148 



GENERAL BIOLOGY 



a circular opening in the center of the flattened surface. 



Difflugia ( ) is another common member of the 



order Lobosa, and is also found in the ooze of ponds. Its shell consists 



Fig. 63. 



A. Amoeba proteus. (After Gruber). 



B. and C. Arcella discoides. (After Leidy). 

 D. Difflugia urceolata. (After Leidy). 



of minute particles of sand and other foreign objects held together by 

 chitin. 



11. Order 2. Heliozoa ( ) Rhizopoda with 



thin, radially arranged pseudopodia, which are usually supported by 

 axial threads. 



Examples : Actinophrys. (Fig. 64.) 



Actinophrys ( ), the sun animalcule, lives 



among the aquatic plants in fresh water ponds 

 and ditches. The body appears vesicular, be- 

 ing crowded with vacuoles. The small organ- 

 isms which serve as food strike the pseudo- 

 podia, pass down to the body, and are en- 

 gulfed ; larger organisms are drawn in by sev- 

 eral neighboring pseudopodia acting to- 

 gether. 



12. Order 3. Radiolaria ( ) 



Marine Rhizopoda with raylike pseudopodia, a 

 central perforated capsule of chitin, and usually 

 a larger enclosing skeleton of silica. 

 Examples: Actinomma, Thalassicola. (Fig. 65.) 

 The shells of the radiolarians, upon sinking to the sea bottom, form 

 radiolarian ooze ; this becomes hardened, producing rock strata as much 

 as 1,000 feet thick. These rocks may take the form of quartzites, flint, 

 or chert concretions. 



13. Order 4. Foraminifera ( ) Rhizopoda, 



mostly marine, with fine, branching pseudopodia which fuse forming a 

 protoplasmic network. 



Examples: Allogromia, Globigerina. (Fig. 66.) 



Allogromia ( ) lives in fresh water and has a 



Fig. 64. 



Actinophrys sol X about 800. 

 (From Bronn.) 



