isk.

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_

Family _Bodonidae_:

1. Body very plastic, Genus *_Bodo_
almost amoeboid

Body not plastic; with large Genus *_Oxyrrhis_
anterior cavity, holding flagella

Family _Trimastigidae_:

1. With an undulatory membrane Genus _Trimastix_
between accessory flagella

Without such membrane; flagella Genus _Costia_
contained in a ventral groove
while at rest

* Presence at Woods Hole indicated by asterisk.

KEY TO MARINE GENERA OF POLYMASTIGIDA.

1. Body flattened; ends rounded; Genus _Trepomonas_
sides hollowed; often with
wing-like processes; cross
section S-shaped

2. Body pyriform; one large Genus _Tetramitus_
asymmetrical groove; 4 flagella

3. Body spherical; many flagella Genus _Multicilia_
equally distributed

KEY TO FAMILIES AND MARINE GENERA OF EUGLENIDA.

1. With deeply-insunk pharynx; 2
no mouth

With pharynx and distinct mouth Family _Peranemidae_

2. Body plastic; usually with Family _Euglenidae_
chromatophores and eye-spot

Body plastic; no chromatophores; Family _Astastidae_
no eye-spot

Family _Euglenidae_:

Body _Euglena_-like, inclosed Genus _Trachelomonas_
in shell with round opening for
exit of flagellum

Family _Astastidae_:

Body with one flagellum Genus *_Astasia_

Family _Peranemidae_:

1. Body striped; plastic; Genus _Heteronema_
two diverse flagella

2. Body striped; not plastic; Genus *_Anisonema_
posterior flagellum longer
than the other

3. Body striped; not plastic; Genus _Entosiphon_
with rod-like organ in pharynx

* Presence at Woods Hole indicated by asterisk.

Genus MASTIGAMOEBA F. E. Schultze '75.

(Kent '81; Buetschli '86; Klebs '92; Senn 1900.)

In general the form is oval and either regular in outline or
irregular through the presence of many pseudopodia. One flagellum
usually quite large and distinct. Differentiation of ectoplasm and
endoplasm distinct or wanting. One to several contractile vacuoles.
The pseudopodia are occasionally withdra