ECHINODERMATA. VERMES. 263 



ing calcareous granules. One end, the head, is abruptly 

 terminated, and has a simple aperture for a mouth, en- 

 circled with feathery tentacles. There are usually five 

 longitudinal rows of ambulacral suckers, but only three 

 are used for locomotion, of which one is more developed 

 than the rest. The mouth opens into a pharynx leading 

 to a long intestinal canal. Holothurians have the singular 

 power of ejecting most of their internal organs, surviving 



FIG. 215. Sea-slugs (Hulothuria). 



for some time the loss of these essential parts, and after- 

 wards reproducing them. They occur on nearly every 

 coast, especially in tropical waters, where they sometimes 

 attain the length of three or four feet. As found on the 

 beach after a storm, or when the tide is out, they are 

 leathery lumps, of a reddish, brownish, or yellowish color. 

 They may be likened to a Sea-urchin devoid of a shell, 

 and long drawn out, with the axis horizontal, instead of 

 vertical. 



Subkingdom IV. YERMES. 



The Yermes, 138 or Worms, form the lowest subkingdom 

 of the bilaterally symmetrical animals. The group in- 

 cludes animals very different in form and rank, and the 

 different classes are widely separated from each other. 



