494 A. B. DAWSON 
openings of the ducts from the granular glands, there usually is 
a slightly thickened zone within which the layer thins as its 
surface slopes down to the mouth of the duct (fig. 6). In such 
places the lower surface of the epidermis projects into the dermis, 
as if drawn down by a tension exerted by the large underlying 
gland. The smaller mucous glands produce no such disturbances 
in the epithelium (fig. 12). 
In general, the form of the epidermal nucleus is determined 
by the shape of the cell in which it hes. The chromatin is 
arranged in an irregular network and no nucleoli are present. 
The cytoplasm is usually homogeneous in appearance, but in 
many cells the nucleus is surrounded by a clear zone (Norden- 
skidld, 05, Bufo). In a few preparations there appeared a 
concentration of densely stained cytoplasm at the deeper poles 
of the nuclei. Prowazek (’01) describes a similar condition in 
salamander larvae and considers it an evidence of degeneration. 
The occurrence of mitosis in any of the cells of the amphibian 
integument except the germinative layer has been denied by 
many investigators. P. Schultz (89) has explained the results 
of Pfitzner (80) and Paulicki (’85) by saying that they studied 
sections which had been cut obliquely. However, Bruno (’06) 
found that in the frog multiplication of cells was not restricted 
to the lowest layer. In Necturus, although mitotic figures may 
have been more common in the germinative layer, there were 
numerous cases where unquestionably mitosis was taking place 
in the higher cell layers. The long axes of the spindles were 
always parallel to the body surface. 
Intercellular bridges are not readily observed in preparations 
of normal tissue. Where, however, there has been some dis- 
turbance, such as a migration of cells to cover a wounded surface, 
they are easily distinguished. It is quite probable that they are 
present in all cases, but in the undisturbed epithelium the cells 
are so closely packed that the fine protoplasmic fibrils are hidden 
from view. 
From the bases of the cells in the germinative layer fine tooth- 
like processes extend into the underlying connective tissue. A 
‘ complete discussion of the relation of epidermis to dermis will 
be postponed till after the outer dermal layer has been described. 
