the mesenchyme and part of the oesopha- 

 gus removed. 



Figure 7. The left half of the same larva. 



Figure- G. Transverse section through stage "C" in 



a plane indicated on Fig. 6. by the letters 

 a-b. 

 Figure 9 .The reconstructed internal anatomy of a 



larva in stag? "D" the ventral ectoderm 

 removed and with it part of the oesophagus . 

 Figure 10. An outline drawing of Fig. 0. on which 



are indicated by lines the planes of the 

 sections which follow in Figs. 11,12,13 

 and 14. 

 figure 11 .Longitudinal section taken through a lar- 

 va in stage "D"in the plane indicated on 

 Fig. 10. by the line m-n. 

 Figuresl2,13 and 14, Transverse sections taken through 

 stage "D" in planes indicated on Fig. 10. 

 by the linos a-b,c-d and e-f . 

 PLATE II. 

 Figure 15 .Ventral view of a larva in staged" to 



show the ciliated bands and first appear- 

 ence of the arm rudiments. 



