ii PHYLUM PROTOZOA 69 



also been shown that the movements of the flagellum create a 

 whirlpool by which minute fragments are propelled down the 

 gullet and into the soft internal protoplasm. There seems to be 

 no doubt that in this way minute organisms are taken in as food. 

 Euglena thus combines the characteristically animal (holozoic) with 

 the characteristically vegetable (holophytic) mode of nutrition. 

 But, in all probability, the Euglena is in large measure saprophytic, 

 the products of the decay of organic matter dissolved in the water 

 being absorbed through the general surface. 



Sometimes the active movements cease, the animal comes to 

 rest and surrounds itself with a cyst or cell-wall of cellulose (G), 

 from which, after a quiescent period, it emerges to resume active 

 life. It is during the resting condition that reproduction takes 

 place by the division of the body in a median plane parallel to 

 the long axis (G). Under certain circumstances multiple fission 

 takes place, and flagellulse are produced, which, sometimes, after 

 passing through an amoeboid stage, develop into the adult form. 



2. CLASSIFICATION AND GENERAL ORGANISATION. 



The Mastigophora form a very extensive group, the genera and 

 species of which show a wonderful diversity in structure and habit. 

 The only character common to them all is the presence of one or 

 more flagella. Some approach plants so closely as to be claimed 

 by many botanists ; others are hardly to be distinguished from 

 Rhizopods ; while the members of one order present an interesting 

 likeness to certain peculiar cells found in Sponges. 



The class is divisible into four orders as follows :- 



ORDER I.--FLAGELLATA. 



Mastigophora having one or more flagella at the anterior end 

 of the body. 



ORDER 2. CHOANOFLAGELLATA. 



Mastigophora having a single flagellum surrounded at its base 

 by a contractile protoplasmic collar. 



ORDER 3. DINOFLAGELLATA. 



Mastigophora having two flagella, one anterior, the other 

 encircling the body like a girdle. 



ORDER 4. CYSTOFLAGELLATA. 



Mastigophora having two flagella, one of which is modified 

 into a long tentacle, while the other is small and contained within 

 the gullet. 



