INTEGUMENT OF NECTURUS MACULOSUS 567 
3. In darkness at low temperatures the melanophores are 
contracted. 
4. In bright light the color of the background has no appre- 
ciable effect. In twilight the melanophores are usually partially 
contracted, and on a white background the amount of contraction 
is increased. 
5. In bright light changes in temperature produce no notice- 
able effects. In darkness, temperatures of 25°C. and over 
inhibit the contracting influence of darkness and the melano- 
phores remain expanded. 
6. Intracoelomic injections of adrenalin cause a complete con- 
traction of the melanophores. 
7. The melanophores appear to be of fixed form, within which 
the pigment granules migrate in ‘contraction’ and ‘expansion.’ 
Glands 
1. The skin glands of Necturus are of two kinds, granular and 
mucous. The mature glands are distinguished by the character 
and staining reactions of their secretion and by other histological 
features. 
2. The bodies of the granular glands are invested by a muscular 
wall. Muscles are never found about the mucous glands. 
3. In all mature glands the cytoplasm of the secreting epi- 
thelium is greatly reduced and the cell walls usually disappear. 
The nuclei of the granular cells are commonly spherical or ellip- 
soidal and stain normally. The nuclei of the mucous cells are 
smaller, irregularly shaped, and stain intensely. 
4. The secretion of the granular glands stains readily in all 
plasma stains and is unaffected by basic stains. 
5. The mucous secretion is never found in the form of granules. 
It is untouched by plasma stains, but is colored by thionin, 
resorein-fuchsin, Delafield’s or Ehrlich’s haematoxylin. 
6. Both types of gland develop by downgrowth from the 
germinative layer of the epidermis and are indistinguishable in 
very early stages. 
7. With the appearance of a lumen the gland cells assume a 
definite form and appearance, which marks them as potential 
