6 INDIVIDUALITY IN ORGANISMS 



soon succeeded by another. Each pseudopodium of an 

 amoeba, for example, is to some extent an individuation 

 of a part of the amoeba protoplasm, but it soon disap- 

 pears or gives way to another individuation, and so on. 

 Between such simple and evanescent individuals as this, 

 at the one extreme, and the human body with its amaz- 

 ingly complex structural and functional order and its 

 relative permanency at the other, there are of course 

 many intermediate conditions. In general, organic evo- 

 lution appears from this point of view to consist in an 

 increasing complexity and stability of order; in other 

 words, the degree of individuation, the unity of the 

 individual, increases in the course of evolution. The 

 series of changes which constitute development becomes 

 more and more definite, constant, and complex in ap- 

 pearance, and the product of these changes, the fully 

 formed individual, shows an increasing complexity and 

 stability of structure and an increasing variety and 

 degree of interrelation of parts. In fact, a progressive 

 morphological and physiological complication seems to 

 occur both in individual development and in evolution. 

 Between the unicellular organism and the adult human 

 being the difference appears to be almost infinite, but 

 the human individual is at the beginning a single cell 

 with much less complex visible structure than many 

 unicellular forms. 



The process of visible structural complication which 

 occurs in both development and evolution is commonly 

 known as differentiation. Different regions of the cell, 

 different cells or cell groups, become different from each 

 other and from the original undifferentiated or so-called 

 embryonic condition. These differences are in general 



