PLATE 3 



EXPLANATION OF FIGURES 



39 and 40 Optical sections through the same trophozoite showing all the 

 nuclei. There are twelve cells in the sporoblasts becoming arranged to form the 

 spores. Only one vegetative nucleus is present. X 2000. 



41 Trophozoite in which the cells have become definitely arranged to form 

 the spores. All the nuclei are shown. The parietal cells surround the capsulog- 

 enous and sporoplasm cells. The capsulogenous cells can be easily distinguished 

 by their larger nuclei. 



42 Trophozoite in which the spores are slightly more advanced than in figure 

 41. Only one spore is shown. A deeply staining body is present in the cyto- 

 plasm of the capsulogenous cells. 



43 Nearly mature spore. Only one capsulogenous cell is shown. 



44 Living trophozoite containing two mature spores. X 640. 



45 Mature spore as it appears when set free in the urine. X 1400. 



46 Mature spore slightly compressed under the cover-glass. X 1400. 



47 Free-hand drawing of germinating spore. 



48 to 55 Different stages in the mitotic division of the sporoblast cells. 

 48 and 49 Prophase. X 2650. 



50 to 52 Polar views of the equatorial plate showing six chromosomes. 

 X 2650. 



53 and 54 Anaphase. X 2650. 

 55 Telophase. X 2650. 



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