40 BRITISH FRESHWATER RHIZOPODA. 
occasionally digitate, and, in the resting phase of the 
organism, persistent. 4. Pelomyxa. 
Body discoid, pseudopodia lobose (hernia-like) ; 
endoplasm containing numerous minute reniform con- 
cretions ; nucleus large, punctate. 5. Lithameba. 
Ameoeboid ; the plasma-body furnished at the pos- 
terior extremity with numerous straight, usually arti- 
culate, protoplasmic filaments. 6. Ourameba. 
Genus 1. AM@BA Ehrenberg, 1832. 
Volvox (pars) Linnaus Syst. Nat. ed. 10, I (1758), p. 820. 
Chaos (pars) Linnzus Syst. Nat. ed. 12, I, pt. 2 (1767), p 
1326 
Vibrio (pars) O. F. Mitten Verm. Terr. et Fluv. I (1773), 
p. 45. 
Proteus (pars)'O. F, Minurr Animale. Infus. (1786), p. 9. 
Non Proteus Baxer Empl. Micr. (1753), p. 260. 
Amiba (pars) Bory pu Sv. Vincent in Dict. class. Hist. Nat. 
I (1822), p. 261. 
Anveba (pars) Eurensura in Abh. K. Akad. Wiss. Berlin, 
1831 (1832), p. 79; and Infus. (1838), p. 126. 
Plasma-body normally a soft irregularly-spherical or 
ovate particle of animated protoplasm, having one or 
more nuclei and pulsating vacuoles, but otherwise struc- 
tureless,and without any apparent investing membrane; 
possessing inherent extensile and contractile power. 
Locomotion effected by lobular expansions or extensions 
of the hyaline ectoplasm, originating on any part of the 
body-surface, and forming in some species broad lobes, 
in others digitate processes, short or elongated (some- 
times branching), active or rigid, blunt or sharply-_ 
pointed. Hndoplasm granular, semitransparent, in 
some rare examples nearly opaque. In the quiescent 
(encisted) state, according to Leidy, the body is purged 
of food and other ingested matter, and becomes 
uniformly globular or elliptic, and invested with 
a structureless membrane. 
Individuals differ greatly in size as well as in vital 
activity, but all have the same plastic body, more or 
