Tyrosinase in Reproductive Organs of Amphibians. 119 



importance of the tyrosinase Phisalix says: " It is probable that the 

 oxidase presides over the oxidations within the organism . . . and 

 plays the role of fixing oxygen in cutaneous respiration." If such 

 is the case, and the production of the pigment in the skin is only a 

 secondary reaction, or the elimination of a byproduct, the study of 

 this enzyme becomes of much greater importance than merely as a 

 pigment-producer. 



In every instance where the mechanism of melanin formation 

 has been elucidated, it has been found that pigmentation is due 

 to the interaction of tyrosinase and a chromogen. It therefore 

 seemed probable that the enzyme might be present in the ovaries 

 of those amphibians which deposit pigmented eggs, and might be 

 responsible for the pigment formation. I have found that tyrosin- 

 ase is present in the ovaries of the green frog, Rana clamata, and 

 the wood frog, Rana sylvatita. Owing to the greater ease in 

 securing material of various ages most of the tests were carried 

 out using material from the green frog. In every instance the 

 intensity, and the rapidity of the development of the tyrosinase test 

 was in inverse proportion to the amount of pigment present in the 

 eggs. Ovaries which were immature, and contained no pigmented 

 eggs, gave a positive tyrosinase test in a very few hours, partially 

 pigmented ovaries required in some instances as much as 96 hours 

 to produce a positive test, while the ovaries which contained ripe 

 eggs failed to give any indication of the presence of the enzyme in 

 168 hours. All solutions were kept sterile by the addition of a few 

 drops of chloroform. When partially pigmented ovaries were 

 used the "blank" (no tyrosin added) usually showed considerable 

 darkening, which, however, did not appear in a boiled check, show- 

 ing that a chromogen was also present. It would, therefore, 

 appear that the pigmentation of the eggs of the frog is due to an 

 oxidation induced by tyrosinase, and that as the pigmentation 

 progresses the amount of tyrosinase decreases, until there is no 

 perceptible amount of the enzyme present in the unfertilized 

 eggs which are fully ripe. 



The tadpoles at the moment of liberation from the egg contain 

 tyrosinase, as do also the larvae of the salamander, Amby stoma 

 punctatum. Inasmuch as the ripe unfertilized ova do not seem to 

 contain tyrosinase, it seemed probable that the enzyme might be 



