PLATE 22.
ALCIPPE LAMPAS.
- Fig. 1, Entire animal (female and two males) greatly magnified, being
an unusually symmetrical specimen, partly copied from Mr. Hancock’s Plate (‘Annal. and Mag. Nat. Hist.’ ser. 2, vol. 4, Pl. VIII). H, horny disc and surface of attachment; a, projection formed by the lower end of the lip of the orifice leading into the sack; m, a pair of males, of their proper proportional sizes, attached in their ordinary position. - 2, Entire animal, much distorted.
- 3, Small portion of a Fusus (copied from Mr. Hancock’s Plate), perforated by the Alcippe; the darker curved marks are the slit-like orifices, leading into the chambers; the latter are seen from the outside, owing to a difference of tint in the shell of the mollusc where worn thin over the chambers; they are represented by the fan-shaped shaded patches.
- 4, One of the orifices, leading into a chamber, much enlarged; a, the curved narrow end, which was open and used when the animal was young, but has since been closed externally by sand or shelly matter, and internally by the upward prolongation of the horny disc; b, rims of an inorganic, calcareous deposit, by which the narrow end of the orifice is kept of the due degree of narrowness.
- 5, Longitudinal section through the outer envelopes of a very symmetrical specimen, giving a lateral view of the included body.
- a, point at the lower end of the orifice of the capitulum, leading into the sack.
- b, end of adductor muscle.
- c, mass of branching ovarian cæca, much developed and protuberant on the under side.
- d, basal point of the quasi-peduncle, projecting beyond the level of the horny disc (H, H).
- e, sack or open cavity: of the two branchiæ or ovigerous fræna, one has been removed with the outer envelopes, the other is hidden by the projection caused by the medial distended mass of the ovarian cæca.
- e′, lateral line of junction of the body to the outer envelopes; which latter have been here cut through in removing the near half of the capitulum and peduncle.
- f, notch separating the capitulum or upper part from the peduncle or lower part of the external covering: this notch varies much in depth.
- g, the end (homologically the carinal end), of the orifice leading into the sack, where the cutting of the outer envelopes has commenced.
- H H, horny disc, cut longitudinally down the middle.
- h, first pair of cirri.
- i, prosoma (homologically the second thoracic segment).
- k, the thoracic segment, which would have borne the second pair of cirri, had such existed.
- l, thoracic segment, which should have borne the third pair.
- m, thoracic segment, which should have borne the fourth pair.
- n, thoracic segment, very small, bearing the fifth pair of cirri.
- n′, fifth pair of cirri, only one cirrus on the near side being represented.
- o′, sixth cirrus, borne on the last thoracic segment, too small to be shown.
- p, caudal appendages.
- 6, one side or lip of the orifice leading into the sack, greatly enlarged, seen on the inner side, formed of an inner membrane, b, (on which the long hairs and an S-like band of spines, too fine to be plainly represented, are placed), and an outer membrane c, studded with short, thick spines, the corium between these two membranes having been removed; a, projection at lower end of orifice; g, upper end of orifice, showing the point where the corresponding side or lip of the orifice has been cut away.
- 7, small portion of the external membrane, showing the star-shaped, hard, projecting points of chitine; but they are here placed too closely together.
- 8, front view of mouth, greatly enlarged, and with the gnathites rather unnaturally separated from each other; h, the first pair of cirri; in front, the outer maxillæ appear like a bilobed lower lip; the inner maxillæ (with their singular membranous swelling behind, see fig. 15), can be distinguished by their long apodemes or horny imbedded bars; behind are seen the one-toothed mandibles, with a swelling behind, probably representing the palpi; all above the mandibles consists of the immensely developed labrum, with the foreshortened ends of the row of long hairs on each side; the fold, or articulation, separating the mouth and body, is seen crossing above the basal ends of the apodemes of the maxillæ.
- 9, Lateral view of the coriaceous button or cushion, c′, on one corner of the upper segment, b, of the pedicel of the sixth cirrus; c, being the lower part of the lower segment of the one ramus of this same cirrus: the hooked hairs are rather distorted.
- 10, The same, viewed from the inner side.
- 11, Lateral view of the labrum, with the mandible, m, attached to it, which latter, from overhanging the œsophagus, shows the position of the mouth; h h, is the first cirrus on the near side; b, is the medial crest of labrum, on the side of which extends a long row of hairs; a a a, delicate membrane of side of body, attached to the margins of the labrum.
- 12, Diagram showing the probable manner in which the young Alcippe bores into the shell of molluscs; a, pupa attached by the antennæ to the outer surface of shell; b, outline of young Alcippe soon after its metamorphosis; the anterior or lower end has increased considerably in length, so as to project beyond the point whence the antennæ rise, and it has now penetrated the shell, being attached to the roof of its incipient chamber by its horny disc, represented by a thick black line; c, is the Alcippe after further growth, when it has succeeded in burying itself; the horny disc is now attached parallel to the surface of the shell; the horny disc of its former state, now lines the narrow end of the slit-like orifice leading into the shelly chamber: the above changes in position are supposed to have been effected quite gradually. The diagram, c, I may add, represents the position of the Alcippe for the rest of its life, the chamber being added to at both ends, sides, and bottom.
- 13, Lateral view of the posterior extremity of the thorax, much enlarged, with its articulated appendages represented only on one side; the four thoracic segments, l, m, n, o, correspond with those represented in fig. 5. In one monstrous specimen, segment n, bore a single cirrus. The posterior thoracic segment, o, bearing the sixth pair of cirri, o′, is very small and obscure, and can be seen only by separating the fifth and sixth pairs of cirri; or by longitudinally bisecting the thorax, and viewing the inner side; n′, fifth cirrus; a, lower segment, b, upper segment of pedicel; c, lower, and d, upper segment of the one ramus, the other ramus being represented by the coriaceous boss c′; o′, sixth cirrus, with similar segments; p, caudal appendage.
- 14, First cirrus.
- 15, Maxillæ, with the lower end of the apodeme cut off, showing the curious membranous swelling on the side towards the mandible.