1 8 INDIVIDUALITY IN ORGANISMS 



define certain terms to be used. The individual which 

 forms the starting-point of a developmental, reproductive, 

 or life-history I shall call the primary individual. This 

 primary individual may give rise by reproduction to 

 secondary individuals, or, by the individuation of certain 

 organs within itself, to partial or organ-individuals. 

 When such secondary, partial, or organ-individuals 

 continue to constitute parts of the unity of the primary 

 individual it is the dominant individual and they are 

 subordinate individuals. The segments of the earth- 

 worm body or the leaves of a plant are such subordinate 

 individuals. When the primary and secondary indi- 

 viduals each constitute a more or less distinct unity 

 though still organically connected they are co-ordinate 

 individuals. In many trees and in some branching 

 colonial animals various branches approach or attain the 

 condition of co-ordinate individuals. Between strictly 

 co-ordinate and the extremes of dominant and sub- 

 ordinate individuals there are of course various inter- 

 mediate degrees. A common or general individuality 

 resulting from the physiological combination of a 

 number of more or less co-ordinate individuals, either 

 similar or of different kinds, is a composite individual. 

 Strictly speaking, all organisms except perhaps some of 

 the simplest unicellular or monoplastic forms are to 

 some extent composite individuals for different cells, 

 and even different parts of a cell may possess a physio- 

 logical unity and order of their own, but since the 

 following chapters are chiefly concerned with the larger, 

 more general, features of organic individuality rather 

 than with its more minute details, the term will be used 

 primarily for the more extreme cases in which a number 



