224 Heredity and Eugenics 



of physiological chemistry are so exceedingly gross that 

 when by any available method either chromogen or enzyme 

 have been removed, they have been changed to a very 

 considerable degree in structure and relations, and possibly 

 in capacity for pigment production. The complexity and 

 almost futile nature of the chemical side of this problem is 

 clearly indicated by the statement (Meischer) that in 

 albumen molecules containing no more than forty carbon 

 atoms there are something like a billion possible stereo- 

 isomeres. It is at once evident how utterly hopeless it is 

 with present methods to expect exact chemical determina- 

 tions of these germinal changes, and the best that the 

 physiological chemist can be expected to do is to show the 

 grosser outlines of the possible processes involved. To 

 determine the exact changes within the germ cell is at 

 present not possible. 



Furthermore, the results of Reichert and Brown upon 

 the investigation of haemoglobin crystals have shown a great 

 array of crystalline forms and structures in this substance 

 in allied mammalia, and it is highly probable that other sub- 

 stances throughout the organic world are equally divergent, 

 equally complex, and equally specific. We must therefore 

 keep in mind that in these color modifications there are 

 always three possibilities — the modification of the chromo- 

 gen base, the modification of the enzyme, or the modification 

 of the capacity for carrying on the process; but present evi- 

 dence, I believe, warrants a stronger belief in the efficiency 

 of modifications in the capacity of carrying on the process 

 more than in the modification of either the chromogen base 

 or the katalyzer, i.e., to modified accelerators and inhibitors. 



In colors due to lipoids, modifications thereof might be 

 attributable to changes in the chromogen base, in the 



