42 FIRST LESSONS IN ZOOLOGY. 



It will thus be seen that the water-vascular system in the starfish is 

 in its functions partly respiratory and partly locomotive, while it is in 

 connection with the vascular system, and thus partly aids in circulat- 

 ing the blood and chyle. There is, besides, a complicated system of 

 true blood-vessels, which are, however, difficult to discover. 



By placing a living starfish in a tank of water one can 

 see how it moves by means of its suckers. When turned 

 upon its back, it can right itself in the following manner: 



FIG. 40. A starfish, which has heen placed on its back, righting itself. 



it twists round the tip of one or more of its rays (Fig. 40) 

 until the feet there situated are able to get a firm hold of 

 the floor of the tank (a); then, by a successive and similar 

 action of feet farther back in the row, the whole ray is 

 twisted round (b), so that the ambulacral surface of the 

 end is applied flat against the floor of the tank (c) ; the other 

 rays or arms then turn, and the starfish is right side up. 

 Mr. Romanes, from whom we have taken the foregoing 

 account; has also proved that the little red spots at the ends 



