plainly show, with the eye. Posteriorly, in the median line, it is 
connected by nearly its entire width, in the upper part, with the brain. 
The volume is about equal to that of the brain. Dorsally, the ganglion 
shows two small elevations, which have been described by WEISMANN 
as indicating an origin from two lateral ganglia. 
The brain is also pyriform, with its base directed upward and 
forward. Antero-dorsally, it is connected with the optic ganglion. 
Laterally, at about its middle, the oculomotor nerves pass out to the 
muscles. Ventro-laterally, near the apex, the antennal nerves are 
seen issuing and at the apex, ventrally, the two oesophageal nerves. 
The long axis of the brain about equals that of the optic ganglion 
and is two-thirds the diameter of the eye. In their greatest width, 
the brain and optic ganglion are about equal and are not quite one- 
half the diameter of the eye. The drawings of WEISMAnN do not 
show these proportions. 
The brain and optic ganglion are covered with a capsule which 
offers considerable resistance to many reagents. 
Internal structure of brain. From serial sections it is 
found that the brain is covered, except at the superficial origin of 
the nerves and over an area located dorso- laterally (Diagram 3), 
with cortical cells. The interior is composed of the medulla, or 
Punktsubstanz, which is divided by commissures and cells into distinct 
sub-divisions, and of three groups of nerve cells. 
The medulla and commissures. The arrangement of the Punkt- 
substanz is best made out in serial sections cut parallel with the 
dorsal surface. The medulla is everywhere continuous, though broken 
up by commissures and cells in places. Beginning at the dorsal 
surface, we note that the medulla is first undivided and crescentric in 
section (Diagram 1). Two dorsal antero-posterior commissures 
next appear and divide the single area into a median and two 
lateral areas (Diagrams 2, 3, 4). The commissures disappear ventrally 
and there is again a continuous, medullary area (Diagram 5). 
Two median antero-posterior commissures appear directly 
with a post-lateral commissure and the fibre bundles of the 
oculomotor nerves. These divide the medulla into several areas. The 
lateral (Hauptmarkballen) areas are divided into an anterior and a 
posterior area by the oculomotor nerves; the median antero-posterior 
commissures define a median area, which is sub-divided into a central 
(centraler Markballen) area and a posterior area by the post-lateral 
commissure (Diagram 6; Fig. 12). 
In the small and medium-sized cell group, posterior to and in 
