20 FIFTY YEARS OF DARWINISM 



force of habits, while * with age heredity acts 

 more strongly, instincts prevail, and adaptation 

 to new conditions of existence and to new ideas 

 become more difficult ; in a word, it is much less 

 easy to combat hereditary tendencies '. Similarly, 

 in the state of maturity now reached by the 

 organic world, Beccari believes that the power of 

 adaptation is wellnigh non-existent. Heredity, 

 through long accumulation in the course of endless 

 generations, has become so powerful that species 

 are now stereotyped and cannot undergo advan- 

 tageous changes. For the same reason, he con- 

 siders, acquired characters cannot now be trans- 

 mitted to offspring. Beccari imagines that 

 everything was different in early ages, when, as 

 he supposes, life was young and heredity weak. 

 In this assumed ' Plasmatic Epoch ' the environ- 

 ment acted strongly upon organisms, evoking the 

 responsive changes which have now been ren- 

 dered fixed and immovable by heredity. 



Even the hypothesis proposed as a substitute 

 for Natural Selection by so distinguished a botanist 

 as Carl Nageli turns out to be most unsatisfactory 

 the moment it is examined. The idea of evolution 

 under the compulsion of an internal force residing 

 in the idioplasm is in essence but little removed 

 from special creation. On the subject of Nageli's 

 criticisms Darwin wrote, Aug. 10, 1869, to Lord 

 Farrer : 



' It is to me delightful to see what appears a mere morpho- 

 logical character found to be of use. It pleases me the more 



