50 COMPARATIVE ZOOLOGY. 
by the vibration of minute hairs, or cilia, lining the ca- 
nals. The microscopic Infusoria have cilia surrounding 
the mouth, with which they draw or drive into the body 
little currents containing nutritious particles. Bivalve 
shells, as the Oyster and Clam, are likewise dependent 
upon this method of procuring food, the gills being 
fringed with cilia. So the singular fish, Amphioxus (the 
only example among Vertebrates), employs ciliary action 
to obtain the infusorial organisms on which it feeds. 
The Greenland Whale has a mode of ingestion somewhat 
unique, gulping great volumes of water into its mouth, 
and then straining out, through its whalebone sieve, the 
small animals which the water may contain. 
(2) Solids—When the food is in solid masses, whether 
floating in water or not, the animal is usually provided 
with prehensile appendages for 
taking hold of it. The jelly- 
like Amoeba has neither mouth 
nor stomach, but extemporizes 
them, seizing its food by merely 
applying its soft body to it, and 
then wrapping itself around it. 
Ae ee re ony Other minute creatures (Fora- 
with pseudopodia extended, x 30. minifera) extemporize arms 
by throwing out thread-like prolongations of their bodies 
(pseudopodia), which adhere to their prey, and then con- 
tract. . 
A higher type is seen in Polyps and Jelly-fishes, which 
have hollow tentacles around the entrance to the stomach 
(Fig. 194). These tentacles are contractile, and, more- 
over, are covered with an immense number of minute sacs, 
in which a highly elastic filament is coiled up spirally. 
When the tentacles are touched by a passing animal, as 
a Crab, they seize it, and at the same moment throw out 
their myriad filaments, like so many lassos, which increase 
