1913 ] Johnson: Pigment Formation in Amphibian Larvae 79 



The same experiment with Hyla tadpoles gave the following 

 data (table 13) : 



TABLE 13 



Length measurements of Hyla tadpoles fed on flour, gluten, and gliadin. 

 Length measurements represent the average length of all the tadpoles 

 in a dish. 



Hyla. Experiment started Feb. 24, 1912 

 Length in mm. 



Food Mar. 6 Mar. 24 



Flour 13.0 18.3 



Gluten 13.3 19.6 



Gliadin 12.2 13.7 



Mar. 24. Tadpoles all nearly the same color, if any difference gluten- 

 fed are darkest, gliadin-fed lightest. 



Gortner (1911b) finds that orcin, resorcin, and phloroglucin 

 inhibit the action of tyrosinase extracted from potatoes, meal 

 worms, and the periodical cicada. He says : ' * It would appear 

 from these data, that aromatic compounds which carry two 

 hydroxyl groups in meta position to each other may act as 

 chemical anti-oxidases on tyrosinase, and completely inhibit its 

 action. Other oxidases are not inhibited, but are able to oxidize 

 these same m-dihydroxl compounds, forming colored bodies of an 

 unknown nature." 



Phloroglucin and resorcin were mixed with liver and fed to 

 Hyla tadpoles. The amounts were not weighed, but about fifteen 

 milligrams was rubbed up with the liver and put into the dish. 

 The tadpoles on resorcin did not thrive, most of them died very 

 soon (table 14) : 



TABLE 14 



Length measurements of tadpoles fed on liver, liver -f- resorcin, and liver 

 + phloroglucin. Measurements represent the average length of all the 

 tadpoles in the dish. 



Hyla. Experiment started Mar. 18, 1912 



Mar. 25 Apr. 11 



Length 

 Food in mm. 



Liver 14.1 



Liver + resorcin 15.4 



Liver + phloroglucin 14.3 



