TESTA CE A 



227 



parent, and punctate'. -Aperture is circular and almost the full 

 diameter of the test. The cyfoplasm is similar to that of 

 Arcella, but the nucleus is usually one. Contradtile vacuojes 

 one or more. Fresh water. 



Pyxidicula operculata (Agardh) (Fig. 89, d). Test smooth; 

 colorless or brown. A single vesicular nucleus. Pseudopodia 

 short, lobose or- digitate. Diameter about 20 microns. On 

 aquatic 'plants. ' 



Genus Pseudochlamys Claparede and Lachmann.- Test 

 discoid, flexible wh^n young. Tjie body protoplasm contains .a 

 central nucleus and several contractile vacuoles.' 



Fig. 89 



a. Arcella vulgaris. X200. 



b. A. dentata. X200. 



c. A. discoides. X200. 



d. Pyxidicula operculata. X800 (After Penard). 



• Pseudochlamys patella Claparede and Lachmann (Fig. 90, a). 



Young test flexible and hyaline, older ones rigid and brown. 



. Young forms often rolled up like a scroll. A short finger-like 



pseudopodium is protruded between the folds. Diameter 40 to 



45 microns. Freshwater plants, under moss, or in soil. ■ 



Genus Difflugiella Cash. Test ovoid, not compressed, 

 flexible transparent membrane; colorless protoplasm filling up 

 the test, usually with chlorophyllous food material. Median 

 pseudopodia lobular or digitate with aciculate ends; lateral 

 pseudopodia long, straight, and fine, tapering to a point. One 

 species. 



1 Difflugiella apiculata Cash (Fig. 90, h, c). Length about 40 

 -microns. Among floating vegetation. 



Genus Cryptodifflugia Penard. Minute test yellowish or 



