130 Wisconsin Academy of Sciences, Arts, and Letters. 
ventral ganglia; there are no doubt glands for the other appen¬ 
dages'. 
Nervous System: —My account is restricted to. the brain and 
ventral cord; the nerves arising from these were so small that, 
while in some instances I could distinguish their origin, I was 
unable to follow them into' the parts' of the body they supplied. 
Most of the nerves have already been worked out by Zenker 
(19), Claus (3), Yavra (17), and Turner (16). The optic 
nerves, the only ones I could trace-, arise from the anterior part 
of the dorsal surface of the fore-brain and pass- directly up¬ 
ward to the eyei. The distance between the brain and eye is 
very short and in only one section could I distinguish the optic 
nerve. Tromj this section it was impossible for 1 me to say 
whether one or three nerves went to- the eye-. 
Brain :—Sagittal sections, both median and lateral, through 
the brain, supra-oesophageal ganglion, shows- a difference be¬ 
tween the anterior and the posterior surfaces, PI. XIII, figs. 21 
and 23. The anterior face is convex and entirely covered with 
nerve cells, the posterior concave face' shows the nerve cells cov¬ 
ering only the dorsal third of its surface'. The axis- of the brain 
is inclined so that dorsally it runs slightly forward. The upper 
end is rounded and continues into the optic ganglion (fore¬ 
brain, Yavra) which is slightly constricted off from that part 
of the brain lying directly underneath it. In these lateral 
views no other divisions of the- brain are seen; the nerve cells 
on the anterior surface appear greatest in number' just above 
the oesophagus, decreasing toward the optic ganglion. 
In PL XIII, fig. 23 is shown a transverse section of the brain 
cut as represented by the line ab in fig. 21. Here the fore¬ 
brain is shown quite distinctly, the fibrillar substance indicat¬ 
ing by its bi-lobed appearance its double origin; the third gang¬ 
lion supposed to take part in its formation not being shown. 
Just ventrad to this, along the lateral surface, are two small 
groups of nerve cells which represent the antemnulary ganglia; 
still more ventrad, near the oesophagus, the ant-ennary ganglia 
can be seen. The short circum-oesophageal commissures con¬ 
verge towards each other as they pass; around the oesophagus 
below which they unite to form the large infra-oesophageal 
