94 



TEXTBOOK OF ZOOLOGY 



right from this view. The body is covered with fine hairlike cilia 

 which are of even length except in the oral groove and at the pos- 

 terior extremity, where they are noticeably longer. The cilia within 

 the gullet are fused together into a sheet, forming the undulating 

 membrane. 



CON-r RACTIL.E 

 VACUO l_E 



ORAl_ GROOVE 



MACRO- 

 NUCI_E.US 



CONTRACTILE 

 VACUOLE 



TRICHOCYSTS 



PEI_l_ICl_E 



Fig. 38. — Diagram showing the structure of Paramecium, much enlarged. 



by T. C. Evans.) 



(Drawn 



The cell is divided into the outer, tough, nongranular ectosarc 

 which is composed of ectoplasm. The outer surface of it is a thin, 

 elastic cuticle or pellicle which is marked in hexagonal areas by the 

 distribution of the cilia. The cilia are direct outgrowths of the ecto- 

 sarc. There are a great many spindle-shaped cavities located in the 

 ectosarc with their long axes perpendicular to the surface. These 

 structures, trichocysts, are filled with a semifluid substance and each 

 opens to the outside through the pellicle. The endosarc, composed of 



