condition. There is no separation between the capitulum and peduncle;
there is no mouth; and the thorax, throughout its whole width, opens
into the anterior part of the animal: the limbs differ greatly from
those both of the mature Cirripede and of the larva, but come closest to
the latter: the preservation of the abdomen is a well-marked embryonic
character. On the other hand, the four rudimentary calcareous valves,
the narrow orifice, the hirsute outer integument, the two muscular
layers, the single eye, and male internal organs, are all characteristic
of the fully-developed condition. The four little valves, as I believe,
represent the scuta and terga, though they are placed considerably below
the orifice: the little bristly points have no homological
signification, and are absent in the male of the following closely
allied species. The four pairs of limbs answer to the four posterior
cirri, as may be inferred from their proximity to the abdominal lobe,
and from the three posterior pairs closely resembling each other, and
differing a little from the first pair; this latter pair corresponds
with the third pair in the hermaphrodite form of Scalpellum. If I am
right in believing that only a single vesicula seminalis is ordinarily
developed in the male, this is a special and singular character.
As stated in the beginning of this description, from the one great fact
of the absolute correspondence of the prehensile antennæ of the
parasite, with those of the hermaphrodite _Scalpellum vulgare_, together
with its fixed condition, its short existence, and exclusively male sex,
I have thought myself justified in provisionally considering it as the
Complemental Male of the Cirripede to which it is attached; but I hope
final judgment will not be passed on this view, until the whole case is
summed up at the end of the genus.[54]
[54] I trust, before long, that some naturalist, with more skill
than I possess, will examine these parasites on _Scalpellum
vulgare_, which unfortunately is the only species of the genus
that can be easily obtained. Fresh specimens, or those preserved
in spirits of wine, are necessary. The action of boiling caustic
potash is very useful in cleaning the prehensile antennæ. If
these latter organs are sought in the hermaphrodite for the sake
of comparison, young specimens, adhering to clean branches of a
coralline, should be procured, and caustic potash used.
2. SCALPELLUM ORNATUM. Pl. VI, fig 1.
THALIELLA ORNATA. _J. E. Gray._ Proc. Zoolog. Soc., 1848, p. 44,
Annulosa, Plate.
_S. (Foem.) valvis 14, sub-rufis: lateribus superioribus
quadranti-formibus, arcu crenâ profundâ notato._
(Fem.) Capitulum with 14 reddish valves: upper latera quadrant-shaped,
with the arched side deeply notched.
Mandibles with three teeth; maxillæ narrow, bearing only four or five
pair of spines.
MALES, two, lodged in cavities on the under sides of the scuta;
pouch-formed, with four unequal, rudimentary valves: no mouth: cirri not
prehensile.
Algoa Bay, South Africa. Attached to Sertularia and Plumularia.
British Museum.[55]
[55] I am greatly indebted to Mr. Bowerbank for specimens of this
extremely interesting species; also to Mr. Morris, to whom Mr.
Bowerbank had given some of the original specimens.
FEMALE.
_Capitulum_ oblong, with the upper portion much produced; valves, 14,
thick, naked, closely locked together, irregularly clouded with pale
crimson; the membrane connecting the valves is not furnished with
spines. On most of the valves there are furrows and ridges diverging
from the umbones, and the lines of growth are plainly marked: in the
valves of the lower whorl, the umbones are slightly protuberant.
_Scuta_, convex, unusually thick, oblong, quadrilateral, with the
occludent margin the longest; lateral margin slightly hollowed out. The
umbo (and primordial valve) is situated at the uppermost point of the
valve, and consequently the growth is exclusively downwards. On the
under side (Pl. VI, figs. 1 _b´_ and 1 _c´_), in about the middle of the
valve, there is a pit (_a_) for the adductor scutorum muscle, the depth
and distinctness of which varies a little; above the pit, and between
it and the apex, there is a transverse, oblong, deeper depression (_b_),
within which, the male is lodged. A small portion of the apex of the
valve projects over the terga.
_Terga_, large, nearly equalling the scuta in area, flat and
sub-triangular; the scutal margin is not quite straight. The apex of the
valve is thick and solid, and must have projected freely for a length
equalling one third of the occludent margin.
_Carina_, laterally broad, angularly bent; slightly widening from the
apex to the base; internally, deeply concave. The position of the umbo
varies, in young specimens it is seated at the uppermost point, and
consequently in such there is no upward growth; in older specimens, from
the junction and upward production of that part on each side of the
valve, which I have called in fossil specimens the intra-parietes, the
valve is added to above the umbo, but to a lesser degree than in _S.
vulgare_. Slight ridges separate the roof from the parietes, and the
parietes from the intra-parietes.
_Rostrum_, minute, narrow, widening a little from the apex downwards,
inserted like a wedge between the umbones of the rostral latera, and
hardly projecting above their upper margins, so as to be easily
overlooked: internally concave.
_Upper Latera_ (fig. 1 _á_), quadrant-shaped, with a deep square notch
cut out of the arched margin, which notch receives the upper point of
the carinal latera; the surface of the valve between the notch and the
umbo is depressed.[56]
_Rostral Latera_, small, gradually widening from the umbo to the
opposite end, which is obliquely rounded.
_Infra-median Latera_, approaching to diamond-shaped, placed obliquely
to the longer axis of the capitulum; or the upper part may be described
as spear-shaped.
[56] The only valve which I have seen at all like this, is a
fossil specimen from the Upper Chalk of Scania; this is described
in my memoir on the Fossil Lepadidæ (Palæontographical Society),
under the name of _Scalpellum solidulum_ (Tab. 1, fig. 8, _e_,
_f_), and is perhaps erroneously there considered as a carinal
latus.
_Carinal Latera_: these appear as if formed of two valves united
together; the upper portion, widening as it ascends in a curved line,
terminates in a rounded margin, which enters the deep notch in the upper
latera; the other and lower portion is shorter, and terminates in a
square margin abutting against the infra-median latera; the umbones of
the carinal latera project beyond the line of the carina.
_Direction of the Lines of Growth in the Valves._--This should always be
carefully observed, on account of the great diversity there is in this
respect between the different species, especially when the recent are
compared with the older fossil species; moreover one of the chief
characters between the genus Scalpellum and Pollicipes, depends on the
direction of the lines of growth. In the scuta, terga, rostrum, and
upper latera of the present species, the chief growth is downwards; in
the carina, in mature specimens, it is both upwards and downwards; in
the carinal latera, both upwards and towards the infra-median latera; in
the infra-median latera chiefly upwards; and, lastly, in the rostral
latera, towards the infra-median latera.
_Peduncle_, short, not half as long as the capitulum; calcareous scales
imbricated as usual, tinged red, almost crescent-shaped, acuminated at
both ends, of remarkable length, so that in each whorl there are only
four scales: a full-sized scale equals in length one of the rostral
latera. The tips of two scales, in one whorl, lie under the middle
points of the carina and rostrum; and in the whorl, both above and
below, a single much curved scale occupies this same medial position.
The peduncle does not seem to have been attached in any definite
position to the horny coralline, as is the case with _S. vulgare_.
Length of capitulum in the largest specimen .2 of an inch.
The _Mouth_ is directed towards the ventral surface of the thorax. The
_Labrum_ is far removed from the adductor muscle, with the upper part
forming an overhanging projection; I believe there are some very minute
bead-like teeth on the crest. _Palpi_, small, narrow, thinly clothed
with bristles.
_Mandibles_, with three teeth, of which the first is distant from the
second; inferior angle not much acuminated, pectinated on both edges.
_Maxillæ_, small, narrow, produced, without any notch, with two large
upper spines, of which one is much thicker than the other; on the convex
upper margin there are some minute tufts of very small hairs.
_Outer Maxillæ_, with few bristles, arranged in a continuous line on the
anterior surface; on the external surface there is a tuft of long
bristles. Olfactory orifices situated laterally, forming two flattened,
tubular projections.
_Cirri._--First pair placed not far from the second; the three posterior
pair not very long, with their segments elongated, not protuberant,
bearing four pair of non-serrated spines, with a single short bristle
between each pair; dorsal tufts small, with one spine longer than the
others. First cirrus rather short, segments not very broad; second
cirrus with the rami nearly equal in length, anterior ramus rather
thicker than the posterior ramus, with three longitudinal rows of
spines.
_Caudal Appendages._--These are minute, rather broad, not half as long
as the lower segments of the pedicels of the sixth cirrus, with four
very long spines at the tip.
_Penis._--There is no trace of a probosciformed penis in the four
specimens examined; and as this organ is present in every ordinary
cirripede, with the exception of _Ibla Cumingii_ which we know to be
exclusively female, so we may infer with some confidence that the form
here described is female, although it is impossible in specimens once
dried to demonstrate the absence of the vesiculæ seminales and testes.
_Affinities._--This is a very distinct species; it is, however, much
more nearly related to _S. rutilum_, than to any other species; and next
to this, to _S. vulgare_; from this latter species it chiefly differs in
the large scales of the peduncle, in the scuta not being added to at
their upper ends, and in the membrane covering and connecting the valves
being spineless; but there is a greater difference in the trophi and in
the cirri. The peduncle of _S. ornatum_ presents some resemblance to
that of the singular cretaceous genus, _Loricula_.
MALE.
All the specimens, as already stated, were dry, but in an excellent
state of preservation, so that after having been soaked in spirits, they
could be minutely examined. In the four which I opened, I found, in a
transverse pouch on the under side of each scutum, a male lodged; in a
fifth dead and bleached specimen, the cavities in the shell for the
reception of the males, were present; and in a sixth young specimen,
also dead, cavities were in process of formation. As compared with
plants, the relation of the sexes in this species may be briefly given,
by saying that it belongs to the class _Diandria monogynia_. I will
first describe the males themselves, and then the cavities in the shell
of the female. The males differ in every point of detail, from the
complemental males of _S. vulgare_, but yet present so close a general
resemblance, that a comparative description will be most convenient.
The general shape of the whole animal is rather more elongated, and I
suspect flatter, but this latter point could not be positively
ascertained in dry specimens. The entire length is greater, being in the
largest specimen 13/400 (instead of at most 11/400), and the width,
7/400 of an inch. The orifice is not fimbriated; the four bristly points
over the calcareous beads are absent. The whole outer integument is much
thinner, owing evidently to its protected position, and is not covered
by little bristles, but with an extremely high power, minute points
arranged in transverse lines can be distinguished. The calcareous beads,
or rudimentary valves, are thin and regularly oval. It is remarkable
that in all the specimens, two on one side were smaller than the two on
the other side,--the smaller beads being 16/6000, and the larger,
22/6000 of an inch in diameter; therefore more than twice the size of
one of the beads in _S. vulgare_, which are only 9/6000 externally in
diameter. From the position of the eye, close to one margin, near the
upper end of the flattened animal, and from the manner in which the
little limbs and spines lay between two of the beads at the opposite
end, it was manifest that these latter, one large and one small,
corresponded with the terga of the other cirripedes, and that the other
two, near the eye, answered to the scuta. The valves being of unequal
sizes on the right and left-hand sides of the animal, is probably
connected with one side being pressed against the hard, shelly valve of
the female; in the same way as the valves in certain Pæcilasmas; are
smaller and flatter on the side nearest to the crustacean to which they
are attached. The eye, in being slightly notched on the upper and lower
edge, shows signs of really consisting of two eyes, which I believe is
always normally the case; it is rather larger, in the proportion of 13
to 11, being 13/12,000 of an inch in diameter, than in _S. vulgare_; and
from the almost perfect transparency of the integuments, is far more
conspicuous than in that species. Hence when the valves of the female
are opened, the black little eye is the first part of the male which
catches the attention. No vestige of a mouth could be discovered.
_Thorax and Abdomen._--The thorax, as in _S. vulgare_, is highly
extensible, and when stretched exhibits the same five transverse folds
or articulations; when contracted, it is broader, so that even the
truncated end of the abdomen is wider than the lower (properly anterior)
end of the thorax in _S. vulgare_. Its thin outer integument is studded
with excessively minute points in transverse rows. The four pair of
limbs are longer than in _S. vulgare_, but the spines on them much
shorter and thicker; each limb (including the first) supports three
spines, of which one is seated on a notch low down on the outside, and
is longer than the other two; of these two, the one on the same side
with the notch, is a little longer than the other. The spines on the
first and second pair of limbs are considerably shorter than those on
the third pair, and these latter, are a little shorter than those on the
fourth or posterior pair. Hence, the spines on the thoracic limbs,
compared with those of _S. vulgare_, present considerable differences,
both in their relative and absolute dimensions. The abdominal lobe is in
proportion rather shorter; its end is less abruptly truncated, and
supports a row of, I believe, six moderately long, and basally thick
spines; these spines are not so long as those surmounting the fourth
pair of limbs. On both lateral margins of the abdomen, rather on the
ventral face, there is a row of, I believe, seven long spines, but it is
very difficult to count the spines in specimens which have been once
dried. I was able to distinguish that the two lower pair of spines on
the ventral surface, are seated a little way one below and within the
other, as in _S. vulgare_. The abdominal spines altogether form quite a
brush, and there are certainly several more than in _S. vulgare_, and
those on the two sides are much longer.
_Antennæ._--The disc is hoof-like, with the upper surface forming a
straight line with the upper edge of the basal segment; the apex is
pointed and clothed with some fine down; there is a single spine
pointing backwards, which rises from the lower flat surface. The
ultimate segment was hidden in laminæ of cement; and I was not able to
make out its structure. There is a single spine on the outer edge of the
basal segment, in the usual position. The entire length of the limb,
measured from the end of the disc to the further margin of the basal
articulation, is 36/6000ths of an inch; measured to the inner margin, it
is; 21/6000ths of an inch; the disc itself is 12/6000ths of an inch
long; these measurements differ a little both absolutely ad
proportionally, compared with those of the antennæ of _S. vulgare_.
_Cavities in the Scuta of the Female for the reception of the
Males._--These extend nearly parallel to the tergal margin, transversely
across the valves, for three fourths of their width; they are seated
above the depression for the adductor muscle, and are more conspicuous
than it; they are deep and well defined, and each exactly contains one
male. The males are placed with their orifices in a little notch in the
occludent margin, and their prehensile antennæ at the further end. The
distance to which the cavities extend across the valve, and their
distance from the upper or tergal margin, varies a little, but chiefly
in accordance with the age of the specimens; for the valve continues to
increase in width, whilst the size of the cavity remains the same. The
occludent margin of the scutum in the largest female, was .1 of an inch
in length; of another, in which there was a fully developed cavity,
.084; of a third, in which there was no cavity, only a slight concavity,
with a preparatory impression, the length of the occludent margin was
.062. The larger and smaller of these three valves, are drawn of their
proper proportional sizes, in Pl. VI, figs. 1 _b´_, 1 _c´_. The
preparatory impression (fig. 1 _c´_, _b_), consists of a narrow, not
quite straight, extremely slight furrow, of slightly irregular width,
bordered on each side by a very minute ridge, which is distinctly
continuous with the inner edge of the occludent margin, both above and
below the cavity. The furrow appears to have been formed by calcareous
matter not having been deposited along this line, during the thickening
or growth of the internal surface of the valve: I suspect, that it
originates at a single period of growth, for I could see no signs of
successively-formed transverse lines. I believe that it is strictly
homologous with the fold, over which the complemental male is attached
in _S. vulgare_, but carried, for a special purpose, much further across
the valve and rectangularly inwards, for in structure and position both
are identical. In comparing the internal views of the scuta in _S.
vulgare_ and _S. ornatum_ (Pl. V, fig. 15 _a´_, and Pl. VI, fig. 1
_c´_), it must be borne in mind, that the latter should be compared, as
clearly shown by the lines of growth, with that portion alone of the
scutum in _S. vulgare_, which lies under the curved ridge connecting the
umbo and tergo-lateral angle. The deep cavity in which the male is
lodged, is formed subsequently to the preparatory furrow, simply by the
gradual thickening of the surrounding surface of the valve, more
especially of a ridge just above the pit for the adductor muscle, and of
another broad ridge just beneath the tergal margin. The deepest part of
the cavity lies parallel to the tergal margin along the upper side, and
here, in the older valves, the preparatory furrow can by care be
distinctly traced. In conformity with the shape of the cavity, the
orifice or notch in the occludent margin of the scutum, is situated at
the point where the preparatory furrow sweeps round and enters. I
believe that the cavity is lined by membrane, and that between the
cavity and the body of the female, there is a complex membranous
layer,--a pouch or bag being thus formed. An imaginary section of this
pouch (with the thickness of all the parts extremely exaggerated and in
a reversed position) is given in Pl. VI, fig. 1 _d´_: _a_ is the shell;
_x_ the cavity, converted, as I believe, into a pouch by, firstly, the
delicate tunic (_c_) lining the sack of the female; secondly, a double
layer (_d_) of corium; and, thirdly, by a special, rather thick
membranous layer (_b_), which thinning out round the cavity coats only
part of the under surface of the scutum. This latter membrane I have not
seen in any other Cirripede, and I believe it is nothing but the tissue,
here not calcified, which, in a calcified condition, ordinarily forms
the valves. On this view, the males may be said to be lodged in pouches,
formed in the thickness of the valves.
_Concluding Remarks._--The males from the absence of a mouth (and no
doubt of a stomach), must necessarily be short-lived, and, I suppose,
are periodically replaced by fresh males.[57] In one instance, the
remnants of the two great compound eyes of the larva, could be seen at
the end of the pouch, opposite the orifice. The larvæ, I conclude, crawl
in at the orifice, one side of which is formed, as we have seen, of
yielding membrane, and scratch out the dead exuviæ of the former
occupant: certainly, the males are less firmly attached to their
pouches, though some small quantity of cement is excreted, than are
other Cirripedes to the objects to which they are attached. The small
size of the female, and her valves not being thickly edged with chitine,
accounts for the males having pouches specially formed for them, instead
of being, as in _S. vulgare_, laterally imbedded in the chitine-border
of the scuta. In hereafter weighing the evidence on the nature of the
parasites in Ibla and in Scalpellum, the fact of the valves of the
supposed female being here modified for the special purpose of lodging
the males, will be seen to be important. If we imagine the male
parasites to be extraneous animals, and that by adhering to the sack of
the Scalpellum, they injure the corium and thus prevent the growth of
the shell over an area exactly corresponding to their own size, and so
form for themselves cavities; yet what can be said regarding the
preparatory furrows? surely these narrow lines cannot have been produced
by the pressure of the much broader parasites. Must we not see in the
furrows, the first marking out, if such an expression may be used, of
the habitation for the male, which has to be specially formed by the
independent laws of growth of the female?
[57] It is possible, though opposed to all analogy, that the
females may be short-lived, and breed only once, in which case
the males would not have to be periodically replaced.
3. SCALPELLUM RUTILUM. Pl. VI, fig. 2.
_S. (Foem. an Herm.) valvis 14 sub-rufis: carinæ tecto plano, utrinque
cristâ rotundatâ instructo; margine basali truncato: lateribus
superioribus latitudine duplo longioribus._
(Fem. or Herm.) Capitulum with 14 reddish valves: carina with the roof
flat, bordered on each side by a rounded ridge; basal margin truncated:
upper latera twice as long as broad.
Mandibles with three teeth: maxillæ narrow, bearing only four or five
pair of spines: segments of the second and third pair of cirri with one
side wholly covered with spines.
MALES, two, lodged in hollows, on the under sides of the scuta;
pouch-formed, with four (?) rudimentary valves; no mouth; cirri not
prehensile.
Hab. unknown; associated with _Dichelaspis orthogonia_. British
Museum.
FEMALE OR HERMAPHRODITE.
There is only a single specimen in the British Museum, and this had
nearly all its valves separated, and many of them in fragments: from its
state of decay, I think the specimen must have been dead, when
originally collected.
_Description._--The capitulum consists of fourteen valves, including
from analogy a rostrum.[58] Valves, apparently covered with membrane,
bearing some thin spines on the margins; clouded with a fine, though
pale, orange tint; surfaces plainly marked with lines of growth.
[58] In my first, and as I thought careful examination of the
separated valves (my only materials) of this species, I mistook
one of the triangular rostral latera for the rostrum, and hence
was unfortunately led into an error in my ‘Monograph on the
Fossil Lepadidæ of Great Britain,’ in which I state that the
present species has only twelve valves in the capitulum; and I
inferred from this, that _S. quadratum_, _S. fossula_, &c., had
only twelve valves; I still believe this to be correct, but the
existence of fourteen valves in _S. rutilum_ and _S. ornatum_,
the recent species to which the above fossils are most closely
allied, no doubt is a strong argument in favour of this higher
number.