No. 2.] DEVELOPMENT OF MARINE ANNELIDS. 25 1 



a. 



<vet\tfal. proto 



Fig. VII. — Diagrams to express the essential difference in the axial relations and the manner of 

 formation of the trunk between Nereis (Wilson '), and A mpkiirite (this paper). A, B, C, and 

 D, Amphitrite ; E, F, and G, Nereis. Line acb, egg axis ; line acp, anterior posterior axis; 

 bp,, blastopore; RI, mesoderm; 7n.d., mid-dorsal region; l.d., latero-dorsal region; para., 

 paratroch ■,pr{?(a., prototroch; som.pl., somatic plate ; t., terminal region ; v.p., ventral plate,- 

 X, that part of somatic plate originally nearest the prototroch. 



