278 THE MICROSCOPICAL NEWS. 
each ocellite is capable of forming an image at the point of junc- 
tion with the optic nerve, it does not at all follow that each is the 
analogue of the vertebrate eye, and that there are formed as many 
complete images of its surroundings as there are facets in the eye; 
for in consequence of the pigment separating cone from cone, each 
single nerve fibre can be impressed only by the light received 
through the single ocellite with which it is connected, and as the 
field of view of each is very small, and they are all turned in 
different directions, a different view 1s presented to each, though 
there would be some such overlap as in a pair of stereoscopic 
photographs. And then who could credit a single nerve fibre with 
the fearful complex function of transmitting the impression of a 
complete image? We must therefore conclude that but a.single 
picture is formed by the eye; that picture may be regarded as a 
mosaic composed of as many points or pieces as there are corneules 
in the eye. It must necessarily be imperfect, not only by reason 
of the limited number of points of which the image is composed, 
but because each nerve-ending is impressed not only with the light 
from a single point, but from all points—and there may be many 
—included in its field of view, however small that may be. 
The next organs to be noticed are the antenne. Each will be 
seen to consist of a large basal joint, followed by a short cup- 
shaped piece, and then a series of larger but gradually decreasing 
joints, the whole organ acquiring a beautiful form by the whorl of 
stiff, bristle-like hairs around the base of each joint. It appears 
certain that the antennz are tactile organs, and that they serve in 
some way for intercommunication between individuals, and there 
appear reasons for believing that in some insects they have also an 
auditory function. Below the antennz, and even exceeding them 
in length, will be seen a pair of filaments, each consisting of four 
joints ; the basal joint springs from the back of the face, and the 
terminal one enormously exceeds the others in length, and all are 
plentifully besprinkled with short, stiff hairs. These are the 
maxillary palpi. ‘They probably perform a tactile function. 
The mouth is situated. below and behind, and from it springs a 
short fleshy trunk, tumid and bilobed at its free end. This organ 
is the so-called tongue or proboscis. In the accompanying 
preparation its lobes, which are covered with bristly hairs, will be 
seen projecting below the face, and in the interior of each will be 
seen two large tubes with numerous branches; their chitinous 
lining is thickened in a manner that will at once recall the idea of 
tracheze, which these tubes, as a matter of fact, really are, though 
they have been appropriated to an entirely different purpose from 
that of respiration. They are channels through which the liquid 
food of the fly is sucked up into the mouth, 
We shall arrive at a more correct understanding of the nature of 
