Riddle, Experiments on Melanin Color Formation etc. 3 1 - 



verification in so far as the crucial tests have been applied. Dur- 

 ham's direct and definite confirmation of the theory by the 

 announced finding of the specific tyrosinases postulated by the 

 theory, cannot be verified. It is demonstrated, moreover, that 

 with our actual methods of extraction no tyrosinase specificity 

 is indicated. 



And further, by way of defining the bearing of this result 

 on certain phases of modern Mendelian theory, we recall merely 

 that it is this 'presence and absence' idea that has, increasingly 

 with the years, become the touchstone of the Neo-Mendelian 

 description and interpretation ; that the characters most studied, 

 and most relied upon by them further to increase the number 

 of discreet individualities in an already broad mosaic of germ- 

 plasm, are just these color characters. And that while these two 

 forms of Mendelian confidence and activity have increased apace, 

 the postulated objective basis of the parent idea, has, through 

 direct investigation during these years, decreased in probability. 

 Although the postulated bases — the roots — of the original 

 theory have tended to wither, ever new twigs and fine flowers 

 of dependent theory have appeared in accelerating profusion. 

 Fact and theory seem here to be travelling in opposite directions. 

 Actually, of course, the extension of theory has been connected 

 with fact of a quite different nature, namely, the behavior of 

 characters in hybridization — a kind of fact, which, no matter 

 how plentiful, cannot prove the assumptions upon which C u e n o t 

 founded his theory. 



It is doubtless "bad form" for us to march out of step; to 

 strike discordant notes; to refuse to join the procession. Never- 

 theless, we find ourselves unable to go with that considerable 

 body of Mendelians who, taking up C u e n o t 's hypothesis, 

 have further pursued the enzymes, activators, inhibitors, chromo- 

 gens; announcing more and more of these definite chemical indi- 

 viduals, and outlining the whole plan of the chemical complex 

 by which color is formed, a 1 1 on the basis of breeding experience. 

 The number of workers so engaged is by no means inconsiderable, 

 and the elaborateness of their declarations concerning the com- 

 position of characters may be judged from announcements made 

 within a year that the magenta color of Antirrhinum has at least 

 six components (4 enz. + 2 chrom.) (W h e 1 d a 1 e) ; that color 

 in general in Antirrhinum is represented by possibly twenty 

 factors (Bauer); and that there are certainly as many as eight 

 such factors back of the coloration of a gray rabbit (Castle). 

 What makes it particulary difficult for us to travel in this direction 

 is that these workers put all these factors into the germ cell and 

 make some very definite assumptions and Statements as to their 

 properties while there. It is assumed, for example, that not only 

 are there several specific color-producing enzymes and chromo- 



