182 THE MECHANICAL FUNCTIONS. 



with great force to these bodies, without the aid 

 of any gkitinous fluid. A conjecture, which has 

 much appearance of probabihty, has been 

 offered, that this power of adhesion is derived 

 from the presence of a great number of ex- 

 ceedingly minute disks, interspersed over every 

 part of the surface, constituting so many 

 suckers, and resembUng, though on a very 

 diminutive scale, the sucking apparatus on the 

 arms of the cuttle-fish. 



The Zoanthiis (Fig. 58) belongs to a tribe of 

 larger polypi, which are generally met with 

 assembled in clusters ; on which account it is 

 termed by Ellis the Actinia sociata, or cluster- 

 animal flower. It consists of a globular body, 

 having a mouth surrounded by one or two rows 

 of tentacula ; and connected below with a firm 

 and fleshy tube, which adheres strongly to the 

 rocks at the bottom of the sea ; so that it re- 

 mains permanently fixed in the same place. 



The genus Vorticella is formed by a small 

 tribe of animals, which, although they have 

 been usually included under the present order, 

 difier from Polypi in having no tentacula, but 

 only cilia, surrounding the margin of a bell- 

 shaped body, which is mounted upon a long 

 and slender foot-stalk (Fig. 77).* Currents are, 



* They also differ from Polypi in having a distinct intestinal 

 canal, with numerous stomachs. 



