356 M. M. Mercatr 
Fig. 16. A bit of endosare from a section of O. intestinalis, showing that 
each endosare spherule lies in an alveolus. The structure of the endoplasma is not 
well shown. Coros. subl.-acetic acid, Euruicu’s triacid mixture. >< 2000 diameters. 
Fig. 17. An optical section of the posterior end of a slender O. dimidiata, 
showing part of the excretory organ. One nucleus, in mitosis, lies surrounded by 
the excretory vacuoles. Only the upper half of this nucleus is drawn. Ten (?) or 
twelve rows of chromatin granules (chromosomes) were present. The general cyto- 
plasmic foam is not shown. Coros. subl.-acetic acid, Detarieip’s haematoxylin. 
x 1420 diameters. 
Plate XV. 
Opalina intestinalis (Figs. 18—31) and O. dimidiata (Fig. 31a). 
Fig. 18. Part of a section stained with methylen blue. Pellicula pale blue, 
ectosare films and spherules green, endoplasma blue (structure very obscure and 
not shown), endosare spherules unstained appearing like vacuoles, nuclear membrane 
blue, nuclear contents not shown, except the nucleolus (pale greenish blue with a 
dark blue vacuolated cap). Coros. subl.-acetic acid, methylen blue. > 2U00 diameters. 
Fig. 19. Another nucleolus from the same preparation as Fig. 18, but with 
two dark blue unvacuolated caps. >< 2000 diameters. 
Fig. 20. An individual stained intra-vitam with toluidin blue. The ectosarc 
spherules are stained, the endosare spherules unstained. The band of ectosare 
spherules shown crossing the cell in front of the posterior nucleus is superficial 
and is half of a complete ring. Very darkly stained bodies of a problematic 
nature are shown. The nuclei were entirely unstained until after all motion of 
the cilia ceased. Then certain masses (of chromatin?) began to stain as indicated. 
This individual was in an early stage of transverse division. > 500 diameters. 
Figs. 21 and 22. Two sections showing the whole of one nucleus, stained 
with safranin and light green. The heavily stained red spherules are chromatin 
spherules. The chromosomes are paler red and granular. (The granules were not 
drawn with the camera. They should be one-half larger and one-third less 
numerous.) The achromatic granules and the large nucleolus are green. Neither 
the chromatin network nor the achromatic films were clearly enough seen to draw. 
The former was composed of extremely delicate threads. Coros. subl.-acetic acid. 
2000 diameters. 
Fig. 23. Part of a section stained with safranin and light green, showing 
cilia, outer contour of pellicula, basal granules of cilia, ectosare with coarser and 
finer fibrillae or films (green, semi-diagrammatic) and green-stained spherules, 
endosare with pink-stained spherules and coarser and finer fibrillae and films (These 
are stained green in this preparation. If left a moment longer in absolute alcohol 
they would be red. It was impossible to draw these with eutire accuracy), nucleus 
with chromatin masses and threads stained red, and the achromatic structures 
green. The three faint red bodies in the nucleus are probably dissolving chromatin 
spherules. All the nuclear structures shown (accurately drawn) lie near the upper, 
uneut, surface of the nucleus. The nucleolus is not in this section. Coros. subl.- 
acetic acid. XX 2000 diameters. 
Fig. 24. A longitudinal section of a nucleus in a late telophase of mitosis. 
Only a portion of the achromatic granules present are drawn. The nucleolus is 
not in this section. Coros. subl.-acetic acid, safranin and light green. X 2000 
diameters. 
