16 
ANIMAL FORMS 
Slipper Animalcule (Paramecium, Fig. 7), abundant in 
stagnant water. 
In this form the cuticle surrounding the 
somewhat cylindrical body is perforated by a great number 
- Fia. 8.—Vorticella, an at- 
tached ciliate infusori- 
an, highly magnified. a, 
fully extended individ- 
ual; ¢.v., pulsating va- 
cuole ; 7, gullet; 7, nu- 
cleus. b, contracted 
specimen. c, small free- 
swimming individual, 
which unites with a sta- 
tionary individual (one 
partly united is shown 
1n specimen b). 
of minute openings through which the 
internal protoplasm projects in the form 
of delicate threads. Each process, 
termed a cilium, works on the same 
principle as the flagellum, but it beats 
with an almost perfect rhythm and in 
unison with its fellows, drives the an- 
imal hither and thither with considera- 
ble rapidity. 
On one side of the body is a furrow 
which deepens as it runs backward and 
finally passes into the gullet (g), which 
leads into the interior of the body. 
Throughout the entire extent it is lined 
with cilia which create strong currents 
in the surrounding water and in this 
way conduct food down the gullet into 
» the body. Embedded in the outer sur- 
face of the body, in among the cilia, 
are also a number of very minute sacks, 
each containing a coiled thread which 
may be discharged against the body of 
any intruder, so that this form is sup- 
plied with actual organs of defense. 
Two pulsating vacuoles (c.v.) or simple 
kidneys are also present, consisting of a 
central reservoir into which a number 
of radiating canals extend. 
19. The Bell Animalcule and other 
species—-The Bell Animalcule ( Vorti- 
cella, Fig. 8) is often found in the same situations as the 
Slipper Animalcule, which in certain respects it resembles. 
It is generally attached by a slender stalk, and where many 
