228 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
and ocellar nerves and posterior eominissures originate from the large 
ganglion cells which in this animal are situated in or near the center of 
the brain. In the last abdominal ganglion also the fibers arising from 
the peripheral ganglion cells can very plainly be seen passing in towards 
theeeuterof the ganglion and mingling with the libers forming it. Hence 
in all probability the fibrous mass of the central part of the brain mostly 
originates from the peripheral or cortical ganglion cells. 
To briefly describe bhe brain of the locust, it is a modified ganglion, 
but structurally entirely different from and far more complicated than 
the other ganglia of the nervous system. It possesses a "central body," 
and in each hemisphere a " mushroom body," optic lobe, and optic gan- 
glion, and olfactory lobe, with their connecting and commissural nerve 
fibers, not found in the other ganglia. In the succeeding ganglia the 
lobes are in general motor; the fibers composing the oesophageal commis- 
sures, and which arise from the oesophageal commissural lobes, extend 
not only to the subcesophageal ganglion, but pass along through the suc- 
ceeding ganglia to the last pair of abdominal nerve centers." 26 Since, 
then, there is a direct continuity in the fibers forming the two main lon- 
gitudinal commissures of the nervous cord, and which originate in the 
brain, it seems to follow that the movements of the body are in large 
part directed or co-ordinated by the brain.-* 27 Still, however, a second 
brain, so to speak, is found in the third thoracic ganglion of the locust, 
which receives the auditory nerves from the ears situated in the base of 
the abdomen ; or in the first thoracic ganglion of the green grasshoppers 
(katydids, &c), whose ears are in their fore legs ; while even the last ab- 
dominal ganglion in the cockroach and mole cricket is, so to speak, a sec- 
ondary brain, since it receives sensory nerves from the caudal stylets 
which are provided with sense organs. 
Description of the sections of the brain. — We will now describe the sec- 
tions upon which the subsequent account of the brain is founded. The 
sections, unless otherwise stated, are frontal,i. e., cut transversely across 
326 We have seen that the two great longitudinal commissures pass directly from the brain into and then 
pass backward from the subcesophageal ganglion, but beyond that point have not traced their course, 
as it is generally supposed that they extend uninterruptedly to the last abdominal ganglia. This has 
indeed been shown to be the case by Michels in his admirable treatise on the nervous system of a beetle 
(Oryctes) in Siebold and Kolliker's Zeitschrift fur wissen. Zoologie, Band 34, Heft. 4, 1880. Michels 
states that each commissure is formed of three parallel bundles of elementary nerve fibers, which pass 
continuously from one end of the ventral or nervous cord to the other. "The commissures take their 
origin neither out of a central "punet substanz (ormarksubstanz), nor from the peripheral ganglion cells 
of the several ganglia, but are mere continuations of the longitudinal fibers which decrease posteriorly 
in thickness, and extend anteriorly through the commissures forming the oesophageal ring to the 
brain." 
327 The following extract from Xewton's paper shows, however, that the infra or subcesophageal gan- 
glion, according to Faivre, has the power of co-ordinating the movements of the body ; still it seems 
to us that the brain may be primarily concerned in the exercise of this power, as the nerves from the 
subcesophageal ganglion supply only the mouth parts. "The physiological experiments of Faivre in 1 857 
(Ann. J. Sci. Nat., torn, viii, p. 245), upon the brain of Dytiscus in relation to locomotion, are of very 
considerable interest, showing, as they appear to do, that the power of co-ordinating the movements of 
the body is lodged in the infra-cesophageal ganglion. And such being the case, both the upper and 
lower pairs of ganglia ought to be regarded as forming parts of the insect's brain." Quart. Jour. Micr. 
Sc., 1879, p. 342. 
