286 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



experimentally b}^ drawing a piece of sea-weed over 

 the surface of a healthy Echinus in the water. The 

 moment the sea-weed touches the surface of the 

 animal, it is seen and felt to be seized by a number 

 of these little grasping organs, and — unless torn 

 away by a greater force than is likely to occur in 

 currents below the surface of the sea — it is held 

 steady till the ambulacral suckers have time to 

 establish their attachments upon it. Thus there is 

 no doubt that the pedicellarise are able efficiently 

 to perform the function which we regard as 

 their chief function. We so regard this function, 

 not merely because it is the one that we observe 

 these organs chiefly to perform, but also because 

 we find that their whole physiology is adapted 

 to its performance. Thus their multitudinous 

 number and ubiquitous situation all over the 

 external surface of the animal is suggestive of 

 their being adapted to catch something which may 

 come upon them from any side, and which may 

 have strings and edges so fine as to admit of being 

 enclosed by the forceps. Again, the instantaneous 

 activity with which they all close round and seize 

 a moving body of a size that admits of their seizing 

 it, is suggestive of the objects which they are 

 adapted to seize being objects which rapidly brush 

 over the surface of the shell, and therefore objects 

 which, if they are to be seized at all, must be ionized 

 instantaneously. Lastly, we find, on experiment- 

 ing upon pedicellaria^, whether in sitit or when 

 separated from the Echinus, that the clasping action 

 of the forccp.^ is precisely adapted to the function 



