INVERTEBRATE ZOOLOGY. 



PROTOZOA. 



Unicellular Animals. 



CLASS 1. Rhizopoda. 



With changeable pseudopodia during adult life. 

 Reproduction by simple division and by spore- 

 formation. 



Subclass 1. Amoebina. 



With lobose pseudopodia. (Amoeba, Arcella, 

 Difflugia.) 



Subclass 2. Foraminifera. 



With fine branching and anastomosing pseudo- 

 podia. Shells, when present, usually calcare- 

 ous. (Lecythium, Globigerina.) 



Subclass 3. Heliozoa. 



Typically spherical in form. The pseudopodia, 

 which radiate from the entire surface of the 

 body, are ray-like, seldom changeable, and 

 usually possess an axial filament. (Actino- 

 phrys, Actinosphserium, Clathrulina.) 



Subclass 4. Radiolaria. 



With ray-like pseudopodia, and with a chitinous 

 capsule inclosing the nuclei. The skeleton, 

 when present, is formed of silica or acanthin. 

 All are marine. (Thallassicolla.) 

 CLASS 2. Mastigophora. 



Motile organs in the form of flagella. Repro- 

 duction by longitudinal division. Colony for- 

 mation is frequent. 



Subclass 1. Flagellidia. 



With a definite anterior end on which there are 

 one or more flagella. The members of one order 

 (Choanoflagellida) have one or more collar-like 

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