thorax and peduncle is more plainly developed, projecting at the point
corresponding to _h_ in fig. 1, Pl. V, 8/1000ths of an inch; in the
middle the fold is notched; it can be traced more easily than in _I.
Cumingii_, running beneath and parallel to the basal edge of the mouth,
to the ventral margin of the body. In the mouth there is hardly any
difference; the maxillæ, however, have two notches even plainer than in
the hermaphrodite _I. quadrivalvis_, or than in the male _I. Cumingii_,
but the depth of such notches is always a variable character; there are
also more spines on the edge in the male of the present species, than in
_I. Cumingii_. Both mandibles and maxillæ in the male _I. quadrivalvis_,
are larger than in the male _I. Cumingii_, to a greater degree than the
larger proportional size of the body in the former will account for; and
this, likewise, is the case with these same organs in the hermaphrodite
_I. quadrivalvis_ compared with the female _I. Cumingii_. The tubular
olfactory orifices are situated in the same peculiar position as in the
hermaphrodite, and as in both sexes of _I. Cumingii_: they are 1/500th
of an inch in diameter, and about as thick as one of the lower segments
in the rami of the sixth cirrus.
The thorax, as in the male of _I. Cumingii_, is quite rudimentary, and
serves as a mere flap to protect the mouth. In the three specimens
carefully examined, the posterior cirri had each only one ramus, whilst
the anterior cirri generally had two: in one specimen, one of the rami
in the anterior cirrus was formed of five segments, and the other ramus
of three segments, both rami being supported on a uni-articulated
pedicel; but on the opposite side of the same individual, the anterior
cirrus was represented by a mere knob. The longer ramus of the anterior
cirrus, in the best-developed individual, barely exceeded in length the
mandibles measured along the line of the teeth! In one specimen between
the bases of the posterior cirri, there were two perfectly distinct
caudal appendages; these, like the cirri, are in a quite rudimentary
condition; one was 5/1000ths of an inch in length, and consisted of
three segments, the upper edges of which had short spines; the other was
shorter, uni-articulated, but spinose. In a second specimen, these
appendages were quite aborted. Close under them, on the inside or
towards the mouth, (that is, in the normal position,) there was a
rudimentary but quite distinct penis, with the apex projecting freely,
and with the sides distinguishable from the ventral surface of the
thorax, for the length of 1/1000th of an inch: the corium lining this
little penis made the terminal orifice plainly visible. The vesiculæ
seminales lie in the usual position, and are conspicuous; they are
slightly tortuous, with their ends blunt: in the specimen so well
preserved in spirits, they were filled with a mass of spermatozoa,
perfectly distinct; and the whole cavity of the body was lined with
globular and pear-shaped testes. Assuredly there was no vestige of
ovarian tubes. From the greater size and excellent preservation of this
specimen, which rendered the examination of the generative system so
easy, I was able to examine the contents of the stomach, in which I
found the delicate epithelial coat, separated as usual, and containing
cellular matter, on which the animal had preyed, but the nature of which
I was unable to make out. The anus was much plainer than in the male of
_I. Cumingii_. I saw the eye distinctly. I could not distinguish the
orifices of the acoustic (?) sacks; and I think I should have seen them,
if they had existed.
_Prehensile Antennæ._--I examined these in the larvæ presently to be
mentioned, and therefore they were in better condition than in the
mature animal when cemented. Their total length, measured along the
outside, from the basal articulation to the end of the disc, is
32/6000ths or 33/6000ths of an inch--that is, one third longer than in
_I. Cumingii_; whilst the hoof-like disc itself is 8/6000ths, or only
1/6000th of an inch longer than this same part in _I. Cumingii_: the
apex of the disc is downy, or bears some excessively minute spines. The
ultimate segment has its end irregularly rounded, with the spines
obscurely divided into two groups, the outer group consisting of two or
three longer and thinner spines, and the inner group of, as I believe,
five rather shorter spines: the longer spines equal in length the whole
ultimate segment. I could not perceive that they were plumose, as in
many other genera. A single, rather thicker and long spine, pointing
backwards, is attached to the under side of the disc, nearly opposite to
the point where the ultimate segment is articulated on the upper convex
surface. Another single, curved spine is attached on the outer side of
the basal segment, near its distal end.
_Development of the Male._--In the specimen before alluded to, which
included two males, one of these was only the 30/1000ths of an inch in
length, and therefore between one fifth and one sixth of the size of the
mature male. It had, probably, undergone only one exuviation since its
metamorphosis, for the larva is nearly as long, namely, 25/1000ths of an
inch. In this young male, the mouth formed one third of the entire
length: it was attached, not as in every other case to the sack of the
hermaphrodite, but low down to the peduncle of the other male.
In the sack with these two males, there were certainly four, I believe
five, larvæ, which in every main point of structure resembled the larvæ
of other pedunculated Cirripedes. From the peculiar form of their
prehensile antennæ, differing in no respect, except in the proportional
lengths of the segments, from the same organ in the male _I. Cumingii_,
I can feel no doubt that these were the larvæ of the male _I.
quadrivalvis_;--for a moment’s reflection will show how excessively
improbable it is, that several larvæ of some other Cirripede, and that a
Cirripede intimately allied to the parasitic male Ibla, should have
forced themselves, without any apparent object, into the sack of the
hermaphrodite Ibla. The larvæ, though not yet attached, were on the
point of attachment, so that the single eye of the mature animal could
be distinctly seen, lying near to the two great compound eyes of the
larva. We have also just seen, that one male quite recently here had
undergone its metamorphosis. The larvæ are 25/1000ths of an inch in
length, and rather more than 10/1000ths in width in the widest part:
they are boat-shaped, the dorsal edge forming the keel of the boat; the
anterior end is only a little blunter than the posterior end; the
quasi-bivalve carapace is smooth. All the essential points of structure
in the larvæ of other Cirripedes at this stage, could be distinctly here
seen,--such as the two compound eyes, with the apodemes to which they
are attached, and the two oblong sternal plates whence the apodemes
spring,--the adductor muscle,--the six natatory legs, with long plumose
spines,--the abdomen, with its three small segments and the caudal
appendages,--the prehensile antennæ already described,--and, lastly, the
two little (auditory?) sacks at the antero-sternal edges of the
carapace, but not so near the anterior extremity as in Lepas. The four
or five larvæ, after having undergone in the open sea the several
preparatory metamorphoses common to the class, must have voluntarily
entered the sack of the hermaphrodite: ultimately would they, on finding
two males already attached there, have retired, and sought another
individual less well provided; or would they all have remained, and so
formed a polyandrous establishment, such as we shall presently see
occurs sometimes in Scalpellum? This must remain quite uncertain.
In this same hermaphrodite specimen of _I. quadrivalvis_, the two
ovigerous lamellæ contained some hundreds of larvæ in the first stage of
development, which were liberated from their enveloping membranes by a
touch of a needle: they were about the 16/1000ths of an inch in length,
and presented all the usual characters of larvæ at this period. What a
truly wonderful assemblage of beings of the same species, but how
marvellously unlike in appearance, did this individual hermaphrodite
present! We have the numerous, almost globular larvæ, with lateral horns
to their carapaces, with their three pair of legs, single eye,
probosciformed mouth and long tail:--we have the somewhat larger larvæ
in the last stage of development, much compressed, boat-formed, with
their two great compound eyes, curious prehensile antennæ, closed
rudimentary mouth and six natatory legs so different from those in the
first stage:--we have the two attached males, with their bodies reduced
almost to a mouth placed on the summit of a peduncle, with a minute,
apparently single eye shining through the integuments, without any
carapace or capitulum, and with the thorax as well as the legs or cirri
rudimentary and functionless:--lastly, we have the hermaphrodite, with
all its complicated organisation, its thorax supporting six pairs of
multi-articulated two-armed cirri, and its well-developed capitulum
furnished with horny valves, surrounding this wonderful assemblage of
beings. Unquestionably, without a rigid examination, these four forms
would have been ranked in different families, if not orders, of the
articulated kingdom.
_Concluding Remarks._--If the creature which I have considered as the
male of _Ibla Cumingii_ be really so, and the evidence formerly given
seems to me amply conclusive, then the animal just described, from its
close affinity in every point of structure with the former, assuredly is
the male of _Ibla quadrivalvis_. But feeling strongly how improbable it
is, that an additional or complemental male should be associated with an
hermaphrodite, I will make a few remarks on the only possible
hypothesis, if my view be rejected,--namely, that the two parasites
considered by me to be exclusively males, are not so, but are
independent hermaphrodite Cirripedes, the female organs and ova (which,
if present, would have been nearly mature, judging from the presence of
spermatozoa in both species) having been overlooked by me in every
specimen: and again, that in the animal described as the female _I.
Cumingii_, I have, though minutely dissecting several specimens, and
finding far smaller parts, such as the organs of sense and nervous
system, entirely overlooked all the conspicuous male organs, though when
I came to _I. quadrivalvis_, and naturally expected to find it likewise
exclusively female, a single glance showed me the great probosciformed
penis, and by the simplest dissection the vesiculæ seminales and testes
were exhibited. Such an oversight is scarcely credible; but even if
assumed, we have to believe in the extraordinary circumstance of the two
parasites being species of an independent genus, not only the very next
in alliance to the animals to which they are attached, but in certain
most important points, namely, the organs of the mouth, actually
deserving a place in the very same genus. Moreover, the two parasites
differ from each other, not only in about the same slight degree, but in
a corresponding manner, as do the two Iblas to which they are attached;
thus the mouths of _Ibla quadrivalvis_ and _I. Cumingii_ are closely
similar, (the difference being barely of specific value,) so are the
mouths of the two parasites; but the parts are larger in the
hermaphrodite _I. quadrivalvis_, than in _I. Cumingii_, so are they in
the parasites. Again, the most conspicuous character in _I.
quadrivalvis_, is the number of segments in the caudal appendages, far
exceeding those in the other species of Ibla, as well as of every other
pedunculated Cirripede, and the parasite of this species has articulated
spinose appendages, far larger than the barely visible, non-articulated
pair in _I. Cumingii_.
Considering the whole case, there seems no room to doubt the justness of
the conclusion arrived at, under the former as well as under the present
species, namely, that these little parasites are the males of the two
species of Ibla to which they are attached;--wonderful though the fact
be, that in one case, the male should pair with an hermaphrodite already
provided with efficient male organs. It is to bring this fact
prominently forward, that I have called such males, Complemental Males;
as they seem to form the complement to the male organs in the
hermaphrodite. We look in vain for any, as yet known, analogous facts in
the animal kingdom. In the genus Scalpellum, however, next in alliance
to Ibla, in which, consequently, if anywhere, we might expect to find
such facts, they occur; and until these are fully considered, I hope the
conclusions here arrived at, will not be summarily rejected. Although
the existence of Hermaphrodites and Males within the limits of the same
species, is a new fact amongst animals, it is far from rare in the
Vegetable Kingdom: the male flowers, moreover, are sometimes in a
rudimentary condition compared to the hermaphrodite flowers, exactly in
the same manner as are the male Iblas. If the final cause of the
existence of these Complemental Males be asked, no certain answer can be
given; the vesiculæ seminales in the hermaphrodite of _Ibla
quadrivalvis_, appeared to be of small diameter; but on the other hand,
the ova to be impregnated are fewer than in most Cirripedes. No
explanation, as we have seen, can be given of the much simpler case of
the mere separation of the sexes in _Ibla Cumingii_: nor can any
explanation, I believe, be given of the much more varied arrangement of
the parts of fructification in plants of the Linnean class, Polygamia.
_Genus_--SCALPELLUM. Pls. V, VI.
SCALPELLUM. _Leach._ Journ. de Physique, t. lxxxv, July, 1817.
LEPAS. _Linn._ Systema Naturæ, 1767.
POLLICIPES. _Lamarck._ Animaux sans Vertebres, 1818.
POLYLEPAS. _De Blainville._ Dict. des Sc. Nat., 1824.
SMILIUM (pars generis). _Leach._ Zoolog. Journal, vol. 2, July,
1825.
CALANTICA (pars generis). _J. E. Gray._ Annals of Philosophy, vol.
x, (new series,) Aug. 1825.
THALIELLA (pars generis). _J. E. Gray._ Proc. Zoolog. Soc., 1848.
ANATIFA. _Quoy_ et _Gaimard_. Voyage de l’Astrolabe, 1826-34.
XIPHIDIUM (pars generis). _Dixon._ Geology of Suffolk, 1850.
(_Herm. et Foem._) _Valvis 12 ad 15: lateribus verticilli inferioris
quatuor vel sex, lineis incrementi plerumque convergentibus: sub-rostrum
rarissime adest: pedunculo squamifero, rarissime nudo._
(Herm. and Fem.) Valves 12 to 15 in number: latera of the lower whorl,
four or six, with their lines of growth generally directed towards each
other: sub-rostrum very rarely present: peduncle squamiferous, most
rarely naked.
Filamentary appendages, none: labrum, with the upper part highly
bullate: trophi, various: olfactory orifices, more or less prominent:
caudal appendages, uniarticulate and spinose, or none.
_Males_, parasitic at or near the orifice of the sack of the female or
of the hermaphrodite: thorax enclosed within a capitulum, furnished with
three or four rudimentary valves, or with six perfect valves: peduncle
either short and distinct, or confounded with the capitulum: sometimes
mouth and stomach absent, and cirri non-prehensile; sometimes mouth and
cirri normal.
Generally attached to horny corallines, in the warmer temperate
seas over the whole world.
I have felt much doubt in limiting this genus: the six recent species
which it contains, differ more from each other than do the species in
the previous genera. Mr. Gray has proposed or adopted generic names for
four of the species, and a fifth certainly has equal claims to this same
rank. These genera have been founded almost exclusively on the number of
the valves; and oddly enough, the numbers have generally been given
wrongly, namely, in Scalpellum, Calantica, Thaliella, and Xiphidium.
Scalpellum blends through _S. villosum_ into Pollicipes; and this latter
genus has an equal right with Scalpellum, to be divided into sub-genera,
three in number. Hence, no less than eight genera might be made out of
the twelve recent species of Scalpellum and Pollicipes, and their
formation, in some degree, be justified; but, in my opinion, this
inordinate multiplication of genera destroys the main advantages of
classification. At one time, I even thought that it would be best to
follow Lamarck, and keep the twelve recent species in one genus; but
considering the number of fossil species, I believe the more prudent
course has been followed, in retaining the two genera Scalpellum and
Pollicipes; more especially as I can hardly doubt, that several other
species will be hereafter discovered.
Having so lately described in the Memoirs of the Palæontographical
Society, the fossil species, I will not here further allude to them,
than to state, that out of the fifteen species therein described, _S.
magnum_ comes very close to the recent _S. vulgare_, and that several
Eocene and Cretaceous species, such as _S. quadratum_, _S. fossula_, and
_S. maximum_, are allied to _S. rutilum_ and _S. ornatum_. _Scalpellum
villosum_, a recent species, has stronger claims than any other species
to be generically separated; and its habits, in not being attached to
horny corallines, are also different, but the identity of its
Complemental Male with that of _S. Peronii_, and its numerous points of
resemblance in structure with the other species, have determined me not
to separate it. _Scalpellum Peronii_, _villosum_, and _rostratum_, in
having a sub-carina,--in the rostrum being pretty well developed,--and
in the Complemental Male being pedunculated, and furnished with a
functional mouth and prehensile cirri, may be separated from _S.
vulgare_, _ornatum_ and _rutilum_; but even between these two little
groups, _S. rostratum_ is in some respects intermediate, namely, in
having three pairs of latera, and more especially in the rudimentary
condition of the valves of its Complemental Male, and in the position in
which the male is attached to the hermaphrodite. The three species in
the second little group, namely, _S. vulgare_, _S. ornatum_, and _S.
rutilum_, are more nearly allied to each other in all their characters,
especially in the characters drawn from their Males, than are the other
three species. _S. ornatum_ and _S. rutilum_ are considerably nearer to
each other than any other two of the species. Upon the whole I conclude
that the six species must be thrown either into five or into four genera
(the first three species making one genus), or all into one genus, and
this latter has appeared to me the preferable course. The separation
even of Scalpellum and Pollicipes, as already stated, is hardly natural.
The fact of these genera having existed from a remote epoch, and having
given rise during successive periods to many species now extinct, is
probably the cause that the few remaining species are so much more
distinct from each other, than is common in the other genera of
Lepadidæ. Whenever the structure of the whole capitulum in the fossil
species is well known, and as soon as more species, recent and fossil,
shall have been discovered, then probably the genus Scalpellum will have
to be divided into several smaller genera.
_Description._--The _Capitulum_ is much compressed, and generally
produced upwards; it is formed of from twelve to fifteen valves, which
are rather thin, and with the exception of _S. ornatum_, almost entirely
covered by membrane, bearing spines: the valves are seldom locked very
closely together. A sub-rostrum exists only in _S. villosum_, which
species leads on to Pollicipes; in _S. vulgare_ the rostrum is
rudimentary and hidden. The scuta, terga and carina, are much larger
than the other valves: these five valves seem to differ essentially
from the others in being at first developed under the form of the
so-called primordial valves: the other valves commence by a small
indistinct brown spot, very different from the hexagonal tissue of the
primordial valves: I saw this very clearly in young specimens of _S.
vulgare_. At first, the scuta, terga and carina, grow exclusively
downwards (and permanently so in most fossil species), and therefore the
growth of the scuta and carina is in an absolutely opposite direction to
what it is in Lepas, Pæcilasma and Dichelaspis. After a short period the
scuta are added to at their upper ends; the portion thus added, stands
at a rather lower level, and projects in a rather different direction
from the first-formed part of the valve, giving to it, in some respects,
the appearance of having been broken and mended. This structure is
common to _S. vulgare_, _S. rostratum_ and _S. Peronii_. The upper
Latera (except in _S. villosum_) grow in the same manner, namely, at
first exclusively downwards, and then both upwards and downwards. The
rostral and carinal latera (with the same exception of _S. villosum_)
have their umbones seated laterally, at opposite ends of the
capitulum,--the umbones of the rostral latera being close to the
rostrum, and those of the carinal pair close to the carina, and
consequently their chief growth is directed towards each other. The
carina in all the species, except _S. villosum_, is either bowed or
angularly bent; in the latter case the lower half is parallel to the
peduncle, and the upper half, extending far up between the terga, is
parallel to their longer axes. In some of the species the carina is
added to almost equally at both ends; in _S. ornatum_ it grows but
little at the upper end, and to a varying degree in different
individuals according to their age; in _S. rutilum_ the umbo is at the
apex, and there is consequently no upward growth; lastly, in _S.
villosum_ the carina widening much from the apex to the basal margin,
grows exclusively downwards, and a portion of the apex projects
freely,--characters all common to the carina in the genus Pollicipes.
The upper latera occur in all the species; in the lower whorl there are
either two or three pair of latera, in the former case the infra-median
pair being absent. The latera differ considerably in shape in the
different species.
The _Peduncle_ is generally rather short, and, with the exception of _S.
Peronii_, is covered with calcified scales. These scales are generally
small, and placed symmetrically in close whorls, in an imbricated order,
with each scale corresponding to the interspace between two scales in
the whorls above and below. In _S. ornatum_, the scales are so wide,
transversely, that there are only four in each whorl. In _S. villosum_,
the scales are spindle-shaped and arranged somewhat irregularly in
transverse rows, not very near to each other. New calcareous scales
originate only round the top of the peduncle, and they continue to grow
only in the few upper whorls; and as the peduncle itself continues to
increase in diameter by the formation of new inner membranous layers and
the disintegration of the old outer layers, the calcareous scales come
in the lower part of the peduncle to stand further and further apart. In
the earliest stage of growth there are no calcareous scales on the
peduncle in _S. vulgare_; they first appear under the carina. Spines are
articulated in great numbers on the surface of the peduncle in _S.
vulgare_, _S. Peronii_, and _S. villosum_, and very short ones on that
of _S. rostratum_.
_Attachment._--All the species, except _S. villosum_, are attached to
horny corallines: the singular means of attachment in _S. vulgare_ will
be described under that species, and is probably common to several of
the other species. The larva in most, or in all cases, when it proceeds
to attach itself, clings head downwards to the branch, and hence the
capitulum comes to be placed upwards, with its orifice fronting the
branch and the carina outwards. The sucking disc of the prehensile
antennæ of the larva, in the five species examined, was a little
pointed, and in shape resembled the hinder hoof of a mule: this may
perhaps be accounted for by the narrowness of the branches of the
corallines, to which it has to adhere: a large circular disc, as in
Lepas, would have been worse than useless: the ultimate segment in most
or all the species, has on its inner side (the segment being supposed to
be extended straight forward) a notch or step, bearing, I believe, two
spines.
_Size and Colour._--Some of the species attain a medium size, others are
small. The valves are generally clouded red or pink, but sometimes
white.