368 



THE CILIATES 



FAMILY PARAISOTRICHIDAE 



In this holotrichasin, trichostomorid 

 family, somatic ciliation is complete, 

 and there is an anterior tuft of longer 

 cilia. The mouth is subterminal, opening 

 just posterior to the concretion vacuole. 



Genus PARAISOTRICHA 

 Fiorentini, 1890 



The cilia form more or less spiral 

 longitudinal rows. The contractile vac- 

 uole is posterior. 



Paraisolriclui colpoidea Fiorentini, 

 1890 is ovoid, measures 70 to 100 by 42 

 to 60 fi and has 34 to 40 rows of cilia. 

 The macronucleus is a thick, ellipsoidal 

 disc. There is a large concretion vacuole 

 at the anterior end. Hsiung (1930) found 

 this species in the cecum of 21 and the 

 colon of 6 out of 46 horses in Iowa. 



of a retractile, conical elevation at the 

 anterior end. The adoral zone of mem- 

 branelles is conspicuous. There are open 

 ring zones of membranelles near the pos- 

 terior end on the dorsal and ventral sides. 

 The pellicle is ridged. There is a club- 

 shaped skeletal plate. A row of several 

 contractile vacuoles runs along the band- 

 formed macronucleus. 



Cycloposthiio)! bipalniatiim (Fiorentini, 

 1890) Bundle, 1895 is more or less rec- 

 tangular, slightly compressed laterally, 

 with a truncate anterior end and a tapering 

 posterior end with a tail-like structure. 

 It measures 80 to 127 by 35 to 57 ju . A 

 longitudinal groove and a light, linear 

 skeletal plate are present on the left side. 

 The macronucleus is hooked anteriorly, 

 and the micronucleus is located near its 

 middle. There are 4 contractile vacuoles. 

 Hsiung (1930) found this species in the 

 cecum of 38 and the colon of 8 out of 46 

 horses in Iowa. 



P. beckeri Hsiung, 1930 resembles 

 P. colpoidea but has only 11 rows of cilia. 

 It measures 52 to 98 by 30 to 52 fj,. Hsiung 

 (1930) found it in the cecum of 8 and the 

 colon of 1 out of 46 horses in Iowa. 



P. minuta Hsiung, 1930 resembles 

 P. colpoidea but has only 20 rows of cilia 

 and measures 38 to 68 by 27 to 36 |i. 

 Hsiung (1930) found it in the cecum of 31 

 and the colon of 3 out of 46 horses in Iowa. 



C. dentifenoii Gassovsky, 1919 meas- 

 ures 140 to 220 by 80 to 110 (n. It resem- 

 bles C. bipahnatiim but has a ventral 

 dentiform projection, and the anterior end 

 of its macronucleus is not hooked. The 

 cuticle is not corrugated. A longitudinal 

 groove is present on the left side, but the 

 linear skeletal plate is quite indistinct. 

 There are 4 to 6 contractile vacuoles. 

 Hsiung (1930) found this species in the 

 cecum of 16 and the colon of 2 out of 46 

 horses in Iowa. 



FAMILY CYCLOPOSTHIIDAE 



This spirotrichasin, entodiniorid 

 family differs from the related Ophryo- 

 scolecidae in that its members have 2 or 

 more bands of membranelles in addition 

 to the adoral zone, instead of 1. Most 

 members of this family occur in equids, 

 but others occur in tapirs, rhinoceroses 

 and elephants, which are related to them. 

 One genus occurs in anthropoid apes. 



Genus CYCLOPOSTHIUM 

 Bundle, 1895 



The body is large and elongate barrel - 

 shaped. The cytostome is in the center 



C. ishikaivai Gassovsky, 1919 differs 

 from all other species of the genus in that 

 the posterior arches of membranelles are 

 nonretractile. It measures 230 to 280 by 

 110 to 130 fj,. Hsiung (1930) did not find 

 it in Iowa horses. 



C. edentatum Strelkov, 1928 resem- 

 bles C. bipalniatum but has 6 to 7 con- 

 tractile vacuoles. It measures 146 to 230 

 by 68 to 93):i . Hsiung (1930) found this 

 species in the cecum of 11 and the colon 

 of 2 out of 46 horses in Iowa. 



C. piscicauda Strelkov, 1928 resem- 

 bles C. bipalmatii»i but lacks both the 

 longitudinal groove and skeletal plate on 

 the left side. It measures 125 to 190 by 



