76 THE OCEAN WORLD. 
salt water. Professor O. Schmidt proposes to divide it into three 
divisions :— ae: 
1. Where the spicules assume a sex-radiate type. To this will 
belong some of the most 1emarkable and beautiful of sponges, as 
Eupletella, Aphrocallistes, Pheronema. ; 
2. Where the spicules are anchor shaped, or of a pyramidal form, 
containing many very familiar genera, especially the genus Songi//a, 
met with in fresh water. 
3. Where the spicules are monaxial, polyaxial, or wanting. Here, 
amid a host of genera and species, would be placed the genus 
Spongia, to one or more species of which the various sponges pre- 
viously alluded to as Sponges of Commerce, must be referred. (For 
Spongia officinalis, see Fig. 9). 
RHIZOPODA. 
Gervais and Van Beneden include under the name of AAizopods, 
or root-fooled animals (so called from fi(a root; mods, odds, footed 
animals), those of the simplest organisation, which may be charac- 
terised by the absence of a distinct digestive cavity, and by the 
presence of diverging processes, or pseudopodia, which admit of 
extension, and are sometimes simple, sometimes branched. ‘These 
pseudopodia can be completely withdrawn into the body substance 
of the Rhizopod, and they receive their technical name from the fact 
that they in many cases assist in the locomotion of these animals. 
The Rhizopods are found both in fresh and salt water, but 
the marine forms are much the more numerous. The class is 
divided into three orders, namely, the Zodosa, the Reticulosa, and 
the Radiolaria, 
Lozposa, OR AMGBINA. 
In nearly all decaying animal and vegetable infusions, not quite 
putrid, upon all odzy beds which have remained for some time 
covered by fresh or sea water, as well as in our lakes and peat pools, 
we find the singular beings which belong to this Order. They are 
among the simplest organisms in creation, being reduced to but a 
mere particle of living matter. Their bodies are formed of a gela- 
tinous substance, without any appreciable organisation. The quantity 
of matter which forms them is so small, that it becomes incredibly 
diaphanous, and so transparent, that the eye, assisted by the powers 
of the microscope, can often only take cognisance of it by a careful 
arrangement of the light. 
