204 



PROTOZOA. 



7! 



PF 



like the substance of a true cell nucleus, when undergoing division. 



The paranucleus too increases in size 

 and becomes striated, and divides into 

 a number of bodies by a single or re- 

 peated division. Some of these bodies 

 produced by the division of the nucleus 

 and paranucleus disappear or are cast 

 out, and others are employed in the 

 formation of the new nucleus and 

 paranucleus. The processes of regene- 

 ration are for the most part not com- 

 pleted until the conjugating animals ' 

 have separated. Conjugation is probably 

 followed by a repeated division (fig. 146). 

 The mode of life of the Infusoria, 

 which principally inhabit fresh water, 

 is very various. Most of them lead an 

 independent life, and take up larger 

 or smaller bodies, even Rotifera, as 

 nourishment. Some, as Amphilej)tus, 

 select fixed Infusoria, as Epistylis and 

 Carchesium, for their prey, and swallow them down as far as the 

 origin of the stalk they then, while fixed on the 

 stalk, secrete a capsule, and divide up into two or 

 more individuals, which pass out. Certain Infu- 

 soria, as the mouthless Opalina, and many Bursa- 

 ridse, are parasitic in the intestine and bladder of 

 Vertebrates. To these belongs the 'Balantidium 

 coli from the large intestine of Man (fig. 147). 



1. Sub-order : Holotricha. - - Body uniformly 

 covered with cilia, which are arranged in longitu- 

 dinal rows, and are shorter than the body. Longer 

 cilia are sometimes found in the region of the 



FIG. 146. ParamtBcium Bursaria 



about one hour after conjugation 

 (after Biitschli) . , nucleolus ; N, 

 nucleus ; P V, contractile vacuole. 

 Two of the nucleoli have become 

 clear spheres. 



FiG.U7.-~aiantid;/im 



coKwith twopulsa- mouth 

 tmg vacuoles (after 



nuc^us U Ues r ^a Besides the Parasitic Opalinfe (Ojjalina! ranarum), with- 

 starcT-V-anule tha^ out moutl1 or anus, the following families belong to this 

 has been eaten, a group : 



ball of excrement is Fam. Trachelidae. Body of changeable shape prolonged 

 passing out of the j n t o an anterior neck-like process. Mouth ventral, without 



longer cilia. TracJtclius orum Ehrbg., Ampliilcptus fasci- 



cola Ehrbg. 

 Fam. Colpodidse. Form of body definite. Mouth ventral, in a depression, 





