FORAMINIFERA AND RADIOLARIA 55 
the bag containing the powdered chalk into it, and 
knead your mock pudding with your fingers. A lot 
of the material will find its way through the calico 
into the water. Go on kneading until about a third 
of the powdered chalk is left. You will now have 
a milky fluid in your basin, which will contain a lot 
of foraminifera. Let the fluid settle, when, of 
course, it will clear, and the white stuff from the 
chalk will fall to the bottom. Take this white stuff, 
put it into a bottle with water, shake well, and pour 
off the water. Do this several times so that the 
foraminifera may be well washed. Then if you have 
no microscope of your own, take your material to 
a friend who has one, and ask him to let you see 
some of it through his instrument. You will be 
delighted with the wonderful forms you can see. 
The Radiolaria (Latin, radius =a ray) are no less 
wonderful than the foraminifera. Their skeletons 
are made of flint (silica), and they assume many 
very wonderful forms. The bodies of these creatures 
are also projected through holes in their covering. 
Fossil radiolaria are found in rocks dating from 
Ordovician times to those of the most recent period ; 
these creatures have had no break in their history, 
and, of course, living specimens are still to be found. 
See Plate 12, 6, for a photo-micrograph of some 
radiolarian skeletons. 
The second great subdivision of the Animal 
Kingdom, the Porirera (pore-bearers), embraces 
the Sponges, which are found in a fossil state in all 
the geological Periods from the Cambrian upwards. 
Sponges are more highly organized than foraminifera 
and radiolaria. Their bodies contain a number of 
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