THE INFUSORIANS. 
11 
ooze. Chalk is largely made n 
Foraminifera; before it becam 
it was a kind of Foraminifer- 
ous ooze. 
Those Ehizopods which se- 
crete a silicious shell are called 
Radiolaria, A 'few (Fig. 6) 
live in fresh-water ponds, but 
the majority live in the sea. 
Their shells possess wondrous 
beauty and variety of orna- 
mentation. 
Some Ehizopods are known 
to develop from little monad- 
like or round germs, which 
move about by means of two 
little active threads or tails.* 
of the calcareous shells of 
hardened into rock-masses 
Fig. 6. — Actinosphcerium, a Radiola- 
rian. a, a morsel of food drawn 
into the cortical layer 6; c, central 
parenchymatous niass of body; d, 
some balls of food-stuff in the lat- 
ter; e, pseudopodia of the cortical 
layer. Highly magnified. 
Class 11. — GREGAKii^iDA. 
General Characters of Gregarines. — These may be best 
defined as parasitic, worm-like Amoebae. They are long 
and slender, of quite definite flattened or cylindrical form 
(Fig. 7) to adapt them to their parasitic life. The largest 
kind {Gregarma gigantea) is like a piece of fine thread, 
half an inch long; it lives in the intestine of the lobster. 
Most Gregarinse are very minute, and are parasites, living 
in the digestive canal of insects. 
Class III. — Iotusoria. 
General Characters of Infusoria. — If we allow a little dried 
grass or hay or a piece of fish to stand in a glass of water 
for a day or two, thus making what is called an infusion, 
and then examine a drop of this water it will be found to 
teem with myriads of microscopic creatures, called Infu- 
sorians, because they are found in infusions. The simplest 
and minutest form of infusorian is the monad (Fig. 8). 
* See Leidjr's Fresh-water Rhizopods of North America, 1879, 
