58 



GENERAL PHYSIOLOGY 



living cell under the microscope, would be an individual. Such 

 a particle, however, cannot be so considered when it is seen how 

 every minute ma^s of living substance, which has not the value of 

 the cell, sooner or later invariably perishes. The capability of self- 

 preservation may, therefore, be added to the conception of the in- 

 dividual and the latter may be defined as follows : An organic in- 

 dividual is a unitary mass of living substance luhich under definite 

 external vital conditions is capable of self-preservation. 



This definition applies to all single, free-living organisms which 

 are spatially separated from one another and are not artificially 

 divided, in other words to all organisms in the form in which they 

 occur in nature. But it includes more than single organisms ; it 

 includes groups of organisms, each one of which is separated from 

 the others by space, but which together form a unit. An example 



-BvLCOrallium rubrum, the precious coral, a, A coral stem containing many individuals ; 6, a 

 single individual highly magnified. (After H.aeckel.) 



of this is a community of ants. The community represents a 

 single individual in so far as it is a unitary whole in which the single 

 parts work together like the parts of an organism. But it consists 

 of many single individuals, males, females, workers, and soldiers. 

 It is thus seen that individuality may be of very different grades. 

 It seems advantageous to distinguish the grades of individuality 

 by terming the more comprehensive form an individual of a higher 

 order, and the forms composing it individuals of a lower order. 

 The condition in the coral-stem is like the relation between the 

 ant-community and the individual ants. The coral-stem (Fig. 3, a) 

 is an individual of a higher order, the single coral-polyp (Fig. 3, b) 

 an individual of a lower order. The sole difference between this 



