CHAPTER IX 



INDIVIDUATION AND. REPRODUCTION IN ORGANISMS 



THE PROBLEM 



Living organisms exist as more or less definite individuals. An 

 individual may be provisionally defined as a more or less complex 

 entity which acts to some extent as a unit or whole. Such a defi- 

 nition emphasizes the unity of the individual, but affords no clue 

 to the integrating factor or factors, i.e., to that which makes a 

 unity, a whole out of the complex. 



Two very conspicuous characteristics of the organic individual, 

 particularly in its more highly developed forms, are its orderly 

 behavior and the definiteness of form and structure which is one 

 feature of this behavior. Nowhere do these characteristics appear 

 more clearly than in the remarkable sequence of events which con- 

 stitutes what we call the development, the ontogeny of the indi- 

 vidual. In the simpler organisms the morphological definiteness 

 is often less conspicuous, both the structure and the behavior being 

 more susceptible of modification by external factors, but the modi- 

 fications are themselves definite and orderly and are manifestly 

 not a direct and specific effect of the external factors which are 

 acting, but rather a reaction of an individual of some sort to an 

 external change. 



In short, although we may attempt to ignore or deny it, as 

 various biologists have done, the fact remains that an ordering, 

 controlling principle of some sort exists in the organic individual. 

 The existence of such a principle does not, however, as has so often 

 been asserted, distinguish the living from the non-living inorganic 

 individual. In an electrical or a magnetic field or in a planetary 

 system, for example, we have individuations of a definite, orderly 

 character, though it is evident that such individuations are not 

 very similar to living organisms. The crystal also is an indi- 

 viduation of a highly orderly and definite character, and the at- 

 tempt has often been made to find some fundamental similarity 

 between living organisms and crystals, but without any great 



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