(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "The Trematoda of British fishes"



- 



■ 



THE 



RAY SOCIETY 



INSTITUTED MDCCCXLIV 




This volume (No. 131 of the Series) is issued to the Subscribers to the 
Ray Society for the Two Years 1944 and 1945, and at a price of 

45/- to the Public. 



LONDON 

MCMXLVII 



06 

THE TREMATODA OF 
BRITISH FISHES 



BY 

BEN DAWES, D.Sc., A.R.C.S., D.I.C., F.L.S. 

(Reader in Zoologj^ University of London, King's College) 



LONDON 
PRINTED FOR THE RAY SOCIETY 

SOLD BY 

BERNARD QUARITCH, LTD. 
11, Grapton Street, New Bond Street, London, W. 1 

1947 



To My Mother 



Made and printed in Great Britain by 

Adlard & Son, Ltd., 

at their works, Bartholomew Press, Dorking. 



PREFACE. 

In writing this monograph, my aim has been to describe the trematodes 
of British fishes more fully than was possible in my book, The Trema- 
toda (Cambridge University Press, 1946), but not to presume to treat 
the subject exhaustively. Because of their inconstant shape, indeter- 
minate growth and structural variability, trematodes are not easy to 
describe or to arrange systematically. Several British zoologists have 
collected fish trematodes and listed their names without describing 
them. The literature contains a few good descriptions, but also some 
very inadequate records, and we owe much of our knowledge of the 
trematode parasites of fishes to continental and American zoologists. 
The distribution of trematodes is sporadic, their discovery fortuitous, 
and it will be evident that more work remains to be done than can be 
done by a single zoologist before our systematic plan of fish trematodes 
can be completed. I have made some additions to our knowledge, 
but there is plenty of scope for further work. 

Some of the forms mentioned in the following pages have not been 
collected as yet in Britain, and it can be argued that these do not 
therefore belong to the British fauna. British marine fishes are not 
confined to British waters, however, and it would be illogical not to 
include, for instance, forms that occur in some of our commonest fishes 
caught off the coast of France or Belgium and in other localities not 
very distant from our shores. In some instances it has been difficult 
for me to decide where an imaginary line should be drawn and what 
forms should be included in or excluded from the list, but I have tried 
to include all the forms we can reasonably expect to turn up in British 
waters sooner or later. The hosts have been denoted by their common 
names in order to save space, but the corresponding scientific names 
are listed on pp. 339-43. 

I am indebted to several zoologists for encouragement and assis- 
tance, but particularly to Professor C. M. Yonge, F.R.S., in whose 
Department of Zoology at Bristol much of the work was done. Dr. 
W. T. Caiman, F.R.S., gave me some friendly advice and criticism, 
and Dr. H. A. Bay lis has been kind enough to check the names of the 
trematodes. Several persons have allowed me to examine specimens, 
and appropriate acknowledgments have been made in the text. 
Most of my own specimens were collected in the Marine Biological 
Laboratory, Plymouth, and I am grateful for the assistance given to 
me by the staff there. I wish also to thank the printers for the con- 
sideration they have shown me and the care they have taken over the 
production of my book. 

BEN DAWES. 

King's College, 
London, W.C. 2 ; 
July 25, 1946. 



CONTENTS 



Preface ........... 

I. The Phylum Platyhelminthes and the Class Trematoda 
II. The Three Orders of the Trematoda .... 

III. The Morphology of the Monogenea .... 

a. External Structure — 

(a) General ........ 

(b) The Prohaptor ...... 

(c) The Opisthaptor ...... 

b. Internal Structure — ■ 

(a) The General Musculature and Parenchyma . 

(b) The Components of the Raptors and their Mode of Action 

(c) The Nervous System and Receptors 

(d) The Digestive System 

(e) The Excretory System 

(f ) The Reproductive Systems 

IV. The Morphology of the Aspidogastrea 

V. The^Morphology of the Digenea . 

i. The Sub-order Gasterostomata . 
n. The Sub-order Prosostomata 

a. External Structure . 

B. Internal Structure — 

(a) The General Musculature and Parenchyma . 

(b) The Nervous System .... 

(c) The Digestive System .... 

(d) The Excretory System .... 

(e) The Reproductive Systems 

VI. Trematodes of the Order Monogenea .... 
Key to the Families and Higher Groups of the Monogenea 

VII. Trematodes of the Order Digenea .... 

Key to the Families of Digenea Parasitic in European Fishes 

VIII. List of Literature ....... 

Alphabetical List of Hosts ...... 

List of Hosts and Their, Parasites .... 

General and Systematic Index ..... 



PAGE 
V 

1 

2 
3 



6 

7 
7 
8 
8 
8 

10 

12 

12 
13 

14 

15 
16 
17 
17 

18 

22 
23 
146 
147 
311 
339 
345 
357 



753 



Abbreviations Used in the Figures. 

A. — ab, retracted ecsoma ; as, anterior sucker ; av, accessory vitelloduct 

connecting the vaginae. 
B. — b, brain ; bs, buccal sucker. 
C. — c, caecum ; ca, copulatory apparatus ; eg, cephalic glands ; eg', caudal 

glands ; ci, cirrus ; cm, closing muscles of haptorial valves. 
E. — e, eye ; e', egg ; e", embryo ; eb, ejaculatory bulb ; ec, excretory canal ; 

ed, ejaculatory duct ; egg, shelled-egg ; ep, excretory pore ; eu, eggs 

in utero. 
G. — ga, genital atrium ; gic, genito -intestinal canal ; gl, lamella of gill ; gp, 

genital pore. 
H. — hd, hermaphrodite duct. 
I. — i, intestine. 
L. — 1, terminal process or lappet ; lc, large clamp ; Lc, Laurer's canal ; Ip, 

process of lip. 
M. — m, mouth ; mc, muscular crest ; my, myoblast. 
O. — o, ovary ; ce, oesophagus ; oo, ootype ; om, opening muscles of haptorial 

valves ; os, oral sucker ; ov, oviduct. 
P. — p, pharynx ; pg, prostate glands ; pr, prostatic vesicle ; pra, anterior 

prostatic vesicle ; prp, posterior prostatic vesicle. 
R. — ro, " ring-organ " ; rs, receptaculum seminis. 
S. — s, larger sucker ; s', small sucker ; sg, shell glands ; sq, squamodisk ; sv, 

seminal vesicle. 
T. — t, testes. 
U. — u, uterus. 
V. — v, vitellarium ; va, vagina ; vd, vas deferens ; vg, vagina ; vn, ventral 

nerve ; vp, vaginal pore ; vs, ventral sucker. 
Z. — zo, zone of the ovary ; zt, zone of the testes. 



&>\CAi 




THE TREMATODA OF 
BRITISH FISHES 



I. THE PHYLUM PLATYHELMINTHES AND THE CLASS 

TREMATODA. 

The phylum Platyhelminthes comprises four well-defined classes, 
the Turbellaria, Temnocephalida, Trematoda and Cestoda. These 
types of flatworm differ notably among themselves. They may be 
monoecious or dioecious, covered with cilia or a cuticle, having or 
lacking a gut and special organs of attachment, and they may have 
very different modes of life and life -histories. Yet they agree in being 
bilaterally symmetrical, triploblastic, accelomate Metazoa devoid of 
a blood vascular system, having a well-developed muscular system, 
a spongy parenchymatous investment to the internal organs, and a 
protonephridial excretory system in which the flame -cell is the funda- 
mental unit. The great majority of Platyhelminthes are herma- 
phrodite. 

Adult Trematoda (flukes) and Cestoda (tapeworms and their 
allies) differ from almost all other Platyhelminthes in their parasitic 
mode of life. A few exceptional Turbellaria habitually associate with 
Mollusca and Echinodermata, and some are parasitic in echinoids and 
holothurians, but the vast majority live in freedom. Temnocephalida 
are passengers, not parasites, because while living attached to fresh- 
water Crustacea they devour insect larvae, rotifers and other small 
creatures, and are thus self-supporting. Adult Trematoda and Cestoda 
habitually nourish themselves at the expense of a host animal. Some 
trematodes attach themselves to superficial parts of the host and are 
called ectoparasites ; others, and all Cestodes, penetrate into the interior 
of the host and five in one of the internal organs, thus being endo- 
parasites. Cestodes can be distinguished from trematodes by the 
absence of a gut, feeding in these worms being by the absorption of 
predigested nutriment through the integument. Detached pro- 
glottides of some cestodes may five independently for a short period 
in the intestine of their hosts, a location in which trematodes also 
occur, and they may be mistaken for flukes by the unwary zoologist, 
but the absence of a gut invariably betrays their true identity. Trema- 
toda, therefore, are ectoparasitic or endoparasitic Platyhelminthes 
having a cuticle and an alimentary canal. 



^ THE TREMATODA OF BRITISH FISHES 

II. THE THREE ORDERS OF THE TREMATODA. 

Zeder (1800) first attempted a systematic classification of parasitic 
worms of all kinds and referred to flukes as " sucking worms." 
Rudolphi (1808) invented the name " Trematoda," which is now in 
general use. During the early part of the 19th century the study of 
trematodes made much progress, and in 1856 two schemes of classi- 
fication were proposed independently : Burmeister divided the 
Trematoda into Malacobothrii, Pectobothrii and Aspidobothrii (groups 
roughly represented by forms now known as distomes and holostomes, 
Polystomids, and Aspidogastrids respectively) ; Leuckart divided 
them into the " Distomea " and " Polystomea," endo- and ecto- 
parasites respectively. Carus, in 1863, renamed Leuckart's groups 
Digenea and Monogenea (the "Trematodes Digeneses" and "Trema- 
todes Monogeneses" of v. Beneden, 1858). On the whole, Leuckart's 
scheme has been the more popular, although in 1892 Monticelli 
attempted to revive the three groups of Burmeister under the new 
names Heterocotylea (monogenetic forms), Malacocotylea (digenetic 
forms) and Aspidocotylea (Aspidogaster) . Faust and Tang (1936) 
made further efforts of this kind, reminding us that while Aspidogaster 
combines the characters of both Monogenea and Digenea, it (and its 
allies) cannot rightly be included in either group because of the equi- 
vocal nature of the life -history, which in some instances is completed 
in a single host, but in others seems to require two. Aspidogastrids 
occur in fishes, chelonians and molluscs, but do not seem to have been 
found in fishes in Britain (though it is likely that they occur here). 
In spite of the fact that they form a very small group they will be 
regarded here as of equal standing with Monogenea and Digenea, 
forming the third order, the Aspidogastrea. 

The three main types of Trematoda can be recognized in a general 
way by superficial characters, the nature of the organs of adhesion 
and the positions of various apertures on the surface of the body. In 
Digenea the adhesive organs are generally two comparatively simple, 
more or less hemispherical, muscular suckers, unaccompanied by 
accessories. One encircles the mouth and is called the oral sucker, 
the other is situated somewhere on the ventral surface of the body 
and is called the ventral, if far back the posterior sucker. In Mono- 
genea adhesion to the host is facilitated by various structures, generally 
more complicated suckers or clamp-like structures, often having a 
more or less complex system of skeletal supports, and accessories 
such as hooks and hooklets, sometimes glands which produce a sticky 
secretion. Price (19346) proposed the term haptor (Gk. haptein, to 
fasten) to denote an organ of attachment without having any morpho- 
logical implication ; I have proposed (Dawes, 1946) to designate the 
haptor near the anterior extremity the prohaptor, that near the 
posterior extremity the opisihaptor. In Aspidogastrids the prohaptor 
is sometimes absent, and the opisthaptor comprises either a single 
row, or three or four rows of suckerlets of a distinctive type {alveoli), 
the whole arrangement sometimes forming an organ which is as 
conspicuous as the " foot " of a gastropod mollusc. 



THE MORPHOLOGY OF THE MONOGENEA 3 

The mouth is almost invariably near the anterior extremity in 
both Monogenea and Digenea, but in one family of the latter (the 
Bucephalidae) it is central, as in some Turbellaria. A second opening, 
the common genital pore, is generally situated a short distance behind 
the mouth, but in Bucephalids it is near the posterior extremity. A 
few trematodes have separate male and female pores which are not 
far apart. Other openings are diagnostic. In Monogenea there is a 
pair of antero -lateral excretory pores, in Digenea a single posterior 
pore. In some Monogenea there is a single, median ventral vaginal 
pore, or a pair of more or less lateral pores, or a dorsal pore ; in Digenea 
there is a single postero-dorsal pore, the opening of Laurer's canal. 
Laurer's canal, which leads into the female reproductive system, is 
absent in Monogenea, and vaginae never occur in Digenea. 

The three orders of the Trematoda are decidedly unequal in the 
numbers of their families, the Digenea containing more than 60 
(about one-third of them confined to fishes) as well as numerous 
unclassified genera, the Monogenea 16 and the Aspidogastrea the 
solitary family Aspidogastridse. Only one family of the Monogenea is 
absent from Europe, but a number of families of the Digenea which 
parasitize fishes elsewhere have not been recorded in this continent. 
Aspidogastrids have been found in Europe, notably in the Volga delta 
and the Don, and also in the Caspian Sea and elsewhere. 



III. THE MORPHOLOGY OF THE MONOGENEA. 

In this section an attempt will be made to give a detailed impression 
(based on my previous account, see Dawes ; 1946) of the external and 
internal structure of Monogenea, so as to render fully intelligible the 
abbreviated diagnoses to be given later. For the most part, internal 
structure has not been studied in the same detail as the external, 
perhaps because taxonomic importance has been attached to superficial 
characters, but also because heavy pigmentation sometimes obscures 
the internal organs, even in the living trematodes. If this sketch 
indicates greater variety in the superficial organs of the Monogenea 
than in their deeper parts, however, it is perhaps because the latter 
are the more stereotyped. 

a. External Structure. 
(a) General. 

Most Monogenea are less than 10 mm. long, but some attain a 
length of 20 or 30 mm., and in shape they are lanceolate, elliptical or dis- 
coidal, sometimes of rather rugged outline. When the body is elongate 
it is often almost cylindrical ; when discoidal it is flat, but sometimes 
convex dorsally and concave ventrally. The lateral margins may 
turn inwards ventrally. The anterior region which bears the mouth is 
generally very mobile, at one moment drawn out into a tapering 
process, but at another strongly contracted, even retracted into the 
body, and it makes frequent exploratory movements. The entire 



4 THE TREMATODA OF BRITISH FISHES 

body is in some measure extensile and contractile, so that the shape is 
anything but fixed. Carefully preserved specimens generally provide 
what might be called the mean shape and show corresponding uni- 
formity internally, but the absence of a fixed form necessarily implies 
greater variability in the topographical relations of the internal organs 
than would be encountered in animals of constant shape. 

The entire body is covered with a cuticle which is rarely as thick 
or as spinous as that of the Digenea, in which greater protection 
against the secretions of the host would seem to be needed, and where 
spines provide purchase during locomotion in crevices and at the same 
time a superficial roughness that assists adhesion under such circum- 
stances. The cuticle of Monogenea is not invariably smooth, however, 
sometimes having a generous sprinkling of spines dorsally and laterally 
in the anterior region. In the absence of spines, sometimes in their 
presence, the cuticle may be raised into papillae. Spines may also 
be localized on disk-like plates called squamodisks posteriorly. The 
cuticle may be continued into the terminal parts of the digestive and 
reproductive systems, and it both covers the haptors and lines their 
cavities. Subcuticular cells are generally sparse, suggesting that the 
cuticle might be a cuticularized epithelium, but alternative modes 
of origin undoubtedly prevail. The cuticle is frequently termed 
" chitinous," but specific tests have not confirmed the presence of 
chitin (see Remley, 1942) and the term should be avoided. 

(b) The Prohaptor. 

, In some Monogenea the prohaptor is a cup- shaped muscular organ 
encircling the mouth, an oral sucker essentially similar to that of 
Digenea, but more feebly developed and less sharply set off from the 
underlying parenchyma. More often, this haptor comprises a pair of 
saucer-like suckers situated some distance from the mouth at the 
lateral margins of the somewhat truncated anterior extremity. These 
anterior suckers are sometimes frilled by a pleated membrane. Less 
conspicuous suckers, called buccal, occupy the lateral walls of the 
prepharynx in many Monogenea, and may be so small as to be evident 
only in sections. Otherwise the prohaptor may be ill-defined and not 
sucker-like, and represented by various structures which have received 
nearly as many names. There may be two symmetrical suctorial 
grooves, one on either side of the anterior extremity, or lateral expan- 
sions of this region called head-lappets, or papilla-like outgrowths of 
more concise shape known as head-organs with associated multicellular 
head-glands which secrete a viscid substance and extrude it through 
special ducts on the surface here. Head- organs vary in number, 
and they provide characters of taxonomic importance ; there may be 
one or two pairs, three pairs, several pairs, or numerous scattered 
individuals. Some Monogenea with neither head-lappets nor head- 
organs have numerous glands opening on lateral glandular areas, 
which may co-exist with anterior suckers. In a few instances a pro- 
haptor is absent, but the mouth may be encircled by a somewhat 



THE MORPHOLOGY OF THE MONOGENEA 5 

membranous structure called a pseudosucker. Whatever its structure, 
the prohaptor brings about the application of the mouth to the sub- 
stratum whilst feeding is in progress, and it may also serve for tem- 
porarily maintaining adhesion while the opisthaptor gains a fresh hold 
on the host during locomotion. 

(c) The Opisthaptor. 

The simplest kind of opisthaptor is just a ventral disk-like out- 
growth of the posterior region, which is generally muscular and may 
be unarmed, or provided with large hooks and much smaller hooklets 
which serve as grapnels. Special muscles cause the recurved tips of 
the hooks and hooklets to bite into the tissues of the host, other 
muscles abstracting them again. The hooks may be supported by two 
transverse cuticular bars, one dorsal and the other ventral, or by a 
single bar. The hooklets are carried over into the adult from the 
larval stage, and are so small as to have been overlooked by many 
investigators, though Price (19376) has reported their presence in 
numerous genera of the Capsalidse and they are well known to occur 
in other families. They number 14-16 as a rule and they persist for 
varying periods when not permanent. They are frequently referred 
to as marginal hooklets because of the usual position, but this qualifi- 
cation is unnecessary and it may be misleading. 

This comparatively simple opisthaptor is characteristic of the 
sub-order Monopisthocotylea, in various families of which certain 
modifications are found. From the simplest type of all, a mere 
eminence bearing hooks and hooklets, a series can be arranged in which 
the opisthaptor becomes sucker-like, but still simple, then septate to 
varying degrees, the ventral surface becoming divided up by slightly 
raised and more or less radial septa into a number of sectors or loculi, 
each with a sucker-like function of its own. The numbers of septa 
and loculi are 6-7, 8 or 10, and the radial symmetry may be disturbed 
by the incompleteness of some of the septa and the fusion of others, 
or may even give way to bilateral symmetry in instances where two 
or more series of loculi are arranged tangentially to the margin of the 
haptor, some members of the series being larger than others. The 
simplest modification is the development of one central loculus and a 
small number of peripheral loculi. A third set of loculi may be 
interposed between the central and peripheral, and bilaterality is 
evident when the posterior loculus is much larger than the others. 
Mention must be made of a modification of another kind, in which the 
haptorial disk of the larva fails to enlarge during growth and is sup- 
planted by a large secondarily developed disk or pseudohaptor bearing 
radial rows of spines. In this type of opisthaptor the true disk persists 
as a rudiment, still bearing the hooklets, on the posterior margin of the 
functional pseudohaptor. 

In the other sub-order, Polyopisthocotylea, the opisthaptor shows 
a higher grade of organization, comprising one pair to four pairs of 
muscular, cup-like suckers or clamp-like organs set on a disk or 



6 THE TREMATODA OF BRITISH FISHES 

cotylophore, or on the ventral surface of the body. In rare instances 
asymmetrical arrangements have been recorded. The number of 
pairs of such structures has been used to distinguish various families 
of the sub-order, but the validity of this is questionable. The terminal 
part of the opisthaptor is subject to further modification, the most 
posterior pair of suckers sometimes being of much reduced size and, 
in one family, set near the tip of an elongate dorsal outgrowth or 
appendage of the disk. Where the opisthaptor has become compli- 
cated in this way, the haptorial armature, consisting of hooks and 
hooklets, has become simplified, though not invariably, or propor- 
tionately. In particular, the bar-like supports for the hooks have 
disappeared. There may be one pair of large hooks, or several pairs of 
smaller ones, some of which may overlie others. In some Polyopistho- 
cotylea cuticular structures of the most fantastic shapes simulate 
hooks, but are really deeply situated layers of cuticular materials 
which serve as supports for the suckers and as a firm basis for the 
insertion of the muscles which work them. Other cuticular skeletal 
structures (sclerites) reach the climax of complexity in the family 
Diclidophoridse ; their nature and arrangement will be considered in 
the diagnoses for the various members of this family. 



b. Internal Structure. 
(a) The General Musculature and Parenchyma. 

Immediately beneath the cuticle, several layers of muscular fibrils 
support the integument of the body and bring about the general 
movements of the animal. The fibrils of the outermost layer extend 
tangentially to the surface in the transverse plane, collectively forming 
a circular layer, which is absent in a few instances. Beneath it, as a 
rule, other fibrils are arranged diagonally and longitudinally in turn, 
the longitudinal layer being relatively thick. These layers of muscles 
function in a complementary manner, the transverse fibrils contract- 
ing when the longitudinal relax, and vice versa, to produce lengthening 
and attenuation of the body at one time, shortening and thickening 
at another. The diagonal muscles mainly augment the effects due 
to the other layers. Additional muscles traverse the parenchyma 
dorso-ventrally and by their contraction flatten the body somewhat. 

The muscular layers are not of uniform thickness, though care 
must be taken in determining their thicknesses lest local contractions 
falsify the determinations. In Hexostoma extensicaudum, the super- 
ficial layer of diagonal fibrils is thinner anteriorly than posteriorly. 
In this trematode the thick longitudinal layer is divided into two 
subsidiary layers separated by parenchyma ; both layers are thicker 
dorsally than ventrally and posteriorly than anteriorly, and the deep 
layer is 4-7 times as thick as the more superficial. Deep and super- 
ficial components of the longitudinal muscle layer play different parts 
in the action of the opisthaptor, and the greater thickness of the former 
is explained by the fact that adhesive action of the suckers depends 



THE MORPHOLOGY OF THE MONOGENEA 7 

on it, release being due to the superficial components (see Dawes, 
1940a). 

The parenchyma is composed of loosely packed cells and fibrils 
which fill the available space around the internal organs. The simplest 
condition is that in which polygonal cells form a tissue binding these 
organs with the integument, but in some instances ecto- and endo- 
parenchyma are differentiated, the former comprising masses of fibrils 
secreted by cells, the latter cellular masses. In some Monogenea the 
parenchyma is a true syncytium which enters into the composition 
of the ducts of various internal organs, here being fibrillar and devoid 
of nuclei. Fibrillar protoplasm invariably stiffens the ends of the body 
and other parts in which rigidity is required. 

(b) The Components of the Haptors and their Mode of Action. 

From what has been said already about the haptors of the Mono- 
genea it will be evident that haptorial action varies considerably. 
Unfortunately this subject has not been studied in detail, so that a 
comparative account cannot be given. I have already (Dawes, 1940a, 
1946) explained it in Hexostoma extensicaudum, but have to admit that 
many other modes probably exist which would repay serious study. 
Where the haptors comprise suckers, the action may be due to intrinsic 
muscles, but in many Monogenea the suckers are fibrous, not muscular, 
and extrinsic muscles which are inserted in the skeletal supports alter 
the degree of concavity to produce, increase or decrease the suction. 

(c) The Nervous System and Receptors. 

Although difficult to demonstrate, the nervous system is not com- 
plex, consisting of two anterior clusters of nerve cells and several 
bundles of fibres. The ganglia are connected by a transverse com- 
missure, forming a rudimentary " brain," from which the nerves issue 
to various regions of the body. The anterior region is well provided 
with nervelets, and three pairs of nerves generally extend posteriorly 
in the dorsal, ventro-lateral and ventral regions. The ventral nerves: 
are the most prominent, and are so metimes linked by transverse com 
missures forming a kind of network in this region. They give off 
nervelets to the opisthaptor, and the prohaptor and pharynx are other 
organs having a rich innervation, though not from the same source. 
The ventro-lateral nerves are invariably smaller than the ventral and 
the dorsal nerves are well developed in some forms, absent in others. 
Most of the nerves are motor in function, as might be expected from 
the feeble development of sense organs, which are more important 
than in Digenea, however, in accordance with the more variable con- 
ditions in the environment. The chief sense organs are paired eye- 
spots, which may have an accessory lens-like structure, or may be 
absent. Tristoma has been credited with a rudimentary kind of 
" taste -org an," but such inferences are hardly justified. In most 
Monogenea, however, numerous sensory nerve-endings exist at the 
base of the integument, particularly near the anterior extremity and 



8 THE TREMATODA OF BRITISH FISHES 

in the kaptors. Apart from the eyes, these may be regarded as the 
principal receptors. 

(d) The Digestive System. 

The alimentary canal is divisible into three parts, pharynx, oeso- 
phagus and intestine. In some Monogenea a prepharynx is interposed 
between the mouth and the pharynx, but this is often a transitory 
structure, being obliterated by movements of the anterior extremity. 
When it is permanent, buccal suckers may be situated in its walls. 
When these are absent, the pharynx may serve as a sucker. This 
part of the gut may be protrusible, and there may be even closer 
resemblance to the Turbellaria when the pharynx is enclosed in a 
pouch. In Capsala the pharynx has a distinctive central constriction, 
and it is sometimes beset with papillae. The intestine is sometimes 
simple and saccular, a condition which may be modified by the develop- 
ment of fenestrations in the region of the gonads, but generally it 
bifurcates near the posterior end of the pharynx. The two caeca thus 
formed may be simple and unbranched, or the crura may unite pos- 
teriorly to form a ring-like intestine. Often the caeca give off median 
and lateral diverticula, and these may have dendritic terminations or 
may form anastomoses. In some Monogenea with a discoidal opist- 
haptor an intestinal trunk may extend into it from a median anasto- 
mosis farther forward, giving off ramifying branches. Where the 
opisthaptor is further complicated by the development of a dorsal 
appendage, branches of the caecal stem may extend into this almost 
to its tip. Differences of a histological nature also exist. The lining 
of the intestine may be a continuous epithelium of cubical or cylindrical 
cells, or the continuity may be broken. Alternatively, cells may be 
absent, the lining apparently consisting of fibrils secreted by the 
parenchyma. Much scope exists for the histological study of this and 
other systems of organs. 

(e) The Excretory System. 

Our knowledge of this system is scanty, but it is built up of flame- 
cells and collecting vessels. The latter may form a network, but 
generally they unite to give rise ultimately to a pair of longitudinal 
canals which are situated in the lateral regions, beginning anteriorly 
as fine vessels, widening and turning about near the opisthaptor and 
extending to the level of the pharynx, where each enters a small 
spherical vesicle which is connected with the exterior by a short, 
straight canal. This general arrangement is never met with hi the 
Digenea, the paired vessels and pores being distinctive. 

(f) The Reproductive Systems. 

Some Digenea are dioecious, but all Monogenea are androgynous. 
The male system comprises a single testis in some instances, but more 
often there are two, three or numerous testes, which occupy the space 



THE MORPHOLOGY OF THE MONOGENEA 9 

between the caeca, tending to fill it when numerous, and generally 
situated behind the ovary. Vasa efferentia unite ultimately to form a 
vas deferens leading to the copulatory organ, which is sometimes quite 
simple, but may be complicated by cuticular accessories of somewhat 
doubtful function. It may be protrusible and eversible (i.e. a cirrus) 
or only protrusible (i.e. a penis), and it generally projects into a shallow 
ventral pit or genital atrium which also receives the terminal parts of 
the female system. When the male and female pores are separate 
they may be median, but are sometimes lateral. The vas deferens is 
sometimes distended to form a seminal vesicle, and the terminal part 
of the male system, or ejaculatory duct, frequently has a cuticular 
lining and glands may open into one part of it, the pars prostatica. In 
a few Monogenea a copulatory organ is absent, but in others it is 
conspicuous and sometimes equipped with hooklets that assist 
copulation. This end may be served, alternatively, by hooklets in 
the wall of the genital atrium. 

In the female system the ovary is rarely globular, as in the Digenea, 
but is generally elongate and much folded, sometimes lobed as well. 
Ova mature in the terminal part and pass into a short oviduct, the 
first part of which may form a chamber, the ovicapt, which can be 
closed at either end by a sphincter and spaces out the ova into a 
steady stream. In a special region of the oviduct, the ootype, the ova 
are fertilized and encapsulated. At this point several ducts converge ; 
they are the vagina or vagince, the vitelloducts, the uterus and the 
genito -intestinal canal. The vagina is not invariably present, and its 
absence is a negative character of some taxonomic importance. When 
a vaginal system is present it may consist of a single tube, or of separate 
tubes forming a pair, or a pair of tubes which merge to form at single 
canal at some point along their length, three conditions which are 
made use of by systematists. The median or lateral positions of the 
vaginal pores have been commented on already. The canals, which 
are sometimes lined with sculptured cuticle, serve as conduits for 
spermatozoa received in copulation and retained till required in a 
chamber, the receptaculum seminis, conveniently near the ootype. 
Where the vagina? are continuous with the lateral vitelloducts they 
possibly serve also as conduits for the removal of unwanted portions 
of shell materials. The vitelloducts are extensive paired canals from 
the vitellaria, follicular organs extending along the lateral regions of the 
body and sometimes encroaching on the median space between 
the caeca. Their main terminal parts extend transversely inwards, 
meeting in a median vitelloduct or a vitelline reservoir. They serve 
for the transference of vitelline cells loaded with droplets of shell 
substance to the ootype. In rare instances the vitellaria are absent ; 
in a few the follicles are associated with the ovary, forming a germ- 
vitellarium, as in some Turbellaria. The uterus is a wide tube which 
receives the shelled eggs and conducts them to the genital atrium. 
Its terminal part, the metraterm, may be muscular, like the vagina, 
and provided with a cuticular lining and structures superficially 
resembling hooks. The remaining canal of the four mentioned, the 



10 THE TREMATODA OF BRITISH FISHES 

genito -intestinal canal, connects some part of the oviduct with the 
right caecum, rarely the left. It is not represented in the Monopistho- 
cotylea, and one possible function of the canal is the removal of super- 
fluous shell fragments deposited in or near the ootype during the 
process of shell-formation. The eggs of Monogenea are relatively 
large and generally provided with polar filaments, or a filament at one 
pole only. In some instances the egg is ovoid, in others the poles end 
in knob-like processes. Otherwise, one pole may have a small thicken- 
ing, the other a long, twisted filament, or one pole a short, hooked 
process, the other a long, straight filament. In rare instances both 
poles are drawn out into very long filaments fifty times as long as the 
capsule, and the filaments may be contiguous so that the eggs are 
laid in chains. All these departures from a regular ovoid form are 
indications that the egg-shell was formed from liquid material, some 
of which was drawn out into a viscid thread prior to hardening. In 
all Trematoda the bulk of this material originates in the vitelline cells, 
which convey it to the ootype, the mould in which the capsule takes 
shape. No doubt the details of egg-formation vary slightly in different 
Monogenea, but I have described elsewhere (Dawes, 19406, 1946) the 
process in Hexostoma extensicaudum. Unicellular glands situated just 
outside the wall of the ootype secrete a thin liquid, but not in sufficient 
amount to account for all the egg-shells formed, so that the name 
shell-glands is misleading. Several possible functions have been 
suggested for this liquid — that it is a nutrient for ova and spermatozoa, 
or a lubricant ensuring the smooth passage of the eggs into the uterus, 
or a hardening agent — but all seem to fall short of the truth. I have 
suggested (19406) that it may form a thin layer upon which shell- 
forming materials from the •■vitelline cells are laid down from the inside, 
and (1946) that it possibly contains agents (electrolytes, for instance) 
which bring about the rapid extrusion of these materials at an appro- 
priate instant. Polar filaments are no doubt formed as rivulets of 
shell material which overflow from the ootype, and their common 
occurrence in Monogenea is an indication that a greater excess of 
material exists than in Digenea. This is probably due to the great 
development of the vitellaria and the smaller numbers of eggs produced. 

IV. THE MORPHOLOGY OF THE ASPIDOGASTREA. 

The order Aspidogastrea (family Aspidogastridae) contains only nine 
genera, but these have a world-wide distribution and are variously para- 
sites of fishes, chelonians, Gastropod and Lamellibranch Mollusca and the 
larger Crustacea. The most familiar form, Aspidogaster conchicola, (Fig. 
29 A, p. 150) inhabits various locations in freshwater mussels of the genera 
Anodonta and Unio, but especially the pericardial cavity, where 20-30 
individuals may be crowded together near the internal opening of the 
kidney. This species occurs in the New World as well as the Old, and 
in China. Faust (1922) discovered it in snails and in the alimentary 
canal of a turtle. Juveniles sometimes occur in the intestine of 
lamellibranchs, occasionally encysted in the pericardial gland. In 



THE MORPHOLOGY OF THE ASPIDOGASTREA 11 

America parasitized Unionida) ingested by fishes, frogs and turtles 
liberate their worms, which continue to live in the new hosts, so that a 
second host is annexed to the otherwise simple life-cycle (Williams, 
1942). Aspidogaster conchicola forcibly fed to the turtle, Pseudemys 
troosti, has continued to live in the stomach for periods up to fourteen 
days (Van Cleave and Williams, 1943). The most complete descrip- 
tion of this trematode was given by Stafford (1896), and I have recently 
(1946) given an account of it, drawing attention to several points in 
the anatomy which would bear closer study. Williams (loc. cit.) made 
a few general remarks concerning the structure of the adult, but he 
was concerned primarily with the larvae and the life history. 

It is unnecessary here to deal with the detailed morphology of 
Aspidogaster conchicola,* but a few points may be noted before passing 
on to other species and genera. The adult worm is about 3 mm. long 
and 1 mm. in maximum breadth, although much smaller specimens 
may be found to have matured. The body is anvil-shaped, the upper 
part containing the viscera, the lower forming an enormous cotylo- 
phore bearing numerous transverse and three longitudinal septa, 
which divide the lower surface into alveoli. At the margin of the 
disk near the indentations which lie opposite the transverse septa 
there are papilla-like marginal organs, which Diesing (1845) described 
as pores, Voeltzkow (1888) as retractile sense organs. Several zoo- 
logists have stated than an oral sucker is not present in the adult, but 
Williams affirmed its presence and it occurs in the adults of other 
species, e.g. A. decatis and A limacoides (see Fig. 29 B, C, p. 150). 

The genus Aspidogaster is characterized by the four rows of alveoli, 
a single testis and the absence of papillae on the central part of the 
cotylophore and of lip-like processes near the mouth. Various species 
of the genus differ in the number of alveoli, which are generally far 
fewer than in A. conchicola. According to I. and B. Bychowsky 
(1934) the numbers of alveoli do not form very reliable criteria of 
specific distinction, but A. conchicola has 28-42 in the middle rows, A. 
limacoides 12-18 and A. decatis 9-10. 

It is unnecessary to enumerate the various genera of Aspidogastrea, 
a key to which has been given (Dawes, 1941, 1946), but three of them 
must be mentioned because their species are parasitic in fishes in 
Europe. They are Macraspis Olsson, 1868, Stichocotyle Cunningham, 
1884, and Cotylogaster Monticelli, 1892. The first two have a single 
row of alveoli, the last three rows. In Macraspis the suckers 
are borne on a disk, marginal organs are present, the mouth is 
terminal and there is a single testis. The type species, M . elegans 
Olsson, 1868, was discovered in the gall-bladder of the rabbit-fish 
in the Skagerrak. In Stichocotyle a disk is wanting, the alveoli 
appearing as separate suckers, marginal organs are absent, the 
mouth is not quite terminal and there are two testes. The type 
species, 8. nephropis Cunningham, 1884, as originally described, was 
a larval form from the Norway lobster in the Firth of Forth, and 

* See Fig. 29 A (p. 150) for a diagram of the reproductive organs. 



12 THE TREMATODA OF BRITISH FISHES 

Monticelli thought it possibly a form of Macraspis, but Odhner (1898) 
discovered the adult, which inhabits the bile-ducts of various rays 
and may be expected to occur in Britain. Nickerson (1902) also 
found the larva in the American lobster, Homarus americanus. Cotylo- 
gaster is further distinguished by the marginal organs, the terminal 
mouth with its oral suckers, and two testes. The type species, C. 
michcelis Monticelli, 1892, was found in the intestine of Cantharus 
vulgaris at Trieste, a second species, C. occidentalis Nickerson, 1899, 
in the same location of Aplodinotus grunniens in North America. 
Another form, at one time included in the genus Aspidogaster, but 
later referred by Eckmann (1932a) to a new genus, Lobatostoma, occurs 
in fishes in North America. The occurrence of the European species 
mentioned in British waters is not improbable, but they would be 
readily recognizable by the generic characters should they appear. 

V. THE MORPHOLOGY OF THE DIGENEA. 

Only about one-third of the families of Digenea exist in fishes, so 
that by confining our attention to parasites of this class of hosts we 
shall overlook much of the variety of structure which characterizes 
the Order. The Digenea of fishes are by no means stereotyped, but 
by comparison with the wealth of forms parasitic in higher vertebrates 
they are comparatively uniform. The body is rarely flat and leaf-like, 
but generally elongate and with tapering or rounded extremities, and 
circular or oval in cross section. Two main types of structure exist 
representing the two sub -orders of the Digenea, namely, the Gastero- 
stomata and the Prosostomata. In the former the mouth is situated 
at or near the middle of the body and the haptor is anterior to it ; in 
the latter this opening is near the anterior extremity, and what might 
be regarded as the main haptor, the ventral sucker, lies behind it. 

i. The Sub -order Gasterostomata. 

This group occurs only in fishes and contains one family, the 
Bucephalidse (syn. Gasterostomidse Braun). Adult gasterostomes 
inhabit the alimentary canal, while larvse occur in Mollusca and encyst 
in various parts of the central and peripheral nervous system of fishes, 
notably in the brain and ear, or on the course of the cranial or spinal 
nerves. Bucephalopsis gracilescens, a common parasite in the pyloric 
caeca of Lophius, is a typical representative of the group. It is about 
6 mm. long, colourless, except for the brown tinge due to eggs in utero, 
and covered with delicate spines. The mouth is situated about one- 
quarter of the distance along the body and is encircled by a globular, 
muscular organ about 0'3 mm. in diameter that is commonly called an 
oral sucker ; but the fact that the organ lies beneath the integument 
shows it to be a pharynx. A slightly larger sucker about 0'4 mm. in 
diameter occupies the anterior tip of the body and is thus well in 
front of the mouth. In other genera this anterior holdfast is of a 
different nature, a sucker having retractile tentacles in Bucephalus, 
a fan-like hood in Rhipidocotyle, a protrusible rostellum or rhynchus in 



THE MORPHOLOGY OF THE DIGENEA 13 

Prosorkynchus. Along with other characters it provides a means of 
distinguishing the different genera. Other characters are fairly 
constant, but the topography of the internal organs may vary some- 
what. The chief organs are a simple sac-like intestine, a prominent 
and undivided excretory vesicle having a posterior pore, and a set of 
hermaphrodite reproductive organs opening by a posterior common 
genital pore. The male reproductive system includes a pair of 
globular testes and of vasa efferentia, a short vas deferens, a large 
cirrus pouch containing an elongate and spinous cirrus, a seminal 
vesicle and numerous prostate glands. The female system comprises 
a globular ovary, which is smaller than either of the testes, a short 
oviduct, an ootype, and the ducts which occur in all Digenea, namely 
the vitelloducts, uterus and Laurer's canal. The vitellaria are coarsely 
follicular and anterior in position, and they are sometimes arranged in 
the form of a bow, their ducts converging on the ootype. Even before 
the eggs are formed the uterus has developed two or three limbs and 
extends far forward before passing back to the genital pore ; in the 
gravid condition it may develop other, rather indeterminate folds also. 
The encysted juvenile Bucephalopsis gracilescens occurs most 
commonly in the haddock. The cysts, which are easily recognized 
by their oval or pear shape and are about 0*6 mm. long, sometimes 
occur in the skin, but more often in the central canal of the nerve cord 
or on the auditory or spinal nerves. The young individuals which 
occupy the cysts singly may be up to 25 mm. in length and already 
they have most of the characteristic organs of the adult. 

ii. The Sub -order Prosostomata. 

Several distinctive types of Prosostomata parasitize vertebrates 
and have long been known by common group-names such as Amphi- 
stomes, Monostomes, Holostomes, Distomes, Echinostomes and 
Schistosomes, which are adequately dealt with in text-books on 
helminthology. Of these general types only the Distomes are repre- 
sented in fishes in Europe, though certain close relatives of other types 
occur in this class of vertebrate. Amphistomes parasitize all classes of 
the Vertebrata, but not in Britain. Mesometra, a genus of what might 
be called Monostomes probably closely related to the Notocotylidae, 
was discovered in Box salpa in Mediterranean waters. Aporocotyle, 
a blood parasite related to the Schistosomatidse, is a parasite of certain 
teleosts, notably flatfishes. Echinostomes are parasites of birds and 
mammals, but certain near relatives, the Acanthostomatidse, occur in 
fishes. Holostomes also parasitize the two highest classes of verte- 
brates, but their larvae occur in fishes, e.g., " Diplostomum volvens " in 
the eye or lens capsule of the Trout and other fishes. The corre- 
sponding adult, Diplostomum spathaceum (Rudolphi, 1819), is an intes- 
tinal parasite of various gulls which feed on the intermediate hosts. 
Distomes form a very large group, and more than a dozen of the 40 or 
more families occur in British fishes. They are easily recognized by 
the two conspicuous suckers, the oral surrounding the mouth and the 



14 THE TREMATODA OF BRITISH FISHES 

ventral situated somewhere on the ventral surface of the body, but 
not at the posterior end. Not all Prosostomata are included in these 
general terms, but few other types are important for the present 
purpose. One family deserves special mention, however, the Didy- 
mozoidae, thread-like cyst-dwellers, some of which lack suckers. Two 
species of the type genus, Didymozoon, have been found in this country, 
where other genera probably exist, although only one genus, Kollikeria, 
has been found so far. 



a. External Structure. 

Prosostomatous Digenea are mostly 5-10 mm. long, though some 
attain a length of 20-30 mm. and thread-like forms become much 
longer. The cuticle is generally thicker than in Monogenea and spines 
are more common. When spineless, the cuticle may be wrinkled, and 
in some instances it is differentiated into narrow transverse zones 
which give it a serrated profile. I have previously (Dawes, 1946) 
outlined theories regarding the nature of the cuticle, which seems to 
have several modes of origin, being in some instances a metamorphosed 
epithelium, in others a secretion produced by cells which afterwards 
sink into the parenchyma. Gland cells sometimes exist in the 
parenchyma, particularly near the mouth, and are said to be of ecto- 
dermal origin. They open by minute ducts which pierce the cuticle. 
Similar glands sometimes open into the anterior part of the gut, 
generally the oesophagus, and possibly produce secretions that assist 
digestion. On the other hand, some glands to which such a function 
has been ascribed are probably part of the apparatus used by the 
cercaria for effecting an entry into the second intermediate or final 
host. Such penetration-glands may be particularly noticeable in 
juveniles, and they are generally lost before the adult stage is reached. 

Nothing further need be stated at this point about the apertures 
on the surface of the body, and little about the suckers, which vary 
very little and consist largely of radial fibrils sharply marked off from 
the underlying parenchyma, a character which contrasts with that 
seen in the haptors of the Monogenea. Equatorial and meridional 
fibrils occur near the rim of the sucker and form a sphincter. The 
cavities of the suckers are invariably lined with cuticle. The oral 
sucker may have a coronet of large spines and sometimes has a number 
of short fleshy processes. Sensory papillae may occur along the margin 
of the ventral sucker. 

In some Hemiuridae the body is divided into two regions, the pos- 
terior part forming an appendage which can be retracted into the 
anterior part, undergoing considerable folding in the process. The 
two regions have been called " body " and " tail," " soma " and 
" abdomen," and " soma " and " ecsoma " respectively. The ecsoma 
has been called the " appendix," the anterior part of the soma the 
' presoma." The ecsoma was once supposed to be a modified tail 
such as occurs in cercariae. Wagener (18606) opposed this view, but 
Monticelli later (1891) revived and defended it. Looss (1896) contested 



THE MORPHOLOGY OF THE DIGENEA 15 

the opinion once more, and later (1907) supported Pratt (1898) in 
regarding the ecsoma as nothing more than a modified part of the 
excretory bladder. Looss observed that an ecsoma occurs in Hemi- 
uridse which inhabit the stomach of the host, not in those which live in 
the oesophagus (e.g. Aponurus, Aphanurus) or intestine (Leciihaster) , 
and that it is present in the larger forms, but not in the smaller, and 
best developed in the largest. He suggested that parasites of the 
stomach require a thick cuticle in order to resist the acidic action of 
the gastric juice, and that such a protective layer would tend to interfere 
with other functions of the surface of the body, possibly with nutrition 
and respiration. The thinner cuticle of the ecsoma would permit 
such functions to be carried out, and retraction of the organ into the 
soma when a high degree of acidity developed in the stomach would 
afford protection. This tentative opinion has never been discarded, 
although some facts tell against it. The functions attributed to the 
integument are doubtful, but in any case the ecsoma may be extended 
or retracted in Hemiurids collected from the stomach of a fish when 
gastric digestion is at its height. Also, the cuticle of the soma and 
that of the ecsoma in several species of Hemiuridse do not show any 
appreciable difference in thickness (Lloyd, 1938), although the staining 
reactions may be different, the ecsoma taking on a sharp and brilliant 
coloration with cytoplasmic stains, the soma an altogether duller and 
less decided tone. This may indicate different physical or chemical 
properties, or merely different external influences during the life of 
the trematode. 

Needless to say, the appearance of the same species of trematode is 
very different when the ecsoma is extended and when it is retracted. 
In the former condition the fluke has a long, tapering posterior end 
similar to that of most other Digenea ; in the latter the posterior end is 
truncated, and the illusion of an additional organ is created by the 
arborescent space (a portion of the external world) which is now 
included in the body. Intermediate stages in the retraction of the 
ecsoma provide additional appearances in which some folding is more 
or less evident. 

Looss also commented at length on alterations of the form and 
topography of the organs in the posterior part of the soma which are 
brought about by retraction of the ecsoma, emphasizing that structural 
characters in the anterior region or "pre -soma" are less variable and 
thus more reliable in taxonomy. One character of some Hemiurids 
in this region is a small, sucker-like ventral pit a short distance in 
front of the ventral sucker. In Looss' opinion the identification of 
species of Hemiuridae which have soma and ecsoma is possible so long 
as the anterior region of the soma is well preserved. 

b. Internal Structure. 

(a) The General Musculature and Parenchyma. 

Some Prosostomata are decidedly muscular, the parenchyma being 
almost filled with contractile fibrils, but others have feebler muscles 



16 THE TREMATODA OF BRITISH FISHES 

and an altogether more delicate texture. Three muscle layers (circular, 
diagonal and longitudinal) are generally arranged in the form of a tube 
beneath the cuticle. Sometimes an additional layer of circular fibrils 
exists beneath the typical layers, and there may be a layer of deep 
longitudinal fibrils separated from the superficial ones by a wide zone 
of parenchyma, as in Cestoda. Dorso- ventral muscles traverse the 
parenchyma in most instances, especially in the lateral regions, which 
are not complicated by the presence of internal organs, but these are 
ill developed when the form of the body is cylindrical. The muscle 
fibrils rarely show the histological characters of other types of 
muscle, but are striated in some cercariae. Giant cells called myo- 
blasts, having a number of processes each inserted in a muscle fibril, 
sometimes occur beneath the general musculature, but are more 
numerous in the vicinity of the suckers. They may themselves be 
arranged in small groups which seem to be syncytial. Special arrange- 
ments of muscles exist in some parts of the body, e.g. near the genital 
pore, where the copulatory organ is operated by extrinsic retractors 
and protractors. The main musculature of the body is generally 
thicker ventrally than dorsally. 

The parenchyma of Prosostomata is more open than that of 
Monogenea, the cells and fibrils forming a loose network of irregular 
spaces filled with liquid and forming a rudimentary " lymph system." 
The general appearance recalls to mind the mesenchyme in early 
embryos of Vertebrata. In juvenile Digenea embryonic cells wander 
through this network to establish in appropriate situations the rudi- 
ments of organs such as the gonads. Other wandering cells resemble 
lymphocytes, and may play a part in the distribution of nutrients and 
other substances about the body. 



(b) The Nervous System and Receptors. 

The nervous system, like that of Monogenea, consists of paired 
ganglia, a supra- oesophageal commissure and paired nerves. The 
" brain " may He far forward, but it gives origin to several nerves 
which extend to the anterior region, numerous branches passing to the 
oral sucker and the integument, and also to three pairs of unequally 
developed longitudinal nerves that extend posteriorly. The ventral- 
most longitudinal nerves are best developed and they may be con- 
nected by commissures to produce a nerve network beneath the 
integument. This may be extended when other commissures link the 
ventral with the lateral, and even the dorsal nerves. From the main 
nerves or the commissures, or both, numerous fibrils extend peri- 
pherally, branching everywhere underneath the integument. They 
are mainly motor nerves, sense-organs being even less developed than 
in the Monogenea. The miracidia and sporocysts of some Digenea 
possess a pair of eye-spots, and in a few instances a third eye is present, 
but such organs are generally absent in adults, although vestiges of 
them may persist for a time. Pyriform cells and fine hair-like pro- 
cesses commonly exist in the integument and may serve as receptors, 



THE MORPHOLOGY OF THE DIGENEA 17 

like the papillae at the margins of the suckers. Other organs of this 
kind which lie close to the mouth have been called " taste -organs," 
but there is no proof that this is their true nature. 

(c) The Digestive System. 

This system is not dissimilar to that of Monogenea, although 
generally bifurcate and unbranched in the Prosostomata of fishes. It 
comprises a muscular pharynx, an oesophagus of variable length and 
a pair of caeca, which may be so short as scarcely to reach the ventral 
sucker, even when this is decidedly anterior, or so long as almost to 
touch the posterior extremity. The pharynx may be rudimentary or 
absent, likewise the oesophagus, which otherwise may be very long 
in ribbon-like Digenea. The oesophagus may be lined with epithelial 
ectoderm or with cuticle, though it is generally fibrillar and homo- 
geneous ; its walls may contain transverse and longitudinal muscles, 
and the ducts of glands may penetrate it. In very elongate Digenea 
this anterior part of the gut may be lengthened by the presence in 
front of the pharynx of a narrow prepharynx, which is absent in oval 
forms. 

The caeca, or intestinal crura, are generally simple and unbranched, 
and they may merge to form a ring-like intestine. In Hemiuridae a 
special region of the gut, the gland- stomach, is interposed between 
them and the oesophagus. In a few Digenea two anterior extensions 
of the caeca pass along the sides of the oesophagus, imparting an H- 
shape to the intestine, and the main crura or the anterior diverticula, 
or both, may possess short lateral outgrowths. In one family there 
is a single median caecum, as in the Bucephalidae — a condition which 
may also arise secondarily when only one caecum develops to the 
full size. In a few instances the intestinal crura do not end blindly, 
but communicate with the exterior by way of the terminal part of the 
excretory system, so that the excretory pore is strictly a cloacal 
aperture. Sometimes there is a true anus, or a pair of anal apertures, 
but this is not common, although more frequent than was at one time 
supposed. Such characters are exceptions to the general rule and 
not important in taxonomy, as their presence or absence in related 
forms shows. Circular and longitudinal muscles may occur in the 
wall of the intestine, which may also have a simple epithelial lining. 
The free ends of the epithelial cells sometimes have thread-like or 
brush-like processes which project into the lumen. 

(d) The Excretory System. 

The usual position of the excretory pore in Prosostomata is pos- 
terior and terminal, though exceptions occur and miracidia and rediae 
have a pair of postero-lateral pores, and the same may be true of 
cercariae which have not yet developed a tail. As the rudiment of the 
tail grows out the two primary pores are carried with it, the two main 
excretory canals coming to lie side by side near the tail-stem. Here 
fusion occurs later on, and the final shedding of the tail at the end of 

2 



18 THE TREMATODA OF BRITISH FISHES 

cercarial life not only preserves a single posterior pore, but destroys 
all evidence of the paired origin of the excretory vesicle. This generally 
receives a pair of canals, which pass directly into it or into a pair of 
cornua near its anterior end. The vesicle may be small and spherical 
or long and tubular, according to the degree and extent of fusion of 
the paired vessels of the early larvae. When the lateral canals are 
prominent, the main vessels form a characteristic Y- or V- shape 
according to the length of the median stem. The former shape is 
characteristic of some families, the latter of others, but neither can 
be accepted without reserve as a familial character. 

Finer canals open into the main excretory vessels, which form a 
pair of longitudinal trunks extending to a level near the pharynx, 
where they may unite, or turn about and extend separately back 
towards the posterior extremity. Each recurring loop generally 
receives tributary canals formed by the fusion of small and still smaller 
factors, the finest of which end each in a flame-cell. The mode of 
branching seen in this part of the system, and the numbers of flame- 
cells which are involved in various groupings, are matters of taxonomic 
importance and can be represented by a shorthand expression, the 
flame-cell formula. The method by which the formula is applied 
was outlined in connexion with the Aspidogastrea in my previous 
work (Dawes, 1946) and need not be repeated here, though it will be 
as well to mention that the number of tributary canals arising from the 
longitudinal trunks is indicated by the number of terms in the expres- 
sion (each term denoting the number of branches formed at a division), 
and that the power to which each term is raised represents the number 
of times branching occurs. As each terminal twig of the system ends 
in a flame-cell, the total number of such units can easily be calculated 
from the formula, which takes account of the duplication due to 
bilateral symmetry. The patterns of flame- cells and ducts provide 
important means of diagnosis, especially for larvse, in which compara- 
tive simplicity prevails ; the chief drawback in the case of adults is 
the difficulty with which the details can be made out, even in living 
trematodes if they are fleshy. 

From this brief statement it will be evident that the excretory 
system is protonephridial, as in Turbellaria. The flame- cell is a 
cellular unit possessing elongate cilia that project into the blind 
terminal capillary and by their movements produce a flickering effect, 
as the name implies. Sometimes the capillaries are cellular or syn- 
cytial, and from certain cells, or parts of the syncytium, tufts of cilia 
may project into the lumen. The way in which flame-cells produce a 
flow of liquid is unknown, and any study of the mechanics of the flow 
would be welcomed by helminthologists. The action of the flame- 
cells prevents stagnation in the terminal canals and the deposition of 
solids which might otherwise occur there. 

(e) The Reproductive Systems. 

Mention has been made already of the dioecious nature of some 
trematodes, but previous remarks might be amplified slightly here. 



THE MORPHOLOGY OF THE DIGENEA 19 

Schistosomes, many of which exhibit sexual dimorphism, have their 
sex determined in the earliest stages of development, the sporocysts 
giving rise to cercarise that will develop into males or females, but 
not both, so that a definitive host which is infected with cercarise 
that came from the same sporocyst has flukes of one sex only. Male- 
producing cercarise develop in the blood vascular system, becoming 
adult in about 40 days, but female-producing cercarise may remain 
immature in the absence of males for periods up to 9 months, attaining 
only one-fifth of the normal definitive size, and having an undeveloped 
ovary and rudimentary vitellaria. In the presence of males, however, 
maturity is reached in about two months, and anomalous females 
complete their development if male-producing cercarise are introduced 
into the blood vascular system of their host. The development of the 
female thus seems to be conditioned by a substance or substances 
secreted by the male. 

Sexual dimorphism may arise out of hermaphroditism, as seems to 
be the case in Didymozoidse, a series of which can be arranged to show 
all stages in its development. Didymozoon scombri and D. faciale, 
parasites of the mackerel, have normal male and female organs of 
unusual thread-like or tubular pattern. Species of Wedlia consist of 
females which develop only the rudiments of the male organs, and males 
which have a non-functional ovary, vitellaria, shell-glands and recep- 
taculum seminis. Nematobothrium filarina is characterized by indi- 
viduals of different thicknesses, the thicker ones forming numerous 
eggs of a golden colour, the thinner ones only a few colourless eggs. 
We know practically nothing about the determination of unisexuality 
and sexual dimorphism in such forms, our knowledge of the general 
anatomy being deficient, except for a few forms which have been 
described fairly recently. Apart from these two main sets of examples, 
Prosostomata are regularly hermaphrodite, the genital organs showing 
a greater variety of structure than in Monogenea, particularly the 
terminations of the genital ducts. The male and female systems 
generally open to the exterior close together in a shallow genital 
atrium, but some Prosostomata of fishes have a deep, tubular atrium 
which resembles a hermaphrodite duct and the terminal part of the 
entire atrium of other forms. The common genital pore is generally 
situated in the median plane between the suckers, but may occupy a 
lateral or even a dorsal position. It may be situated relatively very 
far forward near the mouth, but in the great majority of Prosostomata 
it is just in front of the ventral sucker. 

The male reproductive system comprises a pair of testes and vasa 
efferentia, a vas deferens, seminal vesicle and cirrus, as well as a 
number of accessories which are not invariably present, a cirrus pouch, 
glandular pars prostatica and ductus ejaculatorius. It generally 
develops before the female system (protandry). Occasionally there is 
a single testis, or numerous testes, but generally there are two and they 
may be spherical or ovoid, rarely lobed or branched, and situated 
behind or in front of the ovary, or one on either side of it. The sperma- 
tozoa are thread-like bodies of variable length (0*02-0*2 mm. long) 



20 THE TREMATODA OF BRITISH FISHES 

which are sometimes enclosed in spermatophores, as in Prosorhynchus 
and some rhabdoccele Ttirbellaria. They pass along the vasa efferentia, 
sometimes by the agency of cilia, into the vas deferens and finally the 
seminal vesicle, a dilated region of the male duct in which they are 
stored temporarily. Their ultimate ejaculation during copulation is 
brought about by reflex contraction of the vesicle. 

Some of the modifications of the copulatory organs are of taxonomic 
importance. The typical organ is a cirrus provided with both cir- 
cular and longitudinal muscles, although these may be ill developed. 
Spinelets may arise from the internal wall, to be erected when the 
organ is protruded and thus to help to maintain a firm union with the 
terminal parts of the female system during copulation. Some spine- 
like structures found in this situation, however, are probably less 
rigid than the term indicates and more hair-like. The retracted cirrus 
is generally lodged in a cirrus pouch, which also encloses the pars 
prostatica, i.e. that part of the male duct which is perforated by the 
ducts of prostate glands, whose secretion nourishes the spermatozoa, 
and also the seminal vesicle. Sometimes the vesicle lies outside the 
cirrus pouch, when it is called a vesicula seminalis externa, though 
the type interna is the more usual, and both may exist. Sometimes the 
cirrus pouch is small and the pars prostatica terminates in the paren- 
chyma outside, or the pouch is absent, rarely the cirrus as well. When 
a true cirrus is wanting, a protrusible muscular organ which takes its 
place is formed by fusion of the male and female ducts, and is thus 
homologous with the genital atrium of other Prosostomata. The 
organ is sometimes enclosed in a pouch similar to the cirrus pouch, and 
variously known as a "false cirrus sac", "false cirrus pouch" or 
" sinus sac." A rather fine distinction is sometimes drawn when this 
has continuous muscular walls and is said to be " complete," or has 
sparse and discontinuous muscles and is said to be " incomplete." 

The components of the female reproductive system are similar to 
those of the Bucephalidae, namely, an ovary, oviduct, ootype, uterus, 
Laurer's canal, receptaculum seminis, vitellaria and vitelloducts. The 
ovary is generally smaller than either of the testes and globular, 
though it may be lobed or branched, but is rarely follicular or tubular. 
Generally, it is displaced towards the right, but may occur almost as 
often on the left. Ripe ova travel along a short section of unmodified 
oviduct to the ootype, assisted by a ciliary current. Here they meet 
clusters of vitelline cells which have travelled down the vitelloducts 
and spermatozoa previously stored in the receptaculum seminis, and 
become fertilized and encapsulated. The ootype is a modified part of 
the oviduct which is conveniently situated in relation to other ducts, 
and receives the secretion formed by numerous unicellular shell-glands 
situated immediately outside its wall. The receptaculum seminis 
occurs at the base of Laurer's canal, or in some other situation, but 
never far removed from the ootype. In its absence sperms may 
aggregate in the proximal part of the uterus, which then forms a 
receptaculum seminis uterinum. The uterus varies in length and 
degree of folding, sometimes having a descending limb which extends 



THE MORPHOLOGY OF THE DIGENEA 21 

towards the posterior extremity, then recurring as an ascending limb. 
Both limbs may be intensely folded, the folds filling what space is 
available. Otherwise, the uterus may consist of an ascending limb 
which follows a sinuous course towards the genital atrium. The 
terminal part of the uterus, or metraterm, often has a cuticular lining, 
and may have muscular walls and a lining provided with enigmatic 
structures resembling hooklets. Glands similar to the prostate glands 
may open into the metraterm, which functions as a vagina in most 
Prosostomata, although Laurer's canal has been observed to serve this 
purpose in some. The way in which the eggs receive their shells is 
essentially the same as in the Monogenea, though the formation of an 
operculate egg calls for some modification of the process. According 
to Ujiie (1936a) the peripheral wall is formed first, then the posterior 
end, and finally the operculum. This writer (19366) also suggested 
that two types of shell-glands exist in Digenea, but the use of criteria 
based on differential staining reactions in formulating this opinion has 
been adversely criticized (Dawes, 19406). The shell-glands produce 
a thin secretion, and may contribute to the gelatinous envelopes with 
which the eggs of Pleurogenes and some Haploporidse are provided, but 
they do not form the bulk of the egg-shell. The most plausible hypo- 
thesis is that the secretion causes rapid extrusion of droplets of shell- 
forming substance from vitelline cells which have travelled from the 
follicles of the vitellaria to the ootype. The vitellaria of Prosostomata 
are rarely as well developed as in Monogenea, and when we take into 
consideration also the larger number of eggs produced, this implies 
a more economical use of shell-forming materials, thus explaining the 
rarer occurrence of polar filaments in Digenea. The vitellaria are 
generally lateral and follicular, but they may be compact and are 
sometimes fused into a minute single mass. Some trematodes with 
reduced vitellaria produce fewer eggs with thinner shells, but this is 
not invariably so, implying perhaps an unusually great capacity to 
secrete which compensates for a small size. This point requires 
investigation. 

Laurer's canal extends from a pore on the postero -dorsal surface 
to a point near the ootype. In some instances it has a muscular wall 
and it may have a ciliated hning. The receptaculum seminis is generally 
situated at its base, but is absent in some families. Laurer's canal is 
absent in Derogenes, and although it has been observed to function 
as a vagina in a few Digenea, it probably serves in most as a conduit 
for unwanted fragments of shell-forming substance, thus maintaining 
the ootype in a fit condition for the work it has to do. 

Processes of the eggs are rare in Prosostomata, but a few parasites 
of birds and of fishes have eggs with one or two filaments. Generally, 
the eggs are ovoid and operculate, although opercula are lacking in 
some families, in which case the capsule must split before the mira- 
cidium can emerge. The shape, size and colour of the eggs, as well 
as the presence or absence of polar filaments, are characters of some 
taxonomic importance. Some eggs are very much larger than others — 
a fact which is overlooked when they are not seen side by side unless 



22 THE TREMATODA OF BRITISH FISHES 

careful measurements are made. Perhaps size has been unduly- 
stressed as a taxonomic aid, and in some recent determinations a very 
wide range of sizes has been found in a single species. But the size 
of the eggs must take its place along with other characters, the ensemble 
of which decides specific identity. 

In conclusion, mention may be made of situs inversus, which occurs 
infrequently in regard to asymmetrical organs, but is not of particular 
importance in taxonomy. Malformations are more likely to mislead 
us, but these also seem to be infrequent. Instances are known of 
the atrophy of one testis, or one vitellarium, and such abnormalities 
may be more common than the literature indicates. Perhaps arti- 
facts due to bad fixation are more important, because more common, 
and sometimes misleading about the natural limits of variability in 
a species. Alterations of the proportions of a trematode during growth 
may also, if neglected in a taxonomic study, make specific limits more 
difficult to determine. Many species of Trematoda have been erected 
unnecessarily because sufficient allowance has not been made for the 
rather wide range of variability to be expressed in a group of animals 
which have neither a definite shape nor a definitive size. 

VI. TREMATODES OF THE ORDER MONOGENEA. 

Odhner (1912) divided the order Monogenea into two sub-orders, 
the Monopisthocotylea and the Polyopisthocotylea, characterized 
respectively by the absence or presence of a genito-intestinal canal, 
i.e. a tubular connection between the oviduct and the right caecum, 
rarely the left. Most writers have concurred, but Fuhrmann (1928) 
proposed an alternative tripartite division of the order into the Mono- 
pisthodiscinea, Monopisthocotylinea and Polyopisthocotylinea, the first 
two groups representing subdivisions of Odhner's Monopisthocotylea 
based on a number of characters, but mainly on the absence or presence 
of a sucker-like opisthaptor. Price (1937a) indicated that this scheme 
offers little taxonomic advantage, and Odhner's scheme will be adopted. 
Unfortunately, the genito-intestinal canal is a rather delicate object 
which is not easily discernible in the rather opaque and sometimes 
pigmented body, so that it is a character of doubtful practical value. 
Amongst the correlated characters, however, the nature of the opis- 
thaptor is distinctive and permits easy diagnosis. If this organ com- 
prises a number of suckerlets or clamp-like structures, the fluke belongs 
to the Polyopisthocotylea ; if instead it is a disk-like structure, 
whether an indubitable sucker or merely a region of the body which 
bears hooks, the fluke can be referred to the Monopisthocotylea. 

A complete classification of the Monogenea has not been accom- 
plished in a modern sense, although Price (1936 ; 1937a-c ; 1938a, b ; 
1939a, 6 ; 1940a ; 1942 ; 1943a, 6) has made very substantial progress 
with a scheme of his own, firmly establishing a number of super- 
families, families and lower taxonomic units. It is doubtful if some 
of the super-families have any phylogenetic significance, but they are 
serviceable units in diagnosis. Perhaps before an ideal scheme can 



TREMATODES OF THE ORDER MONOGENEA 23 

be propounded we shall need to consider life -histories and growth 
cycles in greater detail. Little is known about changes in the pro- 
portions of Monogenea during growth, a closer study of which would 
enable us better to assess variability in the relative sizes of organs 
and parts within a species. In dealing also with the shapes and struc- 
ture of various kinds of cuticular hooks, hooklets and sclerites we have 
probably been misled by differences more indicative of the processes 
of growth than of phylogenetic distinction. But in lieu of information 
concerning the growing trematode we have to depened on the characters 
of the adult, which have been put to good use by Price, whose work 
has been liberally drawn on in setting out the scheme which follows. 
Useful suggestions have been made by Sproston (in litt.), particularly 
regarding the Mazocraeidae, a family with which Price has not yet dealt 
in detail, and to her also my thanks are due. 



Key to the Families and Higher Groups of the Monogenea. 

I. Opisthaptor a postero-ventral outgrowth bearing 1-3 pairs of hooks 
and 12-16 hooklets, or a sucker-like disk with or without radial 
septa on the ventral surface and having hooks and hooklets or not. 
Genito-intestinal canal absent . . . MONOPISTHOCOTYLEA. 

1. Opisthaptor having hooks and transverse supports 

O Y ROD ACT Y WIDE A . 

a. Habit viviparous ...... Gyrodactylidje. 

b. Habit oviparous : 

(a) Anterior extremity devoid of head lappets Dactylogyrid^c. 

(b) Anterior extremity having conspicuous head lappets 

CALCEOSTOM ATIDiE . 

2. Opisthaptor unarmed or having hooks without supports 

CAPSALOIDEA. 

a. Prohaptor a pair of anterior suckers or glandular depressions : 

(a) Intestine simple and sac-like . . . Udonellid^:. 

(b) Intestine bifurcate : 

(i) Genital pores nearly together . Capsalidje. 

(ii) Genital pores not nearly together Acanthocotylidje. 

b. Prohaptor not a pair of anterior suckers or glandular depressions : 

(a) Opisthaptor equipped with hooks . Monocotylid^e. 

(6) Opisthaptor not equipped with hooks MiCROBOTHRnD^:. 

II. Opisthaptor comprising few or many suckerlets or clamps arising from 
a discoidal outgrowth or from the naked postero-ventral surface of 
the body. Genito-intestinal canal present . POLYOPISTHOCOTYLEA. 

1. Prohaptor generally an oral sucker, never a pair of buccal suckers ; 

opisthaptor comprising one pair or three pairs of cup-like 
suckers, never clamps . . . P0LY8T0MAT0IDEA. 

a. Opisthaptor having an appendix-like prolongation 

Hexabothriid^. 

b. Opisthaptor lacking an appendix . . Polystomatid^. 

(Not represented in British fishes ; parasites of am- 
phibians and reptiles.) 

2. Prohaptor a pair of buccal suckers ; opisthaptor comprising four 

or many pairs of clamps, or few suckers, each organ having 
cuticular skeletal supports or sclerites . DICLIDOPHOROIDEA. 



24 THE TREMATODA OF BRITISH FISHES 

A. Clamps of the opisthaptor each having two valves which 
grip by a pincer-like action ; sclerites arranged as — 

(a) a semicircular marginal piece in each valve and a uni- 

lateral basal piece, sometimes a rudimentary middle 
piece ...... Mazocrjeidje. 

(b) a pair in each valve combined into a semicircle and a 

well developed and semicircular middle piece 

MlCROCOTYLIDiE. 

(c) as in (b), but modified, the lateral pieces fused, or the 

ventral pieces segmented near the middle, the middle 
piece massive, sometimes thickened . Discocotylid^;. 

(d) as in (6), but modified differently from (c) ; the lateral 

pieces joined without fusion, one pah - being spurred, 

the middle piece meeting additional pieces which 

make a pair .... Gastrocotylidje. 

b. Clamps or suckers of the opisthaptor having a more or less 

constant circular or oval opening ; sclerites arranged as : 

(e) eight pieces of complicated shapes, the middle piece 

in two segments, and sometimes numerous minute 
pieces arranged in rod-like chains to form a sheet 

DlCLIDOPHORJDiE. 

(/) three pieces in each sucker, their shapes variable, but 
the middle piece largest and somewhat X-shaped 

Hexostomatidje . 



Sub-order MONOPISTHOCOTYLEA Odhner, 1912. 

(Monocotylea Blainville, 1828; Tricotylea and Calicotylea Diesing, 1850; 

Tristomeae Taschenberg, 1879 ; Oligocotylea Monticelli, 1903 ; Mono- 

pisthodiscinea and Monopisthocotylinea Fuhrmann, 1928.) 

Prohaptor absent, or a feeble oral sucker, or a pair of anterior 
suckers, or two elongate antero-lateral depressions receiving the duct 
of numerous unicellular glands, or one or more pairs of head-organs 
receiving the ducts of the cephalic glands. Opisthaptor discoidal, its 
ventral surface sometimes partitioned by septa into loculi, never 
subdivided into distinct suckers or clamps, generally having 1-3 pairs 
of hooks and 12-16 hooklets, the hooks often supported by transverse 
cuticular bars. Eyes and a vagina present or absent. Genito -intestinal 
canal absent (except, possibly, in the Protogyrodactylidae, a family of 
Australian Monogenea). 

Super-family GYRODACTYLOIDEA Johnson & Tiegs, 1922. 

Prohaptor absent, or represented by at least one pair of head- 
organs, receiving the ducts of cephalic glands arranged in two groups, 
one on either side of the pharynx. Opisthaptor discoidal or wedge- 
like, bearing 1 pair or 2 pairs of hooks and 1 or 2, rarely 3, cuticular 
supporting bars. Intestine simple and sac-like, or bifurcate and with 
or without short diverticula. Genital pore in or near the median 
plane. Cirrus simple, cuticularized, sometimes having complex 
cuticular accessories. Vagina present or absent. Genito -intestinal 
canal rarely, if ever, present. Habit oviparous or viviparous. 



GYRODACTYLIDiE 25 

Family GYRODACTYLUXE Cobbold, 1864. 

Amphibdellidse Carus, 1885, in part ; Gyradactylidse Monticelli, 1888.) 

r 

Size small. Shape elongate. Head-organs one pair. Opisthaptor 
well developed, generally having 1 pair of hooks and 15-16 hooklets. 
Intestine bifurcate, the crura not uniting posteriorly and being devoid 
of diverticula. Eyes absent. Cirrus armed with a row of spinelets, 
generally equipped with a triangular cuticular plate. Ovary V-shaped 
or lobed and situated behind the testis. Vagina absent. Vitellaria 
absent or compounded with the ovary to form a germ-vitellarium. 
Habit viviparous, the parent containing two or three generations of 
embryos one inside another. Hosts cephalopods, fishes and amphibians. 

Two sub-families can be separated easily : in the Gyrodactylinse 
(parasites of fishes and amphibians) the opisthaptor has 1 pair of 
hooks and 16 hooklets, and the anterior extremity is bilobed, each lobe 
bearing a head organ : in the Isancistrinse (parasites of cephalopods) 
the opisthaptor has 15 hooklets, but no hooks, and the anterior 
extremity is truncated. 

Sub-family Gyrodactylin^e Monticelli, 1892, sensu Johnston & Tiegs, 

1922. 

Genus GYRODACTYLUS Nordmann, 1832. 

This genus has the characters of the sub -family as stated above. 

About 14 species occur in Europe and about 10 elsewhere, although 

some of the species are unnamed and others are of doubtful validity. 

Gyrodactylus elegans Nordmann, 1832. (Figs. 1 A, B, 2 Ba, Ca.) 

Hosts : three-spined stickleback, ten-spined stickleback. 

Location : gills. 

Bradley (1861, pp. 209-10) found numerous specimens of this 
species on sticklebacks in the Hampstead ponds, scattered over the 
surface of the body and attached at one end, " while the other floated 
freely." When fully extended the specimens were about 1 mm. long 
and one -tenth as broad, tapering from the middle towards both ends, 
the anterior end much narrower and bifid, each division having a 
retractile, brush-like extremity which was used "as a tactile organ 
and also for progression." The " disk " was said to be horseshoe 
shape, the curved margins having 16 lobes each with powers of 
independent movement. Through the centre of each lobe runs a 
tendinous cord associated with a hooklet, and in the disk there are 2 
recurved hooks back to back, connected by a ring by which and their 
bases they are freely held in situ. When the bases are " cupped " the 
hooks are erected. Bradley also recognized the pharynx as a spherical 
cavity and behind it a " germ sac " containing the next generation. 
He often found two young ones inside the body of the parent and noted 
that they closely resemble this in form. Bradley and his colleague 
Bowerbank observed the young tear the envelope and free itself, 



26 



THE TREMATOPA OF BRITISH FISHES 



noting that inside it was a young one of a third generation. In some 
specimens still immature the " germ sac " simply contained a number 
of " vesicular corpuscles." 

Houghton (1862, p. 77) first saw specimens on the pectoral fins 
and tail of young sticklebacks of the smooth-spined variety (" Gastero- 
steus leirus ") hatched from a nest of eggs brought from a ditch on 
the Eyton moors (Shropshire). The father fish was literally covered 




Fig. 1. — A, Gyrodactylus elegans; B, hooks and tran verse bar of G. elegans. 
C, hooks of Ancyrocephalus paradoxus. D, Amphibdella flavolineata; 
and E, one of the hooks of the same. F, hooks and transverse bar of 
Tetraonchus monenteron. G, Amphibdelloides maccallumi, and H, hooks 
and bar of the same. (B, C, F, after Luhe, 1909 ; A, after Bychowsky, 
1933 ; D, E, G, H, after Price, 1937a.) 



with two to three hundred specimens, and when it died the " gills " 
were also found to be " full of them." Examining other three -spined 
and also ten-spined sticklebacks from another ditch Bradley found 
most of them infested with moderate number of the parasites. 

Cobbold (1862) also found specimens on the tails of sticklebacks, 
and writing later (1864) about these worms from " the Serpentine, 
Regent's Park," gave an account of the " birth " of the young indi- 
viduals, also mentioning the opinions of other writers. The " daughter 
first showed itself externally as a slight bulge on the centre of the 
parent's body, where the integument yielded in a way suggestive of 



GYRODACTYLID^ 27 

a vaginal opening. As the young one struggled to free itself, there 
was no sign of injury to the parental tissues. The flexed middle 
region of the body first emerged, followed by the anterior extremity, 
some time elapsing before the broad posterior extremity became free. 
The opening in the parent's body was immediately sealed, all that 
remained being a small cavity inside the body. The whole process of 
" birth " took about five minutes. Comparing the " parent " with 
the " daughter," Cobbold could " scarcely aver that the former was 
the larger of the two," but the similarity of size was perhaps more 
apparent than real, the young individual becoming extended as it 
moved about actively, the parent contracting in a quiescent posture. 
Johnstone (1912, p. 47, Fig. 4) has referred to this species specimens 
found on the dorsal and ventral fins of a plaice taken from Morecambe 
Bay, but not on the caudal fin, skin and gills. They were not seen 
in a satisfactory condition, but were 0-4 mm. long and 0-05 mm. 
broad, with 2 recurved hooks about 0-05 mm. long and "6 or 7 
pairs " of smaller marginal hooks (13 indicated in the figure). 
Most of the specimens contained embryos. The record is puzzling, and 
Johnstone had some doubt in identifying the worm as O. elegans, 
though he regarded it as near this species, which has been found in 
various parts of Europe (R. Rhine, Lake Constance, Lake of Lucerne) 
and in America, and occurs on various other freshwater fishes as well, 
notably the bream, tench, loach, crucian carp, minnow and pike, and 
has also been recorded as a parasite of brackish water fishes such as 
the common goby, and marine fishes such as the lumpsucker. Several 
brief descriptions are available (Nordmann, 1832, pp. 106-8, PL 10, 
figs. 1-3 ; Wagener, 1860, pp. 768-93, Pis. 17, 18 ; Gamble, 1896, p. 61, 
fig. 29 ; Benham, 1901, p. 53, fig. Ill, 6-8) ; and Liihe, 1909, p. 11, 
fig. 6). The diagnostic characters of the species seem to be : Size : 
0*5-1-0 mm. long. Shape spindle -like, with a median notch between 
the head-organs. Opisthaptor disturbing the smooth contour of the 
body posteriorly. Basal parts of the 2 hooks having an outer 
margin which curves ventrally to form a space or groove accommo- 
dating the cuticular supports. Main supporting bar almost Y-shaped, 
having a pair of anterior processes with short dorsal lobes and a median 
posterior plate covering the hooks ventrally ; subsidiary bar a delicate 
transverse connection between the dorsal lobes of the main bar. 
Gut : pharynx having 8 short processes, which project into the 
prepharynx and can be protruded through the mouth. 

Gyrodactylus medius Kathariner, 1894. 

Host : minnow. 
Location : gills. 

Baylis (1928) recorded the occurrence of this species near Edin- 
burgh. It has been found also on the continent of Europe in the 
common carp and bream as well, and it occurs in Canada. It is 
supposed to combine the characters of pharyngeal processes such as 
occur in G. elegans, with two simple and unlobed transverse supports 



28 THE TREMATODA OF BRITISH FISHES 

for the hooks, but Johnson and Tiegs (1922) thought it possible that 
the two forms might be identical. For the original description see 
Kathariner (1894, p. 129, PL 7, figs. 3, 8 ; PI. 8, figs. 9-16 ; PL 9, 
figs. 17-24). 

For a fist of other species of Gyrodactylus, none of which have been 
found in Britain, see Dawes (1946, p. 108). The sub-family Isan- 
cistrinse Fuhrmann, 1928, contains only one genus, Isancistrum de 
Beauchamp, 1912, with the solitary species 7. loliginis de Beauchamp, 
1912, which is not a parasite of fishes, but occurs on the gills of Loligo 
media L., and thus may turn up in sea-water aquaria. It is a small, 
squat form about 0-2 mm. long, which, like Gyrodactylus elegans, may 
contain several generations of embryos at the same time. 

Family DACTYLOGYRIDiE Bychowsky, 1933. 

(Gyrodactylidse Cobbold, 1864, in part ; Amphibdellidse Cams, 1885, 

in part.) 

Size small. Shape elongate. Head-organs two or more pairs. 
Cephalic glands lateral, sometimes encroaching on the median region 
in front of the mouth. Opisthaptor fairly well developed, possessing 
or lacking squamodisks, but having 1 pair or 2 pairs of hooks and 
14 hooklets. Ovary globular or elongate and curved, situated in 
front of the testis . Vagina present or absent . Vitellaria well developed . 
Habit oviparous. 

The three sub -families can be distinguished by the numbers of 
hooks and the presence or absence of squamodisks. The opisthaptor 
has only 1 pair of hooks in the Dactylogyrinse, but 2 pairs in the 
Tetraonchinse and Diplectaninae, squamodisks occurring only in the 
latter, where they are dorsal and ventral in the posterior region. 

Sub-family Dactylogyrin^: Bychowsky, 1933. 

{Gyrodactylince Monticelli, 1892, in part.) 

In this group the opisthaptor is well developed, equipped with 
pair of hooks, 1 or 2 supporting bars and 14 hooklets, but lacks 
squamodisks. The crura of the gut unite posteriorly, forming a 
ring-like intestine, eyes are present, the gonads are globular, and the 
ovary situated in front of the testis, and the vagina has or lacks cuti- 
cular skeletal supports. In the genus Dactylogyrus the hooks are 
supported by a single bar, in Neodactylogyrus by two similar or dis- 
similar bars. 

Genus DACTYLOGYRUS Diesing, 1850, sensu Price, 1938. 
(Fig. 2 A, Bb, Cb, Da, b.) 

Dactylogyrus auriculatus (Nordmann, 1832) Diesing, 1850. 

Gyrodactylus auriculatus Nordmann, 1832 (pp. 108-9, PI. 10, figs. 4-9 ; 
G. auricidaris of Wedl, 1857. 

This species has not appeared in Britain, but occurs attached to 
the gills of the bream and carp on the Continent. It was originally 



DACTYL0GYRIDJ3 



29 



described as a very small fluke of the same size as Gyrodactylus elegans, 
and Dujardin (1845, p. 480) gave the length as 0-25 mm., Beneden 
(1858, p. 66, PL 7, figs. 9-11) as 20-25 mm., obviously omitting the 
decimal points. The latter writer first found the trematode attached 
to Diplozoon paradoxum on the gills of the bream. According to 
Luhe (1909, p. 18) the old descriptions and figures are insufficient for 
the identification of the species, and many species have since been 
erected, evidently without reference to the type. None has appeared, 
in Britain, although some of them probably occur here, so that it is 




Fig. 2. — A, diagram of the principal organs of Dactylogyrus, B, copu- 
latory apparatus of Gyrodactylus (a) and Dactylogyrus (b). C, hooklets 
of Gyrodactylus (a), Dactylogyrus (b) and Tetraonchus (c). D, copulatory 
apparatus (a) and lateral cuticular structure (b) of Dactylogyrus chrani- 
lowi. (After Bychowsky, 1933.) 



pertinent to mention the opinion of Nybelin (1937), according to whom 
many trematodes allocated to "D. auriculatus Nordmann " are either 
unintelligible, or under suspicion of belonging to other species, just 
as Dujardin's " G. auriculatus" was distinct from Nordmann's and 
justifiably renamed dujardinianus by Diesing. Several characters 
specified in the original description leave no doubt that "auriculatus 
Nordmann " really belongs to the genus Dactylogyrus sensu lato, 
notably the presence of 4 processes at the anterior extremity, of 
4 eyes and well developed vitellaria. Other characters specified 
are enigmatical, particularly the presence of 20 hooklets arranged 
in a double coronet of 12 and 8 on the outer and inner rows, 



30 THE TREMATODA OF BRITISH FISHES 

which Nybelin regarded as an error of observation. After examining 
a number of species which occur in Sweden, five of them new, Nybelin 
concluded that D. sp. Wegener, 1910, and D. wunderi Bychowsky, 
1931, which were regarded as identical, most closely approach " D. 
auriculatus Nordmann " in general structure. Accordingly, he pro- 
posed to regard both as synonyms of the type-species, but unfor- 
tunately, Price (1938a, p. 49) transferred D. wunderi to Neodactylo- 
gyrus because the hooks are supported by two transverse bars. All 
five of Nybelin's new species belong to this genus, and as he was dealing 
with forms having two bars, it was natural for him to infer that the 
second bar was overlooked in Nordmann's description of auricidatus, 
although his description in an addendum of a sixth new species, D. 
cordus, was of a form with only one bar, and a number of species 
previously described undoubtedly have this character. We must 
conclude, therefore, that as D. sp. Wegener and D. wunderi Bychowsky 
are identical with one another, neither can be synonymous with G. 
auriculatus Nordmann, and both belong to the genus Neodactylogyrus. 
It may be impossible to decide in some early descriptions which of 
these two genera are under consideration, because the distinguishing 
characters make no allowance for the possible oversight by earlier 
writers of one of the transverse bars. Thus D. falcatus (Wedl) was 
credited by Liihe (1909) with one bar and was retained in the genus 
Dactylogyrus by Price (1938a), although Nybelin figures two bars 
(Fig. 10). As I have already given a list (Dawes, 1946, p. 112) of the 
European " species " of Dactylogyrus nothing further need be added 
here, except to state that the specific characters include the shapes, 
sizes and various arrangement of the cuticular structures of the 
opisthaptor and the nature of certain cuticular accessories of the 
copulatory apparatus. 

Genus NEODACTYLOGYRUS Price, 1938. 

(Dactylogyrus Nordmann, 1832, in part.) 

Hooks of the opisthaptor supported by 2 transverse cuticular 
bars ; other characters as in Dactylogyrus. 

Neodactylogyrus megastoma (Wagener, 1857) Price, 1938. 

Dactylogyrus megastoma Wagener, 1857 (a, p. 57, PI. 14, fig. 5 ; PI. 36a, fig. 2). 

The locality in which this trematode was originally found was not 
stated, although Braun (1879-93) gave it as Middle Europe. A 
diagnosis of this trematode, which occurs on the bitter ling carp 
(Rhodeus amarus) and white bream, but has not appeared in Britain, 
was given by Liihe (1909, p. 13, fig. 14). The opisthaptor has hooks 
with sickle-like points and double roots set at right angles, the smaller 
continuing the base of the point, the longer diverging from it. The 
transverse bars are fairly similar, the dorsal having notched extremi- 
ties, the ventral being the more strongly recurved. The marginal 
hooklets are said to number 14. 



DACTYLOGYRID^: 31 

About 21 " species " of Neodactylogyrus occur in Europe, but none 
has appeared in Britain. About 16 other " species " occur in America. 
For a list of the European species see Dawes (1946, p. 113). 

Sub-family Tetraonchinje Monticelli, 1903. 

Cuticle devoid of scales or spines. Opisthaptor lacking squamo- 
disks, but bearing 2 pairs of hooks and 12-16 hooklets. Intestine 
sac-like or bifurcate. Eyes present or absent. Gonads generally- 
globular, not lobed. Vagina present or absent. Price (1937a) gave 
a key to 20 genera, mainly American. One other genus which 
belongs to the sub-family is Linguadactyla. Of the European genera, 
Amphibdella has hooks which are not supported by transverse bars ; 
Ancyrocephalus and Haplocleidus have 2 bars, but the hooks are of 
equal and unequal sizes respectively. Four other genera have only 
1 transverse bar and two of them have hooks of equal sizes, Tetra- 
onchus having a single caecum and Amphibdelloides a pair of caeca. 
The remaining two have hooks of unequal sizes, the opisthaptor being 
lobed and pedunculate in Dactylodiscus, but not in Linguadactyla. 

Genus TETRAONCHUS Diesing, 1858. 

(Gyrodactylus of Wedl, 1857 ; Dactylogyrus of Wagener, 1857, in part ; 
Monocoelium Wegener, 1910 ; Ancyrocephalus of Luhe, 1909, in part.) 

Head-organs numbering two or several pairs and bearing the open- 
ings of the cephalic glands. Opisthaptor fairly well differentiated, 
with 2 pairs of hooks supported by a large bar and 16 marginal 
hooklets. Intestine a simple caecum devoid of diverticula. Eyes 
present. Gonads situated near the middle of the body, vagina absent. 

Tetraonchus monenteron (Wagener, 1857) Dies., 1858. (Figs. 1 F, 2 Cc.) 

Dactylogyrus monenteron Wagener, 1857 (a, pp. 63-7, 69-73, PI. 13, fig. 1 ; 
PI. 36a, fig. 3/) ; Gyrodactylus cochlea Wedl, 1857 (pp. 258-74, PL 3, figs. 32- 
7) ; Ancyrocephalus monenteron (Wagener) of Luhe, 1909 (p. 19, figs. 27, 30). 

Host : pike. 
Location : gills. 

This species occurs in various parts of Europe (Italy, Lake Con- 
stance), and was found by Van Cleave and Mueller (1934, p. 184, PL 28, 
figs. 1-3) in pike at Oneida Lake, New York. According to Sproston 
(in litt.) it also occurs in Britain. Size : 1-2 mm. long. Shape : 
elongate and of uniform girth, tapering slightly posteriorly. Eyes : 
two pairs, the anterior and posterior nearly together. Opisthaptor : 
large and broader than long, the breadth sometimes exceeding that 
of the body. Hooks each having a narrow and sickle-like blade 
and a broad and plate-like base having a stump-like process ; 
transverse supporting bar flattened and dumbbell- or butterfly- shaped ; 
hooklets as indicated in Fig. 2 Cc. Gut : pharynx large and spherical, 
intestine long and sac-like. Reproductive systems : genital pore situated 



32 THE TREMATODA OF BRITISH FISHES 

behind the pharynx ; genital hooklets long and slender ; support of the 
copulatory organ arranged spirally around its tip. Gonads compact 
and situated in the median plane, the ovary in front of the testis. 
Vitellaria extensive laterally and composed of numerous coarse 
follicles. Vagina absent. [Note : — the only other species is T. alas- 
kensis Price, 1937, a parasite of Salmonidse in Alaska.] 

Genus ANCYROCEPHALUS Creplin, 1839. 
(Diplectanum of authors ; Tetraonchus Diesing, 1858, in part.) 

Head-organs generally numbering 3 pairs and bearing the openings 
of the cephalic glands. Opisthaptor less distinct than in Tetraonchus, 
the 2 pairs of hooks supported by 2 transverse bars ; 14 hooklets 
present. Gut bifurcate, the caeca discrete. Eyes present. Gonads 
situated as in Tetraonchus, vagina present. 

Ancyrocephalus paradoxus Creplin, 1839. (Fig. 1 C.) 

Dactylogyrus unguiculatus Wagener, 1857 (p. 61, pp. 64-5) ; Tetraonchus 
unguiculatus (Wagener) Diesing, 1858 (pp. 380-1). 

Host : perch. 
Location : gills. 

This species is well known on the Continent (at Griefswald, 
Vienna, Gedani) and occurs in Britain, a single specimen in my 
collection having been obtained in southern England. According to 
Luhe (1909, p. 18, fig. 28) the trematode is 3-4 mm. long, and the 
elongate body tapers to a small opisthaptor bearing hooks with sickle- 
like points and 2 basal processes, one plate -like and the other knob- 
like, each pair being connected by a beam-like transverse bar. My 
specimen has the following characters : — Size : about 0-8 mm. long 
and 0-23 mm. broad in the middle, but only 0-17 mm. at the level of 
the pharynx. Shape : tapering to a greater extent posteriorly than 
anteriorly and truncated at the anterior extremity. Cephalic glands 
arranged in two groups and slightly behind the pharynx ; head-organs 
ill defined. Opisthaptor about 0-12 mm. broad and somewhat longer, 
its anterior boundary ill-defined ; large ventral hooks fairly similar, 
the base about 0-04 mm. long and 0-02-0-025 mm. broad across the 
wide lobe proximal to the point, which is about 0-02 mm. long, and 
one of which is curved while the other is straight. Smaller dorsal 
hooks slightly smaller, the base about 0-03 mm. long and 0-025 mm. 
broad across the corresponding but knob-like lobe ; points about the 
same size and gently curved. Eyes : those of the anterior pair the 
smaller, 0-046 mm. apart and 0-032 mm. from the anterior extremity, 
those of the posterior pair 0-057 mm. apart and 0-056 mm. from the 
extremity. Pharynx 0-06 mm. diameter, its anterior border situated 
between the eyes of the two pairs. Reproductive systems : genital 
pore near the pharynx, cirrus cuticular and about 0-07 mm. long, its 
distal part slightly bulbous. Testis longitudinally ovoid, 0-09 mm. 
long and 0-07 mm. broad, the hinder boundary at the middle of the 



DACTYLOGYRIDJE 33 

body. Ovary transversely ovoid, measuring 0-06 X 0-045 mm., 
situated just in front of and contiguous with the testis. Vitellaria 
well developed laterally, extending from the level of the pharynx to 
the base of the opisthaptor, the follicles more numerous and densely 
arranged posteriorly. Vaginal pore situated on the right margin of 
the body just in front of the level of the ovary ; vagina cuticular and 
apparently forming a short spiral. Eggs absent. 

Genus HAPLOCLEIDUS Mueller, 1937. 

Hooks of the opisthaptor unequal in size, those of the ventral pair 
only about half as large as those of the dorsal. Cirrus long and spirally 
coiled, or having a spiral fin, generally an accessory piece as well. 
Vagina opening on the left margin of the body. 

The type and two other species of this genus occur in America, 
two species in Europe, one of them H. monticellii (C. de Martiis, 1925) 
Price, 1937, which was described as a species of Ancyrocephalus taken 
from an American catfish (Haustor catus) in Italy, the other H. siluri 
(Zandt, 1924) Price, 1937, which was also originally regarded as 
Ancyrocephalus and occurs in the sleat-fish, Silurus glanis, in Lake 
Constance and in the Vistula, Poland. I have already given a short 
diagnosis of the latter species (Dawes, 1946, p. 116), which is unlikely 
to appear in British waters, although the host descends into brackish 
or salt water and was once recorded as a Scottish river fish. 



Genus AMPHIBDELLA Chatin, 1874. 
(Tetraonchus of Monticelli, 1903.) 

Head-organs numbering 3 pairs. Opisthaptor lobed and clearly 
differentiated, having 2 pairs of hooks of similar sizes which are not 
supported by cuticular bars and 14 hooklets. Gut bifurcate, the 
caeca discrete. Eyes absent. Gonads situated in the anterior region, 
the ovary extending lateral to the caecum of its side. Vitellaria 
extensive laterally, vagina cuticular and lateral. 

Amphibdella flavolineata MacCallum, 1916. (Fig. 1 D, E.) 

Host : torpedo. 
Location : gills. 

This species was discovered on a torpedo (Tetranarce occidentalis) 
and a " sting ray " at Woods Hole and was found by Pees & Llewellyn 
(1941) at Colwyn Bay. British specimens have not yet been described, 
but Price (1937a, pp. 151-3, figs. 1-4) described American specimens. 
Size : 3-8-43 mm. long and 051-068 mm. broad. Head-organs : 
3 pairs, situated near the anterior extremity, receiving the ducts 
of lateral cephalic glands situated in front of the pharynx. Opist- 
haptor lobed, 0-425-0-475 mm. broad, provided with 2 pairs of 
hooks 0-15-0 "16 mm. long and 14 marginal hooklets about 0-01 mm. 
long, one to each lobe. Blade of each hook lacking a shoulder-like 



34 THE TREMATODA OF BRITISH FISHES 

lobe near the base and tapering gradually from base to point. Gut : 
mouth median ventral and 0- 19-0*23 mm. from the anterior extremity ; 
pharynx globular and 0-13-0-15 mm. diameter ; oesophagus very short 
and associated with a pair of clusters of unicellular glands ; caeca simple 
and discrete, extending to the posterior ends of the vitellaria. Repro- 
ductive systems : genital pore median near the bifurcation of the gut ; 
cirrus tubular and about 0-1 mm. long, having a complicated cuticular 
accessory ; seminal vesicle S-shaped and conspicuous. Testis small and 
situated on the left, largely hidden by vitelline follicles ; ovary elongate 
and curved, overreaching the caecum laterally. Vitellaria a long 
series of very coarse follicles lateral to the caeca extending from an 
anterior level near the ootype nearly to the posterior extremity. 
Vagina situated just in front of the ovary on the right side of the bod}^ 
associated with a large receptaculum seminis. Ootype situated just 
in front of the gonads, slender and having gland cells clustered around 
its base. Eggs not observed. 

The type-species, A. torpedinis Chatin, 1874, has been found at 
Naples and elsewhere in the Mediterranean, on the gills of the torpedo. 
According to Price, this species differs from A. flavolineata in the 
nature of the copulatory apparatus and in the size and shape of the 
hooks, each of which has a slender blade which widens before meeting 
the biramous root to produce a shoulder-like process. Chatin gave 
the length of the hooks as 0-085 mm., i.e. only half that of A. flavo- 
lineata. 



Genus AMPHIBDELLOIDES Price, 1937. 

(Amphibdella Chatin, 1874, in part.) 

Closely resembling Amphibdella, but opisthaptor not lobed and 
hooks having only a single supporting bar. 

Amphibdelloides maccallumi (Johnston & Tiegs, 1922) Price, 1937. 

(Fig. 1 G, H.) 

Amphibdella torpedinis Perugia & Parona, 1890, nee Chatin, 1874 ; A. tor- 
pedinis MacCallum, 1916, nee Chatin, 1874 ; A. maccallumi Johnston & 
Tiegs, 1922. 

Host : torpedo (Torpedo nobiliana ; T. marmorata in the Mediter- 
ranean). 

Location : gills. 

This species was described by Perugia & Parona (1890, p. 24, 
PL 1, figs. 12, 13 ; PI. 2, figs, 14-18) and redescribed by Price (1937a, 
pp. 153-4, figs. 5-8). It has been found, but not described, by Rees 
and Llewellyn (1941) at Colwyn Bay. The Italian specimens were 
comparatively large, 3-5 mm. long and 0-42 mm. broad, the opis- 
thaptor 022 mm. diameter and the hooks 0-14 mm. long, their support 
0-084 mm. long. American specimens are sometimes much smaller. 
Size : 1-1-3-5 mm. long and 0-25-0-48 mm. broad. Eyes absent. 



DACTYLOGYRID^ 35 

Head-organs : 3 pairs situated near the anterior tip of the body, 
receiving the ducts of numerous cephalic glands, which form a trans- 
verse band in front of the pharynx and extend back on each side 
nearly to the level of the genital pore. Opisthaptor not lobed and 0-21- 
0-42 mm. broad, having 2 pairs of hooks 0-13-0*17 mm. long 
which taper gradually from base to point and 14 hooklets about 0-01 
mm. long. Supporting bar of the hooks slightly curved, the anterior 
margin concave, 0-064-0-095 mm. long and 0-019 mm. broad. Gut : 
mouth median ventral and 0-13-0-17 mm. from the anterior extremity. 
Pharynx globular and 0-075-0-095 mm. diameter. (Esophagus long. 
Reproductive systems : genital pore median and situated near the 
bifurcation of the gut. Cirrus tubular and about 0-17 mm. long, equipped 
with two accessory pieces about 0-13-0-16 mm. long, one having a 
single curved tip and the other a trifurcate tip or five or more points 
(see Perugia & Parona, 1890, PI. 1, fig. 13). Testis median and very 
elongate, extending almost to the ends of the cseca. Ovary much 
smaller, but also elongate and situated in front of the testis. Vitel- 
laria comprising two lateral arrays of fairly large follicles, which merge 
in a narrow transverse band behind the testis and extend anteriorly 
nearly to the anterior end of the ovary. Vaginal pore situated on the 
right margin of the body near the middle of the ovary ; vagina slender 
and cuticular opening into a large receptaculum seminis lying alongside 
the anterior half of the ovary and on its right. Eggs not observed. 

Genus LINGUADACTYLA Brinkmann, 1940. 

Opisthaptor indistinct, but equipped with 2 pairs of curved 
hooks, those of one pair (dorsal ?) larger than the others, a middle 
piece of oval shape and 12 (? 14) hooklets set in the narrow pos- 
terior region of the body. Gut including 2 separate caeca having 
branched lateral diverticula. Young specimens having 1 pair of 
eye-spots and hooks which are only slightly smaller than those of the 
adult. Gonads situated near the middle of the body ; copulatory 
apparatus comprising 2 cuticular pieces, one of them pointed and 
the other forked ; vagina absent. 

Linguadactyla molvae Brinkmann, 1940. 

Host : blue ling. 
Location : gills. 

This species was discovered at Bergen, Norway, and described in 
great detail by Brinkmann (1940, p. 7, Pis. 1-4, figs. 1-17). Adults 
are permanently attached, and the epithelium of the gill reacts to the 
irritation set up by the opisthaptor by proliferation, which forms an 
annular pad around the posterior end of the parasite. The parasite, 
which is likely to appear in Britain, thus seems to protrude from a 
cyst-like structure on the gills. Size : mature when 2-6 mm. long 
and then rather less than half as broad. Shape : elliptical or tongue - 
shaped, sometimes narrower posteriorly, slightly concave dorsally and 



36 THE TREMATODA OF BRITISH FISHES 

ventrally. Colour : yellowish white, the vitellaria forming dark 
lateral stripes. Prohaptor : cephalic glands apparently absent. Opis- 
thaptor : large and small hooks 0*12 and 0-06 mm. long, in immature 
specimens 1-2 mm. long, in adults 5 mm. long. Large hooks 0-143 mm. 
long and strongly curved, tapering gradually from base to point, each 
with one short and one longer bifurcate root. Small hooks 0-07 mm. 
long and just as curved, each having a single root, the two roots being 
linked by a short triangular or oval cuticular bar. Gut : mouth not 
quite terminal, bordered by a conspicuous dorsal and a less prominent 
ventral lip. Pharynx large. (Esophagus absent. Caeca fairly long, ex- 
tending to the posterior one-third of the body. Diverticula of the caeca 
branched and lined with columnar epithelium. Reproductive systems : 
genital pore median and just behind the bifurcation of the gut. Testes 
numerous, mainly situated between the caeca in the second quarter 
of the body. Vas deferens curving round the left caecum near the 
ovary and continuing diagonally forward, dilated to form a seminal 
vesicle. Prostate gland cells well developed. Copulatory organ 
equipped with two cuticular pieces, one tubular and pointed and 
resting in a groove in the other, which is forked. Ovary pyriform 
and situated just in front of the testes. Ootype median and tubular ; 
uterus short and straight, also median. Vitellaria lateral to the main 
caeca and extending forward to the level of the pharynx ; lateral vitello- 
ducts connected by a transverse vessel in front of the ovary ; main 
unpaired duct arising asymmetrically from the left lateral duct opposite 
the ovary. 

Genus inq. DACTYLODISCUS Olsson, 1893. 

Opisthaptor lobed and pedunculate and having 2 pairs of hooks, 
those of the dorsal pair the larger, and a middle piece of peculiar shape. 
Eyes present. Gonads rounded and situated near the middle of the 
body, cirrus simple. 

Olsson (1893, pp. 7-8, PL 1, figs. 7-10) described the only species 
of this genus, D. borealis, a parasite about 2 mm. long on the gills of 
the grayling and gwyniad in Sweden. Johnston and Tiegs (1922) 
regarded Dactylodiscus as a sub -genus of Ancyrocephalus , but Price 
(1937a) preferred to retain it as a genus till more information about the 
structure of D. borealis is forthcoming. We know practically nothing 
about the head- organs, cephalic glands, hooklets, vagina and other 
important structures. 

About 15 other genera of the Tetraonchinae are known outside 
Europe. Seven of them occur in North America : Actinocleidus 
Mueller, 1937 ; Anchoradiscus Mizelle, 1941 ; Cleidodiscus Mueller, 
1934 ; Diplectanotrema Johnston & Tiegs, 1922 ; Rhabdosynochus 
Mizelle & Blatz, 1941 ; Urocleidus Mueller, 1934 ; and Tetrancistrum 
Goto & Kikuchi, 1917, the last-named occurring also in Japan and 
the Philippines. Four others occur in Australia : Anchylodiscus 
Johnston & Tiegs, 1922 ; Daitreosoma Johnston & Tiegs, 1922 ; 
Empleurosoma Johnston & Tiegs, 1922 ; and Murraytrema Price, 



DACTYLOGYRIDiE 37 

1937. The remaining genera are found in Japan ; Anchylodiscoides 
Yamaguti, 1937 ; Ancyrocephaloides Yamaguti, 1938 ; Haliotrema 
Johnston & Tiegs, 1922 ; and Parancyrocephaloides Yamaguti, 1938. 
Many of these genera have been reviewed by Price (1937a). 

Sub -family Diplectanin^: Monticelli, 1903. 

(Lepidotreminse Johnston & Tiegs, 1922.) 

Opisthaptor equipped with dorsal and ventral squamodisks, or 
plates of cuticle covered with scale-like spines arranged in charac- 
teristic rows, and 2 pairs of hooks, 2 supporting bars and 14 hooklets. 
Vagina present or absent. 

Genus DIPLECTANUM Diesing, 1858, sensu Price, 1937. 

(Dactylogyrus of Wagener, 1857, in part ; Acleotrema Johnston & Tiegs, 
1922 ; Lepidotes Johnston & Tiegs, 1922 ; Squamodiscus Yamaguti, 1934. 

Dorsal and ventral squamodisks having concentric rows of scale- 
like spines, but not spine-like hooks. Hooks of the opisthaptor sup- 
ported by 3 transverse bars. Vagina present or (?) absent. 

According to various writers (Johnston & Tiegs, 1922 ; Fuhrmann, 
1928 ; Van Cleave & Mueller, 1932 ; Sprehn, 1933) this genus was 
regarded as being identical with Ancyrocephalus , but Price (1937a) 
upheld its validity. It was proposed by Diesing for two species 
named by Wagener (1857a) and later (18576) briefly characterized, 
namely Dactylogyrus cequans and D. pedatum. Price has shown that 
although Diesing did not designate a type of the genus Diplectanum, 
the former of these species may be taken as such. It was originally 
found on the gills of the bass, and Price accepts as members of the 
same species specimens from the same species of host described under 
the name D. cequans by Beneden & Hesse (1863), Stossich (1896) and 
Maclaren (1904). The outstanding generic character is the squamo- 
disks, which are lacking in Ancyrocephalus. 

Diplectanum sequans (Wagener, 1857) Diesing, 1858 (p. 381). 

(Fig. 3 A-G.) 

Dactylogyrus cequans Wagener, 1857 (p. 99, PI. 15, fig. 14). 

Host : bass. 
Location : gills. 

This species has been found in the Irish Sea, off the coast of Belgium 
and in the Mediterranean, where three other species occur on other 
hosts. British descriptions of this species are very inadequate. A. 
Scott (1904, p. 35 ; 1906, p. 49, PL 10, fig. 4) merely stated that the 
trematode was plentiful in the Irish Sea. According to the stated 
magnification of his figure the specimen he considered was about 
2*1 mm. long and 0-5 mm. broad, the squamodisks measuring about 
0-13 X 0-20 mm. Three antero-lateral papillae shown probably 



38 



THE TREMATODA OF BRITISH FISHES 



carried the openings of the cephalic glands. T. Scott (1905, p. 117, 
PL 6, fig. 24) described the species in three or four lines, obviously 
confounding the anterior and posterior extremities. The dorsal and 
ventral squamodisks were not noted, a fault in other accounts also ; 
the length was given as about 2 mm. and the illustration indicated 
three pairs of indistinct head-organs. The same writer later (1912) 
repeated the previous mistake, asserting that the " head " is armed 
with two hooked spines on each side of a cleft occupied by a process 




Fig. 3. — Diplectanum cequans. A, entire trematode ; B, anterior end, 
showing the head-glands (solid black), " brain " (in outline) and mouth 
(dotted line) ; C, a squamodisk, showing the arrangement of rows of 
spines ; D skeletal bar for support of the hooks ; E, posterior end, 
showing the skeletal bar in situ, also the hooks, caudal-glands and 
squamodisk ; F, one of the hooks ; G, schematic diagram of the repro- 
ductive systems. (After Maclaren, 1904.) 



thickly covered with minute " prickles." Maclaren found the species 
common on the bass at Trieste, one-third of the fishes examined being 
infested with two to four specimens each, and he gave a good descrip- 
tion (1904, p. 574, figs. A, B, C 1-5 ; PI. 20, figs. 1-12 ; PI. 21, figs. 
13-22). Size: 5-1*5 mm. long and about one-quarter as broad. 
Colour : difficult to see because of the same colour as the gills, beneath 
the filaments of which the parasite lies hidden. Shape : elongate and 
fusiform, but flattened and tapering posteriorly from the level of the 
genital pore. Cuticle bearing numerous small papilla?. Cephalic 



CALCEOSTOMATlDiE 39 

glands forming a large group on either side of the anterior extremity 
and opening by numerous pores, the individual cells pyriform. Caudal 
glands similar to the cephalic, but situated between the squamodisks 
posteriorly, arranged in two pairs, one behind the other. Opisthaptor : 
squamodisks broader than long, measuring 0-13 x 0-15 mm., each 
having small spines arranged in regular rows which are transverse 
posteriorly, become concave near the middle and are U-shaped an- 
teriorly. Hooks : two on each side of the body postero-lateral to the 
squamodisks, each recurved at the tip and having two unequal roots. 
Transverse supporting bars forming a pair meeting in a joint in the 
median plane, curving in the lateral regions to meet the roots of the 
hooks. Gut : mouth a ventral slit not quite terminal and provided 
with lips having short lobes which are somewhat extensile. Pharynx 
prominent. (Esophagus short. Caeca long and unbranched. Eyes : 
two pairs, located in front of the pharynx and mouth. Reproductive 
systems : genital pore displaced to the right just behind the bifurcation 
of the gut. Cirrus 0-2 mm. long and cuticular, also on the right. 
Ejaculatory duct long and muscular, the ejaculatory bulb having two 
chambers, the distal one the larger. Pars prostatica constricted, the 
smaller posterior part surrounded by gland- cells. Testis slightly 
lobed, median and slightly behind the middle of the body. Ovary 
reniform and situated on the left just in front of the testis. Uterus 
short and fairly straight, the receptaculum seminis at its base small 
and globular, the ootype situated nearby. Vagina extending forward 
and to the left to open on the ventro-lateral surface of the body, 
thick-walled and muscular, but having a cuticular lining, its opening 
unarmed. Vitellaria comprising numerous follicles extending from 
the level of the pharynx, where they are most abundant, to the ends 
of the caeca, where they are sparse. Transverse vitelloducts asym- 
metrical, the right anterior to the left, at the level of the ootype. 
Eggs unobserved. 

Four of nine other species of Diplectanum occur in Europe, and 
Price (1937a) regarded all as inadequately described, although pro- 
bably valid. They are D. sciceno3 (Beneden & Hesse, 1863), originally 
described as a species of Epibdella parasitic on the surface of the 
meagre on the coast of Belgium ; D. aculeatum Parona & Perugia, 
1899, found on Corvina nigra ; D. echeneis (Wagener, 1857), found on 
the gilt-head and Couch's sea bream ; and D.pedatum (Wagener, 1857), 
found on a wrasse. The last three occur in the Mediterranean, and 
Maclaren (1904) gave diagnoses of the first two, and also of D. scicence. 

Two other genera of Diplectaninae occur in Australia, one genus 
in U.S.A. 

Family CALCEOSTOMATID.E Parona & Perugia, 1890, emend. 
Poche, 1926, sensu Fischthal & Allison, 1941. 

Prohaptor generally comprising head-lappets at the expanded 
anterior extremity, which has numerous scattered cephalic glands. 
Opisthaptor sucker-like, but not markedly muscular, having or lacking 



40 THE TREMATODA OF BRITISH FISHES 

hooks and hooklets. Eyes present or absent. Intestine with or with- 
out short diverticula. Testis single. Cirrus simple, but cuticular. 
Vagina present or absent. 

Sub-family Calceostomatin^: Monticelli, 1892, emend. 

With the characters of the family. The two European genera can 
be distinguished by the nature of the prohaptor ; in Calceostoma it 
comprises head-lappets, but in Anoplodiscus a pair of pseudosuckers. 

Genus CALCEOSTOMA Beneden, 1858. 

Anterior extremity expanded to form conspicuous ventrally- 
curled head-lappets, pseudosuckers absent. Opisthaptor cup-like, 
having hooks and hooklets or (?) not. Eyes present. Testes elongate, 
ovary branched, vagina absent. 

Calceostoma calceostoma (Wagener, 1857) Johnston & Tiegs, 1922. 

Dactylogyrus calceostoma Wagener, 1857 (p. 99) ; Calceostoma elegans Beneden, 
1858 (pp. 60-3, PL 7, figs. 1-8). 

Host : meagre. 
Location : gills. 

This species has not been found in Britain, but probably occurs 
here, having been found off the coast of Belgium. It was inadequately 
described, but has the following general characters. Size : up to 
10 mm. long. Prohaptor : head-lappets large, taking up one-fifth of 
the length of the body proper. Opisthaptor terminal and discoidal, 
about one -third as broad again as the body, supposedly bearing a 
single centrally situated hook, but the second hook and other cuticular 
accessories probably lost. Eyes not observed, but probably present. 

Another European species, C. inerme Parona & Perugia, 1889 (p. 
747), was discovered on Corvina nigra and the umbrina (Umbrina 
cirrosa) at Genoa and has not appeared in Britain. As the name 
implies, hooks and hooklets are lacking on the opisthaptor, but may 
have been overlooked. The only other species, C. glandulosum John- 
ston & Tiegs, 1922, a parasite of Scicena antarctica in South Queens- 
land, is about 5 mm. long, has 2 pairs of eyes, 2 large hooks and 
certain haptorial accessories, and has been fully described. 

Genus ANOPLODISCUS Sonsino, 1890. 

Prohaptor a pair of pseudosuckers situated at the anterior extremity. 
Opisthaptor cup-like and devoid of accessories. Eyes present. Cirrus 
having a cuticular lining and an accessory piece. Testis situated in 
front of the middle of the body, the ovary in front of it. Vagina 
present. 

The type-species, A. richiardii Sonsino, 1890, occurs on the gills 



MONOCOTYLID.E 41 

of Couch's sea bream in the Mediterranean. Sonsino regarded it as 
related to both Gyrodactylids and Tristomids, but Monticelli (1891, 
p. 108 ; 1095, pp. 65-8, figs. 1-3) extended the meagre description, 
and subsequently the species has had a chequered taxonomic career, 
having been referred at different times to several families (Gyro- 
dactyhdae, Monocotylidae, Microbothriidae, Udinellidae) . Its present 
position is due to Fischthal & Allison (1941). The only other species, 
A. australis Johnston, 1930, was discovered on one of the fins of Sparus 
australis in Sydney Harbour. Other genera of the Calceostomatidse 
occur in America (see Dawes, 1946, p. 120). 

Super-family CAPSALOIDEA Price, 1936. 

Prohaptor absent, or a feeble oral sucker, or a pseudosucker, or 
two lateral glandular grooves. Head organs present or absent. 
Opisthaptor generally a prominent muscular disk partitioned by septa 
on the ventral surface to form loculi and sometimes having hooks, 
but never cuticular supporting bars. Gut : intestine simple and sac- 
like or bifurcate, sometimes having median and lateral diverticula. 
Genital pore median or lateral. Cirrus sometimes cuticular, but never 
equipped with accessories. Testes : sometimes few, or only one testis. 
Vagina present or absent. 



Family MONOCOTYLIDiE Taschenberg, 1879. 

Shape flattened, the outline oval or elliptical. Prohaptor a weak 
oral sucker, or two or more anterior suckers supplied with a sticky 
secretion by the cephalic glands. Opisthaptor a disk having a septate 
ventral surface, generally equipped with 1 pair of hooks and 14 
hooklets. Eyes present or absent. Gut : mouth ventral, not quite 
terminal ; pharynx large ; oesophagus short or absent ; caeca simple and 
long ; intestine sometimes ring-like. Genital pore typically median. 
Cirrus generally cuticular. Testes rarely 3 or many, generally only 
a solitary testis. Ovary curved and sometimes looped round the right 
caecum. Vaginal generally paired, but sometimes a single vagina or 
none. 

The three sub-families which are represented in Europe can be 
distinguished from one another by the nature of the haptors and the 
vagina. In two of them the prohaptor is a feeble oral sucker and 
the opisthaptor has no more than 8 loculi, the Monocotylinae having a 
single vagina, the Calicotylinae a pair of vaginae ; in the Merizocoty- 
linae the prohaptor consists of head- organs and cephalic glands and 
the opisthaptor has more than 8 loculi. 

Sub-family Monocotylinae Gamble, 1896. 

Of the two European genera, Heterocotyle has a feeble oral sucker, 
Monocotyle only a membranous pseudosucker. 



42 THE TREMA.TODA OF BRITISH FISHES 

Genus MONOCOTYLE Taschenberg, 1878. 
Opisthaptor having its ventral surface divided by septa into 8 
equal loculi and equipped with 1 pair of hooks, probably hooklets 
also. Prohaptor sometimes fringe-like and papillate. Eyes absent. 
Testis single. Opening of the uterus marginal. 

Monocotyle myliobatis Taschenberg, 1878. 

This species occurs on the gills of the eagle ray at Naples and 
Trieste, but has not appeared in Britain. According to the descriptions 
of Taschenberg (1878, p. 574) and Perugia & Parona (1890, p. 18, 
PL 1, figs. 4, 5 ; PI. 2, figs. 6, 7) it is 5 mm. long and 2 mm. broad, 
elongate, broadening posteriorly and whitish in colour. The opis- 
thaptor is 1-5 mm. diameter, has 8 radial septa, two in the longi- 
tudinal axis of the body and the remainder equally spaced three on 
each side. The hooks are borne on the most posterior lateral septa, 
are 0-46 mm. long, have very unequal roots and an outwardly directed 
point bent at right angles to the shaft. The prohaptor is 0-53 mm. 
diameter and forms a fleshy fringe-like lip bearing numerous papillae. 
The pharynx is large, 0-29 mm. long and 0-24 mm. broad, and the 
reproductive organs are imperfectly known, certain details illustrated 
by Perugia & Parona being unacceptable. The egg has a long and 
spirally- wound filament at one pole. 

Genus HETER0C0TYLE T. Scott, 1904. 

{Monocotyle of authors ; Trionchus MacCallum, 1916 ; Monocotyloides 

Johnston, 1934.) 

Ventral surface of the opisthaptor having a central depression 
bounded by a ridge from which 8 septa radiate to form peripheral 
loculi, and bearing 1 pair of hooks and 14 hooklets. Prohaptor 
a weak oral sucker. Eyes present or absent. Testis undivided, cirrus 
slender and cuticular, vagina probably always present. 

Heterocotyle pastinacae T. Scott, 1904. (Fig. 4 A.) 

Host : sting ray. 

Location : gills. 

Several specimens on which this species are based were found in 
Dornoch Firth and described briefly by T. Scott (1904, p. 279, PL 17, 
fig. 14 — wrongly given as 15 in the descriptions of the plates) and again 
mentioned by this writer in 1912 (PL 27, fig. 9). Size : 1-44 mm. long 
and about one-third as broad. Shape : ovate to elongate, tapering 
anteriorly, but truncated at the extremity and narrowed just in front 
of the opisthaptor, much flattened. Prohaptor smaller than the 
pharynx. Opisthaptor broader than long in the ratio 13/11 and 
apparently broader than the body in the ratio 4/3, its margin slightly 
crenate, the ventral surface divided by radial septa into eight loculi 
which meet in a small and central diamond-shaped depression repre- 
senting the point of attachment of the whole haptor to the body. 



MONOCOTYLIDiE 



43 



The two posterior loculi, slightly larger than the four anterior, but 
smaller than the two lateral, which are about twice as large as the ones 
in front of them, and like the posterior loculi, are divided into proximal 
and distal portions by a "circular line " as shown in the figure. Hooks 
relatively small and approximately spanner- shaped, inserted into the 
haptor in the septa separating the postero-lateral and the most posterior 
loculi, one on either side. Other characters not determined, but pharynx 
shown very large and oval in outline, lateral bands of vitelline follicles 
extending from its lateral margins to the opisthaptor. 




Fig. 4. — A, Heterocotyle pastinacce. B, Thaumatocotyle concinna. C, T. 
dasybatis ; D and E, an egg and a hook of the same. F. Calicotyle kroyeri ; 
G an egg of the same ; H, a hook, and I, the opisthaptor. (A, B, after 
Scott, 1904 ; C-E, after Price, 1938 ; F, after Lebour, 1908a ; G, H, I, 
original.) 



Two other species occur in America and a third in Australia. 
Price (19386, p. 113) re-examined MacCallum's specimens of H. 
minima, which occurs on the gills of the sting ray and piked dogfish 
at Woods Hole, concluding that it is closely related to and possibly 
identical with H. pastinacw. Brinkmann (1940, p. 76), apparently 
unaware of Price's work, compared the original descriptions and 
reached the same conclusion. In suggesting that Heterocotyle is a 
synonym of Monocotyle, Brinkmann (loc. cit., p. 80) is at variance with 
Price, who, perhaps because the latter genus has been imperfectly 
defined, chose to regard the two genera as distinct. It is doubtful 
if the slightly different nature of the prohaptor is sufficient to warrant 
the recognition of two genera, but further study of the gill-trematodes of 



44 THE TREMATODA OF BRITISH FISHES 

sting rays is necessary before the difficulties can be removed and the 
issue decided. 

Sub-family Calicotylinje Monticelli, 1903. 
Genus CALICOTYLE Diesing, 1850. 

Nybelin (1941, p. 16) proposed the division of this genus into three 
sub-genera, Calicotyle, Calicotyloides and Gymnocalicotyle, the characters 
of which I have previously given (Dawes, 1946, p. 127). This procedure 
is unnecessary and might be misleading, because the six species which 
have been assigned to the genus have not been established beyond 
question. Two species occur in Britain, namely, C. kroyeri and 
C. affinis, C. stossichi occurs in the Mediterranean, two others, C. 
australis Johnston, 1934, and C. inermis Woolcock, 1936, are Australian, 
and the sixth species, C. mitsuhurii Goto, 1894, occurs in Japan. 

Calicotyle kroyeri Diesing, 1850. (Fig. 4 F-I.) 

Hosts : starry ray, skate, thornback ray, shagreen ray, sandy ray, 
spotted ray, long-nosed skate, cuckoo ray, painted ray (in West 
Sweden, the first four of these hosts) . 

Location : cloaca, rarely the rectum, very rarely the gills. 

T. Scott (1902) found this species on the starry ray caught about 
sixty miles south-east of the Shetlands, as well as on specimens of the 
same species of host caught off Aberdeen and in the Clyde, and men- 
tioned his son's finding it on the same host caught in Beaumaris Bay, 
A. Scott (1904) recording its occurrence also in the thornback ray in 
the Irish Sea. Lebour (1908a) found specimens in the cloaca of the 
starry ray, invariably in females, not in males as generally recorded. 
She also found specimens in the uterus (sic) and on the gills of this 
host. Nicoll (1914) found the species on the sandy ray, spotted ray 
and thornback ray at Plymouth, Little (1929a) on the sandy ray at 
Gal way, Baylis and Idris Jones (1933) on the spotted ray at Plymouth, 
Baylis (1939) also recording its occurrence on " skate " at Durham. 
Rees and Llewellyn (1941) noted several hosts, the spotted ray at 
Newquay and the long-nosed skate, cuckoo ray, shagreen ray and 
painted ray on the Irish Atlantic Slope. I have found the trematode 
on the thornback ray at Plymouth, and several times in skate from 
unknown localities which were dissected in the laboratory. The 
species was discovered by Kroyer on the starry ray caught in the 
Kattegat, although Beneden and Hesse (1864) wrongly named the skate 
as the original host, and Beneden (1871) found it on this host off the 
coast of Belgium. It has also been recorded at Naples and Trieste, 
and it has been described by several zoologists, including Wierzejsky 
(1877, p. 550, PL 31) ; Monticelli (1891, p. 108, PI. 6, figs. 33-5) ; 
T. Scott (1902, pp. 299-300, PL 13, fig. 30) ; Lebour (1908a, pp. 39-40, 
PL 5, fig. 1). Size : up to 5 mm. long and nearly as broad. Shape 



MONOCOTYLID^E 45 

variable, the outline sometimes almost circular, but tapering anteriorly 
and having a median indentation at the extremity, the oral sucker 
protruding a little, sometimes triangular and pointed in front, invari- 
ably much flattened. Colour white or pale yellow. Prohaptor an oral 
sucker up to about 0-7 mm. diameter. Opisthaptor a circular disk 
up to about 2 mm. diameter (1-0 mm. in specimens 2-8 mm. long and 
2-7-3-1 mm. broad) and approximately one-third to two-fifths as long 
as the body proper, typically not projecting beyond the body, but 
sometimes overlapping it by more than half its diameter, presumably 
by extension of the short attachment. Ventral opening of the opis- 
thaptor much smaller than the diameter (0-7 mm. broad and 0-6 mm. 
long in a disk 1 mm. diameter), its margin forming a rather delicate 
and inturned fringe, ventral surface having seven radial septa extending 
from a central circular space towards the periphery. Hooks about 
0-3 mm. long from base to the curve of the point and 0-1 mm. in 
greatest breath on a disk 1 mm. diameter, largely imbedded in the 
tissue of the two most posterior septa, directed diagonally forward and 
inward towards the anterior end of the posterior loculus, the points 
turning sharply outwards to underlie the antero-lateral margin of the 
same (not of the shape or having the orientation shown in Diesing's 
figure (1858a, PL 1, fig. 18), or Lebour's (1908a, PL 5, fig. 1). Out: 
pharynx almost spherical and up to 0-4 mm. diameter. (Esophagus 
very short. Caeca fairly long and thick- walled, shaped like an inverted 
question-mark, but sometimes more divergent anteriorly and puckered 
considerably. Excretory system : main canals lateral to the caeca. 
Reproductive systems : genital pore median just behind the bifurcation 
of the gut. Cirrus and ejaculatory bulb lined with cuticle, the former 
curved and about 0-3 mm. long and equipped with a short cuticular 
piece curved into the shape of a figure 9, sometimes sharply pointed, 
but otherwise terminating in a triangular spade-like expansion. 
Testes numerous, filling the region between the curved hinder ends 
of the cseca. Ovary elongate and folded, situated on the right in 
front of the testes. Oviduct extending towards a median receptaculum 
seminis situated near the cirrus. Vaginae arranged nearly in the trans- 
verse plane, their openings ventro-lateral, their terminal parts glan- 
dular. Vitellaria well developed, the follicles filling the parenchyma 
of the lateral regions from the level of the pharynx to the opisthaptor. 
Egg (Fig. 4 G) large and triangular in optical section, about 0-10 mm. 
long and 0-11 mm. broad, having a short filament 0-035 mm. long at 
the posterior pole. 

Calicotyle affinis T. Scott, 1912. Sp. inq. 

Host : rabbit-fish. 

Location : cloaca, rarely on the skin or gills, but sometimes in the 
rectum. 

This species was found and very inadequately described by T. Scott 
(1912, p. 68, PL 7, fig. 1), but described in detail by Brinkmann (1940, 
p. 62, PL 12, figs. 46-8 ; PL 13, figs. 50-2 ; PL 14, fig. 56 ; PL 15, 



46 THE TREMATODA OF BRITISH FISHES 

figs. 57, 58d), who found specimens at Bergen. Scott's specimens 
were taken from a fish caught in the North Sea and were said to be 
larger than C. kroyeri, attaining a length of 9 mm., and of somewhat 
different shape. The prohaptor was overlooked, and the opisthaptor 
had a central space of transversely elongate, not circular shape. Other 
information given is scanty, but Brinkmann supplied sufficient to 
form a good diagnosis. Size: up to 7 mm. long, measured to the point 
of attachment of the opisthaptor, and 3 mm. broad, mature when 
2-3-2-9 mm. long. Shape : oval outline and broadest near the middle 
of the body, acutely pointed anteriorly and broadly pointed posteriorly, 
slightly flattened, but convex dorsally and concave ventrally. Colour 
yellowish -white to orange-red. Cuticle smooth. Prohaptor an oral 
sucker. Opisthaptor similar to that of C. kroyeri, but the central 
loculus elongate in the transverse plane and the hooks 0-4 mm. long, 
excluding the curved points. Gut : pharynx elliptical, oesophagus 
absent, a pair of clusters of unicellular glands occupying the space 
between the pharynx and the anterior ends of the caeca, which are 
fairly long and extend back to a level midway between the testes and 
the opisthaptor, their lining being formed of columnar cells. Excretory 
system : vesicles lacking, lateral canals situated one on either side 
of the body and opening dorsally at the level of the pharynx. Repro- 
ductive systems : genital pore median and near the bifurcation of the 
gut. Cirrus equipped with a long and cuticular accessory arranged in 
three coils. Vas deferens situated on the left side of the body and 
extending in front of the cirrus, here dilating to form a seminal vesicle. 
Testes numerous and situated between the caeca in the middle of the 
body. Ovary very elongate, situated just in front of the testes and 
formed into a transverse U-shaped loop embracing the right caecum, 
its blind end globular. Oviduct very short. Ootype divisible into a 
fertilization chamber flanked by shell-glands which debouch in two 
groups and a more anterior pyriform chamber continuous with a very 
short uterus. Receptaculum seminis globular, situated in the median 
plane just in front of the ovary. Vaginae extending diagonally outward 
from a point near the receptaculum seminis, into which it opens, to 
the pores, which are situated anterior to the genital pore and beneath 
the anterior parts of the caeca on the ventral surface. Eggs of the 
same shape as in C. inermis Woolcock, 1936 (but not described by the 
writer thus named). Vitellaria as in C. kroyeri. 

Brinkmann based his opinion of the specific identity of C. affinis 
on the shape of the body and of the opisthaptor, the zoological status 
of the host and the openings of the vaginae into the receptaculum 
seminis. Neither the first nor the second criteria are of great impor- 
tance, and the last criterion rests on a negative finding after the 
reconstruction of C. kroyeri from serial sections, this species being 
said to have a receptaculum seminis with antero-lateral horns into 
which the vaginae open. The species of Scott is thus not established 
beyond reasonable doubt, but stands as a species inquirenda. 

Calicotyle stossichi Braun, 1899 (pp. 80-2, 1 fig.) was found in the 
rectum of a smooth hound taken from the Mediterranean to the Berlin 



MONOCOTYLIDiE 47 

Aquarium. It has characters in which it resembles C. affinis. The 
lateral margins of the body are almost parallel and the central space 
between the loculi of the opisthaptor is transversely elongate, but like 
C. affinis and other species recognized at the present time, it may 
ultimately become a synonym of C. kroyeri. 

Sub-family Merizocotylinje Johnston & Tiegs, 1922. 

Two European genera can be distinguished by the nature of the 
opisthaptor, which has 4 loculi bordering a central space in Thau- 
matocotyle, but 7 in Merizocotyle. 



Genus MERIZOCOTYLE Cerfontaine, 1894. 
(Meristocotyle Rossbach, 1906.) 

Head-organs numbering 3 pairs. Opisthaptor discoidal, the ventral 
surface having a central circular or oval depression surrounded by 7 
loculi, in addition to which there are 18 marginal loculi, the posterior 
being the largest. Hooks and hooklets present. Eyes absent. Testis 
single. 

Merizocotyle diaphana Cerfontaine, 1894. 

Merizocotyle minor Cerfontaine, 1898. 

Hosts : skate, long-nosed skate. 
Location : gills. 

This species occurs at Roscoff and off the coast of Belgium, but 
has not been recorded in Britain, although almost certain to occur 
here. It was very completely described by Cerfontaine (1895, pp. 
936-46, figs. 1-6 ; 18986, pp. 329-57, figs. 1, 3, 5, 8-11, PI. 13 ; figs. 
1-9, PI. 14). Size : 6 mm. long and about 1-5 mm. broad. Other 
characters (see Dawes, 1946, p. 129). The form " M. minor " was 
discovered in the second host named above and was described by 
Cerfontaine (18986, pp. 357-61, figs. 2, 4, 6, 7, PI. 13) as a smaller 
trematode 3 mm. long and 1 mm. in greatest breadth with a relatively 
large opisthaptor half as long as the body proper, not one-third as 
long, a relatively small and centrally- situated testis and a slightly 
different uterus, differences which do not warrant the specific distinc- 
tion. The only other species of the genus, M . pugetensis Kay, 1942, 
occurs in America. 

Genus THAUMATOCOTYLE T. Scott, 1904. 

(Pseudomerizocotyle Kay, 1942.) 

Head-organs numbering 3 pairs. Opisthaptor discoidal, the ventral 
surface having a central depression surrounded by 4 loculi, in addition 
to which there are 13 marginal loculi, the posterior being the largest. 
Hooks and hooklets present. Eyes present. Testis single. 



48 THE TREMATODA OF BRITISH FISHES 



Thaumatocotyle concinna T. Scott, 1904. (Fig. 4 B.) 

Host : sting ray. 
Location : nasal fossa?. 

This species was found on a fish caught in Dornoch Firth and 
described very inadequately by T. Scott (1904, pp. 278-9, PL 17, 
fig. 15 — wrongly given as 14 in the descriptions of the plates) and 
again mentioned and figured by this writer in 1912 (PL 12, fig. 1). 
Size about 3 mm. long and one -fifth as broad. Shape elongate, the 
margins of the body nearly parallel, the anterior extremity approxi- 
mately triangular, but notched in the median plane. Head-organs : 
3 pairs of small disks arranged along the abruptly tapering margins 
of the anterior region, probably receiving the openings of cephalic 
glands. Opisthaptor discoidal, its length and breadth apparently 
about 0-29 and 0-27 body-length ; outline nearly circular but slightly 
indented opposite the peripheral radial septa, the ventral surface 
divided up into loculi which show bilateral, but not radial symmetry. 
Peripheral loculi numbering 13, the most posterior larger than 
the others and shaped like an equilateral triangle with a blunt apex 
reaching more than half-way to the centre of the haptor. Other 
marginal loculi of nearly equal size and " subquadrate " shape, cut 
off from the central part of the haptor by a tangential septum ; central 
loculi not described, but shown arranged as in Fig. 4 B. Hooks of 
slender rod-like shape, long and straight except at their inwardly 
curved tips, situated slightly lateral to the radial septa of the large 
posterior loculus. Internal organs not described, but pharynx 
apparently very large, its length and breadth about 0-2 and 0-12 
body-length. Testis slightly smaller than the pharynx and situated in 
the posterior half of the body. Vitellaria mainly lateral and extending 
from the opisthaptor to the pharynx, the follicles encroaching on the 
median plane behind and in front of the testis and behind the pharynx. 
According to Price (19386) and Brinkmann (1940), the American 
trematode T. dasybatis (MacCallum, 1916) Price, 1938, which is 
parasitic on the olfactory organs and gills of the same host and other 
hosts at Woods Hole, may be identical with T. concinna. According 
to the re-description by Price (19386, pp. 117-19, figs. 11-14) this form 
(Fig. 4 C) is 1-5-2-6 mm. long, has two pairs of eye-spots, a long and 
cuticular cirrus, paired vaginae with ventral apertures underlying the 
caeca near the middle of the body, and a triangular egg about 
0-100 mm. broad with a long and slender filament projecting from 
the apex. 

Family MICROBOTHRIID^ Price, 1936. 
(Dermophagidae MacCallum, 1926 ; Labontidse MacCallum, 1927.) 

Prohaptor sucker-like or absent. Opisthaptor small and discoidal, 
lacking septa and hooks. Eyes absent. Intestine bifurcate, the caeca 
with or without diverticula. Male and female pores side by side, 
sometimes debouching into an atrium. Cirrus cuticular or muscular, 



MICROBOTHRIIDiE 49 

and provided with a cuticular ejaculatory duct. Vagina single, rarely 
double. One testis or two testes in the Microbothriinse, numerous 
testes in the Pseudocotylinse. 

Sub-family Microbothriin^: Price, 1938. 

(Dermophaginse MacCallum, 1926 ; Labontinae MacCallum, 1927 ; Para- 
cotylinae Southwell & Kirshner, 1937.) 

Three European genera can be distinguished by the nature of the 
gut and the vagina. In Leptocotyle the caeca are devoid of lateral 
diverticula, which are present in the other genera, Leptobothrium 
having a double vagina and Microbothrium a single vagina. Ano- 
plodiscus has been placed in this group, but is probably better placed 
in the Calceostomatida? {q.v.). 



Genus MICROBOTHRIUM Olsson, 1869. 

(Pseudocotyle Beneden & Hesse, 1863 ; Dermophagus MacCallum, 1926, 
nee Dejean ; Philura MacCallum, 1926 ; Labontes MacCallum, 1927.) 

Prohaptor a pair of sucker-like organs in the wall of the pre- 
pharynx. Opisthaptor simple and discoidal or elliptical, and having a 
prominent and ventral groove lined with cuticle. Mouth slit-like and 
not quite terminal. Caeca long and having diverticula with dendritic 
endings. Genital pore median ; cirrus long and muscular ; ejaculatory 
duct lined with cuticle. Testis situated near the middle of the body. 
Vagina a single tube. 

Microbothrium apiculatum Olsson, 1869. (Fig. 5 D, E.) 

Pseudocotyle apiculatum (Olsson) Braun, 1890 (p. 530) ; Philura ovata 
MacCallum, 1926 ; Dermophagus sguali MacCallum, 1926. 

Host : piked dogfish. 
Location : skin. 

This species occurs in the Skagerrak, the Arctic, Canada and U.S.A., 
and was found in an unspecified locality (probably off the west coast 
of Ireland) by Gallien (1937), so that it is of likely occurrence in British 
waters. American specimens have been described by Price (19386, 
p. 184, figs. 1, 2), and I have already given a diagnosis (Dawes, 1946, 
p. 131). 

Microbothrium centrophori Brinkmann, 1940. 

Host : Centrophorus squamosus. 
Location : caudal fin. 

This species was described in detail by Brinkmann (1940, p. 19, 
Pis. 5-7, figs. 18-22 ; PI. 8, figs. 23, 24, 27-28), and I have noted (Dawes, 
1946, p. 132) the chief differences from M . apiculatum, with which it 
may prove to be identical. 

4 



50 THE TREMATODA OF BRITISH FISHES 



Genus LEPTOBOTHRIUM Gallien, 1937. 

(Pseudobothrium Gallien, 1937, nee Guiart, 1935.) 

Prohaptor a pseudosucker encircling the not quite terminal mouth. 
Opisthaptor small and unarmed. Caeca discrete and having a few 
(8 or 9) broad and digitate lateral diverticula. Eyes absent. 
Testis situated between the caeca. Cirrus simple. Ovary small and 
anterior to the testis . Vagina dividing into two branches, both of which 
open into the genital atrium. Other characters as in Microbothrium. 
The genus was re-named because Pseudobothrium Guiart, a genus of 
cestodes, was preoccupied. 

Leptobothrium pristiuri (Gallien, 1937) Gallien, 1937. (Fig. 5 A, B.) 
Pseudobothrium pristiuri Gallien, 1937. 

Host : black-mouthed dogfish. 
Location : skin of the dorsal surface. 

This species was found in the Atlantic west of Ireland and was 
described by Gallien (1937, p. 10, fig. 1, PI. 1, fig. 3). It has not been 
found in British waters, but probably occurs therein. According to 
the original description it is up to 1-6 mm. long and 1 mm. broad, but 
the flat and broadly lanceolate shape and these dimensions are modified 
by muscular movements. The prohaptor takes the form of two 
circular lips situated in the antero -ventral region, and was illustrated 
as comparatively large buccal suckers and labelled " ventouse " on 
one side, but they are not true suckers, but pseudosuckers. For other 
characters see Fig. 5 A, B, and Dawes (1946, p. 132). 



Genus LEPTOCOTYLE Monticelli, 1905. 

(Paracotyle Johnstone, 1911.) 

Prohaptor a feeble oral sucker. Caeca not provided with lateral 
diverticula. Other characters as in Microbothrium. 

Gallien (1937, p. 13) and Price (19386, p. 186) discussed the taxo- 
nomy of the genus and corrected several errors which have arisen. 
The name was first used by Monticelli for a sub-genus of Pseudocotyle 
including his P. minor, Tagliani first using it in the generic sense. 
Tagliani showed that the genus Paracotyle is identical with Leptocotyle, 
but he omitted Monticelli's species from the genus. E. I. Jones (1933) 
re-described " Paracotyle caniculce " and, overlooking Leptocotyle minor, 
regarded it as a species of Microbothrium, A. Scott (1906) having 
considered it a species of Epibdella. Gallien regarded both " Para- 
cotyle caniculoz " and " Microbothrium caniculm " as synonyms of 
Leptocotyle minor, and Price concurred. 



MICROBOTHRIID.*: 



51 




P iZh ^ e f tobothr ^ m P r \^rt ; B, the genital apparatus of the same. 
Snfp^ % J? min0r '< r D ' ^«7*o*^» a^fatom ; E, an egg of the 
F^fw V e ?§o° Le P t0 ™ tyle : mn0r - < A ' B ' after Galli en, 1937 ; D, 
fq'33 ^ C6 ' ' Johnstone, 1911 ; F, after E. I. Jones 



52 THE TREMATODA OF BRITISH FISHES 



Leptocotyle minor (Monticelli, 1888) Monticelli, 1905. (Fig. 5 C, E.) 

Pseudocotyle minor Monticelli, 1888 (p. 16) ; 1890 (p. 191, fig. 4) ; Leptocotyle 
minor Monticelli, 1905 (p. 70); Epibdella sp. A. Scott, 1906 (p. 192, PI. 
9, fig. 1) ; Paracotyle caniculce Johnstone, 1911 (p. 16, figs. 1-4 ; Pis. 1, 2, 
figs. 1—7) ; Microbothrium caniculce (Johnstone) Idris Jones, 1933 (p. 329, 
figs. 1-3), and of Baylis and Idris Jones, 1933. 

Host : rough hound. 

Location : skin of the head just behind the eye, sometimes the 
dorsal fins. 

A. Scott (1906) found several specimens about 2 mm. long on fish 
caught south of the Calf of Man, and gave a recognizable drawing but 
practically no other information about them. Johnstone described 
these specimens, and mentioned that in two years numerous other 
specimens were found on dogfishes kept in the Aquarium tanks at 
Port Erin, but no mature specimen was seen. Little (1929a) found 
specimens on the gills and in the buccal cavity of the same host at 
Galway, and the mature specimens found by Baylis & Idris Jones and 
described by E. I. Jones occurred at Plymouth. The species has also 
been found in the Mediterranean. There are several points of variance 
in the descriptions of Johnstone (1911) and E. I. Jones (1933), notably 
in regard to the structure of the terminal parts of the male reproductive 
system, and to judge by specimens from Liverpool kindly lent to me 
by Professor Daniel, Johnstone's account seems to be the more 
accurate, but some of the observations of E. I. Jones are here shown in 
parentheses. Size : 2 mm. long and 1-2 mm. broad (up to 3-2 mm. 
long and 1-5 mm. broad). Shape : elliptical or oval in outline, pointed 
anteriorly and flattened. Prohaptor : an oral sucker, not quite 
terminal and slightly transversely oval, 0-14 mm. broad. Opisthaptor 
a small and almost terminal discoidal sucker only slightly raised from 
the general surface of the body in the posterior region, lacking hooks, 
booklets and septa and about 0-3 mm. diameter. Gut : prepharynx 
short. Pharynx 0-23 mm. diameter. (Esophagus absent (very short), 
caeca long and without diverticula, extending along a sinuous course 
to a level just in front of the opisthaptor, lined with epithelial cells. 
Excretory system : vesicles ovoid and situated one on either side of 
the pharynx, pores lateral at the level of the oesophagus. Reproductive 
systems : genital pore median and situated just behind the bifurcation 
of the gut. Cirrus pouch thick- walled and muscular, containing the 
cirrus, ejaculatory duct and bulb (also a pars prostatica). Testis 
transversely ovoid, median and just behind the middle of the body. 
Ovary globular or transversely elongate, situated just in front of the 
testis. Vitellaria extensive dorsal and lateral to the caeca, merging in 
the median plane behind the testis, the follicles coarse and pyriform. 
Vaginal pore a longitudinal slit on the left of the genital pore ; vagina 
club-shaped and muscular, but having a cuticular lining, its connec- 
tions with other organs undetermined. Genito- intestinal canal 
apparently absent. According to E. I. Jones the only egg observed 
was large (0-0144 mm. long — an obvious misprint for 0-144 mm.) and 



MICROBOTHRIIDxE 53 

oval, with pointed extremities and a long filament at one pole. I found 
two specimens having one egg each and they were of very variable 
lengths, dimensions of the capsules 0-114-0-145 x 0-042-0-045 mm., 
filaments 0-27-0-32 mm. long. 



Sub-family Pseud ocotylinje Monticelli, 1903. 
Genus PSEUDOCOTYLE Beneden & Hesse, 1865. 

Prohaptor absent. Opisthaptor small and sucker-like, devoid of 
accessories. Eyes absent. Genital pores median and nearly together ; 
testes numerous. Vagina double and separate from the genital atrium. 



Pseudocotyle squatinse Beneden & Hesse, 1865. (Fig. 6 G.) 

Host : monk-fish. 
Location : skin. 

This species has been found in monk-fish caught in the North Sea, 
off the coast of Belgium, at Roscoff and in the Mediterranean. The 
only British record is that of Nicoll (1914, p. 497), who found specimens 
at Plymouth, but did not describe them. The original description 
(4th Appendix, 1865, pp. 11-18, PI. 2, figs. 1-7) was more complete 
than most descriptions by the same writers, and concerned specimens 
5 mm. long and 3 mm. broad of oval and flattened form, but notched 
posteriorly and slightly indented anteriorly. According to one of the 
figures there were about 53 testes, and the eggs were said to be large 
and oblong, truncated at the ends and devoid of filaments. I have 
two specimens obtained from the same host taken from an unknown 
locality and they are of closely similar size and very uniform. Size : 
4-6 mm. long and 2-6 mm. broad near the midbody (2-0 mm. in the 
narrower specimen). Shape : outline oviform, the posterior end 
slightly truncated, the anterior end having a median notch, dorso- 
ventrally flattened. Prohaptor absent. Opisthaptor a small, sucker- 
like disk 0-32 mm. diameter situated on a short peduncle at the posterior 
extremity, sometimes sunk in a slight indentation on the truncate 
posterior margin. Hooks and hooklets absent. Gut : mouth very 
narrow, sunk in the anterior indentation, pharynx ovoid (or heart- 
shaped), 0-32 mm. long and 0-28 mm. broad, situated at the base 
of a capacious mouth-tube (prepharynx) . (Esophagus very short 
(practically absent). Caeca long, discrete, and having long lateral 
diverticula which branch twice or thrice, the most anterior pair (which 
Beneden & Hesse were inclined to regard as the " brain ") directed 
forward at the sides of the pharynx and branching only once or twice. 
Excretory system : vesicles large, having dense parenchymatous and 
much-folded walls situated opposite the origins of the anteriorly- 
directed caeca and slightly behind the pharynx. Reproductive systems : 
genital pore situated near the median plane just behind the bifurcation 



54 



THE TREMATODA OF BRITISH FISHES 



of the gut. Cirrus and ejaculatory duct cuticular, contained within 
a slightly muscular cirrus-pouch. Testes numerous (about 64), 
occupying an oval zone 1-8 mm. long and 0-95 mm. broad, a little 
behind the midbody. Ovary globular, hollow, about 0-38 mm. 
diameter, situated immediately in front of the testes and slightly 
lateral. Receptaculum seminis almost as large as the ovary and 
postero-lateral to it on the opposite side of the median plane. Vitel- 
laria very well developed, occupying broad lateral zones 0-75 mm. wide, 
bounded on the median side by the caeca and enveloping the diverticula, 




0-5 



Fig. 6. — A-F, Udonella caligorum : A, the egg ; B, C, hatching individuals ; 
D, E, young forms ; F, the adult. G, Pseudocotyle squatince. (A-F, 
after Price, 19386 ; G, original.) 



extending from the level of the pharynx almost to the opisthaptor, 
leaving only triangular anterior and posterior regions and an oval 
central region devoid of follicles. Vitelloducts profusely branched, 
the main lateral ducts situated slightly median to the caeca, the trans- 
verse ducts immediately in front of the ovary and the receptaculum 
seminis. Vaginal pores slightly lateral, immediately in front of the 
lateral ends of the transverse vitelloducts, the vaginae extending 
inwards parallel with the latter. Eggs few (only one seen) and of 
irregular ovoid shape, more convex on one side than on the other, 
about 0-156 mm. long and 0-08 mm. broad. 



UDONELLID^E 55 

Pseudoeotyle lepidorhini Guiart, 1938. 

Host : " Lepidorhinus squamosus" 
Location : skin. 

I have been unable to consult the original description of this species, 
which was found off Finistere and has fewer testes and no oesophagus. 

Family UDONELLID.E Taschenberg, 1879. 

Shape cylindrical or spindle -like. Prohaptor, when present, two 
small sucker-like organs augmented by cephalic glands. Opisthaptor 
sucker-like and devoid of septa and hooks. Pharynx large and pro- 
trusible. Intestine sac-like, but sometimes fenestrated near the gonads. 
Genital pore median or slightly lateral. Cirrus absent. Testis median. 
Ovary median and situated in front of the testis. Eggs oval or elongate, 
having one polar filament. Udonella having a pharynx devoid of 
hooks or stylets, other genera (inquirenda) a pharynx provided with 
two hooks (Echinella) or numerous stylets (Pteronella) . 

Genus UDONELLA Johnston, 1835. 

(Amphibothrium Frey & Leuckart, 1847 ; Nitzschia Baer, 1826, in part ; 
Lintonia Monticelli, 1904 ; Calinella Monticelli, 1910.) 

Prohaptor a pair of sucker-like organs. Opisthaptor terminal, 
discoidal and unarmed. Gut having an unarmed bulbous pharynx 
and a simple sac-like intestine, which may be fenestrated in the vicinity 
of the gonads. 

Udonella caligorum Johnston, 1835. (Fig. 6 A-F.) 

Udonella lupi Beneden & Hesse, 1863 (1864, p. 92, PI. 8, figs. 11-14) (on the 
wolf-fish) ; U. merlucii B. & H., 1863 (p. 93) (on the hake) ; U. rnolvce 
(B. & H., 1863) (as Pteronella ; 1864, pp. 94-5, PI. 8, figs. 20-23) (on 
the ling) ; U. pollachii B. & H., 1863 (1864, pp. 90-1, PI. 8, figs. 1-8) 
(on the pollack) ; U. scicence B. & H., 1863 (1864, p. 93, PL 8, figs. 15-16) (on 
the shadow-fish) ; U. triglce B. & H., 1863 (1864, p. 92, PI. 8, figs. 9, 10) 
(on Trigla sp.) ; Nitzschia papillosa Linton, 1898 (p. 508, PI. 40, figs. 1-6) ; 
Lintonia papillosa (Linton) Monticelli, 1904 (p. 117) ; Udonella socialis 
Linton, 1910 ; U. sp. Monticelli, 1889 (on Caligus on the flounder) ; Cali- 
nella myliobati Guberlet, 1936 ; Phylline caligi Kroyer, in Beneden, 1858 
(p. 13 ; see 1861, p. 13) ; Amphibothrium krceyeri Frey & Leuckart, 1847 
(pp. 147-8, PL 2, fig. 2). 

Hosts : Caligus spp. on the halibut, cod, pollack, wolf-fish, ling, 
hake, flounder. Free -swimming Caligus rapax and C. curtus. Anchor - 
ella uncinata on cod. For some other hosts see Dawes (1946, p. 120). 

Location : mainly on the egg-sacs of the female copepod. 

This species was found off the west coast of Scotland by T. Scott 
(1901), and occurs off the coast of France (near Brest) and Belgium, in 
the North Sea, in Canada and various localities in U.S.A. (Woods 
Hole, Tortugas, Monterey Bay). The forms described by Beneden & 
Hesse seem to have got their names from the hosts of the Caligus on 



56 THE TREMATODA OF BRITISH FISHES 

which they were found. Price (19386, p. 194, figs. 12-17) compared 
British specimens collected at Plymouth by Baylis & Idris Jones 
(1933) with American specimens and found that they showed no 
essential differences. But size seems to be somewhat variable ; the 
specimens of Johnston (1835, p. 497, fig. 45 a-c) were about four 
" lines " long, those of Beneden (1858, p. 13) 5-6 mm. long, other 
specimens described being much smaller. Size : 1-1-1-4 mm. long 
and one-quarter or one-fifth as broad (0-25 mm.) at the level of the 
ovary. Shape elongate, almost cylindrical. Cuticle puckered near 
the anterior extremity to simulate annulations. Prohaptor a pair of 
retractile sucker-like organs 0-04-0-06 mm. wide, apparently bearing 
the openings of cephalic glands. Opisthaptor discoidal, 0-19-0-21 mm. 
diameter, devoid of septa, hooks or hooklets. Caudal glands arranged 
somewhat laterally as a pair of groups immediately in front of the 
opisthaptor. Gut : mouth median and not quite terminal ; prepharynx 
present; pharynx ovoid, 0-15 mm. long and 0-085-0-095 mm. wide, 
somewhat protrusible ; intestine simple and sac-like, extending back 
almost to the opisthaptor. Eyes absent. Sensory, papillce : one pair 
anteriorly. Excretory system : vesicles lateral at or slightly behind 
the level of the end of the pharynx. Reproductive systems : genital 
pore beneath the left group of cephalic glands. Cirrus apparently 
absent, ejaculatory duct slender, seminal vesicle at its base and near 
the ootype on the right. Testis median, globular, 0-075-0-095 mm. 
diameter, near the midbody. Ovary 0-133 mm. diameter, median 
and immediately in front of the testis. Vitellaria comprising a few 
large follicles in the lateral regions and extending from the pharynx 
to within a short distance of the opisthaptor. Vagina absent. Ootype 
large and vesicular, having unicellular glands clustered round its base. 
Metraterm very short. Eggs pyriform, measuring 0-133 x 0-042 mm., 
each having a long and slender filament tipped by an adhesive disk. 
Note : the eggs measured were mounted in balsam and wrinkled ; 
possibly living eggs are somewhat larger. Life-history : when newly 
hatched the worm is almost mature, but of small size. The smallest 
individual observed by Price was 0-21 mm. long and 0-057 mm. broad. 
During growth the relative sizes of the ovary and testis vary, the former 
being invariably smaller than the latter in juveniles, but not adults. 
The life-history is as outlined by Beneden (1858, pp. 16-17). 

Genus inq. ECHINELLA Beneden & Hesse, 1863, nee Swains, 1840. 

This genus was erected for a species, E. hirundinis Beneden & 
Hesse, 1863, which was found on C aligns parasitic on the yellow 
gurnard near Brest. According to the original description (1864, 
p. 94, PI. 8, figs. 17-19) it is 2-3 mm. long, elongate and cylindrical 
with an annulated cuticle, a prohaptor represented by two tentacle-like 
organs, a large and sucker-like opisthaptor and a pharynx equipped 
with two cuticular hooks. The colour of this trematode, which is 
possibly identical with Udonella caligorum, was said to be pale rose, 
and the eggs were credited with the same colour and one filament. 



ACANTHOCOTYLID^ 57 

Genus inq. PTERONELLA Beneden & Hesse, 1863. 

This genus was erected for a species, P. ?nolvce Beneden & Hesse, 
1863, which was found on C aligns parasitic on the ling near Brest. 
According to the original description (1864, pp. 94-5, PL 8, figs. 20-3) 
it is 2-3 mm. long, spindle-like, annulated when young, having a 
ciliated wing-like membrane at the anterior extremity, a large sucker- 
like opisthaptor and a pharynx equipped with numerous cuticular 
stylets. The colour was said to be white, and the dark-green eggs are 
laid in clusters with the single filaments joined. This species is also 
probably identical with Udonella caligorum. 

Family ACANTHOCOTYLID^ Price, 1936. 

(Anisocotylidse Tagliani, 1912, in part.) 

Prohaptor : two retractile sucker-like organs surrounded by the 
pores of the cephalic glands. Opisthaptor generally minute and having 
two centrally situated and fourteen marginal hooklets, supplemented 
by a large pseudodisk equipped with radial septa or radial rows of 
spinelets or cuticular concretions, sometimes well developed and 
without a pseudodisk. Genital pores separate, the male pore almost 
median, the female pore marginal. Testes numerous, sometimes one 
testis present. European sub -families distinguished by the nature 
of the opisthaptor, the Enoplocotylinae having a large true haptor 
and no pseudodisk, the Acanthocotylinae a vestigial true haptor and a 
large pseudodisk. 

Sub-family Enoplocotylinje Tagliani, 1912. 
Genus EN0PL0C0TYLE Tagliani, 1912. 

Prohaptor comprising two weak suckers surrounded by the openings 
of the cephalic glands. Opisthaptor large and discoidal, equipped 
with a pair of centrally-situated hooks and 14 marginal hooklets, each 
of which occupies an oval loculus. 

This genus was erected for a species, E. minima Tagliani, 1912, 
which occurs on the skin of the murry in the Mediterranean and has 
not appeared in Britain. 

Sub-family Acanthocotylinje Monticelli, 1903. 
Genus ACANTH0C0TYLE Monticelli, 1888. 

Prohaptor a pair of sucker-like organs surrounded by the openings 
of the cephalic glands. Pseudodisk large and equipped with radial 
rows of irregular spinelets. Gut including caeca devoid of lateral 
diverticula. 

I have given (Dawes, 1946, p. 136) a provisional key for the separa- 
tion of five European species of this genus, and a statement about four 



58 THE TREMATODA OF BRITISH FISHES 

American species and about the only other genus of the Acantho- 
cotylinse, Lophocotyle Braun, which has a naked pseudodisk. The 
European species can be distinguished by the numbers of testes and 
differences in the opisthaptor, although their validity is by no means 
properly established. Acanthocotyle borealis has about 266 spines 
arranged in 32 rows, but in all other instances there are about 20 rows, 
A. elegans and A. oligoterus having about 150 spines, A. lobianchi and 
A. monticellii more than 200. The last-named species differs from 
others in having a smooth cuticle and a pseudodisk with a smooth 
margin, A. elegans also having a cuticle of the same kind, but a 
pseudodisk with a crenulate margin. 

Acanthocotyle monticellii T. Scott, 1902. 

Acanthocotyle branchialis Willem, 1906 ; A. concinna T. Scott, 1902. 

Hosts : thornback ray, spotted ray. 
Location : gill- chamber. 

T. Scott (1902, pp. 300-2, PL 13, figs. 31, 32, 32 A, 33) gave a very 
cursory description of the single specimen found on the thornback ray 
obtained at Aberdeen fish-market, not even specifying the size, which 
seems to have been about 6-6 mm. long and 1-3 mm. in greatest breadth. 
Monticelli examined the specimen and regarded it as a valid new species, 
later describing it (1905), pp. 74-5, figs. 4, 5. Willem (1906, p. 599, 
PL, figs. 1-10) collected ten specimens of what he regarded as a new 
species from the mucus in the gill- chamber of a spotted ray bought in 
the market at Gand and fished off the coast of Belgium. Brinkmann 
(1940, p. 50) gave good reasons for considering this form identical with 
A. monticellii and it is recorded here as a synonym, although Price 
(19386, p. 190) regarded both as valid species. Brinkmann counted 
the numbers of spines shown in the various rows in Scott's figure and 
found them to compare very closely with the figures provided by 
Willem, being significantly different in only one row, whereas the 
Belgian specimens themselves showed variability in this respect in 
several rows. Willem also seems to have settled the question about 
the lateral position of the uterine pore. Size : 5-6-5 mm. long and 
about one -fifth as broad. Prohaptor a pair of anterior suckers and 
associated cephalic glands, not head-organs as indicated in Scott's 
fig. 31. Opisthaptor : pseudodisk about one-fifth as broad again 
as the body, bearing 20 rows of spine-like concretions, mainly 
12-14 in a row and totalling about 224-50, the approximate numbers in 
individual rows starting anteriorly and proceeding back along one 
side 10-14, 11-14, 10-13, 12-14, 12-14, 11-14, 12-14, 12-13, 
9-11 and 7-8. In each row the most central spines are implanted per- 
pendicular to the surface and well spaced, but more crowded peri- 
pherally. True disk borne on a short peduncle attached to the 
slightly indented posterior margin of the pseudodisk, bearing 1 pair 
of centrally-situated hooklets and 14 hooklets in a marginal position, 
each situated on a pyramidal eminence. Reproductive systems : 



ACANTHOCOTYLID^E 59 

testes numbering about 28, situated between the caeca in the pos- 
terior two-thirds of the body proper ; ovary small and ovoid, situated 
just in front of the most anterior testes. Vitellaria made up of 
numerous coarse follicles lateral to the caeca and in that part of the 
body occupied by the gonads. Eggs fusiform, operculate and equipped 
with a filament about as long as the capsule and terminating in a disk. 

Acanthocotyle oligoterus Monticelli, 1899. (Fig. 7 A-E.) 

Hosts : thornback ray, " Raja punctata" 
Location : skin. 

This species occurs at Naples and was described by Monticelli 
(1899a, pp. 115-17, PI. 1, figs. 2, 9 ; PL 2, figs. 12, 14, 20, 24,25c, 27, 
29 ; PI. 3, fig. 48). I have four specimens obtained from an unknown 
British locality which have characters more in conformity with this 
than with other species, although only one of them shows any signs 
of a tuber culate integument. In this instance the tubercles are very 
few and may represent mere wrinkles in the cuticle, which are evident 
as such in other specimens. Size : body proper 3-8-5-0 mm. long 
and 1-0-1-5 mm. in greatest breadth posteriorly. Cephalic glands 
numerous, extending from the prohaptor to a level behind the pharynx. 
Prohaptor a pair of anterior suckers 0-12 mm. diameter in smaller 
specimens, 0-17 mm. broad, and 0-21 mm. deep in the largest, situated 
0-28-0-39 mm. apart. Opisthaptor : pseudodisk oval and attached 
terminally so that more than one-half of the surface area projects 
beyond the end of the body proper, measuring 1-3-1-5 x 1-2-1-25 mm. 
Spines arranged in twenty more or less radial rows and totalling 
140-6, the numbers in the individual rows, starting in front and pro- 
ceeding backwards, 7, 7-8, 7-8, 7-8, 8-9, 7-9, 7-8, 7-8, 5-6, 5-6. 
(Note. — The numbers in the last four rows imply counting from before 
backwards, and including in one row all the spines which fit it and 
excluding those counted even when they fit in more posterior rows, 
when these are dealt with.) True haptor transversely oval in outline, 
situated on a short peduncle in a notch on the posterior border of the 
pseudodisk, 0-055-0-062 mm. broad and 0-040-0-058 mm. long, 
and bearing 16 hooklets each about 0-007 mm. long, 14 of them 
near the periphery having their hooked points directed inwards, the 
central ones on right and left having their points directed forwards and 
inwards. Gut : mouth minute, situated on the ventral surface about 
0-38 mm. from the anterior extremity. Prepharynx very small or 
absent. Pharynx pyriform, and not more than 0-33 mm. long or 
0-29 mm. broad. (Esophagus absent. Caeca long and devoid of 
diverticula, along most of their courses dividing the body into approxi- 
mately equal longitudinal one-thirds. Excretory system : vesicles sac- 
like, situated just in front of the vitellaria, opening to the exterior each 
by a short and straight canal. Reproductive systems : male pore median 
just behind the pharynx. Uterine pore at the same transverse level, 
or slightly anterior to it on the right margin of the body. Testes not 
very numerous (26-32), and arranged in a paired series between the 



60 



THE TREMATODA OF BRITISH FISHES 



caeca extending from the opisthaptor almost to the anterior ends of 
the vitellaria. Ovary globular and situated just in front of the 
receptaculum seminis, which is pyriform and anterior to the testes. 
Ootype and a bilobed glandular mass situated immediately in front 
of the transverse vitelloduct. Vitellaria comprising numerous very 
coarse follicles lateral to the caeca and between the excretory vesicles 
and the opisthaptor, the lateral vitelloducts just median to the follicles 
and lateral to the caeca. Eggs (one seen in each of three specimens) 








ss 



fS> 



*m<m<h^ *«®e 







0-05 



Fig. 7. — Acanthocotyle oligoterus. A, entire trematode (details of the 
opisthaptor omitted) ; B, the pseudohaptor, and C, some representative 
spines from the same ; D, the true haptor, showing the hooklets ; E, 
the egg. (Original.) 



rounded at one pole, pointed and having a short filament at the other, 
0- 15-0- 17 mm. long. 

A. Scott (1906, p. 192, PI. 9, figs. 2-4) described very briefly as 
Acanthocotyle sp. a specimen about 1-8 mm. long which was found in 
washings from trawl refuse from Fishguard Bay and which resembles 
this more than other species. Unfortunately no diagnostic characters 
were given, but according to the figure this rather contracted specimen 
had a very large pseudodisk 0-7 mm. diameter, bearing 20 rows 
of spines totalling about 136 and a true haptor of triangular shape 
equipped with 2 central and 14 marginal hooklets. The testes cannot 
be counted in the figure, being obscured by a large bouquet of about 
31 eggs which must have exceeded 0-3 mm. in length, but they would 
seem to have been fewer than 30. 



ACANTHOCOTYLIDiE 61 

Acanthocotyle borealis Brinkmann, 1940. 

Host : starry ray. 

Location : skin, of the ventral surface. 

This species was found near Herdla, north of Bergen, Norway, and 
was described by Brinkmann (1940, p. 34, Pis. 9-11, figs. 29-45). Size: 
about 4 mm. long and 1-1 mm. in greatest breadth. Shape : elongate 
oval outline, convex dorsally and concave ventrally, truncated 
anteriorly, narrowing posteriorly to the attachment of the opisthaptor. 
Prohaptor : three or four tongue-shaped lobes at the antero- lateral 
angles of the body and associated cephalic glands. Pseudodisk slightly 
broader than the body and attached to it by a short peduncle, having 
a thin membranous border and spines arranged in 32 curved radial 
rows which reach the periphery, but not the centre. Taking the 
rows on one side in order antero -posteriorly the spines in them 
number 8, 9, 9, 9, 10, 8, 9, 9, 9, 9, 10, 8, 8, 7, 6 and 5, and are therefore 
most numerous in the fifth and eleventh rows, the numbers variable, 
but never by more than a single spine in any row. Each spine con- 
sisting of a basal plate and a point directed towards the row in front of 
it, the centrally- situated spines smallest and roughly triangular in 
shape, more peripheral ones larger and curved, and the most peripheral 
ones somewhat smaller than the curved ones and straight. True 
haptor discoidal, 0-1-0-12 mm. diameter, attached by a short peduncle 
and equipped with 2 central and 14 marginal hooklets having sickle- 
shaped points. Other characters : pharynx 0-17-0-20 mm. long 
and 0-10 mm. broad, internally and externally triangular in section. 
(Esophagus absent. Cseca long and simple and lined with an epithelium. 
A group of unicellular glands postero-dorsal to the pharynx opening 
into its lumen. Male pore situated on a small papilla just behind the 
pharynx and slightly on the right side ; the uterine pore on the right 
margin of the body a little farther back. Testes numerous (but 
described as a testicle with a number of lobes) ; cirrus small ; cirrus 
pouch present. Seminal vesicle bipartite ; sperms filiform and about 
one quarter as long as the mature ovum. Ovary somewhat globular. 
Eggs yellowish and club-shaped, 0-5 mm. long and 0-07 mm. broad, 
tapering to a narrow stalk terminating in a plate at one end, apparently 
laid in bundles of four. 



Acanthocotyle lobianchi Monticelli, 1888. 

Host : thornback ray. 
Locution : skin dorsally. 

This species was first found in the Gulf of Naples and was described 
on several occasions by Monticelli (1888, p. 13 ; 18906, p. 190, 1891 ; 
PI. 5, figs. 9, 10, PI. 6, figs. 36-39 ; 1899a, pp. 111-13, PI. 1, figs. 1, 
3-6, 10, PL 2, figs. 11, 15, 16, 18, 21, 22, 25, 26, 31, 33, PL 3, figs. 
34-43, 46-7, 49-58). It is 3-6 mm. long and is supposed to differ from 



62 THE TREMATODA OF BRITISH FISHES 

the preceding species in having a tongue-shaped true haptor bearing 
8 marginal hooklets with their straight roots directed radially 
inwards, but this shape was not consistently illustrated by Monticelli. 
T. Scott found a specimen " in some material from the Firth of Clyde " 
which he thought might belong to this species. 

Acanthocotyle elegans Monticelli, 1890. 

Host : thornback ray. 
Location : skin dorsally. 

This species was also found at Naples and described several times 
by Monticelli (18906, p. 191, fig. 3 ; 1899a, p. 108, PI. 1, figs. 7, 8, 
PL 2, figs. 13, 17, 19, 23, 256, 28, 29, 32, PL 3, figs. 44, 45 ; 1905, p. 73). 
It is supposed to be a small species 2-4 mm. long and, like A. oligoterus, 
was said to have 15 hooklets on the true haptor, although Brinkmann 
proved that the latter species has 14 peripheral and 2 central hooklets 
and thought it very probable that A. elegans has the same number. 

Family CAPSALID^ Baird, 1853. 

(Phyllinidse Johnston, 1846 ; Tristomidse Cobbold, 1877 ; Tristomatidae 
Gamble, 1896; Encotyllabidae Monticelli, 1888.) 

Shape oval or elliptical and flat, constricted anteriorly to form a 
cephalic lobe. Cuticle smooth, or papillate, or spinous dorso-laterally. 
Prohaptor a pair of suckers, or glandular areas, or suckers and glandular 
areas situated on the margins of the cephalic lobe. Opisihaptor 
discoid al and sucker-like, sometimes having its ventral surface formed 
into loculi, equipped with at least 1 pair and sometimes as many as 
3 pairs of hooks and 14 hooklets. Gut : mouth ventral, never 
encircled by an oral sucker ; caeca having median and lateral 
diverticula which may have dendritic terminations. Eyes : 2 pairs. 
Excretory pore dorso-lateral at or near the level of the pharynx. Genital 
pores somewhat lateral, opening into an atrium or not. Gonads : 
ovary median and situated in front of two or more testes. Vagina 
present or absent. In the Encotyllabinse the opisthaptor has a stout 
peduncle, in other sub-families it is sessile. In two sub-families septa 
and loculi exist, in the other two they do not. Loculate forms may 
have 2 testes as in Trochopodinse or many as in Capsalinse, and 
non-loculate forms fall into the sub-families Benedeniina3 and Nitz- 
schiinae on the basis of the same characters. 

Sub-family Encotyllabinje Monticelli, 1892. 

(Encotyllabidse Monticelli, 1888.) 

Genus ENCOTYLLABE Diesing, 1850. 

(Cheloniella Beneden & Hesse, 1863 ; Tristoma of Taschenberg, 1878.) 

Lateral margins of the body turned ventralwards. Prohaptor 
sucker-like, muscular, elliptical, encircled by a wide pleated membrane. 



CAPSALIDiE 63 

Opistkaptor bell-like, pedunculate and septate, and equipped with 
2 pairs of hooks (one pair massive) and 14 (?) hooklets. Genital 
pore somewhat lateral, genital organs arranged as in Trochopus. 

Encotyllabe nordmanni Diesing, 1850 (p. 428). 

Tristotna excavatum of Nordmann, MS. ; T. nordmanni (Diesing) Taschenberg, 
1878 ; Encotyllabe normanni Braun, 1900 (p. 550). 

This species was found in the nostrils of Ray's bream, Brama 
mediterranea and Heliaster chromis, in the Mediterranean, and the original 
description merely states " Longit. corp. \\" ; latit. \" ; longit. 
pedic. acet. §*," but some more rather scanty information was given 
later (Diesing, 1858a, p. 70, PL 1, figs. 11-15; 18586, p. 364) and a 
figure was given by Fuhrmann (1928, fig. 6, p. (2) 6). 

Encotyllabe pagelli Beneden & Hesse, 1863. 

Tristoma pagelli (Beneden & Hesse, 1863) Taschenberg, 1878 (p. 569). 

Host : common sea bream. 
Location : buccal cavity. 

This species was originally found near Brest and has appeared off 
the west coast of Ireland. According to the original description 
(1864, pp. 80-1, PI. 7, figs. 1-11) the living trematode is very lively 
and the movements include the modification of the lateral expansions 
of the body, which are continually being brought together and sepa- 
rated again. Colour straw yellow with a narrow border of rose, the 
peduncle of the opisthaptor pale like the body, but roseate in the 
middle region. Shape narrow oval, the outline wrinkled, slightly 
convex dorsally and concave ventrally, the posterior extremity of the 
body proper somewhat pointed. Prohaptor 2 anterior suckers of 
medium size, each bordered by a thin pleated membrane and having 
a V-shaped cavity. Opisthaptor relatively small and very convex, 
surrounded by a large pleated membrane and bearing in the depths of 
its cup 2 stout curved hooks the points of which cross one another. 
Peduncle thick, circular in section, very contractile, slightly annulated, 
enlarging near its union with the haptor. Gut bifurcate, mouth 
circular. Reproductive systems : genital hooklets 5 in number and 
arranged in a coronet with the points inwardly directed. Eggs dark 
chestnut brown and of bizarre shapes, some having 2 or 3 filaments, 
as well as a filament of great length and flexibility by which each is 
moored. 

Other Species. 

Monticelli (1907) described two species found in Italy, E. paronaz 
(on Crenilabrus pavo) and E. vallei (on the gilt-head). Four species 
occur outside Europe, E. lintoni Monticelli, 1909, on Calamus calamus 
in Bermuda, E. pagrosoma MacCallum, 1917, in U.S.A. and two (E. 
masu Ishii & Sawada, 1938, and E. spari Yamaguti, 1934) in Japan. 



64 THE TREMATODA OF BRITISH FISHES 

Sub-fainily Trochopodin^ Price, 1936, emend Dawes, 1946. 

Two genera must be considered, and in Trochopus there are 10 
septa dividing up the ventral surface of the opisthaptor, in Megalo- 
cotyle only 6 or 7. 

Genus TROCHOPUS Diesing, 1850. 

( Capsa la of Nordmann ; Tristoma of Diesing, 1836; Placunella Beneden 

& Hesse, 1863, in part.) 

Prohaptor a pair of disk-like, almost sessile organs of medium size 
and varying form and appearance. Opisthaptor discoidal, almost 
sessile, provided with a marginal membrane, the ventral surface 
divided by 10 septa into loculi and bearing 3 pairs of hooks and 
14 marginal hooklets. Genital pore just behind the prohaptor on 
the left ; genital atrium long ; cirrus pouch curved, its basal part 
passing over the median plane to the right side of the body. Testes 
numbering 2, ovoid in shape, side by side and contiguous or slightly 
separated, generally at or in front of the middle of the body. Ovary 
globular and situated in front of the testes. Vagina slender, its pore 
situated just behind the common genital pore. 

Trochopus gaillimhe Little, 1929. (Fig. 8 A-F.) 

Host : yellow gurnard. 
Location : gills. 

This species was found at Galway and described in great detail 
by Little (19296, p. 107, figs. 1-8 ; Pis. 9-11, figs. 1-14), who noted its 
brisk movements over the gills by muscular activity and the use of 
the haptors. Size up to 585 mm. long, a specimen 5-03 mm. long 
being 2-78 mm. broad. Shape broad oval or subrectangular outline, 
broadly rounded posteriorly and notched in the median plane, taper- 
ing, but truncate anteriorly. Colour translucent, milky-white and 
faintly roseate. Prohaptor a pair of sessile saucer-like suckers 0-45- 
0-50 mm. diameter provided with a semi-membranous frill containing 
numerous mucous glands arranged in regular radial rows. (The frill 
is subject to shrinkage during fixation and its width was therefore 
undetermined.) Opisthaptor discoidal, convex dorsally, 1*8 mm. 
diameter, having a pleated membranous frill and bearing 12 septa 
and 3 pairs of hooks. Four anterior septa form a group, 3 lateral 
septa on each side two additional groups. These 10 main septa 
converge on the middle of the haptor, forming a space of horse -shoe 
shape with its open end posteriorly. Two additional short septa 
occur in the posterior space, one on either side of the middle line ; 
they barely reach half-way to the middle of the haptor. Marginal 
frill scalloped, each pleat overlapping the next, except posteriorly, 
where about 8 pleats are separate and distinct. Hooks of the first 
pair situated at the junction of the postero-lateral septa, their points 
directed towards the middle of the haptor, 0-1 mm. long and each 



CAPSALID.E 



65 



comprising a long cylindrical " handle " and a minute recurved point. 
Hooks of the second and third pairs much stouter than those of the 
first and 0-30-0-35 mm. long, situated close together and mainly 
embedded in the tissues of the most posterior complete septa, the 
hooks of the second pair the more median. Hooks of the second pair 
having 4-5 condylar processes for the attachment of muscles and 4-5 
rows of serrated ridges distally. Hooks of the third pair tapering 
gradually from a broad base, each having a strong, recurved point. 
Gut : mouth ventral, 0-75 mm. from the anterior extremity, being a 




Fig. S.—Trochopus gaillimhe. A, dorsal view showing the gut and 
gonads ; B, the reproductive organs ; C, the anterior suckers ; D, the 
opisthaptor ; E and F, hooks of the 1st and 2nd (E) and 3rd (F) pairs. 
(After Little, 19296.) 



transverse slit 0-60 mm. wide bordered by prominent anterior and 
posterior lips. Pharynx ovoid, 0-78 X 0-40 mm., its lining bearing 
numerous granular papillate structures. (Esophagus short (0-10 X 0-05 
mm.), caeca having about a dozen lateral and half as many median 
diverticula, all of which tend to branch more than once. Caeca and 
diverticula lined with amoeboid cells with prominent nuclei. Eyes : 
2 pairs, one behind the other, slightly in front of the mouth, those 
of the anterior pair 0-14 mm. apart and 0-44 mm. from the anterior 
extremity, those of the posterior 0-28 mm. apart. Reproductive 
systems : male and female pores opening one behind the other into a 
shallow common genital atrium immediately behind the left anterior 
sucker. Cirrus-pouch membranous, epithelial and lined with thin 
cuticle. Cirrus very long, narrow and folded, encased in cuticle, con- 



66 THE TREMATODA OF BRITISH FISHES 

taining two ducts (a) and (6), each lined with cuticle ; (a) is the con- 
tinuation of the pars prostatica, i.e. the ejaculatory duct, which may 
be packed with spermatozoa ; (b) is smaller, and contains a gelatinous 
substance derived from a large accessory sac (0-45-0-60 mm. long) 
situated beneath the cirrus and pars prostatica. Vas deferens swollen 
at its base to form a W-shaped seminal vesicle. Testes globular, 
0-45-0-55 mm. diameter, but only 028 mm. thick, side by side and 
almost confluent near the midbody. Ovary spherical, 0-40 mm. 
diameter, median, in front of and between the testes. Oviduct short, 
almost at once receiving the unpaired vitelloduct, which extends from 
the vitelline reservoir antero -lateral to the ovary ; beyond this point 
slightly folded to the ootype, which is ovoid and 0-11-0-12 mm. in 
greatest width. Uterus very short, metraterm straight. Vitellaria 
comprising numerous follicles occupying the available space above and 
beneath the caeca throughout the whole extent of the body. Vagina 
0-9-1-2 mm. long, wide at the base, but narrowing towards the external 
opening, which is situated near the genital pores. Receptaculum 
seminis globular or ovoid (0-17 x 0-14-0-17 mm.) and situated at the 
base of the vagina. Eggs pyriform, very large (0-163-0-197 x 0-100- 
0-142 mm.), dark yellow, and having a twisted filament 0-39 mm. long 
attached to the posterior pole. Only one egg found in utero at any 
time, situated either in the ootype or the metraterm. 

Other Species, their Hosts and Distribution. 

Trochopus brauni Mola, 1912 (miller's thumb : Italy). 

T. differens Sonsino, 1891 (black sea bream : Mediterranean). 

T. diplacanthus Massa, 1903 (Placunella pini of A. Scott, 1901) 
(yellow gurnard : Mediterranean, Irish Sea) . 

T. lineatus T. Scott, 1901 (streaked gurnard : in the Clyde, Scot- 
land) . 

T. micracanihus Massa, 1903 (yellow gurnard : Italy). 

T. onchocanthus Massa, 1906 (unidentified fish : Italy). 

T. pini Beneden & Hesse, 1863 (red and yellow gurnards : Brest. 
Also Trigla corax : Italy). 

T. tubiporus (Diesing, 1835) (Tristoma tubiporum Diesing, 1835 ; 
Trochopus longipes Diesing, 1850) (yellow gurnard, red gurnard, 
Cantharus lineatus : Irish Sea, Italy, North- West France) . 

Most of these species are ill defined and the British records very 
doubtful. According to T. Scott (1901, pp. 143-4, PL 8, fig. 18 ; 1905, 
p. 118; 1912, PL 27, fig. 3) Trochopus lineatus is about 3 mm. long, 
broad oval in outline, and has a discoidal opisthaptor with 12 
radiating septa spaced out at fairly regular intervals, the posterior 
2 having their inner ends free, the remaining 10 merging with an 
almost central ring-like septum. The same writer (1912) mentioned 
only 1 small hook on each of the penultimate rays, and 2 other 
pairs of hooks were either overlooked or missing from the specimens, 
which had 2 pairs of eye-spots. A. Scott (1904) claimed to have 
found T. pini (as Placunella) on the yellow gurnard in the Irish Sea, but 



CAPSALID^E 67 

the only characters mentioned were 8 distinct and 2 indistinct " rays " 
in the " posterior sucker." Some information concerning most of 
the species is available in the later paper by Massa (1906). 

Genus MEGAL0C0TYLE Folda, 1928. 

(Trochopus of Mola, 1912, and Massa, 1903, in part; Placunella Beneden 

& Hesse, 1863, in part.) 

Opisthaptor having 6 or 7 septa, other characters as in Trochopus. 
The type-species, M . marginata Folda, 1928, is a parasite of Sebastodes 
nebulosus in North America. Three other species were discovered in 
Europe, but have not appeared in Britain. 

Megalocotyle zschokkei (Mola, 1912) Price, 1939. 

Trochopus zschokkei Mola, 1912. 

Host : miller's thumb. 
Locality : unspecified. 

According to the original description — Size : 2*65 mm. long. 
Shape : elliptical, if the haptors are left out of account. Colour pale 
rose. Prohaptor a pair of cup-shaped anterior suckers 0*35 mm. 
diameter situated relatively close together. Opisthaptor discoidal, 
0*9 mm. broad, having ventrally 7 radiating septa which merge 
centrally, those of the most posterior pair bearing 3 pairs of hooks 
which are set close together and are similar except in size (0'24 mm., 
017 mm., and 06 mm. long in the outer, middle and inner pairs 
respectively). 

Megalocotyle hexacantha (Parona & Perugia, 1889) Price, 1939. 

Placunella hexacantha Parona & Perugia, 1889 (p. 740, fig. 1). Trochopus 
hexacanthus (Parona & Perugia) Massa, 1906 (pp. 59-60, PI. 2, figs. 15-17 ; 
PL 3, figs. 28, 36). 

Host : dusky perch (at Genoa). 

Megalocotyle rhombi (Beneden & Hesse, 1863) Price, 1939. 

Placunella rhombi Beneden & Hesse, 1863 (1864, p. 72, PI. 5, figs. 9-18). 
Trochopus rhombi (Beneden & Hesse) Massa, 1903 (p. 255) (see also Massa, 
1906, pp. 58-9, PI. 2, fig. 1). 

Host : turbot (near Brest). 



Sub-family NiTZSCHUKa: Johnston, 1931. 

Genus NITZSCHIA Baer, 1826, nee Denny, 1842, nee Beneden, 1858, 

nee Linton, 1898. 

(Hirudo Abildgaard, 1794; Nitychia and Nityschia Nordmann, 1833; 
Nitschia Haswell, 1892; Nitzchia Beneden, 1858.) 



68 THE TREMATODA OF BRITISH FISHES 

Nitzschia sturionis (Abildgaard, 1794) Kroyer, 1852 (p. 777). 

Hirudo sturionis Abildgaard, 1794 (pp. 55-6, PI. 6, fig. 1) ; Nitzschia elegans 
Baer, 1826 (pp. 125-6) ; N. elongata of Monticelli, 1909 ; Tristoma sturionis 
of Cuvier, and Blainville, 1847 (pp. 329-30) ; T. elegans of Beneden & 
Hesse, 1864 (pp. 64, 77) ; T. elongatum of Nitzsch, 1826 (pp. 150-1). 

Host : sturgeons. 

Location ; gills. 

This species occurs widely in Europe (North Sea, Baltic Sea, 
Mediterranean) and possibly in America, although Price (19386) was 
of the opinion that N. superba MacCallum, 1921, is the only American 
species. It has been described by Abildgaard (1797, p. 135, PL 3, 
figs. 3-5), MonticeUi (1891, p. 106, PI. 6, fig. 32) and Liihe (1909, p. 
5, fig. 1). Size : 12-23 mm. long. Shape : elongate, broadening 
slightly at the anterior end, tapering slightly towards the opisthaptor. 
Prohaptor : two sucker-like grooves of elongate oval shape diagonally 
arranged at the anterior extremity. Opisthaptor : discoidal and sucker- 
like, with a delicate marginal membrane, but lacking septa and papilla. 
Hooks arranged in 3 pairs, their sizes approximately equal, mar- 
ginal hooklets numbering 14. Gut bifurcate, pharynx relatively 
large. Reproductive systems : genital pore median or slightly to the 
left of the middle line near the bifurcation of the gut. Ovary compact, 
situated in front of the testes, which number up to 27, perhaps 
more, and occupy the space between the caeca in the posterior half 
of the body. 

Price (1939a) proposed the erection of a new species, N. monticellii, 
for the " forma giovane " of N. elongata (= N. sturionis of Monticelli, 
1909), claiming that two species were represented in Monticelli's 
specimens, this form having hooks of unequal lengths on the opisthaptor. 

Sub-family Capsalinje Johnston, 1929, emend Price, 1939. 
(Tristominae Braun, 1893 ; Tristomatinae Gamble, 1896.) 

Two European genera are readily distinguished, Capsala by the 
transversely constricted pharynx and testes which sometimes over- 
step the caeca laterally, and Tristoma by the unconstricted pharynx 
and testes which are confined between the caeca. The genus Cap- 
saloides Price, 1936, resembles Tristoma in these characters, but can 
be separated from it by the distal bifurcation of the posterior rays 
of the opisthaptor and the claw-like tips of the hooks. Two species 
of this genus occur in America, another in Japan, and a fourth species, 
C. perugiai (Setti, 1898), was discovered on Tetrapterus belone at 
Spezia, but has not appeared in Britain. 

Genus CAPSALA Bosc, 1811. 

(Phylline, Oken, 1815, in part ; Tristoma Cuvier, 1817, in part ; Trico- 
tyle Guiart, 1938 ; Tristomella Guiart, 1938 ; Capsala of Guiart, 1938, 

in part.) 

Opisthaptor having posterior septa which are not bifid distally and 
hooks which, when present, do not have claw-like tips. Dorsal 



CAPSALIDJE 69 

marginal spines present or absent. Pharynx having a marked con- 
striction at or slightly behind the middle. Testes generally numerous, 
sometimes extending lateral to the caeca. 



Capsala martinieri Bosc, 1811 (pp. 384-5). (Fig. 9 A, B.) 

Phylline diodontis Oken, 1817 (p. 182, PI. 10, fig. 3 ; based on Martiniere, 
1787, pp. 207-8, figs. 4, 5) ; P. coccinea of Schweigger, 1820 (p. 474) ; 
Tristoma maculatum Rudolphi, 1819 (pp. 123, 430, PI. 1, figs. 9, 10) ; 
T. coccineum of Rudolphi, 1819 (pp. 123, 428), and authors ; T. cephala 
Risso, 1826 (p. 262) ; T. aculeatum of Couch (quoted by St. Remy) ; T. 
molce Blanchard, 1847, of Guiart, 1938; T. rudolphianum Diesing, 1850, of 
Johnston, 1865 (p. 330) ; Capsala maculata (Diesing) of Nordmann, in 
Lamarck, 1840 ; C. rudolphiana (Diesing) of Johnston, 1865 (p. 33) ; C. 
sanguinea Blainville, 1828, and Nordmann, in Lamarck ; C. cephala (Pvisso) 
of Johnston, 1929 ; C. molce (Blanchard) of Johnston, 1929. 

Host : sun-fish. 
Location : gills. 

This species is widespread in Europe and occurs on both the Atlantic 
and Pacific coasts of America. It has been described concisely by 
Price (1939a, p. 79, figs. 19-21), and I have already given a brief 
diagnosis (Dawes, 1946, p. 138), mentioning also unusually large 
specimens collected by Professor Yonge near Bergen. An up-to-date 
diagnosis based on the two sets of specimens can now be given. Size : 
15-28-5 mm. long and 16-30 mm. broad. Shape : almost circular in 
outline, but deeply notched posteriorly, concave ventrally and convex 
dorsally. Cuticle smooth dorsally except near the margins of the 
body, where there is a relatively broad longitudinal band of irregu- 
larly-disposed spines, most of them having 4 cusps, the ventral 
surface covered with numerous minute papillae. Prohaptor a pair of 
large sucker-like organs 1-4 to more than 2 mm. diameter, sometimes 
slightly ovoid. Opisthaptor discoidal and 8 to nearly 14 mm. diameter, 
encircled by a pleated membrane 0-4-0-5 mm. wide, the ventral surface 
bearing numerous papillae and having a central depression of hep- 
tagonal shape and 7 radiating septa peripheral to it. Hooks 
absent, hooklets present. Out : mouth median just behind the pro- 
haptor ; pharynx 2-2-5 mm. long and 1-2-2 mm. broad, having a 
distinct constriction at the second third of its length. Reproductive 
systems : genital pore just behind the left anterior sucker. Cirrus pouch 
club-shaped, its base in the median plane just behind the pharynx ; 
testes very numerous, and occupying most of the central region of the 
body and extending to within 1-5 mm. of the margin behind the 
pharynx. Ovary lobed, 1-5-2-7 mm. long and 2-3-7 mm. broad, situated 
in front of the testes about 2 mm. behind the pharynx. Vitellaria 
comprising numerous follicles occupying most of the space throughout 
the body and extending into the cephalic lobe, but leaving a clear 
lateral zone about 1 mm. wide on each side of the body. Vitelline 
reservoir up to 0-6 mm. diameter, situated in front of the ovary on the 
left. Vagina slender, its pore 0-37-0-45 mm. postero-lateral to the 



70 



THE TREMATODA OF BRITISH FISHES 



genital pore. Ootype ovoid and situated just behind the cirrus pouch. 
Eggs not found. 

Other species of Capsala which have been recorded in Europe 
include C. cutanea (Guiart, 1938), C. grimaldii{ Guiart, 1938), C. inter- 




Fig. 9. — Capsala martinieri. A, entire trematode ; B, part of the 
margin of the body, showing the marginal spinelets. (Original.) 



rupta (Monticelli, 1891), C. onchidiocotyle (Setti, 1899), C. pelamydis 
(Taschenberg, 1878) and G. thynni (Guiart, 1938). None of these 
species has been found in British waters. 



CAPSALID^ 7 1 

Genus TRISTOMA Cuvier, 1817. 
(Capsala Bosc, 1811, in part.) 

Opisthaptor having posterior septa which are not bifid distally and 
hooks which, when present, do not have claw-like tips. Dorsal mar- 
ginal spines, when present, arranged in numerous short transverse 
rows of similar or dissimilar spines. Pharynx nearly globular and 
never constricted at or near the middle. Testes numerous and con- 
fined between the caeca. 

Tristoma coccineum Cuvier, 1817 (pp. 42-3, pi. 15, fig. 10 ; PI. 36 bis, 
figs. 1-3). 

Tristoma papillosum Diesing, 1836 (pp. 313-16, PL 17, figs. 13-16); Capsala 
papillosa (Diesing) of Nordmann, in Lamarck, 1840. 

Hosts : sword-fish, hammerhead shark. 
Location : gills. 

This species occurs in various parts of the Mediterranean (Genoa, 
Naples, Palermo, Messina), and in Canada and U.S.A. Price (1939a) 
showed that Cuvier included two species under this name, one from 
the sword-fish and the other from the sun-fish, the latter being the 
form later known as T. molce Blanchard, 1847, and now considered to 
be one of the synonyms of Capsala martinieri. Diesing (1836) re- 
described forms from both these hosts, but his " T. coccineum " was 
the form from the sun-fish. The remaining form from the sword-fish 
was described as T. papillosum and bore dorsal tubercles, for this 
reason being referred by Price to the species under consideration, which 
is not completely host-specific, one of a number of American specimens 
being found on the hammerhead shark. According to Price (1939a, p. 
84, figs. 29-32) it is 10-12 mm. long and nearly four-fifths as broad ; 
the cuticle has prominent dorsal papillae and 43-54 rows of 2 to 4 
marginal spines, the innermost having 1 cusp, the second and third 
2 to 7 cusps, while the outermost are comb -like. The anterior 
suckers are about 1-3-1-7 mm. diameter, the opisthaptor about 1-8- 
2-4 mm. and its margin 0-17-0-36 mm. wide. The large hooks are 
straight and 0-13-0-15 mm. long, the hooklets 0-015 mm. long. The 
globular pharynx is 1-1-3 mm. long and 1-1-1-5 mm. broad. The eggs 
are fairly large, more or less triangular and with 4 prolongations, 
their dimensions 0-114 x 0-095 mm. 

Tristoma integrum Diesing, 1850 (p. 429). 

Tristoma coccineum Cuvier, 1817, in part ; T. coccineum Cuvier of Taschen- 
berg, 1879 (a, p. 59 and c, p. 296) and authors ; T. rotundum Goto, 1894 
(pp. 245-8, PI. 24, figs. 6-9). 

Host : sword-fish. 
Location : gills. 

This species occurs in various parts of the Mediterranean (Genoa, 
Naples, Venice, Messina) and in U.S.A. and Japan. According to 



72 THE TREMATODA OF BRITISH FISHES 

Price (1939a, pp. 86-8, figs. 33-35) the outstanding differences between 
this and the previous species lie in the arrangement and morphology of 
the dorsal marginal spines, which are numerous (upwards of 300 on 
each side of the body) in this species and not dissimilar in different 
rows. Further details can be found in the paper by Price, and two 
good figures occur in that by Taschenberg (1879c, PL 1, figs. 1,2), these 
having been merged to form one admirable illustration by Braun 
(1893, PI. 8, fig. 1). 

Two other species of Tristoma have been recorded in the Mediter- 
ranean and elsewhere — T. levinsenii Monticelli, 1891 (pp. 101, 122, 
PI. 6, fig. 21) (on Thynnus sp.), and T. uncinatum Monticelli, 1889 
(Boll. Soc. Nat. Napoli, 3, pp. 117-19, PI. 4, figs. 1-7) (on the halibut 
and Pleuronectes sp.). 

Sub-family Benedeniin^e Johnston, 1931. 

(Encotyllabinse Monticelli, 1892, in part ; Ancyrocotylinse Monticelli, 
1903 ; Tristominse Braun, 1893, and of Monticelli, 1892, in part.) 

Three European genera can be separated by the nature of the 
caeca and prohaptor. The caeca of Ancyrocotyle lack diverticula ; those 
of other genera have median and lateral diverticula, and Benede?iia 
has a pair of anterior suckers, Entobdella a prohaptor comprising 
glandular areas only. 

Genus BENEDENIA Diesing, 1858, nee Schneider, 1875. 

{Epibdella Beneden, 1856, in part ; Phylline Oken, 1815, nee Abildgaard, 
1790, in part ; Tristoma Cuvier, 1817, in part.) 

Prohaptor a pair of suckers or sucker-like disks. Opisthaptor 
discoidal, lacking septa, but equipped with 3 pairs of dissimilar 
hooks and 14 hooklets. Testes 2 in number, side by side, and 
confluent. Vas deferens generally not forming a loop in front of the 
ovary, which is anterior to the testes and not separated from them by 
a wide belt of vitelline follicles. Vagina present or absent. 

Benedenia sciaenae (Beneden, 1856), Linstow, 1903 (p. 355). 

Epibdella sciaenae Beneden, 1856 (pp. 502-8, PI., figs. 1-4) ; Benedenia elegans 
Diesing, 1858 (p. 364) ; Phylline scicence (Beneden) Sonsino, 1878 (p. 263) ; 
Tristoma scicence (Beneden) Taschenberg, 1878 (p. 568). 

Host : meagre (in the North Sea, near Ostend and in Italy). 

The original description of this species has not been available to 
me, but MacCallum (1927, p. 298) gave such details as — Size : 18-20 
mm. long and 10-12 mm. broad. Prohaptor a pair of rounded anterior 
suckers. Opisthaptor bearing papillae and short spine -like hooks. 
Cirrus pouch simple and thin- walled. Vaginal pore situated near the 
genital pore. Eggs ovoid, each having one polar filament. Beneden 
(1858, pp. 23-37) specified the length and breadth of the body as 24 x 
12 mm. and the diameter of the opisthaptor as 5 mm., and gave a long 
account of the anatomy unaccompanied by figures. Three hooks 



CAPSALID^E 73 

were mentioned, but only two pairs briefly described. The " tubercles " 
on the opisthaptor were said not to show the regularity seen in Ento- 
bdella hippoglossi. For other accounts of this worm, see Goto (1894, 
p. 233 ; 1899, pp. 269-70, PI. 20, figs. 8, 9) and Monticelli (1891, pp. 
105, 107, 120, 125, 126, PL 6, fig. 23). 

Benedenia monticellii (Parona & Perugia, 1895), Linstow, 1903. 

Phylline monticellii Parona & Perugia, 1895 (p. 2) ; Epibdella monticellii 
(Parona & Perugia) Parona, 1896 (p. 1). 

Host : golden grey mullet (at Trieste). 

According to the original description 6 mm. long and 2-5 mm. broad. 

Prohaptor comprising a pair of large and deep anterior suckers (the 
dimensions of which are given as 0-056 x 0-049 mm.). Opisthaptor 
1-8 mm. diameter, lacking papillae and bearing 2 pairs of hooks, 
respectively 0-016 mm. and 0-011 mm. long. Gut having a triangular 
" oesophageal bulb." [Note. — Price (1939, p. 65) has already pointed 
out that the original description is barely generic, the eyes, vagina, 
eggs and other organs being undescribed, and that the opisthaptor 
probably bears 3 pairs of hooks, not 2, the sizes of which are 
possibly ten times as great as was stated (perhaps as a result of mis- 
prints) .] 

Other Species of Benedenia. 

About 16 species other than those mentioned are distributed in 
various parts of the world (U.S.A., Mexico, Chile, Eastern Russia, 
Japan and elsewhere), but none is known to occur in Europe. 

Genus ENTOBDELLA Blainville, in Lamarck, 1818. 

(Epibdella Blainville, 1828; Phylline Oken, 1815, nee Abildgaard, 1790, 
in part ; Phyllonella Beneden & Hesse, 1863.) 

Prohaptor a pair of elongate glandular areas bordering the cephalic 
lobes. Opisthaptor discoidal and provided with hooks as in Benedenia. 
Vas deferens forming a loop in front of the ovary, which is generally 
separated from the testes by a wide zone of vitelline follicles. Other 
characters as in Benedenia. 

Entobdella hippoglossi (Muller, 1776), Johnston, 1856 (p. 32). 

(Fig. 10A-C.) 

Hirudo hippoglossi Muller, 1776 (p. 220 ; 1788, p. 138, PI. 54, figs. 1-4) ; 
Phylline hippoglossi (Muller) of Oken, 1815 (p. 371) ; Epibdella hippoglossi 
(Muller) of Blainville, 1828 (p. 567) ; Tristoma hamatum Rathke, 1843 
(pp. 238-42, PI. 12, figs. 9-11) ; Nitzschia hippoglossi (Muller) of Taschen- 
berg, 1878 (p. 568) ; Phyllonella hippoglossi (Muller) of Goto, 1899, Pratt, 
1900, and MacCallum, 1927 ; Epibdella bumpusii of Canavan, 1934. 

Host : halibut. 
Location : skin. 

T. Scott (1901, p. 142) stated that this trematode is sometimes very 
common on halibut landed from the steam line-fishing boats at the 



74 



THE TREMATODA OF BRITISH FISHES 



fish market, Aberdeen, but lie gave only a few very general characters 
and neither measurements nor a figure. The trematode is widely 
distributed, having been recorded in the Skagerrak, Denmark, the 
Arctic (Greenland), as well as in Alaska, Canada (Nova Scotia) and 
U.S.A. (Woods Hole ; Swans Island, Me.). Price (1939a, pp. 69-71, 
figs. 1, 7) and Linton (1940, p. 6, PL 14, figs. 164-9) described American 
specimens which agree in all essential details of structure with those 
described by earlier writers, and I have already given a diagnosis 
(Dawes, 1946, p. 144), mentioning four specimens of my own found in 




Fig. 10. — Entobdella hippoglossi. A, the entire trematode; B, some papillae 
from the opisthaptor. C, posterior end of the opisthaptor, showing the 
hooks and papillae (a, b, c represent hooks of the 1st, 2nd and 3rd 
pairs). (Original.) 



British waters. These are rather small, 10-15 mm. long and 7-8-5 
mm. broad, and one of them is figured here for the first time. I have 
since acquired a specimen which is quite as large as the largest American 
specimen dealt with by Price, and here modify the diagnosis to include 
my own small specimens. Size : 10-18 mm. long and 7-0-8-5 mm. 
broad (American forms seem to be rather narrow*), but according to 
various writers up to 24 mm. long and 13 mm. broad. Shape : ellip- 
tical, decidedly flattened, slight lateral constrictions marking oft' the 
cephalic lobe. Prohaptor a pair of elongate glandular areas. Opis- 
thaptor discoidal, very thin and sucker-like, 4-5-7-5 mm. diameter,* 

* Price may be in error regarding the breadth of the body and the size of 
the opisthaptor. He gave the measurements 13-18 mm. and 3-6-4-8 mm. for 



CAPSALID.dE 75 

encircled by a marginal membrane up to 0*17 mm. wide, its ventral 
surface concave, the posterior half bearing radiating rows of papilla? 
about 0-2 mm. broad at the base and 0-2 mm. long, provided with 
3 pairs of hooks and 14 marginal hooklets. Hooks of the first 
pair having the shape of a spear-head, 0-51-0-84 mm. long and 
with a slightly curved median margin ; hooks of the second pair 
slender and with recurved tips, 0-8-1-6 mm. long ; hooks of the third 
pair 0-09-0-16 mm. long, their tips slender and recurved, hooklets 
about 0-02 mm. long. Gut : mouth ventral near the posterior limit of 
the cephalic lobe. Pharynx broader than long, measuring 0-58-0-85 x 
0-85-1-1 mm., the caeca having much- branched lateral diverticula. 
Reproductive systems : common genital pore situated at the posterior 
end of the cephalic lobe on the left margin of the body. Cirrus pouch 
club-shaped, its base slightly on the right and midway between the 
ovary and the pharynx. Testes globular or ovoid and situated side 
by side near the middle of the body, dimensions 1-00-1-32 x 0-92- 
1-16 mm. in my small specimens, 1-7-2 mm. diameter in the larger 
American specimens. Ovary transversely ovoid, 0-6-0-7 x 0-85-1-2 
mm., separated from the more anterior testes by a band of vitelline 
follicles 0-25-0-35 mm. wide. Vitellaria filling up the available space 
throughout the body, but absent from the cephalic lobes and the 
parenchyma immediately around the genital ducts. Vagina slender, 
its pore situated behind and median to the genital pore. Ootype 
ovoid and situated in the median plane behind the cirrus pouch. 
Metraterm slender. Egg (absent from my specimens) tetrahedral, 
about 0-228 mm. broad and having a long slender filament. 

Entobdella soleae (Beneden & Hesse, 1863), Johnston, 1929. 

(Fig. 11 A-F ) 

Phyllonella solece Beneden & Hesse, 1863, and of Little, 1929a ; Epibdella 
solece (Beneden & Hesse, 1863) of Monticelli, 1892, and authors ; E. producta 
(Linstow, 1903) Odhner, 1906. 

Hosts : sole, sand sole. 
Location : skin. 

This species was found by Beneden near Brest and later (1871) off 
the coast of Belgium. T. Scott (1901, pp. 142-3, PL 8, fig. 17) twice 
found it in the Clyde and gave a very short and general description 
of a specimen 6-7 mm. long. A. Scott (1904) recorded its occurrence 
in the Irish Sea, Southern (1912) west of Ireland. Bay lis & Idris 
Jones (1933) found it at Plymouth, where I have also obtained speci- 
mens, and Little found it very abundant (60 out of 100 soles infected 
with 2 to 5 and sometimes as many as 8 specimens each) at 
Galway and gave a detailed description (1929c, pp. 324-37, figs. 1-10 ; 

length and breadth and, taking small figures together, this gives a breadth equal 
to 0-27-0-28 body-length. But his Fig. 1 illustrates a breadth which is 0-63 or 
0-77 body-length, according to whether or not we exclude the opisthaptor from 
the statement of length. The opisthaptor was stated to be 3-6-4-8 mm. diameter, 
i.e., of the same breadth as the body, yet his figure clearly shows its breadth to 
be less than half that of the body, at most four-ninths. 



76 



THE TREMATODA OF BRITISH FISHES 



Pis. 15-17, figs. 1-13). My specimens are fairly small, and I have 
included a few details about them in parentheses in the following 




mJ 0-1 



Fig. 11. — Entobdella solece. A, contracted individual showing the gut and 
gonads ; B, extended individual, showing the gonads and vitellaria ; 
C, hooks of the 2nd pair ; D, those of the 1st pair ; E, the genital 
organs ; F, the opisthaptor. (After Little, 1929c.) 

description. Size : 2-1-5-9 mm. long and 1-05-2-9 mm. in greatest 
breadth (2-85 x 1-30 mm.), according to Scott (1901, p. 142) up to 



CAPSALID^ 77 

6-7 mm. long. Shape oval and much flattened, the two extremities 
bluntly rounded, each with a slight median notch. Colour trans- 
lucent, whitish with a pale lemon tinge, milky -white after death. 
Prohaptor a pair of elongate glandular areas, marked off posteriorly 
by a slight constriction (together 0-25 mm. long and 0-41 mm. broad). 
Opisihaptor sucker-like, 1-54 mm. long and 1*4 mm. broad in a specimen 
5-93 mm. long (0-92 x 0-82 mm.), with a frilled membrane broadest 
anteriorly, where it is 0-23 mm. wide (0-16 mm.). Two main septa 
originating close together slightly in front of the middle of the sucker, 
diverging towards the bases of the hooks of the first pair, then extend- 
ing along the courses of the hooks of the second pair, terminating at 
the posterior margin of the haptor. These septa are connected by a 
transverse septum between the bases of the first hooks. In front of 
them there is a ridge of horse-shoe shape, not very evident in cleared 
preparations, and possibly representing the points of insertion of 
muscles. Hooks numbering three pairs [not two, as stated or figured 
by Beneden and Hesse (1864), Cunningham (1890) and T. Scott (1901, 
1912.) Southern (1912) seems to have first recorded the correct 
armature of the haptor.] Hooks of the first pair in the position stated, 
0-28 mm. long (0-145 mm., not allowing for curvature), half embedded 
in the tissue, consisting of a bifid condylar process and a large recurved 
point. Hooks of the second pair in the position stated, 0-65 mm. long 
(0*42 mm.), almost completely embedded, consisting of a slightly 
curved shaft and a terminal, recurved point. Hooks of the third 
pair small, 0-121 mm. long (0-12 mm.), situated slightly lateral to the 
points of the hooks of the second pair. (Note. — Not having two shafts 
apiece as in "Epibdella producta" according to Linstow.) Eyes : 
2 pairs, the posterior pair slightly the larger and 0-26 mm. apart 
(0-11 mm.) ; anterior pair 0-14 mm. apart (0*8 mm.) and 0-37 mm. 
from the anterior extremity (0-23 mm.). Gut : mouth ventral, 0-40 
mm. from the anterior end of the body (0*25 mm), a wide transverse 
or crescentic slit bordered by prominent anterior and posterior lips. 
Pharynx 0-70 mm. broad (much smaller ; about 0-2 mm.), having 
large multicellular papillae projecting into its cavity. (Esophagus 
practically absent. Caeca long, uniting slightly in front of the opist- 
haptor, provided with numerous dendritic lateral diverticulae and a 
few median branches, especially behind the testes. Caeca and diver- 
ticula lined with large amoeboid cells. Excretory system : main longi- 
tudinal ducts roughly parallel to the lateral vitelloducts, expanding 
somewhat anteriorly, lined with cuticle. Reproductive systems : 
common genital pore as in E. hippoglossi, behind the left glandular 
area of the prohaptor. Cirrus elongate, 1-05 mm. long in a specimen 
5-93 mm. long and 0-21 mm. wide basally near the hind end of the 
pharynx, where it is free in the pouch, traversed by two ducts of equal 
size, (a) and (b) : (a) small, the ejaculatory duct ; (b) large, connected 
with a large, oval accessory sac measuring 0-25 x 0-18 x 023 mm., 
but variable in size, adjacent to the base of the cirrus and median. 
(Note. — According to Little the accessory sac contains a granular 
secretion of large cells on either side of the ootype which is assembled 



78 THE TREMATODA OF BRITISH FISHES 

in the sac by way of afferent ducts ; the secretion is supposed to play 
a part in the emission of spermatozoa.) Seminal vesicle 0*04 mm. 
diameter (? sectional), close to the left margin of the ootype, elongate 
and folded. Pars prostatica Z-shaped, penetrating the postero-dorsal 
end of the cirrus, to continue as the ejaculatory duct. Testes ovoid, 
0-53 x 0-37 x 0*21 mm., side by side and almost contiguous slightly 
behind the midbody. Ovary ovoid, its dimensions 0-28 x 0-37 x 0-28 
mm., median, the longest axis transverse, slightly in front of the testes 
and just in the posterior half of the body. Oviduct almost immediately 
receiving the median vitelloduct. Receptaculum seminis comprising 
three spherical chambers 0-075-0-147 mm. diameter in front of the 
ovary. Ootype ovoid, 0-189 mm. in greatest width when distended, 
0-110 mm. when contracted, situated slightly in front of the recep- 
taculum seminis. Metraterm 1-0 mm. long, passing obliquely to the 
left parallel with the cirrus, thin- walled. Vitellaria comprising 
numerous follicles above and beneath the caeca and diverticula, filling 
the median region of the body at and behind the levels of the gonads. 
Mam vitelloducts lateral, closely following the courses of the excretory 
canals ; transverse ducts forming a large vitelline reservoir, measuring 
0-143 X 0-253 X 0275 mm. immediately in front of the ovary. Eggs 
pyramidal in outline, having the apex directed posteriorly in the 
ootype and prolonged into a long, slender, and twisted filament 0-44 
mm. long. Egg-capsule proper very large, measuring 0-143 x 0-143 
mm. and dark yellow. Vagina enlarged basally to form a receptaculum 
seminis, apparently ending blindly (?) near the anterior end of the 
vitelline reservoir, its pore slightly lateral at the level of the ootype 
and thus far behind the common genital pore. 

Two other species of Entobdella occur in Europe — E. diadema 
(Monticelli, 1902), which occurs on Trygon violacea in Italy, and E. 
steingroveri (Cohn, 1916), which was found on an unidentified fish. 

Genus ANCYR0C0TYLE Parona & Monticelli, 1903. 

(Placunella Beneden & Hesse, 1863, in part.) 

Prohaptor a pair of muscular suckers situated on fleshy pads. 
Opisthaptor sucker-like and with a marginal membrane, 3 pairs 
of hooks and 14 hooklets, the hooks of the third pair lateral to those 
of the second. Gut bifurcate, the caeca devoid of diverticula. Testes 
2 in number and situated behind the ovary, sometimes (?) a single 
testis situated in front of it. Vagina present. 

Ancyrocotyle vallei (Parona & Perugia, 1895) Parona & Monticelli, 
1903. 

Placunella vallei Parona & Perugia, 1895 (a, pp. 3-4). 

Host : pilot-fish. 

Location : gills. 

This species has been found at Trieste and Genoa, but not in Britain. 
According to the very brief original description it is 3 mm. long and 
0-42 mm. broad, the suckers of the prohaptor 0-028 mm. diameter and 



CAPSALIDiE 79 

the opisthaptor 0-056 mm. diameter. The lengths of the hooks are 
0-035 mm., 0-003 mm. and 0-004 mm., and the dimensions of the eggs 
0-014 x 0-007 (misprinted as 0-07) mm. I have been unable to consult 
the redescription by Parona & Monticelli (1903, pp. 117-21, PI. 3, 
figs. 1-6), but Price (1934a, pp. 1-3) has drawn attention to notable 
features of the anatomy, the presence of only two pairs of hooks on 
the opisthaptor and of a single testis situated in front of the ovary — 
characters by which the species can be identified. 

The only other species of Ancyrocotyle is A. bartschi Price, 1934, 
which was discovered on the gills of the pilot-fish in the West Indies 
and was based on two immature specimens. In describing these 
specimens Price (1934a, pp. 1-2, PI. 1, figs. 1, 2) considered the possi- 
bility of their identity with A. vallei, but noted certain differences, 
notably the presence of two testes, which are situated behind the 
ovary, and the structure of the hooks of the second pair. In view of 
the possible identity we can note the characters briefly. Size : 0-83- 
0-97 mm. long and 0-25-0-27 mm. broad. Shape elongate and rectan- 
gular. Prohaptor a pair of sucker-like organs 0-08 mm. diameter, 
situated near the hind ends of pads of tissue. Opisthaptor sucker-like 
and nearly sessile, fringed by a narrow membrane and equipped with 
3 pairs of hooks and 14 marginal hooklets. Hooks of the first 
pair straight and 0-020-0-023 mm. long ; hooks of the second pair 
0-068-0-076 mm. long and situated just behind the first, their tips 
recurved ; hooks of the third pair 0-025-0-028 mm. long and broad and 
flat with slender recurved tips, situated lateral to the second. Hooklets 
0-01 mm. long. Gut : mouth 0-15 mm. from the anterior extremity. 
Pharynx nearly globular, 0-10 mm. long and 0-12 mm. broad. (Eso- 
phagus very short or absent. Caeca very long and unbranched. 
Reproductive systems : common genital pore situated on the left of 
the pharynx. Cirrus pouch arranged diagonally, 0-16 mm. long and 
0-04 mm. broad, its base crossing the median plane. Testes elongate 
oval and side by side near the middle of the body, dimensions 0-18 x 
0-08 mm. Ovary ovoid and situated just in front of the testes, 
ootype a little farther forward. Vagina short, its pore near the 
inner margin of the left caecum about 0-06 mm. behind the pharynx. 

Sub-order POLYOPISTHOCOTYLEA Odhner, 1912. 

(Polycotyla Blainville, 1828; Octobothrii E. Blanchard, 1847; Eupoly- 
cotylea Diesing, 1850; Polycotylea Diesing, 1850, in part.) 

Prohaptor an oral sucker, or 2 buccal suckers, or 2 ventral grooves 
or bothria. Opisthaptor very variable, but always comprising suckers 
or clamps with or without hooks. Eyes rarely present. Vagina present 
or absent. Genito -intestinal canal invariably present. 

Super-family POLYSTOMATOIDEA Price, 1936. 

Prohaptor a terminal or slightly ventral oral sucker. Opisthaptor 
comprising a cotylophore which generally bears 3 pairs of cup-like 



80 THE TREMATODA OF BRITISH FISHES 

suckers and 1-3 pairs of hooks. Suckers sometimes provided each 
with a hook, which is large in Hexabothriidse, but small in Poly- 
stomatidge. Gut comprising a short pre -pharynx, a spherical pharynx, 
a short oesophagus and a pair of caeca with or without diverticula or 
anastomoses. Eyes generally absent. Genital pores debouching in 
an atrium on the ventral surface of the body. Testis single, but 
numerous testes sometimes present. Ovary situated anterior to the 
testis or testes. Vagina double, the openings lateral. Hosts : Amphibia, 
Reptilia and Fishes, rarely Mammalia. Type family : Polystomatidae 
Gamble, 1896, parasites of amphibians and reptiles. 



Family HEXABOTHRIID^ Price, 1942. 

(Onchocotylidse Monticelli, 1903.) 

Prohaptor a fairly well developed oral sucker, or two ventro- 
lateral grooves or bothria. Opisthaptor a circular or rectangular 
disk bearing 3 pairs of suckers, each of which has a large crescentic 
hook and an appendix bearing 1 pair of small terminal suckers and 
1-3 pairs of hooklets. Eyes generally absent, but present in the 
Diclybothriinae. Genital pore median and ventral. Cirrus generally 
devoid of hooklets or spinelets. Testes numerous. Ovary relatively 
large, elongate and folded, the folds situated in front of the testes. 
Vagina double. Hosts fishes, particularly Selachii. In Diclybothriinae 
the appendix of the opisthaptor has 3 pairs of large hooks, in other 
sub -families only 1 pair of small hooks. In Rajonchocotylinse the 
vaginae form a median duct, which enters the vitelline reservoir ; in 
Hexabothriinse they are discrete and open separately into this chamber. 



Sub-family Hexabothriin^ Price, 1942. 

(Onchocotylinae Cerfontaine, 1899 ; Diaphorocotylinte Monticelli, 1903, 

in part.) 

Prohaptor an oral sucker. Opisthaptor comprising a somewhat 
rectangular cotylophore bearing 3 pairs of suckers and a relatively 
long appendix having 1 pair of small and almost terminal muscular 
suckers and 1 pair of hooks. Roots of the large hooks not abruptly 
narrowed at the base of the blade. Vaginas, entering the vitelline 
reservoir separately. Eggs each having a process at one pole or both 
poles, but lacking meridional ridges. 

In Hexabothrium the cirrus is equipped with spinelets, in other 
European genera it is not, but according to Price (1942) the extension 
of vitelline follicles into the appendix of the opisthaptor distinguished 
Neoerpocotyle from Erpocotyle, in which they do not. This does not 
seem to be a reliable criterion of generic distinction, and Neoerpocotyle 
is probably a synonym of Erpocotyle. 



HEXABOTHRIIDJE 81 

Genus HEXABOTHRIUM Nordmann, 1840. 

(Onchocotyle Diesing, 1850 ; Acanthonchocotyle Cerfontaine, 1899.) 

Hooks on the opisthaptor proper of about equal size. Cirrus 
equipped with spinelets. Vitellaria not extending into the appendix. 
Eggs with one polar prolongation. 

Hexabothrium appendiculatum (Kuhn, 1829), Nordmann, 1840 (p. 601). 

Polystoma appendiculatum Kuhn, 1829 (pp. 460-3, PI. 11, figs. 1-3) ; Oncho- 
cotyle appendiculata (Kuhn) of Diesing, 1850 (p. 419) and authors ; Acan- 
thonchocotyle appendiculata (Kuhn) Cerfontaine, 1899 (pp. 461-2, PI. 19, 
figs. 6, 14a). 

Host : nurse hound. 
Location : gills. 

This species occurs in the Mediterranean and at Roscoff. Accord- 
ing to Price (1942, p. 40, footnote) the specimens found in Britain 
and referred to this species by T. Scott (1901, p. 151, PL 8, figs. 30-31 ; 
1912, PI. 27, figs. 11, 12) probably belong to the genus Baj onchocotyle, 
because parasites of the skate and thornback ray, while specimens 
found by Lebour (1908a, p. 44, PL 5, figs. 9-12) belong to Erpocotyle. 
In neither case can precise allocations be made, the descriptions being 
incomplete. Price claimed that the distinguishing characters were 
established by Cerfontaine, who examined a single specimen from what 
is regarded as the type-host, the original and a later description by 
Nordmann (1832) alike being insufficient for specific diagnosis. Accord- 
ing to Cerfontaine this species has the following characters, although 
Olsson (1875, p. 11) found specimens 8-10 mm. long : — Size : 6-7 mm. 
long. Opisthaptor not strictly rectangular, but rounded towards the 
base of the appendix. Hooks of the third pair of suckers smaller than 
those of the first two pairs. Reproductive systems : genital armature 
comprising numerous hooklets which are spike -like and larger than 
those of H. canicula (q.v.), their bases also being larger relative to the 
points. 

Hexabothrium canicula (Cerfontaine, 1899) Price, 1942. (Fig. 12 I.) 

Onchocotyle appendiculata (Kuhn) of Stossich, 1877 ; Acanthonchocotyle cani- 
cula Cerfontaine, 1899 (p. 462, PI. 19, figs. 5, 13, 146, c). 

Hosts : rough hound, nurse hound. 
Location : gills. 

This species occurs off the coast of Belgium, at Roscoff, Naples 
and Trieste. According to Cerfontaine the opisthaptor is rounded 
posteriorly and the hooks of the suckers of the third pair are smaller 
than the others, their claws very small. Reproductive systems : genital 
armature consisting of numerous spike-like hooklets of a feebler nature 
than those of the previous species, their bases less marked off from the 
points. Vagina double, but the two canals very short. Eggs each 
having a single polar filament several times the length of the capsule, 
which is about 0-160 mm. long and 009 mm. broad. 

6 



82 



THE TEEMATODA OF BRITISH FISHES 




Fig. 12. — A-F, Neoerpocotyle catenulata : A, entire trematode ; B, diagram 
of the genital organs, snowing the long and convoluted oviduct ; C, a 
chain of three eggs ; D, the hooklets borne on the appendage of the 
opisthaptor ; E, the hooks from the large suckers on one side ; F, the 
claw and part of the shaft of a hook. G-H, Erpocotyle Icevis : G, the claw 
and part of the shaft of a hook ; H, two eggs of slightly different form. 
I, the egg of Hexabothrium canicula. J, the egg of Erpocotyle borealis. 
(J, after Beneden, 1853 ; remainder after Guberlet, 1933.) 



HEXABOTHRIID^] 83 

Guberlet (1933, p. 327, PL 4, fig. 6) found this species on the gills 
of both hosts at Naples. His specimens were relatively small (3-4-5 
mm. long) and not very evident on the host when alive, lacking con- 
trast with the colour and texture of the branchial filaments, but they 
were readily recognizable by the characters specified by Cerfontaine, 
especially the size and shape of the hooklets surrounding the genital 
pore and the egg with its single polar filament (Fig. 12 I). 

Other Species. 

The only remaining species of Hexabothrium is H. musteli (Mac- 
Callum, 1931) Price, 1942 (Acanthonchocotyle musteli MacCallum, 
1931 ; Onchocotyle musteli (MacCallum) Dollfus, 1937), a parasite on 
the gills of Mustelus canis in U.S.A. (Woods Hole). It has curved 
genital hooklets. 

Genus ERPOCOTYLE Beneden & Hesse, 1863. 

(Squalonchocotyle Cerfontaine, 1899 ; Erpetocotyle of Fuhrmann, 1928.) 

Cirrus devoid of hooklets or spinelets. Vitellaria not extending 
into the appendix. Eggs each having two polar prolongations. Other 
characters as in Hexabothrium. 

Erpocotyle laevis Beneden & Hesse, 1863. (Fig. 12 G, H.) 

Polystomum appendiculatum Thaer, 1850 (pp. 602-3, Pis. 20-22, figs. 1-45), 
nee Kuhn, 1829, in part ; Squalonchocotyle vulgaris Cerfontaine, 1899 (pp. 
457-8, PI. 18, figs. 3, 4, 9 ; PI. 19, fig. 1 ; PI. 20, figs. 5, 8-11 ; PI. 21, figs. 
3, 5, 7, 9). 

Hosts : smooth hound. 
Location : gills. 

This species was found near Brest and occurs elsewhere on the 
continental coast (Roscoff) and in the Adriatic. I have found two 
specimens on the smooth hound at Plymouth. According to Price 
(1942, p. 41) it cannot be identified from the original description (see 
Beneden & Hesse, 1864, pp. 87-9, PI. 7 bis, figs. 1-9), but more or less 
circumstantial evidence enables the identity of the species to be estab- 
lished and the genus to be revived. This conclusion is reached in view of 
the degree of host specificity shown by Monogenea. Price was satisfied 
that this species is congeneric with species allocated by Cerfontaine 
(1899) to the genus Squalonchocotyle and, taking two of these (vulgaris 
and catenulata) into consideration, concluded (on the basis of an 
assumption that the distribution of the vitelline follicles into the 
appendix of the opisthaptor, or only to the end of the body proper, is 
a valid character of taxonomic importance) that the form which most 
closely resembles Erpocotyle lozvis is Squalonchocotyle vulgaris, which is 
regarded as a synonym of Beneden & Hesse's species, so that the 
genus Erpocotyle can be recognized and utilized. 

According to Cerfontaine (1899, p. 457) for "Squalonchocotyle 
vulgaris " (my observations, based on two specimens, shown in paren- 
theses) : — Size : about 12 mm. long, but very extensile to three times 



84 THE TREMATODA OF BRITISH FISHES 

the normal length, then forming a slender cylinder (9-2 mm. long 
and 1-05 mm. broad). Colour dark brown. Cuticle bearing small 
tubercles, which approach the opening of the bell-like oral sucker, but 
do not occur in its cavity (very insignificant). Opisthaptor (T85 mm. 
long, the appendix measuring 1-18 x 0-30 mm.). Claw of each large 
hook bent in a right angle (confirmed), its base clearly separated from 
the shaft and of smaller girth (respective breadths 0-043 mm. and 
0-029 mm.). Hooklets (0*06 mm. long, neglecting curvature) each 
having very unequal roots, the ventral long (0*040 mm.) and curved, 
the dorsal shorter (0-018 mm.) and narrower (tips of the roots 0-04 mm. 
apart). (Suckers 0-40-0-45 mm. diameter, suckerlets 0-25 mm. long 
and 0-16 mm. broad, constricted near the base.) Gut : intestinal 
crura having median and lateral diverticula along their entire length 
(a single median diverticulum extending into the appendix almost to 
the suckerlets). Reproductive systems : (genital pore median, close 
behind the pharynx and 0-88 mm. from the anterior extremity.) 
Vaginal pores slightly behind the level of the genital pore and at the 
lateral margins of the body (confirmed ; position about 0-1 mm. behind 
the level of the genital pore). Cirrus short and more or less globular 
when evaginated (about 0-11 mm. diameter). Uterus following a 
straight course between the ootype and the genital atrium (confirmed). 
Eggs each having two short and straight polar filaments which are 
about as long as the capsule, i.e. 0-200 mm. long (overall length of egg 
and filaments about 0-52 mm., capsule about 0-24 mm. long, anterior 
and posterior filaments 0-11 mm. and 0-17 mm. respectively). 

Guberlet (1933, p. 327, PL 4, figs. 3, 5, 9) found several specimens 
of this species associated with Neoerpocotyle catenulata on the gills of 
Mustelus Icevis at Naples. They were 10-12 mm. long and 0-8-1-4 
mm. broad and the suckers of the opisthaptor were of different sizes, 
those of the third pair smaller than the rest and having hooks 0-87 
mm. long as against 1-2 mm. This was not so in my specimens, the 
suckers being about 0-40 mm., 0-45 mm. and 0-45 mm. diameter 
respectively, the mean length of the hooks (for the two sides) 0-71 mm., 
0-98 mm. and 0-82 mm. Guberlet also observed that the cuticular 
tubercles tend to disappear in preserved specimens, and that the spine - 
lets on the shafts of the hooks near the claw vary both in different 
suckers of the same individual and in different specimens, numbering 
6-10. He determined the size of the egg as 0-22 x 0-06 mm., the 
filaments being 0-13 mm. long. 

Erpocotyle abbreviata (Olsson, 1876) Price, 1942. 

Onchocotyle abbreviata Olsson, 1876 (p. 12, PI. 2, figs. 27, 28) ; Squalonchocotyle 
abbreviata (Olsson) of Cerfontaine, 1899 (p. 375, PI. 19, fig. 3). 

Host : piked dogfish. 

Location : gills. 

This species has been found in the Skagerrak and at Roscoff, but 
not in Britain. According to Cerfontaine (1899) it shares some 
characters with E. canis, but is 7-8 mm. long and has distinctive large 



HEXABOTHRIID^ 85 

hooks, the claw being relatively long, distinct from the shaft, bent at 
a right angle, but having a straight point. Hooklets having straight 
roots. Caeca with median and lateral diverticula, the former not 
well developed. Cirrus long and cylindrical ; seminal vesicle clearly 
differentiated. Uterus more or less convoluted ; vaginal pores as in E. 
cants ; eggs about 0-100 mm. long and with two long polar filaments. 

Erpocotyle canis (Cerfontaine, 1899) Price, 1942. 

Squalonchocotyle canis Cerfontaine, 1899 (pp. 458-9, PI. 18, figs. 1, 2, 7, 12 ; 
PI. 19, fig. 2 ; PI. 20, fig. 12 ; PL 21, figs, 2, 6, 10) ; Onchocotyle appendi- 
culata of Beneden, 1858, nee Kuhn, 1829). 

Host : tope. . 

Location : gills. 

This species has been found off the coast of Belgium and at Roscoff , 
but not in Britain. According to Cerfontaine it has the following 
characters : — Size : 7-8 mm. long. Cuticle bearing tubercles, which 
occur also in the cavities of the haptors. Opisthaptor having large 
hooks of distinctive shape, the claw bent in a right angle, the curve 
continuing to the tip, the base of nearly the same girth as the shaft. 
Large suckers having fleshy rims. Hooklets having short roots, the 
space between these shallow, so that whole shape is triangular, the 
points having two sharp bends. Gut : caeca having median and lateral 
diverticula. Reproductive systems : oviduct displaying several con- 
volutions. Vaginal pores situated just behind the level of the genital 
pore and midway between the median plane and the margin of the 
body. Cirrus long and cylindrical, seminal vesicle having a valve 
at its base. Eggs about 0-100 mm. long, each having two very long 
filaments, but in some instances only one filament, both kinds of egg 
occurring in the same specimen. 

Erpocotyle borealis (Beneden, 1853) Price, 1942. (Fig. 12 J.) 

Onchocotyle borealis Beneden, 1853 (pp. 59-68, figs. 1-11) ; Squalonchocotyle 
borealis (Beneden) of Cerfontaine, 1899 (pp. 456-7, PI. 18, fig. 13 ; PL 19, 
fig. 7 ; PL 20, figs. 13, 14 ; PL 21, fig. 16). 

Host : Greenland shark. 
Location : gills. 

This species has been found near Greenland, in the Skagerrak and 
off the coast of Belgium, but not in Britain. According to Cerfon- 
taine it is 20 mm. long, but Beneden's specimens were 25-30 mm. long 
and 3-4 mm. broad. The claw of each large hook is regularly curved, 
its base continuing the shaft, and the hooklets have a dorsal root 
opposite the point which is longer and more delicate than the ventral, 
the two being separated by a fairly deep space, which Beneden failed 
to observe. The caeca have lateral diverticula which do not anastomose 
throughout their length, but median diverticula of small size only 
anterior to the gonads. Reproductive systems : vas deferens very long 
and convoluted. Vaginal pores a little behind the level of the genital 
pore and halfway between the median plane and the margin of the 



86 



THE TREMATODA OF BRITISH FISHES 




Fig. 13. — A-C, Erpocotyle galeorhini (Sq. abbreviata form A of Dollfus, 
1937) : A, anterior region ; B, a group of eggs ; C, one of the hooks. 
D-G, Erpocotyle eugalei (Sq. abbreviata form B of Dollfus) : D, anterior 
region, showing a chain of eggs leaving the body ; E, one of the hooks ; 
F, a hooklet ; G, region of the body containing the female reproductive 
organs, showing especially the long and convoluted oviduct. H-K, 
Erpocotyle dollfusi (Sq. abbreviata form D of Dollfus) : H, entire animal 
in ventral view ; I, one of the hooks ; J, the anterior region ; K, the 
region of the body containing the reproductive organs. (After Dollfus, 
1937.) 



HEXABOTHRIIDiE 87 

body. Eggs very large, about 0-250 mm. long, and equipped with 
two short polar filaments, which are not longer than the capsule and 
are sometimes folded down on it. 

A number of other species of Erpocotyle occur outside Britain. 
Dollfus (1937) recognized four forms of Squalonchocotyle abbreviate 
(Olsson) which, according to Price (1942), form separate and distinct 
species. All these forms were found on Selachii near the coast of 
Morocco. E. galeorhini Price, 1942 (form A of Dollfus, 1937, p. 402, 
figs. 1-3 ) (Fig. 13 A-C) , on the smooth hound near Rio de Oro ; E. eugalei 
Price, 1942 (form B of Dollfus, 1937, p. 405, figs. 7-12) (Fig. 13 D-G), 
on the tope near Agadir ; E. torpedinis Price, 1942 (form C of Dollfus, 
1937, p. 410, figs. 13-18) ; on the torpedo (T. marmorata) on the Atlantic 
coast of Morocco ; and E. dollfusi Price, 1942 (form D of Dollfus, 1937, 
p. 411, figs. 19-24) (Fig. 13 H-K), on the spinous shark at Rabat. 
These forms — they are hardly likely to remain valid species — differ 
particularly in size, the shapes of the hooks and the form of the eggs 
(Fig. 13). Five other species occur in North America and one in Japan. 

Genus NE0ERP0C0TYLE Price, 1942. 

(Squalonchocotyle Cerfontaine, 1899, in part.) 

Vitellaria extending into the appendix of the opisthaptor. Other 
characters as in Erpocotyle. 

Neoerpocotyle grisea (Cerfontaine, 1899) Price, 1942. 

Onchocotyle appendiculata Taschenberg, 1879 (pp. 24-7, PI. 3, figs. 1-3 ; PI. 4, 
figs. 1, 3-6; Squalonchocotyle grisea Cerfontaine, 1899 (p. 376, PI. 19, fig. 8). 

Host : 6-gilled shark. 

Location : gills. 

This species has been found at Naples and Trieste and also off the 
west coast of Ireland. According to Cerfontaine (1899, p. 461) it is 
about 15 mm. long. The claws of the hooks are not clearly marked off 
from the shaft and are curved at a right angle to it. The hooklets are 
Y-shaped, the roots and point being of about equal size, and the ventral 
root bent towards its own side and terminating in a minute knob. 
The vaginal pores are situated near the genital pore at the level of the 
excretory pores, and the eggs have two short filaments only half as 
long as the capsule, which is about 0-175 mm. long and gradually 
tapers towards the poles. 

Neoerpocotyle catenulata (Guberlet, 1933) Price, 1942. 

(Fig. 12 A-F.) 

Squalonchocotyle catenulata Guberlet, 1933 (p. 328, PI. 4, figs. 1, 2, 4, 7, 8, 10) ; 
Poly stoma appendiculatum Thaer, 1850, nee Kuhn, 1829, in part. 

Host : smooth hound. 
Location : gills. 

This species was discovered at Naples, where Guberlet found four 
out of six hosts parasitized, one with more than fifty worms, most of 
which were immature, but clearly recognizable. It is 7-11 mm. long 



88 THE TKEMATODA OF BRITISH FISHES 

and 1-5 and 1 mm. in greatest breadth and thickness ; the oral sucker 
is 0-5 mm. diameter and the suckers of the rectangular opisthaptor 
are arranged in two parallel rows, those of the most posterior pair 
being slightly the smallest. Each hook has a smooth shaft with a 
slight lateral ridge and a long and sharply-bent claw, and the hooks 
of the most posterior pair are smaller than the remainder, 1-64 mm. 
long instead of 1-80 mm. The appendix is almost cylindrical, about 
2 mm. long and 0-75 mm. thick, its two curved hooklets 0-07-0-08 mm. 
long, each of them having two roots. The internal anatomy was 
described in great detail, which must be neglected here, although 
essential details can be made out in the figure. The distal part of 
the oviduct is notably relatively very long and convoluted, and the 
vaginal pores are situated in the same transverse plane as the genital 
pore and midway between it and the margins of the body, the vaginae 
being long and straight, their girth uniform as they extend back to 
meet the anterior ends of the main vitelloducts. The eggs are pale 
brown, measure 0-127-0-141 x 0-052-0-066 mm. and each has two 
very long filaments 0-3-0-7 mm. long, which are continuous with those 
of adjacent eggs. The eggs are discharged in groups of 10-65, appearing 
in chains of 35 or more, one worm being observed to lay 140 eggs in 
three masses at one time. 

One other species of this genus is N. licha (Rees & Llewellyn, 1941), 
which was found on the gills of Scymnorhinus licha on Porcupine Bank 
(Atlantic seaboard), but has not been described. Five other species 
are known, all of them occurring in North America. 

Sub-family Rajonchocotylin^ Price, 1942. 

Opisthaptor a circular disk bearing 3 pairs of large suckers and 
a postero-dorsal appendix having 1 pair of small suckers. Ovary 
situated in front of the middle of the body. Vaginal joining to form a 
single duct before entering the vitelline reservoir. Eggs devoid of 
polar filaments, but provided with meridional ridges. The two genera 
Eajonchocotyle and Bajonchocotyloides are distinguishable, according to 
Price (1942), by the extension of the vitellaria into the appendix in the 
latter, but not in the former. It is likely that the latter genus will 
ultimately fall as this character is unreliable. 

Genus RAJ0NCH0C0TYLE Cerfontaine, 1899. 

Opisthaptor circular. Ovary in the anterior half of the body. 
Vaginae forming one duct entering the vitelline reservoir, vitellaria 
excluded from the opisthaptor. 

Rajonchocotyle batis Cerfontaine, 1899. (Fig. 14 N-P.) 
Onchocotyle appendiculata Olsson, 1867, nee Kuhn, 1829. 
Host : skate. 
Location : gills. 

This species occurs in the Skagerrak and off the coast of Belgium, 
also off the West coast of Ireland (Irish Atlantic Slope and Porcupine 



HEXABOTHRIIDiE 89 

Bank ; see Rees & Llewellyn, 1941), at Plymouth and elsewhere round 
our coast. According to Cerfontaine (1899, pp. 462-3, PI. 19, figs. 11, 12 ; 
PI. 21, fig. 12) it is 12-15 mm. long. The disk is circular and the 
suckers very large. The hooks are distinctive, the shaft tapering 
sharply in a straight chamfer near the base of the claw, the surfaces of 
contact being of equal girth. The hooklets each have 3 delicate 
branches, that carrying the claw being very short and having a hump 
on the dorsal and more convex side, the others being the roots. The 
vaginal pores are situated far behind the level of the genital pore and 
not far from the median plane, the median vaginal canal being long. 
The eggs have a small tubercle at one pole and are about 0-175 mm. 
long. 

Rajonchocotyle alba Cerfontaine, 1899. (Fig. 14 F-J.) 

Host : burton skate. 
Location : gills. 

This species was discovered at Roscoff and, according to Cerfon- 
taine (1899, pp. 463-4, PI. 18, figs. 5, 6, 8 ; PI. 19, fig. 9 ; PI. 20, figs. 
1-3, 6, 7 ; PI. 21, figs. 1, 4, 8, 11, 13-15) is 8-9 mm. long, the hooks 
long and of uniform girth and tapering near the base of the claw, but 
not in a straight chamfer as in the previous species. Hooklets with 
unequal roots, the dorsal the more massive, and a shallow cleft between 
them. Vaginal pores situated behind the genital pore and midway 
between the median plane and the margins of the body, the median 
vagina short. Eggs having a tubercle at one pole and about 0-180 
mm. long. 

Rajonchocotyle prenanti (Saint-Remy, 1890) Cerfontaine, 1899. 

(Fig. 14 K-M.) 

Onchocotyle prenanti St Remy, 1890 (pp. 41-3) ; O. borealis Stossich, 1885 
(p. 162), nee Beneden, 1853. 

Host : long-nosed skate. 
Location : gills. 

This species has been found at Trieste and at Roscoff, but not 
in Britain. According to Cerfontaine (1899, p. 464, PI. 18, figs. 10, 
11 ; PI. 19, fig. 10 ; PI. 20, fig. 4) it is 8-9 mm. long, the large hooks 
are shorter and of more uniform girth than in the previous species, 
but the tapering of the shaft near the base of the claw is very marked. 
The hooklets have roots between which there is a deep notch. The 
eggs have a tubercle at either pole and are very large, about 0-220 mm. 
long. 

Rajonchocotyle miraletus Rees & Llewellyn, 1941. 

This species was recorded on the gills of the cuckoo ray at Porcupine 
Bank, but has not been described. 



90 THE TKEMATODA OF BRITISH FISHES 

Genus RAJONCHOCOTYLOIDES Price, 1940. 

Vitellaria extending into the appendix. Other characters as in 
Rajonchocotyle. 

Rajonchocotyloides emarginata (Olsson, 1876) Price, 1940. 

(Fig. 14 A-E.) 

Onchocotyle emarginata Olsson, 1876 (pp. 11-12, PI. 2, figs. 23-26) ; O. appen- 
diculata Sonsino, 1891, nee Kuhn, 1829. 

Host : thornback ray. 
Location : gills. 

Price (1940a, p. 76, fig. 1) redescribed this species from a specimen 
sent from Britain and forming part of the collection made at Plymouth 
by Baylis & Idris Jones (1933). Olsson's description was also based 
on a single specimen, which seems to have been mutilated, having 
an opisthaptor with 2 instead of the usual 6 large suckers. It was 
unusual also in having vitellaria which extended into the appendix of 
the opisthaptor, but agreed with the British specimen in this, so that 
Price felt justified in erecting a new genus on account of this character. 
That the two specimens belonged to the same species was assumed on 
this account and because they were found on the same host species. 
The following characters were determined by Price, but my deter- 
minations for six specimens found at Plymouth are given in paren- 
theses. Size : body 5 mm. long (2-5-4-2 mm.) and 1-8 mm. broad 
(0-55-1-10 mm.). {Note.— Olsson (1865, p. 11) gave the length as 12 
mm., the breadth as 0-9 mm., so that his specimen was much more 
elongate than those under consideration ; see also PL 2, fig. 23.) 
Shape : body tapering from its posterior part to an acute point 
anteriorly (not as fusiform, more truncated anteriorly). Prohaptor 
an oral sucker about 0-285 mm. diameter (transversely oval, 0-29- 
0-31 mm. broad and 0-20-0-23 mm. long) (0-4 mm. in Olsson's specimen). 
Opisthaptor about 2-5 mm. diameter (1-35-1-75 mm., the cotylophore 
itself about 0-60-0-75 mm.), having 6 suckers arranged in a circle 
and an appendix 1-36 mm. long and 0-51 mm. wide (1-15-1-20 x 0-28- 
0-48 mm.) terminating in a pair of muscular suckers (which may be 
more deeply situated on account of a superficial invagination) . Large 
suckers about 0-595 mm. diameter (0-35-0-40 mm. diameter in 
small specimens, 0-50 X 0-45 mm. in larger), each containing one 
large hook about 1-14 mm. long (0-68-1-08 mm.). Suckers of the 
appendix about 0-322 mm. long and 0-15 mm. broad (0-16-0-28 x 
0-11-0-17 mm.), constricted at the proximal end (lined with deeply- 
staining material, probably thick cuticle). Small hooks of the 
appendix situated between the small suckers and about 0-04 mm. 
long (up to 0-04 mm. long and 0-02 mm. wide between the bases 
of the roots). Gut : pharynx 0-15 mm. long and 0-115 mm. broad 
(0-11 x 0-095 mm.-0-12 mm. diameter). (Esophagus very short. 
Intestinal crura provided with median and lateral diverticula and 
uniting posteriorly, giving off several short diverticula in the opis- 



HEXABOTHRIID^ 



91 



thaptor and sending a single stem into the appendix almost to the level 
of the small suckers (confirmed). Reproductive systems : genital pore 
situated near the bifurcation of the intestine and 0-475 mm. from the 
anterior extremity (sometimes closer to it). Testes numerous, occupy- 
ing the space between the intestinal crura in the posterior half of the 
body proper (generally extending into the forebody). Ovary looped 




Fig. 14. — A-E, Rajonchocotyloides emarginata : A, entire trematode ; B, 
a small hook ; C, the tip, and D, the whole of a large hook. E, the 
egg. F-J, Rajonchocotyle alba : F, the female organs ; G, the egg ; H 
and I, the whole and the tip of a large hook ; J, a small hook. K-M, 
Rajonchocotyle prenanti : K, the egg ; L, the tip of a large hook ; M, 
a small hook. N-P, Rajonchocotyle batis : N, the tip of a large hook ; 
O, the egg ; P, a small hook. (A-E, after Price, 1940 ; F-P, after 
Cerfontaine, 1899.) 



several times and situated on the right at or slightly in front of the 
midbody anterior to the testes (sometimes considerably in front of the 
midbody). Receptaculum seminis large and situated on the left near 
the ovary. Vitefiaria extending from the level of the genital pore to 
near the tip of the appendix, the follicles following the course of the 
intestine (present in the appendix to very variable extent). Vitelline 
reservoir elongate and situated in front of the ovary. Uterus long 
(forming a few small folds between the gonads and the genital pore). 
Eggs Rugby-football- shaped and very large, measuring 0-170-0-197 x 
0-080-0-097 mm. (0-183-0-219 x 0-067-0-086 mm.), also provided with 
meridional bands. 



92 THE TREMATODA OF BRITISH FISHES 

Sub-family DiCLYBOTHRiiNiE Price, 1936. 

Prohaptor 2 ventro- lateral bothria. Opisthaptor : 3 pairs of 
suckers, each having a large hook, and a posterior lobe bearing 1 
pair of small suckers and 3 pairs of large hooks, two of them similar 
to those of the two large suckers. Eyes present. 



Genus DICLYBOTHRIUM Leuckart, 1835. 

(Diplobothrium Leuckart, 1842.) 

Diclybothrium armatum Leuckart, 1835. (Fig. 15 A-G.) 

Diclibothrium armatum Leuckart, 1835 (p. 764) ; Diklibothrium crassicau- 
datum Leuckart, in Kollar, 1836 (p. 219) ; Diplobothrium armatum Leuc- 
kart, 1842 (pp. 13-18, PI. 1, fig. 6 a-f) ; Hexacotyle elegans Nordmann, 
1840 (p. 597) ; Polystoma (Hexacotyle) armatum (Leuckart) of Dujardin, 
1845 (p. 319) ; ? Erpocotyle circularis Linstow, 1904 (pp. 493-4, figs. 18-20 
[in some offsets pp. 17-18, figs. 1-3]) ; ? Diclibothrium circularis (Linstow) 
of Skwortzoff, 1928 (pp. 563-73, figs. 4-13). 

Hosts : various sturgeons. 
Location : gills. 

This trematode has been found in Russia and elsewhere in Europe 
and occurs in Canada and U.S.A., and was recently described by Price 
(1942, pp. 53-4, figs. 1 M, N ; 2 O, P ; 3 M), who was unable to decide 
with certainty whether all the forms which have been found in stur- 
geons are distinct or belong to the same species, study of specimens 
from European sturgeons being the only means of settling the problem. 
This species has not been recorded in Britain, but it is likely to turn 
up and for that reason a brief diagnosis must be given, the data for 
D. circularis of Skwortzoff being given in parentheses. Size : 2-5-13 
mm. long and 0-22-1-1 mm. broad (3-25-5-88 x 0-41-0-85 mm.). 
Shape elongate and elliptical in section. (Eyes : 2 pairs situated 
dorso -lateral to the pharynx.) Prohaptor : 2 ventral bothria 0-08- 
0-15 mm. wide. Opisthaptor circular or rectangular, 0-32-1 mm. long 
and 0-32-0-8 mm. wide (0-55 x 0-57 mm.), having 6 nearly or quite 
sessile suckers each provided with a large hook, and with a triangular 
posterior appendix 0-22-0-32 mm. long (0-14 mm. ventrally ; 0-2 mm. 
dorsally) and 0-12-0-24 mm. wide bearing 1 pair of small muscular 
suckers and 3 pairs of hooks. Suckers of the main part of the 
opisthaptor 0-20-0-37 mm. diameter (0-21-0-22 mm.), hooks 0-40-0-47 
mm. long. Suckers of the appendix about 0-06 mm. long ; hooks of 
the outer pair 0-44—0-54 mm. long (0-32 mm.), directed postero- 
ventrally ; hooks of the second pair similar to the outer and 0-34- 
0-35 mm. long (0-25 mm.), directed postero-dorsally ; hooks of the 
third pair straight and 0-10-0-12 mm. long (0-08 mm.) and situated 
near the tip of the lobe and directed antero-ventrally. Gut : mouth 
ventral and 0-14-0-40 mm. from the anterior extremity. Pharynx 
ovoid, 0-06-0-10 mm. long and 0-06-0-10 mm. broad (0-1 X 0-08 mm.) 



HEXABOTHKIIDiE 



93 



(oesophagus practically absent, caeca long and united posteriorly). 
Excretory system : pores dorso-lateral at the same level as the posterior 
end of the cirrus. Reproductive systems : genital pore median and 
0-24-0-68 mm. from the anterior extremity (cirrus pouch 0-21 mm. 




Fig. 15. — A-C, " Diclibothrium circularis " : A, the entire trematode (ventral 
view) ; B, the appendix of the opisthaptor (ventral view) ; C, the same 
as B, in side view. D-G, Diclybothrium armatum : D, the entire tre- 
matode (ventral view) ; E, the egg ; F, a hook from one of the suckers ; 
G, hooks from the appendage of the opisthaptor. In B-G, a, b, c repre- 
sent hooks of the 1st, 2nd and 3rd pairs. (A-C, after Skwortzoff, 1928 ; 
D-G, after Price, 1942.) 



long and 0-12 mm. broad), cirrus muscular and 0-16-0-32 mm. long 
(0-05 mm.) and 0-05-0-16 mm. broad, its eversible tip armed with 
short and thickly- set spines extending about 0-04 mm. behind the 
point. Seminal vesicle pyriform, measuring 0-10-0-24 x 0-08-0-18 
mm. (0-14-0-16 mm. long), connected to the base of the cirrus by a 



94 THE TREMATODA OF BRITISH FISHES 

narrow region. Testes very numerous (300 or more), ovary tubular 
and much convoluted, situated near the end of the first one-quarter 
of the body. Vitellaria lateral (extending ventrally and dorsally) 
between the vaginal pores and the posterior end of the body proper 
(ending a short distance in front of the opisthaptor). Receptaculum 
seminis elongate and 0-2 mm. long, situated on the left of the ovary. 
Vaginal pores slightly dorsal and 0-45-1-5 mm. from the anterior 
extremity. Ootype and shell glands situated in front of the ovary. 
Uterus long and sinuous in the median plane. Eggs very large, 
measuring 0-208-0-224 x 0-088-0-140 mm. (0-11-0-14 mm. long), 
polar processes absent. (Note. — Infection with this trematode may be 
heavy. Skwortzoff found 1-11 specimens per host and noted a 70% 
infection of sterlets.) 

Super-family DICLIDOPHOROIDEA Price, 1936. 

Prohaptor a pair of buccal suckers. Opisthaptor a cotylophore 
bearing a paired series of suckers or clamps, or similar structures 
arising from the ventro -lateral surface of the body, sometimes pedun- 
culate, typically 8 in number, but sometimes numerous, each 
having a rather complicated cuticular skeleton of rib-like supports 
numbering 3-8, their arrangement providing familial characters. 
Terminal hooklets present in the larva sometimes persisting in the 
adult. Terminal region sometimes comprising a languet which may 
be equipped with 1-3 pairs of hooklets. Gut comprising a prepharynx, 
bulbous pharynx, short oesophagus and intestinal crura which may 
merge posteriorly and are provided with median and lateral diverticula, 
sometimes with anastomoses. Reproductive systems generally open- 
ing by a common genital pore. Cirrus sometimes equipped with 
hooklets. Ovary generally elongate and folded, situated in front of 
the testes, but sometimes having some of the testes in front of it. 
Vaginal present and generally opening dorsally, or absent. Eggs 
generally provided with filaments. Location : the gills of fishes, rarely 
the skin of fishes or their crustacean parasites. 



Family DICLIDOPHORID^ Fuhrmann, 1928. 
(Choricotylidae Rees & Llewellyn, 1941 ; Dactylocotylidae Brinkmann, 1942.) 

Opisthaptor : 4 pairs of suckers or clamps, generally peduncu- 
late, each organ having 8 cuticular bars of complex shapes, charac- 
teristically arranged ; 4 bars border the opening of the sucker or 
clamp ventrally ; 2 others are bent at right angles, one part of each 
bordering the opening of the sucker dorsally, the other being directed 
towards its centre ; the remaining 2 bars occur in the dorsal wall 
of the organ, one being T-shaped and the other continuing the stem of 

the T beyond the upper limbs (thus, T), the whole arrangement being 
cruciform. The stem of the T-piece has a lamellar extension and with 
its fellow supports the concavity of the organ. The dorsal walls of 



DICLIDOPHOMDiE 95 

the suckers are further supported by two fan-like systems of very small 
rods, each comprising 6 or 7 concentric arcs in which the numbers 
of elements vary. The base of the sucker is formed of a muscular 
cup. Terminal hooks or hooklets invariably absent in adults. Cirrus 
generally equipped with a circlet of curved and grooved (but not 
necessarily bifurcate) hooklets. Beceptaculum seminis generally 
present. Testes numerous. Ovary elongate and folded, generally 
situated in front of the testes. Vagina present or absent. Two sub- 
families can be separated by the characters of the opisthaptor, which 
consists of cup-luce suckers in the Cyclocotylinse, but pincer-like 
clamps in the Diclidophorinse. 

Sub-family Diclidophorin^ Cerfontaine, 1895, sensu Price, 1943 

In Diclidophoroides the opisthaptor is sharply marked off from the 
rest of the body ; in other genera it is not, but in Octodactylus the testes 
are situated exclusively behind the ovary, while in Diclidophora some 
occur in front of it. 



Genus DICLIDOPHORA Diesing, 1850. 

(Dactycotyle Beneden & Hesse, 1863 ; Dactylocotyle Marschall, 1873 ; 
Dactylocotyle " Parona & Perugia, 1899 " of Brinkmann, 1942a, in part.) 

Opisthaptor not sharply set off from the body and comprising 4 
pairs of pedunculate clamp-like organs. Testes numerous and located 
both in front of and behind the ovary. Eggs having polar filaments. 

Diclidophora merlangi (Kuhn, in Nordmann 1832) Kroyer [1851 ?] 

(p. 606). (Fig. 16 A-C.) 

Octostoma merlangi Kuhn, in Nordmann, 1832 (pp. 78, 82) ; Octobothrium 
platygaster Leuckart, 1842 (p. 30) ; Diclidophora longicollis Diesing, 1850 
(p. 417) ; Octoplectanum longicolle Diesing, 1859 (p. 443) ; Octobothrium 
merlangi (Kuhn) of Beneden, 1856, 1858, Monticelli, 1888, Scott, 1900, 
Lebour, 1908 ; Dactylocotyle merlangi (Kuhn) of Cerfontaine, 1895 (b, pp. 
922, 939, 942-3, PI. 1, figs. 4, 8). 

Host : whiting. 
Location : gills. 

This common trematode was found by Beneden (1870) in whiting 
caught off the coast of Belgium, and it has been found by T. Scott 
(1901) in Scotland, by A. Scott (1904) in the Irish Sea, by Lebour 
(1908a) at Cullercoats, by Nicoll (1914) and Baylis & Idris Jones (1933) 
at Plymouth, where I have found it myself, at Galway by Little (1929a) 
and at Aberystwyth by Rees & Llewellyn (1941). It is safe to say 
that it may be found on whiting caught anywhere on our coasts, and 
it occurs in the Mediterranean. Cerfontaine (1895 ; 1898a, pp. 324-5) 
found one hundred specimens, all of which came from the most anterior 
gills and gave a brief diagnosis of them. They were 8-10 mm. long, 
but apparently up to 15 mm. long after death, specimens previously 



96 



THE TREMATODA OF BRITISH FISHES 



studied by Beneden (1858, p. 49) being 14-15 mm. long. Beneden 
observed that the eggs of this trematode have at each pole a filament 
slightly shorter than the capsule itself. Lebour (1908a, pp. 40-1, PI. 
5, fig. 2) found specimens in 75% of the whiting she examined at 




Fig. 16. — A-C, Diclidophora merlangi : A, entire trematode ; B, the genital 
hooklets ; C, one of the clamps. D-F, Octodactylus palmatus : D, the 
entire trematode ; E, the egg ; F, one of the clamps. (Original.) 



Culler coats, generally two or three specimens on a host, but sometimes 
as many as six. Her specimens were about 11 mm. long and 4 mm. 
in greatest breadth. She indicated the position of the genital pore 
immediately behind the bifurcation of the gut (Cerfontaine did not 
mention it) and gave the number of genital hooklets as 12-14. She 
was unable to observe the testes and was misled by Beneden to regard 



mOLTDOPHORTD/E 97 

tliem as a single organ, although they were left out of the figure. She also 
saw the pale yellow egg and supported Beneden's observation regarding 
polar filaments. My own specimens are almost exactly of the shape 
indicated by Cerfontaine. Size : 6-8-10-2 mm. in total length, 2-1- 
2-65 mm. in greatest breadth at the level of the testes. Narrow 
anterior region 2-1-2-9 mm. long and 0-9-1-0 mm. broad, where it 
merges with the wider region. Prohaptor a pair of buccal suckers 
0-10-0-13 mm. long and 0-08 mm. broad, situated with their centres 
0-125-0-135 mm. from the anterior extremity. Opisthaptor : Cotylo- 
phore triangular, 1-7-1-8 mm. long, the breadth along anterior and 
posterior margins being 2-1-2-5 mm. and 0-35-0-45 mm. Peduncles 
equally spaced along the lateral margins of the cotylophore, of about 
equal length (0-5-0-65 mm.), those of the most posterior pair slightly 
longer than the rest, tapering slightly towards the clamps, each con- 
taining a diverticulum of the intestinal crus. Clamps also of about 
equal size, 0-33-0-37 x 0-24-0-27 mm., sclerites as in Fig. 16. {Note. — 
In the interesting specimen figured, one of the clamps of the second pair 
is of abnormally small size, suggesting malformity, but the sclerites 
show the usual arrangement, though they too are smaller and more 
slender.) Gut : pharynx about 0-22 mm. diameter (i.e. much larger 
than the buccal suckers), generally elongate oval in outline, sometimes 
broader than long, caeca having diverticula. Reproductive systems : 
genital pore median and situated 0-50-0-57 mm. from the anterior 
extremity. Genital hooklets numbering 16, each strongly curved and 
deeply grooved, but having a single sharp point. Testes numerous, 
mainly confined between the caeca and behind the ovary, but extending 
laterally to the level of the receptaculum seminis, which is bipartite 
and situated immediately in front of the ovary near the median plane. 
Ovary elongate and folded. Uterus and vas deferens median and little 
convoluted. Vitellaria abundantly developed, the follicles extending 
from just behind the genital pore to the posterior extremity, a few 
entering the base of each peduncle. Eggs not observed. 

Diclidophora denticulata (Olsson, 1876) Price, 1943. 

(Fig. 17 F-K ; 18 A-H.) 

Octobothrium denticulatum Olsson, 1876 (p. 10, PI. 1, figs. 13-17) ; Dactylo- 
cotyle denticulatum (Olsson) of Cerfontaine, 1895 (pp. 923-38) ; D. car- 
bonarii Cerfontaine, 1895 (pp. 929, 931, PI. 1, figs. 1, 5, 9, 10, 11 ; PI. 2, 
figs. 12-20. 

Hosts : coal-fish, poor cod, hake. 
Location : gills. 

This species has been recorded several times from fishes in British 
waters, by Nicoll (1915) in the coal-fish at Aberdeen, by Little 
(1929a) in the same host at Galway, by Bay lis & Idris Jones (1933) in 
the hake at Plymouth, where I have found it in the poor cod, and 
by Rees & Llewellyn in the coal-fish on the Irish Atlantic Slope. 
It was originally described from specimens found on coal -fish caught 
in the Skagerrak, and it occurs in Canada (Nova Scotia) and U.S.A. 

7 



98 



THE TREMATODA OF BRITISH FISHES 




DICLIDOPHOKIDJE - 99 

(Woods Hole). The original specimens were 7 mm. long and 2 mm. 
broad, and the description by Olsson broadly and clearly represented 
the species but contained several errors, notably the supposition that 
the gonads are compact and spherical. Cerfontaine (1895) found two 
to three specimens on each individual host, noting that they are 
generally attached to the second or third gills. His grey specimens 
were 6-13 mm. long and ripe eggs in utero gave the specimens a brown 
tinge. Cerfontaine's description of the action and structure of the 
clamps of the opisthaptor must be considered in detail, such excellence 
being a rarity in the literature. The worm applies its ventral surface 
to the surface of the gill lamella with the posterior extremity directed 
towards the branchial arch, and the clamps grasp groups of filaments 
on the internal and external surfaces (Fig. 18 A). When the worm is 
detached from the host the form is subject to change, the clamps 
curving on their peduncles towards the ventral surface of the body. 
Cerfontaine described the cuticular skeletal supports of the clamps 
in some detail. Each clamp has two valves, one dorsal and the other 
ventral, but during attachment the whole clamp undergoes torsion 
through an angle of about 90°, so that the valve which is anatomically 
ventral becomes topographically anterior so long as adhesion is main- 
tained. The rather complicated skeletal structures which support the 
clamp are best understood by reference to the following parts : 

Anterior valve : facing towards the anterior end of the worm during 
adhesion (anatomically the ventral valve). 

Posterior valve : turned towards the posterior extremity (anatomi- 
cally dorsal). 

Each valve may be regarded as possessing an external and an 
internal surface, the latter bounding the cavity, and four sides, (i) distal, 
bordering the opening, (ii) proximal, near the hinge, (iii) internal, facing 
the body of the worm, and (iv) external, facing outwards. Fig. 18 B 
represents a transparent whole mount of the most posterior clamp on 
the right (though all have fundamentally the same skeletal structure), 
with the anterior valve uppermost. We can consider the sclerites of 
the two valves separately. 

Anterior valve has a central curved sclerite, convex in front, (a), 
which is prolonged on the internal side into a cuticular plaque (b) 
occupying the internal half of the valve and terminating internally 
and below in a thick margin (c). The external half of this valve 
contains a sclerite (d), which is symmetrical with the margin (c) of the 
plaque (b) and extends along the distal margin of this region. Cen- 
trally, the external half of the valve bears numerous (about 30) small, 
cuticular teeth (e), which occupy a prominent superficial position and 
are directed obliquely in a medio -anterior direction. Each tooth has 
a thick base and a conical point. 

Posterior valve has 7 cuticular pieces or sclerites of diverse shapes. 
The most prominent, curved, median sclerite (f) is convex in a pos- 
terior direction. Two much smaller pieces (g, g) articulate with its 
distal extremity and extend along the corresponding margin of this 
valve, one along the internal, the other along the external part of the 



100 



THE TREMATODA OP BRTTJSH FISHES 




Fig. 18. — Diclidophora denticulata. A, longitudinal section passing 
through a gill-lamella of the host and the opisthaptor of the trematode, 
showing the mode of attachment ; B, one of the clamps of the opis- 
thaptor as seen in a whole mount, the anterior valve towards the 
observer ; C, D, E, F, section passing through the clamp respectively 
along the planes indicated by the lines CC, DD, EE and FF ; G, the 
male organ, showing the genital hooklets ; H, the egg (a and b, the 
ends of the short and long polar filaments respectively). For an ex- 
planation of the arrangement of the sclerites a-e in the anterior valve 
and f-k in the posterior valve see the text on p. 99. (After Cerfon- 
taine, 1895.) 



DICLIDOPHORID^ 101 

margin. A large sclerite (h) articulates with the proximal extremity 
of the median sclerite (f ) and extends along the internal, and slightly 
towards the external side at the proximal end of the valve. A small 
sclerite (i) occurs near the internal extremity of (h) and is more or 
less parallel with the median sclerite (f). Finally, two other sclerites 
extend along the external half of this valve, one (k) following the 
external margin, the other (1) articulating with the proximal end of (k) 
and passing obliquely in a medio-posterior direction. 

A number of narrow cuticular bands which vary in form and 
arrangement occur on the internal surface of the posterior valve. 
Similar structures occur on the internal surface of the anterior valve. 
The opening of the clamp is a large gap at the distal extremity, extend- 
ing some distance along the internal and external margins. During 
attachment the gill filaments of the host project through this aperture 
and are gripped by the distal extremities of the two valves (Fig. 18 A). 

Cerfontaine stressed the difficulty of gaining a comprehensive idea 
of the skeletal structures of a clamp when the organ is mounted whole 
as a transparency. His sections greatly assist comprehension and 
are reproduced in Figs. 18 C-F, the planes of section of the whole 
clamp being indicated by corresponding letters, CC-FF in Fig. 18 B 
and topographical aids being added. 

Various muscles are responsible for opening and closing the valves 
of the clamps, but their arrangement has not been worked out in 
sufficient detail. Some of them are indicated in the figures, o.m. 
representing the opening muscles, cm. the closing muscles. 

Price (1943), p. 46, figs. 2, 3) gave a detailed description of American 
specimens 7 mm. long and 1-6 mm. broad at the level of the ovary. 
My own specimen is clearly recognizable from his account and has the 
following characters : — Size : total length 5-9 mm., greatest breadth 
at the level of the ovary 1-75 mm. Cuticle slightly wrinkled. Shape 
tapering gradually from the level of the ovary anteriorly, the bluntly 
pointed anterior extremity constricted at the level of the buccal 
suckers, tapering sharply to the origin of the opisthaptor, about 3-5 
mm. from the anterior end. Prohaptor : buccal suckers ovoid, 0*21 
mm. long and 0-15 mm. broad. Opisthaptor : cotylophore narrowing 
posteriorly (to about 0-9 mm. from 1-4 mm.) ; clamps uniform in size 
and shape, borne on short, stout peduncles, their dimensions about 
0-8 x 0-5 mm. Sclerites as indicated in Fig. 17 G, H. {Note. — The 
plaque on the internal side of the anterior valve is very well developed 
in the clamps of the first three pairs, but is not evident in the clamps 
of the 4th pair (in a preparation counter-stained with light green, which 
renders the sclerites very obvious) . The cuticular supports of clamps 
of the 4th pair are rather more delicate than the others.) Gut : pharynx 
about 0-2 mm. diameter, caeca having numerous lateral diverticula, 
one at least passing into each peduncle. Reproductive systems : male 
genital pore about 0-5 mm. from the anterior extremity. Genital 
hooklets numbering 13, each deeply grooved on the outer side. Testes 
distributed within the cotylophore, as well as the posterior part of the 
body. Ovary far back in the body. Vitellaria tending to fill the 



102 THE TREMATODA OF BRITISH FISHES 

cotylophore as well as the posterior half of the rest of the body. Follicles 
progressively less numerous to the level of the male genital pore and 
a few entering the base of each peduncle. Female genital pore about 
1 mm. behind the male. Egg spindle-shaped, measuring 0-295 x 
0-08 mm., and having a curved filament much shorter than the capsule 
at the anterior pole and a long filament (length about 0-8 mm.) at the 
posterior (only part of which is shown in Olsson's fig. 14). 



Diclidophora luscae (Beneden & Hesse, 1863) Price, 1943. 

Dactycotyle Iusccb Beneden & Hesse, 1863 (1864, pp. 111-12) ; Dactylocotyle 
luscce (Beneden & Hesse) of Cerfontaine, 1895 (p. 922) ; Octobothrium 
luscce (Beneden & Hesse) of Taschenberg, 1879 (a, p. 27). 

Hosts : bib, poor cod. 
Location : gills. 

The earlier records of this trematode concern specimens found near 
Brest and at Roscoff, but Little (1929a) found the trematode in the bib 
at Galway. The original description was very imperfect and had no 
accompanying figure, conveying the impression that there is little to 
distinguish this species from D. pollachii. The length was given as 
6-7 mm. ; the genital hooklets were said to have single points, and the 
eggs two short polar filaments. For some time Cerfontaine (18956) 
failed to find the trematode, but later found it twice at Roscoff and 
described it very clearly (1898a, pp. 315-22, PL 12, figs. 1-5). Size : 
4r-7 mm. long. Shape as in D. pollachii, but more squat, the anterior 
extremity attenuated, but very short, enlargement to maximum 
breadth occuring sharply near the origins of the peduncles of clamps 
of the first pair. Colour clear grey, the gut dark brown, the eggs in 
utero imparting a brownish-yellow colour. Opisthaptor : cotylophore 
trapezoidal and broadest anteriorly, the peduncles robust, each bearing 
a characteristic clamp, the ventral valve of which has irregular nodules. 
Chit : pharynx spherical. (Esophagus fairly long. Bifurcation of the 
intestine near (behind) the level of the male pore (far in front of the 
female pore). Median and lateral diverticula not numerous. Anasto- 
moses very evident in the region of the receptaculum seminis, ovary 
and ootype (the relatively posterior positions of which are regarded 
as characteristic of the species) and in the cotylophore, the ramifica- 
tions passing into the peduncles. Intestine lined with squamous 
epithelium. Reproductive systems : male pore conspicuously anterior 
to the female pore. Testes numerous, occupying the spaces between 
the ramifications of the intestine. Vas deferens short, median and not 
very sinuous, dilating to form a vesicula seminalis near its junction 
with the male organ. Genital hooklets generally numbering 10, 
each having a short and straight base and a strongly curved blade. 
Ovary situated at the transverse level of the peduncles of the first pair, 
folded into an N-shape. Oviduct short and straight and median, 
ootype club-shaped, its expanded portion directed posteriorly and 
situated behind the ovary. Vitellaria as in other species. Recep- 



DICLIDOPHORIDJE 103 

taculum seminis situated in front of the ovary and transverse vitello- 
ducts and on the right. Vagina short and opening ventrally. Eggs 
each having a crozier-shaped filament shorter than the capsule itself at 
one pole and a long filament terminating in a funnel-like structure with 
a milled margin at the other. Crozier-shaped filaments directed 
anteriorly in utero and eggs grouped in bunches because of the entangled 
posterior filaments. 



Diclidophora pollachii (Beneden & Hesse, 1863) Price, 1943. 

Dactycotyle pollachii Beneden & Hesse, 1863 (1864, pp. 110-11, PI. 11, figs. 
23-30) ; Dactylocotyle pollachii (Beneden & Hesse) of Cerfontaine, 1895 (6, 
pp. 938, 941, PI. 1, figs. 2, 6) and 1898 (a, p. 324) ; Octobothrium pollachii 
(Beneden & Hesse, 1863) Taschenberg, 1879 (a, pp. 246-7.) 

Host : pollack. 
Location : gills. 

This species was originally found near Brest, and Cerfontaine 's 
specimens were obtained at Roscoff. T. Scott (1901, p. 150, PL 8, 
figs. 28, 29) found specimens on pollack caught in salmon-nets at Bay 
of Nigg, near Aberdeen, T. Scott (1904, p. 116) in the same host in the 
Irish Sea, and Little (1929a) has found it at Galway. T. Scott gave 
practically no description, merely giving the length as 10 mm., but he 
mentioned minute " prickles " or " spines " on the anterior valve of 
the clamps, and these could hardly have been the well -developed 
" teeth " of D. denticulate/,, and must have been nodules such as were 
seen by Cerfontaine. According to the original description, the length 
of the trematode is 5 mm., but other details are scarcely discernible, 
although the genital hooklets were said to be bifurcate and the egg 
was credited with a filament slightly longer than the capsule at one 
pole and a much longer and crozier-like process at the other. Cerfon- 
taine, who found the worms on the third gills more often than else- 
where, gave a clear diagnosis. Size : 8-13 mm. long. Shape : pointed 
anteriorly, but broadening rather abruptly in the anterior half of the 
body and of uniform breadth farther back. Colour clear dark grey, 
the ramifications of the gut appearing brown. Opisihaptor : the 
clamps and their peduncles not as robust as in D. denticulata, but larger 
than in D. merlangi, and having irregular nodules on the ventral valves. 
Gut : oesophagus shown longer than in D. denticulata and D. mer- 
langi, the crura of the intestine having far fewer median and lateral 
diverticula, particularly in the anterior region, and a few anastomoses 
in the vicinity of the haptorial disk. Reproductive systems : genital 
hooklets generally numbering 14, rarely 11, 10 or even only 9. Testes 
numerous and arranged in groups amidst the ramifications of the 
intestine, many of them lateral to the crura of the intestine. Ovary 
situated far back in the body, only a short distance in front of the 
origins of the haptorial peduncles of the most anterior pair. Eggs 
each having 2 polar filaments, that at the anterior pole the shorter 
and shaped like a crozier, but of a more irregular shape than that seen 



104 THE TKEMATODA OF BRITISH FISHES 

in the egg of D. denticulata. (Note. — Cerfontaine also regarded the 
genital pores of D. pollachii as distinct and separate, like those of D. 
denticulata, but unlike those of D. merlangi.) 



Genus OCTODACTYLUS Dalyell, 1853. 

(Pterocotyle Beneden & Hesse, 1863.) 

Opisthaptor not sharply set off from the rest of the body. Testes 
situated entirely behind the ovary. Eggs devoid of polar extensions. 

Octodactylus palmatus (F.S. Leuckart, 1830) Price, 1943, etnend. 

(Fig. 16D-F.) 

Octobothrium palmatum Leuckart, 1830 (p. 612) ; Octodactylus inhcerens 
Dalyell, 1853 (pp. 262-3, PL 36, figs. 1, 2) ; Octobothrium digitatum Rathke, 
1843 (pp. 242-4, PL 12, figs. 13-15) ; Diclidophora palmata (Leuckart) 
Diesing, 1850 (pp. 417-18) ; Octoplectanum palmatum (Leuckart) Diesing, 
1858 (p. 443); Dactylocotyle molvce Cerfontaine, 1895 (p. 944, PL 1, 
figs. 3, 7) ; Pterocotyle palmata of Beneden & Hesse, 1863 (1864, p. 107, 
PL 11, figs. 1-13), and Lebour, 1908a (p. 41, PL 5, fig. 3) ; Dactylocotyle 
palmata of Cerfontaine, 1895. 

Host : ling. 
Location : gills. 

This trematode is widely distributed in northern European waters, 
occurring off the coasts of Iceland, Norwav, Sweden, Belgium and 
France. T. Scott (1901, p. 149, PI. 8, fig. 27 ; 1912, PI. 27, fig. 8) 
found specimens about 20 mm. long on ling in the Moray Firth and in 
the Clyde, and they have been found on this host at Culler coats by 
Lebour (1908a), at Galway by Little (1929a), on the Irish Atlantic 
Slope by Rees & Llewellyn (1941) and at Plymouth by myself. Early 
descriptions are of little use and sometimes misleading. Dalyell repre- 
sented the trematode upside down. Beneden and Hesse gave a wrong 
impression even of the shape, and gave little useful information 
other than the presence of 16 genital hooklets and wrongly described 
the eggs as pointed at each pole, representing them in figures as 
pointed at one pole, but more or less rounded at the other. Olsson 
(1876, p. 9, figs. 9-12) gave several erroneous characters, notably 
the compact and globular form of the gonads. Dalyell removed 29 
worms from part of the gills of a single host ; Cerfontaine found as 
many as 11, fairly uniformly distributed on right and left, and 
generally attached to the ventral side of the gills of the most posterior 
pair. He gave a useful diagnosis of specimens 10-20 mm. long (dead 
individuals up to 30 mm. long) with an opisthaptor of characteristic 
palmate shape and pedunculate clamps of a robust nature, those of 
the most posterior pair nearly together. He showed clearly that the 
crura of the intestine have numerous median and lateral diverticula, 
but relatively few anastomoses, that the genital pore is situated just 
behind the pharynx, the testes are numerous, the genital hooklets 



DICLIDOPHORID^E 105 

16 in number and the eggs devoid of polar filaments. Lebour 
(1908a, p. 41, PL 5, fig. 3) dealt with three solitary specimens, and gave 
the length and breadth as 12-5 x 2 mm., the number of genital 
hooklets as 16 or 17 and the dimensions of the eggs as 0-20 x 
0-08 mm. She showed clearly the characteristic arrangement of 
uterine folds full of eggs just behind the bifurcation of the gut, but 
gave a wrong impression of the shape of the ovary and omitted the 
testes. 

A specimen of my own, taken from the ling, outstrips the size- 
limit specified by Cerfontaine. Size : 22-5 mm. long, 4-2 mm. broad 
near the midbody, 2-3 mm. broad between levels 0-2 and 0-45 mm. 
from the anterior extremity, about 2-75 mm. broad at the origin of 
the opisthaptor. Shape tapering gradually from the midbody to a 
level 0-45 mm. from the anterior end, then of uniform girth to within 
0-2 mm. from the anterior end, beyond which the body tapers to a 
blunt point. Body tapering also towards the opisthaptor. Pro- 
haptor a pair of buccal suckers, diagonally oval in outline, 0-18 mm. 
long and 0-14 mm. broad. Opisthaptor : cotylophore indistinct, about 
2 mm. long, tapering posteriorly to a breadth of about 0-55 mm. 
Clamps uniform in size and shape, measuring about 0-6 X 0-4 mm., 
their peduncles 0-6-0-8 mm. long and 0-5 mm. broad, those of the 
most posterior pair slightly the longest. Sclerites in general similar 
to those of Diclidophora, arranged as indicated in Fig. 16 F. Gut : 
mouth transversely oval, 0-18 mm. wide, situated 0-1 mm. from the 
anterior extremity. Pharynx longitudinally oval (0-3 X 0-23 mm.). 
(Esophagus very short. Intestine bifurcate, having lateral diverticula 
and in the posterior region (zone of the testes) anastomosing median 
branches, one main branch passing into each peduncle. Reproductive 
systems : genital pore median, 0-4 mm. behind the pharynx and about 
1 mm. from the anterior extremity. Genital hooklets numbering 18, 
each having plate -like roots and strongly curved points, which are 
deeply grooved, but not bifurcate. (Note. — It is easy to get an erroneous 
impression that they are forked and have two closely situated prongs.) 
Testes very numerous (more than 300), extending from a level in front 
of the midbody to the opisthaptor, confined to a median zone between 
the intestinal crura. Ovary elongate, but folded (N-shaped), situated 
immediately in front of the testes in the median plane. Vitellaria 
extremely well developed, mainly lateral to the testes in the posterior 
half of the body, but following the courses of the intestinal anasto- 
moses, extending anteriorly in a pair of broad lateral bands to the 
posterior end of the mass of uterine folds, a few follicles on either side 
extending forward to the midpoint of the narrow anterior region. 
Uterus having a few folds in the narrowing anterior region and many 
folds which almost fill the narrow region itself, but are largely confined 
to the region between the intestinal crura. Eggs very large and very 
numerous (more than 200 in utero), yellow, having an inner lining 
with internally-directed protoplasmic processes about 0-08-0-016 mm. 
long (mainly on one side), devoid of polar filaments and measuring 
about 0-220 x 0-090 mm. 



106 THE TREMATODA OF BRITISH FISHES 

Octodactylus minor (Olsson, 1876) Price, 1943, emend. (Fig. 17 A-E.) 

Octobothrium minor Olsson, 1876 (p. 10) ; Dactylocotyle minus (Olsson) of 
Gallien, 1937 (p. 146, figs. 7-9 ; PL 1, fig. 1) ; Octobothrium palmatum 
forma minor Olsson, 1868 (PL 4, figs. 70, 71. 

Hosts : poutassou, whiting. 
Location : gills. 

Olsson obtained 48 specimens of this species from 15 specimens 
of the poutassou at Bergen. It was found on the whiting south- 
west of Ireland and described by Gallien, and was recorded on the 
same host on the Irish Atlantic Slope by Rees & Llewellyn (1941). 
The description by Gallien is concise and clear. Size up to 5-2 mm. 
long and 1-1 mm. broad at the middle of the body. Colour brown. 
Shape elongate and very flat, tapering towards the extremities. Pro- 
haptor a pair of typical buccal suckers. Opisthaptor : cotylophore 
one-tenth as long as the body and not sharply set off from it, bearing 
four pairs of pedunculate clamps with 2 distinct valves and a ter- 
minal languet. Each clamp having 10 sclerites and a muscular cup 
with a well-developed dorsal wall. Gut : pharynx bulbous. (Eso- 
phagus very short. Intestinal crura long, uniting in the cotylophore 
and sending a branch into each peduncle, and having numerous irregular 
median and dendritic lateral diverticula. Intestine lined with columnar 
cells filled with brown pigment. Excretory system : vesicles at the 
level of the pharynx, pores slightly dorsal. Nervous system : brain 
giving off one pair of anterior and two pairs of posterior nerves, the 
latter comprising a relatively short lateral nerve and a longer median 
nerve on each side of the body. Median nerves uniting in the cotylo- 
phore and sending a trunk into each peduncle. Reproductive systems : 
genital pore just behind the pharynx. Cirrus equipped with 12 
sickle-shaped hooklets. Vas deferens long and sinuous. Testes not 
very numerous, situated in the posterior region (not the anterior as 
Olsson stated) between the ca3ca. Ovary folded (N -shaped) and 
situated in front of the testes near the middle of the body. Arrange- 
ment of various ducts (oviduct, genito-intestinal canal, vitelloducts, 
uterus) very similar to that in Cyclocotyla pagelli {q.v.), the vagina not 
distinctly seen, but joining the receptaculum seminis and opening 
ventrally in the median plane. Vitellaria comprising numerous 
follicles which tend to fill the parenchyma of the whole body. Uterus 
containing a single fusiform egg having two short polar prolongations, 
total length 0-109 mm. (? given as l-900fx). 

Octodactylus morrhuae (Beneden & Hesse, 1863) Price, 1943. 

Pterocotyle morrhuae Beneden & Hesse, 1863 (1864, pp. 106-7) and of Scott, 
1901 (pp. 149-50, PL 8, fig. 25) ; Dactylocotyle morrhuce (Beneden & Hesse) 
of St. Reray, 1898 (p. 551). 

Hosts : cod, whiting. 
Location : gills. 

This species was discovered near Brest, but subsequently found in 
both hosts in Aberdeen Bay by T. Scott (1901), and on the cod at 



DICLIDOPHORIDiE 107 

Gal way by Little (1929a). According to the very incomplete original 
description, which had no figure, it is 14-15 mm. long and has clamps 
which are borne on long peduncles of different sizes, the anterior 
shortest and the most posterior longest. The clamps of right and left 
sides are separated by a deep cleft, as in 0. palmata, and the eggs are 
similarly devoid of filaments. The authors considered the possibility 
of identity with this species, but thought both of them distinct, basing 
this conclusion on the size and colour of the body and the way in which 
the peduncles of the clamps are arranged, only the last character 
having any significance. T. Scott's specimen was 8'5 mm. long and 
3-5 mm. in greatest breadth. The body was said to be uniformly 
very broad posteriorly, but tapering sharply anteriorly. The posterior 
extremity was truncated, but a moderately broad prolongation carries 
two clamps on short peduncles and two other pedunculate clamps 
occur nearly together at its base. The remaining two pairs of clamps 
are situated on the lateral parts of the truncated posterior region and 
are sessile, although longitudinal folds on the ventral surface of the 
posterior region simulate peduncles. The description is certainly 
that of a very odd specimen and the figure suggests considerable 
flaccidity, apart from which resemblance to 0. macruri is closer than 
to any other species of Octodactylus . We may conclude, therefore, 
that the identity of this species is very doubtful ; in some respects it 
resembles both 0. palmata and 0. macruri, but has been described so 
vaguely that no reliable impression of its structure can be gained. 



Octodactylus macruri (Brinkmann, 1942) Dawes, 1946. 

(Fig. 19 A-E.) 

Dactylocotyle macruri Brinkmann, 1942 (a, p. 1, figs. 1-8). 

Host : Macrurus rupestris (=Coryphcenoides rupestris). 
Location : gills. 

This species was found in the Skagerrak and was fully described 
by Brinkmann. Considering the wide distribution of other species 
of this genus, we may conclude that it is a likely member of the British 
fauna and must consider its diagnostic characters. Size : 1-25-3-5 mm. 
long (mean 2-25 mm.) and 0-5-0-75 mm. in greatest breadth immediately 
in front of the opisthaptor. Shape : tongue- or lancet-shaped, 
tapering anteriorly, broadest posteriorly. Prohaptor a pair of ovoid 
buccal suckers 0-065 mm. in greatest length. Opisthaptor : cotylo- 
phore broad, merging imperceptibly with the rest of the body and 
bearing 4 pairs of uniform clamps on short peduncles laterally. 
(Note. — In the living animal the lateral halves of the opisthaptor 
are bent ventralwards and to some extent brought nearer together, 
thus embracing the gill filaments of the host.) Peduncles very 
flexible, the clamps capable of some rotary movement. Each clamp 
comprising anterior (anatomically ventral) and posterior (dorsal) 
valves, both of which are elliptical and hinged onone another trans- 
versely to the long axis. Cuticular sclerites of the two valves 



108 



THE TREMATODA OF BRITISH FISHES 



ill defined, merging gradually into the musculature and connective 
tissue. Anterior valve (ventral) having 3 sclerites (a, b, c, Fig. 19 
C, D), 2 of them (a, c) near the periphery, the third (b) diagonal to 
the median line of the clamp, its base directed towards (c), and con- 
nected with (a) along its entire length by a fine cuticular membrane. 
Posterior (dorsal) valve having 6 sclerites (d-i, Fig. 19 E), 4 of them 
(d, e, g, h) near the periphery, more or less paired (e-g, d-h), another, 
the largest, (f), meeting (e) and (g) distally and extending diagonally 
towards the proximal end of (h). Between the proximal ends of (f) 




Fig. 19. — Octodactylus macruri. A, entire trematode ; B, diagram of the 
reproductive organs ; C, diagram showing the arrangement of sclerites 
in one clamp of the opisthaptor, which is also shown for the ventral 
(anterior) and dorsal (posterior) valves in D and E respectively, (a, b, 
c are sclerites in the ventral valve ; d, e, f, g, h and i those in the dorsal 
valve.) (After Brinkmann, 1942a.) 



and (d) is the sixth sclerite (i), which thus extends parallel with the 
hinge of the clamp. Delicate rod-like sclerites extend in arcs across 
the posterior valve. Gut : pharynx about 0-1 mm. long. Reproduc- 
tive systems : common genital pore median, close behind the pharynx. 
Testes numerous (about 20), situated in the fourth one-sixth of the 
body and confined between the caeca. Vas deferens extending in 
a straight line anteriorly, underlying the ovary and ootype, widening 
near the genital pore into a pyriform seminal vesicle with thick 
walls. Cirrus bulbous, about 0-06 mm. broad and equipped with 10 to 14 
ventrally directed hooklets forming a circlet with the points directed 



DICLTBOPHORTD.T] 109 

laterally. Ovary situated in front of the testes and folded into an 
N- or W-shaped mass, the blind end postero- ventral and on the right, 
the short oviduct emerging anteriorly and on the left. Arrangement 
of the genital ducts as shown in Fig. 19 B. Receptaculum seminis 
ventro -lateral to the closed end of the ovary, genito -intestinal canal 
opening into the right caecum. Ootype longitudinally elongate and 
situated mainly between the ovary and the testes. Uterus straight 
and parallel to the vas deferens. Vitellaria very extensive, their 
follicles occupying all the available space in the body, overlying the 
testes, but not the ovary and ootype, which are surrounded by clear 
parenchyma. Vitelline follicles very large, as few as four taking up 
the entire breadth of the body anteriorly, but smaller posteriorly. 
Eggs not observed. 

Genus DICLID0PH0R0IDES Price, 1943. 

Opisthaptor sharply set off from the rest of the body. Testes 
situated behind the ovary. Other characters as in Octodactylus. 

Diclidophoroides phycidis (Parona & Perugia, 1889). 

Dactylocotyle phycidis Parona & Perugia, 1889 (pp. 743-4, fig. 5) ; Dactycotyle 
phycidis Rees & Llewellyn, 1941. 

Host : greater fork-beard. 
Location : gills. 

This species was originally found in the greater fork-beard at Genoa, 
but was found on the same host by Rees & Llewellyn (1941) on the 
Irish Atlantic Slope. Price (1943a) was diffident about the inclusion 
of this species in the genus Diclidophoroides, so imperfect was the 
original description. British specimens have not yet been described. 

Other Diclidophorince. 

Scott (1901, p. 147, PI. 8, fig. 22) found a trematode about 4 mm. 
long and 2 mm. in greatest breadth on the gills of a Norway pout 
caught about sixty miles south-east of Sumburgh Head, Shetland, 
recording it as " Octobothrium (?) esmarkii (sp. nov.)." So incomplete 
was the description that this form cannot be rightly assigned to a 
particular genus, but it belongs either to Diclidophora or to Octodactylus. 
The best guess that one can make would be to consider it possibly 
identical with Diclidophora luscae. 

Sub-family Cyclocotylin^: Price, 1943. 

(Diclidophorinse Cerfontaine, 1895, in part.) 

Two European genera, Cyclocotyla and Diclidophoropsis , can be 
distinguished by the absence or presence of vaginae. Two other genera 
occur in Japan only and two in America only. One other genus which 
has been referred to this group is Neoheterobothrium Price, 1943, which 
contains two North American species. Price thought it might possibly 



110 THE TREMATODA OF BRITISH FISHES 

contain " Octobothrium leptogaster Leuckart, 1830," which is the type- 
species of Chimcericola, a genus of the Discocotylidse. 

Genus CYCL0C0TYLA Otto, 1823. 

{Octostoma Otto, 1823, nee Kuhn, 1829 ; Cyclostonia Otto, 1823, nee 

Lamarck, 1799 ; Cyclobothrium Cerfontaine, 1895, in part ; Choricotyle 

Beneden & Hesse, 1863 ; Diclidophora Diesing, of Goto, 1894, in part ; 

Mesocotyle Parona & Perugia, 1889.) 

Opisthaptor sharply set off from the rest of the body, the component 
suckers pedunculate or almost sessile and fairly equally spaced out. 
Genital atrium not muscular, cirrus armed with hooks. Testes located 
behind the ovary. Vitellaria extending into the opisthaptor. Vaginae 
absent. 

The type species, Cyclocotyla bellones Otto, 1823 (p. 300, PI. 41, 
fig. 2a-c) was discovered on the dorsal surface of a " Hornhecht " 
(Belones acus) at Naples and has not appeared in this country. Two 
of the other European species, C. chrysophryi (Beneden & Hesse, 1863) 
and C. pagelli (Gallien, 1937), have appeared in Britain and one, C. 
charcoti (Dollfus, 1922) off the coast of Spain. C. labracis (Cerfontaine, 
1895) (Diclidophora labracis Cerfontaine, 1895 (pp. 126-42, PL 3, figs. 
1-15)) was discovered on the bass at White Bank in the North Sea. 
The remaining two European species are C. squillarum (Parona & 
Perugia, 1889) (Mesocotyle squillarum Parona & Perugia, 1889 (pp. 
76-80, 1 PL, figs. la-3a)), a parasite on Bopyrus squillarum at Trieste, 
and C. taschenbergii (Parona & Perugia, 1889) (Diclidophora taschen- 
bergi Parona & Perugia, 1892 ; Dactylocotyle taschenbergi of Stossich, 
1898 (pp. 12-13)). All these combinations were made by Price (1943, 
p. 49). Regarding the last-named species, which was discovered on 
Sargus rondeletii at Genoa and redescribed by Parona & Perugia 
(1892, p. 95, PL 2, fig. 4 ; PL 3, figs. 13, 14), some doubt exists, Llewellyn 
(1941, p. 425) having suggested that the worm should be transferred 
(from Choricotyle, where he tentatively placed it) to the genus Diclido- 
phoropsis, because Cerfontaine (1896, p. 517) believed it to have two 
vaginal pores, situated near the genital atrium. If this conclusion 
was justified, the worm cannot be retained in Cyclocotyla and must be 
placed in Diclidophoropsis. 

Cyclocotyla chrysophryi (Beneden & Hesse, 1863) Price, 1943. 

(Fig. 20 D-F.) 

Choricotyle chrysophryi Beneden & Hesse, 1863 (1864, p. 109, PI. 11, figs. 16- 
22), and of Llewellyn, 1941 (a, pp. 397-405, figs. 1-7) ; C. chrysophrii 
(Beneden & Hesse) Cerfontaine, 1898 (a, p. 303) ; C. chrysophris (Beneden 
& Hesse) Monticelli, 1888 (pp. 11, 16). 

Hosts : gilt-head, common sea bream. 
Location : gills. 

This species was discovered near Brest and has been recorded by 
Rees & Llewellyn (1941), who found it on the common sea bream 
on the Irish Atlantic Slope, and described in detail by Llewellyn 



DICLIDOPHORIDiE 



111 




112 THE TREMATOBA OF BRITISH FISHES 

(1941a). The original description was a very general and incomplete 
account of large specimens 6 mm. long. Size : about 5 mm. long and 
1 mm. in greatest breadth. Colour brown. Shape as in my Fig. 20 D. 
Prohaptor a pair of buccal suckers 0-10 mm. diameter. Opisthaptor 
four pairs of pedunculate, cup-like suckers, having circular or oval 
apertures, and a terminal languet 0-11 mm. long and 0-03 mm. 
broad. Peduncles decreasing in length from before backwards, 
respective length being 1-0, 0-75, 0-50 and 0-46 mm., the most anterior 
directed forwards, the most posterior backwards and intervening ones 
showing an intermediate orientation. Origins of the most anterior 
peduncles separated by the entire breadth of the body. Sclerites 
eight in number, arranged as in my Fig. 20 E, and supplemented by 
systems of small rods as also shown. The base of each sucker is 
composed of a muscular cup. Muscular system including transverse 
muscle bands connecting the peduncles of the same pair and bundles 
from each pair of peduncles which originate in a powerful median 
ventral muscle band. Gut : mouth not quite terminal and transversely 
oval (0-22 x 0-10 mm.) ; pharynx 0-10 mm. diameter, its lumen only 
about 0-007 mm., oesophagus very short, intestine comprising two 
crura with median and lateral diverticula. The crura unite at the 
end of the body proper, the median trunk entering the opisthaptor 
sending a main diverticulum into each peduncle. Nervous system : 
brain dorsal to the oesophagus and giving off a pair of anterior and 
two pairs of posterior nerves. Of the latter the internal are stouter 
and longer than the external, continuing into the opisthaptor, where 
they are connected by a transverse commissure, beyond which they 
give off paired nerves to the peduncles of the first three pairs and are 
connected by a second commissure, behind which the nerves to the 
peduncles of the fourth pair arise. Reproductive systems : common 
genital pore median, beneath the posterior end of the oesophagus and 
0-37 mm. behind the mouth. Testes numbering about 30, all situated 
between the crura of the intestine in the posterior part of the body 
proper. Vas deferens and seminal vesicle somewhat sinuous. Penis 
spherical, 0-03 mm. diameter, generally bearing 8 bifid hooklets, 
rarely 9. Ovary folded and slightly in front of the testes. Recep- 
taculum seminis very large, situated in front of the ovary. Note : 
the female system includes an enigmatic ring-organ, a ring 0-066 mm. 
diameter encircling the oviduct near the ootype. It consists of homo- 
geneous secretion and is of unknown function, though it is suggested 
that it may act as a valve preventing retrogression of the eggs, though 
the latter were unobserved. 

Cyclocotyla pagelli (Gallien, 1937) Price, 1943. (Fig. 20 A-C.) 

Diclidophora pagelli Gallien, 1937 (p. 22, figs. 5, 6 ; PI. 1, fig. 4). 

Host : common sea bream. 

Location : gills. 

This species was erected for one specimen found on a host caught 
off West Ireland. Size : 3-4 mm. long and 1 mm. broad. Shape 



DICLIDOPHORID^ 113 

broadly rounded anteriorly, gradually narrowing posteriorly, thick 
and fleshy. Muscles and parenchyma little developed. Prohaptor 
a pair of rounded, muscular, cup-like buccal suckers. Opisthaptor : 
cotylophore elongate, 0-9 mm. long, broader proximally than distally, 
bearing 4 pairs of suckers on thick lateral peduncles, which become 
progressively smaller in a posterior direction. Suckers deeply concave, 
globular, 0-35 mm. diameter, each having a skeletal framework of the 
type shown (Gallien's fig. 5, my Fig. 20 B), composed of relatively 
thick sclerites (thicker than in Diclidophoropsis) , the median pieces 
(1 and 2 in Gallien's nomenclature) describing a pronounced arc which 
gives the entire organ great depth. The base of the organ comprising 
a thick, muscular cup. Gut : mouth slightly ventral ; prepharynx 
short, pharynx small and spherical, oesophagus very short, practically 
absent ; intestinal crura long and irregular, having numerous branched 
lateral and uneven median diverticula, uniting in the cotylophore and 
sending a branch into each peduncle. Intestine lined by epithelium 
containing much brown pigment. Excretory system : vesicles and 
pores lateral at the level of the pharynx. Nervous system : brain 
giving off 1 pair of anterior and 2 pairs of posterior nerves, of the 
latter one pair (the interval) well developed and entering the cotylo- 
phore, sending twigs into each peduncle. Reproductive systems : 
genital pore located near the level of the pharynx. Testes numerous, 
situated in the space between the caeca in the posterior half of the body 
proper. Vas deferens long and straight, dilated to form a seminal 
vesicle in the anterior region. Cirrus muscular, but ill developed, 
0-06 mm. diameter ; hooklets present, but not precisely determined in 
the whole animal (8 reconstructed in serial sections of the specimen). 
Ovary formed into short longitudinal folds (W-shape), close in front 
of the testes, the medianmost fold containing oocytes. Oviduct 
receiving the short duct of the receptaculum seminis near the anterior 
end of the ovary and the genito-intestinal canal slightly beyond this, 
then continuing in a posterior direction to the ootype, which is situated 
behind the ovary. Vitellaria very well developed, the follicles prac- 
tically filling the rest of the body, transverse vitelloducts at the level 
of the receptaculum seminis, here forming the long, straight median 
duct which enters the oviduct near the ootype. Vagina absent 
(confirmed). Eggs not observed. 



Cyclocotyla charcoti (Dollfus, 1922) Price, 1943. (Fig. 21 A-F.) 

Cyclobothrium charcoti Dollfus, 1922 (a, p. 287, figs. 1-3 ; 6, p. 348, figs. 1-4) ; 
Choricotyle charcoti (Dollfus) of Llewellyn, 1941 (6, p. 424) ; Diclidophora 
sp. Fuhrmann, 1928 (p. (2) 4, fig. 5). 

Hosts : horse mackerel, bogue. 

Location : on Cymothoa oestroides parasitic in the buccal cavity. 

This species was found in the former host near Gijon (Oviedo) 
and in the harbour of Musel, and in the latter at Monaco. Size : 



114 



THE TREMATODA OF BRITISH FISHES 



smaller of two specimens about 3 mm. long and 2-5 mm. in greatest 
breadth, larger about 4-7 mm. long. Shape as in Fig. 21 A, D, 
flattened, convex dorsally and concave ventrally. Cephalic lobe 
very variable in shape, about 0-65 mm. long in the smaller specimen, 
but when fully extended up to two-fifths of total length. Opisthaptor : 
peduncles of the suckers short (up to 0-5 mm. long) and inconspicuous 
when fully contracted. Sclerites 8 in number, arranged as in Figs. 21 




Fig. 21. — Cyclocotyla charcoti. A, a specimen in which the cephalic lobe 
is contracted ; B and C, sclerites of the suckers of the 3rd pair, right 
and left respectively, seen in ventral view ; D, specimen having the 
cephalic lobe well extended ; E, anterior end of D ; F, anterior end of 
a specimen having a contracted cephalic lobe ; G, the egg. (After 
Dollfus, 1922a and b.) 



B, C, representing the supports of R. and L. suckers of the third pair. 
Internal organs incompletely known, but hooklets on the penis number- 
ing 6 and eggs measuring 0-354-0-375 x 0-062-0-076 mm., each having 
a short filament at either pole (Fig. 21 G). 



Genus DICLID0PH0R0PSIS Gallien, 1937. 

Suckers of the opisthaptor pedunculate. Genital atrium not 
muscular ; cirrus equipped with hooklets. Testes situated behind the 
ovary. Vitellaria extending into the peduncles of the opisthaptor. 
Vaginae present. 



DICLIDOPHORIDiE 



115 



Diclidophoropsis tissieri Gallien, 1937. (Fig. 22 A-D.) 

Host : Macrurus Icevis (=Malacocephalus Icevis). 
Location : skin near the gills, but not on them. 

Gallien (1937, p. 15, Figs. 2-4 ; PL 1, fig. 2) obtained about 20 
specimens of this species on 13 hosts, some of which had 5 apiece, off 
West Ireland. Size : 6-7 mm. long when fairly extended and 1 mm. 




Fig. 22. — Diclidophoropsis tissieri. A, entire trematode ; B, diagram of 
the genital organs ; C, a genital hooklet ; D, one of the suckers. (After 
Gallien, 1937.) For numbering of the sclerites in D see the text on p. 1 16. 



broad, but young individuals 3-5 mm. long and 0-7 mm. broad found 
on the same host. Colour white with yellow margins, more translucent 
centrally. Shape elongate and much flattened, gradually narrowing 
anteriorly. Prohaptor a pair of oval buccal suckers of cup-shape 
(dimensions 0-25 X 0-175 mm.) composed largely of muscular fibrils 



116 THE TREMATODA OF BRITISH FISHES 

set perpendicular to the surface. Opisthaptor a small cotylophore 
bearing 4 pairs of pedunculate suckers radially arranged. Peduncles 
long and narrow, extensile and variable (in some instances the suckers 
are lost, all that remains after the accident being the severed peduncles) . 
Each sucker circular in outline, slightly extended in the main axis of 
the peduncle, about 0-75 mm. diameter and having a rigid skeletal 
framework composed of 8 slender sclerites arranged in the form of a 
cross with a circle around it, which serves to keep the sucker perma- 
nently open. Details of the sclerites : continuing the longitudinal axis 
of the peduncle are two arched sclerites, the basal (No. 1) being longer 
than the distal (No. 2) and with forked extremities. From the distal 
ends of piece 1 near the centre of the sucker, two sclerites (Nos. 3 and 
4) extend towards the margin and, bending through an angle of 90°, 
follow this to the proximal end of piece 1 . On each side of the distal 
end of piece 2 two other sclerites (Nos. 5 and 6) extend along the 
margin of the sucker through an arc of about 45°, and continuing to 
the flexures of pieces 3 and 4, two more (Nos. 7 and 8). The 8 sclerites 
are more slender than in some genera. At the base of the sucker 
there is a muscular cup, into which are inserted extrinsic muscles 
which extend along the peduncles and are lost (?) in the parenchyma 
of the posterior part of the body. Gut : prepharynx and pharynx well 
developed, oesophagus very short, intestinal crura widely divergent 
and long, bearing numerous short and irregular diverticula, confluent 
posteriorly in the cotylophore and sending an irregular branch into 
each peduncle. Intestine lined with an epithelium. Excretory system : 
pores slightly dorsal near the vaginal pores. Vesicles large and 
elongate, situated near the anterior ends of the caeca. Lateral canals 
continuing posteriorly to the level of the cotylophore. Nervous system: 
brain well developed, situated above the anterior end of the pharynx, 
giving off 2 anterior and 4 posterior nerve trunks. Of the latter 
one pair is lateral, shorter and less developed, the other ventral, 
joining in the cotylophore and sending a nerve into each peduncle. 
Reproductive systems : genital pore close behind the oesophagus. Cirrus 
muscular, fleshy, armed with 128 (± 5) simple hooklets 0-025 mm. long 
and flexed into an obtuse angle. Testes numerous, filling the median 
space between the caeca in the posterior half of the body proper. Vas 
deferens long and slightly folded. Ovary folded in front of the testes 
in the anterior half of the body. First part of the oviduct convoluted, 
forming a receptaculum seminis uterinum, receiving the long, narrow 
and straight median vagina and median vitelloduct near the hinder 
border of the ovary. Ootype extending dorso-ventrally close behind 
the ovary. Uterus wide and straight, situated ventrally. Vitellaria 
well developed, the follicles being arranged about the caeca, merging 
in the cotylophore and sending a cord into each peduncle. Transverse 
vitelloducts immediately in front of the ovary ; geni to -intestinal canal 
near its hinder end, joining the oviduct between the median vitelloduct 
and vagina. Lateral vaginae extending transversely, their pores 
slightly behind the level of the genital pore. Eggs not observed. 

Some other genera of the Cyclocotylinae which occur outside 



MICROCOTYLTDiE ] 1 7 

Europe have been mentioned already. It remains to mention another 
trematode of uncertain systematic position, Platycotyle gurnardi 
Beneden & Hesse, 1863, which was found on the gills of the grey 
gurnard near Brest and was only very inadequately described (see 
Beneden & Hesse, 1864, pp. 108-9, PL 11, figs. 14, 15). It forms the 
type of the genus Platycotyle Beneden & Hesse, 1863, which is charac- 
terized by a rectangular opisthaptor bearing 4 widely separated suckers 
set on peduncles and by the lack of terminal hooks (see also Pratt, 
1900, pp. 656-7, fig. 27). 

Family MICROCOTYLID^] Taschenberg, 1879. 

Opisthaptor generally comprising numerous clamps (not less than 
16 in the adult), each having 2 pairs of curved lateral half-hoops 
which articulate either with a single median piece or with basal pieces, 
the dorsalmost piece being spurred. Testes numerous. Ovary elongate 
and folded, situated in the middle third of the body, in front of the 
testes. Eggs having polar filaments. 

Sub -family Microcotyun^: Monticelli, 1892. 

(Axininse Nicoll, 1915, in part.) 

With the characters of the family. Differences in the opisthaptor 
serve to distinguish the genera. In Microcotyle the cotylophore is 
almost symmetrical and bears numerous small clamps in a paired 
series ; in two other genera it is asymmetrical, the clamps more 
numerous on one side than on the other, which may lack them, its 
terminal region being spatulate and bearing 2 pairs of hooks in 
Pseudaxine, but of a different shape and without hooks in Axine. 

Genus MICROCOTYLE Beneden & Hesse, 1863. 

Cotylophore more or less set off from the rest of the body or forming 
a kind of frill along its tapering posterior margins, generally symmetrical 
but sometimes having more clamps on one side than on the other, 
frequently with its anterior end projecting from and extending parallel 
to the ventral surface of the body, occasionally set at an angle to the 
main axis of the body. Clamp-like suckers very numerous, hooklets 
absent. Genital atrium sometimes very complex, having an anterior 
or several lateral, or paired posterior outgrowths, sometimes unarmed, 
or having one type or several types of hooklets or spines. Vaginal 
pore equipped with hooklets or not, sometimes associated with a pair 
of dorsal sucker-like pits each with a tongue-like process which can 
be protracted and retracted. In addition to the type-species, M. 
donavini Beneden & Hesse, 1863, this genus contains nearly 70 species. 
At least 16 species have been recorded in Europe, only 5 of them in 
Britain, 22 in Japan, about 20 in North America, 6 in Australia, and 
single species in Egypt, Java, the Philippines and the Galapagos 
Archipelago. G. A. & W. G. MacCallum (1913, p. 223) reviewed 



118 THE TREMA.TODA OF BRITISH FISHES 

30 species, compiling scanty data about them from the works of Parona 
& Perugia (1890-1), Goto (1894, 1899), Vogt (1878), Lorenz (1878), 
and Ariola (1899). Many of the species they dealt with are very 
imperfectly described, and it is very unlikely that all of them and some 
species since erected are valid. 

Microcotyle donavini Beneden & Hesse, 1863 (1864, p. 114, PL 12, 
figs. 1-11). 

Microcotyle canthari Beneden & Hesse, 1863 (1864, pp. 113-14) ; M. chryso- 
phryii Beneden & Hesse, 1863 (1864, p. 148) ; M. erythrini Beneden & 
Hesse, 1863 (1864, pp. 115-16) and probably others. 

Hosts : comber, ballan wrasse. 
Location : gills. 

T. Scott (1905, pp. 116-17, PI. 6, fig(s). 21 (and 22)) obtained 
specimens assigned to this species from the ballan wrasse in the Moray 
Firth and from the same host in the North Sea. Scott merely stated 
that the specimen figured was 5-3 mm. long and had about 34 pairs 
of clamps, and he again represented it in 1912 (PL 27, fig. 4). The 
trematode has also been found near Brest, at Roscoff, and by Sproston 
at Plymouth. The original description of this species is very inadequate. 
The main characters recorded were a relatively very large mouth 
surrounded by a fleshy lip having a median incision, numerous genital 
hooklets of flat and triangular shape, an oval cotylophore bearing an 
unspecified number of clamps (24 pairs indicated in fig. 1), and fusiform 
eggs of reddish colour each of which had a delicate pointed filament 
about as long as the capsule at one pole, and a slightly longer and 
stouter process shaped like a crozier at the other. Microcotyle canthari 
was said to have 30-40 genital hooklets with curved points, the only 
character in the original description which may be said to challenge 
the relegation of the species to synonymy with M . donavini. The 
same kind of genital hooklets was described for M. chrysophryii, and 
this form was admitted to be similar to M. canthari, differing only in 
the characters of the mouth and the buccal suckers, which hardly 
merit the specific distinction. Microcotyle erythrini, also described 
without a figure, is certainly identical with the type-species, having 
similar genital hooklets and eggs. The first of these three forms was 
found on the black sea bream in Italy, the second on the gilt-head in 
Italy, and the third on the pandora near Brest and the bogue and 
axillary bream in Italy. 

Microcotyle labracis Beneden & Hesse, 1863. 

Host : bass. 
Location : gills. 

T. Scott (1905, p. 117, PL 6, fig. 23— not 21 as stated in the heading) 
assigned to this species specimens from an unstated locality which he 
obtained from his son, basing his diagnosis on a general resemblance 
to M. donavini, but twice as many clamps (the figure shows 68 on one 



MICROCOTYLID^E 119 

side and 67 on the other), and an oesophageal bulb of different structure. 
A. Scott (1906, p. 49, PI. 10, fig. 3) mentioned under this name a 
" large " form of unstated size (it must have been about 7-9 mm. long 
and 1-3 mm. broad) from a bass caught in the Irish Sea. The most 
that can be made out from the figure is that it had about 113 clamps 
(55 on one side arid 58 on the other), the entire opisthaptor taking up 
about one-third of the length of the body. According to the original 
description (1864, p. 112, PI. 12, figs. 12-18) the genital hooklets 
have triple points of unequal size, and the reddish eggs a simple filament 
at one pole and at the other a peculiar process about as long as the 
capsule, terminating in a large anchor-like structure perforated near 
the middle. Specimens assigned to this species have been found 
outside Britain at Brest, at Roscoff and in Italy. 

Microcotyle centrodonti Brown, 1929. (Fig. 23 D, E.) 

Host : common sea bream. 
Location : gills. 

This species was discovered on hosts in the Aquarium of the 
Zoological Society, London, the hosts suffering asphyxiation as a 
result of excessive mucus-production by the gills. In the same tank 
with the fatally-infected fishes were specimens of the Mediterranean 
sea bream, which showed an immunity to the trematode, which was 
described in detail by Brown (1929, pp. 67-83, figs. 1-6). (My figures 
were prepared from a specimen kindly presented to me by Miss Brown.) 
Size : 2-5-4-5 mm. long. Shape elongate, tapering towards the 
extremities, the anterior end truncated and the posterior acutely 
pointed. Colour : translucent and off-white. Cuticle thin, but the 
subcuticle thicker and faintly striated. Prohaptor a pair of transversely 
ovoid buccal suckers. 0-06 mm. long. Opisthaptor : cotylophore 
longer than the rest of the body, when fully extended twice as long, 
its anterior end projecting some distance antero-laterally from the 
point of origin, which is marked by a slight constriction, bearing 60 
to 80 pairs of clamps (73 pairs commonly in large specimens) of oval 
shape. Anterior clamps 0-08 mm. broad, those near the posterior 
end only 0-03 mm. broad. Sclerites of the clamps 5 in number, 
namely paired laterals in both the dorsal and the ventral valve, those 
in one valve spurred near the hinge, and a U-shaped middle piece 
with unequal parts about the hinge, the shorter broader than the 
longer and relatively less expanded at its end. Gut : prepharynx 
funnel-like ; pharynx small and spherical ; oesophagus of medium length ; 
caeca terminating behind the testes near the cotylophore and having 
numerous median and lateral diverticula, the former the smaller. 
Reproductive systems : common genital pore near the bifurcation of 
the gut at the anterior end of a genital atrium measuring 0-07 x 0-05 
mm. Copulatory organ a conical fibrous papilla ; vas deferens slightly 
convoluted ; testes numerous (14-23) and situated in the posterior 
one -quarter of the body ; spermatozoa filiform. Ovary elongate and 
coiled, situated just in front of the testes. Uterus wide and straight, 



120 



THE TREMATODA OF BRITISH FISHES 



narrowing distally. Vitellaria lateral and slightly median to the caeca. 
Vaginal pore mid-dorsal a short distance behind the level of the genital 




Fig. 23. — A-C, Gastrocotyle trachuri : A, entire trematode ; B, one of the 
clamps ; C, the terminal languette, showing the 3 pairs of hooks. D. 
Microcotyle centrodonti ; E, one of the clamps. (Original.) 



atrium ; vagina narrow and lacking hooklets. Eggs small, measuring 
0-05 x 0-015 mm., each having a very long and much-convoluted 



MICROCOTYLID/E 121 

filament terminating in a point at one pole, and a much shorter filament 
rather longer than the capsule and terminating in a knob having 
8 curved points at the other. " Dorsal suckers ": two slightly lateral 
sucker-like dorsal pits which form a pair, each with a protractile and 
retractile central " tongue " having 12 simple spines at its free edge. 
(Note. — It was suggested that these organs help to maintain adhesion 
during copulation. They are situated antero -lateral to the vaginal 
pore and occur also in M . alcedinis and M. canthari (?).) 

Microcotyle draconis Briot, 1904 (pp. 126-7). 

Host : greater weever. 

Location : gills. 

Nicoll (1914, p. 497, fig. 6) found two specimens of Microcotyle at 
Plymouth and assigned them to this species, but did not describe 
them, merely mentioning that they had seven " suckers " on each side. 
The specimen figured was found on the same host at Aberdeen, and had 
11 pairs of clamps and about 17 testes. 

Microcotyle fusiformis Goto, 1894 (pp. 192-3, PL 2, fig. 3 ; PL 4, fig. 
6 ; PL 5, fig. 1). 

Host : butter-fish. 
Location : gills. 

Crofton (1940, pp. 318-19) recorded the occurrence of this species 
on the host named at Culler coats. 

Genus AXINE Abildgaard, 1794, nee Oken, 1835. 

(Heter acanthus Diesing, 1836.) 

Body externally and internally asymmetrical. Prohaptor a pair of 
buccal suckers. Opisthaptor extending along one postero-lateral 
margin of the body, and bearing numerous small clamps arranged 
obliquely to the longitudinal axis of the body. Intestine bifurcate, 
the caeca having long median and lateral diverticula. Genital pore 
median near the origins of the caeca. Testes numerous and situated in 
the posterior half of the body ; ovary curved and elongate farther 
forward. Vagina unarmed and generally opening by a pore on the 
left side of the body. 

Axine belones Abildgaard, 1794 (6, pp. 59-60, PL 6, fig. 3a, b). 

Axine triglce Beneden & Hesse, 1863 (1864, p. 117) ; Heteracanthus pedatus 
Diesing, 1836 (pp. 310-13, PL 17, figs. 1, 2) ; Axine orphii Beneden & Hesse, 
1863 (1864, pp. 116-17, PL 12, figs. 19-27). 

Hosts : gar-fish ("A. triglce " on the yellow gurnard). 
Location : gills. 

Specimens of this species obtained from the gar-fish in the North 
Sea were described so briefly by T. Scott (1912, pp. 69-70, PL 7, figs. 



122 THE TREMATODA OF BRITTSH FTSHES 

6, 7) that hardly any information, is available except the length of 
8-10 mm., and the hatchet-like shape of a cotylophore bearing 52 
clamps. Nicoll (1914, p. 496) found specimens on the same host at 
Plymouth, but did not describe them. According to Beneden & 
Hesse specimens of "A. orphii " 5 mm. long have numerous clamps 
(42 shown in their fig. 19), the median sclerite being bifurcate at the 
tip of the long arm, but trifurcate at the tip of the other, and the genital 
hooklets total 26-7, but " trois groupes, places sur une ligne verticale, 
allant en augmentant de nombre." Four groups are represented in 
their fig. 20, a short anterior row of 10, a larger and curved posterior 
row of 18, and two lateral rows with 11 and 12 respectively, similar 
groups in fig. 21 indicating the corresponding numbers 10, 20, 11 and 
13. The eggs were said to be " fusiformes, termines, a leur extremite, 
par une tige mince et courte," but shown in fig. 27 with two long 
polar filaments at least twice as long as the capsule. The same writers 
(1864, p. 117) claimed that " Axine triglce" which was described 
without a figure, differs from "A. orphii " mainly in the general shape, 
colour and size, although the size is unspecified, as well as in the 
disposition of the opisthaptor, which occurred on the left instead of 
on the right. Lorenz, who gave a detailed description of this trematode 
(1878, p. 3, Pis. 1, 2, figs. 1-18), was categorical about the identity 
of "Axine orphii " with A. belones, and A. triglce is equally certainly 
synonymous with this valid species. Size : 4-8 mm. long. Shape : 
very elongate, tapering gradually from the opisthaptor to the anterior 
extremity. Colour milky white, grey laterally. Opisthaptor : cotylo- 
phore terminal, but obliquely set (the left margin being the more 
anterior), bearing a single row of 50-70 small clamps. (Note. — Lorenz 
showed Beneden & Hesse to be mistaken in regarding them as 
suckers.) Median sclerite having unequal limbs, the shorter on the 
left, marginal sclerites numbering 4 on each side (two in each valve 
being of about equal length and adjacent on each side), supplemented 
by a small " Spange " (probably a process of one of the lateral marginals 
on each side. Left valve more " muscular " (fleshy ?) than the right. 
Gut : pharynx ovoid, smaller than the buccal suckers and situated 
slightly behind and between them. (Esophagus and caeca long, the 
latter extending to the cotylophore and bearing numerous short 
median and lateral diverticula along its entire length. Excretory 
system : main lateral canals dorsal to the caeca and alongside the 
oesophagus and uniting anteriorly ; terminal canals situated in the first 
quarter of the body ; pores located on small porso-lateral papillae just in 
front of the genital pore. Reproductive systems : genital pore median 
and slightly anterior to the bifurcation of the gut ; genital atrium 
muscular, its lining bearing two lateral groups of 12-20 hooklets 
arranged in a double row and a ventral hemispherical elevation pro- 
vided with a small circlet of 8-12 hooklets. Cirrus fusiform and 
muscular, having a thick basal annulus bearing 16-24 hooklets ventrally 
and laterally. Vas deferens long and convoluted ; seminal vesicle not 
far from the base of the cirrus. Testes (described as a testis) numerous, 
filling the space between the caeca and behind the ovary, i.e., the pos- 



GASTROCOTYLTDyE 123 

terior half of the body. Ovary J -shaped and situated on the left, the 
long limb being continued as the oviduct, which receives the vitello- 
ducts and vagina near the receptaculum seminis and then turns 
posteriorly, to recur near the ootype, this organ being situated on the 
recurrent (anteriorly- directed) limb. Uterus thick- walled, almost 
median, opening into the genital atrium dorsal to the cirrus. Vagina 
displaying three regions, the basal having thick, muscular walls to a 
point near the junction with the oviduct, the middle capacious and the 
terminal trumpet-shaped. Vaginal pore situated near the left lateral 
margin of the body, but on the dorsal side slightly behind the level 
of the seminal vesicle. Vitellaria restricted to the lateral regions, 
extending from the level of the middle segment of the vagina to the 
cotylophore near the caeca and their diverticula. Eggs each having 
two polar filaments, the shorter sometimes represented by a knob-like 
process, and occurring singly in utero. 



Family GASTROCOTYLID.E Price, 1943. 

(Microcotylidae Taschenberg, 1879, in part ; Axininae Nicoll, 1915, in part.) 

Opisthaptor comprising numerous small clamps arranged in a 
unilateral series along the margin of a very large and asymmetrical 
cotylophore occupying the posterior two-thirds of the body. Clamps 
having sclerites in general similar to those of Microcotylidse, but 
stouter and including an additional pair of submarginal pieces in one 
of the valves. Testes not numerous, occupying the posterior region. 
Ovary elongate and folded, situated in front of the testes. Eggs each 
having two pointed filaments. 

Genus GASTROCOTYLE Beneden & Hesse, 1863. 

In erecting this genus, Beneden & Hesse (1864, p. 117) specified 
that the anterior half of the body is narrow, the posterior wide and 
equipped with minute suckers arranged unilaterally along its entire 
length. An additional character is the nature of the sclerites men- 
tioned for the family. 

Gastrocotyle trachuri Beneden & Hesse, 1863. (Fig. 23 A-C.) 

See Beneden & Hesse, 1864, p. 96, pp. 117-18, PL 13, figs. 1-8. 

Host : horse mackerel. 
Location : gills. 

Idris Jones (1933e, pp. 227-32, figs. 1-4) found at Plymouth and 
described the only six specimens which have appeared in Britain, 
although the trematode is known to occur near Brest and elsewhere in 
the Eastern Atlantic, in the Mediterranean and in Japan. According 
to the original description the genital pore is equipped with very small 
and closely-set hooklets, the cotylophore is situated on the right side 
of the expanded posterior region and bears 32-38 small clamps and 4 



124 THE TREMATODA OF BRITISH FISHES 

bifurcate hooks, those of the external pair the larger, and the fusiform 
eggs have two rather straight filaments about as long as the capsule, 
one at either pole. British specimens have the following characters : — 
Size : 4-7 mm. long and 1-2 mm. broad posteriorly. Shape elongate, 
the posterior two -thirds broad, the anterior one -third narrower and 
tapering to a point. Prohaptor a pair of buccal suckers 0-023 mm. 
long and 0-015 mm. broad. Opisthaptor : cotylophore situated along 
the left side of the broad region of the body, bearing a single series of 
32-40 small clamps 0-08 mm. diameter, as well as a stump-like process 
with 3 pairs of dissimilar terminal hooks, those of the most lateral 
pair much larger than the others. Gut : mouth terminal and very 
small ; pharynx 0-046 mm. long, and 0-030 mm. broad ; oesophagus 
well developed and about 0-2 mm. long, its walls provided with pouches ; 
intestine bifurcate, the crura having numerous median and lateral 
diverticula and anastomozing near the posterior extremity. Repro- 
ductive systems : genital pore situated in the median ventral line 
beneath the posterior part of the oesophagus, its lips bearing 12 long 
and narrow hooklets, each having a bifurcate root and a straight 
shaft, but a sharply- curved tip. Genital atrium muscular and 0-023 
mm. diameter. Testes comprising a compact mass of lobules situated 
in the most posterior region of the body. Ovary elongate and folded 
into the shape of an inverted U, situated in front of the testes, but in 
the posterior half of the broad region. Uterus wide and thin-walled, 
extending along a straight course and opening into the base of the 
genital atrium. Vitellaria very well developed, the follicles scattered 
throughout the body between the hind end of the oesophagus and the 
posterior extremity and extending into the cotylophore. Vaginal pore 
situated in the middle dorsal line just behind the level of the genital 
pore. Eggs not present. Note : E. I. Jones stated that the " arma- 
ture " of the " suckers " is very different from that described by 
Beneden & Hesse, but did not describe them. He kindly lent me 
a specimen 3-2 mm. long and 0-8 mm. in greatest breadth, having 41 
clamps, and I have tried to illustrate this. The sclerites could not be 
made out perfectly and their arrangement defies ordinary powers of 
description, but they are not arranged as he showed them and differ 
in the two valves (Fig. 23 B). 

Family DISCOCOTYLID.E Price, 1936. 

Opisthaptor comprising 3 or 4 pairs of clamps, each typically having 
2 pairs of separate marginal sclerites and a well-developed middle 
segment bearing rows of lacunae extending on either side of a central 
rib and sometimes segmented ; otherwise variously modified, some- 
times having an additional pair of basal segments, in the extreme 
forming by fusion two lateral segments and one median segment, all 
of them U-shaped. Cotylophore sometimes terminating in a languet. 
Lateral vagince present or absent. 

The sub-families can be distinguished by the nature of the opis- 
thaptor and the presence or absence of vaginae. In the Plectano- 



DlSCOCOTYLIDiE 125 

cotylinae there are 3 pairs of clamps and vaginae are absent ; in the 
remaining three groups there are 4 pairs of clamps and vaginae are present. 
In the Anthocotylinae the clamps of the most anterior pair are very 
large, the others very small. In the Chimaericolinae and Discocotylinae 
respectively the opisthaptor is either attached to the body by a narrow 
stalk or not, and the posterior region of the body is narrow and trans- 
versely striated in the former group, but neither narrow nor striated in 
the latter. I have also given (Dawes, 1946, p. 74) some diagnostic 
characters based on the nature of the sclerites. 



Sub-family Discocotylinae Price, 1936. 

Four European genera can be separated by the use of rather 
unusual characters. In Diplozoon only the adults are united in pairs 
in permanent copula ; in Vallisia the body is curiously asymmetrical, 
having a lateral flexure. Other genera are more or less bilaterally 
symmetrical and the components of the opisthaptor are strictly 
symmetrical in Discocotyle, but show asymmetry in Grubea, which has 
4 equal haptors on one side, but only 1 small haptor on the other. 

Genus DISCOCOTYLE Diesing, 1850. 
(Placoplectanum Diesing, 1858.) 

Body elongate and truncated posteriorly. Prohaptor a pair of 
buccal suckers. Opisthaptor comprising 4 pairs of clamps, which are 
generally sessile and disposed along the lateral margins of a somewhat 
rectangular cotylophore. Sclerites of the clamps uniformly developed, 
consisting in each case of 2 pairs of lateral pieces which are dorsal 
and ventral in position and which articulate with or approach the 
extremities of a well-developed U-shaped median piece, the dorsal 
lateral sclerites each having a spur. Genital pore equipped with 
hooklets with one point. Lateral vaginae opening to the exterior in 
the antero-lateral regions, and uniting in the anterior one-third of the 
body to form a long median vaginal canal. 

Discocotyle sagittata (Leuckart, 1842) Dies., 1850. (Fig. 24 A-F.) 

Cyclocotyla lanceolata Zaringer, 1829 (p. 21) (name only) ; Octobothrium sagit- 
tatum Leuckart, 1842 (pp. 49-57, PL 2, fig. 5a-k) ; Placoplectanum sagit- 
tatum (Leuckart) Diesing, 1858 (p. 384) ; Mazocraes sagittatum (Leuckart) 
Southwell & Kirshner, 1937 (pp. 431-3, fig. 3) ; Discocotyle salmonis 
Shaffer, 1916 (p. 257). 

Hosts : sea trout, salmon. 
Location : gills. 

Baylis (1928) recorded the occurrence of this trematode in the sea 
trout at Jersey and (1939) in Yorkshire, Friend (1939) on the same host 
in Scotland, finding it invariably on trout in Talla reservoir (Peebles- 
shire) and elsewhere. I have specimens from the sea trout in Cam- 
bridgeshire. Southwell & Kirshner (1937) found more than one 



126 



THE TREMATODA OF BRITISH FISHES 




DISCOCOTYLID^E 127 

hundred specimens on the pallid mucus -covered gills of a brown trout 
which was found dead in a reservoir in North Wales, death of the host 
being attributed to the parasites. The species also occurs on the 
Continent and in U.S.A. Luhe (1909, p. 7, fig. 3) dealt with specimens 
6-9 mm. long, Southwell & Kirshner with immature specimens 
2 mm. long and 0-35 mm. broad, but also large and broad mature 
specimens measuring 6 by 1 mm. Their description contains several 
errors. The prepharynx was described as the oesophagus, the lateral 
vaginae as the main excretory canals, and the median vagina as the 
" common longitudinal trunk " of the excretory system. But these 
specimens had about 40 testes and very large ovoid eggs measuring 
0-250 x 0-130 mm. 

My specimens differ in the degree of maturity attained and the 
state of contraction of the body, older specimens seeming to have the 
more characteristic shape, others being somewhat attenuated. Size : 
6-5-7-0 mm. long and 1-3-2-2 mm. broad. Shape elongate and a fairly 
uniform girth in the posterior region, or broadest in the middle and 
tapering towards the extremities, the posterior end truncated, the 
anterior constricted to a breadth of 0-3-0-5 mm. about 0-65 mm. behind 
the extremity. Colour off-white. Prohaptor a pair of buccal suckers 
0-13-0-16 mm. long and 0-10-0-12 mm. broad, diagonally arranged just 
behind the anterior margin of the body (which is accidentally over- 
turned in Fig. 24 B). Opisihaptor : cotylophore clearly differentiated, 
sometimes having a shallow posterior notch, 0-8-0-9 mm. long and 
1-1-1-3 mm. broad, but sometimes as broad as the body, or only half 
as broad in the contracted state, generally two-fifths to three-fifths 
as broad. Clamps diminishing slightly in size in a posterior 
direction, those of the anterior pair measuring 0-33-0-38 x 0-23 
mm., those of the most posterior 0-28-0-32 x 0-23 mm. Sclerites 
as described for the genus and shown in Fig. 24 C ; hooklets as 
described by Price (19436, p. 11) for " D. salmonis " absent. Gut : 
prepharynx very short pharynx ; ovoid or spherical, measuring 
about 0-76 x 0-62 mm. or 0-71 mm. diameter ; oesophagus fairly 
long, extending back to the level of the genital pore. Intestinal 
crura very long and wide, dividing the body approximately into 
longitudinal one -thirds, particularly in young specimens, having 
branched median and lateral diverticula which are more evident, 
longer and more branched in older specimens, uniting to form a median 
intestine at the base of the cotylophore and sending long diverticula 
into its tissue. Reproductive systems : genital pore median, and about 
0-5 mm. from the anterior extremity and 0-26 mm. behind the posterior 
end of the pharynx. Testes numerous, numbering about 90, and 
occupying the available space between the intestinal crura in the 
posterior half of the body proper. Vas deferens and seminal vesicle 
slightly convoluted. Ovary elongate and curved, or bunched into a 
mass immediately in front of the testes and slightly lateral, but confined 
within the bounds of the intestine. Vitellaria extensive, the follicles 
mainly arranged lateral to the intestinal crura, but in older specimens 
many median to them, extending throughout the body from the 



128 THE TREMATODA OF BRITISH FISHES 

anterior constriction to the base of the cotylophore. Uterus slightly 
convoluted, and containing about 12 eggs of variable shape and 
sizes measuring 0-310-0-335 x 0-131-0*135 mm., sometimes having 
a nodular process at one pole, occasionally having incompletely-formed 
shells. Vaginse opening to the exterior laterally at the level of the 
anterior constriction and forming a median vagina just behind the 
bifurcation of the gut. Note : one abortive egg was observed to be 
0-122 mm. long and 0-080 mm. broad and to have a shell three times 
the normal thickness, and also a small nodule of shell-forming substance 
near one pole. Normal eggs contained in the uterus are undeveloped. 
Price (loc. cit., p. 12) thought the validity of " D. salmonis " very 
doubtful, but allowed the species to stand in the absence of a modern 
description of D. sagittata. This American form comes within the 
range of variability of the European species and, in spite of differences 
like the size of the eggs and the presence of hooks, must be regarded 
as a synonym of the type-species. Another form which is probably 
identical with this species is D. sybillce (T. Scott, 1909), which was found 
on the gills of the sea trout at Aberdeen, and the same may be true of 
species which have been recorded in Australia and Japan. 

Genus VALLISIA Perugia & Parona, 1890. 

Body asymmetrical, flexed laterally. Cotylophore indistinctly 
marked off from the rest of the body by a constriction and having 
near its margins 4 pairs of sessile clamps with sclerites of Discocotylid 
type, also 1 pair of hooks on a terminal process. 

The only species, Vallisia striata Perugia & Perona, 1890 (p. 21, 
PI. 1, figs. 8, 9 ; Pis. 2, figs. 10, 11) (Octocotyle arcuata Sonsino, 1890) is 
a parasite on the gills of the horse mackerel in the Adriatic. According 
to the original description it is 10-5 mm. long, the anterior part 6 mm. 
and the posterior 4-5 mm., and 1-9 mm. broad, the anterior region 
tapering to a blunt point bearing a circular mouth bordered by 
pleated cuticular lips. The clamps are uniform in size, the major 
axis 0-112 mm. long. Each egg has two polar filaments about as long 
as the capsule, which measures 0-238 X 0-070 mm. 

Genus GRUBEA Diesing, 1858. 

Body symmetrical, but equipped with an asymmetrical cotylophore 
having an ear-like lobe bearing 4 similar clamps on the right side 
and 1 small clamp on the left, as well as 2 pairs of hooks in a 
terminal position. Lips of the genital pore equipped with 2 rows 
of 8 hooks, one row on the anterior margin and the other on the 
posterior, and an additional bipartite hook of larger size in each of the 
lateral angles. 

The only species of this genus, G. cochlear Diesing, 1858 (6, p. 385) 
(Octobothrium scombri Nordmann of Grube, 1855 ; Pleurocotyle scombri 
of Pratt, 1900) was found on the gills of the mackerel and horse 
mackerel at Naples. 



DISCOCOTYLIM] 129 



Genus DIPLOZOON Nordmann, 1832. 

{Diporpa Dujardin, 1845 ; Diplozoum of Burmeister, 1835.) 

Adults united in pairs in permanent copula. Opisthaptor : 4 pairs 
of clamp-like suckers set close together along the postero-lateral 
margins of a rectangular cotylophore. The larvae equipped with 1, 
2, 3 and 4 pairs of clamps at progressively later stages of development. 
Terminal part of the cotylophore equipped with 2 pairs of hooks, 
those of one pair needle-like, those of the other recurved. Intestine 
not bifurcate, but long and having numerous branched diverticula. 
Genital pore situated in the posterior region of each member of the 
copulating pair, encircled by a gonotyl (genital sucker), which fuses at 
maturity with a dorsal papilla bearing the vaginal pore of the other 
individual, corresponding change occurring in the inverse sense, so 
that the male duct of each individual is contiguous with the female 
duct of the other. Testis single, compact, situated close in front of 
the opisthaptor. Ovary elongate and formed into a loop immediately 
in front of the testis. Vitellaria comprising numerous follicles, and 
tending to fill the anterior region of the body in front of the point of 
union of the individuals. Uterus slightly folded, its pore situated 
near the point of fusion of the genital pores. Eggs ovoid, operculate 
and equipped with a long and much- coiled filament at the anopercular 
pole. Parasites of freshwater fishes. 

Diplozoon paradoxum Nordmann, 1832. 

Diporpa dujardinii Diesing, 1850 (p. 420). 

Hosts : various Cyprinidae and other fresh-water fishes, e.g. 3-spined 
stickleback. 

Location : gills. 

This species is well known in widely separated parts of Europe 
(Finland, Russia, Germany, France, Switzerland and Italy) and 
occurs in British fresh-water, although nobody seems to have taken 
the trouble to record its occurrence in Britain. The trematode is 
familiar enough from accounts given in various text-books of zoology 
(Gamble, 1896, pp. 59-61, figs. 27, 28 ; Benham, 1901, pp. 55, 57, 
fig. 4, 1-8) and is figured elsewhere (Braun, 1889-93, PI. 13, figs. 1-5) . 
According to the original description the length is 3-5 " lines," 
according to Luhe (1909, p. 7, fig. 4) 4-11 mm. Both Benham and 
Gamble reproduced figures of the egg, larva, young individuals and 
adults after Zeller, whose works (1872 ; 1888) are still authoritative. 
Beneden (1858, pp. 39-44, PI. 4, figs. 1-12) gave a fairly comprehensive 
account of the anatomy of specimens found on the bream, which 
was the first-known host, and references to the earlier literature. I 
have a single specimen comprising two individuals in copula and have 
provided figures in another place (Dawes, 1946, fig. 21 A, B, a, b). 
Size : anterior region (in front of the point of fusion) 2-64 mm. long, 
region of fusion about 0-6 mm. long, posterior region 2-22 mm. long 

9 



130 THE TREMATODA OF BRITISH FISHES 

and about half as broad. Prohaptor a pair of buccal suckers situated 
very close to the pointed anterior extremity, their anterior borders 
about 003 mm. behind it, mean dimensions 0-132 x 0-116 mm. 
Opisthaptor : cotylophore about 0-4 mm. long and 0-7 mm. broad, 
separated from the rest of the body by a slight constriction, the 
breadth of the body here being about 0-5 mm. Clamps transversely 
elongate, diminishing in size in a posterior direction, the most anterior 
measuring 0-19 X 0-10 mm., the most posterior 0-13 X 008 mm. 
Sclerites of Discocotylid pattern, arranged as shown in fig. 21 b (Dawes, 
loc. cit.). Gut : pharynx longitudinally ovoid, smaller than and 
very close to the buccal suckers, measuring 0-09 x 0-07 mm. Repro- 
ductive systems : anterior region of the body filled with coarse vitelline 
follicles almost to the level of the pharynx. Eggs few (3 in utero), 
very large, but of variable sizes (0-37 x 0-12 mm., 0-33 x 0-10 mm. 
and 0-29 x 0-12 mm.), each having a very long filament formed into 
a compact spiral at one pole. 

The Japanese species D. nipponicum Goto, 1891 (pp. 151-92, 
Pis. 21, 22, figs. 1-25 ; PI. 23, figs. 1-20) is said to be common on the 
gills of the crucian carp and to differ from D. paradoxum in the small- 
ness of the clamps, the greater length of the posterior region of the 
body, the shortness of a connecting canal between the intestine and 
the oviduct, the presence of a pair of " sticky glands " near the mouth 
and the absence of diverticula of the intestine in the posterior region 
of the body, but it is probably identical with the type species. 



Sub-family Anthocotylike Price, 1936. 

Genus ANTH0C0TYLE Beneden & Hesse, 1863. 

Body elongate, tapering from the middle towards the extremities, 
broadening immediately in front of the opisthaptor. Prohaptor a 
pair of small buccal suckers. Opisthaptor comprising 4 pairs of 
clamp-like suckers, the most anterior pair sessile and enormously 
developed, the remaining 3 pairs minute and pedunculate, and a 
minute terminal languette armed with 2 pairs of hooks, those of the 
external pair the larger. Sclerites of large and small clamps alike 
constructed on the characteristic Discocotylid plan. Cirrus equipped 
with 40 hooklets having simple points. Lateral vaginae opening to 
the exterior ventrally near the lateral margins of the body, slightly 
behind the level of the genital pore and continuous with the main 
lateral vitelloducts. Eggs having a short filament about as long as 
the capsule at each pole. 

Anthocotyle merluccii Beneden & Hesse, 1863. (Fig. 25 A-F.) 

Anthocotyle merlucii americanus MacCallum, 1916 (pp. 25-7, figs. 10, 10 A) ; 
A. americanus Price, 1943. 

Hosts : hake, coal -fish. 
Location : gills. 



DISCOCOTYLIDiE 



131 



T. Scott (1901, p. 148, PL 8, fig. 24) obtained a few specimens of 
this widely distributed species on hake landed at the fish market, 
Aberdeen, and in the brief description gave the length as about 
16 mm., but probably less in the living state. The trematode was 
found on the same host from the Irish Atlantic Slope by Rees & 
Llewellyn, and it probably occurs right round our coast, as well as 
near Brest, in the Mediterranean, and in Canada and U.S.A. The 




oo 



Fig. 25. — Anthocotyle merluccii. A, entire trematode (reproductive systems 
omitted) ; B, posterior end, showing the mode of attachment to a gill- 
lamella of the host ; C, one of the small clamps and its peduncle, show- 
ing the sclerites, which are fundamentally similar to those of the large 
clamps ; D, the terminal languette, showing the two pairs of dissimilar 
hooks ; E, the egg ; F, diagram of the organs in the anterior region. 
(After Cerfontaine, 1895.) 



original description (1864, p. 105, figs. 8-12) is very general, but a 
detailed account of structure was given by Cerfontaine (1895a, p. 511, 
figs. 1-9), who found specimens attached to the inner lamellae of the 
gills. Size : 10-15 mm. long. Shape : body tapering to an obtuse 
point anteriorly, broadening progressively towards the middle, 
narrowing in the posterior half, but broadening again to maximum 
breadth in front of the opisthaptor. Opisthaptor : large clamps 
having dorsal and ventral valves, hinged anteriorly and opening 



132 THE TREMATODA OF BRITISH FISHES 

posteriorly by a wide slit bordered by a somewhat pleated membrane. 
Sclerites arranged as a pair of lateral pieces in the dorsal and another 
pair of similar pieces in the ventral valve, as well as a large median 
piece of U- shape which is flexed at the hinge of the clamp and extends 
into both valves. Lateral sclerites of the ventral valve also extending 
over the hinged region and for a short distance into the dorsal valve. 
Numerous delicate rod-like sclerites also line the cavity of the clamp. 
Small clamps each borne on a short peduncle containing bundles 
of muscle fibrils, the sclerites fundamentally similar to those of the 
large clamps. The 2 pairs of hooks borne on the terminal languette, 
which is itself about as large as a small clamp, together with its 
peduncle, dissimilar and unequal in size, those of the outer pair the 
larger and more strongly curved and having median and lateral 
roots, of which the former is the larger (according to Price a third 
pair of hooks was possibly overlooked by Cerfontaine) . Gut : mouth 
terminal, transversely oval, pharynx small (little larger than one of 
the buccal suckers), oesophagus short, intestine bifurcate, the crura 
uniting between the large clamps of the opisthaptor and sending 
several simple diverticula into the cotylophore. Intestinal crura 
having a few short median and more as well as larger lateral diverticula 
which branch only slightly. Excretory system : pores dorsal near the 
lateral margins of the body at the level of the genital pore. Nervous 
system : brain situated at the level of the posterior end of the pharynx, 
giving off 2 pairs of anterior and 2 pairs of posterior nerves, the more 
median posterior nerves being prominent, following the course of the 
intestine, and uniting at the base of the languette, which receives 2 
small nerves. Paired nerves serve the smaller clamps, and a trans- 
verse commissure connects the main nerve trunks between the larger. 
Reproductive systems : genital pore median immediately behind the 
bifurcation of the intestine. Testes numerous, situated in the 
posterior half of the body proper and confined between the intestinal 
crura. Vas deferens median, but sinuous cirrus equipped with 40 
hooklets having simple points. Ovary fl -shaped and having folded 
limbs, situated in front of the testes in the second quarter of the 
body, its blind end in the median plane near the origin of the vas 
deferens and the oviduct. Uterus comparatively straight. Vitellaria 
well developed, extending laterally along the course of the intestine 
between the levels of the vaginal pores and the posterior end of the 
testes. Vaginal pores ventro- lateral, vaginae continuous with the 
main lateral vitelloducts, provided with 2 anastomoses immediately 
in front of the ovary. Eggs clear yellow in colour, each having a 
polar filament about as long as the capsule at each pole. 

In making the sub-species of MacCallum a species, A. americanus, 
Price (19436, p. 14, fig. 1, i-m) admitted that it might be identical 
with A. merluccii, but drew attention to the disparity in size between 
the large clamps on the two sides of the body. This difference 
between American and European specimens is seen to be an un- 
reliable criterion of distinction, when it is considered that in the 
specimens found at Woods Hole and described by Linton (1940, 



DISCO COTYLIDiE 133 

p. 14, PI. 16, figs. 200, 201) the asymmetry is the opposite of that 
noted by Price, the left anterior clamp being larger than the right, as 
in European specimens. Assuming that Cerfontaine overlooked the 
small intermediate hooks (which are 02 mm. long according to 
Price), there is no significant difference between American and 
European forms. 

Sub -family Plectanocotylin^e Monticelli, 1903. 
Genus PLECTAN0C0TYLE Diesing, 1850. 

(Plectanophorus Diesing, 1858 ; Phyllocotyle Beneden & Hesse, 1863 ; 
Plectanocotyle Monticelli, 1888 (in the Octocotylidse)). 

Body elongate, very extensile, tapering towards the extremities, 
but broadening near the opisthaptor. Prohaptor a pair of buccal 
suckers. Opisthaptor a rather narrow cotylophore bearing 3 pairs 
of suckers and an extensile terminal languette, which may assume 
a discoidal shape terminally and on which there are 3 pairs of dis- 
similar hooks. Copulatory organ equipped with a number of delicate 
cuticular rods, as many as 5 on each side. Testes numerous, occupying 
the posterior half of the body. Ovary very elongate and flexed in 
front of the testes. Vaginae absent. Type-species P. elliptica 
Diesing, 1850, recorded in Europe, but found by Kollar, a friend of 
Diesing, on the gills of " Labrax mucronatus " in America and very 
ill- defined. 

Plectanocotyle gurnardi (Beneden & Hesse, 1863) Pees & Llewellyn, 
1941. 

Phyllocotyle gurnardi Beneden & Hesse, 1863 (1864, pp. 103-4, PI. 10, figs. 
1-7) ; Plectanocotyle lorenzii Monticelli, 1899 (6, pp. 1045-53, figs. 1-12) ; 
Plectanocotyle caudata Lebour, 1908 (a, pp. 42-3, PI. 5, figs. 4-7). 

Hosts : yellow gurnard, red gurnard, grey gurnard, streaked 
gurnard. 

Location : gills. 

There are several records of the occurrence of this species round 
our coasts. T. Scott (1901, pp. 147-8, PI. 8, fig. 23) briefly described 
specimens about 2 mm. long and 0-6 mm. broad found on the grey 
gurnard taken off the Scottish coast (locality not specified) and (1905, 
p. 116) referred them to the " species " P. lorenzii, also (1905, pp. 
115-16, PL 6, figs. 19, 20) recording the occurrence of P. gurnardi on 
the grey gurnard in the Moray Firth. A. Scott (1904) found specimens 
on the yellow gurnard caught in the Irish Sea; Lebour (1908a, pp. 
42-3, PI. 5, figs. 4-7) described (as P. caudata) specimens found on 
the grey gurnard at Cullercoats ; Nicoll (1915) reported specimens on 
the red gurnard at Plymouth ; Little (1929a) specimens on the grey 
gurnard and the yellow gurnard at Galway ; and Rees & Llewellyn 
(1941) on the grey gurnard and red gurnard on the Irish Atlantic 
Slope. The trematode also occurs near Brest, off the coast of Belgium 
and in the Mediterranean. The original description concerned 



134 THE TREMATODA OF BRITISH FISHES 

specimens 10 mm. long and of elongate form, tapering towards the 
anterior extremity and decidedly flattened. The main haptors were 
described as 3 pairs of sessile suckers of medium size disposed in 2 
parallel lines and a " languet " equipped with a sucker-like cupule 
bearing 2 pairs of hooks, those of the lateral pair much the larger. 
The eggs of the specimens concerned were oval and had a fairly long 
filament at one pole, and the margin of the genital pore was equipped 
with 5 pairs of hooklets, 2 short ones terminating in a minute globule. 
Lebour's specimens were referred to a new species, although closely 
resembling the forms described by Beneden & Hesse and Monticelli, 
being thought to differ in the short peduncles on which the " suckers " 
were borne. But Lebour showed shrewd powers of judgment in 
suggesting that all three forms represent the same species in various 
stages of contraction. Llewellyn (19416, pp. 431-2, fig. 1) concurred, 
actually finding specimens contracted to intermediate degree as 
compared with the specimens of Monticelli and of Lebour, and also 
showed that the erection of the genus Phyllocotyle was quite un- 
necessary. He rightly relegated P. lorenzii and P. caudata to 
synonymy with P. gurnardi, and made a contribution to our know- 
ledge of the terminal process and its 3 pairs of hooklets. Size : 
4-1 mm. long and about 0-8 mm. in greatest breadth at the middle 
of the body. Shape elongate, tapering towards the extremities, but 
broadening slightly near the base of the opisthaptor. Prohaptor a 
pair of small buccal suckers. Opisthaptor : cotylophore shield- 
shaped and about 1 mm. broad and long, terminating in a small 
process (languet) about 0-7 mm. long which is sometimes enlarged at 
its tip to form a cupule 0-2 mm. diameter which bears 3 pairs of 
hooklets, otherwise borne on a short appendage of uniform girth. 
Hooklets of the outermost pair much the largest and having 2 roots, 
hooklets of the most median pair about half as long and having 2 roots 
or not, hooklets of the pair intermediate in position between the 
lateral and median hooklets minute (and overlooked by Beneden & 
Hesse, and by Monticelli). Clamps forming 3 pairs and set on short 
peduncles which may be inconspicuous. Sclerites not described, but 
probably of typical Discocotylid type. Gut : mouth circular and 
terminal, prepharynx short, pharynx small, oesophagus very short 
intestine bifurcate, its crura largely hidden by vitelline follicles, but 
probably uniting posteriorly. Reproductive systems : genital pore 
(pores ?) just behind the termination of the oesophagus, genital hook- 
lets numbering 5 on either side, the 2 central ones much shorter 
than the others and terminating each in a small knob (as Beneden 
& Hesse indicated, but, as Lebour stressed, not conforming to 
their figures), cirrus cuticular. Testes numerous and situated in the 
posterior region, extending from the middle of the body to a level 
about 0-6 mm. from the anterior end of the opisthaptor. Ovary 
elongate and folded so that one limb crosses the other, situated just 
in front of the middle of the body. Vitellaria well developed in the 
lateral regions along the entire length of the body behind the genital 
pore, the follicles not entering the tissue of the opisthaptor. Uterus 



discocotyud^ 135 

narrow, its terminal part sometimes dilated and filled with eggs of 
pale yellow colour 0-065 mm. long, each having a single polar filament 
about as long as or slightly longer than the capsule. 

Sub -family Chim^ricolinje Dawes, 1946. 

(Chimcericolidce Brinkmann, 1942.) 

Opisthaptor comprising 3 pairs of clamps, each clamp having 
1 pair of lateral sclerites and 1 middle sclerite, all three being horse- 
shoe-shaped. Vaginae absent. 

Genus CHI1VLERIC0LA Brinkmann, 1942. 

(Octobothrium Leuckart, 1827, in part ; Discocotyle Diesing, 1850, in 
part ; Placoplectanum Diesing, 1858, in part ; Octocotyle Diesing, 1850, 

in part.) 

Chimaericola leptogaster (Leuckart, 1830) Brinkmann, 1942. 

(Fig. 26 A-G.) 

Octobothrium leptogaster Leuckart, 1830 (p. 612) ; Discocotyle leptogaster 
(Leuckart) Diesing, 1850 (p. 424) ; Placoplectanum leptogaster (Leuckart) 
Diesing, 1858 (p. 384) ; Octocotyle (Octobothrium) leptogaster (Leuckart) 
Parona & Perugia, 1890 (p. 6) ; Neoheterobothrium leptogaster (Leuckart) 
Price, 1943 (a, p. 51). 

Host : rabbit-fish. 
Location : gills. 

T. Scott (1910, p. 69, PI. 7, figs. 2-5 ; 1912, p. 350, PL 27, fig. 5) 
described a specimen of this species taken from a rabbit-fish from 
the North Sea, remarking that the species is " apparently not rare," 
but the only other British record is that of Rees & Llewellyn (1941), 
who found the trematode on hosts taken off the Irish Atlantic Slope. 
Scott's description is very brief and concerns a specimen 39 mm. long, 
in which the body seems to have been little more than one -third, the 
opisthaptor less than one -tenth, and its transversely- striated peduncle 
nearly three -fifths of the total length. Brinkmann (1942, p. 3, figs. 
1-11) described in great detail even larger specimens found on the 
same host in Norwegian and Swedish waters, and reviewed the 
dimensions of this trematode specified by several of the earlier writers. 
Size : up to 50 mm. long, about 10-12-5 mm. in greatest breadth and 
about 4-5 mm. in greatest thickness. Shape : main part of the body 
proper elliptical and tapering to a uniformly narrow posterior " stalk," 
which is very extensile and contractile, being sometimes twice as 
long as the body proper, but more often only two-thirds as long, and 
sometimes deformed. Cuticle : wrinkled or folded so as to simulate 
segmentation in the " stalk." Prohaptor absent. Opisthaptor : 
cotylophore distinctly marked off and bearing 4 pairs of bowl-like 
muscular clamps having short peduncles, each clamp having 3 sclerites 
of horse -shoe -shape, two of them forming a lateral pair, the third a 
middle piece. Lateral sclerites each having a row of minute cavities 



136 



THE TREMATODA OF BRITISH FISHES 




-0-3 



Fig. 26. — Chimcericola leptogaster. A, the entire trematode showing the 
reproductive systems ; B, the anterior region, showing the zone of the 
vitellaria (line shading) and the extensions anteriorly and underlying 
the testes posteriorly ; C, diagram of the digestive system ; D, the 
opisthaptor, showing the extrinsic muscles of the clamps and the 
peduncles of the latter ; E, a clamp of the right side as seen in anterior 
view, showing the sclerites ; F, a clamp of the left side as seen in ventral 
view, showing the sclerites from a different aspect ; G, diagram of the 
reproductive systems, represented as viewed from the ventral side, and 
spread out transversely and longitudinally the better to show compo- 
nent organs. Note the ascending and descending limbs of the uterus 
(ut), the coiled oviduct (ov) and the anterior transverse vitelloduct (avk). 
(After Brinkmann, 19426.) 



DISCOCOTYLID^ 137 

simulating denticles. Hooklets forming 2 pairs, those of one pair 
minute (about 0-06 mm. long), those of the other somewhat larger 
(see Ruskowsky, 1934, p. 486 ; not evident in Brinkmann's specimens 
or figured in Scott's). Gut : mouth longitudinally oval. Prepharynx 
having a dorsal and 2 lateral pouches with folded walls. Pharynx 
globular and 0-16 mm. diameter, its wall muscular in the anterior and 
glandular in the posterior half. (Esophagus short. Intestine forming 
a large median sac extending back to a level just behind the vaginal 
pores, and here bifurcating to form long caeca which become narrower 
in the " stalk " and extend far into the cotylophore, where they 
terminate in 2 irregular pouches. Median intestine and caeca in 
front of the " stalk " having lateral diverticula which may branch 
once or twice ; intestinal epithelium in the region of the " stalk ' : 
folded to an extent which depends on the degree of contraction of the 
whole worm. Glands : numerous unicellular glands situated around 
the excretory vesicles and the most anterior intestinal diverticula 
opening into the oesophagus. Excretory system : vesicles situated 
one on either side of the body near the foremost diverticula, the 
terminal canals short, the pores lateral at the level of the pharynx, 
the main canals ventro- lateral to the caeca. Reproductive systems : 
common genital pore median and near the oesophagus in the anterior 
one-third of the body proper. Cirrus equipped with numerous 
hooklets 0-018 mm. long, consisting of a slender straight or slightly 
curved shaft and a base about twice as stout. Prostate glands well 
developed, vas deferens extending along a straight course between 
the uterus and the median intestine, widening anteriorly, to form a 
seminal vesicle. Testes numerous and situated in the posterior half 
of the broad anterior region. Ovary lobed and situated in front of 
the testes in the middle one-third of the body proper. Oviduct 
slightly convoluted and curving round the main vitelloducts and the 
genito-intestinal canal, which opens into the left caecum. Ootype 
globular and median, uterus very long and formed into several 
descending and ascending limbs (seven all told) between the ootype 
and the genital pore, metraterm dilated. Vitellaria extending 
throughout the lateral regions as far back as the base of the " stalk," 
from which follicles are excluded. Main lateral masses of follicles 
connected by a bridge formed by others above the anterior half of the 
uterine region and having medio -lateral extensions underlying the 
testes (Fig. 26 B). Vaginal pores situated in the anterior one-third 
of the body proper, terminal parts of the vaginal canals having much- 
folded walls and forming a hemispherical complex including uni- 
cellular glands ; lower parts of the vaginal canals continuous with 
the main lateral vitelloducts, each having a dilatation. Eggs lemon- 
shaped and measuring 0-185 x 0-103 mm. (0-2 x 009 mm. according 
to Parona & Perugia, 1892), operculate at the blunter end, some- 
times having one polar filament which may be much longer than 
the capsule (see T. Scott, 1910, PI. 7, fig. 5). Notes : Brinkmann 
figured what seems to be a subsidiary transverse vitelloduct situated 
just behind the level of the vaginal pores and opening into the vaginal 



138 THE TREMATODA OF BRITISH FISHES 

canals near its extremities. There is a description of this trematode 
by Ruskowski (1934, p. 486, fig. 2). 

Family MAZOCRAEIME Price, 1936. 

(Octobothriidae Taschenberg, 1879 ; Octocotylidse Beneden & Hesse, 
1863 ; Mazocriidae Southwell & Kirshner, 1937 — in part, in each case.) 

Opisthaptor generally comprising 4 pairs of clamp-like suckers 
equally spaced out along the lateral regions of an indistinct cotylophore 
or of the postero-ventral regions of the body. Cuticular supports of 
the clamps relatively simple, each clamp having single dorsal and 
ventral hoops with forked tips which articulate with a straight basal 
piece, sometimes having a rudimentary piece attached to it. Tip 
of the cotylophore invariably provided with 2-3 pairs of dissimilar 
hooklets. Testes generally numerous, but sometimes only a single 
elongate and lobed testis is present, occupying the space between the 
caeca in the posterior region of the body. Ovary elongate and folded, 
situated near the anterior end of the testis or testes. Vitellaria 
lateral and follicular. Vagina, when present, opening by a median 
dorsal pore. Of 3 genera which must be considered, Ophicotyle has 
a cotylophore bearing 2 pairs of small sucker-like organs in addition 
to the usual complement of clamps, which are the only components 
of the haptor in other genera ; Mazocraes has genital hooklets arranged 
in two transverse rows and dorsal vaginae are present ; Kuhnia has 
genital hooklets arranged in 2 longitudinal rows and dorsal vaginae are 
absent. 

Genus MAZOCRAES Hermann, 1782. 

{Octobothrium Leuckart, 1827, in part ; Octostoma Kuhn, 1829 ; Octo- 
cotyle Diesing, 1850 ; Octoplectanum Diesing, 1858 ; Octobothrium 
{Octocotyle) of St. Remy, 1891 ; Glossocotyle Beneden & Hesse, 1863.) 

Opisthaptor comprising an almost triangular cotylophore bearing 
4 pairs of clamps and 2 pairs of dissimilar hooklets, those of the outer 
pair the larger. Genital pore transversely elongate and equipped 
with 12 bipartite hooklets, 5 along each Up and 1 in each of the lateral 
angles (Fig. 27 F-H). Vaginal pore median and dorsal. Eggs 
generally having 2 polar filaments. 

Mazocraes alosae Hermann, 1782 (p. 182, PL 4, figs. 13, 14.) 

Octobothrium lanceolatum Leuckart, 1828, of authors ; Octostoma alosce (Her- 
mann) Kuhn, 1829 (pp. 358-61, PI. 17, figs. 1-3) ; Octocotyle lanceolata 
(Leuckart) Diesing, 1850 (p. 422) ; Octoplectanum lanceolatum (Leuckart) 
Diesing, 1858 (p. 383) ; Glossocotyle alosce Beneden & Hesse, 1863 (1864, 
pp. 102-3, PI. 9, figs. 11-18) ; Octobothrium alosce (Hermann) Cerfontaine, 
1896 (p. 516). 

Hosts : allis shad, twaite shad. 
Location : gills. 

T. Scott (1901, p. 145, PL 8, fig. 21) gave a very meagre account 
of specimens of this species found on both hosts in Scotland (locality 



MAZOCR A^IDJE 139 

unspecified), barely mentioning the shape, the buccal suckers and 
clamps and the hooks, one pair larger than the other, not even 
mentioning the genital hooklets. To judge by the figure and the 
stated magnification, the specimen must have been rather more than 
6 mm. long. No eggs were seen. A. Scott (1906, p. 193, PL 9, fig. 1) 
found numerous specimens on the gills of a shad sent from Carnarvon 
to Liverpool, but neither gave the diagnostic characters nor stated 
the size, although the specimen figures must have been about 7 mm. 
long and 1*3 mm. in greatest breadth, the ill-defined cotylophore 
taking up about 015 of the total length. Bay lis & Idris Jones 
(1933) recorded the occurrence of the trematode in the twaite shad 
at Plymouth, and it has been found near Brest, off the coast of 
Belgium and in the Rhine. Dujardin (1845, p. 313, PL 8, fig. F (12)) 
gave the diagnostic characters, and Beneden (1858, pp. 45-9, PL 5, 
figs. 1-18) described specimens of corresponding size and gave fairly 
good figures. Size : 10-12 mm. long and 1-4-1-5 mm. broad. Shape 
elongate, very slender anteriorly. Colour reddish-grey. Prohaptor a 
pair of minute buccal suckers. Opisthaptor : cotylophore ill-defined 
and rhomboidal, the 4 pairs of clamps arranged in 2 oblique rows 
laterally on extensile and retractile peduncles ; hooklets more or less 
terminal, those of the lateral pair larger than those of the median. 
Reproductive systems : genital hooklets arranged in 2 transverse rows 
of 5 plus 2 somewhat larger ones forming a pair laterally in an inter- 
mediate position. Eggs yellow, very large and almost fusiform 
measuring about 0-26 x 085 mm., according to Beneden having 
two polar filaments about as long as the capsule. According to 
Beneden & Hesse (1864, but see my note under Ophicotyle fintce 
on pp. 140-1) the hooks of the opisthaptor are strongly recurved, and 
the presence of moderately long polar filaments on the eggs was 
confirmed. 



Mazocraes harengi (Beneden & Hesse, 1863) Baylis & Idris Jones, 1933. 

Octocotyle harengi Beneden & Hesse, 1863 (1864, pp. 98-9, PL 9, figs. 1-10) ; 
Octobothrium harengi (Beneden & Hesse) Taschenberg, 1879 (a, p. 244) ; 
Octoplectanum harengi (Beneden & Hesse) of Linstow, 1889 (p. 95) and of 
Nicoll, 1915 (p. 369). 

Hosts : herring, allis shad. 
Location : gills. 

T. Scott (1901, pp. 145-6) mentioned two damaged specimens 
of this species which were found on a herring sent from Annan 
in the Solway Firth. Baylis & Idris Jones (1933) recorded the 
occurrence of the trematode on the allis shad at Plymouth, and 
it occurs also near Brest. Size : about 10 mm. long. Shape 
slender and lanceolate, tapering gradually anteriorly and more 
sharply posteriorly. Prohaptor a pair of buccal suckers of 
moderate size. Opisthaptor : cotylophore bearing 4 pairs of clamps 
and an ovoid posterior prolongation carrying 2 pairs of hooks, those 
of the outer pair much the larger and having a broad base which 



140 THE TREMATODA OF BRITISH FISHES 

narrows abruptly below and a slender point. Gut : mouth having a 
wrinkled (" denticulate ") border ; intestine bifurcate, but without 
apparent lateral diverticula, extending back as far as the clamps of 
the most posterior pair, which project slightly from the margins of 
the cotylophore. Eggs rather narrow, and having 2 delicate polar 
filaments slightly longer than the capsule. 

Mazocraes pilchardi (Beneden & Hesse, 1863). 

Octocotyle pilchardi Beneden & Hesse, 1863 (1864, p. 99, PI. 9, figs. 29-35); 
Octobothrium pilchardi (Beneden & Hesse) Taschenberg, 1879 (a, p. 244) ; 
Octoplectanwm pilchardi (Beneden & Hesse) of Linstow, 1889 (p. 95) and 
of Nicoll, 1915 (p. 369). 

Host : pilchard. 
Location : gills. 

This species was discovered near Brest, but has not been found 
in Britain. According to the original description it is similar to 
M . harengi, but smaller, and has clamps which become progressively 
smaller posteriorly and are set on short peduncles. The eggs were 
said to be rust- coloured, ovoid and equipped with a long filament 
terminating in a small plate-like swelling at one pole and a stump-like 
process at the other. 

Mazocraes heterocotyle (Beneden, 1870) sp. inq. 

Octostoma heterocotyle Beneden, 1870 (p. 67) ; Octoplectanum heterocotyle 
(Beneden) of Linstow, 1885 (pp. 252-3, PL 15, fig. 30), and of Nicoll, 1915 
(p. 369) ; Octobothrium heterocotyle (Beneden) Taschenberg, 1879 (a, p. 245). 

Host : sprat. 
Location : gills. 

This species was found on the coast of Belgium, but unrecorded 
in Britain. 



Genus inq. OPHICOTYLE Beneden & Hesse, 1863. 

{Octobothrium of Taschenberg, 1879, and Saint-Remy, 1891.) 

Body lanceolate and broadest in the posterior half, tapering 
gradually anteriorly and more abruptly posteriorly. Cotylophore 
oval and having 4 pairs of clamps, and a posterior prolongation 
bearing 2 pairs of minute accessory suckers and 2 pairs of hooks, 
those of the lateral pair larger than the others. 

Ophicotyle fintae Beneden & Hesse, 1863. 

Octobothrium fintas (Beneden & Hesse) Taschenberg, 1879 (a, p. 244). 

Host : twaite shad. 
Location : gills. 

Under the name of this trematode, which was found near Brest, 
Beneden & Hesse (1864, p. 101) described a form which answers to 



MAZOCRAEID^ 141 

the generic description, not of Ophicotyle, but of Glossocotyle. The 
reason seems to be the inadvertent interchange in the text of the 
descriptions for Ophicotyle fintce and Glossocotyle alosce. The descrip- 
tive terms used are of a general character, but there is no possibility 
of confounding the two types of opisthaptor. If we assume, however, 
that the specific headings and the references to the figures of PI. 9 
(in the text, but not on p. 134) are correctly set out, there remains a 
difficulty even when the descriptions are interchanged, because the 
absolute sizes indicated in the plate do not conform with the re- 
arranged diagnoses. We must therefore accept the sizes of the two 
worms as originally specified. 0. fintce is about 3 mm. long and, 
apart from the opisthaptor, very similar to Mazocraes alosce, particu- 
larly in the arrangement of the genital hooklets. 

Genus KUHNIA Sproston, 1945. 

(Octostoma Kuhn, 1829, in part, nee Otto, 1823 ; Octobothrium of 

Leuckart, 1842, in part ; Octocotyle Diesing, 1850, nee Goto, 1894, in 

part ; Oetoplectanum Diesing, 1858, in part.) 

Cotylophore of the opisthaptor bearing 4 pairs of almost sessile 
clamps arranged in 2 lateral rows and at least 2 pairs of hooks, the 
inner small and the outer larger and with a ridged shaft and 2 roots. 
Genital hooklets arranged along the lips of a longitudinal slit-like 
genital pore, those of one pair occupying the anterior and posterior 
angles. Vagina absent. Other characters as in Mazocraes. Para- 
sites on the gills of Scombridse. 

Kuhnia scombri (Kuhn, 1829) Sproston, 1945. (Fig. 27 A-E.) 

Octostoma scombri Kuhn, 1829 (pp. 361-2, PI. 17, figs. 4-5) ; Octobothrium 
scombri (Kuhn) of Nordmann, 1832 (pp. 77-8) and authors ; Octocotyle 
scombri of Dujardin, 1845 ; O. truncata Diesing, 1850 (p. 422) ; Oetoplec- 
tanum truncatum of Diesing, 1858 (p. 383) ; Pleurocotyle sco?nbri of 
Taschenberg, 1878 (pp. 575-7) ; Octocotyle major Goto, 1894 (pp. 203-5, 
PL 9, figs. 1-6) ; Octocotyle scombri of Nicoll, 1915 (p. 351) ; Pleurocotyle 
scombri of Nicoll, 1915 (p. 352). 

Hosts : mackerel. 
Location : gills. 

T. Scott (1901, p. 146, PL 8, fig. 20) gave a brief account of 
specimens about 5-5 mm. long which were found on the mackerel 
near Aberdeen. A. Scott found the trematode several times 
(1900; 1904, p. 116; 1906, p. 193, PL 9, fig. 2) on the same 
host in the Irish Sea, merely repeating that it is "a very 
slender species and easily overlooked." His figure indicates that one 
specimen was about 6 mm. long and 0-9 mm. in greatest breadth, 
with an armed genital pore about 0-4 mm. from the anterior 
extremity. Other zoologists have found the trematode in various 
parts of Britain on the same host, Nicoll (1914) at Plymouth, 
Baylis (1928) at Guernsey, Baylis & Idris Jones (1933) at Plymouth, 
and Rees & Llewellyn (1941) on the Irish Atlantic Slope, and it 



142 



THE TREMATODA OF BRITISH FTSHES 




Fig. 27. — A-E, Kuhnia scombri : A, the entire trematode ; B, the opis- 
thaptor ; C, the posterior end of B, showing the hooks ; D, the genital 
hooklets in situ, the anterior region above ; E, one of the clamps. F, 
Mazocraes sp. ? the genital hooklets. (Note. — One hooklet of both the 
anterior and posterior rows apparently missing.) G, showing the full 
complement of genital hooklets in the anterior row ; H, the posterior 
end of the opisthaptor, showing the hooklets. (Original.) 



HEXOSTOMATIDJE 143 

occurs in this host and sometimes in the Spanish mackerel and other 
hosts in the Mediterranean, Russia, Canada and Japan. Size ; 
1-6-5 mm. long and one-tenth to one-sixth as broad. Shape : 
lanceolate and broadest near the middle, tapering towards the narrow 
anterior one- quarter and towards the opisthaptor. Prohaptor : a 
pair of elongate oval buccal suckers. Opisthaptor : cotylophore 
heart-shaped and clearly marked off from the rest of the body, about 
0-2-0-6 mm. long, the clamps arranged in two diverging rows. Large 
hooks of the lateral pair having a stout blade and a ridged shaft 
with a projecting process ; small hooks of the median pair S- shaped 
with a twisted shaft and a sickle-like point (Fig. 27 C). Gut : caeca 
extending into the cotylophore and generally unequal in length, also 
devoid of diverticula. Reproductive systems : genital hooklets of the 
longitudinal series about 0-02 mm. long and with semicircular blades 
which are sometimes sharply bent on the shaft ; hooks of the lateral 
pair about the same size or a little larger and having a broad base 
and blades of lesser curvature. Gonads situated in the posterior 
half of the body proper, the testes behind the ovary. Vitellaria well 
developed laterally and extending from the genital pore almost to the 
base of the cotylophore. Eggs fusiform and operculate, bearing 2 
polar filaments about as long as the capsule, or one slightly shorter, 
but very variable in shape and size, measuring 0-194-0-312 x 0-049- 
0-126 mm., its internal lining sculptured. 



Family HEXOSTOMATID.E Price, 1936. 

Prohaptor a pair of minute buccal suckers. Opisthaptor com- 
prising 4 pairs of sessile, transversely- oval suckers and 2 pairs of 
hooklets. Suckers of the most posterior pair much smaller than the 
others, their reduced sclerites exhibiting some fusion. Sclerites of the 
large suckers numbering 3 in each, their shapes indeterminate, but 
the middle piece somewhat X- shaped. Vaginal pore median and 
dorsal near the level of the genital pore. Vagina bilobed, its distal 
part lined with tuberculate cuticle. 

Genus HEXOSTOMA Rafinesque, 1815, nee Hexastoma Rudolphi, 

1809, nee Hexastoma Kuhn, 1828. 

(Hexacotyle Blainville, 1828.) 

With the characters of the family. Parasites of the tunny. The 
type-species, H. thynni (Delaroche, 1811), occurs at Naples, the 
Balearic Isles and on the Atlantic coast of North America. H. 
thunnince (Parona & Perugia, 1889) at Genoa. A third species, H. 
extensicaudum (Dawes, 1940) was found by F. S. Russell on the gills of 
the tunny in the North Sea. Three other species occur in Japan, and 
one of them, H. acutum (Goto, 1894), was recorded by Baylis (1939) as 
occurring in the North Sea, but this may be a doubtful record in 
view of the new species since described. 



144 THE TREMATODA OF BRITISH FISHES 

Hexostoma extensicaudum (Dawes, 1940a) Dawes, 1946. 

(Fig. 28 A, B 1-4.) 

Hexacotyle extensicauda Dawes, 1940 (a, pp. 271-86, figs. 1-6). 

Host : tunny. 
Location : gills. 

Size : about 11 mm. long. Shape elongate, divisible into anterior, 
middle and posterior regions measuring 1-5 x 1-3, 5-5x3-3 and 
4-0 X 2-6 mm. Anterior region terminating in a median papilla 
0-25 mm. long and 0-3 mm. broad and passing abruptly into the 
middle region, which is separated from the posterior by a narrow 
waist 1-7 mm. broad. Prohaptor a pair of minute buccal suckers no 
more than 01 mm. diameter. Opisthaptor : cotylophore ill denned 
and bearing 4 pairs of suckers, those of the most posterior pair being 
very small, and 2 pairs of hooklets. Suckers of the first 3 pairs oval 
in outline, cup-like, having their long axes in the transverse plane 
and occupying about 0067 of the length of the body. Suckers of 
the most posterior pair more deeply concave than those in front, 
their breadth approximately 0-03 of the length of the body. Ratio 
of the breadths of the small and large suckers 0-45. Hooklets each 
having a strongly recurved point and a " guard " which approaches 
the tip in spanner fashion. Hooklets of the lateral pair 075 mm. 
long, those of the median pair only 001 5 mm. Sclerites of the large 
suckers taking the form of 3 dissimilar pieces, respectively lateral, 
middle and median topographically, the middle sclerite large and 
approximately X-shaped, but differing in shape in the different 
suckers, and sunk deeply in the musculature of the suckers. Sclerites 
of the small posterior suckers rudimentary (or vestigial ?), showing 
some signs of the fundamental tripartite nature. Musculature : outer 
circular muscles of the integument absent or vestigial; oblique and 
longitudinal muscles present, the latter being thicker dorsally than 
ventrally, and posteriorly than anteriorly, divided ventrally into 
superficial and deep components, which function respectively in 
bringing about release and adhesion of the suckers by virtue of their 
insertion in the rim and centre respectively. Gut : pharynx small 
and non-muscular. (Esophagus short and narrow. Caeca long and 
equipped with profusely- branched median and lateral diverticula, 
extending into the cotylophore. Reproductive systems : common 
genital pore near the bifurcation of the intestine at the junction of 
the anterior and middle regions of the body. Genital atrium capacious, 
0-6 mm. long, 0-3 mm. broad and 0-4 mm. deep. Vaginal pore median 
dorsal, close behind the level of the genital pore. Distal part of the 
vagina bilobed, capacious, quite as large as the genital atrium, and 
lined with cuticle bearing numerous tubercles. Copulatory organ 
conical, fibrillar, 0-35 mm. long and 0-2 mm. broad. Vas deferens 
long and convoluted. Prostate glands well developed. Testes 
numerous, but confined to the region between the caeca in the waist 
connecting the middle and posterior divisions of the body. Ovary 



HEXOSTOMATIDiE 



145 



U-shaped and having limbs folded about a dozen times in the trans- 
verse plane in front of the testes. Vitellaria well developed, extending 
throughout the dorsal part of the middle division of the body, their 
follicles equally abundant in the dorsal and ventral regions laterally, 
and consisting of groups of vitelline cells in various stages of secretory 
activity, one cell of each group being large and distended with droplets 




Fig. 28. — Hexostoma extensicaudum. A, entire trematode ; B, the sclerites 
of the opisthaptor, 1-4 those of suckers of the lst-4th pairs. Note. — 
In 1-3 the three sclerites of each sucker are represented from left to right 
as median, middle and lateral pieces ; in 4 the sclerites are shown in situ. 
(After Dawes, 1940a.) 

of shell-forming material. Uterus little folded, the terminal part 
(metraterm) straight. Ootype elongate in the transverse plane and 
situated between the testes and the ovary. Oviduct equipped with 
an ovicapt having 2 sphincters. Eggs not numerous, ovoid and 
very large (0-250 x 0-150 mm.), each having 2 polar filaments about 
0-25 mm. long and hollow in their basal parts. Note: this trematode 
causes much erosion of the tissues of the host, more especially in the 
upper part of the gills, but also near the free edge, where the opist- 
haptor adheres. 

10 



146 THE TREMATODA OF BRITISH FISHES 

VII. TREMATODES OF THE ORDER DIGENEA. 

In the present state of knowledge the complete classification of 
the Digenea cannot be achieved. There is no difficulty in separating 
families, but their arrangement in higher taxonomic units cannot be 
agreed upon. Some writers (Fuhrmann, 1928 ; Sprehn, 1933) have 
simply enumerated families ; others (Poche, 1926 ; Craig & Faust, 
1940) have set out groups such as sub-orders, tribes, sub-tribes and 
super-families, but not with any outstanding success. Many families 
of Digenea stand to-day more or less isolated, and some which have 
been arranged together are not known to be phylogenetically related 
beyond doubt. Classification was at one time based entirely on the 
characters of adults, and both difficulties and doubts arose when it 
became clear that larval characters must also be taken into account. 
Some larval and adult characters proved to be of high taxonomic 
value, notably the excretory system. Cort (1917) first showed and 
others subsequently proved the importance of this system, particularly 
the arrangement of flame- cells and excretory canals which is indicated 
in the flame -cell formula established by Faust. The formula is a 
mathematical expression which indicates the manner in which the 
canals branch, and it is just as applicable to cercariae and rediae, even 
miracidia, as to adults. But several zoologists have issued a note 
of caution against too implicit a reliance on this system in taxonomy, 
noting striking differences in the details in trematodes placed by 
universal agreement in the same family. The number of excretory 
canals and flame- cells often increases during the development of a 
cercaria into a metacercaria or an adult, probably in response to 
particular physiological needs, and similar definitive arrangements do 
not necessarily denote phylogenetic relationship, but may be due to 
convergence in evolution. Force was added to this contention of 
Brown (1933) by Hopkins (1941a), who found that the flame-cell 
formula of the Monorchiidae, which is 2[(2 + 2) + (2 -f 2)], is no less 
characteristic in a number of other families (Microphallidae, Hetero- 
phyidae, Allocreadiidae), as well as in members of others (Fello- 
distomatidae, Zoogonidae), trematodes which differ so markedly in 
structure and life -history that they cannot be closely related. It is 
logical to doubt the taxonomic value of the excretory system in 
instances where a primitive condition seems to persist in unrelated 
forms. We must admit, however, that there is good reason to doubt 
the apparent closeness of the relationship between two trematodes, 
on whatever grounds this is judged, when notable differences exist 
between the characters of the excretory system, especially if they 
occur in both larvae and adults. The types to which cercariae belong 
sometimes indicate relationship, but some character s of certain 
cercariae are of no more than specific value, the cx^jtory vesicle 
ranging from a sac-like form to a Y-shape through various inter- 
mediate shapes. Obviously, taxonomy demands the use of both 
larval and adult characters and difficulties prevail because our know- 
ledge of larvae is scanty. But larvae show more conspicuous adaptive 



DIGENEA 147 

characters than adults and may lead us into error. Of other criteria 
which are available to the taxonomist host-parasite relationships 
were stressed by Szidat (1939a), who claimed degrees of specificity 
which have not been generally acknowledged, perhaps because of 
erroneous diagnosis. Certainly, most of the trematode parasites of 
fishes occur only in this class of vertebrate, and belong to well-defined 
families. To attempt the arrangement of these families into higher 
units is hardly advantageous at present, and will not be attempted. 
The characters given for the families are largely those by which the 
adults may be recognized. 

Key to the Families of Digenea Parasitic in European Fishes. 

(1) Mouth situated near the middle of the bodv 

GASTEROSTOMATA (Bucephalus). 

(2) Mouth situated near the anterior extremity . . (PROSOSTOMATA). 

I. Adults inhabiting the blood vascular system, or cyst-like spaces 
in the tissues. 

a. Parasites of the blood vascular system . . Aporocotylid^. 

b. Cyst-dwellers ...... Dldymozoidje. 

II. Adults not inhabiting the blood vascular system or cyst-like 

spaces. 

a. Ventral sucker absent in the adult . . . Mesometrid^j. 

b. Ventral sucker present in the adult. 

a'. Ovary situated behind the testes ; uterus having 
descending and ascending limbs. 

(a) Vitellaria rarely follicular ; caeca long or short, 

but devoid of anterior extensions (i.e. intestine 
never H -shaped), 
(i) Vitellaria paired and compact ; caeca long ; 

excretory vesicle Y-shaped . Hemiurid^e. 

(ii) Vitellaria rarely paired, generally compact ; 
caeca short, rarely fairly long ; excretory 
vesicle sac-like . . . Zoogonid^e. 

(b) Vitellaria follicular ; caeca long and having a pair 

of anterior extensions (i.e. intestine H -shaped) 

AcCACXEUIDiE. 

b'. Ovary situated in front of the testis or testes. 

(a") Only one testis (two in Monorcheides) ; uterus 
having descending and ascending limbs. 

(a) Vitellaria compact, or only slightly lobed 

HAPLOPORIDiE. 

(b) Vitellaria follicular, but not extensive 

MONORCHnDJE. 

(b") Two testes present ; uterus sometimes having 
only an ascending limb. 
(a) Uterus having only an ascending limb, 
(a') Intestine a single simple caecum 

HaPLOSPLANCHNTD^. 

(&') Intestine bifurcate (i.e. two caeca 
present). 

(a") Cuticle smooth ; excretory vesicle 
Y-, T- or funnel-shaped. 



148 THE TREMATODA OF BRITISH FISHES 



Key to the Families of Digenea Parasitic in European Fishes — cont. 

(i) Excretory vesicle Y-shaped ; 
vitellaria not extending to 
the posterior extremity ; 
receptaculum seminis absent 

AZYGHDiE. 

(ii) Excretory vesicle not Y- 
shaped ; vitellaria extend- 
ing to the posterior ex- 
tremity ; receptaculum 
seminis present Allocreadiid^. 
(&") Cuticle spinous ; excretory vesicle 
Y-shaped. 

(i) Cirrus-pouch present ; cirrus 
and metraterm equipped 
with spine-like structures 

ACANTHOCOLPID JE . 

(ii) Cirrus-pouch absent ; cirrus 
and metraterm not equipped 
with spine-like structures 

ACANTHOSTOMATIDiE . 

(6) Uterus having descending and ascending 
limbs. 
(a') Cirrus-pouch absent. 

(i) Receptaculum seminis absent ; 
pharynx long ; excretory vesicle 
-shaped . Ptychogonimid^;. 

(ii) Receptaculum seminis present ; 
pharynx short or absent ; ex- 
cretory vesicle tubular 

GORGODERIDiE. 

(&') Cirrus-pouch present. 

(i) Oral sucker having six anterior 

processes . . Bunoderid^e. 

(ii) Oral sucker devoid of anterior 

processes . Fellodistomatid^:. 



Sub-order GASTEROSTOMATA Odhner, 1905. 

Mouth ventral, near the middle of the body. Haptor a muscular 
sucker with or without tentacles, or a rhynchus, at the anterior 
extremity. Intestine sac-like. Genital pore ventral, near the posterior 
extremity. Gonads globular, generally near the mid-body or posterior. 
Vitellaria located in the anterior region. Uterus having 2 or 3 folded 
limbs. Cercaria furcocercous. 



Family BUCEPHALID.E Poche, 1907. 
( Gasterostomidse Braun, 1893.) 
With the characters of the sub-order. 



BUCEPHALIDiE 149 

Sub-family Bucephalus Nicoll, 1914. 

Haptor a muscular sucker, simple and globular in Bucephalopsis , 
provided with a number of retractile tentacles or fimbriae in Bucephalus, 
shallow and surmounted by a fan-shaped hood in Rhipidocotyle. 

Genus BUCEPHALUS Baer, 1827. 
(Gasterostomum Siebold, 1848 ; Eubucephalus Diesing, 1855.) 

This genus was erected for a new furcocercous cercaria, Bucephalus 
polymorphus, the name denoting a whimsical likeness to the head of 
an ox, the long furcal rami representing the horns. Gasterostomum 
was the generic name chosen for an adult trematode, G. fimbriatum, 
inhabiting the intestine of freshwater fishes, particularly the perch, 
and shown by Wagener (1858) to be the adult corresponding to 
Bucephalus polymorphus, the name of which by priority rights now 
stands for both the adult and its larva. Manter (1940a) remarked 
on the curious coincidence which makes the name Bucephalus appro- 
priate for the adult, but in this case it is the extended tentacles which 
are comparable with horns. According to Liihe (1909) there is a 
circlet of 6 tentacles, but Nagaty (1937) asserted that the full number 
is 7. They show specific differences in shape and number, and they 
are invariably inconspicuous in the retracted condition, then appear- 
ing as small papillae. 

Bucephalus polymorphus Baer, 1827 (pp. 570-89, PI. 30, figs. 1-27). 

(Fig. 29 D-G.) 

Distoma campanula Dujardin, 1845 (p. 435) ; Gasterostomum fimbriatum 
Siebold, 1848 (v. 1, p. 129) ; G. laciniatum Molin, 1859 (p. 821) ; Bucephalus 
elegans Woodhead, 1930 (pp. 1-10, figs. 1-19) ; B. varicus Manter, 1940 
(a, pp. 335-7, figs. 3-9). 

Hosts : adults in the pike (outside Britain adults in the pike, 
perch, burbot, gudgeon ; metacercarise in the houting, dace, silver 
bream, bleak) ; cercaria? in freshwater mussels (Anodonta, Unio). 

Location : adults in the intestine, metacercariae encysted beneath 
the skin. 

Baylis (1939, p. 474) recorded the occurrence of this species in the 
pike in Wiltshire and Berkshire, and it has been found in France, 
East Prussia, Italy, the Red Sea and America. 

Size and shape : rarely more than 2 mm. long, often about 1 mm., 
but mature when 0-6 mm. long ; elongate and broadest in the middle, 
rounded posteriorly and truncated anteriorly. Cuticle covered with 
minute spines, which are most abundant anteriorly. Haptor oval, 
008-019 mm. long and 007-0-17 mm. broad in specimens 0-6-2-3 mm. 
long. Tentacles 7 in number, 3 dorsal, 2 lateral and 2 ventro-lateral, 
when extended tapering gradually from base to tip and then showing 
2 ventral processes, when retracted having the region behind the tip 
telescoped into the base, sometimes apparently absent. Gut directed 



150 



THE TREMATODA OF BRITISH FISHES 




Fig. 29. — A, Aspidogaster conchicola ; diagram of the genital organs. B, 
Aspidogaster limacoides ; entire trematode in dorsal view ; C, schematic 
diagram showing the connexions between ducts shown in B. D-G, 
Bucephalus polymorphus : D, an individual having extended tentacles ; 
E, the anterior end of the same in end view ; F, an individual having 
partially retracted tentacles ; G, the anterior end of the same. (A, 
after Stafford, 1895; B, C, after Bychowsky and Bychowsky, 1934; 
D-G, after Nagaty, 1937.) 



BUCEPHALID.E 151 

forward or backward, mouth almost central ; pharynx nearly spherical 
(0-03-0-10 mm. diameter) ; intestine a simple sac connected with the 
pharynx by a narrow neck (" oesophagus "). Excretory system 
having a terminal pore and a sac-like vesicle extending almost to 
the haptor. Reproductive systems : genital pore close to the excretory 
pore on the ventral surface, cirrus pouch 0-17-0-57 mm. long and 
005-0-10 mm. broad; seminal vesicle oval, cirrus stout and spinous. 
Gonads globular and arranged one behind another ; ovary foremost, 
on the right side of the body and slightly dorsal to the gut and the 
anterior half of the cirrus pouch, the ovary 0-05-0-13 mm. diameter, 
the testes 0-06-0-19 mm. Vitellaria coarsely follicular, comprising 
9-24 follicles 02-0 06 mm. diameter on either side of the median 
plane just in front of the mouth, not extending more than half-way 
between the mouth and the haptor. Uterus having ascending and 
descending limbs and numerous folds, rarely extending anterior to the 
vitellaria. Eggs small (0-021-0-027 x 0-013-0-023 mm.) and 
numerous, operculate and devoid of filaments or thickenings. 

Early descriptions of this species are incomplete. Wagener did 
not at first (1852a) mention tentacles in " Gasterostomum fimbriatum" 
but later (1858) described tentacles with a single ventral process 
The form " Bucephalus elegans " was credited with tentacles of this 
kind, but Nagaty (1937) recorded remarkable variations in B. poly- 
morphus, some specimens of which have tentacles with a single 
process, although 2 processes are typically present, for this reason 
regarding Woodhead's specimens as belonging also to this species. 
Manter (1940a) disagreed with this conclusion and chose to regard 
Nagaty's specimens as forming a distinct species, B. varicus. But a 
comparison of various slight differences which Manter made in support 
of his claim is not very convincing, although the hosts provide a 
problem. Nagaty's specimens were obtained from several fishes, 
especially species of " Trachynotus " and " Caranax," in the Red Sea, 
Manter 's from species of Caranx at Tortugas and a " small yellow 
jack " in the Pacific, while the normal hosts of Bucephalus polymorphous 
are freshwater fishes. But the cercarise are pelagic and a second 
intermediate host is required in the life cycle, both this and the final 
host being fishes. One intermediate host is the houting, which occurs 
in the sea as well as in fresh water, so that the possibility of marine 
fishes being infected is not entirely remote. Nagaty thus seems to 
have been justified in attributing his specimens to the species Buce- 
phalus polymorphus, from which they could not be separated on 
morphological grounds. Six other species of the genus occur in 
widely separated parts, 2 in India, 2 in America, 1 in southern Russia 
and 1 in Japan. 

Genus BUCEPHALOPSIS Diesing, 1855. 

(Prosorhynchoides Dollfus, 1929.) 

Diesing (1855c) erected a sub-genus, Bucephalopsis, for the larval 
form Bucephalus haimeanus Lacaze-Duthiers, 1854, found in Ostrea 



152 THE TREMATODA OF BRITISH FISHES 

and Cardium in the Balearic Isles. Tennent (1906) fed encysted 
American larvae belonging to this species to various fishes and referred 
the corresponding excysted forms to the species then known as 
" Gasterostomum gracilescens " (Distoma gracilescens Rudolphi, 1819). 
When Nicoll elevated the sub-genus to generic rank he named B. 
gracilescens (Rudolphi, 1819) as its type. Lebour (1908a, p. 9 ; 
1911, p. 425) was not satisfied that American and British forms were 
identical, but only because of differences in size and in the arrange- 
ment of the vitellaria. American forms from the gar were about 
1 mm. long, British forms from the angler about 6 times this length, 
and the vitellaria were arranged in paired clusters or cords respectively. 
Eckmarm (19326) consequently referred the American form to the 
species Bucephalopsis haimeanus (Lacaze-Duthiers, 1854). Nagaty 
accepted this as a valid species, although it seems to me to be a 
synonym of B. gracilescens, whose larva was acknowledged by Lebour 
to be " Bucephalus haimeanus" The identical nature of American 
and British forms seems much more likely when small specimens 
from the angler are used for purposes of comparison, the vitelline 
follicles in many of my own somewhat contracted specimens being 
arranged exactly as Tennent described. 

Nagaty (1937) reviewed 19 species of Bucephalopsis, 4 of them 
new and some of them apparently invalid. Apart from the type 
species, only 4 of these forms have been found in Europe, none in 
British waters, so that they are of interest only in so far as they 
represent possible synonyms of Bucephalopsis gracilescens, which is 
common in Britain. 



Bucephalopsis gracilescens (Rudolphi, 1819) Nicoll, 1914 (pp. 472-91), 

nee Tennent, 1906. (Fig. 30 A, B ; 31 A-K.) 

Distoma gracilescens Rudolphi, 1819 (p. Ill, 409) ; Gasterostomum gracilescens 
(Rud.) of authors. 

Hosts : In Britain, adults occur in the angler and the conger, 
encysted metacercariae in the cod, haddock, whiting, pollack, common 
ling and greater forkbeard, and cercariae in the cockle. 

Location : adults occur in the stomach, pyloric caeca and intestine, 
metacercariae in the nerves, particularly the auditory nerve and the 
spinal nerves near the tail. 

Cobbold (1859, p. 161) first recorded this species in Britain and it 
was not found here subsequently for nearly 50 years, but then became 
known at Cullercoats, St. Andrews, Aberdeen, Liverpool and Ply- 
mouth. It also occurs at Trieste, in the Balearic Isles, near Banyuls 
and at Woods Hole, U.S.A. Lebour (1908a) found heavy infections 
in every angler she inspected on the Northumberland coast, several 
hundred mature specimens in a single host. She also found encysted 
metacercariae in the cranial and spinal nerves of the haddock, cod 
and whiting, these being commonest in the haddock and occurring 
most abundantly on the auditory nerves and in the tail. Johnstone 



BUCEPHALIDiE 



153 




Fig. 30. — A and B, Bucephalopsis gracilescens : C, "Prosorhynchus 
grandis." D, "P. squamatus" E, anterior end of Rhipidocotyle viperce. 
F, "Prosorhynchus aculeatus." G, P. crucibulum. (A— D, after Lebour, 
1908 ; E, after NicoU, 1914 ; F and G, after Nicoll, 1910.) 



154 THE TREMATODA OF BRITISH FISHES 

(1905) also found cysts of this kind in the brain of the cod and haddock 
at Liverpool. Nicoll (19096) found juvenile specimens in the stomach 
of the cod at St. Andrews, and later (1915) recorded similar forms in 
the stomach of the pollack at Aberdeen. These fishes are not the 
normal hosts, and they must have acquired the metacercarise by 
feeding on other gadoid fishes infected with them in the normal 
way. Nicoll (1914) regarded the adults of this species as common 
parasites of the angler at Plymouth, and Bay lis & Idris Jones (1933) 
obtained mature specimens from the angler and conger there. I 
have found large numbers of adults in the angler at Plymouth, 
but not in every individual examined. Olsson (1868, p. 55) estimated 
the numbers of worms inhabiting the gut of a single fish as varying 
between one and two thousand, which must approach the maximum 
number that can be accommodated. 

Lebour's specimens were much larger than my own and showed 
the following characters : Size averaging about 6 mm. in length. 
Colour none, apart from the eggs. Shape continually changing 
in life, but generally elongate, tapering towards the extremities, 
broadest in the anterior region. Cuticle completely covered with 
minute spines. Haptor a sucker 0-4 mm. diameter. Gut : mouth 
situated at the end of the first quarter of the body. Pharynx globular 
and smaller than the haptor (0-3 mm. diameter). Intestine sac-like 
and (according to figs. 1 and 2, PI. 1) projecting anteriorly. Excretory 
system : vesicle club-shaped, extending nearly to the level of the 
mid-intestine, filled with refractive granules. Reproductive systems : 
genital pore almost terminal. Cirrus pouch elongate. Pars prostatica 
narrow. Seminal vesicle pyramidal. Cirrus long and spinous, occupy- 
ing almost the entire length of the pouch. Prostate glands filling the 
peripheral part of the same. Testes oval in outline, situated obliquely 
one behind the other just in front of the cirrus pouch ; ovary globular 
and somewhat smaller, situated on the right between the anterior 
testis and the gut. Male duct and oviduct short ; Laurer's canal 
directed posteriorly. Ootype located between the ovary and the 
anterior testis. Uterus extending forward as far as the gut, then 
posteriorly to the genital pore in juveniles, much convoluted in the 
adult. Vitellaria comprising a chain of large follicles (15-18 shown) 
on each side, extending from a point just behind the haptor to the 
termination of the gut, vitelloducts uniting to form the vitelline 
reservoir just behind and on the right of the ovary. Eggs very 
numerous, small (0 026 mm. long), and golden brown. 

My own specimens do not exceed 3 mm. in length, and most of 
them are no more than 1 mm. long. Many conform to the shape 
described by Lebour, but mass fixation leads to very great differences 
in shape, with consequent alteration in the arrangement of the internal 
organs (Fig. 31 A-K), although the living trematodes show just as 
considerable changes during movement. Well-extended specimens 
have the intestine directed partly forward (I), the vitelline follicles 
in line between the uterus and the haptor and well behind the latter, 
and the gonads far hi front of the cirrus pouch. Contracted specimens 



BUCEPHALID^; 



155 




Fig. 31. — Bucephalopsis gracilescens. A-H, small specimens, all from the 
same host, showing great variability in form and in the topography of 
the internal organs ; I-K, larger individuals from another Angler, show- 
ing similar variability. (A-H are referable to the upper, I-K to the 
lower scale.) (Original.) 



156 



THE TREMATODA OF BRITISH FISHES 



may be broader than long (H) and have vitelline follicles, uterus and 
gut crowded in the anterior region, the gonads, excretory vesicle and 
cirrus pouch filling the posterior. Intermediate states of contraction 
do not produce graded differences in the positions of the internal 
organs, because they are not regular (A-H) ; instead, there is a 
variety of topographical arrangements which defy description. 
Variability does not concern only changes of this kind. In small 
and large individuals the proportions of the organs vary, presumably 
as a result of growth, and relative differences in size occur in some 
instances. Variation in shape tends to vitiate measurements, but 
well extended small and large specimens provided these figures : 





mm. 


mm. 


0-9-1-2 


30 




0-3-0-4 


0-6 




0-20-0-21 


0-24 




0-10-0-11 (dia.) 


0-23 x 013 




0-11-0-13 (dia.) 


0-27-0-35 x 0-18 




0-27-0-36 


0-85 




0021 x 0016 


0-025 x 0018 



Length of the body . 
Breadth of the body 
Diameter of the haptor 
Dimensions of the ovary 
Dimensions of the testes 
Length of cirrus pouch 
Mean size of the eggs 

Comparison of small with larger specimens thus reveals the fact that 
the body is relatively broader, the gonads relatively smaller, the 
cirrus pouch of about the same relative size, but in the contracted 
state of the body appearing proportionately larger, the haptor 
relatively very much smaller, and the eggs absolutely slightly smaller, 
but proportionately much larger. In short, the shape of the body, its 
proportions and the sizes and dispositions of the internal organs are 
all subject to considerable variability, even in specimens of one 
species taken from the same host. For this reason such criteria 
must be used with great circumspection when different species are 
being compared, or when a new species is being set up. Linton 
(1940, pp. 30-3, PI. 18, figs. 245-9) stressed this point regarding 
variability in relation to American specimens from the garfish. This 
is not the place to discuss in detail the species of Bucephalopsis which 
have been reported outside Europe, but some of these will un- 
doubtedly prove to be synonyms of B. gracilescens. Thus B. south- 
welli Nagaty, 1937, cannot be separated from the type species on 
morphological grounds, and other species from the Red Sea may well 
be variants of it whose main differences will be resolved ultimately in 
terms of growth and movements of the body. Another synonym of 
B. gracilescens is B. elongatus Ozaki, 1928, and other Japanese species 
differ from this mainly in the shape and size of the body and the sizes 
of the eggs — all unreliable characters of distinction. Altogether about 
twenty species have been recorded, and two which deserve mention 
here are B. triglce (Beneden, 1870) nee Nicoll, 1909 (Gasterostomum 
triglce Beneden, 1870, p. 30, PI. 3, fig. 15), which was found in the 
yellow and grey gurnards in Belgium, and B. tergestinus (Stossich, 
1883) {Gasterostomum tergestinum Stossich, 1883, pp. 119-20, PI. 2, 
fig. 5), which was found in the black goby and Gobius jozo at Trieste. 



BUCEPHALIDiE 157 

Other species range from Russia to the Red Sea, India, Australia and 
Japan, and one species occurs at Woods Hole. For further informa- 
tion see Dawes (1946). 



Genus RHIPIDOCOTYLE Diesing, 1858. 

(Nannoenterum Ozaki, 1924.) 

When Diesing erected the sub-genus Rhipidocotyle he allocated two 
species to it, but did not name the type. Stiles and Hassall (1908) 
chose " Gasterostomum gracilescens (Rudolphi, 1819)," but in elevating 
the sub -genus to generic rank Nicoll showed that the alternative 
species " G. minimum Wagener, 1852 " must stand as the type, being 
the only one of the two species in which a sucker and a fan-shaped 
hood are combined as implied by the name chosen by Diesing. 
Eckmann (19326) re-examined the type specimens of this species and 
concurred, but showed that " G. minimum " is identical with " G. 
galeatum (Rudolphi, 1819)," which thus became the type. She 
rightly relegated Nannoenterum to synonymy with Rhipidocotyle, 
the only differences between the two being trifling matters of shape 
and the relative positions of the uterus and vitellaria. The type 
species is well known in Britain, but no other species occurs here, 4 
occurring in U.S.A., 1 in Canada, 1 in Japan and 2 in the Red Sea. 



Rhipidocotyle galeata (Rudolphi, 1819) Eckmann, 1932, emend. 

(Fig. 30 E.) 

Monostomum galeatum Rudolphi, 1819 (p. 86, pp. 349-50) ; Gasterostomum 
galeatum (Rudolphi) of Stossich, 1898 (p. 62) ; G. minimum Wagener, 1852 
(pp. 558-63, fig. 2) ; G. triglce (Beneden) of Nicoll, 1909 ; Rhipidocotyle 
minima (Wagener) of Diesing, 1858 (pp. 361-2), and of Nicoll, 1914 
(pp. 492-3) ; R. viperce Nicoll, 1914 (pp. 493-4, fig. 4), nee Beneden, 
1870. 

Hosts : greater weever, lesser weever, red gurnard, yellow gurnard, 
grey gurnard. 

Location : intestine. 

Nicoll (19096) found many specimens of this species in the grey 
gurnard at St. Andrews, naming them Gasterostomum triglce. Later 
(1914) he got a few more specimens from the greater weever at 
Plymouth, recording these as Rhipidocotyle viperce, and others from 
the yellow, grey and red gurnards and the lesser weever, which were 
called R. minima. Little (1929a) found " R. minima " in the grey 
gurnard at Gal way, and Baylis & Idris Jones (1933) found it in 
the yellow and grey gurnards at Plymouth. Size : mature when 
0-7-1-2 mm. long and 0-4 mm. in greatest breadth. Shape: elongate 
oval, truncated at the anterior end, pointed at the posterior. Cuticle 
covered with minute spines. Haptor shallow and sucker-like, not 
very muscular, up to 013 mm. diameter, the hood 5-rayed. Gut : 
pharynx about 05 mm. diameter and 0-8 mm. from the anterior 



158 THE TREMATODA OF BRITISH FISHES 

extremity. Intestine simple, but often obscured by the folds of the 
uterus. Reproductive systems : cirrus pouch very elongate, extending 
forward to a level just in front of the mouth. Cirrus short, but pars 
prostatica long. Gonads grouped together on the right in front of 
the mouth ; the ovary globular, 0-1 mm. diameter and 0-6 mm. from 
the anterior extremity ; the testes 0-12 mm. diameter, one behind the 
other, slightly lateral to and contiguous with the ovary. Vitellaria 
lateral, extending from the level of the ovary to a point 0-25 mm. 
from the anterior extremity, the much-folded uterus filling up the 
available space between them and extending back to a level between 
the testes and the gut. Eggs 0036-0037 mm. long and 0018- 
0021 mm. broad. 

Nicoll (1914, p. 942) amended his description (19096, pp. 23-4) 
of " Gasterostomum triglce" remarking on the great length of the 
excretory vesicle and the relatively posterior position of the pharynx, 
which, in some specimens, is at the level of the anterior testis, but 
in others near the blind end of the cirrus pouch. Variability seems 
to affect the relative sizes of the pharynx and the haptor also, 
for these organs may be of fairly equal or unequal sizes. The 
form " Rhipidocotyle viperce " resembled " E. minima " in general 
appearance, but differed in the arrangement of the gonads and in 
the length of the cirrus pouch. Eckmann seems to have been justified 
in referring these forms to E. galeata, and Nagaty's opinion that 
Nicoll's specimens are " identical with " the American species E. 
septapapillata Krull, 1934, may be taken to indicate that the list of 
synonyms of the type-species is incomplete. 



Sub-family Prosorhynchinje Nicoll, 1914. 

Haptor a rhynchus. 

A number of genera have been referred to this sub -family, but 
they seem to have been resolved into two, most of them representing 
synonyms of Prosorhynchus, but one remaining apparently valid. 
This is Alcicornis MacCallum, 1917, which was erected for A. carangis 
(an intestinal parasite of Caranx ruber brought from Key West to the 
New York Aquarium), but now contains also A. baylisi Nagaty, 
1937, a parasite of Caranx sp. in the Red Sea. The type genus is 
well known in various parts of the world, and I have already made a 
short statement about the synonymy (Dawes, 1946, p. 194). 



Genus Prosorhynchus Odhner, 1905. 

(Gotonius Ozaki, 1924 ; Skrjabiniella Issaitschikow, 1928 ; Mordvilkovia 
Pigulewsky, 1931 ; Dollfusina Eckmann, 1932 ; Dollfustrema Eckmann, 
1934 ; Neidhartia Nagaty, 1937; Pseudoprosorhynchus Yamaguti, 1938.) 

In erecting this genus Odhner (1905) placed in it P. crucibulum 
(Rudolphi, 1819) and two new species, P. aculeatus and P. squamatus, 
which Eckmann (19326) regarded as identical. Nagaty (1937) con- 



BTTCEPHALID^ 159 

curred, but Manter (1940a) had more faith in Odhner's discrimination 
and made a new species, P. caudovatus, for Eckmann's " P. cruci- 
bulum " on account of the polar processes on the eggs. Two forms 
found in Britain, P. grandis Lebour, 1908 and P. triglce sp. inq. 
Nicoll, 1914, were relegated, along with several others, to synonymy 
with P. crucibulum by Nagaty, who recognized along with the type 
and P. aculeatus three species from the Far East and a new species from 
the Red Sea, Manter (1940a) adding three new species from America, 
Srivistava (1937) two more from India. The only species with which 
we are concerned are Prosorhynchus crucibulum in its various forms 
and P. aculeatus. As the main differences by which the latter can be 
distinguished from the former are the oval instead of conical shape 
of the rhynchus and the triangular instead of linear arrangement of 
the gonads, characters which may be regarded as coming within the 
limits of variability of a single species, these two species are regarded as 
identical, for reasons which will be given after structure has been 
considered. 



Prosorhynchus crucibulum (Rudolphi, 1819) Odhner, 1905. 

(Fig. 30 C, D, F, G.) 

Monostoma crucibulum Rudolphi, 1819 (p. 83, pp. 342-3) ; Gasterostomum 
crucibulum (Rud.) of authors ; G. armatum Molin, 1859 (pp. 291, 820) ; 
Bucephalus crux Levinsen, 1881 (pp. 80-1, PL 1, fig. 7a-j) ; Prosorhynchus 
aculeatus Odhner, 1905 (pp. 297, 302, 305) ; P. squamatus Odhner, 1905 (pp. 
297-304, PL 2, figs. 1-5) ; P. grandis Lebour, 1908 (a, p. 13, PL 1, fig. 5) ; 
P. triglce Nicoll, 1910 (p. 495, fig. 5) ; P. costai Travassos, Artigas & Pereira, 
1928 (p. 33, fig. 121) ; P. scalpellus McFarlane, 1936 (pp. 336-7, 7 figs.) ; 
Mordvilkovia elongata Pigulewski, 1931 (pp. 437-8, fig. 2) ; Skrjabiniella 
aculeatus (Odhner) Issaitschikow, 1928 (p. 23). 

Hosts : In Britain, conger, short-spined cottus (father-lasher), 
long-spined cottus, Montagu's sea snail, grey gurnard, cod, whiting. 
Location : intestine and pyloric caeca (abnormally, in the stomach). 

Nicoll (1907) recorded this species as P. squamatus in the long 
spined cottus (listed as Cottus bubalis Euphr. — father-lasher) at St. 
Andrews. Lebour (1908a) found it once in 13 specimens of the 
" bull-head " (father-lasher implied) at Culler coats and described it 
as P. squamatus, other specimens from the cod and whiting being 
called P. grandis. Nicoll (1910) found both P. squamatus and P. 
crucibulum in the conger at Millport and (1914) also at Plymouth, 
where P. triglce was found in the grey gurnard. Little (1929a) 
recorded the occurrence of P. triglce in the grey gurnard, P. aculeatus 
in the conger and encysted stages of P. crucibulum on the gills of the 
cod at Galway. Baylis & Idris Jones (1933) found P. aculeatus in 
the conger and P. crucibulum in both the conger and the angler at 
Plymouth, Jones (1943) in conger off our west coast. Outside Britain, 
the trematode has been found in Italy (at Padua), off the coast of 
Belgium, in the Baltic Sea, near Greenland, in the Red Sea and in 



160 THE TREMATODA OF BRITISH FISHES 

U.S.A. (at Woods Hole). The list of synonyms indicates that it is 
difficult to describe, and it will be as well first of all to deal with forms 
obtained by Nicoll (1910) from the conger in the Firth of Clyde and 
definitely assigned to P. crucibulum. Size : 2-3-7 mm. long when 
mature, greatest breadth about three-eighths of the length. Colour : 
absent in small, yellowish-brown hi large specimens. Shape : elongate 
and slightly flat, truncated anteriorly, pointed posteriorly ; average 
specimens 3 15 mm. long, 1-1 mm. broad. Cuticle : covered with 
scale-like spines, which are more numerous anteriorly. Haptor : a 
very large wedge- or cornucopia-shaped rhynchus measuring 0-62 X 
0-57 mm. in the average specimen, but frequently a button-like 
process in small worms, generally having a projecting circular ridge. 
Gut : mouth almost exactly central. Pharynx globular and 0-21 mm. 
diameter. Intestine ovoid and connected with the pharynx by a 
narrow oesophagus. Overall length about 0-3 mm. Excretory system : 
vesicle comparatively short, extending through the final one-third of 
the body. Reproductive systems : cirrus pouch short and stout, 
situated on the left and co-extensive with the excretory vesicle. 
Gonads variable in relative positions, generally ovary situated on 
the right just behind the pharynx ; testes diagonally arranged a little 
farther back ; diameters of ovary and testes respectively 0-25 mm. 
and 0-28 mm. Uterus having ascending and descending limbs, mainly 
situated on the left, but forming several loops between the gut and 
the vitellaria and several more posteriorly on the right. Vitellaria 
forming a continuous arc of irregular follicles behind the rhynchus 
and in front of the uterus, unequally distributed on right and left. 
Eggs numerous, pale yellow to dark brown in colour, measuring 
0026-0030 x 0016-0021 mm. (mean 0029 X 0019 mm.). 

Nicoll (1910) also redescribed " P. aculeatus," and the following 
points must be noted carefully because they include the main features 
of contrast in what he regarded as two distinct species. Size : 
1-2-5 mm. long when mature, greatest breadth about half the length. 
Shape : almost elliptical, but pointed towards either end, average 
specimen measuring 2 x 0-95 mm. Colour : yellowish- brown. 
Cuticle : covered with scale -like spines. Haptor : a rhynchus which 
may be protruded like a small button, or retracted and then forming 
a shallow, saucer-like depression of simple ovoid shape measuring 
0-27 X 0-15 mm., its diameter nearly twice the depth. Gut : mouth 
little more than one-quarter of the length of the body from the 
posterior extremity ; pharynx 14 mm. diameter ; intestine a simple 
sac extending forward, but not to the middle of the body. Excretory 
system : vesicle extending forward to the level of the anterior testes, 
or slightly in front of the pharynx. Reproductive systems : cirrus 
pouch thick and of moderate length, co-extensive with the excretory 
vesicle. Gonads arranged in the form of a triangle in the posterior 
half of the body as in " P. crucibulum," but in the region of the gut ; 
testes never symmetrical and measuring 0-26 x 0-20 mm. ; ovary 
situated on the right and not much smaller than the testes. Uterus 
having ascending and descending limbs and numerous regular folds, 



BTTCEPHALID^ 161 

mainly between the vitellaria and the gut. Vitelline follicles large , 
forming a regularly arranged arc crossing the body 0-4 mm. from its 
anterior end. Eggs broad oval in shape, measuring 026-0 031 x 
0-016-0-020 (mean dimensions 0-0285 x 0-0185 mm.). 

Nicoll stated that " P. crucibulum " was met with half as frequently 
as "P. aculeatus " in the conger, but is probably quite as common. 
He amended this statement later (1914), stating that the two " species " 
are found in association and are equally common. Apart from the 
size ranges, which overlap slightly, they must have been difficult to 
separate. From Nicoll's descriptions it is not difficult to see the 
characters of P. crucibulum in " P. aculeatus" if we assume that the 
body is more extended anteriorly, but has the rhynchus more con- 
siderably introverted. This would bring the gut, the uterine folds 
and the vitelline follicles into a relatively more anterior position, and 
would destroy what is regarded as a characteristic arrangement of 
the loops of the uterus in " P. aculeatus." Considering the way in 
which the animal can alter its shape, this implies that the two forms 
are identical. Size is not a criterion of distinction, because Nagaty 
found very small specimens of P. crucibulum 0-8-1-8 mm. long, i.e. 
smaller than Nicoll's specimens of "P. aculeatus," and even the 
smallest of them contained eggs, although Nicoll regarded specimens 
less than 2 mm. long as immature. The size range of P. crucibulum 
may be taken as 0-8-6 mm. when mature if we accept the measure- 
ments of Molin (4-6 mm.), Odhner (1-75-2-25 mm.), Ozaki (1-75- 
3-4 mm.) and Eckmann (2-4 mm.) as well as those given. Differences 
in the form and histological appearance of the rhynchus are incon- 
clusive because they take no account of the state of the organ. It 
is odd that Nagaty should regard " P. aculeatus " as a valid species, 
but "P. squamatus " and "P. grandis " as synonyms of P. crucibulum, 
because the last two differ more considerably from the type than the 
first-named, and occur in different hosts (" squamatus " in the long- 
spined and short-spined cottus and Montagu's sea snail, " grandis," 
in the cod and whiting). In "P. grandis," as described by Lebour, 
the vitelline follicles form an arc and the eggs are relatively large 
(about 0033 mm. long), but neither of these characters are significant. 
Extension of the anterior end of the body breaks the arc of follicles, 
and the eggs of small American specimens of "P. squamatus " 
described by Linton (1940, p. 28, figs. 240-2) contained eggs of the 
average dimensions 036 x 0-024 mm. The various forms of P. 
crucibulum which have been described grade almost imperceptibly 
one into another. 

D. O. Jones (1943) redescribed "P. aculeatus" (as Skrjabiniella) , 
wrongly including the name Gasterostomum crucibulum in the synonymy. 
Her specimen was small (1-3 x 0-66 mm.), and showed the general 
characters indicated by Nicoll (1910), but not the regular folds of the 
uterus which Nicoll regarded as characteristic of this form. Her 
Fig. 1 gives a more detailed impression of structure than Nicoll's, 
her Fig. 2 a better idea of the structure of the cirrus, which has a 
lateral opening and a tongue-like terminal process. Structural 

11 



162 THE TREMATODA OF BRITISH FISHES 

characters which Jones made clear include the accommodation of 
the seminal vesicle inside the cirrus pouch, the existence of a recep- 
taculum seminis uterinum and an ovicapt, and the binding together 
of sperms by secretion in the ejaculatory duct. The eggs came 
within the range specified by Nicoll, are slightly pointed at one pole 
and undergo segmentation while still in the uterus. Jones repeated 
the comparison made by Ozaki (1928) between the rhynchus in "P. 
aculeatus " and P. uniporus Ozaki, 1924, which Manter (1940a) 
regarded as its synonym, at the same time mentioning that P. 
magniovatus Yamaguti differs only in the larger size of the eggs. It 
seems likely that other synonyms of P. crucibulum will be found 
among the species obtained in the Galapagos by Manter, who admitted 
that additional material might show P. rotundus to be a synonym of 
P. scalpellus, which Nagaty included in the synonyms of P. crucibulum. 



Sub-order PROSOSTOMATA Odhner, 1905. 
Family ALLOCREADIID^ Stossich, 1904. 

Size and shape : small or medium size, long oval or elongate, 
tapering anteriorly and rounded posteriorly, slightly flattened. 
Cuticle : rarely spinous. Suckers : never very large and rarely far 
apart. Out : prepharynx sometimes long, pharynx small, oesophagus 
of medium length, caeca fairly or very long. Excretory system : 
vesicle tubular or funnel-like with a long and broad median stem, flame- 
cell formula 2[(4 + 4 -f 4) + (4 + 4 -f- 4)]. Reproductive systems : 
genital pore median or slightly lateral near the end of the oesophagus. 
Cirrus pouch large and elongate. Cirrus well developed. Vesicula 
seminalis interna invariably present (sometimes externa also). Testes 
large and globular, one behind the other in the posterior region. 
Ovary spherical or lobed, situated in front of the testes, rarely median. 
Receptaculum seminis large, Laurer's canal present. Vitellaria 
follicular and lateral, mainly in the posterior half or two-thirds of 
the body, sometimes extending anterior to the ventral sucker. 
Uterus having only an ascending limb. Eggs variable in size and 
shape, polar filaments sometimes present. 

There have been a few proposals to split the Allocreadiidae into 
several families, but conflicting opinions as to how this can best be 
done show that the time is not yet ripe for such a change. Four 
sub -famiHes are represented in Britain. Spinous forms belong to 
the Lepocreadiinae and are parasites of marine fishes. Most non- 
spinous forms belong to the Allocreadiinae and, with the exception of 
the type-genus, are also parasites of marine fishes. Two non-spinous 
forms parasitic in freshwater fishes, Crepidostomum and Sphaerostoma, 
belong respectively to the Crepidostomatinae (see p. 192) and the 
Sphaerostomatinae, and in the former the oral sucker has distinctive 
anterior processes. 



ALLOCREADIID^] 163 

Sub-family Allocreadiin^] Looss, 1902. 

Key to genera. 

I. Genital pore median, oesophagus long or short, testes lobed or not. 

1. Testes not lobed, eggs without polar filaments. 

a. Cirrus pouch not projecting behind the ventral sucker. 

(a) (Esophagus long, pars prostatica present, vitellaria 

confined to the region behind the ventral sucker 
(parasites of freshwater fishes) . . Allocreadium. 

(b) (Esophagus short, pars prostatica absent, vitellaria 

extending in front of the ventral sucker (parasites 

of marine fishes) Cainocreadium. 

b. Cirrus pouch projecting behind the ventral sucker Peracreadium. 

2. Testes irregularly lobed, eggs having a filament at the anopercular 

pole ......... Helicometra. 

II. Genital pore slightly lateral, on the left, oesophagus short, testes 
rounded. 

1. Ovary globular, vitellaria extending anterior to the ventral 

sucker, cirrus pouch not extending back behind it . Plagioporus. 

2. Ovary 3-lobed, vitellaria not extending anterior to the ventral 

sucker, cirrus pouch extending back behind it . . Podocotyle. 



Genus ALLOCREADIUM Looss, 1900. 
(Creadium Looss, 1899, nee Vieill., 1816.) 

Allocreadium isoporum (Looss, 1894) Looss, 1900. (Fig. 34 A.) 

Distoma isoporum Looss, 1894 (pp. 49-56, PI. 1, figs. 15-18 ; PI. 5, figs. 102- 
112) ; Creadium isoporum of Looss, 1899 (pp. 570, 571, 595). 

Hosts : Cyprinidse (carp, tench, bream, roach, chub, minnow, 
barbel) and pike on the Continent (Rhine, Lake Constance) ; roach 
in Cambridgeshire and chub in Berkshire (see Baylis, 1939). 

Location : intestine (free in the lumen, not attached to the wall). 

Size : 3-5 mm. long and 0-3-0-75 mm. broad. Shape : elongate 
and spindle-like, broadest just behind the ventral sucker, tapering to 
a point posteriorly, having slight " shoulders " and a cylindrical 
" neck " anteriorly. Colour : white, or pale yellow or red, with 
granules of dark pigment massed at the sides of the pharynx, these 
being the vestiges of the eye-spots of the cercaria. Suckers : about 
equal in size, the ventral larger than the oral at most in the ratio 
14/13 and situated just in front of the middle of the body. Gut : 
prepharynx short. Pharynx much smaller than the oral sucker. 
(Esophagus long, terminating just in front of the ventral sucker, 
caeca very long and of unequal lengths. Excretory system : median 
stem of vesicle narrow, but dilated terminally, extending to the 
posterior testis. Reproductive systems : genital pore situated beneath 
the oesophagus and about 0-3 mm. in front of the ventral sucker. 
Cirrus pouch large and pyriform, 0-45 mm. long and 0-2 mm. broad. 
Testes almost spherical, about 0-5 mm. diameter, one behind the 



164 THE TREMATODA OF BRITISH FISHES 

other behind the middle of the body. Ovary much smaller than the 
testes and near the middle of the body, diameter 0-25-0-3 mm. 
Vitellaria dorsal and lateral to the caeca and confined to the posterior 
half of the body ; follicles large, and tending to fill the available space 
behind the posterior testis. Uterus having a few large loops in front 
of the testes, extending lateral to the caeca above the ventral sucker. 
Eggs few and large (0 09 X 06 mm.), and having thin, horn-yellow 
shells, when laid containing an ovum and 10-15 vitelline cells. 
Development : according to Luhe (1909) the snails Sphcerium corneum 
and 8. rivicola serve as the first intermediate hosts, insect larvae 
(Ephemera vulgata, Chcetopteryx villosa, Anabolia nervosa) as the 
second, containing encysted metacercariae. The cercaria is said to 
be the rhopalocercous Cercaria isopori Looss. Szidat (19396) has 
reminded us that the life-history is by no means established, quoting 
Looss (1894) as writing : ' Was die Jugendform unseres Wurmes 
anlangt, so glaube ich, dieselbe zu kennen, wenngleich die Annahme 
ihrer Zuge horigkeit zu den erwachsenen Thiere nur auf die Ahnlichkeit 
in der Organisation, nich auf den direkten Nachweis durch den 
Versuch gegrundet ist." 

Three other species of Allocreadium occur in Europe, but not in 
Britain, A. transversale (Rudolphi, 1802) Odhner, 1901 (pp. 505-6), 
A. angusticolle (Hausman, 1896) Odhner, 1901 (p. 517) and A. poly- 
morphum Layman, 1933. The first of these occurs in the spined 
loach at Griefswald and Rossiten (East Prussia), where Szidat (1938a) 
found the only specimen discovered for more than 130 years. The 
second of these species occurs in the miller's thumb at Basel and in 
Lake Constance. Looss (1899) referred it to the genus Creadium, 
Nicoll (1909a) to Peracreadium and Hunninen & Cable (1943) 
tentatively to Plagioporus. The life-history of this species was 
studied by Mathias (1937). The third of these species was found in 
Cottus kneri in Lake Bajkal (Russia), associating in the intestine with 
a species of Crepidostomum. 



Genus CAINOCREADIUM Nicoll, 1909. 
Cainocreadium labracis (Dujardin, 1845) Nicoll, 1909. (Fig. 32 D.) 

Distomum (Dicrocoelium) labracis Dujardin, 1845 (p. 398) ; Allocreadium 
labracis (Dujardin) of Johnstone, 1908 ; Echinostoma labracis (Dujardin) 
of Beneden, 1870 (p. 45). 

Host : bass. 
Location : intestine. 

This species occurs in various parts of Europe (Rennes, Catania, 
Isle of Elba) and was found by Johnstone in different parts of the 
Irish Sea (Morecambe Bay, Cardigan Bay). Nicoll (1914) also found 
it, at Plymouth. The bass seems to be a specific host ; the type- 
specimens and specimens found by other zoologists (Stossich, Molin, 
Beneden) invariably came from it. According to Johnstone (1908, 
pp. 44-53, PI. 3 and figs. 1-4) bass taken from the Irish Sea are nearly 



ALLOCREADIIDiE 



165 




Fig. 32. — A, Podocotyle atomon. B, P. atomon var. dispar. C, P. syn- 
gnathi. D, Cainocreadium labracis. E, Helicometra fasciata ; F, an 
egg of the same. G, Lepidauchen stenostoma. H, Crepidostomum 
farionis. (A, after Lebour, 1908 ; B, after Nicoll, 1909 ; C and G, 
after Nicoll, 1913 ; D, after Johnstone, 1908 ; E and F, after Nicoll, 
1910 ; H, after Brown, 1927.) 



166 THE TREMATODA OF BRITISH FISHES 

always infected, although only the largest specimen obtained was 
described. The specimens were said to be unsuitable for histological 
study, and the topography of the internal organs might have been 
altered by the manner of fixation, immersion in fresh water and 
subsequent treatment with formalin, but a clear impression of 
structure was given. Size : comparatively large for an Allocreadiid, 
up to 9-7 mm. long and 2 mm. in greatest breadth. Shape : elongate 
and spindle-like, slightly constricted near the middle. Suckers : 
oral 0-76 mm. diameter, ventral 0-94 mm., but slightly longer than 
broad and situated just in front of the middle of the body ; ratio of 
the diameters in a smaller specimen 7/10. Gut : prepharynx short or 
absent (shown in fig. 1, but not in PI. 3). Pharynx globular. (Eso- 
phagus very short, terminating far in front of the ventral sucker. Caeca 
very long and fairly wide. Excretory system : median stem of vesicle 
long, extending forward at least to the testes, and narrow. Repro- 
ductive systems : genital pore median and situated near the end of 
the oesophagus. Cirrus pouch long and club-shaped, extending almost 
to the hinder margin of the ventral sucker, but not behind it. Seminal 
vesicle wide and straight, or only slightly convoluted. Cirrus narrow, 
thick-walled and unarmed, often protruded. Testes almost spherical, 
their outlines slightly irregular, one behind the other and contiguous 
in the middle of the hindbody. Ovary having 3 equal and rounded 
lobes and a swelling at the base, smaller than the testes and in front 
of them on the right side. Vitellaria mainly lateral, but the follicles 
tending to fill the median space behind the testes, encroaching on it 
in the middle of the body, extending from the posterior extremity to 
the level of the pharynx, the texture in front of the ventral sucker 
very loose. Vitelline reservoir situated just in front of the testes, 
median to the ovary. Uterus forming a number of folds between the 
ventral sucker and the anterior testis ; metraterm commencing above 
the seminal vesicle and decidedly muscular. Eggs measuring 
0-079-0-095 x 0-048-0-064 mm., according to Odhner (1901) 007- 
0-08 x 0-037 mm. 



Genus PERACREADIUM Nicoll, 1909. 

Members of this genus are typically parasites of Labridae. The 
two species which are best known both occur in Britain, but are 
probably identical. A third species, P. perezi Mathias, 1926, occurs 
in the ballan wrasse and the gilt-head, but not in Britain. 

Peracreadium genu (Rudolphi, 1819) Nicoll, 1909. 

Distoma genu Rudolphi, 1819 (pp. 107-8, 397-8) ; Distomum fasciatum 
Stossich, 1893 (p. 64) ; Allocreadium genu (Rudolphi) of Odhner, 1911. 

Hosts : ballan wrasse, (?) shanny, five-bearded rockling. 
Location : posterior end of intestine and rectum. 

This species was described by Odhner (1901, pp. 497-9, PI. 33, fig. 
3), and was found frequently by Nicoll (1910) in considerable numbers 



ALLOCREADIID^E 167 

at Millport, in association with the trematode he called " Helicometra 
pulchella" but which seems to have been H. fasciata. Neither at 
Millport nor at Plymouth, where Nicoll examined various Labridse 
(thirty specimens), was the trematode found in any host but the ballan 
wrasse, although an immature specimen 04 mm. long was found in 
the shanny and was probably an adventitious parasite. Rees 
(1945) found P. genu in the last-named host at Aberystwyth. Nicoll 
remarked on the absence of the trematode on the East coast. His 
specimens were 1-5-2-4 mm. long, but his description (1910, pp. 
326-8) refers to the mean specimen 2 mm. long and 0-6 mm. in 
greatest breadth. Colour : neutral grey. Shape : elongate, some- 
what flat, but thick and broadest near the ventral sucker. Suckers : 
ventral larger than the oral and 0-8 mm. from the anterior extremity, 
dimensions 0-32 x 0-355 mm. and 0-2 mm. diameter. Gut : pre- 
pharynx very short; pharynx globular and 13 mm. diameter, 
oesophagus 0-11 mm. long, caeca long. Excretory system : vesicle 
simple, extending to the anterior testis. Reproductive systems : 
genital pore near the oesophagus. Cirrus-pouch long, extending back 
to the level of the ovary, of uniform girth, containing a convoluted 
seminal vesicle. Small pars prostatica ; long ejaculatory duct, the 
cirrus frequently seen to be inserted in the metraterm of the same indi- 
vidual (as noted by Olsson (1868) for P. commune). Testes irregular 
oval outline, one behind the other and contiguous in the posterior 
third of the body. Ovary globular, just in front and on the right 
of the testes. Receptaculum seminis large, postero-dorsal to the 
ovary. Vitellaria filling the lateral margins of the body behind the 
ventral sucker, encroaching on the median plane behind the testes, 
absent at the level of the ventral sucker, but forming a wedge-shaped 
mass on each side slightly further forward, here extending to the 
pharynx. Follicles of moderate size (004 mm. diameter). Uterus 
short, containing no more than 30 eggs. Eggs yellow, slightly 
thickened at the anopercular pole, measuring 0-080-0-088 x 0-044- 
0056 mm. (mean, 00845 x 0051 mm.). 

Peracreadium commune (Olsson, 1867) Nicoll, 1910. 

Distoma commune Olsson, 1867 (pp. 31-2) ; Distoma labri Beneden, 1870 (p. 
45), nee Stossich, 1886, nee Rudolphi, 1819 ; Allocreadium commune (Olsson) 
of Odhner, 1902. 

Hosts : ballan wrasse, gilt-head (Baillon's wrasse). 
Location : rectum. 



Nicoll (1910, pp. 328-9) found this species less frequently than 
P. genu at Millport, only two specimens being obtained together. 
It was described by Odhner (1902, pp. 499-503, PI. 33, fig. 6), who 
commented on differences from P. genu, but Nicoll had difficulty in 
separating the two species, regarding P. commune as very similar, but 
broader and flatter, tinged with brown, and " not unreadily dis- 
tinguishable " from P. genu by the arrangement of the vitellaria, the 
follicles of which are continuously distributed between the pharynx 



168 THE TREMATODA OF BRITISH FISHES 

and the posterior extremity (i.e. uninterrupted at the level of the 
ventral sucker). Odhner claimed this to be a constant difference 
between the two species, but Nicoll was unable to confirm this and 
could not deny that they might be identical. Odhner found the 
eggs to be much narrower than in P. genu, but this was not true for 
Nicoll's specimens. Other differences concern the pharynx, which 
is almost fusiform in shape, 0-12 mm. long and 008 mm. broad in a 
specimen 2 mm. long, and the ventral sucker, which is oval and 
measures 0-31 X 0-22 mm. Both these characters were regarded by 
Nicoll as distinctive. But it seems likely that they, and also the 
smaller gonads and differently arranged vitellaria, will prove to come 
well within the range of variability of a single species. 



Genus HELIC0METRA Odhner, 1902 nee Travassos, 1928. 
(Loborchis Luhe, in Stossich, 1902.) 

Nicoll (1910, pp. 335-6) briefly reviewed this genus and mentioned 
five species at that time allocated to it, namely Helicometra pulchella 
(Rudolphi, 1819), H.fasciata (Rudolphi, 1819), H. sinuata (Rudolphi, 
1819), H. mutabilis (Stossich, 1902) and H. flava (Stossich, 1903). 
He examined specimens of H. mutabilis and Distomum gobii Stossich, 
1883, which were lent to him from the collection of Stossich by 
Monticelli, but not another related form, Distomum labri Stossich, 
1886, although he relegated all three forms to synonymy with " H. 
pulchella." It is unfortunately true that Nicoll did not take H. 
fasciata and H. sinuata into consideration when naming his specimens, 
and this had dire consequences. Palombi (1929a) studied the 
morphology and life-history of the former species at Naples and reviewed 
the genus, relegating H. pulchella of Nicoll, 1910 to synonymy 
with H. fasciata, which occurs in twenty-one species of fishes in 
Europe (Atlantic and Mediterranean), as well as others in America 
(Florida and Mexico ; see Manter, 1934, p. 172, and 1940a, p. 387). 
Of the three species which Palombi regarded as valid only one has lobed 
testes ; this is Helicometra fasciata, which is the commonest British 
species — possibly the only species occurring here. The other two, 
H. pulchella and H. sinuata, can be distinguished by the diagonal or 
tandem arrangement of the testes and the nature of the vitellaria, 
which in the former are mainly lateral, but in the latter tend to fill 
the posterior region of the body. H. pulchella has been named in 
British waters, although there is some doubt about its occurrence 
here, but H. sinuata is a Mediterranean species. Several other 
species are known, but it will be sufficient to name them. H. torta 
Linton, 1910 and H. execta Linton, 1910, both occur at Tortugas, H. 
plovmornini Issaitschikow, 1928, in the Russian Arctic, and a doubtful 
species called H. gurnardi Thapar & Dayal, 1934, was discovered in 
a grey gurnard in the Aquarium of the Zoological Society, London. 
Before dealing with H. fasciata it might be mentioned that a form 
closely related to H. torta and H. execta has 9 testes arranged in two 



ALLOCREADIIDiE 169 

longitudinal rows and was therefore referred to a new species and 
genus, Helicometrina nimia, by Linton (1910). This is interesting 
because the testes show a tendency to degenerate in Helicometra, 
even some members of the same species having 2, 1 or none, and any 
phenomena of this kind are worth investigating. Apparently the 
multiplication of the testes occurs in several species since referred to 
Helicometrina, H. azumce Layman, 1930, having two rows of 5, H.parva 
Manter, 1933, only 3, and H. elongata Noble & Park, 1937, 9, in 
longitudinal rows of 5 and 4. All four species occur in marine fishes, 
nimia and parva at Tortugas, elongata in California, and azumce in 
Peter the Great Bay. 



Helicometra fasciata (Rudolphi, 1819) Odhner, 1902 (pp. 160-1). 

(Fig. 32 E.) 

Distoma fasciatum Rudolphi, 1819 (p. 97, pp. 373-4) nee Stossich, 1885 (p. 160), 
1886 (p. 32), 1892 (p. 64), 1898 (p. 46); D. gobii Stossich, 1883 (pp. 116-17, 
PI. 2, figs. 6, 7) ; Loborchis mutabilis Stossich, 1902 (pp. 579-82, 1 fig.) ; 
Allocreadium fasciatum (Stossich) Odhner, 1901 (pp. 499-503, PI. 33, fig. 1) ; 
Distoma (Dicrocozlium) fasciatum (Rudolphi) of Barbagallo & Drago, 1903 
(p. 410) ; Helicometra mutabilis (Stossich) Stossich, 1903 (pp. 375-6) and 
1904 (p. 13) ; H. gobii (Stossich) of Wallin, 1910 (p. 61) ; H.flava Stossich, 
1903 (pp. 373-6, 1 fig.) and of Wallin, 1910 (p. 61) ; H. pulchella (Rudolphi) 
of Nicoll, 1910 ; H. epinepheli Yamaguti, 1934 ; H. hypodytes Yamaguti, 
1934. 

Hosts : in Britain, comber, red gurnard, rock goby, gattorugine, 
shanny, ballan wrasse, cuckoo wrasse, gold-sinny, common topknot, 
eel, conger, cornish sucker, gilt-head (Baillon's wrasse), long-spined 
cottus. 

Location : lower intestine. 

Baylis & Idris Jones (1933) recorded this species in the gilt-head 
(Baillon's wrasse) at Plymouth, differentiating it from H. pulchella . All 
the other hosts mentioned stand on the assumption that H. pulchella of 
Nicoll is really H. fasciata, except that Rees (1945) recorded the long- 
spined cottus as a host at Aberystwyth. Nicoll (1910) found specimens 
with lobed testes in the ballan wrasse and conger at Millport, and (1914) 
similar specimens in all the hosts mentioned in the list above, except the 
gilt-head, at Plymouth. Little's record for H. pulchella may refer to 
this species, which occurs at Banyuls and elsewhere in the Mediterranean, 
in Florida, Mexico and the Far East, generally in moderate numbers — 
twenty specimens in a single host. Particularly large specimens have 
been found in the conger. Nicoll (1910, pp. 336-40, PI. 29, figs. 3, 4) 
described the trematode (as H. pulchella), but characters put forward 
by Palombi (1929, a, pp. 244-54, figs. 7-26, PL 10, figs. 1-5) are 
shown here in parentheses. Size : 1 -3-4-3 mm. long, average length 
2-5 mm., and 0-83 mm. broad (1-5-3 x 0-4-0-75 x 0-33 mm.), 
attaining maturity when 1-25 mm. long, sometimes containing 
malformed eggs when only 1-1 mm. long. Colour : very evident at 
maturity in the contents of the intestine because of a rich brown 



170 THE TREMATODA OF BRITISH FISHES 

colour ; juveniles colourless. Shape : long oval outline, much 
flattened behind the ventral sucker, tapering gradually in front of it. 
Suckers : almost globular, the ventral retaining its spherical form 
even when compressed slightly, and larger than the oral, situated 
slightly more than one-third of the body length (or about 0-9 mm.) 
from the anterior extremity ; diameters 0-35 mm. and 0-23 mm. 
(0-22-0-3 mm. and 0-15-0-2 mm.). Gut : prepharynx very short. 
Pharynx almost globular and about 0-1 mm. diameter (0 09 mm.). 
(Esophagus nearly half as long again (0-15-0-3 mm. long, and S-shaped). 
Caeca long, but not quite reaching the posterior extremity. Bifurcation 
of the gut midway between the pharynx and the ventral sucker. 
Excretory system : median canal extending forward to the ovary, 
flame cell formula 2[(2 + 2) + (2 + 2)] (see Hopkins, 19416, figs. 1, 2). 
Reproductive systems : genital pore median near the middle of the 
oesophagus. Cirrus pouch short and narrow (pyriform), straight or 
slightly curved, extending back to or slightly beyond the anterior 
border of the ventral sucker, containing a convoluted seminal vesicle 
and the ejaculatory duct, a distinct pars prostatica being absent, 
although gland-cells open into the duct, (cirrus 015 mm. long). 
Testes irregularly lobed, the lobes 5 to 7 in number and frilled or 
divided into lobules, all indentations being confined to the posterior 
and lateral regions. Anterior testis less lobulated than the posterior. 
Position of the testes one behind the other and contiguous (leaving 
a post-testicular space occupying one-sixth to one-tenth of the body- 
length). Breadth of the testes about 0-37 mm. Ovary smaller than 
the anterior testis and situated in front of and contiguous with it, 
median or slightly lateral, irregularly 3- or 4-lobed and broader than 
long. Receptaculum seminis pyriform (0-11-0-20 mm. long and 
007 mm. broad) and generally on the right of the ovary. Laurer's 
canal present. Vitellaria mainly lateral, following the caeca and 
extending into more lateral regions, continuing in a forward direction 
to the level of the pharynx, here spreading towards the median dorsal 
line, extending posteriorly between the caeca and the excretory vesicle 
to the limits of the posterior testis (merging in the median plane 
posteriorly). Uterus having an ascending limb confined between the 
ovary and the ventral sucker, formed into a spiral of 3 to 5 super- 
imposed loops each slightly in front of the one underneath. Eggs in 
the uterus numbering about 50 at any time, dark brown and moderately 
thick-shelled, convex on one side and concave on the other, having 
a polar filament 6 to 8 times as long as the capsule at the anopercular 
pole ; dimensions 0-063-0-084 mm. long, 0-032-0-037 mm. broad 
and 0-027-0-033 (misprinted as 0-33) mm. in maximum thickness 
from the convex to the concave surface, mean 0-073 X 0033 x 
0-030 mm. (0-060-0-075 x 0-025-0-029 mm. ; filament 0-2 mm. long). 
Eggs still in utero having their filaments directed forwards and 
sometimes intertwined ; ovum unsegmented when the egg is laid. 

Nicoll (1914, p. 476) regarded this as the commonest Allocreadiid 
at Plymouth, remarking that as a parasite of littoral fishes it replaces 
Podocotyle atomon, which predominates on the East coast of Britain. 



ALLOCREADIID^ 171 

It has never been recorded from the North Sea. The main hosts 
seem to be gobies and blennies. Palombi (1929a) reported variability 
in adults, particularly as regards the shape and size of the pharynx, 
the length and position of the cirrus pouch and the shape of the 
ovary. He found the metacercariae of H. fasciata encysted in Leander 
serratus, L. squilla and L. xiphias. Adult specimens found by 
Mathias (1934, pp. 569-71, fig. 2) in Trigla aspera and Scorpcena 
porcus near Banyuls were 2-4-3-5 mm. long and 0-67-0-8 mm. in 
maximum breadth, with suckers 0-20-0-25 mm. and 0-30-0-38 mm. 
diameter and 0-39-0-54 mm. apart. In nearly all of them the testes 
were lobed and the vitellaria scattered in the posterior region, and 
the polar filaments of the eggs were six to eight times as long as 
the capsule, the dimensions of which were given as 0-07-0-08 x 
0011-003 mm. 

Helicometra pulchella (Rudolphi, 1819) Odhner, 1902 (pp. 161-2, fig. 3). 

Distoma pulchellum Rudolphi 1819 (pp. 94, 367) ; Distomum pulchellum 
(Rudolphi) Diesing, 1850 (p. 338) ; D. labri Stossich, 1886 (p. 30), 1887 
(p. 91), 1888 (p. 12) ; Allocreadium labri (Stossich) Odhner, 1901 (pp. 493-6, 
PI. 33, fig. 2) ; Distoma (Dicrocoelium) pulchellum Barbagallo & Drago, 
1903 (p. 410) ; Allocreadium alacre Stossich, nee Looss, of Palombi, 1929 
(p. 13, fig. 5). 

Hosts : Baylis & Idris Jones (1933), and Baylis (1939) recorded 
these at Plymouth as the comber, streaked gurnard, yellow gurnard 
and red gurnard, Little (1929) at Galway as the yellow gurnard and 
streaked gurnard. According to Palombi the hosts at Naples, Trieste 
and Catania are the cuckoo wrasse, greater weever, butterfly blenny 
and Gobius jozo. Rees (1945) named the shanny as a host at Aberyst- 
wyth. 

Location : intestine and stomach (of red gurnard). 

According to Palombi (1929a, pp. 277-81, figs. 27-9)— Size : 
1-35-2 mm. long and 0-65-0-75 mm. in greatest breadth. Shape: 
outline oval, tapering anteriorly. Suckers : oral 0-15-0-20 mm. 
diameter (misprinted as 0-15-0-38 mm. on p. 280 ; see the table on 
p. 281), ventral 0-22-0-25 mm., means 0-18 and 0-24 mm. Gut : 
pharynx broader than long, dimensions 0-066-0-086 x 0-075-0-13 mm. 
(but in the table on p. 281 diameter given as 0-075-0-100, mean 
0087 mm.). Reproductive systems : genital pore ventral to the 
middle of the oesophagus. Cirrus pouch extending along the anterior 
margin of the ventral sucker to a level near its middle. Testes 
globular, diagonally arranged in the posterior half of the body. Ovary 
tri- or multilobulate, and situated in front of the testes and on the 
same side as the more posterior of them. Receptaculum seminis 
globular, as large as the ovary and situated near it. Vitellaria 
extending laterally between the pharynx and the ends of the cseca, 
confluent posteriorly. Eggs variable in size and number, 0-050- 
0-058 mm. long (mean 0053 mm.), the filament not exceeding 0-2 mm. 
in length. 

For a description of Helicometra sinuata (Rudolphi, 1819) Odhner, 



172 THE TREMATODA OF BRITISH FISHES 

1902 see Palombi (1929a, pp. 281-5, figs. 30-33). This species has 
been found in the greater weever and other hosts in various parts of 
Italy (Naples, Trieste, Venice, Portoferraio), and occurs in America 
(Costa Rica). Although larger than H. pulchella it has smaller eggs 
(0042-0050 mm. long), and is distinguishable from this species by 
characters already noted. 

Genus PLAGI0P0RUS Stafford, 1904. 
(Lebouria Nicholl, 1909 ; Caudotestis Yamaguti, 1934.) 

This genus, the synonymy of which has been discussed by Miller 
(1941), is represented in Britain by three species, Plagioporus alacer, 
P. varius and P. idoneus. Another species, P. tumidulus (Rudolphi, 
1819) occurs in European waters, but not British, in the ocean pipe- 
fish and the greater pipe-fish ; another, P. acerince (Pigulewski, 
1931) was found in the ruffe in the R. Sodsch (Ukraine), and a sixth 
species, P. nicolli (Issaitschikow, 1928) occurs in Icelus bicomis in 
the Arctic. 

Plagioporus alacer (Looss, 1901). (Fig. 33 B.) 

Distomum alacre Looss, 1901 (pp. 401-2, fig. 2) ; Lebouria alacris (Looss) of 
Nicoll, 1910, 1914, 1915. 

Hosts : in Britain, ballan wrasse, cuckoo wrasse, gilt-head 
(Baillon's wrasse), gold-sinny, rock cook. 
Location : intestine. 

Johnstone (1907, pp. 186-8, fig. 17) recorded this species at 
Liverpool as Distomum sp. (see Nicoll, 1915, p. 357), and it was found 
by Nicoll (1910, 1914) at Millport and Plymouth. According to 
Looss (1901a, p. 401) its characters are : Size : hardly more than 
1-5 mm. long; greatest breadth near the ventral sucker 0-4 mm. 
Shape : outline oval, pointed at the extremities. Suckers : ventral 
larger than the oral and situated just in front of the middle of the 
body ; diameters 0-3 mm. and 014 mm. Gut : pharynx small 
(007 mm. diameter). (Esophagus fairly long. Caeca long, extending to 
a level midway between the hinder testis and the posterior extremity. 
Bifurcation of the intestine midway between the suckers. Repro- 
ductive systems : genital pore slightly on the left near the termination 
of the oesophagus. Cirrus pouch large and muscular, reaching back 
to a point above the middle of the ventral sucker. Seminal vesicle 
S-shaped. Pars prostatica narrow and of medium length. Ejaculatory 
duct and cirrus scarcely distinguishable. Testes oval or rounded, 
situated one behind the other in the posterior region. Ovary small 
and spherical, situated in front of the testes. Receptaculum seminis 
and Laurer's canal present, the latter rather long. Vitellaria com- 
prising numerous large follicles, extending from the pharynx to the 
posterior extremity; vitelline reservoir placed between the anterior 
testis and the ventral sucker. Uterus short and having a few folds 
between the testes and this sucker. Metraterm about half as long as 



ALLOCRTCADITDJE 173 

the cirrus pouch. Eggs relatively large (008 x 005 mm.), and few, 
yellow and thin-shelled. Nicoll (1910, pp. 332-4, PI. 29, fig. 2) 
described specimens from the ballan wrasse at Millport. They were 
0-8-1-45 mm. long (mean 1 mm.) and 0-46 mm. broad and had larger 
suckers, the oral 0155 mm. diameter, the transversely oval ventral 
sucker situated 0-46 mm. from the anterior extremity and measuring 
0-22 x 0-26 mm., the ratio of the diameters thus about 5/3. Other 
points of structure noted were the large size of the pharynx (0077 x 
0066 mm.) and the length of the oesophagus (009 mm.). The uterus 
contained no more than 20 eggs measuring 0081-0088 x 0-041- 
0054 mm. (mean 0083 x 0049 mm.). 

Plagioporus varius (Nicoll, 1910). (Fig. 33 A.) 

Lebouria varia Nicoll, 1910 ; {Lebouria) alacris Looss of Nicoll, 1909 (p. 8, 
PI. 1, fig. 1) ; Lebouria idonea Nicoll of Johnstone, 1910 (pp. 16-18, fig. 1). 

Hosts : dragonet, cuckoo wrasse, ballan wrasse, plaice, flounder, 
John Dory. 

Location : intestine. 

This species was found by Johnstone (1910) in dragonets from 
Morecambe Bay. Nicoll (1910) thought it almost exclusively con- 
fined to this host, and (1915) recorded its occurrence in the dragonet at 
St. Andrews, Millport, Plymouth and Liverpool, as well as in the 
plaice at Millport. Little (1929a) found it in the flounder at Galway, 
Bay lis & Idris Jones (1933) in the cuckoo wrasse, ballan wrasse 
and dragonet at Plymouth, where I have found it in the John Dory, 
but not in dragonets, wrasses or plaice. Nicoll (19096, p. 8, PI. 1, 
fig. 1) described a specimen found in the dragonet at St. Andrews, 
and (19096, p. 9) a small and immature form from the same host at 
Luce Bay. In a later paper Nicoll (1910, p. 329) mentioned specimens 
obtained in the Clyde, and gave a description based mainly on 
specimens from the south coast, expressing the opinion that this 
species is certainly distinct from Plagioporus alacer, adding that the 
differences are " not by any means striking owing to the rather 
considerable amount of variation which occurs." Comparison of his 
Figs. 1 and 2 shows this qualification to be true ; the two species bear 
a close resemblance, when allowance is made for differences in size. 
Taking the descriptions of Nicoll to be compatible and with a few 
observations of my own in parentheses, we arrive at the following 
characters for P. varia. Size : up to 1-75 mm. long and about 
one-third as broad, smallest specimen obtained 0-32 mm. long (show- 
ing the cercaria to be small) ; specimens 1-1-1-2 mm. long (with or) 
without eggs, length at maturity about 1-25 mm. (10-11 mm.). 
Cuticle : smooth (slightly wrinkled) ; subcutaneous glands numerous, 
particularly in the anterior region. Suckers : in specimens 1-4- 
1-5 mm. long, oral 0-21-0-18 mm. diameter ; ventral transversely oval 
and measuring 0-34-0-35 x 0-29-0-32 mm., the ventral about 0-55 mm. 
from the anterior extremity ; in specimens 11 mm. long and 0-45 mm. 
in greatest breadth, oral 013 mm. long and 0-14 mm. broad, ventral 



174 THE TREMATODA OF BRITISH FISHES 

measuring 0*31 X 0-21 mm., the anterior rim 0-33 mm. behind the 
anterior extremity. Gut : prepharynx short ; pharynx more than 
half as broad as the oral sucker, 014-0-11 mm. long and 0*11-0-10 mm. 
broad (012 x 0-08 mm.). (Esophagus 006 mm. long. Caeca diverging 
widely and terminating slightly behind the posterior testis (midway 
between it and the hind end of the body) . Reproductive systems : 
genital pore median or on the left of the oesophagus (immediately 
beneath the pharynx). Cirrus pouch short and club-shaped, slightly 
curved, not extending back beyond the middle of the ventral sucker. 
Seminal vesicle convoluted. Ejaculatory duct short and nearly 
straight, but sometimes slightly folded. Pars prostatica indistinct, 
but gland- cells present. Testes irregularly ovoid and diagonally 
contiguous, their faces of contact slightly flattened; diameters 
0-2-0-28 mm. (0-09-0-11 x 0-17 mm., the post-testicular space 
0-33 mm. long). Ovary globular and between the anterior testis and 
the ventral sucker on the right, diameter 0-1 mm. Receptaculum 
seminis pyriform, located between the ovary and the testes. Vitellaria 
very well developed, especially in the posterior region, the follicles 
mainly lateral, but spreading to the inner sides of the cseca, com- 
pletely filling the post-testicular space, overlapping the gonads to a 
variable extent, sparse or absent at the level of the ventral sucker, 
abundant in front of it, but not as numerous as posteriorly, their 
anterior distribution variable, sometimes to the pharynx, or only to 
the oesophagus (confirmed). Follicles large, 0-055 mm. diameter 
(004 X 0-025 mm. anteriorly and 0052 x 0-03 mm. posteriorly). 
Uterus containing not more than 20 eggs of elliptical shape, but 
with a somewhat flattened operculum and a slight knob at the 
anopercular pole, not as pronounced as in P. idoneus, dimensions 
0-085-0-092 x 0-038-0-051 mm. ? mean 0-088 X 0-045 mm. (about 
18 eggs whose mean dimensions are 0-081 X 0-052 mm.). Notes : 
Allocation to this species largely depends on the distribution of the 
vitelline follicles, but it must be stressed that this is not invariably 
precisely as determined by Nicoll, follicles sometimes being relatively 
abundant near the ventral sucker. In the last analysis the distinc- 
tions between P. varia and P. alacris will probably prove to be 
insignificant, but it is preferable to maintain the latter as a valid 
species, at least for the present. 

Plagioporus idoneus (Nicoll, 1909). (Fig. 33 C.) 

Lebouria idonea Nicoll, 1909 ; Allocreadium sp. ; under host-name in Nicoll 
(1915, p. 356). 

Hosts : wolf- fish and Anarrhichas latifrons. 

Location : intestine (in large numbers) and stomach (fewer). 

Nicoll (1915) recorded the occurrence of this species at St. Andrews 
and Northumberland (Cullercoats) in the former host, and at Aberdeen 
in the latter (see p. 356). He had described it in a previous paper 
(1909a, p. 441, PI. 9, figs. 9-12). Size : 1-5-2-5 mm. long, 0-7-1-0 mm. 
in greater breadth and 0-2-0-3 mm. thick ; smallest mature and 



ALLOCREADIIDiE 175 

largest immature specimens alike, 1-58 mm. long. Colour : yellow. 
Shape : outline oval, somewhat attenuated anteriorly. Cutaneous 
glands : large ovoid cells in the antero-lateral regions. Muscular 
system : including numerous myoblasts arranged in groups. Suckers : 
oral 0-17-0-28 mm. diameter, ventral near the middle of the body, 
transversely oval, 0041 x 0-031-0-58 x 0-48 mm. (about twice as 
large as the oral). Gut: prepharynx wide. Pharynx relatively large 
(0-15-0-21 mm. diameter). (Esophagus 0-1-0-18 mm. long. Caeca wide 
and long ; bifurcation of the gut midway between the suckers. 
Pharynx and oesophagus lined with cuticle, that of the former deeply- 
staining. Caeca with an epithelial lining and thread-like processes at 
the free ends of the cells. Excretory system : vesicle extending 
forward to the anterior testis. Reproductive systems : genital pore 
midway between the suckers, generally median ; genital atrium small. 
Cirrus-pouch 0-4 mm. long, extending only slightly behind the ventral 
sucker. Seminal vesicle much convoluted ; ejaculatory duct looped ; 
pars prostatica ill-defined. Testes transversely ovoid, their borders 
irregular, obliquely one behind the other and almost contiguous, the 
anterior slightly smaller than the posterior. Ovary globular, slightly 
in front of the anterior testis, but on the right adjacent to the caecum. 
Receptaculum seminis above or in front of the ovary. Vitellaria 
extending from the pharynx to the posterior extremity, the follicles 
filling the post-testicular region and encroaching on the median 
dorsal space in the anterior region, comprising nests of 12-20 cells 
each 0-023 mm. diameter. Uterus confined between the ventral 
sucker and the ovary, containing about 60 eggs of pale yellow colour 
with a knob-like projection at the anopercular pole (more pronounced 
than in P. varia), their dimensions 0071-0075 x 0-039-0-044 mm. 
(mean 0073 X 0041 mm.). 



Genus P0D0C0TYLE (Dujardin ; 1845) Odhner, 1905. 
(Sinistroporus Stafford, 1904 ; Podocotyloides Yamaguti, 1934.) 

Taxonomic matters regarding this genus have been discussed by 
Odhner (1905), Nicoll (1907) and Manter (1926). Park (1937) prepared a 
key to nineteen species, eight of them set up by himself, and included 
the British form Podocotyle atomon var. dispar Nicoll, 1909, but excluded 
the Italian species P. furcata (Bremser, in Rudolphi, 1819) and the 
British form P. atherince sp. inq. Nicoll, 1914. It might be mentioned 
that Park found the distribution of vitelline follicles very variable, 
but chose a number of less variable characters for the separation of 
species, notably the flat or cylindrical form of the body, the straight 
or coiled nature of the seminal vesicle, the relative length of the 
cirrus pouch, the characters of the genital organs and the relative 
positions of the testes. Apparently all European and some other 
forms have a seminal vesicle which is coiled. The best-known and 
type species, Podocotyle atomon, is common in Britain, less common 
species here being P. reflexa, P. syngnathi and P. atherince, which is 
probably a synonym of the type species. Two species occur only in 



176 THE TREMATODA OF BRTTTSH FISHES 

the Russian Arctic. P. odhneri and P. levinseni, both of which were 
erected by Issaitschikow (1928), the first occurring in Gymnacanthus 
tricuspis, the second in the sea-snail and the lumpsucker. The 
species P. furcata occurs in Italy, but not in Britain, in the red mullet 
and the dover sole, and the Swedish species P. olssoni Odhner, 1905, 
has been recorded in " Lumprenus " maculatus and Gadus melano- 
stomus. The forms with which we have to deal can be separated 
by the key : 

I. Testes very close together (cirrus pouch extending behind the ventral 

sucker) ........ P. atherince sp. inq. 

II. Testes considerably apart, or separated by vitelline follicles. 

1. Cirrus pouch not extending behind the ventral sucker P. syngnathi. 

2. Cirrus pouch extending behind the ventral sucker : 

a. (Esophagus twice as long as the pharynx : 

(a) Vitelline follicles not present in front of the ventral 

sucker. . . . . . . .P. atomon. 

(b) Vitelline follicles extending in front of the ventral 

sucker . . . . ... P. atomon var. dispar. 

b. (Esophagus about as long as the pharynx (body cylindrical) 

P. reflexa. 

Podocotyle atherinse sp. inq. Nicoll, 1914. 

Host : sand smelt. 

Location : anterior part of the intestine. 

Nicoll (1914, p. 474, fig. 1) described under this name a solitary 
specimen found at Plymouth, which he could not refer to any known 
species of Podocotyle, and which was even only a doubtful member 
of the genus, but was placed in it with due regard for the shape of 
the ovary, the position of the genital pore and the length of the cirrus 
pouch. Actually, the positions of the testes contradict this diagnosis, 
the specimen in this character resembling a species of Plagioporus. 
The main characters of this trematode are as follows. Size : IT mm. 
long and 0-49 mm. in greatest breadth. Shape : nearly oval in out- 
line, slightly attenuated anteriorly. Colour : dark grey. Suckers : 
oral globular and 0T3 mm. diameter; ventral transversely oval, 
0-21 mm. long, 0-28 mm. broad and situated 0-46 mm. from the 
anterior extremity. Gut : prepharynx absent, pharynx 007 mm. 
diameter. (Esophagus 0T1 mm. long. Caeca wide and long, extending 
almost to the posterior extremity. Reproductive systems : genital 
pore slightly on the left near the termination of the oesophagus. 
Cirrus pouch long and slender, curving round the ventral sucker and 
extending back to the level of the ovary, containing a simple ejacu- 
latory duct and a long and convoluted seminal vesicle. Testes 
irregularly globular and 0T7 mm. long, continuous and diagonally- 
arranged, the posterior one on the right and 0T3 mm. from the 
posterior extremity. Ovary having 3 backwardly-directed lobes and 
situated on the right of the anterior testis, measuring 01 3 mm. along 
the major axis and situated 014 mm. behind the ventral sucker. 
Receptaculum seminis pyriform, just in front of the former testis. 



ALLOCREADIIDJE 177 

Vitellaria mainly confined to the lateral regions between the ventral 
sucker and the hind end of the body, but encroaching on the post- 
testicular space without merging. Uterus having very few folds, and 
containing a small number of eggs measuring 0-069-0072 x 0036 mm., 
each having a knob-like process at the anopercular pole. Nicoll 
suggested that the trematode is probably an abnormal specimen of 
Podocotyle atomon with displaced testes, and this seems to be the 
best solution of a problem which cannot be settled with such scanty 
material. 

Podocotyle syngnathi Nicoll, 1913. (Fig. 32 C.) 

Hosts : greater pipe-fish, broad-nosed pipe-fish, ocean pipe-fish. 
Location : intestine. 

Nicoll (1913a, p. 238, PL 11, figs. 1, 2) found this species at Ply- 
mouth in 4 out of 9 greater pipe-fish, 1 out of 6 broad-nosed pipe-fish 
and 4 out of 8 ocean pipe-fish. Baylis & Idris Jones (1933) recorded 
it in the ocean pipe-fish, also at Plymouth. It very closely resembles 
other species of Podocotyle, differing from them in the noticeable 
shortness of the cirrus pouch. The smallest specimens were found 
in the ocean pipe-fish and were just about to produce eggs when 
2-2 mm. long, contrasting with P. atomon from the same individual 
host, which contained eggs when 1 mm. long. The five largest 
specimens were 4-55-5-95 mm. long (mean 5-36 mm.) and 0-78 mm. 
in greatest breadth posteriorly, but breadth varies from one-seventh 
to one-ninth of the length of the body according to the degree of 
extension. Suckers : oral smaller than the ventral, dimensions 
0-38 mm. diameter and 0-43 X 0-55 mm., ventral 1-25 mm. from the 
anterior extremity, and thus about one- quarter of the distance along 
the body. Gut : prepharynx very short, pharynx about 019 mm. 
diameter. (Esophagus 0-17 mm. long. Cseca long and somewhat dilated 
posteriorly. Excretory system : vesicle long, extending to the anterior 
end of the ovary. Reproductive system : genital pore on the left of 
the oesophagus. Cirrus-pouch short and stout, not extending behind 
the middle of the ventral sucker, containing a comparatively compact 
seminal vesicle and a short ejaculatory duct. Testes diagonally 
ovoid, situated one behind the other in the posterior region, but not 
contiguous; dimensions 0-57 X 0-47 mm., the post-testicular space 
slightly more than 1 mm. long (one-fourth to one-sixth body-length). 
Ovary having 3 posterior lobes, about 0-1 mm. in front of the anterior 
testis. Receptaculum seminis in front of the ovary, more anteriorly 
situated than in P. atomon. Vitellaria of more limited extent, ending 
some distance behind the ventral sucker, tending to fill the posterior 
region, but often interrupted on one side or both sides opposite the 
posterior testis. Transverse vitelloducts in front of the ovary. 
Uterus confined within the boundaries of the caeca between the 
receptaculum seminis and the ventral sucker, containing about 50 
eggs measuring 0-082-0-102 x 0-045-0-050 mm. (mean 0-092 x 
0-047 mm.). 

12 



178 THE TREMATODA OF BRITISH FISHES 

Podocotyle atomon (Rudolphi, 1802) Odhner, 1905 (pp. 320-6, PL 2, 
figs. 9, 10). (Fig. 32 A, B.) 

Fasciola atomon Rudolphi, 1802 (p. 70) ; Distoma atomon Rudolphi, 1809 (pp. 
362-3) ; D. simplex Rudolphi, 1809, and of Olsson (1868, p. 34), Lovinsen 
(1881, pp. 67-9, PI. 3, fig. 1) and Linton (1899, pp. 525-6, PI. 47, figs. 3-7) ; 
D. reflexum Creplin, 1825 (p. 54), nee Olsson, 1868, nee Zschokke, 1890; 
D. angulatum Dujardin, 1845 (pp. 401-2) ; D. ceglefini of Beneden, 1870 (p. 
57), Linstow, 1889, and Stossich, 1886 ; Allocreadium atomon (Rudolphi) of 
Odhner, 1901 (pp. 506-13, PI. 33, figs. 9, 10) ; Sinistroporus simplex 
Stafford, 1904 (pp. 484-5) in part ; Psilostomwn redactum Nicoll, 1906 (pp. 
525-7, PL 13, figs. 9, 10) ; Podocotyle atomon var. dispar Nicoll, 1909 
(— Distomum vitellosum Linton of Johnstone, 1907) ; ? Fasciola ceglefini 
Miiller, 1776 (p. 224). 

Hosts : in Britain, father- lasher, long-spined cottus, Montagu's 
sea snail, 2-spotted goby, butter-fish, viviparous blenny, 3-spined 
stickleback, 15-spined stickleback, bib, whiting, coal-fish, pollack, 
5-bearded rockling, 3-bearded rockling, Norwegian topknot, common 
topknot, sole, plaice, flounder, dab, ocean pipefish, eel, gilt-head. 

Location : intestine and pyloric caeca. 

This familiar species has been found in most places where marine 
trematodes have been sought in this country — at Millport, St. Andrews, 
Culler coats, Plymouth and Liverpool — and elsewhere at Gal way, 
Greifswald, in Greenland, Sweden, Canada and U.S.A. As the list 
of hosts indicates, it is the commonest trematode of fishes of rock- 
pools on the sea-shore and it has been described by several continental 
and British zoologists. The father lasher seems to be the commonest 
host not only in Britain, but also in Sweden and Greenland. The 
taxonomy of the species has been discussed by Odhner (1905, p. 320) 
and by Nicoll (1907, p. 73), so that detailed consideration of the 
synonymy is unnecessary here. Abundant information exists about 
the characters of specimens found in the British Isles, so that it is 
unnecessary also to consider the detailed descriptions of continental 
zoologists, but it will be necessary to examine several statements 
which establish the fact that the species shows great variability. 
Johnstone's brief description (1907, p. 182, fig. 15) of specimens 
found in flounders in the tanks at Piel, Barrow-in-Furness, can be 
considered first of all. These specimens were 2-2-5 mm. long and 
0-25-0-5 mm. broad, elongate, somewhat pointed at the extremities, 
but little flattened. The ventral sucker was nearly twice as large as 
the oral, and borne on an eminence at the end of the first quarter of 
the body, respective diameters being 0-42 and 0-23 mm. A pre- 
pharynx was neither mentioned nor shown, but the gut comprised a 
large pharynx, a short oesophagus and long and straight caeca. The 
genital pore was near the hind end of the pharynx, and the cirrus 
pouch extended behind the ventral sucker. The testes were situated 
in the hindmost one-third of the body, one behind the other, the 
globular ovary occupying a position in front of them. The vitellaria 
comprised 4 longitudinal rows of follicles extending (according to 
the figure) from just behind the ventral sucker to the hinder end of 
the body, with conspicuous vitelloducts, the transverse ones crossing 



ALLOCREADIIDiE 



179 




Fig. 33. — A, Plagioporus varius. B, P. alacer. C, P. idoneus. D, Lepida- 
pedon rachion. E, L. elongatum. F, Opechona bacillaris. G, O. 
retractilis. (A, B. F, after Nicoll, 1910 ; C, after Nicoll, 1909 ; rest after 
Lebour, 1908a.) 



180 THE TREMATODA OF BRITISH FISHES 

the ovary. The uterus, a compact mass of few folds anterior to the 
gonads, containing a small number of eggs about 008 mm. long and 
004 mm. broad. 

Several other British accounts of the structure of this trematode 
are available (Nicoll, 1907, p. 74, PL 1, figs. 1, 2 ; 19096, pp. 6-7 ; 
Lebour, 1908a, p. 16, PL 4, fig. 8), but they can be correlated. Size : 
rarely exceeding 3-5 mm. long, mature when 1 mm., but generally 
1 -5-2-5 mm. long (but according to Levinsen 3-5 mm., and to Olsson 
3-9 mm.). Shape : outline elongate oval, rounded posteriorly and 
attenuated in the very extensile anterior region. Colour : trans- 
lucent greenish-yellow. Cuticle : non-spinous, but striated trans- 
versely and longitudinally, sometimes thrown into irregular wrinkles. 
Suckers : ventral larger than the oral and generally elliptical in 
outline, the oral globular, diameters 0-22-0-42 mm. and 0- 12-0-29 mm. 
in specimens 1-3 mm. long. Both suckers thus diminishing in relative 
size during growth, like the space between them, which may be 
one-third of the body-length in small specimens, but only one-fifth 
in large ones. Gut : prepharynx small, but distinct and about half as 
long as the pharynx, which is 01 mm. diameter. (Esophagus some- 
times twice as long as the pharynx and straight, but otherwise shorter 
and S-shaped, terminating just in front of the ventral sucker. Caeca 
very long. Excretory system : pore terminal, vesicle a long and 
simple sac extending to the level of the ovary, widening near its 
junctions with the lateral canals. Reproductive systems : genital 
pore situated midway between the suckers and on the left of the 
oesophagus. Cirrus pouch long, narrow and somewhat club-shaped, 
extending some distance behind the ventral sucker, containing a large 
bipartite or looped seminal vesicle, a folded ejaculatory duct and a 
tapering cirrus ; a definite pars prostatica absent, but gland- cells 
present. Testes globular and one behind the other and slightly 
separated in the middle of the posterior region, leaving a post- 
testicular space about one-fifth as long as the body. Ovary lobed, 
sometimes trilobed, and situated in front of the anterior testis on the 
right. Receptaculum seminis pyriform and near the ovary, Laurer's 
canal situated on the left. Vitellaria extending from the ventral 
sucker to the posterior extremity, the follicles never distributed in 
front of the sucker and mainly lateral in front, but filling the post- 
testicular space. Uterus generally containing 20 to 60 yellowish- 
brown eggs (according to Odhner, 1905, 20-30, but more than 80 
shown in his fig. 9, PL 33), measuring 0060-0084 x 0040-0045 mm. 
(but specimens from the 15-spined stickleback at St. Andrews con- 
tained unusually large eggs, measuring 0085-0093 x 0051-0-062 mm. ; 
see Nicoll, 19096, p. 6). 

Nicoll (1907) examined sticklebacks from rock-pools, brackish 
ditches communicating with the sea, and streams near their entrance 
to the sea, noting that the fishes taken from streams were never 
parasitized, those from the other habitats being infected to equal 
degrees. In another place (19096, p. 7), where he commented on the 
great variability seen in Podocotyle atomon, he noted that differences 



ALLOCREADIIDiE 181 

affect the characters on which Odhner (1905) depended for determining 
P. reflexa, which was said to differ from the type -species in its more 
elongate and less flattened shape and more closely approximated 
suckers, and that certain other characters used by Odhner are of 
little specific value, citing the relative length of the oesophagus, the 
greater breadth of the testes and greater length of the cirrus pouch, 
the median position of the ovary and the discontinuity of the vitelline 
follicles. He stressed also the fact that freshwater treatment such as 
was used by Johnstone and investigated by himself (1909a, p. 452) 
alters the characters of specimens so that they answer to Odhner's 
description of P. reflexa more closely than to existing descriptions of 
P. atomon, causing elongation of the body, thickening as well, but the 
shortening of the " neck " region, also raising the ventral sucker into 
greater prominence. Only under better conditions of fixation is it 
safe to differentiate between species such as P. reflexa and P. olssoni 
as Odhner did, the characters of greatest reliability then including 
the breadth of the body, the length of the " neck " and the length of 
the cirrus pouch. In none of Nicoll's specimens was the breadth of 
the body less than one-seventh of the body-length, the length of the 
" neck " less than one-sixth of total length, and for this reason Nicoll 
concluded that specimens from the 15-spined stickleback were not 
identical with specimens from the same host which Odhner referred 
to P. reflexa, the specific identity of which he admitted on account of 
the more flattened shape and greater breadth and the much longer 
" neck," and certain characters of the reproductive systems. Nicoll 
regarded these specimens (which were 1-7-2-3 mm. long and had 
suckers 0-14-0-16 mm. and 0-20-0-25 mm. long) as " absolutely 
typical examples of P. atomon, apart from the large size of the ova." 
Commenting further on P. atomon Nicoll was struck with the 
remarkable diversity of form which it presents. It displays variation 
in the extent of the yolk-glands (vitellaria), the length of the cirrus 
pouch, the shape and situation of the testes and, in particular, the 
size of the ova. Yet he proposed (1909a, p. 452) for Johnstone's 
specimens the provisional name Podocotyle atomon var. dispar, 
although his experimental distortion by freshwater treatment of 
typical specimens of usual form militated against this proposal. 
This form must be relegated to synonymity with Podocotyle atomon. 

Podocotyle reflexa (Creplin, 1825) Odhner, 1905 (p. 326) must be 
regarded as a somewhat doubtful species, though it is notable for its 
elongate form. Odhner found it frequently in the 15-spined stickle- 
back and in the grey gurnard on the west coast of Sweden, and Nicoll 
(1915) recorded its occurrence outside British waters in the lump- 
sucker, and at Plymouth in the 5-bearded rockling and the 15-spined 
stickleback. Baylis & Idris Jones (1933) also found it at Plymouth 
in the same species of stickleback and in the 3 -bearded rockling. 
Rees (1945) found it in the 5-bearded rockling at Aberystwyth. 
According to Odhner it has the following characters : — Size : 3-4-5 mm. 
long. Shape : elongate, only one-twelfth to one-seventh as broad 
as long ; forebody one-fifth to one-seventh of total length ; flattening 



182 THE TREMATODA OF BRITISH FISHES 

insignificant or absent. Suckers : approximately as in P. atomon, 
the ventral prominent. Gut : oesophagus generally longer than the 
pharynx. Reproductive systems : cirrus pouch straight, over-reaching 
the ventral sucker by half its length. Cirrus feebly developed. Ovary 
median. Vitellaria discontinuous near the testes, but filling the post- 
testicular region. Eggs 0077-0091 mm. long. 

Some of Nicoll's comments on the points of difference by which 
Odhner recognized this species have already been mentioned. In 
considering variability in P. atomon, this zoologist stressed that the 
cirrus pouch may extend barely beyond the ventral sucker, or nearly 
half-way to the ovary. The vitellaria are extremely variable, and may 
be absent between the testes, or fill most of the available space in this 
situation. Yet some credence was placed on the characters given by 
Odhner, although the manner of fixation can produce in P. atomon 
alterations of structure which will render it more like P. reflexa than 
the species to which it belongs. 

Sub-family Lepocreadiin^e Odhner, 1905. 

Key to Genera. 

I. Pharynx of medium size ; prepharynx and oesophagus present ; ventral 
sucker not significantly smaller than the oral. 

a. Body elongate, or ribbon-like, never flask-shaped. 

(a) Prepharynx long, oesophagus short . . . Lepidapedon. 

(b) Prepharynx short ; oesophagus or pseudo-oesophagus long 

Opechona. 

b. Body flask-shaped, not elongate ..... Neophasis. 
II. Pharynx large (one-tenth as long as the body) ; prepharynx short ; 

oesophagus absent ; ventral sucker smaller than the oral Lepidauchen. 

Genus LEPIDAPED0N Stafford, 1904. 

(Lepodora Odhner, 1905.) 

This genus was erected for Distoma rachion Cobbold, 1858, and 
although Stafford gave no description, his name for the genus has 
priority rights over the name Odhner proposed. It contains two 
species, both of which are well known on both sides of the Atlantic, 
but no key is necessary, shape alone serving to separate them. 

Lepidapedon rachion (Cobbold, 1858) Stafford, 1904 (p. 485). 

(Fig. 33 D.) 

Distomum rachion Cobbold, 1858 (p. 158, PI. 31, figs. 9, 10) ; Distoma incre- 
scent Olsson, 1868, in part ; Lepodora rachicea (Cobbold) of Odhner, 1905 
(pp. 332-8, fig. 3, PI. 2, figs. 12-15) ; Lebour, 1908 (pp. 19, 20, PI. 2, figs. 
2-4) and authors. 

Hosts : haddock, cod, coal-fish, pollack, wrasse. 
Location : intestine. 

Nicoll (1907) found this species in more than half the haddock he 
examined at St. Andrews and (1910) in 55 per cent, of the pollack 



ALLOCBEADIIDiE 183 

and 45 per cent, of the coal-fish examined at Millport. He also 
found it (1914) frequently in the pollack at Plymouth, but not in 
40 gadoids of other species. Lebour (1908a) found it in three- 
quarters of the haddock she examined at Cullercoats, and Little 
(1929a) found it in the cod at Galway. I found 16 specimens of it 
at Plymouth in an unidentified wrasse, and it has been recorded in 
U.S.A. (on the coast of Maine, see Manter, 1926 ; at Woods Hole, 
see Linton, 1940 ; and at Tortugas, see Manter, 1934) and also in 
Canada (see Stafford, 1904, and Miller, 1941). It was described by 
Odhner (1905, p. 332), Nicoll (1907, p. 77, PL 1, figs. 3, 4) and Lebour 
(1908a, p. 19, PI. 2, figs. 2-4). The trematode is sluggish in its 
movements and does not long survive removal from the host. Colour : 
pale yellow, somewhat opaque. Shape : elongate oval, rounded at 
the extremities. Size : 1-88-4-47 mm. long and 0-61-0-90 mm. 
broad, mean size 2-65 x 0-69 mm. (Nicoll) ; 2-4 mm. long and one- 
quarter or one-fifth as broad (Lebour). Cuticle : spinous, spines 
0012 mm. long, having broad bases and arranged in alternating 
transverse rows, becoming sparser near the middle of the body and 
absent in the posterior region except for a few lateral spines. Suckers : 
ventral much smaller than the oral and almost exactly occupying 
the middle of the body, diameters 0-14-0-23 mm. and 0-24-0-38 mm. 
(Nicoll) ; 0-20 mm. and 0-36 mm. in a specimen 3-5 mm. long (Lebour). 
Gut : prepharynx long (0-3 mm.). Pharynx large (0-2 mm. diameter) 
(0-21 x 0-16 mm. ; Nicoll). (Esophagus very short. Caeca wide and 
long, bifurcation of the gut well in front of the ventral sucker. 
Excretory system : pore terminal, vesicle sac-like and short. Repro- 
ductive systems : genital pore located between the oesophagus and the 
ventral sucker slightly on the left. Cirrus-pouch large, partially 
divided by a constriction into anterior and posterior parts, the latter 
behind the ventral sucker and containing a folded seminal vesicle, 
the former mainly in front of it and containing a small cirrus and 
pars prostatica (Note : Lebour referred to a vesicula seminalis 
externa, but mentions an enclosing membrane, this and her figure 
conforming to Nicoll's description of a constricted cirrus-pouch and 
a true vesicula seminalis interna). Testes globular, one behind the 
other in the posterior third of the body. Ovary spherical or ovoid, 
immediately in front of the anterior testis. Receptaculum seminis 
pyriform, situated between the ovary and the anterior testis at the 
level of the transverse vitelloducts and Laurer's canal. Vitellaria 
filling the lateral regions between the ventral sucker and the posterior 
extremity (according to Lebour, extending to the level of the genital 
pore), encroaching on the median plane near the testes. Uterus 
confined to the region in front of the gonads, containing 30 to more 
than 100 eggs of pale yellow colour and more pointed at one pole 
than the other, dimensions 0059-0068 x 0-033-0-040 (Nicoll). 

My specimens of this species, from the intestine of an 
unidentified wrasse, are clearly recognizable from the above 
diagnosis, although the prepharynx is relatively short, the 
vitellaria relatively better developed (though of similar extent), 



184 THE TREMATODA OF BRITISH FISHES 

and the gonads transversely oval instead of spherical. Size : 
1 -55-2-80 mm. long and 0-50-0-65 mm. in greatest breadth in the 
posterior region. Shape and cuticle exactly as described above. 
Slickers : having centres 0-50-0-85 mm. apart, oral 0-22-0-27 mm. 
diameter, ventral 0-14-0-19 mm. diameter and situated 0-6-1-0 mm. 
from the anterior extremity. Gut : prephar}Tix 0-10-0- 15 mm. long. 
PharjTix 0-15-0-19 mm. diameter. (Esophagus very short. Caeca wide 
and long, arising as stated above. Reproductive systems : genital 
pore as stated, cirrus-pouch as described by Nicoll, the anterior part 
cask-shaped and somewhat smaller than the ventral sucker, the 
posterior part containing the seminal vesicle considerably larger than 
this sucker. Testes transversely oval and contiguous almost exactly 
in the middle of the posterior half of the body, dimensions 0-12-0-24 x 
0-32-0-34 mm. (anterior) and 0-21-0-27 x 0-30-0-35 mm. (posterior). 
Post-testicular space 0-21-0-47 mm. long. Ovary of similar shape to 
the testes and immediately in front of the more anterior, 08 mm. 
long and 0-11-0-23 mm. broad. Vitellaria well developed, com- 
prising numerous coarse follicles filling the lateral regions behind the 
level of the genital pore (never extending in front of it), encroaching 
on the median plane in the post-testicular space and approaching as 
near as possible to it in the region of the gonads. Uterus having few 
folds confined to the region in front of the gonads and between the 
cseca. Eggs measuring 0-064-0-071 X 0-033-0040 mm. (i.e. some- 
what longer, but not broader than those examined by Nicoll). 

Note : Lebour (1908a, p. 20) mentioned a larva which she found 
in Cardium edide (described by Lebour, 1907), and which may belong 
to this species. Cercarise were developed in sausage-shaped sporo- 
cysts which riddled the soft parts of the host and contained both 
free and encysted cercarise. Free forms mostly had tails, but the tail 
seems to be cast off prior to encystment and may be seen moving 
independently inside the sporocysts. Cercaria : 0-2 mm. long, oval, 
spinous, having an oral sucker 004 mm. diameter and a much smaller 
ventral sucker, a long prepharynx, a conspicuous pharynx, a very 
short oesophagus and long caeca. The excretory vesicle does not 
conform strictly with that of the adult, being bilobed (i.e. having a 
very short median stem), but as Lebour points out, this character is 
not a serious point of difference, being subject to much modification 
with growth. 

Lepidapedon elongatum (Lebour, 1908) NicoU, 1915. (Fig. 33 E.) 

Lepodora elongata Lebour, 1908. 

Host : cod. 

Location : duodenum and intestine. 

Lebour found this trematode at Cullercoats, twice obtaining a 
few specimens from a single host, but it has not been found since 
anywhere in Britain, although it occurs in widely separated parts of 
U.S.A. (Tortugas, Woods Hole). It may be the species mentioned 
by Odhner (1905, p. 337), but not described. Nicoll (1910, p. 341) 



ALLOCREADIID^E 1 85 

stated that it takes the place of L. raehion in the cod, but whether or 
not this remains true depends on Little's diagnosis (1929a). In some 
respects it seems to be of doubtful validity, but it has been accepted 
by American zoologists. Size : 3-5 mm. long and 0-54 mm. broad. 
Shape : much longer than L. raehion in proportion to the breadth, 
tapering gradually from the middle of the body in an anterior direction. 
Colour translucent and colourless. Cuticle entirely spinous. Suckers : 
ventral slightly larger than the oral and well in front of the middle of 
the body, diameters 12 mm. and 0-10 mm. Gut : prepharynx 
0-3 mm. long, but relatively short. Pharynx 008 mm. long. (Esophagus 
long (0-3 mm.). Caeca wide and long, extending to the posterior 
extremity. Excretory system : vesicle a narrow sac in the dorsal 
region, extending forward almost to the anterior testis. Reproductive 
systems : genital pore much nearer the ventral sucker than the 
oesophagus and on the left. Cirrus-pouch long, its posterior part 
longer than in L. raehion and S-shaped instead of globular (Note : 
this presupposes that the cirrus-pouch encloses the entire seminal 
vesicle, as Nicoll supposed for L. raehion), the seminal vesicle following 
this shape. Pars prostatica, cirrus and genital atrium as in L. raehion, 
the gonads similarly arranged also, but more widely-spaced in the 
posterior region. Testes one behind the other with a small space 
between them, diagonally ovoid (0-36 x 0-30 mm.). Ovary spherical, 
0-24 mm. diameter. Receptaculum seminis pyriform. Laurer's canal 
on the left, its proximal part much swollen. Transverse vitelloducts at 
this level, i.e., slightly behind the ovary. Uterus having few folds, 
containing more than 100 eggs which are more pointed at one pole 
than the other and measure 0066 x 0036 mm. Vitellaria extending 
from slightly behind the ventral sucker to the posterior extremity, 
apparently (according to Lebour's fig. 5, PL 2) not filling the post- 
testicular space, here preserving their bilaterality. Notes : Manter 
(1934, p. 296) found this species in several fishes at fair depths at 
Tortugas (in 1 out of 35 Coelorhynchus carminatus at 200 fathoms ; 
in 1 out of 13 Lcemone?na barbatulum at 140-197 fathoms ; in 1 out of 
6 Urophycis chesteri at 367 fathoms ; and in 1 out of 7 Epigonus 
occidentalis at 250 fathoms), recognizing the species by the longer 
oesophagus, smaller pharynx, failure of the vitellaria to reach the 
ventral sucker and the closeness of the genital pore to this sucker. 
He was unable to separate the species by the sizes of the eggs, which 
in both measured 0059-0068 mm. in length. Linton (1940) recorded 
both species at Woods Hole, and his determinations show the sizes of 
the eggs to be very variable characters, 006-0-07 X 003-004 mm. 
(L. elongatum) and 0-054-0-07 x 0-03-0-04 mm. (L. raehion). 

Genus 0PECH0NA Looss, 1907. 

(Pharyngora Lebour, 1908.) 

Ward & Fillingham (1934) pointed out that in discussing what 
he regarded as an improper method of designating a genus, Looss 
(1907, p. 616) used the name Opechona for a supposititious genus of 



186 THE TREMATODA OF BRITISH FISHES 

which the type would be Distomum bacillare. Quoting opinion IB 
of the International Rules of Zoological Nomenclature to the effect 
that the designation of a type constitutes an indication which estab- 
lishes the validity of the name of the genus, these writers insisted 
that Pharyngora must be relegated to synonymy with Opechona. 
Two species occur in Britain. 

Opechona bacillaris (Molin, 1859) Looss, 1907 (p. 616). (Fig. 33 F.) 

Distoma bacillare Molin, 1859 (pp. 834-5) ; D. (Dicroccelium) bacillare (Molin) 
Stossich, 1886 (p. 58) ; Pharyngora bacillaris (Molin) of Nicoll, 1915. 

Hosts : mackerel, lumpsucker. 
Location : intestine. 

Nicoll (1915) recorded the occurrence of this species in the mackerel 
at Millport, Aberdeen, Plymouth and Cullercoats, and in the lump- 
sucker at St. Andrews and Plymouth. Lebour (1908a, p. 17, PI. 2, 
fig. 1) described two specimens, one of them immature, which she 
found in the mackerel at Cullercoats, and Markowski (1933, pp. 12-13, 
fig. 4) made observations on 90 specimens found in the same host in 
the Baltic Sea, his findings being shown below in parentheses. 
The trematode has also been found in Italy (at Padua) and Sicily 
(at Catania). Size- : 1-9-3-2 mm. long (2-4-5 mm.) and one-quarter 
to one -fifth as broad when contracted, much less when extended. 
Cuticle : contrary to previous findings, spinous (confirmed). (Colour : 
mature individuals brownish, juveniles colourless.) Suckers : oral 
larger than the ventral and having thick walls so as to appear pharynx- 
like ; ventral situated at the end of the first quarter of the body, 
diameters 002 mm. and 0015 mm. (0-27-0-285 mm. and 012- 
0195 mm.). (Note : Lebour's figures, to judge by the illustration, 
are misprints for 0-2 mm. and 0-15 mm.) Gut : prepharynx of 
variable length, sometimes much longer than the conspicuous pharynx, 
generally scarcely visible. (Esophagus a little longer than the pharynx 
when not extended. Caeca extending nearly to the posterior extremity ; 
bifurcation of the gut slightly in front of the ventral sucker (pre- 
pharynx present; pharynx 0-15 mm. long and 0-105 mm. broad; 
oesophagus 006-015 mm. long; pseudo- oesophagus 0-3-0-6 mm. long; 
caeca long). Excretory system : vesicle sac-like, extending to the 
posterior testis. Reproductive systems : genital pore near the anterior 
margin of the ventral sucker and slightly on the left. Cirrus-pouch 
broad club-shaped and 0-04 mm. long, containing a straight ejacu- 
latory duct and a bipartite seminal vesicle which is ovoid in its 
posterior part, somewhat triangular in its anterior part (vesiculae 
seminales interna and externa present). Testes globular and one 
behind the other, but not confluent, in the posterior region (con- 
firmed ; dimensions 0-15-0-345 mm. long and 0-165-0-27 mm. broad). 
Ovary of irregular shape, in front of the anterior testis and separated 
from it by a slight space (3-lobed, 0-075-0-18 mm. long). Recep- 
taculum seminis and Laurer's canal present, the exact positions 
undetermined (dimensions of the former 01 2 x 0-09 mm., situated 



ALLOCREADITDiE 1 87 

between the ovary and the anterior testis). Vitellaria lateral, not 
extending in front of (only slightly in front of) the seminal vesicle, 
underlying the caeca and filling the space behind the testes. Uterus 
having a few folds confined to the region in front of the gonads 
(confirmed). Eggs not numerous, pale vellow, measuring 008 x 
004 mm. (008 x 0-035-0-041 mm.). 

Opechona retractilis (Lebour, 1908). (Fig. 33 G.) 
Pharyngora retractilis Lebour, 1908. 

Host : whiting. 

Location : upper intestine and stomach. 

Lebour (1908a, p. 22, PL 2, fig. 7) found several specimens at 
Cullercoats, and Nicoll (1915) recorded them under the name " bacil- 
laris," his further record of this species at Plymouth being invalidated 
by his supposition (1910, p. 34) that the two species are identical, as 
Markowski (1933a, p. 12) chose to regard them. Ward & Fillingham 
(1934) expressed the alternative view that Lebour 's species may be 
distinct, and the opinion that if the differences between these two 
species are regarded as intraspecific several other species automatically 
become less well established. Lebour suggested that retractilis differs 
from bacillaris in several characters, but she stressed the vesicula 
seminalis externa as a really distinctive character. I found 3 large 
and 4 somewhat smaller specimens in the stomach of the whiting at 
Plymouth, and 27 small specimens from the intestine of 3 hosts of the 
same species there. They differ mainly from Lebour 's specimens in 
the shorter pharynx and smaller testes and eggs, but they cannot be 
allocated to O. bacillaris and must represent O. retractilis, a vesicula 
seminalis externa being clearly evident in some of them. I shall give 
a short diagnosis of Lebour's specimens, and supplement this with a 
brief account of my own specimens of different sizes. 

According to Lebour — Size : 4-6 mm. long and 0-5 mm. broad, 
but very contractile when alive. Shape elongate, gradually tapering 
anteriorly, of uniform breadth between the ventral sucker and the 
anterior testis, tapering and slightly rounded posteriorly. Colour 
translucent and colourless. Suckers : oral of characteristic shape 
and larger than the ventral, which is situated slightly in front of the 
midbody ; diameters 0-20 mm. and 0-12 mm. Cuticle entirely spinous. 
Gut : prepharynx long, but very variable, three times as long as the 
pharynx in extended individuals, hardly apparent in the contracted 
condition. Pharynx 0-12 mm . long and half as broad. (Esophagus long 
(0-4-0-8 mm.). Caeca wide and long ; bifurcation of the gut about one- 
quarter of the distance along the body. Excretory system : vesicle 
very small (about 0-2 mm. long), extending forward only one-third of 
the distance between the pore and the posterior testis. Reproductive 
systems : genital pore slightly in front of the ventral sucker, median 
or slightly lateral. Genital atrium roomy. Cirrus-pouch cylindrical 
(length unspecified), containing besides the anterior part of the 
seminal vesicle (i.e. vesicula seminalis interna) a pars prostatica and 



188 THE TREMATODA OF BRITISH FISHES 

cirrus. Vesicula seminalis externa present. Testes ovoid, but some- 
what irregular, measuring 0-56 x 0-30 mm., one behind the other 
with a small space between them, the hindmost 0-6 mm. from the 
posterior extremity. Ovary heart-shaped, in front of and separated 
from the anterior testis by a small space. Receptaculum seminis 
pyriform, Laurer's canal present. Shell-glands large and conspicuous. 
Vitellaria extending laterally from the ventral sucker to near the 
posterior extremity, filling the space between and behind the testes 
and underlying the caeca. Vitelline reservoir near the shell-glands. 
Uterus having a few folds between the ovary and the cirrus-pouch, 
containing only 20-40 eggs 010 mm. long. Metraterm somewhat 
inflated. 

My own observations include measurements of specimens which 
fall into three size groups, and the figures in the first and second 
parentheses refer to the specimens of the smaller and smallest sizes. 
The smallest specimens had just commenced to form eggs, the uterus 
containing 2 or 3 only, and the three largest specimens were uniform, 
measurements being made on only one of them. Size : 5-8 mm. long 
(2-3-3-4 mm.) (1-9-2-05 mm.) and 0-6 mm. in greatest breadth 
(0-20-0-25) (0-18-0-20 mm.). Cuticle spinous, the spines very small 
and fine. Suckers : oral campanulate or pyriform and broader 
anteriorly, 0-3 mm. long and 0-35 mm. in greatest breadth (0-16- 
0-22 x 0-13-0-21 mm.) (0-16-0-20 x 012-017 mm.). Ventral sucker 
smaller than the oral, 0-2 mm. diameter (0-08-0-14 mm.) (0-09- 
0-11 mm.), its anterior margin 1-75 mm. (0-8-1-3 mm.) (0-7 mm.) 
from the anterior extremity. Gut : prepharynx shorter than the 
pharynx (0-10-0-12 mm. long) (0-08-0-10 mm.), pharynx more or less 
elongate, 011 x 010 mm. (0-11-0-12 x 0075-009 mm.) (010- 
0-12 x 005-0-07 mm.), oesophagus very long (0-3-0-8 mm.) (0-28- 
0-30 mm.), caeca long and narrow, arising immediately in front of the 
genital pore and ventral sucker. Reproductive systems : genital pore 
median, slightly in front of the ventral sucker, cirrus-pouch about 
0-65-0-7 mm. long, and extending approximately to the midbody, 
vesicula seminalis externa well behind it. Testes longitudinally oval, 
and situated one behind the other in the posterior quarter (third in 
small specimens) of the body, dimensions of the anterior and posterior 
respectively 0-55 x 0-35 mm. and 0-45 x 0-40 mm. (0-16-0-27 x 
012-017 mm.) (016-0-19 x 010-011 mm.), 0-5 mm. apart (con- 
tiguous in small specimens). Post-testicular space 0-85 mm. long 
(0-32-0-35 mm.) (0-21-0-25 mm.). Ovary much smaller than the 
testes and situated slightly in front of the more anterior, slightly 
lobed in small specimens. Receptaculum seminis globular, some- 
times larger than the ovary, and overlapping its posterior border and 
the anterior border of the foremost testis. Vitellaria well developed, 
mainly confined to the posterior half of the body, extending from the 
extremity to the anterior end of the cirrus-pouch, but not quite to the 
ventral sucker. Follicles rather coarse and mainly lateral, but filling 
the spaces between the gonads and the post-testicular space. Vitelline 
reservoir smaller than the ovary and between it and the anterior 



ALLOCREADIID^E 189 

testis. Uterus having only a few small folds, mainly between the 
ovary and the posterior end of the seminal vesicle. Eggs large and 
variable, measuring 0080-0093 X 0043-0-054 mm. (0071-0086 x 
0-038-0047 mm. in the small and smallest specimens). 

Genus NE0PHASIS Stafford, 1904. 
(Acanthopsolus Odhner, 1905.) 

The type- species of this genus, JV. pusilla Stafford, 1904, occurs in 
the urinary bladder of the wolf -fish in Canada. It bears a very close 
resemblance to JV. lageniformis, as the re-description by Miller (1941, 
p. 33, fig. 5) shows, but is smaller and has suckers of greater absolute 
size, differing in other characters also. Another species, Neophasis 
oculata (Levinsen, 1881) {Acanthopsolus oculatus (Levinsen) of 
Odhner, 1905 (pp. 328-31, PI. 2, fig. 11) ; Distoma oculatum Levinsen, 
1881 (pp. 64, 67, PL 2, figs. 7, 8)) occurs off the coast of Greenland and 
at Egedesminde, the hosts being the father-lasher and the short- 
spined cottus. I have re-drawn it in Fig. 36 F, and need only mention 
that it is supposed to differ from N. lageniformis and JV. pusilla mainly 
in the shape, the diagonal arrangement of the testes, the absence of a 
receptaculum seminis and the relatively small size of the eggs. Stiles 
& Hassall give a British record of this species, Johnstone (1907, 
pp. 186-8, fig. 17) having mentioned characters in which his Distomum 
sp. from the cuckoo wrasse agreed with D. osculatum Levinsen. In 
the same place, however, Johnstone gave reasons for the unlikelihood 
of identity with this species, and Nicoll (1915, p. 35) allocated his 
specimens to Lebouria, now Plagioporus alacer. The differences 
between the three species mentioned seem to me hardly to warrant 
specific distinctions, and it is my belief that further study will resolve 
them into a single species, Neophasis pusilla. 

Neophasis lageniformis (Lebour, 1910) Miller, 1941. (Fig. 35 G.) 

Acanthopsolus lageniformis Lebour, 1910 (pp. 29-35, PI. 1, figs. 1-8) ; Disto- 
mum sp. Lebour, 1908 (a, pp. 31-3, PI. 3, figs. 6-8). 

Host : wolf -fish. 

Location : upper part of intestine ; juveniles in the stomach, 
pharynx and buccal cavity. 

Lebour (1910, p. 29) described adults of this species found at 
Cullercoats, remarking that when abundant they occurred in hundreds, 
and that they are rarer in spring than in summer and disappear in 
winter. Nicoll (1915) recorded the species as occurring also at St. 
Andrews. Lebour's first record largely concerned small immature 
specimens found in the stomach of the host. They agreed in every 
way with a cercaria which she previously found in sporocysts in great 
abundance in a whelk (Buccinum undatum) taken on the Northumber- 
land coast, except that they had lost the tail. The largest adults were 
found in the upper intestine of three out of twelve wolf-fish whose 
stomachs contained the remains of whelks. They had the following 



190 THE TREMATODA OF BRITISH FISHES 

characters (Lebour, 1910) : — Size: very small, 0-54-1-3 mm. long and 
about half this in greatest breadth posteriorly. Shape : flask- 
shaped, narrowing considerably anteriorly, broad and rounded 
posteriorly, almost circular in transverse section, but slightly flattened 
in front of the ventral sucker. Cuticle spinous, the spines arranged 
in rows, flat and scale-like near the mouth, very sharp further back 
in the anterior third of the body, progressively smaller beyond this to 
the posterior extremity. Eye-spots : two dark brown masses of 
pigment with radiating flecks situated one on either side of the 
pharynx at variable distances from the mouth, according to the state 
of the highly mobile neck. Suckers : of nearly equal sizes, the oral 
slightly the larger in adults. Dimensions : oral 0-06 mm. diameter, or 

007 x 005 mm. in a preserved specimen 0-35 mm. long, 009 x 

008 mm. in one 0-54 mm. long ; ventral 006 mm. diameter in all 
specimens examined (apparently failing to increase in size from the 
full-grown cercaria to the adult), situated just in the anterior half of 
the body. Gut : prepharynx 0-08 mm. long, narrow and thin-walled, 
or so contracted as to appear absent, its wall telescoped by the 
pharynx ; pharynx 0-07 mm. long and two-thirds as broad, oesophagus 
short and broad, caeca long, extending to the posterior extremity 
(correction to Lebour, 1908, p. 32) ; bifurcation of the gut very close 
to the ventral sucker. Excretory system : vesicle pyriform, reaching 
nearly to the level of the testes ; pore slightly dorsal. Reproductive 
systems : genital pore slit-like, median and near the anterior margin 
of the ventral sucker, in life constantly opening and closing. Genital 
atrium small, receiving the male and female ducts on the right and 
left respectively. Cirrus-pouch club-shaped, dorsal to the ventral 
sucker and projecting behind it (in whole mounts curving round it), 
containing a large seminal vesicle constricted into almost equal 
anterior and posterior parts. An ill-developed pars prostatica and a 
long ejaculatory duct and cirrus. The part of the ejaculatory duct 
adjacent to the pars prostatica is provided with sharp " spines " with 
rounded bases ; the cirrus is devoid of them. Vasa deferentia extending 
separately to the seminal vesicle. Testes longitudinally ovoid, 
symmetrical and widely separated in the last quarter of the body, 
008 mm. long and 005 mm. broad. Ovary spherical, lateral and 
slightly in front of the right testis and somewhat smaller than it. 
Oviduct long and convoluted. Receptaculum seminis globular, con- 
spicuous, but small; Laurer's canal present. Vitellaria very well 
developed, the follicles forming groups scattered throughout the 
available space between the pharynx and the posterior extremity, 
mainly dorsal, but partially covering the caeca ventrally. Transverse 
vitelloduct short and wide and situated behind the ovary (shown 
between the testes). Uterus having an ascending limb only, formed 
into few folds distended locally by the relatively enormous single 
eggs. Metraterm having spines similar to but thinner and sparser than 
those of the ejaculatory duct. Eggs very few, seldom more than 4 
and rarely as many as 8, about 0-08-0- 10 mm. long and two-thirds 
as broad, in small flukes as large as the testes. 



ALLOCREADIID^E 191 

The smallest preserved specimens containing eggs were 0-54 mm. 
long, but younger specimens from the pharynx and buccal cavity 
and 0-34-0-50 mm. long showed all stages in the development of the 
vitellaria. Other small individuals described by Lebour (1908a, 
p. 32) and 0-3-0-4 mm. long had suckers of equal sizes (007 mm. 
diameter). The cercarise described by Lebour (1910, p. 32) develop 
in rediae (previously described as sporocysts by Lebour, 1906). The 
liver of the whelk becomes packed with these stages and develops an 
unhealthy brown colour. Smaller redise (0-3 mm. long) are colourless, 
but larger ones (0-5-3-2 mm. long) are yellow, and either short and 
housing 2 or more cercarise, or elongate and containing 16-32. 
Tailed and tail-less cercariae occur in the same redia and the latter 
are commoner, the tail being very easily detached. The body of 
the cercaria is about 0-5 mm. long when alive, contracting to about 
0-35 mm. when preserved, and the shape is indeterminate on account 
of changing movements, but never flask-shaped like that of the 
adult. Other characters are like those of the adults, conspicuous 
rudiments of the gonads occurring in the positions they will continue 
to occupy, in some specimens traces of the genital ducts as well. 



Genus LEPIDAUCHEN Nicoll, 1913. 

Lepidauchen stenostoma Nicoll, 1913. (Fig. 32 G.) 

Host : ballan wrasse (at Plymouth). 
Location : intestine. 

The only two specimens of this species ever found were described 
by Nicoll (1913a, p. 240, PI. 11, fig. 3). Size: 2-9-3-25 mm. long 
and 1-3 mm. in greatest breadth. Shape : long oval outline, broadest 
near the middle of the body, tapering towards the broadly rounded 
extremities and flattened. Cuticle spinous, the spines confined to 
the anterior half of the body. Suckers : oral expanded at its anterior 
end and having a slit-like aperture, 0-55 mm. diameter, ventral of the 
usual form, 0-27 mm. diameter and 1-12 mm. from the anterior 
extremity. Gut : prepharynx small, pharynx very large (0-31 x 
0-34 mm.). (Esophagus absent. Caeca long and widely divergent. 
Reproductive systems : genital pore median and situated beneath the 
pharynx. Cirrus-pouch entirely in front of the ventral sucker, con- 
taining a globular seminal vesicle (other details unobserved). Testes 
fairly large and globular, one behind the other and contiguous with it 
in the posterior region. Post-testicular space 0-45 mm. long. Ovary 
transversely ovoid, in front of and almost touching the anterior 
testis, and slightly on its left, dimensions 0-37 x 0-26 mm. Laurer's 
canal not observed. Sperms observed in the receptaculum seminis 
uterinum. Vitellaria voluminous, filling most of the posterior region 
and extending forward laterally to the level of the pharynx, the 
follicles mainly ventro-lateral, but merging dorsally in front of the 
ventral sucker and ventrally in the posterior region, where they 
approach and partially cover the lateral margins of the gonads. 



192 THE TREMATODA OF BRITISH FISHES 

Uterus having an ascending limb folded between the gonads and the 
ventral sucker, here tending to fill the space between the caeca, the 
first two or three folds containing spermatozoa. Eggs not numerous 
(less than 100), brownish-yellow, measuring 0-078-0-084 x 0-046- 
0-050 mm. Note: Nicoll (1913a) experienced difficulty in defining 
the systematic position of Lepidauchen, regarding it as intermediate 
anatomically between Lepocreadium and Stephanostomum. Later 
(1915, p. 344) he placed it in the Lepocreadiinae. 



Sub-family Crepidostomatin^: nom. nov. 

(Stephanophialinse Nicoll, 1909). 

Genus CREPID0ST0MUM Braun, 1900. 

(Stephanophiala Nicoll, 1909 ; Acrodactyla Stafford, 1904 ; 
Acrolichanus Ward, 1917.) 

Crepidostomum farionis (Muller, 1784) Liihe, 1909. (Fig. 32 H.) 

Fasciola farionis Muller, 1784 (p. 91, PI. 72, figs. 1-3) ; Distoma farionis of 
R. Blanchard, 1891 (pp. 481-3, fig. 38) ; D. laureatum Zeder, 1800 of 
authors ; Crepidostomum laureatum (Zeder) of Braun, 1900 (p. 232) and 
authors ; Stephanophiala laureata (Zeder) of Nicoll, 1909 (a, pp. 398-419, 
PI. 9, figs. 1-5) ; S. transmarina Nicoll, 1909 (a, p. 397) ; S. vitelloba Faust, 
1918 ; Crepidostomum ussuriense Layman, 1930 ; C. vitellobum (Faust) of 
Hopkins, 1931. 

Hosts : sea trout, char, houting, grayling. 
Location : intestine, pyloric caeca, gall-bladder. 

This is a very widely distributed trematode which is common in 
some Scottish and Yorkshire rivers and occurs elsewhere in Britain, 
as well as in France, Austria, Germany, Sweden, Denmark, Finland, 
Russia, Canada, Alaska and U.S.A. Olsson (1876, p. 21, PL 4, 
figs. 1-5) gave a fairly accurate description which was augmented by 
R. Blanchard (1891), particularly in regard to the female reproductive 
organs. Looss (1902, p. 452) first indicated the structure of the 
distinctive anterior papillae. Nicoll (1909a) completely re-described 
the worm after studying four or five mature specimens from each of two 
trout taken from the River Spey, as well as several immature specimens 
from two others taken from a tributary of this river. Brown (1927, 
p. 86, Pis. 6, 7, figs. 1-12) studied adults obtained from the trout and 
grayling of Yorkshire rivers, finding the trematode for the first time 
in the gall-bladder, also investigating the life-history. Baylis (1928 ; 
1939) recorded the occurrence of the trematode in brown trout in 
Hampshire. 

Most writers have dealt with small specimens 2-4 mm. long, but 
Olsson discovered some which were 6 mm. long, and Liihe (1909, 
p. 63, fig. 54) took this into consideration in formulating his brief 
diagnosis. The description given here is largely based on the observa- 
tions of Nicoll, with the findings of Brown shown in parentheses. 
Size : 3-4 mm. long (3-5 mm.) and one-quarter as broad near the 
ventral sucker. Shape : long oval outline, tapering towards the 



ALLOCREADIIDJE 193 

extremities, rounded during contraction of the body, flat. Forebody 
much more mobile than the rest of the body. Colour pale, but distinct 
red (white, neglecting the eggs, as Olsson found ; antero-dorsal region 
covered with scattered pigment granules). Cuticle of uniform thick- 
ness, -0025-0 003 mm. Suckers : oral not quite terminal, almost 
globular and about 0-31 mm. diameter, the anterior border thicker 
(0093 mm. thick) than the remainder (0-05-0065 mm.) (see Nicoll). 
Ventral sucker transversely elongate and about one-third of the 
distance along the body, 0-50 x 0-43 mm. and 0-16 mm. deep. (Ratio 
of the diameters of the suckers 1/1-5, the ventral sucker well within 
the anterior half of the body.) Anterior papillce : 6 tongue-like 
outgrowths of the muscle substance of the oral sucker about 0-3- 
0-4 mm. long (2 ventral, 4 dorsal), their bases all in the same trans- 
verse plane and equidistant from one another ; the ventral near the 
mouth and having bases which bulge into the buccal cavity. Musculo,- 
ture : circular, longitudinal and diagonal fibrils and underlying these 
myoblasts. Subcutaneous glands : pyriform cells (0-036 x 0-019 mm.) 
mainly restricted to the anterior region, many of them opening at 
the rim of the oral sucker. Gut : prepharynx very small. Pharynx 
0-15-0- 19 mm. diameter, but dorso-ventrally flattened. (Esophagus 
about the same length as the pharynx. Caeca long. Prepharynx and 
pharynx lined with cuticle, oesophagus and the anterior parts of the 
caeca having a thick membrane, the posterior parts of the caeca an 
epithelium of vacuolated cells with long fibrillar free processes 
(? artifact). Excretory system : median canal extending to the level 
of the anterior testis, lateral canals to the oral sucker, both having a 
membranous, not an epithelial lining; pore slightly dorsal. Repro- 
ductive systems : genital atrium absent, or represented by a shallow 
depression into which the male and female ducts open side by side 
[ Olsson 's representation of widely- separated apertures erroneous], 
situated beneath the end of the pharynx. Cirrus-pouch club-shaped, 
0-45-0-55 mm. long and 0-12 mm. in greatest breadth, extending to a 
point above the middle of the ventral sucker, its walls containing 
inner circular and outer longitudinal muscles. Seminal vesicle 
elongate oval, measuring 0-2 x 0-04 mm. Pars prostatica globose. 
Gland- cells numerous and confined to the posterior part of the cirrus- 
pouch. Cirrus sometimes formed into a single loop, but variable. 
Testes globular or ovoid, situated one behind the other in the middle 
of the hind- body and close together or separated by a small space ; 
dimensions 0-27 x 0-34 mm. (anterior) and 0-34 x 0-33 mm. 
(posterior). Ovary almost globular, close behind the ventral sucker 
and far in front of the testes, median or slightly lateral, dimensions 
0-23 x 0-19 X 0-16 mm. Receptaculum seminis very small, ovoid 
and situated behind the ovary, giving off a moderately long and 
straight Laurer's canal. Vitellaria very well developed, comprising 
two continuous antero-lateral arrays of follicles between the pharynx 
and the posterior extremity, tending to fill the spaces between and 
behind the testes, mainly lateral to the caeca in front of the ovary. 
Transverse vitelloducts at the level of the receptaculum seminis 

13 



194 THE TREMATODA OF BRITISH FISHES 

Uterus much folded between the testes and the ventral sucker, metra- 
term straight, extending alongside the entire cirrus-pouch, lined with 
cuticle and having muscular walls. Eggs comparatively few (generally 
fewer than 100), more widely rounded at the anopercular pole, bright 
yellow and darkening only slightly in transit through the uterus, 
containing unsegmented ova when laid, measuring 0075-0-080 x 
0040-0044 mm. (0-075 x 0042 mm.) [Hopkins (1934, p. 14) gave 
the dimensions of the eggs as 0-065-0-085 x 0-040-0-050 mm.]. 
(Linton (1940, p. 101) as averaging 0-08 x 004 mm.) Notes : Brown 
found all trout from the River Warfe infected, and also 84 per cent, of 
grayling. The first intermediate hosts are Pisidium amnicum and, 
rarely, Sphcerium corneum, the second include the larvae of mayflies 
(Ephemera danica in England (Brown, 1927) ; Hexagenia sp. in Canada 
(Cooper, 1915)) and the freshwater shrimp, Gammarus pulex (see Baylis, 
1931). Two generations of rediae occur, and these are characterized 
by the absence of procruscula and a functional intestine. The 
cercaria is a Xiphidiocercaria with body and tail of about equal 
length (0-45-0-52 mm. and 0-45 mm.) and 2 conspicuous eye-spots. 
It penetrates the second intermediate host by means of the stylet and 
the secretion of two groups of 3 penetration-glands. The metacercaria 
encysts in the mayfly larva, generally in the fat bodies, sometimes 
in the muscles. The cysts are pyriform (0-26-0-40 x 0-31-0-48 mm.) 
and easily visible through the translucent exoskeleton of the host on 
account of their dark brown colour. The most usual site is the 
ventral surface near the 2nd-5th pairs of gills, and a single host may 
harbour 1-26 cysts, which do not interfere with its development and 
are carried over into the adult stage. Encysted larvae retain the 
eye-spots and develop the anterior papillae, but lose the stylet. 
Encysted forms show clear relationship to the adult Crepidostomum 
farionis, but are only 0-40-0-65 mm. long and 0-13-0-24 mm. broad. 
The suckers at this time are of equal sizes and the eye-spots are 
beginning to disintegrate. The earliest larvae found in the trout 
occurred in the pyloric caeca and showed great advance on the 
encj^sted forms. They were 0-79 mm. long and 0-31 mm. broad, the 
suckers measuring 0-14 mm. (oral) and 0-19 mm. (ventral). Such 
forms still contain obvious vestiges of the penetration-glands. 

Hopkins (1934) examined many specimens of C . farionis from various 
parts of U.S.A. and Alaska, as well as some specimens from Britain and 
descriptions of others, concluding that European and American forms 
differ only in very minor characters, which fall well within the range 
of individual variation. The name Stephanophiala transmarina Nicoll, 
1909 (proposed for what Nicoll regarded as an American species), was 
relegated to synonymy with Crepidostomum farionis, after Hopkins 
had also examined specimens described and named Crepidostomum 
transmarinum by Hunninen and Hunter (1933) and regarded as distinct 
from the European species. Hopkins (loc. cit., p. 12) also gave reasons 
for regarding Crepidostomum ussuriense Layman, 1930, emend, and C . 
vitellobum (Faust) of Hopkins, 1931, as other synonyms of this species. 
The former was found in Salvelinus sp. in Peter the Great Bay. 



ALLOCREADIIDiE 1 95 

Other European species of the genus include Crepidostomum 
auriculatum (Wedl, 1857) Luhe, 1909 (p. 63) {Distoma auriculatum 
Wedl, 1857 ; Acrodactyla auriculata (Wedl) Odhner, 1910 ; Acro- 
lichanus auriculatus (Wedl) Skwortzoff, 1927 ; Acrolichanus similis 
Wisniewski, 1933), which occurs in Acipenser ruthenus L. in the 
Danube, Volga and Oka. Hopkins (1934, pp. 37-8) gave a brief 
diagnosis of this species, and also of C. latum (Pigulewski, 1931) 
(Stephanophiala lata Pigulewski, 1931 (pp. 17-18, fig. 5)), a parasite 
of the rudd in the Ukraine. Crepidostomum suecicum Nybelin, 1932, 
a parasite of various freshwater fishes (grayling, sea trout, turbot, 
miller's thumb and char) in Sweden was regarded as identical with 
C. metcecus (Braun, 1900), a parasite of bats. Hopkins regarded 
fishes as the natural hosts, bats as " accidental " hosts. A Russian 
species of the genus not included in Hopkins' fist is C. baicalense 
Layman, 1933, discovered in Thymallus arcticus and Cottus kneri in 
Lake Bajkal. For accounts of several American species of the genus 
(the best-known of which is C. cornutum (Osborne, 1903), originally 
described as Bunodera) the reader is referred to the monograph by 
Hopkins, which contains much valuable information concerning the 
life-histories of the papillose Allocreadiidse. 



Sub-family Sph^rostomatin^: Poche, 1926. 
(Sphcerostomatidce Thapar & Dayal, 1934.) 
Genus SPHJER0ST0MA Rudolphi, 1809. 
Sphaerostoma bramae (Miiller, 1776) Luhe, 1909. (Fig. 34 B). 

Fasciola bramae, Miiller, 1776 (p. 224, v. 1, PL 30, fig. 6) ; Distoma globiporum 
Rudolphi, 1802 (1809, pp. 364-7) in part ; Sphcerostoma globiporum (Rudolphi) 
Looss, 1899 (pp. 595, 649). 

Host : roach. (Elsewhere in Europe, hosts mainly Cyprinids 
(carp, bream, white bream, bleak, roach, minnow, chub, rudd, barbel, 
loach, etc.), but also perch, grayling, pike, eel.) 

Location : intestine. 

Nicoll (1924) regarded this as one of the nine characteristic 
trematodes of British freshwater fishes and the commonest of them 
all. But like other parasites of its kind, it has been neglected in this 
country, although Baylis (1939) recorded its occurrence in the roach 
in Cambridgeshire. On the Continent it occurs in the Rhine, Lake 
Constance, Lake of Lucerne, the Baltic Sea, Denmark and Norway. 
It was described by Looss (1885, p. 22, PI. 24, fig. 18), and short 
diagnoses of both the species and the genus were given by Liihe (1909, 
p. 142, fig. 110). Markowski (1933, pp. 11-13, fig. 3) described 
specimens taken from the common eel in the Baltic (Chlapowo). 
Size : 1- more than 4-2 mm. long and about three-eighths as broad. 
Shape : outline oval, slightly attenuated at the extremities, the 
anterior region more mobile than the posterior. Suckers : ventral 



196 



THE TREMATODA OF BRITISH FISHES 




Fig. 34. — A, Allocreadium isoporutn. B, Sphcerostoma bramce. C, Azygia 
lucii. D, Bunodera luciopercce. E, Phyllodistomum folium. F, " P. 
angulatum," a synonym of P. macrocotyle. G, Probilotrema richiardii. 
(A-E, after Looss, 1894-5 ; F, after Linstow, 1907 ; G, after Dollfus, 
1937.) 



ACANTHOCOLPID^E 197 

almost twice as large as the oral, about 0-45 mm. diameter in the 
largest specimens and situated near the middle of the body, in smaller 
specimens 1-1-5 mm. long, dimensions 0-25 x 0-31 mm. and 015- 
0-28 mm. Gut : pharynx small, 075 mm. diameter in small 
specimens. (Esophagus long, terminating nearer the ventral than the 
oral sucker. Caeca very long. Reproductive systems : genital pore 
median near the termination of the oesophagus and far in front of 
the ventral sucker. Cirrus-pouch large, but almost confined to the 
forebody, and hardly tapering anteriorly, containing a short and 
thick cirrus, an inconspicuous pars prostatica and a large and folded 
seminal vesicle. Testes rarely having smooth borders, generally 
somewhat lobed or irregularly ovoid and widely separated, the 
anterior close behind the ventral sucker and lateral, the posterior 
near the ends of the caeca and median, diameter in small specimens 
0-13-0-15 mm. Ovary smaller than the testes, 0-10 mm. diameter 
in small specimens, situated nearer the posterior testis and on the 
side opposite the anterior, the receptaculum seminis near it on the 
other side of the body. Vitellaria very well developed, comprising 
numerous large follicles which extend along the dorsal surfaces of the 
caeca, spreading slightly, and along the sides of the oesophagus to the 
level of the pharynx, sometimes restricted to the region behind 
the seminal vesicle or the ventral sucker. Uterus having a few large 
folds which almost encircle the ventral sucker, but sometimes a few 
small transverse folds. Eggs yellowish -brown, measuring 0-057-0-076 
X 0-049-0-06 mm., arranged in the uterus in a single row. According 
to Liihe, the microcercous Xiphidiocercaria, Cercaria micrura Filippi, 
which has a distinctive array of bristles, is the larva of this species ; 
it develops in tubular sporocysts in Bythinia tentaculata, later on 
leaving the snail and penetrating a species of Herpobdella and encysting 
underneath the skin as a metacercaria measuring about 0-42 x 
0-15 mm., contained in an ovoid cyst 0-2 mm. long and 0-1 mm. broad. 



Family ACANTHOCOLPIME Liihe, 1909. 

Liihe (1906) erected a sub-family Acanthocolpinae for a new 
genus and species of trematode, Acanthocolpus liodorus, found in the 
intestine of Chirocentrus dorab in Ceylon, and later elevated it to 
family rank. With this genus he associated the genera Stephano* 
stomum and Deropristis, to which Poche (1926) added Dihemistephanus 
and Acanthopsolus , as well as a new genus, Tormopsolus, which he 
erected for Distomum osculatum Looss, 1901. We have already seen 
that Acanthopsolus is a synonym of Neophasis, although Ward (1938) 
proposed the erection of the sub-family Acanthopsolinae for it in the 
Acanthocolpidae. Miller (1941) re-examined man3^ trematodes of 
Stafford's collection, and suggested that Neophasis would be better 
placed in the Allocreadiidae, tentatively placing it in the Lepo- 
creadiinae, where it is allowed to repose in the present work. The four 
genera with which we have to deal are Stephanostomvm, Dihemi- 



198 THE TREMATODA OF BRITISH FISHES 

stephanus, Deropristis and Tormopsolus, all of which may be referred 
to the family Acanthocolpidae. Several writers have suggested 
drastic revision of the Acanthocolpidae, notably Stunkard (1932) and 
Cable & Hunninen (19416), and this would entail revision of the 
Allocreadiidae also. But we shall need much more information about 
larva? and life -histories before such major changes of a comprehensive 
kind can be made. As the family under consideration stands, its 
main characters are as follows : — Size and shape : medium size, 
elongate and only slightly flattened. Cuticle uniformly spinous, the 
largest spines anteriorly and especially large ones occurring round 
the mouth or on the " shoulders," the smallest spines posteriorly and 
spines of graded intermediate sizes between the extremities. Suckers 
of medium size and not very widely separated. Gut : prepharynx 
fairly long or long. Pharynx fairly large. (Esophagus short. Caeca 
very long. Excretory system : vesicle Y-shaped, having a rather short 
median stem and long lateral canals. Reproductive systems : genital 
pore median and just in front of the ventral sucker. Cirrus- pouch 
very elongate. Cirrus long and equipped with spine-like structures. 
Pars prostatica fairly short ; seminal vesicle small and ovoid. Testes, 
ovary, vitellaria and uterus as in the Allocreadiidae. Receptaculum 
seminis small or absent. Metraterm long and straight and equipped 
with spine-like structures. Eggs not numerous and variable in size, 
sculptured and devoid of filaments. 



Key to Genera. 

I. Oral spines arranged around the mouth in a double row. 

a. Sequence of oral spines not interrupted ventrally . Stephanostomum. 

b. Sequence of oral spines interrupted ventrally . . Dihemistephanus. 
II. Oral spines not differentiated. 

a. Testes situated in the most posterior region of the body . Deropristis. 

b. Testes not situated in the most posterior region of the body 

Tormopsolus. 



Genus STEPHANOSTOMUM Looss, 1899, nee Stephanostoma 
Danielsen, 1880 — an insect. 

(Stephanochasmns Looss, 1900 ; Lechradena Linton, 1910 ; Echino- 
stephanus Yamaguti, 1934.) 

Looss (19016, p. 597) placed five species in this genus — S. cesticillus, 
S. pristis, S. bicoronatum, S. caducum and S. minutum. The third 
and fifth of these have never been found in Britain, but three species 
have been discovered here, namely S. rhombispinosum, S. triglce and 
S. baccatum. Another European species which has not appeared in 
Britain is S. sobrinum (Levinsen, 1881). and several other species occur 
in America (see Linton, 1940). All the species which have been 
found in Britain are imperfectly described, and the distinctive 
characters are ill-defined in some instances. 



ACANTHOCOLPID^ 199 

Stephanostomum cesticillus (Molin, 1858) Looss, 1899 (pp. 696-8 
figs. 21, 22). 

Distoma cesticillus Molin, 1858 (p. 131) ; Stephanochasmus cesticillus (Molin) 
of Looss, 1901 {b, pp. 598-9, fig. 1) ; Echinostoma cesticillus (Molin) of 
Monticelli, 1893 (a, pp. 158-61, PL 5, figs. 56-60 ; PL 6, fig. 68) ; Anoikto- 
stoma cesticillus (Molin) of Stossich, 1899 (p. 15) in part. 

Host : John Dory. 

Location : stomach and intestine. 

Nicoll (1914, p. 477) found four specimens at Plymouth, but did 
not describe them, merely remarking that this was the first appearance 
of the species in Britain. Looss named the angler as the host of S. 
cesticillus, which has appeared at several places in Italy and Sicily 
(Padua, Naples, Trieste, Catania), and gave its main characters. 
Size : 12-5 mm. long and 1 mm. broad. Oral spines numbering 
35-6 in a double series showing a ventral hiatus, spines in the anterior 
row 0-1 mm. long, spines in the posterior row 084 mm. long. 
Suckers : ventral slightly the larger, diameters 0-48 mm. and 0-4 mm. 
Eggs measuring 008 x 0-050-0055 mm. Looss regarded this 
species as closely related to S. bicoronatum, which also shows the 
ventral hiatus in the oral spines and has eggs of the same size, although 
the body is much smaller (6-9 mm. long). This species has fewer 
oral spines, but Stossich counted 24, Looss 30-33. This illustrates 
the main difficulty in dealing with members of this genus, the spines 
being easily lost. 

Stephanostomum pristis (Deslongschamps, in Lamouroux, 1824) 

Looss, 1899. (Fig. 35 A.) 

Distoma pristis Deslongschamps ; Echinostoma pristis (Desl.) Dujardin, 1845 
(p. 433) ; Anoiktostoma (Desl.) Stossich, 1899 (p. 15) ; Stephanochasmus 
pristis (Desl.) Looss, 1901 (pp. 601-5, figs. 3, 5). 

Hosts : cod, whiting. 

Location : intestine and pyloric cseca. 

Lebour (1908a, pp. 24-5, PI. 2, fig. 8) described a single specimen 
found in the cod at Cullercoats. Nicoll (1910, p. 340) described a few 
immature specimens from the same host at Millport, and (1915) 
recorded its occurrence also in the intestine of the whiting at Plymouth. 
Little (1929a) found it in this host at Galway, and it has been reported 
in Normandy and Italy in the poor cod and several other hosts. 
According to Looss (19016) it is 4-5 mm. long, the ventral sucker is 
about half as broad again as the oral, the oral spines are small (0039 
and 036 mm. in the anterior and posterior rows) and number 36 
(but only 28 according to Stossich), and the eggs measure 006 x 
0045 mm. Lebour (1908a, pp. 24-5, PI. 2, fig. 8) described a single 
specimen found in the pyloric caeca of the cod at Cullercoats, Nicoll 
(1910, p. 340) a few immature specimens from the same location and 
host in the Firth of Clyde, and (1915) recorded the trematode in the 
duodenum of the whiting at Plymouth. Difficulties of and probable 
errors in the diagnosis of trematodes of this and other species of 



200 THE TREMATODA OF BRITISH FISHES 

Stephanostomum make it advisable to deal with descriptions separately. 
Nicoll's specimens from the cod were about 1 mm. long and 0-15 mm. 
broad. They had " stout " oral spines arranged in 2 rows of 18 
each and suckers of about equal sizes and 0-12 mm. diameter, the 
ventral possibly slightly the smaller and situated 0-36 mm. from the 
anterior extremity. Lebour's specimen was mature, but had lost 
the oral spines. Size : 7 mm. long and 0-35 mm. broad. Shape : 
thread- or ribbon-like. Suckers : ventral larger than the oral and 
not far behind it (figured in the first sixth of the body), diameters 
019 mm. and 013 mm. Gut : prepharynx long. Pharynx small 
(length 01 mm.). (Esophagus short. Cseca long, extending almost to 
the posterior extremity, and filled with dark fluid. Reproductive 
systems : genital pore near the anterior margin of the ventral sucker. 
Genital atrium small. Cirrus-pouch very long and somewhat curved, 
extending almost half the distance between the ventral sucker and 
the ovary, containing an elongate cirrus whose sheath (?) is lined 
irregularly with spinelets having their points directed forward, a 
pars prostatica and a club-shaped seminal vesicle. Testes ovoid, 
measuring 0-6 x 0-4 mm., one behind the other and 0-5 mm. apart, 
the posterior testis being about 1 mm. from the posterior extremity. 
Ovary spherical, 1 mm. in front of the anterior testis (behind the 
midbody). Vitellaria extending from the base of the cirrus-pouch to 
the posterior extremity, the follicles filling the space between and 
behind the gonads, but discontinuous at their sides, the ducts alone 
present here, and bilateral groups of follicles along the courses of the 
caeca in front of the ovary. Uterus having few loops confined to 
the region anterior to the ovary. Metraterm long and lined with 
spines like those in the cirrus-pouch. Eggs not numerous and about 
0-06 mm. long. 

Stephanostomum caducum (Looss, 1901). (Fig. 35 E, F.) 

Stephanochasmus caducus Looss, 1901 (b, pp. 603-4, fig. 4) ; S. caducus var. 
lusci of Nicoll, 1914 (p. 477). 

Hosts : bib, poor cod, whiting. 
Location : duodenum and pyloric caeca. 

Lebour (1908a, pp. 26-7, PI. 3, figs. 1, 2) described one specimen 
found in the intestine of the whiting at Cullercoats, Nicoll (1914, 
p. 477) specimens from the bib (which were referred to the variety 
lusci), and one immature specimen from the poor cod at Plymouth. 
Little (1929a) found the trematode in the bib at Galway. The 
specimens described by Looss were from the poor cod at Trieste and 
were 4-4- 12 mm. long. In the specimen 4 mm. long the suckers were 
of the same size (017 mm. diameter), the oral spines numbered 48, and 
were 04 and 03 mm. long in the anterior and posterior rows, and 
the eggs measured 0062 x 004 mm. According to Lebour: — Size: 
4-4 mm. long and 0-34 mm. broad. Cuticle completely spinous. 
Suckers of about equal sizes, 0-30 mm. diameter. Oral spines : 48 
in two unbroken rows of 24 each, 0039 mm. long in the anterior row, 



ACANTHOCOLPIDiE 



201 



0033 mm. in the posterior. Gut : prepharynx 0-34 mm. long. 
Pharynx conspicuous. (Esophagus short. Caeca long. Reproductive 
systems : genital pore near the anterior border of the ventral sucker. 
Cirrus-pouch very long, extent and contents as in S. pristis. Spines 
of the cirrus " sheath " arranged in regular groups of three with their 
apices projecting forward. Cirrus when extruded seen to be unarmed. 
(Note : These " spines " thus seem to be of the same nature as the 




Fig. 35. — A, Stephanostomum pristis. B, S. rhombispinosum ; C, anterior 
end of B. D, S. triglce. E, S. caducum ; F, anterior end of E. G, Neo- 
phasis lageniformis. H, Dihemistephanus sturionis ; I, anterior end of 
H ; J, " hooklets " from the metraterm of H. K, Acanthostomum 
imbutiforme ; L, M, anterior end of K. N, anterior end of A. proeteritum. 
(A-F, after Lebour, 1908 ; G, after Lebour, 1910 ; H-J, after Little, 
1930 ; K, L, after Johnstone, 1906 ; M, N, after Looss, 1901.) 



" pili penis " of Olsson (1868) in Deropristis inflata and flexible 
structures of unknown function rather than copulatory accessories.) 
Testes ovoid, 0-35 mm. long. Ovary spherical. Vitellaria extending 
from slightly in front of the base of the cirrus-pouch to the posterior 
extremity ; sequence of follicles uninterrupted at the lateral margins of 
the gonads. Uterus having few loops, metraterm long and equipped 
with regularly- arranged spine-like structures. Eggs measuring 0066 
X 0-036 mm. 

Nicoll gave the following characters for the variety " lusci." 



202 THE TREMATODA OF BRITISH FISHES 

Size : 1-5-3 mm. long, most specimens more than 2 mm. long con- 
taining eggs. Suckers : in a specimen 3 mm. long ventral slightly 
larger than the oral and 0-63 mm. from the anterior extremity, 
diameters 14 and 012 mm. Oral spines : 50 arranged in two rows 
of 25 each, 0-019 and 0-021 mm. long respectively in the anterior and 
posterior rows. Gut : prepharynx 0-21 mm. long, pharynx measuring 
01 x 0-08 mm. Reproductive systems : genital atrium 0-2 mm. 
long. Cirrus-pouch extending 0-49 mm. behind the ventral sucker. 
Testes, ovary and vitellaria as described by Looss, but vitelline 
follicles distributed slightly farther anteriorly, extending a short 
distance in front of the end of the cirrus-pouch. Eggs measuring 
066 x 0-036 mm. Nicoll thought that some of the differences 
between his specimens and those described by Looss (the number 
and sizes of the oral spines and the position of the ventral sucker) 
were attributable to differences in age and size, but that others (the 
inequality of the suckers and the greater extent of the vitellaria) 
were sufficient to warrant the erection of a new variety, if not a new 
species. I do not agree. The inequality of the suckers is a trifling 
distinction, and the distribution of vitellin efollicles unreliable for 
such a slight distinction. I agree, however, about the spines. Many 
zoologists have testified to the difficulty of counting oral spines, and 
the additional spines which Nicoll found merely indicate variability such 
as exists in other species. His suggestion that Lebour's specimens 
may represent a third variety of S. caducum is equally unacceptable, 
because of the almost perfect agreement between her determinations 
tions and those of Looss regarding the number and sizes of the oral 
spines. The eggs are not significantly larger (only longer and 
narrower) in British specimens, and the differences in the relative 
sizes of the suckers inconclusive in the absence of a range indicating 
specific variability. 

Stephanostomum rhombispinosum (Lebour, 1908). (Fig. 35 B, C.) 

Stephanochasmus rhombispinosus Lebour, 1908 (a, pp. 25—6, PI. 2, figs. 9—10) ; 
S. pristis (Deslongschamps) of Stossich, 1886 (a, pp. 45-6, PL 8, fig. 33). 

Hosts : whiting, 5-bearded rockling. 
Location : pyloric caeca. 

Lebour found this species once only, in the whiting at Cullercoats 
in December, and remarked about the resemblance to S. pristis, 
except in the " armature of the head." The only other British record 
was by Rees (1945) at Aberystwyth. 

Size : 5-10 mm. long and about 0-30 mm. broad. Shap>e ribbon- 
like, tapering gradually anteriorly and sharply posteriorly. Colour : 
translucent and colourless. Suckers of equal sizes, 01 6 mm. 
diameter. Oral spines : exact number not determined, apparently 
36 or 38, very flat and of a broad rhombic shape, arranged in two 
rows. Gut : prepharynx 0-4 mm. long. Pharynx 0-10 x 008 mm., 
(Esophagus short and broad. Caeca long, extending to the posterior 
extremity. Other characters : generally as in S. pristis, but testes 



ACANTHOCOLPIDiE 203 

oval and 0-40 mm. long. Posterior testis 0-8 mm. from the posterior 
extremitjr. Ovary about 0-5 mm. in front of the anterior testis. 
Sequence of vitelline follicles interrupted at the sides of the testes, but 
not the ovary ; eggs somewhat larger, 008 mm. long. 

Stephanostomum triglae (Lebour, 1908). (Fig. 35 D.) 

Stephanochasmus triglce Lebour, 1908 (a, pp. 27-8, PI. 3, figs. 3, 4). 

Host : grey gurnard. 

Location : pjdoric caeca and intestine. 

Lebour described a single specimen from the pyloric caeca of the 
host at Cullercoats in February. Size : 3-2 mm. long when con- 
tracted, 4-8 mm. long when extended, and under these conditions 
0-74 and 0-50 mm. broad. Suckers : relatively large, ventral slightly 
larger than the oral ; dimensions 0-28 mm. diameter (ventral) 
and 014 mm. long and 0-26 mm. broad (oral). Oral spines slightly 
damaged, the exact number undetermined, but more than 42 and 
fewer than 56, arranged in two unbroken rows. Gut : prepharynx 
very short when contracted, 0-60 mm. long when extended. Pharynx 
0-20 mm. long. (Esophagus very short. Caeca long. Reproductive 
systems : cirrus-pouch short, club-shaped and only slightly curved, 
extending only 0-3 mm. behind the ventral sucker, containing a 
pyriform seminal vesicle, a very small pars prostatica and a straight 
cirrus. Testes ovoid, 0-52 mm. long. Ovary globular, 0-2 mm. in 
front of the anterior testis. Laurer's canal long and convoluted 
receptaculum seminis not certainly, but possibly present. Vitellaria 
extending from the ventral sucker to the posterior extremity in an 
unbroken sequence of follicles, which fill all available space between 
and behind the gonads. Uterus broad and short, metraterm also 
short. Eggs large, measuring 0099 x 0-056 mm. 

Mcoll's specimen was immature. Size : 2-9 mm. long and 0-6 mm. 
broad. Suckers : ventral larger than the oral, diameters 0-27 and 
0-20 mm. Oral spines : 50 arranged in two unbroken rows, 003 
and 0035 mm. long in the anterior and posterior rows. Gut : pre- 
pharynx 0-32 mm. long. Pharynx measuring 017 x 0-15 mm. (Eso- 
phagus practically absent. Reproductive systems : cirrus-pouch 
extending behind the ventral sucker for a distance not exceeding the 
diameter of the latter. Testes long oval in outline and not quite 
contiguous, dimensions 0-36 x 0-24 mm. Ovary separated from the 
testes by a small space like that between the testes and similarly 
filled with vitelline follicles ; diameter 0-17 mm. 

Stephanostomum baccatum (Nicoll, 1907). 

Stephanochasmus baccatus Nicoll, 1907 (p. 80) ; Distomum valdeinflatum 
Stossich of Johnstone, 1905. 

Hosts : adults in father lasher and halibut. Encysted meta- 
cercariae in angler, long rough dab, lemon sole, dab, witch. 

Location : adults in the intestine and rectum. Larvae in the 
subcutaneous tissues and muscles. 



204 THE TREMATODA OF BRITISH FISHES 

A single adult specimen found in the halibut at Aberdeen was 
described by Nicoll (1907, p. 80), who later described one more speci- 
men taken from the father lasher at St. Andrews. Nicoll (1915) 
recorded the presence of the trematode in the halibut at Aberdeen, 
and (1910) described six immature specimens taken from the father 
lasher at Millport. 

Mature specimen from the halibut : — Size : 3-34 mm. long and 
0-75 mm. broad. Shape : elongate oval outline, attenuated anteriorly 
and rounded posteriorly. Cuticle spinous, the spines irregularly 
arranged, becoming sparse behind the ventral sucker and absent in 
the greater part of this region. Suckers : ventral larger than the 
oral and 0-87 mm. from the anterior extremity; diameters 0-33 mm. 
and 0-23 mm., the oral having a nodule at the lateral margin pro- 
jecting into the lumen. Oral spines : 56 in two alternating rows of 
28, 0-31 mm. long in the anterior, 0-37 mm. in the posterior row, but 
variable. Gut : prepharynx 0-17 mm. long. Pharynx 0-21 x 016 mm. 
(Esophagus very short. Caeca wide and long, dilated at irregular 
intervals. Bifurcation of the gut close in front of the ventral sucker. 
Reproductive systems : genital pore as in other species. Cirrus-pouch 
long and club-shaped, extending far behind the ventral sucker and 
containing a large ovoid seminal vesicle. Pars prostatica well developed. 
Testes 0-38 mm. diameter, ovary 0-21 mm. Vitellaria extending 
from the base of the cirrus-pouch to the posterior extremity, filling 
the available space between and behind the gonads ; follicles small 
and compact. Uterus short, containing few ova (about 14 shown in 
a figure) of large size, measuring 0-087-0-091 x 0-044-0-053 mm., 
pointed at one end, truncated at the other. Specimen from the 
father lasher at St. Andrews : Size : 2-4 mm. long and 0-7 mm. in 
greatest breadth. Suckers : ventral 0-31 mm. diameter, oral 0-18 mm. 
Oral spines : 56 in two rows of 28 ; spines of the anterior row shorter 
than those of the posterior, but sizes variable. Gut : prepharynx 
0-22 mm. Pharynx 0-20 x 0-19 mm. Reproductive systems : testes 
contiguous, 0-3 mm. diameter, the posterior one-ninth of the length 
of the body from the posterior extremity. Ovary 0-17 mm. diameter, 
situated immediately in front of the anterior testis and 0-4 mm. 
behind the ventral sucker. Vitellaria slightly more extensive than 
in the previous specimen, but not extending to the level of the ventral 
sucker. Cirrus-pouch comparatively shorter. Eggs larger, measuring 
0101 x 0-046 mm. 

Later, Nicoll (1910, p. 340) described six immature specimens from 
the father lasher at Millport. Size : 1-25-2 05 mm. long, the length 
at maturity being 2-2 mm. Suckers : in the largest specimens 
ventral 0-22 mm. diameter, oral 017 mm. Oral spines : 56 in two 
rows of 28, but in two specimens 54 in two rows of 27, their length 
0024-0032 mm. 

Lebour (1908a, p. 28) described what she regarded as the encysted 
larval form of this species, which she found commonly in the sub- 
cutaneous tissues of the dab, witch and long rough dab at Cullercoats, 
and which Johnstone (1905, p. 98, PI. 4, figs. 9, 10 ; PI. 5, figs. 14, 15) 



ACANTHOCOLPIDJE 205 

dealt with under the name Distomum valdeinflatum Stossich. Nicoll 
& Small (1909, p. 237) also found the encysted larva in the dab, 
and Nicoll (1910, p. 340) credited Elmhirst with finding it in the long 
rough dab at Millport. The cysts which Johnstone found in the dab 
near Blackpool occurred mainly in the superficial musculature on the 
blind side of the fish, particularly along the bases of the dorsal and 
ventral fins. They were of a pearly lustre and up to 2 mm. diameter. 
The host showed signs of emaciation, its flesh being suggestive of 
measly pork, but there is no proof that this was due to the parasites. 
The trematode lodged within the cyst was 0-72 mm. long when in the 
flexed condition normal to it, about 1-25 mm. long when stretched 
out. The posterior extremity was indicated as dilated, but Johnstone 
may have been misled by a posterior flexure. Unfortunately the oral 
spines were not counted, but they were seen to form a double series. 

Linton (1898), Stafford (1904), Liihe (1906) and Yamaguti (1937) 
have all found cysts of related species and genera in the tissues of 
fishes, and the suggestion that the fish serves as a second intermediate 
host has been amplified by Martin (1938, 1939), who worked out 
the life- history of Stephanostomum tenue (Linton, 1898), which was 
originally discovered in the rectum of the striped bass, Eoccus lineatus, 
at Woods Hole. The ophthalmoxiphidiocercarise of this species 
develop in rediae in the digestive gland of Nassa obsoleta and later 
passively enter the gut of small fishes, penetrate the wall of the 
intestine and encyst as metacercariae, which grow several times as 
large as the cercarise in the liver and mesenteries. In this country 
flatfishes seem to predominate as second intermediate hosts, and the 
angler possibly serves as a facultative host. 

Genus T0RM0PS0LUS Poche, 1926. 

Tcrmopsolus osculatus (Looss, 1901) Poche, 1926. 

Distomum osculatum Looss, 1901 (b, pp. 654-6, fig. 11). 

Looss erected this species for two trematodes obtained from the 
midgut of the rockling (Motella vulgaris). It is a rather puzzling 
form which has not appeared in British waters. Manter (1934, 
p. 289) drew attention to the very obvious resemblance which it 
bears to species of Stephanostomum, particularly S. caducum, and 
thought it probable that in these specimens the oral spines had been 
accidentally lost, as seems feasible. I have given the characters of 
this trematode elsewhere (Dawes, 1946, p. 220). 

Genus DIHEMISTEPHANUS Looss, 1901. 

Dihemistephanus lydiae (Stossich, 1896), Looss, 1901 (b, pp. 605-6, 
628-9, fig. 6). 

Echinostoma lydice Stossich, 1896 (pp. 190-1, PL 8, fig. 1) ; Stephanostomum 
lydice (Stossich) Looss, 1899 (pp. 576, 582) ; Stephanochasmus lydice 
(Stossich) of Looss, 1901. 

Host : sun-fish. 
Location : intestine. 



206 THE TREMATODA OF BRITISH FISHES 

Nicoll (1909&, p. 12) obtained a large number of specimens taken 
from a sun-fish captured in the Firth of Forth and commented on 
their differences in a few particulars from the specimens described by 
Looss. The trematode has also been found at Trieste. According 
to Looss (1901) : — Size : about 4 mm. long and 0-8 mm. in greatest 
breadth at the level of the ventral sucker. Shape elongate, anterior 
end the more pointed. Suckers of about equal size, the ventral 
slightly behind the middle of the body. Cuticle spinous, the spines 
behind the oral series small laterally and dorsally, becoming larger 
posteriorly and typical behind the ventral sucker ; further back 
ventral spines smaller than the lateral and dorsal. Oral spines 
arranged in two incomplete rows, broken ventrally, beginning at the 
sides of the oral sucker and extending over the dorsal side. Spines of 
the two rows of about equal sizes, not larger dorsally, only the inner- 
most spine of the anterior row ventrally on each side somewhat 
smaller than the remainder, its point directed towards the midventral 
line. Anterior row comprising 20, posterior row 19 spines. In the 
ventral hiatus, slightly behind the free border of the oral sucker, is 
another group of shorter and thicker spines (0013 mm. long), arranged 
in an anterior row of 5 and a posterior of 6. The median spine 
of the anterior row straight in the median ventral line. (Looss 
counted these as in the " head- crown," making 50 spines in all, 39 
longer and 11 shorter.) According to Nicoll: — Size: 1-8-2-4 mm. 
long and one quarter as broad at or behind the ventral sucker. 
Shape : elongate and flattened, tapering and almost cylindrical 
anteriorly between the suckers. Cuticle spinous, the spines of very 
variable size in different regions, mainly long, curved and sharp and 
broad in the base, and largest just in front of the ventral sucker. 
Spines in front of the pharynx very small over two ventro-lateral 
patches. Arrangement of the spines similar dorsally, but large 
spines extending slightly more anteriorly. Oral spines : large spines 
arranged in two rows, apparently 18 in the anterior and 17 in the 
posterior row, of equal length (0-04-0-05 mm.) excepting the two 
terminal spines of the anterior row, which are slightly smaller. Ventral 
series of very small spines variable, sometimes 6 and 7 in anterior and 
posterior rows, the numbers varying from 3 to 15, sometimes nil. 
In addition, some specimens show a third and dorsal series of 10 
fairly large spines (0025 mm. long), straight and sharp. Suckers : 
ventral larger than the oral and about 1 mm. behind it, diameters 
0-22-0-27 mm. and 0-19-0-22 mm., the oral funnel-shaped and having 
a thin ventral and a thicker dorsal lip. Gut : prepharynx 01 mm. 
long, but variable, sometimes twice as long, or absent. Pharynx 
fairly large (0-145 x 01 mm.). (Esophagus slightly shorter. Caeca long. 
Reproductive systems : genital pore located near the anterior margin 
of the ventral sucker, slightly on the left. Genital atrium small, 
cirrus and metraterm opening into it on right and left. Cirrus-pouch 
above the ventral sucker, not extending behind it, containing a 
globular seminal vesicle, a large pars prostatica with few gland-cells, 
and a short, straight cirrus. Gonads in the posterior region (the 



ACANTHOCOLPIDiE 207 

post-testicular space being slightl} 7- more than one-seventh of the 
length of the body) in line and contiguous, the ovary foremost 
(dimensions : testes 0-21 x 0-26 mm., ovary 0-17 x 0-12 mm.). 
Vitellaria comprising very numerous follicles in the dorsal and lateral 
regions extending from the posterior extremity to a level between 
the bifurcation of the gut and the ventral sucker, sparse above the 
uterus. Uterus having an ascending limb only, formed into folds, 
some of which overlie the ventral sucker. Metraterm short and 
muscular. Eggs thin-shelled and having blunt poles, very variable 
in size, measuring 0-060-0-072 x 0-032-0-040 mm. (mean 0-066 x 
0-0365 mm.). 

Dihemistephanus sturionis Little, 1930. (Fig. 35 H-J.) 

Host : sturgeon. 

Location : intestine. 

Little (1930, p. 399) obtained his specimens from a fish caught 
in the Bristol Channel (west of Lundy Island) and landed at Cardiff. 
Size : 3-5-6-2 mm. long, 0-49-0-69 mm. in greatest breadth. Shape : 
elongate, in life variable, especially contractile and extensile anteriorly, 
body gradually broadening towards the bluntly rounded posterior 
end. Colour rust, probably because of the eggs. Cuticle spinous ; 
spines backwardly curved, claw-like, becoming larger towards the 
middle of the body, disappearing posteriorly. Suckers : ventral 
smaller than the oral, and circular in outline instead of transversely 
oval, situated in the first fifth or sixth of the body. Dimensions in 
specimens 3-8 mm. and 6-2 mm. long respectively 0-28 x 0-29 mm. 
and 0-28 mm. diameter (ventral) and 0-35 mm. diameter and 0-50 X 
0-40 mm. (i.e. of different relative sizes as a result of growth). Eyes : 
Remains of the eye-spots of the cercaria apparently absent. Oral 
spines numbering 42-44 and arranged in two ventrally interrupted 
rows of 21 or 23 (anteriorly) and 21 (posteriorly), flat and almond- 
shaped, those of the anterior row about half as long as those of the 
posterior and alternating with them. Sizes of the oral spines (in an 
individual 6-2 mm. long) : 

Anterior row : 0-040 x 022 mm. (mid-dorsal), 0-030-0-034 x 
0015-0017 mm. (lateral), 0-047-0-057 x 0-025-0-026 mm. (ventral), 
0040 x 0021 mm. (ventralmost spine) ; ventral hiatus 0-31 mm. 
wide. 

Posterior row: 0083 x 0032-0036 mm. (mid-dorsal), 0051- 
0-083 x 0-030-0-032 mm. (lateral), 0-053-0-057 x 0-026 mm. (ventral), 
0043 x 0-025 mm. (ventralmost spine) ; ventral hiatus 0-38 mm. wide. 

Gut : Prepharynx 0072 mm. long (body 4-5 mm.). Pharynx 
measuring 0-17 x 011 x 0-15 mm. (Esophagus very short (0-1 mm. 
long). Caeca extending to the posterior extremity and widest near the 
anterior testis, lined with amoeboid cells having basal nuclei and highly 
vacuolated pseudopodia. Bifurcation of the gut midway between the 
suckers. Excretory system : pore terminal. Median canal very short 
(0-2 mm. long) and lined with cilia (?). Lateral canals originating mid - 
dorsally near the pharynx, much convoluted in the anterior region, 



208 THE TREMATODA OF BRITISH FISHES 

lined with thin cuticle throughout (?). Reproductive systems : genital 
pore median, slightly crescentic and very close to the anterior margin 
of the ventral sucker. Genital atrium muscular and tubular (0-192 mm. 
long, Oil (sic ?) X 0026 mm. in width and thickness in a worm 
4-5 mm. long), extending round the ventral sucker. Male cirrus long 
(0-5 mm.), incapable of protrusion (!), provided internally with 
numerous anteriorly directed spinelets, some 0053 mm. long. Seminal 
vesicle ovoid (0-54 x 0-26 x 0-30 mm.) and partly divided into two 
unequal chambers by a partition having a circular central orifice 
004 mm. diameter, the anterior twice as long as the posterior chamber. 
Pars prostatica and cirrus-pouch not observed. Vasa deferentia 
entering the seminal vesicle separately. Testes oval or rhomboidal, 
one behind the other in the posterior third or quarter of the body. 
Dimensions 0-27 x 0-25 x 0-37 (anterior) and 0-26 x 0-27 x 0-39 mm. 
(posterior). Post-testicular space 0-56 mm. long (about one-eighth of 
the body-length). Female : ovary spherical or ovoid (0-12 x 0-11 x 
0-18 mm.), situated slightly in front of the anterior testis and on the 
left. Ootype 0-05 mm. long and about 003 mm. in sectional diameter. 
Receptaculum seminis ovoid and on the right of the ovary. Laurer's 
canal present. Vitellaria comprising numerous follicles scattered 
throughout the posterior five-eighths of the body, but mainly dorsal 
and lateral, tending to fill the available space behind the seminal 
vesicle. Vitelline reservoir located between the ootype and the ovary. 
Uterus having voluminous limbs extending to the posterior extremity. 
Metraterm 0-56 mm. long, parallel with the cirrus and on its left, lined 
by numerous anteriorly directed spinelets, up to 005 mm. long and 
sometimes provided with urn-shaped theca, interspersed with cilia. 
Eggs ovoid, yellow and operculate, measuring 0-043-0049 x 0-034- 
0-043 mm., having shells 007-008 mm. thick. Note : Little referred 
this trematode to the sub-family Echinostomatinae and the family 
Fasciolidse — allocations which must be ignored. His description is 
very detailed and well illustrated. 

Genus DEROPRISTIS Odhner, 1902. (Fig. 36 A, B.) 

Odhner erected this genus for two species, Distoma hispidum 
Abildgaard, in Rudolphi, 1819, and D. inflatum Molin, 1859. Neither 
of these species has been recorded in British waters, but their absence 
is very unlikely indeed. Beneden (1870) found the former very com- 
monly hi the sturgeon off the Belgian coast. The latter was originally 
found in the stomach of the eel at Padua, and later found by Olsson 
(1868) at Bergen. Specimens which Beneden found in the eel and 
figured as " Echinostoma hispidum " were regarded by Ward (1938, 
p. 510) as belonging to this species. Odhner showed that the specimens 
of Olsson were identical with those of Molin, and claimed that D. inflata 
occurs in both the eel and the sturgeon. Markowski (1933, pp. 10-11, 
fig. 2) found what must, in spite of anatomical differences, be regarded 
as this species in the intestine of the eel in the Baltic. Both species 
occur in America, and Ward ( 1938) challenged Stafford's determination of 



ACANTHOCOLPIDJE 



209 




Fig. 36. A, B, Deropristis inflata, anterior end and entire trematode re- 
spectively. C, Hemiurus levinseni. D, Brackyphallus crenatus. E. 
Lecithostaphylus retroflexus. F, Neophasis oculata. G, Monorcheides 
diplorchis. (A, after Odhner, 1902 ; E, after Odhner, 1911 ; rest after 
Odhner, 1905.) 



14 



210 THE TBEMATODA OF BEITISH FISHES 

D. inflata in Canada, but Miller (1941) showed the record to be correct. 
Ward studied many specimens belonging to the genus from a wide 
range of localities, including specimens of D. inflata sent to him from 
Europe by Looss. He noted that zoologists had paid special attention 
to the nature and arrangement of the spines and scales, and that 
different accounts are at variance with one another. Olsson seems to 
have been the only writer who made a study of the living worm, and 
he showed that spines are easily lost, mentioning specimens collected 
at Warberg which were devoid of them. Ward rightly inferred from 
this that it is unwise to lay undue emphasis on the spination in Dero- 
pristis, but he noted some of the main features of it which can be 
summarized here. Entire body covered by closely-set rows of sharp 
spines which are largest in the middle of the forebody, becoming 
smaller towards the extremities and absent behind the testes. Large 
and flat ovate spines arranged in rows on the margins of the shoulders, 
and even larger spines situated on the dorsal hump. All the spines 
are smaller and less conspicuous in D. infiata than in D. hispida, but 
the exact number and arrangement could not be determined in either 
species. Ward also noted the distinction between the spines of the 
cuticle and the structures called by the same name which occur on 
the inner lining of the cirrus and metraterm — what Olsson called the 
" pili penis.'" The latter differ from superficial spines in shape, being 
bent to varying extents, and they show different optical and staining 
qualities. According to Ward, they seem to be flexible rather than 
rigid, and although their true nature has not been disclosed, it is certain 
that they are not ordinary spines. 

According to Luhe (1909, p. 85) D. hispida is about 12 mm. long 
and 0-5-0-65 mm. broad, but American specimens taken from the 
sturgeon in the Delaware River at Philadelphia are very much smaller 
(1-9-5-9 mm. long ; mean about 4-3 mm.). Linton (1940) described a 
specimen 7-8 mm. long which came from a small sturgeon at Menemsha 
Bight. Variability in form in the specimens examined by Ward 
was remarkably great. The anterior part of the body (to the margin 
of the ventral sucker) gave a mean measurement 0-76 mm., but a 
range 017-121 mm. The general contraction of the body increased 
its breadth from 0-17 mm. to 0-64 mm. The suckers seem to be less 
variable, the oral practically maintaining its relative size with growth 
(0-08-0-22 x 0-08-0-21 mm.), the ventral diminishing in relative 
size (0-1-0-21 x 0-11-0-22 mm.). The eggs of this species seem to be 
smaller than those of D. inflata. According to the determinations 
of Odhner they are 0038-0043 mm. long, but Ward's measurements 
gave the range 0-036-0-045 x 0-016-0-025 mm., and Linton's specimens 
came within it (0-042 x 0-024 mm.). 

Markowski's specimens of D. inflata were 3-6 mm. long and 0-375 
mm. broad at the " shoulders," on which spines arranged in two 
lateral rows numbered 28 on each side and measured 0-024-0-027 x 
0011-0013 mm. The ventral sucker was slightly larger than the 
oral, the dimensions being 0-10-0-11 x 0-13-0-14 mm. and 0-10-011 x 
0-12 mm. (although given to three places of decimals). Other charac- 



ACANTHOSTOMATIDJE 211 

ters can be seen in Fig. 36 A, b, but the sizes of the eggs can be given 
here, 0-046-0-052 x 0-019-0-024 mm. Linton (1940, pp. 49-50, 
PL 21, fig. 283) gave an account of specimens 2-1-4-9 mm. long and 
0-24-0-43 mm. broad which were found in the American eel, Anguilla 
rostrata. The eggs measured 0-045-0-048 x 0-021-0-024 mm. Ward 
measured the eggs of specimens of D. inflata sent to him by Looss 
and determined the range 0-043-0-049 X 0-023-0-027 mm., which 
Cable & Hunninen (1942) increased to 0-042-0-052 x 0-024-0-026 mm. 
Cable & Hunninen showed (1942a) that Deropristis inflata has a 
modified trichocercous cercaria with a tail bearing a ventral fin-fold 
and six pairs of ventral-lateral tubercles each carrying a short bristle. 
In America this larva develops in a redia in Bittium altematum and 
later encysts in the axial regions and, when the infection is heavy, in 
the parapodia of Nereis virens, and the American eel is almost invari- 
ably infected in the Woods Hole region by devouring the infected 
polychaetes. Incidentally, these writers gave clear figures (PI. 1, 
figs. 1, 2, 4) of the whole and part of the adult D. inflata, taking con- 
siderable trouble to illustrate the peculiar spination, as well as the 
general features of the anatomy. The large spines develop in the 
metacercaria and they become worn in older worms, or are lost, 
giving the dorsal hump a ragged appearance, iittention was drawn 
also to the presence of numerous glands in the anterior region which 
open to the exterior amidst these spines and also on the ventral 
surface. 



Family ACANTHOSTOMATIM] Poche, 1926, emend. Nicoll, 1935. 

(Acanthochasmidse Nicoll, 1914 ; Acanthostomidse Poche, 1926.) 

Sub-family Acanthostomatin^: Nicoll, 1914, emend. Hughes, Higgin- 

botham & Clary, l!)42. 

Acanthochasminse Nicoll, 1915 ; Anoiktostominse Nicoll, 1915.) 

Size and shape : medium size, elongate or very elongate, slightly 
flat. Cuticle spinous, the spines sometimes scale-like and provided 
with 8 or 9 long sharp points each anteriorly, narrower and having 
fewer points posteriorly ; ordinary spines behind the ends of the cseca ; 
especially long spines arranged in a coronet round the mouth. Suckers 
of medium size and not very widely separated. Gut : prepharynx 
short or fairly long. Pharynx small. (Esophagus short. Caeca very long. 
Excretory system : vesicle Y-shaped, having a long median stem and 
lateral canals extending to the pharynx. Reproductive systems : 
genital pore median slightly in front of the ventral sucker. Cirrus- 
pouch absent, cirrus rather small. Testes globular, one directly or 
diagonally behind the other in the posterior region. Ovary spherical, 
situated in front of the testes and near the more anterior testis. 
Receptaculum seminis large, /j Vitellaria fairly well developed and 
follicular, situated between the gonads and the ventral sucker laterally. 
Uterus having descending and ascending limbs and extending almost 
to the posterior extremity, or only an ascending limb which is much- 



212 THE TBEMATODA OF BRITISH FISHES 

folded and confined to the region anterior to the gonads. Eggs fairly 
or very numerous and very small, generally pointed at one pole. 

Genus ACANTHOSTOMUM Looss, 1899. 

(Acanthochasmus Looss, 1900 ; Caimanicola Freitas & Lent, 1938.) 

Acanthostomum imbutiforme (Molin, 1859). (Fig. 35 K-M.) 

Distoma imbutiforme Molin, 1859 ; Echinostoma imbutiforme (Molin) of 
Stossich, 1898, and of Johnstone, 1906 (pp. 177-9) ; Anoiktostoma imbuti- 
forme (Molin) of Stossich, 1899 ; Acanthochasmus imbutiformis (Molin) of 
Nicoll, 1914 (pp. 488), 1915 (pp. 347, 353). 

Host : bass. 
Location : intestine. 

Johnstone (1906) gave a brief description of specimens found in 
fishes caught in Morecambe Bay, and Nicoll (1914) merely mentioned 
the discovery of about 30 specimens at Plymouth, adding a note 
about what seemed to be a larval stage in the broad-nosed pipe-fish. 
According to Looss (19016), who examined 41 specimens found in 
the bass off the coast of Egypt, this trematode is up to 7-5 mm. long, 
and an individual 4 mm. long has oral and ventral suckers 0-27 and 
0-2 mm. diameter respectively. One specimen had 17 large spines 
arranged around the mouth, 5 specimens had 19, but the remaining 
35 had 18 of them. Johnstone's specimens were stated to be 6-5 mm. 
long and to have the following characters : — Cuticle : spinous, spines 
small, straight and closely- set. Oral spines : straight and stout, 
09 mm. long and inserted in a prominent raised lip. Suckers : 
having their centres 1-1 mm. apart; oral larger than the ventral; 
diameters 0-39 and 0-33 mm. Gut : prepharynx conical. Pharynx short 
and situated almost midway between the suckers, but slightly nearer 
the oral. Reproductive systems : genital pore a transverse slit situated 
on a papilla. Testes large and ovoid, situated one behind the other 
far back in the body. Ovary smaller than the testes, but of similar 
shape, and situated in front of them about two-thirds of the distance 
along the body. Vitellaria lateral, mainly in the posterior region 
(shown in fig. 23 b, extending for a distance equal to one-third of the 
body-length in front of the anterior testis). Uterus having limbs 
extending back to the level of the posterior testis. 

Material kindly lent to me by Professor Daniel contained several 
specimens of this species which may have belonged to Johnstone's 
collection, and I examined several of them. Size : 4-9-6-75 mm. 
long and 0-4-0-6 mm. broad. Shape : ribbon-like. Cuticle : spinous, 
the spines very small (less than 0-01 mm. long). Oral spines : num- 
bering 17 and about 0*08 mm. long and 002 mm. thick, the dorsal 
and ventral spines somewhat larger (up to 0-11 mm. long and 0025 mm. 
thick), straight and peg-like. Suckers : oral campanulate, 0-33 mm. 
diameter and about as deep in specimens 4-9 and 5-1 mm. long, tapering 
to about 0-17 mm. basally, the ventral somewhat smaller (0-27-0-30 
mm. diameter), and the centres of the two 1-1 mm. apart (exactly as 
specified by Johnstone). Gut : prepharynx short. Pharynx ovoid, 



AZYGITDiE 213 

measuring about 0-19 x 17 mm. Cseca almost reaching the posterior 
extremity and somewhat dilated at their ends. Reproductive systems : 
agreeing with the descriptions. Cirrus fusiform and muscular ; P. 3 mm. 
long and 008 mm. broad, protruded in these preserved specimens. 
Vitellaria rather indistinct, but apparently more restricted in front 
of the ovary than is shown in Johnstone's fig. 23 B, and occupying a 
shorter zone (about 1-4 mm. long instead of more than 2 mm., as the 
figure indicates). Eggs measuring 0-030-0033 X 0-012-0-014 mm., 
thus contrasting markedly with the figures (0-023-0-024 X 0012 mm.) 
given by Looss. 

The type-species of this genus, A. spiniceps (Looss, 1896), was found 
in the gut of " Bagrus bay ad " in Cairo. It was carefully studied by 
Looss (19016, pp. 629-31, fig. 7), and is particularly interesting because 
of the variation it shows in the numbers of oral spines, 8 specimens 
having 27, thirty-four 28, thirty- five 29, eighteen 30, four 31, and one 
32. This trematode (see Dawes, 1946, fig. 31 a) is 7-9 mm. long and 
1 mm. broad, has oral and ventral suckers 0-7 and 0-4 mm. long, and 
eggs measuring 0029 X 0-013 mm. Other Mediterranean species 
show similar variation in the numbers of oral spines, A. prceteritum 
(Looss, 1901, pp. 633-4, Fig. 10) generally having 21-22 (Fig. 35 N), or 
only 18-19, A. absconditum (Looss, 1901 ; pp. 631-2, Fig. 8) generally 
19, but 18-22. In erecting these two species Looss depended on the 
sizes of the suckers and the numbers of spines, but on examining their 
characters it is difficult to avoid the conclusion that they are identical 
with A. imbutiforme. The internal anatomy is strikingly uniform 
and spines are easily lost, but before a decision can be reached these 
parasites of the bass require further study. 

Family AZYGIID^E Odhner, 1911, sensu Dollfus, 1936. 

Size and shape : small to very large, elongate and flattened. 
Cuticle : thick and non- spinous, sometimes annulated or wrinkled, 
Suckers : fairly or very powerful, the ventral near and sometimes 
much larger than the oral. Gut : pharynx and short oesophagus 
present. Cseca long, but never opening into the excretory vesicle. 
Excretory system : vesicle Y-shaped. Median stem long. Lateral canals 
very long, but never anastomozing near the oral sucker. Reproductive 
systems : genital pore median, never far in front of the ventral sucker, 
whatever may be its position relative to the end of the oesophagus. 
Cirrus-pouch and cirrus small. Testes globular, one just behind the 
other, near or behind the middle of the body. Ovary globular, slightly 
in front of the testes. Receptaculum seminis absent. Laurer's canal 
present. Vitellaria follicular, lateral and extensive, but not reaching 
the ventral sucker or the posterior extremity. Uterus having a slightly 
folded ascending limb only ; no folds existing behind the ovary. Eggs 
small or fairly large, thin-shelled, sometimes sculptured, occasionally 
having a slimy envelope, when freshly laid containing a ciliated larva. 
Cercaria cystophorous. 

There are two genera to consider, Otodistomum and Azygia. The 



214 THE TREMATODA OF BRITISH FISHES 

former consists of elongate parasites of Selachii, in which the ventral 
sucker is much larger than the oral, the latter of ribbon-like parasites 
of Teleostei in which the oral sucker is slightly the larger. 

Genus OTODISTOMUM Stafford, 1904. 

Stafford erected this genus, without defining it, for trematodes 
found in the barndoor skate in Canada which he believed to be Distoma 
veliporum Creplin, 1837. Lebour (1908a) found a similar trematode 
in the stomach of the starry ray at Cullercoats and assigned it to this 
species, also giving a definition of the genus. Odhner (1911) recog- 
nized two species of the genus, 0. veliporum and 0. cestoides (Beneden, 
1870), and gave characters by which he believed they could be separated. 
Nicoll (1915) recorded only the latter species, transferring Lebour's 
specimen to it and recording its occurrence in the skate at Aberdeen, 
where it was found by T. Scott (1909), and in " Raja macrorhyncha" 
also at Aberdeen. Little (1929a) also recorded this species in the 
last-named host at Galway. I have already given a short state- 
ment (1946) of the difficulties which have attended the separation of 
these two species of Otodistomum. It soon became evident that they 
could not be distinguished by morphological characters and use came 
to be made of the size of the eggs and, when this failed, of the thickness 
of the shell, the distribution and host affiliations. Dollfus (1936, 1937) 
studied the genus in great detail and proposed the erection of two 
sub-species of cestoides and three of veliporum,, but Van Cleave & Vaughn 
(1941) showed the former to be identical, and suggested that all 
American forms belong to the species cestoides. The three varieties 
of European forms also seem to be identical with one another, the 
sizes of the eggs (an unsatisfactory character at best) overlapping and 
even encroaching on the size-range given for cestoides. Accordingly, 
I have suggested that one species of Otodistomum only occurs in car- 
tilaginous fishes in both the Old and New Worlds, as well as elsewhere, 
and that it should be known as 0. veliporum. 

Otodistomum veliporum (Creplin, 1837) Stafford, 1904 (pp. 482-3). 

(Fig. 37 A-E.) 

Distoma veliporum Creplin, 1837 (p. 310) ; Fasciola squali grisei Risso (see 
Diesing, 1850, p. 347) ; Distoma insigne Diesing, 1850 (p. 347) : D. micro- 
cephahtm Baird, 1853 (p. 58, PL 2, fig. 2) ; D. cestoides Beneden, 1870 
(p. 17, PL 6, fig. 9) ; D. nigrescens Olsson, 1876 (pp. 19-20, PL 3, fig. 41) ; 
Agamodistomum chimcerm Ariola, 1899 (pp. 8-10, PL 5, fig. 7) ; " veleporum " 
of Maclaren, 1903a (p. 261) ; Xenodistomum welanocystis Stafford, 1904 (p. 
483) ; Otodistomum cestoides (Beneden) of Odhner, 1911 and authors ; Cercaria 
cestoides Nicoll, 1913 ; Otodistomum cestoides cestoides Dollfus, 1937 (p. 429); 
O. c. pacificum Dollfus, 1937 (p. 429) ; O. veliporum leptotheca Dollfus, 1937 
(pp. 434-440, figs. 25-7) ; O. v. veliporum Dollfus, 1937 (pp. 440-1, figs. 
28-30) ; O. v. packytheca Dollfus, 1937 (pp. 441-5, figs. 31-9) ; and probably 
Otodistomum pristiophori (Johnston, 1902) {Distoma pristiophori Johnston. 
1902 (pp. 326-30, PL 13, figs. 1-7)). 

Hosts : in Britain, adults in the skate, starry ray ; elsewhere in 
various Selachii. Larvae in Britain in the witch. 



AZYGIID^ 215 

Location : adults in the stomach, rarely (probably accidentally) in 
the oesophagus, branchial cavities and intestine. Larvae encysted in 
the wall of the stomach. 

The occurrence of this trematode at Cullercoats, Aberdeen and 
Galway has already been noted. Elsewhere it has been found in 
Norway, Sweden, Russia, Belgium, France, Italy, North America 
(Maine, Woods Hole, Alaska, Washington, California, Canada), South 
America (Chili), New Zealand (Dunedin). It is one of the largest 
known trematodes, as the following list of maximum lengths in milli- 
metres given by various writers helps to show : 80 (Stafford, 1904) ; 
70 (T. Scott, 1909 ; Sleggs, 1927) ; 65 (Odhner, 1911 ; Manter, 1926 ; 
Dollfus, 1936) ; 55 (Miihlschlag, 1914) ; 37 (Beneden, 1870) ; 32 
(Lebour, 1908a). Before considering the extreme variability which 
exists in this species it will be as well to examine the diagnostic 
characters given by Lebour (1908a, pp. 29-31, PI. 3, fig. 5) for the 
comparatively small specimen mentioned above. This was found 
attached to the wall of the stomach in the starry ray. Shape : very 
elongate, breadth about one-twelfth of the length, slightly flattened. 
Cuticle : non-spinous, thick and wrinkled. Suckers : ventral exactly 
twice the diameter of the oral (2-4 mm. as against 1-2 mm.) and close 
behind it. Gut : prepharynx absent. Pharynx 0-40 mm. long and 0-35 
mm. broad. (Esophagus very short. Caeca very long, almost reaching 
the posterior extremity and containing a yellowish -brown fluid. 
Bifurcation of the intestine midway between the suckers. Excretory 
system : vesicle Y-shaped, the lateral and median canals meeting 
slightly behind the posterior testis, and the former extending to the 
pharynx and joining close to the oral sucker. Reproductive systems : 
genital pore median and near the pharynx. Genital atrium roomy, 
bearing towards the right side. Cirrus-pouch inflated, narrowing 
considerably near the atrium, its base directed towards the left side. 
Seminal vesicle small and somewhat club-shaped. Testes globular, 
one behind and touching the other, the anterior smaller than the pos- 
terior and at the middle of the body, transverse dimensions 1-3 and 
1-5 mm. Ovary in front, slightly to the right of, and touching the 
anterior testis, globular, but narrowing anteriorly, 1-2 mm. across. 
Receptaculum seminis absent. Laurer's canal present. Vitellaria 
well developed and follicular, filling the anterior half of the space 
behind the testes, at or slightly behind the level of the posterior testis 
thinning out to form two continuous bands of follicles, 2 to 4 deep, 
extending forward to a level close behind the ventral sucker. Trans- 
verse vitelloducts crossing the ovary. Uterus having an ascending 
limb only, formed into wide folds in front of the gonads, narrowing 
towards the metraterm. Eggs fairly numerous, thin-shelled, broad 
oval and 06 mm. long. 

Manter (1926, p. 14) made valuable contributions to our knowledge 
of this trematode, which becomes mature when about 11 mm. long, 
after which the translucent white colour becomes tinged with brown, 
due to the eggs. The ratio of the sizes of the oral and ventral suckers 
is 3/4 or 3/5 (the ratio 1/2 determined by Lebour being most unusual), 



216 



THE TREMATODA OF BRITISH FISHES 



and does not show change with growth. The folds in the cuticle are 
paralleled by folds in the muscles of the circular layer (which thus 
varies considerably in thickness), but not those of the longitudinal. 
The parenchyma is traversed by numerous muscles, mainly longi- 
tudinal, but also diagonal. There is no definite layer marking out 
cortical and medullary regions as in Azygia. Special muscles are 
inserted in the suckers, and connect the oral sucker with the pharynx. 
Muscles form two layers in the wall of the oesophagus. The terminal 




Fig. 37. — A, "Otodistomum veliporum.'''' B, " 0. veliporum leptotheca." 
C and D, O. veliporum pachytheca. E, " Cercaria cestoides " of Nicoll. 
F, Ptychogonimus megastoma ; G, metacercaria of P. megastoma from 
Carcinus mamas ; H, juvenile P. megastoma from the Smooth Hound. 
(A, after Lebour, 1908a ; rest after Dollfus, 1937.) 



parts of the genital ducts, unobserved by Lebour, penetrate a conical 
papilla which projects into the genital atrium, and is similarly provided 
with a layer of cuticle. The papilla is composed of circular, longi- 
tudinal and oblique muscles, but is not a constant character, as Odhner 
(1911) supposed, being ill-defined when retracted, but a prominent 
copulatory organ when protruded. These movements are achieved 
by means of a complex system of muscles, which originate in the layers 
in the integument. The testes vary in size, the anterior being invari- 
ably the smaller, as Lebour found to be the case, but in one specimen 
only. The ovary is invariably smaller than the testes, and may be 
situated on the right or the left side of the body. Protandry is the 
rule. The cirrus-pouch measures 0-84-1-02 x 0-65-0-84 mm. in 



AZYGHDiE 217 

specimens of medium size (23-35 mm. long), and contains a swollen 
and slightly curved seminal vesicle, a somewhat convoluted pars 
prostatica, surrounded by large prostate glands, and a similar ejacu- 
latory duct, which is lined with cuticle. Laurer's canal also has 
a cuticular lining, as has the metraterm. A receptaculum seminis 
is absent, as Lebour surmised. The vitellaria are variable in 
extent and arrangement. When first formed (only a short time 
before the eggs begin to develop) the follicles are very small (0 05 mm. 
dia.), but they enlarge rapidly (to 0- 15-0- 19 mm.) in the adult. The 
massing of follicles across the median plane seen by Lebour is an 
unusual condition ; generally lateral rows are separate and distinct, 
though a strict sequence is not invariably maintained. The distinc- 
tions put forward by Odhner for the separation of 0. cestoides and 
0. veliporum are useless. 

Manter also made a serious attempt to evaluate changes in form 
due to growth, measurements being made on more than 200 specimens 
ranging between 2-3 mm. and 65 mm. in length. The youngest 
individuals obtained were strikingly unlike the adults in the propor- 
tions of the body. When the trematode is 2-3 mm. long the ventral 
sucker occupies a position very little in front of the mid- body. As 
the length of the body increases, the region behind the ventral sucker 
becomes relatively progressively longer, ultimately to yield the 
definitive condition in which both suckers lie within the anterior 
one-fifth of the body. In spite of such considerable changes in the 
proportions, the suckers retain the relative sizes established in the 
early stages of development, but only in relation to one another, 
diminishing in size relative to that of the body as a whole. In the 
young juveniles the ventral sucker is one -fifth of the length of the 
body in diameter, in fully grown adults only one-twentieth. After 
maturity is reached the region of the body containing the uterus, 
i.e. that between the ventral sucker and the ovary, grows relatively 
more rapidly than the posterior region behind the gonads. These 
growth changes, which are intensified and more evident on account 
of the large definitive size attained, are important, not merely as 
regards Otodistomum veliporum, but in all trematodes, and they 
should be determined whenever abundance of material permits. 

According to Manter the distinctive miracidium is non-ciliate 
pyriform and narrow anteriorly, but is constantly changing its shape. 
When fully extended it is slender, elongate, and 009-0- 10 mm. long ; 
when contracted, spherical and 0-045-0-050 mm. in diameter. The 
anterior extremity can be drawn into the body, becoming inverted, 
after the manner of a proboscis. The entire body has a cuticle, which 
bears numerous fine bristles anteriorly. Similar spines occur on 
4 plates (Borstenplatten) in the miracidium of Azygia lucii, and these 
are absent in Otodistomum according to Odhner (1911), although 
Manter observed that the bristles are borne on five areas which radiate 
from the anterior tip of the body. Both bristles and plates are shed 
eventually, and during the process the larva present a curious 
appearance, the strips resembling appendages. 



218 THE TREMATODA OF BRITISH FISHES 

The metacercarise of Otodistomum have been found encysted in the 
wall of the stomach of the witch at Aberdeen by Nicoll (19136, p. 194, 
PL 13, fig. 2), and by T. Scott (1909, pp. 78, 92, PI. 7, figs. 5, 6), who 
(1909, pp. 77-8, 92, PI. 5, fig. 12 ; PI. 7, fig. 3) found juveniles in the 
oesophagus of the flapper skate at Aberdeen. Outside Britain, Olsson 
(1876, p. 19, PI. 3, fig. 41) found cysts in the angler in the Skagerrak, 
and they were recorded as " Xenodistoma melanocystis " in black and 
fibrous cysts in the same host in Canada by Stafford (1904, p. 483 ; 
1907, pp*. 94, 106). Dollfus (1937, p. 447) obtained them from the 
rabbit-fish, as did Wagener (1852, p. 543) and Ariola (1899, pp. 136-8, 
PI. 5, fig. 7) They have been found in Selachii other than those 
mentioned (see Dollfus, 1937). 

Genus AZYGIA Looss, 1899. 

Hassalius Goldberger, 1911; Mimodistomum Stafford, 1904; Megadistomum 

Stafford, 1904.) 

This genus differs from Otodistomum in several distinctive characters 
which are easily observed. The shape of the body is similar, but 
there is more space between the suckers, and the genital pore is nearer 
the ventral sucker, over which the cirrus-pouch lies. The gonads are 
similarly arranged, but nearer the posterior extremity. The main 
canals of the excretory system are similar, but the lateral canals end 
separately in the anterior region. The eggs are somewhat smaller, 
measuring about 0045 x 0021 mm. (Odhner, 1911). The bristles of 
the non-ciliate miracidium do not arise from basal plates (Borsten- 
platten). As Manter (1926) pointed out, contraction of the elongate 
body alters not only the shape, but also the topographical relations of 
the internal organs. Thus, the ovary may lie beside the anterior 
testis instead of in front of it (as in " Hassalius "), and the caeca may 
be thrown into folds. Such conditions have no taxonomic significance 
and must be considered critically. The synoiwms mentioned represent 
modified forms, and they were resolved by Odhner, and Ward (1917), 
Manter (1926), and others have concurred. Several species of doubtful 
validity have been recorded on the Continent, and the American 
species Azygia longa (Leidv) has been well described see Manter — 
(1926, pp. 63-72, figs. 19, 20, 30) and Linton (1940, pp. 105-7, PI. 22, 
figs. 292-7). The only species with which we are concerned is : 

Azygia lucii (Miiller, 1776) Luhe, 1909. (Fig. 34 C.) 

Fasciola lucii Miiller, 1776 (p. 224) ; Distomum tereticolle (Rudolphi) of Looss, 
1894 (pp. 5-18, PI. 1, figs. 1-3 ; PI. 3, figs. 53-63 ; PI. 4, figs. 64-71 ; 
PI. 6, fig. 121) ; Azygia loossii Marshall & Gilbert, 1905 (pp. 483-5, PL 15, 
figs. 5-7) ; Ptuchogonimus volgensis Linstow, 1907 (p. 201) ; Distomum 
volgcnse (Linstow) of Liine, 1909 ; Azygia tereticollis (Rudolphi) Looss, 
1899 (p. 570) and of Odhner, 1911 ((38), p. 519) ; A. volgensis (Linstow) of 
Odhner, 1911 ((38), p. 519); A. robusta Odhner, 1911 ((38), pp. 520-1); and 
perhaps forms discovered outside Europe. 

Hosts : Pike in Norfolk (see Baylis, 1928). Outside Britain, 
perch, burbot, trout, grayling, chub, pike and others. 

Location : stomach and intestine, sometimes oesophagus (Looss). 



AZYGIIDiE 219 

This species occurs in several localities on the Continent (Rhine, 
Lake Constance), where it is said to be very common in the pike 
(Liihe), and in North America. Looss (1894) gave a good description 
and excellent figures, Liihe (1909, p. 49, fig. 45) summarized this 
account, and Odhner (1911, (38), pp. 519-20) added a few points, 
some of which are shown in parentheses. Size : 10-30 mm. long, 
rarely more than 1-5 mm. broad (becoming rather larger, mature 
when 5-6 mm. long). Shape : almost cylindrical. Colour : flesh- 
to rose -red when alive, white when dead. Cuticle : non- spinous and 
thick, wrinkled in the contracted worm. Suckers : oral somewhat 
larger than the ventral, which is situated well within the anterior 
one -third of the body (diameters 1-15 and 0-85 mm.). Gut : pharynx 
well developed and cylindrical (invariably almost twice as long as 
broad, 0-6-0-8 mm. long and 0-35-0-45 mm. broad in specimens 
18-22 mm. in length). (Esophagus very short. Caeca very long, extend- 
ing to the posterior extremity. Contents of the caeca never coloured 
according to Looss, but including fat droplets. Bifurcation of the 
gut very much nearer the oral than the ventral sucker. Reproductive 
systems : genital pore just in front of the ventral sucker. Cirrus- 
pouch almost spherical, only slightly muscular, containing a con- 
voluted seminal vesicle and a short cirrus. Testes ovoid, one behind 
the other, well in the posterior half of the body, and slightly in front of 
the junction of the lateral and median excretory canals. Ovary 
globular or ovoid, only slightly in front of the anterior testis. Uterus 
having an ascending limb only, with numerous small folds confined 
between the caeca, the ovary and the ventral sucker. Vitellaria 
lateral and follicular, extending from only slightly behind the posterior 
testis to a short distance behind the ventral sucker. Eggs clear 
yellowish-brown, measuring 0045 x 0023 mm., those in the terminal 
part of the uterus containing a fully developed, non-ciliated mira- 
cidium. 

The form known as " Ptychogonimus volgensis " was based on a 
single specimen found in the gut of the perch. This measured 
6-2 x 0-9 mm. and showed the following characters : — Suckers : 
oral 0-79 mm. diameter, ventral 0-61 x 0-59 mm. and situated at 
the end of the third eighth of the body. Gut : pharynx two-thirds 
as long and half as wide as the oral sucker. Reproductive systems : 
ovary slightly larger than the testes. Eggs measuring 052 x 
023 mm. Other characters in the diagnosis conform to those of 
A. lucii. Odhner (1911 (38), p. 519) obtained specimens which he 
allocated to this species, stating that the trematode becomes mature 
when 2 mm. long, attains a length of 5 mm., is 0-4-0-75 mm. broad, 
has suckers measuring 0-34-0-58 mm. (oral) and 0-27-0-43 mm. 
diameter (the latter being situated one-third of the distance 
along the body), and a pharynx measuring 0-23-0-42 x 0-14-0-26 mm. 
Manter (1926) saw that no important distinction exists between the 
two forms, and it is likely that they are identical. Odhner (1911 
(38), p. 520) made the species " 0. robusta " tentatively, for forms 
from Salmo spp., but was more categoric. Its chief distinction is the 



220 THE TREMATODA OF BRITISH FISHES 

Jarge size (up to 47 mm. long) and the small, spherical pharynx. 
The latter is a very poor criterion for the distinction of a species, 
though Odhner depended upon it. An unbiased investigator would 
deem the form nothing more than a large specimen of A. lucii. 
Manter (1926) has shown that the dimensions of the pharynx in 
Azygia spp. are subject to considerable variation. It is for these 
reasons that " A. robusta " is regarded as a synonym of A. lucii. 

Family PTYCHOGONIMID^ Dollfus, 1936. 

(Azygiidce Odhner, 1911, in part.) 

Size and shape : fairly small or medium size, oval or elongate, 
slightly flat. Cuticle : non- spinous, but having coarse and irregular 
transverse folds. Musculature : well developed. Suckers : powerful 
and not far apart. Gut : prepharynx very small or absent. Pharynx 
fairly large. (Esophagus absent. Intestinal crura very long, opening 
posteriorly into the excretory vesicle. Bifurcation of the gut dorsal 
to the ventral sucker, first part of the intestine forming a loop between 
the pharynx and the oral sucker. Excretory system : vesicle U-shaped, 
the two main canals forming a small posterior chamber which opens 
to the exterior by a short and straight canal having muscular walls. 
Lateral canals united by 2 transverse anastomoses situated near the 
anterior and posterior borders of the ventral sucker. Reproductive 
systems : genital pore median and situated between the suckers. 
Genital atrium having muscular walls. Genital papilla protrusible, 
sunk in the atrium, surrounded (when retracted) by 3 annular folds, 
the male and female pores opening separately into a small cavity 
near its tip. Cirrus-pouch absent. Ejaculatory duct short. Pars 
prostatica longer. Seminal vesicle very long and convoluted, extending 
behind the posterior border of the ventral sucker. Testes of oval 
outline situated one behind the other in the middle of the body. 
Ovary of similar shape as and situated just in front of the anterior 
testes, separated from the ventral sucker by several folds of the uterus 
and by the transverse vitelloducts. Receptaculum seminis absent, 
Laurer's canal present. Vitellaria follicular, occupying the lateral 
regions behind the ventral sucker, the follicles spreading over the 
ventral surface of the excretory vesicle posteriorly and over the folds 
of the uterus anteriorly. Uterus having descending and ascending 
limbs and extending close to the posterior extremity. Eggs numerous, 
thin-shelled and of medium size, length 0-062-0 067 mm. Miracidium 
non-ciliate and having characteristic rigid bristles anteriorly. Hosts : 
Selachii. 

Genus PTYCH0G0NIMUS Liihe, 1900. 

Ptychogonimus megastoma (Rudolphi, 1819) Liihe, 1900 (p. 489), 
emend. (Fig. 37 F-H.) 

Distoma megastomum Rudolphi, 1819 (pp. 102, 387) ; D. (Brachylaimus) 
megastomum (Rudolphi) of Parona, 1896 ; D. soccus Molin, 1858, of 
Stossich, 1886 (a, p. 64) ; D. lymphaticum Linstow, 1903 (pp. 353-4, figs. 
3-4). 



PTYCHOGONIMID.E 221 

Hosts : in Britain, adults in the smooth hound, unencysted meta- 
cercarise in the Brachyura. 

Location : adults in the stomach ; larvae in the tubules of the 
testes, the vas deferens, and in the coelom near the ovary. 

This trematode was found in 4 out of 6 smooth hounds examined 
at Plymouth by Nicoll (1914, p. 484), who stated that it occurs in 
moderate numbers, but did not describe his specimens. It was 
recorded in this host at Plymouth by Baylis & Idris Jones (1933). 
Nicoll (1915) recorded its occurrence outside British waters in other 
hosts (tope, nurse hound, blue shark). Dollfus (1936) gave a detailed 
account of its history. On the Continent Wedl (1855, p. 383, PI. 2a, 
fig. 16) described specimens from the nurse hound, Kroyer (1852-3, 
p. 851) specimens from the tope, Willemoes-Suhm (1870, p. 179, 
PL 11, fig. 4) specimens from the blue shark. MacLaren (1903a, 
p. 261) gave the host, probably wrongly, as the dentex, and it has 
been found in other fishes. Grobben (1878, p. 145) first reported the 
occurrence of the metacercaria in the testis, tubules and vas deferens 
of Portunus depurator, Monticelli (1890, p. 426) found a juvenile 
specimen in the body cavity of Maia, and Dollfus reported its occur- 
rence in Carcinus mamas, mentioning also that Bouvier (in litt.) 
often found it in Atelecyclus. I do not think larval forms have been 
discovered in Britain, but they might be sought in such hosts as these. 

The adult could be recognized by the characters of the family, 
but the fleshy nature of the body makes study difficult. Dollfus 
(1937, p. 459, figs. 41-58) gave an account of the main features of the 
anatomy. Size : large specimens 6-8-5 mm. long and 2-5-3-5 mm. 
in greatest breadth. Shape : oval, but uniformly slightly narrower 
between the suckers. Cuticle : thickness variable, mainly 0-009- 
0014 mm., but locally 0-025 mm., finely granular and containing 
groups of very small vacuoles. Suckers : of about equal size, the 
oral sometimes slightly the larger, their centres about one-quarter 
of the body-length apart. Reproductive systems : genital pore situated 
just in front of the ventral sucker, the complex genital atrium having 
folds with an intrinsic musculature. Testes transversely oval, some- 
times slightly lobed. Ovary not lobed, situated just in front of the 
anterior testis ; oviduct equipped with a sphincter. Vitellaria made 
up of oval follicles scattered laterally, and to some extent dorsally 
and ventrally, arranged in 3-6 irregular longitudinal rows. Uterus 
comprising descending and ascending limbs having 10-14 regular 
folds on each side of the body. Eggs measuring 0-062-0-067 x 
0036-0038 mm., but possibly as small as 0-057 x 0-024 mm. (see 
Jacoby, 1899, p. 22), or as large as 0-073 X 0044 mm. (see Linstow, 
1903, p. 354), these dimensions probably representing extreme varia- 
tions. Metacercarise measuring 2-8-3 x 0-9-1-0 mm. occur in Car- 
cinus, the smallest individual found in the smooth hound being 1-6 mm. 
long and 0-76 mm. broad. Vaullegeard (1896, p. 666) found many 
specimens still juvenile when 3 mm. long and 1 mm. broad. Reported 
instances of progenesis, or the attainment of maturity while still in 
the intermediate host, require confirmation. 



222 THE TREMATODA OF BRITISH FISHES 

Family HAPLOSPLANCHNID^ Poche, 1926. 

Size and shape : small and pyriform, broadest anteriorly. Cuticle : 
non- spinous. Suckers : well developed, the ventral very deep. Gut : 
prepharynx short. Pharynx spherical. (Esophagus short. Intestine a 
simple caecum having a columnar epithelium. Excretory system : 
pore terminal, vesicle Y-shaped. Reproductive systems : genital pore 
between the suckers. Genital atrium tubular. Gonads comprising a 
single ovoid testis in a posterior position behind the ovary. Vitellaria 
not well developed. Uterus mainly an ascending loop. Eggs of medium 
size, thin-shelled, when laid containing ripe miracidia. 



Genus HAPLOSPLANCHNUS Looss, 1902. 
With the characters of the family, sensu Poche, 1926. 

Haplosplanchnus pachysoma (Eysenhardt, 1829) Looss, 1902 (p. 129). 

(Fig. 38 C.) 

Distoma pachysoma Eysenhardt, 1829 (p. 144) ; Podocotyle pachysomiim 
(Eysenhardt), Stossich, 1898 (p. 26). 

Hosts : in the Mediterranean, thin-lipped and thick-lipped grey 
mullets. 

Location : intestine. 

This extraordinary trematode occurs at Trieste (Italy) and Catania 
(Sicily), but has not appeared in Britain, although there is good 
reason to suppose it may appear. It was described by Looss (19026, 
pp. 119-22, fig. 3). Size : up to 3-3 mm. long, but mature when 
1-2 mm. long. Shape : variable, but generally broad anteriorly 
and pointed posteriorly. Suckers : not far apart, ventral larger than 
the oral and yet of about the same diameter (0-35 mm.), very deep 
(0-8 mm.) and sac-like, almost cylindrical, tying in a thickening of 
the body and having a peripheral sphincter. Reproductive systems : 
genital pore situated near the mouth. Genital atrium tubular. Cirrus 
and cirrus pouch absent. Pars prostatica lying free in the parenchyma. 
Vas deferens convoluted and serving as a seminal vesicle. Testis 
ovoid, posterior in position. Ovary spherical and situated in front of 
the testis. Vitellaria ill-developed, not obviously paired, comprising 
a few follicles between the intestine and the testis, mainly dorsal. 
Uterus having a short descending limb extending only to the anterior 
end of the testis, and a long ascending limb which is folded in front 
of the gonads. Eggs in the smallest mature specimens measuring 
004 x 0-026 mm., in specimens 3 mm. long somewhat larger, measur- 
ing 055 x 031 mm., when laid containing fully developed mira- 
cidia with a large eye-spot. The miracidia studied by Yamaguti 
(1934) hatched out in utcro were uniformly ciliated, had a large 
X- shaped eye -spot and a lens -like body on either side of it. and were 



MONORCHIIDiE 223 

slightly larger than the eggs, measuring 0-06-0-07 x 0027-0030 mm., 
the vacated shells of the eggs 0051 x 0-027 mm. 

Another species of this genus, H. purii Srivastava, 1939, occurs 
in Mugil waigiensis in India. A new genus and species, Laruea 
caudatum, was made by Srivastava (1939a) for other trematodes from 
the same host in India, the genus being said to have a differently 
shaped body and ventral sucker and gonads and vitellaria showing 
different topographical positions. 

Family MONORCHIID.E Odhner, 1911. 

Size and shape : small, oval or elongate, slightly flat. Cuticle 
spinous. Suckers relatively small, the ventral frequently smaller 
than the oral and situated only slightly anterior to the middle of the 
body. Glands abundant in the anterior region. Gut : prepharynx 
short or absent. Pharynx small. (Esophagus short. Caeca long or fairly 
long, but sometimes scarcely extending behind the middle of the 
body. Excretory system : vesicle tubular or Y-shaped, flame-cell 
formula 2[(2 + 2) + (2 + 2)]. Reproductive systems : genital pore 
median and situated near the bifurcation of the gut, or near the left 
margin of the body in this region. Cirrus-pouch large, elongate, 
often extending behind the ventral sucker. Cirrus thick and armed 
with spinelets. Pars prostatica short. Vesicula seminalis interna present. 
Testis large, ovoid or slightly lobed, posterior (two testes in Mon- 
orcheides). Ovary ovoid or lobed, situated on the right in front of the 
testis or testes. Re ceptaculum seminis very small or absent. Laurer's 
canal present. Vitellaria not well developed, but follicular, situated 
in various parts of the body, near or behind the ventral sucker, some- 
times in front of it. Uterus having much folded descending and 
ascending limbs, sometimes coarse subsidiary folds on either side of 
the body. Metraterm short and wide, its terminal part spinous. Eggs 
numerous, but small, and of variable size (0018-0045 mm. long). 

Key to Sub-families. 

I. Body rounded or short oval in outline and flattened ; excretory 
vesicle Y-shaped ; vitellaria near (sometimes in front of) the 
ventral sucker. ...... Monorchun^e. 

II. Body elongate, pointed at the extremities and little flattened ; excre- 
tory vesicle tubular, generally very small ; vitellaria near (some- 
times behind) the ventral sucker . . . Proctotrematin^. 

Sub-family Monorchiin^e Odhner, 1911. 

Genus M0N0RCHIS Looss, 1902, nee Clerc, 1902. 

The main characters of this genus are the short median stem of 
the excretory vesicle, which is thus almost V-shaped, the solitary 
testis, the extent of the cirrus-pouch behind the ventral sucker, and 
the way in which the uterus opens into the medio-lateral border of 
the metraterm, only the distal half of which is spinous. 



224 



THE TREMATODA OE BRITISH FISHES 



Monorchis monorchis (Stossich, 1890) Looss, 1902. (Fig. 38 A, B.) 

Distomum monorchis Stossich, 1890 (pp. 40-1, PL 15, fig. 62) ; D. tartinii 
Stossich, 1899 (p. 6, PL 1, fie. 13) ; Monorchis parvus Looss, 1902 (b, p. 118, 
fig. 2). 

Host : gattorugine. 

Location : intestine (probably wrongly recorded by Nicoll (1915, 
p. 356) as stomach). 

Nicoll (1914, p. 484) mentioned two specimens found in the host and 
location mentioned at Plymouth, but gave no description. The 



A 




1 }&w 





Fig. 38. — A, Monorchis monorchis. B, "Monorchis parvus.'"' C, Haplo- 
splanchnus pachysomia. (After Looss, 19026.) 



trematode has been found also in Cantharus orbicularis and Oblata 
melanura at Trieste, and was described by Looss (19026, pp. 117-8, 
fig. 1). Size: 1-1-2 mm. long and 0-8 mm. broad. Shape: long 



MONORCHIIDiE 225 

oval outline, fairly thick, the posterior end the more sharply pointed. 
Cuticle spinous, the spines more numerous anteriorly. Suckers: 
ventral smaller than the oral and situated slightly in front of the 
middle of the body; diameters (in a whole mount measuring 1-4 x 
0-85 mm.) 0-23 and 0-13 mm. Gut : prepharynx short. Pharynx 
relatively small (0 08 mm. dia.). (Esophagus narrow and as long as 
the pharynx. Caeca long. Reproductive systems : genital pore median, 
near the bifurcation of the gut. Cirrus-pouch very large, extending 
behind the ventral sucker. Cirrus and ejaculatory duct spinous. Pars 
prostatica spindle-shaped. Seminal vesicle sac-like. Testis longitudin- 
ally ovoid with an irregular border, asymmetrically placed in the 
posterior region. Ovary deeply lobed, dorsal, lateral and anterior to 
the testis. Laurer's canal present. Vitellaria two loosely-arranged 
masses of follicles in the antero-lateral regions. Uterus having limbs 
much folded in the lateral regions behind the ventral sucker. Metra- 
term large (half the size of the cirrus-pouch), its terminal part as 
long as the cirrus and similarly spinous, its basal part without spines. 
Eggs very small (about 0021 x 0-012 mm.), yellowish-brown and 
thin-shelled. 

" Monorchis parvus " (Fig. 39 B) was described by Looss as short 
oval in outline, 0-4 mm. long and 0-4 mm. broad, with suckers (in a 
whole mount 0-7 x 0-5 mm.) 0-11-0-12 mm. and 0-059-0-06 mm. 
diameter ; pharynx 0-07 mm. diameter ; vitellaria having fewer follicles ; 
uterine folds slightly less extensive anteriorly, and larger eggs 
(0-023 X 0013 mm.). These differences are not incompatible with 
the smaller size of the specimens and represent unsatisfactory criteria 
of distinction, so that Monorchis parvus, which was found in Sargus 
annularis and 8. rondeletii at Trieste, must be regarded as a synonym 
of Monorchis monorchis. 



Genus M0N0RCHEIDES Odhner, 1905. 

The main characters of this genus are the long median stem of 
the excretory vesicle, which is thus Y-shaped, the presence of 2 
testes, the short extent of the cirrus-pouch, which does not reach 
behind the ventral sucker, and the normal opening of the uterus into 
the metraterm, which is wholly spinous. Monorcheides diplorchis 
Odhner, 1905 (Fig. 36 G) was discovered in " Lumprenus " medius at 
Spitzbergen and has not appeared in Britain. Another species, M . 
soldatovi Issaitschikow, 1928, occurs in Aspidophoroides olriki in 
Russia, and a third, M. cumingice (Martin, 1938), was reared experi- 
mentally in America. According to Martin (19396, 1940) the cercaria 
of this species has 2 eye-spots, suckers of equal sizes and a flame cell- 
formula 2[(2 + 2) + (2 + 2)]. It develops in a sporocyst in the 
visceral mass of the clam, Cumingia tellinoides, and after leaving the 
mollusc by means of the exhalent current, swims about for a time, 
and either passively enters the inhalent siphon or penetrates the 
mantle or foot of a clam of the same species, later shedding the tail, 
penetrating the tissues and encysting as a metacercaria in the tissue 

15 



226 THE TEEMATODA OF BRITISH FISHES 

of one of the siphons (particularly the inhalent) or gills, mantle or 
(very rarely) visceral region. Cercariae do not encyst without indulg- 
ing in a period of free -swimming life. In laboratory experiments 
small puffers (Sphceroides maculatus), flounders and eels were fed 
either with fragments of clam-tissue or whole clams (removed from 
the shell) containing the cysts, and infection followed. 

Sub-family Proctotrematin^: Odhner, 1911, emend. 
Yamaguti, 1934. 

Genus PROCTOTREMA Odhner, 1911. 

In this genus the oral sucker is beaker-like, and the smaller ventral 
sucker is situated about one -third of the distance along the body. 
The oesophagus is very short, the median stem of the excretory vesicle 
very long (almost reaching the ventral sucker) ; the genital pore is 
median. The species P. bacilliovatum Odhner, 1911, was discovered 
in the end-gut of the red mullet at Trieste and has not been found in 
Britain. According to Odhner (1911, vol. 37, p. 249, fig. 2) the main 
characters are as follows : — Size : 0-6-0-8 mm. long and 0-25-0-28 mm. 
broad. Shape : elongate, posterior end somewhat pointed. Suckers : 
oral nearly twice as long as the ventral; dimensions 0-14-0-18 x 
0-10-0-11 mm. and 0075-01 x 0-095-0-115 mm. Gut : pharynx 
0-05-0-06 mm. diameter. Reproductive systems : cirrus short and wide 
and having clusters of spinelets about 0-035 mm. long. Metraterm 
having shorter spinelets. Pars prostatica short. Seminal vesicle con- 
voluted. Testes of variable shape and longer than broad. Ovary 
trilobate. Vitellaria comprising about 8 follicles on each side of the 
ventral sucker. Eggs bacterium-like, 4 times as long as broad (0-031- 
0-033 X 0-008-0-009 mm.), thin-shelled and yellow. 

Genus ASYMPHYLODORA Looss, 1899. 

In this genus the ventral sucker is the larger, the oesophagus is 
long, the median stem of the excretory vesicle short and the genital 
pore marginal. The members of the genus are parasites in the gut of 
Cyprinids. Liihe (1909) recognized four species, but according to 
Witenberg & Eckmann (1934), who found six carp taken from Lake 
Antioch (Syria) to be infected with A. tincce, there is only one species, 
but another has since been found in the common goby in the Baltic, 
A. demeli Markowski, 1935. 

Asymphylodora tincae (Modeer, 1790) Liihe, 1909. 

Fasciola tincce Modeer, 1790 (p. 127) ; Distoma punctatum Zeder, 1800 (pp. 
183-4) ; Distomum perlatum Nordmann, 1832 (pp. 88-98, PI. 9, figs. 1-9) ; 
Asymphylodora ferruginosa (Linstow, 1877) of Liihe, 1909 ; A. exspinosa 
(Hausmann, 1896) of Liihe, 1909; A. imitans (Muhling, 1898) of Liihe,1909 ; 
A. macrostoma Ozaki, 1925 ; A. tincce var. kubanicum Issaitschikow, 1923. 

This species has not been recorded in Britain,* though it is very 
likely to occur here, for it has been found in various Cyprinida3 (tench, 

* Dr. Baylis informs me that Mr. S. Prudhoe has recently found it in the 
barbel in Berkshire. 



MONORCHIIDiE 227 

carp, barbel, bream) on the Continent (Lake Constance, Rhine), in 
Syria, the Kuban and even Japan. The reader is referred to the 
descriptions given in Liihe (1909, p. 93, fig. 73), Witenberg & 
Eckmann (1934, pp. 366-71, figs. 1-3) and Dawes (1946, p. 230, fig. 
35 B), but a brief description can be given here which includes the 
characters of four specimens found in the Rhine and Lake Constance 
and described by Zandt (1924, p. 235). Size : up to about 1-5 mm. 
long and 0-6 mm. broad. Shape : outline oval or spindle -like, variable 
in the living worm, the forebody sometimes being drawn out into a 
long " neck." Colour : reddish or rust-brown, sometimes colourless. 
Cuticle : covered with scale -like spines which, according to Liihe, 
are rectangular (0010 X 0004 mm.) and pointed at the free end, 
more conspicuous ventrally. Glands : well developed anteriorly, 
more scattered in the posterior region. Suckers : oral smaller than 
the ventral; diameters 0-15-0-26 and 0-18-0-34 mm. Gut : pharynx 
about half as large as the oral sucker. (Esophagus 0-15-0-19 mm. 
long and generally S-shaped. Caeca extending into the last quarter of 
the body. Reproductive systems : testis spherical or ovoid and 
0-19-0-38 mm. long. Ovary inconstant in shape, but generally elongate 
and lobed and several times smaller than the testis. Cirrus-pouch 
0-4-0-9 mm. long, size varying with the amount of accumulated 
semen, containing a large seminal vesicle, a short pars prostatica and 
a spinous cirrus, the spines being longer than those of the cuticle. 
Uterus occupying all the available space behind the pharynx, but 
restricted to a more posterior region in small specimens. Metraterm oi 
variable shape, lined with spines, muscular and 0-09-0-17 mm. long. 
Eggs rather elongate, having a flat operculum and also a small knob 
or hook-like filament at the anopercular pole, dimensions 0-021-0-035 x 
0011-0016 mm. 



Asymphylodora demeli Markowski, 1935. 

One to three specimens of this species were found in the intestine 
of each freckled goby taken from the Baltic and examined by Mar- 
kowski (1935, pp. 254-6, PI. 10, figs. 1-4). The distinctive characters 
of the species were given as the different positions of the vitellaria, 
constantly restricted to the posterior region, the small size of the 
cirrus-pouch, the short and straight oesophagus and the shape of the 
eggs. A short description can be given here, and figures of this 
trematode can be found in my book (Dawes, 1946, Figs. 35 D-F). 
Size : 0-285-0-9 mm. long and 0-18-0-45 mm. broad. Colour : rust- 
brown. Shape : oval outline, tapering more gradually anteriorly 
than posteriorly. Cuticle spinous, the spines very small [not shown 
in the figures]. Suckers : ventral (which has 6 wart-like papillae on 
the inner border) larger than the oral and situated in front of the mid- 
body ; dimensions 0-082-0-177 x 0-082-0-19 mm. and 0-068-0-136 mm. 
diameter. Gut : pharynx 004-009 mm. long and 003-0-08 mm. 
broad. (Esophagus short and straight. Caeca long. Reproductive 
systems : genital pore lateral at the level of the posterior margin of 



228 THE TREMATODA OF BRITISH FTSHES 

the ventral sucker. Cirrus-pouch 008-0-136 mm. long and 0027- 
0-049 mm. broad, extending diagonally inwards towards the median 
plane behind the sucker. Cirrus spinous. Testis globular, measuring 
0-041-0-163 X 0-035-0-122 mm. and situated in the posterior region. 
Ovary globular, immediately antero-lateral to the testis, 0-022- 
0-125 mm. long and 16-0 122 mm. broad. Metraterm measuring 
0-054-0-082 x 0027-0046 mm., situated behind the cirrus-pouch, 
having spine-like structures in the inner lining. Vitellaria comprising 
2 postero-lateral clusters of coarse follicles ; transverse vitelloduct 
situated between the ovary and the testis. Uterus folded, the folds 
tending to fill the available space behind the ventral sucker. Eggs 
slightly pyriform and having a knob -like process at the anopercular 
pole; dimensions 0-022-0-027 x 0-011-0-014 mm. 



Family ACCACCELITD.E Dollfus, 1923. 
(Accacoeliinae Odhner, 1911; " Accacceliiden " Looss, 1912.) 

Dollfus (1935) pointed out that Odhner (1911, p. 527) first used the 
name Accacceliinse for a sub-family of the Hemiuridse characterized 
by a long oesophagus and an intestine of H -shape. Looss (1912, 
p. 331) used the term " Accacceliiden " for a group of genera belonging 
to two sub-families, one (Tetrochetinen) containing Tetrochetus and 
Orophocotyle, the other " Accaccelium" an apparently heterogeneous 
assemblage of three genera. Dollfus (1923, p. 345) established the 
group as a family, which was accepted by Odhner (1927) and Fuhr- 
mann (1928), and assigned it to the super-family Hemiuroidea. Size : 
up to 36 mm. in length. Shape very elongate and cylindrical. Cuticle 
non-spinous, sometimes wrinkled or annulated and papillate anteriorty. 
Suckers large and not far apart, the ventral larger than the oral and 
sometimes pedunculate, lobed and having a double margin. Gut : pre- 
pharynx short or absent. Pharynx pyriform or fusiform. (Esophagus 
fairly or very long. Intestine H -shaped, having short anterior exten- 
sions and long posterior extensions which open into the excretory vesicle 
and sometimes have diverticula. Excretory system : median canal 
short, the tributary canals dorsal and ventral, becoming lateral on 
the right and left respectively, sometimes uniting above the pharynx. 
Reproductive systems : genital pore median and just behind the 
mouth. Genital atrium simple or complex. Cirrus-pouch and cirrus 
absent, but a protractile genital papilla sometimes present. Male 
and female ducts sometimes separate, or united to form an hermaphro- 
dite duct. Testes globular, and situated directly or obliquely one 
behind the other. Ovary globular, and situated in the middle line 
just behind the testes. Receptaculum seminis absent, Laurer's canal 
present. Vitellaria variable, the follicles arranged in pyriform masses 
or in sinuous threads or dendritic groups, localized mainly between 
the suckers and the caeca, one vitellarium sometimes vestigial. Uterus 
having descending and ascending limbs, almost reaching the posterior 
extremity and much folded behind the gonads. Metraterm straight, 



ACCACOELIIDiE 229 

and situated ventral to the pars prostatica. Eggs operculate, 
numerous and small, 0026-0036 mm. long. Larvae unknown, but 
metacercaria? living free in various pelagic invertebrates, notably 
ccelenterates. The sub-families can be separated by the existence of 
a protractile copulatory organ in the Accacoeliinae and its absence in 
the Tetrochetinae, in which group the male and female pores are 
separate and no genital papilla occurs in the genital atrium. 

Sub-family Accacceliin^; Odhner, 1911, sensu Dollfus, 1935. 

Key to Genera. 

I. Male and female ducts fused to form an hermaphrodite duct. 

a. Ca3ca and their anterior extensions without diverticula . Accaccdium. 

b. Caeca having diverticula, their anterior extensions not . Accacladium. 

c. Caeca and their anterior extensions having diver- 

ticula ........ Accacladoccelium. 

II. Male and female ducts separate, hermaphrodite duct 

absent ........ Bhynchopharynx. 

Genus ACCACCELIUM Monticelli, 1893, sensu Odhner, 19286. 

(Fig. 39 C.) 

Type and only species A. contortum (Rudolphi, 1819) Looss, 1899 
(p. 632) ; (Distoma contortum Rudolphi, 1819 (p. 118) ; Podocotyle 
contortum (Rud.) Stossich, 1898 (pp. 24-5)), first recorded on the gills 
of the sunfish at Naples, subsequently found in the Atlantic, Canada 
and U.S.A., as well as in the Mediterranean (at Catania) and on the 
gills of M ola nasus in Sweden. Not found in Britain. Ventral sucker 
devoid of muscular expansions. Copulatory organ and hermaphrodite 
duct present. Caeca and their anterior extensions without diverticula. 
Vitelline follicles arranged in small dendritic groups following the 
courses of the caeca, and extending from the level of the testes to just 
in front of the posterior extremity. See Odhner (1928, p. 172), 
Dollfus (1935, p. 215, figs. 3-4) and, for descriptions of American 
specimens, Linton (1898, pp. 528-30, PL 48, figs. 3-7 ; 1940, pp. 
145-6). 

Genus ACCACLADIUM Odhner, 1928. 

Type-species A. serpentulus Odhner, 19286 (pp. 173-4, fig. 3). 
Found in the intestine of the sun-fish at Naples and Bergen, in U.S.A. 
and Japan. Not found in Britain. Ventral sucker devoid of muscular 
expansions. Copulatory organ and hermaphrodite duct present. 
Caeca having diverticula, their anterior extensions lacking them. 
Vitellaria mainly comprising longitudinal rows of follicles, but having 
small ramifying lateral branches, extending between the levels of the 
posterior end of the ventral sucker and the ovary. See also Linton 
(1898, pp. 530-1, PI. 48, figs. 8-11 ; PI. 49, figs. 1-2). 

A second species, A. nematulum Noble & Noble, 1937, was dis- 
covered in association with Mneiodhneria calyptrocotyle in the gut of 
the sun- fish in Monterey Bay, California. 



230 THE TREMATODA OF BRITISH FISHES 

Genus RHYNCHOPHARYNX Odhner, 1928. 

Type and only species R. 'paradoxa Odhner, 1928 (b, p. 167, figs. 
1,2). Found in the intestine of the sun-fish at Naples and Trieste and 
on the Pacific coast of Japan. Not found in Britain. Ventral sucker 
devoid of muscular expansions. Copulatory organ present, but 
hermaphrodite duct absent. Anterior extensions of the caeca each 
having two prolongations, the caeca proper provided with slight 
diverticula and extending posteriorly along a zig-zag course. Vitellaria 
comprising tubules having short dendritic ramifications, extending 
along the caeca between the ventral sucker and ovary. For a short 
description of the pecularities of the pharynx from which this trema- 
tode gets its name, see Dawes (1946, p. 236). 

Genus ACCACLADOCCELIUM Odhner, 1928. 
Hermaphrodite duct and copulatory organ present. Ventral 
sucker having or lacking muscular expansions. The 4 species which 
have been referred to the genus are all intestinal parasites of the 
sun-fish. 

A. nigroflavum (Rudolphi, 1819) Odhner, 1928. 

Distoma nigroflavum Rudolphi, 1819 (p. 118) ; Dist. megnini Poirier, 1885 
(p. 4). 

This species has been found on the Atlantic coast of Europe, at 
Naples and on the Isle of Elba. In Sweden it occurred on Mola 
nasus. It has appeared also in Canada. The ventral sucker is 
devoid of muscular expansions, the caeca and their anterior extensions 
have diverticula, and the vitellaria take the form of long sinuous 
anastomosing threads extending from the level of the pharynx to the 
posterior end of the ventral sucker. 

A. macrocotyle (Diesing, 1858) Odhner, 1928, sensu Monticelli, 1893. 

Distoma macrocotyle Diesing, 1858 (p. 342) ; Podocotyle macrocotyle (Diesing) 
Stossich, 1898 (p. 25). 

This species has been found at Naples, in Sweden (on Mola nasus) 
and in Canada and U.S.A. The original description was based on an 
account by Bellingham (1844, p. 429) of specimens found in Ireland. 
The ventral sucker lacks muscular expansions, the caeca and their 
extensions have diverticula, and the vitellaria comprise fine and very 
sinuous threads extending between the pharynx and a level slightly 
behind the ovary. Further information about this species can be 
found in papers by Linton (1898, pp. 522-3, PI. 45, figs. 8-10 ; PL 46, 
figs. 1-5; 1940, pp. 146-7). 

A. petasiporum Odhner, 1928 (p. 175). (Fig. 39 F, G.) 

This species was found at Naples and Trieste. The ventral sucker 
has muscular expansions, the caeca and their anterior extensions have 
short diverticula, and the vitelline follicles comprise small sinuous 



ACCACCELIIDJE 



231 



threads between the peduncle of the ventral sucker and the genital 
pore. 

A. alveolatum Robinson, 1934. (Fig. 39 A, B.) 

This species was found at Salcombe (Devon) and fully described 
by Robinson (1934, p. 346, PL 13, figs. 1-5). Size : on an average 
6-5 mm. long and 1-5 mm. in greatest breadth. Shape elongate oval 
or spindle-shaped, but not tapering very much at the extremities. 
Preserved specimens rather stout, curved ventrally and circular in 




Fig. 39. — A, B, Accacladocoelium alveolatum : A, semi-diagrammatic recon- 
struction of the genital system ; B, cleared entire trematode. C, Acca- 
ccelium contortum. D and E, Mneiodhneria calyptrocotyle. F and G, 
Accacladocoelium petasiporum. (C and F in side view ; E in dorsal view ; 
rest in ventral view.) (A and B after Robinson, 1934 ; rest after Dollfus, 
1935.) 



cross-section, the posterior end slightly mvaginated to simulate a 
third sucker. Cuticle much wrinkled, especially around the base of 
the ventral sucker. At the posterior extremity, crowded together in 
a zone 0-25 mm. wide, numerous spindle-shaped " papillae " with 
ragged free ends lying outside the cuticle. Histologically they are 
finely granular and stain intensely, but contain no nuclei, and are 
separated by perpendicular ridges of cuticular material, which cross 
one another at right angles to yield a honeycomb structure, with 
compartments about 0-08 mm. deep containing the " papillae." The 
free edges of the " honeycomb " are formed into swollen flanges of 
vesicular cuticle. Nature of the papillae undetermined ; the absence 



232 THE TREMATODA OF BEITISH FISHES 

of glands in nearby tissues suggests that they are not secretor}^ 
products, and they may simply represent masses of debris. Suckers 
about 1-0 mm. apart, the ventral twice as large as the oral ; diameters 
10 mm. and 0-5 mm. Gut: mouth slightly ventral. Pharynx ill- 
developed. (Esophagus extending back for a short distance, then 
turning sharply dorsally, and dividing into right and left branches 
near the anterior margin of the ventral sucker, here giving rise to 4 
anteriorly-projecting diverticula. Caeca provided with forward exten- 
sions, the wholeintestine H-shaped; caeca proper having numerous 
voluminous diverticula, each extension possessing 6 shorter out- 
growths. The ends of the caeca communicate by wide openings with 
the terminal part of the excretory system. Excretory system : main 
canals (vesicle) Y-shaped, terminal part of the median canal forming 
a spacious " cloaca," which is lined with cuticle indistinguishable from 
that covering the body. " Cloacal " aperture terminal. Repro- 
ductive systems : genital pore median and close behind the mouth. 
Hermaphrodite duct short and narrow, lined with cuticle, and pro- 
vided with a small sinus sac, opening on a protrusible (?) papilla 
about 0-1 mm. long. Testes transversely ovoid, one behind the other 
and contiguous (the anterior slightly dorsal to the posterior) near the 
ventral sucker. Pars prostatica well developed. Prostate gland very 
large. Seminal vesicle thin-walled, long and convoluted. Vasa 
deferentia of different lengths, and opening separately into the seminal 
vesicle. Ovary oval in outline, and situated immediately behind the 
posterior testis. Oviduct coiled, entering the right side of the ovary. 
Laurer's canal present. Receptaculum seminis not observed (possibly 
referred to as " shell-gland," situated at the side of the ovary). 
Vitellaria highly modified, one large and ramified above the oral 
sucker and between it and the ventral sucker, the other reduced to a 
single follicle ventro-lateral to the ovary. Main vitelloduct extending 
above and across the testes ; its reduced fellow very short, the two 
meeting in a short common duct near the ovary. Uterus having 
limbs formed into wide transverse folds behind the ventral sucker 
and extending almost to the posterior extremity. Descending limb 
mainly ventral, ascending dorsal, the caeca and their diverticula 
situated between the two. Metraterm narrow and ventral to the 
male duct, widening as it extends back, meeting the uterus above 
the ventral sucker. Eggs not observed. 

Sub-family Tetrochetinje Dollfus, 1935. 

(" Tetrochetinen " Looss, 1912.) 

Key to Genera. 

I. Ventral sucker having a double anterior border ; vitelline follicles 

arranged in small pyriform masses .... Orophocotyle. 

II. Ventral sucker having four prominent petaloid outgrowths ; vitelline 
follicles forming slender cords between the pharynx and the ovary 

Mneiodhneria. 
III. Ventral sucker without special characters ; vitelline follicles forming 

long branching, ramified tubules .... Tetrochetus. 



ACCACCELIIDiE 233 

Genus TETROCHETUS Looss, 1912. 

The only European species of the genus is T. raynerianus (Nardo, 
1827) {Distoma raynerianum Nardo, 1827 (p. 68)), which has been 
found in the intestine of Luvarus imperialis Rafinesque, 1810, at 
Venice, Trieste and Elba. Not yet found in Britain. One other 
species, T. proctocolus Manter (1940, pp. 410-2, figs. 96-7) was found 
in the Galapagos Isles. 

Genus MNEIODHNERIA Dollfus, 1935. (Fig. 39 D, E.) 

(Odhnerium Yamaguti, 1934.) 

One species of this genus is M. calyptrocotyle (Monticelli, 1891) 
(Distoma calyptrocotyle Monticelli, 1891 (p. 110) ; Accacoelium calyp- 
trocotyle of Liihe, 1900 (p. 487) ; Orophocotyle calyptrocotyle of Looss, 
1902 (p. 644)). It was found in the intestine of the sun-fish at Trieste 
and on the Atlantic coast of France, and (in Mola nasus) in Sweden. 
Not so far found in Britain. The other species is M. foliata (Linton, 
1898) (Distoma foliatum Linton, 1898 (p. 532)), which occurs in the 
same location and host off the coast of Massachusetts. In both 
species the ventral sucker has muscular expansions such as occur in 
Accacladocoelium petasiporum, but the absence of a copulatory organ 
and diverticula of the caeca provide distinctive negative characters. 
The vitellaria comprise slender threads extending between the pharynx 
and the ovary. The two species are difficult to separate, and Odhner 
(1928) was inclined to regard the European form as an immature 
stage of the American. Individual variability is the difficulty, as 
Dollfus (1935, p. 209) made clear, some of this writer's specimens 
having very large foliaceous expansions of the ventral sucker like 
those figured by Linton, others very small ones. The reader is 
referred to the paper by Dollfus for a statement of the problem. 
Linton (1940, p. 148) made some statements about American specimens. 

Genus OROPHOCOTYLE Looss, 1902. 

Stossich (1899, p. 5, fig. 9) described a trematode from the intestine 
of the truncated sun-fish at Trieste as Podocotyle planci. Looss 
(1902a, pp. 637-44, figs. 1-4) examined the original specimens, 
founded the genus Orophocotyle and recognized two forms, O. planci, 
and what he (in my opinion unwarrantably) regarded as a new species, 
O. divergens. As a result of his studies he was able to provide an 
extensive diagnosis of the genus, on which the following is based : — 

Body : in the main cylindrical and not very muscular, tapering 
posteriorly and forked anteriorly, where the ventral sucker occupies 
the end of a process of the " neck " region. Cuticle smooth and 
devoid of papillae (such as occur in Accacoelium and Mneiodhneria 
calyptrocotyle). Suckers large and deep, their walls thin, varying in 
appearance according to the stage of contraction, approximately of 
equal sizes, but the oral often larger than the ventral. Oral sucker 



234 THE TEEMATODA OF BRITISH FISHES 

terminal, at its opening a sphincter which is not annular, but consists 
of two isolated parts, one dorsal and the other ventral, each with a 
thick bundle of equatorial fibrils sandwiched between radial fibrils. 
All the bundles extend to right and left of the median plane and meet 
near the margin of the mouth, which can be sharply marked off as a 
lip. The dorsal lip thus formed is larger than the ventral, and both 
are distinct and separate, the lateral parts of the rim of the mouth 
being free of muscle fibrils. Ventral sucker almost cylindrical, the 
topographically anterior border the larger, so that the opening (generally 
a slit) is directed posteriorly. By muscular contraction the sucker 
can be drawn deeply into the lateral process bearing it, even retracted 
into the body. Gut H -shaped. Prepharynx present and opening on 
a conical process in the base of the oral sucker. Pharynx and oesophagus 
also present, the latter short and thin. Caeca long and extending to 
near the anterior extremity, the anterior extensions disposed alongside 
the pharynx. Excretory system : pore wide and terminal, sometimes 
borne on an invagination of the posterior extremity, the unpaired 
stem of the vesicle soon bifurcating at an undetermined point. (Note: 
This possibly refers to the connexions between the caeca and the 
terminal part of the excretory system.) Reproductive systems : 
genital pore median and near the oral sucker. Genital sinus short 
and simple. A definite copulatory organ absent, the male duct 
ending in a slightly individualized pars prostatica surrounded by 
prostate gland- cells lying free in the parenchyma. Seminal vesicle 
very long and tubular, situated close beneath the dorsal surface of 
the body and extending back far behind the level of the process 
bearing the ventral sucker. Gonads globular, the testes lateral and 
slightly behind the middle of the body, the anterior near the dorsal 
and the posterior near the ventral surface. Ovary situated behind 
the testes, the ootype immediately in front of the ovary. Laurer's 
canal short and straight, extending to the dorsal surface. Vitellaria 
unpaired and comprising relatively few follicles formed into four rows 
(dorsal, ventral and lateral to the caeca), extending anteriorly to near 
the base of the sucker-bearing process. Uterus having a short 
ascending limb co-extensive with the vitellaria anteriorly, a long 
descending limb almost reaching the posterior extremity, and a 
recurrent ascending limb proceeding to the genital pore, formed into 
short and wide folds in the posterior region. Eggs numerous, dark 
brown and thin-shelled, measuring 003 X 002 mm. 

Orophocotyle planci (Stossich, 1899) Looss, 1902. (Fig. 40 B.) 

According to Looss (1902a, pp. 637-41, figs. 2-4) : — Length : 
3-3-4 mm. Thickness : up to 0-3 mm. Shape : posterior end of the 
body relatively wide and slightly truncated. Suckers : of approxi- 
mately equal sizes, up to 0-27 mm. long and 0-15-0-18 mm. broad 
(when contracted). Reproductive systems : genital pore approximately 
under the middle of the oral sucker. Shell-glands almost exactly in the 
middle of the body. Some vitelline follicles in the space between 



ACCACCELIIDiE 235 

the testes and ovary. Limbs of the uterus extending back almost to 
the posterior extremity. Eggs measuring 0-028-0-03 X 0-016- 
0019 mm. Seminal vesicle over-reaching the base of the process 
bearing the ventral sucker. 

Orophocotyle divergens Looss, 1902. (Fig. 40 A.) 

According to Looss (1902a, pp. 640, 643, 644, fig. I):— Size: 
slightly smaller than 0. planci. Shape : posterior end of the body 



Fig. 40. — A, Orophocotyle divergens. B, O. planci. (After Looss, 1902a.) 



pointed. Suckers : oral larger than the ventral and thicker than the 
body ; dimensions 0*45 mm. long and 0*33 mm. broad (oral) and 
0-27 mm. long and 0-17 mm. broad (ventral). Reproductive systems : 
genital pore near the posterior end of the oral sucker. Seminal 



236 THE TREMATODA OF BRITISH FISHES 

vesicle extending only slightly behind the base of the process bearing 
the ventral sucker. Vitelline follicles absent between the ovary and 
testes. Shell-glands slightly in front of the middle of the hindbody. 
Uterus having limbs extending only a short distance in front of the 
posterior extremity. Eggs not very different (!) from those of 0. 
planci, measuring 0-028-0-03 x 0018-002 mm. 

Considering the highly extensile and contractile nature of Acca- 
cceliids, it is remarkable that wider variability was not found in the 
sample of specimens from the same host and locality which Looss 
examined, because it might be expected in the members of almost 
any species of trematode. It is practically certain that these two 
forms are identical, and accordingly 0. divergens must be regarded as 
a synonym of 0. planci. 

Family DIDYMOZOIDS Poche, 1907. 

(Didymozoonidse Monticelli, 1888.) 

Habit : pairs or small aggregates of individuals inhabiting cysts 
in the integument of the head, buccal cavity, coelom or kidney, less 
frequently in the oesophagus, the lower regions of the intestine and 
the musculature of their hosts. Sexuality : generally hermaphrodite, 
but showing a tendency towards unisexuality with rudimentary 
hermaphroditismus in some instances. Shape very elongate and 
cylindrical, or narrow anteriorly and broad posteriorly. Cuticle 
smooth. Suckers : oral invariably present, ventral sometimes absent. 
Chit : pharynx very small or absent. (Esophagus sometimes long. 
Caeca very long. Reproductive systems : genital pore situated far 
forward near the mouth. Gonads and vitellaria generally thread-like, 
sometimes tubular. Copulatory organ ill-developed. Uterus having 
descending and ascending limbs, very capacious. Eggs very small 
and very numerous. Excretory system : vesicle sac -like or tubular 
(Y-shaped, but with an exceedingly long median stem). Main genera 
shown below, together with their more general characters : 

Didymozoon. — Hermaphrodite cyst-dwelling Didymozoids, having a 
small, thread-like anterior and a longer and thicker, cylindrical 
posterior region separated by a clearly-marked neck region. Oral 
sucker present or absent, ventral sucker absent. Gonads and vitel- 
laria tubular. Uterus long and having two or three limbs. Genital pore 
situated near the mouth. 

Nematobothrium. — Hermaphrodite Didymozoids, cyst-dwelling or 
not, having a long and uniform, thread-like body, the forebody, hind- 
body and neck-region ill-defined. Oral and ventral suckers, and 
intestine present or absent. Gonads and vitellaria tubular. 

Didymocystis . — Hermaphrodite, cyst-dwelling Didymozoids having 
a slender and elongate anterior and a swollen posterior region of 
variable shape (reniform, comma-shaped, sub-globular). Oral sucker 
present or absent, ventral sucker absent. Intestine present. 

Kollikeria. — Uni-sexual cyst-dwelling Didymozoids, having a spoon- 
shaped anterior and a large reniform or sub -globular posterior region. 



DIDYMOZOID/E 237 

Oral sucker well-developed, ventral sucker also present. Male 
invariably small, having a smaller hindbody, and occupying a hollow 
in the female body. 

Wedlia. — Uni-sexual cyst-dwelling Didymozoids, having a body as 
in KdlliJceria, but lacking a ventral sucker. Males as in Kollikeria. 

Genus DIDYMOZOON Taschenberg, 1879, sensu Odhner, 1907. 

Taschenberg (18796) founded this genus for several unusual 
trematodes which were discovered in cysts on or near the gills of 
several fishes at Naples. One species, which he named D. scombri, 
occurred just inside the gill covers of the Spanish mackerel, and had 
these diagnostic characters : — Size : 18 mm. long. Shape : elongate, 
rounded at both ends, the neck region only slightly narrower than 
the rest of the body. Gut : pharynx spherical. Intestine present. 
Reproductive systems : opening of the uterus situated on a small 
papilla at the anterior end of the animal. Odhner (1907) identified 
specimens of the same species in small mackerel caught off the West 
coast of Sweden, and after elaborating Taschenberg's description, 
designated the species as the type of its genus. Dollfus (1926) and 
others have accepted this designation, but Stiles and Hassall regarded 
Didymozoon as a new name for Wedlia Cobbold, 1860, a verdict with 
which Poche (1926) disagreed. Baylis (1938), who gave a taxonomic 
review of the genus, has also indicated that Didymozoon cannot be 
disposed of as a synonym of Wedlia in this way. Ishii (1935) alter- 
natively referred D. scombri to the genus N ematobothrium Beneden, 
1858, but Baylis pointed out that in the present state of our knowledge 
of N ematobothrium filarina Beneden, 1858, it is impossible to decide if 
these two forms are congeneric. Beneden's description was very 
incomplete, neither suckers nor intestine being seen, while other 
species of N ematobothrium (e.g. N. molae, Maclaren, 1904) have a 
ventral sucker, which does not exist in Didymozoon. The opinion of 
Baylis that it is preferable to retain the two genera, at least until 
more conclusive proof of their identity is forthcoming, is endorsed 
here. 

Didymozoon scombri Taschenberg, 1879 (6, p. 612, PI. 6, fig. iv). 

(Fig. 41 A.) 

(N ematobothrium (Benedenozoum) scombri of Ishii, 1935 (p. 298).) 

Host : mackerel. 

Location : encysted in the buccal cavity, branchial region, etc. 

Johnstone described (1914) cysts containing worms, which occurred 
in various situations, commonly on the roof of the buccal cavity 
beneath the pharyngo-branchials, on the basi-branchials and the 
external surfaces of other parts of the gill-bars and on the internal 
surface of the operculum. The specimens were found by A. Scott in 
mackerel caught just off Walney Island, Barrow-in-Furness. Baylis 
(1938) studied specimens found on the same host-species taken from 



238 THE TEEMATODA OF BRITISH FISHES 

the English Channel, recording (1939) their occurrence in Devon and 
Cornwall. The species also occurs in various parts of Italy (Naples, 
Genoa, Venice, Trieste), in West Sweden (Kristineberg) and in U.S.A. 
(Woods Hole). Johnstone was able to verify the details given in 
Odhner's very complete description. Cysts generally occurring singly, 
but sometimes in groups, measuring 4-5 mm. long and 2-3 mm. 
broad, but sometimes larger, pale yellow in colour because of eggs in 
the trematodes within them, these numbering as many as 13 large 
and 3 small specimens. Trematode. — Size : 15-20 mm. long and 0-5 
to more than 1 mm. in breadth and thickness. Shape very elongate 
and thread-like, the cylindrical body having a somewhat narrow 
anterior and a uniformly, slightly broader posterior region. Internal 
organs : gonads and vitellaria thread-like and continuous with their 
ducts. Cirrus-pouch and prostate glands absent. Other organs 
showing the arrangement indicated in Fig. 41 A. 

According to Odhner, the worm may attain a length of 25-35 mm. 
and a breadth of 1-2-1-75 mm., but Baylis examined a specimen no 
less than 55 mm. long and 2 mm. broad, and Linton (1942, p. 149, 
PI. 23, figs. 305-9) described American specimens assigned to this 
species, finding the aggregate length of seven to be 264 mm., and the 
length of the longest individual 40 mm. Linton gave some dimensions 
of internal organs, and it is noteworthy that there is much variability 
in the size of the testes, which may be large and situated one behind 
the other, or small and side by side, as shown in Odhner's fig. 8. 

Didymozoon faciale Baylis, 1938. (Fig. 41 B, C.) 

Host : mackerel. 

Location : cysts beneath the transparent outer skin of the head 
behind the eye. 

Baylis (1938, pp. 485-90, figs. 1-6) described in detail specimens 
found in the English Channel, later (1939) recording their occurrence 
in Devon and Cornwall. Cysts : yellowish bodies 3-7 mm. long and 
1-1-5 mm. broad, containing from 1 to 4 worms very tightly 
packed in the cyst, 2 or more of them differing enormously in size. 
Trematode. — Size : 0-7-16-3 mm. long and 0-08-1-4 mm. broad when 
permanently mounted in a slightly flattened condition; specimens 
less than 3 mm. long generally without eggs and with undifferentiated 
female reproductive organs, but much variability in the degree of 
maturity attained in relation to size. Shape : anterior region (fore- 
body) lanceolate and somewhat flattened and joined by a narrow 
" neck " with the main part of the body (hindbody), which is generally 
cylindrical. Hindbody increasing in size disproportionately with the 
forebody during general growth, becoming relatively larger in large 
worms, which are folded by flexure in two places so that the anterior 
and posterior ends tend to overlap. Suckers : ventral absent, oral 
oval or pyriform, 0-04-0-08 mm. long and 0-03-0-05 mm. broad, the 
dimensions being roughly proportional to the size of the specimen, 
and very much smaller than in D. scombri (see p. 487*). Gut : pharynx 
hemispherical and very small, measuring about 0018-0024 mm. 



DIDYMOZOIDiE 



239 



diameter. (Esophagus narrow and short, terminating in the anterior 
half of the forebody. Caeca very long and delicate, formed into numerous 
short dorso-ventral loops, extending into the hindbody, but here 
difficult to detect on account of the well- developed genital organs. 
Reproductive systems : genital pore situated on a rounded muscular 
papilla ventral to the oral sucker. Testes two, long and convoluted 
tubular organs occupying the greater part of the body in small speci- 
mens, but only extending one-third of the distance along the body 
in large specimens, continuous with the vasa deferentia and with a 
vas deferens which extends parallel and dorsal to the metraterm 




Fig. 41. — A, Didymozoon scombri. B, D. f addle ; C, embryo of D. faciale 
escaping from the egg. (A, after Johnstone, 1914 ; B and C, after 
Baylis, 1938.) 



along the entire length of the forebody. Ovary and vitellarium long 
and convoluted tubular organs respectively anterior and posterior to 
the oviduct, converging on the ootype and nearby receptaculum 
seminis a little in front of the middle of the body. Uterus very long, 
convoluted and dilated, having an ascending limb extending almost 
to the " neck," a descending limb which almost reaches the posterior 
extremity, and a recurrent ascending limb proceeding to the metra- 
term. Eggs very numerous and very small, thick-shelled, operculate 
and yellow, measuring 0018-0-02 x 0-011 mm. (as compared with 
0-016-0-017 X 0-010-0-0105 mm. for D. scombri). Embryos liberated 
from the eggs with a coronet of spinelets, apparently of two sizes, 
shorter and longer alternating. 



240 THE TREMATODA OF BRITISH FISHES 

Six other species of Didymozoon occur in Europe, but have not 
been found in Britain. D. pelamydis Taschenberg, 1879 (p. 612, PI. 
6, fig. 2) occurs between the lamellae of the gills of the pelamid in 
various parts of Italy (Naples, Genoa, Portoferrajo) and near Algiers. 
According to the original description, it is very elongate, but not 
particularly narrow, the region in front of the " neck " being spoon-like. 
The length is about 30 mm. Dollfus (1935, pp. 224-36, figs. 14-19) 
described the specimens found near Algiers and summed up the 
differences between this species and D. scombri, notably the very long 
oesophagus extending throughout the neck region, the union posteriorly 
of the long crura of the intestine, the existence of a solitary testis, 
which may disappear or fail to develop in one member of the encysted 
pair, and the position of the genital pore behind the oral sucker. 

Less is known about other species. D. sphyrcence Taschenberg, 
1879 (6, p. 612) was found beneath the mucous membrane of the buccal 
cavity in Sphyrcena vulgaris in Italy (Naples, Genoa, Portoferrajo) 
and Sicily (Catania). The original diagnosis indicated a worm 15 mm. 
long and 1-5 mm. broad, the body thus being short and compact, and 
having a rounded posterior extremity, a well-marked " neck " and 
an only slightly broadened region anterior to it. D. auxis Taschen- 
berg, 1879 (6, p. 613, PI. 6, figs. 1, 3), was found on the outer surface of 
the gill-lamellse in the plain bonito at Naples and is 12 mm. long, the 
body elongate and narrow and bent in a right angle, sometimes having 
curved lateral margins. D. tcenioides Monticelli, 1888 (p. 93) was 
found in the muscles of a sun-fish at Naples and Trieste, and off the 
coast of Belgium, but no original diagnosis was given, and the only 
characters mentioned were the ribbon-like body and the position of 
the genital pore in front of the pharynx. Maclaren (1904, p. 613) 
referred the worm provisionally to Nematobothrium. D. tenuicolle 
(Rudolphi, 1819) (Monostoma tenuicolle Rudolphi, 1819 ; pp. 85, 
346, PI. 2, figs. 1-4) was found on the gills and muscles of the opah in 
the North Sea and Sweden, and seems to have a characteristic shape, 
the " neck " being ill -defined and the posterior region somewhat 
flattened. D. pretiosum Ariola, 1902 (pp. 107-8, fig. 11) was found on 
the gills of the tunny at Naples, and has a characteristic swelling at 
the junction of the anterior and posterior regions. 

Genus NEMATOBOTHRIUM Beneden, 1858. 

Four species of this genus have been found in European waters 

and only one of them has been described adequately. None of them 

has been found in Britain, so that a few general details will suffice, 

although the species found at Roscoff can be treated more extensively. 

Nematobothrium molae Maclaren, 1904. 

This species was found on the gills of the sun-fish at Naples, and 
occurs at Roscoff and near Algiers. It has been described in some 
detail by Maclaren (1904, pp. 602-13, PI. 21, figs. 17, 19, 21 ; PI. 22, 
figs. 23-33) . Cysts : the largest 4-5 mm. long containing two inextricably 
intertwined worms, forming a U-shaped mass which, when straightened 



DIDYMOZOIDiE 241 

out, was 7 mm. long, one end of the mass containing the anterior 
ends of the worms and thicker than the other. Trematode. — Size : 
length after fixation and maceration in 30% alcohol estimated to be 
1-1-5 metres. Shape : anterior end narrow and pen-like, 0067 mm. 
diameter at the level of the pharynx. Suckers : oral absent, ventral 
very small and situated about 1 mm. behind the mouth, its diameter 
01 mm. when contracted. Gut : pharynx pyriform and 0-055 mm. 
long. (Esophagus short, bifurcation of the intestine just in front of the 
ventral sucker. Caeca relatively short, terminating just behind the 
commencement of the vas deferens. Excretory system : median canal 
very long, meeting the lateral canals near the ventral sucker. Repro- 
ductive systems : genital pores separate, the female pore slightly 
behind the male pore and just behind the mouth. Gonads tubular 
and continuous with their ducts, extending throughout the length of 
the body. Vitellaria thread-like. Uterus capacious, its fold filling 
the main part of the posterior region. Eggs devoid of filaments ; 
dimensions about 002 x 0015 mm. Dollfus (1935, p. 237) examined 
four cysts found on the same species of host near Algiers, and gave the 
dimensions as 20-25 x 3-5 mm. Unfortunately he was only 
able to extricate fragments of the worms, but he was able to show 
that the eggs vary very much in size as compared with those taken 
from specimens found at Roscoff ; the dimensions of the former were 
0-0175-0-018 x 0-012-0-0125 mm., those of the latter 00155-00195 x 
00113-00112 mm. 

The other species were found on different hosts in different localities. 
N. filarina Beneden, 1858 (pp. 108-11, PL 13, figs. 1-12), was found 
on the gills and in the gill- chamber of the shadow-fish on the coasts of 
France and Belgium. The worms occur encysted in pairs, and Beneden 
likened their appearance to that of a large Gordius, and found no trace 
of suckers. He thought the lack of an intestine to be due to the 
development of the reproductive organs. N. benedeni (Monticelli, 
1893) Maclaren, 1904 (Didymozoon benedeni Monticelli, 1893 (a, p. 137, 
footnote)), was found on the gills of the sun-fish at Naples. When 
Maclaren showed his specimens of N. molce to Monticelli, thinking they 
belonged to N. benedeni, he was informed that they belonged to a 
distinct species. Ishii (1935, p. 298) suggested that N. benedeni is a 
synonym of N. molce ! Undoubtedly they are very closely similar. The 
fourth species, N. guernei Moniez, 1891 (pp. 184-7), was found in the gills 
muscles and intestine of the albacore in Gascony. This species seems 
to be distinguished by its existence in an unencysted condition. 
Maclaren (1904, p. 613, footnote) was doubtful about its position in 
this genus, its author having observed that it is not significantly 
different from Didymozoon, but has no ventral sucker. 

Genus DIDYM0CYSTIS Ariola, 1902. 

Didymostoma Ariola, 1902.) 

Two species of this genus occur in Europe, but not in Britain. D. 
wedli Ariola, 1902 (pp. 105-7, figs. 7-10), has been found in the gills 

16 



242 THE TREMATODA OF BRITISH FISHES 

of the tunny at Nice, Naples and Genoa, near Algiers and in Japan, 
and was described in some detail by Yamaguti (1934, pp. 514-7, figs. 
134-5). The shape is distinctive, the slender anterior region pro- 
jecting from one end of the swollen posterior region, which is comma- 
like, relatively slender and of somewhat beaded appearance. Dollfus 
(1935) surveyed the sizes of the eggs as determined by himself and 
several other writers, giving the range 01 5-0 01 85 x 0-007-0-015 
mm. The other species, D. ihynni Taschenberg, 1879 (p. 612), has 
been found on the gills or the operculum of the tunny at Nice, Naples, 
Trieste, Genoa and Syracuse, and is very similar to the first, the slender 
anterior region projecting from one end of the somewhat reniform 
posterior region. The two species were made by Ariola for the third 
and second forms of Monostoma bipartitum Wedl of Wagener, 1858 
(PI. 9, figs. 15-18 ; PL 9, fig. 2), the first under its present name 
(Ariola, 1902, pp. 105-7, figs. 7-10) and the second as Didymocystis 
reniformis Ariola, 1902 (pp. 101-3, figs. 1-3). 

Genus K0LLIKERIA Cobbold, 1860. 
Kbllikeria filicollis (Rudolphi, 1819) Cobbold, 1860. 

Monostoma filicolle Rudolphi, 1819 (pp. 85-6,247-8); Dist. okenii Kolliker, 
1846 ; D. filicolle (Rudolphi) Beneden, 1858 (pp. 104-7, PI. 10, figs. 1-10) ; 
Kbllikeria okenii (Kolliker) of Ariola, 1906, and of Parona, 1912; Kblli- 
keria (Kbllikerozoum) filicollis of Ishii, 1935 (p. 303). 

Host : Ray's bream. 

Location : gill-arches, gill-rakers, buccal cavity and other situations. 

Johnstone (1911, pp. 35-6, fig. 5) obtained three cysts containing 
this species taken from the first specimen of Ray's bream to be found 
in the Irish Sea. They were 12-25 mm. diameter, and the largest 
contained more than one pair of worms. The description is very 
brief, and the figure indicates one of the females dissected out of the 
cyst. The anterior end of the body is filiform, but the posterior region 
is enormously enlarged and reniform. Males inhabit the same cyst, 
and are filiform and 5-15 mm. long. They also occurred attached to 
the branchial arch between the cysts. 

Genus WEDLIA Cobbold, 1860. 

The only European species of this genus, W. bipartita (Wedl, 1855) 
Cobbold, 1860, has been found on the gill, gill-arch and the skin of the 
head of the tunny and Seriola dumerili at Naples, Trieste, Toscano 
and Nice. It is distinguished by the presence of a pharynx and the 
light attachment between individuals of the two sexes. It was 
described as Monostoma by Wedl, 1855 (pp. 378-80, PI. la, figs. 11-13), 
and as Didymostoma by Ariola, 1902 (pp. 103-5, figs. 4-6). 

Family ZOOGONID^E Odhner, 1911. 

Size and shape : small and frail, oval or elongate, slightly flat. 
Cuticle spinous. Suckers relatively large and at least one -third of the 



zoogonid^ 243 

length of the body apart. Gut : prepharynx short or absent. Pharynx 
and short oesophagus present. Cseca generally very short, rarely 
extending behind the middle of the body. Excretory system : vesicle 
sac-like. Reproductive systems : genital pore near the left margin 
of the body, slightly ventral or dorsal, between the levels of the 
ventral sucker and the bifurcation of the gut. Cirrhus -pouch elongate, 
generally club-shaped, extending medianwards and posteriorly. Pars 
prostatica well developed. Testes globular, widely separated in the 
same transverse plane, generally posterior to the ventral sucker, 
sometimes near its hinder margin. Ovary globular, median, behind 
and between the testes. Laurer's canal and receptaculum seminis 
present, the latter large. Uterus having descending and ascending 
limbs, its folds tending to fill the posterior region of the body. Vitel- 
laria sometimes coarsely follicular, generally small, compact and 
rounded, sometimes forming a single mass. Eggs very variable in 
size (0035-0090 mm. long), thin-shelled, containing developing 
miracidia when laid. Location and hosts mainly in the hind-gut, 
rarely the bladder, of marine fishes. The two sub-families can be 
separated by differences in the vitellaria, which are small and compact 
in Zoogoninae, but family well developed and follicular in Lecitho- 
s'taphylinse. 

Sub-family Zoogonin^: Odhner, 1911. 
In one genus of this group the vitellaria are evidently paired. This 
is the genus Diphterostomum Stossich, 1904, which has three species 
in Europe, but has not appeared in Britain, though it may confidently 
be expected to appear here. Of three genera which have unpaired 
vitellaria, Zoogonus can be recognized by the fact that the bifur- 
cation of the gut is posterior to the ventral sucker, Zoogonoides and 
Zoonogenus by the presence or absence of needle-like sjjinelets on the 
cirrus. 

Genus DIPHTEROSTOMUM Stossich, 1904. 
According to Odhner (1911, vol. 37, p. 241) the main characters 
of this genus are the plump form, the large and transversely elongate 
ventral sucker situated at or behind the middle of the body, the fairly 
long oesophagus and short and sac-like caeca, which are confined to the 
region anterior to the large sucker, the very small excretory vesicle 
and certain characters of the genital system, notably the hour-glass- 
shaped seminal vesicle, the two compact vitellaria and the very 
thin-shelled eggs. 

Diphterostomum brusinse (Stossich, 1889) Stafford, 1905. 

(Fig. 42 H.) 
Distomum brusince (Stossich, 1889 (pp. 25-6, PL 14, fig. 60), and of Looss, 
1901 ; Pleurogenej brusince of Stossich, 1899 (p. 10) ; Brachyccecum brusince 
(Stossich) Barbagallo & Drago, 1903 (p. 410). 

This species occurs in various Labridse, notably the gilthead, and 
in the butterfly blenny at Trieste. It was described by Looss (1901a, 



244 THE TREMATODA OF BRITISH FISHES 

p. 399, fig. 1), and Odhner (1911, vol. 37, p. 241) gave a clear diagnosis, 
which I have given already in another place (Dawes, 1946, p. 247), 
mentioning that Palombi (19296 ; 1930a) has investigated the life- 
history. 

Diphterostomum betencourti (Monticelli, 1893) Odhner, 1911. 

Distomum betencourti Monticelli, 1893 (pp. 190-3, PL 8, fig. 121) ; D. lutea 
Beneden, 1870, nee Baer, 1826 of Monticelli, 1890 ; Pleurogenes betencourti 
of Stossich, 1899 (p. 10). 

This species has been found in the nurse hound at Wimereux, in 
the rough hound off the Belgian coast, and in both these hosts at 
Boulogne. The first description was by Monticelli (1890a, p. 424, 
PI. 22, figs. 21-7), and Odhner (1911, p. 241), gave the characters by 
which it can be distinguished from the previous species (see Dawes, 
1946, p. 247). 

Diphterostomum sargus annularis Vlasenko, 1931. 

This species was found in the host after which it was named, in 
the Black Sea. 



Genus Z00G0N0IDES Odhner, 1902, 

According to Odhner (1911, vol. 37, p. 243) the main characters 
of this genus are the slender form, the short gut — which barely extends 
to the small, centrally-situated ventral sucker — the small and sac-like 
excretory vesicle and certain features of the genital system, notably 
the short cirrus, which occupies about one-third of the length of the 
cirrus pouch and is equipped with needle-like spinelets, the bulb-like 
or cylindrical pars prostatica, the hour-glass-shaped seminal vesicle, 
and the thin-shelled eggs. 

Zoogonoides viviparus (Olsson, 1868) Odhner, 1902 (pp. 62-3, Fig. 2). 

(Fig. 42 A, B.) 

Distomum viviparvm Olsson, 1868 (pp. 28-9, PI. 4, figs. 73-5) ; Zoogonus 
viviparus (Olsson) of Looss, 1901 (p. 439) ; Zoogonoides subcequiporus 
Odhner, 1911. 

Hosts : in Britain, John Dory, dragonet, gattorugme, butterfty 
blenny, wolf-fish, turbot, witch, dab, lemon sole, sole, plaice, thick- 
back sole, long rough dab. 

Location : ower intestine, particularly the rectum. 

This trematode was discovered by Olsson as a parasite of the lemon 
sole. It has been found in many localities in Britain. Nicoll (1907) 
recorded it in the dab, plaice and turbot, and later (19096) in the wolf- 
fish at St. Andrews. Lebour (1908a) found it commonly in the dab, 
long rough dab and plaice at Cullercoats, Johnstone (1909) in the 
plaice at Liverpool. Nicoll (1914) recorded its occurrence in the dab, 



ZOOGONID^ 



245 



plaice, sole, thickback sole, lemon sole, John Dory, gattorugine, butter- 
fly blenny and dragonet at Plymouth and (1915) in the witch, dab, 




Fig. 42. — A and B, Zoogonoides viviparus. C, Zoonogenus vividus. D, 
Zoogonus minis. E, Zoogonus rubellus. F, Deretrema abyssorum. G, 
Lepidophyllum steenstrupi. H, Diphterostomum brusince. A, after 
Lebour, i908 ; B, after Odhner, 1902 ; C, after Nicoll, 1912 ; D, after 
Goldschmidt, 1902 ; E and G, after Odhner, 1902 ; H, after Looss, 
1901a ; F, after Odhner, 1911.) 



plaice and long rough dab at Aberdeen, and the dab, lemon sole and 
plaice at Millport. Little (1929a) has recorded it in the plaice at 
Galway, Baylis & Idris Jones (1933) in the plaice, lemon sole and 
dragonet at Plymouth. I have found dozens of specimens in the 



246 THE TREMATODA OF BRITISH FISHES 

plaice at Plymouth ni} T self. It is common hi Pleuronectidse, but 
does not seem to have been found in the halibut and the flounder, and 
in Soleida?, but Nicoll (1914) regarded the dragonet as one of the 
principal hosts, and noted that it does not occur in gadoid fishes and 

Nicoll (1907, p. 83, PI. 2, fig. 8 ; PL 3, fig. 9) described specimens 
found at St. Andrews. Size : 0-8-1-6 mm. long and 0-31-0-42 mm. 
in greatest breadth. Cuticle : spinous, the spines arranged in a 
regular diamond pattern, covering all except a small region near the 
posterior extremity. Suckers : ventral larger than the oral, but 
never twice as large, as suggested by Odhner (1905) ; oral 0-14-0-16 
mm. diameter. Gut : caeca not extending behind the ventral sucker. 
Reproductive systems : genital pore lateral. Testes ovoid and situated 
postero-lateral to the ventral sucker, but subject to backward and 
forward movements in the living worm. Ovary almost median, but 
sometimes on the right behind and between the testes. Eggs large, 
measuring 0-086-0-094 x 0-042-0-044 mm., each when laid containing 
a miracidium. 

Lebour (1908a, pp. 33-4, PL 4, fig. 1) described specimens found 
at Culler coats, and found the ventral sucker to be twice as large as 
the oral. Size: 1-1 mm. long and 0-4 mm. in greatest breadth. Colour: 
when living, bright red, quickly losing this colour after death. Shape : 
outline oval, somewhat pointed at the extremities. Cuticle : spinous. 
Suckers : diameters 0-24 and 012 mm. Gut : prepharynx very short. 
Pharynx 0-05 mm. long. (Esophagus about twice this length. Caeca 
extending only to a level dorsal to the middle of the ventral sucker, 
Excretory system : vesicle small and oval. Reproductive systems : 
genital pore situated on the left of the bifurcation of the gut (see her 
fig. 1,P1. 4). Genital atrium small. Cirrus-pouch sickle-shaped, cirrus 
armed with spinelets and frequently protruding from the genital pore. 
Pars prostatica well developed. Seminal vesicle bilobed. Vasa deferentia 
.separate and distinct. Testes ovoid, 0-01 mm. broad and situated 
at the sides of the ventral sucker, sometimes extending behind it. 
Ovary almost spherical and 0-01 mm. diameter, situated behind the 
testes and on the right, the receptaculum behind it. Laurer's canal 
present. Vitellaria forming a compact globular mass of follicles on 
the left of the ovary. Uterus having long and winding limbs. Eggs 
thin-shelled and 007-008 mm. long, containing active miracidia. 
Johnstone's specimens from the Irish Sea (1909, pp. 89-90) were only 
slightly smaller (1-03 X 0-33 mm.) and had suckers measuring 0-19 
and 0-12 mm. diameter, the ventral thus being little more than half 
as large again as the oral. 

Finding that five specimens obtained from the wolf-fish in Norway 
had a relatively small ventral sucker, Odhner (1911, vol. 37, p. 244) 
erected for them a new species, Z. subcequiporus. In other specimens 
0-4-0-9 mm. long and 0-25 mm. broad, the suckers measured 17- 
0-21 mm. and 0-11-0-14 mm., causing Odhner to modify his previous 
conception of their relative sizes and submit that the size -ratio is 
3/2. His whole mounts of "Z. subcequiporus " merely extended the 



ZOOGONIDJE 247 

range of size, for the ventral measured 0-17 mm. and the oral 014- 
0-15 mm., i.e. did not differ significantly in this respect from undoubted 
specimens of Z. viviparus. Having plenty of specimens, I selected 
ten at random and measured the length and breadth and the diameters 
of the suckers. In this sample the range of length and breadth of the 
body was 0-6-1-2 mm. and 0-27-0-42 mm. respectively, and the range 
of the diameters of the suckers 0-17-0-22 mm. and 0- 095-0 145 mm., 
the extremes of which give the ratios (ventral /oral) 1-5-1-8. But the 
ratios varied more widely in individual specimens and, arranged in the 
order of ascending body-length, are : 1-5, 1-9, 1-5, 1-6, 2-0, 1-5, 1-6, 1-7, 
1-5 and 1-5. From this it would seem reasonable to suppose that the 
ventral sucker of Z. viviparus may be " twice as large " as the oral, 
or only " half as large again " in specimens of medium to fairly large 
size. The sizes of Odhner's specimens of "Z. subozquiporus " were not 
stated, and in " unpressed " and " pressed " preparations the ratio of 
sizes of the ventral and oral suckers was about 1-2, i.e. relatively 
low. But even so, this character alone is insufficient to provide a 
reliable basis for a new species, and Z. subcequiporus must be included 
among the synonyms of Z. viviparus. 



Genus Z00G0NUS Looss, 1901. 

This genus was erected for Z. mirus, but no diagnosis was given. 
According to Odhner (1911, vol. 37, p. 244) the shape of the body and 
of the excretory vesicle is the same as in Zoogonoides, the main differ- 
ences from which are a longer gut, with short sac-like caeca which 
arise slightly behind the ventral sucker and features of the genital 
system, notably the ventro- lateral genital pore, the non-spinous cirrus, 
the unequally bipartite seminal vesicle, the posterior chamber of which 
is the larger and is sometimes slightly folded, and the slightly larger 
eggs, which display about the same degree of encapsulation as in 
Zoogonoides. 

Zoogonus mirus Looss, 1901. (Fig. 42 D.) 

As described by Looss (1901a, pp. 439-42, fig. 6) this seems to be a 
rather unusual trematode from Labrus merula at Trieste and Rovigno, 
the description differing from that of what seem to have been more 
typical specimens from the same host by Goldschmidt (1902, pp. 870- 
6, figs. 1-6). According to Odhner (1911, vol. 37, p. 244) the length 
and breadth of the body are never greater than 0-6 X 0-18-0-2 mm. 
and the suckers are of nearly equal sizes, the oral 0-08-0-09 mm. 
diameter, its cavity triangular, the ventral 0-09-0-11 mm. diameter 
and situated at the beginning of the second third of the body. The 
pharynx is smaller than either of the suckers (006-007 mm. diameter). 
(According to Goldschmidt, but not Looss, the caeca are small and 
almost spherical.) The cirrus pouch is diagonally arranged, and only 
slightly oversteps the median plane. The miracidia are of larger 
size relative to the eggs than in the northern species, Z. rubellus (and 



248 THE TREMATOBA OF BRITISH FISHES 

measure 0075-0085 x 0-04 mm. according to Looss). This species 
has never been found in Britain. 



Zoogonus rubellus (Olsson, 1868) Odhner, 1902 (pp. 59-61, Fig. 1). 

(Fig. 42 E.) 
Distoma rubellum Olsson, 1868 (p. 40, PL 4, fig. 89). 

Hosts : adults in the wolf-fish ; juveniles in the cuckoo wrasse and 
dab. 

Location : adults in the intestine and rectum ; juveniles in the 
intestine. 

This species was found in the ballan wrasse in West Sweden. 
Nicoll (19096, p. 17, PL 1, fig. 4) described specimens found at St. 
Andrews, some in every wolf-fish examined, and Baylis & Idris 
Jones (1933) recorded the occurrence of juveniles in the cuckoo wrasse 
and the dab at Plymouth. According to Odhner (1911, vol. 37, p. 
245) this is similar to the Mediterranean species, but can be distin- 
guished from it readily when the two are seen side by side, particularly 
by the relatively smaller pharynx (diameter 0-08-0-085 mm.) and 
miracidia 0-1 mm. long. His specimens were 0-9-1-2 mm. long and 
0-25 mm. broad, the oral and ventral suckers 0-1-0-12 and 0-13-0-14 
mm. diameter. Nicoll dealt with somewhat smaller specimens. Size : 
0-75-1-0 mm. long and about one-half as broad. Colour : pale yellow. 
Shape : outline elongate oval, greatest breadth at the level of the 
ventral sucker, resembling Zoogonoides viviparus, but of less delicate 
appearance. Cuticle : entirely covered with minute scale-like spines 
regularly arranged. Suckers : oral not quite terminal, globular and 
1 15-0- 135 mm. diameter; ventral flattened and somewhat larger 
(0-135-0 165 mm. diameter), and situated two-fifths of the distance 
along the body. Gut : prepharynx not generally dilated and shorter 
than the pharynx, which measures 0-10-0-13 X 008-0-09 mm. 
(Esophagus long and terminating behind the ventral sucker. Caeca 
saccular (as indicated in Olsson's figure), not elongate. Reproductive 
systems : testes large and globular, symmetrical and lateral to the 
posterior border of the ventral sucker. Ovary globular, and situated 
in the median plane between the caeca. Vitellaria minute, and situated 
just in front of the ovary. Receptaculum seminis large and on the right 
of the ovary. Genital pore situated on the left margin of the body 
at the level of the opening of the ventral sucker. Cirrus-pouch large, 
and extending medio-posteriorty to a level slightly behind this sucker. 
Seminal vesicle bipartite, the posterior chamber the larger. Pars 
prostatica and ejaculatory duct small. Uterus mainly confined to the 
space behind the caeca, containing miracidia in all stages of development. 

Unlike Odhner, Nicoll inclined strongly to the opinion that Z. 
mirus Looss, 1901, and of Goldschmidt, 1902, is identical with Z. 
rubellus, and I am disposed to agree with him. It is true to say that 
the differences between specimens of the latter species as described 
by Looss and by Goldschmidt outweigh those existing between some 



ZOOGONIDiE 249 

specimens of this species and Z. rubellus, and Odhner gave no good 
reasons for the maintenance of the two species. But the problem 
cannot be solved until development has been studied thoroughly. 
The cercaria which Leidy (1891) described as Distomum lasium and 
which develops in Nassa obsoleta on the Atlantic coast of N. America 
and encysts in polychaete worms, particularly Nereis virens, later 
becoming mature in eels and toadfish, is, according to Stunkard (1938), 
a species of Zoogonus which is identical with both Z. rubellus and Z. 
mirus. Studying larvae at Wimereux afterwards, Stunkard (1940, 
1941) got results which led him to believe that the American specimens 
probably belong to a separate species, Z. lasius (Leidy, 1891) Stunkard, 
1940, but he stressed the fact that it is impossible to decide from 
existing descriptions of adults whether or not European forms should 
be regarded as identical. 

Genus Z00N0GENUS Nicoll, 1912. 

According to Nicoll (1912, p. 202) this genus closely resembles 
Zoogo?ioides, but differs in having an unarmed cirrus, a highly developed 
metraterm and much smaller eggs. 

Zoonogenus vividus Nicoll, 1912. (Fig. 42 C.) 

Host : common sea bream. 
Location : rectum. 

In decribing this trematode, Nicoll (1912, pp. 200-2, PL 9, fig. 2) 
mentioned having found it in 2 out of 11 fishes at Aberdeen and in 5 
out of 8 fishes at Plymouth, but not in any of 6 fishes obtained from 
Billingsgate Market. All the hosts had been dead for some time and 
the parasites " were usually in a more or less macerated condition," 
being particular^ delicate. The trematode has not been identified 
since this time. Size : average specimen 1-4 mm. long and 0-46 mm. 
broad. Colour vivid blood-red in blotches. Shape : outline oval and 
not very flattened, broadest behind the middle of the body. Cuticle 
spinous only in the anterior region, the spines minute. Suckers : 
ventral much larger than the oral and situated behind the middle of 
the body and 0-9 mm. from the anterior extremity; diameters 0-34 
mm. and 0-16 mm. Gut : prepharynx absent. Pharynx 0-07 mm. 
diameter. (Esophagus somewhat shorter than the pharynx. Caeca narrow 
and short, terminating some distance in front of the ventral sucker. 
Excretory system : vesicle sac-like, and filled with yellowish-green or 
brown concretions of irregular shape. Reproductive systems : genital 
pore decidedly lateral, situated on the ventral surface near the termi- 
nation of the left caecum. Cirrus pouch strongly curved and situated 
entirely in front of the ventral sucker. Cirrus devoid of hooklets. Pars 
prostatica bulbous and 008 mm. diameter. Seminal vesicle having a 
larger posterior chamber and a smaller anterior chamber, the former 
measuring 0-1 X 0-07 mm., the latter 008 mm. diameter. Testes 
ovoid and situated dorsal to the posterior quadrant of the ventral 



250 THE TREMATODA OF BRITISH FISHES 

sucker ; dimensions 0-25 x 012 mm. Ovary globular and 0-09 mm. 
diameter, situated a short distance in front of or behind the testes. 
Receptaculum seminis small and situated lateral or dorsal to the 
ovary. Laurer's canal short. Vitellaria forming a small compact 
group of follicles on the right of the ovary or farther back. Uterus 
having limbs much folded behind the ventral sucker, one fold some- 
times occurring on its right side. Metraterm very muscular and 
inflated, situated behind the cirrus-pouch, but in front of the ventral 
sucker. Eggs very variable in size during passage through the uterus, 
measuring about 0-016 x 0012 mm. in the proximal and 0-036 x 
18 mm. in the distal part, but still less than half as large as the 
eggs of Zoogonoides viviparus. 

Sub-family Lecithostaphylinje Odhner, 1911. 

Three genera belonging to this group occur on the Continent, but 
none has appeared in Britain, so that we need not consider them in 
detail. For a key with which to separate them see Dawes (1946, p. 
250). The genus Lecithostaphylus Odhner, 1911, has a species, L. 
retroflexus (Molin, 1859), which was found commonly in the gut of 
Belone acus at Trieste and Palermo, was described briefly by Odhner 
(1911, vol. 38, pp. 115-16, fig. 8) and is shown in fig. 36 E. the genus 
Deretrema Linton, 1910 {Proctophantastes Odhner, 1911) has a species, 
D. abyssorum (Odhner, 1911) Price, 1934, which occurs in the rectum 
of Coryphcenoides rupestris and the haddock in Norway, and was 
described by Odhner (1911, vol. 37, p. 238, fig. 1) ; it is shown in 
my Fig. 42 F. The genus Lepidophyllum Odhner, 1902, has a species, 
L. steenstrupi Odhner, 1902, which inhabits the excretory bladder of 
the wolf-fish in Denmark (found in the Copenhagen collection bj^ 
Odhner), Norway and Sweden, and of Anarrhichas pantherinus in 
Iceland. This species (see my Fig. 42 G) was briefly described by 
Odhner (1902, pp. 68-9, fig. 3 ; 1911, vol. 37, p. 240) and by Stafford 
(1904, p. 487) and Cooper (1916), who examined specimens found in 
Zoarces anguillaris in Canada. The diagnostic characters of these 
three species have alreadv been given bv me in another place (Dawes, 
1946, pp. 250-1). 

Family HAPLOPORIDiE Nicoll, 1915. 
(Haploporinae Looss, 1902). 

Size and shape : small or very small, oval or elongate, having 
a tapering anterior and a rounded posterior end. Cuticle spinous, the 
spines especially abundant anteriorly. Suckers powerful, the ventral 
situated partially or wholly in the anterior half of the body. Gut : 
prepharynx present. Pharynx variable (elongate, spherical or pyriform) . 
(Esophagus long. Caeca fairly short or very short, tubular or oviform. 
Excretory system : vesicle sac-like. Reproductive systems : genital 
pore median and situated in front of the ventral sucker. Genital 
atrium tubular and muscular, forming a sinus having a sinus-sac, 



HAPLOPORIDJE 251 

sometimes larger than the ventral sucker and generally overlying it. 
Vesicula seminales interna and externa present. Testis globular, 
slightly lateral. Ovary globular, generally at the same transverse 
level as the testis, but on the opposite side, sometimes in front of it. 
Receptaculum seminis absent. Laurer's canal present. Vitellaria 
feebly developed, sometimes two small spherical masses or irregular 
clusters, median to the caeca and close together, or lateral to the 
caeca and widely separated, sometimes a single, trifoliate cluster ol 
small follicles ; generally situated between the caeca and the dorsal 
surface of the body. Uterus having descending and ascending limbs, 
sometimes widely separated and lateral, tending to fill the posterior 
region. Eggs small and few, or in fairly large numbers, but never 
numerous, generally containing miracidia with conspicuous eye-spots, 
sometimes having gelatinous envelopes. 

Genus HAPLOPORUS Looss, 1902. 

The principal characters of this genus are the compact and spherical 
paired vitellaria, situated just beneath the dorsal surface and between 
the caeca, which are short and wide and extend only slightly posteriorly 
to the ventral sucker, and the lateral testis. 

Haploporus benedenii (Stossich, 1887) Looss, 1902. (Fig. 43 A-D.) 

Distomum benedenii Stossich, 1887 (p. 95, PI. 10, fig. 39) ; Haploporus 
lateralis Looss, 1902 (c, pp. 138-9, figs. 7-8). 

Host : thick-lipped grey mullet. 
Location : intestine. 

Nicoll (1914, p. 484) obtained a few specimens of this species at 
Plymouth, but did not describe them. According to Looss (1902c, 
pp. 136-8, figs. 5, 6) and with data concerning "H. lateralis " (pp. 
138-9, figs. 7-8) shown in parentheses: — Size: 1 -25-2 53 mm. long 
and 0-53-0-6 mm. broad, but according to Stossich 0-75-1 mm. broad 
when contracted (0-8-0-95 mm. long, 0-38 mm. in greatest breadth 
and 0-27 mm. thick in the hind- body, but behind the uterus only half 
as thick). Suckers: ventral smaller than the oral; diameters 0-19 
and 0-25 mm. (slightly larger than the oral; diameters 0-12 and 0112 
mm.). Gut : pharynx spherical and 0-12 mm. diameter (0068 mm.). 
(Esophagus long, terminating dorsal to the ventral sucker (the same). 
Caeca extending to the level of the testis (to near the middle level of 
this gonad). Excretory system : vesicle large and roomy, shown as 
bicornuate (shown extended and not bicornuate, perhaps merely 
indicating greater attenuation of the body). Reproductive systems : 
" sinus sac " very large, but not reaching the posterior border of the 
ventral sucker (the same, overlying the ventral sucker to near its 
hinder border). Testis large, globular, and situated on the right (very 
lateral, at the same level as the ovary). Ovary small, situated just 
behind and above the ventral sucker. Vitellaria small and almost 
spherical, located on either side of the ovary between the caeca, but 



252 



THE TREMATODA OF BRITISH FISHES 



dorsal to both these (having slight bays in their margins). Eggs 
measuring 0045-0053 X 0030-0034 mm. (0042-0045 x 0023- 
026 mm., a gelatinous envelope not observed with certainty (having 
a gelatinous envelope). Miracidia having a relatively small, X-shaped 




Fi<:. 4.'}. — A and 13, Haploporus benedenii. C and D, "H. lateralis." E and 
F, Saccocoelium obesum. G, Lecithobotrys putrescens. H, Dicrogaster 
perpusilla (contracta). (A, D, F in side view, E in dorsal, the rest in 
ventral view.) (After Looss, 1902c.) 



eye-spot (devoid of eye-spots). "H. lateralis " probably represents 
small specimens of H. benedenii containing imperfectly developed 
embryos, the lack of e3 f e-spots being inexplicable otherwise. Other 
differences which it shows from H. benedenii concern the degree of 
extension of the body and the state of development of the suckers, 
which in other instances are well known to reverse their relative sizes. 



haploporid^: 253 

Genus SACCOCCELIUM Looss, 1902. 

In this genus the compact, triangular vitellaria are widely separated 
and situated lateral to the caeca, which are short and broad oval in 
outline and sharply delimited from the bifurcation of the gut, and 
situated just underneath the dorsal surface of the body, entirely 
behind the level of the ventral sucker. 

Saccoccelium obesum Looss, 1902. (Fig. 43 E, F.) 
Saccoccelium tensum Looss, 1902 (c, pp. 141-2, figs. 12, 13). 

Host : thick-lipped grey mullet. 
Location : rectum (? intestine). 

Nicoll (1914, p. 484) found a few specimens in the intestine of this 
host at Plymouth, but did not describe them. Specimens attributed 
to this species by Looss (1902c, pp. 140-1, figs. 9-11) were obtained 
from this host and from the thin-lipped grey mullet and the golden 
grey mullet at Trieste. The data relating to " S. tensum " are shown 
in parentheses. Size : 0-6-0-8 mm. long, 0-33-0-37 mm. broad and 
about as thick (0-6 mm. long and 0-2 mm. broad and thick). Suckers : 
oral slightly smaller than the ventral; diameters 0-1-0-12 mm. (0-075 
and 0-095 mm.). Gut : pharynx large and elongate, measuring 0-11 X 
008 mm. (of the same shape, but relatively smaller, dimensions 0077 
X 0-051 mm.). Reproductive systems : " sinus sac " not appreciably 
larger than the ventral sucker, extending slightly behind it (large, 
greatly overlying the ventral sucker). Testis lateral (only slightly 
lateral). Ovary situated in front of the testis and slightly behind the 
ventral sucker. Eggs measuring 0-045 x 0-026 mm. (0045 x 0028 
mm.), provided with a gelatinous envelope, each containing a mira- 
cidium with eye-spots (the same). There is absolutely no doubt that 
" S. tensum " is a synonym of S. obesum. 

Genus LECITH0B0TRYS Looss, 1902. 

In this genus the body is elongate and the caeca long and tubular, 
the vitellaria comprising a small number of spherical follicles lateral 
to them. The species Leciihobotrys putrescens Looss, 1902, was found 
in the rectum of the golden grey mullet and described by Looss (1902c, 
pp. 135, 143, fig. 14). It has not appeared in Britain, but I have 
given a short diagnosis (Dawes, 1946, p. 228), and it is shown in Fig. 
43 G. 

Genus DICR0GASTER Looss, 1902. 

In this genus the vitellaria are so near together as to form a single 
group of three or four small follicles resembling a clover leaflet, and are 
situated behind the ends of the caeca in the dorsal region. The species 
D. perpusilla Looss, 1902 (syn. D. contracta Looss, 1902) was found in 
the rectum of the thick-lipped grey mullet and described by Looss 
(1902c, pp. 135-6, figs. 1, 2 ; "contracta," p. 136, figs. 3, 4). It has 



254 THE TREMATODA OF BRITISH FISHES 

not been found in Britain, but probably occurs here. I have given 
a short diagnosis (Dawes, 1946, p. 227), and it is shown in Fig. 43 H. 

Family FELLODISTOMATID^E Odhner, 1911, emend. Nicoll, 1935. 

Size and shape : small or fairly small, oval or elongate oval and 
slightly flattened. Cuticle spinous. Suckers fairly large and not 
widely separated. Gut : pharynx small. (Esophagus short. Caeca of 
medium length or fairly long. Excretory system : vesicle Y-shaped or 
V-shaped, the median stem long or short, the lateral canals long, 
extending to a level near the anterior extremity. Reproductive 
systems : genital pore median or slightly lateral, and situated between 
the ventral sucker and the bifurcation of the gut. Cirrus-pouch well 
developed, generally entirely in front of the ventral sucker. Pars 
prostatica short, wide and muscular. Seminal vesicle bipartite. Cirrus 
stout. Vesicula seminalis frequently containing spermatophores. 
Testes globular, one behind the other in the posterior region, or widely 
separated in the same transverse plane near the middle of the body. 
Ovary globular or slightly lobed, lateral and hi front of the testes. 
Receptaculum seminis absent, Laurer's canal present. Vitellaria 
lateral and follicular, generally situated in the middle one -third of the 
body, rarely approaching the posterior end. Uterus having much 
folded descending and ascending limbs, tending to fill the post-testi- 
cular region. Eggs very numerous, containing developing larvae when 
newly laid. 

The two sub-families are easily distinguished : In the Fellodis- 
tomatinae the body is oval in outline and the testes are side by side ; 
in the Haplocladinse the body is elongate and the testes are arranged 
one behind the other. For keys to the genera see Dawes (1946, pp. 
238, 244). 

Sub-family Fellodistomatin^e Nicoll, 1909, emend. 
Genus FELLODISTOMUM Stafford, 1904. 

This genus can be distinguished from the others of the sub-family 
by the position of the genital pore near the anterior margin of the 
ventral sucker. 

Fellodistomum fellis (Olsson, 1868) Nicoll, 1909. (Fig. 44 A.) 

Dixioma fellis Olsson, 1868 (pp. 44-6, PI. 5, fig. 94) ; Fellodistomum incisum 
(Rudolphi, 1809) of Stafford, 1904 (p. 486) ; F. agnotum Nicoll, 1909). 

Host : wolf -fish. 
Location : gall-bladder. 

Lebour (1908a) found this species in every specimen of the wolf- 
fish she examined at Culler coats. Nicoll also found the worm at 
St. Andrews and (1909a, pp. 458-69, PI. 9, figs. 13-14 [entire worm 
not figured]) discussed the taxonomy of the species and gave a detailed 
description of it. Size : mature specimens 2-5-3-3 mm. long and 



FELLODISTOMATID.E 



255 



about half as broad (1-1-1 -6 mm.), but very extensile and contractile, 
in extreme contraction becoming globular. Colour : yellow ring 
surrounding ventral sucker ; contents of caeca showing dark green, but 




Fig. 44. — A, Fellodistomum agnotum (= F. fellis). B, Bacciger bacciger. 
C, Steringophorus furciger. D, Steringotrema cluthense. E, S. pagelli. 
(A and D, after Nicoll, 1909a ; B and E, after Nicoll, 1914 ; C, after 
Lebour, 1908a.) 



both tints lost in preserved specimens. Suckers : oral globular and 
not quite terminal, diameter 040-0-45 mm. Ventral globular, deeply 
sunk into the body just behind its middle and about twice as large as 
the oral ; diameter 0-9-1-0 mm. Despite their great sizes, suckers not 
very muscular (histological structure described in detail on p. 461). 



256 THE TKEMATODA OF BRITISH FISHES 

Cuticle : covered with rod-like bodies measuring 004 x 0-001 mm., 
which stand up from the surface in a regular arrangement and trans- 
versely wrinkled anteriorly, but not spinous. Subcutaneous glands : 
cells large and numerous ventrally in the forebody and the anterior 
half of the hindbody, ovoid, measuring 045 x 003 mm. and having 
small eccentric nuclei and granular cytoplasm. Gut : prepharynx 
short and provided with circular and longitudinal muscles. Pharynx 
0- 16-0-21 mm. long. (Esophagus practically absent. Caeca wide and 
lined with cuticular membrane anteriorly, but having a cubical or 
columnar epithelium (with free pseudopodia ?) posteriorly. Excretory 
system : median excretory canal short, about 0-2 mm. long and half 
as wide, meeting the lateral canals opposite the anterior borders of the 
testes. Lateral canals extending to the pharynx, mainly beneath the 
caeca. Entire " vesicle " lined with epithelium. Reproductive systems : 
genital pore situated on a large and prominent papilla antero-lateral 
to the ventral sucker. Seminal vesicle bipartite, the posterior com- 
partment the smaller (dimensions 085 x 0-04-0-08 mm. and 085 x 
0-06-0-11 mm.), muscular and having an epithelial lining. Pars pro- 
statica very well developed, occupying most of the cirrus-pouch (018 
X 013 mm.), also muscular. Myoblasts occurring amidst the gland- 
cells. Cirrus short. Genital atrium small. Testes ovoid and symmetrical 
about the middle of the body. Ovary multilobate, immediately in 
front of the testes and behind the ventral sucker on the right. Vitel- 
laria limited in extent beside and slightly in front of the ventral sucker, 
the follicles few and of small size. Uterus having numerous folds above 
the ventral sucker, its first part serving as a receptaculum seminis 
uterinum, the metraterm straight. Eggs measuring about 0042 x 
0023 mm. 

Under the name Fellodistomum agnotum Mcoll (1909a, p. 469, PI. 10, 
fig. 15) described small specimens found in the gall-bladder and 
duodenum of wolf-fish at St. Andrews, along with F.fellis. The main 
diagnostic characters were stated to be a more elongate body, smaller 
and less prominent ventral sucker, anteriorly- situated vitellaria and 
a backwardly-projected uterus. The specimens were fewer than F . 
fellis in the proportion of 1 to 30. In spite of their small size, specimens 
more than 1-05 mm. long were mature, and this seems to have per- 
plexed Nicoll, who found the size of F. fellis at maturity to be 2-5 mm. 
Size : up to 3-3 mm. long and 0-87 mm. broad, sometimes broader, 
but the breadth rarely more than one -third of the length. Shape : 
tapering towards the extremities. Suckers in a specimen 3 mm. long ; 
oral 0-34 mm. diameter, ventral 0-51 mm. ; ratio of the diameters con- 
stantly 2/3 as against 1/2 for F. fellis ; ventral slightly in front of the 
midbody. Gut : pharynx 0-15 mm. long and 012 mm. broad and 
thick. Reproductive systems : as in F. fellis, but testes situated in 
front of the middle of the hindbody. Vitellaria extending from the 
ventral sucker to the pharynx, broader and more compact. Uterus 
having a few loops in front of the testes and limbs extending almost 
to the posterior extremity and very little folded. Eggs somewhat 
larger, measuring about 048 x 024 mm. Despite these differences 



FELLODISTOMATID.JE 257 

it is very difficult to conceive of the existence of two distinct species 
of such rarity and precise host-specificity. Miller (1941) separated 
two mature and one immature specimen of F. agnotum from a single 
immature specimen of F. fellis found in the same location, the gall- 
bladder. This is very unconvincing, and it is certainly better to regard 
Fellodistomum fellis, which has been found in Italy, Sweden and Canada, 
as well as in Britain, as a rather variable species with which F. agnotum 
is identical. 

Genus STERINGOPHORUS Odhner, 1905. 

(Leioderma Stafford, 1904, nee Willemoes-Suhm, 1873.) 

Stafford erected the genus Leioderma for Distomum furcigerum 
Olsson, but this name was preoccupied. Nicoll (1909a, p. 475) empha- 
sized the difficulties of distinguishing Steringophorus from Fellodis- 
tomum, but gave four characters by which this is possible — the presence 
of a distinct oesophagus, the absence of a protruding genital papilla, 
the position of the genital pore near the bifurcation of the gut (and 
thus far in front of the ventral sucker), and the presence of a true 
receptaculum seminis, the last point being proved by Lebour (1908a), 
contrary to the belief of Odhner. To distinguish the genus from other 
genera allied to it, we might add the characters of a globular or ovoid 
cirrus- pouch and vitellaria almost entirely confined to the region behind 
the ventral sucker, which is not situated behind the middle of the body. 

Steringophorus furciger (Olsson, 1868) Odhner, 1905. (Fig. 44 C.) 

Distoma furcigerum Olsson, 1868 (p. 26, Pi. 4, fig. 72) ; Leioderma furcigerum 
(Olsson) Stafford, 1904 (p. 486). 

Hosts : angler, long rough dab, plaice, dab, lemon sole, witch. 
Location : stomach and intestine. 

This trematode is widely distributed, occurring in Britain, Sweden, 
Greenland, Canada, U.S.A. and the Far East, and it was described 
fully by Odhner (1905, pp. 305-10, PI. 2, figs. 6, 7). NicoU (1907a) 
found it in the dab at St. Andrews, Lebour (1908a) in the dab, long 
rough dab, witch, lemon sole, plaice and angler at Culler coats, and 
Nicoll (19136) in the witch and long rough dab at Aberdeen. Nicoll 
(1915) also recorded it in the dab at Aberdeen and Millport, Little 
(1929a) in the dab at Galway, and Baylis & Idris Jones (1933) in 
an immature condition in the lemon sole and the dab at Plymouth. 
It generally inhabits the intestine near the pylorus, and Odhner 
regarded this as the true location. According to Lebour (1908a, pp. 
13-15, PI. 1, figs. 6, 7) it is one of the commonest trematodes on the 
Northumberland coast. Size : T5-3'5 mm. long and broadest at the 
level of the ventral sucker. Shape : spindle-like, but puriform, and 
moving with the broad end foremost when alive ; very active and con- 
tractile. Colour : bright red in the living condition, with a golden tinge 
due to the eggs, fading immediately at death. Cuticle smooth. Suckers : 
ventral slightly larger than the oral, diameters in a specimen 3 mm. long 

17 



258 THE TREMATODA OF BRITISH FISHES 

0-35 mm. and 0-20 mm., ratio of sizes about 5/3. Gut : prepharynx 
small. Pharynx conspicuous. (Ecesophagus as long as the pharynx. 
Caeca narrow and extending a short distance behind the testes. Excre- 
tory system, : median canal extending to a point between the testes, 
lateral canals to the pharynx, the entire vesicle containing highly 
refractive materials which appear intensely dark by transmitted 
light. Reproductive systems : genital pore almost median and slightly 
on the left near the end of the oesophagus. Cirrus-pouch large and 
ovoid, on the left in front of the ventral sucker, containing a seminal 
vesicle which is partially divided into anterior and posterior parts, 
a conspicuous pars prostatica and a very small cirrus, otherwise filled 
with large gland- cells. Testes globular and symmetrical, one on each 
side of the point of union of the lateral and median excretory canals. 
Vasa deferentia extending separately to the seminal vesicle. Ovary 
lobed, situated behind and on the right of the ventral sucker, the 
oviduct emerging from its posterior margin. Receptaculum seminis 
generally recognizable, but small and ovate, situated at the base of 
Laurer's canal. (Note : Odhner affirmed that what Levinsen regarded 
as the receptaculum seminis is just the inflated base of Laurer's canal, 
but Lebour was reasonably certain that a true receptaculum exists, 
although Linton (1940, pp. 39-40, PL 19, figs. 260-5 ; PL 20, figs. 
266-7) supported Odhner 's contention and referred to a receptaculum 
seminis uterinum in describing American specimens). Vitellaria com- 
prising two clusters of follicles extending between the level of the 
middles of the testes and that of the ventral sucker. Vitelloducts 
uniting to form a single transverse duct on each side at the level of the 
ovary, the vitelline reservoir and ootype occupying a position on the 
left of this gonad. Uterus having its limbs formed into wide loops 
between and behind the testes. Eggs numerous, golden-brown and 
ovoid, measuring about 0046 X 0019 mm. (the former figure mis- 
printed as 0-46 mm.). Lebour found the trematode all the year round, 
and it was just as abundant in winter as in summer. Like Nicoll 
(1907a), she noted its association with Zoogonoides viviparus (a parasite 
of the rectum), although it does not generally occur in the same part 
of the intestine. It might be mentioned that the American specimens 
described by Linton were of medium size, 2-0-2-73 mm. long and 0-77- 
0-91 mm. broad, and had absolutely larger suckers measuring 0-35- 
0-38 x 0-42-0-52 mm. and 0-24-0-28 x 0-28-0-30 mm., so that they 
were of relatively more equal size, the ratio ventral /oral being 4-1-4-4/3 
for length and 4-5-5-2/3 for breadth. These specimens contained 
eggs of slightly smaller size, measuring 04 x 02 mm., but Miller 
(1941) showed that the eggs may be larger than either Linton or 
Lebour determined, measuring 0055 x 0-029 mm. in some American 
specimens. 

Genus STERINGOTREMA Odhner, 1911. 

(Steringophorus Odhner, 1905, in part.) 

This genus can be distinguished from other Fellodistomatinae by 
the lateral position of the genital pore near the termination of the 



FELLODISTOMATID^ 259 

oesophagus and well in front of the ventral sucker, the globular form 
of the cirrus-pouch, and the position of the ventral sucker behind the 
middle of the bodv. 



Steringotrema cluthense (Nicoll, 1909) Odhner, 1911. (Fig. 44 D.) 

Steringophorus cluthen-sis Nicoll, 1909 ; Leioder ma cluthense (Nicoll) of Nicoll, 
1910 (p. 347). 

Hosts : dab, lemon sole. 

Location : duodenum and pyloric caeca. 

This species was discovered in the lemon sole taken from the Firth 
of Clyde. Nicoll also found it later (1914) in the dab and the lemon 
sole at Plymouth, where Baylis & Idris Jones (1933) found it in the 
same hosts. Little (1929a) also found it in the lemon sole at Galway. 
It was described by NicoU (1909a, pp. 472-5, PL 10, fig. 16). Size : 
1-5-2 mm. long and about two-fifths as broad (0-6-0-8 mm.). Shape : 
outline oval, but invariably more pointed anteriorly than posteriorly 
and much flattened ; very extensile. Colour : translucent and reddish, 
but not so deeply tinted as Steringophorus furciger. Cuticle : non- 
spinous. Suckers : ventral almost exactly twice as large as the oral 
and situated slightly behind the midbody; oral not quite terminal 
and longitudinally ovoid ; dimensions (in a specimen 2 mm. long) 
0-44 mm. diameter and 0-22 x 0-15 mm. Gut : prepharynx absent. 
Pharynx 0085 mm. diameter. (Esophagus about 0-17 mm .long (some- 
times slightly longer or shorter). Cseca extending back a little beyond 
the testes. Excretory system : vesicle Y-shaped, but having a very 
short median canal, so that it may appear V-shaped, the lateral canals 
extending to the pharynx, filled with highly refractive materials. 
Reproductive systems : genital pore slightly behind the oesophagus and 
on the left. Cirrus-pouch bulbous, or nearly globular, situated 
entirely in front of the ventral sucker, its contents similar to those of 
Steringophorus furciger, but pars prostatica and the two parts of the 
seminal vesicle longer and narrower. Testes diagonally ovoid, sym- 
metrical and outside the lateral excretory canals, midway between 
the ventral sucker and the posterior extremity ; dimensions 0*15 x 
0-12 mm. Ovary multilobate, very small, and situated immediately 
in front of the right testis. Vitellaria extending from the testes to a 
level opposite the middle of the cirrus-pouch, i.e. well in front of the 
ventral sucker. Vitelloducts oblique, meeting between the anterior 
ends of the testes. Uterus having a few folds between and behind the 
testes. Eggs not thin-shelled, measuring 0-044-0-056 x 0-028-0-032 
mm. (Note : Nicoll summed up the chief diagnostic characters as : 
hindbody shorter than forebody ; oesophagus twice as long as the 
pharynx ; excretory vesicle almost V-shaped ; vitellaria extending in 
front of the ventral sucker.) Nicoll (1914, p. 479) reported the absence 
of this trematode from more than 100 lemon sole captured in the North 
Sea. 



260 THE TREMATODA OF BRITISH FISHES 

Steringotrema pagelli (Beneden, 1870) Odhner, 1911. (Fig. 44 E.) 

Distomum actceonis Pagenstecher, 18G3 ; D. pagelli Beneden, 1870 ; D. 
tergestimim Stossich, 1889. 

Host : common sea bream. 
Location : intestine. 

Nicoll (1914, pp. 480-1, fig. 2) obtained a few specimens of this 
trematode from the intestine of a common sea bream sent to him from 
Billingsgate Market, but was unable to ascertain whether the fish was 
caught in the North Sea or the English Channel. Beneden (1870, p. 43, 
PI. 4, fig. 17) described specimens obtained from the same species 
of host off the coast of Belgium. Little (1929a) recorded the occur- 
rence of the trematode in the same host at Galway. Odhner (1911, 
vol. 38, pp. 102-3) very briefly described specimens 1-1-6 mm. long 
and half as broad. They had suckers relatively much larger than 
those of S. cluthense, the ventral 0-4-0-75 mm. diameter and the oral 
0-11-0-12 mm., the ratio of their diameters thus being 1/3-5. The 
gonads were situated at the posterior end of the ventral sucker, behind 
and in front of which the vitellaria extended on each side. The eggs 
were relatively small, measuring 0-048-0-051 X 0028 mm. Nicoll's 
specimens were much larger. Size : 3-6-4-1 mm. long and 1-6-1-8 
mm. in greatest breadth. Shape : both extremities pointed. Suckers : 
oral longitudinally ovoid, 0-48 x 0-39 mm. in a specimen 3-8 mm. 
long. Ventral transversely ovoid, 1-16 x 105 mm. (ratio of sizes not 
quite 1/3), the ventral in front of the midbody, 1-8 mm. from the 
anterior extremity. Gut : pharynx 0-17 mm. diameter. (Esophagus 
somewhat longer. Caeca widely divergent, their ends obscured by 
numerous eggs. Reproductive systems : genital pore midway between 
the end of the oesophagus and the left margin of the forebody. Cirrus- 
pouch ovoid, its end touching the ventral sucker, seminal vesicle large. 
Gonads hidden by the gravid uterus in the hindbody. Vitellaria of 
more limited extent than in S. cluthense, but extending slightly in 
front of and behind the ventral sucker. Eggs brown and thick - 
shelled, measuring 0-057-0-063 X 0033-0037 mm. 

Steringotrema divergens (Rudolphi, 1809) Odhner, 1911. (Fig. 45 A.) 

Distoma divergens Rudolphi, 1809 (pp. 371-2, p. 395) ; Fasciola blennii 
Miiller, 1776 (p. 224). 

Host : butterfly blenny. 
Location : stomach and intestine. 

Nicoll (1914, p. 480) provided the first record of this trematode in 
Britain, finding it in fairly large numbers twice. Bay lis & Idris 
Jones (1933) found it in the same host also at Plymouth. Rudolphi's 
specimen was obtained from the gattorugine, but the trematode has 
been found at Naples, Kiel and Banyuls in the butterfly blenny. 
According to Odhner (1911, vol. 38, p. 103) the worm is more elongate 
than either S. cluthense or S. pagelli, 0-8-1-3 mm. long and 0-35—05 
mm. broad, and only slightly flattened. The ventral sucker is trans- 



FELLODISTOMATIDiE 261 

versely oval, measuring 0-27-0-38 x 0-21-O-27 mm., the oral 15- 
0-16 mm. diameter. The vitellaria are interrupted at the level of the 
ventral sucker, but extend forward to the level of the pharynx and 
backward to the ends of the caeca, and the eggs measure 0-045-0 048 x 
0031 mm. 

Nicoll did not describe his specimens, but briefly compared them 
with those of Odhner, finding the ventral sucker more nearly spherical 
and the ratio of their sizes "6:7 instead of 6 : 8," the oesophagus 
wider and shorter, the caeca not reaching the middle of the testes and 
the ovary indistinctly trilobate. Specimens found by Mathias (1934, 
pp. 567-9, fig. 1) near Banyuls were slightly larger than Odhner 's, 
0-97-2 mm. long and 0-5-1 mm. broad. The oral sucker in these 
specimens is 0- 15-0-20 mm. diameter, the ventral sucker 0-28-0-40 mm. 
long and 0-35-0-48 mm. broad, the two being even more dissimilar 
than Odhner suggested. The eggs contained in these specimens were 
of more variable size, measuring 0040-0055 x 0022-0032 mm. The 
break in the sequence of vitelline follicles was seen to be precisely as 
Odhner affirmed, this character permitting unequivocal diagnosis. 

Genus BACCIGER Nicoll, 1914. 

Nicoll erected this genus without defining it, but we may take it as 
differing from other Fellodistomatinae in the following combination of 
characters. Ventral sucker about half as large again as the oral and 
situated near the middle of the body, the genital pore far in front of it 
near the termination of the oesophagus. Cirrus-pouch ovoid. Vitel- 
laria almost confined to the region anterior to the ventral sucker. It 
is necessary, however, to stress the doubtful validity of the genus, 
which has much in common with Steringophorus. 

Bacciger bacciger (Rudolphi, 1819) Nicoll, 1914. (Fig. 44 B.) 
Distoma baccigerum Rudolphi, 1819 (pp. 108, 398-9. 

Host : sand smelt. 
Location : stomach. 

Nicoll (1914, vol. 90, 481-2, fig. 3) twice obtained a single specimen of 
this trematode in fishes sent to London from Plymouth and not very 
well preserved, the viscera being somewhat decomposed. The speci- 
mens were themselves " badly preserved." Size : 0-95 mm. long and 
0-52 mm. in greatest breadth in a slightly compressed specimen. 
Shape : outline oval, body flattened. Suckers : oral not quite ter- 
minal and 0105 mm. diameter. Ventral situated a little in front of the 
midbody and 0-15 mm. Gut : prepharynx absent. Pharynx small. 
(Esophagus two or three times as long as the pharynx. Caeca very narrow 
and long. Bifurcation of the gut midway between the pharynx and the 
genital pore. Reproductive systems : genital pore about 0-15 mm. in 
front of the ventral sucker. Cirrus-pouch small and stout, situated 
entirely in front of the latter, containing a small and simple seminal 
vesicle, a short and inflated pars prostatica and a short and wide 



262 THE TREMATODA OP BRITISH FISHES 

ejaculatory duct having irregularly folded walls. Testes globular, 
or slightly ovoid, one on each side of the body immediately behind 
the ventral sucker. Ovary globular, somewhat smaller than the 
testes and situated between them. Vitellaria occupying the lateral 
regions of the forebody, extending from the level of the oesophagus to 
that opposite the middle of the ventral sucker. Vitelloducts passing 
diagonally backwards, uniting behind the ovary. Uterus mainly 
behind the testes, here forming numerous folds which are mainly 
longitudinal, the initial folds on the left (where the eggs appear almost 
colourless). Metraterm apparently simple. Eggs small, measuring 
0020-0024 x 0014-0017 mm. {Note: Palombi (1932a, 1933, 
1934a, b) identified Cercaria pectinata Huet, 1891, with this species 
and elucidated the life -history. 

Nicoll compared these adult specimens with specimens of Distomum 
baccigerum (Rudolphi) described by Stossich (1889, p. 27) from 
Atherina hepsetus, regarding them as identical or very closely related. 
He referred to differences indicated in Stossich's figure, the larger 
testes, a more anterior genital pore and a more posterior origin of the 
caeca. Nicoll also made the allocations to family and sub-family 
here shown, but noted that in general build this trematode shows some 
affinity with the Monorchiidse, differing however in the structure of the 
cirrus-pouch and vagina, which exclude it from this family. 

Genus RH0D0TREMA Odhner, 1911. 

In this genus the oesophagus is very short, the cseca extend only a 
short distance behind the ventral sucker, the genital pore is situated 
near the level of the bifurcation of the gut, but on the left side of the 
body, and the cirrus-pouch is somewhat elongate. 

Rhodotrema ovacutum (Lebour, 1908) Odhner, 1911. (Fig. 45 B,C.) 
Steringophorus ovacutus Lebour, 1908. 

Host : long rough dab. 
Location : intestine. 

Lebour (19086, p. 33,) found this trematode rarely (four speci- 
mens, singly) at Cullercoats in summer and early autumn, but 
never found it in whiter. Nicoll (1915) recorded its occurrence at 
Aberdeen. Size : 1-8-2-3 mm. long (under a cover-slip, perhaps much 
longer when alive) and 1-16-1-33 mm. in greatest breadth, at the 
level of the ventral sucker. Colour bright red, turning pale yellow 
with a bright greenish -brown patch posteriorly (due to the eggs) at 
death. Shape : broad oval outline, rounded anteriorly, flattened in 
the region of the ventral sucker, often pyriform. Cuticle non-spinous. 
Suckers : ventral nearly twice as large as the oral and almost in the 
middle of the body; diameters 0-60-0-80 mm. and 0-32-0-40 mm. 
Chit : prepharynx very short. Pharynx small. (Esophagus short and 
narrow. Caeca extending slightly behind the testes. Excretory system : 
vesicle forked as in Steringophorus furciger, but not filled with dark 



FELLODISTOMATJDiE 



263 



matter. Lateral canals distended at their anterior ends near the oral 
sucker. Reproductive systems : genital pore in front of the bifurcation 
of the gut and on the left near the pharynx. Cirrus-pouch 0-3 mm. 




Fig. 45. — A, Steringotrema divergens. B, Rhodotrema ovacutum ; C, the 
same. D, Proctoeces maculatus. E, Tergestia laticollis. F, Haplocladus 
typicus. (B, after Lebour, 19086 ; D, after Looss, 1901a ; rest after 
Odhner, 1911.) 



long, obliquely orientated with the dorsal part on the right and the 
ventral on the left. Seminal vesicle constricted into equal halves. Pars 
prostatica large. Cirrus not seen. Testes ovoid, dorsal and slightly 
posterior to the ventral sucker, 012 mm. long. Ovary not clearly 



264 THE TREMATODA OF BRITISH FISHES 

made out, probably as in Steringophorus furciger, because the vitello- 
ducts unite in much the same place (behind and between the testes). 
Vitellaria extending between the level of the oesophagus to the anterior 
part of the ventral sucker ; on each side a small group of large follicles 
and three main ducts. Uterus having much convoluted limbs filling 
the posterior region. Eggs bright brown with a green tinge, pointed at 
one end and rounded at the other (hence the specific name), measuring 
0046 x 0-026 mm. 

According to Odhner (1911, vol. 38, pp. 100-1, figs. 1-2). Size : 
1-2-1-5 X 0-55-0-63 mm., thickness posteriorly three-quarters and 
anteriorly two-thirds the breadth. Colour flesh-red, with a golden 
ventral sucker. Shape : pyriform and broad anteriorly, or tapering 
uniformly behind the middle. Suckers : ventral 0-4r-0-5 mm. dia- 
meter, oral 0-25-0'27 mm. Gut: pharynx 0-11-0-13 mm. diameter. 
Excretory system : median stem extremely short, extending at most 
only to the middle of the hindbody. Reproductive systems : Cirrus- 
pouch at the anterior end of the ventral sucker, extending dorso- 
ventrally. Pars prostatica very muscular, the bundles of fibrils 
longitudinal. Testes small and rounded, situated behind the ventral 
sucker near the ends of the caeca. Ovary invariably three -lobed 
(clover-leaf shape), slightly on the right over the posterior part of the 
ventral sucker, larger than the testes. Vitellaria extending from the 
level of the pharynx to a little behind the middle of the ventral sucker. 
Uterus filling the hindbody. Eggs measuring about 0048 X 0-028 mm. 
(Note : Odhner noted that abnormal eggs are of common occurrence, 
claiming that those shown by Lebour (fig. 5) are of this character.) 

Genus 0V0TREMA Pigulewsky, 1938. 

This genus was erected for a new species, O.ponticum [pontica] Pigu- 
lewsky,1938 (p. 389, fig. 1) found in the gut of the anchovy (Engraulus 
encrasicholus ponticus) in the Black Sea and unrecorded in Britain. 
The generic characters are an elongate oval body and smooth cuticle. 
Ventral sucker half as large again as the oral and situated one -third 
of the distance along the body. Pharynx rounded. Caeca simple and 
not reaching the posterior extremity. Genital pore not far from the 
bifurcation of the gut and decidedly on the left. Cirrus-pouch ovoid. 
Testes of similar shape situated near the margins of the body pos- 
teriorly, the spherical ovary behind them. Vitellaria symmetrical 
behind the oral sucker. Uterus filling the entire posterior region of the 
body. O. ponticum is a small trematode 0-93-1-08 mm. long and 0-39- 
0-48 mm. broad, with oral and ventral suckers 0-072-0-087 and 0-174 
mm. diameter. The pharynx is only 0043 mm. diameter and, accord- 
ing to the figure, both prepharynx and oesophagus are absent. The 
vitellaria are grape-like and situated in the anterior half of the body 
(shown to extend between the level of the genital pore and well behind 
the bifurcation of the gut to just in front of the hind margin of the 
ventral sucker) ; dimensions of the follicles 0-007 X 0-022 mm. Cirrus- 
pouch extending back to a point above the anterior end of the ventral 



FELLODISTOMATIP^E 



265 



sucker. Genital pore lateral near the bifurcation of the gut. Ovary 
ovoid, measuring 0087 x 0-127 mm. Testes of similar shape and equal 
sizes, 0-101-0104 x 0-130-0-135 mm. The eggs are small and oval, 
the smooth, pale yellow shell being said to have double contours (!) ; 
dimensions 0029 X 0020 mm. The full description of the trematode 
is just as brief as this diagnosis, and it is not clear whether or not the 
species was erected for a single specimen, as seems likely. 

Sub-family Haplocladin^e Odhner, 1911. 

Genus HAPLOCLADUS Odhner, 1911. 

The outstanding characteristic of this genus is the single, asym- 
metrically-placed caecum. Odhner recognized three species and made 
very brief comparions between them, but it is unlikely that they are 
all valid. They were found hi British fishes, and the genus is probably 
represented in this country. 

Haplocladus typicus Odhner, 1911. (Fig. 45 F.) 

Host : horse mackerel (at Trieste and Palermo) . 
Location : " gut." 

According to Odhner (1911, vol. 38, p. 104, fig. 4) this trematode 
is common in Italy. Size : about 4 mm. long and 0-25-0 33 mm. 
broad, specimens only 1 mm. long full of eggs. Suckers : oral 0-2- 
0-25 mm. long and 0-15-0-2 mm. broad, ventral 0-13-0- 17 mm. dia- 
meter and situated 0-4-0-65 mm. from the anterior extremity. Gut : 
pharynx 0-18-0-25 mm. long and 0-1-0-12 mm. broad and thick. 
Reproductive systems : testes in large individuals at or behind the 
middle of the body. Vitellaria extending back to the hinder ends of 
the testes. Eggs brown, measuring 004 x 0-024 mm. According 
to Odhner, the sperms of this species are arranged in spermatophores. 

Haplocladus filiformis (Rudolphi, 1819) Odhner, 1911 (vol. 38, p. 104). 

Host : red band fish (at Trieste). 
Location : " gut." 

This species was said to be distinguishable from H. typicus by the 
more anterior position of the testes and smaller, reddish-brown eggs, 
which were 034-0 037 mm. long. 

Haplocladus minor Odhner, 1911 (vol. 37, pp. 105-6). 

Host : dab (at Kristineberg, rarely). 

Location : " gut." 

Size : 1-3-2 mm. long and 0-2-0-25 mm. broad. Suckers : oral 
measuring 0-16-0-18 x 0-13-0-15 mm., ventral 0-11-0-12 mm. diameter 
and situated 0-35-0-45 mm. from the anterior extremity. Gut : pharynx 
0-15 mm. long and 008 mm. broad. Reproductive systems : testes as 
in H. typicus and eggs of the same size, but pale yellow in colour. A 
furcocercous cercaria thought to belong to this species was found in an 



266 THE TREMATODA OF BRITISH FISHES 

aquarium containing Nucula nucleus and Syndosmya alba at Kristine- 
berg. The body was 0-35 mm. long, the stem of the tail 0-6 mm. long. 
This larva showed the characters of Haplocladus in respect of the 
suckers, the gut and the excretory vesicle. 

Genus PR0CT0ECES Odhner, 1911. 

In this genus there are two long caeca, and the oral sucker is simple 
and of the ordinary type. 

Proctoeces maculatus (Looss, 1901) Odhner, 1911. (Fig. 45 D.) 

Distomum maculatum Looss, 1901 {a, pp. 402-4, fig. 3) ; Proctoeces erythremias 
Odhner, 1911 (vol. 38, pp. 108-9. 

Hosts : Blenniidae and Labridse (on the Continent) . 
Location : intestine. 

Looss obtained specimens of this species 3-2 mm. long in several 
wrasses at Trieste, and Nicoll (1915) recorded its occurrence on the 
Continent in the butterfly blenny. According to Odhner (1911, vol. 
38, p. 108) specimens described under this name have the following 
characters. Size : 2-5 mm. long, 0-5-0-7 mm. broad and 0-3-0-45 
mm. thick, specimens 1 mm. long already full of eggs. Suckers : 
ventral more than twice as long as the oral and situated at the end of 
the first one-third of the body (according to the figure of Looss, some- 
what farther back) ; dimensions 0-42-0-7 x 0-28-0-42 mm. and 0-2- 
0-3 mm. Gut : pharynx 0-15-0-23 mm. long. Reproductive systems : 
vitellaria extending slightly behind the testes. Eggs measuring 
0-072-0-079 X 0-027 mm. in vivo. The form P. erythrceus was said to 
differ from P. maculatus in the smaller size of the ventral sucker 
(0-38-0-4 mm. diameter in whole moimts), shorter vitellaria termi- 
nating at the anterior margin of the posterior testis and much smaller 
eggs, about 0045 mm. long. From the scanty information provided 
in the description, which was unaccompanied by a figure, it is difficult 
to get a clear idea about this trematode, two immature and one 
mature specimens of which were obtained from "Julis lunaris " and 
"Chrysophrys bifasciata " respectively in the Red Sea. 

Genus TERGESTIA Stossich, 1899. 
{Theledera Linton, 1910.) 
This genus is readily distinguished by the unusual oral sucker, 
which has 13 lancet-like processes, and the long caeca. 

Tergestia laticollis (Rudolphi, 1819) Stossich, 1899 (p. 16). 

(Fig. 45 E.) 

Distoma laticolle Rudolphi, 1819 (pp. 117, 421) ; D. polonii of Olsson, 1868 
(p. 29). 

Host : horse mackerel. 
Location : intestine. 



FELLODISTOMATIDiE 267 

Nicoll (19136, p. 192) found a single specimen of this species at 
Aberdeen and remarked that it is not a common parasite in the North 
Sea, although he found it frequently later at Plymouth (1914, p. 483), 
sometimes in fairly large numbers. As a rule, however, only a few 
specimens occur in one host. Nicoll also emphasized the complete 
host-specificity, which is more remarkable now that the trematode 
has been found in at least two other continents. It has been found at 
Trieste and Palermo, in the Black Sea, in Japan, and in America at 
Tortugas and Costa Rica. Odhner gave a description of the worm. 
Size : up to 4 mm. long and 0-2-0-33 mm. broad, but mature when 
1-5 mm. long. Shape : elongate and almost cylindrical or slightly 
flattened and having an arched forebody. Suckers : ventral larger 
than the oral and situated about one-third or one-quarter of the 
distance along the body ; dimensions 0-17-0-2 x 0-2-0-23 mm. and 
0-16-0-18 mm. diameter. Oral sucker having 13 lanceolate processes 
radiating antero- dor sally and antero-laterally, becoming progressively 
smaller from the middle towards the end of each series. Integument : 
immediately behind the oral sucker, formed into 6 diagonally arranged 
folds or ledges on each side. Gut : prepharynx absent. Pharynx 
very elongate, measuring 0-17-0-25 x 0-08-0-10 mm. (Esophagus long, 
its posterior one-third having an epithelial lining, terminating behind 
the ventral sucker. Caeca very long. Reproductive systems : cirrus- 
pouch elongate and extending back on the left to the posterior border 
of the ventral sucker, sometimes a little beyond it. Seminal vesicle 
long and convoluted, occupying the posterior two-thirds of the pouch, 
pars prostatica and cirrus the anterior one-third. Testes globular, 
diagonally arranged in the posterior region, the more anterior on the 
left. Ovary ovoid and situated a short distance in front of the testes 
on the right. Receptaculum seminis absent. Laurer's canal present, 
but its opening obliterated. Vitellaria lateral in the posterior region, 
their anterior ends slightly behind the ventral sucker. Follicles dis- 
playing a rope -like arrangement. Uterus rilling the posterior region. 
Metraterm extending to a point above the mid-point of the ventral 
sucker, its opening bordered by an enormous thickening of longitu- 
dinal muscles. Eggs brownish-yellow, measuring 0-021-0-023 x 0-015 
mm. and containing immature miracidia. 

According to Nicoll (1913) the average length of his specimens was 
2-65 mm., but the specimen from Aberdeen 4-6 mm. Greatest breadth 
is about one -sixth of the length. The oral sucker is longitudinally 
ovoid, measuring 0-23 X 0-19 mm., the ventral globular and 0-28- 
0-29 mm. diameter, or one-ninth of the length of the body, the ratio 
of sizes approximately 2/3. In the large specimen the suckers are 
relatively smaller, the ventral one -thirteenth of the length of the body. 
Other characters are as Odhner determined, but the lateral folds of the 
integument vary in position ; the more posterior three or four of them 
may be situated behind the pharynx in extended specimens. The 
vitellaria are not as extensive anteriorly, reaching the mid-point 
between the ventral sucker and the ovary. The oesophagus may be 
S-shaped instead of straight. 



268 THE TREMATODA OF BRITISH FISHES 

Tergestia acanthocephala (Stossich, 1887) Stossich, 1899 (p. 16). 

Under this name Odhner (1911, vol. 38, pp. 113-14) dealt with a 
trematode 1-1-16 mm. long and 0-23-0-33 mm. broad which was said 
to differ from T. laticollis in the much shorter pharynx, 012-016 mm. 
long and 0-07-0-11 mm. broad, and the more extensive vitellaria 
between the ventral sucker and the posterior extremity. The ventral 
sucker was more than half as large again as the oral, diameters 0-25 
and 0-15 mm. The sizes of the eggs was undetermined. This species 
has been recorded as a parasite of"Belone acus " at Palermo and the 
mackerel and " Seriola dumerilii " at Trieste. Bay lis (1939) listed it 
as a parasite of the mackerel in South Devon. 

Other species are Tergestia pectinata (Linton, 1905) and T. 
priacanthi (MacCallum, 1917), which occur in America, and T '. acantho- 
gobii Yamaguti, 1938, which occurs in Japan. 

Genus ANCYL0C(ELIUM Nicoll, 1912. 

The distinctive character of this genus is in the cseca, which are 
very short, and terminate in front of the ventral sucker. 

Ancyloccelium typicum Nicoll, 1912. 

Host : horse mackerel. 
Location : intestine. 

Only one specimen of this species seems ever to have been found, 
at Aberdeen (see Nicoll, 1912, pp. 198-200, PL 9, fig. 1). Size : 2-25 
mm. long and 0048 mm. broad. Shape : spatulate outline, broadest 
in front of the middle, tapering sharply anteriorly and more gradually 
posteriorly, decidedly flattened. Colour yellow (because of the eggs 
in utero). Cuticle spinous, the spines scale-like, becoming sparser 
and gradually disappearing towards the posterior extremity. Suckers 
small and inconspicuous, the ventral slightly the larger and 0-92 mm. 
from the anterior extremities ; diameters 0-10 mm. and 0-13 mm. 
Gut : prepharynx absent. Pharynx elongate (measuring 008 X 0-043 
mm.). (Esophagus long (0-5 mm.) and narrow. Cseca very short and 
wide, terminating in front of the ventral sucker, and of unusual shape 
(the anterior half directed forwards, the posterior half backwards). 
Reproductive systems : genital pore median, situated between the 
caeca and the ventral sucker. Cirrus-pouch simple and club-shaped, 
anterior and dorsal to the ventral sucker, 0-32 mm. long and 011 mm. 
broad, containing a very short pars prostatica, a comparatively short 
and straight ejaculatory duct, and a large oval seminal vesicle. Testes 
elongate oval, about 019 mm. long and 10 mm. broad, diagonally 
one behind the other, the anterior a short distance behind the ventral 
sucker and on the right, the posterior more median and 0-22 mm. 
behind the sucker. Ovary almost globular, about as large as the 
ventral sucker (0-14 mm. diameter) and between it and the anterior 
testis. Receptaculum seminis and Laurer's canal not observed. 
Vitellaria lateral and asymmetrical, comprising on each side an elongate 



BUNODERIDJE 269 

tubule formed into a rosette-like knot with unequal rays (the anterior 
the longer), that on the right extending from the anterior border of 
the foremost testis to about 0-7 mm. from the posterior extremity, 
that on the left slightly more anterior. Uterus having descending 
and ascending limbs with voluminous folds, but little convoluted, 
extending to the posterior extremity. Eggs very numerous, bright 
yellow, oval in outline, measuring about (mean) 0-024 x 0013 mm. 

Family BUNODERIDiE Nicoll, 1914. 

(Bunoderinse Looss, 1902.) 

Size and shape : small or fairly small and slightly elongate. Cuticle : 
smooth. Suckers well developed and of about equal size, not very 
widely separated, the oral having 6 short muscular processes. Gut : 
prepharynx very short or absent. Pharynx small. (Esophagus fairly 
long and sometimes folded into an S -shape when the forebody is 
contracted. Caeca long or very long. Excretory vesicle : sac-like or 
tubular. Reproductive systems : genital pore median and near, some- 
times anterior to the bifurcation of the gut. Cirrus -pouch mem- 
braneous, not muscular, the contained seminal vesicle partially con- 
stricted into two parts. Pars prostatica small. Cirrus not sharply 
marked off from the ejaculatory duct. Testes globular and directly 
or diagonally one behind the other, posterior to the globular ovary. 
Receptaculum seminis large or small, Laurer's canal present. Vitel- 
laria well developed and follicular, extending laterally between the 
pharynx and the posterior extremity, sometimes approaching the 
median plane behind the testes. Uterus having short sac-like descend- 
ing and ascending limbs, sometimes hardly folded and not extending 
behind the testes or more extensive posteriorly. Eggs not very 
numerous and variable in size. 

Genus BUN0DERA Railliet, 1896. 
With the characters of the family. Limbs of the uterus extending 
almost to the posterior extremity and underlying the testes. Vitelline 
follicles not mingling in the median plane behind the testes. Accord- 
ing to Hopkins (1934) this genus should be regarded as an aberrant 
Allocreadiid related to Crepidostomum. The only European species, 
B. luciopercce, occurs in Britain, Denmark, Sweden, France, Russia, 
Germany, Canada and U.S.A. 

Bunodera luciopercae (Miiller, 1776) Luhe, 1909. (Fig. 34 D.) 

Fasciola luciopercce Miiller, 1776 (p. 223) (1779, pp. 67-8, PI. 30, fig. 7) ; 
F. percce cernuce Miiller, 1776 (p. 224) ; Planaria lagena Braun, 1788 ; 
Fasciola percoe Gmelin, 1790 ; F. percina Schrank, 1790 ; F. nodulosa 
Frolich, 1791 ; Distoma nodulosum Zeder, 1800 and of Looss, 1894 (pp. 33- 
41, PI. 1, figs. 8-10, PI. 5, figs. 92-4) ; Crossodera nodulosa Cobbold, 1860 ; 
Bunodera nodulosa Looss, 1899. 

Hosts : In Britain, perch ; on the Continent, pope, barbel, pike, 
sea trout and others also. 
Location : intestine. 



270 THE TREMATODA OF BRITISH FISHES 

Baylis (1939) recorded the occurrence of this trematode in Hertford- 
shire. Liihe (1909, p. 64, fig. 55) mentioned specimens 1-4-5 mm. 
long with a very mobile anterior region which may form an extended 
" neck-like " process, suckers of about equal sizes and large eggs 
measuring 0-1 X 05 mm. He stated that eyes may be represented 
in young individuals by paired flecks of pigment near the mouth, and 
noted that after death of the host the trematode may wander along 
the alimentary canal and may be found near the anus. 

Hopkins (1934, p. 52) made a careful study of this species based on 
both European and American specimens. After examining specimens 
from the University of Berlin Zoological Museum and the Konigsberg 
Museum he concluded that they conformed with the description of 
Looss (1894) except in three particulars : (a) the excretory vesicle is 
tubular, not forked, and extends forward to the level of the recep- 
taculum seminis ; (6) the vitellaria are lateral to the uterus and ventral 
and lateral to the caeca and generally extend to the posterior extremity ; 
and (c) the eggs are smaller than specified (01 X 005 mm.), measuring 
0066-0075 x 0043-0051 mm. This writer gave a diagnosis which 
is applicable to both European and American specimens, but regarded 
this species as one of the most variable trematodes he had studied, 
mainly because of changes in form consequent upon enlargement of 
the uterus and upon muscular movements of the body, stressing that 
but for the existence of intermediate conditions, extreme specimens 
could easily be regarded as distinct species. The diagnosis mentioned 
modified the generic characters given in the account of Liihe. Size : 
1-4-5 mm. long when adult and one-fifth to one-half as broad. Shape : 
broadest in the middle of the region behind the ventral sucker, rounded 
in transverse section. Suckers of almost equal sizes ; diameters one- 
eleventh to one-fifth body-length ; ventral situated in the anterior 
third or half of the body. Dorsal papillae numbering 4 and slightly 
larger than the 2 ventral ; respective lengths one-fifth to one-third and 
one-seventh to one-fourth the diameter of the oral sucker. Gut : 
prepharynx short. Pharynx ellipsoidal, one -third to one half length of 
the oral sucker. (Esophagus two to three times as long as the pharynx. 
Caeca long and dorso-lateral in position. Excretory system : vesicle a 
broad, undivided sac extending forward as far as the receptaculum 
seminis or ovary, main canals meeting it near the anterior end. Flame- 
cell formula probably 2 [(4+4+4) + (4+4+4)] or closely similar. 
Eyespots : one on each side of the pharynx. Reproductive systems : 
genital pore median or slightly lateral near the bifurcation of the 
intestine (slightly in front, or behind this level). Cirrus-pouch very 
broad and short, rarely extending behind the ventral sucker, its wall 
thin, but definitely muscular. Seminal vesicle long and constricted 
to form two or several chambers ; much convoluted in large individuals. 
Cirrus short and straight or coiled and having a thick muscular wall. 
Prostate gland- cells numbering several hundreds, or fewer in small 
specimens. Testes slightly diagonally arranged, and more widely 
separated in larger than in smaller specimens, the anterior near the 
receptaculum seminis, the posterior near the ends of the caeca. Ovary 



GORGODERID^ 271 

dorso-lateral and a short distance behind the ventral sucker, sometimes 
touching it. Receptaculum seminis larger than the ovary in large 
individuals and immediately behind it. Laurer's canal opening 
dorsally above the caecum furthest from the ovary. Descending limb 
of the uterus narrow and straight and dorsal ; ascending limb enor- 
mously swollen, ventral and almost filling the entire breadth and 
depth of the body in large individuals. Eggs numerous, yellowish, 
operculate and thin-shelled, measuring 0063-0-082 x 0038-0051 
mm. [Note: In " Bunodera nodulosa " of Linton, 1940 (pp. 104, PI. 
22, figs. 290-1) the eggs are much smaller and just as variable in size, 
measuring 0045-0069 X 0030-0045 mm. in specimens 1-12 mm. 
long and 0077 x 0-042 mm. in an individual twice as large (2-25 mm.).] 
Developing miracidia occur in the eggs still in the uterus of larger 
worms. Vitellaria extending as two rather narrow bands from near 
the pharynx almost to the posterior extremity. 

One American species of Bunodera is known, B. sacculata Van 
Cleave & Mueller, 1932, a parasite of Perca flavescens in U.S.A. 

Family GORGODERID^ Looss, 1901. 

Size and shape : small or fairly small and pyriform, broad and flat 
posteriorly, slender and tapering and very mobile anteriorly. Cuticle 
smooth, sometimes papillate. Suckers of medium size, the ventral 
slightly the larger. Gut : pharynx present or absent. (Esophagus 
fairly long. Caeca long. Excretory system : vesicle tubular, pore slightly 
dorsal. Reproductive systems : genital pore median and situated 
between the ventral sucker and the bifurcation of the gut. Cirrus 
and cirrus-pouch absent. Testes globular, lobed or partitioned, 
situated side by side or diagonally one behind the other. Ovary 
globular, lateral and in front of the testes. Receptaculum seminis 
and Laurer's canal present. Vitellaria ill-developed and compact, 
close together in the middle of the body between the caeca. Uterus 
having much folded descending and ascending limbs, which tend to 
fill the posterior region behind the gonads. Eggs numerous and fairly 
large, but of variable size, thin-shelled and almost colourless, tending 
to increase in bulk during passage through the uterus. 

There are two sub-families, the Gorgoderinae, parasites of Teleostei 
(and of frogs), in which the testes are median to the caeca, and the 
Anaporrhutinae, parasites of Selachii, in which the testes are lateral 
to the caeca. 

Sub-family Gorgoderin^e Looss, 1901. 

Genus PHYLL0DIST0MUM Braun, 1899. 

(Spathidium Looss, 1899 ; Catoptroides Odhner, in Looss, 1902 ; 
Microlecithus Ozaki, 1926.) 

It is very unlikely that all the species assigned to this genus are 
valid. I have already given a list of them, and have made a short 
statement about the European forms and their synonyms and about 



272 THE TREMATODA OF BRITISH FISHES 

the possible fate of some others (Dawes, 1946). Lewis (1935) reviewed 
the "species " proposed up till 1932, but he was very generous in regard- 
ing twenty of them as valid. He took great care over the assembling of 
scattered data, but the characters employed in his " key " have con- 
vinced me that some of the differences which are regarded as being 
of specific importance are quite unreliable. For instance, in the first 
broad separation of fifteen " species " from five others he had to 
resort to the use of the spatulate or non-spatulate shape of the body 
and the degree to which the anterior and posterior regions are set off 
from one another — characters which are decidedly variable. Other 
false characters by which it is hoped that species might be separated 
are the size, shape, position and regular or irregular lobes of organs 
such as the testes, the extent to which the uterus is developed, and 
the sparsity or abundance of eggs, all of which depend on the size, 
degree of maturity and senility of the specimens. Since his review 
was written at least nineteen new " species " have been erected, most 
of them from fishes, but some from amphibians (and one exhibiting 
progenesis in Palcemon spp.), mainly in America, but also in Japan 
and India, though none in Europe. The characters which have been 
used sometimes are most trifling, and many of these species are 
obviously invalid. It is my opinion that in the ultimate analysis a 
good many of them will be relegated to synonymity with the well- 
known European species, Phyllodistomum folium, which occurs in 
Central Europe, Sweden and Canada, and was recorded in the three- 
spined stickleback in Cambridgeshire by Baylis (1939). Outside 
Britain, this trematode occurs in the pike, grayling, miller's thumb 
and ruffe. 

Phyllodistomum folium (v. Olfers, 1817) Braun, 1899 (p. 492). 

(Fig. 34 E.) 

Distoma folium v. Olfers, 1817 (p. 45, fig. 15) and of Rudolphi, 1819 
(pp. 96-7, 371-2), and of Looss, 1894 (pp. 18-24, PL 1, figs. 19-22, PL 4, 
figs. 75-80) ; Spathidium folium (v. Olfers) Looss, 1899 (p. 606) ; Phyllo- 
distomum pseudofolium Nybelin, 1926 (p. 12). 

Host: three-spined stickleback (in Cambridgeshire — Baylis (1939)). 
Location : urinary bladder and ureters. 

Size : generally no more than 2 mm. long and 0-25-0 -35 mm. 
broad in the anterior region, three times as broad (1 mm.) in the 
posterior, but sometimes larger. Suckers : proportionate sizes very 
variable, the ventral much larger than the oral in small specimens, 
but the same size in large specimens ; diameters 018-0-25 and 
0-11-0-25 mm., the ventral situated just in front of the middle 
of the body. Gut : oesophagus long, terminating midway between 
the suckers. Caeca long and somewhat dilated at their ter- 
minations near the posterior extremity. Reproductive systems : 
genital pore just in front of the ventral sucker, or midway between 
it and the bifurcation of the gut. Testes rounded and only slightly 
or evidently lobed, obliquely arranged not far apart in the pos- 



GORGODERIDJE 273 

terior region, up to about 0-2 mm. long, but sometimes much larger 
than the suckers. Ovary globular or slightly lobed, about half as 
large as the testes and situated on the right, almost at the same level 
as the anterior testis. Vitellaria two slightly lobed and compact 
masses of follicles situated one on either side of the median plane 
just behind the ventral sucker and in front of the ovary. Uterus 
having long descending and ascending limbs which pass between the 
testes, and form numerous irregular loops in the available space between 
the caeca, sometimes extending posterior to their terminations and 
here spreading to the margins of the body. Eggs numerous and oval 
in shape, very variable in size in different parts of the uterus, when 
first formed measuring about 035-0 036 X 0-018 mm., but later up 
to 0060 x 0-035 mm. 

Lewis (1935) summarized data concerning this trematode, and gave 
figures (PI. 20, figs. 1-5) of specimens described by Looss (1894), 
Odhner (one specimen from Konigsberg which was re-examined) and 
Nybelin (1926), and a specimen from Stafford's collection. The figures 
show clearly that considerable variability may be expected in this 
species in regard to size and shape, the relative sizes of the suckers 
and of the gonads, vitellaria and caeca. When the genus is reviewed — 
and I hope to review it myself — this will be found to embrace many of 
the " species " which stand so precariously at present. Eight species 
have been assigned to the genus in Europe, but one of them (P. 
pseudofolium Nybelin, 1926) is a synonym of P. folium, and another 
(P. megalorchis Nybelin, 1926) is identical with P. simile Nybelin, 
1926, which occurs in the urinary bladder of the miller's thumb, 
grayling, burbot and sea trout in Sweden. Species which still stand 
are : P. conostomum (Olsson, 1876), which was found in the oesophagus 
and on the gills of the houting in Sweden ; P. acceptum Looss, 1901, 
which occurs in the bladder of "Crenilabrus pavo " and "C. griseus " 
at Trieste ; P. macrocotyle (Liihe, 1909) (Syn. P. angulatum Linstow, 
1907) (Fig. 34 F), which occurs in a number of Cyprinids (crucian 
carp, barbel, gudgeon, rudd, roach, chub, bream, white bream) in 
the vicinity of Warsaw ; and P. elongatum sp. inq. Nybelin, 1926, 
which occurs in the ureters of the tench and bream in Sweden. I 
have already given the main characters of these species (see Dawes, 
1946, pp. 275-7). 



Sub-family Anaporrhutlsle Looss, 1901. 
Genus PR0B0LITREMA Looss, 1902. (Fig. 34 G.) 

This genus contains two species, P. richiardii (Lopez, 1888) Looss, 
1902 (pp. 855, 857, 863) and P. capense Looss, 1902 (pp. the same). 
The latter has been found in the coelom of a dogfish near the Cape of 
Good Hope and the former is a parasite in the coelom of various 
Selachii (piked dogfish, smooth hound, and eagle ray) in the Mediter- 
ranean. According to Looss, the two species differ in the relative 
sizes of the suckers, P. richiardii having a ventral sucker which is 

18 



274 THE TREMATODA OF BRITISH FISHES 

much larger than the oral, P. capense suckers of approximately the 
same size, although Odhner (1910, p. 14) showed that the ratio of 
their diameters is 3/4 in large specimens 20 mm. long and 2/3 in small 
specimens 6-9 mm. long. Dollfus (1935, p. 200) examined a specimen 
of P. richiardii which was found free in the ccelom of the piked dogfish 
at Algiers, describing it as a typical individual 10-5 mm. long and 8-3 
mm. broad having oral and ventral suckers measuring 1-75-0-95 and 
2-2-1 mm. diameter respectively. Later (1937, p. 63, figs. 1, 2) he 
described a specimen found in the Zoological Institute at Strasbourg 
which had the following characters : — Size : 13 mm. long and 11-5 mm. 
broad. Shape : outline broad oval, narrowing sharply anteriorly. 
Suckers : oral 1 mm. long and 1-5 mm. broad ; ventral 2 mm. diameter 
and little more than this distance behind the oral. Cuticle bearing 
slender spines of irregular shape. Gut : prepharynx and oesophagus 
absent. Pharynx broader than long, measuring 0-625 X 0-875 mm. 
Caeca long and sacculated. Reproductive systems : testes numerous, 
26 to 30 on each side of the body, lateral to the caeca in the posterior 
region. Ovary 0-76 mm. long and 002 mm. broad, situated between 
the caeca near the anterior ends of the testes, the receptaculum seminis 
between it and the ventral sucker. Vitellaria comprising two lateral 
masses of short and curved tubular follicles immediately in front of 
the testes. Eggs in the terminal part of the uterus measuring 0-059 x 
052 mm., but in the vicinity of the ovary much smaller, measuring 
only 0-048 x 0-040 mm. MonticeUi (1893a, pp. 139-48) described 
specimens 12-18 mm. long and 8-12 mm. broad which differ in several 
small particulars (a short oesophagus is present, the pharynx has a 
central constriction and, according to his fig. 52, PI. 5, the testes 
number 35 and 36 on the two sides of the body). Other species of this 
genus occur in the Antipodes. 



Family HEMIURID.E Liihe, 1901. 

Size and shape : small or of medium size, elongate and somewhat 
cylindrical, the extremities tapering, the posterior often having a 
tail-like process or ecsoma, which can be introverted into the rest of 
the body or soma. Cuticle non- spinous, sometimes annulated. 
Suckers fairly large and not far apart in the anterior region, the 
ventral projecting only slightly from the surface of the body. Gut : 
pharynx small. (Esophagus short Caeca long and entering the ecsoma 
or not. Bifurcation of the gut generally situated between the suckers. 
Excretory system : vesicle Y-shaped, comprising a long median stem 
and long lateral canals which generally unite above the oral sucker. 
Reproductive systems : genital pore median and situated near the 
mouth on the ventral surface. Genital atrium tubular, receiving an 
hermaphrodite duct which is muscular and functions like a cirrus, 
being sometimes provided with a muscular pouch (or sinus sac) which 
is said to be " complete " when the muscles form a continuous layer, 
" incomplete " when they are discontinuous. Pars prostatica and 
seminal vesicle lying free in the parenchyma. Testes globular, side 



HEMIUMDiE 275 

by side or one behind the other, and generally not far behind the 
ventral sucker. Ovary globular and situated behind the testes, 
generally separated from them by folds of the uterus. Receptaculum 
seminis present. Laurer's canal absent. Vitellaria not follicular, but 
comprising a pair of compact groups of follicles, sometimes lobed and 
occasionally thread-like or tubular, generally situated behind the 
gonads. Uterus having descending and ascending limbs, entering the 
ecsoma or not, abundantly folded. Eggs very numerous, thin-shelled 
and small, rarely exceeding 003 mm. in length. Cercaria of cysto- 
phorous type, generally penetrating a copepod. 

In three sub-families an ecsoma is present. In one of them, the 
Hemiurinae, the mouth is overhung by a lip-like process and the vitel- 
larise are only slightly lobed ; in the other two there is no lip-like 
process and the vitellaria have small, finger-like lobes (Sterrhurinse) 
or very long, thread-like processes (Dinurinse). In three sub-families 
the ecsoma is absent. In one of them (Lecithasterinse) the vitellaria 
are unpaired, forming a seven-rayed mass ; in the remaining two the 
vitellaria are paired and a cirrus pouch is absent (Derogenetinse) or 
present (Syncceliinae). 

Sub-family Hemiurin^: Looss, 1899. 

Two genera have to be considered and can be distinguished by the 
nature of the vitellaria, which are paired in Hemiurus, but unpaired 
in Aphanurus. 

Genus HEMIURUS Rudolphi, 1809. 

(Parahemiurus Vaz & Pereira, 1930.) 

Hemiurus appendiculatus (Rudolphi, 1802) Looss, 1899 (p. 641). 

(Fig. 46, A, B, C.) 

Fasciola appendiculata Rudolphi, 1802 (pp. 78-9, PI. 2, fig. 6a, 6) ; Distoma 
appendiculatum Rudolphi, 1808 (xxiv, PI. 5, fig. 2), and of Rudolphi, 1819 
in part (p. 404) ; Apoblema appendiculatum of Juel, 1889, in part (p. 4, 
fig. 17), and of Monticelli, 1891 in part (pp. 502-8) ; A. appendiculatum of 
Looss, 1896 (pp. 131-40, PI. 9, figs. 88-90), nee Muhling, 1898 ; Distomum 
ventricosum Wagener, 1860 (pp. 166-72, PI. 8, figs. 1-7), nee Rudolphi, 
1819. 

This species does not seem to have been recorded in Britain, but 
occurs in various teleosts (twaite shad, perch, burbot, trout, houting, 
river lamprey and others) in widely separated parts of Europe (at 
Trieste, in the Rhine, in the Bay of Palma, Majorca), in Egypt and in 
Canada and U.S.A., and is fairly certain to appear here. Liihe (1901a) 
specified the twaite shad as the principal host and considered the dis- 
tinctive characters of the trematode to be the different sizes of the 
suckers, the ventral significantly the larger, the very long pars prostatica, 
the relatively posterior seminal vesicle and symmetrical testes, and an 
ecsoma of medium length and about one-third as long as the soma. 
Later (1909, p. 137, fig. 105) he gave a diagnosis which is not signifi- 



276 



THE TREMATODA OF BRITISH FISHES 



cantly different from that of Looss (1907, p. 590 ; 1908, p. 103, PL 
7, figs. 1-3), who found this species common in the Nile, as Luhe 
found it to be in the Rhine, and in no way different from specimens 
found at Trieste. Size : soma up to 3-5 mm. long and 0-4-0-65 




Fig. 46. — A-C, Hemiarus appendiculatus (A and B, ventral views showing 
the ecsoma respectively extended and retracted ; C, the same as B, in 
side view). D, H. rugosus. E, F, "H. liihei Odhner " (= H. ocreatus). 
G, H, Aphanurus stossichii in side and ventral view. I, Hemiurus com- 
munis ; J, terminal parts of the genital ducts of I. (A-H, after Looss, 
1908 ; I, J, after Lebour, 1908a.) 



mm. broad and thick ; ecsoma when fully extended about three-quarters 
of the length of the soma. Suckers : ventral twice as large as the oral 
and situated only slightly behind it ; diameters 0-33-0-5 and 17-0-23 
mm. Cuticle : annulations on the dorsal surface hardly ever existing 
behind the level of the pharynx. Reproductive systems : genital 
atrium very short, not longer than the breadth of the sinus sac, which 



HEMIUBID^ 277 

is slender and about 0-25-0-37 mm. long. Anterior part of the seminal 
vesicle having a thick muscular wall. Vitellaria irregularly globular, 
the borders smooth, rarely indented even slightly. Limbs of the uterus 
extending far into the ecsoma, almost to the terminations of the ca3ca. 
Eggs measuring 0-020-0-023 x 0-010-0-012 mm. It might be men- 
tioned that Linton (1940, pp. 119-23, PI. 8, figs. 68-74) gave concise 
descriptions (including measurements) of American specimens which 
have been found in 19 species of fishes in the Woods Hole region. On 
several occasions in September and October only a solitary specimen 
was found in eight to twelve winter flounders, but on one day in late 
July well over a thousand specimens were collected from ten to fourteen 
hosts of the species Pseudopleuronectes americanus at Katania Bay. 



Hemiurus levinseni Odhner, 1905. (Fig. 36 C.) 

Distomum appendiculatum of Olsson, and of Juel, in part. 

This species has not appeared in Britain, but occurs in various 
fishes (the father lasher, Gadus morrhua var. ovak and G. saida) in 
Denmark, Greenland, Canada and U.S.A. It was described by Odhner 
(1905, pp. 348-51, PI. 4, fig. 2), and Looss (1908, p. 106) gave a short 
diagnosis. Size : 1-1-6 mm. long and 0-3-0-5 mm. broad and thick, 
the ecsoma invariably retracted (?) and in this condition about 01 
mm. long. Suckers : oral somewhat larger than the ventral, diameters 
about 0-17 and 14 mm. Reproductive systems : sinus sac about as 
long as the oral sucker and about half as broad again as the ventral. 
Pars prostatica slightly folded. Vitellaria almost spherical and having 
smooth borders. Eggs measuring 0-026-0-028 x 0-012-0-013 mm. For 
descriptions of American specimens of this species see Manter (1926, 
pp. 92-3, figs. 62-3) and Linton (1940, pp. 123-5, PI. 8, figs. 75-7). 

Hemiurus ocreatus (Rudolphi, 1802) Looss, 1899. 

(Fig. 46 E, F.) 

Hemiurus lilhei Odhner, 1905 (pp. 351-2). 

Hosts : herring, pilchard, sprat, salmon, boar-fish, hake, whiting, 
pollack, horse mackerel, mackerel. 
Location : stomach. 

Nicoll (1914) specified the pilchard as the commonest host of this 
trematode, but recorded its occurrence also in the boar-fish, horse 
mackerel, mackerel, whiting and pollack at Plymouth. Later (1915) 
he recorded other hosts, the hake at Aberdeen, the herring at St. 
Andrews and Millport, and cited its discovery by Tosh (1905) in salmon 
in the Tweed. Little (1929a) recorded its occurrence in the hake and 
the grey gurnard at Gal way, and Markowski (1933) in the herring in 
the Baltic. 

According to Looss (1907, p. 590 ; 1908, p. 105, PI. 7, fig. 6 ; PI. 
12, fig. 34) and with observations of Markowski (1933, p. 15, fig. 5) 
in parentheses: — Shape: slender. {Colour: reddish.) Size : 1-5- 



278 THE TREMATODA OF BRITISH FISHES 

1-7 mm. long (2-3-5 mm.) when the ecsoma is retracted, 2-5-2-8 mm. 
when it is extended ; breadth 0-3 mm. and 0-23-0-27 mm. under these 
conditions. Cuticle : annulated, annuli extending on the dorsal 
surface to a level about midway between the ventral sucker and the 
testes (to the ovary). Suckers : ventral nearly twice as large as the 
oral ; diameters 0-17-0-21 mm. and 0-1-0-12 mm. (dimensions 0-18 X 
0-24 mm. and 0-165 x 0-24 mm.). {Gut : pharynx 0-075-0-105 mm. 
diameter. (Esophagus unusually short. Caeca extending far into the 
ecsoma.) Reproductive systems : sinus sac not very slender, together 
with the genital atrium about as long or a little longer than the breadth 
of the ventral sucker. (Pars prostatica well developed. Testes 
diagonally arranged behind the ventral sucker and 0-097-0-135 mm. 
diameter.) Anterior part of the seminal vesicle having a thick mus- 
cular wall. (Ovary spherical, 0-12-0- 165 mm. diameter.) Vitellaria 
irregularly rounded, but having slightly curved borders (confirmed). 
Eggs measuring 0-02-0-022 x 0-011-0-012 mm. (0-025-0-027 x 0-011- 
0014 mm.). 

Hemiurus rugosus Looss, 1907. (Fig. 46 D.) 

Hemiurus stossichi of Liihe, 1901, nee Apoblema stossichii Monticelli, 1891. 

Under this name Looss (1907, p. 591 ; 1908, pp. 105-6, PI. 7, figs. 
4, 5) described a trematode from the stomach of the pilchard 
(sardine) at Trieste which does not seem to differ significantly from the 
previous species. Size : about 3 mm. long when contracted, 4 mm. 
when extended, the breadth and thickness of the contracted trematode 
0-4-0-6 mm., the body tapering anteriorly. Cuticle : annuli extend- 
ing on the dorsal surface to a level below the testes, generally to some- 
where near the ovary. Suckers : ventral half as large again as the 
oral; diameters 0-24—0-28 and 0-17-0-19 mm. Reproductive systems : 
hermaphrodite duct about half as long again as the breadth of the 
oral sucker ; sinus sac notably slender. Wall of the anterior part of 
the seminal vesicle comprising simple bundles of muscles. Vitellaria 
deeply cleft to a variable extent, not evident hi compressed specimens. 
Eggs measuring 0-019-0021 x 0-011-0-012 mm. This species may 
come to be identified with H. ocreatus, and host affiliations suggest 
close relationship, if not specific identity. 

Hemiurus communis Odhner, 1905. (Fig. 46 I, J.) 

Distoma appendieulatum of Olsson, 1868 (p. 46), and of Juel, 1889 (p. 4), in 
part, nee Rudolphi, 1802 ; D. apjiendiculatum of Johnstone, 1907 (p. 180, 
fig. 14. 

Hosts : in Britain, common sea bream, father lasher, long-spined 
cottus, red gurnard, yellow gurnard, grey gurnard, streaked gurnard, 
angler, greater weever, horse mackerel, boar-fish, rock goby, butter- 
fish, cod, bib, poor cod, whiting, haddock, coal-fish, pollack, torsk, ling, 
halibut, long rough dab, common topnot, plaice, dab, flounder, ocean 
pipe-fish, eel, conger, cornish sucker, greater sand eel, lesser sand eel. 

Location : stomach. 



HEMITJRID^ 279 

Lebour (1908a) found two or three specimens of this species in 
each of four whiting, and solitary specimens in the father lasher and 
sand eel at Cullercoats. Nicoll (1915) recorded the occurrence of the 
trematode also in the father lasher, long-spined cottus, grey gurnard, 
butter fish, haddock, cod, sand eel, halibut and common eel at St. 
Andrews ; in the common sea bream, greater weever, angler, pollack, 
torsk, dab and halibut at Aberdeen ; in the cod, poor cod, pollack, 
coal- fish and long rough dab at Millport ; in the whiting and dab at 
Liverpool ; and in the common sea bream, boar fish, angler, long- 
spined cottus, grey gurnard, red gurnard, rock goby, cornish sucker, 
bib, poor cod, whiting, pollack, ling, greater sand eel, common top- 
knot and ocean pipe-fish at Plymouth. Baylis & Idris Jones (1933) 
also found the trematode in the ling, angler, whiting, streaked gurnard, 
conger and father lasher at Plymouth, Little (1929a) in the bib, 
whiting, cod, pollack, flounder, plaice, common sea bream and yellow 
gurnard at Galway. It is common in many Scandinavian fishes. 
According to Looss (1908, p. 106) this species is plumper than H. 
appendiculatus, 1-3 mm. long when the ecsoma is retracted, 2 mm. 
when it is extended, and 04-0-45 mm. broad. The annulations of the 
cuticle occur to a level near the end of the soma ventrally, but not 
behind the oral sucker dorsally, so that in profile the dorsal surface is 
smooth. The ventral sucker is almost twice as large as the oral, but 
both are smaller than in the previous species, their diameters about 
0-3 and 014 mm. Other characters include a fairly thick hermaphro- 
dite duct, which is about as long as the breadth of the ventral sucker, 
a bipartite seminal vesicle in which the anterior chamber has a thin 
wall, irregularly rounded vitellaria and eggs measuring 0019-0021 
X 10-0 01 2 mm. Johnstone's specimens were 5 mm. long and 
1 mm. broad, those described by Lebour (1908a, pp. 36-7, PL 4, figs. 
5-7) 2-8 mm. long and 0-5 mm. broad, and of many specimens which 
I have found in the whiting, bib, grey gurnard and angler at Plymouth, 
the largest was only 2-2 mm. long and 0-34 mm. in greatest breadth, 
the soma 1-4 mm. long and the extended ecsoma 0-8 mm. long. The 
following description is composite. Size : 2-5 mm. long and 0-3-1 
mm. broad, the fully extended ecsoma about one-half or two-thirds 
of the length of the soma. Shape : spindle-like when the ecsoma is 
fully extended, abruptly truncated posteriorly when the ecsoma is 
retracted, greatest breadth near the level of the vitellaria, or the ovary. 
Cuticle : conspicuously striated ventrally and laterally to the end of 
the soma, annuli barely extending behind the pharynx dorsally. 
Suckers : ventral less or more than twice as large as the oral according 
to the size of the body, diameters 0-13-0-17 and 0-25-0-4 mm., the 
ventral far behind the bifurcation of the gut, but hardly more than 
one-third of the length of the soma behind the oral. Gut : pharynx and 
oesophagus small, 004-008 mm. long. Caeca rather wide and extend- 
ing into the extended ecsoma for about one -half its length. Excretory 
system : median stem of the vesicle extending far into the soma, to a 
level just in front of the ovary. Lateral canals continuous just in front 
of the pharynx. Reproductive systems : genital pore slightly lateral, 



280 THE TREMATODA OF BRITISH FISHES 

at or in front of the level of the pharynx, sometimes near the posterior 
margin of the oral sucker. Sinus sac cylindrical, 0-2-0-3 mm. long, 
striated for the first three-quarters of its length, then covered with 
papillae. Pars prostatica long and pursuing a winding course. The 
gland-cells large and conspicuous, joining the hermaphrodite duct 
just behind the oesophagus, separated from the seminal vesicle by a 
sphincter. Seminal vesicle situated immediately behind the ventral 
sucker, divided into anterior and posterior parts, both thin-walled 
and spherical, the posterior slightly the larger. Vasa efferentia meet- 
ing the seminal vesicle separately. Testes globular, the anterior the 
smaller ; diameters 0-08 and 0-10 mm. ; generally situated slightly 
diagonally just behind the ventral sucker, but sometimes midway 
between this structure and the ovary. Ovary spherical, generally 
larger than the testes and situated in the ultimate one -third of the 
soma and, when the ecsoma is extended, about the middle of the body. 
Vitellaria globular or ovoid, smaller or about the same size as the 
ovary and situated slightly behind it. Uterus having capacious 
descending and ascending limbs formed into short and wide folds in 
the available space between and behind the gonads, co-extensive with 
the caeca into the extended ecsoma. Eggs very numerous, clear 
greenish-yellow, measuring 0-019-0-028 x 0-008-0-012 mm. (Notes : 
When the ecsoma is retracted the topographical positions of the various 
organs are much altered, most of the organs being then compacted into 
the anterior two-thirds of the region behind the ventral sucker. Indi- 
viduals with the ecsoma retracted or extended occur not only in the 
same host, but in the same location.) 

Genus APHANURUS Looss, 1907. 

Aphanurus stossichii (Monticelli, 1891) Looss, 1907. (Fig. 46 G, H.) 

Distomum ocreatum of Monticelli, 1887, Stossich, 1888, 1898, nee Rudolphi, 
1819. nee Olsson, 1867 ; Apoblema stossichii Monticelli, 1891 (pp. 512-6), 
PI. 4, figs. 2-4, 8, 9, 13, 15a, 16, 17) ; Hemiurus stossichi (Monticelli) of 
Luhe, 1901 ; Aphanurus virgula Looss, 1907, pp. 591-2 (1908, pp. Ill, 
159, PI. 9, figs. 15-66). 

This species has been found in the pilchard, anchovy, bogue, horse 
.nackerel and some other fishes at Naples and Trieste, and in "Sar- 
dinella aurita " in the Bay of Palma (Majorca). It occurs in the 
stomach and oesophagus of the hosts and I have already given a short 
description of it (Dawes, 1946). Should it appear in Britain, it would 
be readily recognizable by the generic characters, a distinctly and 
completely annulated cuticle, the lack of an ecsoma, the simple un- 
divided condition of the seminal vesicle and the fusion of the vitellaria 
into a single compact mass, which may be deeply incised, but is not 
lobed. 

Sub-family DiNURiNiE Looss, 1907. 

Three genera can be easily distinguished, Leciihocladium by the 
presence of an antero-dorsal " neck-hump " (Nackenbuckel), Dinunis 



HEMIURID^} 281 

and Ectenurus by the long and much- convoluted, or comparatively short 
and little convoluted lobes of the vitellaria, as well as by special 
characteristics of the prostate glands. 



Genus DINURUS Looss, 1907. 

In this genus there is a very well- developed ecsoma, a long and 
convoluted pars prostatica, an ejaculatory duct in which only a short 
region near the seminal vesicle is devoid of prostate gland cells, and 
very long and much convoluted vitelline tubules. 

Dinurus tornatus (Rudolphi, 1819) Looss, 1907. (Fig. 47 A-D.) 

Distoma tornatum Rudolphi, 1819 (pp. 684-5) ; Dinurus barbatus (Cohn, 
1903), Looss, 1907 (1908, pp. 118, 121, pi. 8, fig. 11 ; PI. 9, figs. 19-21) ; 
D. breviductus Looss, 1907 (1908, pp. 118-19, PI. 8, fig. 12 ; PI. 10, figs. 22-3) ; 
D. longisinus Looss, 1907 (1908, pp. 119-23, PI. 8, fig. 13; PI. 10, fi^s. 
24-5). 

Hosts : pelamid, Coryphcena equisetis, C. hippuris. 
Location : stomach. 

This species has not been found in Britain, though it probably 
occurs here, having been recorded for the Red Sea, the Atlantic and 
the eastern coast of North America. According to Looss (1907, pp. 
593-4 ; 1908, p. 117, PI. 8, figs. 9, 10 ; PI. 9, figs. 17, 18) "D. tornatus " 
is up to 3-7 mm. long and 1-2 mm. broad with the ecsoma retracted, 
2-4-5 mm. long and 0-8-1-3 mm. broad with this structure extended ; 
the suckers are of almost equal sizes. In the main the diameters are 
0-5-0-7 mm. (oral) and 0-6-0-8 mm. (ventral), but in specimens of 
medium size 0-4 and 0-5 mm. and in small specimens 0-3 and 0-4 mm. 
Annuli of the cuticle commencing dorsally near the ventral sucker, 
but antero-dorsal region smooth or only finely striated in small speci- 
mens. The sinus sac and hermaphrodite duct reach back respectively 
to the anterior and posterior borders of the ventral sucker when the 
body is extended, and the false cirrus is equipped with cuticular 
hooklets, but not abundantly. The eggs measure 0018-0020 x 
12-0 01 5 mm. "Dinurus barbatus " was said to differ from D. 
tornatus in size (Cohn giving the length of the body as 9-5 mm., Looss 
the dimensions as 7 x 0-4-0-6 mm.) and the presence of lobes of cuticle 
between the suckers, although such outgrowths are evident only in 
specimens more than 3-7 mm. long, so that their true presence or 
absence could not be determined in D. tornatus. Other differences 
were said to include a short and thick sinus sac measuring 0-3 X 0-1 
mm. and situated in front of the ventral sucker; suckers of less equal 
sizes (diameters 0-63-0-7 and 0-45-0-55 mm.) and slightly larger eggs 
(dimensions 0-02-0-022 x 0-015 mm.). These differences are com- 
patible with the larger size of the body in " D. barbatus" and host 
affiliations also suggest synonymity. Of "D. breviductus " all that 
can be said is that while it is of the same size as "D. barbatus " the 
suckers are more dissimilar (diameters 0-6 and 0-3 mm.) and the eggs 



282 



THE TREMATODA OF BRITISH FISHES 



somewhat smaller (dimensions 0-018-0-020 x 0-012-0-014 mm.). The 
host of this form is the pelamid, in which "D. tornatus " was also 




Fig. 47. — A, Dinurus tornatus. B, C, "D. barbatus." D, "Z). brewductus.' 
E, Lecithocladium excisum. F, Ectenurus lepidus. (After Looss, 1908.) 



found. According to Looss, "D. longisinus " is very similar to "D. 
breviductus" but has a relatively longer genital atrium and small eggs 
measuring 0017-0010 x 0011-0013 mm. The host was Cory- 



HEMITTRIDiE 283 

phcena hippuris, in which "D. tornatus " was also found. Taking all 
these forms into consideration the range of variation in the sizes of the 
eggs is 0-017-0022 x 001 1-0015 mm., which is inconsiderable. But 
the range is probably much greater, because in specimens collected 
by Linton (1940, pp. 141-2) near Woods Hole, the dimensions of the 
eggs were 0-013-0015 x 0009 mm. 



Genus ECTENURUS Looss, 1907. 

This genus is distinguished from Dinurus mainly by the limitation 
of prostate gland-cells to a short region of the ejaculatory duct, the 
main part of which is free of them, and by the short and only slightly 
convoluted lobes of the vitellaria. 



Ectenurus lepidus Looss, 1907. (Fig. 47 F.) 

Host : horse mackerel. 
Location : stomach. 

Nicoll (1915) recorded the occurrence of this trematode in the horse 
mackerel at Aberdeen. On the Continent (at Trieste) it occurs when 
mature in the Spanish mackerel, angler and other fishes as well, and 
when immature in the red band fish and other fishes. According to 
Looss (1907, p. 597 ; 1908, p. 124, PL 8, fig. 14, PI. 10, figs. 26-7, 
PL 13, fig. 46) it is about 2 mm. long and 0-25-0-3 mm. broad and thick 
and has a pair of small dorso-lateral outgrowths of the anterior ex- 
tremity, each situated on an underlying cellular pad. The annulations 
of the cuticle are absent from the ventral surface between the suckers 
and from the postero-dorsal surface. The ventral sucker is more 
than twice as large as the oral and generally has a wide opening, the 
diameters of the suckers being 0-2-0-3 and 0-08-0-12 mm. The sinus 
sac is very short and thick, at most reaching back only as far as the 
anterior end of the ventral sucker, and the genital atrium is even 
shorter. The posterior half of the ejaculatory duct adjacent to the 
seminal vesicle is devoid of prostate gland-cells, and the vesicle itself is 
situated behind the ventral sucker. The eggs are almost colourless, 
and measure about 0-02 x 0-01 mm. A closely related American 
trematode, Ectenurus virgula, was described by Linton (1910, pp. 
63-4, fig. 148), and further information about it can be found in a later 
paper by Linton (1940, p. 142, PL 8, fig. 78). 



Genus LECITHOCLADIUM Liihe, 1901. 

Trematodes of this genus are of medium or fairly large size, have a 
well- developed ecsoma, a deep oral sucker in which the short ventral 
border has a median ventral lip with two lateral indentations, a " neck- 
hump," a long and cylindrical pharynx, a long and tubular sinus sac, 
a simple cylindrical seminal vesicle with a thick muscular wall and 
long and convoluted lobes in the vitellaria. 



284 THE TREMATODA OF BRITISH FISHES 



Lecithocladium excisum (Rudolphi, 1819) Liihe 1901. (Fig. 47 E.) 

Distoma excisum Rudolphi, 1819 (pp. 112, 411-12, 685) ; Lecithocladium 
excisiforme of Colin, 1902 (pp. 54-5, PI. 3, fig. 8) ; Distoma cristatum 
Rudolphi, 1819 (pp. 117-18, 422-3) ; Lecithocladium cristatum (Rudolphi) 
Looss, 1908 (pp. 133-4, PI. 11, figs. 30-1, PI. 13, figs. 44-5) ; ? Distomum 
crenatum Molin (1859, pp. 840-2, PI. 1, fig. 3) [nee Pud., 1809] ; ? Lecithocla- 
dium crenatum (Molin) of Looss, 1907 (1908, pp. 134-5 ); ? Lecithocladium 
gulosum (Linton) of Looss, 1907 (1908, p. 135) of Johnstone, 1906 (pp. 175-7, 
fig. 23 C), and of Linton, 1940 (pp. 143-4, PI. 8, figs. 79-82). 

Host : mackerel. 
Location : stomach. 

Nicoll recorded this trematode several times, in 1910 at Millport, 
in 1914 at Plymouth, and in 1915 at Aberdeen and Liverpool. John- 
stone (1906, pp. 175-7, fig. 23c) described the " Liverpool " specimens, 
about six found in a mackerel caught near Walney Island, Barrow-in- 
Furness. Baylis & Idris Jones (1933) also found it at Plymouth. 
Outside British waters the mature trematode has been found in both 
the mackerel and the Spanish mackerel, immature specimens in the 
horse mackerel, bogue, angler, red band fish and other fishes. The 
trematode is widely distributed, specimens having been found at 
Trieste, Naples and Rimini, in the Baltic, Japan and U.S.A. 

Johnstone's specimens were unusually large. Size : 10 mm. long 
and 1-1 mm. broad at the ventral sucker. Cuticle : annuli extending 
round the body, shown as far back as the level of the testes. Shape : 
spindle -like, tapering gradually to a fine point behind the gonads and 
vitellaria, the neck-hump not mentioned or figured. Suckers : ventral 
smaller than the oral, their centres 1-8 mm. apart, oral 0-6 mm. broad 
and having two notches on its ventral lip, ventral globulai, 0-5 mm. 
diameter, its opening 0-24 mm. diameter. Gut : pharynx elongate. 
(Esophagus short, terminating just in front of the ventral sucker. 
Caeca very long, almost reaching the posterior extremity. Repro- 
ductive systems : genital pore situated at the ventral margin of the 
oral sucker. Sinus sac very elongate, shown extending to a point above 
the ventral sucker. Seminal vesicle (wrongly called " cirrus-pouch " 
in both text and figure) ovoid and situated far back in the body, just 
in front of the anterior testis. Pars prostatica long and convoluted. 
Testes situated one behind the other, in the fully extended condition 
near the middle of the body. Ovary somewhat farther back, separated 
from the posterior testis by a fold of the uterus, which is voluminous, 
its limbs extending far into the ecsoma. Vitellaria with long and 
thread-like outgrowths (" about half a dozen contorted tubes "), 
some of which embrace the ovary, but most of which are dorsal to 
it. Eggs measuring 0024 x 0-0135 mm. 

Much smaller specimens than Johnstone's have generally been 
found. According to Looss (1907, p. 598 ; 1908, p. 131, PI. 11, figs. 
28-9 ; PI. 12, figs. 35-6), but with the observations of Markowski 
(1933, p. 18, fig. 7) shown in parentheses : — Size : 3-4 mm. long 
(6 mm.) with the ecsoma retracted, or 6-8 mm. long with this region 
extended, 0-5-10 mm. broad and thick. Suckers : oral much larger 



HEMIUBIDiE 285 

than the ventral ; dimensions 0-65 x 0-5 mm. (0-585 x 0-225 mm.) 
and 0-35-0-45 mm. (0-45 x 0-42 mm. diameter. Cuticle having a 
characteristic curling or crinkling of the annuli (Krauselung) above the 
pharynx, except in specimens under 1-1-5 mm. in length (confirmed). 
Neck-hump feebly developed. Gut : pharynx 0-5 mm. long and 0-25 
mm. broad (0-495 x 0-225 mm.). Eggs measuring 0-02-0-022 x 0-010- 
0012 mm. (0-019-0-027 x 0-011 mm.). {Notes : Looss could not find 
in the cursory description and schematic figures of L. excisiforme by 
Cohn anything to indicate that this parasite of the mackerel is other 
than a contracted specimen of L. excisum. Looss also stated that L. 
cristatum is about the same size as L. excisum, but has more equal 
suckers (dimensions 0-5 x 0-4 mm. (oral) ; 0-45 mm. diameter 
(ventral)), the oral being cup-shaped, a smaller pharynx measuring 
0-4 x 0-2 mm., a well-developed and constant neck-hump, no crinkly 
annuli above the pharynx, and somewhat smaller eggs measuring 
0-018-0-019 X 0-009-0-011 mm. All these differences are of very 
doubtful specific value, and L. cristatum must be regarded as a synonym 
of L. excisum. It was first found in Stromatceus fiatola at Trieste. 
Looss showed that both L. crenatum and L. gulosum were incompletely 
described and sp. inq. The former was discovered in Centrolophus 
pompilius ; the latter has been found in a number of fishes near Woods 
Hole (see Linton, 1940). Other species of Lecithocladium occur in 
America, China, Japan and India. Srivastava (1942) described two 
Indian species in great detail and listed eight others, regarding L. 
excisiforme Cohn as a valid species and proposing other taxonomic 
changes in the genus. 



Sub-family Sterrhurin^e Looss, 1907. 

In three genera of this group there is a small invagination, or 
pre-somatic pit, in front of the ventral sucker ; in Brachyphallus it is 
a transverse, slit-like depression, but in Leciihochirium and Synapto- 
boihrium small and circular, although these two genera can be distin- 
guished, though not easily, by the presence or absence of ventro-lateral 
thickenings in the wall of the oral sucker and of a well-defined dorsal 
lip. In two genera the pre-somatic pit is absent, but in one of them 
(Plerurus) there is a deep concavity between the suckers and the eggs 
are only half as broad as long, while in the other (Sterrhurus) no such 
concavity exists and the eggs are almost spherical. 



Genus STERRHURUS Looss, 1907. 

{Leciihochirium Liiho, 1901, in part.) 

Three species of this genus occur in Europe, but not in Britain, 
and 8 species are said to occur in America. I have already given some 
particulars about the former and the names of the latter (Dawes, 1946). 



286 THE TREMATODA OF BRITISH FISHES 

Sterrhurus fusiformis (Liihe, 1901) Looss, 1907. (Fig. 48 G.) 
Lecithochirium fusiforme Liihe, 1901 (pp. 476, 480, 485, fig. 3). 

Hosts : conger, angler. 

Location : stomach and intestine. 

Baylis & Idris Jones (1933) recorded the occurrence of this 
trematode in both the hosts mentioned at Plymouth, where I have 
found it in the angler. Rees & Llewellyn (1941) found it in the 
conger on the Irish Atlantic slope. D. O. Jones (1943, pp. 52-5, figs. 
7, 8, 10, 11) described a specimen from the conger in an unspecified 
locality, either Millport or Millford Haven. The trematode has also 
been described bv Looss (1907, p. 602 ; 1908, p. 143, PI. 13, fig. 52 ; 
PI. 14, figs. 55, 56), Mathias (1934, pp. 574-6, fig. 4) and others. It 
occurs in the Mediterranean and in U.S.A. 

Size : 3-6 mm. long and 1-1-1-9 mm. broad when the ecsoma is 
retracted, the ecsoma being up to half of the total length in living 
specimens, but contracting to much more insignificant proportions 
when fixed. Colour pale rose or flesh- colour, yellowish anteriorly. 
Shape : tapering gradually towards the anterior end, abruptly trun- 
cated at the termination of the soma, ecsoma tapering gradually. 
Suckers : ventral more than twice as large as the oral and situated 
0-7-1-2 mm. behind it ; diameters 0-5-0-7 and 0-2-0-3 mm., the dorsal 
lip and ventro-lateral thickenings of the oral sometimes insignificant. 
Oral sucker having a pair of extrinsic muscles originating in the ventral 
musculature of the body and inserted in the postero-lateral border. 
Ventral sucker having 7 pairs of similar muscles and an additional 
anterior bundle ; 2 pairs are antero-lateral, the remaining pairs 
lateral, 2 of them dorsal and 3 ventral, all the muscles arising in the 
general musculature of the body wall. Gland-cells located in the 
parenchyma beneath the general musculature, particularly near the 
dorsal lip of the oral sucker and ventrally between the suckers. Gut : 
pharynx 0-11-0-14 mm. diameter. (Esophagus very short. Caeca long, 
but not entering the ecsoma. Reproductive systems : genital pore 
slightly behind the level of the oesophagus, sinus sac spherical and 
larger than the pharynx. Seminal vesicle large and club-shaped, but 
folded. Pars prostatica well developed, the gland-cells surrounding the 
sinus sac. Testes and ovary transversely oval in outline ; dimensions 
0-3 X 0-25 mm. and 0-4 x 0-3 mm. Vitellaria comprising rather 
narrow, tapering processes, sometimes forked at their tips, generally 
numbering 7, arranged like a rosette just behind the ovary and 
measuring 0-5-0-75 x 0-1-0-15 mm. Eggs thick-shelled, deep brown 
in colour, measuring 0-018-0-024 x 0-013-0-018 mm. 

Genus LECITHOCHIRIUM Liihe, 1901. 

(Ceratotrema Idris Jones, 1933, in part.) 

Looss distinguished this genus from Sterrhurus mainly by the 
configuration of the anterior extremity of the body, the oral sucker 
having two lateral and inwardly-projecting thickenings of the ventra 



hemiurid^: 287 

border, and generally overhung by a well- developed lip which is generally 
wide and round, but may be angular. Other distinctive characters 
are the pre-somatic pit between the suckers and the undivided lobes 
of the vitellaria, which are short and stout. Lloyd (1938) regarded the 
presence of the pre-somatic pit as the most critical diagnostic character. 



Lecithochirium rufoviride (Rudolphi, 1819) Luhe, 1901. (Fig. 48 A-C.) 

Distoma rufoviride Rudolphi, 1819 (pp. 110, 406-7); Hemiurus rufoviridis 
(Rudolphi) of Looss, 1899 (pp. 641, 730) ; Distomum ocreatum Molin of 
Johnstone, 1907 (pp. 177-80, fig. 13). 

Hosts : angler, eel, conger. Metacercarise showing metagenesis in 
the shanny. 

Location : stomach. Metacercarise encysted on the abdominal 
viscera, mainly the intestine and liver. 

Johnstone (1907) found this species in the conger in the Irish Sea, 
and it has been recorded in the same host in various localities, by 
Nicoll (1910) at Millport and (1914) at Plymouth, also (1915) at 
Aberdeen. Nicoll found the species commonly in the eel and conger 
at Plymouth, where it was found for the first time in the angler. It 
has since been found in the conger several times, by Little (1929a) at 
Galway, Baylis (1928) at Guernsey, by Baylis & Idris Jones (1933) 
at Plymouth, by Rees & Llewellyn (1941) on the Irish Atlantic 
Slope, and by D. O. Jones (1943) either at Millport or Milford Haven, 
or at both these places, the precise locality being unstated. I have 
found it in the angler at Plymouth and it occurs at Naples. According 
to Nicoll (1914, p. 486) the cysts in the shanny are brown in colour and 
0-7-1-4 mm. diameter, the enclosed trematode about 2 mm. long when 
the ecsoma is retracted. The suckers are well developed, 0-28 mm. 
and 0-4 mm. diameter, and the genital organs functional, fairly numerous 
eggs measuring about 0-015 X 0-009 mm. occurring in the uterus. 
Looss (1908, p. 148) found encysted larvae of a related species in pipe- 
fishes. A brief description of specimens from Naples was given by 
Looss (1907, pp. 602-3 ; 1908, p. 147, PI. 12, figs. 42, 43 ; PI. 14, 
figs. 57-59). Size : 4-5 mm. long and 1-1-5 mm. broad when the 
ecsoma is retracted, up to 7-5 mm. long when it is extended, young 
forms about to produce eggs measuring 3-3-5 x 0-5-0-6 mm. when 
the ecsoma is retracted. Suckers : oral only slightly smaller than the 
ventral ; dimensions in individuals of small, medium and large size 
0-3-0-4 mm. and 0-4^0-5 mm. (small), 0-6-0-7 mm. and 0-7-0-8 mm. 
(medium), 0-8 mm. and 1-0 mm. (largest). Reproductive systems : 
lobes of the vitellaria especially short, only as long as wide. Eggs 
measuring 0022 x 0013 mm. 

Johnstone (1907, p. 177, fig. 13) found more than 100 specimens 
in the stomach of a single conger caught nearly midway between 
Fleetwood and Douglas, I.o.M., noting that in life they are blood-red 
in colour. Fixed specimens were mostly 2-5-5 mm. long, but a 
mounted specimen 8 mm. long was 2-25 mm. in greatest breadth and 



288 



THE TREMATODA OF BRITISH FISHES 



had suckers 0-88 mm. and 0-92 mm. diameter and eggs measuring 
0024 x 0-013 mm. (stated as 0-025 mm. long on p. 179). The 




Fig. 48. A-C, Lecithochirium rufoviride. D, Synaptobothrium cavdiporum. 

E, Plerurus digitatus. F, Lecithochirium gravidum. G, Sterrhurus 
fusijormis. H, S. musculus ; I, the same as H, but with the ecsoma 
partly extended. (After Lcoss, 1908.) 



ventrolateral thickenings of the oral sucker are not specifically 
mentioned, but are clearly shown in the figure. Both the caeca and 
the folds of the uterus were confined to the soma. The gonads were 



HEMIURID^E 289 

nearly spherical, and the vitellaria had 3 lobes on one side and 4 on 
the other, but were of variable shape. 

My own specimens, found in the stomach of the angler at Ply- 
mouth, are clearly recognizable according to the above diagnoses, 
and show the following characters. Size (largest specimen) : total 
length with ecsoma half retracted, 61 mm. Soma 5 mm. long and 
1-6 mm. in greatest breadth at the anterior border of the ventral 
sucker. Ecsoma about 1-13 mm. long and 0-55 mm. broad, probably 
twice as long when fully protruded. Shape : fusiform, tapering 
gradually in a posterior direction behind the ventral sucker. Cuticle 
having very ill-defined annuli in the anterior region. Suckers of 
almost equal size ; dimensions 0-77 x 0-67 mm. (oral) and 0-79 x 
0-70 mm. (ventral), and with centres 1-17 mm. apart, though a folding 
of the caeca suggests that this distance might be increased during 
maximum extension. Ventro-lateral thickenings of the oral sucker 
very obvious in ventral view. Other characters can be neglected in 
view of what follows, showing close conformity. Jones (1943, p. 47, 
figs. 3-6) has provided a detailed re-description of L. rufoviride, from 
which the following characters are taken : — Colour : in life deep 
brownish -orange. Size : when extended 4-6 mm. long and 1-7 mm. 
broad, the ecsoma being half as long as the soma. Cuticle thickest 
between the suckers ventrally. Suckers one -third of the length of 
the body apart, the ventral only slightly larger than the oral, the 
musculature typical, comprising equatorial, meridional and radial 
fibrils. Oral sucker subterminal, almost circular and 0-7 mm. diameter, 
its aperture hexagonal, 0-3 mm. long and 0-5 mm. broad, the ventro- 
lateral thickenings 0-25 mm. in diameter, the overhanging lip 0-2 mm. 
long and flexed ventrally. From certain equatorial fibrils of its 
posterior margin a pair of muscles extend to the ventral integument, 
one on either side of the pharynx. Ventral sucker 0-79 mm. long and 
0-83 mm. broad, its aperture circular and 0-25 mm. in diameter. 
Extrinsic muscles of the sucker arranged 7 pairs, 1 anterior, 2 antero- 
lateral and 5 postero-dorsal. Presomatic pit resembling an accessory 
sucker, but having muscle fibrils indistinctly separated from the 
dense parenchyma and general musculature, with one pair of large 
oblique muscles originating in the dorsal body wall inserted in its 
antero-lateral borders. Gut : pharynx dorsal and posterior to the oral 
sucker and contiguous with it, globular, 0-3 mm. in diameter, com- 
posed mainly of radial fibrils, but having internal circular and external 
longitudinal as well, its cavity lined with cuticle. QEsophagus of 
irregular shape, short, thin-walled, having a cuticular lining and 
then circular and longitudinal muscle fibrils in turn, widening 
posteriorly into a pair of large sacs, limited from the caeca by a pair 
of sphincters. Caeca modified anteriorly into a pair of small globular 
chambers (Driisenmagen of Fuhrmann (1928)), the main part long, 
not quite reaching the ecsoma, mainly dorsal, but approaching the 
ventral surface posteriorly, having a columnar epithelial lining and 
then circular and longitudinal muscle fibrils in turn. Excretory 
system : pore at the tip of the ecsoma, guarded by a sphincter, the 

19 



290 THE TREMATODA OF BRITISH FISHES 

terminal part of median canal modified to form a bladder, the main 
part extending well into the soma anteriorly, approaching the level 
of the testes ; the lateral canals united above and behind the oral 
sucker. Reproductive systems : — Male : testes symmetrical, widely 
separated close behind the ventral sucker, longitudinally ovoid ; 
dimensions 0-33 x 0-29 mm. Vasa deferentia opening separately 
into a tripartite, S -shaped seminal vesicle situated entirely in front 
of the ventral sucker and terminating in a sphincter. Sinus-sac 
incomplete ; pars prostatica mainly lying free in the parenchyma. 
Ejaculatory duct provided with a terminal reservoir. Female : ovary 
on right or left some distance behind the testes, transversely ovoid ; 
dimensions 0-42 x 0-33 mm. Receptaculum seminis present, though 
part of the uterus functions as a receptaculum seminis uterinum, 
Laurer's canal absent. Vitellaria paired, close together below and 
behind the ovary, each having 3-5 short and thick lobes with broad 
bases. Uterus having descending and ascending limbs confined to 
the soma, extending approximately as far as the caeca. Metraterm 
narrower than the uterus, lined with cuticle and having inner circular 
and outer longitudinal muscle fibrils, at its middle a sphincter, around 
it dense glandular parenchyma. Eggs measuring 0018 x 0009 mm. 
(i.e. much smaller than Looss determined). 

Lecithochirium gravidum Looss, 1907. (Fig. 48 F.) 

Apoblema rufoviride (Rudolphi) of Juel, 1889 (p. 6, fig. 18). 

Host : conger. 
Location : stomach. 

The only British records of this species are those of Baylis (1928), 
at Guernsey, and Baylis & Idris Jones (1933), who 'found the 
trematode at Plymouth. On the Continent the mature trema- 
tode occurs at Trieste, Catania and in Sweden in the eel, conger, 
bass and other fishes, and the progenetic larvae in various Labridae, 
the greater pipe-fish and others. Looss (1907, p. 603 ; 1908, pp. 
148-9, PI. 14, fig. 63) gave the following diagnostic characters : — 
Size : 2-5-2-7 mm. long, but 2-9 mm. long when the ecsoma is 
extended, and 0-5-0-8 mm. broad. Suckers : oral smaller than the 
ventral ; diameters 0-17-0-25 and 0-3-0-43 mm. in small individuals, 
0-25-0-33 and 0-45-0-53 mm. in larger, and 0-45 and 0-75 mm. in 
the largest specimens. Vitellaria : lobes sometimes twice as long as 
thick, but in some instances indistinguishable from those of L. 
rufoviride. Eggs measuring about 002 x 0-018 mm. According 
to Looss, this species is distinguished from L. rufoviride by its smaller 
size and the different relative sizes of the suckers. He felt fairly 
certain of its validity, but had to admit that it is very similar to the 
previous species. 

Other species which have been assigned to this genus include 
L. conviva Liihe, 1901a (pp. 474, 476) (found in the conger and 
lodged in the Berlin Collection), L. copulans (Linstow, 1904) Odhner, 



HEMIURID^] 291 

1906 (pp. 59-66) (Synaptobothrium copulans Linstow, 1904 (p. 254, 
figs. 1-4)) from the scald-fish at Louvain (?) and L. physcon Liihe, 
1901a (p. 478), from the angler at Trieste. One other species 
(digitatum (Looss) of Liihe, 1901, which does not occur in Britain) is 
perhaps better placed in the genus Plerurus, and yet another is included 
in Lecithochirium for the first time. 

Lecithochiriumfurcolabiatum (E.I. Jones, 1933) nom. nov. (Fig. 50 H.) 
Ceratotrema furcolabia'a Idris Jones, 1933. 

Host : 5-bearded rockling. 

Location : ccelom ; attached to the parietal peritoneum, liver and 
intestine, and along the course of the portal vein. 

Fourteen specimens were found in one host, none in three hosts 
of the same species from the same locality, Wembury Bay, near 
Plymouth. In attempting to establish the generic distinction of the 
trematode E. I. Jones (1933, pp. 248-52, figs. 1-5) depended on five 
characters, three of which are not acceptable, namely the large size, 
the oval shape and side-by-side arrangement of the testes, and the 
nature of the pre-somatic pit. The remaining characters, a bifurcate 
lip at the anterior extremity and cushion-like thickenings of the oral 
sucker, may be taken as specific. Size : average length 7-7 mm., 
greatest breadth, 1-7 mm. Ecsoma seen only in a retracted condition. 
Colour reddish brown, mottled with green. Suckers : ventral only 
slightly larger than the oral ; mean diameters 0-77 mm. and 0-57 mm. 
Oral sucker subterminal, having 2 ventro-lateral thickenings and 
an ill-developed thickening of the median dorsal wall. Lip arising 
by a broad base from the antero-dorsal surface, having 2 knob-like 
processes capable of great extension, not overhanging the oral sucker. 
Pre-somatic pit not obvious in the living animal or hi whole mounts, 
evident in sections as a pit with a cellular base. Gut : pharynx 
elongate, dimensions 0-24 x 0-16 mm. (Esophagus very short. Cseca 
long, terminating at the level of the retracted ecsoma, and having 
reddish -brown contents. Excretory system : pore at the tip of the 
ecsoma ; terminal part of the median canal modified to form an ovoid 
bladder, the remaining part extending to the level of the testes, the 
lateral canals uniting above the pharynx. Reproductive systems : 
testes longitudinally ovoid, symmetrical and widely separated behind 
the ventral sucker; dimensions 0-72 x 0-45 mm. Vasa deferentia 
opening separately into the seminal vesicle, which is confined to the 
region in front of the ventral sucker. Ovary spherical, lateral and 
some distance behind the testes ; diameter 0-51 mm. Uterus having 
a small descending and a long ascending limb almost co-extensive 
with the caeca. Vitellaria located behind the ovary, somewhat 
variable, generally having 3 main lobes on the left and 4 on the 
right, arising from a common base, longer than broad and wider 
towards their free ends. Metraterm long, reaching almost to the 
ventral sucker. Eggs green, measuring 0-023 x 0-011 mm. 



292 THE TREMATODA OF BRITISH FISHES 

Genus SYNAPTOBOTHRIUM v. Linstow, 1904. 

(Lecithochirium Liihe, 1901, in part.) 

Some writers have considered this genus identical with Lecitho- 
chirium, but it seems to be distinct, comprising Sterrhurids having 
a globular oral sucker which is devoid of ventro-lateral thickenings, 
an ill-defined lip, a pre-somatic pit, reniform eggs, and distinctive 
genital ducts, which are short, narrow and cylindrical, not p3 T riform, 
and include a long metraterm and a long and tubular pars prostatica. 

Synaptobothrium caudiporum (Rudolphi, 1819) Looss, 1907. 

(Fig. 48 D.) 

Distoma caudiporum Rudolphi, 1819 (pp. 96, 370) ; Lecithochirium caudi- 
porum (Rudolphi) of Liihe, 1901.) 

Hosts : adults in John Dory, plaice, angler, yellow gurnard, brill, 
conger, cod, bib ; larvae in the shanny, ballan wrasse, gilt-head. 

Location : adults in the stomach, rarely the buccal cavity ; larvae 
encysted in the viscera, notably the wall of the intestine. 

The first record of this trematode in British waters was by Nicoll 
(1914), who found it in the John Dory, angler and yellow gurnard at 
Plymouth, and obtained encysted individuals from the ballan wrasse 
and gilt-head, later (1915), recording the occurrence of these also in 
the shanny at Plymouth. Little (1929a) found adults in the brill at 
Galway ; Baylis & Idris Jones (1933) found them in the brill, conger 
and yellow gurnard at Plymouth, where I have found them in 
the angler, plaice, bib and cod. The original specimens of 
Rudolphi came from the John Dory, but Looss found others in 
this host and also in the turbot, brill, angler, Spanish mackerel and 
" Platessa passer ." Outside Britain, the trematode occurs at Trieste 
and Rimini. Looss (1907, p. 604; 1908, p. 151, PL 11, figs. 32-3; 
PI. 12, fig. 37 ; PI. 14, fig. 67) described very small specimens about 
1 mm. long with a completely retracted ecsoma, and small specimens 
2-7 mm. long with a half extended ecsoma, the greatest breadth and 
thickness of these being 0-7 mm. The oral sucker is almost exactly 
half as broad as the ventral, the diameters 0-2 and 0-4 mm., or in 
small individuals just attaining sexual maturity 0-13 and 0-25 mm. 
Other characters noted were the long metraterm, extending to a 
point above the middle of the ventral sucker, the vitellaria having 
short and thick, almost finger-like and invariably outstretched lobes 
and the thin-shelled eggs, which are reniform in profile, measure 
0032 x 0013 mm. and contain when laid each a distinctive mira- 
cidium with a small and clear anterior space with a bright central dot. 

I have found this trematode easy to recognize on account of the 
tapering anterior region, the associated small size of the oral sucker, 
and the plumpness of the body, which is broadest near its middle 
and far behind the ventral sucker. My specimens from the plaice, 
bib and cod are no more than 1-5 mm. long, but those from the angler 
have the following characters : — Size : total length with the ecsoma 



HEMIURIDiE 293 

fairly well extended up to 4-4 mm. Length of the soma 3-17 mm. ; 
greatest breadth of soma and ecsoma 1-24 mm. and 0-63 mm. Cuticle 
having very few, fine and indistinct annuli in the anterior part of the 
soma. Suckers : oral markedly broader than long ; dimensions 
0-12 x 0-24 mm. Ventral transversely oval, 0-44 x 0-50 mm., their 
centres about 0-8 mm. apart, oral in some instances having slight 
indications of ventro-lateral thickenings. Gut : caeca extending into 
the ecsoma. Reproductive systems : gonads transversely ovoid, the 
ovary invariably slightly larger than the testes. Terminal parts of 
the genital ducts and seminal vesicle confined to the region in front 
of the ventral sucker. Vitellaria comprising about 7 lobes, variable 
in shape, sometimes very short and stumpy, or much longer than 
broad, club-shaped and having bifurcate tips. Uterus comprising 
numerous rather fine and very distinct folds, the more posterior of 
which penetrate into the ecsoma between the caeca. Eggs (measured 
after preservation) about 0-025 mm. long and 0015 mm. broad. 

Genus BRACHYPHALLUS Odhner, 1905. 
Mention has already been made of the wide cleft that represents 
the pre -somatic pit in this genus, other characters of which are a 
well-developed ecsoma, a globular oral sucker which is devoid of 
ventro-lateral thickenings, and an overhanging lip, annulations of the 
cuticle that have notched posterior margins and thus appear scale- 
like, and genital ducts which include a short and straight pars 
prostatica, a long metraterm, and compact or only slightly lobed 
vitellaria. 

Brachyphallus crenatus (Rudolphi, 1802) Odhner, 1905. (Fig. 36 D.) 

? Fasciola serrulata Muller, 1776 (see Goeze, 1782, p. 173); ? F. sabnonis 
Muller, of Goeze, 1782 (p. 173) ; F. crenata Rudolphi, 1802 (pp. 76-8, PI. 2, 
fig. 5a, b) ; Distoma crenatum Rudolphi, 1809 (pp. 404-5, PI. 5, fig. 1), nee 
Rudolphi, 1810, nee Molin, 1859 ; D. appendieidatum Rudolphi, 1819 
(pp. 404-6), in part ; Distomum ventricosum of Wagener, 1860 (pp. 166-72, 
PI. 8, figs. 1-7), in part ; Distomum ventricosum of Wagener, 1860 (pp. 166- 
72, PI. 8, figs. 1-7), in part; D. ocreatum of Olsson, 1868 (p. 48, PI. 5, figs. 
96-8), nee Rudolphi, 1819, nee Molin, 1861 ; Apoblema appendiculatum 
Monticelli, 1891 (pp. 502-8), in part ; A. appendieidatum Miihling, 1898 
(p. 21), nee Rudolphi, 1802 ; A. ocreatum Juel, 1899 (pp. 4-5) ; ? Distomum 
ocreatum of Linton, 1900 (PI. 35, figs. 16-24) ; Hemiurus crenatus (Rudolphi) 
of Liihe, 1901 (pp. 399-401). 

Hosts : lesser sand eel. 
Location : stomach. 

Nicoll (1907) recorded the occurrence of this trematode at St. 
Andrews, and it has not appeared anywhere in Britain since, although 
it occurs, according to Odhner (1905), in various fishes (father- lasher, 
dab, 3-spined stickleback, lesser sand eel, salmon, sea trout and 
smelt) in Scandinavia and has appeared in the Baltic, and also in 
Canada and U.S.A. Nicoll (1907, pp. 88-9) briefly described speci- 
mens 2-1-2-4 mm. long found at St. Andrews, and it was more fully 
described by Odhner (1905, p. 349, pp. 352-5, PI. 4, figs. 3-5) and 



294 THE TKEMATODA OF BRITISH FISHES 

Lander (1904, pp. 1-28, figs. 1-42). Markowski (1933, pp. 15-16, 
fig. 1) described specimens found in the Baltic, and American speci- 
mens have been described by Manter (1926, pp. 94-5, fig. 53) and 
Linton (1940, pp. 125-9, PI. 11, figs. 109-20). Odhner (1905) dealt 
with specimens up to 2-5 mm. long, but gave the length at the attain- 
ment of maturity as only 0-8 mm., mentioning also Olsson's determina- 
tion of maximum length as 5 mm. He also stressed, as Nicoll did 
later, that the fully-extended ecsoma is nearly as long as the soma, 
which varies only slightly in breadth (0-2-0-5 mm.), and that the 
suckers are of dissimilar size, the ventral half as large again or nearly 
twice as large as the oral, according to the size of the body. The 
eggs of his specimens measured 0024-0029 x 0-011-0-014 mm. 
The characters given by Looss (1907, p. 606 ; 1908, p. 157, PL 14, 
figs. 64-5) may be supplemented by those determined by Markowski 
(1933) and shown in parentheses, most of Nicoll's measurements 
being intermediate : — Size : about 2 mm. long (3-4 mm.) and 0-3 mm. 
broad and thick when the ecsoma is half retracted. (Colour : reddish.) 
Cuticle : annulated to near the end of the soma, but not at all between 
the suckers ventrally. Suckers : of nearly equal size, or the ventral 
slightly the larger ; diameters 0-18 and 0-15 mm. (dimensions 0-30 X 
0-225 and 0-30 x 0-195 mm.). (Gut : pharynx 0-105 mm. long and 
0-165 mm. broad. (Esophagus very short. Caeca long and wide, extend- 
ing into the ecsoma.) Reproductive systems : hermaphrodite duct very 
short, its length not more than one-third of the thickness of the body. 
The pars prostatica extending directly to the seminal vesicle, which 
ends above the middle of the ventral sucker (testes somewhat diagon- 
ally arranged, their diameters 0-18-0-30 mm. Ovary oval and measur- 
ing 0-3 x 0-18 mm.). Vitellaria compact, cruciform and flattened 
(globular ; their boundaries wavy). Eggs measuring 0-026 x 0014 mm. 
(0-016-0-025 x 0-011-0-014 mm.). The eggs of Nicoll's specimens 
came well within this range, but were 0-015-0-016 mm. broad. 

Sub-family Lecithasterin;e Odhner, 1905. 

The two genera of this group which have to be considered can be 
distinguished easily ; in Lecithaster the body is spindle-shaped, and 
the folds of the uterus are aggregated mainly just behind the ventral 
sucker ; in Aponurus the body is broad and cylindrical behind the 
ventral sucker and the folds of the uterus are situated mainly in the 
posterior region. 

Genus LECITHASTER Liihe, 1901. 

(Leptosoma Stafford, 1904 ; Mordvilkoviaster Pigulewsky, 1938.) 

Lecithaster confusus Odhner, 1905. (Fig. 49 A-C.) 

Ditto-mum mollissimum Levinsen of Stossich, 1889 (p. 29) ; Apoblema 
mollissimum of Looss, 1896, in part ; Hemiurus bothryophorus of Looss, 
1899 (pp. 641, 728-9), nee Distomum bothryophoron Olsson, 1869. 

This species occurs in the rectum of the herring and twaite shad, 
and has been recorded in Italy, Egypt, northern waters (Greenland) 



HEMIURIDiE 



295 



and on the Atlantic coast of North America, but not in Britain. 
According to Odhner (1905, p. 359) it is 1-1-5 mm. long and O-3-O-o 




Fig. 49.— A-C, Lecithasler confusus. D, E, L. stellatus. F, G, L. galeatus. 
H, I, Aponurus laguncula. (After Looss, 1908.) 

mm. in greatest breadth at the level of the ventral sucker, which is 
almost twice as large as the oral ; diameters 0-23-0-3 and 0-13-0-16 mm. 
The o-enital pore is situated relatively far forward, underneath the 



296 THE TREMATODA OF BRITISH FISHES 

pharynx, which is 0-07-0-085 mm. diameter. The sinus sac is 0-08- 
0-11 mm. long, the pars prostatica slightly longer than in L. gibbosus, 
and the seminal vesicle extends behind the ventral sucker. The 
lobes of the ovary are short and similar to those of the vitellaria, 
which is somewhat smaller and no more than 0-25 mm. diameter, 
and the eggs measure 0-015-0017 x 0007 mm. (misprinted as 
007 mm.). Looss (1908, p. 164, PI. 15, figs. 70-2) described specimens 
1-2 mm. long and 0-4 mm. in greatest breadth and thickness, stating 
that 1 mm. is a common length. The suckers of these specimens 
came within the range specified by Odhner and the eggs were of the 
same length, but 0-009 mm. broad. Other characters mentioned by 
Looss were the long pars prostatica, which causes the anterior part 
of the seminal vesicle to overlie the ventral sucker and the posterior 
part to extend behind it, the sparse and sometimes scattered prostate 
gland-cells, the 4-lobed ovary with lobes having irregular borders, 
and the short and slightly lobed processes of the vitellaria. Linton 
(1940, pp. 132-5, PI. 11, figs. 121-4) described American specimens 
and fisted the hosts of this trematode near Woods Hole. Hunninen 
& Cable (19436) dealt with the small cystophorous cercarise, which 
are ingested by Acartia, so that metacercarise occur in the hsemoccele 
of the copepod, and with experimental infection of fishes which serve 
as the final host. They also gave good figures of the general structure 
of the adult (fig. 15) and of the excretory system (figs. 16-20). 

Lecithaster gibbosus (Rudolphi, 1802) Luhe, 1901. (Fig. 50 G.) 

Fasciola gibbosa Rudolphi, 1802 (pp. 81-2, PI. 2, fig. 7) ; Distoma gibbosum 
Rudolphi, 1809 (p. 399, PI. 6, fig. 8) ; D. bergense Olsson, 1868 (pp. 43-4, 
PI. 10, fig. 93) ; D. bothryophoron Olsson, 1868 (pp. 42-3, PI. 10, fig. 92), 
and of Linton, 1901 (p. 439, figs. 355-6) ; D. mollissimum of Levinsen, 
1881 (pp. 59-61, PI. 2, fig. 4), nee Stossich, 1899 ; Apoblema mollissimum 
(Levinsen) of Looss, 1896, in part ; Lecithaster bothryophorus (Olsson) of 
Stafford, 1904 (p. 484) ; Derogenes cacozelus Nicoll, 1907 (pp. 90-1, PL 3, 
fig. 10). 

Hosts : sprat, sea trout, smelt, gar-fish, John Dory, comber, horse 
mackerel, whiting, red band fish, ballan wrasse, lesser weever, 
dragonet, 2-spotted goby, red gurnard, grey gurnard, halibut, long 
rough dab, sole, flounder, dab, plaice, norwegian topknot, lesser 
sand eel. 

Location : intestine, rarely stomach or rectum. 

This trematode has been recorded many times in Britain. Nicoll 
(1907) found it in the lesser sand eel, halibut and dab at St. Andrews ; 
Johnstone (1907) got it from the gar-fish on the coast of Lancashire, 
Lebour (1908a) from the grey gurnard and whiting at Culler coats ; 
Nicoll (19096) from the dragonet, smelt and sprat at St. Andrews, 
also (1910) from the red gurnard, 2-spotted goby, ballan wrasse, 
whiting and long rough dab in the Firth of Clyde, and (1914) from 
the comber, horse mackerel, lesser weever, red gurnard, John Dory, 
whiting and norwegian topknot at Plymouth. Nicoll (1915) also 
recorded the occurrence of the trematode in the horse mackerel, 



HEMIURIDiE 297 

John Dory and sea trout at Aberdeen. Little (1929a) found it in 
the flounder and plaice at Galway, Baylis & Idris Jones (1933) 
in the red band fish, and, in an immature condition, in the norwegian 
topknot at Plymouth. Odhner (1905, p. 358) outlined the following 
specific characters: — Size: 1-1-75 mm. long and 0-33-0-55 mm. in 
greatest breadth near the ventral sucker. Suckers : ventral nearly 
twice as large as the oral ; diameters 0-18-0-25 and 0-1-0-14 mm. 
Pharynx : 0-07-0-08 mm. diameter. Reproductive systems : genital 
pore situated beneath the bifurcation of the gut, rather nearer the 
oral than the ventral sucker. Sinus sac about 0-1 mm. long. Pars 
prostatica so long that the seminal vesicle comes to overlie the ventral 
sucker, but without over-reaching it. Lobes of the ovary hardly 
longer than broad, those of the vitellaria somewhat longer. Vitellaria 
about twice as large as in L. confusus ; diameter 0-35-0-5 mm. Eggs 
measuring 0-025-0-027 x 0-013 mm. Looss (1908, p. 164) regarded 
the differences between this species and L. confusus as the larger 
size, smaller suckers, larger eggs, shorter pars prostatica and seminal 
vesicle and longer lobes of the vitellaria. He gave specific characters 
closely similar to those of Odhner. 

Nicoll's immature specimen from the sand eel was damaged, but 
some general characters were noted, the 7- or 8-rayed vitellaria and 
the small caudal appendage. His specimens from the halibut and 
dab (described as Derogenes cacozelus sp.n.) were small, 0-9-1-5 mm. 
long, and the oral and ventral suckers of the largest measured 016 
and 0-23 mm. diameter, the latter being situated 0-6 mm. from the 
anterior extremity. The eggs of these specimens were notably small, 
measuring 0-021-0-023 X 0014-0016 mm. 

Johnstone's specimens from the gar-fish at Foulney Island were 
very briefly described (1907, pp. 185-6, fig. 16) as Distoma mollissimum 
and about 1-5 mm. long, but the figure shows the characteristic lobes 
of the vitellaria. Lebour (1908a), pp. 34-5, PI. 4, fig. 3) gave a lucid 
description of the delicate and fragile specimens found in numbers 
in the whiting and grey gurnard. Size : generally about 1-2 mm. 
long and about 0-4 mm. broad. Colour : transparent and colourless 
except for the eggs. Shape : spindle-like, the posterior end of the 
body slightly constricted, presenting the appearance of a short and 
protruded ecsoma. Suckers : ventral twice as large as the oral and 
situated in front of the middle of the body ; diameters 0-20 and 0-10 mm. 
Gut : pharynx 006 mm. long. (Esophagus very short. Caeca narrow 
and extending nearly to the posterior extremity. Excretory system : 
median stem of the vesicle meeting the lateral canals near the middle 
of the body. Lateral canals uniting behind the pharynx. Reproductive 
systems : genital pore median at the level of the oesophagus. Testes 
globular, situated above and just behind the ventral sucker (shown 
in PI. 4, fig. 3, at different levels and displaced towards the right). 
Vasa deferentia short and meeting the seminal vesicle separately. 
Pars prostatica well developed, the accompanying gland- cells large. 
Seminal vesicle large and spherical, situated on the left of the ventral 
sucker (and, judging by the figure, extending slightly behind it). 



298 THE TREMATODA OF BRITISH FISHES 

Ovary 4-lobed, the lobes short. Receptaculum seminis large and ovoid ; 
oviduct short. Uterus having much folded limbs, the folds shown 
overstepping the left, but not the right caecum. Vitellaria forming a 
7-lobed mass situated behind the ovary, the lobes very much longer 
than those of the ovary. Eggs pale greenish -brown and small, but 
their sizes not specified. (Note : American specimens of this species 
have been described by Manter (1926, pp. 95-6, fig. 61) and Linton 
(1940, pp. 135-6, PI. 11, figs. 125-6), and according to the latter writer 
the eggs vary in size much more than Odhner believed, their dimen- 
sions being 0-024-0036 x 0015-0-018 mm.) 

Two other species of Lecithaster which have not appeared in 
Britain must be mentioned briefly ; they are L. stellatus Looss, 1907 
(pp. 606-7 ; 1908, p. 165, PI. 14, fig. 66 ; PI. 15, figs. 75-6) and L. 
galeatus Looss, 1907 (p. 607 ; 1908, p. 165, PI. 15, figs. 73-4). The 
former was found in the gar-fish, dentex and " Mcena vulgaris " at 
Trieste and the latter in the golden grey mullet on the coast of Egypt. 
I have reproduced drawings of these species in Fig. 49, D, E and 
F, G respectively, and only the main distinguishing characters need 
be noted here. L. stellatus is 1-1-3 mm. long and 0-36 mm. broad 
and thick, with oral and ventral suckers 0-08-0-1 and 0-17-0-2 mm. 
diameter and eggs measuring 0-015-0-017 x 0-009-0-010 mm. L. 
galeatus is much smaller, 0-4-0-45 mm. long, 0-12-0-14 mm. broad 
and 0-1-0-12 mm. thick, with suckers 0-05-0-055 and 0-1-0-12 mm. 
diameter and eggs measuring 0-017-0-019 X 0010-0011 mm. Other 
differences concern the pars prostatica, which is longer in L. stellatus, 
and the ovary, which is not lobed in L. galeatus, but the most notable 
difference concerns the vitellaria, which have long lobes reaching 
the ventral sucker and the posterior extremity in the former, but 
short lobes not significantly larger than the eggs in the latter species. 
As regards the characters of the vitellaria, these two species seem to 
represent extremes, and with the two previously mentioned species 
form a series, stellatus, gibbosus, confusus and galeatus. Making 
allowance for variability due to differences in the size of the body, it 
seems more than likely that some of these species will fall ultimately, 
but all are entitled to stand in the present state of our knowledge, 
and at least until more is known about the growth of L. gibbosus. 
One other species of Lecithaster, L. tauricus Pigulewsky, 1938, occurs 
in the gut of the anchovy in the Black Sea, and other species occur 
in America and Japan. 



Genus AP0NURUS Looss, 1907. 

Two species of this genus occur in Europe, but not in Britain, 
although they may appear here. A. laguncula Looss, 1907, occurs 
in the stomach and oesophagus of the gar-fish, anchovy, greater 
weever, red mullet and other fishes at Trieste, and I have shown it 
in Fig. 49 H, I. According to Looss (1907, p. 608 ; 1908, p. 169, 
PL 13, figs. 53-4 ; PI. 15, figs. 77-8) full-grown and extended specimens 
are about 1 mm. long and 0-25 mm. in greatest breadth and thickness, 



HEMIURID^E 299 

with ventral and oral suckers about 0-2 and 0-1 mm. diameter, or 
only Oil and 006 mm. in specimens just attaining maturity. Other 
distinctive characters are the length of the pars prostatica, which 
equals that of the sinus sac, the shortness of the seminal vesicle, 
which scarcely extends behind the anterior margin of the ventral 
sucker, the globular lobes of the vitellaria and the large eggs measuring 
about 0-027 x 0-016 mm. The species A. tschuginovi Vlasenko, 1931, 
is a parasite of the red mullet in the Black Sea, A. vitellograndis 
Layman, 1930, occurs in eastern Russia, A. trachinoti Manter, 1940, 
in Mexico, and A. sp. Linton, 1940, at Woods Hole. 

Genus inq. LECITHOPHYLLUM Odhner, 1905. 

According to Odhner, the distinctive characters of this genus are 
the position of the genital pore at the hinder margin of the oral sucker, 
the long genital sinus (which is three times as long as in Lecithaster) , 
and longer pars prostatica, the non-lobate ovary and the large and 
thick-shelled eggs, which are about 006 mm. long. 

Lecithophyllum botryophorum (Olsson, 1868). 

Distoma botryojihoron Olsson, 1868 (p. 42) ; D. (Brachylaimus) botryophoron 
(Olsson) of Stossich, 1886 (p. 57). 

Host : argentine (Argentina sphyrcena). 

Location : intestine. 

Nicoll (19096) recorded the frequent occurrence of this species in 
fair numbers (up to 50 specimens in a host) at St. Andrews, but did 
not describe it. Odhner (1905, pp. 359-60) gave the host as Argentina 
silus and the specific characters as follows: — Size : about 2-3 mm. 
long and 0-4-0-5 mm. in greatest breadth near the ventral sucker. 
Shape : anterior region tapering, posterior region of almost uniform 
breadth, the extremity rounded. Suckers : ventral much larger 
than the oral and situated about one-third of the distance along the 
body; diameters 0-25 and 0-15 mm. Pharynx: about 0085 mm. 
diameter. Reproductive systems : sinus sac about 0-3 mm. long, 
almost reaching the anterior border of the ventral sucker. Pars 
prostatica only half as long (0 17 mm.). Seminal vesicle hardly extend- 
ing behind the middle of the ventral sucker. Ovary not lobed, 
0-12 mm. diameter. Vitellaria situated midway between the ventral 
sucker and the posterior extremity, 0-28 mm. diameter. Recep- 
taculum seminis large. Eggs of golden colour, very large, measuring 
0055-0063 x 0026-003 mm. 

Sub-family Derogenetin^e Odhner, 1927. 
Two genera which have to be considered can be distinguished by 
the relative position of the ventral sucker and the shape of the eggs. 
In Derogenes the sucker is situated in the posterior half of the body 
and the eggs are ovoid ; in Derogenoides the sucker is situated slightly 
in front of the middle of the body, and the eggs are drawn out into a 
sharp point at the anopercular pole. 



300 THE TEEMATODA OF BRITISH FISHES 

Genus DEROGENES Liihe, 1900. 

Other distinctive characters of this genus are the spindle-like 
body, which is devoid of an ecsoma, the posterior position of the 
gonads and vitellaria, the small sinus sac, straight pars prostatica 
and unconfined prostate gland- cells, a long and much-folded uterus 
and relatively large and thick-shelled eggs. 

Derogenes various (Muller, 1784) Looss, 1901. (Fig. 50 A, C.) 

Fasciola varica Muller, 1784 (pp. 93-4, PI. 72, figs. 8-11), and of Rudolphi, 
1802 ; Distoma varicum of Rudolphi, 1809 (pp. 396-7) ; D. dimidiatiim 
Creplin, 1829 (pp. 55-6), in part ; D. varicum (Muller) of Olsson, 1868 (p. 40), 
and of Levinsen, 1881 (pp. 54-6, PL 2, figs. 1, 2), vec Monticelli, 1890 ; 
Derogenes minor Looss, 1901 (pp. 437-9, fig. 5) ; D. plenus Stafford, 1904 
(p. 484) ; D. fuhrmanni Mola, 1912 ; D. crassus Manter, 1934. 

Hosts : common sea bream, father lasher, long-spined cottus, pogge, 
yellow gurnard, red gurnard, grey gurnard, angler, greater weever, 
lesser weever, horse mackerel, boar-fish, John Dory, dragonet, lump- 
sucker, butterfly blenny, cod, bib, poor cod, whiting, coal-fish, pollack, 
ling, hake, 3-bearded rockling, torsk, halibut, long rough dab, turbot, 
brill, norwegian topknot, sole, flounder, dab, plaice, lemon sole, salmon, 
sea trout, grayling, sprat, conger, sturgeon. 

Location : stomach, sometimes intestine, oesophagus or buccal 
cavity, possibly due to migration or retroperistalsis. 

Nicoll (1907) recorded this species in the whiting, halibut, turbot, 
brill, dab. and father lasher at St. Andrews ; Johnstone (1907) in the 
whiting off the Cumberland coast ; Lebour (1908a) in the angler, grey 
gurnard, ling, long rough dab and dab at Cullercoats ; Nicoll (19096) 
in the dragonet, grey gurnard, cod and sprat at St. Andrews and 
(1910) in the father lasher, cod, whiting, poor cod, pollack, coal-fish 
and plaice at Millport. Later (1914) Nicoll found the trematode in 
28 species of fishes at Plymouth, and in 1915 he recorded its occurrence 
in 40 fishes in British waters. Little (1929a) found the trematode in 
the bib, pollack, hake, dab, plaice, brill, sole, common sea bream, 
grey gurnard and yellow gurnard at Galway ; Baylis & Idris Jones 
(1933) found it in the whiting, hake, yellow gurnard, red gurnard, 
angler and long-spined cottus at Plymouth, where I have found it 
myself in the plaice, pollack, bib, dragonet and whiting. It also 
occurs at Trieste and near Banyuls in the Adriatic and Mediterranean, 
in Canada and U.S.A., even in the Galapagos Isles. 

Odhner (1905, pp. 360-4, PL 4, figs. 6, 7) described specimens 
1-3 mm. long and about one-quarter as broad and thick, with oral 
and ventral suckers 0- 17-0-23 and 0-33-0-55 mm. diameter and a 
pharynx 0-075-0-13 mm. diameter. The vitellaria of these specimens 
were described as fairly rounded and slightly longer than broad, but 
not lobed, the eggs as golden-yellow and fairly large, 054-0 066 mm. 
long (mainly 0-058 mm.) and 0-028-0-033 mm. broad. Nicoll (1907, 
p. 90) specified 1-5-2 mm. as the most common length, but gave 
3-4 mm. as the upper extreme, mentioning the wide variation recorded 



HEMIURIDJE 



301 



by Stossich, who found specimens 1-5-7 mm. long. Johnstone's 
specimens were 2-2-5 mm. long and 0-56 mm. broad, with suckers 




Fig. 50. — A, Derogenes various. B, Genarches miilleri. C, "Derogenes 
minor." D, Derogenoides ovacutus. E, Hemipera ovocaudata. F, H. 
sharpei. G, Lecithaster gibbosus. H, Lecithochirium furcolabiatum. 
(A, B, after Odhner ; C, after Looss. 1901 ; D. E, after Nicoll, 1913 ; 
F, H, after E. I. Jones, 19336 ; G, after Lebour, 1908a.) 

0-2-0-27 and 0-4-0-43 mm. diameter. They were clearly described 
and figured (1907, pp. 188-92, fig. 18). Lebour (1908a, pp. 55-6, 



302 THE TREMATODA OF BRITISH FISHES 

PL 4, fig. 4) gave a brief but lucid description of relatively large 
specimens, the largest and commonest of which were found in the 
buccal cavity of the long rough dab. Size : on the average about 
4-5 mm. long. Suckers : ventral twice as large as the oral and 
situated behind the middle of the body ; diameters 0-6 and 0-3 mm. 
Gut: prepharynx absent. Pharynx 010 mm. (diameter). (Esophagus 
very short. Caeca very long. Excretory system : median stem of 
vesicle meeting the lateral canals just behind the ventral sucker ; 
lateral canals uniting dorsal to the " oesophagus " (misprint for 
pharynx, or oral sucker). Reproductive systems : genital pore 
situated just behind the oesophagus. Sinus sac small and globular. 
Pars prostatica long and straight, the gland-cells numerous. Seminal 
vesicle longitudinally ovoid. Testes globular and slightly asym- 
metrical, the left generally slightly in front of the right near the 
posterior margin of the ventral sucker. Ovary globular and situated 
on the left just behind and between the testes. Vitellaria ovoid, 
0-4 mm. long and situated midway between the ovary and the posterior 
extremity, slightly diagonally arranged. Eggs golden-yellow and 
very numerous, measuring 0059 x 0-033 mm! (0055 x 003 mm. 
according to Johnstone ; 0-056-0-060 x 0-027-0-034 mm. according 
to Nicoll). 

Specimens of my own taken from the plaice are 1-18-2-40 mm. 
long and 0-46-0-56 mm. in greatest breadth, and gave interesting 
information about the variability in size of the suckers and in the 
general proportions of the body. The oral sucker measured 0-22 mm. 
diameter in the smallest specimens, 0-24 mm. in the largest, the 
ventral sucker giving a corresponding range 0-36-0-44 mm. The 
oral thus diminishes in size relative to the length of the body (from 
0-19 to 0-10), the ventral likewise (from 0-30 to 0-18). The region in 
front of the ventral sucker in small specimens measures 0-47 mm., 
that behind this sucker 0-35 mm., these lengths corresponding to 
0-40 and 0-30 body-length. In the largest specimens the corresponding 
distances are 1-02 and 0-94 mm., representing 0-425 and 0-39 body- 
length. The suckers thus become relatively smaller with increase in 
size of the body, and the spaces between them and behind the ventral 
increase in relative extent. The same features were shown by small 
specimens from the pollack and bib, total length being 0-76-1-07 mm. 
and the ratios of the diameters of the suckers to the length of the 
body 0-145-0-12 for the oral and 0-41-0-30 for the ventral. The 
regions in front of and behind the ventral sucker respectively represent 
0-41-0-44 and 0-30-0-33 body-length. Differences in the sizes of the 
eggs were manifest. In small worms from the plaice their dimensions 
were 0050-0054 x 0030-0033 mm., in large worms from the same 
hosts more uniform, 0-050-0-051 x 0-031-0-032 mm. Taking into 
account specimens from other hosts (pollack, bib, dragonet and 
whiting) the full range of sizes of the eggs was 0-046-0-054 x 0*025- 
0-036 mm. Specimens dealt with by Odhner, Nicoll, Johnstone and 
Lebour, giving the dimensions of the eggs stated above, further extend 
the range, which becomes 0-046-0-066 x 0-025-0-036 mm. The eggs 



HEMIURIDiE 303 

of American specimens described by Manter (1926, p. 103, fig. 5) 
and Lloyd (1938, pp. 111-12, figs. 7-9) come within this size-range, 
but some specimens from Panama which Manter (1940a) described as 
Derogenes sp. had elongate eggs measuring 0-068-0069 x 0027- 
0029 mm., and Linton (1940) mentioned unusually broad eggs 
attaining a maximum of 0-039 mm. We see here the difficulties 
inherent in the use of the dimensions of the eggs as a criterion of 
specific distinction. 

Other species of Derogenes are of doubtful validity. D. minor 
Looss, 1901 (see my Fig. 50 C) was obtained from "Labrus merula " 
and was said to be not larger than 2 x 0-46 mm., with ventral and 
oral suckers 0-33 and 0-22 mm. diameter and eggs measuring 006 
X 0038 mm. The relative sizes of the suckers, like the wide cseca 
and the mulberry-like vitellaria, are unreliable criteria of distinction, 
and this form has been included in the synonyms of D. various. D. 
plenus Stafford, 1904, is another synonym, or a nomen nudum, because 
Miller (1941) could not find specimens of it in Stafford's collection. 
According to Odhner (1905) D. urocotyle (Parona, 1899) is a species 
inquirenda, and so, according to Liine (1901a), is D. affinis (Rudolphi, 
1819). One other species is D. ruber Liihe, 1900, which was discovered 
in the gall-bladder of the streaked gurnard and is the type of the genus. 

It is convenient to mention here Genarches mulleri (Levinsen, 1881) 
(Fig. 50 B), a trematode which closely resembles Derogenes various, 
except in the terminal parts of the genital ducts. This species was 
discovered in the father-lasher and the cod in Greenland. Odhner 
(1905, pp. 365-6, PI. 4, figs. 8, 9) described specimens found in the 
father- lasher on the east coast of Greenland (Franz Josef Fjord) and 
at King's Bay, Spitzbergen. 



Genus DER0GEN0IDES Nicoll, 1913. 

This genus differs from Derogenes in a number of characters, but 
mainly in the position of the ventral sucker slightly in front of the 
middle of the body, the cylindrical sinus sac, the short pars prostatica 
and the distinctive eggs having the anopercular pole drawn out into 
a sharp point. 

Derogenoides ovacutus Nicoll, 1913. (Fig. 50 D.) 

Host : greater weever. 
Location : stomach. 

Nicoll (1913a, p. 243, PI. 11, fig. 6) found numerous specimens in 
one host only, in association with a small number of specimens of 
Derogenes varicus, at Plymouth. This is the only record of the 
occurrence of the trematode in Europe, although another species, 
D. skrjabini Vlasenko, 1931, was found in the intestine of the 3-bearded 
rockling in the Black Sea. Size : 0-6-0-9 mm. long and about 
0-18 mm. in greatest breadth ; individuals of smaller size immature. 



304 THE TREMATODA OF BRITISH FISHES 

Shape elongate, almost cylindrical, and having rounded extremities. 
Cuticle smooth. Suckers : ventral almost twice as large as the 
oral and situated slightly in front of the middle of the body (0-34 mm. 
from the anterior extremity) ; diameters 0-123 mm. and 066 mm., 
the oral preceded by a small fleshy lobe. Excretory system : canals 
similar to those of Derogenes, the median extending to the testes, the 
laterals uniting above the pharynx. Gut : pharynx fairly large 
(0-039 mm. diameter). (Esophagus very short (never longer than the 
pharynx). Caeca straight and long, extending almost to the posterior 
extremity. Reproductive systems : in general as in Derogenes, differing 
most in the structure of the terminal parts of the male system and 
the shape of the eggs. Genital pore at the level of the oesophagus. 
Sinus-sac longer than in Derogenes and cylindrical instead of globular. 
Pars prostatica much shorter. Seminal vesicle small and globular. 
Testes diagonally ovoid, almost symmetrical, measuring 0-12 x 
0-10 mm. and situated about 004 mm. behind the ventral sucker. 
Ovary transversely ovoid; dimensions 0-12 x 0-07 mm., situated 
close behind the testes. Vitellaria globular, almost symmetrical, 
confined between the caeca, close behind the ovary. Receptaculum 
seminis small, situated between the testes and the ovary. Uterus 
having descending and ascending limbs extending to a point near 
the posterior extremity, containing few eggs (about 40) of distinctive 
shape, the anopercular pole being drawn out into a sharp point which 
is invariably directed backwards in the uterus. The dimensions 
of the eggs are 0-033-0-042 x 0-015-0-019 mm. (mean 0038 x 
0-018 mm.). 

Sub-family SYNCCELiiNiE Looss, 1899. 
Genus HEMIPERA Nicoll, 1913. 

In this genus there is a true cirrus-pouch, and the crura of the 
intestine form discrete caeca instead of uniting to form a ring-shaped 
intestine as in Syncoelium. The vitellaria are paired, as in Derogenes. 

Hemipera ovocaudata Nicoll, 1913. (Fig. 50 E.) 

Hosts : cornish sucker, 3-bearded rockling, 5-bearded rockling. 
Location : stomach, sometimes the buccal cavity. 

Nicoll (1913a, p. 242, PI. 11, figs. 4, 5) found this species in only 
4 out of 24 specimens of the cornish sucker at Plymouth, obtaining 
one immature specimen in each case, but two additional mature 
specimens in one of them. Baylis & Idris Jones (1933) found it in 
the buccal cavity of the two rocklings named, also at Plymouth. 
Size : 1-54 mm. long and 0-56 mm. broad at the level of the ventral 
sucker. Shape oval or slightly elongate, almost cylindrical, tapering 
towards the extremities. Cuticle smooth. Suckers globular, relatively 
large, the ventral almost twice as large as the oral, and situated 
slightly behind the middle of the body; diameters 0-40 mm. and 
0-22 mm. Gut : pharynx of medium size, contiguous with the oral 



HEMIUKIDiE 305 

sucker and 0-066 mm. diameter (Esophagus very short. Caeca extend- 
ing outwards, bending sharply and extending back almost to the 
posterior extremity, their ends almost touching one another. Excre- 
tory system : median canal narrow, extending to a point near the 
posterior border of the ventral sucker, the lateral canals extending 
outwards and forward, crossing the caeca, bending abruptly at the 
level of the pharynx and uniting above it. Reproductive systems : 
genital pore median just behind the oesophagus. Cirrus- pouch some- 
what elongate and divided into anterior and posterior parts, the 
latter containing prostate gland- cells. Vesicula seminalis externa 
present. Testes longitudinally ovoid, measuring 0-22 x 0-14 mm., 
symmetrically arranged near the posterior extremity, their long axes 
slightly oblique. Ovary globular, 0-09 mm. diameter, and situated 
on the right of the median plane in front of the testes and just behind 
the ventral sucker. Vitellaria ovoid and compact, larger than and 
situated on the right and left of the ovary, but smaller than the testes, 
measuring 0-15 x 0-08 mm. Receptaculum seminis small, but 
perhaps of inconstant size Laurer's canal apparently absent. Uterus 
having a very small descending limb, but a long and slightly folded 
ascending limb, containing less than 30 eggs, each provided with a 
typical operculum, but having a tapering anopercular pole drawn 
out into a long filament. Capsule measuring 10 x 027 mm. 
Filament 0-2 mm. long and invariably directed backwards in the 
uterus, sometimes intertwined with other filaments. 

Hemipera sharpei E. I. Jones, 1933. (Fig. 50 F.) 

Host : red band fish. 

Location : under the operculum. 

In 12 specimens of the red band fish trawled from 30 fathoms 
at Plymouth, only one specimen of this species was found. It was 
described by E. I. Jones (1933, pp. 252-4, figs. 6-9), who also com- 
pared it with H. ovocaudata. Size : 4-8 mm. long and 0-85 mm. 
broad at the level of the ventral sucker. Shape : elongate, bluntly 
rounded posteriorly. Suckers : ventral exactly twice as large as the 
oral and well within the posterior half of the body ; diameters 0-74 mm. 
and 0-37 mm. Gut : pharynx 0-116 mm. in diameter. (Esophagus 
very short. Caeca very long. Excretory system : median canal shorter 
than in H. ovocaudata, extending only to a point behind the ovary, 
the lateral canals uniting above the pharynx. Reproductive systems : 
genital pore median and close behind the oesophagus. Cirrus-pouch 
present, described as short and muscular, but no details given. Testes 
globular, 0-24 mm. diameter, obliquely side by side near the posterior 
extremity. Ovary spherical, 0-14 mm. diameter, in front of the 
testes and some distance behind the ventral sucker. Vitellaria 
angular, 19 mm. across, to right and left between the ovary and 
the testes. Receptaculum seminis and Laurer's canal present. Uterus 
practically without a descending limb, much folded between the 
ovary and the ventral sucker, and having several transverse folds in 

20 



306 THE TREMATODA OF BRITISH FISHES 

front of the latter. Eggs ovoid, not curved, and having a very long 
filament at the anopercular pole (capsule measuring 0-100 X 
0038 mm. ; length of the filament not stated, but shown (Fig. 9) 
about ten times as long). The filaments do not intertwine in utero. 

All the differences which this species shows from H. ovocaudata 
are explicable in terms of growth. Nicoll (1913a) remarked that 
possibly none of his specimens were mature, and this may account 
for the unusual shape of the eggs, because the first eggs formed by 
many trematodes are of an abnormal character. It may well be 
that H. sharpei of the size which has been studied has transcended 
this phase and is nothing more than a full-grown example of H. 
ovocaudata, but a definite decision cannot be reached until more 
specimens have been found and studied. 

Family MESOMETRID^E Poche, 1926. 

Size and sliape : small or fairly small, flattened and oval or circular 
in outline. Suckers : ventral absent in the adult. Oral not quite 
terminal, sometimes having a short process on either side. Gut : 
prepharynx very long. Pharynx small. (Esophagus very short or 
absent. Caeca of medium length and very wide, sometimes together 
forming an intestine of horse-shoe shape, bifurcation situated near 
the middle of the body. Excretory system : pore slightly dorsal, 
canals and their factors forming a network. Reproductive systems : 
genital pore median, near the middle of the oesophagus. Cirrus-pouch 
absent. Testes ovoid and situated side by side between the caeca. 
Ovary slightly lobed, median and posterior to the testes. Vitellaria 
well developed, mainly lateral and dorsal to the caeca, but spreading 
towards the median plane at both ends of the caeca. Uterus having a 
slightly folded ascending limb only, the folds confined between the 
caeca. Eggs fairly large and devoid of polar filaments, but sometimes 
having a terminal process. 

Genus MES0METRA Liihe, 1901. 

Two species of this genus are said to occur in the bogue at Naples 
and Trieste, Mesometra orbicularis (Rudolphi, 1819) and M. brachy- 
cozlia Liihe, 1910, the latter of which is undoubtedly a synonym of 
the former. The bogue is a rare visitor to the shores of Britain, so 
that neither of these trematode forms is very likely to appear here. 
I have already (Dawes, 1946) given the characters specified by Liihe 
(19016, pp. 51-6, figs. 1-3 ; pp. 55-7, figs. 4-5), and nothing further 
need be mentioned, unless it is the rarity of monostomes in fishes. 

Family APOROCOTYLIDiE Odhner, 1912. 

(Sanguinicolidae Graff of Fuhrmann, 1928, in part.) 

Shape elongate and spindle-like, the anterior extremity sometimes 
comprising a proboscis-like structure. Cuticle spinous or smooth. 
Suckers absent. Gut : pharynx absent. (Esophagus long. Caeca long 



APOBOCOTYLIMS 307 

and provided with anterior extensions, so that the whole intestine is 
H -shaped, or very short and comprising several irregular lobes. 
Excretory system : vesicle Y-shaped, the median stem short, pore 
terminal or slightly dorsal. Reproductive systems : genital pore or 
pores median or lateral in the posterior region. Cirrus-pouch absent, 
cirrus small. Testes follicular, the follicles numerous. Ovary 
globular, sometimes bilobed, situated behind the testes. Vitellaria 
well developed and follicular, paired and lateral, the vitelloduct 
unpaired and unilateral. Laurer's canal and receptaculum seminis 
absent. Uterus fairly short and containing only a few oval or spindle- 
shaped eggs, or very short (virtually absent), the ootype in this case 
containing a single rather angular egg. Hosts : Fishes, notably 
Cyprinids and Silurids. 

The two genera belonging to this family can be distinguished 
readily by the nature of the gut ; in Aporocotyle the intestine is 
H -shaped, the long caeca having anterior extensions, but in San- 
guinicola the main stem gives off a few short and irregular lobes. 
The two genera have been regarded as the types of different sub- 
families (even families ; see Nicoll, 1934), but the status of the family 
itself is uncertain, Szidat (1939a) proposing to regard it as a sub- 
family, the Aporocotylinae, in the family Schistosomatidae, other 
members of which are also parasites of the blood vascular system, but 
in other classes of vertebrates. 



Genus APOROCOTYLE Odhner, 1900. 
Aporocotyle simplex Odhner, 1900. (Fig. 51 A, B.) 

This trematode occurs in the gills of the flounder and dab at Kris- 
tineberg, Sweden, so that there is some likelihood of its appearing 
in Britain. According to Odhner, who described it (1900, p. 62, 
fig. a) solitary individuals are generally found, rarely 2 to 7. Size : 
3-5-5 mm. long, 045-0-75 mm. broad and 0-10-0-15 mm. thick. 
Shape : elongate and flattened, the lateral margins of the body almost 
parallel, the anterior extremity somewhat pointed, the posterior 
rounded, the last quarter of the body invariably narrower than the 
first. Cuticle spinous, the spines small and fine, arranged in small 
groups which are especially well developed on the antero-ventral 
surface, evident at the lateral margins of the body along its whole 
extent and about 0-06 mm. long. Suckers absent. (Note: The 
spines are feeble organs of attachment ; adhesion is so light that 
gentle shaking of the gill in water serves to release the worm.) Gut : 
mouth slightly ventral. Pharynx absent. (Esophagus very long (about 
1 mm.) Intestine H-shaped, comprising simple caeca extending to the 
posterior extremity and anterior extensions of their proximal ends, 
which extend along the sides of the posterior two-thirds of the 
oesophagus. Caeca invariably filled with blood and consequently 
coloured golden-yellow. Excretory system : pore not quite terminal, 
but slightly dorsal, the median canal very short, the lateral canals 



308 



THE TREMATODA OF BRITISH FISHES 



extending forward underneath the caeca. Reproductive systems : 
common genital pore not far from the posterior extremity on the 
dorsal surface, strictly near the inner margin of the left caecum close 
behind the posterior limits of the testes. Cirrus and cirrus-pouch 
more or less pyriform, but curving forward to a point near the middle 
line immediately behind the testes. Vasa efferentia numerous, vas 
deferens a short median tube. Testes numerous (about 130), con- 
fined to a rectangular field between the anterior two -thuds of the 
caeca, and thus extending back to about 1 mm. in front of the posterior 
extremity. Ovary rounded or transversely ovoid, about 0-18 mm. 




Fig. 51. — A, Aporocotyle simplex; B,theeggof^4. simplex. C, Sanguinicola 
inermis ; D, the cercaria of C. E. F, Distoma miescheri. (A, B, after 
Odhner, 1900 ; C, D, after Scheming, 1923 ; E, after Heitz, 1918 : F, 
after Liihe, 1909.) 



diameter, situated behind the cirrus-pouch mainly on the right, its 
right border touching the right caecum. Oviduct extending diagonally 
backwards, soon receiving the median vitelloduct in the middle line, 
then turning forward to the spindle-shaped ootype behind and 
on the right of the ovary. Receptaculum seminis uterinum present. 
Uterus formed into a compact mass of numerous small folds in the 
space between the ovary, cirrus-pouch and most posterior testes. 
Metraterm extending transversely across the median line immediately 
behind the testes. Vitellaria comprising numerous follicles lateral 
to the caeca and oesophagus, especially abundant anteriorly, where 
they occur on both median and lateral aspects of the anterior diver- 
ticula. Egg (only once found by Odhner) of distinctive shape, some- 
what spindle-shaped and large (measuring 0-125 x 0033 mm.), 
containing an ovum and a mass of vitelline cells. {Note : Odhner 



APQROCOTYLIDiE 309 

found the uterus filled with ova and vitelline cells, but not encapsulated 
eggs. This can hardly be regarded as a normal condition.) 

Genus SANGUINICOLA Plehn, 1905. 
(Janickia Kasin, 1929.) 

Sanguinicola inermis Plehn, 1905. (Fig. 51 C, D.) 

Hosts : Cyprinidse. 

Location : blood vascular system. 

This species has been regarded in turn as a turbellarian, a cestode 
and a trematode. Odhner (1911, vol. 37) was responsible for the 
final decision, and he corrected some of Plehn's observations. Scheur- 
ing (1923, p. 265, figs. A-D ; PL 23, figs. 1-14) re-examined the 
trematode, which occurs in Europe, but has not appeared in Britain. 
Size : 1 mm. long and 0-3 mm. broad, but of somewhat variable 
proportions as a result of contraction and extension. Shape lanceo- 
late, tapering sharply near the anterior end and more gradually in 
the posterior half of the body, convex dorsally. Cuticle bearing very 
fine spinelets arranged in diagonal rows. Musculature : circular, 
longitudinal and dorso- ventral muscles present in fine bundles. Gut : 
mouth very small and situated at the anterior extremity. Pharynx 
absent. (Esophagus long, extending to the anterior third of the body. 
Intestine represented by 4-5 short, lobed sacs (rarely 6, generally 4). 
Glands : associated with the digestive system, unicellular and situated 
mainly near the oesophagus, but extending into the space between 
the gut and the ovary. Excretory system : pore posterior and 
terminal, median canal short, lateral canals extending into the anterior 
half of the body median to the longitudinal nerves. Nervous system : 
brain and two main longitudinal nerves present, the latter connected 
by a transverse commissure about one -third of the distance along the 
oesophagus. Reproductive systems: genital atrium absent; male and 
female pores separate and slightly lateral, the latter on the median 
side of the former at the posterior fifth of the body. Testes numerous, 
arranged in a paired series of small irregular masses on either side of 
and near the middle line in the middle third of the body, commencing 
immediately behind the gut. Vas deferens median and straight at 
its origin, between the testes, but having 2-4 folds further back, 
turning dorsally near its junction with the cirrus. Cirrus-pouch 
weakly developed, but muscular, cirrus forming an acorn-like re- 
tractile papilla. Seminal vesicle absent. Cirrus and vas deferens 
having an epithelial lining. Ovary having two large lateral lobes 
(butterfly- shaped) immediately behind the testes. Oviduct extending 
in a slightly folded condition to the ultimate seventh of the body 
(where it turns in an anterior direction) and having an epithelial 
lining. At the posterior end it meets the median vitelloduct and 
ootype. Vitellaria comprising numerous follicles almost filling the 
anterior region, but mainly lateral to the gut and testes, extending 
as far back as the anterior end of the ovary. Vitelloduct single from 



310 THE TREMATODA OF BRTTISH FISHES 

its origin anteriorly, extending back along the left side of the oesophagus 
and the testes, slightly folded behind the ovary. Uterus virtually 
absent, represented by a short metraterm generally containing only a 
solitary egg. Receptaculum seminis absent. Eggs of characteristic 
shape, " elliptical in transverse, triangular in longitudinal section," 
containing a centrally situated ovum and 5 (rarely 6) vitelline cells, 
size variable, measuring 0030-0068 mm. (according to Odhner, 
about 0040 mm. long in situ in the metraterm, but much larger, 
0070 mm., when found in the blood of the host. Miracidium 0038- 
0-052 mm. long and 0025-0035 mm. broad, having two characteristic 
anterior processes and a boring spine, two eye-spots, and a gut. 
Sporocysts of very variable size, 0-19-0-47 mm. long; cercaria like- 
wise variable, the total length being 0-34-0-41 mm. (0-16-0-17 mm. 
according to La Val, 1852) ; 0-63-0-70 mm. according to Ercolani, 
1881, 1882). 

Trematode of Uncertain Position. 

Distoma miescheri Zschokke, 1889. (Fig. 51 E, F.) 

Host : salmon. 
Location : River Tweed. 

This trematode was discovered in salmon from the River Elbe, 
Germany, and Tosh (1905) made the British record. Nicoll (1924) 
categorically denied that this trematode is a parasite of any species of 
British marine fish, regarding the identification as very doubtful, 
though I fail to see why. The structure is very imperfectly known, 
but brief descriptions were given by Luhe (1909, p. 141, fig. 100) and 
Heitz (1918, pp. 339-42, PI. 5, fig. 1). The former writer mentioned 
separate genital pores, while the latter was probably more accurate in 
regarding the genital pore as a single opening, but seems to have 
confounded the vitellaria with " lateral diverticula " of the caeca in 
the posterior region, a situation in which Liihe figured a group of 
follicles. Size : up to 12 mm. long and 0-7-0-8 mm. broad and thick. 
Suckers : ventral larger than the oral and not far behind it, globular 
and standing out from the ventral surface of the body. Gut : pharynx 
much smaller than the oral sucker. (Esophagus short. Caeca long, 
but not quite reaching the posterior extremity. Reproductive systems : 
genital pore(s) situated ventrally near the margin of the oral sucker. 
Cirrus pouch small. Seminal vesicle externa elongate, according to 
Heitz, 0-54 mm. long. Testes small, and situated one behind the 
other in the third quarter of the body. Ovary globular, larger than 
the testes and situated only a short distance behind them, the recep- 
taculum just in front of it. Vitellaria well developed and much 
lobed, according to Liihe, occupying much of the posterior region 
behind the ovary. 



311 

LIST OF LITERATURE. 

Abildgaard, P. C. (1790), Almindelige Betragtninger over indvolde-orme, 
bemaerkninger ved Hundsteilens Baendelorm. (Skr. af naturh. selsk. 
Copenhagen, 1, 26-64.) 

(1794a), Beskrivelse af en nye igle ; paa gjellerne af Storen. (Ibid., 3, 

55-60.) 

(17946), Beskrivelse af en nye snylte orm, paa Hornfiskers giellen. 



(Ibid., 3, 59-60.) 
Ariola, V. (1899), Di alcuni trematodi di pesci marini. (Boll. Musei zool. anat. 

comp. Genova, IV, No. 81, 1-10, PL figs. 1-7) (also in Atti Soc. ligustica 

sc. not. geogr. Genova, X, 129-38, PI. 5, figs. 1-7.) 
(1902), Contributo per una monografia dei Didymozoon. I. Didymozoon 

parassite del Tonno. (Arch, parasit. Paris, 6, No. 1, 99-108, text-figs. 1-11.) 
(1906), Monostoma filicolle Rudolphi e Distoma okeni Kolliker. (Zool. 



Anz., Leipzig, 30, 185-6.) 

Baer, K. E. von (1827), Beitrage zur Kenntnis der niederen Thiere. (Nov. 

Acta Akad. Leop. Carol, 13, II. Bonnse, 524-762) (abstract published in 

1826.) 
Baird, N. (1853a), Catalogue of the species of entozoa or intestinal worms contained 

in the collection of the British Museum. (London, 1-132.) 
(18536), Descriptions of some new species of entozoa from the collection 

of the British Museum. (Proc. Zool. Soc. Lond., No. 249, Part 21, 18-25, 

PI. 30, figs. 1-7 ; PI. 31, figs. 1-4.) 

(1855), same title as the preceding. (Ann. Mag. Nat. Hist. Lond., 2, 



15, No. 85, 69-76.) 
Barbagallo, P., and Drago, U. (1903), Primo contributo alio studio della 

fauna elmintologica dei pesci della Sicilia orientale. (Arch, parasit. Paris, 

7, 3, 408-27.) 
Baster, J. (1759), Opuscula subseciva, observationes miscellaneai de animalculis et 

planti > (juibu«ftj mmarinis eorumque ovariis et seminibus continentia. (Harlem. ) 
Baylis, H. A. (1928), Records of some parasitic worms from British Vertebrates. 

(Ann. Mag. Nat. Hist. Lond., (10), 1, 329-43.) 
■ (1931) Gammarus pulex as an intermediate host for trout -parasites. 

(Ann Mag. Nat. Hist., (10), 7, 431-5.) 

(1938), On two species of the trematode genus Didymozoon from the 

mackerel. (J. Mar. Biol. Ass. U.K., U.S. 22 485-92.) 

(1939), Further records of parasitic worms from British Vertebrates. 

(Ann. Mag. Nat. Hist, (11), 4, 473-98.) 

and Idris Jones, E. (1933), Records of parasitic worms from marine 



fishes at Plymouth. (J. Mar. Biol. Ass. U.K., n.s. 18, 627-34.) 
Beauchamp, P. de (1912), Isancistrum loliginis n.g., n.sp. Trematode parasite 

du calmar [etc]. (Bull. Zool. Soc. Fr., 37, 96^9.) 
Beneden, P. J. van (1853), Espece nouvelle du genre Onchocotyle vivant sur les 

branchies du Scimnus glacialis. (Bull. Acad. Belg. CI. Sci., 20, 3 (9), 59-68.) 

(1855), Sur les vers parasites du poisson lune (Orthagoriscus mola). (Ibid., 

22, 2, 520-7.) 

(1856), Note sur un trematode nouveau du maigre d'Europe. (Ibid., 23, 

502-8.) 

(1858), memoire sur les vers intestinaux. (Suppl. 2, C. R. Acad. Sci. Paris 

(1861), 1-376, Pis. 1-27.) 

(1868), Le genre Dactycotyle, son organisation et quelques remarques 

sur la formation de l'ceuf des trematodes. (Bull. Acad. Belg. CI. Sci., (2), 25, 
22-37.) 



312 THE TREMATODA OF BRITISH FISHES 

Beneden, P. J. van (1870), Les poissons des c6tes de Belgique, leurs parasites 
et leurs commenseaux. {Mem. Acad. R. Belg. CI. Sci., 38, 1-100, Pis. 
1-6.) 

and Hesse, C. E. (1864), Recherches sur les bdellodes (hirudinees) et 

les trematodes marins. {Ibid., 34, 1-148.) 

- (1865), Idem, troisieme et quatrieme appendices. {Ibid., 35, 



1-18.) 
Benham, W. B. (1901), The Platyhelmia, Mesozoa and Nemertini. (In A Treatise 

on Zoology, ed. Lankester, Part 4, 1-195.) 
Blainville, M.H.D. de (1828), Vers, in Dictionnaire des sciences naturelles. (Paris.) 
Blancbard, E. (1847), Recherches sur l'organisation des vers. {Ann. Sci. Nat., 

ser. 3, Zool., 8, 271-341.) 
Blanchakd, R. (1891), Notices helniinthologiques {2 me serie). {Mem. Soc. zool. 

Fr., 4, 420-89.) 
Bosc, L. A. G. (1811), Sur deux nouveaux genres de vers. {Nouv. Bull. Soc. 

Philom. Paris, An. 4 (51), 2, 384-5.) 
Bradley, C. S. (1861), On the occurrence of Gyrodactylus elegans on sticklebacks 

in the Hampstead ponds. {Proc. Linn. Soc. Lond. {Zool.), 5, 209-10.) 
Brandes, G. (1894), Fridericaniella ovicola n.g., n.sp. Ein neuer monogenetischer 

Trematode. {Abhandl. naturf. Oesellsch. zu Halle, 20, 305-11.) 
Brattn, M. (1879-93), Platyhelrninthes. I. Trematodes. (Vol. " Vermes " in 

Bronn's Klassen u. Ordnungen d. Thier-Reichs, Leipzig, 4, Abt. la, 303-925, 

text-figs. 1-36, Pis. 1-34.) 

(1893), II. Bericht uber thierische Parasiten. Trematodes. {Zbl. Bakt., 

(1), 13, Nos. 5-6, 176-90.) 

(1896), Trematoden. Ergebn. Hamburger Magalhaensische Sammelreise, 

3, 7 pp., 1 pi., 3 figs.) 

(1899), Eine neue Calicotyle-Axt des Mittelmeeres. {Zbl. Bakt. (Orig.), 

26, 80-2.) 

(1900a), Einige Bemerkungen iiber die Fascioliden der Chiroptera. {Zool. 

Anz., 23, 387-91.) 

(19006), Trematoden der Chiroptera. {Ann. K. K. Natur-hist. Hofmus. 



Wien, 15, 217-36.) 
Bremser, J. G. (1819), Ueber lebende Wurmer im lebenden Menschen. (Wien.) 

(1824), Icones helminthum sy sterna Rudolphi entozoologicum illustrantes. 

(Vienna.) 

Brinkmann, A., jr. (1940), Contributions to our knowledge of the Monogenetic 

o 

Trematodes. {Bergens Mus. Arbok., 1939-40. Naturvitensk. rekke, Nr. 1, 
117 pp., 15 pis., 58 figs.) 

(1942a), On some new and little-known Dactylocotyle species, with a dis- 
cussion on the relations between the genus Dactylocotyle and the " family " 
Diclidophoridae. Gbteborgs Kungl. Vetensk.-och Vitterhets-Samhdlles Handl., 
Sjdtte-Foljden, ser. B, 1, No. 13, 32 pp., 8 figs.) 

(19426), On " Octobothrium " leptogaster F. S. Leuckart. {Ibid., 2, 



No. 3, 29 pp. 11 figs.) 

Briot, A. (1904), Nouvelle espece de trematode, Microcotyle draconis (n.sp.). 
(C. R. Soc. Biol. Paris, 56, 126-7.) 

Brown, E. M. (1929), On a new species of monogenetic trematode from the gills 
of Pagellus centrodontus. {Proc. Zool. Soc. Lond., 67-83, figs. 1-6.) 

Brown, R J. (1927), On Crepidostomum farionis O. F. Mull. (= Stephanophiala 
laureata Zeder), a distome parasite of the trout and grayling. I. The life- 
history. {Parasitology, 19, 86-99.) 



LIST OF LITERATtJEE 313 

Brown, F. J. (1933), On the excretory system and life-history of Lecithodendrium 

chilostomum (Mehl.) and other bat trematodes, with a note on the life-history 

of Dicrocodium dendriticum (Rud.). (Ibid., 25, 317-28.) 
Burmeister, H. (1856), Zoonomische Briefe. Allgemeine Darstellung der 

thierischen Organisationen. (Leipzig.) 
Bychowsky, B. J. (1929), Trematoden der Fische in der Umgebung von Stadt 

Kostroma. (In Russian.) (Trav. Soc. Nat. (Sect. C. R.) Leningrad, 59, 13- 

26 ; German resume, 26-7.) 

(1933), Beitrag zur Kenntnis neuer monogenetischer Fischtrematoden 

aus dem Kaspisee nebst einigen Bemerkungen uber die systematik der 
Monopisthodiscinea Fhurmann. (Zool. Anz., Leipzig, 105, 17-38, figs. 1-17.) 

Bychowsky, I., and Bychowsky, B. (1934), Uber die Morphologie und die 
Systematik des Aspidogaster limacoides Diesing. (Z. Parasitenk., 7, 125-37.) 

Cable, R. M., and Hunninen, A. V. (1941a), Studies on the life history of 
Siphodera vinaledwardsii (Linton) (Trematoda : Cryptogonimidse). (J. 
Parasit., 27, Suppl. Abstr. 10, 13.) 

(1941&), The systematic position of the genus Deropristis Odhner, with 

respect to a proposed revision of the trematode families Acanthocolpidse 
and Allocreadiidae. (Ibid., 27, Suppl. Abstr. 14.) 

(1942), Studies on Deroptistis inflata (Molin), its life-history and affi- 



nities to trematodes of the family Acanthocolpidae. (Biol. Bull., 82, 292- 

312.) 
Cable, S. H. (1942), Studies on the life-history of Siphodera vinaledwardsii 

(Linton) (Trematoda : Cryptogonimidae). (J. Parasit., 28, 407-22.) 
Carus, J. V. (1863), Raderthiere, Wurmer, Ccelenteraten und Protozoen. (In 

Peters, Carus, and Gerstaecker, Handb. d. Zool., Leipzig, 2, 422-600.) 

(1884), Prodromus fauna? mediterranean, sive descriptio animalium maris 

mediterranei incolarum. Vol. I : Ccelenterate, Echinodermata, Vermes, 
Arthropoda. (Stuttgart, 524 pp.) 

Cerfontaine, P. (1894), Sur un nouveau tristomien, Merizocotyle diaphanum 
(n.g., n.sp.). (Bull. Acad. Belg. CI. Sci., 64, 3s, 27, 936-48.) 

(1895), Le genre Dactylocotyle. (Ibid., 65, 3s, 29, 913-46.) 

(1896), Contributions a l'etude des Octocotylides. (I. Le genre Antho- 

cotyle. II. Le genre Dactylocotyle. III. Les Diclidophorinae.) (Arch. Biol., 
14, 497-560.) 

(1898a), Contributions a l'etude des Octocotylides. IV. Nouvelles obser- 
vations sur le genre Dactylocotyle et description du Dactylocotyle lusca?. 
(Ibid., 15, 301-28.) 

(18986), Le genre Merizocotyle. (Ibid., 15, 329-66.) 

(1899), Les Onchocotylinae. (Ibid., 16, 345-478.) 



Chatin, J. (1874), Etudes sur des helminthes nouveaux ou peu connus. (Ann. 

Sci. nat. Zool. (6), 1, 18 pp.) 
Cobbold, T. S. (1858), Observations on entozoa with notices of several new 

species, including an account of two experiments in regard to the breeding 

of Taznia serrata and T. cucumerina. (Trans. Linn. Soc. Lond., 22, 155-72, 

363-70.) 

(1861), Synopsis of the Distomidse. (Proc. Linn. Soc. Lond., Zool., 5, 

1-56.) 

(1862), Note on Gyrodactylus elegans. (Quart. J. Micro. Sci. Lond., 2, 

35-9.) 

(1864), Entozoa : an introduction to the study of helminthology, with 

reference, more particularly, to the internal parasites of man. (London, 480 
pp., 82 figs.) 



314 THE TREMATODA OF BRITISH FISHES 

Cobbold, T. S. (1879), Parasites : a treatise on the Entozoa of man and animals, 

including some account of the Ectozoa. (London, 508 pp., 85 figs.) 
Cohn, L. (1903), Zur Kenntnis einiger Trematoden. (Zbl. Bald., 34, 35-42, 4 

figs.) 
Cooper, A. R. (1915), Trematodes from marine and freshwater fishes, including 

one species of ectoparasitic turbellarian. {Trans. Roy. Soc. Can., Sect. 4, 

ser. 3, 9, 181-205, Pis. 1-3, figs. 1-24.) 
Cort, W. W. (1937), Homologies of the excretory system of the forked- tailed 

cercariae. (J. Parasit., 4, 48-57.) 
Craig, C. F., and Faust, E. C. (1940), Clinical Parasitology. (Henry Kimpton, 

Loud, 772 pp.) 
Creplin, F. C. H. (1825), Observationes de entozois. (Gryphisw.) 

(1829), Novw observationes de entozois. (Berol.) 

(1837), Distoma. (In Ersch und Gruber, Allg. Encyclop. Wiss. 

u. Kilnste, Leipzig, Sect. 1, part 29, 309-29.) 

(1839), Eingeweidew (inner. (Ersch und Gruber, Allg. Encyclop. Wiss. 

u. Kilnste, 277-302.) 

(1842), Endozoologische Beitrage. {Arch. Naturg., 1, 315-39, PL 9, 

figs. 1, 2.) 

(1851), Nachtrage von Creplin zu Gurlt's Verzeichniss der Thiere in 



welchen Endozoen gefunden worden sind. 4te Nachtrag. {Ibid., Jahrg. 
17, 269-310.) 
Crofton, H. D. (1940), A note on Microcotyle fusiformis Goto, a fish trematode 
new to Britain. {Parasitology, 32, 318-9.) 

(1941), A record of trematode parasites from Mola and Raniceps raninus 

(Linn.). {Ibid., 33, 209-10.) 

Cunningham, J. T. (1887), On Stichocotyle nephropis, a new Trematode. {Trans. 
Roy. Soc. Edin., 33, 273-80.) 

(1890), A treatise on the common Sole. (Plymouth, pp. 148.) 

Cuvier, G. (1817), Le regne animal. . . . (Paris, 4, 2255 pp., 15 pis.) 

Dalyell, J. G. (1853), The powers of the Creator displayed in creation. . . . 

(London.) 
Dawes, B. (1940a) Hexacotyle extensicauda n.sp., a monogenetic trematode from 

the gills of the tunny {Thunnus thynnus L.). {Parasitology, 32, 271-86.) 

(19406), Notes on the formation of the egg capsules in the monogenetic 

trematode Hexacotyle extensicauda Dawes, 1940. {Ibid., 32, 287-95.) 

(1941), On Multicotyle purvisi n.g., n.sp., an aspidogastrid trematode from 



the river turtle, Siebenrockiella crassicollis, in Malaya. {Ibid., 33, 300-5. 
(1946), The Trematoda. (Cambridge University Press, 644 pp.) 



Delaroche, F. (1811), Sur deux animaux vivants sur les branchies de poissons. 

{Nouv. Bull. soc. Philom. Paris, 270-3.) 
Diesing, K. M. (1835), Aspidogaster limacoides, eine neue Art Binnenwurm. . . . 

{Med. J. oesterr. Kaiser staates, Wien, 16, n.s. 7, 420-30, 1 pi.) 

(1836), Monographic der Gattung Tristoma. {Nova acta Phys.-med. Acad. 

nat. curios., Vratislavise et Bonnae, 18, 1, 1-16.) 

(1850), Systema helminihum I. { Vindobonse, 1-680.) 

(1851), Idem II. (Vindobome, 1-588.) 

(1855a), Sechzehn Gattungen von Binnenwurmern und ihre Arten. 

(Denkschr. Akad. Wiss. Wien, 9, 171-85.) 

— (18556), Neunzehn Arten von Trematoden. {Ibid., 10, 59-70.) 

(1855c), Revision der Cercarien. {S. B. Akad. Wiss. Wien., 15, 377-400.) 

(1858a), Vierzehn Arten von Bdelliden. {Denkschr. Akad. Wiss. Wien, 

14, 63-80.) 



LTST OF LITERATURE 315 

Dtesing, K. M. (18586), Revision der Mvzhelnrinthen Abt. Trematoden. (S. B. 

Akad. Wiss. Wien, 32,207-90.) 
(1859), Nachtrage und Verbesserung zur Revision der Myzhelminthen. 

{Ibid., 36, 421-54.) 
Dogiel, V., and Bychowsky, B. (1934) Die Fischparasiten des Aral-Sees. {Mag. 

Parasit., Leningr., 4, 241-344 (Russian) ; German summary, 345-6.) 
Dollfus, R. P. (1922a), Cyclobothrium charcoti, n.sp., trematode ectoparasite 

sur Meinertia cestroides (Risso). {Bull. Zool. Soc. Fr., 47, 287-96.) 
(19226), Complement a la description de Cyclobothrium charcoti mihi. 

{Ibid., 47, 348-52.) 

(1923), Remarques sur le cycle evolutif des Hemiurides. {Ann. Parasit. 

Hum. Comp., 1, No. 4, 345-51, figs. 1-4.) 

(1926), Sur l'etat actuel de la classification des Didymozoonidse Monti- 

celli, 1888 (= Didymozoidae Franz Poche, 1907). {Ibid., 4, 148-61.) 

(1927), Sur une metacercaire progenetique d'hemiuridae (Tremat. 

Digenea). {Bull. Biol. France et Belg., 61, 49-57.) 

(1935), Sur quelques parasites de poissons recoltes a Castiglione (Algerie), 

I. {Bull. Stat. Aquic. Peche Castiglione, year 1933, 2nd fasc, 199-279.) 

(1936), Parasitologia Mauritanica. Helmintha (III). Trematodes de 

Selaciens et de cheloniens. {Bull. Comm. A. O. F., 19, No. 4, 397-519, 
figs. 1-61.) 

(1937), Les trematodes Digenea des Selaciens (Plagiostomes) Catalogue 



par hotes. Distribution geographique. {Ann. Parasit. Hum. Corny., 15, 
57-73, 164-76,259-81.) 
Dujardin, F. (1845), Histoire natureUe des Helminthes ou vers intestinaux. (Paris. 
654 pp., Pis. 1-12.) 

Eckmann, F. (1932a), Uber zwei neue Trematoden der Gattung Aspidogaster, 

(Z. Parasitenh., 4, 395-99.) 
(19326), Beitrage zur Kenntnis der Trematoden-familie Bucephalidse, 

(Ibid., 5, 94-111.) 

(1934), Rectifications de nomenclature. {Ann. Parasit. Hum. Comp., 



12, p. 256.) 

Ercolani, G. (1881), DeH'adattamento delle specie all'ambiente, nuove ricerche 
sulla storia genetica dei Trematodi, I. {Mem. R. Accad. Bologna, 4th ser., 
2, 237-334.) 

(1882), Idem, Memoria II. {Ibid., 3, 43-111.) 

Eysenhardt, K. W. (1829), Einiges fiber Eingeweidewurmer. {Verg. Ges. 
naturf. Frde. Berlin, 1, No. 3, 144-52.) 

Fantham, H. B. (1938), Lecithostaphylus spondyliosomce n.sp., a trematode 
parasite of the Hottentot fish, Spondiliosoma blochii, found in South African 
waters. (Trans. Roy. Soc. S. Afr., 26, 387-93.) 

Faust, E. C. (1919), The Excretory System in Digenea, I-III. (Biol. Bull. 
Woods Hole, 36, 315^4.) 

(1922), Notes on the excretory system in Aspidogaster conchicola. (Trans. 

Amer. Micr. Soc, 41, 113-17). " 

(1932), The excretory system as a method of classification of digenetic 

trematodes. (Quart. Rev. Biol., 7, 458-68.) 

and Tang, C.-C. (1936), Notes on new Aspidogastrid species, with a 



consideration of the Phylogeny of the group. (Parasitology, 28, 487-501.) 
Fischthal, J. H. (1942a), Three new species of Phyllodistomum (Trematoda 
Gorgoderidse) from Michigan fishes. (J. Parasit., 28, 269-75.) 



3 16 THE TREMATODA OF BRITISH FISHES 

Fischthal, J. H. (19426), Phyllodistomum etheosiomce n.sp. (Trematoda : Gorgo^ 
deridas) from percid fishes. (Ibid., 28, Suppl. Abstr., p. 18.) 

(1943), A description of Phyllodistomum etheostomce Fischthal, 1942 

(Trematoda : Gorgoderidse) from percid fishes. (Ibid., 29, 7-9.) 

and Allison, L.N. (1941), A colpenter on ureter ozcetes Fischthal and Allison, 



1940, a monogenetic trematode from the ureters of the black basses, with a 

revision of the family Calceostomatidae (Gyrodactyloidea). (•/. Parasit., 

27, 517-24, 1 pi.) 
Folda, F. (1928), Megalocoiyle marginata, a new genus of ectoparasitic trema- 

todes from the rock fish. (Publ. Puget Sound Biol. Sta., Seattle, 6, 196-206.) 
Frankenberg, G. von (1937), Phyllodistomum folium als Parasit des Stichlings. 

(Microkosmos, 30, 66-7.) 
Frey, H., and Leuckart, R. (1847), Lehrbuch der Anatomie der wirbellosen 

Thiere (vol. 2 of R. Wagner's Lehrbuch der Zootomie, ed. 2, Leipzig.) 
Friend, G. F. (1939), Gill-parasites of brown trout in Scotland. (Scot. Nat., 

123-6.) 
Frolich, J. A. (1891), Bevtrage zur Naturgeschichte der Eingeweidewurmer. 

(Abh. natf. Ges. Halle, 25, 52-113, 17 figs.) 
Fuhrmann, O. (1928), Trematoda. (In Kukenthal u. Krumbach, Handbuch d. 

Zool., 2, 1st half (2), 1-140, 175 figs.) 

Gallien, L. (1937), Recherches sur quelques trematodes monogeneses nouveaux 
ou peu connus. (Ann. Parasit. Hum. Comp., 15, 9-28, 146-54.) 

Gamble, F. W. (1896), Platyhelminthes and Mesozoa. (Cambridge Natural 
History, 2, 1-96, 47 figs.) 

Goldberger, J. (1911), 1. Some known and three new endoparasitic trematodes 
from American fresh-water fish. 2. On some new parasitic trematode 
worms of the genus Telorchis. (Hyg. Lab. Bull., No. 71, 47 pp., 6 pis.) 

Goldschmidt, R. (1902), Ueber Bau und Embryonalentwicklung von Zoogonus 
mirus Lss. (Zbl. Bakt., 32, 870-6.) 

(1905), Eireifung, Befruchtung und Embryonalentwicklung des Zoogonus 

mirus Lss. (Zool. Jb. Anat., 21, 604-54.) 

Goto, S. (1890), On Diplozoon nipponicum n.sp. (J. Coll. Sci., Tokyo, 4, pp. 

151-92.) 
(1894), Studies on the ectoparasitic trematodes of Japan. (Ibid., 8, 

1-273.) 
(1899), Notes on some exotic species of ectoparasitic trematodes. (Ibid., 

12 263-95.) 
Goto, S., and Kikuchi, H. (1917), Two new trematodes of the family Gyro- 

dactylidae. (Ibid., 39, 1-22.) 
Graeffe, E. (1860), Beobachtungen fiber Radiaten und Wiirmer in Nizza. 

(Nouv. mem. soc. helv. sc. nat. Zurich, 17, 1858, 59 pp., 10 pis.) 
Grobben, C. (1878), Beitrage zur Kenntnisder mannlichenGeschlechtsorganeder 

Decapoden, nebst vergleichenden Bemerkungen fiber der fibrigen Thoraco- 

straken. (Arb. Zool. Inst. Univ. Wien, 1, Pt. 1, 57-150, pis. 1-6.) 
Grube, E. (1855), Bemerkungen fiber einige Helminthen und Meerwurmer. 

(Arch. Natg. Berlin, 21 Jahrg., 1, 137-58.) 
Guberlet, J. E. (1933), Notes on some Onchocotylinse from Naples with a 

description of a new species. (Publ. Sta. Zool. Napoli, 12 (3), 323-36, PI. 4, 

figs. 1-10.) 

(1936), Two new ectoparasitic trematodes from the sting ra}% Myliobatis 

calif ornicus. (Amer. Midi. Nat., 17, 954-64.) 

(1937), Trematodos ectoparasitos de los peces de la costas del Pacifico. 

(An. Inst. Biol. Univ. Mix., 7, 457-567.) 



LIST OF LITERATURE 317 

Guberlet, J. E., and Bonham, K. (1938), Ectoparasitic trematodes of Puget 
Sound fishes — Acanthocotyle. (Amer. Mdl. Not., 20, 590-602.) 

- Hansen, H. A., and Kavanagh, J. A. (1927), Studies on the control of 
Gyrodactylus. {Univ. Wash. Pub. Fisheries, Seattle, Wash., 2 (2), 1-13.) 

Gtjiart (1938), Trematodes parasites provenant des campagnes sc.ientifiques de 
S.A.S. le Prince Albert de Monaco (1886-1912). 

Hausman, L. (1896), Ueber Trematoden der Siisswasserfische (Vorlaufige 
Mitteilung). (Zbl. Bakt., 19, 389-92.) 

(1897), Idem. (Rev. Suisse Zool., 5, 1-42, 12 figs.) 

Heitz, A. (1918), Salmo salar Lin., seine Parasitenfauna und seine Ernahrung 
im Meer und im Susswasser. (Arch. Hydrobiol. Plankt., 12, 311-72, 485-561.) 

Hermann, J. (1782), Helminthologische Bemerkungen. Erster Stuck. (Natur- 
forscher, Halle, 17, 171-82.) 

Hess, W. N. (1928), The life-historv and control of Dactylogyrus sp. (J. Parasit., 
15, 138-9.) 

(1930), Control of external fluke parasites on fish. (Ibid., 16, 131-6.) 

Hickman, V. V. (1934), On Coitoc&cum anaspidis sp. nov., a trematode exhibit- 
ing progenesis in the freshwater crustacean Anaspides tasmanice Thomson. 
(Parasitology, 26, 121-8.) 

Hinton, M. A. C, Tucker, B. W., Parker, H. W., and Norman, J. R. (1935), 

List of British Vertebrates. (Brit. Mus. Nat. Hist., 66 pp.) 
Hockley, A. R. (1937), An investigation of holostomiasis in Avon coarse fish. 

(Rep. Avon. Biol. Res. Southampton, 4, 103-6.) 
Holl, F. J. (1929), The Phvllodistomes of North America. (Trans. Amer. 

Micr. Soc, 48, 48-53.) 
Hopkins, S. H. (1931), Studies on Crepidostomum II. The "Crepidostomum 

laureatum " of A. R. Cooper. (J. Parasit, 18, 79-91.) 
(1933), The morphology, fife histories and relationships of the 

papillose AllocreadiidaB (Trematodes). Preliminary Report. (Zool. Anz. 

Leipzig, 103, 65-74.) 

(1934), The papillose Allocreadiidse. (III. Biol. Monogr., 13 (2), 1-80.) 

(1940), The excretory systems of Tergestia Stossich, 1899, and Cornu- 

copula adunca (Linton, 1905). (Trematoda.) (Trans. Amer. Micr. Soc, 59, 
281-4.) 

(1941a), New genera and species of the family Monorchiidae (Trematoda), 



with a discussion on the excretory system. (J. Parasit., 27, 395-407.) 

(19416), The excretory systems of Helicometra and Cymbephallus (Trema- 
toda), with remarks on their relationships. (Trans. Amer. Micr. Soc, 60, 41-4.) 

Houghton, W. (1862), On the occurrence of Gyrodactylus elegans in Shropshire. 
(Ann. Mag. Nat. Hist., (3), 10, 77.) 

Huet, L. (1891), Une nouvelle cercaire (C. pectinata) chez Donax anatinum. (J. 
anat. physiol., Paris, 27, 162-5, figs. 1-4.) 

Hughes, W. F. (1928), Some trematode parasites on the gills of Victorian 
fishes. (Proc. Roy. Soc. Vict., 41, n.s. 1, 45-54.) 

Hunninen, A. V., and Cable, R. M. (1941), The life history oiPodocolyle atomon 
(Rud.) (Trematoda : Fam. Opeccelidse). (J. Parasit., 27, Suppl. Abstr. 8, 
12-13). 

(1943a), The life history of Podocotyle atomon (Rudolphi) (Tre- 
matoda : Opeccelidse). (Trans. Amer. Micr. Soc, 62, 57-68.) 

(19436), The life history of Lecithaster confusus Odhner (Tre- 
matoda : Hemiuridse). (J. Parasit., 29, 71-9.) 

and Hunter, G. W. iii (1933). On the species of Crepidostomum in 

trout. (Trans. Amer. Micr. Soc, 52, 150-7.) 



318 THE TREMATODA OE BRITISH EISHES 

Hunter, G. W., and Hunter, W. S. (1934), The life-cycle of the yellow grub of 
fish, Clinostomum marginatum (Rud.). (J. Parasit., 20, 325.) 

Hunter, W. S., and Hunter, G. W. (1935), Studies on Clinostomum. II. The 
miracidium of C. marginatum (Rud.). (Ibid., 21, 186-9.) 

Issaitschikow, I. M. (1923), On the parasitic worms of Cyprinoid fishes of the 

rivers of Kuban. (Russian.) (Trud, eksp. Vet., 2, 12 pp.) 
(1924). Parasitic worms from the Sea of Azov. (Russian.) (Trudy 

Sibir. Vet. Inst. Omsk., 6, 1-28.) 
(1928), Zur Kenntnis der parasitischen Wiirmer einiger Gruppen von 

Wirbelthieren der russischen Arktis. (Russian.) (Ber. wiss. Meeresinst. 

Moscow, 3, 2, 1-79.) 

(1933), Contributions to parasitic worms of some groups of vertebrates 



from the Russian Arctic. (Russian.) (Trans. Oceanogr. Inst. Moscow, 3, 
1-36, plus German summary.) 
Ismi, N. (1935), Notes on the family Didymozoonidse (Monticelli, 1888). (Jap. 
J. Zool, 6, 279-335.) 

(1936), Some new ectoparasitic trematodes of marine fishes. (Japanese, 

English summary.) (Zool, Mag. Tokyo, 48, 781-90.) 

and Saw ad a, T. (1938), Studies on the ectoparasitic trematodes. (Livro 

Jub. Prof. Travassos, Rio de Janeiro, Brasil, 231-43.) 

Jacob, E. (1940), Zur Behandlung einiger parasitarer Fischkrankheiten. (Bed 

tierdrtzl. Wschr., 161-2). 
Jacoby, S. (1899), Beitrage zur Kenntnis einiger Distomen. (Inaug. Diss. Univ. 

Konigsberg, 1-30, and Arch. Naturg., year 66, 1, Dez. 1899 (1900), 1-30, 

Pis. 1-2, figs. 1-16.) 
Jahn, T. L., and Kuhn, L. R. (1932), The life history of Epibdelkt melleni Mac- 

Callum, 1927. A monogenetic trematode parasitic on marine fishes. (Biol. 

Bull. Woods Hole, 62, 89-111.) 
Johnston, G. (1835), Illustrations in British zoology. (Mag. Nat, Hist. Lond., 

53, 8, 494-8.) 
Johnston, S. J. (1902), Contributions to a knowledge of Australian Entozoa. 

No. II : On a new species of Distomum from the sawfish shark, Pristio- 

phorus cirratus Lath. (Proc. Linn. Soc. N.S.W., 3, No. 107, 326-30, PI. 13, 

figs. 1-7.) 
Johnston, T. H. (1929), Remarks on the synonymy of certain tristomatid 

genera. (Trans. Proc. Roy. Soc. S. Aust., 53, 71-9.) 
(1930), A new species of trematode, of the genus Anoplodiscus. (Aust. 

J. Exp. Biol. Med. Sci., 7, 108-12.) 
(1931), New trematodes from the Subantarctic and Antarctic. (Ibid,, 

8, 91-8.) 

(1934a), New trematodes from South Australian elasmobranchs. (Ibid., 

12, 25-32.) 

(19346), Notes on some Monocotylid trematodes. (Proc. Linn. Soc. 

N.S.W., (251-2), 59, 62-5.) 

and Tiegs, O. W. (1922), New Gyrodactyloid trematodes from Australian 



Fishes, together with a reclassification of the superfamily Gyrodactyloidea. 
(Ibid., 37, 83-131.) 
Johnstone, J. (1905), Internal parasites and diseased conditions of fishes. 
(Trans. Biol. Soc. Liverpool, 19, 98-120.) 

(1906), Idem. (Ibid., 20, 151-85.) 

(1907), Idem. (Ibid., 21, 170-203.) 



LIST OF LITERATURE 319 

Johnstone, J. (1908), Redescription of a trematode parasite, Allocreadium labracis 

(Duj.), from the Bass. {Ibid., 22, 44-53.) 
(1909), Internal parasites and diseased conditions of fishes. (Ibid., 

23, 87-100.) 

— (1910), Internal parasites of fishes from the Irish Sea. (Ibid., 24, 16-17.) 

(1911), Internal parasites and diseased conditions of fishes. (Ibid., 

25, 16-50.) 

(1912), Idem. (Ibid., 26, p. 47 of Rep. 20 Lanes. Sea-Fish. Lab. for 1911.) 

(1914), Idem. (Ibid., 28, 127-44.) 



Jones, D. O. (1943), The anatomy of three digenetic trematodes, Skrjabiniella 
aculeatus (Odhner), Lecithochirium rufoviride (Rud.) and Sterrhurus fusi- 
formis (Liihe) from Conger conger (Linn.). (Parasitology, 35, 40-57.) 

Jones, E. I. (1933a), Fertilization and egg formation in a digenetic Trema- 
tode, Podocotyle atomon. (Parasitology, 24, 545-7.) 

(19336), On Ceratotrema farcolabiata, n.g. et n.sp., and Hemipera sharpei, 

n.sp., two new digenetic trematodes of British fishes. (Ibid., 25, 248-54.) 

(1933c), Studies on the Monogenea (Trematoda) of Plymouth. I. Micro- 

boihrium caniculce (Johnstone, 1911). (Ibid., 25, 329-32.) 

- (1933a 1 ). Correction. (Ibid., 25, 410.) 
(1933e). Studies on the Monogenea of Plymouth. Gastrocotyle trachuri 



v. Ben. and Hesse, 1863. (J. Mar. Biol. Ass. U.K., 19, 227-32.) 
Juel, H. O. (1889), Beitrage zur Anatomie der Trematodengattung Apoblema 
Duj. (Vet.- Ah. Stockholm Handl, 15, No. 6, 46 pp.) 

Kathariner, L. (1895), Die Gattung Gyrodactylus v. Nordm. (Arb. zool. Inst, 

Wurzb., 10, 125-64.) 
Kay, M. W. (1942), Notes on the genus Merizocotyle Cerfontaine, with a descrip- 
tion of new species. (Trans. Amer. Micr. Soc, 6, 254-60.) 
Kofoid, C. A. (1899), On the specific identity of Cotylaspis insignis Leidy and 

Platyaspis anodontoz Osborn. (Zool. Bull. Boston, 2, 179-86.) 
Kolliker, A. (1849), Zwei neue Distomen Distoma pelagice und D. okenii. (Ber. 

Zool. Anstalt Wurzburg, II, 1847/48, 53-7.) 
Kroyer, H. (1838-^0 : 1846-53), Danmark's Fiske. (Copenhagen.) 
Krull, W. H. (1934a), Studies on the life-history of a trematode, Rhipidocotyle 

septapapillata n.sp. (Trans. Amer. Micr. Soc, 53, 408-15.) 
(19346), Some observations on the cercaria and redia of a species of 

Clinostomum, apparently C. marginatum (Rudolphi, 1819) (Trematoda). 

(Proc. Helminth. Soc. Wash., 1, 34-5.) 
Kuhn, J. (1829a), Description d'un nouveau genre de l'ordre des douves et de 

deux especes de Strongyles. (Mem. Mus. hist, nat., 18, 357-68.) 
(18296), Description d'un nouvel epizoaire du genre des Polystoma, que 

se trouve sur les branchies de la petite rousette (Squalus catulus) ; suivie 

de quelques observations sur le Distoma megastomum et le Cysticercus 

Leporis variabilis de Bremser. (Ann. Sci. d'Obser. Paris, 2, 460-5.) 
Kulwiec, Z. (1927), Untersuchungen an Arten des Genus Dactylogyrus Diesing. 

(Bull. Internat. Polon, Sci. Lett. B. Sci. nat. Cracovie, 113-44, Pis. 20-1, 

13 figs.) 

Lacaze-Duthiers, H. de (1854), Memoire sur le Bucephale Haime, helminthe 
parasite des huitres et des bucardes. (Ann. sci. nat., 4th ser., 1, 294-302.) 

Lahille, F. (1918), Nota sobre Monostoma mutabile y la classificacion general de 
los Trematodes. (Buenos Aires Phys. Rev. Soc. Arg. Ci. Nat., 4, 328-31.) 

Lamarck, J. B. P. A. de M. (1818), Histoire naturelle des animaux sans vertebres. 
(5, Paris, 612 pp.) 



320 THE TEEMATODA OF BRITISH FISHES 

Lander, C. H. (1904), The anatomy of Hemiurus crenatus (Rud.) Liihe, an 
appendiculate treraatode. (Bull. Mus. Comp. Zool., 45, 1-28.) 

La Rue, G. R. (1926), Studies on the trematode family Strigeidae (Holostomidse). 
No. 1, Pharyngostomum cordatum (Diesing) Ciurea. (Trans. Amer. Micr. 
Soc, 45, 1-8.) No. 2, Taxonomy. (Ibid., 45, 11-19.) No. 3, Relation- 
ships. (Ibid., 45, 265-81.) 

La Valette Saint-George, A. J. H. de (1855), Symbolw ad trematodum 
evolutionis historiam. (Berolini, 38 pp., 2 pis.) 

Layman, E. M. (1930), Parasitic worms from the fishes of Peter the Great Bay. 
(Bull. Pacif. Fish Res. Sta., 3, 1-120.) 

(1933), Les vers parasitaires des poissons du lac Bajkal. (Trav. Sta. 

limnol. Lac Bajkal, 4, 5-93.) (Russian ; German summary.) 

and Borovkova, A. M. (1926), Vers parasites de la raie (Raja radiata 



Don) d'apres les materiaux de la 15 e expedition helminthologique de la 
Confederation. (Trav. Lab. Parasit. Univ. d'Etat Moscou, 1, 9-26, figs. 
1-13.) 
Lebour, M. V. (1907), On three mollusc-infesting trematodes. (Ann. Mag. 
Nat. Hist. (7), 19, 102-6.) 

(1908a), Fish trematodes of the Northumberland Coast. (Rep. Nor- 

thumb. Fish. Comm. for 1907, 23-67 [but 3-47 in my reprint, this paging 
having been used], 5 pis.) 

(19086), Trematodes of the Northumberland Coast No. 2. (Trans. Nat. 

Hist. Soc. Northumb., 3, n.s., 28-45.) 

(1910), Acanthopsolus lageniformis n.sp., a trematode in the catfish. 

(Rep. Northumb. Sea Fish. Comm. for 1909 and to June 15, 1910, 29-35.) 

(1916-18o), Medusae as hosts for larval trematodes. (J. Mar. Biol. 

Ass. U.K., n.s., 11, 57-9.) 

(1916-186), Some parasites of Sagitta bipunctata. (Ibid., 11, 201-6.) 

(1923), Note on the life-history of Hemiurus communis. (Parasitology, 

15, 233-5.) 

(1935), Hemiurus communis in Acartia. (J. Mar. Biol. Ass. U.K., 



20, 371-2.) 

Leidy, J. (1891), Notices of Entozoa. (Proc. Acad. Nat. Sci. Phil., 42, 

410-18.) 
Lepeskin, V. D. (1914), Zur Ovogenese der Zoogonus mirus. (Moskva J. Sect. 

Zool. Soc. Nat., 2, 1-85.) 
Leuckart, F. S. (1827), Versuch einer naturgemdssen Eintheilung der Hel- 

minthen nebst dem Entwurfe einer Verwandschafts- und Stufenfolge der Thiere 

uberhaupt. (Heidelberg.) 

(1828), Breves animalium quorundam maxima ex parte marinorum 

descriptiones. (Heidelberg.) 

(1830), Isis. 

(1835), Froriep's Notizen 46, 1835, p. 88, Isis, 1836, p. 764. (Report in 

Versamml. deutscher Naturf. u. Aerzte in Bonn, 1835.) 

(1842), Helminthologische Beitrage. (Zool. Bruchstucke, 3, 60pp., 2 pis.) 



Leuckart, K. G. F. R. (1857), Bericht iiber die Leistungen in der Naturgeschichte 

der niederen Thiere wahrend des Jahres 1856. (Arch. Naturg. Berlin, 22, 

165-272.) 
Levinsen, G. M. R. (1881), Bidrag til Kundskab om Gronlands Trematod- 

fauna. (K. Danske Vidensk. Selsk. Forh., 49-84.) 
Le'wis, F. J. ( 1935), The trematode genus Phyllodistomum Braun. (Trans. Amer. 

Micr. Soc, 54, 103-17.) 
Linstow, O. von (1877), Enthelminthologia. (Arch. Naturg.. 43, 173-98, 

Pis. 12-14.) 



LIST OF LITERATURE 321 

Linstow, O. VON (1878), Neue Beobachtungen an Helminthen. (Ibid., 44, 
218^5, Pis. 7-9.) 

(1878-89), Compendium der Helminthologie. (Hanover.) 

(1879), Helminthologische Studien. [Ibid., 45, 165-88, Pis. 11, 12.) 

(1880), Helminthologische Untersuchungen. (Ibid., 46, 41-54, PI. 3.) 

(1882), Helminthologische Studien. (Arch. Naturg., 48, 1-25, Pis. 1, 2.) 

(1885), Beobachtungen an bekannten und neuen Nematoden und Trema- 

toden. (Ibid., 51, 235-55, Pis. 13-15.) 

(1894), Helminthologische Studien. (Jenaische Zs. Naturw., 28 (n.f. 

21), 328-42, Pis. 22-3.) 

(1903), Neue Helminthen. (Zbl. Bakt. Orig., 35, 352-7, figs. 1-8.) 

(1904), Ueber eine neue Art der Copula bei Distomen. (Zool. Anz. 

Leipzig, 28, 252-4.) 

(1907), Zwei neue Distomum aus Lucioperca sandra der Wolga. (Ann. 



Mus. Zool. St. Petersburg, 12, 201-2, fig. 1.) 
Linton, E. (1898), Notes on trematode parasites of fishes. (Proc. U.S. Nat. 
Mus. (1133), 20, 507^8.) 

(1901), Parasites of fishes in the Woods Hole region. (Bull. U.S. Fish. 

Comm. 1900, 405-92.) 

(1905), Parasites of fishes of Beaufort, North Carolina. (Bull. U.S. 

Bur. Fish. 1904, 24, 321-428.) 

(1907). Notes on parasites of Bermuda Fishes. (Proc. U.S. Nat. Mus., 

33, 83-126, Pis. 1-15.) 

(1910), Helminth fauna of the Dry Tortugas. II. Trematodes. (Publ. 

Carnegie Inst. Wash., No. 133, 11-98.} 

(1940), Trematodes from fishes mainly from the Woods Hole region, 



Massachusetts. (Proc. U.S. Nat. Mus. (3078), 88, 1-172.) 
Little, P. A. (1929a), The trematode parasites of Irish marine fishes. (Para- 
sitology, 21, 22-30.) 

(19296), Trochopus gaillimhe n.sp., an ectoparasitic trematode of Trigla 

hirundo or Trigla lucerna. (Ibid., 21, 107-19.) 

(1929c), The anatomy and histology of Phyllonella solew Ben. & Hesse, 

an ectoparasitic trematode of the sole, Solea vulgaris Quensel. (Ibid., 
21, 324-37.) 

(1930), A new trematode parasite oiAcipenser sturio L. (Royal Sturgeon), 



with a description of the genus Dihemistephanus Lss. (Ibid., 22, 399-413. 
Llewellyn, J. (1941a), A description of the anatomy of the monogenetic 

trematode Choricotyle chrysophryi. (Ibid., 33, 397-405.) 
(19416), A revision of the Monogenean family Diclidophoridse Fuhrmann, 

1928. (Parasitology, 33, 416-30.) 

1941c), The taxonomy of the monogenetic trematode Plectanocotyle 



gurnardi (v. Ben. & Hesse). (Ibid., 33, 431-2.) 
Lloyd, L. C. (1938), Some Digenetic trematodes from Puget Sound Fish. (J. 

Parasit., 24, 103-33.) 
and Guberlet, J. E. (1932), A new genus and species of Monorchidae. 

{Ibid., 18, 232-9.) 
Loewen, S. L. (1929), A description of the trematode Catoptroides lacustri n.sp., 

with a review of the known species of the genus. (Parasitology, 21, 

55-62.) 
Lonnberg, E. (1891), Mitteilungen iiber einige Helminthen aus dem Museum 

der Universitat Kristiania. (Biol, foren. forhandl. Verh. d. biol. Ver. 

Stockholm, 3, p. 15.) 
Looss, A. (1885), Beitrage zur Kenntnis der Trematoden. (Z. wiss. Zool., 41, 

390-446, PI. 23.) 

21 



322 THE TREMATODA OF BRITISH FISHES 

Looss, A. (1894), Die Distomen unserer Fische und Frosche. Xeue Untersuch- 
imgen uber Bail und Entwicklungs der Distomenkorpers. (Biblioth. 
Zool, 16, 1-296, 9 pis., 192 figs.) 

(1896), Recherches sur la faune parasitaire de l'Egypte. Premiere 

Partie. (Mem. Inst. Egypt., 3, 1-252.) 

(1899), Weitere Beitrage zur Kenntniss der Trematoden-Fauna Agyp- 

tens, zugleich Versuch einer natiirlichen Gleiderung der Genus Distomum 
Retzius. (Zool. Jb. Syst., 12, 521-784, Pis. 24-32, figs. 1-90.) 

(1900), Nachtragliche Bemerkungen zu den Narnen der von mir vorge- 

schlagenen Distoniengattungen. (Zool. Anz. Leipzig, 23, No. 630, 601-8.) 

(1901«), Ueber einige Distomen der Labriden des Triester Hafens. 

(ZU. Bakt., 29, 398-405, 437^2.) 

(19016), Ueber die Fasciolidengenera Stephanochasmus, Acanthochasmus 

und einige andere. {Ibid., 29, 595-606, 628-34, 654-61.) 

(1902a), Zur Kenntnis der Trematodenfauna des Triester Hafens. 

I. Ueber die Gattung Orophocotyle n.g. (Ibid., 31, 637-44.) 

(19026), Uber Monorchis Monticelli and Haplosplanchnus n.g. (Ibid., 

32, 115-22.) 

(1902c), Die Distomen-Unterfamilie der Haploporinae. (Arch. Parasit., 

6, 129^3.) 

(1902a 7 ), Uber neue und bekannte Trematoden aus Seeschildkroten. 

(Zool. Jb. Syst., 16, 411-889.) 
(1907), Zur Kenntnis der Familie Herniuridae. (Zool. Anz. Leipzig, 

3, Nos. 19/20, 585-619.) 

(1908), Beitrage zur Systematik der Distomen. Zur Kenntnis der 



Familie Hemiurida;. (Zool. Jb. Syst., 26, 64-180, Pis. 7-15.) 
— (1912), Uber den Bau einiger anscheinend seltener Trematodenarten. 

(Zool. Jb.Suppl.,15, 1, Feschr. z. 60 geb. J. W. Spengel, 323-66, Pis. 17-19, 

figs. 1-22.) 
Lorenz, S. (1878), Ueber die Organisation der Gattungen Axine und Micro- 

cotyle. (Arb. Zool. hist. Univ. Wien, 1, 405-36, Pis. 1, 2, figs. 1-18 ; PI. 3, 

figs. 1-6.) 
Luhe, M. (1900), Ueber die Gattung Podocotyle (Duj.) Stoss. (Zool. Anz., 23, 

No. 624, 487-92.) 
(1901a), Ueber Hemiuriden (Ein Beitrag zur Systematik der digenetischen 

Trematoden). (Ibid., 24, No. 647, 394-403, figs. 1, 2 ; No. 650, 473-88, 

fig. 1.) 
- (19016), Ueber Monostomum orbiculare. (Zbl. Bakt., 29, 49-60.) 
(1909), Parasitische Plattwurmer. I. Trematodes. (In Siissicasser- 



fauna Dentschlands (Brauer), Jena, 17, 1-217, 188 figs.) 

MacCallum, G. A. (1913a), Further notes on the genus Microcolyk. (Zool. Jb. 
Syst., 35, 389^02.) 

(19136), Notes on four trematode parasites of marine fishes. (Zbl. 

Bakt. Orig., 70, 407-13.) 

(1916), Some new species of parasitic trematodes from marine fishes. 

(Zoopathologica, New York, 1, 3-38.) 

(1921), Studies in helminthology. (Ibid., 1, 137-284.) 

(1926a), Deux nouveaux trematodes parasites de Carcharhinus commer- 

sonii : Philura ovata et Dermophthirius carcharhini. (Ann. Parasit. Hum. 
Comp., 4, 162-71.) 

- (19266), Dermophagus squali n.g., n.sp. (Ibid., 4, 330-2.) 
(1926c), A propos des genros Philura et Dermophthiriua MacCallum, 



1926. (Ibid., 4, 386.) 



LIST OF LITERATURE 323 

MacCallum, G. A. (1927a), Rectification de nomenclature. (Ibid., 5, 382.) 

(19276), A new ectoparasitic trematode, Epihdella melleni sp. nov. 

(Zoopathologica, New York, 1, 291-300.) 

(1931), Four new species of trematode worms of the sub-family Oncho- 

cotylinae. (Proc. U.S. Nat. Mus. (2892), 79 (26), 1-8.) 

and MacCallum, W. G. (1913a), Four species of Microcotyle, M. 

pyragraphorus, mucroura, eueides and acanthophallus. (Zool. Jb. Syst., 
34, 223-44.) 

(19136), On Aspidogaster ringens (Linton) and A. kemostoma 

n.sp. (Ibid., 34, 245-56.) 
Maclaren, N. (1903a), On trematodes and cestodes parasitic in Fishes. (Rep. 

Brit. Ass. Adv. ScL, 72 (Belfast, 1902), 260-2.) 
— (19036), Ueber die Haut der Trematoden. (Zool. Anz., 26 (702), 516-24.) 

(1904), Beitrage zur Kenntnis einiger Trematoden (Diplectanum cequans 

Wagener und Nematobothrium molce n.sp. (Jena Z. Xaturwiss., 38, 573- 
618.) 

Maddox, R. L. (1867), Some remarks on the parasites found in the nerves, 
etc., of the common haddock. (Q. J. 3Iicrosc. Sci., 7, N.S., 87.) 

Manter, H. W. (1926), Some North American fish trematodes. (III. Biol. 
Monogr., 10, 1-138.) 

■ (1931), Some digenetic trematodes of marine fishes of Beaufort, North 

Carolina. (Parasitology, 23, 396-411.) 

(1933), The genus Helicometra and related trematodes from Tortugas, 

Florida. (Pap. Tortugas Lab. Publ. Carnegie Inst. Wash., 28 (No. 435), 
Paper 11, 167-82.) 

(1934), Some digenetic trematodes from deep-water fishes of Tortugas, 

Florida. (Ibid. (435), Paper 16, 257-345.) 

(1937), The status of the trematode genus Deradena Linton with a 



description of six species of Haplosplanchnus Looss (Trematoda). (SJerjabin 
Jub. Vol., 381-7.) 

— (1939), Digenetic trematodes of fishes of the Galapagos Islands and their 
relationships. (•/. Parasit., 35 (Abstr.), 25.) 

— (1940a), Digenetic trematodes of fishes from the Galapagos Islands and 
the neighbouring Pacific. (Rep. Coll. A. Hancock Pacific Exp., 1932-8, 
2 (14), 329-497.) 

— (19406), The geographical distribution of digenetic trematodes of marine 
fishes of the tropical American Pacific. (Ibid., 2 (16), 531-47.) 

— (1940c), Gasterostomes (Trematoda) of Tortugas, Florida. (Pap. 
Tortugas Lab. Publ. Carnegie Inst. Wash., 33 (No. 524), 1-19.) 

(1941), Observations on the geographical distribution of digenetic 



trematodes of marine fishes. (J. Parasit., 27 (Abstr.), 72, 33^.) 
Markell, E. K. (1943), Gametogenesis and egg-shell formation in P robot itrema 

californiense Stunkard, 1935 (Trematoda, Gorgoderidae). (Trans. Amer. 

Micr. Soc, 62, 27-56.) 
Markewitsch, A. T. (1933), Neue Dactylogyrus-Art (Monogenea) aus dem 

Ukraine. (Zool. Anz. Leipzig, 103, 18-20.) 
Markowski, S. (1933), Die Eingeweidewiirmer der Fische des Polnischen 

Balticums (Trematoda, Cestoda, Nematoda, Acanthocephala). (Arch. 

Hydrobiol. Ichthyol., Suwalki, 7, 1-58, 34 figs.) 
(1935), Die parasitische Wiirmer von Gobius minutus Pall, des polnischen 

Balticums. (Bull. int. Acad. Cracovie, 2, 251-60.) 
Martiis, C. de (1925), Nuovo gyrodaetylide parassita nella cavita olfattiva di 

Amiurus catus L. (Boll. Soc. Xat. Xapoli, 1924, 36, 2s, 16 (ann. 38), 

76-81.) 



324 THE TREMATODA OF BRITISH FISHES 

Martin, W. E. (1938a). Studies on the trematodes of Woods Hole : The life 
cycle of Lepocreadium setiferoides (Miller & Northup), Allocreadiidse, and 
the description of Cercaria cumingice n.sp. (Biol. Ball., 75, 463-74.) 

(19386), The life cycle of Stephanostomum tenue (Linton), family Acantho- 

colpidse. (J. Parasii., 24, Abstr., 27.) 

(1939a), Studies on the trematodes of Woods Hole. II. The life cycle 



of Stephanostomum tenue (Linton). (Biol. Bull. W.H., 77, 65-73.) 
(19396), The life cycle of Honor cheides cumingice (Martin), (Trematoda, 

Monorchidse). (J. Parasit., 25, Abstr., 18.) 
(1940), III. The life cycle of Monorcheides cumingice (Martin), with 

special reference to its effect on the invertebrate host. (Biol. Bull., 79, 

131-44.) 
Massa, D. (1906), Materiali per una revisione del genere Trochopus. (Arch. 

Zool. Napoli, 3, 43-71.) 
Mathias, P. (1934), Sur quelques trematodes de poissons marms de la region de 

Banyuls. (Arch. Zool. exp. gen., 75, 567-81, 6 figs.) 

(1937), Cycle evolutif d'un trematode de la famille Allocreadiidse 

Stossich (Allocreadium augusticolle (Hausmann)). (G. R. Acad. Sci., 205, 
626-8.) 

McFarlane, S. H. (1936), A study of the endoparasitic trematodes from marine 

fishes of Departure Bay, B.C. (J. Biol. Bd., Canada, 2, 335-47.) 
Miller, M. J. (1941), A critical study of Stafford's report on " Trematodes of 

Canadian Fishes " based on his trematode collection. (Canad. J. Res., 

D 19, 28-52.) 
Meserve, F. G. (1938), Some monogenetic trematodes from the Galapagos 

Islands and the neighboring Pacific. (Rep. A. Hancock Pacific Exp., 

2 (5), 31-88.) 
(1943), Phyllodistomum coatneyi n.sp., a trematode from the urinary 

bladder of Ambystoma maculatum (Shaw). (J. Parasit., 29, 226-8.) 
Mizelle, J. D. (1938), Comparative studies on trematodes (Gyrodactyloidea) 

from the gills of North American freshwater fishes. (III. Biol. Monogr., 

17, No. 1, 81.) 

(1940a), Studies on Monogenetic Trematodes. II. New species from 

Tennessee. (Trans. Amer. Micr. Soc, 59, 285-9.) 

(19406), III. Redescriptions and variations in known species. (J. 

Parasit., 26, 165-78.) 

(1941), IV. Anchor adiscus, a new Dactylogyrid genus from the Blue- 
gill and the Stump-knocker Sunfish. (Ibid., 27, 159-63.) 

and Blatz, V. (1941), Studies on Monogenetic Trematodes. VI. Two 



new Gvrodactylid genera from Florida fishes. (Amer. Midi. Nat., 26, 

105-9.)" 
Modeer, A. (1790), Tillagningar. (Kgl. svensk. Vetensk. Acad, nye for LL 

Stockholm, 126-30.) 
Mola, P. (1912), Die Parasiten des Cottus gobio. (Zbl. Bakt., 65, 491-504.) 
Moniez, R. (1891), Sur les differences exterieures que peuvent presenter ies 

Nematobothrium, a propos d'une nouvelle espece. (Rev. biol. Nord France, 

3, 184-7.) 
Molin, R. (1858), Prospectus helminthum, quae in prodromo faume helmin- 

thologicse Venetian continentur. (SB. Akad. Wiss. Wien, 30, No. 14, 

127-58.) 
(1859), Catalogo di verrni intestinali da lui trovati nelle provincie venete. 

(Atti 1st. Ven., Venezia, 1858-9, 2 ser., 4, No. 5, 400-9.) 
(1861), Prod romus Fauna? helminthologica? venetse, (Denkschr. k.Akad. 

Wiss. Wien, 19, 189-338, Pis. 1-15.) 



LIST OF LITERATURE 325 

Monticelli, P. S. (1888), Saggio di una morfologia dei trematodi. (Tesi per 
ottenere la private docenza in zoologie nella R. TJniversita di Napoli, 3-130.) 

(1889a), Elenco degli elminti raccolti dal Capitano G. Chierchia durante 

il viaggio di circumnavigazione della r. corvetta " Vettor Pisani." (Boll. 
Soc. Nat. Napoli, ser. 1, 3, No. 1, 67-71.) 

(18896), Di un distoma deWAcanthias vulgaris. Nota preliminare. 

(Ibid., ser. 1, 3, 132-4.) 

(1889c), Notes on some entozoa in the collection of the British Museum. 

(Proc. Zool, Soc. Lond., Nos. 21-22, 321-5, PI. 33.) 

(1890a), Elenco degli Elminti studiati a Wimereux nella primavera 

del 1889. (Bull, sci France et Belgique, 22, 4th ser., 1, 417-44, PI. 22, figs. 
1-27.) 

(18906), Note elmintologiche. (Boll. Soc. Nat. Napoli, ser. 1, 4, 

189-208.) 

■■ — (1891), Di alcuni organi di tatto nei Tristomidi. Contributo alio studio 

dei Trematodi monogenetici. Parte 1. (Ibid., ser. 1, 5, 99-134, Text-fig. 
1, Pis. 5, 6, figs. 1-41.) 

(1892a), Dei Monostomum del Box Salpa. (Atti Accad. Sci. Torino, p. 271 . ) 

(18926) Cotylogaster michcelis n.g., n.sp. e revisione degli Aspidoboth- 

riidse. (Festschr. z. 70 Geburtst. R. Leuckarts, Leipzig, 168-214, Pis. 21-2.) 
(1893a), Studii sui Trematodi endoparassiti. Primo contributo di 



osservazioni sui Distomidi. (Zool. Jb. Suppl. Ill, 1-230, Text-figs. A-C, 

Pis. 1-8, figs, i-xviii, 1-137.) 
(18936), Intorno ad alcuni elminti della collezione del Museo Zoologico 

della reale Universita di Palermo. (Nat. sicil. Palermo, 12, Nos. 7-8, 167-80 ; 

No. 9, 206-8, PI. 1, figs. 1-12.) 

(1899a), II genere Acanthocotyle. (Arch. Parasit, Paris, 2, 75-120.) 

(18996), Di una nuova specie del genere Plectanocotyle. (Atti Accad. 

Torino, 34, 1045-53.) 

(1902), A proposito di una nuova specie del genere Epibdella. (Boll. 

Soc. Nat. Napoli, 15, 137-45.) 

(1903), Per una nuova classificazione degli Heterocotylea. (Monit. 

zool. ital, 14, 334-6.) 

(1904), II genere Lintonia Monticelli. (Arch. Zool., 2, 117-24.) 

(1905), Osservazioni intorno ad alcune specie di Heterocotylea. (Boll. 

Soc. Nat. Napoli (1904), ser. 1, 18, 65-80.) 
(1907), II genere Encotyllabe Diesing. (Atti 1st. Sci. not. Naples, 59, 

23-35.) 
(1908), II genere Nitzschia von Baer. (Annuario museo. zool. Napoli, 

N.s. 2, 27, 19 pp.) 

(1909), Identificazione di una n.sp. del genere Encotyllabe (lintonii 

Monticelli). (Boll. Soc. Nat. Napoli (1908), 22, ser. 2, 2, 86-8.) 

(1910), Calinella craneola n.g., n.sp. Trematode nouveau de la famille 



des Udonellidse provenant des campagnes de S.A.S. le Prince de Monaco. 
(Ann. Inst, ocean. Monaco, 1, 1-9.) 
Mueller, J. F. (1934), Parasites of Oneida Lake Fishes. Part IV. Additional 
notes on parasites of Oneida Lake fishes, including descriptions of new 
species. (Roosevelt Wild Life Ann., 3 (3-4), 335-73.) 

(1936a), Studies on North American Gyrodactyloidea. (Trans. Amer. 

Micr. Soc, 55 (1), 55-72.) 

(19366), New gyrodactyloid trematodes from North American fishes. 

(Ibid., 55 (4), 457-64.) 

(1937), The Gyrodactylidse of North American freshwater fishes. (Fish 

Culture, 3 (1), 1-14.) 



32f) THE TREMATODA OF BRITISH FISHES 

MtJHLiNu. 1'. (1898), Die Helminth-Fauna der Wirbeltiere Ostpreussens. (Arch. 
Naturg., 1, 1-118.) 

Mi hlschlag, G. (1914), Beit rag zur Kenntnis der Anatomie von Otodistomum 

reliporum (Creplin), Distomum fuscum Poirier und Distomum ingens Moniez. 

(Zool. Jb. Syst., 37, 199-252, Text-figs. A-P, Pis. 9, 10, figs. 1-12.) 
Muller, O. F. (1776), Zoologicce danicce prodromus seu animalium Danice et 

Norvegice indigenarum charactered nomina et synonyma imprimis popular ium. 

(Havnise.) 

(1779), Zoologica danica seu animalium Danice et Norvegice rariorum et 

minus notorum descriptiones et historia. (First ed. 1777, last 1788-1806.) 

Murray, F. V. (1931), Gill trematodes from some Australian fishes. (Para- 
sitology, 23, 492-506.) 

Nagano, K. (1930), On the intermediate host of Asymphylodora tinea' in Japan. 

(Trans. II Ann. Meet. Parasit. Soc. Japan, 24.) (Japanese.) 
Nagaty, H. F. (1937), Trematodes of fishes from the Red Sea. Part I. Studies 

on the family Bucephalidae Poche, 1907. (Egypt. Univ. Faculty Med. 

Publ, 12, 1-172.) 
Nardo, D. (1827), Ueber den After der Distomen. (Z. org. Phys. 1, Eisenach, 

68-9.) 
Nickerson, W. S. (1895), On Stichocotyle nephropis Cunningham, a parasite of 

the American Lobster. (Zool. J. Anat., 8, 447-80, 3 pis.) 

(1902), Cotylogaster occidentalis n.sp. and a revision of the family Aspido- 

bothridse. (Ibid., 15, 597-624, 2 pis.) 

Nicoll, W. (1906), Some new and little-known trematodes. (Ann. Mag. Nat. 
Hist., (7), 17, 513-26.) 

(1907), A contribution towards a knowledge of the entozoa of British 

Marine Fishes. Part I. (Ibid., (7), 19, 66-94.) 

(1909a), Studies on the structure and classification of the digenetic 

trematodes. (Quart. J. Micros. ScL, 53, 391-487.) 

(19096), A contribution towards a knowledge of the entozoa of British 

marine fishes. Part 2. (Ann. Mag. Nat. Hist., (8) 4, 1-25.) 

(1910), On the entozoa of fishes from the Firth of Clyde. (Parasit- 
ology, 3, 322-59.) 

(1912), On two new trematode parasites from British food-fishes. 

(Ibid., 5, 197-202.) 

(1913a), New trematode parasites from fishes of the English Channel. 

[Ibid., 5, 238-46.) 

(19136), Trematode parasites from food-fishes of the North Sea. (Ibid., 

6, 188-94.) 

(1914), Trematode parasites of fishes in the English Channel. (J. Mar. 



Biol. Ass. U.K., N.S. 10, 466-505.) 

— (1915), A list of the trematode parasites of British marine fishes. (Para- 
sitology, 7, 339-78.) 

— (1924), A reference list of the trematode parasites of British freshwater 
fishes. (Ibid,, 16, 127^4.) 

- (1934, 1935), Vermes section in Zool. Pec. (Zool. Soc. London), 
and Small, W. (1909), Notes on larval trematodes. (Ann. Mag. Nat. 



Hist., (8) 3, 237^6.) 

Noble, A. E., and Noble, G. A. (1937), Accacladium nematulum n.sp.,a trema- 
tode from the Sunfish Mola mola. (Trans. Amer. Micr. Soc, 56, 55-60.) 

and Park, J. T. (1937), Helicometrina elongata n.sp. from the 

Gobiesocid fish Caularchus meandricus, with an emended diagnosis of the 
trematode genus Helicometrina. (Ibid., 56, 344-7.) 



LIST OF LITERATURE 327 

Nordmann, A. von (1832), Mikrographische Beitrdge zur Naturgeschichte der 
wirbellosen Thiere. First Part. (Berlin, 118 pp.) 

(1833), Zu Diplozoon paradoxum. (Ann. sci. not., 30, 372-98.) 

(1840), Les vers (vermes). (In Lamarck, Histoire naturelle des animaux 

sans vertebres, Paris, 2, Ed. 3, 542-686.) 

Xybelin, O. (1924), Dactylogyrus vastator n.sp. (Ark. Zool. Stockholm, 16, 
No. 28, 1-2, 3 figs.) 

(1926), Zur Helminthenfauna der Siisswasserfische Scliwedens. I. Phyllo- 

distomum. (Goteborgs Vetensk. Samh. Handl. (4), 31, 3, 1-29.) 

(1932), Crepidostomum suecicum n.sj>., ein Trematode mit ungewohnlich 

weiter morphologischer Variationsbreite. (Ark. Zool. Stockholm, 25, B 1, 
1-6.) 

(1936), Bunocotyle cingulata Odhner, ein halophiler Trematode des 

Flussbarsches mid Kaulbarsches der Ostsee. (Ibid., 28 B, 10, 1-6.) 

;1937), Kleine Beitrage zur Kenntnis der Dactylogyren. (Ibid., 29 A, 



3, 1-29, 28 figs. 

Odhner, T. (1898), Uber die geschlechtsreife Form von Stichocotyle nephropsis 
Cunningham. (Zool. Anz. Leipzig, 21, 509-13.) 

(1900), Aporocotyle simplex n.g., n.sp., ein neuer Typus von Ecto- 

parasitischen Trematoden. (Zbl. Bakt., 27, 62-6.) 

(1901), Revision einiger Arten der Distomengattung Allocreadium 

Looss. (Zool. Jb. Syst,, 14, 483-520.) 

(1902), Mitteiluno-en zur Kenntnis der Distomen. (Zbl. Bakt.. 31, 

56-9, 152-62.) 

(1905), Die Trematoden des arktischen Gebietes. (Fauna Arctica, 4, 

289-372, figs. 1-4, Pis. 2-4.) 

(1906), Die wahre Bau des Synaptobothrium copulans v. Linstow, 1904, 

einer von ihrem Autor verkannten Distomide. (Zool. Anz., 30, 59-66.) 

(1907), Zur Anatomie der Didymozoon : ein getrenntgeschlechtlicher 

Trematode mit rudimentarem Hermaphroditismus. (In Zool. Stud, 
tillagnade, Prof. T. Tullberg, Uppsala, 1907, 309-42.) 

(1910), Nordafrikanische Trematoden grosstenteils vom weissen Nil. 

(Res. Sived. Zool. Exped. to Egypt and White Nile, 1901, No. 23a, 1-170.) 

(1911), Zum naturlichen System der digenen Trematoden. I. Angio- 

dictyidse (Zool. Anz., 37, 181-91). II. ZoogonidaB {ibid., 37, 237-53). 
III. Steringophoridse (ibid., 38, 97-117). IV. Azygiidse {ibid., 38, 513-31). 

(1912), Die Homologien der weiblichen Genitalwege bei den Trematoden 

und Cestoden. (Ibid., 39, 327-51.) 

(1913), Noch einmal die Homologien der weiblichen Genitalwege der 

monogenen Trematoden. (Ibid., 41, 558-9.) 

(1914), Cercaria setifera Monticelli. Eine Larvenform von Lepocreadium 

album Stoss. (Z. Beitr. Uppsala, 3, 247-55.) 

(1924), Remarks on Sanguinicola. (Quart. J. Micros. Sci., 68, 403-11). 

(1927), tiber Trematoden aus der Schwimmblase. (Ark. Zool. Stock- 
helm, 19a, N:o 15, 1-9, figs. 1, 2.) 

(1928«), Weitere Trematoden mit anus. (Ibid., 20b, N:o 2, 1-6, 

figs. 1-5.) 

(19286), Rhynchopharynx paradoxa n.g., n.sp., nebst Revision der Acca- 



coeliiden von Orthagoriscus mola. (Zool. Anz., 77, 167-75.) 
Oken, L. (1815), Lehrbuch der Naturgeschichte, 3 Theil ; Zoologie. 1 Abt. ; 

Fleischlose Thiere, 1, part 1, 842 pp., 40 pis. 
Olfers, J. F. M. de (1817), De vegetativis et animatis corj)oribus in corporibus 

animalium reperiundis. (Berol.) 



328 THE TREMATGDA OF BRITISH FTSHES 

Olsson, P. J. (1868), Entozoa, iakttagna hos skandinaviska hafsfisker. I. 
Platyhelminthes. (Lund's Univ. Arsskrift, 4, Art. 8, 1-64, Pis. 3, 4, figs. 
52-108.) 

(1869a), Nova genera parasitantia Copepodorum et Platyhelminthum. 

(Ibid., 6, 6 pp.) 

(18696), Om entozoemas geografiska utbrecbiing och f orekomst hos olika 

djur. (Forhandl. ved. Skand. Naturforsk. Cristiania, 10 M de, 481-515.) 

(1876), Bidrag till Skandinaviens helminthfauna. (Kongl. Svenska 

Vetensk. Akad. HandL, 14, N:o 1, 1-35, Pis. 1-4, figs. 1-71.) 

- (1893), Idem. II. (Ibid., 25 (12), 1-41, Pis. 1-5, figs. 1-81.) 
(1896), Sur Chimcera monstrosa et ses parasites. (Mem. Soc. Zool. Fr., 



9, 499-512, figs. 1-9.) 
Osborne, H. L. (1903), Bunodera cornuta sp. nov. : a new parasite from the 

crayfish and certain fishes of Lake Chautauqua, N.Y. (Biol. Bull., 5, 

63-73.) 
Otto, A. W. (1823), Beschreibung einiger neuen Mollusken und Zoophyten. 

(Nova Acta Acad. nat. curios, Bo?ince, 11, 273-314.) 
Ozaki, Y. (1924), Studies on the gasterostome trematodes with descriptions of 

three new genera. (Preliminary note : Japanese.) (Dobutsu Gaku Zasshi, 

36, 173-201, 12 text-figs., PI. 4.) 
(1925), On a new genus of fish trematodes, Genarchopsis, and a new 

species of Asymphylodora. (Jap. J. Zool., 1, 101-8.) 

(1928a), Some gasterostomatous trematodes of Japan. (Ibid., 2, 



35-60.) 

(19286), On some trematodes with anus. (Ibid., 2, 5-33. 



Ozerska, W. N. (1926), Parasitic helminth fauna of Don Region, Russia. 
(Russian.) (Trudy Gos. Inst. Eksper. Vet. Moskow, 2, 103.) 

Palombi, A. (1929a), Ricerche sulciclo evolutivo di Helicometra fasciata (Rud.). 
Revisione delle specie del genere Helicometra Odhner. (Pubbl. Staz. zool. 
Napoli, 9, 237-92, 33 figs.) 

(19296), II ciclo biologico de Diphterostomum brusince Stossich (Tre- 

matode digenetico : Fam. Zoogonidse Odhner). (B. C. Accad. Lincei, 
(6), 10, 274-7.) 

(1930a), II ciclo biologico di Diphterostomum brusince Stossich. (Trema- 

tode digenetico : Fam. Zoogonid?e Odhner.) Considerazioni sui cicli 
evolutivi delle specie affini e dei trematodi in generale. (Pubbl. Staz. zool. 
Napoli, 10, 111-49.) 

(19306), II ciclo evolutivo di Diphterostomum brusince Stossich. (Riv. 

Fis. mat.-sci. nat. Napoli, ser. 2, 4, 8, 1-3.) 

(1931a), II polimorfismo dei Trematodi. Ricerche sperimentali sul 

Helicometra fasciata (Rud.). (Ann. Mus. zool. Univ. Napoli, n.s. 6, No. 5, 
1-8.) 

(19316), Per una migliore conoscenza del Trematodi endoparassiti dei 

pesci del golfo di Napoli. I. Steringotrema divergens (Rud.) e Haploporus 
benedeni (Stoss.). (Ibid., n.s. 6, 15 pp.) 

(1932a), Bacciger bacciger (Rud.) Nicoll, 1914 forma adulta di Cercaria 

pectinata Huet, 1891. (Boll. Soc. Nat. Napoli, 44, 217-20.) 

(19326), Rapporti genetici tra Cercaria setifera MonticeUi (non Joh. 

Miiller) ed alcune specie della famiglia Allocreadiida?. Brevi notizie sul 
ciclo biologico di Podocotyle atomon (Rud.). (Ibid., 44, 213-6.) 

(1934a), Gli stadi larvali dei Trematodi del Golfo di Napoli. I. Contri- 
bute alio studio della morfologia, biologia e sistematica delle cercarie marine. 
(P?<66. Staz. zool. Napoli, 14, 51-95.) 



LIST OF LITERATURE 329 

Palombi, A. (10346), Bacciger bacciger (Rud.). Trematode digenetico : fam. 
Steringophoridse Odhner. Anatoniia, sistematica e biologia. (Ibid., 13, 
438-78.) 

(1937a), La cercarise di Mesometra orbicularis (Rud.) e la sua trans- 

formazione in Metacercaria. Appunti sul ciclo evolutivo. (Riv. Parassit. 
Roma, 1, 13-17.) 

(19376), II ciclo biologico di Lepocreadium album Stossich sperimental- 

mente realizzato. (Ibid., 1, 1-12.) 

(1938a), Gli stadi larvali dei trematodi del golfo di Napoli. Secondo 

contributo alio studio della morfologia, biologia e sistematica delle cercarie 
marine (II gruppo delle cercarie cotiloeerche). (Ibid., 2, 189-206.) 

(19386), Metodi impiegati per lo studio dei cicli evolutivi dei Trematodi 

digenetici. Materiale per la conoscenza della biologia di Podocotyle atomon 
(Rud.). (Livro Jub. Prof. L. Travassos, Rio de Janeiro, 371-9.) 

(1940), Gli stadi larvali dei trematodi del golfo di Napoli. 39 contributo 



alio studio della morfologia, biologia e sistematica delle cercarie marine. 

{Riv. Parassit., 4, 7-30.) 
Park, J. T. (1936), Two new trematodes, Slerrhurus magnatestis and Tubilo- 

vesicula californica (Herniuridse) from littoral fishes of Dillon's Beach, 

California. (Trans. Amer. Micr. Soc, 55, 477-82.) 
(1937a), A revision of the genus Podocotyle (AUocreadiinse), with a 

description of eight new species from the Pool Fishes from Dillon's Beach, 

California. (J. Parasit., 23, 405-22.) 

(19376), A new trematode, Genitocotyle acirrus gen. nov., sp. nov. (Allo- 



creadiidse), from Holconotus rhodoterus. (Trans. Amer. Micr. Soc, 56, 
67-71.) 
Parona, C. (1894), 1'Elmintologia italiana da suoi primi tempi all'anno 1890. 
Storia, sistematica, corologia e bibliografia. (Atti. Univ. Genova, 13, 1-734.) 

(1896), Helminthum ex Conradi Paronce Museo Catalogus. Sect. I. 

Trematodes. (Genova, 4 pp.) 

(1911, 1912), V Elmintologia italiana da, suti primi tempi alVanno 1910. 

Bibliografia, sistematica, corologia. Storia. (I, 1911, 502 pp. ; II, 1912, 
540 pp.) 

(1919), II tonno e la sua pesca. (R. Comitato Talassografico Italiano, 



Mem. 68 (Venezia, 265 pp.).) 
Parona, C, and Monticelli, F. S. (1903), Sul genere Ancyrocotyle(n.g.). (Arch. 

Parasit. Paris, 7, 1, 117-21, PI. 3, figs. 1-6.) 
Parona, C, and Perugia, A. (1889), Di alcuni trematodi ectoparassiti di pesci 

marini. Nota preventiva (Resligusticse 8). (Ann. Mus. Stor. Nat., 27, 2, s. 7, 

740-7.) 
(1890a), Intorno ad alcune Polystomeae e considerazioni sulla 

sistematica di questa famiglia. (Atti. Soc. Ligust., Genova, 1, No. 3, 225-42.) 
(18906), Nuove osservazioni sulT Amphibdella torpedinis Chatin. 

(Ann. Mus. Stor. Nat., 29, 2, s. 9, 363-7.) 
(1892), Note sopra trematodi ectoparassiti (Res Ligusticse, 17). 

(Ibid., 32, 2, s. 12, 86-102.) 

(1895), Sopra due nuove specie di Trematodi ectoparassiti di pesci 



marini (Phylline monticellii e Placunella vallei). (Atti. Soc. Ligust., 6 (1), 

84-7 ; and Boll. Mus. Zool. Anat. Comp. Genova, (1895a), No. 31, 1^.) 
Patzelt, H. (1930), Dos Trematodos parasitos de Sardinella aurita Cuv. y Val. 

Aphanurus stossichi Mont, y Hemiurus appendiculatus Rud. (Notas Res. 

Inst, oceanogr. Madrid (2), 45, 1-23, 10 figs.) 
Pelseneer, P. (1906), Trematodes parasites de Mollusques marins. (Bull. Sci. 

Fr. Belg., 40, 161-86. 



330 THE TREMATODA OF BRITISH FISHES 

Perugia, A., and Parona, C. (1890), Di alcuni trematodi ectoparassiti di pesci 
adriatici. {Ann. Mus. Stor. Nat. (1889-90), 28, 2a, s. 9 (19), 16-32.) 

Pigulewsky, S. W. (1931), Neue Arten von Trematoden aus Fischen des Dnjepr- 
bassins. (Zool. Anz., 96, 9-18.) 

(1932), Fischparasiten des Dnjeprbassins (Russian). (Ann. Mus. zool. 

Acad. Leningrad, 32, 1931, 425-50 ; German summary, 451-2.) 

(1938), Zur Revision der Parasitengattmig Lecithaster Liihe, 1901. 



(Livro Jub. Prof. L. Travassos, Rio de Janeiro, 391-7.) 
Plehn, M. (1905), Sanguinicola armata und inermis (n.g.,n.sp.) n. fam. Rhyncho- 
stomatidse. Ein entoparasitisches Turbellar im Blute von Cypriniden. (Zool. 
Anz., 29, 244-52, 8 figs.) 

(1908), Ein monozoischer Cestode als Blutparasit (Sanguinicola armata 

und inermis Plehn). (Ibid., 33, 427-40, 6 figs.) 

Poche, F. (1907), Einige Bemerkungen zur Nomenclatur der Trematoden. (Ibid., 
31, 124-6.) 

(1926), Das Svstem der Platodaria. (Arch. Naturg. 91 Jahrgang (1925), 

Abt. A, Heft 2, 1-240 ; Heft 3, 241-458.) 

Popoff, P. (1926), Zur Fauna der parasitisch lebenden Wurmer des Don-Fluss- 
systems. Die parasitischen Wurmer des Brachsens (Abramis bra-ma). 
(Russ. Hydrobiol. Z. Saratov, 5, 64-71 ; French summary, p. 79.) 

Pratt, H. S. (1898), A contribution to the life history and anatomy of the appen- 
diculate distomes. (Zool. Jb. Anat., 11, 3-40.) 

(1900), Synopsis of North- American Invertebrates, 12. Part I. The 

Heterocotylea or monogenetic forms. (Amer. Nat., 34, 645-62, 50 figs.) 

(1902), Part 2. The Aspidocotylea and the Malacocotylea, or digenetic 



forms. (Ibid,, 36, 887-910 ; 953-80, figs. 1-130.) 

(1910), Monocotyle floridana, a new monogenetic trematode. (Paji. 

Tortugas Lab., 4, Carnegie Inst, Wash. Publ. (133), 1-9.) 

Price, E. W. (1934a), New Monogenetic trematodes from marine fishes. (Smith- 
sonian Misc. Coll., 91, No. 18, 1-3.) 

(19346), A new term for the adhesive organs of trematodes. (Proc. 

Helminth, Soc. Wash., 1 (2), p. 34.) 

(1936), North American monogenetic trematodes. (Bull. Geo. Wash. 

Univ. Wash., 1934-6, Summaries of Doctoral theses, 10-13.) 

(1937a), North American monogenetic trematodes. I. The superfamily 

Gyrodactyloidea. (J. Wash. Acad. Sci,, 27, 114-30 ; 146-64.) 

(19376), Redescriptions of two exotic species of monogenetic trematodes 

of the family Capsalidae Baird from the MacCallum collection. (Proc, 
Helminth. Soc, Wash., 4, 25-7.) 

(1937c), A new monogenetic trematode from Alaskan salmonoid fishes. 

(Ibid., 4, 27-9.) 

(1938a), A new species of Dactylogyrus (Monogenea ; Dactylogyridae) 

with the proposal of a new genus. (Ibid,, 5, 48-9.) 

(19386), North American trematodes. II. The families Monocotylidse, 

Microbothriidse, Acanthocotylidse and Udonellidse (Capsaloidea). (J. Wash. 
Acad. Sci., 28, 109-28 ; 183-98.) 

( 1939a), Idem, III. The family Capsalidse (Capsaloidea). (Ibid., 29, 63-92.) 

( 19396), Idem, IV. Polystomatidae (Polystomatoidea). (Proc. Helminth. 

Soc. Wash., 6, 80-92.) 

(1940a), A redescription of Onchocotyle emarginata Olsson, 1876 (Trema- 



toda ; Monogenea). (Ibid., 7, 76-8.) 

— (19406), A review of the trematode superfamily Opisthorchioidea. (Ibid,, 
7, 1-13.) 



LIST OF LITERATURE 331 

Price, E. W. (1942), North American monogenetic trematodes. V. The family 
Hexabothriidse n.n. (Polystomatoidea). (Ibid., 9, 39-56.) 

(1943«), Idem, VI. The family Diclidophoridae (Diclidophoroidea). (./. 

Wash. Acad. Sci., 33, No. 2, 44-54.) 

(1943&), Idem, VII. The family Discocotylidae (Diclidophoroidea). 



(Proc Helminth. Soc Wash., 10, No. 1, 10-15.) 

Railliet, A. (1896), Quelques rectifications a la nomenclature des parasites. 

(Bee. Med. Vet, 73, 8, s. 3, No. 5, 157-61.) 
Rathke, H. (1843), Beitrage zur Fauna Norwegens. (Nor. act. Acad. Caes. 

Leop. Carol, 20, 1-264.) 

(1844), Nachtragliche Bemerkungen zu den Beitragen zur Fauna 

Norwegens. (Arch. Naturg., 10 Jahrg., p. 259.) 

Rankin, J. S., jun. (1938), Studies on the trematode genus Brachycozlium Duj. 

I. Variation in specific characters with reference to the validity of the 

described species. (Trans. Amer. Micr. Soc, 57, 358-75.) 
Rees, G., and Llewellyn, J. (1941), A record of the trematode and cestode 

parasites of fishes from the Porcupine Bank, Irish Atlantic Slope and Irish 

Sea. (Parasitology, 33, 390-6.) 
Remley, L. W. (1942), Morphology and life history studies of Microcotyle spini- 

cirrus MacCallum, 1918, a monogenetic trematode parasitic on the gills of 

Aplodinotus grunniens. (Trans. Amer. Micr. Soc, 61, 141-55.) 
Richiardi (1902), Sopra una specie nuova di Didymozoon. (Atti Soc. Tosc Sci. 

Nat., Processi verbali, 13.) 
Risso, A. (1826), Histoire naturelle des principales productions de V Europe 

meridionale et principalemente de celles des environs de Nice et des Alpes 

Maritimes. ( Paris . ) 
Robin, C. (1846), Anatomie d'un organe decouvertsur l'ombre (Scicena umbra C). 

(Proc verb. Soc. phil. Paris, 28 Nov., and Ulnstitut, 15, No. 683, 1847.) 
Robinson, V. C. (1934), A new speciesof Accacceliid trematode (Accacladocoelium 

alveolatum n. sp. from the intestine of a sun-fish (Orthagoriscus mola Bloch.). 

(Parasitology, 26, 346-51.) 
Rudolphi, C. A. (1809), E?itozoorum sive vermium intestinaUum historia naturalis. 

Vol. II. (Amstelod.) 

(1819), Entozoorum Synopsis. (Berolini.) 

Rttskowski, J. S. (1934), Sur les vers parasites des chimeres. (Ann. Parasit. 
Hum. Comp., 12, 482-91, 6 figs.) 

Saint-Remy, G. (1891), Synopsis des trematodes monogeneses. {Rev. Biol. Nord. 
France, 3, 405-16, 449-57 ; 4, 1-21, 90-107.) 

(1898), Complement du Synopsis des trematodes monogeneses. (Arch. 

Parasit,, 1, 521-71.) 

Scheuring, L. (1920), Die Lebensgeschichte eines Karpfenparasiten (Sanguini- 
cola inermis Plehn). (Allgem. Fisch. Zeit., 45, 225-30.) 

(1923), Der Lebenszyklus von Sanguinicola inermis Plehn. (Zool. Jb. 

Anat., 44, 265-310.) 

Scott, A. (1901), Some additions to the fauna of Liverpool Bay. (Trans. Biol. 
Soc. Liverpool, 15, 344.) 

(1904), Some parasites found on fishes in the Irish Sea. (Ibid., 18, 

113-23.) 

(1906), Faunistic Notes. (Ibid., 20 (Rep. N.S.-F. Lab. No. 14, for 1905) 



47-57.) 

Scott, T. (1901), Notes on some parasites of fishes. (19th Ann. Rep. Fish, 
Bd. Scotland, III, 120-53.) 



:\'A-2 THE TREMATODA OF BRITISH FISHES 

Scott, T. (1902), Idem. (20$ Ann. Rep. Fish. Bd. Scotland, III, 288-303.) 
(1904), On some parasites of fishes new to the Scottish marine fauna. 

(22nd Ann. Rep. Fish. Bd. Scotland, III, 275-80.) 
(1905), Observations on some parasites new or rare in Scottish waters. 

(23rd Ann. Rep. Fish. Bd. Scotland, III, 108-19.) 

(1909), Some notes on fish parasites. (26th Ann. Rep. Fish. Bd. 

Scotland, III, 73-92.) 

(1911), Notes on some trematode parasites of fishes. (28th Ann. Rep. 

Fish. Bd. Scotland, III, 68-72.) 

(1912), Some trematodes parasitic on British fishes. (Trans. Edin. 



Field Nat. and Micr. Soc. (1910-11), 6, 344-53.) 
Serkova, O. P., and Bychowsky, B. E. (1940), Asymphylodora progenetica n.sp. 

nebst einigen Angaben iiber ihre Morphologie und Entwicklungsgeschichte. 

(Mag. Parasitol. Inst. Zool. Acad. Sci. U.R.S.S., 8, 162-75.) 
Setti, E. (1899), Secondo contributo per una revisione dei tristomi e descrizione 

di una nuova specie. (Atti Soc. Ligust., 10 (2), 117-25 ; see also Ibid., 

10 (1), 71-84.) 
Sewell, R. B. S. (1922), Cercarise indicse. (Ind. Journ. Med. Res., 10, Suppl. 

No., 370 pp., 32 pis.) 

Shaffer, E. (1916), Discocotyle salmonis nov. spec, ein neuen Trematode om 
den Kiemen der Regenbogenforelle (Salmo irideus). (Zool. Anz., 46, 257-71.) 

Shen, T. (1930), Sur un gasterostomide immature chez Siniperca. (Ann. 
Parasit. Hum. Comp., 8, 554-61.) 

Siebold, C. T. (1848), Lehrbuch der vergleichenden anatomic der wirbellosen Thiere. 
(Berlin.) 

(1849), Gyrodactylus, ein ammenartiges Wesen. (Zeitschr. iviss. Zool., 1, 

347-63.) 

Siwak, J. (1931), Ancyrocephalus vistulensis sp.n., un nouveau trematode 
parasite du silure (Siluris glanis L.). (Bull. int. Acad. Cracovie, B II, 
669-79.) 

Skwortzoff, A. A. (1927), Ueber den anatomischen Bau des Saugwurnies des 
Sterlets des Wolga-Fluss-systems, Acrolichanus auriculatus (Wedl, 1856) 
(Russian). (Samml. Helm. Arb. K. I. Skrjabin gewidmet Moscow, 276-86 ; 
German summary.) 

(1928), Uber die Helminthenfauna des Wolgasterlets. (Zool. Jb. Syst., 

54, 557-77.) 

Sleggs, G. F. (1927), Notes on cestodes and trematodes of marine fishes of 
Southern California. (Bull. Scripps Inst. Oceanogr. La Jolla, Calif., Techn. 
Ser., 1, No. 6, 63-72.) 

Sonsino, P. (1890), Studie e notizie elmintologiche. (Atti Soc. tosc. sci. not. 
Pisa, Proc. verb., 7, 99-114.) 

(1891), Di un nuovo Microcotyle raccolto dell' Umbrina cirrhosa. (Ibid.) 

Southern, R. (1912), Clare Island Survey, Part 56. Platyhelmia. (Proc. Roy. 

Irish Acad., 31, 18.) 
Southwell, T., and Kirshner, A. (1937), Parasitic infections in a swan and in a 

brown trout. (Ann. Trop. Med. Parasit., 31, 427-34.) 
Sprehn, C. (1933), Trematoda. (In Grimpe u. Wagler, Die Tierwelt der Nor d- u. 

Ostsee, Leipzig, Lief 24, Tiel 4c, 1-60.) 
Srivastava, H. D. (1939a), The morphology and systematic relationship of two 

new distomes of the family Haplosplanchnidae Poche, 1926, from Indian 

Marine food fishes. (Ind. J. Vet. Sci., 9, 67-71.) 

(19396), Three new parasites of the genus Acanthocolpus Liihe, 1906 

(family Acanthocolpidae). (Ibid., 9, 213-16.) 



LIST OF LITERATURE 333 

Srivastava, H. D. (1939c), Two new trematodes of the family Monorchidse 
Odhner, 1911, from IndianMarine food fishes. (Ibid., 9, 233-6.) 

(1942), New hemiurids from Indian marine fishes, III. (Parasitology , 

34, 124-7.) 

Stafford, J. (1896), Anatomical Structure of Aspidogaster conchicola. (Zool. 
Jb. AnaL, 9, 477-560.) 

(1904), Trematodes from Canadian fishes. (Zool. Anz., 27, 481-95.) 

(1905), Trematodes from Canadian vertebrates. (Ibid., 28, 681-94.) 

Steelman, G. M. (1938), A description of Phyllodistomum caudatum n.sp. 

(Amer. Midi. Nat., 19, 613-16.) 
Steen, E. B. (1938), Two new species of Phyllodistomum (Trematoda : Gorgo- 

deridse) from Indiana fishes. (Ibid., 20, 201-10.) 
Steinberg, D. (1931), Die Geschlechtsorgane von Aspidogaster conchicola Baer 

und ihr Jahrezyklus. (Zool. Anz., 94, 153-70, 11 figs.) 
Stiles, C. W., and Hassall, A. (1908), Index- Catalogue of Medical and Veterinary 

Zoology. Subjects : Trematoda and trematode diseases. (Hyg. Lab. Bull., 

No. 37, 401 pp.) 
Stossich, M. (1883), Brani di elmintologia tergestina, Ser. 1. (Boll. Soc. Adr. 

Sci. Nat. Trieste, 8, 1, 111-21.) 

(1886a), I distomi dei pesci marini e d'acqua dolce. Lavoro niono- 

grafico. (Progr. d. Ginnasio comm. sup. Trieste (anno 1886), 1-66.) 

(18866), Brani di elmintologia tergestina, III. (Boll. Soc. Adr. Sci. 

Nat. Trieste, 9, Table 8, fig. 33.) 

(1887), Brani di elmintologia tergestina, IV. (Ibid., 9, 90, 184.) 

(1888), Appendice al mio lavoro " I distomi dei pesci niari ni e d'acqua 

dolce." (Progr. d. Ginnasio comm. sup. Trieste (anno 35, 1887-8), 95-105.) 

(1890a), Elminti della Croazia. (Soc. Hist. Nat. Groatica. V. Godina, 

Zagreb, 129-36.) 

(18906), Elminti veneti raccolti del Dr. Alessandro Conte de Ninni. 

(Boll. Soc. Adr. Sci. Nat. Trieste, 12, 49-56.) 

(1891), Nuova serie di elminti veneti. (Soc. Hist. Nat. Groatica, VI, 

Agram, 4 pp.) 

(1892), Osservazioni elmintologiche. (Ibid., VII, 10 pp.) 

(1896), Ricerche Elmintologiche. (Boll. Soc. Adr. Sci. Nat. Trieste, 17.) 

(1898), Saggio di una fauna elmintologica di Trieste e provincie conter- 

mini. (Program, civ. scuola r. sup., 1-162.) 

(1899), Appunti di Elmintologia. (Boll. Soc. Adr. Sci. Nat. Trieste, 19.) 

(1900), Osservazioni elmintologiche. (Ibid., 20, 89-103.) 

(1902), Sopra una nuova specie delle Allocreadiinse. (Arch. Parasit., 5, 

578-82.) 

- (1903), Una nuova specie di Helicometra Odhner. (Ibid., 7, 373-6.) 
(1904), Alcuni Distomi della collezione elmintologica del Museo di 



Napoli. (Ann. Mus. Napoli, 1, No. 23, pp. 14.) 
Stunkard, H. W. (1917), Studies on North American Polystoniidse, Aspido- 

gastridae, and Paramphistomidse. (III. Biol. Monogr., 3, No. 3, 1-114.) 
(1929), The excretory system of Cryptocotyle (Heterophyidse). (J. 

Parasit., 15, 259-66.) 
(1938), Distomum lasium Leidy, 1891 (Syn. Cercariceum linioni Miller 

and Northup, 1926), the larval stage of Zoogonus rubellus (Olsson, 1868) 

(Syn. Z. mirus Looss, 1901). (Biol. Bull, 75, 308-34.) 

(1940), Life history studies and specific determination in the trematode 



genus Zoogonus. (J. Parasit., 26, Supp. 33^4.) 

(1941), Specificity and host relations in the trematode genus Zoogonus. 

(Biol, Bull, 81, 205-14.) 



334 THE TREMATODA OF BRITISH FISHES 

Stunkard, H. W., and Dunihue, F. W. (1933), Gyrodactylus as a parasite of 

the tadpoles of Rana catesbiana. (J. Parasit., 20, 137.) 
and Nigrelli, R. F. (1934), Observations on the genus Sterrhurus 

Looss. with a description of Sterrhurus branchialis sp. nov. (Trematoda, 

Hemiuridae). (Biol. Bull, 67, 534-43.) 
Sumner, F. B., Osburn, R. C, and Cole, L. J. (1913), A biological survey of the 

waters of Woods Hole and vicinity. {Bull U.S. Bur. Fish. ,31, (1911), 860 pp.) 
Syogaki, Y. (1936), Aspidogaster conchicola Baer. Structure and occurrence, 

Japan. (Zool. Mag. Tokyo, 48, 56-9.) 
Szidat, L. (1938a), Uber Allocreadium transversale Rud., 1802 aus Misgurnus 

fossilis L. {Ibid., 10, 468-75.) 

(19386), Pseudobilharziella filiformis n. sp., eine neue Vogelbilharzie aus 

dem Hockerschwan, Cygnus olor L. (Ibid., 10, 535-44.) 

(1939), Beitrage zum Aufbau eines natiirlichen Systems der Trema- 

toden. I. Die Entwicklung von Echinocercaria choanophila U. Szidat zu 
Cathcemasia Mans und die Ableitung der Fasciolidae von den Echinostomidae. 
(Z. Parasitenk., 11, 239-83.) 



Tagliani, G. (1912), Enoplocotyle minima nov. gen. nov. sp. Trematode rnono- 
genetico parassita sulla cute di Murcena helena L. (Ricerch. anat. e sistem. 
Arch. Zool. Napoli, 5, 281-318.) 

Taschenberg, E. O. (1878), Helminthologisches. (Z. ges. Naturw., 51 (3F), 3, 
562-77.) 

(1879«)> Zur Systematik der monogenetischen Trematoden. (Ibid., 52 

(3F), 4, 232-65.) 

(18796), Didymozoon, eine neue Gattung in Cysten lebender Trematoden. 

(Ibid., 52 (3F), 4, 605-17 ; PL 6, figs. 1-5.) 

(1879c), Beitrage sur Kenntnis ectoparasitischer mariner Trematoden. 



(Abh. d. naturf. Ges. zu Halle, 14, Hft, 3, 295-343 ; PL I, figs. 1-6 ; PL 2, 

figs. 1-9.) 
Texnent, D. H. (1906), A study of the life-history of Bucephalus haimeanus : 

a parasite of the oyster. (Quart. J. Microsc. Sci., 49, 99-133.) 
Thaer, A. (1850), Ueber Polystomum appendiculatum (Onchocotyle appendiculata 

Diesing). (Arch. Anat. Physiol, wiss. Med., Jahrg. 1850, 602-32.) 

(1851), De polystomo appendiculato. (Diss, Berolini, 32 pp.) 

Thapar, G. S., and Dayal, J. (1934), A new species of the genus Helicometrct 

from the intestine of Trigla gurnardus. (Proc. Ind. Sci. Congr. Calcutta, 

21, 261.) 
Timon-David, J. (1933), Contribution a l'etude du cycle evolutif des Zoogonides 

(Trematodes). (C. R. Acad. Sci., 196, 1923-4.) 

(1934), Recherches sur les trematodes parasites des oursins en Mediter- 

ranee. (Bull. Inst. Ocean. Monaco, No. 652, 16 pp.) 

(1935), Sur les Wedlia parasites de l'estomac du thon (Trematodes ; 

Didymozoonidse). (Ibid., 670, 11 pp.) 

(1936), Sur revolution experimentale des metacercaires de Zoogonus 

mirus Looss, 1901 (Trematodes, Famille des Zoogonidse). (C. R. Assoc. 
Frang. Avanc. Sci. Marseille, 1936, pp. 274-6.) 

(1937o), Etude sur les trematodes parasites des poissons du Golfe de 

Marseille (Premiere liste). (Bull. Inst. Ocean. Monaco, 717, 1-24.) 

• (19376), Les kystes a Didymocystis wedli duthon: etude anatomo-patho- 

logique. (Ann. Parasit., 15, 520-3.) 

(1938), On parasitic trematodes in Echinoderms. (Livro Jub. L. Tra- 

vassos, Rio de Janeiro, Brasil, 467-73.) 



LIST OF LITERATURE 335 

Tosh, J. R. (1905), On the internal parasites of the Tweed salmon. (Ann. Mag. 

Nat. Hist. (7), 16, 115-19.) 
Travassos, L. (1928), Fauna helminthologica de Matto Grosso (Trematodeos, 

I parte). {Mem. Inst. Oswaldo Cruz, 21, 309-72.) 

Artigas, P., and Pereira, C. (1928), Fauna helminthologica dos peixes 

de agua doce de Brasil. (Arch. Inst. Biol., Sao Paulo, 1, 5-68.) 

Tubangui, M. A. (1931), Trematode parasites of Philippine vertebrates. IV. 
Ecto-parasitic flukes from marine fishes. (Philipp. J. Sci,, 45 (1), 109-17.) 

Ujiie, N. (1936a), On the structure and function of Mehlis gland on the formation 
of the egg shell of EchinocJiasmus japonicus. (J. Med. Ass. Formosa, 35, 
1010.) 

(19366), On the process of egg shell formation in Clonorchis sinensis. 

(Ibid,, 35, 1894.) 

Van Cleave, H. J. (1921), Notes on two genera of ectoparasitic trematodes from 
freshwater fishes. (J. Parasit., 8, 33-9.) 

and Mueller, J. F. (1932), Parasites of Oneida Lake fishes. Part I. 

Descriptions of new genera and new species. (Roosevelt Wild Life Ann., 
3 (1), 5-71.) 

(1934), Part 3. A biological and ecological survey of the worm 



parasites. (Ibid., 3 (3-4), 161-334.) 
Van Cleave, H. J., and Vaughn, C. M. (1941), The trematode genus Otodistomum 

hi North America. (J. Parasit., 27, 253-7.) 
and Williams, C. O. (1943), Maintenance of a trematode, Aspidogaster 

conchicola, outside the body of its natural host. (Ibid., 29, 127-30.) 
V aullegeard, A. (1896), Sur les helminthes des Crustaces decapodes braclryoures 

et anomoures. (Assoc, franc. Avancement Sci. Congr. Bordeaux (1895), 

24 (2), 662-8.) 
Vaz, Z., and Pereera, C. (1930), Nouvel hemiuride parasite de Sardinella aurita 

Cuv. et Val., ParaJiemiurus n.g. (C. R. Soc. Biol., 103, 1315-17.) 
Verma, S. C. (1936), Studies on the family Bucephalidae (Gasterostomata). Part 

I. Descriptions of new forms from Indian fresh-water fishes. (Proc. 

Nat, Acad. Sci. India, 6, 66-89.) 
Verrill, A. E. (1875), Brief contributions to zoology from the museum of Yale 

College. 33. Results of dredging expeditions off the New England coast in 

1874. (Amer. J. Sci. and Arts N. Haven, 110, 3s (55), 36-43.) 
Vlasenko, P. V. (1931), Zur Helmmthfauna der Schwarzmeerfische. (Trav. 

Sta, biol. Karadagh, 4, 88-136, 26 figs. Russian ; German resume 127- 

34.) 
Voeltzkow, A. (1888), Aspidogaster conchicola. (Arch. zool. Wiirzburg, 8, 

249-92.) 
Vogt, C. (1849), Note sur quelques habitants des moules. (Ann. sci. nat., 3rd 

Ser., Zool., 12, 198-203.) 
(1878), Ueber die Fortpflanzungsorgane einigerectoparasitischer mariner 

Trematoden. (Z. wiss. Zool, 30, Suppl., 306-42.) 

Wagener, G. R. (1852«), Enthelminthica, No. 3. Ueber eine Distomengattung, 
Gasterostoma v. Siebold. (Arch. Anat. Physiol, wiss. Med., 555-69.) 

(18526), Ueber einen neuen in der0^raceramott,s£ro.sagefundenenEinge- 

weidewurm, Amphityches wrna Grube und Wagener. (Ibid., 543-54, Pis. 
14-15, figs. 1-7.) 



336 THE TREMATODA OF BRITISH FISHES 

Wagener, G. R. (1857a), Beitrage zur Entwicklungsgeschichte der Eingeweide- 
wiirmer. Ein v r on der Hollandischen Societat der Wissenschaften zu Haarlem 
I. J. 1855 gekronte Preisschrift. (Naturk. Verh. holland maatsch. wet. 
Haarlem, 2 Versamel, 13, 1-112.) 

(18576), Helminthologische Bemerkungen aus eineni Sendschreiben an 

C. Th. von Siebold. (Z. wiss. Zool. Leipzig, 9(1), 73-90.) 

(1858) Enthelminthica No. 6. Ueber Distoma campanula (Gastero- 

stoma fimbriatum Siebold) Duj. und Monostoma bipartitum Wedl. (Arch, 
naturg., II, 24, 250-6.) 

(1860a), Ueber Gyrodactylus elegans von Nordmann. (Arch. Anat. 

Physiol, wiss. Med., 768-97.) 

(18606), Ueber Distomum appendiculatum R. (Arch. Naturg., 26 Jahrg., 



1, 165.] 
Wallin, I. E. (1910), A new species of the trematode genus Allocreadium. (Stud. 

Zool. Lab. Univ. Nebraska, No. 96, 50-64.) 
Ward, H. B. (1917), On the structure and classification of North American 

parasitic worms. (J. Parasit., 4, 1-12.) 

(1918), Parasitic flatworms. Trematoda. (In Ward and Whipple, 

Freshwater Biology.) 

(1938), On the genus Deropristis and the Acanthocolpidse (Trematoda). 

(Livro Jub. Prof. L. Travassos, Rio de Janeiro, 509^-21.) 

and Fillingham, J. (1934), A new trematode in a toadfish from South- 



Eastern Alaska. (Proc. Helminth. Soc. Wash., 1, 25-31.) 
Wedl, K. (1855), Helminthologische Notizen. (S. B. Ahad. Wiss. Wien, 16, 
371-95, Pis. 1-3, figs. 1-33.) 

(1857), Anatomische Beobachtungen uber Trematoden. (Ibid., 26, 

241-78, Pis. 1-4.) 

(1862a), Ueber die Helminthenfauna iEgyptiens. (Ibid., 44, 225-40, 



463-82.) 

(18626), Remarks on Gyrodactylus. (Translation in Cobbold, 1862.) 



Wegener, G. (1910), Die Ektoparasiten der Fische Ostpreussens. (Schrift. d. 
phys.-okonom. Ges. Konigsberg i, Pr., 50, 3, 195-286.) 

Wierzejski,. A. (1877), Zur Kenntniss des Baues von Calicotyle kroyeri Dies. 
(Z. wiss. Zool., 29, 550-82.) 

Wilde, J. (1937), Daclylogyrus macrocanthus Wegener als Krankheitserreger auf 
den Kiemen der Schleie (Tinea tinea) .... (Z. Parasitenk., 9, 203-36.) 

Willem, V. (1906), Deux trematodes nouveaux pour la faune beige. Acantho- 
cotyle branchialis nov. sp. et Distomum turgidum Brandes. (Bull. Acad. 
CI. Sci. Belg., 8, 522-3, 599-612.) 

Willemoes-Suhm, R. von (1870), Ueber einige Trematoden und Nemathel- 
minthen. (Inaug. Diss. Fak. Gottingen Leipzig, 29 pp., Pis. 11-13 ; also in 
Z. wiss. Zool, 21, 175-203, Pis. 11-13.) 

Williams, C. O. (1942), Observations on the life history and taxonomic relation- 
ships of the trematode Aspidogaster conchicola. (J. Parasit., 28, 467-75.) 

Wisniewski, L. W. (1933), Acrolichanus similis n. sp. trematode nouveau des 
Salmonides. (Ann. Parasitol., 11, 188-95.) 

Witenberg, G., and Eckmann, F. (1934), Notes on Asymphylodora tincce (Trema- 
toda). (Ann. Mag. Nat. Hist., (10), 14, 366-71.) 

Woodhead, A. (1929), Life history studies on the trematode family Bucepha- 
lidse. (Tra?is. Amer. Micr. Soc, 48, 256-74, figs. 1-13.) 

(1930), Idem II. (Ibid., 49, 1-16, figs. 16-24.) 

Woolcock, V. (1935), Digenetic trematodes from some x4.ustralian iishes. (Para- 
sitology, 27, 309-31.) 



LLST OF LITERATURE 337 

Woolcock, V. (1930), Monogenotic trematodes from some Australian fishes. 

(Ibid., 28, 79-91.) 
Weight, R. R., and MacCallum, A. B. (1887), Sphyranura osleri : a contribution 

to American helminthology. (J. Morphol, 1, 1, 1-48.) 
Wu, K. (1938), Progenesis of Phyllodistomum lesteri sp. nov. (Trematoda ; Gorgo- 

deridse) in fresh-water shrimps. (Parasitology, 30, 4-19.) 

Yamaguti, S. (1934), Studies on the helminth fauna of Japan. Part 2. Trema- 
todes of fishes, I. (Jap. J. Zool., 5 (3), 249-541.) 

( 1937a), Idem, Part 19. Fourteen new ectoparasitic trematodes of fishes. 

(Lab. Parasitol. Kyoto Imp. Univ., 1-28.) 

(19376), Idem, Part 19. Hexacotyle dissimilis n. sp. on gills of Thynnus 

thynnus. (Studies Helminth Fauna Japan, 20-2.) 

(1938), Studies on the helminth fauna of Japan. Part 21. Trematodes 



of fishes, IV. (Kyoto, 139 pp.) Part 24. Trematodes of fishes, V. 
Jap. J. Zool, 8, 15-74. 
Yumoto, Y. (1936), On the minute structure of the egg-shells of Clonorchis 
sinensis, and on its abnormal eggs. (J. Med. Assoc. Formosa, 35, 8 (No. 377), 
1845-6.) 

Zandt, F. (1924), Fischparasiten des Bodensees. (Zbl. Bakt. Orig., 92 (3-4), 

225-71.) 
Zaringer, J. B. (1829), Quwdam de hist, natur. atque descriptio sceleti salmonis 

farionis. (Diss. Friburgi Bris.) 
Zeder, F. G. H. ( 1800), Erster Nachtrag zur Naturgeschichte der Eingeweidewurmer 

von J. A. E. Goeze. (Leipzig.) 
Zeller, E. (1872), Untersuchungen iiber die Entwicklung des Diplozoon para- 

doxum. (Z. wiss. Zool., 22, 168-80.) 

(1888), Ueber den Geschlechtsapparat des Diplozoon paradoxum. (Ibid., 

46, 233-9.) 

Ziegler, A. E. (1883), Bucephalus und Gasterostomum. (Ibid., 39, 537-77, 

PI. 32, figs. 1-12 ; PI. 33, figs. 13-28.) 
Zschokke, F. (1884), Recherches sur l'organisation et la distribution zoologique 

des vers parasites des poissons d'eau douce. (Arch. Biol., 5, 153-241, 

Pis. 9, 10.) 

(1896), Zur Faunistik der parasitischen Wurmer von Susswasserfischen. 

(Zbl. Bakt., 19, 772-84, 815-25.) 

(1890), Erster Beitrag zur Parasitenfauna von Trutta salar. (Verhandl. 

naturf. Ges. Basel, 8, 761-95.) 

— ■ and Heitz, A. (1914), Entoparasiten aus Salmoniden von Kamtschatka. 

(Rev. Suisse Zool, 22, 195-256.) 



22 



339 



ALPHABETICAL LIST OF HOSTS (BRITISH FISHES). 



Note. — The scientific names are those used in the List of British Vertebrates 
(Hinton, Tucker, Parker and Norman ; 1935). 



Albacore 

Allis shad 

Anchovy 

Angel-fish 

Angler 

Argentine 

Atherine — see sand smelt. 

Axillary bream 

Ballan wrasse 

Barbel 

Bass 

Bergylt — see ballan wrasse. 

Bib ... . 

Black-mouthed dogfish 

Black sea bream . 

Bleak .... 

Bloch's topknot — see common topknot. 

Blue ling 

Blue shark 

Boar-fish 

Bogue 

Bordered ray — see burton skate. 

Bream 

Brill . 

Broad-nosed pipefish 

Brown trout — see trout. 

Bullhead — see miller's thumb. 

Burbot 

Burton skate 

Butterfish . 

Butterfly blenny . 

Carp . 

Cat-fish — see wolf-fish. 

Char . 

Chub . 

Coal-fish 

Cod . 

Comber 

Common eel — see eel. 

Common goby 

Common sea bream 

Common topknot 



Germo alalimga (Gmelin). 
Alosa alosa (L.). 
Engraulis encrasicholus (L.). 
Squatina squatina (L.). 
Lophius piscatorius L. 
Argentina sphyraena L. 

Pagellus oivenii Giinther. 

Labrus bergylta Ascanius, 
Barbus barbus (L.). 
Morone labrax (L.). 

Gadus luscus L. 

Pristiurus melastomus (Rafinesque] 

Brama raii (Bloch). 

Albumus alburnus (L.). 

Molva byrkelange Walbaum. 
Carcharinus glaucus (L.). 
Capros aper (L.). 
Box boops (L.). 

Abramis brama (L.). 
Scophthalmus rhombus (L.). 
Siphonostoma typhle (L.). 



Lota lota (L.). 
Raja marginata Lacepede. 
Pholis gunnellus (L.). 
Blennius ocellaris L. 

Cyprinus carpio L. 

Salvelinus sp. 
Squalius cephalus (L.). 
Gadus virens L. 
Gadus callarias L. 
Serranus cabrilla (L.). 

Gobius minutus Gmelin. 

Pagellus centrodontus De la Roche. 

Zeugopterus punctatus (Bloch). 



340 



THE TBEMATODA OF BRITISH FISHES 

( 'onger conger (L.). 



Conger .... 

Corkwing — see (Baillon's wrasse) 

Cornish sucker 

Couch's sea bream 

Crucian carp 

Cuckoo ray . 

Cuckoo wrasse 

Dab . 

Dace . 

" Darkie Charlie " 

Dentex 

Dover sole — see sole. 

Dragonet 

Dusky perch 

Eagle ray . 
Eel . * . 

Eel-pout — see viviparous blenny. 
Electric ray — see torpedo. 
Elleck — see red gurnard. 

Father lasher . 
Fifteen-spined stickleback 
Five-bearded rockling . 
Flapper skate — see skate. 
Flounder . 

Freckled goby — see common goby. 
French sole — see sand sole. 
Fuller's ray — see shagreen ray. 



Gar-fish 

Gattorugine 

Gilt-head 

Gilt-head (Baillon's wrasse) 

Golden grey mullet 

Goldfish 

Gold-sinny . 

Grayling 

Green-bone — see gar-fish. 

Greenland shark . 

Greater fork-beard 

Greater pipe-fish . 

Greater sand eel 

Greater spotted dogfish — see nurse hound. 

Greater weever 

Grey gurnard 

Grey mullet 

Gudgeon 

Gunnel — see butter-fish. 

Haddock 

Hake .... 

Halibut 



Lepadogaster gouani Lacepede. 
Pagrus pagrus (L.). 
Carassius carassius (L.). 
Raja ncevus Miiller and Henle. 
Labrus mixtus L. 

Limanda limanda (L.). 
Leuciscus leuciscus (L.). 
Scymnorhinus licha (Bonnaterre). 
Dentex dentex (Gmelin). 

Callionymus lyra L. 
Epinephelus gigas (Brunnich). 

Myliobatis aquilla (L.). 
Anguilla anguilla (L.). 



Coitus scorpius L. 
JSpinachia spinachia (L.). 
Onos mustehis (L.). 



Platichthys flesus (L.). 



Belone belone (L.). 
Blennius gattorugine Bloch. 
Sparus aurata L. 
Crenilabrus melops (L.). 
Mugil auratus Risso. 
Carassius auratus (L.). 
Ctenolabrus rupestris (L.). 
Thymallus thymallus (L.). 

Somniosus microcephalus Day. 
Urophycis blennoides (Brunnich). 
Syngnathus acus L. 
Ammodytes lanceolatus Lesauvage. 

Trachinus draco L. 
Trigla gurnardus L. 
Mugil sp. 

Gobio gobio (L.). 



Oadus ceglifinus L. 
Merluccius merluccius (L.). 
Hippoglossus hippoglossus (L.). 



ALPHABETICAL LIST OF HOSTS (BRITISH FISHES) 341 



Hammerhead shark . . 
Herring .... 
Homelyn ray — see spotted ray. 
Horse mackerel . 
Houting .... 



Sphyma zygoma (L.). 
Clupea harenqus L. 

Trachurus trachurus (L.). 
Coregonus oxyrhynchus (L.). 



John Dory . 


. Zeus faber L. 


Lampern — see river lamprey. 


Lemon sole 


. Microstomus kitt (Walbaum). 


Lesser sand eel . 


Ammodytes tobianus L. 


Lesser spotted dogfish — see 


rough hound. 


Lesser weever 


Trachirius vipera Cuvier and Valen 




ciennes. 


Ling .... 


Molva molva (L.). 


Loach 


Cobitis barbatula (L.). 


Long-nosed skate 


Raja oxyrhynchus L. 


Long rough dab . 


Hippoglossoides platessoides (Fabri 




cius). 


Long-spined cottus 


Cottus bubalis Euphrasen. 


Lump-sucker 


Cyclopterus lumpus L. 


Mackerel 


Scomber scombrus L. 


Meagre 


Scioena aquilla Risso. 


Megrim 


Lepidorhombus ivhiff-iagonis (Wal 




baum). 


Miller's thumb . 


Cottus gobio L. 


Minnow 


Phoxinus phoxinus (L.). 


Monk-fish . 


Squatina squatina L. 


Montagu's sea-snail 


Liparis montagui (Donovan). 


Murry 


. Murcena helena L. 


Norwegian topknot 


Phrynorhombus norvegicus (Giinther) 


Nurse hound 


Scyliorhinus stellaris (L.). 


Ocean pipe-fish . 


. Entelurus aiquoreus (L.). 


Opah .... 


Lampris luna (Gmelin). 


Painted ray. 


Raja microcellata Montagu. 


Pandora 


Pagellus eryihrinus (L.). 


Pelamid 


Sarda sarda (Bloch). 


Perch .... 


Perca fluviatilis L. 


Pike .... 


Esox lucius L. 


Piked dogfish 


Squalus acanthias L. 


Pilchard ( sard i no) 


. Sardina pilchardus (Walbaum). 


Pilot fish . 


Naucrates ductor (L.). 


Plaice .... 


Pleuronectes platessa L. 


Pogge 


Agonus cataphractus (L.). 


Pollack 


Gadus pollachius L. 


Poor cod 


Gadus minutus L. 


Pope .... 


Acerina cernua (L.). 


Pout — see bib. 




Poutassou . 


Gadus poutassou (Risso). 



342 



THE TREMATODA OF BRITISH FISHES 



Rabbit fish . 
Red band-fish 
Red gurnard 
Red mullet . 
River lamprey 
Roach 

Rock cook . 
Rock goby 
Rough hound 
Rudd . 
Ruffe — see pope. 



Saithe — see coal-fish. 

Salmon 

Sand smelt . 

Sand sole 

Sandy ray . 

Scad — see horse mackerel. 

Scald-fish 

Sea snail 

Sea trout — see trout. 

Shadow fish — see meagre. 

Shagreen ray 

Shanny 

Short-spined cottus — see father lasher. 

Silver bream 

Six-gilled shark . 

Skate .... 

Smear dab — see lemon sole. 

Smelt .... 

Smooth hound 

Sole .... 

Spanish mackerel 

Sparling — see smelt. 

Spinax 

Spined loach 

Spinous shark 

Spotted ray. 

Sprat . 

Starry ray . 

Sting-fish — see lesser weever. 

Sting ray .... 

Stone loach — see loach. 

Streaked gurnard 

Striped wrasse — see cuckoo wrasse 

Sturgeon .... 

Sun-fish .... 

Sword-fish .... 

Tench .... 

Ten-spined stickleback . 
Thickback sole 
Thick-lipped grey mullet 
Thin-lipped grey mullet 



Chimcera monstrosa L. 
Cepola rubescens L. 
T rigla cuculus L. 
Mullus surmuletus L. 
Lampetra fiuviatilis (L.). 
Rutilus rutilus (L.). 
Centrolabrus exoletus (L.). 
Gobius paganellus Gmelin. 
Scyliorhinus caniculus (L.). 
Scardinius erythrophthalmus (L. 



Salmo solar L. 

Alherina presbyter Cuvier. 
Pegusa lascaris (Risso). 
Raja circularis Couch. 

Amoglossus latema (Walbaum). 
Liparis liparis (L.). 



Raja fullonica L. 
Blennius pholis L. 

Blicca bjozrnka (L.). 
Hexanchus griseus (Gmelin). 
Raja batis L. 

Osmerus eperlanus L. 
Mustelus mustelus (L.). 
Solea solea (L.). 
Pneumatophorus colias (Gmelin). 

Spinax spinax (L.). 

Cobitis taznia L. 

Echinorhinus spinosus (Gmelin). 

Raja montagui Fowler. 

Clupea sprattus L. 

Raja radiata Donovan. 

Trygon pastinaca (L.). 

T rigla lineata Gmelin. 

Acipenser sturio L. 
Mola mola (L.). 
Xiphias gladius L. 

Tinea tinea (L.). 
Pygosteus pungitius (L.). 
Microchirus variegata (Donovan). 
Mugil chelo Cuvier. 
Mugil capita Cuvier. 



ALPHABETICAL LIST OF HOSTS (BRITISH FISHES) 343 



Tliornback ray .... 

Three- bearded rockliiig 

Three-spined stickleback 

Tinker — see ten-spined stickleback. 

Tittlebat — see three-spined stickleback. 

Tompot blenny — see gattorugine. 

Tope . . * . 

Torpedo 

Torsk . 

Trout . 

Truncated sun-fish 

Tunny 

Turbot 

Twaite shad 

Two-spotted goby 

Vivijjarous blenny 

White bream — see silver bream. 
Whiting .... 
Witch .... 

Wolf-fish .... 



Raja clavata L. 

Onos tricirratus (Bloch). 

Gasterosteus aculeatus L. 



Eugaleus galeus (L.). 

Torpedo nobiliana Bonaparte. 

Brosme brosme (Miiller). 

Salmo trutta L. 

Ranzania truncata (Retzius). 

Thunnus thynnus (L.). 

Scophthalmus maximus (L.). 

Alosa finta (Cuvier). 

Gobius ruthensparri Euphrasen. 

Zoarces viviparus (L.). 



Gadus merlangus L. 
GlyptocepJialus cynoglossus (L.). 
Anarhichas lupus L. 



Yellow gurnard 



Trigla lucerna L. 



345 



LIST OF HOSTS AND THEIR PARASITES. 

Note. — The order in which the hosts are taken is that given in the List of 
British Vertebrates. An asterisk denotes that the record is not British. For 
details regarding many of these non-British records see Dawes (1946). 

Centrophorus squamosus (Gmelin). 

*Microbothrium centrophori. 

*Pseudocotyle lepidorhini. 
Scymnorhinus licha (Bonnaterre). 
Chlamydoselachidje. Squalonchocotyle licha. 



PETROM YZO NID^E . 

Lampetra fluviatilis (L.). 

Hemiurus appendiculatus. 



Hexanchus griseus (Gmelin). 
Neoerpocotyle grisea. 

SCYLIORHINIDiE. 

Scyliorhinus stellaris (L.). 

Hexabothrium appendiculatum. 

H. canicula. 

Ptychogonimus ?negastoma. 
Scyliorhinus caniculus (L.). 

Leptocotyle minor. 

Hexabothrium canicula. 

Diphterostomum betencourti. 
Pristiurus melastomus (Rafinesque) 

Leptobothrium pristiuri. 

CARCHARINIDiE. 

Carcharinus glaucus (L.). 

* Ptychogonimus megastoma. 
Eugaleus galeus (L.). 
Erpocotyle canis. 
Ptychogonimus megastoma. 
Mustelus mustelus (L.). 
*Calicotyle stossichi. 
Erpocotyle lazvis. 
* Neoerpocotyle catenulata. 
Ptychogonimus megastoma. 
*Probolitrema richiardii. 
Sphyrna zygcena (L.). 
*Tristoma coccineum. 

Squalidje. 

Echinorhinus spinosus (Gmelin). 

^Erpocotyle dollfusi. 
Squalus acanthias L. 

Microbothrium apiculatum. 

*Otodistomum veliporum. 

^Erpocotyle abbreviata. 

* Probolitrema richiardii. 



Squatinid^e. 

Squatina squatina (L.). 
Pseudocotyle squatince. 

Torpedinid^e. 

Torpedo marmorata Risso. 
*Amphibdella torpedinis. 
Amphibdelloides maccallu mi. 
^Erpocotyle torpedinis. 
Torpedo nobiliana Bonaparte. 
Amphibdella flavolineata. 

Rajid,e. 

Raja montagui Fowler. 

Calicotyle kroyeri. 

A canthocotyle mont icell i i . 
Raja microcellata Montagu. 

Calicotyle kroyeri. 
Raja clavata L. 

Calicotyle kroyeri. 

Acanthocotyle monticellii. 

A. oligoterus. 

A. lobianchi. 

A. elegans. 

Rajonch ocotyloides emarginu ta . 

JStichocotyle nephropis. 

Otodistomum veliporum. 
Raja radiata Donovan. 

Calicotyle kroyeri. 

* Acanthocotyle borealis. 

*A. verriUi. 

Otodistomum veliporum. 
Raja noevus Miiller and Henle. 

Calicocotyle kroyeri. 

Rajonchocotyle miralet us. 



346 



THE TREMATODA OF BRITISH FISHES 



Rajidje (continued). 

Raja circularis Couch. 
Calicotyle kroyeri. 
Raja fullonica L. 

Calicotyle kroyeri. 
*Otodistomum veliporum. 
Raja lintea Fries. 

*Otodistomum veliporum. 
Raja marginata Lacepede. 

*Rajonchocotyle alba. 
Raja batis L. 

Calicotyle kroyeri. 
*Merizocotyle diaphana. 
Rajonchocotyle batis. 
Otodistomum veliporum. 
Raja oxyrhynchus L. 
Calicotyle kroyeri. 
*Merizocotyle diaphana. 
* Rajonchocotyle prenanti. 

Trygonid^e. 

Trygon pastinaca (L.). 

Heterocotyle pastinacce. 
Thaumatocotyle concinna. 

Myliobatid^j. 

Myliobatis aquila (L.). 
*Monocotyle myliobatis. 
Probolitrema richiardii. 

CHIIYLERIDiE. 

Chimcera monstrosa L. 
Calicotyle affinis. 
Chimcericola leptogaster. 
*Macraspis elegans. 
^Otodistomum veliporum (metacer 
carise). 

AciPENSERIDiE. 

Acipenser sturio L. 
*Nitzschia sturionis. 
*N. monticellii. 
*Diclybothrium armat u m . 
Dihemistephanus sturionis. 
*Deropristis hispidum. 
*D. inflatum. 
*Sterrhurus musculus. 
*S. grandiporus. 
*Lecithochirium rufoviride . 
* Br achy phallus crenatus. 
*I)eroge?ies various. 



Clupeidje. 

Glupea harengus L. 

Mazocraes harengi. 

Hemiurus ocreatus. 
*Lecithaster confusus. 
*L. gibbosus. 
*Derogenes varicus. 
Clupea sprattus L. 

*Mazocraes heterocotyle. 

Hemiurus ocreatus. 

Lecithaster gibbosus. 

Derogenes varicus. 
Alosa alosa (L.). 

Mazocraes alosw. 

M. harengi. 

*Hemiurus appendiculatus. 
*H. ocreatus. 
Alosa finta (Cuvier). 

Mazocraes alosa}. 
*Ophicotyle fintae. 
*Hemiurus appendiculatus. 
*Lecithaster confusus. 
Sardina pilchardus (Walbaum). 
*Mazocraes pilchardi. 

Hemiurus ocreatus. 
*H. rugosus. 
*Aphanurus stossichii. 
Engraulis encrasicholus (L.). 
*Ovotrema ponticum. 
*Aphanurus stossichii. 
*Aponurus laguncula. 
*Lecithaster tauricus. 

Salmonidje. 

Salmo salar L. 

Discocotyle sagittata. 
*Podocotyle atomon. 
*P. reflexa. 

Hemiurus ocreatus. 
*Brachyphallus crenatus. 
*Lecithaster gibbosus. 

Derogenes varicus. 

"Distoma miescheri." 
Salmo trutta L. 

Discocotyle sagittata. 
*D. sybillce. 

Crepidostomum farionis. 
*C. suecicum. 
*Azygia lucii. 
*Bunodera luciopercce. 
*Phyllodistomum simile. 
* Hemiurus appendiculatus. 
*BrachyphaUu8 crenatus. 



LIST OF HOSTS AND THEIR PARASITES 



347 



Salmonid.e (continued). 

Lecithaster gibbosus. 
Derogenes various. 
Salvelinus alpinus (L.). 

Crepidostomum farionis. 
*C. suecicum. 
Coregonus pennantii Cuvier and Valen- 
ciennes. 
* Dactylodiscus borealis. 
Coregonus oxyrhynchus (L.). 
* Discocotyle sagittata. 
Bucephalus polymorphic (metacer- 

carise). 
Crepidostomum farionis. 
*Phyllodistom um conostom um. 
*Hemiurus appendiculatus. 
* Derogenes various. 
ThymaUus thymallus (L.). 
* Dactylocotyle borealis. 
^Discocotyle sagittata. 
Crepidostomum farionis. 
*C. suecicum. 
*Azygia lucii. 

Phyllodistomum folium. 
*P. simile. 
Derogenes various. 

ARGENTINIDiE. 

Argentina sphyrama L. 

Lecithophyllum botryophorum. 

OSMERIDJE. 

Osmerus eperlanus L. 

*Brachy phallus crenatus. 
Lecithaster gibbosus. 
*Lecithochirium rufoviride. 

ESOCIDJE. 

Esox lucius. 

* Gyrodactylus elegans. 
Tetraonchus monenteron. 
Bucephalus polymorphus. 

* Allocreadium isoporum. 
*Sphcerostoma bramce. 
Azygia lucii. 
*Bunodera luciopercce. 
* Phyllodistomum folium. 
*Hemiurus appendiculatus. 

CYPBINIDiE. 

Cyprinus carpio L. 

* Gyrodactylus elegans . 
*G. medius. 



*G. gracilis. 

*Dactylogyrus auriculalus. 

*Z). anchoratus. 

*Z). crassus. 

*D. dujardinianus. 

*D. falcatus. 

*D. formosus. 

*D. minutus. 

*D. vastator. 

*D. wegeneri. 

*Neodactylogyrus cryptomeres. 

*N. difformis. 

^Aspidogaster decatis. 

*A llocreadium isoporum. 

*Sphairostoma bramce. 

*Sanguinicola inermis. 
Carassius carassius (L.). 

* 'Gyrodactylus elegans. 

*Dactylogyrus dujardianus. 
D. falcatus. 

*Neodactylogyrus cryptomeres . 

*Diplozoon paradoxum. 

*D. nipponicum. 

* Phyllodistomum macrocotyle. 
Carassius auratus (L.). 

*Dactylogyrus auriculalus. 

*D. anchoratus. 
Barbus barbus (L.). 

* Aspidogaster decatis. 

*AUocreadium isoporum. 

* Sphcerostoma bramce. 
* Asymphylodcra tincce. 

*Bunodera luciopercce. 

* Phyllodistomum macrocotyle. 
Gobio gobio (L.). 

* Gyrodactylus gracilis. 
*G. major. 

*Neodactylogyrus cryptomeres. 
*Trochopus brauni. 
*Diplozoon paradoxum. 

* Aspidogaster limacoides. 
^Bucephalus polymorphus. 

* 'Phyllodistomum macrocotyle. 
Tinea tinea (L.). 

^Gyrodactylus elegans. 

* Allocreadium isoporum. 
* Asymphylodora tincce. 

* Phyllodistomum elongalum sp. inq. 
*Spha3rostoma bramce. 
*Sanguinicola inermis. 

Phoxinus phoxinus (L.). 
^Gyrodactylus elegans. 
*G. medius. 
*Dactylogyrus tuba. 



348 



THE TREMATODA OF BRITISH FISHES 



Cyprinidje (continued). 

*Neodactylogyrus borealis. 

*N. gamellus. 

*N. micracanihus. 

*N. suecicus. 
Diplozoon paradoxum. 

* Allocreadium isoporum. 

*Sphcerostoma bramce. 
Squalius cephalus (L.). 

*Dacfylogyrus tuba. 

*Neodactylogyrus dijform is. 

*N. parvus. 
Ancyrocephalus forceps. 

*Asp idogaster lima co ides. 

^Allocreadium isoporum. 

*Sphcerostoma bramce. 

*Azygia lucii. 

*Phyllodistomum macrocotyle . 
Leuciscus leuciscus (L.). 

*Gyrodactylus elegans. 

*Dactylogyrus cordus. 

*D. tuba, 

^Bucephalus polymorphus (rnetacei-' 
cariae). 

*Sphcerostoma bramce. 
Rutilus rutilus (L.). 

*Gyrodactylus elegans. 

*£. gracilis. 

*Dactylogyrus cordus. 

*D. dujardianus. 

*D. fallax. 

*D. similis. 

*D. trigonostoma, 

*D. sphryna. 

*Neodactylogyrus crucifer. 

*N. gamellus. 

*N. micracanihus. 

*N. suecicus. 

* Ancyrocephalus forceps. 

*Diplozoon paradoxum. 

*Aspidogaster limacoides. 
Allocreadium isoporum. 
Sphazrostoma bramce. 

*Phyllodistomum macrocotyle. 
Scardinius erythrophthalmus (L.). 

*Gyrodactylus gracilis. 

*Dactylogyrus fallax, 

*Neodactylogyrus difformis. 

*N. gracilis. 

*N. crucifer. 

*N. difformis. 

*Diplozoon paradoxum. 

*Bucephcdus polymorphus. 

*Sphcerostomu bramce. 



*Crepidostomum latum. 
*Phyllodistomum macrocotyle. 
*Sanguinicola inermis. 
Blicca bjcernka (L.). 

*Neodactylogyrus alatus. 
*N. cornu. 
*N. distinguendus. 
N. megastoma. 
*Diplozoon paradoxum. 

* Aspidogaster limacoides. 

* Bucephalus polymorphus (metacer- 

carise). 
*Sphcerosto?na bramce. 
*Phyllodisto?num macrocotyle. 
Abramis brama (L.). 
*Gyrodactylus elegans. 
*G. medius. 
*G. parvicopula. 
*Dactylogyrus auriculatus. 
*Z). dujardinianus. 
*D. falcatus. 
*Diplozoon paradoxum. 
*Aspidogaster limacoides. 
* Allocreadium isoporum. 
*Sphcerostom<i bramce. 
*Asymphylodora tincce. 
*Phyllodistomum macrocotyle. 
Alburnus alburnus (L.). 
*Gyrodactylus sp. 
*Neodactylogyrus alatus. 
*N. fraternus. 
*N. minor. 
*N. parvus. 
* Bucephalus polymorphus (metacer- 

carise). 
*Sphcerostoma bramce. 

COBTIIDJE. 

Nemacheilus barbatula (L.). 

*Gyrodactylus elegans. 

*/Sphcerostoma bramce. 
Cobitis tcenia L. 

*Gyrodactylus cobitis. 

*G. latus. 

*A llocreadium trans uersale. 

Anguillidje. 

Anguilla anguilla (L.). 

^Bucephalus polymorphus. 
*Peracreadium commune. 

Helicometra fasciata. 

Podocotyle atomon. 
*Sphcerostoma bramce. 



LIST OF HOSTS AND THEIR PARASITES 



349 



Anguillid.-e {contin tied). 

*Deropristis inflata. 
*Azygia lucii. 

Hemiurus communis. 
*Sterrhurus grandiporus. 
*iS. musculus. 

Lecithochirium rufoviride. 
*L. gravidum. 
* Lecithaster gibbosus. 

MURiENIDiE. 

Murcena helena L. 

*Anoplocotyle minima. 
*Sterrhurus grandiporus. 

Congridje. 
Conger conger (L.). 

Bucephalopsis gracilescens. 

Prosorhynchus crucibidum. 

Helicometra fasciata. 
^Podocotyle atomon. 

Hemiurus communis. 

Sterrhurus fusiformis. 
*S. grandiporus. 

Lecithochirium rufoviride. 
*L. gravidum. 
*L. conviva. 

Synaptobothrium caudiporum. 

Derogenes varicus. 

BELONIDiE. 

Bel one belone (L.). 

*Cyclocotyla bellones. 

Axine belones. 
*Lecithostaphylus retroflexus. 

Lecithaster gibbosus. 
*Aponurus laguncula. 
* Tergestia acanthocepha la . 

SYNGNATHID.E. 

Entelurus cequoreus (L.). 
*Plagioporus tumidulus. 
Podocotyle syngnathi. 
P. atomon. 
Hemiurus communis. 
Syngnathus acus L. 

*Plagioporus tumidulus. 
Podocotyle syngnathi. 
* Lecithochirium gravidum. 
*Leciihostaphylus retroflexus. 
Siphonostoma typhle (L.). 
Podocotyle syngnathi. 
Acanthostomum imbutiforme 
(larvse). 



MacFIURID.E. 

Coryphcenoides rupestris Gunner. 

*Octodactylus macruri. 

*Deretrema abyssorum. 
Malacocephalus laevis (Lowe). 
Diclidophoropsis tissieri. 

MERLUCCIIDiE. 

Merluccius merluccius (L.). 

Udonella caligorum (on Caligus). 
Diclidophora denticulata. 
Anthocotyle merluccii. 
^Lepidapedon rachion. 
Hemiurus ocreatus. 
Derogenes varicus. 

Gadidje. 

Gadus callarias L. 

Udonella caligorum (on Caligus 

and Anchorella). 
Octodactylus morrhuos. 
Bucephalopsis gracilescens (meta- 

cercariae). 
Prosorhynchus crucibidum (meta- 
cercarise). 
^Podocotyle atomon. 
Lepidapedon rachion. 
L. elongatum. 
Stephanostomum pristis. 
*Hemiurus levinseni. 
H. communis. 

Synaptobothrium caudiporum. 
Derogenes varicus. 
*Genarches mulleri. 
Gadus ceglifinus L. 

Bucephalopsis gracilescens (meta- 

cercarise). 
^Podocotyle atomon. 
Lepidapedon rachion. 
*Deretrema abyssorum. 
Hemiurus communis. 
* Lecithaster gibbosus. 
Gadus luscus L. 

Diclidophora luscoz. 
Podocotyle atomon. 
Stephanostomum caducum. 
Hemiurus communis. 
Synaptobothrium caudoporum. 
Derogenes varicus. 
Gadus minutus L. 

* Bucephalopsis gracilescens (meta- 

cercarise). 
Diclidophora dentic ulata. 



350 



THE TKEMATOD.A OF P.TtTTTSH FTSHES 



( ;aj.)id.e (continued). 

D. luscce. 

Stephanostomum caducum. 
*S. pristis. 

Hemiurus communis. 

Derogenes various. 
Gadus merlangus L. 

Diclidophora merlangi. 

Octodactylus minor. 

0. morrhuce. 

Bucephalopsis gracilescens (meta- 
cercarise). 

Prosorhynchus crucibidum . 

Podocotyle atomon. 

Opechona retractilis. 

Stephanostomum pristis. 

S. caducum. 

S. rhombispinosum. 

Hemiurus ocreatus. 

H. communis. 

Lecithaster gibbosus. 

Derogenes varicus. 
Gadus poutassou (Risso). 

Octodactylus minor. 
Gadus virens L. 

Diclidophora denticulata. 

Anthocotyle merluccii. 
* Bucephalopsis gracilescens (meta- 
cercariae). 

Podocotyle atomon. 

Lepidapedon rachion. 

Hemiurus communis. 

Derogenes varicus. 
Gadus pollachius L. 

Udonella caligorum (on C aligns). 

Diclidophora pollachii. 

Bucephalopsis gracilescens (meta- 
cercariae). 

Podocotyle atomon. 

Lepidapedon rachion. 

Hemiurus ocreatus. 

H. communis. 

Derogenes varicus. 
Urophycis blennoides (Brunnich). 

Diclidophoroides phycidis. 

Bucephalopsis gracilescens (meta- 
cercariss). 
*Hemiurus levenseni. 
Lota lota (L.). 

*Diplozoon paradoxum. 
* Bucephalus polymorphus. 
* Podocotyle atomon. 
*Crepidostomum suecicum. 
*Azygia lucii. 



*PhyUodistom um si mile . 
* Hemiurus appendiculatus. 
Molva molva (L.). 

Udonella caligorum (on Caligus). 
*Pteronella molvce (on Caligus). 

Octodactylus pahnatus. 

Bucephalopsis gracilescens (meta- 
cercarise). 

Hemiurus communis. 

Derogenes varicus. 
Molva byrkelange Walbaum. 

*Linguadactyla molvce. 
Onos mustelus (L.). 

Peracreadium genu. 

Podocotyle atomon. 

P. reflexa. 

Stephanostom urn rhombispinosum. 
*S. pristis. 
*tTormopsolus osculatus. 

Lecithochirium furcolabiatum. 

Hemipera ovocaudata. 
*Lecithocladium excisum. 
Onos tricirratus (Bloch). 

Podocotyle atomon. 

P. reflexa. 

Derogenes varicus. 
*Deroge?ioides ovacutus. 

Hemipera ovocaudata. 
Brosme brosme (Muller). 

* Prosorhynchus crucibulum. 

Hemiurus communis. 

Derogenes varicus. 

Lamprididje. 

Lampris luna (Gmelin). 
*Didymozoon tenuicolle. 

Zeus faber L. 

Plagioporus varius. 
Stephanostomum cesticillus. 
Zoogonoides viviparus. 
Synaptobothrium caudiporum. 
Lecithaster gibbosus. 
Derogenes varicus. 

CAPROIDiE. 

Capros aper (L.). 

Opechona bacillaris. 
Hemiurus ocreatus. 
H. communis. 
* Lecithochirium rufoviride. 
Derogenes varicus. 



LIST OF HOSTS AND THETR PARASITES 



351 



Serranid-k. 

Morone labrax (L.). 

Diplectanum cequans. 

Microcotyle labracis. 
? Rhipidocotyle galeata. 

Acanthostomum imbutiforme. 
*A. prazteritum. 
*tSterrhurus musculus. 
*Lecithochirium gravidum. 

Cainocreadium labracis. 
Epinephelus gigas (Briinnich). 
*Megalocotyle hexacanthus. 
Serranus cabrilla (L.). 

Microcotyle donavini. 

Helicometra fasciata. 
? H. pulchella. 
? Lepidapedon rachion. 

Lecithaster gibbosus. 
*Sterrhurus musculus. 

Percid^j. 

Perca fluviatilis L. 

*Dactylogyrus auriculatus. 
*Z>. uncinatus. 
*Neodactylogyrus tenuis. 

Ancyrocephalus paradoxus. 
^Bucephalus polymorphus. 
*Sphazrostoma bramce. 

Azygia lucii. 

Bunodera luciopercaz. 
*Hemiurus appendiculatus. 
Acerina cernua (L.). 

*Dactylogyrus amphiboihrium. 
*Plagioporus acerince. 
*Sphazrostoma bramce. 
*Bunodera luciopercce. 
*Phyllodistomum folium. 

Carangid^e. 

Trachurus trachurus (L.). 

*Cyclocotyla charcoti (on Cymothoa). 
* Microcotyle Uchio3. 

Gastrocotyle trachuri. 
*Vallisia striata. 
*Grubea cochlear. 
*Haplocladus typicus. 

Tergestia laticollis. 
*T. acanthocephala. 

Ancyloozlium typicum, 

Hemiurus ocreatus. 

H. communis. 
*Aphanurus stossichii. 

Entenurus lepidus. 



* Lecithocladiu m excisum. 
Lecithaster gibbosus. 
Derogenes varicus. 

Naucrates ductor (L.). 
*Ancyrocotyle bartschi. 
*A. vallei. 

Bramid.^. 

Bra-ma raii (Bloch). 

*Encotyllabe nordmanni. 
*Trochopus differ ens. 
^Microcotyle chrysophryi. 
*M. acanihurum. 
*M. donavini (as canthari). 
Kbllikeria filicollis. 

SciAENIDiE. 

Sciazna aquila Risso. 

*Calceostoma calceostoma. 
*Diplectanum sciaznaz. 
Benedenia sciaznaz. 
*Nematobothrium filarina. 

Mullid^:. 

Mullus surmuletus L. 
*Podocotyle furcata. 
*Proctotrema bacilliovatum. 
*Aponurus laguncula. 
*A. tschuginovi. 
Derogenes varicus. 

Sparidje. 

Dentex dentex (Gmelin). 

* iPtychogonimus megastoma. 
*Sterrhurus musculus. 

Pagellus centrodontus (De la Roche). 
Encotyllabe pagelli. 
Cyclocotyle chrysophryi. 
C. pagelli. 

Microcotyle centrodonti. 
Zoonogenus vividus. 
Steringotrema pagelli. 
Hemiurus communis. 
Derogenes varicus. 
Pagellus owenii Gunther. 

^Microcotyle donavini (as eryihrini). 
Pagellus erythrinus (L.). 

* Microcotyle donavini (as eryihrini). 
Spondyliosoma cantharus (Gmelin). 

*Trochopus tubiporus. 
Box boops (L.) 

*Cyclocotyle. charcoti. 



352 



THE TREMATODA OF BRITISH FISHES 



SPARID/E (continued). 

* Microcotyle donavini (as erythrini). 
*Aphanurus stossichii. 
*Lecithocladi um excisum. 
*Mesometra orbicu laris. 
Sparus aurata L. 

*Diplectanum echeneis. 
*Encotyllabe vallei. 

Cyclocotyla ch rysoph ry i . 

Microcotyle chrysoph ry i . 

Podocotyle atomon. 
*Diphterostomum brusince. 

Synaptobothrium caudiporum 

(larvae). 
^Microcotyle canthari. 
Pagrus pagrus (L.). 

*Diplectanum acheneis. 
*Anoplodiscus richiardii. 

Cepolidje. 

Cepola rubescens L. 

*Haplocladus filiformis. 
* Lecithocladium excisum. 

Lecithaster gibbosus. 

Hemipera sharpei. 
*Aphamtrus stossichii (as virgula). 

Labridje. 

Labrus bergylta Ascanius. 

Microcotyle donavini. 
*Cainocreadium labracis. 

Peracreadium genu. 

P. commune. 

Helicometra fasciata. 

Plagioporus alacer. 

P. varius. 

Lepidauchen stenostoma. 
* Diphterostomum brusince. 
*Zoogo?ms rubellus. 

Synaptobothrium caudiporum 
(larvae). 

Lecithaster gibbosus. 
*Derogenes varicus. 
Labrus mixtus L. 

^Peracreadium commune. 

Helicometra fasciata. 
*H. pulchella. 

Plagioporus alacer. 

P. varius. 
^Lecithaster gibbosus. 

Zoogonus rubellus (larvae). 
Creuilabrus melops (L.). 

Peracreadium commune. 



Helicometra fasciata . 

Plagioporus alacer. 
Ctenolabrus rupestris (L.). 

Helicometra fasciata. 

Plagioporus alacer. 
Centrolabrus exoletus (L.). 

Plagioporus alacer. 

Ammodytidje. 

Ammodytes lanceolatus Lesauvage. 
Hemiurus communis. 
*Brachyphallus crenatus. 
Ammodytes tobianus L. 
*Gyrodaetylus sp. 
Brachyphallus crenatus. 
Lecithaster gibbosus. 
Hemiurus communis. 

Trachinid^e. 

Trachinus draco L. 

Microcotyle draconis. 
Rhipidocotyle galeata (as vipercv). 
Helicometra pulchella. 
*H. sinuata. 
Hemiurus communis. 
*Aponurus laguncula. 
*Sterrhurus musculus. 
^Lecithaster gibbosus. 
Derogenes varicus. 
Derogenoides ovacutus. 
Trichinus vipera Cuvier and Valen- 
ciennes. 

Rhipidocotyle galeata (and as viperce 

and minima). 
Lecithaster gibbosus. 
Derogenes varicus. 

SCOMBRIDJE. 

Scomber scombrus L. 
*Grubea cochlea. 

Kuhnia scombri. 
^Podocotyle atomon. 

Opechona bacillaris. 

Didymozoon scombri. 

D. faciale. 
*Tergestia acanthocephala. 

Hemiurus ocreatus. 

Lecithocladium excisum. 
^Lecithaster gibbosus. 
Pneumatophorus colias (Gmelin). 
*Didymozoon scombri. 
* Lecithocladium excisum. 
*Ectenurus lepidurus. 



LIST OF HOSTS AND THEIR PARASITES 



353 



Scombrid.e (continued). 

*Synaptobothrium caudiporum. 
Thunnus thynnus (L.). 

*Capsala onchidiocotyle. 

*'?Hexastoma acutum. 
H. exlensicaudum. 

*H. ihunnince. 
H. thynni. 

* Didymozoon pretiosum. 

*Didymocystis thynni. 

*Wedlia bipartite,. 

*Sterrhurus imocavus. 
Germo alalunga (Gmelin). 

*Nematobothrium guernei. 
Katsuwonus pelamis (L.). 

*Didymozoon auxis. 
Sarda sarda (Block). 

*Didymozoon pelamydis. 
Dinurus tornatus. 

Luvarid.e. 

Luvarus imperialis Rafinesque. 
*Tetrochetus raynerianus. 

XlPHIID^E. 

Xiphias gladius L. 

*Tristoma ccccineum. 

T. integrum. 
*Wedlia xiphiados. 

Gobiid.e. 
Gobius niger L. 

* Bucephalopsis tergestinum. 
Gobius paganellus Gmelin. 

Helicometra fasciata. 

Hemiurus communis. 
Gobius ruthensparri Eupkrasen. 

Podocotyle atomon. 

Lecithaster gibbosus. 
Gobius minutus Gmelin. 
*Gyrodactylus elegans. 

* Asymphylodora demeli. 

Callionymidjs. 
Callionymus lyra L. 
Plagioporus varius. 
Zoogonoides viviparus. 
Lecithaster gibbosus. 
Derogenes varicus. 

Blenniid^e. 
Blennius gattorugine Bloch. 
Helicometra fasciata. 

23 



Monorchis monorchis. 

Zoogonoides viviparus. 
*Steringotrema divergens. 
Blennius ocellaris L. 

^Helicometra pulchella. 
* Diphterostomum brusince. 

Zoogonoides viviparus. 
*Proctozces macukitus. 

Steringotrema divergens. 

Derogenes varicus. 
Blennius pholis L. 
? Peracreadium genu. 

Helicometra fasciata. 
*H. pulchella. 

Lecithochirium rufoviride (larvae). 

Synaptobothrium ca udipoi'um 
(larvae). 

Pholid.e. 

Pholis gunnellus (L.). 

Microcotyle fusiformis. 
Podocotyle atomon. 
Hemiurus communis. 

Zoaecidje. 

Zoarces viviparus (L.). 
Podocotyle atomon. 

Anarhichadid^;. 

Anarhichas lupus L. 

Udonella caligorum. 
^Plagioporus idoneus. 
^Podocotyle atomon. 

Neophasis lageniformis. 
*N. oculata. 
*Neophasis pusilla. 
*A canih ostomum imbutiforme. 

Zoogonoides viviparus. 

Zoogonus rubellus. 

Fellodistomum fellis. 
* Lepidophyllum steenstrupi. 
*Derogenes varicus (as plenus). 
Anarhichas latifrons Steenstrup and 
Hallgrimsson. 

Plagioporus idoneus. 

MUGILID.E. 

Mugil chelo Cuvier. 
*Gyrodactylus sp. 
^Microcotyle mugilis. 
*Haplosplanch?ius pachysoma. 
Haploporus benedenii (and as 
lateralis). 



354 



THE TREMATODA OF BRITISH FISHES 



Mugilid^e (continued). 

Saccocoslium obesum (and as ten- 
sum). 
*Dicrogaster perpusilla (and as 
contracta). 
Mugil capito Cuvier. 

*Haplosplanchnus pachysomia. 
*Saccoccelium obesum. 
Mugil auratus Risso. 
*Benedenia monticellii. 
*Haploporus benedenii (as lateralis). 
* Haplosplanchnus pachysoma. 
*Lec ithobotrys putrescent. 
*Saccocozlium obesum. 
* Lecithaster galeatus. 

Atherinid.e. 

Aiherina presbyter Cuvier. 
Podocotyle athermoe. 
Bacciger bacciger. 



TRIGLIDiE. 

Trigla lucema L. 

*Echinella hirundinis (on Caligus). 

Trochopus diplacanthus. 

T. gaillimhe. 
*T. heteracanihus. 
*T. micracanthus. 
*T. pini. 

T. tubiporus. 

Axine belones (as triglce). 

Plectanocotyle gurnardi (as lorenzi). 

RMpidocotyle galeata (as minima). 

Helicometra pulchella. 

Hemiiirus communis. 

Synaptobothrium. caudiporum. 

Derogenes varicus. 
Trigla cuculus L. 
*Trochopus pini. 

T. tubiporus. 

Plectanocotyle gurnardi. 

RMpidocotyle galeata (as minima). 

Helicometra fasciata. 

H. pulchella. 

Hemiurus communis. 

Lecithaster gibbosus. 

Derogenes varicus. 
Trigla gurnardus L. 

*Udonella caligorum (as triglce). 
*Platycotyle gurnardi. 

Plectanocotyle gurnardi (as lorenzi). 



Rhipidocotyle galeata (as minima) 

Prosorhynchus crucibulum (as 
triglce) 
* Podocotyle atomon. 

Helicometra gurna rd i . 

Stephanostomum triglce. 

Hemiurus communis. 
*H. ocreatus. 

Lecithaster gibbosus. 

Derogenes varicus. 
Trigla lineata Gmelin. 

Trochopus lineatus. 

Plectanocotyle gurnardi. 

Helicometra pulchella. 

Hemiurus communis. 
*Derogenes ruber. 

COTTIDyE. 

Cottus gobio L. 

*Gyrodactylus gracilis. 
* Trochopus brauni. 
*Megalocotyle zschokkei. 
*Dij)lozoon paradoxum. 
*Allocreadium angusticolle. 
*Phyllodistomum folium. 
*P. simile. 
Cottus scorpius L. 

*Gyrodactylus grcenlaiidicus. 

Prosorhynchus crucibulum. 

Podocotyle atomon. 
*Peracreadium commune. 
*Crepidostomum suecicum. 

Stephanostomum baccatum. 
*S. sobrinum. 
*Neophasis oculatus. 
* Steringophorus furc iger. 
*Hemiurus levinseni. 

H. communis. 
* Brachyphallus crenatus. 
^Lecithaster gibbosus. 

Derogenes varicus. 
*Genarches mulleri. 

Cottus bubalis Euphrasen. 

Prosorhynchus crucibulum (as 
squamosum). 
*Peracreadium commune. 
Helicometra fasciata. 
Podocotyle atomon. 
Hemiurus communis. 
Derogenes varicus. 
Agonus cataphractus (L.). 
*Derogenes varicus. 



LIST OF HOSTS AND THEIR PARASITES 



355 



Cyclopteridje. 

Cyclopterus lumpus L. 
*Gyrodactylus elegans. 
*Podocotyle levensini. 
*P. refiexa. 

Opechona bacillaris. 

Derogenes various. 



Lip arid m. 

Liparis liparis (L.). 

*Podocotyle levensini. 
Liparis montagui (Donovan). 

Prosorhynchus crucibulum (as 

squamosus). 
Podocotyle atomon. 



Gasterosteid^e. 

Gasterosteus aculeatus L. 
Gyrodactylus elegans. 
*G. rarus. 
Diplozoon paradoxum. 
Podocotyle atomon. 
Phyllodistomum folium. 

* Brachyphallus crenatus. 
Pygosteus pungitius (L.). 

Gyrodactylus elegans. 
*G. rarus. 
Spinachia spinachia (L.). 
Podocotyle atomon. 
P. refiexa. 

Botbibm. 

Arnoglossus laterna (Walbaum). 

* Lecithobothrium copulans. 

* Synaptobothrium caudiporum. 
Scophthalmus maximus (L.). 

Calicotyle kroyeri. 
*Megalocotyle rhombi. 
^Podocotyle atomon. 

Zoogonoides viviparus. 
*Hemiurus rugosus. 
*Sterrhurus musculus. 
* Leciihochirium gravidum. 
*L. rufoviride. 

Derogenes varicus. 
*Synaptoboihrium caudiporum. 
Scophthalmus rhombus (L.). 

Synaptobothrium caudiporum. 

Derogenes varicus. 
Phrynorhombus norvegicus (Gunther), 

Podocotyle atomon. 



Lecithaster gibbosus. 
Derogenes varicus. 
Zeugopterus punctatus (Bloch). 

Helicometra fasciata (as pulchella). 
Podocotyle atomon. 
Hemiurus communis. 

PLEURO NECTIDiE . 

Hippoglossus hippoglossus (L.). 

Udonella caligorum (on Caligus). 
*Tristoma levinsenii. 
*T. uncinatum. 

Entobdella hippoglossi. 

Stephanostomum baccatum. 

Hemiurus communis. 

Lecithaster gibbosus. 

Derogenes varicus. 
Hippoglossoides platessoides (Fabricius) . 

Stephanostomum baccatum (meta- 
cercariae). 

Zoogonoides viviparus. 

Steringophorus furciger. 

Rhodotrema ovacutum. 

Hemiurus communis. 

Lecithaster gibbosus. 

Derogenes varicus. 
Limanda limanda (L.). 

Podocotyle atomon. 

Stephanostomum baccatum (meta- 
cercariae). 

Zoogonoides viviparus. 

Zoogonus rubellus (juveniles). 

Steringophorus furciger. 

Steringotrema cluthense. 
*Haplocladus minor. 

Hemiurus communis. 
* Brachyphallus crenatus. 

Lecithaster gibbosus. 

Derogenes varicus. 
*Aporocotyle simplex. 
Pleuronectes platessa L. 

? Gyrodactylus elegans. 

Plagioporus varius. 

Podocotyle atomon. 

Zoogonoides viviparus. 

Steringophorus furciger. 

Hemiurus communis. 

Synaptobothrium caudiporum. 

Lecithaster gibbosus. 

Derogenes varicus. 
Microstomus kitt (Walbaum). 
^Podocotyle atomon. 

Stephanostomum baccatum (ineta- 
cercarise). 



^ 



356 



THE TKEMATODA OF BRITISH FISHES 



Pleuronectidje (continued). 

Zoogonoides viviparus. 

Steringophorus furciger. 

Steringotrema cluthense. 

Lecithaster gibbosus. 

Derogenes various. 
Glyptocephalus cynoglossus (L.). 

Stephanostomum baccatum (meta- 
cercariae). 

Otodistomum veliporum (larvae). 

Zoogonoides viviparus. 

Steringophorus furciger. 
Platichthys fiesus (L.). 

Udonella caligorum (on Caligus). 
*Cainocreadium labracis. 

Plagioporus varius. 

Podocotyle atomon. 
^Zoogonoides viviparus. 
* 'Steringophorus furciger. 

Hemiurus communis. 

Lecithaster gibbosus. 

Derogenes varicus. 
*Aporocotyle simplex. 

SOLEID.E. 

Solea solea (L.). 

Entobdella solece. 

Podocotyle atomon. 
*P. furcata. 

Zoogonoides viviparus. 

Derogenes varicus. 
Pegusa lascaris (Risso). 

Entobdella soleai. 
Microchirus variegatus (Donovan). 

Zoogonoides viviparus. 

Molidje. 

Mola mola (L.). 
*Capsala cutanea. 
*C. grimaldii. 
*C. interrupts. 
C. martinieri. 
*C. onchidiocotyle. 
*C. pelamydis. 



*C. thynni. 

Dihemistephanus lydice. 
*Accacoelium contortum. 
*Accacladium serpentulus. 
*A. nematulum. 
*Bhynchopharynx paradoxa. 

Accacladocozlium alveolatum. 
*A. nigroflavum. 
*Mneiodhneria calyptrocotyle. 
*Orophocotyle calyptrocotyle. 
*Didymozoon taznioides. 
*Nematobothrium benedeni. 
*N. molce. 
*K6llikeria filicollis. 
Ranzania truncata (Retzius). 
*Orophocotyle divergent. 
*0. planci. 

Gobiesocidje. 

Lepadogaster gouani Lacepede. 

Helicometra fasciata (as j)uhJiella). 
Hemiurus communis. 
Hemipera ovocaudata. 

Lophud^}. 

Lophius piscatorius L. 

Bucephalopsis gracilescens. 

Prosorhynchus crucibulum (meta- 
cercariae). 

Stephanostomum baccatum (larvae). 
*S. caducum. 
*S. cesticillus. 
*Otodistomum veliporum (larvae). 

Steringophorus furciger. 

Hemiurus communis. 
*Ectenurus lepidus. 
*Lecithocladium excisum. 

Sterrhurus fusiformis. 
*S. grandiporus. 
*S. musculus. 

Lecithochirium rufoviride. 
*L. physcon. 

Synaptoboihrium caudiporum. 

Derogenes varicus. 



GENERAL AND SYSTEMATIC INDEX. 



357 



abbreviata Olsson — Erpocotyle, 84 
absconditum Looss — Amnihostomum, 

213 
abyssorum Odhner — Deretrema, 250 
acanilwcephala Stossich — Tergestia, 268 
Acanthocolpidae, 197 
— genera of, 198 
Acanthocotyle, 57 
Acanthocotylidse, .37 
Acanthocotylinse, 57 
Acanthostomatida?., 211 
Acanthostomatinee, 211 
Acanthostomum, 212 
Accacladium, 229 
Accacladocoelium, 230 
Accacceliidse, 228 

Accacceliinas, key to genera of, 229 
Accaccdium, 229 

acceptum Looss — Phyllodistomum, 273 
acerime Pigulewski — Plagioporus, 172 
Actinodeidus, 36 
aculeatum Parona and Perugia — Di- 

plectanum, 39 
acuta /a Goto — Hexostoma, 143 
aequwns Wagener — Diplectanum, 37, 

Fig. 3. a-g 
alacer Looss — Plagioporus, 172, Fig.33,B 
alaskensis Price — Tetraonchus, 32 
alba Cerfontaine — Rajonchocotyle, 89, 

Fig. 14, f-j 
Alcicorais, 158 
AllocreadiidaB, 162 
Alloc readiinse, key to genera of, 163 
Allocreadium, 163 
alosai Hermann — Mazocraes, 138 
alveola turn Rohinsoii-Accacladocoslkim, 

231, Fig. 39, a, b 
Amphibdella, 31, 33 
Amphibdelloides, 31, 34 
Anchoradiscus, 36 
Anchylodiscoides, 37 
Anchylodiscus, 36 
Ancylocoelium, 268 
Aticyrocephaloides, 37 
Ancyrocephaliis, 31, 32 
Ancyrocotyle, 78 
Anoplodiscus, 40 



Anthocotyle, 130 

Anthocotylinse, 130 

Aphanurus, 280 

apiculatum Olsson — Microbothrium, 49, 

Fig. 5, d, e 
Aponurus, 298 
Aporocotyle, 13, 307 
Aporocotylidae, 306 
appendiculatum Kuhn — Hexaboihrium, 

81 
appendiculatus Rudolphi — Hemiurus , 

275, Fig. 46, a-c 
armatum Leuckart — Diclybolhrium, 92, 

Fig. 15, a-g 
Aspidogaster, 11 
Aspidogastrea, 10-12 
Asymphylodora, 226 
atherince Nicoll — Podocotyle, 176 
atomon Rudolphi — Podocotyle, 178, Fig. 

32, A, B 

angusticolle Hausman — ^4 llocreadium , 

164 
auriculatum Wedl — Crepidostomum, 

195 
auriculatus Nordman — Dactylogyrus, 

28 
australis Johnston — Anoplodiscus, 40 
«wa;*s Taschenberg — Didymozoon, 240 
J.a;me, 121 

azumce Layman — Helicometrina, 169 
Azygia, 218 
Azygiidse, 213 

baccatum Nicoll — Stephanostomum, 203 

Bacciger, 261 

bacciger Rudolphi — Bacciger, 261, Fig. 

44, b 
bacillaris Molin — Opechona, 186, Fig. 

33, f 

baciUiovatum Odhner — Proctotrema, 226 
baicalense Layman — Crepidostomum, 

195 
bartschi Price — Ancyrocotyle, 79 
fra^s Cerfontaine — Rajonchocotyle, 89, 

Fig. 14, n-p 
baylisi Nagaty — Alcicornis, 158 
bellones, Otto — Cyclocotyla, 110 



358 



INDEX 



belones Abildgaard — Axine, 121 
benedeni Monticelli — Nematobothrium , 

241 
Benedenia, 72 
benedenii Stossich — Haploporus, 251, 

Fig. 43, a-d 
Benedeniinse, genera of, 72 
bete7icourti Monticelli — Diphterostomum, 

244 
bicoronatum Looss — Stephanostomum, 

198 
bipartita Wedl — Didymocystis, 242 
borealis Brinkmann — Acanthocotyle, 61 
borealis Olsson — Dactylodiscus, 36 
borealis Beneden — Erpocotyle, 85, Fig. 

12, J 
botryophoron Olsson — Leciihophyllum , 

299 
brachycodia Liihe — Mesometra, 306 
Brachy phallus, 293 
bramos Miiller — Sphcerostoma, 195, Fig. 

34, b 
brauni Mola — Trochopus, 66 
brusince Stossich — Diphterostomum, 

243, Fig. 42, h 
Bucephalidse, 148 
Bucephalinse, genera of, 149 
Bucephalus, 149 
Bucephalopsis, 151 
Bunodera, 269 
Bunoderidse, 269 

caducum Looss — Stephanostomum, 200, 

Fig. 35, e, f 
Cainocreadium, 164 
Calceostoma, 40 

calceostoma Wagener — Calceostoma, 40 
Calceostomatidae, 39 
Calceostomatinae, 40 
Calicotyle, 44 
Calicotylinae, 44 
caligorum Johnston — Udonella, 55, Fig. 

6, a-f 
calyptrocotyle Monticelli — Mneiodh- 

neria, 233, Fig. 39, d, e 
canicula Cerfontaine — Hexabothrium, 

81, Fig. 12, i 
canis Cerfontaine — Erpocotyle, 85 
capense Looss — Probolitrema, 273 
Capsala, 68 
Capsalidae, 62 
Capsalinae, 68 
Capsaloidea, 41 
carangis MacCallum — Alcicomis, 158 



catenulata Guberlet — Neoerpocotyle, 87, 

Fig. 12, a-f 
caudiporum Rudolphi — Synaptoboth- 

rium, 292, Fig. 48, d 
centrodonti Brown — Microcotyle. 119, 

Fig. 23, d, e 
cesticillus Molin — Stephanostomum, 

199 
cestodes, relationship to trematodes, 1 
charcoti Dollfus — Cyclocotyla, 113, Fig. 

21, A-F 
Chimazricola, 135 
Chimsericolinae, 135 
chrysophryi, Beneden and Hesse — 

Cyclocotyla, 110, Fig. 20, d-f 
Cleidodiscus, 36 
cluthense Nicoll — Steringotrema , 259, 

Fig. 44, d 
cochlear Diesing — Grubea, 128 
commune Olsson — Peracreadium , 167 
communis Odhner — Hemiurus, 278, 

Fig. 46, i, J 
conchicola Baer — Aspidogaster, 10, Fig. 

29, a 
concinna T. Scott — Thaumatocotyle, 48, 

Fig. 4, b 
confusus Odhner — Lecithaster, 294, Fig. 

49, a-c 
conostomum Olsson — Phyllodistomum, 

273 
contortum Rudolphi — Accaccelium, 229, 

Fig. 39, c 
conviva Liihe — Lecithochirium, 290 
copulans Linstow — Lecithochirium, 290 
copulatory organs, of Prosostomata. 20 
cornutum, Osborne — Crepidostomum, 

195 
Cotylogaster, 11 
crenatus Rudolphi — Brachyjmallus, 293 

Fig. 36, d 
Crepidostomum, 192 
crueibidum Rudolphi — Prosorhyn chus, 

159, Fig. 30, c, d, f, g 
cumingice Martin — Monorcheides. 225 
cutanea Guiart — Capsala, 70 
cuticle, of Digenea, 14 
Cyclocotyla, 110 
Cyclocotylina?, genera of, 109 

Dactylodiscus, 31, 36 
Dactylogyridse, 28 
Dactylogyrinse, 28 

Dactyhgyrus, 28, Fig. 2, a, Bb, cb, 
Da, b 



INDEX 



359 



Daitreosoma, 36 

dasybatis MacCaUum — Thaumatocotyle, 

48 
decatis Eckmann — Aspidogaster, 11 
demeli Markowsky — A symphylodora, 

227 
denticulata Olsson — Diclidophora, 97, 

Fig. 17, f-k, 18, a-h 
Deretrema, 250 
Derogenes, 300 

Derogenetinae, genera of, 299 
Derogenoides, 303 
Deropristis, 208, Fig. 36, a, b 
diaphana Cerfontaine — Merizocotyle, 47 
diadema Monticelli — Entobdella, 78 
Diclidophora, 95 
Diclidophoridae, 94 
Diclidophorinae, genera of, 95 
Diclidophoroidea, 94 
Diclidophoroides, 109 
Diclidophoropsis, 114 
Diclybothriinse, 92 
Diclybothrium, 92 
Dicrogaster, 253 
Didymocystis, 241 
Didymozoidae, 236 
Didymozoon, 237 
differ ens Sonsino — Trochopus, 66 
Digenea, key to families of, 147 
Dihemistephanus, 205 
Dinurinae 280 
Dinurus, 281 
Diphterostomum, 243 
diplacanihus Massa — Trochopus, 66 
Diplectaninae, 37 
Diplectanotrema, 36 
Diplectanum, 37 

diplorchis Odhner — Monorcheides, 225 
Diplozoon, 129 
Discocotyle, 125 
Discocotylidae, 124 
Discocotylinse, genera of, 125 
Distoma miescheri, 310, Fig. 51, e, f 
divergens Looss — Orophocotyle, 235, 

Fig. 40, a 
divergens Rudolphi — Steringotrema, 60, 
Fig. 45, a 

Echinella, 56 

echeneis Wagener — Diplectanum, 39 

Ectenurus, 283 

eggs ; general characters of, 10, 21 

— mode of formation inMonogenea, 10 

— mode of formation in Digenea, 21 



elegans, Monticelli — Acanthocotyle, 62 
elegans Nordmann — Gyrodactylus, 25, 

Fig. 1, a, B 
elegans Olsson — Macraspis, 11 
elliptica Diesing — Plectanocotyle, 133 
elongata Noble and Park — Helico- 

metrina, 169 
elongatum Lebour — Lepidapedon, 184, 

Fig. 33, e 
elongatum sp. inq. Nybelin — Phyllo- 

distomum, 273 
emarginata Olsson — Bajonchocotyle, 90, 

Fig. 14, a-e 
Empleurosoma, 36 
Encotyllabe, 62 
Encotyllabinse, 63 
Enoplocotyle, 57 
Enoplocotylinae, 57 
Entobdella, 73 
Erpocotyle, 83 

" erythrceus " Odhner — Proctoeces, 266 
esmarkii T. Scott — " Octobothrium^ 

109 
eugalei Price — Erpocotyle, 87, Fig. 13, 

D-G 

excisum Rudolphi — Lecithocladium, 

283, Fig. 47, e 
execta Linton — Helicometra, 168 
extensicaudum Dawes — Hexostoma, 144, 

Fig. 28, a, b, 1^ 



faciale Baylis — Didymozoon, 238, Fig. 

41, b, c 
falcatus Wedl — Dactylogyrus, 30 
farionis Muller — Crepidostomum, 192, 

Fig. 32, h 
fasciata Rudolphi — Helicometra, 169, 

Fig. 32, e 
fellis Olsson — Fellodistomum, 254, Fig. 

44, a 
Fellodistomatidse, 254 
Fellodistomatinae, 254 
Fellodisiomum, 254 
female organs of Digenea, 20 
filarina Beneden — Nematobothrium, 241 
filicollis Rudolphi — Kdllikeria, 242 
filiformis Rudolphi — Haplocladus, 265 
fintce Beneden and Hesse — Ophicotyle, 

140 
flame-cell formula, 18, 146 
flavolineata MacCallum — Amphibdella, 

33, Fig. 1, d, e 
foliata Linton — Mneiodhneria, 233 



360 



INDEX 



folium v. Olfers — Phyllodistomum, 272, 

Fig. 34, e 
furciger Olsson — Steringophorus, 257, 

Fig. 44, c 
fvrcolabiatum E. I. Jones — Lecitho- 

chirium, 291, Fig. 50, h 
fvsiformis Goto — Microcotyle, 121 
fusiformis Luhe — Sterrhurus, 286, Fig. 

48, g 

gaiUimhe Little — Trochopus, 64, Fig. 8, 

A-F 

galeata JIudolphi—JRhipidocotyle, 157, 

Fig. 30, e 
galeatus Looss — Lecithaster, 298 
galeorhini Price — Erpocotyle, 87, Fig. 

13, A-C 
Gasterostomata, 148 
Gastrocotyle, 123 
Gastrocotylidae, 123 
Genarches, 303 

gremi Eudolphi — Peracreadium, 166 
gibbosus Rudolphi — Lecithaster, 296, 

Fig. 50, G 
gland -stomach of Hemiurids, 17 
glandulosum Johnston and Tiegs — 

('(ilceostoma, 40 
Gorgoderidae, 271 
Gorgoderinae, 271 
gracilescens Rudolphi — Bucephalopsis, 

12, 152, Fig. 30, a, b ; Fig. 31, a-k 
gravidum Looss — Lecithochirium, 290, 

Fig. 48, f 
grimaldii Guiart — Capsala, 70 
grisea Cerfontaine — Neoerpocotyle, 87 
Grubea, 128 

gueniei Moniez — Nematobothrium, 241 
gurnardi Beneden and Hesse — Platy- 

cotyle, 117 
gurnardi Beneden and Hesse — Plectano- 

cotyle, 133 
gurnardi Thapar and Dayal — Helico- 

metra, 168 
Gyrodactylidse, 25 
Gyrodactyloidea, 24 
Gyrodactylus, 25 

ha imeanus Lacaze-Duthiers — Bucepha- 
lopsis, 151, 152 
Haliotrema, 37 
Haplocladinse, 265 
Haplocladus, 265 
Haplocleidus, 31, 33 
Haploporida3, 250 
Ha ploporus, 251 



Haplosplanchnidae, 222 

Haplosplanchnus, 222 

haptors, types of, 2 

harengi Beneden and Hesse — Mazo- 

craes, 139 
Helicometra, 168 
Helicometrina, 169 
Hemipera, 304 
Hemiuridae, 274 

— soma and ecsoma of, 14 

— subfamilies of, 275 
Hemiurinae, genera of, 275 
Hemiurus, 275 
Heterocotyle, 42 

heterocotyle Beneden — Heterocotyle, 140 

Hexabothriidae, 80 

Hexabothriinse, genera of, 80 

Hexaboihrium, 81 

hexacanthus Parona and Perugia — 

Megalocotyle, 67 
Hexostoma, 143 
Hexostomatidae, 143 
hippoglossi Miiller — Entobdella, 73, Fig. 

10, A-C 

hirundinis Beneden and Hesse — Echi- 

nella, 56 
hispida Abildgaard, in Rudolphi — 

Deropristis, 210 

idoneus Nicoll — Plagioporus, 174, Fig. 

33, c 
imbutiforme Molin — Acanthostomum, 

212, Fig. 35, k-m 
inerme Parona and Perugia — Cal- 

ceostoma, 40 
inermis Plehn — Sanguinicoh, 309, Fig. 

51, C, D 

inflata Molin— Deropristis, 208, 210, 

Fig. 36, a, b 
integrum Diesing — Tristoma, 71 
interrupta MonticeUi — Capsala, 70 
Isancistrum, 28 
isoporum Looss — Allocreadium, 163, 

Fig. 34, a 

Kollikeria, 242 

kroyeri Diesing — Calicotyle, 44, Fig. 

4, F-I 
Kuhnia, 141 

labracis Beneden and Hesse — Micro- 
cotyle, 118 

labracis Dujardin — Cainocreadium, 164, 
Fig. 32, d 

Icevis Beneden and Hesse — Erpocotyle, 
83, Fig. 12, G, h 



INDEX 



361 



lagenijormis Lebour — Neophasis, 189, 

Fig. 35, G 
lagunculus Looss — Aponurus, 298 
lasius Leidy — Zoogonus, 249 
laticollis Rudolphi — Tergestia, 266, Fig. 

45, e 
Laurer's canal, 21 
Lecithaster, 294 

Lecithasterinae, genera of, 294 
Lecithobotrys, 253 
Lecithochirium, 286 
Lecithocladium, 283 
Lecithophyllum, 299 
Lecithostaphylinae, genera of, 250 
Lecithostaphylus, 250 
Lepidapedon, 182 
Lepidauchen, 191 
Lepidophyllum, 250 
lepidorhini C4uiart — Pseudocotyle, 55 
lepidus Looss — Ectenurus, 283, Fig. 

47, f 
Lepocreadiinae, key to genera of, 182 
Leptobothrium, 50 
Leptocotyle, 50 
leptogaster Leuckart — Chimcericola, 135, 

Fig. 26, a-g 
levinseni OcLhner — Hemiurus, 277, Fig. 

36, c 
levinsenii Monticelli — Tristoma, 72 
licha Rees and Llewellyn — Neoerpo- 

cotyle, 88 
limacoides Diesing — Aspidogaster, 11, 

Fig. 29, b, c 
Linguadactyla, 31, 35 
lineatus T. Scott — Trochopus, 66 
lintoni Monticelli — Encotyllabe, 63 
Lobatostoma, 12 

lobicmchi Monticelli — Acanthocotyle, 61 
longa Leidy — Azygia, 218 
loliginis de Beauchamp — Isancistrum, 

28 
Lophocotyle, 58 

lucii Muller — Azygia, 218, Fig. 34, c 
luciopercce Muller — Bunodera, 269, Fig. 

34, d 
luscoz Beneden and Hesse — Diclido- 

phora, 102 
lydice Stossich — Dihemistephanus, 205 

maccallumi Johnston and Tiegs — 
AmpJiibdelloides, 34, Fig. 1, g, h 

Macraspis, 11 

macrocotyle Diesing — Accacladocoelium, 
230 

macrocotyle Liihe — Phyllodistomum, 273 



macruri Brinkmann — Octodactylus, 107, 

Fig. 19, a-e 
maculatus Looss — Proctceces, 266, Fig. 

45, d 
marginata Folda — Megalocotyle, 67 
martinieri Bosc — Capsala, 69, Fig. 9, 

A, B 

inasu Ishii and Sawada — Encotyllabe, 63 
Mazocraes, 138 
Mazocraeidw, 138 

medkis Kathariner — Gyrodactylus, 27 
Megalocotyle, 67 

" megahrchis " Nybelin — Phyllodisto- 
mum, 273 
megastoma Rudolphi — Ptychogonimus, 

220, Fig. 37, f-h 
megastoma Wagener — Neodactylogyrus, 

30 
Merizocotyle, 47 
Merizocotylinse, genera of, 47 
merlangi Kuhn, in Nordmarm — Dicli- 

dophora, 95, Fig. 16, a-c 
merlucii Beneden and Hesse — Antlw- 

cotyle, 130, Fig. 25, a-f 
Mesometra, 306 
Mesometrida?, 306 

metcecus Braun — Crepidostomum, 195 
michartis Monticelli — Cotylogaster, 12 
micracanihus Massa — Trochopus, 66 
Microbothriida3, 48 
Microbothriinse, genera of, 49 
Microbothrium, 49 
Microcotyle, 117 
Microcotylidse, 117 
Microcotylinse, genera of, 117 
miescheri Zschokke — Distoma, 310, Fig. 

51, E, F 
minima Tagliani — Enoplocotyle, 57 
minor Monticelli — Leptocotyle, 52, Fig. 

5, c, E 
minor Odhner — Haplocladus, 265 
minor Olsson — Octodactylus, 106, Fig. 

17, A-E 

minutum Looss — Stephanostomum, 198 
miraletus Rees and Llewellyn — Rajon- 

chocotyle, 89 
mirus Looss — Zoogonus, 247, Fig. 42, d 
Mneiodhneria, 233 

molce Maclaren — Nematobothrium, 240 
molvo3 Beneden and Hesse — Pteronella, 

57 
molvce Brinkmann — Linguadactyla, 35 
monenteron Wagener — Tetraonchus, 31, 

Fig. 1, f, 2, cc 



362 



INDEX 



Monocotyle, 42 

Monocotylida?, 41 

Monocotylinae, 41 

Monogenea, key to groups of, 23 

Monopisthocotylea, 24 

Monorcheides, 225 

Monorchiida?, key to subfamilies of, 
223 

Monorchiinse, 223 

Monorchis, 223 

monorchis Stossich — Monorchis, 224, 
Fig. 38, a, b 

monticellii de Martiis — Haplocleidus, 33 

monticellii Parona and Perugia — Bene- 
denia, 73 

monticellii Price — Nitzschia, 68 

monticellii T. Scott — Acanthocotyle, 58 

morrhuce Beneden and Hesse — Octo- 
dactylus, 106 

miilleri Levinsen — Genarches, 303, Fig. 
50, b 

Murraytrema, 36 

muscular layers, 6, 16 

musteli MacCallum — Hexabothrium, 83 

myliobatis Taschenberg — Monocotyle, 
42 

myoblasts, 16 

Nematobothrium, 240 

nematulum Noble and Noble — Acca- 

cladium, 229 
Neodactylogyrus, 30 
Neoerpocotyle, 87 
Neophasis, 189 
nephropis Cunningham — Stichocotyle, 

11 
nicolli Issaitschikow — Plagioporus, 172 
7iigroflavum Rudolphi — Accaclado- 

cozlium, 230 
nimia Linton — Helicometrina, 169 
nipponicum Goto — Diplozoon, 130 
Nitzschia, 67 
Nitzschiinse, 67 
nordmanni Diesing — Encotyllabe, 63 

obesum Looss — Saccocozlium, 253, Fig. 

43, E, F 
occidentalis Nickerson — Cotylogaster, 12 
ocreatus Rudolphi — Hemiurus, 277, 

Fig. 46, e, f 
" Octobothrium esmarkii," 109 
Octodactylus, 104 

oculatus Levinsen — Neophasis, 189 
oligoterus Monticelli — Acanthocotyle, 59, 

Fig. 7, a-e 



onchidiocotyle Setti — Capsala, 70 

Opechona, 185 

Ophiocotyle, 140 

orbicularis Rudolphi — Mesometra, 306 

Orophocotyle, 233 

osculatus Looss — Tormopsolus, 205 

Otodistomum, 214 

ovacutum Lebour — Rhodotrema, 262, 

Fig. 45, b, c 
ovacutus Nicoll — Derogenoides, 303, Fig. 

50, d 
ovocaudata Nicoll — Hemipera, 304, Fig. 

50, e 
Ovotrema, 264 

pachysoma Eysenhardt — Haplosplanch- 

nus, 222, Fig. 38, c 
pagelli Beneden and Hesse — En- 
cotyllabe, 63 
pagelli Beneden and Hesse — Steringo- 

trema, 260, Fig. 44, e 
pagelli Gallien — Cyclocotyla, 112, Fig. 

20, a-c 
pagrosoma MacCallum — Encotyllabe, 63 
palmatus F. S. Leuckart — Octodactylus, 

104, Fig. 16, d-f 
paradoxa Odhner — Rhynchopharynx, 

230 
paradoxum Nordmann — Diplozoon, 129 
paradoxus Creplin — Ancyrocephalus, 32, 

Fig. 1, c 
Parancyrocephaloides, 37 
parenchyma, 7 

paronce Monticelli — Encotyllabe, 63 
pastinacce T. Scott — Heterocotyle, 42, 

Fig. 4, a 
pedatum Wagener — Diplectanum, 37 
pelamydis Taschenberg — Capsala, 70 
Peracreadium, 166 
perezi Mathias — Peracreadium, 166 
perpusilla Looss — Dicrogaster, 253, 

Fig. 43, h 
perugiai Setti — Capsala, 68 
petasiporum Odhner — Accacladocoslium, 

230, Fig. 39, f, g 
phycidis Parona and Perugia — Diclido- 

phoroides, 109 
Phyllodistomum, 271 
physcon Liihe — Lecithochirium, 291 
pilchardi Beneden and Hesse — Mazo- 

craes, 140 
pini Beneden and Hesse — Trochopus, 

66 
Plagioporus, 172 
Platycotyle, 117 



INDEX 



363 



Plectanocotyle, 133 

Plectanocotylinae, 133 

planci Stossich — Orophocotyle, 234, Fig. 

40, b 
plovmornini Issaitschikow — Helico- 
metra, 168 
Podocotyle, 175 
pollackii Beneden and Hesse — Diclido- 

phora, 103 
polymorphu m Layman — A llocreadium, 

164 
polymorphus Baer — Bucephalus, 149, 

Fig. 29, d-g 
Poryoj)isthocotylea, 79 
Polystomatidae, 80 
Polystomatoidea, 79 
ponticum Pigulewski — Ovotrema, 264 
prceteritum Looss — Acanthostomum, 213 
prencmti Saint-Remy — Rajonchocotyle, 

89, Fig. 14, k-m 
pretiosum Ariola — Didymozoon, 240 
pristis Deslongschamps, in Lamouroux 

—Stephanostomum, 199, Fig. 35, a 
prist iuri Gallien — Leptobothrium, 50, 

Fig. 5, a, b 
proctocolus Manter — Tetrochetus, 233 
Proctoeces, 266 
Proctotrema, 226 
Proctotrematinae, 226 
Prosorhynchinse, genera of, 158 
Prosorhynchus, 158 
Prosostomata, general types of, 13 
Pseudocotyle, 53 
Pseudocotylinse, 53 
" pseudofolium " Nybelin — Phyllodis- 

tomum, 273 
Pteronella, 57 
Ptychogonimidae, 220 
Ptychogonimus, 220 
■pugetensis Kay — Merizocotyle, 47 
pulchella Rudolphi — Helicometra, 171 
purii Srivastava — Haplosplanchnus, 

223 
pusilla Stafford — Neophasis, 189 

rachion Cobbold — Lepidapedon, 182, 

Fig. 33, d 
Rajonchocotyle, 88 
Rajonchocotylinae, genera of, 88 
Rajonehocotyloides, 90 
raynerianus Kardo — Tetrochetus, 233 
reflexa Creplin — Podocotyle, 181 
retractilis Lebour — Opechona, 187, Fig. 

33, g 
retro flexus Molin — Lecithostaphylus, 250 



Rhabdosynochus, 36 

Bhipidocotyle, 157 

Ehodotrema, 262 

rhombi Beneden and Hesse — Megalo- 

cotyle, 67 
rhombispinosum Lebour — Stejihano- 

stomum, 202, Fig. 35, b, c 
Rhynchopharynx, 230 
richiardii Lopez — Probolitrema , 273, 

Fig. 34, g 
richiardii Sonsino — Anoplodiscus, 40 
rubellus Olsson — Zoogonus, 248, 

Fig. 42, e 
ruber Luhe — Derogenes, 303 
rufoviride Rudolphi — Lecithochirium, 

287, Fig. 48, a-c 
rugosus Looss — Hemiurus, 278, Fig. 

46, d 

Saccocoelium, 253 

sacculata Van Cleave and Mueller — 

Bunodera, 271 
sagittata Leuckart — Discocotyle, 125, 

Fig. 24, A-F 
Sanguinicola, 309 
sargus annularis Vlasenko — Diphtero- 

stomum, 244 
sciamm Beneden — Benedenia, 72 
scicena3 Beneden and Hesse — Diplec- 

tanum, 39 
scombri Kuhn — Kuhnia, 141, Fig. 

27, a-e 
scombri Taschenberg — Didymozoon, 

237, Fig. 41, a 
septapapillata Krull — Rhipidocotyle, 

158 
serpentulus Odhner — Accacladium, 229 
sharpei E. I. Jones — Hemipera, 305, 

Fig. 50, f 
situs inversus, 22 
siluri Zandt— if aplocleidus, 33 
simplex Odhner — Aporocotyle, 307, Fig. 

51, A, B 

sinuata Rudolphi — Helicometra, 171 
skrjabini Vlasenko — Derogenoides, 303 
sobrinum Levinsen — Stephanostomum, 

198 
solece Beneden and Hesse — Ento- 

bdella, 75, Fig. 11, a-f 
solda tovi Issaitschikow — Monorcheides, 

225 
souihwelli Nagaty — Bucephalopsis, 156 
sp. Linton — Aponurus, 299 
spari Yamaguti — Encotyllabe, 63 



364 



IXDEX 



Sphcerostoma, 195 

Sphaerostomatinae, 195 

sphyrcence Taschenberg — Didymozoon, 

240 
spiniceps Looss — Acanthostomum, 213 
squatinos Beneden and Hesse — Pseudo- 
cot yle, 53, Fig. 6, G 
steenstrupi Odhner — Lepidophyllum, 

250 
stellatus Looss — Lecithaster, 298 
stenostoma Nicoll — Lepidauchen, 191, 

Fig. 32, g 
Stephanostomum, 198 
Steringophorus, 257 
Steringotrema, 258 
Sterrhurus, 285 
Stichocotyle, 11 

stossichi Braun — Calicotyle, 46 
striata Perugia and Parona — Vallisia, 

128 
sturionis Abildgaard — Nitzschia, 68 
sturionis Little — Dihemistephanus, 207, 

Fig. 35, h-j 
suecicum Nybelin — Crepidostomum, 195 
sybillce T. Scott — Discocotyle, 128 
Synaptobothrium, 292 
Syncceliinae, 304 
syngnaihi Nicoll — Podocotyle, 111, Fig. 

32, c 

tcenioides Monticelli — Didymozoon, 240 

torta Linton — Helicometra, 168 

tenue Linton — Stephanostomum, 205 

tenuicolle Rudolphi — Didymozoon, 240 

Tergestia, 266 

tergestinus Stossich — Bucephalopsis, 
156 

Tetrancistrum, 36 

Tetraonchinae, 31 

Tetraonchus, 31 

Tetrochetinae, key to genera of, 232 

Tetrochetus, 233 

Thaumatocotyle, 47 

thynni Delaroche — Hexostoma, 143 

thynni Guiart — Capsala, 70 

thynni Taschenberg — Didymocystis, 242 

thunnince Parona and Perugia — Hexo- 
stoma, 143 

tineas Modeer — Asymphylodora, 226 

tissieri Gallien — Diclidophoropsis, 115, 
Fig. 22, a-d 

Tormopsolus, 205 

tornatus Rudolphi — Dinurus, 281, Fig. 
47, A-D 



torpedinis Chatin — Amphibdella , 34 
trachinoti Planter — Aponurus, 299 
trachuri Beneden and Hesse — Gastro- 

cotyle, 123, Fig. 23, a-c 
transversale Rudolphi — A Uoc rt a d i um, 

164 
triglce Beneden — Bucephalopsis, 156 
triglai Lebour — Stephanostomum, 203, 

Fig. 35, d 
Tristoma, 71 

Trochopodinae, genera of, 64 
Trochopus, 64 

tschuginovi Vlasenko — Aponurus, 299 
tubiporus Diesing — Trochopus, 66 
Turbellaria, relationship to Trematoda, 

1 
tumidulus Rudolphi — Plagioporus, 172 
typicum Nicoll — Ancylocoslinm, 2b8 
typicus Odhner — Haplocladus, 265. Fig. 

45, f 

Udonella, 55 

Udonellidae, 55 

Urocleidus, 36 

urocotyle Parona — Derogenes, 303 

uncinatum Monticelli — Tristoma, 72 

vallei Monticelli — Encotyllabe, 63 
vallei Parona and Perugia — Ancyro- 

cotyle, 78 
Vallisia, 128 
varius Nicoll — Plagioporus, 173, Fig. 

33, a 
various Muller — Derogenes, 300, Fig. 

50, a, c 
vdiporum Creplin — Otodistomum, 214, 

Fig. 37, a-e 
virgula Linton — Eotenurus, 283 
vitellograndis Layman — Aponurus, 299 
vividus Nicoll — Zoonogenus, 249, Fig. 

42, c 
vimparus Olsson — Zoogonoides, 244, 

Fig. 42, a, b 

wedli Ariola — Didymocystis, 241 

Wedlia, 242 

lounderi Bychowsky — Dactylogyrus, 30 

Zoogonidae, 242 

Zoogoninae, 243 

Zoogonoides, 244 

Zoogonus, 247 

Zoonogenus, 249 

zschokkei Mola — Megahcotyle, b7