38 BRITISH FRESHWATER HELIOZOA. 



Habitat. Aquatic vegetation in still waters. 



Distribution. ENGLAND. Birmingham (Hoi ton). 

 I KELAND. ? Wicklow ( Air] i fir). 



The colonies in this species are seldom so compact 

 as is the case with R. viridis; they usually number six 

 to twelve individuals, although Leidy records thirty- 

 eight in one group, which however shortly broke up 

 into three portions. The individuals are placed a 

 little distance apart, being connected together by 

 strands or bands of plasma which lengthen out when 

 a colony is moving ; these strands are disposed in a 

 fairly regular manner and appear to have a pseudo- 

 podial origin, that is the plasma forming them collects 

 around a pseudopod. 



The spicules are characteristic of this species and 

 distinguish it from others of the same genus ; Hertwig 

 and Lesser first described them as half rings, but 

 Penard found them to be elliptical plates with thickened 

 edges, which in the mass have a lunate or semi- 

 circular appearance. 



The granules enclosed in the ectoplasm have the 

 appearance of starch grains ; the green cells which 

 may be entirely absent or present more or less nume- 

 rously are sometimes no doubt living symbiotically in 

 their host, in which case contractile vesicles may be 

 absent as recorded by several observers. 



The endoplasm is usually distinguishable merely as 

 a nearly central light coloured circle. It contains the 

 nucleus placed eccentrically with respect to the peri- 

 phery of the animal and a central grain from which 

 the pseudopodial axes originate. 



The nucleus is pale in colour, spherical or slightly 

 pyriform and almost entirely occupied by the nucleolus. 



The pseudopodia are numerous, very long and 

 straight and may be either smooth or granuliferous. 



Leidy (op. cit., PI. XLII, fig. 5) illustrates the 

 method of ingesting an algal zoospore by a solitary 

 individual. 



