THE PARS BUCCALIS OF THE HYPOPHYSIS 27 



became incorporated gradually into the albinous graft. In this 

 invading tissue, and indeed in those parts of the albinous graft 

 which clearly had not suffered an invasion by the epidermis of 

 the host, epidermal melanophores could readily be distinguished 

 which curiously displayed, for a considerable interval, a state 

 of great contraction. In the end the albinous transplant was 

 as abundantly supplied with melanophores as was the normal 

 epidermis. Although the free pigment of the albinous graft 

 increased more slowly than did the epidermal melanophores, 

 yet this too ultimately exhibited a normal condition. Thus, 

 after an interval not exceeding two months, both the free pig- 

 ment and the epidermal melanophores of the albinous trans- 

 plant had assumed the characteristics typical of the epithelium 

 of the normal host. 



The sequence of changes in a dark graft to an albinous host 

 is of a quite different nature from the alternate just described. 

 Although there appeared to be a slight reduction in both the 

 amount of the free pigment and the number of the melanophores 

 of the epidermis, yet these changes were of a minor nature. No 

 extensive migration of the melanophores from the normal trans- 

 plant where they were thickly congregated into the sparsely 

 supplied surrounding albinous epithelium occurred, nor by any 

 other process did any great reduction in the number or pigment 

 content of the transplanted melanophores take place during 

 the interval that the animals were under observation (two 

 months). These cells, once formed, appear to retain their 

 integrity. This would appear to be the correct interpretation 

 of the non-effect upon the pigment cells of hypophysectomy in 

 the midlarval stages (Adler). 



The effect of various diets upon the pigment cells 



We have just shown by the skin exchanges that the atypical 

 physiological state of the xantholeucophores and epidermal 

 melanophores of the albino is directly referable to an alteration 

 in the tissue juices which in turn is probably of an 'hormonal' 

 nature. If, then, this endocrine disturbance which is inaugu- 



