56 ADAPTATION AND PROGRESS 



series of mechanical impacts, none the less real because invisible, 

 or disguised by the fact that some of them are precipitated by 

 voluntary effort of the individual itself." l 



The influence on the organism of such environmental forces as 

 food and climate has never been seriously questioned. The 

 mooted points are such as these: (i) the inheritance in any 

 degree of characters thus acquired, and if so, the method; (2) the 

 presence and potency in the organism of a vital, directive force; 

 (3) the character of the variations whether continuous or dis- 

 continuous; and (4) the process by which variations come to 

 have such qualitative difference as to give rise to new species. 

 The most vital point in the controversy today, especially among 

 the followers of Weismann, is as to whether or not any environ- 

 mental influence can affect heredity, working either through the 

 blood or through the central nervous system, and if so, what such 

 influences are and how the effect is produced. 



In the development of the doctrine of adaptation in theories of 

 biological evolution, five names stand out with such prominence 

 as to demand special consideration: Lamarck, Charles Darwin, 

 Weismann, De Vries and Mendel. 



Jean Baptiste de Lamarck (1744-1829) 



Use-Inheritance 



Pemberton in his Path of Evolution thus characterizes the work 

 of Lamarck: — 



He rendered to mankind the eminent service of arousing attention to the 

 probability that all change in the organic as well as in the inorganic world, 

 was the result of law and not miraculous interposition. His theories of 

 the origin of species were, that the organs of the body were modified by the 

 desires and will of the individual in response to external condition. The 

 changes thus induced would be transmitted to their offspring, subject, 

 moreover, to like changes from new conditions so that, if illimitable time was 

 granted, it would account for the formation of the highest order of animals 

 from the lowest organisms. In accordance with this doctrine he held that 

 man himself was derived from the species next below him, the anthropoid 

 apes. 2 



1 Pemberton, Path of Evolution, p. 294. 



'' Op. cit., p. 294. 



