DIFFLUGIA. 6 



has many species but is so well defined that very few 

 have at any time been assigned erroneously to a 

 different genus, perhaps only D. constricta and D. 

 globulus, both of which Ehrenberg described as Arcellas, 

 the latter however with a query. Besides Lecqnereusia 

 modesta some other species first included in Difflugia 

 are now considered to be generically distinct, forming 

 the types of such genera as Pkri/ganella, Pontigulasia, 

 and Trinema, and in 1880 Vejdovsky proposed to 

 remove from it Difflugia corona under the name of 

 Corona cor mil a. 



FIGS. 33-35. Difflugia Leclerc : 33, D. oblonga ? ; 34, D. acuminata ; 

 35, Lesquereusia modesta. After Leelerc, loc. cit., ff. 3, 5, and 1 a. 

 All x about 150. 



This genus is more largely represented than any 

 other in the rhizopodal life of our lakes and ponds. 

 The tests vary in degree of opacity according as they 

 are covered with extraneous matter or otherwise ; 

 generally they have a rough exterior, but forms are 

 frequently met with in which the test, though opaque, 

 is comparatively smooth, except for the presence of a 

 few, and those generally large, scattered sand-grains. 

 The varieties lacustris and venusta of D. oblonga 

 Ehrenb. differ from the type in having a more or less 

 transparent test composed of chitinous membrane with 

 a surfacing of angular scales which vary in size and 

 are probably siliceous. 



