PLATE 3 



EXPLANATION OF FIGURES 



5 Cross section of the larva in the stage shown in figure 4 in a plane indicated 

 on figure 4 by the dotted line A-B. 



6 Cross section of the same larva in a plane indicated on figure 4 by the 

 dotted line C-D. 



ABBREVIATIONS 



Bp, Point at which the blastopore M, Stomodeuni. 



closed. RAE, Right anterior enterocoeie. 



G, Gut. RPE, Right posterior enterocoele. 



LAE, Left anterior enterocoele. R2, Anlage of radial canal No. 2. 



LPE, Left posterior enterocoele. RJt, Anlage of radial canal No. 4. 



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