584 
THE AM CEB A. 
shell is wanting, and its place supplied by a cover composed of matted sand-grains. The 
gi eater number of these creatures are formed by a succession of buds, each bud remaining in 
connection with that from which it sprung, and thus forming a composite body, which some- 
times is rather complicated in its structure. Sometimes when the buds are merely arranged 
in a line, the result is a straight, rod-like form, divided into a series of joints, marking the 
’■spots where the buds have in their sequence issued from each other. If, on the other hand, 
each bud grows a little on one side of its predecessor, a spiral form is the result, and a 
nautilus-like shell is formed. The resemblance to this mollusk is further increased when each 
bud becomes rather larger than that from which it sprung. 
The arrangements of the Foraminifera hitherto in use have mostly been founded upon the 
mode of growth ; but Dr. Carpenter has clearly shown that this character is so extremely 
variable, that no reliance can be placed upon it. In a single genus, there is every gradation 
between the straight and the spiral forms ; and, in many instances, a shell which commences 
in a spiral will end in a straight line. 
As, therefore, the already existing systems have been shown to be based on false prin- 
ciples, and the arrangement which is to supplant them has not been fully decided upon, we 
will not occupy our space by insisting upon the characters by which the systems are estab- 
lished, but merely proceed to a brief description of the localities in which the various species 
may be found. 
The greater number of the species are found in Europe, and are now known by the 
names of Dentalina, Polystomella, Rosalina, and Quinqueloculina. Some other species are to 
be found in Central America. 
Another sub-class of Ehizopods is named Polycystina, and is notable for the singular 
structure of the shells, which are pierced in regular patterns, without orifices, and are often 
prolonged into curious spikes and projections that give them a most wonderful beauty when 
seen under a good microscope. They are, in general, smaller than the Foraminifera, and are 
found in the mud of various seas, especially those of the West Indian islands. The marvellous 
variety which is obtained by the carrying out of two principles, namely, the piercing of holes 
and the projection of spikes, is almost incredible ; and the delicate tracery of the patterns thus 
produced is so artistic as to have been happily compared to the hollow ivory balls carved by 
the patient hands of Chinese artists. 
There is one little creature, which is supposed by many physiologists to belong to the 
Rhizopoda, but whose position is very uncertain, and even its class not clearly ascertained. 
This is the JN’octiluca, a tiny being, about as large as the head of a minikin pin, which is 
remarkable for its phosphorescent power. If a vessel be filled with sea-water, and brought 
into a dark room, the Noctiluca fills it with little sparklets of bluish light, which shine for an 
instant like stars in the firmament, and which can be induced to give out their momentary 
radiance by tapping the vessel, or even by a heavy footfall on the floor of the room. 
Each of these little beings is furnished with a minute tail-like appendage, by means of 
which it is enabled to proceed through the water ; and on certain favorable occasions they fill 
the sea with their luminous hosts, and cause each wave to become a breaking mass of liquid 
fire. A ship passing through the sea leaves a fiery wake behind her keel, and when the boat- 
men lift their oars from the sea, they appear to drop flames from the blades as they are raised, 
all dripping, into the air at every stroke. 
Although so small as to be microscopic in their dimensions, they are yet large enough to 
be discerned by the unaided eye, and can therefore be isolated without difficulty and placed in 
the field of the microscope. 
In the accompanying illustration will be seen an odd-looking object, which is considered 
as belonging to the Rhizopods, though not possessing any shell. 
This creature, called Am<eba, is remarkable for the fact that it really has no outline 
and no shape, for its body is continually altering its figure ; so that the rounded object 
which was seen in the microscope but a few minutes before, will, in that short space of 
time, have protruded a number of elongations that look like fingers of a glove or the rays of a 
star-fish. 
