ioo ASSOCIATION OF ORGANISMS THE WEB OF LIFE 



(fig. 1089), which is closely allied to the common Bell- Animalcule 

 (Vorticella), a non- colonial form. And another colonial form 

 (Codosiga), represented in the same figure, also has solitary 

 relatives. In cases where a number of units are associated 

 together it is clearly advantageous that there should be a "divi- 

 sion of labour", on similar principles to those which have increased 



B 



Fig. 1089. Colonial Animalcules, enlarged to various scales. A, Epistylis; c, c, small individuals conjugating with 

 large ones; d, d, d, d, individuals undergoing fission. B, Codosiga. c, Proterospongia. 



the output and improved the quality of manufactured articles. 

 There are certain colonial Animalcules which exhibit an early 

 stage in division of "physiological" labour. Of this an excellent 

 example has already been given (see vol. iii, p. 333) in Volvox, 

 where some members of the colony become specialized in con- 

 nection with propagation by means of eggs. As another instance 

 we may take Proterospongia (fig. 1089), which consists of nu- 

 merous individuals imbedded in a gelatinous substance. Some 

 of these are charged with the duty of securing food for the colony, 

 and the projecting end of each such individual is surrounded by a 



