PLATES 



EXPLANATION OF PLATES 



All drawings were made with the aid of the camera lucida under a magnification 

 of 130 diameters. All whole-mount drawings were made from either the fixed or 

 living egg and checked. Variations in the size of the surface views is due to a 

 difference in the size of the eggs. The sections were not uniformly magnified. 

 Stippling has been adopted for the sake of clearness. 



REFERENCE LETTERS 



a., anterior 



a. a., anterior antennae 



b.c, body cavity 



hi., bladder 



br., brain 



bu.c, buccal cavity 



b.w., body wall 



c, cilia 



C.C., cleavage cavity 



cin., cingulum 



C.I., cerebral lobes 



coe., coelom 



cid., cuticula 



d., dorsal 



d.a., dorsal arms 



d.g., digestive glands 



e., eye spot 



e.cp., egg capsule 



ect., ectoderm 



emb., embryo 



ent., entoderm 



ft., foot 



gn., ganglion 



i.e.sh., inner egg-shell membrane 



k.t., kidney tubule 



La., lateral antennae 



III., lumen 



J7i., muscle 



m.c, muscle cell 



mes., mesoderm 



m.f., muscle fiber 



7no., mouth 



n.h., ncphridial band 



oe., oesophagus 



o.e.sh., outer egg-shell membrane 



ov., ovary 



ovd., oviduct 



p., posterior 



p.b., polar body 



ph., pharynx 



pr., proctodaeum 



p.s., polar spindle 



r.t., recurrent tubules 



St., stomach 



sto., stomodaeum 



ta., tag (flame cell) 



tr., trochal disc (trochus) 



tro., trophi 



ts., testis 



u., uterus 



ur.s., urogenital sinus 



v., ventral 



v.m., vitelline membrane 



vt., vitellarium 



A, left macromere 



B, anterior macromere 



C, right macromere 



D, posterior macromere 



fli, b^, cS dS d^-S ect., first generation 

 of ectomeres 



a^, 6^, c^, d', a--S etc., second genera- 

 tion of ectomeres 



a', b^, c^, d^, a^-S etc., third generation 

 of extomeres 



E, entoderm (mesentoblast) 



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