458 Blastocystis hominis 
from different sources which may lead to their being regarded as be¬ 
longing to one species, is easily explained by a convergence resulting 
from the parasites which produce the blastocysts losing their character¬ 
istics during the process of degeneration. 
7. No certain stages of sporulation were seen, as described by 
Alexeieff, and the nuclear structure, although variable, never resembled 
that given in his description. It is therefore probable that Alexeieff’s 
Blastocystis enierocola is different from the forms described in man under 
the same name. 
EXPLANATION OF PLATES XVI AND XVII 
Figs. 1-27. Case No. 2. 
Figs. 1^. Production of blastocysts from Limax amoebae by the formation of a 
central vacuole. 
Figs. 5-13. The same, by the formation of a central chromatic reticulum. 
Figs. 14-17; 22, 23. Blastocysts with well-developed cytoplasm. 
Figs. 18-21. Linear cytoplasm. 
Fig. 24. Stage suggesting sporulation. 
Figs. 25, 26. Dark staining sphere. 
Fig. 27. Sphere with alveolar structure. 
Figs. 28-64. Case No. 1. 
Figs. 28-39. Production of blastocysts from Limax amoebae by the formation of 
a central chromatic reticulum. 
Figs. 41, 42. Well-developed cytoplasm. 
Figs. 40, 43, 45, 52, 53. Linear cytoplasm. 
Figs. 46, 47. Gradual disappearance of the sphere. 
Figs. 48-51. Dark staining sphere. 
Figs. 54-58. Large blastocysts showing disappearance ol cytoplasm. 
Figs. 59-64. Division. 
Figs. 65-82. Case No. 3. 
Figs. 65-69. Production of blastocysts from Chilomastix. 
Figs. 70-73. Vesicular nucleus. 
Fig. 74. Disappearance of the nucleus. 
Figs. 75-77. Involution of the cytoplasm. 
Fig. 78. Dark staining sphere appearing in rounded Chilomastix. 
Figs. 79, 80, 82. Blastocysts with dark staining sphere. 
Fig. 81. Division. 
Figs. 83-94. Case No. 4. 
Figs. 83-85. Production of blastocysts from rounded forms of Chilomastix. 
Figs. 86, 87. Forms with vesicular nuclei. 
Fig. 88. Only chromatic granules present. 
Fig. 89. Division. 
Figs. 90, 94. Linear cytoplasm. 
Fig. 91. Form suggesting sporulation. 
Figs. 92, 93. Dark staining sphere. 
