of the peduncle, and surrounding the stomach, there are numerous,
little, rather irregular globular balls, with brown granular centres, so
closely resembling the testes in other Cirripedes, though of smaller
size, that I cannot doubt that this is their nature: they were much
plainer, larger, and more numerous in some specimens than in others. The
vesiculæ seminales can seldom be made distinctly out; but having cut
one specimen transversely across the thorax, they were as plain as could
be desired, lying parallel and close to each other above the rectum,
(the animal being in the position as drawn,) and therefore in their
normal situation. Each had a diameter four times as great as that of the
rectum. In this individual the contents seemed (whether from
decomposition or state of development, or from my not having used high
enough power, I know not,) merely pulpy; but I have since found, in
another specimen, masses of the most distinct spermatozoa, with the
usual little knots on them, associated with numerous cells, about as
large as and resembling those which I have examined in living
Cirripedes, and from which I have every reason to believe the
spermatozoa are developed. The vesiculæ seminales unite and terminate
under the two extremely minute caudal appendages, and here I think I saw
an orifice; but there is certainly no projecting, probosciformed penis.
Having dissected the six specimens with the utmost care, and having
scrupulously examined the ovaria in other Cirripedes during their early
stages of development, even before the exuviation of the larval
locomotive organs, and in specimens of smaller size than the male Ibla,
I am prepared to assert that there are no ovaria, and that these little
creatures are exclusively males. It should be borne in mind, that in
some of the specimens there were perfect spermatozoa in the vesiculæ
seminales (as likewise in some of the males of _I. quadrivalvis_), and,
therefore, if these individuals had been hermaphrodites, their ova would
have been, at this period, well developed, and ready for impregnation:
in this state it is almost impossible that they could have been
overlooked. Moreover, it is probable that such ova would not have been
very small, for the larvæ whence the parasitic males are derived, attain
(as might have been inferred from the known dimensions of their
prehensile antennæ, and as we shall show actually is the case in _I.
quadrivalvis_,) the size common amongst ordinary Cirripedia.
_Concluding Remarks._--That these animals are true Cirripedes, though
having so different an external appearance from others of the class,
admits of not the least doubt. The prehensile antennæ, enveloped in
cement and including the two cement-ducts, would have been amply
sufficient, without other parts--for instance, the mouth, by itself
perfectly characteristic with each organ, together with the whole
alimentary canal, constructed on the normal plan,--to have proved that
they were Cirripedia. Under the head of the closely-allied _Ibla
quadrivalvis_, we shall, moreover, see that the males are
developed from larvæ, having every point of structure--the peculiar
quasi-bivalve shell, the two compound eyes, the six natatory legs,
&c.,--characteristic of the Order. But in some respects, the males are
in an embryonic condition, though unquestionably mature, as shown by the
spermatozoa;--thus, in the thorax and mouth opening throughout their
whole width into the cavity of the peduncle, that is, homologically into
the anterior part of the head, and in the viscera being there lodged
instead of in the thorax and prosoma, there is a manifest resemblance to
the larva in its last stage of development: the absence of a
probosciformed penis, the spineless peduncle, the food being obtained
without the aid of cirri, and the length of the rectum, are likewise
embryonic characters. Not only are these males, as just remarked,
Cirripedia; but they manifestly belong to the Pedunculated Family. If a
specimen had been brought to me to class, without relation to its sexual
characters, I should have placed it, without any hesitation, next to the
genus Ibla; if the mouth alone had been brought, I should assuredly have
placed it actually in the genus Ibla: for let it be observed how nearly
all the parts resemble those of _Ibla Cumingii_, excepting only in size
and in being less hairy. The trophi are arranged in the same peculiar
position as in the female; the labrum is largely bullate, without teeth
on the crest; the palpi, though relatively smaller, are of the same
shape; so are the mandibles; the maxillæ are more rounded and less
prominent, but have the same exact size relatively to the mandibles;
the outer maxillæ have the same, quite peculiar pointed outline, and the
olfactory orifices are tubular, and hold the same unusual position. It
is most rare to find so close a resemblance in the parts of the mouth,
except in very closely allied genera, and often species of the same
natural genus differ more. Again, in the long oesophagus and constricted
stomach there is a resemblance to Ibla. In the male of _Ibla
quadrivalvis_, the caudal appendages are multi-articulate; now, this is
a character confined to four genera, namely, Ibla, Alepas, Pollicipes,
and Lithotrya. I may add, that large tubular olfactory orifices are
confined to the same genera, together with Scalpellum. Lastly, it
particularly deserves notice, that the prehensile antennæ, in having a
hoof-like and pointed disc, with a single spine on the heel, much more
closely resemble these organs in Scalpellum, certainly the nearest ally
of Ibla, than in any other genus; they differ from the antennæ in
Scalpellum, only in the ultimate segment not having a notch on one side.
These organs, unfortunately for the sake of comparison, were not found
in the female and ordinary form of Ibla. The full importance of the
above generic resemblance in the antennæ, will hereafter be more clearly
seen, when their classificatory value is shown in the final discussion
on the sexual relations of Ibla and Scalpellum.
Here, then, we have a pedunculated Cirripede _very much_ nearer in all
its essential characters to Ibla than to any other genus, and
exclusively of the male sex; and this Cirripede in six specimens, from
two distant localities, adhered to an Ibla exclusively of the female
sex. May we not, then, safely conclude that these parasites are the
males of the _Ibla Cumingii_? Considering that, in the same class with
the Cirripedia, there is a whole family of crustaceans, the Lerneidæ, in
which the males, compared with the females to which they cling, differ
as much in appearance as in Ibla, and are even relatively smaller, I
should not have added another remark, had there not been under the head
of the following species, and of the next genus Scalpellum, a class of
allied facts to be advanced, which in some respects support the view
here taken, but in others are so remarkable and so hard to be believed,
that I will call attention to the alternative, if the above view be
rejected. The ordinary _Ibla Cumingii_ must have a male, for that it is
not an hermaphrodite can hardly be questioned, seeing how easy it always
is to detect the male organs of generation; and we must consequently
believe in the visits of a locomotive male, though the existence of a
locomotive Cirripede is improbable in the highest degree. Again, as the
little animal, considered by me to be the male of _I. Cumingii_, is
exclusively a male, (for there were no traces of ova or ovaria, though
the spermatozoa were perfect,) we must believe in a locomotive Cirripede
of the opposite sex, though the existence in any class of a female
visiting a fixed male is unknown:[48] in short, we should have
hypothetically to make two locomotive Cirripedes, which, in all
probability, would differ as much from their fixed opposite sexes, as
does the Cirripede, considered by me to be the male of _I. Cumingii_,
from the ordinary form. This being the case, I conclude that the
evidence is amply sufficient to prove that the little parasitic
Cirripede here described, is the male of _Ibla Cumingii_.
[48] It deserves notice, that in the class Crustacea, both in the
Lerneidæ and in the Cirripedia, the males more closely resemble
the larvæ, than do the females; whereas amongst insects, as in
the case of the glow-worm in Coleoptera, and of certain nocturnal
Lepidoptera, it is the female which retains an embryonic
character, being worm-like or caterpillar-like, without wings.
But in all these cases, the male is more locomotive than the
female.
If we look for analogies to the facts here given, we shall find them in
the Lerneidæ already alluded to, but in these the males are not
permanently attached to the females, only cling, I believe, to them
voluntarily. The extraordinary case of the Hectocotyle, originally
described as a worm parasitic on certain Cephalopoda, but now shown by
Kölliker to be the male of the species to which it is attached, is
perhaps more strictly parallel. So again in the entozoic worm, the
_Heteroura androphora_ the sexes cohere, but are essentially distinct:
“this singular species, however,” according to Professor Owen,[49]
“offers the transitional grade to that still more extraordinary
Entozoon, the _Syngamus trachealis_, in which the male is organically
blended by its caudal extremity with the female, immediately anterior to
the slit-shaped aperture of the vulva. By this union a kind of
hermaphroditism is produced; but the male apparatus is furnished with
its own peculiar nutrient system; and an individual animal is
constituted distinct in every respect, save in its terminal confluence
with the body of the female. This condition of animal life, which was
conceived by Hunter as within the circle of physiological possibilities,
has hitherto been exemplified only in the single species of Entozoon,
the discovery of the true nature of which, is due to the sagacity and
patient research of Dr. C. Th. Von Siebold.” In Ibla, the males and
females are not organically united, but only permanently and immovably
attached to each other. We have in this genus the additional singularity
of occasionally two males parasitic on one female.
[49] Cyclopædia of Anatomy and Physiology, p. 142.
I have used the term parasitic, which perhaps ought strictly to be
confined to cases where one creature derives its nutriment from another,
inasmuch as the male is invariably and permanently attached to and
imbedded in the female,--from its being protected by her capitulum, so
that its own capitulum is not developed--and from its feeding on minute
animals infesting her sack. The male Ibla must seize its prey, guided
probably by its well-developed olfactory organs, through the movement of
its long, flexible body, furnished with muscles, and with the mouth
seated on the summit. We have already seen one instance of a Cirripede,
the Anelasma, obtaining its food without the aid of cirri, by means of
its probosciformed, flexible mouth. The eye can serve only to announce
to the male when the female opens her valves, allowing occasionally some
minute prey to enter. In ordinary Cirripedes the penis is long,
articulated, and capable of varied movements, I presume for the purpose
of impregnating each separate ovum: the male Ibla has no such organ; and
no doubt the whole body, furnished like the penis with longitudinal and
transverse muscles, serves the same purpose! I may remark, that it seems
surprising that so small a male should secrete sufficient semen to
impregnate the ova of the female, but the ova are not nearly so numerous
in Ibla as in most genera of Cirripedes; and the smallness of the males
in some parasitic Crustacea has already been alluded to. The male must
always be younger than the female, for the latter must first grow large
enough for the larva of the male to crawl into her sack. Whether the
male lives as long as the female I know not, but he certainly lives for
a considerable period and increases in size, as shown by the depth to
which the end of the peduncle is imbedded. Moreover we shall see, under
the next species, that the male is metamorphosed from a larva, not one
sixth of its own size.
In the male Ibla, abortion has been carried to an extraordinary and, I
should think, almost unparalleled extent. Of the twenty-one segments
believed to be normally present in every Crustacean, or of the seventeen
known to be present in Cirripedes, the three anterior segments are here
well developed, forming the peduncle: the mouth consists as usual of
three small segments: the succeeding eight segments are represented by
the rudimentary and functionless thorax, supporting only two pair of
distorted, rudimentary and functionless cirri: the seven segments of the
abdomen have disappeared, with the exception of the excessively minute
caudal appendages; so that, of the twenty-one normal segments, fifteen
are more or less aborted. The state of the cirri is curious, and may be
compared to that of the anthers in a semi-double flower; for they are
not simply rudimentary in size and function, but they are monstrous, and
generally do not even correspond on opposite sides of the same
individual. As males in other classes of the animal kingdom often retain
some female characters, so here (though the case is not strictly
analogous[50]) the male possesses the cementing apparatus, which
homologically is part of an ovarian tube modified.
[50] Certain plants offer a closer, though not perfect, analogy.
Thus, in the florets of some compositous flowers, the pistil,
besides its proper female functional end, serves to brush the
pollen off the anthers; while, in the florets of some other
compositæ (see the account of Silphium in ‘Ch. K. Sprengel Das
entdeckte Geheimniss der Natur’), the pistil is functionless for
its proper end, the flower being exclusively male, but its style
is developed, and still serves as a brush. So in the male Ibla,
part of the ovaria, in a modified condition, is still present,
and serves as a cementing apparatus.
The individuals in every other genus (with the exception of Scalpellum),
in the several families, in the three Orders of Cirripedia, are
hermaphrodite or bisexual. Why, then, is Ibla unisexual; yet, becoming,
in the most paradoxical manner, from its earliest youth, essentially
bisexual? Would food have been deficient, and was the seizure of
infusoria by another and differently constructed individual, necessary
for the support of the male and female organs? The orifice of the sack
of the female is unusually narrow; would the presence of testes and
vesiculæ seminales have rendered her thorax and prosoma inconveniently
thick? Seeing the analogous facts in the six, differently-constructed
species of the allied genus Scalpellum, I infer there must be some
profounder and more mysterious final cause.
2. IBLA QUADRIVALVIS. Pl. IV, fig. 9.
ANATIFA QUADRIVALVIS. _Cuvier._ Mém. pour servir ... Mollusq.
1817, Art. Anatifa, Plate, figs. 15, 16.
IBLA CUVIERIANA. _J. E. Gray._ Annals of Philosophy, vol. x, New
Series, Aug. 1825.
---- _J. E. Gray._ Spicilegia. Zoolog. Tab. iii, fig. 10.
TETRALASMIS HIRSUTUS. _Cuvier._ Regne Animal, vol. iii, 1830.
ANATIFA HIRSUTA. _Quoy_ et _Gaimard_. Voyage de l’Astrolabe, Pl.
xciii, figæ. 7-10, 1834.
_I. (Herm.), valvis et pedunculi spinis sub-flavis: basali tergorum
angulo, introrsùm spectanti, hebete, quia margo carinalis inferior
longiùs quam margo scutalis prominet._
_Hermaph._--Valves and spines on the peduncle yellowish: basal angle of
the terga, viewed internally, blunt, owing to the lower carinal margin
being more protuberant than the scutal margin.
Caudal appendages four times as long as the pedicels of the sixth
cirrus: rami of the first cirrus unequal in length by about six
segments.
_Complemental Male_, with a notched crest on the dorsal surface, forming
a rudiment of a capitulum: maxillæ well furnished with spines.
Kangaroo Island, South Australia (Mus. Brit., given by Cuvier to
Leach); Adelaide, South Australia (Mus. Stutchbury); King
George’s Sound, Voyage of Astrolabe; New South Wales, attached
to a mass of the Galeolaria decumbens, (Mus. Hancock).
HERMAPHRODITE.
All the external parts so closely resemble those of _I. Cumingii_, that
it would be superfluous to describe more than the few points of
difference. The horny substance of both scuta and terga is uniformly
yellow; though in dryed specimens, from the underlying corium being seen
through the valves, these generally have a tinge of blue.
The _Scuta_, viewed internally, are less elongated transversely; they
have their basal margins slightly more hollowed out, and the fold on the
upper free and horn-like portion rather deeper.
The _Terga_, viewed internally, have the apex of the growing or
corium-covered surface higher relatively to the scuta than in _I.
Cumingii_; and the basal angle is much broader, owing to the lower
carinal margin being much more protuberant than the scutal margin. The
spines on the peduncle are all yellowish-brown, and are rather longer
than in _I. Cumingii_. I observed in three or four specimens, that the
lowest part of the peduncle had become _internally_ filled up with the
usual, brown, transparent, laminated cement, cone within cone, so that
this lower part was rendered rigid and stick-like; this latter effect, I
apprehend, is the object gained by the formation of cement within the
peduncle, of which I have not observed any other instance. The entire
length of the largest specimen was one inch; some other specimens were
only half this size.
The thorax and prosoma are of the same shape as in _I. Cumingii_, and in
the largest specimen, about one tenth of an inch square; the prosoma, as
in that species, is hairy. In the _Mouth_, all the parts are closely
similar to those of _I. Cumingii_, but one third larger; the crest of
the labrum is a little roughened with minute points: the palpi are
squarer and blunter at their extremities: the mandibles have their
second and third teeth nearly equal in size to the first, and they do
not appear pectinated: the maxillæ have their spinose edge very nearly
straight: the outer maxillæ are pointed. The olfactory orifices are
similarly situated, and of similar shape; they are dark coloured.
_Cirri._--These also are similar to those of _I. Cumingii_; the
segments, however, of the three posterior cirri have each four pair of
spines, placed very close together in a transverse direction. First
cirrus has its two rami unequal in length by about six segments. The
anterior rami of the second and third cirri are thicker, and more
thickly clothed with spines, than the posterior rami, to perhaps a
greater degree than in _I. Cumingii_. In the posterior cirri, the upper
segments of the pedicels are nearly as long as the lower segments.
_Caudal Appendages_, four times as long as the pedicel of the sixth
cirrus, and three fourths of the length of the rami of this same cirrus:
segments thirty-two in number, and therefore as many as those forming
the sixth cirrus: the upper segments are much thinner and longer than
the basal segments; each furnished with a circle of short bristles;
whole appendage excessively thin and tapering: the two closely
approximate.
_Colour._--From some well-preserved dryed specimens in Mr. Stutchbury’s
possession, it appears that the sack, cirri and trophi, were dark blue,
as in _I. Cumingii_; after being long kept in spirits, these parts
become brown.
_Generative System._--The penis (Pl. IV, fig. 9 _a_) is very singular in
structure; it is of the ordinary length, but of small diameter; it
tapers but little; it consists of a moveable articulated, and a fixed
unarticulated portion; this latter is smooth, much flattened, not
divided into segments, and projects straight out under the caudal
appendages; it is about one third of the length of the entire penis; it
corresponds with a part present in all Cirripedes, but here surprisingly
elongated. The articulated portion consists of separate segments, twenty
in number, quite as distinct as those of the cirri; each one is oblong,
being longer by about a third part than broad; each has a few short
bristles round its upper margin; the terminal segment has a circular
brush of bristles. The vesiculæ seminales are easily seen, though they
are narrow; they are slightly tortuous; they enter the prosoma, and lie
on each side of the stomach; their outer case has a ringed structure,
but is not fibrous; the contents in the best specimen consisted of a
mass of spermatozoa, which I saw with perfect distinctness. The testes
are unusually large and egg-shaped.
_Ova_, spherical, 5/400ths of an inch in diameter, united as usual into
two ovigerous lamellæ. The ovigerous fræna are extraordinarily small,
and might be very easily overlooked; their length, in a full-sized
specimen, was only 7/400ths of an inch, and they projected only 2/400ths
from the inner surface of the sack. The glands on their margin, to which
the lamellæ adhere, are pointed oval, with an extremely short footstalk,
and that rather thick; the entire length of gland and footstalk, being
only 2/3000ths of an inch. The larvæ, in their first stage of
development, offer the usual characters, and closely resemble those of
Scalpellum; the probosciformed mouth, however, is remarkably prominent,
and the limbs unusually thick.
_Affinities._--This species most closely resembles _I. Cumingii_, and
cannot be distinguished externally, except by the absence of the blue
colour on the marginal and interior portions of the valves; and this can
hardly be ascertained without separating and cleaning them, owing to the
blueness of the underlying corium. Internally some slight differences
may be perceived in the form of the valves. Considering these so slight
differences, it is highly remarkable that this species should be
hermaphrodite, whilst _I. Cumingii_ is unisexual. There is a greater,
though still slight, difference in the included animal’s body; the palpi
in _I. quadrivalvis_ are blunter, the mandibles smoother, the olfactory
orifices darker-coloured; the rami of the first cirrus more unequal, the
spines more numerous on the segments of the posterior cirri, and lastly
and most conspicuously, the caudal appendages are very much longer
relatively to the length of the sixth cirrus, than in _Ibla Cumingii_.
COMPLEMENTAL MALE.
I have examined one specimen of the hermaphrodite _I. quadrivalvis_,
preserved in spirits from Kangaroo Island, and one dry from Adelaide,
both places in South Australia, and four from an unknown locality,
purchased from Mr. Sowerby; and within five out of these six specimens,
males were attached. In one of them, two males of different ages were
included, one adhering to the peduncle of the other: in _I. Cumingii_,
also, it may be remembered, there was a case of two males parasitic on
one female. I may add that I opened another quite young specimen, from
Adelaide, not counted with the above, and it was without a male. The
males in the five specimens were attached low down, at the rostral end,
almost in a horizontal position, stretching across the bottom of the
sack; one of them, however, was placed considerably on one side. One
individual which I measured, was 16/100ths of an inch in length, and
5/100ths in width in the widest part, namely, about half down the
peduncle. I may state, for the sake of comparison, that the
hermaphrodite to which this individual was attached, was, including the
peduncle and capitulum, one inch in length, that is, six times as long
as the male, and one fifth of an inch in width, that is, four times as
wide. The above measurements show that the male of this species is
rather more than twice as large as that of _I. Cumingii_. In consequence
of this greater size, I dissected, with the utmost care, the one
specimen which was excellently preserved in spirits, and found every
part, with a few exceptions, so exactly the same as in the male of _I.
Cumingii_, only larger and more conspicuous, that it will be sufficient
to indicate the few points of difference.