432 



ELEMENTARY BIOLOGY 



of each cell is practically independent of that of its neighbor, 

 there is some differentiation as to cell structure, and there is a 

 great deal of common activity. 



459. Differentiated individuals. Among the Coelenterata 

 (to which branch belong the hydra, jellyfish, sea anemones, 

 and corals) we find species in which the individuals are quite 

 independent, others in which there are colonies of similar 



individuals, and still 

 others in which the 

 individuals are differ- 

 entiated in structure 

 as well as in func- 

 tion (Fig. 228). The 

 11 Portuguese man-of- 

 war" consists of sever- 

 al kinds of individuals, 

 - nutritive, locomo- 

 tive, and reproductive. 



In this ant (Ponera pennsylvanicd), as in so many 460. Colonial ani- 



others, the worker, a, is easily distinguished from the mai^ A hrvir^ tVi^c^ 

 female, 6, and the male, c. (After Wheeler) 



simple colonial ani- 

 mals we find forms in which the interdependence within the 

 species is chiefly confined to reproduction and the care of 

 the young (see pp. 331 ff.), but toward the upper end of each 

 of two very important branches the Arthropoda and the 

 Vertebrata there appears a form of colonial life which is very 

 significant to us, from a practical point of view as well as from 

 a theoretical one. 



In an ant colony there may be one or several queens or 

 female ants, thousands of workers, and many soldiers. After 

 the colony is started, the queen may lay eggs continually. The 

 workers extend the nest and keep the structures in repair. 

 They also go forth to forage for food, look after the eggs, 

 larvae, and pupae, and clean out all foreign matter that cannot 

 be used (Fig. 229). In some species the soldiers are quite 



FIG. 229. Ant individuals 



