THE INFUSORIA. 
585 
It can elongate itself to almost any extent, can then throw out its strange protrusions so 
as to resemble a club with a spiked head, or it can gather itself into a rude globular mass, as 
if pinched out of dough by a single 
squeeze of the hand, allowing the 
soft substance to protrude between 
the fingers. It has no particular 
stomach, but extemporizes that 
organ out of any part of its body 
with which its food happens to 
come in contact, literally pushing 
the food into its body and then 
digesting it without requiring 
any special apparatus for the 
purpose. 
Some of the Lobose Rhizopods, 
as these creatures are called, are 
also furnished with a shelly or 
horny covering, such as the Arcel- 
lina, where the shield is cap- 
shaped, or the Difflugia, where it 
is pitcher-shaped, the animal pro- 
truding itself from that part which 
represents the mouth of the jug. 
Many physiologists suppose that 
the Amoeba is not a perfect being, but it is merely the larval state of some animal with a higher 
development, such as tlie Arcella and other shell-bearing Rhizopods. 
The genus Perinidium may be known by the furrow that runs transversely around the 
body, and is furnished with cilia. The integument of the body is membranous. The Tripos 
Perinidium is remarkable for its power of shining by night. It may be recognized by the 
shelly case, which is concave, smooth, and is developed into three horns, two being long and 
the other comparatively short. The longer horns are in front. Its length is about 150th of an 
inch.. The Kerona also belongs to this order, and is found in fresh water, where it may often 
be seen in considerable numbers. Besides the usual cilia, it is furnished with instruments of 
progression that enable it to climb and creep, and are formed like bristles or booklets. Its 
length is rather variable, but is about equal to that of the Peridinium. 
AMCEBA — Amceba princeps. 600 times enlarged, a and b show the same animal in 
changed form. 
INFUSORIA. 
E now come to the Infusoria, creatures which are all of very minute dimensions, 
and respecting which there is great uncertainty prevailing. As with the pre- 
ceding class, no definite system has yet been invented by which they can be 
arranged ; and in many cases physiologists are undecided whether the tiny 
beings are veritable species, or whether they are but the larval forms of higher 
beings ; while, in some cases, it cannot be precisely ascertained whether they 
belong to the animal or vegetable kingdom. 
Without, therefore, occupying our space with disquisitions which would require a volume 
for their full elucidation, we will proceed at once to some of the more remarkable forms among 
these curious beings. 
Vot„ III.— ?4. 
