466 
HENRY F. NACHTRIEB 
indicate very imperfect killing and hardening or rough after- 
treatment the processes on the free surface of the cover cell are 
more pronounced than they are in well preserved material. In 
some of the preparations many of the cover cells have a relatively 
clean cut surface, but none of them appear as clean cut as the sur- 
face cells of the ordinar}^ lining epithelium. These facts suggested 
various experiments which I have not had an opportunity of 
making. 
In view of the facts before me I believe the free surface of the 
cover cell is more or less plastic and can be temporarily projected 
into jnore or less pronounced pseudopodia. The position of the 
nucleus is not that usually occupied by the nuclei of secretory 
cells. The shape of the cell is also not typical of secretory cells. 
But the intimate connection between the mucus and the cell 
compels the inference of an active relationship between the two. 
The subcutaneous connective tissue is quite slimy — indeed the 
general appearance and behavior toward reagents of both the 
nuclei and the ground substance stamp this as a mucoid support- 
ing tissue. And it may be that the cover cells function primarily 
as the excretors of the mucus formed in the underlying connec- 
tive tissue. 
The flagellated cell, shown in detail in fig. 10, as a rule has a 
rounded base, the edge resting on the expanded bases of contigu- 
ous cover cells. As a rule the base of the cell is slightly shrunken 
away from the basement membrane. This condition is so com- 
mon in even apparently perfectly preserved material that these 
spaces jnust be looked upon as normal lymph spaces. The flagel- 
lated cell differs from all other epithelial cells in that its cytoplasm 
below and around the lower half of the nucleus contains distinct 
loosely distributed, granules, which stain more deeply than the 
rest of the cell substance but not as deeply as the chromatin 
granules in the nucleus. In sections of platino-aceto-osmic ma- 
terial stained with iron hematoxylin these granules have a deep 
blue color. They are quite uniform in size and generally ap- 
pear more or less spherical. In many cells the granules appear 
to be wanting in a narrow area next to the cell wall, and the cell 
below the nucleus presents a clear unstained peripheral area sur- 
