212 



ANDREWS. 



[Vol. VII. 



Such simple areas appear as the first indications of the eyes 

 in the larval Polychaetae, and may, perhaps, remain upon the 

 cephalic branchiae of some sedentary adults (Serpulidae), as organs 

 sensitive to changes in illumination. 



With the increase in the amount of the clear receptive proto- 

 plasm and increase in the efficiency of the organ, there was an 

 elongation of the cells (2) and restriction of the pigment to 



s. 



Diagram 2. — 1-5, successive stages in hypothetical formation of annelid eye. 

 Cuticle represented by long parallel lines ; lens and vitreous body by short lines; 

 pigment by large dots, and protoplasm by fine ones. The rods remain clear. 



their less sensitive areas. Such eyes may reappear in the forma- 

 tion by budding (Fig. 65), and seem to be retained in some 

 larvae, as Fig. 66, and in Polygordius (Figs. 6^, 6%), and are 

 probably represented by the stages shown in Figs. 57, 60. 



The cuticular ends of the cells next become modified as re- 

 fracting bodies (3), perhaps a spherical lens in each cell, next 

 the cuticle, as indicated in Figs. 46, 69, 70. 



