np.pl 



fr.brtd 



prut 



prut |Q| 



l.rnus -V 

 itetsacs * 



nenrpl 



-prut 



KLjL-JMod 



7/ara 



tent 



FIG. 362. Nereis. Later stages in the development. A, stage at which the prototroch and the 

 apical tuft of cilia first become distinct. B, somewhat later stage, hi which the stomodaeal 

 invagination is being formed, and the rudiments of the mesoderm bands are distinct ; C, late 

 trochophore stage, in which there are rudiments of the setigerous sacs ; D, somewhat later 

 stage, in which the parapodia have begun to become prominent and the provisional setae 

 project freely ; B, larva with three segments, an. anus ; ap. til. apical cilia ; ap. pi. apical 

 plate ; eye, eye ; fr. bod. frontal bodies ; int. intestine ; 1. mus. longitudinal muscle ; mes. 

 mesoderm ; mo. mouth ; neur. pi. neural plate ; para, parapodia ; pig. ar. pigmented area ; 

 prot. prototroch ; tens. h. sensory hairs ; set. sacs, setigerous sacs ; sorn. second somatoblast 

 and group of cells formed from it ; st. stomodaeum ; tent, peristomial tentacles. (After 

 E. B Wilson.) 



442 



