FIRST LESSONS IN ZOOLOGY. 



class comprises the sea-cucumbers or Holothurians. In the 

 sea-cucumber, as its name implies, the body is usually long, 

 cylindrical, with a tendency to become worm-like. The skin 

 is not solid, and is muscular. Around the mouth are situ- 



FIG. 50. Pentacrinus. b, disk with mouth. (Natural size.) 



ated the ten branching gills, while there are usually suckers 

 arranged in five rows along the body. 



The trepang or beche-le-mer (Holothuria edulis) is col- 

 lected in the Moluccas and Australian seas, and when dried 

 is sold for soups in Chinese markets. 



The infant Holothurian (Fig. 51, A) is a transparent, 



