ANATOMY OF THE NERVE CENTRES. 467 
situated behind the corpus centrale; its base rests on the 
floor of the central cavity; the metacerebron is immediately 
behind it, chiefly represented by a transverse commissure. 
The apex of this ganglion is situated in the posterior part of 
the longitudinal fissure, between the internal corpora fungi- 
formia; its axis is traversed by numerous fibres, which form 
the roots of the nerve to the ocelli. 
The Nerve of the Ocelli.—This nerve is single in the Blow-fly ; 
it emerges from the apex of the pyramidal ganglion as a single 
cord, which divides into three branches immediately beneath 
the three ocelli, and ends in the retinz of these organs. 
In the Cricket there are three distinct ocellary nerves—two 
lateral and a single median nerve. 
According to Viallanes [185, Mem. 5], the median ocellary 
nerve in the Cricket arises by two roots, one on either side. 
These roots join the deep origins of the lateral nerves, and 
may be traced in part at least to a small internal tubercle, 
which projects from the inner surface of the posterior part of 
the hemisphere. The nerve to the ocelli in the Blow-fly has, I 
believe, a similar connection with the hemisphere, although 
many of its fibres come from the nerve-cells of the pyramidal 
ganglion. 
d. The Sensory Ganglia. 
The Olfactory or Antennal Ganglia are a pair of spheroidal 
ganglia, which project from the front of the brain. They are 
united with each other by a strong commissure. Each 
ganglion is connected with the corresponding hemisphere by a 
peduncle, consisting of four principal bundles of fibres. 
r. Bellonci’s Bundle traverses the hemisphere from before 
backwards, and terminates in the gray matter between and 
below the corpora fungiformia. These fibres were first seen 
by Bellonci [183] in the Diptera. 
2. The Trabecular Bundle (Pl. XXIX., Fig. 2) decussates 
with its fellow in the middle line, and joins the trabecula of the 
opposite side. 
