]68 POPULAR HISTORY OP THE AQUARIUM. 



Digestive Organs. 



In some cabinets may be seen a conical body composed 

 of a circle of complicated bones^ ending at the apex in a 

 circle of teeth meeting in the centre. These bones and 

 teeth are the biting and grinding apparatus of our Echinus. 

 They are placed in the centre of the body, with their grind- 

 ing surfaces towards each other, and united by very power- 

 ful muscles : altogether a most formidable and compHcated 

 engine of attrition. Scattered over the surface of the shell 

 are great numbers of small bodies among the spines, called 

 pedicellariiBj the use of which is not yet ascertained. They 

 have been considered by some naturalists as parasitic animals 

 living on the Echinus. But there seems to be Httle reason 

 to doubt that they are some organs belonging to the Sea-Egg 

 itself. Tliey are cylindrical bodies, fixed by a slender pedi- 

 cle, and terminating in a set of pincers. They are flexible, 

 and bend about in various directions. The pincers consist 

 of three beautifully sculptured teeth, some sharp and long, 

 others shorter. On the possible purpose for which the 

 Echinus is provided with these organs, Mr. Sans suggests 

 that Nature may have given the pedicellarm, in addition 

 to the spines and suckers, "as a sort of antennse, partly to 



