LIVING SUBSTANCE 



59 



case and that of the community of ants is that here the individuals 

 of the lower order are in physical connection with one another. 



It will be advantageous to look about the organic world and see 

 what different grades of individuality are to be found. The 

 community, the colony, is evidently the highest grade, for a sum of 

 communities is not a new and higher unit. The next lower stage 

 in the community is the person. The coral-colony can be regarded in 

 a certain sense as a person which consists of single organs ; this 

 relation, however, is clearer in another group of Coelenterata, the 

 Siphonophora. The Siphonophora represent persons which consist 



FIG. 4. Stephalia corona, a Siphonophpre. A, Longitudinal section ; B, external view ; sb, swim- 

 bladder ; sgr, swimming-bells ; go, sexual glands ; hi/, gastric tubes ; o, chief gastric tube ; t, 

 tentacles. All the organs are single individuals. (After Haeckel.) 



of a number of variously developed organs. Some of these organs 

 are for purposes of movement, others for nutrition, others for re- 

 production, others for protection of the whole body, and all are 

 grouped in regular order about a longitudinal axis (Fig. 4). But 

 all the organs are single individuals, for the embryology of the 

 Siphonophora shows that they all arise from morphologically 

 homologous parts by budding ; and that in certain cases single in- 

 dividuals, as, e.g., the swimming-bells, can separate themselves from 

 the stem and lead an independent existence as medusae. It is 

 seen, therefore, that the person of the Siphonophora can be con- 

 sidered as a colony of single organs, and that the stage of indi- 

 viduality of the person includes the lower stages of individuality 

 of the organs. Careful dissection of an organ, e.g., a human arm, 



