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THE AMERICAN NATURALIST [Vol. XLV 



genesis toward the complex conditions of to-day, or in 

 other words, in its racial evolution. Moreover, it is con- 

 ceivable upon this basis how in later stages of phylogeny, 

 as new chemical configurations or new chemical substances 

 were developed, some of these could bridge back into 

 relations with more primitively established substances 

 and thus bring about ontogenetic short-cuts in develop- 

 ment, or how, on the other hand, these abridgments 

 might result in part from alterations in the more primi- 

 tive molecular configurations. Eacial reversions would 

 be interpretable, at least in part, on the ground of the 

 suppression of recently added processes or materials 

 rather than on the reassertion of independently existing 

 germs which had become latent. 



The question arises, does not the very fact of the exact- 

 ness with which the chromosomes are divided show that 

 they are of greater fundamental importance than the 

 cytoplasmic substances? Such a conclusion does not 

 necessarily follow. The cytoplasmic substances of con- 

 cern in development exist in the unfertilized egg appar- 

 ently largely in a neutral or relatively inactive condition. 

 The requisites are that these cytoplasmic substances be 

 of a certain constitution and that there be a certain mini- 

 mum amount of each. As insuring the presence of this 

 indispensable minimal quantity there probably exists 

 more or less of a surplus, but a surplus of this kind 

 would not necessarily alter the result, as on my supposi- 

 tion the necessary quantitative conditions which deter- 

 mine the directing of the chemical reactions in the devel- 

 opmental processes are not brought about in this initial 

 resting substance, but in the products of its fermentation, 

 and the quantity of these at any given unit of time will 

 depend upon the quantity of the ferment. Thus it is 

 evident that by having the series of ferments accurately 

 apportioned as we seemingly do in the chromosome, there 

 can be an adequate quantitative and therefore qualita- 

 tive regulation of the chemical processes without the con- 

 troller being considered of fundamentally greater im- 

 portance than the substances controlled. 



