2^6 HAECKEL 



zoological problem. In his General Morjphology 

 he had expounded his brilliant ideas on the subject 

 of individuality, and now he encountered in the 

 flesh one of the greatest marvels of animal 

 individuality. He had shown how the higher 

 individual is always made up of a community, 

 a kind of state, of lower individuals. In the 

 simplest instance there are the cells. Each of 

 them is an individual. Millions of these indi- 

 viduals, banded together with division of labour 

 for great collective operations, make up the human 

 frame, and therefore the human ^' individual." 

 In the same way others form a beetle, a snail, or 

 a single medusa. Sometimes, however, these 

 higher individuals enter in turn into social 

 combinations to form still higher communities. 

 Human beings form social commonwealths, with 

 division of labour among the individuals. Bees 

 and ants form their communities in the same 

 way. But in the latter cases the texture of the 

 community seems to be much looser than in the 

 preceding one. It is not so easy for the imagina- 

 tion to grasp a human commonwealth or a colony 

 of bees as a real '' over-individual." It is, there- 

 fore, extremely instructive to find that at least 

 one animal community of this kind is of so firm 

 a texture that even on the most superficial 

 examination it is recognised at once as an 

 individual. This is found in one of the groups 

 of the medusae, the siphonophores, or social 

 medusae. 



A number of single medusae, each of which 



