34 C. M. CHILD. 



matter of fact, if a quantitative change in metabolism is sufficient 

 to alter the structure to any marked degree, 'che effect of the 

 change may persist in the part or parts concerned for a time 

 or perhaps indefinitely after the conditions have ceased to act. 

 But we cannot expect always to find characters of this sort perma- 

 nently inherited, even if the germ cells are most intimately cor- 

 related physiologically with the soma, for as soon as the gametes 

 are isolated and undergo dedifferentiation their rate of metabolism 

 becomes very largely independent of the conditions to which 

 they were subjected as parts of the organism. In some cases 

 the effects of such quantitative changes may reappear to some 

 extent for a generation or two, but they soon fade out. The non- 

 inheritance of such characters does not then afford any evidence 

 either for or against the independence of germ plasm and soma. 

 In order to obtain direct evidence upon this point we must first 

 know something of the nature of the processes which give rise 

 to a certain character, and second, something of their correlative 

 effect upon other parts of the body. Then we shall be able to 

 determine what their inheritance or non-inheritance means. 



It is not, I believe, too much to say that at present we have no 

 positive evidence from the data now at hand concerning inherit- 

 ance that the germ cells are independent of the soma. The estab- 

 lished facts are simply that many individually acquired somatic 

 characters are not inherited. We do not know, however, whether 

 it is possible for them to be inherited even if the germ cells are 

 integral physiological parts of the organism. 



The inheritance of a character, whether it results from direct 

 influence of factors of the external world upon the reproductive 

 cell or cell mass or from the influence of changes in the soma, 

 cannot depend merely upon the production of a change of any 

 kind in the processes in the reproductive element, for many such 

 changes disappear at once or very soon when conditions are 

 altered. It must depend rather upon the establishment of a new 

 dynamic equilibrium in the system and an equilibrium which is 

 relatively stable, so that every change in conditions does not 

 destroy it. This is doubtless the reason why so many attempts 

 to produce mutations or new genotypes have been unsuccessful. 

 As our knowledge of the dynamic processes in organisms increases 



