“Myriochele heeri, Malmgren (P1. XXVA. fig. 14, a, b, c).
Myriochele heeri, Malmgren, Annulata Polychæta, p. 102, Tab. vii. fig. 37.
Habitat.—Dredged at Station 20 (to the east of the Antilles or Caribbee Islands), March 12, 1873 ; lat. 18° 56' N., long. 59° 35' W. ; depth, 2975 fathoms; bottom temperature 36°·0, surface temperature 75°·0 ; sea-bottom, red clay.
After the dredge-line was veered to 4000 fathoms, nearly five miles, it was brought up full of red mud, Sir Wyville Thomson tells us, and having entangled about the mouth and imbedded in the mud many of the tubes of this species.
Sir Wyville Thomson reports2 that "the tubes with their contents were handed over to Dr. v. Willemoes-Suhm, who found the worms to belong to the family Ammoeharidæ (Claparède and Malmgren), closely allied to the Maldania or Clymenidæ, all of which build tubes of sand or mud. The largest specimens dredged are 120 mm. in length by 2 mm. in width. The head is rounded, with a lateral mouth. There is no trace of cephalic branchiæ. The worm consists of only from seventeen to twenty segments ; the first few of these are very long, about 17 mm., while those of the posterior portion of the body are only 5 mm. in length. The segments are not divided from one another ; but the tori uncinigeri, which are occupied by the hair-like set, and the elevations bearing small uncini, indicate the beginning of a new segment. The number of small hooks on the tori uncinigeri is very large. . . . There is a pair of glands in each of the segments, from the second to the seventh. The position and structure of these has been described by Claparède in the genus Owenia, in which, however, there are only four pairs. Most of the specimens examined are females, and contain many eggs.
"There is no doubt that this Annelid is closely allied to the genus Owenia, but it differs from it in the absence of cephalic branchiæ. Malmgren has, however, already proposed the name of Myriochele for a form in which this absence of branchiæ occurs. The description of the northern form, on which Malmgren's genus is founded, is not at hand, so that it is impossible in the meantime to determine whether the two forms are identical or specifically distinct."
The foregoing account by the lamented Dr. v. Willemoes-Suhm is the more valuable because the condition of the preparation is unsatisfactory. All the larger tubes had been slit and their contents removed ; and, as the animals are quite pulpy and devoid of either head or tail, very little information can be gleaned from them. Moreover, careful search revealed no trace of either extremity of the body in the small fragmentary tubes, and none amongst the microscopic slides.
The hooks occur on somewhat shorter pads than in Owenia, and the crown is bifid (Pl. XXVA. figs. 14, a, b, c). Malmgren's figure of the hook, which, with his description of Myriochele heeri, was published in 1867,1 is nearly, but not quite, in accordance with the structure of that in the present form, for the inferior fang or tooth in his figure is too short, but this is probably due to position. In certain views, indeed, only one fang is visible, so that it is probable they arise nearly on a level, or are truly bifid.
The hooks in the genus Myriochele conform to the foregoing type, though Dr. Hansen describes and figures a remarkable exception in the collection made during the Norwegian North Atlantic expedition. In this species (Myriochele Hansen2) the bifid terminal region is separately articulated to the shaft. This is unusual in the group.
The bristles present toward the tip very fine lateral serrations, no distinct spikes being noticeable in the preparation.
The food of the Annelid consists of the reddish mud amongst which it dwells. Sir Wyville terms this red clay—mud containing a number of gritty particles, though on the whole comparatively smooth, and with scarcely a trace of carbonate of lime. A minute examination of the contents of the alimentary canal shows that the sand-grains are rare and small, and that a few Diatoms (chiefly circular) and occasionally a beautifully reticulated Radiolarian are present.
Further insight, however, is obtained into the nature of the sea-bottom by an investigation of the tubes, which are composed of a somewhat tough, pale, chitinous secretion internally, and externally coated with sand-grains and other structures. Conspicuous amongst the latter are numerous globular or rarely moniliform arenaceous Foraminifera of an ochreous colour, while the microscope shows a large number of more minute arenaceous forms, some apparently divided into chambers, innumerable fragments of sponge-spicules, curious circular stellate disks, and tips of peculiar spines (hollow at the base). Few or no Diatoms are visible on the tubes.
There can be no doubt, therefore, that living arenaceous Foraminifera abound on this sea-bottom of reddish clay, and with the Diatoms and Radiolarians contribute to the support of such higher forms as Myriochele.”
(McIntosh, 1885)