THE SIMPLEST ANIMALS OR PROTOZOA 



27 



Slipper Animalcule (Paramwcium, Fig. 9), abundant in 

 stagnant water. In this form the cuticle surrounding the 

 somewhat cylindrical body is perforated by a great number 

 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 (#), 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. 



28. The Bell Animalcule and other 

 species. The Bell Animalcule ( Vorti- 

 cella, Fig. 10) 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 



FIG. 10. Vorticella, an at- 

 tached ciliate infusori- 

 an, highly magnified, a, 

 fully extended individ- 



. ual ; c.v., pulsating va- 

 cuole ; g, gullet ; n, nu- 

 cleus, b, contracted 

 specimen, c, small free- 

 swimming individual, 

 which unites with a sta- 

 tionary individual (one 

 partly united is shown 

 in specimen b). 



