84 PATTEN. [Vol. I. 



parallel lines at right angles with a similar set in the adjacent 

 plate. The plates of the pedicles resemble, in some respects, 

 the plates in the argentea of Pecten and other Molluscs, and I have 

 suggested that they may have a similar function ; i.e., they act as 

 reflectors to intensify the light impressions in cases where a 

 great deal of light is necessary, or when there is little light at 

 the animal's disposal. The fact that the pedicles are usually 

 present in nocturnal insects harmonizes with this interpretation. 

 The rounded outer ends of the retinophorae are capped with 

 protoplasmic thickenings, in which the nuclei are situated. 



Below the nuclei is an enormous crystalline cone nearly half 

 as long as the ommatidium. Near the centre of the eye, almost 

 at the inner ends of the crystalline cone, the opposite halves of 

 the calycal wall develop granular thickenings, sickle-shaped in 

 cross-sections, which increase in size as the diameter of the 

 retinophorae diminishes. 



Surrounding the retinophorae are seven oddly-shaped retinu- 

 las of different apparent lengths, four of which are nearly black, 

 while the remaining three are filled with light-brown pigment. 



The retinulae seem to terminate at the apex of the pedicle in 

 the knob-like swellings containing the nuclei ; this, however, is 

 not so, for they are continued outwards as extremely delicate 

 membranes, similar to those of the retinulae of Area. Toward 

 the outer surface of the eye the united terminal membranes of 

 each group of retinulae form a delicate sheath, loosely surround- 

 ing the style and calyx. Toward the outer surface of the eye 

 the sheath divides into seven hyaline thickenings, which abut 

 against the inner face of the cornea, to form, at the corner of 

 each facet, regular four-armed figures. Each thickening of the 

 sheath represents the outer end of a retinula. 



One of the retinulae is remarkable for its great size and 

 peculiar shape. At the beginning of the laminated structure 

 of the pedicle the axial wall of this cell becomes scalloped, 

 each fold projecting into the end of a plate. 



The pigmented collar of the retinophorae is formed by a circle 

 of four cells arranged in two pairs. Each cell is continued 

 inward as a slender colorless rod, or baeillus. The outer edges 

 of the collar cells contain refractive, granules, which, in reflected 

 light, are yellowish-white and perfectly opaque. The cells are 



