Flagellates 



103 



observation, even when the jerky movements of the 

 attached cell give evidence of its presence and its 

 activity. It swings in front of the cell in long serpen- 

 tine curves, and draws the cell after it as a boy's arms 

 draw his body along in swimming. 



Many flagellates are permanently unicellular; others 

 remain associated after repeated divisions, forming 

 colonies of various forms, some of which will be shown in 

 accompanying figures. 



Carteria This is a very minute flagellate of spherical 

 form and bright green in color (fig. 300). It differs 

 from other green flagellates in having four flagella : the 

 others have not more than two. It is widely distrib- 

 uted in inland waters, where it usually becomes more 

 abundant in autumn, and it appears to prefer slow 

 streams. Kofoid's notes concerning a maximum occur- 

 rence in the Illinois River are well worth quoting : 



"The remarkable outbreak of Carteria in the autumn 

 of 1907 was associated with unusually low water, and 



