COMPLEX MECHANISM. 235 



teeth or jaws consist of five pieces of triangular 

 shape, fitting together into the form of a cone 

 in the centre of which is an additional tooth. 

 This cone occupies the middle of the orifice in 

 the base of the shell, and the teeth or jaws of 

 which it consists are attached to the arches around 

 the orifice, by means of powerful muscles, and 

 are furnished with others enabling them to work 

 upon each other so as to triturate and grind the 

 substances on which the animal preys. To this 

 purpose the jaws are so perfectly adapted that 

 very hard substances exposed to their action are 

 speedily reduced to a pulp. 



The elaborate and complex mechanism which 

 is presented to us in the structure of the sea- 

 urchin, cannot be perceived by the intelligent 

 and candid observer without those convictions 

 which consummate excellence in the adaptation 

 of animal mechanism rarely fails to originate. 

 (( In a moderate sized urchin," observes Professor 

 Forbes, ee I reckoned sixty-two rows of pores in 

 each of the ten avenues. Now as there are three 

 pairs of pores in each row, their number mul- 

 tiplied by six and again by ten, would give the 

 great number of three thousand seven hundred 

 and twenty pores ; but as each sucker occupies a 

 pair of pores, the number of suckers would be 

 half that amount, or eighteen hundred and sixty. 

 The structure of the egg-urchin is not less com- 

 plicated in other parts. There are above three 

 hundred plates of one kind, and nearly as many 

 of another all dovetailing together with the 



