1881.] The Brain of the Locust. 297 
nervous connection with the rest of the brain. This section also 
clearly indicates the origin of the optic nerve, which passes behind 
the stalk of the mushroom body, and also the relation of the fibers 
of the stalk to the calices, as they appear to penetrate far into the 
interior of the body of each calyx. 
The Double Stalk (cauliculus and peduncle ).—These names are 
applied to the larger and smaller divisions of the stalk of the 
“mushroom body.” They are represented in the eighteenth sec- 
tion (Fig. 4) where the outer part of the stalk (cawliculus) sup- 
ports the outer calyx, and the inner slenderer column of fibers 
supports or ends in the inner division of the calyx. These two 
bundles of fibers are somewhat curved, but as they do not appear 
in sections 16 and 19, must be less than séo of an inch thick. 
Their fibers are seen to penetrate deeply into the base of the 
calices, and thus to directly communicate with the fine granular 
substance of the calices. 
Lhe Calices.—The cups of the mushroom bodies in the locust 
differ decidedly in form from those of the cockroach, and this 
part of the mushroom body is more variable in form in the differ- 
ent orders of insects than any of the other parts of the brain. It 
is nearly obsolete, or, as Flogel states, ‘‘ not more than rudiment- 
ary” in hemipterous insects (notably Syromastes), and is less 
completely developed in many smaller moths, beetles, and flies, 
as well as Neuroptera (_4schna), according to Flogel, than in the 
larger moths, in the Orthoptera, and especially in the Hymenop- 
tera, where it is well developed. We have been unable to find it as 
yet in the brain of myriopods or of the spider. In the locust each 
body is more or less rounded and rudely saucer-like rather than 
cup-like, with the rim very thick; the hollow of the cup, if it be 
hollow, is small in proportion to the thickness of the saucer-like 
cup. The diameter of a calyx is about sic. The anterior edge 
reaches to the front edge of each hemisphere of the brain, but 
does not extend to the back part of the brain. The relations ina 
vertical, z. ¢., longitudinal section of the mushroom body to the 
rest of the brain are seen in Pl. 1, Fig. 8a. It thus appears 
that the double stalk is situated near the center of the brain, and 
that the cup projects far forward, but posteriorly does not extend 
behind the antennal lobes or the commissures. In section 18 
(Fig. 4) the calices are seen to be double, the outer (a. ca/. ) attached 
to the cauliculus (caw.) and the inner arising from the peduncle. 
VOL, XV.—NoO, IV. ar 
