THE ORIGIN OF THE MIDDLE OCELLUS OF 
THE ADULT INSECT. 
(PRELIMINARY COMMUNICATION.) 
CHUJIRO KOCHI. 
Many years have passed since Leydig and Brandt called at- 
tention to the fact that one of the three ocelli in the adult insect 
situated in its median line was double. I do not know whether 
there exists to-day any accurate theory of the origin of this 
middle ocellus. Most entomologists have simply regarded it 
as the fusion of two ocelli which once occurred separately in 
the ancestral form. If this theory is true, there must be some 
relics left in the generalized type of the insect by which we 
may trace out the original number of the ocelli, Z.e., two pairs 
in all. 
Among all the orders of the insects the Orthoptera is per- 
haps the most generalized one. Among the Orthoptera I 
shall refer to the cockroach as being one of the oldest, least 
modified, and, in many ways, very instructive for comparing 
it with the other specialized forms of insects. 
The head of the cockroach (B/atta orientalis) is vertically 
elongated, having a semicircular outline above, and narrowing 
downwards. The dorsal part of the head is the vertex, and 
a median suture may be seen traversing it from before back- 
ward, and dividing between the eyes into two branches, one of 
which passes toward the articulation of each antenna to form 
a V-shaped suture. The cephalic portion of this suture is the 
front, which was called the *clypeus" by Huxley, as well as 
by Miall and Denny in their work on the anatomy of this 
insect, Perhaps they did not notice that the clypeus was a 
small sclerite, situated above the labrum, and separated from 
the front by a curved suture at the point a. This suture also 
divides the gena from the front on each side of the head. 
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