PLATE VII. 



Fig. 31. Considerably later stage. The itomere has disappeared. The cell has 

 grown much in size. The path left by the itomere is more marked than be- 

 fore. 



Fig. 32. About the same stage, showing a cross-section of the forming axial fila- 

 ment, with the fibers of the cytoplasmic reticulum radiating from it. 



Fig. 33. Later stage. The axial filament more nearly formed. The centrosome 

 has moved nearer its base. 



Fig. 34. Later stage in the formation of the axial filament. The cell has begun 

 to elongate. The cytoplasm is broken up into elongated vacuoles extending 

 parallel to the axial filament. 



Fig. 35. Much later stage. The cell body has elongated a great deal. The 

 membrane of the posterior part of the cell has disappeared. On the side of 

 the nucleus opposite the insertion of the axial filament there is a large trans- 

 parent acrosome. At this stage the nucleus has reached its greatest size. 



Fig. 36. About the same stage of a smaller cell. Acrosome not shown in the 

 section. 



Fig. 37. The nucleus has become condensed and elongated. The acrosome 

 stains more densely. The cytoplasm contains strands of linin extending 

 parallel to the axial filament. 



Fig. 38. The nucleus has become still further condensed and has elongated con- 

 siderably. Acrosome stains darker. 



Fig. 39. The nucleus is still more condensed and takes a black stain. Acrosome 

 also stains more strongly. 



