( st hxr 4) 
the factors that make comprehension of its function so 
difficult. 
Anatomical knowledge, then, like the other methods of 
inquiry, tells us that at present we know very little about how 
or what an insect sees. It is highly probable that its sight is 
very different from our own, and that continuous picture- 
vision forms no part of it; while it appears to be even 
possible that the compound-eye may have two or three 
distinct kinds of perception. There is every reason for sup- 
posing that the ocular powers of insects are very perfect in 
their way, although that way may be very different from ours. 
Indeed, it would seem to be quite possible, if not probable, that 
a company of gnats dancing in the rays glinting through the 
bushes on a summer evening or in the afternoon of an autumnal 
day, may by means of acute perceptions of lights and shades 
be enjoying an ocular treat as varied and as exhilarating to 
them as the prospect we enjoy from the summit of Righi or 
Pilatus is to us; while at the same moment, by means of an 
extreme sensitiveness to movement and its direction, they 
may be taking part in a rhythmical concert of no mean 
order of excellence. 
I have devoted so much time to the consideration of the 
sense of sight, that I must not attempt to discuss the other 
senses at any considerable length. Probably the one next 
in importance to insects is that of smell. The earlier 
naturalists began trying to understand the sense of smell in 
insects by supposing it to be similar to our own. In the 
Vertebrata the organs of smell are invariably placed in con- 
nection with their respiratory organs, a free current of air 
through the olfactory organs being absolutely essential. This 
being known, a habitat for the sense of smell in insects was 
sought at the commencement of the air-passages, especially in 
the stigmata; this, however, has now been nearly abandoned, 
chiefly because no adequate nervous structures have been de- 
tected there; and the sense of smell in insects is now thought 
to be located in the antennex or in some of the parts of the 
mouth. Investigation has revealed a number of remarkable 
minute structures in the antenne that are pretty certainly 
sense-organs, but to what extent they can properly be called 
