I io PHYLUM PROTOZOA THE SIMPLEST ANIMALS. 



cells), with which they live in intimate mutual partnership (symbiosis). 

 Most Radiolarians float on the surface of the sea; others live below 

 the surface at varying depths ; and some are abyssal. They are 

 abundant as fossils, and of much importance in the formation of the 

 ooze of great depths. 



Examples. Thalassicola^ Eucyrtidium^ and the colonial Collozoum 

 and Spharozoum. 



FIG. 51. A pelagic Foraminifer Hastigerina (Globigerina] 

 murrayi. After Brady. 



Note central shell, projecting calcareous spines with a protoplasmic 

 axis ; also fine curved pseudopodia and vacuolated protoplasm. 



C. Predominantly active forms (ciliate and flagellate), 

 generally called Infusorians. Protozoa, with a definite rind and 

 with 1-3 undulating flagella, are included as (8) Flagellata, a very 

 large group, among which are such familiar forms as the common 

 Eiiglena of ponds ; the Monads ; Volvox, a colonial form ; Codosiga, a 

 colony in which the individual cells are furnished with a collar (Choano- 

 flagellata). The Haemoflagellata are important blood parasites, generally 

 called Trypanosomes (see p. 121). 



