MELANIN COLOR FORMATION. 33! 



and Gessard, state that these pigments result from the action of 

 an oxidizing enzyme (tyrosinase) upon a chromogenic substance ; 

 there are good reasons for supposing that things happen simi- 

 larly in the pigmentation of the skin ; there should be, however, 

 in this case, either two different chromogens and only one enzyme, 

 or only one chromogen and two enzymes, the one for the blackish 

 pigment and the other for the yellow pigment. We adopt pro- 

 visionally, for convenience of language, this latter hypothesis. 



" The germ plasma of a gray mouse should contain potentially 

 the three substances which, by their reciprocal reactions later 

 produce the deposition of pigment in the hair ; and doubtless 

 these three substances are contained in the potential state within 

 many of the material particles of the germ plasma (representa- 

 tive particles or qualitative substances of the egg mnemons). 

 In a gray mouse (black and yellow pigmented) there are three 

 mnemons, one for the chromogen and two for the two ferments ; 

 in a black mouse there are only two mnemons, one for the 

 chromogen and another for the formative enzyme of black 

 pigment. 



" In regard to albinos, all is explained if we admit that their 

 germ plasma contains only the mnemons of the enzymes, that of 

 the chromogen being totally absent. With these conditions, 

 colored hair cannot be formed in albinos, since one of the sub- 

 stances indispensable to the reaction is absent, but one easily 

 understands that the albino will transmit to its progeny either the 

 mnemons for the two enzymes, or one mnemon only, if it pos- 

 sesses but one." 



The Mendelians have one further point to confirm the faith 

 that is in them. Soon after the appearance of the paper by 

 Cuenot, Durham undertook to find whether in the skins of black, 

 chocolate, yellow and albino mammals there is the appropriate 

 enzyme in each for the production of its particular color --when 

 this acts upon a tyrosin solution. Only a short preliminary 

 statement ('04) of the results has appeared ; and although posi- 

 tive results were reported for the black, chocolate and yellow 

 pigments, it is evident that from no point of view can these re- 

 sults be regarded as satisfactory ; particularly because the ex- 

 tracts used by her are stated to have had a reddish color before 



