56 Journal of Entomology and Zoology 



The parts of the nervous system are : 



1. The superficial radial nerves. The chief branches: (a) 

 muscular nerves, (b) cutaneous nerves to tube-feet and to skin and 

 to spines. On each nerve to the tube-feet a ganglion is formed at 

 base of each tube-foot and strands run dorsally and centrally to the 

 intervertebral ganglia and ventrally to the two ventral ganglia or 

 epineural ganglia, (c) branches communicating with the lateral 

 nerves of the disc on each side of each radial nerve which in turn 

 have altogether 10 interradial nerves near the center of the disc 

 and branches to the superficial nerve plexus. 



2. The superficial oral nerve is pentagonal in shape and gives 

 off: (a) nerves to the stomach, (b) a pair of dental nerves. 



3. The deep radial nerves give off nerves to the muscles of the 

 arms. 



4. The deep oral ring gives off: (a) interradial superior 

 nerves, (b) interradial internal nerves. 



5. The genital nerves, independent of the others. Five dif- 

 ferent nerves between each radial area in the disc. 



There are no eyes. The skin has no cuticle except at certain 

 points and these are the only ones where sense cells are located. 

 The tube-feet and spines are sensitive to touch. The palps are 

 sensitive to touch as well as parts of the general surface. The 

 extremity of the palps have sensory functions. The terminal 

 tentacle, it is thought, may be olfactory in function. The oral 

 palps have sensitive papillae well supplied with nerve cells. 



The structure of the nervous system is somewhat like star- 

 fish but the central cords are parallel with more evident nerve cells 

 and the strands seem to have a more complicated structure. 



Hamann's work is perhaps the most valuable in this group. 

 Delage and Herouard make chief use of this in their work. Teus- 

 cher 1876, Land, '76, Smith, '79, and Ludwig, '80, are the other 

 chief contributors who have considered the nervous system. 



