224 



FRESH-WATER BIOLOGY 



59 (72) 



60 (61) 



FIG. 300. 

 X no. 



61 (60) 



62 (69) 



63 (66) 



64 (65) 



Shell without internal partition or diaphragm. 



Difflugia Leclerc 



60 



Aperture not central. 



Difflugia constricta Ehrenberg 1841. 



Difflugia constricta. 

 (After Leidy.) 



Shells of various forms from nearly spherical to oval and elon- 

 gate. Aperture always eccentric. Pseudopodium single, rarely 

 observed. Spines sometimes developed from the fundus. This 

 species is closely related to Centropyxis aculeala. A common 

 species, widely distributed. Large forms may reach 200 M in 

 length. Most individuals are very much smaller. 



Aperture central 62 



Shell typically spherical 63 



Margin of aperture smooth 64 



Neck deeply constricted; aperture small, with margin always re- 

 curved Difflugia urceolata Carter 1864. 



This species is without spines, but a variety, D. urceolata var. 

 olla, may possess a few short stubby spines developed from the 

 fundus. The protoplasm does not fill the shell. Pseudopodia 

 numerous; nuclei many. Found in the ooze of pond water. Large 

 forms reach a length of 350 n. 



FIG. 301. Difflugia urceolata. X 75- (After Leidy.) 



65 (64) Neck, when present, not deeply constricted; aperture wide, with 

 margin seldom recurved. . . . Difflugia lebes Penard 1893. 



In many respects this species resembles the preceding one. 

 The thin, recurved collar is sometimes present but the aperture 

 is much larger. The shell is very fragile. Nuclei sometimes more 

 than loo. Found in ooze at the bottom of ponds, lakes, etc. 

 Very large, some reaching 400 n in length. 



FIG. 302. Difflugia lebes. x 60. (After Penard.) 



66 (63) Margin of aperture not smooth. 



67 (68) Margin with numerous teeth. 



67 



Difflugia corona Wallich 1864. 



Shell composed of large sand grains but very smooth and regular 

 in outline. Teeth usually more than twelve in number, very evenly 

 arranged. Nucleus single. Pseudopodia numerous and large. 

 From six to nine spines usually developed from the fundus. A very 

 common species in ooze of ponds. Length, with spines, 200 to 250 /*. 



FIG. 303. Difflugia corona. Oral view. X 90. (After Leidy.) 



68 (67) Margin with few blunt lobes. 



Difflugia lobostoma Leidy 1874. 



Shell ovoid or nearly spherical, usually with a quadrilobate aper- 

 ture. However, the lobes are somewhat irregular, a trilobate aperture 

 sometimes appearing. Pseudopodia few. Found among algae and in 

 the ooze of ponds; common. Average length 150 /LI- 

 FIG. 304. Difflugia lobostoma. Oral view. X 105. (After Edmondson.) 



69 (62) Shell never spherical 70 



