CILIATA 



153 



of cilia, which are stout and reseiiiLle fine-pointed eirrhi. 

 In Dysteria the cilia are exclusively ventral, and the naked 

 dorsal surface has its pellicle condensed into a bivalve shell ; a 

 posterior motile process (" foot ") and a complex pharyngeal 

 armature add to the exceptional characters of the genus. 



The Aspirotrichaceae are well known to every student of 

 " Elementary Biology " by the " type " Paramecium (Fig. 55), 

 so common in infusions, especially when containing a little 

 animal matter. P. hursaria often contains in its endosarc the 



Fig. 56. — Trachelius orwiii. A, general view ; B, sectiou through sucker ; C, section 

 through contractile vacuole and its pore of discharge, al, Alveolar layer of ecto- 

 plasm ; cil, cilia; c.v, contractile vacuole ; m, mouth ; K, nieganucleus ; s, sucker, 

 from which pass inwards retractile myonemes. (After Clai-a Hamburger.) 



green symbiotic Flagellate Zoochlorclla. Colpoda cucullus, very 

 frequent in vegetable infusions, usually only divides during 

 encystment, and forms a brood of four. Phuronema chrysalis 

 (Fig. 57) is remarkable for its habit of lying for long periods 

 on its side and for its immense undulating membrane, forming 

 a lip on the left of its mouth ; Glaucoma has two, right and left. 

 The Heterotrichaceae present very remarkable forms. Spiro- 

 stomum is nearly cylindrical, and, a very giant, may attain a 



extension of the front of the body above and beyond the mouth ; all three swim with 

 jieculiar grace. Trachelius (Fig. 56) has a distinct cup-shaped sucker behind the 

 mouth, and is remarkable, like Loxodcs, for the branching disposition of its 

 endosarc. 



