PLATE 4 



EXPLANATION OF FIGURES 



19 The pigmentary system" of a 'light and heat' adapted 38/6.0 normal frog 

 tadpole which exhibited a contraction of the epidermal melanophores under the 

 influence of this stimulus. Fixed 5}/^ months after the operative stage by dropping 

 into Helly's fluid. Liver diet. X226. 



20 The pigmentary system of a 'light and heat' adapted 46/0.5 albino frog 

 tadpole. Fixed 5J^ months after epithelial hypophysectomy by dropping into 

 Helly's fluid. Liver diet. X226. 



21 The pigmentary system of a 46/0.1 albino frog tadpole, supplied with a 

 continuous diet of posterior lobe, 'standard' environment. Fixed by dropping into 

 Helly's fluid, 4}/^ months after epithelial hypophysectomy. X226. 



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