a. Peristome drawn out into Family _Spirochonidæ_
funnel-like process; parasitic
b. Adoral zone and circlet of cilia Family _Lichnophoridæ_
at opposite end. Adoral zone (one genus, *_Lichnophora_)
left-wound. Parasitic.
c. Adoral zone a left-wound spiral. Family _Vorticellidæ_
Attached or unattached forms.
* Presence at Woods Hole indicated by asterisk.
Genus LICHNOPHORA Claparède '67.
(Gruber '84; Fabre-Domergue '88; Bütschli '88; Wallengren '94;
Stevens 1901.)
Small or medium-sized colorless animals, extremely elastic and
flexible. The anterior part, bearing the adoral zone, is round or
oval in ventral view, and has a flat ventral and a highly arched
dorsal surface. The posterior end of the animal is reduced to a
stalk-like structure which is broadened at the extremity to form
a sucking disk. The surface of this disk and the surface of the
peristome may be brought into the same plane by the characteristic
bending of the stalk portion. A ciliated girdle is placed at the
edge of the sucking disk. A well-developed adoral zone incloses the
peristome; it begins at the mouth on the left side and includes
nearly all of the peristome in its left-wound spiral, the extremity
approaching closely the end near the mouth. The macronucleus is a
long-beaded structure, or it may be in several parts connected by
strands (Gruber). The contractile vacuole is on the left side in the
region of the mouth. Salt water.
Lichnophora macfarlandi Stevens. Fig. 58.
The body is elongate; oral disk variable in form, attachment disk
clearly defined and constant. The stalk is very contractile and
elastic, constantly changing in shape. When detached from the host
the animal moves with a very irregular and indefinite motion. When
attached it moves freely over the surface on its pedal disk. The
latter is bordered by four membranes composed of cilia. A distinct
axial fiber extends from the pedal disc to the peristome and gives
off a number of branches. This fiber is analogous to the myonemes
in _Vorticella_. An indistinct longitudinal furrow can be made out
occasionally. The nucleus is in 5 or 6 separate pieces, of which 1
is found in the pedal disk and 1 or 2 in the neck.
On the egg capsules of _Crepidula plana_; also reported upon annelids
at Woods Hole.
Length 60µ from disk to extremity of the peristomial disk.
[Illustration: Fig. 58.--_Lichnophora macfarlandi_.]
This form does not agree in all respects with Stevens's species, but
the agreement is so close in other respects that I believe it can be
safely identified as _L. macfarlandi_. The mode of life is different,
and the macronucleus is different, there being from 25 to 30
fragments in Stevens's form and only 5 or 6 in the present one. There
is, however, the same evidence of chain formation in both of them.
The length of the oral cilia in Stevens's form is 18µ in fixed and
30µ in living forms. In the Woods Hole form the cilia are not more
than half that length.