting cells, each surrounded by a little clear 

 protoplasm and by much pigment belonging to these and to the 

 smaller pigment cells. 



Sections still nearer the central area of the eye show only 

 transversely cut, filament-like, pigmented ends of cells, seen best 

 where shrunk from one another, as in material hardened in 

 Merkel's liquid. 



When the eyes are depigmented in Grenacher's liquid, either 



