INTEGUMENT OF NECTURUS MACULOSUS 533 
The walls of the mucous glands in Necturus consist of but 
two layers, the connective-tissue sheath and the gland epithelium. 
The muscle layer is absent. No tunica propria or basement 
membrane is present. Arnold (’05) describes in the mucous 
glands of the frog a membrane, composed of very fine wavy 
fibers, which extends between the gland epithelium and the 
muscle layer. This membrane stains intensely in elastin stains. 
Nothing comparable to this was observed in Necturus. 
d) Muscles of granular glands. Smooth muscles on glands 
were first demonstrated histologically by Hensche (’56), though 
earlier observers had noted movements of the living glands. 
Practically all writers since then have recognized the existence 
of muscles on the large granular glands. Reese (’05), however, 
in his brief description of the integument of Cryptobranchus, 
states that ‘‘The muscular layer sometimes described cannot 
be made out.”’ Calmels (’83) and Seeck (’91) evidently mistook 
transverse sections of muscle fibers for epithelial cells. In Bufo 
agua (Shipley and Wislocki, ’15) the muscles are attached to the 
collar and run down over the gland body in a spiral manner. 
In Bufo americanus (Muhse, ’09) the fibers are arranged meri- 
dionally, and it often requires several fibers to complete the 
circuit of the gland. There is, therefore, in this animal no definite 
arrangement of the muscle nuclei in any given region as Esterly 
(04) found in Plethodon, where the nuclei of the contractile 
cells, contrary to the description of Nicoglu (’93) and Vollmer 
(93) for Triton, ‘‘lie in the upper region of the glands just out- 
side the uppermost gland cells, yet still well beneath the epi- 
dermis.” Further, Esterly (p. 236) states “That those observers, 
who describe muscle nuclei on the periphery of the gland sacs, 
have mistaken connective-tissue nuclei for them, seems to me 
very probable.”’ 
Drasch (95) found in the salamander, around the periphery 
of the large poison glands, a complete layer of smooth muscle 
fibers united by wide anastamoses into a syncytium, and Esterly 
(04) and Muhse (’09) describe branching muscle fibers on the 
lower part of the gland. Several writers (Eberth, ’69; Leydig, 
76a; Nicoglu, ’93; Heidenhain, ’93 a, ’93 b; Drasch, 794; Ancel, 
