294 



ESSENTIALS OF ZOOLOGY 



the heel part ; while the posterior portion, which is generally broader 

 but pointed, represents the sole portion. 



At one side is a depression, the oj^al groove, which passes diagonally 

 from the anterior end to about the middle of the body. It is broad 

 and shallow anteriorly but it becomes narrow and deeper as it ends 

 in a mouth, which leads to the gullet. The groove usually extends 



CIUI A 



CON T R ACTlt_e 

 VACUOLE 



ORAU GROOVe 

 MACRO— 



nucl.e:us 



MICRO- 



Nuci_eus 



MOUTH 

 SUL.t_ET 

 FOOD VACUOl-E 

 ANAL. PORE 



CO NT R AC T I 1_'e 

 VACUOLE 



TRICHOCYSTS 

 PELLlCue 



Fig. 99. — Paramecium, much enlarged to show structure. 



Evans. ) 



(Drawn by Titus C. 



obliquely from right to left in P. caudatum as the animal is viewed 

 from the oral side. Occasionally cultures are found in which the 

 majority of the individuals show the groove extending from left to 

 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 



