Chapter J 

 The Evolution of Individuality 



In a preceding part we have followed the evolution of organisms from 

 their primitive beginnings to man. At first, the organisms are relatively 

 simple as far as the differentiation of their organs and the character of 

 their organismal differentials are concerned. They are still very plastic, re- 

 sponding readily with a modification of organ and tissue formation to certain 

 changes in the environment. They also reproduce with ease lost parts of their 

 body, even relatively small pieces having the power to do so. Presumably 

 this relatively great plasticity of the organs and the relative simplicity of the 

 organismal differentials are connected with each other. * 



With advancing evolution, the plasticity of the organism, its readiness to 

 respond to the environment, decreases ; more and more the organism becomes 

 a fixed, closed system, in which structural complexity and integration in- 

 crease; at the same time, the organs become more specialized and the or- 

 ganismal differentials more differentiated and individualized. The increasing 

 independence of the environment applies not only to the adult organism, but 

 also to the embryo, whose development, in the higher organisms, takes place 

 within the body of the adult mother ; in this way the influence of environmental 

 factors on development is more completely excluded. Within the mother's 

 body the greater specialization of the organ and organismal differentials takes 

 place, the finer structural differentiation and the fuller integration occur and 

 a more individualized organism is formed. It is born in a state in which the 

 animal is more or less fully developed as far as its structural characteristics 

 are concerned. 



Concurrently and intimately connected with this increase in the specializa- 

 tion of organ and organismal differentials and in the individualization of the 

 organism, a greater refinement in the immune mechanisms is established. This 

 latter change adds still further to the individualization of the organism and 

 tends to transfer a greater part of its reaction to certain environmental 

 alterations from the external world into the interior of the ariimal. We can 

 consider the gradual refinement of the organismal differentials and of the 

 processes on which their manifestation depends, as well as the increasing 

 delicacy and significance of the immunity reactions, which are largely based 

 on corresponding changes in the various differentials, as mechanisms of 

 defense on the part of the organism as a whole against interference from the 

 outside, and therefore as mechanisms guaranteeing the integrity of the or- 

 ganism and its increased independence of the environment. As a result of 

 these alterations, there is a change in the circuit of relationship between or- 

 ganism and environment, in that the influence of the environment on the or- 

 ganism becomes less and the effect of the organism on the environment be- 

 comes greater in the course of evolution. With this increasing refinement of 



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