STAR-FISH AND SEA-URCHINS. 285 
spines, and pedicellarize within reach of that part, and 
even beyond it, immediately converge and close in 
upon the needle, grasp it, and hold it fast. This simul- 
taneous movement of such a little forest of prehensile 
organs is a very beautiful spectacle to witness. In 
executing it the pedicellariz 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 pedicellariz 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 
pedicellarize—proof which we 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 pedicellarie, 
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 with their 
sucking discs. That the grasping and arresting of 
fronds of sea-weed in this way for the purposes of 
locomotion constitute an important function of the 
pedicellarize, may at once be rendered evident 
