16 BRITISH HYDROID ZOOPHYTES. 



its future progeny, is the common supply of 

 nutriment which it can always obtain, and 

 which is kept circulating through the connect- 

 ing channels of the colony. 



Division of labour. We have here, in 

 this " select " polypite a primitive example of 

 the principle of division of labour ; all its 

 energies, in many cases, being devoted to its 

 special function, just as the various cells of 

 which our bodies are composed have their 

 particular characteristics and special duties. 



Specialised individuals. Among the 

 hydroid colony the specialisation of individuals 

 is not confined to the example previously stated. 

 There are others whose functions are not 

 so clearly understood (Hydractinia). Refer- 

 ence will be made to these in the description 

 of the specimens. 



Sexes of " reproductive" buds. At 



certain seasons of the year these "select" 

 polypites throw out the reproductive buds. 

 These on a given colony, may be either all 

 male, or all female, or there may be some 

 male and some female, but the former 

 disposition is the more usual. 



