292 The Brain of the Locust. [April, 
the central body. The calices are each seen to be so furrowed and 
uneven as to appear in the section as two separate portions, Two 
important nerves (Pl. 11, Fig. 4, f. @. 2.) are seen to arise from the 
commissural lobes, and to pass upwards, ending on each side of 
the upper furrow, near the origin of what we think are possibly 
the ocellar nerves (a. c. 2. ?). 
Section rg (Pl. 111, Fig. 1) passed through the back of the brain 
(compare Fig. 4, of the same plate, which represents a vertical or 
longitudinal section of the brain), through the cesophageal com- 
missures, and the back edge of the calices, while the antennal 
lobes and a part of the optic lobes are well seen in the section. A 
transverse commissural nerve (¢¢ z) connects the two antennal 
lobes, and the commissural nerves are seen to cross at the bottom 
of the furrow. 
Section 20 (Pl. 11, Fig. 2), which passes through the extreme 
back of the brain, shows in this plane four transverse bundles of 
nerve fibers connecting the two hemispheres, 7. ¢., the inferior 
(inf. n.), two median (m. n.) and a superior nerve (sup. .). In 
this section the relations of the optic ganglion and eye to the 
brain are clearly seen, the optic ganglion being situated in the 
' posterior region of the brain. It will also be seen that the two 
hemispheres are at this point only connected anteriorly. 
In sections 22, 23 and 24 the brain nearly disappeared, and 
only the optic ganglia were cut through by the microtome, affording 
instructive sections of the three lenticular masses of white un- 
stained granulo-fibrous substance surrounded by ganglion cells. 
Internal Topography of the Brain—Disregarding the envelope 
of cortical ganglionic cells, though they are evidently of primary 
importance in the physiology of the insect’s brain, we will now 
describe the internal topography of the brain. It consists pri- 
marily of an irregular net-work of nerve-fibers, inclosing masses 
of granulated nerve matter. This mass is divided into a number 
of separate areas or lobes, of which the “central body” (corpus 
centrale of Flogel and Newton) is single and situated between or 
in the median line of the two hemispheres. There is also a primi- 
tive superior and inferior central region, better shown, however, in 
the brain of the embryo and larval locust than in the adult. Be- 
sides these areas are the rounded masses or “lobes,” 7. ¢., the 
optic, antennal, or olfactory and commissural lobes; the optic 
nerves arising from the optic lobes, the antennal nerves from the 
