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.
[Illustration: Fig. 28.--_Lacrymaria lagenula_.]
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.
[Illustration: Fig. 29.--_Lacrymaria coronata_.]
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.
[Illustration: Fig. 30.--_Trachelocerca phoenicopterus_.]
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.
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 heliozoön.
Length 35µ; greatest width 30µ. 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_.
[Illustration: Fig. 31.--Side and top views of _Mesodinium cinctum_.]
Genus TIARINA R. S. Bergh '79.
(Claparède & 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; Möbius '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_.