﻿118 昆蟲 $ 雜誌 第參 卷第參 • 四 欲 



are nearlv as large as the central lour ones and lie in extremely 

 proximal to the bottom of the retinula. 



(d) Sensory nerve fibers entering the retinula can be detected 

 four in number in the dorsal eye while six in the ventral eye. All 

 can be traced clearly from the bottom of the retinula up to the 

 proximal to the largest nuclei. That is, the dorsal eye four nerve 

 fibers occupy the proximal halves of and along the axes of the 

 retinular cells (fig. lb), and in the ventral eye two of the six fibers 

 stretch in comparatively small extent, not to be found beyond the 

 nuclei Rk? 一 g, while the other four reach the nearly middle portion 

 of retinula (c- f. fig- 2a and 2b). 



(e) There is a great difference between the dorsal and the ventral 

 eye in respect to the shape and structure of rhabdome. In the dorsal 

 eye the rhabdome is a three winged rod oi in the other words it 

 represents a three rayed star shape in its cross section (fig. 丄 a, lb, r.) 

 It is consisted of three rhabdomeres of V-shaped, which closely 

 applied together and accompanying a grantlar portion of retinular 

 cells (fig. 6). The rhabdome of the ventral eye, however, is simpUy 

 cylindrical rod-shaped (fig. 2b, r), not separable into rhabdomeres, 

 and the adjacent area of the retinular cells represents no granular 

 adpearance but another structure. 



(f ) Pigment granules scattered in retinular cells are considerably 

 scarce in amount in the dorsal eye, but remarkablly rich in the 

 ventral eye. 



(g) Piprnent found in the pigment celis is brownish yellow in the 

 dorsai eye while dark brown in the ventral eye. 



2. Differences in structure as above mentioned show that the vision 

 by the ventral eyes should be more accurate than that by the dorsal 

 eyes. Further the dorsal eyes may sometimes yield the superposi- 

 tion images owing to their ill development of retinular pigment, as 

 being easily recognizable that certain light obliquely entered an 

 omma can not be absorbed completely by it but through its retinular 

 cells may be received by the neighboring ommatidia. While living 

 state, I suppose, the dragonfly seems to watch for enemies, com- 



