HANSEN, H.J. 1897
The Choniostomatidae, a family o
Crustacea Malacostr

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THE CHONIOSTOMATIDAL

A FAMILY OF COPEPODA,
PARASITES ON CRUSTACEA MALACOSTRACA

BY

Dr. H. J. HANSEN INVERTEBRATE
\ ZOOLOGY
‘Prustaces

UT OA heh be) |

WITH THIRTEEN COPPER PLATES

AT THE EXPENSE OF THE CARLSBERG FUND

We want facts, not inferences, observations,

not theories, for a long time to come.

»Natural Sciences, 1896

COPENHAGEN

ANDR. FRED: HOST & SON, PUBLISHERS

1897

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PTLSON LIBRARY

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THE CHONTOSTOMATI DAL

AP RAMPEYS OF COREE ODA,

PARASITES ON CRUSTACEA MALACOSTRACA

BY

Dr. H. J. HANSEN

WITH THIRTEEN COPPER PLATES ,
AT THE EXPENSE OF THE CARLSBERG FUND
We want facts, not inferences, observations,

not theories, for a long time to come.

»Natural Science«, 1896.

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SBtional Muses

COPENHAGEN

ANDR. FRED. HOST & SON, PUBLISHERS

SEP 0 ¥ 19865

1897

COPENHAGEN — PRINTED BY H. H. THIELE

PREFACE.

his work contains an account of forty-three species of Copepoda, all parasitic on mala-
. Crustacea, and all belonging to the same family. When in 1890 I began
my study of this group, there were published descriptions of only three species, and mention
had been made of a fourth. Two more have been since described and a seventh named,
but not described; so that until now (July 1897) only five species have been reaJly made
known. In the present work I increase this number about nine times, and yet, most
likely, my discoveries only extend to one fifth or one sixth or perhaps a much smaller part
of the species extant. I have been brought to this conclusion by the consideration that no
less than thirty-three of my species have been found exclusively on Crustacea in the
Zoological Museum of the Copenhagen University. What multitudes of these animals are
likely to be discovered, when some day the large foreign museums acquire rich collections
of non-decapod Malacostraca, and when this material is submitted to a thorough research!
On the whole, my studies of late years have given me the impression that of nearly all the
Crustacea living on the bottom of the sea — the Decapods excepted — we only know
from about half down to a very small percentage of existing species. Especially to the
parasitic forms does this apply, and I think one of the most important results of the present
work is to show the wealth of a group, which hitherto has occupied only a very diminutive
place. It may be added that, in the course of the last two years, I have found on the
material brought home from the sea near Iceland and Greenland by the »Ingolf« expedition
several new forms which cannot be included in the present treatise, but which will be
subjected to future examination.
A chance led me to this study. In dissecting a female of Jdothea marina (L.) I
discovered in its marsupium an unknown parasite belonging to the Epicaridea, and further
researches led to the discovery of a number of specimens of this species and of a form

nearly akin to it on Edotia nodulosa (Ky.). Both parasites were afterwards described from

my material by Giard and Bonnier (the genus Clypeoniscus G. and B.). Those authors had
just previously described an Epicarid living as a parasite on Ampelisca diadema Costa.
What I had found on Idotheidse tempted me to go on looking for Epicaridea, so I examined
our Ampeliscidee and found — not these forms, — but several species of Choniostomatidee
as well as another most remarkable parasite, which I described in 1892 under the name of
Rhizorhina Ampelisce H. J. H. Professor Sars has told me (1886) that he had found some
species of Spheronella on Amphipoda. Now, as my own discoveries had called forth my
interest, I began in the Copenhagen Museum an examination of the material of Amphipoda
and later on of the other orders of Malacostraca.

Professor G. O. Sars lent me all his material of this family for my researches, and
he further provided me with newly discovered forms — seven in all, — of which four are
particularly interesting; two of the most remarkable genera, the parasites on Myside, are
owing entirely to him — for all of which I have great pleasure in offering the eminent
naturalist my best thanks. — The Rev. Canon A. M. Norman, F. R. 8., lent me the types
of Aspidoecia Normani Giard and Bonnier, and the Rey. Th. R. R. Stebbing, F. R. S.,
determined for me some Amphipoda from the Mediterranean, the West-Indies, the Cape and
Hong-Kong, for which I beg these gentlemen to accept my thanks.

Last, not least, I wish to express my warm gratitude to the managing Committee
of the Carlsberg Fund for having allowed me a considerable sum to defray the expenses of
the present work.

The English translation from the Danish manuscript is the work of Miss Louise

yon Cossel.

IV.

CONTENTS:

Introductonym Reman koi ciesiertetet ete lase edetereelatel et fere fale farerta testes tote iele) lolol le) -ve >
Corenall GISIOHIGH] WIG: scnvnascooscucds opo000e0ns nono OnoDonoo pouGoRsouGoERaoDd
General Representation of the Family ..................00- ese steer rete neers
A. Structure and Development ..... 0.00.0 c ccc rcs svete teste tenet eee eee
als Ulla) Ita gogo oucocoodouboe Gos cc ce sD be sb oopoueodrosceaneurouDoopdnDod
papal bre wie earerersrsscterevavsistete o everersieiechelcreial sie rs vel nla orelevcie overs iavere crs oholaccloiciinieleyeeKeiluenels
c. The Ovisacs and the Development of the Eggs.............-.+----++-----
Gh, ANne: jie) ILIA os poem goood sobs cnoe nou OU ODD CpeMCCOnOnUGUOOEDOo aE
e. The post-larval Development; the Pupe ...........-- badeentcousoNuouDOms
B. Habitation, Biology and Distribution...........2..cc0es seers eee eset e eee

a. The Place of the Hosts in the System and the Habitation of the Parasites.
lis ANGO ial Sere Oi WING: EGS! o ooconnog 05 soeccssagsouun deo dU od pcHHOEneenaS

CuNumbersotebarasitessonl cache particulary EOStem tree strete) stele islets t-te) 1-1
d. Number of Species of Parasites on the same Species of Host............

e. Number of Species of Hosts of the different Families.................2055
f. Occurrence together with Parasites of other Orders or Classes ............
Gy INOWAEMIMAGN. 5 soososccpaobocasenscbndeH pogHOSSRESooUOOUOOUODU DOU IODUnC
h. The Influence of the Parasites on their Hosts................00:ee cece

i. Geographical and Bathymetrical Distribution of the Family ...............

j. Geographical Distribution of the particular Species relatively to that of their Hosts .........

k. Frequency of the Parasites in Proportion to their Fertility................

CRPAD OEM CLASSTPLCULUON yore ice eis ciel oicle tions ciaesrs stats iste sisted israse ateeiclasyeistaiors/@elievere eis 20s\e.e 6

aml iMitationwands Gharacters Oly them SpeClesis err tertecie teerate stele cttlele stele octets
blimitationsandiGharacterssot they Genera severe circle ajeleiisie eters eile ciel

G CHORAGIERS OF tne Memos sccechooacheoanaoceconcouncdcon oonooegcuUDOS
dublacesotathesMannilveinmthes Sy Stemucys trefoil re itoieeicieteleke lees tcletstetel stelierer=
Deapeniien Or Cana) atl Seees occbecsusagscscsuecsnaesouccconcraaoucocouce
th, SHGROMOAIERE Ws REsaocgcasccdaneg donb Uon Onc oU Nou paoEdcaosonoonsoDdoudGd
lik, LACTOGISIRS We tba goonaoun on cepep os bppoEDoD DOO FONQoUdoUU DOO Dado suDOeC
UTES DE CENORELLC SALE NS KSYjaeete pe tet teltetelatetetotsteetasataoreds\bsteteererey atte tetetey tated terete y-ti el er
Ap Ramana (ON /Neiy MOE os ao oons ocauooueDe d0oosocgpooRME DOO UdOOOSUbOnOS

Dee arasltesmo me UTC aeteteteversyeveveee sts)ereneretenatsietcret=fetskeval ctor ave ayar= ol s(atobay<tayetara) arate) ove

Gs IRIMASIES Ch WEE, <5 onccosdon das sonccoUdausseaceuadHnoonoousoueonodG

ine, Ohara ley dbl8 os onencgesuoadocoadcucdDAooaB OOOO KemNnOOnadIdoodboued
> MOREE. Te Bithy5.0.0000000 soap sunsoncopoSooOH eNO SUaKCOnosUEUEUOIOS dOnOOnC
Vales pi doccian Giardwand mB Onntenerreryrertceiteteiscrtsrioite clorcis ciere cisrereeeleiateesctshsierais

IST EMEHOM OF WAG THEUGS sccccoonponscod0ceonnob ue sabosesb5pDoDEORdO sD COOUGOODROOC

Errata

/

I. INTRODUCTORY REMARKS.

he majority of the species here described I found in examining systematically for this

purpose the collections of the Zoological Museum in Copenhagen. Throughout a number
of years the two directors of the entomological department, the late Professor J.C. Schiodte
and his successor, Inspector Dr. F. Meinert, have taken care not only to acquire as many
species as possible, but — of the smaller forms — also as many individuals as could be
procured, so that of a good many northern Amphipoda, and of a great number of Danish
Amphipoda, Cumacea, etc., the museum possesses hundreds of specimens. This has been of
the greatest use to me in my researches, for while a few of the parasites — at least of
those found on our own material — are met with rather frequently, the greater number are
very rare, and a considerable part so scarce, that only one or two specimens are found on
each hundred of the animals examined. As a matter of course, I have examined numerous
species without finding a single parasite.

Of the following forty-three species only one lives on the outside of its host (Mysida
verze), two occur in the branchial cavity of Cumacea, two in the branchial cavity of Hippolyte ;
all the remaining species are only found in the marsupium of the female of Amphipoda
Gammaridea, Isopoda, Cumacea and Myside vere (or sometimes in young individuals of
Amphipoda on the ventral side of the thorax between the gills). In the Isopoda, the
Myside, and sometimes in the Amphipoda, parasites can be seen by looking through the
plates of the marsupium. In most Amphipoda and in Cumacea the marsupium has to be
submitted to a closer examination; some of the plates have to be lifted up and examined
through a lens; in the small forms even the adult parasites can only be discovered by help
of a simple microscope. Where a closer search of an infested marsupium is required, it is
usually necessary to place the host in a hollow ground glass-plate under water, and to
examine it very carefully twenty or thirty times magnified under a simple microscope, in
order to be able to discover the male animals which are generally 1/:—1/s mm. in length,
as well as the free larve and the pups, and to find out the way in which these minute
animals are hinged.

2

Parasites are not at all easy to deal with; when taken out, everything — except
perhaps tolerably large females and ovisacs — must be kept in glycerine on an object-
glass, for if males, pup, etc. are put in spirit, they are generally difficult to find and to
get out of the tubes. For this use the glycerine must always be strongly diluted with water,
otherwise the animals shrink very much, and the females especially are very apt to lose
their shape. The water is made to evaporate by standing exposed to the air. Neither the
females nor the males nor the animals in any stage of development, can bear the pressure
of a glass-cover, or of part of it, without losing their natural shape. In order to make
drawings of the entire animals or of parts of the females, the following method was employed:
I took very small covers (frequently a middle-sized cover was cut into four parts), and
placed a very thin wooden wedge under the middle of the back edge of the cover, so that
by very carefully pulling the wedge a little, I made the glass touch the animal, or part of
it, just sufficiently to keep it in a certain position; by means of a hair, which was introduced
through the opening, its attitude could easily be changed. In this way I was able after
some practice to manipulate a male of the length of '/smm., so that I could make accurate
illustrations of one specimen seen from below and sideways without damaging it at all.
After use the animal and all the parts that had been examined were placed under a large
elass-cover in the way described above, and the opening was closed with varnish. The
female was always dissected, in order to submit the head and the genital area to a careful
examination. The latter part was treated in the following way: with a sharp and very
small knife I cut through the animal a little above the genital region, after which this part
was placed under a simple microscope which magnified it a hundredfold; the inside of it
was cleaned with a knife, so as to leave only the muscles of the genital apertures and one
or both of the receptacula seminis. I specify this proceeding, which I learned by degrees
through rather troublesome experiences, partly that the reader may judge of the accuracy
of my illustrations, partly to enable future students, who may not possess such ample material,
to conquer the difficulties with comparative ease.

As far as possible, I have everywhere given figures of an adult female, a male and
an oyisac (Sometimes adding one or two pupz) magnified to the same scale, in order to show
the relative size of the two sexes, the ovisacs and eggs. The size of the male compared.
with the female and the ova varies very much in the different species. For the convenience
of the student, and in accordance with earlier statements (1890), I have always figured the
males vertically from the ventral side and laterally from the left-hand side. While in
symmetrically shaped Arthropoda, in dorsal or ventral view, I generally arrange the position
of the legs and figure those on one side to correspond with those on the other, with the
parasites described in the present work I have not ventured to do this. The animals were
often a little crooked on account of a slight pressure, to which they had been exposed in
the marsupium; maxillipeds and legs were found straddling in different directions, and as a |
rule were too small to allow of much alteration in their attitude, without great risk of

3

damage ensuing. I only ventured slight attempts at construction, not being able to calculate
how the details — e. g. legs of males and larvae — would appear, if drawn in a position
differing from the one in which they were found. As a rule [ have figured the aninals
with all the irregularities they presented, and the limbs in the position they happened to
occupy at the time of drawing. Where I had several specimens at my disposal, of course
I chose the one which was most suitable for illustrat on.

I must briefly mention one point in my nomenclature. In 1893 I stated (in » Zool.
Anzeiger«) that the two pairs of limbs which had been formerly named the first and second
pairs of maxillipeds, ought to be regarded as the second pair of maxille and a pair of
maxillipeds. Shortly afterwards Dr. W. Giesbrecht gave very detailed proofs of the same
fact (Mitth. Zool. Stat. Neapel, 11. B.). [I also proposed to introduce the names »maxillule
and »maxilla« (in analogy with the commonly used names »antennule« and »antenne«) for
the two pairs of jaws, and [ shall here avail myself of these short, convenient and very
intelligible names.

In conclusion a few remarks may be offered about the plan of the present work.
For several reasons I have contented myself with representing the external structure of the
adult animals and their post-embryonic development, and I have spent an exceedingly long
time, partly in finding females and eggs, males, larve and pupx, partly in studying the
material I had discovered. The result is that at present scarcely any moderately large
family of genuinely parasitic Copepoda is so well known as the Choniostomatide. I have
found the males of thirty-two of the forty-three species, the larve of twenty-three, the pupe
or other stages of the post-larval development of a pretty considerable number of species.
At the same time I must call attention to the great and numerous gaps in the knowledge
of the metamorphosis of these animals, which vary remarkably according to the different
species. On their embryology I do not enter at all, and their anatomy is almost totally
omitted; I could not have given information of any value unless I had stayed long enough
at the seaside to enable me to collect a large supply of living animals of several species,
but this would have considerably delayed and increased the work, which is rather voluminous
as it is; so, not being able to present an exhaustive study of these topics, I have — contrary
to the habit of numerous authors — only treated what was indispensable to classification
(the genital region and receptacula seminis). Besides, I should advise students not to enter
upon the anatomy of forms so small, difficult and for the most part rare, before having
acquired a thorough autoptical knowledge of representatives of various other families among
parasitic Copepoda.

Il. GENERAL HISTORICAL VIEW.

eee I am obliged to go much into detail in this chapter, not only in order to
Ll give a summary of our previous knowledge and its defects, but also and particularly
in order to throw light on a number of very objectionable postulates, reflections and theories
put forward by Mssrs. A. Giard and J. Bonnier in their two (four) papers. Very short contri-
butions (by G. O. Sars and J. Sparre-Schneider) are mentioned in the special part.

W. Sarensky: Spheronella Leuckarti, ein neuer Schmarotzerkrebs (Archiv fiir Natur
geschichte, 34ter Jahrgang, 1868, p. 301

322. Taf. X). The author has given a very
extensive account of this new genus and species, the first form which was discovered of
this family. He has found females, males, eggs, larve and pups, in fact all stages, and
on the whole his descriptions are good, but unfortunately the illustrations are rather rude,
which is indeed a pity, as the species happens to belong to the most difficult group of the
large genus. I do not think it necessary to point out some slight differences between the
author's account and my own, e. g. his incorrect statement of the number of joints in the
antennule of the larve etc., but it must be mentioned that he has overlooked the rudimentary
antennee (2nd pair) in the male and the female, that his very detailed description of the
rostrum is not correct, as he has taken the hairs outside the membranous border of the
mouth for »Radiirfalten« in the membrane itself (p. 303), and that his long description of
the more solid chitine lists of the rostrum is too diagrammatic. This is connected with his
quite wrong idea on the maxillule, about which he writes: »Es sind niimlich zwei solcher
Kiefern vorhanden, welche eingliedrig sind und an ihrem Ende eine Borste tragen« (comp.
my description below). On the other hand it must be acknowledged that he has found and
described correctly the legs and the caudal stylets of the female, but in the male he mis-
interprets the stylets, taking them for a third pair of legs; he has found spermatophores etc.
Furthermore, his representation of the genital area is defective, and he has overlooked
receptacula seminis, but he is right in stating that the female has no anus. He also gives
a somewhat detailed account of the embryology of these parasites, making out their stages
of development till they appear as full-grown larvae, but this part of the development I have

2)

scarcely studied at all. Finally he describes three stages of the pup, mentioning their
want of internal structure during the first stage and their considerable growth, but he has
failed to understand their mouth, nor does he mention the possibility of a very different
development of the two sexes. He concludes with some reflections on the place which the
new form ought to occupy in the system, thinking — with good reason — that it »in keine
der bis jetzt aufgestellten Familien vollkommen hineinpasst« (p. 320), but that it is nearest
akin to the Lerneide on account of similarity in the structure of the mouth, an opinion
which I cannot share (s. below). Salensky took his species at Naples on an Amphipod
which was many years after determined by Della Valle as Microdeutopus gryllotalpa Costa.
About its occurrence on males as well as on females he has a statement (p. 302) which will
be mentioned later on in the part headed »Habitation, biology and distribution<«.

Max Weser: Die Isopoden gesammelt wihrend der Fahrten des Willem Barents in
das nérdliche Eismeer in den Jahren 1880 und 1881 (Bijdr. tot de Dierkunde, 1884). The
author informs us (p. 35) that in a vesicular swelling on the carapace of a specimen of
Hippolyte Gaimardii M. Edw. he found four globular bodies which contained either eggs or
larve, and he thought they were »Bopyriden-Larven im ersten Larven-Stadium« and that
the eggs »werden wohl schubweise abgesetzt vom Weibchen und von einer gemeinsamen
Hiille umgeben«. His suggestion of Bopyrid-larve is a great mistake; what he found were
the ovisacs of a Choniostoma. The statement is only of interest in so far as it indicates
a locality of the genus; the fact that this otherwise excellent author happens to be the
first who found such ovisacs appears more than valueless to me, considering how he explains
the matter, and I only mention it here, because it relates to my remarks in the criticism
of Giard and Bonnier.

H. J. Hansen: Oversigt over de paa Dijmphna- Togtet indsamlede Krebsdyr (Dijmphna-
Togtets zool.-bot. Udbytte, 1887). In this paper (p. 271—278, Tab. XXIV, fig. 7—7h),
I gave a detailed description of the female, of ova and larve of a species found on Hippolyte
Gaimardii M. Edw. and Hipp. polaris (Sab.) in the Kara Sea, and I gave it the name of
Choniostoma mirabile. Furthermore, on this torm I established a new family, Choniostomatide ;
I did not know Salensky’s paper at the time, but when Prof. G. O. Sars had called my
attention to it, I mentioned it in the French résumé worked out later on (p. 511); however,
I maintained my new genus. In the female I found antennule, antenne and a mouth with
supposed mandibule, the anterior branch of the maxillule and the maxille. The description
of the mouth is not quite correct, as I did not mention the membranous mouth-border, but
I found the hairs which I thought proceeded from the margin of the mouth; I also over-
looked the rudimentary maxillipeds, nor did I find the genital apertures. The description
of the larva is pretty correct on the whole, but I have with some hesitation mentioned four
joints instead of three in the antennule, nor have I understood its olfactory seta as such.
In 1889 Giard and Bonnier were of the opinion that the specimen found by me on Hippolyte
polaris belonged to another species which they called Choniostoma Hanseni; this opinion

6

was based on the fact that it was much larger and lived on another species. The animal
did in fact prove to differ from Choniostoma mirabile; however, the two reasons alleged by
the authors proved to be wrong, for a female with eleven ovisacs found on Hippolyte Gai-
mardw and proving to be identical with the species on Hipp. polaris, was even somewhat
smaller than the largest Choniostoma mirabile. Consequently Chon. Hansenii is found on
two species of Hippolyte, whereas Chon, mirabile has as yet only been noticed on one.

A. Giarp and J. Bonnier: Sur un Epicaride parasite d'un Amphipode et sur un
Copépode parasite d’un Epicaride (Comptes-rendus de l’'Acad. des Sciences, 29 avril 1889).
This preliminary note is only mentioned here for the sake of completeness, as its contents
are largely worked out in the following publication.

A.Giarp and J. Bonnizr: Note sur UAspidoecia Normani et sur la famille des
Choniostomatide (Bull. scientifique de la France et de la Belgique, T. XX. 1889, p. 341—72,
Pl. X—XI). In this paper the authors have partly described and figured the Aspidoecia
Normani, the new species and genus established in their preliminary note, partly given a
very detailed critique of all that has been written on the subject. Each of these parts de-
serves a special mention. Of their new species the authors have examined a female with
five oyisacs and two males attached to it, sitting on the back of the carapace of Hrythrops
microphthalma G.O.Sars (belonging to Mysidze ver) under an obliquely placed Epicarid,
Aspidophryxus Sarsi Giard and Bonnier. Accidental circumstances led them to adopt the
following conclusion as the most plausible: »qu il existe un rapport soit de parasitisme soit
de mutualisme« (p. 353) between Aspidoecia and Aspidophryxus (which is a mistake; 9: below);
they say that the female Copepod »était reliée a / Aspidophryxus par un appareil fixateur«
(p. 344), though such an object does not exist, and they declare that it »adhérait certainement
a la Mysis par une ventouse« (p. 344), which is not the case either, as it is attached by
what later on I shall call »the adhesive plate«, a congealed substance forming a plate-like
cover on the forehead in front of the mouth, and which is secreted by the »glandes cémen-
taires« mentioned by the authors (p. 349). In their description of the female (p. 347—50)
they mention »les deux points chitineux« (entrances to the receptacula seminis), and they
give a correct description of the genital apertures, except that the small opening which they
call »pore de fécondation«, and of which they say that it serves »évidemment a l’entrée des
spermatozoides«, does not serve this purpose at all. They have found »la ventouse« on the
head, but they cannot make out whether the mouth is situated at the bottom of it (which
it does), or whether it is found »a la partie supérieure de la ventouse, celle-ci servant
uniquement a la fixation du parasite«. Finally, they have overlooked the antennule, the
maxillule and the maxilla. However, it must be borne in mind that having had only one
individual which they were not allowed to dissect, it would be unfair to expect them to be
able to study the organs of this small and extremely difficult animal much better than they
have done. With regard to the male the case is different; it is much easier to examine,
besides they had two specimens. After having studied my own material of the same species,

U

T came to results which differed very much from the figures and descriptions of the authors.
Though feeling convinced that I had studied animals belonging to their species, I wanted
to make quite sure of it and asked the Rev. Canon A. M. Norman to lend me the animals which
had served as types to the French authors, and I received a male and a female. The male
was kept in a preparation made by Mssrs. Giard and Bonnier, but it was considerably
flattened in an oblique direction, these animals —as stated above — not being able to with-
stand the pressure of a glass-cover; its position was about the same as that shown on
pl. XI in their paper. The spot where the animal was found was encircled by a red ring
on the glass-cover, and there could be no doubt that it lay just as it had been placed by
the authors. I did not open the preparation, as all I wished to see was clear enough. I
found what I expected: perfect similarity between this specimen and my own males —, and
the statements of the authors proved to be incorrect in the following important points:

1) »Les pattes nageoires font complétement défaut, ou sont réduites & des appendices
difficilement visibles (pt.)«. The first part of this sentence is right, but to judge from the
specimen in hand, the two dots marked pt. are spots possessing a slight deviation in the
refraction of light, and situated beneath the inner side of the skin; according to my expe-
rience with other animals, they are accidental.

2) »La partie postérieure du corps est divisée en deux renflements arrondis renfermant
chacun une sphere a contour trés net dont le contenu est formé de quatre sphéres appliquées
les unes contre les autres et déformées par pression réciproque comme les blastoméres d’un
oeuf au stade quatre de segmentation. Les deux sphéroides sont des spermathéques« (p. 346—47).
In the following pages I also call the two globules spermatothece, though I am not abso-
lutely certain that they are not testicles; so far we agree, but no further. In the male of
their preparation there was no vestige of a fold in the middle of the body. The spermato-
thecz showed inward folds which were not nearly so regularly arranged as it would appear
from their description and figuring of the contents, nay they seemed to be empty. A careful
and exact adjustment of the microscope showed that the granular substance usually contained
in the animal was owtside the spermatothece, though a less accurate adjustment might give
the impression that it also was inside; filled spermatothecw have a very different look. The
folds are easily explained by the flattening of the animal through the pressure to which it
had been exposed.

3) About the antennule they write: »elles sont formées d'une saillie basilaire sur
laquelle est inséré un article unique en bdtonnet terminé par une pointe courte«. However,
this »saillie basilaire« in their preparation is considerably longer and somewhat different in
shape from their figure of it; it is in fact the antennule itself (comp. my figure pl. XII,
fig. 3k.). What they call »un article« is the olfactory seta; nor is its extremity so slender
and pointed as they represent it.

4) They say about the mouth (p. 346): »La membrane de la ventouse est soutenue
par de fins rayons chitineux constituant les génératrices du tronc-céne. Ces rayons ont été

8

vus par Savensky et par Hansen dans la ventouse de Spheronella et de Choniostoma.
Mais le premier de ces observateurs les a considerés comme de simples replis de la mem-
brane; le second n’a pas vu la membrane et a pris les rayons pour des cils chitineux. Un
examen trés attentif peut seul permettre d’éviter cette double erreur«. In spite of this well
worded phrase, I must observe that they have not arrived at any better result than the
predecessors they criticise. The membrane exists without folds and without »rayons chitineux<«,
for these »rayons« are free hairs, »cils chitineux«, which originate at the base of the mem-
brane, leaning freely against it on the outside, and in their own preparation these hairs, as
usual, stand clearly out beyond the edge of the membrane.

5) »La premiére patte machoire (mapi) est réduite a un long stylet droit aigu,
beaucoup plus simple que l’organe correspondant du male de Spheronella« (p. 346). What
they describe and figure here is only the terminal joint of the mavilla (according to my
definition of this pair of limbs); it is not straight, but slightly curved, in their own type
specimen, as well as in my drawing (pl. XII, fig. 3 k.). They have also overlooked the
very large, long and broad basal joint, which appears distinct enough in their own type; if
they had seen it, they would have found the missing resemblance with Spheronella, and it
seems difficult to understand this gap in their observation.

6) However, the climax of the incomprehensible is reached in their description of
the maxillipeds. In their text they mention three joints, of which »le troisiéme se prolonge
en une dent crochue«, yet this »dent« is drawn as a claw-like joint, which is well
separated by an articulation and can be folded up towards the joint above it. But in
examining their type specimen, I found that it agreed perfectly with my figure on pl. XII;
what they describe and draw as the three first stout joints, indeed is only one single joint
without a vestige of the two articulations they mention and figure. The »dent crochue« is
really jointed on, as they figure it, but furthermore, in their own preparation it consists
of two distinet joints, and I cannot have misunderstood their text, for their statement
about the claw »a laquelle fait face un petit tubercule pointu« is fairly correct. So,
seeing that their own type specimen agrees exactly with my illustrations, I leave it to
the reader to compare their description, and especially their figure, with mine, and to find
out how they can possibly have been so much mistaken; as for me, I am at a loss to
understand it.

I have two reasons for yiving this detailed demonstration of the mistakes committed
by the authors in their description and figure of this male specimen. In the first place I
wish to verify in detail the identity of their species with my own, secondly I wanted to be
able to refer to this substantiation in the following pages, where I shall have to point out
that in a later paper the same authors have made considerable mistakes in their description
of two other forms, of which I have not seen their type specimen.

The authors (p. 356) state their opinion that the family Choniostomatide is nearest
akin to Chondracanthide, Lernzopodide and Ascomyzontide. I agree with them as to

9

Lermeopodidee; Chondracanthida seem to me to differ much more, and Ascomyzontidxe do
not show any real relationship.

The authors quote and criticise at great length all that has been written about this
family, but in their eagerness to exhaust the matter, they seem to go a little too far. They
give a long quotation from H. Kréyer: »Monografisk Fremstilling af Slegten Hippolyte’s
nordiske Arter (Kg). Danske Vidensk. Selsk. Skrifter, Nat. Math. Afh. IX, 1842, p. 263—64)
in order to prove that this excellent investigator was the first to discover an animal of this
family, and. that his specimen belonged to the genus Choniostoma. ‘They quote the passage
in Danish (p. 368—69) and in a French translation; the latter is correct, except in three
points, of which one may be called a very free translation, whereas the others are indeed
important mistakes and will be mentioned presently. “Kroyer states that he has found a
specimen of Hippolyte gibba (from Spitzbergen), whose carapace was much swollen on both
sides; however, he found no Bopyrid in it, but about a score of sub-globular, yellowish white
bodies of different size (from °/5‘’ to nearly 11/2‘’ in diameter), which were lying free and
unconnected side by side. He supposes them to be eges of an unknown parasite and adds:
»the smaller ones I found filled with a yolk-like, granulous substance« {»de mindre af dem
har jeg fundet opfyldte af en eggeblommeagtig, grynet Masse«|, which Giard and Bonnier
translate as follows: »Les plus petits étaient remplis d'une masse grenue ressemblant a des
oeufs«, but this gives a very different meaning from the word »yolk-like«, and may quite
well be understood, as if the globules were ovisacs containing the eggs of a Choniostoma,
though Kréyer’s expression does not imply such an idea at all. Kréyer continues: »In the
larger globules, which were probably very near maturity, I have noticed a rather long
(6—7'), thin, vermiform body. It may be, that some leech-like animal develops itself out
of these eggs« [»i de storste, som rimeligviis vare nerved Modenhed, har jeg iagttaget et
temmelig langt (6—7‘“) tyndt, ormedannet Legeme. Maaske udvikler der sig altsaa af
disse Aig et igleagtigt Dyr«|. Judging from the two sizes indicated by Kroyer, we might
suppose that the larger globules were females, the smaller ones ovisacs of a Choniostoma,
but it seems to me very improbable, that a naturalist like Kroyer should not have seen
that the small globules in reality contained eggs or larve, instead of supposing their
contents to be a yolk-like, granulous substance, and his statement that he found a vermiftorm
body about 13—15 millim. in length in the large globules, must in my opinion do away with
any idea that it could be the female of a Choniostoma (comp. my description of this genus
later on). But then, how shall we explain that Giard and Bonnier could advance such an
opinion? Well, in their translation of Kréyer’s description of the contents of the large
globules, they translate the first words: »7 de storste« |»/m the larger ones«| by: »prés des
plus gros« which gives quite a different meaning, allowing this remarkable, vermiform body

to be taken for a free animal belonging to another class. Thus two faults in their trans-
lation of Kroyer lead them to find a similarity which does not really exist between a Cho-
niostoma with its ovisacs and Kréyer’s description. IT am unable to tell what the objects

2

10

examined by Kroyer could be, but the suggestion that the large globules which, according
to his statement, contained a long, vermiform body of about half an inch or a little more
in leneth, should be females of a Choniostoma, indeed seems overbold to me, even in our
golden age of loose conjectures, and if we could really suppose Kroyer to have made such
extraordinary mistakes in his statements, we should indeed consider them worse than
worthless and deserving of everlasting oblivion. When in 1889 I[ read this passage by
Giard and Bonnier, I remembered, that while working at my previous investigation of
Choniostoma, | had perused the short paragraph in Kréyer’s excellent monograph: »Et Par
Bemerkninger om Snyltedyr paa Hippolyfer« |»Some remarks about parasites on Hippolyte«|
(p. 262—65) without finding anything at all applying to the parasite I was going to describe.
On p. 371 the two authors write further: »I] est singulier que Hansen ait laissé passer
inapercue Vobservation de Werner, et surtout le passage beaucoup plus important de son
compatriote Kroypr«. I shall presently make a few remarks about Weber, and as far as
regards my overlooking Kréyer, I will only observe that it would certainly have been wiser
of Mssrs. Giard and Bonnier, whose success in finding a pretty good proof in favour of their
assertion was entirely owing to two rather unfortunate faults in translation, to consider
whether they themselves had. not read Kroyer wrongly, before accusing me of having done
so, especially as this countryman of Kroéyer’s has repeatedly expressed his appreciation of
him, precisely in the report on the results of the Dijmphna-expedition, and who about twenty
pages earlier (p. 258) has pointed out Kroyer’s description of small, but interesting, joints
in the antennz and in the mandible-palp in another Copepod.

Concerning the censure of my ignoring Max Weber, I will make a few remarks.
In my dissertation: Fabrica oris Dipterorum, 1883 (Naturh. Tidsskr. 3 R. B. XIV), in order
to avoid unnecessary length, I did not mention all authors and their opinions, but confined
myself to the statement (p. 8) that I had made a rule of leaving out writers whom I did
not consider as having added new elements of importance to the existing knowledge of its
|the mouth’s} structure, or its use for classification, or whose incorrect views had proved
to be of no importance. I have followed the same principle in later works, but it seems
that, in order to avoid the accusation of ignorance, I shall have to use the same precaution
as in my dissertation, where, immediately after the quoted passage, I enumerate the authors who
are not mentioned, because they are unimportant with regard to the subject in hand, though
they may be excellent in their treatment of other branches. I do not think that I had
noticed the above-mentioned erroneous observation by Max Weber before publishing my
essay (of which separate copies were distributed in July 1886), and I cannot tell now if
I should have quoted it, had [ known it then, but, as a matter of fact, I had read and
understood it before I wrote the French résumé (in which, as mentioned above, I corrected
my omission with respect to Salensky’s (to me) important work) and I purposely forbore
mentioning Weber, considering his observations irrelevant, though four or five lines would
have been sufficient to reproduce their essence. The interest attached to his statements

11

consists in his indicating new a locality for Choniostoma on the other side of Nova Zemblia
opposite to mine (the Kara Sea), and that an otherwise very deserving author has committed
a most peculiar mistake. That is all; whether I ought to have mentioned the subject is a
matter of opinion; at the time I thought it might as well be left out.

I shall pass over several other remarks which might call for censure, and take up
some hypotheses set forth rather hesitatingly by the authors, p. 352—-53. After having
declared themselves at a loss to understand that a Choniostoma with its ovisacs can cause
a swelling in the carapace of a Hippolyte entirely resembling that which is produced by
Gyge Hippolytes, they write: »I] nous parait beaucoup plus vraisemblable d’admettre que le
Jopépode a infesté les Hippolytes déja parasités par les Gyge, et quwil supplante les Epicarides
ou tout au moins profite pour se loger de la déformation produite par ces derniers«. To
this conclusion they add a doubt which I think rather irrelevant, and say further: »Néau
moins en rapprochant l’éthologie d’Aspidoecia de celle de Choniostoma, il nous semble
bien probable qu'il existe un rapport, soit de parasitisme, soit de mutualisme, entre ces
parasites et les Epicarides des genres Aspidophryaus et Gyge«. However, they go still
further. They have found a genus of Epicaridea, Podascon G. and B., on a species of the
genus Ampelisca, and Salensky has found numerous examples of a Spheronella in all stages
on an Amphipod of an altogether different family. Here we should think it would be rather
difficult to establish a connection between the Epicaridea (Podascon) and the Choniostomatidee
(Spheronella), which live »exactement dans les mémes conditions«; nevertheless they continue:
»on peut se demander s'il n’a pas existé autrefois entre ces deux groupes de parasites des
rapports analogues a ceux que nous avons cherché a démontrer entre les autres Choniosto-
matidés (Aspidoecia et Choniostoma) et certains Epicarides«. With the word »autrefois«
the authors resort to the past, but it will be impossible in a case like the present one to
gain any perfect or imperfect knowledge concerning the former state of things. We confess
that this invention would be ingenious if — as sometimes’ happens where an excellent thing
is carried to an extreme — it had not overstepped the limit and become ridiculous.

My experience, which is based on very extensive researches, enables me to declare
that, as far as the present time is concerned, these hypotheses, which the authors repeat
with additional remarks in two later papers, are entirely destitute of foundation.

Of infested Isopoda this work mentions four examples of three species with three species
of Spheronella; of Cumacea with parasites in the marsupium twenty-four examples belonging
to six species (the parasites belong to five species), and of these six species I have examined
several hundred specimens, in order to find those that were infested. Of two species of
Cumacea seventy-three instances were found with (two species of) Homocoscelis under the
carapace; finally, one hundred and forty examples of Amphipoda (belonging to twenty-eight
species) were found and proved to be infested with twenty-eight species of Spheronella and
Stenotocheres. Of these twenty eight species of Amphipoda I have examined several thousand
specimens. So the result is, that of all three orders together I have seen about two hundred

9

12

and forty specimens belonging to thirty-eight species infested with Choniostomatide, but neither
on these, nor on any other of the thousands of individuals belonging to these thirty-eight
species, have I found one single Epicarid. So we have done with thirty-eight of my species
of Choniostomatide, and of the five remaining species two may be passed over, viz. the species
of the genus Mysidion, for neither I nor any other author have found any Epicarid in the
marsupium of the hosts of Mysidion, viz. the genera Erythrops and Parerythrops. Only on
the outside of the body of the species belonging to the genus Hrythrops, and in the branchial
cavity of two species of Hippolyte, others as well as myself have found altogether three
species of Choniostomatidz, and at the same time species of Epicaridea. As a rule the
animals of each order were found on separate specimens; in one case observed by myself,
and in one case mentioned by Giard and Bonnier, animals of both orders were found on the
same specimen. Still it can be proved that these two quite different types of parasites,
though perhaps in very rare cases they may be in each others way, stand at least in no
other mutual relation. As for Choniostoma Hansenii, I can prove that the animal itself
produces the swelling on the carapace (comp. my special description of this animal), and in
the only case where Choniostoma and Gyge were found on the same side under the carapace,
a male and a still smaller female of the latter genus had lodged themselves in a large
swelling, which was inhabited by an adult female Choniostoma with eleven oyisacs. As for
the last of my species — Aspidoecia Normani — I have found it on twenty-one specimens
of all five species of the genus Erythrops, but I found no Epicarid on any of these animals.
Moreover, the occurrence of Aspidoccia, not only on the shield, but also on the exterior side
of the thorax and on the six abdominal segments, as well as on the eyes, proves sufficiently
that it stands in no connection whatever with Aspidophryxus, which parasite lives only
on the carapace.

Immediately after the paragraph criticised above the authors write: »Toutes ces
considérations sont sans doute fort hypothétiques, mais elles penvent inspirer de nouvelles
recherches et indiquer la voie aux investigateurs. Elles ont de plus l'avantage de rattacher
par un lien éthologique commun les types de Copépodes si étranges qui constituent la famille
des Choniostomatide«. This »lien éthologique« is quite broken now and will scarcely ever
be restored. As for the first part of the quotation, I regret to say that it has indicated
no path to me, and that, far from having been inspired by their »considérations«, I have
been obliged to waste time and space upon proving the untenability of some unwarranted
hypotheses. To suggest such hypotheses indeed is not very difficult, and most zoologists
have imagination enough to invent scores of them. If productions of this kind had any real
value, it would be easy to promote the progress of science. But I confess that, though I
honow everybody who is capable of suggesting a theory which proves to be well founded
and fertile in results, I have always felt and, as time goes on, feel more and more distaste
for superficial conjectures.

13

A. Denna VALLE: »Gammarini del Golfo di Napoli« (Fauna und Flora des Golfes von
Neapel, 20. Monographie, 1893, 4to). In the chapter » Parassiti dei Gammarini« (p. 289—90) the
author informs us of some observations he has made, and suggests some hypotheses about
Spheronella. The species on which Salensky found his Speronella Leuckartii is said to be
Microdeutopus gryllotalpa, and the author has found it in the locality indicated by the
discoverer of the species. He further states that he has found the same Spheronella on
Ampelisca diadema Costa, where it lives under the same conditions as Podascon Della Vallei
G. and B. And he proposes three hypotheses, viz. that Spheronel/a changes colour according
to its residence, in order to look like the eges of the two different species of hosts; that
it does not live at the expence of the host itself, but by consuming its progeny, and that
for some time after having left the egg, the young Spheronella is entoparasitic, not ecto-
parasitic, developing itself in the oviduct and consuming the eggs successively as they appear.
In support of this last conjecture he states that he has found on an Ampelisca a Spheronella
with its multitude of ovisacs, which host at the same time »racchiudeva in uno dei suoi
ovidutti, verso l’estremo esterno, uno piccolissima Spheronella, m cui nondimeno erano gia ben
visibili le uova quasi mature« (p.290), but in spite of this rather peculiar observation, his
conjecture seems unduly hasardous, as an attentive perusal of Salensky’s excellent treatise
with the description of the pupa stage, which follows the larval stage, would have shown
its absurdity. Besides, Giard and Bonnier have refuted all these hypotheses in a later
paper; they justly maintain that there is a physiological reason for this castration (» castration
parasitaire«) effected by the parasite on its host, and they consider the form found on Am-
pelisca as a different species from Sph. Leuckartii, in which no doubt they are right. So I
think I need not throw further light on these questions. —

About Rhizorhina Ampelisce H.J.H. the author in his Bibliographia, p. 897, only
writes: »Questo nuovo Copepodo rassomiglia molto alla Spheronella Leuckarti, Salensky. The
quality of this resemblance is treated in the following pages.

A. Giarp et J. Bonnier: »Swr deux types nouveaux de Choniostomatide des cotes de
France: Spheronella microcephala, G. et B. et Salenskia tuberosa, G. et B. (Comptes-rendus
de l’Acad. d. Sc., 25 sept. 1893). The contents of this preliminary note appear in a later
essay, much enlarged and — in one point — altered.

A. Grarp et J. Bonnier: » Contributions a Vétude des Epicarides (Bull. Scientif. de la
France et de la Belgique T. XX V, 1895 — the part headed: » Les Spheronellides, p. 462—85,
Pl. XII—XIIT). This part calls for a detailed comment.

The authors describe and figure the female and eggs of Spheronella microcephala

G. et B., a species found on four specimens of Ampelisca tenuwicornis Lilljeborg from Croisic.
Doubtless the frame of the head is incorrect, for a list like the one represented in the
illustration (Pl. XII, fig. 43) as going from the outermost posterior angle towards the median
line behind the base of the maxille, does not exist. If there is a connection between the
frame and the sub-median skeleton -— which by the by they have not seen — but which is

14

never wanting in any Spheronella, there must also be a list behind the maxillipeds. How-
ever, the whole frame seems to me most problematical, nor have I found it in specimens
which, as far as I can judge, belong to the same species. I should not have dared to
suppose so great a fault in this illustration, if IT had not seen their type specimen of the
male of Aspidoecia, which enabled me to ascertain their astonishing mistakes in the repre-
sentation of several organs, especially in the maxilla and the maxillipeds (comp. above p. 7—8).
Moreover, they have decidedly overlooked the maxillule, which I have never found wanting
in any female of this family. About the maxille (oles maxillipédes internes«) they say that
they are »formés de quatre articles« (p. 464), but this is wrong, for these limbs in all
females, males and larve of this family contain at most three joints, and the two last joints
are even frequently so completely fused that we only find two distinct joints, as shown in
my illustration (pl. VIIT. fig. 2d) of the head of this species. Neither do I doubt that their
representation of the maxillipeds with their strange flexion and the second joint thick and
quite as long as the first, is entirely wrong. Their description and figure of the genital
region (p.465, pl. XII, fig. 44) is not successful either. By the words of the text: »un are
de cercle chitineux (c) qui, postérieurement, se termine par deux branches...« and by the
illustration, it is seen that they have turned the whole part wpside down, as in reality both
branches turn forward towards the head of the animal, seen from the ventral side (comp.
my fig. 2a on pl. VIII). The chitinous arch with its branches is pretty correct. Their
representation of the genital apertures and their muscles is perfectly correct, while the
apertures marked a and designed as being »les ouvertures d'une paire de grosses glandes
... les glandes collétériques« — are the orifices of the receptacula seminis (comp. my de-
scription below and my figures of several other species of the genus). In fig. 2f on pl. VIIT,
as in several other instances, I have not represented these orifices, but after a renewed
examination of the same species, I can state that the orifices, leading to the receptacula seminis
in my Sph. microcephala G. and B., are found precisely in this place, and from these openings
each of the middle-sized receptacula — forming an oblong sac — curyes gently backward
and somewhat inward towards the centre. I am at a loss to understand anything about
these glands illustrated by the authors. They also represent a pair of very large »receptacula
seminis« as opening into the genital apertures; though unable to explain what they are, I
am positive that they are not what the authors suppose them to be. Finally, what they
describe as follows: »Au centre méme de l’aire génitale il existe un espace cordiforme clair
(ec), avec trois petites vésicules granuleuses aux trois sommets, la supérieure étant la plus
grande et la plus nette; toute cette partie est située profondément, sous le tégument« is
certainly no organ or organs, but accidental formations produced by coagulation or the like.

The authors have taken their species on Ampelisca tenuicornis Lilljeborg from Croisic
(south coast of Brittany), and their determination of the host has been confirmed by the
eminent Carcinologist, Prof. G. O. Sars. The specimens described later on in this work,
which I have considered as belonging to the same species, were taken on Ampelisca typica

15

Sp. Bate. During the interval between the appearance of the first publication and that of
the principal essay 1 corresponded with the authors about these questions, and as they quote
some of my written statements, [ must make a few remarks. It is not only the fact that
Sph. microcephala had been found in Denmark on Ampelisca typica and in France on Amp.
fenwicornis, Which I may have thought »trés curieux«, but in examining a large quantity
of Danish material of Amp. fenwicornis, not only had [ found no specimen of Sph. microcephala
whatever, but I had found several specimens of a very different species (Sph. /ongipes n. sp.),
so it struck me as »very curious« that Amp. tenwicornis from the Danish coast had a parasite
which it had not near the French coast, while in the latter locality it had a parasite belonging
to the same genus, and which was not found on the Danish Amp. fenwicornis, though this
very parasite lives in Denmark, but had passed on to Amp. typica. However, I will add
that future researches may prove both species of parasites to live on both species of hosts
in either locality. In this case we shall wonder no longer, but until further notice we
have reason to find the circumstance curious.

Subsequently the authors enter upon a critique of Della Valle’s observations and
hypotheses. To the species found by Della Valle on Amp. diadema Costa, they give the
name of Sph. diadema G. and B., which consequently is put down without description.
However, as I have briefly stated the principal points of Della Valle’s observations on a
former page, I may pass them over here; I will only add that [ am not prepared to judge
of the value of the reflections set forth by Giard and Bonnier about the colour of the eges
of parasites — though I can say for certain that Della Valle’s opinion is wrong. On
p. 462—63 the authors repeat the above criticised suggestion of a connection between Cho-
niostomatides and Epicaridea: »Les Choniostomatides sont-ils des parasites des Hpicarides
dont ils prendraient la place en les faisant périr, ou les Hpicarides facilitent ils seulement
Tentrée des Choniostomatides en produisant sur les Malacostraca des détormations et une
castration parasitaire plus ou moins complete? C'est cette derniére hypothése qui nous
parait actuellement la plus vraisemblable«.

That Della Valle had found a species of Spheronella on two specimens of Ampelisca
diadema, and a species of the genus Podascon (an Epicarid) on two other specimens of the
same Amphipod indeed was the only fact of interest which had occurred since their previous
work in 1889, but this fact only proves that a fourth species of Choniostomatide has been
added to the three, of which it has been stated above that they live on species infested
with HEpicaridea, and this is of the slightest importance compared with the statistics I give
on p. 11—12, and the conclusions drawn from these statistics and from my observations.

We now arrive at the most unfortunate idea advanced by these authors, their
grouping of Choniostomatide H. J. H. and of Herpyllobiide H. J. H. as subfamilies (with
the suffix ine) of the family Spheronellide G. and B. In order to refute this combination
— one of the most inappropriate I have ever met with in Carcinology — and some hypotheses
connected with it, I shall also have to mention the family Herpyllobiide.

16

In 1892 I published an essay: »Rhizorhina Ampelisce n. gen. n. sp. En ny til
Herpyllobiide n. fam. horende Copepod, snyltende paa Ampelisca levigata Lilljeb. (Entomol.
Meddelelser, 3. B. 5. Hefte p. 207—834, Tab. III), which in the first place contains a detailed
description of the above-mentioned new and very curious form, in the second place makes
an important contribution to the knowledge about Herpyllobius Stp. and Ltk.; finally the

new family Herpyllobiide is established, and the genera — seven in all — which can with
more or less certainty be referred to it, are grouped together. Two of these genera,
Trophoniphila MW’ Intosh and Oestrella M’ Intosh, are described so defectively that we prefer
not to consider them in this place. The female of the other five genera has a globular or
oblong body without any vestige of mouth or limbs; posteriorly are two genital apertures,
each with its ovisac. The front part of the female of Rhizorhina forms a short, slender
stalk, which pierces the skin of the gill of its host; the inside of this stalk consists of two
tubes. Just beneath the skin of its host the stalk expands very much, the tubes are consi-
derably dilated, they separate and ramify irregularly throughout the gill, even entering
somewhat into the body of the host. In the genera Herpyllobius Stp. and Ltk. and Ewry-
silenium M. Sars, the stalk, which consists of a single tube, is found on the ventral side of
the body, pierces the skin of its host and expands inside it like a collar, but this collar is
surrounded by the root of a large, oblong, foliaceous or irregularly sausage-shaped body,
which is decidedly homologous with the tubes of the Rhizorhina, and, like these, has the
function of drawing nourishment from the host to the external, limbless body, whose business
it is to develop the eggs. In Saccopsis Ley. and Bradophila Ley. Levinsen has indeed found
the stalk, but no body at the expanded end of it in the body of the host. However, he had
but slight material of both forms to work with, so I will now state as my personal opinion,
that a body, or one or two tubes, may have proceeded from the stalk into the body of the
host; otherwise it would be impossible to understand how the parasites could get their food.
Moreover, I may mention that, when (in Noy. 1896) I spoke to the author, Inspector
G. M. R. Levinsen, about the matter, he felt inclined to share my opinion. Giard and Bonnier
(in their above-mentioned paper) describe a new parasite, Salenskya tuberosa, of which a
single specimen was found on Ampelisca spinipes Boeck from Croisic. They confess (p. 474)
that it »présente certainement une tres grande ressemblance avec Rhizorhina ampelisce ....
et nous avons longtemps hésité a maintenir le genre Salenskya, crée par nous {in the preli-
minary note] quelques mois apres la publication du travail de Hansren«. Still they think
they are justified in maintaining it, »au moins provisoirement«, on the following basis:

»Au lieu d’étre fixé a son hote par des racines rappelant un peu celles de Succulina,
ou par un renflement comparable a celui des Herpyllobius, la femelle de Salenskya possede
un appareil chitineux spécial, qu'on pourrait rapprocher plutot de celui de Saccopsis terebellidis
figuré par LEVINSEN...... «(p. 475). I have just spoken of Saccopsis, and 1 will now express
my opinion that if a specimen of Salenskya is found again on Amp. spinipes, and the part

of the host occupied by the parasite is cut off, this part will contain internal tubes exactly

NG

like those I have described in Rhizorhina; the two apertures mentioned and described by
the authors are the roots of these tubes. Separate copies of my essay about Rhizorhina
were distributed in July 1892 (one of them was sent to the authors). Their preliminary
note, in which they establish Salenskya, mentioning its »appareil fixateur en forme d’amphi-
disque ou de bouton de manchette«, is dated Sept. 25th 1893, but it is quite evident that,
at the time their manuscript was sent to the press, they had not read my essay. So, having
but one specimen of the animal to work upon, they committed the same mistake which I
had made with my first specimen of Rhizorhina: without having any idea of the tubular
system inside the host, I detached the visible part of the parasite, thus breaking the stalk
which united it to the hidden part. After what I have just said about their investigation
of the male Aspidoecia, I am quite justified in not trusting their statements in a question so
difficult as that concerning Salenskya, where their judgment rests on the examination of but
one individual. The result is that the genus Salenskya G. and B. must be cancelled, being
established only on this one single character. Whether their species differs from Rhizorhina
Ampelisce will have to be proved by ascertaining if the slight differences between our repre-
sentations of the males agree with facts. Though this on the whole may possibly be the case,
I doubt that they are right in stating that the larva of the parasite they describe has two
orifices for the ducts of the genital organs; I have only found one hole surrounded by a
somewhat thickened ring.

The authors quote from their preliminary publication (p. 475—76) a long passage,
in which they suggest »progénése« and »dissogonie« in the male of Salenskya. They now
give up these theories, saying: »Les recherches de Hansen prouvent que chez Rhizorhina
la métamorphose régressive existe bien chez les males de ce genre d'Herpyllobiine et
qu'elle est tout aussi accentuée que chez les Choniostomatine.« However, the last sentence
which is meant to establish a relationship between the two groups to each other, is very
misleading, as the male of Rhizorhina (and Herpyllobius) is a body entirely without limbs,
mouth or any other external organ or internal muscles, with nothing in fact but genital
organs, the male of any Choniostomatid whatever is a highly developed animal with anten-
nule, a very complex mouth with mandibles, besides maxillule, maxilla and maxillipeds
with some joints, internal muscles etc. So in saying: »Ce charactére différentie] {»pro-
eénése« in Salenskya and other Herpyllobiide] entre les deux sous-groupes ne peut done
étre maintenu«, they are perfectly right, but such a negative feature does not imply
any kinship.

However, the principal points are contained in the following paragraph, and in
order to criticise it I am obliged to quote the last half of p. 476 and a little of p. 477 in
their paper; [ will, however, divide the quotation into three parts. They write: »Le reste
de lorganisation concorde dune facon remarquable, non seulement chez la femelle ot, en
raison de la dégradation, toute comparaison peut sembler dépourvue de valeur, mais aussi
chez les males et les embryons: méme tendance a la disparition de la deuxiéme paire

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18

dantennes, méme structure de l'appareil buccal avec la ventouse si spéciale et les appendices
transformés en stylets, méme disposition des membres thoraciques, etc.

Les jeunes individus surtout présentent une ressemblance extraordinaire et indiquent
nettement la parenté des deux groupes.

Mais il est un caractére du male sur lequel nous désirons particuliérement attirer
l'attention, parce qu il est trés exceptionnel et qu’on ne le retrouve dans aucune autre
famille de Copépodes, en dehors des Choniostomatine et des Herpyllobiine.

Les canaux excréteurs des glandes génitales males débouchent dans la partie cépha-
lique de Vanimal et dans le voisinage de la bouche«.

Let us examine this a little more closely. Though the authors think that the
larve in particular show »une ressemblance extraordinaire«, we find that these larve, which
indeed may be said to be in the first Cyclops-stage, resemble each other less than the
larve of a Choniostomatid and of an Achtheres respectively, according to the illustration
given by Claus (Zeitschrift wissensch. Zoologie B. XI, Taf. XXIII, fig. 5). At any rate,
the likeness between the mouths of the larve of a Rhizorhina and of that of a Choni-
ostomatid is not so great as the authors seem to think, and it is certainly much smaller
than that between the mouth of a larve of the last-mentioned group and e. g. of a larva
of Pennella. The maxille of the two groups deviate much from each other in shape and
position ete. Several great differences between the males of Choniostomatide and of Her-
pyllobiide have been pointed out above, and we shall soon mention more. The differences
between the adult females also seem to be so great that we are struck by the astonishing
boldness of the assertion that: »en raison de la dégradation, toute comparaison peut sembler
dépourvue de valeur«. In the former type, the Choniostomatide, the female possesses at
least the antennule, a well-developed mouth with mandibles, maxillule and maxille; in
the latter, the Herpyllobiide, the body has no vestige of these organs or of any limbs, and
in the three genera which are examined so thoroughly, that our knowledge about their
nutrition is perfectly reliable, we know that it takes place through a large mysterious body
(in Herpyllobius and Silenium) or through an equally mysterious tubular system (hizo-
yhina) which is found in the body of the host, and which has a most curious, hitherto
unexplained development (comp. my essay about Rhizorhina). Indeed, I can find no other
likeness between the females of these families than the small size of their bodies, their sub-
globular or oval form, and their two genital apertures, and as this last character seems
to be common to all parasitic Copepoda, we might as well pass it over.

But still more objectionable is the statement printed in italics, that in the males
of both families the genital aperture is found on the head near the mouth. I shall begin
by speaking of Herpyllobiidee. The authors substantiate their opinion in these words: »Ce
caractére, tellement extraordinaire que nous ne l’avions signalé qu’avec réserve dans notre
étude sur Aspidoecia et dans nos recherches plus récentes sur Salenskya, Hansen l’a mis

19

completement hors de doute dans son beau travail sur Rhizorhina ...« This requires a
comment. I have proved the following facts. The males of Rhizorhina and of Herpyllobius
are not the larve. The larva fastens itself to the female by a gluey substance, after which
all its muscles etc. are dissolved; the limbs are emptied of their contents and the whole
plasma of the larva contracts and surrounds itself with a new skin, thus forming a male
without limbs, mouth or other external organs, and without visible internal organs except testicles
and their efferent ducts which gradually develop themselves. In the Rhizorhina this male
remains inside the skin of the larva, pushing its remarkable spermatic ducts out through
the hole in front of the mouth of this dead case. In the Herpyllobius the skin af the
larva bursts, the male fastens itself with its front, and the spermatic ducts proceed (behind
the attached end) through the split produced by the bursting of the larval skin. So in
both cases the male is transformed to such a degree as to render a morphological orientation
rather uncertain; at all events, we can no longer speak of »le voisinage de la bouche», as
there is no mouth at all. This description of the male of Herpyllobiidee will also give a
sufficient idea of the immense difference between this animal and the males of Choniosto-
matidee which, moreover, fix their spermatophores on the females in the usual way.

The authors continue: »Chez tous les Spheronellide, les canaux génitaux miles
servent aussi a l’excrétion d'une substance cémentaire avec laquelle le male se fixe sur la
femelle dune facon plus ou moins durable. Ce role nouveau et ces connexions singuliéres
des canaux génitaux constituent a coup str le trait le plus saillant de la morphologie de la
famille des Spheronellide, telle que nous la comprenons«, namely Choniostomatids and Her-
pyllobiide together. The authors are bold indeed; they do not hesitate to suggest one
hypothesis after another, the second more erroneous than the first. Now, to begin with
Herpyllobiide, who has said anything that could justify the statement that the genital organs
of the male secrete the viscous substance by which the animal attaches itself? The authors
have seen nothing themselves, and they cannot base their statement on my essay about
Rhizorhina, as I maintain that the larva of this animal attaches itself by a gluey matter
proceeding from the mouth before the male is developed and before there is any indication of
genital organs. The male keeps inside the skin of the larva, which remains attached to the
female, and no further fixation takes place’). How then must we qualify the sentence the
authors pronounce as if it were proved? To put it mildly, we can only call it a product
of imagination. — We shall now turn to the second division of their »Spheronellide«: the
Choniostomatidz, and here again we shall have an opportunity of considering their above
quoted lines in italics: »Les canaux excréteurs des glandes génitales males débouchent dans
la partie céphalique de l’animal et dans le voisinage de la bouche«.

‘) In the Herpyllobius the male attaches itself a second time by its front end, but the genital aperture
is found at some distance behind this fixation (Entom. Meddel. |. c. p. 230).

3°

20

The authors have proved (1889) that in Aspidoccia the male is hinged by a thread
which proceeds from a hole on the ventral side of the front part of the head: »ce filament
est secrété par deux grosses glandes cémentaires probablement homologues de celles qui
servent a la fixation chez les Cirripédes«. No doubt it is this comparison on which they
base their opinion that the genital aperture is found on the head, and also that the spermatic
glands secrete the viscous substance which forms the thread, as these organs are believed
to perform this double function in the Cirripeds). A slight basis indeed for such remarkable
statements! The observation about the hingement of the male is correct, but then, has the
thread to disappear in order to allow the spermatophores to come out of the hole, or is the
order of the two processes to be inverted, or does the male possess another genital aperture
on its front near the base of the thread? Unfortunately we get no answer to all these
legitimate questions — though indeed we can scarcely imagine any possibility besides these
three. No, the doctrines about the genital aperture on the head and the double function of
the sexual organs in the Choniostomatide are postulates without any foundation. Within
the family mentioned it is an ordinary phenomenon to find the male attached by a thread;
this prevents it from being washed away and allows it to creep as far as the thread can
reach, giving it frequent opportunities to fix its spermatophores on the entrances to the
receptacula seminis. Besides, the genital aperture is not found on the head; in Spheronella
paradoxa I have been able to prove the existence of two genital apertures at a short
distance from each other on the ventral side of the trunk: from each spermatotheca proceeds
an efferent duct forward and obliquely towards the median line, and these canals open on
the posterior side of the depression between the first pair of trunk-legs, or at least somewhat
behind the basis of the maxillipeds. But then, what remains of the hypotheses advanced as
facts by the two authors, that the genital aperture of the male in the Choniostomatid is found on
the head, and that the »canaux génitaux« secrete the viscous substance by which the animal
attaches itself? Nothing, absolutely nothing! And what remains of their best proof -— based
on these organs —, that Choniostomatide and Herpyllobiide ought to be grouped in one
family? Equally: nothing! except a rather surprising impression of the loose method of the
authors: to establish unreliable conjectures as facts in order to prove an absurdity.

Though I suppose that most readers have now formed a pretty clear idea of the
great differences between the two families, I will give a summary. The likeness between
the two families is limited to the following features: both are parasitic Copepoda, in which
the males are several or many times smaller than the females; in both sexes the body is
small, sub-globular or oblong; the last larval stage of Herpyllobiide is the first Cyclops
stage, it resembles to a certain degree the larva just coming out of the egg in the Cho-

1) | will not here enter upon criticisms which have appeared elsewhere about Darwin’s unfortunate
statements upon this subject, nor on Giard’s later suggestions concerning Rhizocephala.

21

niostomatide. The differences between the families will be shown most clearly by giving a
short description of each. In the Choniostomatide both sexes possess af least antemnule, a
mouth with mandibles, maxillule and maxille, and the males have always maxillipeds, and
they fix their spermatophores on the females in a normal way. The female deposits its eggs
in one or two free lumps or, in most cases, in ovisacs, of which at least four or five and
sometimes more than twenty are found; the larve attach themselves by an adhesive plate
on the forehead and — whether passing through the pupa stage or not — develop them-
selves into animals of either sex. In Herpyllobiide both sexes lack antenne, mouth and
appendages; the females project a mysterious body or two ramified tubes into the host
and draw nourishment through these organs. The males project from the anterior part of
their body in advance of the mouth of the larval skin two long spermatic ducts, which are
formed by a secretion in the genital organs, and through these canals nearly the whole sub-
stance of the body, having been transformed in the service of propagation, is transferred
into the female. The female has two ovisacs; the larva attaches itself by a gluey sub-
stance proceeding from the mouth, and is transformed into a limbless male or female. In
the latter case the animal forms a stalk which pierces the skin of the host, inside which
it dilates and develops into the above-mentioned organ of nutrition. — Whereas the Cho-
niostomatide, on the whole, fit in well among the other families of parasitic Copepoda, the
Herpyllobiids remove themselves from the others by a series of very peculiar features,
occupying a more isolated position than any other of the families.

This, I hope, will be sufficient to prove that the juxtaposition by the authors of
the two families in question as sub-divisions of one family, is contrary to all sound classi-
fication. I think also that sufficient light is thrown on the characters and hypotheses of
the authors. The present work being a kind of monograph, I found it necessary to write
this rather detailed critique of their publication. However, this task has not been at all
pleasant to me, because in another branch, the Epicaridea, they have published works
which must be considered the principal sources of our knowledge about important groups
belonging to this large and difficult family. In the interest of the authors and of carci-
nology, as well as for my own sake, I wish they had not published their four, at least not
the two last of their contributions (the preliminary note in 1893 and their final essay
1895) about Choniostomatide. It would indeed have been very natural to postpone the
publication of their two last papers, as their material of these animals (whose manipulation
presents considerable technical difficulties) was rather scanty, and as, even as early as 1891,
they know that I was preparing a work based on very abundant material. (L need scarcely
add that the fact of their publishing a report about one species previously to myself affects
me very little; indeed I might easily have secured this priority by some »preliminary note«).
If, nevertheless, they were intent upon describing their few animals, their researches might
and ought to have been much better, and they ought to have abstained from filling up real

bo

22

or imaginary gaps by a number of unproved assertions and unwarranted hypotheses regarding
structure, biology and classification.

Nowadays many authors have a remarkable weakness for publishing innumerable
immature notes, for building zoological card-houses, drawing up genealogical trees and
inventing theories and hypotheses, especially where they know very little. Where they have
acquired considerable knowledge based on thorough study of a large material, as a rule,
they abstain more from hazardous conjectures. One result indeed has been obtained: Zoo-
logy has been encumbered with endless preliminary notes, with papers abounding in faulty
and defective representations and unaccountable postulates and reflections, so as to render
the study of it troublesome to an almost unsurmountable degree.

Jutes Bonnier: Résultats scientifiques de la Campagne du »Caudan« dans le
Golfe de Gascogne, Aout-Septembre 1895. Edriophthalmes. (Amn. de l'Université de Lyon,
1896)1). In an appendix to this valuable work the author describes and figures a new
species, Spheronella sedentaria Bonn., which he has discovered in the branchial cavity of
Cyclaspis longicaudata G. O. Sars of the order Cumacea, in a depth of 960 metres, lat.
449 5‘N., long. 4°45‘ E. He found an adult female, four ovisacs and a small specimen,
which he considers to be a young female, but which is no doubt a male. The species
belongs to my new genus Homoeoscelis, and comes very close to my H. minuta. He begins
by describing the small specimen, and his description of its body, the borders of its head,
its antennule, mavxillipeds, trunk-legs and caudal stylets is essentially correct. He also
corrects Salensky’s erroneous conception of the caudal stylets as a third pair of legs, but
he has certainly overlooked the maxillule (comp. my drawings of the males of my species:
pl. IL, fig. 1i—1k and pl. XII, fig. 1f—1g). which are never wanting in any species ot
the whole family — unless the outer part of the mandibles possibly may be the larger part
of the maxillule, which might indeed be supposed from the drawing. The hairs surrounding
the membranous border of the mouth are overlooked, and the basal joint of the maxilla which
he mentions (his »maxillipéde interne<) does not exist; what he takes for this joint is no
doubt a part of the sub-median skeleton. As will appear from my subsequent description,
the only feature by which the male and a young female of the same size of the genus
Homoeoscelis can in all cases be distinguished from each other, is the distinctness of the
genital apertures in the female. The author has found no such apertures, and this circum-
stance, as well as the occurrence of the animal together with an adult female, indicates
that it must have been a male. The author's comparison of the female with the small
specimen is correct; only his description of the genital area calls for a few remarks. He

1) A special copy of this paper, kindly sent me by the author, arrived on Febr. 11th 1897, so that
the present remarks had to be written and inserted in my work when a large part of the fair copy of it
was already written.

23

is of the opinion that each of the genital apertures is provided with a separate frame, of
which he presents a drawing (fig. 5e), but the anterior part of these frames is scarcely
correct in drawing, as it is not likely to reach up to the »pore de fécondation« (orifice of
the receptaculum seminis) which — we see — here for the first time is proved to exist
in an animal of this family. Neither has he seen the median part of the firm chitine of
the genital area which unites the two »frames«, but it must be pointed out, that without
a special dissection — in which, moreover, a certain amount of practice is desirable —
these details are difficult to discover. The whole description of the two small specimens
is considerably better than the above-mentioned joint work on this family by the same
author and Prof. A. Giard.

Il. GENERAL REPRESENTATION OF THE FAMILY.

le order to facilitate the use of this large section it is divided into three chapters, the
first of which contains a general view of the structure and development of the animals,
the second of their habitation, biology and distribution, the third some general observations
about the classification. Each of these chapters contains several sub-divisions.

A. Structure and Development.
a. The Female.

This sex is known in all species. The body is nearly always a little flattened —
seldom more than a little; if seen from below or from above it is ovate or globular. The
young specimens are generally much longer than they are broad; the adults are now a little
longer than they are broad, now the reverse; sometimes their broadest dimension is a little
in front of, sometimes a little behind the middle. Specimens which are going to lay, or
have commenced laying eggs, are always somewhat — probably as a rule much — larger
than old ones which are emptied of eggs (pl. 6, fig. 3a shows such a female which is going
to lay eggs, fig. 3c a female (with a male) which is emptied of eggs, both enlarged to
the same scale). In consequence of this evacuation the animals frequently shrink and
become vaguer of outline. We often happen to see specimens which have become crooked
and irregular from pressure, otherwise all the animals are naturally symmetrical. The
size of the adults varies considerably; in most species the diameter of the animal seen
from below is */s—1'/2mm.; it can even decrease to about ‘3mm. (Homocoscelis mediter-
ranea), and Choniostoma Hansenii G. and B. can obtain a lenght of 53 and a breadth
of 55mm. As a rule there is a certain proportion between the size of the parasite and
that of its host; however, it must be borne in mind that the parasites themselves differ
in size according to their habitation in the marsupium or under the carapace; in the latter
place they are comparatively smaller. As a matter of course, small Amphipoda cannot

bo
Or

support large parasites, whereas large species like Calliopius leviusculus Ky., Munnopsis
typica M. Sars and Hippolyte, are inhabited by large animals.

In most species the regular, rounded, ovate or globular shape of the body is inter-
rupted in front or a little behind the anterior margin on the ventral side by a small pro-
truding head, which as a rule is tolerably well defined at the basis. In the adults it
is most frequently very small, compared with the trunk; in small, and_ particularly in
recently hatched specimens (pl. VII, fig. 2e, and especially pl. III, fig. 2c) it is of a very con-
siderable size. The reason of this difference is that the head and its organs do not grow or
at most grow very little, whereas the trunk greatly increases in size, in order to give room
for the mighty production of eggs. In some forms there is no separate head at all, so that
its (very small) organs: antennule, antenne, mouth, maxillule, maxilla and maxillipeds, are
situated near each other anteriorly on the ventral side of the vaulted body. In Stenothocheres
(pl. I) the thorax has two rather small pairs of limbs; in the other genera these limbs are quite
minute or wanting altogether. In Stenothocheres we find a distinctly marked, prominent
abdomen. — In no species the body shows any vestige of segmentation.

This will give a general idea of the females. In giving a closer description of their
structure I think the best plan is to begin with Spheronella and kindred forms, as the
genus Stenothocheres, though in two important points — the size and development of the
trunk-legs and the existence of an abdomen — more closely related to less transformed Cope-
poda, in other respects is less qualified for serving as base of the description.

I. Homocoscelis, Spheronella and Choniostoma. Many species have a prominent,
well defined head: the back, front part and sides are evenly vaulted and pretty well chiti-
nised, and the chitinous border to the front and on the sides stands out a little beyond the
ventral side, which is partly covered by a soft membrane, and has a somewhat concave
surface. Seen from below, the sides of the head are arched posteriorly, for the above-
mentioned protruding lateral borders are somewhat removed from the outline of the head;
they are generally ciliated, whereas the margin of the frontal border is mostly hairless. As
a rule, a narrow, arched, transversal list, or two narrow, parallel lists, proceeding from the
posterior ends of the lateral margins and passing behind the basis of the maxillipeds, forms
or form the posterior limit of the head. Sometimes this list is interrupted at the median
line (pl. IIT, fig. 2c), sometimes it does not reach the lateral margins (pl. VIII, fig. 1d).

Choniostoma (pl. XI) at first sight seems to have no distinct head at all, however,
the above-described borders in front, posteriorly and on each side remain, forming a frame
round the soft area, in the middle of which the mouth and its appendages are situated.
The front part of this frame in Chon. Hansenii (pl. XI, fig. 2d) rises a little beyond its sur-
roundings, thus representing the only remaining part of the anterior and upper surface of
the head.

Spher. Acanthozonis (pl. VII, fig. 5a and 5b) presents a fine intermediate form
between Choniostoma Hansenii and the species that have a well defined, prominent head

4

26

(illustr. on pl. IT to pl. VII ete.). In all species with well-developed head, or at least with
the frame left, we see behind the frontal margin and inside the lateral parts of the frame
a broad band of thin, soft skin. Somewhat behind the middle of the frontal margin is the
rostrum (proboscis) with antennze and maxillule, and from this part backward towards, or
quite up to the list behind the basis of the maxillipeds, we see a system of plates or lists.
This system, which I shall call the swb-median skeleton, is partly or all the way divided
into two halves by softer skin along the median line; its structure differs in nearly every
species; as a rule it expands considerably in the middle of its lateral margins. The inner
margin of the basal joint of the maxilla touches the outer margin of the front part of the
expansion, whereas the maxillipeds are articulated behind the expansion touching the outer
margin of the narrower posterior part of the skeleton.

In several species of the genus Spheronella, namely Spher. microcephala, S. dispar,
S. insignis, S. Munnopsidis and S. marginata (pl. VIII, fig. 2d; pl. LX, fig. 3f and fig. 4¢;
pl. X, fig. 4b, and pl. XIII, fig. Gd), there is no separate head and no harder chitinous borders
(only in S. marginata and in S. microcephala there is a low border or a transverse list in
front of the mouth (pl. XIII, fig. 6d, pl. VIII, fig. 2e)), whereas the sub-median skeleton exists,
strongly developed as a solid plate in S. Munnopsidis (pl. X, fig. 4b), much reduced in S. dispar
and S. insignis (pl. LX), and particularly so in S. marginata.

The Antennule. In all species, except the five without separate head and without
frame, the antennule are well developed, and in these they are articulated to the solid frame,
each at one of the angular points where the lateral margin merges into the frontal margin (comp.
e.g. pl. IL, fig. 1h and fig. 3a, pl. XI, fig. 1a). Each antennula is usually composed of three
joints, of which the second is generally the shortest, the third the longest. The front angle
of the first joint is mostly provided with two or three shorter or longer sete; the terminal
joint is rather well provided with bristles of different length, among which an olfactory seta
(b) can be frequently pointed out. In the genus Homoeoscelis the antennule become 2-jointed
by the fusion of the second and third joints (pl. XLII, fig. 1d). In Spher. decorata (pl. VIL,
fig. 3e) the first and second joints are coalescent. In Spher. marginata the antennule
(pl. XIII, fig. Gd) are constructed as in Homoeoscelis. In the other four species of Spheronella,
which are devoid of separate head and of frame, the antennule are situated at the same
points, but fastened to the thin membrane, besides being shorter and reduced so as to show
only indistinctly separated joints or no division at all.

The Antenne. These organs I have been unable to discover in the species of the
genus Homoeoscelis, and in Spher. modesta, S. dispar, S. insignis, S. marginata, S. Munnopsidis
and S. micerocephala, whereas they exist in the other species of Spheronella and in Chonio-
stoma. They are always placed on the side of the rostrum itself near the margin of its
expanded basal part, and they are always short, slender, generally 3-jointed (e. g. pl. V, fig. 2d),
without hairs and terminating in one shorter or longer seta. In a few species, e.g. Spher.
decorata, the number of joints is reduced to two, in Spher. antillensis (pl. III, fig. 2c) they are

rudimentary, 1-jointed and have a very short seta, and so they are in the seven remaining
species belonging to the group of Spher. Leuckartu Sal. (comp. the systematic part).

The Rostrum. It is always of good size and bluntly conical, or like a cylinder
with dilated base. Its structure is very complex, and we will begin by studying its distal
part, for the representation of which Choniostoma Hansenii (pl. X, fig. Ga and fig. 6b) will
serve as type. In fig. 6a the cylinder is seen sideways and without the expanded part at
its base. At the margin of the terminal face of the cylinder origimates a membrane which
has the shape of a kind of border or very short inverted cone. In looking at it from the
distal end (fig. 6b) we see that the membrane covers the whole terminal face, having the
shape of a cup or perhaps rather of a flat funnel, as it leaves an oblong aperture at the
bottom in the centre; this is the entrance of the mouth, beyond the margin of which the
points of the mandibles are seen to proceed. In front of the mouth the membrane is divided
in the middle by a deep incision; the opening thus produced is filled by an odd median plate,
on each side of which is another plate which is partly covered by the membrane. In the
illustration these parts are marked d. The membrane is downy at its edge (fig. 6b), and
the whole inner surface of the funnel is covered with peculiar dots, which are smaller near
the edge than towards the centre, and which probably represent tiny knots. Outside the
membrane are seen a number of cylindrical hairs which are sometimes furcate at the apex
(b). They are articulated to the distal edge of the cylinder at the base of the membranous
border and, being longer than its height, proceed somewhat beyond its free margin. When
— as in the present instance — the rostrum is cut off, it is easy enough to see that these
hairs do not exist within the membrane, but only lean against it. In some species, e. g. in
Spheronella curtipes (pl. X, fig. 2d), the membrane (viz. the free part of it) is considerably
broader, in others narrower, than in Choniostoma Hansenii. The hairs in some species are
much more numerous and much thicker than in others, and they often converge or diverge very
irregularly, according to the position they happen to occupy; in a few species I was not able
to discern them. My figures as a rule are too small to allow of drawing the membrane, but
these hairs are drawn as well as it could be done. It must be observed that the shape of
the mouth varies considerably in specimens of the same species; [ have found it more or less
funnel- or cup-shaped, in accordance with the angle formed by the membranous border and
the surrounding hairs against the terminal face. In the systematic part of the present work
the free part of the membrane together with the hairs is called the mouth-border.

The outer surface of the rostrum shows several harder chitinous lists, and when the
rostrum is examined from its distal end, some harder parts are seen through the semi-dia-
phanous membrane as circles, which are interrupted in front at the median line. In my
opinion the distal part of the rostrum must be explained as being a highly modified Jabiwm,
or rather hypopharyna, which forms a kind of sheath round the mandibles and stretches so
far towards the front that its edges approach very near to each other, and that the above-
mentioned median part marked d. must be considered as the /abrwm. However, I am not

4°

28

able to account more fully for the structure of these parts and the attachment of the mandibles.
When looking at the rostrum from its distal end (fig. 6b), we see them through the inter-
mediate substance, like narrow lists in appearance, the free distal points of which are visible
in the mouth-aperture and are somewhat different in shape on the right and the left
mandible. Departing from the points, they turn outward, at the same time running down
the rostrum, their basal end lying inside its walls rather far from the aperture of the mouth.

It is only the distal part of the rostrum which can be considered as formed by the
hypopharynx and the labrum, the proximal part must be chitine belonging to the ventral side
of the head itself, which here has become cone-shaped or forms the foot and the proximal
part of the cylinder. I draw this conclusion from the fact that the antenne, where they
are found, proceed from the basal part of the cone or from the foot (Choniostoma, pl. XI,
fig. 2d), and that the maxillulze are situated on its lateral surfaces (see e. g. pl. X. fig. 6a, ¢,
and many illustrations of heads of females seen from below). But these last-mentioned
mouth-organs must be treated separately.

The Maxillule ave found in all species. Each maxillula consists of a somewhat oblong
plate which almest throughout its whole length is coalescent with the middle and the more
proximal part of the rostrum, and in the latter place this coalescence is so complete that it
becomes impossible to distinguish the outline of the proximal part of the maxillula (fig. 6a),
whereas its distal part (c) detaches itself from the lateral surface of the cylinder. Here it
divides itself into two branches, the anterior of which forms, now a shorter or fairly long,
now, and mostly, a very long process, which looks somewhat like a proximally very thick
and distally more slender seta. The posterior branch has a quite similar structure. These
two more or less setiform processes I consider as the principal branches of the maxillula;
they are never wanting, and as a rule they are somewhat curved (in the specially examined
specimen of Choniostoma their terminal half was sinuous), and on examining the head from
below, the anterior branch of the maxillula is mostly seen to proceed beyond the foremost
part of the lateral margin of the mouth-border, the posterior branch behind the posterior
part of the same lateral margin, whereas the distal part of its plate and the base of the
two branches are covered by the lateral part of the mouth-border, through which they can
be seen (e. g. pl. V, fig. 2d and especially fig. 3d). Besides, in most species the maxilla
possesses as an additional branch a process shaped like a stout and usually long seta,
articulated to that part of the maxilla which is coalescent with the rostrum, and often so
proximally that, in looking at the head from below, we get the impression that it is situated
outside the basis of the maxilla. The basal part of this additional branch is frequently set
off by an articulation. This branch is wanting only in Homoeoscelis and in the three species
of Spheronella which are parasites on Cumacea, and which have no separate head.

The whole rostrum is movable, so that its distal part with the mouth is turned
more or less forward or backward, now protruding, now receding considerably, which
differences are seen most distinctly by observing the head sideways, and comparing the

29

position of the rostrum with the lateral margins of the head (comp. the rostrum in the
numerous figures of males seen from left side).

The Maaxille ave always (except in one single species mentioned below) well deve-
loped, often very powerful. They are situated far from each other, somewhat behind the
base of the rostrum, on the outer margin of the sub-median skeleton, the expansion of
which reaches their inner margin and frequently extends behind their posterior margin.
Typically they have three joints, of which the first one is very thick, often not much longer
than broad; the second and third joints together are usually shaped like a slender, distally
somewhat curved cone, which can be folded up like a claw against the oblique terminal
margin of the basal joint, and as a rule these two joints are coalescent, though sometimes
we find them very distinctly separated (e. g. in Spheronella insignis, pl. LX, fig. 4c). The
basal joint is often provided with one or two protruding knots or taps, and its terminal
margin at the articular membrane is frequently furnished with hairs, or, as in Spher.
Munnopsidis, with some peculiar cylindrical bristles or fine processes (pl. X, fig. 4b); in
Spher. decorata (pl. VIII, fig. 3e) and in S. modesta (pl. LX, fig. 2d) a part of the articular
membrane between the first and the second joint is decorated with rather numerous small
chitinous taps. The terminal joint usually ends in a point; in Spher. dispar (pl. LX, fig. 3f)
the apex is blunt, but has several fine, setiform points. In Spher. marginata (pl. XIU,
fig. 6d) the maxille are quite rudimentary.

The Maxillipeds are well developed in Spheronella and in Homocoscelis. They are
articulated on the posterior part of the sub-median skeleton and are usually somewhat
closer to each other than the two maxilla. They consist typically of four joints, of which
the basal one is thick, very long and always distinctly longer, often much so, than the
others together; these can be folded up against it in a very acute angle. The basal joint
is often decorated with processes, spines, rather long hairs, shorter or very short hairs, or
very fine, conical taps; the hairs and taps are arranged in spots, stripes or rings. The
second and third joints are slender, distinctly or indistinctly articulated or quite fused
together without the slightest distinction. The third joint has generally on the inner side
of its distal end a spine, which in those species of Spheronella which live on Cumacea,
is provided with fine points, besides being sometimes broad and flat (pl. XIII, fig. 6d). The
iast joint is more slender than the others, somewhat curved and often ending in a point
with one or two spines on the inner side behind the point; in most of the Spheronelle
living on Cumacea the joint expands a little towards its somewhat flattened and rounded
extremity, along the margin of which we see numerous fine and short, setiform processes.
A somewhat similar structure is noticed in Spheronella Munnopsidis (pl. X, fig. 4b). In
Spher. microcephala (pl. VIL, fig. 2d) the maxillipeds are weak and comparatively rather
small, second and third joints coalescent and very short, the last joint very small and
stunted. In the genus Choniostoma the maxillipeds are quite rudimentary (pl. XI, fig. 1a, ¢
and fig. 2d), and reduced to two very small or quite diminutive joints.

30

Before leaving the head I will mention some peculiar formations, which I am at a loss
to understand. In Spher. frontalis we notice at the middle of the frontal margin (pl. VIII,
fig. 1d) a strange cup-shaped, rather large expansion in which I have been unable to find any
hole which might be the outlet from some gland. In Spher. modesta, on the ventral side of
the protruding frontal border, inside its margin we see a square of considerable size (pl. LX,
fig. 2d, x) with rounded corners, which seems to be pierced with rather numerous holes.

The Trunk. The body — except the head — of course corresponds to thorax and
abdomen, but in the three genera treated here, the latter never appears as a separate part;
we must consider it as being represented by the genital area and its surroundings, which,
however, are not marked by distinct outlines. I beg to give notice that, as a separate
abdomen only appears in the genus Stenothocheres (s. below) and in no other genus of the
whole family, I shall — for practical reasons —in mentioning and describing all the genera,
except Stenothocheres, always both here and in the systematic part use the word »trunk« for
the whole body, except the head.

The shape of the trunk is mentioned above, for as the head, at least in adult spe-
cimens of most species, is very small, I can refer to my description of the body (p. 24—25).
The skin — except on the genital area —is very thin, often quite naked, sometimes covered
with hairs behind the head, being naked everywhere else, sometimes hairy all over. In several
species the trunk is more hairy during the early, not half-developed stages, than when the
animals have grown to their full size, so e. g. in Spher. danica, whose young ones are covered
all over with peculiar thin, flat hairs, whereas the older specimens are either quite naked or
have only a hairy part behind the head. In Spher. Calliopii (pl. I, fig. 3d and fig. 3g) the
trunk has a rather close coat of very peculiar three-branched hairs growing out from tiny
knots, the middle hair being longer than the two others. In Spher. irregularis (pl. XII,
fig.5¢ and fig. 5d) somewhat similar two- and three-branched hairs are seen.

In most species the trunk has two pairs of entirely uniform legs, but in a good
number of species (as in Spher. microcephala, and in all eight species of the Spheronella living
on Cumacea and Isopoda) legs are entirely wanting. The legs are placed on the ventral
side, now at some distance within the outline, now at the lateral margin, and as a rule there
is no considerable difference in the distances between the first pair and the head, between
the first and second pairs and between the second pair and the leg-like caudal stylets. In
Homoeoscelis the legs, though small, are comparatively conspicuous, each apparently consisting
of a diminutive, short and rather thick basal part, from which proceeds a much longer, very
narrow, conical, almost setiform branch and a pair of very short bristles or a short tap as
an indication of a second branch. In Spheronella and Choniostoma the legs are nearly always
exceedingly small; in recently hatched or young specimens they are as a rule easy to find,
but as they do not grow, they are often very difficult to point out in adult animals. Hach
leg consists of a small cylindrical joint ending in two short sete. In Spher. longipes (pl. VU,
fig. 2a and fig. 2e) only, the legs are somewhat larger, particularly because one of the sete

31

is long. In Spher. Acanthozonis (pl. VII, fig. 5a and fig. 5b) they are reduced to rounded
eminences without sete.

A genital area is found in all species of these three genera, and it is in some cases
much smaller, in others somewhat larger than the head. In its most developed form it is a
more or less thickly chitinised plate, which is sometimes nearly circular (Spheronella
curtipes, pl. X, fig. 2e), mostly considerably broader than it is long, and not unfrequently with
a more or less concave anterior or posterior margin. In this plate we find the genital
apertures more or less close to each other, so that the distance between them is nearly
always shorter than the length of each; they are usually placed near the posterior margin,
seldom in the middle or even nearer the anterior margin. Sometimes the central part of
the plate or two rather lateral parts of it are thin-skinned (pl. II, fig. 3b), and in this last
case the plate is really reduced to an oval ring with a median longitudinal band. In Spher.
Munnopsidis (pl. X, fig.4c) the plate is more than twice as broad as it is long, and a large
inner part of the same shape as the outline is more thin-skinned; the genital apertures are
placed transversely and somewhat further from each other than the length of each. In other
species the plate is reduced to about two thirds of a more or less oval, transverse ring, the
posterior margin of which is close to the genital apertures, whereas the sides are further
removed from them. A further reduction is noticed e.g. in Spher. frontalis (pl. VII, fig. 61),
where the more conspicuous parts consist only of a chitinous arch behind and outside each
genital aperture, the two arches yet being connected in the median line. In Spher. micro-
cephala (pl. VIII, fig. 2f) the genital area is much longer than it is broad, and the chitinised
part of it forms a semi-circle which opens towards the front, its two extremities running
forward and forming two rather long, nearly parallel and partly dilated lists. The genital
apertures are — as stated above — nearly always closer to each other than the length of
each, besides they are curved and placed in an oblique direction, so that their convex sides
turn towards each other, and their anterior ends are much closer together than the posterior
ones; e.g. in Spher. microcephala, and especially in Spher. Munnopsidis, these apertures
are turned so as to be almost or quite transverse; and in Spher. Munnopsidis the distance
between them is greater. Each genital aperture is provided with two chitinous lists, the
lips, of which the hindmost one is nearest to the median line and covers the front part of
the other lip, when the genital aperture is closed. From the outer lip proceeds a strong
muscle outward and obliquely forward, its proximal end being attached to the inner side of
the plate or to the ring mentioned above. The contraction of this muscle pulls outward the
outer lip, thus opening the genital aperture (pl. XI, fig.4d). For this purpose the skin close
outside the outer lip is always thin (in many figures kept in a grey tint) though the sur-
rounding parts may be a pretty hard chitinous plate.

In front of each genital aperture, at a shorter or longer distance from it, though
always within the genital area, is a very diminutive orifice which forms the entrance to
an oval or somewhat elongate vesicle, the receptaculum seminis (pl. I, fig. 3a,r). These two

32

orifices are shown only in some of the illustrations of the genital region, and they are
often very difficult to find, if one or each of them has not a spermatophore attached to it;
this, however, is rather frequently the case; sometimes we find even two spermatophores, or
at least their stalks, on each orifice (pl. XITI, fig. 1e). Such a spermatophore is a globular

or ovate vesicle with a stalk twice or three times as long as itself; this stalk — a thin
tube — is attached to the skin closing on the above-mentioned orifice, or sometimes — by
mistake — outside it (pl. LV, fig. 2c, where we find one spermatophore on each orifice and

the stalk of a third one outside it). The two receptacula, when filled, have a strong
refraction of light, which as a rule makes them easy to find. Their outlines are traced with
dotted lines in some of the illustrations. — In Spher. Munnopsidis I have found in the an-
terior part of the plate two holes (pl. X, fig. 4c, k) corresponding to those in Mysidion
abyssorum and Aspidoecia (see p. 34—35).

In the species which have trunk-legs there is always a pair of caudal stylets shaped
somewhat like the legs. Jn Homocoscelis (pl. 11 and pl. XIII) they are a little thicker and
longer than the legs; in Spheronella and Choniostoma they consist either of a cylindrical, a
rounded or a triangular joint terminating in two or three sete (which rather frequently fall
off during the preparation): they are sometimes longer, sometimes shorter than the sete of
the legs (as e.g. pl. VII, fig. 2e). In Spheronella Acanthozonis each caudal stylet has one
single rather long seta (pl. VII, fig. 5d). In Spher. modesta, which has no trunk-legs, each
stylet consists of a rather short, thick joint, from the inner posterior angle of which proceeds
an acute »joint« twice as long but scarcely half as thick, which must be considered as a trans-
formed seta, and outside it are seen one or two simple setze (pl. LX, fig. 2e). Nearly all the
other species which lack trunk-legs are devoid of caudal stylets as well. The place of these
stylets varies much; in most species they are situated close together, either on the plate or
the ring, a little behind the genital apertures, or close behind the posterior margin of the
ring or plate, but in the species belonging to the group of Spheronella Leuckartii they are
situated pretty far or very far from each other, and also more or less far behind the genital
area (pl. II, fig. 2e and fig. 3b).

The remarkable fixation of Spheronella paradoxa will be described in the systematic
part; here it may be sufficient to draw attention to it.

II. Stenothocheres (pl. I). This genus, comprising two species, deviates considerably from
the three recently mentioned genera, and in at least two important features: — larger trunk-legs
with two branches and a separate abdomen — it comes nearer to the less transformed Copepoda.

The body is sub-ovate or nearly globular; its abdomen is comparatively rather small
and prominent posteriorly on the ventral side or on the hind margin itself. It has no separate
head, not even the vestige of a frame (like the one in Choniostoma). The sub-median skeleton
is reduced to a plate in front of each maxilliped (pl. I, fig. 1e,h and fig. 2f), and this plate
may extend forward like a list between the maxilla and the outside of the rostrum. An-
tennule, antenne, rostrum, maxilla and maxillipeds occupy a larger space on the ventral

side of the body than in the other genera. The antennule (fig. 1a, a and fig.2¢) are of
medium length, without distinct articulation, they have a few rather short sete, among them
one olfactory (fig. le, b). The antenne (comp. fig. le and fig. 2f) are placed somewhat
obliquely outside and in front of the rostrum, but not on its basal part; they are of medium
length, in Sf. egregius (fig. 1e, ¢) probably 3-jointed, with a couple of short terminal seta of
unequal length; in S¢. Sarsii (fig. 2f, c) they are weak, with indistinct articulation. The rostrum
is on the whole like that in Spheronella, though it must be observed that the mouth-border
is very narrow. The maxillule (fig. Le, e) are on the whole like those of Spheronella, the
principal branches rather short or of medium length, the additional branch wanting. The maxille
(fig. la, f; fig. le and fig. 2f) are powerful and do not show any important differences from
those species of Spheronella which are parasitic on Amphipoda. The same remark can be
applied to the maxillipeds with regard to their structure, but these limbs, compared with
the maxillee, ave shorter and slenderer than in most species of Spheronclla, and we may
add that the second and third joints are always fused into one single comparatively short
joint, which -at most is a little longer than the pointed terminal joint and lacks the spine
at the distal inner angle, as the terminal joint lacks a spine inside its apex.

The trunk is naked all over (so is the whole body with all its appendages). The
trunk-legs are placed differently from those of the preceding genera; both pairs being
situated on the ventral side at a good distance within the lateral margin, the first pair
(fig. la, m) somewhat behind the middle of the body, and the second pair (fig. 1a, n) close
in front of the basis of the abdomen. Both pairs, though rather small, are very large
compared with those of the preceding genera. Each leg consists of a peduncle with two
branches not distinctly set off by articulation, and as a rule the outer branch is the longest.
In the first pair the outer branch terminates in two strong sete of unequal length, in the
second one (fig. 1g, u and fig. 2i) each branch apparently consists of two joints, of which
the terminal one is somewhat spine-like, but it must be preferred to consider each branch
as being composed of one joint with a long and very thick terminal spine.

A comparison between the figures 2a and 2d shows that in the same species the
abdomen may be found more or less distant from the posterior margin on the ventral side
of the trunk, according as the animal is more or less swelled with eggs. The abdomen is
not set off from the trunk by an articulation; it consists of a broad, rather stout basal part
with arched lateral margin (fig. 1g and fig. 2i), and a narrower terminal part with a more
or less deeply incised extremity, which forms two very short and clumsy, badly defined caudal
stylets (fig. 1g, t), each with four thick sete. The abdomen seen from below (fig. 1g and
fig. 2i), presents near the outer margins of the basal part two very long genital apertures
() in their whole or a considerable part of their length; in the abdomen seen sideways
(fig. 1h), the genital aperture (g) shows its longest extent, and the muscle which opens it (m)
is directed towards the dorsal side of the abdomen. Fig. 1h also shows a receptaculum
seminis (1) as a large oblong vesicle, placed a little above the abdomen. I have repeatedly

5

34

seen two such receptacula, but I cannot indicate their external orifices, as, strangely enough,
I have never found spermatophores on any of the rather numerous specimens I have examined.

ILL. Mysidion (pl. XI—X1I). The head is pretty well defined from the trunk, but
so feebly chitinised in front and at the sides that the frontal and lateral borders are wanting.
The antennule are much reduced and either 2-jointed or 1-jointed (pl. XII, fig. 2a, and
fig. 1a, a). Antenne seem to be wanting. Mouth and maxillule as in Spheronella. The
basal joint of the maxillze has at the inner edge one or two processes, and the appendage
is a powerful prehensile organ. The basal joint of the maxillipeds has irregular outlines.
Trunk-legs and caudal stylets are wanting. There is no genital area: the genital apertures
are situated very far from each other (pl. XI, fig. 3b and fig. 3e); each of them has — besides
the lips — its own skeleton, consisting of a list which is semi-circular or forms the larger
part of a defective oval, the longest diameter of which runs parallel with the median line
of the animal, and the opening of which is turned towards this line. The genital aperture
is situated close to the posterior part of the list, and the muscles radiate towards its foremost
part. The receptaculum seminis — odd, as far as I can see — is situated in the median
line, far in front of the genital apertures (pl. XI, fig. 3e). The skin covering it is closely
set with many — as many as twenty-six — spermatophores (s), and between them are seen
stalks of other vanished spermatophores, some of these sticking together in bulks which
cover the skin so completely that, in spite of several attempts, I have been unable to find
the entrance or entrances to the receptaculum seminis. In fig. 3e the letter » marks recep-
taculum seminis, which on each side opens into an obliquely backward running duct, which
I have been able to follow towards the genital aperture (comp. the following genus). In
Mysidion abyssorum I have found in the semi-circle surrounding the genital aperture a hole
(or perhaps rather a spot, covered with a thin membrane pierced with small holes (pl. XII,
fig. 2b, k) forming the outlet from a gland which I have found, though I have not been
able to examine it more closely, and whose function is incomprehensible to me. — Several
parts of the head of this animal are frequently covered with a viscous substance, by which
it fastens itself to the marsupium of the host. This substance, in the females as well as in
the males and the larve, is probably secreted by glands placed in front of the mouth (comp.
the female of the following genus).

TV. <Aspidoecia (pl. X11). This genus (one species) approaches very near to Mysidion.
In this place only its most important characters will be mentioned, an exhaustive description
being given in the special part of this work. The body is considerably broader than it is
long, the head is distinctly defined from the trunk and pretty well chitinised, with rounded
forehead and sides. The front is covered by a large adhesive plate (fig. 3d, s) by which
the animal is attached, this plate at the same time covering the 1-jointed antennule (fig. 3h, a).
Antenne are wanting; the maxillule are very small, without additional branch; the mouth
is normal, but I have found no hairs along the mouth-border; the maxille are like those in
Spheronella; maxillipeds are wanting. Trunk-legs and caudal stylets are wanting. Hach

35

of the genital apertures — as in Mysidion — has its own list, which in this animal forms
a ring (fig. 3i); in the front part of this ring we see a rather large hole (k) which serves
as opening to a gland (comp. Mysid. abyssorum). The genital aperture (g) lies up to the
part of the ring which is turned towards the median plane of the animal. Contrary to
Mysidion, the distance between the rings varies between being a little greater and very
much smaller than the diameter of each. A long way in front of the genital apertures
we see two knots a little apart from each other (fig. 3g, r‘, fig. 3e, 0) which show as it
were irregular cracks in the thick chitine; no doubt they form the entrances to the recep-
taculum seminis (fig. 3e,r) which is odd, much broader than it is long, and at each side
bends backward, thus continuing as two almost parallel ducts, which are wide, at the
middle sowewhat narrowed, and run to the genital apertures. No spermatophores have
been found.

b. The Male.

Out of my forty-three species I know the males of thirty-two, viz. of all species of
the genera Stenothocheres, Homoeoscelis, Mysidion and Aspidoecia, as well as of twenty-five
out of the thirty-four species of Spheronella. So in nine species of Spheronella and in the
two species of Choniostoma the males are still unknown. With respect to the latter genus
particularly the gap is keenly felt.

The male is always much smaller than the adult female — as a rule quite dispro-
portionally so. In three species only: Spher. frontalis, S. decorata and S. curtipes, its length
exceeds 4/2 mm. The largest male I know belongs to S. cwrtipes and measures ‘92 mm. in
length and °/s of this size in breadth. In most species the length is about !/4—1/5 mm., and
the length somewhat exceeds the breadth. The smallest normal males [I have found in
Aspidoecia Normani, two specimens of which were respectively 147 and -138 mm. long.
In Mysidion abyssorum the normal male seems to be about -164 mm. long, though I have
found two perfectly dwarfish specimens, of which one was ‘099 mm. long — and this is one
of the smallest of adult Copepods hitherto discovered, however, it may be that these two
specimens were recently hatched and had not grown to their full size (s. below under »post-
larval development«). The genus Homocoscelis shows least difference between the male and
the female, especially H. mediterranea, of which the largest female was °31 mm. long,
32mm. broad and rather flat, whereas the male was 174 mm. long, ‘096 mm. broad and
equally thick. The greatest difference between the sexes I have found in Spher. microcephala,
in which the largest female was 144mm. long, of the same breadth and almost. perfectly
globular, whereas the male without counting the rostrum was ‘18mm. long, 15mm. broad
and ab. ‘11mm. thick, which gives a volume of between S800—1000 times smaller than
the female.

The body, as a rule, is somewhat longer than broad, and seen from below, varying
from sub-globular to an elongate oval, seen sideways, the back is strongly vaulted, the

5

36

ventral side almost flat, and the animal is nearly always somewhat broader than it is thick.
In the genus Homoeoscelis (pl. IL and pl. XIII) as in Spher. curtipes (pl. X, fig. 2f and fig. 22)
the body is much longer than it is broad, the length varying from 1°/s to a little more than
twice the breadth: besides, in S. curtipes it is curved, so that, seen from the side, it presents
a moderately concave ventra) outline. The length of the head varies between a little more
and a little less than half of the total length, in Spher. frontalis (pl. VIL, fig. 6a—6b) it does
not take up a third part. The body is usually broadest somewhat behind or almost on a
line with the base of the maxillipeds. In Spher. modesta (pl. LX, fig. 2f) the greatest breadth
lies before the middle of the maxilla; in several species it is rather far behind the head,
and in this case the trunk is somewhat or much larger than the head, viz. in Spher. Bonniert
(pl. VIL, fig. 1a), in S. fronfalis (pl. VIL, fig. 6a) and in Mysidion abyssorum (pl. XII, fig. 2e).
A distinct abdomen is found only in the genus Sfenothocheres. Antennule, antenna, rostrum,
maxillule, maxilla and maxillipeds are much like those of the female, still we find a number
of minor differences which must be mentioned. Trunk-legs and caudal stylets are well
developed in all the species whose females possess these organs, though as a rule they differ
very much in the two sexes, and they are also found in a few species, as Spher. microcephala
and S. modesta, whose females lack both trunk-legs and caudal stylets, or only trunk-legs.
In Spher. dispar, S. insignis, S. marginata, as well as in the genera Mysidion and Aspidoecia,
the males have not the slightest rudiment either of trunk-legs or of caudal stylets.

In the genus Stenothocheres the antennule, the antenne, the rostrum and the mouth-
appendages are situated on the foremost rather flatly vaulted part of the ventral side of the
body. In all the other genera the surrounding of the rostrum and the mouth-appendages in
front and at the sides lie more or less deep and are limited anteriorly by an outstanding
border, which is frequently rather high or forms a slanting plate, at the sides by very
conspicuous lateral borders, which usually run nearly parallel from the front towards the
base of the maxilla, whence they curve more or less outward towards the lateral margins
of the animal and vanish somewhat behind the base of the maxillipeds. The shape of these
lateral borders is rather variable and difficult to describe, but the numerous illustrations
will show two outstanding rounded plates bending like a cape towards the base of the
maxilla, and outside these protruding borders we can always see something of the slanting
lateral surfaces of the head, when looking at the animal from the yentral side. The frontal
border is sometimes distinctly separated from the lateral ones, but it usually forms a direct
or nearly direct continuation of them; in most forms it is evenly curved; in Spher. elegantula
(pl. LL. fig. 2f) and in kindred species it has a deep incision on each side, by which the
frontal plate is divided into a large, median, almost square part and two much smaller
rounded lateral lobes. In Spher. Calliopii (pl. II, fig. 5h) the frontal margin is divided into
six lobes, in S. decorata (pl. VUII, fig. 3f) the frontal plate is much elongated, with the
anterior end cut off transversely and with several incisions, one in the middle and two on
each side, by which it is divided into four square and two low triangular lobes, all of which

37

bear small spiniform processes on their outer margin. In Spher. dispar (pl. 1X, fig. 3h) and
in Spher. insignis (pl. X, fig. 1b and fig. 1c) the frontal plate expands in a most peculiar
way. Seen from below, the head tapers very much towards the front, whereupon it dilates
to an almost circular plate or a transverse oval with acute lateral angles; the sides and the
front margin of the circular plate and the front margin of the oval project into a series of
closely situated spiniform little processes; on the ventral side of the plate we see a chitinous
ring, from the inner edge of which four processes run towards the centre; in S. dispar these
processes do not meet, but form the surroundings of a cross-shaped space, whereas in S. insig-
nis they meet in the centre, thus forming a cross, and dividing the space into four parts,
(which perhaps are pierced with small holes). The purpose of this peculiar ring is un-
known to me.

The part surrounded by the protruding frontal and lateral borders frequently lies
very deep, and where the lateral borders are high, sometimes, as in Spher. curtipes (pl .X,
fig. 2f and fig.2¢), they hide the rostrum and the maxille, if the animal is seen from the
side; as a rule a lateral view shows these organs in almost their whole, or in half of their
length. Several males of the same species may show great individual difference in this
point, whereas on the other hand, there are species, as e. g. Spher. curtipes, mm which the
rostrum and the maxille are always partly invisible because of the height of the lateral
borders, in other species again, as in Spher. microcephala (pl. VIII, fig. 2 ¢ and fig. 2h), the
borders are so low, that the above-mentioned organs are always visible in nearly their
whole length.

The sub-median skeleton, which is found in all females and has been described as
far as this sex is concerned, is also seen in all males, and in most respects shows a similar
structure, but in most species of the genus Sphwronella it is produced into free processes.
Three pairs of such processes may be found. ‘Those of the first pair are usually rather short
and broad, sometimes rounded, in S. microcephala (pl. VIII, fig. 2 ¢ and fig. 2 h, i) pretty
long, slender and pointed, being situated behind or below the basis of the maxille; some-
times, as in S. elegantula (pl. Il. fig. 2f and fig. 2 @), they extend backward over the basal
part of the maxillipeds. The second pair of processes are found most frequently, and may
become much longer than any of the other two pairs; they proceed at a shorter or longer
distance from each other between the maxillipeds, and are sometimes parallel, sometimes or
mostly diverging. The third pair appears in very few species only, as in S. paradoxa
(pl. ILI, fig. 4h and fig. 41), in S. Metopw and in S. Holbolli (both on pl. V.); they proceed
between and a little behind the second pair and are much shorter than these ones. In the
systematic description of the species I use the terms: first, second and third pair, in speaking
of these processes.

The Antennule are found in all species; in Sfenothocheres they are situated in front
of and outside the antenne, in all other forms they are found on the lateral margins of the
head, where these merge into the frontal margin. They are constructed much like those of

38

the females, e.g. where the antennule of the females are well developed and 3-jointed, those
of the males are equally so, and where they are reduced in size or in number of joints. we
generally — though not always (Spher. microcephala, Mysidion commune) — find a similar
reduction in the male. In Spher. microcephala (pl. VIL) the antennule of the female are
very short and 1-jointed, those of the male long and likewise without distinct articulation.
In Mysidion commune (pl. XI and pl. XII) those of the female are very short and 1-jointed,
those of the male short and 2-jointed. Their bristles are much the same as in the female,
and they have frequently a rather conspicuous olfactory seta. The greatest reduction is noticed
in Aspidoecia (pl. XII, fig, 3k and fig. 31), the antennulz of which consists of a very short,
naked joint terminating in an olfactory seta which is several times longer than the antennula.

The Antenne are altogether so like those of the female that a special description of
them is superfluous; where they are wanting or reduced in the female, they are equally so
in the male.

The Rostrum is very like that of the female, but seems now and then to be longer
and more slender; in Spher. microcephala it is much longer than that of the female (pl. VIII).
In several species, e. g. in Spher. modesta (pl. LX), the mouth-border is much broader, its
hairs at least are considerably longer in the male than in the female.

The Mazillule ave always found and are constructed like those of the female. In
dissecting the head of a male of Spher. frontalis [ found that, in addition to the two long —
though unequally long — principal branches and the long additional branch, the maxillula
of this animal possesses a fourth shorter one (pl. VII, fig. 6d), which proceeds within the
base of the anterior principal branch. As this supplementary branch is not likely to be
discovered without undertaking a dissection expressly for this purpose, I cannot tell whether
it is found in the female as well; without dissecting the rostrum I have looked for it in
vain in the female as well as in both sexes of other species of Spheronella. Fig. 41 in
pl. IUL. will give a good idea of the rostrum with antenne and maxillule in a male which
possesses all these organs in their typical form.

The Maxille ave well developed in nearly all species and are in the main constructed
like those of the females; sometimes they are somewhat smaller, sometimes rather larger, in
Aspidoecia (pl. XIT) much larger. Occasionally we find differences of detail in the two
sexes; in Spher. capensis the basal joint of the male has at its distal end, where the inner
and the posterior side meet, a rather high, prominent plate, the margin of which runs out
into spiniform processes (pl. VI, fig. 1 ¢ and fig. 1 d); this excrescence is wanting in the female.
In the male of Spher. insignis the posterior side of the basal joint is provided with a conside-
rable number of peculiar processes (pl. X, fig. 1c) which the female lacks. In Spher. margi-
nata (pl. XIIT) whose female has rudimentary maxilla, these organs in the male have about
the same general shape and size as in kindred species, but all three joints are fused together.

The Maxillipeds are well developed in all species and essentially like those of the
females, though in the male the basal joint is frequently provided with hairs, and also some-

39

times with processes, whereas in the female there are no processes and fewer or no hairs
etc. In Mysidion commune the male possesses on the outer side of the basal joint a knot-
like excrescence and a process of very considerable size (pl. XI, fig. 3g and fig. 3h), and
its second joint has a conspicuous process, all of which are wanting in the female. In Aspi-
doecia (pl. XII) the female lacks maxillipeds; in the male, though somewhat smaller than
usual, they are well developed: the basal joint is much as in Stenothocheres, but the second
joint, which as in several other forms consists of two completely fused joints, is exceedingly
short, somewhat shorter than the terminal joint.

Trunk-legs and caudal stylets. The occurrence of these organs is mentioned above
on p. 36. In Homoeoscelis (pl. IL and pl. XIII) there is but a slight difference between
the two similarly shaped pairs of trunk-legs and the caudal stylets, and as both are like
those of the female, they do not require further mention; we shall only add that they are
sometimes rather larger than, sometimes of the same size as those in the other sex. In Sfenotho-
cheres (pl. I) the trunk-legs are very similar to those of the female and of almost equal size,
however, as the trunk of the female is large, that of the male small, of course the legs of the
latter are much more conspicuous and appear larger. In the male the basal part of the legs
stands more out from the body, and the longer robust terminal spine on the outer branch is
longer than in the female; the other differences are insignificant. Thus, in Stenothocheres
Sarsii the spine on the inner branch of the second pair of legs is curved like a hook, in
Sten. egregius it is less curved, and in the illustrated specimen the right and the left spine
curve differently. Behind and above the basis of the second pair of legs both species show
two considerable spines which are situated close together on a small projection; L should
think they might possibly be considered as rudiments of a third pair of legs, but I do not
presume to have any definite opinion about the matter. The abdomen is small, with short,
distinct, rather broad stylets, not set off by an articulation, and each provided with four
spines, of which the two innermost are the longest and thickest.

In Spheronella, as a rule, there is a great difference between the two pairs of trunk-
legs and between each of these and the caudal stylets. The shape and size of the trunk-
legs vary much according to the species, and the appearance of the legs as well as of the
stylets presents very great variation on account of the very different length of their terminal
sete. In this genus the first pair of legs usually originates outside and behind the basis of
the maxillipeds, nearly in the middle between the lateral margins and the median line of the
trunk, at the bottom of a pretty broad transverse depression. Each leg consists of a basal
part, a peduncle, differing much in length and breadth (sometimes, as in Spher. intermedia
(pl. V, fig. 3f and fig. 3g), this part in exceedingly large), and of two branches, one of
which is generally longer than the other, sometimes the one is wanting altogether. As a rule,
none of the branches are articulated on the peduncle, and frequently one or both of them
terminate in sete, one of which is longer than the others, the one on the outer branch
often exceedingly lony, occasionally half as long as the whole animal. The second pair of

40

legs is situated at or behind the middle of the trunk, and if seen from below, near or on
the lateral margin; as a rule it is shorter than the first pair, the peduncle is not much
thicker than the rather short inner branch, whereas the outer branch — if there is one —
is triangular and often ends in a short seta. The terminal sete of the inner branch vary
as much in length as those of the outer branches of the first pair of legs, and one of them
can attain to half the length of the animal. The candal stylets are usually situated rather
close to each other, most frequently near the posterior end of the body, sometimes very much
to the front about at the middle of the trunk, especially where it is very large, as in Spher.
Bonnieri and in S. frontalis (pl. VII); in the latter species they even appear in front of the
second pair of legs. Both stylets as a rule are rather short, sometimes very short, nearly
cylindrical; one terminal seta on each stylet is often rather or very long, occasionally excee-
ding in length the above-mentioned long sete on the trunk-legs. — Several species of
Spheronella deviate now im one, now in more respects, from this description which is based
on the main bulk of the species. In Spher. modesta (pl. IX, fig. 2f and fig. 2h) the first,
and especially the second pair of legs are considerably reduced in size etc., whereas the
caudal stylets are comparatively large and constructed like those of the female (see above).
In S. decorata (pl. VII, fig. 3f and fig. 3g) the two pairs of trunk-legs are very much
alike, each leg consisting of a short basal part with two short branches, and each branch
ending in a thick, but rather short seta; caudal stylets are wanting. Concerning S. microce-
phala (pl. VILL, fig. 2g and 2h) which deviates considerably and is difficult to understand,
I refer to my description in the systematic part of this work. In S. curtipes (pl. X, fig. 2f
and fig. 2@) both pairs of legs are very small, slender and 2-jointed, the caudal stylets are
quite minute and situated far from each other on the posterior margin of a long and broad,
but not niuch projecting eminence, the posterior angles of which are decorated with peculiar
rounded processes and knots (might the whole formation possibly be a reduced abdomen ?).
It has been mentioned already that trunk-legs and caudal stylets have disappeared altogether
in several species of Spheronella as well as in Mysidion and Aspidoecia.

In the species belonging to Stenothocheres and Aspidoecia the body of the male is
quite naked, whereas all the other species are more or less clothed with hairs. In not
a few species the frontal margin is furnished with very short hairs or with fine spiniform
processes (the species of Spheronelia which live as parasites on Cumacea). In nearly all
species the margin of the lateral borders of the head are trimmed with a series or a stripe
of hairs usually of medium length, which as a rule extends towards the front in a curve
round the base of the antennule, ending just in front of it; posteriorly it follows the lateral
margin up to its curved extremity, whence (or a little in front of it) the stripe continues
across the sides and the back, now straight on, now curving or in a broken line, now advan-
cing, now receding obliquely. This line I consider as forming the boundary between the
head and the trunk, its hairs being now very long (pl. III, fig. 31; pl. VI, fig. 1d), now of
the same length as those which cover the sides of the trunk. Sometimes (e. g. pl. IV, fig. 3 h)

41

we see instead of a single line a wider or narrower band of hair going from the posterior
extremity of the lateral margin up across the back, and behind this line or band is a larger
or smaller transverse naked area, whereas the other parts of the trunk: the back, the sides,
the posterior extremity and the ventral surface, are closely covered with shorter or longer
hairs, with the exception of a transverse band in front between the first pair of legs — and
frequently their surroundings — which is naked. These hairs are usually simple; in Spher.
frontalis (pl. VII, fig. 6a, fig. 6b and fig. 6h) and in Mysidion commune (pl. XI, fig. 3 @ and
fig. 3h) the trunk is closely covered all over with transverse minute knots, each of which
bears several (in S. frontalis at least many of them ten) fine hairs. In Spher. Giardii the
trunk is covered with 2- or 3-branched hairs similar to those mentioned above in the
female of S. Calliopu and in S. irregularis. In the male of S. Calliopii (pl. III, fig. 3h
and fig. 3i) the hairs of the boundary line between the head and the trunk are particularly
long, whereas the dorsal surface and the posterior extremity are covered with fine. dots
resembling the roots of hairs, though I have been unable to find any hairs, and across the
back to the exterior angles of the first pair of legs we find a narrow, naked band; the
ventral surface behind the caudal stylets is provided with ordinary hairs. In Spher. microce-
phala (pl. VIII, fig. 2¢ and fig. 2h) the hair-covering is less developed than in any of the
other species, as only the hindmost part of the lateral borders of the head and the ventral
surface of the trunk are covered with hairs, the other parts of the body being naked. Ina
few species we find hairs in front of the base of the maxillipeds, and in Spher. chinensis
(pl. ILL., fig. 1a) and kindred species there is a bunch or a short band of hairs outside the
base of the maxillule.,

As to the internal structure of the male I confine myself to the following observa-
tions. In a well-preserved specimen we usually perceive through the transparent skin two
larger or sinaller globular bodies in the middle of the trunk or somewhat more to the front;
in Stenothocheres they are situated close to the front of the abdomen behind the base of the
second pair of legs. I will call these bodies spermatothece, though I cannot make out
whether they have really the function of such organs, or whether they are the testicles them-
selves. I have illustrated them in several forms, as Spher. paradoxa (pl. II, fig. 4 h, q),
S. capensis (pl. VI, fig. 1 ¢), S. Bonnieri (pl. VI, fig. 1a, q), S. frontalis (pl. VII, fig. 6 a, q)
and Mysidion commune (pl. XI, fig. 3g, q); in this last species the spermatothece are
particularly large and obliquely situated (probably a case of anomaly or of accidental pressure
in the figured specimen, for in the next species: Mysidion abyssorum (pl. XII, fig. 2 ¢, q)
they are normal). In Aspidoecia Normani the specimen illustrated (pl. XII, fig. 3k) showed
a single, but very large spermatotheca (q), but in a couple of other specimens I saw two
considerably smaller and normally situated spermatothece. In Spher. paradoxa I succeeded in
finding the genital apertures very close to each other on the posterior wall of the depression
which runs across the front part of the trunk on its ventral surface. From each spermato-
theca a rather short duct goes forward and obliquely towards the median line to its aperture.

6

42

In Homoeoscelis minuta (pl. I, fig. 1i and fig. 1k) I have found the rather small spermato-
thecee (though they are not illustrated) close together in the line between the hindmost pair
of trunk-legs, and I think I have found the two genital apertures in close proximity in the
posterior wall of the ventral depression — which is particularly conspicuous in fig. 1k —
in a line between the first pair of legs.

In a number of species belonging to Spheronella I have found a most peculiar struc-
ture beneath the larger part of the skin of the head at its back and sides. It appeared most
distinctly in S. paradoxa, where I saw very plainly beneath the skin a single layer of
rather large hollow spaces; fig. 4k in pl. IIT is drawn to the same scale of enlargement
as fig. 4i and shows the skin and two rows of the afore-mentioned hollow spaces beside
each other. In S. Metope (pl. IV, fig. 3i) the spaces were filled and appeared in outline
as shown in the illustration.

The males are sometimes hinged on the females, but much more frequently on the
gills or on the marsupial plates of the host by a thread which proceeds from the median
line of the front close in advance of the rostrum. This thread is secreted by a gland or
glands and can presumably be produced by the males of all species. The shortest thread I
found in Homocoscelis minuta, in two specimens, in one of which its length was similar to
that of the first joint of the maxilliped, in the other somewhat shorter. In e. g. Spher. para-
doxa (pl. IL, fig. 4h,s) the thread is about 3/s of the length of the animal, in Stenothocheres
Sarsvi (pl. I, fig. 2k,s) a little shorter and in S. abyssi (pl. IV, fig. 2 d) even a little longer
than the whole animal. I found the longest thread in a specimen of Aspidoecia Normani,
where it was between twice and three times as long as the animal, whereas in the spe-
cimen illustrated in pl. XII, fig. 3k it was scarcely half as long as the male. This last
instance shows that the length of the thread can vary very much in the same species, but
this is not usually the case, as in some species a shorter, in others a long thread is always
found. In all the above-mentioned and in several other species the thread is always simple
and cylindrical, generally a little dilated towards the distal end by which it attaches itself,
and not unfrequently the end is expanded into a disk. Deviating forms of this thread are
met with in the species of the genus Mysidion, and especially in the species which I have
placed together below under the heading of the Spheronella Leuckartii-group. In Mysidion
the proximal part of the thread is simple, the distal part appears in two varieties; either,
as in Mysidion abyssorum (pl. XII, fig. 2g), it shows two considerable fusiform expansions,
the middle parts of which are each surrounded by a peculiar collar-shaped ring, or, as in
Mysidion commune (pl. XI, fig. 3h,s), the apical part is very thick and above it the
thread dilates still more and becomes fusiform; its widest part has a collar-like ring, and
a similar ring surrounds it somewhat higher up, where the thread is only half as wide. In
the species belonging to the Spher. Leuckartii-group we often find the male hinged by a thread
Which varies in extent between nearly half and almost the full length of the animal, and is
constructed in the following way: it is divided into two parts, either of equal length, or

43

the proximal part longer than the distal one, the former ending in a thick, bell-shaped and
thick-skinned, hairy expansion (pl. II, fig. 4b); the distal part comes out of the bell in
which its extremity forms a little ball; its other extremity expands into a disk which is
elued on to the Amphipod. I have found several of such threads and examined them as
carefully as possible, but it is quite incomprehensible to me how the animal has been
capable of producing them.

ce. The Ovisacs and the Development of the Eggs.

1. The Ovisacs. Of forty-one species the ovisacs have been found, and only in
two species of Spheronella they are wnknown to me. In the two species of the genus
Stenothocheres they ditfer so much from those met with in the other genera, that I prefer to
leave out this genus for the present, setting it aside for separate treatment.

In Homoeoscelis, Spheronella, Choniostoma, Mysidion and Aspidoecia each female
deposes several — no doubt at least four or five — or many ovisacs, which, if not deformed
by pressure, are sub-globular, oval or, in Mysidion, of a short pyriform shape. In Homoeo-
scelis minuta, of which I have examined a large material, I can assert that the female
deposes at most eight ovisacs, though usually but five to seven are found; in Choniostoma
the maximum seems to be twelve, in Aspidoecia thirteen to fourteen, in Mysidion seventeen
or still more. In the numerous species of Spheronella which live in the marsupium of
Amphipoda, I cannot indicate the maximum of the ovisacs, partly because my material of
each particular species is too small, or because not unfrequently a couple or more of females
are lodged in the same marsupium, partly because, in many cases, one cannot be certain
that some of the sacs have not been washed away. Better information can be given about
some species living in the marsupium of Isopoda and Cumacea: in Spher. Munnopsidis I
found one female with twenty ovisacs, in S. decorata the same number, in one specimen
of S. modesta twenty-two, in another twenty-eight ovisacs, all laid by one single female.
This latter number may be supposed to be about the maximum, not only in the above-
mentioned species, but in the whole family. It is very difficult to indicate the smallest
number of ovisacs made by normal females of the different species, as, for one thing, it has
to be ascertained, whether the specimen in hand has altogether finished laying eggs, and a
considerable material has to be examined for this purpose alone; still, though I have not
done this, I think I can say that the number is never less than four or five, perhaps seldom
less than five or six. In all five genera each ovisac is smoothly rounded, its eggs being
as usual enclosed in a common membrane. In Homocoscelis, Spheronella and Choniostoma
all ovisacs are deposed freely without being attached to the female or having any real
connection with each other. Indeed, we see rather frequently some, or many, of the
ovisacs sticking together, or one, or several of them, adhering somewhere to the body
of the female; however, this kind of adhesion is of a secondary, quite unimportant nature,

6*

44

and is certainly owing to the fact that the membrane surrounding the ovisac was not
sufficiently stiffened, when — or shortly after — the ovisac was laid. In Mysidion and
Aspidoecia all ovisacs, from the moment they are laid till the larvae have swum out, are
hinged to the lips of the genital apertures by stalks, which are rather short (in Myszdion),
or very short (in Aspidoecia), so that we see pretty frequently six to seven, or sometimes
more ovisacs hinged at one genital aperture (pl. XI, fig. 3b); fig. 2b in pl. XII shows
how the lips of the genital aperture and the part behind them are covered by a plate formed
of a coagulated viscous substance, from which the stalks of the ovisacs proceed; the plate
must be considered as the coalescent basal parts of the stalks.

The genus Stenothocheres deviates considerably from the other genera, but unfor-
tunately I am not prepared to represent its conditions as precisely as I should like to do.
Of one of its two species I have seen but one single female with eggs, of the other (Sé.
egregius) my material is indeed very abundant, but not particularly good, some of it being
very old, and most of it, though of later date, having shrunk somewhat, because its hosts
— while still alive — had been put into too strong spirit. Im many cases I only found a
single lump of eggs, which was rather larger, or considerably larger than the female, had
no regular form, and was not surrounded by a common membrane. Sometimes, but not
always, this lump seems to consist of two — seldom three — smaller coalescent lumps;
four instances were of a more instructive nature. A female of S¢. Sarsii showed two lumps
of about equal size, one of which was free, the other (no doubt accidentally) adhering to the
female. One of them is illustrated in pl. I, fig. 2c, which shows the irregular shape and
want of a common membrane, as well as the size in proportion to the largest female which
is illustrated in fig. 2a and magnified to the same scale. The three other cases have been
observed in Sé. egregius; in all of them the female had doubtless finished laying eggs. In
one case two smaller, short oval lumps were glued together at their extremities, one con-
taining seven, the other nine eggs; in the second there were two lumps, one of them a
little larger, the other a little smaller than the female; in the third case there was an
oblong lump containing ten eggs, the young animals of which were a little more than half-
developed, six to seven larve which were about to break out of the shells, and thirteen
free larve; all this indicated that the eggs had been laid at intervals. It seems probable,
on the whole, that the eggs are not laid all at the same time, but successively, though the
intervals must be rather short, whereas the ovisacs, at least in most and probably in
all the other genera, are deposed at rather considerable intervals; this is easily seen from
the fact that among ovisacs deposed by the same female, we often find one or two which
have evidently been laid recently, whereas some others contain more or less developed larve.
We sum up our observations in the following statement, that in Stenothocheres the eggs are
deposed in one single large and free lump, or in a couple of smaller and free lumps of
irregular form and without the common membrane which belongs to a proper oyisac; and
finally, it seems rather probable that the eggs are not laid all at the same time.

45

We have now to deal with sevéral other questions, some of which are difficult to
answer definitely, namely: the size of the ovisacs compared with that of the females in the
different species, their relative size in females of the same species and of different species,
the number and size of the eggs in the ovisacs of the different species, and the fertility of
each species. Here, however, we at once meet two difficulties: the one mentioned above
on p. 24, that shortly before her laymg eggs the female is always somewhat (and no doubt
usually much) larger than after it, and in most cases it is quite impossible to procure spe-
cimens which are going to lay eggs, such as have half done and such as have quite done
laying eggs; most frequently one only finds from two to five specimens altogether, all of
which have half done or quite done, or else one or two of them are not full-grown; besides,
an ovisac is somewhat smaller when it has just been laid, than later on, when the larve
break out of it, for during the development the ovisac increases somewhat in size,
getting at the same time less firm, as each egg, which is always globular or polyhedrous
at the beginning, becomes elongated. Making allowance for this fact, it is seen that in
most species there is not usually much difference between the sizes of the ovisacs deposed
by the same female, whereas in some species the ovisacs often, though not always, differ
very much in dimension (pl. X, fig. 4a; pl. XI, fig. 3c). There is a great difference, on
the other hand, between the average size of the ovisacs compared with the adult females of
each species; comp. e. g. the proportion between fig. 3a and fig. 3c¢ in pl. LIT with that
between fig. 4a and fig. 4d in the same pl. Of course, we may say that as a rule the
ovisacs are comparatively smaller in the species which depose a very large number of them
than in those which lay rather few, yet even in these the ovisacs sometimes do not exceed
middle size. In the species whose females are large, as a matter of course, the ovisacs are
much larger than in the small species.

The number of eggs contained in the ovisacs naturally depends on the size both of
the eggs and of the sacs. It is true, I have not measured the eggs of various forms, but
as I know the larve that come out of the eggs in more than half of my species, as the
length of these larve varies between about ‘15 mm. and -30 mm. only, and as they show no
relatively great differences either of breadth or thickness, I possess a pretty accurate standard
for judging the relative size of the eggs, for, evidently, the largest eggs (judging from the
larve: those of Spher. decorata and of the genus Choniostoma) cannot be much more than
double the diameter of the smallest (in the genus Homoeoscelis). The further result is, that
in the species whose females are very small, as Stenothocheres egregius (pl. 1), Homoeoscelis
minuta (pl. Il), and especially in Hom. mediterranea (pl. XIII), the eggs must by very large
compared with the females, whereas the eggs must be proportionally small where the females
are very large, as in Spher. Calliopi (pl. IIL) and in the two species of Choniostoma
(pl. X and pl. XI). That these statements agree with facts appears very clearly from the
illustrations of the eggs and females of the above-mentioned species; — it must be borne

46

in mind that the female and eggs of the same species are always illustrated enlarged on
the same scale.

As the difference of size between the very small species (or rather those whose
adult females are very small), as Homoeoscelis minuta and H. mediterranea, and the very
large ones, as Choniostoma mirabile and Ch. Hansenii, is exceedingly great (s. above p. 24),
and the difference between the eggs not being.greater as just stated, it follows that, with
equal proportion between fertility and volume, the large species lays manifold more eggs
than the small one. To abide by our example: the number of ovisacs in Homoeoscelis
amounting to about eight, in Choniostoma to about twelve, it is evident that in the small
species we find few, in the large ones numerous eggs in each ovisac, and this fact is indeed
proved by the following figures: in an ovisac of Homocoscelis minuta are found only about
14 to 18 eggs, in H. mediterranea no more than about 6 to 10, whereas in a middle-sized
ovisac of Choniostoma mirabile I have counted 1057 eggs. If, in.a smaller species, as e. g.
Spher. dispar and S. modesta, the number of ovisacs increases to about twenty, or, as in the
latter species, to about twenty-eight, the quantity of eggs contained in an ovisac is naturally
rather small (pl. LX, fig. 3e, fig. 3¢ and fig. 2c), whereas in the gigantic Spher. Munnopsidis,
of which species one specimen — consisting only of a half-emptied skin — was about 5 mm.
in diameter, the number of ovisacs may indeed amount to twenty, still the average number
of eggs in each ovisac (in this species I have found great variety in the size of ovisacs of
the same specimen) is nevertheless very great, as is shown quite distinctly in fig. 4a on pl. X.

The entire bulk of eggs deposed by a female — as stated above — is always larger
than the animal itself after it has laid them, and it is often so marvellously large, compared
with the female, that we hardly understand the possibility of it (s. pl. XI, fig. 3a). This
state of things, however, may be partly explained by the fact that the ovisacs are deposed
at certain intervals (about a possible deviation in Stenothocheres, see above), and that conse-
quently the eggs can be gradually developed in the female. If we find seven or eight
ovisacs in a female, the development of at least one or two of these is nearly always so
far advanced, that the larve are in the Nauplius stage; where ten or eleven, or still
more, Ovisacs are found, one or two of these usually contain almost or quite full-grown
larve. The length of time which elapses between the laying of the first and of the
last ovisac in specimens containing a large number of these sacs, as Spher. decorata
and the other species living in the marsupium of Cumacea, seems to be about equal
to that which the first laid ovisac requires for its development: the division of the
germ, the Nauplius stage, and the development of the larva with numerous limbs, though
I cannot tell how many days are required for this process. The two species which lay
the smallest number of eggs are the diminutive forms Homoeoscelis mediterranea and
Stenothocheres egregius, the former has as many as eight ovisacs containing in all 60 to
70 eggs, whereas Sf. egregius, as a rule, only lays about 30 eggs (I have found between

16 and 42 eggs, the latter number in an exceptionally large specimen). The largest species,

AT

viz. Spher. Munnopsidis and the two species of Choniostoma, lay the largest number of
eggs. In a specimen of Ch. mirabile with eleven ovisacs 1 counted the eggs in one of these
presumably of middle size, and I found 1057 eggs, so the number of eggs laid by this
specimen may be said to amount to 11,620, and if we take this figure as the normal
quantity in Ch. mirabile of the Kara Sea, at any rate we do not exaggerate. In Spher-
Munnopsidis the number of eggs seems to be even much higher, however, it would scarcely
be possible to calculate the exact amount. Between these last-mentioned species and
Stenothocheres egregius the other species present a variety of transitions, as far as fertility
is concerned. In a following chapter about distribution etc. I shall have an opportunity
of making some further observations on these rather remarkable differences.

Il. The development of the eggs. As for the division of the germ and the earlier
part of the embryological development, which I have not studied myself, I shall refer to the
representation of Salensky. As in all Copepoda a Nauplius stage is developed (pl. XI, fig. 1¢
and fig. 1d); but this stage never becomes free, it evolves itself into the stage of a highly
organised larva, of which a detailed description is given below. When this larva, which
corresponds with the first Cyclops stage in other parasitic Copepoda, is full-grown, it breaks
out of the egg-membrane and of the ovisac. As for the details concerning the development
of the Nauplius stage and of the larva, I must again refer to Salensky.

It may be added that in material preserved in spirit (and I have seen no other)
the ovisacs, when younger, are of a light yellowish colour, but they gradually get whiter,
as the larve are developed.

d. The free Larva.

I. The Material. Of several species 1 have found free larve, which were either
swimning out of, or had recently swum into the marsupium, and these specimens, of course,
were excellent, showing the normal shape of the larve. Of a number of species I have
procured a rich material of larva by pulling them out of an ovisac; they were good enough
when taken while about to break out of the egg-membrane, though the body might be
somewhat soft and not extended in its full length,» thus showing a vaguer outline which did
not quite correspond with that of the swimming specimens. Sometimes I had to content
myself with younger animals, which had to be pulled out of their egg-membranes, and which
had indeed a well-developed mouth, maxilla, maxillipeds etc., but whose cephalothorax was
decidedly shorter and stouter than those of the full-grown larve, and which also showed
other signs of unfinished development, so that no reliable observations could be made of
difficult parts, as e.g. the branches of the maxillule. Finally, of a few species I had only
larvee which had swum into the marsupium of a new host, where they had attached them-
selves (9: below), and in these the cephalothorax, as a rule, was shorter and broader
than in the free specimens. Of some species I had larve of this kind as well as of others,

48

that had been taken in a free state, or had been pulled out of an ovisac. All this put
together gives the result, that I have been able to examine the larvee of twenty-three species,
lacking only the larva of Stenothocheres Sarsii and nineteen species- of Spheronella; thus L
possess the larva of Sten. egregius, of fifteen species of Spheronella and of all seven species
of the four remaining genera. Fortunately the fifteen species of Spheronella represent nearly
all the more important types of this large genus.

As for the illustrations, I beg to notice that I have frequently omitted the two pairs
of natatory legs, or at least their branches, as their representation, as a rule, would have
been exceedingly difficult, and the omission is of little consequence, as the number and the
arrangement of the natatory hairs are very much alike in the different species. In some
cases the abdomen is also left out. My representations of the maxillule include all that a
careful study enabled me to observe; however, I am inclined to think that a better material
would sometimes have allowed me to discover one — occasionally two — more branches.

IL. Structure of the Larve. The length of the body usually varies between -20 and
°25mm.; the longest larva I found belonged to Spher. decorata, and it is ‘30mm. long, the
shortest, 15 mm. in length, belongs to Homoeoscelis minuta. The body is divided into two
parts: the cephalothorax and the abdomen. The cephalothorax is somewhat depressed,
usually oval and about 11/2 time as long as it is broad, sometimes (DZysidion, pl. XII, fig. 2h)
more elongated, almost double as long as it is broad; it consists of two divisions, namely,
the cephalothorax properly speaking, and a single trunk-segment (pl. III, fig. 3k), which are
joined by a rather sinuate articulation, whereas the trunk-segment is between five and eight
times (in a single case about eleven or twelve times) shorter than the anterior division.
I have found behind the segment mentioned a very short portion which looked like the
rudiment of a second free segment (pl. III, fig. 3k) and belonged to the cephalothorax, not
to the abdomen; I cannot, however, say anything definite about this part and will content
myself with stating what I have observed. The abdomen is narrow, and its length varies
between a little more than one sixth and rather more than one third of that of the cephalo-
thorax; it always consists of three distinctly separated segments and has two caudal stylets,
which as a rule are plainly articulated on the third segment, but sometimes are coalescent
with it (e.g. pl. I, fig. 11).

The foremost half of the large anterior division of the cephalothorax is always
provided with antennule, antennze, rostrum with mandibles, maxillulee, maxillze and maxillipeds;
the hindmost half has a longer or shorter odd pouch, which turns backward, decreasing in
width towards its distal end (pl. I. fig. 11, 1); its posterior part forms a free, either pointed
or rounded bag along the ventral surface, often covering the transversal band which unites
the first pair of natatory legs (pl. III, fig. 31), sometimes even the band between the second
pair of natatory legs (pl. II, fig. 11). The first pair of natatory legs is situated at the
posterior extremity of the first division of the cephalothorax, whereas the second pair
proceeds from the free trunk-segment. It may be mentioned finally, that Salensky has

49

shown the existence of an eye (op. cit. p. 314, Taf. X, fig. 21 and 23, oe), which in the illu-
stration is drawn as situated on the ventral side of the forehead »in Form yon zweien am
oberen Theile etwas verdickten sichelf6rmigen Pigmentflecken, welche in der Mitte sich
beriihren und eine x-formige Figur darstellen«. As a matter of course, the eye must be
found on the dorsal surface, but I have been unable to find it on my larve, probably
because the spirit had dissolved the pigment.

The Antennule are always rather short; they consist typically of three joints, the
second of which is usually short and not unfrequently coalescent with the first, in which
case we only perceive two joints. The first, and particularly the third joint, are provided
with pretty long sete; the terminal seta of the third joint is very long, and from the lower
side of this joint proceeds always a single, particularly long olfactory seta (pl. I, fig. 11, b),
which is at least double, usually several times, the length of the whole antennula; sometimes
this seta is exceedingly long, as e.g. in Spher. dispar (pl. [X, fig. 3k) and in Spher. insignis
(pl. X, fig. le), where it reaches further than the middle of the abdomen, nay in the last-
mentioned species the olfactory seta in itself is longer than the whole cephalothorax. The
antennulz are always attached pretty far from each other at the edge of the cephalothorax,
the area between them forming what I call the front. Close to the inner margin of the
base of the antennula we often see an oblique list; moreover, in nearly all species of
Spheronella which are parasitic on Cumacea, the front is decorated with one or several
rows of delicate and peculiar processes, which decoration reaches its highest development in
Spher. decorata (pl. VILI, fig. 3i and fig. 31). In Spher. modesta these processes are replaced
by transverse lists (pl. [X, fig. 21).

The Antenne proceed behind, and usually at the same time somewhat obliquely
inside the antennule, but never from the base of the rostrum. Sometimes they are conside-
rably shorter. than the antennule, sometimes about the same length, and in the genus
Homoeoscelis (pl. 11, fig. 11 and pl. XIII, fig. 1h) more than double the length. In Spher.
marginata (pl. XIII, fig. 6g) only two joints are found, in all other species they consist of
three or four joints, three of which are always distinct, but it is often difficult to make out
for certain, whether the eminence from which the supposed second joint proceeds, is a real
joint, or in other words, if the apparent basal joint consists of two joints; as, however,
Spher. antillensis has four very distinct joints (pl. IL, fig.2e), this is probably the typical
number. The terminal joint is nearly always short and usually ends in a long, thick seta,
beside which we frequently find a shorter one. The next joint is now rather short, now
long, or very long, and where the antenna is long, it is on account of the length of this
joint, as the basal joint, or where there are four joints, the two first of these are never
elongate, but sometimes (pl. IX, fig. 2i and fig. 3k) comparatively broad. In Mysidion
(pl. XII, fig. 2h) the antenne are very small, and in Spher. microcephala (pl. VIII, fig. 21)
almost rudimentary, in both cases 3-jointed, with an exceedingly short terminal seta.

The Rostrum seems to correspond only with the more distal part of this organ in

7
(

50

the female and the male, for not only are the antenne situated a little outside its base, but
the maxillule are found quite, or nearly quite, outside it. The general structure of the
mouth is like that of the adult animal; the mandibles are frequently seen in the opening,
but the hairs of the mouth-border are always short, frequently so short. that they can only
be discovered with the greatest difficulty.

The Maxillule are difficult to understand, and it is very difficult to discover all
their sete. As mentioned above, in the various illustrations of the larve I have drawn
what I have found, but I am pretty sure that I have not everywhere found all the elements.
The highest development I met in Spher. Calliopii (pl. ILI, fig. 31) as well as in the species
which are parasitic in the marsupium of Cumacea, as Spher. decorata (pl. VIL, fig. 31),
S. modesta (pl. LX, fig. 2i) and S. dispar (pl. LX, fig. 3k). In these figures we see obliquely
behind and outside the rostrum on each side four sete, the two hindmost of which are
coalescent or adjacent at their base, one or both of them being plumose. Obliquely from
these and somewhat nearer to the rostrum proceeds a third seta, which turns. straight
towards the front, and obliquely before this one again, there is a fourth, shorter seta. I[
suppose that all these four setz belong to one maxillula, the basal part of which is not
separated from the ventral side of the head. In Spher. marginata (pl. XIII, fig. 6g) the
innermost seta is reduced to a short process. In most of the other forms I have only been
able to find three sete, e.g. in Spher. microcephala (pl. VIL, fig. 2i) and in Choniostoma
mirabile (pl. XT, fig. le), or two, or only one. In Stenothocheres egregius (pl. I, fig. 11) I have
found a maxillula (e) which reminds me much of those in the adult animals, as it consists
of a short, basal part, from which proceed two thick sete, of which the hindmost is shorter,
the foremost very long. In the genus Homoeoscelis (pl. I, fig. 11 and pl. XIII, fig. 1h) I
have been unable to find vestiges of maxillule.

The Maxille nearly always consist of three distinct joints, and are very much like
those of the adult animals, though the stout basal joint, as a rule, is narrower and the two
next joints are longer than in the adult; these two joints are slender, and the last one
somewhat curved and claw-like. In Homoeoscelis only the two last joimts are entirely
coalescent, forming one curved joint, which moreover along the larger part of both margins
is provided with exceedingly fine and short setiform processes (pl. XIII, fig. 1h). As a rule
all three joints are simple and smooth, but in those species of Spheronella which live in
the marsupium of Cumacea, the inner margin of the third jomt is coarsely or finely serrated,
and the first joint has on its inner margin, against which the second joint can be folded
up, a double row of fine cylindrical processes (pl. VIII, fig. 8n and fig. 30), and a similar

decoration is seen in Spher. Maunnopsidis (pl. X, fig. 4d). — The two maxille are always
situated at some — usually at a considerable — distance from each other.

The Maaillipeds, as a rule, are placed close behind the maxille, and also generally
somewhat closer to the median line than these; in Homoeoscelis only (pl. Il, fig. 11 and
pl. XII, fig. 1h) there is a great distance between these two pairs of appendages. The

51

maxillipeds are always of considerable size, they are very like those of the males, and
always consist of four distinct jomts. Their rather stout basal joint is nearly as long as,
or somewhat longer than, the three following joints together; the second and the third are
very slender, and their joint length is a little longer, or somewhat shorter, than the last
joint, which is extremely slender, almost setaceous, slightly curved and pointed. All the
joints are nearly always smooth and naked; in Spher. Maunnopsidis the fourth joint has
towards its apex three spiniform processes (pl. X, fig.4d), and in Mysidion abyssorum there
are five or six somewhat similar processes along the more central part of the immer margin
(pl. XII, fig. 2h); the third joint at its extremity is always furnished with a spine inside
the articulation of the fourth joint.

In most figures I have carefully illustrated the sub-median skeleton, which consists
of lists running backward from the base of the rostrum and the maxillule, surrounding the
base and forming the articulation of the maxilla and the maxillipeds.

The two pairs of natatory legs of each specimen are very much alike, and they differ
very little, comparatively, in the various species. Each leg consists of a good-sized peduncle,
which is particularly broad in Stenothocheres egregius (pl. 1, fig. 11, m and n), somewhat nar-
rower, or rather narrow, in the other species (see particularly pl. VIL, fig. 2i); from the
posterior margin proceed at some distance from each other two one-jointed, about equally
long branches, and the outer branch, which proceeds from the end of the peduncle, is broader
than the inner one and rather dissimilar in outline. The outer branch of the first pair of
legs, as a rule, has four rather short, naked sete on its outer margin, two very long
plumose setze on its terminal margin; on the inner margin it has either two very long
plumose set (pl. IX, fig. 3k) or one of this kind and one much shorter, naked seta (pl. I,
fig. 11). The outer branch of the second pair of legs is very like that of the first pair, but
its outer margin has only three shorter, simple sete, its terminal margin two, and its inner
margin two exceedingly long plumose setz, all four of which are longer than in the first
pair of legs. The inner branch of the first pair of legs has four, of the second pair three
very long, plumose sets on its inner margin, and in both pair of legs two similar sete
on its terminal margin (all these sete are longest in the second pair), whereas the
outer margin has only one single seta, which is either short and naked, or very long and
plumose. These are the results of my researches in the few species whose natatory legs
have been examined with special care, but it must be observed that these species belong to
three genera: Stenothocheres, Spheronella and Choniostoma. Eyen if an examination of more
species should show greater variety in the number of sete, such differences are not at all
likely to be considerable, and furthermore, it is in most cases exceedingly difficult to count
the setze accurately, as the legs are very frequently folded up or standing on edge; therefore
it would be all but impossible to make any practical use of the presence or absence of such
a seta as characteristic mark of species or genera. — The two legs belonging to each pair
are, as usual, united by a prominent, movable transverse band (pl. I, fig. 11, m‘ and n’).

7*

(

52

The first abdominal segment always dilates considerably from its base towards its
end, and the free posterior angle has a powerful, often spiniform, seta, the length of which
varies between being a little longer than the following segment (Stenothocheres, pl. 1, fig. 11)
and being longer than the whole abdomen, and plumose in its distal half (Choniostoma,
pl. XI, fig. le). Inside or outside this seta and close to it there is always another seta,
which, as a rule, is much shorter, and only in Spher. microcephala (pl. VIII, fig. 21) is
remarkably long, though somewhat shorter than the first one. The second segment is
sometimes shorter, and in this case not unfrequently somewhat narrower, than the first one,
e.g. in Choniostoma, sometimes quite as long, and always without sete. In Stenothocheres
(pl. I, fig. 11) the third segment, together with the not separated caudal stylets, forms a large
and broad, elongate segment, much larger than any of the preceding ones, and incised
posteriorly in the median line. In all other species the third segment, together with the
caudal stylets, is nearly always somewhat, and generally much, smaller than the second
segment, and the stylets are sometimes not set off from the segment, but most frequently
distinctly articulated on it as two short, almost cylindrical joints. Each stylet has always
a very long and thick, sometimes plumose, seta, which in Stenothocheres egregius is only a
little longer than the abdomen, in Mysidion and Aspidoecia somewhat longer, though not
nearly half as long as the cephalothorax, in Homoeoscelis, Spheronella and Choniostoma
longer than half the length of the cephalothorax, and sometimes attaining to three quarters
the length of this part, e.g. in Spher. dispar (pl. LX, fig. 3k). Outside this long seta each
stylet has in Stenothocheres four, in the other species two or three, comparatively short sete.

Whereas there were great differences between the females among themselves and
between the males among themselves in the different genera and species, we see from the
detailed description given above, that all larva I know are surprisingly uniform, so much
so, that I have been able to find rather insignificant generic characters only in Stenothocheres
and Homoeoscelis, as distinct from the four other genera; at the same time the larve of
Mysidion and Aspidoecia — whose females deviate much from those of the other genera
with regard to receptaculum seminis, the position of the genital apertures and the hingement
of the ovisacs — deviate less from various larvee of Spheronella, than these differ from
each other.

Il. Further Development of the Larve. The larve, after making their way out
of the ovisac, — at least as a rule, swim out and seek a new host. I cannot deny the pos-
sibility that one or a few of the larve may remain in the branchial cavity or in the
marsupium of the mother’s host, though I doubt it very much. In a marsupium which
was infested beforehand [ have repeatedly found one or several larvee, which were
decidedly invaders. [ met with the greatest invasion in a specimen of Hippolyte Gaimardii,
where in one of the branchial cavities I discovered a very young female of Choniostoma mirabile
and certainly more than fifty larvae and pup hinged on the gill-fibres (s. the special
description below).

When the larva has found its new host, it attaches itself either beneath the cara-
pace to the branchiz or in the marsupium to one of its plates, to one of the gills, or simply
to the ventral surface of the body, or to the basal part of a leg, and in case it attaches
itself to a not full-grown female of Amphipoda, of course it must content itself with one of
the three last-mentioned places. The larve of Aspidoecia fasten themselves either outside
on the dorsal surface of the host (an Mrythrops), if they are growing into females, or on
a female of their own species (pl. XII, fig. 3b), if they are going to be males. The fixation,
which is very solid, is effected by a viscous substance, which expands itself so as to form a
larger or smaller plate on the front (pl. IV, fig. 1e,s; pl. VIII, fig. 2i; pl. XI, fig. 1e,s).
This viscous substance must be secreted of a gland in the front part of the head, the orifice
of which, however, I have tried in vain to find; the gland itself must be studied from fresh
material. (It was pointed out long ago by several authors, that the larve of various Caligide,
of Achtheres etc., in their first stage fasten themselves in a somewhat similar manner by a
»Stirnband« (Claus).) The larva, after hinging itself in this way. relaxes the grip of its
limbs and hangs quite free; thereupon it begins to change form, bending forward the last
joint of the maxillz, and its cephalothorax getting gradually shorter and broader (pl. XT,
fig. Le; pl. LV, fig. le); how short and broad it may occasionally become, may be seen on
pl. [V, by comparing fig. 1c, which represents a free larva, and fig. 1d, which represents
a larva that has reached its full breadth, and which no doubt is going to develop into a
male; fig. le is an intermediate form shortly after the fixation. Then the muscles etc. in
all the limbs and in the abdomen dissolve themselves, and the contents of these organs are
transferred into the cephalothorax, the muscles of which have also been dissolved, and finally
this united substance is surrounded by a new skin under the old one. The subsequent
development will be treated in the next division.

e. The post-larval Development; the Pupe.

The post-larval development, which takes place between the larval stage just described
and the appearance of adult males and of females (which, though very small, in all important
features resemble the egg-laying specimens), offer the greatest deviations between the different
forms, but, unfortunately, the representation I am capable of giving is very fragmentary.
The larva in many cases develops into a pupa, out of which evolves the female, and, in
some cases, the male; in other cases the male is developed immediately from the larva etc.,
and in Mysidion the metamorphosis is more complicated. I know the complete development
only of two species of Spheronella and of Homocoscelis minuta, but the two first-mentioned,
in particular, are fortunately very different from one another; I know, moreover, the develop-
ment of the male in Aspidoecia, and of the females belonging to the species of the Spher.
Leuckartii-group. Finally I have found a pupa of each of four other species of Spheronella

5A

(S. Argisse, S. longipes, 8S. microcephala and S. insignis), numerous pupe of Choniostoma
mirabile, and three different stages of development of Mysidion commune.

Let us begin with the simplest form of development. Ona completely adult female of
Aspidoecia Normani, sitting on the dorsal surface of the abdomen of Evythrops serratus
G. O. Sars, I found four larve attached (pl. XII, fig. 3b, where one of the larve is left
out and two of the others designated by a v.) One of these came off easily, when touched,
and it appeared that its skin had begun to burst along the lateral margin; on a closer
examination it burst somewhat more, and it proved to contain a full-grown male. In this
state the preparation is illustrated in pl. XII, fig. 3m. The spermatothece of the male
were filled, and it had a very short and very thick frontal thread (s). This instance sutfi-
ciently proves, that the male develops itself directly in the larva, without the intermediate pupa
stage and without a second moult. IL also found a single larva, which had placed itself
directly on the carapace of the host, but its examination gave no result, its development not
being far enough advanced. However, I have found exceedingly small females sitting on
different parts of the host, and I have not the slightest doubt that the larvee which are
going to become females, attach themselves directly to the host, though I do not know,
Whether they pass through the pupa stage or change directly into females, yet I feel
inclined to accept the latter alternative, seeing that the parasite sits on the outside of its
host, thereby running the risk of falling off very easily.

We now come to a species in which both sexes pass through a pupa stage, namely
Spher. Giardii (pl. VI, fig. 3i, fig. 3k and fig. 31). I have found three male pupz and
not a few female ones. The body is of a short ovate shape; the males are more oblong and
smaller, *125 mm. in length (fig. 3k), the female pupee stouter and varying in length between
125 mm. and -142 mm. (fig. 31, which is drawn on the same scale of enlargement as fig. 3 k).
In the female the foremost two thirds of the ventral surface form a broad, naked, odd area,
whereas the whole remainder of the body is closely covered with rather short hairs. The
male pupa is covered with hairs like the female, except that part of the back which corre-
sponds to the head and the fipper parts of its lateral surfaces, which are naked (fig. 3k).
Fig. 31 shows a male pupa from below, fig. 3k from the side; the antennule (a), the
antenne (c), the maxillule, the maxilla, the maxillipeds, the trunk-legs and the caudal sty-
lets are seen as naked, smooth, pouch-shaped processes, whereas the mouth is developed as in
the adult animal; in front of the mouth we notice a semicircular, rather vaulted and prominent
area, and between the maxilla and the maxillipeds two pairs of oblong, somewhat prominent
knots, corresponding with the sub-median skeleton. The female pupa has also a free mouth
and all the same processes and projecting parts as the male, from which, however, it is
easily distinguished, not only by the above-mentioned difference in the extent of the hair-
coat, but also by the size of the processes which stand in the place of the trunk-legs, and
which are very small, whereas in the male pup these organs — especially the first pair
— are much larger and furcate at the end This difference between the trunk legs, which

55

entirely agrees with that in the adult animals, proves in a. satisfactory way that my
suggestion with regard to the sexes is correct. One of the illustrated male pupe (fig. 3 k)
is fastened by a frontal thread, which is about one third the length of the body and conside-
rably dilated towards the end, but its extreme expanded part is of a different quality and
forms a disk-like plate. In the other male pupa (fig. 31) the thread is shorter and some-
what thicker, but its distal end is broken off. The fixation of the female pupa is effected
by a thread, which is so short that the front part of the animal is pressed against the gill,
or the plate of the marsupium, to which it is attached. — It is stated above that the pupz
have a well-developed mouth, and it would seem probable that at least the female pupe
take food and grow a little. Undoubtedly the males and females come out directly of their
respective pup, like the females of the species belonging to the group of Spher. Leuckarti,
in which [I have observed the fact myself. Only one point seems to present some difficulty,
namely, that my male pupe are only °125 mm. in length, whereas the male animals are
between “17 and 21 mm. lone and of a similar shape. With regard to this point I refer
to my observation of the growth of the male of Spher. paradoxa mentioned below on p. 57—d8.

Homoeoscelis minuta. A single pupa (pl. I, fig. 3b) was found hinged by a frontal
thread to the gill-bearing epipod. The pupa is ‘18 mm. long, of an elongate oval shape and
naked all over. We see the pouch-shaped processes in which the antennulz (a), the antennz (c),
the maxille (f), the maxillipeds (g), the first pair of trunk-legs (m), the second pair (n) and
the caudal stylets (p) are developed; but besides all these, we notice between the second
pair of trunk-legs and the caudal stylets a pair of very small, most peculiar processes (x),
which are possibly a rudimentary third pair of legs that do not develop any further, and
which disappear again. The mouth with the mandibles is like the pupa of Spher. Argisse
(s. below); the frontal thread is scarcely a fourth of the length of the animal, it is simple,
with a discoid expansion at the end. This pupa was hinged in the branchial cavity between
two adult males attached in the same way, but there was no female, and these two circum-
stances make it more than probable that the pupa was a female, especially, as in a large
materia! of this species I have seldom found more than one male, and never more than two
males and one female in the same branchial cavity. Later on I found in two specimens

respectively two and three pups, one among the latter of which — being no doubt younger
than the others — was somewhat smaller and had less developed rudiments of limbs, though

otherwise it was similar to the other four, all of which agreed with the above-described
specimen. (The frontal thread in one of the specimens was half as long as the body).
Considering that (as stated above) I have never found more than one female and two males
in the same branchial cavity, the four large pupae must either all be males, or — which is
probable — be male and female pup. So, judging from the sex of the minutely described pupa,
there is no difference between the development of the two sexes, and this agrees very well with the
fact that recently hatched females can sometimes be distinguished from the males only by
possessing genital apertures, as in several males the spermatothecse are not distinctly seen.

56

At least with regard to the structure of the pupe we know, Spheronella Argisse,
Spher. insignis and Choniostoma mirabile come rather close to the two preceding species ;
each of them will now be treated separately.

Spheronella Argisse. Of this species I have found a single female pupa (pl. TV
fig. 31 and fig. 3m), which in the most important features agrees with the female pupa of
S. Giardii. The body is ovate, naked all over, -15 mm. in length, and, like the last-men-
tioned species, provided with the pouch-like processes, in which antennule (a), antenne (c),
maxillule (e) maxilla (f) maxillipeds (g), trunk-legs and caudal stylets (p) are developed, and
all these processes show about the same relative size as the corresponding organs in the
females compared with each other; moreover, the mouth is distinct, and the mandibles are
also seen in fig. 31. The animal is attached by a very peculiar crooked funnel of conside-
rable size (s), which is of course made of a viscous substance, and its narrower, though
comparatively thick, base proceeds from the front.

Spheronella insignis. Of Diastylis cornuta Boeck a single pupa was found (pl. X,
fig. 1h), 14 mm. in length and sub-globular in shape. The mouth is well developed, as in
an adult female; antennule, maxillule, maxilla and maxillipeds are seen as protruding naked
pouches of somewhat irregular shape; in front of the mouth are found two rather large, odd,
connected areas, and close behind them a smaller spot on each side of the median line; in
front of, and in an oblique direction from, the maxillule, there are several small areas, and
finally a large transverse area, expanded in the middle, which joins the bases of the maxilli-
peds. All these areas are naked, and more or less prominent compared with the surroun-
ding skin. Except these organs and areas and the surface between them, the whole ventral
surface of the pupa and its sides are covered with hairs of medium length; the back is
covered in the same way on its most anterior part and on its posterior half, whereas a broad,
transverse area extends over the larger part of its anterior half; this area is naked, and
closely covered all over with irregular projections of a comparatively rather considerable
size, the real shape of which can only be recognised when seen obliquely, whereas a perpen-
dicular view gives the impression that this surface is covered with numerous irregular lines,
forming ovals, oblong spots or simply flourishes. I have been unable to find out with
certainty the sex of this interesting pupa, as the adult male of this species is devoid of
trunk-legs; however, I consider it to be a female.

Choniostoma mirabile. On the gills of a Hippolyte Gaimardii M.-Edw. 1 have
found a number af larve, which showed all the stages transitional to that of the pupa,
besides numerous fully developed pup (pl. XI, fig. 1 g—1k). A comparison between the
figures 1h, 1i og 1k, which are drawn to the same scale of enlargement, will show that
the pup differ much in size and somewhat in shape; the largest specimen I have measured
is 38 mm. broad and -27 mm. long, the smallest only ‘27 mm. broad and °19 mm. long,
and one specimen, which was still enclosed in the skin of the larva, is only “19 mm. broad

and ‘18 mm. long. So the pupe grow very considerably after breaking out of the larval

57

skin, and there can be no doubt that they take nourishment through their well-developed mouth
(s. later on under Spher. danica.) They are always considerably depressed, the anterior
margin is long, now quite straight, now a little concave, in the younger specimens occasio-
nally a little convex; the lateral margins converge rather considerably backward and merge
more or less evenly into the posterior margin. The mouth is pretty well developed, with
distinct mandibles (fig. 1g), and is situated much to the front on the ventral surface; it is
surrounded by rather small pouch-like processes: antennule (a), antennze and maxille, and
behind it is found a rather large, peculiar area. Near the anterior margin on the ventral
surface is seen a body with an irregularly curved posterior margin, and this is the adhesive
plate (s), by which the animal is hinged. The parts just described on the ventral surface
are surrounded by a naked area, whereas the greater part of the remainder of its surface
is provided with hairs, which are sometimes arranged in rows of two or three or more,
sometimes are more scattered, and the hairs which grow close to the edge are rather long,
the more central ones are short; the larger part of the dorsal surface is naked. Fig. 1i
and fig. 1k reveal that the contents of the pupa — perhaps on account of alcoholic influence
— do not reach the outer skin, whereas fig. 1h shows a very large and entirely filled
pupa; fig. 1i, the specimen represented on a larger scale, so far shows the same as the two
illustrations just mentioned, but it reveals at the same time that the inner body has its
own skin with distinct sets at its margin. The male of Choniostoma being wnknown, |
cannot decide how far all the specimens found are only female, or both female and male pupz.

We now come to a species — Spheronella paradoxa — whose development differs
very much from that of Spher. Giardii, or that of Homoeoscelis minuta, and the forms
which, according to my just stated (though rather defective) knowledge, are related to these
species. In Spher. paradoxa both sexes develop themselves without passing through the stage
of an independent pupa properly speaking, nevertheless there is a considerable difference of
aspect between the development of the sexes. Let us first examine the development of the
male. I had a very considerable material of larvee, which were hinged by their front, and
in which the cephalothorax was nearly as broad as long, besides being very thick (pl. LV,
fig. 1d); however, as it was impossible to me, in spite of careful searching, to find a single
male pupa, I conceived the idea of submitting my big larve to a thorough examination, and
in a single specimen I fancied that I saw two spermatothece through the skin. I succeeded
in taking away the skin of this larva, and I found a young male with hairs on its abdomen,
rather short caudal stylets, and two spermatothecse, whereas the limbs were still for the
most part rather indistinct. Hereby, then, we have got the proof that the males come out
directly of these big larve (comp. Aspidoecia, p. 54), still there remains a single point which is
not fully explained. My rather numerous males are — with very rare exceptions — about
245 and -27 mm. in length, though one of the big larvee is only ‘19 mm. long, the empty
abdomen included, and the cephalothorax of one of the largest of these larvee is only “16 mm.
in length (in pl. ILI, fig. 4¢ I have represented a male, in fig. 4e such a larya enlarged on

8

58

the same scale, and a comparison between these two figures offers a pretty good illustration of
the different sizes seen from below). Fortunately I have found a single male which without
any doubt, judging from its inward and outward condition, is quite recently hatched, and
which is only “18 mm. in length, consequently O02 mm. longer than the above-mentioned
cephalothorax; now, if we consider the prominent frontal border in the male and its rather
more elongate shape, this slight difference is accounted for. The result is, that immediately
after hatching, the male must grow to some extent, for, as males of small size in this (as in
other) species are pretty rare, we have good reason to suppose that this growth is compara-
tively rapid.

The female apparently passes through a pupa stage. I have found three such »pupe«
altogether, which were all about the same size; the specimen illustrated in pl. IV, fig. 1f
is 174 mm. long. The body is ovate, somewhat flattened and attached at the front by a
broad adhesive plate (s). In the illustration several limbs are seen, but, on closer examina-
tion, it appears that all these organs are those of the larva: antennule (a), antennz (c),
maxillz, maxillipeds (¢), first pair of natatory legs (m), second pair of natatory legs (n) and
abdomen (0), in other words, the animal is enclosed in the skin of the larva, whose appen-
dages and abdomen are not only emptied of their contents, but have shrunk, so as to be almost
unrecognisable. There is no mouth. Under the skin we see the scarcely developed mouth,
the maxille and the folded macxillipeds of the young female. So the skin of the larva has
acquired the appearance of a pupa; a real pupa does not exist. The animal cannot possibly
take any nourishment. Fig. 1g in pl. IV represents a young female that has just burst
the ventral side of the »skin of the pupa«, whereas its ragged dorsal part still hangs on to
it; this specimen was only -207 mm. in length, consequently only ‘034 mm. longer than the
pupa represented. This young female was still attached by the adhesive plate (s) of the skin
of the larva.

A pupa deviating from those of the above-mentioned types is found in Spheronella
danica, Spher. chinensis and closely allied species, which, together with Spher. Leuckarti,
form a small group, which I have named after this species. Salensky (in his op. cit.) has
described and illustrated several stages of development of Spher. Leuckartii, and his obser-
vations agree very well with mine, only I have been able to make some additional statements.
The pupa is ovate, sometimes naked on its anterior part (pl. III. fig. 2f), though, as a rule,
it has only a smaller naked spot in the midst of the ventral surface (pl. II, several figures);
otherwise it is all over pretty closely covered with rather short hairs; from the anterior
end, which is always narrower or more pointed, proceeds a tuft of longer hairs, and in the
midst of these is a rather short thread, which ends in a disk (pl. II, fig. 6 e), by which the
pupa is hinged, either to one of the plates of the marsupium, to the inner side of the basal
joint of a leg, or to a gill. (Usually this frontal thread proceeds from a small depression
with flat bottom, however, in one case, I have noticed that it proceeded from a stouter,
short, cylindrical eminence (pl. II, fig. 4d and fig. 4e). On the posterior half of the above-

59

mentioned naked spot we find a somewhat prominent mouth (pl. IT, fig. 6e and fig. 6f;
pl. ILI, fig. 2), which is supported by some chitinous lists, the two longest of which point
straight forward, are as long as, or somewhat longer than, the diameter of the mouth and
enclose the anterior half of the naked spot. Of mouth-appendages we only see the well-
developed mandibles, the points of which project in the orifice of the mouth; the hairs round
the mouth-border are apparently wanting (but perhaps the magnifying power of my micro-
scope does not suffice to discover them). Outside the anterior half of the mouth, and beneath
the naked area in front of it, several muscles are seen, which evidently serve the action of
the mouth. The pupz of the same species show great difference of size. In Spher. chinensis
a small pupa is 146 mm., a large one -24 mm. in length, and both are illustrated in pl. II,
fig. Ge and fig.6d magnified on the same scale. But I have found a much greater difference
in Spher. danica, of which species I have seen nine pup: the smallest (pl. II, fig. 4d) is
only ‘115 mm. long and ‘O85 mm. broad, an other (fig. 4c) is 185 mm. long, and the largest
is 25 mm. long and 194 mm. broad, thus somewhat more than double the length and
double the breadth of the smallest specimen. In the small pupe TI have not been able to find
the vestige of any organ, and their contents — except the muscles of the mouth — consisted
of a granular substance. Salensky writes (op. cit. p. 317): »Weder innere Organe, noch
selbst irgend welche Formelemente liessen sich im Innern wahrnehmen; doch kénnte méglicher
Weise der Darmkanal vorhanden sein und nur durch die zahlveichen Kérnchen verdunkelt
werden« —,; later, on p. 318, he describes the mouth, but he has seen neither the man-
dibles nor the muscles, nor has he been aware that he had a mouth before him, and he
concludes his statement about his youngest specimen, which is ‘12 mm. long, in the following
words: »Das Wachsthum geht in dieser Periode sehr rasch vor sich«. his last observation
I consider to be correct, and as it appears from the above-stated measurements, that the
pupa during its development grows to a manifold larger volume, 7/ 7s clear that it must take
nourishment through its mouth, of which we have given a description, but it must be left to
new examinations of fresh material to explain how this is effected, if there really exists an
intestinal tube — which we must naturally suppose — but the contents of young and half-
grown pup preserved in alcohol have made the impression on me of being evenly granulous,
without organs. In the above-mentioned largest (-24 mm. long) pupa of Spher. chinensis
(pl. I, fig. 6b) and in the largest (25 mm. long) pupa of Spher. danica I found young
females, and Salensky writes (p. 319): »Das letzte von mir gesehene Stadium zeigte das
unter der Puppenhaut schon vollkommen ausgebildete Thier mit allen Anhiingen. Die Puppe
hat eine Liinge von 0,27 Mm. erreicht....; an ihrer Oberfliiche sind keine Verinderungen
sichtbar«; whereupon he describes the animal, though without mentioning that it is a female,
however, this is easily seen from his illustration. My specimen of Spher. chinensis (pl. II,
fig. 6 f) shows antennulee, mouth, maxilla, maxillipeds, the two pairs of trunk-legs, the not
yet fully developed genital apertures and the caudal stylets, which are seen through the
hairy skin. It is seen that the mouth of the young female is situated far more to the front
8

60

than that of the pupa, and is much larger. The largest pupa of Spher. danica agreed
entirely whith fig. 6f, except in one remarkable point: the mouth of the female projected
freely through the skin of the pupa (though I was unable to discover any rent or larger
opening in the skin), thus presenting the extraordinary sight of two mouths protruding
beyond the ventral surface of the pupa; the mouth of the female is situated a little behind
the front extremity, that of the pupa nearly in the middle of the surface; the diameter of
the latter in proportion to that of the former being as seven to ten. — Fig. 2¢ in pl. IL
illustrates such a young female belonging to Spher. antillensis, which has rent and thrown
off about the front third of the skin of the pupa, whereas the hindmost part of the body is
still enclosed in the larger posterior part of the skin, including the mouth of the pupa, and
as the same animal is illustrated in fig. 2a magnified on the same scale as the ovisac
exhibited in fig. 2b,a comparison of these two figures will show clearly, how much the
animal grows from its stage as an egg up to the moment when it comes out of the pupa.

But what about the male? The animal which Salensky found in its earliest stage
as pupa, and of which he has had several specimens, according to his description and
illustration is only the female, and of the pupz I have seen, the smaller ones contained no
animals, and the very large ones contained females. As mentioned above, a pupa containing
a female of Spher. danica is *25 mm. long, but a male which, judging from its appearance,
seemed to be recently hatched, was only -15 mm. long, whereas a full-grown male of the
same species was ‘24 mm. in length. So we notice here the same growth of the young
male as mentioned above in Spher. paradoxva, but at the same time we find that the full-
grown male is somewhat smaller, and the recently hatched male only a little more than
half as long as the large pupa (25 mm.). As the small pupze examined by Salensky and
by myself never contained any animal, if is very probable that the male of this species, as
well as that of Spher. paradoxa, is developed directly from the larva, and the size of the
recently hatched male agrees perfectly with this supposition. Unfortunately, of all my eight
species of this group I have only seen very few larvee, however, the contents of a single
specimen of these seemed to indicate that a male, not a pupa, was developing in it, still its
erowth was not sufficiently advanced to decide the question with absolute certainty.

Of Spher. longipes I have found a single specimen of a pupa (pl. VII, fig. 2 g),
which essentially coincides with those belonging to the group Spher. Leuckartii. This pupa
is ab. ‘17mm. long and -11 mm. broad, rather elongate, as we see; the lateral margins run
almost parallel in part of their length, the front extremity is somewhat pointed and has a
small orifice, out of which a short broken thread is protruding. The pupa is quite naked
and possesses in the centre of its ventral surface a small, but well developed, projecting
mouth, at the front and at the sides of which some chitinous lists and muscles are noticed.
Its contents consist of a granular substance, in which no organs are indicated; only towards
the front extremity we see — as shown in the illustration — some vague indications of an
organic structure.

61

In this place I will briefly mention an organism, which I found on the glass after
having prepared Spher. microcephala, and which, I suppose, is the pupa of this rather
deviating species. It is somewhat depressed (pl. VIII, fig. 2k); its outline is ovate with a
straight posterior margin, whereas its rounded front margin bears a somewhat protruding
adhesive plate (the stripes of which are too strongly marked in the illustration); its dorsal
surface is provided with some short hairs, the ventral surface is naked. It is 20 mm. long, has
neither mouth nor other outer organs, nor do we find distinct indications of internal organs.

In Mysidion commune the metamorphosis is more complicated than in the preceding
forms, but, unfortunately, my material is not large enough to allow me to elucidate it in all
details, besides, the forms in hand present several features which I do not understand. I
have found altogether three stages of development, two instances of the earliest, one of the
medium, and two of the last and largest stage. I will begin with this last stage, which
indeed presents a kind of semi-pupa, or a young female in possession of features which it
afterwards loses. The two specimens found are of about equal size, the one illustrated in
pl. XII, fig. 1d is ‘31 mm. long. The body is elongate ovate, rather pointed at the
front extremity, which has a mouth provided with a border and its surrounding hairs; on
its sides are the maxillule, and on the ventral surface, a little behind the mouth, are the
maxille and the maxillipeds, which, though well developed, in some small, unimportant
points deviate from those of the adult female; on the dorsal side, at a rather good distance
from the mouth, we find the one-jointed organs, which for a long time I considered to be
the antennul (a), but which no doubt are better explained as being the antenne. On the
ventral surface, at a considerable distance from the posterior extremity, we see an odd,
strongly protruding, elongate and somewhat pointed process (x), and nearer the posterior
margin, somewhat up on the back, the scarcely fully developed crescent (r) which surrounds
the future genital aperture. In the middle of the back appears an odd, rather low, blunt
excrescence, from which proceeds a most peculiar fixation-thread, consisting of two divisions.
The first part (u) is somewhat shorter and thinner than the basal joint of the maxilliped,
and its distal part is tubular; from the inside of this tube the second division comes out as
a thread, which is thin in a considerable part of its length, then dilates rapidly and widely
(v), forming a low collar at its widest expansion; it continues beyond the collar rather thick,
in the middle somewhat thinner; this part is hollow, very light and is no doubt furnished
with very thin walls, and its end is fastened to a plate of the marsupium of the host. Can
this singular fixation-thread be considered as homologous with the frontal thread of other
pupe? This would seem probable, though it is placed rather far backward; how it is
produced is incomprehensible to me, but its distal end is very like the thread I have de-
scribed in the male of Mysidion abyssorum, and its proximal part exhibits great likeness to
the frontal thread in the male of Spher. danica. Somewhat in front of this thread, on each
side, at a short distance from the outline of the back, we see a conical process (t), which
for a long time was inexplicable to me, but which I suppose must be explained as the

62

antennule; according to this interpretation they ought to have been marked »a« in the
illustration, and the antenne not »ac, but »c«. Somewhat behind the fixation-thread I
found a pair of bodies (z) which were situated at a short distance from each other and
looked as if they were pasted on; whether they belong to the animal [ do not know, though
T suppose they do, as one of the specimens was provided with both these small bodies, the
other with one of them. The hindmost part of the body and a smaller part of the surface
surrounding the large ventral process, are provided with a number of rather short hairs.

Fig. 1¢ in pl. XIL shows the stage of development which immediately precedes the
afore-described stage. The only specimen found is 24 mm. long; the scale of enlargement
is like that of the last stage. The body has about the same shape, and the mouth, the
maxilla, maxilla (f), maxillipeds (g) and antennz (a) have a similar structure and position;
but the antemule (t) are placed further backward than in the more advanced stage, almost
behind the middle of the animal; their form is somewhat vague. The dorsal fixation-thread
(u and v) proceeds at some distance behind the middle of the median line of the back; it
is almost constructed as in the older stage, but is considerably longer, and its distal part
is much less stout. The crescent of the genital aperture (r) is not found on the dorsal, but
on the ventral surface, near the posterior extremity of the body. The odd ventral process
(x) is situated almost in the middle between the base of the maxillipeds and the posterior
end of the body; it is rather short and very stout and broad; it is indeed a projection,
which has on its top a well-developed mouth (y) with mandibles, and whose sides and front
part are provided with chitinous lists, like those which surround the mouth of the pupa in the
group Spher. Leuckartii; on the side this skeleton forms a figure (y’), which, seen as in
the drawing obliquely sideways, looks very much like a maxillula; however, on closer
examination it turns out not to be any appendage. Now we should feel much inclined
to think, that the pupa just described does indeed represent an animal provided with an
apical mouth in the act of breaking out of the skin of the pupa, the mouth of which is
marked »y«, however, repeated and careful examinations of the admirably preserved pupa,
which L have been able to roll under a glass-cover, and to study from all sides, give the
result, that 7 as really an animal with a larger apical and a smaller, but very well developed
ventral mouth, the latter of which disappears in the following stage, only leaving the odd
ventral process x in fig. 1d. That the existence of two mouths in the same animal is per-
fectly incomprehensible to me. goes without saying. — The whole animal is naked.

Finally I have found two badly preserved, infinitety small pupz of about equal size,
one of which is illustrated in pl. XI, fig. 3i. The body is 136 mm. long, shortly ovate,
with a well-developed mouth at the rather pointed front extremity, and a little more back-
ward on the ventral side maxille and maxillipeds, the former of which being of pretty good
size, but with thin walls and of a somewhat vague form, whereas the maxillipeds are almost
smaller than the maxillee, 2-jointed, and very weak. Beneath the skin, between the maxillz,
is seen a pretty large, anteriorly inflexed ring (x), which seems to be the beginning of a

63

mouth. The pupa appears to have been attached by a dorsal thread, as in the preceding
stage, however, it is too badly preserved to allow of a more precise definition. I am
unable to give any more details about this stage; I do not see at all how it can be an
earlier stage in the development of the female, and consequently be followed by the two
above-described stages; so it may possibly be a male pupa; however, it must be left to the
future to solve these and other problems in the remarkable development of MZysidion commune.

IT have now communicated in detail all I know about the post-larval development of
the forms of this family. Being unable, on account of the great gaps, to generalize very
much, I have preferred to collect all L know in this place, instead of contenting myself with
making a shorter extract and distributing the greater part among the forms in question in
the later systematic representation. Though I think I have found a series of rather intere-
sting facts, this is only the beginning of a complete elucidation of the very peculiar meta-
morphosis of these animals with their extraordinary variations in the different species. It
would indeed repay the trouble to carry out such an investigation in numerous representatives
of this family, but it would at the same time present enormous difficulties, on account of
the nature, as well as of the rarity, of the material.

B. Habitation, Biology and Distribution.

a. The Place of the Hosts in the System and the Habitation
of the Parasites.

Of the forty-three species examined by me, two (the genus Choniostoma) live in the
branchial cavity of two species of the genus Hippolyte Leach, which belongs to the tribe
Caridea of the order Decapoda; two species (the genus Homocoscelis), live in the branchial
cavity of two species belonging respectively to the genera Diastylis Say and Iphinoé Sp.
Bate, which two genera belong to widely differing families of the order Cumacea; one species
(the genus Aspidoecia) lives on the outside of the body (on the carapace, on the back and
the sides of the last free thoracic segment and of the six first abdominal segments, as well as
on the eye-stalks) of the species of the genus Hrythrops G. O. Sars, which belongs to Mysidee
vere. All the remainder — thirty-eight species — live in the marsupium of species
belonging to the following orders: Mysidacea, Cumacea, Isopoda and Amphipoda; however,
their distribution within these orders is rather interesting. In Mysidacea I have only found
two species (the genus Mysidion) on the genera Erythrops G. O. Sars and Parerythrops
G. O. Sars, belonging to Mysidz verze, and the three species on which they are found live
— according to G. O. Sars — in a depth varying from 30 to 300 fathoms. An examina-

64

tion of a very large material of Danish species of the genus Mysis Latr. (sens. Sars in
1879), and of Macropsis Slabberi (v. Ben.), as well as of a number of specimens of Gastro-
saccus Norm. -—~ all shallow water species, — gave a negative result, neither did I find any
parasite on numerous specimens of a species of Mysidee taken in shallow water in the West-
Indies, nor on a great number of specimens belonging to two pelagic species of the genus
Siriella Dana. In Cumacea I haye found altogether five species of the genus Spheronella
on six species belonging to the genera Diastylis Say, Eudorella Norm. and Iphinoé Sp.
Bate, which three genera belong each to one of the eight families established by G. O. Sars,
whereas an investigation of numerous other species, among which a very large material of
several species which were taken in Denmark in very considerable quantity, as Couna scor-
pioides (Mont.), Lamprops fasciata G. O. Sars, Leucon nasicus Kr. Leucon nasicotdes Lilljbg.,
Leucon acutirostris G. O. Sars, Hudorellopsis deformis (Kr.) Diastylis resima (Ky.) and

Leptostylis ampullacea (Lilljbg.j, gave a negative result. Within the order Isopoda, these

parasites — altogether three species of the genus Sphewvonella — are only found in two
species of the genus Janira Leach and in Munnopsis typica M. Sars, all three forms
belonging to the large tribe Asellota, whereas an investigation of numerous forms belonging
to other families, among which some species of Idothea F., Astacilla Cordiner, and Gnathia
Leach, were represented by a great number of specimens, gave no result. (Of the small
order Tanaidacea I have examined a good number of specimens from Denmark and numerous
specimens of several species from Sicily, without finding a single parasite). The chief
quantity of the parasites, namely twenty-eight species (the genus Sfenothocheres and about
three quarters of the genus Spheronella), were found on Amphipoda, and within this order
exclusively on Gammaridea (on twenty-eight species). An inspection of a great number of
specimens of different species of Caprellidaee and of some specimens of Cyamidze gave no
result. (Among the material from the »Ingolf« expedition I found in 1895 on an Avygina
Kr. a species, which will be described in the report on the results of this expedition). Of
Hyperiidea I have only examined a few species. In giving a short general view of the
occurrence of the parasites within the Gammaridea-group, I will avail myself of the twenty-
five families adopted by G. O. Sars in his new important work: »An Account of the Cru-
stacea of Norway, Vol. I, Amphipoda«; they are found in one or more representatives of
the following fourteen families: Pontoporeiide (the genera Bathyporeia Lindstr. and Argissa
Boeck), Ampeliscid (the genus Ampelisca Kr.), Amphilochidz (the genera Astyra Boeck,
Amphilochoides G. O. Sars and Gitanopsis G. O. Sars), Stenothoide (the genera Stenothoé Dana
and Metopa Boeck), Oediceride (the genus Perioculodes G. O. Sars), Paramphithoide (the genus
Paramphithoé Bruz.), Epimeride (the genus Acanthozone Boeck), Syrrhoidx (the genus Bruzelia
Boeck), Calliopiide (the genus Calliopius Lilljbg.), Atylidee (the genus Paratylus G. O. Sars),
Gammarid (the genus Cheirocratus Norm.), Photide (the genera Lemboides Stebb., Protomedeia
Kr., Leptocheirus Zadd., Gammaropsis Lilljbg. and Microprotopus Norm.), Corophiid (the genus
Corophium Latr.) and Dulichiide (the genus Dulichia Ky.). Of the remaining eleven families the

65

majority are small, with one or very few genera and rather few species, but the family
Phoxocephalide is pretty considerable, the family Podoceride is large, and the family
Lysianasside is exceedingly large (in Sars’ work thirty-three genera), wherefore it seems
interesting to me that no parasite of our Choniostomatida has been found on any species
belonging to these families. One species was found in the Mediterranean in the genus
Microdeutopus Costa, belonging to the Photide, another species has been quite recently
discovered in Cyclaspis G. O. S., belonging to the family Cumide, and these genera are the
only two mentioned in the literature of the subject, in which I have not personally observed
the parasites of this family. To give an account of the forms the examination of which led
to no result, would be too tedious, neither would it prove much; I will only say that I have
examined a good number of exotic species, most of which were only represented by a few
specimens, besides nearly all of the large material our museum possesses of Gammaridea
from Denmark, Greenland and the Kara Sea, and many of these species were represented
by from fifty to hundreds of specimens. In F. Meinert’s three papers, of 1877, 1880
and 1890 respectively, about Danish Malacostraca, and im my own similar papers about the
fauna of Western Greenland and of the Kara Sea, will be found the names of most of the
northern and arctic species examined, of which I have had a large material.

In a later paragraph I shall mention a little more in detail the following pheno-
menon which stands in a certain connection with the matter above, namely, that of several
species a considerable material from a large sea can be examined without showing a single
parasite, whereas sometimes a smaller material of the same species from another sea reveals
several parasites. This proves that we cannot conclude that a species is not infested, from
the fact that an investigation of hundreds of specimens from different localities of a certain
country has not led to the discovery of any parasite. In most cases such examinations must
be undertaken on a much larger scale than I have been able to do, before any value can
be attached to the negative results.

b. Age and Sex of the Hosts.

It serves our purpose best to divide the hosts into two sections according to their
parasites, viz. whether the typical residence of these animals is in the marsupium or in other
places. I will begin by the latter section, repeating my above statement that I only have
examined five species of parasites which do not live in the marsupiun.

Aspidoecia Normani, which, as has just been said, lives on the outside of the body
of species belonging to the genus Evryfhrops, I have found on young specimens as well as
on adult males and females, but in the latter the marsupium was either empty, or occupied
by a species of the genus Mysidion. The two species of the genus Choniostoma live in the
branchial cavity of two species of the genus Hippolyte. From the Kara Sea I have seen

4)

66

altogether seven infested specimens, four of which were adult females without eggs, and each of
these females was infested with one adult parasite, three of which having laid numerous ovisacs;
two of the hosts were males: one was an adult infested with a parasite with numerous ovisacs, the
other was a little smaller with eight smaller parasites; and finally, the seventh host was a female
with eggs containing half-developed young ones, on its right side was an empty swelling on the
carapace about two thirds of the normal size, on the left side a very small and quite young
female, and besides numerous larve and pupx hinged on the gills. - The two species belonging
to the genus Homoeoscelis live in the branchial cavity of two species of Cumacea; of one
of these: Iphinoé trispinosa (Goods.), I have seen seven infested specimens: one female,
whose marsupium contained a Spheronella, three not quite full-grown females, one of which
— whose marsupium was in an early stage of development — was infested on one side with
a female, a male, and eight ovisacs, in one of which were full-grown larve. The three last
specimens were a male before the last moulting and two adult males, one of which with an
adult female and two ovisacs, a young female and a male in one branchial cavity, the
other containing only a half-grown female. Of the other species, Diastylis lucifera (Iky.), 1
have seen sixty-six infested specimens —— most of them females, in at least three cases young
males, but not a single adult male, though this last circumstance is of less weight than
might be expected, as our naturalists have neglected to throw out the surface-net at night
and in the evening in order to catch the full-grown roving males. About three fourths of
the females had a well-developed marsupium; in more than two thirds of these it was empty,
but in at least thirteen cases is was filled with half or fully developed young ones, never
with eggs. Females which had not yet begun laying eggs appeared in females of Diastylis
with young ones in the marsupium, as well as in specimens without marsupium; there were
found likewise female parasites with the full number of ovisacs in females of Diastylis with
young ones in the marsupium, and in younger specimens without marsupium. — In a sub-
sequent paragraph I shall have an opportunity of entering into further consideration of these
statements; more special statistics are found in the systematic part.

We now come to the thirty-eight species which live typically in the marsupium of
forms belonging to four different orders. I may say at once that the ten species which
appear in Mysidacea, Cumacea and Isopoda, I have only found in perfectly developed mar-
supia, but it must be added that I have also constantly found at least one older female
with ovisacs in such a marsupium, so I know nothing about the stage of development of the
host at the time when the first (and often only) female attached itself to it as a larva; 1
have examined numerous specimens of Cumacea, in which the marsupium was beginning to
develop itself (it appeared as small plates), but without finding any parasite. Amphipoda
presented somewhat different facts. Salensky writes about Spher. Leuckartii (op. cit. p. 302):
»Das Thier fand sich in der Bruthéhle der Weibchen und an der unteren Fliache der ent-
sprechenden Brustsegmente der Miéinnchen und war an den iiusseren Bedeckungen des
Wirthes mittelst eines besonderen Saugapparates befestigt.« By this »sucking apparatus«

67

the author means the rostrum, but this observation is not just, for the attachment certainly
takes place by a frontal thread; moreover, I suppose that the animals Salensky took for
males were in fact somewhat younger females without marsupiun, founding this suggestion
partly on his (otherwise bad) description of the host »Amphitoé sp.«, — according to Della
Valle: Microdeutopus gryllotalpa Costa, — in which he does not say a word about the very
great difference in the »hand« of the first pair of trunk-legs between the two sexes, partly
on the fact that I have never found a Spheronella on any adult male; whether some of the
not full-grown specimens on which I found typical marsupium-parasites, were young males,
IT cannot tell, but I doubt it. The twenty-four of the species parasitic on Amphipoda I
have found exclusively in marsupia, and though, in not full-grown animals, I may not
unfrequently have overlooked larvz, pups or very diminutive females, in any case I cannot
have overlooked many females with ovisacs. Only in the following four species of Amphi-
poda: Metopa Bruzelii (Goés), Argissa typica Boeck, Protomedeia fasciata Kr. and Ampelisca
tenuicornis Lilljbg., have I found parasites in specimens without or with half-developed
marsupium. In a specimen with scarcely half-developed marsupium of Metopa Bruzelii, two
larvee were found, and in a still younger one without marsupium, a single larva. In two
young females without marsupium of Argissa typica appeared respectively one pupa and a
tiny female of Spher. Argisse. In a young specimen of Profomedeia fasciata Kr., trom
Greenland, were found a not half-grown female and a male of Spher. Bonniert. Spher.
longipes I found in nine specimens of Ampelisca tenuicornis; two of these only were females
with fully developed marsupium, the third was a young female with half-developed marsupium,
which contained a not half-grown female of the parasite; the six remaining specimens were
young, without marsupium, and on each of the five of these I found a single female between
not half-grown and very small, — in one case even recently hatched; in the sixth spe-
cimen there were only two Joose larve. The result hereof is, that in Amphipoda I have
not found a single adult female in a specimen without entirely developed marsupium, and
never ovisacs except in marsupia. It is probable that larvee not unfrequently fix themselves
to immature females, beginning their development there, and thus entailing the necessity
that larvee as well as young females, and rarely males, remain on the host, while it passes
through its last moultings; however, as said above, not a single observation has been made
of ovisacs being found in females not fully developed, which by the by, seems natural
enough, as they would certainly be washed away, if they were laid. However, I cannot
prove that most specimens are infested before the marsupium is fully developed. No doubt,
the larve seek either perfectly mature females — and at least rather often those whose
marsupium is already infested by at least one (halfgrown or quite adult) female and a male
—, or such younger specimens as are so far advanced, that they will have got their
marsupium before, or at the time when the females that have developed themselves out of
some of them, are ready to begin laying eggs. Whether the larve of species that live in

Shy

68

the marsupium of Isopoda, Cumacea and Mysidacea sometimes, or often, fix themselves to
not full-grown females, I repeat, I cannot tell.

I will add that in three cases (in Ampelisca tenuicornis, Protomedeia fasciata from
Denmark, and in the same from Greenland) I found in the marsupium, together with one
female Spheronella without ovisacs (in two cases a male attached to it), four to six of the
Amphipod’s own eggs, in one case with half-developed young ones. In the marsupium of an
Ampelisca typica 1 found a large female and two ovisacs of Spher. microcephala and two
of the Amphipod’s own eges. In Ludorella truncatula I found one of its own eggs together
with an adult female, three ovisacs and a male; in another specimen were found no less
than twenty-four of its own eggs together with an almost adult female and two larve which
were invaders.

c. Number of Parasites on each particular Host.

In the systematic part of this work I give a kind of statistics of each species,
accounting for my findings, and giving numerous data concerning the number of each sex,
of the ovisacs and the stages of development found on each particular host. Of this con-
siderable material [ put down some extracts here, which will give a condensed view of this
matter. Of Aspidoecia Normani which lives fixed on the outside of Hrythrops, I have often
found one or several females of very different sizes on the same host, in one case as many
as six females with ovisacs, three younger females and one larva on one single specimen. In
a large material of Diastylis luceifera with Homocoscelis minuta in the branchial cavity, I
have never found more than one female, as a rule only one male, very seldom two males
on one specimen, whereas of Iphinoé trispinosa, infested with Hom. mediterranea, only four
specimens have been thoroughly examined by me; one of these had two females, six ovisacs and
two males in the same branchial cavity, one had an adult and a young female, two ovisacs and
a male in the same branchial cavity, one carried a male in one branchial cavity, a female
with eight ovisacs and a male in the other. Of the species of :Choniostoma which live in
the branchial cavity of Hippolyte, | have found only one specimen of an adult female on a
host, whereas of younger female parasites one specimen contained three in one branchial
cavity, five in the other; in another specimen I saw an empty swelling covering one of the
branchial cavities, whereas the other contained one female which was far from half-grown,
besides certainly more than fifty larvee and pupz hinged on the gill-fibres; however, I doubt
very much whether most of these would have been able to develop themselves into adult
females (and perhaps males) on this shrimp; it seems to me rather doubtful that the animal
should be able to afford the nourishment required, and still more so whether the parasites
would find sufficient room to grow.

In the parasites living in the marsupium we find the greatest differences as to
the nunbers of them on one host, but at the same time it must be observed that while

69

some species as a rule only contain a single female and a male, sometimes two males and
seldom two females in the same marsupium, in other species we pretty frequently find two,
three, or more females and several or many males on the same host. Of twenty-six out of
twenty-eight adult specimens of Metopa Bruzelii (Goés) infested with Stenothocheres egregius
which were examined and noted, there were found only one female and frequently also one,
seldom two males on each specimen; in one specimen were found only eggs and young
ones, in one two females and no male. In Cumacea and Isopoda the marsupium never
contained more than one female, often also a male, sometimes two, and in a single case
three males, besides, in one case [ found one pupa, in another, where no male existed, some
invading larve. In Mysidacea some deviations are observed; of adult females we very
rarely find more than one specimen, but rather frequently also one or two young females
or tiny young ones which have not gone through the whole metamorphosis, besides frequently
one or more, in one single case even ten males; (as for further details, s. statistics in the
systematic part). In one specimen of Erythrops serratus there had lived at least three
females with ovisacs and one male. Several Amphipoda infested with species of Spheronella
as a rule only show one single female (with one or two males), others not unfrequently two
or three females, mostly of somewhat different age, but here I will mention some cases of
peculiarly abundant invasion. In one specimen of Calliopius leviusculus (Kr.) were found
one female with eight ovisacs and five males, in another specimen si females with twenty-
five ovisacs and two males, but the richest finds were supplied to me by Spher. paradowa
in species of Bathyporeia. In one specimen [ found one large female, two small females,
no ovisacs, eight males, four broad larvae, sixteen »male pupse« and one »female pupa«; in
another specimen four females of widely differing size, four ovisacs, eight males, two larvae
and one »male pupa«; in a third animal three large females, two very small females, three
ovisacs, two larve and seventeen males, the largest number of the male sex I have ever
found. —— The result of a large infestation is that the marsupium of the host swells to the
same extent as if it were filled with its own half or almost fully developed young ones.

d. Number of Species of Parasites on the same Species of Host.

On most species of hosts I have only found a single species of Choniostomatide,
yet in several cases I found two species of parasites, now of the same genus, now of
different genera, on the same species of hosts, sometimes even on the same specimen; nay
[ have happened to discover three species of parasites, not only on the same species, but
on one single specimen. As the particular cases are interesting in several respects, I will
enumerate them here. On Metopa Bruzelii trom Godthaab (through a renewed examination
with the assistance of Sars's new important work, I have made sure that all infested
specimens really belonged to this species, and not partly to Metopa sinuata G. O. Sars) were
found in the marsupium of specimens from the same locality, now Stenothocheres egregius,

70

now Spheronella Metope, but never both forms in the same specimen. In a large material
of the same host from another Greenlandish locality appeared a number of specimens of the
former, not one of the last-mentioned parasites. On specimens of Hippolyte Gaimardii
M.-Edw. from the Kara Sea appeared now Choniostoma mirabile, now Ch. Hansenii, and
the latter species was also found in Hipp. polaris (Sab.) from the same sea. In Danish
specimens of Ampelisca tenuicornis Lilljby. I have found Spharonclla longipes; whereas Giard
and Bonnier have found in specimens of the same species from le Croisic (Brittany) the
very deviating Sphar. microcephala. Danish specimens of Protomedeia fasciata Ky. were
infested with Spher. Giardii, and Greenlandish specimens with the closely related species
Spher. Bonnieri. On a specimen of Iphinoé trispinosa (Goods.) from Messina Homocoscelis
mediterranea was found in the branchial cavity and Spheronella marginata in the marsupium.
In Norwegian specimens of Erythrops serratus G.O. Sars and Prythrops abyssorum G. O Sars
we not unfrequently find a species of Mysidion in the marsupium, and one or several
specimens of Aspidoecia Normani on the outside of the body of the same species. In one
specimen I found two specimens of the latter species on the outside of the body, an adult
and a young female of Mysidion abyssorum, and a young female of Mys. commune in the
marsupium, which makes three species of parasites on one animal.

e. Number of Species of Hosts of the different Parasites.

The answer to this question presupposes the answer to another, namely that of the
limitation of the parasitic species, and as this latter question is not treated in detail till
later on in a separate chapter, I will content myself with mentioning the results of this
examination, using them in answering the question indicated by the heading.

Twenty-nine of my species, as a matter of fact, are only found each on one particular
species. Of the remaining fourteen species eight (belonging to the group of Spher. Leuckartii) are
also limited each to one particular species; however, it may perhaps be questioned whether these
eight species can really be maintained as such, or must be regarded as chance varieties of a
single species (see later on). The remaining six species must be mentioned each separately.
Choniostoma Hansenii has been ascertained in two species: Hippolyte Gaimardii M.-Kdw. and
Hippolyte polaris (Sab.). Of Spheronella insignis indeed T have only had a small material which
was taken on Diastylis cornuta Boeck and Diastylis levis Norm.; however, the difference between
the parasites of the two species was so slight, that my experiences from other species led
me to consider them as belonging to one species. The species found by Giard and Bonnier
on Ampelisca tenuicornis Lilljbg. from le Croisic, which they have described under the name
of Spher. microcephala, as far as I can see, is identical with the species described by me
in this work under the same name, and this is taken on Ampelisca typica Sp. Bate in Danish
waters. Spheronella paradoxa I have found on Bathyporeia norveyica G. O. Sars, Bathyporeia
pelagica Sp. Bate and B. Robertsonii Sp. Bate, and even if it were proved that the two

71

last-mentioned cannot be maintained as separate species, but must be considered as one, at
any rate this parasite has been taken on two good species of the same genus. But now
we come to a remarkable fact, viz. that three adult females have been taken on three
specimens of Perioculodes longimanus (Sp. Bate) belonging to a different family altogether,
and these females I have not been able to distinguish from those taken in Bathyporeia. If
some day the male of the parasite is found in Perioculodes, probably the interesting question
will be settled, whether the same parasite can be found in animals belonging to such widely
differing families. Mysidion commune I have found on the following three species: Pare-
rythrops obesus G. O. Sars, Erythrops serratus GO. Sars and Er. abyssorum G. O. Sars;
moreover, it seems likely that it will be found in some other species of Hrythrops living
in Norway. Finally, I will state as my opinion that the parasites living on all five Nor-
wegian species of the genus Evrythrops, belong to the same species: Aspidoecia Normani.

[ will sum up by stating what I consider as an established fact, namely that
several species of Choniostomatidee live each on two or more species of the same genus
or of two closely related genera, probably even to a considerably greater extent than I
have been able to ascertain; perhaps, in exceptional cases, they may be found on animals of
different families. On the other hand, I certainly think with regard to several species, that
each of them infests only its particular species of hosts, and this result exactly agrees with
what is known about the biology of other parasitic families belonging to Arthropoda. Only
with regard to Epicaridea, Giard and Bonnier have made the assertion that each parasite has
its particular host and is found on no other species, an assertion which L think is incorrect,
seeing that this division also comes in under the rule which applies to Choniostomatidz’).

f. Occurrence together with Parasites of other Orders or Classes.

In nearly all orders of Malacostraca have been found species of the group or family
Epicaridea belonging to Isopoda. Giard and Bonnier have expressed the opinion that
there exists a certain connection between Choniostomatidz and Epicaridea; but this objectionable
hypothesis I have mentioned above in detail (p. 11—12), and at the same time I have stated
all I know from my own experience and most of what has appeared in literature about the
occurrence of Epicaridea on the species which, according to our present knowledge, are
infested by Choniostomatidee. I have written that of Cumacea, Isopoda and Amphipoda
together, I have seen about 240 specimens belonging to thirty-eight different species infested
with Choniostomatide, but that neither in any of these 240 specimens, nor in any other of
the thousands of animals belonging to these thirty-eight species, have I found one single
specimen of any Epicarid. In Italy Della Valle has found two specimens of Ampelisea

1) It may be added here that in my treatment of the Malacostraca from the “Ingolf”expedition I shall
give more detailed information about the arctic Epicaridea.

12

diadema Costa infested with a species of Spheronella (S. diadema Giard and Bonnier, without
description) and two other specimens of the same Amphipod with Podascon Della Valle: Giard
and Bonnier. Of Decapoda there have only been found as yet Choniostomatide on Hippolyte
Gaimardii M.-Edw. and on Hipp. polaris (Sab.); both these species, we know, are not
unfrequently infested, either with Hemiarthrus abdominalis (ky.) under the abdomen, or with
Gyge Hippolytes (Kr.) in the branchial] cavity. In a specimen infested with Choniostoma J. Sparre
Schneider has observed a specimen of Hemiarthrus, and on a specimen of Hipp. Garmardii,
under a large swelling on the right side of the animal, I have found eleven ovisacs and an
adult female of Chon. Hansenii, as well as an adult male and a tiny female (smaller than
the male) of Gyge Hippolytes, and besides, under the apparently normal left side of the
carapace, a male of Gyge. In the species of the genus Erythrops (order Mysidacea), G. O. Sars
has found the Epicarid Aspidophryxus peltatus G.O.8., and Giard and Bonnier have reserved
this name for the form found on Ey. erythrophthalmus (Goes) (£. Goésii G. O. 8.), and
established a new species, A. Sarsii G. and B., for the form which lives on L. microphthalmus
G.O.S. Giard and Bonnier have found their type specimens of the latter species (the value
of which future examination will have to decide) on the same specimen as their type
specimens of Aspidoecia Normani, and I have found a specimen of Aspidophryxus on an
Er. erythrophthalmus sent to me by Prof. Sars as infested with Aspidoecia, but this parasite
must have fallen off before the animals were sent to me, if it was ever there at all.

The genus Sylon Kr., belonging to Rhizocephala, lives, as we know, on the ventral
side of the abdomen in some species of Hippolyte, but I have not found it on any specimen
infested with Choniostoma. The remaining species belonging to Rhizocephala and Copepoda,
which are parasitic on Malacostraca, have all been taken on forms on which no Choniostomatidee
have been found.

Together with Spheronella paradoxa I have found repeatedly in the marsupium of
Bathyporeia several specimens of a species belonging to the family Tyroglyphide (the
order Acarida).

Of other parasites I have only detected some Protozoa on the branchize and the
marsupial plates in the material of Malacostraca with Choniostomatidz examined by me.

So I have arrived at the result that there exists no connection at all between
Choniostomatidee and any of the other parasites of different orders found on the same

species of hosts.
g. Nourishment.

T cut a bit of skin of an Hrythrops in the place where an Aspidoecia had been
attached, cleaned it with caustic potash from muscles and viscous substance, and discovered
a small hole, where the mouth of the parasite had its place. And this seems very natural
indeed; in the first place, the mandibles appear quite well qualified for producing such a
hole; secondly, the mouth is doubtless suctorial, and lastly, the female, which is permanently

13

attached, must draw her nourishment from the host in order to be able to grow to a bulk
which, adding its own volume after having finished laying eggs, to that of the eggs it has
produced, is frequently hundreds of times larger than the volume of the larva at the time
when it attached itself, and after having fixed itself it is impossible for the animal to
procure the nourishment necessary for this enormous growth in any other way than by a
hole worked through the comparatively solid skin of the host, whose blood must form the
food of the parasite.

Hereby we have found a fixed starting-point in this question, and it is more than
probable that the females of all the other Choniostomatide also grow and nourish themselves
by sucking the blood of their host through a hole they have gnawed. At the same time, it
seems rather probable that the females of many of these species, either voluntarily or invo-
luntarily, e. g. by pressure of another specimen, or by the bulk of ovisacs, are pushed out
of their place and have to gnaw a new hole for themselves. I have frequently found a
female in such an attitude relatively to some of the ovisacs it had laid, or the ovisacs
arranged in such a manner as to make me suppose that the animal had changed place.

How far the males of this family take food, I do not know, but as their mouth is
as well developed as that of the females, it seems likely that they do it while young, and
perhaps not when they are old (about their growth, s. above on pag. 57—5s). I consider it rather
doubtful whether the larve take food, but I am quite certain that the pupae, which are
provided with a mouth, and about whose considerable growth several facts have been stated
above, nourish themselves in a way similar to that of the females.

h. The Influence of the Parasites on their Hosts.

Giard and Bonnier have proved that parasitic Crustacea of different groups (as
Entoniscine, Rhizocephala) cause a »castration parasitaire« in their hosts. In the last of
their papers quoted above they mention Della Valle’s untenable hypothesis that Spheronella
eats the eggs of its host, and they maintain that this suggestion is wrong, and that this is
also a case of »castration parasitaire«, after which they continue: »Dans des cas trés rares,
Phote ayant été infesté tardivement, cette action {namely the castration| ne s’exerce pas
aussi énergiquement, et quelques oeufs peuvent étre pondus et fécondés, comme nous l'avons
vu une fois chez Clypeoniscus {a genus belonging to Epicaridea which they have treated in
the same paper, and which they use as example and parallel), mais ce sont 1a des exceptions.
En général, Vhote est infesté avant qu'il ne soit arrivé a l'état adulte. Sous l'influence du
parasite, son développement génital est arrété sans que la croissance discontinue, de sorte qu’a
lépoque ott devrait se produire normalement la maturité sexuelle, la progéniture légitime
est remplacée par le parasite et les embryons de celui-cic«. This explanation, on the whole,
agrees well with the numerous data which I have given above on p. 65— 68 in the division
about the age and sex of the hosts, from my observations about my thirty-eight species

10

74

which live in marsupia. In the afore-mentioned place it is stated that only in six cases I
found the eggs of the host together with a parasite, and it may be added here that in
almost 160 cases I only found parasites (one or more specimens), but no eggs of the host,
in the marsupium. But at the same time I[ have stated that I have found no parasite on
any specimen of Cumacea or [sopoda in which the marsupium was wanting, and of Amphipoda
I have only found altogether twelve specimens belonging to four species, whose marsupium
was either wanting or only half developed, and on which, nevertheless, I found parasites;
all these, without exception, were half-mature or tiny females, or larvee (one male). However,
this material is too small to allow me fully to adopt the opinion of the authors that the
host »en g@énéral« is infested before its maturity; in the fully developed marsupium of
several specimens of Corophiwm crassicorne Bruz. I have found only a half-developed or still
younger female and either a male, a larva, or a pupa, but no adult females. But it is
certainly an established fact that, as a rule, we notice a »castration parasitaire« in the
hosts which have parasites in their marsupium.

It is much more doubtful whether the four species living in the branchial cavity of
Hippolyte and Cumacea, are usually, or sometimes, capable of causing a » castration parasitaire «
of their hosts. In page 66, and particularly later on, in the systematic part, detailed infor-
mation is given about the age and sex of these hosts, but I do not think we can draw
definite conclusions from these statements. I have said that I have found specimens of
Diastylis lucifera containing a female of Homocoscelis with the full number of ovisacs in
the branchial cavity, and the young ones of the host in the marsupium, but knowing neither
the time required for the development in the marsupium of the eggs and young ones of
the host, nor the time required by the parasite for its own growth and the laying of all
its ovisacs, it seems impossible to me to draw a definite conclusion with regard to a »ca-
stration parasitaire«; however, that such a castration may take place, seems to follow from
the aboye-stated fact that the marsupium of more than two thirds — namely thirty-one —
of the infested adult females was empty, whereas in thirteen specimens it was filled with
young ones; yet it must be observed that in the non-infested females, the marsupium was
found to contain eges or young ones in 182 specimens, whereas it was empty in 74 specimens. —
[t is rather probable that Aspidoecia Normani causes a castration, as the marsupia of the
four infested females which were not occupied by Mysidion, were empty.

The fowr species living in the branchial cavity of Hippolyte and Cumacea cause a
swelling of the carapace of the host, which, to begin with, increases in size with the growth
of the parasitic female, and thus — at least in Cumacea, and probably also in Hippolyte —
continues gradually increasing with the number of ovisacs. In Hippolyte the swelling may
reach the same size as if it enclosed a large Gyge, and in the subsequent description of
Choniostoma Hansenii, it will be proved that this parasite itself produces the swelling. In
Diastylis lucifera the swelling assumes a somewhat other shape, though it may be very
conspicuous.

75

Finally it may be added, that in those specimens of Hippolyte in whose branchial
cavity was found an adult female with ovisacs of Choniostoma, the gills belonging to the
two foremost pairs of trunk-legs were either somewhat reduced, or had quite disappeared,
and in one case the three other gills situated more behind appeared a little curled, as a
sign of degeneration. In one specimen, which was infested with several smaller females,
the gills were slightly curled.

i. Geographical and Bathymetrical Distribution of the Family.

Of the forty-three species described here, sixteen come from Denmark, and one of
these was also found at le Croisic; eight are from Norway, eight from West-Greenland, and
two of these also in the Kara Sea, three only from the Kara Sea, besides the two which
are also found in Greenland, four from Sicily, two from the Pacific near the East-coast of
Asia, one from the Cape, and one from the West-Indies. It may be added that in the
most northern part of Norway and in the Barents Sea there has been found an undetermined
species of Choniostoma, though no doubt one of those which occur in the Kara Sea, that
one species (Spheronella Leuckartii Sal.) was taken at Naples, another species (Homoeoscelis
sedentaria (Bonn.)) in the Atlantic off Gascogne, and besides, a non-described Spher. diadema
G. and B. in the Mediterranean. Without counting Norway, whose species — with one
exception — have been discovered and sent me by Prof. G.O.Sars, the number of species
from the different countries and seas is nearly proportional to the material which our museum
possesses of Amphipoda and Cumacea — the two orders in which most parasites have been
found — from the same localities. From this fact we can pretty safely draw the conclusion
that the examination of a manifold larger material than was at my disposal, e. g. from the
Mediterranean and from eastern Asia, will bring numerous unknown forms to light. The
above statements also suggest the probability that the family is distributed over all seas,
though of course I cannot form any precise notion how far its geographical distribution
will extend, when some day the chief bulk of the existing species has been discovered, for,
as stated in the preface, I think there can be no doubt that their number amounts to
hundreds.

Unfortunately I am not prepared to give many data concerning the bathymetrical
extent of my species, for in most cases I lack precise indication of the depth im which the
special hosts have been found. Most of the sixteen Danish species and four species from
the Mediterranean were taken in a depth of between a few and twenty-five fathoms, but
unfortunately I cannot state precisely in how shallow water the most littoral species is
generally found, or may sometimes be found; it may be stated, however, that a specimen
of Bathyporeia with its parasite, Spheronella paradoxa, was taken ina depth of between eight
and eighteen feet. Stenothocheres egregius was taken in a depth of forty fathoms, a few
specimens in a depth of between forty and sixty fathoms; my only specimen of Spher.

10*

76

curtipes came from a depth of a hundred fathoms. Possibly a large part of the specimens
of the three forms which live on Mysidacea were taken as far down as one to two hundred,
some even to three hundred fathoms, but as the hosts in question may occur in a depth of
less than a hundred fathoms, I cannot say anything definite about them. So it may be
stated here, that in the material from the »Ingolf«expedition I found a couple of specimens
parasitic in Cumacea, from a depth of respectively a thousand and thirteen hundred fathoms,
which sufficiently proves that the family also occurs in a very considerable depth.

j. Geographical Distribution of the particular Species relatively to
that of their Hosts.

It appears from the preceding paragraph that each of the forty of my species was
taken in one particular country (as Denmark, Norway, Sicily etc.), or in a particular, com-
paratively smaller sea. Only three species (Spheronella microcephala, S. decorata and
Choniostoma Hansenii) show a wider distribution. As a matter of course, we shall gradually
find that most species of Choniostomatidze have a much wider range than is known at present,
but from this I do not think we can draw the conclusion that they are as widely dispersed
as the species on which they live. In a smaller material of Iphinoé trispinosa (Goods.)
from Messina I found seven specimens with parasites, one specimen even with two parasitic
species, but in a larger material of the same species from Denmark I have been unable to
find a single parasite. In a pretty considerable material of Calliopius leviusculus (Ky.) from
the East-coast of Asia between lat. 40° and 51° N. I found seven specimens with parasites
(Spheronella Calliopii), but my examination of several specimens from West-Greenland, and
numerous specimens from Denmark, gave a negative result. (Yet it must be mentioned that
Sars, in his work on the Amphipoda, considers the Danish specimens to belong to another
species, Call. Rathkei (Zadd.), but I doubt whether this will be maintained in the future).
Several specimens of Hippolyte Gaimardii M.-Edw. from the Kara Sea were infested; at
the most northern coast of Norway, Sp. Schneider, and at West-Greenland E. Vanhotten, have
found Choniostoma in the same species, but I have examined without result a very large
material of the same Hippolyte collected from numerous localities near the Danish coast,
and I feel inclined to think that these parasites do not occur in the waters surrounding
this country. The same may be said about Diastylis Rathkei (Kr.), of which in about half
of the females with marsupium from West-Greenland and from the Kara Sea, I found
Spheronella decorata, whereas of the same species from different Danish localities I have
examined at least several scores of adult females without finding any parasite.

k. Frequency of the Parasites in proportion to their Fertility.

In mentioning the eggs of the parasites, I pointed out (p. 46—47) the enormous difference
of fertility between the species with very small and those with very big females. Of

17

Hippolyte Gaimardii M.-Edw. T have had a large material from the Kara Sea, and one of
similar size from West-Greenland; in the former I only found six infested specimens: four
with Choniostoma mirabile, two with Ch. Hansenii; in the latter I found none at all, though a
few specimens of Ch. Hansenii have been discovered there at least either on H. Gaimardii
or on H. polaris. On the latter species I found one Ch. Hansenii from the Kara Sea
and one Chon. sp? from the coast of West-Greenland, though H. polaris is not unfrequent
in the former, and of common occurrence in the latter locality. This shows distinctly
enough that the genus Choniostoma with its two very large and particularly fertile species
is pretty scarce in the Kara Sea and rare in West-Greenland. Most of the middle-sized
and rather small species of parasites I have found in between very few and about seven
specimens of their respective hosts, though my material of the latter was frequently very
rich. Only of two parasites: Stenothocheres egregius and Homoeoscelis minuta have 1 found
a great number of specimens in a large material of their respective hosts: Metopa Bruzelii
(Goés) and Diastylis lucifera (Kr.). The first-mentioned parasite is the least prolific of all
my species, and the second, in this respect, comes nearest to it among the species of which my
material of infested hosts was sufficiently large; moreover, the hosts came from several localities.
That the number of parasites cannot be determined only by the number of infested hosts,
has been proved above, as of some species, e. g. the two afore-mentioned: Stenothocheres
egregius and Hom. minuta, we seldom find more than one female and one male on each
host, whereas on others we pretty frequently find several females and males as well as
pup in one host, but the only parasite of which, from the last-mentioned reason, I have
found as many specimens as of the above-named species, is Spheronella paradoxa (living on
Bathyporeia, a genus of very frequent occurrence in Denmark); it belongs to the smaller
species and, as it seems, does not lay more than four of five ovisacs, which are comparatively
large. All these data decidedly point in one direction, but considering the insufficiency of
my material, I will take good care not to lay down any rule or law which might possibly
not prove quite tenable, and I will content myself with suggesting the direction. We might
feel inclined to suppose that the conditions of life of most of these parasites are pretty
similar, and that consequently the most prolific species would occur most frequently, the
more so, as there is such an enormous difference in their fertility, that a species like Choniostoma
mirabile lays at least more than three hundred times as many eggs as Sfenothocheres egregius ;
however, the above-mentioned examples prove in a striking manner that such a conclusion
cannot be drawn. Consequently there must be circumstances to account for the fact that
the two least prolific species: Sten. egregius — taken in two localities — and Hom. minuta —
taken in several, probably in many places at considerable distance from each other — occur
much more frequently than the prolific and very prolific species. An explanation of this
fact is required, and I will attempt to explain it, at least partly. No doubt, the critica]
point in the life of the parasites must be the short period during which the full-grown,
though very small, larve leave the ovisac and their mother’s host in order to seek a new

78

host for their own further development. and no doubt, a considerable number of the larve
of all species are destroyed while swimming about, partly because many of them cannot find
their object in due time. Then again, there must be circumstances which cause a compara-
tively smaller percentage of the brood of the least prolific species, and an enormous percen-
tage of the brood of the most prolific species, to be destroyed during this period. This,
again, must be supposed — at least partly — to have something to do with the difference
of the number of specimens of the species which constitute the hosts. Now, as the larvee
of the most prolific species seek large forms, those of the least prolific small forms, and as
the large forms, as we know. are found on an average in much smaller number than the
small forms, it follows that the larve by which they are sought, have as a rule much less
chance of finding them in due time, for, as previously stated in detail, there is no considerable
difference in the structure and size of the different larvae, — e. g. the larva of Choniostoma
mirabile is only about one eighth longer than that of Stenothocheres egregius, but, as far as I can
see, scarcely so vigorous and so well adapted for swimming, (comp. the peduncles of the natatory
legs in the two species; pl. I, fig. 11, and pl. XI, fig. 1 e). — On the base of my material
of parasites and of my knowledge of the biology of the hosts, I might set forth several points,
thus giving a wider scope to the discussion of these matters, but for various reasons I
abstain from doing so.

C. About Classification.

a. Limitation and Characters of the Species.

Of small Crustacea, such as Cladocera, Ostracoda and free-living Copepoda, there
are in most cases some or many specimens of each species at the student's disposal for
determination of the forms, and even where these animals are so small that the compound
microscope has to be used in order to determine them, most of them can stand the pressure
of a glass-cover, and as a rule it is unnecessary to submit the specimens to much parti-
cular preparation, except where a description of them has to be given; finally, most species
have a very fixed shape. All these factors help to facilitate the determination of the species.
In Choniostomatids the circumstances are different. The animals are so rare, that of most
species only a single specimen or a few specimens of each sex can be procured; neither
males nor females can bear the pressure of a glass-cover; the males are so small, that they
cannot be examined without high magnifying power, and before the examination particular
care has often to be taken in placing them in the preparation, and though the females are
much larger, the parts of their body which have to be investigated are exceedingly small

79

and very difficult or impossible to examine in detail on intact specimens, so that in numerous
cases one is obliged to undertake a difficult dissection, and to place the head and the genital
area in a preparation; lastly, the general form of the body in both sexes, and particularly
in the females, is far less fixed than in the free-living forms. On account of these circum-
stances it is sometimes difficult to form a positive judgement about some species, e. g. in
how far they present varieties of one species, or form separate species. It is sufficiently
well known that a similar difficulty is not unfrequent with regard to the free forms, and
from what has been said about Choniostomatidae, it is easy to understand that, with respect
to this family, the difficulties are sometimes so great that a final settlement of some questions
must be left to the future.

It has been specially mentioned that most species of Choniostomatidee have been
found each on its particular species of Malacostraca, but, at the same time, I can prove to
a certainty that the same species can be found on different species of the same genus (e. ¢.
Choniostoma Hansenii on two species of Hippolyte), or even in forms of two different genera
(Mysidion commune on Parerythrops and on two species of Eryfhrops); and further, on the same
species of host one may find two species of parasites in the branchial cavity or in the mar-
supium, nay even two species in the same marsupium (Mysidion commune and Mysid. abys-
sorum in Er, abyssorum). ‘The result hereof is that we cannot absolutely take for granted
that we know a parasite, because we have found it on a certain host, nor that a parasite
belongs to an unknown species, because it is found in a host that is not mentioned in this
work. All the same, in most cases the host is of the greatest importance in determining a
parasite, and where parasites are found in new hosts, most frequently they will prove them-
selves to be new species.

Most of the species established in this work have been easy to distinguish from each
other, and in the majority of cases there has been no hesitation at all in establishing the
different species. It is mentioned above that on Perioculodes longimanus (Sp. Bate) I found
females which were exactly like the Spheronella paradoxa living on species of Bathyporeia
Lindstr., but as the male belonging to the females found on Perioculodes is wanting, I have
not been able to decide whether the same species really lives on forms of different families.
On account of rather small material, [ have also had a little doubt concerning the identity
of the forms found on Diastylis cornuta Boeck and D. levis Norm.; but with regard to this
question, as well as to Aspidoecia Normani, I refer to the subsequent special representation.
The greatest difficulty | met with in the species very closely allied to Spheronella Leuckartii
Sal. Of these species I have established eight, taken in six genera belonging to four
different families of Amphipoda, and four of these species of hosts (belonging to four different
families) came from Denmark, two from Sicily, one from the West-Indies, one from Hong-
Kong. The difficulties were so great, that I hesitated for a long time whether to establish
them each separately, or as belonging all to one species. Though this question will be
treated more thoroughly in the systematic part, I thought it right to call attention to it here.

80

We now come to the question concerning the characters of the species. It appears
hat everywhere, except within the just mentioned group of Spher. Leuckartii, the males
offer a considerable number of excellent and, as a rule, easily observed characters. In this
respect they generally surpass the females; they are not only easier to examine, but the
shape and decoration of the frontal margin, the processes from the sub-median skeleton, their
often very peculiar two pairs of trunk-legs and the hair-coat of their trunk frequently afford
excellent characters, which do not occur in the other sex. Other distinctive marks are not
unfrequently found in the antennule, the maxille and the maxillipeds, in the presence or in
the want of caudal stylets, and in the former case, often in the length of their longest
terminal seta etc. But, at the same time, we must point out that minor differences in the
general shape of the body, in the distance of the caudal stylets from the posterior extremity,
in the length of very long sete, are frequently seen in specimens of the same species; also,
that such a feature as the rostrum protruding or receding may give a very different appear-
ance to the animal. In the females the chief characteristics are found in the structure and
the organs of the head, especially the antennule, the maxilla and the mavxillipeds, and in
adult specimens usually in the genital area, (in Mysidion, however, in the arch round each
genital aperture). As a rule the heads of the females are much more uniform than those of
the males, and must be examined with great care; the size of the genital area compared with
that of the head, its form, the extent of the solid chitine, as well as its hair-covering or want of
hair-coyering, often afford good characters; nevertheless, it is often necessary to make a prepara-
tion, and as far as my experience goes, one must frequently pass over several smaller differences,
as some variation may be found in the same species. The caudal stylets, their position etc., or
the want of them, is always of importance. Within the genus Spheronella, the females of
many species have trunk-legs, whereas these appendages are wanting in others, but in adult
specimens they are often so hard to find, that the character drawn from their presence is
not easy to make use of, and one has to examine the animals very carefully before being
able to deny their existence. In the adult females of very few species we notice a peculiar
haircoat, but it must be remembered that in Choniostoma Hansenii the younger specimens
are more hairy than the adults, and e. g. in Spheronella danica, the trunk of the young
ones is closely covered all over with hair, that of the adults mostly or totally naked. In
the females the general shape of the body is sometimes rather characteristic, but often
rather variable according to chance circumstances, e. g. some kind of pressure, or the periods
of beginning and ceasing to lay eggs.

But, in order to find good characters of the species, we are not confined to the
males and females only. In a large material it is not difficult to procure larve of a number
of species, partly free specimens, partly in preparing those contained in one or some of the
ovisacs. Of all the five species found in the marsupium of Cumacea, the larve are known
to me, and these not only differ from all other larve yet found, they also show very distinct
differences among themselves, particularly in the frontal decoration and in the two distal

81

joints of the maxille; however, I may also observe that I have found very considerable
difference in the length of the olfactory seta of the antennule between larve of the same
species (Spher. modesta). Most other larvee we know also differ from each other in a
number of features: length of the olfactory seta of the antennule, structure of the antenne,
the relative size of the abdominal segments and of the caudal stylets, and the length of their
long sete, sometimes (Mysidion) also in the presence or absence of fine processes on the
terminal joint of the maxillipeds. However, in one case, namely in the genus Chonio-
stoma, I have not been able to find any difference between the larve of the two closely
allied, yet distinctly separate species. — The size of the ovisacs and the size of their eggs
compared with the female present considerable differences between the species, yet they do
not naturally form good distinguishing marks. Finally, the few pupe known to me differ
very much according to species, except those belonging to the group of Spher. Leuckarti.

b. Limitation and Characters of the Genera.

All the species may be classed under six genera, which offer an almost regular
gradation in the reduction of the females. The males too become considerably degraded,
but not to such a degree as the females. This gradual reduction is combined with great
changes in the way of laying the eggs, whereas there are very little differences and no
reduction at all in the structure of the larvee, and the post-larval development is too little
known to allow of making general statements about it. Consequently, the arrangement of
the genera in the systematic part is easily and naturally carried out in considering the
eradual reduction indicated.

The first genus, Sfenothocheres, deviates from all the following by possessing a distinctly
prominent abdomen, by the more conspicuous and distinctly two-branched trunk-legs of the
females, and by the way they lay their eggs: in one or two (rarely three) free lumps of
indefinite form — not in ovisacs, where the eggs are surrounded by a distinct common mem-
brane. In the two first mentioned characters the genus approaches the less reduced forms
of Copepoda. In the other five genera there is no abdomen, the trunk-legs of the females
are small with at most one distinct branch, generally consisting of one single joint, or they
are altogether wanting, and the eggs are deposed in several or in numerous ovisacs.

These five genera are naturally divided into two groups: in the three first, viz.
Homocoscelis, Spheronella and Choniostoma, the genital apertures of the females are situated
close together and surrounded by a more solid plate, ring or semicircular list, inside which
are also found the entrances of the two receptacula seminis; the ovisacs, when laid, are
free, not attached to the female. In the other group: Mysidion and Aspidoccia, the genital
apertures of the female are often placed at a greater distance or very far from each other; each
has its crescent or ring, and far in front of them is situated one receptaculum seminis; the
ovisacs are hinged on the lips of the genital apertures. In the first group most females

11

82

and most of the males known have 3-jointed antennule, distinct antennz, distinct and, in
the males, often very considerable trunk-legs as well as caudal stylets, whereas a few species,
through a reduction of these parts, form a transition to the genera of the last group, having
antennule which are 2-jointed or quite indistinctly articulated, and no antenne, trunk-
legs or caudal stylets in either of the two sexes. Another slight difference between the two
groups may still be mentioned, namely, that in the males the maxillipeds, especially their
distal part, is stouter and more normally developed in the first than in the second group.

Homoeoscelis does not deviate very much from Spheronella, though it differs distinctly
in having trunk-legs and caudal stylets, which are similarly shaped in the same individual, as
well as in the two sexes, and whose form differs very much from that in the female of
Spheronella; finally, the larve of this genus differ from all others in their very long antenne
and in the great distance between the maxille and the maxillipeds. It is also a character
of this genus that its species occur in the branchial cavity of Cumacea. In Choniostoma,
unfortunately, the male is unknown; the female only differs from Spheronella in haying
rudimentary maxillipeds; however, this feature, as well as the fact that its species live in
the branchial cavity of Hippolyte, appear to me sufficient to maintain the genus. Mysidion
and Aspidoecia are distinguished most decidedly by differences in both sexes and in the
mode of living, which it is hardly necessary to mention in detail, and Aspidoecia is the
most reduced of all forms of the family, both sexes having 1-jointed antennule, no antenne,
very small mavxillulae without additional branch, and, as a matter of course, no trunk-legs
or caudal stylets; moreover, the mavxillipeds are entirely wanting in the female, and their
distal part is greatly reduced in the male.

No less than thirty-four of the here described species are referred to the genus
Spheronella, and these species differ very much from each other in several respects which,
at least apparently, are of considerable importance: 1) Antennule mostly 3-jointed in both
sexes, sometimes shorter and either 2-jointed or with indistinct articulation. 2) Antenne closely
similar in both sexes, generally pretty well developed, in some species rudimentary, in others
wanting. 3) Maxillule almost alike in both sexes, generally with an additional branch, some-
times without it. 4) Maxille rudimentary in the female of S. marginata, well-developed in all
other forms. 5) Trunk-legs and caudal stylets are good-sized in the males of most species, but
are wanting in a few; these appendages are found in most of the females, though they are very
small; they are wanting in some forms, and it may be said that where they are wanting in the
male, they are also wanting in the female of the same species, though the reverse is not always
the case. 6) The peculiar attachment of the female in S. paradoxa. — In spite of these salient
differences I have not ventured to divide the genus into two or more genera, as I have been
unable to discover any feature of sufficiently decisive importance. For it is easy enough to say, as
many authors do, that if a species (as e. g. S. paradoxa) presents some striking characteristic,
it must be set apart as the type of a new genus, but frequently we have no guarantee that
such a feature is really of sufficient importance. We meet a similar difficulty where several

83

species have the distinct negative character of wanting trunk-legs and caudal stylets in both
sexes, for as there are species which, though wanting these organs in one sex, not in the
other, or through the male having trunk-legs, but no caudal stylets, form a transition to the
species in which both sexes possess trunk-legs and caudal stylets, one cannot very well set
apart the first mentioned species as a separate genus. Jf I can find no leading principle

to guide me in carrying out the division of a large genus, the elements of which seem to be

heterogeneous, and if I am not obliged to undertake a division in order to bring about an
equivalence with previously established acceptable genera, I prefer putting off the division till
the discovery of new forms has thrown new light on the question. If I had had to subdivide
Spheronella, the result would have been, not two or three, but six or seven genera (some of
which would have consisted of only one or a couple of species), in order to establish a pretty
correct equivalence, but these new genera would not have been tolerably equivalent with
such types as Homoeoscelis, Mysidion ete.

ec. Characters of the Family.

An examination of the genera will show very clearly that, in spite of several diffe-
rences, they are all very closely related and belong to the same family. We will here
attempt to give a summary of all its more important characters, some of which separate it
from one, some from another, of the rather numerous families of parasitic Copepoda, for it
would be impossible to give a condensed characteristique with merely exclusive features, our
knowledge of several points in the organisation and development of other families being
too defective.

The adult Females ave ovate or sub-globular. The head occupies only a smaller or a
minute part of the greatly swollen, unsegmented body; the abdomen is comparatively rather small
and unsegmented, or mostly altogether wanting. Antennul 1-3-jointed; antennze small or wan-
ting; rostrum good-sized, comparatively stout with cup- or funnel-shaped mouth provided with a
border formed by a membrane which is interrupted only in front and supported outside by free
hairs; maxillule consisting of a basal part almost entirely fused with the rostrum, and of two
or three usually setiform branches; maxillze short and powerful prehensile limbs consisting of a
stout basal joint and a slender, 1- or 2-jointed, somewhat claw-shaped, distal part; maxillipeds
rarely wanting, mostly appearing as good-sized grasping appendages, consisting of a long, rather
stout basal joint and a shorter, slender, 2- or 3-jointed distal part. We often find two pairs of
rather small or minute trunk-legs, each of which consists of one single joint or sometimes of a
peduncle with one or two unjointed branches; the legs are wanting in not a few species. Caudal
stylets present or wanting. Some species, at least, can hinge themselves by an adhesive plate
or a frontal thread. Spermatophores (found in many species) consisting of a globular or oval
vesicle on a rather long thread-shaped stalk.

ities

84

The Males ave several or many times smaller than the females, oblong or sub-globular.
The head forms a little more or a little less than half of the unsegmented body. Abdomen nearly
as in the females. Antennule, antenne, rostrum, maxillule and maxillipeds nearly similar to
those of the females. Frequently, though far from always, we find too pairs of trunk-legs,
which are often good-sized and two-branched, with long terminal sete, but very rarely jointed.
Caudal stylets frequent. They hinge themselves by a rather long, or very long frontal thread.

Development. The eggs are deposed in one or two (rarely three) free, irregular
lumps, or most frequently, in several (at least four or five) or many (up to twenty-eight)
ovisacs, which, as a rule, are free, though sometimes hinged on the lips of the genital
apertures. The Nauplius stage is passed through in the egg; the forthcoming larva is in
the first Cyclops stage, with an oval, somewhat depressed cephalothorax, which is divided
far back by one articulation, and a 3-jointed abdomen with caudal stylets, each with a very
long terminal seta. Cephalothorax with 2- or 3-jointed antennule, provided with a very long
olfactory seta, 2-, 3. or 4-jointed antenne; rostrum in the main as in the adults, maxillule with
— as a rule — indistinct basal part and (one) two, three or four setiform branches; 2- or 3-
jointed maxille and 4-jointed maxillipeds, both pairs chiefly constructed as in the adults;
finally, two pairs of natatory legs, each with two 1-jointed branches. Out of this larva, which
hinges itself by a frontal adhesive plate, the males not unfrequently, the females sometimes,
appear directly, without passing through any intermediate stage. In other species the larva
develops into a pupa, out of which the male proceeds. In most species the same meta-
morphosis is gone through by the female; in one case the female passes through at least
one additional intermediate stage. Where a pupa is found, it is always hinged; besides it
is nearly always provided with a mouth and increases considerably in size. After hatching
the males grow comparatively rather little, and the same is the case with the head of the
females, whereas the trunk of this sex swells excessively.

A distinctive mark of this family is the above (p. 27—28) described mouth, which
appears, not only in the female and in the male, but — as far as its most important features
are concerned — also in the larva, and nearly always in the pupa.

d. Place of the Family in the System.

During the last thirty years and more, the parasitic Copepoda have been very little
studied, and not a single really leading work has appeared about this subject. Several
authors have established a series of genera, some of which might easily be ranged in the
old families, while others stand rather isolated. Some smaller families have also been
instituted. If, however, we try to get a general view of our present knowledge. we find
that several families are badly defined, and others so imperfectly known, that we cannot
form a definite opinion of their place in the system: whether they belong to one
of the established families, or must be taken as types of new families. The reasons

85

of this uncertainty are partly, that the males of too few forms are known, partly — and
particularly — that the metamorphosis of numerous genera among the old families and of
the more abnormal forms is entirely unknown, and that the structure of the mouth in the
adults as well as in the larve is often badly studied, etc. A revision of the classification
of the parasitic Copepoda would be most desirable and ought to be based upon a thorough
study of the external structure of both sexes, and upon numerous new data which throw light
ou the post-embryonic development; that a representation of the internal structure of numerous
types would be excellent, goes without saying, but even without undertaking this gigantic
work such a revision as the above-mentioned would be exceedingly useful. However, as
such a work does not exist, I do not see that it can be of much use to discuss the relation-
ship of the Choniostomatide and their place in the system more in detail, so [ will content
myself with some few remarks.

The last detailed systematic arrangement of the parasitic Copepoda was undertaken
by A. GersTarcKker in » Bronn’s Klassen und Ordn. des Thier-Reichs, fiinfter Band, erste
Abth.« p. 721—729, and this part was published about 1870. Perhaps we might also
mention the more condensed grouping in »C. Craus: Grundziige der Zoologie, B. I, 1880,
p. 554—58,« as it is set up by the author who has also gained great distinction in this
domain of carcinology. By studying these treatments and several papers on special groups,
I have found out that the family Choniostomatide stands far apart from all hitherto established
families, except Lernzeopodidx, from which, however, it also ditfers considerably. If Salensky
in his often mentioned paper means that Spheronella comes nearest to Lerneidee, because he
thinks that in the structure of the mouth and in the form and position of the maxille and
the maxillipeds, it resembles Lernea branchialis in the pairing stage, we admit indeed that
the resemblance in the structure of the mouth is doubtless very striking, but in other respects
the various larval stages of Lernea and Pennella differ widely from the larvee and pupz of
Choniostomatide, and the subsequent development of the two genera of Lernzide, as we
know, differs so thoroughly from that of the Choniostomatidee, moreover, the structure and
egg-laying of the female of Lernea is so exceedingly different from these features in our
family, that a closer relationship is entirely out of the question: in my opinion Lerneide
and Choniostomatide stand very far from each other. But undeniably it stands even farther
apart from Herpyllobiide, though Giard and Bonnier have attempted to unite it with this
most remarkable family, which differs widely from all other parasitic Copepoda. They do so
by establishing a new family: Spheronellide, which they subdivide into Choniostomatinz
and Herpyllobiine. This peculiar classification I have criticised at length in my general
historical view (p. 15—21), to which I refer. The same two authors, in their earlier work,
published in 1889, say that Choniostomatidse comes nearest to Chondracanthide, Lernzeopodidee
and Ascomyzontide. The first and the last of the families in several respects — e. g. in
the structure of the mouth — deviate so much from Choniostomatide, that any closer
relationship is out of the question; indeed our family stands widely apart from both,

86

but as for Lerneopodide, there is a considerable resemblance in various points, e.g. in the
structure of the male and the female, and especially in that of the larve; at the same time,
there are numerous and important differences. However, as the family Lerneopodide is
comparatively well known'), I do not think it necessary to repeat and compare all the
characteristics of the two families, but will content myself with stating my opinion that the
Choniostomatide, though coming much closer to the Lernzopodide than to any other form
of parasitic Copepoda, yet differ very much from them in the way they lay their eggs, in
their development after the first larval stage, in several peculiarities in the internal and
external structure of the male (e. g. in that of the mouth), and most conspicuously, in the
structure of the mouth, the antenne and the maxillipeds of the female. A comparison of the
figures in: W. Kurz: Studien tiber die Familie der Lerneopodiden (Zeitschr. fiir wiss.
Zool., B. XXIX, 1877)« with my present work, will give the best idea of the resemblances
and the differences between the adults of these two families. In elucidation of the matter
IT will add, that Kurz concludes from the development that the pair of limbs which in the
females of Lernzopodide are fused together into one long arm that serves as organ of
fixation, are the »first pair of maxillipeds.« If this be correct — which is quite possible
— this appendage would correspond to what I term the maxille.

1) In the above-mentioned ,Grundziige* (p. 557—58), Claus enumerates most of its characteristics and
refers to the most important accounts of its structure and development.

IV. DESCRIPTION OF GENERA AND SPECIES.

Conspectus of the Genera, based on the Females.

A. Abdomen is found, it protrudes from the trunk, is comparatively rather small. unseg-
mented and not set off by an articulation. Eggs are laid in one free lump or in a two
(or three) lumps without distinct shape. (Live in the marsupium of Stenothoide, a
family of Amphipoda)..... . sou nee gosebomeape o Ib Suanodoaooaray Wy eine

B. Abdomen is wanting, though caudal stylets are frequently found. Eggs are laid in a
smaller or greater number of ovisacs.

a. Genital area is found; genital apertures close together and surrounded by a common
plate, ring or semi-circle, which is more solidly chitinised than the remainder of the
skin. The entrances into the two receptacula seminis are situated within the genital
area. The ovisacs are deposed freely.

«. Trunk-legs and caudal stylets apparently consist of a very small, short basal
part which tapers into a comparatively rather long and very narrow conical
branch. Live in the branchial cavity of Cumacea. . Il. Homoeoscelis n. gen.

6. Trunk-legs and caudal stylets not unfrequently wanting; if found, they are

very small, generally sub-cylindrical and terminating in two — the caudal
stylets sometimes in one or three — sete. Live in marsupia.
8. Maxillipeds good-sized and at least always longer than the maxillxe. Live

in the marsupium of Amphipoda, Cumacea and Isopoda. ILL. Spheronella Sal.

mn
Sn

Maxillipeds quite rudimentary, several or many times shorter than the

maxilla. Live in the branchial cavity of Hippolyte Leach, a genus of

DE capodameenenaeae ae eee Soe oe ee Ve, (ChontosiomamEl. JE

b. Genital area wanting; the genital apertures often situated at a considerable distance
from each other, each having its own arch or ring of solid chitine. The odd recep-
taculum seminis is far from the genital apertures. The ovisacs hinged on the lips
of the genital apertures.

88

«. Maxillipeds good-sized. Genital apertures very far from each other, placed
very near the line where the hind margin and the lateral-margin meet. Live
in the marsupium of the genera Hrythrops G. O. 8. and Parerythrops G. O.
Sars, belonging to Mysidacea................ V. Mysidion n. gen.
fp. Maxillipeds wanting. Genital apertures closer together, somewhat up on the
dorsal surface. Live attached outside on the back and on the sides of the
body or on the eye-stalks of the genus Evythrops G. O. Sars, belonging to
Miysidacea ae gacces aise criss eee coe .... WL. Aspidoecia Giard and Bonn.

I. Stenothocheres n. gen.

FEMALE. The body somewhat longer than broad; naked all over. The head which
is comparatively good-sized, is not marked out from the trunk; it has neither frontal nor
lateral borders. Antennule comparatively long, without distinct articulation and with few
sete. Antenne middle-sized. The mouth-border with very short hairs. Maxillule without
additional branch. Maxille robust, without hairs. Maxillipeds of scarcely medium size, second
and third joints coalescent, all joints without hairs, spines or processes. Sub-median skeleton
very feebly developed, consisting only of a plate in front of each maxilliped. The trunk-legs
are situated rather far from the lateral margin; they are comparatively of considerable size
and consist of a basal part with two unjointed branches, each as a rule ending in a strong
or spiniform seta, besides, on the outer branch of the first pair of legs, is found a
smaller seta. Abdomen pretty well developed, consisting of a robust basal part and a
narrower distal part, which passes without articulation into two short and broad caudal
stylets, each of which bears four sete of unequal length. Genital area wanting. Genital
apertures situated partly on the lateral surface, partly on the ventral side of the basal part
of the abdomen, more or less close to its lateral margin. Two large receptacula seminis,
the entrances of which have not been found. — Spermatophores have not been noticed.

MALE. Agrees with the female in most features, so that only some characters
need be pointed out. The head is not marked out, it occupies about half of the body. The
trunk-legs are situated at a short distance inside the lateral margins of the trunk; both pairs
are comparatively very considerable, with a thick basal part. A little behind and outside
the second pair of trunk-legs proceed a pair of spines (pl. I, fig. 21, x), which are possibly
the rudiments of a third pair of legs. Only the narrower, distal part of the abdomen can
be distinguished from the trunk. The body is naked, but on its dorsal side, and especially
on its front part, it is furnished with moderately small, irregular protuberant knots, and on

89

the ventral side, particularly outside a line between the base of the antennule and the first
pair of trunk-legs, with peculiar, irregular stripes or with keels and knots.

OVISACS. Real ovisacs are not found; the eggs are laid in one free lump or in
two (or three) lumps.

LARVA. Is only known of one species. Antenne about the length of the anten-
nule. The maxillule have a short but distinct basal part and two stout branches, the anterior
of which is very long. The maxillipeds are situated closely behind the 3-jointed maxille ;
all joints of both pairs are smooth. The peduncle of the natatory legs is very broad.
The third segment of the abdomen, together with the broad caudal stylets, which are not
set off by an articulation, is almost as broad as and nearly double the length of the second
segment. The longest seta of the caudal stylets is only a little longer than the abdomen
and not nearly half the length of the cephalothorax.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The two species known live each in a species of the genera Metopa
Boeck and Stenothoé Dana. Hitherto found only in Norway and at the western coast of
Greenland.

REMARKS. My material of the Amphipod family of Stenothoide, which contains
a great multitude of species, being somewhat limited, because I have only seen a few spe-
cimens of most Greenlandish and Danish species, it may be expected that researches made
in a large material will lead to the discovery of a number of new species of this inter-
esting genus.

Conspectus of the Species.

The basal joint of the mavxillipeds in both sexes conspicuously longer than that of
the maxille. The female without median frontal process. The male elongated.
1. St. egregius 0. Sp.
The basal joint of the maxillipeds in both sexes almost shorter than that of the
maxilla. The female has a median frontal process. The male is short and broad.
2. St. Sarsvi n. sp.

|. Stenothocheres egregius n. sp.
(Pl. I, fig. 1 a—11.)

FEMALE. A very large specimen is “63 mm. long. The specimen represented

(fig. 1a and fig. 1b) is ab. ‘59 mm. long and -46 mm. broad. The body as a rule a little

longer than broad, apart from the abdomen evenly rounded; seen laterally (fig. 1 b), the ventral

side is rather flat, the back strongly convex. No median frontal process between the bases

of the antennule. The antennz distinctly jointed; the terminal joint furnished with two short

sete of unequal length. The basal joint of the maxillipeds conspicuously longer than that of the
12

90,

maxille. Hach maxilliped proceeds from a chitinous list (fig. 1 e,h), projecting between the
bases of the maxilla. The proximal part of the abdomen two to two and a half times
broader than the distal part. Hach of the triangular caudal stylets (fig. 1g, t) has four
setze, the foremost of which is short, the apical one moderately long.

MALE. A well developed specimen is 196 mm. long and ‘11 mm. broad — thus
good-sized in proportion to the female (fig. 1c: fig. 1a). So the body is a good deal longer
than broad (fig. 1i). On the ventral side, stretching from the base of the antennule outside
the maxille, the maxillipeds and the legs, backward towards the abdomen, and from the
appendages towards the lateral outline, are found a comparatively small number of irregular
stripes or grooves. On the basal part of the first pair of legs we see some irregular pro-
jections and taps; similar though blunter taps or knots are spread more scantily over the
dorsal side of the animal, whereas the frontal part is closely covered with larger knots.
Antennule shorter than in the following species. The basal joint of the maxillipeds longer
than that of the maxillz and more robust than in the following species. In the second
pair of legs the apical spine on the inner branch is frequently somewhat curved, but not
hooked. Of the setze on the caudal stylets, the apical one is thick and longer than the
others. — A frontal thread was found in a few cases; it was about as long as the animal
(fig. 1 ¢), simple and somewhat dilated towards the distal end.

EGGS. They are very large (fig. 1d compared with fig. 1a), and are deposed in a
large, loose, irregular lump, or in two (or very rarely three) lumps; the greatest number
found is forty-two, the usual number is about thirty.

LARVA (fig. 11). Length of the body (except caudal sete) 22 mm., which shows
that it is longer than the male, though its volume is somewhat smaller. Cephalothorax
oval, somewhat longer than broad. The front has a transverse band which curves backward,
ending at a short distance from the base of the antennule. Antennule 3-jointed; olfactory
seta at least double their length, reaching a little behind the middle of the cephalothorax.
Antenne of medium length, 3-jointed; basal joint broad and longer than broad, about the
same leneth as the second joint; third joint short, terminating in two or three sete, one of
which is stout and as long as the second and third joints together. Second and third joints
of the maxillipeds of about equal length. The longest seta at the hindmost angle of the
first abdominal segment a little longer than the second segment. Each caudal stylet fur
nished with five setee, one of them a little longer than the abdomen, two of the others a
little longer than the last segment plus the caudal stylets. (See besides the diagnosis of
the genus).

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. On Metopa Bruzelii (Goés) from two localities near the western coast
of Greenland. In a glass labelled: »Godthaab, deep water [probably 40—60 fathoms], in
Sertularia, Holboll«, were found numerous specimens of Met. Bruzelii (Goés) and of M. sinuata
G. O. Sars, as well as a number of specimens of M. longicornis Boeck, M. longimana Boeck

91

and M. neglecta H. J. H., and an examination of all these only exhibited parasites on eight
adult females of M. Bruzelii; in five specimens this Stenothocheres was found, in three
others Spheronella Metope n. sp. (s. later on). The second locality is: »lat. 66° 30’ N.,
long. 54° 50‘ W., forty fathoms, stones with many Balani, 5. VIII. 1886, Th. Holm<;
here was taken a very great number of Met. Bruzelii and of M. sinuata, but whereas the
latter is free from parasites, Stenothocheres occurs frequently in the first mentioned species,
while no specimen of Spher. Mctope was found. Unfortunately the abundant material from
this locality was somewhat roughly handled, as the animals while still alive had been put
into too strong spirit. I investigated and put down statistics on the contents of the marsupia
of twenty-three infested females, which, added to those from the former locality, makes a
total of twenty-eight. In one case neither females nor males were found, but at least twelve
larvee and a lump of six eges without larvee. In another case only one not halfdeveloped
female was found; in a third marsupium two females, but neither males nor eggs. In twenty-
five cases a female was found, and often a male besides, in one case even two males (once
I also found a normal male and the larger part of the skin of a dead male), and finally, I
frequently met with eggs or recently hatched larvee. Concerning the eggs, I refer to the
description given on p. 44. The female was always seen in the foremost part of the mar-
supium, the male and the eggs behind. Only in a few cases a frontal thread was found
in the male. Subsequently more material of Met. Bruzelii was examined (adult females as
well as young specimens), in order to find — if possible — stages of development. Several
finds in adult females corresponded to the above stated results, but in one young female
with scarcely half-developed marsupium I succeeded in finding two larvee which had evidently
swum in beneath the body of the animal, and in a young specimen without marsupium [
found a single larva. From all these data it may be concluded that, at least as a rule, the
female is infested before the marsupium is quite developed. At least one of the last-men-
tioned larve had hinged itself by the usual adhesive frontal plate, but about the subsequent
development I learned nothing.

2. Stenothocheres Sarsii un. sp.
(Pl. I, fig. 2a—21,)

FEMALE. The largest specimen (fig. 2a) is swollen to such an extent that the
body is vaulted beyond the abdomen, so that this part does not add to its length or breadth
which are respectively °80 mm. and 69 mm. The specimen exhibited in fig. 2d and fig. 2
is only ‘67mm. in length. Seen from below, the body (apart from the abdomen) is a short,
at the ends rather flattened oval; seen laterally (fig. 2e), the ventral surface is rather flat,
the back considerably vaulted. Between the base of the antennule is found an odd, blunt,
horizontal process of considerable size. The antennz weak, with indistinct articulation, the distal

12*

92

joint terminating in a short spine. The maxillipeds comparatively short and slender, their
basal joint almost shorter than that of the maxille. The proximal section of the abdomen
more than three times broader than the distal section (fig. 21); each of the oblong caudal
stylets furnished with four setze, the foremost of which is the longest. — Fig. 2a shows
that this specimen possessed two long frontal threads (s), the proximal parts of which are
united into one single thread.

MALE. The largest specimen (fig. 2k and 21) measures to the extremity of the
caudal stylets -27 mm. in length; breadth -24 mm.; a rather considerable size compared
with the female (fig. 2b: fig. 2a). So, the body is proportionally only a little longer than
broad and somewhat depressed. The ventral surface outside the limbs from the base of the
antennule to the abdomen, the posterior part of the sides, the hindmost part of the back,
the stout basal part of the trunk-legs and the inner branch of the first pair, are closely
covered with peculiar, very irregular eminences, which are partly shaped like keels, partly
like knots or short, acute taps. The median part between the maxillipeds and the trunk-
legs shows fewer keels and stripes. The dorsal side has very few knots, whereas the front
part of the head is covered with numerous blunt knots. The mavxillipeds like those of the
female. The terminal spine on the inner branch of the posterior legs is strongly curved
and hooked. Of the sete of the caudal stylets, the two apical ones are stout and of sub-
equal length. — The frontal thread (fig. 2k, s) a little shorter than the animal, simple, slender,
yet somewhat thickened towards the distal end.

EGGS. Much smaller, but also much more numerous than in the preceding species.
In one female were found two somewhat oblong lumps of eggs of about equal size and of
irregular shape; they did not show any trace of larvee. One of these lumps is exhibited in
fig. 2c, enlarged to the same scale as the largest female, fig.2a, and a comparison of these
figures with the male (fig. 2b) will show the relative size.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. On Stenothoé marina (Sp. Bate) from Norway. The locality cannot
be precisely indicated, but, according to Sars, the host occurs along the southern and western
coast of Norway up to the Nordland coast (Tjété). I have only seen two infested specimens
lent me by Prof. G. O. Sars, after whom I have named this remarkable form discovered by
him. One of the hosts was a female with marsupium, in which were found an adult female,
a very small female and the two afore-mentioned lumps of eggs, one of which, probably by
chance, was adhering to the abdomen of the female, whereas the other was free and situated
more to the front; the female had attached one of its above-mentioned frontal threads to it,
which I think shows that the animal must have moved after deposing this lump. The other
host was also a female; its marsupial plates were somewhat smaller, though they appeared
to be quite developed, being furnished with marginal sets, and in this specimen were found
an adult female, a male and an empty skin of a somewhat smaller male.

Sc

II]. Homoeoseelis n. gen.

FEMALE. The head small and distinctly defined from the circular, rather
depressed trunk. Frontal and marginal borders and sub-median skeleton well developed.
Antennul of scarcely medium length, 2jointed. Antenne wanting. Mouth rather small,
the mouth-border being somewhat narrow, with well developed hairs. Maxillule without
additional branch. Maxillee about middle-sized, smooth. Maxillipeds of medium size, second
and third joints coalescent. Body entirely naked in the adults, at the utmost a few hairs
on the sides behind the head; in the recently hatched and younger specimens the hair.
covering resembles that of the male. The trunk-legs are situated on the lateral margins;
they are small, each apparently consisting of a rather thick, short basal part which is jointed
without articulation to an elongated, very narrow conical, sometimes partly hairy branch, at the
base of which the basal part bears either a few set or just a vestige of another branch.
Abdomen wanting. Well developed genital area with a transverse chitinous arch, opening
towards the front and surrounding the genital apertures, which are situated close together,
and the entrances of receptacula seminis. Rather close behind the genital area are the two cau-
dal stylets which are a little thicker and longer than the legs. — Spermatophores frequently seen.

MALE. Body seen from below elongated ovate, from nearly twice to a little more
than twice as long as broad. Length of the head somewhat exceeding a third of the total
length. (The antennule 2- or 3-jointed, and very small antenne are perhaps found in one
species). In other respects all the other organs of the head, as well as the trunk-legs and
caudal stylets, mostly agree with those of the female. The trunk, except the anterior part
of the ventral surface, is covered rather closely all over with comparatively short hairs.

OVISACS. Are deposed freely, and are of moderate or rather large size, containing
few, six to eighteen, eggs which are very or exceedingly large. The number of sacs laid
by one female can amount to eight.

LARVA. Is known of both species. Antenne much longer than in any other
genus, more than twice the length of the antennule, owing particularly to the fact that the
penultimate joint is very much elongated; the terminal seta is very long. Maxillule I have
been unable to discover. Maxille only 2-jointed, the second and third joints being fused
and forming one curved joint, which, moreover, along the larger part of both margins is
furnished with extremely fine and short, setiform processes. Maxillipeds far behind the
maxille; all joints smooth; second joint half or scarcely half as long as the third one.
Peduncle of the natatory legs rather slender. Third segment of the abdomen together with
the small caudal stylets distinctly articulated to the segment, much smaller than the second
segment. The longest seta of the caudal stylets sometimes shorter, sometimes considerably
longer than half of the cephalothorax.

POST-LARVAL DEVELOPMENT. Observed only in one species and described
above, p. 5d.

94

HABITAT. The animals live in the branchial cavity of Cumacea, causing a gradual
swelling of the carapace above the place which is occupied by the parasite and its ovisacs.
A parasite with several ovisacs may be found on immature specimens of both sexes as well
as on adult females. Two infested adult males have also been found. The larve infest not
only immature specimens, but frequently also females with marsupium. The two species
here described come respectively from Denmark and from Messina (and a deep-sea species
was found on a Diastylis brought home by the »Ingolf« expedition)’).

REMARKS. The genus is distinguished partly by the shape of the trunk-legs,
partly by the similarity of both pairs in the male as well as in the two sexes mutually, and
by their resemblance to the caudal stylets. In giving the genus its name, I have tried to
allude to this conformity in the appendages. The females are very small, more so than in
any other genus, which harmonises well with the scanty room left for them in the branchial
cavity of their rather small hosts. The males, on the contrary, are uncommonly large in
proportion to the females: in the large species about half the length, in the small one even
longer than a middle-sized adult female. (In H. mediterranea the antennule of the male
are decidedly 2-jointed; what in fig. 1f on pl. XIII appears to be a short basal joint, is an
angular excrescence proceeding from the head. On the other hand, the antennule of H.
minuta sometimes appear to be 3-jointed, as the two last joints, though coalescent, are
separated by a distinct line, which, however, is too strongly marked in the drawing.)

Conspectus of the Species.

In the female the basal joint of the maxillipeds is comparatively more slender, a
good deal longer than half the breadth of the head at its base. Trunk-legs and caudal
stylets of the male are long, longer than half the breadth of the body, and furnished with
Nairseapouteall over ube md 1Stall ell teense eee eee em eee 1. H. minuta nv. sp.

In the female the basal joint of the maxillipeds comparatively stout, scarcely longer
than half of the head at its base. Trunk-legs and caudal stylets of the male shorter, not
nearly half the breadth of the body, and with very few or no hairs. 2. H. mediterranea n. sp.

1. Homoeoscelis minuta n. sp.
(PII, fig. 3a—3b; pl. I, fig. 1a—t11).
FEMALE. The largest specimen (fig. 1b), which had not begun laying eggs, is
‘52mm. in length and 49mm. in breadth. A female which has nearly finished laying eggs
(fig. 1c) is only “35mm. long and 39mm. broad. The frontal margin has seven small incisions

1) J. Bonnier, in his above-mentioned treatise, published probably in Febr. 1897, under the name of
Spheronella sedentaria Bonn. described a species belonging to this genus. He found it in the branchial
cavity of Cyclaspis longicaudata G.O.Sars, taken in a depth of 960 metres in *Le Golfe de Gascogne”.

95

(fig. 1h) and very short hairs. Basal joint of the maxillipeds rather slender and a good
deal longer than half of the breadth of the head at its base. The genital area (fig. 3a)
more than double as broad as long; between, behind and obliquely outside the genital apertures,
as well as behind the caudal stylets, are a number of very fine hairs.

MALE. A normal specimen (fig. Li and fig. 1k) is -20mm. in length and ‘O09 mm.
in breadth, or about half the length of a middle-sized adult female (comp. fig. 1d with fig. 1b
and fig. 1c). The body between scarcely double and a little more than double as long as
broad. The frontal margin seems to be like that of the female; the incisions are extremely
difficult to see (the hair-covering in fig. 1i is too long). Basal joint of the maxillipeds of a
shape similar to that of the female. Trunk-legs and caudal stylets long, longer than half
the breadth of the body, and very distinctly furnished with hairs about all over the distal half.

OVISACS. Of medium or rather large size, globular or shortly ovate (fig. Le and
fig. 1f). As a rule there are fourteen to eighteen very large eggs in each sac. It is a not
common occurrence to find eight ovisacs with one female, and a greater number has never
been observed.

LARVA. A free specimen (fig. 1g) is 15 mm. in length. Its cephalothorax is
nearly double as long as broad. Having only one such specimen in hand, I prepared some
larve out of their egg-membranes and examined them more closely; one of them is seen in
fig. 11. We notice that its cephalothorax is still somewhat shorter and broader than that
of the freely swimming larva, and the animal is only 14mm. in length. The olfactory seta
of the antennul turned backward reaches beyond the posterior extremity of the cephalothorax.
Distance between the maxilla and the maxillipeds about as long as the basal joint of the
latter. Second abdominal segment as long as the first. The longest seta of the caudal
stylets considerably longer than half the length of the cephalothorax, about half the length
of the body in the free specimen.

POST-LARVAL DEVELOPMENT. Described in detail above, on p. 55.

HABITAT. In the branchial cavity of Diastylis lucifera (Kyr.) from Denmark. The
parasite I have found in sixty-six specimens, the special locality of fifty-seven of these are
unknown to me; five specimens were taken at Hellebzek (four by Dr. Joh. Petersen, one by
the author), and four in the following four stations of the expeditions of »Hauch«: Stat. 25
(110 fathoms), Stat. 368 (13 fath.), Stat. 370 (15 fath.) and Stat. 383 (14 fath.)*). Hither
the right or the left side is infested; in no specimen have I found both sides infested. Only
one female and generally also one male, rather seldom two males, are found in the same
branchial cavity. Where the parasite has laid several ovisacs, the carapace of the host is very
considerably swollen, and frequently this swelling rises somewhat above the median dorsal line.

1) Details about the exact localities of these stations, the description of the bottom ete. is found in:
»C. G. Joh. Petersen: Det videnskabelige Udbytte af Kanonbaaden ,Hauch‘s Togter i de danske Have indenfor
Skagen i Aarene 1883—86*, p. 1—33, 1893. In my descriptions of several of the following species, other
stations from these cruises will be quoted and may be looked for in the afore-mentioned work.

96

An adult parasite, especially when it has laid several ovisacs, is easily seen through the carapace,
but if we want to find out if a specimen without swelling is infested with larvee, pups or
recently hatched specimens, we must examine it carefully under a good dissecting microscope.

I will try to give special statistics of my material, but unfortunately, at the beginning
of my investigation some years ago, I omitted to put down sufficient notes about a few of
my specimens, so [ cannot give as perfect statements as I should like. Of 433 specimens
of Diast. lucifera, 66 were infested, 367 were not. Of the latter, 182 were females with
eges or young ones in the marsupium, 74 females with empty marsupium, 28 adult
males, 7 young males (before the last moulting) and 76 young females (some of them
may have been males without rudiments of abdominal appendages). Of the 66 infested
specimens 13 were females with young ones in the marsupium, (there was not one
with eges), 31 females with well-developed though empty marsupium, no adult males, 3
young males and 15 young females; concerning 4 specimens sufficient notes are wanting,
at all events none of them was an adult male. Of the 62 specimens, 33 contained
an adult female with one or more ovisacs, and also, of course, a male, and of these 33
hosts, 4 were females with young ones in the marsupium, 13 were females with empty
marsupium, 13 young females and 3 young males. In 29 of the 62 specimens was found
either a moderately large female without eggs, or one (or two) males, or in many cases
recently hatched specimens or pupee, and in at least one case, only one recently entered
larva. Of these 29 hosts, 9 were females with young ones in the marsupium, 18 were
females with well-developed, empty marsupium, and 2 young females (without marsupium).
No help is needed to draw various conclusions from these figures; I will only observe that
the number of males collected is too small to allow us to conclude that they are never
infested (s. the following species).

REMARKS. The three infested specimens first observed were discovered by the
Inspector, Dr. F. Meinert, whom I had asked to look out for eventual parasites in determining
the Cumacea from the cruises of the »Hauch«. With respect to the figures it may be
observed that in fig. la I haven given a drawing (in the same enlargement as fig. 1 b and 1¢
etc.) of a rather young female, whose limbs are remarkably long, as in the male (fig. 1d),
and which has already four spermatophores attached to its genital area, though it is far
from being old enough to begin laying eggs. Fig. 3a (pl. 1) exhibits two spermatophores (s)
fixed at the entrances to the receptacula seminis (r), which are seen through the skin and
are indicated by dotted lines.

2. Homoeoscelis mediterranea n. sp.
(PI. XIII, fig. 1a—th).

FEMALE. The specimen represented (fig. 1a) is 28 mm. in length, °23 mm. in
breadth; the largest specimen taken out measures ‘31 mm. in length, °32 mm. in breadth.

97

The frontal margin uninterrupted, with scarcely any hairs. The basal joint of the maxillipeds
moderately stout (fig. 1d), scarcely longer than half the breadth of the head. The genital
area (fig. le) not nearly twice as long as broad; the whole area between the genital apertures
and the caudal stylets, a narrow part behind the latter, and an area outside the soft mem-
brane which borders the genital apertures, are covered with rather short hairs. The
remainder as in the preceding species.

MALE. The well-developed specimen illustrated (fig. 1f and fig.1¢) is 17mm. long
and ‘09mm. broad, thus a little more than half the length of the largest female. The body
more clumsy than in the preceding species, not twice as long as broad. Frontal margin
and maxillipeds as in the female. Trunk-legs and caudal stylets shorter, not nearly half
as long as the breadth of the body, and with very few or no hairs.

OVISACS. Rather large (fig. 1c), shortly ovate or sub-globular. There may be
five to twelve, but generally we find six to ten comparatively extremely large eggs in each
ovisac, and as many as eight ovisacs have been found with one female.

LARVA. In one ovisac were found larvee nearly on the point of swimming out;
one of these is figured (fig. 1h); its body is ‘15mm. in length, and the cephalothorax is
very elongated. The olfactory seta of the antennulz reaches the posterior extremity of the
cephalothorax. Distance between the maxillz and the maxillipeds considerably shorter than the
basal joint of the latter. Second abdominal segment scarcely the length of the first. The
long sete of the caudal stylets considerably shorter than in the preceding species, not half
the length of the cephalothorax and frequently much shorter.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. In the branchial cavity of Iphinoé trispinosa (Goods.), at Messina.
In May and in the beginning of June 1893 I caught fifty-eight specimens in all ages of
this species in the harbour of Messina, in a depth of ten to twenty fathoms, and seven out of
these were infested with the parasite. It was only found in specimens which were either
much more than half-grown or full-grown, so that no parasite appeared on a single one of
the numerous specimens which were only half-grown or still younger. A female with the
marsupium containing Spheronella marginata (s. later on), had on its right hand side a
considerable swelling, in which were two adult females, two males and six ovisacs. In a
female with less than half-developed marsupium, the left branchial cavity contained a male;
the right hand side of the carapace, especially its posterior part, bulged very much, and
under the hindmost part of it were found an adult female, in front of it a male and eight
ovisacs, the foremost of which was evidently newly laid, whereas another, which was lying
close up to the female, contained full-grown young ones; this arrangement showed clearly
that the female had changed place. An adult male contained in its left branchial cavity
one half-grown female. Another adult male contained, also in its left hand side, one adult
female, one young female, one male and two ovisacs. The three remaining hosts, viz. a
male before its last moult and two not quite adult females, have not been dissected, but it

13

98

could be observed through the carapace that in one of the specimens (a female), the parasitic
(no doubt adult) female had not begun laying eggs, whereas the two other specimens lodged
not a few ovisacs beneath their carapace.

REMARKS. In this small species the female is smaller and the eggs comparatively
larger than in any other form of this family hitherto found. It is closely allied to Homoe-
oscelis minuta, though the male in particular is easily distinguished from this species by
its shorter legs. It may be observed that an examination of numerous specimens of [phinoé
trispinosa from Denmark gave a negative result.

III. Spheeronella satensky (1868).

FEMALE. Head small, generally, though not always, defined from the trunk,
which is ovate or globular, sometimes even a little broader than long. Maxillipeds large
or rather large and at least always longer than the maxilla. Trunk-legs sometimes wanting;
if found, they always consist of one minute cylindrical joint with a couple of terminal sete,
or they are reduced to small eminences. Genital area is found and always well developed,
so that the genital apertures — which are rather or very close together — and the entrances
to the two receptacula seminis, which are situated close in front of them, are surrounded
or at least bordered posteriorly and at the sides by common rather solid chitine. Caudal
stylets are sometimes wanting; if found, they are shaped somewhat like the trunk-legs and
terminate in one, two or three sete. — Spermatophores frequently observed.

MALE. This sex is known in a little more than two thirds (twenty-five) of the
species. The body, seen from below, is ovate or sub-globular (seen laterally, the back is
much vaulted, the ventral side rather flat, sometimes even concave in the middle). The
head always furnished with frontal and lateral borders. The trunk is covered with hairs
on the larger part of the ventral surface, as a rule, also on its sides and on the whole or
part of the back. Trunk-legs and caudal stylets sometimes wanting, but generally found,
and in this case differmg much from each other. The trunk-legs always deviating very
much from those of the females.

OVISACS. Always deposed freely.

LARVA. Observed in scarcely half of the species. Antenne at most a little
longer than the antennule, sometimes very short. Maxillipeds situated close behind the
maxilla. Peduncle of the natatory legs of medium breadth or narrow. Posterior abdominal
segment together with the caudal stylets nearly always smaller than the penultimate segment.
Long seta of the caudal stylets longer than half the length of the cephalothorax.

POST-LARVAL DEVELOPMENT. Known or partly known in several species
(s. above).

99

HABITAT. The marsupium of Amphipoda, Cumacea and Isopoda. Younger females
and animals in various stages of development of some species are also found on the ventral
surface of the thorax in Amphipoda. Found in Denmark, Norway, Greenland, in the Kara
Sea, the Mediterranean, off Cuba, and finally on the East-coast of Asia between about lat.
22° and 51°N.

REMARKS. This genus is very large. Subsequently thirty-four species will be
described, besides S. Leuckartii Sal., which I have not seen (and S. diadema G. and B.
which has not been described). The above given diagnosis of the genus is rather meagre,
and it is easy to see that some of the characteristics are qualified by an »either .. . ore.
The obvious reason is that many of the species in several respects vary considerably among
themselves. Above, on p. 82—83 I have already given a general view of the most important
of these differences, stating my reasons for not feeling justified — in spite of these differences —
to divide the genus into several genera.

It is impossible, for two reasons, to give complete analytical keys of the two sexes
in all species, firstly, because the male is unknown in nine species, secondly, because the
differences between the females and between the males in one small division are too vague
to be represented with sufficient preciseness in such a conspectus. However, in order to
procure a kind of general view, I will divide all species into three groups according to the
orders of their hosts, subsequently giving as good a conspectus as possible of each of the
two sexes in the species of each group. In this place [ will only give the analytical keys
of the first division; the other keys will be found immediately preceding the divisions to
which they belong.

a. Parasites on Amphipoda.

It may be observed that the males of this group always have well developed trunk-
legs and caudal stylets. In the larve the front is never furnished with processes or lists
in the sub-median part (there are one or two rather small lists near the basis of each
antennula), the basal joint of the maxilla is smooth, without combs, and the terminal joint
not serrated.

1. Conspectus of the Females.

The figures preceding the names of the species indicate their number in the subsequent
representation. In this conspectus all species are included except S. abyssi n. sp., of which
my knowledge is too fragmentary (s. the description below).

1. Head with distinct frontal border and distinct prominent lateral borders. Genital area
TorRORYRIAP THN IONE - 525 gig -olpeto.to'eo pp Gua or cetera Con arneCeomcn dnona Gc OmrioeDaranarmnne 2

bo

Mey

100

Head without distinct frontal border; lateral borders wanting. Genital area longer
thant \broadh. 4) se cae ees pee a he ee eee ee 26. S. microcephala G. and B.
Antenne quite rudimentary. A tuft of hair near the base of each mavxillula.
Group: S. Leuckartii Sal.
including the following species: .. . 7. S. elegantulan. sp., 2. S. Atylin. sp., 3. S. danica
n. sp., 4 S. vestita n.sp., 5. S. Leptocheiri n. sp., 6. S. messinensis
n. sp., 7. S. chinensis n. sp., 8. S. antillensis n. sp.

Antenne pretty well developed. No hair-tufts near the base of the maxillule ... 3
Frontal! marein without; expansion imi they middle) a4 is elen a eileen nenen ener 4
Frontal margin with a flatly cup-shaped expansion in the middle . . 25. 8. frontalis n. sp.
Trunk covered with short hairs, 2- or 3-branched at their basis............ 5
Mrinkenaked ors wath rather tew-simp] eunalrs is teas menln ennai 6
Caudal stylets situated between the genital apertures. The trunk thickly covered
WED} WAITS; se cas, aap o5sctte Sockge eecle reel (auc ece mene CM Re IMs ee 9. S. Calliopwi n. sp.

Caudal stylets situated behind the genital apertures. Hair-covering less thick.
10. S. irregularis N. sp.
Trunk fastened to the host by a very short ventral thread. . . 77. 8. paradoxa n. sp.
Trunks never attached stomthehoStitsmemce nena mentee t nem meneame ena area ee a
Trunk-legs — if found — cylindrical, with two sete .................. 8
Trunk-legs distinct, rounded eminences without sete .... 24. S. Acanthozonis n. sp.
Maxillipeds good-sized; their basal jot much longer than that of the maxille ... 9
Maxillipeds rather small; their basal joint not much longer than that of the maxille.
28. 8. Dulichie n. sp.
Drunk-legs sit found we withesh ort SCtce mena sien meinen en ae 10
One of the terminal set of the trunk-legs remarkably long, about three times as long

as! the, legs iste Vacca ane eens ears eee rs ee ee 21. S. longipes n. sp.
Genital area naked or with rather few and — as a rule — scattered hairs .... 11

Genital area provided on each side with a curved line of long hairs.

15. S. Holbolli n. sp.
Genital fareastormin syeassolidsp] ate semama ae ean nee 12
Genital area for the most part thin-skinned, the more solid chitine forming a greater
part ola; TING 2. sce sy AE NS co Sega S Glan Se One A eee ee 13
Numerous hairs between the base of the maxilla and the maxillipeds. Genital area
witha mumber ol scattered hairsvae ae cee ee ene 16. S. intermedia n. sp.
No hairs between the base of the maxilla and the maxillipeds. Genital area naked.

17. S. capensis n. sp.
No transverse list between head and trunk behind the base of the mavxillipeds.

13. S. Argisse@ ni. sp.

17.

Wee

o bo

on

101

At least one transverse list between head and trunk behind the base of the maxillipeds . . 14

Head with naked lateral margins (margins of the lateral borders). ......... 15
Headmwithmhainvalaterdlemanoin Shere enewees mewelchietslscstsl os sss cls sau elie bee 16
Antennule rather short and clumsy. Sub-median skeleton without a process at the
basal mnnensanolLesofsthemmcixallliedSiemaeuete eset let eee 14. S. Metope n. sp.
Antennule moderately long and slender. Sub-median skeleton with a small process at
the basal inner angle of each maxilliped............ 18. S. Gitanopsidis n. sp.
Exceedingly short hairs on the lateral margins of the head. Basal joint of the maxil-
lipedssmodenatelyeshontmandsStOUteates lene setae ici). sae ehae sale) 5 ile
Moderately long hairs on the lateral margins of the head. Basal joint of the maxillipeds
lonemandieslemdery) op. tiene ce ete rye ge acme see eel) s hearer are 22. S. Amphilochi n. sp.

Caudal stylets behind or on the posterior margin of the ring of the genital area.

19. S. Giardia n. sp.
Caudal stylets at some distance in front of the posterior margin of the ring of the
Penital Paneer minaetise ce) teh cel stole Grek sn ellsee, Gediseumenel taeeticp atts 20. S. Bonniert n. sp.

2. Conspectus of the Males known.

Dorsal surface of the trunk with (at least) a transverse line or belt of hairs, or covered
with, hairs; ‘all over 275.2 4): Need gain toteht aa hes one Meee ne ae SE 2
Morsal surface of the trunk quite; naked’) 22 Ss 4s 552.5 o. 26. S. microcephala
Frontal border with two very deep and broad incisions dividing it into three plates,
the median one of which is large, long and broad and nearly square, the lateral ones
NUE AS MOLLCTP i tea iste eS -chc. cb Mics Sanda inane) s aiineranil She Group of S. Leuckartii
Frontal border not deeply incised, the margin crenate or entire. ........... 3
Frontal margin crenate, forming six lobes of which the most external ones are low.
9. S. Calliopia
ByontalemancimeentirG: esese eels ei eee era soe) PE Ne Le Pee Eek ORL ee eal shot epoca os Sar 4
Trunk covered with single hairs or with (at most) 3-branched setaceous hairs (3 hairs
PLOCEEMIN SM IMOMMeAG NY tinivalkT10t) Mememem nen iemtmemreienl smettentey Collcmreute. feulcicmretlrsli-ttett<itcun-Ur-u- 5
Trunk covered with tiny oblong transverse knots, from each of which proceed about
ten very fine hairs, radiating backward and sideways.......... 25. 8. frontalis
Each caudal stylet with a very conspicuous seta, which is from about thrice to many
(HUTHSS ine Aigireailn oe {ANS AVIG 6 oc aca. o pepe ee Gls ob be oa of Se oo go eo cic 6
Each caudal stylet with two or three moderately short setae, none of which is very
Conspicuous wandenot) thrice the lenetheor theystylet 2.9)... 0. es 12
First pair of legs 1-branched, the branch ending in a long seta......... sah
First pair of lees 2-branched, the outer branch ending in a long and a shorter seta,

~l1

the inner branch in a conspicuous, shorter or longer terminal seta .......... 9

10.

10’.

alate

lila

12.

We

13.

13’.

102

Sub-median skeleton with two pairs of processes (second and third pairs) between the
bases of the maxillipeds. Terminal sete of the caudal stylets somewhat longer than
save) [ORIEL afoyoan, Csi (ne) Ine 5 5 oo hk oo ooo 11. S. paradoxa
Sub-nedian skeleton with only one pair of processes (second pair) between the bases
of the maxillipeds. Terminal sete of the caudal stylets scarcely the length of the

basal jointof thesmaxillipeds. 5.2.4 1 < svar Sy) sen eee eee nen eae 8
Basal joint of the maxille without any prominent plate........ 16. S. intermedia
Basal joint of the maxillze with a prominent plate with spiniform marginal processes
round the distal, inward and backward turning angle. ......... 17. S. capensis
Terminal seta of the caudal stylets somewhat longer than the terminal seta of the
Outersbranchyor ihe mtinstspalrsotelees| ae eye icneieae nen mene ena nee 12. S. abyssi

Terminal seta of the caudal stylets a little or much shorter than the terminal seta of
the outer branchwofethe firsts paliao ly 10'S eure memes ens 10
Terminal seta of the caudal stylets at least four to six or eight times longer than the
stylets, and much longer than the secondary seta of the outer branch of the first pair
OF VOSS jee ro he icc et Ra a Can acta On ar 11
Terminal seta of the caudal stylets only about three times the length of the stylets
and not longer than the secondary seta of the outer branch of the first pair of legs.

13. S. Argisse
Terminal seta of the inner branch of the first pair of legs equal in length to, or longer
than the distance between the base of the same leg and the end of its outer branch.

14. S. Metope
Terminal seta of the inner branch of the first pair of legs somewhat shorter than the
distance between the bases of the same legs and the apex of their outer branch.

15. S. Holbélli
First pair of legs with a long seta at the apex of the single branch, none on the

OUMAMANKIOTI BI oO Re ube o Gok bb mona oenaadoe yoo 6 18. S. Gitanopsidis
First pair of lees with two branches, the terminal sete of which are shorter than the
leg: va.seta, On the ontersprocessi=... as) see eene ene ee eee 13

Trunk not much larger than the head, with setaceous hairs, proceeding two or (generally)

(TRESS TCM UR indy HEN co ooo doo oe npooo oon evo DoS 19. S. Giardii

Trunk more than double the size of the head, with moderately thin, normal hairs.
20. S. Bonnier.

About species 1—8: Group of Spheronella Leuckartii.

In seven species belonging to the genera Paratylus G.O. Sars, Cheirocratus Norm.,

Leptocheirus Zadd., Gammaropsis Lilljbge., Microprotopus Norm. and Corophiwn Latr., taken

in Denmark, Sicily, Cuba and Hong-Kong, I have found parasites which bear a close resem-

103

blance to one another and to Spher. Leuckartii Sal. from Naples. The Danish forms which
are taken on animals of the two first and the two last-mentioned genera, deviate quite
as much from each other as from the exotic forms, and quite as much as the latter deviate
from each other. In studying a not very large material of specimens taken on two of
the genera (Cheirocratus and Corophium) it appeared, on the one hand that the hair-
covering of the females sometimes, but not always, varied very much according to age
(Salensky already found that the recently hatched females of S. Leuckartii were more hairy
than the adults), on the other hand that adult, egg-laying females taken on the same species
(Cheirocratus Sundevalli) also varied much with respect to the quality of their hair-covering
on the anterior part of their trunk and on the genital area, and to the appearance of tufts
of hairs on various parts of the ventral side of the head; however, these last-mentioned
differences seem to be accounted for by the fact that one of the adult specimens had retained
part of the hair-covering it had had when young. Between adult females taken in the same
species there was some difference in the distance between the caudal stylets and the genital
area, still the differences in this area and in the situation of the caudal stylets were much
smaller in animals taken in the same species than in several of the forms taken in hosts of
different species. The size of the egg-laying females was very different, varying according
to the size of the infested species, so that a specimen from Cheirocratus was thrice the
length of one from Gammaropsis. There was considerably less difference of structure between
the males of various species than between the females, and much less difference of size.
Some of the differences found between the males were decidedly of an individual or acci-
dental nature. These data placed me in the dilemma of either considering all the animals
I had found as belonging to one species, though a very variable one, infesting animals of
widely differing families of Amphipoda, and being spread over an immense geographical area,
or to admit the eight species established here. Future naturalists who will have a much
larger material at their disposal to throw light on the varieties of individuals taken in the
same species, and at the same time will have many parasites from hosts of different genera,
must pronounce the final verdict on this matter. (Perhaps some day it will be possible to
solve the question, whether parasites from one genus often can infest animals belonging to other
genera, by cultivating in an aquarium non-infested specimens of the genera that are to be
examined, together with infested and non-infested animals of another genus; then perhaps it
will be seen, whether the larvae, which no doubt swim about only a short while, exclusively
seek specimens of the same species as the host of the mother, or whether they also infest
and develop themselves on the other genera). Not having found any parasite on Microdeu-
topus gryllotalpa Costa, I must consider Spher. Leuckartii Sal. as a ninth (to me unknown)
species. Unfortunately Salensky’s description and figures are far from being sufficiently exact
in the details with which we are here concerned. If my species were to be united into one, no
doubt it would have to be under the name of S. Leuckartii, but I will conclude with the remark
that I consider it rather improbable that such an arrangement would prove to be well-founded.

104

I think the best plan is to begin by giving an account of the features which are
common to all species, subsequently describing each species separately. A tuft of hairs
outside the base of the maxillule in both sexes, and the shape of the frontal border in the
male, are probably the most characteristic features which distinguish them from all other
species of the genus Spheronella.

FEMALE. Body ovate or sub-globular, with well-defined head. Antennule of
about medium length, 3-jointed, the last joint provided with rather short sete. Frontal
margin naked. Antennz rudimentary (pl. III, fig. 2¢,c¢), but generally visible. The mouth
of middle size. Sete of the mouth-border of medium length. Mavxillule provided with an
additional branch; outside and somewhat behind their base a peculiar, pretty large tuft of
hairs turning outward. Mavxille of medium size. Maxillipeds normal, with hairy spots on
their basal joint. The sub-median skeleton between the rostrum and the base of the maxilli-
peds forms rather broad longitudinal plates, but there is no transverse list on the ventral
side at the posterior limit of the head. The lateral margin of the head provided with a
row or a stripe of moderately long hairs. Trunk-legs and caudal stylets always distinct
(e. g. pl. II, fig. 6a). Genital area much narrower than the head, broader than long, plate-
like or only with a solid ring which has no opening in front. The curved genital apertures
turn their front extremity forward, their hind extremity sideways, and their distance from
each other is shorter than the length of each. Caudal stylets either on the posterior margin
of the genital area (pl. II, fig. 5b) or, as a rule, behind or far behind it (pl. LU, fig. 3).

MALE. This sex is known of six of the species. The body is from one third to
one half longer than broad. The head about the size of the trunk. The frontal border
produced so as to form in advance of each antennula a pretty large, rounded, distally ciliated
lobe, which is separated by a deep and broad incision from the odd, long, broad and almost
square median plate, the sides of which are often somewhat diverging, sometimes parallel;
its slightly curved anterior margin, as well as the distal part of the lateral margin, are
furnished with fine and short hairs. Antennule, antenne, rostrum, maxillule, the hair-tuft
at their basis, maxillee and maxillipeds, chiefly as in the female. The sub-median skeleton
with first and second pairs of processes well developed; first pair rather prominent, triangular,
pointed, situated close in front of or overlapping the base of the maxillipeds; second pair
situated at the inner angles of the maxillipeds, elongated, extending over the basal part of
the trunk, and more or less diverging. Lateral margin of the head ciliated; from its posterior
extremity a narrow belt of long hairs extends upward over the side and in an oblique
direction across the back. The ventral surface, the sides and the hindmost part of the trunk
are covered with moderately long, posteriorly towards the back with very long hairs, leaving
a large naked area behind the above-mentioned transverse belt. The legs of moderate and
sub-equal length; the first pair consist of a peduncle, one branch, and a short conical
process on the outer side at the apex of the peduncle; the proximal part of the peduncle is
stout and rather broad; the branch which must be homologous with the outer one in the following

105

species, is shorter than the peduncle and terminates in two sete, one short, the other longer
or somewhat shorter than the peduncle plus the branch, and finely plumose; the outer process
terminates in a short seta. The branch — at least in most cases — is not distinctly set
off from the peduncle by an articulation; if nevertheless this seems to be the case sometimes,
it may be owing to an optical delusion. The second pair of legs consist of a rather short
and slender peduncle and two branches, the outer of which is short, conical and terminates
in a short seta, the inner one agrees with the branch on the first pair of lees and terminates
in similar setee') (the outer branch is never set off by an articulation). The caudal stylets
are comparatively long, with a seta which is shorter than the stylet and proceeds from its
inner angle. — The animals are sometimes hinged by a frontal thread (pl. II, fig. 4b), the
very complex structure of which is described above on p, 42-43.

OVISACS. They are ovate, in the large species of comparatively medium size, in the
small ones very large compared with the females, and in the small species the female probably
lays only four to five, in the largest species as many as ten ovisacs (possibly even more).

LARVA. Known in only two species: S. elegantula and S. antillensis (pl. ILL,
fig. 2e); the latter is the one described here. Cephalothorax seen from below, a somewhat
elongate oval. On the front, inside the base of each antennula, two lists, running so as to
form a somewhat acute angle, but they do not quite meet. Antennule 3-jointed, the olfactory
seta reaching a little beyond the middle of the cephalothorax and measuring less than three
times the length of the antennula. Antenne somewhat longer than the antennule and
specially characteristic by consisting of four joints of sub-equal length and a terminal seta
which is longer than the two last joints together, or about as long as the three last joints.
Of maxillule only two naked branches have been found. Maxille rather robust. Mavxilli-
peds of scarcely medium length, second and third joints of about sub-equal length. Peduncle
of the natatory legs moderately slender. Abdomen proportionally short and broad; the long,
stout seta at the posterior angle of the first segment reaches far beyond the extremity of
the caudal stylets; third segment very short, and the not defined caudal stylets also short,
their terminal seta more than three quarters the length of the cephalothorax.

POST-LARVAL DEVELOPMENT. Very peculiar; we refer to the description
given above on p. 58—60.

HABITAT. All my eight species were found exclusively in fully developed marsupia
which contained no eggs or young ones of the host. Salensky states that his S. Leauchkartii
were found both in females and in males, but the latter, no doubt, were young females
(comp. above, p. 66—67).

1) For a long time I considered the branch on the first pair of legs to be not the outer but the inner
one, and the conical process to be the outer branch of the leg, but a comparison with some of the other
species (e. g. S. Metope and S. Giardii) will prove the interpretation adopted to be correct. Perhaps the
interpretation of the branches of the second pair of legs will not prove to be correct, but for the present it
is impossible to decide this question with any certainty.

14

106

|. Sphzronella elegantula n. sp.
(Pl. IL, fig. 2a—2g.)

FEMALE. An adult specimen (fig. 2a) was 1°31 mm. long and 1:16 mm. broad;
the head is a little more than middle-sized, the trunk globular. One of the specimens
dissected differed considerably in hair-covering from the two others and may be described
first. Tufts or rows of hairs were found on the proximal part of the inner side of the basal
joint of the maxillze and on the skeleton in front of and outside the articulation of the maxill,
in front of the anterior inner angle of the maxillipeds, above their posterior inner angle and
behind their articulation. The greater part of the trunk was naked; a moderately broad,
transverse belt behind the head was rather closely covered with most peculiar hairs, which
are also found on the genital area. This area (fig. 2) is considerably broader than long,
and the solid chitine forms a rather broad ring and a median list which is broad posteriorly;
the distance between the genital apertures is of medium length; the caudal stylets are situated
far from each other and at a considerable (though not equally considerable) distance from
the posterior margin of the area. The region between the caudal stylets, the interval between
these stylets and the genital area, the posterior part of the genital area, the part in front
of it and just inside its outline are more or less densely covered with most peculiar, very
broad, somewhat flattened, long hairs, which, however, are so strangely transparent and
membranous, that their outlines are difficult to follow, whereas, on the contrary, their bases
form conspicuous ovals, one half of which is more distinct than the other (in fig. 2 e all these
ovals are drawn, but only very few of the hairs themselves). — In another specimen the
ventral side of the head had hairs only in front of the basis of the maxille and at the
anterior and posterior inner angles of the articulation of the maxillipeds. Behind the head
the trunk had a belt provided with short and fine, basally somewhat dilated hairs. The
genital area had nearly the same shape as that of the preceding specimen, but its posterior
margin was slightly more concave; the caudal stylets were situated a little nearer (but not
equally near to) the area, and the part between and behind the genital apertures, as well
as the skin stretching from the genital area to a good distance behind the caudal stylets was
less densely furnished with hairs of the same shape as those on the front part of the trunk,
while the membranous hairs were entirely wanting. — A third specimen agreed essentially
with the last-mentioned one.

MALE. The largest specimen is ‘31 mm. in length, the smallest, which is not full-
grown, measures 23 mm. It is of medium size compared with the female (fig. 2b :
fig. 2a). The body comparatively slender (fig. 2f). The lateral margins of the median
frontal plate diverge distally, the anterior angles are sharp. The processes between the base
of the maxillipeds are long or very long; the trunk-legs proportionally long; the terminal
seta of the branch on the first pair and of the inner branch in the second pair longer
than the leg.

107

OVISACS. Of medium size (fig. 2), only slightly differing in size.

LARVA. Only one specimen was found, it was hinged. Its cephalothorax is very
broad and thick; the condition of the contents seems to indicate that the larva was developing
into a male (comp. above, p. 60). Except in this clumsiness of shape, it agrees entirely
with the larva of S. antillensis (pl. IL, fig. 2 e).

HABITAT. The marsupium of Cheirocratus Sundevalli (Rathke) from Denmark;
till now found only in four specimens. In one specimen were found: one adult female, two
males and six ovisacs; in the second: one adult female and four pup; in the third: one
adult female, one male and ten ovisacs; finally, in the fourth: one adult female, three males
(one of them hinged to the base of the hindmost gill), six ovisacs and one larva hinged on
the base, of the penultimate gill.

REMARKS. The above-described difference in the hair-covering of the adult females
appears remarkable to me. The female is larger, the male longer and more slender than in
any of the following species.

2. Spheronella Atyli n. sp.
(Pl. Ul, fig. 3 a—3 b.)

FEMALE. The largest specimen was ‘99 mm. in length, a specimen with seven
ovisacs only ‘66 mm. Shape like the preceding species. Two specimens have been dissected,
and the skeleton of their heads (fig. 3a) was found to want all the hair-tufts described
in the afore-mentioned species, so as to leave only the tuft of hairs at the base of the
maxillule, which is a distinguishing mark of the group. The trunk naked except a belt
behind the head, which is covered with numerous, but exceedingly fine and short hairs.
The genital area (fig. 3b) considerably broader than long, the solid chitine forms a ring,
the larger part of which is rather broad, as well as a median list; anterior and posterior
margins considerably concave; moderately long distance between the genital apertures; the
caudal stylets are situated far from each other and at a long or very long distance from the
area; genital area and its surroundings naked, except the usual, narrow arch outside each
genital aperture.

MALE. Length -22 mm. More like the male of S. chinensis (pl. III, fig. 1a)
than like that of the preceding species. The body is clumsier than in this species, the
median frontal plate is shorter, with converging margins and rounded anterior angles. The
trunk-legs more slender than in S. elegantula; the terminal seta on the branch of the
anterior legs shorter than the leg, that on the inner branch of the posterior pair slightly
longer than the lee.

OVISACS. Comparatively larger than in the preceding species, differing little from
one another in size.

14°

108

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Paratylus Swammerdamii (M.-Edw.) from Denmark.
Found only in five specimens. Two of these contained only one adult female each, the third
had an adult female and a male, the fourth one male and seven ovisacs. The fifth spe-
cimen contained no female, but thirteen ovisacs, but whether all these belong to one single female
which has fallen out, cannot be decided; some of the sacs contain almost fully developed larve.

3. Spheronella danica n. sp.
(Pl. Il, fig. 4a—4e; pl. XIU, fig. 2a.)

FEMALE. The largest specimen was ‘88 mm. in length, ‘76 mm. in breadth.
Shape of the body much the same as in S. chinensis. It will be to the purpose to begin
with a description of this specimen. The most proximal part of the basal joint of the maxilla
is hairy on its inner side; there is moreover an area densely covered with hairs in front of,
and a similar one behind the base of the maxillipeds. A part of the trunk behind the head
is furnished with a number of fine, simple hairs, the remainder of it is naked. The genital
area (fig. 4a) is somewhat broader than long, the greater part rather solidly chitinised; the
genital apertures at moderately long distance from each other; the caudal stylets far from
each other, but not very far from the posterior margin of the area; between and behind the
genital apertures the area is furnished with normal, fine hairs, and so is the skin extending
from the area to somewhat behind the caudal stylets. — A much smaller specimen, only
‘45 mm. long, has a comparatively large head, and its trunk is a little longer than broad.
Distribution of hairs on the head as in the large specimen; the trunk seems to be quite
naked, and the genital area, which was not cut off, is well developed and — as far as can
be judged — seems to agree with that of the large specimen (a spermatophore was also
attached to it). — In a somewhat smaller specimen, 41 mm. long, which was dissected,
the hairs behind the base of the maxillipeds were wanting, the trunk was hairy anteriorly
as in the largest specimen, but the genital area was not developed (pl. XIII, fig. 2a), the
more solidly chitinised part being represented only by a rather small area surrounding the
entrances to the receptacula seminis (one of these is indicated by a dotted line). The genital
apertures themselves are as in the adult animal, but the caudal stylets are situated close
behind them, and the surface between and behind these apertures extending beyond the stylets,
is furnished with normal hairs. — Another specimen which is even a little smaller, measuring
‘407 mm. in length, deviates in many respects from the preceding animals. The body is a
nearly elongate oval; the head which takes up a good deal more than one third of the
whole length, and which is very large, has, in addition to the hairs found in the large
specimen in front of and behind the base of the maxillipeds, conspicuous tufts or stripes of
hairs on the inner side of the base of the maxille and on the skeleton in front of and

109

outside the articulation of these appendages. The trunk is closely covered all over with
the peculiar membranous hairs which are mentioned above as having been found on the anterior
part of the trunk and on the genital area of the one specimen of S. elegantula. — Two still
smaller specimens — the smaller one only 34 mm. long and ‘19 mm. broad, — are very like the
last-mentioned specimen, which shows that these three very young animals differ very much
from the older ones in the hair-covering of the head and — particularly — in that of the
trunk. As a matter of course, the genital area is not developed in these small specimens,
but the animal mentioned as measuring ‘41 mm. shows that, at least sometimes, this area
does not develop its final shape till some time after the animal has lost the hair-covering
that was characteristic of it when young. For want of ampler material I cannot decide
whether this course of development is the rule in this species.

MALE. A large specimen is ‘24 mm. in length. It is somewhat more clumsy than
the male of S. elegantula, but on the whole closely resembles this species, as e. g. in the
shape of the median frontal plate, which, however, is a little shorter, and in the legs, the
long terminal setz of which are longer than each leg; but the anterior pair of trunk-legs
seem to be smaller, compared with the basal joint of the maxillipeds, than in the afore-
mentioned species; the caudal stylets are hardly so long. — The smallest male found is
only -15 mm. long, but it seems to be just hatched, for the frontal plate is bent downward,
the rostrum backward and the antennule turn backward (comp. p. 60).

OVISACS. Are pretty large, but occasionally show great difference of size, being
shortly oval or sub-globular.

LARVA. A single hinged specimen was found, but is lost.

POST-LARVAL DEVELOPMENT. Nine pupe have been found, all closely
covered with hairs (fig. 4¢—4e); the smallest 115 mm., the largest -25 mm. in length. As
for more particulars, I refer to the detailed account on p. 59—60.

HABITAT. The marsupium of Corophium crassicorne Bruz. from Denmark. In
one specimen were found one pupa and the smallest above-mentioned female; in another the
smallest female but one and one male; in a third specimen a young female and a hinged
larva; in a fourth the largest female but one, one male and four ovisacs of very different
size; in a fifth specimen a small female; in a sixth animal the largest female, one pupa and
two males, both fixed by a frontal thread, one of them being an adult, while the other was
the above-mentioned, recently hatched individual. In a seventh specimen four ovisacs were
found, no female, but the anterior halves of two males, which had evidently been destroyed
before the host was caught. Finally, in an eighth specimen, two ovisacs and seven pupe,
two of which were situated each on one side of the marsupial plate of the sixth (right) leg,
one on the gill of the penultimate (left) leg, one on the inner side of the basal joint of the
posterior left leg.

110

4. Spheronella vestita n. sp.
(Pl. Il, fig. 5a—5 b.)

FEMALE. The largest specimen (fig. 5a) is 49 mm. long and ‘335 mm. broad;
the body is ovate, and the proportionally very large head occupies about one third of the total
length; another specimen of the same shape is only 44 mm. long. Tufts or stripes of hair
are found on the inner side of the basal joint of the maxille, on the skeleton outside their
articulation, in front of and behind the basal part of the maxillipeds, as well as above the
middle of their articulation. The trunk is densely covered all over with peculiar, very
broad, apparently shorter than broad, obliquely proceeding »scales«, which are transformed
hairs. The genital area of the large specimen (fig. 5b) is cut off; it was shortly oval and
somewhat broader than long, yet somewhat longer compared with the breadth than the pre-
ceding species; its solid chitine forms a ring which is rather broad in front, posteriorly it
seems to be open; the distance between the genital apertures is moderately great; the caudal
stylets are situated on the posterior margin of the area, and the distance between them is
rather considerably smaller than in the preceding species; the region between and behind
the genital apertures and the part surrounding the caudal stylets are closely covered with the
above-described »scales«, while the remainder of the skin inside the ring has much fewer
»scales«, and the ring itself is almost naked. The genital area of the smaller specimen
seems to agree essentially with that of the larger one.

MALE. Length: -234 mm. Resembles the male of the preceding species, but the
median frontal plate seems to be a little longer and the second pair of legs a little shorter.
OVISACS. They are somewhat to not very much smaller than the females.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Microprotopus maculatus Norm. from Denmark;
found only in two specimens. In one animal were found: one female (the largest), one
male and four ovisacs, which are oblong, glued together and contain larve which are more
or less, but not fully developed. In the other specimen were found: one female, one male
and five ovisacs, each of which was somewhat smaller than the female.

REMARKS. In the shape of the body, the hairs-tufts on the head and the
peculiar close covering of »scales« on the trunk, the two females found agree essentially
with the scarcely half-grown or very small females of S. danica; they are, however, some-
what larger than these; each of them had a spermatophore attached to it and a developed
genital area, from which we may conclude that they are both adult and have laid the ovisacs
which were found together with them. This supposition is confirmed by the circumstance
that the hosts are too small to contain parasites of the size of S. danica.

111

5. Spheronella Leptocheiri n. sp.
(Pl. XIII, fig 3a—3 e.)

FEMALE. The only specimen found (fig. 3a) was ‘76 mm. long and “64 mm. broad;
its head somewhat exceeding middle size, the trunk almost globular. On the sub-median
skeleton of the head (fig. 3c) there are no hairs at the articulation either of the maxillee
or of the maxillipeds, but a few hairs are found (though not drawn in the illustration) at
the base of the inner side of the basal joint of the maxille. The trunk is naked, except a
comparatively small area behind the median part of the head, which is provided with a
number of extremely short and fine hairs. Genital area (fig. 3d) much as in S. Afyli, but
the anterior extremities of the genital apertures come much nearer to each other, and the
ring is somewhat narrower. The distance between the caudal stylets is very great, and
between the stylets and the posterior margins of the area it is rather considerable; the
whole area and its surroundings are naked.

MALE. Length -20 mm. (fig. 3e). The shape a little more clumsy than in S. elegan-
tula; the median frontal plate of medium Jength, its lateral margin somewhat converging,
but the anterior angles are acute and a little produced. The trunk-legs a little longer,
or at least not shorter, than the long terminal seta.

OVISACS. I have only found an incomprehensible abnormity, viz. the outer mem-
branes of two ovisacs, one of them containing only one single egg, the other a large and a
small one; otherwise they were empty bags.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. In the marsupium of a Leptocheirus guttatus Grube, taken by me near
Siracusa on rocky ground, twelve to twenty-five fathoms, in June 1893, were found: one
female, two males and the two just mentioned, nearly empty membranes of ovisacs. (The
host is determined by the Rev. Th. R. R. Stebbing).

6. Sphzronella messinensis n. sp
(Pl. XIII, fig. 4a—4 c.)

FEMALE. ‘The only specimen found (fig.4a) was ‘44mm. long and ‘32 mm. broad ;
the body sub-ovate, the head proportionally large and the trunk scarcely longer than broad.
In fig. 4b are shown some hairs at the base of the inner side of the basal joint of the
maxille, and on the sub-median skeleton a row of hairs in front of the anterior inner angle
of each maxilliped. The trunk quite naked. The genital area (fig. 4c) of similar shape to
that of S. elegantula, consequently much broader than long, the larger part solidly chitinised ;
distance between the genital apertures moderately great, but they are turned so much that
their inner and front extremity advances only very little beyond the posterior extremity, the

112

result being that their muscles are nearly parallel with the median line. The caudal
stylets are situated far from each other, but close behind the posterior margin of the genital
area. The whole area and its surroundings are naked.

MALE. Unknown.

OVISACS. Three oblong sacs have been found, their average length being like
that of the female.

LARVA. Unknown.

POST-LARVAL DEVELOPMENT. A_ pupa densely covered with hairs all over
is 22 mm. in length and -16 mm. in breadth.

HABITAT. In the marsupium of a specimen of Gammaropsis melanops G. O. Sars,
taken by the author in the harbour of Messina in May 1893, were found: one female, three
ovisacs and one pupa. (The Rey. Th. R. R. Stebbing has kindly determined the host; he
writes: »The specimen is imperfect, but appears to be Gammaropsis melanops G. O. Sars«).

REMARKS. It must be supposed that the ovisacs were laid by the small female
which was found together with them, and to which a spermatophore was attached, for the
host is so small that the parasite must of necessity be small too. So it appears that in this
respect this species is like S. vestita, but there is this difference, among others, that the
trunk and the genital area are perfectly naked.

7. Sphzronella chinensis n. sp.
(Pl. II, fig. 6a—6f; pl. III, fig. 1a—1c.)

FEMALE. The only specimen found (fig. 6a) was 1:01 mm. long and ‘88 mn.
broad; the head a little above medium size, the trunk globular. The base of the maxillz
and the part in front of the maxillipeds covered with hairs, as in the preceding species.
The trunk rather scantily furnished with most peculiar membranous hairs, the base of which
forms a very broad and flattened oval, and from this broad base the flattened hair increases
somewhat in breadth, whereupon it is rounded off rather abruptly, which gives the whole
hair almost the outline of an egg, the tapering end of which is cut off. The genital area
has about the same shape as in S. vestifa, so it is longer compared with the breadth than in
the other species, and forms a short oval, but the larger part of it is solidly chitinised ; the
distance between the genital apertures is a little shorter than in S. vestita, but their form
and direction are as in this species; the distance between the caudal stylets is of medium
length and about equal to their distance from the area. The area is provided with mem-
branous hairs, which in several places form a covering as close as the »scales« in S. vestita;
finally, the surface extending from the area to somewhat beyond the caudal stylets is furnished
with similar hairs; the greater part of these hairs are much narrower than those of the
trunk and also different in shape, the hair in its proximal part being of equal width and
then gradually tapering ends in a point.

113

MALE. The only specimen found (pl. III, fig. 1a—1b) is 174 mm. long. The
body comparatively somewhat shorter and broader than in S. elegantula; the median frontal
plate of medium length, a little broader at the end than behind the middle, with rounded
anterior angles. Trunk-legs, the first pair particularly, a little shorter and somewhat more
slender than in S. elegantula and a little shorter than the long terminal seta.

OVISACS and LARVA. Unknown.

POST-LARVAL DEVELOPMENT. ‘Two pupz have been found, one of them
146 mm. long (fig. 6c), in which no animal had as yet developed itself (fig. Ge) (the strongly
coagulated contents are marked in the drawing by darker shading); the other, °24 mm. in
length (fig. 6d, hair-covering omitted) contains an almost fully developed female (fig. 6 f).
Both pupx, a more detailed mention of which is given on p. 58—60, are closely covered
with hairs all over, except on the area in front of the mouth.

HABITAT. The marsupium of Corophium Bonellii M.-EKdw. from Hong-Kong.
In one specimen were found: one female, one male and one pupa, in another one pupa. The
hosts were taken by H. Koch (1872) and kindly determined for me by the Rev. Th. R. R.
Stebbing.

8. Sphzronella antillensis n. sp.
(Pl. TH, fig. 2a—2f,)

FEMALE. There have only been found very small, recently hatched specimens and
a single large one, which was quite torn. We begin by describing the latter. Rather few
hairs are seen on the proximal part of the inner side of the basal joint of the maxille, and
a small tuft in front of the foremost inner angle of each maxilliped. The trunk is quite
naked. The genital area (fig. 2d) chitinised and shaped almost as in S. Atyli, but the
anterior and posterior margins are somewhat less concave; the distance and position of the
genital apertures as in the last-mentioned species, but the caudal stylets are somewhat closer
together and only at a short distance from the posterior margin of the area; the area and
its surroundings naked. — In the three young ones, two of which are recently hatched and
the third on the point of moulting (fig. 2c), the hair-tufts on the head are exactly like those
of the adult specimen. In the two specimens the trunk is naked, in the third it is furnished
with a number of exceedingly short and fine hairs, which occupy a short part behind the
head. The genital area is not developed, thus agreeing with the above-described area in a
young one of S. danica; between and behind the genital apertures are found a number of
very fine hairs.

MALE. Unknown.

OVISACS. Of medium size, somewhat elongate (fig. 2b); an ovisac which was
measured appeared to be *35 mm. in length and -27 mn. in breadth.

15

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LARVA. Fig. 2e shows the drawing of a larva (of the natatory legs only the
base is represented); it measures -15 mm. in length, and it is used as type in the description
on p. 105 of the larva in this group of species.

POST-LARVAL DEVELOPMENT. One pupa, °185 mm. in length (fig. 2f) is
naked on about the front half of its body, while the posterior part is furnished with numerous
very fine and short hairs. Another specimen, 172 mm. in length, is well provided with
hairs all over, like the pup of S. daniea and S. chinensis. A third specimen (fig. 2a and
fig.2.c) had lost the foremost third part of its skin, where a young female, 245 mm. long,
was just emerging; the part of the skin of the pupa which encloses the trunk of the female
has the usual hair-covering.

HABITAT. The marsupiun of Corophium Bonellii M.-Edw. from Cuba. In one spe-
cimen were found a very young female and one larva (or perhaps three larve)'); in another the
female shown in fig. 2a, which has burst the skin of the pupa; in a third the pupa drawn
in fig. 2f; in a fourth a recently hatched female; in a fifth the anterior part of a female,
four ovisacs glued together and a pupa covered with hairs, hinged on a gill; finally, in a
sixth specimen were found one large, but torn female and two ovisacs. The hosts were
taken by Mr. Iversen (1871) and determined by the Rev. Th. R. R. Stebbing.

REMARKS. It is most remarkable that both this and the former species, S. chinen-
sis, occurred in hosts of the same species, from two localities as far removed from each other
as Cuba (West-Indies) and Hong-Kong. These localities are no doubt correctly stated, as
it is scarcely possible that there can be any mistake in the old labels on the two glasses
which contained the hosts. And indeed, there is a great difference, not only in the hair-
covering of the trunk, but also in the shape of the genital area in the females of the para-
sites from the two localities, so that one is perfectly justified in establishing them as two
separate species. — Whether the afore-mentioned difference in the hair-covering of the pup
is of any importance, cannot be decided from this find.

9. Spheronella Calliopii n. sp.
(PL. Ill, fig. 3a—3 1.)

FEMALE. A large specimen is 2°38 mm. in length and 2°05 mm. in breadth, and
the head, which is rather small, is well defined from the sub-globular trunk. In somewhat
smaller specimens the trunk is more oblong. The median part of the frontal margin is
provided with short hairs (fig. 3d). Antennule of medium length, 3-jointed, with rather
short terminal setee. Antenne small, but distinct, the number of joints — probably two —

1) With regard to two of these larvie notes are wanting; they were possibly found together with the
third one.

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could not be ascertained; the terminal seta is rather long. The mouth is rather large; the
mouth-border of medium breadth; the maxilla provided with a well developed additional
branch. The maxillee moderately large, the distal margin of the basal joint is furnished with
hairs along the larger part of the articular membrane (fig. 3c). The maxillipeds (fig. 3 f)
scarcely of medium length, all jomts separated, the basal joimt somewhat clumsy, provided
at its distal margin with a few short rows of hairs, a similar row a little outside the middle
of the inner margin, and a tuft at the same distance from the base on the opposite margin;
the terminal joint ending in three points. The sub-median skeleton between the rostrum and
the maxillipeds consists of a pair of moderately narrow lists on each side; the skeleton
between the maxillee and the maxillipeds has a long transverse belt of hairs, some of which
are long (in fig. 3d the hairs are only drawn on one half of the head.) The lateral margin
of the head, as far forward as somewhat behind the base of the antennule, is furnished with
numerous moderately long hairs, a little outside of which another row of similar hairs, ad-
vancing forward outside the base of the antennule to somewhat in front of it. The trunk
is closely covered all over with short, most peculiar hairs, each of which is divided from its
base into three branches, the central one of which is double the length of each of the other
two. Trunk-legs are found. The genital area is much narrower than the head, it is as
long as broad (fig. 3¢) and solidly chitinised all over; the oblique genital apertures are
rather far apart, the caudal stylets situated close together between the distal parts of the
genital apertures. The whole genital area is almost naked, except some rows of normal,
fine hairs between the genital apertures, furthermore, a crescent-shaped area in front of and
outside the anterior half of the genital area is likewise naked, whereas the peculiar hair-
covering of the posterior part of the trunk extends up to the caudal stylets and to the
posterior extremities of the genital apertures.

MALE. A large male is ‘30 mm. in length, whereas an abnormally small, probably
far from adult specimen is only -182 mm. long; the proportion between length and breadth
is approximately as 4 to 3. So the male is very small in proportion to the adult female
(fig. 3b: fig3a). The head is about the size of the trunk (fig. 3h and 3i). The frontal
border is very considerably produced, and its margin furnished with a row of fine, very
short hairs; it is crenate, being divided into three pairs of rounded lobes, the outermost
pair of which is much lower and broader than the others. The antennule much like those
of the female. The antenne short, having at least two joints; terminal seta long. The
rostrum, maxillule and maxilla nearly similar to those of the female. The maxillipeds
differ from those of the other sex in having the basal joint longer, more slender and almost
naked. The sub-median skeleton without processes and naked. The lateral margin of the
head fringed with hairs of medium length, and a little in front of the posterior end of the
margin originates a very narrow stripe of long hairs, which runs upward across the side,
and further in a somewhat oblique line a little backward across the back of the animal, the
hairs being exceedingly long in the dorsal part of the stripe. Behind this stripe, the back,

‘ 15*

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the sides and the posterior part of the animal are very closely covered with tiny dots which
resemble the base of fine hairs, yet no such hairs could be seen. From the outer angle of
the first pair of legs this curious area is crossed by a narrow naked stripe which runs
upward in an oblique direction and somewhat backward across the side and the back (fig. 31);
the ventral surface of the trunk between the legs and the caudal stylets is covered with
moderately long hairs. The first pair of legs are good-sized, with a broad basal part and
both branches well developed; the inner branch, which is a little shorter than the outer one,
is pointed, the outer branch is blunt, terminating in two sete, one of which is plumose and
double the length of the branch. The second pair of legs about as long as, or a little
shorter than, the outer branch of the first pair, having near its base a short conical outer
branch with a short terminal seta, whereas the terminal seta of the inner branch is still
longer than that of the outer branch of the first pair of legs. The caudal stylets of mode-
rate length, terminating in some sete, the longest of which is only a little longer than
the stylet.

OVISACS. Globular or oval (fig. 3c) and rather small in proportion to the adult
female (fig. 3a); the eggs in each ovisac comparatively small and pretty numerous.

LARVA. The length of a free specimen (fig. 3k) 24 mm. The cephalothorax ovate.
The front (fig. 31) has an oblique list inside the anterior angle of each antenmnula; this
appendage is 2-jointed, its olfactory seta reaching somewhat beyond the middle of the
cephalothorax, and being somewhat more than double the length of the antennula. The
antenne a little shorter than the antennule, 3-jointed, first and second joints of equal length,
the third joint short, provided with a terminal seta which is of equal length to, or longer
than, the two last joints combined. The maxillule each with four branches, the foremost
and inner one of which is rather short, the three others long and powerful, the hindmost
bending backward and distinctly plumose. The maxille normal, with smooth joints. The
second joint of the mavxillipeds slightly longer than the third one, the fourth joint with a
few setz inside the apex. The thick seta at the posterior angle of the first abdominal
segment reaches somewhat beyond the extremity of the caudal stylets; the third segment is
very short, and the caudal stylets more or less distinctly set off, their terminal seta being
about as long as the cephalothorax.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Calliopius leviusculus (Kr.) from the East coast of
Asia between lat. 40° N. and lat. 51° N. In a large material were found altogether seven
specimens infested with parasites. One specimen is from »lat. 40° N., long. 134° E., Capt.
Andréa, 1869«; in its marsupium were found two moderately small females, the smallest
male found, no ovisacs, but numerous — about thirty-three — free larve. Three specimens
are from »lat. 45° 40’ N., long. 139° E., Andréa, 1869«; in the largest of them were found
six females, two males and twenty-five ovisacs, in the second specimen four females and six
ovisacs, in the third three females, twenty-four ovisacs and at least two males (the host has

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not been closely examined). Two specimens are from »lat. 49° 30’ N., long. 142° 8 E.,
Sartung in Sachalin, Andréa, 1869«; they have not been closely examined. One specimen
is from lat. 51°.N., long. 141° 20’ B., »in sea-weed«, Andréa, 1869«, and in its marsupium
were found: one female, five males and eight ovisacs (none of them containing developed
larvee). — In several specimens the marsupium was very much extended by the parasites;
the hosts were always sterile.

REMARKS. The female is easily recognised by its hair-covering and its peculiar
genital area; the male differs from all other species by its crenate frontal margin and by
the peculiarly dotted surface of the back aud the sides of the trunk.

With regard to the determination of the host, I will add that I myself was incapable
of distinguishing the numerous specimens from East Asia from Greenlandish specimens; there-
fore I sent some of the non-infested Asiatic specimens to Prof. G.O. Sars, who in his new
important work about the Norwegian Amphipoda, writes on p. 450, that he was unable to
distinguish them from the Norwegian Call. leviusculus. So it is interesting that I have
found no parasite in specimens from Greenland, nor in any of the very numerous Danish
specimens which have been referred to this species, but it must be observed that in Sars’
opinion these animals belong to Call. Rathkei (Zadd.), about which, however, Sars himself

does not seem to be absolutely certain, whether it can be maintained as a species.

10. Sphzronella irregularis un. sp.
(Pl. XII, fig. 5 a—5 4.)

FEMALE. The only specimen found (fig. 5a) was ‘73mm. long and ‘59mm. broad;
the body is ovate, the head tolerably defined. The sub-median part of the frontal margin
furnished with a number of moderately long hairs. (The antennule broke off under the
preparation). The antenne 3-jointed, with a terminal seta (which broke off). The maxillie
normal. The maxillipeds with all four joints distinctly separated; the basal joint naked, the
terminal joint with trifid apex. The sub-median skeleton consists of narrow lists, and a
distinct, centrally uninterrupted, list runs between the head and the trunk; between the
base of the maxilla and the maxillipeds runs a pretty long transverse stripe of long hairs.
The lateral margins of the head with a thin row of moderately long hairs. The whole
surface of the trunk is rather sparingly trimmed with peculiar hairs, which consist of a very
small but comparatively thick basal part, from which proceed two, sometimes three hairs, of
which the one proceeding from the centre of the basal part is always much longer than the
other or the two others. The trunk-legs are distinct. The genital area (fig. 5d) in my
only specimen is so irregular in shape that it must be misshaped; it is a little narrower
than the base of the head, most of its median part is thin-skinned, the more solidly chitinised
part forming a kind of heart-shaped ring with an opening to the front. The genital aper-

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tures are rather far apart and tured forward in an oblique direction: the skin between
them is closely covered with normal hairs of medium length, and this hair-coat extends for-
ward as far as to the orifices of the receptacula seminis and backward as far as behind the
genital apertures, whereas the peculiar hairs of the trunk are found on nearly all the
remainder of the area. The well-developed caudal stylets are situated within the chitinised
part, close together a little behind the genital apertures; each of them is provided with two
seta, one of which is exceptionally long.

MALE. Unknown.

OVISACS. They differ somewhat in size and are more or less oblong; an ovisae of
medium size (fig. 5b) is 44mm. long, 36mm. broad; the eggs are large and not numerous.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. In the marsupium of a female of Mefopa rubrovittata G.O. Sars were
found one female (with three spermatophores) and four ovisacs.

ll. Sphzronella paradoxa n. sp.
(Pl. I, fig. 4a—41; pl. IV, fig. La—t h.)

FEMALE. <A very large specimen is 1:26 mm. in length, the animal represented
in fig. 4a is ‘92 mm. and that in fig. 4b only ‘71 mm. in length. In the older specimens
the body is not regularly globular, for its ventral surface shapes itself more or less con-
spicuously into a very broad, low cone, near or from the top of which proceeds a short
thread by which the animal is fastened in the marsupium of the host; in consequence of
this shape the animal does not show its longest dimension in the distance from its small,
but well defined, head to or behind the genital area. In order to explain these peculiarities
it will be to the purpose to mention the young specimens. A young animal which is breaking
out of the skin of the pupa (fig. 1 g) is -207 mm. in length, with an oblong, normal trunk.
A somewhat larger specimen, ‘36 mm. long, is represented in fig. 1h; at some distance
behind the middle of the ventral surface of the trunk we see a proximally broad, short,
conical projection (t), which terminates in a short, pretty thick thread, the end of which is
expanded into a small disk (u) and this disk is fastened, e.g. to one of the gills of the host.
In the specimen represented the conical part has been flattened and pushed to one side.
This attachment continues throughout the life of the animal, and as a rule the thread gets
very much twisted (fig. 4a and fig. 4b). because the animal turns itself, and at the same
time it gradually gets its longest diameter from the base of the thread, or a little behind
it, up to the dorsal surface somewhat behind the head, whereas the genital area, the place
of which is shown in fig. 4b by a spermatophore, becomes situated more or Jess high up
on the dorsal surface; in other words: nearly the whole ventral surface forms a much
stronger, somewhat conical curve and a much more extensive area than the back, which no

119

doubt has something to do with the strain caused by the attachment. As fig. 4a shows,
the animal is almost symmetrical.

The frontal margin is fringed with short, fine hairs (fig. 1a). The antennule are
rather long, with very long terminal sete. The maxillulae with well developed additional
branch. The maxillz and the maxillipeds normal, naked, the latter pair having all four
joints distinctly separated, and the terminal joint ending in three or four points. The sub-
median skeleton with a tolerably broad list near the maxille; a list between the head and
the trunk which is not interrupted in its centre; no hairs whatever surrounding the base
of the various appendages. The lateral margin of the head provided with a narrow stripe
of rather short hairs. The trunk perfectly naked; trunk-legs very small, easily found in
small specimens, but scarcely to be detected in large ones. ‘The genital area (fig. 1b) is
narrower than the head and somewhat broader than long; its chitinised part forms a posteriorly
somewhat concave, rather narrow ring, the anterior half of which is more feebly chitinised
than the posterior part, or, as in fig. 1b, it is sometimes altogether wanting; the genital
apertures are situated near each other and turn forward in an oblique direction. The caudal
stylets are found close together on the chitinous ring quite near the genital apertures; at
least in two adult specimens they were without setae — which may have been broken oft by
the preparation, for they are found in small specimens (fig. 1 g and 1h). (Besides in fig. 1b
are seen the orifices of the receptacula seminis, which are marked by a dotted line). Genital
area and surroundings naked.

MALE. A large specimen is ‘27 mm. in length. The body is somewhat elongate
oval, the breadth being about one third shorter than the length, consequently it is of pretty
good size in proportion to the female (fig. 4c : fig. 4a). The head is somewhat larger
than the trunk (fig. 4h and 4i). The frontal border is rather produced, its margin evenly
curved and naked. Antennule, antennsze, mouth, maxillule and maxille essentially as in
the female (fig. 41 will give an idea of a strongly protruding rostrum and show the maxillula,
with its additional branch proceeding from a kind of foot, and the antenna). The maxil-
lipeds very long and slender, all joints well separated, the basal joint provided with a few
hairy spots. The sub-median skeleton with all three pairs of processes; the first pair (at
the base of the maxill) are blunt; the second pair which originate nearly at the anterior
angle of the base of the maxillipeds, are long, turn backward and are distally somewhat
curved, and between their posterior parts are found the third pair of processes, which are
pointed, but not half the length of the second pair. The lateral margin of the head is
provided with a stripe of moderately long hairs, and from its posterior end, which curves
upward, the hair-covering is continued obliquely upward and somewhat backward across the
side and back of the animal: behind this line, the back, the sides and the ventral surface
of the ttunk are covered with hairs of medium length, yet on the back, somewhat behind the
anterior limit of the hair-covering, we see a transverse area which is naked and rather
short (at the median Jine); the anterior part of the ventral surface is also naked. The head

120

of the male in its posterior and lateral parts shows the peculiar feature (mentioned above
on p. 42) of large, hollow spaces beneath the skin (fig. 4k).

The first pair of trunk-legs are long and consist of one branch, and it is no doubt
the outer branch which is preserved (sometimes even it appears to be set off by an articu-
lation); the peduncle is long, proximally rather large, partly hairy; the branch ends in a
seta which is nearly as long as the whole leg. The second pair of legs consist of a shorter,
cylindrical basal part and a somewhat longer, a little more slender, cylindrical branch, which
terminates in a seta which is even considerably longer than that of the first pair of legs.
The caudal stylets are thick, their terminal seta being even longer than that of the second
pair of legs, and about half to more than half the length of the whole animal. — The male
is frequently found hinged by a frontal thread (fig. 4h, s) which measures about three eighths
of the length of the body, and the distal part of which dilates gradually towards the end.

OVISACS. They are oblong, varying trom a moderate to a very large size; the
specimen represented in fig. 4d is “69mm. in length and ‘50 in breadth; it contains rather
numerous eggs which are comparatively large.

LARVA (fig. 1c). Length ‘22mm. The body slender; the cephalothorax about ?/s
longer than broad; the front with an oblique list inside the anterior angle of the antennule.
Antennule 2-jointed; olfactory seta comparatively short, less than double the length of the
antennwla and about a third of the length of the cephalothorax. Antenne considerably
shorter than the antennule, the first joint (comp. fig. le, for in fig. 1¢ there is a fault in
the engraving) pretty thick, of the same length as the second one, third joint short, and
the terminal seta equalling in length the two last joimts combined. Of the maxillule we
find the posterior branch and one of the anterior branches in the shape of long sete, the
hindmost of which is naked, and close in front of its base is seen a rather small conical
process (fig. le), which is a rudimentary branch. Maxille and maxillipeds normal, with
smooth joints. Abdomen chiefly as in S. Calliopii; however, the last segment and the
caudal stylets which are distinctly set off, are a little larger, but the terminal seta is
scarcely so long, a little more than half the length of the animal.

POST-LARVAL DEVELOPMENT. The attachment of the larva and subsequent
ereat change of form (fig. 1d), as well as the highly interesting development, is described in
detail above, p.57—58, to which we refer.

HABITAT. The marsupium of Bathyporeia norvegica G. O. Sars, B. pelagica Sp. Bate
and B. Robertsonii Sp. Bate from Denmark. In a considerable material I found altogether

eleven infested specimens, two of which are B. norvegica, tour B. pelagica and tive B. Robertsonii').

1) G.O.Sars, in his excellent work: “An Account of the Crust. of Norway, Vol. I’, admits altogether five
species of Bathyporeia from Norway and the Baltic. Of these species B. norvegica G.O Sars and B. gracilis
G. O. S. are decidedly good, and well distinguished from the three others, but whether these three species
can be maintained, or have to be reduced at least to two (in regarding B. pilosa Lindstr. as a freshwater-
form of B. pelayica), perhaps even to one, is difficult lo decide, and must be submitted to a new, thorough

121

I can indicate the special localities of only three specimens of B. pelagica: they were all
taken in the Kattegat on the cruises of the »Hauch«, two at St.486 (in a depth from between
eight to eighteen feet, on sandy bottom, and the third at St. 113 (depth: four fathoms, on
coarse, White sand). — In order to give an idea of the unique degree in which this species
infests its host, it will be sufficient to copy my notes on the contents of the marsupium in
five of the most infested specimens. In one animal were found: three large females, all
attached, one to a gill, the other to one of the plates of the marsupium, further: two very
small attached females, seventeen males, three good-sized ovisacs and two larve, one of
which was hinged to a gill. In another specimen were found: one large female, ten males
(at least three of which were hinged, one on each side of the same gill, the third to another
gill, and they were so solidly attached that I could examine the phenomenon more closely);
further: one ovisac, one rather broad larva and four thick larvee (»male pupze«). In a third
specimen were found: four females of very different size (in one specimen, the longest diameter
of which measured 41 mm., the ventral thread was -13 mm. in length), eight males, four
ovisacs, one narrower and one broader larva, as well as one »male pupac«. In a fourth
specimen occurred: one large and two small females, eight males, no ovisacs, four broad
larve, sixteen »male pupe« (six of which were hinged on the gill of the third right leg
together with a broad larva) and one female pupa.

In the marsupium of three specimens of Perioculodes longimanus (Sp. Bate) (= Mono-
culodes Grubei Boeck) from Denmark I have found females which I cannot possibly distinguish
from this species. In one specimen occurred: one female, the longest diameter of which is
‘47 mm., and four ovisacs of sub-equal size, one of them was 39mm. in length and °30 mm.
in breadth; on each of the other two specimens was found only one female, the larger one
of which measured ‘71 mm. On account of similarity in their mode of attachment, in the
structure of the antennulze with their long terminal sete, in the hairs on the frontal margin,
in the shape of the maxille and of the maxillipeds and in the essential features of the
structure of the genital area, I must for the present admit these animals as belonging to
S. paradoxa, but as long as the male is not known, it is safer not to pronounce any definite
judgment about such small and rather difficult forms.

REMARKS. The name of the species is chosen on account of the very peculiar,
hitherto unique, ventral attachment of the female.

12. Sphzronella abyssi n. sp.
(PI.IV, fig. 2a—2e).
FEMALE. The only specimen found was ‘96mm. in length, 1:13 mm. in breadth,
somewhat irregularly crooked and rather flattened (fig. 2a). The head was squeezed against

investigation. In this work I have accepted the established species in separating B. pelagica and B. Robertsonii
from each other according to the existence or non-existence of spines on the dorsal part of the fourth
abdominal segment.

16

the lower surface of the body, but was lost before I could get it drawn. The trunk is
naked; I have found no trunk-legs, but they probably exist nevertheless. The genital area
(fig. 2c) is much narrower than the head and consists of a plate well chitinised all over,
which is about one half broader than long, with flatly convex anterior margin and deeply
concave posterior margin; the genital apertures oblique, the distance between them moderately
large (in the drawing they are both open) and two long-stalked spermatophores are shown,
as well as half the stalk of a third one. The caudal stylets (one of them is torn off) are
situated close together on the smooth membrane adjoining the posterior margin of the plate;
the latter and its surroundings are naked.

MALE. A _ good specimen is *25 mm. in length, and the body seen from below
(fig. 2d), is regularly ovate. Compared with the female it is about middle-sized (fig. 2b : fig. 2a).
The head is considerably larger than the trunk. The front is not strongly produced, its
anterior margin is evenly rounded and naked. The antennule are tolerably strong, the
terminal setze short. The antenna are long, 3-jointed, the conical terminal seta the length
of the last joint. The mouth is small. The maxillule with an additional branch of medium
length. The basal joint of the maxilla has a conical process where the posterior and
the inner side meet. The basal joint of the maxillipeds is long and naked, the three other
joints distinctly separated. The sub median skeleton with the first pair of processes not
developed, the second pair are long, somewhat diverging and feebly curved. The lateral
margin of the head has only very few hairs; somewhat before reaching its posterior angle
the hair-coyering expands a little, then continues as a thin fringe upward and backward in
a very slanting line across the back, leaving only a small dorsal part of the trunk to be
seen behind it. On the back, close behind this fringed line, is a considerable naked area,
so that only the hindmost extremity of the trunk, the larger part of its lateral surface and
the ventral surface between the legs have a rather thin covering of moderately short. hairs.
At the back and the sides we see empty spaces beneath the skin similar to those in
S. paradoxa. The first pair of trunk-legs are rather long; the clumsy peduncle is continued
in a pretty long and clumsy outer branch, while the inner branch is a short cone; the
former terminates in two sete, one of which is considerably longer than the whole leg, nay
even longer than the basal joint of the maxilliped, whereas the other seta is about three
times shorter; the immer branch ends in a long seta which is a little shorter than the basal
joint of the maxilliped. The second pair of legs are moderately long, unbranched, ending
in two sete, one of which equals in length the short seta on the outer branch of the first
pair of legs, whereas the second somewhat exceeds in length the long seta of the last-
mentioned outer branch. The caudal stylets are of medium length, their terminal seta even
somewhat longer than any of the other sets, and measuring nearly two thirds of the length
of the whole animal. — The frontal thread in the specimen drawn in fig. 2d is a little longer
than the animal, very fine, and feebly expanded at its distal end.

123

OVISACS. They are of middle size; those hitherto found are somewhat irregular
trom pressure, oblong (fig. 2a), the longest ‘69mm. long. The eggs large, not numerous.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Astyra abyssi Boeck from Finmarken (Norway).
In one specimen were found: the female mentioned, with the two ovisacs glued together and
adhering to its foremost part, and a third one glued to its ventral surface, besides two males,
one of which was fastened by the frontal thread shown in the drawing. In another specimen
were found only four ovisacs, and these were discovered in examining some specimens of
the above-mentioned Amphipod kindly offered to our Museum by Prof. G. O. Sars, upon which
on my applying to him, he lent me his whole material for investigation, and [ discovered
the specimen which supplied me with both sexes of the parasite.

REMARKS. The description of the female is, unfortunately, very defective on
account of the loss of the head. The male is exceedingly characteristic owing to the
unique development of the terminal sete of its trunk-legs and caudal stylets.

13. Sphzronella Argisse n. sp.
(PLIV, fig. 3a—3n).

FEMALE. The only adult specimen (fig. 3a) was somewhat shrunk and rendered
crooked by pressure; its length was °85mm.; a small, recently hatched specimen represented
in fig. 3c (enlarged on the same scale as fig. 3a) and strongly magnified in fig. 3d, is crooked
and empty; its length is 15mm.. The head is small and well defined. The frontal margin
is naked. The antennule have moderately long terminal sete. The antenne are 3-jointed,
their terminal seta quite as long as the last joint. The mouth-border of medium breadth.
The maxillule with additional branch. The maxilla smooth. The maxillipeds slender,
their basal joint naked, the following three joints distinctly separated, the terminal joint
pointed. The sub-median skeleton has narrow longitudinal lists inside the maxillz and no real
transverse list at the median line behind the base of the maxillipeds; it is naked all over.
The lateral margin of the head provided with rather short and fine hairs. The trunk quite
naked; the trunk-legs well developed in the young ones, and probably also present in the
adults. The genital area (fig. 3f) broader than the head (fig. 3a), somewhat broader than
long; the solid chitine forms a semi-circle which opens towards the front; it is very broad
posteriorly and decreases gradually in breadth; its two extremities form irregular lobes
with inward curving points; the posterior margin is semicircular. The genital apertures
oblique, the distance between them of medium length (in fig. 3f they are wide open and
a spermatophore is attached to the entrance of one of the receptacula seminis). The caudal
stylets are small but well developed and situated close together on the firm chitine imme-
diately behind the genital apertures. The whole genital area is naked (the young one
represented in fig. 3d has no genital area yet).

16°

124

MALE. In the largest specimen the length of the body is -19mm.; seen from
below (fig. 3g), it is short and broad, only a little longer than broad, its circumference is
nearly rhombic, with broadly rounded angles. The second specimen is of the same length,
but is considerably more slender, though scarcely as slender as the male of the following
species (S. Metope). So the male is rather small compared with the female (fig. 3a,
where a male is marked m). The head is not a little larger than the trunk (fig. 3h). The
front is somewhat produced, its anterior margin naked, slightly convex in the middle, slightly
concave towards the sides somewhat in front of the antennule. Antennule, antennze, mouth
and maxillule essentially as in the female. The basal joint of the maxilla has a short
conical process on its posterior side. The maxillipeds of medium length; their basal joint
has several stripes and spots covered with hairs, and their inner margin an incision and
two considerable, shortly conical processes, which can only be seen distinctly when looking at
the maxilliped from in front (fig. 3k) or from behind, so that all its joints present themselves
on the same plane; the terminal joint has a small spine inside its point. The sub-median
skeleton has its first pair of processes developed into short conical taps which turn outward,
one behind the base of each of the maxille; posteriorly, between the bases of the maxillipeds,
the skeleton takes the shape of a pretty considerable, somewhat raised area, the median
part of which extends into a broader plate, cut off posteriorly ; laterally are found the second
pair of processes which are shaped like long narrow cones, a little curved near their base
and turned straight backward. The lateral margin of the head provided with a row of
moderately long hairs, and from its posterior angle the hair-covering is continued as a belt
upward and rather obliquely backward across the side and the back. The dorsal part
and the upper lateral parts of the head show hollow spaces beneath the skin. The dorsal
surface of the trunk with a broad and pretty long, naked area, in front of which is found
the above-mentioned, moderately narrow belt of hairs of medium length; the lateral surfaces
of the trunk, its posterior extremity and the greater part of its ventral surface are closely
covered with hairs of medium length. The first pair of trunk-legs of about medium length;
the basal part broad; the inner branch is a short knot, the outer branch of medium length
and ending in two sete, one of which is almost half the length of the body, the second
about a third or scarcely a third the length of the first one, besides, the branch has on its
outer side a conical process which ends in a short seta; the terminal seta of the inner
branch is scarcely the length of the shorter terminal seta of the outer branch. The second
pair of legs are short, the inner branch with one short and one extremely long terminal
seta, which almost exceeds in length the one on the outer branch of the first pair of legs;
the outer branch is a conical tap terminating in a thin seta which is a little shorter than
the leg. The terminal seta of the caudal stylets not more than about thrice the length

of the stylet, and the same length as, or shorter than the secondary seta of the outer branch
of the first pair of legs.

125

OVISACS. They are very large and somewhat oblong (fig. 3b); those [ found were
a little flattened, the one drawn is ‘74 mm. in length. Hach of the ovisacs containing
numerous middle-sized eges.

LARVA. The only specimen found (fig. 3n) is *22 mm. in length. Inside the base
of the antennula an oblique, somewhat geniculated, pretty considerable list. The antennule
2-jointed, their terminal seta exceptionally long; the olfactory seta scarcely half the length
of the cephalothorax. The antennz somewhat shorter than the antennulee; the second joint
of the same length or a little longer than the first one; third joint short, its terminal seta
about as long as the whole antenna. Of the maxillule I have only been able to find a
single rather short branch on one side. The second joint of the maxillee proportionally long
and rather slender, the third joint comparatively short; the joints smooth. The abdomen
much as in S. paradoxa, however, the long setz of the first segment extend a little further
behind the caudal stylets, and the terminal sete of these stylets are scarcely half the length
of the body.

POST-LARVAL DEVELOPMENT. A single pupa (fig. 31 and fig. 3m) has been
found and is mentioned above on p. 56.

HABITAT. Argissa typica Boeck from the west-coast of Greenland. In the
marsupium of a female was found the large female represented and a male attached to it,
besides an unattached male, a larva and four ovisacs, two and two glued together, all
without larvee and not varying much in size. In an immature specimen without marsupium
was found the pupa represented; in another young specimen the recently hatched female
represented in fig. 3¢ and 3d; it was hinged to a gill by a rather broad, triangular (in
fig. 3d visible) adhesive plate, which on the gill expanded into a circular disk.

REMARKS. The female presents very few peculiar characters, whereas the very
beautiful male is distinguished from kindred species by several characters. A lateral view
of the male, when placed under the microscope, so as to leave out the dorsal outline, pre-
senting only the part immediately above it, shows the peculiar aspect of the spaces beneath
the skin represented in fig. 31.

14. Sphezronella Metope n. sp.
(PI. IV, fig. 4a; pl. V, fig. 1a -1g).

FEMALE. The specimen represented in fig. 1a, which is the largest and best, is
‘40mm. in length and 33 mm. in breadth; the head is tolerably large and well defined from
the sub-globular trunk; probably the female can become somewhat larger. The frontal margin
is naked (fig. 1d). The antennule of about medium length, with rather short sete. Tbe
antenne good-sized, 3-jointed; the basal joint short, the terminal seta about the length of
the last joint. The mouth-border of about medium breadth. The maxillule with well

developed additional branch. The basal joint of the maxilla with a conical process on the
boundary between the inner side and the posterior side. The maxillipeds tolerably robust;
the basal joint smooth and naked; (whether the second and the third joints are separated
could not be made out with certainty); the last joint has a few short setz inside its point.
The sub-median skeleton has narrow lists inside the maxilla and a well-developed list between
the head and the trunk behind the base of the maxillipeds; no hairs on the skeleton between
the appendages. The lateral margins of the head naked. The trunk naked; the trunk-legs
distinct. The genital area (fig.4a) much narrower than the head, much broader than long;
the solid chitinised part forms a somewhat sinuous semi-circle, which posteriorly has a narrow
interruption at the median line, and anteriorly a very broad opening; the hindmost sub-
median part is nearly straight, the anterior corners bent inward; the ring itself is rather
narrow except outside the posterior extremity of each genital aperture, where it expands on
the inward side. The genital apertures are large, strongly curved and situated close together ;
the well-developed caudal stylets are found in very close proximity on the soft skin which
divides the ring on its posterior side. The genital area is naked, except a number of very
fine hairs on the ring near the caudal stylets and on a smaller spot behind them.

MALE. The only specimen (fig. 1f—1g) is ‘20mm. in length; its breadth is a little
more than two thirds of the length. This shows that it is tolerably small compared with
the chief bulk of males, but extremely large compared with the female (fig. 1b: fig. 1a). The
animal is flatly rounded anteriorly and with very obtuse angles in the middle of its lateral
margins; its head is only a trifle larger than its trunk. The front is feebly produced, its
margin is naked. Antennule, antennze, mouth, maxillule and maxilla much as in the female.
Maxillipeds of medium length, the basal joint with smooth inner margin, and a moderately
large part of the outer surface provided with hairs, these, as usual, arranged in stripes and
spots; the terminal joint as in the female. The sub-median skeleton with all three pairs of
processes developed; the first pair, behind the maxillze, are broadly rounded, depressed,
plate-like; the second pair long, slender, almost cylindrical and strongly diverging; the third
pair are situated at some distance from each other between the second pair and are not
half the length of these. The lateral margin of the head is furnished with hairs (and as in
much the greater number of species, this hair-covering begins in front of the base of the
antennulz), continues in an oblique direction upward and backward across the side and
the back, forming laterally a rather narrow band of moderately long hairs, being reduced
on the back almost to a line of very long hairs. Behind this line the back has a long,
naked transverse area, whereas the remainder of the back, the sides, the posterior extremity
and the ventral surface — except on its foremost part — are closely covered with hairs of
medium length. The dorsal and upper lateral parts of the head have hollow spaces beneath the
skin. The first pair of trunk-legs are short, with a broad basal part and two short, sub-
cylindrical branches situated far apart from each other; the outer branch ending in two
sete, one of which is about the length of the second joint of the maxillipeds, whereas the

second is not much shorter than half the length of the body; the inner branch ending in a
lone seta which, however, is somewhat shorter than that of the outer branch, and which in
the only specimen examined is rather unlike in the two sides. The second pair of legs are
much as in S. Argisse, yet somewhat more slender; the outer branch ends in a short seta,
the inner one in two set, which are both a trifle longer than the two set on the outer
branch of the first pair of legs. The caudal stylets are of medium size, each ending in two
sete, one of which is of the same length as, or a little longer than the stylet, the other
about five times the length of it.

OVISACS. They are sub-globular and disproportionately large; the longest dia-
meter of one of the smallest is ‘37 mm., and of one of the largest, represented in fig. 1c,
even ‘41 mm., consequently larger than the female (fig. 1¢: fig. 1a), but as all ovisacs contain
about half-developed young ones and, as a matter of course, are larger than those whose eges
have preserved their original form, these measures cannot be compared immediately and
without reduction with those of the other species. The eggs are rather few in number and
proportionally very large.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Metopa Bruzelii (Goés) from West-Greenland off
Godthaab, »deep water« [probably 40—60 fathoms], in Sertularia, C. Holbéll. In one spe-
cimen were found: one female and three ovisacs; in another: one female and two ovisacs;
in a third: one female, one male, and three ovisacs glued together in a lump. These three
specimens were found in a material, of which five other specimens were infested with
Stenothocheres egregius (comp. this species).

15. Spheronella Holbolli n. sp.

(Pl. V, fig. 2a—2¢.)

FEMALE. The largest specimen fig. 2a is 1°44 mm. in length and 1:57 mm. in
breadth. The head is rather small, well defined. Frontal margin naked. Antennule, an-
tennze, mouth, maxillule, maxilla and sub-median skeleton much as in S. Metope; there
are, however, two lists between the head and the trunk behind the maxillipeds. The
maxillipeds are of medium size; their basal joint having some small, scattered groups of
short hairs, the three following joints distinctly separated, and the last jomt ending in several
very fine spiniform processes (fig. 2d). The lateral margin of the head hairy; the hair-
covering begins outside the antennule, continues in a stripe of moderately long hairs and
expands posteriorly into a comparatively broad area with shorter hairs. The trunk is naked;
the trunk-legs distinct. The genital area (fig. 2e) a little narrower than the base of the head,
much broader than long; the solid chitine forms an almost rectangular, transverse plate,
which is somewhat narrower anteriorly than posteriorly; the posterior angles are very

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broadly rounded, the median part of the posterior margin has a broad and very deep incision;
the median part of the plate, outside and especially in front of the genital apertures, consists
of soft membrane. The genital apertures are rather large, strongly curved and situated
pretty close together. The caudal stylets are very small and situated near each other on
the soft membranous part on a line with the posterior margin of the chitinous plate. On
each side of this plate, at a considerable distance from the margin, runs a very long, curved
line of very long, outward turning hairs, and from the part between the genital apertures
towards the caudal stylets run four stripes, anteriorly very narrow, posteriorly broader,
of extremely short, fine hairs.

MALE. The best preserved specimen has become crooked through pressure (fig. 2f);
it is ‘21mm. in length, consequently of small size compared with the female (fig. 2b: fig. 2a)
and has a broad shape similar to that of the male of S. Argisse (represented in pl. LV,
fig. 3¢—3h), whereas in hair-covering and in the structure of the trunk-legs etc. it bears
great resemblance to 8. Metope (pl. V, fig. 1f—1g). The head seems to be somewhat larger
than the trunk. The front is somewhat produced as in S. Argisse, but the margin scarcely
concave in front of the antennule. Antennule, antenne, mouth, maxillule and mavxille
essentially as in S. Metope. The basal joint of the maxillipeds has a short, broad, conical
process on its inner surface, besides several groups or stripes of moderately long hairs; the
last joint is digitated, at the apex ending in about four points. The three pairs of pro-
cesses of the sub-median skeleton are somewhat like those of S. Metope, but the first pair
are longer and more pointed, the second pair a little shorter and more or less diverging.
The lateral margin of the head is fringed with somewhat longer hairs than in S. Metope,
and from its posterior angle a somewhat broader stripe of longer, and dorsally very long
hairs runs almost vertically upward across the side and the back; behind this stripe is a
moderately long, naked, dorsal transverse area, whereas the remainder of the trunk is covered
with hairs as in S. Metope, however, the hairs are proportionally longer and coarser. The
dorsal and lateral parts of the head have hollow spaces beneath the skin. The first pair of
trunk-legs nearly as in S. Metope@; the most important difference is that the terminal
seta of the inner branch is considerably shorter, and shorter than the distance between
the base of the leg and the end of the outer branch. The second pair of legs are some-
what larger than in S. Mefope, but the shape and sete are much the same as in this
species. The caudal stylets end in a single seta which is scarcely as long as in the pre-
ceding species.

OVISACS. They are comparatively rather small (fig. 2¢), sub-globular or oval,
differmg rather slightly in size; one of the largest which is ‘63 mm. in length and 52 mm.
in breadth, is represented. The eggs are proportionally rather small and pretty numerous.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Paramphithoé Boeckii H. J. H. trom West-Green-
land, off Godthaab, »deep water« {probably 40—60 fathoms], on Sertularia, C. Holboll. In

129

one specimen were found: one female and one male, and in front of the female were lying
seven ovisacs, behind it one; another specimen contained one female and one male.

REMARKS. The genital area of the female in several respects (shape, chitinisation
and arrangement of hairs) deviates much from all the other species. By the name given to
this species I have commemorated Lieutenant-Captain Inspector C. Holboll, to whom the
study of Greenlandish Malacostraca owes so much, and who more than half a century ago
sent home rich collections of these animals. A considerable part of this material was worked
out by H. Kroyer. In the writings of this author we also find interesting biological observa-
tions by Holbdéll concerning Greenlandish species of Lysianasside etc.

16. Sphzronella intermedia n. sp.
(PL V, fig. 8a—3h.)

FEMALE. The largest specimen is ‘89 mm. in length, -81 mm. in breadth and
somewhat flattened; the specimen represented in fig. 3a is ‘57 mm. long and ‘47 mm. broad.
The head in the adult specimen is well defined and rather small. The frontal margin provided
with fine and close hairs (fig. 3d). The antennule moderately long, with long sete. The
antenne much as in the three preceding species, but the basal joint equals in length one
of the two following joints. The good-sized mouth with a rather broad border. The
maxillule with well-developed additional branch. The basal joint of the maxilla without any
process. The maxillipeds with a slender, naked basal joint, the three other joints all sepa-
rated, the terminal joint has two short spines inside its point, and a single one on the out-
side. The sub-median skeleton has a single, rather narrow list inside each maxilla; a trans-
verse area in front of the basis of each maxilliped is covered with numerous tolerably long
hairs; between the head and the trunk two chitinised transverse lists. The lateral margin
of the head with a fringe of hairs. which off the maxillee and the maxillipeds spreads over
a pretty considerable triangular area. The trunk very sparingly set with simple, rather
short hairs, which are closest together behind the sides of the head; the trunk-lees distinct.
The genital area (fig. 3e) large, quite as broad as the base of the head (fig. 3a), somewhat
broader than long; the whole area forms a solid plate which is nearly heart-shaped, deeply
incised in front and with a semicircular posterior margin. The genital apertures are some-
what curved, but their direction is nearly parallel with the median line of the animal, and
they are situated pretty near each other close behind the deep incision of the anterior margin
of the plate. The plate is furnished with a number of irregularly scattered hairs, and the
caudal stylets are situated close together at a good distance inside the posterior margin of
the plate, a little behind the genital apertures. (In the illustration we also see the orifices
of the receptacula seminis, which are marked by dotted lines.)

17

130

MALE. The only specimen is 19 mm. in length and a trifle narrower; compared
with the female represented, it is tolerably large (fig. 3b : fig. 3a), but only of medium size
compared with the largest female. Seen from below (fig. 3f), the body is nearly pentagonal;
the anterior outline, which only in its middle part is formed by the slightly curving frontal
margin, but towards the sides of parts belonging to a lower level, is but feebly curved and
comparatively broad, the lateral angles are obtuse, but the posterior margin of the body
forms a rather broad curve. The head is somewhat larger than the trunk. The afore-
mentioned, scarcely produced frontal border has a fringe of hairs. The antennule are slender,
of medium length and provided with long sete. The antennz and the maxillule much as in
the female; the mouth smaller than in the latter. The maxilla have a distinct conical
process on the posterior side of the basal joimt. The basal joint of the maxillipeds has a
sinuate inner margin, its outer surface is supplied with hairs, and its anterior side has two
transverse rows of tolerably long hairs; the last joint ends in three points of unequal length.
In the sub-median skeleton are only found the two first pairs of processes; the first pair
which are situated behind the mavxille, are broad, somewhat produced and rounded, the
second pair which are situated between the maxillipeds, are scarcely of medium length and
feebly diverging. The lateral margin of the head fringed with long hairs, and the ear-
shaped arch round the base of the antennule distinguishes itself particularly by its very
long hairs. The stripe of hairs which proceeds from near the posterior angle of the lateral
margin, running upward across the side and the back, is somewhat more oblique than in
S. Holbélli, and its hairs are somewhat shorter, otherwise the hair-covering of the trunk and
its dorsal, naked transverse area are much as in this species, and the same resemblance
appears in the empty spaces beneath the skin of the head. The first pair of legs consist of
a very broad and rather long, hairy basal part, from which proceeds a single moderately
long branch, which terminates in a single seta of the length of the whole leg or of the first
joint of the maxillipeds. The second pair of legs entirely like those of the former species,
the only terminal seta of the inner branch about the length of that of the first pair of legs.
The very thick caudal stylets have a terminal seta which is scarcely as long as that of the
second pair of legs.

OVISACS. They differ very much in size, even if not containing larvae. Of ten
ovisacs belonging to the same female the smallest one is globular and has a diameter of
30 min., the largest (represented in fig. 3c), is ‘53mm. long and 43mm. broad. In another
female was found a still larger ovisac which is ‘64 mm. in length and 49 mn. in breadth.
So these oyisacs are large compared with the females, and the eggs themselves are large
and not numerous.

LARVA. I have found two ovisacs containing larve which were serviceable, yet
not quite capable of swimming away, and these specimens have served as models for fig. 3h.
A list curving somewhat like an S is seen inside the anterior angle of the antennula. The

olfactory seta of the 2-jointed antennuke is long, a little shorter than the cephalothorax.

The antennze somewhat shorter than the antennulz, the first joint a little shorter and thicker
than the second, the third joint short, and its seta scarcely as long as the two last joints
combined. Of the maxillule I have only found two sete. The second and third joints of the
maxille proportionally pretty long; all joints smooth. The second joint of the maxillipeds
shorter than the third one. The seta on the posterior angles of the first abdominal segment
reach far beyond the caudal stylets, which are small and distinctly separated from the small
third segment. The body not having quite reached its final shape, the relative length of
the terminal sete of the caudal stylets cannot be indicated with full certainty, but they
are probably half the length of the body.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Bruzelia typica Boeck from Norway. The species
was discovered by Prof. G. O. Sars, who sent me one female and eight ovisacs mutually
glued together, two of them with the lary described. Later on he presented our Museum
with some specimens of the host taken at Mosterhayn in a depth of 150 fathoms, and in
one of these specimens I found two ovisacs, beneath them the female represented, and
behind this female eight ovisacs glued together in a lump (none of them containing larvee),
but I am uncertain whether all these ovisacs were laid by the female found, or whether
eight of them were not rather laid by a female which may have fallen out. At last I
bought Prof. Sars’ whole material and found in one specimen a female (the largest), a male
and four good-sized ovisacs mutually glued together.

REMARKS. The species is nearly related to S. Holbdlli, yet both sexes distinguish
themselves from it by several good characters, the female e.g. by the fringe of hairs on the
frontal margin and by the hairs in front of the maxillipeds, the male by the structure of the
first pair of legs.

17. Sphzronella capensis n. sp.
(PI. V, fig. 4a—4c; pl. VI, fig. la—id.)

FEMALE. The only specimen (fig. 4a) was ‘52 mm. in length and 45 mm. in breadth,
shortly ovate, broadest in front of the middle and scarcely as thick as broad. The head,
which is well defined, and the genital area are both found on the ventral surface of the
body, at some distance from the anterior and the posterior end respectively. The frontal
margin naked. The antennule of medium length, with long sete, the terminal seta much
longer than the whole antennula (fig. 1a). The antenne, the mouth, the maxillule and the
maxilla much as in S. intermedia; the maxillipeds with a somewhat shorter, naked basal
joint and with a pointed terminal joint, without distinct secondary spines. The sub-median
skeleton with a moderately narrow list inside the maxilla, naked all over; behind the
maxillipeds two transverse lists between the head and the trunk. The lateral margin of

the head naked. The trunk naked; only one trunk-leg is supposed to be found. The genital
ile

132

area (fig. 1b) broader than the head (fig. 4a), a little broader than long, and consisting of a
somewhat angular chitinous plate, which has a membranous part outside and behind the
genital apertures. These apertures are somewhat curved, their direction is approximately
parallel with the median line of the animal; their distance from each other is less than
moderately great, and they are situated somewhat in front of the posterior margin of the
area, but behind the middle of it. The whole area is naked, and I have been unable to
find caudal stylets. In the middle of the area we see the orifices (0) of the receptacula
seminis, one of which (r) is represented by a dotted line.

MALE. The only specimen is ‘166mm. long and almost as broad (fig. 1¢ and 1d);
though actually small, compared with the female, it is more than middle-sized (fig. 4b:
fig. 4a). Seen from below, in general shape and in most details it resembles the male of the
previous species. The head a trifle larger than the trunk. The frontal margin is naked.
The antennule proportionally long, slender, with long sete. The antenne and the maxillule
much as in the previous species; the mouth small. The maxille differ from all other species
in the structure of the basal joint, which in its distal part close to the boundary between
the inner side and the posterior side is provided with a protruding plate, the margin of
which runs out into a number of spiniform, partly somewhat curved processes; the claw can
be folded up along the inner side of this plate, which is very conspicuous in a lateral view
of the animal (fig. 1d); the basal joint, besides, has a knot-like protuberance on its outer
side. The mavxillipeds are long; their basal joint has a sinuate inner margin and several
shorter and longer transverse rows of moderately long hairs on the anterior surface; the
terminal joint seems to be bifid at its apex. The sub-median skeleton has only the same two
pairs of processes as the preceding species, the first pair somewhat produced and rounded,
the second pair comparatively close to each other, rather short, triangular, pointed, slightly
diverging. The ear-shaped arch surrounding the base of the antennula is furnished with
hairs of medium length, and from that point the hair-covering continues in a broad stripe of
similar hairs along the whole length of the outside of the protruding lateral border of the
head; from the posterior angle of this border a fringe of particularly long hairs runs upward
and backward across the side and the back in a very slanting line. On the back behind
this line we find the usual naked area, which indeed is rather long, but much narrower than
in the preceding species; the remainder of the back, the sides, the posterior end and the
ventral surface are rather densely covered with hairs of medium length. The hollow spaces
beneath the skin of the head as in the preceding species. The first pair of legs much as
in S. intermedia, except that there is a shorter process on the exterior side of the branch
near its base, and the terminal seta is a little shorter than the basal joint of the maxillipeds.
The second pair of legs also much as in the preceding species, but the outer branch is
reduced to a smaller excrescence; the terminal seta of similar length to the first pair of
legs. The caudal stylets rather thick; the terminal seta quite the length of those of the legs.

133

OVISACS. They are moderately large, without considerable difference of size; one
of the largest is represented in fig. 4c, it is shortly ovate, and its longest diameter is ‘37 mm.
The eggs are moderately large, somewhat numerous.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. In the marsupium of a female of Lemboides afer Stebb. from South
Africa, at or near the Cape of Good Hope, were found: one female, one male and eleven
ovisacs, the latter united in two lumps, one of them with eight, the other with three ovisacs.
Our material of the host is examined and described by the Rev. Th. R. R. Stebbing.

18. Sphzronella Gitanopsidis n. sp.
(PL VI, fig. 2a—2z.)

FEMALE. The only specimen found (fig. 2a) is ‘97mm. in length and ‘85mm. in
breadth; the head well defined and the trunk sub-globular. The frontal margin naked
(fig. 2d). Antennule comparatively long, with moderately long sete. Antenne 3-jointed;
their basal joint of the length of the second joint (is incorrectly reproduced in the drawing);
the terminal seta about the length of the last joint. The mouth of medium size. The
maxillule with a good-sized additional branch. The basal joint of the maxilla with a small
tap on the posterior side. The maxillipeds slender, the basal joint naked, the following
three joints mutually separated, the last joint with a couple of spines inside the point. The
sub-median skeleton with rather narrow longitudinal lists and with a pretty small process
inside the inner angle of each maxilliped; a considerable, centrally much expanded transverse
list behind the maxillipeds, between the head and the trunk. The trunk naked; the trunk-
legs distinct. The genital area (fig. 2e) somewhat narrower than the head (fig. 2a), much broader
than long; the more solid chitine forms a broad, anteriorly open, semi-circle, of which a rather
small or large lateral part is slightly, the remainder solidly chitinised. The genital aper-
tures are rather oblique, they are moderately far apart from each other, and they are situated
close up to the anterior margin of the solid chitinous list, while the caudal stylets are placed
close together immediately behind its posterior margin; the whole area is naked.

MALE. The only specimen found (fig. 2f—2¢) is but 153 mm. long and °120 mm.
broad, consequently smaller than any other male of this genus, but I am unable to say
whether it is quite full-grown; it is also small compared with the female (fig. 2b : fig. 2a).
Seen from below, it is oblong with obtuse lateral angles and broadly rounded anteriorly and
posteriorly. The head as large as the trunk. The frontal border considerably produced,
evenly rounded, its margin naked. The antennule of medium length, the terminal seta the
length of the antennula. Antenne, mouth, maxillule and maxilla essentially as in the
female. The maxillipeds of medium length, their basal joint on its anterior side provided
with some groups of very fine hairs. The first pair of processes of the sub-median skeleton

134

short and rounded, the second pair short, somewhat produced and strongly converging.
The lateral margin of the head in its whole length supplied with hairs of medium length;
somewhat in front of the posterior extremity of this margin begins the line which runs
upward and backward in a somewhat oblique direction across the side and the back; in the
latter place the hairs become long, but in this species this line only forms the anterior
boundary of a broad belt of hairs of medium length, behind which we find the usual naked
transverse area, which is rather long and also broad; the remainder of the trunk: its sides,
posterior extremity and ventral surface, are closely covered with hairs, part of which are
proportionally rather long. The head has empty spaces beneath its skin. The first pair of
trunk-legs are rather small, with a single, pretty short branch, and a tolerably short and
thick process on the outer side at its base; the branch ends in two sete, one of which is
short, the other long, but scarcely the length of the basal joint of the maxillipeds. The
second pair of legs are of less than medium size, with a shorter outer branch and a some-
what longer inner branch; the terminal seta of the outer branch scarcely half the length of
the whole leg, whereas the inner branch has a short seta on its outer side, and the terminal seta
is nearly the length of that of the first pair of legs. The caudal stylets rather short, each
with a pair of terminal sete, which are somewhat thicker and longer than the hairs of
the trunk.

OVISACS. Only two are found; they are tolerably large and of about equal size;
the one represented (fig. 2c) somewhat flattened and rather triangular in outline, its longest
diameter being 59mm. The eggs pretty numerous, about middle-sized.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Gitanopsis arctica G. O. Sars from Varangerfjord
(the most northern part of Norway) at Vadsé. Prof. Sars discovered the parasite in a single
specimen, which he subsequently lent me, and in which were found: one female, one male
and two ovisacs.

19. Sphzronella Giardii n. sp.
(PI. VI, fig. 83a—31.)

FEMALE. One specimen (fig. 3¢) which has laid six ovisacs and no doubt has
finished laying eggs, and which is oblong and somewhat shrunk, measures “63 mm. in length
and -45 mm. in breadth, whereas another female (fig. 3a), which had not yet begun laying
eggs, is 124mm. long and 131mm. broad — consequently broader than long — and about
double the length and nearly three times the breadth of the first mentioned specimen. The
head is proportionally small and well defined from the trunk. The frontal margin is naked
(fig. 3e). Antennule of medium length, pretty robust, with short apical sete. Antenne
3 jointed, the second joint longer than the first or the third; the terminal seta of medium
length. The mouth-border of medium breadth. The maxillule with a good-sized additional

135

branch. The maxilla normal, with smooth basal joint. The maxillipeds scarcely of medium
length; the basal joint pretty robust, naked; second and third joints coalescent; the last
joint with a spine inside the point. The sub-median skeleton much as in S. Holbélli. On
each of the lateral borders of the head we find an area — more narrow towards the front
and broad posteriorly —, which is closely covered with exceedingly short and fine hairs.
The trunk is naked; trunk-legs are found. The genital area (fig. 3f) is much narrower
than the head (fig. 3a), much broader than long; the solidly chitinised part forms a some-
times narrow, sometimes tolerably broad semi-circle (in the latter case as in the following
species, fig.4d), which opens broadly towards the front, with the foremost end of each side
curved somewhat inward; the posterior margin is tolerably concave, and from the median
part of the ring proceeds a considerable plate, which occupies the rather broad space be-
tween the oblique, somewhat curved genital apertures, advancing somewhat beyond their
anterior ends, and being cut off anteriorly by a straight line. The caudal stylets a little
apart, situated on or closely behind the posterior margin of the solid chitine. The whole
genital area is naked.

MALE. It attains a length of about -21mm.; seen from below (fig. 3g), it is only
about one sixth narrower than long, and seen laterally (fig. 3h), it is very thick; compared
with the female, it is about middle-sized (comp. fig. 3c, fig. 3a and fig. 3b). The head scarcely
as large as the trunk. The frontal border but feebly produced and naked. The antennule
a little more slender than in the female, their sete a trifle longer. The antennze and the
maxillule as in the female; the mouth-border proportionally broader than in the latter. The
basal joint of the maxilla provided on its posterior side with a comparatively pretty long,
oblique tap. The basal joint of the maxillipeds longer than in the female, with about three
conical processes on the inner margin; on the distal part of the anterior side about three
transverse stripes of ordinary hairs, on its proximal part two to four tiny, naked, transverse
keels and a group of hairs at the base; the terminal joint with a couple of spines close inside
the point. The sub-median skeleton with the two first pairs of processes distinct; the first
pair small, the second pair long and parallel. From in front of the base of the antennula the
lateral margin of the head is furnished with a line of hairs of medium length, which from the
posterior end of the margin proceeds upward and forward in a slightly oblique direction
across the side and the back. Behind this boundary, the back, the sides and the ventral
surface of the trunk are closely covered with setaceous hairs of medium length; however, a
careful examination shows that the trunk is covered with numerous small, somewhat oblong,
transverse knots, from each of which proceed two or (more commonly) three hairs, the central
one of which is the longest. (This arrangement, which is difficult to observe, is not repro-
duced in fig. 3g and fig. 3h, as it was not discovered till after the plate was printed).
However, on the back, far from the anterior boundary of the hair-covering, we find a short
and not very broad, naked transverse area. The first pair of trunk-legs have a peduncle of
medium breadth, a rather short inner branch and a little longer outer branch; each branch,

136

as a rule, ends in one or two short and one longer sete, the latter of which, however, is
only half or scarcely half the length of the basal joint of the maxillipeds (sometimes there
are two about equally long sete at the end of the outer branch), and finally a rather short
seta on an angular process of the peduncle outside the outer branch. The second pair of
legs comparatively pretty long, with a short outer branch at their base, ending in a shorter
seta, while the inner branch ends in several sete, the longest of which is distinctly longer
than the setz of the first pair of legs. The caudal stylets are rather small, with short sete.
— The frontal thread is between two thirds of or the entire length of the whole body,
simple, ending in a thick disk.

OVISACS. ‘They are of medium size (fig. 3d), without great mutual difference (at
least if not containing young ones), for the most part shortly oval; the ovisac represented is
‘47mm. long and 39mm. broad. The eggs of medium size, not very numerous.

LARVA. I have found no free specimen, and the larve which I pulled out of the
ovisacs were not sufficiently developed to allow of giving a description of them.

POST-LARVAL DEVELOPMENT. Some pupx of both sexes have been found
(fig. 3i—31), and their interesting development is described on p. 54—5d,

HABITAT. The marsupium of Protomedeia fasciata Ky. from Denmark. In a
large material without specialised locality are found eleven infested specimens; a twelfth
one was taken by Dr. Joh. Petersen in the Kattegat at Stat. 403 (twelve fathoms). Only
seven of these twelve specimens have been very closely examined, but a statistic account of
four of them will be sufficient. Im one specimen were found: the femaie represented in
fig. 3c, with a male adhering to its ventral surface, and six ovisacs partly glued together.
In another specimen were found: a good-sized female, a male and seven ovisacs, thus di-
stributed: three ovisacs were lying beside and in front of the female, the remaining four
and the male lying behind it; finally, a pupa was hinged to the base of the gill of the
hindmost leg but one. In a third specimen occurred: one good-sized female, five males,
three ovisacs and five pup; four of the males and all the pup were hinged to gills, to
marsupial plates or to the epimera of the second — sixth pair of legs. In a fourth spe-
cimen appeared the extremely large female represented in fig. 3a, one male and one pupa;
the female occupied the front half of the marsupium, whereas its hindmost half was occupied
by six of the host’s eggs, containing young ones about half developed; in which the limbs
were very distinct.

20. Sphzronella Bonnieri n. sp.
(PI. VI, fig. 4a—44; pl. VII, fig. la—1b.)

FEMALE. ‘The specimen represented in fig. 4a — the largest one found — measures
‘97mm. in length and ‘94mm. in breadth. In the head and its organs of this species com-
pared with the preceding, I have not been able to find any deviation which would seem

137

qualified to form a character of species. Trunk naked; trunk-legs present. Genital area
(fig. 4d) essentially as in the preceding species, for in S. Giardii the chitinised semi-circle
can be almost as broad as in S. Bonnieri; the only deviation found is the situation of the
caudal stylets which in the latter are placed a little more towards the front on the ring
itself, but whether this is a valid character, | am not prepared to decide.

MALE. Considerably larger than in S. Giardii, two specimens being respectively
28 mm. and 29mm. in length, but they differ chiefly from that species in the swollen
appearance of the trunk, — its volume several times exceeding that of the head — and in
a very different hair-covering (fig. 1a and fig. 1b). Its frontal margin, antennule, antennee,
mouth, maxillulze, maxille and maxillipeds do not exhibit really good characters. The first
pair of processes of the sub-median skeleton seem to be longer, whereas the second pair are
a little shorter than and differ in shape from S. Giardii. The hair-covering of the lateral
border of the head as in this species, but the border itself is shorter and vanishes outside or
a little behind the base of the maxilla, and from this point the boundary line between the
naked head and the hair-covered trunk runs upward and backward in a slightly oblique
direction across the side and the back. The whole dorsal surface, the sides and the ventral
surface, except its foremost pretty considerable part, are closely covered all over with simple,
moderately long hairs which grow separately (not as in S. Giardii two or three from the
same little eminence); the back without naked transverse area. On account of the swelling
of the trunk, the legs and the caudal stylets are much further removed from the lateral
and the posterior outline than in nearly all other species, and the caudal stylets are situated almost
in the middle of the ventral surface. Both pairs of trunk-legs are proportionally smaller,
and their long terminal setz a little shorter than in S. Giardii; from the peduncle of the
first pair of legs outside the outer branch proceeds a distinct process ending in a seta, but
the other differences in the length of the seta etc. between this and the preceding species
are of slight or no value.

(Three, but not the fourth, of the males found are more or less closely wrapped up
in long, fine threads, or rather, it looks as if a thread were wound round the body in
numerous curves and with projecting nooses, but I have tried in vain to find out the origin
and nature of these remarkable threads. Fig. 4b exhibits one of the closely wrapped
specimens.)

OVISACS. These are oval or shortly oval (fig. 4c), a little larger than and with
somewhat larger eggs than in S. Giardii, otherwise as in this species. The ovisac repre-
sented (fig.4c¢) is 53mm. long and 43 mm. broad.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. Protomedeia fasciata Kr. from West-Greenland. I have found it in
old specimens which were determined by Kroyer, but unfortunately I neglected at the time
to put down statistics about the number of hosts ete. of the parasites found, viz.: one adult
female, one half-grown female, one very small female, one male without surrounding threads

18

138

and three ovisacs. JI found further in the marsupium of a female from the harbour of
Godthaab (2—3 fathoms, sand with sea-weeds, collected by Th. Holm 3/vir 1886): one adult
female, one male in a close wrapping of threads, and two ovisacs glued together; in the mar-
supium of another female from the same locality were found: one adult female, one closely
wrapped male, and six of the host’s own eggs; in a young female without marsupium, taken
in a depth of ten to fifteen fathoms in that harbour were found: one small female, only
‘34mm. in leneth and nearly as broad, on which, nevertheless, occurred two spermatophores,
and a male, round which a few threads were spun, was also attached to it.

REMARKS. It is an interesting fact, that the same Amphipod, Protomedeia fasciata
Kr., has one parasite in Denmark and another very closely allied species in West-Greenland.
The two parasitic species seem to be distinguishable from each other with certainty only by
the differences between their males.

21. Sphzronella longipes n. sp.
(PI. VII, fig. 2a—2g).

FEMALE. One single tolerably large, but flattened and ill-treated specimen has
been found, which measures -73 mm. in length and ‘92mm. in breadth, and besides, several
well preserved specimens, all of which, however, are but scarcely half-grown or recently
hatched, so that the largest one (fig.2a) is not more than -46 mm. long and somewhat longer
than broad, while a very small specimen, represented in fig.2d and fig. 2e, is only ‘26 mm.
long, and the proportion between the length and breadth of this animal is as 7 to 4. The
head is well defined. The frontal margin naked. Antennulz rather long and slender, with
long terminal sete. Antennee 3-jointed, third joint shorter than the second (fig. 2c, c); terminal
seta about the length of the two last joints combined. Mouth-border of medium breadth.
Maxillulee with well developed additional branch. Maxillae with smooth basal joint. Maxil-
lipeds rather long and slender; basal joint naked, second and third joints coalescent, last
joint digitated at the end with three exceedingly short points. The sub-median skeleton
with a somewhat narrow list inside the maxillee, naked all over; no transverse list between
the head and the trunk. Lateral margin of the head naked. Trunk naked. Trunk-legs
compared with those of the other species of this genus exceptionally good-sized, consisting
of a proportionally rather long cylindrical joint, from the end of which proceeds a proximately
thickened very long seta, three to four times the length of the joint, and besides another
seta equal to, or somewhat exceeding the length of the joint. About the genital area no
information can be given; in the small specimens it is not developed. The caudal stylets
considerably shorter than the legs, each ending in three sete of unequal length, the longest
of them almost equalling in length the short seta of the trunk-legs.

MALE. Unknown.

139

OVISACS. Of about equal size, elongated oval (fig. 2b); the specimen represented
measures ‘71 mm. in length and -46 mm. in breadth. Eggs numerous, about middle-sized.
Judging from the size of the ovisacs, the adult females of this species must be supposed to
be 1mm., or somewhat more, in length.

LARVA. A specimen found free (fig. 2f) is 16mm. long. Cephalothorax more than
1/2 time longer than broad. The front with a long, almost straight list inside the base of
the antennula. Antennule 3-jointed; olfactory seta about three times longer than the an-
tennula and scarcely half the length of the cephalothorax. Antennz much as in the larva
of S. intermedia. Of the maxillule only a single seta has been discovered. First joint of
the maxille of a little more than medium length, smooth; the two others normal. Second
joint of the maxillipeds shorter than the third. Abdomen small, its first segment somewhat
longer and a trifle broader than the second, and its long seta reaching a little beyond the
ends of the caudal stylets; second segment scarcely longer and not broader than the third,
from which the relatively good-sized caudal stylets are well set off, but their long sete are
defective in my two larve.

POST-LARVAL DEVELOPMENT. A single pupa (fig. 2g) found on the glass
during the preparation is ‘17mm. long and ‘11 mm. broad; it is described above on p. 60.

HABITAT. Ampelisca tenwicornis Lilljbg. from Denmark. I have found the
parasite on nine specimens, six of which were rather young, without marsupium. On each
of five of these occurred a not half-grown or very small female (in one case it was evidently
just hatched); on the sixth specimen I found two free larve. In a specimen with half-
developed marsupium occurred one not half-grown female. The two other hosts were females
with fully developed marsupium; in one of them occurred five ovisacs, in the other the above-
mentioned flattened female and four of the host’s own eggs.

REMARKS. By the very long sete of the trunk-legs this species is easily di-
stinguished from all other hitherto known species of this genus.

22. Spheronella Amphilochi n. sp.
(Pl. VIL, fig. 3a—3b).

FEMALE. The only specimen found was adult and measured 54mm. in length
and ‘40mm. in breadth. The head (fig. 3a) is well defined from the trunk. The frontal
margin with short and very fine hairs. Antennule tolerably long, with pretty long sete.
Antenne 3-jointed, the basal joint appears shorter than the following joints; the terminal
seta about the length of the last joint. Mouth-border of about medium breadth. Maxillulee
with rather short additional branch. Basal joint of the maxillaze smooth. Basal joint of the
maxillipeds long, slender and naked, second and third joints coalescent, last joint ending in
a point. Sub-median skeleton naked, but a peculiar characteristic in this species is that the

18*

140

hindmost, broadest and thinnest of the two transverse lists which are found on the ventral
side between the head and the trunk, is provided with short hairs throughout its whole
length. The lateral margin of the head supplied with hairs of medium length, which anteriorly
are arranged only in a single line, but somewhat in front of the base of the maxillz begins
a broader area, which runs obliquely backward and outward. The trunk naked; trunk-
legs not found, but no doubt present. The genital area (fig. 3b) not quite as broad as the
head, somewhat broader than long; the more solid chitine forms about two thirds of a ring,
which opens broadly in front; laterally the ring is narrow, but posteriorly it is broad, its
median part forming an area which consists of an expansion of the hindmost part of the
ring and of a triangular process advancing anteriorly between the genital apertures and
dilating into a smal] plate in front of the anterior extremity of the apertures; the whole
median part of this area again is occupied by an oblong, anteriorly pointed area of thin
skin. The genital apertures come pretty close together in front and are situated quite near
the advancing process just described; they are rather oblique and a little curved. The
caudal stylets are situated on the hindmost -part of the just mentioned membranous little
central area; each of them ends in two or three setee. one of which is quite exceptionally
long. The margin and the foremost part of the chitinous plate situated between the genital
apertures, are provided with fine hairs, some of which are rather long; some hairs are also
scattered outside the genital apertures on the thin membrane covering their muscles.

MALE. Unknown.

OVISACS. The two ovisacs found are irregularly shaped, probably owing to
pressure; they are somewhat oblong and flattened; the largest is -42 mm. in length. The
eges middle-sized, not numerous.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. In the marsupium of a specimen of Amphilochoides pusillus G. O. Sars
from Denmark were found: one female and two ovisacs adhering to each other.

REMARKS. The female of this small species is no doubt well characterised by
the hairs on its head, the structure of the genital area and the particularly long seta of
the caudal stylets. The name of S. Amphilochi is perhaps not quite suitable, but is was
given, and the plate engraved, before a renewed examination of the host by means of the
new work by G.O. Sars, revealed that it belonged to a species of the recently established
genus Amphilochoides G.O.S. not hitherto observed in Denmark.

23. Spheronella Dulichie n. sp.
(Pl. VII, fig. 4a—4qd).

FEMALE. The only specimen found (fig. 4a) is -72 mm. in length, ‘59 mm. in
breadth and a little thinner than broad, The head of very good size in proportion to the

141

trunk, well defined and unusually broad in proportion to its length. The frontal margin
naked (fig.4¢). Antennulz short, with tolerably short sete. Antenne well developed, but
partly broken off. Mouth good-sized, mouth-border of medium breadth. Anterior branch of
the maxillule very long, additional branch rather short. Basal joint of the maxillz hardly
middle-sized, smooth. Maxillipeds proportionally small, much shorter than in any of the pre-
ceding species; the basal joint, in proportion to its length, rather thick, naked; second and
third joints coalescent, last joint pointed. The sub-median skeleton deviating much in ap-
pearance from those in the preceding species (comp. fig.4c), naked. Lateral margin of the
head with a series of moderately short hairs. Trunk naked; trunk-legs small, with short
sete. Genital area (fig. 4d) much narrower than the head, considerably broader than long,
forming a transverse, pretty solidly chitinised plate, which is sub-oval, yet a tolerably large
part of the posterior margin forming a straight line; the genital apertures are large, the
distance between them of about medium length; they are furthermore considerably curved,
and the anterior half of their inner lip nearly parallel; their posterior extremities are found
a little in front of the posterior margin of the plate. The caudal stylets are situated close
together on the posterior margin of the plate; they are small, with shorter setz. The
part of the plate which is situated behind the genital apertures, and a narrow area sur-
rounding the membranous part, which, as usual, is found outside each genital aperture, are
furnished with numerous fine and rather short hairs; the remainder of the genital area
is naked.

MALE. Unknown.

OVISACS. Compared with the female found, they are very large (fig. 4b: fig. 4a)
and without much difference in size: the largest, which is represented, is ‘56 mm. in length.
The eggs are large, not numerous.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. In the marsupium of a female of Dulichia monacantha Metzger from
Denmark were found: one female and four ovisacs.

REMARKS. The female is easily distinguishable from all other species by its very
short, but otherwise quite normally constructed maxillipeds.

24. Sphzronella Acanthozonis n. sp.
(PI. VII, fig. 5a—5d).

FEMALE. ‘The only specimen found is very large, namely 42 mm. in length,
34mm. in breadth, and nearly as thick as broad. The body seen from below (fig. 5b), is
regular and rather shortly ovate, narrowest towards the front, the head and the genital
area situated at a not very short distance from the anterior and the posterior outline re-
spectively, and the trunk-legs very far from the lateral outline; seen laterally (fig. 5a), the

142

head protrudes somewhat like a small triangle, besides, we see a knot-like protuberance,
somewhat in front of the middle, at a short distance from the outline of the back. The
head is exceedingly small in proportion to the trunk, and it is distinguished by the particular
solidity of the chitinised parts to the front and on the sides, which, moreover, laterally and
anteriorly extends considerably on the lower surface, so as to render the area with the
appendages somewhat smaller than in the other species. The frontal margin naked (fig. 5c).
Antennule slender, of medium length, second jot proportionally longer than in the preceding
species, the seta of about medium length. Antenne 3-jointed, basal joint short, second
joint longer than the third, and the latter longer than the seta. Mouth large, with border
of medium breadth. Additional branch of the maxillule well developed. Mavxille rather
small, their basal jomt smooth. Maxillipeds comparatively short and slender, yet somewhat
longer than in S. Dalichie@; the basal jomt has one or two stripes of excessively short hairs
(not shown in the drawing) on the inner side, and similar hairs on the inner part of the
terminal margin; second and third joints separated, the last joint pointed. Sub-median
skeleton provided with thick lists, naked; a double list between the head and the trunk,
somewhat behind the base of the maxillipeds. Lateral margin of the head naked. Trunk
naked; the trunk-legs are small but conspicuous, rounded knots without setae — thus deviating
much from all other species. Genital area (fig. 5d) somewhat narrower than the head, much
broader than long, firmly chitinised all over; it has a Jong, somewhat concave, anterior
margin, convex, oblique lateral margins and a shorter, deeply incised, posterior margin.
The genital apertures situated somewhat behind the middle of the plate; they are of medium
size, close together anteriorly, and somewhat diverging posteriorly. The caudal stylets in
close proximity on the plate close to its posterior margin; they are small, each ending in a
rather long seta. The whole genital area naked. (In the illustration the orifices of the
receptacula ‘seminis are seen at a short distance in front of the genital apertures).

MALE, OVISACS, LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. In the marsupium of a female of Acanthozone cuspidata (Lepech.)
from the Kara Sea was found a single female.

25. Sphezronella frontalis n. sp.
(Pl. VII, fig. Ga—6i; pl. VIII, fig. La—te).

FEMALE. The largest specimen (fig. 1a) is 184mm. long and 1°71 mm. broad,
and the thickness about three fifths of the breadth. The body is narrower towards the
front, and its long posterior outline is sligthly concave in the middle. The head nearly
middle-sized and distinctly defined from the trunk. An excellent character of this species
is that the naked frontal margin expands in the middle into an oval, transverse, flat cup
(fig. 1d), the breadth of which somewhat exceeds the diameter of the basal joint of the

143

maxillipeds. Antennule scarcely of medium length, with sets of medium length. Antenne
3-jointed, first joint short, the third longer than the second, but shorter than the seta. Mouth
rather large, with mouth-border of medium breadth. Basal joint of the maxillee smooth. Ma-
xillipeds middle-sized, proximal part of the basal joint with some transverse lines of short, fine
hairs on their anterior side; second and third joints separated, the last joint ending digitated in
four or five points. Sub-median skeleton very powerful, naked, with a double list between head
and trunk somewhat behind the base of the maxillipeds. Lateral margin of the head has a
tolerably broad longitudinal belt of short and fine hairs. Trunk naked; trunk-legs normal.
Genital area (fig. 6i) much narrower than the head: the solid chitine really consists of two
halves, each of them forming an oblique, irregular arch, which begins within the genital
aperture a little behind the anterior angle of its lips, whence it continues very close to the
lips, following their direction to the posterior angle, then advancing forward and outward
in an oblique line; its anterior extremity curving a little inward; the two arches connected
between the genital apertures are strongly curved and placed at a pretty considerable
distance from each other. The caudal stylets are somewhat apart and comparatively far
from the genital area; their setee have no doubt fallen off. The skin between the genital
apertures is closely covered with very short and fine hairs, which also extend somewhat
further backward, though not nearly as far as to the caudal stylets; besides, a tolerably
large part of the chitinous arches — not their anterior part, however, — is furnished with
fine hairs.

MALE. It is large in proportion to the female (fig. 1b: fig. la), indeed quite ex-
ceptionally so, namely 69mm. long and 53mm. broad. The head occupies only between a
third and a fourth of the whole body, consequently it is very short and also narrow, compared
with the large trunk (fig. Ga—6b). The frontal border somewhat produced; the margin
evenly curved, without cup, naked. Setee of the antennul tolerably long. Antenne (fig. 6c)
seem to be 4-jointed; the basal joint short and coalescent with the skeleton of the head;
the connective membrane between the third and fourth joints is long, the terminal seta very
long, yet somewhat shorter than the antenna, with a transverse division not very far from
the base. Mouth as in the female. Mavxillule (fig. 6d) with two long principal branches,
the anterior one the longest, and at the base of it an extra branch of about half of its
length; the additional branch (e’) is long, and its basal part forms a pretty thick, articulated
foot. Maxille as in the female. Maxillipeds tolerably long; basal joint powerful, its
inner margin armed with a pair of rather short, pointed processes (fig. 6e); its anterior
surface is decorated in a peculiar way by scattered areas covered with long hairs alternating
with partly large groups of very small, transverse eminences supplied with very short hairs;
its other sides are decorated in a more or less similar way; second and third joints separated ;
the terminal joint ending in at least a couple of points. The first pair of processes of the
sub-median skeleton short and blunt, the second pair long and projecting straight backward;

144

the base of each of these merges gradually into a strong list, and these two lists run
forward, nearly parallel, towards the posterior margin of the rostrum. Lateral margin
of the head with a stripe of moderately long hairs, which from the posterior angle of
the margin continues upward in a vertical line across the side and the back, but the
hairs of this part are long. The whole trunk, except the foremost part of the ventral
surface, is closely supplied with peculiar, small, transverse eminences, each of which
(fig. Gh) bears about ten hairs, which radiate backward and obliquely sideways; on the
greater part of the trunk these hairs are short, but on its hindmost third part, following
a line from the caudal stylets obliquely backward and outward towards the second pair of
trunk-legs, and thence further, obliquely backward, they are pretty long. Trunk-legs com-
paratively small. The first pair (fig. 6a and fig. Gf) consist of a clumsy peduncle with two
branches, the outer one a little shorter than the peduncle and ending in two about equally
long, hairy sete, the longest of which is not twice the length of the branch, and rather
thick; the inner branch is difficult to understand, it is of the same length as, but much
thinner than the outer one, with an articulation in its middle and, especially outside this
articulation, provided with a number of hairs. The second pair of legs (fig. 6g) about the
length and breadth of the outer branch of the first pair; on the outer side, at a short distance
from the basis, a short, blunt process (presumably an outer branch) ending in a seta, and
the leg ends in two hairy sete, the longest of which is double the length of the leg and
very thick. The caudal stylets are situated far to the front on the ventral surface, a little
behind the middle of the trunk; they are rather slender, each ending in a hairy seta, which
is equal in length to the longest seta of the second leg.

OVISACS. They are middle-sized (fig. 1c), oblong, somewhat flattened; the specimen
represented has young ones in the Nauplius stage, and is 103mm. in length and ‘69 mn.
in breadth. Eggs numerous and small.

LARVA. Fig. 1e is drawn from specimens pulled out of the egg-membranes. The
front on each side inside the base of the antennula has a long, oblique list, the ends of
which are curved inward. Antennule 3-jointed; the olfactory seta about half the length of
the cephalothorax. Antenne almost the length of the antennule; second joint somewhat
longer and considerably more slender than the first one, the third joint very short, the
terminal seta the same length as or longer than the second joint. Maxillule as in S. Calliopii,
with four branches which, however, are shorter and more slender than in this species, and
the hindmost branch only is hairy (not, as in the drawing, the penultimate one as well).
The joints of the maxille each of medium length, smooth. Second joint of the maxillipeds
considerably shorter than the third. Segments and sete of the abdomen as in S. Calliopii,
with the exception that the long sete of the caudal stylets are only half the length of the
body (and perhaps even relatively shorter in the free swimming larva).

POST-LARVAL DEVELOPMENT. Unknown.

145

HABITAT. The marsupium of Ampelisca macrocephala Lilljeborg from Denmark.
Only a single infested specimen has been found, and in the anterior part of its marsupium
occurred: a deformed female, which had probably finished laying eggs, one male and seven
mutually adhering ovisacs, one of which contained full-grown larvee; in the hindmost part
appeared the large female represented, one male and six mutually adhering ovisacs; one
ovisac had fallen out before its place was ascertained.

REMARKS. The name of the species points to the remarkable cup on the frontal
margin of the female. The male deviates much from all other hitherto known forms.

26. Sphzronella microcephala Giard and Bonnier.
(Pl. VII, fig. 2a—2k).

Spheronella microcephala Giard and Bonnier, Compt.-rend. de !’Acad. des Sc., 25 sept. 1893.
— — _— Bull. scientifique de la France et de la Belgique, T. XXV,
fase. 2, 1895, p. 464, pl. XII, fig. 40—47.

FEMALE. The largest specimen, which had only just begun laying eggs, was
144mm. in length and of the same breadth and thickness (fig. 2a), sub-globular, yet a little
produced and almost pointed towards the front, which is due to the fact that the trunk
merges evenly into the head without any separation. The frontal border is present as a
small crescent-shaped transverse plate (fig.2e), which is scarcely double the length of the
diameter of the mouth; lateral borders are wanting (fig. 2d); so we only find the various
appendages and a tolerably developed sub-median skeleton, but, as the lateral parts of the
skeleton, viz. the lateral borders, are wanting, this parasite differs from all the preceding,
but agrees with several of the following species of this genus, im having no lateral limitation
to the surroundings of the mouth-limbs. Antennulz very short, without distinct vestiges of
articulation, with a seta on the anterior margin at a short distance from the base (no doubt
corresponding to the usual pretty long seta at the anterior angle of the first joint), and
four terminal sete of unequal length, the longest of which are a little longer than the
antennula. Antenne seem to be altogether wanting. The mouth of medium size, with a
rather narrow mouth-border. Maxillule well developed, with good-sized additional branch.
Maxille far removed from the rostrum and much closer together than in any other species
of the genus; the basal joint large and smooth. Maxillipeds small and feeble; their basal
joint pretty short, very slender and naked, the second and third joints fused into a very
short and slender joint; the last joint scarcely half the length of the preceding, rounded at
the end; the reduced state of the two (or three) last joints, in particular, proves this pair
of appendages to be almost valueless as prehensile organs. The sub-median skeleton is
provided with a somewhat prominent list on each side of and at a short distance from the

19

146

median line; a narrow list is found between the maxillee; the whole skeleton is naked. The
trunk entirely naked; trunk-legs wanting. The genital area (fig. 2f) deviates strongly from
all other species; it is considerably larger than the head (fig. 2a) and much longer than
broad. The solid chitine forms posteriorly a narrow semi-circle which opens towards the
front, each branch dilating anteriorly on the internal side to a considerable breadth, after
which both branches run on parallel a long way, at the same time gradually declining in
breadth; the whole structure may also be described by saying, that there are two anteriorly
pointed, posteriorly broader, mutually parallel lists, which again decrease in breadth in their
hindmost part, converge, and at last join in a semi-circle. The somewhat curved genital
apertures are situated at some distance from each other, so that their outer ends come close
to the inner side of the semi-circle; their muscles run forward and a little outward towards
the broadest part \of the lists, close in front of the foremost part of the semi-circle. (About
the orifices of the receptacula seminis which are omitted in the drawing, see above on p. 14.)
The whole area is naked, and caudal stylets are altogether wanting.

MALE. The body, apart from the rostrum, is ‘18mm. in length; seen from below,
it is ovate, only about one sixth longer than broad; the thickness in proportion to the breadth
is almost like two to three; so it is exceedingly small compared with the female (fig. 2b:
fig. 2a). It deviates strongly from all other species, and in spite of much study and long
deliberation, I have been unable to understand all its details. Head and trunk of about
equal size. The frontal border is not produced, its margin flatly curved, naked. Antennule
long, without articulation, with sete of medium length. Antenne wanting. Rostrum unusually
long, very broad at its base, and in the specimens found, strongly protruding, which gives
it, when seen from below, the shape of a large, distally blunt cone, projecting considerably
beyond the frontal margin. Maxillule as in the female. Basal joint of the maxilla some-
what compressed, broad between the foremost and hindmost angles; the basal margin is
long, and its acute posterior angle is further removed from the head than the articulation
of the second joint; its outer side is armed with a pair of conical taps. Maxillipeds of
medium length, the basal joint somewhat fusiform, on the inner and anterior sides some
areas covered with numerous extremely short hairs; second and third joints coalescent,
last joint pointed. The sub-median skeleton possesses only the first pair of processes, each
of which being long, very slender and nearly setiform (fig. 2h, i), and being a prolongation
of a list running inside the maxille. The lateral margin of the head is prolonged backward
to the middle of the trunk, and it is provided with a stripe of rather short hairs which are
situated more or less close together. The ventral surface of the trunk is for the most part
covered with tolerably short hairs, many of which are arranged in transverse rows, whereas
the back, the lateral surface and the hindmost extremity are naked. I have been unable to
understand the basal parts of the trunk-legs, I cannot even make out with absolute certainty
which pair are the foremost. I consider the narrow pair of appendages which are situated
near the median line to be the caudal stylets, and the limbs which are seen a little outside

147

these appendages, to be the first pair of trunk-legs, the lateral legs would then make the
second pair. The proximal part of the first pair of trunk-legs being incomprehensible to
me, [I must content myself with referring to fig. 2g, which is drawn as accurately as pos-
sible; the distal part is a rather short and broad joint divided at the posterior outer angle
by a rather deep incision into two unequal processes, the outer one of which is conical and
ends in a shorter seta, while the inner one is broader and is cut off posteriorly in a straight
line, bearing on its end a small joint which terminates in a pretty long seta, of more than
half the length of the basal joint of the maxilliped. The second pair of legs resemble the
distal part of the first pair, but their outer process (outer branch?) is shorter, with the terminal
seta somewhat longer, the inner process lacks the small joint, whereas its seta is a little
shorter than in the first pair of legs. Each of the caudal stylets is a tap ending in a pair
of conspicuous, though not long, sete, besides having a short seta proceeding from an angular
expansion on the outside at the base; each stylet is a direct prolongation of a long, anteriorly
somewhat expanded, prominent list, which runs forward towards the base of the trunk. The
caudal stylets, the distal part of the first pair of legs and the second pair of legs are situated
almost on the same transverse line.

OVISACS. They are pretty small, mostly somewhat flattened, their circumference
varying between a circular and a very oval shape; the specimen represented in fig. 2 ¢ is
‘72 mm. long and scarcely more than half as broad. As many as fifteen ovisacs may be
found in one female. The eggs of medium size, not numerous.

LARVA. The body of a specimen (fig. 2i) which had just attached itself, is *25 mm.
in length. It deviates very much from all the other known larvee of the genus, and partly
of the family, in its extremely short antenns, its long and very slender maxilla and maxilli-
peds, its slender natatory legs and very slender abdomen. The front without lists, in the
specimen figured it is covered throughout its whole breadth by the viscous substance which
attaches it to the host. Antennule 2-jointed, olfactory seta rather long, about three fourths
the length of the cephalothorax. Antenne extremely short, almost rudimentary, 3-jointed,
with a proportionally thick, but very short, seta on the penultimate joint, and an exceedingly
short terminal seta. Mouth very large. Of the maxillule I have discovered three very fine
branches, the anterior one moderately long, the two others a little shorter. Maxille long
and very slender, the basal joint, in particular, is comparatively very long and extremely
slender; all joints smooth. Basal joint of the mavxillipeds long and very slender, second
joint unusually long, and considerably longer than the third one. The posteriorly free pouch
on the ventral side of the cephalothorax small and very short. The second section, the free
segment, of the cephalothorax proportionally much smaller than in other species. Peduncle
of the natatory legs unusually slender. Abdomen considerably more slender than in other
species; the long seta projecting from the posterior angle of the first segment, is more than
double the length of that part of the abdomen which is posterior to the point where this
seta projects, the second somewhat shorter seta is also unusually long. Second segment a

19%

148

little shorter than the first one, and somewhat longer than the third one combined with the
not defined caudal stylets; the terminal sete of these stylets almost two thirds the length of
the whole body.

POST-LARVAL DEVELOPMENT. After the preparation I found on the object-
glass an individual (fig. 2k) which I consider to be a pupa of this species; it is mentioned
above on p. 61.

HABITAT. The marsupium of Ampelisca typica Sp. Bate from Denmark. In one
specimen occurred: one female, two males, twelve ovisacs, three of which were free, and
nine adhering to each other in a lump (two of them with scarcely quite developed larve),
and finally, two larvee which had evidently been attached. In another specimen were found:
one female and some ovisacs; in a third: one female and fifteen ovisacs, thirteen of which
adhered to each other in a lump (and one of them contained developed larvze); in a fourth
specimen were found: one male (the largest represented), two free ovisacs and two of the
host’s own eggs.

REMARKS. This parasite in all its stages is far removed from all other species
of this genus, still the differences are not of such a quality that I have felt justified in
establishing the species as a type of a new genus, as which, in my eyes, it would not be
fully equivalent to the other genera. Guard and Bonnier have described the female and
ovisacs of a species taken in Ampelisca tenwicornis Lilljeborg from le Croisic (Brittany),
but in spite of the great differences between their description and my own of the head and
its appendages, I nevertheless consider my species identical with theirs, and I refer to my
detailed critique of their account given above on page 13—14.

b. Parasites on Cumacea.

In six species of Cumacea I have found parasites in the marsupium, and I have
referred them to five species. Hitherto they have occurred only in fully developed marsupia.
These five species show mutually very great ditference in both sexes, nevertheless, they are
distinguished in several features from the species found on Amphipoda; the larve of all
these parasites, especially, are characterised by some peculiarities which are not noticed in
any of the previously described larve, whereas a few of them appear in the larva of
S. Munnopsidis which lives in Munnopsis typica M. Sars belonging to the order Isopoda.
For several reasons, among others in order to avoid unnecessary repetitions in the descrip-
tion of the two sexes and the larvee of each species, it may be to the purpose to give a
view of their peculiarities.

THE FEMALES. Antenne only 2-jointed or, mostly, wanting. The mouth-border
moderately broad or narrow. The basal joint of the maxillipeds decorated on the anterior side
with small groups or rows of very short or rudimentary hairs, which, in many cases, only look
like small, distinct dots; the spine proceeding from the distal inner angle of the penultimate

149

joint is large, and one of its margins is provided with a row of very short setiform processes.
Trunk-legs seem to be altogether wanting.

THE MALES. They are always distinguished by a very peculiar — though mutually
extremely varying — development of the frontal border, the margin of which is in a great
measure decorated with numerous fine, or exceedingly small, spiniform processes, which are
mostly arranged in a single line. Trunk-legs and caudal stylets either tolerably small, or
— frequently — altogether wanting.

OVISACS. They are middle-sized or pretty small, but exceptionally numerous, for
in three of the species occurred about twenty, in a fourth even twenty-eight sacs, which
decidedly had been laid by the same female.

THE LARVA. The front is decorated, either with some good-sized lists, mutually
connected on each side, or (mostly) with numerous fine processes, arranged in one or more
rows. Each maxillula has four branches. The basal joint of the maxilla has a double comb
of fine, almost cylindrical, apically rounded processes along the margin, against which the
second joint is folded (pl. VIII, fig. 30); the third joint has two or more pointed processes
along its inner margin. The second joint of the maxillipeds much shorter than the third.
Abdomen of medium length, or (mostly) tolerably long and powerful; first segment good-
sized, and the sete proceeding from its posterior angle extending to, or somewhat beyond,
the caudal stylets; second segment about as long as or a little longer than the first one
and a little more voluminous; third segment very short, and the caudal stylets set off by a
distinct articulation.

1. Conspectus of the Females.

Maxalleemwelladevelopedts aux cat. cnet, 6) rs, Gut) eyo cele sree ae pee uctel yee econ eos ee

, Wewallles Cus miGlinngMmehAve Gaon Goeco0eud0050 04 .. 31. S. marginata n. sp.
2. An odd, good-sized, vaulted eminence, provided with a prominent median plate, a little
behind and inside the base of the maxillipeds............. 27. 8S. decorata n.sp.

2’. No eminence behind the maxillipeds ...... ear ee en a heer on eas oar tS 3
3. The head weil defined from the trunk, with frontal border and lateral borders well
developed. Caudal stylets well developed............... 28. S. modesta n. sp.

3’. The head not defined from the trunk, frontal border and lateral borders wanting. No
Gam dal StyleUsier pt pecan Orn cti testes, ete, chiar oie ais uy ay ee amet eames 4

4. The solid chitine of the genital area surrounds the genital apertures posteriorly and
lbneerelin, MO BimIOUhy, coco cous buoueeoooouuedoneg as 29. S. dispar sp.
4’. The solid chitine of the genital area surrounds the genital apertures on all sides.
30, S. msignis n.sp.
2. Conspectus of the Males.

(Peele DNkel COS NTeSON time serane a Aes thas oye ae op ees uaeiek ay Toau es ay rk olan well ap eobiat cat ees 2
1’. Trunk-legs (and caudal stylets) wanting altogether ...... Pid tem sua te aionuterr ay yd 3

150

2. Frontal border produced into a good-sized, anteriorly blunt, plate. Caudal stylets wanting.
27. S. decorata

2’. Frontal border slightly produced. Caudal stylets good-sized... 2... . 28. S. modesta
3. Front strongly produced; seen from below, it tapers considerably towards the distal end,
then expands into a tolerably broad disk, the margin of which — except posteriorly —

is provided witha sinele: row Ob fine) PLOCESSeS) jon.) ie) sc) oiler eueeuennen iste AL 4
3’. Front broad and somewhat emarginate in the middle: fie margin with some rows of
fINCMPNOCESSESSEs arse he ehcrss sf thes vee sen eviorey Sane neds Hoe poo ooo 6 aL. S, TanAm aI
At Hrontalledisken canliyaccrncullar =r ss cere oe re eet renee EP
4’. Frontal disk broader than long, with rectangular lateral angles... . . 30. S. insignis.

27. Spheronella decorata n. sp.
(Pl. VII, fig. 3a—30o; pl. IX, fig. 1a—1b.)

FEMALE. The largest specimen, represented in fig. 3a, is 2°15 mm. in length and
247 mm. in breadth, and it has laid six ovisacs; another specimen, only 1°33 mm. Jong and
1°52 mm. broad, has laid eight ovisacs. Thus the body is broader than long. The small
head is distinctly defined from the trunk; it is comparatively well chitinised all over, except
in the part which surrounds the mouth-appendages and is limited by the low lateral borders,
and this part, forming a triangle, is prolonged anteriorly beyond the antennule, continuing
a rather good distance along the dorsal side of the head, where this peculiar extension termi-
nates in an acute angle (fig. 3d). So there is no real frontal border. Antennule (fig. 3e) short,
2-jointed, the two first joints being coalescent; sete short. Antenne tolerably short, 2-jointed,
the basal joint short, second joint longer and thicker, terminal seta short. Maxillule well
developed, additional branch good-sized, with a distinct foot. Maxillee middle-sized, basal
joint smooth, but numerous chitinous taps appear on the inner side of the large membrane
between the first and the second joints. Maxillipeds.powerful and comparatively pretty long;
the basal joint on its anterior side and on a small part of its inner side, bears four or five
groups of very small prickles (rudimentary hairs), arranged in transverse belts; further, at
a short distance from the distal margin, a transverse row of very fine hairs, besides similar
hairs on the distal margin itself; second and third joints coalescent, the distal spine long
and rather slender, with fine processes on its inner margin; last joint a little expanded
towards its rounded, flattened end, which terminates in numerous fine processes arranged in
a line. The sub-median skeleton slightly developed; a ventral transverse list between head
and trunk, and adjoining the anterior margin of this list, an odd, good-sized, considerably
vaulted eminence, which is rounded, a little broader than long, and provided at its median
anterior part with a rounded protruding plate. Lateral margin of the head naked. Trunk
naked. Genital area (fig. 1a) considerably smaller than the head (fig. 3a), nearly as long as

151

broad; the solid chitine forms a somewhat irregularly shaped plate (fig. 1a), in which a
tolerably large area of the anterior third part is thin-skinned and partly merging in the
skin surrounding the plate (though in two dissected specimens the shape of the plate and of
the membranous part were somewhat different, the present description will do for both).
The genital apertures are seen far to the front on the posterior half of the plate; they are
strongly curved and situated at a moderately long or rather short distance from each other,
in such a position that their muscles turn very much sideways and a trifle forward. The
space between the genital apertures has some longitudinal stripes of very short hairs; the
remainder of the area is naked. At a short distance behind the apertures appear a couple
of small cones, which doubtless are the rudimentary caudal stylets.

MALE. A good-sized specimen is 55 mm. long and -42 mm. broad, which is large
indeed, though, considering the proportion between the sexes in other species, it is but
mniddle-sized (fig. 3b: fig. 3a) comparatively to the females, which are large. Seen from below,
its shape is very characteristic, almost hexagonal, the posterior margin of the trunk forming
a somewhat convex line, its lateral outline being moderately long and somewhat concave,
whereas the head has a long, slightly curved, lateral outline and a very short anterior
margin. The head nearly the size of the trunk. The frontal border strongly produced,
with converging lateral margins; terminal margin short, cut off in a straight line, with a
pretty deep incision in its median part, while distally each lateral margin has two deep and
rather broad incisions and, somewhat in front of the antennula, a slight depression; these
incisions form three pairs of lobes, the hindmost of which are low, the others good-sized with
almost right angles; the terminal margin of all the lobes is furnished with a row of nume-
rous minute processes. Antennule short, 2 jointed, with short sete. Antennz of scarcely
medium size, 3-jointed, second joint the longest; terminal seta the length of the last joint.
Mouth-border a little broader than in the female; maxillule as in the female. Mavxille
(fig. 1b) nearly as in the female, and the two last joints coalescent as in the other sex.
Maxillipeds of medium length, basal joint rather slender, otherwise this joint as well as the
others constructed and equipped (fig. 3f and fig. 3h) as in the female. The sub-median
skeleton has the two first pairs of processes, first pair about middle-sized, second pair power-
ful, long and diverging slightly backward. The lateral border of the head has a peculiar
shape, curving strongly towards the base of the maxillee, then turning backward and obliquely
sideways almost at right angles; the margin fringed in the middle with moderately long
hairs, anteriorly and posteriorly with long hairs, and from its hindmost end a narrow stripe
of extremely long hairs runs upward across the side of the animal, where it curves slightly
forward (fig. 3g), then continues across the back in an oblique line. Behind this stripe the
back and sides, as well as the ventral surface of the trunk, are densely covered with mode-
rately long, and in front of the second pair of legs, with long hairs. About the middle of
the back of the trunk is seen a short and very narrow transverse area. First pair of trunk-
legs pretty small, their basal part indistinctly defined, and from this part proceed two

152

tolerably small branches of equal length, each of which consists of a somewhat thicker,
very short joint, from the end of which proceeds a thick, but rather short, partly hairy seta.
The second pair of legs are situated at the posterior angles of the trunk and greatly resem-
ble the first pair, but the basal part is even more indistinct, the joint of the inner branch
much shorter than that of the outer branch, and the terminal setae — particularly that of
the outer branch — longer than in the first pair. Caudal stylets altogether wanting.

OVISACS. They are pretty small or of medium size, circular or oval and mostly
somewhat flattened; the ovisac represented in fig.3c¢ is one of the larger ones and is ‘94mm.
in length. Eggs numerous and comparatively small.

LARVA. Fig. 3i
ege-membrane. The larva is °30mm. long and so slender that its cephalothorax is a little

30 are drawn from specimens which had just broken out of the

more than twice as long as broad. The front is richly decorated (fig. 31): its margin with
a series of rather short and very short processes which begin at some distance from the
base of the antennula and stop a short distance from the median line; the eight or ten pro-
cesses nearest to this line are really situated somewhat within the margin and are much
longer than the more lateral processes which proceed trom the edge; somewhat inside the
more lateral part of the frontal margin appears on each side a long, oblique row of tolerably
long, narrow processes, turning forward and outward in an oblique line; somewhat behind
them we see a curved transverse list, and at the inner angle of this list — consequently in
front of the mouth at a short distance from the median line — four or five rather long, and
especially comparatively thick, anteriorly somewhat diverging processes with rounded apex.
Antennule 2-jointed, their olfactory seta somewhat more than half the length of the cephalo-
thorax. Antenne equal in length to the antennule; first joint broad, sometimes with a strong
indication of being formed of two coalescent joints (fig. 3m), the first of which is short
(comp. the following species); second joint of the same length as or a little longer than the
first; third joint short, with two terminal seta, one of them short, the other nearly the
length of the two last joints combined. The maxillule have all four branches well developed,
the outermost being the longest, curved outward and backward, hairy. The basal joint of the
maxillee has two rows of processes (fig. 30), but one of them is often covered by the second
joint (fig. 3n), which has no sete; the third joint has two good-sized processes on its inner
margin, but the distal one, which is the largest, is smaller than the long, curved, terminal
part of the joint. Abdomen pretty long; a description of it is found above on p. 149. Sete
of the caudal stylets more than three fifths the length of the body.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. Found in the marsupium of six specimens of Diastylis Rathkei (Ky.)
from West-Greenland and in one specimen from the Kara Sea, but not in Denmark. — It
may be pointed out that I have found parasites in nearly half of the adult females from the
two localities mentioned, which I have seen, whereas an investigation of several scores of
females from various Danish waters gave a negative result. In one specimen occurred: one

153

female (the one figured), no male, but six free ovisacs; in another specimen were detected:
one female, one male and eight free ovisacs (all with eggs); in a third: one female, one
male and nine ovisacs (four of these glued together); in a fourth: one female, one male, and
nine ovisacs (some of them with Nawplii). In a fifth specimen I discovered: one female,
two males and twenty ovisacs, ten of which adhered to each other in one lump, four in
another; several of them contained larvee, some of which had even thrown off the egg-
membrane. In a sixth specimen, at least seventeen ovisacs adhered to each other in a big
lump which surrounded the female, so that only part of one of its sides helped to form the
outer wall of the lump, while a male was sitting in a hole between the ovisacs on the
opposite side; the whole lump had shaped itself after the cavity of the marsupium, it was
nicely smoothed and had a slight longitudinal groove on the surface, which was turned
towards the ventral side of the animal; all the ovisacs were more or less flattened and
fitted together like mosaic; some of them contained eggs, some of them halfdeveloped, others

oD

quite developed larvee.

28. Spheronella modesta n. sp.
(PIX, fig. 2a—2i).

FEMALE. It always seems to be longer than broad, ovate, and a specimen which
had laid numerous ovisacs, was 1:23 mm. long and °87 mm. broad (fig. 2a). The head is
small, well defined from the trunk. The frontal border rather considerably produced; its
margin naked and centrally a little emarginate; close behind this margin on the lower side is an
odd, tolerably good-sized square area (fig. 2d, x) with rounded comers; the area seems to
be pierced with rather numerous holes. Antennule pretty long and powerful, 3-jointed,
with some sete of medium length. Antenne wanting. Principal branches of the maxillule
rather short, additional branch long. Basal joint of the maxille large and smooth; a number
of taps are seen on the distal part of the commecting membrane between the first and the
second joint; second and third joints separated. Maxillipeds good-sized, their basal joint has
several rather short transverse rows of very fine, short hairs, second and third joints separated ;
the last joint terminates in a point inside which it has some spines; the spine at the end
of the third joint shorter than in S. decorata, but of a similar shape and equipment. Sub-
median skeleton well developed, with three pairs of longitudinal lists, parts of which are
rather broad, inside the maxilla; no eminence behind the base of the maxillipeds. The
lateral margin of the head has a row of short hairs. In one specimen the trunk is quite
naked, in another it has a number of simple, moderately long hairs which are partly arranged
in rows on a minor area behind the head. Genital area smaller than the head (fig. 2 a),
much broader than, or about twice as broad as. long (fig.2e); it is a chitinised, somewhat
irregular and, according to the individuals, somewhat differently shaped plate with a cen-
trally inflexed posterior margin; the genital apertures oblique and considerably curved,

20

154

not very far apart, and their hindmost extremity pretty close to the posterior margin of
the plate; the plate is naked but for very few hairs between the anterior part of the genital
apertures. The caudal stylets, situated close together and near the posterior margin of the
plate, are very peculiar: each stylet consisting of a rather short, but thick joint, on the
inner posterior angle of which is articulated a »joint« twice as long, but scarcely half as thick,
which must be explained as a transformed seta, outside which are seen one or two simple sete.

MALE. It is of medium size compared with the female (fig. 2b: fig. 2a); a good-
sized specimen is 28mm. long and ‘22 mm. broad. Seen from below, its broadest dimension
appears far towards the front, off the maxilla, and seen laterally, it is unusually thick.
The head — considered as extending to the limit of the hair-covered part — is considerably
smaller than the trunk (fig.2h). The frontal border but slightly produced; it has five inci-
sions, and six small lobes (fig. 2g), each of which is twice as broad as one of the lateral
incisions, and their slightly curved terminal margin is furnished with a row of fine,
spine-shaped processes. Antennule 3-jointed, scarcely of medium length, with tolerably short
sete. Antenne wanting (fig. 2f). The mouth-border provided with long hairs, considerably
longer than in the female. Maxille of medium size, their basal joint bearing some normal
hairs at the margin of the distal connecting membrane, second and third joints scarcely
separated from each other. Basal joint of the maxillipeds rather long, at its base a small
area with minute prickles, and at its distal end a few hairs; the other joints as in the
female. The sub-median skeleton possesses the two first pairs of processes; the first pair
are removed further backward than usual, and a little overlapping the base of the maxilli-
peds, they appear as pretty good-sized, somewhat protuberant, thick cones; the second pair
are all but rudimentary. The ear-shaped stripe surrounding the base of the antennula is
provided with long hairs, the short lateral margin of the head with moderately long hairs,
and from its posterior extremity to off, or a litte behind, the base of the maxilla the anterior
limit of the hair-covered part runs obliquely forward and upward along the side of the
animal (fig.2h), then curves very slightly and continues in a straighter line across the back;
the result is that the naked part of the body becomes unusually small, compared with the
remainder. The median part of the ventral side of the trunk, in front of the caudal stylets,
has an extremely close covering of fine hairs of medium length; the remainder of the ventral
surface, as well as the sides and the back up to the boundary of the hair-coat are closely
covered all over with pretty coarse, tolerably long, or long hairs, and each of these proceeds
from a distinct little knot; rather frequently, though by no means always, the long hair
seems to proceed from the centre, and a much shorter one from each end of such a knot,
but the denseness of the covering renders a close examination exceedingly difficult and
uncertain. The first pair of trunk-legs consist of a relatively small basal part, from which
proceeds a single, short, almost cylindrical branch without terminal seta. The second pair
are so small and so much hidden in the dense hair-coat, that I have been unable to discern

with certainty more than a single tap, which is shorter than the surrounding hairs. The

155

caudal stylets are found at a considerable distance from the posterior margin of the trunk;
they are comparatively large and nearly of a similar structure to those of the female, only
I have not been able to find any ordinary seta beside the one which is shaped like a joint.

OVISACS. They are small (fig. 2c), nearly round, frequently somewhat flattened,
with but few eggs, but then again as many as twenty-eight ovisacs may be found with one
female. The longest diameter of one of the ovisacs represented (containing eggs) is ‘42 mm.
The eggs of about medium size.

LARVA. The specimens examined, of which the one partly represented in fig. 2i
had a total length of -23mm., were pulled out of the egg-membranes, so the shape of their
body in a free state camot be determined with absolute certainty, however, their cephalo-
thorax seems to be comparatively somewhat shorter and broader than that of the preceding
species, and to agree more with S. dispar. The larva is easily distinguished from all the
other species by having no processes whatever on its front, instead of which, however, we
find half its surface occupied by three pairs of transverse, partly curved, outwardly connected
lists. In many specimens, e. g. the one figured, the olfactory seta of the antennule is
remarkably short, not half the length of the cephalothorax, whereas in other specimens I
have found it reaching to the natatory legs (this difference is inexplicable to me). Antenne
much as in the preceding species, except, indeed, that the broad basal part consists of two
pretty distinctly separated joints, the first of which is short; so the antenna is 4-jointed.
Maxillule much as in S. decorata. First joint of the maxille as in the preceding species,
second joint with some fine hairs on the ventral side of the distal end; third joint sometimes
as in S. decorata, but most frequently with three processes on the inner side, and then the
curved end of the joint itself is generally shorter than the most distal of the processes.
Abdomen as in S. decorata.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Fudorella emarginata (Ky.) from Denmark. In a
large material I have found altogether seven infested specimens. The following statistics
‘an be given. In one specimen were found: one shrunk female, three males and thirteen
mutually adhering ovisacs, most of them with eggs, some of them with Nawplii; in another
specimen occurred: one good-sized female, one male and twenty-two mutually adhering ovisacs,
a few of which contained developed larve. In a third specimen the female and the ovisacs
together formed an oblong lump; the female, which was good-sized, was so closely surrounded
by the considerably flattened, mutually pretty firmly adhering ovisacs, that only a very small
part of it was visible on the side turning towards the ventral surface of the host; of
ovisacs I found twenty-eight, some of which contained eggs, most of them brood in different
stages, but in hardly any of them were the larve ready to burst the egg-membrane; a single
male was attached to the outside of the lump.

REMARKS. In the structure of the caudal stylets in both sexes, and in the frontal
area of the female, this parasite differs from all other species.

20°

156

29. Sphzronella dispar n. sp.
(PL. IX, fig. 3a—3k)

FEMALE. A large specimen (fig. 3d)') which had only laid three ovisacs was
‘69 mm. long and ‘79mm. broad, thus being broader than long; two other specimens without
ovisacs were of the same shape and size, whereas a fourth specimen (fig. 3a), which had laid
about a score of ovisacs, was much smaller, 49 mm. in length and ‘38mm. in breadth, thus
being longer than broad. The head is not defined from the trunk at all, and the area
bearing the mouth-appendages is surrounded by asoft membrane; the usual chitinised parts, suchas
frontal border and lateral borders, are altogether wanting (fig. 3f). Antennulz short, 2-jointed,
with about three pretty short sete. Antenne wanting. The sete of the mouth-border I
have not been able to discern with certainty. Maxillule small, with tolerably short prin-
cipal branches, and additional branch wanting. Basal joint of the maxille smooth; the
connecting membrane between the first and the second joint without chitinous taps; second
joint distinctly separated from the third, which is comparatively long and slender, and termi-
nates in a few fine setaceous branches. Maxillipeds of medium size, but appear to be weak;
the basal joint being provided on its anterior side with several irregular rows of very short
and fine hairs; second and third joints fused into one rather clumsy jot with a somewhat
sinuous outline, the distal spine being a little broader than in the preceding species; the
last joint terminates bluntly and its end is surrounded by a row of numerous, very short
and fine setee. The sub-median skeleton is much reduced. The trunk is naked. The genital
area is rather small (fig. 3d), much broader than long (fig. 3g); the solid chitine forms a
kind of semi-circle which opens towards the front, its sides are narrow, and its posterior
part broad. Genital apertures comparatively large, much curved, anteriorly parallel, and
not far apart, the space between them solidly chitinised. The whole area naked; caudal
stylets wanting.

MALE. It is middle-sized or pretty large in proportion to the female (fig. 3b:
fig. 3d and fig. 5a); its length is ‘21mm. to -22mm. Seen from below (fig. 3h), its outline
comes Close to that of S. decorata, but its front is very different. Head and trunk of about
equal size. The front much produced, its lateral margins converging strongly a long way,
till the distance between them is a little shorter than the diameter of the mouth, after which
their anterior extremity expands into a disk, which is a little Jarger than the mouth, and
thus is situated on a short peduncle. The larger part of the free margin of the disk is
furnished with a row of slender, almost setaceous processes, and on the ventral surface of the
disk, towards its base, we see a small chitinous ring; on its inner side this ring is provided
with four expansions, which turn towards its centre and constitute the surrounding of a

1) The mouth-appendages (as is partly shown in the drawing) were placed in an abnormal position
by pressure,

157

cross-shaped very small area. Close behind the peduncle of the disk, the lateral margin of
the elongated front is provided with a low. longitudinal keel (fig. 3h, y), which bears a row
of rather short setaceous processes. The antennule are short, without distinct articulation,
very sinuous in outline, and most sparingly provided with set; one of these is a peculiar
olfactory seta, placed at some distance from the apex, on the posterior side. Antenne
wanting. Mouth-border rather narrow. Maxillule somewhat larger than in the female ,
without additional branch. Maxille small and constructed like those of the female, except
the third joint, which is pointed. Basal joint of the maxillipeds long and somewhat slender,
on their anterior side proximally decorated with areas and rows, partly of minute prickles,
partly of very short hairs, distally provided with several transverse rows of somewhat longer
hairs; second and third joints coalescent, last joint essentially as in the female. The sub-
median skeleton with the two first pairs of processes conspicuous; the first pair (i) of medium
size, triangular and situated a little behind the base of the maxillse; the second pair (j), which
are placed inside the base of the maxillipeds, are moderately long, shaped like narrow cones
and strongly diverging. The lateral margin of the head essentially like that of the species
which live typically on Amphipoda; in its whole length, from a point somewhat in front of
the base of the antennula, furnished with long hairs; off the base of the maxilla, and before
reaching the posterior end of the lateral margin, the outline of the hair-coat runs upward
and slightly forward on the side of the animal till, on the middle of the side, it turns
backward, then again continuing straight upward across the back, in a line with the posterior
end of the lateral margin (fig. 3i). Sides and back of the trunk closely covered with
proportionally long hairs; the central and posterior part of the ventral surface covered with
hairs of medium length, while basally, and for a part, sub-laterally, it is quite or almost
naked. Trunk-legs and caudal stylets altogether wanting.

OVISACS. They are middle-sized in proportion to the females, but here I have
met with the peculiar fact that the smaller ovisacs with few eggs, represented in fig. 3e,
have been laid by the small female drawn in fig. 3a, whereas the larger ovisacs, each
containing several more eggs, enlarged on the same scale and represented in fig. 3e, have
been laid by the large female drawn in fig. 3d. The eggs are comparatively large.

LARVA. A free specimen (fig. 3k) is °2]1mm. in length. The cephalothorax is an
oblong oval (the length in proportion to the breadth is as 13:8). It can be distinguished
from the other species by the decoration of its front: there are no naked lists, but from one
antennula to the other, with only a very short central interruption, runs a transverse curve
of fine processes; on the sub-median part of the front the anterior ends of the processes
are decidedly a little removed from the frontal margin. whereas in the more lateral part,
they almost reach the margin, and this is due to a break in the transverse curve just in
the middle between the median line and each antennula, so that the sub-median processes
recede a little. The olfactory seta of the antennule is extremely long, nearly as long as
the cephalothorax and, when turned backward, reaching the middle of the abdomen. Antenne

158

much like those of the preceding species, only the penultimate joint and the long terminal
seta are comparatively a little shorter. Maxillule as in the preceding species. Basal joint
of the maxilla as in S. decorata, second joint distally provided with a number of tolerably
long, stiff sete, third joint has at its inner margin four processes, the outermost of which
is much longer than the others and conspicuously longer than the curved end of the joint.
Abdomen as in the two preceding species; the sete of the caudal stylets somewhat exceeding
half the length of the body.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Ladorella trancatula (Sp. Bate) from Denmark. In
a Jarge material I found only four infested specimens; one of them has no special locality,
whereas the three others were taken in the Kattegat on the cruises of the »Hauch«, two of
them at Stat. 383 (fourteen fathoms), the third at Stat. 387 (seventeen fathoms). In one
specimen (from Stat. 387) occurred: only one female and one male; in another (from Stat. 383):
one female, two larve (intruders) and about twenty-four of the host’s own eggs; in a third
specimen (from Stat. 383) were detected: one female, one male, three mutually adhering ovisacs
and one of the host's own eggs. In the fourth specimen were discovered: an oblong lump
consisting of about a score of firmly adhering ovisacs, partly covering a female which was
lying towards the front, further: a male and a disturbed ovisac, the larva of which were
breaking out.

30. Sphzronella insignis n. sp.
(Pl. IX, fig. 4a—4g; pl. X. fig. la—ih.)

To begin with, I will observe that I have assigned to this species specimens from
two species of the genus Diastylis, viz. D. levis Norm. and D. cornuta Boeck. However,
from each of these species I possess only one female, one male and some full-grown larve.
To the differences between the two females I can attribute no value, and the differences
between the two males from the two species of hosts are not greater than those which I
have found in other forms of the family between specimens taken on the same species of
hosts; between the larvee there is no difference. However, in order to present the deviations
found, I give three double sets of figures, and point out the differences in the corresponding
text; but, in spite of the scantiness of my material, I really do not doubt that it is the
same parasite which lives in both species of hosts.

FEMALE. A specimen (from D. lavis) was 1:16 mm. long, ‘88mm. broad (fig. +a),
and somewhat flattened. The head is not defined from the trunk, and it agrees very closely
(fig. 4c) in all details with the preceding species. The antennule (fig. 4¢ from D. levis,
fig. 4f from D. cornuta) scarcely offer any characteristic, and the same remark applies to
the mouth. The branches of the maxillule, at least in the specimen from D. levis, is some-
what longer than in S. dispar; additional branch wanting. The maxille a little smaller

159

than in the former species. The last joint of the maxillipeds and the terminal spine on the
penultimate joint in the specimen from D. levis are not very different from S. dispar, and
distally much less expanded than in the specimen from D. cornuta (fig. 42), but this difference
is scarcely of any value. The trunk is naked. The genital area, in both specimens, is a
rather small, transverse plate of irregular shape, and for the most part very thin, which, in
the specimen from D. cornuta (fig.4e) is about twice as broad as long, on the whole remin-
ding of a rectangle; in the specimen from D. /@vis (fig. 4d) it is comparatively a good deal
longer, somewhat heart-shaped, having a concave front margin, and an irregular, lobed
posterior margin; in both specimens the genital apertures are middle-sized, somewhat oblique
and curved, anteriorly not far apart; the area is naked, caudal stylets wanting. (The
differences in the shape of the genital areas are indeed very considerable, but in both spe-
cimens the plate is so irregularly shaped, so unsymmetrical and so feebly chitinised, that I
do not think its shape is of any importance; on the contrary, I expect that other specimens
of this species will exhibit other shapes of the plate.

MALE. In proportion to the female, it almost exceeds medium size (fig. 4b : fig. 4a);
the specimen from D. levis (fig. 4b and fig. la—1b) is -29 mm. long, the one from D. cornuta
(fig. le—1d) -31mm. long. The specimen from D. levis is — seen from the side (fig. La)
— considerably thicker than the other specimen (fig. 1d), however, this thickness seems to
be due to a swelling of the body which is scarcely normal. Otherwise there are no other
differences between the two specimens than those which may be detected in comparing
fig. 1 b and fig. 1 ¢. viz. some slight deviations in the anterior part of the front and in the
hai-covering in front of the antennule. -— Seen from below, it bears great resemblance to
S. dispar, but the greatest breadth of the body lies more backward, and it deviates especially
in the somewhat different shape of the front, and in the equipment of the maxille and of
the sub-median skeleton. The distance from the antennule to the narrowest part of the
frontal plate is shorter than in S. dispar; the expanded distal part is not circular, but
considerably broader than long, limited to the front by a regular arc, the third of a circle,
and decorated with processes as in S. dispar; the lateral angles are almost rectangular,
and posteriorly the dilated part is limited by oblique lines. From the base of this expansion,
backward along the lateral margin itself, runs a pretty good-sized keel (fig. 1b, y), which is
also limited by an are of a circle, and which is armed with setaceous processes similar to those
of the median expansion. In the middle of the ventral side of the expansion we find the
small chitinous ring mentioned in the description of S. dispar, but in S. insignis the four
processes are prolonged and meet in the centre so as to form a cross within the ring.
Antennulee, mouth and maxillule nearly as in S. dispar. Maxille small; their basal joint
has on its posterior side proximally a row of tolerably small, rather clumsy, processes
directed backward, distally some much smaller processes; the third joint is well set off and
acute. Basal joint of the maxillipeds scarcely as long as in S. dispar, its anterior side
furnished with several rows of hairs; the other joimts nearly as in the preceding species.

160

The sub-median skeleton without processes, but the part obliquely inside and behind the
base of the maxillze is covered with pretty numerous sete. Shape and hair-covering of the
lateral margin of the head nearly as in S. dispar; from its posterior extremity the boundary
of the hairy part proceeds at first vertically upward across the side of the animal, then
somewhat obliquely backward across the back. The back and sides of the trunk and the
posterior part of the ventral surface are closely covered with rather long hairs, nearly all
the remainder of the ventral side has hairs of medium length. Trunk-legs and caudal
stylets wanting.

OVISACS. In D. levis they were small, almost globular, with few eggs; in D.
cornuta they differed considerably in size, from rather small to middle-sized, and were irregular
on account of mutual pressure. Eges of medium size.

LARVA. There is no appreciable difference between the larve found in D. levis
and in D. cornuta. A well-developed free larva from D. cornuta is 20 mm. long and has
served as type for fig. le—lg. It bears great resemblance to S. dispar, but is sharply
distinguished by several characters. The cephalothorax like that of the last-mentioned
species. The decoration of the front is very characteristic (fig. 1f): a transverse list is found
inside the base of the antennule; further, a sinuate transverse series of processes, with a
broad central interruption, runs from one antennula to the other; the inner half of this
series begins far behind the frontal margin, below the anterior side of the rostrum, thence
it continues in an oblique direction running forward and outward towards the margin,
consisting only of five or six longer processes; then comes a little break in the row, the
next process being somewhat further removed from the frontal margin, after which the row
is continued to the anterior angle of the antennula, but in its latter part the processes are
shorter than the sub-median ones. The olfactory seta of the antennule is even longer than
in S. dispar, as, when bent backward, it may reach as far as the posterior end of the
second abdominal segment. Antenne and maxillule as in the preceding species. Second
joint of the maxilla without sete (fig. 1g), third joint with three or four processes on its
inner margin, the outermost of which is longer than the curved extremity of the joint, but
scarcely longer, at least not considerably so, than the penultimate process. The abdomen
and its sete as in the preceding species.

POST-LARVAL DEVELOPMENT. In D. cornuta a single pupa was found (fig. 1h),
which is ‘14mm. in length and sub-globular. It is described in detail above on p. 56.

HABITAT. The marsupium of Diastylis cornuta Boeck and D. levis Norm. from
Denmark. In a specimen of D. cornuta were found: an empty skin of one female, one male
and seven small ovisacs with young ones in different stages, as well as twelve free larve
and one pupa. In one specimen of D. /@vis occurred an oblong lump of adhering ovisacs
surrounding a female; they were irregularly shaped on account of pressure; on one side of
the lump the larger part of one side of the female was uncovered, and on the side turning
towards the abdomen of the host, there was a longitudinal impression in the lump, in which a

161

small part of the body of the female was visible, and a male was situated somewhat behind
it; there were at least twenty ovisacs, some of them containing eggs, most of them young
ones in very different stages of development, and one of them contained perfectly deve-
loped larve.

31. Sphzronella marginata n. sp.
(Pl. XIII, fig. 6a—6h).

FEMALE. The only specimen found (fig. 6a) was ‘58mm. long and °39 mm. broad,
oblong ovate. The head (fig. 6d) is not defined from the trunk. A frontal border is rather
feebly developed and runs in a slightly curved line from a point a little in front of one
to a little in front of the other antennula, and behind this line the skin is sunk and a
little softer than in front of it; but lateral borders and lateral skeleton are entirely wanting,
and the sub-median skeleton is reduced to a posteriorly geniculate, anteriorly ramified list
between the rostrum and the base of each maxilliped. The antennule (a) are short, with
two well separated joints, with a tolerably long seta at one angle of the first joint, a much
shorter one at the middle of this joint, and two very short sete at the end of the last
joint. Antenne wanting. Hairs of the mouth-border rather long. The maxillule have
very short principal branches; additional branch wanting. The maxillve (f) are quite rudimen-
tary, each consisting only of a very small pointed conical joint, which looks rather like a
process. Basal joint of the maxillipeds extremely swollen, especially its proximal part, which
on its inner side and on half of its anterior side is furnished with four long, straight,
transverse rows of fine, short hairs, while the distal part of its exterior side and the outer
part of its anterior side have two transverse rows of similar hairs; second and third joints
are coalescent and form together a long and very thick joint, the apical spine of which is
very broad and flattened and provided with a number of extremely fine points at its oblique
terminal margin: the last jomt is short, very broad, dilated towards the flattened end, the
oblique terminal margin of which is furnished with numerous very fine points. On the head,
a little in front of the base of each maxiliped, are seen rows and stripes of more or less
short or long hairs. The trunk is naked. The genital area (fig. Ge) is somewhat broader
than long and consists of a thin plate surrounded by a thick border, which is wanting on the
greater part of the anterior margin, and its free anterior angles are curved somewhat
inward and backward; the plate with curved lateral margins and posteriorly emarginate.
The genital apertures are very large, very close together, and their posterior extremity
nearly reaches the hind margin of the plate; moreover, they are considerably curved, and
their anterior ends are somewhat diverging, their posterior ends very much so, while their
muscles are turned obliquely outward and strongly forward. Close behind one of the genital
apertures appears a very small caudal stylet, which is furnished with a pair of yery short

21

sete; the other stylet is wanting; the whole area is naked. (In fig. 6e to the front the
two receptacula seminis are indicated by dotted lines).

MALE. The only specimen found is tolerably large in proportion to the female
(fig. Gb: fig. 6a); it is 21mm. in length, but on account of pressure it is somewhat crooked, so
that the normal shape of its body cannot be precisely determined. The frontal border is rather
considerably produced, its margin very long, somewhat emarginate in the middle and forming
on each side of this inward curve a gently convex margin, which on its upper, as well as its
lower side, is! provided with a narrow border of numerous short (in the drawing a little
too short) setaceous processes; further, across the lower side of the front a little in advance
of the rostrum, runs a long, straight, very narrow list, which almost reaches the lateral
margin, and which is armed with a series of very small conical processes. Antennule
small, terminating in a setaceous point and with only a single, moderately long seta, which
no doubt is olfactory. Antenne wanting. Mouth-border with long hairs. Anterior principal
branch of the maxillule developed only as a somewhat protruding rounded corner; the hindmost
principal branch extremely short, tap-shaped; additional branch wanting. Maxille small,
all three joints entirely fused together, with no vestige of articulation, but the general
outline of the maxilla nearly as in S. dispar, however, its distal part is very slender and
terminates in a point. Basal joint of the maxillipeds a little more than medium length, not
swollen, smooth; on its anterior side near the apex it has a large process, the basis of which
is constricted, while the remaining part forms an oval knot parallel with the outline of the
joint; second and third joints are fused into a single short joint with a short and broad
terminal seta, whereas the last joint is very short, broad and flattened, with denticulated
terminal margin. Nearly on a line with the anterior angle of the base of the maxilipeds
are seen, close to each other, two small, short, conical processes, whereas other processes
are wanting; but inside of and behind the posterior angle of the maxillipeds are found
peculiarly shaped lists. The lateral margin of the head developed as in the two preceding
species; from the base of the antennula it is furnished with rather long hairs, and from
the posterior angle of the margin, as far as I have been able to see, the boundary of the
hairy part runs upward and somewhat obliquely backward across the side and the back.
The trunk, on its back, its sides and the posterior half of its ventral surface, is covered
with long hairs; the anterior half of its ventral surface is naked. Trunk-legs and caudal
stylets wanting.

OVISACS. ‘Those that have been found are rather small (fig. 6c), yet, as each of
them contains six or seven nearly or fully developed larvie, they must be considerably larger
than when they were laid. The ovisac represented is 34 mm. in length and -27 mm. in
breadth.

LARVA. Though very similar to those of the nearest preceding species, it presents
various good characters (fig. 6g). Length of the body ab. 21mm. The cephalothorax is
an oblong oval, a little narrower than in the two last-mentioned species. The front has a

163

curved list in advance of the base of the antennula; from the margin, in front of this list,
runs a transverse series of shorter processes; finally, from the part before the rostrum,
extending outward and forward up to the anterior margin, we see an area covered with
some rows of similar processes placed close together. The olfactory seta of the antennule
extends at least far back on the second abdominal segment. The antennee differ widely from
those of the four preceding species; they are short, 2-jointed, the first joint is moderately
long and rather thick, the second joint is only half its length and ends in two set, one
of which is short, the second a little longer than the first joint. The innermost and foremost
branch of the maxillule, which e.g. in S. dispar is situated far in front of the three other
branches, in S. marginata is placed further backward, so as to be nearly at the same height
as the two branches closest to it, besides being reduced to a short process; the outermost
branch here is shorter than the two intermediate ones, and seems, moreover, to be naked.
First jot of the maxille as in the four preceding species, second joint without terminal
sete, the third one (fig. Gh) serrated, having some very fine acute processes at its inner
margin. Second joint of the maxillipeds short, third joint exceptionally long, several times
the length of the second. Abdomen comparatively somewhat smaller than in the nearest
preceding species, but the mutual dimensions between the segments are the same; the long
sete of the first segment extend pretty considerably beyond the end of the caudal stylets,
and the terminal setz of these stylets are more than half the length of the body.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Iphinoé trispinosa (Goods.) from Messina. In a
specimen which had Homocoscelis mediterranea (s. p. 97) in its branchial cavity occurred:
one female, one male and four ovisacs containing larve. This was the only specimen
infested with this parasite in the material mentioned more specially above on p. 97.

REMARKS. The most noteworthy feature in this interesting species is no doubt
that its maxilla as well as its maxillipeds differ so much in the two sexes, and at the
same time, in both sexes, especially in the female, deviate widely from these appendages
in all other hitherto known species, not only of this genus, but of the whole family.

a. Parasites on Isopoda.

In three species of Isopoda, all belonging to the group Asellota, [I have discovered
three species of the genus Spheronella. The females of two of the species show great
similarity to the normal species of the genus which live on Amphipoda, but the third species
deviates very considerably from these parasites. The only characters common to the females
of all three species are: antennz seem to be wanting; the mouth is large with a broad or
very broad mouth-border, the hairs of which are remarkably thick; the maxillule are well
developed, with long principal branches and at least very distinct additional branch; the

2\*

164

maxillee are normal, with a large, thick basal joint; the maxillipeds are 4jointed; the genital
area is plate-sshaped. The male is known only in one of the two first mentioned species,
but it differs widely from all the other males known of the family. Of the species (S. Man-
nopsidis), the female of which deviates most from the species found in Amphipoda, I have
found scarcely quite developed larve, which in the structure of antenne and maxille come
close to the species of the genus which live in Cumacea, but they differ from these parasites
in having the second joint of the maxillipeds much longer than the third, whereas the
fourth joint is armed with three spiniform processes on the distal part of the inner margin
The larva of the two other species, unfortunately, is unknown. So the knowledge of this
little group is rather defective.

Conspectus of the Females.

1. The head distinctly defined from the trunk, frontal and lateral borders well developed.
Genital apertures: obliqnezandmclosestosethermsemensn eno) c rele ene einen ene 2
1’. The head not defined from the trunk, no frontal or lateral borders. Genital apertures
transverse, comparatively far from each other ....... . 34. S. Munnopsidis n. sp.
2. The genital area is a very large plate, only a little broader than long, and the longest
dimension of the muscles of the genital apertures is shorter than the distance from
their outermost extremity to the margin of the plate... .... 32. S. curtipes n. sp.
2’. The genital area is a large plate, considerably broader than long, and the muscles of
the genital apertures are a good deal longer than the distance of their outermost
extremity from the margin of the plate............ .... od. S: Gffinis Desp:

32. Spheronella curtipes n. sp.

(Pl. X, fig. 2a —2g).

FEMALE. ‘The only specimen found (fig. 2a) is 24 mm. long, 2°2 mm. broad and
considerably flattened; anteriorly the body tapers a little. The head is well defined, but
very small, and especially very short, nearly twice as broad as long (fig. 2d). The slightly
curved frontal margin is furnished in its whole length with excessively short hairs. An-
tennulee of about medium length, 3-jomted, the terminal setae somewhat shorter than the
antennula. Antenne not found. Mouth very large, with extremely broad mouth-border.
The maxillulee have tolerably long and powerful principal branches and a good-sized additional
branch. Mavxille very large, the basal joint long and very thick, smooth. Basal joint of
the maxillipeds long and slender, bearing a few short hairs at the distal end, otherwise
naked; the three other joints slender, and the last joint provided with a single spine a
little inside its pointed end, The sub-median skeleton has a broad list inside the maxille,

165

and a transverse row of long hairs is seen in front of the base of each maxilliped; two
lists are found between head and trunk behind the maxillipeds. The lateral margin of the
head has a tolerably broad stripe of rather short hairs; this hair-covering extends upward
on the proximal part of the lateral surface of the head, besides forming a narrow transverse
belt immediately behind the head across the anterior part of the trunk. Except this hairy
belt the trunk is naked, and trunk-legs I have not been able to find. The genital area is
much larger than the head (fig. 2a) and consists of a very large round plate which is a
little broader than long (tig. 2e); the central part of the plate is more thinly chitinised
(marked in the drawing by a light greyish tint), whereas the larger part of it is thick
and light brown. The genital apertures which are situated a little in front of the centre
of the plate, are exceedingly small in proportion to its size and are found close toge-
ther; their anterior extremities run nearly parallel, further backward they diverge
considerably; their muscles are turned a little forward and strongly outward, but do not
reach half the distance to the margin of the plate. The thin part of the plate in front of
and partly outside the genital apertures is furnished with a number of short hairs, and a
considerable part of the thinner area of the plate behind the muscles has some very short
hairs; close behind the genital apertures we see the caudal stylets which are exceedingly
small, and in front of these a diminutive transverse area very Closely covered with extremely
short hairs; the remainder of the plate is naked (in the drawing one of the receptacula
seminis is indicated by a dotted line and marked r).

MALE. It is large compared with the female (fig. 2b: fig. 2a), and in reality com-
paratively very large, exceeding in size all other males of the whole family: the smaller
one of my two specimens measuring *84mm., the larger one “92mm. in length. In shape it
stands far apart from all species known. Seen from below (fig. 2f), its length is to the
breadth as 5 to 3; the animal is broadest at or a little in front of the middle, somewhat
narrower towards both flatly rounded ends; moreover, the head is much shorter than the
trunk. Off the posterior margin of the mouth the lateral border of the head is very sloping,
bending strongly outward, and more backward it forms a deep imward curve stretching poste-
riorly to a point a little outside the base of the maxille; these arched borders and the

frontal border combined form the sides of a deep cup, the posterior part of which — if it
were not wanting — would pass across the base of the maxillee; in the middle of this cup

the rostrum is situated. Seen laterally (fig. 2¢), the body is strongly curved, its ventral
side being pretty deeply concave, the dorsal outline very convex. This line, moreover, is
divided by three bends which are rather far apart and at equal distance from each other;
the foremost of these bends is on a line with the mouth, and coinciding with it at the back
the boundary of the hair-covering runs in a slightly oblique line towards the posterior angle
of the outstanding lateral border of the head, whereas from the two other dorsal bends
transverse depressions continue a good way on the lateral surface of the trunk. Finally, we
see on the hindmost half of the ventral side of the trunk a large, but not very thick, flatly

166

vaulted, almost square protuherance, which in a lateral view of the trunk makes it appear
very different from other species. The frontal border is considerably produced, the larger
median part of the margin is slightly curved, naked, separated by a rather deep incision
from a lower, evenly rounded lohe which extends to the angle close in front of the base of
the antennula; this lobe is much thinner than the remainder of the frontal border and
supplied with very short marginal hairs. The antennule are moderately short, 3-jointed,
with short sete. The antennz are very short, probably only 1-jointed, with a short seta.
The mouth rather large, the mouth-border of medium breadth. Maxillule normal, with a
long additional branch. The basal joint of the maxilla is small and smooth, the two
following joints (as in most other species) are coalescent. Maxillipeds fairly small, with the
normal proportion between the joints; the basal joint is slender, provided on the anterior side
with some hairs at both ends; the last joint is sligthly digitated at its end. The sub-median
skeleton has two pairs of processes, the first pair robust, the second pair rather short
and strongly diverging; the part between the maxille and the maxillipeds is furnished with
numerous moderately short hairs. The above-mentioned boundary of the hair-covering between
the head and the trunk has a pretty narrow belt of rather short hairs and dorsally of hairs
of medium length; the back, the sides and the posterior end of the trunk are furnished with
extremely short hairs, and this covering reaches ventrally to the second pair of legs and
to the protuberance on the posterior half of the trunk; the anterior ventral half is naked,
except a pretty good-sized transverse area stretching from the first pair of legs to the
lateral margin which is furnished with rather short hairs, and finally, the protuberance
is covered nearly all over with pretty similar hairs. The trunk-legs very small, each
consisting of two generally somewhat oblong joints of about equal size and ending in one
or two sete which are of the same length or a little shorter than the leg. Each of the
posterior angles of the afore-mentioned protruding ventral part is produced into several
rather short, usually rounded eminences and processes, some of which are very thick, others
fairly slender; the stoutest of them bears a single pretty long, thick seta, and on the po-
sterior part of the protuberance, closely inside of the innermost eminence of the posterior
angles, we find a short, oblong caudal stylet jointed on; the two stylets accordingly being
very far apart. (Spermatothece: appear underneath the foremost third of the protuberance).

OVISACS. They are middle-sized, shortly ovate (fig. 2c) or sub-globular, but slightly
differing in size; the largest specimen is 1°6mm., the smallest 1°3mm. in length. The eggs
comparatively small and numerous.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Janira spinosa Harg. from the Davis Straits at
lat. 66° 32 N., long. 55° 34‘ W., 100 fathoms; Th. Holm °/vi 1884. In a specimen
occurred: one female, two males and twelve ovisacs, two of them with eggs and two with
Nauplii.

167

33. Spheronella affinis n. sp.
(PI. X, fig. 3a—34.)

FEMALE. The only specimen in hand is ‘87 mm. long, *90 mm. broad, and its
thickness is about #/1 of its breadth; seen from below (fig. 3a), it is posteriorly broad and
flatly rounded, anteriorly somewhat produced, and its lateral outline a little concave at some
distance from the head. The head is small, well defined, somewhat broader than long (fig. 3)
and thus considerably narrower than in S. curtipes. The frontal margin curves strongly
forward and is naked. Antennule, maxillule and maxillipeds exactly like those of the pre-
ceding species, whereas the mouth-border is a little narrower. Basal joint of the maxille a
little less clumsy, with two tolerably small processes situated at some distance from each
other where the inner and lower sides meet. The sub-median skeleton has a narrow list
inside the maxille, and behind their base a transverse stripe of long hairs (drawn only on
one side in the figure). The lateral margin of the head has a rather narrow stripe of
tolerably short hairs, and this covering does not continue upward on the lateral surface of
the head. Somewhat more than the anterior half of the trunk is furnished with short hairs;
trunk-legs are wanting. Genital area much larger than the head (fig. 3a), consisting of a
fairly solid, yellowish, centrally somewhat thinner and lighter plate (fig. 3d), which is con-
siderably broader than long, rounded; its anterior margin is almost straight. its posterior
margin convex; a little behind the middle the proportionally very small genital apertures
are situated close together, their muscles turning outward and a little forward and reaching
beyond half the distance towards the margin of the plate. The area is naked, except the
part between the genital apertures, which is provided with a number of short hairs; caudal
stylets [ have not been able to find. (Fig. 3d. shows a fragment of the stalk of a sperma-
tophore and the outlines of both receptacula seminis.)

MALE. Unknown.

OVISACS. With a female occurred six ovisacs mutually glued together, all of
them short and broad, somewhat angular, the largest a little flattened; none of them con-
tained advanced larve. They differed very much in size, the largest being *77 mm. in length,
the specimen drawn (fig. 3b) 63mm. long and broad, the smallest 47mm. long. The eggs
numerous and tolerably small.

LARVA and POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Janira maculosa Leach from Herd, Norway. Prof.
G.O. Sars discovered a single infested specimen and lent it me; I found one female, the
posterior half of which was surrounded by six ovisacs mutually glued together. The parasite
was lying with its head turned obliquely forward and somewhat sideways. — An examination
of our pretty considerable material of this Isopod from Greenland and Denmark gave a
negative result.

168

34. Spheronella Munnopsidis n. sp.
(Pl. X, fig. 4a—4d.)

FEMALE. The only specimen found was torn and half empty; it was ab. 5 mm.
in length and a little shorter than broad. The head is very small and not separated from
the trunk at all; frontal and lateral borders are altogether wanting, whereas the sub-median
skeleton is developed into a single, good-sized, solid plate, to which the maxilla and maxilli-
peds are articulated (fig. 4b). Antennule rather short, not distinctly jointed, but the length
of the first joint is easily seen, as its distal anterior angle protrudes in the usual way and
is furnished with setz which, however, are short; the sete on the distal part of the
antennule are scarcely of medium length. Antenne are wanting. The mouth is good-sized
and the mouth-border broad. The principal branches of the maxillule are pretty long, the
additional branch a little shorter. The maxilla are good-sized; their basal joint smooth,
supplied with two rows of short, thick, blunt sete or small processes along the inner margin
of the skin that connects it with the second joint. Basal joint of the maxillipeds of medium
length; on the inner side of its distal half are two areas of extremely short hairs; second
joint of normal length, somewhat dilated towards its distal end, on the inner side of which
are seen some minute hairs; third joint short and clumsy; in the left maxilliped it has at
its distal inner angle a short and very broad, rounded spine which is furnished with
exceedingly short hairs; in the right maxilliped this spine is wanting, but the joint is still
shorter and broader, and its inner margin is hairy; in the left maxilliped the fourth joint is
tolerably short and hairy along the rounded end, in the right maxilliped excessively short
and hairy along both margins. Sub-median skeleton quite naked. Trunk naked; trunk-legs
wanting. Genital area somewhat larger than the part occupied by the mouth-appendages;
it consists of a transverse plate which is a little more than twice as broad as long, fairly
rectangular, but the outline is irregularly sinuate; properly speaking, this plate consists of
a moderately broad ring of thick yellow chitine surrounding a thinner light area, which,
however, is somewhat more solidly chitinised than the skin which surrounds the ring. The
genital apertures are situated comparatively far apart, each at one end of the thinner area
and on its posterior margin; their distance from each other somewhat exceeds the length of
each; their direction is almost rectangular to the longitudinal axis of the animal, so that
their muscles are turned nearly straight in adyance parallel with the axis, and their hindmost
lip is strongly curved. Somewhat in front of each genital aperture we see at the posterior
margin of the foremost transverse list of the frame a circular hole (k), which is no doubt
the orifice of a gland which otherwise I have been able to detect only in Mysidion abys-
sorum and in Aspidoecia. Only one of the receptacula seminis (r) is shown in the drawing,
but to the orifice of each receptaculum is fixed a spermatophore, one of which (s) is well

preserved, whereas of the other (s') only the stalk is left. These orifices are situated

169

obliquely in front of and at some distance from the genital apertures and somewhat closer
to the median line than the apertures. The whole genital area is naked. Caudal stylets
are wanting.

MALE. Unknown.

OVISACS. They differ widely in size, as fig. 4a shows; in the marsupium repre-
sented occurred twenty ovisacs, which are irregularly shaped and angular on account. of
mutual pressure, and the largest of them which contains halfdeveloped young ones, is
2°73 mm. in length and 1°74 mm. in breadth, the smallest ab. ‘92 mm. long and °75 mm.
broad. In another specimen the ovisacs are oval or sub-globular.

LARVA. None of the ovisacs contained fully developed larvee. I took some larvee
out of the ovisac which contained the most advanced specimens and prepared them out of
their membranes, so that I succeeded in giving a representation (fig. 4d) of several of the
most important appendages, but about the final shape of the larva etc. no detailed account
can be given. The front has no decoration, at most a small list inside the anterior angle
of the antennule. The olfactory seta of the antennula is tolerably short, may be about half
the length of the cephalothorax. The antennze of medium length, 4-jointed, the two first
joints broad, the third one slender, longer than the second, the fourth joint short, and its
longest terminal seta shorter than the tbird joint. The mouth-border exceptionally broad
with distinct, thick hairs. The basal joint of the maxille has two dense combs of fine
processes (one of which is not visible in the drawing), second joint is slender, third joint has
some spines on its inner margin. Second joint of the maxillipeds much longer than the
third; the fourth joint has three conspicuous, slender and spiniform processes at the distal
part of its immer margin. The abdomen of less than medium size; its first segment almost
longer and somewhat broader than the second one, and its long spines reach far beyond the
caudal stylets, which are distinctly set off from the small third segment. The setz of these
stylets seem to be proportionally pretty short.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Munnopsis typica M. Sars from the Kara Sea.
Fig. 4a represents the greater part of a large specimen of the host, in which the ovisacs of
the parasite are visible through the diaphanous plates of the marsupium. The marsupium
was pretty strongly extended, it contained twenty ovisacs, partly with eggs, partly with
Nauplii or with more developed larv, but — as stated above — none of these was ready
to swim out; the above described female was lying against the ventral side of the host towards
its anterior end. In a smaller specimen were discovered nine ovisacs; the female and some
sacs had evidently been washed out.

170

IV. Choniostoma #. J. H. (1886).

FEMALE. The body is somewhat flattened; seen from below, it is broader than
long, nearly pentagonal, with rounded angles, one of which forms the centre of the posterior
margin, and two on each side, whereas the anterior margin forms but a slight curve and
is longer than the distance between the lateral angles on each side, and between the
hindmost lateral angle and the posterior central angle. The head is situated on the
ventral side a little behind its anterior margin, and the skeleton is transformed into a
transverse ring-shaped frame which is considerably broader than long, and the anterior part
of the frame, which forms the frontal border, may sometimes rise a little above the skin in
front of it, whereas the remainder, or sometimes the whole frame, is on a level with the
ventral plane. The frame surrounds a good-sized, thin-skinned area, in or a little behind the
middle of which the rostrum and the mouth-appendages are found. The antennule are nor-
mal, 3-jointed and inserted on the rg. The antenne are certainly 3-jointed and furnished
with a terminal seta. The mouth is good-sized, the mouth-border of about average breadth.
Maxillule well developed, with a long additional branch. Maxille powerful, constructed as
in the typical species of Spheronella. Maxillipeds rudimentary, each consisting of two very
small or quite diminutive joints. Trunk-legs and caudal stylets — where such are found —
as in Spheronella. The genital area is more than twice as broad as it is long; the thickest
chitine is found in the middle and along the lateral margins; the genital apertures are
situated close together in the middle of the area, and close in front of them appear the
orifices of the long sausage-shaped receptacula seminis, which are turned obliquely forward
and outward. — No spermatophores have been observed.

MALE. Unknown.

OVISACS. They are always deposed freely, their shape is sub-globular, and as
many as eleven or twelve may be found in one female. Hach ovisac contains an exceedingly
great number, on an average at least one thousand, minute eggs (comp. my figures p. 47).

LARVA. Is known of both species and is quite similar in structure to the larve
of some of the species of Spheronella living in Amphipoda; the only differences are, that
the cephalothorax is shorter and broader, and the spiniform sete at the posterior angles
of the first abdominal segment longer, and especially thicker, than in any Spheronella
known to me.

POST-LARVAL DEVELOPMENT. ‘The pup found are described in detail above
Die

HABITAT. The branchial cavity of two species of the genus Hippolyte Leach
belonging to the order Decapoda, and the presence of the parasite causes the part of the
carapace which is situated above the intruder and its ovisacs to vault strongly, so as to
form a large swelling, which as a rule is exactly similar to that caused by Gyge Hippolytes

on p. 56

171

(Kr.). Hitherto found only in the Kara Sea, the Murman Sea, near Tromsé (Norway) and
off the West-coast of Greenland, and the genus has been found only on Hipp. Gaimardii
M.-Edw. and Hipp. polaris (Sab.).

REMARKS. The genus contains only two species. As, in spite of the most careful
investigation, the male has not been found, our knowledge is defective in an important point.
Judging from the structure of the female, the ovisacs, the larva and the pupa, the genus
comes very near to Spheronella, and the only really good character appears to me to be
the rudimentary maxillipeds of the female. A biologically important character is that — as
stated above — it lives in the branchial cavity of Decapoda Caridea, as the genus Homoeo-
scelis lives in the branchial cavity of Cumacea.

Conspectus of the Females.

The frame of the head is an almost regularly transverse oval and provided exteriorly on
each side with a very long list which proceeds from the centre of the lateral outline and runs
outward, and especially backward, in an oblique direction. .... . 1. Ch. mirabile H. J. H.

In the frame of the head the foremost lateral angle is strongly produced, forming a
good-sized, fairly broad and not quite short projection, a large part of which is covered by
the skin, whereas the very long lateral, essentially backward running list mentioned in the
preceding species is wanting... . 2. Ch. Hansenii Giard and Bonnier (without description).

|. Choniostoma mirabile H. J. H.
(PI. X, fig. 5a—5e; pl. XI, fig. 1a—1k.)
Choniostoma mirabile H, J. Hansen, Dijmphna-Togtets zool.-bot. Udbytte, 1887+), p.271—78, Tab. XXIV,
fig. 7—7h.

— — Guard and Bonnier, Bull. scient. de la France et de la Belgique, T. XX, 1889, p.346, etc.
— — Giard and Bonnier, Bull. scient. de laFr. et d. |. Belg. T. XXV, 1895, p. 479.

FEMALE. The specimen represented in fig. 5a is 35 mm. in length, 4 mm. in
breadth; its shape is described in the diagnosis of the genus. The smallest specimen found
is a young one, 1°35 mm. long and 1-28 mm. broad, thus a little longer than broad, almost
circular in appearance, and somewhat flattened like the adult. The area surrounded by the
frame of the head (fig. 1a) is regularly rounded, somewhat shorter than broad; the anterior
part of the frame is fairly narrow between the antennule, scarcely rising above the surrown-
ding soft membrane and exhibiting outwardly only a very narrow list, while its broader
part (indicated by a dotted line) is covered by the skin. The lateral and posterior parts of

1) Separate copies of my contribution were distributed in the beginning of July 1886, whereas the whole
volume with the résumé appeared in 1887.

22*

172

the almost regularly oval transverse frame are fairly broad, and from the centre of the
lateral outline proceeds a very long solidly chitinised list (k’) outward, and especially back-
ward, in an, oblique direction; its proximal part is pretty broad, and its hindmost extremity
extends even a little beyond the posterior margin of the frame. Inside the acute angles
formed at the origin of the lists, and at the points where the curved lateral margins of the
frame meet the almost straight posterior margin, we perceive thick solid parts (k”) which,
as lying beneath the skin, in this as in the following species are indicated by dotted lines,
and outside the frame by a light shade. In the soft membrane between the anterior part of
the frame and the rostrum appear two small, oval, tolerably solid chitinous rings (t) situated
rather far from each other, and each surrounding a very small area; obliquely in front of
them, and somewhat closer together, are two smaller and feebler, almost circular rings (u).
The antennule (a) are short, with sete of nearly medium length, among which is a single
sensory seta (b). Antenne (c) of almost average length; they seem to be 3-jointed, having
an exceedingly short basal joint, whereas the two next joints are well developed, the termi-
nal seta being of the same length as, or longer than the last joint. Mouth-border of medium
breadth. Maxilles middle-sized; basal joint smooth. Maxillipeds (¢) quite rudimentary
and difficult to detect, each consisting of two diminutive joints, the last of which is pointed.
The sub-median skeleton (h) forms on each side, obliquely inside and partly behind the
maxilla, a plate which is pierced with a hole and divided by incisions into irregular lobes.
The head is naked all over. The trunk is naked in the adults as well as in the above-
mentioned very young specimen; the latter has small trunk-legs, whereas I have not been
able to discover these appendages in the large specimens. The genital area (fig. 1b) has
very oblique and anteriorly strongly converging lateral margins; one of the receptacula seminis
(r) is represented in the drawing.

MALE. Unknown.

OVISACS. They are scarcely middle-sized (fig. 5b and 5c : fig. 5a), sub-globular,
with slight difference in size where the contents are equally developed (while fig. 5b com-
pared with fig. 5c shows the usual difference of size between an ovisac containing eggs and
another with full-grown larvee). The longest diameter in the ovisac shown in the drawing
fig. 5b, is 18mm. As many as twelve ovisacs may be found in one female. The eggs are
relatively extremely small and excessively numerous.

LARVA. The specimen represented in fig. le is °24mm. long, but, as it was hinged
to a gill (by the adhesive plate s) in order to undergo its metamorphosis, the cephalothorax
is somewhat shorter and broader than in a specimen, which has not yet hinged itself (and
the third joint of the maxille is bent forward); fig. 1f shows the front part of a larva pre-
pared out of an ovisac. As I have met with no larva about to swim out, or with one which
had just entered the branchial cavity of a new host, I am unable to determine the shape of
the cephalothorax in the free larva with absolute certainty, however, it seems to be some-
what broader than in any other of the larvee I have observed, and not much longer than

173

broad. The front has a curved list inside the anterior angle of each antennula (some trans-
verse stripes shown in fig. 1f, I am unable to explain). Antennulze 3-jointed, olfactory seta
comparatively short, not half the length of the cephalothorax. Antenne a little longer than
the antennule, in all respects like those of Spher. dispar, except that the broad basal part
sometimes seems clearly to consist of two joints (fig. 1 f), while sometimes only one joint is
discernible (fig. 1e) The maxillule consist of three moderately long naked branches, which
spring from a low eminence. The joints of the maxillze are smooth, the last one seems to
end in two extremely short points. Second joint of the maxillipeds a little shorter than the
third. The peduncle of the natatory legs fairly broad. First abdominal segment somewhat
longer and considerably broader than the second, and the sets of its posterior angles twice
the length of the following segments and the caudal stylets, exceptionally thick and hairy
on their distal half; third segment much smaller than the second; the caudal stylets pretty
well defined, and their setse about °/1 the length of the cephalothorax.

POST-LARVAL DEVELOPMENT. On the gills of a Hippolyte appeared specimens
of all the transitional stages between larva and pupa, besides numerous pupz (fig. 1g—1k)
of somewhat different shape and considerable difference of size. With regard to these pupz
I refer to p. 56—57 where a detailed account of them is given.

HABITAT. The branchial cavity of Hippolyte Gaimardii M.-Edw. from the Kara
Sea. In a female without eggs I discovered under a swelling of the carapace on the left
side: one female and twelve ovisacs, the contents of which presented the most different
degrees of development; in one ovisac, for instance, appeared full-grown larve; the five
gills of the host, belonging to the trunk-legs, were all a little curled, the two foremost,
especially, were distinctly deteriorated. Beneath a large swelling of the carapace of another
female Hippolyte without eggs occurred one female and nine ovisacs, which, however, have
not been all taken out, nor the gills examined. In a third female without eggs one female
and six ovisacs appeared under a swelling on the right side of the carapace; the two fore-
most of the gills of the trunk-legs were atrophied, the three others were normal. A female
of the host with numerous eggs containing half-developed young ones, had on its right side
a swelling on the carapace about 2/3 of the normal size, but parasites and ovisacs had dis-
appeared, and so had the two foremost of the gills of the trunk-legs; the three hindmost
were normal, without brood of parasites. There was no swelling on the left side of the
carapace, but far to the front appeared the small above-mentioned female which was 1°35 mn.
in length, moreover, in the two foremost of the gills of the trunk-legs, occurred numerous
pup and hinged larvz in all stages transitional to that of the pupa, altogether twenty-one
pup and fourteen larvee; the hindmost gills also revealed some larve and pup, but each
of them only a few, except the penultimate, which contained many at one end. The larve
and pups were attached to the surface of the foliaceous gill-fibres at their base; sometimes,
though seldom, two were situated close to each other, sometimes they were found far in
between the origin of two gill-fibres.

174

REMARKS. What I described and figured in »Dijmphna-Togtet« as Ch. mirabile,
were specimens of this species; besides, I was of the opinion that all my specimens on
Hipp. Gaimardii, and an exceedingly large specimen on Hipp. polaris, belonged to the
same species. Giard and Bonnier, in their paper of 1889, supposed that the large specimen
detected on Hipp. polaris, was of another species, especially because it occurred on another
species of host, and they named it Ch. Hanseni, but without material of course they could
give no description. Their supposition proved right to a certain extent, as the parasite on
Hipp. polaris did really belong to a species which differs from Ch. mirabile, but it became
evident at the same time that Ch. Hansenti is found in Hipp. Gaimardii as well. After
this discovery I examined in our Museum all the specimens kept of both species of Hippolyte,
and in a very large material of Hipp. Gaimardii from the Kara Sea I succeeded in finding
two more specimens infested with small parasites, one of which is the above-mentioned spe-
cimen with larve and pup on its gills, whereas the parasites on the other specimen belong
to Ch. Hansenii. 1 suppose the larvee and pup found to pertain to this species, because
they occurred together with the small female (1°35 mm. in length), but L must point out that
this proof is not quite decisive, as allowance must be made for the possibility that these
larvee and pupe may belong to the following species, or some of them to Ch. mirabile,
others to Ch. Hansenii. It is worth noticing that I have not been able to detect any
difference between larvee taken out of the ovisacs of either species.

Max Weber describes ovisacs taken in the branchial cavity of Hipp. Gaimardii
from the part of the Murman Sea which is South of Nova Zemblia, and these ovisacs
decidedly belong to this genus, but the species cannot be determined. — J. Sparre Schneider
in: »Tromso Museums Aarshefter 14, 1891«, p. 112, says that be has found » Choniostoma
mirabilis« on a specimen of Hipp. Gaimardii from Hillesé in the Malangen-Fjord (on p. 98
he furthermore states that the same specimen was also infested with a Phryxus |Hemiarthrus
abdominalis (Kr.)|), and that he had moreover observed it near Troms6; but it cannot be ascer-
tained here either, whether it is Ch. mirabile, Ch. Hansenii, or both species, which have been seen.

In a large specimen of Hipp. Gaimardii from the Davis Straits, lat. 66° 30° N.,
long 54° 50‘ W., forty fathoms, under a swelling of the carapace eight ovisacs occurred,
and the foremost gills were reduced and contained two pups, but as the female was wanting,
in this case also it is impossible to determine the species. However, we may state at once
that not this species, but Ch. Hansenii was discovered later on at the coast of West-Greenland.

2. Choniostoma Hansenii Giard and Bonnier (without description).
(Pl. X, fig. 6a—6b; pl. XI, fig. 2a—2f,)
Choniostoma Hansenii Giard and Bonnier, Bull. scient. de la France et de la Belgique T. XX, 1889,

p. 366 [without description].
— — Giard and Bonnier, Bull. scient. de la Fr. et d.1. Belg. T. XXV, 1895, p. 479.

175

FEMALE. The largest specimen is 5°3 mm. long, 5°5 mm. broad and ab. 3°9 mm.
thick; the specimen represented in fig. 2a, which had laid eleven ovisacs, was 3°15 mm. long,
3°65) mm. broad and 2°7 mm. thick; the young specimen drawn in fig.2b, was 1°7 mm. long
and broad. The anterior part of the frame of the head (fig. 2 d) rises somewhat above the
skin in front of it; it is tolerably narrow in the middle, broader towards the base of the
antennule; the foremost lateral angle of the frame is strongly produced and forms a con-
siderable, tolerably broad and not quite short, outstanding, rounded projection, a large part
of which, however, is covered by the soft skin. A good deal of the lateral borders and of
the short hindmost part of the frame is likewise covered by soft skin similar to that of the
surroundings, and on each side, where the lateral and the anterior parts meet, we see, more-
over, two good-sized chitinous parts beneath the skin. On the other hand, the long list which
in Ch. mirabile runs outward and backward from the centre of the exterior side of the
frame, is altogether wanting. The two pairs of small rings in the skin in front of the
rostrum are advanced to close behind the anterior part of the frame; the sub-median pair
are larger, the more lateral pair much narrower than in the preceding species. The anten-
nule are a little longer than in Ch. mirabile, and have longer sete. The antenne’ are
also longer than in the last-mentioned species. distinctly 3-jointed, the basal joint short, the
two next joints about sub-equal in length, the terminal seta longer than the third joint.
Mouth-border fairly broad. Maxille good-sized, larger tban in Ch. mirabile. Maxillipeds
rudimentary, yet somewhat larger than im the preceding species and otherwise of the same
structure. The hindmost part of the sub-median skeleton consists on each side of a tolerably
narrow, posteriorly somewhat expanded list; as in the preceding species a long and robust
branch proceeds anteriorly from the exterior side outward just behind the base of the maxilla.
In front of the antennulee, before and outside the foremost free lateral angle of the frame,
and thence more or less backward outside its lateral margins, we see in the adult specimens
a number of fairly short or short setae (fig. 2d), obliquely outside the lateral angle some
very long sete; fig. 2a, moreover, shows a fairly broad stripe furnished with scattered
sete running from each lateral angle somewhat forward and strongly outward along the
ventral surface of the animal towards its anterior outline. Younger specimens (fig. 2b) not
only have setae — some of them very long — on these last-mentioned parts (fig. 2 e), but
also a number of similar sete on the sides and on a small part of the ventral surface, as
well as a few scattered sete on the back, whereas the greater part of the ventral side is
naked. The trunk-legs are very distinct in the smaller specimen represented in fig. 2b, but
in the larger animal (fig. 2a) I have not been able to find any. The lateral margins of the
genital area (fig. 2f) differ somewhat in shape from Ch. mirabile, being geniculate in the
centre, so that only their foremost half turns inward. As in the preceding species, the
genital area sends forth from its posterior central part two strongly diverging, tolerably
short lists, between which, in the half-grown as well as in the adult specimens, we find the

176

caudal stylets situated close together; they are very small, and each of them is provided
with a pair of fairly long sete.

MALE. Unknown.

OVISACS. They resemble those of the former species. The ovisac represented
in fig. 2c is 17mm. long and 14mm. broad. In one female were found eleven ovisacs.

LARVA. Specimens which are full-grown though they have been pulled out of an
ovisac, resemble those of the former species to such a degree that I have not been able to
find a single distinguishing mark which appeared to me valid.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The branchial cavity of Hippolyte polaris (Sab.) and Hipp. Gaimardii
M.-Edw. from the Kara Sea. My material from this locality is as follows: in a female
without eggs of Hipp. polaris appeared beneath a large swelling on the left side of the
carapace, the above-mentioned gigantic specimen. In an adult male of Hipp. Gaimardi occurred
under a swelling on the right side of the carapace: a female (represented in fig. 2a) and
eleven ovisacs (containing eggs, Nauwpli and fully developed larvee respectively); besides an
adult male and a much smaller, exceedingly young female of Gyge Hippolytes (Kr.); the
two foremost gills of the host, pertaining to the trunk-legs, had disappeared, the three hind-
most ones were well preserved; under the apparently sound left-hand side of the carapace
of the host, one male Gyge was discovered. In another somewhat smaller male of Hipp.
Gaimardii occurred in the front part of the left branchial cavity three rather small females,
placed obliquely in a longitudinal row, in the right branchial cavity five similar females,
three of them far to the front. All the parasites were of sub-equal size and about 1°6 to
17mm. in length; the gills were somewhat crumpled, and the carapace showed small cavities
on its inner side in the parts which covered most of the parasites, though its outside did
not as yet show any real swellings. No Hpicaridea were discovered.

This species has been found besides at the West-coast of Greenland: in the Karajak-
Fjord, district Umanak (on ab. lat. 70?/3° N.), by Dr. E. Vanhotfen. This naturalist having
informed me in a letter that he had found Choniostoma, I asked him to lend me his material,
and he kindly placed it at my disposal, as well as his own particulars about it. He pos-
sessed in all four females; two of these belonged to Ch. Hansenii, he had found them free
in a bow-net, and he writes about them: »... . die ich lose fand, und die aus Krebsen
stammen miissen, welche in meiner Reuse sich hiuteten oder verzehrt wurden«; about the
others he writes: »Ein drittes Exemplar wurde in H. Gaimardii...., em viertes in H. po-
laris.... gefunden«; one of these was Ch. Hansenii, but the other was »zur Hiilfte aut-
geschnitten«, so that I could not determine it, and I do not know in what species
of host the specimen had been found. So at least three of the four parasites per-
tained to this species, moreover, it seems very probable that it lives in both species of
Hippolyte.

177

Besides, it is not at all unlikely that at least some of the specimens from the
Davis Straits, from the most northern part of Norway (Malangen and Tromsé) and from
the Murman Sea mentioned under the preceding species, belong to this one.

REMARKS. This species is sharply distinguished from Ch. mirabile, especially by
the shape of the frame of the head. It offers an exellent example of the fact that the same
species of parasite may be found in two different species of hosts; besides, the specimen with
the eight young females shows very clearly indeed that it is the parasite itself which causes
the swelling in the carapace of the host, and that it does not — as suggested by Giard and
Bonnier — lodge itself on or together with a Gyge, or in a swelling formed and afterwards
left by this parasite.

VE Mysidion n. gen.

FEMALE. The body shortly ovate. The head pretty well defined from the trunk,
but in elderly specimens it is usually found in front on the ventral side of it, as an
anteriorly and laterally rather well defined eminence; frontal border is wanting, and the skin
in front and on the sides of the wanting or at most very indistinctly marked lateral border
is rather thin. The antennule are either fairly short and 2-jointed or almost rudimentary,
I-jointed. Antenne seem to be wanting. The mouth moderately large, the mouth-border
narrow, but frequently partly covered with a viscous substance. Maxillulee well developed,
with a good-sized additional branch (pl. XII, fig. 2a,e’). Maxille powerful; the basal joint
has at its terminal margin one or two processes, against which the last joint can be folded
up. The maxillipeds rather short and weak; their basal joint has an irregularly sinuate
outline; second and third joints fused into one short joint, terminal joint of nearly average
length, pointed. The trunk is now naked, now in a few places most sparingly provided
with single hairs of about medium length; trunk-legs and caudal stylets altogether wanting.
No genital area is found; the genital apertures are placed very far apart at the place where
the posterior and the lateral outlines meet (pl. XI, fig. 3b); each aperture has — besides
its usual two lips — its own skeleton consisting of a list which forms a semicircular curve
(pl. XII, fig. 2b), or the greater part of an oval (pl. XI, fig. 3f), the longitudinal direction
of which is parallel with the median line of the animal, and whose open side turns
towards this line (pl. XI, fig.3e); the hindmost lip of the genital aperture is quite close to
the posterior part of this list, and the muscles radiate forward to its anterior part. The
entrance (or perhaps rather: entrances) to the odd receptaculum seminis (pl. XI, fig. 3e, 1) is
or are situated at the median line far in front of the genital apertures; the membrane which
covers the receptaculum is often closely covered with a great number —as many as twenty
six — of spermatophores, among which are seen, moreover, stalks of other spermatophores, the
vesicles of which have disappeared. — The spermatophores (at least in MZys. commume) are some-
what elongated ovals. — Various parts of the head, as lateral margins, mouth etc., are frequently

92
23

178

partly covered with the gluey substance, by which the female is attached to the inside of the
marsupium, and it seems as if in these cases the animal had got its head irregularly covered
with glue just after this substance had been secreted and before its becoming stiff (dry).

MALE. This sex is known in both species. The body is short and clumsy. On
the dorsal side of the head, somewhat in front of the hair-coat and at some distance from
the median line, we see a knot or short cone (pl. XI, fig. 3h, x). The head is provided with
well developed frontal and lateral borders. Antennule short, 2-jomted. Antenne wanting.
Hairs of the mouth-border short, but distinct. Maxillule and maxille as in the female.
Maxillipeds rather anomalous: their basal joint curved, at least with one good-sized, thick
process on the outer side of its distal end; second and third joints coalescent, the terminal
joint conical. The sub-median skeleton without processes at the base of either maxilla or
maxillipeds. The trunk hairy; trunk-legs and caudal stylets wanting. The frontal thread
furnished with peculiar expansions.

OVISACS. ‘Typically they are shortly pyriform and attached to the lips of the
genital aperture by a fairly short stalk. Fig. 2b in pl. XII shows the genital aperture (g),
the lips of which are covered with a stiffened secretion, which, besides, forms a pretty large
plate (h) covering the hindmost end of the semicircular list and the skin nearest to it; from
this plate proceed numerous, distally thickening threads, which are cut off in the drawing
(i); they are the stalks of the ovisacs, so the plate must be understood as being the coales-
cent basal parts of these stalks. The ovisacs are numerous, twelve, fourteen, seventeen, or
even more (see Mys. abyssorum), sometimes varying exceedingly in size (pl. XI, fig. 3c), and
mutual pressure not unfrequently having caused their shape to become irregular and their
attachment difficult to discern (pl. XI, fig. 3a); frequently again, they are af about equal size,
of regular shape, and their attachment easy to observe (fig. 3b).

LARVA. It is known in both species, and on the whole only differs from the
species of Spheronella living in Amphipoda by the shortness of the sete of the caudal
stylets, these sete being not nearly half as long as the cephalothorax.

POST-LARVAL DEVELOPMENT. Is partly known in one of the species, and
the stages known, which are very remarkable, are described in detail above on p. 61—63.

HABITAT. In the marsupium of species belonging to the genera Erythrops
G. O. Sars and Parerythrops G.O.S. (family Myside, order Mysidacea) from Norway.

REMARKS. ‘This genus is admirably distinguished from the three preceding genera
by the following characters: the genital apertures in the female are placed far apart from
each other and from the odd receptaculum seminis, each has a skeleton of its own, finally,
the ovisacs are attached to the lips of the genital apertures. In the three last characters
it agrees with the following genus, but in the latter the female lacks maxillipeds, the genital
apertures are much closer to each other etc. The males differ from all the preceding genera
and agree with the following in possessing the two dorsal knots on its head. The meta-
morphosis deviates very strongly from anything else I have observed of this kind.

179

For my whole abundant material of this and of the following genus I am indebted
to Professor G. O. Sars. It consisted partly of infested Mysida with indication of their
localities, partly of similar animals without such indication, further, of parasites taken out
of their hosts, the latter not being mentioned; these last animals have scarcely been used
at all. I have determined the hosts in accordance with the above-mentioned naturalist’s well-
known excellent work about the Myside of Norway, but I have felt bound to follow Steb-
bing in adopting the older names of two of the species. — Besides, in his »Report on the
Challenger Schizopoda« G. O. Sars himself mentions having observed in the genus Erythrops
»a peculiar Lernzid, apparently the Spheronella leuckartii of Salensky«, otherwise he does
not give any more details about his finds.

Conspectus of the Species.

1. The Females.

Antennz almost rudimentary, 1-jointed. Head naked... .. . 1. M. commune Nn. sp.
Antenne larger, 2-joited. <A lateral longitudinal belt on the head and a conside-
rable area behind the maxillipeds covered with hairs.......... 2. M. abyssorum 0. sp.

2. The Males.

The head tapering considerably towards the front, provided with a narrow frontal
border. The basal joint of the maxillipeds has on its outer side a shorter process in the
centre and a long one at its distal end. The trunk is covered with. innumerable minute
transverse eminences, from each of which project several short hairs... .. 7. M. commune

The head anteriorly broad, almost truncate, with a moderately broad frontal border.
The basal joint of the maxillipeds has on its outer side only a single tolerably large process
placed at its distal end. The trunk is without transverse eminences, the hairs normal, of
AVL AC CMO SUM ease ees euncter sac TNs Jep'e rats, sbi sel gfescictea,.2) '» Giroyar ems 2. M. abyssorum.

|. Mysidion commune n. sp.
(PI. XI, fig. 3a—3i; pl. XII, fig. 1a—14d).

FEMALE. In fig. 3a are represented the essential contents of a marsupium, con-
sisting of a shrivelled female and seventeen ovisacs; the whole bulk was 2°9 mm. long and
23mm. broad. The female represented in fig. 3b is more normal, large, and had probably
not finished laying eggs; it is 114mm. in length and ‘94mm. in breadth, shortly ovate, and

23*

180

part of its posterior margin is nearly straight; it is seen from the dorsal side, the frontal
part of the head is turned backward, and the maxillipeds (g) forward; however, this
position is an anomaly, no doubt produced by pressure acting on its very soft skin in the
marsupium during its growth. — The head (fig. 1 a) without real lateral borders, and in
the adults, the part surrounding the mouth-appendages is irregularly folded up against these
appendages, or even overlapping the outer side of the maxillipeds. The antennule (a) almost
rudimentary, as broad as long, 1-jointed, ending in several very short sete. Somewhat in
front of the antennule are seen two taps (u), the nature of which is quite incomprehensible
to me (possibly cones of viscous substance secreted through the orifices of glands?). The
terminal margin of the basal joint of the maxillz is concave, rising at its posterior angle
into a broad, rather short process. The maxillipeds have no spine at the distal inner angle
of their penultimate joint. The lower side of the head naked all over. The list of the
genital apertures forms about two thirds of an oval ring.

MALE. It is small in proportion to the female (fig. 3d: fig. 3b). The specimen repre-
sented in fig. 3h is 164mm. long, the one drawn in fig. 3g, measures 174mm. The body
is not flattened. Seen from below, the head nearly equals the trunk in length, but the
latter is somewhat thicker; seen sideways, the outline of the hair-coat runs from the base
of the maxillipeds somewhat obliquely backward up across the side and the back, so that
the dorsal line of the head becomes much longer than that of the trunk, and the short
conical processes (x) are placed a little in front of the hair-covering. Seen from below, the
lateral borders of the head converge from behind their centre up to a point in front of the
base of the antennulee, so that the frontal border becomes very narrow; in proportion to its
breadth it is considerably produced, and has a strongly curved, naked anterior margin.
Antennule short, 2-jointed; second joint somewhat shorter as well as narrower than the first
one, furnished with a few short sete. Maxille large; the terminal margin of the basal joint
essentially as in the female. The basal joint of the maxillipeds has on its outside in the
centre a fairly short, thick, rounded process, and distally a thick and very long, slightly
curved process; the next joint (second and third fused together) has a larger or smaller
outstanding process somewhat on the boundary between the anterior and the outer side.
The lateral margin of the head is furnished with a row of fine, rather short hairs, and a
similar row is seen somewhat outside the margin. The trunk is closely covered all over
with very small transverse eminences, from each of which spring several short, fine hairs.
— The frontal thread, if found, is long and of peculiar shape; in fig. 3h such a thread,
lettered with an s, is shown as fixed to a marsupial plate (t); it is somewhat longer than
the male, thin in the greater part of its length, then dilates pretty quickly and evenly
towards its distal end, forms a collar-like ring, continues dilating, and forms a second ring
at the thickest part of its expansion; beyond this ring it is still thick, though slowly de-
creasing in circumference, and at last increases a little up to the distal end, by which it
attaches itself.

181

OVISACS. They are mentioned in the description of the genus. In pl. XI, fig. 3b
and fig. 3¢ are drawn on the same scale of enlargement, thereby illustrating the relative
size etc. of the ovisacs. The largest of the ovisacs, represented in fig. 3d, is ‘90 mm. in
length and contains larvee, of which only six are drawn.

LARVA. Full-grown larve prepared out of an ovisac agree closely with those of
the following species; the only difference I have been able to find is, that the inner side
of the terminal joint of the maxillipeds is smooth in this species and spinous in the following
one. As for the rest, the reader is referred to the description of the next species.

POST-LARVAL DEVELOPMENT. The stages found are described in detail
above on p. 61—63.

HABITAT. The marsupium of Lrythrops serratus G. O. Sars and Parerythrops
obesus G. O.8., and a female together with the following species in the marsupium of
Erythrops abyssorum G.O.S.; all from Norway. The following special data can be given.
In a specimen of Parer. obesus without special locality, one large female was found attached
to the inner side of the hindmost right marsupial plate near its base; it carried fifteen
ovisacs, one of which was empty; and two males appeared together with it. In an Lr.
serratus (with two specimens of Aspidoecia) without special locality, occurred: an almost
empty female (with twenty-one spermatophores), carrying fourteen ovisacs of widely differing
sizes, one of them half emptied of young ones, another quite empty, and to the latter were
attached six males, one of which had four spermatophores fixed to the ventral side of its
trunk; further: an empty, partly destroyed skin of a seventh male, another male (the eighth)
fixed by a frontal thread, and a larva about to become a pupa. fr another Hr. serratus,
the locality of which was not specified, was discovered one large female (type specimen of
fig. 3b) attached by its head to the basal part of a marsupial plate and carrying thirteen
ovisacs (six and seven), and together with it a halfgrown female and a female in the
stage represented in fig. 1d, each fixed to a separate marsupial plate by a dorsal thread.
In one specimen of Hr. serratus (with at least one Aspidoecia), from Kyali, a part of the
contents of the marsupium was washed away, but still three adult females, all with ovisacs,
and one male were found; in a specimen of the same species from Sunde, the marsupium
contained only one female with two ovisacs. Another specimen of the same species from
Sunde was highly interesting. Its marsupium contained, to begin with, the bulk represented
in fig. 3a, the greater part of which consisted of a rather shrivelled female with seventeen
ovisacs, some of which contained eggs, others Nawplii or pretty old larvee, two were nearly
emptied of larvae, and one of the ovisacs was three-lobed, the majority of the others more
or less distinctly pyriform. The bulk was placed as follows: the part of it which is upper-
most in the drawing, was foremost in the marsupitn, the part of it which turned towards
the abdomen of the host, was flat, but the opposite, ventral side strongly arched, as shown
in the illustration. This bwk contained, moreover, two males, the pupa fastened by a dorsal
thread and drawn in fig. 1c, and a very small pupa, like the one represented in fig. 31.

182

Between the marsupial plates of the host were further found: three males, two of them
attached by frontal threads to a marsupial plate, on its edge and a little inside it on the
surface; and finally: the minute pupa drawn in fig. 3i, and the very young female represented
in fig. 1d, which was attached to one of the plates by a dorsal thread.

And lastly, in the marsupium of an Lr. abyssorum, infested with the following
species (to which we refer), occurred a very young female which adhered to the female of
the other species.

2. Mysidion abyssorum n. sp.
(PL. XI, fig. 2a—2).

FEMALE. A specimen containing fourteen ovisacs was 1°39 mm. long and ‘965 mm.
broad; its shape much like that of the specimen of Mys. commune represented on pl. XJ,
fig 3b, but its head was not turned upward on the dorsal side, it was placed as usual
anteriorly and, if anything, on the ventral side. The general outline of the head as
in the preceding species. Antennule (a) rather short, 2-jointed, basal joint thick, second
joint short, terminating in some short sete and a much longer olfactory seta. No taps
on the anterior side of the head. The basal joint of the maxilla has on its terminal
margin two good-sized processes, one of them near the centre, the other at its posterior
end. The maxillipeds are armed with a conspicuous spine at the distal inner angle of
the penultimate joint. The part of the head which corresponds to the lateral border is
furnished in its whole length with a fairly broad belt of rather short hairs, and some-
what behind the base of the maxillipeds we see a very good-sized, odd, triangular area,
covered with moderately short hairs; the longest line of this triangle is tured towards the
front, the opposite hindmost angle is on the median line; and finally, on each side, between
the maxilla and the maxilliped, is a rather small, transverse, hair-covered area. On the
trunk behind the head we see some scattered hairs. The list of the genital apertures is
almost semicircular (fig. 2b), with a hole (h) at its anterior end. (This hole, no doubt, is the
orifice of a gland, and — strangely enough — I have not been able to find it in the pre-
ceding species, but I have found it in Aspidoecia and in Spheronella Munnopsidis; however,
IT cannot make out with certainty whether it is one tolerably large hole, or perhaps rather
a small area with a very thin membrane pierced with a number of small holes).

MALE. A specimen of normal size is ‘164 mm. long, nearly of the same breadth
and somewhat flattened (fig. 2e and fig. 2f), thus of small size compared with the female.
A couple of specimens were abnormally small, one of them only 099 mm. in length (their
size in proportion to the normal male is shown by comparing fig. 2d and fig. 2c), similar in
shape to the larger specimens, so these males are considerably smaller than any other male
of this family, but it remains an open question, whether they are adults, or — perhaps more

183

likely — recently hatched animals (comp. my observations about other species, stated above
on p. 58 and p. 60). — The head is much narrower and somewhat shorter than the trunk;

seen laterally (fig. 2f), the limit of the hair-coat runs from the base of the mavillipeds
upward and in a slightly oblique direction forward across the side and the back, and the
two flatly conical eminences (x) are placed somewhat in front of the limit. Seen from below,
the distance between the outstanding lateral borders of the head is much shorter than its
broadest diameter; in fig. 2e — partly on account of the position of the animal — the out-
standing frontal border does not reach the front outline of the head. The frontal border
scarcely attains to medium breadth, yet it is much broader than in the preceding species,
slightly produced, with pretty well curved margin. Antennul rather short, 2-jointed; second
joint somewhat shorter and a little narrower than the first one, with comparatively short
seta and a sensory seta which nearly equals the others in length. Maxille of medium
size; the terminal margin of the basal joint as in the female. The basal joint of the maxil-
lipeds has on its outer side only one process which is placed at its distal end and which,
though good-sized, is much smaller than in Mys. commune; the next joint has no process,
but bears a pretty large spine inside the base of its short terminal joint. Everywhere,
except on the front part of its ventral surface, the trunk is covered with simple hairs of
nearly average length. We see furthermore on the ventral side two long lines (fig. 2e, u),
running right and left of the median line at some distance from it; posteriorly they are
further removed from this line, and near the posterior margin they recurve, continue forward
and outward, and soon vanish altogether; what these two lines are meant for is quite
incomprehensible to me. — The afore-mentioned dwarfish specimens were attached by a
peculiar frontal thread (fig. 2d and fig. 2g), which is a little longer than the body; the thread
(in both specimens) was fusiform near its centre, and thickened by a high collar at. its
broadest point, and somewhat in front of its distal end appeared a similar, but still wider
expansion with a similar collar; the distal end by which it is attached (not drawn in the
figure), seems to have been discoid.

OVISACS. They are exactly like those of the preceding species, varying in the
same way as to size and shape.

LARVA. A full-grown specimen pulled out of an ovisac is represented in fig. 2h,
(the natatory legs are omitted); it is 196 mm. long. The cephalothorax very elongated,
scarcely twice as long as broad. The front has a sinuate oblique list inside the base of
each antennula. The purpose of the two transverse stripes rendered in the illustration, is
not clear to me. Antennule 3-jointed; olfactory seta scarcely half the length of the
cephalothorax. Antenne very short, consisting of three very short, comparatively thick
joints, the last one terminating in an exceedingly short seta. Of the maxillule only
two branches are seen, one of them long, powerful and originating comparatively
far towards the front, the other very short, spiniform and situated further backward.
The basal joint of the maxille bears some very short hairs at the distal end of its inner

184

margin, the second joint tolerably short, the third one of about medium length, smooth, and
in the specimen drawn, as well as in other larve taken out of the same ovisac, this joint
is curved forward in the same way as in the hinged specimens of other species. The basal
joint of the maxillipeds is long, the second joint a little shorter than the third; the fourth
joint has five or six setiform processes along the central part of the inner margin. The
peduncle of the natatory legs is rather slender. The abdomen of medium length; the first
segment somewhat longer and broader than the second, and the sete of its posterior angles
reaching only a little beyond the caudal stylets; the third segment somewhat narrower and
shorter than the second; the caudal stylets well set off, their setze unusually short, not nearly
half the length of the cephalothorax. — Fig. 2i shows a larva in the act of changing into
a pupa (or a male?); it is represented in a dorsal view; the cephalothorax is short and broad;
the outline of the contents is shown by an inner line.

POST-LARVAL DEVELOPMENT. Unknown.

HABITAT. The marsupium of Erythrops abyssorum G.O.S. from Norway. In a
specimen without indication of locality (bearing a specimen of Aspidoecia), occurred a large
female with fifteen ovisacs of widely differing sizes, as well as a considerable lump of empty
ovisacs, which could not be counted; no male. In another specimen without locality (with
two small specimens of Aspidoecia), appeared one female with fourteen ovisacs, extremely
varying in size, and a great deal of them adhering to each other, one of them being empty;
moreover, a female glued to an ovisac; no male, but the above-mentioned small female of
Mys. commune. In a specimen from Kyalo (bearing one large and four small specimens of
Aspidoecia on its carapace), occurred one completely torn female with twelve fine, almost
equally large, mostly short and broad, somewhat flattened ovisacs, which on account of
mutual pressure were somewhat polyhedrous in shape; among them were found a male, also
the head and the skin of the anterior fourth part of the trunk of another female, and_ to

€

this skin were attached five males and the broad larva represented in fig. 21; furthermore,
I found two good normal males and the two above-mentioned dwarfish males, which were
fastened to the marsupial plates by their frontal threads, — which makes altogether ten
males —; finally four broad larvee which had no doubt been hinged, and the contents of

which were undergoing the transformation.

VI. Aspidoecia Giard and Bonnier (1889).

FEMALE. The body is considerably broader than long. The head, which is pretty
well defined, occupies a somewhat different position relatively to the genital apertures, from
that of the earlier forms: in fig. 3c the genital apertures in relation to the head are placed

185

some distance up on the dorsal side of the animal; fig. 3f is drawn in such a position as to
show the head a little behind the middle of the trunk, and fig.3@ presents the same animal
turned half round, with its genital apertures (r) behind the central point, and the entrances
of receptaculum seminis (r’) far to the front; so we arrive at the result that the distance
from the anterior limit between the trunk and the head along the dorsal surface of the
animal to the genital apertures is considerably shorter than the distance from the base of
the maxillze past the receptaculum seminis to the genital apertures. (The same proportions
also appear in fig. 3b). — The head is pretty well chitinised; the anterior and lateral parts
evenly rounded (fig. 3h); no outstanding frontal and lateral borders. Antennulz (a) rather
short, 1-jointed; antennz wanting. The mouth exceeding average size; mandibles robust;
hairs of the mouth-border not to be detected (though they probably exist). Maxillule very
small, principal branches short, additional branch wanting. Maxille middle-sized, normal,
with smooth joints. Masillipeds altogether wanting. The sub-median skeleton forms a plate
which fills up the whole surface between the maxille, but ends a little behind their base.
The head quite naked. The trunk naked; trunk-legs and caudal stylets wanting. As in
Mysidion, no genital area is found, but each genital aperture possesses (besides the lips),
its own skeleton, which consists of a tolerably good-sized, somewhat wry ring (fig. 3e, e;
fig. 3i,e) formed of a pretty broad list, but the part of it (fig. 3i, f’) which is turned obliquely
inward and forward is more thinly chitinised than the remaining larger part. The genital
aperture (g) is placed against that part of the ring which turns towards the median line of
the animal, and the muscles (m) by which the aperture opens go in the opposite direction;
to the front, in the list of the ring itself, is a good-sized hole (k), which is the orifice of a
gland. The distance between the two rings varies from being a little larger (fig. 3g) to
much smaller than the diameter of each ring. Far in front of the genital apertures are
seen two knots at a short distance from each other (fig. 3b, r’; fig. 3g, r’, and especially
fig. 3e, 0), which show, as it were, irregular cracks in the thick chitine; most likely we
stand here at the entrances of the receptaculum seminis, though I have not been able to
trace regular holes, nor have I found spermatophores on the females. The receptaculum
seminis (fig. 3e,r) is large, odd and much broader than long; at each end it curves evenly
backward, and continues as a wide, centrally somewhat narrower, and distally again ex-
panding duct, which is about parallel with the other duct and runs up to the genital
aperture itself.

MALE. The body is not a third longer than broad, of a tolerably normal shape,
but altogether hairless (fig. 3k and fig. 31). The head somewhat longer than the trunk, but
the latter somewhat broader; the frontal border strongly produced, and the lateral borders
well developed; on a line with the front extremity of the maxilla, and on the border between
the sides and the back, we see the two low conical eminences. Antennulze extremely short,
1-jointed, with a single seta (b) which is olfactory and several times the length of the antennula.

24

186

Antenne wanting. Mouth middle-sized; mouth-border provided with very distinct hairs.
Maxillule small, probably constructed like those of the female, and without additional branch.
Maxille extremely large, the basal joint much compressed and very broad; the two last
joints, which are entirely fused, form a long and powerful, proximally somewhat curved,
distally almost straight joint. The basal joint of the maxillipeds somewhat smaller than in
most species of Spheronella, second and third joints fused into one exceedingly short joint,
which has no spine at its distal inner angle; last joint slender, pointed, perceptibly longer
than the penultimate one. The sub-median skeleton without processes on its posterior part.
The trunk without legs and caudal stylets. (Fig.3k only shows one single, but exceptionally
large spermatotheca (q), but this no doubt is an anomaly in the specimen illustrated,
as in two other individuals I found, as usual, two much smaller and normally situated
spermatothece.

OVISACS. They are hinged to the lists of the genital apertures, sub-globular or
shortly pyriform, from scarcely middle-sized to small; their number can amount to thirteen
or fourteen. Eggs of average size, not numerous.

LARVA. Resembles in nearly all its features (fig.3m) the larve of certain Species
of Spheronella parasitic on Amphipoda. The essential differences found are as follows: the
second joint of the maxille is short and comparatively thick (fig. 3n), the third joint is
finely serrated at its inner margin; the seta of the caudal stylets is short, not half the
length of the cephalothorax.

POST-LARVAL DEVELOPMENT. The male comes out of the larva (fig. 3m)
directly, without any intermediate stage. Whether the female passes through the pupa stage
is not known, but it appears more probable to me that its development resembles that
of the male.

HABITAT. The females live attached to the eye-stalks, the carapace, the back
and sides of the free thoracic segment and the six first abdominal segments of all species
of the genus Hrythrops G.O. Sars (order Mysidacea), in Norway.

REMARKS. The genus comes very near to Mysidion, and the characters by
which both genera are distinguished from those previously described are stated in the
remarks about the last-mentioned genus. From the latter the female differs in the lack of
maxillipeds, in the tolerably short distance between the genital apertures, in the ring by which
each of these apertures is surrounded, and by the two conspicuous chitinous knots above
the receptaculum seminis. The male deviates both from Mysidion and from all other genera
in the minute size of the antennule and in the smallness of the distal part of the maxillipeds.
And this genus deviates from all other forms by living attached to the outside of the free
surface of its hosts. — The whole of my large material collected by Prof. G. O. Sars I have
referred to one species; the subsequent remarks about this parasite will form a supplement
to the above account of the type.

187

1. Aspidoecia Normani Giard and Bonnier.
(Pl. XU, fig. 3a—3n)?).
Aspidoecia Normanit Giard and Bonnier, Compt.-rend. de l’Acad. d. Sciences, 29 avril 1889.
_ — iard and Bonnier, Bull. scient. de la France et de la Belgique, T. XX, 1889,

p. 342 etc., pl. X—XI.
= _- Giard and Bonnier, Bull. scient. d. 1. Fr. et d. 1. Belg. T. XXV, 1895, p. 479.

FEMALE. The specimen represented in fig. 3b is an adult female (with two
rudimentary ovisacs and three attached larvee), which is 65 mm. long and °75 mm. broad
and is attached to Hr. serratus G.O.S.; the specimen represented in fig. 3c and taken on
the same species (with two males, x, hinged by frontal threads) is 536 mm. long and ‘685 mm.
broad; the individual drawn in fig. 3f and fig. 3g and found on Er. abyssorum G.O.S8. is
*82 mm. long, 1:03 mm. broad and one of the largest in hand. Fig. 3h shows the head,
seen from below, cleaned with caustic potash, so as to show the antennulze, whereas fig. 3d
shows the head partly in front, as it is attached to the female by a large adhesive plate
(s) which covers the antennule. Far to the front on the head, beneath the skin, and far
apart from each other appear a pair of peculiar rather large hollow spaces (t) with a strange
refraction of light, somewhat like that of a viscous substance, but what they are meant for
I cannot make out. In the specimen cleaned with potash the antennule (fig. 3h,a) are seen
to consist of one single, comparatively broad joint with convex inner margin, whereas the
outer margin is furnished with several short sete. In most individuals the genital rings
are closer together than the length of the diameter of each (fig.3e); in the larger, but not
in the smaller, younger specimens living on Lr. abyssorwm, they are further apart than
this line (comp. the remarks below).

MALE. The smallest specimen from Hr. serratus is 138mm. long (fig. 31), another
specimen from the same species is 147 mm. long and °120 mm. broad (fig. 3k); a specimen from Er.
abyssorum is ‘158mm. in length. The frontal border is strongly produced in all specimens
and slightly emarginate in the middle. The frontal thread is even, though a little expanded
at its distal end; in the specimen drawn in fig. 3k, it is scarcely half the length of the
body, im another specimen (fig. 3a, m) between twice and three times the length of the animal.

OVISACS. Mentioned in the diagnosis of the genus.

LARVA. Of larve I have found only a few specimens, one of them attached at
the front to the carapace of a host (fig. 3a, 1), the others fastened to females, and about to
develop into males. So the shape of a free specimen cannot be described. Proportionally
the cephalothorax of the attached specimens is not broad; in one of them its breadth is
12mm., the length of the body 20mm. Antennule 3-jointed, the olfactory seta about half
the length of the cephalothorax, minus its free segment (fig. 3m). Antenne fairly short,

1) On pl. XII the name of the species is written Normanni instead of Normani.
94*

188

3-jointed, basal joint thick and pretty long, the two next joints thin and short, terminal seta
short. Maxillule? — Maxille (fig. 3n) with smooth basal joint, second joint short and
comparatively thick, third jot of average length with finely serrated inner margin. Maxil-
lipeds (fig. 3n) proportionally rather below medium size, second joint longer than the third,
terminal joint smooth. Peduncle of the natatory legs moderately broad. Abdomen much as
in Mysidion, but the third segment is as long as the second.

POST-LARVAL DEVELOPMENT. My observations and conclusions are stated
in detail in the general part p. 54.

HABITAT. In the diagnosis of the genus I have enumerated the different parts
of the body to which the females may be seen attached. They have been found in all the
northern species of the genus Hrythrops, viz. Er. erythrophthalmus (Goes) (= Er. Goésti G. O.8.),
Ey. elegans G.O.8. (= Er. pygmeus G. O.8.), Er. microphthalmus G. O. 8., Er. serratus
G.O.8. and Er. abyssorum G.O.S. About the depth in which these species live, and about
the remainder of their biology, I refer the reader to the monograph by Sars. Most of my
twenty-one infested specimens were without special locality, some specimens of Hr. serratus
and Er. abyssorum were taken off Kvalé, one Er. erythrophthalmus off Tjoto. The parasites
appear on adult males, on immature females and on females with marsupium, but in the
latter the marsupium was either empty or filled with a parasite of the genus Mysidion. To
show the occurrence of the parasites, I will give the following extract of my notes arranged
according to the hosts.

1. Er. erythrophthalmus (Goés). On a female from Tjoté in which the development
of the marsupium had commenced, appeared a large parasite with fourteen ovisacs on the
back of its second abdominal segment. _

2. Er. elegans G.O. 8. In a female whose marsupium was disturbed, occurred
three parasites, two on the back of the second abdominal segment; one of these animals
was nearly full-grown, the second somewhat smaller; the third, almost adult, female, was
found on the back of the sixth abdominal segment near its posterior margin. On a female
without marsupium were found altogether five females: one half-grown specimen on the upper
side of the right eye, at the boundary between the cornea and the stalk; another somewhat
smaller specimen on the inner side of the same eye-stalk; on the dorsal side of the carapace
were two good-sized individuals, and a large one with three ovisacs, each containing only
one egg, was attached to the second abdominal segment, at the centre of its dorsal side.

3. Er. microphthalmus G.O.S. On a specimen with empty marsupium appeared
a large female without eggs on the dorsal side of the last thoracic segment. In a female
without marsupium was found a large parasite with six ovisacs on the dorsal side of the
second abdominal segment. On a male I met with a large parasite with six ovisacs on the
back of the first abdominal segment.

4. Py. serratus G.O.S. In an adult male was seen a good-sized female on the
upper side of the right eye close behind the cornea. In a female with marsupium containing

189

Mysidion, occurred two parasites, one of which — a female with twelve ovisacs — was
placed to the front on the carapace, a little to the left of the median process, the other —
a female with three ovisacs — was placed on the dorsal side of the last thoracic segment.
On a young individual without marsupiun appeared two parasites, one of them — a female
without eggs — nearly in the centre of the back of the second abdominal segment, the
other, a female with two males hinged by their frontal threads (fig. 3c), somewhat to the
right side on the back of the first abdominal segment. In a hardly adult female (from IKvals),
on the dorsal part of the second abdominal segment (fig. 3b), I found an adult female with
two minute ovisacs without eggs, and four larve (v), one of which fell off on being touched,
so that it was not drawn in fig. 3b, but it is the specimen represented in fig. 3m with an
adult male beneath the larval skin.

5. Er. abyssorum G. O.S. On a female with empty marsupium: five parasites, viz.
two very small females on the right side of the thorax close behind the carapace; and at a
short distance in front of these animals, on the carapace itself, one small and one good-sized
female, to the latter of which was attached near its mouth a strongly impaired male with
a large spermatophore, and the anterior half of another male was fixed by a thread to the
side of the trunk; finally: at the centre of the dorsal surface of the sixth abdominal segment,
a good-sized female (fig. 3f and fig. 3g) — all parasites without ovisacs. In a female (from
Kval6o) with Mysidion abyssorum in its marsupium, occurred five parasitic females, all on
the carapace; one of them, which was very small, was situated somewhat behind the middle
of and a little above the left lateral margin, the four others were placed close together at
some distance behind the centre on the back and a little down on the right side; one of
these was very small, the two others a little larger, the fourth large, without ovisacs, but
with two larve attached to it. On an adult male (fig. 3a) appeared altogether nine parasitic
females and one larva: one female (a) with six ovisacs is placed on the left hand side of
the carapace; somewhat behind it and further up towards the back, the larva (1) is situated;
in an irregular transverse row on the dorsal side of the first abdominal segment are found
altogether five females, one of them pretty small, the four others large(a), two of them each
with one, the two others together with many ovisacs, which can scarcely be counted accu-
rately without a dissection; on the back of the second abdominal segment is placed a female
with seven ovisacs, as well as a male (m) hinged to the female by a long thread, which
had the larval skin on its anterior end; to the right of the latter large female is found a
very small female, and on the boundary between the second and the third abdominal
segment, a tolerably small female (in the illustration the last two specimens are marked b.)

REMARKS. I must consider the parasites on all five species as belonging to the
same species. In the females of the four smaller species of hosts, the distance between
the genital apertures is from much to a little smaller than the diameter of each ring, in
not full-grown individuals of the largest specimen, Er. abyssorum, this distance varies from
being a little shorter than to about the same length as the diameter, but in the adult spe-

190

cimens it is appreciably longer. The females which are parasites on the smallest species of
Erythrops, in their adult stage attain to a much smaller size and, as a rule, produce a smaller
number of ovisacs than the females which live on larger and the largest species; thus: the
females are small in Lr. elegans(= pygmeus), larger in Er. serratus, largest in Er. abyssorum.
That the distance between the genital apertures is larger in Er. serratus than in Er. elegans
or Er. microphthalmus, and largest in Er. abyssorum, seems to me to be accounted for by
the fact, that the entire skin of the trunk, and, as a matter of course, also the part between
the genital apertures, grows more in the large than in the small species, whereas the rings
themselves and the head of the animals do not grow; this will also be seen by comparing
fig. 3c with fig. 3f plus fig.3g, for in the first mentioned figure is represented on a larger
scale a specimen which is about one third narrower than the one drawn in fig. 3f and fig. 3g:
in the two last figures the head and the genital rings are much smaller, compared with
the trunk, than in fig. 3c, but the distance between the genital rings is much greater in
fig. 3¢ than in fig. 3c. I have come to this conclusion by examining the material, and the
fact that I have not been able to find any difference between the males of the parasites
from Er. serratus and Er. abyssorum — the male from Er. microphthalmus will be men-
tioned presently — speaks strongly in favour of my opinion, that all these parasites belong
to the same species.

Giard and Bonnier have established the genus and the species on a female with five
ovisacs and two males taken on Hr. microphthalmus from Solemsfjord near Floré, Norway.
Finding the female with her males sitting under one end of an obliquely placed specimen
of Aspidophryxus Sarsi G. and B., they were led to suppose that the Copepod was parasitic
on the last-mentioned form, but this is not the case, and the occurrence of the two parasites
close to each other is quite accidental. (In my large material I have found no more than
one Aspidophryxus, which was placed on the back of an Er. erythrophthalmus, which had
no Aspidoecia on it). Based on the examination of the female, and especially of one of the
males, which has been studied by the authors, I have given a detailed critique of their
account above, on p.6—-8, to which the reader is referred. Here I will only observe that
in examining their male, I did not find any difference between this specimen and those
which I had in hand myself, so I am perfectly sure of the correctness of my determination.

Figure
la.

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il ©
il ol,
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she

il a.

Sige

— © a ©

ro po ro bw bw bo WS tO
a

bo
—
baa

EXPLANATION OF THE PLATES.

PLATE L

1. Stenothocheres egregius n. gen., n. sp.

Female seen from below, >< 58; a@. antennula, c. antenna, f. maxilla, g. maxilliped, m. first
trunk-leg, x. second trunk-leg, p. caudal stylet, 7. genital aperture.

The same female seen from left side.

Male seen from below, > 58; s. frontal thread.

Three eggs, X 58.

Head of female, < 192; b. olfactory seta of the antennula, ¢. antenna, ¢. maxillula, h. sub-
median skeleton.

First trunk-leg of female seen from the inner side, X 240; 7. inner branch.

Abdomen and posterior part of the trunk of female seen from below, 240; g. genital
aperture, ¢. caudal stylets, w. trunk-leg of second pair.

The same parts as in fig. 1g seen from left side, 240; g. genital aperture, m. its muscles,
r. receptaculum seminis, uv. trunk-leg.

Male seen from below, >< 255; a. antennula, 0. its olfactory seta, ¢. antenna, d. mouth,
e. maxillula, f. maxilla, g. maxilliped, m. first trunk-leg, . second trunk-leg, 0. abdomen.
The same male seen from left side; e¢. maxillula.

Larva seen from below, > 230; on the right side of the figure the second trunk-leg, on
the left side the branches of the first trunk-leg are omitted. 0. olfactory seta of the anten-
nula, e. maxillula, 7, pouch, m. first pair of trunk-legs, m’. transverse outstanding list between

’

the legs of the first pair, ». second pair of trunk-legs, n’. transverse list between the legs

of the second pair, 0. abdomen, p’. long seta of the caudal stylet.

2. Stenothocheres Sarsii n. sp.

Large female seen from below, > 26; s. frontal threads.

Male seen from below, > 26.

Lump of eggs, X 26.

Smaller female seen from below, X 48.

The same female seen from left side.

Head of female, >< 165; antennule omitted; c. antenna.

Antennula of female, 170; the olfactory seta partly broken off.

Trunk-leg of first pair of female seen from below, XX 170; e. exterior branch.
Abdomen and posterior part of the trunk of female, X 170; g. genital aperture.

Figure
2k.

21.

il toy,

4a.
4b.

192

Male seen from below, > 170; s. frontal thread, a. spines, perhaps rudiments of a third
pair of trunk-legs.

The same male seen from left side, X 170; a. spines, perhaps rudiments of a third pair
of trunk-legs.

3. Homoeoscelis minuta n. gen., n. sp.
Genital area and surroundings of female, X< 190; e. solid chitinous list, 7. receptaculum
seminis, s. spermatophore, ¢. caudal stylets.
Pupa hinged by a frontal thread to the epipod of the host, 170; a. antennula, ec. antenna,
f. maxilla, g. maxilliped, m. first trunk-leg, 2. second trunk-leg, p. caudal stylet, s. frontal
thread, w. rudiment of a third trunk-leg?

Pi heal

1. Homoeoscelis minuta n. gen., n. sp. (continued).
Not full-grown female, with four spermatophores, > 62.
Large female which had not begun laying eggs, x 62.
Female which had nearly finished laying eggs, X 62.
Male, X 62.
Rather small ovisac, & 62.
Fairly large ovisac, * 62.
Free larva, X 62.
Head of female, * 226.
Male seen from below, 182. (The hairs on the frontal margin are too long).
The same male seen from left side.
Larva, prepared out of the egg-membrane, X 266.

2. Spheronella elegantula n. sp.
Adult female with two spermatophores, >< 27.
Male, X 27.
Ovisac, X 27.
Rupaaeexe Dis
Genital area and its surroundings of female, > 162. Of most of the membranous hairs
only the base is drawn.
Male seen from below, >< 147. The maxilliped and the distal part of the first trunk-leg on
the left side were wanting.
Another and very large male seen from left side, > 143.

3. Spheronella Atyli n. sp.
Head of female, * 132.
Genital area and its surroundings of female, < 232.

4. Spheronella danica n. sp.

Genital area and its surroundings of an adult female, > 213.
Frontal thread of male, < 236.

Figure
4c.
4d.
he.

~

bo po to to
on

jo}

LNs}
=

193

Pretty large pupa seen from below, X 70.
Small pupa seen from right side, > 70.
Anterior part with the thread of the pupa shown in fig. 4d, >< 285.

5. Spheronella vestita n. sp.
Female, with a spermatophore, >< 100. The hair-covering of the trunk is only indicated on
its anterior part, but with the exception of the outline on the left side of the figure, only
the bases of the hairs, the “scales”, are drawn,
Genital area and its surroundings of female, >< 251; 7. receptacula seminis, indicated by
dotted lines.

6. Sphexronella chinensis n. sp.
Female, 38.
Male, X 38.
Pretty young pupa, 38.
Old pupa, > 38. The hair-covering omitted.
The pupa shown in fig. 6 ¢ seen from below, >< 148.
The pupa shown in fig. 6d seen from below, > 114. Appendages, mouth and genital
apertures of the young female are seen through the skin of the pupa.

PLATE IIL.

1. Spheronella chinensis n. sp. (continued).

Male seen from below, 198.
The same male seen from left side.
Antennula of female seen from below, >< 284.

2. Spheronella antillensis n. sp.
Young female, having thrown off the anterior third part of the skin of the pupa, X 48.
Ovisac, X 48.
The young female shown in fig. 2a, > 188; ¢. antenna.
Genital area and its surroundings of female, 294. On the right side of the figure the
receptaculum seminis is indicated by a dotted line, and a spermatophore attached to its
orifice.
Larva seen from below, > 316. Of the natatory legs only the base of the peduncles is
drawn.
Pupa seen from below, > 119.

3. Spheronella Calliopii n. sp.
Female, x 12.
Male, x 12.
Ovisac, 12.
Head of female, 83. The hairs on the lateral borders and on the sub-median skeleton
drawn only on the left side of the figure.
Distal part of the left maxilla of female seen from below, >< 166.

Left maxilliped of female seen from below, > 166,

194

Genital area and its surroundings of female, >< 150.

Male seen from below, 121.

Another male seen from left side, 151.

Larva seen from above, 117.

Larva seen from below, >< 185. Most part of the long sete of the caudal stylets and the
hairs on the branches of the left natatory Jeg of the first pair (thus on the right side of
the figure) and of the right natatory leg of the second pair are omitted.

4. Spheronella paradoxa n. sp.
Female seen from below, > 30.
Another female with a spermatophore seen from right side and attached by its ventral
thread to a marsupial plate, x 30.
Male, 30.
Ovisac, X 30.
Hinged larva, developing itself into a male, >< 30.
“Female pupa’ seen from below, > 30.
Young female that has just burst the “skin of the pupa” (the shrivelled skin of the larva),
SK a).
Male seen from below, > 134; q. spermatothece, s. frontal thread.
Another male seen from left side, < 134.
The dorsal side of the head of the male shown in fig. 4i, exhibiting the hollow spaces
beneath the skin, * 134.
Much protruding rostrum of a male, exhibiting the mouth-border, the antenna and the ma-
xillula with its two principal branches and the additional branch, >< 270.

PLATE IV.

1. Spheeronella paradoxa n. sp. (continued).

Head of female, >< 263.

Genital area of female, >< 220. The receptacula seminis indicated by dotted lines; the
caudal stylets without sete.

Free larva, >< 167. Parts of the natatory legs omitted.

Hinged larva, developing itself into a male, > 103. Comp. pl. Ill, fig. 4 e.

Anterior half of the cephalothorax of a larva which had been hinged a rather short time,
> 236; s. adhesive plate.

“Female pupa” seen from below, 170. The female develops itself beneath the larval
skin which has shrunk extremely, and most of the appendages of which are seen: a. anten-
nula, c¢. antenna, g. maxilliped, m. first natatory leg, ». second natatory leg, o. abdomen,
s. adhesive plate.

Young female that has just burst the ‘skin of the pupa” (the same animal as shown in
pl. Ill, fig. 4¢), seen from right side, 150; s. adhesive plate.

rather young female, seen from below, >< 88: ¢. ventral projection terminating in a thread;
wu. the disk-like expanded end of the thread,

195

fieans 2. Spheronella abyssi n. sp.

2a. Female with two ovisacs adhering to its anterior outline, >< 26.

2b. Male, < 26.

2c. Genital area of female, >< 174. The genital apertures are open; one caudal stylet is absent;
two spermatophores and the proximal part of the stalk af a third one are seen.

2d. Male seen from below, 152.

2e. The same male seen from left side.

3. Spheronella Argissze n. sp.

3a. Adult, but shrunk and crooked female with a male atlached to it near the genital area
< 30; m. male.

3b. Ovisac, X 30.

3c. Recently hatched female attached to a gill, & 30.

3d. The same female, < 240.

3e. Part of the sub-median skeleton, right maxilla and the proximal part of right maxilliped of
the adult female, seen from below, > 276; e. maxilla, 7. base of the maxilliped.

3 f. Genital area, with one spermatophore, of female, >< 150.

3g. Male seen from below, 205.

3h. The same male seen from left side.

3 i. Outlines of hollow spaces beneath the dorsal skin of the head of the male, >< 205.

3k. Right maxilliped of male seen from the anterior side, >< 316. At the proximal end is shown
a process of the second pair of the sub-median skeleton.

3 1. Female pupa seen from below, > 162; @. antennula, c. antenna, e¢. maxillula, f. maxilla,
g. maxilliped, p. caudal stylets, s. funnel-shaped adhesive plate.

,

3m. The same female pupa seen from left side.
3n. Anterior half of cephalothorax of larva, >< 260.

4. Spheronella Metopz n. sp.

4a. Genital area of female, 254; 0. orifice of one of the receptacula seminis.

PEATE: Vv.

1. Spheronella Metopx n. sp. (continued).
1a. Female, X 68.
1b. Male, X 68.
lc. Ovisac with about half-developed young ones, X 68.
1d. Head of female seen from below, >< 224.
le. Greater part of the head of female seen from left side and showing the antennula (the sete
omitted), rostrum with antenna and maxillula, the maxilla, and the base of the maxilliped.
f. Male seen from below, X 185.
g. The same male seen from left side.

2. Sphexronella Holbélli n. sp.
2a. Female, X 20.
2b. Male, X 20.

25*

Figure

Qe.

Ovisac, X 20.

Head of female, X 152. The distal part of one maxilliped broken off.

Genital area of female, 125.

Male, somewhat crooked, seen from below, > 173. The distal part of one maxilliped broken off.
The same male seen from left side.

3. Spheronella intermedia n. sp.
Smaller female, with two spermatophores, >< 48.
Male, X 48.
Ovisac, X 48.
Head of female, 270.
Genital area of female, > ISI.
Male seen from below, >< 203.
The same male seen from left side.
Cephalothorax of larva, 223. Natatory legs totally and appendages on right side of the
figure almost totally omitted.

4. Spheronella capensis n. sp.
Female, X 53.
Male, X< 53.

Ovisac, xX bs:
PLATE Vi.

1. Spheronella capensis n. sp. (continued).
Head of female, 342.
Genital area of female, >< 196; 0. orifice of one receptaculum seminis, r. The other recep-
taculum not drawn, but its orifice is seen.
Male seen from below, > 243.

The same male seen from left side.

2. Spheronella Gitanopsidis n. sp.
Female, 28.
Male, X 28.
Ovisac, 28.
Head of female, 202. (The antenne not quite correct, comp. the description).
Genital area of female, >< 205; ¢. caudal stylets.
Male seen from below, > 255.

The same male seen from left side.

3, Spheronella Giardii n. sp.
Adult female which had not yet begun laying eggs, > 28.
Male, X 28.
Female which no doubt had finished laying eggs, and with a male adhering to its ventral
surface, X 28.

lea OR
Ovisac, X 28,

Figure

3e. Head of female, 236,

3 f. Genital area, < 239.

3g. Male seen from below, > 183.

3h. Another male seen from left side, >< 183. In this and in the preceding figure the hairs of
the trunk are not correctly drawn, comp. the description p. 135.

3 i. Male pupa seen from below, >< 194; the distal part of the frontal thread broken. off.

3k. Another male pupa seen from left side, < 190; a antennula, ¢c. antenna.

3]. Female pupa seen from left side, > 190.

4. Spheronella Bonnieri n. sp.
4a. Female, X 30.
4b. Male wrapped up in threads (comp. p. 137), >< 30.
4c. Ovisac, X 30.
4d. Genital area, 168.

PLATE: VIL

1. Spheronella Bonnieri n. sp. (continued).
la. Male seen from below, >< 174; q. spermatothec.
1b. The same male seen from left side.

2. Spheronella longipes n. sp.
2a. About half-grown female, 37.
Ob ea Ovisac es 1.
2c, Basal part of antennula, rostrum with antenna (¢) and maxilula, and maxilla of a very young

female seen from left side, >< 310.
2d. Very young female, x 37.
2e. The same female, < 205.
2 f. Cephalothorax of larva, 288. The natatory legs omitted.
2g. Pupa seen from below, > 164.
3. Spheronella Amphilochi n. sp.

3a. Head of female, 264.
3b. Genital area of female, 254.

4, Spheronella Dulichizw n. sp.
4a. Female, X 41.
4b. Ovisac, X 41.
4c. Head of female, < 120.
4d. Genital area of female, * 194.

5. Spheronella Acanthozonis n. sp.
a. Female seen from right side, X !/2.
b. The same female seen from below, > 12/2.
ce. Head of female, 79.
d. Genital area of female, > 77,

or or or OH

Figure
6 a.

3D:

198

6. Spheronella frontalis n. sp.
Male seen from below, X 66; g. spermatotheca (the other spermatotheca is seen to the left).
The hairs on the lateral margin of the head and on the trunk drawn only on the left side
of the figure; of the maxilliped on the same side only the basal jomt is drawn and its hairs
are omitted.
Another male seen from left side.
Antenna of male, 280.
Maxillula of male seen from the exterior side, >< 280; e.’ additional branch.
The proximal larger part of the basal joint of the left maxilliped of male seen from the
anterior side, >< 185.
First right trunk-leg of male seen from below, >< 265.
Second right trunk leg of male seen from below, > 265.
Small part of the skin of male from the dorsal side of the trunk a little in advance of the
middle, > 280.
Genital area of female, > 166; ¢. caudal stylets (their sete no doubt broken off).

PLATE VIII.

1. Spheronella frontalis n. sp. (continued).

Female, < 16.

Male, X 16.

Ovisacy >< 1165

Head of female, & 108. The antennula on left side of the figure almost totally omitted.
Larger part of cephalothorax of larva (with the peduncles of first pair of natatory legs), >< 200.

2. Spheronella microcephala Giard and Bonnier.
Large female, < 21.
Male, X 21.
Ovisac, < 21.
Head of female seen from below, 334.
Plate representing the frontal border, mouth and one maxillula of another female seen from
below, 334.
Genital area of female, >< 116. Receptacula seminis and their orifices omitted.
Male seen from below, >< 206.
The same male seen from left side, > 208; i. process of the first pair from the sub-median
skeleton.
Larva with an adhesive plate covering the front, >< 196. The branches of the natatory legs
omitted.
Animal considered to be a pupa of this species, >< 135.

3. Spheronella decorata n. sp.
Large female, 11.
Male, X 11.
Ovisac, X 11.

199
Figure
3d. Head of female seen from in front, >< 66.
3e. Head of another female seen from below, >< 117.
3 f. Male seen from below, > 81.
3g. Another male seen from left side, 81.
3h. Distal part of a maxilliped of male, >< 296.
31, Adult larva seen from below, 154. The setie of two of the natatory legs omitted.
3k. Another similar larva seen from left side. A part of the olfactory seta, the greater part of
the long caudal seta and most of the sete of the natatory legs omitted.
3 1. Frontal decoration of larva, > 308.
3m. Antenne of larva seen from below, ab. 250.
3n. Right maxilla of larva seen from below, 312.
30. The two proximal joints of left maxilla of larva seen in an oblique direction.

PLATE IX.

1. Spheronella decorata n. sp. (continued).

1a. Genital area of female, « 94.
1b. Left maxilla of female seen from below, 323.

2. Spheronella modesta n. sp.

a. Female, X 23.
b. Male, < 23.
Ovisacs — some containing eggs, others young ones —, 23.
d. Head of female, 230; ax. peculiar area.
e. Genital area of female, 180.
f. Male seen from below, X 138.
g. Frontal border and one antennula of the same male, < 264.
h. Another male seen from left side, 138.

i. Anterior part of larva, 294.

ro bp tO bw b bw vo 9 t9

83. Spheronella dispar n. sp.

3a. Small adult female, > 37.

3b. Male, X 37.

3c. Ovisaes laid by the female shown in fig. 3a, 37.

3d. Large adult female, >< 37.

3 e. Ovisacs laid by the female shown in fig. 3d, 37.

3 f. Head of female, 185. Of the antennula on the right side of the figure only the base
is indicated.

3g. Genital area of female, 243.

3h. Male seen from below, 202; 7. first process of the sub-median skeleton, 7. second process
of the same, y. lateral keel behind the peculiar frontal plate.

3.i. Another male seen from left side, < 219.

3k. Larva, 275. The sete of two of the natatory legs omitted.

iS
Qu

=

So
lve]

ik Be

fac]

200

4. Sphearonella insignis n. sp.

VW OF

Female from Diastylis levis Norm., >< 25.

Male from Diast. levis, < 25.

Head of the female shown in fig. 4a, 160. Of the antennula on the right side of the
figure only the base is indicated.

Genital area of the female shown in fig. 4a, >< 186.

Genital area of a female from Diast. cornuta Boeck, 173.

Right antennula of the female from Diast. cornuta seen from below, >< 290.

Distal part of right maxilliped of the female from Diust. eornuta, >< 290.

PLATE X.

1. Spheronella insignis n. sp. (continued).

Male from Diast. levis seen from left side, >< 67.

Anterior part of the male shown in fig 1a and seen from below, 208; x. peculiar ring,
y. lateral keel, v. frontal plate.

Male from Diast. cornuta seen from below, 160.

The same male seen from left side.

Larva from Diast. cornuta, > 151. The branches of the natatory legs omitted.

Front part of the larva shown in fig. le, 275.

Right maxilla of the same larva, >< 350.

Pupa from Diast. cornuta seen from below, >< 207.

2. Spheronella curtipes n. sp.
Female, 12.
Male, 12.
Ovisac, X< 12.
Head of female, 192. The distal part of one maxilliped broken off.
Genital area of female, > 71; r. one receptaculum seminis — the other omitted.
Male seen from below, > 51.
Another male seen from left side, >< 47.

3. Spheronella affinis n. sp.
Female, > QS8.
Ovisac, X 28.
Head of female, >< 292. The hairs of the sub-median skeleton drawn only on the right side
of the figure.
Genital area of female, > 146. Both receptacula seminis are indicated by dotted lines, and

on the orifice of one a stalk of a spermatophore is attached.

4. Spheronella Munnopsidis n. sp.
Anterior half (namely: the head with the basal part of the antenns, and the larger part of
the thorax with the first pair of legs and the basal portion of the three following pairs of
legs) of an adult female of Munnopsis typica M. Sars, the extended marsupium of which is
occupied by a female parasite with twenty ovisacs; many of the ovisacs are seen through the

marsupial plates. The host is seen from below, 1/8.

Figure
4b,

4c.

4d.

or or
erp

or

6 a.

6 b.

il Bi,

1h.

201

Area on the female answering to the head and showing the antennule and its other organs,
$< OR

Genital area of female, >< 68; g. genital aperture, %. hole (or very small thin-skinned area
with minute holes), 7. one receptaculum seminis indicated by a dotted line, with a stalk of a
spermatophore, s’., attached to its orifice; s. spermatophore attached to the orifice of the
other receptaculum which is not drawn.

Antennula, antenna, maxilla and maxilliped from the right side of a not quite full-grown larva
seen from below, 196.

5. Choniostoma mirabile H. J. H.

Female seen from below, X 4.

Ovisac with eggs, XX 4.

Ovisac with full-grown larve, >< 4. (These three figures, fig. 3a—3c, are also found in my
report in *Dijmphna-Togtets zool.-bot. Udbytte’’.)

6. Choniostoma Hansenii Giard and Bonnier,

Rostrum of female cut off and seen from right side, > 203; a. membrane of the mouth-
border, b. hairs of the mouth-border, ¢. maxillula, ¢’. additional branch of the maxillula (its
distal part is broken off, but indicated by dotted lines).

Larger part of the terminal face of the rostrum shown in fig. 5a, 321; d. labrum, e. mandible.

PLATE Xd.

1. Choniostoma mirabile H. J. H. (continued).

Head of female, > 104; a. antennula, b. olfactory seta, ¢. antenna, g. rudimentary maxilliped,
h. sub-median skeleton, /. frame of the head, &’. lateral process of the frame, /’’. chitinous
knots belonging to the frame and lying partly beneath the soft skin, ¢. posterior chitinous
ring, w. anterior chitinous ring.

Genital area of female, >< 104; e. solid chitine, 7. one receptaculum seminis indicated by
dotted lines (the other receptaculum is omitted). The genital apertures are open.

Young one in the Nauplius stage seen from left side, >< 81.

Young one in the Nauplius slage seen from below, > 81. (Fig. le and 1d are found in
“Dijmphna-Togtet’’.)

Hinged larva, X 210; s. adhesive plate. The sete of the two natatory legs on the left side
of the figure are omitted.

Anterior part of a full-grown larva pulled out of its egg-membrane, >< 261.

Pupa seen from below, 110; «@. antennula, s. adhesive plate. Posteriorly and on the sides
the outline of the contents is somewhat remoyed from the margin, and posteriorly are seen
the hairs of the animal shining through the skin of the pupa.

Large pupa seen from below, > 40.

Smaller pupa seen from below, > 40; s. adhesive plate. The contents marked with a
greyish tint.

Small pupa seen from below, 40.

26

Figure
eae
ab.

3)
°

| b.

202

8. Choniostoma Hansenii Giard and Bonnier (continued).
Adult female, 79/4.
Small female, ?9/s.
Ovisac, xX 79/4.
Head of an adult female, 130.
Part of the skin of the ventral side outside the head of a small female, 130.
Genital area of an adult female, >< 128.

“N

3. Mysidion commune n. gen., n. sp.
The contents of the marsupium of an Evythrops s rratus G. O. S. seen from below and con-
sisting of the female parasite with ils seventeen ovisacs, >< 12.
Another female with its ovisacs from Hr. serratus seen from above (the head situated on the
dorsal side and its front turning backward),
only in three of the thirteen ovisacs.

25; g. maxillipeds. The contents indicated

Four ovisacs of another female, >< 25. In the largest ovisac only a small part of the con-
tents, namely six larve, are drawn.

Male, X< 25.

Posterior half of the ventral surface of female, >< 42; e. skeleton surrounding one genital
aperture; 7. transition between the receptaculum seminis and one of its ducts, s. spermatophores.
Left genital aperture with its lips, muscles and the surrounding skeleton seen from below, >< 190.
Male seen from below, > 258; g. spermatothecw. The hair-covering of the trunk drawn
only on one side.

Another male seen from left side, >< 258; s. frontal thread, ¢. part of a marsupial plate of
the host, a. conical eminence on the dorsal side of the head.

Very small pupa seen from below, >< 188; 2. outline of a mouth (?) beneath the skin of the
pupa. — This and all the other figures of this parasite are drawn from animals taken on
Erythrops serratus GO. S.

PLATE XII.

1. Mysidion commune n. gen., n. sp. (continued).
Head of female, > 182; a. antennula, w. process of unknown nature (perhaps. stiffened
viscous substance on the opening of the gland producing it).
Pupa with. dorsal thread, > 25. (The same enlargement as in fig. 3b—3d on pl. XI.)
Pupa seen obliquely, >< 182; a. (misseript for ¢.) antenna, f. maxilla, g. maxilliped, 7. skeleton
surrounding the future genital aperture, ¢. (misscript for a.) antennula, w. basal part of the
dorsal thread shining through the animal, ». distal part of the thread, x. eminence at the
mouth of the pupa stage, y. mouth of the pupa stage, y’. chitinous lists on the side of the
rostrum of the pupa. The mouth and the maxillule of the young female are seen at the
anterior end of the animal.
Very young female in possession of characters which it loses afterwards, >< 182; a. (misscript
for ¢.) antenna, 7. skeleton surrounding the future genital aperture, ¢. (misscript for @.) anten-
nula, wv. basal part of the dorsal thread, v. distal part of the dorsal thread, a. odd ventral
process situated at the place of the mouth of the papa stage, 2. body of unknown nature,

203

Figure 2. Mysidion abyssorum n. sp.

2a. Head of female, < 182; a. antennula, e’. additional branch of the maxillula.

2b. Genital aperture and the surrounding skeleton of female, >< 123; g. genital aperture, A. plate
formed of a kind of viscous substance and covering the lips of the genital aperture and the
skeleton behind them, 7. stalks of ovisacs, the basal parts of which are confluent and form
the plate mentioned, & hole (or very small thin-skinned area with minute holes) at the
anterior end of the skeleton,

2c. Male, 43.

2d. Very small male with frontal thread, > 43.

2e. Normal male seen from below, >< 256; e. maxillula, g. spermatotheca, w. line of unknown
nature,

2 f. Normal male seen from left side, * 236; a. conical eminence on the dorsal side of the head.

2g. Frontal thread of one of the minute males, 260.

2h. Larva seen from below, 264. The natatory legs are omitted.

2 i. Hinged larva seen from above, X 125.

3. Aspidoecia Normani Giard and Bonnier. *)

3a. Male of Hrythrops abyssorwm G. O. Sars seen from above and infested with nine female parasites
of very different size and one larva, >< 1%/2; a. larger female, b. smaller females, 7. larva,
m. mnale. The posterior part of the abdomen of the host is omitted.

3b. Female with two rudimentary ovisacs (w.) and three larve (v.) attached to the dorsal surface
of the second abdominal segment of Erythrops serratus G. O. Sars, >< 24; 7°. chitinous knots
where the entrances to the receptaculum seminis must be found.

3c. Sub-adult female attached to the back of the first abdominal segment of an Er. serratus and
seen from the dorsal side, >< 39; x. two males hinged by their frontal thread, y. part of the
skin of the host.

3d. Head of a female from Er. serratus, seen much from in front, >< 350; d. mouth, e. maxillula,
s. adhesive plate, ¢. internal space possessing a peculiar refraction of light.

3 e, External genital organs and receptaculum seminis of the female whose head is shown in fig. 3d,
< 70; e. solid ring, g. genital aperture, /. hole in the ring, 0. chitinous knots, 7. receptaculum
seminis with its ducts.

3 f. Adult female from Er. abyssorum, >< 24; the head is seen in the middle.

3g. The same male seen from the side opposite of that of fig. 3f; r. ring around a genital aper-
ture, 7’. chitinous knots.

3h. Head of the female shown in the two preceding figures, cleaned with caustic potash and seen
from below, 350; @. antennula,

3 i. Genital aperture and its surroundings of the female shown in fig. 3f, > 170; e. ring-shaped
skeleton, f’. less solidly chitinised part of the ring, g. genital aperture with its lips, #. hole
in the ring, m. muscles.

3k. Male from Er. serratus seen from below, >< 291; 6. olfactory seta of the antennula, g. sper-
matotheca. (In other specimens two spermatothecee were found.)

3]. Another male from Ey. serratus seen from left side, >< 324.

1) On the plate is written Normanni instead of Normani.

26°

Figure
3m.

ha.
Ab.

hc.

204

Larva which was attached to the female shown in fig. 3b, its skin is burst along the lateral
margins, and it contains a fully developed male, >< 184; a. antennula of the larva, b. olfactory
seta of the antennula, s. viscous substance proceeding from the front of the male.

Right maxilla and maxilliped with a part of the sub-median skeleton of the larva shown in
fig. 3a as attached to the carapace of Hr. abyssorum and marked /.; the organs are scen
from below, > 330; h. sub-median skeleton.

PLATE XII
(Supplements to pl. Il, HI and X.)

1. Homoeoscelis mediterranea n. sp.
Female, 110.
Male, X 110.
Ovisac, X 110.
Head of female, >< 312. The short hairs on the lateral margins omitted.
Genital area and its surroundings of female, >< 322; the receptacula seminis are indicated by
dotted lines; on the orifice of one are attached a spermatophore and the basal part of the
stalk of another spermatophore, on the orifice of the other are seen parts of the stalks of
two spermatophores.
Male seen from below, 230.
Male seen from left side, >< 230.
Full-grown larva seen from left side, 297. Most of the natatory legs omitted.

2. Spheronella danica n.sp. (Supplement to fig. 4 on pl. IL)
Genital area and its surroundings of a scarcely half-grown female, < 216.

8. Spheronella Leptocheiri n. sp.
Female, 36.
Male, 36.
Head of female, 165.
Genital area and its surroundings of female, 216; e. solidly chitinised ring, g. genital aper-
tures, m. muscles, 7. receptacula seminis, ¢. caudal stylets.
Outline of a part of a male seen from below, showing the processes of the sub-median
skeleton, one maxilliped, the legs on the right side and the caudal stylets, >< 276.

4. Spheronella messinensis n. sp.
Female with two spermatophores, > 62.
Head of female, 214.
Genital area of female, X 274. The receptacula seminis are indicated by dotted lines, and a
spermatophore is attached to the orifice of one.

5. Spheronella irregularis n. sp.
Female with three spermatophores, > 41.
Ovisac, X 41.

205
Figure
5. Head of female, X 204. Antennule, one maxilliped and the distal part of the antenne are
broken off; the hairs almost totally omitted on the right half of the figure,

5d. Genital area of female, > 202.

6. Spheronella marginata n. sp.

6a. Female, < 41.

6b. Male, x 41.

6c. Ovisac, 41.

6d. Head of female, > 190; a. antennula, f. rudimentary maxilla.

6 e. Genital area of female, >< 280. Only one of the caudal stylets is found. The receptacula
seminis indicated by dotted lines.

6 f. Male seen from below, > 190. The trunk misshaped by pressure,

6g. Cephalothorax of a full-grown larva, X 273. The natatory legs and most of the olfactory
seta on the right side of the figure omitted.

6h. The two distal joints of a maxilla of the larva, 273.

Biavaveul has

Page 4, line 6, for “J. Sparre-Schneider” read “J. Sparre Schneider”.
— 7, line 5 from bottom, for ‘antennule” read “antennula”.
— 9, line 5 from bottom, for ‘in” read “within”.
— 11, line 1, for “new a” vead “a new”.
— 11, line 8 from bottom, for ‘twenty-four’ read “twenty-one”.
— 11, line 2 from bottom, for “Stenotocheres” read “Stenothocheres”.
— 13, line 5 from bottom, for “Croisic” read “le Croisic’. — The same error is found in p. 14, line & from
bottom, and in p. 16, line 11 from bottom.
— 18, line 17, for “larve” read “larva”.
— 33, line 1 and 2, for “of medium length” read “comparatively long”.
— 37, fine 4, for “acute” read ‘rectangular’.
— 37, line 7 from bottom, for “S. Holbolli” read “S. Holbélli”.
— 47, line 12 from bottom, for “larva” read ‘larve”.
— 52, line 18, for “Homoeoscelis” read *Homoeoscelis minuta”.
— 52, line 16 from bottom, for “larva” read “larve”.
— 54, line 17 from bottom, for “smaller, 125mm.” read “between “125mm. and ‘147 mm.”.
— 59, line 9, for “at least the female pupe” read “the pupa of both sexes”.
— 55, line 13, for “125mm.” read “147 mm.”.
— 93, line 7, for *body” read “trunk”.
-— 115, line 2, for “maxille” read ‘maxillulie”.

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HJ Hansen: Choniostomatide .

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4. Spher. danica n sp.
HiT Hansen: del

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H. J Hansen: Choniostomatida.

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1. Homoeoscelis mediterranea ni ygen.nsp 2. Spheronella dantca x sp 3 Spher. Leptochetrt n sp
4. Spher. messinensis np 5. Spher. trregularts n. sp CO. Spher. margitnata n. sp.

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