32O OSCAR RIDDLE. 



cussion to state that I shall first describe some of the facts of 

 color development as they are known at present from chemical, 

 pathological, and physiological experience ; and afterward sketch 

 very briefly the nature of the Mendelian terminology ; this to be 

 followed by some discussion of my point of view. Such facts 

 of color will be considered as have bearing on the following 

 points : 



Do the known facts of the genesis, nature and history of color 

 characters harmonize with, supplement, modify, or radically differ 

 from, the demands of present Mendelian interpretation ? Do 

 they enable us to decide as to whether color characters are 

 qualitative or quantitative in nature ? Are color differences cases 

 of continuous or discontinuous variability ? Can these facts 

 throw light upon the existence or nature of unit characters ? 

 What of the purity of gametes ? Do these facts indicate a dif- 

 ferent or sounder basis for the interpretation of Mendelian, or 

 other inheritance? What justification or light, if any, is thrown 

 upon the present practices of (a) adding " factors " in order to 

 account for the inheritance phenomena exhibited by a character ; 

 ($) of tying all these " factors " together and postulating that all 

 pass (by means of their representatives) through the germ cells ? 



SOME FACTS OF MELANIN COLOR FORMATION. 



In a consideration of the facts of the origin of melanin color- 

 ation, one might deal at some length with the distribution and 

 histogenesis of melanin. Though several interesting and illumi- 

 nating facts lie in each of these directions, I shall dismiss these 

 two phases of the origin of melanin colors with the single state- 

 ment that the melanins are usually dark, amorphous or granular 

 pigments, chiefly of intracellular, animal origin ; extending within 

 this kingdom from the trypanosomes (Protozoa) to man. There is 

 no vertebrate species (unless we may think of pure albinos as such), 

 but has this coloring matter in one or several parts of its body. 

 It is, however, the chemical and physiological phases of the 

 origin of color that it is most desirable to discuss, and it is 

 from this angle of approach that we find most of the facts which 







bear on the Mendelian description of heredity. 



Our knowledge of what has been called the " mechanics of 



