118 BRITISH FRESHWATER RHIZOPODA. 



British Isles the length usually varies from 20 to 26 /x. 

 Colourless tests occasionally occur. 



3. Pseudodifflugia horrida Penard. 

 (Plate LIT, figs. 1-4.) 



Psendodifflugia horrida 



PENARD Faune Rhiz. Leman (1902), pp. 452-453, 5 figs. ; Sarcodines 



Brands Lacs (1905), pp. 115, 596, 604-606, 3 figs. ; Sarcodines in Cat 



Invert. Suisse (1905), p. 91. 



MURRAY in Proc. R. Soc. Edinb. XX Y (1905), p. 615. 

 WAILES & PENARD in Proc. R. Irish Acad. XXXI, LXV (1911), p. 19. 



Test of medium size, dark grey or brown in colour, 

 opaque, oviform, slightly compressed, flexible, especi- 

 ally around the aperture ; covered with a rough coating 

 of foreign particles and projecting diatom-frustules ; 

 aperture terminal, of variable shape ; the plasma clear, 

 granular, with few inclusions, entirely filling the test; 

 nucleus small, with a single large nucleole ; one or two 

 contractile vesicles usually present ; pseudopodia long, 

 attenuate, straight. 



Length 35-60 /A ; breadth about three quarters of the 

 length ; aperture about half of the breadth ; thickness 

 about nine tenths of the breadth. 



Habitat. Aquatic vegetation. 



ENGLAND. Cheshire (Cash). 



SCOTLAND. Loch Ness, Inverness-shire (Penard). 



IRELAND. Inishbofin, Galway. 



Penard noticed that the individuals found in Loch 

 Ness were infested with large numbers of bacteria of 

 very small diameter and about 20 /u in length, similar 

 to, but much more numerous than, those found in the 

 Swiss members of this species; in addition to these 

 bacteria the majority of the Loch Ness individuals 

 contained parasites in appearance like degenerate 

 Peranema (Duj.) but wanting the flagellum; they 

 were 15 to 20 /A in length ; their life-history is un- 

 known. Similar parasites are found in the Heliozoon 

 Raphidiophrys viridis. Ciliates are often seen in the 



