THE BRAIN OF THE LOCUST. 
239 
cerebral lobe and the optic ganglion. The oesophagus is situated be- 
neath the cleft under the lower cerebral lobes. The next section (13) 
passes behiad the brain, not touching it. These sections are inch 
thick. 
Structure of the subcesoyhageal ganglion (PL XII, Fig. 10). — In its form 
this nerve center is more like the brain than the first thoracic ganglion. 
The figure is drawn from the youngest embryo observed. The ganglion 
seen in section is very much larger and quite different in shape from the 
thoracic ganglia. It expands above the lower fissure between the two 
sides, being very deep and narrow, while the superior farrow is broad 
and shallow. The internal paler portion (when magnified 400 diam- 
eters) is seen to consist of granules. The stratum of outer cells (the 
future ganglion cells) is thickest on the outside of the upper part of the 
ganglion, .and at the base of each hemisphere. 
The brain of the f reshly -ha tched larva of C. spretus. — In the larva but a 
few hours after hatching, the brain, so far as I can learn from four sec- 
tions, does not essentially differ from that of the embryo just before 
hatching, as the interval is apparently too short for a decided change to 
take place. It is evident that by the end of the first larval stage the 
brain attains the development seen in the third larval state of the two- 
banded species. 
For illustrations of the different larval and pupal stages of develop- 
ment of the locust the reader is referred to the first Report of the Com- 
mission (Plates I, II, III). 
Third larval stage of Caloptenus bivittatus (PL XIII, Fig. 1-3). — In the 
third larval condition of another species, the common Caloptenus bivit- 
tatus of our gardens, the different parts of the brain have attained 
nearly the same structure and proportions as in the adult. PL XIII, 
Fig. 1, represents a section passing through the front of the brain, and 
also the lateral ocelli and the right eye. The ganglion cells surrounding 
and filling the calices are smaller and more crowded than elsewhere. 
The mushroom bodies are now formed, though the trabecule are not to 
be seen in our section, but the entire double stalk and calices are very 
clearly seen. The fibers from the stalk are observed to extend along 
the inner edge of each calyx and to suddenly stop just beyond the mid- 
dle. The granular calices contain slight irregularities and sinuous lines, 
as shown in Fig. 2, i. cal., o ca., but to what these appearances are due 
it is difficult to say ; there are also a few scattered large granules. As 
the section passes through the front of the brain, where the hemispheres 
are separated by the frontal furrow, the lobes are not well marked, but 
the substance is made up of irregular intercrossing bundles of fibers, 
with the interspaces filled with granulated matter. In Fig. 3 the regu- 
lar saucer-like form of the calyx is well shown. Fig. 2 is an enlarged 
view of the right side of Fig. 1, and at this stage large important bundles 
of fibers are seen passing into the optic, antennal, and commissural 
lobes. 
