CHAP. V 



Social Life of Animals 



co-operation, surrender of individuality, of sociality at a low 

 level, but it is unwise to apply these words to creatures 

 so simple. All that we certainly know is that some of the 

 simplest animals form loose colonies of units, that the gulf 

 between them and the higher animals is thus bridged, and 

 that the bridging depends on coherence. Our first con- 



FIG. 19. Siphonophore colony, showing the float (a), the swimming-bells ($) ; 

 the nutritive, reproductive, and other members of the colony beneath. (From 

 the Evolution of Sex ; after Haeckel.) 



elusion, therefore, is, that the possibility of there being any 

 higher animals depends, primarily at least, not on competition 

 but on the coherence of units. 



Our next step is this : When we study sponges, or 

 zoophytes, or most corals, or some types usually classed as 



