CILIATA. 



199 



one or more rings of large cilia round the edge of 



a raised lid- 

 like flap which is capable of being shut down. There is also an in- 

 ferior row of cilia upon this flap running to the 

 mouth. The free-swimming Infusoria often 

 possess in addition to these delicate cilia and 

 zones of cilia, thicker hairs and stiff bristles, 

 and more or less bent hooks, which are em- 

 ployed in locomotion and for attachment. 



Certain fixed Infusoria as Stcntor (fig. 138) 

 and Cothurnict secrete external coverings or 

 shells, into which they retract themselves. 

 Nourishment is taken in in a few cases by 

 endosinosis through the whole surface of the 

 body, e.y., the parasitic Opalina. The Acineta 

 feed themselves by sucking the body of their 

 prey. They are without a mouth, and are 

 incapable of taking in solid food. But they 

 possess a number of long, narrow, contractile 

 tentacles, which radiate from the surface of 

 their bodies, and have the form of delicate tubes, 

 presenting a structureless external wall and a 

 semi-fluid granular axis. The Acineta applies 

 one or more of these organs to the body of an 

 extraneous organism, when the substance of 



interior of the 



FIG. 



pullet ; 

 vacuole 



FT, pulsatinp 

 2V, nucleus. 



granular 



axis of the 



the latter travels down the 

 tentacle into the body of 

 the Acineta (fig. 139). 



By far the greatest num- 

 ber of Infusoria possess an 

 oral aperture, usually near 

 the anterior pole of the 

 body, and a second aperture 

 which acts as anus, and 

 which can be seen in a 

 definite part of the body as 

 a slit during the exit of the 

 excreta. 



rrii 11 i Fio. 139. Acincla, ferrttnlequinum Ehvbjr., which is 



The ^body parenchyma, Mickinp thcbod / of & J. M Illfus ,, rl!111 (Ku.-hci.vs) 



which is bounded by the (after Lachmann). T, sucking tentacle ; V, vacuole ; 

 , . N, nucleus. 



external membrane, is 



divided into a viscid exoplasm and a more fluid cndoplasrn, into 



