205 



Figure 156: Ophiothrix savignyi (Mortensen, 1938). 



General view of the larva. 



b — basal rods; pd — posterodorsal arms; tpb — transverse processes of the basal rods. 



Remaining legend same as in Figure 154. 



Figure 157: Ophiocoma scolopendrina (Mortensen, 1937). 

 General view of the skeleton. Note the absence of processes on the basal rods. 



the hydrocoels begins. The left as well as the right hydrocoel remain con- 

 nected with the axocoel through small canals (Figure 159). The canal on the 

 left side of the larva later transforms into the stone canal. 



Locomotion : With the appearance of the fourth pair of arms, the ciliated 

 band enlarges but the pattern of larval movements does not change. Strathmann 

 (1971) determined that the speed of horizontal movement of the larvae 

 is roughly 0.5 mm/sec and the length of the cilia in the band 25-30 \x.m. At 

 this stage, in some species vibratile lobes bordered with cilia develop between 

 the posterolateral, postoral, and posterodorsal arms (Figure 160). Their 



