<'" BRITISH FKESHWATKR H KLK >/OA. 



composed of a silicious material, was found by Pehard 

 to be of a cliitiiions character, being readily dissolved 

 in boiling sulphuric acid and destroyed by the heat 

 from a blow-pipe. 



The apertures in it are separated from each other by 

 narrow bars having raised or thickened borders, and 

 although the openings are usually somewhat polygonal 

 in shape thev alwavs have the angles rounded. 



' ^ 



he peduncle or stalk is hollow and either has an 

 enlarged base or root-like filaments bv which it is 



* , 



attached to some support : young individuals after 

 emerging from the mother capsule frequently attach 

 themselves to it and may again in their turn serve as 

 supports for a younger generation ; in this way chains 

 and small colonies are formed consisting of two or 

 three up to seven or eight individuals (Fig. 192) ; 

 capsules are sometimes found devoid of stalks which 

 become severed owing to a constriction that takes place 

 close to the capsule, the animal thus regaining its 

 freedom of movement. 



The apices of cone-shaped expansions of the plasma 

 usually give rise to the pseudopodia, two or three of 

 which often diverge from a single orifice and a common 

 point of origin : they are also frequently forked and 

 appear devoid of any central axis. 



The contractile vesicle is normally single in mature 

 individuals, but is often or even usually indistinguish- 

 able ; in young forms two or three can often be seen. 



\ arious methods of propagation have been observed ; 

 simple division, either binary or multiple, up to six or 

 seven in number, is the most common, the young 

 emerging through an aperture of the capsule in an 

 amoeboid form, after which they either at once secrete 

 first a stalk and then a fine pellicle \vhich eventually 

 becomes the capsule, or they may again divide or they 

 may encyst ; the cysts are spherical with a chitinous 

 envelope covered with fine points or projections and 

 have a single centrally placed nucleus. Mature 

 individuals are often found encysted, and two cysts, 



