The Tunicates, or Ascidians 



475 



In the family Cynthiida the brightly-colored red and yellow 

 species of Cynthia are known as sea-peaches by the fishermen. 

 The sea-pears, Boltenia, are fastened to long stalks. These have 

 a leathery and wrinkled tunic, to which algae and hydroids 

 freely attach themselves. Into the gill-cavity of these forms 



FIG. 281. Stycla yacutatensia (Hitter), a simple Ascidian. Family Molgu- 

 lidce. Yakutat Bay, Alaska (After Ritter.) 



small fishes, blennies, gobies, and pearl-fishes often retreat for 

 protection. 



The social Ascidians constitute the Clavellinida . They are 

 similar to the Aseidiidte in form, but each individual sends out 

 a bud which forms a stem bearing another individual at the 

 end. By this means large colonies may be formed. 



The suborder, Ascidics composites, contains the compound 

 Ascidians or colonies enveloped in a common gelatinous "test." 

 These colonies are usually attached to rock or seaweed, and the 

 individuals are frequently regularly and symmetrically arranged. 

 The bodies are sometimes complex in form. 



