STAR-FISH AND SEA-URCHINS. 285 



spines, and pedlcellari?e within reach of that part, and 

 even beyond it, immediately converge and close in 

 u[)on the needle, grasp it, and hold it fast. This simul- 

 taneous movement of sucli a little forest of prehensile 

 organs is a very beautiful spectacle to witness. In 

 executing it the pedicellarici3 are the most active, 

 the spines somewhat slower, and the feet very 

 much slower. The area affected is usually about 

 half a square inch, although the pedicellarise even 

 far beyond this area may bend over towards the 

 seat of stimulation, which, however, from their small 

 size they are not able to reach. 



And here we have proof of the function of the 

 pedicellariie — proof which w^e consider to be im- 

 portant, because, as I have before said, the use of 

 these organs has so long been a puzzle to naturalists. 

 In climbing perpendicular or inclined surfaces of 

 rock, covered with waving sea-weeds, it must be of 

 no small advantage to an Echinus to be provided on 

 all sides with a multitude of forceps, all mounted 

 on movable stalks, which instantaneously bring 

 their grasping forceps to bear upon and to seize a 

 passing frond. The frond being thus arrested, the 

 spines come to the assistance of the pedicell arise, 

 and both together hold the Echinus to the support 

 furnished by the sea-weed. Moreover the sea-weed 

 is thus held steady till the ambulacral feet have 

 time also to establish their hold upon it w^th their 

 sucking discs. That the grasping and arresting of 

 fronds of sea- weed in this way for the purposes of 

 xocomotion constitute an important function of the 

 pedicellarige, may at once be rendered evident 



