INTEGUMENT OF NECTURUS MACULOSUS Bol 
lining the duct, which, in fact, seems to be nothing more than a 
large intercellular space extending from the body of the gland 
through to the outer surface of the epidermis. 
The ducts of the mucous glands (fig. 12) appear as straight 
cylindrical openings piercing the epidermis. The cells lining 
the duct are usually definitely arranged with their long axes in 
planes at right angles to the long axis of the duct and encircling 
it. In perpendicular sections, therefore, the cells are seen in 
end view and appear smaller than the ordinary epithelial cells. 
Their nuclei also stain deeply. The transition from the body 
of the gland to the intercalary region and duct is sharper than 
in the granular glands. 
b) Intercalary region. The collar or intercalary region is 
present in both kinds of glands in Necturus, but is more highly 
developed in the granular glands. 
For the poison glands in Triton, Nicoglu (’93) and Heidenhain 
(93 a, 793 b) have described the collar as a structure consisting 
of some four cells arranged in a ring around the base of the duct. 
Vollmer (’93) finds the ‘Schaltstiick’ often absent in Triton, and 
Esterly (04) states that in Plethodon it is not demonstrably 
present except in one or two questionable cases. Schultz (’89) 
has described a sphincter muscle composed of a band of muscle 
fibers running around the neck of the gland, and Phisalix (’00 a) 
refers to an ‘orbicular’ muscle in this same region. Arnold (’05) 
finds that there is sometimes an approach to a circular arrange- 
ment of cells at the neck of the gland, but there is nothing to 
indicate that they are of a muscular nature. LHsterly (04), 
however, describes both dilator and constrictor muscles about 
the mouths of the poison glands of Plethodon. These muscles 
are ectodermal and lie wholly within the epidermis. They have 
to do with the manipulation of the lumen of the duct during 
the expulsion of the secretion. Drasch (’94) described an epi- 
thelial plug which he believed served to restrain the contents 
of the gland and was forced out when the secretion was expelled. 
In Necturus the structure of the intercalary region is very similar 
to that of the glands of the toad (Muhse, ’09). In sections 
parallel with the surface and cut through the collar, the inter- 
