[Ill.u.s.tration: Fig. 12.--_Codonosiga botrytis_.]

Genus BODO (Ehr.) Stein.

(Stein '59, Butschli '83; Klebs '92; Senn 1900.)

The body is naked, usually amoeboid in its changes, and provided with two flagella, one of which is usually trailed along under and behind the animal. The anterior end is usually pointed, with the flagella arising from a minute depression; the posterior end is rounded.

Specific characters very difficult to a.n.a.lyze. Fresh and salt water.

Bodo globosus Stein. Fig. 13.

The body during movement is globular or ovoid, without any anterior process. The trailing flagellum is invariably much longer than the vibratory one. The contractile vacuole lies in the anterior half of the body. Solid food particles are taken in near base of flagella.

Length of body 9 to 12; diameter 8 to 11. Common.

[Ill.u.s.tration: Fig. 13.--_Bodo globosus_.]

Bodo caudatus (Duj.) Stein. Fig. 14.

Synonyms: _Amphimonas caudatus_ Duj.; _Diptomastix caudata_ Kent.

The body is variable in shape, but usually flattened and pointed posteriorly. An anterior process is almost always present, and below this the flagella are inserted in a minute depression. The contractile vacuole is close to the base of the flagella. The flagella are about the same size, the anterior one usually somewhat longer. Common. Length 12 to 18.

This species was seen by Peck '95 and described as a small flagellate.

[Ill.u.s.tration: Fig. 14.--_Bodo caudatus_.]

Genus OXYRRHIS Duj.

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

Medium-sized forms, somewhat oval in shape, with a rounded posterior end. The anterior end is continued dorsally in a somewhat attenuate pointed process. At the base of this process is a large cavity or funnel, on the dorsal wall of which, or on a projection from this wall, are two equal-size flagella. When at rest, the flagella are directed backwards. The nucleus is central. In moving, the posterior end is invariably in advance. This genus is exceptional among Mastigophora in that division is transverse instead of longitudinal.

Oxyrrhis marina Duj. Fig. 15.

With the characters of the genus. Contractile vacuole not seen.

Length 28 to 40.

[Ill.u.s.tration: Fig. 15.--_Oxyrrhis marina_.]

Genus ASTASIA Ehr.

Flagellates with one flagellum, a spindle-form body and a high degree of plasticity, the contour constantly changing. A distinct, usually striped cuticle is invariably present. "Eye-spots" are absent. Fresh and salt water.

Astasia contorta Duj. Fig. 16.

_Astasia inflata_ Duj. '41.

The body is colorless, transparent, and flexible. It is largest in the center, thence tapering at the two extremities. The surface of the cuticle is obliquely striated, giving to the animal a distinctly twisted appearance. The contractile vacuole is in the anterior neck-like portion of the body. The flagellum is inserted in a distinct oesophageal tube, into which the contractile vacuole empties. This tube is continued into a deeper pharyngeal apparatus of unknown function.

Common in decaying algae. Length 60; greatest diameter 30.

[Ill.u.s.tration: Fig. 16.--Two aspects of _Astasia contorta_.]

Genus ANISONEMA Butschli

Flagellates with two flagella, of which one is directed forwards and is concerned with the locomotion of the animal, while the other is directed backwards and drags after the animal when in motion. Body slightly compressed dorso-ventrally (fig. 17, section). An oral furrow is present on the ventral side and the two flagella originate in it (fig. 17, at left). The vacuole is on the left side. Food vacuoles are present in the posterior part. The nucleus is central.

Movement creeping.

Fresh and salt water.

Anisonema vitrea (Duj.) Fig. 17.

Synonyms: _Tropidoscyphus octocostatus_ Stein '83; _Sphenomonas_ Kent '81; _Ploeotia vitrea_ Senn 1900.

With the characteristics of the genus. It differs from freshwater forms in having eight furrowed surfaces running somewhat spirally from the posterior to the oral end. Length 50; width 23. This attractive flagellate was quite common in decaying algae at Woods Hole; its shaking movement, its peculiar furrowed surfaces, and, above all, its perfectly transparent, vitreous appearance, were well described by Dujardin. Stein's _Tropidoscyphus octocostatus_ is a fresh-water form which may possibly be a distinct species, especially as it is described with both flagella directed forwards.

[Ill.u.s.tration: Fig. 17.--_Anisonema vitrea_.]

Genus DISTEPHa.n.u.s Stohr.

An aberrant flagellate bearing a single flagellum and a silicious skeleton resembling those of the Radiolaria. The skeleton consists of two rings of different diameter parallel with one another and connected by silicious bars. From the wider ring half a dozen bars radiate outwards and a similar number of short thorn-like bars point inwards obliquely. The color is yellow, and except for the flagellum the form might easily be mistaken for a Radiolarian, as has been the case repeatedly.

Distepha.n.u.s speculum Stohr.

_Dictyocha speculum_ Stohr; _Dictyocha_ Auc.

With the characters of the genus.

A single specimen only of this very interesting form was seen at Woods Hole. It occurred in a collection of tow made near the end of the wharf during the evening.