8 INDIVIDUALITY IN ORGANISMS 



is the foundation of individual unity and order, but in 

 attempts to solve the problem of the individual this 

 fact has not always been clearly recognized. 



This underlying capacity for unity and order finds 

 its primary expression in what is commonly called 

 the polarity and S3rmmetry of the individual. These 

 terms polarity and symmetry refer to the fact that in 

 the appearance and maintenance of the structural and 

 functional order in the individual certain geometrical 

 relations, characteristic for each individual, are dis- 

 tinguishable. These relations are commonly expressed 

 in terms of axes or planes. To say that an individual 

 possesses a polar axis or a plane of symmetry is merely 

 a convenient way of stating the fact that it is possible to 

 conceive as drawn through the individual a line or a 

 plane with reference to which order is perceptible. 

 Such a geometrical conception is an abstraction from 

 the fact that order is actually perceptible to a greater 

 or less degree in all directions. It is merely a selection 

 of those ideal lines or planes to which the order is most 

 directly, simply, or permanently related, and these then 

 serve as a system of co-ordinates, so to speak, to which 

 the order is conveniently referred. 



The geometrical relations of order differ in different 

 individuals. In some cases the order is referable to a 

 system of lines passing through a common center and is 

 designated as radial or radiate. In other cases the 

 order is referable to one or a certain number of axes and 

 is therefore an axiate order, and it is often convenient 

 to refer to planes instead of axes of symmetry. In the 

 living individuals as they exist in nature various com- 

 binations of these relations occur. In the starfish, for 



