492 A. B. DAWSON 
C. General observations 
The large perennibranchiate urodele, Necturus maculosus 
Raf., on which these studies were made, has the typical soft 
skin of the water-inhabiting Amphibia. The surface of the body 
is smooth, exhibiting no modifications or prominences such as 
appear in other Amphibia due to the massing of the large glands 
in the dermis. In a shallow aquarium, in clear water, the 
numerous pinhole-like openings of the individual gland ducts 
are visible even to the naked eye. No secretion can be detected 
on the surface of the body while the animal is resting quietly. 
When picked up a clear slimy secretion immediately appears 
and the animal quickly wriggles from the grasp. It is only when 
violently stimulated mechanically, chemically, or electrically 
that the gray granular secretion is expelled. That which is 
first discharged floats away free in the water, but the later dis- 
charge is held imbedded in an ever-increasing amount of clear 
slime which envelops the entire surface of the animal. 
In favorable light the lateral-line system can be clearly dis- 
tinguished on the living animal, the several tracts, above and 
below the eyes, over the snout and jaws, and along the sides 
of the body, appearing as series of short broken lines. This 
system has already been completely mapped for Necturus by 
Kingsbury (’95), and studied histologically by Takahashi (09). 
The color of Necturus is so variable that no complete descrip- 
tion will be attempted. The pattern is produced by a mingling 
of black and yellow pigments on a white background. Above, 
the animal usually appears a dark uneven brown with a more or 
less pronounced black mottling; below, the pigmentation is less 
dense and the pattern more regular. The mottling is caused by 
a grouping of the large black chromatophores of the dermis. 
Around these black areas a narrow yellow margin can often be 
distinguished. Occasionally the spots run together to form black 
bands of considerable length, the most common and conspicuous 
being a pair extending along either side of the head from the 
nostrils to a point immediately anterior to the large plume-like 
gills. In some cases, however, the mottling is entirely lost and 
the upper surface presents a finely granular appearance due to 
the equal distribution of the melanophores and xanthophores. 
