115 



Figure 75: Left and right hydropores 

 in the early larva of Asterias vulgaris 



(from Field, 1892). 



Ihc — left hydrocoel; Ihp — left 



hydropore; rhc — right hydrocoel; 



rhp — right hydropore. 



through contraction of the dorsal musv les, 

 which produces considerable flexion of .he 

 larva on the dorsal side (Strathmann, 1971, 

 Movement of the giant bipinnariae of Luidia 

 ciliaris and L. sarsi occurs through contrac- 

 tion of muscles in the elongate anterior part of 

 the larva; apparently, the ciliated bands of the 

 larvae of these species (unlike L. foliolata) do 

 not participate in locomotion (Tattersall and 

 Sheppard, 1934; Strathmann, 1971). 



Nervous system and sense organs : Ear- 

 lier authors assumed that larvae of sea stars 

 possessed a diffused nerve plexus under the 

 epithelial cover (Gemmill, 1914; Tattersall and 

 Sheppard, 1934). Burke (1983), while investi- 

 gating the nervous system of the bipinnaria of 

 Pisaster ochraceus using the glyoxalic method 

 and electron microscopy, observed no such 

 plexus, but demonstrated the presence of ax- 

 onal tracts at the base of the ciliated band and 



Figure 76: Development of coeloms in the bipinnaria of Asterias rubens (from Gemmill, 



1914). 

 ac — axocoel; Ihc — left hydrocoel; Is — left somatocoel; rs — right somatocoel; 



vh — ventral horn. 



