Lagenodifflugia vas (Leidy, 1874)
Diagnosis: Test pyriform, often with a well-marked constriction of the neck, frequently circular in cross-section but sometimes slightly compressed, composed mainly of agglutinated mineral particles bound by an organic cement: aperture terminal, circular: internally the shell is partitioned into two regions by a diaphragm constructed as part of the shell wall but having a single, usually central orifice. Nucleus with numerous nucleoli of different size, the largest ones in the periphery, intermigled with smaller ones; in general nucleoli are smaller towards the center.
Dimensions: Length 125-348 µm; nucleus 54 µm (n=1). Leidy gives a test length of 2/5 mm = 400 µm.
Ecology: Freshwater, between water plants and in sediments; also in wet Sphagnum.
Remarks: The original description is of Joseph Leidy (1874): “Test composed of angular quartz particles, generally coarse, shape pyriform, with the neck constricted where it joins the body; fundus obtuse; mouth large, circular. Entosarc bright green from the abundance of chlorophyll granules. Length of test 2/5 mm.; neck one-fourth to one-third the length of the test. Abundant in Absecon Pond, New Jersey.”
Stump (1943) made a study of the nuclear division of the organism. During metaphase eight to twelve “chromosomes” form a well-defined equatorial plate; average time for completion of the division was found to be eighty minutes.
Resembling Difflugia pyriformis in appearance except for the deeply constricted neck.