Section I

PahtII

An
Introduction

TO

NEMATOLOG\

7

B. G. Chilwood ac M B. Chitwood
Babylon, N. Y.

NATHAN AUGUSTUS COBB
18S9-I932

Born in Spencer, Ma««.; B. Sc. Worcester
Polytechnic Institute (1881); Instructor in
chemistry and natural history at Williston
Seminary, Easthampton, Mass. (1881-1887);
Ph. D. University of Jena (1888); Investi-
gator at Naples Zoological Station (1888);
commercial advertiser at Sydney, N. S.
Wales (1889); temporary professor of zo-
ology in University of Sydney (1889-1890);
pathologist. Department of Agriculture,
N. S. Wales (1891-1901); special commis-
sioner on Agriculture for N. S. Wales, visit-
ing Europe and United States (1901-1904);
director. Division of Physiology and Path-
ology, Hawaiian Sugar Planters' Experiment
Station (190S-1906); Agricultural Technolo-
gist, U. S. Department of Agriculture ( 1907-
1928); Principal Nematologist, U. S. De-
partment of Agriculture (1929-1932).

Plant pathologist, parasitologist, inven-
tor, nematologist, ornithologist; crystallog-
rapher, poet, romanticist and dramatist of
nematology.

From Coob. lOlti.

C*»yrl|hl, 1938. by M. B. Cklti>;oi

Section I

Pakt II

An
Introduction

TO

NEMATOLOG\

T

B. G. Chitwood & M. B. Chitwood
Babylon, N. Y.

NATHAN AUGUSTUS COBB
18S9-1932

Born in Spencer, Masc; B. Sc. Worcester
Polytechnic Injtitute (1881); Instructor in
chemistry and natural history at Williston
Seminary, Easthampton, Mass. (188I-I887);
Ph. D. University of Jena (1888); Investi-
gator at Naples Zoological Station (1888);
commercial advertiser at Sydney, N. S.
Wales (1889); temporary professor of zo-
ology in University of Sydney (1889-1890) ;
pathologist. Department of Agriculture,
N. S. Wales (1891-1901); special commis-
sioner on Agriculture for N. S. Wales, visit-
ing Europe and United States (1901-1904);
director. Division of Physiology and Path-
ology, Hawaiian Sugar Planters' Experiment
Station (1905-1906); Agricultural Technolo-
gist, U. S. Department of Agriculture ( 1907-
1928); Principal Nematologist, U. S. De-
partment of Agriculture (1929-1932).

Plant pathologist, parasitologist, inven-
tor, nematologist, ornithologist; crystallog-
rapher, poet, romanticist and dramatist of
nematology.

QL .
391. N
C 57

F

From Cujb. lOIU. Tr Am. Micr Sw.-. v IS I I ) : 7-23

C«»yrl|ht. 1038. by M. B. Chltwtoi

PREFACE

THE authors wi.sh to exjircss tlicir aiipreeiation to tho various
workers and institutions wliich supported the first part. Sucli
support, even in so limited a field, will assure eompletion of
the series.

Tins ])art, covering- as it does, the digestive tract and associated
structures, includes most of the characters commonly used in identifica-
tion. In order to give as compivhensive a survey as possible numy of
the illustrations are semidiagianniiatic (those not shaded). In all cases
they are based on camera lucida sketches. The side view series of
diagrams may be assumed to have the dorsal side at the readers left
unless otherwise specified.

The authors wish to express their appreciation to Doctor G.
Steiner, Doctor J. R, Christie and ]\[iss K. i\[. Buhrer, all of the Divi-
sion of Nematology. U. ,S. Bureau of Plant Industry, for theii- helpful
criticism.

B. G. C. & M. B. C.

CHAPTER V
CEPHALIC STRUCTURES AND STOMA

Tlio various structures which go to niako up tlie copliulic
region of ncinatodcs cannot be classified iu a single category.
Yet tlieir study is naturally interlocked liotli in [iractical and
develoiunental anatomy, l.'nder the general hi'ading "Cephalic
structures" we shall discuss lips, iiseudidaliia, cephalic ivapillae,
cephalic setae, amphids, proludae, collarettes, cordons and
labial dentition while under the heading "Stoma" that part of
the digestive tract Ijetween the oral opening and the anterior
end of the esojihagus will be considered. Of necessity, a dis-
cussion of cei)halic structures must include parts of the ner-
vous system, external cuticle and sometimes stomatal develop
ments. Likewise, a discussion of the stoma overlaps to some
extent both with the cephalic structures and the esophagus.

1. CEPHALIC STRUCTURES

Cephalic structures have been used, to a limited extent, as
taxonomic characters since the appearance of Schneider's mono
graph (IStKi') whicli included in face, as well as lateral and
medial views of the anterior extremity of many of the larger
nematodes. Such studies were extended liy de Man (188G-
1907) investigating free living nenias and von Drasche (1883)
working with parasitic nemas of Diesing and Molin's collec-
tions. Certain generalities came to be accepted as a result of
the observations of Schneider and von Drasche. These were
as follows: (1) That ascarids and heterakids have three lips,
one dorsal and two subventral; (2) That spiruroids have two
lateral "lips" and (3) That parasitic nemas generally have
four submedian and two lateral cephalic papillae. The first
two of these jioinfs are for the most part acceptable to us today
but the third is no longer tenable. In i)arasitic nemas Looss
(1902) introduced the use of cephalic structures in strongylid
taxonomy causing them to be considered an integral part of
generic and specific descriptions in this group but, apparently
due to lack of interest or inadequacy of parasitological tech-
nic, little advance was made beyond Schneider, von Drasche,
and Looss until very recently. In free-living nemas somewhat
more steady progress has been made, partially attributable
to the smaller size which makes critical study convenient and
partially due to more widespread technical training. Though
numerous workers have contributed to our knowledge of free
living nenias, the chief impetus has come from the work of
Cobb and Steiner. The glycerin .jelly technic (see Cobb, 1920,
and Chitwood and Wehr, 1934) developed in the laboratory
under Cobb was introduced to the various visitors and asso-
ciates; this technic made the stuily of nemas from en face
practical.

Knowledge of the liasic anatomy of the anterior end is due
to the contributions of Goldschmidt (1903), JIartini (1916),
and Hoeppli (192.'5). The confusion of two types of sensory
organs, tactile structures (papillae) and chenioreeeptors (am-
phids) in parasitic nemas caused much misunderstanding
though Goldschmidt recognized the difference between the dor-
.sal lateral organ (amphid) of Ascaris Jnmhricoidcs and the
other sensory organs. The same differences both in the ter-
minal sensilla and the internal nervous connection were brought
out by Zur Strassen (1904), Looss (1905), and Martini (1916)
in Siphonalaimus spp., Ancylostoma duodenale and Oxyuris
rqui, respectively. Zur Strassen even went so far as to state
definitely that the dorsal lateral organ of Ascaris is the same as
the circular lateral organ of Sipliniwlaimiis. Other -n-orkers
entirely ignored these observations until Cobb (1913) renamed
the lateral organs amphiilx defining them as paired cephalic
structures of specialized (unknown) function. It remained
for the same author later (1923, 1924, 1928) to establish the
general existence of pore like amphids in parasitic nemas
through observation and constant reiteration that they are
not "lateral papillae." Since then information has gradually
accumulated showing their universal presence in the Nema
toda. We shall not go into their internal anatomj- at the
present time since they are connected with the nervous system.
It will be sufficient to note that each amphid is essentially a
lateral or dorsolateral organ connected internally with the
laieroventral commissure and with a gland (Fig. 3). Near
the external orifice there is a dilation of the gland duct (am-
phidial pouch) in which nerve fibers terminate (the sensilla)
(Fig. 8) ; the pouch is connected with the exterior either
directly by an amphidial tube and pore or it opens into a
pocket, circle or spiral external cuticular modification. In
this part, only the external manifestation of the amphid (i. e.,
pore, pocket, spiral, etc.) will be considered.

In 191H Filipjev introduced the external form of the am-
phids of free-living nemas as a family and subfamily charac-
ter, later (1929, 1934 a, b) raising its use to suborders.

In the meantime information regarding the number and
arrangement of cephalic sensory organs in both parasitic and
free living nemas was .■iccumulating and Chitwood and Wehr
(1932, 1934) brought out papers on the evolution and basic
jilan of cfjihalic structures with special reference to parasites
while Stekhoven and de Coninck (1933), de Coninck (1935)
and Stekhoven (1937) brought out similar papers with spe-
cial reference to free living nemas. Differences in findings
are for the most part matters of interpretation due to op-
posed schools of thought; the differences being in basic
philosophy as to the evolution of nemas and not in the organ-
isms themselves. The one school, represented by Filipjev,
Stekhoven, and de Coninck regard polymyarian nemas as
primitive and meromyarian nemas as neotenic while the other
school, represented by Looss, Steiner and the writers, consider
meromyarian nemas as primitive and polymyarian nemas as
more highly evolved. The consequences are that each group
sees the Xematoda from a separate point of vantage.

The basic plan of the anterior end appears to be six lips,
two subdorsal, two lateral, and two subventral. On the sum-
mit of each lip there is a papilla, these six papillae constitut-
ing the internal circle and being known as internodorsals (id),
internolaterals (il), and internoventrals (iv) ; situated more
posteriorly on each of the submedial lips there are two papillae
while on each of the lateral lips there is one papillae; these
papillae constitute the external circle and have been named
according to their position (Fig. 8a) : dorsodorsals (dd),latero-
dorsals (Id), ventrolaterals (vl) (or externolaterals, el), lat-
eroventrals (Iv) and vcntroventrals (vv). All of the members
of the external circle are seldom exactly the same size or at
exactly the same level. Stekhoven and de Coninck (1933)
would therefore speak of them as constituting two circles
and in some forms this is indeed the ease. However, the
papillae of the external circle are not always segregated in
the same pattern. Thus the ventrolateral papillae tend to agree
w'ith the dorsodorsal and ventroventral papillae in their rela-
tive development in the Aphasmidia while they tend to agree
with the laterodorsal and lateroventral papillae in the Rhab-
ditina, Strongylina and Ascaridoidea. For that reason we
regard the external circle as subdivisible into two papillary
groups.

Fusion and reduction of cephalic papillae commonly modify
the apparent cephalic arrangement but one can practically
always recognize remnants of the original papillae and all
cases may be explained in terms of the diagram presented
(Fig. 8A).

As pointed out by Chitwood (1932) and the writers (1933)
the cephalic papillary nerves are hexaradiately ^symmetrical
and one would expect a hexaradiate symmetry to be basic for
the papillae. Therefore, the external circle should consist of
12 papillae instead of 10. However, no rudiments of a dor-
solateral pair are know-n except in some species of the Mon-
hysteridae and Linhomoeidae. If these forms were the more
primitive, one would expect to find rudiments of the afore-
mentioned papillae in other groups and this is not the case.

The bilaterally symmetrical amphids are separately inner-
vated and cannot be considered a part of the cephalic papillary
symmetry. Unlike the papillary nerves, the amphidial nerves
enter the nerve ring indirectly, through a commissure and their
original position probably was posterior to the labial region
as indicated by embryonic rhabditids and adult aphasmidians.
Likewise, the amphidial orifice was probably larger and a bit
like the plectoid amphid, if one is to interpret on the basis
of embryonic rhabditids. As pointed out by the writers (1933)
one cannot assume any existing form to represent the pro-
tonematode but if one combines characters of the genera
Sliabditis and Plectii.i a conmion denominator of all nematodes
is found. One cannot interpret aphasmidians entirely in terms
of Ehabditis nor phasmidians in terms of Plectus, but the con-
verse is moderatelj' natural. Thus the amphids and papillae
are basically labial in i)osition in phasmiilians while the am-
phids in aphasmidians are basically postlabial (a more primi-
tive arrangement) and some of the pai)illae may be postlabial
in position (a less primitive arrangement).

Kegarding the basic number of lips, there are two choices.
One may assume primitive triradiate symmetry in accordance
with the symmetry of the esojihagus as did Baylis and Daub-
ney (192C) or a hexaradiate symmetry in accordance with the

55

papillary airangenicnt as aid tiie writers (i'.i:i:<i. Since the
lips are not forinefl from the esophageal primordium but from
the cells of tlie anterior end (clavate cells of the papillary
nerves and arcade lobes) the esophagus has nothing to do with
them. The clavate cells are hexaradiately symmetrical while
the arcade is bilaterally symmetrical with a gross triradiate
and an actual 9-radiate symmetry (Fig. 4(36). Tlie actual
Sl-radiate symmetry is subdivisible into a triradiate and a
hexaradiate formation rather than into three triradiate sys-
tems. We shall assume a hexaradiate symmetry as basic.
Taking either extreme, six distinct lips or three distinct lips
one finds repetitive series of transitions from the one to the
other in the large groups. The lips themselves are subdivisible
into two portions, the apical part, bearing the internal circle
of papillae and the basal part, bearing the external circle of
jiapillae and amphids in the Phasmidia and at least one sub-
division of the external circle in the Aphasniidia. In some
instances the tw^o parts of a lip may be represented by sepa-
rate lobes as in Spironoura affine and Parascaris eqiiorinn
(Fig. 37) while in other instances, O-ri/iiris equi, Metonchn-
laimiis pristiunis (Figs. 57 and 63) only the a|iical lobes nmy
persist.

Original lips may totally disappear and be replaced by newly
formed structures such as the pseudolabia of sjiiruroids, the
probolae of ceplialobids and the pseudonchia of filariids.

In the study of cephalic structures the student should be
([uite critical. It is not uncommon for two workers examining
the .same species to find greater differences than one worker
would find examining representatives of two families. Lateral
and medial views are often quite helpful but without an en
face view they may be meaningless. It is due to this fact
that the majoritj' of older descriptions of the cephalic struc-
tures of parasitic nemas must be considered valueless. In
examining en face views great care should be taken in focus
ing the microscope, and oil immersion is essential even in the
study of the largest species.

A. PHASMIDIA

Phasmidians are similar to one another in the possession of
simple external amphids, usually pore like and labial in posi-
tion. The cephalic .sensory organs are nearly always papilli-
form and in the most extreme cases are no more than setose
papillae. In cases of reduction or fusion of the external circle
it is always the dorsodorsals and ventroventrals that tend to
disappear. The physiognomy of the various members of the
subclass will be dealt with systematically.

Ehabditina. Members of the suborder Rliabditina (Figs.
r)4-.5ri) characteristically have six lips but three lipped forms
are C|uite common and many genera have no lips. The cephalic
papillary arrangement is likewise diverse.

Rhabditidae. — Both six and three-lipped forms are common
in the Rhabditidae and one finds every conceivable variation
between the two. In SliahiJitis terricota there are six large
separate lips, an internal circle of six well developed papillae
and an external circle of ten well developed papillae ; the latter
are not absolutely equal in form or size, the dorsodorsals and
ventroventrals being similar as are the laterodor.sals and latero
ventrals while the ventrolaterals are more or less intermediate
between the others. Bhabditis liicanii has three basally bilobed
lips and the same number and aiiangement of papillae but in
this instance the ventrolaterals are small and like the dorso
dor.sals and ventroventrals. Other rhabditids vary between
these types some having di.screte, some confluent lips; in some
the labial region is set off from the remainder of the bod.v
while in others tliis is not tlie case. In all instances the am-
phids are dorsolateral and laliial in position and pore-like in
character.

In Diploscaptcr curonafa the lips have been entirely trans-
formed into a pair of medial, outwardly acting, distally bifur-
cate fossores and a pair of lateral lamellae. Neither papillae
nor amphids have been satisfactorily studied.

C^yliniirogasterids have six discrete lips which may or ma.y
not be set off from the remainder of the body; there is an
internal circle of six reduced pajiillae. In Lonf/ibncca rivipara
and /,. lasiiira there is an external circle of four well develojH'd
li.'jpillae (laterodoi'sals and lateroventrals) and in the latter
veiitrcdaterals are also present but reduced. In Ci/linilraf/nxtrr
lonz/istoma there arc six well developed (Id., vd., and Iv.) and
four reduced (dd. and vv.) pai>illae. The amphids are dorso-
lateral and labial in all forms.

In the family Diplogasteridac the two chief groui)s b.-i.sed
upon the eso])hagus, Alloioncmatinae and Diplogasterinae,
seem to differ also in cephalic characters. Members of the
Alloioncmatinae usually have rather distinct lips, six (.11
loioncma appcnilioiilatum. v. iliibium) or four (Clicilobim qua
<lril<il)ia1ii.'.) ; in the latter instance the submedial lips .are

fused : only six papillae have been observed, these presumably
being the laterodorsal, lateroventral and ventrolaterals. Al-
loionematids have pore like, labial, dorsolateral amphids and
a simple hexagonal oral opening. The clo.sely related family
Strongyloididae is characterized by two lateral lips, this being
practically the only character distinguishing the free-living
generation from such genera as AUoionrma and Rhabdito-
phancs. Diplogasterids usually have no lips (Diplogaslir
flctur, Mononclwides ainericanus (Syn. Diplogaster americanus) )
but instead they have a thin circum-oral membrane supported
by longitudinal rugae which project anteriorly from the stoma.
The number and degree of development of the rugae differs
in the various species. In other genera inconspicuous rem-
nants of six lips may be present ( Prist iiiin-lnis, Rliabditidaidrs,
Odonlopharjini') . Among the forms thus far studied, Pris
tionclius acrivora is the only one known to show the full com-
ponent of papillae (16) ; in this instance the dorsodorsal and
ventroventral papillae are reduced while the others are well
developed. In all other members of this subfamily studied the
internal circle and the externomedial papillae are rudimentary
or apparently absent. The remaining six papillae are often
conically setose. Another peculiarity of the group is that the
amphids vary from pore like and labial in position to slit or
transvensely elliptical (with similarities to PIcctiis).

The family Cephalobidae contains forms with six lips (Paiia-
grolaimiis siibclotinatiis), three lips (Ccphalobiis pcrsegnis,
Trici'iihalobus longicaudatiis) three simple (Acrobeloides
Ijiitschlii) or bifid labial probolae and sometimes six cephalic
probolae (Acrnbelcs coinplexus). Labial probolae are cuticu-
lar labial structures which apparently replace the lips. They
may be recognized by the fact that they are separated from
the papillae bearing labial rudiments by a groove; cephalic
probolae are known to occur only toincidentally with labial
probolae, pro.ject anteriorly and often bear the cephalic papil
lae at their bases { Acrnbelcs bodcnhcimeri). Lips, on the
contrary, bear papillae close to their apices. Another repre-
sentative of this odd group (Chambersiclla rodcns) possesses
six inwardl.v acting odontia internal to which there are si.\ cir-
ri ( ? cephalic probolae). When lips are present the full com-
ponent of cephalic papillae (1(3) are often observable but in
other instances they become difficult to recognize.

Of the remaining families of the Rhabditoidea the Steiner
nematidae {Ncoaplrrtaiia glascri) have a rounded oral opening,
no lips, and the full component of well developed papillae and
the Angiostomatidae (Angiostoma pletlwdontis) have three in-
conspicuous lips and the full component of papillae while the
Drilonematidae are devoid of lips and have only the external
circle of papillae, eight in Dicelis nira and four in Vngclla
sccta. Drilonematids may also have large hook-like teeth pro-
jecting from the stoma {Vngclla sccta).

Rejiresentatives of the Tylenchoidea have not been sufficiently
studied to make many statements regarding their cephalic
characters. As a rule the labial region is distinct, the lips
inconspicuous, six in number, and bearing four papillae and
the amphids. In a few forms such as Angiiina trilici and
Ratylcnchus similis an internal circle of six papillae have been
observed, these papillae being internal to the lips. In some
tylenchids such as Tloplntaimvs hradys the labial region is
striated and sujiported by a sderotized framework. In at
least one form (Nrotylrnchus abiilbnsiis) there is a medial )>air
of supplementary li|is between the original si.x lips.

StrongyIjINA. Stri:ng)/liiidca. — The nuijority of representa-
tives of the s\iperfamily Strongyloidea have no lips or they are
greatly reduced or rudimentary. In all instances the ampliids
are dorsolateral or lateral and labial in position.

In the family Strongylidae lips are absent and in their place
one finds the external corona radiata or leaf crown (Fig. ."iCi).
As we interpret these structures, they represent the divided
apical lobes of the original lips; they may number from six
to 40 or nujre. The labial region is generally set off from the
remainder of the body by a groove but it is not divided longi
tudinally as when large lips are present. Within this family
the internal circle is usually rudimentary or apparently absent
but it may be represented by reduced internolaterals (Slrongy-
liis cqiiinus). The external circle is reiiresented by four large,
often setose, sulmu'dian jKi|iillae each of which apparently con
sists of two origin;il papillae that have fused (dd. — Id. and
vv. — Iv.) ; ventrolateials are rudimentary.

The closely relatecl family Syngamid.'ie su]iplies interesting
examples for c(»miiarison with tin- .Strong.vlidae. In Stcphanu-
nis dcniatus and Siingannis trachea the oral opening is sub-
hexagonal or one might .say there are six rudimentary lips
while in Dclclroccplialiis dcmidiatiis there are six distinct lobes
which might e({ually well be termed an external corona radiata
iir rudimentary laliial lobes. In all three ff.rms the internal
circle is reduced bnl, nevertheless, distinct and the external

piri-li" i-oiisists of ton papillae. Tlu'io ia a distinct toiidenc.v
tinvanl fusion of papillae with eoiiieident leduction in size of
the dorsoilorsals, ventrolaterals and ventroventrals the median
pairs of the external eirele hein^ nearly eonii)letely fused in
Sti i>liiiniiru.i (liiitdliis, partially fused in Siiiiiiaiiniii travhia
and separate but approaehinj; in pairs in Dchtroci pUaUis ilemi
iliatiix. As in the Stron);ylidae the laliial region is usiuilly set
off liy a Ki'oove hut unlike the StrouKylidae, the nu'dial papillae
of the external eirele are never in the form of duplex setose
papillae ( Fig. ."ill).

The family Aneylostomatidae is eharaeterized by the absenee
of both lips and a eorona radiata; instead the oral opening
is nuxlified to the funetion of i>rost(Mnatal teeth or eutting
edges. .\s exeinplilied by Nccalor ami ricanns the full eom
ponent of papillae are represented, all of them being reduced
with the exeeption of the laterodorsals and lateroventr.nls and
one finds the nu'dial pairs of the external eirele elosely ap
proximate as in the .Syngamidae. The labial region is not
set off by a groove as in the previously mentioned families.

The family Diaphanoeephalidae is eharaeterized by a dor

soventrally elongate oral o|U'ning and is without lips, leaf
erown, |irostoniatal teeth or eutting edges. The full eomponent
of papillae is represented, there being an internal eirele of
six reilueed jiapillae and an external eirele of four incuni
pletely fuse<l subnu'dial and two simple ventrolateral (Kali-
ci'plialiis sp.).

The family Cloaeinidae is partieularly noteworthy becau.se
of the presence of six massive lips, the laterals somewhat lower
than the subuu'di:ins. In Zoniotaimu.t svtiffra the internal
circle is represented by reduced internolaterals and the external
circle by four ( ! duplex) conoid ijapillae.

Trirhnsl rifnf/i/hii'tra. Kepi'esentjit i\'es tif this superf:imily
often have a dislinet ceiihalie inllation or cuticular helmets of
numerous si)eeiali/.ed forms which are used as generic charac
ters. They are always devoid of a leaf crown and seldom
show rudiments of either six or three lips. The oral opening
may be of diverse form but is nearly always surrounded by
an inconspicuous eircumoral membr.-ine. Kepresentatives
studied by the writers have an internal circle of six reduceil
papillae and an external circle of 10 simple i)apillae (medials

Ceijh;ili<- regions in the Khaljditnidea. AC — RlijilMiilidae. ])-
M — DtploEiisteridne. N-0 — Ithutidin.sidne. P — .Strongyloididae.
Q — Angiostoiiiatidjie. R-S — Orilonematidae. T — Steinernenia-
tidae. L'-V — (.'ylindrogasleridae. W-.\A — Cephalobidae. A —
JibnhilitiM terrirntn ; B — Khnbtlith anpfra; (' — Dipliinrapter ror~
tintttn ; 1) — Ithiihililiiloidps sp. ; E — Arrostwlnis tnletlni; F — Ly-
cnloimtm ilifriniji ; (J — Odontopfiarj/rur lonpifiimlfitii ; II — AUoin-
nfwu apprntUcultitum v. duhitt : I — PyitiHoneltun tifrirora ; J —
JtiplujfitMter prttir ; K — Monont'hoitl^/t ii iiieririinnn ; 1. — Tj/tn-
phnriinx Mtrinta; M — HutleritiH htitleri; N — Entoiiielan etitomf-
lag; (> — RhnhtlutH i>n»lrepton ; P — St rnni/ylnidftt rantmmi ; Q —
Artffiostotnii plethndontiji : K — Unijella ttfcta; S — Dirfilis nira ;
T — Xeoaplfrlnnn i/taxeri ; U — Ci/lindrofftt^ler ; V — Lnnj/ibuct-a
Ifmiura: \\ — Cfphatahns pprHfjjnix : X — Pnii/ijjrnluiwtiM vuhf-
lonytittiM : Y — Xrn3}iplfs rtnnith-.rns ; Z — VhdtiiberHieUft ntdens ;

.\.\ — Acrobetoideil butschlU. K-K — After Rahm. 1929. Arc-li.
Inst. Biol. V. 2. G — After de Man, 1912, Zool. Jahrb. .\bt. Sjst.,
V. 33 (6). 11— After Chitwood and Mcintosh. 1934, I'roc'. Helm.
Soi-. Wash. V. 1(2). I — .\fter .Sti-iner. 1934. Proc. Helm. Soc.
Wash., V. 1(2). L-M — After Goodey, 1929, J. Helminth., v.
7(1). P — After Alicata. 1935, U. S. I). A. Tech. Bull. 489.
R — After Cobh, 1928, J. Wash. Acad. Sc, v. 18(7). S — After
Chitwood and Lucker, 1934, Proc. Helm. Soc. Wash., v. 1(2).
T — After .steiner, 1929, J. Wash. Acad. Sc. v. 19(19). U —
After Steiner. 1933, .1. Parasit. v. (20(1). V — .\fter Mcintosh
and Chitwood, 1934, Parasit. v. 26(1). W-X — After Thorne,
1937, Proc. Helm. Soc. Wash. v. 4(1). Y and AA— After
Thorne, 1925, Tr. Am. Micr. Soc. v. 44(4). Z — After Cobb,
1920, Contrib. Sc, N'emat. 9, Remainder original.

57

approaching in pairs), six medials partially or completely
fused) or four (ventrolaterals apparently absent).

Metastrongi/loidea. Members of this superfaniily have
neither the corona radiata of the Strongyloidea nor the cephalic
inflation of the Trichostrongyloidea. Lips, if present, are mucli
reduced except in Hetastrongylus which has six massive lips,
the largest of which are lateral. The oral opening is usually
rounded and the labial rudiments, if present (Filariopsis ara-
tor, Steniirus sp.) set somewhat far back from the mouth and
bear upon them only the internal circle of papillae. The same
tendency of papillary reduction and fusion observed in the
Strongyloidea and Trichostrongyloidea follows also in this
superfaniily, medials of the external circle being smaller as
are also the ventrolaterals {Filariopsis, Stenurus, Dictyocauliis,
Metaslrongylus) .

AsCABiDiNA. Members of the Asearidina usually have three
lips, one dorsal and two subventral (Fig. .57). While the in-
ternal circle of papillae is always reduced or rudimentary the
two supcrfamilies differ as regards the external circle. In the
Oxyuroidea the ventrolateral papillae are ahvays rudimentary
or absent while in the Ascaridoidea these papillae are well
developed.

Oxyuroidea. In this superfamily the Thelastomatidae appear
to be most primitive as regards cephalic papillae, for tlie ex-
ternal circle consists of eight quite separate papillae practically
equal in size (Leidynciiia appendiculatum, ProtrclUna flori-
dana, Aoriirus philippinensis) . However, in this family lips
are usually absent, tliere being a delicate circumoral membrane.
In a few exceptional forms three reduced lips may be preserved
(Fontonrma brachyyastcr) and sometimes a lobing of the cir-
cumoral membrane may give the appearance of six reduced
lips, two medial, four submedial (Aoriinis pliilippine7isis) .

The family O-xyuridac appears to be a direct development
of the Thelastomatidae in other structural characters but the
fact that most members of this family retain three distinct lips
(Enterobiiis vcrmicularis) and one form (Oiryuris rqui) pre-
serves the rudiments of six lips, seems to indicate that they
must have originated rather early in thelastomatid phylogeny.
Unlike thclastomatids, oxyurids have only four well developed
papillae of the external circle. We interpret these as com-
pound papillae formed by reduction of the mediomedials (dd.
and vv.) and their complete fusion with the lateromedials (Id.
and Iv.). Secondary labial changes produce forms with two
lateral lips by disappearance of the dorsal lip (Macracis mon-
liystcra) and others with four lips by division of the dorsal lip
(Aspicnluris irtraplcra) . Perhaps the strangest case of labial

modification occurs between the closely related genera Well-
coinia and Syphacia. In the former genus there are the usual
two subventral and one dorsal lip while in the latter genus
there is one ventral and two subdorsal. This absolute reversal
in symmetry of the lips is not accompanied by reversal in
other organs; the dorsodorsal papillae of Syphacia are on the
subdorsal lips, each of which has two compound papillae and
an amphid in the usual symmetry ; the ventral lip has no
papillae.

The family Rhigonematidac is like the Oxyuridae in number
of cephalic papillae and the subfamily Rhigonematinae con-
tains forms with the common three lip symmetry (Rliigoncma
infcctum) . However, the other subfamily, Icthyocephalinae,
presents a startling modification of symmetry. The head is
divided forming two .jaws and contrary to general opinion
and to all other nematodes, the jaws are dorsal anil ventral
instead of lateral. The four compound papillae and lateral
pore like amphids retain their normal positions not being modi-
fied by the change in symmetry.

Members of the Atractidae are the most diversified in ce-
phalic characters of the whole suborder Asearidina. Many of
these forms are highly specialized and yet one must concede
them a very ancient position in the Oxyuroidea very close to
the Thelastomatidae. Like the oxyurids and rhigonematids
they have only four compound papillae in the external circle
and in this respect the thclastomatids should be more primitive.
Six, three, and two lipped forms all occur in the Atractidae.
The genus Atractis has six well developed lips not unlike
Rhabditis tcrricola, while Crossocepltaliis has three lips like
oxyurids. Pidchroce phala retains the three lips but has in ad-
dition cuticular projections from the labial region which may
take innumerable forms but each element is grossly similar to
an insect wing. Ilcth, on the other hand, has two lateral lips
with corrugated edges and is provided with a spinate cephalic
collarette, while in Labiditni.s f/iilosus the dorsal lip is replaced
by a tuft like appendage. In the ransomnematids {Heth,
Piilchrocephala etc.) the highly specialized or ornamental
cephalic structures are confined to the female and do not make
their appearance until the last molt.

Ascaridoidea. Members of the Ascaridoidea generally have
three large conspicuous lips; the ventrolatei'al papillae and
the other members of the external circle are all well developed.
Throughout the entire group the medial pairs of the external
circle are incompletely fused. One cannot assume ascaridoids,
having the full component of papillae, arose from oxyuroids
liut neither can one assume the reverse for the entirely sepa-

FlG. 55.

Ceiilialic rfjrioii in the T,vI('iichoi(iae. A-K aiui (> T' — T.vlen-
chidat*. M-N — Alljintoneniatidnc. A — Aiis/uitm tritivi; B —
Ditylf.nehus dipfraci; C-]0 — Neutj/lpnchutt abulhomi.s (('-D, fe-
mnle; K, ninle) ; F-H — liottilrnrUun ftimiUs (F, ft^iniile at last
molt: O. upper, head nf adult fiMuale and l()wer, adult male;
H, adult female); I — I'drati/lriieh ii.s wiU'rophnUon ; J — Aphelen-
ehoidt's paridiniiH : K — Aplu'lfnrliu.s avenue; L — Uelerotf/leii-
chus uberrans ^ adult fiee-livins feuiale) ; M — AUuntnnemu
mirahile (adult free-living female); N — Choiulronemu pufi.sali;

O — Hnpluluiuius brudjis : V — liiili/leiielnis rDhu.^ilus. A — After
Stciner, 1925, rhvtiipalh., v. 15(<l). CI) — .\tler Steiner,
19:il, J. Wash. Aead. Sc, v. 21(21). E — After .Steiner and
Buhrer, l!i:t2, J. Wash. Aead. Sc., v. 22(l(i). F-H — After
■Steiner and Buhrer. lilil:!, /tschr. Parasitenk., v. 5(2), Jj-M —
After Bnvien. 1{);J7, .Scime t.vpes of association between nema-
todes and insects. N — After Christie and Chitwood, lOill, J.
Wash. Acad. Se., v. 21(15). O — .-Vfter Steiner and Le Hew,
li>:j;j, Zool. Anz. V. 101(9-10). Reiuaituler origitial.

58

rate median pairs of tliolastDiii.-iliils i-miM liarillv Iimvc ariscii
from any known ascariiloid.

In cephalic papillary arranKi'inout ascariilciiil.s show jirac-
tically no diversity but in laliial developments diversity is
marked.

Members of the Cosinoeereidae (Cosmocriciuilis iliduic),
Ileterakinae {H< IrraVi.s- naUiiiiif) and Aseariilidae (Axcaris
liinibriCDidis) all have three larRe liiis. Tn addition to the lips
tliere may l)e ixisteriorly directed cuticular cordons (Aspido-
ilfia and nrtn-oc)iiUiis, Ileterakinae and Anisakinae resp.) and
between the lips there may be interlabia (I'orri>ciucnm and
Piiraxriiri.i, Anisakinae and Ascaridinae resp.). The lips, them-
selves, may bear denticles on their internal surfaces (Porro-
ciiiriim, Ascaris) ; the apical lobes may be separated from the
basal loites by grooves {Parascdris) \ ;nid the labial l)ulp may
assume dix'erse forms which .are considered spi'cilic ( PoJydcl-
phis qiiO(lrici)nii.i and P. hiidiUicrli) . Members of the Subu-
lurinae differ from other ascaridoids in that the lips are
reduced to apical lobes bearing only the internal circle of
papillae and there may be three (Suhiiliira distans) si.x, or
more api)arent lobes. The grossly twelve lobed oral opening
of Aiildiiocrphahis pcrtimclis is Interpreted as having ludiments
of six lips (the apical lobes) separated by si.\ interlabia.
Within the Kathlaniidae all manner of labial multiplicity is
known, the genus Spcctiitux being characterized as Ijaving six
lips, SpiidiioKra as having three lips, Kalhhinia with about
16 labial divisions and f'i.ssoplii/Jiis with a bilaterally syuinietric
head. Of these only Spironoura and Cissophyltis have been
carefully studied. In Spironoura the lips are essentially as-
caroid with the apical lobes separated from the basal by
grooves. In Ci^sophylus ro.ieiis the dorsal lip is reduced, and
transformed into a three pronged odonfium while the subven-
tral lips are massive and dentate.

C.\M.VLL.\NINA. The .suborder Camallanina (Fig. .'18) differs
from the Rhabditina, Strongylina and Ascaridoidea in that
ventrolateral papillae are entirel.v unknown. Well developed
lips are never present but rudiments of lips or lateral jaws
may occur.

Caniallaiioidea. Most of the members of this superfaniily
have no lips but instead two lateral ,iaws. However, the gen-
era Omiia and Uaploiirma (Cucullanidae) as described by
Hsii (1933) and the genus Procamiillniuis as described by Li
(193.1) preserve a less specialized condition. In Omcia six
labial rudiments (apical lolies) are present, in Uaplnncma
lijis are absent and in ProcamaUaniis the oral opening is
hexagonal. The internal circle is in all in.stances reduced in
size and the external circle represented by four papillae
(duplex in Cucullanidae and simple in Camallanidae).

Vraciincnhndca. Dracunculoids are devoid of both lips and
jaws, the rounded oral opening being surrouniled by a very
thin circunioral membrane external to which there may (Dra-
ciitwiiliis, Avoiserpens) or may not (Philomeira, ^[icroph•ll}■a)
be a cutieularized circunioral elevation. The internal circle
is well developed (a more iirimitive condition than in the
Camallanoidea) and so also are the eight members of the ex-
ternal circle. In Micropleiiia and PhiUnnctrii all of the papil-
lae remain distinct while in Draciinculiis and Avioserpen.i the
medians of the external circle are partially fused. In Dra-
ciinriiliis the internodorsals and internovenfrals fuse in the de-
velopment of the female while the male retains the generalized
condition. Members of the Dracunculidae also have a thickened
cuticular helmet which projects anteriorly forming the cir-
cunioral elevation and posteriorly so as to surround the an
terior end of the esophagus.

SpiRt'RlN.\. Like the Camallanina, this suborder contains no
forms with ventrolateral cephalic papillae and true lips, if
present, are represented only by rudimentary apical lobes.
The first superfaniily Spiruroidea shows a marked tendency
toward the formation of false lips, p.iciidiilabia, developed
from the prorhabdicms of the stoma while the second super-
family, Filarioidea, is characterized by the absence of both
lil's ami pseudolabia. In their place there may be various
types of Labial structures. Within the entire suborder the
internal circle of papillae is reduced, rudimentary or appar-
ently absent.

Spirurindra. The majority of .spiruroids (Fig. .",S) have two
lateral i)seudolabia but there is one exceptional group, the
Thelaziidac. This group is apjiarently the most i>rimitive of
the superfaniily and within it the development of pseudolabia
is reproduced. The Thelaziinae, Spirocercinae, and Ascarop-
sinae contain forms with a rounded to hexagonal oral opening,
the hexagonal form apparently corresponding to rudimentary
ai)ical lolies of six original lips. The internal circle of papil
lae is slightly reduced in all forms except Physoccphaliis in
which it is rudimentary. The externodorsals and externoven

Fio. 56.

Cephalic regions in the Strongylina. A-E — Strongjlidae. F-H —
Synganiidae. 1 — Ancylostomatidae. J — Diaphanocephalidae. K —
Cloacinidae. L-P — Triohostrongylidae. Q-R — Pseudaliidae. S-T —
Metastrongylidae. A — Slioni/i/lus equinus : B — ilurshidia faleifern ; C —
CyUndruitharyiuc rhotlesiensis ; 1) — Oesophagoatomum denlntum ; E —
Cyelirocj/clus insiffne. P — Si/ngamus trachea; G — Delelrnrrphalua
dfmidiatuK: H — Stepfianurus dentatuti: I — \ecator amfricanua : J — •
Kttlicephaltiit sp.; K — Zoninltiimus Helifera; h — Amidostomum cyngi;
M — Epoiiiifliontowlim unrinalum ; N — Allintoiihius ngctireius ; O —
Cheiropteroneiua glohocephala ; P — Tncholeipfrin penrHfi; Q — FilarioP'
Bis arntnr; R — Sfi'ntirus iiiinor; .S — DU'tgocaulus filaria; T — Mrta-
stronmihiK ehmgalii.1. B — After Witenburg, 1925, Parasit. v. 17(3).
C — '.After Yorke & Maplp.stone, 1926. Nematode para.'iites of vertebrates.
I^-T.\fter Wehr. li):i:i, J. Wash. Ac-ad. Sc, v. 23(18): 391-396. M —
After Wetzel, 1!131, Proe. I". S. Nat. Mus. (2864) v. 78(21): 1-10.
Q— After Welir, 1935, J. Wash. Acad., Sc, v. 25(9). Remainder
original.

59

tials are distinctly separate from tlie laterodorsals and latero
ventrals in all members of the family but they are near the
size of the laterodorsals and lateroventrals in some forms,
{Thelazia californiensis, Psciidofilaria pertenue, Ascarops
strongylina) and are reduced or rudimentary in other forms
{Cylicospirura subaequalis, Spirocerca lupi) . In many of the
.species one notes six euticular projections of the prostom
(Spirocerca lupi, Ascarops strojigylina). As shown by Chit-
wood and Wehr (1934) the third stage larva of Phi/socephalus
scrahilii.-; has both the six rudimentary labial lobes and six in-
ternal euticular projections of adult Ascarops. The circumoral
membrane (labial lobes) disappear in the adult and the origi-
nal internal euticular projections assume the form of paired
trilobed lips which are termed pseudolabia. It is notable that
these projections bear the internal circle of papillae but the
papillae are rudimentary, not merely reduced as in other the
laziids. It is on the basis of these observations that the heads
of other spiruroids are interpreted.

The family Spiruridae apparently contains tlie next most
primitive representatives of the Spiruroidea. In these forms
the pseudolabia are usually trilobed and with the exception of
Hedruris they do not bear the external circle of papillae. In
the Habronematinae (Habroneina) and Hedrurinae (Hedruris)
the median pairs of the external circle are very close together
or partially fused, there being an accompanying reduction in
the size of the dorsodorsals and ventroventrals while in the
Tetramerinae (Tetramcres americana) and Spirurinae (Proto-
spirura spp., Mastophorus spp.) there are four compound
papillae due to more or less complete fusion. Labial struc-
tures are highly varied in this group and very valuable as
generic and specific characters. Paired medial interlabia are
present except in the Spirurinae and their shape, relative size

and complexity make very useful taxonomic characters (Tetra-
mcres, Hedruris, Seurocyrnea, etc). The pseudolabia are di-
verse in size, gross appearance and sometimes they ha\j char-
acteristic dentition. (Mastophorus vs. Protospirura) . Tetra-
mcres americana is anomalous in that the female has neither
pseudolabia nor interlabia, a sexual dimorphism coinciding
with the degeneration of the female to the form of a repro-
ductive sac.

The family Aeuariidae is interpreted as being most closelj'
related to the Spirurinae of the family Spiruridae. As in the
latter subfamily, there are only four well developed papillae,
these being apparently the completely fused dorsodorsal-latero-
dorsals and ventroventral-lateroventrals. Unlike spirurids, the
pseudolabia of aeuariids are not trilobed and they bear the
four papillae. I'rojeeting posteriorlj- from the pseudolabia
aeuariids always have some type of euticular ornamentation
these ornaments taking the form of cordons in the Acuariinae,
a spined cephalic collarette in the Seuratiinae, and four va-
riously formed appendages in the Schistorophiuae.

Passing now to the Gnathostomatinae we find that the pseudo-
labia have assumed a more massive size, become fleshy, but
retained their lobed character. There are four double papillae
in all forms, the degree of fusion varying in the different
genera. Of this family the Spiroxyinae is undoubtedly the
most primitive for it contains such forms as Spirojrys contnrta
which superficially resemble Protospirura and Mastophorus of
the Spirurinae. The subfamily Spiroxyinae differs from the
Spirurinae in tliat the pseudolabia are massive, and bear the
external circle of papillae in the former subfamily while they
are inconspicuous and the papillae situated posterior to them
in the latter subfamily. Gnathostomatids such as Tanqua
have similar papillae but the pseudolabia are more irregularly

Cephalic regions in the Asciiridina. A-C — Thehi.'^toriuitidiic.
O-H — Atractidac. I-J — Rliiffoneniatidae. K-N — Oxyiiridae, O —
Cosniocercidae. I*-Q — Kathlaniidae. R-T — Heterakidae. V-\ —
Ascarididae. A — Lfidurifiiia cranifera ; B — Protrfllina fitirifln.na ;
(' — AoruruN philijfiiinansin ; D — Pvlchrorfiifiata sp.; E — Hefh
Airiiiirp}nnii : K — Atraclin sp. ; G — CrnHsfK'fiilinhtu vivipiints; H —
Prohtttttnijfria rivipttra ; I — Rhif/on^mn inffftlim; J — Icthyocephn-
lu8 sp. : K — Oxyuri« fqui; L — EiiterohiuK vermirulttrin ; M — As-
piculurU tetraptera; N — Dermatnxps rcUijrrn-; () — Cosmorcrcoidett
dukae ; P — Spironoura uffine ; Q — Cinsopln/fns rntteuy; R — Siihu-

hirn itis-tinis ; S — A iilnmn'i'iilmhts pfrdiiirlis ; T — Ijrtfriikis jjiillimie ;
U — Porroi'iifcttm cheni; V — Poli/deijiliiK qundrit^orniji : \V — Pidy-
delptti« hoddaerti: X — Parttscaris equoriim ; Y — Ascaris himbri-
cnides. A-B — After Ohitwood, 1932, Ztschr. I'arasit., v. 5(1);
C — After Chitwood & Chitwood, 19114, Philipp, J. Sc, v, 52(4).
S — After Baylis, 19:i(l, Ann. & Mag. Nat. Hist, s, 10, v. .5. U—
After Hsu, 1933, J. Parasit. v. 19(4). V-W — After Baylis. 1921,
Parasit. V. 12(4). X — After Yorke & Maplestone, 192(5, Nema-
tode parasites of vertebrates. Remainder original.

60

liilifil :ui(i i>(istoii(ir to tluin tlicir is a laiKO c<'|i1i:iIk- Imlli
fornioil l)V till' anterior expansion iif four internal posteriorly
extending eloseil saes, the l>allonets (Ttinqtm). Xeitlier tlii'
Anevracaiitliinae nor the Spirox.vinae have a ceplialie Imlb
liiit some authors have reeoriled hallonets in Anciirafantliiis.
The eeplialie liulti apjiarentlv t'linetions as a hohlfast. beint;
eollapseil when the anti'rior enil is inserted into the niueosa
and thereafter liein^; inllated. Spines or ret rose annnlation
are provided to aid in this funetion. Anciiractuilhii.i with four
posteriorly direeted eephalie a|ipendages resembles Scliistoro-
fihiis of tlie Aeiiariidae but the ineoniplete fusion of the ee-
phalie papillae and the lobed tleshy i>seudolabia seem to de(i
nitely plaee it in the (inathostoniatidae.

The I'h.vsalopteridae ap|iarently represent the liiial eonelu
sion of evohitionary tendencies in the Spiruroidea. Here we
find paired, massive tleshy, unlobed pseudolabia bearing both
amphids and four completely fused compound pajiillae (latero
dorsal dors<idorsal and lateroventral vi'utroventral ). Tlie va
rious species of this family have been divided into genera by
Schulz (1027) on the basis of their dentition. The genus
Pliysalopit ra is characterized by the presence of four teeth on
the internolateral face of each pseudolabium, an internal
group of three, two being sublateral and one lateral, an<l a
single externolateral tooth. Tliiihiinnrn is similar but the
teeth on one side are always rudimentary. Abbrcviata, has the
same later.-il teeth but instead of sublaterals the entire margin
of each pseudolabium is dentate and there are four double
submedial teeth. Whether or not these teeth correspond to the
original pseudidabial lobes is problematical but their develop-
ment as laliial structures seem to place them clearly in the
category of otloiilin which stateuu'nt also applies to the teeth
of Protosjiirura, ^^astophorus, Odontospirura, etc. of the fam-
ily Spiruridae.

FUarioidra. Many tilarioids have neither lips, pseudolabia,
nor any other types of labial structures (Fig. 59), Such
forms (IJirofilaiia. Dipvl alone ma. Elacophora) are placed in
the family Dipetalonematidae. They are characterized by the
absence of any structure which might be conceived to be of aid
in feeding or penetration of tissue. The oral opening is
roundeil and bordered by a very delicate cireumoral membrane.
The ma.iority of the remaining forms have some type of ce-
phalic armature, such an armature sometimes taking the form
of a cireumoral elevation which may bear lateral (Uicluilo-
nenm) or other anterior tooth like projections (pseudonchia),
sometime taking the form of a sclerotized* helmet (Squamo-
filaria), sometimes having both cireumoral elevation and hel-
met (Dichrili))ir)iia), and sometimes taking the form of lateral
sclerotized tridents (Diplofriaena). These forms are all in-
cluded in the family Filariidae. The remaining two families,
Stephanotilaridae and Desmidocereidae each contain but one
genus and may later be more closely associated with the other
two families. The former family has one or two circles of
cephalic spines while tlie later is devoid of external armature
but possesses two internal cutieular pro.jections of the prostom
which ma.v lie homologous to the pseudolabia of siiiruroids.
In the number of cephalic papillae the super-family Filarioidea
is a remarkably constant group. There are always eight sub-
equal large papillae which tend to take the form of two circles.
However, we interpret these papillae as representing a sub-
divided external circle and the dorsodorsal and ventroventrals
are usually anterior (Dicheilonema, Dirofilaria) to the latero-
dorsals and lateroventrals. The internal circle is apparently
absent except in a few genera where it is represented by re-
duced internolaterals (DipetaJancma. Litomosa, and Desmido-
circa). Many writers would interpret the four anterior papil-
lae of tilarioids as the internal circle but we cannot do this
because in our comparative studies it is notable that throughout
the entire Phasmidia there is a tendency toward reduction in
papillary size. This tendenc.v affects the internal circle first,
and tliereafter the externomedians. Furthermore, the rear-
rangement of the external circle into two circlets as a tendency
in the order Spirurida is noticeable in iticroplcura (Dracun-
culoidea) and Pst mlnfilaria (Spiruroidea) in both of which
there is the full component of papillae.

R. APHASMIDIA

Aphasniidians have externally modified amphids in all except
the parasitic forms and even in these the modification per-
sists in many of the Mermithoidea. Filip.jev (1918, 1929, 19.S4)
used the morphology of the amphiils ;is one of the prime char-

*The term sclerotized i.s used in ttie reiiminder of this text to indi-
cate hardening witliout siRnif.ving tlie chemical composition. Eventually
the chemistry of specialized cutii^ulnr structures will be discussed.
Though many nemic st-mrtures superticially resemble cbitin. this sub-
stance has been demonstrated only in the egg shell

Meters of nia.joi groups. .More recently Stckhoveii «nd de
Coiiinck (19.'i:t) have rcalliriiied such usage with modification.
Of the many amiihidial variants, there are tliree primary types
in the .\ph:isinidia, these being the .'spiral, circular, and cya-
lliiform (iiocketiike). One easily recognizes transitions from
(ini.ipin to (lispirc .-ind mull ispiri , and other series from unispire
lliiougli (iiKsliiin marl:, to sIiiplicril.-< criiok : these latter may be
termed modified spir;il amphids. Transition lietween unispire
and circular is also an obvious step often indicated by ;i per-
sistent break in the circle. Stekhovcn and de Coninck (1933)
further derive the rcniform (transversely elongate) amphids of
Oiritmailnra from the circular amphids of Mwralaimiin. In-
Icrrelationsliip of these amphidial types seems scarcely ques-
tiouiible and this fact is used jis a basis for the order Chro-
madorid.'i.

The cyathiform type of aiiipliiil. characteristic of the order
Knoplida. seems at first glance to be of an entirely different
formation but as we sli;ill see later, it also appears to liave
been derived from something close to the unispire.

Cephalic sensory org.-ms in the .\pliasmidia universally have
one jioint in common, the lateral p.-ipillae of the external circle
are externolateriil rather than vcntrol.ateral in iiosition. This
is correlated with the post labial position of the amphids and
is, perhaps, more primitive than the rhabditoid (and general
lihasmidian) arrangement. The size of cephalic setae presents
another interesting field for observation; the external circle is
always larger than the internal circle and whether the external
circle is subdivided {Plectus, laimclla) or not (Paracanlhnn-
cltiis, .tnlicoma, Theri.<itus) the elements are always of two
sizes. If there are four large setae these are laterodorsal
and latcroventral. but if there are six they are dorsodorsal.
ventroventral and externolateral. The coni|ionents of the in-
ternal circle are often papilla like and h;ive been overlooked
by many observers; the smaller members of the e-xternal circle
may also be overlooked. It may be stated, however, that with
scarcely an exception the full component of cephalic papillae
is present. Supplementar.v cephalic papillae or setae also
occur and are very apt to cause confusion in the nomenclature.
Two or more pairs of sublateral setae next to the ampliid
(paramphidial setae) are of the most common occurrence such
being quite common in the Axonolaimoidea and Monhysteroi-
dea. The only ea.se of apparently true duplication of cephalic
setae occurs in some monhysteroids {Tlicristii.i) in which the
externolaterals are double. Mergence of somatic with cephalic
setae (or papillae) is an unusual but not uncommon phenom-
enon. In such cases (Eiistrongylide.i, Mononchus, Metachro-
maihira) the .sublateral or submedial somatic setae extend to
the head region and become confused with the external circle
of cephalic setae. Such added setae may become so numerous
as to completely obscure the normal symmetry (Slrincria).
Fusion of cephalic sensory organs, so common in the Phasmidia,
seems to be non-existent in the Aphasmidia.

Labial structures are entirel.v too diverse in this class for
one to make satisfactory general statements. Both six and
three liiiped forms occur in the two orders but six lips aro
definitel.v preponderant.

MONHY.STEKIN.V. In cephalic sensory organs the suborder
Monhysterina (Fig. 60) exhibits no real distinguishing char-
acter from the Chromadorina, one can speak only of tendencies.
The lips may be well developed, entire (Plcctu.<i), they may be
represented only by the apical lobe (Axonolaimiis) or they
may be absent (SphaeroIaimii.<!) . In no instance are lips ob-
viously replaced by cheilostomatal or prostomatal rugae.

Plectoidca. The Plectoidea is undoubtedly one of the most
interesting groups of the entire Aphasmidia for it contains the
potentialities of every structural diversity of the subcla.ss. In
tactile organs the great majority of the forms are uniform hav-
ing an internal circle of six pajiillae and a subdivided external
circle of six papillae (dd., vv. and el.) and four setae (Id. and
Iv.). Paramphidial setae are unknown in the group. The di-
versity of amphidial form in the group provides clues to the
relationships of the whole Aphasmidia. In Anonehus mirabilis
and Plectus rliisophilus one sees the typical unispire amphid,
a double contour structure, each edge being the side of the
groove. In Aphan<ilaimu.<i aqualicu.<t and CaiiKicalaimux pry-
therchi there are nearly closed, unispire amjihiils of single con-
tour but if one observes these en face, one sees that the central
protuberance is present. These amphids are also unispire
grooves. The broken circle (singh' contour) amiihid of L<p-
tolaimu.i maximu.i has not been studied en face but other species
of the genu-s are known to have unispire amphids. Anaplcclus
(jranulu.iux (Phctu.K graiiulo.suK) is the final summation of all
others for it combines features of the circular, unispire and
cyathiform amphids. One might even term it a "universal
amphid." At the surface it is a transversely elliptical, but
internally it is both unisiiire and cyathiform. One might argue

61

oo

Fig. 58
62

th;it till' pli'i-tdiil aiiipliiil cniiie to its fdnii.-itidii tliroutili sub-
niorgoncc of :i spiral aiiipliiil or tliat tlio sjiiral aiiipliiil dovel-
opoil from till' pli'i'toiil tliroU);li cnicrtjencH'. Ill I'itluT case,
tliis type must lie eonsiilereil a ecimmon Jenoiiuiiator of the
A|iliasmiilia.

Do Coniiuk Oi''^-)^ •'»« roi'i'utl.v iilaccd tlie family Bustianii-
(lae in approximate relation witli pleetoiils on tlie basis of am-
pliidial and male supplementary orj;an eliaiaeters. In this
grmip he ]>laees PrixmatDhiimuK. Tiipylii, Tiilobus and Bas-
tiania. Gross similarity in esophagi support his view hut the
writers cannot accept it. The three former Ki^nfi-i seem best
placed in the Knojilina (Tripylidao). Do (^ininck notes varia-
tion in Ha.stiuiiiii itart\rili.i from unispire to transverse (cyathi-
fornO. The writers may add that in Iliistioiiiii cjilin a sinKle
specimen had one unispire and one broken circle ampliid.
Bastionia and Oddiilohiimii.i are odd iilectoids in havinfi; 10
ceplialic setae, the external circle being partially sulidivided.
The oddity goes even further in that the six anterior setae
(dd., el., vv.^ are slightly longer than the four posterior (Id.
and Iv.). Thus we find the ()-(i-4 symmetry of Plectoids re-
mains but the size relationships in the two external .subdivisions
are reversed. The genera Bnntinnia and 0<lnnti)laimi(s seem
best placed in the family Hastianiidae as an appendix to the
Plectoidea.

A.r(inol(iimoidta. In tlii.s superfaniily one finds the same
base symmetry as in the Plectoidea, namely an internal circle
of six papillae, a subdivided external circle of six papillae or
slKirt setae (dd., el. vv.) and four long setae (Id. and Iv.). In
addition paramphidial setae are apt to be found .just posterior
to the cephalic setae. Such .setae may be four (two pairs) in
number, preamphidial (Sabnticria loni/icaudala) or postamphi-
dial (Laimilla quadristiosa) or they may be eight in number
(four pairs) {Odontiijdiora anpiistilaiiiia, Axonohiiniiis siib-
similis, A. ndi>nlop}ivri)ides).

The family Comesomatidae is rather uniform in having nuil-
tispiral amphids but the Axonolaimidae, are even more diverse
than the Plectidae. Aracalnimiis (Arncolaimoidcs) ^osierae
Axonolaimii.s siibximilis and Odontophora have rather distinct
double contour unispire ani|diids, Arat'olaiiniis ci/liiidrolaimus
has a broken circle to single contour ampliid and Ci/liiulro-
laimiis commumis a circular ampliid. The amphids .show nu-
merous gradations in elongation from the unLspire type in
AxonnJaimus subsimiU/< to the inverted U of Axonolalmus spino-
sus and shejiherds crook, PscudoIcUa granuUfera. As in the
Plectoidea, each external aniphid is a spiral groove, posterior
closure of which leaves a central elevation. Argialonlaimiis elc-
gans represents the sole instance of multispire amphids in the
Axonolaimidae. However, the Diplopeltinac introduce still
another variant, the presence of lateral shields accompan.ving
the amphids (Didelta). In this group one may trace a repeti-
tion of the unispire — question mark — circular amphid devel-
opment.

^f(>nhl|■'<fcroidca. Monhysteroids have great diversity in ce-
phalic symmetry. The most common arrangement 13 an inter-
nal circle of six papillae and an undivided external circle of 10
or 12 setae. Stekhoven and de Coninck (10.S3) characterized
the group as typically hexaradiate. The one unifying charac-
teristic is that the amphids are nearly invariably circular.

The family Linhonioeidae includes some forms such as
Ml talinhomonis typicus and Dcsmolaimiis ^relandicus with a
subdivided external circle of six jiapillae and four setae (Id.
and Iv.") or (> (5-4 symmetry; others such as Piiniliiihomocns
Irptunis, i[(inh}jstrriiim traiisitans and JIalhicma xpinosiim with
an undivided external circle of six short and four long setae
or 6(6-4) symnietr.v; and still others such as Linhomoeus
eUnigatus with an undivided external circle of four short and
six long setae or 6- (4-6) symmetry. There usually are, in
addition, eight paramphidial setae. The genus Spliaerolaimns
presents an arra.v of setae that has not as yet been satisfac-

torily interpreted. One linds the normal internal circle of
six papillae followed by a circle of six short setae (f dd., el.
and vv. ) followed by a circle of Hi setae, in eight jiairs, two
pairs sulilateral, two submedi:il; in addition there are two pairs
of preaiiiphiilial setae and somatic setae arranged in eight
longitudinal rows (submedial and siiblateral). One might, pro-
visionally, assume that four papillae of the external circle
(Id. and Iv.) have been overlooked and somatic .setae have
added to ceiihalic setae. On this basis the symmetry may be
characterized as filO (4?-0) + 16 (8-8) + 4 (2-2).

Members of the Monhysteridae sometimes have but six
elongate setae (6-4-6) such as Cylolaimium ohliixiriiiiilalitvi
but more coninionly there are 10 or 12 setae in the external
circle. IliilmKiiicliiix mnrrampliiilinn and Tlurisliis sitiisiis rep-
resent the more typical arraiigenieiit with six pafiillae in the
internal circle, six short and six long setae in the external
circle. Of the latter circle the longest six are the dorsodorsal,
ventroventral and dorsolateral. Duplication of the externolat-
eral results in a large dorsolateral and a small ventro-
lateral. Such symmetry may be characterized as 6-12 (6-6).
Paired sublateral preamphidial setae are also present. Scap-
trcUa cincta has a peculiar combination of axonolaimoid and
monhysterid symmetry. The presence of 6 short setae in the
internal circle and 12 setae in the external circle is characteris-
tically monhysterid but the external circle consists of setae in
three sizes; four are very long (Id. and Iv.), 6 are moderately
long (dd., vv., and dl.) and two are short (vl.). Therefore,
the external circle might be characterized (2-6-4). Omicro-
ncma liloriiim and Slrint-ria sp. represent types with increased
cephalic setae. In the former instance three circles are de-
scribed, an internal circle of six setae, an intermediate circle
of four sublateral setae and an external circle of 18 setae in
six groups of three, an arrangement which may be noted 6-4-18.
It seems possible that a restudy of OmicrnniiHa will show it
to be a sphaerolaim. Stfineria, on the other hand, is typically
monhysterid in character having an internal circle of six
papillae and an external circle of 10 or 12 setae (according
to the species). In addition to the cephalic setae, nnnierous
somatic setae are grouped anteriorly in eight longitudinal
rows, four submedial and four sublateral.

Siphunolaimiis has an internal circle of six papillae, an ex-
ternal circle of 10 setae of which the four sublaterals (Id. and
Iv.) are the largest; this 6-10 (6 + 4) symmetry is more like
ParaUnhomoens than any other forms discussed.

The circular amphid with central fleck is often mentioned
as a characteristic of linhonioeids but the central fleck is
neither confined to that group nor obvious in all members.
As in plectoids, a central elevation represents the inner side
of the amphidial groove, be it circular or spiral. The rela-
tive height between grooves determines the gross "presence"
or "absence'' of a central fleck.

Paramphidial setae of some type arc nearly always present
in monhysteroids; most commonly these are four in number,
sublateral preamphidial in position. In addition to which
there may be four sublateral postamphidial or four submedial
preamphidial setae.

Six separate or three more or less lobed lips may be pres-
ent in monhysteroids but if so, they are generally reduced, the
labial elevation bearing faint longitudinal ridges: which are
developments of the cheilorhabdions.

Chkomadorin.\. Jlenibers of this suborder show all of the
diverse .symmetry arrangements (Fig. 61) of cephalic setae
and nearly all of the amphidial forms present in monhysterins.
True lijis are seldom ajiparent but very highly developed
cheilostomatal rugae usually t.ake their place.

Chromadoroidea. The family Microlaimidae is characterized
by unLspire, postlabial amphids, an internal circle of six papil-
lae and a subdivided external circle of six papillae or short
setae and four long setae, 6-6-4 symmetry. True lips are

Fig. 5H.

Cephnlic ref^ions in the rurTiallanoide.-i. T^racuneuloidea and
Spiruroidea. A-C — Caniallanidae. D-F — C'ucullanidap ; G-H —
Philometridae. I-J — Drarunrtilidae. K-V — Thelaziidae. W-KK
(except Z) — .Spiruridae. LL-NN & Z — Aruariidae; OO-PP &
UU-VV — Physaloptcridae. QQ-TT — Cnathostomalidac. A — Proc-
amallanus fulvvlrticonU ; B — CtimalUinus sweeti: V — CamaUanun
iiiicrorrplifiluM : 1) — Omfio hoe/t/jlii; E — Ha/ihniptim sinensis: V —
CucuUitnttti friittae: (i — M irrnplfurti vivipura : II — PhiUnitetra ru-
bra; I — Drtn'uneutuit nieitinenjiis. male: J — Dra*'uncuhis medinfn-
SIM, female: K — Thflnzia caUfornienHix : L — Psfudufilnriu ])prtf7tue :
M — OxyHjiirttra mnnsotii ; N — Spirorcrca lupi: O — CyUrospiritra
ttuhnrfiimlitt ; P — Ajifarops strtintn/Jinti ; Q — Physncephnluif HfXttla-
tun: li — SinintitfMia pnrndoxn ; .S — Leiurin tcplorfphidus ; T — Strep-
topfiaruniiH artiiatiiH : V — Riclidnrin roJoradienfiiK : V — Gntttjj/lo-
neriia pntrhrnm: W — Spirtira ri/tipUtiritp>i ; X — Protnspirurti ntt-
midica ; Y — Rhitbdnrhotui kidderi: Z--~Stf{tophnrtt/t Htelhte-polaris.
AA — •Spinitectus cnrolini ; BB — Huhronema microstoma; CC —

l>rnsrhia metniKtoma : DD — firurociirnrn unrinipfnijt ; EE — Para-

hronrma inilirlim; FF — Odaiitospirura rrtinpfniji ; GCi Masln-

phiinis miiriK; HH — Ci/slUlirnla stigmnlun; 11 — Hedniris sp.
•IJ — Trlramfres iimericana (male) : KK — Aacnrophis harvoodi.
I,L — -Icrinria anllniris; MJf — Tsrria coronula: NN — Sehinto-
phorus ciic\illat<iit: 00 — Skriabinoptera phrynoHoum ; PP—Thu-
hiniara leiolopismue ; QQ — Kpiroxys rontnrta ; RR — Hnrtertin fjal-
liiwnim: S.S — Tnnqun tiara; TT — inri/raranlhus pinnatifidut ;
VV — Abbreriala mnrdrna; VV — Physaloptera maxitlarix. A —
After Li, in:!.5, .T. Parasit., v. 21(2). B — After Moorthy, 1937,
J. Parasit.. v. 2:i(.'!). D-E' — After Hsu, 1933, Parasit.. v. 24(4).
L — After Sandgrouiid, 1935, Rev. Zool. Hot. .\fr. v. 27(2). EE —
After Bavlia, 1921, Parasit., v. 13(1). FF — After Welir, 1933,
Prnc. IT.'S. Nat. Mus., (29.i8) v. 87(17). Z. MM. NN— After
Welir. 1934 J. Wash. Arad. Sc. v. 24(8). Remaining fiEures
based upon Ohitwood & Wehr, 1934, Ztschr. Parasit. v. 7(3) and
iinpuldished observations.

63

rudimentary or absent, and li! more or less projeetable eheilo
stom rugae are present. Cliromadorids differ from micro-
laims only in tliat the amjihids are moved anteriad, usually to
the level of the cephalic setae, and vary from unispire (OtJon-
lijnrma) to reniform (Pn)chniiniiilora) . The C'yatliolaimidae.
and Tripyloididae, differ from luicrolaimids aud cliromadorids
in having an undivided external circle. In all forms studied
by the writers there are four small and six large (dd., el., and
vv.) papillae or setae in the external circle. De C'oninck
(193.5) characterizes cyatholaimids as having two circles of six
papillae and an external circle of ten setae. Since he specifies
no form as exemplifying this condition we must judge by our
own observations. In some cyatholaimids particularly members
of the Choanolaiminae such as HalicJioanolaimiis robtistiis, the
fiber trunk of each of the papillae of the internal circle shows
in optical cross section much like a papilla but then it bends
nearly at right angles over the stomatal cavity before reach-
ing the true sensory terminus. Thus, by optical illusion one
may see more papillae than exist. Rudimentary lips and
heavy stomatal rugosities (usually 12) are conspicuous fea-
tures of most members of the Oyatholaimidae (Gammnnema.
Ealichrianolaimus, Paracanthotichns and Pomponema) while
three well developed lips occur in members of the Tripyloidi-
dae. Both circular and unispire amphids are known in these
families but multispire are the rule.

Dcsmodnroulra. Like microlaimids and cliromadorids mem-
bers of this superfamily have an internal circle of six papillae
and a subdivided external circle of six papillae or short setae
and four long setae (laterodorsal and lateroventral). Mono-
posUiia hcralata and Spirina parasitifera are typical exam-
ples. Somatic setae arc quite apt to become nearly cephalic
in position as in Mrtachroinailnra ontjxoidc.t and Croconema
mammilla turn but by careful study one can usually segregate
the two types. Helmet formation is often a conspicuous des-
modoroid feature but this has been previously mentioned with
the cuticle. Amphids in desmodoroids are primarily spiral, the
unisjiire prevailing {Epsiloncma, Spirina) but closed unispire
(Milachromailora oni/jroidcs), circular (Moiwposlliia hcxalata),
multi.spire (Richtersia hcauforii) and elongate or shepherd's
crook amphids (Ceramnnema) also occur. True lips are rudi-
mentary, sometimes indicated by six rudiments and stomatal
rugae often replace them but these also disappear with reduc-
tion in stoma.

Desmoscolecoirlca. The amphids of desmoscolecoids are a
characteristic feature, usually being described as vesiculate.
They are rather bubble like but internally one may distinguish
evidences of a unispire character. Due to their small size the
head of only one species, Desmnscolex americanus, has been
studied en face. In this form there are six minute lips each
bearing at least one (?two) papillae. Four large cephalic
setae are known in all forms. Thus we may ])resnme a possible
desmodoroid relationship.

Enoplina. Members of the suborder Enoplina may have
three, six or no lips, cephalic papillae or cephalic setae, but
they are all similar in having cyatliiform amphids.

Tripyloidea. Included in this group (Fig. 62) are many
forms which show relationships to other groups. The Monon
chidae, with six lips, an internal circle of six papillae and an
external circle of ten papillae, seem clearly related to doiy-
laimoids. The family Tripylidae includes closely related forms
with diverse symmetry. Tlie genus Tripi/la is characterized by
three lips, an internal circle of six papillae and a subdivided
external circle of six papillae or short setae and four papillae
or long setae (Id. and Iv.). Trilobiis lo7ifiii.i and Prisma! olai-
mnx intrrmeiliiis have six small lips (apical lobes), an inter-
nal circle of six papillae and an externa! circle of 10 setae,
four being short •■md six long (Id., el., and vv.). De Coninck
places these forms in the Bastianiidae close to PJcctiis but we
cannot agree with this placement on the basis of eso))hageal
characters. Undoubtedly the Tri])yloidea is the most primi-
tive groujj of the order Enoplida, and hence most closely re-
lated to the I'lectoidea but it is customary to i)lace primitive
groups with tlie forms that they gave rise to rather than with
other primitive groups.

The family Ironidae includes forms which may {Ironiix.
IroneVa) or may not (Crypt onchus') have cephalic setae. If
such are present the external circle is subdivided with six
anterior papillae or setae and four posterior setae (Id. .-ind
Iv.). Lips may be moderately distinct but .are usually rudi-
mentary or absent.

Jinopldidra. With the except ion of the (Jxystomiiiinae the
Knoploidea (Fig. tiS ) hold quite closely to a six-ten symmetry
with an undivided external circle of which there are four small
and six large setae (d<l., el., and vv.). In the single excep-
tional group, tlie external circle is subdivided, with six large

anterior and four large posterior setae (Huhilaiiiiii/i carnlinicn-
sis and Oxiisfnmina iiliilia). Lips are seldom well developed in
enoploids but one finds three massive apical lobes in E)uyploidcs
and Endid-ilnimiis. three small apical lobes in Etuiphis, Jnti-
roiiia and Antiplttsioma. Si.x small apical lobes are general in
the Oncholaiminae but even such lobes are not apparent in
forms such as Bolbilla lenitidens and Enchelidium pauli.

In most enoploids the amphids are typically cyathiform but
in the Oxystomininae they are longitudinally elongate (Oxii-
stamina alplia, Halalaimiis caroliniensis). De Coninck (1936)
considers the oxystomins related to the genus Aratolaimus
and derives the amphids by elongation. This point requires
more critical study. If the o.xystomin amphid is a modified
spiral, then it must be an open groove while if it is an elon-
gate pocket, it is open only at its anterior end. Thus far such
information has not been presented.

DoRYL.\iMiNA. Like the Enoplina, the suliorder Dorylainiina
(Fig. 64) is characterized by cyathiform amphids but in para-
sitic members of this group the amphids may become externally
pore like. The cephalic papillae of dorylaimins, like those of
mononchids and phasmidians, never take the form of setae.

Dorylaimoidca. Members of this group for the most part,
have six rather well developed lips; sometimes the lips are
set off from the remainder of the body as in mononchs and
rhabditids. The full component of cejihalic papillae are recog-
nizable, there being an internal circle of six and an external
circle of 10. Members of the latter circle are usually of two
slightly different sizes and at two different levels on the lips.
The large cyathiform amphids are situated just posterior to
the labial region. Thorne (193.5) described the amphids of
diptherophorids as ere.scentic with reminiscences of spiral fea-
tures.

Mermithoidva. Functional lijis do not occur in mermithoids,
the original lips being represented only by fiber tracts of the
six papillary groups. These fiber tracts are {Mesomermis
bursata, Hoxamermis albicans) usually referred to as "papil-
lae" in the literature. Careful study shows each of the four
submedian "papillae"' end in three tactile sensory organs
(true papillae) while each of the laterals end in two; this
corresponds exactly to the normal papillary symmetry with 16
papillae. The amphids may be associated with the lateral lip
rudiment (Hcxanirrmis albicans) or they may be quite separate
from it (Mfsonicris biirsiita). One finds all manner of am-
phidial t.ypes from large cyathiform as in Mesomermis to ex-
ternally minute pore-like structures as in some Hexamermis.
In addition, instances are known in which the amphids are
joined dorsally by a fiber tract, a condition particularly com-
mon in the genus Pnramertnis. A shift of the oral opening
ventrally is not uncommon in mermithoids {Eumermis, Lim-
nomermis) and this migration is not accompanied by a shift
of cephalic papillae, though the anqiliids may assume a more
dorsal position.

I'richiiroidea. Cephalic papillae and amphids have been stud-
ied in only one member of this superfamily, Tricliuris suis. In
this instance lips are absent, six papillae and externally pore
like amphids were observed. The position of the lateral papil-
lae (presumably of the external circle) in a true lateral posi-
tion seems distinctly to indicate aphasmidian relationships.

DIOCTOPHYMATINA. Dioctojihymatoids are well known for
their cephalic symmetry or lack of it. Lips are absent in all
members of the group. The oral opening in the Pioctophyma-
tidae is surroiindeil by a cuticular circumoral membrane while
in the Soboliiihyniatidae the body extends anteriad beyond
the true oral opening forming an oral sucker. Presence of
modified somatic muscle tissue and body cavity in this sucker
is distinct evidence that the true oral opening should be re-
garded as the base of the sucker cavity; presumably, the
cephalic papillae are on its infernal surface.

"Cephalic jiapillae" are so numerous in members of the
Dioctophymatidae (Eustron-gylides ignotus, Dioctophyma re-
nale) as to completely confuse one first observing them. The
total number and arrangement varies within the species but
certain iiaiiillae remain constant (Fig. 64). These latter are
the true cephalic papillae; the others are considered as somatic
jiaiiillae extending anteriorly from the lateral areas. There
is an intern.'il circle of six pajiillae and an external circle of
four small (Id. and Iv.) and six large jiapillae (dd., el. and vv.).
This symmetry is the same as that to be found in a large part
(if the Dorylaiinoidea and Enoploidi'a. If is in definite op-
position to fli:if founrl in ]diasmidians such as the Si)iruroidea
to which these nomas are sometimes compared. The amphids
of dioctophymatids are posterior to the externolateral jiapillae,
sometimes ajipearing to be narrow, cyathiform, sometimes
l>ore-like.

64

2. STOMA

Till' stnictuir lit' till' sliiiiia has noiuiallv Ihtii uscil :is a
laxiiiuiinic cliaraitcr .since the ln(;iiiiiinn of iicniatdldK.v. Its
wide iisr fur tin' I'lassitii-atiim <if Kiciups iif all lanks makes a
liiiiroiiKli ediisideratiim of its evolution neeessarv. That its
nioiplioldn.v has avt'-At vahu' ran scarcely lie ilonliteil li.v aiiv
worker in tin' liehi l)Ut the weight that may lie (jiven to its Ki'"ss
form seems duliioiis. Since the method of feeding and char-
acter of the food itself is limited liy the stoma and its arma-
ture, this orKiiii is prolialily more ilirectly intlnenced liy en-
vironment than any other. A radical clianue of feeilinj; lialiits
of closely related forms would reiniire chantje in stomatal mor-
phology if forms are to survive. Likewise it is not at all in-
conceivalile that (luite unrelated nemas coming to feed in the
same manner might eventually liecome grossly similar as re-
gards stomatal morphology. For the aliove reasons one must
consider stomatal inorjihology very closely.

Only lun' author, fold) (llUiO. has .'ittempled to use stomatal
morphology as a ma.jor character. This author made the
"presence'' or "alisence" of a stoma ("pharyn.v. " Inn'cal
capsule I'tc.) the li:isis of dividing the ''Xeniates" into two
classes, I.;iimi;i :ind ,\I;\iinia. This classification based upon a
single character tot;illy withcnit correlation with an.v other
organ has nothing in coninum with other classifications. Though
their viow|ioints ma.v lie iliametricall.v oiiposeil, the classifica-
tions of other writers all have considerable in common and
they all are at eomidetp variance with that of Cobb. The
"presence" or "absence" of a stoma seems to be a rather
bad point for da.ssification purposes since all nematodes have
something corresponding to the stomatal region.

Filip.iev (1934') considered enoploids such as Lrptoxo malum
which have no definite clear cut stoma as the more i)rimitive
while the writers regard forms such as Kluihililis and Phcliis
with distinct elong;ited stomat;i as primitive. Steiner (lO.'iS)
proposed a nomenclature for tin' parts of the stoma which we
shall follow as far as possible indicating hdmologons regions
and structures and the apparent evolutionary trends and varia-
tions as we interpret them.

The cylindrical stoma of Shabililis may be divided into three
lirimary divisions (1) cheilnstom — lip cavity, (2) profostom —
cylindrical part of stoma and (:•!) trlontnm — end cavity, which
in this form is often ternu^d the glottoid apparatus. The cor-
responding walls of the stoma are termed cheilorhabions, pvo-
torlialidions and telorhabdions, respectively. The walls of the
protostom, i. e., protorhabdions, in Rliabdilis are less distinctly
subdivisible into three parts (a) prorhalidions, (b) mesorhab-
dions. (e) nu'tarhabdions the corresponding regions being termed
prostom, mesostom and metastom, respectively. In rhabditids
the division between niesorhabdions and metarhabdions is
scarcely visible in many species bnt manifests itself more
prominently in relateil forms. The first subdivision, i. e., pro-
rhabdions vs. nieso metarhabdions is qnite obvious and has long
been recognized as the "month collar or month cuff." The
basic parts of the stoma are apparently innate in the man-
ner of their deposition and ma.v best be observed in molting
specimens or in specimens treated with reagents such as weak
acids and alkalis. On the basis of studies made in this manner
it would .seem that the appearance of .pointed prntorhalidions
in representatives of diverse groups is not convergence in the
strict sense bnt rather manifestation of an innate chanicteris-
tic which is ordinarily masked.

The stoma may take diverse shapes due to modifications of
its parts and nniny different types of arni.iture are developed
according to the p.'uticniar group involved. One of the most
common types of armann'nts are teeth. Historically the term
tincliio has been nuist commonly aj^plied to such structures
tlnnigh by derivation (oexoj = hook, the barb of an
arrow) its use does not seem apt. More recently the term
ii(l<iiili<i (65oes =: a tooth) has been apjilied and .seems the
more i>roin'r but in such case it should not be confused with
the limited definition given by Cidd) (lUlin. This author
defined iiilniilia as teeth arising by modification of the labial
region while the term uncliia was used by him to denote teeth
arising more posteriad. Hecanse of the common co existence of
both onchia and odontia, (in the Cobbian si'nse) one has need
for two terms .-ind the writers feel that though the first term is
inapt, it is lu'vertlieless worthy of preserv;ition. We there-
fore retain Cobb's definitions.

Xumerous other words are commonly used in a descriptive
manner in specialized gronjis. Thus a region of the stoma or
the margin of lips may be described as ilinlah- (having teeth)
or ihnticiildli' (having small teeth); basal onchia in the Stron-
gyloidea .'ire riescribed .-is lancets; and the term foxsorex is

used f<ir outwardly .'icting teeth at the anterior extremity
(oftin odontia I. In some instaiu'es, as in the tylenchids, the
stoma is transformed into a protrusible spear, termed a sltima-
liixtjil, while in others (dorylaimids ) the stoma is to a greater
or lessei' extent filled li.v a large tooth, in which case the spear
or stylet is termed an onchiostyl. Other sjiecializalions will
be iliscussed with the various groups.

( '<in\'i'rgence of stomatal foi-mation accounts for the origin
of stylets in four separate groups: the Tylenchoidca, of the
rii.'ismidia, the Si|ilionolaimidae ( .Monhysteroidea ), some repre-
sentatives ( .tiiiiiiini)iil<x) of fhe Camacolaimidae ( I'lectoidea )
and the entire l>ory]aimina. Simil:ir convergence .'iccounts for
liaired jaws formed essenti:illy by tlu' stomata rather than the
lips in the Kalic('jihalid;ie ( Strongyloiilea I , Icthyocephalidae
(Oxyuroidea) and Camallanidae and Cucullanidae (Camalla-
noidea). One must be very hesitant in concluding relationships
based upon such characters.

In describing the stoma it is the common practice to speak
of certain jiarts or regions as being chitinized. As will be seen
later, there is no real evidence that either the stoma or the
denticular structures are actually chitin and we shall use the
noncommittal tei'm arlrritf i^rd for hardened i-efi'active regions.

A. I'lIAS.MIDIA

In each of the large groups of the I'hasmiilia some forms
e.xist that possess a cylindrical stonni verv similar to that of
Ulidbrlilix.

HiiADDlTlNA. This suborder (Fig. rA) is divided chiefly
on the base of the stoma into two superfamilies, the Kliabdi-
toidea in which the stoma is not transfornu'il into a .stylet and
tlie Tylenchoidoa in whi<'h such a transformation has taken
place.

In the Khabditoidea there are two families, Hh.-ibditidae and
Rhabdiasidae, in which the stoma is of a generalized structure
consisting of cheilostom, iirotostom and telostom, the iirotostom
being cylindrical, not surrounded by strong esophageal tissue.
The parts are all well sclerotized and divisions of the protostom
are not distinct. It is interesting that in the parasitic genera-
tion rhalidiasids have a relatively short ( Rlinhilias) or sub-
globular (Entomcla.i) stoma with well sclerotized walls show-
ing no indications of cheilostom or telostom. This transforma-
tion takes place in the development of the inilividual after
it enters the host.

The family Cylindrogasteridae (Loni/ibiirca, Cjilindnipastrr)
is probabl.v the next most closely related group and herein we
again find a cylindrical stoma, distinct cheilorhabions and
telorhabdions (in form of small plates) and a greatly elon-
gated protostom subdivisible only into pro- and meso metas-
toms. Cephalobids, differ considerably in stomatal appearance,
there being a more or less cylindrical stoma in PiiiKif/nilaimus
and a collapsed stoma in Acrobeloidc.i and Ceplialubus. In all
cases the stomatorhabdions are rather separate, giving the im-
pression of a segmented stoma due to areas lacking in sclero-
tization; the extent of "degeneration" in stomatorhabdions is
apparently correlated with the amount of esophageal muscula-
ture surrounding the stoma. With complete collap.se of the
stoma (Duiibiii/lia) there is an entire absence of sclerotization
and the base of the original stomatal region (telostom) is in-
dicated only by a break in the esophageal musculature. The
consequent "stomatal region of the esophagus" is termed a
vrstibiilc. Such a vestibule is all that remains in the related
family Steinernematidae {XcoapUcta7Ui).

The Diplog.-isteridae is a highly variable grouji containing
forms which link it with the Rhabditidae, Cephalobidae, Stron-
gyloididae and Tylenchidae. Several series of genera are
known in the Diidogasterinae. IthiibditiddiiU x has a cylindri-
cal piotostom sclerotized as in Ithnbditis but the cheilorhab-
dions are non sclerotizeil and the tebirhabdions .-isymnn'trically
developed; the closely related genus AcrnslicUii.i has <listinct
cheilorhalidions liut the )prostom .■ind mesostom e;ich form a
distinct cavity, followed by a modified met;istom containing a
large dor.sal tooth. Oddiildplinri/ii.r and Biitliriiix may be eon
sidered further nu'mbers of this "dotible stoma" series. Xrn-
diploffaxti r may be considered as a sirle branch of such a series
originating from a form not unlike Klinbdilidiiidix in which
collapse of the stoma was followed by loss of sclerotization of
stom.-itorhabdions with conseipunt convergence with cejihalobids
and steinernematids in the resulting vestibule. .\ second line
of evolution seems to be indicated by a series from Rhabiliti-
doidi'x to MiiiiiDirliiiidis ii mi rirniiiix, Diploi/axtrr ficlor, Prixfion-
rliiix aeriviira and t<'rminate with l.iicolnimux. In this series
there is coll.-ip.se ami non sclerotization of the metarhabdions
accompanied by .shortening ami thickening of the jiro- and
mesorhnbdions, the development of a massive dorsal and a

65

right subventral tooth and finally by complete amalgamation
of these structures in Lycolaimus. The third and last line of
evolution seems to antedate Ehabililoides in that the cheilor-
habdions are preserved. Ti/lopJiari/n.r and Tylcnchudon have a
stoma that clearly simulates a stomastostyl, the stylet guide
being formed by the cheilorhabdions, the anterior part of the
stylet by prorhabdions, the shaft (or stylet) by meso-metar-
habdions and basal knobs by telorhabdions. Such forms are
retained in the Diplogasteridae since there is no proof that
the "stylets" are protrusible. TylopJiarynx am\ Tylenchodon
form a definite link with the Tylcnehidae. We have omitted
remarking thus far on the presence of sclerotized rugae in the
Diplogasterinae. As has been previously noted, members of this
group have either no lips or much redneed lips. In many forms
the prostom is longitudinallj- broken into numerous heavily
sclerotized rugae, these rugae having much the same appear-
ance as the internal leaf crown of strongylids. The degree of
development of the rugae seems to be correlated with the size
and degree of development of th dorsal tooth {Pristionchiis
aerivora, Diploi/dxter fictor, Mononchoiiles iimeric(inus). As to
the origin and end of the series previously mentioned, there are
some who would see the series in reverse, i. e., proceeding from
short stoma, amalgamated forms such as Lycolaimus to cylindri-
cal stoma forms such as BJiahditiiloides. In reply we may state
that study of young larvae show the series to be correctly
oriented. Forms with a short or divided stoma in the adult
stage have a more cylindrical, elongated, less divided stoma in
the larval stage.

It has been previously noted that the Tylenchoidea (Fig. 55)
have a stomatostyl homologous with the stoma of rhabditoids,
probably having developed through some such forms as Tylen-
chodon or Tylophdrynx. Such a stylet consists of four ))asic
sclerotized parts (l) cheilorhabdions (st.vlet guide), (2) pro-
rhabdions (conoid or insertable part of stylet), (3) meso-
metarhabdions (stylet shaft) and (4) telorhabdions (stylet
knobs). The stylet guide or cheilorhabdions are best devel-
oped in tylenchids with a sclerotized cephalic region such as
Enploloiiniis and Pratyloichiis but may be relatively distinct
in less heavily sclerotized forms such as Xeotylcjichus. The
basal knobs (telorhabdions) are primarily three in number but
may be bilobed, particularly in cases where they are anteriorly
bent such as Boplolaimiis bradys* In tylenchids the greatest
diversity is in degree of development of the basal knobs and
relative size of the stylet. A few forms such as Apheh nchus
avcnae, have no basal knobs and a very delicate stylet. Others
such as AvJiclrnclidides parieliniis have weak knobs and a deli-
cate stylet while Ditylenclnis dipsaci has both moderately de-
veloped. Hoplolaiinu.'! bradys represents a type with massive
stylet while Paratylcnchus and Criconema have a massive and
greatly elongated stylet which may extend posteriorly into the
metacorpus. A few instances are known in which there is sexual
dimorphism in the degree of stylet development.

The entire family AUantonematidae is characterized by stylet
degeneration, the cheilorhabdions and telorhabdions being most
effected by this tendencj". Stylet development in this famil}-
seems to be primarily dependent upon the life history, the stylet

Fig. 59.

Cephalic regions in the Filarioidea.
A, E-F, J-L— Dipetalonematidae. B,
G-I — Filariidae. C — Desmidocercidae,
D — Stephanofilariidae. X — Dirofilaria
immitis; B — Dieheilonema rheae ; C —
Desriiidocerca ttuniulicfi ; D — Stephano-
filfiria stilffii; E — Elaeopkora schnfi-
deri; F — Dipetnlon^ma gracile ; G —
Squnmofilaria thoracis; H — Setaria
critiltw; I — Diplotriaena sp. : J — C(ir-
dUtnftnn ristlidinis ; K — Litomosoides
haitilitti: L — Litomosa amer'ictnia. E —
.After Wehr & Dikmans, 1935, 7.ooI.
Anz. V. 110(7-8). G — After Tubangui,
1934, Philipp. J. Sc. v. 55(2). L —
After Mcintosh & Mcintosh, 1935, Proc.
Helm. Soc. Wash. v. 2(1).

Returning to the other subfamily of the Diplogasteridae, the
AUoionematinae we find less variation in stomatal develop-
ment. In AUoionema and E)iabdHophancs the cheilostom and
prostom form the functional stoma and their rhabdions are
well sclerotized but not always distinctly recognizable; the
meso-metarhabdions may or may not be well sclerotized but
they are always surrounded b,y esophageal tissue and the telor-
habdions are rudimentary. Strone/yloides ra7isomi (Strongy-
loididae) passes through this stage in its larval development
preceding complete collapse of the niesostom with vestibule for-
mation SclcnrcUa of the AUoionematinae apparently proceeds
even further in this line of evolution with shortening and amal-
gamation of the eheilostom-prostom, the result being a nearly
complete convergence with Lycolaimus*

The remaining two families of the Ehabditoide.a are insuffi-
ciently known for a general characterization of their stomata ;
we cite the figures of Aiii/iostoiiia ph lliodonlis (.\ngiostomati-
dae), Vicelis nira and Vnr/rlla .s(ctn (Driloneniatidae) as repre-
sentatives of the groups.

*The Rliabditinae — AUoionematinae — Diplogasterinae complex seems
to exhaust practically all of the possible combinations of stoniatal,
esopliageal and bursal cliaracters. Aside from ttmth formation — absence
of valved bull) and ceplialic cbara(;ters tliere is little or no correlation.
One might easil.v prefer to arrange the narrow bursate cylindroid stoma,
forms of the Rhabditidae (Rlifihtlifnidr.s. RhiibditrUa) and Diplogas-
terinae (lihtthditidoides. Nfridipliif/iiyfrr) together an(J the short stoma
Lj/coUiimUH with SehnepIIa in the AUoionematinae. However, on tlie
basis of present evidence this would cause an unwarranted confusion
and would he even more arbitrary than the present division.

being best developed in very young larvae and degenerating or
entirely disappearing after whatever stage has passed in which
the organism enters its host animal. Thus Cobb (1928) showed
that the stylet is vestigial in adult males while it is well de-
veloped in non-gravid females; the males and females copulate
while free-living after which the male dies but the female re-
enters its host. The stylet of the female also becomes de-
generate after entrance into the host.

Stronoylina. Stomata in the suborder Strongylina
(Fig. ri(i) give one of the clearest cases exemplifying the bio-
f/cnetic law that ontogeny recapitulates phylogeny. Though
the structure in the adult stage is highly varied in the first
stage larva it is always of a more or less rhabditoid form. In
adult strongyloids the stomatorhabdions are always heavily
sclerotized, the stoma well developed and capacious while in
adult trichostrongyloids and metastrongyloids the stomato-
rhabdions are usually weakly sclerotized and the stom,a re-
duced or rudimentary. Though the stoma becomes reduced or
rudimentary in many representatives of the Strongylina, such
reduction occurs through shortening rather than through over-
growth of esophageal tissue. Vestibule formation which oe-

*Tho anterior part of tlie stylet, as well as the cheilorhabdions are
cast off with the exuvium at the last molt of Diti/trnrhus. It likewise
diiTers in chemical nature. However, the extent of molting is no evi-
dence of hfunology for the entire stomatal and esophageal lining is
cast off at tile last molt of CtntiaUatuts, Anct/lostoma and Af/amprTnis
while apparently only the cheilorhabdions molt in Rhabditii) and first
.1 nri/lftxtitmti larvae.

66

curs in so iiiany otlior K'ciips (RlmlKlitoiilcii, Ascariiloidca,
Spiruioiiioa and Caniallanoiiica > is I'DnspiiUdiislv absent in the
StronK.vlina.

Slniniiiihiitlfa. First stage stronK.vloids Ijave a stmiia iden-
tical witii that of KlKihililiti. 'I'liis stcinia uradiially c(ill;ipses
in the second stage and in tlie tliii'd stage it may simulate a
stoniatostyl. Cold) (1il:;,'i) descrilied tlie third stage larva of
Xicdliir ami ricdiiii.s as possessing a styli't liut as shown liy
Stekhoveu (l!'-t>) this was a false interpretaticui. The lunu'n
of the stoma is merely partly closed and non functional in this
stage, the so called stylet not heing protrusilile. A similar
appearance occurs in third stage Illiahdilis larvae when they
enter the resistant phase.

In the adult stage there are two genera of the Strimgylidac
with a rhaliditdiil stoma namely CiiUnilriijihitriinx and PlKiiipi-
(/(KtlrDitf/jihis. Interiireting on the hasis of these two forms,
the chief part of the stoniatal wall, the so-called buccal cap-
sule of strongyloids corresponds to the amalgamate(l (iroto-
rhalidions of h'ltnbililis. The telorhabdions ir. some instances
l('illiniln>iih(irtinx. CiiUcoencIn'') may l)e represented by a
transverse sclerotized basal plate but iisually are not distin-
guishable. It has previously been noted that the external ca-
rona radiata seems to be homologous to the apical lobes of
the original lips. The internal corona radiata appears to be a
development of the cheilorlijibdions (Cnliiulrdphariin.r. Strrin-
finhis). Progressive shortening of the protorhalidions .accounts
for such forms as CylicDCi/iiii.t, Miirxhidiii and Orxdiiliafinstn-
miim. Thickening of the protorhalidions and dilation of the
protostom account for Stronguhis and its satellites. Teeth
originating at the base of the stonui (lancets') are a common
develo|iniint of tlw Strongylidae, Syngamidae and .^ncylosto-
m.atidae. Such oncliia are considered products of the telorhab-
dions. In ad<lition, one often notes a large dorsomedial tooth
or a tube in the dorsal wall of the stoma; this tooth or tube
is also thought to be a product of the telorhabdions though
it may extend to the anterior end of the protostom (Strniujii-
his) and is actually the duct of the dorsal esophageal gland.
It is often termed the dorsal gutter.

Stomata in the Syngamidae are rather subglobular as in
many of the Strongylidae but they differ in that the protorhab-
dions have six longitudinal thickenings, two medial and four
sublateral ( Siinfinmii.i. Drhtroct phiiliif:. Slrphniiiini.i) . In the
Diaidianoceiihalidae (KalicephaJii.i) the protorhalidions are
split sagitally forming a pair of lateral jaws and tliej' usually
have four bmgitudiual thickenings on each side. In addition
the telorhabdions form a thick, sclerotized basal plate.

In the Ancylostoniatidae the stoma usually has a distinct
dorsal bend and is asymmetrically developed as in Strnnpjihis
due to the large dorsal gutter. In addition there may be either
teeth (Anriiloxtoma) or cutting edges developed from the
cheilorliabdions on the ventral side.

TricliDstriinfiiilinds and metastrongyloid.s are both character-
ized by marki'd stoniatal reduction. Usually there are no dis-
tinctly sclerotized stoniatal structures. However in a few
forms (Amidiislomiim, Fpomiilioitfomiim-Trirliostronfii/liilne
and Steniirus-Pseiidaliiilar^ .sclerotized protorhalidions persist
to the adult stage. In the Trichostrongyloidea .subventral lan-
cets arc occasionall.v present ( Amiilostomiim) and the dorsal
esophageal gland usually empties into the stoma. In the latter
instance its duct often takes the form of a sclerotized onchium
which may be the only sclerotized part of the stoma (Tricho-
Uipiriii. Tlaeniiinchiis). In metastrongyloids teeth of all forms
are apparently absent (Filiiriopf:is, Slntiirus, Dirljiocniiliis and
^tt'tastrl>nfll|]|ls). It is interesting to note that trichostrongy-
loids revert to their ancestral stoniatal form, IDiabiliti.s, in the
first stage larva while metastrongyloids only ]iartially revert
in that stage for they have distinct cheilorliabdions and pro-
rhabilions of rhabditoid form but though the mesostom and
telostom are recognizable the rhabdions are non-sclerotized.

Asc.\RiDiNA. Most ascaridins (Fig. 'i') either have a
rudimentary stoma or a weakly sclerotized vestibular region
but some representatives of the more ancient families, Thela-
sfoniatidae and Atractidae preserve a cylindrical rhabditoid
stoma. Thus Leidyiii ma cranifcra and Piubsfmaiiria vivipara
both have stomata in which the various stoiiiatorhabdions are
distinctly sclerotized. In Protrcllinn and Aoriinm of the
Thelastoniatidae one notes progressive shortening of the sto-
niatorhabdions and loss of sclerotization. The telorhabdions
may jiersist in the form of basal teeth or laminae or they nia.v
entirely disa[)pear. The dorsal esojdiageal gland never empties
into the stoma as in the Strongyloidea. In the Atractidae a
cylindrical jirotostom (TIfih, Prtthstmai/ria) ^ weakly sclero-
tized stoma with collapsed mesostom (Alractin) and vestibule
(Crossocrphahm) are all known to occur. In the O.xyuridae
the protostom is always greatly shortened, often feebly sclero-
tized (Kulrrohius) but the telorhabdions are commonly large

and conspicuous laminae (Oxi/iiriti). The family Rhigonenia-
tidae is characterizeil by a rudimentary stoma surrounded by
esophageal tissue (vestibule). The stomatorhabdions an- non-
sclerotized, with the exception of the cheilorliabdions of h'lii-
fiont ma ; these latter take the form of three sclerotizi'd dentate
.jaws, internal to the lips. In Iclhiioci phaliis the stom.-ital
region of the esojdiagus is horizontally split forming paireil
.j.aws.

The subfamily Subulurinai^ of the Asearidoidea is the only
group of that superfamily in which the stoniatal region is not
surrounded by esojihagcal tissue. Herein the short heavily
sclerotized jirotoscnn is followed by a dentate telostom (Siibii-
liira tli.itnn.s. Aulonorrphaliis pcramrlix) which is strongl.v remi-
niscent of OxiiKris and Enti'fdhiux. The other families have
weakly or non-sclerotized iirotorhabdions, the stoma coll.-ipsed
Mnd of subtriangular or triradiate form in cross section. In
the Cosmocercidae, Kathl.-uiiiilac and lleter.-ikin.-ie the base of
the vestibule (stoniat.-il region of esophagus) is evidenced by a
break in esophageal tissue at the original position of the telo-
rhabdions. In the Ascarididae, with the exception of Criisso-
plionis there is not the slightest evidence of the original stoma.
The esophagus seems to extend unintcrrn|ited to the tiase of
the liiis. The single exceptional genus gives the final proof
that the anterior end of tlie esojihagus of ascarids is homolo-
gous to the vestibule of cosmocercids and heterakids for in
Crnssophonix there is not only a distinct vestiliule but the
metastoni is dilated and distinct telorhabdions are visible.

('.\M.\I,1,AX1N.\. The first superfamily, Camallanoidea, is
characterized by the presence of a well devidojied stoma in
most forms and at least a distinct vestibule in the remainder
while the second superfamily, Uracunculoidea, has a rudimen-
tary stoma, the stomatorhabdions are non-.sclerotized in all
forms (Fig. ^S). None of the adults in the Camallanoidea
have that which might be termed a rhabditoid stoma but Pro-
ramalhinus most clo.sely approaches it. In this form the stoma
is barrel-shaped, cheilorhabdicuis are not distinct, jirotorhab-
dions amalgamated and heavily sclerotized and followed by a
transverse ring-shaped telorhabdion. Li (193.T) has shown
that as in other groups the larva more closely apjiroaches
the rhabditoid stoma than does the adult for in the first
stage larva the stoma is much more narrow and cylindrical.
In adults of other genera of the Camallanidae (CarnaJlaniis
xweeti, C. americanus, etc.) the prostom is sagitally slit, form-
ing two lateral jaws; longitudinal ridges of the internal wall
of the protostom make their appearance and paired, sclero-
tized medial tridents are formed at the external surface of the
stoma. Somatic muscles are attached to both the tridents and
the exterior surfaces of the jaws.

In the Cucullanidae one observes, though not as completely,
a repetition of the evolution in the f'amallanidae. Omcia is
the only form which retains the primitive, non-esophageal
tissue surrounded stoma but even in this case there is little
resemblance to the cylindrical stoma. Haploncma and Sciiralinn
ajipear to be products of some genus like Omcia in which the
stoma collapsed, stomatorhabdions degenerated and were cov-
ered with esophageal tissue forming a vestibule. Ciiciillanus
may be interpreted as more ancient than Omria in distinct
retention of pro- and meso-metarhabdions but less primitive
in that the entire stoma is surrounded by esophageal tis.sue and
sagitally divided forming lateral jaws. This is likewise one
of the very few exceptional cases wherein esophageal tissue
surrounding the stoma is not correlated with stomatorhabdiou
degener.'ition.

SpiitiRix.v. Most members of the Sjiiruroidea (Fig. 58)
have a rather cylindrical stoma with strongly sclerotized proto-
rhabdions, but distinct cheilorhabdions are unknown. The sto-
mata of practicall.v all forms are specialized to some extent
and none can be regarded as prototypes of the superfamily.
However, various members of the Thelaziidae (Oxiispinira,
Axcarnps, Spirocerca and Ehabciocliona) indicate that a cylin-
drical protostom subdivisible into pro- and mesostomata and
reduced telostom with plate like telorhabdions were charac-
teristic of the ancestor. One cannot but be struck by the simi-
larity of the stomata of Lntu/ibucca and Ctilindrojinslir to
spiruroids both in this respect and in the tendency toward
bilaterality in cephalic structures. Nevertheless there is too
wide a gap between the Cylindrogasteridae (Fig. r)4") and
Spirurida for one to assume relationships at the present time.
In a few forms of the Thelaziidae (TheJazin. Pxriulafihiria)
the protorhalidions are shortened and amalgated but in the ma-
jority (Oxi/xpirura. Axcarnps, etc.) the protostom is elongated
and there are six oiichia at the junction of protostom and mesos-
tom. These oncliia may take varied forms, sometimes rounded
(Axcarapx) and sometimes bi- or trifurcate (Ciilicnspirura) :
in still other instances they may be dentate (Lciiirix) and
scmietinies opposed by medial iilates (Simondsia, Lciiiris).

Fig. 00.

Cephalic regions in the Monhysterina. AC, K-F. H — -T'lcrtidae.
D, G, I — Camacolaiinidae. J-K — Bastianiidae, L-U — Axonoliiimi-
dae. V-Y — Coinesomatidae. Z-FF — Linhomt>eidae. G(»-0() — Mon-
hysteridae. PP — Siphonolainiidjie. A — Fleet us rhizophilus (dorsal
riglit) ; B — Antiplectus gramdosus ; C — A miplectus prnniilosiis
< median view) ; I) — A nffuino'ules Htulosum ; K-— A nonchti.s mira-
}fUis ; FV — Teratorephalus coniutufi; G — ApiKinoliiimus minntirutt :
H — Lfptolaimus nia.ritnus ; I — Cntnarolaiinns prythcrchi ; .1 -Odrm-
ffihiimiis t'lilorosiiH : K — Ba^iifniiu f.rili'S; h — Araeohiinius cyiitxli'O'
liiiiiitts : M—Arai'nUtimiiJt zttsii-rne ; X — Aet/inloftlaimus elrpans ;
I ) — CiiVindrolaitnUH rnniniunis ; P — Axonnldiniits sp inns us ; Q —
.1 .rdiitthiiiii us tnhmliiphnrnides ; H — A .ronnUiiiiiiis siifisiiiiHis ; S- —
Odonfopfiorn a ntjust ilfiima ? : T- — Didrlta uuiriilnfn ; V —Pspudo-
JpUh fjrunuUffin (dorsal riffht) ; V — Suhfitirrin lon</ic(iudata ; W —
Comesoma minirvum ; X — Doi't/Iaiinopsis inftiitupicus .- V — Liihuflhi
quadrisetfisd ; 7. — LinliomoeuM elouptitus ; W — lialiufiiin sfiiim-

sniii : RB — Monhi/sterium transitans; CC — Tripi/lium carcinico-
luiii : DD — Parnlinhomoeus leptitrus: EE — Metalinhomoeus typi-
t'Us : FF — Sphnerolaiwus sp. ; (IG — Hdlanoiirhus inacrauiphidnm ;
U}1 — Ci/tolaiwium obtii sir tut datum ; 11-J.T- Strhterin sp. ; KK —
OunrroneuKi Htniiuiii ; ij\.~Thcristus sctosus ; yiM-^yi—.SraptreUit
rinrtn .■ O0~l!hi/iirliouemn cinrtum ; PP — SiphonoUiimus sp. D,
ir, L. Q, R. (Ui. HH -After Cliitwood. 19:{(i, Proc. Helm. Soc,
Wash., V. :i (1). F— After Cobb, 1914, Tr. Am. Mii-r. Soc, v. 33,
1 — After Chit wood. 1935, Pror. Helm. So.-. Wash., v. 2 (1). J &
O — After de Man. 1884. Die frei in der reinen Krde— Xematnden
X — After Stekhoven, 1<J31, Ztschr. Morph. v, 20 (4). T, U, AA
C.C, KK, 00 -After Cohh, 1920, Contrih. Sc. Nemat. 9. \V — After
Chitwood, wrM. Proc. Helm. Soc. Wash., v. 4 (2). Z — After
de Man 1HS9. M.-m. Soc. Zool. France, v. 2. T)1>-EE— After

(le Mini. liiliT. 11. id.,

20. Remainder original.

()S

Spiral or triiiisvcrse riiKos'tics of tho protostoni are eoiifinod
to tlio sulifaiiiily Ascanipsinae. Similar runiisitios aro known
only in tin' k''""" I'li<iiiiii<iii.Kln>iiii!ihi.i <if tlii' StronKylidao.
Basal oncliia (lanrcts) an- known only in l!icliihiii<i, prcsint
ing rcniarkalili' (■onvi'r>;cni'i' witli tlic Stroncyliilai'. Careful
coi:siili'ration of tlu' stoniatal formation in tlii'la/.iiils is essential
to an umierstanilinK of the stomata of other spiruroiils. The
larva of PhuxoccphalKs has six prostomatal oneliia and no lips
like the adult . I xcd ro/>s. Durinp later development the cireu
moral membrane is apparently lost at the same time the prostom
is everteil. This results in the six prostomatal teeth cominK to
occupy an external position and they form the basis of two
lateral trilobed pseudolabia. The writers interpret the stomata
of other families of spiruroiils as of this everted type. Later
ilevelopmeuts of the prorhabdions ( pseudolabia) have been
discussed with other labial structures.

Members of the Spiruridae tend to have a rather wide,
cylindrical well scleroti/.ed nu'sostoui which may beconu' lateral
ly flattened in sonu" genera (Spinim, Proto.vpinira) but ex-
treme development of i)seudolabia and interlabia may obscure
the stoma {Ti-lramrrcs male and Uedniri.i). Acuariids are
rather uniform in the possession of a long narrow cylindrical
niesostoni.

Passing to the (Jnathostomafidae and I'hysalopteridae we
see the first and only tendency toward vestibule formation in
the Spirnroidea. The genera Spiroj-i/s and Harlcrtia (Gnathos-
tomatiilae) are the only representatives which retain a sclero-
tizeil mesost(]m and in these forms the stonui is much short-
ened and surrounded by esojihageal tissue. Thnhunavii (Physa-
lopteridael retains a laterally compressed vestibule while
Physahipti ra. Abbrtviata, Skrjabinoptcra (Physalopteridae\
TaiKjuii and dnathdstoma (Gnatliostomatidae) have completely
rudimentary stomata, the esophageal tissue proceeding unin-
terrupted to the base of the pseudolabia. At the anterior end,
in such forms, the esophageal lumen becomes dorsoventral be-
fore connecting with the labial bases.

The Filarioidea (Fig. .19) might be considered the "astoma-
tous" twin of the Spiruroidea. A few genera, however, are
known to have rather distinct, sclerotized stomata. It is in-
teresting to note that such forms are not dissimilar to thela-
ziids. Drstnidoccrca is a striking counterpart for it not only
has a cylindrical stoma but also a pair of lateral prostomatal
onchia which may be homologous to those of the spiruroids.
Litnmosn has a short stoma practically identical with that of
Thclazia while LHomosoides has a cylindrical stoma with
separate distinct stomato-rhabdions. Even in such forms as
Dirofilaria immitis one must assume a cylindrical stoma in the
not too dim ancestry because such a stoma, although weakly
sclerotized, is present in the third stage larva.

P.. APHASMIDIA

As in the Phasmidia, stoniatal morphology in the Aiihasmidia
is of no value as an ordinal character. Forms with a rudimen-
tary stoma occur in each large group and in man3- of the
groups series extend from the cylindroid type, through various
modifications ending in instances of convergence.

II0XHY.STERIXA. Members of the Monhysterina (Fig. 60)
have one character in common and opposed to the related
rhromadorina, namely, that the chcilorhabdions do not take
the form of twelve sclerotized longitudinal ridges, (odontia),
replacing lips. However, in axonolaimids and monhysterids one
may sometimes note a longituilinal sclerotization which is ap-
parently the homologue, or even predecessor of the chromado-
roid type.

Plecliiiiira. AnapUctu.i (ininiijosii.t provides us with the
aphasmidian version of Rliabililis not only in esophagus and
lips but also in the stoma. The cheilostom is hexangular, the
proto-stom, subtriangular in cross section, f'heilorhabdions and
protorhabdions are well sclerotized, telorhabdions only faintly
sclerotized. Anaplcclus is unusual in that the protostoni has
parallel walls; in most plectoids the walls converge posteriorly.
In Leptdlaimiix mnrimiis the stoma is extremely long and nar-
row, protorhabdions distinct while in some related forms the
stoma collai)ses forming a greatly elongate vestibule. AiioncJiii/i
viirabilix and Trrdtiici phnhix rorniiliis exemplify shortening
and dilation of the stoma with distinct .ioints at .iunction of
pro- and nicsorhabdions. In Trrntocrphaliis the i)rotorhabdions
are further modified taking the form of six inwardly acting
teeth or odontia.

The family Camacolainiidae is characterized by a diminu
tion in stomata in all forms. In AphaiKihiiiiiiix aqiuiliriix the
stoma is minute, cylindroid, with practically non-sderotized
protorh.'ibdions while in Camacnlaimiin pruHicrchi only the dor-
sal stomatal wall is sclerotized and it projects anteriorly as an
onchium. An-ffuinftidrs stffhisiini is a further examjile of the

same tendency, in this instance the dorsal onchium is .separate
thrcnighout its length teriiiinatiKi; i)osteriorly in two knobs.
Ani/iiiiiiiiih .1 is a striking paralhd to Dilj/linchuii dipnuci of the
Tylenchoidea but we must classify the spear as an onchiostyl
in this instance.

Passing to the liastianiidae, we may .judge that the "asto-
matous" Hiixliania arose from some such form as Oilonlnhtinuis
whi(h has a greatly elongate, narrow stoma.

Concluding our resume of the Plectoidea we note that non
muscul.'ir esophageal tissue extends beyond the mesorhabdions
in such members of the genera AnnpU ctus and Pled us as have
been studied. Comparing with lOinlnlilin, we would consider
this as a more advanced evolution.iry devidopinent. Such a
view is borne out by the somatic musculature of the forms
studied. Since there are representatives in the Plectoidea
{ Animrhiis), .Axonolaimoidea I Axandldimux) and Monhysteroi
(lea (Ualaniinchus) in which esophageal tissue does not exteiul
anteriad, we must conclude Ana phcl 11,1 while i>rimitive, does
not fulfill all oblig;ifions of the Aph:ismidian ancestor. Com-
bining cephalic characters and general stomatal outline of
Anaplecliis with the more primitive stomatal and somatic mus-
cle characteristics of Ananchns we may, perhaps, have the
proper picture.

Axoni)luiiiiiiiiha. Primarily axonolaimoids have a cylindroid
or conoid i)rotostoni. In the .Vxoncilaiminae the protostoni is
conoid, the nu'sostom surrounded by esophageal tissue; the chei-
lostom is anteriorly conoid. Thus in Axonolaimus we have a
close parallel with PIrctiis. Twelve weak longitudinal .sclero-
tizafions of the cheilostom are usually evident in Axoiuihiiiiiiis
species. In Oddnloplmni iinpiisiddimo these 12 .sclerotizations
arc anteriorly fused forming six large outwardly acting odon-
tia. As we shall later see in dealing with the Chromadorina,
the 12 odontia replacing lips in that group probably originated
in a form near AxonoUiimiix. The same tendency of the chcilo-
rhabdions, with multiplication of elements may be seen in the
Monhysteroidea.

Inconspicuous, weakly sclerotized, cylindroid stomata occur
in the subfamily Cylindrolaiminae which includes forms in
which esophageal tissue extends to the anterior end of the
protostoni {Aracolaimns zostcrar) and forms in which this is
not the case (Ci/liii-droUiiinus comiiiiini.s. Aii/ialiHilaiiinis tie-
(jans). Cylindroid or collapsed stomata occur in representatives
of the Campylaiminae (Pxeiidohlhi iirantilifrra) and Biplopel-
tinae (Didelta maculata). In the former type the protorhab-
dions terminate anteriorly in three small teeth, a parallel to
Dori/laimopsis.

The Comesomatidae have stomata of two general types. In
the first the stoma is cylindroid, the protorhabdions are well de-
veloped and terminated anteriorly by three equal teeth (Dory-
laimopsis mctatypiciix and Laimella iiiindrisetosa) ; the entire
protostoni is surrounded by esophageal tissue. In the second,
the protostoni is collapsed, the rhalidions are non-sclerotized,
the esophageal tissue transforms the stomatal region to a
vestibule (Sabalieria lon<iicaiidata, Comesoma minimum). In
both instances the chcilorhabdions are short and do not con-
verge anteriorly as in AxnnotaimiiK.

Monhysteroidea. Stomatal diversity in this superfamily has
thus far prevented adequate revision of the group into com-
pact small units. In the ina.iority of instances, when the stoma-
torhabdions are well sclerotized esophageal tissue does not sur-
round them (except Tripj/Uum carcinicohim). We may presume
that when the .stoma is rudimentary as in Theri.itti.^ or Ci/tn-
laimium, it reached this condition through shortening rather
than vestibule formation and collajisc. A few forms with a
large consjiicuous stoma arc retained in this group; such are
Bhynchdncma cinctum with an extremely long cylindrical sto-
ma, Halandnfhns macramphidum, Omieronema Utorium and
Sphaerolaimiis sp, with wide, heavily .sclerotized stomata. In
Spliaerolaimus the chcilorhabdions consist of innumerable scler-
otized rugae. These same rugae are retained though the pro-
tostom has disappeared in Theri.'ttu.s .ictosit.i, Stcineria sp. and
other typical monhysterids. In Seaptrella cincta. on the con-
trary, one finds the cheilorhabdions transformed into six out-
wardly acting odontia .-is in Odontdplioni of the .\xonolaimoiilea.
Many linhomoeids {.Tersrlielliti/jia punticn. Mnnhyxleriiim Iran-
.litan.'i) have no distinctly sclerotized rliabdioiis and in the re-
mainder one notes degrees in shortening and reduction. Thus
in I.inhomoeii.i elnnt/atii.i and Ilalinrma .'ipinosiim the entire
stoma is short and wide. In the former one notes subequal
cheilorhabdions and |)rorhabdions with posteriorly converging
nu'sorhabdions. Paralinliiimneiis Jeptiiriis and Metalinhomneiifi
typicu.i seem to be further steps in stoniatal reduction of this
series.

Siphonolaims are ;i group apart, having the entire protostoni
transformed into a stomiitosfyl as in the Tylenchoidea but there
is little or no resemblance in the org.'in itself.

<V.<

In leaving the Monhysterina, one ma.v note that prostomatal
teeth, if present, are anterior, small and subequal. Sometimes
a dorsal, anteriad pointing tooth is described in monhysterids.
Such a structure is present at the base of the stoma in Scap-
trella, it is non-selerotized, and is probably an esophageal de-
velopment through which the dorsal esophageal gland has its
orifiee. Heavily sclerotized dorsal teeth do not occur in this
group, a distinct contrast with the group to follow.

CirROMADORiNA. Muscular esophageal tissue always sur-
rounds the protostom in members of this suborder (Fig. 61).
Forms with a rudimentary stoma are numerous but they arise
through collapse of the protostom rather than shortening. If
the protorhabdions are well sclerotized the cheilorhabdions
form odontia replacing the lips except in the Tripyloididae.
Onehial development is usually apparent, taking the form of a
large dorsal tooth opposed by smaller subventral ones.

Chromadoroidea. Of this superfamily the Microlaimidae ap-
pear to be most primitive from the standpoint of stomatal char-
acters, including, as it does, forms with a subeylindrical pro-
tostom and protorhabdions terminated anteriorly by ouchia
(Etiimolaimiis revaliensis) . In this instance the dorsal onchium
is retrorse and the subventrals mere sclerotized oppositional
thickenings. In Statenia trichiira the same structure obtains
except that the subventral ouchia are also retrorse and but
slightly smaller than the dorsal. In MwroJaimiis dimorpluis
and Bolbdlainnis cabbi the dorsal onchia assume a mesostoma-

tal position and are axially directed, the smaller subventral
onchia being slightly posterior and oppositional in character.
In all microlaimids tlie protorhabdions are moderately sclero-
tized and comi)letely surrounded by muscular esophageal tis-
sue; the base of tlie stomatal region is usually indicated by a
groove or tissue differentiation. Cheilorhabdions take the form
of 12 odontia replacing the lips in function but seldom pro-
truding beyond them.

In the Chromadoridae examples of the same tendencies are
evident, Prochroiiiadora ncrlii)! corresponding to Stalinia and
Odonloncma gitido-schncideri to Bulbohiimtis. In addition the
stomatal region may not be set off posteriad (Chromadora,
Sj)iIop)toreUa paradoxa) ; the prostomatal dorsal onchium in
this case may be small or large, the protostom collapsed or
apparent. Cheilorhabdions take the form of 12 odontia as in
the Microlaimidae.

In the Cyatholaimidae tliere are two chief stomatal types.
In the Cyatholaiminae the cheilorhabdions always take the form
of 12 conspicuous odontia which may pro.iect anteriorly be-
yond the labial region {Piimponcma mirabilc) ; the prostom
is wide, meso- and metastom narrow, with converging weakly
sclerotized mesorliabdions. A large dorsal axial onchium at
the junction of the pro- and mesostomata is usually present
and may be opposed by smaller subventral teeth (Acantlion-
cldis vivipanis). Choanolaims differ in that axial mesostonia-
tal teeth are inconspicuous or absent and the mesostom does

Cephalic regions in the Chroinadorina. A-F — Microlaimidae.
G & U — Tripyloididae. H-K — Chromadoridae. L, N-S — Desmo-
doridae. M — Epsilonematidae. T — De.smoscolecidae. V-AA —
Cyatholaimidae. A — Aclirnmadora monohyntern ; H — Statenia tri-
chura; C — Aticrotninius diynorphus ; D — Ethmolainius revaUensis ;
K — HnlhntfiiiniiH rithhi : littlhotaimus rohhi (.section tllroii^h stoma-
tal rPKion): G — ltiitliiilainiu.s cnhhi. H — Chrnmndnrn sp. ; I —
Spilopliorflla /tnrtnloxa ; J — Prorhromndorn nrrlffii ; K — Odnulo-
Tlfma iiliida-Ni'hneideri; L — DeKtiindnra firaj(h'ii.\is ; M — Kfinilnnf-
iitnt'ul (s<'h('matic) : N — Crnconeiiiit iHitr/imilhitinri : O — Spirinn
piiraKJtifiTti ; I* — Mfla^hroinadnra anyxnidpti : Q — Mrtarh nitmt-
dorn nnyxii'uten (stomatal region) ; R — Metachromadora onyxoides

(labial region) ; .S — Motwijnuthia hfxalata ; T — DpsmOHColex aitit'ii-
canus: V — Tripyhndea vittnaris: V — Acnnthonchvn rivipnrutt ; W
— Clieironrlnm bidbasa ; X — Halirhnniiolaimvs dolicharuti ; Y —
SynotH'hiplla inineatn; Z — Gnmmanfinia ferox; AA — Pomponeriia
mirahiU. (J — After Fililvtev. 1922, Art. Inst. .-Vgron. Slauropol.,
V. 1 (IC). .1 & K— .\fter Filip.iev, 19:i0. Arch. Hydroliiril., v. 20.
Ij — After de Man, IHSH, Mem. Soc. Z.)c)l. France, v. 2. M — After
Steiner, 19:)0. Deutsche Sudpolar Expedition. N — After Steiner
& Hoeppli, 1926, Arch. Schiffs.-u, Tropenhyg., v. 30. O — After
Cohb, 1928, J. Wa.sh, Acad. Sc. W — After Filipjev, 1918, Trav.
Lab. Zool. Stat. Biol, Sebastopol, v, 2 (4). Remainder original.

not have I'oiivorfjiiiir walls. In all instances tlio iiiesorliahilions
are divided into twci or more elements to their base. In true
ehoanolainis {Ilnlirhniiiinliiiinns ilolichitnts, (iom nutncintt ftrox)
the |ii(islom is like an inverte<l eone and the niesostom sliort,
|irisnioidal : cheilorhalidions fuse posteriorlv, lieinj; continuous
with six i)rostonialal ami mesolouiatal ruyae. Somi'tinies, in
addition, there are nunu'rous di'Mlicles at the junetions of jiro
anil uu sorlialiilions { Ildlii'liiniihildi mux) . On the basis of sto
matal eliaraeters we should, jierhaps, reeoRnize the sulifaniilv
Selaehinematinae ;is a valid Rroup of the Cyatholaimidae.
While tlu'v are undouliti'dl.v elosely related to elioanolainis
they ditTer in that cheilorhalidions are feebly developed and
the stiunatal eavity greatly redueed. The protorhabdions are
fused into three or two numdibles terminatinj; anteriorly in
several teeth. Of the diverse types, Si/no'ichii lUi Iniiicalu
seems the most Ki'nerali/ed sinee it has three eipml mandibles,
one dorsal and two subventral; eaeh of these mandibles is
distally bitid and bears several hook like oneliia. ('luininrhiis
bnlliosifs exemplifies a jiartial reduction of the dors.al mandibli'
while S< liifJiiiiniui firii.r (see cover. Sec. 1, I',art 1) reiiresents
complete reiluction in the dor.sal ni;indible and hy]iertropliy of
the subventrals into lateral jaws.

The Tripyloididae seem misplaced in the Chromodoroidea, yet
their relationship with the eyatholaims on the liasis of otlier
characters makes their position here obligatory. In these forms
oheilorhabdions do not take the form of odontia. Instead
there are three large lips. Protorhabdions may exhibit numer-
ous .joints, the protostom being on the whole inverted, wide
conoidal in form (Triiti/Uiidix viitffaris. Batlii/laimus cahhi).

DrniiKiildrdidta. Whenever the jirotorliabdions are distinctly
selerotized and the protostom not collapsed, desmodoroids
(Mrtochrdmailora ony.roiil<\i, Mdnopdsthia hexalaia, Dismoddra
sciihtriisis) exhibit all of the characteristics of the Chromadori-
dae, but quite often the stoma is completely atrophied, in
which case protorhabdions cannot be detected (Ccramonema
rfficiihitiim, Fig. 28). Though axial teeth are present in Spi-
rilla parasitifcra the protorhabdions are feebly developed and
cheilorhalidions not apparent.

Pig, 62.

Ceplialic regions in the Tripjioidea. A-C — Tripylidae. D-G — ironidne.
H — Mormnchidae. A — Prijtnuitolitinntit intermediuH. B — Triiiyla sp.
C — TrilnhttH Innpug, I) — Syrini/otaiinuH sniargiilu/t (upper) and ,S.
breviramliitiis (lower). E — IrniniH iyttdvus. F — Crypfonrhuft niidiiH.
G — Irnnclla prismutohiiniu. H — Mnnonrhufi gerlacht'l. I> — .Vftcr Cobb,
1928. J. Wa.sh. Acad. Sc, v. 1« (9). H — After de Man, 19U4, Expi-d.
Antarrt. Belg. Remainder original.

I)< siiKinrolrroidia. So far as known, this group must be
characterized as liaving a rudimentary .iitonui witli no visible
stoniatorh.'ibdiuns.

KnoI'I.i.na. Mi'mbers of the submclcr Knoplina do not
liavi' ;i protrusible onchiostyle and the eheilorhabilions do not
take the form of 12 odontia as in the Chromadorin.'i. In u
few instances they may form a transverse denticulate ridge.
In su(di instances tliey do not form .an armature of the lips
as sometimes occurs in tlu' Monhysterina.

Tripi/ldidta (Fig. ()2). Herein are groui)ed four families,
separable on stom.atal cliaracters, the Ironidae, with a inucli
(•long;ite narrow stonui and heavily selerotized protorh.alxlions,
the .Maimidae with a rudimentary stonm, the Mononchidae with
a cap.acious stonui and very heavily selerotized stomatorhab-
dions, and the Tripylidae with weakly selerotized protorhab-
(lions.

Mononchs usually have a subglobular stoma with a massive
dorsal jirostoniatal oneliium; the hatter may lie oppo.sed by a
variety of dental structures taking the form of tr;insverse d<'n-
ticulate ridges, longitudinal ventral ridges or small unchia

Fin. 03.

Cephalic regions in tlie Enoploidea. .\-F & L — Enoplidae. (J K &
M-Q — Om-holainiidae. A — Enoptus cominlitiijt. B — Eurystnwintt iniifri~
cana. V — Enoploides amphioxi. D — Anticoma Jitoris. E — Phonod^r-
mopsia lonyisetue. F — Rkabdodemania minima. G — Oxy-ftomina alpha.
H — HulnUiimus caroUniensis. 1 — Kn^hetidiiim pauli, v. dentifulatunit
female. .1 — Knrhpiidium pauli, v. dentirulatum, male. K — liolhella
tenuidfns. L — ThoraroMtoma { PaeudocfUn) sp. M — Mctonrholaimus
printiurutt. N — Onrhotaimellus rlarndiscus. O — Aiwplostoma vii-iparum.
P — Poiydonfus iiinrinus. Q — P.ifudfipflat/onfnia eifyans. B, D, K, F,
H — After rhitwood, 1930, Tr. Amcr. Micr. Soc, v. f,a (2). C — After
Filipiev, 19IK, Trav. Lab. Zool. Stat, Biol. Sebnstopol, v. 2 (4). I, J —
After .Micolet/.kv. 19;)0, Vid. Medd. fra Dansk. .\atur. Foren.. v. 87.
K — After Cobb, 1920. Contrib. Sc. Nemat. 9. N — After de Man, 1890,
Mem. iSoc. Zool. France, v. 3. O — After de Man, 1907. Mem. Soc.
Zool. France, v. 20. I'-Q — After Kreis, 1934, Capita Zool., v. 4 (5).
Remainder original.

71

(Mononchus gerhichei). Monanchiis tiinhridgcnsis has all of the
family ehaiacteristics except that the stoma is of moderate
length and cylindioid. Such a form would be the presumptive
ancestor of the family.

In the Tripylidae, onchia, if present, are basal. The weakly
sclerotized protorhabdions may be many .jointed {Trilobus
longus), or not .iointed (Prismatolaimiis intermedius). The
stoma may be subcylindrical (Prismatolaimiis), conoid (Trilo-
bus) or collapsed (Tripyla). Dorsal or subventral asymmetri-
cally placed denticles are sometimes present.

In the Ironidae the long subcylindrical to prismoidal stoma
is always surrounded by esophageal tissue and sometimes set
off as a stomatal swelling (Irnnella prismatolaima) . Except
in Cryptonchiis the cheilorhabdions take the form of outwardly
acting odontia (fossores). In Iro7ius ignaviis the dorsal odon-
tium is double and the subventrals simple while in Ironella
prixmatdlaima the reverse is the case. SyringDlaimiis smargidiis
and DolicliolainiKS obtiisiis have three double equal odontia.

Enoploidca (Fig. 63). The families Oncholaimidae and
Enoplidae are separable through the fact that only the sto-
matal base is surrounded b.v esophageal tissue in the Oncholai-
midae while the mesostom and often the prostom is surrounded
by muscular esophageal tissue in the Enoplidae.

In the Oncholaiminae the stoma is typically capacious to
subglobular, and armed with three unequal conoid mesosto-
matal onchia which act as orifices of the eso]ihageal glands.
One of the subventral onchia usually being the largest (Mc-
foncholaimvs prislivnis). Sometimes the onchia are multiple
(Polydont IIS mariniis) and sometimes there is but one, the large
subventral ( OncholaimeHiis clavndisciis). A small residue of
more primitive species with cylindroid stoma persist as in so
many other groups (Pseiidopelagonema elegans, Anoplostoma
vivipanim).

The subfamilies Eurystomininae and Enchelidiinae appear
as slightly modified oncholaims. The stoma is more elongate,
the stomatorhabdions are usually .jointed and the onchia at-
tenuated to a needle-like point. In these groups one subventral
onchium is highly developed while the other two are minute if

present (Bolbdla lenuidcns). In addition the cheilorhabdions
or prorhabdions may bear minute denticles (Evrystomina
americana). Sexual dimorphism in stoniata makes its ajipear-
ance in enchelidiids in a most surjirising manner. The adult
male has a completely rudimentary stoma while the female has
a highly developed stoma (Enchclidiiim paiiU).

In the Enoplidae .stomata are definitely on the wane, being
rudimentary in the Oxystomininae and Phanodermatinac, rep-
resented chiefly by three mandibles in Enoplinae and usually
quite inconspicuous in the Leptosomatinae. In both, EnopUis
communis and EnopUndcs amphioxi, the mandibles are the only
sclerotized parts of the esophageal lining; these latter are an-
teriorly bifid and axially hooked. At their bases one finds the
three esophageal gland orifices. In some enoplids it is said that
small onchia corresponding to those of ilctoncholaimiix arc
present at the base of the mandibles.

In Bhabdodi' mania minima (Leptosomatinae) we have an
example showing the maximum of stomatal development in the
Enoplidae; the protosom is wide, the mesostom conoidal, the
walls are moderately .sclerotized. Three mesostomatal onchia
are present. In other leptosomatids such as Anticoma litnris
and Pscudocclla sp. the stoma is completely collapsed and on-
cilia, if present, are minute.

1)0RYL.\IMIN'.\. The suborder is characterized by the pres-
ence of a protrusible onehiostyl at least in the larval stages.
It now seems that this structure persists to the adult stage
in many forms in which its presence is not suspected. The
group also differs from the Enoplina in that the esophageal
glands never empt.v into the stoma or rudiment thereof.

Dorylaimoidca (Fig. 64). Oncliiostyls are always well de-
veloped and a conspicuous feature of adult dorylaimoids. Ac-
cording to the observations of Thome (1930, 1935) the onehio-
styl originates as a subventral tooth such as one notes in
Xygolaimus brachyuris or Sectonema rentralis. Such an onehio-
styl is described as mural. Further development of a ventral
groove finally results in a hollow cylinder through which food
passes (Dorylaimus siagnalis, Actinolaimus sp.) in which
case the stylet is a.rial. Evidence of its original formation is

Cephalic regions in the Dorylainiina ami 'J'o;;'"l'l'>'"^-
tina A-D F & R— Dorylaimidae. K, H-I— Diphlhero-

K-L N Q— Mermithidae. O— Trichinellidae. P— Trithuri-
dae' A— Don/la im II « stagnalw: B— SfOlo/wmd vnitraltt:
V^Slliinliiiiiiiii hnivhlliirlH; V>—Aeti,u,Uiiiiiu« sp ; y.—Diph-
Iherovhora perplexanti (dorKal on riRht Bide) ; V—Tvlenchn-
UimMH aequalis (median view) ; C — Kustroupylides iffrwttui.
H—Trichndnrun <ih(iM»»; l—Diptilherophnra commvnw;
J — T^eplonchim ijrnnulnsun ; K — Einiirrwm hrhmngi: L,
MfnomrnniK biirKnIn; M—Dioclophumi< rrimle (1st stage
larva)- N — Mermis mhniiireiieenti (1st stage larva): <)—
Trichinelln i>pirnli« (1st staEe larva); V—Tru-hosommdei-
eratmeauda (Ist stage larva); Q— Hf.rni;if rmw nlhiran« ;

H — Xiphinenia aiiifricnnuni. A — After Tliiirm- & Swanger,
1936, Capita Zool., v. 6 (4). B-C — After Tliorne. 1930, J.
Agric. Res., v. 41 (6). E & H — After Cobli, 1H13, J.
Wash. Acad. Sc, v. 3. F— After Colib, IHIH, U. .S. D. A..
B. P. I., Agric. Tech. Circ. 1. I — After de Man. 1884,
Die frei in der reinen Erde . . . Nematoden. J — After
fobh, 1920, ('(intrih. Sc. Nemnt. 9. K-L — After St*iner,
1929, Znnl. Jahrh. Atit. Syst., v. ^7. M — After Lukasiak.
1930 Arch. Biol. .Snc.^ Sc. & I>ettres Varsovie. v. 3 (3).
N — After Cohh, 1920, ,T. Parnsit.. v. i;i. O-P — After Fuel-
lehorn, 1923, Arch. Schiffs. & Tropenhyg., v. 27. Q— After
Rauther. 1906. Zool. .lahrb. Aht. Anat.. v. 23, Remainder
original.

indiciitod liv tlio tloi-snlly (itiHfiuc stylrt api'iturc. It is of fur
tlu'i- iiitiTOst to iioto tli:it in slU'li foriiis as Ddiiiliiiniiix anil
AftiniiUiiiiiiix the stylot is fornio(i as a cyliniicr in one of tin'
snlivcntral soi'tois of tlio I'sopliaRoal wall; a new stylot moves
up to its final position at eaeli molt; while forminR, the onehial
cylinder lias an ojien eraek on the side awa;/ friim the lumen.
Most ilorylainiids Iiave little ovidenee of the original proto-
rhal>ilions, tliose being best preserved in Xi/ffolaimus and
ActiiKihiimun. The latter is a most unusual member of the
group having a radially striated eheilorhabdion and four mas-
sive, onehium like, stylet guides in addition to heavily selero-
tized Jiru and inesorliabilidiis and sli/li t fiuulinii riiifl. Since
the latter structure is absent in sucli forms as Xi/j/dldiiinin we
may iiresume it to be the modified telorhabdions or metarliab-
dions. However, its homology has not been determine<l. Tn
dorylaimids the stylet may become tremendously elongated
(Triclimlonis obtii.tus, Lcpldiirhus flranittitsiis) and in addition
it may he terminated in three flanges (Tiilincliolaimiis acqua-
lis) or knobs (Xiphintma amcriranvm). In the latter in
stance we have a case of total convergence witli tylenehoida in
gross stylet morphology. The guiding ring and oblique stylet
aperture provides us with a elue to its dorylaim origin. Stylets
with fl.'inges or knobs usually show a .joint (Xijiliinrma) ; this
.joint indicates the extent of the true st.vlet. The anterior part
is the only part formeil in the esophageal wall; the posterior
part with flanges or knoljs, is fornieil in situ and may be con-
sidered a differentiated continuation of the esophageal lining.

The developmental origin and significance of the stylet in
Diphthirophora comminiis and D. perplcrans have not been
solved as yet. These forms have a short massive stylet with a
comi)licated dorsal arch at its anterior end and three large
knobs at its posterior end.

Mrrmithoidca (Fig. 04). The first stage larva of such mer-
mithoids as A(/a»iir»ii.<i ilt'cniidatii, Mennis siibiiii/rcxceiis and
nrjiinnrmis albicans have an onchiostyl quite similar to that
of Voiiilaimiis and the stoma is completely atrophied. In the
adult, as a rule, one can distinguish no .semblance of stylet or
stoma, and the esophageal lining extends to the oral opening,
hut in a few forms a very minute stylet rudiment has been
described.

Trichuroidia (Fig. 64). Fiilleborn (1923) showed that the
first stage larvae of Trichiiris trichiura, Trichinclla spiralin
and Trichnsomoidex crax.iicaiala all have distinct stylets. It
is customarj- to assume that all trace of stylet disappears in
the adult stage but Li (1933) has found a distinct func-
tional stylet in adult Triclinris triclitira and the writers have
seen one in adult Trichtiris riilpix. Such stylets are very
difficult to observe in fixed material and should be studied intra
vitam, possibly with the addition of such stains as crystal
violet or iodine — 1 per cent sulphuric acid. Of all trichuroid
stages observed by the writers, the neotenic male of Triclioso-
mnidi's crassicaiida has a stylet most easily studied.

DlO('TOPHYM.\TlN.\. In adult dioctophymatins the stoma
is entirely rudimentary; no distinct cavity nor stomatorhab
dions can be observed and the esophagus extends to the oral
opening. Orifices of three large esophageal glands at the oral
opening seem to indicate definite affinities with enoploids. How-
ever, Lukasiak (1930) described a protrusible st.vlet in the
first stage larva of Dioctuphi/ma renale. If this observation is
verified it will lenil additional weight to the trichuroid-diocto-
phymatoid relationshiii. Such a relationship was first pro-
posed liy Rauthcr (1918) on the basis of gonads and is sup-
ported by the similarity of eggs, spicule and protractor muscles
of the spicule.

Bibliography

Bastian, H. C. 1X6.1. — Monograph on the Anguillulidae, or
free nematoids, marine, land, and fresh w-ater; with de-
scriptions of 100 new sjjecies. Tr. Ijinn. Soc. Lond., v. 25
(2): 73-l,S4, pis. 9-13, fig.s. 1-24S.

1S66. — On the anatomy and physiology of the nema-
toids, parasitic and free ; with ob.servations on their zoo-
logical position and affinities to the echinoderms. Phil.
Tr., Lond., v. l.">6: r)4.')-63S, pis. 22-28.
B.wus, H. A. 1921. — A new genus of nematodes parasitic in
elephants. Panisit. v. 13 (1): r>7-66, figs. 1-7.

1921. — On the classification of the Ascaridae. U. The
polydelphis group; with some account of other a.scarids
parasitic in snakes. Parasit. v. 12 (4) : 411-426, figs. 1-7.

1923. — Idem. III. .\ revision of the genus Dujardinia
Oedoelst, with a dcscrijition of a new genus of Anisakinae.
Ibid., V. ITi (3): 223-232, figs. 1-8.

1930. — Some Jleterakidae and Oxyuridae [Nematoda]
from Queensland. Ann. & Mag. Xat. Hist. s. 10, v. .t:
.3.".4-306. figs. 1-10.

M.wi.is, II. A. and DAniNKV, K. I9J2.— Keport on the i>ara-
sitic ni'nuitodes in the colh'ction of the Zoological .Survey
of India. Mem. Ind. .Mus. v. 7 (4): 264 347, figs. l-7."i.

1926. — A .synopsis of the families and genera of
Ncniatoda. London. Urit. Museum. 277 pp.
Hl'TsruM, O. 1873. — Beitriige zur Kenntniss iler freiiebenden
Nematoden. Nova Acta Deutsch. Akad. Xatnrf, v. 3(i (.',):
1144; |)ls. 17 27, figs. 1 ()9.
Ciin'wooi), H. (i. 1932a. — The basic plan of the nervous system
of nematodes. J. Parasit., v. 19 (2): 167.

19321). — A synopsis of the nematodes parasitic in in-
-sects of the familv HIattiil:ic. Ztsclir. I'ar.-isit. v. ."i (1):
14-50; figs. 1 59. '
Chitwood. R. (i. and CinTWOOii. .\I. B. 1933. — The characters
of a protonematoile. .1. P;ira«it., v. 20 (2): 130.

1934. — Nematodes parasitic in Philippine cockroaches.
Philipp. J. Sc. V. 52 (4): 381 392; pis. 13, figs. 119.
CmrwooD, H. «. and Wkhr, E. K. 1932.- The value of head
characters in nematode taxonomv and rel.-itionsliips. ,J.
Parasit., v. 19 (2) : 167-168.

1934. — The value of cephalic structures as characters
in nematode classification, with special reference to tlie
Spiruroidca. Ztsclir. I'aiasit.. v. 7 (3): 273-335, figs. 1 20,
1 plate.
(IllKI.STlE, .J. B. 1924. — [The embryology of .Ic/diiiriniix dfcaii-
data.] ,1. Parasit., v. 11: 111-112,'fig. 1.

1!I31. — Some nemic parasites ((Jxyuridae) of Coleop-
terous larvae. J. Agric. Res., v. 42 (8) ! 463-482; figs. 114.

1936. — Life history of Ai/amrniiis drraiidatn, a nema-
tode parasite of grasshopiiers and other insects. .1. .\grie.
Res., v. 52 (3): 161198; figs. 1-20.
Cobb, N. A. 1898. — Extract from Ms. report on the parasites
of stock. Misc. Publ. No. 215, Dept. Agric, N. S. Wales,
62 pp., 129 figs.

1913. — [New terms for the lateral organs anil ventral
gland. 1 Science, N. S., v. 37 (952): 498.

1913. — New nematode genera found inhabiting fresh
water and non-brackish soils. .1. Wash. .\cad. Sc, v. 3
(10): 432-444, 1 pi. attached.

1915. — Sf'Iachinema, a new nematode genus with re-
markable mandibles. Contrib. Sc. Neniat. (4): 113-116.

1917. — Notes on nemas. Contrib. Sc Nemat. (5):
117-128.

1917. — The Mononchs i Manoncliutt Bastian, 1866). A
genus of free-living predatorv nematodes. Contrib. Sc.
Nemat. (6): 129-184, figs. l-Vo. Also in Soil Sc, v. 3
(g) : 431-486.

1918. — Estimating the nema population of the soil,
r. S. D. A., B. P. I. Agric. Technology Circ. No. 1, 48
pp., 43 figs.

1919. — The orders and classes of nenias. Contrib. Sc.
Nemat. (8): 214-216.

1920. — One hundred new nemas. Contrib. Sc. Neniat.
(9) : 217-343, figs. 1-118.

1920. — Microtechnique. Suggestions for methods and
apparatus. Tr. Amer. Micr. Soc, v. 39 (4): 231-242,
figs. 1-6.

1922. — A new sjiecies of Xiiflolaimiis, an outstanding
genus of the Dorvlaimidae. .1. Wash. Acail. .Sc, v. 12
(18): 416-421; figs. 1-2.

1923. — The pharynx and :ilimentary canal of the hook-
worm larva-.V (cafor (imcri<'(i«».s\ .1. Agric. Res., v. 25
(8) : 359-361, plate 1. Ibid., (shortened). .1. Parasit., v. 9:
244-245, fig, 5.

1923. — Amphids in ]iai;isitic nemas. .1. Parasit., v.
9: 244.

1923. — Interesting features in the anatomy of nemas.
J. Parasit., v 9: 242 243 ; figs. 3-4.

1923. — Notes on Paruti/Ienchns. a genus of nemas.
Contrib. Sc Nemat. (14):' 367 370; 1 fig. Also in .1.
Wash. Acad. Sc, v. 13 (12): 254-257; 1 fig.

1923. — An emendation of Eoplolaimus Daday, 1905,
nee auctores. J. Wash. Acad. Sc, v. 13 (10): 211-214;
figs. 1-4. Contrib. Sc Nemat. (13): 363-366; figs. 1-4.

1924. — The amphids of Caconemn (nom. nov.) and
of other nemas. J. Parasit., v. 11: 118 119; fig. N.

1924. — Food of rhabilites and their relatives with de-
scriptions of two new rhabdites and a new rhabditoid
genus. .1. Parasit., v. 11: 110-117, figs. K and M.

1924. — Notes on the amphids of nemas. J. Parasit.,
V. 11: 110-111; figs. F H.

1924. — Amphids on oxyurids. .1. I'arasit., v. 11: 108.

1925. — Amphidial structures in nemas. J. Parasit.,
V. 11: 222-223.

73

1926. — The species of Mermis. A group of very re-
markable nemas infesting insects. J. Parasit., v. 1.3: 66-
72; figs. 1-3.

1928. — The fossores of Syrinqnlainuis. J. Parasit., v.
1.5: 69.

1928. — A new species of Syringolaimus. With a note
on the fossorium of nemas. Contrib. Se. Nemat. (19):
398-492; figs. 1-3. Also in J. Wash. Acad. Sc, y. 18 (9):
249-2.53; figs. 1-3.

1928. — VncjeUa secia n. gen., n. sp. A nemic parasite
of the Burmese Oligochaete (earthworm) Eutyphoeus
ranis. Contrib. Sc. Nemat. (16): 394-397; figs. 1-4. Also
in J. Wash. Acad. Sc, v. 18 (7): 197-200; figs. 1-4.

1928. — Hou-ardula benigna. A nemic parasite of the
cucumber-beetle (Diabrotica) . Contrib. Sc. Nemat. (10):
345-352; figs. 1-8.

1928. — Nemic Spermatogenesis. Contrib. Sc. Nemat.
(16): 377-387; figs. 1-15.

1928. — Spirnxys ami/dar n. sp. .1. Parasit., v. 15:
217-219; figs. 1-6.

1928. — The amphids of the nema Physniopfera phrytio-
soma. 2 figs. J. Parasit., v. 15: 70.
CONINCK, L. A. DE, 1935. — Contribution a la Connaissanee des
Nematodes libres du Congo Beige. I. Lcs nematodes libres
des niarais de la Nyamuamba (Rowen/.ori) et des sources
chaudes du Mont Banze (Lac. Kivu). Rev. Zool. & Bot.
Afric, V. 21 (2-3): 211-232, 249-326, figs. 1-80.

1936. — M elaraeolai moiil es oxystoma n.g. n. sp. (Nema-
toda) en zijne afleidung van Araenlaimoides de Man,
1893 door Allometrie. (avec resume en Fran9ais). Biol.
Jaarb. 182-204; figs. 1-6 and A-C.
CONINCK, L. A. DE and Stekhoven, .J. H. S. 1933.— The free
living marine nemas of the Belgian Coa.st II. With general
remarks on the structure and the .system of nemas. Mem.
Mus. Boy. Hist. Nat. Belg. (58), 163 pp., 163 figs.
DRA.SCHE, R. VON, 1883. — Revision der in der Nematoden-
Sainmlung des k.k. zoologischen Hofcabinetes befinliche
Original-Examplare Diesing's und Molin's. Verhandl.
d.k.k. zool. -hot. Gesellsch. in Wien (1882), v. 32: 117-138,
pis. 7-10.
FiLipjEV, I. N. 1918. — Free-living marine nematodes in the
vicinity of Sevastopol. Biol. Stantsii Ross. Akad. Nauk.
s. 2 (4) : 1-352, 11 pis. Russian.

1929. — Two new species of Actinolaimiis from South
Africa. Ann. & Mag. Nat Hist. s. 10, v. 4: 433-439.
figs. 1-2.

1930. — Les nematodes libres de la bale de la Neva
et de I'extremite orientale du Golfe de Finlande. Arch.
Hydrobiol., v. 20: 637-699. v. 21: 1-64; figs. 1-33.
FOw.EBORN, F. 1923. — Uber den " Mundstachel' ' der Tricho-
tracheliden-Larven und Bemerkungen iiber die .iiingsten
Stadien von Triclweephalus Irichiirnix. Arch. Schiffs. &
Tropenhyg., v. 27: 421-425; pi. 11, figs. 1-18.
GoLDSCHMiDT, R. 1903. — Histologische Untersuchungen an
Nematoden. I. Die Sinnesorgane von Ascaris lumbricoides
L und A. megalocephala Cloqu. Zool. Jahrb. Abt. Anat.,
V. 18 (1): 1-57; pis. 1-5, figs. 1-40.
Hagmeiek, a. 1912. — Beitrage zur Kenntnis der Mermithiden.
I. Biologischen Notizen und systematische Beschreibung
einigcr alter und neuer Arten. Diss. Heidelberg. 92 pp., 5
pis. Also Zool. .lahrb., Abt. Syst., v. 32: 521-612.
Hesse, R. 1892. — Ueber das Nervensystem von Ascaris mega-
loccphala. Ztschr. Wiss. Zool.. v. .54 (3): 548-568; pis.
23-24, figs. 1-20. Also Diss. Halle, 23 pp., 2 pis.
Hetherington, D. C. 1923. — Comparative studies on certain
features of nematodes and their significance. 111. Biol.
Monog., v. 8 (2): 1-62; pis. 1-4, figs. 1-47.
Hoeppli, R. 1925. — Uber das Vorderende der Ascariden.
Ztschr. Zellforseh., v. 2 (1): 1-68; figs. 1-27, 1 pi., figs.
1-12.
HoKPPLi, R., and Hsii, H. F. 1929. — Helminthologische Bei-
trage aus Fukien und Chekiang. II. Parasitische Nemato-
den aus Vogeln und eineni Tummler. Arch. Schiffs. &
Tropenhyg., v. 33 (1): 24-34; pis. 1-5, figs. 1-22.
Hsu, H. F. 1933. — On some parasitic nematodes collected in
China. Parasit., v. 24 (4): 512.541; figs. 1-46.

1933. — Remarks on some moriihological characters of
parasitic nematodes of man and dog with descriptions of a
new Gnrzia species from Yangtze beaked sturgeon. Chi-
nese Med. J., V. 47: 1289-1297; figs. 1-7.

1933. — Some species of Porrocaecum (Nematoda) from
birds in China. J. Parasit., v. 19 (4): 280-286; jils.
2-3, figs. 1-18.

1935. — A study of some Strongyloidea and Spiruroidea
from French Indo-(;hina and of Thclazia chungkingen-

sis Hsii, 1933, from China. Ztschr. Parasit., v. 7 (5) :
579-600; figs. 1-31.
Hsu, H. F., and Hoeppli, E. 1933. — On some parasitic nema-
todes collected in Amoy. Peking. Nat. Hist. Bull., v. 8:
155-168; figs. 1-15.
Imminck, B. D. C. M. 1924. — On the microscopical anatomy of
the digestive system of Stro/igylus ediiitatiis Looss. Arch.
Anat., Hist, and Embryol., v. 3(4-6): 281-326, figs. 1-46.
Jagerskiold, L. a. 1897. — Ueber den Oesophagus der Nema-
toden besonders bei Strongylus armatus Eud. und Vocli-
miiis diiodcnaUs Dubini. Bihang K. Svenska Vetensk. —
Akad. Handl., Stockholm, v. 23(5): 26 pp., 2 pis.
Li, H. C. 1933. — On the mouth-spear of Trichocephalus iri-
chiunis and of a Trichocephalus sp. from monkey, Macacus
rhesus. Chinese Med. J., v. 47; 1343-1346; pi. 1. figs. 1-2.
1935. — The ta.xonomy and early development of Pro-
camaUanvs fvlvidraconis n. sp., J. Parasit., v. 21(2):
103-113; pis. 1-2, figs. 1-10.
Looss, A. 1902 (1901). — The Sclerostomidae of horses and
donkeys in Egypt. Rec. Egvpt. Govt. School Med. 25-139,
pis. 1-3; figs. 1-172.
LUKASIAK, J. 1930. — Anatomische und Entwicklungs-ge-
geschichte Untersuchungen an Dioctophyme renale. (Goeze,
1782) [Eiistrongylus gigas Rud.] Arch. Biol. Soc. Sc. and
Lett. Varsovie, V. 3: 1-ioO; pis. 1-6, figs. 1-30.
Magath, T. B. 1919. — Camallanus americatius nov. spec. Tr.
Am. Micr. Soc, v. 38(2) : 49-170; figs. A-Q, pis. 7-16, figs.
1-134.
Man, J. G. de. 1884. — Die frei in der reinen Erde und im siis-
sen Wasser lebenden Nematoden der niederlandischen
Fauna. 206 pp., 34 pis., 145 figs. Leiden.

1886. — Anatomische Untersuchungen iiber freilebende
Nordsee-Nematoden. 82 pp., 13 pis., 29 figs. Leipzig.

1888. — Sur quelques nematodes libres de la mer du
nord, nouveaux ou pen connus. Mem. Soc Zool. France.
V. 1(1): 1-51; pis. 1-4, figs. 1-20.

1889. — Troisieme note sur les nematodes libres de la
mer du nord et de la manclie. Mem. Soc. Zool. France,
V. 2: 182-216; pis. 5-8, figs. 1-12.

1890. — Quatrieme note sur les nematodes libres de la
mer du nord et da la manche. Mem. Soc. Zool. France,
V. 3(2-3): 169-194; pis. 3-5, figs. 1-10.

1904. — Nematodes Libres. Resultats Voyage du S. Y.
Belgica. Exped. Antarct. Beige. Anvers. 51 pp., 11 pis.

1907. — Sur quelques especes nouvelle ou peu connues
de nematodes libres habitant les cotes de la Zelande.
Mem. Soc. Zool. France, v. 20: 33-90; pis. 1-4, figs. 1-17.
Marcinowski. K. 1909. — Parasitiseh und semiparasitisch an
Pflanzenlebende Nematoden. Arb. K. Biol. Anst. Land. u.
Forstwirt. v. 7(1): 1-192^ figs. 1-76, pi. 1.
Martini, E. 1916. — Die Anatomie der Oxyuris curvula. Ztschr.

Wiss. Zool., v. 116: 137-534; figs. 1-121, pis. 6-20.
MiroLETZKY, H. 1914. — Freilebende Siisswas.ser-Nematoden
der Ost-Alpen. Zool. Jahrb., Abt. Syst. v. 36(4-5): 331-
546; pis. 9-19, figs. 1-36.

1922. — Neue freilebende Nematoden aus Suez. Sit-
zungsb. Akad. Wiss. Wien. Math.-Naturw. Klasse. Abt.
1, v. 131(4-5): 77-103, figs. 1-13.

1930. — Freilebende marine Nematoden von Sunda-In-
scln. I. Enoplidae. Vidensk. Medd. Dansk. Naturh. Foren
y. 87: 243-339, figs. 1-24.
Ortlepp, R. J. 1932. — Some helminths from South African
Chiroptera. 18. Rpt. Direct. Vet. Serv. and Animal Ind.,
Union S. Africa: 183-195, figs. 117.
Rahm, G. 1929. — Nematodes parasitas e semi-parasitas de di-
versas plantas culturaes do Brasil. Arch. Inst. Biol. v.
2: 67-136; pis. 13-23, figs. 1-145.
Rautiier, M. 1918. — Mitteilungen zur Nematodenkunde. Zool.
Jahrb., Abt. Anat., v. 40: 441-514; fig.s. A-P, pis. 20-24,
fig.s. 1-40.
Sandground, J. H. 1933. — Scientific results of an expedition
to rain forest regions in Eastern Africa. Bull. Mus. Comp.
Zool., V. 79(6): 341-366, figs. 1-22.

1935. — A redescription of Filaria perteniie Rodhain.
1919 ;ind the creation of a new genus, Protofilaria, for its
reception. Rev. Zool. Bot. Afric, v. 27(2): 248-253, figs.
1-5.

1935. — Spinira michiganensis n. sp. and Biciularia

halli n. sp., two new parasitic nematodes from Eutamias

striafvs Ii/steri (Richardson). Tr. Am. Micr. Soc, v.

44(2): 155-166; pi. 28, figs. 1-9.

Schneider, A. 1866. — Monographic der Nematoden. 357 pp.,

122 figs., 28 pis. 343 figs. Berlin.
Siiui-z, R. En. 1927. — Die Familie Pliysalopteridae Leiper,
1908, (Nematodes) und die Prinzipien ihrer Klassification.

74

I

S;iiniiil. Ili'lininlh. Arln'it. I'idC. K. I. Skrj;il>in ^fi'wiilnict.

Moskva: L'STaiL', 1 pi.
Skrjabin, K. I. ISIK). — ifaterialy poKoliiiinto faimic I'.ir.i

Riiaia (ciiiitriliiitions a rptuclo lioliniiitluiIoKiciiic ilii I'nra-

gliay) ZddloKii'li. Vesnik, I'ctiiiKiail, v. 1, pt. 1, pp. 7ll.">

73.'); -J lies., pis. L'4 2."., figs. 1 27.
Stein-kr, G. l!il(i. — Fnilohoiulo Xomatodi-n aus dor Baientsoe.

Zool. Jahrb., Abt. Syst. v. :i!l( .')-(i) : .■n(>7(i, pis. l(i :!(i.

Hks. l-4ti.

1SU7. Chci- liir Vi'iw.-iiidlsi-liat'tsviTlialliiisso iind ilic

Systt'inatisi'lii' .StidliiiiK dcr Mt'riiutliiili'H. Zool. An/.., v.

48(9) : 2G3 :2(i7.

iyi8. — Studien an Xeniatodcn aus ilcr Niedorclbc. I

Toil, ifoiinitliiden. Mitt. Zool. >riis. Handmrtr. (2 Boi-

hoft. daliili. llanUmiK Wiss. .\nst.t v. :i.'.: 7.' 100; fins.

1 i:i.

II'IM. — Die von A. Monaril Ki'saiimu'ltoii Xeniatoden.
dor Tit'fi'nfauna des Neuonlnirnorsoes. Bull. Soc. Neu
idiattd. Si-. \at., v. 43: 1-104: tigs. 118.

1023. — Limii'olo Morniitliiden aus dcni Sarckgi'birge
and der Torne Lappmark. Naturwiss. Untcrsucdi. Sarekgo-
birg. Sclnved.— Lajipland, V. 4(8): 80.")-827: figs. 1-29.

1923. — Beitrago zur Konntnis dor Mcrniithiden 2 Toil.
Morinithidou aus Paragua.y in dor 8animlung dos Zoologi-
solion Musounis zu Berlin. Pp. 90-110, figs. 1-34.

1924. — Some nenias from the alinu-ntary tract of the
Carolina tree frog (Hiila caroUncn.^iis Pennant). J. Para-
sit., V. 11: 1-32, figs. 1 -(55.

1924. — A remarkable new gonus and species of nicr-
mithid worms from Jamaica. Proc. U. S. Nat. Mus.
(2527), V. 6.)(14): 1-4, pis. 1-2.

192:'). — The problem of host selection and host speciali-
zation of certain plant-infesting nomas and its application
in the study of neniie pests. Phvtopath., v. 1.5(9): 499-
534; figs. 1-8.

1929. — Xcoaplectana ulusrri, n. g., u. sp., (Oxyuridae),
a new nemic parasite of the Japanese beetle (Popillia
.iaponica Newm.). J. Wash. Acad. Sc, v. 19(19): 436-
440; fig. 1, A-I.

1929. — On the gross morphology of Acrobeles (Acro-
beles) crossatiis n. sp. (Rhabditidae, Nematodes) found in
diseased bulbs of Iris tiiir/iiitaiia Boiss. and Rent, with
remarks on its ecology and life cycle. Ztsclir. Morpli., v.
15(4): 547-558, figs. 1-13.

1930. — The nemic fauna of tlio slinio fiu.x of the Caro-
lina Poplar. J. Agric. Res., v. 41 ((i): 427-434; figs. 1-3.

1933. — The nematode Cylindrogaster lonflistoma (Ste-
fanski) Goodey [sic], and its relationship. J. Parasit., v.
20(1) : 6()-CS, "fig. 1.

1935. — Opuscula miscellanea neniatologica I. Proc.
Helm. Soc, Wash., v. 2(1) : 41-45; figs. 1-3.

1936. — Opuscula miscellanea neniatologica IV. Proc.
Helm. Soc, Wash., r. 3(2): 74-80; figs. 22-25.
Steinesi, G., and Albint, F. M. 1933. — On the morphology of
Deontostoma caUfornicum. n. sp. (Leptosouiatinao, Nema-
todes). J. Wash. Acad. Sc, r. 23(1): 25-30; figs. 17.

SrKiNiMt, G., ;ind IIoki'IM.i, K. 1926. — Studii's on the e.toskcle-
ton of some J:ii)anoso ni:irine nomas. Arch. ScliilTs. &
Tropenhyg., v. 30: 547-57(i; figs. A Q, plate.s 12.

Stkkiioven, J. 11. St'iiuuKMANs. 1926. — Ncw facts concerning
the larvae of Anchiiloslnma caninum and yrcatnr amrri-
caniis, Proc. 3r(l. l'.ni-P;icific Science Congress. Tokvo.
Pp. 2577-258(1.

1937. — Parasitic Nomatoda. Kxi)loration du I'arc
.\";itional .\lbert, Mission G. P. do Witto (1933 1935)
Fasc. 4: 1 40; figs. 1-116.

Stkkiiovkn, J. 11. S., and Coxinck, L. A. t)K. 1933. — Mor-
pliologische Frage zur Sysfeinatik dor freilobondon Nenia
toden. Vorhandl. Dout.sch. Zool. (ieselLsch. : 138-143:
figs. 1-2.

STlt.\ssEN, O. zuit. 1904. — Anthraconcmn, oiiu' nouo Gattung
froilebender Nematoden Zool. Jahrb. Sui>pl. 7, Fest-
schrift Weismann: 301-346; figs. A-J, pis. 15-16, figs. 19.

TuoK.N'K, (i. 1925. — The gonus Arrobrle.i von Liustow, 1877.
Tr. Am. Micr. Soc, v. 44(4): 171 210; figs. 140.

1930. — Predacious nomas of the gonus Xi/golaimii.i
and a new gonus. Scclnm ma. J. .\gric. Ros., v. 41(6):
445-406; figs. 1-18.

1935. — Notes on free-living ;ind plant parasitic nema-
todes. II. Proc. Holm. Soc. Wash., v. 2(2): 96 98.

1937. — A revision of the nematode family Ce|)halo-
bi<lae Chitwood and Chitwood, 1934. Proc Helm. Soc
Wash., V. 4(1): 1-16; figs. 1-4.

Thorne, G., and Swanoer, H. H. 1936. — A monograph of the
nematode genera Dori/laimus Dujardin, Aporcelaimus n. g.,
Dori/laiiiKiitlt'.s n. g.. and Pungcnius n. g. Capita Zool.,
V. 6(4): 1-223; pis. 1-31, figs. 1-188.

Walton, A. C. 1936. — A new species of ZancMophnrus from
C r yptob ranch Jis alleganicnsis. Tr. 111. State Acad. Sc,
V. 28(2): 267-268, figs. 1-7.

Wedl,, C. 1856. — Uober die Mundworkzougo von Xematoilon.
Sitzungsb. Math. Naturw. CI., v. 19(1): 33-68; pis. 1-3,
figs. 1-3.

Wehr, E. E. 1933. — A now nematode from the Rhea. Proc
U. S. Nat. Mus. (2958) v. 82(17): 1-5; figs. 1-3.

1933. — Descriptions of two new parasitic nematodes
from birds. J. Wash. Acad. Sc, v. 23(8): 391-396; figs.
1-8.

1934. — Descriptions of three bird nomatodos, incluiling
a new genus and a new species. J. Wash. Acad. Sc, v.
24(8): 341-347; figs. 1-15.

1935. — A revised classification of the nematode super-
family Filarioidoa. Proc. Helm. Soc. Wash., v. 2(2):
84-88.

1935. — A restudy of Filariopsis arator Chandler, 1931,
with a discussion of the systematic position of the genus
Filarinpsis van Thiol 1926. J. Wash. Acad. Sc. v. 25(9):
415-418, figs. 1-7.

Wu, H. W. 1934. — Notes on the parasitic nematodes from an
Indian elephant, Sinensia, v. 5(5-6): 512-533; figs. 1-28.

75

CHAPTER VI
THE ESOPHAGUS INCLUDING THE ESOPHAGO-INTESTINAL VALVE*

1. GENERAL MORPHOLOGY

The esopliagi of nematodes are extremely diveree in both
gross anatomy and mode of function ; this diversity is corre-
lated with the widely differing feeding habits as well as with
the phytogeny of this organ, the result being an assembly of
numerous types with examples of convergence and of diver-
gence. In addition features of no apjiarent present value to
the organism are often preserved.

The esophagi of all nematodes have a few characteristics in
common, for example their fundamental triradiateness, one ray
of the lumen being directed ventrally (though torsion may
cause a complete reversal in some regions), a cuticular lining;
marginal nuclei and fibers connected with the rays of the lumen
or railii, radial muscles and nuclei located in the regions be-
tween the esophageal radii; nerve cells of the esophago-sym-
pathetic system; and glands emptying into the lumen of the
esophagus or into the stoma.

The esophagus in cross section has three sectors (Fig. 6'i) ,
a dorsal sector and two subventral sectors. Cell walls are not
distinguishable in the esophagus as a whole; it is, therefore,
syncytial. However, the cell walls of nerve cells are usually
distinct and the protoplasm of each of the esophageal glands
usually retains its identity. The nuclei of the marginal and
radial fibers are so placed as to leave no doubt that each be-
longs to a .specific part of the fillers and therefore functions
separately.

Through their contraction the radial muscles cause dilation
of the esophageal lumen; the marginal fibers are apparentl.v
static rather than contractile and the marginal tissue and
protoplasm, according to Martini (1908), correspond to the
epithelium and form the cuticular lining of the esophagus.
The esophagus is often covered externally b.y a semicuticular
membrane which may possibl.v be a product of the marginal
tissue. Longitudinal supporting fibers are usually absent in
the esophageal wall. The esophageal glands apparently serve
a digestive capacity, the secretion being either ejected through
the mouth in case of extracorporeal digestion or passed into
the intestine with the food and aiding in intracorporeal diges-
tion. Other possible functions of the esophageal glands will
be discussed later.

Nemic esophagi evidence man.v degrees of cell or nuclear
constancy; Looss (1896) first discovered nuclear constancy
with reference to the radial, marginal and gland nuclei in
ascarids. Since this observation, representatives of the major
groups have been studied liy us with the result that we find
many large groujis characterized by a certain number of nu-
clei of a given type, arranged in a definite manner ; loss of
nuclear constancy is characteristic of certain groups, and evo-
lution from forms with few cells or nuclei to forms with many
cells or nuclei nia.v be traced.

Other points of systematic value in the stud.v of nemic esoph-
agi are: The form of the lumen and esopliageal lining, the
position of the esophageal gland orifices, the form of the
gland ducts and tubules, and finally, the form of the esophago-
intestinal valve.

The esophageal lumen itself may be triradiate, the sides of
the radii converging distally (Fig. 65B), or they may terminate
in incomplete tubes (Fig. (ifiA). In either case the esophageal
lining may have thickened attachment points at which the ra-
dial muscles are inserted (Fig. (i.5B) ; whenever the radii ter-
minate in marginal tubes, or whenever attachment points are
l)resent, the radial muscles are said to be concentered (Fig.
6.5C) while in other instances thev are usuallv dispersed
(Fig. 6.-.D).

The dorsal esophageal gland orifice is usually at or near the
anterior end of the esophagus. In some cases it is fituated on
a dorsal tooth projected into the stoma (Strongylus, Ancylos-
tanid, OticlidlaiiniiK) hut in other cases the orifice is far re-
moved from the anterior end (Aphrlrnchaiilrs Prionchulus,
Diirjihiiniiis) . The subventral glands, on the contrary, usually
have their orifices in the posterior part of the esophagus (meta-

corpus) and only in rare instances do they extend to the an-
terior end (Enoploidea, Tripyloidea, Dioctophymatoidea). As
a general rule, the duct of an esophageal gland is situated in
the middle of a sector and branches are given off into the
protoplasm from each side of the central duct. In large forms
it has been found that these branches terminate blindly in the
form of tubules and the protoplasm is not in direct relation
with the lumen. Onl.v the terminal duct is lined with cuticle.
Because of the numerous cases of convergence in gross form,
the structural diversity will be discussed group by group unit-
ing >)oth the gross anatomy and the histology in order that
evolutionary trends ma.v be more readil.v observed.

A. SUBCLASS PHASMIUIA

All phasmidians have one point in common with respect to
the esophagus, namely, the subventral esophageal glands always
have orifices far removed from the anterior extremity. On the
basis of gross morphology they show no obvious separation into
groups but on the basis of histology and developmental anatomy
they are divisible into two groups, the orders Rhabditida and
Spirurida. In the Rhabditida the esophagus shows evidences,
in its larval stages at least, of being composed of two major
parts, an elongate corpus and a short bulbar region, while in
the Spirurida it is composed of a short muscular anterior part
and a long wide glandular part. These are fundamental dif-
ferences established in the histology of the organ.

Rh.-vbditin.A-. The esophagus of members of the sub-
order Rhabditina consists of a cylindroid corpus (further divisi-
ble into procorpus and metacorpus*), a narrow isthmus and a
pyriform or elongate bulbar region. In some forms, such as
Mhahditis (Fig. (i.l), the bulbar region contains a well de-
veloped valve, while in others, such as DipJut/aster (Fig. 76),
no such valve is present. It will suffice for our purposes to
describe the esophagus of Ithabilitis and compare the other
forms with it.

The esophageal lumen of Rliabditix ti-rricula varies accord-
ing to the region, the rays of the lumen of the procorpus ter-
minating in well developed marginal "tubes" (Fig. 67ab),
those of the met.-icorpus in smaller "tubes" and those of the
isthmus and bulbar region in acute angles. The lumen is
modified at the valve and the lining thickened (Fig. 68c). The
procorpus contains IS nuclei: six radial nuclei (ri-„) in one srt
(RI) near the base of the procorpus, one being on each side
of each sector (Fig. 67a-b), and 12 nerve cell nuclei (ni-n) ar-
ranged in three chains, one in the center of each sector. The
radial muscles are concentered in six liands corresponding to
the six radial nuclei. The metacorpus (Fig. 66 & 67c-d) con-
tains 28 nuclei: three bilobed marginal nuclei (nii-j) in one set
(MI)t, six radial nuclei (r7-i=) in one set (RID, and 19 nerve
cell nuclei (ni.i-,,i) forming three chains as in the procorpus.
The isthmus is anucleate while the bulb contains 30 nuclei, as
follows: six marginal (nu-n, nh-a'*, three of which are in the
prevalvar region (Mil) and three in the postvalvar region
(Mill); 12 radial (r,:,-,s, r,„-j,, r-i.-;.,), a set of six of which
are in the prevalvar region (RIII) and groups of three in
the valvar ( R IVa) and postvalvar regions (R IVb) ; nine
nerve cell nuclei (uii-.n) and three esophageal gland nuclei
(gi-a). The esophago-intestinal valve has a simple triradiate
lumen ; its wall consists of an internal layer of transverse
fibrous tissue containing two n\udei and an external circular
la.ver containing three nuclei.

The esophagus of Hhabflilis functions as follows: Contrac-
tion of the radial muscles in the procorpus tends to triangulate
the lumen thereby increasing its volume; thereafter contrac-
tion of the radial muscles of the metacori>us cause dilation of
its luiiH'n while relaxati(m of the mu.scles of the ])rocorpus and
dilation of the bulb;ir valve occur. In order to discuss the
nu'chanism of the bulbar valve we shall label the jiarts; the
esophageal lining has a .series of three thickened regions. Dur-
ing rest the first piece (1) is convex anteriorly while the

*StrictIy speaking (tie esopliHKo-intcstiiml valve i.s part of the csdplia-
gus. Howevpr. in conformity with roniinnn usage, the term esophagus
a.s usHd herein excludes the esophago-intestinal valve unless otherwise
specified.

*These terms are suhstituted for jirecorjuis and postcorpus (p. 10)
at the suggestion of Dr. Steiner.

tXot uncommnnly flip marginal nlU'lei may aj>pear to lie double, in
forms with marginal tubes at the termination of esophageal radii; in
such cases the lobes are designated mi„.n)i,,, etc.

76

(Inr dg/d

,. & -.■■■■ K3 ^3i.

Fig. 71

/

Fic. 68

O u

t

Fig. 65, Diagrams of esojihaei. A-D — Cross spttions showing vari-
ous types of muscle arranKf-niftit, (.\— Radii of esophageal luitien ter-
minated by tubes, musculature cfincentered : ex. RhnbdUis. Lfidjinemay
Heterakis and first stage strnngyles, PJfctus and Axonolnimus : B —
Sides of radii converging distally, mus<nilature concentered, attachment
points present; ex, Oesophagostomum. CamaUanun, CuculUinun, Sphnero-
laiwiis and Metachromitdora .- C — Sides of radii converging distally,
musculature concentered, no attachment points, ex. Ethntolniinus, Mo-
nopoHtkia, Sphilophorella. Acanthnnchus ; D — Sides of radii parallel,
musculature dispersed, ex. Asroris, Phi/snJnptera, TlwriMtuK. Tripylti) .
E — Diagram of rhal)ditid psr»ithagii.«i showing parts of esophagus and
relative position of radial tubes of lumen, dne — -dorsal escphagi-a!
nerve, sv ne sub ventral esophageal nerve, sd et subdorsal and v et
ventral esophageal tnlifs, mf marginal fibers. Ir radius of lumen, ap
attachment point, pr ro procorpus, me ro metacorpus, i isthmus. >» Imlh.
Original.

Fic. *>(>. Diagram showing nuclei of metacorpus in RhabditiM.

Fio. 67. Diagram showing groups of nuclei in esoi)hagus of Rbnb-
diti/t terricola as occurring in cross se4tion. a-b~ -Procorpus; c-d —
metacoriius ; e-f — bulb.

Fig. 68. Jfhabditis terricoln, esophageal cross sections, a — procorpus;
b — metacorpus ; c-f- — Fhabditift lamhdiensis bulb.

Fic. 69. Ditf/IfiichuN dipsari. Sections through corpus.

Fii!. 7<K Ditf/lenrhus dipnaci (Sections through bulbar region).

Fk;. 71 . Ditylenrhtis dip/tari ( Reconstructon of esophagus with nu-
I'lei in position.

Fins. 72-7,'*. .1 plielctu'hux a re nap. 72 — pr(M'ori>us ; 7^-— metacor-
pus; 74 — bulbar region ; 7.'» - -region of glandular appendage.

FlOS. 66-75— After Cbitw. & Chitw. 1936. .7. \Vash. Arad. Sc. v.
26 (2) ; Fig. 65 original.

77

second and tliird pieces (2-3) nearly touch one another. Con-
traction causes a reversal of the position of 1, point a (Fig.
97E-F) becoming nearly a.xial and point 6 moving from an
axial position to a point formerly occupied by o. This is ac-
complished by contraction of the radial muscles of the pre-
valvar region (associated with ris-is) and possibly of the
valvar region (associated with rw-si). Opposition to this move-
ment, i. e., return to the position of rest, is accomplished by
muscles of the valvar region (rni-2i). Movement of piece 1
to a position of dilation is followed by dilation of the lumen
opposite pieces •'-■:} in series (through contraction of the post-
valvar radial muscles associated with r-<«-2i), opening of the
esophago-intestinal valve and, finall.v, closure of this structure.
There is no evidence that the marginal fibers are ever con-
tractile. They appear to function entirely in the capacity of
"fixed points" upon which the sectors are "hinged." In the
corpus, relaxation proceeds slowly while contraction or dila-
tion is spasmodic. Perhaps the tubular form of the esophageal
radii contributes to the opposition of the radial muscles be-
cause of their elasticity. Muscle fibers definitely opposed by
other muscle fibers are found only in the valvar region of the
bulb. All muscle fibers of the esophagus are perpendicular or
oblique to the esophageal axis; there are no circular or longi-
tudinal fibers.

In Rhabditis. the dorsal esophageal gland orifice is at the
anterior end of the procorpus (Fig. 76), the short cutieularly
lined terminal duct is followed by a small ampulla and a long
canal extending to the bulb where it becomes lost in the mass
of dorsal esophageal gland protoplasm; the canal extends near-
ly to the base of the bulbar region where the gland nucleus is
situated. The subventral gland orifices are situated at the
base of the metacorpus and, likewise, each is provided with an
ampulla and a canal leading jiosteriorly to the bulbar region.
The mass of the subventral gland protoplasm is lateral in
position (i. e., in the lateral part of the subventral sectors)
and their nuclei are in the valvar region.

The nerve cells, previously mentioned, form the esophngo
sympathetic system which consists of a nerve trunk in the
center of each esophageal sector, these trunks being connected
by tliree commissures, one at the base of the corpus, one in
the prevalvar region and one in the postvalvar region. This
system is connected with the central nervous system by means
of a pair of nerves from the subventral trunks through the ex-
ternal surface of the procorpus.

Other members of the superfamily Rhabditoidea with a
valved bulb apparently have the same structure as that de-
scribed above. In T)ipl<ic/as1ir (Fig. 76), and similar forms, in
which the valve is absent but the radial muscles of the Vnilbar
region not degenerate, slightly larger marginal "tubes" occur
in the corpus and the radial muscles associated with rio-n seem
to act together instead of as two separate groups. Sliabdia.i
and Strviigyloides present peculiarities in that the esophagus
has a well developed valve in the free-living generation and
first stage larva of the parasitic generation, but this structure
degenerates in the later development of the parasitic genera-
tion though there is no change in the number or arrange-
ment of the esophageal nuclei.

In the superfamily Tylenchoidea, actual degeneration of the
radial muscles of the bulbar region takes place but the .30
nuclei of this region which correspond to those in Rhahfliti.i
still remain (Figs. 70 71). This degeneration of the muscula-
ture is correlated with increase in size of the esophageal glands
which form practically the entire bulbar region in forms such
as Uitylcnchvs Jipxaci and may even extend beyond the ba.se
of the esophagus as one or more eso])hageal aiipendages as in
Aphelenchim avenae (Figs. 7.5-76). In a few forms, such as
Aphcleiirliiix and Aplirlewhoides, Cobb (1923) showed that the
dorsal gland orifice is situated in the anterior part of the
metacorjius instead of the anterior i)art of the procorpus as
is generall.y the case. In many tylenehids the metacorpus is
unusually large and acts as the chief "pump" of the esopha-
gus, while in the Allantonematidae the musculature of the
entire esophagus appears degenerate.

Stronoymna. — Members of the suborder Strongylina have
!in esophagus which is grossly clavate to cylindroid but in
sonu' instances f.'iint indications of procorpus, metacorpus.
and bulbar region are observable in the adult. The first stage
larvae of strongyloids and many trichostrongyloids have an
esophagus identical with that of Hhabdilis : during the second
and tliird stages the esojihagus becomes more elongate and
the valves of the bulbar region disappear resulting in an
esophagus reminiscent of that of Diplofia.iirr except that the
metacorjius is not enlarged or as distinctly set off. With pro-
gressive development the various regions become grossly oblit-
erated to a greater or lesser degree. Metastrongyloids <liffer
from strongyloids aiul most trichostrongyloids in that first

stage larva does not have a valved bulb, but more closeI.r
corresponds in its morphology to the second and third stage
larvae of the other two superfamilies.

The detailed structure of the esophagi of strongylins was
studied by Jagerskiold (1897), Looss (1905), Imminck (1921,
1924) and the writers (1934, 1935). It was found that the
marginal, radial, and gland nuclei agree in number with those
of Eltabditis but the prevalvar radial nuclei (r,,i-io) are ar-
ranged in two groups of three nuclei each, near the center of
the sectors. There is no essential difference in arrangement of
the nerve cells though there is considerable variation as to the
total number observed (from 29 in iletastrongyliis dongalns
to 44 in Strongylus eflentatum). The triradiate esophago-in-
testinal valve seems to be composed of seven cells. The sub-
ventral esophageal gland nuclei are quite minute in members
of the Strongyloidea and thus f.ar gland orifices near the
nerve ring have been observed but rarely. This may be corre
lated with the hypertrophy of the dorsal gland characteristic
in such forms, and it may have a distinct bearing on the feed-
ing habits.

The musculature is always "concentered" rather than "dis-
persed" in strongylins, and the lumen may have marginal
tubes as in Mctasfronpyhis or there may be a series of thicken-
ings of the esophageal lining forming attachment points as in
(h'xiipjiiigo.stoiiiiim deiitatiim (Fig. 7S) and Ancylostoina duo
denale.

ASCARIDINA. — More work has been done on the esophagi
of representatives of the suborder Ascaridina than of repre-
sentatives of other groups. It was in Parascaris equoriim that
the orifices of esophageal glands were observed for the first
time in any nematode by A. Schneider (1866). Subsequent
work has been carried out bv Jagerskiold (1893, 1894), Ham-
ann (1895), Looss (1890), Ehlers (1899), Jerke (1901), K. C.
Schneider (1902), Goldschmidt (1904, 1909, 1910), Martini
(1916, 1922), Kulmatycki (1918, 1922), Allgen (1921), Muel-
ler (1929, 1931), Hsii (1929, 1933), Plenk (1924, 1925, 1926),
Chitwood (1931), Chitwood ,^nd Hill (1931), Chitwood and
Chifwood (1933, 1934, 1936), de Bruvn (1934), and Maekin
(1936).

In ascaridins the esophagus varies in gross morphology
more than in any other group. The members of the super-
family Oxyuroidea are less diverse in detailed anatomy than
are the members of the snperfamily Ascaridoidea. In the
former group, the esophagus in the adult stage is basically
rhabditoid, having, with a few questionable exceptions, a cylin-
droid corpus, a more or less distinct isthmus, and a valved
bulb. In numerous forms, such as Syphacia and 0.ryuris, the
corjius may be clavate while in a few, such as Ransotnncnia, it
may be fusiform. In some forms the metacorpus is enlarged
and either cylindroid as in Leidyncma or ovoid as in Hammer-
.iclnniilliclla : in oild types the entire corpus is pyriform (Aoni-
riis) and in still others the procorpus only is fusiform (Ozolai-
miix). The isthmus also is diverse in gross appearance, some-
times being greatly elongated as in Atractis or Aorurus, some-
times only moderate in size as in Tlielastoma, sometimes
recognizalile only as a groove as in Ehigonema and some-
times subglobular as in Labidiiriis. Less diversity occurs
in regard to the bulb; it is valved except in a few genera
such as Drrmatoxys and Lciperenia but the degree of develop-
ment of the valves differs greatl3' between the typical rhabdi-
toid form of Thelastoiim and the much reduced type of O.rytiris.

One would ])resume that forms such as Lridynrtiia (Fig. 70)
and HdinmcrxchmidticUa represent the primitive t.vpe since
the metacorpus is enlarged as in Rhahditis and since careful
study proves the corpus to be subdivided into pro- and meta-
corpus even in forms in which these parts otherwise are not
grossly separable. However, primitivity apparently does not
appl.y here since in the genera Leidyncma and Hammerschmid'
tirlla the esoiihagus does not reach this stage of development
until adulthood of the female. The .juvenile females, as well
as the adult neotenic males, have a c.vlindrical corpus as in
Thelastoma. Sexual dimorphism in the esopliagus as well as
cephalic structures, stomata, and cuticular ornamentation is
one of the outstanding oddities of the Thelastomatidae and
Ransomnematinae. Developmental modifications, without aji-
parent bearing on relafionshi]), have also been described in
O.ryiiris iipii by Ihle and Van Oordt (1921) and Wetzel
(1930); in this species the fourth stage larva has a pseudos-
toin fornu'd by the dilation of the entire corpus (Fig. 97 O).

In their detailed anatomy, the oxyuroids show less diversity.
The lumen of the corpus u.sually shows the marginal "tubes"
as in Rhabditis and sometimes in addition (or sometimes in-
stead of them) the esophageal lining has distinct cuticular
thickenings or attachment points for the radial muscles. The
three esophageal glands (some statements to the contrary)
open as in IHnihdilis, i. e., the dorsal m-ar the base of the

78

stcitiia, tin' sulivi'iitrjls iic:ir tlic li;is(' (if llic ini't:iciirpus. 'I'lic
iiiiinln'r ami arranninu'iit of the micliM cDncspdiicls totally or
a|ipr(i.\iiiiat('ly to h'iKilxtilis in all forms stiiiiicd witli niu' ex-
<-i'ptiiiii: Martini (l!M(i) rooonls three nuclei in each of the
siilivcntral I'sopliajreal glands of Oxi/iirix e(iiii which fact might
oonceivalily be ihn' to either Kigantism or Tnisinterpretation.
The esophatro-intestinal valve is triradiate, more or less rhah-
ditoi<l. and contains five to seven nnclei.

The Ascariiloidia imhules some forms which have esophagi
of the tlielastomatid type sndi as Cosnioo'icoitlrs. With the

exception of the Ascari<iiilae (in which no iinlication of a sto-
matal region is ajiiiarent) and the Sulnilnrinae (in which there
is a short wide stoma) the stomatal region in the Ascaridoidea
is surronniled liy esophageal tissue containing radial muscles.
The mollified stomat.'il region so formed is termed a i:fnlibulr.
In some ascaridoids, the isthmus is obliterated, the hull) being
in direct continuity with the eori)us such as Ilitirakis, while
in still others (Spirdnoura) , it may be ovoid to spheroid; a
few forms have no valves, the bulbar region being elongated
(Qiiiiniicrio } and others have a cylindrical eso|)hagus eithiT

CAMALLANUS

CUCULLANU5

DiaKranis of esophagi, including representatives of the {Leidynema, CephuloheliUH) , Ascaridoidea {Spirononra

Hhabditoidea (Khabdititt, Dii'l'iffastcr) . Tylenchoidea (/>i- to Contrnraeeum) , CaiiialhinoideA iCamaUanntt, Cucul- \r /^j

ti/tenchux. Apheleurlnin) , StronKyloidea (OfnophaynHto- lanujt), Dracunculoidea {Mirropleura to Phitonfwa). \ r

mum), Metastrongyloidea {Metantrunf/ylus) , Oxyuroidea Original.

79

with 01- without a i.listiiu-tly si't off bulbar region (Ascaii'lia
and Ascarix, Toxiicara and Contracaeciim, etc.). It is in the
latter group that we have the outstanding diversity of the
su])erfaniily. While the liulbar region is always distinct in
the larva when removed from the egg it may totally disappear
from the standpoint of gross examination during later stages
in its development (Ascaridia, Ascaris. To.r<iscaris, etc.)- In
other forms it remains grossly unmodified but becomes rela-
tively smaller due to the disproportionate increase in length
of the corpus (To-rornra) and in some it becomes elongated
forming a short cylindroid glandular region (Anisal-is) . Forms
which retain a bulbar region often have one or more posteriorly
directed bulbar appendages {Contracaeciim, M'idticaeciim) .
The internal structure varies fully as much as the gross ap-
pearance and its variations will be dealt with separately.
Ascaridoids with a valved bulb invariably have marginal

"tubes'' in the legion of the corpus and concentrated radial
fibers but the esopliagoal lining is without thickened attach-
ment points in all forms.

Meroniyarian forms such as cosmocercids and kathlaniids
have approximately the same nuclei as are present in rhabdi-
toids and oxyuroids (one group of three large marginals and
two groups of six large radials in the corpus; two groups of
three marginals, one group of six radial and two groujis of
three radials, and three ghuul nuclei in the bulb). Polymyarian
forms, such as heterakids and ascaridids show evidence of ad-
diti(jnal cell division in the esophagus, for in heterakids there
is an additional group of six radial nuclei in the procorpus
making a total of 30 radials and the subventral esophageal
glands are each binucleate. In ascarids there are .3(5 radials
and 12 marginals, the additional nuclei (six radials and three
marginals) being situated anterior to or opposite the orifice

Pios. 77-SO

Di.'igranis .sliriwing distriljution of nuclei in tlie esophagi of Metn-
xtraniiyUix etoni/afn.i (77), Op.snphanostitmum dfntalum (78), Leidj/-

neiiia iii>iii'inliciilnhiiii (79), iind Ueteiakin j/nHi'inif (HO), .\fter (_'hitw.
& Cliitw., ,1. Wnsli. ;\cml. He.

80

(if tlic (l()is;il <'s(ipli;i|;cal kIhiuI. 'PIic iiiitoiior ladiiils ( Ki|{.
si I ill this r.isi' .iri' idcutcil in tlir i cntfr of tlii'ir soctois, ill
two groups of tliri'i', the reiiiiiiiiiiiK r;nlial k'"'M"' "^ "'c fofpus
arc tiroki'ii, i. i'., I'lii-h group of six is siilidiviiit'd into two
groups of thri'o, ono in earh srctor am! those nuch'i iiiav or inav
not heeonie eentrallv loeated aceoriliiig to the |)artieiilar genus.
Members of the Asearididai' liave only three esopliageal ghinil
nuelei and for that reason .Iscdiiilia, witli liiiitieleate sutiveii
tral ghinds, though the esolihagus is eylindrieal, must lie jilaeed
in the Ueterakidae.

Whether or not thi' esophagus retains its gross separation
into corpus and Inilliar regions in the adult, the two regions
are histologieally separable the base of the corpus being in
dicated liy the basal eoinniissure of the nietaeoriius. In aseari-
diiis the esojihageal glands undergo many peculiar modifications
(see llsii, llfji', lil.'i.S^. The dorsal gland situated near the
base of the bulbar region is bilobed in .l.wvin.v liniiliricoidcii
the lobes are marginal and connected by a fine strand. In
this form lobes of tin' liorsal gl.'ind I'xtend int<i tin' siibventral
sectors of the corpus giving the appi'arance of fusion of tis-
sues. However, in such forms the subventral glainls do not
e.\tend into the anterior part of the esoph;igus. .\ccording to
H.sii, 193.^, the dorsal gl.ind nucleus completely surrounds the
esophageal lumen in .inisal'is and becomes ventrall.v situated
in Toxocara and Conlracaicam. Thus, though the ventrally
situated bulbar apjiendage in Contrncdcfiiiii rejiresents the two
subventral sectors of the esophagus and may or may not contain
small lobes of the subventral esophageal glainls, it is cliietly
formed }ty the much enlarged d<irs;il glanil (Pig. 7<i\

have arisen. There are two superfaniilics, raniallanoidea and
Draeunculoidea, the forinei being char;icteri/,ed by ndatively
well develoi>ed musculature usn.'illy having ciiticular attadi
Mient jioints for the radial muscles ami an esophago-intestinal
valve that is either Iriradiate or shows reminiscences of this
condition, while the latter group has enonnoiisly developed
esojihageal glands, relatively meager musculature in the glandu-
lar ri'gion, no atlaclinient jioints and a dorso vent rally llattened
esoph:i go-intestinal \al\'t'.

Ksophagi of Caniallanoids have b('en studied by .Jiigerskiold
(litOin, Magath (Ull!!), Tornquist (l!i:tl), andll.sii (lit33).
('tiiiKillunns iiiicroci phaliix has a so called "divided" esophagus
( i'igs. 7fi & !t8 K-F). Here the dorsal gland orifice is some-
what posterior to the base of the stoma, the subventral gland ori-
fices at the .'interior end of the posterior part of the esoiihagus.
In the anterior part of the esojihagus there are IH radial nuelei
anil six marginal nuclei, the railials in four groups, two groups
of three anterior to the dorsal gland orifice and two groups of
six jiosterior to this level; the marginals are in two groups,
one situated near the level of the dorsal ghind orifice, the other
between the third and fourth radial grouiis. In the iiosterior
part of the esophagus there are likewise IH radials in four
groups and six marginals in two groups. Here the first group
of six radials is situated near the anterior end of this jiart
of the esoiihagus at the level of the subventral gland orifices,
the second group of six radials somewhat anterior to the mid
region of this part, and the third and fourth groups of three
radials near the ba.se of the esophiigus. One marginal group
is .lust posterior to the level of the siilt\t'iitral gland orifices

{"JIplIli!! B iLplnAi'

■A I. J,

tl'.

htv

"IT

L SV t

-t'

'• -: "

^

I-

^S*

n»

n-j

'^/

C

•^

% "-r,.

","•"'

r,

-;;.?

^
s.

"

t,

'..

m, '„

m.

'., «!

\^;- '■:

k.

liA

METOTaOHl^Tl.US 1

.0 I D kb

"V %

m."° %

Efil

ft SV

D L-J.

V bvlOL

LOl D koOLls. 1.

',

Ti 'i* M 'i m

rr

1

m, ^A

"

'- '..

^"

't, r^^

fT

r^ r

'.. '..

r 'r

'" IT

. 'i: ™

'■• r

i,

t.

r^

r^

'..

M.c.o.,.!;,.. 1

p ;v I n I L ;v—
. Ij'. bL LP I 0 LP ti.tiv I >

r, ' 'A'^ 't ',\}', ''.1
'.. '..'{•'.. '.!>': ':*■
0,. ',,1 '„ '-1 '-.0.

',. ',,\ 'it '•• '" ••
< . >

m„ i'Si "1.

*■'

"EVTBi

^TST

01- l5v|v

0 "m ''

V •" 1".. Ti

n ■•'M r

" ml ^

i- i.

a!

lisv

0

V ISVIOL

>L|SV 1 V

n, S;

'•

a,

"'

'- '„

'" r^

'■

m, "1,

n,^

". n„

"...
"«•

\l

n,, m.

h'--^"

V, "r„m
r

^' ^

t.

H.,....„' •]

„C. '' ^_m, c, o'c.

jSVlOL LP I D ILD

':; l?',,""!? -'^

\i^ IDLLOI-glLO DdVv rV

'* *>, •"»

f, f ,

•>-■•.■

H jv I II I \r^T-

I HV IPL LOl D ILO OlTsv 7

m • m.

's

'- m,. '„ m« 0.

vToi-Ji-ol o IloIolVvi vl

^, I' ^ I i ''

I

'■^^'■^

f

f "' ; "•

Tallies iif I'.-iipluiKiiil miili-iir distrilml inn of I'liiisiMiiliiin.-.. (Irigiiial.

Spirurid.\. — The essentially different funn nt' the esopha
gus in the order Spirurida has tieen previously mentioned. The
fact that the esophagus is always histologically divisible into
a short muscular anterior part and a long glandular posterior
part is not of cour.se, noticeable in many forms with cylindroid
or even elavate esophagi. However, the fundamental signifi-
cance of this type of organization is evidenced by the absence
of any stages in the life history showing reminiscences of the
rhabditoid esophagus such as were mentioned for the Strongy
lina and Ascaridina.

(■.\.\I.VLr,.\yix.\. — The sulionler Cainallaniiia i-oiitnins forms
in which the esophageal glands are primarily uninucleate;
secondarily a few forms with iiiultiniii'lente glands appear to

while the other is near the level of the third group of radials.
It would appear obvious from the nuclear distribution (Fig.
■SI) that the posterior or glandular region corresponds not
only to the bulbar region of Jfliahihlis or Ascari.i but also to
the metacorpus of Ulitihditis and part of the metacorpus region
of Axcari.i, since the bulbar region in these forms contains
only six marginal and 12 radial nuclei while the posterior part
of C(imtill(inu.i contains IS radial and six marginal nuclei.
This view is supported by the fact that the commissure of the
metacorpus is situated in the anterior part of the gl.-indular
region of the esophagus of Ciimnlliniiis.

In ('iiciillaniix though the esophagus is davate instead of
being divided (Fig. 7<i) we observed essentially the same

81

nuclear arrangement and gland orifice positions in the posterior
swollen region. The nuclei correspond to those of the posterior
part of the camallanid esophagus.

Esophagi of dracunculoids were studied b.v Jagerskiold
(1894), zur Strassen (1907), Mirza (1929), Hsii (1933), and
Yamaguti (193.5). In gross features the esophagus may be
cylindrical as in Micropleura, clavate or fusiform as in Philo-
metra, divided into a short narrow anterior muscular part and
a long wide posterior glandular part as in Phikinema, Draciin-
ciiliis and Avioserpens. In DraciinciilKS and Ai^ioserpens the
glandular region is constricted in the latitude of the nerve
ring (Fig. 76). In Draciinculii.t, Avioserpens and Philometra

y^

yj~p

<=>

the anterior end of the esophagus takes the form of a sub-
globular swelling but does not do so in PhUoncma and Micro-
pleura.

The radial and marginal nuclei in DraciincKliis, Avioserpens
and Micropleura follow the same arrangement as in Camallanus,
R I and E VI being divided groups. All these nuclei are also
in the same position relative to the level o'f the orifice of the
esophageal glands. In Uracu7i.eulus and Avioserpens the region
posterior to the constriction at the nerve ring corresponds to
the posterior part of the esophagus of CamaUanus ; in the two
former genera an additional peculiarity is observed ; the dorsal
esophageal gland and its nucleus are tremendously enlarged

voiy

RiCTULARIA

ASCAROPHIS PHYSALOPTERA OElSMIOOCERCtLLA MONOPETALONEMA OiPLOTRI AENOIDES

SPHACROLAImuS SIPH0N0LAIMU5

Fid

Diagrams of esophagi; including representiitivi^s of the
Spiruroidea (Rictularia to Phyaaloptera) , PMIarioidt-a (IJps-
midocerceUa to Diplotriaenoides), Plectoidea (Plertus to Annn-

OESMOLAIMUS THERISTUS

rhuff), Axonolaiinoidea (Axoiwfniinus) , Chroniadoroidea (Para-
cnnthonchus, Tripf/louies) , Monhysteroidea (Sphafntlaiwns to
Theristu8) . Original.

82

(Kr. 81). In Philomiira tlie fourth and fifth Rioups of r.i(li;il
nuclei (K IV anil R V) aio also divideil intii two siili);i"iip>^
each, Imt the niaiEinals and radials retain tlie same relative
piisitiiins as in Druciinciitii.K; liowever, in the latter the snli
ventral t;l:'"ds ( ^'iK. Td) are K'eatly redueed in size. V;inia
Kiiti ( IMii.'i) descM-ilied a Kenus, IcUiiinfihiiid. with a imsteriiir
(fl.'indular appendatle similar to that ohsei-ved in i'(mlnini( rii iii.
liowever a study of the histoloRV of this sirnetiire li.as not
lieen made.

Philoni ma represents the ultimate in esoidiaReal );l''"'d de
velopment of the Draeunenloidea. This genus has the typieal
spiruroiiitilarioid esophagus, a fact that opens the tiuestion
whether or not it is eorreetl.v placed in the suborder Camalla
nina. .Ml three csojihageal gland orifices are located in the
posterior, much eidarged glamlular region of the esophagus
and the esophageal glands are multinucleate. The radial nu
clei of all six groups are arranged in triplets, i. e., all six
groups are subdivided; since there are three gro\ii)s of r.adials
in the anterior muscular part of the esophagus one would
.judge this part to be homologous to the anterior jxirtion of
the es<iphagus of CaimiUaniix : the position of the subventral
gl.-md orifices (Fig. 7t)) is in support of this view. The dcu-sal
gl.-ind orifice is shifted consider.-ibly jjosteriad in this form.
The esophageal glands each contain several hundred nuclei of
varying sizes often arranged in api)arent "constellations'"
such as one would expect from nuclear budding induced
by gigantism. Perhaps this case is analogous rather than
liomidiigous to that of the multinucleate glands of spiruroids.
In the spiruroids the many gland nuclei ajiparently arose
through typical division because they are approximately equal
in size. If Philonrma did arise separately the gigantism of
these glands in Draninctihis and Philomcira might be corre-
lated with the unequal nuclear divisions (amitosis.M in the
gland of Philonema.

.'iPiRl'Rlx.v. — There are two esophageal features common
to the forms contained in the suborder S|)irurina, namely,
that the esojihageal glands are always nudtinucleate and that
the dorsal gland always opens in the glandular (posterior)
part. Esophagi of members of this group are grossly cylindri-
cal or divided into a short anterior muscular j)art and a wide
posterior glandular part. Even in forms with a cylindrical
esophagus these two parts are distinguishable on the basis
of their consistency. The gross form of the esophagus appears
to be of no phylogenetic significance since changes from dis-
tinctly "divided esophagi" to cylindrical esophagi occur
sporadically within groups of closely related genera.

In all except one family the marginal and radial nuclei
are of the same number as in the suborder Caniallanina (totals
of 12 and 3(i respectively) ; in this one exccjitional family,
the Physalopteridae. there appears to be a ncm limited num-
ber of radi.-il nuclei (Fig 81) ; the radial nuclear sets usually
are all .subdivided, three in each group, but in some forms
(Fig. 81) the second, third or fourth may be partially or not
at all subdivided. Regardless of the gross apparent extent of
the glandular region, in all forms the anterior mu.scular part
contains only the first 12 radial nuclei and the posterior glan-
dular part contains 24 ladial nuclei (or more as in PhiisnJoptria
maxillaris) ; the anterior part does not, therefore, correspond
to the entire anterior part of the esophagus of CiniKiIhiiiiix.
Since the fifth and sixth groups of radial nuclei of Ciiiiitillaiiiix
a])pear to correspond to the radial nuclei of the bulb of lilinh-
ililix and the fifth and sixth groups of Ascnris. one would
conclude that the remainder of the esophageal nuclei are homol-
ogous to those of the corpus; since the second group of mar-
ginal nuclei is typically anterior to or ojiposite the third group
of radial nuclei, the third and fourth groups of radial nuclei
of Camallaniin are probably homologous to the second group
of radial nuclei of Rhabditis which has divided in this form;
hence the second group of marginal nuclei and third and
fourth groups of radial nuclei are homologous to the nieta-
corpus; if, likewi.se, the first group of radial nuclei of Hhah-
ililiti divided as also the first group of marginal nuclei of this
form (the marginals migrating anteriorly) then the honuilogies
indicate that whatever region contains the first and second
grou]) of radial nuclei in a s|iiruroid is the procorpus. There-
fore, we may say with a reason;ible degree of certainty that
the anterior muscular region of these forms is the prnriirpiis
and the posterior glandular region is mrldrorims and hiillxtr
rrflinn.

The esophageal glands of spiruroids anrl fil.-irioids have
very many nuclei, varying from a minimum of about 3(1 each
to a maximum that can scarcely be estimated in forms such as
Phjixdhiptrra. The increase in nuclear number in these forms
has apparently [irogressed with regularity in division since
the nuclei arc fairly ecpial in size.

The esoph:igeal lumen may be simple triradiate as in liirlii-
lurid riil(}r(iili< ii.si.s (Fig. 82), somewhat dilated but convergent
peripherally as in .IscarDphis or contain nuirginal "tubes"
as in llixiiiiiliiccrca iiiimiilirti and Diphilriai iioidi x (Fig. 82).
FurfheruHjre the esophageal lining may have thickened regions
as in MiiiiDjii liiliiiKiim ]t)itisnUinim, sometimes with distinct
atlacliiTicul p(]irits, or it luay be unmodified. Thus f.ar the l>os
silile phylogculic significance of such structures has not been de-
termineil but niodilii'ations ajipear to be nuist pronouni'ed in the
forms found in body cavities or tissues, i. e., Filarioidea. The
form (if the esophago intestinal valve changes from a dis-
tinctly triradiate shajie such as is found in Hiciiilaria to a
(|(U-so\'entrally flatteucil structure such as is found in Plu/.salrt/}-
tcnt.

Further infoj-maliou on uucle.ar arrangement, esophageal
lining .'ind shape of hnnen .'iiid esophago-intestinal valve, will
result in substauti.al evidence hearing on the inter-relationship
of meudiers (d* the suborder Spi?'uriii;i.

H. SI'KCI.ASS .\1'11.\SM1I)I.\

.Aphasruidians as a wijole have no single esophageal feature
in common. Like the subclass Fhasniidia they are divisible into
two ma.jor groups on the basis of the esojihagus, the first order,
('hroniadorida, corresponding to the order Rhabditida, contains
forms in which the eso|ihagus is primarily divisible into cori)US,
and bulbar region, the second order, the Enoplida, contains
forms in which this division is not grossly apparent.

r'H!iOM.\DORin.\. — The esophagi of members of this order
have three uninucleate esophageal glands; the dorsal gland
orifice is situated at or near the base of the stomatal region
(never, so far as is known, does the glaiid empty directly into
the stoma through a tooth) ; the subventral gland orifices are
at the base of the corjuis. Rei)resentatives of this order have
l)ecn studied by the writers (193(!).

The suborder Monhysterina contains forms in which the
esophago-intestinal valve is relatively well developed, often
quite elongated, and dorso-ventrally flattened, or ro\inded
rather than triradiate.

Of the whole Apliasmidia the representatives of the super-
family Plectoidea nuist closely approach the Rhabditoidea, for
in this group forms such as Plrctns have a rhabditoid esopha-
gus w^ith a well developed valve in the bulb, but unlike Rhab-
ditis the pro- and metacorpus are seldom apparent on gross
study. The lumen of the corpus terminates marginally in dis-
tinct tulies and the valve of the bulb works in a manner
similar to that of Rlinhditix. Other plectoids have an elongated
luilbar region without valves and in some forms the cori)Us
also may be quite elongate ( Lcpiolainuis) , while in others
< Aiinncliux), the entire esophagus may be cylindrical (Fig. .*2).
The musculature of the bulbar region may be reduced so that
this region forms an elongate glandular swelling (Camacolai-
inns, Anguinoidcs, AphannUumns) similar to that part of the
esophagus of Diljjhnchux. and in still other forms such as
OnchiKm nceUatum the esophageal glands may project poste-
riorly beyond the base of the esophagus. It would appear,
therefore, that not only in stylet and stomatal formatiim but
also in esophageal formation the Plectoidea present a parallel
series to the Rhabditina. In two points all plectoids are simi-
lar, the esophageal lumen of the corpus peripherally is termi-
nated by marginal tubes and the esophago-intestinal valve is
definitely dorso-ventral in symmetry (Figs. 83-84).

The corpus of all forms contains four groups of six radial
nuclei (24) and two groups of three (or three double) margi-
nal nuclei (total (i or 12). The radial muscles of the corpus
are more or less concentered but no forms are thus far known
in which the lining is thickened forming attachment points.
As in Rhahditix in the bulbar regiim there are 12 radial and
(5 (or 12) marginal nuclei, the first set of 6 radials and the
first set of marginals forming the jirevalvar region; the suc-
ceeding radials are arranged in two groups of three which
together with the second set of marginals form the post-
valvar regicm. In Anuplictiix pnniidoxnx (Fig. 83) and simi-
lar forms with unusually well developed " tubes "" at the ends
of the esophageal radii the marginal nuclei of each group
are double, cme member of each i>air being on each side of
each tube, while in forms such as Camaeotaimiix prijihrrrhi in
which the tubes are minute (Fig. 84), no such doubling of
m.'ugin.'il nuclei occurs.

Rei>resentatives of the suiierfamily .Vxonolaimoidea have
esophagi like plectoids except that no representative of this
group has a valved bulb .and no forms are known in which the
bulbar region is ]irincii)ally glandular through enlargenu-nt of
esophageal gl.-inds at expense of muscular tissue (Figs. 82 &
S4). The entire cscjpliagns may be clavate (Cnmrxinna. !<nhnli<-

S3

Fig. 83. Esophagus of Anuplectiix iiiniiiiln.iu.i. A-F — procorpus;
F-Li — jiietacorpus : M-S — bulb.

Fio. M4. A-C — Anaplerfu.t grannlnsua. ( .\ — longitudinal sfction
through bulb and I'.fophago-intnstinal valvp. ) BC — Cross si'i'tions,
through esojihago-intestinal valvi' (also includes very small part of
bulb with n:-j.3o). 1>-F — Anonchna miriihilin. (D — corpus at base of
stoma: K — corpus somewhat further posterior; F — bulbar region).
(M — CaiiiitedlaimtiH /irillherflii 1(1 — Corpus; H — base of bulbar region
showing g, and n-j^.^u: I — esophago-intestinal valve). J — Axonftlainiim
ipinomts, (corpus). K-M — Sabatirria vulgaris (K — Corpus; L-M —

Fro. stl

esophago-intestinal valve). N-P — Pamcanthonchus sp. (N — Anterior
part of corpus; () — ^corpus somewhat more posterior; P — esophago-in-
testinal valve).

Fic. H.l. TripiiUnm fiirciiiirohim v. calkumi. (A — Stoniatal region;
B-C — eoriius; 1) — bulbar region; E-P — esophago-intestinal valve).

Fin. 86. A-C — Microlnimus sp. (A — Corpus; B-C — esophago-intesti-
nal valve). D-K — Chrnmadora sp. (I)-I — Serial sections through bulbar
region; J-K — esophago-intestinal valve).

All after Chitw. & Cbitw., I9:lf>, J. Wash. Acad. Sc, v. 2B (8).

84

rill) or till' foi|)iis may remain grossly distinct (.Ijo/iufiiimiix,
AriitiilniniNx) ; the l)ull)ar rcRioii is always ratlior cliinKatc,
lu'vi'r in tlii' form of a clotinitc Imlli. As a riiU' ono may ilis
tinK»>^l> procorpiis and nu'ta('ori)iis in totomount specimens
tlir»n);li the idianue in the esoi)liaf;eal lining ( Fijj. 1.">K) as the
size of tlie marginal tubes l>eeonies reduced; no forms are
known with thickened attachment points for the radial muscles
altluingh the muscles themselves are concentered.

The nuclei of the esophagus of axonolaimoiils are essentially
as in Phftiis except that in some forms {Salinlirria viil(iari.s)
the six iiosterior radial nuclei tend to assvime a hexa ratlier
than a trisynimotry in their arrangement. Tlu' esophago
intestinal valve is as elongated as in jilectiuds an<l of slightly
different form (Fig. S4 LM^ ; it contains aliout 111 to 1^ nuclei.

Kepresentatives of the superfamily Monhysteroidea are of
three general types, liiiliomoeids, monhysterids and sii)hono-
laims all characterized liy a smaller number of radial nuclei
than is found in |)lectoids and axonolaimoids. The I.inhomoei
dae contains forms with a clavate esophagus which may (Dix-
)iu>ltiiniiis) or may not (I.inh<iiiioci(.i) ho terminated liy a well
marked nniscular swelling or hulli ; the esophago intestinal

valve is usually delinitidy I'longaled l.ut rri.iy be rather short
( N/)/i(i(/i(/(iiHiH.v ). In these forms the radial muscles are con-
centered and this condition is usually accompanied by thickened
cuticular attachment points on the lining (Figs. Kli, H'>, H7).
The esophageal hnnen while mo<lified due to these attachment
points is devoid of marginal tubes. Forms such as Tripylium
carclnicoliim, Trrxchrlliiir/iii pontica and l)i wmohiimus zeclan-
(Urns, V. iniiiricditiix have only .'id to T.i radial nucdei, the re-
duction or difference in number being in the metacori)U8; the
second group of marginals is also apparently lacking in Tcr-
.ichiiliiu/i<i. We find in tlii^se forms the same i>eculiar distri-
bution of the radial nuclei of the jiosterior part of the bulb
previously mentioiu'd in the axonolaimoids (Fig. !HI). The
esophago intestinal valve of linliomoidds is often associated
with specially differentiated intestinal cells t Triiii/liinii) and

Vm. 87. A-I> — ThtriitfuH /fpfosun. EI — TfrsfUeUingia pontirn { K —
rnrpiis; K — bulbar region; G-I — serial sections throueh csophago-in-
testinni valve). J — T>cnmoUtimnn zeelayuii<"HM v. niupricnnus ( I^^hgitudi-
nal section through bulb, and esophago-intestinal valve). "'

Fl(!. 88. EthmoJaimujt revalienms. (A — Stoma tal reRion ; B — ror-

pus ; r-(; — bulbar roKi<'n ; HI — esophago- intestinal valve) .

KiG. rt!>, MojmpoMthin hi'.valntn, AC — corpus (A — in stomatal region;
H — just posterior to tlie orifice of dorsal gland; C — near base). D-G —
bulbar rvgion. H — esophago-intestiual valve.

All after Chitw. & Chitw.. 1936, J. Wash. Acad. Sc. v. 26 <8).

85

in some forms sueli as DesmvUiiinus this structure forms a sep-
arate and distinct organ which may be termed the ventricular
column (Figs. 82, 87J). Monhysterids (Figs. 82, 87A_-D)
have a more cylindrical esophagus, though never a distinct
linhomoeid bulb, and the ventricular column is never elon-
gated ; the posterior radial nuclei have the same odd type of
arrangement as linlionioeids but the radial musculature is of a
dispersed type throughout, the esophageal lining without thick-
enings, the lumen very simply triradiate and the esophago-
intestinal valve less elongate but otherwise similar to that of
TerscheUingUi (Fig. S7G-I) ; the latter structure contains 19
to 23 nuclei. Siphonolaims have a very short corpus, an elon-
gate isthmus, a short glandular bulbar region and a short
esophago-intestinal valve containing six nuclei. The nuclei of
the bulbar region are as in linhomoeids and monhysterids but
only three marginal and 18 radial nuclei are present in Sipho-
nolamiis conicus. Monhysteroids are peculiar in having very
minute marginal nuclei (Fig. 87A).

In the suborder Monhysterina one first encounters paired
pigment spots in the subdorsal or dorsolateral regions of the
procorpus in a few genera of the Camacolaimidae (Onchinm
ocellatum) and A.xonolaimidae {Araeo!aimus). These peculiar
structures are situated in the dorsal parts of the subventral
sectors (dorsolaterally ) or the lateral parts of the dorsal sector
(subdorsally) ; there is, in the first mentioned genus, a pair
of acorn like pigment masses each provided with a hyaline
lens. While these are termed ocelli, no one has thus far con-
nected them with sensory nerves. In MonhysUra pahiilicoln
similar ocelli are situated in the body cavity dorsal to the
esophagus.

CHROMADORIKA. — lu the subordcr Chromadorina the eso-
phago-intestinal valve is usually short though sometimes
elongate but never dorso-ventrally tiattened ; it always retains
its triradiate character. None of the representatives of this
group preserve semblance to rhabditoid or plectoid esophagi.

In the Chromadoroidea the esophagus consists essentially
of a cylindrical corpus and a bulbar region (Fig. 91); the
esophageal lumen is triradiate, the lining unmodified, so far
as known, though the radial uruscles are definitely concentered.
Members of the Chromadoridae such as Cliroiiiaihna and Etlimo-
Jaimus revaliensis have a very short esophago-intestinal valve
containing 12 or 1.3 nuclei (Figs. 86, 88); 12 marginal and 30
radial nuclei are present in the esophagus, the posterior nuclei
of the bulbar region being arranged in tw^o typical groups of
three. In Microlaimns dentatum the esophago intestinal valve
containing 11 nuclei is elongate reminding one of Tersehel-
liii(/i(i, but differs from that form in being triradiate (Fig.
8<) B-C). Chromadoroids show no tendencies toward diminu-
tion in nuclear numbers such as was noted in monhysteroids
but, rather the opposite. Several "additional nuclei" make
their first appearance in this group; the arrangement and
positi(m of these nuclei (s, c, and x) are characteristic of both
chromadoroids and desmodoroids (Fig. 00).

f'yatholaims generally have a much elongated trijiartite bul-
bar region or a cylindrical esophagus. In representatives of the
former type {Paracanihonclnix coccti.i) the lumen of the esoph-
agus may be slightly enlarged marginally (Fig. 84 N-P).
(jhoanolaims and tripyloids, on the contrary, have a typical
triradiate lumen with long rays as in monhysterids rather
than the short rays and minute lumen typical of the Chroma-
dorina. All of these foims have a rather large and well de-
veloped but short esophago-intestinal valve.

Desmodoroids have the same general esophageal organiza-
tion and the same general pattern of nuclear distribution
(Fig. 89) as do chromadoroids but the esophageal lining may
have thickened cutieular attachment points (Mclaclirnmadoru
oiiiixoides) .

The so-called "multiple huDi'' of chromadoroids and des-
modoroids deserves special ]i]cnti(]n. In both superfamilies one
may trace series of foruis from a subspheroid bulb to a sub
cylindroid tripartite bulb thence to a cylindrical esophagus.
The apparent sub-division of the buUiar region in forms such
as Monopoxlliia lu-.rtilata and EUiniolaimii.i revaliensis (Fig. 91)
into two jiarts is due to a particular arrrangement of the mus-
culature and glandular tissues and a break in the thickness of
the esophageal lining at the points where one muscle ceases
and another begins. This break indicates the separation of
radial subgroui)S of muscles containing nuclei r.n-.ii and
r:ii-:»i resi)ectively and is essential to the function of this type
of bulb. The musculature containing the radial nuclei rr,.j,i is
in the anterior part of the trip.-irtite bulb ami tlir corresjiond-
ing muscles are a separate functional unit.

I'iguK'nt spots in the anterior part of the corpus are com
monly found in nu'inbers of the (^hromadoridae .'ind like those
previously nirnticmi'd in the Ciini.-icohi imid.-io and Axnnolainii

dae they are situated in the subdorsal marginal regions of
the esophagus but in this case the pigment is diffuse rather
than concentrated aud is not provided with a lens. It seems
proper to designate ihese as mere pigment spots while reserv-
ing the term ocelli for concentrated pigment bodies accom-
panied by lenses. De Man (1889) described true ocelli situated
dorsal to the esojdiagus in the body cavity of Cyathtilaimus
demani (Syn. Cyalholainuis ocellatiis of de Man).

The esophagi of desmoscolecoids have not as yet been ade-
quately studied. The esophagus is grossly rather cylindroid
but narrow, the three esophageal glands projecting posteriorly
indicating a leduction in the musculature of the bulbar region.
Such forms (Fig. 17) have well developed, brilliantly col-
ored pigment bodies dorsal to the base of the esophagus.

Enopuda. — The esophagi of representatives of this order
commonly (always?) have five or more uninucleate or multi-
nucleate esophageal glands. The esophagus usually has an
elongate muscular anterior part followed by an elongate
glandular posterior part, such divisions resembling those of
spiruroids and filarioids. The location of the esophageal gland
orifices varies widely in the group.

ENOPLiN.i. — Esophagi of representatives of this sub-order
have been studied by Marion (1870), de Man (1886,
1904), Jcigerskiold (1901), Turk (1903), Rauther (1907) and
the writers (1937). In general we find tw-o types of esophagi
in this group : the first type in which the esophageal glands have
orifices rather near their nuclei, that is, in the posterior glandu-
lar part of the esophagus (such forms are included in the super-
family Tripyloidea) ; and the second type, in which the sub-
ventral esophageal glands open anteriorly either near the base
of the stomatal region or in subventral teeth (such forms may
occur in either of the superfamilies Enoploidea or Tripvloi-
dea ) .

In the Tripyloidea the esophagus either is cylindrical (Prion-
chulus, Tripyla) or consists of an elongated narrow corpus
and a slightly wider elongate glandular region ( Alaimiis) ;
in all such forms studied there are five uninucleate esophageal
glands, one dorsal and four subventral (Fig. 91). Mononchs
such as Prionchuliis muscornm have concentered radial muscles
and well developed cutieular attachment points (Fig. 92) ; the
esophago intestinal valve which is triradiate and quite massive
(Fig. 92M), contains 22 nuclei in P. muscorum. A total of 36
radial and nine marginal nuclei have been observed, the radials
(12 in procorpus, 12 in metacorpus and 12 in glandular region)
are arranged in sets of six, indicating that even those of the
posterior gioup act as a single unit rather than as two units
as in rliabditids, plectids and chromadorids. Nuclear distri-
bution (Fig. 90) indicates quite definitely that the glandular
region of the esophagus of Prio^ieliuliis as well as other tripy-
loids, enoploids and dorylaimoids is homologous to the bulbar
region of the orders Rhabditida and Chroniadorida rather than
the glandular region of spiruroids since it does not contain the
radial nuclei characteristic of the metacorpus (total nunilier
of radials 18 in spiruroids). The five esophageal gland nu-
clei are subequal in size and each of the accompanying glands
opens nearly directly into the esophageal lumen (Fig. 94D).

In Tripyla papillata and Trilohns lemgiis the musculature is
dispersed, no cutieular attachments are present and the esoph-
ago intestinal valve is quite massive, consisting of an external
part containing six or seven large nuclei and an internal part
containing up to 100 nuclei (Fig. 94 E-L). This peculiar
structure, sometimes termed a pseudo-bulb, or bulb, is com
monly thought to be a part of the esophagus irroper but this
does not appear to be the case. It is a further development
of the type of valve found in Prionchuliis. The five esophageal
glands are similar to those of the latter genus except that the
dorsal and the fii'st pair of subventral esophageal glands extend
to the base of the stomatal region where they open.* Alaimiis
is similar to Tripyla except that the radial muscles are con-
crnlered ; the triradiate esophago-intestinal valve is quite small
and inconspicuous, and the subventral glands do not extend
l>eyond the enlarged glanil\ilar region.

In the sujierfamily Enoploidea the gross form of the esopha-
gus varies considerably, there being types with a cylindrical
esoiihagns, types in which the narrow corjnis is followed by a
gradually I'xpanding elongate glandular region (conoid") and
t.vpes in which the coipus is slightly narrower and set off in-
ternally from an elong.ate cylindrical bulbar region. Due to

*On the bnsis of esopliageal structure the current concept of the supei--
f.'ii?iily Tripyloideft must tie revised, preferahly to include the Tronidae.
Tlie i)osition of the gliind orifices as previously stated for Ti'ipi/lii (PP-
1 (i and .'J2) is not in accordance with present tindiiif^s. Temporarily,
the alisence of cutieular duplication at the he.-id may he considered the
limiting character of the Tripyloidea (includinir the Tronidae) as op-
I)osed to the J)resence of cutieular duidication in the Enoploidea. Tjater
we hope to lie in a position In adrl further characters to substantiate
this revision.

86

p

V rA

\ 'A

'^i o".

"/

"*

1

1. n, "V.

^

•W "V.

"V.

n

p..,.-. 1

M^

t

l?v

U liJiBl.

lBiS M ^

OL m'l V

r. n. ',

'. ". ;■

n
n

''*, "

n

n

" "" ;.

v

",.

""

'.-

r^

'„

",,

u

K 'c'"

«"°~"'» 1

R JV

D

LSV

r

n^ r

'. ,""

, ", '„

;• "' ,'

",.

^F

a,

, '..,

'V f,

0#

r

fV. '"

0/

n 0,

h

1# "

if- 'is

V.

"« L "«

C*M«COtAlUUS 1

« !V

B

^ ?^

m, 1, m.

'"' "/ 0

f,

r n '

r.

a.

""• ''/.

m "'j

r

r

« '/I

r

fi

n '^*
" n

';/~

''5- '^'

"«

"j* "it-'irt

Ooiin.iiMonii 1

a 5V

B

lSv 1

r, n^ - n.r.

'!.<;.

^'..

".*

a.

a.

"i m.

n
r

1,

f

m m

1.

^. :

8-

-V,"--!.

e<

rMlWllTUJ 1

P V

b

I ?^

%

"'

^- „

n"

n
n

r ""/

* n,

r "

n

n

^

m m^

" m

r "

r r

n
n

n

J*

- rr,.

n

8j

"» "« ^,

J,

1

B JV

D

LSV

"1#
' n

n

"V rv, "1-

'- ^, '-

"1. "Vi

m

^ '„

r.

r

1.™.

'„ V

r

. i'

r
6. "m

'.

V„ ""

i"V.

»„.»o..™». 1

B SV

D

■nrJh,

Ji'

%* "^

n,. -n.

-Hi

"1.

r. n, '„

',4 ^ 'f

r^

"V ',

'i. ^f

%

r,^

f^

^

T,

n.

"w "#

>■ I>

"Ji

n, "I

, "■■ 1

IV.,

'(■ ".. "

»

"., 'f

fi

»,.

n

n„

""',.

'«

r^^

"■■j^

n," "^

n
li, n

>"«

"/«

" 8.

«/

'.^

, I,

">,

"

',1 n«

n/,

0) m„

A«0»<OL*iuu>

6

L !V

m„ n)

y %."* !^

'.

• '>

'. '

'..

'.. ^ '.

'•' "' r

">. ". "1.

n

"t 1, n^

".«

n

\ fT

r "i*

"n,.

n .

•'.0 "

n
n "

'""""C

'•

n m

6, ffl

" r. r

'

V ISVIBL LEI D ILD TJirnyTT

'» Ti. m

m, 01,

1^ <^r^»

B SV

0

LSV

V ISUltL

,BI 6 ILb

ftl Kvl V

f, a r.

n '
■^^ "', ^

•"z* fly, *;.

n

m, m

' r-
' "« '
I "■' '^

TtMCMILL^NOI* 1

RiV

s 1

lS'v I

■'U r, V "l 'r " '

n

n

",.

n,,

a.

n„

"..

m^ m^

r

',. C,

■i/ "

""

r„

'^

8' ",; -;

r„

3lFH0HOL«>MUJ 1

n 5V

5V 1

V Isv I6l

Lb 1 B iLb

TTT ^vl V 1

m

nij m,

n. r>

r "' r

r

"' r

'' r

' r,

r

7' :•

m^ ^ m^

^<\

1

".» s.

n.

",<

n '■"

t'

"< "„ "^

"» m,

'm "„ '->

/«

r^

sr "-''

"«

!,

5.

O/l

r„ "

•

8,

e.

e.

'„ '-

n, n« n.*

I-/.

ET«M0L«.MU3

H 5V

D 1 ^v I

V 1 W 1 Pn

lDI 5 lib DLtr/! V 1

" n

"•

\ 0

' 1, r.

'■,0 S-

r,^

•a n

1

it r\„ "

s, n,j s^

.„ , s.

0. "-.r,.

:- 8. ^

-' ^^

"v

■v,

"., "« IV,

MONO«»OJTm* 1

HW

n

I, ^v 1

^ ISV IDL

^D\ D 1 LD

Pll

SV 1 V

' ^

f f
1

""i

r

n

Aj

X,

n, r

^. n. '.

'»

rij

K \ «.

(TI, m

s

n, '•

r n r

f r

n, '
r n Cj,

m

s, 8,

5;, '"S

5,

r
%

e

n

""lO

"<

\-.,-..o.. 1

15V I PL

I' '«

". "^.^

p ■SV

El

1 ^v

"i

r^ r,

',

% ". c,

»;, ", r.

r, n, r^

". r..

n. n. ,^

r, n,

r.

\-

m, '^">.

"-",/'"'

"„ "" "

'" "..

"^n.

> >

"„ C

L^' "

^,;" '!

\"

' "n

r "<

<<■■' '..

"" u

\

i.

1.

t.

"..

W 1

1- C»O.L« 1

KIW

^V

n 1 n li n

t r

*r m

'■

^

r, 0

r r

r r^

" "•

"*

n^

■^ »,

^ n.

' ""^«

"f^

n

'*K,

n

ft n"

"• "V "^f '^it 1

r

f

"

?"

^, "- "-

'■" >",> "i. 'fl

S. S' g'

U-, 0. 'V''" "i* i-T"

t«..,rotl,N*

M^V

— TI —

I ^ 1

B ILB

", 1

m^

^- . ?

f

r

^1^

-V,"*'

'".

n "

0

r;^

"C

",, ",. '^1

"//

'V,

>wi

"#r m

m,

"...

5^

r^

f,-

^

"«

r^^

"

"*

ft

S"

8,

S'

8,

8r

8'

flrf.

r,„

Hm

"■">"=-

OLAIXU*

',.".. r^ '--V?/''

V I^V^IlJL

1"' H im

ni K^'^i V

m, n, "^

n

n

''4 I",

r r

n r

r^ r

r * '

* ^1,

m^ rr

"-•

'^'i m

r

"

"»

n

'i.r,/

r

U""

^W

'=' ",. 7

'^ „'"

-v """1,

n" ^'

t.

8'"

s.

»,/•'" "

^. fl- '

^ r,;-

t.

*;. •""

8.

r

."WW

',/

T»l».L« 1

psw

D

1-,5V

' n 't

••. n. ',

'* n, '»

n«

"*

"»

"• r

n,

'*■ n„ "

'* n, ''

"; n,„'»

n

n

n

i^.-

m, r

i;-^

r.

f

'■• "„ ^

",. "./■'

•^i!

i^.j

n"

'„",.

". 8. '-

™- v,.„

1^

"■«.!;'•

r

f;.-S;-R.-:";pr

r..

8,

'. '\ -"', «• nl,

M

Vr.'-.h..! 0.7

Pa.ONCxuLUl 1

^

57 m nrggisianSvuc

to.

"'^Jvi'

8i

'K.

8.

%

Tables of esophageal nuclear distribution of Aphasinidians. Chitw.
& Chitw., Ifl.'ifi, J. Wash. Acad. Sc, v. 26 (8) & 19:!7. v. 27 (12).

87

the distriliutum (if i:iiliiil nmselcs tlic i-or.iiid t.viie of esoiiliagus
may be nmltilnilbai- (Folygaxirophora, Bolbella), creiiate in
outline (Pliainiilcnnopsis) or smooth in contour (Oxystomitia,
Eiirystomina, Li'ptosomatum) . Among the latter, two tj'pes
are distinguishable in regard to the muscular development.
In Oxy.slo))iina and its relatives the musculature is poorly
developed while in the remaining forms it is well developed.
In the Oncholaiminae the esophagus is of a cylindrical t.vpe,
the esophageal lining simple, the bnnen also simiile and tri-
radiate throughout; the esophago-intestinal valve is triradiate,
moderately elongate and contains numerous nuclei. There are
12 marginal nuclei but only 2' radial nuclei in Mttniifliolaimus

liri.itiiirKX and according to their distriliution (Fig. ilO). we
may judge that compared with Triin/lii, the third group of
radial nuclei (of Metone)wlaimtis} represents a case of fail-
ure of cleavage of the last set of radials of the corpus of
Tripyla. In the latter form the final cleavage results in the
third and fourth sets (Bill and RIV) or 12 nuclei while in
Metoncholaiinii.i only six nuclei are present. Likewise the three
giant radial nuclei (Fig. 94 OP) of the bulbar region also
may represent a cleavage failure. In this form one dorsal
and two pairs of subventral gland nuclei are to be found in
the posterior part of the esophagus; separate orifices of the
two glands in each sector liave not been distinguished. The

METACMROMADOHA ETMMOLAIMUS

MtTONCMOLAlUUS EjRrSTOMINA PHA NODEBMOPSIS ANTICOMA LEPTOSOMATUM ENOPLUS

m

1}

^ (^

r

ty (^

(It)

PBIONCHULUS DORYLAIMUS ACAMERMIS

Vu:. 91

niuEranis of csophani ini-hiiiing reprcsiintiitivp.'! of ploidiM (.Mfliiiirliiiliiinni.t In Eiiniilim), Ti-ipyluidcii
the IJHsmodiiroidca (.M rtiii-hrnniiidora, Monoiio.ilhia) , {Tripyln, I'rinnrlnihis) , Dorylainioidea. Trichuroi
rhrcMiiadoroidi-a (KUimoluimus. ilifrnlaiiiniii) , Kno- den und Dioildphyiiiatoidca. OiiEinal.

88

Fm. 93

ApamermiM dpcoudntn. A — Prepnraj>itif larva. (Note pritiiury esopli- host. (Note dcvflopnu-nt of sticlnuytfs.) After Chri'^tie. 1936. J.
ageal glands, subd. oe. gl., subv. oe. gl.) , B — Larva after 4 days in Agric. Res., v r)2 (3 ) .

89

D-bu,ha. .e.i„„ at ,evH of dor.., .,.n,. oH«ce, ^i?:i;iv4w;";;;?;: ih;^,^^::!;:^^;^!^-":^ '^^r'nT^!^!^,;o,^^!f';^^:i

90

Kliinchiliir pi(itiiiil;isiii of tlio siilivoiitiiil scctins seems tii lu'
('(iiitimioiis iiiicl ciiii' (•(iiicluiies tliat in tliis ciise tlie suliventi:il
nWiiuis ;irc liiiuu-le:ite ; the ducts freiii nil three kI"!"!*' exteiiil
anteiiorl.v into the teeth of tlie stoma wlieie eaeh (ipeiis in a
niinnte imre. Kaiither (1!MI7) reeonleil four esophageal n'-i'i'l^
in the siiliventral seetors of Onrlidlaimiix viih/aris. He foiiml
separate pores for the liimlmost pair sitnateil somewhat an
terior to the nerve riiiR ami ilorsal to the center of their re-
spective seetors.

Kiiri/sliimina oiiiciirdiifi lias a ver.v similar esophagus to
Mtiiiiichiildiiniis but its narrow part (corpus) has distinet cu-
tieular attachment points anil the musculature is concentered
in the corpus ( Kig. !>4T) Imt not in the liulliar region; Ull
radial nuclei are i)resent, there heing 1>< in tlu' corpus as in
Ml l(inc}i<il<iiiiiiix. liut there are 12 in the glandular (liulhar)
region arranged in two sets of six as in TiipjiUi anil Primi-
rhiiliix. The esophageal glands extend the entire length of the
esophagus as in oncholaims but only tliree gigantic gland
nuclei (Fig. !14U) have been observed, the right subventral
being much the largest. Onl.v eight luielei have been seen in
the esojihago intestinal valve, the anterior part of wliieh is
triradiate while the posterior part is dorsoventnill.v flattened.

Knnjihi.s' romniiini.i has a cylindrical esoph.agus more like that
of oncholaims than Eiirjixtiniiiiia but .3.'? r.adial nuclei are prcs
ent, the corpus containing the full number of l!4 nuclei as in
Tii/ijihi. while the bulbar region (glandular part) contains
only nine as in Mi Idiichnhiimiis, the last group of three indi-
cating again a ease of suiiiuessed cleavage (Fig. O.T.Ai-.X.A ).
'I'here are three large subequal esophageal gland nuclei in the
bulbar region and the corresponding glands eaeh has an ori-
fice at the anterior end of the esophagus, at the base of the
teeth. The short, well developed, triradiate esophago-intestinal
valve of Eiiopliis contains ll-l.l nuclei (number questionable).
Rauther (1007) obtained the same total as the writer's (i.e.,
IIHI nuclei which includes nerve cell nuclei and esophago-in-
testinal valve nuclei) but he differs in some eases as to the
functions he attributes to specific ones. He also describes two
lateral glands (the nuclei of which we designate xi_-j in Fig.
;•(! & !).")S ) near the mid region of the esophagus which open an-
teriorly near the level of the amphids in the marginal region.
We agree that these proliably are esophageal glands but were
unable to distinguish their orifices.

The esophagus of Phanodennopsis Innfjiselae is interesting
because it is representative of forms with a crenate glandular
esophagus which is commonly termed "cellular." The illu-
sion of cells (Fig. 91) is created through the localization of
extremely sparse musculature at intervals, separating swollen
regions of nearly exclusive glandular tissue. Though the
esophagus is conoid and crenate the nuclear distribution is
similar to that found in Eiinplii.i with the following e.xceptions:
There are ,3(1 radial nuclei, tlie most posterior group being sub-
divided into two .sets of three nuclei; the two chief suliventral
gland nuclei are much enlarged as are the glands, while the
dorsal gland nucleus is situated far forward and much reduced
in size, and the small subsidiarj- (lateral glands of Rauther)
subventral gland nuclei are situated near the dorsal gland
nucleus (Fig. E14FF). The chief subventral glands (Fig.
94GG) empty into the stoma while the dorsal and subsidiary
glands appear to have their orifices posterior to the nerve ring.

Leptnsomatiim eJongaliim, representative of still another
t.vpe, has multinucleate subventral esophageal glands. The
conoid esophagus is of smooth contour, somewhat vesiculate
internally. The anterior part (corpus) contains the same
nuclei found in PJiaiioihrinopsis while the posterior jiart con-
tains such a large number of nuclei (about -.3 in each chief
subventral gland) that it would be difficult to designate the
types accurately. The dorsal gland is uninucleate, the nucleus
(Fig. 94X) much larger than other nuclei of the esophagus:
the subventral gland orifices are at the anterior end of the
esophagus while the dorsal gland orifice is somewhat further

(M-X — Corpus: 0-P — bulbar region: Q — e.sopJuigo-intestiii.il valve:
K — longitudinal sagittal through regions shown in <)-Q dorsal to
reader's right). S-U — EuriiHtominn americana (S — anterior part of
corpus: T — posterior part of corpus; TT — glandular region). V — .I71/1-
rnma litnris. Near anterior end of esophagus, subventral gland orifice
and suttdorsal (dorsolateral) ducts. \V-X — Lepto/foriui/nw rlonuatuin
V. acephfdatitiii. (AV — Region of ocelli. ~t ducts also visible: X — glandu-
lar region). V-DD — CrupfonrhuH nudua, (Y — posterior end of glandu-
lar region; I>D — corpus). Z-('(" — Ironti/t ipnfivJtH (Z-head; AA — dor-
sal gland orifice; (stomatal region); BB — beginning of corpus or
end of stoniatal region: CC — posterior j)art of glandular region (corpus
proper is like fig. I>r>). EE-OG — Phaiioilfrinopxijt loniiiKfUir. (Ep] —
Posterior part of corpus; FF — anterior part of glandular region;

GG posterior jiart of glandular region). HH-II — Dorpldii.iujt nbtiisi-

caudata. (IIII — (.'orpus at level of stylet cell: II — glandular region at
level of dorsal gland nucleus). .T.T-KK — Tn'phnwhiutH sp. f Glandular
region sliowing five esophageal gland nuclei,)

posterior. In the corpus the musculature is concentered (Fig.
94\V) and the esopli;ige:il lining thick but without attachment
points. According to .lagerskiidd (1901), Turk (1903) and
Rauther (1907) the esopluigi of the related genera Thoracas
loma and ('i/lirdldimiia (which ;ire grossly cylindrical) have
similar esophagi except Unit the esophageal lining has defi
nite cuticular attachment points. Rauther was able to dis-
tinguish small subsidiary subventral (lateral) glands as in
Kniipliis. Other enoplids, such as Anlinima (Fig. 94V) and
Iili(ib(l(i(l( mania, with cylindrical esoiihagi have gland orifices
in similar positions to tho.se jibove described, with a simple
i.e., enoploiil esojdiageal lining.

In tlie wliole order Knoplida jiigment spots or ocelli occur
only in the superfamily l']noidoide;i, families Knoi)lidae and
Oncholjiimidae, and are of s]ior;idic ;ippearance in these groujis.
In the Onchiihiimimie such |iigment is rather diffuse in the
musculature of the corjms while in Etiiipliix it is concentrated
in ;i pair of subdorsal spots in the m;irgin:il ;ireas near the
anterior end. Well developed "ocelli" li:ive been described
in l>eptosiimatids, phanodermatids and enchelidiids.

I'inally we come to the f:imily Ironidae which in many ways
:ipi)ears to have closer affinities with the Mononchidae and
Dorylaimidae than with other enoploids. Ironitx (Fig. 94Z-CC)
and IrnncUa liave cylindrical esophagi with well developed
cuticular attachment points, concentered radial muscles, and
." subequal esojihageal glands. TJke Enoplux, nnchnlaimnx,
and Tripi/la. three of the glands have orifices into the stomatal
region. I'ri/pt (inch 11.1 niiihi.s; though otherwise very similar to
Irnviis, h:is its esophageal glands confined to the posterior part
of the esojihagus (Fig. 941)1) & V). Tt seems, therefore, to be
intermediate between such forms as Prioncliiiliis and Irnniis.

t)ORVi,.\rMiNA. — This suborder is jierhajis more couii)act
in fundamental esophageal organization than the suborder
Enoplina though the gro.ss morjihology is certainly more di-
verse and includes more odd types (Fig. 91). Dorylaimins
have one point in common with each other and with the family
Mononchidae, namely that none of the esophageal glands ex-
tend to the stomat,al region. The suborder contains superfami-
lies with esophagi of two types, one in which the glandular
region is tremendously elongated, the subventral glands re-
duplicated and ])rotruding from the esophageal contour, and
the other in which the glandular region is either short or only
moderately elongated, and in which only two pairs of subven-
tral glands are present. This latter group includes the soil
and aquatic species of the superfamily Doryiaimoidea while
the former group includes the parasitic nemas of the super-
families Mermitlioidea and Trichuroidea.

Dorylaimoids have a cylindrical corpus followed by eitlier
an elongated cylindrical glandular region (Dorylaimidae) or a
short P3'riform glandular region (Diphtherophoridae, Lep-
tonchidae) the parts sometimes separated in the latter instance
by a more or less distinct isthmus; the esophageal lumen is
subtriangular anteriorly, rapidly becoming minute and tri-
radiate with marked cuticular thickenings of the esophageal
lining (Fig. 94HH); the musculature is strongly concentered.
The radial musculature is well developed throughout the
esophagus in leptonchids and dorylaimids but r;itlier degen-
erate in the glandular region of diphtherophorids.

Donjiaimiis i)btii.tiraii)hitiix has an esophagus extremely simi-
lar to that found in Pii<i))cliiiliiii for the anterior part (corpus)
contains four sets of six radial nuclei (three sets in the nar-
row part, one at the junction of the anterior and posterior
parts) and only one set of three marginals (Fig. 90) ; the
posterior glandular (bulbar) region contains two sets of six
radial and two sets of three marginal nuclei, the hindmost
set of radi.'ils being somewhat subdivided but arranged in a
manner indic;iting they act as a unit. Each of the five esopha-
geal glands has its orifice near the level of the nucleus with a
very short duet. The dor.sal gland bifurcates, each branch
continuing to divide dichotcunously and the branches enter the
subventr;il seetors, eventu;illy coming to fill the entire non-
muscuhir part of the esophagus ;interior to the subventral
glands (Fig. 94II). These latter are found in two pairs
considerably jiosterior to the dorsal gland; the first subventral
gland on the right .side is considerabl.v smaller than the others.
The esophago-intestinal valve of dorvlainiids is very well de-
veloped, elongate, dorsoventrally tlatteued, :ind contains 27
nuclei.

There is in addition to the usual number of nuclei of the
esophagus a large nucleus in the left subventral sector which,
with its surrounding protophism, acts as ;i generative nucleus
of the stylet (Fig. 941111). .\s previously st;iteil the stylet is
formed in the procorpus and moves .-interiorly to take its final
position ;itt;iched to the anterior end of the esophageal lining.

LrplnnrJiHs has an esnph:igus apparentl\' identical internall.v

i»l

with that of dorylaiiiiids hut only three large esophageal glands
have been observed ; iiresumably both of the first pair of
subventral glands in this instance are small. Triploncliium
of the Diphtherophoridae has very feebly developed, if any,
thickened cutieular attachment points of the esophageal lining,
and the dorsal and first pair of subventral gland nuclei (sit-
uated at the same level) is only slightly smaller than the
posterior subventral pair (Pig. 94 JJKK).

The esophagi of the mermithoids have been studied by Eau-
ther (1906), Hagmeier (1912), G. W. Mijller (19.31), Christie
(1936) and the writers (1935, 1937) as ivell as many others
who have added scattered bits of information. The peculiarity
of the mermithoid esophagus is its relatively great length and
tenuousness. In the adult stage, which does not feed, the
greater part of the esophagus posterior to the nerve ring ap-
pears as a slender tube covered with a bit of ])rotoplasm to
which various types of cells are attached at intervals. The
esophageal musculature appears to be entirel.v degenerate.
One must turn to the larval stages of mermithids for an un-
derstanding of these structures.

The preparasitic larva has an esophagus consisting of a
short anterior part terminated by a muscular swelling and
followed by an elongate narrow posterior part with which
glands are associated. There are three unicellular elon-
gate esophageal glands extending posteriorly into the body
cavity from the base of the anterior (non-glandular) portion,
the dorsal being considerably larger than the subventrals;
these primary glanclst (Fig. 93) become atrophied after the
entrance of the larva into its host. In addition there is a
double series of large cells (stichocytes) attached to and co-
extensive with the posterior part of the esophagus. These
cell.s are secondary esophageal glands, probably representing a
reduplication of the posterior pair of subventral esophageal
glands of dorylaims and enoplids. In the parasitic stage these
glands become much enlarged (Fig. 93) and later they too
atrophy as the larva approaches adulthood. The lining of the
esophagus of mermithids is rather clearly triradiate in the
preparasitic larva, becoming subtriangular in later stages un-
til finally the basic triradiate character is scarcely discernible
(Fig. 96A-E). In Aflamcrmis decatulata 48 large nuclei cor-
responding to the marginals and radials are present, most
of them arranged with little indication of pattern, and there
is even less indication of muscular fibers in the parasitic lar-
vae (Fig. 96). There arc 27 such nuclei anterior to the ori-
fices of the primary glands indicating that this region corre-
sponds to the corju'.s while there are 21 in the posterior part,
indicating that it corresponds approximately to the bulbar
region. These nuclei are situated within the wall of the
esophagus proper. Each of the glands of both types has an
orifice not distant from its nucleus. There is one peculiarity
of the esophagus which does not seem reconciled with the tre-
mendous esophageal gland development in the parasitic stage,
namelj', that the lining disappears posterior to the orifice of
the last stichocyte and the lumen does not connect with the
degenerate intestine. The stichocytes are fpiite obviously
functional and it is difficult to believe that fluid food is not
drawn in through tlie esophagus but if so, we do not know
its destination. The number of stichocytes varies from four
to 16 or possibly more, according to the particular form.

The peculiar esophagus of trichuroids has long been a sub-
,iect for study. Eberth (1860, 1863), Leuckart (1S66), Eau-
ther (1918), G. W. Miiller (1929), Christenson (193.5) and
the writers (1929, 193.'>, 1937) have investigated various forms
of this group. Ward (1917) proposed a separate suborder
for trichuroids and mermithoids (Trichosyringata) based on
the peculiarity of the esophagus. The esophagi of mermithoids
and trichuroids are similar but not fundamentally different
from other nematodes. Ward stated "A type of radically
different character is the cai)ill:iry esophagus ... It consists
of a row of cells, pierced throughout its entire length by a
delicate tube." The cells of which he speaks are stichocytes
or esophageal glands attached to but not "pierced by" the
esophagus proper which is to a greater or lesser degree em-
bedded in these cells. As in mermithids, the wall of the
esophagus contains its own nuclei. Much discussion has cen-
tered around the significance ;ind nature of the structures, but
since the points now are clear, further discus.sion seems un
necessary.

The anterior part of the esophagus of Trirhiiris iivis is nar-
row and muscular, terminated by an elong.-ited swelling; the
lumen is trir.-idiate, the lining thick but without attachment
points. Within this region, besides nerve cells, one group of
three marginal nuclei and two groups of six distinct radial
nuclei are present. On this basis one might presume it to be
the iirocorpus but within the terminal swelling a set of three

large nuclei of esophageal glands is present (Fig. 91 & 961).
These glands, whose orifices are posterior to the nerve ring,
doubtless correspond to the primary glands of mermithids.
The posterior part of the esophagus is cjuite narrow and em-
bedded in a single series of large cells (cell body ' 'zellkorper"
of authors). The narrow "tube" or esophagus proper is
triradiate to hexaradiate and has its own wall containing
radial nuclei as well as nerve cells occurring at intervals. Con
trary to general supposition, this wall contains well developed
radial muscle fibers (Fig. 96M). The large cells in which
it is embedded are esophageal glands, each having a separate
orifice reached or formed by a tube through the esophageal
wall. This being the case, there is no fundamental difference
from other nematodes in which the esophageal glands may
come to lie outside the esophageal contour (Contracaeciim,
Aphelencluis, Onchium) . Because of the fact that in larval
trichuroids the stichocytes are more or less alternatel.v paired
and the orifices in the adult tend to alternate it seems reason-
able to assume that the single row stichosome of Trichurix
is a later evolutionary development from a double row of
stichocytes such as is found in mermithoids. This view is sup-
ported by the illustrations of .lanicki and Rosin (1930) of the
esophageal region of Cj/stoopsi.i which shows two rows of
stichocytes. The number of stichocytes seems to be variable
to some extent within a given species of trichuroid.

At the end of the esophagus, unlike mermithoids, we find a
direct connection of the esophagus with the functional intestine
formed by a dorsoventrally flattened esophago-intestinal valve
such as is present in dorylainioids. Two large cells (Fig. 960)
described as glands with direct openings into the esophageal
lumen, by Eberth (1860, 1863), are attached to the esophagus
at its base. Neither Eauther (1918) nor the writers were
able to distinguish any protoplasmic connection of these cells
with the esophageal lining or any tubules in the cytoplasm
of these cells. It now seems possible that these cells are en-
larged mesenterial cells, homologous to the series of smaller
cells supporting and covering the esophagus and stichosome
(p. 45).

DiocTOPHYMATiN.\, — The esophagus of the suborder Diocto-
phymatina has received little attention since the first re-
port of Schneider (1866) that the walls of the cylindrical
esophagus of such forms contain numerous longitudinal
"tubes." No additional information was added until the
subject was recently reopened by the writers (1937). The
esophageal lining is simple, the lumen triradiate and the well
developed musculature dispersed in representatives of this
group. There is no division, either grossly or internally, into
anterior and posterior parts. The three massive esophageal
glands have their orifices at the anterior end of the esophagus
and begin branching dichofomously near the level of the
nerve ring; glandular tissue is thereafter interspersed between
the radial fibers to the base of the esoidiagus. It appears that
there are 36 radial and nine marginal (or possibly 121 nuclei
in the esophagus. The radials are arranged in suligroups of
three, one near the center of each sector. The esophago-in-
testinal valve is triradiate.

The highly remarkable esophageal glands deserve special
note. Each has a short terminal duct lined with cuticle, fol-
lowed by a short, thick walled primiiry tubule which bifurcates
into secondary tubules. In Sobnlipliiime haturini the second-
ary tubules appear to be lined with cilia (Fig. 95FF). Here
and in EustronQi/lides these secondary tubules branch dicho-
fomously, time after time, throughout the length of the esoph-
agus and come to nearly fill the non-muscular part of their
sectors (Fig. 95CC-DD) but do not enter other sectors. The
marginal tubules end blindl.v (Fig. 97C) and their position is
taken by others formed by the branching of the more centrally
located tubules. In Dioctopliipna renale the .same condition
exists with the exception that the secondary tubules of the
dorsal gland do not undergo further branching (Fig. 1I5BB)
and tubules from the subventral glands take ;i marginal jiosi-
tion in the dorsal sector (Fig. 97B). In all cases we find
dense glandular ])rotoi)lasm containing numerous gland nuclei
(Fig. 95CC-DI)) surrounding the tubules. There are literally
hundreds of such nuclei. Whether the subventral glands cor-
respond only to the anterior pair of subventral esophageal
glanils or to both anterior and posterior jiairs of subventral
glands of enoplids is uncertain.

The dioctoiihymatid esophagus resembles the enoplid esopha-
gus in the position <if the orifices of the esophageal glands and
.•ilso resembles to some extent that of the leptosomatids in the
multinucleate condition of the gl;uids. However, the jieculiar
dichotomous branching of the tubules has its only parallel in
the branched dorsal gland of Dorylaimus.

92

Fia. 95

A-AA — EnopUis rniiiminii.i v. uirridinnnlin. (Serial sections with a anterior to CC; EE — level o£ secondary tubules: VV — secondary

few left out! BB — Dinrlniiliiinm rennlr. CC-GG — Sohnliphynie hriluri'ni. tubule enlarged; GO — acidophylic granules in base of subventral gland

(CC — basal region of esophagus, radial nucleus also showing) ; I)I> — tubules. Original.

93

Fk;. 96

A-K — At/aiiiermin deeandnta. (4 mm lon^ i)!irasitic larva.) (A-B —
Anterior end of esophagus containing ])rohleinatic nuclei, smnll, and
first group of radial nuclei, larger; ('--just anterior to nerve ring
including r,,.,:..; J)— at posterior level of jn-iniavy glands showing most
posterior glaru] orifice and one primary gland nucleus, the other gland
stopped anterior to this sei-tion Large cell to the right is the first
stiehoryte; K — mid-stichosomi' region showing esophageal tube, r type
nucleus, two stichocytes and branched tubule). F-Q — Tr'whuris oris.
(F — Section through '.i auteriormnst nuclei 8i.;i: G — section at level
of first marginal group: II--section at level of first radial group; 1^

94

section dorsal priuuiry esophageal gland. J — stichocyte enclosing esoph-
agus at level of radial nucleus; K^tubule orifice and bran<-hing : L —
stichocvte surrounding esojdiagus in wall of which there is a small
nucleus ( i nerve) ; M — ^esophageal wall frcun .stichosome surrounded
region, slained with fuchsin to show musculJiture ; N — Esophageal
■Willi from stichosome surrounded region containing red blood corpuscle
in lumen; O — F,nd of esophagus witli 2 accompanying cells (lower):
1' — Esopliatro-intestinal valve and intestine; Q — I-ongitudinal section
showing relationship of sticliocytes and riuli;il nuiscb^ cells to esoidiagejil
lumen ) . Original,

2. ESOPHAGO-SYMPATHETIC NERVOUS
SYSTEM

The i>H'srnci' nf lU'ivo eolls in tlu' \v:ill nf tlir rs(i|ilKij;us was
first nu'iilidiu'il l)v l,(ioss {ISDIi) .•mil this svstciii was iloscrihcil
lirii'tly ill Aiii\ul<i.\ti>imt diioilinalr li.v tliat writi'r in l!ill."i. Later
(1!M0) (uildschiiiidt stmlicd tin' system in Axcaris liimhrirDidci
followed liy Martini (lUllil in (Kriiiiria iipii, ImmincI: (li'-l,
l!)2-i) in SIroiiiii/his rilentiilii.'i, de Hruyn (1!IH4) in Angiisli
carriim holoph mm, and vaiimis cdiservations l)y the writers
(1933, 1!IH7) refer to freeliviiiK ami jiarasitie forms.

In substance, tliis system consists of tliree loiiKifiiiiina!
nerves, one situated near tlie center of each sector and extend
ing from the base nearly to the anterior end of the esophagus
( Fiff. 97K). These nerves contain in their course a series of
nerve cells and two or three commissures .ioining the lonKi-
tudinal nerves. In most forms we find a conimisure at the
li.ase of the eoriius. another in the anterior ]iart of the Inilbar
region and a third in the jiosterior part of the bulbar region.
Nerve cell nuclei may usually be distinguished from the other
t.vpes of nuclei though the.v vary considerably in size, but in
smaller forms it is often not possible to identify all nuclei
with certaint.v. In such ca.ses one must place reliance purel.v
upon considerations based on comparative anatomy. In the
ma.jority of instances no attempt has been made to trace the
nerve fibers but the nerve cell pattern has been recorded and
found to be of considerable value from the standpoint of
comparative histology. In ver.v large nematodes the nerve
cells of the esophagus are often disproportionately small and
may easil.v be overlooked. This seems a probable reason for
the small number of such cells reported to occur in ascarids
and spiruroids. In forms with multinucleate esophageal
glands the nerve cells may be easily confused with gland
nuclei. Of course, it is also possible that in such forms
(always devoid of a valved bulb") there is no need for the
complicated esophago-synipathetic system of smaller forms.

In Spironoura affine (i"'ig. 07A) there are seven cells in
each nerve anterior to the nerve ring (Fig. 97P) ; two of these
are glia cells (ni..,, nm-i'i), the remainder nerve cells (n,.i«').
The nerve fibers give off lateral branches (Fig 97P) into the
radial muscle regions. No further nerve cells are present in
the proeorpus. The metacorpus contains three large nerve cells
in the dorsal nerve (n2<, a., .ni) and five nerve cells in each
subventral nerve (n22-M. -.-.n, -.a--.,,). At the base of the
metacorpus we find a well develojied commissure between nn.-.u
and 11:12-31. The bulbar region (Fig. S)7Q) contains nine cells
attributable to the nervous system of which at least two
(041-42) and possibly a third (nri«) are probably glia cells.
There are two commissures in the bulbar region, an anterior
and a posterior (Fig. 97A). The connection of the esophago-
sympathetic with the central nervous system has not been ob-
served for Spironoura. However, we presume it to be similar
to that of Ascaris in which a process of each of the subventral
nerves passes through the external wall of the esophagus near
the level of the dorsal gland orifice (Fig. 97R). This process
continues posteriorly on the outside of the esophagus connect-
ing with a bipolar cell and through this cell with the nerve
ring.

Goldschmidt recorded only 17 cells in this .system in Ascaris
Iiimbricoidc.i in which Hsii recorded 18 cells; de Bruyn re-
corded 27 in Anffusticariim Imloptcrum and Martini 20 in
Oxyurin rqui. All of these writers mention cells of dubious or
unknown significance in the esophagus, particularly in the pro-
corpus. Our own observations on Ascaris Jiimbricoides indi-
cate that a set of si.x cells near the level of the dorsal gland
orifice are homologous to nj-o of Spironoura.

The peculiar distribution of nerve cells in representatives
of the suborder Enoplina is worth.v of particular note since it
is very probably indicative of relationship. As ma.v be seen
from the diagrams (Fig. 90) niii-211 and n.a-.n are usuall.v
marginal in position in the subventral sectors as are nai-.n in
the dorsal sector. Together with n2t. and Um the h.tter nuclei
form a quadrangle in forms such as Tripi/la pnpiVata, Dorif-
laimus ohtjisicnudntns and MrioiychoJaimus prist innis.

3. FINER STRUCTURE OF THE
ESOPHAGUS

Fiber.';. — ronsiderable discussion has taken place as to
whether or not the marginal fibers are contractile. Haniann
(189.".), Rauther (1907), Allgen (1921), Plenk (1924, 1925,
1926) and Looss (190.1) maintained that the marginals are
contractile, while Looss (1890), Schneider (1902), Gold-
schmidt (1904) and Martini (191(i, 1922) hold that they are
supporting or skeletal structures and observations of the writ-

ers support this view. In the inargin.il region of .Isruris
one finds two types of fibers, a first type, extending from the
esojihageal lining to the esophage:il covering, ;i .second type
extending limgitiKlinally in two more or less distinct rows, one
on each side of the esoidi;ige.il margin. This second type, the
"fiber plates" of Goldsohiiii<it (1904), is known only in
ascarids.

The radial fibers extend more or less perpendicularly from
the esoiihagcal lining to the extern.'il covering of the esopha-
gus but often run rather obliipiely so that their contraction
might easily shorten the esophagus to a moderate extent.
K. <'. Schneider (1902) characterized the radial fibers as
striated muscle. This view was supporteii by Martini (191fi)
though other .■luthors including (ioldschinidt (1904) disagree,
stating that the appearance of striation is due to a minute
.system of su|iporting fibrils. Convincing evidence of striation
of the muscle is not yet established. It is therefore con-
cluded th;it if such is jiresent, it must be of a rather peculiar
character hardly comiiaiable to striated muscle in other or-
ganisms.

Finally the "fenestrated membr;ine" described by Gold-
schmidt (1904), Kulmatycki (1918, 1922) and de' Bruyn
(1934) in ascarids shall be discu.s.sed. This is a longitudinal
membrane between the external and the internal coverings of
the esophagus beginning at some distance from the head, end-
ing near the ba.se of the esoidiagus. The writers find no indi-
cation of such a structure. However, Kulmatycki (1922)
states that it is actually double and in places can be seen to
be a distinct tube. He illustrates that which is obviously an
esophageal gland tubule. Since the gl;ind branches coincide
with the location of the "fenestrated membrane," and since
we can find no other structure fitting the description, the
whole probably is a misinterpretation.

Ducts .\nd Tubules. — The internal structure of the
esophageal glands has been very little studied and a generali-
zation from the meager information available would be pre-
sumptuous. In the past the glands have been considered as
rather simple structures, most investigators regarding the ducts
as in direct continuity with the gland protoplasm. Actually,
this is never the case. The esophageal gland ducts are con-
tinuous with tubules of various types. When the gland orifice
is some distance from the actual beginning of the gland sub-
stance, there is a long unbranched central duct. This duct
ma.v continue after reaching the glandular region and give
off lateral paired side branches, "pinnate branching." The
terminations of the branches may be "tubular'' or "alveolar
(acinus)."

Hsii (1933) speaks of "simple tubular" glands in Philo-
vietra and Draciiiu'iilus hoiidcmrri stating that other nematodes
have "branched tubular" glands. It is very easy to fall into
error regarding such structures, particularly when the glands
terminate in acini or branched acini. This is, in fact, the
case in regard to the glands of BracuncuJtis dahomrnsis, the
subventral ones being compound branched alveolar glands,
while the dorsal is apparentl.v of the simple branched alveidar
type.

In forms such as Ascaris hnnhricoidcs the dorsal gland is
simple (piiinately branched); the suhventrals are coniiiimnd
(palmatel.v branched) and tubular. In Phi/.tahiplrra majillaris
all three glands are simple (pinnately branched) and appar-
ently tubular (Fig. 98H). However, one has difficulty in
tracing the secondary and tertiary tubules; the.v might easily
terminate in acini. The compound form of the dichotomously
branching tubular glands of dioctoph.vmoids is obvious, as are
the simple branched tubular glands of Trichiiris ovi.i and
Agamcriiiis dccaiidata (Fig. 96).

Alveolar glands are particularl.v difficult to stud.v. Preser-
vation of the tubules in satisfactory condition for stud.v is
actually a rarit.v and for answer to many of the problems one
must look to living specimens. Quite often the lobulations
of the gland protoplasm itself are mistaken for the tubules.
Such lobulation is dependent upon muscle distribution and may
have no bearing on the tubular system (the stichocytes of
Trichiiris oris and Agamcrniis dccaiidala have branched tubules
though the glands are not highly lobulated).

"('llKOMlDl-\."- Working with Ascaris liimhricnidcs Gold-
schmidt (1904) described bodies in the plasma of the muscles
associated with the radial nuclei. The.v stained intensely with
hematoxylin and he termed them chromidi;i. These bodies he
cimceived to be "vegetative" nuclei originating from the
radial nuclei. Vejdovsky (1907) and Bilek (1909) considered
them artefacts but Hirschler (1910, 1912) demonstrated their
existence in the living cell. Neither Hirschler, v(m Kemnitz
(1912) nor Kulmatycki (1922) found any evidence that they
originated from the nucleus. These bodies are found only in

95

Km

A — Kecoiistructioii of esophagus of Siiiroiiiniia show-
ing nuclei, glands and esoiih.-jgo-s.vmpathetic. (Dnrsa
to reader's right.) B — Dioclophiima renale, esophageal
gland tubule branching. C—Soholiphyme balurini, esoph-
ageal gland tubule. I) — AKi-nris lumbricoiden , dorsal
esophageal gland tubule. E-F — Rhabditoid bulb, (E—
at rest; F — contracted). G-M — Ascaridid esophagi and
intestines. (G — Anndicaecum: H — iTiffM.vdcnfCHm ; 1 —
Dujardinin huUcornin ; J — Dujiirdiniti heUcina; K — Con-
tracaecum; L — Pnrrocaeciiw : M — AiiUakis) ■ N — Dia-
gram of esophageal symmetry, (d. dorsal area; dli dorso-
lateral area of dorsal sector; dl;, dorsolateral area of sub-
ventral sector; dl dorsolateral (i. e., subdorsal) esoph-

ageal radius: sd subdorsal area, -
subvential area; vl ventrolateral area; vr ventral esoph-
ageal radius). O— Cri/iirw <■'/"'. (Fourth stage larva).
|..Q_A'pire,u.u,™ (tffiof. esophago-syiiipathetic nervous
system. ( I>— Diagrannin.lic connection of cells dorsa
view compare with A.; Q— Detail of right subventral
nerve trunk, lateral view). R— /tscnnV lumbrxcmdes
(Esophago-sympathetic nervous systeui, diagrammatic dor-
sal view, d" & N after Chitw. & Hill,
forsch, V. 14 (4). G-M, after Baylis.
12 (3); O, after Ihle & Oordt, 1921.
Akad Wetensch. Amsterdam.

19;12, Ztschr. Zell-
1 920 Parasit., v.
I'roc. Sec. Sc. K.

90

i'la. •)«

B-r— ;r1p™,"*,''''"''7"''''r- ,<-^-At level of subventr;.! gU,nd nrifice-

esophageal appendix^ef"^ ^J i est nal "a7c um' h;;,',''''' "'" <»""«-'.">^

t.ssue cell). E.P-0,,,,;,,„,,„;" r,y;X/'X^ Ve- ;,,?,';h '■"""'"'"« Bland nuclei, and

leve, o, fi,., ,.„„„ ,„ ,„Hia, nu-lei; F'l':^rnd!.t. 'i'e^r a^K l\ S.Vnf ^!^'T"- ^^ ' ' ' '

lar reeion. note I "ad a nnHo,, ;''';''''''''T'' '""■'■'""'•"—( <iland«-

Sland nuclei, and due' ,n,„"h .^ " A c * 'r'" r^'V".', ■"■'"'/■ "''"-'•»•■••'

l>, after Hamann. 189.5, Die Neinatllel-

U7

the large ascaiids and are most numerous in tlie vicinity of
the radial nuclei, but they may also occur in the marginal
areas or at considerable distance from the nuclei. They vary
in number and appearance. When few are present they tend
to take the form of coiled fibers, and when many are present
the form of thick flecks; both forms may be seen in a single
chromidium. Kulmatycki (1922) found such structures as well
as a golgi body in cells of the spicule sheath, thereby eliminat-
ing the possibility that the ehromidia are homologues of
the golgi body ; he named them ascaridochondria, relating
them to mitochondria, chondrosomes, etc. ' ' C'hromidia ' ' occur
in marginal areas of Anonchus mirabilis (Fig. 84 D-F), even
more spectacularly than in Ascaris. Their significance, today,
is unknown.

Ocelli and Pigment Spots. — The occurrence of pigment
masses in the Aphasmidia has been mentioned. That such
structures exist, has been known since the time of Bastian.
Because of their general appearance they have been widely ac-
cepted as photoreceptors despite a total absence of evidence
that they are connected with the nervous system. Brownish to
red granules may be rather irregularly and generally dis-
tributed in the esophageal tissue of such forms as oneholaims.
Similar pigmented granules may be slightly more concentrated
in the subdorsal marginal areas of forms such as Enoplus and
Chromadora. In these forms there is a definite pair of "pig-
ment spots" but the pigment also extends posteriorly from
the spots and may be present to a considerable extent in the
.subventral marginal regions of the esophagus. Rauther (1907)
regarded the pigment granules of Enophis and Oncliolaimus
as excretory granules and thought they were eliminated through
the esophageal glands. We find no evidence of the "refractive
granules" in the ducts of the esophageal glands and see no
reason to assume they are excretion products. Schulz (1931b)
upon finding the spots to be within the esophagus in Enoplus
reaffirmed Rauther 's interpretation and differentiated such
bodies from true ocelli (with lenses) which he observed in
Leptosomatum, Thoracostoma and Pnrnsi/mplocostoma. In the
latter type he described the lens as an invagination of the
superficial cuticle of the bod.v surrounded by pigment and con-
nected with a special ocellus cell. He states that he does not
believe the true ocellus is connected in any way with the
esophagus. On the contrary, the writers have found the ocelli
of Lcptosomafiim clongatum to be completely enclosed within
the wall of the esophagus ; the lens seems to be formed from
the external covering of the esophagus and no special cell is
associated with the ocellus. We must conclude that even in
this instance the ocellus is a part of the esophagus. If it is
innervated, as one would presume, then the esophago-sympa-
thetie nervous system must include also, the "optic nerve."
In the Desmoscolecoidea, there is definite evidence that the
pigment bodies are outside the esophagus; in this group the
posterior part of the esophagus is degenerate and the esopha-
geal glands outside the general contour. In Monliystera
paluilicnla true ocelli are present; these are likewise situated
outside the esophagus.

There remains one additional case of pigmentation in the
cephalic region associated with photoperception. In the gravid
female of MermiK svbnigrescens Cobb (1926, 1929) described
diffuse reddish pigment anterior to the nerve ring. Such
pigment is absent from the head of young females and males,
only being found in specimens ready to deposit eggs. Though
the exact location of the pigment was not determined, the
case is interesting since it supplied the only actual evidence
of photoperception in a nematode, for egg laying only takes
place in the light, ceasing in darkness. That heat is not the
stimulus is indicated by the fact that such "egg laying"
females will continue to lay eggs though placed on ice in a
dish of water so long as the light continues.

Bibliography

Allgen, f'AM,. 1921. — Ubcr die Natur und die Bedeutung
der Fasersysteme im Oesophagus einiger Nematoden. Zool.
Anz., V. .•)3(3/4): 76-87, no figs.

Baylis, H. a. 1920. — On the classification of the Asearidae.
I. The .systematic value of certain characters of the ali-
mentary canal. Parasitol., v. 12(3): 2.)4-264, figs. 1-6.

BiLEK, F. 1909. — Ueber die fibrillaren Strukturen in den Mus
kel und Darmzellen der .\scariden. Ztschr. Wiss. Zool.,
v. 93: 62.''>-637, pla. 27-28, figs. 1-20.

Bruvn, W. M. de. 1934. — Beitrjige zur Kenntnis von Aniiiix-
licomim holoptcriim (Rud.) einem Neriiatoden aus Trx-
tuilo qracca L. Diss. Amsterdam. 120 pp., 47 figs., 4 pis.,
8 figs.

Chitwood, B. G. 1930. — The structure of the esophagus in the
Trichuroidea. J. Paraiiit., v. 17: 3.5-42, pis. 5-6.

1931. — A comparative histological study of certain

nematodes. Ztschr. Morph., v. 23(1/2) : 237-284, figs. 1-23.

1935.— The nature of the "Cell body" of Trichuris

and "Stichosome" of Agavtermis. J. Parasit., v. 21(3):

225

1936. — The value of esophageal structures in neniic
classification. J. Parasit., v. 22(6): 528.
Chitwood, B. G., and M. B. 1933. — The histological anatomy
of Ccphalobelliis papilUger Cobb, 1920. Ztschr. Zellforsch.,
V. 19(2): 309-355, figs. 1-34.

1934. — The histology of nemie esophagi. I. The esoph-
agus of Sliabdias eiistreptos (MacCallum, 1921). Ibid.,
V. 22(1): 29-37, figs. 1-4.

1934. — Idem. II. The esophagus of Helerakis gal-
linae. Ibid., v. 22(1): 38-46, figs. 1-4.

1934. — Idem. III. The esophagus of Oesnphagoslo-
mtim dentatum. (Rudolphi). J. Wash. Acad. Sc. v.
24(12): 557-562, figs. 1-3.

1935. — Idem. IV. The esophagus of Metastrongt/IiiD
elongatns. Ibid., v. 25(5): 230-237, figs. 1-4.

1936. — Idem. V. The esophagus of Rliabditis, Angiiih
lulina and Aphelenchiis. Ibid., v. 26(2) : 52-59, figs. 1-6.

1936. — Idem. VI. The esophagus of members of the
Chromadorida. Ibid., v. 26(8): 331-346, figs. 1-10.

1936. — Idem. VII. The esophagus of Leidyneina ap-
pendiculatnm (Leidy, 1850). Ibid., v. 26(10): 414-419,
figs. 1-4.

1937. — Idem. VIII. The esophagi of representatives of
the Enoplida. Ibid. v. 27(12): 517-531, figs. 1-2.
Chitwood, B. G., & Hill, C. H. 1932. — A note on the esopha-
geal glands of Ascaris liinibricoidcs. Ztschr. Zellforsch.,
V. 14(4): 605-615, figs. 1-17.
Christenson, Reed O., 1935. — Studies on the morphology of
the common lungworm, CapiUaria aerophila (Creplin,
1839). Tr. Am. Micr. Soc, v. 54(2): 145-154, figs. 1-3,
pi. 27.
Christie, J. R. 1936. — Life History of Agamermis decaudaia,
a nematode parasite of grasshoppers and other insects. J.
Agric. Res., v. 52(3): 161-198, figs. 1-20.
Cobb, N. A. 1926. — The species of Mermis. J. Parasit., v.
13: 66-72, figs. 1-3, pi. 2, fig. 2.

1929. — The ehromatropism of Mermis subnigrescens,
a nemic parasite of grasshoppers. J. Wash. Acad. Sc,
V. 19(8): 159-166, fig. 1.
Ebeeth, C. J. 1859. — Beitrage zur Anatomie und Physiologic
des Trichocephalus dispar. Ztschr. Wiss. Zool. 10 Band,
2 Heft.

1860. — Bcitriige zur Anatomie und Physiologic des
Trichocephalus dispar. Ztschr. Wiss. Zool. v. 10; 233-258,
pis. 17-18, figs 1-24.

1863. — Untersuchungen iiber Nematoden. Leipzig,
77 pp., 9 pis.
Ehlers, H. 1899. — Zur Kenntnis der Anatomie und Biologie
von Oxyuris ciirvula Arch. Naturg., 65 J., v. 1 (1): 1-26
pis. 1-2, figs. 1-20.
Goldschmidt, E. 1904. — Der Chromidialapparat lebhaft funk-
tionierender Gewebszellen. (Histologische Untersuclmngen
an Nematoden II). Zool. .lahrb. Abt. Anat., v. 21 (1) : 41-
140, figs. A-Q, pl.s. 3-6, figs. 1-62.

1909. — Das Skelett der Muskelzelle von Ascaris etc.

Arch. Zellf., v. 4 (1): 81-119, figs. AC, pis. 6-9, figs. 1-19.

1910. — Das Nervensystem von Ascaris liinibricoidcs

nnd megalocephala. III. Teil. Festschrift R. Hertwig, v. 2:

255-354'^, figs. 1-29, pis. 17-23, figs. 1-125.

IIagmeier, a. 1912. — Beitrage zur Kenntnis der Mermithiden.

Diss. Heidelberg. 92 pp., 4 pis., 55 figs. Also Zool. .Tahrli.,

v. 32 (6): 521-612, figs. a-g. pis. 17-21.

Hamann, O. 1895. — Die Nemathclminthen, v. 2, pp. 1-120, pis.

1-9, Jena.
IIkinp;, P. 1900. — Beitrage zur .Anatomie und Histologic der
Trichocephalen insbesondere des Trichocephalus affinis.
Centrabl. Bakt. I. Abt., v. 28: 779-787, 809-817, pis. 1-2,
figs. 1-13.
HiRscHLER, J. 1910. — Cytologische Untersuclmngen an Ascaris-
zellen. Bull. Internat. Acad. Sc. Cracovie., v. 78: 638-645.
1912. — Uber einige strittige Fragen den .Ascariden
cytologic. Verb. VIII. Internat. Zool. Kongress in Graz:
932-936.
H.'^i', H. F. 1929. — On the esophagus of Ascaris liimhrieoides.
Ztschr. Zellforsch., v. 9 (2) : 313-326, figs. 1-10.

1933. — On Dracuticulus houdemrri n. sp. Vracunculus
globocephalus, and Drnciincuhis medinensis. Ztschr. Para-
sit., V. 6 (1): 101-118, fig.s. 1-38.

1933. — A study of the oesophageal glands of some

98

specii'S iif Spiniiiiiili':i Mini h'il:iriiiiilr:L. ZlsiOir. I'mMsil.,
V. IS (3) : L'77-L'S7, litis. 1 li.

1SI33.— Stiuiy (if the oesopli;iKc;il kI^hhIs nf ii:ir;isitic
Nematoiia, siiiu'ifiimily AsciiiDiilt'a. ('Iiim'sc Moil. .1., v.
47: 1^47-lL'SS, ps. llil. t\gs. 1 ."iH.

1!)33. — Tlie osopliaKoal glands of iwMiatmlos. I.iiik'i'aii
Sc. J., V. 12 (8uppl.^: 13 21.
Bsv, H. F. and Hokitli, R. 1SI33.- Dio Oisnpliattusilnisi'ii
eiiiiT Praltphix sji. und von Tliolazia calliiiacda (Xcniatu
da) Ztschr. I'aiasit., v. (i (3): 273-27{i, (iijs. 13.
Illi.E, I. K. \V. anil t)OKDT, G. .T. VAN. 1!>21.— On the laiv;il
devclojinipnt of Oxjiiiris c(jni (Schrank). I'roc. Sec. Sc. K.
.Vkad. Wetensch. Anistcrdani, v. 23; (;03-(il2, liRS. 1().
I.MMiNCK, B. D. C. M. 1!I21. — BijdraKO tot do konnis va den
boiin van den voonlaini van Schrnstiiiinnn idi iiliit kiii Looss.
Diss. Leiden.

1924. — On the niicroscoiiical anatomy of the diKOstive
system of Slronffi/fnx cihnlatiis IjOoss. .\rcli. Anat., v. 3
(4-(i) : 2S1 32ti, "figs. 1 40.
.I.'\(jekski6ld, L. a. lSil3. — BidraK till KaMniMliniirn oni Noma-
todorna. Diss. Stockholm. 8(1 pji., .") pis., figs. 1-43.

1894. — Beitrage zur Kenntnis dor Nomatodon Zool.
.lalirli. Abt. Anat., v. 7 (3): 449-532, pis. 24-28.

ls!i7. — Ueber den Oesophagus dor Neni.-itoden beson-
dois lii'i Stronflnliix armatiis Rud. nnd Docliniiiis diKidr-
nulls Dubini. I5ihang K. Svonska Votonsk.-Akad. Handl.
Stockholm, v. 23, Afd. 4 (."■), 2t) pj)., 2 figs., 1 pi.. Hgs. 1-6.
1909. — Nomatodon aus .-Vegypton und doni Sudan.
Results Swedish Zool. Exped. to Kgypt and White Nile,
1901. No. 2o: 66 pp., 23 figs., 4 pl-s.
J.\NirKi, C and R.\siN, K. 1930.^Bemerkungen iiber Cystoop-
si.1 acipcnseri des Wolga -Sterlets, sowio iiber die Entwick-
lung dieses Nematuden ini Zwischenwirt. Ztschr. Wiss.
Zool., v. 136 (1): 1-37, figs. 1-26.
Kesin'ITZ, G. voisr. 1912. — Die Morphologie des Stoffwechsels
bei Ascaris ttivibricoides. Arch. Zellf., v. 7: 463-603, figs.
1-9, pis. 34-38.
KrLM.\TTCKl, W. J. 1918. — Einige Bemorkungon iiber den
Ban der Deckmuskclzellon im Oesophagus sowie dessen
Funktion bei Axcuris inctiah/ccpliala. Anat. Anz., v. .51
(1): 18-29, figs. 1-4.

1922. — Benierkungen iiber den Bau einigor zellen von
Ascari.i meffalocrplialn, mit bosonderor Beriicksichtigung
des sogenannten Cliromidialapparates. Arch. Zellforsch.,
V. 16: 473-551, pis. 22-26, figs. 1-36.
Leuckart, K. G. p. R. 1866. — Untersuchungen iiber Tricliiiia
spiralis. 120 pp., 7 figs., 2 pis. Leipzig & Heidelberg.

1876.— Die Menschlichen Parasiten., v. f; 513-882, 119
figs. Leipzig, v. 2: 368-369.
Loos.s, A. 1895. — Stroni/nhis si(btilis n. sp., ein bischer unbe-
kannter Parasit des Jlonschen in Egypt. Centrabl. Bakt.
Abt. I., V. 18 (6) : 161-169, figs. 1-8.

1896. — LTeber den Bau des Oesophagus bei einigen
Ascariden. Centrabl. Bakt. I Abt., v. 19 (1): 5-13.

1901. — The Sclerostomidae of horses and donkeys in
Egypt. Eee. Egypt. Govt. Sch. Med., pp. 25-139, pis. 1-13,
figs. 1-172.

1905. — The anatomy and life history of Agchylostoma
diiodenale. Rec. Egypt. Govt. Schl. Med., v. 3: 1-158, pis.
1-9, figs. 1-100, pi. 10, photos 1-6.
Mackin, J G. 1936. — Studies on the morphology and life
history of nematodes in the genus Spironoura. Univ. 111.
Bull., V. 33 (52), 64 pp., 69 figs.
Macath, T. B. 1919. — Camallanus amerieanus nov. sjioc. Tr.
Amer. Micr. Soc, v. 38 (2) : 49-170, figs. A-Q, pis. 7-16,
figs. 1-134.
Man, J. G. de. 1886. — Anatomische Untersuchungen iiber
freilebende Nordsee-Nematoden. 82 pp., 13 pis. Leipzig.
1889. — Troisieme note sur les nematodes libre de la
nier du nord et de la nianche. Mem. Soc. Zool. France,
V. 2: 182-216, pis. 5-8, figs. l-12e.

1904. — Nematodes libres. Resultats du voyage du S.

Y. Belgica. Exped. Antarct. Belg. Anvers. 55 pp., 11 pis.

Marion, A. 1870. — Nematoides non jiarasites marins. ."Vnn. Sc.

N;it. Paris. Zool., 5. s., v. 13, art. 14, Hill pp., pis. 16-26.
.Marimni, K. 1916. — Die Anatomic der Oj-//Hri.v currH/d. Ztschr.
Wiss. Zool., v. 116: 137 534. figs. 1121, pis. (i-2n.

1922. — Uebor die Fibrillonsystenio im Pharynx dor
Nonuitodon. Zool. Anz., v. 54 (97l0): 193 198, 1 fig.
MlKZA, M. B. 1929. -Bcitrage zur Kenntnis des Baues von
Diiiriinniliis itiKtininsis. Volsch. Ztschr. P;irasit., v. 2 (2):
129156, figs. 1 33.
Mi'l-l.Kit, G. W. 1929.— Die Ernahning einigor Trichuroideen.
Ztschr. Morph., v. 15 (1/2): 192-212, fig.s. 115.

1931.— Ueber Merniithidcn. Ibid., v. 24 (1): 82 147,
fig.s. 1 34.
.MiKM.K.K, .1. F. 1931.— The csojihagi-al glands of Asraris. Zlschr.

Zollfoisch., v. 12 (3): 43(5 4.50, pis. 1-5, figs. 1 21.
Pi.ENK, II. 1924. — Nachweis von Qiicrstroifung in samtlichcn
Muskolfasern von Asraris mrqahin phulii. Ztsclir. Anat. &
Entwickl. 1 Abt., V. 73: 358 388, figs. 1 29.

1925.- Zur Ilistologie der Muskolfasern vim Ascaris
Lumhru-us und Hiriido. Vorh. der Anat. Gos. voni 21-24
April, 1925, 34 Vers, in Wion. Erg. heft zum 60 Bd. An:it.
Anz. (1925-26) : 273-275.

1926. — Boitrage zur Ilistologie dor Muskolfasern von
Ifiriido und J.iimbriciis. ncbst Borichtigungcn zu moinoii
I'ntorsuchiingon iiber don Bau der J.vciiri.f— und Mollusken-
muskolf;isoni. Ztschr. Mikrosc. Anat. Forsch., v. 4: 163-
202, figs. 1-27.
Rai TiiKR, M. 1906. — BeitrJige zur Kenntnis von Mermis albi-
cans V. Sieb. Zool. Jahrb. Abt. Anat., v. 23 (1): 1-76,
pis. 1-3, figs. 1-26.

1907. — Uebor den Bau des Oesophagus nnd die Lo-
kalisation der Nierenfunktion bei freilebenden Nematoden.
Ibid., V. 23 (4) : 703-738, pi. 38, figs. 1-9.

1918. — Mitteilungen zur Nematodonkumle. Zool.
Jahrb., Abt. Anat., v. 40: 441-514, pis. 20 24. figs. 1-40.
Schneider, A. 1866. — Monographie der Nematoden. 357 pp.,

122 figs., 28 pis., 343 figs. Berlin.
Schneider, K. C. 1902. — Lehrbuch der vergleichondon His

tologie der Tiere. 088 pp., 691 figs., .lena.
ScHULZ, E. 1931a. — Betrachtungen iiber Augon froilobcndcr
Nematoden. Zool. Anz., v. 95 (9/10): 241-244, figs. 1-3.
1931b. — Nachtrag zu der Arbeit: Betrachtungon iiber
die Augen freilobender Nematoden. Zool. .\nz., v. 96
(5/6) : 159-160, fig. 1.
Stadelmann, II. 1891. — Ueber den anatoniisclien Bau des
Strmtfii/lus coin-oUit us Ostertag nebst einigen Benierkun-
gen zu seiner Biologie. Diss. 39 pp. Berlin.

1892.— Idem. Arch. Naturg., 58, J., v. 1 (2) : 149-176.
pi. 1-.
Stekhoven, J. H. ScHUURMANS and Botman. P. J. 1932. —
Zur Ernrihrungs-biologie von Proleptus obtiisiis Du.i. und
die von dicsoni Parasiten hervorgerufen reaktivon .\endor-
ungen des Wirtsgewebes. Zeit. f. Parasitenk. (Z. F. W. Z.
Ab. F.). V. 4 (2): 220-239.
Stbassen, O. zur. 1907. — Filaria medinensis und Iciithiianetim.
Verhandl. Deutsch. Zool. Gesellsch. 17 J., 110-129, figs. 1-8.
TOBNQUIST, N. 1931. — Die Nematodenfamilien Cucullanidiie
und Camallanidao — etc. Goteborgs K. Vetensk.-o. Vit-
terhets-Samh. llandl., 5 f., s. B, v. 2 (3), 441 pp., pis. 1-17.
Ti'RK, F. 1903. — Ueber einige im Golfo von Neapel freileben-
den Nematoden. Thesis. Leipzig. 67 pp., pis. 10-11. Also
Mitth. Zool. Stat. Neapel, v. 16 (3): 281-348, pis. 10-11.
Veolia, p. 1916. — The anatomy and life history of the Har-
monchiis contortiis (Rud.). 3rd & 4th Rpt. Vet. Res. Union
S. Af. pp. 349-500, 28 pis., figs. 1-60, charts 1-18.
Vejdovsky, F. 1907. — Neue Untersuchungen iiber die Reifung
und Befruchtung. Konigl. Bohm. Gesellsch. Wiss. Prag.
(Not seen.)
Ward, H. B. 1917. — On the structure and classification of
North American parasitic worms. J. Parasit., v. 4: 1-12.
Yam.\guti, S. 1935. — Studies on the helminth fauna of Japan.
Part 9. Nematodes of fishes, I. Jap. J. Zool., v. 6 (2) :
337-386, figs. 1 65.
Wetzel, R. 1930.— On the biology of the fourth stage larva
of Oxi/iiris rqiii (Schrank). J. Parasit., v. 17 (2): 95-97,
pi. 12.

99

CHAPTER VII
THE INTESTINE OR MESENTERON

A. GENERAL MORPHOLOGY

The intestine of nematodes is a tube the wall of which is
composed of epithelial cells. Its gross morphologj' does not
vary markedly in different groups of nematodes. Usually it
is a simple, more or less straight tube accommodating itself
to the reproductive organs and space in the body cavity.

Subdivisions of Intestine. — The intestine may be divided
into three regions: the anterior part or ventricular region; mid-
region or intestine proper; and the posterior part or prerectal
region. The ventricular and prerectal regions commonly differ
from the mid-region in the height of the cells and shape of
the lumen. Usually, there is also some difference in the type
of cell inclusions present in these regions. When a region is
quite definitely differentiated from the remainder of the intes-
tine it is herein termed either a ventriculus (anterior) or pre-
rectum (posterior) while an adjectival usage is retained when
the differentiation is not marlced.

Appendages. — Two types of cecae or diverticulae occur in
the ventricular region, one directed anteriorly, the other pos-
teriorly. The first t.vpe is by far the more common, occurring
in various degrees of development in memliers of several groups
in the Phasniidia. Only one free-living nematode is known
with such a structure, namely Eliabdilis c.nlinrlrica, and in this
instance the cecum is ver.y small, scarcely a third of the in-
testinal diameter in length. Likewise but one member of the
Strongylina, Grammocephahis (Ancylostoniatidae) has been
described as po.ssessing a short intestinal cecum and but
a few representatives of the order Spirurida (Dacnitis spp. and
Dichelynf spp.) have such structures. The cecae in these forms
are quite small. Development of ventricular cecae is most
common in the Ascaridoidca. sporadicall,v occurring in such
forms as Cimtracaccnm, Avfiusticdrriim and .tiiipUfaiciim (As-
carididae, Anisakinae). In the last mentioned forms the
cecum may be very large (Fig. 97 G-M), extending far beyond
the base of the esophagus, even to the nerve ring. A posterior-
ly directed cecum (Fig. 09D) is known to exist only in females
of the genus Leiili/nema (Thelastomatidae).

No satisfactory explanation of the intestinal cecum develop-
ment in nematodes has yet been made. The sporadic occurrence
of this structure does not seem to be correlated with feeding
habits. Phylogeny throws no light on the subject, for closely
related forms may differ in this respect. Though the cecum is
always a development of the vrnlriciilar region its cells do
not differ cytologically from the remainder of this region,
indicating no functional specialization (Fig. 98D).

TjAyers. — The intestinal wall consists of a single layer of
ej)ithelial cells which usually bear on their internal surface a
bncillary layer (Stabchensaum, liordcur en brousse), and some
times a distinct siibbacillary Inyrr (Deckschicht) is apparent.
The external surface of the cells may be quite naked, or it may
be covered by a distinct basal lameUa. a " musculari? mnco-
sae," and a mesenierml mrmbranr. One or more of these
coverings may be present or the.v all may appear to be absent.

Sometimes the protojilasm of the epitlielial cells is divisible
into distinct zones. The ecto])lasmie zone is a la.ver of dense
cytoplasm bordering the sides of the cell: when definitely
thickened on the side of the cell facing the lumen it is called
a plasma cap (Fig. 10.3.T3, Z.S"). The remainder of the cell is
termed the endoplasm ; it contains the nucleus, cell inclusions
and sometimes other structures such as plasma strings (Fig.
in.'i.lri), basioplasm (Fig. Kl.'i.Ki), basal fibrillae, etc.

Thr BaciUary and Siibbarilhtry I.ayrrx. — The baeillary layer
consists of an internal border apjiearing to be made up of
fine rods or "cilia" bene;ith which one often finds a sub-
l)acillary layer (Deckschicht) which stains with iron-hematoxy-
lin. The first layer varies markedly in ai)pearance, the bacilli
sometimes l)eing rather large and well sejjarated, sometimes
compact, sometimes fine and hair like. Tender ordinary circum-
stances the baeillary layer has a compact .appearance but the
cleuients h;ivc been seen (piite discretely in living si)eciniens of
Khabililif: slrongyloiiles. In general, the baeillary and sub-
bacillary layers are most highly develojied (thickest) in repre-
sentatives of the Strongylina (Fig. 10i!K) and impart a char-
acteristic appearance which one is not likely to confuse with

that of other nematode groups. S )metinies due to fixation the
b.'icillary layer may have pulled away from the epithelium,
giving the ajipearance of a ])erilrophic membrane. Like the
liacillary la.ver of other organisms it is digested by proteolytic
enzymes and is therefore non-chitinous. (The peritrophic
membrane of arthropods is chitin).

Somewhat extended discussions of the significance of the
baeillary layer have been given in the past. Since this layer
is not i)eculiar to the Nematoda, but occurs in the intestine of
various groups of worms as well as in arthropods and verte-
brates, conclusions based on the study of nematodes alone
could scarcely be considered valid. The several viewpoints
expressed have been as follows: (1) The bacillar.v layer is a
development of minute tubes which aid in resorption or ex-

A-C — Third stage larval strongyles showing oligocyty. ( .\ — Gyalo-
repfialiis capUutun ; B — Cylicoeercus gohli; C — Cylicoceycus ctttiiuUus) .
1> — hfidiiiiema appendicutatiim (Adult feTiiale showing cecum). A-C,
after I.ucker, IHIifi, Pror. Helm. .Snr. W.Tsh . v. 3(1). 1), after Chit-
wood, l!t:i2, /tsi-hr. I'araBitenk., v. .t(1).

I no

Klc-.. 100

Intestinal cell inclusions, A — Ifhiihditis slrnnffi/lititlfs (Living intestinal cell, surfaci
view : large radially striated rhabditin spliaerncrystals and small, snluble granules). B — Thfri/i
tuK «f/o.v?i* (Area of intestinal cell showing nucleus (not shaded], rhabditin sphaerocrystals
and olivaceous sphaeroids [small, sliaded|)_ C — Diti/leufhus dipffaci (Cell to left with foui
shaded nuclei, numerous colorless fat droplets and small black (actually purple] protein globule;
[stain, crystal violet]). D — Diploscupler cnrnnafn (fat globules black, olivaceous spliaeroid
shaded, nucleus colorless, crystals colorless.

cuoles I osniic ] )

black, olivaceous spliac
Original.

Rlitibditts monhystera.
1914, J. Parasit. v. 1(1).

Flii. 101
Rhabditin sphaerocrystals

seen in polarized light. .\fte

erction; (2) it is itsi-lf a secretion iirodiu-t of jiroteetive na-
ture; (3) it is a layer of amalRaiiiat<'(l or degenerate cilia.
The second possibility seems least iirohable in the light of com-
parison by which one finds tlie layer very well developed in
forms ivhich hold to a liquid or semiliquiil diet (Ehahditis,
Trichiirif:) and is absent in some forms with a "solid" diet
(MelonchiiJdimiis). Quack (U>]:-li, following Biitseliii's alveo-
lar theory of protoplasm, held the bacilli of the bacillary and
suhtiacillary layers to be rows of vacuoles and not actual en-
tities, wliile Hetlierington (UtL>3) held the bacillary layer to
be cilia and the subbacillary la.^er basal granules. Upon the
basis of appearance and comparative morphology one must
conclude that Hetlierington 's view is the more probable. The
function is a problem for general zoology rather than nema-
tology.

Prntoplasmic zones. — The presence of protoplasmic zones,
likewi.se, seems to be of no special significance in nematology
since differentiation into ectoplasm and eiidoplasin iL of wide-
spread occurrence in cells of living anim;ils. Certain authors,
such as K. (\ Schneider (1902), have seen fit to call the plasma
cap of Ascaris a "nutritorische zone." Quack has shown that
in Ascaris such material is not confined to the periphery but
extends into deeper parts of the cell as irregular masses
(plasma strands) in Ascaris and may l)e so distributed as to
form a mantel (Quack's fig. '21). fioldschmidt (1904) in-
terpreted the strands as a "Chromidiala|)parat " but Ilirschler
(1910), von Kemnitz (1912), and Quack (MILS) all have found
this to be an error. Quack found tliat starved specimens of
Ascaris showed no diminution in the plasma ca|) or plasma
strands and hence eliminated the iiossibility that the material
involved is absorbed albumen, concluding that it is differentiat-
ed functional cytoplasm (Compare Figs. 103.I-M).

External coverings. — In large inyriocytons (see p. lO.'O nema-
todes one often finds a homogeneous, slightly basophilic layer
in immediate contact with the external cell surface, this layer
being termed the ha.ml lamella (Fig. 10.3.T7, ZC). Apparently
this layer is a differentiation acting as a suppcirting structure
or it is a secretion product of the intestinal epithelium. It is
not subdivided into areas corresponding to the cells and the
ectoplasm is attached to it rather than continuous witli it.
Fibrillar strands of the ectoplasm re.-ich its surface but do
not appear to enter into it as one might expect if it were
merely a differentiation of the outer cell surfaces. It acts
mure in the nature of a sheath and has affinity for collagen

stains. At the present time there is no actual i)roof that the
basal lamella is formed by the intestine. Though such a layer
is plain in Ascaris, Pliji.ialiiplera, Tanqiia. Trichuris nntX Vioeto-
pln/ma, in other forms it is generally not visible. The extent
of its development is obviiuisly not correlated witli phylogenetic
relationships but rather with cell numbers for in all of the
above mentioned forms the intestine is myriocytous.

In most free-living nematodes one can discern no distinct
mesenterial sheath over the intestine but in Dorylaimns as
well as in the ma.iority of parasitic nematodes an extremely
thin membrane isolates the intestine from the body cavity and
is termed the p.seudocoelomic membrane (see p. 4.t). Beneath
the membrane or mesentery, muscle filters may be present but
such fibers do not form a continuous layer and they are
usually confined to the posterior part of the intestine (]). 42).
However, in unusual instances they may form a c.iarse mesli
work (Fig. lO.SH) which in cross section gives the appear-
ance of a separate muscle layer. Such muscle fibers are classi-
fied as specialized somatic muscles rather than as a mK-iriilaris
niusra.^ae.

B. MODIFICATIONS OF SUPERFICIAL
APPEARANCE; FORM OF LUMEN

The superficial appearance of the intestine as observed in
toto depends upon the total number of cells, the character of
the cells and the character of cell inclusions. The shape of
the intestinal lumen is likewise dependent on the number of
cells, the form of the cells and whether or not they are equal
or unequal in height.

Cki.i, Xumiikr. — Like the hypodermis and musculature, the
intestin<' of various nematodes presents a series of stages in
increaseil complexity: this series recapitul.-ites to a greater or

101

a lesser extent the ontogeny of the individual. As long ago as
1866, Schneider called attention to the fact that strongyles
have an intestine composed of but a few cells, 18-20, there
being only two in a given intestinal circumference. Maupas
(1900) noted that rhabditids also have but few intestinal cells
in the adult stage, 30 being recorded in Shabdilis elegans
while 18 were counted in newly hatched larvae of this species.
Similarly Pai (1928) found only 18 intestinal cells in adult
Turhatrix aceli and the writers find 64 intestinal cells in adult
Rhabditis sirongyloidcs and 20 in first stage larvae. On the
other extreme we have forms such as Ascaris lumbricoides with
innumerable intestinal cells (about 1,000.000), forms such as
Heterakis gaUinae with about 12,000 and intermediate forms
such as Prionchiihin, Hi/strignathiis, and Metoncliolaimus with
about 600, 400, and 5,000 respectively. In forms with 64 or
less intestinal cells the most notable and obvious feature is
that the cells tend to be longitudinally elongate and rectangu-
lar (Figs. 99A-C, lOOC, 102C). When the number is 64 (Fig.
lOOA) the characteristic hexagonal appearance is first notice-
able in only a few of the cells but when the number reaches
128 all are hexagonal.

The picture becomes clearer when this information is ex-
amined in the light of embryonic development. Martini (1903)
found that when 10 cleavages have occurred the definitive larva
is formed — an organism with a theoretic number of 1,024 cells.
However, there is a definite lag of cleavages in the endodermal
stem cell since the cells of this line actually number 16 to 20
instead of 128 as would be expected if no lagging occurred.
Comparing this information with facts concerning the somatic
musculature one notes that the tenth cleavage has taken place
in the mesodermal stem cell since 64 cells are present at hatch-
ing, this being the total number to be expected, as well as the

typical number of cells in adult meromyarian nematodes. From
this point of view, one might say that the course of regular
cell division has not been fulfilled in a nematode with less
than 128 intestinal cells and that cell division has only pro-
ceeded beyond "completion" when the intestinal cell number
exceeds 128.

Thus, on the basis of the number of intestinal cells, one
may cla-ssifj- nematodes into two groups, namely those which
have not exceeded the ' ' fore ordained ' ' number and those
which have exceeded this number. For the first condition we
propose the term lAigocytous while for the second condition
the term polycytotis may be used. However, there is a tre-
mendous variation in the possible number of cells in the latter
instance and for descriptive purposes a further division seems
to be advantageous. Such a division is difficult but one finds
a moderate correlation between the number and height of cells
in a cross section and the total number of cells of the intestine.

Forms with less than 8,224 cells (16 cleavages) have more
or less cuboidal epithelium with a maximum of 20-;')0 cells,
usually of equal height, in a given circumference. Where
raised areas occur in the lumen they are generally due to high
individual cells. On the other hand forms with over 8,224 cells
have 100 or more in a given circumference and definite plicae
or villae are formed by groups of higher cells. The term
polycytous is arbitrarily limited to forms with the former
type of intestine (256-8,224 cells) while the term myriocytous
is introduced for forms with the latter tvpe of intestine (over
8,224 cells).

Cell Char.\cter. — It has previously been noted that cells
in various regions of the intestine may differ in character;
upon some occasions specialized cells may be scattered in the
intestinal epithelium. Forms in which such cells are present

Fia. 102. I.XTESTIN'AL CELLS IN THK RIUBDITINA AND STRONGYLINA

A-C — RliahilitiH Ifirrirolit (A — Cross, C — horizontal .section of intt-s-
tine; B — partially dissolved .si)haerocry,stals in neutral violet); D-E —
PnnnurnliiiintiH HiilifUtnsjntitu ( L> — Cross, E — longitudinal section of in-
testine) : F-G — liliithdiaH ettstreptoH. (Cells seen in cross section, F —

anterior. G — mid to posterior): H-.I — Dih/h'twhus tlipsari (I — longitu-
dinal serlinn; H & ,T — cross sections): K — Oesnphfiffostomum denta-
tutu (Cross section): L-M — S'tronyt/lus pdfnttitutt (L — Surface view;
M — isolated sjihaerocrystals) .

102

limy 111' li'iiiu'ii li, t< rdCiilDiix wliilc f<iniis in wliirli tlic ullrrna
tive is triio may lie tcrnu'd hiininfi/ldiis.

Ceu, Size. — The intestinal lumen may be rdimileil, sub
|)oly(jonal or quite irreKular. A lumen of snidiitli ei>nt<iur
occurs in oligoeytous forms, thouttli even in such forms it may
become irrcKular due to folds or ru^ai', involving the entire
epithelial wall. A sub|iolynonal binien is characti'ristic of
polycytous forms wherein each individual cell tends to cause
a concavity in the outline of the lumen. Sonu'tinu's in pnhicy-
tons forms, but nuire commonly in myriocytnus forms, there are
definite projections of cells into the hnneii, such cells being
taller than their neighbors; these groups of cells form villi or
plicae (Fig. lO.S E, F, I). This inequality in the height of
cells in a given cross section may be termed anixncjiUi while
the reverse would be isncytii.

NrcLEAR Nl'MBER. — As a rule intestinal cells in nematodes
are uninucleate but exceptions to this rule are becoming more
and more numerous with critical observation. The causes of
polyiuicleation are not known; one can only inter]iret from
scattered observations. Normal "Ciigantism" of oligocytous
forms appears as one of the factors. Treniondo\is increase in
cell size siudi as occurs in Strotif/j/lus rqiiiniis, where one finds
single intestinal cells 4 mm long by .'>(H1 M wide, apparently
increase the requirements of nuclear material to such an extent
that a uninucleate cell nuiy be at a disadvantage. Given an
equivalent amount of nucleoplasm many nuclei provide for
more nuclear surface and a closer association of cytoplasm
with nucleoplasm than could be obtained with a single nucleus.
One might say that nemas inherently unable to cojitinue cell
cleavage compensate for this by undergoing nuclear division
when natural forces no longer limit their size. Polynucleation
is known to occur only in iiarasites. When characteristic of
the entire intestine it is usually present in an entire natural
group, but the exceptional sporadic cases (CnatJinstoma, PhUn-
vietra) are not explainable at jiresent.

Increase in cell size in tylenchids can not be the cause of
polynucleation since these forms are no longer than rhabditids.
Quite obviously an insufficient amount of information has thus
far been gathered to permit far reaching general conclusions.

Classifying nematodes according to the number of cells of
the intestine, number of nuclei, specialization or lack of special-
ization, and equality or inequality of cells provides an in-
teresting survey of the Nematoda. Examples of the known
types are given in the accomiianying table.

TABLE 1

Cell Nuclear Cell Cell

No. No. Size niaraeter

Oenus (1) (2) (,S) (4)

Rhabditis + + + +

Ditylenchus -.... + — + +

Chondronema — + + -f

Strongylus - + — -\- +

Rhabdias — + + -j-

Hystrignathus — + + +

Spironoura = + — +

.\scaris = + — +

Phy.saloptera = + — -|-

Tanqua ^ + — -|-

Onathostoma = — + +

I'hilometra ^ — — +

Prionchulus — + + +

Metoncholaimus — -(- + —

Monhystera + + -|- 4"

.\nonchus + + + +

Plectus - — 4- 4- +

Halanonchus - — + + +

Dorylaimopsis — + + —

Svnonchiella - — -|- -f- —

Tripyla ± + + +

Leptosomatum — + + —

Enoplus - - — + + +

Ironus - -— — + + —

Dorylaimus — + + +

Lcptonchus ? + + + +

.\gameris - — — + +

Trichuris ^ + — +

Dioctophvma = + — +

(1) (2) (.3) (4)

-|- is oligoey- -|- is uninucle- + is isocytous + is honiocy-

tons ate — is anisocy- tous

— is polycy- — is polynu- tous — is heterocy-

tous cleate tous
:= is myriocy-

tous

C. CELL INCLUSIONS

Under this hi'ading ;ire included all substiinces which are
not 11 part of the active cytojilasni whether organic or inor
ganic, food reserves or waste products. Numerous types of
stored food and waste products have been (di.served and in
addition there is a residuum of luui-classilied material termed
sphaeroids or granules. Food reserves are known to include
glycogen, rhabditin, fats, and protein. Waste jiroducts are
for the most part not classified chemically.

(1) RESERVE KOOD MATERI.M,S

(Hi/riif/rn. This substance, when present, is in a liquid or
seniiliquiil state, since it is water soluble. In fresh material
it may be icb'utitied through its coloraticpii with iodine iiotas-
siumioilide solution or the Rest's carmine technic as described
by Lee (l!t2.S). (iiovannola (lit.^fi) has recently emi)loyed the
new Hauer (li(33) technic for staining glycogen in the intes-
tine of iireiiarasitic larval Anctiloxlnma faninum, Necalor
amrricaniis, and Xippnstroiifiiiliix miins. Tt is always best to
use a saliva enzyme control, because that which is removed by
.saliva is presumptively carbidiydrate in nature. Busch {ISIO.'i),
von Kemnitz (]il]2) and Quack (191.3) found glycogen to he
the chief stored food in the intestinal epithelium of adult
Asraris and Striytu/iihiii. diovannola rejiorted glycogen to be
the chief f<iod reserve in the larvae of parasitic nematodes
jireceding an<l during rapid growth.

Hhahdiliii. This occurs as birefringent sphaerocrystals de-
scribed by Maupas (1900), Cobb (1914) and .lacobs and Chit-
wood (l!t,'?7) from the intestinal epithelium of Rhabililis spp.
The sphaerocrystals are grey in color, bright sjiots in dark
field illumination and bright spots with a central cross when
observed between crossed Nichols of a polariscope (Figs.
lOOA-B & 101). They are slowly soluble in cold water, more
rapidly on boiling; they are moderately soluble in .'i% for-
malin, and in lOTr acetic acid; rapidly soluble in dilute and
concentrated hydrochloric, sulfuric, and nitric acids, in ")0%
formalin, and in sodium and ammonium hydroxides; they are
insoluble in alcohol, glycerin, and xyol. When the intes-
tines of specimens are mashed out under a cover slip and ex-
posed to saliva or diastase at 37..5°C., these birefringents dis-
appear from the intestine in one-half to one hour while ap-
proximately twice this time is necessary in water and in in-
activated saliva controls. Iodine-potassium iodide has no ef-
fect. Presumably rhabditin is a carbohydrate but attemjits to
starve specimens and reduce the number of crystals were with-
out effect. They disappear, however, when the larvae enter
the encysted third stage (become "dauer" larvae).

Similar sphaerocrystals were described from the intestine of
Tlirrixliis xetn.iiis by the writers (1938).

Fats and Fatti/ Aciilx. These substances are present as
colorless globules imiiarting a grey opaque color to the or-
ganism. In dark field illumination they appear as bright
circles, and between crossed Nichols they are not visible. Such
material may be identified through its coloration with Sudan
III, Scharlach R, Nile blue sulphate, osmic acid, and Fleni-
ming's Strong fixative. It is not dissolved by saliva, water,
or hydrochloric acid and gives neither .xanthoproteic nor nin
hydrin reactions. It is, of course, soluble in alcohol, xylol
and ether. Standard histological technic results in the ap-
pearance of large empty spaces or vacuoles wherever fats
were present in the cell. Semipermanent mounts of small
nematodes may be obtained by alcohol fixation, and evapora-
tion to glycerin in Scharlach R or Nile blue sulphate accord-
ing to the procedure of fioodey (1930). Pleasing temporary
mounts can >)e made by placing living specimens in alcoholic
solutions of Scharlach R. The most exact method is to cut
the specimen, let the intestine flow out of the body and
stain with Scharlach R, osmic acid or Flemming's fixative. If
desirable they may be counterstained with haematoxylin. Per-
manent prejiarations may be made by sectioning osmicated
specimens.

Von Kemnitz (1912) and Quack (1913) found fat globules
in small amount in the intestine of adult A.tcari.i and Strangy-
lux. Giovannola (193(i) concluded that fat is the primary food
reserve in larval iiarasitic nematodes in stages preceding a pe-
riod of fasting. He further states that the quantity of fat
globules is an index to the "physiological age" of prcparasitic
strongyloid larvae. More critical investigaticms along such
lines would seem promising. Goodey (1930) identified fat
globules in the intestine of representatives of the Tylenchidae,
Rliabilifidae, Diplogasteridae, Ceiihalobidae, Plectidae, and
Momuichidae. The writers have identified fat as the chief
form of stored food in Cephalnbrlliix and BlaUicola (Thelas-
toinatidae), Chondronema (Allantonemafidae), Spironnvra

103

(Katlilaniidae), and various tylenclis, hoplolainis and cricoiie-
matids and Dori/laimus stagnalis.

Stored Protein. Such substances occur as non-birefiingent
colorless globules similar to fat globules in transmitted light
and dark field illumination. As described by Chitwood and
Jacobs (1937), they are insoluble in water, alcohol, xylol, ether,
and Vi-saturated ammonium sulphate; dissolve in 10% acetic
acid and in 5% KOH ; are not affected by saliva ; are pale
yellow in Flemming's fixative; give positive xanthoproteic and
ninhydrin reactions; and are digested by artificial gastric
juice. The globules stain with gentian violet or haematoxjdin;
they also stain blue with Nile blue sulphate and orange with
Scharlach R. These reactions apparently place them as com-
plex proteins of a con,iugated nature. The majority of glo-
bules of Agamermis are composed of this type of substance
and not fats as is commonly supposed. Similar globules have
been identified by the writers (1938) in the intestine of Dity-
len.e]nis dipsaci (Fig. lOOC). It is quite possible that the
colorless, insoluble (in 'Icoholxylol), basophilic globules, pres-
ent in Bhabditis, Ponafirolaimus, Aphelenchoides and Plectitx
etc., are of the same nature. The fact that such globules stain
with Nile blue sulphate in the same manner as fatty acids
indicates that staining technics are not necessarily indicative
of fat. Proteins may stain as do fats but they may be dis-
tinguished through their insolubility in fat solvents, digestion
in artificial gastric juice, and postive xanthoproteic and nin-
hydrin reactions.

(2) WW-STt; PRODUCTS

Inorganic Sphaerocnistalf;. Reddish-brown, weakly bi-re-
fringent sphaerocrystals occur in the intestine of many para-
sitic nematodes, including Asearis, Camallaniis, Strongylns,
Ancylostoma, and Trieliiiris. These structures are similar in
appearance to rhabditin both in transmitted light and between
crossed Nichols, although in totomount preparations and sec-
tions they are not liirefringent. The optical activity in this
case can only be observed when the crystals are isolated. Un-
like rhabditin, they are dark in dark field illumination and
are insoluble in water, acetic acid, NaOH (all concentrations)
and saliva. They are also insoluble in alcohol and xylol and
are not affected by gastric or jiancreatic enzymes. Askanazy
(1896), Looss (1905) and Faure-Fremiet (19r2) regarded
them as products of haenu)globin resorption, while Lievre
(1934) was unable to establish the presence of haemoglobin
in the intestine of Ascaris lumbricoidex and Parascaris
eqworum by spectroscopic analyses. He demonstrated the pres-
ence of haemoglobin by this means in 7.)% of the specimens
of Toxocara cants examined. A'on Kenmitz (1912) identified
them as zymogen granules and Quack (1913) identified them
as gypsum (CaS04.2II,0 ). The writers find that these crystals
may be obtained relatively- pure by boiling the intestine in
10% KOH and wa.shing in a centrifuge. Crystals prepared
in this manner are not charred by heating on a gla.ss slide to
the melting point of glass. They may be dissolved liy heating
in concentrated HOI and when cooled recrystallize in the gen-
eral habit of CaS04.2H=0. Such crystals are birefringent and
obliquely extinct. This is presumptive evidence that they are
gypsum. However, a reddish-brown residue is left when the
slide is dried. This residue stains blue in dilute HCl-potas-
sium ferrocyanide, indicating the presence of iron; direct ex-
periments on the sphaerocrystals jiroduces the same result in
partially dissolved ( swollen 1 crystals. Some compound con-
taining iron is evidently present as an adsorption within the
sjihaerocrystals. As evidence of the association of sjihaerocrys-
tals with a blood feeding mode of life, Tornquist (1930) point-
ed out that ('aiiKiUaniix. which is known to feed on blood, has
them, while Ciiciithiini.i. wliicli does not feed on blood, does not
possess them. One might add that adult oxyurids and thelasto-
matids, as well as the first three larval stages of Strongylns. and
Camallanus are also devoid of them. The evidence is entirely
circumstantial. The occurrence of grossly similar insoluble
sphaeroids in the intestine of Theristus setosus (see Olivaceous
sphaeroids) and other free-living nematodes casts some doubt

on the above interjuetation since they also contain iron. Lievre
(1934) interprets positive tests for iron in the intestine of
Asearis as due to substances obtained from animal and vege
table food, not haemoglobin.

Olivaccovs sphaeroids. Reddish brown, apparently non-bire
fringent sphaeroids were observed by the writers (1938) in the
intestinal cells of Tlieristus setosus (Fig. lOOB). They have
the following characteristics: Not blackened by osmic acid;
not colored by Scharlach R, insoluble in alcohol; ninhydrin
and xanthoproteic reactions negative; blue in neutral violet;
blue in crystal violet, blue in nile-blue sulphate; not digested
by artificial gastric juice or diastase; soluble in 10% HCl and
2% KOH but not in ^0% acetic acid or 2% HCl; blue in
potassium ferricyanide followed by 1% HCl. From these ob-
servations it seems that the sphaeroids must consist of an or-
ganic ferrous iron salt or a salt of a weak base (Fe(OH)«) and
a weak acid. Similar sphaeroids were also observed in Dory-
laimtis stagnatis and an unidentified oncholaimid and Diptos-
capter cnronata (Fig. lOOD).

Crystals. Stefanski (1916) and Cobb (1918) observed poly-
hedral colorless birefringent crystals in the intestine of Ironus.
They are very similar in appearance (Fig. lOoP) to triple
phosjihate, and, according to Stefanski, they are very soluble
in acetic acid and potassium hydroxide; slightly soluble in
hot water and insoluble in cold water, alcohol, ether, chloro-
form, and acetone; are not stained by iodine-potassium-iodide,
but stain with eosin and fuchsin. Isolated colorless polyhedral
crystals have also been observed in Tripyla (Fig. lO.^A).

Crystal aggregates in mermithids were observed bv Meiss-
ner (18.53), Rauther (1906), Ilagmeier (1912) and'christie
(1936). These are first seen in vacuoles of the post nodal re-
gion of preparasitic larval Agamermis deeaiidata. Their num-
ber increases with age and in old adult specimens similar
crystals have been observed in the body cavity. They are very
similar in appearance (Fig. 107D) to uric acid and allantoin;
are birefringent, obliquely extinct; insoluble in water, alcohol,
ether, 10% ammonium hydroxide, 10% acetic acid, 10% HCl,
glycerin, and V^ -saturated ammonium sulphate. Presumably
they represent a nitrogenous product.

In niploscapter comnata large (piadrate tablets, colorless to
yellowish brown, have been observed by the writers (Fig.
lOOD). Like oliv.aceous sphaeroids, they are non-birefringent,
soluble in 2% sodium hydroxide and 10% hydrochloric acid
but are insoluble in 1% HCl, alcohol and glycerin. They give
a negative ninhydrin reaction and a positive potassium fer-
ricyanide— 1% HCl reaction. Therefore they appear to be a
ferrous iron compcjund, probabl.v organic in nature. It is
possible that they may be crystals of the same substance com-
posing the olivaceous sphaeroids.

(3) JnSCEI.L.\NEOUS "URANULES"

In the majority of instances the cell contents of the nema-
tode intestine have not been studied chemically. The term
"granule" is, of course, chemically meaningless. Since at
least four distinct substances are known to exist in a sphaeroi-
dal state, namely, rhabditin, fat, protein, gypsum and oliva-
ceous sphaeroids each form must be considered with care.
With living specimens, dark field illumination is sufficient to
separate the globules of fat and protein from the sphaerocrys-
tals of rhabditin and gypsum. In addition, the first two are
colorless while the last three are yellowish brown to reddish
brown. However, still other types may be discovered. Non-
birefringent brownish or yellowish refractive "granules" are
present in the intestinal epithelium of Mctnncholaimtis, Si-
phonolainiits, Ironus, and otlier forms. Such "granules" are
strongly refractive and non staining (? olivaceous sphaeroids).
In addition one finds moderately refractive basophilic "gran-
ules" in the intestine of such forms as Dori/laimopsis, and
Plectiis, and special cells of the intestine of Synonchirtla.
Cobb (1922) has described birefringent sphaerocrystals in
s])ecial cells of Ei(rystomina as " marionellin " and we find
these to be relatively insoluble and basophilic. In other forms
acidophilic "granules" have been observed. For morphologi-

Fii;

lOI!. INTHSTINE IX AiSCAKIDIN A, SIMRITRIXA AND OAMALLANINA

A — Rhiyoneina ittfecta. B-C — Spirnnoura nffine, (B — cross; C —
longitudinal in prcrectal rcRioii showing parasites). D — Heterakin
iiaUinae. E-F — Oxjntrit etiui (E — superficial: P — longitudinal). G-H
— Macruris fiinnlii/nlfrn (<t — cross; H — supei-iicial) . I — Anisakinid
internal view showing ridges as seen in dissection .T-Q — Aticaris
InmhrietyidfH (.1 — noimal; 1. bacillary layer; 2. subbacillary layer; 'A.
plasma cap: 4. endophtsni; .5. jilasnia string; fi. basioplnsni ; 7. basal
lamella.; K — liinucleate cell, one nucleus degenerating; L — early cy-
tnyilasmic degeneration: M — lale cytolplasniic degeneration; N — nor-
mal nucleus; (> — early degenerating nucleus; T* — mid degenerating
nucleus; Q late (le'.;eneriitiMg nucleus). R S Tnjorfirti rtinin ( R—

intestinal cell with Ca.ial silver; S — with Iodine vapor, glc. glycogen,
grn i insoluble gran\ile (sphaerocrystal) T-U — (Inaihostoma spini-
(ji'nini V — liirtutarifi I'nlnradiensiti (grn b basophilic granule). W-
V — Pliihinietra rubra ( W — surface view; X — ventricular region; Y- — ■
uiidregion ) . Z — Phf/.^nJoplera retujta (1. Bacillary layer; 2. .sub-
bacillary layer; 3. plasma cap; 4. endoplasm ; 5. plasma string; 6.
basal lamella). AA — Tnnqvfi tiara. BB — A,scaropliis (CystidirnJa
liarivoadi) . TC — Camattanas atnerirarxan. K-F, after Martini. 1916,
Ztschr. Wiss. Zool. v. 110; I, after Cobb. 1SK8, Heilraege 7,ur Anat-
oniie und Ontogenie dec Nenuxtoden ; R-.S, after .\rgeseanu, 19.')4.
Crnnpt, Rend. S«ic. Biol, v. 110; remainder original.

104

^.AT

..©;>••■

■'('©^r©Y

\ \-'i^!^'?>-

u V^

Km:, hi:;

I o.->

eal purposes the term globule will be restricted to those inclu-
sions which are known to be nonbirefringent and appear as
bright circles in dark field illumination, i.e. fats and proteins.
The term sphaerocriistal is restricted to inclusions known to
be birefringent, while sphnrroid is applied to strongly refrac-
tive nonbirefringent or apparentl.v nonbirefringent bodies,
and granule is reserved for moderately or weakly refractive
bodies of unknown optical activity. It will appear obvious
that weakly birefringent substances such as gypsum may easily
be classified as sphaeroids pending critical study.

The function of gypsum, sphaeroids, and granules is for
the most part unknown. Sphaerocrystals of gypsum were seen
to be thrown out or "excreted" from the cells of Ascaris
and Slrongylus. The yellowish brown sphaeroids of Jthahdiiis
and Ironus were also observed to be eliminated from the in-
testine (Fig. lOoR).

(i) INTESTINAL PARASITES

Protozoan parasites are apt to occur in the intestinal cells
as well as in other organs of nematodes and might easily be
confused with cell inclusions or degenerating cells. Jlicoletzky
(1922) described sporozoan parasites of the intestinal wall
of Dorylaimus carteri and Plectuf: cirraUt.i, and Kudo and
Hetherington (1922) described a microsporidian named Thrln-
hania renifonnis from the intestinal epithelium of Mastophorus
muris. The writers have encountered similar forms (Fig.
103C) in the intestine as well as the musculature, gonads, and
chords of Spironnura affine. It is sufficient, for the present,
to merely call attention to their existence. Many protozoan
and fungous parasites of nematodes have been described and
such information will be presented in a later part.

D. COMPARATIVE MORPHOLOGY

Up to the present time no consistent attempt has been
made to record, much less present, specific information regard-
ing the intestine in the various groups of the Nematoda. All
workers recognize various impressions upon which they may
have an "intuition" as to the group to which a nematode
may belong. Whenever it is possible, in morphology, to re-
duce these .sensory impressions to words, it invariably con-
tributes to our understanding of relationships and to the trans-
fer of knowledge from one worker to another. The present
writers must of necessity deal in terms of examples. B.v giv-
ing a sufficient number of examples, it is hoped that a skele-
ton outline may be provided around which others can build a
structure of some value.

Eltnbdilina. For the members of the Rhabditina we have
the observations of Maupas (1900), Cobb (1914), Goodey
(1930), and Giovannola (1936) as our only direct attacks on
the problem, but numerous observations from the time of
Biitschli, preserved chiefly in the form of drawings, serve as
a foundation upon which we may build.

The Rhabditina may be characterized as oligocytous, homocy-
tous, and isocytous with the excciition of the Rhabdiasidae,
Drilonematidae, and Allantonematidae, which appear to be
wholly or in part polycytous. Rhabdilis (Fig. 3, lOOA, 101,
102.\-C), Turhatrix, and Diploganler retain the simple uninu-
cleate condition in the intestinal epithelium. In these forms
the cellular outlines are distinct and quite often emphasized
by the absence of cell inclusions. The intestinal lumen tends
to be flattened; the cells alternate, giving a zig-zag appear-
ance in lateral view. Free-living stages of the Rhabdiasidae
are also oligocytous, and in general quite similar to BhabdUix,
while the parasitic adult is very definitely polycytous, the cells
cuboidal (Fig. 102F-Ct). Ventricular and prerectal regions
arc almost alwa.vs differentiated from the remainder of the
intestine through absence of, or marked diminution of, cell
inclusions. The intestine cells of many species of Sliabditix
contain birefringent sphaerocrystals of rhabditin, but this
substance has not been identified in an,y other members of the
suborder. Si)haeroids, apparently nonbirefringent or weakly
birefringent, are very noticeable in the para.sitic female of
Shabdias but these are of the insoluble t.vpe. Anteriorly the
intestinal circumference consists of about 12 cells, very low,
containing few or no inclusions. In the mid-region there are
six to eight somewhat higher cells containing a moderate num-
ber of small sphaeroids, numerous larger basophilic globules
and small basophilic granules (Fig. 102F), while posteriorl.v
the sphaeroids are larger, more numerous, and the basophilic
bodies minute and numerous (Fig. 102G). In these forms
the sphaeroids are a deep red-brown in color.

Maupas (1900) noted that in some species of h'habdilis

birefringents are absent. In such forms he found "albumino-
fatty" globules to be more prevalent.

Cephalobids are usualh- described as having an intestine
composed of two series of cells (rows). Though the lumen
is dorsoventrally flattened and often appears zig-zag, as in
Bhabditis, no cell walls are distinguishable in sectioned Pana-
grolaimus siibelongaius (Fig. 102E). The nuclei are near
the lumen, two to six, and usually four, in a given circum-
ference, with a total of about 210. Since disappearance of
cell walls occurs in the fourth stage larva, at the same time
as nuclear division (there are about 20 uninucleate cells in the
third stage larva), it seems best to interpret this form as
primarily oligocytous, secondarily polynucleate and/or syncy-
tial. Perhaps polynucleate cells will eventur.lly be distinguished
as in tylenchids. The cephalobid intestine in section is charac-
terised by its large faintly basophilic globules, scattered brown-
ish shells, and large empty spaces which presumably were
filled with fatt.v substances.

The Tylenchoidea present a picture in contrast to the Rhab-
ditoidea when the intestine is considered. Although Debray
and Maupas (1896) were able to distinguish 16 cells forming
the intestine of Ditylenchus dipsaci in the fourth stage larva,
distinct cells have seldom been observed in the adult members
of the Tylenchidae. The intestine appears as an opaque mass
of large globules, very beautiful in dark field illumination,
but not visible in polarized light. This material is of a fatty
character. Sections of D. dii)saci and Aphrh nchoidcs parie-
tinus fail to show clear evidence of cell walls (Figs. 102H-J)
in the adult stage. In dissected specimens the large quad-
rinucleate cells are seen (Fig. lOOC). The cytoplasm is highly
vacuolate due to the removal of fats, Basophilic globules are
also seen in sections, but these appear to be very erratic in
disposition. In D. dipsaci the lumen is dorsoventrally flat-
tened anteriorly and zigzagged posteriorly (Fig. 102H-.1) ; .56
nuclei were counted in one specimen. In A. parictinus the in-
testine is quite similar except that its sides in the mid-region
tend to be more nearly equal and tend to surround the gonads.
In this form a maximum of two nuclei has been observed in
one section and on one side of the intestine. It is notable
that the lumen is relatively much smaller in tylenchids than
in rhabditoids, and the bacillary layer relativel.v shorter and
more compact. Apparently we have no increase in the number
of intestinal cells, 16, between hatching and adulthood. In
Chondronema passali, the only representative of the Allan-
tonematidae studied, the intestine is definitely polycytous, there
being four to six hexagonal cells in a circumference. The cells
are filled with fat globules as in the tylenchids. Unlike the
latter, however, no bacillary layer appears to line the round
intestinal lumen. The lumen contains a glassy-appearing sub-
stance, possibly of protein nature, which is slightly basophilic
and apparently represents partially digested body fluid from
the host. Aside from the presence of a few birefringents
(nature unknown) in the posterior end of the intestine of
Chondronema, there is no known case in which either ventricu-
lar or prerectal regions differ from the mid-region in members
of the Tylenchoidea.

Strongylina (Figs. 99 & 102). The Strongylina as a group
appear to be oligoc.vtous or low polyc.vtous and the cells are
polynucleate as noted in Strongylux by Schneider (1866),
Looss (1901) and Quack (1913') and in Anci/lnstoma hy Looss
(190.5). Other representatives of the same suborder (Ste-
phayiurus, Oesopliagostomum, Ostcrtagia, Lnngisfrinia, Mita-
strongyhis and Dictyocaulus) examined liy the writers exhibit
the same characteristics. The intestine consists of two rows
each of 10 or more cells, each cell containing 10 to .500 nuclei.
The smaller numbers, 10 to 20 nuclei, occur in members of
the Trichostrongyloidea. In such forms as Ostcrtagia there
are two rows of nuclei in each intestinal cell, four in an in-
testinal circumference while in Trichostrongylus instabilis
Looss (189,5) found each of the two cell rows of the intestine
to contain a single row of nuclei. About 40 to 50 nuclei are
present in an intestinal cell of Ocsojdiagostomum, 500 in one
of Sirongylus while no reliable estimate has yet been made for
Melaxlrongyliis. The sliajie of the lumen is quite diverse, be-
ing dorsoventrall.v flatteucd in Osti rtngia, irregular due to
longitudinally folded walls in Stcpliaiiurus, or rounded to
ovoid in Oesopliagostomum and Mclastrongylus. A thick,
compact liacillary la.vcr resting on a well ileveloped subbacillary
layer is characteristic of the Strongyloidea. Wetzel (1931)
and Lueker (1935, 1936, 1938) have "made use of the specific
intestinal cell ciuistancy of the third-stage larvae of horse
strong.vles as a means of dift'erentiating the species in this
stage. Thus Wetzel found two rows of eight long subtriangu-
lar cells in Strongylus equinus, two rows of ten cells in S. eden-
taUis, and two rows of 16 cells in iS'. vulgaris. Trucker found a
total of only eight cells in the intestine of Cylieodontophorns

106

till raji'ct inns, ('nUcoarcii.i ffohli,' and ('. caliiinl iix larvae, of
12 in (Ijitiloct phaliix cniiitnlii.s anil of Iti in I'ah riostiniiiiin
rul^ii. Siniilai- iilcnliliration of spocios of sti-onKyliii paiasitos
of slu'i'p lias ln'cn sliowa piacticalili' liy Dikiiians and Andrews
(lSi:i3) on the liasis of the intestinal eells of the third stajje
larvae.

Intestinal nnelei of stroUK'vlins aie spliaeroid in sneli ex
freniely iHverKent forms as Osli rtaiiia aiul Slrdiimiliis while in
Ocxoiiliiiiitisldmiiiii, Sli iihaiiuriis, Auci/hixdiiiiii ami Kiiliciiilm
lus they are irreRiilarly elongate or even tulioid. There is
usually a slight, tluuiKli distinet, diminution in the mimlier of
insoluble spliaeroerystals both in the ventrieular and prereetal
regions of mendiers of the Strungylina; in sneh ri'gions the
lumen is often slightly larger ami the epitlu'lium thinner than
in the remainder of the intestine. Glycogen, storeil in the
endoplasm, ajipears to be the ehief food reserve. Like tylen
choids, however, there is relatively little absorjitive surface
in the strongylin intestine.

Axctiriilina (Fig. 103). The Asearidina present a very dif-
ferent picture for this group is polycytous to myriocytinis.
Polynueleate eells are rare; they never constitute more than
a small proportion of the intestinal cells in a sjiecies. In-
.soUible sphaerocrystals ojipi^ir to be absent in the Oxyuridae,
Thelastomatidae, and K;itlilaniidac while they are present in
members of the Rliigoneniatidae, Ileterakidae, and Ascarididae.
The smaller representatives of the Thelastomatidae lliltiili'
c.nhi, I't iilialtihcUu.i) and Oxyuridae ( J/dcrac/.s) are polycytous
and isocytous while larger oxyuroids such as Oxi/iiris <'(iiii and
Entcrobitis vcrmicuhiri.s as well as rhigoneniatids, kathliuiiids,
heterakids, and ascaridids are myriocytous and anisoeytous.
Distinct ventricular enlargements are characteristic of the
polycytous oxyuroids such as Marraci.i, Bhitticiila. and Crphalo-
beUiis though such may also occur in some myriocytous forms
such as HcUrakis. In addition .sections of the intestine of
polycytous oxyuroids (also Spiroiioiim) show numerous large
vacuolate areas which correspond to f;it globules seen in the
living specimens. Passing to the myriocytous forms we find
the ventricular region less and less apparent with increased
cell number. There is also a marked tendency toward anisoeyty
manifesting itself in Rhifioiuma by the formation of an ob-
long lumen; in SpirDimurd by an I-shaped lumen formed by

*Reg.>irdiiig Ci/lifocercus yiiWi Lucker (1938) .states that the lunieu
passes between the tirst three cells "through the cytoplasm of the five
posterior cells." He assures us that there are only 8 nuclei and 8 cells
in the third stage larvae. It still seems possible tliat he may have over-
loolted something. Compare figs. 100 C, 102 H .1. and figs. 99 C.

two staggered liiiigit wdinal ridges (Mackin, l'.l3li; and in
lit li nil:i.s by .a triangular lunu'n or three longituilinal ridges
( Hakcr, lii.'iii). Tuft or villus formation has been ile.seribed
as a further development of anisoeyty in Oxi/iiris iijiii by .Mar-
tini (I'.iKi); in this instance the tufts which are composed of
numiTous ei'lls may give a hexagonal ajipearance when seen in
toto (Fig. KiriK)." .Jagerskicild (1H<)3, 1.S!I4; described groups
id' elongate cells especially developed in the anterior part of
the intestine of ('(inlriifiwcum xpiciiUi/niim, of ('. Dxcnldtiim
and IliipliidiiiiCdri.i dicipiins ; such cell groups reduce the lumen
to a narrow, folded canal. Similar cell groups, according to
Cobb (1«K8), take the form of V-shaped ridges (Fig. \Ki\) in
Atiisiihis .siniplrr. Anisoeyty in Ascftris, on thi' other hami,
is limited in such a manner that the small cells are lateral
and the lumen, conse(|uently, takes the form of a dorsoven
trally llattened tube (Fig. 0(10). (llycogen constitutes the
chief stored food in Axrtiri.i according to Kemnitz (l!ll'J> and
Quack (llH.'f) while glycogen is absent in (Ixjiiiris according
to .Martini (liIKi) and this is in agreement with the writers'
lindings that fatty substances are the energy reserves of
oxyurids while ajipearing in negligible quantity in ascaridids.

I'jilynucleate cells with two to three nuclei have been ob-
served upon rare occasions in Spironoitra but they appear to
be (piite common in the lateral areas of the intestine of As-
raris. Ehrlich (litOll) associated [lolynucleation in /l.irari.s
with niudear degeneration but Quack (lillH) was unable to
substantiate this view. Rather extensive studies of both nu-
clear and cytoplasmic "degeneration" have been made with
this form by Ehrlich, Quack, and Guieyssc-I'ellissier (IIIO!)).
Nuclear degeneration involves an enlargement of the nucleus,
increased basophily .■inil the formation of strongly refractive
sphaeroids (Fig. lO^N-Q) within the nucleus; these changes
are followed by elimination of the cell, or a portion of the
cell containing the nucleus, into the intestinal lumen. So-
called cytoplasmic degeneration (Fig. 10.3M) involves the for-
mation of an acidophilic mass, usually near the base of the
cell, inclusion of normal cytoplasmic sphaerocrystals within the
mass, movement of the whole toward the lunu'n and final
elimination. Martini (191(i) illustrated such elimination of
"degeneiate cells'' in Oji/nris. The regularity of the occur-
rence of "degeneration" in Ascaris leads one to suspect that
it is a normal physiologic process not necessarily retrogressive
in nature. Assuming that insolul)le sphaerocrystals are waste
products, "cytoplasmic degeneration" might be considered a
mode of excretion. In h'luibdias and Slrdnm/lus it has been

Fio. 104. INTESTINE IN rilROM.VDUK 1 1).\

A-B — Sf/nonc-hiella trvncata. C — Monhj/fttern ramhnri. D — Aio-
nolaimus Hpinosun. E — W'ilsonptna hnriUivnruH. ¥ — Tripplium carcini-
rohiw V. calkiniti. G — Vorylahnopttfs metafypiru/t. H — AnaplectUH granu-

Itiatis. I — HttUchtttinnlttimus rnhufitns, J — Ethytwlaimujt rfimlifnAis.
K — Ayionclni/t mirnhiliA. Ij — Chrnmadora sp. M — Stilanonrhuit vtnc-
rantpbidum. N — Chromadora sp. O — Chronognitter gracilin. Original.

107

previously noted that sphaerocrystals are normally eliminated
in the faeces.

Spirurida (Fig. 103). For the order Spirurida there is a
surprising dearth of recorded knowledge concerning the in-
testine. Jagerskiold (1893, lSi)4), Magath (1919), Hether-
ington (1923) and Tornquist (1931) seem to have been the
only authors who gave the intestine consideration. It is pe-
culiar that in this group there appear to be as many instances
of marked dissimilarity of the intestine in closely related forms
as there are instances of similarity. All of the members of
this order appear to be myriocytous with the possible excep-
tions of Gnathoxtoma and Philometra : the latter have rela-
tively few, large, polynucleate cells (Fig. 103U & W). In-
soluble sphaerocry.stals are present in Philometra, Dracunculus,
Microplciira, CamallanKs, Gnathostama, and Ttinqiin, while they
are absent in Ascarojihis (Metaironeina) , Cticidlanus, Pliysalop-
tera and Eictularia. Basophilic globules, probably of a pro-
tein nature, are present in Rictiilaria. Most of the represen-
tatives of this group have very tall, narrow intestinal cells
and are anisocytous because the epithelium exhibits either
longitudinal ridges and valleys or villi. However, three forms
are conspicuous exceptions to this rule, namely, Camallanus,
A.icarophis and Gnalhostoma. Diversity in height of cells and
character of the bacillary layer and basal lamella are also
conspicuous features of the group.

Chromadorida (Fig. 104). In the Chromadorida the only
observations regarding the intestine have been of an incidental
nature. We have records such as those of de Man (1884) in
which species of the genus Monhystera are differentiated on
the basis of their having a black or grey intestine and "two
cell rows" or more than two cell rows. The rich red-brown
to black pigmentation of the intestine of Siplionolaimus was
recorded by zur Strassen (1904). The number of cells in an
intestinal circumference was mentioned by Cobb (1920) in
many forms of this group. Zur Strassen (1904) and Schepo-
tieff (1908) were the only previous workers to study sections
of forms of this order.

Members of the family Plectidae have relatively few intes-
tinal cells, 120 to 930, the form with the smallest number,
Anonchus, being oligocytous while the remaining forms stud-
ied, Plectus, Chronogasier, and Wilsonema are polycytous.
Anonclius and Chronogasier have only four cells in a circum-
ference, a very low bacillary layer, flat lumen, and large eosino-
philic granules. Wilsonema has up to eight cells in a circum-
ference, a lobed lumen, high bacillary layer and no granules
and Plectus has up to 12 cells, a rounded lumen, high bacillary
layer and basophilic globules ( "? protein).

In the family Camaeolaimidae, Aphanolaimiis has around
100 cells (oligocytous), a flat lumen, a high bacillary layer,
four cells in a circumference and basophilic globules like
Plectus while Camacolnimns has around 2ri6 cells (low poly-
cytous), a rounded lumen, low bacillary layer, six cells in a
circumference and reddish-brown nnn staining granules.

Sabatieria and Dorylaimopsis, of the Comesomatidae, are
polycytous, having 2^G to 500 intestinal cells, six to eight in a
circumference, tliey also have a flattened lumen, a low bacil-
lary layer and large basophilic globules. They differ from
one another in that Sabatieria is apparently homocytous while
Dorylaimopsis is heterocytous having scattered cells contain-
ing large acidophilic masses (Fig. 104G).

In the Axonolaimidae the intestine is approximately as in
the Comesomatidae, there being around 256 cells, six in cir-
cumference, a rounded to flat lumen and reddish-brown, non-
staining, sphaeroids. Ijike Sabatieria, Axonolaimvs appears
to be homocytous.

In the Monhj'steridae there are two quite different types
of intestine. In the first, exemplified by Mojiliystera and
Theristus, the lumen is niultiradiate (Fig. 104C) tlioiigh there
are, respectively, 60 and 120 cells, two and four in circumfer-
ence; the l)acillary layer is low and compact and the intestinal
inclusions are brownish or grey and basophilic. In the second,
exemplified by Ualanoncliiis, there are about 566 cells, six to
16 in a circumference; the bacillary layer is relatively higher,
less compact, the lumen irregular, and the sphaeroids are
brownish and non staining.

Linhomoeids commonly have few intestinal cells in a cir-
cumference, usually two in the mid-regio7i of the intestine,
but the total number of cells varies considerably. Tripylium
has 26 cells while Terschellingia and Desmolaimiis exhibit
around 128; the lumen is flat to rounded, the bacillary layer
low, compact (not resolvable in Tripylium but so in the other
two exam|)les) ; the colorless globules in Tri|)ylium are soluble
in alcohol (therefore presumably fatty), while in Terschellingia
and Desmolaimus the cell inclusions are sphaeroids, slightly
brownisli, and insolubU".

ITnlike other inonhysterids and linhomrn'ids, tlu' sijilK»n(ilaini

intestine is deep red to black in color, the pigmentation being
due to refractive, insoluble sphaeroids. Zur Strassen (1904)
found the intestine of SipJionolaimus weismanni to consist of
22 cells in circumference and to be composed of a total of
6,000 cells (estimation from statements in description) ; its
lumen is rounded, the bacillary layer unusually high.

Members of the Chromadoridae, Microlaimidae and Des-
modoridae fall within the lower limits of polycyty, varying
within the narrow range of 128 to 256 cells. Seemingly all
have a four cell circumference in the mid-region though
there may be six to eight in a circumference in the ventricular
region. Members of these families have a very low bacillary
layer and a rounded to subpolygonal lumen; a moderate num-
ber of somewhat basophilic sphaeroids is usually present and
in addition, from the coarse vacuolate appearance of the cyto-
plasm, one might suspect a considerable amount of fatty
substances. These three families appear to be homocytous and
isocytous.

Members of the Cyatholaimidae, on the contrary, are more
distinctly polycytous, varying in cell number from around
256 to 1,000 with from three to 12 cells in circumference; they
appear to be uniformly heterocytous. In HaUchoanolaimus
the normal cells contain brown sphaeroids (often appearing
in section as basophilic shells) while the scattered heterocytes
are devoid of these bodies but contain instead, large vacuoles
packed with baso|)hilic globules. In Synonchiella the normal
cells are vacuolate, without sphaeroids, and the heterocytes are
dense, filled with basophilic globules (Fig. 104A). The simi-
larity of the intestine of Haliclioanolaiinus to that of Dory-
laimopsis is very striking.

Schepotieff (1908) described the intestine of Desmoscolcx
as consisting of few cells and as containing very large brown-
ish globules which were insoluble in alcohol-xylol.

Enoplida (Figs. 105-107). The order Enoplida, containing
both simple and complex free-living forms, as well as diverse
types of parasites, shows extreme variation in the form of
tlie intestine.

Within the Tripyloidea, Stefanski (1916) studied the cell
inclusions of Ironus and Cobb (1917, 1918) described the
intestine of Ironus and Mononchus. Ironus is polycytous and
heterocytous (Fig. 106), the number of heterocytes apparently
varying with the species. The ordinary cells contain yellowish
non-staining sphaeroids which appear as shells with irregular
contents in formalin preserved material. These sphaeroids are
sometimes eliminated through the anus (Fig. 105O). Tripyla
(Fig. 105A-C) is homocytous and barely polycytous, having
136 to 150 intestinal cells, a low bacillary layer, acidophilic
granules and scattered polygonal crystals. Prionchulus is like-
wise polycytous and homocytous (Fig. 105D-E); the species
differ in having from 170 to "00 intestinal cells; anteriorly
the cells in a circumference are more numerous, higher, and
have a much more pronounced bacillary la^-er than in the mid
region but no definite ventriculus is present. Like Ironus,
Prionchulus has acidophilic granules but crystals are absent.

In the Enoploidea Tiirk (1903), Jagerskiold (1901), and de
Man (1904) studied the intestine of Thoraensfoma and CvH-
colaimus and Rauther (1907) that of Enoplus; Cobb (1922,
1924a) investigated the intestine of Eurystomina and Ajiti-
coma and Chitwood (1931) that of Metoncholaimus. So far
as known, all members of this group are markedly polycytous,
isocytous, and have uninucleate cells. With the exception of
Enoplus they are all heterocytous and even in this form cells
are occasionally found which differ from their neighbors in
the presence of large acidophilic bodies. Tiirk found the homo-
cytes of Thoracostoma to contain greenish-brown granules.
Specimens kept in clean white sand had a clear intestine free
from such inclusions. He judged these inclusions to be re-
sorption vacuoles of plant food. Occasional heterocytes he
interpreted as fat cells (Fig. 105M-N). A bacillary layer ap
pears to be totally absent in Metoncholaimus, Thoracostoma
anil Cylicolaimus. This layer is represented merely by a
peripheral condensation in Eurystomina (Fig. 105G-H) and
Leptosomatum (Fig. 105L) while it is nuxlerately high and
distinct in Enoplus and very high, especially in the ventricular
region, of Phanodermopsis. The ordinary cells (homocytes)
of Phanodermopsis contain yellowish non staining sphaeroid
shells (J'ig. 1051) while the corresponding cells of Lepto-
somatum have a conspicuously vacuolate plasma (? fat vac-
uoles) and a few baso])hilic globules; the homocytes of the
remaining forms contain acidoidiilic granules. Heterocytes
in Eurystomina and Phanodermopsis' are filled with basophilic
globules while the heterocytes of Leptosomatum include a large
amorphous acidophilic vacuole and those of Metoncholaimus
may either be basophilic with a large vacuole or ciintain scat-
tered large yellowish non staining sphaeroids (Fig. 105F).
Chitwood :in.i Cliitwood (\'XM') identified fats .■ind ferrous

lOS

Fig. 105. INTESTINE IN ENOPLIDA
A-C — Tripyla papillata (A — posterior part; B — surface view; note sphiieroid;
C — ventricular region). D-E — Prionchulus lutiscorum (D — ven-
tricular region : E — mid-region) . F — MetnnclioJaimua prist ivrns.
G-H — Kuri/stoininn ameii^^ana. I — Phftnodermopsis Innui^^taf.

J-K — EnopluH communis v. meridional is (J — mid-region ; K — ven-
tricular rcgiiin ) . I.— Lppt OHO ninfmn ffntii/tit n ni v. ari-pfmlatu iii . v
M-N — Thorncostoma strasseni. 0-Q — Ironus tfiiuicaudatus {O —

109

rectum ; P — isolated crystals; Q — isolated de-
generate sphaeroid shells) . R — Dioctophi/ma rejiale. S-U — Dory-
Iniinus stagnalis (S — mid region: T — posterior part of prerectum;
XT — prerectum) . Y-'W — Leptonchus sp. (X — ventricular region ;
\V — mid-region). M-N, after Tuerk. 1903. Mitt. Zool. Stat. Xeapel,
v 1 '> ; remainder original.

Fig. 106

Ironua tenuicaudainti , (Note specialized intestinal cells containing large globules,
also small polyhedral crystals in ordinary intestinal cells). After Cobb. 1918, Con-
trib. So. Neniat. 7.

iron salts a.s the chief cell inclusions of an oncholaimid.

The number of dorylaimoids of which the intestine lias been
studied is inadequate. Members of the Dorylaimidae all seem
to be polycytous but the number of cells in an intestinal cir-
cumference varies from four to 20. Anteriorly the baeillary
layer is highest in the ventricular region and posteriorly a
conspicuous change is notable in this layer in the prerectum.
Throughout ventricular and mid-regions the cells contain yel-
lowish brown non-staining sphaeroids (appearing as shells in
section) while these structures are absent in the prerectum.
The latter is set off as a distinct section of the intestine in
the Dorylaimidae (Figs. 20-21) and Leptonchidae and may
even be subdivided into two distinct units in Actinolaimus.
Leptonchus resembles dorylaimids in general but differs in
that the number of intestinal cells is smaller ( foligocytous)
and the cells contain massive basophilic globules. Nothing is
known concerning the intestine of the diphtheroiihorids aside
from the fact that they have no prerectum.

The intestine of the Mermithoidea has been given more at-
tention than that of other groups because, as was early recog-
nized, the peculiar nature of the intestine constitutes one of
the major characteristics of the group. Schneider (1860) first
recognized that the solid mass of tissue which Meissner (1853)
called the ' ' Fettkorper" corresponds to the mesenteron of
other nematodes. The work of Meissner (1S53, 1856), Schnei-
der (1860), Rauther (1906, 1909), Hagmeier (1912), Steiner
(1933), and Christie (1936) makes it possible to characterize
the mermithid intestine as an organ of food storage in which
the larva, during the parasitic stage, stores the nutrient mat-
ter on which it draws throughout adult life and reproduction.
In order to meet these re((uirements the intestine grows an-
terior to the base of the esophagus, regularly reaching the level
of the nei've ring. Rauther (1909) observed a lumen (Fig.
107F) in the anterior part of the intestine of Mermis sp. and
interpreted this part of the intestine as a caecum. Steiner
(1933) stated that in some mermithids the trophosome has an
axial cavity and a wall of polynucleate cells, while in others
the axial cavitj' disappears but the polynucleate cellular condi-
tion persists, and in still others the cell walls disappear form-
ing a syncytium. Rauther found that the intestine of Hexa-
mermis albicans consists of two longitudinal rows of cells each
containing 10 to 15 nuclei in the adult stage while the writers
found the intestine of Agamcrmis dccaiidata (Figs. 107A-C)
to be four to 10 cells in circumference and each cell to contain
22 to 25 nuclei. The total number of cells in these forms ap-
pears to fall within the upper limits of polycyt.v. In Hi/-
dromermis sp. the nuclei are relatively' larger (Fig. 107E) and
apparently less numerous than in the jireviousl.v mentioned
forms but unfortunately no exact information is available.
Large vacuoles containing crystals or crystal aggregates have
been observed in several mermithids in all stages from the
preparasitic larva to the senile adult; these crystals accumulate
with age, becoming a conspicuous feature of specimens after
reproduction has ceased. The increase in crystals and vacuoles
coincides with diminution of intestinal globules. Rauther
(1906) compared the crystals with uric acid but was unable
to obtain an unmistakable murexide reaction. Ccmcerning the
globules of nutritive reserve, the following observations have
been made on Apaviermis dccaudata: Sections of young para-
sitic larvae contain onl.v a few basophilic globules in a rather
dense cytoplasm (Fig. 107B) ; the larvae at emergence and
the young adults are literall.y packed with such globules in a
vacuolate cytoplasm; the cells of specimens in the emerging
larvae and adults are filled with colorless, oily appearing glo-
bules (whence the name fat bod.y) ; according to Chitwood
and Jacobs (1937) onl.v a small proportion of these globules
is fat, the great ma,iorit.v being protein.

The superfamily Trichuroidea is typically myriocytous, ani-
soc.ytous, homoc,ytous and the intestinal cells arc uninucleate.
Villus formation in Trichiiris is uniform, the subpolygonal
units (groups of cells) causing much the same appearance as
large individual cells in surface view; from this standpoint
tliere is distinct parallelism with O.riiuri.i (Fig. 103E). Ac-
tuall.v each unit is comjiosed of 50 to 100 tall narrow cells.
The l)acillar.v layer is fpiite liigh in the mid region and the
basal layer is unusually thick. Reddish-brown sphaerocrystals
are present throughout the mid-region of the intestine.

The intestine of the dioctophymoids is much like that of the
trichuroids, differing only in that the bacillar.v layer (Fig.
lfl5R) may reach a height nearly equal to that of the cell
proper. The sphaerocr.vstals are localized on the side toward
the lumen and villi are not uniform.

110

J

Kit;

Intestine of mermithoids. A-1) — At/attierntw deanidata (A — tro-
phosonie of senile male, disserted alive; not* remnants of protoplasm
near edge of cells and large vacuoles: B — Cross section of large larva
(1 cm) from body cavity of grasshopper showing dense protoplasm,
at times protein globules [shaded] begin to appear, nuclei circles with

central nucleolus; C — Cross section of adult, non-senile showing nu-
merous protein globules, note relatively minute nuclei; I> — f'rj'stals as
seen in A). E — Hi/ilronifrmifi sp, (longitudinal section of adult), F —
Cross section of entire Mfrniin sp, showing intestine with luineti. A-E,
original: F, after Rauther. 1909, Ergeb, u, Fortschr. Zool. v. 1(3).

Bibliography

Argeseanu, S. 1934. — Les constituants de la cellule intestinale

ties ascarides. Conipt. Rend. Soc. Biol. Paris, v. 11(5: 7;")4-

7o6, figs. 1-2.
AsKANAZY, M. 181H5. — Der Peitsclienwurm ein blutsaugendcr

Parasit. Deutsches Arch. Klin. Med. v. 57(1-2): 104-

117, pi. 2, figs. 1-9.
Baker, A. D. 193(5. — Studies on Hetrrdkis galUnae (Gmelin,

1790) Freeborn, 1923, a nematode parasite of fowls. Tr.

Ro.val Canad. Inst. v. 20(2): 179-215, v. 21(1): 51-86,

pis. 1-15, figs. 1-1(54.
Bauer, H. 1933. — Mikroskopiscli-cliemischer Naclnveis von

(il.vcogen und einigen anderen Pol.vsaceliariden. Ztsclir.

Mikr. Anat. Porscli. v. 33: 143-160."
Best, F. 1906. — Ueber Karminfarbung dcs Glycogens uud

der Kerne. Ztschr. Wiss. Mikr. y. 23: 319-322.
BiLEK, F. 1909. — XJeber die fibrillaren Strukturen in den

Muskel und Darmzellen der Ascariden. Ztsclir. Wiss. Zool.

V. 93: 625-667, pis. 27-28, figs. 1-20.

1910. — Noch ein Wort iiber der fibrillaren Strukturen

in den Darmzellen der Ascariden. Anat. Anz. v, 36: 17-25,

figs.
Bonnet, R. 189... — Schlussleisten der Epithelzcllen. Deutsche

Med. Wochenschr. Ver. Berlin, p. 58.
Bbaui.t, a., & Leoper, M. 1904. — La gl.vcogene dans le devel-

oppemont de certains parasites (cestodes et nematodes).

J. Physiol. & Path. Gen. v. 6: 503-512.
BuscH, F. W. C. M. 1905. — Sur la localisation dn glycogene

chez quelques parasites intestineaux. Arch. Intermit.

Physiol. V. 3: 49-61, figs. 1-8.
f'HiTWOOD, B. G. 1931. — A comi);irative histological stud^- of

certain nematodes. Ztschr. Morph. v. 23(1-2): 237-2S4,

figs. 1 23.
Chitwood, B. G., & CiiiTWOOD, M. B. 1933.~The histological

anatomv of CcjtlialnhrUnfi pnpUUqcr, Cobb, 1920. Ztschr.

Zellforsch. v. 19(2): 309-355, figs. 33-34.

1938. — Further notes on intestinal cell inclusions in

nemas. Proc. Holm. Soc. Wash. v. 5(^1) : 16-18.
Chitwood, B. G., & jAfons, L. 1938. — Stored nutritive ma-
terials in the trophosome of the nematode, Agamermis

decaudata (Mermithidae). J. Wash. Acad. Sc, v. 28(1):

1213.
Christie, J. R. 1936. — Life liistorv of Aoanx'i'mi-i drcaudatn,

a nematode parasite of grasshoppers and other insects.

.1. Agric. Res. v. 52(3): 161-198, figs. 1-20.

Cobb, N. A. 1888. — Beitrage zur Anatomie und Ontogenic der

Nematoden. Diss. Jena. 36 pp., 3 pis.

1914. — Rhabditin. Contribution to a science of Hema-
tology. J. Parasit. v. 1(1): 40-41, 1 pi., figs. 1-6.

1917. — The niononchs {Mo7i<»ichus Bastian, 1866), a

genus of free living predatory nematodes. Contrib. Sc.

Nemat. (6): 129-184, 68 figs. Also in Soil Science v. 3:

431-486.

1918. — Filter-bed nemas: Nematodes of the slow sand

filter-beds of American cities. Contrib. Sc. Nemat. (7):

189-212, figs. 1-9.

1920. — The use of the polariscope in determining the

character of cell inclusions in nemas. .1. Parasit. v. 6: 200.
1920. — One hundred new nemas. Contrib. Sc. Nemat.

(9): 217-343, 118 figs.

1922.— .l/arioncna. Contrib. Sc. Nemat. (11): 353-

358. Also in J. Wash. Acad. Sc. v. 11(21): 504-509.

1924a. — Minute birefringents in living cells. .1. Par-
asit. V. 11: 102-104.

1924b. — Specialization in the cells of the intestine of

some nemas. J. Parasit. v. 11: 108-109.
Darrib.\, A. R. 1930. — Contribucion a! estudio del Gangttle-

trral'is spumosa Med. Paises Calidos v. 3(6): 481-513,

figs. 1-28.
Debr.\y, F., & M.^UFAS, E. 1896. — Le Tylenchiis dcvastatrix

Kiihn et la maladie vermieulaire des fevcs en Algorie. 55

pp., 1 pi., 17 figs. ."Mger.
DiKMANS, G., & Andrews, .1. S. 1933. — A comparative mor-
phological stud.v of the infective larvae of the common

nematodes parasitic in the alimentary tract of sheep.

Tr. Am. Micr. Soc. v. 52(1): 1-25, pis. 1-6.
Ehrlich, R. 1909. — Die physiologische Degeneration der

Epithelzellen des .Vscaris Darmes. .\rcli. Zellforsch. v. 3:

81-123, pis. 2-4.
Faxre-Fre.miet, E. 1913. — T,a cellule intestinale e' le liquide

cavitaire de I'Axcaris mrqaloccphala. Compt. Rend. Soc.

Biol. V. 74(11): 567-569.'
Gehuchten, a. van. 1893. — Contributicm a I'dtudc du m^can-

isme de 1 'excretion cellulaire. La Cellule, v. 9: 951 17, figs.

1-20.
GlOVANNOLA, A. 1936. — Energy and food reserves in the de-
velopment of nematodes. J. I'anisit. v. 22(2): 207-218,

figs. 1-7.
GlROl'D, A. 1922. — Note sur la tube digestif i'Ascarin holop-

lera (Rudolphi). Arch. Zool. Exper. & Gen. v. 61(1):

notes & rev.: 17 20, figs. 1-2.

Ill

1926. — Signification des batonncts basaux (ie ccrtaines

cellules, en particulier des cellules intestinales d'ascarides.

Zool. Bericht. v. 10: 318 (Abstract of 1924, C. R. Ass.

Anat., 19. Reunion, Strasbourg: 142-148). Original not

seen.

1927. — La cellule intestiuale des nematodes. Th^se

d'agregation. Not seen.
(ioi.DSCHMlDT, R. 1904a. — Der Clironiidi:ilapiiarat lebhaft

funktionierender Gewebezellen. Hiol. I'entilbl. v. 24(7):

241-2."il, figs. 1-4.

1904b.— Idem. Zool. Jahrb., Abt. Anat. v. 2U1): 41-

140, figs. A-Q, pis. 3-8, figs. 1-62.
GoODEY, T. 1930. — On the presence of fat.s in the intestinal

wall of nematodes. J. Helminth, v. 8(2): 8y-88.
GUERRINI, G. 1910. — I)i alcuni fatti di secrezione studianti

neir epitclio intestiuale dell' Ascaris meqahtcepluila. Arch.

Parasit. v. 14(2): 193-223, figs. A-D.
Guieysse-Pelli.ssier, a. 1909. — fitude de la division karyo-

kinetique des cellules epitheliales de I'intestin iVAscaris

mcqalocephnla. Compt. Rend. Assoc. Anat., v. 11: 82-91,

figs'. 1-4.
H.VGMEIEK, \. 1912. — Beitrage zur Keuntnis der Mermithiden.

Diss. Heidelberg. 92 pp., 4 pis., .5.5 figs. Also in Zool.

.Jahrb., Abt. Syst. v. 32: 521-612.
HetiierinCiTON, D. O. 1923. — Comparative studies on certain

features of nematodes and their significance. 111. Biol.

Monog. V. 8(.2): 1-62, pis. 1-4, figs. 1-47.
Hirschi-er, J. 1910. — Cytologische Untersuclmngen an As-

eariden-Zellen. Bull. Internat. Akad. Sc. Cracovie. Math.

& Nat., s. B. (7B): 638-645.
T.MMiNCK, B. D. C. M. 1924. — On the microscopical anatomy

of the digestive system of Stronffi/liix edentatits Looss.

Arch. Anat. v. 3(4-6): 281-326, fig's.' 1-46.
.Jacoks, L., & Chitwood, B. G. 1937. — A preliminary note on

"rhabditin" sphaerocrystalloids. Proc. Helm. Soc.

Wash. V. 4(2) : 60.
Jaegerskioeld, L. a. 1893. — Bidrag till kannedonien om

Nematoderna. Diss. 86 pp., .5 pis. Stockholm.

1894. — Beitrage zur Keuntnis der Nematodcn. Zool.

Jahrb., Abt. Anat. v. 7(3): 449-532, pis. 24-28.

1901. — Weitere Beitrage zur Kenutnis der Nematoden.

K. VetenskapsAkad. Handl. v. 35(2): 1-80, pis. 1-6.
.Ianow.ski, .J. 1930. — Vacuome appareil de Golgi et mitochon-

drics dans les cellules epitheliales de I'intestin moyen

chez Ascaris m((ialoccfhaki. Compt. Rend. Soc. Biol. v.

104: 1092-1093, figs. 1-3.
.To.sEPH, H. 1903. — Bcitriige zur Flimmerzellen und Centro-

somenfrage. Arb. Zool. Inst. Univ. Wien. v. 14(1): 1-80,

pis. 13, figs. 1-61.
Kkmnitz, G. von. 1912. — Die Morphologic des Stoffvvechsels

bei Ascaris liimbricoides. Arch. Zellforsch. v. 7(4): 463-

603, figs. A-,T, pis. 34-38.
Kudo, R., & HETiiERiNmx)N, D. C. 1922. — Notes on a niicro-

sporidian parasite of a nematode. J. Parasit. v. 8: 129-

132, figs. 1-30.
KuLMATYKi, W. ,T. 1922. — Bemerkungen iiber den Ban einiger

Zellen von Ascaris mcgalocephala mit besonderer Beriick-

sichtigung des sogenannten Chroniidi;ilnpparates. Arch.

Zellforsch. v. 16: 473-551, pis. 22-26, figs. 1-36.
Lee, Bolles. 1928. — Mierotomists' Vade Mecuni. 9 ed. Blakis

ton, New York.
LiEVRE, II. 1934. — A propos de I'hematophagie des Ascaris.

(V)mpt. Rend. Soc. Biol. Paris, v. 116: 1079.
Looss, A. 1895. — Stronijylus subtilis, n. sp., ein bischer un-

bekannter Parasit des Menschen in Egypten. Centrabl.

Bakf. I). 18(6): 161-169, figs. 1-8.

1901 (1902).~Thc Sclerostomidae of horses and don-
keys in Egypt. Rec. Egypt. Govt. School. Med. :25-139,

pis. 1-13, figs. 1-172.

1905. — The anatomy and life history of Agchi/Uislnma

(luodcnalc. Rec. Kgypt. Govt. School Med., v. 3 : 1-58,

pis. 1-9, figs. 1-100, jiiiotos 1-6.
LiJCKER, .T. T. 1934. — The niorpliology and develoi)ment of

the preparasitis larvae of Ptilrriuslomiim ratzii. .1. Wash.

Acad. Sc. V. 24(7): 302-310, figs. 112.

1935. — The morphology and development of the in

fective larvae of Cylicodirntophnriis iili ra)ic1iiiiis (Ihle).

J. Parasit. v. 21(5)': 381-385. figs. 13.

1936. — Comparative morplujlogv :ind development of

infective larvae of some horse strongvles. I'roc. Helm. Soc.

Wash. V. 3(1): 2225. fig. 9.

1938. — Description and differentiation of infective

larvae of three species of horse strongvles. Proc. Helm.

Soc. Wash., V. 5(1): 1-5, figs. 1-2.
LuKJANOw, S. W. 1888. — Notizen iiber das Darmepithel bei

Ascaris mystax. Arch. Mikr. Anat. v. 31: 293-302.
Mackin, J. G. 1936. — Studies on the morphology and life his-
tory of nematodes in the genus Spironoura. Univ. 111.

Bull., V. 33(52), III. Biol. Monogr. v. 14(3): 1-64, pis. 1-6.
Magath, T. B. 1919. — CamaUaniis amcricaniis nov. spec. Tr.

Am. Micr. Soc. v. 38(2): 49-170, figs. A-Q, pis. 7-16, figs.

1-134.
Man, J. G. de. 1884. — Die frei in der reinen Erde und im

siissen Wasser lebenden Nematoden der niederlandischen

Fauna. Leiden. 206 pp., 34 pis. 145 figs.

1904. — Nematodes libres. Resultats du Voyage du

S. Y. Belgica. Anvers. 51 pp., 11 pis.
JlARTlNl, E. 1903. — Ueber Furchung und (iastrulation bei

('nciiUaniis elcgans Zed. Ztschr. Wiss. Zool. v. 74(4) : 501-

556, pis. 26-28.

1916. — Die Anatomie der Oxyuris cnrvula. Ztschr.

Wiss. Zool. v. 116: 137-534, figs. 1-121, pis. 6-20.
Maupas, E. 1900. — Modes et formes de reproduction des

nematodes. Arch. Zool. Exper. & Gen. 3. s., v. 8: 461-624,

pis. 16-26.
Meissner, G. 1853. — Beitrage zur Anatomic und Physiologic

von Mermis albicans. Ztschr. Wiss. Zool. v. 5(2-3): 207-

284, pis. 11-15, figs. 1-55.

1856. — Beitrage zur Anatomic und Physiologic der

Gordiaceen. Ztschr. Wiss. Zool. v. 7: 1-140, pis. 1-7.
MicoLETZKT, H. 1922. — Die freilebenden Erd-Nematoden.

Arch. Naturg. v. 87 (1921) Abt. A. (8): 79-91, fig.s. G-P.
Quack, M. 1913. — Ueber den feineren Ban der Mitteldarm-

zellen einiger Nematoden. Diss. Heidelberg. 50 pp., 3

pis. Al.so in Arch. Zellforsch. v. 11(1): 1-50, figs. a-L,

pis. 1-3, figs. 1-36, 1-18.
Rauther, M. 1906. — Beitrage zur Keuntnis von Mermis al-
bicans v. Sieb. Diss. Jena, 76 pp., pis. I -3, figs. 1-25.

1907. — Ueber den Bau des Oesophagus und die Loka-

lisation der Nierenfunktion bei freilebenden Nematoden.

Zool. .Tahrb. Abt. Anat. v. 23(4) : 703-740, pi. 38, figs. 1-9.
1909. — Morphologic und Verwandtschaftsbeziehungen

der Nematoden. P>geb. & Forstschr. Zool. v. 1(3): 491-

596, figs. 1-21.
Ro.MEis, B. 1913. — Ueber Plastosomen und andere Zellstruk-

turen in den Uterus, Darm, und Mu.skelzellen von Ascaris

incqaloccpliahi. Anat. Anz. v. 44 (11-12): 1-14, 1 pi., figs.

1-11.
ScHRPOTiEPP, A. 1908. — Die Desmoscoleci<len. Ztschr. Wiss.

Zool. V. 90: 181-204, pis. 8-10.
Schneider, A. 1860. — Bemerkungen iiber Mirmis. Arch.

Anat., Physiol. &. Wiss. Med. pp. 243 252, pi. 6, figs. 1318.
1866. — Monograi>lne der Nematoden. 357 p])., 122

figs., 28 pis. Berlin.
SrnNElDEK, K. 1902. — Lehrbuch der vergleicheuden histologic

der Tiere. i»8S pj)., 691 figs. Jena.
Stepan.ski, W. 1916. — Die freilebenden Nematoden des Inn,

ihre Verbreitung und Svstematik. Zool. .\nz. v. 46

(12-13) : 363-385, figs. 14.
Steiner, G. 1933. — Sonu> nuir|ihological and jihysiological

characters of the niermithids in their relationshii) to para-
sitism. J. Parasit. v. 19 (3) : 249-2.50.
Strassen, O. zur. 1904. — Anihraconcma, eine neue Gattung

freilebender Nematoden. Zool. Jahrb. Suppl. 7, Festschr.

z. 70. Geburtst. A. Weisnuinn, pp. 301-346, figs. .\-J, pis.

15-16, figs. 1-9.
Taylor, A. L. 1936. — The genera ;iu(l speci<'s of the Cricone-

matinae, a subfamily of the Auguillulinidae (Nematoda).

Tr. Am. Micr. Soe. v. 55(4): 391-421, figs. 1-63.
Tornquiwt, N. 1931. — Die Nematodenfamilien Cuculhmidae

und (';im;ill:inidae. Goteborgs K. Vetensk. — o. Vitterhets

— Samh. Handl., 5. f., s. B, v. 2 (3) 441 pp., pis. 1-17.
TfuK, F. 1903. — Ueber einigc ini Golf von Xeapel frei Ie

bende Nematoden Diss. Ixnpzig. Also in Mitth. a. d.

Zool. Stat, zu Neapel v. 16: 281-348, pis. 10-11.
ViGNON, P. 1901. — Recherches de cytologic generale sur les

epitheliums. Arch. Zool. fixper. & Gen. 3. s., v. 9: 371-

715, figs. 1-6, i)ls. 15-25.
Wktzel, R. 1931.— On the differentiation of the third stage

h'lrva of Slriinoiiliis ((jiiiniis, S. rih nialiis, :ind S. vulgaris.

J. Parasit. v. 'l'7(4): 235.

112

CHAPTER VIII

THE POSTERIOR GUT
(STRUCTURES OF THE PROCTODEUM)

Till' oxistoiU'O of :i riiiniilcti' diKostive tract tciiiunati'd l)v
HH aims and of separate sexes was diseovered b.v Tyson (1683)
in Axiuiris; lie probably observed tlie spicules also hut was un-
able to interpret tlieni correctly. Soon afterwards it was estab-
lished that the intestine of the female connects by means of a
valve or siiliincter with the |iosterior gut (rectum) and thence
with the outside through a ventrally situate<l anus. With one
exception, the female reproductive system never connects with
the rectum; in the genus Iliiiuiiniin TritrassDx, lilLMI (Atrac-
tidac) the vagina joins the rectum (Fig. lOSL) to form a cloa-
ca. This condition is api)roaclied in several other forms particu
larly Aonirusi oflilc (= .(. siibvloatiis Christie, lO.'?!, Thelasto-
niatidae) and Eustroniiiiliilcs tricolor Sugimoto, U)31 (Diocto-
phynuifidae"! but an internal .junction of vagina and cloaca
exists only in Hoiiddiiia. In the male, the reproductive system
always joins the rectum, forming a cloaca from the walls of
which various copulatory structures develop. Since there is
usually a definitely elongate tail, the anus or cloacal opening
is ventral. In exceptional groups characterized by the absence
of a tail, such as the Trichuroidea and I)ioetoi>hyuuit(>idea and
in scattered representatives of other groups the anus or cloacal
opening may be terminal or subterminal. Male strongylins can
hardly be placeil in this category since the dorsal ray repre-
sents the tail and the iicnital cone is developmentally a ventral
outgrowth of the cloacal lips. The intestino-rectal valve, cloaca,
spicules, gubernacuhini and telamon are all included under
the general heading of posterior gut since, with the exception
of the intestino-rectal valve, they are wholly formations of the
proctodeum. The valve is quite diverse, formed sometimes
chiefly, sometimes entirely from endodermal tissue, but in all
instances it functions as a part of the rectum. Other structures
are essentially modifications of the rectum and will be dis
cussed from that standpoint.

A. RECTITM, INTESTINO-RECTAL VALVE AND
RECTAL GLANDS

The rectum is a more or less flattened, subtriangular or irreg-
ular tube lined internally by a cuticular layer underneath
which there is a layer of large epithelial cells, and covered ex-
ternally by mesenterial and muscle tissue. Leuckart (1876)
was under the impression that the cuticular layer of the rectum
was continuous not only with the external cuticle but also with
the bacillary layer of the intestine. Voltzenlogel (i;t02) found
Leuckart to be in error regarding the latter connection. The
cuticular lining of the rectum ends slightly posterior to the
junction of mesenteron and proctodeum leaving the rectum
naked for a short distance. Though Voltzenlogel made this
observation on Ascaris it was confirmed by Martini (1916) for
Oj-i/iiris and the writers for such diverse forms as Metoncholai-
mns, CrphahibeUus, Dioctophjima and Trichiiris (Oncholaimi-
dae, Thelastoniatidae, Dioctophymatidae, and Trichuridae, re-
spectively). All investigators have found the rectal cuticle to be
continuous with the external cuticle. It is knowai to be cast off
at the molt with the remainder of the e.xuvium. Voltzenlogel
and Martini both ob.served that the fiber layers and striation
of the external cuticle cease at the inner side of the anal lips;
farther inward the rectal lining consists of cortical, matrix
and basal layers (see p. 30). However, there is considerable
thickening of the first two layers in most parasitic nenias.

It is impractical to discuss the rectal epithelium without
first considerng the rectal glands since there has been much
confusion in interpretation. Walter (1856) was supposed by
Bastian (1866) to have first seen the large cells at the junc-
tion of the intestine and rectum in Cosmocerca trispinosa
(Oj-l/iiriii ornala) and to have mislabeled them nerve cells. Ac-
tually Walter was entirely correct; the structures he illustrated
were the paired preanal ventral ganglia. Shortly thereafter
Claparede illustrated the cells now known as rectal glands in
"Ascaris commutata" and "A. miicronatd" labeling them
anal glands. Since that time similar structures have been re-
ported from many parasitic nematodes, l^berth (1860, 1863) il-
lustrated "anal glands" in Ilcleralis vcsiciilaris, Draschia
megastnma, and Passaliinis ambifiuns ; Macalister (1865) men-
tioned thom in Atractis dactyhira and was the first to suggest

that they might be liomologues of the Mjalpighian tubules of
insects; Hastian (1865) described anal glands in Anticoma
si)p., Linhomoriis, Ilalichoanolaimiis, and Cijntholaimus ; Biit
schli (1873) described anal glands in Khabditis aspcra :
Leuckart (1876) mentioned six anal glands in Anciihistuma ;
de Man (]88(i) described various cells .-iround the rectum in
Enoplus, Onrhohiiinus, and Anticoma as anal glands; Hesse
(1802) working on Parnscaris interpreted the large cells as
"Gewebepolster" cells; Augstein (18!t4) observed anal glands
in Dictjiocaidiis filaria; Shijiley (18SI4) described anal glands
in Toxascaris Iransfiii/n but later (1897) presumed them to be
identical with the giant " biischelformige Organo" ((.'oelomocy-
tes, see p. 45); Jagerskiiild (1893, 1894) described anal glands
and a unicellular sphincter muscle in Contracacciim clavatiim:
Ilamann (1895) gave a very good description of both rectal
glands and rectal epithelium in Gocsia (Anisakinae) ; Ehlers
(1899) and .lerke (1901) mentioned rect.-il glands in Oxiiuris
f(;«i; Looss (1901) described cells forming a " rectal ligament "
in members of the Strongylidae considering the whole group
of cells in this region as being non-glandular; Voltzenlogel
(1902) gave an excellent description of the rect.al glands, rectal
epithelium, etc., of Ascaris; Looss (1905) denied the existence
of recta! glands in Ancylostoma and interpreted these cells as
part of a "rectal ligament" which view was concurred in by
Imminck (1924) working on SIrongybis, Tornf|uist (1931)
working on CiiciiUanns and Camallaniis and Mackin (1936)
studying Spironoiira ; Martini (1916) published thorough de-
scriptions of the rectal glands, epithelium and musculature of
0.ryuris; finally Magath (1919) considered the rectal glands as
sarcoplasm of the sphincter muscle.

Controversy over the function of cells of the rectal region
has confused the picture, especially since some workers deny
the existence of fun(?tiona! glands opening into the rectum.
Recently the writers (1930, 1931, 1933) observed the orifices of
such glands into the rectum in Kliabilitis, Hetcrakis, Macracis,
Cephatobclhis, and Eystrifinatliiis (Rhabditidae, Heterakidae,
Oxyuridae and Thelastoniatidae respectively) and similar gland
orifices were reported by Baker (1936) for Hetcrakis. It does
not, however, necessarily follow that all of the structures in
the past termed glands are homologous with the structures de-
scribed by the above mentioned authors. As will be seen later,
rectal glands are by no means a universal feature in nematodes.
However, it is considered certain that the structures described
by Jager.skiold, Hamann, Voltzenlogel and Martini are rectal
glands.

Hamann reports that the rectal epithelium of Goesia is
composed of two pairs of cells, one pair anterior and one pair
posterior to the rectal glands (Fig. 108J). In Ascaris, Volt-
zenlogel found four large epithelial cells forming an anterior
circle (Fig. 1081) and additional cells posterior to them but
the latter were not constant in position. In Oxynris Martini
describes the rectal epithelium as composed of seven cells, an
anterior ring of three, (one dorsal and two subventral) and
two pairs of cells arranged in tandem posterior to the first
group (Fig. 109W-X). In females of Goczia, Ascaris, and
Oxyiiris there are three rectal glands projecting into the body
cavity and having processes which penetrate the rectal epitheli-
um. Voltzenlogel was the first to show that there is sexual di-
morphism in the number of rectal glands; he reported six rectal
glands for male ascarids; Martini later found the same number
in males of Oxyiiris.

Confusion in regard to the structures has been due to two
factors; the rectal glands may be embedded in the lateral and
dorsal chords or they may be associated with the vas deferens.
Thus Mackin described tlie rectum of Spironoiira as composed
of 10 cells in the female, three forming a "rectal ligament,"
and 14 in the male, two in a dorsal "ligament," two in a
"genital ligament," and one in each of two ligaments extend-
ing to the lateral chords. All of the cells designated "ligament
cells" liy Mackin are rectal glands; those of the "genital
ligament" are embedded in the wall of the vas deferens but
have separate orifices into the rectum (Fig. IIOMM). The
"small ej.'iculatory glands" described by Chifwood (1930,
1931) in h'liabihlis (Fig. 3, ej 2) Mnrinris and UrtrraVis and

113

A-D-DinctopI„jma renale (A-Cross section through ^posterior pan"' l:;-™^,,,^-'^'^ orrtract" r°'„m^^^^^^

A-D—Dioctophuma renaU (A— ijross secuou ^'"""s.. i"--- ■"• .-_ p„ithelium and protractor muscle; u— L.ross seiv.
o£ male showing spicular pouch, mtest.no and vas deferens B ^^"^«",'^,'"„ junction of rectum and vas deferen

Cross section through cloaca and spicule near its entrance into

s). E-P — Tripyla

114

by Baker (1936) in Iliteraki.i' :ir.' ;ilsn rectal glaiuls ami
0(irresiio7id to the cells (if the "(;<'nit:il litjniTiciit " ilescriheil by
Mackiii.

From these observatidiis, it aiipears that three rectal tjlanils
in the female ami six in the male is the rule for nu-nibers of
the Hhabilitoiilea ami Ascariilina and for at least sonic members
of the Si)iriiroidea. However, rectal Khinds appear to be totally
absent in tlie Tylenchoidea. The rectal ligament cells described
by Looss and Imminck for stronKyloids are in part rectal
glands. Such glands occur in representatives of all suborders
of the Phasniidia but appear to be absi'nt in a few isolated
types and gronps such as Ihaciiiiciihis, l)ir(ifihiii<i and tylen-
choids. I'erliaiis the absence of rectal glands in these forms
will be explained in the future on physiological grounds when
their function becomes known.

In the Aphasmidia no single case has thus far been definitely
established of the existence of rectal glands. Tlxiugh men-
tioned by Kberth USfiH), Bastian (lS(!."i) ami de .Man (1H86)
it is notable that no later mention was made of such glands
by de Man (liHH") nor by Jiigerskiold (li)01). The best sub-
stantiated record of such occurrence is in Enoplus cnmmunis
as illustrated by de JIan (ISSi!). The writers have been able
to identify the numerous cells shown by that author as at-
tached to the rectum but all appear to be sejiarated from the
rectal lumen liy the cuticular rectal lining (Fig. 108 BB).
This is in sharp contrast to the established cases such as
Spironoiira and Ilvtiral-is (Fig. lOSN, 110 Y & MM) in which
there is a distinct break in the cuticle at the level of each gland
orifice. It is concluded that in Fnopliis communis the cells in
question are merely epithelial cells. Careful study of Ci/licolai-
miix and Thoracostoma by Jiigerskiold (1901) and Tiirk
(1903), of Trichurishy Rauther (1909, 1918), of Mrloncholai-
mii.i, Li'plosomatnm. Tripijla. Prionchidiis, Dioctoplnima, Soho-
Uphymc, Aphanolaimus, JJalichoiinolaimus, Paracanthonchits
and Dnri/Inimnpsis by the writers f;iiled to reveal rectal glands
in a single case. In Anaplcctiif: urnniihtsiis. female totomount
specimens apjiear to show three rectal glanils but we have not
been able to verify the point in sections. Pending further
proof it is concluded that aphasmidians are usually without
rectal glands. In the male of Dornlaimii.t prolificus (Fig. 21)
there is a group of four pairs of cells near the anterior end
of the prerectum which appear to be glandular; in living
specimens one may trace a slender tube leading from each cell
posteriad nearly to the intestine rectal valve where each tube

*In Hfteraki.'i galUnae one finds si.x additional smaller cells in the
body cavity, a dorsal pair, one situated on each side nf and between
tlielarje pair of tandem dorsal rectal glands (Fig. 108, N P). and
two subventral pairs, one situated nn each side of each of the large
ventral rectal glands (Fig. 108 P, R). These cells seem to have ducts
into the cells to which they are attached. They may conceivably be
subsidiary rectal glands. Increase in rectal gland luimher from Ihree
to six and possibly to 12 seems to support the view of Macalister that
they are homologues of the malpighian tubules of insects. Martini
(191.11 aptly indicated the unicellular rectal glands of nematodes as
precursors of the groups of unicellular glands of Mnrrohiotufi which
in ttiTn are undoubtedly forerunners of the multicellular tubular glands
of other tardigrades. These last mentioned are. in turn, considered as
identical with the malpighian tubules of insects. Tliis view, though
questioned by Seurat (1920) seems logical in view of the fact that
multicellular tubular glands normally, in evolution, arise by reduplica-
tion of associated unicellular glands with common acini.

papiUata (E — Cross section of male in region of cloaca and spicular
pouches; F — Longitudinal section in same region). G — Pnrascaris
f quorum (Longitudinal section through proximal end of spicule show-
ing spicular cells). H — Asrnris liimhrirnule-^ (Longitudinal section
through caudal region of male). I — Parasrariji equorum (Longitudi-
nal section through caudal region of male). J — (ioezia ^annulata
(Longitudinal section through caudal region of female). K — Paras-
carts equnruw (Cross section of tnale anterior to intestino-rectal
valve). L — Rondonia rnndoni (Lateral view showing vagina open-
ing into rectum). Jl-R — Heterakis ffrillhuie ( .\11 illustrations of
male. M — .\t level of intestino-rectal valve; N — At level or rectal
gland orifices: O — .\t level of preanal sucker; P — Reconstruction of
cloacal region: Longitudinal section at intestino-rectal viilvc showing,
sphincter muscle, double dorsal gland and secondary dorsal gland;
R — Cross section considerably anterior to intestino-rectal valve show-
ing paired subventral glands and their accompanying cells, secondary
glands). .S-V — Lpptnsomatum elonpntum v. acephnlntum (S-^Intes-
tino-rectal valve, inner cells are intestinal; T — Section following S:
U — Rectum showing epithelial cells: V — Preadult male showing spicu-
lar primordia). W — Doriilnimns stapnulis (Cross section showing
rectum of female). X-7,—3Ielo>u-holaimus prisliurus (X — Cross sec-
tion of male at level of infestino-rertal valve: Y — Cross section of
cloacal region of male showing spicules and gubernaculum : Z —
Longitudinal section of female: there is no evidence of rectal glands
or a break- in the rectal cuticle such as one would expect in that
case). A.\ — EnniKtoiinna amerirnnit (Cross sex-tion of male at
cloacal opening). BB-JJ — EnopJiis rmnmunis v. m^ridionnlis (BB —
Longitudinal section of female in rectal region, as in Z, there is no
evidence of rectal glands: CC — Cross section of preadult male show-
ing primordia of spicules and gubernacular crura; DD-JJ — Serial
sections through cloacal region of male, beginning postanal and going
anteriad. some sections omitted between most anterior sections).
G-I & K, after Voltzenlogel, 1902, Zool. Jahrb., Abt. Anat., v. 16;
J. after Hamann, 1895, Die Nemathelminthen v. 2: L, after Baylis,
1936, Ann. & Nat, Hist. s. 10, v. 17; remainder original.

turns veiitr:id :inil ilisappears between the vas deferens and the
intestine; the homologues of the above mentioned cells are not
know II.

The iiilestino-rectiil valve is a very simple structure, con-
sisting, in oligocytous forms such as Ulinhililis, of the poste-
rior p:irls of the jirerectal intestinal cells surrounded by a
sphincter muscle. In iiolycytous and myriocytous nematodes
the intestin.il cells in the valve region become much smaller,
more numerous, and ;ire often devoid of a bacillary layer. They
may form a valve either by rcHexure into the intestinal lumen
or "ext<>nsion into the rectal lumen (Fig. IIISQ ic 109W).

The niusciilature controlling the intestino rectal valve, rec-
tum, and amis has already bei-n brietly discussed (ii. 43). The
existence of a uninucleate sphincter muscle was first made
known by .liigerskiold (18!»3, 1S94) and Cilson and I'antcl
(1894). Later workers have often confused other structures
with the siiliincter and described sphincter muscles with two,
four or more nuclei (Magath, 1919, in CamallanHs, and Chit-
wood, 19.'il, in M(irriicix). Reexamination of representatives
of all groups of the Nemiitoda by the writers establishes tlie
unicellul;ir sphincter as universally present. It is a circular
band of libers containing a single nucleus which may be dorsal,
ventr:il, or lateral in jiosition. Its innervation jirocess I'xtends
anteriorly to the dorsal nerve in Ascarix according to Volt-
zenlogel. This muscle closes the intestino rectal valve jireventing
reentry of materials from the rectum into the intestine during
defecation.

The dejire.ssor ani, an II shajied muscle, is likewise unicellu-
lar and of universal occurrence. It is this muscle that elevates
the dors.-il wall of the rectum causing materials to be drawn
into the rectal cavity; it then elevates the )Kisterior lip of the
anus tlius permitting defecation. The rectum is devoid of circu-
lar muscles and for the most ]iart defecation is accomplished
by pressure. Subventral and subdorsal somato-intestinal mus-
cles (Fig. .")2) probably supply the pressure by dilating the
prcrectal lumen, thus drawing materials into that region from
the mid-region of the intestine and forcing them into the
rectum by relaxing at the same time that the rectal sphincter
relaxes and the anterior part of the depressor ani contracts;
by such means the rectal cavity is filled. Thereafter the rectal
sphincter contracts, the anterior part of the depressor ani re-
laxes and the posterior part contracts; pressure on the walls
of the distended rectum by the body tiuid causes it to collapse
and the waste products to be forced out.

B. CLOACA

The vas deferens enters the rectum from the ventral side in
males of all groups with the sole exception of the Trichuroidea.
In trichuroids Rauther (1909, 1918) found that the vas def-
erens enters the rectum dorsolaterally (Fig. 110 Z-DD). In
phasmidians the .junction of vas deferens with hind gut is
nearly simultaneous with or immediately posterior to the
intestino-rectal valve so that practically no rectum exists;
the whole of the hind gut is tlien transformed into cloaca. In
some aphasmidians, particularly enoploids, the vas deferens
is apt to .ioin the rectum somewhat more posteriad so that
both a rectum and a cloaca may coexist.

C. SPICULAR POUCH

With few exceptions, which will be discussed later, the
spicules enter the cloaca from the dorsal side immediately an-
terior to the anus. They develop in a pair of cell masses, the
spicular primordia, which develop as proliferations of the dor-
sal wall of the cloaca, first described correctly by Seurat (1920)
in Falcaiixtra himbilirnxix (Fig. ] 10 00). Schneider assumed
the presence of a single primordium in nematodes with two
spicules but this is incorrect. Previous to the formation of the
spicules the primordia arc without a lumen, as may be seen in
Enoplux (Fig. 108 CC), but later developmental phases in-
dicate that the spicuhir primordia should be interpreted as
instances of suppressed evagination followed by terminal in-
vagination. The primordia become differentiated in such a
manner that they form a pouch which contains the spicules.
As shown by Voltzenlogel (1902) the pouch is lined with a
cuticle continuous with th;it of the cloaca. It is covered by an
epithelium which is also continuous with that of the cloaca.
When two spicules are jiresent, the paired spicular pouches
always .ioin before entering the cloaca. In parasitic nematodes
this pouch and the protractor muscles of the spicules form an
obvious s]iiciilar covering termed the sheath. In free-living
nematodes the spicular pouch is often extremely delicate* and
easily overlooked. Possibly for this reason Tiirk (1903) denied
the existence of a pouch in Thoracostoma where it had been
previously observed ;ind illustrated by Jiigerskiold (1901).

*The pouch wall and cuticle were inadvertently omitted in Fig. 49
E, L, M. They are delicate but nevertheless present in this form.

llj

Ftn. 1»»
IKi

It li;is lu'i'ii soon in ;ill t'ri'i' living m'iii;itiuli's .sliiilic'd b.v tlic
writrrs. The protrai'tor imisi'li's iif tlio spii'iiU's t'uiiii a cdiii
I)lt'ti' loiiKitiuliiial nuisi'lo layer on tlie surface (if the poueli in
most parasitie nematinles l)iit in free-livini; iieiiiateiles these
imiseles are iiiiire euiiiiiuiiilv eonliiieil tii tlie ilcirscihiteral sides.
The piiueli aiiil aeeenipanvint; iiuiseles are iiiiist ediispieiuiiis in
Tri/u/hi and Triiihincltiiun iif the free living nematodes and
(livi' an appearanee ( FiR. lO^b") whieli is peeiiliar to tliese
Ki'nera and their rehitives. In the Stnmn.vlina and Dieetiipby-
matina the spieuhir poueh eommonly Joins the eloaea sonu' dis-
tanee anterior to the anus and in the Triehuroidea tliis tendeiuy
is carried to an extreme (Fig. 110 PD). In otlier groujis of
nematodes the spicules can scarcely ever lie said to lie within
the cloaca even for a short distance; actually they niercdy pass
thr<iuf;li a common eloaeo-siiicular orifice. Mueller (lil:2."i) and
Chitwciod and Chitwood (I'.KiH) found the spicules of PrcilifituK
and Ct phaldhcUiiS to have a .sejiarate aperture iniineiliately
posterior t<i the cloacal oiiening.

The spieular pouch should under no circumstances Ije con
fused with the so-called spieular sheath of I'ricliiiris, which
was nanu'd the cirriin liy Kauther (190!l). It is a unique oc-
currence in the Nematoda tliat in Tricliiiri.i and relatives the
lining of the cloaca (cirrus) is itself everfilile anil often armed
with teeth (Fig. lOitL) ; this structure is capable of being
inserted with the spicule into the vagina during cojinlafion and
undoubtedl.v serves as a true jienis. It is in direct ccmtinuity
with the external cuticle ami when refracted there are three
layers (Fig. 110 AA) of cloacal lining. The feces must pass
through the cirrus for evacuation to take jilace.

1>. Sl'ICT'LKS

Nematodes usually have two spicules, each spicule being es-
sentially a tube covered by a sclerotized cuticle and containing
a central protoplasmic core. Its cuticular covering is continu-
ous with the cuticular lining of the spieular pouch and from
that standpoint the spicules may be regarded as evaginations
of the spieular pouch. The cuticle is often layered, the outer
layer (Fig. 109 CO being colorless and structureless while
the inner layer or layers arc tan to brownish and sometimes are
composed of numerous jirismoidal elements. In other cases the
spicules may ajijiear to be spongy or reticulated (Fig. 110 NN).
The prismoidal elements (Fig. lOSt CC) should not be confused
with the so called striation such as occurs in Stenunis (Fig.
.S3 K), Profo.itron.gylus (Fig. 110 EE), etc. Such striation is
due to the extension of the selcrotized ribs into a weak or non-
sclerotized flange. The central proto[ilasmic core of the spicule
may or may not contain the njclei of the spieular epithelium.
These cells and nuclei are often situated anterior to the proxi-
mal end of the spicules, surrounded by the retractor muscle.
Their number is variable, four being recorded in Ascaris (Fig.
108 G & K). Ordinarily one finds each spicule provided with
two retractor muscles and two jirotraetor muscles. Both pairs
of muscles are attached to the proximal end of the spicule.
The retractors extend anteriad and toward the lateral chord
wliere they may be attached to the body wall either sub-
dor.sally, dorsolaterally or ventrolaterally dependent upon the
species involved. The protractors tend to surround the spieu-
lar sheath and may be inserted postanally to the body wall or
to the dorsal side of the spieular pouch. In those groups in
which a single spicule is present, the retractor muscles extend
to both the right and the left body walls. In exceptional in-
stances the protractors and retractors are composed of numer-
ous cells which form a longitudinal muscle layer on the
.spieular pouch (Figs. lOS A, C & 110 DI) ) that is quite char-
acteristic of the groups involved (Triehuroidea and Dioctophy-
matoidea). As a rule each spicule may be divided into three

sections, the he:id ( (•.■ipitnhini ), shaft (calomus), and blade
(lamin:t). The lie.'id is the modified portion of the |iroxiiiial
end; the sliiifl is the tube like part between the head and the
blade; the blade is the dist.'il portion which is usually tlangi'd
(Fig. 110 DD lOK). Tlieie may be one or two tiaiiges: if one.
it is ventral as seen in cross section and if two, one is dorsal
and one ventral (Fig. 110 MM). Though such dilTerentiation
of the spicule into regions is the rule, no such regions are
apparent in Dioctoplnjma or Tiir)iiiri.i. Extensive iliversity oc-
curs in the sjiicular form.

Two is the basic number of spicules in neuuitodes and the.v
originate from a double spieular primordia as stated by .Seurat
(l!li;0). However a single spicule occurs in m.any groups of
nematodes. It is a characteristic of the Triehuroidea, Diocto
phyni.atoidea, Oxyuridae and Thelastomatidae •■ind also occurs
in isolated genera of tlie Desmoiloridae ( M iinopnHthia) , and
Mermithidae { Jl j/droincrmis) . In other groups it is not un
conim<in for tin* spicules to be dislall.v fused .and stages with
lu'arly conqilete fusi<in are known. Thus, in Ithubditi.'i strunfiii-
UudcK (Fig. 10i( EE, II-.I), R. ttrricola (Khabilitidae) and
Xi nialoiUrus axpitiosux (Triehostrongylidae) the distal ends
of the si)icules are fused. In the subfamily Ransomnematinae
of the Atraetidae, there is a complete series of stages in fusion,
including forms such as Canwi/a with two entirely separate
spicules. 111 III and Aiir/ra with nearly completely fused spic-
ules, and I'lilchroccphala with no siiicules. In the Mermithidae
there is a similar series from Mrrmit: with two sep.arate spic-
ules, to Paraini'rmis ilrf/an.s (Fig. lO'.l UK) with fiartially fuseil
spicules, and lljiilromirmis with a single sjiicule. (ienera and
species completely devoid of spicules are of sporadic occur-
rence but usu.-ill.v, if not always, such forms are confined to
groups characterized by a tendency toward spieular fusion or
presence of a single spicule. Tims we find TrichineUa of the
Triehuroidea, A.ipicidiiris, Dcrniatoxi/s and several but not all
species of Pharjingodon (all representatives of the Oxyuri-
dae), Uiistrinnnlhus of the Thelastomatidae and Piilchnicipltahi
of the Atraetidae characterized by the absence of spicules.
There have been two divergent views on the interpretation of
unpaired spicules. One group, led by Schneider (ISOO), main-
tains that it is a neotenie character resulting from a failure
of division of an originally unpaired spieular priniordium. As
has been previously noted, this view^ is based on the erroneous
assumption that in two-spicule nematodes the sjiicular prinior-
dium is originally single. Other authors have considcre<l the
single spicules as resulting from reduction by loss of one
spicule. In view of the .several series showing spieular fusion,
this theory seems hardly tenable. As Cobb (ISOS) iiointed
out, the retractor muscles of the single spicule fornij go to
both sides of the body wall, indicating the double character
of the spicule.

Diversities in spieular morphology are too numerous to be
covered completely. The general form is often quite diagnostic,
being used as generic and specific characters throughout the
Nematoda. Unfortunately the shapes vary so much and are
sometimes so complicated that one must rely chiefly on illus-
trations. Cobb (1S<I8) provided some descriptive terms which
might well be more widely applied (Fig. 109 NN). As a rule
the spicules of free living nematodes are equal and similar.
In parasitie nematodes, jiarticularly the various groups of the
■ Spiruroidea, Filarioidea, and some species of the Ileterakidae,
Cucullanidae, Camallanidae and Atraetidae the sjiicules are
unequal and dissimilar. Asymmetry in the form of the spic-
ules is given varying significance in the different groups. Usu-
ally the left spicule is longer than the right but in some forms
the converse is the case (Ileierakis galVinae) . The blade of
the longer s|)icule is generally alate (Fig. 109 T) and some-
times bears a distal hook. The shorter spicule is usually heav-

FlG. 109

A-C — HiiOHtronnithtu rubidrts (A — Lateral view of male tail: B —
ventral view; O — Detail of telanion, specimen cleared in phenol).
D-K — ^ff^ntun elegitns (D — Lateral view of male tail: E — tip of spic-
ules). F — Tetriiweres Ineriuiji (Full length of male, showing greatly
elongated left spicule). CJ — Oittprliipin rlrrmnrim'ta (Spicules and
eiihernaculuni) : H-,7 — XenuttatlirnM nutiinositx (H — Ventral view of
male tail, setaceous spicules distall.v fused: T & J — Lateral and ven-
tral view of spicule tips). K — Miirithidia fUphnsi (.Spicules). T>— -
TrirhnriM i-tit/ns (Tij) of cirrus and spicule). M-N — " Huhrimfnia"
sfiirnti (Tiyis of left and right spicules). O-I* — Cj/nthtilitiiinift orrt-
liitiiK (Spicules and gubernaculuiu) . Q-R — Parartitiflinnrhits raefus
(Spicules and gubernaculum) . S — Dfrnfilnria repenn (spicules). T —
OawiUdofilnrin sp. (Spicules). V — Trirlionlroniri/h" prnhnUnny

(Spicules and gubernaculum). V — Dicheilonptim horridmr (Ventral
view of male tail, reversed sides). W-X — Oxiinritt fqiii (\V — Longi-
tudinal section of female rectum: X — Dorsal view- of female rectum).
y-Z — Stpnunis mlnnr (Lateral and ventral views of male tail). A.\ —
Frolfptiifi ohtiiyiin (Reconstriicti'in of cloacal region of male). BB —
Hiliiiiii linuira (Spicules). ('(,' — Tricliuris lulpis (Tip of spicule af-

ter exposure to Faiieliild's trypsin). DD-EE — RhnhdiltK utrongiilnhhs
(Spicules, distall.v fused). FF — Ontrrlnffin trifidn (Spicules and
gubernaculum). CtJ-MM — Uiioittronfjiilu/t riibidiin (Serial sections
tlirough i-loacal region of male showing telamon. gubernaculum. spic-
\iles, spieular jiouch and cloaca). N'N — Various spieular shapes (1,
arcuate: 2, hamate; :i, arcuate distally: 4, falcate; .i. setaceou-s; 6,
sigmoid; 7. linear: S, fusiform: !l, elongate; 10. bent or boomerang
sbapcd; 1 1. cuneiform ; 12. Lsbaped). D-E, after Ilagmeier. 1912,
Zool. .lalirb.. Abt, Svst. v. ;i2 : F, after Seurat 191:'.. Bull. Sue. Nat.
Africjue Nord Alger "v. .'> : G, U & FF, after Kalantarian. 192S. Trud.v
(iosudarstv. Inst. Kksjier. .Moskva, v. ;") ; H-J. after Ra.iewska, 19:il.
Ztsilir Infekt. v. 40; K. after Wu, 19.14, Sinensia v. .5: M-N & V,
after Skriabin, 1917, I'arasit. v. 9: OR. after de Man. 1 SS9. Mem.
Soc. Zool'. France, v. 2: \V X. after Martini. 191(i. Ztscbr. Wiss.
'/....I « nw: . v.'/ ..ft...' UiivHc :itwl Diiuhnev 192.T Parasit.

Zool

<[.ooi. V. 10(i: YZ, after Riivlis iiud Daubne.v. 192.5. Parasit.
v 17: AA, after ,1. F. .Mueller, 192.5. .1. Parasit. v. 12; BB. after
Raiew9l;a.ia. 192S, Die Setarien etc.; NN, after Cobb, 1898. Misc.
I'ubl. No. 2 1.1, Dept. Agrir. N. S. Wales; remainder original.

117

ior and nfton ti'iniinatt's in a massive liook (Fig. 100 M, N, T).

Wliilo oftiMi specific, the form of tlie spicules sometimes varies
anil more tlian one sjiecimen should ahvavs he studied. TIk'
writers found marked variation in spicular nuo plioloKv i"
ItirofiUiria immitin from an abnormal host (.nmskrat). In
addition to the normal type, a specimen in which the left
spicule blade was dcRenerate and another in which the left
spicule was absent were fouml in a sin^;le muskrnt. Such
tinilinf;s cause one to be scunewhat dubious of the numerous
species of filariids beinp; described at the present time, and
difTerentiated chiefly or wholly on diversity in spicular form.

Differences in spicular niori)hology of related s])ecies may
be due to the degree of ceidialation, length and differentiation
of the shaft, or length and character of the blade. The blade
may be highly twisted as in Dichcihincmn (Fig. 100 V);
twisting and irregularity of the blade is p.-irticularly character-
istic of scune genera of the Trichostrongylidae (Fig. B, II, FF).
In addition the blade may be distally branched (Fig. 100 A,
MM^ or the flanges se]iarafed from the tube.

The s|iicules are seldom very long in proportii.n to the body
in free living nematodes, one of the most outstan<ling excep-
tions to this rule being Miloiicholaimiis pri.ttiiini.i (Fig. 18)
in which the spicules are one-twentieth of the body length
(seven times as long as the anal body diameter). In parasitic
nematodes both the absolute and relative spicule lengths may
be many times greater. Thus, Wehr (103.3) found the two
equal sjiicules of Oilmitospinira cclinpenis (Spiruridae. Ha
bronematinae) to attain lengths of 1011 mm in specimens
If)- to 17 mm. Ransom (1004) found the left siiicule of
Go7ip;ilonrma infiluvicoltj to attain 17 to 10 mm in specimens
17 to 10 mm long (when retracted it twists and extends
through only three-fourths of the body length) ; in the same
form he found the riglit spicule to be only 0.1 mm long. Seu-
rat (1013) found that the left spicule of Trirameres inermin
reaches 1.187 mm in length and the right only O.Ol't mm in
specimens of a total length of 2.12.') mm (Fig. 100 V) . Long
spicules most commonly occur in representatives of the Spiru-
roidea, Filarioidea, Dioctophymatoidea, and Triehuroidea and
in those forms where the vagina is long and tubular. One
might attempt to correlate the length of the vagina with that
of the spicules were it not that one finds related species with
vaginae of about equal length and spicules relatively much
smaller.

E. gub?:rnaculum and telamon

The gubernaculum is by eommon definition a cuticular thick-
ening (selerotization) of the dorsal wall of the cloaca. This
definition is at once misleading. The gubernaculum is formed
from the wall of the spicular pouch. Proximally it is usuall.v
not in direct contact with the spicular cavity but is to be seen
as one or more plates in the wall of the spicular pouch; dis-
tally it may come to be the dorsal wall of the pouch or it may
pro.ieet free into the lumen (Fig. 110 U). The cuticle of the
gubernaculum, like that of the spicules, is in direct continxia-
tion with the pouch lining but unlike the spicules its sclero-
tized la.vers nia.v extend be.vond this covering internall.v. The
gubernaculum is essentially a plate in the groove of which the
spicules move. This condition is seen in many nematodes such
as Uliabditis (Fig. 40 L), Ancylostoma, etc. In others, how-
ever, the medial part of the plate may protrude into the spicu-
lar pouch separating the spicules. The posterior part of the
gubernaculum may then be termed the corpiix and the anterior
(medial) piece, the ciinciif:. Where this division occurs the
spicules are usually alate. In Spironoura (Fig. 110 A-U) the
gubernaculum divides near its proximal end giving off an
anterior branch (cuneus) which comes to lie free in the spicular
pouch; each dorsal spicular flange thus runs in a groove formed
by the cuneus and corpus of the gubernaculum.

Hall (lOUl) proposed the term tidamon for an "ornamental
su|iporting structure" formed in the ventral and lateral walls
of the cloaca of Ili/oxlronfiitliis rtibiiliis (Fig. 100 (!). This
structure differs from the gubernaculum and si)iculeH in stain-
ing capacity and is more like the external cuticle. As may be
seen from sc'ction (Fig. 100(;(i-M.M) Hall's interpretation as
to the origin of the telamon is correct. If is an immovable
sclerofized part of the doacal wall which apparently serves to
turn the spicules posteriorly when they are prolruiled from
the spicular pcjucdi into the cloaca; otherwise the spicules might
lireak through the ventral doacal wall. Ordinarily such a pro-
tective structure would be unnecessary since the spicular pouch
orifice is imnu'diately opposite the cloacal opening but in the
Sfrong.vlina this is not the case.

.Since Hall's original publication much confusion has resulted
from the applicafiijn of the terms gubernaculum and telamon,
Iiarf icularly in the Metastroug.vlidae. Camercui (1027) used
the term telamon for lateral iirofrusible branches (crura) of
the corpus which he described as "ornamental supiiorting
structures near the cloacal aperture'' (Fig. 110 FK.I.IJ.
Oebauer (1032) applied the term telamon to a medial ventral
selerotization of the spicular pouch (Fig. 110 EE) (the struc-
ture now known as the capitulum) and the term gubernaculum
to the unpaired and paired subdorsal sclerofizations of the
spicular pouch (corpus and crura). The structures involved
have been di.scussed by Shu 'Its, Orlov and Kutass (1033), and
by Dikmans (103.'>). A restudy of Priilo.ilronfmliis indicates
that the former authors correctly interpreted the entire com-
plex as a gubernaculum. The most important differentiation
between guliernaculum and telamon is that the IcUimon is
formed dirccllji from, the cloacal linini) while the fiubcrnacu-
hnn is formed from the spicular pouch. Though the guber-
naculum is primarily dorsal, it is also primarily medial, i. e.,
it may develop proximal to the union of the spicular pouches
and, as in Spironoura it ma.y be composed of two or nuire parts
which are heavily sclerotized, these parts being joined by
feebly sclerotized regions. Thus the medial (ventral) piece
(Fig. 110 RS) termed the telamon by Gebauer, is actually a
part of the gubernaculum named the capHuhim by Shu 'Its,
Orlov and Kutass: the two posteriorly directed pieces (crura)
termed the telamon by Cameron and the gubern.'icul\im by
Gebauer are joined anteriorly to the capitulum by the un-
paired piece, corpus (Fig. 110 S).

The confusion in terminology has led workers in other groups
to misapply the term telamon. Thus Steiner and Albin (1033)
termed the anterior parts of the gubernaculum (crura) of
Deontostoma caUfornicnm (Fig. 37, 4-5) a telamon. In so far
as the writers are aware, a true telamon does not exist outside
the Strongylina.

The gubernaculum is often complex in free-living nematodes
and the various jiarts are worthy of discussion. Do ilan (1880)
described the gubernaculum of Enoplus communis (Figs. 110
A, C-D) as being composed of three parts: an unpaired medial
piece (termed cuneus, projecting anteriorly into the cloacal
cavity between the spicules) to which is joined posteriorly and
laterally a less sclerotized structure (corpus) which in turn
has two strongly sclerotized lateral pieces (crura). These
lateral pieces jiroject into the cloacal cavity on each side of
the spicules, each of which moves in a separate groove between
cuneus and crura, guided posteriorly by the corpus. In other
aphasmidians many variations of the above described arrange-
ment are known to occur. In Acautlwiiclius liviparus (Fig.
15 M), and Paracanthonchus caeciis (Fig. 100 Q R) the ends
of the crura are dentate while in Ciiatliohiimiis clon-flatus they
are denticulate. There is a marked diversity in develojiment
of the parts in closely related forms. Thus de Man (1880)
found the crura to be quite massive and apjiarently detached
(cuneus and corpus absent) in Paracanthonchus caccus while

A-P — Spirnrtoitra nffine f Kathlaniidae] (Serial cross sections through
spicules and gubernaculum). Q-S — Protnslrnngiilus rupricnprae [Meta-
strongylidael (Q — Cross section of shaft, i.e., ralonuis, of spicule; R —
Cross sections of gubernaculum and blade, i.e., lamina of spicules) -
T-Y — Spironnura nffine (T — SpinOes and gubernaculum cleared in_ 10
per cent NaOH) ; U — Gubernaculum and spicular ala in longitudinal
section: V — Intestino-recta] valve and dorsal gland of female, longi-
tudinal section: W-Y — Sections of female through intestino-rcctal region
showing dorsal and subventral rectal glands and their orifices). Z —
Trickuris kuis (Cross section of male near cloacal opening). AA — T.
trichiura (Cross section near cloacal opening). BB — T. sui/t (Cross
section of cloaca with spicular pouch about to emerge from its walls:
according to Kauthcr more posteriorly the cloacal walls completely
surround the spicule forming a double layer). CC — 7'. siiiy (Recon-
struction of male tail: ac-cording to Rautlier the internal lining of the
cirrus is continuous with the cloacal lining anteriorly and is not the lin-
ing of the spicular pouch. The ut^per part of the cloaca has a double lin-
ing, the two layers fusing proximally). DD — T i^ulpi^ (Tail of male

cleared in phenol). EE — Protostrongylus auslrinrtm (Gubernaculum and
spicules labelled by Gebauer: correct terminology in parenthesis) . FF-HH
— Pmtttstrntii/iihis ritpricaproe (Gubernaculum in various views). II
— P. korlii (Gubernaculum): JJ — P. raillifli ( liubernaculum ) . KK —
P. leurkurti (Gubernaculum). LL — Cy:<toeuiitu.t ni{/rfsrt'n« (Guber-
naculum). ilM — Spironoura affine (Cross section of male at junction
of rectum and vas deferens showing orifices of dorsal, ordinarj- sub-
ventral and sccondan,- subventral rectal glands; cuticle is absent in
region of gland orifice). NN — Dirlyornulug Jilnria (Lateral view of
male tail showing spongy type of spicules). OH — Fiilcauslrn liimb-
dienniji (\'entral view of rectal region of prcadult nuile showing spicu-
lar primordia). Z. BB & CC, after Raulhcr 191 H. /.ool. Jahrb., Abt.
Anat. v. 40. AA, after Kauther. 1909, Ergeb. u. Fortschr. Zool. v. 1;
EE-HII. after (icbauer, 1932. Ztschr. Parasitenk. v. 4: Il-I.b. after
Schulz. drlov & Kutass, 1933, Zool. Anz. v. 102; NN', after Yorke
& Maplestone, I92(i Nematode Parasites of Vertebrates^ 0(
.Seurat, 1920, Hist. Xat. Nernat. Berberie: remainder original.

119

in Ci/atholdimiis ocellatiis he found tlie cuneus-corpns (Fig.
109 OP) extremely large, the crura considerably smaller and
in addition he found a small anterior ventral piece (capitulum).
In the latter species the spicules are guided anteriorly, pos-
teriorly, medially and laterally. In other forms such as Syrin-
golaimus striatocaitdatiis (Pig. Ill E) and Anoplnstoma vivi-
panim, de Man (1888, 1907) described well developed
grooved crura accompanied by a weak corpus and in these eases
each spicule moves in a groove of the corresponding crura.
In Thrristiis iHiniiiiiKlicd (Fig. Ill F-G) the gubernaculum
appears to surround the spicules, and de Man (1890) found it
to be scarcely differentiated into separate parts, but tlie medial
region pro.iects as a cuneus between tlie spicules and the lat-
eral parts partially surround the spicules and serve as crura.
In SphacrolaimiiK hirsiiliis (Fig. Ill HI) the same author
found a gubernaculum much like that of Theristtis but a capit-
ulum in addition. Another type of variation, particularly
characteristic of the Axonolaimidae and Linhomoeinae, though
sometimes occurring in other groups, is due to the presence of
two posterior prolongations of the corpus, termed the apophy-
ses. In Tcrschellinpia lonf/icauilnla the spicules are separated
by a distinct cuneus and held in position laterally by flanges
of the corpus, no distinct crura being present, while in Metalhi-
homneus typiciis (Fig. Ill J-K) capitulum, cuneus, crura, cor-
pus, and apophyses may all be distinguished.

The musculature of the gubernaculum has been previously
described (p. 43) but the origin and insertion of the various
muscles is not as limited as previously indicated. The guber-
naculum often behaves as though hinged at the .junction of
the spicular pouch and cloaca. Muscles (protractor gubernac-
uli) attached to the proximal ends of the gubernaeular corpus,
crura or the distal ends of the apophyses extend posteriorly to
the ventral body wall and their contraction moves the distal
ends of the corpus, crura, and cuneus anteriorly, forcing the
spicules outward, their tips pushed anteriorly (into the fe
male). Muscles from the proximal ends of the crura in such
an instance (Enoplus) extend laterally and ventrally to the
body wall; their contraction moves the distal ends of the various
gubernaeular parts posteriorly withdrawing the spicules.

FUNCTION OF THE SPICULES

Thougli it was recognized by Schneider (1866, p. 244) that
the spicules are never hollow and that spermatozoa do not or-
dinarily flow "through them," the conception that they are
hollow and act as true intromittent organs has somehow per-
sisted. A locatory and excitatory function has been ascribed
to the spicules bv Schneider (1866), Biitschli (1872), Rauther
(1909, 1918, 19.30), Seurat (1920), Baylis (1929), Mueller
(19.30) and Chitwood & Chitwood (1933). On the other hand,
Looss (190.")) and zur Strasscn (1907) considered that the two
flanged spicules in AncyhisUima and Pliilonietra come together
in the form of a tube and that the sperm flows between them.
The transmission of sperm down the groove or between the
grooves of flanged spicules has been considered probable by
Mueller (1925), Baylis (1929) and Rauther (1930). In cases
where the spicule or spicules are devoid of flanges, their cross
section being practically circular throughout (Ascaris, Trichv-
ris, l)iocl(iphymn) there seems to be no conceivable way
by which they could "conduct the sperm." Regarding this
type of spicule, Mueller (1930) was of the opinion that they
are withdrawn during the period of sperm movement for he
found a copulating pair of Ascaris in which, upon section, the
spicules were found luif to be inserted. However, observations
of copulating nematodes in which the s|)icules have been seen
alternately inserted and withilrawu have been numerous and
Mueller's finding seems hardly significant. The spicules take
an active part in cojiul.'ition aiul we have merelv to define that
part.

In forms with flanged spicules, do the flanges ever form a
tube or groove by which the sperm pass to the female? Tube
formation by two spicules in forms such as SpiroiKiiira, Anvy-
Insfoma Jiiid PraUistronpyhis is undeniable. This tube is formed
by the orientation of the spicules by the gubernaculum (Fig.
110 A-T, 33K) while they are still in the spicul;ir jmuch.
There seems to be no way liy which the sperm could gain
entrance to this closed tube after it reaches the cloaca.

The spicules miglit more plausibly play the role of sperm
transmitters in forms where the spicules are dissimilar and
one of them is flanged or where the spicules are distally fused
with a median groove. Mueller (192.")) described such an in
stance in Prnlrphis in which he noted that the blade of the
left spicule had wide flanges forming a nearly complete tube
open proxinially as well as distally. He also found a cloaca-
spicular canal connecting the up]ier part of the cloaca with the
spieular pouch ,iust anterior to the beginning of the spicular

blade (Fig. 109 AA). Such a condition has been seen neither
before nor since. The writers can more easil.v think of flanges
as primarily for the purpose of increased rigidity and it is
conceivable that the flanges aid in keeping an open passage-
way into the vaginal lumen.

The movement of the spicules back and forth during co]uila-
tion would serve not only to keep the vulva and vagina open
but also, at least to some extent, would actually propel the
sperm into the female.* Branching of the spicular blade and
twisted spicula formation such as occurs in trichostrongyles
(Fig. 109 U, FF) would seem to be particularly adajited to
such activity. In forms with markedl.v unequal and ilissimilar
spicules it is notable that the vagina is always quite long and
tubular. Seurat (1920) advanced the view that in such sjiecies
the short spicule opens the lips of the vulva and the proximal
region of the vagina while the long spicule assures the progres-
sion of the sperm in the long vagina. It is true that the short
spicule usually has a large hook which would lie well adapted
as a holdfast.

The gubernacidum is, of course, primarily a spicular guide
and prevents the spicules from breaking through tlie wall of
the spieular pouch and cloaca when exerted. In such forms as
Tersehellingia, Enoptiis and Spironoiira it may also act as a
levator. Ordinarily the gubernaculum is not everted during

*Seurat states that the spicules are absolutely inuiiohile during copu-
lation but in living free-living nematodes such as Hhabditis the ivriters
have observed alternate withdrawal and insertion over extended periods.

Kiu. 1 1 1
A-C — KnopUm coiumvnis (A — Gubernaculum, ventral view; B —
spicule; C — gubernaculum). D — E. hrpviti (Gubernaculum and tips
of spicules). K — Syriniiolninius atr\atnea\idntus. F-G — Theristus nor-
jiiandica (Spicules and gubernaculum, lateral view, F and ventral
view, G). II-l — Sphat'tolaimtts hirsuliis (H — Detail of guhefnaculum
as seen in I). .J-K — ^fet(tUnhomo^'u.^< ti/picug (J — \'entral view; K —
lateral view). L-M — Anoplontoma vlripfinnn ( L — Ventral view; M —
detail of gubernaculum). A-D, after de Man, 1886, Nordsee Nema-
toden; E, after de Man, 1888, Mem. Soc. Zool. France, v. 1; F-G,
after de Man. 1890, Ibid., v. 3; H-M, after de Man, 1907. Ibid., v. 20.

120

i'ii|nil:itiuiL lull 111 tdrnis willi ilriil i(iil:iti' (ii- ili'iil:iti' riina sui-li
IIS ParacdnllKDirhiis iiiul CiHi/liohiiiiiiis (Fit;. l"i' OR) it woiilil
si'Oin tlint tlu'.v iii'f iidiiiiti'il for (;rippiii(; tlio vulvar lips and
liiililiiiK' IIh' vulva (i|icii.

Bibliography

Al.lcATA, J. 10. l!i;!." (IlCifi). Karl.v ilcvcli)iiiiu'iitnl staKos of

luniatoiU's (n'liiriiiif; in swine. I'. S. Dcpt. .Agrir. 'I'oili.

Bull. No. 4S!t, SKi pp., 30 (i)js.
AlHisTKiN, O. 18i>4. — Slroiii/iilKx lihtria \i. Diss, Leipzig. ■)4

pp., :; pis. Also in Aic-li. Naturg. 00 J., v. 1 l,;i): :2."i."i-

304, jils. 13 14.
H.\KKR, A. 1). 1!I3(). — Studies on Utterakis rialliiuic, i. nematode

parasite of fowls. Tr. Ro.v. ("aiiad. Inst., v. 20 (2): 1711

21"), V. 21 (1): "il-SG; figs. A (i, pis. 1 l.l, figs. 1-1()4.
B.\STIAN, 11. (". 18(i."i. — Monogia|)li on tlie Anguillulidae, or

free neinatoids, marine, land, and freshwater; witli de

scriptions of 100 new speeies. Tr. Linn. Soe. Loud., v. 2.')

(2) : 73-1S4. pis. <t-13, figs. 1-248.

18()(!. — On the anatomy and pliysioliigy of the lU'ina

toiils, parasitie and free; with observations on their zoo

logieal position, and affinities to the eeliiiiodiiiiis, I'liil.

Tr. Lond., v. ir)6: ;14."i-i;3S, pis. 22 2S.
Bayi,is, H. a. I!t29. — A manual of helmintlioloKy, iiiedieal and

veterinary. 303 pp., 200 figs. London.

1930. — The nematode genus Rotuloiiiti Travassos. Ann.

& Mag. Nat. Hist. s. 10, v. 17: 606-610, figs. 1-2.
Baylis, H. a. and Daubney, R. 192o. — A revision of the

lungworms of C'etacea. Parasit., v. 17 (2): 201 210, figs.

1 2.1.
Bl'KTSCHLl. O. 1872. Beobaehtungen iiber mehrere I'arasiteii.

Areh. Naturg. .1. 38, v. 1 (2): 234-24!!, pis. 8-<i.

1873. — Beitriige zur Kenntniss der freilebenden Xe-

niatoden. Nova Acta K. Leop.-C'ar. Akad. Naturf., Dres-
den, v. 36 (.">): 124 pp., pis. 17-27, figs. 1-69.
Cameron, T. W. M. 1927. — Studies on three new genera and

some little-known species of the nematode family Proto-

strongylidae Lciper, 192(). ,J. Helminth., v. 5 (1) : 1-24,

figs. 1-14.
CIUTWOOD, B. G. 1930. — Studies on some physiological func

tions and morphological characters of midhiliiis (Rhab

ditidae. Nematodes). J. Morph. & Phvsiol., v. 49 (1):

2.J1-27.5, figs. A-H, pis. 1-3, tigs. 1-24."

1931. — A comparative histological study of certain

nematodes. Ztschr. Morph. & Oekol., v. 23" (1/2): 237-

284, tigs. 1-23.
CiiiTWOOD, B. G. and Chitwood, M. B. 1933. — The histological

anatomy of Ccpliatohellus papiUiger Cobb, 1920. Ztschr.

Zellforseh., v. 19 (2): 309-355, figs. 1-34.
Christie, J. R. 1931. — Some nemic parasites (Oxyuridae) of

coleopterous larvae. J. Agric. Res., v. 42 (s") : 463-482,

figs. 1-14.
Ci.aparede, E. 18.')9. — De la formation et de la fecondation des

oeufs chez les vers nematodes. Mem. See. Phys. & PHst.

Nat. Geneve., v. 1.5 (1): 1-101, pis. 1-8.
Cobb, N. A. 1898. — Extract from MS. report on the parasites

of stock. Dept. Agric, Sydney, N. S. Wales. Misc. Publ.

No. 215, 02 pp., 129 figs.
Dikman.s, G. 1930. — Two new lungworms, Protostrongylus co-

burni n. sp., and Pneumostrongyhis alpe.nae n. sp., from

the deer, Odocoileits virqinianvs. in Michigan. Tr. Am.

Micr. Soc, V. 04 (2): 138-144, pl.s. 2o-26.
Eberth, C. J. 1860. — Zur Organisation von HeieraTcis vesicii-

laris. Wiirzburg Naturw. Ztschr., v. 1 : 41-60, pis. 2-4,

figs. 1-29.

1863. — Untersuchungen liber Neiiiatoden. 77 pp., 9

pis. Leipzig.
Ehlers, H. 1899. — Zur Kenntnis der .Vnatomie uiid Biologic

von Ojcj/uris ciirviila Rud. Diss. Marburg, 26 pp., 2 pis.,

20 figs.' Also in Arch. Naturg. 0.1 J., v. 1 (1): 1-26, pis.

1-2, figs. 1-20.
Gebauer, O. 1932. — Zur Kenntnis der Parasiteiifauna der

Genise. Ztschr. Parasit., v. 4 (2): 147-219, figs. 1-70.
GiLSON, G. and Pantel, J. 1894. — Sur quehiues cellules mus-

culaires de I'Ascaris. Anat. .-Vnz.. v. 9 (23): 724 727,

figs. 1-2.
(!i,.\.ue, H. 1910a. — Beitriige zu einer Mmiograidiie der Neina

todenspecies Ascaris felis und A.scaris caiii.i. Ztschr. Wiss.

Zool., V. 9.5 (4): 5.51.593, figs. 1-20.

1910b. — Beitriige zur Systeiiiatik iIit Ncni.-itinlcii. Zool,

Anz., V. 3.5: 744-759, figs. 1-5.
Haombier, a. 1912. — Beitriige zur Kenntnis der Merinitliidcn.

Diss. Heidelberg. 92 pp., 5 pis., 55 figs. Also in Zool.

,Iahrb. Abt. Syst., v. 32 (6): 521-612, figs, a-g, pis. 17-21,

figs. 1-55.

II M, I., M. ('. 1921. Two new genera of nematodes with a note

on a neglected nematode structure. Proc. V. S. Nut. Mus.

v. 59(2386): 541-54(i, figs. 12.
IIamann, 1895. — Die XeiiiatlMliniiillien (2). Die Xeiiiatoden.

120 pp., 11 pis.
Hksse, R. 1892. — I'eber lias .\ervensysteni von Ascaris mtga-

tiinphaUt. Ztschr. Wiss. Zool. v. 54(3): 548 568, pis.

23 24, figs. 1-20.
list . 11. F, 1933. — Some species of Porrocaecum ( Neniatoda )

from birds in China. .1. Parasit. v, PU4): 280 285, pis.

2-3, figs. 1 18.

19331). — On some (larasitic iiciiialoiles colh'cted in

China. Parasit. v. 24(4): 512-541, figs. 1 46.
I.\i,\ii.\( K, B, 1). C. M. 1924. — On the niicrosco|)ical anatomy

of the digestive system of Slrongi/liis edinlaliis Looss.

Arch. Anat., Hist. & Embrvol., v." 3(4-6): 281326, figs.

146.
.lAKiir.K.sKiotXD, L. A. 1893.— Bidr.ig till Kiinnedomen oni

Nematoderna. Diss. Stokludm. 86 jip., 5 pis., 43 figs.

1894. — Beitrage zur Kenntnis der Nematoden. Zool.

.Jahrb. Abt. Anat. v. 7(3): 44!i-532, pis. 24-28.

1901. — Weitere Beitriige zur Kenntnis der Neinatoilen.

Kongl. Svenska Veteiiskaps Akad. llainll. v. 35(2): 1-80,

Ills. 1-6.

1909. — Nematoden aiis Aegypteii iiiiil deiii Smlaii. Re-
sults of the Swedish Zoological Expedition to Egvjit and

the White Nile, 1901. 00 pp., 4 pis.
,Terke, M. 1901. — Zur Kenntnis der Oxyuren des Pferdes.

Diss. Jena. 64 jip., 1 pi.
Kai.antarian, E. V. 1928.— Zur Trichostrongyliden fauna der

Schafe .Armeniens. Trudy Gosudarstv. Inst. Eksper. Vet.

Moskva, V. 5(2): 40-57, figs. 1-24 (Russian).
Leuckart, R. 1868-1876. — Die Menschichen Parasiten. Leip

zig & Heidelberg, v. 2, 882 pp., 401 tigs.
Looss, A. 1901. — The Sclerostomidae of horses and donkeys in

Egypt. Rec. Egypt. Govt. School Med. pp. 25 139," pis.

1-13, figs. 1 172.

1905. — The anatomy and life history of Aurlii/loxlama

thi<xhnalrTlu\K Rec. Egyjit. Govt. ScIhmiI" .\led„ v. ,3: 1-158,

pis. 1-9, figs. 1-100, pi. 10, photos 1-6.
^^ACALIST^;R, A. 1805. — On the presence of certain secreting

organs in Neiiintoides. Ann. & Mag. Nat. Hist. 3. s. (91),

V. 16(4): 45-48.
Mackin, J. G. 1936. — Studies on the morphology and life his-
tory of nematodes in the genus Spironoura. ITniv. 111.

Bull. V. 33(52), III. Biol. Monogr. v. 14(3): 64 pji., pis.

1-6, figs. 1-69.
Magath, T. B. 1919. — CamaUaniis nmericaniis nov. spec. Tr.

Am. Micr. Soc. v. 38(2): 49 170, figs. A Q, pis. 7-16, figs.

1-134.
Man, .T. G. de, 1886. — Anatomische Untersuchungen uber

freilebende Nordsee-Nematoden. 82 pp., 13 pis.

1888. — Sur quelques niMiiatodes libres de la mer du

nord, nouveaux ou pen connus. Mem. .Soc. Zool. France

v. 1; 1-51, pis. 1-3, figs. 1-20.

1889. — Troisieme note sur les nematodes libi'es de la

mer du nord et de la manche. M6m. Soc. Zool. France

V. 2: 182-216, pis. 5-8, figs. 1-12.

1890. — Quatrieme note sur les nematodes libres de la

mer du nord et de la manche. Mem. Soc. Zool. France

V. 3: 169-194, pis. 3-5, figs. 1-10.

1904. — Nematodes libres. Resultats du voyage du S.

Y. Belgica. Exped. Antarct. Belg. Anvers. 55 pp., 11 pis.
1907. — Sur (luelques especes nouvelles ou pen connues

de nematodes libres habitant les cotes de la Zelande. Mem.

Soc. Zool. France v. 20:33-90, pis. 1-4, figs. 1-17.
Martini, E. 1913. — Feber die Stelliing der Nematoden iiii

System. Verhandl. Zool. Gesellsch. v. 23: 233-248.

1916. — Die Anatomic der Ori/iins ciirvuhi. Ztschr.

Wiss. Zool. v. 116: 137-534, figs. 1-121. pis. 6-20.
Mueller, J. F. 1925. — Some new features of nematode mor-
phology in Prnlipliis obtiisiix Du.jarilin. ,1. Parasit. v.

12: 84-90, pi. 10, figs. 1 10.

1930. — The mechanism of copulation in the nematode

Ascaris himbricaidi's. Tr. .-Xni. Jlicr. Soc. v. 49(1): 42-45,

pi. 6, figs. 1-4.
Rajewsky, S. a. 1928. — Die Setarien mid deren pathogene-

tisclie Bedcutung. Trudy Gosudarstv. Inst. Eksper. Vet.

Moskva, V. 5(1): 53-108, figs. 1-34. German summary.
1931. — Zur Characteristik der Nematoden der Gattung

XduainiJinis Ransom, 1907. Versiich einer Monographi

sclien Bearbeitiing. Ztschr. Tnfektskrank, v. 40: 112 136,

pis. 4-10, figs. 1 61.
Ransom, B. H. 1904. — A new nenuitode (Gongyloni ina inglic-

vicohi) parasitic in the crop of chickens. U. S. D. A. Bur.

Anim. Ind., Circ. No. 64, 3 pp., 2 figs.

121

1911. — The nematodes parasitic in tin alimentary

tract of cattle, sheep, and other ruminants. U. S. D. A.,

Bur. Anim. Ind. Bull. No. 1:37, 132 pp. 1.52 figs.
R.\UTHER, M. l'.»09. — Morphologie und Verwandtschaftsbezie-

liungen der Nematoden. Ergeb. & Fortschr. Zool. v. 1(3) :

491.596, figs. 1-21.

1918. — Jlitteilungen zur Nematodenkunde. Zool.

Jahrb. Abt. Anat. v. 40: 441-514, figs. A-P, pis. 20-24,

figs. 1-40.

1930. — Vierte Klasse des Cladus Nemathelminthes.

Nematodes, Nematoidea = Fadenwiirraer. Handb. Zool.

(Kukenthal & Krumback) v. 2, 8 Lief.. 4. Teil, Bogen

23-32, pp. 249-402, figs. 267-42(3.
Sandground, J. H. 1933. — Report on the nematode parasites

collected by the Kelley-Eoosevelts expedition to Indo-China

with descriptions of several new species. Ztschr. Para-

sitenk. v. 5(3/4): .542-583, figs. 1-33.
Schneider, A. 1866. — Monographie der Nematoden. 357 pp.,

122 figs., 28 pis. Berlin.
Seurat, L. G. 1913. — Observations sur le Tropidocerca iner-

■mis Linstow. Bull. Soc. Hist. Nat. Afrique du Nord, Al-
ger, V. 5(8) : 191-199, figs. 1-11.

1920. — Histoire naturelle des nematodes de la Ber-

berie. Premiere partie. Morphologie, developpement,

ethologie et affinites des nematodes. 221 pp., 34 figs. Alger.
Shipley, A. E. 1894. — Notes on nematode parasites from the

animals in the Zoological Gardens, London. Proc. Zool.

Soc. Lond. (3): 531-533, pi. 35, figs. 1-6.

1897. — Note on the excretory cells of the Ascaridae.

Zool. Anz. V. 20: 342.
Shul't.s, R. Ed., Orlov, I. W., & Kutass, A. J. 1933.— Zur

Systematik der Subfamilie SjTithetocaulinae Skrj. 1932

nebst Beschreibung einiger neuer Gattungen und Arten.

Zool. Anz. V. 102(11-12): 303-310, figs. 1-10.
Skrjabin, K. I. 1917. — Sur quelques nematodes des oiseaux

de la Russie. Parasit. v. 9(4): 460-481, pis. 18-19, figs.

1-19.
Strassen, 0. ZUR. 1907. — Filaria medincnsis und Ichtlnjonema.

Vcrhandl. Deutsch. Zool. Gesellsch. 17 J., 110129, figs. 1-8.
SuGlMOTO, M. 1932. — On the parasitic nematode (Eustrongy-

lides tricolor Sugimoto, 1931) in the proventrieulus of the

Formosoan domestic duck. J. Soc. Trop. Agric. v. 4:

103-110, figs. 1-4, pi. 2.
ToERNQUiST, N. 1931. — Die Nematodenfamilien Cucullanidae

und Camallanidae nebst weiteren Beitragen zur Kenntnis

der Anatomie und Histologic der Nematoden. Gotenborgs

K. Vetensk. — o Vitterhets. — Samh. Handl., 5. f., s. B, v.

2(3), 441 pp., pis. 1-17.
Travassos, L. a. 1920. — Esboco de uma chave geral dos

nematodes parasites. Rev. Yet. & Zootech. Rio de Janeiro

V. 10(2): 59-70, 1 table.
TuERK, F. 1903. — Ueber einige im Golfe von Neapel frei

lebende Nematoden. Thesis Leipzig. 67 pp., pis. 10-11.

Also in Mitt. Zool. Stat. Neapel, v. 16: 281-348, pis. 10-11.
Tyson, E. 1683. — Luiiibricits teres, or some anatomical ob-
servations on the round worm bred in human bodies. Phil.

Tr. Lond., (147), v. 13: 1.54-161, 1 pi., figs. 1-4.
VoLTZENLOOEL, E. 1902. — Untersuchuugen iiber den anato-

mischen und histologischen Bau des Hinterendes von As-

caris megalocephalii und A.icari.s lumbricoiden. Diss. Jena.

32 pp., 3 pis. Also in Zool. Jahrb., Abt. Anat. v. 16(3):

481-510, pis. 34-36.
Walter, G. 1856. — Beitriige zur Anatomie und Physiologic

von Oxyuris ornata. Ztschr. Wiss. Zool. v. 8(2) : 163-201,

pis. 5-6, figs. 1-28.

1858. — Fernere Beitrage zur Anatomie und Physi-
ologic von Oxyuris ornata. Ztschr. Wiss. Zool. v. 9(4):

485-495, pi. 19, figs. 29-34.
Wehr, E. E. 1933.— A new nematode from the Rhea. (2958)

Proc. U. S. N. M. V. 82(17): 1-5, figs. 1-3.

122

CORRECTIONS FOR PART I

ABBREVIATIONS

F'iigc 4, coluiiin 1, line L'S, /oA.i tii roiid io'.vj.

Pago 4, column L', liiu' 13, 1S56 a-b to read 1SG5 a-b.

Page ."i, coliiinn i. lino ."),!, (Jem to road Idem.

Pago ];!, column 1, lino 1, of Fig. 12, Dictyocaiiliis ririimrous
to read Dicli/octinliis riripanis.

Page 13, column '2. lino i .'1, of Fig. 12 ilolote F tlirough
Parasit.

Page 19, column 1, lino 1, Fig. 18, Mi'toticlidliiiiiiiis iiristiiirix
to read Metoncholaimiis pristiiinis.

Pago 21, column 1, lino ti. Morpluiloii/c to road Moriiholnr/'w.

Pago 22. column 1. lino l.S, Fig. 23, Xincma pcrfccliim to
read Si/ala striata.

Page 23, column 2. last line. Xiii< iiin iirrfi'ctiiiii to road Xi/aln
striata.

Page 24, cohinm 1, lino 2, Fig. 31, Ascnriihic to road A.f-
carididae.

Page 27, column 2, line 1. Fig. 37, Strntr to road Stcincr.

Pago 32, column 1, line 1, Footnote, Stroiu/iius riiiiiniis to
road Slron^iyliis rqiiiiius.

Page 33, column 2, lino 67, Monnprapln to road Moiioiirapliir.

Page 42, column 2, lino 4S, Dictophi/inatinn to read Diocto-
phymatina.

Page 4-3, column 2, lino 111. Vriii nsl' to rcail Vetrnsk.

Page 46, column 2, line 41, founded to road rounded.

Page 4!>, column 2, line 12, fnngiforoiis to read fungivorou.<<.

Page .^0. column 1, line 68, delete or absent.

Page -"1, column 1, line l.i, .Home to read stoma.

Page .51, column 2, line 23, Refle.rted to read reflexed.

Page 51, column 2, line 42, reflcrted to read reflexed.

Page .i2, column 1, line 1, Ambnilatory to read ambulatory.

Page ■'>2, column 1, line ."i9, Eurysiominae to read Eury-
stomininae.

Page .52, column 2, lino 41. Trt radon/ niatidae .should bo boM
face type.

Page .52, column 2, line 42, Mermitliidae should be bold
face type.

Page 53, column 2, ptr, pmlorhahdian should road protor-
habdion.

a!, a la ;

au, anus;

a p. apophysis;

eiil, calomus;

eap, capitulum ;

e gl, caudal gland ;

ei, cirrus;

d, cloaca ;
('", corpus ;

0 m, eopulatory nniscle;
rru, crura ;

eu, cnn, en, ounous ;

d r gl, dorsal rectal gland:

e, nucleus in osophago-intostinal valve;
rp e, epithelial coll ;

g, gland coll nucleus;

gub, gubernaculum;

h, depressor ani ;

t m, somato-intcstinal muscle ;

int, intestine ;

lam, lamina ;

1 sp, loft spicule;

HI, marginal nucleus;

ui e, mesenterial ccdl ;

H-, norvo coll nucleus;

/)««, spicular pouch ;

p gub, protractor muscle of gubornai-ulum ,

;> sp, protractor mu.scle of spicule;

r, radial nucleus ;

r gl, rectal glaml ;

r sp, right spicule ;

.s', (piestionable nucleus;

s)i, sheath ;

.V m, sphincter muscle;

sp. spicule ;

sup or, sup])lemontaiy organ;

•vr r gl, subventral rectal gland;

tel. tolamon ;

(• (7, vas deferens ;

X, questionable nucleus.

123