cup alone 12 mu.
This minute form looked so much like a choanoflagellate that I
supposed it to be one until I discovered an empty case (Fig. 8).

[Illustration: Fig. 8.--_Codonoecea gracilis_.]

Genus MONAS (Ehr.) Stein '78

(Kent '81; Buetschli '86; Klebs '97; Senn 1900.)

The body is small, globular or oval and either free-swimming or
fastened by one of the two flagella. The body is sometimes a little
amoeboid, with short pseudopodial processes. In addition to the main
flagellum, there are usually one or two small flagella at the basis
of the larger one. The nucleus is usually anterior, and one or two
contractile vacuoles are present.

Monas sp. Fig. 9.

An extremely small form (3 mu) attached by a thread of
protoplasm--perhaps a flagellum, to algae. The body is ovoid and
the main flagellum is about four times the length of the body. The
contractile vacuole is posterior. Only one specimen was seen and
upon this I shall not attempt to name the species.

[Illustration: Fig. 9.--_Monas_ sp.]

Genus MONOSIGA Kent '81.

(Buetschli '86; France '97; Senn 1900.)

Small colorless forms of Choanoflagellida, always naked and solitary.
The posterior end is attached directly to the substratum, or
there is a short stalk not exceeding the body in length. Kent '81
distinguished nine species, but Buetschli questioned the accuracy
of many of these, and in this he was followed by France '97, who
recognized three species--_Monosiga ovata_, _M. fusiformis_, and _M.
augustata_. Fresh and salt water.

Monosiga ovata S. Kent '81. Fig. 10.

Synonyms: _M. brevipes_ S. K.; _M. consociata_ S. K.; _M. limnobia_
Stokes.

The individuals are unstalked or provided with a very short stalk
less than the body in length. The form is spherical or ovate,
broadest at the base and tapering to the extremity. The collar is
somewhat variable in size. In the Woods Hole forms it was about
the length of the body. Oil particles present. Contractile vacuole
posterior, nucleus anterior.

Fresh and salt water. Length of body without the collar 5 mu.

[Illustration: Fig.10.--_Monosiga ovata_.]

Monosiga fusiformis S. K. Fig. 11.

Synonyms: _M. steinii_ S. K.; _M. longicollis_ S. K.

The individuals are unstalked, minute, and of a general flask-shape.
The body is swollen centrally and tapers slightly at each end. There
is no stalk, the body being fixed by the attenuate posterior end.
There are two contractile vacuoles and