RHIZOPODA. 
HE whole arrangement of the beings which we are now T about to examine is still 
very obscure, and the best zoologists of the present time have declared that any 
system which has been hitherto adopted can only be considered as provisional. 
Some writers, for example, unite the Rhizopoda with the Infusoria, while 
others rank them among the Polyzoa ; and others again consider them to be 
intermediate between the radiata and those simple forms of animal life which 
are appropriately named Protozoa. After taking into consideration the various 
systems that have been propounded by different authors, I have come to the conclusion that, 
at all events, as a provisional arrangement, the Rhizopoda ought to be ranked as a distinct 
class, and placed in the position which they here occupy. 
The name Rhizopoda is of Greek origin, and literally signifies “root-footed.” It is a very 
appropriate title, inasmuch as they put forth certain filamentous appendages from their bodies, 
which look very like the tender rootlets of plants, and serve a double purpose, namely, as 
organs of progression, and as instruments whereby they may catch their prey. 
Some of these beings are quite unprotected, their soft gelatinous bodies being devoid of 
any covering ; others are inclosed in a horny case, pierced with openings, through which the 
filaments can be projected ; while the greater number of the known species are furnished with 
shells very similar in form to those of the mollusks, and in some cases wonderfully similar to 
the highly complicated dwelling of one of the highest mollusks, the pearly nautilus. 
These minute though beautiful beings exist in numbers that are only rivalled by the 
sands of the sea for multitude ; and the vast hosts of these creatures can be barely estimated 
even when we know that many large cities are built wholly of the dead skeletons of these 
microscopic beings, and that in a single ounce of sand from the Caribbean Sea nearly four 
millions of these shells have been discovered. The living species are not nearly so numerous 
as the fossil. They can be captured in various w T ays. If, for example, growing algse be 
plucked, and placed in a glass vessel of sea-water, the Rhizopods will leave the algae, and 
settle on the sides of the vessel. If they live in muddy substances, such as the “ oyster-ooze,” 
which is especially prolific in Rhizopod forms, the upper layer of mud should be taken off and 
stirred up in a vessel of clear sea- water, when the creatures will sink to the bottom of the 
vessel, and may easily be separated. 
These modes are adopted for living specimens, but if the dead skeletons only are required, 
they can be procured in many ways. One of the simplest methods of finding Rhizopod shells 
is, to shake the dust out of sponges, and to examine it when laid thinly on black paper. An 
ordinary pocket magnifier is employed in the search, and the shells are readily seen against 
the black background. For removing them I always employ a single bristle, stuck into 
a handle — one taken from a shaving-brush is, perhaps, the best adapted to the purpose — and 
take up the shells singly by wetting the tip of the bristle. 
There is also another method whereby the empty shells may be obtained in considerable 
numbers. The sand, mud, or other substance, in which they reside, should be well dried, 
heated, and then stirred into water. As the chambered cells of the Rhizopods will be filled 
with air, they will float on the surface of the water, and can be skimmed off without much 
difficulty. 
The first sub-class of these beings is the Foraminifera, so called on account of the tiny 
openings, or foramina, with which the pretty shells are pierced. Sometimes, however, this 
