ONE-CELLED ANIMALS AND SPONGES. 127 
which living cells are mainly | Sili’cious (Lat. sz/ex, flint), made 
composed. of a substance like glass. 
Rhi zop’o da (Gr. rhiza, root, and | Spic’ule (Lat. dim. of spicum, a 
pous), Protozoa having pseudo- spike), a bit of hard material 
podia for locomotion. formed in the tissues of sponges 
Sar'code (Gr. sarx, flesh) the fleshy and other lower animals. 
part of a sponge. 
