54 University of California Publications in Zoology [Vol. 11 



contain elements which govern the formation of pigment inde- 

 pendently of the effect of the food upon the size of the organism. 



It was found that most of the tadpoles showed a large or 

 medium amount of pigment excepting those that were fed on 

 yolk of egg, which showed a much smaller amount. Experi- 

 ments showed that when lecithin was fed along with foods which 

 ordinarily produced much black pigment that a much smaller 

 amount of pigment was produced. Experiments with tyrosinase 

 showed that the tyrosinase reaction could in a measure be in- 

 hibited by the addition of lecithin or the products of digestion 

 of egg yolk. The experiments thus give an example of a chemical 

 substance inhibiting the tyrosinase reaction and when fed to the 

 tadpoles inhibiting to some extent the production of melanin 

 pigment in the epidermis. 



This investigation has been carried on in the zoological lab- 

 oratory of the University of California under the direction of 

 Professor Harry Beal Torrey, and I am greatly indebted to him 

 for his continued help and encouragement. I also wish to expre&s 

 to Professors T. B. Robertson and H. C. Biddle of this Univer- 

 sity my thanks for their kind interest and assistance in questions 

 of physiological and organic chemistry. 



B. CURRENT THEORIES OF PIGMENT FORMATION 

 In relating these results to the current theories of color for- 

 mation and inheritance it will be convenient to consider Weis- 

 mann 's germinal selection theory, aspects of the Mendelian theory 

 of inheritance, and the results of recent biochemical investiga- 

 tion. 



Weismann postulates determinants, aggregations of ultimate 

 "vital units" capable of transmission through the germ cells and 

 able to determine "hereditary characters" of the body. Their 

 presence determines the specific development of a particular part 

 of the body which may consist of a group of cells, a single cell 

 or a part of a cell. A struggle for existence between the biophores, 

 the smallest elements composing the determinants, continues 

 throughout the development of the embryo, different biophores 

 being able to appropriate different amounts or kinds of nourish- 

 ment. These differences in nourishment cau.se inequalities in the 



