impregnation of the ova in the females and hermaphrodites, it may be
observed that in the two male Iblas, the elongated moveable body seems
perfectly adapted for this end; in the males of the first three species
of Scalpellum, the spermatozoa, owing to the manner in which the thorax
is bent when protruded, would be easily discharged into the sack of the
female or hermaphrodite; this would likewise probably happen with the
complemental male of _S. rostratum_, considering its position within the
orifice of the capitulum, between the mouth and the adductor scutorum
muscle. The males of _S. Peronii_ and _villosum_ being fixed a little
way beneath the orifice of the sack, below the adductor muscle, are less
favorably situated, but the spermatozoa would probably be drawn into the
sack by the ordinary action of the cirri of the hermaphrodite, and
therefore would at least have as good a chance of fertilising some of
the ova, as the pollen of many dioecious plants, trusted to the wind,
has of reaching the stigmas of the female plants. Regarding the final
cause, both of the simpler case of the separation of the sexes,
notwithstanding that the two individuals, after the metamorphosis of the
male, become indissolubly united together, and of the much more singular
fact of the existence of Complemental males, I can throw no light; I
will only repeat the observation made more than once, that in some of
the hermaphrodites, the vesiculæ seminales were small, and that in
others the probosciformed penis was unusually short and thin.
Viewing the parasitic males, in relation to the structure and appearance
of the species to which they belong, they present a singular series. In
_S. Peronii_ and _S. villosum_, the internal organs have the appearance
of immaturity; the shape of the capitulum is specially modified for its
reception between the scuta of the hermaphrodite, and several of the
valves have not been developed. This atrophy of the valves, is carried
much further in _S. rostratum_. In Ibla, many of the parts are embryonic
in character, but others mature and perfect; some parts, as the
capitulum, thorax, and cirri, are in a quite extraordinary state of
atrophy; in fact, the parasitic males of Ibla consist almost exclusively
of a mouth, mounted on the summit of the three anterior segments of the
21 normal segments of the archetype crustacean. In the males of the
first three species of Scalpellum, some of the characters are
embryonic,--as the absence of a mouth, the presence of the abdominal
lobe, and the position of the few existing internal organs; other
characters, such as the general external form, the four bead-like
valves, the narrow orifice, the peculiar thorax and limbs, are special
developments. These three latter parasites, certainly, are wonderfully
unlike the hermaphrodites or females to which they belong; if classed as
independent animals, they would assuredly be placed not in another
family, but in another Order. When mature they may be said essentially
to be mere bags of spermatozoa.
In looking for analogies to the facts here described, I have already
referred to the minute male Lerneidæ which cling to their females,--to
the worm-like males of certain Cephalopoda, parasitic on the
females,--and to certain Entozoons, in which the sexes cohere, or even
are organically blended by one extremity of their bodies. The females in
certain insects depart in structure, nearly or quite as widely from the
Order to which they belong, as do these male parasitic Cirripedes; some
of these females, like the males of the first three species of
Scalpellum, do not feed, and some, I believe, have their mouths in a
rudimentary condition; but in this latter respect, we have, amongst the
Rotifera, a closely analogous case in the male of the Asplanchna of
Gosse, which was discovered by Mr. Brightwell[62] to be entirely
destitute of mouth and stomach, exactly as I find to be the case with
the parasitic male of _S. vulgare_, and doubtless with its two close
allies. For any analogy to the existence of males, complemental to
hermaphrodites, we must look to the vegetable kingdom.
Finally, the simple fact of the diversity in the sexual relations,
displayed within the limits of the general Ibla and Scalpellum, appears
to me eminently curious; we have (1st) a female, with a male (or rarely
two) permanently attached to her, protected by her, and nourished by any
minute animals which may enter her sack; (2d) a female, with successive
pairs of short-lived males, destitute of mouth and stomach, inhabiting
two pouches formed on the under sides of her valves; (3d) an
hermaphrodite, with from one or two, up to five or six similar
short-lived males without mouth or stomach, attached to one particular
spot on each side of the orifice of the capitulum; and (4th)
hermaphrodites, with occasionally one, two, or three males, capable of
seizing and devouring their prey in the ordinary Cirripedial method,
attached to two different parts of the capitulum, in both cases being
protected by the closing of the scuta. As I am summing up the
singularity of the phenomena here presented, I will allude to the
marvellous assemblage of beings seen by me within the sack of an _Ibla
quadrivalvis_,--namely, an old and young male, both minute, worm-like,
destitute of a capitulum, with a great mouth, and rudimentary thorax and
limbs, attached to each other and to the hermaphrodite, which latter is
utterly different in appearance and structure; secondly, the four or
five, free, boat-shaped larvæ, with their curious prehensile antennæ,
two great compound eyes, no mouth, and six natatory legs; and lastly,
several hundreds of the larvæ in their first stage of development,
globular, with horn-shaped projections on their carapaces, minute single
eyes, filiformed antennæ, probosciformed mouths, and only three pair of
natatory legs; what diverse beings, with scarcely anything in common,
and yet all belonging to the same species!
[62] ‘Annals of Natural History,’ vol. ii, (2d series, 1848,) p.
153, Pl. vi. Mr. Dalrymple has published a very interesting paper
on the same subject in the ‘Philosophical Transactions,’ (p.
342,) 1849; and there is another Memoir by Mr. Gosse in the
‘Annals of Natural History,’ vol. vi, (1850,) p. 18.
_Genus_--POLLICIPES. Pl. VII.
POLLICIES. _Leach._ Journal de Physique, tom. lxxxv, Julius,
1817.[63]
LEPAS. _Linn._ Systema Naturæ, 1767.
ANATIFA. _Brugière._ Encyclop. Méthod. (des Vers), 1789.
MITELLA. _Oken._ Lehrbuch der Naturgeschichte, 1815.
RAMPHIDIONA. _Schumacher._ Essai d’un Nouveau Syst. &c., 1817
(ante Julium).
POLYLEPAS. _De Blainville._ Dict. des Sc. Nat., 1824.
CAPITULUM (secundum Klein). _J. E. Gray._ Annals of Philos., tom.
x, new series, Aug. 1825.
[63] This is one of the rare cases in which, after much
deliberation, and with the advice of several distinguished
naturalists, I have departed from the Rules of the British
Association; for it will be seen that _Mitella_ of Oken, and
_Ramphidiona_ of Schumacher, are both prior to _Pollicipes_ of
Leach; yet, as the latter name has been universally adopted
throughout Europe and North America, and has been extensively
used in geological works, it appears to me to be as useless as
hopeless to attempt any change. It may be observed that the genus
_Pollicipes_ was originally proposed by Sir John Hill (‘History
of Animals,’ vol. iii, p. 170), in 1752, but as this was before
the discovery of the binomial system, by the Rules it is
absolutely excluded as of any authority. In my opinion, under all
these circumstances, it would be mere pedantry to go back to
Oken’s ‘Lehrbuch der Naturgeschichte’ for the name _Mitella_,--a
work little known, and displaying entire ignorance regarding the
Cirripedia.
_Valvæ ab 18 usque ad 100 et amplius: lateribus verticilli inferioris
multis; lineis incrementi deorsùm ordinatis: sub-rostrum semper adest:
pedunculus squamiferus._
Valves from 18 to above 100 in number: latera of the lower whorl
numerous, with their lines of growth directed downwards: sub-rostrum
always present: peduncle squamiferous.
Hermaphrodite; filamentary appendages either none, or numerous and
seated on the prosoma and at the bases of the first pair of cirri;
labrum bullate; trophi various; olfactory orifices generally highly
prominent; caudal appendages uni-articulate and spinose, or
multi-articulate.
Attached to fixed, or less commonly to floating objects, in the
warmer temperate, and tropical seas.
It has been remarked, under Scalpellum, how imperfectly that genus is
separated from Pollicipes; and we have seen under _Scalpellum villosum_
that the addition of a few small valves to the lower whorl, would
convert it into a Pollicipes, most closely allied to _P. sertus_ and
_spinosus_. It has also been shown, that the six recent species of
Pollicipes might be divided into three genera, of which _P. cornucopia_,
_P. elegans_, and _P. polymerus_, would form one thoroughly natural
genus, as natural as Lepas and the earlier genera; _P. mitella_ would
form a second; and _P. sertus_ and _P. spinosus_ a third; but I have
acted to the best of my judgment in at present retaining the six species
together. As far as the valves of the capitulum are concerned, it would
be very difficult to separate _P. mitella_ from _P. sertus_ and
_spinosus_.
_Description._ The number of valves in the capitulum has in this genus
acquired its maximum. The number varies considerably in the same
species, and even on opposite sides of the same individual, and
generally increases with age. It is more important, that the number of
the whorls in _P. cornucopia_, and in the two following closely-allied
forms, also increases with age. In _P. sertus_ and _P. spinosus_, even
the number of the whorls varies in different individuals, independently
of age. The valves are arranged alternately with those above and below;
they are generally thick and strong, making the capitulum somewhat
massive; in some species they are subject to much disintegration; but in
others, the apices of the several valves, especially of the carina and
rostrum, are well preserved, and project freely: they are covered with
membrane, which, differently from in most species of Scalpellum, either
does not bear any spines, or only exceedingly minute points. In all the
species there is a sub-rostrum and sub-carina, and often beneath these a
second sub-rostrum and sub-carina. In medium-sized specimens there are
at least 20 valves in the lowermost whorl. The carina is either straight
or curved, but never rectangularly bent, and is always of considerable
breadth. None of the valves are added to at their upper ends. The scuta
have a deep pit for the adductor muscle. The valves lie either some
little way apart, or more commonly close together. In _P. mitella_ the
scuta and terga are locked together by a fold, and the valves of the
lower whorl overlap each other in a peculiar manner, resembling that in
which the compartments in the shells of Sessile Cirripedes fold over
each other.
The _Peduncle_ is of considerable length in some of the species, and
rather short in others; it is, in every case, clothed with calcified
scales. The scales in the first four species are placed alternately and
symmetrically; they are formed and added to in the same manner as in
Scalpellum; they differ in size according to the size of the individual,
and consequently the lower scales on the peduncle, formed when the
specimen was young, are smaller than the upper scales; the lower scales
are separated from each other by wide interspaces of membrane, owing to
the continued growth of the peduncle by the formation of new layers of
membrane, and the disintegration of the old outer layers. Each scale is
invested by tough membrane (or has been, for it is often abraded off),
in the same manner as the valves; each is furnished with one or more
tubuli, in connection with the underlying corium. In _P. sertus_ and _P.
spinosus_, the scales are small, spindle-shaped, and not of equal sizes,
and the rows are distant from each other, so that their alternate
arrangement is not distinguishable; in these two species, new scales are
formed round the summit of the peduncle, and the growth of each is
completed whilst remaining in the uppermost row; but, besides these
normal scales, such as exist in the other species of Pollicipes and in
Scalpellum, new scales are formed in the lower part of the peduncle,
which are generally of very irregular shapes, are often larger than the
upper ones, are crowded together, and sometimes do not reach the outer
surface of the membrane. This formation of scales in the lower part of
the peduncle, independently of the regular rows round the uppermost
part, is perhaps a feeble representation of the calcareous cup at the
bottom of the peduncle in the genus Lithotrya. The prehensile antennæ
will be described under _P. cornucopia_.
_Size._--Most of the species are large: and _P. mitella_ is the most
massive of the Pedunculated Cirripedes.
The _Mouth_ is not placed far from the adductor muscle. The labrum is
highly bullate. The mandibles have either three or four main teeth (Pl.
X, fig. 1), with often either one or two smaller teeth inserted between
the first and second. The maxillæ (Pl. X, figs. 13, 14), have their
edges either straight and square, or notched, or more commonly with two
or three prominences bearing tufts of finer spines. The outer maxillæ
(fig. 17) generally have a deep notch on their inner edges, but this is
not invariable. The olfactory orifices in most of the species are highly
prominent.
_Cirri._--The first pair is never placed far distant from the second.
The posterior cirri have strong, somewhat protuberant segments; and
between each of the four or five pair of main spines (Pl. X, fig. 27),
there is a rather large tuft of straight, fine, short bristles. The
second and third pair have the basal segments, either of the anterior
rami, or of both rami, so thickly clothed with spines (fig. 25), as to
be brush-like: in _P. mitella_, however, the third pair is like the
three posterior pair in the arrangement of its spines, in this respect
resembling the sessile Chthamalinæ. The caudal appendages are either
uni-articulate and spinose, or multi-articulate: it is remarkable that
there should be this difference in such closely allied species as _P.
cornucopia_ and _P. polymerus_: the short, obtuse, obscurely-articulated
caudal appendage of the former species (fig. 22) makes an excellent
passage from the uni-articulate (fig. 19) to the multi-articulate form,
as in _P. mitella_.
The stomach, in those species which I opened, is destitute of cæca; the
hepatic glands are arranged in straight lines; the rectum is unusually
short. The prosoma is well developed.
In _P. cornucopia_, _P. elegans_, and _P. polymerus_, there are numerous
filamentary appendages both on the prosoma, and at the bases of the
first pair of cirri: these appendages are occupied by testes, and I
suspect stand in relation to the length of the peduncle and consequent
great development of the ovaria. In order to give space for the
filamentary appendages, the sack (generally roughened by small
inwardly-pointing papillæ) penetrates more deeply than usual into the
upper part of the peduncle. There are small ovigerous fræna in _P.
sertus_, _P. spinosus_, and _P. mitella_: in the three other species,
the frænum or fold occupies the usual position on each side, and is
large; but in one specimen carefully examined by me, I was unable to see
any glands; and in another specimen, the ovigerous lamellæ were not
attached to the fræna; hence I conclude that the fræna are functionless
in these three species.
_Affinities._--I have already remarked on the close relationship between
this genus and Scalpellum; there is also some affinity with Lithotrya.
_Distribution._--All over the world. The _P. cornucopia_ ranges
from Scotland to Teneriffe: the _P. polymerus_ is found in
opposite hemispheres in the Pacific Ocean, extending from
California to at least as far as 32° south of the Equator.
_Geological History._--Having so lately given, in the ‘Memoirs of the
Palæontographical Society,’ a full account of all the fossil species
known, I will not repeat here the conclusions there arrived at. I will
only state, that species of Pollicipes are found in all the formations,
extending from the Lower Oolite to the Upper Tertiary beds.
1. POLLICIPES CORNUCOPIA. Pl. VII, fig. 1.
POLLICIPES CORNUCOPIA. _Leach._ Encyclop. Brit. Supp., vol. iii,
1824.
---- SMYTHII, var. _Leach_. Ibid.
LEPAS POLLICIPES. _Gmelin._ Systema Naturæ, 1789.
---- GALLORUM. _Spengler._ Skrivter Naturhist. Selskabet, Bd. i,
Tab. vi, fig. 9, 1790.
_P. capitulo, valvarum duobus aut pluribus sub-rostro verticillis
instructo: valvis albis, aut glaucis: pedunculo, squamarum densis
verticillis symmetricè dispositis._
Capitulum with two or more whorls of valves under the rostrum; valves
white or gray; scales on the peduncle symmetrically arranged in close
whorls.
Maxillæ with three tufts of fine bristles, separated by larger spines:
segments in the first cirrus less than half the number of those in the
sixth cirrus: caudal appendages multi-articulate: filamentary appendages
attached to the prosoma.
Coast of Portugal; mouth of the Tagus. England,[64] Ireland, and
the Frith of Forth in Scotland. Mediterranean (according to
Brugière): Teneriffe: Mogador, Africa.
[64] This species is said by Montagu (‘Test. Brit. Supplement’)
to have been found attached to drift timber in the Frith of
Forth, and to the bottom of a wrecked vessel towed into
Dartmouth. According to Mr. W. Thompson (‘Annals of Nat. Hist.’
vol. xiii, p. 436), it has been found attached to wood-work near
Dublin.
Capitulum, obtusely triangular, massive: valves close together, rather
thick, with their exterior surfaces convex, naked, except in the lower
parts, where united together by tough, greenish-brown membrane,
destitute of spines. The edges of the orifice are widely bordered by
membrane, coloured fine crimson red. The valves, in a specimen with a
capitulum above three quarters of an inch long, were 52 in number; in a
specimen one fifth of an inch long, only between 20 and 30. Two whorls
of valves are distinct beneath the carina and rostrum. In one specimen
in Mr. Cuming’s collection, with a capitulum 1.4 of an inch long, there
were three whorls beneath the rostrum, and four beneath the carina. The
scuta, terga, and carina are much larger than the other valves.
_Scuta_, oval, the basal and tergo-lateral margins sweeping into each
other, and the apex pointed; internally (Pl. VII, fig. 1 _a_) the pit
for the adductor muscle is deep.
_Terga_, larger than the scuta, internally (fig. 1 _a_) slightly
concave; carinal margin much curved and protuberant; basal angle blunt;
scutal margin either curved with the upper part straight, or formed of
two almost distinct lines, corresponding with the tergal margin of the
scutum, and with one of the sides of the upper latus.
_Carina_, much curved, extending far up between the terga, internally
deeply concave, widening much from the top to the bottom; basal margin
highly protuberant, with a central portion either truncated and very
slightly hollowed out, or bluntly and rectangularly pointed, with the
apex itself rounded.
_Rostrum_, not one third of the length of the carina, concave,
triangular, with the basal margin slightly protuberant. Of the other
valves, including the sub-carina and sub-rostrum, the shape of their
inner surfaces is sub-triangular, with the basal margin convex;
externally the umbones are pointed, and slightly curled inwards, so as
to overlap each other like tiles: the smaller valves, however, of the
lower whorls (fig. 1 _a_) are more or less transversely elongated, so as
to become almost elliptic instead of triangular. Of the latera, the
upper pair, which corresponds to the interspace between the scuta and
terga, is the largest, but barely exceeds in size the pair answering to
the carinal latera in Scalpellum, which lie between the terga and
carina: the next largest pair is the rostral, or that between the scuta
and rostrum. Some, however, of the lower latera are of nearly equal
size.
_Peduncle_, narrower, but generally longer than the capitulum; upper
part encased with small calcareous scales, with their apices curved
inwards, and overlapping each other. The inner surface of each scale is
triangular, with the basal margin protuberant. The scales continue to
grow or be added to, only in about the ten upper whorls, which form but
a small part of the whole peduncle; in the lower part, the scales become
further and further separated from each other. The surface of
attachment, in full-grown specimens, is broad; but in two very young
specimens, which I removed with great care after the action of potash, I
found the peduncle ending in a filiform prolongation, such as often
occurs in _Scalpellum vulgare_ and in _Lepas fascicularis_. At the
extremity of the pointed peduncle, there were seated the larval
prehensile antennæ, of which the following measurements are given to
show how minute they are.
_Inch._
Length, from apex of disc, to the further
edge of the basal articulation 20/6000
Breadth of basal segment, in broadest part 6/6000
Hoof-like disc, length of 6/6000
Ultimate segment, entire length of 6/6000
“ “ breadth, in broadest part 6/20000
The disc resembles a broad, rounded hoof, very little longer than broad,
and narrowed in at the heel; the apex is not at all pointed, and bears
some minute and thin spines. There is one large spine on the under side
of the disc; and another on the basal segment, on the outside, in the
usual position. The ultimate segment is long and thin; it has a notch on
the inner side (the segment supposed to be stretched forward), bearing
two or three long flexuous spines; and there are three or four other
spines on the summit: altogether there is a close resemblance with the
antennæ in Scalpellum, excepting that the hoof-like disc is not here
pointed.
_Colours._--Valves internally tinted, in parts, grey; peduncle, brown;
corium of sack, purplish-brown, of peduncle, rich coppery brown; cirri,
banded dorsally, and with the front surfaces of the segments,
purplish-brown. Edge of the orifice of sack, fine crimson red. The
specimen here described had been dried for a few weeks, and was then
moistened.
_Dimensions._--The largest specimen which I have seen, in Mr. Cuming’s
collection, had a capitulum 1 and 4/10ths of an inch long; a fine
specimen, from Teneriffe, was 9/10ths in length. In a specimen with a
capitulum 1/20th of an inch long, and about the same in breadth, there
were eighteen valves; so that, besides the principal valves, five pair
of latera, the sub-carina, and sub-rostrum, were already developed, and
on the upper part of the peduncle, there were many calcareous scales.
_Filamentary Appendages._--The prosoma is well-developed, with thirteen
or fourteen pair of short, blunt filaments, placed close together in two
longitudinal rows; those nearest the thorax are the longest; outside
this double row, on each side, there is a row of papillæ, indicating a
tendency to the formation of two other rows of filaments. There is a
pair of longer filaments, one on each side of the mouth, pointing
upwards, and thinly clothed with long spines; at the bases of the first
pair of cirri there is a second pair of filaments, shorter and bearing a
few minute spines. The bottom of the sack is studded with small rounded
papillæ, with roughened summits.
_Mouth_, not placed very far from the adductor muscle.
_Labrum_, highly bullate, equalling, in its longitudinal diameter, the
rest of the mouth; upper part square, not overhanging the lower part;
there are some small teeth on the crest.
_Palpi_, oval, outer and inner margins nearly alike, thickly clothed
with spines.
_Mandibles_, with three very strong, yellow teeth; inferior point broad,
coarsely pectinated. In one specimen, on one side, the third tooth was
represented by two smaller teeth.
The _Maxillæ_ bear three conspicuous tufts of fine bristles, separated
by larger spines; the first tuft is placed close to the two, upper,
large, but unequally-sized spines; the second tuft is placed in the
middle, and the third at the inferior angle. The two latter tufts stand
on prominences; between the two upper tufts there are three pair, and
between the two lower tufts four or more pair of rather strong spines:
(see the figure, 13, Pl. X, in the allied _P. polymerus_.)
_Outer Maxillæ_, with the inner edge divided in the middle by a
conspicuous notch, and with the bristles above and below short, making
two _equal_ combs. On the exterior surface, the bristles are longer and
more spread out. Olfactory orifices prominent, protected by a punctured
swelling between the bases of the first pair of cirri.