HEDRIOOYSTIS SPINLFEEA. 65 



nearly filling the capsule ; plasma bluish in colour, 

 granular ; nucleus single, placed sub-centrally ; a single 

 contractile vesicle normally present ; pseudopodia long, 

 radiating, straight, tenuous ; habit solitary. 

 Diameter of capsule 8/x to 12 /x. 



Habitat. Wet moss. 



Distribution. SCOTLAND. Isle of May (Brown}. 



Up till now no individuals have been found provided 

 with a pedicel or stalk, but this may be due to these 

 having been broken off during collection. 



Four genera of Heliozoa have not yet been recorded 

 from the British Isles, and it is thought that a brief 

 diagnosis of each of the species included in them would 

 be welcome. 



The genus Raphidocystis comprises species usually similar 

 to those included in the genus Raphidiophrys, but some or all 

 of the investing spicules are of special shape. 



Raphidocystis simplex, (Schaudinn) Pen. (Acanthocystis 

 simplex Schaudinn) is similar to an Acanthocystis in structure 

 but has no envelope of tangential spines, the body being 

 surrounded by a pellucid mucilaginous investment from which 

 tapering spines, equal to the diameter of the body in length, 

 radiate. Diameter 15 /LI to 22 /u. Africa. 



R. stellata Pen. has the mucilaginous investment crowded 

 with small spherules ; the radial spines are covered by 

 plasma and thus form permanent axes to the pseudopodia. 

 Diameter 12 /j. to 19 ^u without envelope. 



R. tubifera Pen. The external envelope consists of numerous 

 oval scales placed tangentially, and radial spicules of a funnel- 

 shape. Diameter 18 ^i without envelope. 



R. lemani Pen. (Acanthocystis lemani Pen.). (Fig. 184, 

 p. 28.) The thick transparent envelope of this species has 

 embedded in it minute mushroom-shaped spicules, and protrud- 

 ing from it radially wineglass-shaped spicules and numerous 

 loug tubular spines. Diameter 18 /u to 25 ju without envelope. 



R. ghctinosa Pen. The pellucid mucilaginous envelope 

 contains numerous Y-shaped spicules ; no radial spines present. 

 Diameter 12 fj. to 13 fj. without envelope. 



The genus Pinaciophora Green 2 contains one species, P. 

 Jluviatilis Greeff (Fig. 185, p. 28), in which the external 

 envelope is formed of circular imbricated discs each per- 



o" 



