30 . INVERTEBRATE ANIMALS, 
Co AP Toba. 11, 
RHIZOPODA. 
THE next class of the Protozoa which we have to consider 
comprises the most characteristic and typical forms of the 
whole sub-kingdom. The name of AAzzopoda, or “ root-footed ” 
animalcules (from the Greek, r/zza, root ; and odes, feet), is de- 
rived from the fact that they all possess the power of throwing 
out at will from various parts of the body the processes of sar- 
code which have been already spoken of as pseudopodia, and 
by which they both move and obtain food. In fact, the RAZzzo- 
poda may be shortly defined as Protozoa which have no mouth 
and possess the power of giving out pseudopodia. ‘The pseudo- 
podia vary a good deal in shape and in other characters in 
different orders of the Rkzzopoda, but they have invariably the 
character of being nothing more than temporary threads or 
finger-like processes of sarcode, which can be thrust out at 
will, and which melt again into the substance of the body 
when they are withdrawn. 
Four distinct types of structure are known in the A&fzzo0- 
poda, and these constitute as many distinct orders, which are 
known by the names of the Monera, Amebea, Foraminifera, 
Radtolaria, and Spongida. 
ORDER I. MonERA—This name has been proposed .for a 
small group of organisms which merely require to be men- 
tioned. They are all microscopic in size, and inhabit the sea. 
Their sarcode-body is entirely structureless and devoid of defi- 
nite organs of any kind. They have the power, however, of 
throwing out innumerable processes of the body-substance or 
‘“‘pseudopodia,” and these agree in their characters with those 
which will be afterward described as characterising the Fora- 
mintfera. ‘They are, namely, very long and delicate filaments 
of sarcode, which unite in various directions so as to form 
