Genus COLPIDIUM Stein '60
(Bütschli '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 œsophagus. There are usually two undulating membranes which do not extend beyond the mouth borders. The right undulating membrane extends down into the œsophagus 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; Paramœcium colpoda Ehr. '38, Quennerstedt '67; Plagyiopyla nasula Kent '81, G. & R. '86; Glaucoma pyriformis G. & R. '86; Tillina campyla Stokes '85, '88.
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Fig. 38.— Colpidium colpoda. [ ENLARGE ] |
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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 œsophagus 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 45µ, width 20µ. 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.