RHIZOPODA 15 



Suborder 1. AMCEBIDA. 



ItJuzopoda having lobose pseudopodia which may be finger-shaped or 

 pointed, but are usually not reticuhite; shell of chitin or silica usually 

 present, to which sand or other foreign bodies may be attached: 3 families. 



Key to the families of Amochida: 



cti Naked Amoebida 1. Amcebidae 



tta Amoebida with a shell. 

 &i Shell membranous, often with sand and other foreign bodies imbedded in 

 it 2. Arcellidae 



&2 Shell composed of regular plates of silica or chitin ; pseudopodia sharp and 

 often branching and sometimes slightly anastomosing. . . .3. Euglyphidae 



Family 1. AMCEBIDAE. 



Shell-less RMzopoda, whose pseudopodia are not reticulate; body 

 without definite form and under ordinaiy conditions constantly changing 

 its shape by throwing out pseudopodia, although covered by a euticula of 

 greater or less delicacy: about 19 genera, with numerous species in both 

 fresh and salt water. 



Key to the genera of Amoohidae here described: 



ffi Nucleus absent 1. Protamceba 



02 Nucleus present and usually distinct. 



6i Numerous nuclei, vacuoles, and retractile bodies present 2. Pelomyxa 



6o Numerous nuclei, vacuoles, and retractile bodies not present. 



Ci Pseudopodia membrane-like, ectosarc reddish 3. Plakopus 



Cj Pseudopodia not membrane-like, 

 rfi Pseudopodia more or less lobose, sometimes slender and spine-like. 



Ci Animals not parasitic 4. Amceba 



^2 Animals parasitic 5. Entamceba 



dz Pseudopodia very long, radiating spine-like from body. 



6. Dactylosph^rium 



1. Protam(EBA Haeckel. Minute forms without nucleus or con- 

 tractile vacuole, in constant motion, with short pseudopodia: 4 species; 

 in salt and fresh water. 



P. primitiva Haeckel. In fresh and salt water. 



2. Pelomyxa Greeff. Very large forms constantly flowing by 

 means of short pseudopodia; body with^ numerous nuclei, vacuoles and 

 hyaline rods ; diameter up to 2 mm. : 4 species ; in fresh water. 



P. palustris Greeff. Without projections at hinder end. 



P. villosa Leidy. Possesses numerous posterior projections; about 

 1 mm. in length; body dark and opaque. 



P. carolinensis H. V. Wilson. No rods present, but numerous 

 minute crystals; 1 mm. in diameter. 



3. Plakopus F. E. Schulze. Body changes slowly in form and with 

 pointed pseudopodia which are often joined together by a broad mem- 

 brane: 2 species; in fresh water. 



