348 OSCAR RIDDLE. 



at least has strayed very wide of the facts ; it has put factors 

 in the germ cells that it is now quite certainly our privilege to 

 remove ; it has declared discontinuity where there is now proved 

 continuity ; it has postulated preformation where there is now 

 evident epigenesis. 



Is it too much to expect that the further application of such 

 tests as the one here presented in outline for the melanin colors 

 will in the end remove many of the Mendelian " factors " from 

 the germ cells? That many of their " characters " will come to 

 rest on a more proximate basis ; will be known to have their 

 "determination " and origin in very general germinal powers, and 

 in somatic conditions obtaining previous to, or at the time of, 

 their development? Will not other Mendelian discontinuities 

 then begin to disclose gradations, and other qualitative differences 

 then appear more and more as quantitative sequences ? 

 LABORATORIES OF EXPERIMENTAL THERAPEUTICS AND ZOOLOGY, 

 THE UNIVERSITY OF CHICAGO, 

 January, 1909. 



LITERATURE CITED. 

 Abel, J., and Davis, W. 



'96 The Pigments of the Negro's Skin and Hair. Jour. Exp. Med., I., p. 361. 

 Abderhalden, E., and Schittenhelm, A. 



'05 Ausscheidung von tyrosin und leucin in einem falle von cystinurie. Zeit. f. 



Physiol. Chem., XLV., p. 468. 

 Albrecht, H. 



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 Bateson, W., and Sanders, Miss E. R. 



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'06 Progress of Genetics. 

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 Bertrand, G., and Mutermilch, W. 



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 Bertrand, G. 



'08 Recherches sur la melanogenesis : Action de la Tyrosinase sur la Tyrosine. 



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'98 Beitrage zur vergleichenden physiologic der verdauung. I. Die verdauung 

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