1881. ] The Brain of the Embryo and Young Locust. 377 
diameters, the relation of parts being exactly as in the adult (see 
Pl. 11, Fig. 3). The base of the two divisions of the double stalk 
arise suddenly, as if inserted into or resting simply upon, rather 
than arising from, the trabecule; the bases of the cauliculus and 
peduncle being in the same line with the base of the center of 
the upper division of the central body. It appears as if a few 
nerve fibers passed under the base of the stalk between it and the 
trabecula; at any rate, I have been unable to observe either in 
the pupa, or larva, or adult among a number of preparations, any 
continuity between the trabecule and the double stalk. 
In this section the curving of the double stalk backwards and 
the passage in front of this double column is to be clearly seen, 
and is just as we have described it from similar sections of the 
adult brain (Fig. 3 of Pl. 1). The ball-like masses in the ceso- 
phageal commissures are as distinctly shown as in the adult. 
Section 11 passes behind the central body, not showing it nor 
the basal part of the double stalk of the mushroom body. This 
section, and those behind it, show well the structure of the optic 
ganglion. In section 11 the three lenticular bodies clearly 
appear. 
The main, and almost the only difference between the second 
pupa and the adult appears to be in the degree of development of 
the central body. In the second pupa (PI. rv, Fig. 3) it is rather 
more elementary than in the adult, the upper and lower series of 
unicellular bodies being a little shorter and rounder, nearer their 
primitive condition, and the septa between them are plainly 
fibrous. Their contents are as finely granular as the adjoining 
parts of the body. 
Section 11 is instructive as showing a bundle of directly 
ascending and obliquely ascending fibers from the back part of 
the trabecula, of which a portion is contained in the section. 
Two large bundles enter the commissural lobes, one from above 
and one from the inner side under the central body, the bundle 
from above passing down into the lobe from around the upper side 
of the trabecula. From this fact we should infer that there is a 
partial nervous communication between the trabeculae and the 
commissural lobes. The fibers enveloping the trabecula above 
are more numerous, the mass of fibers much thicker than in sec- 
tion 10, showing that what we supposed to be fibers separating 
the stalk from the trabecula appear to be really such. 
