1881.] The Brain of the Locust. 299 
The lobes are, as described by the other observers, filled with 
ball-like yellowish masses, which stain dark by osmic acid, much 
as in the commissural lobes. Nerve fibers are seen in section 19 
to pass from one antennal lobe to the other in the rear of the cen- 
tral body and of the trabeculae, while other nerve fibers are seen 
to pass into the optic lobes and the commissural lobes. This 
system. of intra-lobal nerves demonstrates that there is a nervous 
intercommunication between these cerebral lobes and the gan- 
glionic chain of the entire body. 
The Commissural Lobes.—From these large bodies proceed the 
two great longitudinal commissural nerves, forming the connect- 
ing threads of the nervous cord, and which extend from the brain 
to the last abdominal ganglion, passing through the intermediate 
nerve centers. The lobes are filled with ball-like masses, of the 
same general appearance as in the antennal lobes, but more dis- 
tinct and numerous. 
Comparison of the Brain of the Locust with that of other insects. 
—Newton rightly regards the cockroach’s brain as a generalized 
form of brain, which may serve as a standard of comparison. 
The cockroach is geologically one of the oldest of insects; its 
external and internal structure is on a generalized plan, and the 
brain conforms to this order of things. Our knowledge of the 
cockroach’s brain is derived from the photographs and account 
of Flogel, and Newton’s excellent descriptions and figures, sup- 
plemented by two sets of sections made for us by Mr. Mason, but 
which unfortunately, are quite defective as regards the trabecule 
and stalk of the mushroom body. The shape of the calices of 
the cockroach, as already stated, is very different from that of 
these bodies in the locust, and indeed from any other insect yet 
examined, the cup being very deep and the sides thin; but the 
intimate structure seems nearly the same in the two insects. 
In the cockroach the antennal and commissural lobes are of 
much looser texture, with large and numerous ball-like masses 
(ballensubstanz); these are, when magnified 400 diameters, not 
only larger, but more distinct from the rest of the nervous matter 
of the lobe than in the locust. When magnified, as mentioned, 
the ball-like masses appear to be simple masses of finely granular 
nervous matter, with darker granules, mtich like the rest of the 
granular portions of the brain, but with coarser granular masses 
than in the substance of the optic lobes. These ball-like masses _ 
