INTEGUMENT OF NECTURUS MACULOSUS yi 
opinion regarding the relation between the mucous and granular 
types. Some, although they admit the possibility of replace- 
ment of one type by the other, hold that each kind of gland has 
a separate development and that the cells never become trans- 
formed into anything different from what they originally were. 
Others, while they recognized two functional types of glands as 
being present in the skin, nevertheless believe that the granular 
cells have a mucous stage and later become differentiated toward 
a special function. 
According to those who contend that there is but one kind of 
gland, the small or mucous glands are young stages of the large 
or granular ones. This view is not entirely unlike that expressed 
by those who hold that the granular glands are differentiated 
from those of the mucous type. 
In Necturus two groups of seemingly quite different glands 
are found. Some are large, well rounded, and completely filled 
with a dense granular secretion. Others are smaller and do not 
present the plump appearance of the larger glands. The secre- 
tion in these is fibrous or vesicular and stains lightly in ordinary 
preparations. ‘There is nothing in the form or character of the 
smaller glands to indicate that they are young stages in the 
development of the granular type. ‘Their general appearance 
would rather lead one to regard them as discharged granular 
glands. I have been unable, however, to find any genetic rela- 
tion between the two types; on the contrary, there is every evi- 
dence that we are dealing with two distinct types which differ 
in development, in histological structure, in the character and 
staining reactions of their secretion, and in their physiological 
activities. Mixed glands are occasionally found. They repre- 
sent stages in the replacement of the mucous glands by glands 
of the granular type. It also appears possible that a perma- 
nently mixed condition may exist. After expulsion of secretion 
the granular glands may regenerate, but the replacing epithelium 
is never mucous in character. 
