No. 2.] EYES OF POLYCH^TOUS ANNELIDS. 191 



and regarded as a plug of epidermal cells, separated from the 

 retina by a sharp membrane. The retina is composed of pig- 

 mented cells with clear rods. In the presence of that mem- 

 brane and in the presence of nuclei, both in the retinal rods 

 and in the element of the lens, this eye would appear to differ 

 from that of Podarke fundamentally. Leaving out the mem- 

 brane and nuclei, the eye agrees essentially and closely with 

 those here described. Both membrane and nuclei I regard as 

 probably artificial products, produced by the methods employed. 



POLYNOIDiE. 



Lepidonotus squamatus Kinberg. 



These annelids remain closely appressed against the surfaces 

 upon which they crawl, and do not lead as free a life as do most 

 of those hitherto described in this paper. 



The four small eyes are on the dorsal aspect of the head, the 

 anterior further apart but not larger than the posterior pair. 



When isolated the retinal cup is found filled by a lens mass 

 that projects from its orifice or pupil in the form of highly 

 refracting conical bodies resembling pieces of ice. The whole 

 cup is filled with these lens elements or separate lenses, each 

 connected at one end with the layer of retinal rods, by means 

 of a delicate thread or process that may be drawn out as if 

 viscid. 



When macerated the retinal cells (Fig. 51) are found to be 

 very short and thick with short clear rods and abundant black 

 pigment in the rod end of the body of the cell. This pigment 

 is composed of very fine granules having a sooty black color, 

 even when isolated. In one case a retinal rod was seen con- 

 tinuous with one of the lenses or lens elements (Fig. 50). Here 

 the short retinal rod expands as a swollen oil-like mass, the lens 

 element, surrounded by a membrane-like contour that continues 

 down over the retinal rod. 



Owing to the great thickness of the cuticle and to the hard 

 refractory nature of the lens good sections of the entire eye are 

 difficult to obtain. The best show, as in Fig. 52, some of the 

 lens elements still remaining, and in places connected with the 

 rods, though elsewhere much shrunken. 



