CELLS LINING THE PERITONEAL CAVITY 415 
membrane than between the nucleus and the surface. Here and 
there a cell contained a vacuole in the base of the cell, though 
it was very difficult to determine whether these were inter- or 
intracellular. Most of the cells had no vacuoles. But every 
cell, without exception, contained a group of trypan blue granules 
near the basal pole of the nucleus and often forming a slight cup 
around it. Careful examination showed that there were a con- 
siderable number of types of arrangement; some cells contained 
an irregular circle of dye-granules; others a solid, round clump; 
others, a cap on the lower pole of the nucleus, and some, an 
irregular patch with knobs, projections, etc. Here and there 
an occasional granule appeared in the upper part of the cell, 
or a line of them extended up around the nucleus in an arm-like 
manner. Some of the cells were very heavily laden with granules 
which extended often up around half of the nucleus. Practi- 
eally all the blue granules were the same size, about $4 to > u 
in diameter. None of them was very large, as in clasmatocytes, 
and yet few were very fine, as in ordinary normal mesothelial 
cells. Here and there one found cells which were considerably 
flatter, being about half cuboidal, and here the dye-granules were 
again located in the region of the cell just medial to the nucleus. 
These flattened cells seemed to be from the edge of the ovary 
near its attachment and suggested a transition to normal peri- 
toneal mesothelium. When the transition from the flat meso- 
thelium to the cuboidal germinal epithelium was studied it was 
found to be most interesting. Here transition cells showed less 
and less staining in the characteristic area down to the ordinary 
mesothelial cell with its patch of granules and perinuclear rosette. 
Animals stained with carmine presented precisely similar 
pictures, the variations from the reaction to trypan blue were 
very considerably less than in areas such as the spleen or dia- 
phragm. But there was slight tendency to surround the nu- 
cleus, and the irregularities of staining were always more sharply 
shown in the animals stained in trypan blue than in those stained 
in carmine. In many areas in the sections of the ovaries from 
animals stained with carmine, cells were found just beneath the 
layer of the germinal epithelium proper and forming a nest-like 
