short one

Genus *Monosiga       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 covering Genus Proterospongia * Presence at Woods Hole indicated by asterisk.

Key to families and marine genera of Heteromastigida.
1.	Two flagella nearly equal in size	Family Bodonidæ
	One main and 2 accessory flagella	Family Trimastigidæ
Family Bodonidæ:
1.	Body very plastic, almost amœboid	Genus *Bodo
	Body not plastic; with large anterior cavity, holding flagella	Genus *Oxyrrhis
Family Trimastigidæ:
1.	With an undulatory membrane between accessory flagella	Genus Trimastix
	Without such membrane; flagella contained in a ventral groove while at rest	Genus Costia
* Presence at Woods Hole indicated by asterisk.

Key to marine genera of Polymastigida.
1.	Body flattened; ends rounded; sides hollowed; often with wing-like processes; cross section S-shaped	Genus Trepomonas
2.	Body pyriform; one large asymmetrical groove; 4 flagella	Genus Tetramitus
3.	Body spherical; many flagella equally distributed	Genus Multicilia

Key to families and marine genera of Euglenida.
1.	With deeply-insunk pharynx; no mouth	2
	With pharynx and distinct mouth	Family Peranemidæ
2	Body plastic; usually with chromatophores and eye-spot	Family Euglenidæ
	Body plastic; no chromatophores; no eye-spot	Family Astastidæ
Family Euglenidæ:
	Body Euglena-like, inclosed in shell with round opening for exit of flagellum	Genus Trachelomonas
Family Astastidæ:
	Body with one flagellum	Genus *Astasia
Family Peranemidæ:
1.	Body striped; plastic; two diverse flagella	Genus Heteronema
2.	Body striped; not plastic; posterior flagellum longer than the other	Genus *Anisonema
3.	Body striped; not plastic; with rod-like organ in pharynx	Genus Entosiphon
* Presence at Woods Hole indicated by asterisk.

Genus MASTIGAMŒBA F. E. Schultze '75.