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body, each layer being composed of independent cells. The 

 superficial layer lies beneath the epidermal basement membrane, 

 and is separated by a considerable interval from the deeper layer 

 situated just above the corial melanophores. These cells bear 

 guanine and xanthine, and when expanded, give the silvery and 

 iridescent color effects so marked in hypophysectomized tadpoles. 

 The dark engrafted individuals, when examined under a binoc- 

 ular microscope, showed great expansion of the epidermal and 



Fig. 4 Surface view of whole mount of skin from engrafted larvae, 

 two layers of melanophores epidermal and corial are greatly expanded. 



The 



subepidermal melanophores of the skin as compared with the 

 normal controls. The degree of expansion of the superficial 

 melanophores of the experimented larvae is striking, the much 

 branched and irregular network of cellular processes apparently 

 forming a dense reticulum. The expansion of the subepidermal 

 pigment cells is so great that an opaque sheet of melanin is found. 

 In the light-colored controls, the melanophores are contracted into 

 dark ovoid masses, and there is no network or reticulum of epi- 

 dermal melanophores. It is possible, however, to find in any 



