178 Education through Nature 



it is called the dorsal. The entire surface of the body is 

 covered with hairs or cilia, which are in constant vibratory 

 motion. Along the edges of the body this can be seen 

 without difficulty, but upon the surface they are visible 

 only as fine dots. The cilia are of two kinds: The loco- 

 motor cilia, which are quite small and cover nearly the 

 whole of the body; at the posterior end of the body 

 there is a small tuft of much larger cilia. Around the edges 

 of the eight-shaped outline of the anterior end is a row of 

 much larger cilia. These give rise to current by which 

 floating particles of food are carried into the mouth which 

 is situated on the posterior end of the figure eight. 



b. Appendages. The appendages of the body are of 

 four kinds and they all are processes of the cuticle, (i) 

 The fine cilia which serve for swimming. (2) The 

 cirri. They are placed on the ventral surface of the 

 body and serve for locomotion in pediform motion. Hence 

 called legs. The cirri are the stoutest cilia. (3) Mem- 

 branellae which are short flattened cilia which when end- 

 ing in a point are hard to distinguish from cirri. They 

 create the whirlpools by which the food is brought to 

 the mouth. (.4) Undulating membranes placed in the 

 mouth to assist in taking in of the food. 



c. Internal organs and structure. The Paramecium 

 is a mass of protoplasm representing a single cell. The 

 surface of the body is covered by a thin, delicate, trans- 

 parent cuticle and beneath this lies the cortex. These 

 two constitute the ectoplasm. The cilia are processes 

 of the cortex which protrude through holes in the cuticle. 

 A great number of radial striations in the cortex mark 

 minute oval sacs, the trichocysts, from which long, fine, 

 stiff filaments are shot forth and project beyond the cilia 

 when the animal is irritated. Their function is that of 

 offence and protection. The Paramecium possesses a 

 distinct mouth and oesophagus which open to the exterior 

 through an oblique funnel-shaped depression known as 

 the vestibule situated at one side of the body. This short 

 ciliated tube leads into the endoplasm. Within the cortex 

 is the endoplasm. It is much more granular than the 

 ectoplasm. It usually contains oil-globules, colored particles, 

 and various foreign bodies which are not found in the 



