216 THREE CRUISES OF THE “ BLAKE." 
nelids and starfishes, or crabs and actiniz. Finally, we come to 
those communities among invertebrates where the subdivision of 
labor is carried out so far that the different individuals possess 
special functions. These cases belong to the same phenomena : 
they illustrate thé interdependence of the animal and vegetable 
kingdoms, and the influence of special conditions of existence 
upon the development of the animal and vegetable life of our 
shores, continental slopes, and deep-sea basins. 
