VII 



PHYLUM ECHINODERMATA 



173 



4. THE HOLOTHUROIDEA 



Also widely different from the Star-fishes in the general 

 form of the body are the Holothurians (class Holothuroidea). 

 Some of these are known as Sea-slugs from their slug-like 

 appearance, others as Sea-cucumbers. One is termed the 



FIG. 91. Cucumaria planci. Entire animal seen from the ventral surface. 

 (From Hertwig's Lehrbiich, after Ludwig!) 



" Cotton-spinner " from the cottony filaments which it 

 discharges when irritated or removed from the water. 

 Certain large tropical forms which abound on coral reefs in 

 the Pacific are used as food, and form the object of a fishing 



