10 BRITISH FRESHWATER RH1ZOPODA. 



accidental, but their frequent recurrence justifies the 

 conclusion that they point to some organic distinction ; 

 and Penard, with that insight which characterizes all 

 his observations, has described several forms under 

 varietal names. Between the pyriform and oblong 

 examples of this variable species there are intermediate 

 forms which cannot be classified. Those figured may 

 be taken as showing the limits of variation in the 

 species. 



The largest examples of D. oblonga are found in the 

 ooze of shallow pools. Those occurring in bogs and 

 amongst Sphagnum are frequently dwarfed. 



Var. venusta (Penard). (Plate XVII, figs. 4 and 5.) 



Difflugia pyriformis var. venusta PENAED Fauiie Rhiz. Leman 

 (1902), p. 220, f. 5 (p. 218); AVERINTZEV in Trudui 

 S.-Peterb. Obslich. XXXVI (1906), 2, p. 300; Scuou- 

 TEDEN in Ann. Biol. Lacustre, I, 3 (1906), pp. 342, 346. 



Test in general outline resembling that of var. clavi- 

 formis, but very much smaller and of different composi- 

 tion, being constructed of thin chitinous material, and 

 semi-transparent, its surface covered with amorphous 

 glossy scales. With a graceful outline and obtusely- 

 pointed apex the sides swell outwards to the broadest 

 diameter, thence (for about two -thirds of the length) 

 taper more or less concavely downwards to the small 

 truncated mouth. The protoplasm with nucleus and . 

 pseudopodia as in the type. 



Dimensions: Average length 175 // ; breadth at 

 broadest part 45-50 //,. 



Ponds at Northenden and elsewliere in Cheshire, 

 frequent. Pond at Chipperfield, Herts (A. Earlancl). 



This is one of the most graceful of the smaller 

 varieties of D. oblonga and perhaps the least abundant. 

 It preserves its characters fairly constantly, but is 

 somewhat variable in length. Usually it is associated 

 with the preceding, and with D. lanceolata Penard, 



