THE UNIVERSITY

OF ILLINOIS

LIBRARY

1

NATURAL HISTORY SURVEY

ILL
v.3cop.4

ILLINOIS BIOLOGICAL
MONOGRAPHS

Vol.111 January. 1917 No. 3

Editorial Committee

Stephen Alfred Forbes William Trelease

Henry Baldwin Ward

Published under the

Auspices of the Graduate School Bt

THE University of Illinois

Copyright, 191 7

By the University of Illinois

Distributed May 5, 1917

STUDIES ON NORTH

AMERICAN POLYSTOMIDAE,

ASPIDOGASTRIDAE, AND

PARAMPHISTOMIDAE

WITH ELEVEN PLATES

BT

HORACE WESLEY STUNKARD

Ooatributlona from the
Zoological Laboratory of the ITniversity of flUnols under
the direction of Uenrjr B. Ward, No. 84

THESIS

Submitted in Partial Fulfillment of the Requirements for the

Degree of Doctor of Philosophy in Zoology

in the Graduate School of the

University of Illinois

1916

TABLE OF CONTENTS

PAGE

Introduction 7

Polystomidae 9

Historical Review of the Family g

The Genus Polystoma i6

Anatomy and Histology of the Polystomidae 19

Polystoma orbiculare Stunkard 1916 31

Polystoma opacum Stunkard 1916 _ 34

Polystoma megacotyle Stunkard 1916 37

Polystoma microcotyle Stunkard 1916 39

Polystoma coronatum Leidy 1888 40

Polystoma liassalli Goto 1899 42

Polystoma oblongum Wright 1879 44

Key to the Species of the Genus Polystoma 46

Aspidogastridae 47

Aspidogaster conchicola von Baer 1827 48

Cotylaspis insignis Leidy 1856 49

Cotylaspis cokeri Barker and Parsons 1914. SO

Classification of the Family 57

Paramphistomidae _ 60

Historical Review of the Family 60

The Genus Alassostoma 64

Alassostoma magnum Stunkard 1916. 66

Alassostoma parvum Stunkard 1916 69

The Genus Zygocotyle _ 71

Zygocotyle ceratosa Stunkard I9i6._ 72

Classification of the Family 75

Relation of the Families to the Order 80

List of New Species 84

Bibliography 85

Explanation of Plates _ 91

2871 XORTH AMERICAN POLYSTOMIDAE—STUNKARD

INTRODUCTION

The knowledge of the trematodes of North America is verj' scanty.
Information at hand consists largely of brief and scattered papers and
comprehensive studies on the morphology of the larger groups are want-
ing. Such studies are needed as contributions to the knowledge of adult
forms, and it is apparent also that knowledge of the anatomy and tax-
onomy of the adult is demanded in the solution of life history problems.

This paper contains the results of a study on the structure
and classification of North American representatives of the families
Polystcmidae, Aspidogastridae, and Paramphistomidae. Because of cer-
tain structural and developmental features these three families are of
particular interest and importance not only in the taxonomy but also in
the phylogeny of the trematodes. The Polystomidae differ from all other
known Heterocotylea in that they are endoparasitie ; the Aspidogastri-
dae are both eetoparasitic and endoparasitie, develop both directly and
by means of an intermediate host, and in the adult condition are para-
sites of both vertebrates and molluscs ; while the Paramphistomidae are
the only forms retaining a primitive posterior sucker. These facts are
significant and it is probable that further study into the structure and
life history of these forms will throw considerable light on the general
problems of development and taxonomy of the trematodes.

During the past three years the writer has made parasitological
examinations of over three hundred North American fresh-water turtles.
These comprise sixteen species collected from widely scattered localities.
For assistance in securing this material, grateful acknowledgments are
due Dr. N. A. Cobb of Washington, D. C, Professor A. W. Orcutt of
Denison University, Professor W. E. Burge of the University of
Illinois, Professor J. E. Ackert of Kansas State Agricultural College,
and Professor W. W. Cort of Macalester College. The material of
Alassosioma parvum was collected and turned over to me by Mr. T. B.
Magath. A type specimen of Polystoma coronatum Leidy from the U. S.
National Museum was placed at my disposal for study. The work was
begun at the suggestion of Professor Henry B. Ward and carried on
under his direction. Part of the material used in the investigation
came from his private collection, and for this material as well as for
criticisms and suggestions in the course of the work the writer wishes to
express his appreciation.

8. ILLINOIS BIOLOGICAL MONOGRAPHS [288

All the forms described in this paper were studied as toto mounts ;
where sufficient material was available sections were made, and many
were studied alive. The importance of the study of the living specimens
can not be overemphasized as the best method of tracing the excretory
system. Also, by observing the living animal as it moves, it is possible
to measure the extent of normal variation in form that occurs in a single
specimen as different shapes are assumed concomitant with the move-
ments of the animal ; in forms with such soft bodies and variable shapes,
a study of preserved material alone has in many cases given false con-
ceptions concerning morphological relationships of organs and systems.
In toto mounts a support under the coverglass is necessary to prevent it
from flattening and distorting the normal shape of the aspidogastrids
and to avoid crushing the caudal disc of the polystomes. For the stain-
ing of specimens to be mounted in toto, better results were obtained by
the use of carmine than by hematoxylin stains. For staining sections
the method that proved most valuable was to use the hematoxylin stains
for differentiating the nuclear elements and various plasma stains for
counterstaining.

289] NORTH AMERICAN POLYSTOMIDAE—STUNKARD

POliYSTOMIDAE

HISTORICAL REVIEW OF THE FAMILY

In 1758 Roesel von Rosenhof described and figured a "leech" from
the urinary bladder of the frog. This is regarded as identical with the
well known European parasite of the urinary bladder of the frog,
described by Frohlich (1791) as Linguahda integerrimum. M. Braun
(1792) described Planaria iniciniilata from the urinary bladder of the
green water-frog and his description is so specific that there can be no
doubt that he had the same form described by Frohlich the previous
year. Zeder (1800) founded the genus Polystoma to contain the three
species, Linguatula integerrimum Frohlich which he rechristened Poly-
stoma ranae, P. serratitm, and P. pinguicola. According to Stiles and
Hassall (1908) the type was clearly intended to be P. ranae = Planaria
jtncinulata, and altho Braun had described the form correctly with the
suckers and hooks at the posterior end of the body, Zeder erroneously
stated in his characterization of the genus that the suckers were at the
anterior end. P. serratum had been designated by Frohlich (1789) as
type of the genus Linguatula and P. pinguicola had been designated by
Treutler (1793) as type of the genus Hexathyridium. That Zeder was
in error in including these species in the genus Polystoma was demon-
strated by later studies. However Rudolphi (1809) retained them in the
genus Polystoma and listed three other species: P. taenoides Rud., P.
denticulatum, Rud., and P. venarum (Treutler 1793) Zeder 1803.
Among these species, it is probable that Treutler 's description was of an
artifact rather than a parasite, and the other two have been removed to
the Linguatulidae.

Polystoma thynii was described from the gills of Scomber thynnus
by Delaroche' (1811). Rudolphi (1819) renamed this species P. duplica-
tum and added a new species P. ocellatum from the throat of Emys
europa. This species is regarded as identical with that described by
Kuhl and Hassalt (1822) from the nasal cavity of Ilalichelys atra. P.
logiginis was described by delle Chiaje (1823) from Loligo vulgaris.
Blainville (1828) oriented the polystomes correctly and transferred P.
integerrimum, P. ocellatum, and P. thynii to a new genus Hexaeotyle,
naming H. thynii as type. According to the rules of zoological nomen-
clature, however, the genus Polystoma must be retained. Kuhn (1829)

10 ILLINOIS BIOLOGICAL MONOGRAPHS [290

described P. appendiculatum from Squalus catulus. Dujardin (1845)
transferred Diclibothrittm crassicaudatum Leuck. 1835 = Diplobothrium
armatum Leuck. 1842 to the genus Pohstoma, and listed as additional
species, P. duplkatum, P. pinguicola, P. ocellatum, P. integerrimum, and
P. appendiculatum. Diesing (1850) named P. loliginis and P. appendic-
ulatum as tj-pes of new genera Solenoeotjle and Onchocotyle. He re-
moved P. armatum to the genus Diclibothrium Leuck. and retained in
the genus Polystoma only the species P. integerrimum and P. ocellatum.
The genus Polystoma together with the genera Tetrastomum, Gry-
porhynchus, Hexathyridium, Notocotyle, Aspidocotyle, and Aspidogas-
ter were included by the same author in the tribe Polycotylea.

In his revision Diesing (1859) reduced the trematodes to the rank
of a tribe and divided the group into three subtribes: Acotylea, Coty-
lophora, and Plectanophora. The second of these subtribes he subdivi-
ded into three families : Monocotylea, Tricotylea, and Polycotylea. The
last of these corresponds almost identically with his former tribe Poly-
cotylea. He rejected Gryporhynchus. and added the genera Ancyroceph-
alus, Plagiopeltis, Heptastomum, Onchocotyle, Cyclocotyle, and Solen-
oeotyle. In the family Polycotylea he recognized two subfamilies:
Aplacocotylea with the suckers set directly in the body, and Placocotylea
with the suckers set in a median posterior plate. In the latter he in-
cluded the genera Onchocotjde, Polystoma, Cyclocotyle, Aspidocotyle,
Aspidcgaster, and Solenocotyle.

Then followed the great work of van Beneden (1858) with an ex-
perimental demonstration of the "direct" development of the many-
suckered ectoparasitic trematodes, and the "indirect" development of
the distomes. For these two groups he proposed the names Monogenea
and Digenea. In the former he recognized two families: the Tristomi-
dae with a single posterior sucker, and the Polystomidae with several
posterior suckers. In the Polystomidae he included the genera Polystoma,
Diplozoon, Octobothrium, Axine, Onchocotyle, Calceostoma, and Gyro-
dactylus.

Later van Beneden and Hesse (1863) made the genera Oetocotyle
( = Octobothrium), Udonella, and Gyrodactjdus types of new families,
thus increasing the number of families to five. Many additional genera,
both old and recently described, were now for the first time placed with
the Monogenea. But in the family Polystomidae these authors retained
only two genera, Polystoma and Erpocotyle ; and in the genus Polystoma
was listed only a single species, P. integerrimum.

Taschenberg (1879) reverted to the earlier classification of van
Beneden and adopted the division of the monogenetic trematodes into two

291] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 11

groups Tristomeae and Polystomeae, which he I'egarded as families
Under the Polystomeae as subfamilies he listed Polystomidae, Octoboth-
ridae ( = Octocotylidae), Gyrodactylidae, and the new subfamily Miero-
cotylidae ; the latter including Microcotyle, Axine, Gastrocotyle and the
entirely unlike genera, Aspidogaster, Cotylaspis and Aspidocotyle. To
the Polj'stomidae he added the genera Onehocotj'le and Diplobothrium,
and in the genus Polystoma included the two species P. integerrimum
and P. ocellatum.

In regard to the previously mentioned forms St. Remy (1891) fol-
lowed the family and subfamily divisions of Taschenberg, tho adding
new genera to each of the subfamilies and removing Aspidogaster, Coty-
laspis, and Aspidocotyle from the Microcotylidae. To the Polystomidae,
Wright and Macallum had added the genus Sphyranura, and in the genus
Polystoma were listed the new species P. dbloagum Wright and P. coro-
natum Leidy.

Increased knowledge of the trematodes disclosed so many exceptions
to their classification according to life history that Montieelli (1892)
proposed a new arrangement of the group, based on morphological char-
acters. To contain the forms previously classed as Monogenea, he pro-
posed the suborder Heterocotylea. He raised the Monocotylidae and
Gyrodactylidae from subfamily to family rank, making five families in
the Heterocotylea. In the family Polystomidae he retained the sub-
families Polystominae, Oetocotylinae, and Mierocotylinae of former
authors.

So far as the Polystomidae are concerned, the synopsis of Pratt
(1900) does not differ from that of St. Remy and Montieelli.

Later Montieelli (1903) worked out a new classification of the
Heterocotylea, separating the forms on the basis of differences in the ad-
hesive apparatus. He arranged the families in two tribes, Oligocotylea
and Polj'cotylea, the former containing the forms with few suckers and
the latter those with many suckers. This division he says is not of great
systematic importance but may be of practical value in the identification
of families. In the Oligocotylea he included the families Tristomidae,
Monocotylidae, Udonellidae, Calceostomidae, Gyrodactylidae, and Dieo-
tylidae ; and in the Polycotylea the families Polystomidae, Octocotylidae,
Hexacotylidae, Platycotylidae, Pleurocotylidae, and Microcotylidae.
Among these the Udonellidae, Octocotylidae, and Microcotylidae are
raised from subfamily to family rank, and the Calceostomidae, Dieoty-
lidae, Hexacotylidae, Platycotylidae, and Pleurocotylidae are new fam-
ilies. The family Polystomidae contained the single genus Polystoma
with the species P. integerrimum, P. ocellatum, P. oblongum, P. coro-
natum, and P. hassalli.

12 ILLINOIS BIOLOGICAL MONOGRAPHS [292

Discussing the classification of ilontieelli, Odhner (1912) stated that
he considered the number of suckers of secondarj' importance and the
system based on them therefore lacking in fundamental systematic sig-
nificance. Accordingly he rejected the work of !Monticelli, and using the
older classification of Monogenea, divided the forms within the group on
the basis of differences in the female reproductive ducts. He discussed
the relationship of the ducts of the female genital sj-stem in various trema-
tode and cestode genera, and stated that he was convinced as was claimed
by Stieda that Laurer's canal of the trematodes should be regarded as
homologous with the vagina of the eestodes. Intervening authors, Looss
(1893), Goto (1894) and several other writers, had considered Laurer's
canal of the Malacocotylea as homologous ^vith the genito-intestinal canal
of certain Heterocotylea, and not with the vagina of the eestodes. Odh-
ner argued that Laurers canal was the primitive vagina of the trema-
todes and that there had been a change of vaginal function from this
canal to the terminal part of the uterus, with the resulting degeneration
of the former duct. It now served in his opinion only to carry off excess
spermatozoa, together with yolk and shell substance not used in the for-
mation of the eggs. He adds that there is no evidence on which to base
an explanation of the transfer of the seat of vaginal function from
Laurer's canal to the terminal part of the uterus; it must onty be accepted
as a fact.

According to Odhner, in the group of moncgenetic trematodes, two
very different structures are included under the term vagina. One pres-
ent in the Tristomidae, ISIonocotylidae, and Gyrodaetylidae opens to the
exterior on the left side of the ventral surface, and at the inner end is
enlarged to form the seminal receptacle. This tube he considered homo-
logous to the vagina of the eestodes and Laurer's canal of the digenetic
trematodes. The other structures which he did not consider homologoiis
to this true vagina were the ducts of the Octocotylidae, Polystomidae,
and Microcotylidae, which function as vaginae and open into the vitelline
collecting ducts. These are paired and open to the surface either ven-
trally, laterally, or dorsally. Contending that they had arisen sui generis,
he proposed for them the name "ductus vaginalis." Considering
the question of whether the paired or unpaired condition of these
ducts was primitive, he argued that originally the duct was
unpaired and opened ventrally; that the opening became divided
and the duct split, therefore the Y-shaped duet of Rajonchoeotyle
must be considered as a stage in the development of the paired condition
of the ducts. A further separation would give the lateral openings of
Polystoma. In the Mierocotj'lidae the openings have migrated dorsally
and fused producing a single dorsal tube. Odhner could find no homo-
logue for the genito-intestinal canal and since he maintained that it was

293] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 13

not homologous with Laurer's canal, concluded that it had arisen sui
generis.

On the basis of these differences in the female genital ducts he
divided the Monogenea into two suborders : Monopisthoeotylea and Poly-
opisthocotylea. The former is characterized by the absence of the genito-
intestinal canal, the presence of a "true vagina" and a single pos-
terior organ of attachment; the latter by the presence of the genito-
intestinal canal, "ductus vaginalis," many posterior adhesive organs,
and the absence of a "true vagina." In the Monopisthoeotylea
he included the families Tristomidae, Monocotylidae, Udonellidae
and Gyrodactylidae ; and in the Polyopisthocotylea the families
Polystomidae, Microcotylidae and Octocotylidae. He pointed out that
by the removal of the genus Sphyranura, the Oligoeotylea, the first of
Monticelli's tribes agrees entirely with his suborder Monopisthoeotylea.
In the second of Monticelli's tribes, however, the Diclidophorinae, to-
gether with the genera Dactylocotyle and Hexacotyle, should be re-
moved from the Octocotylidae and placed with the Microcotylidae, since
they more nearly agree with the latter forms in internal structure.

The next year Odhner (1913) reaffirmed his idea of the homology
of the vagina of the cestodes and Laurer's canal of the distomes,
but explained therewith that his denial of the homology of the
genito-intestinal canal and Laui'er's canal had been based on an error of
Cerfoutaine in describing an unpaired vagina as present in the genus Dac-
tylocotyle. On examination of this genus he had found that a "true
vagina" was absent, and concluded that the "true vagina" of the Mono-
pisthoeotylea which he had homologized with Laurer's canal was never
present together with the genito-intestinal canal. From this he decided
that the "true vagina" was homologous with the genito-intestinal canal
and therefore with Laurer's canal. Now maintaining the homology of
the "true vagina" and the genito-intestinal canal he is in my opinion
obliged to dismiss the presence or absence of the genito-intestinal canal
as a basis of difference between his suborders, and explain why in one
group this canal opens to the exterior on the ventral side of the body
and in the other opens into the intestine. His homology of the "true
vagina" and the genito-intestinal canal is a most serious error since it
would invalidate the distinguishing feature which separates the two
suborders.

I propose to show that the organ which functions as a vagina is
homologous in all the monogenetic trematodes, and that there can be no
division of the group on the basis of differences suggested by Odhner.
In fact, the work of Odhner is based on an incorrect assumption and
false homologies. Starting with the assumption that Laurer's canal is
homologous to the vagina of the cestodes, he has missed the truth in his

14 ILLIXOIS BIOLOGICAL MOXOGRAPHS [294

entire discussion and when at a loss to explain a structure has derived it
sui generis. His later paper (1913) admitting the homology of Laurer's
and the genito-intestinal canals corrected one mistaken contention, but
his separation of the female copulatory ducts into a true vagina and
"caualis vaginalis" seems entirely without foundation. There is no evi-
dence to support the idea that the single vagina is not homologous to the
paired vaginae. In fact, Odhner described the paired vaginae as arising
by the division of a single unpaired tube, probably ventral in position.
He derived this tube sui generis, and cited no reason why it is not homo-
logous with the ventral unpaired vagina of the Monopisthocotylea. Fur-
ther lie gives no means of distinguishing between the two.

Looss (1893) presented a strong argument to prove that Laurer's
canal is not a vagina, nor homologous to the vagina of the cestodes.

Goto (1894) reveiewed the literature up to that date and gave a
careful and detailed study of the canalis gcnito-intestinalis. Making a
very clear and comprehensive analysis of the question and summarizing
evidence from a wide study of eetoparasitic forms, he concluded that the
genito-intestinal canal and Laurer's canal are homologous and that
neither are homologous with the vagina of the Monogenea. He showed
that in the group there is a perfect series of vaginae from a truly paired
to a truly unpaired condition. He discussed the idea of Braun who re-
garded the presence of a single vagina as the result of a simple atrophy
of one of the originally paired vagiua, with the conclusion that the rela-
tions of the ducts "point strongly to the view that the unpaired vagina
has been formed by the union and subsequent displacement of the ori-
ginally paired vaginae, and not as Braun supposes by the atrophy of one
of them."

In the present study, the histological character and the relative posi-
tion and relationships of the ducts of the female system support the con-
tention of Looss and Goto that Laurer's canal is homologous with the
genito-intestinal canal, and affords no evidence that these duets have any
further homologue. A review of the literature and the study of the ducts
in the three families discussed in this paper has convinced me that
Laurer's canal is homologous to the genito-intestinal canal ; and the vagina
of the Monopisthocotylea is homologous with the originally single, sub-
sequently paired, and secondarily fused vaginae of the Polyopisthocotylea.
It makes no difference whether the single or paired condition is regarded
as primitive. Given a single unpaired vagina as described by Odhner
for the Monopisthocotylea ; by a division of the external part and subse-
quent lateral migration of the openings, the paired vaginae of the Poly-
opisthocotylea are explained. These ducts entering the body from the
sides, lying parallel with the vitelline ducts and discharging into the

295] NORTH AMERICAN POLYSTOMIDAE—STUNKARD IS

same cavity, became fused at their internal ends with the vitelline ducts
and this union continued outward to the location where the vitelline
ducts turn toward the follicles and the vaginae branch off to open to the
exterior. The advantage of a single duct over two ducts lying side by
side is obvious, and the fusion of two parallel ducts is not uncommon in
other groups. With a further dorsal migration of the opening of the
vaginae there would be a separation of the vitelline and vaginal canals
and a dorsal fusion of the vaginae would give the single dorsal vagina of
Octobothrium, Axine, and Microcotyle. The earlier fusion of the vitel-
line and vaginal canals would retard the secondary fusion of the internal
ends of the dorsal vaginae and this explains the single dorsal pore and
internally paired vagina of Axine heterocerca which is used by Odhner
as an argument supporting his idea that in the Monogenea two different
structures are included under the term vagina.

I agree with Odhner that the seminal receptacles of Sphyranura are
homologous to the paired vaginae of Polystoma, and that this furnishes
a splendid example of the change whereby the terminal part of the uterus
has assumed the eopulatory function. It may be that further specializa-
tion in this direction, due to the endoparasitic habit and self fertilization,
may explain the absence of the vagina of the distomes.

It now remains only to account for the absence of the genito-in-
testinal canal in the Monopisthocotylea. Odhner stated that this struc-
ture is homologous with Laurer's canal, and in his (1912) paper called
attention to the fact that Laurer's canal is a "rudimentary organ"
which serves no essential function. The vestigeal character of Laurer's
canal is believed in by most writers — Looss, Monticelli, Brandes, Goto,
etc. This structure is entirely lacking in some distome groups and in
others is represented by a blind sac opening from the ootype. Since the
genito-intestinal canal is admittedly homologous to Laurer's canal and
the latter is known to be a vestigeal structure, it appears reasonable to
suppose that it has degenerated in the Monopisthocotylea.

There is a possibility that the Monopisthocotylea instead of having
lost a genito-intestinal canal may have arisen from a group of the Tur-
bellaria which had no homologous structure, but this explanation seems
very improbable. Haswell (1907) described in certain Australian poly-
clads a tube which formerly had been considered an accessory or dorsal
vagina but which in certain forms opened into the intestine. The pres-
ence of this genito-intestinal canal in polyclads, he says, ' ' strengthens the
contention, so ably supported by Goto, that the genito-intestinal canal
and not the vagina of the Heterocotylea is the equivalent of the Laurer's
canal of the Malacocotylea."

The absence of the genito-intestinal canal in the Monopisthocotylea

16 ILLINOIS BIOLOGICAL MONOGRAPHS [296

is undoubtedly a feature of distinct taxonomic importance, and the work
of Odhner is an advance step in the formation of a natural system and
the final classification of the monogenetie forms. Since the arrangement
of Monticelli, based on the character of the adhesive apparatus, so nearly
agrees with that of Odhner which in reality is based on the presence or
absence of a genito-intestinal canal, it appears that both these features
are of large importance in the taxonomy of the group. Present evidence
is insufiBcient to decide which is of greater significance. Further study
may show that there is complete agreement in classifications based on
both features.

Odhner (1912) argued that the removal by Monticelli of Sphyranura
from the family Polystomidae on the basis of the difference in number
of suckers was not justified. As previously stated, the writer agrees with
Odhner that the seminal receptacles of Sphyranura are homologous with
the vaginae of Polystoma, and the agreement in type of genital ducts in-
dicates a closer relationship between these genera than is assigned in the
system of Monticelli. Sphyranura undoubtedly should be placed with the
Polyopisthocotylea. There are, however, wide and fundamental differ-
ences between it and the genus Polystoma, and while future researches
may discover intermediate forms which will make it possible to include
them with certainty in a single family, for the present such a grouping is
hardly justified and the two families should be retained, altho the name
Dicotylidae of Monticelli does not conform to the rules of zoological
nomenclature.

THE GENUS POLYSTOMA

The family Polystomidae as considered in this paper contains only
the genus Polystoma. The members of this genus are widely distributed,
species having been described from aU the continents except South
America. The species are not only widely distributed geographically,
but also vary widely in type of host and in locatisn within the host.
They are parasitic in the urinary bladder of frogs and toads and on the
gills of frog larvae, and also infest the urinary bladder and pharyngeal
cavity of many species of turtles.

The structure and development of Polystoma integerrimum has been
investigated by Stieda (1870), ZeUer (1872 and 1876), WiUemoes-Suhm
(1872), Halkin (1902), Goldschmidt (1902), and Andre (1910). Zeller
(1876) described two forms of P. integerrimum, one which became ma-
ture in the urinary bladder of the frog, and the other which became, ma-
ture on the gills of the frog tadpole. These two forms of the parasite
show wide differences in size and internal structure. The form which
becomes mature in the urinary bladder is much larger, has a lobed
testis, external vaginae, and a long coiled uterus which contains many

297] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 17

eggs. The form maturing on the gills of the tadpole has a spherical
testis, lacks external vaginae and a long coiled uterus, and has a small
uterine cavity in which a single egg develops. Halkin and Goldschmidt
liave investigated the early stages in this form, but the writer has been
unable to find any reference to work on the later larval stages. The
findings of Zeller are so unusual that one is led strongly to suspect he
confused two different species.

The descriptions of P. ocellatum by Rudolphi (1819) and Kuhl and
Hassalt (1822) are very brief; that by Willemoes-Suhm (1872) contains
one plate, and Looss (1885) figured only the structures at the distal ends
of the excretory tubules.

The description of P. oblongum Wright (1879) contains sufficiently
detailed information for a specific diagnosis and is illustrated by three
figures. Stafford (1905) reported P. oblongum from the palate of Chry-
semys picta and the same location in Chelydra serpentina, but since
Wright originally described the species from the urinary bladder of
Aramochelys odoratus, Braun reviewing Stafford's article considered
the form from the oral cavity as a different species. The form described
by Leidy as P. ohlongum, was reinvestigated by Goto (1899) and proved
to be a different species from that described by Wright, but the material
he reports was in such a poor state of preservation that renewed study
was impossible and so the form must remain unknown.

Leidy 's (1888) description of P. coronatum is so brief that it is al-
most valueless ; a type specimen mounted as a toto preparation has been
available for the present study and many additional points of structure
are added to the original description.

P. hassalli was described by Goto (1899) from the urinary bladder of
Cinostemum pennsylvanicum and has been collected by the writer from
the urinary bladder of Aromochelys odoratus, A. carinatus, and Chelydra
serpentina, as well as from Cinostemum pennsylvanicum. Additional
data correct and supplement the description of Goto.

Johnston (1912) described P. iulliense from the urinary bladder of
two species of Hyla from New South Wales, Australia. Beauchamp
(1913) described P. alluaudi from an unknown batrachian from the lower
prairies of Kinangop, Africa ; the material was collected by the African
expedition of Alluaud and Jeannel. Stewart (1914) described P. kachu-
gae from the urinary bladder of the water tortoise, Kachuga lineata, at
Lucknow, India.

In the genus Polystoma present evidence supports the validity of the
following described species listed in the order of description :

P. integerrimum Frolich 1791. From the urinary bladder of froga
and toads and the gills of frog larvae ; Europe.

18 ILLINOIS BIOLOGICAL MONOGRAPHS [298

P. oceUatum Rudolphi 1819. From the throat and nasal canity of
Emys europa and Halichelys atra; Europe.

P. oblongum Wright 1879. From the urinary bladder of Aromo-
chelys odoratus; North America.

P. coronatum Leidy 1888. From the fauces of the terrapin; North
America.

P. hassalli Goto 1899. From the urinary bladder of Cinosternum
pennsylvanicum, Aromochelys odoratus, A. carituitus, and Chelydra ser-
pentina; North America.

P. bulliense Johnston 1912. From the urinary bladder of Hyla
phyllochros and H. Lesueurii; Australia.

P. alluaudi, Beauchamp 1913. From an unknown batrachian;
Africa.

P. Icachugae Stewart 1914. From the urinary bladder of Kachuga
lineata; India.

In the present work evidence is submitted to justify the inclusion of
the following new species:

P. orbiculare Stunkard 1916. From the urinary bladder of Pseu-
demys scripta and Chrysemys marginata; North America.

P. opacum Stunkard 1916. From the pharynx of Trionyx ferox and
Malacoclemmys lesueurii; North America.

P. megacotyle Stunkard 1916. From the mouth of Chrysemys mar-
ginata; North America.

P. microcotyle Stunkard 1916. From the mouth of Chrysemys mar-
ginata; North America.

With the exception of P. integerrimum, the members of the genus are
very rarely found and the number of individuals discovered is verj- small.
Wright described P. oblongum from two specimens; Leidy, P. corona-
tum from four specimens ; Johnston had sixteen specimens of P. hulliense;
Beauchamp described P. alluaudi from a single specimen; Stewart had
only two specimens of P. kachugae. The writer had only a limited num-
ber of individuals of any species; P. microcotyle was described from a
single specimen; P. orbiculare from nine specimens; P. opacum and P.
megacotyle each from three specimens. Because of the limited amount
of material, it has been impossible to attempt special technique to differ-
entiate the various organ systems, and the descriptions are therefore in-
complete in certain particulars. The general morphological features are
however described in sufficient detail that clear specific diagnoses can be
made, and in certain instances the finer structure and histology of the
organs has been described.

299] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 19

ANATOMY AND HISTOLOGY OF THE POLYSTOMIDAE

The species that have been included in the genus Polystoma show a
much wider range of structural variation than is usually present in a
natural genus. There are wide differences in the character of digestive
and reproductive systems, and variation exists in the type of adhesive
apparatus.

There is wide variation in size ; P. integerrimum, the largest known
species measures up to 12 mm. in length, and P. hassalli is only 1.3 to 2
mm. in length. The width is one-third to one-fifth of the total length.
All the worms that have been included in this genus have a flattened,
elongate oval body which at the posterior end bears a large ventral
muscular disc or cotylophore. The body is more or less pointed at the
anterior end and at the posterior end may or may not have a constriction
just before the attachment of the caudal disc. As in all trematodes the
shape is subject to considerable variation as the animal elongates and
contracts. Locomotion is accomplished by attaching the anterior sucker
and then bringing the caudal disc forward; as a result of the terminal
attachments and the "looping" method of progression, the dorsal line of
the body is more or less arched and the ventral surface is concave. In
certain species at the openings of the vaginae on the lateral or ventro-
lateral margins of the body, there are prominent swellings, the "Seiten-
wiilste ' ' of Zeller. These structures are not present in any of the known
North American species.

Organs of Attachment. — -The caudal disc bears on its ventral face
the chief organs of attachment. These consist of suckers and hooks, the
former arranged in pairs, three suckers on each side of the median line.
The two posterior suckers are close together and those of the middle pair
are separated by a considerable distance, while the anterior pair may or
may not be near each other. In all previously reported forms except P.
alluaudi, the anterior suckers are separated by a considerable distance,
giving the disc the shape described by Leidy as eordiform (Fig. 27). In
the single specimen of P. alluaudi described by Beauchamp, both the
caudual and cephalic suckers are separated, while those of each side are
contiguous. In P. orhiculare the anterior suckers are in the same close
proximity as the caudal pair, and each sucker of the disc is separated
from the two adjacent to it by uniform distances, making a perfect circle
of suckers (Fig. 1). In the six species described by the writer these
suckers are complicated structures, set more or less deeply in the paren-
chyma of the caudal disc. Their structure, character of insertion, mus-
cular attachments, and relation to the surrounding tissue indicate that
they are protrusible and retractile, and in fact such movements may be
observed by watching the live worm.

20 ILLINOIS BIOLOGICAL MOXOGRAPHS [300

The suckers are cup shaped (Fig. 34), and in all the species describ-
ed in this paper are constructed on an elaborate cuticular framework.
According to Zeller the sucker forms as a ridge around a larval booklet
and later sinks into the parenchyma, and this method of origin explains
the cuticular covering of the external and internal surfaces of the cup.
Running across between these cuticular membranes, there are short re-
fractive fibers which constitute the mass of the wall of the sucker (Fig.
35). Wright and Macallum (1887) describing similar fibers in the walls
of the suckers of Sphyranura say, "Instead of the substance of the
sucker being formed of muscular fibers disposed in three directions, and
capable of modifying the shape of the cavity, as in the distomes, it is not
possessed of contractility in Sphyranura (and probably in Polystoma),
and is formed of prismatic fibers, rather of a supportive than a muscular
character, arranged perpendicularly between the concave and convex
limiting membranes of the suckers." Goto (1894) described similar
fibers in the suckers of Axine, Microcotyle, Octocotyle, Dielidophora,
Hexacotyle, and Onchocotyle and considered them to be more of an elastic
than a contractile nature. They are, he states, different from the ordi-
nary muscular fibers of the body and from those of the suckers of the
Tristomidae and Monocotylidae, as well as from those of the anterior
sucker of Onchocotyle, both in optical charactei-s and in reaction toward
staining fluids. The structure of the suckers in these forms and their
mode of operation are discussed by Goto at considerable length, but as the
suckers he described are constructed on a different type of cuticular
framework from that present in the genus Polystoma, obviously the type
of suctorial action is different.

In all the species described in this paper, the fibers which form the
walls of the posterior suckers are similar to those described by Wright
and Macallum and Goto; the cuticular framework is also flexible and
elastic, but is of a different type from that described by Goto. In the
polystomes investigated by the writer, with the exception of P. integer-
rimum, the sucker consists of three sections or zones which may be desig-
nated as basal, intermediate, and external or distal (Fig. 36). The ex-
ternal part or rim of the sucker is supported by numerous cuticular rods
formed by the thickening at regular intervals of the cuticular lining.
These rods are bent outward, their curvature maintaining the flare of the
rim of the sucker. Distally they terminate just inside the rim of the cup
and basally they are continuous with and are processes from a band of
cuticula which passes around the sucker and separates the external and
intermediate portions. In toto preparations this band appears to be
divided into sections that are almost square, each with a circular area in
the center that increases and decreases in size as the focus is changed.

3C11 NORTH AMERICAN POLYSTOMIDAE—STUNKARD 21

Sections show that the euticular lining of the sucker is folded outward
against the convex wall with which it is fused, thus interrupting the con-
tinuity of the fibrous wall (Fig. 35). The two sides of this invaginated
euticular sac or ring are fused at regular intervals, leaving small pockets
alternating with the places of fusion. These small openings in the euti-
cular band are conspicuous by reason of their different refractive index
and show very plainly with a dark field illumination as the square or
rectangular sections with the circular areas in the center (Fig. 34).
There is apparently no relation between the number of these sections in
the euticular band and the number of euticular thickenings which serve
as supports of the external section.

The middle section of the sucker extends basally from the previously
described euticular band to a somewhat similar evagination of the euti-
cular lining into the wall of the sucker, but this evagination does not ex-
tend to the external euticular covering of the sucker and only partially
divides the fibrous wall. This middle or intermediate portion of the
sucker is supported by thickenings of the euticular lining, processes that
extend peripherally from the euticular band which passes around the
sucker at its base. These supporting ridges are not arranged at regular
intervals and they are much fewer in number than the euticular rods
which support the external section. They are often branched, tho not
more than a single bifurcation was observed.

The basal portion of the sucker is circular, similar in structure to the
portions previously described ; it has internal and external limiting mem-
branes with fibers extending between. At its center the euticular and
fibrous wall is interrupted and there is the structure described by John-
son (1912) as the connective tissue plug, which appears as a central disc
or button, and to which the retractor muscles are attached. This central
disc has thickened euticular edges and bears the larval booklet. Figure
44 illustrates the method of operation of the suckers. Muscles are at-
tached to the external wall of the distal and intermediate portions of the
sucker and the contraction of these muscles retracts the two external
zones, with the accompanying protrusion of the basal part. Whether the
small hooks at the bases of the suckers are functional is doubtful. As
previously described, the euticular supports do not extend quite to the
external margin of the sucker, leaving a soft plastic edge which can be
applied all the way around even on an irregular surface. "With the con-
traction of the muscles attached to the basal disc, a vacuum is produced
and forms a powerful means of adhesion. Since the walls of the sucker
are not contractile and the suckers vary only slightly in size in a single
species, the size of the suckers has been used by the writer as a character
■ for determining specific identity.

22 ILLIXOIS BIOLOGICAL MOXOGRAPHS [302

A euticular framework similar to that present in Polystoma was
described by Wright and Macallum for the suckers of Sphyranura osleri.
They say: "As the wall of the sucker is itself destitute of contractility,
another arrangement exists for modifying the shape of the cavity. Its
walls is really divided into three concentric zones, which by special ex-
trinsic muscles can be worked independently. The two circular lines
which separate these zones, are marked by an infolding of the investing
membrane, which forms a sort of joint, permitting an independent move-
ment of the zones."

The collection of Professor Ward contains a single series of sections
of P. integerrimum from Germany, and in this specimen the type of
skeletal structure just described is absent. Figure 45 shows the charac-
ter of the suckers in this form. The caudal disc typically bears eighteen
hooks. Sixteen are similar in size and shape, arranged as follows: six
in a row between the anterior suckers, one situated inside each sucker
at the base, and four between the two posterior suckers. In addition to
these hooks there is a pair of great hooks, several times the size of the
small hooks, between the two posterior suckers. The shape of these hooks
and their arrangement are shown in Figures 37 to 43. In many cases
there is only one pair of the small hooks between the caudal suckers ; in
such eases in addition to the great hooks there is a third pair, similar in
shape to the great hooks and intermediate in size between the great and
small hooks.

The sixteen small hooks are present on the caudal disc of the larva
before the suckers are formed and are called larval booklets by Wille-
mocs-Suhm (1872), but Zeller (1876) says: "Die sechszehn kleinen
Hakchen mit ihren Oesen, welche die Haftscheibe angehoren und welche
bei der Polystomum larva so ausserordentlich deutlich zu erkennen ist,
sind nicht, wie Willemoes-Suhm meint, nur 'Larvalorgane'. Sie werden
nicht abgeworfen, sondern sind wie ich auf das bestimmeste wiederholen
muss, bei der erwachsenen Thiere noeh sammtlieh vorhanden, sehr
beweglich und gewiss nicht ohne Bedeutung fiir ein festeres Anheften."
Jolm.ston (1912) in the description of P. bulliense says: "Four larval
booklets are present in a row on the ventral surface near the posterior
edge of the disc or cotylophore. I have been able to find no trace either
in the living worms or the fixed material, of tlie larval booklets which
P. integerrimum and other species bear near the anterior edge of the
disc. There is a small anchor shaped liook in the base of each sucker.
All these hooks either disappear as the animal increases with age, or very
readily become detached. In only one out of sixteen specimens have the
whole four posterior booklets been present ; and in only two others were
any booklets at all to be seen. In all other specimens no booklets could
be made out."

303] XORTH AMERICAN POLYSTOMIDAE—STUNKARD 23

lu my own material I find that the larval hooklets are invariably
present in the bases of the suckers, but of the other larval hooklets, us-
ually several are absent and often those present are so arranged that it is
difficult to see how they could function in attachment. Those at the an-
terior edge of the caudal disc are seldom regularly arranged, and in
many cases (Figs. 37 to 43) are in such irregular and unusual positions
with reference to each other that the use of one would interfere with the
action of the others.

The great hooks are invariably present in the species in which the
caudal disc is cordiform in shape, i. e., where the two anterior suckers are
separated by a distance exceeding that between the two posterior suckers.
In the species P. alluaudi and P. orbiculare the disc is circular and the
great hooks are absent. Usually the cordiform disc is wider and the cir-
cular disc is narrower than the body. At first it seemed possible to
separate the genus into two subgenera, one in which the disc is circular
and the great hooks are absent and another with a cordiform disc and
great hooks present, but there seems to be no such clear line of separation.
In P. arbiculare a large number of ehitinous spicules are present on the
disc, some between the suckers and the others in the central area of the
disc. In P. opacum the disc is intermediate in shape ; it is difficult to
determine whether it is circular or cordiform, and the great hooks are
present altho they are not more than half the size of those in other species
(Fig. 40). In P. hassalli the disc at times may be circular and the great
hooks are strongly developed (Fig. 31).

Body Covering. — The body is covered with a non-cellular, unarmed
cuticula, which is turned in at the external openings of the various sys-
tems. It does not have a uniform appearance but is traversed by lines
which extend perpendicular to the surface of the body.

Musculature. — The musculature consists of the dermo-museular sac,
the muscles of the adhesive apparatus, and dorso-ventral strands with
much-branched fibers which traverse the body at irregular intervals. The
muscles of the body wall consist of an external circular layer, an interme-
diate layer of diagonal fibers, and inside the latter, bundles of longitud-
inal fibers. In all the species studied, the inner longitudinal fibers are
more strongly developed than either of the other layers. Stieda (1870)
in P. integerrimum did not distinguish between the two external muscle
layers and described only two layers of muscles, an outer layer of an-
nular fibers, some of which were not exactly circular and crossed each
other, and an inner layer of longitudinal fibers. Zeller (1876) was in
error when he described the diagonal fibers as inside the longitudinal
layer in P. integerrimum. The arrangement of the muscles of the body
wall in Polystoma is the usual condition in the Heterocotylea, and a

24 ILLIXOIS BIOLOGICAL MOKOGRAPHS [304

similar arrangement has been described in Calicotyle, Axine, Nitzschia,
Tristomum, Octobothrium, Temnocephala, Microcotyle, Octocotyle, and
Monocotyle. In Diclidophora Goto (1894) described an additional layer
of longitudinal fibers between the circular and diagonal layers. He states
that in Onchocotyle and Hexacotyle the circular fibers seem to be en-
tirely lacking. In the genus Polystoma there are strong sets of longitudinal
fibers near the median line on the ventral side of the body. They could
be traced anteriad only to the testis. Posteriad they pass into the caudal
disc and together with fibers from the body wall are inserted on the sides
and in the bases of the bothria. Muscle strands from both sides of the
body pass to each of the suckers (Fig. 29) and smaller groups of fibers
from each sucker to each of the others. In addition to the dorso-veutral
muscles which extend between various points of the body wall, there are
other fibers from the body wall to the internal organs.

Mesenchyma. — The mesenchymal tissue of the body does not sliow
a differentiation into ectoparenchyma and endoparenchyma as described
by Brandes (1892) and other writers; it is not of a uniform character,
but presents differences in appearance at different points in the same
specimen. It may take the form of compact cellular tissue, or of vacuo-
lated cells, or there may be large vacuoles apparently between cells, or
the cellular structure may be entirely lacking, there being only a reticu-
lum of fibrous tissue. The parenchyma is traversed by many muscle
strands, and the dorsal and lateral regions are occupied by the enormous-
ly developed vitellaria (Figs. 19, 23).

Alimentary System. — The digestive apparatus consists of a terminal
anterior or oral sucker, a pharynx, a short esophagus and a bifurcate in-
testine. The oral sucker (Fig. 6) is not fully homologous with that of
the distomes. There is no external limiting membrane, branched muscle
fibers passing from the inside lining of the sucker to the body wall.
Posteriorly it is limited and separated from the body parenchyma by
special strands of fibers which pass from the body wall to the wall of the
digestive tube and are attached there just anterior to the pharynx. A
contraction of these fibers causes the constriction between the anterior
sucker and the body parenehj^ma which is sometimes seen. Longitudinal
muscle fibers from the body parenchyma penetrate this posterior boun-
dry of the anterior sucker and pass to the wall of the sucker. Annular
muscles, situated just inside the cuticular lining, pass around the sucker
from side to side. Situated among the muscle fibers there are large
secretory cells. Johnston described the structure as a weakly developed
or incipient oraj sucker. The anterior sucker, pharynx, and esophagus
are lined with cuticula continuous with that of the external surface of
the body.

/

I

/

305] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 25

The pharynx is approximately spherical, altho various states of eon-
traction influence its shape to some extent. It does not lie directly in the
long axis of the body but obliquely, the lumen extending from the some-
what ventral anterior opening from the oral sucker to a more dorsal pos-
terior opening into the esophagus or intestine. In certain species it is
composed of two portions, (Figs. 6, 33) tho both are enclosed in the same
external capsule. In the anterior portion there are many strong annular
fibers and this part probably acts as a sphincter, altho there are also
radial fibers which extend from the external limiting membrane to the
cuticula of the lumen. In the posterior part the annular fibers are con-
fined almost entirely to the external region and a small central zone
(Fig. 25). The muscle fibers are branched and non-nucleated. Scattered
among the fibers in the posterior part there are large nuclei, each with a
deeply staining nucleolus and surrounded by a granvilar or flaky ai-ea
that is continued by a fine duct traceable by the presence of the same
granular substance and leading to the lumen of the pharynx. Goto
described somewhat similar nuclei in the pharynx of Diclidophora and
regards them as remnants of the cells that have produced the muscle
fibers. The writer is inclined to the view that in Polystoma the granular
substance is a secretion. No extra-esophageal glands were obsers'ed, but
that the secretion of the pharyngeal cells is salivary was not demon-
strated.

A short esophagus may be present in certain species (Fig. 6) but in
most cases the pharynx appears to open directly into the intestine at the
juncture of the right and left ceca. There maj' be a short median or
paired lateral pockets of the intestine extending anteriad from the junc-
tion of the ceca.

There is wide variation in the type of the intestinal diverticula. In
P. integerrimum the ceca are much branched and these branches ramify
thru the body and the caudal disc (Fig. 45). In P. alluaudi the ceca oc-
cupy the same location but are merely lobed and have no secondary
branches, tho they are united posteriorly. In P. bulliense, according to
Johnston, "a diverticulum from the buccal cavity runs backwards, ven-
tral to the pharynx, and for a distance equal to its length forming a me-
dian unpaired buccal pocket." In all other known species there is a
simple bifurcate intestine, the ceca terminating just anterior to the caudal
disc. In two specimens of P. hassalli, however, the ceca are connected
posteriorly; in one of them the ends of the ceca are continuous and in
the other there is a connection some distance anterior to the ends of the
ceca (Fig. 30). The walls of the diverticula are composed of a delicate
fibro-membranous tissue upon which rests the digestive epithelium. The
epithelial layer consists of columnar cells whose nuclei lie near the fibro-

26 ILLINOIS BIOLOGICAL MOSOGRAPHS [306

membranous sheet and which have large, rounded, often vacuolated bodies
extending irregularly into the canal. The protoplasm of the cells ia
granular.

Excretory System. — In this family as in all Heterocotylea, there are
two excretory pores, situated on the dorsal surface about midway between
the median line of the body and the lateral edge of the worm, near the
level of the caudal margin of the pharjTix (Fig. 27, 33). These open
from vesicular expansions, which when filled are almost spherical and
when empty have folded walls. The descending collecting duct originates
in the region of the pharj-nx from the fusion of smaller ducts and passes
posteriad to the region of the caudal disc where it turns cephalad and
continues as the ascending collecting duct to open into the excretory
vesicle. Both the descending and ascending ducts receive smaller
branches at irregular intervals; at the caudal end of the body a canal
joins the tubes of the two sides and a similar connection exists between
the descending ducts just anterior to the pharynx. From this anterior
communicating canal a branch enters the anterior sucker near the median
line. The excretory vesicles are lined with a thin layer of cuticula con-
tinuous with that of the external surface of the body and the collecting
ducts and accessory branches have a fibro-membranous wall in which
nuclei are occasionally embedded. In P. integerrimitm, Zeller described
many connections of the collecting ducts of the two sides thru anastomoes
of their smaller branches. He also described cilia on the walls of the col-
lecting ducts. Looss (1885) described the excretory system of P. ocella-
tiim. He says the collecting ducts are not ciliated throuout, but only in
occasional areas, and describes cilia in the capillaries. These capillaries
are long and at the distal end are very much coiled. In this coiled part
the capillary is divided so that two flame cells discharge into each coil
and are emptied by a single capillarj-. The caliber of the excretory ves-
sels is verj' minute, and altho varying somewhat as a result of distention,
lacunar expansions were not observed. Because of the limited amount of
material, much of which was received in a preserved condition, no at-
tempt was made to trace the exeretorj- system in living worms of this
family. The vitellaria completely obscure the excretory ducts in toto
preparations. The secondary ducts are so small and so often collapsed
that it is impossible to follow their continuity with certainty in sections.

Nervous System. — The morphology of the nervous s3-stem of P.
integerrimitm was described in detail by Andre (1910). He described a
supra-esophageal brain from which three pairs of nerves pass anteriad
and three pairs posteriad. In another paper (1910a) he gave a detailed
description of the eyes of P. integerrimum. In the present work no
special study of the nervous system was made and no new facts were
adduced.

307] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 27

Male Reproductive System. — The testis is a much branched structure
in P. kachugae; in P. integerrimum it is lobed, and in the other known
species it is oval or spherical. It is situated near or slightly anterior to
the middle of the body. A duct designated an internal vas deferens was
described in P. integerrimum by Zeller, but Ijima (1884) traced the true
relations of this tube and showed that it passes from the ootype to the in-
testine. Goto (1894) proposed the name canalis genito-intestinalis for
this structure which is discussed in a later section. The vas deferens
arises from the dorso-cephalic margin of the testis and passes dorsad and
anteriad. It extends dorsal to the ootype, between the dorsal margins of
the ovary and uterus to the level of the genital pore where it turns ven-
trad and enlarges to form the seminal vesicle (Fig. 13). From the semi-
nal vesicle a duct passes thru the cirrus sac, opening into the genital
atrium (Fig. 26). The vas deferens is small and has a fibro-membran-
ous wall, and the seminal vesicle has a lining of columnar epithelium.
The cirrus sac is composed of an external muscular waU enclosing a mass
of parenehymous tissue which surrounds the ejaculatory duct. This sac
is very small in P. integerrimum and P. hassalli. Ventrally it opens into
a common genital atrium (Fig. 26). The ejaculatory duct terminates in
the genital papilla, which when retracted is surrounded by a deep depres-
sion. In the musculature between this depression and the wall of the
cirrus sac are embedded the roots of the genital hooks. "When the hooks
are retracted there is a shallow depression between them and the wall of
the sac. With the contraction of the wall of the cirrus sac the genital
papilla and the circle of genital hooks are extruded thru the pore. In
most of the species the hooks are sickle shaped with the points project-
ing outward, and with muscles attached to the outside of the hook at the
juncture of the root and shank. These muscles undoubtedly serve as a
fulcrum, and the extrusion of the papilla rolls the hooks outward bury-
ing their points in the eutieula lining the wall of the vagina of the copu-
lating worm (Fig. 24). In P. alluaudi Beauehamp described three
genital hooks, P. integerrimum has eight, and other species sixteen,
thirty-two, and forty. In P. hassalli the genital hooks are small, straight
and have a wing like process at the middle.

Zeller described a prostate gland in P. integerrimum, consisting of
masses of large cells situated around the cirrus, and traced ducts from
these cells to the lumen of the ejaculatory duct. Johnston in P. bulliense
says, "Two laterally placed, small groups of gland cells represent the
prostate." The statement of Zeller that a gland is present around the
cirrus of P. integerrimum is certainly correct. In the species described
in this paper, a similar gland is present in the parenchyma around the
genital sinus. The cells (Fig. 12) are globular or pyriform, stain deeply

28 ILLINOIS BIOLOGICAL MONOGRAPHS [308

and possess a distinct nucleus and nucleolus. Their ducts could not be
traced to the ejaculatory duct but in many cases appear to lead to the
body wall near the margin of the genital sinus. In P. orhiculare, P.
opacum and P. megacotyle the cirrus sac is large and many nuclei are
present around the ejaculatory duct in the dorsal part of the sac. These
nuclei are large, with distinct nucleoli, and are surrounded by a deeply
staining area of granular or flaky substance, but no cell boundries could
be made out.

Female Reproductive System. — In all known species but one, the
ovary is oval or comma shaped. In P. kachugae it is described by Stew-
art as a "curved sausage-shaped organ, the curve forming all but a com-
plete circle. The fundus is somewhat bulbous." This structure is
usually not more than one half the size of the testis, is situated a short
distance anterior to that organ, and in a given species may lie on either
side of the body. In all the species studied by the writer it is comma
shaped, the larger part is ventral, anterior, and lateral, and terminal
region is dorsal, posterior, and mesal. The ova are formed in the large
part and the ovary is divided into zones of growth, ova of increasing size
being present in each succeeding zone (Fig. 23).

In the species described in this paper the viteUaria consist of masses
of foUicles occupying the dorsal and lateral regions of the body. Each
follicle consists of several cells which may vary much in appearance ; the
difference is due to the phase of secretory activity of the cells. In the
peripheral part of the gland the ceUs are usually small, with granular or
flaky protoplasm, a distinct nucleus and nucleolus; whereas those more
centrally located may be two or three times their size, the extra-nuclear
area being either vacuolated or filled with droplets of a yellow substance
(Figs. 19, 20). In some cells the secretory droplets are scattered uni-
formly thruout the cell. The presence of the material in the cells often
renders the body so opaque that the diverticula can not be seen. The
glandular secretion is apparently identical with that which forms the shell
of the egg, and this observation further confirms the statement of Gold-
schmidt (1909) that the so-called vitellaria secrete the shell of the egg.
Small ducts from the follicles (Fig. 11) unite and discharge into longi-
tudinal collecting ducts. These extend along the sides of the body, later-
al to the ceca and dorsal to the excretory tubules ; on either side of the
body there is an anterior and a posterior branch which unite just behind
the level of the ovary and the common duct discharges into the external
end of the vitello-vaginal canal. In P. hulliense, Johnston reports : ' ' The
lateral vaginal swellings are formed by a large number of papillae, per-
forated by fine canals, which after a very short course, open into a fairly
wide sperm reservoir, situated one on either side, just under the swell-

309] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 29

ings. From these reservoirs, a wide vaginal txibe on either side runs
backwards and inwards, to open into the anterior lateral yolk duet."
A similar condition is described and figured by Zeller for P. integerri-
mum. In all other species in which the structure has been described, the
vaginae are open funnels leading mediad and dorsad from their openings
on the ventro-lateral surface of the body, and uniting just below the in-
testine with the common vitelline ducts to form the vitello- vaginal canals.
The cuticular lining of the vaginae is very thick and in the parenchyma
around the vaginae there are large cells of secretory type (Fig. 24). The
vitello-vaginal canals lead medially and unite, either forming a duet
which discharges into the ootype (Fig. 32) or opening separately into
the ootype (Figs. 3, 16, 24).

From the ovary the oviduct passes posteriad and ventrad, opening
into the ootype. Immediately anterior and dorsal to the opening of the
oviduct, there branches from the ootype a small tube which after a some-
what twisted double loop opens into the intestine of the side in which the
ovary is situated. This genito-intestinal canal has been the source of
much controversy and its presence or absence is the diagnostic feature of
Odhner's two groups of monogenetic trematodes. Mehlis' gland, the shell
gland of earlier authors, is never largely developed and is difficult to
find in some specimens where it is represented by a few nuclei in the
parenchyma around the ootype. Zeller for P. integerrimum and John-
ston for P. iulliense described prominent "shell glands", and Stewart
for P. kachugae described ' ' a group of glandular cells found at the same
transverse level as the ovary, but on the opposite side of the midline.
They appear to be connected with the corresponding vagina, but their
function is obscure." Since they are in the precise location of the
Mehlis' gland, one is led to suspect that Stewart was confused in regard
to the connections and relations of this group of ceUs, altho in in-
dividuals of other species studied by the writer, there are groups of
large glandular cells in the parenchyma surrounding each vagina.

The ootype is continued by a tube which passes anteriad on the op-
posite side from the ovary, and which leads to the uterus. Previous
writers have called this tube the oviduct and Johnston (1912) says,
"From the ootype, the oviduct runs forward to a point in front of the
ovary, whence it bends sharply backwards and runs in a straight course
close to the ventral surface, almost to the level of the cotylophore, where
it opens into the wide uterus. ' ' The use of the term oviduct for the tube
leading from the ootype to the uterus is confusing and objectionable.
Looss (1899) says, "Der Theil des weibMchen Leitungswegen, der den
Keimstock mit dem ootjrp verbindet, ist der oviduct oder Keimgang,"
and this terminology is found in general use thruout the literature. In a
large number of trematode genera the ootype opens directly into the

30 ILLINOIS BIOLOGICAL MONOGRAPHS [310

uterus. In the Polystomidae however, there is a definite specialized tube
leading from the ootype to the uterus. This duct is not homologous with
the oviduct, it is separated from that duct by the ootype, and further,
in the specimens examined by the MTiter the histological character of the
two are not precisely the same. The epithelial lining of the oviduct is of
the flattened type, and that of the second duct more columnar. Such a
duct is present in many cestode genera and is called the uterine duct.
The same name is proposed for the tube leading from the ootype to the
uterus in the Polystomidae, altho with the understanding that its use is
independent of the question of homologies of the female ducts in trema-
todes and cestodes.

In P. hulliense the uterine duct opens into the uterus not at the end
but on the side, and there is a posterior uterine pocket. The uterus ex-
tends as a wide elongated sac from the extreme posterior end of the body
to the common genital sinus. In P. alluaudi the intracecal area is occu-
pied by the uterus and eggs are present almost as far posteriad as the
caudal union of the ceca. In P. integerrimum there is a long uterus
which extends in many loops anterior to the ootype, and contains a large
number of eggs. In all other known forms, the uterus is situated at the
level of the ovary on the opposite side of the body, and contains a single
large egg or embryo. Zeller (1876) described a similar condition for
the ectoparasitie form of P. integerrimum. Figure 14 shows a verj- early
embyro of P. orhiculare and Figure 23 a much later stage of development
in P. megacotyle. No shell is present in the former case, altho it may
have been lost in sectioning. There must be some provision for the
growth of the embryo and the shell can not be rigid during the uterine
period. Where the oviduct arises from the ovary, at its union with the
ootype, and at either end of the uterine expansion sphincter muscles pro-
duce short contracted portions of the tube. In all the species studied by
the writer, with the exception of the vitelline tubules, all ducts of the
female system have a fibro-membranous wall and an epithelial lining,
which in the ootype, uterine duct, and uterus consists of tall columnar
cells with distinct boundries and single nuclei. Describing the epithelial
ceUs lining the ootype in certain other monogenetic forms Goto (1894)
says that because of their appearance and reaction to stains he strongly
suspects theii' glandular nature, but since a shell gland is present he can
not understand their function. In certain species of Polystoma Mehlis'
gland is much reduced or absent, and in these forms the cells of the
epithelial lining of the ootype appear to be secretive (Figs. 8, 9). This
agrees with the present conception that the vitellaria secrete the shell
substance and Mehlis' gland the fluid in which the eggs are suspended.

The genital pore is situated on the ventral surface in the median

311] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 31

line, just posterior to the bifurcation of the digestive tract. It opens
from a common genital sinus (Figs. 13, 26) into which the uterus dis-
charges and thru which the cirrus is extruded. The opening from the
uterus into the genital sinus is posterior and ventral, while the cirrus sac
opens into the dorsal part of the atrium.

When the two specimens of P. opacum from Trionyx ferox were
placed in a watch glass, they soon came in contact and immediately
started copulation, the cirrus of each worm was inserted in the right
vagina of the other, and the two worms attached to each other, both with
the anterior suckers and those of the caudal disc that could be brought in
position for adhesion. Attempts to separate the worms failed, so an
effort was made to fix them in the copulating condition, but they separated
on the application of the killing fluid. This explains the statement of
Johnston: "On one side only, in the specimens sectioned, was the
vaginal tube filled with sperms; that on the other side was empty."
Benham (1901) and Mac Galium (1913) state that copulation in poly-
stomes has been observed only by Zeller.

POLTSTOMA ORBICULARE Stunkard 1916
[Figures 1 to 14]

The material of this species consists of six specimens from the
urinary bladder of Pseudemys scripta from Raleigh, North Carolina,
one specimen from the urinary bladder of Chrysemys marginata from
Chicago, Illinois, and two specimens from the urinary bladder of Chry-
semys marginata from Creston, Iowa.

The body is an elongate oval, slightly more pointed anteriorly than
posteriorly, and in two of the specimens with slight indentations of the
body walls at the vaginae and at the posterior margin of the anterior
sucker. These worms (Fig. 1) varied in length from 2.7 to 3.75 mm.
and in width from 0.9 to 1.2 mm. The caudal disc is circular, 0.8 to
1.07 mm. in width, and bears the six suckers arranged symmetrically
in a circle. The suckers are approximately 0.3 mm. in diameter, and
are separated by regular equal intervals. No hooks could be found on
the caudal disc with the exception of the single minute larval booklet
in the base of each sucker. These are 0.016 mm. in length and could be
seen only under favorable conditions.

The anterior sucker (Fig. 6) is 0.25 to 0.27 mm. in length and
0.37 to 0.42 mm. in width. It opens into the pharynx, a spherical struc-
ture 0.24 to 0.28 mm. in diameter. There is a short esophagus visible
in sagittal sections altho it is not distinguishable in toto preparations.
The ceca meet anteriorly in a wide curve and extend as simple tubes

32 ILLINOIS BIOLOGICAL MONOGRAPHS [312

almost to the posterior end of the body. They have no branches and
terminate blindly. In caliber they vary from 0.04 to 0.116 mm.

The testis is spherical or oval, usually slightly longer than broad,
and measures 0.29 to 0.39 mm. in width and 0.36 to 0.5 mm. in length.
It is near or slightly anterior to the middle of the body. The sperm
duct arises at its anterior margin and, lying dorsal to the ootype, passes
anteriad. In front of the ovary it turns ventrad and expands into the
seminal vesicle. At the outer end of the seminal vesicle the duct is
encircled by a sphincter muscle, and then known as the ejaculatory
duct passes thru the cirrus sac to open into the genital atrium (Figs.
3, 13). The cirrus sac is almost spherical, and consists of an external
muscular capsule filled with parenchymatous tissue enclosing a central
canal. In the dorsal part of the sac there are radial muscles passing
from the wall to the central duct, and among these fibers a few large
nuclei. More ventrally there are sets of muscles developed around the
central duct and these are connected to the wall of the sac. Externally
the central canal terminates at the apex of a papilla which is separated
by a deep depression from the muscular ring that bears the hooks of
the genital coronet. This conical muscular ring is protrusible and is
separated from the wall of the cirrus sac by a second depression. The
invaginations on either side of the genital coronet allow for the extru-
sion of the coronet of hooks with the genital papiUa on the contraction
of the wall of the cirrus sac, while the muscles attached to the central
canal and the muscular ring bearing the genital hooks serve as retract-
ors. The genital coronet consists of sixteen hooks, similar in size and
shape; they have an external sickle-shaped part or shank which turns
outward and a root or basal part of about the same length embedded
in the musculature (Figs. 2, 13). The basal part is straight and hollow
and the internal end is bifurcate. It bears many fine cuticular processes
which are particularly prominent near its union with the shank. In the
body parenchyma around the terminal part of the cirrus sac there are
large unicellular glands (Figs. 12, 13).

The ovary is lateral and may be situated on either side of the body.
It is 0.1 to 0.25 mm. anterior to the testis. It is ovoid in shape, ^vith
the larger part in which the ova are being formed anterior and ventral,
and the oviduct arising from the dorsal posterior region. In sections it
appears to be marked into zones, with larger and fewer cells present in
each succeeding zone. It is 0.1 to 0.148 mm. in width, 0.14 to 0.185 mm.
in length and in one specimen cut in cross sections 0.175 mm. in depth.
The oviduct arises as a very small tube and immediately expands (Fig.
3). This expanded portion extends posteriad and ventrad and by means
of a short constricted tube opens into the ootype, a specialized region

313] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 33

of the female duct where the vitello-vaginal canals are received and the
genito-intestinal canal is given off. The genito-intestinal canal twists
in a double loop and then opens into the intestine of the side upon
which the ovary is located (Fig. 10). The vaginae are ventro-lateral in
position and open to the exterior by funnel shaped mouths. The vitel-
laria occupy the dorsal and lateral regions of the body; they extend
anteriad to the pharynx and posteriad to the caudal disc. There is a
Strand of follicles across the dorsal side of the body just behind the
pharynx, and then the follicles are entirely extracecal in the field ante-
rior to the testis; posterior to the testis the vitellaria overlie the ceca
and extend to the center altho they are scanty along the median line.
Ventrally the vitellaria are entirely extracecal. Collecting duets run
longitudinally, laterad of the ceca ; and just below the cecum of either
side the common vitelline ducts formed by the union of the anterior
and posterior longitudinal ducts unite with the internal ends of the
vaginae to form the vitello-vaginal canals. These canals open directly
into the ootype, one on either side, and are thus continuous, forming a
canal thru the body from side to side. Mehlis' gland is represented by
many nuclei which lie in the parenchyma around the ootype and uterine
duct. This latter duct passes anteriad and laterad on the opposite side
from the ovary ; it is smaller than the ootype in diameter and the epithe-
lial lining is lower. After a slight expansion it is constricted and then
opens into the uterus. The uterus contained a single eg^ or embryo.
Figure 14 shows a morula-like mass of cells found in one specimen; in
the other specimens there were large spherical eggs, each enclosed in a
yellow shell. They vary from 0.21 to 0.24 mm. in diameter.

The excretory system shows no departure from the typical form
and while it can not be completely followed in sections, the larger ducts
occupy the characteristic positions. The descending collecting ducts
arise in the region of the anterior sucker and pass posteriad, lying lat-
eral and ventral to the ceca. They wind back and forth in short curves
and at the posterior end of the body turn anteriad and pass in the same
winding course to the excretory vesicles. Both descending and ascend-
ing ducts receive small branches at irregular intervals. The excretory
pores are lateral and dorsal, at the level of the bifurcation of the
intestine (Fig. 7).

This species agrees with P. alluaudi in shape of caudal disc and
absence of great hooks, but differs from that species in type of uterus,
number of hooks in the genital coronet, and in the character of the
intestinal diverticula and testis. P. oriiculare agrees with P. hassalli
in the number of genital hooks, but the hooks are different in size and
shape ; P. hassalli has the great hooks of the caudal disc well developed

34 ILLINOIS BIOLOGICAL MONOGRAPHS [314

whereas they are absent in this species. In certain particulars P. or-
biculare resembles P. opacum, but the two species have different num-
bers of hooks in the genital coronets ; they differ also in the relative size
of caudal suckers. The great hooks of the caudal disc are present in
P. opacum. The two species differ also in that one is parasitic in the
urinary bladder and the other in the oral cavity.

POLYSTOMA OPACUM Stunkard 1916
[Figures 15 to 21]

Two worms of this species were obtained from the esophagus of a
single specimen of Trionyx ferox from Newton, Texas, and another
from the esophagus of Malacoclemmys lesueurii from the same region.
These trematodes were the same color as the lining of the esophagus
and so firmly attached that they were removed only with great difficulty.

The worms (Fig. 15) measured 4, 3.75, and 3.25 mm. in length and
1, 0.85 and 0.8 mm. respectively in width. The body has an elongate
oval outline, is flattened dorso-ventraUy, and observed in living condi-
tion, shows great variations in shape. In an extended condition it nar-
rows at either or both ends, and the contracted form may be not more
than half the length when extended, and broadly oval or quadrate in
outline. The caudal disc is slightly wider than the body in the mounted
specimens, measuring 1.09 and 1.21 mm. in width while each sucker is
approximately 0.4 mm. in diameter. The suckers have a chitinous skele-
tal framework, as is described in the generic discussion. In the external
meridinal band there are thirty-two divisions, which number corre-
sponds to the number of hooks in the genital coronet. The suckers are
arranged in a circle, altho the anterior pair are separated by a distance
slightly exceeding that between the posterior pair. Between tlie
anterior suckers there are many chitinous spicules, and in one specimen
two of the larval booklets. Chitinous spicules are present on the sides
of aU the suckers and over the ventral surface of the disc. Between the
posterior suckers there are three pairs of hooks, viz. two pairs of the
small larval hooks and one larger pair, but the great hooks are relatively
much smaller than the corresponding hooks in other species in which
they are present (Fig. 40). The larval booklets are 7 to 9/t in length
and the great hooks are 75/* in length. The chitinous spicules present
on the disc have no definite arrangement and their points may stand
in any direction; the three larval hooks between the anterior suckers
of one specimen have no definite relative position and their hooks point
in different directions; those at the posterior edge of the disc are set

315] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 3S

in a row at more or less regular intervals and their hooks all point
backward.

The cuticular covering of the body is about 14/i in thickness, and
on the contraction of the body is thrown into minute folds and furrows.

The anterior sucker is oval, 0.2 to 0.22 mm. in length and 0.23 mm.
in width. It opens into the pharynx (Fig. 18), a spherical structure
.0.3 mm. in width. There is a broad nerve commissure crossing the an-
terior part of the pharynx which contains large ganglion cells. From
this dorsal commissure a nerve passes ventrad on either side of the
pharynx.

The digestive tract is of the simple triclad type, the pharj-nx is fol-
lowed by a short esophagus, 0.17 mm. in length in the sectioned worm,
and the diverticula extend as simple tubes almost to the posterior end
of the body. They are about 0.15 mm. in diameter and terminate blindly,
dorsal to the middle pair of suckers (Fig. 21). The ceca are lateral but
close together, separated by only 0.2 to 0.25 mm. They have the usual
fibro-membranous coat and epithelial lining, and were empty in the
sectioned individual.

The testis is spherical or slightly longer than broad in well extended
specimens. It is slightly anterior to the middle of the body and is com-
posed of a large number of lobes or strands of cells, compacted and
enclosed in a membranous capsule. Cells with the chromatin of their
nuclei in all stages of division and mature spermatozoa were observed
in sections. The sperm duct arises at the anterior dorsal margin of the
testis and curves dorsad and eephalad. Anterior to the uterus it turns
ventrad and expands to form the seminal vesicle. From the seminal
vesicle a small ejaculatory duct leads through the cirrus sac and opens
into the common genital sinus.

The ovary is ovoid or comma shaped, situated a short distance
anterior to the testis, and in aU three specimens is located on the left
side of the body ; but since in other species it may lie on either side, it
is probable that the examination of a larger number of individuals
would show specimens with the ovary on the right side. In dorsal view
it is from 0.16 to 0.2 mm. in length and 0.08 to 0.12 mm. in width, while
in the specimen that was sectioned it is 0.08 mm. in width and 0.3 mm.
in depth. The oviduct arises at the dorsal posterior margin and curves
posteriad, mediad, and ventrad where it opens into the ootype. The
vitello-vaginal canals open separately into the ootype, just ventral to the
origin of the genito-intestinal canal. The latter duct passes laterad,
then dorsad and anteriad, turns mediad almost to the median line of
the body, then dorsad and laterad, and opens into the intestine of the
side in which the ovary is located. The uterine duct passes to the right

36 ILU.XOIS BIOLOGICAL MOXOGRAPHS [316

sight of the body, then dorsad and anteriad where it opens into the
uterus. Mehlis' gland is present altho not well developed, and the cells
are scattered along the uterine duct as well as around the ootype, altho
they are not so numerous in the former as in the latter location. The
vaginae open to the surface on either side at the ventro-lateral margins
of the body, at the level of the posterior margin of the ovary (Fig. 16).
On either side the inner ends of the vaginae unite just below the ceea
with the common ducts from the vitellaria to form the vitello-vaginal
canals. These open separately and directly into the ootype. The %'itel-
laria consist of large compact follicles, underlying the entire dorsal
surface of the body from the pharynx to the caudal disc, except the
region over the ovary. The vitellaria are reduced and only a few folli-
cles are present in the region over the testis and they are entirely absent
in a circular area over the ovary. Ventrally the vitellaria do not extend
mediad of the ceca. The vitellaria are so extensively developed that they
obscure the internal structures and render the body opaque, and this
character suggested the name of the species. Common collecting duets
run longitudinally along the body lateral to the intestinal diverticula
and these discharge into the vitello-vaginal canals as previously de-
scribed. In each of the specimens there is a single large egg in the
uterus, and in the one sectioned the uterus extends cephalad of the
genital pore and to a point 0.03 mm. from the bifurcation of the intes-
tine. The eggs are broadly oval, 0.25 mm. long by 0.2 mm. wide. The
shell is yellow, refractive to light, and apparently composed of the same
substance that occurs in small droplets in the vitellaria.

The uterus and cirrus sac open into the genital sinus; the opening
of the cirrus is anterior and dorsal to that of the uterus. The common
genital pore is situated in the median line, about 0.12 mm. caudad of
the bifurcation of the intestine. Embedded in the wall of the cirrus sac
and with their points forming the so-called coronet, the genital hooks
in appearance suggest the corolla of a flower. There are thirtj'-three
of these hooks in one mounted specimen and thirty-two in the other. In
entire length they measure 0.05 mm., the shank or projecting part com-
prising about half the total length.

P. opacum agrees with P. alluaudi and P. orhiculare in shape of
caudal disc, but P. alluaudi has but three spines in the genital coronet,
and a long post-ovarian uterus which contains many eggs. P. orhiculare
has a larger anterior sucker, smaller caudal suckers, a smaller pharj-nx,
fewer vitelline follicles, and only half as many hooks in the genital
coronet. P. opacum differs from P. coronatum and P. microcotijle in
the shape of the caudal disc and in the reduced condition of the great
hooks of the disc.

317] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 37

POLYSTOMA MEGACOTYLE Stunkard 1916
[Figures 22 to 26]

The material of this species consists of three specimens from the
mouth of Chrysemys marginata from Creston, Iowa. One worm was
cut into cross sections and the other two mounted as stained toto
preparations.

These worms (Fig. 22) have an elongate ovoid shape. Widest in
the region just anterior to the caudal disc, they gradually become nar-
rower anteriorly, and posteriorly they taper rapidly to a caudal tip
which is set in thfe antero-central part of the caudal disc. The worms
are 2.5 to 2.7 mm. long and 0.71 to 0.78 mm. in width. The caudal disc
is cordiform and the suckers are so large that they slightly overlap each
other. The suckers are arranged in about four-fifths of a circle around
the lateral and caudal margins of the disc. Measurements thru the disc
from side to side at the level of the cephalic suckers are from 1 to 1.4
mm., thru the middle pair 1.2 to 1.8 mm., and thru the caudal suckers
0.68 to 0.7 mm. The disc bears the characteristic armature of hooks.
Across the anterior margin there are three larval booklets in one speci-
men and four in the other, but their arrangement is not regular or
definite and their position would indicate that they do not function in
attachment. In the specimen reproduced in Figure 22 the two hooks
of the right side have their points almost together and their bases apart.
In the bases of the suckers there are small larval booklets, and one pair
similar in size and shape between the two caudal suckers. Also between
the posterior suckers (Fig. 41) there is the pair of great hooks and a
pair of hooks the same shape as the great hooks and intermediate in size
between the great and larval hooks. The hooks measure in length : lar-
val 0.017 mm., great hooks 0.116 mm., and the pair intermediate in size
0.058 mm.

The cuticular covering of the body is approximately 5/a in thick-
ness on the dorsal and 3 to 4/a in thickness on the ventral surface. It
is turned in at the external openings and lines the digestive tract to the
bifurcation.

The anterior sucker is set off from the remainder of the body by
a slight constriction. It is oval, its longest axis crosswise of the body,
somewhat flattened posteriorly, and measures 0.28 mm. in length by
0.35 to 0.42 mm. in width. It is followed by the pharynx (Fig. 25)
which is 0.35 to 0.38 mm. long, 0.38 to 0.44 mm. broad, and in the sec-
tioned worm 0.34 thick. No esophagus was observed; the ceca meet
anteriorly in a wide curve and extend almost to the posterior end of the
body. They are 0.06 to 0.11 mm. in diameter, and have an epithelial

38 ILLINOIS BIOLOGICAL MOXOGRAPHS [318

lining 0.017 to 0.035 mm. in thickness set upon a fibro-membranous base.
The vitellaria are so thick that the diverticula can not be traced in toto
preparations.

The testis is situated near the center of the body; it is spherical
or oval, 0.28 to 0.33 mm. long, 0.33 to 0.38 ram. wide, and in the sec-
tioned worm 0.28 mm. thick. The course of the vas deferens and the
character of the male organs are similar to those in the previously
described species. The genital coronet contains thirty-six hooks in one
and forty-two in the other toto preparation. They are similar in size
and shape, have a straight basal portion with bifid end which is embedded
in the wall of the cirrus sac, and a sickle shaped shank which projects
into the genital atrium. The basal portion is the same length as the
shank and each part measures 0.03 mm.

The ovary (Fig. 23) is a broad comma-shaped organ, situated about
midway between the pharynx and testis, on either side of the body.
The larger part is anterior and ventral and contains many nuclei of
forming ova, and there are zones of developing ova, each with larger
and fewer cells until dorsally and posteriorly the oviduct is given oflP.
The oviduct passes mediad, expanding slightly, and then posteriad and
ventrad to open into the ootype. This structure is in the ventral part
of the body, just anterior to the testis (Fig. 24) ; from the sides it re-
ceives the vitello-vaginal canals and gives off the genito-intestinal canal.
This canal after winding in a double loop opens into the intestine on the
same side as the ovary. It was empty in the sectioned worm. The
external openings of the vaginae are situated on small prominences
ventro-lateral in position, altho there is a single large opening to the
exterior. The vitellaria consist of masses of follicles occupying the dor-
sal and lateral areas of the body. They form a sheet of gland cells on
the dorsal side of the body posterior to the testis. They are somewhat
reduced along the median dorsal area in the anterior half of the worm
and entirely absent only in small fields over the testis and uterus. They
extend along the sides of the body and ventrally are limited by the ceca.
On either side, at the level of the ootype, a common duct from the longi-
tudinal collecting ducts passes ventrad and just below the cecum unites
with the vagina of that side to form the vitello-vaginal canal which
discharges into the ootype. The uterine duct leads to the uterus, which
in each of the specimens contained a large egg. A section of the egg is
shown in Figure 23. The eggs are oval, 0.15 by 0.18 mm., and in the
sectioned worm the egg is 0.24 mm. in thickness. From the uterus a
small duct passes anteriad and ventrad, opening into the genital atrium,
posterior and ventral to the cirrus sac.

The excretory system agrees with the general description given.

319] NORTH AMERICAN POLYSTOMIDAE-STUNKARD 39

The descending and ascending ducts are 6 to 11/t in diameter ; when
empty their walls collapse.

P. megacotyle differs from all known American forms in the large
number of hooks present in the genital coronet, and in this character
agrees only with P. ocellatum. The species differs from P. ocellatum,
however, in the difference in size of the anterior sucker and pharynx
as well as in the size of the caudal suckers. P. megacotyle differs from
P. microcotyle in the number of genital hooks and in the size of the
posterior suckers. P. megacotyle has a larger pharynx, larger caudal
suckers, and a larger number of gental hooks than P. coronatum.

I
POLYSTOMA MICROCOTYLE Stunkard 1916

[Figures 28 and 29]

This species is described from a single specimen from the mouth
of Chrysemys marginata from Creston, Iowa. The worm was stained
and mounted in toto (Fig. 28).

It is 3 mm. long, and 0.78 mm. in width. The caudal disc is cordi-
form, 1 mm. in width at the level of the anterior suckers, 1.07 mm.
thru the middle pair, and 0.74 mm. thru the caudal pair of suckers.
Each sucker is 0.28 mm. in diameter and with the exception of the
longer distance between the anterior suckers, they are separated by
almost regular equal distances. The distance between the anterior
suckers is about four times as great as that between the posterior pair.
Four larval booklets are present between the two anterior suckers, three
in a row but with their hooks pointing in different directions, and the
fourth some distance posterior to the others (Fig. 29). Between the
posterior suckers there are three pairs of hooks : the pair of great hooks,
one pair of larval hooks, and a third pair intermediate in size between
the great and larval hooks. The hooks of this third pair are the same
shape as the great hooks. The larval hooks are 0.017 mm. long, the
great hooks are 0.116 mm. long, and the pair intermediate in size are
0.061 mm. long.

In this specimen as the suckers are small the musculature of the
caudal disc shows very plainly (Fig. 29). Muscle strands from the
ventral side of the body and others from the body wall pass to the bases
of each of the suckers. Others pass to the outside of the different suck-
ers and are inserted on the distal and intermediate zones of the suckers,
serving as retractors in the operation of the organs. Many break up
into smaller fibers and can not be traced. From the base of each sucker
the muscles spread out in a fan shaped manner and fibers can be traced
not only to the large strands from the body wall but also small fibers

40 ILLIXOIS BIOLOGICAL MOXOGRAPHS [320

pass from the base of each sucker to each of the other suckers, ilany
of the muscles branch and ramify thru the tissue of the disc.

The anterior sucker is 0.2 mm. long and 0.42 mm. wide ; the pharj'nx
is 0.37 mm. long and 0.4 mm. in width. No esophagus is visible in the
single toto preparation and only the anterior part of the intestine can
be seen.

The testis is slightly anterior to the middle of the body; it is oval,
0.36 mm. in length and 0.42 nun. in width. The sperm duct can be
traced dorsally and anteriorly; eephalad of the ovary it expands into
a seminal vesicle which stains deeply due to the presence of spermatozoa.
The genital coronet contains thirty-two hooks, equal in size and similar
in shape.

The ovarj' is on the left side of the body, about midway between
the testis and the genital pore. The oviduct arises at the median pos-
terior margin and passes mediad, but the structure of the ootype could
not be made out. The uterus can be distinguished at the level of the
ovary on the opposite side of the body and is empty. Laterally the
vaginae are visible and the vitello-vaginal canals can be traced mediad
a short distance from the ceca. The viteUaria are strongly developed,
anteriorly they extend to the middle of the pharynx, and posteriorly
to the caudal disc. There is a strand of foUicles across the body from
side to side between the pharynx and the level of the genital pore. The
foUicles occupy the dorsal and lateral regions of the body but anteriorly
are reduced in the median area and are absent in the fields over the
testis and ovary. They obscure the ceca caudal to the testis. No vitel-
line ducts were seen.

The excretory vesicles appear one on either side of the bodj* dor-
sally, at the level of the bifurcation of the intestine.

In number of genital hooks this specimen agrees only with P. coro-
notum Leidy. A comparison with a type specimen of P. coronatum
shows that in the latter form the pharynx and testis are much smaller
and the suckers of the caudal disc are much larger.

POLYSTOilA CORONATUM Leidy 1888
[Figure 27]

This description was made from a single type specimen from the
United States National Museum. The worm was stained and mounted
in toto.

Leidy (1888) says the host is the common food terrapin, and the
previous j'ear, speaking of eating terrapin, he mentions Emys pahistris
and Emys rugosa. Braun (1879-1893) lists the species from Cistudo

321] NORTH AMERICAS POLYSTOMIDAE—STUNKARD 41

Carolina. Goto (1899) in discussing the specimen described by Leidy
as P. ohloiigum, refers to the food terrapin as E. rugosa.

Leidy gives no figure and his description states : " Polystomum coro-

natum Body when elongate lanceolate. Caudal disc wider

than the body, cordiform, with three pairs of bothria and with the body
attached between the anterior two pairs; changeable in form to oblong,
circular or quadrate; with three pairs of minute hooks between the
anterior part of bothria and with a larger pair and two smaller pairs
between the last pair of bothria. Genital aperture with a circular or
transverse oval coronet of thirty-two hooks of equal length. No eyes
visible. Length, elongated from 4 to 6 mm; contracting to about half
the length and widening proportionately."

The specimen from which the present description was made (Fig.
27) is 3.15 mm. long and 0.83 mm. in width. The greatest width is at
the level of the vaginae; the body tapers rapidly anteriorly, widening
again slightly at the anterior sucker. From the level of the vaginae
the body gradually grows narrower posteriorly to its insertion into the
caudal disc. The disc is 1.24 mm. wide at the level of the anterior
suckers, 1.2 mm. thru the middle pair and 0.78 mm. thru the caudal pair
of suckers. Each sucker is approximately 0.37 mm. in diameter, and
constructed as previously described. There are thirty- two small di-
visions in the peripheral cuticular band of the only sucker in which they
could be counted. The disc bears the usual eighteen hooks; the six
larval booklets at the anterior margin of the disc are situated in a row
equidistant from the anterior edge of the disc, the two lateral hooks
on either side are nearer each other than the more centrally located one
is to the median one of that side. Larval booklets are present in the
bases of the suckers and one pair is present between the caudal suckers.
Between the caudal suckers there are present also both a pair of great
hooks and a third pair intermediate in size between the two. The larval
booklets are 0.02 mm. in length, the hooks of intermediate size are 0.051
mm., and the great hooks are 0.132 mm.

The anterior sucker is oval, 0.16 mm. long and 0.4 mm. wide; the
pharynx is circular in outline, 0.3 mm. in diameter. No esophagus can
be seen in the toto preparation and behind the posterior margin of the
testis the ceca are obscured by the viteUaria.

The testis is slightly anterior to the center of the body, circular in
outline, and 0.3 mm. in diameter. The vas deferens could not be distin-
guished; the cirrus sac in ventral aspect is 0.19 mm. in diameter; the
genital coronet contains thirty-two hooks, similar in size and shape, the
shanks being sickle-shaped.

The ovary is situated on the right side of the body, about its own

« ILLINOIS BIOLOGICAL MONOGRAPHS [322

diameter anterior to the testis; in ventral view it is circular, 0.094 mm.
in diameter. The oviduct passes posteriad and mediad, and the ootype
appears as a darkly stained area. The vaginae can be distinctly seen
and laterad of the ceca on either side there is a large cavity communi-
cating with the exterior. The uterus is empty; the folded walls of the
cavity are visible on the left side of the body. The vitellaria are strongly
developed. Masses of follicles occupy the dorsal and lateral regions of
the body but ventrally do not extend mediad of the ceca. Anteriorly
they extend to the region of the pharynx; there is a strand across the
body just behind the pharynx and in the intereecal area anterior to the
testis they are largely interrupted, permitting the structures in this
region to be made out. None of the vitelline ducts are ^'isible.

The excretory vesicles are anterior to and slightly laterad of the
ceca at the level of the caudal margin of the pharynx, but no ducts
could be seen.

POLYSTOilA HASSALLI Goto 1899

[Figures 30 to 33]

This species was described by Goto (1899) from the urinary blad-
der of Cinosternum pennsylvaniciim from Maryland. The writer has
since collected the species from other hosts and localities. A single
specimen was found in the urinary bladder of Aromochelys carinatus
from Newton, Texas; five were collected from the urinary bladder of
Aromochelys odoratus from Raleigh, North Carolina; two from the
urinary bladder of Cinosternum pennsylvaiiicum, from Ealeigh, N. C. ;
and three from the urinary bladder of Chelydra serpentina from Walker,
Iowa.

The worms (Figs. 30, 31) vary from 1.3 to 2 mm. in length and
from 0.4 to 0.65 mm. in width. The caudal disc varies in shape from
hexagonal to cordiform and is of approximately the same width as the
body. The suckers are 0.12 to 0.16 mm. in diameter. The eighteen
hooks of the caudal disc have the usual arrangement and are described
by Goto. However, he reports the larval hooks as being 0.33 mm. in
length and the great hooks between the caudal suckers as 0.125 mm. in
length. This is evidently a typographical error, since he figured the
great hooks as about four times the size of the small ones. In the pres-
ent material the great hooks are the same length as stated by Goto and
the smaller ones are 0.033 mm. in length, which agrees with the figures
of Goto by a change of one place in the decimal point.

The anterior sucker is ovoid, more pointed anteriorly. It may be
longer in either the anterior-posterior or lateral axis and varies in diame-
ter from 0.22 to 0.33 mm. The pharynx is spherical or oval and varies

323] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 43

in width from 0.1 to 0.14 mm. ; it may be longer in either axis. There
is no esophagus, but in some specimens a median pocket of the intestine
extends anteriad from the bifurcation to the pharynx. In others, and
this is a more usual condition, lateral pockets of the intestine extend
anteriad, one on either side of the pharynx (Fig. 33). The anterior
sucker and pharynx are lined with cuticula; the intestine with the
usual digestive epithelium. In those specimens in which the uterus
contains an egg, the large size of the egg causes the ceca to be widely
separated at the uterine level and they approach each other behind the
uterus. In one specimen, median branches from the two ceca fuse and
form a posterior connection of the diverticula (Fig. 30), and in another
the two ceca are united at their ends.

The testis is situated ventrally, just behind the middle of the body.
It is a somewhat shapeless mass, roughly oval in outline, crosswise of
the body, extending between the ceca just posterior to the uterus. The
vas deferens passes anteriad, dorsal to the ovary and between it
and the uterus; anterior to the uterus the sperm duct turns ventrad,
enlarges to form a seminal receptacle, and then passes thru the cirrus
sac, opening into the genital atrium (Fig. 32). The cirrus hooks are
sixteen in number, 0.028 mm. in length, straight, and with a wing like
process at the middle as described by Goto.

The ovary is comma shaped or ovoid in outline, situated obliquely
in the body, on either the right or left side. Typically the ovary is on
one side of the body and the uterus on the other, but the enormous size
of the egg causes the uterus to occupy a more or less central position,
crowding the ovary far to one side. The ovary is 0.058 by 0.065 mm.
in the smallest and 0.085 by 0.12 mm. in the largest worms, altho the
size of the ovary does not correspond precisely with the size of the
worm. The oviduct arises at the dorsal median and posterior part of
the ovary and after a dorsal loop it turns posteriad and ventrad to open
into the ootype. Mehlis' gland is present. The genito-intestinal canal
branches from the ootype and after a short winding course opens into
the intestine near the ovary. From the ootype, the uterine duct passes
laterally to the opposite side of the median line and then anteriorly
and dorsally to open into the dorsal posterior part of the uterus. The
vitellaria extend from the pharyngeal region to the anterior margin
of the caudal disc; there is a row of follicles across the dorsal surface
behind the pharynx but they are absent between the ceca anterior to
the testis. According to Goto, "lobes not very numerous, separated
from one another, mostly confined to the lateral portion of the body,
but also present in the median portion behind the testis." The vaginae
are ventro-lateral, midway between the anterior and posterior ends of
the body. There are no vaginal prominences, the vaginal openings are

44 ILLINOIS BIOLOGICAL MONOGRAPHS [324

single, and internally they unite with ducts from the longitudinal vitel-
line ducts to form the vitello-vaginal canals, as described for the
other species. They do not open separately into the ootype, but the
two vitello-vaginal canals open into a common reservoir from which a
duct passes dorsad and discharges into the ootype (Fig. 32). In a few
of the specimens the uterus is empty and in others it contains a single
large egg, the size of which varies within wide limits. The smallest
eggs are 0.11 by 0.25 mm. and the largest 0.18 by 0.34 mm. The pos-
terior edge of the uterus is at the level of the vaginae, and anteriorly
there is a small duct from the uterus to the ventral posterior part of
the genital atrium. The genital pore is in the median line, a short
distance posterior to the bifurcation of the alimentary tract.

The excretory pores are slightly more posteriorly situated than in
the previous described species. Descending and ascending ducts occupy
the characteristic positions.

POLYSTOMA OBLONGmi Wright 1879

This species was described by "Wright (1879) from the urinary
bladder of Aromochelys odoratus. I have had no opportunity to work
on material of the species and the following discussion is based on the
description of Wright. According to that author P. oblongum measures
up to 2.5 mm. in length and 1.5 mm. in width. The body is oblong in
shape, tho capable of considerable variation. The caudal lamina is some-
what narrower than the greatest width of the body and is shorter than
broad. The arrangement of the suckers and hooks is similar to that in
P. integerrimum; the suckers are 0.2 mm. in diameter; the large hooks
are 0.15 mm. and the small hooks are 0.015 mm. in length.

The mouth is on the ventral surface of the rounded anterior end.
The pharynx is bowl-shaped and the intestinal ceca are without anasto-
moses or branches. The description of the excretory system is very
meager; concerning it he says that only the convoluted lateral stems
were observed near the anterior end.

The testis is situated in the posterior third of the body, the vas
deferens passing dorsad and anteriad to the genital pore, which lies im-
mediately behind the bifurcation of the intestine. The cirrus coronet is
described as consisting of sixteen alternately large and small hooks. The
free end of each is sharply curved, while the attached end is shaped like
a cross the transverse piece of which is longer on one side than the other.
The longer pieces measure 20;ti and the shorter ones 15/x.

Doubt is expressed concerning the disposition and relations of the
female organs. The ovary is described as situated in front of the testis
on the right side of the body, but it seems probable that the organ figured

325] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 45

as the " (shell gland?) " is really the ovary. The lobes of the vitellaria
are scattered and extend from the pharynx to the caudal lamina or disc.
It is doubtful whether Wright was correct in his statement that "The
transverse duct seemed to pass inward dorsally from the intestinal ceca,"
since in all other known species the vitelline ducts are ventral in position.

The uterus is described as containing a single large egg or embryo.
The egg shell is thin and is destitute of the short stump present in that
of P. integerrimum, but has a rather large operculum. In two cases the
embryo had already escaped from the shell and moved actively within
the uterine chamber. It is a Gyrodactylus-like larva, similar to that of
P. integerrimum, with eye spots disposed in the same fashion. It is
devoid of cilia, and movement seemed to depend entirely on the muscles
and hooks of the caudal disc. The latter had a rounded outline except
posteriorly where there was a square projection bearing the four small
posterior hooks. The disc measured 0.114 mm. across and the twelve
small anterior hooks were disposed at regular intervals on the margin of
the rounded part. There was no trace of suckers. The small hooks had
already attained their definitive size and form. The two large hooks
were situated considerably further in from the margin than in the adult,
and measured only 0.024 mm. instead of 0.15 mm. in length, which dif-
ference it is stated was due to the shortness of the immersed portion, in
which, however, the notch was already formed.

In shape, as well as relative position and size of organs, P. ohlongum
strongly resembles P. hassalli. It is significant also that both are from
the urinary bladder of Aromochelys odoratus. P. oblongum is slightly
longer and broader than P. hassalli, the posterior suckers are larger and
the small hooks of the disc are only about half the length of those in
those in P. hassalli. The two species agree in number of genital hooks,
but in the former species the hooks are alternately large and small and
with the free end sharply curved, while in P. hassalli they are straight
and uniform in size.

The species in the genus Polystoma have been arranged in the form
of an analytical key utilizing the more prominent or more useful
diagnostic structures in separating the different forms. This key is
found on the following page.

46 ILf^INOIS BIOLOGICAL MONOGRAPHS [326

KEY TO THE SPECIES OP THE GENUS POLYSTOMA

Uterus long, contains many eggs 2

Great hooks present on the caudal disc 3

Ceca branching P. integerrimum

Ceca not branching P. huUiense

Great hooks not present on caudal disc P. alluaudi

Uterus short, contains a single egg 7

Great hooks present on caudal disc 8

Genital hooks of equal length 9

Not more than sixteen genital hooks 10

Genital hooks eight in number;

ectoparasitic form P. integerrimum

Grenital hooks sixteen in number P. hassalli

Genital hooks more than sixteen in number 13

Genital hooks thirty-two in number 14

Caudal suckers large, adjacent but not contiguous,

pharynx, smaller than anterior sucker P. coranatum

Caudal suckers small, widely separated, pharynx equal in

size to anterior sucker P. microcotyle

Genital hooks more than thirty-two in number _. 17

Testis simple 18

Caudal suckers large, overlap P. megacotyle

Caudal suckers small, separated P. ocellatum

Testis branched P. kachugae

Genital hooks unequal in length P. ohlongum

Great hooks of caudal disc reduced or absent . 23

Genital hooks sixteen in number P. oriiculare

Genital hooks thirty-two in number P. opacum

1

( 6)

2

( 5)

3

( 4)

4

( 3)

5

( 2)

6

( 1)

7

(22)

8

(21)

9

(12)

10

(11)

11

(10)

12

( 9)

13

(16)

14

(15)

15

(14)

16

(13)

17

(20)

18

(19)

19

(18)

20

(17)

21

( 8)

22

( 7)

23

(24)

24

(23)

327] NORTH AMERICAN ASPIDOGASTRIDAE—STUNKARD 47

ASPIDOGASTRIDAE

Because of its peculiar multiloculate adhesive apparatus, Burmeister
(1856) called attention to the difference between the genus Aspidogaster
and the remainder of the trematodes, and suggested a division of the
Trematoda into (1) Malaeobothrii for the distomes and holostomes,
(2) Pectobothrii for the polystomes, and (3) Aspidobothrii for Aspido-
gaster. Subsequent writers however continued to include Aspidogaster
with the polystomes until Monticelli (1892) revived the classification
of Burmeister, but named the three suborders into which he divided the
trematodes, Heterocotylea, Aspidoeotylea, and Malacocotylea.

In the classification of Monticelli, the Aspidoeotylea contained the
single family Aspidobothridae. Poche (1907) proposed to make the
name of the family agree with the rules of zoological nomenclature
according to which "The name of the family is formed by adding the
ending -idae to the stem of the name of its type genus. ' ' Thus the name
of the family must become Aspidogastridae.

The family is of special interest to students of trematode mor-
phology. The form of the adhesive apparatus, with its retractile mar-
ginal organs, the separation of the body into dorsal and ventral portions
by a muscular partition, the sac-like alimentary tract, and the details
of the genital organs are peculiar to the group. The family contains
both eetoparasitic and endoparasitic species, forms with direct develop-
ment and at least one species which has an intermediate host, while the
hosts infested by the adult parasites include both invertebrates and
vertebrates, species having been reported from molluscs, fishes, and
turtles.

Summaries or revisions of the group have been made by Diesing
(1850, 1859), Tasehenberg (1879), Hoyle (1888), MonticeUi (1892),
Braun (1879-1893), and Nickerson (1902).

Only three species representing two genera of the family are known
from North America, Aspidogaster conchicola von Baer 1827, Cotylaspis
insignis Leidy 1856, and Cotylaspis cokeri Barker and Parsons 1914.
Eepresentatives of each of these species were available for the present
study. The first two species are well known; concerning A. conchicola
no further data were obtained, but a few corrections are made to former
descriptions of C. insignis.

48 ILLINOIS BIOLOGICAL MONOGRAPHS [328

Cotylaspis cokeri has been mentioned but once in print, but on the
basis of extended studies this form had been fully described and its
position as a new species demonstrated in a thesis submitted by the
writer in partial fulfillment for the degree of Master of Arts in the
Graduate school of the University of Illinois in June 1914. The fol-
lowing October Barker and Parsons (1914), having also been working
on this form independently, published a brief description naming it
Cotylaspis cokeri. Since I had completed my work on it before the
appearance of their note and the publication of their final report has
been delayed it seems proper to give here a detailed description of the
species.

ASPIDOGASTER CONCHIGOLA von Baer 1827

About fifty specimens from the pericardial and renal cavities of
Andonta corpulenta from Havana, Illinois, and a similar number of
specimens from the same organs of Quadrula undulata from North
Judson, Indiana, constitute the material of this species available for
study.

A detailed comparison of these specimens with the descriptions of
A. conchicola as given by Voeltzkow (1888), Stafford (1896), and other
writers, shows that they belong to that species and substantiates the obser-
vations of Leidy (1851), Kelly (1899), and Kofoid (1899), that A. con-
chicola occurs in this country. So far it is the only species in the genus
known from moUuscan hosts.

Kelly (1899) made a parasitological examination of 1537 individ-
uals of forty-four species of unios from Mt. Vernon, Iowa, Havana,
Illinois, and Lewisburg and Phoenixville, Pennsylvania, and included
in his report results of the examination of seventy-seven individuals
belonging to eighteen species, made by Kofoid in 1895 and 1896. In
four hundred thirty-five cases A. conchicola was found in the pericar-
dium only, in seventy-five in the kidneys only, and in one hundred
thirty-four cases both cavities contained the parasite. The presence of
the mature trematode in the pericardium and of eggs within the nephri-
dia was not infrequent. Of the 1537 specimens examined, forty-one
per cent were parasitized with A. conchicola and thirty-seven of the
forty-four species were infested with the parasite.

No further data on this species were obtained by the present study.

329] XORTH AMERICAN ASPIDOGASTRIDAE—STUNKARD 49

COTYLASPIS INSIGNIS Leidy 1856
[Figure 56]

The material of this species consists of specimens from Anodonta
inibecilis, A. corpulenta, LampsUis gracilis, and Unio pustulosis from
Havana, Illinois, and others from Anodonta ferrus and A. ovata from
Reed 's ' Lake near Grand Rapids, Michigan. The material proved to
belong to the same species and was identical with C. insignis Leidy.

Leidy first discovered the parasite in the Unionidae of the Schuyl-
kill River and founded the genus to receive the new species. His generic
and specific diagnosis (1858) follows: "Body curved infundibuliform,
anteriorly eylindro-conical, posteriorly expanding into a subcircular or
oval ventral disc with numerous acetabula arranged in a triple series.
Mouth infero-terminal, with prominent upper lip, and protractile into
a cup or disc like acetabulum. Intestinal apparatus as in Aspidogaster,
eyes two, distinct, black, situated on either side of the head. Generative
apertures inferior between the head and ventral disc."

According to the same author, C. insignis, the type species is:
' ' Translucent white or pink white, upper lip snout like, conical, ventral
disc crenate at the margin : acetabula twenty-nine, oblong quadrate, the
outer rows continuous in front and behind forming a circle. Length
from one-half to one line; ventral disc from one-fourth to one-half line
in diameter. Adheres to the outer surface of the renal organ and
upper margin of the foot, within the cleft of the upper branchial cavity
of Anodonta fluviatUis and A. lacustris."

Forbes (1896) reported this parasite in the river clams at Havana,
Illinois. Osborn (1898) described the species from Lake Chautauqua,
New York, as Platyaspis anadantae. Kofoid (1899) corrected this
error, demonstrating that Leidy 's genus is entitled to recognition, and
establishing the specific identity of Platyaspis anadantae Osborn with
C. insignis Leidy. Kelly (1899) reporting on the examination of over
sixteen hundred individuals of forty-four species of Unionidae found the
parasite in twenty-four different species of molluscs and in eighteen per
cent of the individuals examined.

Osborn (1904) gives a review of the literature, an account of the
distribution, habits, external and internal anatomy of the mature worm,
and a description of a very young individual. The young specimen
described has a simple ventral sucker, no eye spots, no marginal organs,
two entirely distinct excretory systems, and wholly separate pores. This
condition of the excretory system is compared with the condition in
redia and cercaria and according to Osborn favors the idea suggested
by Leuckart that the Aspidogastridae are sexually mature redia.

so ILUNOIS BIOLOGICAL MONOGRAPHS [330

COTYLASPIS COKERI Barker and Parsons 1914
[Figures 46 to 55, 57, 58]

From four to twenty-five specimens were found in the intestine
of each of seven specimens of Malacoclemmys lesueurii from Newton,
Texas.

The worms (Figs. 46, 47, 52) average 1.5 mm. in length by 0.7
mm. in width, altho there is considerable variation in relative length
and width due to the movements of the animal. The body is composed
of two parts, an anterior dorsal forebody and a posterior ventral adhe-
sive disc. "When extended (Fig. 46), the forebody has the shape of a
cornucopia, the larger end attached obliquely to the central two-thirds
of the dorsal surface of the adhesive disc. In this condition the worm
has an elongate form, projecting beyond the adhesive disc a distance
equal to the length of that structure: in a retracted condition (Fig. 52)
it is compact and may not project beyond the disc. The total length
of the worm varies therefore with the state of extension of the forebody,
from the length of the adhesive disc to twice that distance.

The adhesive disc (Figs. 47, 57) is a muscular organ, a multilocu-
late sucker, used for attachment and locomotion. It has a crenate oval
outline, the dorsal surface is arched, and the ventral surface is flattened.
The ventral surface is divided by two longitudinal and eleven cross
ridges into thirty-two acetabula, which are arranged in three rows;
there are twenty-two • peripheral alveoli enclosing ten median alveoli.
In this statement, the alveolus at either end is counted in the peripheral
rather than the median row, tho in location included in both. These
compartments change in shape with the movements of the animal, be-
coming oval or quadrangular. The shape and size of the disc are rela-
tively constant, measurements of the disc in twenty mounted toto speci-
mens vary only from 1.2 to 1.4 mm. in length and from 0.58 to 0.78
mm. in width. This structure recalls the moUuscan foot, and it has
often been termed the foot altho the morphological comparison is not
precise.

Movement consists of extension of the forebody, which furthermore
may be turned in any direction, and in the less striking and more re-
stricted movement of the disc. The disc has a tendency to turn up at
the edges, especially at the anterior and posterior ends. In adhesion
the organ may act as a unit, or the separate alveoli may function inde-
pendently. In locomotion there is a regular series of movements, the
forebody is extended and attached by the sucking action of the mouth
funnel, then the disc is loosened and the forebody contracted, bringing
the anterior part of the disc near the mouth, when the disc is attached

331] NORTH AMERICAN ASPIDOGASTRIDAE—STUNKARD 51

and the series of movements repeated. The worm moved rapidly across
the field of the microscope.

Body Covering. — Externally the worms are covered by a non-
cellular cuticula, which is thickest on the dorsal side of the body and
thinnest on the ventral surface of the adhesive disc (Figs. 49, 53). It
is without hooks or spines, and on the dorsal surface reaches a thickness
of 5/1, while on the ventral surface of the disc it is only about 1/* in
thickness. The cuticula is turned in at the external openings and lines
the external portions of the canals of the alimentary, excretory and
reproductive systems.

Musculature. — Immediately inside the cuticula is the three layered
dermo-muscular wall, circular longitudinal and oblique muscles occur-
ring in the order mentioned, the circular lying next to the cuticula
and in all parts of the wall being better developed than the others. The
musculature is delicate and in some places the longitudinal and oblique
muscles are very scanty. The musculature of the ventral side of the
forebody is continued posteriorly in a thin sheet, the so-called septum
or diaphragm (Fig. 53), which lies just above the limiting membrane
of the musculature of the disc and extends posteriad as far as the caudal
end of the cirrus sac. In C. insignis Osborn described this structure
as passing posteriad as far as the caudal end of the ovary and in other
genera it is more strongly developed. The parenchymous muscles of
the body are long, often much branched, and most abundant in locations
where they connect different parts of the body wall with each other or
with adjacent internal structures. In the anterior part are many well
developed muscles of this type used in the movement of that region.
Running longitudinally among the vitellaria, as well as dorso-ventrally
among the viscera there are many muscle fibers. Sphincters and dilators
occur at the genital pore, excretory pore, at the base of the mouth funnel,
and at the opening between the pharynx and the intestine.

The disc is separated from the forebody by a limiting membrane
(Figs. 49, 53). This membrane runs parallel to the general course of
the external ventral surface of the disc, projecting ventrad at each
ridge. Extending between this membrane and the external wall there
are muscle fibers, often much branched especially at the ends. The
ventral projections of the limiting membrane into the ridges of the
disc form two sides of long triangular prisms, which extend longitudi-
nally and transversely above the musculature of the disc. One face
of each of these prisms is dorsal and the opposite angles extend ventrad
forming the ridges which separate the disc into fossettes. These ridges
are composed of fibrous connective tissue in which a few nuclei are
embedded.

52 ILLINOIS BIOLOGICAL MONOGRAPHS [332

I
Alimentary Tract. — The mouth funnel is a cup shaped muscular
structure (Fig. 51) which functions as an organ of adhesion. There
is no oral sucker. The mouth funnel is 0.08 to 0.1 mm. in diameter,
sub-terminal in position. There is no prepharynx, the mouth funnel
opens directly into the pharynx. The latter is a spherical muscular
organ 0.09 to 0.1 mm. in diameter. As described by Osboru for C.
insignis, it is followed by a very short esophagus, which in the anterior
part has a cuticular lining and in the posterior part where the esopha-
gus passes over into the intestine, a lining of flattened epithelial cells.
The intestine is an elongate sac or tube extending on the dorsal side
of the body 0.1 to 0.2 mm. posterior to the caudal edge of the testis.
It varies but slightly in caliber, averaging about 0.075 mm. in diameter.
The wall consists of a fibro-membranous sheet upon which rests a layer
of columnar epithelial cells. The large deeply staining nuclei of the
epithelial cells lie in the basal part while many delicate elongate proc-
esses extend out into the lumen of the canal.

Male Reproductive Organs. — The testis is large, single, median, its
anterior margin lying at the center of the adhesive disc. It is almost
spherical and measures 0.25 to 0.35 mm. in diameter. Cells of various
sizes and with the chromatin material in various stages of division, as
well as mature spermatozoa are to be seen in sections. The sperm duet
arises at the anterior part of the testis and turns to the left, entering
the side of a long, much-coiled seminal vesicle (Fig. 48). This vesicle
is a large tube, 0.1 to 0.175 mm. in diameter, extending from the region
of the testis to the cirrus sac. It is coiled eight to sixteen times and in
aU mature specimens is filled with spermatozoa. Terminally it is con-
stricted into a small tube which enters the large cirrus sac. This latter
structure (Fig. 53) is 0.145 to 0.2 mm. wide and 0.2 to 0.25 mm. long,
has a strong muscular wall, and is pyriform in shape, the smaller end
opening anteriorly at the genital pore. Inside the cirrus sac there is
a dilated, curved portion of the duct which has muscular walls and is
lined with epithelial cells. Surrounding the duct and filling the cirrus
sac are the large cells of the prostate gland. These are pyriform and
average 26/n long by 17/i wide. In living specimens the cirrus was
observed in the extruded condition.

Female Reproductive Organs. — The ovary is a small organ, ovoid
in shape, averaging 0.16 mm. in length, 0.1 mm. in width, and 0.05 mm.
in thickness. It is located (Figs. 46, 52) at the right of the median
line, slightly anterior to the middle of the body. The oviduct arises
(Fig. 48) at the posterior ventral margin of the ovary and passes
posteriad; receives a short common vitelline duct, and then expands
into two or three irregular enlargements. Mehlis' gland is present, the

333] NORTH AMERICAN ASPIDOGASTRIDAE—STUNKARD 53

nuclei lying in the parenchyma around the ootype. The uterus passes
posteriad on the lateral side of the collecting duct of the excretory
system as far as the caudal end of the testis where it turns to the median
line. It passes ventrad and anteriad beneath the testis ; in front of the
testis it turns dorsad and toward the ovary, but just before reaching
the ovary it turns and crosses to the opposite side of the body and then
passes with little deviation to the genital pore. There is a strong sphinc-
ter at the distal end of the uterus (Fig. 54). Eggs were present at
various places in the course of the uterus and when the worms were
placed in tap water, the eggs near the pore were extruded. The eggs
are few in number, not more than six being present in any specimen.
They vary from 0.071 to 0.086 mm. in width and from 0.137 to 0.145
mm. in length. The average of twenty-five is 0.075 by 0.141 mm.

The vitellaria (Figs. 46, 49) are arranged along the sides of the
body, extending from the posterior end to the level of the cirrus sac.
The follicles are more numerous and closer together in the posterior
region, gradually becoming fewer in the anterior part of the vitelline
zone. They lie just above the limiting membrane which forms the
dorsal boundary of the musculature of the adhesive disc, and number
up to forty on each side. They vary in size, measuring from 10 to 40/ia
in diameter. In some specimens they appear to be arranged in a double
row on each side with the follicles placed alternately, but there is com-
mon and wide variation from this condition. Collecting ducts extend
along the median face of the vitellaria and at the level of the ootype
pass mediad where they unite to form a small receptacle which empties
into the ootype. In C. cokeri the vitelline follicles are smaller and fewer
in number than in C. insignis.

The genital pore (Fig. 54) is double, situated in the median line
on the ventral side of the forebody, dorsal and anterior to the adhesive
disc. There is no genital atrium, the two ducts open to the exterior
separately, the opening of the cirrus sac is on the right and that of the
metraterm is on the left. Barker and Parsons described a genital atrium
opening thru a common pore, but I fail to find such a structure. In
C. insignis, Osborn described a single genital opening and a genital
atrium, but in sections of C. insignis I find the same condition as in
C cokeri.

Excretory System. — Most of the observations on this system were
made on living specimens. As the water evaporated from under the
coverglass the worm was flattened and the larger excretory tubules
could be easily followed. The pore (Fig. 50) is median, dorsal, near
the posterior end of the body. There may or may not be a small papilla-
like prominence around the pore. There is a single excretory vesicle,

54 ILLINOIS BIOLOGICAL MOSOGRAPHS [334

situated between the large flask like ends of the collecting ducts and
the pore. In the pulsations of this organ, the anterior ventral part
contracted and the constriction passed posteriad and dorsad, expelling the
fluid thru the pore. The two collecting ducts extend cephalad from the
excretory vesicle, one on either side of the forebody, median to the vitel-
laria. Just posterior to the pharj'nx each duct divides, sending a branch
cephalad on the lateral side of the pharynx and anterior sucker, and a
second branch turns caudad. This caudal branch subdivides into a
branch leading to the region of the genital pore, and a longer larger
branch which passes posteriorly to the region of the testis and receives
many smaller side branches. Cross sections (Fig. 49) show the collect-
ing ducts to be dorsal in position. In morphological and histological
features the excretory system of C. cokeri is similar to that of C. insig-
nis. Osborn gives a comparison of the excretory system in that species
with the same system in other genera of the family.

Sensory Structures. — There is a dorsal nerve commissure crossing
the anterior part of the pharynx, and nerves were traced running ceph-
alad and caudad from it. In about half of the specimens mounted in
toto, a pair of black pigment spots is present on the dorsal commissure.
In others only a single spot is visible and in a few specimens none could
be found. In all the sectioned worms, however, both "eye spots" were
observed, altho in some they were very small and diflScult to find. These
structures are dorsal and anterior to the pharj-nx (Fig. 58) and consist
of a large number of black pigment granules. No lens is present.
Barker and Parsons report that ej-e spots were not found.

At the ends of the cross partitions of the adhesive disc are the mar-
ginal organs (Fig. 55). These structures occui* in the interstices be-
tween the muscular ridges of the ventral disc and its peripheral wall.
Such an organ consists of a fine tube about 20^ in length and l/i in di-
ameter, leading dorsad from the ventral surface of the ridge and termi-
nating in a large spherical cavity in the form of a bulb. The entire or-
gan is lined with cuticula, continuous with that of the external surface
of the body. The external half of the canal possesses a thick wall com-
posed of annular muscles, while the internal portion has a thin wall with
a few annular fibers and is often curved or looped. At the external end
of the inner portion there is a flask-like enlargement which is connected
with the heavy waUed region by a short constricted portion about 2,u in
length. Longitudinal fibers pass from the wall of the distal part of the
canal to points near its inner end or to the wall of the cavit}'. This lat-
ter structure is spherical or oval 15 to 20/i in diameter, and emptj' in
most of the sections. It has a fibro-membranous wall and in a few cases
is filled with homogenous granular substance or fluid. In other sections

335] NORTH AMERICAS ASPIDOGASTRIDAE—STUNKARD SS

the bulb contains a few granules or "concretionary bodies", but in struc-
ture these appear identical with the cuticular lining of the cavity. As
mentioned above the organs are located in the angles between the muscu-
lar ridges and the wall of the disc, and are set in a mass of non-staining
fibrous connective tissue. Some of the fibers pass dorsad from the bulb
between the muscular ridges to the limiting membrane of the disc, but
in appearance these are similar to the others and there is nothing to in-
dicate that they are nervous in character. However in one section,
stained with Heidenhain 's iron haematoxylin, there is a nerve fibril pass-
ing around the bulb and terminating on the inner end of the heavy walled
portion of the canal (Fig. 55). Other nervous structures were not ob-
served. The connective tissue contains manj^ nuclei, similar in size and
shape, and in no case was a connection between these nuclei and the
marginal organ observed. No glandular cells and no evidence of a se-
cretion were found. In the study of living specimens it was noted that
the marginal organs were everted and retracted as the worm moved.
Everted they appeared as membranous sacs and their movement was
rapid and precise. No evidence was found to indicate that these organs
possess a glandular function ; the character of their movement and the
nerve fibril leading to the canal as demonstrated incline the writer to re-
gard these structures as sensory.

Similar organs have been reported as present in all the genera of
the family except Stichocotyle. They were first noted in Aspidogaster
by Dujardin (1845) who described them as pores or orbicular glands.
Voeltzkow (1888) observed in Aspidogaster that they were protrusible
and retractile, and for this reason decided they were sensory. Monti-
celli (1892) described them in Cotylogaster michaelis and supported the
idea of their sensory character. Nickerson (1902) described in Cotylo-
gaster occidentalis a bundle of fibers which he regarded as a nerve en-
tering the bulb at its basal end, and a cluster of bipolar nerve cells lying
upon the side of the bulb against which the canal is coiled when retracted.
He stated that the presence of the bipolar cells establishes the sensory
character of these organs. He described the bulb as filled with vesicular
or granular material, and tho no nuclei were discernible, regarded
this as cytoplasm of granular cells in different stages of activity.

Loess (1902) in Lophotaspis vallei described two types of structures
as occurring in the interstices between the muscular ridges of the ventral
disc. Those around the periphery of the disc at the ends of the cross
ridges he called ' ' marginal bodies ' ' and those at the intersections of the
ridges he called "tentacles." The first he compared M'ith the marginal
organs of other aspidogastrid genera, and the tentacles differ only slightly
in details of structure. He stated there was nothing in the structure

56 ILLINOIS BIOLOGICAL MONOGRAPHS [336

of the marginal bodies to warrant the former belief in their sensory
character. Granules in the cavity he regarded as droplets of a secretion ;
and in the connective tissue dorsal to the cavity he described sac-like
spaces with fine granular contents, and he found also nuclei but was un-
certain whether they lay in the spaces or between them. The marginal
bodies he regarded as glandular organs altho doubtful as to their exact
function. He described the tentacles as having a spindle-shaped cavity
with glandular apparatus around the inner end, and a canal leading from
this blind end to the limiting membrane which formed the dorsal wall of
the musculature of the adhesive disc. He considered these structures as
adhesive or absorptive, but states that their physiological significance
was doubtful.

Osborn (1904) in C. insignis described the marginal organs as con-
sisting of three parts, the canal with its muscular wall, the cavity, and a
dorsal fibrous part. The fibrous part he regarded " as a trunk of nerve
fibers running at least to the muscles of the organ and perhaps partly
sensory as well." The central cavity possessed "a lining of moderate
thickness composed of cuticle outwardly but of nucleated epithelium on
the inner side." This cavity he found empty or with one or more "con-
cretionary objects. ' ' He says, ' ' This indicates that secretion is going on
the products being removed from time to time. I think the muscles de-
scribed above may be used in discharging these products, the longitudinal
fibers may act as dilators of the outlet, needed to enable such large ob-
jects to make their escape. ' ' Later he states, " I do not find in Cotylaspis
any evidence of a glandular structure in the fibrous part, and do con-
sider the bulbous part as epithelial and secretory."

The marginal organs apparently differ somewhat in structure in
the different genera. Of all the authors. Loess alone seems to have
morphological evidence for his conclusion that in Lophotaspis they are
glandular in character. The statement of Osborn that in Cotylaspis
insigtiis the bulb is partly lined with cuticula and partly with secretive
epithelium, I regard as doubtful. Certainly in my sections of that spe-
cies (Fig. 56) the bulb is lined with cuticula thruout. In the dorsal part
of the cavity shown there are many small structures but they appear to
be composed of the same material as the lining cavity. If they are cutic-
ular, this would argue against the glandular character of the organ since
in its functional activity the material wovild be swept out with the secre-
tion instead of accumulating and forming such large objects as he shows
in his figure. Furthermore it would be almost if not entirely impossible
for such large bodies to pass thru the small canal which leads to the ex-
terior. These "concretionary objects" are apparently the only basis
for Osborn 's claim that the organs are glandular since he stated that he

337] NORTH AMERICAN ASPIDOGASTRIDAE—STUNKARD 57

found no glandular structure in the fibrous part. Instead of supporting
I believe that they are subversive to the idea of the glandular nature of
th« organ.

In my material the fibers which pass dorsad from the bulb are iden-
tical in appearance with the adjacent connective tissue and do not ap-
pear to be nervous. The muscular wall of the canal is I believe, used
primarily in the eversion and retraction of the external part of the canal.
In living specimens under observation the everted part of the marginal
organ was about the size and shape of the thick-walled distal portion of
the canal, and this is probably the only part protrusible. With this ever-
sion, the base of the thick walled portion to which the nerve is distributed
would be at the tip of the everted structure in a position to function in a
sensory capacity.

Comparisons. — This is the third aspidocotylean described from tur-
tles, the two previously reported forms being Cotylaspis lenoiri Poirier
1886, and Lophotaspis valid Stossich 1899, both African species. Poirier
described C. lenoiri from the intestine of Tetrathyra vaillanti from Sen-
egal, and Looss (1902) reports it as occurring also inTrionyx notilica of
the Nile. Lophostaspis vallei is parasitic in the stomach of Thalassochelys
corticata. Cotylaspis cokeri is very different from Lophotaspis, but shows
considerable resemblance to C. lenoiri. However, a comparison of the
description of C. lenoiri with specimens of C. insignis and C. cokeri shows
decided difference in the size and shape of the worms and of the adhesive
disc, in the number of alveoli and marginal organs, in the sive of ovary
and testis, of cirrus sac, and of eggs. The three forms agree in essential
morphological features and fit the diagnosis of the genus Cotylaspis as
given by Leidy, but are equally clearly good species in that genus.

CLASSIFICATION OF THE FAMILY

The last classification of the Aspidogastridae was made by Nickerson
(1902). Since additions and changes have subsequently been made,
further revision seems advisable. The present arrangement is largely
based on the work of Nickerson and brings the classification to date.
Present information supports the validity of the following genera.

I. Aspidogaster von Baer 1827. Type species, A. conchicola von
Baer.

Oval adhesive disc, four rows of alveoli, marginal organs present,
mouth subterminal, no oral sucker, one testis.

This genus contains A. conchicola which infests the pericardium and
renal organs of various species of Unionidae in Europe and North Amer-
ica. It is also found in gastropods and in the immature condition in
th« intestine of Unionidae. Other species of this genus are A. limacoides

58 ILLINOIS BIOLOGICAL MONOGRAPHS [338

Diesing 1834 from the intestine of a fish (Leuciscus) in Europe, a form
which Stafford (1896) and Kofoid (1899) suspect of being identical with
A. co-nchicola. The species A. macdonaldi was placed in this genus by
Montieelli (1892) and removed to Lophotaspis by Looss (1902). Linton
(1905) described A. ringens from the intestine of Micropognon undula-
tus and Trachinotus carolimis at Beaufort, North Carolina. MacCallum
and MacCallum (1913) gave a more complete description of A. ringens
and described A. kemostoma n. sp., both from the intestine of Trachinotus
carolinus.

II. Cotylaspis Leidy 1857. Type species, C. insignis Leidy.
Oval adhesive disc, three rows of alveoli, marginal organs present,

mouth subterminal, no oral sucker, one testis.

This genvis contains the species C. insignis, C. lenoiri, and C. cokeri.
C. lenoiri was described by Poirier (1886) as a species of Aspidogaster.
Montieelli (1892) created a new genus Platyaspis to contain Poirier 's
species, evidently overlooking the similarity between it and the form re-
ported by Leidy. He declined to accept the genus Cotylaspis, suggesting
that C. insignis was a species of Aspidogaster. Braun (1879-1893) as-
cribed the species to Aspidogaster. Kofoid (1899) established the val-
idity of Leidy 's genus but contended that the genus Platyaspis should be
retained for Poirier 's species. Nickerson (1902) argued that tlije differ-
ences between the African and American species are not of generic im-
portance and suppressed the genus Platyaspis, making Aspidogaster
lenoiri Poirier and Platyaspis lenoiri (Poir. 1886) Montieelli 1892, syn-
onomous with Cotylaspis lenoiri Poir. Cotylaspis insignis occurs ectopara-
sitically in the mantle cavity of Unionidae in North America ; C. lenoiri
is from the intestine of Tetrathyra vaillanti of Africa; and C. cokeri is
from the intestine of Malacoclemys lesueurii of North America.

III. Macraspis Olsson 1868. Type species, M. elegans Olsson.

A single row of confluent acetabula in adhesive organ, marginal or-
gans present, mouth terminal, one testis.

The single species is parasitic in the gall bladder of Chimaera mon-
strosa, a fish from the coast of Europe.

IV. Stiehocotyle Cunningham 1884. Type species, S. nephropis
Cunningham.

A single row of more or less distinct acetabula, marginal organs lack-
ing, mouth subterminal, oral sucker absent, two testes.

Cunningham's original description was of the larva and Montieelli
(1892) declined to recognize its generic importance, thinking it might
be a form of Macraspis. Odhner (1898) by discovering the adult and
tracing the life history, established the genus. Adults live in the bile
ducts of the liver of rays ; larvae occur encysted in the wall of the intes-

339] NORTH AMERICAN ASPIDOGASTRIDAE—STUNKARD 59

tine of the larger marine Crustacea. Cunningham described it from the
Norwegian lobster, Nephrops, and Nickerson (1895) reported it from the
American lobster, Homarus americanus.

V. Cotylogaster Monticelli 1892. Type species, C. michaelis Mon-
ticelli.

Adhesive disc with three rows of alveoli, marginal organs present,
mouth terminal, oral sucker present, two testes.

Two species have been described ; C. michaelis occurs in the intestine
of Canthanis vulgarus, a European fish, and C. occidentalis Nickerson
1899 is parasitic in the intestine of Aplodinotus grunniens of North
America.

VI. Lophotaspis Looss 1902. Type species, L. vallei (Stossich)
1899.

Adhesive organ with four rows of alveoli, marginal organs present at
all the intersections of the ridges of the adhesive disc, cirrus absent.

Loos in 1901 reported L. adhaerens as belonging to a new genus of the
Aspidogastridae, but was not aware that Stossich two years before had
described the same form as Aspidogaster vallei. Looss later (1902) de-
scribed and figured the form under the name of Lophotaspis vallei. In the
same paper he compared A. macdonaldi with L. vallei and placed the
former species in the genus Lophotaspis. This trematode was reported
but not named by Macdonald in 1878, and named by Monticelli (1892)
as a species of Aspidogaster. Nickerson (1902) declared it to be an as-
pidogastrid, but different from all other known species, and predicted that
a new genus would have to be erected for it when its structure was better
known. Macdonald reported one hundred eighty extensile structures,
like the tentacles of a snail, occurring at the margins and intersections
of the ridges of the adhesive disc. Nothing is known of the internal
structure. Looss in placing the form in the genus Lophotaspis stated :
"Mit ihrer tentakeltragenden Bauchscheibe bildet die Art aber ganz
zweifellos einen fremden Eindringling in der Gattung Aspidogaster, da
dessen typischen Art jedenfalls solche Tentakel nicht besitzt. Qerade
diesen auffallended Character aber teilt sie mit Lophotaspis; bin ich
geneigt, A. macdonaldi Monticelli, trotzdem bei ihm die Genitaloffnung
weiter riickwarts liegt als bei Lophotaspis vallei, aus dem genus Aspido-
gaster herauszunehmen and zu Lophotaspis zu stellen."

60 ILLINOIS BIOLOGICAL MONOGRAPHS [340

PARAMPHISTOMIDAE

HISTORICAL. REVIEW OP THE FAMILY

The genus Amphistoma was created by Rudolphi (1801) ; concerning
it Stiles and Hassall (1908) state, "Rudolphi deliberately renamed a
previously validly named genus, namely Strigea Abildgaard, 1790, re-
ferring clearly to this fact both in 1801a, 50-51, and 1802b, 92. He makes
but one combination {Amphistoma siibclavatum) , but since Amphistoma
is clearly a new name proposed for an older one (Strigea), which Rud.
changed on the alleged ground that it was inappropriate, Amphistoma
should be suppressed in favor of Strigea and take the same species as
type."

Fischoeder (1903) stated: "In Bezug auf den Namen Amphisto-
mum ^vill ich jedoch, wie schon gesehen (1901), nochmals darauf hin-
weisen, dass der Name Amphistoma von Rudolphi (1801) als neue
Bezeichnung fiir die Gattung Strigea Abildg. 1790 eingefiihrtworden ist.
Der Name Amphistoma kommt daher nach dem Prioritatsgesetz als
synonym zu Strigea in Fortfall. Die urspriingliche einzige und also
aueh typische Art der Gattung Strigea Abildg. 1790 (Amphistoma Rud.
1801) M'ar Planaria strigis Goeze 1782 Amphistoma macrocephaliim Rud.
1809 Holostomum macrocephalum Nitsch. 1819) . Wenn daher der Name
Strigea wieder zu Geltung wieder bebracht werden soil, so darf er nur
fiir die heutige Gattung Holostomum weitergefiihrt werden, wahrend
die heutige Gattung Amphistomum einen anderen Namen erhalten
muss. Ich habe in: Zool. Anz. 1900, V. 24, p. 367 den Namen
Paramphistomum vorgeschlagen und, die Eintheilung nach dem Fehlen
Oder Vorhandensein der Pharyngealtaschen beibehaltend, in der Fam.
Paramphistomidae Fischdr. (Amphistomidae Montic. 1888) die Unter-
famUien Paramphistominae und Cladorchinae Fischdr. unterschieden.
In diesen beiden Unterfamilien lassen sich die bekannten Formen unter-
bringen. ' ' The names Paramphistomum and Paraphistomidae have been
accepted by Liihe, Looss, Odhner, and other writers and are used in this
paper.

The paramphistomes of mammals were the first forms of this family
discovered, and they have been the subjects of extensive study by Fisch-
oeder (1903) and Stiles and Goldberger (1910) ; a number of species are
known.

341] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 61

I have been unable to find any record of work done on the param-
phistomes of fish between that of Diesing (1836) and MacCallum (1905).
Daday (1907) described two species of Diplodiscus, two species of a new
genus he called Microrchis, three species of a new genus named Pseudo-
cladorchis, and added Amphistoma oxycephalus Dies, with two new
species to the genus Chiorchis. He included a section on the anatomy
and histology of the forms.

The only paramphistomes from amphibians are four species of Dip-
lodiscus reported from frogs : D. subclavatus from the frogs of Europe,
D. temperatus from those of North America, and D. megalochnis and
D. microchrus from Australian frogs.

Information concerning paramphistomes of reptiles is very scanty.
Braun (1901) lists three species from turtles: Amphistoma grande Dies-
ing, A. scleroporum Creplin, and A. sp. Bellingham. Bellingham (1844)
listed Amphistoma sp. from the intestine of Chelonia imbricata but gives
no description, so this species should receive no further consideration.
Braun (1901) supplemented the description of Creplin (1844) by a brief
report of the single specimen of A. scleroporum from the museum at
Greifswald, but the worm was sexually immature and consequently
the observations were limited. A. grande was collected by Natterer
from the intestine of five species of turtles in Brazil, but the descrip-
tion of Diesing is confined to the external appearance and the material
may have comprised more than one species. One other species is known
from turtles, a form described by Looss (1902) as A. spinulosum from
the intestine of Chelone mydas. The description of Looss is very com-
plete but because of the scarcity of known species and our limited knowl-
edge of the group, at that time he refrained from any attempt at classi-
fication. He stated that the species is probably closely related to A.
scleroporum and A. grande.

In addition to the description of the species, Looss (1902) discussed
the question of the oral sucker and the pharynx in the group and com-
piling evidence from comparative anatomy and embryology, he argued
that the anterior sucker of the amphistomes should be regarded as homolo-
gus to the oral sucker of the distomes. In this paper also he described
the muscular thickening at the caudal end of the esophagus as a pharynx
and described a peristaltic contraction of the organ from the anterior
to the posterior end, altho in an earlier paper (1896) he had stated that
the esophageal thickening of Gastrodiscus was not a true muscular
pharynx. Concerning this latter structure, Odhner (1911) says, "Ich
verwende diese Bezeichnung, weil es mir doch nicht so ganz sicher
erscheint, dass es sieh hier um ein dem gewohnlichen Distomenpharynx
homologes Organ handelt. Auch wenn es so ware, konnte iibrigens der

62 ILLINOIS BIOLOGICAL MONOGRAPHS [342

ziemlieh verschiedene Bau einen besondern Namen rechtf ertigen ; der
Oesophagiis miisste aber dann konsequenterweise als Praphar\iix
bezeichnet werden." In his later paper Looss (1912) referred to this
organ as an esophageal bulb.

The arrangement of the fibers in concentric lamellae and the func-
tion of the organ, acting as sphincter instead of a dilating pumping or-
' gan, argue against its homology with the pharynx of the distomes. These
conditions I found myself in the two species of the new genus Alasso-
stoma. However in the other of my new forms, Zygocotyle ceratosa, in
stead of concentric muscle lamellae, the fibers at the sides of the lumen
extend radially. A thickening of the esophageal musculature is de-
scribed for Gastrodiscus, Homalogaster, Diplodiscus, Microrchis, Chior-
chis, Schizamphistoma, Alassostoma, and Zygocotyle. In agreement with
Looss (1912), the MTiter regards the tube leading from the oral sucker
to the intestine at the esophagus and the muscular thickening of the
wall of the esophagus as an esophageal bulb.

In this same paper Looss (1912) reinvestigated the species Amphis-
toma scleroporum and described its structure in detail. Discussing the
taxonomy of the species he says, "Die Frage nach den Verwandtschaft-
lichen Bezeichnungen des Amp. scleroporum ist insofern leicht beant-
wortet, als seine enge Verwandtsehaft zu A. spinulosum, auf die ieh
schon friiher vermutungsweise hinwies (1902b, p. 437) jetzt offen zutage
tritt. Ich wiirde nicht zogern, beide Arten in dieselbe Gattung ein-
zureihen, wenn nicht gewisse, wenn auch kleine Differenzen im anatom-
ischen Baue existierten die meiner Auffassung nach innerhalb von wirk-
lich natvirlichen Gattungen nicht vorkommen. Diese Differenzen bes-
tehen, 1. in dem Fehlen des vor dem Mundsaugnapfe gelegenden starken
Sphincters von A. scleroporum bei A. spinulosum; 2. der Eeduction der
Saugnapftaschen, die bei A. spinulosum deutlich, bei A. scleroporum
nicht nach aussen hervortreten ; 3. dem Fehlen der kleinen Seitenzweige
an den vordersten Enden der Blasenschenkel von A. scleroporum bei
A. spinulosum; 4. in dem etwas abweichenden Bau der Dotterstocke (bei
A. scleroporum in der Mitte fast zusammen and ohne eigentliehe quere
Dottergange, bei A. spinulosum rein seitlich mit langen queren Dotter-
gangen) ; 5. in dem etwas verschiedenen Verhalten der Lymphschlauche
(ungemein reiche Verzweigung im Umkreise der Saugnapfe bei A.
scleroporum, kaum angedeutete Verzweigung bei A. spi7iulosum) . Bin
ich demnach auf Grande dieser Untersehiede auch iiberzeugt, dass in den
beiden Arten Eeprasentanten je eines besondern G^nus vorliegen, so
geniigt fiir meinen gegenwartigen Zweck doch die formelle Aufstellung
der Gattung Schizamphistomum fiir A. scleroporum, in die ich A. spinu-
losum vorlaufig provisorisch einbeziehe. Als die wesentlichen Charak-

343] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 63

tere dieser Gattung oder der Unterfamilie, zu der sie sich friiher oder
spater auswachsen wird, betrachtet ieh den Aufbau der Excretionblase
aus zwei sehr langen, bis ins Kopfende einfaclieii, unter sich uicht ver-
bundenen Schenkeln und den Aufbau des Lymphgefasssystemes aus
jederseits drei in der Umgebung der Saugnapfe verastelten Schlauchen."

He might well have added to his list of differences that in S. spinu-
losum there is a single loop of the excretory vesicle wound dorsally
over the cecum of each side while in S. scleroporum there are eight loops
winding irregularly around the cecum of each side. In the same article
(p. 355) speaking of the excretory system in paramphistomes of mammals
he says this system is situated deep in the body and in the larger groups
is a stable and conservative organsystem. In a former paper Looss
(1902 :837) says, "Zwisehen der Species einer natiirlichen Gattung
bestehen anatomische Unterschiede nieht; die Speciescharaktere werden
dargesteUt allein durch Differenzen in der Grosse des Korpers und der
einzelnen Organe, Hand in Hand mit denen leichte Veranderungen ihrer
Form, ihrer Lage und wenn sie reieher gegliedert oder in eine Anzahl
von Theilstiicken zerfallen sind, Aenderungen in der Zahl der Glieder
resp. der Theilstiicke gehen konnen." As a matter of fact, the argument
of Looss in my opinion appears to show clearly that S. scleroporum and
S. spinulosum are not members of the same genus; as indeed he has al-
ready suggested himself that in future researches a new genus will have
to be created to contain S. spinulosum.

The single paramphistome reported from snakes was described ^by
Cohn (1903) as Amphistomum dolichocotyle, and in his (1904) classifi-
cation of the Diplodiscinae placed in the genus Catadiscus. It is from
the intestine of Herpetodryas fuscus.

The only paramphistomes previously known from North America
are Amphistoma grande, reported by Leidy (1888) from the intestine of
the terrapin; two specimens from the small intestine of the muskrat
which according to the same author, "appear to belong to Amphistoma
subtriqiietrum" ; Diplodiscus temperatus Stafford long considered iden-
tical with D. suiclavatus Dies. ; and Wardius ziiethicus Barker and
East, from the cecum of Fiber zibethicus. The reports of Leidy contain
no description except the length of the worms. Barker and East suspect
that Leidy 's specimens from the muskrat belong to their new genus and
species Wardius zibethicus; and it is not unlikely that the specimens from
the terrapin are specifically identical with those described here as Alasso-
stoma magnum Stunkard 1916. Neither the description of Stafford
nor that of Barker and East contains complete anatomical information.
Stafford distinguished between the lymph and excretory systems.
Barker and East make no mention of the lymph system; they

64 ILLINOIS BIOLOGICAL MONOGRAPHS [344

state that the oral sucker is wanting and describe the anterior sucker as
the pharynx, notwithstanding the arguments of Pratt (1900), Looss
(1902) and Stiles and Goldberger (1910) that the anterior sucker of the
amphistomes is homologous with the oral sucker of the distomes.

The material of this family available for the present study consisted
of representatives of two species from North American turtles, and an-
other species from the duck, Anas platyrhynchos. A study of the liter-
ature showed that these forms could not be included in any previously
described genera.

THE GENUS ALASSOSTOMA

A new genus Alassostoma is formed to include the two species from
turtles. The genus is characterized by the presence of large oral evag-
inations which open independently into the oral sucker, an esophageal
bulb composed of concentric muscle lamellae, a hermaphroditic duct,
germ glands near the middle of the body in the median line, both testes
anterior to the ovary, vitellaria consisting of small scattered follicles in
the lateral, and posteriorly in median areas of the body, Laurer's canal
opening in the mid-dorsal line anterior to the opening of the excretory
vesicle. Alassostoma magnum is to be taken as type of the genus, and
in it is included also the new species A. parvum.

The genus Alassostoma has the type of lymph and excretory systems
present in the genus Schizamphistoma and designated by Looss as char-
acteristic of the subfamily to which that genus belongs. Looss (1912)
predicted that with the discovery of other forms it would be necessary
to create a new subfamily to contain them, and at that time stated the
subfamily characters. With the discovery of a second genus, so similar
to Schizamphistoma that the two must be included in the same subfamily,
the formal recognition of the new subfamily is necessary. Schizamphis-
toma Looss was designated as type and the name of the subfamily be-
comes Schizamphistominae. The subfamily contains the genera Schiz-
amphistoma, including also S. spinulosum which as already indicated by
Looss and discussed in this paper is tj'pe of a new genus, and the genus
Alassostoma. The distinguishing characters of the subfamily as stated
by Looss are two long excretory vesicles which extend singly to the an-
terior end of the body and a lymph system composed of three canals on
either side of the body which run longitudinally and break up into many
sinuses in the regions of the suckers.

Comparisons. — When one compares the species A. magnum, and A.
parvum with descriptions in the literature, they are seen to agree most
closely with Schizamphistomum scleroporum and S. spinulosum Looss.

345] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 65

Mention has previously been made of the anatomical differences existing
between these species and a statement ventured that such wide and fun-
damental differences should not be present in a natural genus. A. mag-
num agrees with S. scleroporum in general appearance and size, in type
of excretory and lymph systems, character of vitellaria, and in
general type of reproductive and alimentary organs; but A. mag-
num has large oral evaginations, which pockets are reduced and do not
extend outside the sucker in S. scleroporum, and A. magnum lacks the
preoral sphincter which is present in ;Si. scleroporum. In A. magnum
the uterus and cirrus sac open to the surface thru a common hermaphro-
ditic duct; in S. scleroporum they open separately. Looss (1899 : 551)
says one of the most important of generic characters is the structure of
the copulatory organs. In A. magnum the testes are further posteriad
and the ovary is situated one-fourth to one-third of the body length from
the posterior end instead of at the level of the anterior margin of the
acetabulum as is the case in S. scleroporum. In S. scleroporum the testes
and ovary are widely separated and in A. magnum they are compara-
tively close together. These differences appear to be of sufficient impor-
tance to exclude the American species from the genus Schizamphistoma.

A. magnum agrees with S. spinulosum in the presence of oral evag-
inations and lack of preoral sphincter, but differs from it in the manner
of the coiling of the excretory vesicles, in the presence of a common herm-
aphroditic duct and in the character of the vitellaria, as well as the rela-
tive positions of the testes and ovary. The morphological facts show
differences too fundamental to permit the inclusion of both these species
in a single genus.

Alassostoma parvum agrees with A. magnum in general morpho-
logical features, presence of oral evaginations,, lack of preoral
sphincter, type of lymph and secretory systems, character of geni-
tal organs and ducts, also in relative position of testes and ovary. A.
parvum therefore agrees with and differs from S. scleroporum and S.
spinulosum in the same manner as A. mxignum. That the two forms are
not different developmental stages of the same species is shown by the
great difference in the size of the worms and the relative differences in
the size of suckers and genital organs. One of the species of A. magnum
10 mm. long is not sexually mature, while in the sectioned specimen of A.
parvum which is less that 3 mm. long spermatoza were present in the tes-
tes and vas deferens. Further, ova were present in the oviduct, and tlie
ootype and anterior part of the uterus were filled with spermatoza.
Eggs were present in only one of the seven specimens of A. magnum and
the absence of eggs in the three specimens of A. parvum does not signify
that it is a young stage of A. mxignum. A. magnum is large and has

66 ILLINOIS BIOLOGICAL MONOGRAPHS [346

small suckers and A. parvum is small and has relatively large suckers,
and this feature suggested the name Alassostoma.

ALASSOSTOMA MAGNUM Stunkard 1916
[Figures 59 to 65]

The material of this species consists of one worm from Pseudemys
troosti from Havana, Illinois ; one from P. elegans from the same locality ;
two from P. elegans from Chicago, Illinois ; and three specimens from an
unknown turtle from Marshall, Missouri. The first four specimens were
collected by the writer from the large intestine near its juncture with
the small intestine, and the material from Marshall, Mo.,bears the label,
"From cloaca of turtle."

In the preserved state the worms are 10 to 12 mm. in length, 3 to 5
mm. in breadth, and 1.5 to 2 mm. in thickness. One specimen studied
in the living condition, measured 18 mm. in length when fully extended ;
preserved it is 11 mm. long, 3.8 mm. wide and 2 mm. thick. One fixed
specimen 10 mm. long and 3 mm. wide is not sexually mature.

In the living state the worms are clear, hyaline, with the digestive
ceca visible as brown lines. Their movements are very slow. In shape
(Fig. 59) they are more or less oval, with the acetabulum forming
a slight caudal projection. The acetabulum is slightly sub-terminal, cir-
cular or ovoid, usually wider near the anterior than the posterior end.
The opening is necessarily relatively narrower than the sucker itself, in
one specimen the opening is merely a slit, 1.4 mm. long, 0.38 mm. wide
near the anterior end and posteriorly tapering to a point. In the largest
specimens the acetabulum is 2.5 mm. long by 2 mm. wide, and in the
smallest it is 2 mm. by 2 mm.

The cuticular covering of the body is unarmed, and measures 10 to
12/i in thickness. It is turned in at the openings of the excretory and
reproductive systems and lines the digestive tract to the bifurcation.
The dermo-muscular wall has the circular, longitudinal, and oblique layers
well developed and inside the oblique layer there is an additional layer
of longitudinal fibers (Pig. 60). Dorso-ventral fibers are scanty or
lacking and the parenchyma of the bodv is very loose and vacuolated
(Fig. 64).

Alimentary tract. — The oral sucker is terminal, spherical to ovoid
in shape, usually longer in the antero-posterior axis and somewhat wider
anteriorly than posteriorly. It is deeply set in the parenchyma of the
body and measures 0.9 to 1.35 mm. in length and 0.6 to 0.9 mm. in width.
Radial fibers pass from the external limiting membrane to the cuticxda
lining the sucker; in a cross section thru the sucker (Fig. 65), the inside

347] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 67

two-thirds of the outer half is a nuclear zone and all the nuclei are col-
lected in this area. Half way between the nuclear zone and the lumen
there is a narrow band of circular fibers. The oral evaginations arise at
the caudal end of the oral sucker by two separate openings, one on either
side, and extend dorsad and caudad. They are 0.35 to 0.6 mm. long,
flattened dorso-ventrally, 0.15 to 0.2 mm. in width. These sacs are lined
with cuticula and their wall is continuous with that of the oral sucker.
Externally there is a layer of longitudinal fibers and inside this sets of
annular fibers (Fig. 63). Oblique and radial fibers are occasionally seen
but are very scanty.

The esophagus is 0.6 to 1.3 mm. in length ; it is lined with cuticida
and the wall contains external longitudinal and internal annular fibers.
At the caudal end of the esophagus, just anterior to the bifurcation of
the alimentary tract, there is a prominent esophageal bulb. It varies
from 0.65 to 0.95 mm. in length and from 0.33 to 0.5 mm. in width; it
is formed by a thickening of the annular fibers of the wall of the esoph- '
agus. A cross section is represented in Figure 60 and shows the eighteen
concentric lamellae of muscles. No nuclei are present in these annular
muscles. Both the oral evaginations and the esophagus are surrounded
by clusters of deeply staining cells (Fig. 63). Looss (1896) described
similar cells in Gastrodiscus and believed they secrete the lining of the
esophagus. The ceca are flattened laterally and are of very unequal
caliber, small lateral evaginations occur on opposite sides at the same
level recalling the condition in some of the Turbellaria. The diverticula
extend almost to the acetablum, about 0.37 mm. intervening. They have
a muscular coat consisting of external annular and internal longitudinal
fibers and an epithelial lining of columnar cells which show faint long-
itudinal striations (Fig. 62).

Male Reproductive Organs. — The testes are slightly lobed, oval,
longer in the transverse diameter, and vary in size from 0.27 by 0.35 mm.
to 0.45 by 0.9 mm. They are situated one behind the other or in con-
tracted specimens slightly on opposite sides of the median line. They
are approximately the same size in any one specimen and are separated
by about the length of one of the testes, tho in contracted specimens they
may lie closer together. The vasa efferentia arise from the dorsal anter-
ior margins, the duct from the posterior testis on the left and the duct
from the anterior testis on the right side of the body. They pass dorsad
and cephalad, and 0.4 to 0.5 mm. caudad of the bifurcation of the diges-
tive tract they unite to form a much coiled seminal vesicle, which near
the pore passes into a small, poorly developed cirrus sac. In sectioned
individuals it could be seen that the seminal vesicle was filled with sper-
matoza. In one specimen the coils of the vesicle extend thru twenty

68 ILLINOIS BIOLOGICAL MONOGRAPHS (348

cross sections each 15/i in thiqlmess, and the tube is so coiled that in a
section of the worm there are ten or fifteen sections of the vesicle. In an-
other individual cut in frontal sections the seminal vesicle extends antero-
posteriorly thru 0.57 mm. The prostate gland is enclosed by the cirrus
sac and fills the entire region between the wall and the central canal.
The cells are more numerous in the posterior part of the sac, gradually
becoming fewer in the anterior region. The sac is approximately 0.37
mm. long and 0.185 mm. in diameter. It is dorsal on the right side of
the body, and the terminal end of the uterus is ventral on the left side
of the body.

Female Reproductive Organs. — The ovary is spherical or oval, 0.275
to 0.35 mm. in length and 0.33 to 0.57 mm. in width, in or near the me-
dian line, about the width of the caudal testis behind the latter. The
oviduct is very small and arises from the dorsal margin of the ovary (Fig.
61). After a coil posteriad Laurer's canal is given off and passes in a
winding course to the dorsal surface. There is no receptaculum seminis.
Just after the origin of Laurer's canal, the oviduct passes into ilehlis'
gland, where the vitelline duct is received. There is no vitelline re-
ceptacle in either of the sectioned worms, but the right and left ducts are
very large. They meet in the median line posterior and ventral to
Mehlis' gland, and a duct passes to the ootype. The uterus coils an-
teriad, either between or around the testes and opens thru the hermaphro-
ditic duct to the genital pore.

The genital pore is in the median line ventral to the esophageal bulb,
and there is a small genital sinus. The cirrus sac and metraterraal por-
tion of the uterus open to the exterior thru a common hermaphroditic
duct (Fig. 60).

The viteUaria consist of smaU irregularly shaped follicles, lying al-
most entirely in the ventral half of the body and extending from the re-
gion of the cephalic testis to the caudal ends of the ceca. Anteriorly
they are extracecal, but posteriorly they extend into the intracecal area ;
near the ends of the ceca about half of the follicles are between the di-
verticida.

Eggs were present in only one specimen. Here there were three;
they measured 0.1 by 0.13 mm.

Lymph System. — This system consists of three canals passing long-
itudinally on either side of the body, one lateral and two mesal of each
cecum. Of the median pair, one is dorsal and the other ventral (Fig.
59). These canals are not straight but wind about and give off branches
at various points. These branches subdivide in turn and at the ends the
main trunk breaks up into numerous smaller branches so that the entire
body is penetrated by ramifications of this system. The ceca, the genital

349] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 69

organs, and the suckers are especially well supplied with lymph sinuses.
Excretory System. — The excretory pore is in the median line on the
dorsal surface, near the posterior end of the body, and the median termi-
nal vesicle extends internally and anteriorly. It gives off a brancli to
either side and these branches of the collecting vesicle pass anteriad,
winding about the cecum of either side in many loops or coils. In sections
(Fig. 64) the tube may appear on either side, above, or below the cecum;
in a single section it may be cut in two or three places or a loop may puss
half to two-thirds of the way around the cecum. No connections between
the collecting ducts of the two sides could be seen, and they were traced
to the region of the oral sucker.

ALASSOSTOMA PARVUM Stunkard 1916

[Figures 66 to 71]

Three individuals of this species were collected from the cloaca of
a single specimen of Chelydra serpentina from Urbana, Illinois. One
was retained as an alcoholic specimen, one was stained and mounted as
a toto preparation, and the third was cut into cross sections.

The worms (Fig. 66) are thick with almost parallel sides, rounded at
the posterior end and tapering slightly anteriorly. Just in front of the
acetabulum the body narrows slightly and then widens posteriorly due
to the presence of two lateral prominences or evaginations, one on either
side at the level of the anterior part of the acetabulum. The worms are
2.8 to 3 mm. long and 0.78 to 0.08 mm. wide, the points of greatest width
are at the level of the testes and thru the posterior lateral prominences.
The sectioned worm is 0.8 mm. in width and 0.54 mm. in thickness. The
acetabulum is subterminal, oval, 0.8 mm. in length and 0.7 mm. in width
in the toto preparation. The inside measurements of the same sucker
are 0.56 mm. in length by 0.4 mm. in width and the opening is 0.45 mm.
in length and 0.21 mm. in greatest width.

Alimentary Tract. — The oral sucker is terminal, ovoid, 0.46 mm.
long by 0.37 mm. wide, and in the sectioned worm 0.32 mm. in depth.
In the mounted specimen tlie sucker is widest posteriorly, and from the
posterior dorsal part on either side there is an oral evagination. These
arise separately and are 0.055 mm. long. Among the fibers of the oral
sucker there are many nuclei; they are situated in the peripheral half
of the sucker and are confined to the central two-thirds of the external
half. There are also among the muscle fibers glandular cells with ducts
to the lumen of the sucker. The esophagus is somewhat coiled but ex-
tends thru 0.2 mm. and is surrounded by large deeply staining gland
cells. The posterior part is enlarged by the thickening of the annular
muscles of the wall which forms the esophageal bulb (Fig. 70). This

70 ILLINOIS BIOLOGICAL MONOGRAPHS [350

structure comprises twelve concentric rings or lamellae of muscles. It
is 0.2 mm. long by 0.14 ram. wide in the toto specimen and 0.314 mm. in
depth in the sectioned individual. The diverticula extend posteriad al-
most to the cephalic margin of the acetabulum. In sections they are oval,
and flattened laterally. In the intestine of the sectioned worm there are
masses of small nuclei, possibly from the epithelial lining of the cloaca
of the host.

Male Reproductive Organs. — The testes are oval, in the toto speci-
men they are 0.17 mm. long by 0.17 mm. wide, and in the sectioned worm
0.17 mm. wide by 0.29 ram. thick. They are situated one in front of the
other in the median line and in the ventral part of the body. They are
close together, separated only by a thin fibrous sheet. The vasa eileren-
tia arise at the dorsal margins of the testes; the duct from the caudal
testis pass anteriad and anterior to the cephalic testis unites with the
duct from this latter testis. The vas deferens immediately expands into
a long much-coiled seminal vesicle whieli passes anteriad and into the
cirrus sac (Fig. 69). Inside the cirrus sac the tube continues in large
coils; the terminal part is surrounded by the cells of the prostate gland
and opens to the surface thru a short hermaphroditic duct. There is a
small genital papilla (Fig. 71).

Female Reproductive Organs. — The ovary is oval ; in the toto speci-
men it is 0.098 mm. long and 0.088 mm. wide, and in the sectioned worm
it is 0.95 mra. wide and 0.134 mm. thick. It is median in position and
situated midway between anterior and posterior ends of the body. The
oviduct arises at the dorsal posterior margin and passes dorsad and pos-
teriad' into Melilis' gland. This gland is large and well developed.
Here Laurer's canal is given off and passes in short coils to the dorsal
surface. Just after the origin of Laurer's canal a short common vitelline
duct opens into the ootype and the oviduct passes ventrad. It expands
to form the initial part of the uterus, turns anteriad, and is filled witJi
masses of spermatoza. The expanded portion of the iiterus extends an-
teriad half the distance to the caudal testis and then the tube contracts,
passes dorsad and in a winding course over the testes. Anterior to the
testes it turns ventrad and enters the hermaphroditic duct on the pos-
terior ventral side. The vitellaria extend from the region of the testes
to the caudal ends of the digestive ceca and consist of scattered lobes,
mostly ventral in position. Anteriorly they are extracecal but behind
the ovary they are intracecal as well.

No eggs were present in any of the specimens.

The genital pore is in the midventral line, just posteror to the bi-
furcation of the alimentary tract. There is a genital sinus but no geni-
tal sucker.

351] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 71

Lymph System. — The lymph system is similar to that described for
A. magnum and consists of the three longitudinal canals on either side
of the body, one canal lateral to each cecum and a pair, one dorsal and
the other ventral, mesal to the diverticulum of either side. The secon-
dary branchings could not be traced but lymph sinuses are present in sec-
tions in all parts of the body, and those around the acetabulum are shown
in Figure 68.

Excretory System. — The excretory pore is median, dorsal, at the
level of the cephalic margin of the acetabulum. A short median vesicle
passes ventrad and anteriad and divides into two collecting vesicles as in
A. magnum. These pass ventrad and posteriad, one on either side, loop
around the caudal ends of the diverticula, and then turn anteriad, wind-
ing around the ceca in many irregular coils so that in sections they ap-
pear lateral, mesal, ventral or dorsal to the intestine; often the tube is
cut two or three times in the same section or a single section may show
a coil encircling the cecum for half or more of its circumference (Fig.
67). Anterior to the bifurcation of the alimentary tract the ducts con-
tinue in the lateral areas of the body and can be traced almost to the oral
sucker.

THE GENUS ZYGOCOTYLE

The only known form with which the paramphistomes from the duck
can be compared is Amphistoma lunatum. This species was described
by Diesing (1836) ; the material had been collected by Natterer in Brazil,
South America, from the cecum of Anas melanotus, A. ipecutiri, A.
'tnoschata, Himantopus wUsonii, and also from the cecum of Cervus
dichotomus. Fishoeder secured the original specimens from the Vienna
museum and (1903) gave a more extended description of the form, altho
his study was restricted to the examination of toto preparations. He
stated that the citation of Cervus dichotomus as a host of this form is
probably an error, and the same suspicion had been mentioned by Diesing
(1850). It is at once apparent that the present species is very similar
to A. lunatum. Both are parasites of American ducks, and are the only
paramphistomes at present known from avian hosts. They are nearly
equal in size, are similar in shape, have a subterminal oral sucker, re-
productive systems that compare very closely, digestive tracts similar
in character, and acetabula of the same form consisting of an anterior
section and a posterior overhanging lip which terminates on either side
in a small cone-like projection.

Amphistoma lunatum has been placed as an appendix to every classi-
fication of the paramphistomes that has ever been attempted. With the
discovery of a form so similar, the two must belong together and a
new genus is proposed to contain the two species. The peculiar divided

72 ILLINOIS BIOLOGICAL MOXOGRAPHS [352

condition of the acetabulum suggested the name Zygocotylo as appropriate
for this genus. Zygocotyle ceratosa has been designated as tj-pe and in
the genus is included also the species Amphistoma lunatum.

As diagnostic characters of the genus Zygocotyle may be mentioned
the subterminal oral sucker, the posterior sucker divided or provided
with caudal overhanging lip, absence of cirrus sac and separate openings
of the male and female ducts. Others Avill undoubtedly appear when
the character of the excretory and lymph systems are known. The genus
Zygocotyle differs from all other known genera of the Paramphistomidae
in the ventral position of the oral sucker and the peculiar character of
the acetabulum. It differs from the Gastrodiscinae in the shape of body
and absence of ventral papillae, and from the Gastrothylacinae in the ab-
sence of the ventral pouch. In the lobed testes and absence of cirrus
sac it agrees with the Paramphistominae, but the oral evaginations ex-
clude it from that group. The absence of cirrus sac and the lobed form
of the testes will not permit its inclusion with the Cladorehinae. The
characters of the Diplodiscinae are so poorly defined that a comparison
is unsatisfactory ; in this group however, a cirrus sac is present and both
suckers are terminal. As none of the existing subfamilies will include
the genus, a new subfamily will probably have to be made to contain it.
Since the present classification of the Paramphistomidae is somewhat un-
certain, and the structure of the excretory and lymph systems of this
genus are as yet unknown, no further attempt at classification of the
group is made at this time.

ZYGOCOTYLE CERATOSA Stunkard 1916
[Figures 72 to 79]

The material of this species consists of eight specimens from the in-
testine of Anas platyrhynchos from Rock County, Nebraska. The intes-
tine of the duck had been cut open in places and together with its con-
,tents preserved in formalin. The fixation of the parasites is so poor
,that the excretory and lymph system can not be traced, altho remnants
of both appear in sections.

These worms (Fig. 72) vary in length from 3 to 6 mm. and in width
from 1.45 to 2.14 mm. In dorsal or ventral aspect they are elongate oval
jn shape with the acetabulum forming a small terminal projection. The
cross section is a flattened oval and toward the ends of the body becomes
more circular. The acetabulum is subterminal and consists of two parts
(Fig. 77), an anterior part extending dorsally and anteriorl.v into the
body and a posterior overhanging lip which terminates on either side
in a little horn or conical projection 0.12 to 0.2 mm. in length. The

353] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD IZ

.cephalic part extends anteriad about 0.46 mm. from the anterior margin
pf the opening of the sucker. The opening of the acetabulum is oval
approximately 1.1 mm. in length and 0.74 mm. in diameter. The sep-
tum or partition which divides the sucker extends almost to the opening
^nd appears to separate an anterior circular part from the remaining
portion but there is a single oval opening of the acetabulum.

The euticula is unarmed, slightly thicker on the dorsal surface. On
the ventral surface it is about 12/x in thickness and reaches 30/ti in thick-
ness on the dorsal surface. It is not homogeneous, but is traversed by
fine crinkled lines extending from internal to external surfaces, which
give it a reticulated appearance. The entire dorsal surface of the body
is underlaid with large gland cells filled with a substance staining deeply
with haematoxylin ; and their ducts lead to the dorsal surface. The con-
tents of the gland cells and their duets have the same appearance and
staining reaction as the euticula of the external surface. The dermo-
piuseular sac consists of the usual circular, longitudinal, and oblique
layers, the circular layer is next to the euticula. From the body wall
there are many large dorso-ventral muscle strands extending thru the
body.

Alimentary Tract. — The oral sucker is subterminal, circular or
slightly oval in shape, 0.37 to 0.53 mm. in diameter. The oral evagina-
tions are 0.15 to 0.22 mm. in length and 0.07 to 0.1 mm. broad ; they
branch one on either side from a common sinus (Fig. 74) which opens
into the dorsal side of the posterior part of the oral sucker. The esoph-
agus leads from the oral sucker to the intestine ; it is 0.05 to 0.37 mm.
in length and is surrounded by a layer of deeply staining cells. Its
caudal portion is surrounded by an esophageal bulb. This structure is
oval, 0.2 to 0.45 mm. in length, 0.18 to 0.23 mm. in width, and 0.35 mm.
in thickness in the specimen cut in cross sections. It is situated obliquely
in the body, the anterior end is ventral and the posterior end more dorsal
in position. The muscles are not arranged in concentric lamellae as in
the previously described paramphistomes ; there is a capsule of external
longitudinal fibers and the body of the organ is composed of fibers ex-
tending on the sides from the central canal to the external capsule and
above and below the canal the fibers extend across from the lateral walls
of the bulb (Fig. 73). The alimentary tract is lined with euticula to
the bifurcation. The ceca are flattened laterally and the lateral walls
are sinuous giving them a very irregular appearance. They have a mus-
cular wall composed of outer circular and inner longitudinal fibers and
extend almost to the opening of the acetabulum, about 0.1 to 0.15 mm.
intervening. They terminate just caudad of the excretory pore.

Male Reproductive Organs. — The testes lie one behind the other in

74 ILLIXOIS BIOLOGICAL MONOGRAPHS [3S4

the median line, the caudal testis is almost in the center of the body, and
the cephalic testis is about 0.2 mm. in front of it. They are about the
same size, lobulated, oval, crosswise of the body, almost touching the
cecum of either side. They are ventral in position, almost touching the
ventral body wall and not extending far into the dorsal half of the worm.
They vary in size from 0.2 by 0.3 mm. in the smallest to 0.55 by 0.78 mm.
in the largest specimen. The vasa efferentia arise from the anterior
dorsal margins, the right tube from the anterior and the left tube from
the posterior testis. Near the genital pore they unite and form a much
coiled seminal vesicle which has a thickened muscular wall. This struc-
ture extends thru twenty-five cross sections cut lO/i thick. The termi-
nal part that leads ventrad to the genital pore is expanded, the walls are
thinner, and this part is surrounded by the cells of prostate gland. A
cirrus sac is absent, the male and female tubes open to the exterior in-
dependently at the apex of a slight ventral prominence. The opening
of the male duct is immediately anterior to that of the female (Fig. 78).

Female Reproductive Organs. — The ovary is oval, lobulated, cross-
wise of the body, about the shorter diameter of the testis behind that or-
gan. In the smallest specimens it is 0.2 by 0.33 mm. and in the largest
0.33 by 0.52 mm. The oviduct arises at the dorsal margin as a very small
tube and passes dorsad where Laurer's canal is given off. This canal
winds in short curves to the dorsal surface, opening anterior to the ex-
cretorj' pore (Fig. 79). After the origin of Laurer's canal the oviduct
passes posteriad and ventrad into Mehlis' gland where a short common
vitelline duct is received. The uterus then coils irregularly in close folds
to the genital pore. The uterine coils are largely in the dorsal part of
the worm altho they may extend into the ventral portion and coil around
the testes. Laterally the coils of the uterus are limited by the ceca. The
terminal part has a slight thickening of the wall but not a distinct de-
limited metraterm. The vitellaria are well developed, large follicles ex-
tending in the extracecal areas from the level of the pasterior edge of
the oral sucker to the anterior margin of the opening of the acetabulum.
They are limited medially by the ceca and laterally extend almost to the
body wall. They are more ventral than dorsal in position.

Eggs are present in large numbers. In size they average 0.14 by
0.083 mm.

Comparison. — Zygocotyle ceratosa agrees with Z. lunata in length,
width, and size of oral sucker, but in the former species the oral evagi-
nations are smaller, the esophagus is much shorter, the testes and ovary
are oval and lobed instead of circular, and the ceca do not extend to the
opening of the acetabulum. In Z. ceratosa the acetabulum is nearer the
ovary, and the vitellaria are entirely extracecal while in Z. lunata they
extend between the ceca.

355] NORTH AMERICAN. PARAMPHISTOMIDAE—STUNKARD 75

CLASSIFICATION OP THE FAMILT

Our present classification of the Paramphistomidae is largely the
result of the work of Monticelli, Otto, Fischoeder, Cohn. Daday, .Stiles
and Goldberger, Looss, and Odhner.

The first division of the group was made by Monticelli (1892)
when he separated Gastrodiseus from the rest and created the subfamily
Gastrodiseinae. Fischoeder in a series of papers described several spe-
cies from mammals, and formulated (1903) the second scheme of classi-
fication. He created two subfamilies : Paramphistominae in which the
testes are lobed, and paired oral evaginations and cirrus sac are absent ;
and Cladorehinae characterized by branched testes and the presence of
paired oral evaginations and cirrus sac. Recent additions to our knowl-
edge of the family have, however, rendered it difficult to use these dis-
tinctions satisfactorily. Cohn (1904) created the subfamily Diplodisc-
inae to contain the genera Diplodiscus, Opisthodiscus, and Catadiscus.
He characterized the subfamily as follows: "Amphistomiden von ged-
rungener, konischer Form und runden Querschnitt. Mundsaugnapf gut
ausgebildet, mit zwei retrodorsal Tasehen. Ein grosser Endsaugnapf,
iiber welchem dorsal der Excretionsporus liegt. Mundoffnung termi-
nal, Darmschenkel bis zu Endsaugnapf reichend, relativ sehr breit.
Leben im Enddarm von Amphibien und Reptilien." The characteriza-
tion is inadequate, since the anatomical features are shared by almost
half the members of the family, and obviously further study of this
group is necessary to establish its validity and determine its true diag-
nostic features.

Stiles and Goldberger (1910) proposed a new classification of the
group. They created a new superfamily Paramphistomoidea to contain
the forms previously classed as amphistomes. They removed Gastrodis-
eus Leuck., and Homalogaster Poir. from Fischoeder 's subfamily Clad-
orehinae and created a new family Gastrodiscidae to contain these gen-
era. They created another new family Gastrothylacidae to contain the
general Gastrothylax, "Wellmanius, Carmyerius, and Fisehoederius. The
family Paramphistomidae and the two cited above comprise the three
families in the superfamily Paramphistomoidea. Stiles and Goldberger
also created a new subfamily Stephanopharynginae to contain the genus
Stephanopharynx, and added the new genus Cotylophoron to the sub-
family Paramphistominae. They recognize further the subfamily Dip-
lodiscinae Cohn and list the four subfamilies Paramphistominae, Cla-
dorehinae, Diplodiscinae, and Stephanopharynginae in the family Par-
amphistomidae. They placed Balanorchis in the subfamily Cladorehinae
notwithstanding Fischoeder 's statement that such an arrangement could
not be considered.

76 ILLINOIS BIOLOGICAL MONOGRAPHS [356

Braun (1911) reviewing the article, objects to the rank of superfam-
ily for the paramphistomes and says placing them on an equality of rank
^vith the Faseioloidea is not justifiable.

The work of Stiles and Goldberger is criticized at the hands of
Odhner (1911) as follows: "Dies alles zeigt nun evident, wie wenig
Verstandnis die betreffenden Autoren fiir die moderne natiirliche
Digenensystematik haben Mir scheint nun diese "Argu-
mentation" ebenso wie viel anders (die neue topographische Terminol-

ogie) in -derselben arbeit sehr "unwise" zu sein die Amphistomen

entsprechen im systematischen Range einer einzelnen Distomenfamilie
und nicht, wie Stiles and Goldberger gelaubt haben, der Summe samt-
licher dieser Familien."

Looss (1912) also gives a critical review of the paper: Die Charak-
terisierung der Arten, Gattungen usw. baut sich auf, einerseits auf eine
pedantisch ins einzelne gehende Analyse und Beschreibung der Korper-
form und der Topographic von Darm und Genitalapparat, anderseits
auf eine konsequente Ignorierung der beiden Tatsachen, dass die Tiere,
als Organismen, innerhalb gewisser Grenzen natiirlich variieren, und
dass Korperform sowohl wie Topographic der Organs mit dem Wachstum
gesetzmassige, mit der Kontraktion a priori nicht bestimmbare Verander-
ungen erleiden. Der Aufbau von Lymph — und Excretionsapparat
bleibt voUig unberucksiehtigt. Dass die Amphistomen ein "Lymphge-
fasssystem" iibcrbaupt besitzen, scheint den Autoren unbekannt zu
sein. "

The classification of Stiles and Goldberger as pointed out by other
authors is based on superficial characters and the elevation in rank of
the family and groups within the family is in most cases unwarranted.
However, the subfamily Gastrothylacinae of these authors appears to be
clearly distinguished by the presence of the large ventral pouch, and in
my opinion should be retained.

Looss (1912) considers the lymph and excretory systems of major
importance in classification. As characters of the new subfamily Schiz-
amphistominae he mentioned the type of IjTnph and excretory systems.
Since the lymph system has not yet been described in other subfamilies,
the former diagnoses based on body form, types of digestive and repro-
ductive systems, presence of ventral pouch, etc., must be retained for the
present. Moreover, since so many of the forms are incompletely de-
scribed, and considerable difference of opinion exists in regard to the
taxonomic value of the different features, the classification of the group
is still uncertain. As Looss (1912) says, "Jeder Klassifikationversuch,
der der bau von Excretions — und Lymphgefasssystem ausser acht lasst,
mag sich wohl einen Klassifikationsversuch nennen, kann aber niemals

357] NORTH AMERICAN PARAMPHJSTOMIDAE—STUNKARD 77

Anspruch darauf eriieben, als naturlicher oder (was dasselbe ist)
wissenseliaftlicher Klassifikationsversuch anerkannt zu werden. ' ' In the
same article he states that for many years he has been engaged in prepar-
ing a revision of the amphistomes but has not yet completed the work
which will present a classification based on the structure of the lymph
and excretory systems and the copulatory apparatus.

The only arrangements of the genera of the family that have been
made heretofore are those of Fishoeder and of Stiles and Goldberger.
The classification of Fischoeder does not appear adequate and that of
Stiles and Goldberger is far from satisfactory, but for sake of complete-
ness both are appended in outline.

Classification of Fischoeder (1903)
Paramphistomidae

Paramphistominae
Paramphistomum
Gastrothylax
Stephanopharynx

Species inquirendae, A. gigantocotyle
A. explanatum
Cladorchinae
Cladorchis
Gastrodiscus
Homalogaster
Diplodiscus
Chiorchis

Species inquirendae; A. liawkesi, A. collinsi, A. oma-
tum, A. papUlatum, A. tuberculatum, A. emarginatum,
and A lunatum.
(Subfamily nov.)
Balanorchis

Classification of Stiles and Goldberger (1910)
Paramphistomoidae
Gastrodiscidae

Gastrodiscus '

Homalogaster
Gastrothylacidae

Gastrothylacinae
Gastrothylax
Wellmanius
Carmyerius
Fischoederius

78 ILLINOIS BIOLOGICAL MONOGRAPHS [358

Paramphistomidae

Paramphistominae

Paramphistomum

Cotylophoron
Cladorchinae

Cladorchis

Taxorchis

Chiorchis

Microrchis

Pseudocladorchis

Pseudodiseus

Balanorchis

"Watsonius

Pfenderios
Diplodiscinae

Diplodiscus

Catadiscus

Opisthodiscus
Stephanopharynginae

Stephanopharj-nx

As a result of my studies on this family, certain data have been
added and some doubtful points cleared up. The discovery of the two
species of the new genus Alassostoma and the demonstration of their po-
sition as members of a new genus in the subfamily Schizamphistominae
Looss establishes that group. The description of the new genus and
species Zygocotyle ceratosa throws considerable light on the previously
isolated and obscure species A. lunatum Dies. In conclusion I present
a tentative revision of the paramphistomes. In the main it is my inter-
pretation of the status of the group and its subdivisions. The new genera
of Stiles and Goldberger are included without comment altho certain au-
thors do not recognize their validity. I have had no opportunity to work
on this material and consequently any judgment on my part must appear
unwarranted- Because of the scarcity of known forms and the incom-
pleteness of most of the descriptions it is impossible to present a final
classification. The following arrangement is provisional and likely to
be replaced whenever a natural system can be formulated for the family.

Paramphistomidae Fischoeder 1901
Gastrodiscinae MonticeUi 1892
Gastrodiscus
Homalogaster
Paramphistominae Fischoeder 1901

359] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 79

Paramphistomum

Stephanopharynx .

Cotylophoron
Cladorchinae Fischoeder 1901

Cladorchis

Taxorchis

Chiorchis

Pseudodiscus

Microrchis

Pseudocladorchis

Watsonius

Pfenderius
Diplodiscinae Cohn 1904

Diplodiscus

Opisthodiscus

Catadiscus
Gastrothylacinae Stiles and Goldberger 1910

Gastrothylax

Wellmanius

Carmyerius

Fischoederius
Schizamphistominae Looss 1912

Schizamphistomum

(Gen. 7WV.) spinulosum

Alassostoma

Genera of uncertain position
(new subfamily) Fischoeder 1903

Balanorchis

-(new subfamily) see text p. 71

Zygocotyle

80 ILLINOIS BIOLOGICAL MONOGRAPHS [360

RELATION OF THE FAMILIES TO THE ORDER

The trematodes are generally regarded as descended from a tur-
bellarian-like ancestor which possessed a posterior sucker. "With the
assumption of the parasitic habit adaptations began in various directions.
The ectoparasitic forms retained many of their former characters while
the added protection and food supply afforded those specializing toward
endoparasitic existence provided for perpetuation and distribution of
the species thru the excessive development of the reproductive apparatus.
The development of the ectoparasitic forms is simple and direct while
that of most if not all endoparasites has been complicated by the inter-
polation of one or even more secondary or intermediate hosts.

The differences in type of adhesive apparatus may in a general way
be explained thru differences in habit. The oral sucker has developed
thru continued adhesion by the anterior end in maintaining position, in
locomotion, and in securing food. In the Gasterostomidae the mouth is
on the ventral surface and an independent anterior sucker is developed,
altho this is undoubtedly a secondary feature, as in the cereariae of these
forms there is a single anterior oral sucker. In response to the constant
necessity for strong adhesion the ectoparasitic species have developed
accessory posterior organs of attachment, while in most of the endopara-
sitic forms the acetabulum has migrated anteriad or disappeared entirely.

The general classification of MonticeUi, which is followed in this
paper, is based primarily on the character of the adhesive apparatus.
In the Heterocotylea the posterior sucker has been replaced by a disc
which bears suckers and hooks ; in the Aspidocotylea the acetabulum has
become specialized into a multiloculate adhesive organ ; and in the Mal-
acocotylea the acetabulum may be retained in its primitive terminal posi-
tion, or it may have migrated anteriorly, in certain cases being reduced
and in others disappearing entirelj'. In the young individuals of many
forms in each of the three groups there is a single posterior sucker and
this fact adds weight to the theory that the present groups are descended
from a primitive form with a simple posterior sucker. In the young
stages of aU the Aspidogastridae there is a simple posterior sucker and
the worm closely resembles a young distome. In the early stages of the
Heterocotylea the reversion to the ancestral conditions is not so complete,
and specialization in this group shows clearly that it is widely separated

361] NORTH AMERICAN PARAMPHISTOMIDAE—STUKKARD 81

from the other two suborders which thru the presence of similar young
forms appear to be more closely related.

The morphological structure and direct development of the Polys-
tomidae at once places them with the Heterocotylea. In the adoption
of an endoparasitic mode of life, however, thy show a distinct departure
from the other members of the suborder. The present study of the
Polystomidae has emphasized the unusual morphological variation and
wide geographic distribution which exists in the family. This may mean
either that the family is very old and has been subjected to conditions
producing wide variation, or that the group really lacks family entity
and consists of various heterocotylean forms which have specialized in
the direction of an endoparasitic habit and that the morphological re-
semblance is eenogenetic.

Pratt (1908) reviews the literature and arguments for convergent
development which are based on trematode' morphology. Johnston
(1914) argues for divergence as the true explanation of the variation of
the species of Pneumoeneces, Gorgoderinae, Brachycoelinae, etc., and
believes that the elucidation of trematode phylogeny may be sought in
the study of the relationships between the distribution of trematode
parasites and the distribution of their hosts. No doubt the likenesses
and differences in the structure of present species are the result of both
convergence and divergence; yet it seems that the distributional factor
emphasized by Johnston is not of major importance. Parasitic distri-
bution could precede the distribution of the primary and secondary hosts
only in ease the parasites changed to new primary or secondary hosts.
Bdt today more than one species may serve as primary or secondary
host; the parasite is probably in a restricted degree able to adapt its
life history physiologically so other species may serve as hosts, and
primitively this adaptability may have been greater than now. The
distribution of the parasites certainly depends to a large extent on the
distribution of the primary host, and to a less extent on the distribution
of the secondary host, but the presence of two similar parasites in the
same region does not prove that their hosts had primitively the same
or different parasites. The life history of the trematodes is so imper-
fectly known that at present no final decision can be made on this basis.

The wide variation in structure of the members of the genus Poly-
stoma can not be adequately explained thru migration, or thru differ-
ences in the age of the parasite, type of host, or location in the host. In
the genus so far as is known, the long uterus containing many eggs is
confined to species infesting the urinary bladder of amphibian hosts of
the Old World. However in respect to other characters, e. g., the shape
of the caudal disc and absence of great hooks, these amphibian forms of

82 ILLINOIS BIOLOGICAL MONOGRAPHS [362

the Eastern hemisphere disagree with each other and agree with forms
parasitic in the urinary bladder and oral cavity of North American
turtles. The turtle parasites have a very similar structure, whether
parasitic in the urinary bladder or in the pharyngeal cavity. Further-
more, if the observations of Zeller are correct and the individuals of
P. integerrimum becoming mature on the giUs of tadpoles lack external
vaginae and have a spherical testis and a single egg in the uterus, one is
entirely at a loss to explain the variation existing in the genus.

In the Aspidogastridae the young individuals have an oral sucker
and a small posterior acetabulum without dividing ridges, and very
closely resemble young distomes. The mode of infection is almost en-
tirely unknown, and this offers a promising field for investigation. The
discovery of the sexual form of Stiehocotyle by Odhner (1898) estab-
lishes the fact that at least one species of the Aspidogastridae has an
intermediate host. Nicfeerson (1895) observes, "Owing to the well
known tendency of fresh water conditions to obliterate larval life, it may
well be that Aspidogaster has secondarily lost a more or less compli-
cated series of changes, which have been retained by its relatives inhabit-
ing salt water." The presence within the family of both direct and
indirect development, together with other characters common to both
the Heterocotylea and Malacocotylea designate it as an intermediate
group. The morphological structure is similar to that of the Mala-
cocotylea while the manner of development is similar to that of the
Heterocotylea. Whether the Aspidogastridae are primitive forms or
are secondarily degenerate is as yet undecided. The simple and archaic
character of the intestine, the eye spots, the direct development and the
ectoparasitic habit as it occurs in the family, together with the para-
sitic infection of molluscs by adult forms strongly suggests a very primi-
tive and ancient group. It is probable that complete evidence concern-
ing the structure and life history of this family would go a long way
toward solving the problem of whether the invertebrate or the vertebrate
is the original host and the attendant problem of the origin of double
hosts.

The Paramphistomidae appear to be a primitive family of the
Malacocotylea that have retained the original caudal sucker, altho
certain species show specializations of the organ from the simple spher-
ical type. Considerable light is thrown on the relationships of the
Malacocotylea by the recent work of Odhner on a natural system for the
digenetic trematodes. He strongly advocates the view that the mono-
stomes are a group which have no family entity, and consist of individual
forms derived from various distome groups which have alike lost the
acetabulum. Pointing out close and fundamental agreement in internal

363] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 83

structure he argues that the monostome family Angiodictyidae is really
a subfamily of the Paramphistomidae. He shows essential morphological
agreement between Distoma quadrangulum Daday and the fish amphis-
tomes. His examination of the original specimen of Aspidocotyle con-
firms the statement of Braun (1879-1893) that this form belongs to the
amphistomes, altho its relation to the other members of the group is
uncertain. Further he states that the Gasterostomidae by the structure
of the cerearia as shown in the oral sucker and the presence and relations
of the oral evaginations, doubtless belongs to the Paramphistomidae.
His derivation of the gasterostomes thus from amphistome-like forms of
frogs is plausible since the frogs serve as food for the hosts of the
gasterostomes. To Odhner's argument may be added that the divided
condition of the body in Gastrodiscus recalls the similar condition in
certain Aspidogastridae and suggests a possible relationship between
these forms. The morphological comparisons of Odhner and other
writers appear to show very clearly that divergence and convergence
have both had great influence on the phylogeny of certain trematode
families.

M ILLINOIS BIOLOGICAL MONOGRAPHS [364

LIST OF NEW SPECIES

PAGE

Alassostoma magnum 66

Alassostoma parvum 69

Polystoma megacotyle 37

Poly stoma microcotyle 39

Polystoma opacum _ _ 34

Polystoma orhiculare 31

Zygocotyle ceratosa _ 72

A preliminary description was given in the Journal of Parasitology,
3:21-27.

365] NORTH AMERICAN POLY STOMIDAE— STUN KARD 85

BIBLIOGRAPHY
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1907. Genito-intestinal Canal in Polvclads. Zool. Anz., 31 :643-644.
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1888. Trematoda. Encyc. Brit. 9 ed., 23 :53S-540.

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88 . NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD [368

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3»] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 89

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90 NORTH AMERICAN POLYSTOMIDAE—STUNKARD [370

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27:238-275, 2 pl.

371]

NORTH AMERICAN POLYSTOMIDAE—STUNKARD

91

EXPLANATION OF PLATES

All figures except those of reconstruction were drawn with the aid of a
camera lucida and were made from permanent mounts.

Abbreviations used

a

acetabulum

nc

nerve commissure

b

esophageal bulb

0

ovary

cm

circular muscles

oc

eye spot

cs

cirrus sac

od

oviduct

e

esophagus

om

oblique muscles

ed

excretory duct

00

ootype

ep

excretory pore

op

oral evagination

gp

genital pore

OS

oral sucker

gc

genito-intestinal canal

ov

egg

h

small booklets

p

postate gland

hd

hermaphroditic duct

Ph

pharynx

i

intestine

sp

septum

I

Laurer's canal

sv

seminal vesicle

Im

longitudinal muscles

t

testis

Is

lymph sinus

u

uterus

It

limiting membrane

ud

uterine duct

m

mouth

V

vitellaria

md

median dorsal lymph canal

vd

vas deferens

mg

Mehlis' gland

vg

vagina

mo

marginal organ

vl

vitelline duct

mt

metraterm

w

vitello-vaginal canal

mv

median ventral lymph canal

373] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 93

PLATE I

94 ILLINOIS BIOLOGICAL MONOGRAPHS 1374

EXPLANATION OF PLATE

POLYSTOMA ORBICULARE

Fig. I. Entire specimen, extended, ventral view. X 35-

Fig. 2. Hook from genital coronet X 225.

Fig. 3. Reconstruction of genital apparatus from frontal sections. X I35-

Fig. 4. Sagittal section thru caudal disc. X 87.

Fig. 5. Frontal section thru caudal disc. X VZ-

Fig. 6. Sagittal section thru oral sucker and pharynx. X 140.

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PLATE I

375] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 95

PLATE II

96 ILLIXOIS BIOLOGICAL MONOGRAPHS [376

EXPLANATION OF PLATE

POLYSTOMA ORBICULARE

Fig. 7- Frontal section. X 35-

Fig. 8. Frontal section of ootype and beginning of uterine duct. X i8s.

Fig. 9. Frontal section of ootype and end of right vitello-vaginal canal, five

sections ventral to Figure 8. X 185.
Fig. 10. Frontal section, o6type region of same specimen as Figures 8 and 9,
showing ovary, uterus, oviduct, uterine duct, genito-intestinal canat
and vas deferens. X 140.
Frontal section showing vitellaria and origin of vitelline ducts with

granular secretion in the cells and duct. X 87.
Frontal section thru cirrus sac at the juncture of the shanks and roots of
the genital hooks, showing the genital papillae cut across, and a sec-
tion of the duct from the uterus at the bottom of the figure. X 250.
Reconstruction of male genital apparatus from sagittal sections. X 140.
Frontal section thru uterus showing embryo in stage of a morula-like
mass of cells. X 700.

Fig.

II.

Fig.

12.

Fig.

Fig.

13-

14-

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STUXKARD XORTH AMERICAX POLYSTOMIDAE PLATE II

377] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 97

PLATE III

98 ILLIXOIS BIOLOGICAL MONOGRAPHS [378

EXPLANATION OF PLATE

POLYSTOMA OPACUM

Fig. 15. Entire specimen, extended, ventral view. X 20.

Fig. 16. Reconstruction of genital apparatus from toto preparation and cross

sections. X 50.
Fig. I". Hook from genital coronet. X SSO.
Fig. 18. Frontal section thru the anterior sucker and pharynx, showing in section

nerve commissures and vitellaria. X 60.
Fig. 19. Cross section of body thru uterus and cirrus sac. X 60.
Fig. 20. Cross section of body thru the testis. X 60.
Fig. 21. Cross section thru the anterior pair of bothria. X 60. '

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379] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 99

PLATE IV

100 ILLINOIS BIOLOGICAL MONOGRAPHS [380

EXPLANATION OF PLATE

POLYSTOMA MEGACOTYLE

Fig. 22. Entire specimen, ventral view. X 27.

Fig. 23. Cross section of body thru ovary and uterus. X 60.

Fig. 24. Cross section of body thru vaginae and anterior part of the testis. X 60.

Fig. 25. Cross section thru the pharynx near the posterior end. X 85.

Fig. 26. Cross section of seminal vesicle and cirrus sac. X 140.

POLYSTOMA CORONATUM

Fig. 27. Entire specimen, ventral view. X 27.

lUJXOIS BIOLOGICAL MOXOGRAPHS

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PLATE IV

381] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 101

PLATE V

tt2 ILLINOIS BIOLOGICAL MONOGRAPHS [382

EXPLANATIOX OF PLATE

POLYSTOMA MICROCOTYLE

Fig. 28. Entire specimen, ventral view. X 27.

Fig. 29. Ventral view of caudal disc, showing arrangement of musculature and
hooks. X43-

POLVSTOM.\ HASSALLI

Fig. 30. Entire specimen, ventral view, ceca connected posteriorly. X 45.

Fig. 31. Entire specimen, ventral view, in which there is no posterior connexion
between the ceca. X 40.

Fig. 32. Reconstruction of genital apparatus from frontal sections. X 135.

Fig- 2Z- Frontal section thru the dorsal part of the uterus, showing oral sucker,
pharynx, nerve commissures, intestine, excretory vesicles and ducts,
vitellaria and smaller tubes of the ootype region. X 60.

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PLATE V

383] NORTH AMERICAN POLYSTOMIDAE—STUNKARD 103

PLATE VI

104

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1384

EXPLAXATIOX OF PLATE

Fig.

34.

Fig.

35-

Fig.

36.

Fig.

37.

Fig.

38.

F-ig.

39.

Fig.

40.

Fig.

41.

Fig.

42.

Fig.

43.

Fig.

44.

Fig. 45.

Suckers .^xd Hooks of V.^8I0l•s Species of Polystomes
Polystotr.a orbiculare, bothriuin from caudal disc. X 140-
Polystoiiia orbiculare. frontal section thru bothrium. X 140.
Polystoitia obiculare, optical section of bothriuin showing cuticular

framework. X 140.
' Poly stoma opacum, hook from base of sucker. X 165.
Polystoma ofiacuin, hook from anterior margin of caudal disc. X 165.
Polystoina microcotyle, hooks of posterior margin of disc. X 165.
Polystoma opacum, hooks of posterior margin of disc. X 165.
Polystoma megacotylc, hooks of posterior margin of disc. X 165.
Polystoma coroiiatuiii, hooks of posterior margin of disc. X 165.
Polystoma orbiculare, hook from base of sucker. X 165.
Polystoma orbiculare, frontal section thru a sucker illustrating the method

of operation ; the external zones are retracted with the resulting

protrusion of the basal part. X 140.
Polystoma iittcgerrimum, frontal section thru a sucker showing type of

cuticular framework. Compare with text and types illustrated in

other figures. X 100.

lELIXOIS BIOLOGICAL MOXOGRAPHS

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PLATE VI

38S] NORTH AMERICAN ASPIDOGASTRIDAE—STUNKARD 105

PLATE VII

106 ILLINOIS BIOLOGICAL MONOGRAPHS [386

EXPLANATION OF PLATE

COTYLASPIS COKERI

Fig. 46. Entire specimen, extended, dorsal view. X 40.

Fig. 47. Ventral view of entire specimen showing position of marginal organs

and divisions of the adhesive disc. X 40.
Fig. 48. Reconstruction of reproductive organs from frontal sections. X 80.
Fig. 49. .Cross section of body at the level of the ovary showing the ovary, uterus,

seminal vesicle, intestine, excretory ducts, and a follicle of the

vitellaria. X 87.
Fig. 50. Diagrammatic representation of the excretory system from a living

specimen, dorsal view. X 40.
Fig. 51. Oblique section of body just posterior to the genital pores, showing in

section the mouth funnel, pharynx, cirrus sac, uterus, septum ,ind

adhesive disc. X 87.
Fig. 52. Entire specimen, contracted, dorsal view. X 40.

ILLl.XOIS BIOLOGICAL MOXOGRAPHS
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VOLUME 3

STUXKARD NORTH AMERICAN' ASPIDOGASTRIDAE PLATE VII

■IV.

V' ■

387] NORTH AMERICAN ASPIDOGASTRIDAE—STUNKARD 107

PLATE VIII

108 ILLIXOIS BIOLOGICAL MONOGRAPHS [388

EXPLANATION OF PLATE

COTYLASPIS COKERI (EXCEPT FiGURE S6)

Fig. $3. Sagittal section thru the anterior end of body showing musculature, di-
gestive and reproductive organs. X 200.

Fig. 54. Frontal section thru the openings of the genital pores. X 85.

Fig. 55. Section thru a marginal organ ; a muscle fiber is seen at the left of the
figure and on the other side a nerve fibril passes to the inner end of
the thick walled part of the canal. In this section the canal is cut
across and can not be traced from the bulb to the exterior. X 580.

Fig. 56. Section thru a marginal organ in Cotylaspis insignis. X 580.

Fig. 57. Frontal section thru the adhesive disc showing arrangement of muscula-
ture. X 95-

Fig. 58. Section thru the anterior part of the forebody showing the base of the
mouth funnel, anterior part of the pharynx, nerve commissure and
eye spots. X 800.

ILLIXOIS BIOLOGICAL MOXOGRAPHS
53

VOLUME 3

STUXKARD XORTH AMERICAX ASPIDOGASTRIPAE PLATE \III

389] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 109

PLATE IX

110 ILLINOIS BIOLOGICAL MONOGRAPHS [390

EXPLANATION OF PLATE

Alassostoma magnum
Fig. 59. Entire specimen, ventral view. X 9.
Fig. 60. Cross section thru the genital pore showing the terminal parts of the

cirrus sac and uterus, the hemaphroditic duct, genital sinus, four

layers of muscles in the body wall and the muscle lamellae of the

esophageal bulb. X27.
Fig. 61. Diagrammatic representation of female genital apparatus reconstructed

from cross sections. X40.
Fig. 62. Section of the wall of the intestine. X360.

Fig. 63. Cross section thru the oral sucker and the oral evaginations. X 40.
Fig. 64. Cross section of body at the level of the ovary showing in section the

ovary, uterus, Laurer's canal, the ceca, vitellaria, lymph spaces and

excretory ducts. X 16.
Fig. 65. Cross section thru the oral sucker showing arrangement of muscle fibers

and position of the nuclear zone. X 35.

ILLINOIS BIOLOGICAL MONOGRAPHS

VOLUME 3

STUNKARD

NORTH AMERICAN PARAMPHISTOMIDAE

PLATE IX

391] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 111

PLATE X

112 ILLIXOIS BIOLOGICAL MOSOGRAPHS [392

EXPLANATION OF PLATE

Alassostoma parvum
Fig. 66. Entire specimen, ventral view. X 27.
Fig. 67. Cross section of body posterior to the ovary showing coils of the

excretory ducts. X 70.
Fig. 68. Cross section thru the posterior part of the acetabulum showing lymph

spaces around the sucker. X "o.
Fig. 69. Cross section a short distance posterior to the genital pore showing in

section, the uterus, the cirrus sac, and above the latter organ three

loops of the seminal vesicle. X 70.
Fig. 70. Cross section of esophageal bulb with clusters of surrounding cells. X "o.
Fig. 71. Cross section of body thru the genital pore showing hermaphroditic duct,

cirrus sac, lymph spaces and the character of the parenchyma. X 90.

ILLISOIS BIOLOGICAL MONOGRAPHS
66 .^'"^ 67

VOLUME 3

STUNKARD NORTH AMERICAN' PARAMPHISTOMIDAE PLATE X

J93] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 113

PLATE XI

114 ILLISOIS BIOLOGICAL MOXOGRAPHS [39+

Fig.
Fig.

72.
72-

Fig.
Fig.

74-
75-

Fig.

76.

Fig.

77-

Fig.

78.

Fig.

79-

EXPLANATION OF PLATE

Zygocotyle ceratosa
Entire specimen, ventral view. X u.
Cross section of esophageal bulb, showing the arrangement of the muscle

fibers. X 45- Compare with Figures 60 and 70.
Cross section of bodj' thru the origin of the oral evaginations. X 45.
Sagittal section thru the anterior part of the body showing oral sucker,

an oral evagination and the anterior part of the esophagus. X 45.
Sagittal section of posterior part of body thru one side of the acetabulum.

X27.
Sagittal section of the posterior part of the body near the median line,

showing the ovary, eggs in the uterus, Laurer's canal, and the shape

of the acetabulum. X 27.
Sagittal section thru the body one section at the side of the genital pores

showing the folded wall of the uterus and the ejaculatory duct

which in this species is without a cirrus sac. X 136.
Representation of the sagittal section thru the openings of Laurer's canal

and the excretory vesicle. X 90.

ILLIXOIS BIOLOGICAL MONOGRAPHS

STUXKARD NORTH AMERICAN PARAMPHISTOMIDAE PLATE XI

UNIVERSITY OF ILLINOIS-URBANA

S7D.5ILL CDI14

ILLINOIS BIOLOGICAL MONOGRAPHS URBANA

31918-17

01

01

7753408