With 2 or more flagella; one trails Order HETEROMASTIGIDA. behind

With 3 or more flagella, none of which Order POLYMASTIGIDA. trails

Large; firm body wall; 1 or 2 flagella; Order EUGLENIDA. mouth or pharynx, or both

Medium size; with chlorophyll, Order PHYTOFLAGELLIDA. no mouth, usually colonial

Small; silicious skeleton; parasitic Order SILICOFLAGELLIDA. on Radiolaria or free (One genus,
          
                                Distephanus Stoehr)

KEY TO THE FAMILIES OF MONADIDA.

No mouth; 1 or 2 flagella:  amoeboid Family Rhizomastigidae with lobose or ray-like pseudopodia

Mouth at base of single flagellum; Family Cercomonadidae plastic; no pseudopodia

One flagellum; inclosed in gelatinous Family Codonoecidae or membranous cups

One flagellum; tentacle like process Family Bikoecidae at base of flagellum; inclosed in cup

One main flagellum and 1 or 2 Family Heteromonadidae accessory flagella

KEY TO MARINE GENERA OF MONADIDA.*

Family Rhizomastigidae: 

1.  Flagellum repeatedly thrown off     Genus *_Mastigamoeba_
and reassumed                       in part

   2.  Flagellum never thrown off 3

   3. a.  Pseudopodia lobose Genus Mastigamoeba

      b.  Pseudopodia ray-like Genus Mastigophrys

Family Codonoecidae: 

   1.  Goblet-shaped cups adherent Genus *_Codonoeca_
      by stalk

Family Heteromonadidae: 

   1.  The long flagellum vibratory Genus *_Monas_

   2.  The long flagellum rigid; Genus Sterromonas
      shorter one vibrates

   * Presence at Woods Hole indicated by asterisk.

KEY TO MARINE QENERA OF CHOANOFLAGELLIDA.

1.  Without gelatinous 3
or membranous test

2.  With gelatinous 4
or membranous test

3. a.  Attached forms: 

1.  Without a stalk, or with Genus *_Monosiga_
a very short one

2.  With a long, simple, stalk Genus *_Codonosiga_

3.  With a long, branched, stalk Genus Codonocladium

b.  Free-swimming Genus Desmarella

4.  Colonial, and with a gelatinous Genus Proterospongia
covering

* Presence at Woods Hole indicated by asterisk.

KEY TO FAMILIES AND MARINE GENERA OF HETEROMASTIGIDA.

   1.  Two flagella nearly equal in size Family Bodonidae

      One main and 2 accessory flagella Family Trimastigidae