56 



FOUNDATIONS OF BIOLOGY 



flagellated individuals each of which lives a practically in- 

 dependent existence in organic union with its fellows. The 

 chief contribution of each of these cells to the economy of the 



FIG. 18. Volvox globator, a large colony of flagellated unicellular or- 

 ganisms in which the various cells have become organically connected, 

 and certain cells specialized for reproduction. A, mature colony (highly 

 magnified) showing sperm, $ , and eggs, $ , in various stages of devel- 

 opment. B, four cells (more highly magnified) showing the connections 

 between three 'somatic 1 cells, and the early differentiation of a repro- 

 ductive cell, rp; CD, contractile vacuole ; st, ' ey espot ' or stigma. (From 

 Hegner, after Kolliker.) 



whole results from the lashing of its flagella, which helps to 

 propel the colony through the water. But, under certain 

 conditions, some of the cells become specialized for repro- 

 duction and form new colonies which sooner or later are set 



