Part 10 (2/2)
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 pa.s.s 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; Butschli '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 ma.s.s, 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 a.n.u.s 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 Butschli 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 ca.n.a.l whose swellings are frequently taken for additional contractile vesicles (Butschli); in the marine form described below the ca.n.a.l 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; greatest width a.s.sumed on contraction 85; when normal about 50.
[Ill.u.s.tration: Fig. 32.--_Loxophyllum setigerum_, var. _armatum_. a, b, c, ventral, dorsal, and lateral aspects.]
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