HOW CILIATES FEED 261 



tractile elements in the ectoplasm, known as myo- 

 nemes, or myophan striations. The cilia normally 

 move fairly slowly and regularly, creating a definite 

 current, generally towards the mouth. Certain of 

 the cilia are much longer than others, and move 

 more rapidly, and these have been seen entangling 

 food for the Ciliate and propelling it towards the 

 mouth. Such longer cilia are sometimes termed 

 cirri. Again, the cilia in some cases are so close 

 that they unite together and form a continuous 

 structure like a membrane. The appearance of some 

 members of the Ciliata in which the membrane is 

 well developed is suggestive of some remarkable 

 flagellate at times, but some free cilia are always 

 present. 



The free-swimming Ciliates living in fresh or salt 

 water are remarkably active. They move quickly by 

 means of their vibrating cilia and myonemes, and 

 can turn round rapidly. One end always is directed 

 forwards. This the anterior end often contains 

 the cell mouth, or cytostome, which varies greatly in 

 form. A free-swimming form like Paramcecium has 

 a funnel-shaped side aperture prolonged into a narrow 

 gullet, or cytopharynx, lined with cilia which waft 

 food particles inwards. The cytostome in a form 

 like Enchelina is small and slitlike, and capable of 

 opening and closing. During " feeding times " the 

 boundaries act as lips, and open for the introduction 

 of food ; then during digestion they are closed so 

 that the orifice is practically obliterated. An inter- 

 esting parasite from the caecum of the horse, 

 Blepharocorys (Fig. 49), has a mouth overhung by 



