MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 509 



Key to Families 



2. Peristome almost free, leading to short and 



narrow oral funnel which is absent in one 



family 3 



Peristome runs deeply into a funnel-like 



hollow and is mostly covered. .Family 7. Bubsariidae 



3. On right edge of peristomial membranelle 



zone a narrow zone without cilia; on 

 right of this, in front of mouth, an undu- 

 lating membrane: between this and 

 membranelle zone a peristomial frontal 



field difficult to see 4 



Frontal hold surrounded wholly or in part 

 by spiral adoral zone 7 



4. Adoral zone stretches diagonally to poste- 



rior right on ventral side; many forms 

 have an elongated portion which twists 



spirally around the body Family 1. Metopidae 



Adoral zone runs for most part in direction 

 of long axis and, just before the mouth 

 opening, bends sharply to right 5 



5. Gullet and undulating membranes absent: 



mouth usually closed and difficult to 

 find; opens as a slit for food-taking 



Family 2. Reichenowellidae 

 Oral funnel distinct; in typical forms an 

 undulating membrane or a double cili- 

 ated furrow before the mouth 6 



6. Parasitic forms Family 4. Plagiotomidae 



Free-living forms Family 3. Spirostomidae 



7. Frontal field not ciliated; one large undu- 



lating membrane on its right edge 



Family 5. Condylostomidae 

 Frontal field ciliated; no undulating mem- 

 brane 8 



8. Frontal field not drawn out in wings; free 



or in jelly tests Family 6. Stentoridae 



Frontal field drawn out in 2 wings, in flask- 

 shaped tests Family 6. Folliculinidae 



9. Free-living, flat, marine forms; ciliated on 



ventral side only; adoral zone surrounds 

 anterior ventral surface; mouth on left 

 edge near middle of body Family 9. Peritromidae 



Ectoparasitic marine forms; both ends of 

 body discoid, in middle neck-like 



Family 10. Lichnophoridae 

 Family 1. Metopidae Kahl 1927. 



1. Ciliation of body uniform '- 



Ciliation reduced ; body with "head" region 4 



2. Ectoplasm soft, yielding 3 



Ectoplasm stiff, carapace-like, spirally 



keeled ( renus Tropidoatractus Levander 



3. Flat oval to ovoid moss forms; C. V. on 



ventral middle; broad, insunk stripings 



Genus Bryometopus Kahl 

 Form diverse; free living in water; C. V. 



terminal; peristome typical Genus Metopus Clap, and Lach. 



