NADIDA.
flagella; no mouth

Small; plasmic collar around the Order CHOANOFLAGELLIDA.
flagellum

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 aster