200 TORREY 



TEXT-FIGURE 5. 



Diagrams to indicate the direction of the shifting of the embryonic areas. Line 

 acb, egg axis ; line acp, anterior posterior axis of the trochophore ; bl, blastopore ; 

 /, area migrating from the prse-trochal region through the dorsal gap in the proto- 

 troch ; M, ccelomesoblast ; pr, prototroch ; x, ventral plate ; vl, ventro-lateralregion. 



