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." [Illustration: Fig. 6.--_Heterophrys myriapoda_.] KEY TO ORDERS OF FLAGELLIDIA. Small, body usually amoeboid; 1 or more Order MONADIDA. 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_ Stöhr) KEY TO THE FAMILIES OF MONADIDA. No mouth; 1 or 2 flagella: amoeboid Family _Rhizomastigidæ_ with lobose or ray-like pseudopodia Mouth at base of single flagellum; Family _Cercomonadidæ_ plastic; no pseudopodia One flagellum; inclosed in gelatinous Family _Codonoecidæ_ or membranous cups One flagellum; tentacle like process Family _Bikoecidæ_ at base of flagellum; inclosed in cup One main flagellum and 1 or 2 Family _Heteromonadidæ_ accessory flagella KEY TO MARINE GENERA OF MONADIDA.* Family _Rhizomastigidæ_: 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 _Codonoecidæ_: 1. Goblet-shaped cups adherent Genus *_Codonoeca_ by stalk Family _Heteromonadidæ_: 1. The long flagellum vibratory Genus *_Monas_ 2. The long flagellum rigid; Genus _Sterromonas_ shorter one vibrates * Presence at Woods Hole indicated by asterisk.