PSYCHE, 267 
head, separate again and run side by side 
beneath the muscular mass which occu- 
pies most of the head, over the double 
cephalic ganglion and curve over toward 
the labrum. Before these two opposite 
branches first unite they emit from their 
anterior surface similar parallel branches, 
which also run beneath the muscular 
mass toward the anterior and lower part 
of the head; some curve upward and 
embrace the muscular mass from below ; 
half way between the spiracle and the 
top of the head, this arching branch 
emits from its posterior surface a slender 
offshoot, which, together with another 
branch, coming almost direct from the 
spiracle, passes toward the tracheae of 
the opposite side, unites at the median 
line with a similar set from the opposite 
tracheae, and then terminates. 
Circulatory system. The dorsal ves- 
sel is a straight tube, lying along the 
middle of the back, next the integument, 
and seems to be composed of an exces- 
sively delicate, whitish, pellucid film, 
is searcely 0.5 mm. in diameter, uni- 
form throughout, and terminates at 
the very end of the body in a_ well 
rounded tip. 
Nervous system. Viewed from above, 
the cephalic ganglia consist of a pair of 
short, obovate, nearly globular lobes, 
closely joined by their inner edges ; they 
are situated in the very middle of the 
head, just above the commencement of the 
alimentary canal, and on a level, above, 
with the top of the frontal triangle. 
From the lower anterior outer angle of 
each lobe, the optic nerve, large at base, 
but gradually tapering beyond, passes 
downward, forward, and outward, in a 
straight course toward the ocelli; as 
it reaches them it expands 
broad field comprising the ocelli,— black 
conical masses, their apices plunged 
in the nervous tissue forming the field. 
Just behind the origin of the optic nerve 
another independent nerve arises, ex- 
tending to the upper portion of the ten- 
dinous cord which terminates the great 
muscular mass of the head and moves 
the mandibles. A little further removed 
from the optic nerve, and on the lower 
anterior edge of each lobe, a little within 
the middle, another slender nerve arises, 
which runs in a straight course to the 
base of the antennae. 
From the lower outer edge of each 
cephalic lobe a nervous cord passes down- 
wardand a little backward, the two em- 
bracing the oesophagus, and then con- 
verges until they unite in the suboesopha- 
geal ganglion, ahorizontal lenticular disk, 
situated at the base of the head just 
above its hinder edge; just beneath the 
oesophagus these embracing cords are 
united by a cross thread; this sub- 
oesophageal ganglion throws out lateral 
nerves, directed forward and outward, 
and is strapped in its place by transverse 
muscles, one just in front and another 
just behind it, which originate together 
on the floor of the body; and the hinder 
of which is strengthened on each side by 
a secondary muscle, which runs back- 
ward beside the cord for a short distance, 
divaricating slightly. 
The ganglia of the body-segments are 
situated in or near, generally a little in 
advance of, the middle of each segment, 
as far as the seventh abdominal segment, 
where there is a pair, in close proximity, 
into a 
