Order II. CONCHULINA. 

 Family 1. ARCELLIDA (continued). 



B. DlFFLUGINA. 



Genus 18. DIFFLUGIA Leclerc, 1815. 



Difflugia LECLEEC (pars) in Mem. du Mus. II (1815), p. 474, 



t. xvii. 

 Arcella EHRENBERG (pars) in Abth. Akad. Wiss. Berlin, 



1841, p. 410. 



Test varying from globular to elongated, pyriform, or 

 acuminate, symmetrical in outline, and circular in trans- 

 verse section (save in a few species which are more or 

 less compressed or unsymmetrical) ; the crown conical, 

 rounded, plain, or furnished with mamillary or linear 

 protuberances. In structure variable, consisting (in 

 most of the larger forms) of sand-grains, large and 

 small, sometimes of diatom-frustules, agglutinated on 

 a chitinous base ; the mouth usually truncating a more 

 or less distinct neck, its outline plain, crenulate, or 

 lobed ; the plasma occupying the greater part of the 

 test and usually attached to the internal walls by 

 threads of ectoplasm. The nucleus single (except in 

 a few cases) and comparatively large, but obscured, 

 in most forms, by the thickly-incrusted test; con- 

 tractile vacuoles (one or more) situated in the upper 

 region of the protoplasm, in proximity to the nucleus. 

 Pseudopodia variable, two to six or (rarely) more, 

 digitate, blunt, simple, knotted, or branched, usually 

 consisting of colourless ectoplasm, but sometimes 

 penetrated by the granular endoplasm. . 



[The genus Difflugia was founded by Leclerc in 1815 

 for two Rhizopods still retained in it and one since 

 removed to Lecqiiereusia, a genus distinguished from 

 Difflugia by Schlumberger in 1845 but included in it 

 by Perty in 1852 and by Leidy in 1879. Difflugia 



