in. CILIATA: IIOLOTRIOIIA, HUTEIiOTlUCMA. 



200 



groups of markedly smaller microspores. The latter separate and 

 fuse completely with the macrospores, only a small cnticnlar sac 

 persisting to indicate the fvision. The nuclear phenomena are 

 miTch the same as with Parammcmm, allowance being made for 

 the permanance of the fusion. 



Order I. Holotricha. 



The Holotricha are doubtless the most primitive Ciliates, since 

 the cilia on all parts of the body are similar: being at most slightly 

 stronger at one end of the body or on the inside of the cytostome. 

 15est known are the species of ParamcBciuiii* (fig. 144) occurring 

 in stagnant water. Opalina ranarvm * lives in the intestine of the 

 frog. It Licks mouth, has numerous similar nuclei, no mieronu- 

 cleus and no conjugation. The small encysted Opnlinm pass out 

 with the fffices, and are eaten by the tadpoles, which thus become 

 infected. 



Order II. Heterotricha. 



Like the Holotricha the Heterotricha 

 '^ ~ <^^ are everywhere ciliated, but they have a 



, ' \ tract of stronger cilia, the adoral ciliated 



^ spiral. This is a Ijand of cilia beginning 

 , at some distance from the cytostome and 



leading in a spiral course into the mouth. 

 It consists of rows of cilia united into 

 ' membranellai ' placed at right angles to 

 the course of the spiral. In tlie best- 

 known heterotrichans, the Stentors * (fig. 

 148), the peristomial area, surrounded by 



'It 



Fm. 148. F-iG. U9. 



Fig. Ui^.—St>-ntor poh/morplius. (After Stein.) a, peristomial area; b, root of Ijypo- 



stome; », ccjntraetile vacuole; », nucleus; o, cytostome; i\ adoral ciliated spiral; 



f, tiypostome (excavation for inoutli). 

 Fig, U\S.~BnUinlidiiim coli. (After Leuckart.) 



