sparingly and quite irregularly studded with minute, much-branched
filaments (Pl. IV, fig. 3, highly magnified); these are occasionally as
much as l/5th of an inch in length; the degree of branching varies much,
but is generally highly complex; the ordinary diameter of the branches
is about 1/200th of an inch; their tips are rounded, and even a little
enlarged, and frequently torn off, as if they had been attached to or
buried in the flesh of the shark, in which the whole peduncle is
imbedded. These filaments are formed of, and are continuous with the
external transparent membrane of the peduncle, and they contain, up to
the tips of every sub-branch, a hollow thread of corium, prolonged from
the layer internally coating the whole peduncle. In all other Lepadidæ,
the peduncle increases in length, chiefly at the summit where joined to
the capitulum, and in diameter, throughout nearly its whole length,
except close to the base; but, owing to the constant disintegration of
the outer surface, the old outside coat does not split in defined lines,
like the membrane of the capitulum. In Anelasma, however, owing to the
imbedded position of the peduncle, the old outer coats are preserved,
the lines in which they have split during continued growth being thus
exhibited: those in the uppermost part almost symmetrically surround the
peduncle, showing that here, as in other Lepadidæ, has been one regular
line of growth; but in the lower part the lines are extremely irregular;
and what is almost unique, it appears that the blunt basal end is
constantly increasing in length and breadth, and, apparently, at a
greater rate than any other part. I judge of this latter fact, from the
whole bottom of the peduncle being covered with numerous curved, or
nearly circular, lines of natural splitting, the nature of which can be
best understood by examining the much-enlarged drawing (Pl. IV, fig. 3)
of a small portion (taken by chance) of the membrane of the base, seen
from the outside, and bearing some of the simplest branched filaments:
other branches, as may be seen, have been cut off. This manner of growth
explains the broad, blunt basal termination of the peduncle, so unlike
that in other Lepadidæ. New membrane is formed, not continuously as in
other cases, under the whole surface of the old membrane, but in
irregular patches; thus the portion marked (_a_) runs under (_b_), but
not under the little circles (_c_, _c_), for these are the last-formed
portions and underlie the membrane (_a_) and (_b_). I do not understand
how the splitting of the old membrane is effected; but no doubt it is by
the same process by which the membrane of the capitulum in other genera,
as in Scalpellum, splits symmetrically between the several valves. In
the branched filaments it is particularly difficult to understand their
growth, for it is not possible, after examining them, to doubt that they
continue to increase, and send off sub-branches, which it would appear
probable, penetrate the shark’s flesh like roots. I may remark that one,
or more commonly two or three branched filaments stand nearly in the
centre of each circular line of exuviation or splitting. The branched
filaments first commence as mere little pustules, and these appear to be
most numerous at the bottom of the peduncle.
The final cause of the downward growth of the bottom of the peduncle, is
obviously to allow of the animal burying itself in the shark’s body, in
the same way as Coronula and Tubicinella become imbedded by the downward
growth of their parietes in the skin of Cetacea. The only other genus of
Lepadidæ, in which the growth of the peduncle is at all analogous, is
Lithotrya, in this genus, however, the animal burrows mechanically into
soft rock or shells.
I looked in vain for cement, or for the cement-glands, (but the specimen
was in an extremely unfavorable state for finding the latter) or for the
prehensile antennæ of the larva. No doubt this Cirripede at first
becomes attached in the same way as others, but after early life, I
suspect it is retained in its place, by being so deeply imbedded in the
shark’s body, and perhaps by the root-like branched filaments. The
irregular growth and splitting of the membrane at the base of the
peduncle, where the prehensile antennæ of the larva must originally have
been situated, would account for not finding them.
The inside of the peduncle (fig. 2 _g_) was gorged, in the specimen
examined by me, with immature ova. The innermost muscular layer consists
of longitudinal bundles of unusual size, but placed rather far apart
from each other; these do not extend to the very base of the peduncle,
and at the upper end they curve inwards, almost to the middle of the
under side of the diaphragm, separating the peduncle and capitulum.
Outside these longitudinal muscles, there are delicate transverse ones,
but apparently there are no oblique muscles in the upper part of the
peduncle, as in other Lepadidæ; near the bottom, the transverse muscles
form a thicker layer with many of the bundles running in oblique lines.
_Mouth._--uLovén has not described this part quite accurately, owing to
his not having used high enough magnifying powers. He states that the
trophi are soft and functionless, which is far from the case. The whole
mouth (fig. 2 _d_), is unusually small; it is, to a certain extent,
probosciformed, and being curved a little downwards, projects slightly
over the adductor muscle, to which it is closely placed. The labrum does
not project more beyond the general surface of the body, than in many
other Cirripedes, but the probosciformed structure is caused by the
elongation of the surface fronting the thorax. The summit of the mouth
stands above the level of the top of the pedicels of the first pair of
cirri. The labrum is slightly hollowed out in the middle of its upper
margin; it can scarcely be called bullate, in which it differs from all
other Lepadidæ; on the other hand, the outer and inner folds of the
labrum are not so close together as in Balanus. On each upper corner,
there is, as usual, a small rounded prominence, close to which there is
a second slight, rounded, spineless swelling; these latter represent the
quite rudimentary _Palpi_.
The _Mandibles_ (figs. 4, 5) are more highly developed than the other
trophi; they are, however, very minute, the toothed edge being only
about 16/1000th of an inch in length, measured in its longest direction;
the edge is unusually thick, with the teeth placed rather on one side;
this organ, when viewed on the labrum side (fig. 5), shows two large
teeth placed low down, with the inferior angle pectinated and broadly
truncated; but when viewed on the other or maxillæ side (fig. 4),
several large and small teeth, placed alternately and irregularly in
pairs, are seen extending along the whole edge. The mandibles are
furnished, as usual, with three principal sets of muscles attached to
the basal fold of the mouth.
The _Maxillæ_ (fig. 7) are still smaller than the mandibles; the spinose
edge being only the 1/100th of an inch in length; the edge, instead of
being square, and furnished with a double row of long spines, as in all
other Cirripedes, is rounded, thick, club-shaped, and with the side
facing the mandibles, thinly and irregularly strewed with short, thick,
very minute spines; there is a large broad apodeme (_a_), in the usual
place, but it is much more transparent and flexible than common: there
are also the usual muscles. In other cirripedes, the mandibles alone
seem to force the prey down the oesophagus; but here, the mandibles and
maxillæ equally stand over the orifice, and their adjoining spinose
faces and edges, seem excellently adapted to force, by their united
action, any minute living creature down the passage.
The _Outer Maxillæ_ are almost in as rudimentary a condition as the
palpi; they are quite spineless; viewed externally, they appear like two
smooth, blunt, very minute projecting points; but viewed internally, the
membrane forming the supra-oesophageal hollow seems to be united
actually to their tips, so that they do not project at all. I was
surprised to find that the longitudinal muscles going to these organs
were developed, in proportion to the other muscles, quite as fully as in
ordinary cirripedes: hence, these two little outer maxillæ, no doubt,
serve as an under lip, and possess the usual backward and forward
movement.
The surface of the probosciformed mouth facing the first pair of cirri,
has a deep central longitudinal fold, and rather more than half-way
down, a transverse fold; just above this latter fold, and therefore
quite below the outer maxillæ themselves, the two olfactory orifices are
seated; these are unusually large, and the sack into which they lead, is
most unusually large and deep. In this Cirripede, I was first enabled to
observe that the membrane lining the sack is tubular, and open at the
bottom.
_Cirri._--There are, as usual, six pair, and not of very small size;
they have a shapeless and rudimentary appearance; they are coloured,
like the rest of the body, blackish purple: they are quite spineless,
and not articulated, but their anterior faces are either obscurely or
very plainly lobed, so that in some (for instance in the third pair, Pl.
IV, fig. 6), nine or ten prominent steps could be counted, manifestly
representing so many segments. The rami are equal in length in the first
pair, and slightly unequal in the second and third pair; these two
latter are longer than either the first or three posterior pair. There
is a small interspace as usual between the first and second pair of
cirri. Internally, the cirri are occupied, even up to their tips, by
delicate striæ-less muscles. The external membrane of the thorax and
limbs, when examined under a very high power, is seen to be covered with
minute toothed scales, as in most Cirripedes.
The thorax is articulated as usual: the posterior part, however, is
smaller, and tapers more suddenly than in other species, and this
corresponds with the smaller size and more rudimentary condition, of the
three posterior pair of cirri, compared with the anterior pair. The
prosoma is hardly at all developed. The orifice (Pl. IV, fig. 2 _e_) of
the acoustic (?) sack, beneath the first cirrus, is unusually large.
There are no filamentary appendages.
_Alimentary Canal._--The membrane lining the oesophagus is unusually
thin: it is furnished with the ordinary constrictor muscles, and others
radiating from them like spokes of a wheel. The stomach is lined by
unusually prominent biliary folds, which in the duodenum are transverse,
sending forth, however, short folds at right angles; and these latter,
in the proper stomach, become so much developed that the folds appear
longitudinal. The rectum extends inwards, about as far as the base of
the fourth pair of cirri, but is very short, owing to the little
development of the three posterior segments of the thorax. The anus is
seated in its usual place, at the dorsal basis of the penis, and is
hidden by loose folds of skin; but there are no distinct caudal
appendages. The stomach, in the specimen examined, was quite empty.
_Reproductive Organ._--The penis (fig. 2, _c_) is thick, short (about
twice as long as the sixth cirrus), constricted at the base, ringed,
spineless, with the terminal aperture large; internally it is well
furnished with muscles. The two vesiculæ seminales, appeared to be
unusually small; and one was much smaller than the other; they do not (I
believe) become united into a common tube, till near the apex of the
penis. They were empty; and, I presume, from the state of the ova, that
their contents had lately been discharged. The whole thorax was filled
with a white, fibrous and cellular mass, consisting perhaps of the
testes in their undeveloped state. The individual dissected by me,
appeared to have been defective in its last act of reproduction, for
there were only two or three ova attached to the frænum on one side, and
not very many on the other. The ova are much less elongated than is
usual; they are of a remarkable size, namely 22/1000ths of an inch in
their longer diameter; the membrane by which they are united into a pair
of lamellæ is remarkably strong; the frænum (Pl. IV, fig. 2 _f_) on each
side is large, strong, with rounded edges, pale coloured and hence
conspicuous; on the side nearest the body, the whole surface is covered
with club-shaped glands, having very short footstalks, and being in
total length 5/6000ths of an inch; these glands secrete a reticulated
layer of gut-formed fibres, attached to the ovigerous lamellæ. In the
specimen described by Lovén, the lamellæ (fig. 1, and fig. 2, _b_, _b_)
appear to have been very large: and in that examined by myself, the
peduncle was gorged with immature ova, showing that the female
reproductive powers were ample, though at the foregoing period, only a
few eggs had been formed.
_Habits._--According to Lovén, this species lives imbedded in the skin
of _Squalus maximus_ and _spinax_, in the North Sea: I suspect that it
is not closely compressed in its cavity, otherwise, I do not see the use
of the two layers of muscles round the whole peduncle; it probably
adheres to the sides of the cavity by the tips of the branched,
root-like filaments; owing to the flexible nature of the capitulum, this
Cirripede can offer little resistance to the water, and, therefore, is
little likely to be torn out of its cavity. I have no doubt that it can
fold the membrane of the capitulum, like a cloak, round its thorax and
cirri; but it certainly can offer far less resistance, than other
Cirripedes, to any enemy. This creature must obtain its food, and
considering its productiveness much food must be required, in a manner
quite different from nearly every other member of its Order. As the
whole of the peduncle is imbedded, and as the mouth is probosciformed,
with the labrum a little curled over the adductor muscle, I conclude
that this Cirripede can reach minute animals crawling by on the surface
of the shark’s body.
It must be borne in mind that the mouth, as in all Cirripedes, has the
power of independent movement, and that the mandibles and maxillæ are
here beautifully adapted to catch and force down any small living
creature into the muscular oesophagus; the rudimentary outer maxillæ,
moreover, no doubt have the power of scraping, like a lip, anything
towards these prehensile organs. It will hereafter be seen, that the
male of _Ibla Cumingii_, in which the cirri are quite rudimentary,
obtains its food in a somewhat analogous manner, though in this case the
whole peduncle moves, and not merely a probosciformed mouth: it deserves
attention, that in the male Ibla and in Anelasma, in neither of which
the cirri are prehensile, the palpi are rudimentary and useless. I am
tempted to believe, that the largely developed olfactory sacks, and
perhaps, likewise, acoustic (?) sacks, in Anelasma, replace, by giving
notice of the proximity of prey, the loss of tactile cirri. It should be
remembered that all Cirripedes subsist on animals which happen to swim
or float within reach of the cirri; but here it is only those which
happen to crawl within reach of the probosciformed mouth. It would,
however, be rash to assert that the cirri in Anelasma, considering their
muscular though feeble structure, may not be of some slight use, when
thrown over the prey, in preventing its escape.
Professor Steenstrup informs me that, from late observations, it appears
that this animal always adheres to the shark’s body in pairs. I regret
extremely that I have not been able to examine a pair: that the
individual examined by me was bisexual, I can hardly doubt, though the
male organs certainly were feebly developed; it appears probable, that
the individual described by Lovén was likewise bisexual: but after the
facts presently to be revealed regarding the sexes in Ibla and
Scalpellum, it is quite possible that the male and female organs may be
developed in inverse degrees in different and adjoining individuals.
The genus Anelasma is, I think, properly placed between Alepas and Ibla.
In several of its characters, such as the absence of calcareous valves,
the broad blunt end of the peduncle, the spineless cirri, the small size
of the trophi, and more especially the absence of transverse striæ in
those muscles, which in mature cirripedes are thus furnished, we see
that this genus is in some degree in an embryonic condition.
_Genus_--IBLA. Pls. IV, V.
IBLA. _Leach._ Zoolog. Journal. vol. ii, July, 1825.
ANATIFA. _Cuvier._ Mem, pour servir, ... Mollusques, Art. Anatifa,
1817.
TETRALASMIS. _Cuvier._ Regne Animal, 1830.
(_Foem. et Herm._) _Valvæ 4, corneæ: pedunculus spinis corneis,
persistentibus vestitus._
(Fem. and Herm.) Valves four, horny: peduncle clothed with persistent,
horny spines.
Body partly lodged within the peduncle; mandibles with three teeth;
maxillæ with two obscure notches; outer maxillæ pointed; olfactory
orifices prominent; caudal appendages multiarticulate.
_Male and Complemented Male_, parasitic within the sack of the female or
hermaphrodite; mouth and thorax seated on a long tapering peduncle, but
not enclosed within a capitulum; mouth with normal trophi, but palpi
small and almost rudimental; cirri rudimental, reduced to two pairs;
penis reduced to a pore; caudal appendages rudimentary.
Attached to fixed littoral objects: Eastern Hemisphere.
_General Remarks._--As there are only two species as yet known, and as
these resemble each other in every respect most closely, a generic
description would be a useless repetition of the full details given
under _Ibla Cumingii_. I have taken this latter species as the type,
from having, owing to the kindness of Mr. Cuming, better and more
numerous specimens. Ibla and Lithotrya are the only two recent genera in
which the body of the animal is lodged within the peduncle; but there is
no distinction of any importance, though useful for classification,
between the capitulum and peduncle; and these two parts, as we have
seen, tend to blend together in some species of Conchoderma and Alepas.
The entire absence of calcareous matter in the valves and spines of the
peduncle, at first appears very remarkable; but we have seen a similar
fact in Alepas, and there is an approach to it in some varieties of
_Conchoderma aurita_ and _C. virgata_. In all four valves of Ibla, the
umbones, or centres of growth, are at their upper points. The horny
spines on the peduncle, are the analogues of the calcareous scales in
Scalpellum and Pollicipes; and in this latter genus, two of the species
have their scales, almost cylindrical, placed irregularly, with new ones
forming over all parts of the surface, and not exclusively at the
summit,--in which several respects there is an agreement with Ibla. The
shape of the body (_i. e._ thorax and prosoma, Pl. IV, fig. 8 _a´_) is
peculiar; but it is only a slight exaggeration of what we have seen in
several genera, and shall meet again in some species of Scalpellum. The
presence of hairs on the outer membrane of the prosoma is a peculiarity
confined to this genus amongst the Lepadidæ, though observed in the
sessile genus, _Chthamalus_. The caudal appendages in the _I.
quadrivalvis_ attain a greater length than in any other species of the
family, being four times the length of the pedicels of the sixth cirrus.
A far more important peculiarity is the fact of the oesophagus, in both
species, running over or exteriorly to the adductor scutorum muscle,
instead of, as in every other species, close under this muscle. I took
great pains in ascertaining the truth of this singular anomaly: the
course of the oesophagus is approximately represented in Pl. IV, fig. 8
_a´_ by faint dotted lines. The stomach has no cæca; the biliary folds
are longitudinal; there is a marked constriction at the line
corresponding with the junction of the thorax and prosoma. There are no
filamentary appendages.
The generative system gives the chief interest to this genus. We here
first meet with Males and Females distinct; and, within the limits of
this same restricted genus, the far more wonderful fact of
hermaphrodites, whose masculine efficiency is aided by one or two
Complemental Males. The complemental and simple males closely resemble
each other, as do the female and hermaphrodite forms; but under the two
following species I enter into such full and minute details on these
remarkable facts, that I will not here dilate on them. I may add that,
at the end of the genus Scalpellum, I give a summary of the facts, and
discuss the whole question. The penis (Pl. IV, fig. 9 _a_) in the
hermaphrodite, _I. quadrivalvis_, is singular, from the length of its
unarticulated support, and from the distinctness of the segments in the
articulated portion.
As ovigerous fræna occur in the usual place in _I. quadrivalvis_, though
much smaller than in any other species, I have no doubt that they occur
in _I. Cumingii_, although I failed in observing them. The glands on the
margin, in _I. quadrivalvis_, are singular, from not being borne on a
long, hair-like footstalk.
_Affinities._--Ibla, though externally very different in appearance from
Scalpellum, is more nearly related to that genus than to any other; in
both genera some species have the sexes separate, the imperfect males
being parasitic on the female, and other species are bisexual or
hermaphrodite, but aided by parasitic complemental males. In Scalpellum,
again, the oesophagus pursues a sinuous course, resembling that in Ibla,
though it does not pass exteriorly to the adductor scutorum muscle. The
disc of the prehensile antennæ of the larva, in both genera, has an
unusual oblong form, like a mule’s hoof; there is also an affinity
between the two genera in the size and form of the ova, in the prominent
orifices of the olfactory cavities, and in the peduncle not being naked;
though, in these two latter respects, in the structure of the cirri, and
in the multiarticulate caudal appendages, there is an equal affinity to
Pollicipes and Lithotrya. I have already shown that Alepas is likewise
related to Ibla.
1. IBLA CUMINGII. Pl. IV, fig. 8.
_I. (foem.) valvarum marginibus lateralibus, et superficie interiore,
cæruleis: pedunculi spinis plerumque annulis cæruleo-fuscis._
Fem.--Valves coloured, along the lateral margins and on the upper
interior surface, blue: spines on the peduncle, generally ringed with
blueish-brown.
Caudal appendages barely exceeding in length the pedicels of the sixth
cirrus: rami of the first cirrus unequal in length by about two
segments.
Male,--with scarcely a vestige of a capitulum: maxillæ with fewer spines
than in the female.
_Hab._--Philippine Archipelago, Island of Guimavas; invariably
attached to the peduncle of _Pollicipes mitella_, in groups of
two or three together; Mus. Cuming. Tavoy, British Burmah
Empire; Mus. A. Gould of Boston.
FEMALE.
The capitulum is formed of four valves, but is hardly distinct from the
peduncle. The latter includes, in its wide upper part, the animal’s
body. The valves, namely, a pair of scuta and terga, are composed of an
extremely hard, horny substance, or properly chitine, and do not contain
any calcareous matter; they are extremely flat or thin, and both pairs
project freely, like curved horns, to a considerable height above the
sack enclosing the body: the terga project about twice as much as the
scuta, and their flat apices generally diverge a little. The tips of the
valves are frequently broken off; their surfaces are plainly marked or
ribbed by the layers of growth, which are wide apart. The bases of the
valves externally are hidden by the long spines of the peduncle.
_Scuta._--These are shorter and broader than the terga; their internal
(Pl. IV, fig. 8 _b´_) growing or corium-covered surfaces are slightly
concave, triangular, with the basal margin longer than the other margins
and slightly excised in the middle: there is no depression for the
strong adductor muscle: the internal surface of the free horn-like
portion, has a small central fold (formed by an oblique crest) running
from the summit of the triangular growing surface to the tip of the
valve: in perfect specimens, the growing and the free horn-like portions
(the latter represented much too long in fig. 8 _a´_ and _b´_) are about
equal in length: the basal portion of one side of the scutum overlaps
the tergum.
_Terga._--The internal glowing surface (fig. 8 _b´_) is almost
diamond-shaped, and less in area than the sputa: external surface
rounded; internal surface of the free horn-like portion, slightly
concave.
_Colour and Structure of Valves._--The external surfaces of the scuta
and terga are yellow along the middle, plainly marked by zones of
growth, and finely ribbed longitudinally: the internal surfaces and
sides of the horns of the two valves, are coloured fine blue or purple;
in the terga, however, the internal surface is mottled with yellow. In
some specimens, especially in one from Tavoy, each zone of growth was
only very narrowly edged with blue. When a thin layer is removed from
one of the valves, the dark blue or rather purple appears by transmitted
light a beautiful pale blue; and it is a very singular fact, that this
blue portion is permanently turned by very gentle into a fiery red; the
same singular effect is produced by muriatic and acetic acids. This blue
part is much harder than the yellow; the latter exhibits, under a high
power, a folded structure, and is penetrated by a few tubuli, whereas
the harder blue portion has a cellular or scaled appearance. The spines
of the peduncle exhibit, in a smaller degree, similar phenomena.