162 DARWINISM AND HUMAN LIFE 



the important question of tlie transmissibility of 

 acquired disease. When the question is carefully 

 considered, it seems possible to distinguish be- 

 tween (1) abnormal or deranged processes which 

 have their roots in germinal peculiarities or de- 

 fects (variations), and (2) abnormal or deranged 

 processes which have been directly induced 

 in the body by acquired modifications, i.e. as 

 the results of unnatural surroundings or habits, 

 including the intrusion of parasites. There is 

 very little evidence to suggest that this second 

 kind of disease is heritable as such, though the 

 indirect effects may influence the offspring. When 

 we go further and come to understand that pre- 

 natal infection is not inheritance, that inheritance 

 of a predisposition to a disease is not inheritance 

 of the disease, that the general weakening of the 

 offspring through disease in the parent is a very 

 different matter from the transmission of a specific 

 disease, we are almost irresistibly led to the con- 

 clusion that in the sense in which the word " in- 

 herited " is used in biology, there are no inherited 

 diseases. What does seem to be inherited, how- 

 ever, is a defectiveness or degeneracy of the germ- 

 plasm which finds one expression in the parent and 

 another in the offspring. 



Facts and Possibilities. — The evidence in 

 support of the transmission of acquired characters 

 is either very anecdotal or very uncritical, and, 

 until some cogent cases are forthcoming, the 

 thoroughgoing scepticism which Weismann ex- 

 pressed many years ago remains justified. 



Besides the unsatisfactory nature of the evidence, 

 we have to admit the difficulty of imagining any 

 means whereby a modification of a particular 



