426 W. H. GASKELL. 



of the pigment layer, reveals an extraordinary sight ; scattered 

 about over the whole field of view of the microscope are seen 

 rod-like bodies, some crescent-shaped, some nearly straight, 

 some shaped like a hook, others like an elongated S, all 

 apparently attached to the edge of one or other of these square 

 or oblong-shaped masses, and diflferentiated from them by 

 their greater refracting power. They lie in connection with 

 the bodies to which they are attached at different angles to 

 each other, but occasionally a number of them appear to be 

 regularly arranged in respect to the pigment layer. In this case 

 they present very closely the appearance given in fig. 25, PI. 

 XXVIII, which is taken from Grenacher (22), and represents 

 the pigment free ends of the nerve-end cells of an eye of an 

 Acilius larva with their attached rhabdites ; in other cases the 

 appearance is very like that represented in fig. 24, PI. XXVIII, 

 which is a reproduction of Lankester and Bourne's (21) picture 

 of a section through the nerve-end cells and rhabdomes of a 

 Euscorpius eye. 



In fig. 22, PI. XXVIII, I give an accurate copy of a 

 magnified portion of the section in fig. 20 c, PI. XXVII. 



These bodies, then, which appear on section somewhat 

 square or conical, according to the direction in which they 

 happen to be cut, with their rod-like, highly refractile 

 attached pieces, are by no means mere coagulated albumen, but, 

 on the contrary, are the terminal parts of the nerve-end cells, 

 with the rhabdites attached to them, which project freely beyond 

 the pigment layer, and form the layer of rods as pictured and 

 described in de Graaf's original paper (24) on the pineal eye 

 of Anguis. The arrangement of the pigment of the nerve-end 

 cells, and of the rods, calls to mind very forcibly the figures 

 of the larval eye of Dytiscus and Hydrophilus as figured in 

 Grenacher (22) and Patten (25). In specimens stained by 

 hsematoxylin no such distinct appearance of rod-like bodies 

 can be seen ; but here we find, in between the square or poly- 

 gonal cell-like masses, lines and strands of substance which 

 stain very much darker than the rest of the tissues of the eye, 

 and in this respect resemble cuticular structures. 



