Opalina. 211 
Pellicula. 
All species studied have a pellicula of appreciable thickness 
which is quite distinct from the subjacent cytoplasm (Figs. 3, 6, 7, 8, 
Pl. XIV). With many stains it colors differently from the ecto- 
plasm. Some of these differentiating stains are gentian violet, methyl 
violet, methylen blue, thionin, fuchsin, dahlia, Enruicn’s triacid mix- 
ture, and DreLarrevp’s haematoxylin. With methylen blue the whole 
ectoplasm is stained green while the pellicula is pale blue (Fig. 18, 
Pl. XV); with methyl violet the pellicula has a lighter shade than the 
ectoplasm; with thionin the pellicula is unstained while the ectosare 
is green; with fuchsin the light red pellicula is readily distinguished 
from the more faintly colored ectoplasm. Dahlia gives perhaps 
the clearest picture, the pellicula being a very faint purplish gray, 
while the ectoplasma is purple. The contrast between the green 
pellicula and the blue ectoplasma after staining with Euruicn’s 
triacid mixture is also very marked. With all stains used the pelli- 
cula seems homogeneous. 
I have not been able to demonstrate with entire clearness the 
minute longitudinal ridges which Marer describes as present on the 
outer surface of the pellicula. The longitudinal striae are very clear 
in surface views of tangential sections, but none of my cross sections 
give satisfactory views of the ridges. In some sections stained with 
DELAFIELD’s haematoxylin they are faintly seem. One cannot, how- 
ever, doubt the accuracy of Marer’s description, for his work is 
clearly very careful. 
ZELLER figures the outer surface of the body as breaking into 
thin narrow strips after treatement with acetic acid. He called 
these strips muscle threads. From my own preparations it seems 
probable that what he described were strands of pellicula which had 
separated along the course of the lines of cilia (cf. Maier, 1903, p. 80). 
Ectosare. 
Sub-pellicular layer. 
Immediately beneath the pellicula, between it and the usually 
large alveoles which fill the greater part of the ectoplasm, there is 
a thin layer of finely alveolar protoplasm (Fig. 8, Pl. XIV). In the 
outer part of this layer lie the basal granules of the cilia. Other 
granules, similar in size, lie more internally in the same layer. They 
resemble in size the granules that lie at the nodes and along the 
