106 



TROTOZOA 



Order II. Heterotricha. 



I^ikc the TTololricha tlic Iletorolricha arc cvcrvwhcrc ciliated, l>ul they have 

 a tract of slninger cilia, the adoral ciliatetl spiral, beginning at some distance 

 from the cvtostome and leading in a spiral course into the moutli. It consists 

 of rows of cilia united into imiiibraiicllic placed at right angles to the course of 

 the spiral. In the SInilors'''' (fig. 153), the peristomial area, surrounded by 

 the spiral, forms the broader enci of the body, which ta]icrs toward the other 

 end, bv which the animal may attach itself. Muscle fibres running lengthwise 

 immediately under the cuticle produce energetic moxements. Balaiilidiiim 

 coli (fig. 154) appears in the large intestine of men ill with diarrhwa, it also occurs 

 in swine without causing sickness. Other jiarasites of man are B. iiiiiiiiliiiii 

 and Xyciotlicrus faba. 



Order III. Peritricha. 



The Peritricha have a broad peristome area around the cytostome; the oppo- 

 site end has a corresponding pedal disc or is narrowed like a goblet and ends in a 

 stalk (fig. 155). Only the adoral ciliated siiiral is constant. It arises from the 

 swollen margin of the peristomial area, and continues on the 'operculum,' a 



i/st. 



Fig. 155. — Carchcsium polyp'nium (after BiitschliV Ixfl, a single animal; right, 

 three stages of dix'ision. cv, (.ontraetile \aeiiole; ;/, maeronucleus; n' , niicrtinueleiis; 

 N-i\ food vacuoles; os, c\'lophar\'nx; f^cr, peristome; r.v, reser\-e)ir o{ contractile \'acuole; 

 iiiii, uiiilulatiiig meniliranc; vst, vestibule; ■icJ', ring on which a posterior circle of cilia 

 may i.le\'elc)p, 



ciliated disc which projects free frotii the peristomial area, but in contraction is 

 drawn close against it, the peristome li])s fokling over all. besides, there nniy 

 be a temporary or permanent circle of cilia near the hinder end. The nucleus 

 is usually sausage-shaped, much bent, and with the small micronucleus in its 

 hinder angle (tig. 155, ;;'). 



The VoRTici':Li,iii,K(figs. 152, 155), are attached by a long stalk which 

 contains a slightly spiral muscle, di\iding in the body into fine filirilkv which 

 extend under the cuticle to the ])eristome. When the muscle in the stalk con- 

 tracts it becomes coiled into a corkscrew spiral, drawing back the animal, and 



