54 BRITISH FRESHWATER RHIZOPODA. 
The animal makes a slow but continuous advance, 
and during its movements the semi-fluid endoplasm 
flows longitudinally, in distinct streams, modifying, 
by pressure, the form of the contractile vacuole, 
which at one moment may be circular and the next 
elongated or irregularly outlined. The endoplasm is 
finely granular, colourless, or tinged with green from 
the presence of minute chlorophyl particles, and it 
contains also a limited number of larger granules or 
crystalline bodies of irregular shape. 
Dimensions : Length 25-451; greatest breadth an- 
teriorly 20-35 pu. 
In ponds amongst submerged vegetation, usually 
common. 
The contractile vesicle, in this species, is curiously 
modified by the flow of the endoplasm. Whilst 
changing in position but slightly, its form exhibits 
constant variation. It will reappear, after discharge, 
sometimes as two separate vesicles of small size; these 
gradually enlarge, and ultimately unite ; and the organ 
not infrequently presents an oval or distorted outline. 
Amebu striata has been, by some, regarded as a young 
state of A. verrucosa Hhrenb.  Leidy (‘ Freshw. Rhiz. 
N. Amer.’) so describes and figures it. Apart from 
the fact that it is a much smaller organism, and 
possessed of characters of its own, which are constant, 
it is rarely found in association with A. verrucosa in 
the adult state. : 
6. Ameba guttula Dujardin. 
(Plate V, fig. 4.) 
Amiba guttula Dusarpin Infus. (1841), p. 285; Crtvier in 
Nat. Canad. VII (1875), p. 276. 
Ameba guttula Perry Kenntn. kleinst. Lebensf. (1852), 
p. 188, t. vii. f. 18; Prircnarp Hist. Infus. new ed. 
(1852), p. 203, and ed. 4 (1861), p. 549, t. xxu, f. 6; 
AvgrpacH in Zeits. f. wiss. Zool. (1856), p. 414, t. xxii, 
ff. 17, 18; Wiiramson in Pop. Sci. Rev. V (1886), p. 197, 
