THE LARGE GROUP OF THE SiMVLLEST ()IU;\MsM< 



!■)<» 



diagonally beating cilia which cover the body cause the rotation of 

 the Paramecium on the longitudinal axis. Since the cilia in the oral 

 groove are longer and capable of more vigorous motion, th(> b<,<lv 

 tends to swerve toward the left. As the water passes down the <,ral 

 groove towards the gullet, the waving undulatinq mnnhranv f<,r,ne,l 

 of ciha fused together, guides particles of potential food down the 

 gullet by means of its wavelike motion. At the inner e.id f..od 

 vacuoles are formed within the body. The food vacuoles an<l other 

 granular inclu.sions shift about in a definite course within the cndo- 

 plasm of the cell. Gradually the food particles within a given vacuole 

 are digested by means of 

 enzymes formed in the endo- 

 plasm and released into the 

 food vacuole. The digested 

 food material is absorbed 

 into the protoplasm, there 

 to build up living matter or 

 to be used later in the release 

 of energy. Food wastes are 

 passed out of the cell through 

 the anal spot. Excretion of 

 wastes may also take place 

 through the cell-membrane 

 by diffusion, or through two 

 contractile vacuoles, one at 

 each end of the cell, which 

 consist of a central cavity 

 with canals radiating out 

 from it into the endoplasm. 

 Many experiments have 

 been made to test the sensi- 

 tiveness of Paramecium to 

 various stimuli. As in other 

 living cells responsive to 

 stimuli, factors of the envi- 

 ronment have a distinct in- 

 fluence upon its movements. 

 Paramecium swims in a spi- 

 ral course partly as a result of its shape and the arrangement and 

 diagonal beating of the cilia, and partly on account of the anteriorly 



anLericfT end. 



i pellicle- 



ccxTial 



■^^CXOLCole 



— ectoplccSm. 

 •--endoplasm 



--oral droavQ, 

 - -moLcth 



;- gullet.. 



....■Cood,\roc\jio\Q. 



arxxl ^pot 



Contractile ,, 



^_^ -.tricHocy^t 



.;\^,,<o^..„ cilicx. 



'"'^<:'.. posterior ond. 



Internal structure of Pdrdnirritirn attula- 

 lurn. The cilia cover the cut ire surface of 

 the cell and are somewhat Ioiiltit .iI I In" jmis- 

 terior em]. 



