Ch. X] 



THE FLAGELLATES 



411 



forms are elaborate and ornate, and many of the free kinds 

 exhibit elongated projections of diverse sorts. Many of 

 them change their forms readily in the manner of the 

 animal Amceba. One of the floating colonies, Uroglena, 

 rises to economic importance because of the disagreeable 

 oily odor and taste which it imparts to water supplies when 

 the plants are killed and broken against the walls of the 

 pipes. 



A distinctive feature of the Flagellates is the obvious re- 

 lationship between them and the simple animals. Not 

 only do they possess distinctly animal characteristics in their 

 active locomotion, amoeboid movements, contractile vacu- 

 oles, and red pigment spots (the possession of chlorophyll 

 and the formation of thick-walled resting spores being their 

 plant characteristics), but they also exhibit perfect gra- 

 dations to the ciliate Infusoria, which are unquestioned 

 animals. They represent a group, indeed, which is neither 

 plant nor animal, 

 but intermediate, 

 forming a bridge, 

 as it were, between 

 the two kingdoms. 



Ecologically the 

 Flagellates are 

 mostly free-swim- 

 ming micro-hydro- 

 phytes. Phyloge- 

 netically they are 

 low in the scale 

 of evolution, and 

 their obvious rela- 

 tion to animals suggests that they are a survival from an 

 ancient group which gave origin to the Green Alga? in one 



I dinct ion and to the Protozoa, which are animals, in the 

 other (Fig. 275). Their relations to the Cyanophyceae are 



Fia. 281. — Typical forms of the Peridincce; 

 X about 500. 



The presence of two cilia in grooves at right 

 angles is characteristic. (From Van Tieghem.) 



