502 A. B. DAWSON 
into the intercellular spaces. If this does occur one would expect 
to find some evidence of at least a temporary dissolution of the 
cell wall. In two cases mononuclear leucocytes were found 
within the bodies of the club cells. In one the invading cell 
had rounded up and appeared to he at rest; in the other (fig. 5) 
the leucocyte was surrounded by a clear zone and its nucleus 
was elongated as if the cell had been in an active state when 
killed. No evidences of degeneration were noted in either case, 
and the entry of the leucocytes into apparently healthy cells 
would seem to denote a dissolution of the cell membrane, at 
least locally. In view of certain facts which will be stated later, 
it is also significant that in both cases the wandering cell made 
its appearance at the top of the club cell. 
Another feature of the club cells is their distribution. Leydig 
(76 a) noted that they were absent from the edges of the tail 
fin of many urodeles. Both Carriére (’85) and Paulicki (’85) 
have described them as being absent from the snout and extremi- 
ties of the appendages as well as from the dorsal and ventral 
edges of the tail. 
In Necturus restrictions in distribution similar to those re- 
ported by Carriére and Paulicki are found, and over the body 
there is a tendency toward local grouping, which is quite evident 
in whole mounts of strips of skin viewed with low power. Accord- 
ingly, in histological preparations made from different regions the 
club cells may appear very plentiful or may be entirely wanting. 
2. Function. Although these cells are large and easily seen 
and have been observed by many investigators, their function 
still remains to a large extent an unsolved problem. Many 
theories have been advanced, but none are satisfactory. Langer- 
hans (’73) regarded them as early stages in the development of 
the so-called beaker-cells which, in the toad (P. Schultz, ’89; 
Muhse, ’09), aid in separating the horny molt from the under- 
lying stratum of cells. Pfitzner (’79) believed the cells of Leydig 
produced a slimy secretion which escaped into the intercellular 
spaces and possessed the power of protecting the outer cell 
layers from injury due to contact with the water. 
Cohn (’95) thought that the cells were of a poisonous nature, 
similar to that of the large granular glands, and that they did 
