Opalina. 3Db 
dicate the boundary between ectosare and endosare. Coros. subl.-acetic acid, iron 
haematoxylin (well extracted). > 2000 diameters. 
Fig. 6. Part of a cross section of O. obtrigona, showing cilia (semi-dia- 
grammatic), pellicula, rows of basal granules of cilia, large alveoles of ectosare 
containing finely granular ectosare spherules (gray), granular endosare spherules 
(more darkly stained) each in an alveole (some of these endosare spherules Jie in 
strands of endoplasma which have pushed out into the ectosarc), three nuclei in 
two of which one sees masses of chromatin lying against the nuclear membrane, 
while all show the superficial network of chromatin with nodal thickenings. The 
achromatic structures in the nuclei are not drawn, and the fine-meshed cytoplasm 
is but conventionally shown as granular. Some of the rows of basal granules and 
cilia are double because the rows are dividing where the body broadens, so as to 
cover the broader body surface. Coros. subl.-acetic acid, iron haematoxylin (well 
extracted). >< 2000 diameters. 
Fig. 7. Part of an oblique section of O. intestinalis, showing pellicula, well 
stained ectosare spherules (some granular), unstained endosare spherules looking 
like vacuoles, and nucleus. The boundaries between the different alveoles of the 
ectosare were not well shown. nor was the structure of the endosare clear. Coros. 
sublL.-acetic acid, dahlia. > 2000 diameters. 
Fig. 8. Part of an oblique section of O. intestinalis, showing  pellicula (its 
ridges are drawn at the left of the figure). basal granules of cilia, sub-pellicular 
layer of ectosarc, and the alveolar layer of ectosarc, each alveole containing one 
ectosare spherule. Coros. subl.-acetic acid, methyl violet. >< 2000 diameters. 
Fig. 9. Three ectosare spherules from a section of O. intestinalis. Coros. 
subl.-acetic acid, iron haematoxylin (not much extracted). > 2000 diameters. 
Fig. 10. Ten endosare spherules from the same animal as in Fig. 9. The 
last two spherules show the not infrequent dumb bell shape. The last spherule 
shows superficial granules. Coros. subl.-acetic acid, iron haematoxylin (not much 
extracted). >< 2000 diameters. 
Fig. 11. An endosare spherule from a section of O. obtrigona. This slender 
dumbbell-shaped spherule shows the nearest approach to division [ have found in 
the endosare spherules of Opalina. Coros. subl.-acetic acid, iron haematoxylin 
(not well extracted). >< 2860 diameters. 
Fig. 12. Five endosare spherules from a section of O. ranarum, showing 
internal (alveolar?) structure. In each instance the left side of the figure representa 
the side of the spherule toward the outer surface of the body. Coros. subl.-acetic 
acid, iron haematoxylin (long extracted). >< 2860 diameters. 
Fig. 13. Five endosare spherules from a section of O. intestinalis. All are 
from the same animal, yet one sees that they are differently stained, indicating 
difference of condition. Coros. subl.-acetic acid, iron haematoxylin (not much 
extracted). > 200U diameters. 
Fig. 14. Six ectosarc spherules from the same animal as in Fig. 13. This 
animal was considerably shrunken and the spherules of the ectosare and endosare 
were also. Cvuros. subl.-acetic acid, iron haematoxylin (not much extracted). > 2000 
diameters. 
Fig. 15. A bit of unusually coarse-meshed endoplasmic foam from a section 
of O. caudata. Coros. subl.-acetic acid, DELArieLp’s haematoxylin. >< 1485 diameters. 
