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CAREY P. McCORD AND FLOYD P. ALLEN 



just prior to and thirty minutes after feeding 5 mgm. fresh 

 pineal gland. A true evaluation of the relative pigmentation 

 may be had by comparison of the tadpoles of figure 3 with the 

 periphery of those in figure 4. The dark color in the center 

 of the bodies in figure 4 is due to the opacity of the denser vis- 

 cera and intestinal contents and not to a difference in the pig- 

 mentation of the skin. 



f 



• • ^ 



Figs. 3 and 4 Photographs made by reflected light. 



Fig. .3 Normal tadpoles — just prior to pineal feeding. 



Fig. 4 Same tadpoles 30 minutes after feeding acetone extract of pineal 

 gland. The darker portions of these tadpoles are due to denser viscera — heart, 

 gills, intestinal contents, etc. The degree of translucency is identical in all parts 

 of the skin. 



If a portion of the skin from a light and from a dark tadpole 

 be dissected loose and examined under a microscope the reason 

 for the difference in shade will be readily apparent, (figs. 6 and 

 7), The two types of melanophores are present. In the nor- 

 mal (dark) piece of skin the sub-epidermal melanophores (fig. 6, 

 Sub. M.) are expanded to such an extent that they form an opaque 

 sheet in which there are left a few scattered openings. In the 



