336 OSCAR RIDDLE. 



the Mendelian who accepts tKis terminology in no position to 

 deny the development of the melanin series on a basis of closely 

 graduated powers of tyrosin oxidation, and so without any basis 

 on particles or factors, whatever. It is, moreover, as plain as it 

 is certain, that this degree of oxidising poiver covers several of 

 these factors (A, B, E, I, D) which are thus reduced to one ; 

 while the kernel of this formula the C, or chromogen, goes out 

 entirely as a factor, /. c., something capable of being shuffled in 

 the germs since as we have pointed out, such a chromogen is 

 universal in protoplasm. 



DISCUSSION. 



If the later oxidations those which produce color of the 

 tyrosin compounds are each individually controlled by a separate, 

 specific enzyme, why are not the several earlier oxidations of the 

 same compounds similarly conditioned ? If assumption will give 

 us the whole series of tyrosin oxidations only on condition of 

 their production by means of separate and distinct enzymes, why 

 should it hesitate to put the whole vast array of oxidations of all 

 aromatic, or even of all organic compounds on a similar basis - 

 a separate and specific enzyme, separately heritable, for each 

 step in oxidation ? This is certainly not true. 



It is impossible at present to announce the limits to the speci- 

 ficity of enzymes, and of the oxidases generally ; but it can be 

 said that it is pretty generally conceded that the oxidases present 

 less specificity than do the digestive enzymes (see Wilcock, '06). 

 That which weighs most heavily against the Mendelian assump- 

 tion of a high specificity of tyrosin oxidizing enzymes is, however, 

 the result of Bertrand's special study of tyrosinase which indicates 

 no such specificity (quoted p. 324 of this paper). 



But granted the greatest possible specificity of these enzymes, 

 the Mendelian description of color inheritance becomes even 

 more untenable ; for Gessard and Bertrand have shown that 

 "black" is the end-result of a series of successive oxidations 

 and this final color can be attained only by having all of the 

 intermediate stages actually attained. This means that the 

 animal that transmits the enzyme for black, /. e., produces black 

 colored offspring, must at the same time transmit also the enzyme 



