OBSERVATIONS ON THE PARS INTERMEDIA OF THE PITUITARY IN THE CRESTED NEWT UNDER VARIOUS LIGHT CONDITIONS

SUMMARY The adenohypophysial pars intermedia of the crested newt reared under natural light conditions (M.I. = 3 to 4) is characterized by: a) secretory cells exhibiting moderately developted rough endoplasmic reticulum and fairly numerous secretion granules displaced to the apical cell region facing the perivascular space, and b) by non-glandular, spider-shaped cells. In the animals exposed to continuous illumination in white containers the skin is seen to become paler (M.I. = 1 to 2). The secretory cells of the pars intermedia appear crammed with secretion granules. Profiles of the rough endoplasmic reticulum are scanty. On the contrary, in the animals reared in the dark in black containers, a striking skin darkening takes place (M.I. = 4 to 5). The pars intermedia secretory cells reveal a definite decrease in the population of endocellular granules and a developed, rough endoplasmic reticulum, characterized by enlarged cisternae filled granular or filamentous material. Among the glandular cells, under ...