SOCIAL LIFE OF ANIMALS 



75 



one another grow to be different, and perform different 

 functions according to the caste to which they belong. 



Many are nutritive in form like the little freshwater 

 Hydra tubular animals with an extensile body and with 



FIG. 20. AN ILLUSTRATION OF COLONY-MAKING AMONG THE 



PROTOZOA. 



The organism (Dendrosoma radians) is one of the suctorial Infusorians 

 (Acinetaria). The usual cilia or flagella are replaced by tentacle-like 

 suckers, which grapple with passing Infusorians. By budding and bud- 

 ding a colony of numerous members is formed. They are connected at 

 the base by a spreading stolon, which is fixed to a substratum. Here 

 and there to the left may be seen oval young ones, which have a ciliated 

 and free-swimming phase before they settle down to start a new r colony. 



(After Saville-Kent.) 



a terminal mouth wreathed round bv mobile tentacles. 



*/ 



On these the whole nutrition of the colony depends. 

 Beside these there are reproductive ' persons," which 

 cannot feed, being mouthless, but secure the continu- 



