RHIZOPODA. 938 
a network, in which the particles of food are entangled: The 
body is completely naked, and the MJonera differ from the 
Foraminifera, chiefly if not entirely, in this absence of any 
hard covering or shell. 
ORDER IJ. AM@BEA.—-This order is characterised by the fact 
that the pseudopodia are mostly blunt and finger-like in shape, 
and that the sarcode of the body contains the structures known 
as the “nucleus” and “ contractile vesicle.” 
As the ¢yfe of the order may be taken the Ameéa or Proteus- 
animalcule, so called because of the incessant and illimitable 
changes of form which it exhibits (Gr. amozbos, changing). The 
Amba is a little microscopical creature which may commonly 
be detected in stagnant water, especially where there is decay- 
ing vegetable matter. When examined under the microscope, 
all that would probably be seen at first would be a shapeless or 
irregularly-spherical mass of gelatinous, jelly-like sarcode, con- 
Fig. 3.—Morphology of Rhizopoda. a Ameba radiosa, showing the pseudopodia, 
the contractile vesicle, nucleus, and vacuoles; 4 Diffugia, with the pseudopodia 
protruded from the anterior end of the carapace ; c Detached sponge-particles or 
“sarcoids ;” d Ciliated sponge-particles of Grantia ; e Sponge-particle of the 
fresh-water sponge (Sfozgzd/az) with a single cilium. : 
taining scattered granules. Soon the creature might be observed 
to push out a finger-shaped prolongation of its own substance > 
and it would soon be found that similar processes or pseudo- 
podia could be pushed out at will from almost any point of the 
body and again retracted within it without leaving any trace 
behind. As a result of this, the form of the animal is constantly 
changing, and hence its common name of Proteus-animalcule 
(fig. 3, a). By means of these temporary processes of sarcode, 
the Ameba both moves and obtains food. Locomotion is 
effected in a kind of creeping manner, the animal pushing out 
the pseudopodia in one direction and then pulling the body in 
the same direction. In the same way, when any minute particle 
of food, such as a microscopic plant, comes within its reach, the 
