No. 2.] EYES OF POLYCH^TOUS ANNELIDS. 183 



which is, perhaps, merely the aggregate of the more dense polyg- 

 onal bases of the retinal cells. 



The interpolation of slender cells and occurrence of nuclei m 

 two zones increase the difficulty in interpretation from sections 

 alone The arrangement appears to be as in Marphysa, and 

 a-ain there is some evidence that, as too diagrammatically indi- 

 cated in Fig. 37, the lens filaments are but the continuations of 

 the more attenuated retinal cells. 



Eunice violaceo-maciilata Elders. 



Specimens from Green Turtle Cay, Bahamas, have eyes like 

 those of the two preceding annelids, and serve to clear up some 

 doubtful points in the interpretation of these eyes. 



The cuticular stalks of the large eyes have definite perfora- 

 tions or axial canals (Fig. 32) ; that is, the cuticle is invaginated 

 as a short tube, and then thinning out, becomes continuous with 

 the surface of the lens. 



The epidermis following this ingrowth becomes here, as m 

 the preceding cases, continuous with the pigmented retinal cup. 

 Moreover, the greatly elongated, slender cells of the epidermis 

 are repeated in the correspondingly elongated retmal cells (see 

 also Fig. 43, as compared with Fig. 37 or 38). 



The lens would appear to be nearly liquid at its centre but 

 more dense at the periphery. Here it is continuous with the 

 cuticle, which does not extend far into the optic cup, but grad- 

 ually becomes less refracting and dense till it merges mto, 

 and is one with, the peripheral part of the more granular, less 



refracting lens. 



In the retina there is little doubt that the much-attenuated, 

 slender cells that are crowded in amongst the thicker but very 

 long ones are actually continued out to the lens as slender fibrils 

 between the rods (Fig. 43)- These fibrils, lens fibrils, appear 

 thus to perforate the line indicating the boundary of the rod 

 pigment, just as the clear axes of the larger rod cells do 



Some views of the common epidermis of the head lead one to 

 infer that here also the attenuated cells amongst the larger 

 epidermal cells have a close connection with the cuticle, like 

 that of the above cells with the lens. In tangential sections 

 across the rods (Fig. 36), we meet again with these slender lens 

 filaments, or attenuated rods of slender cells as they seem to be, 



