. Fresh-water biology. Freshwater biology. 2 24 FRESH-WATER BIOLOGY 59 (72) 60 (61) Shell without internal partition or diaphragm. Difflugia Leclerc 60 Aperture not central. Difflugia constricta Ehrenberg 1841. Fig. 300. X no. 61 (60) 62 (69) 63 (66) 64 (6S) 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 aculeata. A common species, widely distributed. Large forms may reach 200 n in Difflugia constricta. length. Most i
. Fresh-water biology. Freshwater biology. 2 24 FRESH-WATER BIOLOGY 59 (72) 60 (61) Shell without internal partition or diaphragm. Difflugia Leclerc 60 Aperture not central. Difflugia constricta Ehrenberg 1841. Fig. 300. X no. 61 (60) 62 (69) 63 (66) 64 (6S) 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 aculeata. A common species, widely distributed. Large forms may reach 200 n in Difflugia constricta. length. Most individuals are very much smaller. (After Leidy.) Aperture central. Shell typically spherical. Margin of aperture smooth. 62 63 64 Neck deeply constricted; aperture small, with margin always re- curved. Difflugia urceolata Carter 1864. This species is without spines, but a variety, D. UKeolala 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 35011. Fig. 301. Difflugia urceolata. X 75. (After Leidy.) 65 (64) Neck, when present, not deeply constricted; aperture wide, with margin seldom recurved. Difflugia lehes 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 100. Found in ooze at the bottom of ponds, lakes, etc. Very large, some reaching 400 11 in length. Fic. 302. Difflugia tebes. X 60. (After Penard.). 66 (63) Margin of aperture not smooth. 67 (68) Margin with numerous teeth. .... 67 Difflugia corona WaUich 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
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
