464 THE NERVOUS SYSTEM. 
and (5) the peduncle of the corpus centrale. Other sets of 
fibres can be traced to the thalamic lobe (Pl. XXXII., Fig. 
2, th) and the metacerebron (Pl. XXXIII., Fig. 2). 
The Commissures of the Lateral Halves of the Cerebron.—Irre- 
spectively of the complex corpus centrale already described, 
and the commissures of the procerebral lobes and antennal 
ganglia, the floor of the central cavity of the cerebron consists 
largely of transverse commissural fibres, connecting the oppo- 
site lobes of the cerebron and the opposite optic ganglia. 
The floor of the central cavity, which separates it from the 
cesophagus, is thin in front, but very thick behind. It is not 
possible to trace the course of the individual bundles of fibres 
which form this floor, many of them certainly connect the two 
optic peduncles, and others probably pass from the right optic 
peduncle to the left mesocerebral lobes, others are apparently 
loops, or arciform fibres connecting the lateral halves of the 
mesocerebron with each other. 
The Trabecular System.—The peduncles of the external and 
internal calices (Pls. XXIX. and XXXIL., Fig. 2), plunge into 
the lobes of the mesocerebron, and unite with each other at an 
acute angle above and behind the thalamic lobe to form the 
trabeculz (Balken, Flégel [177]). The trabecula in the Blow-fly 
is comparatively short ; it is connected with the thalamic lobe 
(Pl. XXXL., Fig. 1) and enlarges above the procerebron into the 
caput trabeculae, which gives off two processes (Pl. XXX., 
la, li), called respectively the anterior and internal tubercles. 
I regard the anterior tubercle as identical with the anterior 
horn (Vorderhorn) of Flégel [177]; it is the anterior tubercle of 
Viallanes, and the cauliculus of Newton [180]. 
In the Cricket the anterior tubercle is far larger than in the 
Blow-fly, but from Viallanes’ figures it appears to have the 
same relations to the surrounding parts. 
The connections of the trabecular system of fibres with the 
rest of the nervous system are very complex. Although the 
trabecule apparently end in rounded extremities, this appear- 
ance is due to the radiation and decussation of their fibres with 
each other. The internal tubercles probably end in the same 
