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THE

VOYAGE OF H.M.S. CHALLENGER.

VACKOM LORE ae

REPORT on the Hyproma dredged by H.M. 8, Challenger during the
years 1873-76. By Professor G: J! ye “ALLMAN, MDL? EDs
ER C25. le Bios: <o-H. MER EA, C.MZS., &e.

PART IL—PLUMULARIDA.

INTRODU CLLON,

Ix the descriptive zoology of the Plumularide a considerable amount of literature
already exists. ‘The British species have, in more recent times, been studied by several
observers, and more especially by Hincks,! whose valuable History of the British
Hydroid Zoophytes has greatly facilitated the labours of such zoologists as have since
worked at species from other seas. Among the more important recent contributions to
our knowledge of foreign forms must be mentioned the descriptions given by Busk,” of
the species collected during the exploratory expedition of the “ Rattlesnake” ; the memoirs
by Kirchenpauer,? in which a large number of new species contained in various
continental collections has been described and figured ; and that by G. Ossian Sars,* in
which we find descriptions and figures of many new and interesting Plumularide from

1 A History of the British Hydroid Zoophytes, by Thomas Hincks, London, Van Voorst, 1868.
2 Narrative of the Voyage of H.M.S. “ Rattlesnake,” London, 1852. Account of the Polyzoa and Sertularian Zoo-
phytes, by George Busk, Appendix, vol. i.
z Reteahedaner. Ueber die Hydroidenfamilie Plumularide. Abhandl. aus der Gebiete der Naturwiss. von dem
naturwiss. Verein in Hamburg, Bd. v., vi., 1872 and 1876.
4G. O. Sars, Bidrag til ane om Norges Hydroider. Forhandl. Vidensk. Selsk. 7 Christinia, Aar 1873.

(ZOOL. CHALL. EXP.—PART xx.—1883,) Ul

2 THE VOYAGE OF H.M.S. CHALLENGER.

the North Atlantic. Heller! has described several new Plumularide from the Adriatic.
To Professor Millen Coughtrey,’ of Otago, we owe descriptions of New Zealand species,
and to Surgeon James Armstrong,® of the Indian Medical Department, descriptions of
species collected by him on the eastern shores of India.

Besides the expedition of the Challenger, other recent exploratory expeditions have
largely added to our knowledge of this group. The exploration of the Gulf Stream, by
the United States Coast Survey,* has brought to light many new and beautiful forms,
the voyages of the ‘“ Porcupine”’ have made us acquainted with new species from
the North Atlantic, and the explorations by the United States Coast Survey Steamer
“Blake” in the Carribbean Sea and along the Atlantic Coast of the United States have
brought to our knowledge the occurrence in those regions of a rich plumularian fauna,
among which are several new and highly interesting forms.°

To the number of species thus determined and described the collection of hydroids
brought home by the Challenger makes a large and valuable addition. Of this collection
the family of the Plumularide forms a considerable proportion. Among these, four
species, namely, Acanthella effusa, Acanthocladium huxleyi, Aglaophenia macgillivray:,
and Lytocarpus longicornis had been already described by Busk from the voyage of the
“ Rattlesnake,” and one, namely, Lytocarpus secundus, by Kirchenpauer, from specimens
brought home by Semper from the Pelew Islands. The Challenger also obtained from
dredgings off Bermuda a species (Aglaophenia ramosa) already described in the Report
on the Hydroida of the United States exploration of the Gulf Stream.

The only form which can be identified with a species occurring in the European seas
is Cladocarpus formosus. This species was dredged by the “ Porcupine” from the seas
lying to the north of Scotland, and by the Challenger from the seas of Japan. The species
is a well-marked one, and the great distance between the Atlantic and Pacific stations
without any intermediate station having been discovered, is a remarkable and signifi-
cant fact.

But by far the greater part of the Plumularide brought home by the Challenger consists
of species new to science, while among these a considerable number must be assigned to

’ Prof. C. Heller, Die Zoophyten und Echinodermen des adriatischen Meeres, Wien, 1868.

* Millen Coughtrey, Notes on the New Zealand Hyrdoida. Journal of the New Zealand Institute, vol. vii.
1874.

* Description of some new species of Hydroid Zoophytes from the Indian Coasts and Seas, by Surgeon James
Armstrong, Marine Survey Department. Journal of the Asiatic Society of Bengal, vol. xlviii., 1879.

* Geo, J. Allman, Report on the Hydroida collected during the exploration of the Gulf Stream, by L. F. De
Pourtalés, United States Coast Survey. Mem. of Mus. Comp. Zool. at Harvard College, vol. v., No. 2, 1877.

* Geo, J. Allman, Report on the Hydroida collected during the expeditions of H.MS. “ Porcupine.” Trans, Zool.
Soc. Lond., 1873.

® Reports on the results of dredging under the supervision of Alexander Agassiz in the Caribbean Sea in 1878-79,
and along the Atlantic Coast of the United States during the summer of 1880, by the U.S. Coast Survey Steamer
“ Blake,” Commander J. R. Bartlett, U.S.N.,. commanding. Report on the Acalephe by J. Walter Fewkes. Bull. Mus.
Comp. Zool. at Harvard College, vol. viii. p. 127.

REPORT ON THE HYDROIDA, 3

genera now specially constituted for their reception. Many are of great interest in the
light they throw on the external morphology of the group, and in the aid which
they afford towards a philosophic conception of the significance of parts otherwise
enigmatical.

I believe, therefore, that the value of the collection will be enhanced, and its
instructiveness made more available if the technical description of the species be preceded
by a few introductory remarks on the general morphology of the Plumularidz, more
especially on such points as receive important illustration from the species described in
the present Report.

GENERAL MorPHOLOGY OF THE PLUMULARIDA.

The Plumularidz constitute a very natural section of the Calyptoblastic Hydroids.
Their hydrothecz are always sessile, and are carried on one side only of the supporting
ramulus. Nematophores of a definite form, and with a definite arrangement, are always
present. The gonangia are either fully exposed and destitute of any special protective
apparatus, or they are enclosed or otherwise protected by more or less modified portions
of the hydrocaulus.*

The Plumularide admit of division into two primary sections, characterised by the
condition of the nematophores. In one—the Eleutheroplea (Pls. I, II., &c.),—the
nematophores are attached only by their proximal end, and in almost every case are to a
certain extent moveable on their point of attachment. In a very few instances the
moveable nematophores are associated with nematophores of the fixed type (PI. VIII.
figs. 1-3).

In another section—the Statoplea (Pls. XL, XII, XIII., &c.)—the nematophores are
adnate to the chitinous periderm for a greater or less portion of their length, or are fixed
by a base too wide to admit of movement on the surface of attachment. No nemato-
phores of the moveable type ever occur in this section.

Each of these sections admits of a further division into two main groups—the
Phylactocarpa (Pls. XI., XII, XIIL, &c.),” in which the hydrocaulus has become modified
so as to form a more or less complete protection for the gonangia, and the Gymnocarpa
(Pls. If., IIL, IV., &e., and Pl. VIII. and Pl. XIX. figs. 1-3), in which no protective
apparatus is present.

1 For definitions of the terms here used see p. 17.

2 'The collection contains no example of the phylactocarpal Eleutheroplea. For our knowledge of the occurrence
of phylactocarpal forms among the Eleutheroplean Plumularidz, we are indebted to Mr. J. Walter Fewkes, who detected
the presence of this condition in two Hydroids, Hippurella annulata and Callicarpa gracilis, obtained by the dredge of
the U.S. Coast Survey Steamer “Blake.” Bull. Mus. Comp. Zool., loc. cit.

4 THE VOYAGE OF H.M.S. CHALLENGER.

Tn accordance with these differences, the great leading groups of the Plumularide may
be systematically arranged as in the following scheme :—

Gonangia with special ) ELEuTHEROPLEA
protective apparatus, PHYLACTOCARPA,
{ Moveable nematophores
5 ELEUTHEROPLEA. . :
| always present, a Gonangia destitute of ) 5,
5 : : ELEUTHEROPLEA
A | special protective ap-
| GYMNOCARPA.
| {| paratus,
4
5 { Gonangia with special | SratopLEa
= | protective apparatus, PHYLACTOCARPA.
~ | Moveable nematophores
4 i ae STATOPLEA. : :
Ay never present, Gonangia destitute of SanOPTE
| | special protective ap- Rare
| paratus, ‘

The opportunities of examining the Hydroida in a living state, or even in dead speci-
mens which have the soft parts sufficiently well preserved, are so comparatively few, that
the systematist is compelled to have recourse to the chitinous periderm, as affording almost
the only available grounds for determination and classification.

This chitinous external skeleton, however, presents so many points of high morpho-
logical interest, that the classification thus based upon it is by no means an arbitrary and
artificial one.

A correct idea of the morphology of the chitinous skeleton in the Plumularide will
be best obtained by comparing with one another the modifications of form which it
presents when examined in the various parts of the colony or hydrophyton in the
different groups.

Morphology of the Trophasome.

Hydrocaulus.—The hydrocaulus of the Plumularide, both in the Eleutheropiea and
the Statoplea, may be formed either of a single tube (monosiphonic) or it may be
fascicled or polysiphonic. The fascicled condition may exist in the main stem and in the
principal branches, but the ultimate ramuli or hydrocladia are always monosiphonic.
The polysiphonic condition gradually gives place to the monosiphonie in passing from
the proximal to the distal parts of the colony, the fascicled stem sending off bundles of
tubes to form the branches, and these again throwing off smaller bundles to form
secondary branches, until finally, in the distal parts of the colony, the fasciculation has
become exhausted, and a monosiphonic condition has taken its place.

The tubes which compose the fascicled portions of the hydrocaulus communicate
laterally with one another. In Aglaophenia coarctata (Pl. XIX. figs. 7-9) this communica-
tion is plainly seen to be effected by very short tubular processes which are given off from

REPORT ON THE HYDROIDA. 5

the component tubes, those of two juxtaposed tubes meeting one another and inosculating
in such a way as to suggest the conjugation of a Zygnema (fig. 1).

Hydrothece —In all the Plumularide hydrothecee are borne on special ramuli,
which are usually disposed in pinne, and for which the convenient term hydrocladium,
as proposed by Kirchenpauer, may be adopted. Ina few species (PI. IV. figs. 3, 4) hydro-
thecze are also carried directly by the stem.

In the Eleutheroplea the margin of the hydrotheca is, with, so far as I know, only
one exception,’ invariably destitute of all trace of serration. The peculiar ridge which
I have termed the “ intrathecal ridge,” and which constitutes a characteristic feature in
the Statoplea, is never present in the Eleutheroplea.

Fic. 1.—Longitudinal section of the polysiphonic stem of Aglaophenia coarctata, showing the lateral offsets
through which the component tubes communicate with each other.

In the Statoplea the margin of the hydrotheca is in most instances deeply serrated
(Pl. XL, &c.). In a few it presents only an indistinct crenation (Pl. XIV.), while in a
few it is quite entire (Pl. XVIL). In almost every case there is present in the
hydrotheca of the Statoplea a slightly projecting chitinous ridge (Pl. XL, &c.), which
runs on the inner surface of the walls transversely from behind forwards, but with a more
or less oblique direction, and which more or less completely encircles the cavity of the
hydrotheca, thus forming an imperfect septum, which divides the hydrotheca into a
proximal and a distal portion. This is the intrathecal ridge, which, as just said, is never
present in the Eleutheroplea. In some species of Statoplea, what has the appearance of a
similar ridge running from before backwards may be seen in the anterior portion of the
hydrotheca (Pls. XV. and XVIII.). This, however, is only the optical expression of a fold
in the walls of the hydrotheca.

1The exception here referred to is found in an Eleutheroplean Plumularidan not yet deseribed. For an
opportunity of examining it I am indebted to Miss Gatty. Among other very exceptional characters, the margin of
the hydrotheca is here provided with a strong anterior mesial tooth, and with a strong lateral tooth on each side.

6 THE VOYAGE OF H.M.S. CHALLENGER.

In one remarkable genus of Statoplea contained in the Challenger collection (Dip-
locheilus (Pl. VIII. figs. 4-7), the hydrotheca presents a double margin formed by the
development of an external chitinous sheath round the upper third of the hydrotheca,

Nematophores.—The presence of nematophores, whether fixed or moveable, constitutes
the most characteristic feature in the Plumularide. The nematophores are hollow
chitinous bodies, more or less cup-shaped or tubular, and having their cavity in communi-
eation with that of various parts either of the trophosome or of the gonosome, Their
contents consist of protoplasm, in which thread-cells are often immersed, and which has
the faculty of emitting pseudopodial prolongations which often attain great development,

Those nematophores which belong to the fixed type are usually blunt spine-like bodies,
with a continuous cavity and a terminal orifice, and with one or sometimes two lateral
orifices. The terminal orifice is usually oblique or deeply emarginate.

The nematophores of the moveable type are more constant in form. They are funnel-
or trumpet-shaped, and never provided with lateral orifices. They are mostly bi-thalamic,
their cavity being divided into a proximal narrow chamber and a distal wide cup-
shaped chamber, separated from one another by a transverse perforated septum, The
distal chamber opens by a wide terminal orifice, which is usually deeply emarginate on
one side.

Nematophores are either hydrocladial, hydrocauline, or gonosomal, according to the
special part of the colony with which they are in immediate connection. An accurate
knowledge of their arrangement and modifications will be best- acquired by examining
them separately in the two great Plumularian sections.

‘ Bodies resembling the nematophores of the Plumularidie have, however, been found in other Hydroids’
Hincks (loc. cit., p. 230, pls. i. iv. fig. 2) has constituted the genus Ophiodes for a remarkable Hydroid closely
allied to Haleciwm, in which he had discovered certain singular bodies in the form of long cylindrical, very contractile
tentacula-like appendages, each protected at its base by a small chitinous cup, through which it communicates with the
coenosare of the colony, and terminating distally ina spherical capitulum, loaded with thread-cells. They occur here and
there on the stem, at a slight distance below the hydrotheca, but are chiefly found scattered on the creeping stolon.

Bodies closely resembling these have been found by G. O. Sars (Joc. cit., p. 109, pl. iv. figs. 5-8) in a Hydroid which
he refers to the genus Ophiodes of Hincks, under the name of Ophiodes parasitica. This determination is not accepted by
Hincks, who proposes for Sars’s Hydroid the new generic name of Ophionema, believing it to belong to the Plumularidie
instead of regarding it with Sarsas a near ally of Halecium. Notwithstanding, however, the resemblance of Sars’s figures
to a Plumularian, it is plain to me that the affinities of his Ophiodes parasitica are really with Haleciwm, and that the
Norwegian zoologist had a true conception of its nature when he referred it to Hincks’s genus Ophiodes, The
tentacula-like organs in Ophiodes would seem to take the place of the nematophores of the Eleutheroplean Plumularidze.
They appear, however, to stand on a much higher grade of development than true nematophores, and to have passed
out of the condition of mere protoplasm into that of a multi-cellular organ. If this be so we should not be justified
in assigning to both the same significance.

Belonging apparently to the same group of appendages are certain minute bodies which occur in Oplorhiza parvula,
a little Hydroid allied to Lafoéa, obtained during the United States exploration of the Gulf Stream. They are here in
the form of tubular receptacles, which are developed on the hydrorhizal network, and enclose a granular fleshy column,
which supports a cluster of thread-cells (Hydroids of Gulf Stream, p. 14, pl. vii. figs. 1-8). In a nearly allied form,
Lafocina tenuis, Sars, from the Norwegian seas, the hydrorhiza supports appendages which would seem to be essentially
of the same kind (G. O. Sars, loc. cit., p. 119, pl. v. figs. 1-5). Minute fleshy processes of doubtful significance haye also

REPORT ON THE HYDROIDA. 7

Nematophores in the Statoplea.

a. Hydrocladial nematophores.—These are arranged in two sets on every internode
of the hydrocladium, and consist of an azygous or mesial nematophore and a pair of lateral
nematophores. The mesial nematophore is in the form of a tubular process springing
from a point of the hydrotheca-bearing internode immediately below the hydrotheca, to
the front wall of which it becomes in almost every instance adnate for a greater or less
extent of its length. Ina very few cases the mesial nematophore of the Statoplean
Plumularide, while fixed immovably by its base, remains free for the rest of its course,
having no adhesion to the hydrotheca (Pl. XVI. figs 1-3). In a single instance (Aglao-
phenia bispinosa of the Gulf Stream Report’) a second mesial nematophore is developed
in a longitudinal line behind the first.

The mesial nematophore communicates through its base with the cavity of the inter-
node, just below the hydrotheca. In that portion of it which is adnate to the front of
the hydrotheca it communicates by means of a longitudinal sht-hke aperture with the
cavity of the latter. It is always open at its distal extremity, where an aperture, usually
very oblique, allows of the projection of its protoplasmic contents im the form of free
pseudopodia. Besides the terminal and the longitudinal slit-like aperture there is also in
many cases an aperture on its inner or hydrothecal side (Pl. XV.), just beyond the point
where its distal portion becomes free from the walls of the hydrotheca. Occasionally an
imperfect transverse septum exists in some part of its course (Pl. XX. figs. 4, 5).

The mesial nematophore is in a few cases adnate to the walls of the hydrotheca for its
entire length. In most cases, however, its distal extremity is continued for some distance
as a free process. This free distal portion of the mesial nematophore varies much in
length. In Aglaophenia proper it is generally quite short, but in some other genera it
attains a great length, being developed in the form of a long curved horn (Pl; VEE).

The lateral nematophores in the Statoplea are tubular, cup-shaped, or crescentic bodies,
always two in number, situated symmetrically one on either side of the hydrotheca, nearly
on a level with its orifice or thecostome. They spring from the hydrothecal internode
with the cavity of which they communicate by their base. They terminate distally by
been described by G. O. Sars (loc. cit. p. 112, pl. iv. fig. 10) as developed below the hydrothece in his Halecitwm
gorgonoide.

Mr. Busk, in a letter which I have recently had from him, describes from a specimen in his collection but from
an unknown locality a Hydroid whose affinities are with the Sertularide rather than with the Plumularide, and which
yet carries on the front of every hydrotheca a small sessile nematophore-like body. Whether this is to be regarded as
a true nematophore or not, can scarcely be asserted with confidence from the examination of a dried specimen. Its
peculiar position, lying as it does on the front wall of the hydrotheca, without any apparently direct communication with
the hydrocaulus, is certainly against placing it in the same category with the true nematophores. The Hydroid is also
very exceptional in other respects, and Mr. Busk regards it as the type of a new genus, for which he proposes the name

of Greeneia.
1 Hydroids of the Gulf Stream, p. 46, pls. xxvii. xxviii.

00

THE VOYAGE OF H.M.S. CHALLENGER.

an open orifice which is usually very oblique. In some very rare cases (Pl. VIII. figs.
4—7, and Pl. XIX. figs. 1-3) the lateral nematophores are absent.

In a singular and beautiful species (Acanthocladium hualeyi, Pl. 1X.) contained
in the Challenger collection, the hydrocladia become towards the dorsal extremities of the
branches atrophied, lose their hydrothece, and are converted into spine-like appendages,
which carry from base to apex two longitudinal alternate series of minute cup-shaped
nematophores (Pl. XX. fig. 3).

b. Cauline nenatophores.—These are usually small, cup-shaped bodies, situated on
various parts of the hydrocaulus, with the cavity of which they communicate. They are
generally disposed in linear series (Pl. XVII.) on the main stem and principal branches,
and often form definite symmetrical groups of two at the points where the hydrocladia
spring from the stem. Though quite different from the moveable nematophores of the
Eleutheroplea,—being seated on a wide base which fixes them to the stem,—they would
seem to be in many cases easily detached.

c. Gonosomal nematophores.—The system of nematophores attains in the gonosome
of the Phylactocarpal Statoplea a remarkable development. The characteristic denticles
which are found on the margins of the leaflets, which combine to form the walls of the
corbula (Pls, XI. and XII.) in Aglaophenia, are only slightly modified nematophores.
These denticles are tubular with a terminal orifice, and their cavity is in communication
with that of the leaflet, while this opens into the common basal rachis of the corbula.
In most cases a nematophore is specially developed at the base of each leaflet in the form
of a spur. In one remarkable form (Pl. XX. fig. 6) branching chitinous ridges are
developed on the walls of the corbula, and enclose cup-shaped nematophores in bifurcations
of their branches.

But nematophores are largely developed not only in the corbula, but in the other
forms of Phylactocarp, where they constitute a very characteristic feature. They occur in
such cases along the branches of the Phylactocarp, or along the common basal rachis, and
are usually present in the form of denticles or cup-shaped bodies, arranged in two opposite
or alternate series. In Lytocarpus spectabilis (Pl. XV.) they are in the form of a pair
of stout opposite spines on every internode of the phylactocarpal rachis, and are each
provided with a terminal aperture and also with a lateral aperture close to the base
(fig. 5). In Lytocarpus racemifera (Pl. XIL) there is, in addition to the par of
opposite spine-like nematophores on each internode, an azygous spine on the front of
the internode (figs. 4-6). A similar azygous spine-like nematophore is in Lyto-
carpus spectabils carried by that internode of the rachis which supports a gonangium
(fig. 2, p. 44).

REPORT ON THE HYDROIDA. 9

Nematophores in the Eleutheroplea.

The nematophores here belong, in almost every instance, exclusively to the moveable
type. In very rare cases (Pl. VIII. figs. 1-3) the moveable nematophore is associated
with a fixed nematophore developed in other parts of the same colony.

a. Hydrocladial nematophores.—The hydrocladial nematophores in the Eleutheroplea
are, as in the Statoplea, disposed in two sets—mesial and lateral. The mesial nemato-
phore is never, as in the Statoplea, adnate to the front of the hydrotheca, and is almost
always removed to a point at some distance from the hydrotheca at its proximal side.
It is this azygous nematophore which in very rare cases differs from the others in being
immovable. In one instance, that of Schizotricha multifurcata (Pl. VII. figs. 4, 5),
the single mesial nematophore is replaced by a pair of nematophores, one on each side of
the internode. In some cases an azygous nematophore is also found on the hydrothecal
internode at the distal side of the hydrotheca, while in Plumularia armata (Pl. IV. figs.
3, 4) this part of the internode supports, instead of a single mesial nematophore, a pair of
lateral nematophores.

In every case the hydrothecze of the Eleutheroplea are flanked, as in the Statoplea, by
a pair of lateral nematophores.' Each of these is usually borne on the summit of a hollow
chitinous process, which springs from the internode at either side of the hydrotheca.
The process varies much in length, and is sometimes obsolete.

The hydrocladia of the Eleutheroplea differ from those of the Statoplea in being very
often provided with internodes which do not carry hydrothece (PI. I. figs. 1-4). The
internodes thus destitute of hydrothecze carry nematophores which are either solitary or
are disposed in a longitudinal series on the front of the internode.

b. Cauline nematophores.—These are borne, generally in considerable numbers, along
the stem and branches, and are often disposed in pairs close to the points from which the
ultimate ramuli or hydrocladia spring (Pl. V.).

c. Gonosomal nematophores—When these are present in the gymnocarpal Eleuthero-
plea they spring from the gonangium, where they are usually disposed in a symmetrical
pair on its proximal end, and are here in connection with the base of the blastostyle
(Pl. IV. figs. 2, 6). In some cases they are connected with other parts of the blastostyle,
which is then pushed out of the axis of the gonangium, and lies in contact with its wall
(Pl. IV. fig. 4). In such-cases the wall of the gonangium is perforated along the course
of the blastostyle, and the contents of the nematophores, which are developed externally,
communicate through the perforations with the blastostyle.

In another very remarkable form (Sciwrella indivisa, Pl. V.) the blastostyle is
extensively ramified, and the ends of the ramification impinge on definite points sym-

1 In the rare cases in which these lateral nematophores are stated to be absent, I believe that they have either been
overlooked in consequence of their minuteness, or have fallen away from their points of attachment.

(ZOOL, CHALL. EXP.—PART xx.—1883.) U2

10 THE VOYAGE OF H.M.S. CHALLENGER.

metrically disposed on the walls of the gonangium. Over each of these points a nemato-
phore is developed externally, while a perforation in the chitinous walls allows of the
free communication of the contents of the nematophore with the subjacent branch of the
blastostyle.

In the only two known species of phylactocarpal Eleutheroplea the nematophores are
developed in abundance along the sides of the appendages, which combine to form the
peculiar phylactocarps of these Hydroids.’

That the nematophores play a very important part in the economy of the Plumularide
would appear from the fact of their early appearance and of their persistence. In
the development of the trophosome they are in many cases, if not in all, the first
zooids of the colony to make their appearance, preceding the hydranths and hydrothece ;
while, as we shall afterwards see, they remain behind in certain cases in which the
hydranth and hydrotheca, which would normally belong to them, have become entirely
suppressed.

I have endeavoured to show elsewhere’ that their phylogenetic or paleeontological
significance is scarcely less important, for I believe we have good grounds for maintaining
that the ancient graptolites represent hydroid organisms, in which the nematophores were
the only zooids of the trophosome which had been developed.

Morphology of the Gonosome in the Phylactocarpal Plumularide.

The gonosome in the phylactocarpal forms of the Plumularidee is full of interest, pre-
senting as it does some significant morphological facts, and affording instructive examples
of the extent to which variation of form may exist consistently with the retention of
homological identity.

The term phylactocarp may be used as a sufficiently convenient general expression for
the various forms under which the apparatus destined for the protection of the gonangia
shows itself in the phylactocarpal Plumularide. This apparatus is referrible to one or
other of two types: it consists either of one or more variously modified hydrocladia, or
of a separate appendage to the hydrocladium quite distinct from the hydrocladium itself.

The commonest and longest known form of phylactocarp is the corbula of Aglaophenia
(Pls. XI. and XII.). This consists of a peculiarly modified hydrocladium, which supports
on each side a row of ribs or coste in the form of flattened leaf-like appendages, and
between these two rows a row of gonangia. ‘The leaflets of each side arch over the
gonangia, and enclose them in a basket-shaped receptacle. They are furnished with
numerous short teeth-like nematophores on one or both edges, recalling somewhat the

' See J. W. Fewkes, Bull. Mus. Comp. Zool., loc. cit.
° Gymnoblastic Hydroids, p. 179.

REPORT ON THE HYDROIDA. 11

serrated margin of a leaf, and they are here usually adnate to one another, so as to form a
completely closed case (Pl. XI. fig. 4, and Pl. XII. figs. 4 and 8). In other instances
they contract no adhesion by their edges, and the corbula is then open (PI. XI. figs. 5
and 9).

That the corbula is a modified hydrocladium there can be no doubt. It takes exactly
the place of a hydrocladium, while its proximal end is in the form of a short peduncle,
which holds it to the stem, and which still retains the normal condition of the ramulus,
and carries a scarcely modified hydrotheca. The floor or rachis of the corbula is a simple
continuation of this peduncle, with the hydrothecze entirely suppressed.

In determining the morphological significance of the corbula, the meaning of the
cost or leaflet-like ribs becomes an element of primary importance. Now the key to
this will be found in certain other forms of the protective apparatus, and I believe we
shall be justified in regarding the coste as the greatly modified mesial nematophores
of the suppressed hydrothecee, complicated by the development on them of secondary
nematophores, and thrown alternately to the right and left in accordance with their new
protective function. This will become apparent after an examination of the phylacto-
carpal apparatus in other genera.

The form of phylactocarp referrible to the type found in the Lytocarpus (Aglaophenia)
myriophyllum of the European coasts, affords the means of clearing up this point in a
way which will scarcely admit of doubt. Two beautiful species, Lytocarpus (Aglaophenia)
distans, and Lytocarpus (Aglaophenia) bispinosa, obtained during the exploration of the
Gulf Stream by the United States Survey,’ are especially significant in the light they
throw on the morphology of the corbula, while another beautiful species, Acanthocladium
hualeyi, occurring in the Challenger collection (Pl. X., and Pl. XX. fig. 1), is scarcely
less instructive.

In all these, as well as in Lytocarpus myriophyllum, the phylactocarp is, as in the true
corbula, an obviously modified hydrocladium. After retaining for some distance from its
point of origin the normal character of the hydrocladium, and supporting one or more
hydrothec, each with its usual mesial and lateral nematophores, it is continued in an
altered form, and develops a double series of long ribs, which carry numerous small
nematophores along one or both edges, remain quite distinct from one another, and form
the walls of an open basket or cage (Pl. XX. fig. 1), along whose floor the gonangia
are distributed from the proximal to the distal end. Now, in this continuation of the
hydrocladium the hydrothec are not, as in the true corbula, suppressed. We find,
on the contrary, that every rib carries a hydrotheca at its base, the rib with its basal
hydrotheca being raised on a peduncle from the rachis or floor of the cage. The pair of
lateral nematophores belonging to each of these hydrothecee may be recognised in nearly
its usual condition, while the mesial nematophore, though holding its normal position with

1 Hydroids of the Gulf Stream, pp. 44 and 46, pl. xxvi. figs. 1-8, and pls, xxvii, and xxviii,

12 THE VOYAGE OF H.M.S, CHALLENGER.

regard to the hydrotheca, becomes much elongated and transformed into the great pro-
tective rib.

The whole morphology of the corbula thus becomes beautifully distinct. We have
only to complete the transformation by supposing the costal hydrothece, with their
peduncle and lateral nematophores to become suppressed, and the ribs to become con-
fluent by their edges, in order to convert the curious open cage of Lytocarpus myrio-
phyllum, and of the Gulf Stream and Challenger Plumularians, into the ordinary closed
Aclaophenian corbula.

In the two species of the Gulf Stream exploration (Lytocarpus distans and Lytocarpus
bispinosa), the hydrocladium, which is to become transformed into a phylactocarp, retains
its normal condition for a greater distance than in Acanthocladium huxleyi continuing
to bear from three to five scarcely altered hydrothecee before the change begins which
results in the formation of a phylactocarp.

An intermediate condition will be found in those instances of an open corbula (Aglao-
phenia filicula and Aglaophenia attenuata, Pl. XI. figs. 5 and 9), in which, while the
hydrothecee as in the ordinary closed corbula become suppressed, the leaflets remain
distinct from one another.

A very interesting and instructive form of phylactocarp is found in Lytocarpus
racemiferus (Pl. XIII.). In this beautiful Plumularidan, the hydrocladia on each side for
a certain length of the principal branches become, as in the other instances, modified
so as to form protective supports for the gonangia (fig. 4). The modification here
consists in the entire suppression of the hydrothecee, while the mesial and lateral nemato-
phores are retained in a scarcely altered form. The hydrothecal internodes also continue
distinct, and the places of the suppressed hydrothecee are taken by the gonangia, which
are thus disposed in a single series, one on each internode, from the proximal towards
the distal end of the rachis. Near the distal end, however, the suppressed hydro-
theese are not replaced by gonangia, though here, on every internode, we still find the
three nematophores, the mesial and the two lateral, of the absent hydrotheca. In this
form of phylactocarp there are no rib-like appendages ; and the mesial nematophores,
which in other forms become converted into ribs, here retain their normal condition.

In Lytocarpus spectabilis (Pl. XV.) we have another instructive example of a
phylactocarp in which no ribs are developed. Here, as in the instances already cited,
the phylactocarps take the places of hydrocladia, of which they are obvious modifications
(fig. 4). The proximal internode carries a hydrotheca with its normal mesial and
lateral nematophores, but im all the other internodes the hydrothece with their mesial
nematophores are suppressed, while the lateral nematophores are retained as a pair of
strong blunt spines.

In the specimen from which the figures on Pl. XV. had been drawn, no gonangia
were developed on the phylactocarps. In another, however, a gonangium (fig. 2, p. 44)

Way? Ine ”

REPORT ON THE HYDROIDA. 15

was present on the second internode, which was here larger than the others, and carried
a mesial as well as a pair of lateral nematophores; while the continuation of the rachis
was arched over the gonangium, and had the persistent lateral nematophores of each
internode curved backwards so as to be directed towards the convex side of the arch. It
would seem to be only on the second internode that a gonangium is borne, and here it
takes the place of the hydrotheca, which, had it not been suppressed, would have
belonged to this internode, while the mesial and lateral nematophores are retained.

In Lytocarpus saccarius, a species from Ceylon,’ the gonangia are borne near the
distal extremity of short ramuli, which are hydrocladia in which the transformation has
been less complete than in the cases described above. In the specimens examined these
ramuli were composed each of three internodes. The proximal two internodes carried
hydrothece in all respects like the other hydrothece of the colony, but im the distal
internode the hydrotheca was suppressed, while its mesial and lateral nematophores
remained with but little modification, and the solitary gonangium occupied the place of
the suppressed hydrotheca.

In Lytocarpus secundus (Pl. XIV.) certain hydrocladia undergo a remarkable modifi-
cation in order to become converted into phylactocarps. Their internodes, which are
reduced to seven or eight in number, lose their hydrothecz entirely, and carry each a
long curved spine-like appendage, which is supported on the end of a short process of the
internode, and bears a double row of eup-like nematophores, several nematophores of a
similar form being sessile on the internode itself (fig. 5).

Though no gonangia were developed in the specimens examined, it will scarcely
admit of doubt that the hydrocladia thus modified are true phylactocarps. Analogy
would, perhaps, justify us in regarding the spine-like appendages as the mesial nemato-
phores of the suppressed hydrothecee, while the lateral nematophores have left no
representatives. A comparison of these appendages with the cost of a true corbula at
once suggests itself, nothwithstanding their disposition in a continuous series along the
mesial line of the rachis, instead of being thrown alternately to the right and left. In the
absence of gonangia, however, the exact relations of the parts of the phylactocarp to the
gonangia, which may yet become developed on it, cannot be ascertained with certainty.

In the only known forms of Eleutheroplea in which phylactocarps have been detected
these structures appear to be in all essential points modified hydrocladia, a number of
which combine to form the phylactocarp. In Hippurella annulata, as described by Fewkes,
the hydrocladia lose their hydrothece, and assume a verticillate disposition, arching over
the gonangia, which are borne by the stem near their bases. In Callicarpa gracilis,
Fewkes, the hydrocladia undergo a similar modification, and, moreover, become dichotom-
ously branched.’ This dichotomous division of a hydrocladium is not without analogy,

1 Linn. Soc. Jowrn. Zool., vol. xii. p. 277, pl. xxii. The species is there referred to the genus Halicornaria,
2 Bull, Mus, Comp. Zool., loc. cit., p. 134, pls. i., ii.

14 THE VOYAGE OF H.M.S. CHALLENGER.

for it has its representative in the condition of the ordinary hydrocladia in the Eleuthero-
plean genus Schizotricha of the present Report.

In all the instances now described, the phylactocarps must, as we have seen, be
regarded as more or less modified hydrocladia. To those which remain for consideration
we must assign an entirely different significance, for we now find them to be variously
formed appendages, which though specially developed as in the former for the protection
of the gonangia, are superadded to the hydrocladia, which retain their normal form.

In Cladocarpus pectiniferus (Pl. XVII.) the phylactocarp is a bifureating branch
which springs from the proximal end of a hydrocladium, and supports the gonangia
along its sides. It is destitute of hydrothece, and carries along its entire length a
double series of opposite nematophores, which have assumed the form of long, spine-like
processes, giving a pectinated character to the phylactocarpal branches. In Cladocarpus
Jormosus of the Challenger and ‘“ Porcupine” expeditions (Pl. XVI. figs. 4 and 5), and in
Cladocarpus paradiseus, Cladocarpus dolichotheca, and Cladocarpus ventricosus, of the
Gulf Stream exploration, we find a branched phylactocarp essentially similar to that just
described,

The morphological significance of the phylactocarp in Cladocarpus is not so obvious
as in that of other Plumularide. In Cladocarpus pectiniferus (Pl. XVII. fig. 3), Clado-
carpus formosus (Pl. XVI. fig. 5), and in some other species, the mesial nematophore of
the hydrotheca, immediately behind which the phylactocarp springs, is entirely absent ;
and this fact, supported by the analogy afforded by other forms of phylactocarp, would
lead us to regard the phylactocarp here as representing in a greatly modified form the
mesial nematophore of the proximal hydrotheca

a view which is scarcely invalidated by
the fact that it springs from a point not absolutely in the mesial line of the internode.

There are, however, other cases in which the mesial nematophore of the proximal
hydrothece is still present, and then we may perhaps regard the phylactocarp as
representing the mesial nematophore of a hydrotheca which had been itself totally
suppressed—a view which is justified by the analogy of other forms of phylactocarp, to
the formation of which, as we have seen, the greatly modified mesial nematophores of
suppressed hydrothece largely contribute.

In Pleuwrocarpa ramosa, a remarkable Statoplean from St. Vincent, Mr. Fewkes
describes the phylactocarp as composed of a series of ribs which take the places of
hydrocladia near the proximal end of a branch, the hydrocladia towards its distal end
remaining in their normal condition.’ Though no gonangia appear to have been present
in the specimen, there can be no doubt of the structure in question being a true phylacto-
carp; and then I should regard the ribs as representing the phylactocarpal appendages in
Cladocarpus with the hydrocladia, which in this genus carry them suppressed. They are
described by Mr. Fewkes as carrying along their length long tubular nematophores, and,

1 Bul. Mus. Comp. Zool., loc, cit., p. 136, pl. iii. fig. 2,

ae tt

RAGE angen rele bent Se Pot
arte Cale Wh “ Q

REPORT ON THE HYDROIDA. 15

were it not for their unbranched condition, they would closely resemble the phylactocarpal
appendages of Cladocarpus pectiniferus of the present Report. I have here taken for
granted that the entire structure is, as interpreted by Mr. Fewkes, a modified branch rather
than a hydrocladium, though the fact which he mentions of its carrying along its proximal
portion, which forms a kind of peduncle for the phylactocarp, a series of hydrothece
presents a difficulty in the acceptance of this view. Mr. Fewkes does not give a
magnified figure, and it is possible that what look like hydrothece are really only large
cauline nematophores.

Ramification.

The Plumularidze present considerable differences in the details of their ramification.
What may be regarded as the typical ramification in both the great sections of the
Plumularide shows itself in a simple or branched stem, from two opposite sides of which
the ultimate ramuli or hydrocladia are given off. These ramuli are thus disposed in a
regularly pinnate manner, and give to the colony the elegantly plumose aspect by which
the designation of the typical genus has been suggested. In most species the pinne are
alternate, but in a few, as in Plumularia catharina, for example, they are opposite.

In some rare cases the hydrocladia are confined to one side of the stem (Monostachas
dichotoma of the Gulf Stream exploration!). In Streptocaulus pulcherrimus of the Chal-
lenger (Pl. XVI. fig. 1), they are disposed in a continuous spiral along a simple stem.
Here, however, the hydrocladia really spring from one side only of the stem, and then,
by a revolution of the stem round its axis, the lower end remaining fixed, the hydrocladia
are thrown into the beautiful spiral characteristic of the genus. In Antennularia antennina
of the European seas the hydrocladia are disposed in regular verticils round the stem,
while in other species of Antennularia (Pl. IV. figs. 5, 6), the verticillate arrangement
gives place to a scattered one. In Sciwrella indivisa (Pl. V.) they are in four longi-
tudinal alternating series. In Hippurella*® they are pinnately disposed on the proximal
portion of the branches, but distributed on all sides towards the distal extremities. In
Antennella no proper stem is developed, and the hydrocladia are borne directly by the
hydrorhiza.

The main stem may be quite simple, or it may be more or less branched. In the
latter case the ramification is usually irregular, but it is sometimes regularly dichotomous
(Monostechas dichotoma). In some cases, as in Lytocarpus spectabilis (Pl. XV.) and
Aglaophenia macgillivrayi (Pl. X.), the stem gives off branches, which, though destitute
of hydrothec, are disposed in perfectly regular pinne, These primary pinne give
support to the true hydrotheca-bearing pinne, and the ramification thus becomes doubly

1 Hydroids of the Gulf Stream, p. 37, pl. xxii. figs. 1-5.
* Hydroids of the Gulf Stream, p. 86, pl. xxi. figs. 7, 8.

16 THE VOYAGE OF H.M.S. CHALLENGER.

pinnate. In such forms of ramification the primary pinne are almost always opposite,
while the ultimate pinnz or hydrocladia are alternate. Sometimes, however (Pl. XIX.
fiz. 4), the primary pinnee are also alternate.

In some rare cases (Pl. I. fig. 5) the hydrothecee-bearing pinne are themselves pin-
nately branched, the branches also carrying hydrothece, like the pinne from which they
spring.

Definitions of the principal terms used in the descriptive morphology of the Hydroida

Hyprosoma.—The entire hydroid colony.

KcropErM.—The most external of the three organised layers of which the body of
every hydroid is composed.

EnpoperM.—The most internal of the three organised layers of which the body of
every hydroid is composed.

MersoperM.—An organised layer which lies between the ectoderm and endoderm.
The above are the three embryonic layers which are persistent, and admit of being
recognised during the life of the hydroid.

Prrisarc.—The unorganised chitinous excretion by which the soft parts are to a
oreater or less extent invested.

Zoorps.—The more or less independent products of non-sexual reproduction, forming
by their association the hydroid colony.

TropHosoMe.—The entire assemblage of such zooids as are destined for the nutrition
of the colony.

GonosomE.—T'he entire assemblage of such zooids as are destined for the sexual
reproduction of the colony.

Hyprantus.—The proper nutritive zooids, or those which carry the mouth and proper
digestive cavity and which are almost always furnished with tentacles.

HyprotHEca.—The cup-like chitinous receptacles which protect the hydranths in
the calyptoblastic genera.

THECOSTOME,—The external orifice of the hydrotheca, which permits of the extrusion
and retraction of the hydranth.

InTRATHECAL Ripce.—An imperfect septum by which, in many Plumularide, the cavity
of the hydrotheca is transversely divided into a proximal and a distal portion.

Hypropuyton.—The common basis of the hydrosoma by which its zooids are
connected into a single colony.

HyproruizA.—The proximal end of the hydrophyton by which the colony fixes itself
to other bodies.

HyprocavuLus.—All that portion of the hydrophyton which intervenes between the
hydrorhiza and the hydrothecee or hydranths. It usually consists of a main stem and

REPORT ON THE HYDROIDA, ie

branches. It is polysiphonic or fascicled, when it is composed of several mutually
adherent tubes; monosiphonic when consisting of a single tube. In some species the
cavity of its perisarc is constricted at intervals by annular ridges or imperfect septa—
intracauline ridges.

Hyprociapia.—The hydrotheca-bearing ramuli—almost always the ultimate ramuli
—of the hydrocaulus in the Plumularidee.

Racuis.—That portion of the hydrocladium which supports the hydrothece. That
portion of the phylactocarp which supports the costz or their equivalents.

InternopE.—The part of the hydrocaulus which intervenes between any two
consecutive joints.

Cawosarc.—The common organised fleshy portion of the hydrophyton; the living
bond by which the zooids are organically united to one another.

NematopHores.—Peculiar bodies developed in certain genera from definite points of
the hydrosoma, and consisting of a chitinous receptacle with protoplasmic contents, in
which thread-cells are usually immersed. They are eminently characteristic of the
Plumularide.

GonopHoreE.—The ultimate generative zooid which gives origin directly to the
generative elements—ova or spermatozoa.

Gonanctum.—An external chitinous receptacle within which in the calyptoblastic
genera the gonophores are developed.

BuiastostyLe.—An extension of the ccenosarec through the axis of the gonangium in
the form of a fleshy column frum whose sides the gonophores are developed as buds.

Acrocyst.—An external sac which in certain hydroids is formed on the summit of the
gonangium, where it constitutes a receptacle into which the ova are discharged in order
to pass within it through some of the earlier stages of their development.

Puyacrocarr.—A part of the gonosome specially modified for the protection of the
gonangia in certain genera (phylactocarpal) of the Plumularidee.

CorsuLta.—A form of phylactocarp constituting a basket-shaped receptacle which
encloses groups of gonangia in certain phylactocarpal Plumularidee.

Cost#,—Rib-like appendages which form part of the protective arrangement in
certain phylactocarps.

Gymnosiastic.—The condition of a hydroid when no external receptacle (hydrotheca
or gonangium) invests either nutritive or generative buds.

CatyprosLastic.—The condition of a hydroid when an external protective receptacle
(hydrotheca or gonangium) invests either the nutritive or generative buds,

(ZOOL. CHALL. EXP.—PART Xx.—1883.) U3

DESCRIPTION OF GENERA AND SPECIES.

PLUMULARID.

KELEUTHEROPLEA.,

Sub-family

Plumularia, Lamk. (in part).

Plumularia, Lamarck, Hist. Nat. des An. sans Vert., Ist ed., 1815,
Aglaophenia, Lamouroux, Hist. des Pol. Coral. flex., 1816.

Plumularia flabellum, n. sp. (Pl. I. figs. 1-4).

Trophosome.—Colony attaining a height of about five inches, stem springing from a
dense mass of entangled filaments, much branched, branches pinnately disposed, main
stem and principal branches strongly fascicled, hydrocladia alternate, averaging about
three-tenths of an inch in length; hydrotheca-bearing internodes separated from one
another by a single internode destitute of hydrotheea. Hydrotheca adnate by its entire
height to its internode; hydrotheeal internode carrying, besides the pair of lateral
nematophores, a single mesial nematophore, which springs from a point at some distance
below the hydrotheca ; intervening internodes carrying a single mesial nematophore.

Gonosome not known.

Plumularia flabellum is a very beautiful Hydroid. Its primary branches, which are
of unequal length, and given off at irregular distances, are pinnately disposed and set
with hydrocladia, while many of the primary branches also send off pinnately-disposed
ramuli, which, like the primary branches, are themselves destitute of hydrothece, but
carry pinnately-disposed hydrocladia. Hydrocladia are also borne by the main stem in
the intervals of the branches. The pinnate disposition of all the branches and ramuli,
and the fact of their lying in one and the same plane, confer upon the colony the flabelli-
form habit which has suggested the specific name.

This fine species was dredged off Marion Island, 26th December 1873, from a depth
of 50-75 fathoms.

Plumularia lawa, n. sp. (PI. I. figs. 5, 6).

Trophosome.—Colony attaining a height of about four inches, stem much and irregu-
larly branched, rooted by a dense mass of entangled filaments, main stem and principal

20 THE VOYAGE OF H.M.S. CHALLENGER.

branches fascicled, hydrocladia springing from the branches at distant and irregular inter-
vals, and being themselves set with rather distant, pinnately-disposed alternate hydrocladia.
Hydrothece campanulate, every internode of the hydrocladia carrying a hydrotheca, which
is adnate to the supporting internode for about two-thirds of its height ; lateral nemato-
phores very short, cup-shaped, not reaching the margin of the hydrotheca; mesial
nematophores like the lateral in form, one borne by every internode at the proximal, and
one at the distal side of the hydrotheca.

Gonosome not known.

Plumularia laxa is a very remarkable form, rendered striking by its somewhat diffuse
habit, and by the doubly pinnate arrangement of its hydrotheca-bearing ramuli.

In this doubly pinnate condition of the hydrocladia we have a very exceptional
character, for though it is not unusual among the Plumularidee for the ultimate hydro-
thecal pinnze to be borne by ramuli also pinnately disposed on the main stem or primary
branches, such ramuli rarely carry hydrothecee. The primary hydrocladia of the present
species vary in length from about three-tenths to six-tenths of an inch ; the secondary
hydrocladia attain a nearly constant length of about two-tenths of an inch.

Dredged in Station 168, April 4, 1874, lat. 36° 56’ S., long. 150° 30’ E.; 120
fathoms.

Plumularia dolichotheca, n. sp. (Pl. I. figs. 7, 8).

Trophosome.—Colony attaining a height of about three inches, stem irregularly
branched, monosiphonic, hydrocladia alternate, about two-tenths of an inch in length,
divided into internodes of unequal length, each carrying one, two, or three hydrothece.
Hydrothec deep, thimble-shaped, adnate to their internodes by their entire height, and
with the lateral nematophores springing from a point close to the margin of the hydrotheca;
mesial nematophore sub-calicine only, and found only below the proximal hydrotheca of
the internode.

Gonosome not known.

Plumularia dolichotheca presents several very unusual characters. It is, with the
exception of Plumularia frutescens of the European shores, the only Plumularian with
which I am acquainted in which more than one hydrotheca is carried by one and the same
internode. While in the present species some of the internodes of a hydrocladium carry
as usual only one hydrotheca, others carry two, or even three. When two or more hydro-
theese are carried by a single internode, it is only the proximal hydrotheca which is sub-
tended by a nematophore. This nematophore is supported on a small tubercle-like process
of the internode, while the corresponding points below the more distal hydrothece show no
trace of the tubercle, a fact which affords evidence that the absence of the nematophore
is not due to its having been accidentally detached.

Under the name of Plumularia cylindrica, Kirchenpauer describes a species—also from

REPORT ON THE HYDROIDA. 21

Zamboanga—which in the form of the hydrothece and in the general habit of the colony
closely approaches Plumularia dolichotheca. It differs from it, however, in every internode
of the hydrothecal pinne carrying only one hydrotheca, and in the opposite instead of
alternate disposition of these pinne.

Plumularia dolichotheca was dredged off Zamboanga, Philippines, 30th January 1875,
from a depth of 10 fathoms.

Plumularia insignis, n. sp. (Pl. IL).

Trophosome.—Colony attaining a height of about eighteen inches, main stem fascicled,
sending off in all directions simple jointed branches, along whose entire length the hydro-
thecal pinnze, about two-tenths of an inch in length, are alternately disposed. Hydro-
thecee deep conical, adnate by their entire height to the supporting mternodes, which are
separated from one another by an intervening much shorter internode, destitute of hydro-
theca; mesial nematophores situated one on the hydrothecal internode at the proximal side
of the hydrotheca, and one on each of the intervening internodes.

Gonosome.—Gonangia situated on the hydrocladia-bearing branches, each at the base
of a hydrocladium.

This very beautiful species is rendered especially striking by its large size and its
plume-like ramification. The gonangia present in the specimen seem to be young, and to
have scarcely yet attained their ultimate form. Several specimens of a little isopodous
crustacean continued to adhere to the stem, and are represented in the drawing.

Station 145, December 27, 1873, lat. 46° 40’ S., long. 37° 50’ E.; depth, 310 and
150 fathoms.

Plumularia abietina, un. sp. (Pl. IIL).

Trophosome.—Colony attaining a height of about nine inches, main stem fascicled for
some distance from its root, and sending off scattered, usually simple jointed branches,
which carry alternate hydrothecal pinnz, rather less than two-tenths of an inch in
length, and commencing from a point at some distance from the origin of the branch.
Hydrothecs deep conical, adnate by their entire height to the supporting internodes, which
are separated from one another by an intervening much shorter internode, destitute of
hydrotheea; a single mesial nematophore, borne by the hydrothecal internode at the proxi-
mal side of the hydrotheca, and another on each of the intervening internodes.

Gonosome.—Gonangia ovate, borne by the hydrocladia-bearing branches, each close to
the origin of a hydrocladium.

The Hydroid here described comes very near to Plumularia insignis ; indeed, so nearly
related are the two forms, that we should almost be justified in regarding the difference

between them as merely varietal.

22 THE VOYAGE OF H.M.S. CHALLENGER.

Plumularia insignis, however, is altogether a larger and much more robust form, while
the hydrocladia are longer and occupy a greater length of their supporting branches, ex-
tending from the distal extremity of these nearly to the base. In Plumularia abietina,
on the other hand, a considerable portion of the branch towards its proximal end is desti-
tute of hydrocladia.

The specimen had numerous individuals of an Avicula-like fry adhering to it, a
feature which has been reproduced in the drawing.

Dredged off Prince Edward’s Island, from a depth of 150 fathoms (7%).

Plumularia stylifera, n. sp. (Pl. TV. figs. 1, 2).

Trophosome.—Colony attaining a height of about an inch and a half, stem simple
monosiphonic, hydrocladia alternate, about one-tenth of an inch in length, and with the
hydrotheca-bearing internodes usually separated by an intervening internode which does
not carry a hydrotheca. Hydrothecze rather large, adnate only by their base to the
supporting internode, flanked on each side by a long slender process, which springs from
the internode and carries a lateral nematophore on its summit; a single mesial
nematophore borne by the hydrothecal internode at the proximal side of the hydrotheca,
and another by the intervening internode.

Gonosome.

Gonangia springing from the hydrothecal internodes at the proximal side
of the hydrotheca, ellipsoidal, with a truncated summit which opens by a lid, and with a
pair of nematophores carried near its proximal end.

The great leneth of the process which supports the lateral nematophore on each side
of the hydrotheca presents a striking feature. The present species, however, is not the
only one in which this process attains a considerable length. It is nearly as long in the
European Plumularia catharina and in other species closely allied to the latter, as well as
in Antennularia fascicularis of the present Report.

Plumularia stylifera has many points of affinity with Plumularia catharina, which it
resembles not only in the long style-like process which supports the lateral nematophore,
but in the presence of a pair of nematophores on the proximal end of the gonangium, and
in the general form of the hydrothecze and their supporting pinnee. Indeed, it differs
from it mainly in its more delicate habit and shorter and more approximated hydrocladia,
which are disposed alternately on the stem instead of being opposite, as in Plunularia
catharina.

Dredged off Nightingale Island, Tristan d’Acunha, Station 135, from a depth of
100-150 fathoms,

Plumularia armata, n. sp. (Pl. IV. figs. 3, 4).

Trophosome.—Colony attaining a height of about two inches; stem monosiphonic
irregularly and sparingly branched, divided into internodes, each of which carries a hydro-

REPORT ON THE HYDROIDA. 23

theca; hydrocladia alternate, rather more than one-tenth of an inch in length, arising one
from every internode of the stem close to the base of a hydrotheca. Hydrothece deep,
conical in front view, cylindrical in profile, adnate by somewhat more than half their |
height to the supporting internode, flanked on either side by a short tooth-like process,
which carries a long lateral nematophore; a single mesial nematophore borne by the
hydrothecal internode at the proximal side of the hydrotheca, and another at its distal
side in the hydrocladia, while in the stem the single mesial nematophore is replaced in
the distal portion of each internode by a pair of lateral nematophores.

Gonosome.—Female gonangia borne along the stem, each springing by a very short
peduncle from a point opposite to the origin of a hydrocladium, large, ovate with
truncated summit, carrying from base to summit along one side a single linear series of
nematophores.

Male gonangia developed in the same colony with the female, and borne exclusively
by the internodes of the hydrocladia, springing by a short peduncle from the internode at
the proximal side of its hydrotheca, very much smaller than the female, crescentic in
form, destitute of nematophores, and with rounded summit curved towards the
supporting internode.

Plumularia armata is a small and delicate Hydroid. The condition of the gonosome
is very exceptional. The nematophores, which are developed on the outside of the female
gonangium, constitute in themselves a very unusual and striking feature. These extend
in a continuous series along the course of the blastostyle, with which they communicate
through perforations in the chitinous walls of the gonangium. In order to allow of this
communication, the blastostyle is thrown out of the axis of the gonangium, and lies
against the inner surface of its walls, immediately under the series of nematophores.

In Sciurella indivisa of the present Report we also find the gonangium carrying
numerous nematophores. Here, however, the nematophores are not arranged in a single
series, but form symmetrically disposed groups.

Striking, however, as is the development of gonangial nematophores in these instances,
it is only an extreme case of what occurs in several other Eleutheroplean Plumularide,
as in Plumularia catharina and allied species, and in Antennularia fascicularis, and the
two species of Schizotricha described in the present Report. In all these a pair of
nematophores is developed from the base of the gonangium, and there communicates
with the proximal end of the blastostyle.

Another very exceptional, though by no means unique character, is found in the
presence of both male and female gonangia in the same colony. These differ not only in
form but in situation. The large ovate female gonangia, with their series of parietal
nematophores, are borne exclusively on the stem, which, like the hydrocladia, is
composed of a series of hydrotheca-bearing internodes, while the very much smaller
crescentic male gonangia are confined to the hydrocladia.

24 THE VOYAGE OF H.M.S. CHALLENGER.

Notwithstanding the many exceptional characters of this curious Plumularian, |
believe it will be better to keep it in the genus Plwmularia, rather than construct
for it a new one.

Under the name of Plumularia obconica, Kirehenpauer describes a Plumularian from
the Gulf of St. Vincent, Australia, which in many respects resembles the present species.
Its female gonangium carries, asin this, on the outer surface of its walls, a longitudinal
series of nematophores. Like Plumularia armata, also, the species is moneecious, carrying
male and female gonangia in the same colony, while the main stem is divided into
internodes, each carrying a hydrotheca, as in Plumulamia armata. It differs, however,
from Plumularia armata in its shallower hydrotheca, with plicated margin, and in the
conical roof of its female gonangium, while the stem is unbranched, and carries the hydro-
cladia in such a way as to give them an obviously secund disposition. Kirchenpauer,
moreover, describes the nematophores of the trophosome as monothalamic, those of the
gonosome being of the usual bithalamic type. In Plumularia armata both sets of nemato-
phores are bithalamic.

The collection contains but a single specimen of Plumularia armata. It was dredged
at Station 163, off Port Jackson ; depth, 30-35 fathoms ; bottom, red clay.

Antennularta, Lamk.

Antennularia, Lamarck, Hist. Nat. des An. sans Vert., Ist ed., 1815.
Nemertesia, Lamouroux, Hist. des Pol. Coral. flex., 1816.

Antennularia fascicularis, n. sp. (PI. IV. figs. 5, 6).

Trophosome.—Colony attaining a height of upwards of three inches; stem thick,
sub-dichotomously branched, formed of a multitude of coalesced tubes, which give off on
all sides irregularly scattered hydrocladia, which carry the hydrothece on alternate
internodes, and are about two-tenths of an inch in length. Hydrothecee rather large,
campanuliform, adnate by their base only to the supporting internode, flanked on each
side by a long style-like process, which supports on its summit a lateral nematophore ;
one mesial nematophore carried by the hydrothecal internode near its proximal end, and
three by the intervening internode.

(ronosome.—Gonangia springing laterally from the hydrothecal internodes each at
the proximal side of a hydrotheca, obovate, supported on a short stalk and carrying a pair
of nematophores close to its proximal end.

A more extended comparison of Antennularia antennina of our own shores, in which
the hydrocladia are verticillate, with those forms in which they are more or less scattered,
has led me to regard this difference as of less systematic importance than I had formerly
believed, and has induced me to assign to it a specific rather than a generic value. When,

REPORT ON THE HYDROIDA. 25

therefore, no other difference of greater importance exists, I believe it will be best to
follow the earlier systematists, and combine all such forms under a single genus, of which
the well-known Antennularia antennina may be taken as the type.

The hydrocladia of Antennularia fascicularis spring from the outer tubes of the
polystphonic stem, each hydrocladium being supported on a short process from the
tube, and having at its proximal end two short internodes followed by a long one, all
three destitute of hydrothecee. In the deep hydrothecee, Antennularia fascicularis
further contrasts with the typical Antennularie, whose small shallow hydrothece are, as a
rule, characteristic of the genus ; while the position of the gonangia on the hydrothecal
internodes, instead of being borne in the axils of the hydrocladia, affords another
distinctive feature.

The proximal end of the specimen in the collection had been broken off, so that
nothing can be asserted with exactness regarding the height attainable by the colony or
the characters of the hydrorhiza.

Antennularia fascicularis is wanting in the graceful habit by which most of the
Plumularide are characterised, the thick strongly fascicled stem, and the irregularity of
the fine hair-lke ramuli, giving it a somewhat inelegant habit, which contrasts with
the lightness and grace of most other species.

Dredged off Nightingale Island, Tristan d’Acunha, from a depth of 100-150 fathoms.

Sciurella, nov. gen,

Name, a diminutive noun formed from Sezwrus, a squirrel, in allusion to the squirrel-taillike
disposition of the hydrocladia.

Generic Cuaracter. Trophosome— Hydrocladia not disposed in pinnee, but spring-
ing from many points round the circumference of chord-like stems.

Gonosome.—Gonangia situated in the axils of the hydrocladia, provided with sym-
metrically disposed horn-like processes, and enclosing a ramified blastostyle, whose
branches are in connection with moveable nematophores distributed over the surface of
the gonangium.

The species on which the genus Sevwrella has been founded has the general aspect of
Antennularia antennina. From this, however, it differs not only in the disposition of
the hydrotheca-bearing ramuli, but in the much more important character presented by
the remarkable gonangia with their ramified blastostyle, their horn-like processes, and the
nematophores carried on their walls. These nematophores belong to the ordinary
moveable type, and communicate through perforations in the walls of the gonangium
with the prolongations of the ramified blastostyle.

(ZOOL. CHALL, EXP,—PART Xx.—1883.) U4

i)
oo

THE VOYAGE OF H.M.S. CHALLENGER.

Sciurella indivisa, n. sp. (Pl. V.).

Trophosome.—Colony attaining a height of ten inches ; stem simple, monosiphonie,
springing in clusters from the hydrorhiza; hydrocladia closely set, about two-tenths of
an inch in length, arranged in four longitudinal alternating series, which extend from the
summit of the stems to within a short distance of the base. Hydrothecee deep, nearly
cylindrical, adnate by their entire height to the supporting internode, every internode of
the hydrocladium carrying a hydrotheca, and having, im addition to the lateral nema-
tophores, a single mesial nematophore near its proximal end.

Gonosome.—Gonangia in pairs from the axils of the hydrocladia, urn-shaped in front
view, with two symmetrically placed hollow lateral processes near the distal end;
gonangial nematophores carried by the lateral processes, by the summit of the gonangium,
and by its sides near the base.

As already stated (see p. 22), 1am not disposed to regard a scattered or multiserial
disposition of the hydrocladia as affording sufficient grounds for generic separation from
those forms of Antennularia in which the hydrocladia are verticillate. While, however,
the disposition of the hydrocladia in Sciwrella indivisa would thus not in itself afford a
character by which this species could be generically separated from Antennularia, such
a character is found in the remarkable form of the gonangia, with their branching blasto-
style and the nematophores to which their walls give support.

The general resemblance of Sciurella indivisa to Antennularia antennina is so close,
that, without the aid of a lens, a specimen of one of these hydroids might be easily
mistaken for the other. The gonangium, though urn-shaped when viewed in front, is
compressed laterally, and when viewed in profile is seen to have its axis curved backwards
nearly in a semicircle.

The ramification of the blastostyle in the gonangium presents considerable symmetry,
and was similar in every instance examined. A strong branch is sent offon each side into
the lateral projections, and each of these branches sends out three short processes and one
long one, which all pass directly to the perforations in the walls of the gonangium, in order
to communicate with the corresponding nematophores which le free on the outer surface of
the walls. The short processes pass to nematophores which le near the distal end of the
gonangium, while the long processes pass down, one on each side, to communicate with
two nematophores situated near the base of the gonangium.

The deep hydrothecee of Sczwrella indivisa contrast with the small shallow hydro
thecee by which most species of Antennularia are characterised.

Dredged off Somerset Island Cape York, Torres Strait ; 5-10 fathoms.

i)
“NI

REPORT ON THE HYDROIDA.

Acanthella, nov. gen.

Name, a diminutive noun formed from dkava, a thorn, in allusion to the spine-bearing
terminations of the branches.

Generic Cuaracter. Trophosome.—Hydrocladia pinnately disposed ; hydrocladia-
bearing branches terminating in simple jointed prolongations in which the places of
the hydrocladia are taken by spine-like appendages.

Gonosome not known.

The genus Acanthella, so far as regards its trophosome, represents among the Eleu
theroplean section of the Plumularide the genus Acanthocladiwm of the Statoplea. The
peculiar terminations of the branches are essentially the same in both, and the lateral
spines which these support are in both cases the morphological equivalents of hydrocladia.
No part of the gonosome was present in the specimens of the only species referrible to

Acanthella.

Acanthella effusa, Busk, sp. (Pl. VL).
Plumularia effusa, Busk, Voyage of the “ Rattlesnake,” 1852, vol. 1. p. 400.

Trophosome.—Colony attaining a height of twelve inches ; main stem springing from
a dense mass of entangled filaments, monosiphonic, giving off a multitude of scattered
subdivided branches, which carry the hydrocladia, every subdivision ending in a spine-
like continuation which is composed of numerous internodes, each internode supporting
two or more stout blunt spines; hydrocladia one-tenth of an inch in length. Hydrothecee
pitcher-shaped, with entire margin, adnate by their whole height to the rachis ; mesial
nematophore single, springing from a point close to the base of the hydrotheca, lateral
nematophores springing from points close to its margin ; hydrocladial imternodes
separated from one another by a very well-marked joint, and each carrying a hydrotheca.

Gonosome not known.

Acanthella effusa is a remarkable and beautiful species, and, like Acanthocladium
affords in the curious terminations of its branches an example of the extent to which
the hydrocladia may be modified, and yet allow of the recognition of their homological
significance.

A very obvious transition may be traced from the simple spines, which occur towards
the distal extremity of the branch, backwards into the true hydrotheca-bearing ramuli.
In fact some of the posterior or more proximal spines still carry near the base a single
hydrotheca, with its mesial and lateral nematophores. These spines are also borne on the
summit of a thick process from the internode, while the more distal spines are not only
quite destitute of hydrothecz, but are directly confluent by their base with the iter-
nodes which carry them. In the angle between these more distal spines and the sup-

28 THE VOYAGE OF H.M.S. CHALLENGER.

porting internode, two small nematophores of the ordinary Eleutheroplean type are
developed.

The close proximity of the mesial nematophore to the base of the hydrotheca, as seen
in the present species, is also a very unusual feature in the Eleutheroplea.

Kirehenpauer?* describes and figures a Plumularian brought by von Martens from the
Philippine Islands. He refers it to the Plumularia effusa of Busk, a species obtained
in Torres Strait during the exploratory voyage of the “ Rattlesnake.”’ In the form of
the hydrothece, and of their supporting pinne, and in the form and arrangement of
the nematophores, the species figured by Kirchenpauer agrees closely with that here
described. No notice, however, is. taken of the series of spine-bearing internodes in
which the branches of Acanthella terminate. Specimens of the present species from the
collection of the Challenger have been examined by Mr. Busk, and referred by him to the
Plumularia effusa of the voyage of the “ Rattlesnake,” and an opportunity he has given
me of comparing the Challenger Hydroid. with authentic specimens of his Plumularia
effusa, has convinced me of the justice of this identification.

Acanthella effusa was dredged off Cape York, Torres Strait, and also from reefs off
Zamboanga, at a depth of 10 fathoms.

Schizotricha, nov.. gen.

Name from oxi€w, to divide, and Opié, a hair, in allusion to the bifurcation of the hydrocladia.

GENERIC CHARACTER. Trophosome.—Hydrocladia pinnately disposed, once, twice, or
oftener bifurcating.

Gronosome—Gonangia springing from the hydrocladia.

The genus Schizotricha is essentially characterised by the bifurcation of its hydrotheca-
bearing ramuli. The collection contains two species, in one of which the ramuli bifurcate
only once, while in the other, three, four; or probably a greater number of bifurcations

are present.

Schizotricha unifurcata, n. sp. (PL. VIL. figs. 1-8).

Colony attaining a height of about five inches; stem irregularly
branched, fascicled, rooted by a dense mass of entangled filaments ; hydrocladia alternate,

Trophosome.

about seven-tenths of an inch in length, dividing each into two similar branches at a short
distance from its origin. Hydrothecee with even margin, rather deep, adnate to the sup-
porting internode by their entire height ; besides the pair of lateral nematophores, there
is a single mesial nematophore carried by the internode near its proximal end; a hydro-
theca without nematophores carried in the angle of the bifurcation.

1 Kirchenpauer, loc. cit., Band vi.
2 Voyage of “ Rattlesnake,” vol. i. p. 400.

oe ih

REPORT ON THE HYDROIDA. 29

Gonosome.—Gonangia carried by each branch of the hydrocladia near to the bifurca-
tion, pyriform, supported on a short peduncle, and with a basal segment which carries a
pair of laterally placed nematophores.

This fine species forms wide flabelliform tufts with rather rigid stems, and with the
hydrocladia nearly an inch in length. The hydrocladia are each supported on a short
process of the stem; to this is articulated the first segment of the hydrocladium ; this
segment is very short, is destitute of hydrotheca, and is immediately followed by a long
segment in which the bifurcation takes place, and which carries in the angle of bifurcation
a hydrotheca without nematophores. One branch of the bifurcation always commences
by a short internode destitute of hydrotheca; every other internode of the branches
carries a hydrotheca.

Besides the form here described, there occurs also a variety (see fig. 3), in which the
hydrothecal ramuli scarcely exceed half the length attained by these ramuli in the typical
form.

The typical form was dredged in Christmas Harbour, Kerguelen, from a depth of 100
fathoms. The variety with short hydrocladia was dredged also off Kerguelen Island, from
a depth of 10 to 60 fathoms.

Schizotricha multifurcata, n. sp. (Pl. VII. figs. 4, 5).

_ Trophosome.—Colony attaining a height of about nine inches; stem sparingly
branched, fascicled, rooted by a mass of entangled filaments; hydrocladia alternate,
attaining about four-tenths of an inch in length, bifurcating three, four, or a greater
number of times. Hydrothecee with even margin adnate to the internode by their
entire height, flanked by a pair of lateral nematophores, and also subtended by a similar
pair of nematophores on the same internode, a hydrotheca without nematophores carried
in the angle of every bifurcation.

Gonosome.—Gonangia carried by the internodes of the hydrocladia, each springing
from a point situated laterally, and just below a hydrotheca, pyriform, supported on a very
short peduncle, and having a wide basal segment which carries a pair of nematophores.

This is a very graceful species, with flexile stems much longer and less profusely
branched, and with shorter hydrocladia than in Schizotricha unifurcata, A remarkable
feature in the specimen examined consisted in the hydrothecal mternodes, carrying at the
proximal side of the hydrotheca a pair of laterally situated nematophores, instead of the
azygous mesial nematophore usual in the Eleutheroplean Plumularide. The gonangia
also, besides the two nematophores which were always present on its basal segment, often
carried here a third one. This fact, however, scarcely seems to be constant.

In every bifurcation one of the branches is connected with the internode from which
it springs, by a short internode destitute of hydrotheca, but carrying a pair of nemato-
phores.

30 THE VOYAGE OF H.M.S8. CHALLENGER.

Here, as in Schizotricha unifurcata, the first bifurcation takes place in the second seg-
ment of the hydrocladium, this segment carrying a hydrotheca without nematophores in
the angle of the bifurcation, and being preceded by a very short segment destitute of
hydrotheca.

Dredged at Station 151, February 7, 1874, off Heard Island; depth, 75 fathoms ;
bottom, mud.

Polyplumaria, G. O. Sars.

Polyplumaria, G. O. Sars, Forhandl. Vidensk. Selsk. i. Christiania, 1873.
Diplopteron, Allman, Trans. Zool. Soc. Lond., 1873.

Generic CHaracter. Trophosome.—Hydrocladia each with an accessory hydrotheca,
bearing ramulus, which springs from its proximal internode. ,
Gonosome.—Gonangia borne by the basal segment of the primary pinne.
In a report on the Hydroids collected during the expeditions of H.M.S. “ Porcupine,”

read at a meeting of the Zoological Society of London in February 1873, I described

as a new genus and species, under the name of Diplopteron insigne, a very beautiful
Plumularian dredged off the north-west coast of Spain, from a depth of 364 fathoms,
during one of these expeditions.1

G. O. Sars had, however, in the same month, but a few days earlier, described under
the generic name of Polyplumaria, a Hydroid from the Norwegian Seas, which I believe

2

must be generically associated with the Hydroid of the “ Porcupine.”? The priovity of
description thus hes with Sars, and though he does not appear to me to have seized on
the essential characters of the genus, the name Diplopteron must sink into a mere
synonym of Polyplumaria.

I have here modified the diagnosis of Diplopteron as originally given, a diagnosis
which, founded as it was on a single species, was too exclusive to admit forms which ought
not to be generically separated. In the three species of which the genus Polyplumaria
now consists, the most striking feature is the accessory ramulus, to which the hydrothecal
pinne give origin. This ramulus springs from every hydrothecal pinna near to its origin,
and is itself composed of internodes which carry hydrothece similar to those of the
pinna from which it springs.

Sars, it is true, does not describe the accessory ramulus as constant, but as it was
never wanting in any of the specimens ‘examined by me, being, on the contrary, always
very characteristic, I cannot but regard its absence from some of the branches in Sar’s
specimens as accidental.

* Report on the Hydroids collected during the expeditions of H.M.S. ‘ Poreupine.” Trans. Zool. Soc. Lond.,
vol. viii. p. 8.

2 G, O. Sars, Bidrag til Kundskaben om Norges Hydroida. Forhandl. Vidensk. Selsk. i. Christiania, 1873.

REPORT ON THE HYDROIDA. 31

Polyplumaria pumila, n. sp. (Pl. IV. figs. 7, 8).

Trophosome.—Colony attaining a height of one or possibly two inches ; stem strongly
fascicled and giving off opposite pinne, which do not carry hydrothecze, and are also
fascicled ; hydrocladia alternate, scarcely exceeding one-twentieth of an inch in length,
borne on the main stem and primary pinne, each giving off its accessory ramulus from a
point close to the base of the proximal hydrotheca ; hydrothecal internodes continuous.
Hydrothece cylindrical, rather distant, adnate only by their base to the rachis, and with
the internodes which support them carrying besides the lateral nematophores a single
mesial nematophore at the proximal, and another at the distal side of the hydrotheca.

Gonosome.—Gonangia pyriform, with obliquely truncated summit.

The specimens were fragmentary, and did not afford sufficient evidence of the size
attained by the perfect colony ; but it is probable that it reaches a height of between one
and two inches. Itis thus a very much smaller, and altogether more delicate species than
the Diplopteron insigne of the “ Porcupine,” which attains a height of about six inches.

The accessory ramuli carry one, two, or three (possibly in some cases more) hydrothece,
and have a rather long proximal internode, which is always destitute of hydrotheca.

I was unable to find in the present species the second pair of minute lateral nemato-
phores which in Polyplumaria (Diplopteron) insignis is developed at the distal side of
the hydrotheca. Polyplumaria pumila is further distinguished from Polyplumaria
insignis by the more cylindrical form of the hydrothece, which do not present the slightly
everted margin which gives a somewhat campanulate form to the hydrothecee of
Polyplumaria insignis. All the known species are doubly pinnate.

The gonangium is borne on a short cylindrical peduncle, and has a truncated summit
and a short transverse segment at its very much contracted base.

All the species as yet discovered are inhabitants of the deeper sea zones.

Dredged at Station 75, July 2, 18738; lat. 38° 37'N., long. 28° 30’ W.; depth, 450
fathoms ;. bottom, sand.

Heteroplon, nov. gen.

Name, from érepos, dissimilar, and ézAov, a weapon, in allusion to the presence of two different
kinds of nematophores.

Generic Coaracter. Z'rophosome.—Hydrocladia pinnate ; hydrothecal internode with
the lateral nematophores moyeable, and with a mesial fixed spine-like nematophore below
the hydrotheca.

Gonosome not known.

The genus Heteroplon combines the characters of the Eleutheroplean with those of
the Statoplean Plumularide. The hydrothece are flanked each by a pair of moveable
nematophores of precisely the same kind as in the typical Eleutheroplea, while the mesial

32 THE VOYAGE OF H.M.S. CHALLENGER.

nematophore which lies below the hydrotheca is fixed, and resembles that of the ordinary
Statoplean genera in all respects, except in the fact of its being quite detached from the
hydrotheca, and in the presence of an imperfect septum close to its distal extremity, thus
showing a tendency to the bithalamic form of the Eleutheroplean nematophore.

In all other important points the species on which the genus Heteroplon has been
founded presents the essential features of the Eleutheroplea, with which, notwithstanding
the presence of a fixed nematophore, it must be associated.

Leteroplon pluma, n. sp. (Pl. VIII. figs. 1-3).

Trophosome.—Colony attaining a height of about four inches; stems sparingly branched
monosiphonic, springing in groups from a creeping stolon; hydrocladia about one-fourth
of an inch in length, carrying a hydrotheca on every internode, a hydrotheca also carried
by the stem close to the origin of every hydrocladium, stem with groups of two or
three short internodes at irregular intervals. Hydrothecee with entire margin, adnate to
the rachis by about three-fourths of their height; lateral nematophores borne each on a
short process of the hydrothecal internode ; hydrothecal internode also carrying a single
moveable nematophore at the distal side of the hydrotheca; mesial fixed nematophore
close to the proximal end of the internode, in the form of a short, blunt, somewhat curved
spine, with an oblique terminal orifice.

The hydrothecal pinnee of the present species are closely set along the stem, and the
general habit of the colony is more that of an Aglaophenia than of a Plumularia—a feature
which is not without interest when viewed in connection with the presence of the fixed
nematophore. Notwithstanding, however, the presence of a fixed nematophore, and the
Aglaophenia-like habit of the species, the whole assemblage of characters is so decidedly
that of the Eleutheroplean Plumularidee, that there need be no hesitation in assigning it

to this group.
The specimen was dredged at Station 162, April 2, 1874, off East Moneceur Island,
Bass Strait, from a depth of 38 to 40 fathoms ; bottom, sandy.

Sub-family—S TATOPLEA.
Section—PHYLACTOCARPA.

Acanthocladium, nov. gen.

Name from dkavOa, a thorn, and «Addos, branch, in allusion to the spiny terminations of the
branches.
Generic CHaracter. Trophosome.—Distal portion of branches destitute of hydro-
cladia, whose places are taken by a long, spine-like appendage on each internode.
Gonosome. —Phylactocarp replacing a hydrocladium, and consisting of a rachis with

REPORT ON THE HYDROIDA. 33

two series of pinnately-disposed, alternate, free ribs, each rib carrying near its base a
hydrotheca. Gonangia springing from the rachis.

The remarkable mode in which the branches of Acanthocladium terminate, recalls the
very similar condition presented by the genus Acanthella ; but while Acanthocladium is
a Statoplean form, Acanthella belongs to the Eleutheroplea. The gonosome of Acanthella
is unknown, but the specimens of Acanthocladium hualeyi the only species of the
genus as yet discovered, are, on the contrary, abundantly provided with this important
element of the colony. The phylactocarp of Acanthocladium belongs to the same type
as that of the Aglaophenia distans and Aglaophenia bispinosa of the Gulf Stream Report,"
every rib carrying, as in these last, near its base a modified hydrotheca, The distal portion
of the rib is in all these cases the greatly modified mesial nematophore of this hydrotheca,
while the proximal portion is a peduncle which springs from the rachis and supports the
modified hydrotheca and its appendages. (See p. 11).

Acanthocladium hualeyi, Busk, sp. (Pls. [X. and XX. figs. 1-8).
Plumularia hucleyi, Busk, Voyage of the ‘ Rattlesnake,” vol. i. p. 395, 1852.

Trophosome.—Colony attaining a height of fifteen inches; stem fascicled, springing from
a dense cushion of fine entangled tubes, undulated, giving off pimnately-disposed alternate
simple branches about two inches in length, which carry the hydrocladia and terminate each
in a jointed prolongation which is composed of numerous (twelve to sixteen) internodes,
every internode carrying a slightly curved spine, which is supported on the extremity of
a short process from alternate sides of the internode, and carries two rows of small cup-
shaped nematophores ; hydrocladia alternate, short, about one-tenth of an inch in length.
Hydrothecxe approximated, wide and rather shallow, with an anterior parietal fold and a
very short intrathecal ridge; orifice of hydrotheca with its plane parallel to the axis of
the short internode, margin crenate ; mesial nematophore adnate to the entire height of
the hydrotheca wall, and then continued as a long, free, curved spine which arches over the
orifice of the hydrotheca ; lateral nematophores short, crescentic.

(ronosome.
branches near their middle, every series having the unmodified hydrocladia at its proximal

Phylactocarps developed in a continuous series on each side of the

and usually also at its distal side; costa of phylactocarp twenty-six to thirty in number
springing alternately from the sides of the rachis, over which they arch, each carrying a
double row of cup-shaped nematophores, and at about one-third of its length from the
base, a single small deep hydrotheca. Gonangia ovoid, springing from the rachis, each
close to the origin of a costa.

The long flexile undulating stem and simple plume-like branches of Acanthocladium

1 Allman, Report on the Hydroida collected during the exploration of the Gulf Stream, by L. F. De Pourtalés, United

States Coast Survey, 1877, p. 44, pl. xxvi. figs. 1-8, and p. 46, pls. xxvii., xxvill.

(ZOOL, CHALL, EXP,—PART xx.— 1883.) U5

34 THE VOYAGE OF H.M.S. CHALLENGER.

huxleyi confer upon this beautiful species an aspect which in gracefulness is perhaps
not surpassed by any other Plumularian.

The hydrothecee are remarkable from the way in which the orifice lies in a plane
parallel to the axis of the supporting internode, instead of being, as in most cases, nearly
at right angles to it. The internodes are very short, and the hydrothecze are consequently
brought unusually near to one another. The deep serration of the hydrotheca margin
usual in the Statoplean section, here gives place to a shallow crenation, and the very long
curved continuation of the mesial nematophore beyond the orifice contributes still fur-
ther to the singular aspect of the hydrotheca. In the front of the hydrotheca is a
strong parietal fold, having some resemblance to an anterior intrathecal ridge, while the
true intrathecal ridge is nearly obsolete.

The stem and branches, notwithstanding thei slenderness, are polysiphonic, the
accessory tubes ceasing a little before the distal termination of the branches, which then
become monosiphonic for the remainder of their course.

The gonophore can be seen through the walls of the gonangium to be encircled just
below its summit by a wreath of refringent spherules, similar to those to which Kirchen-
pauer first drew attention in the gonophore of his macrorhynchial section of Aglaophenia.
He believed them to be confined to this group, and incorrectly regarded them as ova.’

The phylactocarps are for the most part longer than the hydrocladia, and with the
symmetrical arrangement of their parts are objects of great beauty, while they are full of
interest in the evidence they afford of the extent to which various parts of an organism
may become modified in order to fit them for a change of function.’

Mr. Busk has identified the present species with the Pliumularia hucley: of the
voyage of the “Rattlesnake,” ? and a comparison of the Challenger Hydroid with authentic
specimens from the collection made during that voyage, has enabled me to confirm this
determination.

Dredged at Station 188, September 10, 1874, lat. 9° 59’ S., long. 189° 42’ E.; depth,
28 fathoms; bottom, mud. Also at Station 190, September 12, 1874, lat. 8° 56’S%.,
long. 136° 5’ E.; depth, 49 fathoms ; bottom temperature 23°°9 C; bottom, mud.

Aglaophenia, Lamouroux (in part).

Plumularia, Lamarck, Hist. Nat. des An. sans Vert., 1815.
Aylaophenia, Lamouroux, Hist. des Pol. Coral. flex., 1816.

Aglaophenie macgillivrayi, Busk, sp. (Pls. X. and XX. figs. 4-6).
Plumularia macgillivrayi, Busk, Voyage of the “ Rattlesnake,” vol. 1. p. 400, 1852.
Trophosome.—Colony attaining a height of upwards of fifteen inches ; stem fascicled,

1 Kirchenpauer, loc. cit., Band v., Ueber die Hydroidenfamilie Plumularide, p. 16.
* See general remarks on the morphology of the Phylactocarp, p. 10.
% Busk, Voyage of the “Rattlesnake,” vol. i. p. 395.

REPORT ON THE HYDROIDA. 35

sending off closely-set opposite primary pinne, which are destitute of hydrothecs, but
carry from end to end the proper hydrotheca-bearing pinnee, which are about one-tenth of
an inch in length, alternately disposed, and borne also by the main stem in the intervals of
the primary pinne. Hydrothecw closely approximated, rather deep, with a well-marked
intrathecal ridge, margin entire, sigmoidally curved ; mesial nematophore adnate by its
whole length to the hydrotheea, with its sides parallel in profile, diverging from below
upwards in front view, its distal end terminating close to the margin of the hydrotheca
by a wide orifice, a short distance behind which is a transverse septum-like fold ; lateral
nematophores wide, overtopping the hydrotheca ; hydrothecal internode with strong
obliquely-directed intra-cauline ridges.

Gonosome.—Costze of phylactocarp intimately fused together, so as to form a long
nearly cylindrical, completely closed corbula, whose sides support seven or eight trans-
verse series of slightly elevated ramified ridges, with every branch supporting a wide
cup-shaped nematophore, and with a strong spur-like nematophore at the hase of each
series.

Aglaophenia macgillivray’ presents many features in which it differs from the typical
Aglaophenie. Its doubly pinnate ramification affords in itself a character which contrasts
markedly with the ramification of nearly all the other known species. This character
shows itself in the thick, strongly-fascicled stem being closely set with opposite pinne,
which are themselves destitute of hydrothece, but give support to the proper hydrocladia,
which are disposed in alternate pinne from end to end of the opposite or primary pinne.
Here and there the primary pinnz become developed into long branches, which then re-
peat in all respects the ramification of the stem. The absence of true serration in the
margin of the hydrotheca, and the bithalamic condition conferred on the mesial nemato-
phore by the presence of an imperfect septum, are other important points in which Aglao-
phenia macgillivray: differs from the typical Aglaophenie ; while in the corbula, with its
parietal ramifying ridges, we find a still further distinctive feature.

A comparison of the Plumularidan here described with authentic specimens of Plumu-
larvia macgillivrayi, Busk, brought home by the “ Rattlesnake,”" establishes the identity of
the “Rattlesnake” species with that of the Challenger. Kirchenpauer places it in his
special section or sub-genus of Aglaophenia, to which he gives the name of Pachy-
rhynchia, and which he bases on the supposed excessive width of the mesial nemato-
phore, believing the nematophore to surpass in this respect the hydrotheca to which
it belongs.? I am unable, however, to accept this character as a ground for the establish-
ment of a distinct group, more especially as its reality is not borne out by an examination
of well-preserved specimens, and Kirchenpauer’s figures seem to have been made from
specimens whose had state of preservation rendered them deceptive. The mesial

1 Voyage of H.M.S. “ Rattlesnake,” vol. 1. p. 400.
2 Kirchenpauer, loc. cit., p. 20,

36 THE VOYAGE OF H.M.S. CHALLENGER.

nematophore of Aglaophenia macgilivray, though large, is very far from attaining
the width of the hydrotheea to which it is attached, and does not, either in size or form,
depart so much from the normal condition as to justify us in assuming it as the ground
on which to base a distinct seetion of the phylactocarpal Plumularide (Aglaophenia of
Kirchenpauer in its widest sense) ; and the remaining small number of species which
Kirchenpauer places in his Pachyrhynchia do not seem to afford any stronger grounds than
Aglaophenia macgillivray? for the creation of a separate systematic group. In the long
corbula, with its closely adnate costa and parietal ridges, and in the even margin of the
hydrotheca, more important differences may perhaps be recognised, but still nothing to
demand a separation from the other members of the genus.

A closely allied if not identical form—the Aglaophenia cupressina of Lamouroux, has
been identified by Kirchenpauer with a Plumularian brought by Semper from the Pelew
Islands, where, according to Semper, it is known by a vernacular name suggested by its
stinging properties. Another of the Challenger species (Lytocarpus secundus, see below,
p. 42), likewise brought by Semper from the Pelew Islands, would seem, according to
the report of it given by this zoologist to Kirchenpauer, to be also one of those Hydroids
whose formidable stinging powers cause it to be dreaded by the natives.

Aglaophenia macgillivray attains a size greater than that of any other Ag/aophenia
with which I am acquainted. Though the specimen from which the drawing has been
made had lost a portion of its proximal end, what remains of the colony measures in
height fifteen inches.

Dredged at Zamboanga, Philippines, 30th January 1875, from a depth of 10 fathoms,

Aglaophenia filicula, n. sp. (Pl. XI. figs. 1-6).

Trophosome.—Colony attaining a height of about three ches ; stem monosiphonie,
simple, rooted by a creeping tubular fibre ; hydrocladia about one-fourth of an inch in
leneth, alternate. Hydrothecee deep, thimble-shaped, margin serrated, with the median
tooth slightly longer than the lateral teeth; intrathecal ridge near the base of the
hydrotheca, extending obliquely forwards and upwards ; mesial nematophore adnate to
the walls of the hydrotheca for about three-fourths of their height, and then becoming
free as a beak-like process which scarcely overtops the margin ; lateral nematophores
tubular, overtopping the margin of the hydrotheca.

Gonosome.—Corbule somewhat crescentic, with about seven pairs of costee, which are
adnate to one another by their edges, with a row of tubular denticles at the lines of junc-
tion, and with a spur-like denticle at the proximal end of each row; a single free costa
with dentated edges at the proximal end of the corbula.

Other corbulz having the costze all free occur in the same colony.

The simple stems of Aglaophenia filicula spring from the creeping hydrorhiza, in

REPORT ON THE HYDROIDA. Bi

groups of closely approximated plumes. The mesial nematophore is provided with an
imperfect septum near its distal extremity. The most remarkable fact, however, connected
with the species is the occurrence of two different forms of corbula

a closed and an open
—in the same colony. The closed corbula is rather short, and with its rachis so curved as
to give it a somewhat crescentic form, with the concavity looking downwards. The
curvature of the open corbula is less marked. In the open form the coste are entirely
distinct from one another ; they are oval in outline, each margin set with tubular denticles,
and every costa having a tubular spur-like denticle at its base. On the proximal margin
of every costa in the open corbula, and close to its origin, is a slit-like aperture which leads
into its cavity.

T am unable to assign a meaning to the presence of two different kinds of corbula in
one and the same colony, and I do not know of a similar occurrence in any other species.
That the two kinds of corbula are not different stages in the development of a single form
would appear from their similarity in size, and the apparently mature condition of both,
with their thick chitinous periderm ; nor is it likely that at the time of maturity the closed
corbula had become converted into the very differently formed open one by a process of
dehiscence. Though in none of the open corbule could I find gonangia, it is yet possible
that the difference may indicate a difference of sex. It is also possible that the open form
may be an abnormal and imperfect condition of the corbula, not essential to the species,
or universally occurring in it. With this uncertainty I have deemed it better not to
include the presence of two forms of corbula as an essential character in the diagnosis of
the species.

Aglaophenia filicula is an inhabitant of the deeper sea zones, having been dredged
along with Aglaophenia acacia, at Station 75, July 2, 1873, lat. 38° 37’ N., long. 28°
30’ W.; depth, 450 fathoms ; bottom, sandy.

Aglaophenia attenuata, n. sp. (Pl. XI. figs. 7-9).

Trophosome.—Colony attaining a height of about two inches ; stem slender, monosi-
phonic, slightly and irregularly branched ; hydrocladia very short, scarcely exceeding one-
twentieth of an inch in length, alternate. Hydrothecze closely approximate, deep, margin
deeply dentate, with the mesial tooth bifid, anterior wall depressed just below the margin ;
intrathecal ridge well marked, extending transversely across the hydrotheca, at the junction
of the lower and middle third of its walls ; mesial nematophore stout, adnate to the walls
of the hydrotheca for somewhat more than half their height, and then extending asa
short, thick, free beak, which does not reach the margin of the hydrotheea ; lateral nemato-
phores stout, reaching the level of the hydrotheca margin.

Gonosome.—Corbula open, with about seven pairs of costa, which are quite distinct
from one another, and carry a row of tubular denticles on each margin ; rachis with a
spur-like denticle at the base of each costa,

38 THE VOYAGE OF H.M.S. CHALLENGER.

Aglaophenia attenuata is a small and delicate species.. The anterior bifid tooth of
the hydrotheea and the open corbula afford good diagnostic characters. The spur-
like nematophores at the base of the cost are well developed.

A comparison of the open corbula of Aglaophenia attenuata with the proper Lytocarpal
phylactocarp, as, for example, that of Lytocarpus myriophyllum, or of Lytocarpus racemi-
ferus, and Acanthocladium huxleyc of the present Report will show that the mere fact of
the coste not being adnate by their edges affords no sufficient ground for generic
separation from Aglaophenia, more especially as in one species at least (Aglaophenia
filicula, see p. 36) closed and open corbulz are borne by the same colony ; in Aglaophenia,
however, the cost of the corbula, whether open or closed, are always more or less in the
form of flat serrated leaflets, without hydrothece: or other appendages; while in such
open forms of phylactocarp as occur in the genera Lytocarpus and Acanthocladium the
coste are either long, curved, rod-like or sabre-shaped appendages, each carrying a
hydrotheca, or are in the form of a series of strong spines without hydrotheca, or are
simply replaced by a series of large nematophores.

Dredged in Simon’s Bay, Cape of Good Hope ; depth, 10-20 fathoms.

Aglaophenia acacia, n. sp. (PI. XII. figs. 1-4).

Trophosome.—Colony attaining a height of about six imches ; stem monosiphonic,
pinnately branched, branches opposite or sub-opposite, rather distant, carrying the hydro-
eladia, which are about two-tenths of an inch in length, and are also borne by the main
stem in the intervals of the branches. Hydrothecze deep, with deeply serrated margin.
intrathecal ridge very short, situated just above the fundus of the hydrotheca ; mesial
nematophore adnate to the wall of the hydrotheca for about one-half their height, and
then terminating as a free short spine which does not reach the level of the hydrotheea
margin ; lateral nematophores stout, slightly overtopping the margin.

Gonosome.—Corbule rather short and deep, with about six pairs of closely adnate
costee.

The habit of Aglaophenia acacia is somewhat loose and spreading. The main stems
continue unbranched for four or five inches from the root, and then give off opposite or
nearly opposite branches, which confer on the species a very distinctive aspect. The dis-
position of the primary branches is truly pinnate, while these again carry the pinnately
disposed hydrocladia. The ramification is thus properly bipinnate, though the distances
between the primary branches and between the hydrothecal ramuli give to it an aspect
very different from that of Aglaophenia macgillivrayi, and of other bipinnate Plumu-
lavide with their closely approximated branches and hydrocladia.

Aglaophenia acacia is a deep-water species, having been dredged along with
Aglaophenia filicula, at Station 75, July 2, 1873, lat. 38° 37’ N., long. 28° 30’ W.;
depth, 450 fathoms ; bottom, sandy.

REPORT ON THE HYDROIDA. 39

Aglaophenia calamus, n. sp. (Pl. XI. figs. 5-8).

Trophosome.—Colony attaining a height of about five inches; stem monosiphonic,
simple, or with a few branches springing from its anterior aspect ; hydrocladia rather
close, about two-tenths of an inch in length. Hydrothece with the margin deeply
serrated ; intrathecal ridge short, near the floor of the hydrotheca ; mesial nematophore
adnate to the walls of the hydrotheca for about half their height, and then continued as a
short spur-like process, which does not reach the level of the hydrotheca margin ; lateral
nematophores somewhat flask-shaped, slightly overtopping the margin.

Gonosome.—Corbula rather long, cylindrical, with about seven pairs of adnate coste,
each costa carrying four or five tubular denticles, and with a spur-like denticle at its base.

Aglaophenia calamus shows no divergence from the typical Aglaophene. It is a
species with rather close-set hydrocladia, and with a tendency to send off short branches
from the anterior side of the plume.

Dredged off Bahia, from a depth of 10 to 20 fathoms.

Aglaophenia courctata, n. sp. (PI. XIX. figs. 7-9).

Trophosome.—Hydrophyton attaining a height of upwards of six inches; stem
fascicled, sending off alternate rather distant branches, along which the hydrocladia are
disposed in alternate pinne, which scarcely attain a length of two-tenths of an inch.
Hydrothecie closely approximated, deep, with the margin crenate, and with a prominent
tooth in front ; mesial nematophore strong, adnate to the hydrotheca walls for about two-
thirds of the height of the walls, and thence continued as a short free process, which does
not reach the level of the hydrotheca margin, and with a wide emarginate orifice; lateral
nematophores thick, tubular, not overtopping the hydrotheca.

Gonosome not known.

The hydrothece of the present species are so closely approximated that the lower end
ofeach is included in the orifice of that which lies at its proximal end. They are
unusually deep, and the margin, instead of presenting the ordinary dentate condition, is
merely crenate, with an anterior mesial point in the form of a sharp tooth. The branches
which support the hydrocladia are divided by oblique joints into a series of wedge-
shaped internodes, each internode sending off a single hydrocladium. ‘The main stem is
strongly fascicled, and the nature of the communication between its component tubes
may be easily seen. These communicate with one another by very short lateral offsets,
each tube emitting numerous such offsets, whose ends meet those of corresponding offsets
from the neighbouring tubes (fig. 1, p. 5).

No part of the gonosome was present in the specimen, and there is perhaps no better
veason for assigning it to Aglaophenia than to other genera of Statoplean Plumularide.

40 THE VOYAGE OF H.M.S. CHALLENGER.

Aglaophenia, however, being the longest-established and the largest of the Statoplean
genera, may, in the absence of any strong reason to the contrary, be made to receive
it until the discovery of the gonosome shall decide its true generic allocation.

The specimen is fragmentary, the hydrorhizal extremity beime absent.

Dredged off Zamboanga, Philippines, January 30, 1875, from a depth of 10 fathoms.

Lytocarpus, Kirchenpauer.

Aglaophenia (section Lytocarpia), Kirchenpauer, Abhandl. aus dem Gebiete der Naturwiss. yon
dem naturwiss. Verein in Hamburg, Band y. 1872.

Generic Coaracter. TZ'rophosome.—Stem doubly or singly pinnate. Hydrothecze
with serrated or undulated margin, and with the mesial nematophore opening externally
by one or two orifices.

Gonosome.—Phylactocarps always open, consisting of modified hydrocladia which
never form corbule.

Kirchenpauer has given the name of Lytocarpia to a group of phylactocarpal Plumu-
laridee, which he regards as a subordinate section or sub-genus of A glaophenia, while
he takes as a type of the section the Aglaophenia myriophyllum, Linn.’ The forms thus
separated possess very definite characters, and I believe it will be better to regard them
as constituting a true genus of equal value with Aglaophenia. As such I have here
united a number of Challenger species, which I believe may be properly associated with
those brought together by Kirehenpauer in his section Lytocarpia. Ihave found it,
however, necessary to modify, to a certain extent, Kirchenpauer’s definition, and have
changed the termination of the name so as to bring it more into accordance with the
usual form of generic designations.

The Plunularide belonging to the genus Lytocarpus, while their trophosomes rarely
differ from those of the Aglaophenia, have very differently formed gonosomes. In both
Aglaophenia and Lytocarpus the phylactocarp is a modified hydrocladium. In
Aglaophenia the modification results in the formation of two series of flat leaflets, which
almost always become intimately united by their edges, so as to form a closed corbula in
which the gonangia are included, or, if not actually united, still lie so close to one
another that the corbula thus produced forms a sort of cage in which the gonangia are
contained exactly as in the closed form. In Lytocarpus, on the other hand, true
corbule do not occur, and the leaflets of the latter are replaced by more or less cylin-
drical or sabre-shaped or spine-like appendages, which are never united to one another so
as to form a closed chamber,

’ Kirchenpauer, loc. cit. p. 20.

--.- al"

REPORT ON THE HYDROIDA. 41

Lytocarpus racemiferus, n. sp. (Pl. XH).

Trophosome.—Colony attaining the height of about twelve inches ; stem fascicled,
much and irregularly branched, main branches all directed towards one side of the stem ;
hydrocladia alternate, scarcely exceeding one-tenth of an inch in length. Hydrothecz
rather deep, margin serrated, teeth blunt ; intrathecal ridge well marked, situated near
the fundus of the hydrotheca; mesial nematophore adnate to the walls of the
hydrotheca for nearly their entire height, and then continued as a short, blunt beak,
which scarcely overtops the hydrotheca and has both a terminal and a lateral orifice ;
lateral nematophores slightly overtopping the hydrotheca.

Gonosome.—Phylactocarps in the form of long racemes, laden with gonangia, spring-
ing from certain branches of the trophosome at points near the origin of the branches
from the stem, and there taking the places of the proximal four or six hydrocladia, con-
sisting of a series of internodes having every internode provided with one median and two
lateral spines, each of the proximal five to eight internodes carrying also an ovate pedun-
culated gonangium.

Lytocarpus racemiferus is an exceedingly beautiful species. The direction of the
principal branches from one side only of the main stem give it a habit not usual among
the Plumularide. The phylactocarps, with their pedunculated gonangia, form elegant
racemes, grouped near the proximal ends of the branches, where they replace the
hydrocladia of this part of the branch. Towards its distal end the branch carries the
ordinary unmodified hydrocladia, which are continued to its extremity.

The phylactocarps are, in the present species, of much morphological significance, and
must be viewed as hydrocladia modified by the suppression of the hydrothece, whose
places are taken towards the proximal end of the phylactocarp by the gonangia, and
whose mesial and lateral nematophores have undergone but little change, and are
represented by the three spines carried by each internode. These spines retain their
essential character as nematophores, and are each provided with a terminal oblique
orifice. Several of the more distal internodes are destitute of gonangia and carry only
the spines.

The gonangia are supported on rather long peduncles, which spring from between
the bases of the two lateral spines, and are subtended by the mesial spine. The
gonophore occupies the centre of the gonangium, from whose walls it is separated by a
clear space, across which may be seen a wreath of highly refringent spherules, by which
the summit of the gonophore is encircled. The sex could not be determined with
certainty.

Dredged off Bahia. Depth 10-20 fathoms.

(zooL, CHALL. EXP.—PART xx.—1883.) U6

42 THE VOYAGE OF H.M.S. CHALLENGER.

Lytocarpus secundus, Kirchen. (Pl. XTV.).

Aglaophenia (section Lytocarpia) secunda, Kirchenpauer, Abhandl. aus dem Gebiete der Natur-
wiss. von dem naturwiss, Verein in Hamburg, Band v. 1872.

Lrophosome.—Colony attaining a height of more than two and a half feet; main stem

3
fascicled, rooted by an entangled mass of fibres, and emitting, along nearly its entire length,
short branches which carry the hydrocladia, and which, though regularly disposed in alter-
nate pinne, are all directed towards the same side of the stem; hydrocladia: about two-
tenths of an inch in length. Hydrothecee rather deep, with crenate margin ; hydrothecal
ridge short and broad, situated near the base of the hydrotheca; mesial nematophore adnate
to the hydrotheca walls for about two-thirds of the height of the walls, and terminating
as a short, free, blunt spine, which does not reach the level of the hydrotheca margin ;
lateral nematophores thick, spout-shaped processes not overtopping the hydrotheca.

Gonosome.—Phylactocarps replacing the hydrocladia at short intervals along the
hydrocladia-bearing branches, each consisting of a jointed rachis, supporting on every
alternate internode a long curved spine, which carries from its base to its apex a double
series of wide cup-shaped nematophores, similar nematophores being also borne by the
rachis.

No gonangia were present in the specimens.

Lytocarpus secundus is a remarkable and beautiful Hydroid, rendered very striking by
‘its large size, and by its regularly disposed primary branches. These are each about
two inches in length, and though at their origin given off as pinne from opposite sides of
the stem, become all directed towards one side, thus giving a secund character to the
ramification. In some of the larger specimens a few branches are given off irregularly
towards the base of the stem.

Another very striking feature is found in the curious comb-like phylactocarps. These
are shorter than the hydrocladia, generally about half their length, and their rachis, like
that of the hydrocladia, consists of a consecutive series of nearly equal internodes, which
in the phylactocarp are about eighteen or twenty in number. From the same side of
every alternate internode there is sent off a short thick process which supports the long
shghtly curved spine, the spines thus carried in a single series along the rachis giving to
the phylactocarp its resemblance to a comb. Large regularly disposed cup-shaped
nematophores are arranged from the base to the apex of the spine in two alternate or
sub-opposite series. The spine is itself hollow, with a terminal orifice. Nematophores
entirely similar to those of the spine are scattered over the rachis.

Though no gonangia were developed in the specimens, I take it for granted that the
comb-like organs are true phylactocarps. The spine-like appendages (the teeth of the
comb) are probably the representatives of the mesial nematophores of suppressed
hydrothece.

REPORT ON THE HYDROIDA. 43

In all the specimens examined the phylactocarps were enveloped in a glairy mass,
insoluble in boiling water, but completely soluble in a solution of caustic potash. I have
no doubt of this being the remains of the protoplasmic contents of the nematophores, and
that in the living state it had been emitted as pseudopodial outflows from the cup-shaped
nematophores here so largely developed.

I believe that the present species must be identified with the Aglaophenia (Lyto-
carpia) secunda of Kirchenpauer,! though in some points, especially in the form of the
hydrotheca and of the comb-like phylactocarps, it can scarcely be brought into complete
accordance with Kirchenpauer’s figures. Kirehenpauer’s specimens were obtained in the
South Sea, the China Sea, and the Pelew Islands. From the last-named locality they
were brought by Semper, who, according to Kirchenpauer, regarded the species as one of
those so much dreaded by the natives on account of its stinging properties.

The limits of the plate would not allow a figure to be given of more than a portion of
the entire Hydroid. The Challenger collection contains a specimen which is more than
two and a half feet in length.

Dredged off Zamboanga, Philippines, 30th January 1875, from a depth of 10 fathoms.

Lytocarpus spectabilis, n. sp. (Pl. XV.).

Trophosome.—Colony attaining a height of five inches; main stem strongly fascicled
sub-dichotomously branched, the branches closely set with opposite primary pinne, which
are fascicled at their origin, and destitute of hydrothee, but which carry the alternately
disposed hydrocladial pinnze ; hydrocladia about one-tenth of an inch in length, borne
also by the main stem in the intervals of the primary pinne. Hydrothece wide,
with undulated margin, an anterior parietal fold, and a very short intrathecal ridge ;
mesial nematophore thick, adnate to the hydrotheea walls for somewhat more than half
their height, and then continued as a strong, free, spine-like process, which shiehtly
overtops the hydrotheca margin, and has a lateral as well as a terminal aperture ; lateral
nematophores spine-like, conical, overtopping the hydrotheca.

Gonosome.—Phylactocarps given off at intervals among the hydrocladia, each replac-
ing a hydrocladium, and consisting of a jointed rachis composed of some eight or nine
internodes, the proximal internode carrying an ordinary hydrotheca, and each of the
following internodes sending off two opposite, strong, conical spine-like processes, each
with a terminal and a lateral orifice. Gonangium nearly sessile, borne by the modified
second internode of the rachis.

Lytocarpus spectabilis is a beautiful bipinnate form, and presents in its details several
features of interest. The margin of the hydrotheca, instead of presenting the serrated
condition usual among the phylactocarpal Plumularide, is merely sinuous, while the

1 Kirchenpauer, oz, cit., p. 35, pls. iii. fig. 1.

44 THE VOYAGE OF H.M.S. CHALLENGER.

anterior fold in its walls confers on the hydrotheca an aspeet which, though not confined
to the present species, is by no means common, Besides its terminal orifice, the mesial
nematophore is provided with a very distinct lateral orifice, close to the point at which
it ceases to be adnate to the hydrotheca.

In the specimen from which the drawings in the plate had been made, no gonangia
were developed on the phylactocarps. The collection, however, contains another specimen
in which they are present, and here they were always found singly on the inter-

Fic. 2.—Phylactocarp of Lytocarpus spectadilis.

a. Proximal internode carrying a hydrotheca.

b. Second internode carrying a gonangium.

c. Representative of the mesial nematophore of this internode.
d. Representative of lateral nematophore,

e. Continuation of the phylactocarp beyond the gonangium,-hearing internode.

J, f. Representatives of the lateral nematophores belonging to the internodes of this continuation,
g. Gonangium.

h. Gonophore.

node which immediately succeeded the proximal or hydrotheca-bearing internode of the
rachis. The phylactocarps which thus carried gonangia had also undergone a peculiar
modification, which consisted partly in an enlargement both in length and width of
the gonangium-bearing internode, the solitary gonangium being borne by a rounded
prominence which lay between the two lateral spines of the internode, while in
this internode there also existed a small mesial spine, by which the gonangium was sub-
tended, and which did not exist in the others, Further, the whole of the more

C', ae

REPORT ON THE HYDROIDA. 45

distal portion of the phylactocarp was curved over the gonangium and its supporting
internode, while its lateral spines were all directed backwards away from the concavity of
the curve.

The morphological significance of the phylactocarp is here sufficiently obvious. There
can be no hesitation in recognising in it a modified hydrocladium, in which all the hydro-
thecse, except that borne by the proximal internode, have been suppressed. It is algo
evident that the pair of lateral spines carried by every other internode represents the
lateral nematophores of the suppressed hydrotheca. Except on the proximal or hydro-
theea-bearing internode, and on that on which a gonangium is developed, no representative
of the mesial nematophore is to be found. On the gonangium-bearing internode, how-
ever, a mesial spine is carried by the front of the internode, at a short distance behind the
gonangium, and this plainly represents the mesial nematophore of the suppressed hydro-
theca. The gonangium here takes precisely the place which would have been occupied
by a hydrotheca had this been developed.

It may be a question whether the phylactocarps described above, which when
examined were found destitute of gonangia, are provided with gonangia at other times, or
whether they are really sterile ramuli, with some other physiological significance ; at all
events, the difference between them and those on which gonangia were present is very
remarkable, and it is difficult to see how, after they have attained the form described, they
could undergo such modification as would convert them into the fertile phylactocarp. The
two forms, however, may be of different sexes, and he both equally destined to carry
gonangia.

Lytocarpus spectabilis comes near to Aglaophenia rostrata of Kirchenpauer, a species
which Kirchenpauer, who has not seen its gonosome, places in his section Macrorhynchia.
The present species, however, is a much stronger form, and with longer hydrocladia.
The hydrocladia, moreover, are alternate in Lytocarpus spectabilis, while in Aglaophenia
rostrata they are described as opposite.

Dredged at Zamboanga, Philippines, 30th January 1875, from a depth of 10 fathoms ;
also at Station 186, Torres Strait, September 8, 1874; lat. 10° 30’ S., long. 142° 18’ E;
depth, 8 fathoms; bottom, coral sand.

Lytocarpus longicornis, Busk, sp. (Pl. XIX. figs. 4-6).
Plumularia longicornis, Busk, Voyage of the “ Rattlesnake,” vol. 1. p. 399, 1852.
Trophosome.—Colony attaining a height of about three inches ; stem fascicled, irregu-
larly branched, supporting closely set pinnately arranged alternate monosiphonic ramuli,
which are themselves destitute of hydrothece, but give off all along their length the very
short hydrothec-bearing ramuli, which are close set, alternate, about one-twentieth of

46 THE VOYAGE OF H.M.S. CHALLENGER.

an inch in length, and though pinnate at their origin, are all directed unilaterally towards
the distal ends of the main stems. Hydrothece deep, flask-shaped, with a deep antero—
posterior constriction just below the margin ; margin entire, directed forwards ; mesial
nematophore adnate to the hydrotheca wall for nearly half the height of the wall, and
then continued for about the same distance as a free beak-like process, which is provided
with a lateral as well as a terminal orifice ; lateral nematophores in the form of long
tubular cylindrical processes, which project far beyond the margin of the hydrotheca,

Gonosome not known.

The type of form presented by the hydrotheca of the present species is very remark-
able. The deep antero-posterior constriction, the nearly vertical direction of the hydrotheca
mouth, with its even margin, so exceptional among the Statoplean Plumularidee, and the
long cylindrical lateral nematophores which project like a pair of ears over the margin,
confer on it an aspect singular and strikmg. The constriction below the hydrotheca
mouth is entirely confined to the antero-posterior direction, so that though very striking
in profile, it is not apparent in a front view of the hydrotheca.

Fic, 3. Origin of a primary pinna in Lytocarpus longicornis, showing the splice-like joint
near the proximal end of the pinna.

a, Main stem.

4, Proximal portion of pinna.

ce, Distal portion. The bases of the secondary pinne or hydrocladia are seen with a secund disposition, along
the length of the primary pinne.

d, Splice-like joint separating the proximal from the distal portion of the primary pinna, and filled with
a colourless chitin,

The doubly pinnate ramification of the colony, with the unilateral direction of the very
short hydrocladia, afford other striking characters. The hydrocladia are carried each on
the summit of a strong process of the primary pinne, and being all directed towards one
side of these, their really pinnate disposition may be easily overlooked. The basal
process on which each stands has on its inner side a tubular nematophore.

The primary pinnze, or those which being themselves destitute of hydrothece: support

Ne

REPORT ON THE HYDROIDA. 47

the hydrocladia, are alternate, a very unusual condition in the bipinnate Plumularida, in
which the primary pinnee are almost always opposite.

Each primary pinna is supported on’ a short process of the stem, and its proximal end
is separated from the remainder of the pinna by a very oblique joint, and forms an acute
wedge-shaped segment, on which the distal portion is, as it were, spliced (see woodcut).
The joint is occupied by a colourless chitin, and when viewed in profile appears as a broad
transparent line, which strongly contrasts with the opaque brown periderm of the rest of
the pinna. The curious splice-like joint thus formed is very striking and characteristic.

Among the Plumularide described and figured by Kirchenpauer,' are three—Aglao-
phenia philippine, Aglaophenia urens, and one which he believes he can identify with the
Plumularia longicornis of Busk. The hydrothecz of all these resemble in many points
those of the present species, though the habit of the colonies is entirely different. In two
of them, Aglaophenia philippina and Aglaophenia wrens, he has observed the gonosome.

Kirchenpauer refers them all to Aglaophenia in the wide sense in which he would
understand this genus, and places them in a subordinate section or sub-genus of Aglao-
phenia, to which he gives the name of Macrorhynchia. The group Macrorhynchia,
however, as defined by Kirchenpauer, can scarcely be accepted, for there may be found
Statoplean Plumularidee which agree in having the long two-apertured mesial nematophore
on which the group has been founded, and whose gonosomes are yet so different as to
render it impossible to associate them in the same genus. Indeed, the form of gonosome
which Kirchenpauer assigns to his Macrorhynchia may well be referred to the type which
characterises his Lytocarpia.

The absence of gonosome in the specimens obtained by the Challenger renders it
impossible to assign the present species with certainty to a definite genus, but the close
resemblance of its hydrothecxe to those of the three species just mentioned, in two of
which the gonosome has been observed, will perhaps justify us in giving it a place in the
genus Lytocarpus,—a position, however, which, until its gonosome has been examined,
must have a purely provisional value.

Mr. Busk’s specimens of his Plumularia longicoriis were obtained during the expedi-
tion of the “ Rattlesnake,”? and the species defined in the account given of the Hydroids
brought home by that expedition, From a comparison of authentic specimens in Mr.
Busk’s possession, with the Lytocarpus longicornis of the present Report, I have
satisfied myself of the specific identity of the two forms.

Dredged at Zamboanga, Philippines, January 30, 1875, from a depth of 10 fathoms.

1 Kirchenpauer, loc. cit., pp. 45-47.
2 Busk, Voyage of the “ Rattlesnake,” vol. i. p. 399.

48 THE VOYAGE OF H.M.S. CHALLENGER.

Streptocaulus, nov. gen.

Name from orperros, twisted, and xavAds, a stem, in allusion to the torsion of the stem round its
axis.

Generic Coaracter. Trophosome.—Hydrocladia disposed in a continuous spiral
round the stem. Hydrothecee with entire margin. Mesial nematophore not adnate to
the walls of the hydrotheea.

(ronosome not known.

The species on which the genus Streptocaulus has heen founded is rendered very
striking by the spiral instead of pinnate disposition of its hydrocladia. Even here,
however, we may regard the hydrocladia as having primarily a semi-pinnate arrangement,
or as being confined to one side of the stem, while a torsion of the stem round its axis—
the proximal end remaining fixed—causes the hydrocladia to fall into a continuous spiral.
So remarkable a form of ramification may well be assumed as affording a character of
generic value. ‘The absence of serration in the margin of the hydrotheca, and still more
the detachment of the mesial nematophore: from the hydrotheca, are also characters
very unusual among the Statoplean Plumularide.

Streptocaulus pulcherrimus, nu. sp. (Pl. XVI. figs. 1-8).

Trophosome.—Colony attaining a height of about nine inches; stem simple, fascicled,
wavy; hydrocladia nearly an inch in leneth, occupying about the distal half of the stem.
Hydrothecee deep, thimble-shaped, margin with a single tooth-like extension in front ;
mesial nematophore in the form of a free conical spine, with a terminal and a lateral
aperture, springing from a point of the hydrothecal internode immediately below the
hydrotheca ; lateral nematophores pyriform, overtopping the hydrotheca.

The habit of this beautiful Hydroid is very different from that of every other known
species. Among Statoplean forms it is the only species as yet discovered in which the
disposition of the hydrocladia is not strictly pinnate.

Dredged in Porto Praya, St Jago, from a depth of 100 fathoms.

Diplocheilus, nov. gen.

Nume from durAvos, double, and xetAos, a lip, in allusion to the duplicature of the hydrotheca
margin,

Generic Cuaracter. Trophosome.—Hydrotheca with a duplicature of its walls forming
an external calycine envelope, which surrounds the hydrotheca for some distance behind
the orifice. Mesial nematophore in the form of a shield-like process not adnate to the
hydrotheca ; lateral nematophores absent.

REPORT ON THE HYDROIDA. 49

Gonosome not known.

In the external calyx-like duplicature of the hydrotheca walls of the remarkable
Plumularian on which the genus Diplocheilus has been founded, we have a character
which is absolutely unique among known Plumularians. A scarcely less exceptional
character is found in the absence of lateral nematophores, and in the reduction of the
mesial nematophore to a sessile, shield-like process unconnected with the hydrotheca,

Diplocheilus mirabilis, n. sp. (Pl. VIII. figs. 4-7).

Trophosome.—Colony attaining a height of two or three inches, sparingly branched ;
stem monosiphonic, divided into internodes by oblique joints; hydrocladia about two-
tenths of an inch in length, having their internodes separated by very oblique joints.
Hydrothecee widening from below upwards, and with the margin everted; mesial
nematophore very short and wide, forming a concave shield-like process, with a central
perforation at a short distance below the hydrotheca.

Gonosome not known.

Diplocheilus mirabilis presents unmistakable points of affinity with both Eleuthero-
plean and Statoplean Plumularidz. ‘To the Statoplean forms it is connected by its fixed
nematophores, and this character is presented not only by the mesial nematophore of the
hydrothecal internode, but by certain cauline nematophores which are developed on the
internodes of the stem. To the Eleutheroplea it shows an affinity by the non-serrated
margin of its hydrotheca, and by the very oblique joints which separate the internodes
of the hydrocladia, a character which specially recalls a similar condition in the Catharina
eroup of the Eleutheroplea.

Its position among the Statoplean rather than among the Eleutheroplean Plumularidee
must be regarded as decided by the entire absence of moveable nematophores.

Diplocheilus mirabilis—the only known species of its genus—is represented in the
collection only by a fragmentary specimen.

Dredged at Station 162, April 2, 1874, off Moncceur Island, Bass Strait; depth,
38-40 fathoms ; bottom, sandy.

Cladocarpus, Allm.
Cladocarpus, Allman, Trans. Zool. Soe. Lond., vol. viii., 1873.

Generic Cuaracter. Zvrophosome.—A simple or branched hydrosoma, with pinnately
disposed hydrocladia.

Gonosome.—Gonangia not included in corbule, or protected by any other form of
modified hydrocladium, but borne on the sides or at the base of special protective branches,

which are appendages of the hydrocladia,
(ZOOL. CHALL, EXP.—PART xx.—1883.) LUE 7;

50 : THE VOYAGE OF H.M.S. CHALLENGER.

The genus Cladocarpus was founded for a Hydroid obtained in the eastern part of
the North Atlantic, during one of the expeditions of H.M.S. ‘ Porcupine.”? The same
species also occurs in the collection of the Challenger. The essential characters of the
genus are found in the nature of the phylactocarp, which differs from that of every other
phylactocarpal Plumularidan in the fact of its not being a transformed hydrocladium, but
a special appendage which springs from the hydrocladium. The hydrocladium itself has
undergone no essential modification, the greatest change which in any case takes place
consists in a greater or less diminution of its length, caused by a reduction in the number
of its internodes and hydrothecee.

In all the species of Cladocarpus at present known, the phylactocarps are twig-like
appendages, more or less ramified, destitute of hydrothece, but richly provided with more
or less modified nematophores. In every instance known they spring from a hydrocladium
immediately behind its first or proximal hydrotheca, and the gonangia they are destined
to protect are borne either by the phylactocarp itself or by the common stem close to the
origin of the hydrocladium from which the phylactocarp springs.

Besides Cladocarpus jformosus, the original species of the ‘ Porcupine,” the
Challenger collection contains another fine species. Three other species of the genus are
among the Hydroids dredged during the exploration of the Gulf Stream by the United
States Coast Survey,’ while to the same genus I must refer a Plumularidan dredged
by G. O. Sars in the North Atlantic, and described by him under the name of

3

Aglaophenia bicuspis.’ They appear to be all inhabitants of deep water.

Cladocarpus pectiniferus, n. sp. (Pl. XVIT.).

Trophosome.—Colony attaining a height of about six inches ; stem slender, monosi-
phonic, simple, springing from a tuft of tubular filaments ; hydrocladia alternate, distant,
attaining the leneth of an inch. Hydrothecee distant, deep, narrow, nearly cylindrical,
with entire margin, and destitute of intrathecal ridge ; mesial nematophore small, quite
detached from the hydrotheca; lateral nematophores cylindrical, overtopping the
hydrotheca.

Gonosome.—Phylactocarp springing from the proximal internode of the hydrothecal
ramulus, and consisting of a very short stem, which immediately divides into two jointed
and pectinated branches which carry the gonangia on their sides,

The present species is closely allied to Cladocarpus dolichotheca and Cladocarpus
ventricosus of the Gulf Stream exploration. From both these species it differs in the
single bifurcation and pectinated branches of the phylactocarp, and in the fact that the

1 Report on the Hydroida collected during the Expeditions of H.M.S. “ Porcupine.” Trans. Zool. Soc. Lond., 1873,
rol. vill. part 8.

* Hydroids of the Gulf Stream, p. 49, pls, xxx,-xxxiii, 3 G. O. Sars, loc. cit., p. 98, tab. ii. figs. 7-10,

REPORT ON THE HYDROIDA. ol

gonangia are borne on the branches of the phylactocarp instead of being carried at its
base by the stem. From Cladocarpus ventricosus it further differs in the cylindrical
instead of ventricose form of the hydrotheca.

The pectination of the branches of the phylactocarp is due to the presence of
nematophores, which are disposed in two opposite series from the base to the summit of
the branch, and which, instead of remaining in the usual condition of small sessile cups,
have become developed into long cylindrical tubes. In Cladocarpus dolichotheca and
Cladocarpus ventricosus, the nematophores, which are also present on the branches of the
phylactocarp, are disposed in a single series, and retain their normal form.

The hydrocladial internodes of Cladocarpus pectiniferus are provided with numerous
transverse intra-cauline ridges, situated at equal distances from one another. Owing to
the transparency of the chitinous periderm, these are very distinct, and give to the
internode the appearance of being divided into distinct chambers by regular septa—a

character which is very obvious and striking.

The hydrotheca of the internode, from which the phylactocarp springs, is destitute of
mesial nematophore, and the phylactocarp springs not exactly from the mesial line of the
internode, but from a point a little to the side of this, just below the hydrotheca. The
absence of a mesial nematophore, in its normal form, is here not without significance, and
affords grounds for believing that the phylactocarp, notwithstanding its slight displace-
ment, is its homological representative.

Cauline nematophores are borne in asingle series along the front of the stem, and give
to its lower end, where this is destitute of pinne, an appearance easily comparable to that
of some of the single-sided graptolites. Like most deep-water species, Cladocarpus
pectiniferus is distinguished by the delicacy and transparency of its chitinous periderm.

Dredged at Station 76, July 3, 1873, lat. 38° 11’ N., long. 27° 9’ W.; depth, 900
fathoms ; bottom temperature, 4°°2 C. ; bottom, globigerina ooze.

Cladocarpus formosus, Allm, (Pl. XVI. figs. 4, 5).

Cladocarpus formosus, Allman, Trans. Zool. Soc. Lond., vol. viii., 1873.

Trophosome.—Colony attaining a height of about four inches ; stem simple or very
sparingly branched, fascicled below, becoming monosiphonic distally, springing from a
tuft of delicate tubular filaments ; hydrocladia alternate, attaining a length of about one
inch. Hydrothece cylindrical, with crenate margin ; mesial nematophore divided by an
imperfect transverse septum into a proximal and a distal half, adnate for somewhat more
than half its length to the hydrotheca, then becoming free, attaining the level of about
half the height of the hydrotheca, and opening by a wide terminal emarginate orifice ;
lateral nematophores short, cup-shaped, very slightly overtopping the hydrotheca.

Gonosome.—Phylactocarp in the form of a slender branch, which springs from the

52 THE VOYAGE OF H.M.S. CHALLENGER.

proximal internode of a hydrocladium, bifurcating three or four times, and carrying an
ovate, nearly sessile gonangium at the angle of every bifurcation ; branches of the phylac-
toearp set with two series of alternately disposed cup-shaped nematophores.

Cladocarpus formosus was also obtained during one of the expeditions of H.M.S.
‘* Porcupine,” and has been described in the Report on the Hydroids then collected.'| The
specimen in the Challenger collection is a very fine one, and with its long flexile pinnne
and its phylactocarps clustered in a continuous series along their bases, forms a striking
and beautiful object.

The condition of the mesial nematophore of the hydrothecal internode is exceptional.
a proximal or basal portion, which, like the

This nematophore consists of two portions
mesial nematophore, as usually seen, is simply continuous with the internode, and a
distal portion, which is separated from the proximal by a transverse joint.

No mesial nematophore is present on the internode which carries the phylactocarp.
This springs from the internode somewhat out of the mesial line, and just below the
hydrotheca. Cladocarpus formosus thus agrees with Cladocarpus pectiniferus in the
evidence it affords as to the homological significance of the phylactocarp.

Dredged at Station 236, June 5, 1875; lat. 34° 58’ N., long. 139° 30’ E.; depth,
775-420 fathoms; bottom temperature, 2°8 C.; bottom, mud.

Sub-family—S TA TOPLEA.
Section—GyYMNoCARPA.
Halicornaria, Busk, M.S. (in part).

GENERIC CHArActerR. T'rophosome.—Hydrocladia pinnately disposed. Hydrothecee
with mesial and lateral nematophores.

Gonosome.—Gonangia destitute of special protective apparatus.

The genus Halicornaria was instituted by Busk, who included under it all the then
known Plumularian forms whose gonangia were not protected by corbule. It is here
used in a more restricted sense, and is confined to such Plumularide as have their
trophosome constructed on the general plan of Agluophenia, but whose gonosomes never
develop any form of phylactocarpal apparatus.

Halicornaria plumosa, u, sp. (P). XVIUL).

Trophosome.—Colony attaining a height of six inches; stem simple, monosiphonic,
springing at intervals from a creeping ramified fibre ; hydrocladia about half an inch in
length, alternate. Hydrothecee wide, with a deep lateral notch and a strong anterior

? Loc. cit., p. 478, pl. lxviii.

REPORT ON THE HYDROIDA. D9

parietal fold ; intrathecal ridge obsolete ; mesial nematophore adnate to the hydrothecal
walls for the entire height of the walls, and then projected as a strong curved spine for
about the same height ; lateral nematophores wide, conical.

Gonosome not known.

Halicornaria plumosa is a singularly beautiful species. Though it is highly probable
that I have correctly referred it to the genus Halicornaria, this determination cannot,
in the absence of the gonosome, be regarded as otherwise than provisional.

One of its most striking features is seen in the very long mesial nematophore, which
is adnate to the anterior wall of the hydrotheca for its entire height, and is then
continued as a long, curved, horn-like spine for nearly the same distance. The margin
of the hydrotheca, instead of presenting the serrated condition usual in the Statoplean
Plumularidze, is seen, when viewed in profile, to have a deep obliquely-directed notch on
‘ach side, but is otherwise destitute of serration. The deep fold in the anterior walls of
the hydrotheca, though occurring in other species, is also characteristic.

Tn its long mesial nematophore it presents a character in which it would agree with
Kirchenpauer’s Macrorhynchia section or sub-genus of Aglaophenia. For reasons, how-
ever, already mentioned,’ the Macrorhynchia of Kirchenpauer can scarcely be accepted as
a definite group.

The present species appears to come near to the Hulicornaria speciosa of the Gulf
Stream exploration.” In general habit there is a close agreement between the two,
while in both the wide hydrotheea has an anterior parietal fold, and its margin—though
in the Gulf Stream species this does not present the deep lateral notch of Halicornarva
plumosa—is in both destitute of true serration, being in Halicornaria speciosa merely
crenate. The mesial nematophore, however, in Halicornaria speciosa is not continued
beyond the margin of the hydrotheca in the form of the long, curved, beak-like process
seen in Halicornaria plumosa.

That the Gulf Stream species is a true Halicornaria there is no doubt, for the gono-
some was present in the specimens examined, and removed all difficulty as to generic
identification.

Dredged at Station 122, September 10, 1873, off Barra Grande, Brazil, from a depth

of 32 fathoms.

Azygoplon, nov. gen.

Name from afdyos, unpaired, and éhov, a weapon, in allusion to the absence of the lateral
nematophores.
Generic Cuaracter. Trophosome.—Hydrocladia pinnately disposed. Mesial nema-
tophore adnate to the walls of the hydrotheca ; no lateral nematophores.

1 See above, p. 47.
2 Hydroids of Gulf Stream, p, 54, pl. xxxiv.

54 THE VOYAGE OF H.M.S. CHALLENGER.

Gonosome.—Gonangia springing from the stem, and destitute of special protective
apparatus.

The genus Azyyoplon is essentially characterised by the very exceptional condition
of having no lateral nematophores—a condition which, except in Diplocheilus, does not
occur elsewhere among the known genera of Plumularide. So far as is yet known,
Azygoplon is represented by one species only.

Azygoplon vostratum, n. sp. (Pl. XEX. figs. 1-3).

Trophosome.—Colony attaining a height of upwards of three inches ; stem much and
irregularly branched, monosiphonic ; hydrocladia about two-tenths of an inch in length.
Hydrothecee rather shallow, with one strong marginal tooth on each side, and a long
beak-like process in front; mesial nematophore adnate for its entire length to the
anterior wall of the hydrotheca, and then bearing on its summit a free membranous
scoop-shaped appendage.

Gonosome.—Gonangium nearly spherical, narrowed into a short stalk at its point of
attachment to the stem close to the base of a hydrocladium.

This is a very remarkable Hydroid. The form of the hydrotheca is exceptionally
striking, for instead of the serrated margin usual in the Statoplean Plumularidee, this
condition is here replaced by a single strong tooth on each side and a long beak-like
projection of the margin in front. The mesial nematophore

the only one present in the
genus—is divided into two portions by a transverse joint ; the proximal portion is the
proper nematophore, and is, as in the mesial nematophore of other Statoplean forms, a
simple continuous projection of the hydrothecal internode, and is adnate for its entire
length to the anterior walls of the hydrotheca; the distal portion consists of a free
membrane bent into a scoop-shaped form, the concavity of which is turned towards the
hydrotheca and embraces its anterior wall.

The stem is divided into internodes by transverse joints, and every internode gives off
from alternate sides a hydrocladium. The joints by which the internodes of the hydro-
cladia are separated from one another are unusually well marked—a feature in which
Azygoplon rostratum approaches the Eleutheroplean rather than the Statoplean forms.

The specimen had been broken away from its hydrorhizal end, and on this account
no exact assertion can be made of the height which the species may attain.

Azygoplon rostratum comes very near to a species described and figured by Kirchen-
pauer under the name of Aglaophenia avicularis, from specimens brought from Bass
Strait. If it were not for the very different form of the mesial nematophore, I should
have regarded the Challenger species as identical with that of Kirchenpauer.

Dredged at Station 161, April 1, 1874, off the entrance to Port Philp; depth, 38
fathoms ; bottom, sandy. f

OT re My het acts wt

-GHOGRAPHICAL AND BATHYMETRICAL DISTRIBUTION.

We do not yet possess the data necessary for a complete exposition of the geoeraphi-
cal distribution of the Plumularidxe. It may be generally asserted of this group that it
attains its greatest development in the warmer seas of both hemispheres, and that in
tropical and sub-tropical regions it has its maximum in multiplicity of form, in the size
of the colonies, and in individual profusion.

The dredgings of the Challenger and of the United States Exploration of the Gulf
Stream would further seem to point to two centres of maximum development within the
area thus indicated,—an eastern centre, which is situated in the warm seas around the
Philippines and other islands of the East Indian Archipelago, and a western centre,
which will be found in those which lie around the West Indian Islands, and bathe the
eastern shores of Central and Equinoctial America. From these two centres the largest
known Plumularian colonies have been obtained, and we learn, on the authority of
Semper, that the natives of the Philippine Islands regard with dread, in consequence of
their formidable stinging powers, some of the great Plumularians which occur around
their shores. |

These eastern and western centres of Plumularian distribution remind us of the two
great centres in which the Cheiroptera have their maximum development, as scen in the
gigantic bats of both hemispheres,—centres of Cheiropteran distribution which are nearly
coincident with these regions of maximum development in the Plumularidee.

In bathymetrical distribution the Plumularidee present considerable variation.
Among the species described in the present Report some are quite littoral, having been
dredged from depths ranging between 8 and 20 fathoms. The greater number however
of the Challenger species have been obtained from depths between 20 and 150 fathoms,
while the dredge has brought up three species, Aglaophenia filicula, Aglaophenia acacia,
and Polyplumaria pumila, from a depth of 450 fathoms. The striking and beautiful
genus Cladocarpus consists of eminently deep water forms, and of the two species here
described one, Cladocarpus formosus, was obtained in the Japan Seas from a depth
varying between 420 and 775 fathoms—the same species having been dredged by the
“Porcupine ” in the seas lying to the north of Scotland from 167, 560, and 632 fathoms
—while Cladocarpus pectiniferus was dredged by the Challenger off the Azores from 900
fathoms. This last is the greatest depth from which any Plumularidan is known to have

been obtained,

Fig.

PLATE I.

Figs.. 1-4.—Plumularia flabellum.

1.—Natural size.

g. 2.—Portion of a hydrocladium magnified ; lateral view.

Fig. 3.—Same ; front view.
Fig. 4.—Portion of branch, with origin of hydrocladia.

Fig

S

Figs. 5, 6.—Plumularia laa.

e. 5.—Natural size.

. 6.—Portion of hydrocladium giving origin to a secondary bydrotheca-bearing ramu-

lus ; magnified.

Figs. 7, 8.—Plumularia dolochotheca.
7.—Natural size.

8.—Portion of hydrocladium ; magnified.

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7.8 PLUMULARIA DOLICHOTHECA.

|.4 PLUMULARIA FLABELLUM.

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PLATE I.
Figs. 1-4.—Phamulavia insignis.

1.—Natural size.

2.—Portion of hydrocladium, magnified ; lateral view.

3.—Same ; front view.

4.—Portion of branch with immature gonangia.

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‘Figs. 1-4.—Plumularia abietina.

Fig. 1.—Natural size, with young Avicula-like Mollusca attached to the stem and branches.

Fig 2.—Portion of hydrocladium magnified ; lateral view.
Fig. 3.—Same ; front view.

Fig. 4.—Portion of a branch with gonangium.

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PLATE IV.

Figs. 1, 2.—Plumularva stylifera.

o, 1.—Natural size.

. 2.—Portion of a hydrocladium with gonangium ; magnified.

Figs. 3, 4.—Plumularia armata.

a. 3.—Natural size.

. 4.—Portion of stem with hydrocladia and male and female gonangia ; magnified.

Figs. 5, 6.—Antennularia fascicularis.

o. 5.—Natural size.

6.—Portion of stem with hydrocladia and gonangium ; magnified.

Figs. 7, 8.—Polyplumaria pumila.

. 7.—Natural size.

. 8.—Portion of main stem, with two primary pinne and hydrocladia ; magnified. One

of the primary pinnee carries a gonangium, and every hydrocladium bears
an accessory ramulus,

The Voyage of HMS ‘Challenger’ Plumularide.Pl1V

1,2 PLUMULARIA STYLIFERA 3,4 PLUMULARIA ARMATA.
5,6 ANTENNULARIA FASCICULARIS. 7,8 POLYPLUMARIA PUMILA.

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PLATE V.

“evans | ; Figs. 1-4.—Sciurella indivisa.
“a “fe Fig. 1.—Natural size. A

i cane Fig. 2.—Portion of hydrocladium, magnified ; lateral view.
i oi Fig. 3—Same ; front view with gonangia. a

i” | Fig. 4.—Internode of stem with origins of hydrocladia.

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SCIlUREEEA

PLATE VI.

Figs. 1-4.—Acanthella effusa. ‘ ‘.
Fig. 1,—Natural size.

Fig. 2.—Portion of hydrocladium, magnified ; lateral view.

Fig. 3.—Same ; front view. “6 ‘ :
se +e us Fig. 4.—Portion of renee near its distal end, showing the spine-hke appendages eared nm
¥ by every internode, and here replacing the iageeee io

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AGCANTHELLA EFFUSA.

PLATE VII.

ee : Figs. 1-3.—Schizotricha unifureata. aan”

:. y Fig. 1.—-Natural size. Pa. bs :
aa | Fig. 2.—Portion of a hydrocladium, magnified : showing its single bifurcation Sud the
a gonaneia carried by the ramuli. oo
eS Fig. 3.—Variety of same species with bere Reorindia oneal size.

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Figs. 4, 5.—Schizotricha multifurcata. -

¥ ry.
Fig. 4.—Natural size. has
re Fig. 5.—Portion of a hydrocladium, magnified; showing three bifurcations and the

a ' gonangia borne by the ramuli.

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PLATE VIII.

Figs. 1-3.—Heteroplon pluma.

g. 1.—Natural size.

. 2.—Portion of hydrocladium, magnified ; front view.

3.—Portion of stem with hydrocladia ; lateral view.

Figs. 4-7.—Diplocheilus mirabilis.

ig. 4.—Natural size.

5.—Portion of stem with two hydrocladia, magnified ; showing front and back views
of hydrothecee.

Fig. 6.—Internode of a hydrocladium with its hydrotheca ; half profile.

7.—Portion of hydrocladium consisting of two internodes, each with its hydrotheca ;

half profile.

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PLATE IX.
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: a. For magnified details see Plate XX. figs. 13

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For magnified details see Plate 0.6 figs. Ler ey “i f

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PLATE XI.

. : Figs. 16 = Agtnopnense filicula.

¥; Fig. 1.—Natural size. | : |

a ' Fig, 2.—Portion of hydrocladium, magnified ; lateral view.

“y Fig. 3.—Same; front view. ; os

2 Fig. 4.—Corbula, closed form. . (yes 2
Fig. 5.—Corbula, open form. | : oy F

rn Fig. 6.—One of the costze of the open form of corbula, showing the slit-like orifice. ar a
er its base. es N bs aay
a Figs. 7-9.—Aglaophenia attenuata.

, Fig. 7.—Natural size. |

| Fig. 8.—Portion of a hydrocladium ; magnified.

Fig, 9.—Corbula.

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1.6 AGLAOPHENIA FILICULA.

PLATE XII.

Figs. 1-4.—Aglaophenia acacia. me Ae ets 3 ;
Fig. 1.—Natural size. * ’ 7 ae a eo
Fig. 2.—Portion of hydrocladium, magnified ; lateral view. |
Fig. 3.—Same ; front view. | | :
Fig. 4.—Corbula. ie

Figs. 5-8.—Aglaophenia calamus.
Fig. 5.—Natural size.
Fig. peep rion of hydrocladium, magnified ; lateral view.
Fig. 7.—Same ; front view.

Fig. 8—Corbula.

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5-8 AGLAOPHENIA CALAMUS.

1.4 AGLAOPHENIA ACACIA.

PLATE XIII.

Figs. 1-6.—Lytocarpus racemiferus,
Fig. Naser size, at
Fig. 2.—Portion of hydrocladium, magnified ; lateral view.
Fig, 3.—-Same ; front view.
Fig, 4.—A branch with phylactocarps loaded with gonangia.
Fig. 5.—Portion of a phylactocarp still further magnified,

Fig. 6.—Distal end of phylactocarp.

The Voyage of HMS ‘Ch allenger”

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LYTOCARPUS RACEMIFERUS.

a | _ PLATE XIV. ates
ee Figs. 1-5.—Lytocarpus secundus. — os
P 7 “ ' Fig. 1.—Natural size. rip aecen y
- Fig. 2.—Portion of hydrocladium, magnified ; lateral view. aE :
= ‘Be Fig. 3.—Same ; front view. Par, gee! } or 2:
- , a4 : J tacett
, Zo Fig. 4.—Portion of a branch with hydrocladia and phylactocarps. te
: ; ay Fig. 5.—Portion of a phylactocarp, still further magnified.
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LYTOCARPUS SECUNDUS.

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PLATE XY.

Figs. 1-5,—Lytocarpus spectabilis.

Fig. 1.—Natural size, . .

y y
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Fig. 2.—Portion of hydrocladium, magnified ; front view. | :

we Fig. 3.—Same ; lateral view. . ioAs ae i
5 ; as Fig. 4.—Portion of a branch near its distal end where it has become monosiphonie, with.
Sag hydrocladia and phylactocarps. = i
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PLATE XVI.

i ppc Figs. 1-38.—Streptocaulus pulcherrinus. hi i)

u : Fig. 1.—Natural size. :

m Fig. 2.—Portion of hydrocladium, magnified ; lateral view. “

PA eS vee
mari? * Fig. 3.—Same ; front view. Acs
bs Figs. 4, 5.—Cladocarpus formosus. Rt

Fig. 4.—Natural size. ; Jf
Pent Fig. 5.—Portion of stem carrying a hydrocladium with phylactocarp and onangia ;
; magnified, ee: She Pee

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PLATE XVII.

Figs. 1-5.—Cladocarpus pectiniferus.
Fig. 1.—Natural size.

2.—Portion of a colony, taken from near the distal end, with phylactocarps and
gonangia ; magnified.

Fig. 3.—Portion of a hydrocladium, still further magnified ; lateral view. The origin of
a phylactocarp is seen close to its proximal end.

Fig. 4.—Same ; front view.

Fig. 5.—Part of the stem near its proximal end ; showing cauline nematophores arranged
in a single linear series.

The Voyage of HM.S. Challenger”

CLADOCARPUS PECTINIFERUS.

Plurnulapidge.P1. XVII

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PLATE XVI nh
; og | Figs. 1-4,—-Halicornaria plumosa. 5

a

.

- Fig. 1.—Natural size. BY et ke cone
ae Fig. 2.—Portion of stem with hydrocladia ; magnified.
ae ‘ Fig. 3.—Portion of hydrocladium, still further magnified ; lateral view.

one y Fig. 4.—Same ; front view.

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PLATE XIX.

Figs. 1-3—Azygoplon rostratum.
1.—Natural size.
2.—Portion of a hydrocladium, magnified ; lateral view.

3.—Portion of stem with hydrocladia and gonangia ; front view.

Figs. 4-6.—Lytocarpus longicornis.
4.—Natural size.
5.—Portion of hydrocladium ; magnified.

6.—Portion of a primary pinna, with origins of hydrocladia.

Figs. 7-9.—Aglaophenia courctata.
7.—Natural size.
8.—Portion of hydrocladium ; magnified.

9.—Portion of a branch with origins of hydrocladia, showing wedge-shaped inter-
nodes.

The Voyage of HM.S.Challen ger! Plumularidz PLXIX.

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1.3 AZYGOPLON ROSTRATUM. 4.6 LYTOCARPUS LONGICORNIS.
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PLATE XX.

Figs. 1-38.—Acanthocladium huxleyi. Magnified details.

1.—Portion of a phylactocarp with a gonangium. ‘The points from which the other
gonangia had been detached are seen close to the bases of the costee.

. 2.—Portion of a hydrocladium with two hydrothecz ; lateral view.

3.—Distal extremity of a branch, showing the spine-like appendages by which the
hydrocladia are here replaced.

Figs. 4-6.—Aglaophenia macgillivrayt. Magnified details.

e. 4.—Portion of a hydrocladium ; lateral view.

Same ; front view.

e. 6,—Corbula.

yage of HM.S Challenger j

1.3 ACANTHOCLADIUM HUXLEYI.

4_6 AGLAOPHENIA

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