PROTOZOA. 



149 



Order III. Radiolaria. Numerous simple thread-like 

 pseudopoclia which do not interlace. The structure of the 

 central mass of protoplasm is complicated. Most of the 

 species form silicious skeletons of beautiful forms (fig. 5), 





FIG. 5. A Radiolarian, Haliomma erinaceus (from Hertwig). a, external 

 latticed spherical skeleton; ck, central capsule; i, internal skeleton; n, 

 nucleus; u-k, extra capsular protoplasm. 



the rods of which run to the centre of the cell. Like the 

 Foraminifera these live at the surface of the ocean and 

 contribute to the ooze at the bottom of the sea. 



CLASS II. INFUSORIA. 



These animals, which receive their name from their 

 abundance in infusions of vegetable matter, have the 

 body covered with a denser portion or cuticle, so that 

 pseudopodia cannot be protruded. Instead they have 

 delicate permanent processes, which when few in number 

 and long and whip-lash-like are called ftagella, when 

 short and numerous are called cilia. Both are capable 



