292 SUCKERS AND PORES. 



Situated at regular intervals between the tubercles 

 are ten broad bands, disposed in pairs, and contain- 

 ing many hundreds of very minute perforations, or 

 ambulacral orifices, as they are generally termed by 

 naturalists. 



Through these apertures issue numerous sucker- 

 like feet, closely resembling those of the Star-fish, 

 but endowed with far greater powers of contraction 

 and extension. 



The number of suckers is very great. In an 

 Urchin measuring exactly three inches in diameter, 

 by aid of a hand lens, I counted no less than 3300 

 pores in the ten avenues. Now, these pores are 

 always situated in pairs, and as each sucker occupies 

 a pair of pores, it will give 1650 as the total amount 

 of suckers. 



There is no doubt that it is almost entirely by 

 means of these curious organs that the Sea-Urchin 

 is enabled to move about from place to place, al- 

 though no less an authority than Professor Agassiz 

 asserts to the contrary. ' How, in fact/ says this 

 author, ' could these small tentacula, situated as they 

 generally are in that part of the body which is never 

 brought into contact with the ground when the 

 animal moves, and overhung by calcareous solid 

 spines how, I ask, could these flexible tubes be 

 used as organs of motion ? It is an undeniable fact, 

 and I have often observed it myself, that it is with 

 their spines the Echini move themselveSj seize their 



