SEA-FISHERIES LABORATORY. 213 



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 setae 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 

 setae 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. 

 Excepting 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 setse scattered over 

 the surface of the body and appendages, which are possibly 

 tactile in function. Probably the seta3 upon the anten- 

 nules, which are richly supplied with nerves from the 



