PLATE 2 



EXPLANATION OF FIGURES 



5 Embryo of Entosphenus wilderi, 191 hours old. The black area represents 

 the germ-cell region. The line ab is the plane of the section in figure 11. 



6 Embryo 238 hours old. The shaded area indicates approximately the 

 position of the germ cells. The planes ab and cd are the planes of the sections 

 in figures 12 and 13. 



7 Larva 274 hours old. The lines ef, cd, and ab are the planes of the sections 

 in figures 14, 15 and 16, respectively. 



8 Larva 299.5 hours old. The line ab is the plane of the section in figure 17. 



9 Larva 359.5 hours old. 



10 Larva 8 mm. long (37 days, 14.5 hours). The distribution of the germ 

 cells is shown by dots. Thirty-six germ cells were found in a larva of this stage. 

 The position of the various 10/i sections craniad of the anal aperture is shown by 

 vertical lines. 



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