﻿THE ENTOMOLOGICAL MAGAZINE, Vol. III. Pt. Ill & IV. 117 



RESUME. 



Ill the present paper the author describes the results of a his- 

 tological study on compound eyes of dragonflies. rhe material of 



the study is composed of two species, Somatochlora viridiaenea 



and Sympetrum frequense, between which being represented noth- 

 ing fundamentally different from each other so far as the histological 

 structure concerns. Althouth the present results agree in many 

 respects with those hitherto recorded by authors, still involve, at the 

 same time, several important findings, adverse or entirely new to our 

 knowledge as being abridged in the following lines. 

 1. The compound eye of the dragonfly is a kind of so-called 

 " Doppelauge ，， in which the ommatidia consisting the dorsal area of 

 the eye (dorsal eyes) are different in structure and in function from 

 those composing the ventral area (ventral eyes). Differences be- 

 tween these two kinds of ommatidia are as follows : 



{^3.) Corneal lens, crystalline cone and retinula are thicker and 

 longer in the dorsal eye (fig. i) than in the ventral eye (fig. 2). 



(b) A retinula is composed of eight cells in both kinds. In the 

 ventral eye, however, one of them becomes gradually abortive and 

 at last its nucleus entirely faded away during metamorphosis. E- 

 ventually we can count only seven nuclei in the ventral eye of the 

 imago (fig. 2) while eight in the dorsal eye (fig. i). 



(c) In the dorsal eye, one of these nuclei (Rk^) lies very distal 

 in a retinula and rather small in size. The next one (Rk?, is found 

 in less distal and extremely small in size. ihe another four nuclei 

 (Rkg^o) occupy the middle portion in the entire length of retinula, 

 each lying in different level though in slightest degree, and largest 

 in size. The remaining two (Rky^g) situating in most proximal are 

 as small as the second nucleus. 



In the ventral eye, the general scheme of arrangement of the 

 nuclei is almost similar to the dorsal eye with a little modification. 

 One of the differences is the disappearance of the second nucleus 

 and the other is the full development of the last two nuclei which 



