Chapter I: Part 1

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Contributions from the Biological Laboratory of the U. S. Fish Commission, Woods Hole, Massachusetts.

MARINE PROTOZOA FROM WOODS HOLE.

by

GARY N. GALKINS, Department of Zoology, Columbia University.

_Bulletin of the United States Fish Commission_ 21:415-468, 1901

Comparatively little has been done in this country upon marine Protozoa. A few observations have been made by Kellicott, Stokes, and Peck, but these have not been at all complete. With the exception of Miss Stevens's excellent description of species of _Lichnophora_ I am aware of no single papers on individual forms. Peck ('93 and '95) clearly stated the economic position of marine Protozoa as sources of food, and I need not add to his arguments. It is of interest to know the actual species of various groups in any locality and to compare them with European forms. The present contribution is only the beginning of a series upon the marine Protozoa at Woods Hole, and the species here enumerated are those which were found with the algæ along the edge of the floating wharf in front of the Fish Commission building and within a space of about 20 feet. Many of them were observed in the water and algæ taken fresh from the sea; others were found only after the water had been allowed to stand for a few days in the laboratory. The tow-net was not used, the free surface Protozoa were not studied, nor was the dredge called into play. Both of these means of collecting promise excellent results, and at some future time I hope to take advantage of them.

My observations cover a period of two months, from the 1st of July to the 1st of September. During that time I was able to study and describe 72 species representing 55 genera, all from the limited space mentioned above. In addition to these there are a few genera and species upon which I have insufficient notes, and these I shall reserve until opportunity comes to study them further.

I take this opportunity to express my thanks to Dr. Hugh M. Smith for many favors shown me while at Woods Hole.

In dealing with these marine forms from the systematic standpoint, two courses are open to the investigator. He may make numerous new species based upon minor differences in structure, or he may extend previous descriptions until they are elastic enough to cover the variations. The great majority of marine protozoa have been described from European waters, and the descriptions are usually not elastic enough to embrace the forms found at Woods Hole. I have chosen, however, to hold to the conservative plan of systematic work, and to make as few new species as possible, extending the older descriptions to include the new forms.

The different classes of Protozoa, and orders within the classes, are distributed more or less in zones. Thus the Infusoria, including the Ciliata and the Suctoria, are usually littoral in their habitat, living upon the shore-dwelling, or attached, water plants and upon the animals frequenting them. It is to be expected, therefore, that in forms here considered there should be a preponderance of Infusoria. Flagellated forms are also found in similar localities, but on the Surface of the sea as well; hence the number described in these pages is probably only a small proportion of the total number of Mastigophora in this region. The Sarcodina, including the Foraminifera and the Radiolaria, are typically deep-sea forms and would not be represented by many types in the restricted locality examined at Woods Hole. Two species, _Gromia lagenoides_ and _Truncatulina lobatula_, alone represent the great order of Foraminifera, while the still larger group of Radiolaria is not represented at all.

The Protozoa described are distributed among the different orders as follows:*

Class SARCODINA.
Subclass RHIZOPODA.
Order AMOEBIDA.
1. _Amoeba guttula_ Duj
2. _Amoeba_ sp.
3. _Trichosphærium sieboldi_ Schn.
Order RETICULARIIDA.
Suborder IMPERFORINA.
4. _Gromia lagenoides_ Gruber.
Suborder PERFORINA.
5. _Truncatulina lobatula_ Walker & Jacob.
Subclass HELIOZOA.
Order APHROTHORACIDA.
6. _Actinophrys sol_ Ehr.
Order CHLAMYDOPHORIDA.
7. _Heterophrys myriapoda_ Archer.
Class MASTIGOPHORA.
Subclass FLAGELLIDIA.
Order MONADIDA.
8. _Mastigamoeba simplex_, n. sp.
9. _Codonoeca gracilis_, n. sp.
10. _Monas_ sp.
Order CHOANOFLAGELLIDA.
11. _Monosiga ovata_ S. Kent.
12. _Monosiga fusiformis_ S. Kent.
13. _Codonosiga botrytis_ (Ehr.) J. Cl.
Order HETEROMASTIGIDA.
14. _Bodo globosus_ Stein.
15. _Bodo caudatus_ (Duj.) Stein.
16. _Oxyrrhis marina_ Duj.
Order EUGLENIDA.
17. _Astasia contorta_ Duj.
18. _Anisonema vitrea_ Duj.
Order SILICOFLAGELLIDA.
19. _Distephanus speculum_ Stöhr.
Subclass DINOFLAGELLIDIA.
Order ADINIDA.
20. _Exuviælla lima_ Clenk.
21. _Exuviælla marina_ Clenk.
Order DINIFERIDA.
22. _Gymnodinium gracile_ Bergh.
23. _Glenodinium cinctum_ Ehr.
24. _Glenodinium compressa_, n. sp.
25. _Peridinium digitale_ Pouchet.
26. _Peridinium divergens_ Ehr.
27. _Ceratium tripos_ Nitsch.
28. _Ceratium fusus_ Ehr.
29. _Amphidinium operculatum_ Clap. & Lach.
Class INFUSORIA.
Subclass CILIATA.
Order HOLOTRICHIDA.
Family ENCHELINIDÆ.
30. _Lacrymaria lagenula_ Cl. & Lach.
31. _Lacrymaria coronata_ Cl. & Lach.
32. _Trachelocerca phoenicopterus_ Cohn.
33. _Tiarina fusus_ Cl. & Lach.
34. _Mesodinium cinctum_, n. sp.
Family TRACHYLINIDÆ.
35. _Lionotus fasciola_ Ehr.
36. _Loxophyllum setigerum_ Quenn.
Family CHLAMYDODONTIDÆ.
37. _Nassula microstoma_ Cohn.
38. _Chilodon cucullulus_ Müll.
39. _Dysteria lanceolata_ Cl. & Lach.
Family CHILIFERIDÆ.
40. _Frontonia leucas_ Ehr.
41. _Colpidium colpoda_ Ehr.
42. _Uronema marina_ Duj.
Family PLEURONEMIDÆ.
43. _Pleuronema chrysalis_ Ehr.
44. _Pleuronema setigera_, n. sp.
45. _Lembus infusionum_, n. sp.
46. _Lembus pusillus_ Quenn.
Family OPALINIDÆ.
47. _Anoplophrya branchiarum_ Stein.
Order HETEROTRICHIDA.
Family BURSARIDÆ.
48. _Condylostoma patens_ Müll.
Family HALTERIDÆ.
49. _Strombidium caudatum_ From.
Family TINTINNIDÆ.
50. _Tintinnopsis beroidea_ Stein.
51. _Tintinnopsis davidoffi_ Daday.
Order HYPOTRICHIDA.
Family PERITROMIDÆ.
52. _Peritromus emmæ_ Stein.
Family OXYTRICHIDÆ.
53. _Epiclintes radiosa_ Quenn.
54. _Amphisia kessleri_ Wrzes.
Family EUPLOTIDÆ.
55. _Euplotes charon_ Ehr.
56. _Euplotes harpa_ Stein.
57. _Diophrys appendiculatus_ Stein.
58. _Uronychia setigera_, n. sp.
59. _Aspidisca hexeris_ Quenn.
60. _Aspidisca polystyla_ Stein.
Order PERITRICHIDA.
Family LICHNOPHORIDÆ.
61. _Lichnophora macfarlandi_ Stevens.
Family VORTICELLIDÆ.
62. _Vorticella marina_ Greeff.
63. _Vorticella patellina_ Müller.
64. _Zoothamnium elegans_ D'Udek.
65. _Cothurnia crystallina_ Ehr.
66. _Cothurnia nodosa_ Cl. & Lach.
67. _Cothurnia imberbis_ Ehr.
Subclass SUCTORIA.
Family PODOPHRYIDÆ.
68. _Podophrya gracilis_, n. sp.
69. _Ephelota coronata_ Wright.
Family ACINETIDÆ.
70. _Acineta divisa_ Fraip.
71. _Acineta tuberosa_ Ehr.
Family DENDROSOMIDÆ.
72. _Trichophrya salparum_ Entz.

* This classification includes only the orders and families
represented at Woods Hole

Genus AMOEBA Auct.

The pseudopodia are lobose, sometimes absent, the body then progressing by a flowing movement; the body consists of ectoplasm and endoplasm, the latter being granular and internal, the former hyaline and external. There is always one nucleus and one vacuole, but both may be more numerous. Reproduction takes place by division or by spore-formation. Fresh-water and marine.

Amoeba guttala Duj. Fig. 1.

A minute form without pseudopodial processes, extremely hyaline in appearance, and characterized by rapid flowing in one direction. The body is club-shape and moves with the swollen end in advance. A comparatively small number of large granules are found in the swollen portion, while the smaller posterior end is quite hyaline. Contractile vacuole absent, and a nucleus was not seen. Frequent in decomposing vegetable matter. Length 37µ. Traverses a distance of 160µ in one minute.

The fresh-water form of _A. guttula_ has a vacuole, otherwise Dujardin's description agrees perfectly with the Woods Hole forms.

Amoeba? Fig. 2.

A more sluggish form than the preceding, distinguished by its larger size, its dense granulation, and by short, rounded pseudopodia, which, as in _Amoeba proteus_, may come from any part of the body. A delicate layer of ectoplasm surrounds the granular endoplasm, and pseudopodia formation is eruptive, beginning with the accumulation of ectoplasm. Movement rapid, usually in one direction, but may be backwards or sideways, etc. Contractile vacuole absent; the nucleus is spherical and contains many large chromatin granules. Length 80µ; diameter 56µ.

Genus TRICHOSPHÆRIUM Schneider '78

Synonym: _Pachymyxa hystrix_ Gruber.

Marine rhizopods, globular or irregular in form, and slow to change shape. Dimorphic. Both forms multinucleate during vegetative life. Pseudopodia are long, thin, and thread-form, with rounded ends. Their function is neither food-getting nor locomotion, but probably tasting. The plasm of both forms is inclosed in a soft gelatinous membrane. In one form the jelly is impregnated with needles of magnesium carbonate (Schaudinn), but these are absent in the other form. The membrane is perforated by clearly defined and permanent holes for the exit of the pseudopodia. Reproduction occurs by division, by budding or by fragmentation, but the parts are invariably multinucleate. At the end of vegetative life the needle-bearing form fragments into numerous mononucleate parts; these develop into adults similar to the parent, but without the spines. At the end of its vegetative life this new individual fragments into biflagellated swarm-spores which may conjugate, reproducing the form with needles. Size up to 2 mm.

Trichosphærium sieboldi Schneider. Fig. 3.

With the characters of the genus. A form which I have taken to be a young stage of this interesting rhizopod is described as follows:

A minute, almost quiescent, form which changes its contour very slowly. The membrane is cap-like and extends over the dome-shaped body, fitting the latter closely. The endoplasm is granular and contains foreign food-bodies. Nucleus single, spherical, and centrally located. Pseudopodia short and finger-form, emerging from the edge of the mantle-opening and swaying slowly from side to side or quiescent. The most characteristic feature is the presence of a broad, creeping sole, membranous in nature and hyaline in appearance. This membrane is the only evidence of ectoplasm, and it frequently shows folds and wrinkles, while its contour slowly changes with movements of body. The pseudopodia emerge from the body between this membrane and the shell margin. Contractile vacuole absent. Length 42µ, width 35µ. In decomposing seaweeds, etc.

Only one specimen of this interesting form was seen, and I hesitate somewhat in placing it on such a meager basis. It is so peculiar, however, that attention should be called to it in the hope of getting further light upon its structure and mode of life. Its membranous disk recalls the genus _Plakopus_; its mononucleate condition, its membranous disk, and the short, sometimes branched, pseudopodia make it difficult to identify with any phase in the life-history of _Trichosphærium_. I shall leave it here provisionally, with the hope that it may be found more abundantly another time.

Genus GROMIA Dujardin '35.

(Dujardin 1835; M. Schultze '62; F. E. Schultze '74; Leidy '77; Bütschli '83; Gruber '84.)

The form is ovoid or globular, and the body is covered by a tightly fitting, plastic, chitin shell, which, in turn, is covered by a fine layer of protoplasm. The flexibility of the shell makes the form variable as in the amoeboid types. The thickness of the shell is quite variable. The pseudopodial opening is single and terminal. The pseudopodia are very fine, reticulate, granular, and sharply pointed, and form a loose network outside of the shell opening. Nucleus single or multiple. Contractile vacuole is usually absent. Fresh and salt water.

Gromia lagenoides Gruber '84. Fig. 4.

This species is not uncommon about Woods Hole, where it is found upon the branches of various types of algæ. The body is pyriform, with the shell opening at the larger end. The chitinous shell is hyaline and plastic to a slight extent, so that the body is capable of some change in shape. The shell is thin and turned inwards at the mouth-opening, forming a tube (seen in optical section in fig. 4) through which the protoplasm passes to the outside. The walls of this tube are thicker than the rest of the shell, and in optical section the effect is that of two hyaline bars extending into the body protoplasm. A thin layer of protoplasm surrounds the shell and fine, branching, pseudopodia are given off in every direction. The protoplasm becomes massed outside of the mouth-opening and from here a dense network of pseudopodia forms a trap for diatoms and smaller Protozoa. The nucleus is spherical and contains one or two large karyosomes. The protoplasm is densely and evenly granular, without regional differentiation. I have never observed an external layer of foreign particles, such as Gruber described in the original species.

Length of shell 245µ; largest diameter 125µ.

Genus TRUNCATULINA D'Orbigny.

A group of extremely variable foraminifera in which the shell is rotaline; i. e., involute on the lower side and revolute on the upper (Brady). The shell is calcareous and coarsely porous in older forms. The characters are very inconstant, and Brady gives up the attempt to distinguish the group by precise and constant characters.

Truncatulina lobatula Walker & Jacob.

Synonyms: See Brady '84 for a long list.

"It is impossible to define by any precise characters the morphological range of the present species. Its variations are infinite." (Brady, p. 660.)

This very common form, which occurs in all latitudes, was found frequently among the algæ at Woods Hole. Its characters are so difficult to define that for the present I shall limit my record to this brief notice. Size of shell 230µ by 270µ.

Genus ACTINOPHRYS Ehr.

The body is spherical and differentiated into granular endoplasm and vacuolated ectoplasm, but the zones are not definitely separated. There is one central nucleus and usually one contractile vacuole. The pseudopodia have axial filaments that can be traced to the periphery of the nucleus. Fresh and salt water.

Actinophrys sol Ehr., variety. Fig. 5.

Synonyms: See Schaudinn '95.

The diameter is about 50µ; the vacuolated ectoplasm passes gradually into the granular endoplasm. This is the characterization given _A. sol_ by Schaudinn, and it applies perfectly to the freshwater forms. If I am correct, however, in placing an _Actinophrys_-like form found at Woods Hole in this species, the description will have to be somewhat modified. In this form (fig. 5) there is no distinction between ectoplasm and endoplasm, and there is an entire absence of vacuoles. The nucleus is central, and axial filaments were not seen. The single specimen that I found looked much like a Suctorian of the genus _Sphærophrya_, but the absence of a firm cuticle and the presence of food-taking pseudopodia with granule-streaming makes it a very questionable Suctorian, and 1 place it here until further study throws more light upon it.

Diameter of body 40µ; length of pseudopodia 120 to 140µ.

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.

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 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.

KEY TO MARINE QENERA OF CHOANOFLAGELLIDA.

1. Without gelatinous 3
or membranous test

2. With gelatinous 4
or membranous test

3. a. Attached forms:

1. Without a stalk, or with Genus *_Monosiga_
a very short one

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 Genus _Proterospongia_
covering

* 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, Genus *_Bodo_
almost amoeboid

Body not plastic; with large Genus *_Oxyrrhis_
anterior cavity, holding flagella

Family _Trimastigidæ_:

1. With an undulatory membrane Genus _Trimastix_
between accessory flagella

Without such membrane; flagella Genus _Costia_
contained in a ventral groove
while at rest

* Presence at Woods Hole indicated by asterisk.

KEY TO MARINE GENERA OF POLYMASTIGIDA.

1. Body flattened; ends rounded; Genus _Trepomonas_
sides hollowed; often with
wing-like processes; cross
section S-shaped

2. Body pyriform; one large Genus _Tetramitus_
asymmetrical groove; 4 flagella

3. Body spherical; many flagella Genus _Multicilia_
equally distributed

KEY TO FAMILIES AND MARINE GENERA OF EUGLENIDA.

1. With deeply-insunk pharynx; 2
no mouth

With pharynx and distinct mouth Family _Peranemidæ_

2. Body plastic; usually with Family _Euglenidæ_
chromatophores and eye-spot

Body plastic; no chromatophores; Family _Astastidæ_
no eye-spot

Family _Euglenidæ_:

Body _Euglena_-like, inclosed Genus _Trachelomonas_
in shell with round opening for
exit of flagellum

Family _Astastidæ_:

Body with one flagellum Genus *_Astasia_

Family _Peranemidæ_:

1. Body striped; plastic; Genus _Heteronema_
two diverse flagella

2. Body striped; not plastic; Genus *_Anisonema_
posterior flagellum longer
than the other

3. Body striped; not plastic; Genus _Entosiphon_
with rod-like organ in pharynx

* Presence at Woods Hole indicated by asterisk.

Genus MASTIGAMOEBA F. E. Schultze '75.

(Kent '81; Bütschli '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 glass 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 algæ. Length 10µ.

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 21µ; of cup alone 12µ. This minute form looked so much like a choanoflagellate that I supposed it to be one until I discovered an empty case (Fig. 8).

Genus MONAS (Ehr.) Stein '78

(Kent '81; Bütschli '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 (3µ) attached by a thread of protoplasm--perhaps a flagellum, to algæ. 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.

Genus MONOSIGA Kent '81.

(Bütschli '86; Francé '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 Bütschli questioned the accuracy of many of these, and in this he was followed by Francé '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 5µ.

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 9µ; length of collar 3µ.

Genus CODONOSIGA (Jas. Clark '67).

(Bütschli '78; Kent '81; Francé '97; Senn 1900.)

This genus, as modified by Francé, 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 Bütschli to 1. Francé 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.

Francé 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; (Francé).

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 22µ over all; the body was 5µ, the collar 3µ, and the stalk 14µ. No colonies were seen, and only a few individuals upon red algæ.

Genus BODO (Ehr.) Stein.

(Stein '59, Bütschli '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 analyze. 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 12µ; diameter 8 to 11µ. Common.

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 18µ.

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

Genus OXYRRHIS Duj.

(Kent '81; Bütschli '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 40µ.

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 algæ. Length 60µ; greatest diameter 30µ.

Genus ANISONEMA Bütschli

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 50µ; width 23µ. This attractive flagellate was quite common in decaying algæ 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.

Genus DISTEPHANUS Stöhr.

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.

Distephanus speculum Stöhr.

_Dictyocha speculum_ Stöhr; _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.

KEY TO FAMILIES OF DINOFLAGELLIDIA.

1. No crossfurrow; two free flagella Family _Prorocentridæ_

2. One or more cross-furrows 3

3. Cross-furrow nearly central Family _Peridinidæ_
(cf. _Oxytoxum_)

Cross-furrow close to Family _Dinophysidæ_
anterior end

Several cross-furrows Family _Polydinidæ_
and flagella (One genus, _Polykrikos_.)

KEY TO MARINE GENERA OF PROROCENTRIDÆ.

Diagnostic characters: The transverse furrow is absent and the two flagella arise from the anterior end of the body. The shell may be bivalved.

1. No tooth-like process dorsal Genus *_Exuviælla_
to the flagellum

2. With tooth-like process dorsal Genus _Prorocentrum_
to the flagellum

* Presence at Woods Hole indicated by asterisk.

KEY TO MARINE GENERA OF PERIDINIDÆ.

Diagnostic characters: The cross-furrow is nearly central (see, however, _Oxytoxum_); the body may or may not have a shell; the shell may or may not be composed of distinct plates; the plates are distinguished as _equatorial_ (_i.e._, bordering the cross-furrow), _apical_, and _antapical_, while still another, the "rhombic plate", may be present, extending from the cross-furrow to the apex.

1. Without distinct shell Genus *_Gymnodinium_

With a distinct shell 2

2. Shell not composed of definite 3
plates

Shell composed of definite plates 4

3. Cross-furrow replaced by Genus _Ptychodiscus_
thin-skinned band

Cross-furrow well defined; Genus _Protoceratium_
reticulate markings raised
on shell-surface

Cross-furrow well defined; Genus *_Glenodinium_
no markings

4. Two parts of shell equal or 5
nearly equal

Two parts of shell very unequal 11

5. With transverse flagellum in 6
a distinct furrow

Transverse flagellum not in a 10
furrow

6. With horns, or with wing-like 7
processes

Without processes of any kind 9

7. Processes small, wing-like, Genus _Diplopsalis_
around flagellum-fissure

Processes horn-like 8

8. Anterior part with 7 equatorial Genus *_Peridinium_
and 1 rhombic plates

Anterior part with 5 equatorial Genus _Gonyaulax_
and no rhombic plates

Anterior part with 3 equatorial Genus *_Ceratium_
and no rhombic plates

9. Anterior part with 14 equatorial Genus _Pyrophacus_
and 1 rhombic plates

Anterior part with 7 equatorial Genus _Goniodoma_
plates

Anterior part with 4 equatorial Genus _Amphidoma_
plates

10. Apical extremity drawn out Genus _Podolampas_
into a tube

Apical extremity not drawn out Genus _Blepharocysta_
into a tube

11. Cross-furrow deep, with great Genus _Ceratocorys_
ledge-like walls

Cross-furrow wide, no ledge-like Genus _Oxytoxum_
walls

* Presence at Woods Hole indicated by asterisk.

KEY TO MARINE GENERA OF DINOPHYSIDÆ.

Diagnostic characters: The cross-furrow is above the center of the body, and its edges, as well as the left edge of the longitudinal furrow, are usually produced into characteristic ledges; those of the cross-furrow usually form great funnel-like anterior processes, while those of the longitudinal furrow usually form great, lateral, wing-like processes ornamented by ribs and other markings.

1. Without shell; longitudinal Genus *_Amphidinium_
furrow may open & close

2. With shell; longitudinal furrow 3
unchangeable

3. With distinct apical funnel 4

No apical funnel Genus _Phalacroma_

4. With great wing-like ledge 5

Ledges very small; body long, Genus _Amphisolenia_
needle-like

5. Ledge of longitudinal furrow 6
extends to posterior end

Ledge of longitudinal furrow Genus _Dinophysis_
does not extend to posterior end
(Recorded by Peck ('93-'95) as very abundant at Woods Hole
and in Buzzards Bay.)

6. Ledge is continued dorsally to Genus _Ornithocercus_
the cross-furrow

Ledge is not continued dorsally 7

7. With deep dorsal cavity; Genus _Citharistes_
secondary funnel not notched

No dorsal cavity; secondary Genus _Histioneis_
funnel deeply notched

* Presence at Woods Hole indicated by asterisk.

Genus EXUVIÆLLA Cienkowsky '82.

(Klebs '81; Pouchet '83, '86.)

The form varies from globular to ovoid, with occasionally a sharp posterior end. Shells are usually somewhat compressed, and consist of two valves, which frequently slide one over the other in such a manner as to show the structure with great clearness. The right shell may have a distinct indentation in the anterior edge. There are two lateral, discoid, brown chromatophores, each of which possesses a central amylum granule. The nucleus is posterior. Salt water.

Exuviælla lima Ehr. Fig. 18.

Synonyms _Pyxidicula_ Ehr.; _Cryptomonas_ Ehr.; _Prorocentrum lima_ Kent; _Amphidinium_ Pouchet.

The shell is ovate, rounded and swollen posteriorly. The anterior border of both shells is slightly indented. The shell is quite thick. The animal moves through the water very slowly. Dark brown in color. Length 48µ; width 44µ.

Exuviaella marina Cienkowsky. Fig. 19.

A smaller form than the preceding, more elliptical in outline, with a thinner shell and with large granules throughout the endoplasm. The nucleus is spherical and subcentral in position and possesses a distinct central granule. This may be a small variety of _E. lima_.

Genus GYMNODINIUM Stein '78.

(Bergh '81; Kent '81; Pouchet '83, '85; Entz '84; Schütt '95.)

The general structure of these forms is similar to that of _Glenodinium_; the most striking and positive difference is the absence of a shell. The animals are, as a rule, spherical, yet they may be pointed at the two ends or at one of them. They are also frequently flattened dorso-ventrally. The transverse furrow may be either circular and straight around the body or may describe a spiral course, passing even twice around the body. The flagella arise near cross-furrow or, in some cases, in longitudinal furrow. Chromatophores may or may not be present and food-taking is holozoic, in many cases at least. In some cases ectoplasm and endoplasm can be distinguished. Fresh and salt water.

Gymnodinium gracile Bergh '82, var. sphærica, n. Fig. 20.

The body is divided by the transverse furrow into a shorter anterior and a longer posterior part. The longitudinal furrow is broader at the posterior extremity than at the cross-furrow. The structural feature upon which this new variety is made is the unvarying plumpness of the body, making it almost spherical, except for a slight flattening dorso-ventrally. The nucleus is large and ellipsoidal, with characteristic longitudinal markings of chromatin. The endoplasm is evenly granular, with a number of large ingested food bodies. The color is brown, not rose-red as in Bergh's species, nor is the Woods Hole form as large as the latter. Length of body 68µ; width 55µ. Common.

Genus GLENODINIUM (Ehr.), Stein '83.

(Bergh '82; Bütschli '86; Pouchet '85; Daday '86.)

Small globular forms with two distinct furrows, one transverse around the body, the other longitudinal upon the face only. The shell is soft and structureless with a distinct aperture near the meeting point of the two furrows. The endoplasm usually, but not always, contains a bright red eye-spot.

Fresh and salt water.

Glenodinium compressa, n. sp. Fig. 21, a, b, c.

This species resembles _G. acuminata_ of Ehrenberg except that it is strongly compressed laterally. The longitudinal furrow extends nearly to the extremity of the animal. It begins as a narrow slit and widens as it progresses upon the left side; it also becomes much deeper on this side and at the bottom of the depression the longitudinal flagellum is inserted. The transverse furrow runs evenly around the body near the upper pole, giving to the shell almost the aspect of an _Amphidinium_. Brown chromatophores may or may not be arranged radially about a central amylum granule. One striking characteristic is the depth of the two furrows. The nucleus is elongate and somewhat curved; it lies against the posterior wall of the rather thick shell. Not uncommon.

Length 40µ; breadth 32µ; width 18µ.

The posterior end of the animal is often somewhat pointed and this point frequently becomes attached, so that the animal whirls around upon it as upon a pivot.

Glenodinium cinctum Ehr. Fig. 22.

The body is globular, smooth, and homogeneous. Brown chromatophores arranged radially, each in the form of a cone, the base of which rests against the shell while the points turn inward. A bright-red eye-spot may or may not be present; when present it is placed near the junction of the two furrows. The longitudinal furrow is small. Fresh water and salt.

Length and diameter the same, 21µ.

This species was observed by Peck '93.

Genus PERIDINIUM Ehr. '32, Stein '83.

(Claparède & Lachmann '58; Bergh '81; Pouchet '83; '85; Gourret '88; Bütschli '86.)

The form is globular, ovoid or elongate, the apex frequently drawn out into a long tube. The transverse and longitudinal furrows are quite distinct, the former having often a spiral course about the body. The two halves of the body are similar, the posterior being somewhat shorter; the anterior half has seven equatorial plates, an oral plate, two lateral apical plates, and one or two dorsal plates. The two antapical plates frequently have a tooth-like process. The bodies are colorless, green or brown.

Fresh and salt water.

Peridinium digitale Pouchet. Fig. 23.

Synonyms: _Protoperidinium digitale_ Pouchet; _Protoperidinium_ Bergh p. p.; _P. divergens_ Peck.

The shell is covered with pits of large size. The posterior part is hemispherical and surmounted by a single horn or spine. The transverse furrow is very oblique, and its two extremities are united by a sigmoid longitudinal furrow. The anterior half bears two spines or horns of different size, and variable. The nucleus is spherical or ellipsoidal and placed in the posterior half of the shell.

Length 68µ; diameter 54µ. Common.

Although the description of Pouchet's _P. digitale_ differs in some respects from a careful description of the Woods Hole form, I think the species are the same. The chief difference is in the single horn of the posterior half; in Pouchet's form this is furrowed by a narrow groove which runs to the S-shaped longitudinal furrow. In the Woods Hole form I was unable to make out such a furrow. The flagella, also, were not seen. This same form was pictured by Peck '95 as _P. divergens_.

Peridinium divergens Ehr. Fig. 24.

Synonym: _Ceratium divergens_ Kent.

The shell is spheroidal, widest centrally, attenuate and pointed posteriorly; the anterior portion is armed with two short, pointed horns, each of them having a toothed process at the basal portion of the inner margin. They are frequently colorless and beautifully transparent, the body being free from large opaque granules; again they are colored brown or yellow. The nucleus is large and elongate and finely granular. 75µ long and 68µ in diameter. Common.

Genus CERATIUM (Schrank).

(Stein '78; Perty '52; Clap & Lach. '58; Bergh '82; Pouchet '83; Gourret & Roeser '88; Bütschli '85; Kent '81; Senn 1900; Schütt '98.)

The general shape is a flattened sphere with three long processes or horns. The cross-furrow is either spiral or circular; the longitudinal furrow is usually wide and occupies the greater part of the anterior half of the shell. The shell is thick, reticulate or striped, and sometimes provided with short spines; often distinctly porous. The anterior half is composed of 3 equatorial and 3 apical plates, the latter being continued into the horn-like process. The posterior half is composed of 3 equatorial and one apical plate continued into the posterior horn. The right posterior plate is continued into a similar horn which may remain rudimentary or be continued into a considerable process. Similarly the left posterior horn is usually developed, but remains small. There may be from 2 to 3, 4, and 5 horns. Chromatophores usually present, green to yellow brown.

Fresh and salt water.

Ceratium tripos Ehr. Fig. 25.

The body is somewhat triangular and bears three horns, two of which are shorter than the other one and slightly curved upward.

Length, including the horns, 290µ.

Ceratium fusus Ehr. Fig. 26.

Synonym: _Peridinium fusus_ Ehr.

The animal is very elongate, due to the presence of two long horns at the extremities of the body. Color, yellow with chromatophores. Length 285µ; width 23µ.

Both of these species are common in the tow and in the algæ at the edge of the wharf. Both of them are mentioned by Peck in '93 and '95.

Genus AMPHIDINIUM Clap. & Lach.

The body is ovoid to globular and usually much flattened dorso-ventrally. The anterior portion is very much reduced and is somewhat head-like or cap-like. The longitudinal furrow extends through the entire posterior body length and is apparently capable of widening and narrowing. It is probably naked (see here Klebs, Pouchet, Bütschli), although Stein maintained that there is a delicate cuticle-like shell. Chromatophores of brown or green colors present and usually grouped radially about a central amylum granule. The nucleus is posterior.

Fresh and salt water.

Amphidinium operculatum Clap. & Lach. Fig. 27.

The body is oval and flattened. The transverse furrow is at the extremity (posterior) of the body and the small portion, which is thus apparently cut off, is the cap-like or operculum-like structure which gives the name to the species. Klebs maintains that the two furrows are not connected, but in this he is certainly mistaken, provided we have the same species under consideration. Very common about Woods Hole.

Length from 40 to 50µ; width 30µ; thickness 15µ.

KEY TO INFUSORIA.

1. With cilia Subclass _Ciliata_. 3

2. Without cilia (in adult state) Subclass _Suctoria_
tentacles

3. a. Without a specialized fringe of Order _Holotrichida_
large cilia (ad. zone)

b. With general covering of cilia Order _Heterotrichida_
+ adoral zone

c. With cilia on ventral side Order _Hypotrichida_
+ adoral zone

d. With cilia in region of adoral Order _Peritrichida_
zone, and about mouth only

KEY TO FAMILIES OF THE HOLOTRICHIDA.

A. Mouth closed except during food 1
ingestion; no undulating membrane

Mouth always open; with undulating 2
membrane

1. _Gymnostomina_.

a. Mouth terminal or subterminal. Family _Enchelinidæ_
Food is swallowed and not
introduced by currents

b. Mouth terminal or subterminal; Family _Trachelinidæ_
body frequently drawn out into
long process; mouth may have
specialized framework.

c. Mouth central or posterior; Family _Chlamydodontidæ_
pharynx with supporting
framework

2. _Trichostomina_.

a. Mouth anterior or central; Family _Chiliferidæ_
pharynx short or absent;
peristomial depression faint
or absent

b. Mouth central; pharynx long, Family _Urocentridæ_
tubular; cilia in two broad
zones

c. Mouth posterior; form Family _Microthoracidæ_
asymmetrical; cilia dispersed
or limited to oral region

d. Mouth anterior or central. _Paramoecidæ_
Peristomial depression (One genus, _Paramoecium_)
clearly marked.

e. Mouth at end of long peristome Family _Pleuronemidæ_
running along ventral side;
body dorso-ventrally or
laterally compressed; left edge
of peristome with great, sail-
like undulating membrane

f. Mouth and pharynx distinct, Family _Isotrichidæ_
posterior; cilia uniform.
Parasites in ruminants.

g. Mouth absent; body vermiform, Family _Opalinidæ_
cilia uniform. Usually
parasites.

KEY TO MARINE GENERA OF ENCHELINIDÆ

Diagnostic characters: Form ellipsoid or ovoid; the mouth is invariably terminal and is usually round--more rarely slit-formed; it is closed except when food is taken. An oesophagus when present is a short, invariably non-ciliated tube which is usually surrounded by a more or less clearly defined buccal armature. The anus is usually terminal. Large food particles are swallowed, never introduced by currents.

1. Body naked 3

2. Body inclosed in a shell or coat 7

3. a. Cilia uniform about the entire 4
body; body symmetrical

b. Cilia in the mouth region 5
longer than the others; body
symmetrical

c. Bristles, or tentacles, in 6
addition to cilia

4. Mouth terminal; body ellipsoidal Genus _Holophrya_
to ovoid

5. a. Mouth terminal; body elongate, Genus _Chænia_
flexible, and elastic

b. Mouth terminal; "neck" highly Genus *_Lacrymaria_
elastic; entire body
flexible; conical "head"

c. Mouth terminal; "neck" highly Genus *_Trachelocerca_
elastic; entire body
flexible; "head" square

d. Mouth terminal; "neck" highly Genus _Lagynus_
elastic; no separate
mouth-bearing portion

6. a. Body asymmetrical; bristles Genus _Stephanopogon_
in addition to cilia

b. Body symmetrical; 4 small Genus *_Mesodinium_
tentacles from mouth; cilia
and cirri in girdles

7. Shell composed of small Genus *_Tiarina_
sculptured pieces; cilia long,
uniform

* Presence at Woods Hole indicated by asterisk.

Genus LACRYMARIA Ehr. '30.

(Ehrenberg, C. G., 1838; Perty '52; Claparède & Lachmann '58; Stein 59-83; Quennerstedt '66, '67; Fromentel '74; Kent '81; Gruber '84; Gourret & Roeser '86; Bütschli '88; Schewiakoff '89.)

Body short to very long flask-shape; for the most part contractile, especially in the neck region. The posterior end is rounded or pointed. The main character is the mouth-bearing apex, which "sets like a cork in the neck of the flask." One or more circles of long cilia at the base of the mouth portion or upon it. The body is spirally striped. Contractile vacuole terminal, with sometimes one or two further forward. Macronucleus central, globular to elongate, sometimes double. Food mainly bacteria. Fresh and salt water.

Lacrymaria lagenula Clap. & Lach. Fig. 28, a, b.

Synonym: _L. tenuicula_ Fromentel '74.

Body more or less flask-shape, two or three times as long as broad, with conical apex, which is slightly elastic and protrusible; surface obliquely striate, with well-defined lines, 14 to 16 in number; cilia uniform on the body, with a crown of longer ones at the base of the conical proboscis. The body cilia are not thickly placed except around the proboscis. The endoplasm is thickly packed with large granules (food particles) in the anterior half and with finely granular particles in the posterior half. The elongate macronucleus lies a little above the center among the larger granules; the contractile vacuole is double, one on each side of the median line and at the posterior end of the body among the finer granules. The anus is posterior. Length 90µ to 160µ; greatest width assumed 65µ. When fully expanded the posterior end assumes a curious polyhedral form. (Fig. 28 b.)

This form differs slightly from others of the same species as described by different observers, the most striking difference being the presence of two contractile vacuoles in place of the usual one. These are very slow to fill and grow to a large size before diastole. The membrane is very tough and retains its form easily under pressure of the cover glass. Another characteristic feature is the flattening of the surfaces between the striæ. Decaying algæ.

Lacrymaria coronata Cl. & Lach. '58. Fig. 29.

Synonyms: _L. lagenula_ Cohn '66; Möbius '88; _L. cohnii_ ? Kent '81; _L. versatilis_ Quen. '67.

Form flask-like and similar to _L. lagenula_, contractile but tough. The contractile vacuole is terminal, the proboscis is short, slightly raised and separated from the body by a deep cleft; the buccal cilia are inserted part way up on the proboscis. Form changeable, from short, sac-like to elongate and vermiform. Length 85µ.

This species is not very different from _L. lagenula_, but I noted that in addition to the elongate nucleus, the body striæ are much more apparent here and seem to sink into the cuticle, giving the periphery, especially at the collar region, a curious crenulated effect. The endoplasm is very densely granular and colored a blue-green, probably from food particles. The number of striæ is much larger than in the preceding species. The membrane is very tough and retains the shape of the body, even with the full pressure of the cover glass. Micronucleus and trichocysts were not observed.

Genus TRACHELOCERCA (Ehr. '83) Cohn '66.

(Quennerstedt '67; Gruber '87; Entz '84; Kent '81; Gourret & Roeser '88; Bütschli '88; Schewiakoff '89; Shevyakov '96.)

The only well-known representative is very elongate, large (up to 3 mm. Van Beneden), and very contractile. The main feature of importance in distinguishing it is the 4-part structure of the mouth region, which, however, may not be obvious. Pharynx faint and smooth. Contractile vacuole terminal. Macronucleus in one central body or in numerous pieces scattered throughout the cell. Salt water.

Trachelocerca phoenicopterus Cohn '66. Fig. 30.

Synonyms: _T. sagitta_ Ehr. '40, Stein '59; _T. tenuicollis_ Quennerstedt '67, Kent '81; _T. minor_ Gruber '87, Shevyakov '96.

The body is extremely elongate and ribbon-like, and this, combined with its wonderful power of extension and retraction, makes it one of the most curious and interesting of microscopic forms. The anterior end is square or cylindrical; the type species has a four-sided mouth, but many specimens may be found which have a plain cylindrical mouth region. One reason for this may be the fact that the extremity gets broken off. In one instance I noticed a very large form with the anterior end under some debris, which evidently held it tight, for the body of the ciliate was thrashing back and forth and twisting itself into knots, etc., like a nematode worm. Finally, the anterior end broke off with about one-tenth of the body; the remainder, in an hour, had regenerated a new anterior end with long cilia, but with no indication of four sides. The small anterior piece was also very lively, moving about and eating like the normal animal; its history, however; was not followed. This species appears to be variable in other ways as well; thus, in some cases the posterior end is rounded (cf. Entz '84); in others it is pointed (cf. Kent '81, Cohn '66, et al.).

Again, the macronucleus may be a single round body (Entz '84, Bütschli '88) or in two parts (Kent '81), or in many parts scattered about the body (Gruber). In the Woods Hole forms the tail is distinctly pointed and turned back sharply, forming an angle at the extremity. The cilia on this angular part are distinctly longer than the rest. The function of this posterior part is apparently to anchor the animal while it darts here and there upon the tail as a pivot, contracting and expanding the while. The body is finely striated with longitudinal markings; when contracted there are no transverse markings nor annulations. The nucleus is in the form of many fragments scattered throughout. Length of large specimen 1.7 mm.

Genus MESODINIUM Stein '62.

(Maupas '82, '84; Entz '84; Shevyakov '96.)

The main part of the body is globular or conical, with a short, platform-like oral region, and a deep annular groove about the middle of the body. The oesophagus is rather long, and smooth or longitudinally striped. One or more rings of cirri rise in the groove. If more than one ring of cirri are present, the anterior set usually point forward and lie close to the anterior part of the body. The posterior set, on the other hand, cling close to the posterior region of the body and give to it a peculiar encapsuled appearance. The most characteristic feature is the presence of four short tentacle-like processes which can be protracted and retracted from the oral region. (Mereschowsky says that the entire anterior half is more or less contractile.) The macronucleus is horseshoe-shaped or ovoid and is situated in the posterior half of the body. The contractile vacuole is also posterior.

Movement consists in rapid swimming, with rotation on its axis, or in creeping by means of its anterior cirri, or in sudden jumping, by which it apparently clears a distance of 20 times its diameter in one bound. Mouth parts may also be used for attachment to foreign bodies. The moving periods alternate with quiescent periods, during which the organisms with their outstretched and radiating cirri resemble the heliozoön _Actinophrys_.

Mesodinium cinctum, n. sp. Fig. 31.