A Monograph on the Sub-class Cirripedia Part 25

The _Sub-carina_ lies close under the carina, and is placed almost transversely to the longer axis of the capitulum; external surface arched and smooth, the whole having the shape of half of a cone, with the apex a little curved outwards; seen internally, it may be said to be formed of two triangular wings placed at right angles to each other; basal margin straight; in size equalling the carinal latera.

_Rostrum_, lying almost transversely to the longer axis of the capitulum, under the basal margins of the scuta; in shape (fig. 6 _a_) closely resembling the sub-carina, but about one third larger than it; larger also than either the rostral or carinal latera; seen externally, appears like a half cone; seen internally, is formed of two triangular wings (with curved edges), placed at right-angles to each other.

_Upper Latera_, internally flat, oblong, twice as long as broad; upper end square, truncated; upper half rather wider than the lower half; fully twice as large as either of the lower latera. The basal points extend below the basal margins of the scuta. The umbo is placed a little above the centre.

_Rostral Latera_, minute, scarcely exceeding one third of the size of the carinal latera, and very much less than the rostrum; they are placed transversely under the basal point of the upper latus, or rather between it and the baso-lateral angle of the scutum; basal margin, as seen internally, straight; upper margin arched; rostral angle produced; internally flat; the whole valve is very thick and solid, so that the umbo which lies at the rostral end, projects rectangularly outwards.

_Carinal Latera_, oblong, nearly quadrilateral, with the upper angle produced; placed obliquely, parallel to the lower half of the upper latera; umbo slightly prominent, seated near the apex, with three rounded ridges proceeding from it; internal surface very slightly concave.

_Peduncle and Attachment._--The peduncle is short, not equalling the capitulum in length. The whole surface is most thickly clothed with minute spines, which are not visible when the specimen is dry; I think it probable that they may sometimes all drop off before a new period of exuviation. The peduncle does not (at least in the specimens which I have examined, which were grouped in a bunch) taper at the lower end to a point; and after careful examination, I feel sure that the cement does not debouch from several successively formed orifices, as in _S.

vulgare_ and as in some Pollicipes, but only from the two original orifices in the prehensile antennae of the larva. In these latter organs, the sucking disc is hoof-like and pointed, and is narrower than the basal segment. The ultimate segment has on its inner side (supposing this segment stretched straight forwards,) a notch or step bearing at least three spines. The proportions of the different parts differ slightly from those in _S. vulgare_; but, as I shall hereafter have to give all the measurements, I do not think them worth repeating here. In the one large group of specimens examined by me, in Mr. c.u.ming's possession, all were attached symmetrically to the coralline, as in the case of _S. vulgare_, capitulum upwards, and their carinas outwards.

_Length_ of capitulum about three quarters of an inch; width about half an inch; entire length, with peduncle, a little more than one inch.

The _Mouth_ is placed far from the adductor muscle.

_Labrum_, with its basal margin much produced; upper part highly bullate, forming a rounded projection equalling the longitudinal axis of the rest of the mouth; crest without any teeth.

_Palpi_, triangular, with the two margins, thickly clothed with bristles; on each side of the mouth, near where the palpi are united to the mandibles, there is a slight, orbicular, shield-like swelling.

The _Mandibles_ (Pl. X, fig. 3) have nine or ten very unequal teeth, with the inferior angle rather broad and pectinated; of these, there are four main teeth, of which the second is always the smallest, and between the four, one or two small teeth are interpolated; so that the total number is either nine or ten, and often varies on the two sides of the same individual, as likewise does the shape of the inferior angle.

_Maxillae_, with the edge nearly half as long as that of the mandibles, supporting from seventeen to twenty pairs of spines; the upper pair is only slightly larger than the others; a part near the inferior angle projects slightly beyond the rest of the nearly straight edge. The apodeme, at its base or point of origin, is unusually broad and flat.

_Outer Maxillae_, large and triangular. The inner margin is slightly concave, and continuously covered with short spines. The outer margin is bilobed, as in _S. vulgare_, with the basal part supporting a great tuft of long bristles, of which the greater number turn outwards, and almost cover the olfactory orifices. The latter are slightly prominent, placed some way apart from each other, with the above-mentioned tufts of bristles between them. All the spines of the trophi are in some degree doubly serrated.

_Cirri._--The first pair is seated rather far from the second pair, and the prosoma being little developed, the shape of the body nearly resembles that of _S. vulgare_. The posterior cirri are elongated, very little curled, with the segments much flattened, not at all protuberant, bearing from five to seven pair of long serrated spines, with a few small spines in an exterior row; between each pair there is a very minute tuft of small bristles; the upper lateral rim of each segment is toothed with small spines; spines of the dorsal tufts, long, serrated.

_First pair_, elongated, having numerous segments, namely, seventeen, whilst the sixth pair in the same individual had only twenty-one segments; rami nearly equal; segments short, nearly cylindrical, thickly clothed with long serrated spines. The _second_ and _third_ pair are nearly equal in length; they have their anterior rami slightly thicker than their posterior rami, both being much more thickly clothed with spines, than are the three posterior pair of cirri. Pedicels, rather short, with their inner edges not forming a projection, as in _S.

vulgare_.

_Caudal Appendages_ (Pl. X, fig. 20), uni-articulate, flat, rounded at their ends and moderately long; clothed most thickly, like brushes, with very fine bristles, which latter are serrated, and are longer than the appendages themselves.

_p.e.n.i.s_, of small size, narrow, pointed, and thickly clothed with delicate hairs; in length equalling only one fourth of the sixth cirrus.

_Ovigerous Fraena_, small, semicircular; entire edge thickly covered with glands. Ovarian tubes, within the peduncle, fully developed as usual.

_Affinities._--This species differs from all the others in the absence of calcareous scales on the peduncle; but it has no other character which at all justifies its generic separation. In the shape of the scuta and carina it comes nearest to _S. vulgare_. Taking all the characters together, it is scarcely possible to say to which of the other species it is most closely allied, having close affinities with all. In the entire structure, however, of the Complemental Male, immediately to be described, this species certainly comes nearer to _S. villosum_ than to any other species. I may add, that in _S. villosum_ the latera are almost rudimentary, and therefore tend to disappear, whereas in _S.

Peronii_ it is the calcareous scales on the peduncle which have actually disappeared.

COMPLEMENTAL MALE. Pl. VI, fig. 3.

I examined, owing to the great kindness of Mr. Cunning, six dry specimens of the hermaphrodite _S. Peronii_, from Swan River, and one in spirits from another locality, in the British Museum. Out of these seven specimens, only three appeared to have had parasites attached to them, and these I infer, from reasons to be more fully given at the end of the genus, are Complemental Males. One of the three specimens, however, had two males close together. These parasites were firmly cemented to the integument of the hermaphrodite, in a fold, in a central line between the scuta, a little below (the animal being in the position in which it is figured) the adductor scutorum muscle, and therefore some way below the umbones of these valves. When the scuta are closed, the parasites, from their small size, are enclosed and protected. In every detail of structure, they are obviously pedunculated Cirripedia.

The _Capitulum_ (Pl. VI, fig. 3) has six valves; namely, a pair of scuta and of terga, a carina, and a rostrum, all united by finely-villose membrane, furnished near the orifice with some much longer and thicker spines. The capitulum is truncated in a remarkable manner, the orifice not being, as in the hermaphrodite, in the same line with the peduncle, but almost transverse to it, and therefore almost parallel to the surface of attachment. The largest specimen measured transversely, through the scuta and terga, was 30/1000ths of an inch in breadth; another was only 26/1000ths to 27/1000ths: this latter specimen, measured longitudinally, from the base of the carina to the tips of the terga, was 15/1000ths of an inch. A scutum of the largest specimen was 17/1000ths in length. The scuta and terga are broadly oval, with the primordial valves very plain at their upper ends. I may here mention, that in a central line between the scuta, I observed the _apparently_ single, minute, black eye, as in ordinary Cirripedia.

The _Carina_ is straight, triangular, and internally slightly concave; its basal margin descends far below the basal points of the terga.

The _Rostrum_ is shorter, and internally more concave than the carina: I believe it projects more abruptly outwards than is represented in the figure.

The _Peduncle_ commences some little way below the scuta: it is narrow and very short: it is finely villose: it is lined by delicate transverse striae-less muscles, within which there are the usual stronger, longitudinal muscles. The base is flat and truncated. I examined, and carefully compared, the prehensile antennae with those of the hermaphrodite, and found every part and every measurement the same. The full importance of this ident.i.ty will hereafter be more fully insisted on. The antennae are represented of their proper proportional size in fig. 3.

_Mouth._--The labrum, as in the hermaphrodite, is highly bullate, and far removed from the adductor scutorum muscle. The _Palpi_ are small and triangular, with their blunt apices clothed with a very few scattered bristles.

_Mandibles_, with only three teeth, and the lower angle minute, slightly pectinated; the first tooth is distant from the second, and larger than it. Width of the whole organ, .0021 of an inch.

_Maxillae_, bearing only a few spines, furnished with a long apodeme; beneath the upper large pair there is a notch, under which there are two spines of considerable size and a small tuft of fine bristles; width .001 of an inch, and therefore only 1/16th of the size of the same organ in the hermaphrodite: the relative sizes of the maxillae and mandibles are the same in the male and hermaphrodite.

_Outer Maxillae_ blunt, triangular, with a few thinly-scattered bristles on the inner face; those on the outside being longer.

_Cirri._--The First pair is far removed from the second; the rami are very short, barely exceeding the pedicel in length; they are formed of only four segments, each bearing a pair of spines; but on the end of the terminal segment, there are three spines, of which the central one is very long. Second pair also short. In the sixth pair there are five or six elongated segments, each bearing three pair of long spines; dorsal tufts large. The cirri are furnished with transversely-striated muscles.

The _Caudal Appendages_ exist as two very minute plates, with a few bristles at their apices.

The _p.e.n.i.s_ is not ac.u.minated, with four bristles at the end; it is short, equalling only the lower segment of the pedicel of the sixth cirrus. In the one specimen preserved in spirits, I unfortunately omitted to search for the vesiculae seminales; I cannot doubt that such existed, but it would have been important to have ascertained whether they contained spermatozoa. I made out, most distinctly, that there was no trace of ovarian tubes within the peduncle; and my a.s.sertion may be believed when I state, that I traced the two much finer and more transparent cement-ducts, from the prehensile antennae up to the body of the animal: in Lepas I have _repeatedly_ detected, with ease, the ovarian tubes within the peduncle, before the calcification of the valves had even commenced, and therefore at a much earlier period of growth than in these parasites. Consequently I am prepared to affirm, that these parasites are not females, but that, as far as can be judged, from external organs, they are exclusively males.

_Concluding Remarks._--In comparing the capitulum of the hermaphrodite with that of the complemental male (Pl. VI, figs. 6 and 3), we must be struck with the differences in their shape, in the number, relative sizes, and forms of the several valves. It should, however, be borne in mind, that the scuta and carina in the hermaphrodite at first grow exclusively downwards; so that if we remove the upper portions subsequently added, the difference in shape in these valves is not so great as it at first appears. The rostrum in the male is of much larger relative size; whilst of the upper latera there is not a trace, although in the hermaphrodite these valves are larger than the rostrum. The terga, compared with those of the hermaphrodite, differ more essentially than do the other valves; and the manner in which the primordial valves project, shows that from the first commencement of calcification, the lines of growth have followed an unusual course. The great breadth and shortness of the terga is evidently related to the shortening of the whole capitulum, and the transverse position of the orifice; and this shortening of the capitulum, no doubt, is rendered necessary for its reception and protection within the shallow furrow between the scuta of the hermaphrodite. Finally, if we compare the internal parts of the hermaphrodite and male, the differences are considerable, though partly to be accounted for by the youth of the latter: the form and position of the labrum, and the distance between the first and second pair of cirri, is the same in both; but the mandibles and maxillae differ considerably.

To put the case as I have before done, if a specimen of one of these parasites had been brought to me to cla.s.s without any information of its habits,--the downward direction of growth in all the valves, the presence of a rostrum, the villose outer integument, all the details of the prehensile antennae, the form of the animal's body, and the position of the labrum, would have convinced me that, though a quite new genus, it ought to have stood close to Scalpellum, and nearer to it than to Ibla.

6. SCALPELLUM VILLOSUM. Pl. VI, fig. 8.

POLLICIPES VILLOSUS on Plate (TOMENTOSUS in text). _Leach._ Encyclop. Brit., Suppl., vol. iii, 1824, Pl. lvii.

---- VILLOSUS.[59] _G. B. Sowerby._ Genera of Sh.e.l.ls, Pollicipes, fig. 3, 1826.

CALANTICA HOMII. _J. E. Gray._ Annals of Phil., vol. x, p. 100, 1825.

[59] As Mr. Sowerby has adopted the name _villosus_, I have followed him; though as _tomentosus_ is used through some mistake by Leach in the text, both names have equal claims as far as priority is concerned.

In Lamarck, 'Animaux Sans. Vert.,' the _P. villosus_ of Sowerby is made synonymous with _Anatifa villosa_ of Brugiere, which is certainly incorrect, although the _A. villosa_ of this latter author is not positively known.

_S. (Herm.) valvis 14: sub-rostro praesente: carina paene recta: laterum paribus tribus; pari superiore triangulo._

(Herm.) Capitulum with 14 valves: sub-rostrum present: carina nearly straight: three pair of latera; upper latera triangular.

_Mandibles_ with four teeth, of which the second is the smallest: maxillae with a projection near the inferior angle: no caudal appendage.

COMPLEMENTAL MALE, attached externally between the scuta, below the adductor muscle; pedunculated; capitulum formed of six valves, with the carina not descending much below the basal angles of the terga: mouth and cirri prehensile.

Eastern Seas[60] (?) attached to sh.e.l.ls and rocks. Mus. Brit.; College of Surgeons; c.u.ming.

[60] No habitat is attached to any of these specimens; but Mr.

Sowerby informs me that he has seen specimens attached to the _Modiola albicostata_ of Lamarck, which sh.e.l.l is said by the latter author to be found in the seas of India, Timor, and New Holland.

HERMAPHRODITE.