498 A. B. DAWSON 
larvae as being adequate to explain the condition in Necturus, 
then the light lines would represent sectioned walls of alveoli, 
and the homogeneous densely stained masses would be identified 
as a contained secretion. 
When the margin is well defined, the stain is limited entirely 
to it; but, in other cases, relatively large, flat, black plates of 
irregular outline are seen distributed through the cytoplasm in 
the vicinity of the nuclei of the cuticular cells (fig. 15). In these 
cells, farther away from the nuclei and toward the outer surface, 
the stain is taken also by fine scattered granules, which grow 
more numerous toward the outer margin, and become arranged 
immediately below the surface in fairly definite, parallel rows. 
Later stages show these rows of granules merged together to 
form the small rod-like masses which are characteristic of the 
fully developed margin. ‘The reactions to mucin stains reported 
by O. Schultze (07) were not obtained in Necturus, but resorcin- 
fuchsin, which stains this region so intensely, also stains readily’ 
the contents of the mucous glands. 
These observations indicate that the cuticular margin is, in 
part at least, a secretion product, but not an extracellular one. 
The material which is laid down within the margin is elaborated 
in the deeper lying parts of the cells and moves to its final position 
in the form, of fine densely staining granules. While we have no 
conclusive evidence that the cuticular margin is composed of 
closely packed, elongated alveoli, still the appearance is quite 
suggestive of such a structure, and it is quite conceivable that 
the secretion granules do collect in the alveolar spaces and later 
coalesce to form the homogeneous masses described. 
In the row of cells immediately below the ‘covering-layer,’ 
staining reactions very similar to those already described are 
obtained. Flat densely-stained plates are seen grouped around 
the nuclei, and in the ends of the cells nearest the cuticular layer 
the concentrations of fine, dark granules are very conspicuous. 
This condition suggests that here is a replacing layer, in which 
some preparation has already been made for the new duties which 
must be assumed when the outer layer is cast off. 
