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Marine Protozoa from Woods Hole - Bulletin of the United States Fish Commission 21:415-468, 1901
by Gary N. Galkins
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E-text prepared by Ronald Calvin Huber, while serving as Penobscot Bay Watch, Rockland, Maine, and Joseph E. Loewenstein, M.D.



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 algae 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 algae 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. Trichosphaerium 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 Stoehr. Subclass DINOFLAGELLIDIA. Order ADINIDA. 20. Exuviaella lima Clenk. 21. Exuviaella 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 ENCHELINIDAE. 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 TRACHYLINIDAE. 35. Lionotus fasciola Ehr. 36. Loxophyllum setigerum Quenn. Family CHLAMYDODONTIDAE. 37. Nassula microstoma Cohn. 38. Chilodon cucullulus Muell. 39. Dysteria lanceolata Cl. & Lach. Family CHILIFERIDAE. 40. Frontonia leucas Ehr. 41. Colpidium colpoda Ehr. 42. Uronema marina Duj. Family PLEURONEMIDAE. 43. Pleuronema chrysalis Ehr. 44. Pleuronema setigera, n. sp. 45. Lembus infusionum, n. sp. 46. Lembus pusillus Quenn. Family OPALINIDAE. 47. Anoplophrya branchiarum Stein. Order HETEROTRICHIDA. Family BURSARIDAE. 48. Condylostoma patens Muell. Family HALTERIDAE. 49. Strombidium caudatum From. Family TINTINNIDAE. 50. Tintinnopsis beroidea Stein. 51. Tintinnopsis davidoffi Daday. Order HYPOTRICHIDA. Family PERITROMIDAE. 52. Peritromus emmae Stein. Family OXYTRICHIDAE. 53. Epiclintes radiosa Quenn. 54. Amphisia kessleri Wrzes. Family EUPLOTIDAE. 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 LICHNOPHORIDAE. 61. Lichnophora macfarlandi Stevens. Family VORTICELLIDAE. 62. Vorticella marina Greeff. 63. Vorticella patellina Mueller. 64. Zoothamnium elegans D'Udek. 65. Cothurnia crystallina Ehr. 66. Cothurnia nodosa Cl. & Lach. 67. Cothurnia imberbis Ehr. Subclass SUCTORIA. Family PODOPHRYIDAE. 68. Podophrya gracilis, n. sp. 69. Ephelota coronata Wright. Family ACINETIDAE. 70. Acineta divisa Fraip. 71. Acineta tuberosa Ehr. Family DENDROSOMIDAE. 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 37 mu. Traverses a distance of 160 mu 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 80 mu; diameter 56 mu.



Genus TRICHOSPHAERIUM 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.

Trichosphaerium 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 42 mu, width 35 mu. 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 Trichosphaerium. 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; Buetschli '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 algae. 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 245 mu; largest diameter 125 mu.



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 algae 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 230 mu by 270 mu.

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 50 mu; 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 Sphaerophrya, 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 40 mu; length of pseudopodia 120 to 140 mu.



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 80 mu; 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 10 mu). 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 Penard '90, in the case of Acanthocystis. Diameter of entire globe 35 mu; of the body without the jelly 18 mu. The extremely fine granular pseudopodia are 8 to 35 mu long. Common among algae.

This form was probably meant by Peck '95, when be figured "a heliozooen."



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 Stoehr)

KEY TO THE FAMILIES OF MONADIDA.

No mouth; 1 or 2 flagella: amoeboid Family Rhizomastigidae with lobose or ray-like pseudopodia

Mouth at base of single flagellum; Family Cercomonadidae plastic; no pseudopodia

One flagellum; inclosed in gelatinous Family Codonoecidae or membranous cups

One flagellum; tentacle like process Family Bikoecidae at base of flagellum; inclosed in cup

One main flagellum and 1 or 2 Family Heteromonadidae accessory flagella

KEY TO MARINE GENERA OF MONADIDA.*

Family Rhizomastigidae:

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 Codonoecidae:

1. Goblet-shaped cups adherent Genus *Codonoeca by stalk

Family Heteromonadidae:

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 Bodonidae

One main and 2 accessory flagella Family Trimastigidae

Family Bodonidae:

1. Body very plastic, Genus *Bodo almost amoeboid

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

Family Trimastigidae:

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 Peranemidae

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

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

Family Euglenidae:

Body Euglena-like, inclosed Genus Trachelomonas in shell with round opening for exit of flagellum

Family Astastidae:

Body with one flagellum Genus *Astasia

Family Peranemidae:

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; Buetschli '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 algae. Length 10 mu.



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 mu; of 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).



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.



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.



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 mu; length of collar 3 mu.



Genus CODONOSIGA (Jas. Clark '67).

(Buetschli '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 Buetschli 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 mu over all; the body was 5 mu, the collar 3 mu, and the stalk 14 mu. No colonies were seen, and only a few individuals upon red algae.



Genus BODO (Ehr.) Stein.

(Stein '59, Buetschli '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 12 mu; diameter 8 to 11 mu. 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 18 mu.

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



Genus OXYRRHIS Duj.

(Kent '81; Buetschli '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 mu.



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 mu; greatest diameter 30 mu.



Genus ANISONEMA Buetschli

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 mu; width 23 mu. 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.



Genus DISTEPHANUS Stoehr.

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 Stoehr.

Dictyocha speculum Stoehr; 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 Prorocentridae

2. One or more cross-furrows 3

3. Cross-furrow nearly central Family Peridinidae (cf. Oxytoxum)

Cross-furrow close to Family Dinophysidae anterior end

Several cross-furrows Family Polydinidae and flagella (One genus, Polykrikos.)

KEY TO MARINE GENERA OF PROROCENTRIDAE.

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 *Exuviaella 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 PERIDINIDAE.

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 DINOPHYSIDAE.

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 EXUVIAELLA 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.

Exuviaella 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 48 mu; width 44 mu.



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; Schuett '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. sphaerica, 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 68 mu; width 55 mu. Common.



Genus GLENODINIUM (Ehr.), Stein '83.

(Bergh '82; Buetschli '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 40 mu; breadth 32 mu; width 18 mu.

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, 21 mu.

This species was observed by Peck '93.



Genus PERIDINIUM Ehr. '32, Stein '83.

(Claparede & Lachmann '58; Bergh '81; Pouchet '83; '85; Gourret '88; Buetschli '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 68 mu; diameter 54 mu. 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. 75 mu long and 68 mu in diameter. Common.



Genus CERATIUM (Schrank).

(Stein '78; Perty '52; Clap & Lach. '58; Bergh '82; Pouchet '83; Gourret & Roeser '88; Buetschli '85; Kent '81; Senn 1900; Schuett '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, 290 mu.



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 285 mu; width 23 mu.

Both of these species are common in the tow and in the algae 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, Buetschli), 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 50 mu; width 30 mu; thickness 15 mu.



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 Enchelinidae Food is swallowed and not introduced by currents

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

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

2. Trichostomina.

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

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

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

d. Mouth anterior or central. Paramoecidae Peristomial depression (One genus, Paramoecium) clearly marked.

e. Mouth at end of long peristome Family Pleuronemidae 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 Isotrichidae posterior; cilia uniform. Parasites in ruminants.

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

KEY TO MARINE GENERA OF ENCHELINIDAE

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 Chaenia 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; Claparede & Lachmann '58; Stein 59-83; Quennerstedt '66, '67; Fromentel '74; Kent '81; Gruber '84; Gourret & Roeser '86; Buetschli '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 90 mu to 160 mu; greatest width assumed 65 mu. 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 striae. Decaying algae.



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

Synonyms: L. lagenula Cohn '66; Moebius '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 85 mu.

This species is not very different from L. lagenula, but I noted that in addition to the elongate nucleus, the body striae 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 striae 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; Buetschli '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, Buetschli '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 heliozooen Actinophrys.

Mesodinium cinctum, n. sp. Fig. 31.

Body spherical to pyriform, constricted near the middle, the constriction dividing the body into dissimilar parts. The anterior part is broadly pyriform, somewhat plastic and hyaline, with an oral extremity which is sometimes hollow, sometimes evaginated and convex. Upon this flexible anterior part there are four short but distensible tentacles. The posterior part is granular and usually filled with food particles; it is well rounded and holds the nucleus and contractile vacuole. The entire body is surrounded by a fine cuticle. The nucleus is elongate and extends through the greater part of the posterior half. The contractile vacuole lies on one side, near the girdle. The mouth is on the anterior pole in the tentacle region. The motile organs are cirri and cilia, all inserted in the constriction. There are two sets of cirri and one of cilia; the latter stand out radially from the girdle and are usually in motion. The cirri of one set, the anterior, extend forward about twice the length of the anterior half; those of the posterior set closely engirdle the lower half, reaching not quite to the posterior extremity. These are somewhat hyaline and are closely approximated, giving the impression of a tight-fitting crenulate casing about the lower half. The cirri are sharply pointed, much broader at the base, and the two sets are so placed that, looked at from above, they have the appearance of a twisted cord. (Fig. 31 b.) Movement erratic; sometimes the animal swims steadily forward with mouth in front; again it shoots across the field of the microscope, either backward or forward or sideways, through the action of its powerful cirri. It is often quiet, usually mouth downward, and is held in place by adhesion of the tentacles. In this position it looks strikingly like a heliozooen.

Length 35 mu; greatest width 30 mu. Not uncommon.

The chief features by which this species is distinguished from the frequently described M. pulex of Europe are the number of anterior cirri and the ring of true cilia in place of the central girdle of cirri. The European form is described with four anterior bristles; the present form has from 28 to 32. The radial cilia differ decidedly from the more powerful cirri and they are not in one plane, so that counting is difficult; they are not closely set. The presence of tentacles makes these forms of especial theoretical interest, especially in the light of the origin of Suctoria.



Genus TIARINA R. S. Bergh '79.

(Claparede & Lachmann '58.)

Body subcylindrical, pointed posteriorly, two and one-half times as long as broad; encased in covering composed of separate pieces arranged in five girdles. The pieces bear processes which rest against neighboring pieces of the girdle. Mouth large, anus terminal near contractile vacuole. The macronucleus is simple and round. Salt water.

Tiarina fusus (Cl. & Lach.) emend R. S. Bergh.

Synonyms: Coleps fusus Cl. & Lach. '58; Daday '86; Moebius '88, Lauterborn '94; Shevyakov '86.

This form, which resembles Coleps rather closely, was placed as a separate genus by R. S. Bergh. The skeletal parts consist of five zones of needles composed of an organized substance and embedded in the cortical plasm, the last zone coming to a point at the posterior end. The needles have lateral processes, which give a latticed appearance to the casing. The cilia are long, with a specialized crown of still longer ones at the oral end; they arise outside of the skeletal elements and do not pass between them, as in Coleps.

KEY TO MARINE GENERA OF TRACHELINIDAE.

Diagnostic characters: Body bilateral, or asymmetrical by local prolongations; usually compressed or flattened laterally, the left side more convex than the right. The essential feature is the position and character of the mouth. This is either a long slit extending from the anterior end well down the ventral surface, or the posterior part only of a ventral furrow remains open as a round or elongate mouth some distance from the anterior end. The entire mouth region of the body is usually drawn out into an elongate tapering proboscis which is generally curved dorsally at the extremity. An oesophagus is short or absent altogether; when present it is supported by a stiff buccal armature. Cilia are uniform about entire body or limited to the flat right side. Food is swallowed.

1. a. Proboscis easily distinguished 2 from the main body

b. Proboscis not marked off from Genus *Loxophyllum main body; body flat; both surfaces striated

2. a. Mouth runs the entire length Genus Amphileptus of proboscis; entire body uniformly ciliated

b. Mouth runs the entire length Genus *Lionotus of proboscis; body flat; right side only is ciliated

c. Proboscis much drawn out, Genus Dileptus flexible; mouth at its base

* Presence at Woods Hole indicated by asterisk.

Genus LOXOPHYLLUM Dujardin '41.

(Duj. '41; Wrzesniowski '69; Quennerstedt '65; '67; Cohn '66; Entz '84; Gourret & Roeser '88; Buetschli '88; Shevyakov '96.)

The body is flat and somewhat leaf-shape, flexible, and elastic. The anterior end is somewhat proboscis-like and flexible, but is not sharply demarcated as in Lionotus. The central portion of the body is developed into a more or less arched dorsal mass, which usually contains the nuclei and contractile vacuoles. As a result of this local thickening, the body is surrounded by a thin hyaline margin. This, however, may be absent on the right side in some species. The mouth reaches from the anterior extremity to a short distance from the end, and usually approaches the left edge. An anus is present near the posterior end of the dorsal swelling. Trichocysts are numerous on the ventral surface, and often on the dorsal surface, where they are inclosed in minute papilla-like swellings. Cilia-distribution controverted. Maupas and Buetschli hold that ventral surface alone is ciliated; others (Kent and Dujardin) that cilia are uniformly distributed. The entire body, dorsal and ventral surfaces alike, are uniformly striated. The contractile vacuole lies posteriorly, on the right side and in the dorsal swelling. In the fresh-water form L. meleagris, it is connected with a long canal whose swellings are frequently taken for additional contractile vesicles (Buetschli); in the marine form described below the canal is not developed and a series of vacuoles takes its place; these are all contractile. The macronucleus may be single, double, quadruple, band-formed, or rosette-formed. Movement is steadily progressive and peculiarly gliding. Fresh and salt water.

Loxophyllum setigerum Quenn. '67.

Synonyms: Litosolenus armatus Stokes '93; Litosolenus verrucosa Stokes '93.

The body is flattened, irregular in outline, obtusely pointed anteriorly, the point being turned to the right; rounded posteriorly. The left edge is nearly straight, the right considerably arched with a few setae on the posterior half. Contractile vacuoles are numerous, dorsal in position and on the right side. The macronueleus is beaded, the several spheres connected.

Variety armatum (Cl. & Lach.) Fig. 32.

Under the name Litosolenus armatus, Stokes described a form from brackish water near New York, which should unquestionably be referred to the genus Loxophyllum, and I believe to Quennerstedt's species setigerum. While the latter possesses only a few setae, the former has a number of them, and Stokes described his species as having a variable number. For this reason I include the Woods Hole form under the tentative name armatum, as a variety of Quennerstedt's L. setigerum. The flat margins are distinctly striated longitudinally, and faintly marked radially, on the dorsal surface. Longitudinal elevated striae also run the length of the dorsal hump and upon the entire ventral surface. The ventral surface is alone ciliated. Upon the edges of the flat border are sharp-pointed, colorless, spine-like processes, situated at equal distances around the entire periphery except at the anterior end. Each spine is thick at the base and tapers to a full point which is curved upward—i. e., dorsally (fig. 32, a, b). The entire body is plastic and contractile, turning its leaf-like edge readily over objects upon which it creeps. The cilia are fine and uniform, with a tendency to lengthen in the oral region.

Length 100 mu; greatest width assumed on contraction 85 mu; when normal about 50 mu.



Genus LIONOTUS Wrzesniowski '70.

(Incorrectly called Litonotus by many. Entz '84; Gruber '84; Buetschli '88; Kent '81; Schewiakoff '89; Shevyakov '96.)

The body is elongate and somewhat lance-shaped, widest at the central part and tapering to a point at the anterior end. The posterior end may be similarly tapered or rounded. The anterior end frequently proboscis-like, flat, and flexible, while the entire body is more or less elastic and contractile. The right side is flattened and alone provided with cilia, while the left side of the body proper is arched; on the left side of the proboscis is a row of coarse cilia resembling an adoral zone, and a row of trichocysts. A long peristome stretches down the thin, ventral side of the proboscis, and the mouth proper is situated at the junction of the proboscis and body; the mouth, as a rule, is invisible. The ciliated right side alone is striated in the majority of species. The contractile vacuole may be single or multiple, usually in the posterior region of the body and dorsal in position. The macronucleus is usually double, rarely single or quadruple, but may occasionally break into numerous smaller pieces. Movement, free-swimming or gliding, with especial tendency to get under clumps of foreign matter.

Fresh and salt water.

Lionotus fasciola Ehr. Fig. 33.

Synonyms. Amphileptus fasciola Ehr. '38; Dujardin '41; Lachmann '56; Cohn '66, Diesing '65. Loxophyllum fasciola Claparede & Lachmann '58; Balbiani '61. Loxophyllum duplostriatum Maupas '83. Shevyakov '96.

Body frequently brown or brilliant yellow in color, somewhat sigmoid in form with tapering anterior end, the extremity of which is turned dorsally. The proboscis is about half the entire length and is not sharply marked from the rest of the body but tapers gradually, its base being equal to the diameter of the body at its middle point. The body is slightly contractile and the posterior end is carried to a rounded point, but not into a distinct tail. Unlike the fresh-water variety, this one has no hyaline margin nor hyaline caudal region, and the contractile vacuole is double or multiple on the dorsal side near the posterior end. Cilia are present only on the under (right) side, with, however, a row of large cilia marking the course of the elongate mouth, upon its left side. The right side is striated, the left arched and without markings. The endoplasm is finely granular with, however, larger food particles in the process of digestion, while specimens are occasionally seen with the natural form completely lost through distortion caused by over-large captures (Cf. also Wrzesniowski '70, p. XXIII, fig. 32). Movement continuous, slow, and gliding; very little tendency to jerking movements. Macronucleus double, both parts spherical, and placed in about the center of the larger part of the body; closely approximated but not, as Schewiakoff described, connected. In conjugation, a large form unites with a smaller one, the mouth parts being connected. Details of conjugation and macronuclei not made out. Length 200 mu to 600 mu.



KEY TO MARINE GENERA OF CHLAMYDODONTIDAE.

Diagnostic characters: Form usually ellipsoid, never very elongate. Transverse section of body circular or elliptical. The mouth is usually some distance from the anterior end and may be in the posterior part. Sometimes it is in the center of the ventral surface, again on the right side. The oesophagus invariably has a well-developed buccal armature, or a smooth peculiarly built oesophageal tube. Food particles of large size.

1. Body cylindrical. Cilia about Genus *Nassula entire body

Body flat 2

2. a. Without a caudal process 3

b. With a caudal process 5

3. a. Anterior end angular 4 on left side

b. Anterior end rounded Genus Chlamydodon

4. a. Dorsal striae and cilia present, Genus Orthodon ventral cilia longer

b. Dorsal striae and cilia absent; Genus *Chilodon posterior end not pointed

c. Dorsal striae and cilia absent; Genus Scaphidiodon posterior end pointed

5. a. Caudal spine with posterior 6 bristle-like cilia

b. Caudal spine without posterior Genus Trochilia bristle-like cilia; ventral cilia reduced

6. a. With pigment spot on anterior Genus AEgyria angle

b. Without such pigment spot Genus Onychodactylus

c. Cilia on right edge only of Genus *Dysteria greatly reduced ventral surface

* Presence at Woods Hole indicated by asterisk.

Genus NASSULA Ehr. '33

(Dujardin '41; Stein '67; Cienkowsky '55; Cohn '66; Clap. et Lach. '58; Kent '81; Maupas '83; Entz '84; Fabre-Domergue '88; Buetschli '88; Shevyakov '96.)

The body is ovoid or cylindrical, with well-rounded ends, and in some cases slightly flattened. The mouth is ventral and placed some distance from anterior end (1/4 to 1/3 total length). A slight depression on the ventral surface marks the mouth region, which is further indicated by larger and more powerful cilia. The rest of the body is uniformly ciliated. The entire body is marked by clearly defined spiral stripes. The mouth is circular and the oesophagus is supported by a considerable armature, which usually extends dorsally and to the left, rarely to the right. In some cases the structure of this armature is indistinct; again it can be clearly seen to consist of definite rods (Staebchen). The anus is probably always terminal. Contractile vacuoles are variable in different species. In some cases there is but one, which is placed at the posterior end or centrally on the ventral side; in others there may be four—two dorsal and two ventral. In many cases trichocysts are uniformly distributed. Sometimes the body is colorless; again, and more often, it is brightly colored with red, blue, brown, or black pigment. The macronucleus is globular and central, occasionally band-form and with numerous attached micronuclei. Food substance varied, usually vegetable matter, see, however, below. Cysts are globular. Movement is a steady progression, combined with rolling.

Nassula microstoma Cohn '66. Fig. 34.

Synonyms: Paramoecium microstomum Cl. et Lach. '58, Gourret et Roeser '88; Isotricha microstomum Kent '81.

Body subcylindrical, rounded at each extremity, not quite twice as long as broad. A slight depression on one surface marks the position of the mouth, this depression being indicated by a row of longer cilia. The mouth is extremely small and is surrounded by a curious buccal armature. This is not made up of bars or rods, as in most species of Nassula, but appears perfectly smooth and uniform except for the considerable swelling at the inner end. The cuticle is firm and unyielding and marked by longitudinal and somewhat spiral rows of cilia and trichocysts. Under the microscope this is one of the most pleasing forms found at Woods Hole. Its color is yellowish brown from the presence of brilliant particles of coloring matter held in the cortical plasm, and, as it slowly rolls along, these particles and the black trichocysts give to the organism a peculiar sparkling effect. The macronucleus is almost central; the contractile vacuole posterior. The endoplasm appears well filled with food bodies, some of which could be distinguished as Amphidinium and Glenodinium.

Length 55 mu; greatest diameter 30 mu.



Genus CHILODON Ehr.

(Dujardin '41; Engelmann '78; Stein '54, '58; Kent '81; Buetschli '88; Gruber '83; Cienkowsky '55; Moebius '88; Clap. et Lach '58; Wrzesniowksi '65; Shevyakov '96.)

Small forms, greatly flattened dorso-ventrally and almost egg-form in outline. The anterior end is bent distinctly to the left and forms a characteristic process, which, together with the entire margin of the body, is soft and flexible. The posterior end is, as a rule, broadly rounded. The ventral surface is finely striate, and this surface alone is ciliated. The lines of cilia converge at the mouth, and at this region the cilia are somewhat larger and more distinct, thus forming a functional adoral zone. The mouth is median and is situated in the anterior half of the body. It is surrounded by a well-defined armature, composed usually of from 10 to 16 rods. The contractile vacuoles are quite varied and from one to many in number, the number increasing with the size of the individual. The macronucleus is usually single, elliptical in form, and centrally placed; one micronucleus. Reddish granular pigment and trichocysts are occasionally present.

Chilodon cucullulus Muell., sp. Fig. 35.

Synonyms; Colpoda cucullus O. F. Mueller; Loxodes cucullulus; Chilodon uncinatus Ehr. '58, Perty '52, Dujardin '41; L. dentatus Duj., etc.

This extremely variable form has received so many different names that it hardly pays to enumerate them. It is one of the commonest and most widely spread ciliates known, although at Woods Hole I was surprised to see it so rarely. It is the type species of the genus and needs no further description. The specimens observed at Woods Hole had numerous contractile vacuoles and were 42 to 45 mu long and from 28 to 32 mu wide.



Genus DYSTERIA Huxley '57.

(Cl. et Lach. '58; Entz '84; Moebius '88; Shevyakov '96.)

Small forms, firm in outline, and colorless or slightly colored. The body is somewhat clam-shaped, flattened, slightly curved or straight on the right side, the other more convex. The true ventral side is only a narrow strip along the right and anterior edge of the body, the apparent ventral side being a fold of the very large dorsal surface which comes around ventrally, forming a valved structure somewhat analogous to a clam shell. Cilia are limited to the outer edge of the small ventral surface, which also bears a peculiar spine at the posterior end. Behind this spine are larger cilia. The mouth opening lies in the anterior widened portion of the ventral surface and is connected with a smooth tubular pharynx. The right half of the dorsal side, i.e., the apparent dorsal side, is arched and bears longitudinal ridges. Two to four contractile vacuoles are placed on the ventral side. The macronucleus is usually dorsal, elliptical, and cleft, with one micronucleus attached. Fresh and salt water.

Dysteria lanceolata Cl. et Lach. Fig. 36.

Synonym: Cypridium lanceolatum Kent '81.

Outline of the flattened body ovoid; body consists of two valve-like portions; the edge of the right valve is nearly straight, that of the left valve more or less sinuous; anteriorly it is cut away, obliquely and posteriorly it has a deep indentation in which the seizing spine rests. The cilia are confined to the ventral surface, here reaching, however, from the anterior dorsal extremity to below the posterior indentation. Posteriorly the cilia become larger, corresponding to the larger cirri of D. armata, which are posterior to the spine. The mouth lies between the two valves and is surrounded by a long and smooth buccal armature which passes downward and backward to the left a distance equal to about half the entire body length. The macronucleus is situated in the dorsal region in the central part of the body. There are two contractile vacuoles, one behind the center of the buccal armature, the other near the inner end of this organ. Movement is in circles, the animal moving around quite rapidly when not attached by its posterior process. It is colorless and measures 45 mu in length by 27 mu in width. Claparede & Lachmann and Shevyakov describe it as 70 mu long.



KEY TO MARINE GENERA OF CHILIFERIDAE.

Diagnostic characters: Mouth never lies behind the middle of the body; the oesophagus is but slightly developed. The undulating membranes are placed either on the edge of the mouth or in the oesophagus. A peristomial depression leading to the mouth is absent or very slightly indicated.

1. Mouth in the anterior half, Genus *Frontonia undulating membrane on left edge only; right edge continued in a long ventral furrow

2. Two undulating membranes; mouth Genus *Colpidium central; no caudal bristles

3. Two undulating membranes; caudal Genus *Uronema bristle

Genus FRONTONIA Ehr. (Cl. & Lach. '58?).

(Ehrenberg, subgenus of Bursaria '38; Claparede & Lachmann '58; Buetschli '88; Shevyakov '96.)

Form elongate and cylindrical, or often flattened dorso-ventrally, with round or pointed ends. It is usually plastic and contractile. Cilia are evenly distributed about the body and are similar in length. The large, open mouth lies on the anterior half of the ventral surface, and is elongate and oval in outline. On its left edge is a well-defined membrane which stretches across to the right side of the mouth. On the right edge is a small, longitudinally striped tract which is free from trichocysts and smooth in appearance. This tract is continued posteriorly in a long furrow, which in some cases reaches the posterior end of the animal. A few rows of cilia in this furrow vibrate differently from the others and give the effect of a membrane (Buetschli). The oesophagus is extremely short and hard to make out. The body is usually covered uniformly with trichocysts, often of considerable size. There are 1 or 2 vacuoles with long canals radiating throughout the endoplasm. The macronucleus is oval and centrally placed. Micronuclei vary from one to many. An anal opening is placed at the end of the long ventral furrow. The plasm is colorless or green by the presence of Zoochlorella, or colored brown or black by pigments. In these cases there is a considerable pigment mass on the anterior end. Movement is regular, forward, and combined with rotation. Food consists of foreign objects, diatoms, other protozoa and the like. Fresh and salt water.

Frontonia leucas Ehr. Fig. 37.

Synonyms: Frontonia vernalis Ehr. '38; Bursaria leucas Allman '55, Carter '56; Panophrys leucas Duj. '41, Stein '67; Panophrys vernalis Dujardin '41, Stein '67; P. chrysalis Duj. '41, Fromentel '74; Cyrtostomum leucas Stein '67, Kent '81.

Form ovoid, elongate, occasionally a little flattened dorso-ventrally. Mouth in the anterior third of the body. The left edge of the mouth carries a distinct undulating membrane; the right edge is plain, longitudinally striated and bears cilia. It is slightly depressed and the depression is carried posteriorly in the form of a shallow furrow which reaches to the posterior end. The contractile vacuole is on the left side, the spheroidal nucleus on the right side of the furrow. The body is uniformly covered with fine cilia, and the periphery is uniformly studded with large trichocysts, except along the furrow. Food consists of dinoflagellates and other small forms. Color dark brown to black.

Length 330 mu; width 200 mu.

This form differs considerably from the fresh-water Frontonia leucas as described by Schewiakoff '89, especially in the extreme length of the peristomial furrow, in the position of the nucleus and contractile vacuole, and in the nature of the water canals. These in the Woods Hole form are very irregular in size and very much branched, not uniform as in Lieberkuehn's (see Buetschli) figure of Frontonia leucas, nor radiating as in Schewiakoff's description. This may be the same species as Frontonia marina, of Fabre-Domergue '91, whose description and figure I have not seen.



Genus COLPIDIUM Stein '60

(Buetschli '88; Maupas '83.)

The general form is oval, slightly compressed laterally with the dorsal side strongly arched. The ventral side is slightly incurved. The anterior end is somewhat smaller than the posterior end, which is broadly rounded. The mouth is placed some distance from the anterior end in an oral depression and opens into a tubular oesophagus. There are usually two undulating membranes which do not extend beyond the mouth borders. The right undulating membrane extends down into the oesophagus and appears to be attached to the walls of the latter. The body stripes in front of the mouth are twisted to the left. The anus is terminal and the contractile vacuole may be terminal or situated forwards in the dorsal region. The macronucleus is spherical and has one micronucleus attached. Food consists mainly of bacteria. Movement rapid, but interrupted.

Fresh and salt water, common in infusions.

Colpidium colpoda Ehr., sp. Fig. 38.

Synonyms: Colpidium cucullus Kent '81; C. striatus Stokes '85; Kolpoda cucullus Duj. '41; Paramoecium colpoda Ehr. '38, Quennerstedt '67; Plagyiopyla nasula Kent '81, G. & R. '86; Glaucoma pyriformis G. & R. '86; Tillina campyla Stokes '85, '88.

The body is oval, somewhat larger posteriorly, and a little compressed dorso-ventrally. The anterior end is twisted a little from the right to the left (more evident in fresh-water forms), and leans somewhat toward the ventral side. Under this portion, on the ventral side, lies the mouth in a large depression just above the middle of the body. The entire body is covered with uniform and delicate cilia, which are placed in longitudinal rows. These rows are almost straight on the dorsal side, but bend on the ventral surface, following the contour of the twisted anterior portion. The endoplasm is finely granular; the oesophagus leading into it is very distinct. Schewiakoff ('89) describes two membranes, an inner and an outer; Maupas ('83) describes them as right and left. In the present species I was able to make out only one. The macronucleus is central, spherical in form, and bears a single minute micronucleus. The contractile vacuole is posterior and dorsal to the long axis of the body. The anus is ventral to this axis and also posterior. Length 45 mu, width 20 mu. Common.

This marine variety is much smaller than the fresh-water form and the form differs in a number of respects, viz, in the anterior torsion and in the structure of the mouth. These may be, however, only individual variations of a widely spread species, and I believe it is perfectly safe to describe this as Colpidium colpoda.



Genus URONEMA Duj. '41.

(Quennerstedt '69; Cohn '66; Kent '81; Buetschli '81; Schewiakoff '89; Shevyakov '96.)

Minute forms; colorless and constant in body form. The form is oval, slightly compressed on the ventral side, while the dorsal side is distinctly arched. The membrane is distinctly marked by rather widely separated striae. These occasionally have a spiral course about the body; in all cases they can be easily counted. The mouth is large and placed near the center of the ventral surface. It is sometimes approached by a very shallow depression or peristome from the anterior end, and marked by two rows of cilia. An undulating membrane extends down the mouth. Oesophagus absent. A long, stiff bristle extends outwards from the posterior end. The contractile vacuole is terminal or subterminal and near the anal opening. The macronucleus is spherical, centrally placed, and with one micronucleus closely applied. Movement is rapid and usual forwards in a straight line, often found resting, however, with outstretched cilia in contact with some foreign body. Food mainly bacteria. Fresh and saltwater, usually in decomposing vegetable substances.

Uronema marina Duj. Fig. 39.

Synonyms: Enchelys triquetra Dujardin; E. corrugata Duj.; Cryptochilum griseolum Maupas '83; Philaster digitiformis Fabre-Domergue '85.

Small animals with ellipsoidal form and about twice as long as broad. The mouth lies in the upper half of the body and bears a well-developed undulating membrane upon its left edge. The membrane is longitudinally striped and covered with long and vibratile cilia. The right edge of the mouth bears cilia which are about the same in size as the body cilia, but are more closely inserted (Schewiakoff). The most characteristic feature is the long caudal bristle, which is extremely delicate and about two-thirds the length of the body. Schewiakoff thinks this bristle has a sensory function. I could not make this out, for although other protozoa ran against this bristle, often bending it well over to one side, the animal showed no sign of irritability but lay quiescent. A spherical macronucleus with attached micronucleus lies in the center of the body. The contractile vacuole is posterior in front of the bristle. The macronucleus was found to be double, as though just divided, in a large percentage of cases. This may be a precocious division of the nucleus long before signs of the body division are evident. Such a phenomenon, however, is rare, the macronucleus usually dividing at a late stage of cell division. Length 30 to 50 mu; width 15 to 20 mu. Common in decomposing algae.



KEY TO MARINE GENERA OF PLEURONEMIDAE.

Diagnostic characters: The mouth is at the end of a long peristome running along the ventral side; the body is dorso-ventrally or laterally compressed. The entire left edge of the peristome is provided with an undulating membrane which occasionally runs around the posterior end of the peristome to form a "pocket" leading to the mouth. The right edge of the peristome is provided with a less-developed membrane. There may or may not be a well-developed pharynx.

Body small; not produced into Genus *Pleuronema neck-like elongation

Body medium-sized; anterior end Genus *Lembus produced into neck-like elongation

* Presence at Woods Hole indicated by asterisk.

Genus PLEURONEMA Dujardin '41.

(Perty '52; Clap. & Lach. '58; Stein '59, vol. I; Quennerstedt '67; Kent '81; Buetschli '88; Schewiakoff '89; Shevyakov '96.)

Small to medium-sized ciliates, with an unchanging form. They are somewhat lens-shape and laterally compressed, the two surfaces about equally arched. The ventral surface is nearly straight or but slightly arched; the dorsal is quite convex. The anterior and posterior extremities are equally rounded. The peristome begins as a small depression, but becomes larger until it takes in nearly all of the ventral surface. The depression becomes much deeper at about the center of the body, and is especially marked on the left side of the peristome. In this deeper portion is the mouth, with an almost imperceptible oesophagus. Upon the left edge of the peristome is a high, undulating membrane, sail-like in appearance when extended. This may stretch around the posterior edge of the peristome and upon the right aide, thus forming a pocket by means of which the food particles are directed into the mouth. The rest of the right edge of the peristome is occupied by closely approximated powerful cilia (Buetschli) or a second undulating membrane (Stein). The body cilia are relatively long. Trichocysts and caudal bristles may be present. The contractile vacuole is subterminal and dorsal; it is questionable whether there are canals leading to it. A round macronucleus with one micronucleus is in the anterior half of the body. The anus is terminal. Food is chiefly bacteria. Movement combines springing with swimming and rotation. Fresh and salt water.

Pleuronema chrysalis Ehr., sp. Fig. 40.

Synonyms: Pleuronema crassa Dujardin '41; P. marina Duj. '41; Fabre-Domergue '85; P. coronata Kent '81; Paramoecium chrysalis Ehr. '38; Lembadion orale G. & R. '88; Histiobalantium agile Stokes '85, '88.

The body is ovoid, slightly flattened, rounded at both ends, the anterior end sharper than the posterior. The ventral surface is almost entirely taken up by a peristome which extends from the anterior end posteriorly three-quarters of the body length. The posterior end of the peristome is straight, the left curved, following the depressed portion. The body is covered with fine cilia in longitudinal lines, except on the peristome. The mouth is small and situated in the hollow of the peristome near the left border. On the left peristome edge is a large undulating membrane. It begins near the anterior end of the body and increases in height posteriorly following the peristome edge around on the right side. This posterior bend of the membrane causes the appearance of a full sail, so often seen. It can be entirely withdrawn and folded together in the peristome. On the right edge of the peristome are large, powerful cilia. The contractile vacuole is central and dorsal; the macronucleus is in the anterior half of the body, with one attached micronucleus. Food consists of bacteria. Not very common. Fresh and salt water. It often remains quiet, with membrane and cilia outstretched, as though dead, but suddenly gives a spring and is gone.



Pleuronema setigera, n. sp. Fig. 41.

Body colorless, elongate, and with the general form of a cucumber, the posterior end being somewhat pointed. The mouth and relatively small peristome are situated in the lower third of the body. The peristome begins as a shallow furrow at the center of the ventral surface and dips sharply into the buccal depression, which is deep and turned toward the posterior end. The left edge of the peristome bears a high undulating membrane, which extends anteriorly only as far as the center of the body; posteriorly it passes around to the right edge of the peristome, thus forming the characteristic membranous pocket. Inside the oral depression is a second undulating membrane, running down to the mouth. This is small and without an oesophagus. The body is clothed with long setose cilia which are frequently fully outstretched when the animal is resting, a slight tremor of the large membrane alone indicating vitality. Posteriorly these appendages are drawn out into long filiform setae, the number varying in different individuals from three to nine or ten. These are extremely fine and difficult to see without a high power (e.g. 1/12 oil) and careful focussing of the substage condensor. Like P. chrysalis, the resting periods are terminated by sudden springs, otherwise the movements are steady and forward. The macronucleus is central, and the contractile vacuole posterior and terminal. Length 45 mu to 50 mu; greatest diameter 17 mu. In decaying algae.

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