CHAPTER IV 



CIRRI OF BARNACLE AND 

 SPINES OF ECHINI 



Radulae. 



A T all times the ' tongues ' of the gaster- 

 -* opoda form very attractive objects for 

 microscopic observation, inasmuch as they dis- 

 play a marvellous arrangement of elegant horny 

 or chitinous teeth. The teeth are arranged in 

 patterns and rows with mathematical precision. 

 By their number, position, and arrangement 

 as well as by their individual shapes they are 

 of importance in characterising the families, 

 genera, &c. 



The c tongue ' in every instance greatly assists 

 the creature either as a rasp for grinding sea- 

 weed, or as a hole-borer when used for drilling 



57 



