52 MUTISM FI.'KSHWATKR HELIO/OA. 



inner one consisting of a single layer of oval silicious 

 plates slightly imbricated, the outer one consisting of 

 two kinds of silicious spines, one kind very numerous, 

 long and slightly bifurcate at the extremities, the 

 other kind less numerous, shorter, with widely bifur- 

 cate extremities, the basal ends of all the spines 

 provided with flattened plates which form a con- 

 tinuous spherical investment ; plasma usually coloured 

 green by chlorophyll granules ; endoplasm colourless, 

 granular, eccentric ; nucleus large, placed eccentrically, 

 pyriform or irregular in shape, containing a large 

 nucleolus; central granule present; pseudopodia long, 

 not tenuous, slightly granuliferous ; contractile vesicles 

 absent except in colourless individuals. 



Diameter of outer envelope usually 35 /u, to 60 p,, 

 but may attain 100 ^ or more (150 ^ Schaudinn) ; 

 length of the shorter spines equal to about half the 

 diameter of the body, that of the longer spines two to 

 three times as much ; pseudopodia equal in length to 

 twice the diameter of the body or more. 



Hithit'if. Lakes, ponds and moorland pools; not 

 common. 



Distribution. - - ENGLAND. - Terrington, Yorkshire 

 (!!>*/); Dunham, Cheshire (C<ixh) ; Easedale, Derby- 

 si i ire and Sheffield district (Brown); Epping Forest, 

 Essex (Gash); Bournemouth, Hants (Walling ton) ; 

 Barnes, Surrey (G. S. West]. 



IRELAND. ? Wicklow (Archer) ; Clare Island and 

 Achill Island, Mayo (Wall^ t y Penard). 



The spines appear to be hollow and are attached 

 together by the plates at their basal ends, which form 

 a continuous outer investment enclosing a clear zone 

 around the body proper ; nearly midway in this zone 

 is the second investment of oval discs ; these however 

 are usually indistinguishable until the outer spines 

 have been removed. 



The bifurcated ends of the spines are characteristic 

 of the species and serve to identify it under abnormal 



