74 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



pebbles, or other objects by the serpentine movements of these 

 arms, and can also swim free in the water by moving a pair of 

 arms much as we would move our own arms in swimming. 

 When placed upon its aboral surface the animal can quickly 

 recover its normal position. 



In ordinary locomotion one or more of the arms are clasped 

 about an object and the rest of the body drawn forward to that 

 position, when the same or adjacent arms reach out again to an 

 advanced position and the animal moves rapidly forward. The 

 more posterior of the arms help push the body along at the 

 same time that those in front are pulling. 



There is no definite orientation of the body, and any of the 

 arms may go in front, so that when the animal desires to change 

 its direction it does not turn the body, but merely advances an 

 arm which was previously in the rear. It may thus go in any 

 direction without turning the body. 



When spines are well developed along the sides of the arm 

 they aid materially in furnishing a means of attachment to any 

 desired object. The rudimentary tube-feet, or tentacles, also aid 

 the arm in keeping its hold, although they are not provided with 

 the sucking disks present in those of the starfish and sea-urchin. 



The motion of the arms is controlled by the circumoral nerve 

 ring. When this ring is cut, the movements of the adjacent 

 arms are impaired; and, when it is cut between each pair of 

 adjacent arms, coordinated movements are entirely destroyed. 



The habits and response to stimuli of these animals have been 

 the subject of much study in recent years. Cowles has recently 

 shown* that the tube-feet are capable of selecting food materials 

 with much precision and passing them from one tube-foot to 

 another until the mouth is reached. Even when removed from 

 the body the arm still reacts to food, and nutritive particles are 

 carried from tip to base of the severed arm, while inorganic 

 objects are seized and quickly dropped. 



The ophiuran reacts positively to solid vertical walls, and 

 the effect of such a stimulus is retained for some time, for when 

 an animal is removed a short distance from its hiding place it 

 moves in the direction of the same spot without error. This 



* Stimuli Produced by Light and by Contact with Solid Walls as Factors in the 

 Behavior of Ophiuroids. Journ. of Exp. Zool., vol. ix, 19 10. 



