85 
of the stomach. The next pair supply the second pair of 
feet. They course along the median nerves as far as the 
sternal fork and then diverge. Just under the sternal 
fork a branch is given off which appears to pass to the 
muscles of the posterior region of the cephalo-thorax. 
The median pair course close together, and unless 
carefully examined are easily mistaken for a single nerve. 
There is a distinct division, however, which is apparent 
even in the roots. Between the second and third pairs 
of feet a strong branch is given off which passes to the 
third pair of feet. The nerves then diverge, and just 
before entering the fourth thoracic segment give off a 
branch that passes to the fourth feet. The main trunks 
course on through the genital segment, still further 
diverging. Shortly after entering the broad part of this 
segment a third branch is given off which takes a semi- 
oval course along the ventral surface of each half of the 
segment, finally passing to the sete of the fifth feet. On 
entering the abdomen the main trunks split into two 
branches, one passing to the anus and the other to the 
sete on the apex of the caudal stylets (Plate III., fig. 2). 
Each nerve, after leaving the main trunk, sends out 
numerous branches which pass to the various muscles 
controlling the appendages innervated by that nerve. 
[xcepting the nerve passing to the fifth feet, the branches 
are not shown in the figure (Plate III., fig. 1). There 
is considerable difficulty in tracing the endings of the 
branches when they pass amongst the muscles. 
The chief sense organs connected with the nervous 
system are the conspicuous eyes which are described above 
(p. 71). There are also the numerous sete scattered over 
the surface of the body and appendages, which are possibly 
tactile in function. Probably the setae upon the anten- 
nules, which are richly supphed with nerves from the 
