No. 19.] ECHINODERMS OF CONNECTICUT. 2/ 



an important function in the collection and discharge of the waste 

 products of the body. 



,..../rc. 



Fig. 2. Diagram of water-vascular system of starfish ; m, madre- 

 poric plate ; s. c, stone canal ; T, Tiedemann's body ; 0. t, oral 

 tentacle; t. f, tube-foot; amp, ampulla; r. c, radical canal; c. c, 

 connecting canal; r, ring canal. 



Circulatory System. — ■ A complex system of vessels running 

 parallel with the vessels of the water-vascular system is termed 

 the perihasmal system. The principal vessels of this system are 

 divided into two parallel chambers by a vertical septum. In 

 the septum is a smaller central canal which contains a small 

 amount of fluid, and is ' thought to constitute the true blood 

 system. This latter has therefore radial and circular canals, 

 parallel both to the water-vascular and to the perihasmal system. 

 The radial vessels are shown in section in Fig. i. 



Nervous System. — The nervous system consists of a nerve 

 ring surrounding the mouth, with a large radial nerve extending 

 outward along the roof of the ambulacral groove of each arm 

 and terminating in an orange-colored eye-spot at the tip of the 

 arm. From the radial nerves minute branches are given off 

 to each tube-foot and ampulla, to the superficial integument, 



