416 R. S. CUNNINGHAM 
mass bordered beneath by the basement membrane. These 
cells were stained exactly like the cells of the surface, having a 
small patch of the red granules around one pole of the nucleus, 
though they were notoriented in any especial manner. Whether 
these cells are derivatives of the layer of germinal epithelium or 
whether they are other cells reacting in a similar manner to the 
dyes is not yet clear. 
DISCUSSION 
The characteristic reaction to vital dyes which has been de- 
scribed for the general peritoneal mesothelium certainly suggests 
that there is a similarity in function which extends throughout 
the membrane, and perhaps may even include the germinal 
epithelium of the ovary. The differences noted between diverse 
areas such as spleen and diaphragm may eventually prove to 
be specifically bound up in the peculiar functions of the organs 
which they cover, or may be due to differences in environment, 
such as blood supply, movements of viscera, or other physical 
factors. ‘The characteristic location of the vital dye-granules 
in the various types of mesothelial cells may have some bearing 
on the differences in the physiological activities of the organs 
which the cells cover, but our information is far too limited at 
present to even hazard a guess concerning these interpretations. 
Obviously, the observations reported here may assist in the 
settlement of two general questions. In the first place, there 
has been much discussion regarding the relationship between 
the fibroblasts and serosal lining cells, some authors having 
maintained them to be the same fundamental type of cell mani- 
festing different physical characteristics under different environ- 
ments, and others having considered them as entirely different 
final types. The second question, in regard to which these 
findings may be of importance, is the relationship between 
the germinal epithelium and the general serosal mesothelium, 
on the one hand, and between the germinal epithelium and the 
structures of the ovary proper, on the other. 
Evans and Scott (’20) have succeeded in separating the fibro- 
blasts from the clasmatocytes by their reactions to vital dyes, 
