Genus ZOOTHAMNIUM (Bory de St. Vincent 1824) Stein '38, '54.
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Fig. 61.— Zoothamnium elegans. [ ENLARGE ] |
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Colorless and highly contractile forms growing in small or large colonies. The form and structure of the individuals is not different from [Vorticella]. The colonies are usually richly branched upon the dichotomous plan and the entire colony is contractile. The main character is that with each division of the individual the stalk also divides, each daughter cell getting one-half of the parent stem. The stems therefore remain in communication, so that a simultaneous contraction results, and the colony as a whole is withdrawn. In some species so-called macrogonidia, or larger sexual individuals, are developed alongside the usual ones. Fresh and salt water.
Zoothamnium elegans D'Udekem '64? Fig. 61.
The bodies are variable—peristomial border widely dilated, tapering and attenuate posteriorly. The pedicle is slender, smooth, and transparent, and branches sparsely at its distal extremity. There are but few zooids (3 to 4). The ciliary disk projects conspicuously beyond the peristomial border. The pharyngeal cleft is very distinct and extends beyond center of body. Length of body 80µ.
Genus COTHURNIA (Ehr. '31) Clap. & Lach. '58.
Colorless forms of medium size-in some cases they may be green by Zoochlorella. The general structure is similar to that of [Vorticella], but the individuals are elongate and occupy houses. The macronucleus is invariably long and band-form. The distinguishing character is the colorless or brownish lorica of quite variable form but always attached. These houses may be finger-formed, with widened center, or widened mouth, or constricted mouth, and the like. Ring-formed swellings are frequently developed. Sometimes the mouth becomes twisted and the lorica is therefore bilateral. The houses are attached either directly to some foreign object or by means of a short stalk. The animals are similarly fastened to the lorica, sometimes directly, sometimes by means of a short stalk. When they contract they draw back to the bottom of the lorica; when expanded they usually stretch out of the mouth opening. In some forms there is an operculum, by means of which the opening of the shell can be closed when the animal is retracted. Fresh and salt water.
The number of species of Cothurnia has become so great that the difficulty in placing forms is almost sufficient to discourage the systematist; as Bütschli well remarks, the variations in the theca have been made the basis of new species so many times that the genus is almost as confused as Difflugia among the rhizopods or Campanularia among the hydroids. The length of cup, of stalk, the presence of annulations on stalk or cup, etc., have given rise to many specific names, the majority of which I believe can be discarded. According to such differentials the same branch of an alga holding a hundred specimens of [Cothurnia crystallina] yield 10 or 12 species, whereas they are merely growth stages of one and the same form.
Cothurnia crystallina Ehr. Fig. 62.
Synonyms: Vaginicolla crystallina Ehr., Perty, Eichwald; V. grandis Perty; V. pedunculata Eichwald; Cothurnia crystallina Claparède & Lachmann, D'Udek.; C. gigantea D'Udek; C. maritima, C. crystallina Cohn; C. grandis Meresch.
The form of the cup shows the greatest differences; sometimes it is cylindrical, sometimes elongate thimble-shape, sometimes pouch-shape, corrugated or smooth on the sides, and wavy or smooth on border. Frequently the basal part becomes stalk-like, but this is very short. When present, the stalk may or may not have a knob-like swelling. The animal within the cup may or may not be borne on a stalk, and this stalk may or may not be knobbed. The cups are colorless or brown. The animal is very contractile and may stretch half its length out of the cup or retract well into it. There is no operculum. The length of the cup varies from 70µ to 200µ (C. gigantea; Vag. grandis, etc.). From Entz.
There is nothing to add to Entz's characterization of this species, which is found both in fresh and salt water. The variability of the cup and stalk is quite noticeable in the Woods Hole forms.
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Fig. 62.—Cothurnia crystallina. [ ENLARGE ] |
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Cothurnia imberbis Ehrenberg, var. curvula Entz. Fig. 63.
Synonyms: C. imberbis Kent et al.; C. curvula Entz; C. socialis Gruber?
The lorica is swollen posteriorly, narrowest at the oral margin, bent on its axis and is supported on a short stalk. It is perfectly smooth and without annulations. The animal itself has no definite stalk. When fully expanded the animal emerges but slightly from the margin of the cup. Fresh and salt water. On red algæ. Dimensions of Woods Hole form: Cup 50 to 55µ long; greatest diameter 22µ; length of stalk 4 to 5µ.
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Fig. 63.—Cothurnia imberbis. [ ENLARGE ] |
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Cothurnia nodosa Claparède & Lachmann. Fig. 64.
| A. | Smooth cup.—Cothurnia maritima Ehr., Eichwald, Stein, Kent. |
| B. | Cross-ringed cup.—C. pupa Eichwald, Stein, Cohn; C. nodosa Cl & L.; V. crystallina Entz '78; C. pontica Meresch., Kent; C. cohnii and pupa Kent; C. longipes Kellicott '94. |
The cup is elongated, swollen centrally, tapering at oral end and conical at base or rounded. Oral opening either circular or elliptical. Cross rings may or may not be present, and the cup is either smooth or annulate. Length of cup 70µ to 80µ. The stalk which supports the cup is extremely variable in length. The animal is borne upon a stalk of variable length within the cup.
Entz states that the many variations which this species exhibits run into each other so gradually that he does not believe it wise to separate them. The Woods Hole forms which I found on algæ of various kinds were nearly of a size, and did not vary much from the one figured. Kellicott '94 described a Cothurnia from Woods Hole under the name of C. longipes, which I believe is only a long-stemmed variety of C. nodosa. My form has the following dimensions: Cup 75µ; cup stalk 38µ; animal stalk 14µ.
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Fig. 64.—Cothurnia nodosa. [ ENLARGE ] |
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| Key to families of Suctoria. | ||
| a. | Unattached forms; ventral cilia present; one suctorial tentacle | Hypocomidæ |
| b. | Attached forms; thecate and athecate tentacles simple, one or two in number | Urnulidæ |
| c. | Thecate; posterior end of cup drawn out into stalk; walls perforated for exit of tentacles | Metacinetidæ |
| d. | Stalked or unstalked; globular; tentacles of different kinds, some knobbed, others pointed | Podophryidæ (2 genera *[Ephelota], *[Podophrya)] |
| e. | Naked or thecate; stalked or not; tentacles numerous, usually knobbed and all alike | Acinetidæ |
| f. | Naked; athecate; tentacles numerous, all alike, knobbed and grouped in tufts. They may be simple or branched. | Dendrosomidæ |
| g. | Sessile forms resting on basal surface or on a portion raised like a stalk; tentacles many; short and knobbed; distributed on apical surface or localized on branched arms | Dendrocometidæ |
| h. | Stalked or sessile; tentacles long, rarely knobbed, supported on proboscis-like processes | Ophryodendridæ |
| * Presence at Woods Hole indicated by asterisk. | ||