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.” 
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: (z) 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 BapPTiIsTE 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.? 
1 Pemberton, Path of Evolution, p. 294. 
* Op. cit., p. 294. 
