1. An inhibition of moulting occurs after hypophysectomy (total or pars anterior removal only) in mature and immature Triton cristatus. Cornification of the outer epidermal layers continues and the animal gradually becomes grimy as these layers accumulate. The thyroid glands of such animals become inactive.
2. Moulting was induced in hypophysectomised animals by means of inoculations of fresh anuran pars anterior lobes and in one case by injections of an aqueous alkaline extract of bovine anterior lobes. A study of the thyroid glands of these animals supports the conclusion that the moulting is brought on by the stimulation of the thyroids to release a considerable fraction of their colloid content. It thus appears that the inhibition of moulting is really an indirect result of pars anterior removal. Hypophysectomy results in an inactivation of the thyroid gland and the resultant lack of circulating thyroid hormone is responsible for the failure to moult.
I wish to express my appreciation to Prof. F. A. E. Crew for the hospitality of the laboratory in the Animal Breeding Research Department, the University of Edinburgh, during the autumn of 1930 when part of these experiments was carried out. I am indebted also to Dr. B. P. Wiesner and his co-workers for supplying me with the extracts used in the experiments