Sensory Organ of Star-fish 61 



organs and its circum-oral or central nervous 

 system. 



With reference to the instinctive behaviour 

 of Echinodermata, an ordinary star-fish is able 

 by the use of one or more of its arms and sucker 

 feet to hold on to the bottom or to the sides of 

 its tank; the muscles of the arm then contract 

 and draw the animal's body up to the point its 

 feet have grasped ; it thus moves forward, either 

 along the bottom or up the side of the tank. 

 When a star-fish reaches the surface of the 

 water it comes to a stand, as its sucker feet can 

 only act efficiently beneath the water. Under 

 these conditions a star-fish stretches out its 

 uppermost arms along the surface of the water 

 so as, if possible, to meet with something it can 

 cling to; if it succeeds in doing this, it relin- 

 quishes its hold on the side of the tank and 

 swings itself on to the object it has grasped. 

 Mr. Romanes remarks with regard to behaviour 

 of this kind that the activity and co-ordination 

 manifested by the animal's acrobatic move- 

 ments are surprising, and have almost an intel- 

 ligent appearance. 1 



1 Romanes on Jelly-fish, p. 269. 



