138 



PHYLUM PROTOZOA — THE SIMPLEST ANIMALS 



flagellate forms, as Euglena, and in many Ciliata, as Stentor, Stylo 

 nichia, one species of Paramcecium, Volvox and the allied forms, are 

 also symbiotic Alga), which have lost the power of independent exist- 

 ence. The evidence for this is, however, insufficient, and this explana- 



COL 



■ Fig. 64. — A Monad Infusorian. — After Saville Kent. 



N., Nucleus; C.V., contractile vacuole; 

 F.V., food vacuole ; F.P., an external 

 food particle ; the arrows indicate how 

 the particles are swept ; COL., trans- 

 parent collar in the middle of which the 

 flagcUum (FL.) works. 



tion will not apply in cases like that of VorticeUa viridis, where the 

 green colouring matter is uniformly distributed through the protoplasm. 

 In many cases there is, besides the chlorophyll, a brown pigment, 

 identical with the diatomin of Diatoms. In many of the Flagellata 

 there are one or more bright pigment spots at the anterior end of the 



