ORDER 



FIG. 6. 



He R o sphce' ra echlnoid'es. 

 Spiny Radiolarian. (Greatly 

 enlarged. ) 



BRANCH PROTOZOA. 

 RADIOLARIA (ra di o la'rf a). 



The Radiolarians are characterized 

 by the possession of a silicious (si ir- 

 shus), not calcareous, armor from which 

 often project a multitude of long di- 

 verging spines. No pulsating vacuole 

 has as yet been discovered, though the 

 body is much more granular than in 

 the previous order. The pseudopodia 

 are capable of being extended to a 

 great distance, often forming a deli- 



cate net-work outside the shell,* and variously used. 



CLASS INFUSORIA (In fu so'rl a). 



We now come to those Protozoans which, unlike the 

 Rhizopods, have an elastic covering for the body, pro- 

 vided with one or many whip-like prolongations. These 

 prolongations incessantly lash the water, as organs of 

 locomotion, or whip the food into an opening in the cov- 

 ering, or sac. From this opening, the food passes to the 

 central portion of the body. One or more nuclei and a 

 contractile vacuole are invariably present. Many of the 

 forms possess, also, a thin membranous covering, or cu- 

 ticle (ku'ti kl). 



INFUSORIA make their appearance in vessels of water, 

 either salt or fresh, which contain decomposing animal 

 or vegetable matter. From their abundance in these in- 

 fusions they derive their name. 



* These animals are found in large mimbers on the surface of the ocean, and 

 their dead shells, like those of the Foraminifera, are not infrequently found in 

 the solid rocks of the land, showing conclusively that such rocks were once cov- 

 ered by the ocean. 



