1913 J Johnson: Pigment Formation in Amphibian Larvae 73 



show plainly that lecithin and egg yolk inhibit to some extent 

 the action of certain tyrosinases of vegetable and animal origin. 

 This being so, what will be the effect when lecithin is fed to the 

 tadpoles along with a food which produces marked pigmentation ? 



F. EFFECT OF LECITHIN UPON PIGMENTATION 



Experiments were accordingly made to determine the effect 

 of lecithin when it is fed along with a food that ordinarily pro- 

 duces considerable pigment. When lecithin was mixed with the 

 food it was placed in the dishes every other day after the dishes 

 had been cleaned and the food and water renewed. The amount 

 of lecithin used was not weighed each time, but it probably 

 varied between fifteen and twenty milligrams in weight. It 

 dissolved after eight or ten hours. 



Of two lots of Rana tadpoles, one was fed albumen and the 

 other albumen and lecithin. Following are the notes on the 

 experiments. Table 5 shows the length measurements on different 

 dates. 



TABLE 5 



Length measurements of Sana tadpoles fed on albumen and albumen plus 

 lecithin. Length measurements represent average length of all the 

 tadpoles. Eight tadpoles in each lot. 



Eana. Experiment started Feb. 6, 1912 

 Length in mm. 



Food Feb. 19 Feb. 26 Mar. 5 Mar. 25 



Albumen 17.6 18.6 19.3 21.5 



Albumen + lecithin 18.2 21.1 23.0 26.5 



Feb. 21. Tadpoles fed on albumen plus lecithin are lighter than those 

 fed on albumen alone. The difference is small but distinct. 



Mar. 5. Tadpoles fed on albumen plus lecithin are very plainly lighter 

 and larger than tadpoles fed on albumen. 



Mar. 14. (Same as Mar. 5.) 



Mar. 25. Color difference seen before is now scarcely noticeable. Size 

 difference very plain. 



Apr. 2. Color difference plain once more. 



Apr. 10. On account of the size difference it is difficult to compare the 

 two sets of tadpoles with accuracy. One tadpole fed on albu- 

 men plus lecithin is darker than the others but the rest are 

 lighter than the albumen-fed tadpoles, showing a yellowish 

 brown tinge rather than black. 



