THE BEAIN OF THE LOCUST. 
229 
the face from before backwards ; in cutting thus through the head, twelve 
sections were made before the front part of the brain was touched, the 
thirteenth grazing the front of the brain. Section 14 passed through the 
anterior part of both calices, but did not touch the stalk of the mush- 
room body (these terms will be explained farther on). It passed through 
the central region of each hemisphere, including the front part of the 
trabecules or base of the stalk of the mushroom body. The section passed 
through the commissural lobes, the lower third being composed of ganglion 
cells, but the substauce of the commissure itself is filled with the ball- 
like masses of " marksubstanz." The commissures to the suboesophageal 
ganglion were not touched, and do not appear in the section, since they 
arise from the back of the brain. 
In section 15 no additional organs are exposed. In section 16 (PI. 
X, Fig. 1) the trabecular are seen, when magnified 225 diameters, to 
be composed of ascending fibers, which form the base or origin of the 
double stalk of the mushroom body. 
Section 17 (PI. X, Fig. 2) is the most important of all the sections, as 
the entire mushroom body and the central body are cut through, together 
with the antennal lobes, and the commissural lobes, and also the origin 
of the optic nerves. 
In section 18 (PI. X, Fig. 4) the double nature of the stalk of the 
mushroom body is seen ; the optic lobes are now well marked, and the 
razor grazed the back of the commissural lobes, as well as the inner 
side of the optic ganglion. The section passed behind the trabecular and 
the base of the stalk aud through the back of the central body. The 
calices arc each seen to be so furrowed and uneven as to appear in the 
section as two separate portions. Two important nerves (PI. X, Fig. 
4, p. a. ».) 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 (o. c. n.f). 
Section 19 (PI. XI, Fig. 1) passed through the back of the brain (com- 
pare Fig 4. of the same plate, which represents a vertical or longitudinal 
section of the brain), through the oesophageal commissures, 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 (t c n) con- 
nects the two antennal lobes, and the commissural nerves are seen to 
cross at the bottom of the furrow. 
Section 20 (PI. XI, 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, i. e., the inferior {inf. »..), 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 
