464 THE XI-. R VOL ' V ^ 1 ^ TEM. 



and (5) the peduncle of the corpus centrale. Other sets of 

 fibres can be traced to the thalamic lobe (PI. XXXII., Fig. 

 2, th} and the metacerebron (PI. XXXI 1 1., 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 

 oesophagus, 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 

 rr.esocerebron with each other. 



The Trabecular System. The peduncles of the external and 

 internal calices (Pis. XXIX. and XXXII., 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 

 trabeculse (Balken, Flogel [177]). The trabecula in the Blow-fly 

 is comparatively short ; it is connected with the thalamic lobe 

 (PI. XXXI., Fig. i)and enlarges above the procerebron into the 

 caput trabecula;, which gives off two processes (PI. XXX., 

 / a, I i), called respectively the anterior and internal tubercles. 

 I regard the anterior tubercle as identical with the anterior 

 horn (Vorderhorn) of Flogel [177J ; it is the anterior tubercle of 

 Yiallanes, and the cauliculus of Newton [180]. 



In the Cricket the anterior tubercle is far larger than in the 

 r.li\v-lly, but from Viallanes' figures it appears to have the 

 same relations to the surrounding parts. 



The cninn < lions of the trabecular system of fibres with the 

 rest of tlu nervous system are very complex. Although the 

 trabecubu 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 



