Genus HETEROPHRYS Archer.

The body is globular with but slight differentiation into ectoplasm and endoplasm; one nucleus in the latter; contractile vacuoles one or many; pseudopodia on all sides, thin, and with peripheral granule-streaming; surrounded by a globular, rather thick coat of jelly, which is hyaline inside and granular on the periphery. Fresh and salt water.

Heterophrys myriapoda Archer. Fig. 6.

Synonym: H. marina Hert. & Less. '74.

Fig. 6.—Heterophrys myriapoda.
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Diameter 25 to 80µ; pseudopodia twice as long as the body diameter; the plasm often contains chlorophyll bodies (Zoochlorella). The granular part of the gelatinous layer is thick (up to 10µ). The spine-like processes are very thin and short. (Schaudinn '95.) The marine form found at Woods Hole probably belongs to this species, as described by Schaudinn. The short pseudopodia which give to the periphery a fringed appearance are quite regularly placed in connection with the pseudopodia. The latter are not so long as twice the body diameter, the longest being not more than equal to the diameter of the sphere. The body inside of the gelatinous covering is thickly coated with bright yellow cells similar to those on Radiolaria. The animal moves slowly along with a rolling motion similar to that described by Pènard '90, in the case of Acanthocystis. Diameter of entire globe 35µ; of the body without the jelly 18µ. The extremely fine granular pseudopodia are 8 to 35µ long. Common among algæ.

This form was probably meant by Peck '95, when be figured "a heliozoön."

Key to orders of Flagellidia.
Small, body usually amœboid; 1 or more flagella; no mouth	Order [Monadida].
Small; plasmic collar around the flagellum	Order [Choanoflagellida].
With 2 or more flagella; one trails behind	Order [Heteromastigida].
With 3 or more flagella, none of which trails	Order [Polymastigida].
Large; firm body wall; 1 or 2 flagella; mouth or pharynx, or both	Order [Euglenida].
Medium size; with chlorophyll, no mouth, usually colonial	Order Phytoflagellida.
Small; silicious skeleton; parasitic on Radiolaria or free	Order Silicoflagellida. (One genus, [Distephanus] Stöhr)

*Key to the families of Monadida.*
No mouth; 1 or 2 flagella: amœboid with lobose or ray-like pseudopodia	Family [Rhizomastigidæ]
Mouth at base of single flagellum; plastic; no pseudopodia	Family Cercomonadidæ
One flagellum; inclosed in gelatinous or membranous cups	Family [Codonœcidæ]
One flagellum; tentacle like process at base of flagellum; inclosed in cup	Family Bikœcidæ
One main flagellum and 1 or 2 accessory flagella	Family Heteromonadidæ

Key to marine genera of Monadida.*
Family Rhizomastigidæ:
1.	Flagellum repeatedly thrown off and reassumed	Genus [Mastigamœba*] in part
2.	Flagellum never thrown off	3
3.	a. Pseudopodia lobose	Genus [Mastigamœba]
	b. Pseudopodia ray-like	Genus Mastigophrys
Family Codonœcidæ:
1.	Goblet-shaped cups adherent by stalk	Genus [Codonœca*]
Family Heteromonadidæ:
1.	The long flagellum vibratory	Genus [Monas*]
2.	The long flagellum rigid; shorter one vibrates	Genus Sterromonas
* Presence at Woods Hole indicated by asterisk.

Key to marine genera of Choanoflagellida.
1.	Without gelatinous or membranous test				3
2.	With gelatinous or membranous test				4
3.	a.	Attached forms:
			1.	Without a stalk, or with a very 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.