PLATE 2 



EXPLANATION OF FIGURES 



13 The pigmentary system^' of a normal 43/9.0 ''*frog tadpole, 'standard' environ- 

 ment, showing the successive layers of free pigment and ohromatophores.'" The 

 animal was fixed by dropping into Helly's fluid 101 days after the operative stage. 

 Liver diet. X226. 



14 The pigmentary system of a 43/0.1 albino frog tadpole, 'standard' environ- 

 ment. Fixed by dropping into Helly's fluid 101 days after epithelial hypophy- 

 sectomy. Liver diet. X226. 



15 The pigmentary system of a 10-mm. (total length) normal frog tadpole, 

 'standard' environment. Dropped into Helly's fluid 22 days after the operative 

 stage. Liver diet. The epidermal melanophores are just appearing. X226. 



" All the drawings of the pigment cells (figs. 13 to 23) were made from skin whole 

 mounts taken from the dorsal region of the body. 



''* The total length of the specimen is shown by the first figure, the hind-leg 

 length by the second. 



'^ In the pigment cell drawings the most superficial layer is shown on the left, 

 the deepest on the right. From left to right they are in order, (a) the layer of free 

 epidermal pigment, (b) the layer of epidermal melanophores, (c) the xantholeuco- 

 phores, (d) the deep melanophores. 



116 



