114 



Figure 74: Development of coeloms in the bipinnaria of Patina peclinifera. 

 ac — axocoel; Is — left somatocoel; rs — right somatocoel. 



described in the section on feeding of the larva. The water current created by 

 the cilia of these bands enables the capture of food particles and concomi- 

 tantly locomotion of the bipinnaria. In this case the preoral lobe is directed 

 forward. In the bipinnariae of sea stars of the family Asteriidae, the size of 

 the processes increases with bipinnarial growth and they transform into long 

 movable arms. The posterolateral and posterodorsal arms (Figure 77) become 

 the longest (Gemmill, 1914; Kume and Dan, 1968). Since the ciliated band 

 extends over the elongate processes of the bipinnaria, the total length of the 

 band increases considerably. In many sea stars, however, the ciliated band 

 on the arms is not well developed and does not participate in the capture of 

 food; it functions only in larval locomotion. The beating of the cilia on the 

 arms is directed from the base to the tip of the arm. The speed of movement 

 of the bipinnaria of Asterias rubens is about 2.0 cm/sec (Konst^ntinova, 

 1966). Movement of the bipinnaria in a reverse direction is not performed by 

 reversal of direction of ciliary beating (as done in the pluteus), but rather by 

 the larva turning around. The bipinnaria executes a turn during swimming 



