Chapter 25

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 striæ-less muscles, within which there are the usual stronger, longitudinal muscles. The base is flat and truncated. I examined, and carefully compared, the prehensile antennæ with those of the hermaphrodite, and found every part and every measurement the same. The full importance of this identity will hereafter be more fully insisted on. The antennæ 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.

_Maxillæ_, 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 maxillæ and mandibles are the same in the male and hermaphrodite.

_Outer Maxillæ_ 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 _Penis_ is not acuminated, 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 vesiculæ 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 assertion may be believed when I state, that I traced the two much finer and more transparent cement-ducts, from the prehensile antennæ 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 maxillæ 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 class 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 antennæ, 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 Shells, 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 Brugière, which is certainly incorrect, although the _A. villosa_ of this latter author is not positively known.

_S. (Herm.) valvis 14: sub-rostro præsente: carinâ pæne rectâ: 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: maxillæ 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 shells and rocks. Mus. Brit.; College of Surgeons; Cuming.

[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 shell is said by the latter author to be found in the seas of India, Timor, and New Holland.

HERMAPHRODITE.

_Capitulum_ with fourteen valves, consisting of a pair of scuta and of terga, a carina, (which five valves are much larger than the others,) a rostrum, sub-rostrum, sub-carina, and three pair of small latera. All the valves are covered by membrane, as are the calcareous scales on the peduncle; and this membrane everywhere is densely clothed with spines. The upper valves are not very thick; they stand rather close together. The eight valves of the lower whorl are more solid, and are placed far apart; they are small, tending to become rudimentary. None of the valves are added to at their upper ends, in which respect this species differs remarkably from the others of the genus, and approaches in character to Pollicipes.

_Scuta_, with a deep hollow for the adductor muscle, triangular, with the basal margin elongated, and protuberant.

_Terga_, large, flat, triangular, basal point blunt, with the carinal margin slightly hollowed out, and the scutal margin protuberant. Apex solid.

_Carina_, rather longer than the terga, straight, gradually widening from the upper to the basal end, deeply concave. In young specimens the upper part is slightly bowed inwards. Apex solid.

_Sub-carina_, with the inner surface crescent-shaped; the umbo points transversely outwards; in width it exceeds the largest of the latera.

_Rostrum_, triangular, internally (fig. 8 _a_) concave; basal margin slightly hollowed out, and deeply notched; rather less in width than the carina; short, with the umbo pointing upwards and outwards. In young specimens the apex curves a little inwards.

_Sub-rostrum_, with the inner surface transversely elongated (fig. 8 _b_), slightly crescent-shaped, about two thirds as wide as the rostrum. The apex points transversely outwards.

_Latera_, three pair; the middle pair apparently corresponds with the upper latera of the other species of the genus. The two other pair of latera, together with the rostrum and sub-carina, form a whorl. The sub-rostrum lies by itself, a little beneath this whorl. The latera are smaller than the rostrum or the sub-carina. They are placed far distant from each other; their inner surfaces are triangular; their umbones point upwards; the rostral pair is smaller than the other two pair, which are of equal size. The exact position of the rostral latus differed on the two sides of the specimen examined; apparently its normal position is at the baso-lateral angle of the scuta.

_Peduncle_, wide at the summit, longer than the capitulum; calcified scales small, not arranged very regularly; flattened, spindle-shaped, rather far separated from each other; imbedded in membrane, so that even their summits are rarely uncovered. The surface of the membrane is thickly clothed with spines, which are strong, thick, yellow, pointed, and furnished with large tubuli running to the underlying corium. These spines are arranged in groups of from three or four, to five or six. Besides these larger spines, the whole surface is villose with very minute colourless spines, not above 1/20th of the length of the larger ones. The surface of attachment is broad. This species, not being symmetrically attached to a coralline, the peduncle does not curve, as in most of the other species, towards the rostrum.

The capitulum is above half an inch in length.

_Mouth._--The labrum is much produced downwards, but yet the mouth is not very far distant from the adductor muscle: the upper part is bullate, forming a small overhanging point, and in longitudinal diameter equals the rest of the mouth. _Palpi_ blunt.

_Mandibles_ with four teeth, strong, short, thick, the second tooth much smaller than the others; inferior angle broad, pectinated.

_Maxillæ_ with a long, rather sinuous edge, which, near the inferior angle, has a narrow projecting point, bearing rather finer spines; there is, also, apparently, a very minute tuft of small spines close under the two large upper spines: there are, altogether, about twenty pair of spines, without counting the smaller ones.

_Outer Maxillæ_, with the inner edge slightly concave, continuously covered with bristles; exteriorly, with a prominence covered with longer bristles. Olfactory orifices prominent, protected by a slight punctured swelling between the bases of the first pair of cirri.

_Cirri._--Prosoma moderately developed; first pair of cirri rather far removed from the second pair. The segments of the three posterior pair are not elongated, short, slightly protuberant in front, bearing four or five pairs of strong spines; a little below each pair, there is an intermediate tuft of very fine straight bristles, of which the upper tuft is the largest; on the lateral upper rims there are some short, strong spines; dorsal tufts rather small and thick; spines all more or less serrated, especially on the broad basal segments of the three anterior cirri. Pedicels of the cirri not particularly protuberant in front. First cirrus with rami, slightly unequal in length; not short; basal segments much thicker and more protuberant than the upper segments. Second cirrus; anterior ramus with six or seven basal segments highly protuberant, and crowded with spines; posterior ramus with about six segments, similarly characterised. Third cirrus with the anterior ramus having six, and the posterior ramus five segments, also similarly characterised.

_Caudal Appendages_ absent, there being only a slight swelling on each side of the anus.

The _oesophagus_ runs parallel to the labrum, and enters obliquely the summit of the stomach, which is destitute of cæca: the biliary envelope is longitudinally plicated.

There are no _Filamentary Appendages_.

_Testes_ large, branched like a stag’s horns, attached in a sheet to the ventral surface of the stomach: the vesiculæ seminales enter the prosoma, and have their reflexed ends not very blunt. The _Penis_ is rather narrow, with the terminal half plainly ringed, and bearing tufts of fine bristles arranged in circles, one tuft below the other; on the basal half there are only a few scattered minute bristles.

_Affinities._--In the downward growth of all the valves, in the presence of a sub-rostrum, in the shape of the scuta, carina, and more especially of the triangular latera, in the form of the peduncle, with its irregularly-scattered calcified scales, in the shape of the animal’s body, in the structure both of the mandibles and maxillæ, in the arrangement of the spines, both on the anterior and posterior cirri, _Scalpellum villosum_ most closely resembles, or rather is identical with, Pollicipes. Had it not been for the formation of the valves forming the capitulum, and from the presence of Complemental Males, I should have placed this species alongside of _Pollicipes spinosus_ and _sertus_. In not having caudal appendages, _S. villosum_ differs from all the species of Scalpellum and Pollicipes; but this organ is variable to an unusual degree in Pollicipes.

COMPLEMENTAL MALE. Pl. VI, fig. 4.

From the kindness of Professor Owen, Mr. Gray, and Mr. Cuming, I have been enabled to examine six specimens of this species; and on two of them I found Complemental males. They were attached in the same position as in _S. Peronii_; namely, beneath the adductor muscle, in the fold between the scuta, so as to be protected by the latter when closed. This parasite is six-valved, and has a close general resemblance with that of _S. Peronii_, but differs in very many points of detail. It is represented of the natural size at _á_ fig. 4. The capitulum is 43/1000ths of an inch, measured across the scuta and terga; and the same measured from the base of the carina to the top of the capitulum; hence it is broader, by a quarter of the above measurement, and considerably higher than the male of _S. Peronii_. From the capitulum being higher, that is, not so much truncated, the orifice is placed more obliquely. The membrane connecting the valves is finely villose, and is besides furnished with spines, conspicuously thicker and longer than those on the male _S. Peronii_. The scuta and terga are much more elongated, a scutum being here 35/1000ths of an inch in length. The carina descends only just below the basal points of the terga, instead of far below them. The rostrum is a little broader and more arched than the carina; it is 2/1000ths in length, and therefore more than two thirds of the length of the carina, the latter being 28/1000ths of an inch from the apex to the basal margin. The primordial valves, with the usual hexagonal tissue, are seated on the tips of the scuta, terga, and carina, but not on the rostrum; so that these valves follow the same law of development, as in the ordinary and hermaphrodite form of Scalpellum. The scuta (_a_, fig. 4, greatly enlarged), the terga (_b_), and carina (_c_) of the male, resemble the same valves in the hermaphrodite, much more closely than do these valves in the male and hermaphrodite _S. Peronii_. The rostrum has not its basal margin hollowed out, and is very much larger relatively to the carina, than in the hermaphrodite. The large relative size of the rostrum in the complemental male both of this species and of _S. Peronii_, is a remarkable character, which I can in no way account for.

The peduncle is narrow and short, but in a different degree in the two specimens examined. It is naked. The prehensile antennæ were not in a good state of preservation: the disc is narrower than the basal segment, and only slightly pointed, in which important respect it differs from the same part in the foregoing species; at its distal end, rather on the inner side, there are two or three spines, apparently in place of the excessively minute hairs, which are found at the same spot in some or in all the other species of Scalpellum, and in Ibla: similar strong spines occur in Pollicipes. Unfortunately, for the sake of comparison, I was not able to find the prehensile antennæ in the hermaphrodite _S. villosum_.

_Mouth._--Labrum bullate, with teeth on the crest. _Palpi_ blunt, spinose.

_Mandibles_, with three teeth; inferior point rather strongly pectinated.

_Maxillæ_, with a considerable notch under the upper pair of large spines; inferior part of the edge not prominent.

_Outer Maxillæ_, with the spines on the inner edge arranged into two groups. Olfactory orifices tubular and prominent, with some long bristles near their bases. In the mandibles having only three teeth, in the maxillæ being notched and in the lower part not being prominent, and, lastly, in the bristles on the inner face of the outer maxillæ being arranged in two groups, these several organs differ from those in the hermaphrodite.

_Cirri._--First pair short, with only three or four segments in each ramus: second cirrus, with the basal segments not very thickly clothed with spines: sixth cirrus with seven segments, not protuberant in front, each bearing four pairs of spines, without intermediate tufts.

_Caudal appendages_, none. This is an interesting fact, considering that these organs are likewise absent in the hermaphrodite _S. villosum_,--an absence highly remarkable, and confined to the genus Conchoderma and the one species of Anelasma.

_Penis_ thick, not tapering, rather exceeding in length the pedicel of the sixth cirrus, square at the end, and furnished with some spines. In one specimen, I believe I distinguished the vesiculæ seminales: if so, they contained only pulpy matter, and not spermatozoa. There were no ovarian tubes within the peduncle, which was lined by the usual muscles; I traced the two delicate cement-ducts, running from within the antennæ close up to the animal’s body. Hence in this case, as in that of _S. Peronii_, I dare positively affirm that ovarian tubes do not occur; for it is out of the question that I could have traced the cement-ducts, and, at the same time, overlooked the far larger and more conspicuous ovarian tubes, into which, moreover, the ducts, had they existed, would have run. Consequently, these parasites are not females; but judging from the probosciformed penis, and from the presence, as I believe, of vesiculæ seminales, they are males.

The complemental males of the present species, and of _S. Peronii_, so closely resemble each other, that what I have stated regarding the affinities of the latter, are here quite applicable. It is singular how much more alike the parts of the mouth and the cirri of these two complemental males are, than the corresponding parts in the two hermaphrodites: this no doubt is due to the two males having been arrested in their development, at a corresponding early period of growth. Several of the characters, by which the hermaphrodite _S. villosum_ so closely approaches, and almost blends into the genus Pollicipes,--such as the thicker cirri, with the intermediate tufts of bristles, the small second tooth of the mandibles, and the little brush-like prominence on the maxillæ,--are not in the least apparent in the complemental male.

SUMMARY ON THE NATURE AND RELATIONS OF THE MALES AND COMPLEMENTAL MALES, IN IBLA AND SCALPELLUM.