SUCKING-FEET OP STAR-FISHES. 171 



In the true Star-fishes, or Asteriadce, the body itself 

 is divided into rays like those of a star. The rays are 

 channelled on their lower surface, and pierced by holes, 

 through which protrude a multitude of suckers, that 

 serve for organs of prehension, to grasp food, and for 

 organs of motion to enable the animal to change its 

 position. It is exceedingly curious to watch the activity 

 that exists among these numberless sucking-feet when 

 a living Star-fish is placed on its back in a shallow 

 vessel of water. If it had previously been touched on 

 the lower surface, all the feet will have recoiled within 

 the body, leaving nothing visible but a series of minute 

 tubercles ; but, when the Star-fish is allowed to recover 

 its ease, they will quickly issue, like so many worms, 

 from their holes, and, after moving backwards and for- 

 wards through the water, will bend round in the direc- 

 tion of the nearest ground : those that first reach it will 

 affix their suckers, and by contracting will pull down a 

 portion of the body, so as to enable others to attach 

 themselves, until, a sufficient number of suckers being 

 attached, their conjoint power is sufficient to bring 

 round the body of the Star-fish to its proper position. 

 These sucking-feet, or cirrhi, are tubular, and filled 

 with fluid when fully extended. The mechanism by 

 which they are extended is very simple. Each is con- 

 nected with a globular vesicle contained within the 

 body of the Star-fish immediately beneath the hole 

 from which the sucker issues. When the animal wishes 

 to extend the feet, the sides of the vesicle forcibly 

 contract, and in so doing propel the fluid which they 

 contain into the tubular feet, which then elongate and 



