PYCNOGONIDA[393]
Remote, so far as we at present see, from all other Arthropods, while
yet manifesting the most patent features of the Arthropod type, the
Pycnogons constitute a little group, easily recognised and
characterised, abundant and omnipresent in the sea. The student of the
foreshore finds few species and seldom many individuals, but the dredger
in deep waters meets at times with prodigious numbers, lending a
character to the fauna over great areas.
[Illustration:
FIG. 262.—_Pycnogonum littorale_, Ström, × 2.
]
The commonest of our native species, or that at least which we find the
oftenest, is _Pycnogonum littorale_ (_Phalangium littorale_, Ström,
1762). We find it under stones near low water, or often clinging
louse-like to a large Anemone. The squat segmented trunk carries, on
four pairs of strong lateral processes, as many legs, long, robust,
eight-jointed, furnished each with a sharp terminal claw. In front the
trunk bears a long, stout, tubular proboscis, at the apex of which is
the mouth, suctorial, devoid of jaws; the body terminates in a narrow,
limbless, unsegmented process, the so-called “abdomen,” at the end of
which is the anal orifice. The body-ring to which is attached the first
pair of legs, bears a tubercle carrying four eye-spots; and below, it
carries, in the male sex, a pair of small limbs, whose function is to
grasp and hold the eggs, of which the male animal assumes the burden,
carrying them beneath his body in a flattened coherent mass. In either
sex a pair of sexual apertures open on the second joints of the last
pair of legs. The integument of body and limbs is very strongly
chitinised, brown in colour, and raised into strong bosses or tubercles
along the middle line of the back, over the lateral processes, and from
joint to joint of the limbs. The whole animal has a singular likeness to
the Whale-louse, _Cyamus mysticeti_ (well described by Fr. Martins in
1675), that clings to the skin of the Greenland Whale as does
_Pycnogonum_ to the Anemone, a resemblance close enough to mislead some
of the older naturalists, and so close that Linnaeus, though in no way
misled thereby, named it _Phalangium balaenarum_. The substance of the
above account, and the perplexity attending the classification of the
animal, are all included in Linnaeus’s short description:[394]
“Simillimus Onisco Ceti, sed pedes omnes pluribus articulis, omnes
perfecti, nec plures quam octo. Dorsum rubrum, pluribus segmentis;
singulis tribus mucronibus. Cauda cylindrica, brevissima, truncata.
Rostrum membranaceum, subsubulatum, longitudine pedum. Genus dubium,
facie Onisci ceti; rostro a reliquis diversum. Cum solo rostro absque
maxillis sit forte aptius Acaris aut proprio generi subjiciendum....
Habitat in mari norvegico sub lapidibus.”[395]
[Illustration:
FIG. 263.—Dorsal view of _Nymphon brevirostre_, Hodge, × 6. Britain.
]
The common _Pycnogonum_ is, by reason of the suppression of certain
limbs, rather an outlying member than a typical representative of the
Order, whose common characters are more strikingly and more perfectly
shown in species, for instance, of _Nymphon_. Of this multiform genus we
have many British species, some of the smaller being common below
tide-marks, creeping among weeds or clinging like Caprellae with
skeleton limbs to the branches of Zoophytes, where their slender forms
are not easily seen. In contrast to the stouter body and limbs of
_Pycnogonum_, the whole fabric of _Nymphon_ tends to elongation; the
body is drawn out so that the successive lateral processes stand far
apart, and a slender neck intervenes between the oculiferous tubercle
and the proboscis; the legs are produced to an amazing length and an
extreme degree of attenuation: “mirum tam parvum corpus regere tam
magnos pedes,” says Linnaeus. Above the base of the proboscis are a pair
of three-jointed appendages, the two terminal joints of which compose a
forcipate claw; below and behind these come a pair of delicate,
palp-like limbs of five joints; and lastly, on the ventral side, some
little way behind these, we find the ovigerous legs that we have already
seen in the male _Pycnogonum_, but which are present in both sexes in
the case of _Nymphon_. At the base of the claw which terminates each of
the eight long ambulatory legs stands a pair of smaller accessory or
“auxiliary” claws. The generative orifices are on the second joint of
the legs as in _Pycnogonum_, but as a rule they are present on all the
eight legs in the female sex, and on the two hindmost pairs in the male.
One of the Antarctic Nymphonidae (_Pentanymphon_) and one other
Antarctic genus less closely related (_Decolopoda_) have an extra pair
of legs. No other Pycnogon, save these, exhibits a greater number of
appendages than _Nymphon_ nor a less number than _Pycnogonum_, nor are
any other conspicuous organs to be discovered in other genera that are
not represented in these two: within so narrow limits lie the varying
characters of the group.
[Illustration:
FIG. 264.—_Nymphon brevirostre_, Hodge. Head, from below, showing
chelophores, palps, and ovigerous leg.
]
In framing a terminology for the parts and members of the body, we
encounter an initial difficulty due to the ease with which terms seem
applicable, that are used of more or less analogous parts in the Insect
or the Crustacean, without warrant of homology. Thus the first two pairs
of appendages in _Nymphon_ have been commonly called, since Latreille’s
time, the mandibles and the palps (Linnaeus had called them the palps
and the antennae), though the comparison that Latreille intended to
denote is long abandoned; or, by those who leaned, with Kröyer and
Milne-Edwards, to the Crustacean analogy, mandibles and maxillae. Dohrn
eludes the difficulty by denominating the appendages by simple numbers,
I., II., III., ... VII., and this method has its own advantages; but it
is better to frame, as Sars has done, a new nomenclature. With him we
shall speak of the Pycnogon’s body as constituted of a trunk, whose
first (composite) segment is the cephalic segment or head, better
perhaps the cephalothorax, and which terminates in a caudal segment or
abdomen; the “head” bears the proboscis, the first appendages or
“chelophores,” the second or “palps,” the third, the false or
“ovigerous” legs, and the first of the four pairs of “ambulatory” legs.
The chelophores bear their chela, or “hand,” on a stalk or scape; the
ambulatory legs are constituted of three coxal joints, a femur, two
tibial joints, a tarsus, and a propodus, with its claws, and with or
without auxiliary claws.
=The Body.=—The trunk with its lateral processes may be still more
compact than in _Pycnogonum_, still more attenuated than in _Nymphon_.
In a few forms (e.g. _Pallene_, _Ammothea_, _Tanystylum_,
_Colossendeis_) the last two, or even more, segments of the trunk are
more or less coalescent. In _Rhynchothorax_ the cephalic segment is
produced into a sharp-pointed rostrum that juts forward over the base of
the proboscis. The whole body and limbs may be smooth, tuberculated,
furnished with scattered hairs, or sometimes densely hispid.
[Illustration:
FIG. 265.—=A=, _Colossendeis proboscidea_, Sabine, Britain; =B=,
_Ammothea echinata_, Hodge, Britain; =C=, _Phoxichilus spinosus_,
Mont., Arctic Ocean. (The legs omitted.)
]
The proboscis varies much in shape and size. It may be much longer or
much shorter than the body, cylindrical or tumid, blunt or pointed,
straight or (e.g. _Decolopoda_) decurved; usually firmly affixed to the
head and pointing straight forwards; sometimes (_Eurycide_,
_Ascorhynchus_) articulated on a mobile stalk and borne deflexed beneath
the body.
=Chelophores.=—The first pair of appendages or chelophores are wanting
in the adult _Pycnogonum_, _Phoxichilus_, _Rhynchothorax_, and
_Colossendeis_.[396]
In _Ammothea_ and its allies they are extremely rudimentary in the
adult, being reduced to tiny knobs in _Tanystylum_ and _Trygaeus_, and
present as small two-jointed appendages in _Ammothea_; in this last, if
not in the others also, they are present in complete chelate form in the
later larval stages.
[Illustration:
FIG. 266.—=A=, =B=, Chelophores of _Ascorhynchus abyssi_, G.O.S. A,
Young; B, adult. (After Sars.) =C=, Anterior portion of _Ammothea
hispida_, Hodge, Jersey: late larval stage (= _Achelia longipes_,
Hodge), showing complete chelae. =D=, Chela of _Eurycide hispida_,
Kr.
]
In _Eurycide_, _Ascorhynchus_, and _Barana_ they are usually less
atrophied, but yet comparatively small and with imperfect chelae, while
in some Ascorhynchi (_A. minutus_, Hoek) they are reduced to stumps.
[Illustration:
FIG. 267.—Chelae of species of Nymphonidae: =A=, _Nymphon
brevirostre_, Hodge; =B=, _Boreonymphon robustum_, Bell; =C=,
_Chaetonymphon macronyx_, G.O.S.; =D=, _Nymphon elegans_, Hansen.
]
[Illustration:
FIG. 268.—Proboscis and chelophores of _Cordylochele longicollis_,
G.O.S. (After Sars.)
]
In _Pallenopsis_ the scape of the chelophore consists of two joints, as
also in _Decolopoda_ and some _Ascorhynchus_: in _Nymphon_,
_Phoxichilidium_, _Pallene_, and _Cordylochele_ of one only; in all
these the terminal portion or “hand” forms a forcipate “chela,” of which
the ultimate joint forms the “movable finger.” In some species of
_Nymphon_ the chela is greatly produced and attenuated, and armed with
formidable serrate teeth on its opposing edges; in others it is
shortened, with blunter teeth; in _Boreonymphon robustum_ the claws are
greatly curved, with a wide gap between. In this last, and in
_Phoxichilidium_, the opposing edges are smooth and toothless. In
_Cordylochele_ the hand is almost globular, the movable finger being
shortened down, and half enclosed by the other.
[Illustration:
FIG. 269.—_Eurycide hispida_, Kr., showing stalked proboscis and
zigzag palps.
]
=Palpi.=—The second pair of appendages, or palps, are absent, or all but
absent, in the adult _Pycnogonum_, _Phoxichilus_, _Phoxichilidium_,
_Pallene_, and their allies. In certain of these cases, _e.g._
_Phoxichilidium_, a knob remains to mark their place; in others, _e.g._
_Pallenopsis_, a single joint remains; in a few Pallenidae a sexual
difference is manifested, reduction of the appendage being carried
further in the female than in the male. The composition of the palps
varies in the genera that possess them. In _Nymphon_ there are five
joints, and their relative lengths (especially of the terminal ones) are
much used by Sars in defining the many species of the genus. The
recently described _Paranymphon_, Caullery, has palps of six or seven
joints. In the Ammotheidae the number of joints ranges from five or six
in _Tanystylum_ to nine (as a rule) in _Ammothea_ and _Oorhynchus_, or
ten, according to Dohrn, in certain species of _Ammothea_.
_Colossendeis_ and the Eurycididae have a ten-jointed palp, which in
this last family is very long and bent in zigzag fashion, as it is, by
the way, also in _Ammothea_. The terminal joints of the palp are in all
cases more or less setose, and their function is conjecturally tactile.
=Ovigerous Legs.=—Custom sanctions for these organs an inappropriate
name, inasmuch as it is only in the males that they perform the function
which the name connotes.[397] They probably also take some part, as
Hodgson suggests, in the act of feeding.
[Illustration:
FIG. 270.—Ovigerous legs of =A=, _Phoxichilus spinosus_, Mont.; =B=,
_Phoxichilidium femoratum_, Rathke; =C=, _Anoplodactylus
petiolatus_, Kr.; =D=, _Colossendeis proboscideus_, Sab.
]
[Illustration:
FIG. 271.—Terminal joints of ovigerous leg of _Rhynchothorax
mediterraneus_, Costa.
]
[Illustration:
FIG. 272.—_Nymphon brevirostre_, Hodge. Terminal joints of ovigerous
leg, with magnified “tooth.”
]
In _Pycnogonum_, _Phoxichilus_, _Phoxichilidium_, and their immediate
allies they are absent in the female; in all the rest they are alike
present in both sexes, though often somewhat smaller in the female than
in the male. They are always turned towards the lower side of the body,
and in many cases even their point of origin is wholly ventral. The
number of joints varies: in _Phoxichilidium_ five, _Anoplodactylus_ six,
_Phoxichilus_ seven; in _Paranymphon_ eight; in _Pycnogonum_ nine, with,
in addition, a terminal claw; in the Ammotheidae from seven (_Trygaeus_)
to ten, without a claw; in Pallenidae ten, with or without a claw; in
_Rhynchothorax_, _Colossendeis_, _Eurycide_, _Ascorhynchus_, _Nymphon_,
ten and a claw. The appendage, especially when long, is apt to be wound
towards its extremity into a spiral, and its last four joints usually
possess a peculiar armature. In _Rhynchothorax_ this takes the form of a
stout toothed tubercle on each joint; in _Colossendeis_ of several rows
of small imbricated denticles; in _Nymphon_ and _Pallene_ of a single
row of curious serrate and pointed spines, each set in a little
membranous socket.
[Illustration:
FIG. 273.—_Nymphon strömii_, Kr. Male carrying egg-masses on his
ovigerous legs.
]
[Illustration:
FIG. 274.—Terminal joints (tarsus and propodus) of legs. =1=,
_Chaetonymphon hirtum_, Fabr.; =2=, _N. strömii_, Kr.; =3=, _Nymphon
brevirostre_, Hodge; =4=, _Ammothea echinata_, Hodge; =5=,
_Ascorhynchus abyssi_, G.O.S. (All after Sars.)
]
=Legs.=—The four pairs of ambulatory legs are composed, in all cases
without exception, of eight joints if we exclude, or nine if we include,
the terminal claw. They vary from a length about equal to that of the
body (_Pycnogonum_, _Rhynchothorax_, _Ammothea_) to six or seven times
as much, perhaps more, in _Nymphon_ and _Colossendeis_, the fourth,
fifth, and sixth joints being those that suffer the greatest elongation.
The seventh joint, or tarsus, is usually short, but in some Nymphonidae
is much elongated; the eighth, or propodus, is usually somewhat curved,
and usually possesses a special armature of simple or serrate spines.
The auxiliary claws, sometimes large, sometimes small, lie at the base
of the terminal claw in Ammotheidae, Phoxichilidae, in _Phoxichilidium_,
in most Pallenidae, in nearly all Nymphonidae. Their presence or absence
is often used as a generic character, helping to separate, e.g.,
_Pallene_ from _Pseudopallene_ and _Pallenopsis_, and _Phoxichilidium_
from _Anoplodactylus_; nevertheless they may often be detected in a
rudimentary state when apparently absent. The legs are smooth or hirsute
as the body may happen to be.
[Illustration:
FIG. 275.—Legs of =A=, _Pallene brevirostris_, Johnston; =B=,
_Anoplodactylus petiolatus_, Kr.; =C=, _Phoxichilus spinosus_,
Mont.; =D=, _Colossendeis proboscidea_, Sabine; =E=, _Ammothea
echinata_, Hodge, ♂.
]
[Illustration:
FIG. 276.—_Boreonymphon robustum_, Bell. Male with young, slightly
enlarged. Faeroe Channel.
]
=Glands.=—In some or all of the appendages of the Pycnogonida may be
found special glands with varying and sometimes obscure functions. The
glands of the chelophores (Fig. 280, p. 522) are present in the larval
stages only. They consist of a number of flask-shaped cells[398] lying
within the basal joint of the appendage, and generally opening at the
extremity of a long, conspicuous, often mobile, spine (e.g. _Ammothea_
(Dohrn), _Pallene_, _Tanystylum_ (Morgan), _Nymphon brevicollum_ and _N.
gracile_ (Hoek)). They secrete a sticky thread, by means of which the
larvae attach themselves to one another and to the ovigerous legs of the
male parent. In _Nymphon hamatum_, Hoek, the several filaments secreted
by the separate sacculi of the gland issue separately. In _Pycnogonum_
the spine on which the gland opens is itself prolonged into a long fine
filament, and here, according to Hoek, the gland is in all probability
functionless and rudimentary. Hoek has failed to find the gland in
_Ascorhynchus_, and also in certain Nymphonidae (e.g. _Boreonymphon
robustum_, Bell), in which the young are more than usually advanced at
the time of hatching. The gland has also been described by Lendenfeld
and others in _Phoxichilidium_, whose larvae do not cling together but
live a parasitic life; in this genus the long spine or tubercle is
absent on which the orifice is usually situated, and, according to
Lendenfeld, the secretion issues from many small orifices set along the
opposing edges of the chela. Of the two species described by Dohrn as
_Barana castelli_ and _B. arenicola_, the former has the spine of
inordinate length, more than twice as long as the whole body, chelophore
and all; while in the latter (which species rather resembles
_Ascorhynchus_) the spine is altogether absent.
In the palps and ovigerous legs of the adult are found glandular bodies
of a hollow vesicular form with a simple lining of cells, the vesicle
being divided within by a septum with a central orifice, the outer and
smaller half opening to the exterior. These glands are probably of
general occurrence, but they have been but little investigated. They lie
usually in the fourth and fifth joints of the palp, and the third and
fourth joints of the ovigerous leg. Hoek describes them in
_Discoarachne_ (_Tanystylum_) as lying within the elongated third joint
of the palp, and opening by a sieve-plate at the end of the second
joint. In _Ammothea_ (Dohrn) and _Ascorhynchus_ (Hoek) they open on a
small tubercle situated on the fifth joint of the palp. In _Nymphon_,
Hoek describes them as opening by a small pore on the fourth joint of
the ovigerous leg. Dohrn failed to find them in _Pycnogonum_, but in
_Phoxichilus_, _Phoxichilidium_ and _Pallene_ he discovered the glands
appertaining to the palps, though the palps themselves have disappeared
in those genera; he has found the glands also in _Ammothea_, in larvae
that have not yet attained their full complement of legs.
The males in nearly all cases are known to possess glands in the fourth
joints or thighs of all the ambulatory legs, and these glands without
doubt act as cement-glands, emitting, like the chelophoral glands of the
larvae, a sticky thread or threads by which the eggs and young are
anchored to the ovigerous legs. In some species of _Nymphon_ and of
_Colossendeis_ Hoek could not find these, and he conjectures them to be
conspicuous only in the breeding season. While in most cases these
glands open by a single orifice or by a few pores grouped closely
together, in _Barana_, according to Dohrn, and especially in _B.
arenicola_, the pores are distributed over a wide area of the femoral
joint.[399] In _Discoarachne_ (Loman) and _Trygaeus_ they open into a
wide chitinised sac with tubular orifice. While the function of these
last glands and of the larval glands seems plain enough, that of those
which occur in the palps and ovigerous legs of both sexes remains
doubtful.
In their morphological nature the two groups of glands are likewise in
contrast, the former being unicellular glands, such as occur in various
parts of the integument of the body and limbs of many Crustacea; while
the latter are segmentally arranged and doubtless mesoblastic in origin,
like the many other segmental excretory organs (or coelomoducts) of
various Arthropods.
By adding colouring matters (acid-fuchsin, etc.) to the water in which
the animals were living, Kowalevsky demonstrated the presence of what he
believed to be excretory organs in _Phoxichilus_, _Ammothea_, and
_Pallene_. These are small groups of cells, lying symmetrically near the
posterior borders of the first three body-segments, and also near the
bases of the first joints of the legs, dorsal to the alimentary
canal.[400]
[Illustration:
FIG. 277.—Longitudinal section through one “antimere” of the proboscis
in _Phoxichilus charybdaeus_. _G_, _g′_, Principal and secondary
ganglia; _h_, sieve-hairs; _L_, lip; _mt_, oral tooth; _N_, _N′_,
inner and outer nerve-cords; _t_, proboscis-teeth. (After Dohrn.)
]
=Alimentary System.=—The proboscis is a very complicated organ, and has
been elaborately described by Dohrn.[401] It is a prolongation of the
oral cavity, containing a highly developed stomodaeum, but showing no
sign of being built up of limbs or gnathites. The mouth, situated at its
apex, is a three-sided orifice, formed by a dorsal[402] and two lateral
lobes; and hence the proboscis has been assumed by some, on no competent
evidence, to be constituted of a degenerate pair of appendages and a
labrum or upper lip. Each of the three lobes which bounds the mouth
shows the following structures: firstly, a lappet of external chitinised
integument, overlapping, as the finger-nail overlaps the finger, a
cushion-like lip, ridged after the fashion of a fine-cut file in some
species, hairy in others, on the inner surface where the three lips meet
to close the orifice of the mouth. Below this again is a prominent tooth
(Fig. 277, _mt_), supported, as are the lips, by a system of chitinous
rods, which are but little developed in the genus here figured, though
conspicuous and complicated in others. Transverse ridges run across the
angles where adjacent lips meet, and the whole mechanism constitutes an
efficient valve, preventing the escape of swallowed food. The greater
portion of the proboscis is occupied by a masticating or triturating
apparatus, the oesophageal cavity expanding somewhat and having its
walls densely covered, in three bands corresponding to the antimeres,
with innumerable minute spines (_h_) or needles, sometimes supplemented
by large teeth (_t_) that point forwards somewhat obliquely to the axis
of the proboscis.[403]
In the curious East Indian genus _Pipetta_ (Loman) the sucking and
sifting mechanism is low down in the proboscis, and the organ is
prolonged into a very fine tube, the lips growing together till they
leave an aperture of only ·007 mm. for the absorption of liquids.
In some cases, where the proboscis itself is short, as in _Pallene_,
this mechanism is carried backwards into the fore-part of the body; and,
in the latter genus, the narrow oesophagus which succeeds the
masticatory apparatus is likewise provided with extrinsic muscles.
[Illustration:
FIG. 278.—Transverse sections through the proboscis of _Ph.
charybdaeus_. =A=, Anterior, through the principal ganglionic mass
(_G_); =B=, posterior, at the level of the sieve-hairs (_h_).
_Coec_, Intestinal caeca; _Dil. M_, dilator muscles; _N_, inner
nerve-ganglion, with circular commissure; _N′_, outer nerve; _or_,
chitinous lining of oral cavity; _R M_, _Ret.M_, retractor muscles.
(After Dohrn.)
]
[Illustration:
FIG. 279.—Transverse section through the basal joint of the third leg
in _Phoxichilus charybdaeus_, ♀. _Cut_, Cuticle; _Hyp_, hypodermis;
_Int_, intestinal caecum; _N_, nerve-cord; _Ov_, ovary; _Sept_,
septum. (After Dohrn.)
]
The oesophagus is followed by a long gastric cavity, which sends forth
caecal diverticula into the chelophores (when these are present), and
four immensely long ones into the ambulatory legs. The caeca are
attached to the walls of the limb cavities, especially at their
extremities in the tarsi, by suspensory threads of connective tissue,
and the whole gut, central and diverticular, is further supported by a
horizontal septal membrane, running through body and legs, which
separates the dorsal blood-vessel and sinus from the gut, the nervous
system and the ventral sinus, giving support also to the reproductive
glands. A short and simple rectum follows the gastric cavity.
In _Phoxichilus_, which lacks the three anterior appendages in the
female and the two anterior in the male, two pairs of caeca run from the
gut into the cavity of the proboscis (Fig. 278, B, _coec_.).[404]
=Circulatory System.=—The heart has been especially studied by Dohrn in
_Phoxichilus_. It consists of a median vessel running from the level of
the eyes to the abdomen, furnished with two pairs of lateral valvular
openings, and sometimes, though not always, with an unpaired one at the
posterior end. The walls are muscular, but with this peculiarity that
the muscular walls do not extend around the heart dorsally, in which
region its lumen is only covered by the hypodermis and cuticle of the
back. The blood-spaces of the body are separated into dorsal and ventral
halves by the septal membrane already referred to, which is perforated
in the region of the lateral processes by slits placing the two cavities
in communication; this septal membrane runs through the limbs to their
tips, and far into the proboscis, where it is attached to the edge of
the superior antimere. The blood is a colourless plasma with several
kinds of corpuscles, of which the most remarkable are amoeboid, actively
mobile, often coalescing into plasmodia. The course of the circulation
is on the whole outwards in the inferior or ventral sinus, inwards
towards the heart in the superior, save in the proboscis, where the
systole of the heart drives the blood forwards in the dorsal channel.
The beat is rapid, two or three times in a second, according to Loman,
in _Phoxichilidium_. Especially in the species with small body and
exaggerated legs, the movement of the circulatory fluid is actuated more
by the movements of the limbs and the contractions of the intestinal
caeca than by the direct impulse of the heart.
=Nervous System.=—The nerve-chain consists of a fused pair of
supra-oesophageal ganglia, which innervate (at least in the adult) the
chelophores, and of ventral ganglia, whence proceed the nerves to the
other limbs. The ganglia of the second and third appendages are fused
with one another, sometimes also with the ganglia of the first
ambulatory legs; the ganglia of the three posterior pairs of legs are
always independent (though the development of their longitudinal
commissures varies with the body-form), and they are succeeded by one or
two pairs of ganglia, much reduced in size, situated in the abdomen, of
which the posterior one innervates the muscles of the abdomen and of the
anal orifice. Each lateral nerve divides into two main branches, which
supply the parts above and below the septal membrane. The nerve-supply
of the proboscis is very complicated. Its upper antimere is supplied
from the pre-oral, its two lateral antimeres from the first post-oral,
ganglion, and each of these three nerves divides into two branches, of
which the inner bears six to eight or more small ganglia, which annular
commissures passing round the pharynx connect one to another. Of these
ganglia and commissures the anterior are the largest, and with these the
outer lateral nerve-branches of the proboscis merge. The immediate
origin of the nerves to the chelophores is from the median nerve that
springs from the under side of the supra-oesophageal ganglion to run
forward into the proboscis, but it is noteworthy that the chelophores
receive twigs also from the lateral nerves of the proboscis which arise
from the post-oral ganglia.
=Eyes.=—Eyes are the only organs of special sense known in the
Pycnogons. The deep-water Pycnogons, in general those inhabiting depths
below four or five hundred fathoms, have in most cases imperfect organs,
destitute of lens and of pigment, so imperfect in many cases as to be
described as wanting. It is rare for the eyes to be lacking in
shallow-water species, as they are, for instance, in _Ascorhynchus
minutus_, Hoek, dredged by the _Challenger_ in 38 fathoms, but, on the
other hand, it is no small minority of deep-water species that possess
them of normal character and size, even to depths of about 2000 fathoms.
In all cases where eyes are present, they are simple or “monomeniscous”
eyes, four in number, and are situated in two pairs on an “oculiferous
tubercle,” sometimes blunt and low, sometimes high and pointed, placed
on the so-called cephalothorax, or first, compound, segment of the body.
The anterior pair are frequently a little larger, sometimes, as in
_Phoxichilidium mollissimum_, Hoek, very much larger, than the
posterior. The minute structure of the eye has been investigated by
Dohrn, Grenacher, Hoek, and Morgan. The following account is drawn in
the first instance from Morgan’s descriptions.[405]
The eye of a Pycnogon (_Phoxichilidium_) is composed of three layers, an
outer layer of specialised ectoderm cells (hypodermis) that secrete the
cuticular lens, a middle layer of visual or retinal elements, and an
inner layer of pigment-cells. The elements of the middle layer consist
of much elongated cells, whose branching outer ends are connected with
nerve-fibrils and interwoven in a protoplasmic syncytium, whose middle
parts are occupied by the nuclei and whose inwardly directed ends form
the retinal rods or bacilli. The pigment-cells of the inner layer are of
various forms, those towards the middle of the eye being small and
flattened, those at the sides being, for the most part, long and
attenuated, so seeming, as Morgan remarks, to approximate in character
to the retinal elements. The pigment-layer is easily dispersed and
reveals beneath it a median vertical raphe, caused by the convergence of
the cells of the middle layer from either side, and along the line of
this raphe the optic nerve joins the eye, though its subsequent course
to its connection with the retinal elements is obscure. It is at least
clear that the retina is an “inverted” retina, with the nerve-connected
bases of its cells lying outwards and their bacillar extremities
directed inwards.
In a longitudinal vertical section of the eye of a larva (_Tanystylum_),
at a stage when three pairs of walking legs are present, Morgan shows us
the pigment-layer apparently continuous with the hypodermis just below
the eye, and in close connection with the middle layer at the upper part
of the eye. From this we are permitted to infer a development by
invagination, in which the long invaginated sac is bent and pushed
upwards till it comes into secondary contact with the hypoderm, so
giving us the three layers of the developed eye. This manner of
formation is precisely akin to that described by Parker, Patten, Locy,
and others for the median eyes of Scorpions and of Spiders, and the
organ is structurally comparable to the Nauplius- or median eye of
Crustacea. But neither in these cases nor in that of the Pycnogon is the
whole process clear, in consequence chiefly of the obscurity that
attends the course of the optic nerve in both embryo and adult. For
various discussions and accounts, frequently contradictory, of these
phenomena, the reader is referred to the authors quoted, or to Korschelt
and Heider’s judicious summary.[406]
There seems to be a small structure, of some sort or other, between the
ocelli on either side. Dohrn thought it might be auditory, Loman that it
might be secretory, but its use is unknown.
=Integument.=—The chitinised integument is perforated by many little
cavities, some of them conical and tapering to a minute external pore,
the others more regularly tubular. Sometimes, but according to Hoek
rarely, the tubular pore-canals communicate with, or arise from, the
conical cavities. The pore-canals transmit a nerve for the supply of
sensory hairs, often forked, which arise from the orifice of the canal
in little groups of two or more, sometimes in rosettes of eight or nine.
These setae are small or rudimentary in _Ascorhynchus_ and totally
wanting in _Colossendeis_; they appear to be extremely large and
stellate in _Paranymphon_. The conical cavities contain proliferated
epithelial cells, blood corpuscles, and cells of more doubtful nature
that are perhaps glandular. According to Dohrn, glands exist in
connection with both kinds of integumentary perforations, and he
suspects that they secrete a poisonous fluid in response to stimuli
affecting the sensory hairs; Hoek, on the other hand, is inclined to
ascribe a respiratory function to the cavities; but indeed, as yet, we
must confess that their use is undetermined.
=Reproductive Organs.=—In each sex the generative organs consist of a
pair of ovaries or testes lying above the gut on either side of the
heart; in the adult they are fused together posteriorly at the base of
the abdomen, and send long diverticula into the ambulatory legs. In the
female _Phoxichilidium_, at least, as Loman has lately shown, the fusion
is complete, and the ovary forms a thin broad plate, spreading through
the body and giving off its lateral diverticula. The diverticula of the
testes reach to the third joint of the legs, those of the ovaries to the
fourth, or sometimes farther. The ova ripen within the lateral
diverticula, chiefly, and sometimes (_Pallene_) exclusively, in the
femora or fourth joints of the legs,[407] which, in many forms, are
greatly swollen to accommodate them; the spermatozoa, on the other hand,
are said to develop both within the legs and within the thoracic
portions of the testis. The genital diverticula may end blindly within
the leg, or communicate through a duct with the exterior by a valvular
aperture placed on the second coxal joint. Such apertures occur, as a
rule, on all the legs in the females, in _Rhynchothorax_ and
_Pycnogonum_ on the last only. In the males an aperture is present on
all the legs in _Decolopoda_ and _Phoxichilidium_; on the last three in
_Nymphon_ and _Phoxichilus_; in most genera on the last two; in
_Pycnogonum_ and _Rhynchothorax_ on the last only.
Very commonly the female individuals are somewhat larger than the males,
and in some species (_Ammothea_, _Trygaeus_) the latter are
distinguished by a greater development of spines or tubercles on the
body and basal joints of the legs (Dohrn).
The act of fecundation has been observed by Cole[408] in
_Anoplodactylus_. The animal reproduces towards the end of August.
Consorting on their _Eudendrium_ (Hydroid) colony, the male climbs upon
the female and crawls over her head to lie beneath her, head to tail;
and then, fertilisation taking place the while, the hooked ovigerous
legs of the male fasten into the extruding egg-masses and tear them
away. The whole process is over in five minutes. The fresh egg-masses
are more or less irregular in shape, and white in colour like little
tufts of cotton.
Each ball of eggs that the male carries represents the entire brood of
one female, and in _Phoxichilidium_ Loman has seen a male carrying as
many as fourteen balls. Fertilisation is external, taking place while
the eggs are being laid. The spermatozoa have small rounded heads and
long tails, and are thus unlike the spermatozoa of most Crustacea.
=Development.=—Until the hatching of the embryo, the eggs of the
Pycnogons are carried about, agglutinated by cement-substance into
coherent packets, on the ovigerous legs of the males. They are larger or
smaller according to the amount of yolk-substance present, very small in
_Phoxichilidium_ and _Tanystylum_ (Morgan), where they measure only ·05
mm. in diameter; larger in _Pallene_ (·25 mm.); larger still (·5–·7 mm.)
in _Nymphon_. In _Pallene_ each egg-mass commonly contains only two
eggs; in the other genera they are much more numerous, rising to a
hundred or more in _Ammothea_ (Dohrn). The egg-masses may be one or more
on each ovigerous leg, sometimes (_Phoxichilidium angulatum_, Dohrn) a
single egg-mass is held by both legs; they are extremely numerous in
_Phoxichilus_, and in _Pycnogonum_ they coalesce to form a broad pad
beneath the body. The fact that it is the male and not the female that
carries the eggs was only announced in 1877 by Cavanna;[409] before, and
by some even after his time, the two sexes were constantly
confused.[410]
[Illustration:
FIG. 280.—Young larva (nat. size ·1 mm.) of _Ammothea fibulifera_,
Dohrn. _C.G_, Brain; _gl_, _gld_, gland and duct of chelophore;
_pr_, proboscis; I, II, III, IV, appendages. (After Dohrn.)
]
Segmentation is complete, symmetrical in the forms with smaller eggs,
unequal in those burdened with a preponderance of yolk (Morgan). In
_Pallene_, as in the Spider’s egg, what is described as at first a total
segmentation passes into a superficial or centrolecithal one by the
migration outwards of the nuclei and the breaking down of the inner ends
of the wedge-shaped segmentation-cells. The blastoderm so formed becomes
concentrated at the germinal pole of the egg. A thickened portion of the
blastoderm (which Morgan compares to the “cumulus primitivus” of the
Spider’s egg) forms an apparently blastoporal invagination (though
Morgan calls it the stomodaeum), and from its sides are budded off the
mesodermal bands. Meisenheimer has recently given a minute account of
the early development of _Ammothea_, a form with small yolkless eggs.
Here certain cells of the uniform and almost solid blastosphere grow
inwards till their nuclei arrange themselves in an inner layer of what
(so far as they are concerned) is a typical gastrula, but without any
central cavity. The inner layer subsequently, but slowly, differentiates
into the mid-gut, and into dorsal and lateral offshoots, the sources of
the heart and of the muscles and connective tissues respectively. The
further development of the egg takes place, as is usual in Arthropods,
by the appearance, in a longitudinal strip or germ-band which enwraps
the yolk, of paired thickenings which represent the cerebral and
post-oral ganglia, and of others from which arise the limbs. Of these
latter, the chelophores are the first to appear, on either side of the
mouth; in _Pallene_ the fourth pair appears next in order, followed by
the fifth and sixth, and by the third and seventh just before the
hatching out of the embryo; the second is lacking in this particular
genus. Thus in _Pallene_ (Dohrn, Morgan), and in some others, e.g.
_Nymphon brevicollum_ (Hoek), the free larva is from the first provided
with its full complement of limbs. Certain other species of _Nymphon_
hatch out in possession of four or five pairs of limbs, but in the great
majority of cases studied the larval Pycnogon is at first provided with
three pairs only, the three anterior pairs of the typical adult.[411]
Numerical coincidence, and that alone, has often led this “Protonymphon”
larva to be compared with the Crustacean Nauplius. In the annexed figure
of a young larval _Ammothea_ (_Achelia_), we see the unsegmented body,
the already chelate chelophores (furnished with the provisional
cement-glands already described), the other two pairs of appendages each
with a curious spine at its base, the gut beginning to send out
diverticula (of which the first pair approach the chelophores) but still
destitute of the anus (which is only to be formed after the development
of the abdomen), the proboscis, and one pair of eyes situated close over
the pre-oral ganglia. The subsequent changes are in this genus extremely
protracted, and terminate with the loss of the chelae, a process which
occurs so late in life that the chelate individuals were long looked
upon as belonging to a separate genus, the original _Ammothea_ of Hodge,
until Hoek proved their identity with the clawless _Achelia_.
The developmental history of _Phoxichilidium_ and _Anoplodactylus_ is
peculiar. The young larvae have the claws of the second and third
appendages hypertrophied to form enormous stiff tendril-like organs,
with which they affix themselves to the bodies of Hydroid Zoophytes
(_Coryne_, _Eudendrium_, _Tubularia_, _Hydractinia_, etc.), feeding as
the adults do: afterwards losing these elongated tendrils in a moult,
they pass into the gastral cavity of the Hydroid; in our native species
the larva issues from the Hydroid and begins its independent life at a
stage when three pairs of ambulatory legs are present and the fourth is
in bud.[412] The _Phoxichilidium_ larvae were first noticed by Gegenbaur
in _Eudendrium_,[413] again by Allman in _Coryne eximia_.[414] George
Hodge made detailed and important observations,[415] and showed, in
opposition to Gegenbaur, that it was the larva which entered the Hydroid
and not the egg that was laid therein.[416]
[Illustration:
FIG. 281.—Larva of _Phoxichilidium_ sp., showing tendril-like
appendages of the larval palps and ovigerous legs. (After Dohrn.)
]
Moseley has the following interesting note in his _Challenger
Report_:[417] “The most interesting parasite observed was a form found
in the gastric cavities of the gastrozoids of _Pliobothrus symmetricus_
(West Indies, 450 f.), contained in small capsules. These capsules were
badly preserved, but there seemed little doubt that they contained the
remains of larvae of a Pycnogonid, so that the deep-sea Pycnogonids,
which are so abundant, very possibly pass through their early stages in
deep-sea Stylasteridae.... The gastrozoids containing the larvae were
partly aborted.”
A Pycnogon larva, doubtfully ascribed to _Nymphon_, has been found
living in abundance ectoparasitically on _Tethys_ in the Bay of
Naples.[418]
=Habits.=—Of the intimate habits of the Pycnogons we can say little.
_Pycnogonum_ we often find clinging, as has been said, close appressed
to some large Anemone (_Tealia_, _Bolocera_, etc.), whose living juices
it very probably imbibes. The more slender species we find climbing over
sea-weeds and Zoophytes, where sometimes similarity of colour as well as
delicacy of form helps to conceal them; thus _Phoxichilidium femoratum_
(_Orithyia coccinea_, Johnston) is red like the Corallines among which
we often find it, _P. virescens_ green like the filamentous Ulvae, the
Nymphons yellowish like the _Hydrallmania_ and other Zoophytes which
they affect. On the New England coast, according to Cole, the dark
purple _Anoplodactylus lentus_, Wilson (_Phoxichilidium maxillare_,
Stimpson), is especially abundant on colonies of _Eudendrium_, whose
colour matches its own, the yellowish _Tanystylum orbiculare_ frequents
a certain yellowish Hydroid, and of these two species neither is ever
found on the Hydroid affected by the other; while, on the other hand,
_Pallene brevirostris_, whose whitish, almost transparent body is
difficult to see, is more generally distributed.[419] The deep-sea
Pycnogons (_Colossendeis, Nymphon_) are generally (if not universally)
of a deep orange-scarlet colour, a common dress of many deep-sea
Crustacea.
The movements of the Pycnogons are singularly slow and deliberate; they
are manifestly not adapted to capture or to kill a living prey. Linnaeus
accepted from J. C. König the singular statement that they enter and
feed upon bivalve shells, “Mytilorum testes penetrat et exhaurit”; but
the statement has never been reaffirmed.[420]
Loman describes _Phoxichilidium_ as feeding greedily on _Tubularia
larynx_, and especially on the gonophores. It grasps them with its
claws, sucks them in bit by bit till the proboscis is filled as far as
the sieve, whereupon that part of the proboscis squeezes and kneads the
mass, letting only juices and fine particles pass through into the
alimentary canal. The lateral caeca and the rectum are separated by
sphincter muscles from the stomach; the former are in turn filled with
food and again emptied; the contents of the alimentary canal are in
constant rolling movement, and the faeces are eliminated by the action
of a pair of levatores ani, in round pellets.
The Pycnogons, or some of them, can swim by “treading water,” and
_Pallene_ is said by Cole to swim especially well; they more often
progress half by swimming, half by kicking on the bottom. They move
promptly towards the light, unless they have Hydroids to cling to, and
Cole points out that when they crawl with all their legs on the bottom
they move forwards towards the light,[421] but backwards when they swim
in part or whole. The legs move mostly in a vertical plane, horizontal
movements taking place chiefly between the first and second joints.
_Tanystylum_ is uncommonly sluggish and inert; it sinks to the bottom,
draws its legs over its back and remains quiet, while _Pallene_, by
vigorous kicks, remains suspended.
The long legs of the Pycnogons are easily injured or lost, and easily
repaired or regenerated. This observation, often repeated, is as old as
Fabricius: “Mutilatur etiam in libertate sua, redintegrandum tamen; vidi
enim in quo pedes brevissimi juxta longiores enascentes, velut in
asteriis cancris aliisque redintegratis.” In such cases of
redintegration of a leg, the reproductive organ, the genital orifice,
and the cement-gland are not restored until the next moult.[422]
=Systematic Position.=—To bring this little group into closer accord
with one or other of the greater groups of Arthropods is a problem
seemingly simple but really full of difficulty.
The larval Pycnogon, with its three pairs of appendages, resembles the
Crustacean Nauplius in no single feature save this unimportant numerical
coincidence; nor is there any significance in the apparent outward
resemblance to isolated forms (e.g. _Cyamus_) that induced some of the
older writers, from Fabricius downwards and including Kröyer and the
elder Milne-Edwards, to connect the Pycnogons with the Crustacea. To
refer them, or to approximate them to the Arachnids, has been a stronger
and a more lasting tendency.[423] Linnaeus (1767) included the two
species of which he was cognisant in the genus _Phalangium_, together
with _P. opilio_. Lamarck, who first formulated the group Arachnida
(1802), let it embrace the Pycnogons; and Latreille (1804, 1810), who
immediately followed him, defined more clearly the Pycnogonida as a
subdivision of the greater group, side by side with the subdivision that
corresponds to our modern Arachnida (“Arachnides acères”), and together
with a medley of lower Crustacea, Myriapoda, Thysanura, and Parasitic
Insects; he was so cautious as to add “j’observerai seulement, que je ne
connais pas encore bien la place naturelle des Pycnogonides et des
Parasites,” and Cuvier, setting them in a similar position, adds a
similar qualification.[424]
Leach (1814), whose great service it was to dissociate the
Edriophthalmata and the Myriapoda from the Latreillian medley, left the
group Arachnida as we still have it (save for the inclusion of the
Dipterous Insect _Nycteribia_), and divided the group (with the same
exception) into four Orders of which the Podosomata, i.e. the
Pycnogonida, are one. Savigny (1816), less philosophical in this case
than was his wont, assumed the Crustacean type to pass to the Arachnidan
by a loss of several anterior pairs of appendages, and appears to set
the Pycnogons in an intermediate grade, marking the pathway of the
change. He considered the seven pairs of limbs of the Pycnogons to
represent thoracic limbs of a Malacostracan, and, like so many of his
contemporaries, was much biased by the apparent resemblance of _Cyamus_
to _Pycnogonum_. The reader may find in Dohrn’s Monograph a guide to
many other opinions and judgments, some of them of no small
morphological interest and historical value[425]; but it behoves us to
pass them by, and to inspect, in brief, the case as it stands at
present. The obvious features in which a Pycnogon resembles a Spider or
other typical Arachnid, are the possession of four pairs of walking
legs, and the pre-oral position and chelate form of the first pair of
appendages; we may perhaps also add, as a more general feature of
resemblance, the imperfect subservience of limbs to the mouth as
compared with any of the Crustacea. The resemblance would still be
striking, in spite of the presence of an additional pair of legs in a
few Pycnogons, were it not for the presence of the third pair of
appendages or ovigerous legs of the Pycnogon, whose intercalation spoils
the apparent harmony. We are neither at liberty to suppose, with Claus,
that these members, so important in the larva, have been interpolated,
as it were, anew in the Pycnogon; nor that they have arisen by
subdivision of the second pair, as Schimkewitsch is inclined to suppose;
nor that they have dropped out of the series in the Arachnid, whose body
presents no trace of them in embryo or adult. In a word, their presence
precludes us from assuming a direct homology between the apparently
similar limbs of the two groups,[426] and at best leaves it only open to
us to compare the last legs of the Pycnogon with the first abdominal, or
genital, appendages of the Scorpion and the Spider. On the other hand,
if we admit the seventh (as we must admit the occasional eighth) pair of
appendages of Pycnogons to be unrepresented in the prosoma of the
Arachnids, then, in the cephalothorax of the former, with its four pairs
of appendages, we may find the homologue of the more or less free and
separate part of the cephalothorax in _Koenenia_, _Galeodes_, and the
Tartaridae. There is a resemblance between the two groups in the
presence of intestinal diverticula that run towards or into the limbs,
as in Spiders and some Mites, and there are certain histological and
embryological resemblances that have been in part referred to above; but
these, such as they are, are not adequate guides to morphological
classification. We must bear in mind that such resemblances as the
Pycnogons seem to show are not with the lower Arachnids but with the
higher; they are either degenerates from very advanced and specialised
Arachnida, or they are lower than the lowest. Confronted with such an
issue, we cannot but conclude to let the Pycnogons stand apart, an
independent group of Arthropods[427]; and I am inclined to think that
they conserve primitive features in the usual presence of generative
apertures on several pairs of limbs, and probably also in the
non-development of any special respiratory organs. But inasmuch as the
weight of evidence goes to show that subservience of limbs to mouth is a
primitive Arthropodan character, the fact that the basal elements of the
anterior appendages have here (as in _Koenenia_) no such relation to the
mouth must be taken as evidence, not of antiquity, but of
specialisation. In like manner the suctorial proboscis cannot be deemed
a primitive character, and the much reduced abdomen also is obviously
secondary and not primitive.
=Classification.=—No single genus more than another shows signs of
affinity with other groups, and no single organ gives us, within the
group, a clear picture of advancing stages of complexity. On the
contrary, the differences between one genus and another depend very much
on degrees of degeneration of the anterior appendages, and we have no
reason to suppose that these stages of degeneration form a single
continuous series, but have rather reason to believe that degeneration
has set in independently in various ways and at various points in the
series. But while we are unable at present to form a natural
classification[428] of the Pycnogons, yet at the same time a purely
arbitrary or artificial classification, conveniently based on the
presence or absence of certain limbs, would run counter to such natural
relationships as we can already discern.
The classification here adopted is a compromise between a natural
system, so far as we can detect it, and an artificial one.
Two forms, separated from one another by many differences, show a
minimum of degeneration, namely _Decolopoda_ on the one hand, and the
Nymphonidae on the other. The former genus has five pairs of legs, and
this peculiarity is shared by _Pentanymphon_. In both groups the three
anterior limbs are all present and well formed, save only that the
ovigerous legs, which have ten joints in _Decolopoda_, are reduced to
five joints in the Nymphons, and their denticulate spines, of which
several rows are present in the former, are reduced to one row in the
latter; on the other hand, a greater or a less degeneration of these
limbs marks each and all of the other families.
_Decolopoda_ is very probably the most primitive form known, though it
has characters which seem to be the reverse of primitive in the dwarfish
size of its chelophores and the crowded coalescent segmentation of the
trunk. _Colossendeis_, in spite of its vanished chelophores, is probably
closely allied: the shape and segmentation of the body and the several
rows of smooth denticles on the ovigerous legs are points in common. The
Eurycydidae are closely allied to Colossendeidae; they agree with
_Decolopoda_ in the two-jointed scape of the chelophore, and with
Ammotheidae in the deflexed mobile proboscis. The true position of
_Rhynchothorax_ is very doubtful.
The Nymphonidae and Pallenidae are closely allied, and the
Phoxichilidiidae have points of resemblance, especially with the latter.
_Nymphon_ compares with _Decolopoda_ in the completeness of its parts,
and is more typical in its long well-segmented body, and in its
highly-developed chelae; but it already shows reduction in the scape of
the chelophore, in the palps, and in the armature of the ovigerous legs.
The Phoxichilidae and Pycnogonidae (Agnathonia, Leach; Achelata, Sars),
though differing greatly in aspect, are not improbably allied to one
another; and whether this be so or not, the complete absence of
chelophores and of palps affords an arbitrary character by which they
are conveniently separated from all the rest.
The following table epitomises the chief characters of the several
families:—
┌────────────────────┬──────────┬────────────┬───────────┬─────────┐
│ PYCNOGONIDA. │Proboscis.│Chelophores.│ Palps. │Ovigerous│
│ │ │ │ │ legs. │
├────────────────────┼──────────┼────────────┼───────────┼─────────┤
│ │ │ │ │ │
├────────────────────┼──────────┼────────────┼───────────┼─────────┤
│(=Cryptochelata=, │ │ │ │ │
│Sars)— │ │ │ │ │
│ DECOLOPODIDAE │ Fixed, │ Complete, │ 10 joints │10 joints│
│ │ decurved │small, scape│ │ ♂, ♀ │
│ │ │ 2–jointed │ │ │
│ │ │ │ │ │
│ │ │ │ │ │
│ COLOSSENDEIDAE │ Somewhat │ 0 │ 10 │ 10 ♂, ♀ │
│ │ mobile, │ │ │ │
│ │sometimes │ │ │ │
│ │ decurved │ │ │ │
│ EURYCIDIDAE │ Mobile, │ Scape │ 10 │ 10 ♂, ♀ │
│ │ stalked, │ 2–jointed, │ │ │
│ │ deflexed │ chelae │ │ │
│ │ │rudimentary │ │ │
│ _Hannonia_ │ „ │Rudimentary │ 0 │ 10 ♂, ♀ │
│ │ │ │ │ │
│ AMMOTHEIDAE │ Mobile, │ „ │ 4–9 │ 10 (or │
│ │ deflexed │ │ │less) ♂, │
│ │ │ │ │ ♀ │
│ │ │ │ │ │
│ ? RHYNCHOTHORACIDAE│ Large, │ 0 │ 8 (5) │ 10 ♂, ♀ │
│ │ fixed, │ │ │ │
│ │ aberrant │ │ │ │
├────────────────────┼──────────┼────────────┼───────────┼─────────┤
│(=Euchelata=, Sars)—│ │ │ │ │
│ NYMPHONIDAE │ Large, │Large, scape│ 5 (7) │8–10 ♂, ♀│
│ │ fixed │ 1–jointed │ │ │
│ │ │ │ │ │
│ │ │ │ │ │
│ PALLENIDAE │ „ │ „ │ 0 or │ 10 ♂, ♀ │
│ │ │ │rudimentary│ │
│ │ │ │ │ │
│ PHOXICHILIDIIDAE │ „ │ „ │ 0 │ 5–6 ♂ │
│ │ │ │ │ │
│ │ │ │ │ │
├────────────────────┼──────────┼────────────┼───────────┼─────────┤
│(=Achelata=, Sars) │ │ │ │ │
│ PHOXICHILIDAE │ Large, │ 0 │ 0 │ 7 ♂ │
│ │ fixed │ │ │ │
│ │ │ │ │ │
│ PYCNOGONIDAE │ „ │ 0 │ 0 │ 9 ♂ │
│ │ │ │ │ │
└────────────────────┴──────────┴────────────┴───────────┴─────────┘
┌────────────────────┬──────────┬─────┬───────────────┬─────────┐
│ PYCNOGONIDA. │ Teeth on │Legs.│Trunk-segments.│ Genital │
│ │ do. │ │ │Openings.│
├────────────────────┼──────────┼─────┼───────────────┼────┬────┤
│ │ │ │ │ ♂ │ ♀ │
├────────────────────┼──────────┼─────┼───────────────┼────┼────┤
│(=Cryptochelata=, │ │ │ │ │ │
│Sars)— │ │ │ │ │ │
│ DECOLOPODIDAE │Four rows,│ 5 │ Condensed, │ 1, │ 1, │
│ │ simple │ │ coalescent │ 2, │ 2, │
│ │ │ │ │ 3, │ 3, │
│ │ │ │ │ 4, │4, 5│
│ │ │ │ │ 5, │ │
│ COLOSSENDEIDAE │Many rows,│ 4 │ Coalescent │ 1, │ 1, │
│ │ simple │ │ │ 2, │ 2, │
│ │ │ │ │3, 4│3, 4│
│ │ │ │ │ │ │
│ EURYCIDIDAE │More than │ 4 │Well segmented │3, 4│ 1, │
│ │ one row, │ │ │ │ 2, │
│ │ serrate │ │ │ │3, 4│
│ │ │ │ │ │ │
│ _Hannonia_ │Scattered │ 4 │ „ │ „ │ „ │
│ │ spines │ │ │ │ │
│ AMMOTHEIDAE │ Few, │ 4 │ Condensed, │ „ │ „ │
│ │scattered,│ │ segmented │ │ │
│ │serrate or│ │ │ │ │
│ │ smooth │ │ │ │ │
│ ? RHYNCHOTHORACIDAE│ Toothed │ 4 │ „ │ 4 │ 4 │
│ │tubercles │ │ │ │ │
│ │ │ │ │ │ │
├────────────────────┼──────────┼─────┼───────────────┼────┼────┤
│(=Euchelata=, Sars)—│ │ │ │ │ │
│ NYMPHONIDAE │ One row, │ 4–5 │Well segmented │ 2, │ 1, │
│ │ serrate │ │ │3, 4│ 2, │
│ │ │ │ │(5) │3, 4│
│ │ │ │ │ │(5) │
│ PALLENIDAE │ „ │ 4 │ „ │(1, │ „ │
│ │ │ │ │2), │ │
│ │ │ │ │3, 4│ │
│ PHOXICHILIDIIDAE │ One row, │ 4 │ „ │ 1, │ „ │
│ │ simple │ │ │ 2, │ │
│ │ │ │ │3, 4│ │
├────────────────────┼──────────┼─────┼───────────────┼────┼────┤
│(=Achelata=, Sars) │ │ │ │ │ │
│ PHOXICHILIDAE │Scattered,│ 4 │Well segmented │ 2, │ 1, │
│ │ simple │ │ │3, 4│ 2, │
│ │ │ │ │ │3, 4│
│ PYCNOGONIDAE │ Small, │ 4 │ Segmented, │ 4 │ 4 │
│ │irregular │ │ condensed │ │ │
└────────────────────┴──────────┴─────┴───────────────┴────┴────┘
CLASS PYCNOGONIDA.[429]
Marine Arthropoda, with typically seven (and very exceptionally eight)
pairs of appendages, of which none have their basal joints subservient
to mastication, the first three are subject to suppression, the first
(when present) are chelate, the second palpiform, the third ovigerous,
and the rest form ambulatory limbs, usually very slender and long; with
a suctorial proboscis, a limbless, unsegmented abdomen, and no manifest
respiratory organs.
[Illustration:
FIG. 282.—_Decolopoda australis_, Eights. =A=, × 1: from a specimen
obtained at the South Shetlands by the _Scotia_ Expedition. =B=,
First appendage, or chelophore. (=A=, original; =B=, after Hodgson.)
]
=Fam. 1. Decolopodidae.=—Appendage I. dwarfed, but complete and chelate,
scape with two joints; II. 9–10–jointed; III. well developed in both
sexes, 10–jointed, the terminal joints with about four rows of teeth;
five pairs of legs, destitute of accessory claws; genital apertures on
all the legs (Bouvier).
_Decolopoda australis_, Eights[430] (1834), a remarkable form from the
South Shetlands, recently re-discovered by the _Scotia_ expedition. The
animal is large, seven inches or more in total span, in colour scarlet;
it was found in abundance in shallow water and cast upon the shore. The
body is greatly condensed, the proboscis is “clavate, arcuated
downwards,” and beset with small spines. A second Antarctic species, _D.
antarctica_, has been described by Bouvier. The presence of a fifth pair
of legs distinguishes _Decolopoda_ from all known Pycnogons, except
_Pentanymphon_. Stebbing would ally _Decolopoda_ with, or even include
it in, the Nymphonidae; but the presence of a second joint in the
chelophoral scape, the number of joints in, and the armature on, the
ovigerous legs, and the deflexed proboscis, are all characters either
agreeing with or tending towards those of the Eurycididae; while the
Colossendeidae would be very like _Decolopoda_ were it not for the
complete suppression of the chelophores. It seems convenient to
constitute a new family for this remarkable form.
=Fam. 2. Colossendeidae= (=Pasithoidae=, Sars).—Appendage I. absent in
adult; appendage II. very long, 10–jointed; appendage III. 10–jointed,
clawed, with many rows of teeth; auxiliary claws absent; segments of
trunk fused; proboscis very large, somewhat mobile; genital apertures,
in at least some cases, on all the legs.
_Pasithoe_, Goodsir (1842), which Sars assumes as the type of the
family, is here relegated to _Ammothea_.[431] _Colossendeis_, Jarszynsky
(1870) (_Anomorhynchus_, Miers (1881), _Rhopalorhynchus_, Wood-Mason
(1873)), remains as the only genus commonly accepted: large, more or
less slender short-necked forms; world-wide, principally Arctic,
Antarctic, and deep-sea; about twenty-five species.[432] The largest
species, _C. gigas_, Hoek, from great depths in the Southern Ocean, has
a span of about two feet. The North Atlantic _C. proboscidea_ and
Antarctic _C. australis_ are very closely related to one another.
Carpenter would retain the genus _Rhopalorhynchus_ for _R. kröyeri_,
W.-M. (Andamans), _R. clavipes_, Carp. (Torres Straits), and _R.
tenuissimus_, Haswell (Australia), all more or less shallow-water
species, excessively attenuated, with the second and third body-segments
elongated, the caudal segment excessively reduced, the club-shaped
proboscis on a slender stalk, and other common characters. _Pipetta
weberi_, Loman (1904), is a large and remarkable form from the Banda
Sea, apparently referable, in spite of certain abnormal features, to
this family; the proboscis is extraordinarily long and slender; the
palps have eight joints, the ovigerous legs eleven.
=Fam. 3. Eurycididae= (=Ascorhynchidae=, Meinert).—Appendage I. more or
less reduced; appendage II. 10–jointed (absent in _Hannonia_); appendage
III. 10–jointed, clawed, with more than one tow of serrated teeth;
proboscis movably articulated and more or less bent under the body;
auxiliary claws absent.
[Illustration:
FIG. 283.—_Eurycide hispida_, Kr.; side view.
]
_Eurycide_, Schiödte (1857) (_Zetes_, Kröyer, 1845): Appendage I. with
two-jointed scape, without chelae in adult; one species (_E. hispida_,
(Kr.)), from the North Atlantic and Arctic, and two others from the East
Indies, recently described by Loman. _Barana arenicola_, Dohrn (1881),
is nearly allied. _Ascorhynchus_, G. O. Sars (1876) (_Gnamptorhynchus_,
Böhm, 1879; _Scaeorhynchus_, Wilson, 1881), very similar to _Eurycide_,
with which, according to Schimkewitsch, it should be merged, includes
large, smooth, elongated forms, with long neck and expanded frontal
region, and a long proboscis lacking the long scape that supports the
proboscis in _Eurycide_; about twelve species, world-wide, mostly
deep-water. _Barana castelli_, Dohrn, from Naples is akin to the
foregoing genera, but seems to deserve generic separation from _B.
arenicola_. _Ammothea longicollis_, Haswell, from Australia, is, as
Schimkewitsch has already remarked, almost certainly a _Eurycide_, as is
also, probably, _Parazetes auchenicus_, Slater, from Japan.
_Hannonia typica_, Hoek (1880), from Cape Town, is a remarkable form,
lately redescribed by Loman. The chelophores are much reduced, the palps
are absent; the ovigerous legs are 10–jointed, and clawed; the terminal
joints of the latter bear long straight spines, scattered over their
whole surface; the proboscis is borne on a narrow stalk, and sharply
deflexed. The eggs form a single flattened mass, as in _Pycnogonum_.
While the lack of palps would set this genus among the Pallenidae, the
remarkable proboscis seems to be better evidence of affinity with
_Ascorhynchus_ and _Eurycide_.[433]
_Nymphopsis_, Haswell (1881), is a genus of doubtful affinities, placed
here by Schimkewitsch. The first appendage is well-developed and
chelate; the palps are 9–jointed, the ovigerous legs are 7–jointed, none
of the joints being provided with the compound spines seen in _Nymphon_
and _Pallene_. It is perhaps an immature form. Schimkewitsch has
described another species, _N. korotnevi_, and Loman a third, _N.
muscosus_, both from the East Indies.
=Fam. 4. Ammotheidae.=—Akin to Eurycididae in having the proboscis more
or less movably jointed to the cephalic segment, and appendage I.
reduced, non-chelate in the adult; the body is compact and more or less
imperfectly segmented; appendage II. 4–9–jointed; appendage III.
clawless, and the number of joints sometimes diminished, with a sparse
row of serrated spines; auxiliary claws usually present.
_Ammothea_, Leach (1815) (including _Achelia_, Hodge (1864) = the old
non-chelate individuals): appendage I. very small, 2–jointed; appendage
II. 8–9–jointed; caudal segment fused with last body-segment; about
eighteen species, four from the South Seas, two or three from the East
Indies, the rest mostly Mediterranean and North Atlantic, in need of
revision. _Ammothea longipes_, Hodge, is the young of _Achelia hispida_,
Hodge; and _Ammothea magnirostris_, Dohrn, is apparently the same
species. _A. fibulifera_, Dohrn, seems identical with _Achelia
echinata_, Hodge (of which _A. brevipes_, Hodge, is the young), and so
probably is _A. achelioides_, Wilson; _Endeis didactyla_, Philippi
(1843), is very probably the same species. _A. uniunguiculata_, Dohrn (?
_Pariboea spinipalpis_, Philippi (1843)), has no auxiliary claws.
_Leionymphon_, Möbius (1902), contains nine Antarctic forms, allied to
_Ammothea_ (including _A. grandis_, Pfeffer, and _Colossendeis gibbosa_,
Möb., which two are probably identical), with characteristic transverse
ridges on the body, a large proboscis, a 9–jointed palp, and somewhat
peculiar ovigerous legs. _Cilunculus_, _Fragilia_, and _Scipiolus_ are
new genera more or less allied to _Leionymphon_, described by Loman
(1908) from the Siboga Expedition.[434] _Tanystylum_, Miers (1879)
(including _Clotenia_, Dohrn (1881), and _Discoarachne_, Hoek (1880)),
has appendage I. reduced to a single joint or a small tubercle, and
appendage II. 4–6–jointed; world-wide; about eight species. _Austrodecus
glacialis_ and _Austroraptus polaris_ are two allied Antarctic species,
described by Hodgson (1907), the former a curious little form with a
pointed, weevil-like proboscis, no chelophores, and 6–jointed palp.
_Trygaeus communis_, Dohrn (1881), from Naples, has a 7–jointed, and
_Oorhynchus aucklandiae_, Hoek (1881), a 9–jointed palp; the former has
only seven joints in the ovigerous leg. _Lecythorhynchus armatus_, Böhm
(1879), with rudimentary 2–jointed chelophores, and _L._ (_Corniger_)
_hilgendorfi_, Böhm, with small tubercles in their place, both from
Japan, have also 9–jointed palps: the former, at least, is apparently an
_Ammothea_. Several insufficiently described genera, _Phanodemus_, Costa
(1836), _Platychelus_, Costa (1861), _Oiceobathes_, Hesse (1867), and
_Böhmia_, Hoek (1880), seem to be referable to this group; all have
chelate mandibles, and may possibly be based on immature forms.
Goodsir’s _Pasithoe vesiculosa_[435] is, in my opinion, undoubtedly
_Ammothea hispida_, Hodge, and so also, I believe, is his _Pephredo
hirsuta_; _P. umbonata_, Gould[436] (Long Island Sound), is, with as
little doubt, _Tanystylum orbiculare_, Wilson.
=Fam. 5. Rhynchothoracidae.=—The animal identified by Dohrn as
_Rhynchothorax mediterraneus_, Costa (1861), is a minute and very
remarkable form, without chelophores, with large 8–jointed palps,
reduced by fusion to five joints, and 10–jointed, clawed ovigerous legs,
which last are provided on the last five joints with peculiar toothed
tubercles. The general aspect of the body is somewhat like that of an
_Ammothea_, which genus it resembles in the ventral insertion of the
ovigerous legs and the somewhat imperfect segmentation of the body. It
differs from Ammotheidae in the possession of a claw on appendage III.
It is highly peculiar in the structure of the mouth, in having a long
forward extension of the oculiferous tubercle jutting out over the
proboscis, in the extreme shortness of the intestinal caeca and ovaries
which scarcely extend into the legs, and in the absence of cement-glands
from the fourth joint of the legs; these last are present only in the
third joint of the penultimate legs. A single pair of generative
orifices are found on the last legs. A second species, _R. australis_,
Hodgson, comes from the Antarctic.
[Illustration:
FIG. 284.—_Rhynchothorax mediterraneus_, Costa. =A=, Body and bases of
legs; =B=, terminal joints of palp. (After Dohrn.)
]
=Fam. 6. Nymphonidae.=—Appendage I. well-developed, chelate; II.
well-developed, usually 5–jointed; III. well-developed in both sexes,
usually 10–jointed, the terminal joints with one row of denticulated
spines.
_Nymphon_, Fabr. (1794), about forty-five recognised species, of which
some are but narrowly defined. Closely allied are _Chaetonymphon_, G. O.
Sars (1888), including thick-set, hairy species, about eight in number,
from the North Atlantic, Arctic, and Antarctic; and _Boreonymphon_, G.
O. Sars (1888), with one species (_B. robustum_, Bell, Fig. 276), also
northern, in which the auxiliary claws are almost absent. _Nymphon
brevicaudatum_, Miers (= _N. horridum_, Böhm), an extraordinary hispid
form from Kerguelen,[437] is also peculiar. _Pentanymphon_, Hodgson
(1904), from the Antarctic (circumpolar), differs in no respect save in
the presence of a fifth pair of legs; one species.
The only other genus is _Paranymphon_, Caullery (1896) (one species,
Gulf of Gascony, West of Ireland, Greenland), in which the palp is
(6–)7–jointed, the ovigerous leg 8–jointed, and the auxiliary claws are
absent.
=Fam. 7. Pallenidae.=—As in _Nymphon_, but appendage II. absent or
rudimentary.
[Illustration:
FIG. 285.—_Pallene brevirostris_, Johnston, ♀, Plymouth.
]
_Pallene_, Johnston (1837): about ten species (Mediterranean, North
Atlantic, Arctic, Australia). _P. languida_, Hoek, Australia, lacks
auxiliary claws, and is otherwise distinct; but _P. novaezealandiae_, G.
M. Thomson, is typical. _Pseudopallene_, Wilson (1878):[438] appendage
III. clawed; auxiliary claws absent; four (or more) species (North
Atlantic, Arctic, Antarctic). _P._ (_Phoxichilus_) _pygmaea_, Costa
(1836), and _P. spinosa_, Quatref., seem to belong to this genus or to
_Pallene_. _Cordylochele_, G. O. Sars (1888): closely allied, but with
front of cephalic segment much expanded and chelae remarkably swollen,
includes three very smooth, elongated, northern species, to which
Bouvier has added one from the Antarctic; _Pallene laevis_, Hoek, from
Bass’s Straits, is somewhat similar. _Neopallene_, Dohrn (1881): as in
_Pallene_, but with a rudimentary second appendage in the female, and no
generative aperture on the last leg in the male (one species,
Mediterranean). _Parapallene_, Carpenter (1892): as in _Pallene_, but
without auxiliary claws, and with the two last segments of the trunk
(which in _Pallene_ are coalesced) independent (about ten species, East
Indies and Australia); _Pallene grubii_, Hoek (_Phoxichilidium_ sp.,
Grube, 1869), is probably congeneric. _Pallenopsis_, Wilson (1881):
appendage I. 2–jointed; appendage II. rudimentary, 1–jointed; appendage
III. clawless; auxiliary claws present; slender forms, including some
formerly referred to _Phoxichilidium_; about fifteen species,
world-wide. _Pallene dimorpha_, Hoek, from Kerguelen, with 4–jointed
palps, deserves a new generic appellation. _P. longiceps_, Böhm, from
Japan, with rudimentary 2–jointed palps in the male, is also peculiar.
[Illustration:
FIG. 286.—_Phoxichilidium femoratum_, Rathke, Britain. =A=, The animal
with its legs removed; =B=, leg and chela.
]
=Fam. 8. Phoxichilidiidae.=—Appendage I. well-developed; II. absent;
III. present only in the male, having a few simple spines in a single
row. The last character is conveniently diagnostic, but nevertheless the
Phoxichilidiidae come very near to the Pallenidae, with which, according
to Schimkewitsch and others, they should be merged; the two families
resemble one another in the single row of spines on the ovigerous legs
and in the extension of the cephalic segment over the base of the
proboscis.
_Phoxichilidium_, M.-E. (1840): appendage III. 5–jointed; five or six
species (Mediterranean, North Atlantic, Arctic, Australia, Japan).
_Anoplodactylus_, Wilson (1878): appendage III. 6–jointed; auxiliary
claws absent or very rudimentary; about twelve species, cosmopolitan, of
which many were first referred to _Phoxichilidium_. _A. neglectus_,
Hoek, comes from 1600 fathoms off the Crozets. _Oomerus stigmatophorus_,
Hesse (1874), from Brest, seems to belong to one or other genus, but is
unrecognisable. _Anaphia_, Say (1821), is in all probability identical
with _Anoplodactylus_, and if so the name should have priority.
_Halosoma_, Cole (1904), is an allied genus from California.
[Illustration:
FIG. 287.—_Anoplodactylus petiolatus_, Kr., Britain. =A=, Dorsal view;
=B=, side view.
]
=Fam. 9. Phoxichilidae.=[439]—Appendage I. and II. absent; appendage
III. present only in the males, 7–jointed, with minute scattered spines;
auxiliary claws well-developed; body and legs slender. The only genus is
_Phoxichilus_ (auctt., non Latreille, _Chilophoxus_, Stebbing, 1902);
the type is _P. spinosus_, Mont. (non Quatrefages), from the N.
Atlantic, and _P. vulgaris_, Dohrn, _P. charybdaeus_, Dohrn, and _P.
laevis_, Grube, are all very similar. _Endeis gracilis_, Philippi
(1843), is probably identical with _P. spinosus_, or one of its close
allies. There are also known _P. meridionalis_, Böhm, _P. mollis_,
Carp., and _P. procerus_, Loman, from the East Indies; _P. australis_,
Hodgson, from the Antarctic; _P. böhmii_, Schimk., of unknown locality;
and forms ascribed to _P. charybdaeus_ by Haswell and by Schimkewitsch
from Australia and Brazil.
=Fam. 10. Pycnogonidae.=—Appendages I. and II. absent; appendage III.
present only in the male, 9–jointed, with small, simple spines;
auxiliary claws absent or rudimentary; body and legs short, thick-set.
The only genus is _Pycnogonum_, Brünnich (1764) (_Polygonopus_, Pallas,
1766); the type is _P. littorale_, Ström, of the N. Atlantic (0–430
fathoms), to which species have also been ascribed forms from various
remote localities, _e.g._ Japan, Chile, and Kerguelen. _P.
crassirostre_, G. O. Sars, a northern and more or less deep-sea form, is
distinct, and so also are _P. nodulosum_ and _P. pusillum_, Dohrn, from
Naples. _P. stearnsi_, Ives, from California, is like _P. littorale_,
except for the rostrum, which resembles that of _P. crassirostre_. _P.
magellanicum_, Hoek, _P. magnirostre_, Möbius, both from the Southern
Ocean; _P. microps_, Loman, from Natal, and four others described by
Loman from the East Indies, are the other authenticated species. Of _P.
philippinense_, Semper, I know only the bare record; and _P. australe_,
Grube, is described only from a larval form with three pairs of legs.
_P. orientale_, Dana (first described as _Astridium_, n.g.), is also
described from an immature specimen, and more resembles a _Phoxichilus_.
=The British Pycnogons.=
Dr. George Johnston,[440] the naturalist-physician of Berwick-on-Tweed,
Harry Goodsir,[441] brother of the great anatomist, who perished with
Sir John Franklin, and George Hodge[442] of Seaham Harbour, a young
naturalist of singular promise, dead ere his prime, were in former days
the chief students of the British Pycnogons. Of late, Carpenter[443] has
studied the Irish species; and the cruises of the _Porcupine_, _Triton_,
and _Knight Errant_ have given us a number of deep-water species from
the verge of the British area.
In compiling the following list, I have had the indispensable advantage
of access to Canon Norman’s collection, and the still greater benefit of
his own stores of endless information.[444]
_Pseudopallene circularis_, Goodsir: Firth of Forth.
_Phoxichilidium femoratum_, Rathke (_P. globosum_, Goodsir; _Orithyia
coccinea_, Johnston) (Figs. 270, B; 286): East and West coasts,
Shetland, Ireland.
_Anoplodactylus virescens_, Hodge (? _Phoxichilidium olivaceum_,
Gosse): South coast.
_A. petiolatus_, Kr. (Figs. 270, C; 275, B; 287) (_Pallene attenuata_
and _pygmaea_, Hodge; _Phoxichilidium exiguum_ and _longicolle_,
Dohrn): Plymouth, Firth of Forth, Cumbrae, Irish coasts.
_Ammothea_ (_Achelia_) _echinata_, Hodge (Fig. 265, B; 274, 4; 275,
E): Plymouth, Channel Islands, Isle of Man, Cumbrae, Durham (Hodge),
West of Ireland. We have not found it on the East of Scotland. _A.
brevipes_, Hodge, is presumed to be the young. Two of Dohrn’s
Neapolitan species, _A. fibulifera_ and _A. franciscana_, are in my
opinion not to be distinguished from one another, nor from the
present species.
_A. hispida_, Hodge (Fig. 266, C) (_A. longipes_, Hodge (_juv_); _A.
magnirostris_, Dohrn;? _Pasithoe vesiculosa_, Goodsir;? _Pephredo
hirsuta_, Goodsir): Cornwall and Devon (Hodge and Norman), Jersey.
The form common on the East of Scotland would seem to be this
species. The Mediterranean _A. magnirostris_, Dohrn, appears to be
identical.
_A. laevis_, Hodge: Cornwall (Hodge), Devon (Norman), Jersey (Sinel).
_Tanystylum orbiculare_, Wilson (_Clotenia conirostre_, Dohrn):
Donegal (Carpenter).
_Phoxichilus spinosus_, Mont. (Fig. 265, C; 270, A; 275, C): South
Coast, Moray Firth, Firth of Clyde, Ireland. A smaller and less
spiny form occurs, which Carpenter records as _P. laevis_, Grube,
but Norman unites the two under the name of _Endeis spinosus_
(Mont.).
_Pycnogonum littorale_, Ström (Fig. 262): on all coasts, and to
considerable depths (150 fathoms, West of Ireland).
_Nymphon brevirostre_, Hodge (_N. gracile_, Sars) (Figs. 263, 264,
267, A; 272, 274, 3): common on the East Coast; Herm (Hodge),
Dublin, Queenstown (Carpenter). Our smallest species of _Nymphon_.
_N. rubrum_, Hodge (_N. gracile_, Johnston; _N. rubrum_, G. O. Sars):
common on the East Coast; Oban (Norman), Ireland (Carpenter).
_N. grossipes_, O. Fabr., Johnston (_N. johnstoni_, Goodsir):
Northumberland, East of Scotland, Orkney, etc., not uncommon.
_N. gracile_, Leach (_N. gallicum_, Hoek; ♂ _N. femoratum_, Leach):
South of England, West of Scotland, and Ireland.
_N. strömii_, Kr. (_N. giganteum_, Goodsir) (Figs. 273, 274, 2): East
Coast, from Holy Island to Shetland.
_Chaetonymphon hirtum_, Fabr. (Fig. 274, 1): Northumberland (Hodge),
Margate (Hoek), East of Scotland, and Ireland, not uncommon. There
seems to be no doubt that British specimens agree with this species
as figured and identified by Sars. _N. spinosum_, Goodsir (East of
Scotland, Goodsir; Belfast, W. Thompson), is, according to Norman,
the same species. Sars’ Norwegian specimens figured under the latter
name are not identical, and have been renamed by Norman _C.
spinosissimum_, but are said by Meinert and Möbius to be identical
with _C. hirtipes_, Bell.
Hodge (1864) records _Nymphon mixtum_, Kr., and _N. longitarse_, Kr.,
from the Durham coast. His full list of the recorded species of
other authors also includes the following doubtful or unrecognised
species: _N. pellucidum_, _N. simile_, and _N. minutum_, all of
Goodsir.
_Pallene brevirostris_, Johnston (_P. empusa_, Wilson;? _P. emaciata_,
Dohrn) (Figs. 275, A; 285): all coasts. Examples differ considerably
in size and proportions, as do Dohrn’s Neapolitan species one from
another. We have specimens from the Sound of Mull that come very
near, and perhaps agree with, Sars’ _P. producta_, a species that
scarcely differs from _P. brevirostris_, save in its greater
attenuation; the same species has also been recorded from Millport
and from Port Erin.
_P. spectrum_, Dohrn: Plymouth (A. H. Norman).
Besides the above, all of which are littoral or more or less
shallow-water species, we have another series of forms, or, to speak
more correctly, we have two other series of forms, from the deep
Atlantic waters within the British area. In the cold area of the Faeroe
Channel we have _Boreonymphon robustum_, Bell; _Nymphon elegans_,
Hansen; _N. sluiteri_, Hoek; _N. stenocheir_, Norman; _Colossendeis
proboscidea_, Sabine; _C. angusta_, Sars. In the warm waters south and
west of the Wyville-Thomson ridge we have _Chaetonymphon spinosissimum_,
Norman; _Nymphon gracilipes_, Heller (non Fabr.); _N. hirtipes_, Bell;
_N. longitarse_, Kr.; _N. macrum_, Wilson; _Pallenopsis tritonis_, Hoek
(= _P. holti_, Carpenter); _Anoplodactylus oculatus_, Carpenter, and _A.
typhlops_, G. O. Sars; and to the list under this section Canon Norman
has lately made the very interesting addition of _Paranymphon spinosum_,
Caullery, from the _Porcupine_ Station XVII., S.S.E. of Rockall, in 1230
fathoms. Lastly, and less clearly related to temperature, we have
_Chaetonymphon tenellum_, Sars; _N. gracilipes_, Fabr.; _N.
leptocheles_, Sars; _N. macronyx_, Sars; _N. serratum_, Sars; and
_Cordylochele malleolata_, Sars.
Of the species recorded in the above list as a whole, _Anoplodactylus
virescens_, _Nymphon gracile_, and _Pallene spectrum_ reach their
northern limit in the southern parts of our own area; _Ammothea
echinata_, _Anoplodactylus petiolatus_, _Pallene brevirostris_, and
_Phoxichilus spinosus_ (or very closely related forms) range from the
Mediterranean to Norway, the last three also to the other side of the
Atlantic; _Nymphon brevirostre_ and _N. rubrum_ range from Britain,
where they are in the main East Coast species, to Norway. Of the
Atlantic species, other than the Arctic ones, the majority are known to
extend to the New England coast.
INDEX
Every reference is to the page: words in italics are names of genera
or species; figures in italics indicate that the reference relates
to systematic position; figures in thick type refer to an
illustration; f. = and in following page or pages; n. = note.
_Abalius_, _312_
Abdomen, of Malacostraca, 110;
of _Acantholithus_, =178=;
of _Birgus_, =176=;
of _Cenobita_, =176=;
of _Dermaturus_, =178=;
of _Hapalogaster_, =178=;
of _Lithodes_, =178=;
of _Pylopagurus_, =178=;
of Trilobites, 235;
of Scorpions, 297;
of Pedipalpi, 309;
of Spiders, 317;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 431;
of Podogona, 440;
of Phalangidea, 440, 443;
of Acarina, 457;
of Pentastomida, 489;
of Pycnogonida, 502
Abdominal glands, of Chernetidea, 432
Abyssal region (marine), 204;
(lacustrine), 209
_Acantheis_, _418_
_Acanthephyra_, _163_
Acanthephyridae, _163_
_Acanthoctenus_, _415_
_Acanthodon_, _388_
_Acanthogammarus_, _138_
_Acantholeberis_, _53_
_Acantholithus_, _181_;
_A. hystrix_, =178=
_Acanthophrynus_, _313_
Acari, 454 (= Acarina, _q.v._)
Acaridea, 454 (= Acarina, _q.v._)
Acarina, _258_, _454_ f.;
parasitic, 455;
external structure, 457;
spinning organs, 457;
internal structure, =459=;
metamorphosis, 462;
classification, 464
_Acaste_, _249_
_Accola_, _390_
_Acerocare_, _247_
Achelata, _529_
_Achelia_, _534_;
_A. longipes_, =506=
_Achtheres_, _75_;
_A. percarum_, =75=
Acidaspidae, _251_
_Acidaspis_, 226, 227, 230, 231, 235, 241, _251_;
_A. dufrenoyi_, =250=;
_A. tuberculata_, larva, =240=;
_A. verneuili_, 231;
_A. vesiculosa_, 231
Aciniform glands, =335=, 349
_Acoloides saitidis_, 367
_Acroperus_, _53_;
_A. leucocephalus_, =52=
_Acrosoma_, _410_
Acrothoracica, _92_
_Actaea_, _191_;
habitat, 198
Actinopodinae, _387_
_Actinopus_, _387_
Aculeus, of scorpion, 303
_Admetus_, _313_
Aegidae, _126_
_Aegisthus_, _61_
_Aeglea laevis_, _169_;
distribution, 212
Aegleidae, _169_
_Aeglina_, 227, _249_;
_Ae. prisca_, =248=
_Agelena_, _416_;
_A. brunnea_, 367;
_A. labyrinthica_, 352, 353, 378, 380, 381, 416;
_A. naevia_, 339
Agelenidae, 325, 352, 353, _415_
Ageleninae, _416_
Aggregate glands, 335, 349
_Aglaspis_, _279_
_Agnathaner_, _66_
Agnathonia, _529_
Agnostidae, _244_
Agnostini, _243_
_Agnostus_, 222, 223, 225, 231, 234, _245_;
_A. integer_, =245=
_Agraulos_, _247_
_Agroeca_, _397_;
_A. brunnea_, cocoon, =358=
_Albunea_, _171_;
respiration, 170;
distribution, 201
Albuneidae, _171_
_Alcippe_, _92_;
_A. lampas_, =92=, 93
Alcock, on Oxyrhyncha, 192;
on phosphorescence, 151
_Alepas_, _89_
Alima, larva of _Squilla_, 143
Alimentary canal, of Crustacea, 14;
of Phyllopoda, 28;
of Cladocera, 42;
of _Squilla_, 142;
of Malacostraca, 110;
of
Trilobites, 222;
of Arachnida, 256;
of _Limulus_, 268;
of Scorpions, 304;
of Pedipalpi, 310;
of Spiders, 329;
of Solifugae, 427;
of Pseudoscorpions, 134;
of Phalangidea, 444;
of Acarina, 459;
of Tardigrada, 480;
of Pentastomida, 491;
of Pycnogous, 513
_Alitropus_ (Aegidae), habitat, 211
Allman, on larvae of Pycnogons, 523
_Alloptes_, _466_
_Alona_ (including _Leydigia_, _Alona_, _Harporhynchus_,
_Graptoleberis_), _53_
_Alonopsis_, _53_
Alpheidae, _163_;
habitat, 198
_Alpheus_, _163_;
reversal of regeneration, 156
Alveolus, of palpal organ of Spiders, 322
_Amaurobius_, _399_;
_A. fenestralis_, 399;
_A. ferox_, 399;
_A. similis_, 399;
spinnerets, =326=
_Amblyocarenum_, _388_
_Amblyomma_, _470_;
_A. hebraeum_, 456, 470
Amblypygi, _312_
_Ammothea_, 505, _534_;
_A. achelioides_, 534;
_A. brevipes_, 541;
_A. echinata_, =505=, =509=, =510=, 534, 541, 542;
_A. fibulifera_, =522=, 534, 541;
_A. franciscana_, 541;
_A. grandis_, 534;
_A. hispida_, 534, 535, 541;
_A. laevis_, 541;
_A. longicollis_, 533;
_A. longipes_, =506=, 534, 541;
_A. magnirostris_, 534, 541;
_A. typhlops_, 542;
_A. uniunguiculata_, 534
Ammotheidae, _534_
_Amopaum_, _452_
Ampharthrandria, _61_
Amphascandria, _57_
_Amphion_, _251_
Amphipoda, _136_ f.;
pelagic, 202;
fresh water, 211
Ampullaceal glands, 335, 349
Ampycini, _243_
_Ampyx_, 231, _245_;
_A. roualti_, =230=
Anabiosis, in Tardigrada, 484
_Analges_, 455, _466_
Analgesinae, _466_
_Ananteris_, _306_
_Anaphia_, _539_
Anaspidacea, _115_;
distribution, 211, 217
Anaspidae, _89_
_Anaspides_, _115_, 117;
relation to Schizopoda, 112;
distribution, 211;
_A. tasmaniae_, 115, =116=;
habitat, 211
Anaspididae, _115_
_Anelasma squalicola_, _89_
_Anelasmocephalus_, _452_
_Angelina_, _247_
_Anisaspis bacillifera_, _387_
Anisopoda, _122_
_Anomalocera pattersoni_, =60=;
distribution, 202, 203
Anomopoda, _51_
_Anomorhynchus_, _532_
Anomura, _167_;
relation to Thalassinidea, 167
_Anoplodactylus_, 511, _538_;
_A. lentus_, 524;
_A. neglectus_, 539;
_A. oculatus_, 542;
_A. petiolatus_, =508=, =510=, =539=, 541, 542;
_A. virescens_, 540, 542
_Anopolenus_, _247_
Antarctic zone (marine), 200
Antarctica, evidence on, 200, 217
Antennae, of Crustacea, 5, 8;
of Phyllopoda, 24;
of Cladocera, 37;
of Copepoda, 55;
of Cirripedia, 81 f.;
of Ostracoda, 107;
of Malacostraca, 110;
of Anomura, 168;
of _Corystes cassivelaunus_, 170, 183, 189;
used in respiration, 170;
of Trilobites, 237
Antennary gland, 13 (= green gland, _q.v._)
_Anthrobia_, _406_;
_A. mammouthia_, 334, 366
_Anthura_, _124_
Anthuridae, _124_
Ants and spiders, 370
_Anyphaena accentuata_, _397_
Aphantochilinae, _414_
_Aphantochilus_, _414_
Apoda, _94_
Apodidae, 19, 21, 22, 23, 27, 28, 29, 31, _36_, 241
_Aponomma_, _470_
Appendages (_incl._ legs, limbs), of Crustacea, 7;
of Entomostraca, 18;
of Phyllopoda, 24;
of Cladocera, 40;
of Copepoda, 55;
of Cirripedia, 80 f.;
of Ostracoda, 107;
of Malacostraca, 110;
of _Nebalia_, 111;
of Eumalacostraca, 113;
of _Anaspides_, 115;
of Mysidacea, 118 f.;
of Cumacea, 120;
of Isopoda, 121 f.;
of Amphipoda, 136 f.;
of Stomatopoda, 142;
of Euphausiacea, 144 f.;
of Decapoda, 152;
of Macrura, 153;
of their larvae, 159;
of Anomura, 167 f.;
of _Birgus_, 175;
of Brachyura, 181 f.;
alterations caused by parasites, 100 f.;
by hermaphroditism, 102 f.;
of Trilobita, 236, =237=;
of Arachnida, 255 f.;
of _Limulus_, =262=, 263;
of _Eurypterus_, 285 f.;
of Scorpions, 301, 303;
of Pedipalpi, 309;
of Spiders, 319;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 432;
of Podogona, 440;
of Phalangidea, 443;
of Acarina, 458;
of Tardigrada, 479;
of Pentastomida, 493;
of Pycnogons, 503 f.
_Apseudes spinosus_, =123=
Apseudidae, _122_
Apstein, 335
_Apus_, 21, 23, 25, 28, 30, 32, 34, _36_, 221, 242, 243;
segmentation, 6;
_A. australiensis_, 36;
_A. cancriformis_, 36;
habitat, 34
Arachnida, introduction to, 255;
segmentation of body, 255–6;
primitive, 256–7;
coxal glands, 257;
endosternite, 257;
sense-organs, 257;
classification, 258
Araneae, _258_, _314_ f.
Araneida, _314_
Araneina, _314_
_Araneus_, 408 n.
_Aratus pisonii_, 195
_Arbanitis_, _388_
_Archaeolepas_, _84_;
_A. redtenbacheri_, =84=
_Archea_, _411_;
_A. paradoxa_, 383;
_A. workmani_, 411
Archeidae, 321, _411_
_Archisometrus_, _306_
Arctic zone, 199
Arcturidae, _127_
_Arcturus_, _127_
Arcyinae, _410_
_Arcys_, _410_
_Arethusina_, 223, 230, _251_;
_A. konincki_, =250=
_Argas_, 457, _469_;
_A. persicus_, 469;
_A. reflexus_, 469
Argasidae, _469_
_Arges_, _252_
_Argiope_, _408_;
_A. aurelia_, 340, =379=;
_A. bruennichi_, 408;
_A. cophinaria_, 349, 365;
_A. trifasciata_, 408
Argiopidae, 406 n.
Argiopinae, _408_
Argulidae, _76_
_Argulus foliaceus_, =77=
_Argyrodes_, _402_;
_A. piraticum_, 367;
_A. trigonum_, 367
Argyrodinae, _402_
_Argyroneta_, 336, _415_;
_A. aquatica_, 357, 415
_Ariadna_, _395_
_Ariamnes_, _402_;
_A. flagellum_, =318=
_Arionellus_, _247_
_Aristaeus_, _162_;
_A. crassipes_, 159;
_A. coruscans_, phosphorescence, 151
_Armadillidium_, _129_
_Artema_, _401_
_Artemia_, 23, 24, _35_;
_A. fertilis_, anal region, =23=;
head, =26=;
limb, 27;
_A. salina_, 23, 33, 36;
_A. urmiana_, 23
_Arthrolycosa antiqua_, 383
Arthropoda, 4;
segmentation, 7;
a natural group, 17
Arthrostraca, _121_
_Asagena_, _404_
_Asaphellus_, _249_
Asaphidae, _249_
Asaphini, _243_
_Asaphus_, 222, 225, 227, 229, 235, 236, _249_;
_A. cornigerus_, 227;
_A. fallax_, eye, =228=;
_A. kowalewskii_, 227;
_A. megistos_, 236;
_A. platycephalus_, 236
_Ascidicola rosea_, _66_
Ascidicolidae, _66_
Asconiscidae, _130_
_Ascorhynchus_, 505, _533_;
_A. abyssi_, =506=, =509=, 519;
_A. cryptopygius_, 513 n.;
_A. minutus_, 517;
_A. ramipes_, 513 n.
Ascothoracica, _93_
Asellidae, _128_
Asellota, _127_
_Asellus_, _127_;
habitat, 209, 211;
_A. aquaticus_, 127, 209;
_A. cavaticus_, 209, 210;
_A. forelii_, 209
_Aspidoecia_, _76_
Astacidae, _157_;
distribution, 213, 216
_Astacoides_, _157_;
distribution, 213
_Astacopsis_, _157_;
distribution, 213;
_A. franklinii_, 214
_Astacus_, 104, _157_;
appendages, =10=;
distribution, 213;
hermaphroditism, 104
_Astacus gammarus_ (= _Homarus vulgaris_), _154_
_Asterocheres violaceus_, =67=
Asterocheridae, _67_
_Asterope oblonga_, =108=
_Astia_, _421_;
_A. vittata_, =381=
Astigmata, _465_
_Astridium_, _540_
_Atax_, 462, _472_;
_A. alticola_, =472=;
_A. bonzi_, 472
Atelecyclidae, _190_
_Atelecyclus_, _191_;
respiration, 189
_Atops_, _247_
Attidae, 376, 381, _419_
_Attus_, _421_;
_A. pubescens_, 372, 421;
_A. saltator_, 372, 421
_Atya_, _163_
_Atyephyra_, _163_;
habitat, 210
_Atyidae_, 159, _163_;
distribution, 212
Atypidae, _390_
_Atypoides_, _391_
_Atypus_, _391_;
_A. abboti_, 356;
_A. affinis_, 356, =391=;
_A. beckii_, 391
Auditory organ, of _Anaspides_, 116;
of Decapoda, 153;
of Mysidae, 119
_Augaptilus filigerus_, _59_
_Austrodecus glacialis_, _535_
_Austroraptus polaris_, _535_
Autotomy, 155
_Avicularia_, _389_
Aviculariidae, 316, 327, _386_;
bite of, 365;
poisonous hairs of, 365
Aviculariinae, _389_
Axial furrows, 223
Baglivi, 361
Baikal, Lake, Crustacea of, 212
_Balanus_, _91_;
_B. porcatus_, shell, =90=;
_B. tintinnabulum_, 91;
anatomy, =90=
_Ballus variegatus_, =420=
_Barana_, 506, 513, _533_;
_B. arenicola_, 512, 513, 533;
_B. castelli_, 512, 513 n., 533
Barnacles, origin of term, 79
Barrande, J., on development of Trilobites, 238;
on their classification, 243
_Barrandia_, _249_
Barrois, 435 n.
_Barrus_, _429_
Barychelinae, _389_
Basse, on Tardigrada, 481
Baster, Job, 503
Bates, 373
_Bathynomus giganteus_, _126_;
habitat, 205
_Bathynotus_, _247_
_Bathyphantes_, _406_
_Bdella lignicola_, =471=
Bdellidae, 458, _471_
Beecher, C. E., on facial sutures of _Agnostus_ and _Olenellus_, 225;
on development of Trilobites, 238;
on their classification, 243
Beetle-mites, 467
Beetle-parasites, 470
_Belinurus_, 275, 279;
_B. reginae_, =278=
_Belisarius_, _308_
Belt, 368, 371
_Beltina_, 283 n.
Bernard, 311, 424, 426, 433 n., 434 n.
Bertkau, 323, 365, 395 n.
Beyrich, E., on facial suture of _Trinucleus_, 226
Billings, E., on appendages of Trilobites, 236
Bipolarity, 200
Birds and Spiders, 370
Birds’ feather Mites, 466
_Birgus_, _181_;
_B. latro_, habits, 174;
structure, =175=, =176=
Black Corals, Cirripedia parasitic on, 93, 94
Blackwall, 348, 359 n., 365, 368, 385
Blindness, in Crustacea, 149, 209, 210;
in Spiders, 334
Blood, haemoglobin supposed in, 30, 68
Boas, on classification of Malacostraca, 113
_Boeckella_, distribution, 216
_Boeckia_, _138_
_Böhmia_, _535_
_Bolocera_, _Pycnogonum_ with, 524
_Bolyphantes_, _406_
Bomolochidae, _71_
_Bomolochus_, _71_, =72=
Bon, 360
Bont-tick, 456
_Boophilus_, 456, _469_;
_B. australis_, capitulum of, =468=
Bopyridae, 130, _133_
Bopyrina, 129, 130, _132_
_Bopyrus fougerouxi_, _133_;
male, =133=;
adult female, =134=
Bopyrus larva, of Bopyrina, 129, 133
_Boreomysis_, _120_;
_B. scyphops_, distribution, 201
_Boreonymphon_, _536_;
_B. robustum_, =506=, 507, =511=, 512, 542
_Bosmina_, =52=, _53_;
occurrence in Southern hemisphere, 216;
_B. longirostris_, habitat, 206
Bosminidae, _53_;
appendages, 41;
alimentary canal, 42
Bothriuridae, 306, _308_
_Bothriurus_, _308_
Bouvier, 528 n.
Boys, 348, 360, 376
_Brachybothrium_, _391_
_Brachymetopus_, _251_
_Brachythele_, _390_
Brachyura, _181_;
eyes, 150
Branchiae (= gills) of Crustacea, 16;
of Decapoda, 152;
of _Limulus_, 269;
of Eurypterids, 288
_Branchinecta_, 25, _35_;
_B. paludosa_, 35;
range, 34
Branchiopoda, _18_ f.
_Branchiopodopsis_, _35_;
_B. hodgsoni_, 35
Branchiostegite, 152
Branchipodidae, 19, 22, _35_, 241
_Branchipus_, 25, _35_, 233, 242, 511 n.;
thoracic limb, =10=;
nervous system, 30;
_B. spinosus_, habitat, 33;
_B. stagnalis_, 35;
eggs, 32
Branchiura, _76_
Brauer, on development of Scorpions, 263, 301 n., 305
Breeding (see Reproduction)
British forms, of Cladocera, 51;
of Pycnogons, 540
Bronteidae, _249_
_Bronteus_, 228, 235, _249_;
_B. brongniarti_, eye, 229;
_B. palifer_, eye, 229;
_B. polyactin_, hypostome, =233=;
_B. irradians_, macula, =233=
Brood-pouch, of Cladocera, 46, 47;
of Peracarida, 118
_Broteas_, _308_
_Broteochactas_, _308_
Brünnich, 502
Buckler, 330
_Bucranium_, _414_
Bulb, of palpal organ of Spiders, 322
_Bumastus_, 235, 236, _249_
_Bunodella_, _279_
_Bunodes_, _279_
Buthidae, _306_
Buthinae, _306_
_Buthus_, _306_;
_B. occitanus_, =299=, =300=, =302=
_Bythotrephes_, 38, _54_;
reproduction, 47;
_B. cederströmii_, =42=
Cabiropsidae, _130_
_Caecidotea nickajackensis_, habitat, 210;
_C. stygia_, habitat, 210
Caeculinae, _472_
_Caeculus_, _472_
Calamistrum, =326=, 354, 385, 392, 399, 410
Calanidae, _57_
_Calanus_, _57_;
_C. finmarchicus_, distribution, 203, 204;
_C. hyperboreus_, 55, =56=, 58
_Calappa_, _187_;
respiration, 186;
habitat, 198;
distribution, 201;
_C. granulata_, =186=
Calappidae, _187_
_Calathocratus_, _452_
_Calathura brachiata_ (Anthuridae), _Duplorbis_ parasitic on, 95
_Calicurgus annulatus_, 369
Caligidae, _73_
_Caligus nanus_, =74=;
_C. rapax_, 74;
_C. lacustris_, 74
_Callianassa_, _167_;
habitat, 198;
_C. subterranea_, 167;
gut, 14
Callianassidae, _167_
_Callinectes_, _191_;
_C. sapidus_, 191
Calman, on classification of Crustacea, 112, 113
_Calocalanus plumulosus_, =58=
_Caloctenus_, _418_
_Calommata_, _391_
_Calymene_, 225, 230, 235, _249_;
_C. senaria_, 236;
_C. tuberculata_, =224=
Calymenidae, _247_
Calyptomera, 38, _51_
Calyptopis, larva of _Euphausia pellucida_, =144=
_Cambaroides_, distribution, 213
_Cambarus_, _157_;
hermaphroditism, 103;
distribution, 213;
_C. stygius_, distribution, 213
Camerostome, 452
Campbell, 327
_Camptocercus_, _53_;
_C. macrurus_, 48
_Cancer_, _191_;
_C. pagurus_, 191
_Cancerilla_, _68_;
_C. tubulata_, 68
Cancridae, _191_
_Candace_, _60_;
_C. pectinata_, 60
Candacidae, _60_
_Candona_, _107_;
_C. reptans_, =107=
Canestrini, 464
_Canthocamptus_, _62_;
habitat, 206
Capitulum, of Cirripedia, 81;
of Acarina, 457, 468, 471
_Caponia natalensis_, _395_
Caponiidae, _395_
_Caponina_, _395_
_Caprella acutifrons_, _140_;
_C. grandimana_, =139=
Caprellidae, _139_
Carapace, of Phyllopoda, 19 f.;
of Cladocera, 38;
absence of, in Copepoda, 55;
of Malacostraca, 114
Carcinoplacidae, _195_
_Carrinoscorpius_, _277_;
_C. rotundicauda_, 277
_Carcinus_, _191_;
_C. maenas_, 188, 191;
gut, 14;
respiration, 189, 190;
distribution, 198;
_Portunion_ parasitic in, =135=;
_Sacculina_ parasitic on, 96
_Cardisoma_, _196_;
distribution, 201
Caridea, _158_, _163_;
metamorphosis, 161
_Caridina_, _163_;
_C. nilotica_, distribution, 212
Carniola, caves of, 34
Carpenter, on segmentation of Arthropods, 6, 263;
on affinities of Trilobites, 242;
on Irish Pycnogons, 540
Caruncle, 470
Caspian Sea, Crustacea of, 215
_Caspiocuma_, _121_
Catometopa, _193_ f.;
habits, 194, 195
_Catophragmus_, =91=
Caudal organs, 311
Caullery, on Liriopsidae, 132 n.
Causard, 332
Cavanna, 520
_Cecrops_, _74_
_Cenobita_, _181_;
relation to _Birgus_, =176=
Cenobitidae, _181_
_Centropages hamatus_, 203;
_C. typicus_, distribution, 203
Centropagidae, _58_
_Centropelma_, _416_
_Centropleura_, _247_
Centrurinae, _306_
_Centrurus_, _306_
Cephalic shield, 223
_Cepheus ocellatus_, =467=
_Cerataspis_, _162_
_Ceratolichas_, _252_
_Ceratopyge_, _247_
_Cercophonius_, _308_
_Ceriodaphnia_, 37, 39, _51_
_Ceroma_, _429_
_Chactas_, _308_
Chactidae, 306, _307_
Chaerilidae, 306, _307_
_Chaerilus_, _307_
_Chaetolepas_, _89_
_Chaetonymphon_, _536_;
_C. hirtipes_, 541;
_C. hirtum_, =509=, 541;
_C. macronyx_, =506=;
_C. spinosissimum_, 541, 542;
_C. tenellum_, 542
_Chaetopelma_, _389_
Charontinae, _313_
_Chasmops_, _249_
Cheeks, of Trilobites, 223, 225
Cheese-mites, 466
_Cheiracanthium_, _397_
Cheiruridae, _250_
_Cheirurus_, 235, _251_;
_C. insignia_, =250=;
_C. pleurexacanthus_, 236
Chelicerae, of Xiphosura, 263 f.;
of Eurypterida, 285;
of Scorpions, 303;
of Pedipalpi, 309;
of Spiders, 319;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 432;
of Podogona, 439;
of Phalangids, 443;
of Acarina, 458
_Chelifer_, 436, _437_;
development, =435=;
_C. cancroides_, 437;
_C. cyrneus_, =437=;
_C. ferum_ 437
Chelifera, _122_
Cheliferidae, _436_
Chelophores, of Pycnogons, 505
_Chernes_, =432=, 436, 437, _438_
Chernetes, 430
Chernetidea, _258_, _430_ f.
Cheyletinae, _473_
_Cheyletus_, 458, _473_
Chilaria, 260, 271, 287, 292
_Chilobrachys_, _390_;
_C. stridulans_, =328=, 329
_Chilophoxus_, _539_
_Chiltonia_, _139_;
distribution, 217
_Chiridium_, 432, 436, _437_;
_C. museorum_, =437=
_Chirocephalus_, _35_;
_C. diaphanus_, =20=, =24=, =25=, =27=, 29, 32, 33, 35
_Chlorodinus_, habitat, 198
_Chlorodius_, _191_
Chondracanthidae, _72_
_Chondracanthus zei_, =72=
_Choniostoma_, _76_
Choniostomatidae, _76_
_Chthonius_, 436, _438_
Chun, on phosphorescence and eyes, 150
_Chydorus_, _54_
_Cilunculus_, _535_
Circulatory (= vascular) system, of Crustacea, 11;
of Arachnids, 256;
of _Limulus_, 268 f.;
of Tardigrada, 482;
of Pentastomida, 491;
of Pycnogons, 516
_Cirolana_, _126_
Cirripedia, _79_ f.;
metamorphosis, 80;
anatomy, 83;
sex, 87, 105
CLADOCERA, _19_, _37_ f.;
carapace, 38;
dorsal organ, 39;
appendages, 40 f.;
alimentary canal, 42;
heart, 43;
reproduction, 43–50;
British genera, 51–54;
extra-European, 54;
pelagic, 207, 208
Claparède, 331, 462 n.
Clarke, J. M., on the eye of _Calymene senaria_, 229;
of _Harpes_, 231
Claus, on Copepoda, 55;
on _Nebalia_, 111;
on discovery of metamorphosis of Decapods, 153 n.;
on Pycnogonida, 527
Claw-tufts, 389
Clerck, 384, 408 n.
_Clibanarius_, _181_
_Clotenia conirostre_, 541
_Clubiona_, 337, 368, _397_;
_C. compta_, 397;
_C. corticalis_, =396=, 397
Clubioninae, _397_
Clypeus, 316
_Clytemnestra_, _61_
_Coelotes atropos_, _416_
Cole, 520, 524, 525, 528 n.
_Colossendeis_, 505, _532_;
_C. angusta_, 542;
_C. australis_, 533;
_C. gibbosa_, 534;
_C. gigas_, 532;
_C. gracilis_, 505 n.;
_C. proboscidea_, =505=, =508=, =510=, 533, 542
Colour, adaptation in, of Crustacea, 159
Colulus, =317=, 319
Commensalism, of Hermit-crabs, 172;
of _Pinnotheres_, 195
Complemental males, of Cirripedes, 83, 86, 99, 106
_Conchoderma_, _88_;
_C. virgata_, =88=
Conocephalidae, _247_
_Conocoryphe_, 231, _247_;
_C. sulzeri_, =248=
Conocoryphidae, _247_
_Conolichas_, _252_
_Conothele_, _388_
_Constantia_ (_Macrohectopus_), _138_;
occurrence, 212
Cook, 425 n.
Copepoda, _55_ f.;
fresh-water, 59, 62;
pelagic, 202;
life-cycle of fresh-water, 209
_Copilia vitrea_, _69_, =70=
_Cordylochele_, 506, _537_;
_C. longicollis_, =507=;
_C. malleolata_, 542
_Corniger hilgendorfi_, _535_
_Coronula diadema_, _91_
Corophiidae, _139_
_Corophium_, _139_
Corycaeidae, _69_
_Corystes_, _188_, _190_;
habitat, 198;
_C. cassivelaunus_, respiration, 170, 189;
metamorphosis, =182=, =183=
Corystidae, _190_
Cosmetidae, _449_
Costa, da, 221
Coxal glands, 257;
of _Limulus_, 270;
of Scorpions, 306;
of Pedipalpi, 311;
of Spiders, 337
Coxopodite, of Trilobites, 237
Crab, Hermit-, 171–173;
River-, 214;
Robber-, 174;
Shore-, 188, 189, 198;
Edible, 188;
Spider-, 191;
Land-, 195;
enemies of, 192
Crab-spiders, 412 (= Thomisidae, _q.v._)
_Crangon_, _164_;
_C. antarcticus_, distribution, 200;
_C. franciscorum_, distribution, 200;
_C. vulgaris_, 158, 164;
distribution, 199
Crangonidae, _164_;
distribution, 199
_Crangonyx_, _138_
Crayfish, 154, _157_;
distribution, 213, 215
Crevettina, _137_
Cribellatae, 324, 385, 386 n.
Cribellum, =326=, 354, 385, 386, 392, 398, 410
Croneberg, 460
_Cruregens_, _124_;
_C. fontanus_, habitat, 210
Crustacea, organisation, 1 f.;
segmentation, 5;
appendages, 8 f.;
body-cavity and coelom, 11;
kidneys, 13;
alimentary canal, 14;
reproductive organs, 15;
respiratory organs, 16;
compound eyes, 146;
growth and sex in, 100;
metabolism, 104;
distribution, 197;
pelagic, 202, 207;
littoral, 197, 206;
abyssal, 204, 209;
fresh-water, 205;
subterranean and cave, 209
Crustacés aranéiformes, 501 n.
_Cryphaeus_, _249_
_Cryphoeca_, _416_
_Cryptocellus_, _439_;
_C. simonis_, =439=
_Cryptocerus_, _414_
Cryptoniscidae, _130_
Cryptoniscina, _129_, 130
Cryptoniscus, larva of Epicarida, 129, =131=, 132
_Cryptophialus_, _92_;
_C. minutus_, 92, 93;
_C. striatus_, 93
_Cryptostemma westermannii_, _439_
Cryptostemmatidae, _440_
_Cryptothele_, _400_
Ctenidae, _418_
Cteninae, _418_
_Cteniza_, _388_;
_C. ariana_, 355
Ctenizinae, _388_
_Ctenocephalus_, _247_
_Ctenophora_, _412_
Ctenopoda, _51_
_Ctenopyge_, 232, _247_
_Ctenus_, _418_
Cucullus, 440
_Cuma_, _121_
Cumacea, 114, _120_;
of the Caspian, 215
Cumidae, _121_
Cyamidae, _140_
_Cyamus ceti_, _140_
Cybaeinae, _415_
_Cybele_, _251_
_Cyclaspis_, _121_
_Cyclestheria_, _37_;
_C. hislopi_, 37
_Cyclodorippe dromioides_, eyes, 149
_Cyclograpsus_, _196_;
distribution, 200
Cyclometopa, _188_ f.;
respiration, 189, 190
Cyclopidae, _61_, 62;
subterranean, 209
_Cyclops_, _62_;
_C. fuscus_, habitat, 207;
_C. strenuus_, habitat, 207, 208;
_C. stygius_, habitat, 210
_Cyclosa conica_, _409_
_Cyclosternum_, _389_
_Cydrela_, _399_
_Cymodoce_, _126_
_Cymonomus_, _188_;
_C. granulatus_, =185=;
eyes, 149, 186;
_C. normani_, 186;
_C. quadratus_, _186_
_Cymothoa_, _126_;
habitat, 211
Cymothoidae, _126_
_Cyphaspis_, _251_
Cyphophthalmi, 443, 444, _447_
Cypridae, _107_;
subterranean, 209
Cypridinidae, _108_
_Cypris_, _107_;
_C. reptans_, parthenogenesis, 108
Cypris larva, of Cirripedia, 80, =82=;
of _Sacculina_, =97=, =99=
_Cyrtauchenius_, _388_;
_C. elongatus_, funnel of, =356=
_Cythere dictyon_, _108_
Cytherellidae, _109_
Cytheridae, _107_
_Dactylopisthes digiticeps_, =405=
_Dactylopus tisboides_, _62_
_Daesia_, _429_
Daesiinae, _429_
Dajidae, _130_
_Dalmanites_, _249_;
_D. imbricatulus_, eye, =228=;
_D. limulurus_, =250=;
_D. socialis_, larvae, =240=
_Danalia curvata_, _130_, =131=, =132=
_Daphnella_, _51_;
testes, 44
_Daphnia_, 37, 38, 39, _51_;
ovary, =45=, 48;
_D. magna_, 50;
_D. obtusa_, =51=
Daphniidae, _51_;
appendages, 40;
alimentary canal, 42;
reproduction, 48;
reactions, 50
Darwin, on Cirripedia, 80, 85, 86, 92, 94
_Dasylobus_, _450_
Decapoda, _152_ f.;
systematic position, 114;
alimentary canal, 14;
pelagic, 202;
subterranean, 210;
Rhizocephala parasitic on, 95, 101;
Bopyridae parasitic on, 133
_Dechenella_, _251_
_Decolopoda_, 504, _529_, _532_;
_D. antarctica_, 532;
_D. australis_, =531=, 532
Decolopodidae, _531_
Defective orb-webs, 349
_Deiphon_, 235, _251_;
_D. forbesi_, =250=
_Delena_, _414_
Delobranchiata, _258_, 259 f.
_Demodex_, _465_;
_D. folliculorum_, =465=
Demodicidae, 455, _465_
_Dendrogaster astericola_, _94_
_Dermacentor_, _469_
Dermanyssinae, _471_
_Dermanyssus avium_, _471_
_Dermaturus_, _181_;
_D. hispidus_, =178=
_Desis_, _415_
Deutovum, 462
Development, of Monstrillidae, 64;
of Cirripedia, 80;
of Rhizocephala, 96;
of Epicarida, 130;
of Stomatopoda, 142;
of Shrimps and Prawns, 159;
of Loricata, 165;
of Hermit-Crabs, 179;
of Brachyura, 181;
of Trilobites, 238 f.;
of _Limulus_, 275;
of _Scorpio_, 305;
of Pseudoscorpions, 434;
of Mites, 462;
of Tardigrada, 483;
of Pentastomida, 493;
of Pycnogons, 520
_Diaea_, _412_;
_D. dorsata_, 413
Diaphragm, of Solifugae, 427
_Diaptomus_, _59_;
distribution, 208, 216;
_D. caeruleus_, habitat, 208;
_D. castor_, habitat, 206;
_D. gracilis_, habitat, 206
Diastylidae, _121_
_Diastylis_, _121_;
_D. goodsiri_, 121;
_D. stygia_, =120=
_Dichelaspis_, _88_
Dichelestiidae, _68_;
classification, 63
_Dichelestium_, _68_
Dick, 363
_Dicranogmus_, _252_
_Dicranolasma_, _452_
_Dictyna_, _398_;
_D. arundinacea_, 399;
_D. uncinata_, 399
Dictynidae, 352, 353, _398_
Digestive system, = alimentary canal, _q.v._
_Dikelocephalus_, _247_
Dimorphism, high and low;
in Decapoda, 103;
in Tanaids, 123
_Dindymene_, _251_
Dinopinae, _410_
_Dinopis_, _410_
_Dinorhax_, _429_
_Diogenes_, _181_
_Dionide_, _245_
_Diphascon_, 485;
_D. alpinum_, 487;
_D. angustatum_, 487;
_D. bullatum_, 487;
_D. chilenense_, =486=, 487;
_D. oculatum_, 487;
_D. scoticum_, 487;
_D. spitzbergense_, 487
Diplocentrinae, 306, _307_
_Diplocentrus_, _307_
_Diplocephalus bicephalus_, =405=
Diplostichous eyes, 301
_Diplura_, _390_
Diplurinae, _390_
_Dipoena_, _403_
_Discoarachne_, 512, _535_
Distribution, of Crustacea, 197 f.;
(stratigraphical) of Trilobites, 222
Doflein, on eyes of deep-sea Crustacea, 148, 150
Dohrn, 504, 513, 519
Doleschall, 365
_Dolichopterus_, 283, _291_
_Doliomelus_, _415_
_Dolomedes fimbriatus_, _416_
_Dolops_, _78_
Domed webs, 350
_Donachochara_, _406_
Donnadieu, 457
_Dorippe_, 185, _188_
Dorippidae, _188_
_Doropygus_, _66_;
_D. pulex_, =66=
Dorsal organ, of Phyllopoda, 22;
of Cladocera, 39
Doublure, 232
Doyère, on Tardigrada, 481;
on their systematic position, 483
_Doyeria_, 485;
_D. simplex_, 480, 487
Drassidae, 324, _396_
Drassinae, _396_
_Drassus_, _397_;
_D. lapidosus_, =396=, 397
_Drepanothrix_, _53_
_Dromia_, _184_;
_D. vulgaris_, =184=
Dromiacea, _183_;
metamorphosis, 182;
relation to Macrura, 184;
habitat, 198
_Dromidia_, distribution, 200
Dromiidae, _184_
_Drymusa_, _393_
Dufour, 385
Dujardin, 464 n.;
on systematic position of Tardigrada, 483
_Duplorbis_, _95_;
_D. calathurae_, 99
_Dynomene_, _184_
Dynomenidae, _184_
_Dysdera_, _394_;
_D. cambridgii_, 394;
_D. crocota_, 395
Dysderidae, 317, 319, 336, _394_
_Dysderina_, _394_
Dysderinae, _394_
_Ebalia_, _188_
_Echiniscoides_, 485;
_E. sigismundi_, 477, 486
_Echiniscus_, 480, 485;
_E. arctomys_, 486;
_E. gladiator_, 486;
_E. granulatus_, 486;
_E. islandicus_, 486;
_E. muscicola_, 486;
_E. mutabilis_, 486;
_E. oihonnae_, 486;
_E. quadrispinosus_, 486;
_E. reticulatus_, 486;
_E. spinulosus_, =479=;
_E. spitzbergensis_, 486;
_E. testudo_, =478=;
_E. wendti_, 486
Echinoderms, _Dendrogaster_ parasitic on, 94
_Echinognathus_, 283
Ecribellatae, _385_
_Ectatosticta davidi_, _393_
_Ectinosoma_, _62_
Edriophthalmata, 112, 121
Eggs, of Phyllopoda, 32;
of Cladocera, 44;
of Copepoda, 59, 62, =66=, =67=, =71=, =74=;
of Branchiura, 77;
of Syncarida, 114;
of Peracarida, 123;
of Hoplocarida, 141;
of Eucarida, 144;
of Trilobites, 238;
of _Limulus_, 275;
of Pedipalpi, 309;
of Spiders, 358;
of Solifugae, 424;
of Pseudoscorpions, 434;
of Phalangidea, 442;
of Acarina, 456;
of Tardigrada, 478;
of Pentastomida, 493;
of Pycnogons, 520
Ehrenberg, on systematic position of Tardigrada, 483
_Eleleis crinita_, _396_
_Ellipsocephalus_, 224, 235, _247_;
_E. hoffi_, =248=
Embolobranchiata, _258_, 259, 297 f.
Emmerich, on facial suture of _Trinucleus_, 226
_Encephaloides_, _193_;
_E. armstrongi_, 192, =193=;
habitat, 205
Encrinuridae, _251_
_Encrinurus_, 227, 235, _251_
_Endeis didactyla_, _534_;
_E. gracilis_, _539_;
_E. spinosus_, 541
Endite, 9, =10=
Endopodite, 9, =10=;
of Trilobites, =237=
Endosternite, 257, 305, 330
Endostoma, of _Eurypterus_, 287
_Engaeus_, _157_;
_E. fossor_, distribution, 213
_Enoplectenus_, _418_
_Enterocola_, _67_;
_E. fulgens_, =67=
Entomostraca, defined, 6;
diagnosis, 18;
of littoral zone, 197;
fresh-water, of southern hemisphere, 216
Entoniscidae, 130, _134_
_Enyo_, _400_
Enyoidae, _399_
_Eoscorpius_, 298
_Epeira_, _409_;
_E. angulata_, =315=, =409=;
_E. basilica_, 350, 351;
web of, =351=;
_E. bifurcata_, 359;
_E. caudata_, 359;
_E. cornuta_, 409;
_E. cucurbitina_, 372, 409;
_E. diademata_, 335, 340, 343, 345, 359, 366, 380, 409;
anatomy, =332=;
cocoon, =358=;
silk, 360;
spinnerets, =325=;
_E. labyrinthea_, 350;
_E. madagascarensis_, 360;
_E. mauritia_, 349;
_E. pyramidata_, 409;
_E. quadrata_, 366, 409;
_E. triaranea_, 350;
_E. umbratica_, 409
Epeiridae, 376, 377, _406_
Epeirinae, _408_
Ephippium, =48=
_Epiblemum_, _420_
Epicarida, _129_;
sex in, 105
Epicaridian, larva of Epicarida, =130=
Epicoxite, of _Eurypterus_, 287
_Epidanus_, _449_
Epigyne, 319, 333, 378
Epipharynx, 459
Epipodite, 9, =10=
Episininae, _402_
_Episinus truncatus_, _403_
Epistome, of Eurypterida, 291;
of Pseudoscorpions, 431, 436;
of Phalangidea, 443
Erber, 355, 356
_Eremobates_, _429_
Eremobatinae, _429_
Eresidae, _398_
_Eresus cinnaberinus_, _398_
_Eriauchenus_, _411_
Erichthoidina, larva of Stomatopod, =143=
Ericthus, larva of Stomatopod, =143=
_Erigone_, _405_
Erigoninae, _404_
_Eriophyes_, _465_;
_E. ribis_, 455, =465=;
_E. tiliae_, 465
Eriophyidae, _464_
_Eriphia_, _191_;
_E. spinifrons_, 191
Erlanger, von, on development and position of Tardigrada, 483
_Ero_, _411_;
_E. furcata_, 366, 411;
cocoon, =358=;
_E. tuberculata_, 412
Eryonidae, _158_;
habitat, 204
Eryonidea, _157_
Erythraeinae, _473_
_Estheria_, 21, 22, =23=, _36_;
_E. gubernator_ and _E. macgillivrayi_, habitat, 33;
_E. tetraceros_, 36
Eucarida, 114, _144_ f.
_Euchaeta norwegica_, _58_
Eucopepoda, _57_ f.
_Eucopia australis_, =119=
Eucopiidae, 113, 114, _118_
_Eudendrium_, Pycnogons on, 520
_Eudorella_, _121_
_Eukoenenia_, _423_;
_E. augusta_, 423;
_E. florenciae_, 423;
_E. grassii_, 423
_Eulimnadia_, _36_;
_E. mauritani_, 36;
_E. texana_, 36
_Euloma_, 230
Eumalacostraca, _112_ f.
Eupagurinae, _180_
_Eupagurus_, _180_;
_E. bernhardus_, commensalism, 172;
distribution, 199;
_E. excavatus_, parasitic castration of, 101;
_E. longicarpus_, metamorphosis, =179=;
_E. prideauxii_, commensalism, 172;
_E. pubescens_, distribution, 199
_Euphausia pellucida_, _145_, =146=
Euphausiacea, _144_
Euphausiidae, 113, 114, _144_;
larval history, 145;
eyes, 150
_Eupodes_, _471_
_Euproöps_, 278
_Eurycare_, 232, _247_
_Eurycercus_, _53_;
alimentary canal, 42;
_E. lamellatus_, habitat, 207
_Eurycide_, 505, _533_;
_E. hispida_, =506=, =507=, =533=
Eurycididae, _533_
_Eurydium_, 485
_Euryopis_, _404_
_Eurypelma_, _389_;
_E. hentzii_, 361, 370
_Euryplax_, _195_
Eurypterida, _258_, 278, 283 f.
Eurypteridae, _290_ f.
_Eurypterus_, 283 f., 290, 291, 292;
_E. fischeri_, =284=, =286=, =289=
_Eurytemora_, _59_;
_E. affinis_, habitat, 206
_Eusarcus_, 283, _291_
Euscorpiinae, _308_
_Euscorpius_, 298, _308_;
_E. carpathicus_, 299
_Eusimonia_, _429_
_Euterpe acutifrons_, _61_, =61=;
distribution, 203
_Euthycoelus_, _389_
_Evadne_, _54_;
young, 47
Excretory system (including Renal organs), in Crustacea, 12;
in Arachnids, 257;
in _Limulus_, 270;
in Tardigrada, 481;
in Pentastomida, 491
Exner, on mosaic vision, 148
Exopodite, 9, =10=;
of Trilobites, =237=
Eyes, compound, of Crustacea, 146, =147=;
physiology of, 148;
of deep-sea Crustacea, 149;
connexion with phosphorescent organs, 151;
regeneration of, 6;
of Trilobites, 227 f., =228=;
of _Limulus_, 271;
of Eurypterida, 285;
of Scorpions, 301;
of Pedipalpi, 309;
of Spiders, 315, 334; of Solifugae, 426;
of Pseudoscorpions, 431;
of Phalangidea, 442;
of Acarina, 458;
of Pycnogons, 517
Fabre, on habits of Spiders, 298 f.;
of Tarantula, 361 f.;
on Wasp _v._ Spider, 368 f.
Facet, of Trilobites, 235
Facial suture, 225 f., 232
Falanga, 424
False articulations, 444
False-scorpions, 430
_Fecenia_, _399_
_Filistata_, _391_;
_F. capitata_, 392;
_F. testacea_, 392
Filistatidae, 319, 336, _391_
Finger-keel, 303
Fixed cheek, 225, 226, 227
Flabellifera, _124_ f.
Flabellum, 270
Flacourt, 363
Flagellum, in Solifugae, 426, 428;
in Pseudoscorpions, 433
Forbes, 374
Ford, S. W., on development of Trilobites, 238
Forel, on Lake of Geneva, 206
_Formicina_, _405_
Formicinae, _405_
_Formicinoides brasiliana_, =318=
_Fragilia_, _535_
Free cheek, 225, 226, 227
Fresh-water, Crustacea, 205 f.;
Spiders, 357
Furcilia (Metazoaea), larva of _Euphausia_, 145
Fusulae, 325, 335
_Galathea_, 169, _170_;
_G. intermedia_, _Pleurocrypta_ parasitic on, =133=;
_G. strigosa_, =170=;
gut of, 15
Galatheidae, _169_
Galatheidea, _169_
Galea, 433, 436
_Galena_, _412_
_Galeodes_, _429_, 527;
nervous system, =428=;
chelicera, =429=;
_G. arabs_, 425;
_G. araneoides_, 425
Galeodidae, _428_
Gall-mites, 455, 464
Gamasidae, _470_
Gamasinae, _470_
_Gamasus_, 460, 461, 463, _470_;
_G. coleoptratorum_, 470;
_G. crassipes_, 470;
_G. terribilis_, 461
Gammaridae, _138_
_Gammarus_, 137, _138_;
of Lake Baikal, 212;
of Australia, 216;
_G. locusta_, 138, =138=;
_G. pulex_, 138
_Gampsonyx_, _115_, 118
Garstang, on respiration of crabs, 186 n.
Garypinae, 436, _437_
_Garypus_, 431, 436, _437_, 438;
chelicera, =432=;
_G. littoralis_, 430
Gaskell, 270, 277, 334
_Gasteracantha_, _410_;
_G. minax_, =410=
Gasteracanthinae, 317, _409_
_Gastrodelphys_, _73_
Gastrolith, of Lobster, 155
Gaubert, 525 n.
_Gebia littoralis_, _167_
Gecarcinidae, _196_
_Gecarcinus_, 194, 195, _196_
Gegenbaur, 523
_Gelanor_, _411_, 412
_Gelasimus_, 194, _196_;
habitat, 198;
distribution, 210;
_G. annulipes_, =194=
Genal angle, 225
Gené, 461
Genital operculum, of Eurypterida, 288, =289=, 291
_Genysa_, _388_
_Gerardia_, _Laura_ parasitic on, 93
_Geryon_, _195_
_Giardella callianassae_, _73_
Gibocellidae, 448
_Gibocellum sudeticum_, _447_
Giesbrecht, on Copepoda, 57;
on phosphorescence, 59
Gigantostraca, _258_, 283 f.
Gill-book, =270=
Glabella, 223
Glabella-furrows, 223
Glands, of Tardigrada, 481;
of Pentastomida, 490, 491;
of Pycnogons, 511;
coxal, of Arachnids, 257, 270, 337;
green, of Malacostraca, 110;
poison-, of Arachnids, 337, 360;
spinning, of Spiders, 335;
of Pseudoscorpions, 434
Glaucothoe, larva of _Eupagurus_, =179=, 180
_Gluvia_, _429_
_Glycyphagus_, _466_;
_G. palmifer_, 466;
_G. plumiger_, 466
_Glyphocrangon_, _164_;
_G. spinulosa_, 158, =164=
Glyphocrangonidae, _164_
_Glyptoscorpius_, 283, 291, 294
_Gmelina_, _138_
_Gmogala scarabaeus_, _394_
_Gnamptorhynchus_, _533_
_Gnaphosa_, _397_
_Gnathia maxillaris_, _124_;
life-history of =125=
Gnathiidae, _124_
Gnathobase, 10, 264
_Gnathophausia_, _119_, 256 n.;
maxillipede of, =10=
Gnathostomata, 56
_Gnosippus_, _429_
Goldsmith, 362
Gonads, = reproductive organs, _q.v._
_Gonodactylus_, _143_;
_G. chiragra_, 143
Gonoplacidae, _195_
_Gonoplax_, _195_;
_G. rhomboides_, 195
Gonyleptidae, 442, 448, _449_
Goodsir, Harry, 535, 540
_Gordius_, parasitic in Spiders, 368
Gossamer, 342
Graells, 364
_Graeophonus_, _309_
Graff, von, on position of Tardigrada, 483
Grapsidae, 193, _195_;
habitat, 198, 201
_Graptoleberis_, _53_
Grassi, 422
Green gland, 110 (= antennary gland, _q.v._)
Gregarious Spiders, 340
Grenacher, 517
_Griffithides_, _251_
Gruvel, on Cirripedia, 80, 86
Guérin-Méneville, 439
Gurney, on Copepoda, 62;
on Brachyuran metamorphosis, 181 n.
_Gyas_, _450_
_Gylippus_, _429_
_Gymnolepas_, _89_
Gymnomera, 38, _54_
Gymnoplea, _57_
Hadrotarsidae, _394_
_Hadrotarsus babirusa_, _394_
Haeckel, on plankton, 203
_Haemaphysalis_, _469_
Haematodocha, 322
_Haemocera_, _64_;
_H. danae_, life-history, =64=, =65=
Haemocoel, 5, 11
_Hahnia_, 325, _416_
Hahniinae, _416_
Halacaridae, _472_
Halocypridae, _108_
_Halosoma_, _539_
_Hannonia typica_, _533_
Hansen, on Choniostomatidae, 76;
on Cirripede Nauplii, 94;
on classification of Malacostraca, 113
Hansen and Sörensen, 422, 439, 443, 448
_Hapalogaster_, _181_;
_H. cavicauda_, =178=
Hapalogasterinae, _181_
_Harpactes hombergii_, _395_
Harpacticidae, _61_, 62;
habitat, 206
Harpedidae, _245_
_Harpes_, 225, 226, 230, 231, 234, _246_;
_H. ungula_, =248=;
_H. vittatus_, eyes, =228=
_Harporhynchus_, _53_
Harvest-bugs, 454, 473
Harvestmen, 440, = Phalangidea, _q.v._
Harvest-spiders, 440, = Phalangidea, _q.v._
Harvesters, 440, = Phalangidea, _q.v._
_Hasarius falcatus_, _421_
Haustellata, 501 n.
Haustoriidae, _137_
_Haustorius arenarius_, _137_
Hay, on name _Lydella_, 486 n.
Heart, of Phyllopoda, 29;
of Cladocera, 43;
of _Nebalia_, 112;
of Syncarida, 115;
of Peracarida, 118;
of Isopoda, 122;
of _Danalia_, 132;
of Amphipoda, 136;
of _Squilla_, 142;
of Eucarida, 144;
of _Limulus_, 268;
of Scorpions, 305;
of Pedipalpi, 311;
of Spiders, 331;
of Solifugae, 427;
of Pseudoscorpions, 434;
of Phalangidea, 445;
of Acarina, 460;
of Pycnogons, 516
Heart-water, 470
Hedley, on home of cocoa-nut, 174
_Heligmonerus_, _388_
Heller, 455
_Hemeteles fasciatus_, 367;
_H. formosus_, 367
_Hemiaspis_, 278;
_H. limuloides_, =278=
Hemioniscidae, _130_
_Hemiscorpion lepturus_, _307_
Hemiscorpioninae, 306, _307_
Henking, 447, 460
Hentz, 367
Herbst, on regeneration of eye, 6 n.
_Hermacha_, _388_
Hermaphroditism, 15;
caused by parasite, 101, 102;
partial and temporary, 102;
normal, 105;
in Cymothoidae, 126;
in Isopoda Epicarida, 129;
in Entoniscidae, 135;
in _Caprella_, 140
_Hermippus_, 317, _399_;
_H. loricatus_, =400=
Hermit-crab, 167, 171;
commensalism, 172;
reacquisition of symmetry, 173;
regeneration of limbs, 156
Hermit-lobster, 167
Herrick, on the Lobster, 154
_Hersilia_ (Araneae), _401_;
_H. caudata_, =400=
Hersiliidae (Araneae), 326, _400_
Hersiliidae (Copepoda), _73_
_Hersiliola_, _401_
Heterarthrandria, _58_
_Heterocarpus alphonsi_ (Pandalidae), phosphorescence, 151
_Heterochaeta papilligera_, _60_
_Heterocope_, _59_
_Heterogammarus_, _138_
_Heterometrus_, _307_
_Heterophrynus_, _313_
_Heteropoda venatoria_, _414_
Heterostigmata, _471_
_Heterotanais_, _123_
Hexameridae, _91_
_Hexathele_, _390_
Hexisopodidae, _429_
_Hexisopus_, _429_, =429=
_Hexura_, _391_
_Hippa_, _171_;
_H. emerita_, distribution, 202
Hippidae, _171_
Hippidea, _170_;
habitat, 198
_Hippolyte_, _164_;
distribution, 200;
_H. varians_, 164
Hippolytidae, _164_;
distribution, 199
Hodge, George, 523, 540
Hodgson, 508
Hoek, on Cirripedia, 80;
on Pycnogons, 505, 512, 513
Holm, G., on _Agnostus_, 225;
on _Eurypterus_, 285 n.
_Holmia_, 236, 242, _247_;
_H. kjerulfi_, 242, =246=
Holochroal eye, 228
Holopediidae, _51_
_Holopedium_, 38, _51_
_Homalonotus_, 222, _249_;
_H. delphinocephalus_, =223=
_Homarus_, _154_;
habitat, 200;
excretory
glands, 13;
_H. americanus_, 154;
_H. vulgaris_, 154
_Homoeoscelis_, _76_
_Homola_, _184_;
distribution, 205
Homolidae, _184_
_Homolodromia_, _184_;
_H. paradoxa_, resemblance to Nephropsidae, 184
Hood, of Phalangidea, =442=, 452
Hoplocarida, 114, _141_
_Hoploderma_, _468_;
_H. magnum_, =467=
_Hoplophora_, _468_
Horse-foot crab, = _Limulus_, _q.v._
Hoyle, on classification of Pentastomids, 495
_Hughmilleria_, 283, 290, 292
Humboldt, on _Porocephalus_, 488 n.
Hutton, 424
_Huttonia_, _398_
_Hyale_, _139_
_Hyalella_, 137, _139_;
distribution, 211, 217
_Hyalomma_, _469_
_Hyas_, 192, _193_;
distribution, 200
_Hyctia nivoyi_, _421_
Hydrachnidae, _472_
_Hydractinia_, Pycnogons on, 523
_Hydrallmania_, Pycnogons on, 524
_Hymenocaris_, _112_
_Hymenodora_, _163_
_Hymenosoma_, _193_;
distribution, 200
Hymenosomatidae, _193_
Hyperina, _140_
Hypochilidae, _393_
_Hypochilus_, 336, _393_;
_H. thorelli_, 393
_Hypoctonus_, _312_
Hypoparia, 243
Hypopus, 463
Hypostome, of Trilobites, 233, 237;
of _Bronteus_, =233=;
of Acarina, 469
_Hyptiotes_, 349, _411_;
_H. cavatus_, snare, =350=;
_H. paradoxus_, 350, =411=
_Iasus_, 165, _167_;
distribution, 200
_Ibacus_, _167_
_Ibla_, _88_;
_I. cumingii_, =88=;
_I. quadrivalvis_, 88, 89
Ichneumon flies, and Spiders, 367
_Icius_, _421_;
_I. mitratus_, =382=
_Idiops_, _388_
_Idothea_, habitat, 211
Idotheidae, _127_
Ihle, J. E. W., 526 n.
_Ilia_, _188_;
_I. nucleus_, =188=;
respiration, 187
_Illaenus_, 229, 231, 235, _249_;
_I. dalmanni_, =248=
_Ilyocryptus_, 40, _53_
_Inachus_, 192, _193_;
_I. mauritanicus_, _Sacculina_ parasitic on, 97 f.;
parasitic castration in, =101=;
temporary hermaphroditism of, =103=;
_Danalia_ and _Sacculina_ parasitic on, =131=
Integument, of Pycnogons, 518
Irregular Spider-snares, 351
_Ischnocolus_, _389_
_Ischnothele dumicola_, =390=
Ischnurinae, 306, _307_
_Ischnurus ochropus_, _307_
_Ischnyothyreus_, _394_
Ischyropsalidae, _451_
_Ischyropsalis_, 444, _451_
Isokerandria, _69_ f.
_Isometrus europaeus_, _306_
Isopoda, _121_ f., 242
_Ixodes_, _469_;
_I. ricinus_, =469=
Ixodidae, _469_
Ixodoidea, 455, 462, _468_
_Janulus_, _403_
Jaworowski, on vestigial antennae in a Spider, 263
Johnston, George, 540
Jumping-Spiders, 419
_Karshia_, _429_
Karshiinae, _429_
Katipo, 363, 403
King-crab, =_Limulus_, _q.v._
Kingsley, on Trilobites, 239, 243 n.;
on breeding habits of _Limulus_, 271
Kishinouye, on _Limulus_, 274, 275
Klebs, on the frequency of human Pentastomids, 494
Knight Errant, 540
Koch, C., 397 n.
Koch, L., 397 n.
_Kochlorine_, _92_;
_K. hamata_, 93
_Koenenia_, _422_, 527, 528;
_K. mirabilis_, =423=
Koltzoff, 15
König, 524
_Koonunga cursor_, _117_;
distribution, 211
Koonungidae, _117_
Korschelt and Heider, on neuromeres in Arachnids, 263
Kowalevsky, 513
Kraepelin, 303, 306, 312 n., 428
Kramer, 460
Kröyer, 504, 526
_Labdacus_, _418_
_Labochirus_, _312_
Labrum, of Trilobites, 233
_Labulla_, _406_
_Laches_, _399_
_Lachesis_, _399_
Lacinia mobilis, 114
Laemodipoda, _139_
Laenger, on the frequency of human Pentastomids, 494
Lakes, characters of fauna of, 206;
English, 207, 208;
Baikal, 212;
Great Tasmanian, 216
_Lambrus_, 192, _193_;
_L. miersi_, =193=
_Lamproglena_, _68_
Lampropidae, _121_
_Lamprops_, _121_
Langouste, 165
Laniatores, 448
Lankester, on Crustacean limb, 9;
on classification of Arachnids, 258, 277;
on _Limulus_, 274, 305
_Laophonte littorale_, 62;
_L. mohammed_, 62
_Laseola_, _404_
_Lathonura_, _53_
_Latona_, _51_
Latreille, 385, 408 n., 412, 504, 526
_Latreillia_, _185_;
distribution, 205
_Latreillopsis_, _185_;
_L. petterdi_, 185
_Latreutes ensiferus_, habitat, 202
_Latrodectus_, 362, _403_;
_L. 13–guttatus_, 364, 403;
_L. mactans_, =362=, 363, 403;
_L. scelio_, 403
_Laura_, _93_;
_L. gerardiae_, 93
Laurie, 309 n., 310, 311
Leach, 526
_Lecythorhynchus armatus_, _535_
Leeuwenhoek, on desiccation in Tardigrada, 484
_Leionymphon_, _534_
Lendenfeld, von, 512, 523
_Lepas_, _87_;
metamorphosis, 80;
anatomy, 82;
_L. australis_, Cypris, =82=;
_L. fascicularis_, Nauplius, =81=;
_L. pectinata_, pupa, =82=
_Lephthyphantes_, 327, _406_
_Lepidurus_, 23, 24, _36_;
heart, 29;
_L. glacialis_, range, 34;
_L. patagonicus_, 36;
_L. productus_, 36;
carapace, 20;
telson, =23=;
_L. viridis_, 36
_Leptestheria_, _36_;
_L. siliqua_, 37
_Leptochela_, _163_
_Leptochelia_, _122_;
_L. dubia_, dimorphism, 123
_Leptoctenus_, _418_
_Leptodora_, _54_;
appendages, 42;
alimentary canal, 43;
ovary, 44, =45=;
_L. hyalina_, =54=
Leptodoridae, _54_
Leptoneta, _393_
Leptonetidae, _393_
_Leptopelma_, _389_
_Leptoplastus_, _247_
Leptostraca, _111_, 242;
defined, 6;
segmentation, 7
_Lernaea_, _74_;
_L. branchialis_, =74=, =75=
_Lernaeascus_, _73_
Lernaeidae, _74_
_Lernaeodiscus_, _95_
_Lernaeopoda salmonea_, _76_
Lernaeopodidae, _75_
_Lernanthropus_, _68_;
blood, 30, 68
_Lernentoma cornuta_, =72=
Leuckart, on Pentastomida, 490, 492;
on development of, 494;
on sub-genera of, 495
_Leuckartia flavicornis_, _59_
_Leucon_, _121_
Leuconidae, _121_
_Leucosia_, _188_
Leucosiidae, _188_;
respiration, 187;
habitat, 199
_Leydigia_, _53_
Lhwyd, Edward, on Trilobites, 221
Lichadidae, _252_
_Lichas_, 222, _252_
Lichomolgidae, _70_
_Lichomolgus_, _71_;
_L. agilis_, =71=;
_L. albeus_, 71
_Ligia oceanica_, =128=
_Ligidium_, _129_
Lilljeborg, on Cladocera, 51 n.
_Limnadia_, 21, 22, _36_;
_L. lenticularis_, 22, 36
Limnadiidae, 20, 23, 28, 29, _36_
_Limnetis_, 20, 21, 22, _36_;
_L. brachyura_, =21=, 24, _36_
Limnocharinae, _472_
_Limnocharis aquaticus_, _472_
_Limulus_, 256, 292;
nervous system, 257;
classification, 260, 276;
segmentation, 260, =261=, =262=, =266=, =270=, 272;
appendages, 263;
habits, 265, 271;
food, 267;
digestive system, 268;
circulatory system, 268;
respiratory system, 269;
excretory system, 270;
nervous system, 270, =272=;
eggs and larvae, 274, =275=;
ecdysis, 274;
used as food, 275–6;
affinities, 277;
fossil, 277;
_L. gigas_, 276;
_L. hoeveni_, 277;
_L. longispina_, 264, 274;
_L. moluccanus_, 264, 274, 276, 277;
_L. polyphemus_, =261=, =262=, 264, 271;
_L. rotundicauda_, 275, 277;
_L. tridentatus_, 276
Lindström, on facial suture of _Agnostus_ and _Olenellus_, 225;
on eyes of Trilobites, 228 f.;
on blind Trilobites, 231 f.;
on maculae of Trilobites, 233
Lingua, 459
_Linguatula_, 488 n., 495;
_L. pusilla_, 496;
_L. recurvata_, 496;
_L. subtriquetra_, 496;
_L. taenioides_, 489, 492, 493, 494, 496;
frequency of, 489;
larvae of, 489, 494;
hosts of, 496
Linnaeus, 408 n., 502
_Linyphia_, _406_;
_L. clathrata_, 406;
_L. marginata_, 406;
_L. montana_, 406;
_L. triangularis_, 406
Linyphiinae, _405_
_Liobunum_, 447, _450_
Liocraninae, _397_
_Liocranum_, _397_
Liphistiidae, _386_
Liphistioidae, 383
_Liphistius_, 317, 383, 385, _386_;
_L. desultor_, =386=
Liriopsidae, _130_
_Lispognathus thompsoni_, eyes, 149
Lister, M., 341, 342
_Lithodes_, _181_;
_L. maia_, 176, =177=, =178=
Lithodidae, _181_;
evolution of, 176 f.
Lithodinae, _181_;
distribution, 199, 201
_Lithoglyptes_, _92_;
_L. varians_, 93
_Lithotrya_, _87_;
_L. dorsalis_, =87=
_Lithyphantes_, _404_
Littoral region, of sea, 197;
of lakes, 206
Liver (gastric glands), of Crustacea, 14;
of Branchiopods, 29;
of _Limulus_, 268;
of Arachnids, 304 f., 331
Lobster, distribution, 199;
Mysis stage, 153;
natural history, 154 f.
Lockwood, on habits of _Limulus_, 265, 271
Loeb, 525 n.
Loman, 331, 514, 525
Lönnberg, 425
_Lophocarenum insanum_, =405=
_Lophogaster_, _119_
Lophogastridae, 113, 114, _119_
Loricata, _165_
Lounsbury, 456, 461
Love-dances, among spiders, 381
Lovén, on Trilobites, 226
_Loxosceles_, _393_
Lubbock, 375
Lucas, 364
_Lucifer_, _162_
Lung-books, 297, 308, 336;
origin of, 305
_Lupa_, _191_;
_L. hastata_, =191=;
resemblance to _Matuta_, 187, 189
_Lycosa_, _417_;
_L. arenicola_, 357;
_L. carolinensis_, turret of, =357=;
_L. fabrilis_, =417=;
_L. ingens_, 418;
_L. narbonensis_, 361, 366;
_L. picta_, 357, 372, =417=;
_L. tigrina_, 357, 369
Lycosidae, 359, 375, 381, _417_
_Lydella_, 479, 485;
_L. dujardini_, 477, 486
Lynceidae, _53_;
alimentary canal, 43;
winter-eggs, 48;
reproduction, 49
Lyncodaphniidae, _53_
Lyonnet, 319, 320
Lyra, 328
Lyriform organs, 325, 422
_Lysianassa_, _137_
Lysianassidae, _137_
_Lysianax punctatus_, commensal with hermit-crab, 172
M‘Cook, 334, 339, 340, 346, 350, 352 n., 365 n., 366, 367 n., 369 n.
M‘Coy, F., on facial suture of _Trinucleus_, 226;
on free cheek of Trilobites, 227
M‘Leod, 336 n.
_Macrobiotus_, 480, 485;
_M. ambiguus_, 487;
_M. angusti_, 486;
_M. annulatus_, 486;
_M. coronifer_, 487;
_M. crenulatus_, 487;
_M. dispar_, 487;
_M. dubius_, 487;
_M. echinogenitus_, 487;
_M. harmsworthi_, 487;
_M. hastatus_, 487;
_M. hufelandi_, 480, =482=, =483=, 486;
_M. intermedius_, 486;
_M. islandicus_, 487;
_M. macronyx_, 477, 483, 487;
_M. oberhäuseri_, 486;
_M. orcadensis_, 487;
_M. ornatus_, 487;
_M. papillifer_, 487;
_M. pullari_, 487;
_M. sattleri_, 487;
_M. schultzei_, =480=;
_M. tetradactylus_, =478=;
_M. tuberculatus_, 487;
_M. zetlandicus_, 486
_Macrocheira kämpferi_, 192
_Macrohectopus_ (= _Constantia_), _138_, 212
_Macrophthalmus_, _196_
_Macrothele_, _390_
_Macrothrix_, 37, _53_
Macrura, _153_ f.
Macula, 233
_Maia_, _193_;
distribution, 205;
_M. squinado_, 192;
alimentary canal, 15
Maiidae, _193_
Malacostraca, _110_ f.;
defined, 6;
classification, 113, 114;
fresh-water, 210 f.
Malaquin, on _Monstrilla_, 63 n.
Male Spider, devoured by female, 380
Malmignatte, 364, 403
Malpighian tubes or tubules, 12, 257, 311, 331, 427, 434, 460
Mandibles, of Crustacea, 8;
of Arachnida, 319
Mange, 465
_Maracaudus_, _449_
_Margaropus_, _469_
Marine Spiders, 415
_Marpissa_, _421_;
_M. muscosa_, =420=;
_M. pomatia_, 421
Martins, Fr., 502
Marx, 350
_Masteria_, _390_
_Mastigoproctus_, _312_
_Mastobunus_, _449_
Matthew, G. F., on development of Trilobites, 238
_Matuta_, _188_;
habitat, 198;
_M. banksii_, =187=
Maxilla, 8;
of Decapoda, 152;
of Spiders, 321
Maxillary gland, 13
Maxillipede, 8;
of Copepoda, 55, 78;
of Malacostraca, 113;
of Zoaea, 180, 181, 182
_Mecicobothrium_, _391_
Mecostethi, 443, 447, _448_
_Mecysmauchenius segmentatus_, _411_
Meek, 363
_Megabunus_, _450_, 451