PROTOZOA II 
genus found in the soft debris at the bottom of clean ponds 
and ditches, and on the surface of aquatic plants. The shell is 
chitinoid, and arched on the upper surface, flat on the lower, so 
Fic. 3.—Portion of a Pelomyzxa, highly 
magnified. 
1. Clear external layer of protoplasm, 
ectoplasm. 
bo 
. Central protoplasm, crowded with 
granules, etc.—endoplasm. 
. Pseudopodia. 
. Refractive bodies. 
. Nuclei. 
a Oo — WwW 
. Cylindrical crystals scattered through 
the protoplasm. 
that it is somewhat dome-shaped or hemispherical in form. 
In the centre of the flat surface is a circular opening through 
Fie. 4.—Arcella vulgaris, Ehr. 
Shell. 
. Protoplasm within the shell. 
. Protoplasm without the shell—pseudo- 
podia. 
. Nucleus ; there is more than one. 
. Contractile vacuole. 
. Aperture of shell. 
. Space where the protoplasm has with- 
drawn from shell. 
. Gas vacuoles. 
oo bh) 
STD OE 
ioe) 
which the protoplasm protrudes in the form of blunt pseudopodia. 
The protoplasm within the shell encloses more than one 
nucleus, several contractile vacuoles, arranged round the circular 
