1881. ] The Brain of the Embryo and Young Locust. | 375 
body is formed, but our sections do not show any traces of a 
mushroom body. The sections are frontal, and we will describe 
them in order. The fifth section is through the head and front 
part of the eyes, but does not graze the brain itself. 
Section 6 passes through the outer portion of the optic and an- 
tennal lobes, now clearly differentiated. 
In section 7 the cerebral lobes are seen, and in section 8 are 
larger, as are the optic lobes, while the antennal lobes are some- 
what reduced in size. Section 10 passes through the cerebral lobes 
and also grazes the optic lobes, passing through the optic ganglion. 
Section 11 shows the central body,-separated from the upper 
cerebral lobes by a thin layer of loose ganglionic cells. The re- 
lation of the central body to the upper and lower ee lobes 
is well shown in this section. 
Section 12 passes through the lower cerebral lobes and the upper 
left cerebral lobe and the optic ganglion. The cesophagus is 
situated beneath the cleft under the lower cerebral lobes. The 
next section (13) passes behind the brain, not touching it. These 
sections are sto inch thick. 
Structure of the Subesophageal Ganglion—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 furrow is broad and shallow. The internal paler 
portion (when magnified 400 diameters) 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 Jreshly-hatched Larva of C. spretus. —In the 
larva but a few hours after hatching, the brain, so far as I can 
learn from four sections, 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 Caloptenus. 
For illustrations of the different larval and pupal stages of de- 
velopment of the locust, the reader is referred to the first Report 
of the Commission (Plates 1, 11, 11). 
