38 BRITISH FRESHWATER RH1ZOPODA. 



Test of medium size, pyriform, not compressed, 

 yellowish in colour, formed of a flexible chitinous 

 membrane encrusted with foreign particles and diatom- 

 frustules ; aperture circular, usually bordered by an 

 incurved crenulate margin ; plasma partially filling the 

 test, colourless but containing numerous granules of a 

 brick-red colour ; nucleus single, containing a single 

 nucleole ; a single contractile vesicle usually present ; 

 pseudopodia few, not long, digitate, simple or forked. 



Length 66-105 /A; diameter 42-70 /A; aperture 16 

 30 p. 



Habitat. Aquatic vegetation. 



ENGLAND. Isle of Man; Cumberland; Westmor- 

 land ! and Lancashire (Brown) ; N. & W. Yorkshire ; 

 Sheffield District (Brown) ; Derbyshire (Brown) ; Isle 

 of Wight ; Devonshire ; Cornwall. 



WALES. North Wales. 



SCOTLAND. Kircudbrightshire and Wigtonshire 

 (Brown,). 



IRELAND. Mayo and the islands off Clew Bay ; 

 Inishbofin, Galway ; Limerick ; Kerry. 



The animal is very frequently found encysted, in 

 a spherical form ; when it is active the plasma is 

 attached to the fundus of the test by several epipodes 

 by means of which it can, when alarmed, retreat 

 rapidly into its test. The pseudopodia are usually one 

 or two in number and the circulation of the plasma 

 carries many of the red globules for some distance 

 into them. 



The test even when empty is easily recognized, and 

 the internal crenulation of the aperture is usually well 

 defined and quite characteristic ; the neck is occasion- 

 ally slightly constricted. 



In localities where it occurs it is usually abundant ; 

 it is found on the Continent of Europe and in North 

 America. 



