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species they are so small as almost to escape notice; but not so are . the cirri. These are two in number on the feet which possess them. The inferior is very small in general, except on the first segment of the body, but the superior is long, and subulate in form. These appendages are always attached to the feet, and in many species of the group present good characters for distinguishing them. The feet themselves are divided into two branches, very distinct froin each other, one called the dorsal, the other the ventral (Plate II., Figs. 23 and 24). On each of these, in the very substance of the foot, there is always present one spine (acicula), and one or two bundles of bristles, or setæ, spring from each of the branches into which the foot is divided. The setæ of the dorsal branch are sometimes very complicated in structure (Plate II., Figs. 15, 16, and 17); those of the ventral are simple, or forked.
The sea-mouse (Mus marinus of Linnæus), or Aphrodita aculeata, is a common worm on our coasts, and is frequently thrown ashore on our sands after a high tide. Of all the Annelides known to us, in Great Britain at least, the sea-mouse is the most brilliant in the iridescent colours of its bristles. “Reflecting the sunbeams from the depths of the sea,” says Linnæus, “it exhibits as vivid colours as the peacock itself spreading its jewelled train.” It frequently occurs ten inches in length, and is of an oval shape. The back of the animal is of a dull colour, and the scales are completely concealed by a matted covering of fine bristles, closely interwoven, so as to resemble a kind of felt. The beautiful iridescent hues mentioned above, and at page 104, belong entirely to the immense number of long hairs, or flexible setæ, with which the sides are clothed (Plate II., Fig. 13).
It creeps at a slow pace, and, as we are informed by Dr. Johnston, is a favourite prey of the cod-fish, in whose stomach specimens, in a perfect condition, are sometimes found.
Another species, the porcupine sea-mouse (Aphrodita hystrix), also a native of our coasts, differs from this one, particularly in having none of the felty covering on the back, but displays the scales, or elytra, ranged in a double series along the whole length. We have figured this species in our Plate III., Fig. 1. It is not so large as the common sea-mouse, being only two or three inches long, nor is it so brilliant in its colours. The back is covered with large irregularly heart-shaped scales, and the sides are spinous, with golden and brown-coloured setæ. The ventral branch of the feet is large, conical in shape, and of a brownish-yellow hue. On the elytra-bearing feet we see two fasciculi of bristles. That implanted
immediately on the outside of the scales has the setæ spread out upon them, and are subulate, not denticulated, slightly curved, and of a clear brown colour, with golden reflections. The second fascicle is inserted more externally still upon a tubercular peduncle, and the bristles are long, very stout, and terminate in a lanceolate point, with the edges denticulated, the teeth curving down towards the base. These are the barbed arrow-shaped setæ described above, and represented in Plate II., Figs. 15, 16, and 17. The dorsal branch of those feet which do not possess scales or elytra (Plate II., Fig. 2-1) has a single bundle of bristles, which are less strong than those of the corresponding branch of the other feet, and instead of being barbed, are merely sharp-pointed and simple, not denticulated. The setæ of the ventral branch are the same in both feet, are less numerous, and forked at the extremity.
The porcupine sea-mouse occurs chiefly on our southern coasts, as at Weymouth, Falmouth, etc. Milne Edwards states it to occur only in the Mediterranean, and on the coast of France; but it is now known to inhabit our shores also.
Belonging to this group of Aphrodiseans, there is another set of worms with scales on their back, several species of which are found on the British shores. These belong to the genus Lepidonotus, or the scale-back worms as they are called. They differ from the Aphrodites, or sea-mice, in many respects, especially in the armature of the mouth, and the position of the elytra on the inferior part of the body. Some have the back completely covered by these scales, whilst others have it naked in the centre, and others, again, have scales only in a small portion of the body. The species which inhabit the coasts of Great Britain are a decidedly carnivorous set of animals. Dr. Johnston informs us that they prey upon living invertebrate animals, and that the stronger individuals among them do not hesitate to kill and eat the weaker of their own and allied species.
One of the most common of our British species is the roughscale-back (Lepidonotus squamatus). It varies much in size, according to the situation in which it occurs, being from one to two inches in length, and about a quarter of an inch in breadth. It occurs in most parts of our coasts. I have often found it nestling among dead shells, such as those employed in making oyster beds, and have dredged it from a depth of six to ten feet. Usually slow in its motions, it appears dull and languid ; but when disturbed, it can run with considerable speed, though it swims with difficulty. Those who have watched its motions say it retreats from the light,
quitting its haunts cautiously and timidly at night, as if dreading its enemies, or as if it were in quest of prey. In colour, it is of a uniform cinereous brown on the back, but the belly is of a pearly lustre and occasionally iridescent. In shape it is rather depressed, and is of about equal breadth at the two extremities. The back is furnished with twelve pairs of scales, each of which meets and slightly overlaps its opposite fellow in the centre, and thus covers the whole surface. They are rather large in comparison with the size of the animal, are roughened all over with minute brown granulations, and are ciliated on the outer edges. The head is completely covered by the first pair of scales; but when exposed it shows itself of a reddish hue, and exhibits four small black eyes, three (so called) antennæ, bulbous near the point, and two palpi longer than the antennæ and swollen near the apex. The cirri, attached to the feet, are white, but ornamented with a black ring a little below the sharp point in which they terminate. They originate from above the dorsal branch of every alternate foot, and under the scales. The animal has twenty-five pairs of feet, and the bristles, which spring from the two divisions (dorsal and ventral), are of a golden yellow colour. Those belonging to the dorsal branch are of two kinds, one slender, flexible, and subulate in form; the other rather stouter, gently curved, pointed, and serrulated for about half their length (Plate II., Fig. 9). Those of the ventral branch are still stouter and longer, slightly bent near the tip, and serrulated with a short series of teeth on the outer edge (Fig. 11). There are about 270 of these bristles in each segment, and as there are twentyfive pairs of feet, we thus have 7230 setæ of exquisite structure in each individual.
“These details,” says Mr. Gosse, "convey but a feeble and imperfect notion of the numerous and elaborate contrivances which are so profusely bestowed upon these mean and grovelling worms; but they show how careful is their Creator of their well being; how lavish of his mercies towards his meanest creatures.”
There is a curious species of scale-back worm occurring on our southern coasts and in Ireland. It is found also on the coast of France.
Oërsted, Johnston, and other authors limit the generic appellation Polynoe to this worm, though Milne Edwards and many others bestow the name of Polynoe on all the species of Lepidonotus alike. The worm under consideration is the scolopendra-like scale-back (Polynoe scolopendrina). It is of a linear, elongated form, and is frequently found four inches in length. The most marked difference
between the genera Lepidonotus and Polynoe (as now restricted) is, that the species belonging to the latter are very long and slender, and the hinder portion of the body is generally left uncovered by the scales, which are not so well developed as those of Lepidonotus. It is difficult, says Dr. Johnston, to describe the colouring of this fine worm.
The general hue, however, of the dorsal part of the body is, according to M. Milne Edwards, who describes it from the living worm, brownish, with a yellow band running down throughout its whole length, and having a row of brown spots, one occurring on each segment. Towards the base of the feet we see several streaks of yellowish red, and a small yellowish spot, corresponding to the rather elevated branchial tubercle. The dorsal cirri are brown, and the scales of the back of a light brownish colour, marbled with white. The feet are yellowish, and the head, when uncovered by the scales, is of a rosy tint. The scolopendralike scale-back is a timid animal, living in sheltered places, and what is curious in its history is, that it frequently forms for itself a kind of tubular case, constructed of sand and fragments of shells, agglutinated together by a mucus given off from its body, as in the case of the Terebellæ, in whose company it is generally found.
Another species of scale-back worms, belonging to a group called by Milne Edwards the Vermiform Aphrodiseans, is the Sigalion, a long, narrow worm, with numerous scales continued to the end of the body. The most remarkable difference between this genus and Lepidonotus is, that the scales and cirri occur simultaneously on the feet, instead of alternating. One species was described as British, by Dr. Johnston, in “Loudon's Magazine,” in 1833, under the name of the Boa-shaped Sigalion (Sigalion boa). This fine worm is about eight inches long, and only a quarter of an inch in breadth. The scales are about 140 in number on each side, and the feet are very numerous. These organs are divided, as in Lepidonotus, into two branches, the dorsal branch having setaceous, simple setæ, serrulate on the upper half (Plate II., Fig. 9), those of the ventral being compound and billhook-shaped (Fig. 19).
When placed in a basin of sea-water, this animal, we are informed, appears sluggish; but it burrows in loose sand with great rapidity, being enabled to do so by the play of its innumerable feet.
Family AMPHINOMACEA.—The anneloids belonging to this group differ in some essential particulars from the Aphroditacea. They
possess no scales or elytra, but have an uninterrupted series of arborescent or shrub-like branchiæ on each side of the body, attached to almost every segment, and usually not alternating with cirri. In the restricted family Amphinomidæ, there is a crest or fleshy-looking caruncle on the back of the mouth segment, which is more or less prominent and well developed. The animals are in general more vermiform than the Aphrodites or sea-mice, and the feet are divided into two branches of considerable size, placed at a little distance from each other. These large branches are each provided with a fascicle of bristles; those of the dorsal branch being in general long, numerous, capillary, and terminating in a fine point, serrated for a greater or less distance below the apex, those of the ventral being either strong and simply curved (Plate II., Fig 1) or furcate. There are no species of the genus Amphinome found in Great Britain, being natives, for the most part, of warm climates; but some of the representatives possess such lovely and bright colours, that we have been induced to figure one (Plate III., Fig. 2), Amphinome didymobranchiata.
This fine species is one of the most beautiful of them all. It is about five or six inches long, the back is generally of a light olive green colour, and the segments of the body are rather narrow, and separated from each other by a fine, nearly black line. The belly is light yellow, and the caruncle or crust, and the branchiæ on each side, are of a bright carmine. The setæ of the first are long, numerous, very fine and slender, and of a pure white. The caruncle or crest is large and fleshy, covering nearly five of the first segments. The branchiæ are peculiar in form, from which it derives its specific name. In most of the species these organs have only one branch; but in this they are divided into two, not arising from the same stem, but at a little distance from each other, both being arbuscular in form. The seta of the dorsal branch of the foot are exceedingly numerous, straight, sharp-pointed, and slightly serrated on the edge; those of the ventral branch are stouter than those of the dorsal, are rather blunt, somewhat curved at the extremity, and are toothed or bluntly serrate near the point. The cirri are rather slender, and tinged with carmine near the free extremity. This species is a native of the sea near the Island of Ascension, and Mr. Watson, who first, I believe, brought specimens to this country, informs me that they are collected there by the boatmen who sell them to the visitors to the island as objects of curiosity. They pretend that they are of a venomous nature, and are able to inflict serious wounds upon those who incautiously handle them. Mr.