Genus MASTIGAMOEBA F. E. Schultze '75.

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

In general the form is oval and either regular in outline or irregular through the presence of many pseudopodia. One flagellum usually quite large and distinct. Differentiation of ectoplasm and endoplasm distinct or wanting. One to several contractile vacuoles.

The pseudopodia are occasionally withdrawn, and the flagellum is the sole means of locomotion. In some cases the flagellum turns into a pseudopodium, and, conversely, the pseudopodium at one end may become a flagellum (see below). In some rare cases the ectoplasm secretes a gelatinous mantle. Reproduction not observed.

Fresh and salt water.

Mastigamoeba simplex, n. sp. Fig. 7.

A very small form, first seen in the flagellated stage, aroused my interest by reason of the fact that its flagellum lost its regular outline and became amoeboid, turning to a pseudopodium, while at the same time other pseudopodia were protruded from different parts of the periphery. In this condition ectoplasm and endoplasm could be made out with the clearest definition. After the pseudopodia were well formed, the body became flat and closely attached to the gla.s.s slide. In a short time one of the pseudopodia became longer than the rest; the body became more swollen; the pseudopodia were gradually drawn in, with the exception of the more elongate one; this became active in movement and finer in diameter, until ultimately it formed a single flagellum at the anterior of a small monadiform flagellate.

The process was repeated two or three times under my observation, so that I am convinced that it was not a developmental form of some rhizopod. Several of them were seen at different times during the summer, and they were always of the same size and form in the flagellated or amoeboid condition. I did not make out their reproduction, and I shall not be satisfied that this is a good species until their life history is known.

In decaying algae. Length 10.

[Ill.u.s.tration: Fig. 7.--_Mastigamoeba simplex_.]

Genus CODONOECA James Clark '66.

(Kent '81.)

Small forms inclosed in cup or "house" of ovoid or goblet shape, colorless and probably gelatinous (chitin?) in texture, and borne upon a stalk. The monad does not completely fill the test.

Contractile vacuole single, posterior.

Codonoeca gracilis, n. sp. Fig. 8.

The cup is urn-shaped with a well-defined neck or collar borne upon a shoulder-like end of the body. It is hyaline, colorless, and carried upon a stalk equal in length to the cup or shorter than this. The animal does not fill the cup, nor is it attached by a filament to the latter. There is a single flagellum. The nucleus is minute and lateral in position; the contractile vacuole is in the posterior end of the body. Total length of cup and stalk 21; of cup alone 12.

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

[Ill.u.s.tration: Fig. 8.--_Codonoecea gracilis_.]

Genus MONAS (Ehr.) Stein '78

(Kent '81; Butschli '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) 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.

[Ill.u.s.tration: Fig. 9.--_Monas_ sp.]

Genus MONOSIGA Kent '81.

(Butschli '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 Butschli 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. limn.o.bia_ 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.

[Ill.u.s.tration: 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 one nucleus, which is situated a little above the body center. Fresh and salt water. Length without collar 9; length of collar 3.

[Ill.u.s.tration: Fig. 11.--_M. fusiformis_.]

Genus CODONOSIGA (Jas. Clark '67).

(Butschli '78; Kent '81; France '97; Senn 1900.)

This genus, as modified by France, is distinguished from the preceding by the possession of an unbranched stalk much longer than the body length. The body is naked and of various shapes, and the individuals are solitary or colonial upon a single stalk. Kent '81 enumerates no less than 10 species, which were cut down by Butschli to 1. France admits 4--_C. botrytis_ Jas. Clark; _C. grossularia_; _C. pyriformis_, and _C. furcata_, all S. Kent--but regards the second and third as merely form varieties of the first.

Codonosiga botrytis (Ehr. sp.) Jas. Clark '67. Fig. 12.

France gives the following synonyms: _Epistylia botrytis_ Ehr.; _E. digitalis_ Stein, _Zoothamnium parasitica_ Stein; _Anthophysa solitaria_ Fresenius; _Codonosiga pulcherrima_ Jas. Clark; _Monosiga gracilis_ S. Kent; _M. globulosa_ S. Kent; _Codonosiga pyriformis_ Kent; _C. grossularia_ Kent; (France).

The individuals are small and provided with a long unbranched, or terminal, simply split stalk. The individuals are single or colonial.

The Woods Hole form measured 22 over all; the body was 5, the collar 3, and the stalk 14. No colonies were seen, and only a few individuals upon red algae.