DEVELOPMENT OF A MYXOSPORIDIAN 361 



much less and appears perfectly homogeneous, never granular 

 as in the ordinary mononuclear trophozoite (fig. 3) . Occasionally 

 such cells lie side by side while similar cells containing two nuclei 

 are not uncommon (figs. 4 and 5). The appearance of these 

 binucleate cells strongly suggests that they are formed by the 

 fusion of two cells like that shown in figure 3, while figure 6 

 may plausibly be interpreted as a somewhat later stage in which 

 the nuclei are partially fused, and figure 7 may represent a later 

 stage after complete fusion of the nuclei. If the above inter- 

 pretation be correct figure 7 represents the earliest stage of the 

 definitive trophozoite, formed by the fusion of two similar gam- 

 etes, in which the cytoplasm has not yet developed the granular 

 structure so characteristic of the later stages. 



On the other hand, were it not for figure 6, the cells shown in 

 figures 3 to 7 might just as plausibly be interpreted as differ- 

 ent stages in the division of a cell like figure 7, in which case 

 the sequence of the different stages w^ould be just the reverse 

 of that suggested above. Although I have devoted much time 

 to the study of these stages, I am still unable to decide which 

 is the correct interpretation. The cell shown in figure 6 is the 

 only case I have found where the nuclei appeared to be fusing. 

 On the other hand I have found no case in which the nuclei 

 appeared to be undergoing division in cells characterized by a 

 small amount of homogeneous cytoplasm. Several cases of 

 nuclear division in the larger mononuclear trophozoites have been 

 observed, but they can always be distinguished by the relatively 

 larger amount of granular cytoplasm. 



For the present, then, it must be considered doubtful whether 

 the stages shown in figures 3 to 7 represent a case of copulation 

 or simply a method of multiplication by division of small mono- 

 nuclear trophozoites. 



