DEVELOPMENT OF A MYXOSPORIDIAN 351 



has convinced me that there are never more than twelve nuclei 

 present and that there is no trace of 'residual nuclei' at any stage. 

 This is, of course, in accordance with the conditions found in 

 the disporous forms. 



The cells of the fully developed pansporoblasts are much alike 

 except that the capsulogenous cells are larger and there is a 

 deeply staining region in the cytoplasm at one side of the nucleus 

 (fig. 78). The nuclei in these cells are also somewhat larger and 

 the chromatin is less compact. Two of the nuclei shown at a 

 lower level in the figure are larger and more flattened than the 

 others and are probably in 'parietal cells' which form the valves 

 of the spore membrane. 



Figures 81 and 82 show later stages in the development of 

 the spores which lie in a common cavity formerly occupied by 

 the pansporoblast. Each spore is made up of six cells and here 

 is no trace of 'residual nuclei' (figs. 81 to 83). In all essential 

 respects they are like the spores of the disporous. form (figs. 41 

 and 42, 80 to 82). Practically the only difference is in the cap- 

 sulogenous cells which, in the polysporous forms contain, previous 

 to the formation of the polar capsules, numbers of rounded 

 granules staining deeply with the plasma stain. As previously 

 stated I have been unable to distinguish any difTerence between 

 the mature spores of the disporous and polysporous forms. 



The process of mitotic division in the cells of the polysporous 

 trophozoites is essentially the same as in the disporous, so that a 

 detailed description is unnecessary. Figures 84 to 89 show the 

 different stages of the process. The most striking difference is 

 in the larger size of the chromosomes and the better develop- 

 ment of the mitotic figure. As in the disporous form no sign of a 

 centrosome was seen at any stage. I wish to emphasize the fact 

 that while the chromosomes are much larger, the number is the 

 same as in the disporous form. Moreover, as in the latter, the 

 chromosomes are evidently in three pairs differing in size (figs. 

 86 to 87). One pair is considerably larger than the others; one 

 pair is somewhat smaller; while the other pair is intermediate 

 in size. 



