232 



THE MECHANICAL 1 UNCTIONS. 



sLiiTouud the opening of the mouth. (See Fig. 121.) 

 These feet, or arms, or tentacida, if we choose so to 



call them, are long, slender, and flexible processes, 

 exceedingly irritable, and contractile in every part, 

 and provided with numerous muscles, which are 

 capable of moving and twisting them in all direc- 

 tions with extraordinary quickness and precision. 

 They are thus capable of being employed as instru- 

 ments, not only of progressive motion, but also of pre- 

 hension. For this latter purpose they are in many 

 species peculiarly well adapted, because, being per- 

 fectly flexible as well as highly muscular, they twine 

 with ease round an object of any shape, and grasp 

 it with prodigious force. In addition to these pro- 

 perties they derive a remarkable power of adhesion 

 to the surfaces of bodies from their being furnished 

 along the whole of their inner sides with numerous 

 suckers, or acetabula. Each of these suckers, as 

 shown separately in Fig. 122, is usually supported 

 on a narrow neck, or pedicle, and strengthened at 

 its circumference by a ring of cartilage. Their 

 internal mechanism is more artificial than the 

 simple construction already described (p. 120): for 

 when the surface of the disk is fully expanded, as 



