Evidence from Somatic Hist o genesis 33 



cytoplasm instead of in the chromosomes. This effort is 

 just as misdirected as is the effort to make chromatin the 

 sole hereditary substance. According to the organismal 

 conception, all life phenomena, including those of inheri- 

 tance, consist in the activities and interactivities of an 

 enormous number of substances and units and forces, all of 

 which, in exhaustive analysis, are dependent upon the organ- 

 ism as a living whole. It is, therefore, as futile to hunt in 

 one corner as another for the physical basis of heredity 

 in an exclusive and more or less metaphysical sense. Any 

 one who has grasped this idea will know beforehand that 

 the proposal to make mitochondria fully explain heredity is 

 doomed to failure no less certainly than was the proposal to 

 make chromosomes or any one kind of cell element play such 

 a role. But hypotheses, the falsity of which might have been 

 seen before they were tested, may still be useful. If those 

 who propose them can be convinced of their fallacy in no 

 other way than by testing them then it is better that they 

 should be tested even though much time and labor be given 

 to the task. Again, the evidence brought out which dis- 

 proves an hypothesis may be highly useful in establishing 

 some alternative general view. This result has been espe- 

 cially striking in the case of the mitochondrial hypothesis of 

 hereditary substance. By bringing the cell-body back into 

 the field of interest, from which it had been largely excluded 

 so far as heredity was concerned, by the nuclear inheritance 

 theory, the mitochondrial hypothesis has resulted not merely 

 in proving that mitochondria are not bearers of heredity 

 in the elementalist sense, but that in a rational sense they 

 are sometimes rather closely concerned in the production 

 of hereditary structures ; and, of even greater importance, 

 that still other cytoplasmic material is likewise so concerned. 

 The only reason why the mitochondrial theory of hered- 

 ity is less interesting than the chromatin theory is that 

 there is so much less observational evidence in support of it. 



