THE PARS fiUCCALIS Of THE HYPOPHYSIS 23 



light in color, these cells rapidly increase in number and melanin 

 content; by a 15 mm. stage they have numerically and struc- 

 turally attained the mature larval condition (fig. 17, table 1). 

 Their appearance in the albino is more tardy. They do not 

 appear as early and are always diminished in number and melanin 

 content as shown by figures 16 and 18, which were drawn from 

 albinos of the same age and size as the normals from which 

 figures 15 and 17, respectively, were drawn. A partly con- 

 tracted condition is also evident from their earliest appearance. 



No evidence has accrued from these studies which suggests 

 that the diminution in the number of epidermal melanophores 

 suffered by the albino is affected by a migration of the epidermal 

 melanophores into the corium as suggested by Allen. On the 

 other hand, the evidence all points to the developmental and 

 functional independence of the two systems of melanophores. 

 The first melanophores to appear are those in the corium, and 

 there is at no time any evidence that their number is augmented 

 by a migratory process from the epidermis. The formation of 

 the epidermal melanophores from the beginning is apparently 

 partially inhibited in the albino, an inhibition which is expressed 

 not only in the diminished number of cells, but in their melanin 

 content as well. 



One of the remarkable features in this pigmentary disturbance 

 is its early appearance. Whether referable to some missing 

 hormone of the anterior lobe or to other hormonal disturbances 

 provoked by the operation, it appears clear that hormones are 

 already produced by the small groups of embryonic cells con- 

 stituting the endocrine glands at a time when the latter exhibit 

 but little if any of the structural differentiations which char- 

 acterize the adult internal secretory organs. 



Epidermal transplants 



We have detailed at some length the pigmentary disturbances 

 which result from the early loss of the epithelial hjrpophysis in 

 the tadpole. It is now of interest to inquire whether this func- 

 tional upset is due directly to an alteration in the quality of 



