CHAPTER V 



THE INHERITANCE OF ACQUIRED CONDITIONS IN THE 

 HIGHER ANIMALS 



DIRECT adaptation, or direct equilibration in the Spencerian 

 sense, can be proved to occur in a certain order of cases, both at 

 the lower end of the scale and at the upper, and this adaptation 

 may manifest itself as an acquirement of additional properties, 

 as well as by loss of properties already possessed by the individual. 

 But now, to advance further, it is necessary to bring forward the 

 evidence obtained from medical research that acquirements, 

 whether of defect or of excess, if they may be so termed, are 

 passed on to the next generation. 



There can be no question that they are in the case of the 

 bacteria, but here so intimate and so direct is the relationship 

 between the organism and the environment that while, as already 

 stated, the longer the environment has acted on a given species 

 of microbe the longer the microbe retains the impressed property, 

 I cannot state dogmatically that there is any biochemical property 

 that is specifically fixed, still less, therefore, that any acquire- 

 ment remains fixed. 



With reference to the higher animals we recognize full well 

 that the problem to be answered is girt with numerous restric- 

 tions, that conjugation and amphimixis in general act as a factor 

 tending to neutralize and dissipate the evidence of such heredity, 

 that in mammals we have narrowly to distinguish between 

 conditions of germinal origin (which alone are truly inheritances) 

 and those acquired during the uterine phase of existence ; again 

 between conditions of germinal origin and those impressed upon 

 the offspring during extra-uterine existence. Take the question 

 of the inheritance by the children of the tuberculous of a tuber- 

 culous diathesis : how are we to assure ourselves that, when the 



