318 GENERAL PHYSIOLOGY 



Adaptation to external conditions as a result of selection pre- 

 supposes a continual inheritance of innate characteristics, and 

 Weismann ('92, 1) holds the view that the inheritance of innate 

 characteristics alone comes into the question of change in the 

 organic world. Since Darwin believed that acquired character- 

 istics also are transmitted, Weismann, as the defender of the one- 

 sided theory of selection, is, in a certain sense, more Darwinian 

 than Darwin himself. Others, such as Haeckel ('66), Eimer 

 ('88), and Herbert Spencer ('93), are also of the opinion that 

 the inheritance of such characteristics as are acquired during the 

 individual life is of great importance in the transformation of 

 organisms. Naturally there always arises here the question 

 whether these characteristics are properly adapted to external 

 conditions or not. If not, they likewise are soon set aside by 

 selection in the struggle for existence. But at the present time 

 the question whether only innate or also acquired characteristics 

 are inherited, constitutes the point of chief interest for those who 

 theorise upon heredity : and, in spite of much discussion, it still 

 waits for a definitive answer. 1 



If, finally, a brief examination be made of the nature of the 

 changes that living substance has undergone from its origin down 

 to the present, the fact appears that it has developed from simple 

 to constantly more complex forms and organisation. The result is 

 that the most complex organisms occur at the present time, being 

 represented by the flowering-plants and the vertebrates, in which 

 special parts have become widely differentiated for the exercise of 

 very special occupations. It has frequently been said that in the 

 developmental series of organisms from the earliest beginnings 

 down to the present there may be seen a continual advance a 

 progressive perfecting. This idea embraces an error which it was 

 the whole endeavour of the Darwinian theory to avoid, viz., that 

 of teleology. The conception of advance, of perfecting, involves a 

 goal toward which the advance is directed. Without this it is an 

 empty conception. In reality, however, there does not exist in 

 the development of organisms a predestined goal toward which 

 the development is striving any more than in any chemical 

 reaction. Organisms can only follow, and must follow in a definite 

 direction, when the proper external conditions are present. 

 Changes in them are dependent solely upon changes in their 

 environment. The employment, therefore, of the idea of advance 

 or perfecting is evidence merely of an anthropocentric stand- 

 point ; we introduce ourselves into the development as the goal. 

 For whatever reason this is done, the goal is an artificial thing 

 which does not exist in nature ; the assumption that mankind is 

 more perfect than an amosba is not justified by reality. It is 

 simply a conventionality to call development a perfecting. 



J Cf. p. 180. 



