46 



COLLEGE ZOOLOGY 



consisting of a great number of individuals held together by a 

 gelatinous matrix. This form is often responsible for the " oily 

 odor " of drinking water caused by the escape of small droplets 

 of an oil-like substance from the cells. 



Volvox (Fig. 27) is a colonial Flagellate found in fresh- 

 water ponds. It may consist of as many as twelve thousand 



Fig. 27. — Volvox globator, a large colonial Flagellate. A, a sexually ripe 

 colony, showing microgametes, $ , and macrogametes, 9 . i n various stages of 

 development. B, a portion of the edge of the colony highly magnified, show- 

 ing three flagellate cells united by protoplasmic threads, and a single repro- 

 ductive cell, rp; st, stigma; cv, contractile vacuole. (From Bourne, after 

 Kolliker.) 



cells. Protoplasmic strands connect each cell with those that 

 surround it (Fig. 27 B); physiological continuity is thus estab- 



