Stonry—Limitation of Insect Vision. 2438 
general insight into the process by which vision through com- 
pound eyes is carried on. Doubtless much detailed information 
of the minute anatomy of these interesting structures has been 
reached by microscopic anatomists; but I am not acquainted 
with it, and have been obliged to rely on my own imperfect obser- 
vations. It is, however, likely that, notwithstanding the diligence 
of microscopists, much still remains to be explored; and this, I 
hope, may be followed up more intelligently if the general 
optical process is understood. It is on this account that I have 
endeavoured to trace it out, and especially because, among my 
scientific friends in Dublin, there are to be found some of the 
most competent persons thoroughly to explore the whole of this 
interesting subject. 
I have hitherto said nothing about vision through the iso- 
lated eyes with which insects are also furnished. ‘They cannot, 
from the minuteness of their lenses, give them nearly so good 
vision of distant objects as man enjoys. And the limit is very 
possibly still more restricted by their being furnished with but a 
moderate number of rods and cones. It would be of interest to 
ascertain by observation whether this is so, and to collect such 
data as would enable us to estimate with tolerable exactness how 
far the imperfection goes. 
