10 BRITISH FRESH WATER RH1ZOPODA. 



the agency of pseudopodia. In the Amcebina, Arcellida, 

 and other lobose forms, these " changeable processes " 

 are usually few in number, short, digitate, and blunt 

 at the tip ; or they may be broad and lobose in the 

 Amoebse they are most frequently so whilst in the 

 Euglyphae and others, included in what Leidy classed 

 as the Filosa, they are acicular, sometimes short, but 

 more frequently of considerable length, and capable of 

 branching, and also, in a small number of forms, of 

 anastomosing. These acicular pseudopodia may be 

 rigid and susceptible of little apparent change for 

 longer or shorter periods ; often, however, they change 

 rapidly, or they may whilst fully extended (e. g. 



PIGS. 2 and 3. Examples of pseudopodia. 2. Digitate and 

 branching pseudopodia of Amaha proteus, showing also nucleus 

 (n.)and contractile vacuole (c.v.). x about 150. 3. Eruptive 

 (hernia-like) pseiidopodium of Lithamceba discus. 



C ijplwderia) sway to and fro, bend at an acute angle, 

 or become curved, or take other forms. In some of 

 the Reticularia (Proteomyxa, Ray Lankester) they 

 branch out remarkably, and form a widely-spread net- 

 work, which, like a spider's web, serves to capture 

 prey. This is conspicuously the case in Penardia. The 

 Heliozoa in some cases (probably in most) have radial 

 filaments, the centre of which is occupied throughout its 

 entire length with a thread of " stiffened protoplasm." 

 In the Amcebde changes of form are sometimes very 

 rapid. The production of pseudopodia, or rather the 

 contributing cause, has been a subject of lively con- 

 troversy. The theories of the early observers were as 



