1913] Johnson: Pigment Formation in Amphibian Larvae 57 



for black, i.e., produces black-colored offspring must at the same 

 time transmit also the enzyme for brown, chocolate, red, yellow, 

 etc. (more accurately, an enzyme for each step of oxidation from 

 tyrosin to black melanin), without the absence of a single one." 

 In a footnote (p. 337) he adds: "The sort of specificity of 

 enzymes that has thus far been assumed by the Mendelians has, 

 however, been of a different sort; namely, that for the produc- 

 tion of each color only one enzyme is necessary, but the enzyme 

 which produces any particular color is specifically different from 

 those which produce other colors; . . . ." 



Riddle (1909, p. 336) maintains that with tyrosinase able to 

 produce a series of colors, several of Castle's factors (A, B, E, 

 I, and D) may be reduced to one, tyrosinase, while C, the 

 chromogen, may be left out entirely as a factor since such a 

 chromogen is "universal in protoplasm." In conclusion he asks: 

 "Is it too much to expect that the further application of such 

 tests as the one here presented in outline for the melanin colors 

 will in the end remove many of the Mendelian * factors' from 

 the germ cells ? That many of their ' characters ' will come to rest 

 on a more proximate basis; will be known to have their 'deter- 

 mination' and origin in very general germinal powers, and in 

 somatic conditions obtaining previous to, or at the time of, their 

 development ? ' ' 



Gortner (1910a, 1911a, 1911c) has recently published results 

 of similar investigations on the meal worm, cicada, and potato 

 beetle. He finds that in the meal worm the chromogen is 

 secreted only as needed for pigmentation and is present in exceed- 

 ingly small amounts at any one time, that tyrosinase is present 

 in both the pupa and beetle, but the chromogen is apparently 

 lacking in the pupa stage, the only stage without pigmentation. 



In the case of the periodical cicada, the tyrosinase is not 

 found in the body of the pupa or the adult but is apparently 

 secreted with the new cuticula since the oxidase is present in 

 water in which the newly emerged adults have been washed. 

 In his study of the Colorado potato beetle (Leptinotarsa decem- 

 lineata Say) Gortner finds the pigmentation "produced by the 

 interaction of an oxidizing enzyme of the tyrosinase type, and 

 an oxidizable chromogen. The color pattern is caused by the 



