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Full text of "On Balantidium coli (Malmsten) and Balantidium suis (sp. nov.) with an account of their neuromotor apparatus"

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ON BALANTIDIUM COLI (MALMSTEN) AND 

BALANTIDIUM SUIS (SP. NOV.), WITH 

AN ACCOUNT OF THEIR NEURO- 

MOTOR APPARATUS 



A THESIS ACCEPTED IN PARTIAL SATISFACTION OF 
THE REQUIREMENTS FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 
AT THE UNIVERSITY OF CALIFORNIA 



BY 



JAMES DALEY McDONALD 



1922 






' ' *- 



UNIVERSITY OF CALIFORNIA PUBLICATIONS 

IN 

ZOOLOGY 

Vol. 20, No. 10, pp. 243-300, pis. 27-28, 15 figures in text May 8, 1922 



ON BALANTIDIUM COLI (MALMSTEN) AND 

BALANTIDIUM SUIS (SP. NOV.), WITH 

AN ACCOUNT OF THEIR NEURO- 

MOTOR APPARATUS 



BY 

j. DALEY MCDONALD 



UNIVERSITY OF CALIFORNIA PRESS 

BERKELEY, CALIFORNIA 

1922 



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' 

* ' J J 




ON BALANTIDIUM COL I (Malmsten) AND BALANTIDIUM St 
WITH AN ACCOUNT OF THE i NEUROMOTOR APPARj 



by 

J.Daley McDonald 



- - 



Submitted in partial fulfillment of the requir* 
for the degree of Doctor of Philosophy 



Is Approved : ci-fr^ Pasadena, California 




UNIVERSITY OF CALIFORNIA PUBLICATIONS 

IN 

ZOOLOGY 

Vol. 20, No. 10, pp. 243-300, pis. 27-28, 15 figures in text May 8, 1922 



ON BALANTIDIUM COLI (MALMSTEN) AND 

BALANTIDIUM SUIS (SP. NOV.), WITH 

AN ACCOUNT OF THEIR NEURO- 

MOTOR APPARATUS 

BY 

j. DALEY MCDONALD 



CONTENTS PAGE 

Introduction 244 

Acknowledgments : 245 

Material and technique 245 

Occurrence and geographic distribution 246 

Studies of living organisms 246 

Systematic position of genus and species 248 

Balantidium coli 249 

Balantidium suis sp. nov 250 

Method and use of measurements 254 

Other specific characters 258 

Balantidium from man 261 

Morphology 262 

Ectoplasmic structures 263 

Pellicle , 263 

Ectoplasm 266 

Cilia 270 

Basal apparatus of cilia 271 

Ciliary movements 273 

Cytostome 276 

Oral plug 280 

Contractile vacuoles 280 

Endoplasmic structures 282 

Endoplasm 282 

Food vacuoles , '. 282 

Macronucleus 282 

Micronucleus 283 

Neuromotor apparatus 284 

Motorium .' 285 

Circumoesophageal fiber 285 

Adoral ciliary fiber 286 



244 University of California Publications in Zoology [VOL. 20 

PAGE 

Adoral ciliary rootlets 286 

Radial fibers . 286 

Discussion 288 

Summary 293 

Literature cited , 294 

Explanation of plates 298 



INTRODUCTION 

The earliest observation of Protozoa of the genus Balantidium has 
in several instances been accredited to Antony von Leeuwenhoek 
(1708). During an attack of dysentery he detected motile organisms 
in the discharges. At that time no discrimination had been made 
between ciliated and flagellated protozoa and his account of his obser- 
vations is not sufficiently complete to make possible the classification 
of the organisms which he found. However, he stated that they were 
about the size of red blood corpuscles, which would indicate that they 
were intestinal flagellates and not Balantidium, which is very much 
larger. 

Malmsten (1857) was the first to describe Balantidium coli. This 
species has become better known than the other species of the genus, 
due to its being the cause of a specific dysentery known as balantidiasis. 
Two persons suffering from this disease came to Malmsten for medical 
attention during 1856-57. Pie was assisted in the study of protozoans 
which he found in the excreta from these two patients by the zoologist 
Loven who believed that the parasites were new to science and so pre- 
pared a careful description of them accompanied by figures. For the 
organism they suggested the name Paramoecium ( ?) coli. Since that 
time infections with Balantiddum coli have been reported in increasing 
numbers and some cytological studies 'have been made, though much 
more attention has been given to the problems of prophylaxis and 
treatment of the disease which this species causes than to the parasite 
itself. 

The first record of Balantidium coli as a parasite of pigs was made 
by Leuckart (1861). Stein (1862) also studied these forms from pigs 
and he was the first to assign them to the genus Balantidium. The 
genus had been established by Claparede and Lachmann (1858) with 
Balantidium entozoon from the frog as the type species. More recently 
Strong (1904), Brumpt (1909), Walker (1913), and others have car- 
ried on investigations on this parasite of pigs in order to become 
acquainted with the problems involved in the infection of man. 



1922] McDonald: On Balantidium eoli and Balantidium suis 245 



ACKNOWLEDGMENTS 

It has been my privilege to study the morphology of Batantidium 
coli and Balantidium suis (sp. nov.) under the direction of Professor 
Charles A. Kof oid, to whom I am indebted for helpful suggestions and 
for oversight of the entire work. Acknowledgment is due Professor 
William W. Cort for many valuable criticisms. I also take this oppor- 
tunity to express my appreciation of the courtesy of Mr. E. B. Brown, 
superintendent of the Oakland Meat and Packing Company, who 
kindly granted me permission to work in the company's abattoir and 
also facilitated the work in every possible way. 



MATERIAL AND TECHNIQUE 

The material for these studies was obtained almost exclusively from 
pigs killed by the Oakland Meat and Packing Company, Stockyards, 
California. At their abattoir I was permitted to work in the room 
where the pigs were dressed, which made it possible to obtain the 
material from the intestine before it had cooled below the normal body 
temperature. To determine the presence of the balantidia a small slit 
was made in the caecum and a drop of the contents withdrawn with 
a pipette. This drop was quickly placed on a warm slide and exam- 
ined with a microscope. If the animals were present they would be 
detected very readily for they are exceedingly active ; in most cases 
they occurred in numbers sufficiently large that from one to ten could 
be seen in every field when a 16 mm. objective was used. This method 
was rapid enough to allow all pigs to be examined as fast as they were 
killed and dressed. 

A sample from the caecum was not relied upon as critical in the 
determination of infection until examination of the entire length of 
the intestine had been made in several instances. In order to discover 
the normal distribution throughout the intestine it was removed entire 
and taken to the laboratory of the abattoir. Incisions were made every 
one or two feet, beginning with the duodenum and continuing to the 
rectum, and samples examined from each of these incisions. In no 
cases were balantidia found more than three feet above the ileocaecal 
valve, and only in two or three instances were any at all present in 



246 University of California Publications in Zoology [ VoL - 20 

the small intestine. In the caecum and first three or four feet of the 
colon the balantidia were always more active and more numerous than 
elsewhere. Posteriorly from this region they were found in progressive 
stages of encystment until in the rectum the majority were completely 
encysted. 

OCCURRENCE AND GEOGRAPHIC DISTRIBUTION 

Approximately 200 pigs were examined. They had been raised in 
the Sacramento Valley, except for one lot from Los Banos, California, 
and a lot from the state of Nevada. Of the 200 pigs examined 68 
per cent were infected. The examinations were made at nine separate 
times between September, 1913, and May, 1918, ten to sixty individuals 
being examined each time. In five of the nine lots every pig was 
found to be infected. The lowest percentage of infection was 13 per 
cent, in the lot shipped from Nevada. This indicates a very general 
infection of pigs with Balantidium in this region of the United States. 

Stiles (cit. Strong, 1904), Bel and Couret (1910), and others have 
previously found the organisms in pigs in the United States. Leuckart 
(1861), working in Germany, was the first to find Balantidium in pigs. 
Since then Stein (1862), Eckecrantz (1869), and Prowazek (1913) 
have reported them from the same country. In 1871 Wising noted 
their occurrence in pigs in Sweden. Grassi (1882) and Calandruccio 
(1888) have found the parasites in swine in Italy. Rapchevski (1882) 
reported the occurrence of balantidia in Russia. In France they have 
been found in pigs by Railliet (1886), Neumann (1888), and Brumpt 
(1909). Strong (1904), Walker (1913), and several others have 
noted the occurrence in pigs in the Philippine Islands. Similar reports 
from China have been made by Maxwell (1912), and Mason (1919) ; 
from Cuba by Taboadela (1911) ; and from South America by Bayana 
(1918). These citations indicate that BalantiMum coli is probably as 
widely distributed geographically as is its host, the pig. 



STUDIES OF LIVING ORGANISMS 

The balantidia are very sensitive to changes of temperature. When 
the medium in which they are swimming is cooled a few degrees they 
slow up their movements very decidedly. After a time they become 
almost perfectly spherical, in which form their activitiy is restricted 
to a rotary motion with little or no progression. In this condition they 
will live for six or eight hours at ordinary room temperature. 



1922] McDonald: On Balantidium coli and Balantidium suis 247 

In order to avoid the deleterious effects caused by cooling and by 
increased bacterial action, most of the studies on living organisms were 
made at the abattoir. When continuous observation over a long period 
was desired, however, the material was conveyed to the laboratory in 
thermos bottles and kept in the incubator at 37.5 C. In tfris~manner 
material could be kept for three days. Ultimate degeneration of the 
organisms seemed to be due more to the increase in the bacterial con- 
tent of the medium than to any other cause. During observation either 
an electric warm stage or the microscope warm oven designed by Long 
(1912) was employed. Of the several vital stains used, neutral 
red proved most satisfactory in the differentiation of the neuromotor 
apparatus. 

Fixation and staining. The following fixatives were used : Schau- 
dinn's fluid, Zenker's fluid, formalin, osmic acid, and picromercuric 
fluid (according to the formula by A. D. Drew, used by Yocom, 1912). 
Quick action was one of the most important factors in the fixation, 
and was usually obtained by having the killing fluid hot (60-80 C.) 
and using an amount at least equal to the amount of the material to 
be fixed. Frequently the action was so nearly instantaneous that the 
cilia on the killed animals retained their exact relative position (see 
fig. N). After fixation the material was thoroughly washed, iodine 
alcohol being used if mercurial salts were present. Material was pre- 
served in 70 per cent alcohol. 

Before staining, the preserved material was usually concen- 
trated by elimination of lighter debris by centrifuging and the heavier 
by sedimentation. Water was found to be a more satisfactory medium 
for these operations than either alcohol or salt solutions. In case sec- 
tions were to be made, additional care was taken in the concentration 
process and then the material was handled according to the methods 
employed by Metcalf (1909) and by Sharp (1914). 

Iron haematoxylin gave uniformly the best results in staining. For 
cysts, however, on account of their imperviousness, it was necessary to 
use Delafield's haematoxylin to which had been added a small amount 
of acetic acid. In addition to the first mentioned stain, Mallory's con- 
nective tissue stain was used on sections. 



248 



University of California Publications in Zoology [ V L - 20 



SYSTEMATIC POSITION OF GENUS AND SPECIES 

Claparede and Lachmann (1858) removed Bursaria entozoon from 
the genus in which it had been placed by Ehrenberg (1838) and 
created for it the new genus Balantidium. This genus was of the 
family Bursaridae and the order Heterotricha. The twenty-two species 
of the genus that have been described to date are listed below. 



KNOWN SPEOIES OF THE GENUS BALANTIDIUM 



Species 
Balantidium entozoon 

Balantidium coli 

Balantidium duodeni 
Balantidium elongatum 



Balantidium medusarum 
Balantidium amphictenides 

Balantidium gyrans 
Balantidium viride 
Balantidium minutum 
Balantidium giganteum 
Balantidium helenae 



Balantidium graeile 



Balantidium 
Balantidium 
Balantidium 
Balantidium 
Balantidium 
Balantidium 
Balantidium 
Balantidium 
Balantidium 
Balantidium 



rotundum 

faleiformis 

ovale 

hyalinum 

littorinae 

testudinis 

hydrae 

piscicola 

caviae 

orchestia 



Original description by 
Ehrenberg, 1838 

Malmsten, 1857 

Stein, 1862 
Stein, 1862 



Mereschkowsky, 1879 
Entz, Sr., 1888 

Kellicott, 1889 
Willach, 1893 
Schaudinn, 1899 
Bezzenberger, 1903 
Bezzenberger, 1903 



Bezzenberger, 1903 

Bezzenberger, 1903 
Walker, 1909 
Dobell, 1910 
Dobell, 1910 
Chagas, 1911 
Chagas, 1911 
Entz, Jr., 1913 
Entz, Jr., 1913 
Neiva et al, 1914 
Watson, 1916 



Hosts 

Rana esculenta 
Rana temporaria 
Sus scrofa 
Homo sapiens 
Ban a esculenta 
Triton cristatus 
Triton alpestris 
Triton marmoratus 
Rana esculenta 
Rana temporaria 
Bougainvillea, Obelia, 
Eucope, Broda sp.? 
Amphictenis, 
Turbellaria marina 
Aquatic worm 
Columba sp.? 
Homo sapiens 
Rana esculenta 
Rana cyanophlyctis 
Rana tigrina 
Rana limnocharis 
Rana hexadactyla 
Rana cyanophlyctis 
Rana hexadactyla 
Rana esculenta 
Rana palustris 
Rana tigrina 
Rana tigrina 
Littorina 
Testudo graeca 
Hydra olygactis 
Piarectus brachypomus 
Cavia aperea 
Orchestia agilis 
Talorchestia longicornis 



1922] McDonald: On Balantidium coli and Balantidium suis 249 

The wide diversity of hosts, ranging from hydroids and crustaceans 
to the warm-blooded vertebrates, including man, must demand a wide 
versatility on the part of the parasite. Considerable structural varia- 
tion is apparent even on cursory examination, and some of these 
structural differences might be sufficiently marked to servTT for generic 
differentiation. A new generic division would seem desirable, but the 
suggestions of Biitschli (1884) and Schweier (1900) in this direction 
have not been generally accepted. 

BALANTIDIUM COLI MALMSTEN (1857) 

SYNONOMY: 

Paramoecium (?} coli Malmsten, 1857. 
Plagiotoma coli, Claparede and Lachmann, 1858. 
Leucophyra coli, Stein, 1860. 
Holophyra coli, Leuckart, 1861. 
Balantidium coli, Stein, 1862. 

Up to the present time only one species, Balantidium coli, has been 
described as parasitic in pigs. It was first described by Malmsten 
(1857) who, noting its likeness to Paramoecium colpoda (Ehrenberg), 
suggested the name Paramoecium (?) coli. During the following year, 
Claparede and Lachmann (1858) reproduced one of Malmsten 's orig- 
inal figures and after considering his description transferred the 
species to the genus Plagiotoma. In 1860, Stein, using the description 
by Malmsten (1857), pointed out that the organism was not a Para- 
moecium and Relieved that it properly belonged in the genus Leuco- 
phyra. Leuckart in 1861 discovered a ciliate in the intestine of pigs 
which he concluded was identical with the one already described, but 
he was not satisfied with the genus to which it had been assigned by 
Stein (1861) and believed that its closest relation was with Holophyra 
in which genus it should be placed. In. 1863 he still retained this view 
but suggested the appropriateness of the establishment of a new genus. 
But Stein (1862) had already recognized those characters of the 
species which showed its close relation to Balantidium entozoon and 
had placed it in the genus Balantidium. 

During the present investigation the following specific character- 
istics have been found very constant. The individuals of the species 
Balantidium coli are ovoid in form, the more pointed end being an- 
terior; length varies from 30/* to 150/t; breadth varies from 25,/A to 
120ju, ; in the majority of individuals the length is 1.3 times the breadth ; 
the greatest transverse diameter intersects the longitudinal axis poster- 



250 University of California Publications in Zoology [ VoL - 20 

ior to its midpoint; the adoral zone is approximately terminal, and 
the anterior tip of the body lies within it; the plane of demarcation 
between the apical cone of the ectoplasm and the endoplasm is approx- 
imately at right angles to the long axis of the body ; the macronucleus 
is elongate but the length usually does not exceed three times the 
breadth; two contractile vacuoles are present, a smaller one located 
anteriorly and a larger one located posteriorly; a posterior cytopyge 
is usually distinctly visible. 

BALANTIDIUM suis SP. NOV. 

Early in the work of examining pigs for Balantidium coli it became 
evident that this protozoan showed extreme variation in shape. In 
many instances the diversity occurred among individuals from the 
same host. Further observations led me to believe that there were 
two fairly distinct types, the one, longer and more slender as compared 
with the other which was distinctly ovoid. Measurements have been 
recorded by various writers of Balantidium coli from man. Malmsten 
(1857) in the original description gave the length as 60-10CV; breadth, 
50-70/i. Solojew (1901) recorded the length as 65/*, the breadth as 
40/A. Wising (1871) states that the length varies from 50-100/z, while 
the breadth varies from 40-50/*. Prowazek (1913) gave the length as 
52-71/x, the breadth, 40-58/*. Leuckart (1861) measured balantidia 
from swine and found the length to be 75-110/x and the breadth 70/x. 
Still others give dimensions, but all are inadequate for the determina- 
tion of the occurrence of types with distinct proportions. First, with 
one or two exceptions all dimensions have been taken of balantidia 
found in man, and from these it might not be safe to draw conclusions 
regarding diversity among those found in pigs. In the second place, 
the measurements given are either averages or else represent extreme 
limits. In either case they are practically useless in determining indi- 
vidual variations, for even in the case of extreme types the range 
between limits is so great that two, or even more, distinct types, based 
on proportions of breadth to length, might be included. Nowhere 
has there been found a series of individual measurements which would 
make it possible to determine whether variations were continuous or 
discontinuous. To obtain such a series of measurements was the pur- 
pose of the phase of the work about to be described. 

Material which was to be used in taking the measurements was 
killed and preserved with all possible care. Hot Schaudinn's fluid 
was used in all cases, the material being quickly and thoroughly mixed 



1922] McDonald: On Balantid/ium coli and Balantidium suis 251 

into a large quantity of it so that action would be as nearly instan- 
taneous as possible, thus avoiding distortion. Osmic acid vapor was 
tried but Schaudinn's fluid gave equally good results and was more 
convenient for manipulation. Material was never allowed to cool 
before fixing, for on cooling the individuals tend to become spherical. 
Several attempts were made to measure living organisms but their 
ceaseless activity at normal temperature (.37.5 C) made this almost 
impossible and slowing them up by the use of Irish moss or by cooling, 
as mentioned above, caused them to become distorted. If there were 
changes due to fixation, the logical expectation would be that the error 
would be on the side of conservatism for such changes would tend to 
obliterate rather than accentuate the division into two groups ; for the 
shape of the elongate forms would be more changed by the fixative, 
the tendency being for them to shorten and broaden and thus approach 
the ovoid type. However, in the method of fixation used, I am sure 
that distortion was so slight as to be negligible. 

Following fixation the material was carefully washed and carried 
slowly through the lower grades of alcohol to 70 per cent in which 
the material was kept for measuring. A drop of the material from 
which measurements were to be taken was placed on a slide, covered 
with a coverglass, the excess of fluid removed, and the edges sealed 
with vaseline to prevent evaporation. Just enough fluid was removed 
from under the coverglass to reduce the depth of the medium so that 
the majority of the animals would lie flat, and yet not enough to allow 
the coverglass to exert any pressure. The exertion of pressure on the 
animals, however, would ordinarily be prevented by the presence of 
large particles of foreign material. The object of having animals lie 
flat on the slide was to avoid the error which would otherwise be caused 
by foreshortening. A slight elevation of one end would make con- 
siderable error in the determination of the length of the animal. 

The slide was then placed on the microscope and systematically 
examined by the use of the mechanical stage. Beginning at the upper 
left-hand corner and progressing as one would in reading a book, every 
individual encountered in the survey was measured. The only excep- 
tions made were in case the animal was not lying flat or showed marked 
signs of distortion. This procedure avoided selection which might 
unconsciously be made by the observer. For making the measurements 
a 4 mm. objective was used in combination with an ocular-micrometer 
inserted in 9x compensating ocular. With the magnification given by 
this combination the limit of error did not exceed one micron. 



252 



University of California Publications in Zoology [VOL. 20 



The longitudinal axis and the longest transverse axis of each indi- 
vidual were measured, and the ratio of length to breadth computed 
(see Table I). 



TABLE I 



COMPARATIVE MEASUREMENTS OF 
BALANTIDIUM COLI 

INDIVIDUALS FROM PIG No. 1 
(Bal. suis, with five exceptions) 



ONE HUNDRED INDIVIDUALS EACH OF 
AND BALANTIDIUM suis 

INDIVIDUALS FROM PIG No. 4 
(Bal. coli, with one exception) 



Length in 
microns 


Breadth in 
microns 


Ratio of 
length to 
breadth 


Length in 
microns 


Breadth in 
microns 


Ratio of 
length to 
breadth 


114 


42 


2.71 


99 


75 


1.32 


108 


51 


2.11 


96 


81 


1.19 


63 


36 


1.75 


126 


75 


1.68* 


90 


45 


2.00 


118 


87 


1.36 


93 


48 


1.94 


111 


87 


1.28 


72 


39 


1.85 


87 


75 


1.16 


126 


69 


1.83 


90 


66 


1.36 


87 


48 


1.82 


105 


75 


1.40 


108 


57 


1.90 


78 


66 


1.18 


102 


54 


1.89 


90 


63 


1.43 


117 


51 


2.30 


87 


72 


1.21 


120 


57 


2.10 


87 


72 


1.21 


96 


42 


2.29 


99 


75 


1.32 


84 


39 


2.12 


105 


75 


1.40 


120 


48 


2.50 


89 


75 


1.19 


117 


48 


2.42 


81 


63 


1.28 


93 


51 


1.83 


81 


66 


1.23 


96 


51 


1.89 


75 


63 


1.19 


72 


57 


1.26* 


84 


69 


1.22 


75 


54 


1.39* 


69 


60 


1.15 


111 


51 


2.14 


90 


66 


1.36 


111 


54 


2.03 


93 


75 


1.23 


84 


36 


2.31 


87 


69 


1.26 


69 


39 


1.77 


90 


81 


1.11 


78 


51 


1.52* 


105 


90 


1.16 


81 


45 


1.80 


87 


69 


1.26 


111 


45 


2.42 


84 


72 


1.17 


81 


45 


1.80 


66 


58 


1.14 


84 


45 


1.86 


75 


60 


1.25 


90 


45 


2.00 


81 


63 


1.29 


84 


42 


2.00 


81 


60 


1.35 


90 


42 


2.12 


99 


78 


1.27 


117 


57 


2.03 


87 


69 


1.26 


60 


33 


1.82 


78 


63 


1.24 


108 


57 


1.90 


81 


60 


1.35 


108 


57 


1.90 


105 


75 


1.40 


96 


48 


2.00 


90 


60 


1.50 


75 


42 


1.79 


93 


78 


1.18 



* Other characters showed that these individuals were of the other species rep- 
resented in the table. 



1922] McDonald: On Bala/ntid/ium coU and Ealantidium suis 253 



TABLE I (Continued} 



INDIVIDUALS FROM PIG No. 1 
(Bal. suis, with five exceptions) 



INDIVIDUALS FROM PIG No. 4 
(Bal. coli, with one exception) 



Length in 
microns 


Breadth in 
microns 


Ratio of 
length to 
breadth 


Length in 
microns 


Breadth in 
microns 


Ratio of 
length to 
breadth 


105 


57 


1.85 


69 


60 


_ JL.15 


99 


57 


1.74 


81 


54 


1.50 


105 


54 


1.95 


87 


66 


1.32 


54 


27 


2.00 


84 


69 


1.22 


57 


30 


1.90 


78 


60 


1.30 


36 


24 


1.50* 


66 


51 


1.29 


81 


31 


2.23 


66 


54 


1.22 


75 


42 


1.78 


96 


66 


1.45 


66 


33 


2.00 


81 


54 


1.50 


78 


36 


2.08 


84 


66 


1.28 


93 


39 


2.39 


114 


87 


1.31 


63 


36 


1.74 


87 


69 


1.26 


102 


48 


2.06 


93 


72 


1.29 


78 


39 


2.00 


84 


72 


1.17 


81 


42 


1.93 


102 


65 


1.58 


87 


48 


1.82 


87 


63 


1.38 


93 


45 


2.03 


99 


66 


1.50 


84 


42 


2.00 


81 


72 


1.13 


81 


39 


2.04 


78 


63 


1.24 


75 


39 


1.93 


102 


75 


1.36 


78 


45 


1.74 


66 


48 


1.38 


75 


37 


2.01 


75 


57 


1.32 


100 


45 


2.11 


84 


66 


1.27 


81 


39 


2.04 


93 


66 


1.40 


72 


39 


1.85 


72 


58 


1.24 


84 


40 


2.06 


96 


72 


1.33 


90 


42 


2.07 


90 


68 


1.32 


78 


36 


2.08 


60 


39 


1.54 


102 


48 


2.06 


87 


69 


1.26 


81 


37 


2.10 


69 


54 


1.28 


66 


37 


1.78 


90 


69 


1.31 


87 


36 


2.41 


69 


54 


1.28 


78 


42 


1.86 


72 


60 


1.20 


84 


42 


2.00 


75 


57 


1.47 


90 


38 


2.37 


75 


62 


1.2X 


66 


35 


1.89 


72 


63 


1.14 


78 


42 


1.86 


90 


75 


1.20 


97 


44 


2.20 


74 


66 


1.12 


79 


37 


2.07 


72 


54 


1.33 


98 


42 


2.32 


60 


50 


1.20 


90 


45 


2.00 


84 


58 


1.45 


87 


49 


1.78 


84 


64 


1.31 


90 


36 


2.50 


88 


60 


1.47 


81. 


35 


2.31 


99 


75 


1.32 


69 


48 


1.44* 


75 


54 


1.39 



* Other characters showed that these individuals were of the other species rep- 
resented in the table. 



254 



University of California Publications in Zoology [ V L. 20 



TABLE I (Continued} 



INDIVIDUALS FROM Pia No. 1 
(Bal. suis, with five exceptions) 



INDIVIDUALS FROM PIG No. 4 
(Bal. coli, with one exception) 



Length in Breadth in 
microns microns 


Ratio of 
length to 
breadth 


90 


54 


1.68 


66 


33 


2.00 


76 


38 


2.00 


78 


42 


1.86 


90 


57 


1.58 


66 


40 


1.65 


81 


39 


2.04 


96 


39 


2.43 


75 


38 


1.98 


84 


39 


2.18 


51 


30 


1.70 


75 


39 


1.92 


84 


40 


2.05 


116 


47 


2.48 


84 


36 


2.32 


81 


39 


2.04 


75 

Aver- 


45 


1.68 






age 86 


43 


1.99 



Length in 
microns 


Breadth in 
microns 


Ratio of 
length to 
breadth 


81 


69 


1.18 


66 


52 


1.27 


93 


63 


1.48 


81 


75 ' 


1.08 


96 


75 


1.28 


114 


90 


1.27 


75 


60 


1.25 


87 


72 


1.21 


84 


60 


1.40 


87 


63 


1.38 


84 


63 


1.33 


72 


60 


1.20 


90 


66 


1.36 


84 


72 


1.16 


93 


72 


1.29 


87 


58 


1.50 


93 


72 


1.29 



86 



66 



1.30 



While taking the measurements of each individual, observations were 
made regarding the position of the mouth, the type and size of macro- 
nucleus, number and location of contractile vacuoles, and any other 
characters which might aid in differentiation. 

In the handling of the data on dimensions I have followed in a 
general way the method used by Jennings (1908) in differentiating 
races of Paratniaecium. For the purpose of this work, however, the 
results seemed more lucid if, instead of plotting length and breadth 
along separate axes, the ratio of length to breadth was computed for 
each individual and if these ratios were then plotted on the abscissa 
while the numbers of individuals having each of these ratios were 
plotted on the ordinate. In computing the ratios the quotient was 
carried to the second decimal place. But in the construction of the 
curves only intervals of tenths (or first decimal place) were used; 
thus, for example, all ratios occurring between 1.25 and 1.34 inclusive 
were grouped as if they were 1.3. This had two advantages : first, it 
produced a smoother, steeper curve than would result if smaller inter- 
vals were taken, using the same number of individuals measured, and 
emphasized group rather than individual variations. Second, this 
grouping reduced any error which might result from the observer 
showing a preference for one graduation of the micrometer when 



1922] McDonald: On Balantidium coli and Balantidium suis 255 

an individual measured more than one but less than another whole 
division of the scale ; e.g., such a preference might result in the tabu- 
lation of several individuals having a length of 72/t, and of none with 
a length of 7 1/*,, though in reality all lay within these two limits and 
as many were as near to one as to the other. 

As previously mentioned, the graduations along the ordinate 
represent the number of individuals, each small interval representing 
one individual. In Jennings' (1908) work these intervals represent 
percentages of the total number of individuals. But it happens that 




I.I 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 

Fig. A. Graphic representation of the variation in the ratio of length to 
breadth among 200 Balantidium chosen at random from samples of material taken 
from several different pigs. The number of individuals is measured on the ordi- 
nate, the ratios on the abscissa. The dotted line is the curve resulting from the 
combination of the two curves shown in figure B, superimposed here to facilitate 
comparison. 

in the graphs shown in figures B and C, the number of individuals 
showing a certain ratio is identical with the percentage of the total, 
for in these cases the total is 100 individuals. 

Figure A represents graphically the result of the first attempt 
to determine the existence of different types. Measurements were 
made of 200 individuals. At least ten slides were used in getting 
these measurements and they were prepared from samples taken from 
nearly as many different pigs. It will be noted that the curve pro- 
duced by plotting the ratios of these individuals is decidedly bimodal. 
One mode represents those individuals which are approximately 1.2 
times as long as wide, while the other represents those which are 1.6 
to 1.8 times as long as wide. 

These findings seemed to fully justify my early suspicions that 
there were two very different types of balantidia parasitic in pigs. 



256 



University of California Publications in Zoology [VOL. 20 



But it was decided to conduct one more experiment, for corroboration, 
under slightly different conditions and with especial care in fixation 
of the material. It had been noted that though often both types 
occurred in the same pig (which was the case in most of the samples 
used in the first measurements), still one type might be greatly in 
excess, or there might be only one type present. In getting material 





1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 



2.2 2.3 2.4 2.5 2.6 



Fig. B. Graphic representation of the difference in ratio of length to breadth 
between two carefully selected lots, of 100 individuals each, of Balantidium from 
separate hosts. The continuous line represents those from one pig (nearly all are 
Balantidium coli) ; the broken line, those from the other pig (nearly pure infection 
with Balantidium suis). 

Fig. C. This graph shows the variation in the ratio of length to breadth among 
100 Balantidium secured from a case of balantidiasis in man. 

for this second set of measurements, it seemed best to take it from pigs 
which had, as nearly as could be determined, pure infections of the 
respective types. Fortunately these requirements were fulfilled in 
the next lot of pigs examined. Both samples of material, the one con- 
taining the ovoid and the one containing the elongate type, were 
treated in exactly the same way. They were killed at the same time 



1922] McDonald: On Balantidium eoli and Balantidium suis 257 

with the same fluid (in separate containers) and in the same water 
bath. Thence to 70 per cent alcohol the treatment continued identical. 
One hundred individuals from each sample of material were measured. 

From these measurements the graphs shown in figure B were con- 
structed in the same manner as the preyious one, except" that the 
curves of the separate samples were plotted separately on the same 
axis. The continuous line represents the individuals from one pig and 
the broken line those from the other. The mode of the first curve 
occurs at 1.3. If the ratios 1.2 and 1.4 be included with 1.3, it is found 
that 80 per cent came within these limits. Of the entire number of 
individuals in the lot only one showed a ratio of 1.6 and one as high 
as 1.7, while there were none with a higher ratio. The second curve 
reaches its highest point at 2.0, while 71 per cent of the entire number 
measured is included between 1.8 and 2.2. A number of individuals 
have ratios above 2.2, while one had a ratio as great as 2.7. Five indi- 
viduals have ratios below 1.6, at which point the curves begin to over- 
lap ; but in practically every one of these individuals there were 
observed characters (which are discussed below) that made it quite 
evident that they were really of the type represented by the other 
curve. 

Upon comparing figures A and B their likeness is very striking, 
the second being corroborative of the results shown by the first. That 
both are bimodal is evident. However, the low points, the point of 
demarcation of the two groups, do not occur at the same place ; 
in the first it is at 1.4, while in the second it occurs at 1.6. Also the 
median of the first mode in figure A occurs at 1.2 while in figure B 
it is at 1.3, and the median of the second mode in figure A is at 1.7 
while in figure B it occurs at 2.0 ; that is, in figure A the entire curve 
is shifted to the left, meaning that all ratios are decreased or that all 
individuals approach nearer to the spherical shape. This shifting is 
greatest in the case of the second mode. This in conjunction with 
the greatest breadth of the second curve in figure B is what would 
be expected if the premise in regard to the effect of fixation discussed 
above (page 251) is correct. Extra care was used in the fixation of 
the latter lot of material whereas in the former only the ordinary pre- 
cautions were taken. At any rate these differences between the two 
groups do not detract from the evidence which they offer that there 
are two distinct types of balantidia parasitic in pigs. 

The value of these curves in showing race or species differentiation 
is directly proportional to the extent to which any other factors which 



258 University of California Publications in Zoology [VOL. 20 

might produce a bimodal curve are non-operative. Factors involved 
in faulty technique were eliminated as far as possible. Over the effect 
of growth or age variation, however, the observer has no control. The 
possibility of these variations producing such curves as the one above 
is precluded by reference to the data from which the curves are con- 
structed. Among the individual measurements recorded in Table I 
it will be noted that there are small individuals measuring 27 X 50/x, 
and others measuring 42 X 50/x; and that among the larger individ- 
uals, some measure 50 X 120/*, and some, 90 X 150/x. Further study 
of Table I shows that the two types are found among all sizes of 
individuals; consequently the variation of body proportions repre- 
sented by the graphs is not correlated with variations of size, and 
probably not with the age or growth of the individuals. 

That the variation could be accounted for by the occurrence of 
fission seems unlikely. Individuals might continue to elongate until 
binary fission occurred, and then by this process they might be 
shortened and the body proportion changed. Two considerations 
oppose this explanation. In figure A nearly equal numbers are of the 
respective types; in figure B each example contained almost exclusively 
one type of individual. In the former material very few dividing 
individuals were found, while in the latter not a single individual was 
seen in fission in either sample of material. But to accord with the 
above explanation one would expect to find many dividing forms 
among the elongate individuals represented by the broken line. In 
the second place, if this explanation were valid one would expect 
curves showing variation of body proportions to be continuous. Such 
is not the case, as is shown in figures A and B where the curve is 
bimodal due to a decided decrease of individuals having proportions 
intermediate between the two types. 

The possibility of any effect from gametic variation, was eliminated 
by the study of conjugating forms, through which it was determined 
that isogamy was the rule. Likewise the possibility of influence of 
the quality of intestinal content of the host was eliminated by the 
frequent occurrence of both types in the same host. Other factors it 
would seem must be of minor importance and should give way for 
more positively corroborative evidence which may be found in cor- 
related morphological difference. 

Other specific characters. In addition to the differences in relative 
lengths of the axes, one notes a distinct difference in the points of 
intersection, due to the variation in the shape of the types as pictured 



1922] McDonald: On Balantidium coli and Balantidium suis 259 



in figures D, E, F, G, and H. The one form resembles very closely 
a hen's egg, the small end being anterior. In this case the longest 
diameter crosses posterior to the midpoint of the longitudinal axis. 
In the elongate type, usually the posterior end is as much drawn to 








Figs. D-H. Camera lucicla drawings of Balantidium suis sp. nov. (figs. D 
and E), and Balantidium coli (figs. F, G, and H), showing specific differences. 

a point as is the anterior, and often more so. In these cases the longest 
diameter intersects the longitudinal axis at or anterior to its midpoint. 
Coincident with the taking of measurements a careful search was 
made to detect other morphological differences which might occur 
between the two forms and be of aid in distinguishing one from the 
other. The earliest difference to be noted related to the macronucleus. 
The macronucleus in the ovoid type is relatively short, being approxi- 
mately !/3 the length of the entire organism. It is customarily bean- 
shaped in appearance, but may be almost straight or so sharply bent 



260 University of California Publications in Zoology [ V L. 20 

at its middle as to form a short V (fig. I), and its width averages about 
0.4 to 0.5 of its length. In. the slender types the macronucleus is rela- 
tively long and slender, being approximately % of the entire length 
of the organism. It is ordinarily sausage-shaped, but it may also be 
in the form of a straight rod slightly enlarged toward the ends, or 
it may be so curved as to form an almost complete ring. In contrast 
to the form described above, the width in this case is about 0.2 to 0.3 
of its length. Differences so great as these, viz., a length 2 to 3 times 
the breadth in one case and 4 to 5 times the breadth in the other are 
easily recognizable without actual measurement. These figures rep- 
resent the average and do not mean that the limits of the two never 
overlap. This difference in nuclei serves as one of the easiest and 
surest ways of distinguishing the two types, for though the organism 
during locomotion may modify its proportions tremendously this does 
not noticeably affect the nucleus. It has been impossible to determine 
any difference between the micronuclei of the two types. 

A very noticeable difference concerns the relative position of the 
cytostome. In the ovoid type the cytostome is almost, though never 
quite, terminal (see figs. F, G, and H). As mentioned previously, the 
anterior end is ordinarily drawn out to form a fairly decided point 
which lies within the area enclosed by the adoral cilia. In the slender 
type the cytostome is more laterally placed. The posterior limit of the 
right lip of the cytostome may extend ventrally to a point % of the 
length of the animal, in which case the dorsal portion of the adoral 
circlet of cilia may pass approximately through the terminal point 
of the body, but in normal form this point will never be within the 
adoral area. The parts which make up the adoral region of the 
animals show no fundamental differences except variation in the rela- 
tive position of parts due to the lateral displacement of the cytostome. 
For example, the plane of demarcation between ectoplasm and endo- 
plasm, which is approximately vertical to the long axis of the animal 
in the ovoid form, is at a decided angle, the ventral edge lying farther 
posterior in the elongate forms (see figs. D and E). 

In the opinion of some authors the ventral displacement of the 
mouth is very significant (Delage and Herouard, 1896; Minchin, 
1912). These authors believe that the ventral displacement of the 
cytostome is progressive with evolution of the organism; i.e., that in 
the more primitive types the cytostome is terminal while in advanced 
groups it is successively displaced farther ventrally. Viewed in this 
light, the position of the mouth is here of considerable significance as 



1922] McDonald: On Balantidium coli and Balantidium suis 261 

a specific character. Attempts to discriminate between the two forms 
on the basis of cytopyge or vacuoles were without result. 

The specific differences just discussed have seemed to indicate a 
sufficient degree of separation of the two types to warrant iho~ division 
of the ciliates of the genus Balantidium which occur in the pig into 
two distinct species. The description by Malmsten (1857), in con- 
junction with the figures (Malmsten, pi. 1, figs. 1-6) which he pub- 
lished, make it practically certain that the ovoid type is the one 
originally described by him and to which he gave the name Para- 
moecium (?) coli. 

So far as I have been able to determine, the elongate species above 
described has never before been distinguished from Balantidium coli. 
For this new species I suggest the name Balantidium suis. As a sum- 
mary of the specific characters discussed above I give the following 
description : 

Balantidium suis sp. nov. Body elongate; length approximately 
twice the breadth and varies from 35 to 120/* ; breadth from 20 to 60/x ; 
usually tapers more posteriorly, is blunter anteriorly, longest diameter 
transects longitudinal axis anterior to its midpoint ; adoral region ven- 
trally placed, cytostome % of way posteriorly along ventral surface; 
nucleus rod or sausage-shaped, at least one-half the length of the entire 
organism, its width about one-fourth of its length ; the species is para- 
sitic in the pig. 

The specific name, Balantidium suis, seemed fitting since it indi- 
cated the common host, Su$ scrofa. Whether or not this species occurs 
in man it has not been possible to determine conclusively. A review 
of published case records of balantidiasis seems to show that it does 
not, but only a few of these records are accompanied by figures or 
descriptions of the organisms which are adequate for making positive 
discrimination. Fortunately, I have been able in two cases to make 
some direct observations. 

Through the kindness of Mr. W. H. Barnes, of the Department of 
Pathology of the University of California, I was permitted to study 
sections of the human intestine which he had obtained at an autopsy 
following a fatal attack of balantidiasis. Imbedded in the serous and 
subserous layers were numerous balantidia. Measurements to show 
proportions were of little value under the conditions, for the form 
of each organism was largely determined by pressure, exerted by sur- 
rounding tissues. But from other characters, the type of nucleus 
especially, it was conclusively determined that the species there present 
was Balantidium coli. No individuals of Balantidium suis were found. 



262 University of California Publications in Zoology [ V OL. 20 

Measurements of balantidia as they occur free in the human intes- 
tine were made possible through the kindness of Dr. E. L. Walker, 
of the Hooper Institute of Medical Research, who loaned me several 
slides which he had prepared while in the Philippine Islands. This 
material had been stained with haematoxylin. Using the same pre- 
cautions as in previous work, a total of 100 individuals was measured. 
The data were handled as before and the resulting graph is shown in 
figure C. In comparison with previous graphs it will be noted that 
this graph closely approaches coincidence with the curves representing 
Balantidium coli, for its mode is at 1.3 while the extreme portion of 
length and breadth is 1.5. 

In addition to slides of human material, there was also loaned 
material from one pig and from one monkey. It is interesting that 
each showed a pure infection with Balantidium coli. The monkey 
(Monkey No. 10, Table I; Walker, 1913) had been experimentally 
infected by feeding it cysts from a pig, but not the pig from which 
the above-mentioned material was taken. Therefore this material 
yields no evidence regarding the validity of the specific differentiation 
nor the possibility of Balantidium suis becoming established in mon- 
keys or in man. 

There is no likelihood of confusing the new species, Balantidium 
suis with Balantidium minutum (Schaudinn, 1899). The differences 
are very marked. The body of the latter is oval, pointed anteriorly, 
more like Balantidium coli. The peristome reaches to the equatorial 
plane. There is but a single vacuole while there are two in each of 
the species considered here. The macronucleus is spherical, whereas 
it is elongate in both Balantidium coli and Balantidium suis. 



MORPHOLOGY 

Balantidium coli (Malmsten) and Balantidium suis sp nov. are 
ciliated protozoans, barely visible to the unaided eye, and are in a 
general way sac-shape (balantidium, little bag). Viewed through the 
microscope they appear grayish green in color. The homogeneity of 
the cell contents is broken by the presence of the nuclei, the contractile 
vacuoles, the food vacuoles, and sometimes by the presence of highly 
refractile bodies, the paramylum bodies. The entire surface of the 
body, except that of the oral plug, is covered with fine cilia. The cell 
contents are retained by a thin transparent pellicle which is protective 



1922] McDonald: On Balantidium coU and Balantidium suis 263 

in function. The cytoplasm is distinctly differentiated into ectoplasm 
and endoplasm. The former constitutes a thin layer just underneath 
the pellicle and in it is situated the basal apparatus of the cilia. The 
layer of ectoplasm thickens greatly at the anterior end of the animal, 
to form, as it were, a matrix for the cytostome and its accessory appa- 
ratus. Within the ectoplasm, but not set off from it by a sharp line 
of demarcation, is the endoplasm. In the endoplasm are numerous 
food inclusions, often present in the form, of starch or paramylum 
bodies. The macronucleus and the micronucleus are also within it, 
but seem to have no constant position in the cell. The .macronucleus 
is either bean-shaped (as in Balantidium coli) or elongate and sausage- 
shaped (as in Balantidium suis). There are two contractile vacuoles, 
the larger being situated anteriorly and the smaller posteriorly. They 
lie closely beneath or may be entirely surrounded by ectoplasm, thus 
belonging really within that layer. 

So far as can be determined the animals show no modification with 
respect to a substratum, yet the lateral and posterior displacement of 
the cytostome has lead to the designation of that side, toward which 
displacement occurs, as ventral, and the opposite surface as dorsal. 
This terminology is very nearly universal in the literature on Balan- 
tidium, and the correlated terms of right and left are used in the 
original description of the family Bursaridae (Stein, 1867) and the 
genus Balantidium (Claparede and Lachmann, 1858). The dorsal 
side may be somewhat more convex than the ventral ; this occurs not 
infrequently in Balantidium suis, though, due to the plasticity of the 
organism, this is by no means constant. No part of the body is differ- 
entiated for skeletal purposes. The anal aperture or cytopyge is at 
the posterior tip and may be present as an actual aperture or only 
as an extreme thinning of the ectoplasm and pellicle at this point. In 
connection with it there is usually a rectal vacuole which serves as a 
storage reservoir for solid waste awaiting extrusion. 



ECTOPLASMIC STRUCTURES 

Pellicle. The entire body is covered by an extremely thin but 
resistant pellicle (pel., figs. I and L). The pellicle seems to be some- 
what thickened, as shown by a higher degree of refractibility, along 
the margin of the lips of the cytostome where it turns in to form the 
lining of the oesophagus and the groove in which the oral cilia are set ; 
otherwise, it is nowhere noticeably specialized. It shows alternating 



264 



University of California Publications in Zoology E V L. 20 




post. c. v 



Pig. I. Balantidium ooli. Ventral view showing principal structures. The 
adoral cilia, with exception of one at either side, are indicated by basal granules 
only. The adoral membranelles are also represented solely by the basal apparatus. 
Ectoplasm is shaded, and ciliary rootlets are shown on one side only. X 1250. 
ad. oil., adoral cilia; ad. cil. /., adoral ciliary fiber; ad. mcmb., adoral membranelles; 
ant. c. v., anterior contractile vacuole; bg., basal granule; bg. ad. cil., basal granules 
of adoral cilia ; cil., cilia ; oil. r., ciliary rootlet ; dr. oes. /., circumoesophageal fiber ; 
cytpg., eytopyge ; ect., ectoplasm ; enl. ad. cil. r., enlargement of adoral ciliary root- 
let; end., endoplasm; gr. b., granular band of ectoplasm; long. /., longitudinal 
fibers; moo., macronucleus ; mic., micronucleus ; mot., motorium; nuc.memb., 
nuclear membrane; oes., oesophagus; or.pl., oral plug; or.pl.f., oral plug fibers; 
pel., pellicle ; per., margin of peristome ; post. c. v., posterior contractile vacuole ; 
rad. /., radial fiber ; ret. v^ rectal vacuole. 



1922] McDonald: On Balantidium coli and Balantidium suis 265 

ridges and grooves, the cilia passing through the bottom of the latter, 
but this condition is not due to longitudinal thickenings in the pellicle 
itself, but to the fact that it is closely applied to the ectoplasm which 
is thus furrowed. It can often be separated in " blisters 'J_ from the 
ectoplasm by tannic acid or weak alcohol, and when thus removed it 
shows regular longitudinal rows of perforations through which the 
cilia pass out from the ectoplasm. In this condition its transparency 
is very evident. The pellicle is not extremely impervious. For 
instance, when the active animals are introduced into normal salt 

ad. memb. _ 

cyst. 




dr. oes. f. II / 



or. pi. f. 



per. 



Fig. J. The neuromotor apparatus of the adoral region, anterior view. X 2000. 
., adoral ciliary fiber; ad. memb., adoral membranelles ; ~bg.ad.cil., basal 
granule of adoral eilia; dr. oes. f., circumoesophageal fiber; oytst., cytostome; 
mot., motorium; or.pl., oral plug; or. pi. f., oral plug fibers; per., margin of peri- 
stome. 

solution plasmolysis takes place very quickly, and they present a 
grotesque appearance as they swim about with several huge depres- 
sions in their surfaces due to the shrinkage. Intra vitam stains such 
as neutral red and Janus green also penetrate very quickly. Resist- 
ance to pressure and mechanical change, however, is very marked, and 
is due to its tenacity and flexibility, both of which qualities are shown 
when the animal forces itself through an opening much smaller than 
the normal diameter of its body (fig. K) and also by the extreme flat- 
tening which it withstands under the increasing pressure of the cover- 
glass when evaporation of the preparation is allowed. As previously 
mentioned, these qualities indicate that the pellicle is protective and 
retentive in function rather than supportive or skeletal. 



266 University of California Publications in Zoology [ V L - 20 

These organisms show remarkable mobility when observed under 
conditions as nearly normal as possible. I have attempted to depict 
something of this plasticity in figure K. As they travel amid the 
debris in the intestinal contents, which has been removed with 
them, a tendency to penetrate is much more noticeable than any 
avoiding reaction. Instead of reversing the ciliary action, backing 
away and taking a new direction as would paramaecia, the balantidia, 
when they come in contact with a solid object, rather appty themselves 
to the surface, round up, and seem to roll along it. After a moment 
of such slow contortion, they may swim away in a new direction, 






Fig. K. Diagrammatic illustration of the plasticity of the organism, resulting 
in ability to pass through remarkably small openings. 

determined by the direction of the anterior end. They avail them- 
selves of the slightest opportunity to force their way through or 
between any obstacles. The anterior end, especially the thickened 
ectoplasmic portion, becomes at such times decidedly elongate and 
conical (fig. K, 6). The cilia of this region beat spirally producing a 
boring action as this anterior tip is protruded into any slight opening. 
This action has in many instances been observed to cause two obstacles, 
either of which was larger than the organism itself, to separate 
sufficiently to allow it to pass between. The aperture need not be 
one-half of the diameter of the animal for the latter will constrict 
(fig. K, c) and the fluid contents flow through anteriorly as it 
progresses, resembling the process of putting a bag of beans through 
a small hole in a board. Throughout observations of the activity of 
these organisms, one is impressed with their fitness for penetrating 
the mucous lining of the intestine and the underlying tissues. Its 
thigmotropic response, its boring action, and its extreme plasticity, 
all seem to be adaptations for the function of penetration. 

Ectoplasm. Immediately underneath the pellicle, the cytoplasm 
is differentiated to form the ectoplasm (ect., fig. I; pi. 27, figs. 1-7). 
The ectoplasmic layer, except at the anterior end, does not exceed two 



1922] McDonald: On Balantidium coli and Balantidium suis 267 

microns in thickness. The anterior end of the animal, that is, all 
anterior to a transverse plane which would transect the body at a 
point % to y 5 of the way to the posterior end, is composed entirely 
of ectoplasm. In this cone-shaped area is located the cytostome and 
a large part of the neuromotor apparatus. The protoplasniTof this 
region seems to be homogeneously granular in fundamental structure.. 
It stains very deeply with haematoxylin ; so deeply in fact, that in 
differentiation it is necessary to destain other parts of the body almost 
completely before this part reaches a degree of transparency suitable 
for study. With Mallory's connective tissue stain this region also 
stains very densely, taking on both the brilliant red and the deep blue 
elements of the stain, in different structures, as will be explained below. 
This extensive thickening of the ectoplasm at the anterior end is clearly 
shown in the figures by Leuckart (1861) and has been noted by nearly 
all who have studied the animal more recently, but I have failed to 
find any discussion of its significance. This same phenomenon occurs 
in the Ophyroscolecidae, as pointed out by Sharp (1914) in his work 
on Diplodinium and by Braune (1913) in Ophyroscolex. In these 
cases the change seems to be correlated with the high degree of activity 
and specialization of the anterior end of the animal ; in Diplodinium 
in connection with its selective feeding, and in Balantidium in con- 
nection with both feeding and activity of this entire region in pene- 
trating the mucosa of the intestine. The centering of the neuromotor 
apparatus in this region gives additional evidence in regard to this 
question which will .be discussed further in connection with the de- 
scription of that apparatus. 

Throughout the entire investigation of the minute structure of this 
animal, I have been unable to demonstrate the presence of any definite 
plane of demarcation between endoplasm and ectoplasm, such as the 
" ectoplasmic boundary layer" described by Sharp (1914) in Diplo- 
dinium, and shown in plate IV, figure 3 of his paper. Many of the 
fixed preparations used in the search for such a layer were sections 
of the animal, treated as nearly as possible according to the technique 
used by him and stained, as were his preparations, with Mallory 's con- 
nective tissue stain. So far as it was possible for me to determine, 
any sharp boundary line between ecto- and endoplasm is lacking. On 
the contrary, they merge into one another and only in a general way 
can it be said where one terminates and the other begins. 

Prowazek (1913, fig. 2) describes, in Balantidium coll, "ein Art 
von Zwischenmembran " which appears as wavy lines in optical sec- 



268 University of California Publications in Zoology [VOL. 20 

tion. According to his interpretation this "Querlinie" separates the 
protoplasm of the cell body into two regions, the * * apical zone, ' ' which 
I have described above as a thickening of the ectoplasm, and the rest 
of the cell protoplasm. The extent of this * * Zwischenmembran " he 
does not note, but his text figures (1 and 2) do not show it as extending 
quite to the pellicle, but instead as stopping short of the pellicle at a 
distance about equivalent to the thickness of the ectoplasm at that 
point. This is significant in my interpretation of this region, namely, 
that what appears as a continuous line or plane when viewed from 
the side is in reality, as shown in cross-sections (pi. 27, figs. 6 and 7), 
a set of diverging fibers. These fibers take origin from dark-staining 



oil 




cil. r. 

end. 

Fig. L. Portion of the peripheral region of a cross-section of Balantidium coli, 
showing the structure of the ectoplasm and arrangement of cilia, somewhat dia- 
grammatic. X 1500. b. ff., basal granule; oil., body-cilia; oil.r., ciliary rootlet; 
end., endoplasm; gr. &., granular band of ectoplasm; hy. &., hyaline band of ecto- 
plasm; pel., pellicle. 

enlargements on the longitudinal fibers in the wall of the gullet and, 
diverging, pass peripherally until they turn posteriorly at the very 
inner edge of the thin layer of ectoplasm which covers the remainder 
of the body (pi. 28, figs. 9-12). Even in lateral view careful focusing 
will often show that the apparent ' ' membrane ' ' is really discontinuous, 
showing breaks and irregularities as one focuses on different levels 
and hence can not be considered as a true membrane. The arrange- 
ment of these fibers will be described more exactly under the discussion 
of the neuromotor apparatus. 

The ectoplasm which constitutes a layer less than 3 microns in 
thickness around the remainder of the periphery of the cell shows 
a definite and somewhat complex structure. In tangential sections 
of the surface, which are so thin that they do not include much of the 
underlying endoplasm, one detects alternating light and dark longi- 
tudinal spiral bands (gr.b., hy.b., fig. N). These bands are parallel 
to the rows of cilia and very nearly equal in width. In cross-sections 
(fig. L) they are seen to extend nearly, if not quite the full depth of 



1922] McDonald: On Balantidium coli and Balantidium suis 269 

the ectoplasm. As one follows these bands (or "stripes," as they are 
named by Johnson (1893, in his work on 8 tent or) anteriorly they seem 
to lose their distinctness when they become continuous with the apical 
cone. In some individuals, however, one can follow them some distance 
into this cone, but never is there the same degree of differentiation of 
the two areas in this region. 

In the living animals, which are often quite opaque due to inclu- 
sions, it is nearly impossible to distinguish these longitudinal light and 
dark bands. With neutral red the dark or granular band stains 
faintly. With the haematoxylin stains used in thin sections of fixed 
material the dark band seemed to be finely granular in fundamental 
structure. The granularity in this case must be determined largely 
by the general appearance and stainability, for the individual granules 
are so small as to defy identification. There is no indication, however, 
of alveolar structure, so that the term granular is probably the more 
applicable and will be used to distinguish this from the light band. 
The latter takes only faintly the stains used and seems hyaline in 
structure. The granular bands lie directly beneath the ridges in the 
cuticle which occur between the rows of cilia. Or more correctly, 
the ridges on the surface of the animal are produced by the projection 
of these granular bands outwardly beyond the hyaline bands. These 
latter are directly beneath the grooves of the surface where the cilia 
pass through the cuticle and attach with the basal granules which lie 
in longitudinal rows; a single row in each hyaline band. The ciliary 
rootlets (cil. r., figs. I and L) extending in from the basal granules 
proceed diagonally inward and pass into the interior margin of the 
granular band. 

Stein as early as 1876 pointed out these alternating dark and light 
stripes in Stentor. To the granular and bright stripes, Biitschli 
(1889) gave the names ' ' Riffenstreif en " and " Zwischenstreif en, " 
respectively. Johnson (1893) gives a careful description of these 
bands as they occur in Stentor coeruleus. He notes that they vary 
greatly in width, and this is true in Balantidium; but both bands are 
much narrower than in Stentor, the combined width of the two not 
exceeding two microns. In Stentor coeruleus Johnson (1893) gives 
the width of the granular band as 22/x and that of the bright band 
as 7/x, these measurements being taken just under the adoral zone. It 
is interesting to note that in Balantidium coli the granular band is also 
slightly wider than the bright band. These bands become narrower 
from the region of the greatest circumference of the animals toward 



270 University of California Publications in Zoology [ VoL - 20 

each end, which is comparable with the arrangement in Stentor, 
though in the latter the narrowing must necessarily take place in the 
posterior direction only. The above author mentions the branching 
of stripes, but this does not occur in Balanticfrium so far as I have been 
able to determine. As the bands pass posteriorly, however, they 
become less distinctly differentiated and are hard to follow, and it 
might be that further study with more intensive stains would reveal 
a union in the region of convergence at the posterior end. More recent 
work has added to the number of Heterotricha that show this sort of 
differentiation of ectoplasm. Maier (1903) shows the striped nature 
of this layer in Prorodon and Spirostomum, while Neresheimer (1903) 
confirms the structure found by Johnson ( 1893 ) in Stentor. Schuberg 
(1887) also indicates a comparable plan of structure in Bursar la. 
The granular ridges of ectoplasm between the furrows in which the 
anal cirri are situated in Euplotes patella, discovered by Yocom 
(1918), may be comparable with the bands which occur in Hetero- 
tricha. 

Cilia. The entire surface of Balanticbium coli, with the exception 
of the oral plug, is thickly beset with cilia (cil., ador. c., fig. I). These 
are of two kinds, viz., those which make up the adoral row of cilia 
and which measure from 8 to 12/A in length, and those covering the 
body, which vary from 4 to 6ju. Those covering the apical cone form 
an intergradation between the two. On this surface the cilia which 
occur immediately posterior to the adoral row are only slightly shorter- 
and slightly more slender than the adoral cilia themselves. Passing 
posteriorly they gradually become shorter and less cirrus-like until 
they reach the base of the apical cone. Thence posteriorly they retain 
the uniform size. 

The body cilia are comparatively short and very slender. So small 
are they in fact that to observe a single one is nearly impossible. In 
slides prepared by the usual methods no stain remains in the cilia if 
destaining is carried sufficiently far to differentiate other structures. 
Iodine (Weigert's solution) gives a fairly satisfactory stain for tem- 
porary mounts. The arrangement of cilia may be determined most 
readily by using a heavier stain and then observing the distribution 
of basal granules. Neutral red proves very satisfactory for this pur- 
pose. The cilia occur in longitudinal, slightly spiral rows, following 
the grooves between the ridges in the pellicle. These rows originate 
immediately posterior to the groove in which the adoral cilia are set 
and for a very short distance pass almost meridionally ; very soon, 



1922] McDonald: On Balantidium coli and Balantidium suis 271 

however, they turn toward the left, that is, in a counter-clockwise 
direction when the animal is viewed from a point exactly in front. 
They continue their spiral direction until almost to the posterior end 
when they again follow a meridional path to their termination. In 
passing the entire length of the body any single row of cilia twists to 
the left approximately 120, or one-third the entire circumference. 
Whether some rows terminate or become continuous with contiguous 
rows before reaching the posterior tip of the animal, I have been 
unable to determine, for both basal granules and granular bands 
become very indistinct in this region even in the best preparations. 
The number of rows was counted with difficulty in several cross- 
sections from the equatorial regions of different animals, and it was 
found to vary from about 60 in small individuals to 120 in larger ones. 
No correlation between the variation in the number of rows of cilia 
and the species of the animal could be determined, but this is possibly 
due to the limitation of observation. 

Basal apparatus. The cilia perforate the pellicle and attach to 
the basal granules which lie immediately underneath (fig. L). The 
latter are small and apparently spherical or oval. They stain very 
deeply black or blue with haematoxylin. In the living animal they 
are readily emphasized by the use of neutral red, and less so by Janus 
green. In preparations stained with Mallory's connective tissue stain 
these granules show brilliantly red with the acid fuchsin, as do the 
other parts of the neuromotor apparatus and also the micronucleus. 
Longitudinally the granules are so closely placed that it is impossible 
to observe whether they are actually connected by a fibre. Cross- 
sections show that the cilia of one row have no transverse connection 
by any sort of stainable fiber with those of the next row. The rows 
of basal granules lie close beneath the depression in the pellicle in 
the hyaline or bright band of the ectoplasm. A ciliary rootlet (cil. r., 
figs. I and L) extends from each basal granule centrally toward the 
endoplasm. It does not proceed in an exact radial line but rather 
diagonally toward the right until it enters the granular band near 
the inner surface of the latter. The ciliary rootlets in some cross- 
sections appear to have an exactly radial direction. In such cases, 
however, the granular band is somewhat diagonal in the opposite 
direction. This variation is probably produced either by torsion of 
the animal or by the direction of the effective beat of the cilia at the 
instant of fixation. The diagonal direction of the rootlets is readily 
detected in tangential sections. In focusing down through such a sec- 



272 University of California Publications in Zoology [ V OL. 20 

tion, the rootlet is invariably seen to run from the basal granule 
toward the observer's right into the contiguous granular band on that 
side. Thus, to avoid any confusion that might arise from the terms 
right and left, in a cross-section of the animal viewed from the anterior 
surface (such a view is shown in fig. L) the ciliary rootlets swerve in 
the counter-clockwise direction and enter the granular band lying 
immediately in that direction. 

As the rootlet enters into the granular band it apparently enlarges 
thus forming a secondary basal granule. In some cases this may stain 
even more deeply than the basal granule itself, and appear as a definite 
body somewhat elongated in the direction of the circumference of the 
animal. It was thought at first that this might be the cross-section of 
a longitudinal fiber or myoneme. But the study of numerous tan- 
gential sections has failed to show the presence of any longitudinal 
fiber within the granular band. The stainability varies greatly and 
in preparations which have stained lightly the ciliary rootlets appear 
to fray out and merge into the granular band, while still retaining 
deeper color than the rest. Which interpretation is correct it is 
difficult to say, but the latter seems the more probable, especially in 
view of certain relations with the neuromotor apparatus which will 
be discussed later. 

Putter (1903) reproduces a figure from Studnicka (1899) showing 
in a schematic way five types of attachment of the cilia with their 
basal apparatus. Of these, two, at least, represent cases in which two 
basal granules or a diplosome are present. Saguchi (1917) in his 
studies on ciliated cells of Metazoa says in part regarding the basal 
granules of certain ciliated cells from amphibian larvae, ' * With favor- 
able staining the basal corpuscles appear as diplosome or dumbbell 
shaped granules. One of these is situated at the upper the other at 
the lower border of the cuticle." In Balantidium coli the arrange- 
ment with respect to protoplasmic layers is quite different, though 
the cilia seem to follow somewhat the same plan of structure even to 
the presence of rootlets. 

The most fruitful comparison may be made with the .basal appa- 
ratus of cilia in Isotricha prostoma as described and pictured by 
Braune (1913). In this organism he describes diplosomic structure 
of the basal apparatus, in which the basal granule lies directly beneath 
the pellicle. The cilia, however, extend beyond the basal granule into 
the underlying layer the * * Zwischenschicht " of Eberlein, and ter- 
minate in the "Grenzschicht" with a second granule, which upon 



1922 J McDonald: On Balantidium coli and Balantidium suis 273 

maceration remains attached to the basal end of the cilium. So the 
basal apparatus in Balantidium coli even to the relative location of 
the basal granules is almost identical with that in Isotricha prostoma. 
In Balantidium, however, as mentioned above, the "Grenzschicht" 
seems to be lacking. The comparison becomes more significant in view 
of the fact that both ciliates are parasitic in the digestive tract of 
mammals, and both are in much the same state with reference to 
the degree of specialization and degeneration correlated with habits 
of the parasitic mode of life. So that in general morphology they 
seem to be more alike, though they are in separate orders, than do 
Diplodinium ecaudatum and Balantidium coli, which are in separate 
suborders only. 

Ciliary Movements. 

Locomotion is the chief function of the cilia except for those of 
the adoral zone. The balantidia swim in approximately a straight 
line and not in a spiral course as do paramoecia. They do, however, 
rotate on their axis as they progress. This rotation is generally from 
left to right, that is, in a counter-clockwise direction when viewed from 
a point in front of the animal. A few instances of reversal of the 
direction have been seen, but it is not at all common. The direction 
of rotation, i.e., from left to right, seemed at first inexplicable, since 
this was not compatible with the direction of the rows of cilia. The 
rows of cilia, as described above, are comparable to the threads of a 
left-hand screw. In order to penetrate, such a screw must be turned 
in a clockwise direction (when viewed from the point, not from the 
head). Such, also, is the direction of rotation, of balantidia which one 
would expect to find if the arrangement of the cilia were the con- 
trolling factor, but the rotation is in the reverse direction. In the 
further study of the problem, I fortunately obtained some very thin 
tangential sections of animals on which the fixative had acted so 
quickly that the cilia were stopped instantly and left in the relative 
positions assumed in normal ciliary action. 

Figure N is a camera lucida drawing of such a section. By analysis 
of the position of the cilia on this and other like sections, it was 
possible to determine the complete cycle of a single cilium. This cycle 
is diagrammatically represented in figures M and 0. Figure N 
includes about two and one-half cj^cles of action as represented by 
the waves. The dark portions are produced by the prostrate position 
of the cilia at the termination of the effective stroke. The lighter 



274 University of California Publications in Zoology t v L - 20 



areas between are due to the fact that the cilia are recovering their 
vertical position and hence are viewed very nearly endwise. The 
position of consecutive cilia in any single row, from one point in a 
wave to a similar point in a following wave will fairly represent the 
successive positions taken by a single cilium in making one complete 
cycle. Figure M was made in this way. The arrow represents the 
long axis of the animal. From this diagram it is seen that the cilium 
at the end of the effective stroke lies rather close to the surface of 
the body and not along the row but decidedly to the left from it. In 




-a 





Fig. M 



Fig. N 



Fig. O 



Fig. M. Diagrammatic representation of the successive steps in one complete 
beat of a cilium of Balantidium coli. It also illustrates the positions of the respec- 
tive cilia of a single row between the points a and & in fig. M, at which points the 
cilia are in a prostrate position at the end of their effective stroke. The arrow 
indicates the long axis of the animal. 

Fig. N. Tangential section of Balantidium coli. The cilia still retain respec- 
tive positions which they had in the normal swimming movements of the organism. 
X 1500. 

Fig. O. Diagram illustrating the effect of the ciliary action in the rotation of 
the organism. The arrow represents the long axis of the animal; ab., the direction 
of the rows of cilia ; cd., the direction of effective stroke of a cilium attached 
at the point of intersection of the three lines; the ellipse is described by the tip 
of the cilium. 

recovery it straightens up and passes anteriorly, thence to the right, 
crossing the row, of which it is a part, at right angles. At this point 
the cilium leans anteriorly only slightly from the vertical. The 
effective beat is produced by the quick stroke of the cilium posteriorly 
and to the left, and continues until the cilium has crossed the row again 
and lies close to the surface and extends to the left as represented 
by the position of the last cilium shown in figure M. According to 
the classification given by Putter (1903), the movement of the cilia 
of Balantidium would be called^ infundibular. As will be noted from 



1922] McDonald: On Balantidium eoli <md Balantidium suis 275 

figure 0, the funnel described by the complete beat .of the cilium 
is somewhat irregular, the rim outlined by the tip of the cilium is 
elliptical, and the base of the cilium, i.e., the neck of the funnel, is 
not central but is situated below the anterior focus of the ellipse. 
The ellipse described by the tip of the cilium lies in a plane which is 
not parallel to the surface of the animal, but which approaches it 
much more closely posteriorly. It was possible to corroborate the 
action of the cilia in observations on the living material. The cilia of 
the apical cone are somewhat larger than the other cilia of the body, 
and are closely coordinated in their action. In balantidia which were 
allowed to cool until action had slackened considerably, these cilia 
were observed to make their effective stroke at a decided angle to the 
rows of cilia. For instance, in the boring action in connection with 
the process of penetration described above, these cilia will beat in an 
almost exactly transverse direction, always from right to left. In 
further corroboration of this interpretation of the movements of the 
cilia is the fact that it explains the rotation of the animal during 
progression. It will be seen from figure that the effective stroke 
of any single cilium will be in the direction cd. This line crosses both 
the arrow, representing the long axis of the animal, and the line a&, 
representing the rows of cilia, making an angle of approximately 
20 with the latter. That is, the line cd forms an angle with the arrow 
on one side about equal to the angle on the opposite side made by the 
line ah. It clearly follows that if the effective stroke is in the direction 
cd then rotation will be from left to right and not vice versa as would 
be the case if the cilia beat in the direction of the rows in which they 
are arranged. The structure of the basal apparatus is significant in 
view of the direction of the effective stroke of the cilia, viz., posteriorly 
and to the left. The cross-section shown in figure L is viewed anter- 
iorly and shows that the ciliary rootlet from each basal granule passes 
to the right and enters the granular band on that side of the hyaline 
band in which the basal granule lies. Without giving to the ciliary 
rootlets any motor or skeletal function, it still seems logical that they 
conform in a general way to the axis of the cilium, for the latter during 
the greater part of its movement inclines to the posterior and left of 
the row of which it is a constituent. 

The peristome (per. fig. J) may be said to comprise all that part 
of the organism which lies within the row of adoral cilia. In the 
active animal it is variable in shape. At times it is almost round 
while at other times it may become a mere slit or groove. In what 



276 University of California Publications in Zoology [ V L - 20 

seems to be its more normal proportions, however, it is approximately 
pear-shaped with the stem end of the pear directed ventrally. In 
Balantidium eoli the adoral zone commonly includes the most anterior 
point or apex of the animal at least its dorsal margin passes through 
this point. In Balantidium suis, the anterior tip of the animal lies 
wholly outside of this zone, the latter having migrated too far ventrally 
to include it. 

The cytostome (cytst., fig. J) does not occupy the whole interior 
of the peristome, but is situated at its ventral end. There is some 
indication that this aperture may be completely closed by the oral 
plug (or. pi., fig. I) which comprises the rest of the peristome within 
the adoral row of cilia. This oral plug bears no cilia. It is exceed- 
ingly mobile, adapting itself readily to the almost constantly changing 
shape of the apical cone. It lies dorsal to the cytostome and is not 
exactly bilaterally symmetrical since it is pushed somewhat to the left 
to make room for the oesophagus. It extends inward, thinning as 
it does so, until it terminates about the beginning of the endoplasm. 
It is ectoplasmic, but very finely granular as compared with the rest 
of the ectoplasm. Mallory's connective tissue stain ordinarily gives 
it a decidedly bluish tinge with slight spots of red only where there 
are certain neuromotor fibers. Its action in feeding is very hard to 
follow, but its high degree .of mobility impresses one when watching 
the activities of the organism, and may be demonstrated with fixed 
material by its extreme protrusion (pi. 28, fig. 14). In addition to 
this, the fact that it is intimately connected with the neuromotor 
apparatus would indicate that it functions in selective feeding. The 
oesophagus (oes., fig. I; pi. 27, figs. 48) beginning at the cytostome, 
passes inwardly, not quite radially but swerving slightly to the right. 
It may be followed definitely through the ectoplasm and for a very 
short way into the endoplasm where it ends blindly. So far as I 
have been able to determine, it is a uniform tube-like opening without 
evident enlargements or constrictions. Prowazek (1913), however, 
gives in part the following description, ". . . . es sehnt sich jedoch 
nicht direct trichterformig in die Tiefe, da man von der drei scharfe 
Konturen noch nachweisen kann (fig. 1)." While studying living 
forms stained with neutral red, I have often observed specimens in 
the exact position of the one shown by Prowazek (1913, p. 7, text 
fig. 1). The lines shown by him were easily recognizable, deeply 
stained with the neutral red, but I could interpret them only in the 
following way. The most anterior line which he shows seems to be 



1922] McDonald: On Balantidium coli and Balantidium suis 277 

clearly the ventral lip of the peristome ; the second line was identical 
with the deep staining motorium (fig. I) in the forms which I studied, 
and the most posterior line seemed identical with the ring of enlarge- 
ments on the rootlets of the adoral cilia which lie close about the 
oesophagus. The margin of the peristome is slightly raised^ forming 
a ridge or lip. This ridge is most pronounced from the midventral 
point, dorsal along the right margin of the cytostome, but as it pro- 
ceeds around it becomes rather inconspicuous and wholly disappears 
on the left side. Thus the cytostome has the appearance of opening 
under a ledge, the ledge formed by the lip of the right side. 

The peristome is delimited by an almost complete spiral circlet of 
cilia, the adoral cilia (ad. cil., fig. I). The exact point of origin of 
the row is hard to determine but it is approximately at the ventral 
edge of the peristome, i.e., on the ventral lip of the cytostome. From 
here it proceeds in a sort of groove, along the right margin, around 
the dorsal margin, and down the left margin of the peristome. A 
short distance in advance of the ventral point, the row of adoral cilia 
turns into the cytostome and continues in a spiral course down the 
oesophagus ; entering at the left dorsal side and ending in the ventral 
wall about halfway down. Thus these cilia in their entire course make 
one complete left-hand spiral, beginning on the ventral lip, passing 
around the peristome and down the oesophagus, terminating in its 
ventral wall. 

Over the lip of the cytostome between the point where the adoral 
cilia turn into the oesophagus and the midventral point where this 
row of cilia has its origin, the longitudinal rows of body cilia turn in. 
Each of these rows, of which there are ten or twelve altogether, con- 
tinues down the oesophagus until it meets the row of adoral cilia. 
Since this latter enters spirally, there is a ciliated patch on the ventral 
wall of the funnel-shaped 'oesophagus which is roughly the shape of a 
right triangle, the base of which is the lip of the cytostome. The 
hypotenuse is the row of adoral cilia which makes an acute angle with 
the longitudinal row of body cilia which enters in the mid line and 
which represents the third side of the triangle. 

The adoral cilia, except where they lie within the oesophagus, are 
completely separate each from the other. This is easily verified by 
watching their action especially in a disintegrating animal, or one 
cooled to slow up ciliary movement, under which condition coordina- 
tion is frequently interrupted, and a single cilium will be seen acting 
independently of its neighbor. Additional evidence is to be found in 



278 University of California* Publications in Zoology [VOL. 20 

the individuality of each basal granule. There is no evidence of fusion 
of granules, though adjoining granules are connected by a neuromotor 
fiber. However, in the triangular area mentioned above, there is con- 
siderable evidence that the cilia are united to form membranelles. It 
is very difficult to watch the action of these cilia, and the above con- 
clusion was reached largely through a study of fixed material. In 
cross-sections (pi. 27, fig. 4) the cilia of the region seem to be very 
close together and quite regularly to be connected by, or to form, a 
sheet of almost transparent substance. The regularity of this occur- 
rence would lead one to believe that it is the normal structure and not 
due to entanglement of the cilia in foreign matter. In addition, the 
basal granules of this region (pi. 27, figs. 4 and 5) do not stand out 
separately, but are so closely packed that they give the appearance 
of a single deeply stained mass. I have been unable to distinguish 
separate granules in the inner portion of the area and it seems likely 
that actual fusion of the granules may have occurred. The basal 
apparatus of this region is so densely packed and takes stain so readily 
that in certain views it may easily be mistaken for the motorium. As 
a result, it seems plausible to interpret this area as the basal apparatus 
of membranelles which lie in a plane transverse to the axis of the 
oesophagus. If this region be interpreted as a primitive oral groove 
or cytostome, a forerunner of such an elaborate arrangement as occurs 
in Euplotes patella (Yocum, 1918) or in Stentor, then comparison is 
very significant, for in the latter two the membranelles also run trans- 
versely in the cytostome. The only difference, then, between these 
organisms and Balantidium in this regard would be the difference in 
shape and extent of the area. 

The adoral cilia (ad. til., fig. I) are approximately double the 
length of the body cilia, i.e., from 6/x to S/A in length or, in the very 
large individuals, they may reach a maximum length of 10/x. In 
fundamental structure they are like the body cilia, but the relative 
position of parts is somewhat different. Immediately beneath the 
pellicle each cilium bears a basal granule and from this a fiber con- 
tinues inward which passes between the adoral plug and the surround- 
ing ectoplasm. The sum of all the fibers from adoral cilia marks off 
very distinctly the conical cytostomal region from the surrounding 
ectoplasm. They seem to constitute the only partition between the 
protoplasm of the two areas, for I have not been able to detect any 
membrane in this region making a complete separation of the adoral 
region from the rest of the apical cone. Where the fibers pass from 



1922] McDonald: On Balantidium coli and Balantidium suis 279 

the ectoplasm of this cone into the endoplasm, each bears an enlarge- 
ment which stains very deeply. This enlargement is undoubtedly 
homologous with the inner enlargements of the basal apparatus of 
the body cilia for it bears the same relation to the basal granule and 
the cilium. It is farther removed from the basal granule but it main- 
tains exactly the same relation to the ectoplasm and endoplasm, that 
is to say, in either case this enlargement lies in the plane between the 
two. From each enlargement a radial fiber extends laterally along 
the base of the apical cone to the periphery of the cell. The portion 
of the ciliary rootlet which continues inward from this enlargement is 
very distinct and may often be traced almost to the posterior end of 
the animal (fig. I). In no instance has it been possible to demonstrate 
any attachment or connection of the posterior ends of these rootlets. 
They often cross near the center of the organism and then fade out, 
becoming indistinguishable in the endoplasm. For a short distance 
inward from the oesophagus they are so closely placed dorsally and 
laterally that they form a kind of wall, but ventrally they are less 
numerous and likely to be much shorter, so that the pseudo-wall is 
not complete. It is sufficient, however, to direct the food for some 
distance into the endoplasm. There is no such high degree of differ- 
entiation here as Sharp (1914) found in the oesophagus of Diplo- 
dinium ecaudatum. 

The homology of the adoral and body cilia is evidenced by the com- 
plete series of gradations from the one to the other which exist in the 
cilia of the apical cone (fig. I). The cilia which are proximal to the 
adoral cilia are almost identical with them. They are slightly smaller, 
but each has the basal granule beneath the pellicle, a fiber connecting 
this with an enlargement at the plane of differentiation of ectoplasm 
from endoplasm, and the rootlet extending posteriorly.- The inner en- 
largement is much smaller and the ciliary rootlet shorter than those of 
the adoral cilia. These enlargements are connected with the enlarge- 
ments of the adoral cilia by the radial fibers mentioned above. Passing 
posteriorly the cilia become progressively smaller, the basal granule 
and the enlargement closer together (due to the approach of the trans- 
verse plane of demarcation between ectoplasm and endoplasm to the 
pellicle), and the ciliary rootlets become progressively shorter and less 
distinct, until the cilia of the marginal area of the apical cone become 
identical with the body cilia. This apical cone then shows us a com- 
plete gradation of differentiation between the body cilia and the adoral 
cilia, and proves their homology. 



280 Umverstiy of California Publications in Zoology [VOL. 20 

Feeding is the chief function of the adoral cilia. They are closely 
coordinated in action, as is shown by the fact that in degenerating in- 
dividuals they will beat in unison after other cilia beat only erratically 
or have ceased entirely. Coordination is most pronounced in the cilia 
of the left lip. The action of the adoral cilia produces a strong eddy 
in the surrounding medium with the vortex of the eddy within the 
peristome. In the above description it was noted that the right lip 
projected slightly forming a ledge or bank. The current produced 
by the cilia strikes against this ledge and solid objects are deflected 
into the underlying cytostome. The natural rotation of the animal 
on its longitudinal axis as described above aids in this process, for the 
right lip thus acts as the blade of an auger. The food particles pass 
down the oesophagus and collect at the inner end in a sort of droplet. 
After several bits have been collected, the droplet begins its circulation 
in the endoplasm as a food vacuole. 

The closure of the cytostome in all probability is effected by the 
oral plug. The latter is very mobile and contains fibers of the neuro- 
motor apparatus. It has frequently been seen to project anteriorly 
in a knoblike protrusion (pi. 28, fig. 14). This same phenomenon was 
observed by Wising (1871). In view of its situation, its sensitivity, 
and its mobility, it seems plausible to interpret it as an oral plug 
with essentially the same function as the oral disk of Diplodinium 
ecaudatum (Sharp, 1914). 

The discharge of indigestible portions of the food takes place at 
a constant point at the posterior end of the animal, the cytopyge (cyt., 
fig, I). It is an opening, however, only at the time of discharge. 
At other times there is only a thinning of the cortical layer which can 
be identified with comparative ease in fixed material. In the living 
organism the process of defecation was frequently observed. The 
undigested particles become segregated at the extreme posterior end 
in a sort of vacuole, the rectal vacuole (ret. v., fig. I; pi. 28, fig. 13). 
After this vacuole has become of considerable size (often filling one- 
third of the cell in degenerating forms) the pellicle over the cytopyge 
ruptures and the contents are discharged. The pellicle quickly forms 
again closing the aperture, collection of indigestible particles in the 
rectal vacuole continues, and the process is repeated. 

The contractile vacuoles (post. c. v., ant. c. v., fig. I) are two in 
number, usually situated on the dorsal side, one anteriorly, well up 
toward the apical cone, the other in the posterior one-third of the 
organism. There is a great deal of variation in their location in 
different animals, though in the individual their situation seems to be 



1922] McDonald: On Ealantidium coli and Balantidium suis 281 

very constant, at least throughout the limit of possible observation. 
These vacuoles seem clearly to originate within the ectoplasm. When 
fully distended they encroach far upon the region of the endoplasm 
and it becomes impossible to tell whether or not they are entirely sur- 
rounded by ectoplasm ; but from their origin such might be suspected 
to be the case. Also such is the case in many related forms, for 
example, Diplodinium eodudatum (Sharp, 1914) and Euplotes patella 
(Yocom, 1918). 

The pulsation of the vacuoles was observed in several instances 
for a long period of time. The rate of pulsation varies considerably, 
occurring as rapidly as once in every thirty seconds under some 
conditions, while under others a complete cycle from discharge to 
discharge occupies a period of five minutes. In degeneration the 
pulsation is likely to be very much retarded or may cease entirely, 
the vacuoles becoming enormously distended and breaking together 
thus forming one large vacuole occupying fully one-half of the interior 
of the organism. Following this the animal ruptures and disintegrates. 
The observation of a considerable number of normal individuals has 
shown the usual cycle to be as follows. At two points in the ectoplasm 
small droplets of clear liquid appear. These increase in size and 
become the vacuoles usually seen. Contributing vacuoles or channels 
such as occur in Paramaecium have never been noted. When they have 
reached sufficient size (10/x, to 15/* in diameter in the ordinary indi- 
vidual), they change from their spherical shape and begin to bulge, 
each on the side toward the other. These bulges elongate until they 
meet at a midpoint. At this midpoint a new vacuole arises and into 
it, through the channels thus formed, the two vacuoles discharge their 
contents. This large middle vacuole almost immediately discharges 
to the exterior through the pellicle, and at the same time the other 
two vacuoles re-form. However, the discharge of the middle vacuole 
may be delayed until the other two are well formed and then the 
individual has three vacuoles present. This and other variations are 
not uncommon and should be taken into account in the use of the 
number of vacuoles as a basis for classification. Leuckart (1861) 
described a third contractile vacuole though he did not give its rela- 
tive position to the other two and he did not describe the process of 
contraction. He reported that he had observed the vacuoles "drop- 
like" through the cytoplasm and wandering from place to place. 
Solojew (1901) described the two vacuoles and observed a canal con- 
necting the two, but he did not explain its function in discharge of 
the contents. 



282 University of California Publication* in Zoology [VOL. 20 



ENDOPLASMIC STRUCTURES 

Endoplasm. Within the ectoplasm the body is composed of the 
endoplasm (end., pi. 27, figs. 7 and 8; pi. 28, figs. 9 to 12) and the 
inclusions therein. The endoplasm is less dense than the ectoplasm 
and more coarsely granular. It is quite fluid, having a fairly definite 
circulation in the active organism. From the inner end of the 
oesophagus the direction of flow is posteriorly along the ventral sur- 
face dorsalward just before reaching the posterior end, thence an- 
teriorly along the dorsal surface. Just as it reaches the ectoplasm 
of the apical cone, it is deflected posteriorly down through the central 
portion of the body dorsal to the rootlets of the adoral cilia. This 
course can be followed readily by observing the circulation of the food 
vacuoles. 

The food vacuoles are customarily globular and may contain starch 
granules, bacteria, or indigestible particles, of the food of the host. 
The ingestion of bacteria is probably abnormal since it seldom occurs 
except when the number of bacteria in the medium has increased 
greatly during incubation. The starch granules may occur in enor- 
mous numbers especially when the host has recently been fed on grain. 
Red blood cells have not been noted in any of the balantidia observed 
during the work. 

That Balantidium may be cannibalistic is the only possible in- 
terpretation of several findings. In these instances small individuals 
were lying within the endoplasm of extremely large individuals 
(100 X 125/i) and were in a state of disintegration. The larger indi- 
viduals were Balantidium coli in every case and the smaller may have 
been Balantidium suis, for both species were present in the material ; 
but disintegration of the latter had progressed so far that specific 
identification was uncertain. The possibility of interpreting this 
phenomena as sporulation, which was described by Walker (1909), 
is precluded by the disintegration of the included organism and the 
fact that the normal vegetative phase of the nuclei of the large indi- 
vidual is unmodified. Further evidence is to be found in the fact 
that never more than a single individual has been found inside 
another, while sporulation would produce several. 

Macronucleus. As is generally the case in ciliates, balantidia are 
binucleate, having a large macronucleus and a small micronucleus. 
The macronuclei of Balantidium coli and Balantidium suis are slightly 



1922] McDonald: On Balantidium eoli and Balantidium suis 283 

different with respect to size and proportions as noted above (page 
259), but structurally they are so closely alike that one description 
will suffice for both. The macronucleus (mac., fig. I, pi. 28, figs. 13 
and 14) always lies in the endoplasm but otherwise is not^constant 
in location. Immediately surrounding it is an area in which the endo- 
plasm is less granular and less dense in appearance, due perhaps as 
Yocom (1918) has suggested of Euplotes patella to more rapid oxida- 
tion in this region. It is elongate and may be straight and rodlike 
or it may be sharply bent into a horseshoe shape. In any case its 
diameter increases toward either end, giving it something of a dumb- 
bell shape. This constriction in the central region and enlargement 
at each end is more marked in Balantidium coli than in Balantidium 
suis. The nucleus is delimited by a definite nuclear membrane 
(nuc. m., fig. I) which is especially apparent in material in which 
the macronucleus has shrunk due to faulty technique. Within this 
membrane are packed rather densely the masses of chromatin. The 
chromatin never occurs in equal sized regular granules but rather in 
unequal very irregular masses, sometimes of considerable size (1 to 2/x, 
in greatest dimension). Often there is a sort of vacuolated area, 
usually near one end of the macronucleus, which is free from chroma- 
tin. The significance of this vacuolated area I could not determine. 
It does not seem to be due to degeneration and is not related to any 
phase of reproduction. It is in no way comparable to the ' ' reconstruc- 
tion band" described by Griffin (1910) and by Yocom (1918) in 
Euplotes worcesteri and Euplotes patella, respectively. The chromatin 
stains black with haematoxylin so that the macronucleus is the most 
conspicuous structure in a stained individual. When Mallory's con- 
nective tissue stain is used, the macronucleus takes on an orange hue. 
Micronucleus. The micronuclei (mic., fig. I) of both species of 
Balantidium parasitic in pigs are exceedingly small, not exceeding 
5/x. in diameter. In the resting or vegetative phase the micronucleus 
is subspherical and its flattened side lies close against the nuclear 
membrane of the macronucleus. It may even lie in a depression in 
the macronucleus in which position it is scarcely distinguishable from 
the granules of the latter. It is surrounded by a nuclear membrane 
readily recognized when the micronucleus is undergoing mitosis. In 
a few instances the chromatin has appeared indistinctly granular but 
it is customarily so closely packed that it looks like a single solid mass. 



284 University of California Publications in Zoology [ V L. 20 



NEUROMOTOR APPARATUS 

The term neuromotor apparatus denotes an integrated system of 
fibers, with a coordinating center, which is present in some Protozoa, 
and which is credited with the power of conductivity of nervous im- 
pulses, and hence functions in the coordination of the motor organelles 
of the cell. The term was first used for ciliates by Sharp (1914) in 
his account of the structure of Diplodiniwm ccaudatum. Since then 
it has been employed by Kofoid and Christiansen (1915), Kofoid 
(1916) for flagellates, and by Yocom (1918) and by Taylor (1920) 
in their studies of the morphology and behavior of Euplotes patella. 

The neuromotor apparatus of Balantidium coli can scarcely be 
considered apart from the motor organelles of the cell. To insure 
clarity in the description and discussion which follows, the motor 
organelles, previously described in some detail, will be briefly reviewed. 
With the exception of the oral plug which surrounds the cytostome 
the organism is thickly beset with cilia. Of these, the adoral cilia are 
largest. They are distributed about the margin of the peristome in 
a row which ends in the membranellar region in the ventral wall of 
the oesophagus. The rootlets of these cilia are exceedingly long, reach- 
ing well into the posterior third of the cell, where they end without 
any connection or attachment. They have two enlargements, the first 
being the basal granule which lies just beneath the pellicle, and the 
second being located at the junction of ectoplasm and endoplasm. 
The remainder of the cilia are arranged in longitudinal spiral rows. 
The most anterior cilia of these rows, i.e., those nearest the adoral 
cilia, are nearly as sturdy as the adoral cilia themselves. But, pro- 
gressing -posteriorly in the rows, the cilia become continuously smaller 
until they reach their minimum size at the base of the apical cone of 
ectoplasm. Likewise the ciliary rootlets become shorter, and the dis- 
tance between the basal granules and the secondary enlargements of 
the rootlets becomes less and less as one approaches the base of the 
apical cone. This is shown in figure I. The remainder of the way 
posteriorly the cilia are of uniform size, and the secondary enlarge- 
ment of the basal apparatus of each cilium is the termination of the 
ciliary rootlet and lies in the granular band of ectoplasm near its 
plane of junction with the endoplasm. 

In Bala/ntidium coli five distinct parts constitute the complete 
neuromotor apparatus, namely (1) a motorium or coordinating cen- 
ter, embedded in the ectoplasm close by the oesophagus, and from it 
fibers pass out to the oral plug and the motor organelles ; (2) a circum- 



1922] McDonald: On Balantidium coli and Balantidium suis 285 

oesophageal fiber, beginning and ending in the motorium and giving 
off branches as it passes through the oral plug; (3) a fiber connecting 
the adoral cilia and the cytostomal membranelles with the motorium ; 
(4) the adoral ciliary rootlets passing posteriorly from the basal 
granules of the adoral cilia, each bearing an enlargement where it 
passes from ectoplasm into endoplasm, and finally ending without 
attachment in the endoplasm of the cell; (5) the radial fibers taking 
origin from the enlargements of the adoral ciliary rootlets and passing 
radially to the ectoplasmic layer where they turn posteriorly into the 
granular band. 

The motorium (mot., figs. I and J) when viewed in ventral aspect 
has somewhat the appearance of a reversed letter J. It lies within 
the ectoplasm of the apical cone, close to the ventral and right walls 
of the oesophagus. The part of the motorium corresponding to the 
vertical shaft of the J lies along the right wall of the oesophagus, and 
its anterior terminus is situated just inside and slightly dorsal from 
the point of origin of the right lip of the cytostome. The curved end 
of the J is posterior and passes ventrally and anteriorly around the 
oesophagus and ends close to the inner termination of the rows of 
adoral cilia. In the middle region a sharp slit-like constriction is often 
very conspicuous. It is with the part of the motorium anterior to this 
constriction, that the circumoesophageal fiber and the adoral ciliary 
fiber have their origin. The portion posterior to this constriction is 
quite variable both in size and in stainability. This variation is very 
suggestive of the behavior of the parabasal body of certain flagellates 
as described by Kofoid and McCulloch (1916), Swezy (1916), Kofoid 
and Swezy (1919). These authors have shown that the parabasal body 
is not kinetic in function but instead is a reserve or reservoir of 
material easily transformed into energy, which reservoir fluctuates 
according to the physiological condition of the animal. No direct 
evidence can here be advanced establishing such a function for this 
posterior portion of the motorium, but the fact of its fluctuation in 
volume and its variation in chemical nature (as shown by stains) 
would lead one to suspect that such an interpretation is correct. 

The oircumoesophag&al fiber (dr. oes. /., figs. I and J) takes origin 
from the anterior extremity of the motorium and passes into the oral 
plug. Its course is very close to the inner, i.e., oesophageal, surface 
of the plug. It encircles the oesophagus completely but in the mem- 
branellar area it becomes very hard to follow. Certain sections (pi. 27, 
fig. 3), however, seem to show that it unites again with the motorium. 
It is not a smooth fiber but bears irregular enlargements from which 



286 University of California, Publications m Zoology [VOL. 20 

fibers pass both posteriorly and anteriorly into the ectoplasmic mass 
of the oral plug. These branches make no observable connections, but 
seem to fade out in the ectoplasm. Morphological evidence would 
indicate that this portion of the neuromotor apparatus is concerned 
solely with the activities of the very mobile oral plug. The adoral 
ciliary fiber (ad. cil. f., figs. I and J) also arises from the motorium. 
This fiber attaches to the motorium just anterior to the constriction. 
It passes directly to the basal granule of the first cilium of the adoral 
row from which it passes on and makes connection with each of the 
basal granules of the entire row. It turns inward following the row 
of adoral cilia along the dorsal or left-hand margin of the membranelle 
area. Here its course is exceedingly hard tq determine, but like the 
circumoesophageal fiber, some sections seem to show its connection 
with the posterior end of the motorium. 

The remainder of the neuromotor system is not directly connected 
with the motorium. The adoral ciliary rootlets (ad. cil. r., fig. I) pass 
inward from the basal granules of the adoral cilia through the ecto- 
plasm of the apical cone into the endoplasm and well into the posterior 
third of the organism where they end, not abruptly but by fading out. 
There is absolutely no indication of any attachment of their inner 
ends. Just posterior to the middle of the cell there is usually a very 
distinct crossing of the ciliary rootlets from the opposite sides of the 
peristome. Each of these adoral ciliary rootlets bears a decided enlarge- 
ment at the point where it passes from the ectoplasm into the endoplasm. 
The aggregation of these enlargements gives the appearance in cross- 
sections through this region (pi. 27, fig. 6) of a zone of large, deeply 
staining granules about the oesophagus. Each of these enlargements 
gives rise to a fiber which passes radially outward in a transverse 
plane. These have been termed the radial fibers (rad. /., fig. J ; pi. 27, 
fig. 6). Each of these radial fibers as it passes peripherally connects 
with small enlargements of the rootlets of the cilia of the apical cone. 
The rootlets of the cilia of the apical cone are like those of the adoral 
cilia except that they shorten progressively as they near the periphery, 
at which point they scarcely extend into the endoplasm at all, becom- 
ing identical with those of body cilia. Since the radial fibers and the 
enlargements of the ciliary rootlets lie in the plane of contact between 
the ectoplasm and the endoplasm they very clearly mark the limit of 
the two. At the periphery the radial fibers turn posteriorly and 
become lost in the granular band. This last fact is very suggestive, 
since the terminal enlargements of the rootlets of the body cilia lie in 
these granular bands. 



1922] McDonald: On Balantidium coli and Balantidium suis 287 

It has not been possible to demonstrate a posterior continuation 
of the radial fibers within the granular bands. If they do not continue 
posteriorly, making connections with the enlargements of the rootlets 
of the body cilia, then the logical alternative seems to be to attribute 
the function of conductivity to the granular band of ectoplasm itself. 
There must be some means of conduction of stimuli, for the body cilia 
are concerted in their action, though not to so high a degree as in 
the case of the cilia of the apical cone. Protoplasm is generally con- 
ceded to have the power of conducting stimuli. So here in Balan- 
tidium coli there seems to be a transition from conduction by the 
undifferentiated protoplasm which serves as a- matrix for the ciliary 
apparatus, to a condition in which there is a differentiation of the 
protoplasm into fibers or strands to serve the purpose. Moreover, the 
increasing degree of differentiation is directly correlated with the 
increasingly high degree of coordination of the motor organelles. 

It will be seen from the figures and the above description that 
Balantidium coli is equipped with a notably integrated system of 
fibers bearing such morphological relations as would make the assign- 
ing to them of the function of coordination perfectly logical. The 
motorium is connected directly only with the oral plug and the adoral 
cilia. But through ciliary rootlets and the radial fibers all of the 
cilia of the apical cone are in connection with the adoral cilia. And 
if the function of conductivity may be attributed to the granular 
bands of the ectoplasm, into which the radial fibers turn and become 
lost to view, and in which the enlargements of the ciliary rootlets of 
the body cilia lie, then all of the motor organelles of the organism are 
reached by the neuromotor apparatus, and by it the coordination of 
these organelles may be explained. 

Attributing to the various fibers described above the quality of 
conductivity and to the whole neuromotor apparatus the function of 
coordination of all of the locomotor organs in swimming and feeding, 
microdissection experiments carried on by Taylor (1920), we may 
consider the functions of the various parts from that point of view. 
The main role of the motorium is to act as a coordination center. The 
circumoesophageal fiber would serve to correlate the movements of the 
oral plug with those of the adoral cilia in feeding and in avoiding- 
reactions. The ciliary rootlets and radial fibers make possible the 
coordination of all of the locomotor organs in swimming and feeding, 
and especially the cilia of the apical cone which are employed in the 
boring movement of the organism. 



288 University of California Publications in Zoology [ V O L - 20 



DISCUSSION 

Up to the present time systems of intracytoplasmic fibers and 
accessory neuromotor masses comparable to that found in Balantidium 
coli have been fully described in several flagellates and a few ciliates. 
The very primitive type occurring in Naegleria gruberi (Schardinger) 
has been described by Wilson (1916). Kofoid (1916) and Swezy 
(1916) have made a critical comparative study of the motor systems 
of those flagellates, in which the} 7 have been most carefully studied. 
That there is a striking similarity in the neuromotor systems of flagel- 
lates and ciliates is clearly pointed out by Yocom (1918). 

Among the ciliates, intracytoplasmic fibers have been known for 
some time and there have been several descriptions of them and several 
conflicting views as to their function (Engelmann, 1880; Biitschli, 
1889; Schuberg, 1891; Maier, 1903; Prowazek, 1903; Griffin, 1910; 
Braune, 1913). Sharp (1914), however, was the first to describe fully 
a completely integrated fibrillar system with a central neuromotor 
mass, to which he applied the term neuromotor apparatus. 

Of the neuromotor apparatus of ciliates that of Balantidium coli 
is the third to be quite fully worked out. In 1914 Sharp described 
the neuromotor apparatus of Diplodinium ecaudatum (Fiorentini). 
This apparatus consists of six parts. The central motor mass, or 
motorium, lies in the area of thickened ectoplasm at the anterior end 
of the animal between the dorsal and adoral membranelle zones. A 
fiber connects the motorium with the basal granules of the dorsal mem- 
branelles, a branch from which runs along the base of the inner dorsal 
lip. Another fiber connects the motorium with the basal granules of 
the adoral membranelles. A set of opercular fibers leave the motorium 
and pass along underneath the operculum. Lastly, the motorium has 
a definite connection by means of a fiber with what Sharp called the 
circumoesophageal ring. There is also a set of fibers in the wall of 
the oesophagus, which he termed the oesophageal fibers, and which 
he believed took their origin from the circumoesophageal ring. All of 
these structures as well as the micronucleus Sharp found had an 
affinity for the acid fuchsin when Mallory's connective tissue stain 
was used. 

In Euplotes patella (0. F. Miiller) the neuromotor apparatus, as 
described by Yocom (1918), is made up of five distinct parts. The 



1922] McDonald: On Balantidium coli and Balantidium suis 289 

motorium is a somewhat bilobed mass and lies in the ectoplasm at 
the anterior end of the organism close to the right anterior corner of 
the triangular cytostome. From the left end of the motorium five 
main longitudinal fibers pass posteriorly, diverging slightly, and each 
joins with one of the five anal cirri. The exact relation of thes^ fibers 
to the basal plates of anal cirri has been very carefully determined 
by Taylor (1920). Leaving the right end of the motorium a fiber 
passes to the membranelles of the adoral zone. Directly connected 
with this fiber is the "sensory structure" of the anterior lip. Lastly, 
there are dissociated fibers in connection with the frontal, ventral, and 
marginal cirri. In Euplotes, as in Diplodinium, all parts of the 
neuromotor apparatus as well as the micronucleus stain brilliant red 
with acid fuchsin. 

For facilitating comparison, it might be well to summarize briefly 
the neuromotor apparatus of Balantidium coli, as described above. 
It consists in this organism of five distinct divisions. The motorium 
is a J-shaped mass situated in the thickened ectoplasm of the anterior 
end of the animal close to the cytostome and oesophagus. From it 
arises the circumoesophageal fiber, which gives off branches to the 
oral plug. A second fiber takes its origin from the motorium and 
connects with the basal granules of the adoral cilia. The adoral ciliary 
rootlets pass inward from the basal granules of the adoral cilia, and 
may extend well into the posterior third of the cell. The radial fibers 
take their origin from enlargements of the adoral ciliary rootlets, 
at the point where they enter the endoplasm. They pass outward 
radially, making connection with the ciliary rootlets of the cilia of 
the apical cone, and at the periphery turn posteriorly and cannot 
be traced farther in the granular bands of the ectoplasm. As in the 
previous forms just summarized, the neuromotor apparatus as well as 
the micronucleus of Balantidium coli is selective for acid fuchsin. 

Of the three examples of neuromotor systems so far fully worked 
out and described, each represents a different order of the class 
Ciliata: Diplodinium being of the order Oligotricha; Euplotes being 
of the order Hypotricha ; and Balantidium being of the order Hetero- 
tricha. Yet in spite of the diversity of forms there is a remarkable 
similarity in the neuromotor system. The presence of a motorium is 
common to all three. In each of the three organisms it is located at 
the anterior end of the animal and lies wholly within the ectoplasm 
near the cytostome. By means of fibers it is connected with a part 
or all of the motor organelles of the animal. Another feature of the 



290 University of California Publications in Zoology [VOL. 20 

fibrillar portion of the apparatus common to all three forms is the 
strand connecting the motorium with all of the* adoral cilia or mem- 
branelles, as the case may be. Finally, the system, in all cases, shows 
an affinity for acid fuchsin. 

The circumoesophageal ring present in Diplodinium is represented 
in Balanticbium by the circumoesophageal fiber running through the 
oral plug. The oral plug forms the wall of the greater part of the 
oesophagus, and the fiber lies very close to the oesophageal surface. 
From this fiber there are given off fibers which pass both anteriorly 
and posteriorly in the mass of the oral plug. These fibers are strik- 
ingly similar in location to the oesophageal fibers, described by Sharp 
(1914) in the wall of the oesophagus of Diplodinium and believed by 
him to arise from the circumoesophageal ring. Sharp points out that 
these fibers approach very close to the micronucleus though there was 
no demonstrable connection with it. In Balantidium this possibility 
is precluded by the shortness of the oesophagus which in no case 
extends inward to a point anywhere near the micronucleus. At times 
when the organism is viewed from the proper angle, the ciliary root- 
lets of the adoral cilia may have the appearance of ending in the 
proximity of the micronucleus and suggesting a connection with it. 
No such connection exists, however, as may be readily demonstrated 
in large numbers of whole mounts and still better in sections where 
these rootlets may be traced far posterior to the micronucleus, passing 
it some considerable distance away. In the vegetative phase, it is 
certain that no structural connection exists between any part of the 
neuromotor apparatus and the micronucleus. 

Of the three neuromotor systems of ciliates here considered, that 
of Balantidium is clearly the least centralized, though none the less 
a unified structure. In Diplodinium all motor organelles connect 
directly with the motorium, and in Euplotes the same is true of all 
except the marginal cirri which have no connection whatever, whereas 
in Balantidium only the adoral cilia have direct connection with the 
motorium while the cilia of the apical cone (and those of the body, 
too, if they have any connection whatever) are connected with it only 
indirectly through the radial fibers and the rootlets of the adoral cilia. 
This lesser degree of centralization of the neuromotor apparatus may 
perhaps be explained by the lesser degree of specialization of locomotor 
organelles. Whereas in Diplodinium the body is devoid of cilia and 
the dorsal and adoral zones of membranelles are the sole motor organ- 
elles, and in Euplotes the locomotor organelles are restricted to the 
cytostomal membranelles and a few cirri on the ventral surface, in 



1922] McDonald: On Balantidium coli and Balantidium suis 291 

the case of Balantidium the entire organism, with the exception of 
the oral plug, is covered with cilia. So the slightly lesser degree of 
specialization in the neuromotor apparatus would be the logical expec- 
tation if modification of intracytoplasmic structures is correlated 
with modification of external structures with which they have~a~direct 
connection or of which they form an integral part. 

From the point of view of efficiency, also, the arrangement in 
Balantidium is readily explainable. The locomotor activities of the 
organism may be separated into three main sorts, swimming, feeding, 
and boring, this last very likely being used in penetration of the 
intestinal wall of the host. In swimming the coordination of the entire 
locomotor apparatus is necessary. In feeding, and in boring, particu- 
larly, the coordination of the adoral cilia with those of the apical cone 
is extremely essential. Such coordination would be most effectively 
brought about by a direct connection of the parts concerned, and this 
direct connection is accomplished by the uniting of all of the rootlets 
of the cilia of these two regions by means of the radial fibers, without 
the interpolation of the motorium. 

Throughout the above discussion the assumption of a neural func- 
tion for the neuromotor apparatus, i.e., the power of conductivity of 
stimuli resulting in coordination of parts, has been based on two 
general types of evidence, morphological and experimental. The 
chemical evidence, that is, the affinity for acid fuchsin, as presented 
by Sharp (1914) for Diplodinium and by Yocom (1918) for Euplotes, 
seems slightly less convincing in the case of Balantidmm. In the last 
named organism not only does the micronucleus, which has no connec- 
tion with the neuromotor apparatus, show an affinity for acid fuchsin 
but so also do certain cytoplasmic inclusions, which if not food par- 
ticles are at least undoubtedly concerned in some way with metabolism 
and have no morphological relation to the neuromotor apparatus. 
Yocom (1918) states that there is more of the orange G in the micro- 
nucleus giving it a different shade from the parts of the neuromotor 
apparatus in the case of Euplotes; but in Balantidmm I have been 
unable to detect any such differentiation. 

Morphological evidence for attributing neural function to the 
neuromotor apparatus has been clearly presented by Yocom (1918) 
in his discussion of the apparatus in Euplotes. The evidence found 
in Bakmtidium is not strikingly different. There is in the latter 
organism the same intricate relationship between the neuromotor 
apparatus and the motor organelles. The most active cilia, i.e., the 
adoral cilia, are directly connected by the adoral ciliary fiber with 



292 University of California Publications in Zoology [VOL. 20 

each other and with the motorium. The cilia of the apical cone are 
connected with the adoral cilia by the radial fibers and so indirectly 
with the motorium. In this case, however, coordination with the adoral 
cilia is most essential and this corresponds with their intimate con- 
nection. These morphological interrelations all point to a neural func- 
tion for the neuromotor apparatus. 

Very convincing experimental evidence of the neural function is 
to be found in the results of Taylor's (1920) microdissection experi- 
ments on Euplotes patella. In Euplotes there is a fiber connecting the 
adoral membranelles with the motorium, and also a fiber connecting 
each of the five anal cirri with it. In a series of experiments Taylor 
severed various ones of these fibers and observed very carefully the 
effect on the movements of the animal. He then compared these move- 
ments with the normal movements which he had previously carefully 
analyzed and classified. Severing of these fibers resulted in lack of 
coordination of the parts thus disconnected and resulted in abnormal 
movements. Incision made in other parts of the cell, but which did 
not sever neuromotor fibers did not so result. In the words of the 
author, "It is apparent, then, that the destruction of the motorium 
or the severing of some or all of its attached fibers is alone accountable 
for modification in the perfect and efficient coordination between the 
series of membranelles and the anal cirri. We may, therefore, regard 
these normal morphological relationships as conditioning the animal's 
usual behavior both in creeping and in swimming." 

The general occurrence among Protozoa of protoplasmic modifica- 
tion to form organelles for locomotion, feeding, digestion, excretion, 
and protection has been known almost as long as have the Protozoa 
themselves. The functions of such organelles have not been difficult 
to determine. One might equally well expect to find modifications 
correlated with the conduction of stimuli, but the establishing of 
neural function is not so easy. This difficulty in conjunction with the 
traditional idea of the simplicity of the Protozoa has resulted in con- 
servatism in crediting any intracellular structures with the function 
of conductivity. The recent detailed morphological studies on Proto- 
zoa and the experimental work of Taylor (1920), however, leave little 
doubt regarding the matter. This account of the neuromotor appa- 
ratus of Balantidium coU and Balantidium suis presents additional 
evidence of the likelihood of a quite general occurrence, in the Pro- 
tozoa, of intracytoplasmic specialization resulting in a more or less 
integrated system for purposes of coordination. 



1922] McDonald: On Balantidium coli and Balantidium suis 293 



SUMMARY 

1. Pigs are very generally infected with balantidia as shown by 
the findings in previous investigations, many of which were carried 
on in foreign countries, and by the finding of 68 per cent infection 
among the two hundred pigs examined during the present investi- 
gation. 

2. There are two species of the genus Balantidium that are para- 
sitic in the intestinal tract of pigs, namely, Balantidium coli and 
Balantidium suis (sp. nov.). 

3. Balantidium coli is the species first described by Malmsten 
(1857) from man, and later by Leuckart (1861) as a parasite in pigs. 

4. Balantidium suis (sp. nov.) has not hitherto been distinguished 
from Balantidium coli. The former differs from the latter in being 
more elongate and being broadest anterior instead of posterior to the 
equatorial plane; in having a more slenderly proportioned macro- 
nucleus ; and in having the mouth displaced ventrally, instead of being 
almost terminal, which causes the plane of demarcation between ecto- 
plasm and endoplasm in this region to slant posteriorly toward the 
ventral surface instead of being perpendicular to the longitudinal 
axis, as is the case in Balantidium coli. 

5. So far as recorded facts will justify conclusions, it seems un- 
likely that Balantidium suis occurs as a parasite of man, but instead 
that Balantidium coli is the cause of balantidiasis. Whether or not such 
is the case, it is very desirable that the occurrence of the two species 
in pigs be taken into account in future work on experimental infection, 
for to a failure to distinguish between the two species may be due 
the seemingly conflicting results of previous experiments. 

6. The cilia of the two species are homologous. Variation occurs 
in size and relative position of parts only. The basal apparatus is 
essentially diplosomic, consisting of a basal granule connected by a 
ciliary rootlet to a secondary enlargement. The former is situated just 
beneath the pellicle ; the latter lies in the plane of demarcation between 
ectoplasm and endoplasm. The adoral cilia are largest, the basal granule 
and secondary enlargement are farthest removed from one another, as 
the ectoplasmic thickening is greatest in this region, and the ciliary 
rootlet may extend far into the endoplasm. The cilia of the apical 
cone intergrade between the adoral cilia and the body cilia. As one 



294 University of California Publications in Zoology [ VOL - 20 

progresses posteriorly, they become smaller in size, the secondary 
enlargement approaches the basal granule as the ectoplasmic layer 
becomes thinner, and the extension of the rootlet into the endoplasm 
becomes shorter. The body cilia are smallest and their rootlets 
terminate in the secondary enlargement. The cilia of the anterior 
end are highly concerted in action. They beat in such a way as to 
give the animal a remarkable boring motion which probably serves 
in the penetration of the mucosa of the intestine. 

7. Both species possess a neuromotor system. This is a highly 
developed and integrated system consisting of five correlated parts. 
The motorium, lying within the ectoplasm near the cytostome, gives 
rise to a circumoesophageal fiber. In addition, there is a heavier fiber 
which connects it with the basal granules of the adoral cilia. The root- 
lets of the adoral cilia extend far into the endoplasm, usually well into 
the posterior one-third of the cell. Where they pass from ectoplasm 
into endoplasm each adoral ciliary rootlet bears an enlargement and 
from this arises a radial fiber which passes to the periphery, turns 
posteriorly, and disappears in the granular band of ectoplasm. In 
passing to the periphery these radial fibers connect with enlargements 
of the rootlets of the cilia of the apical cone. 

Transmitted February 26, 1921. 

Zoological Laboratory, University of California, 
Berkeley, California. 



1922] McDonald: On Balantidium coli and Balantidium suis 295 



LITERATURE CITED 

BEL, G. S., and COURET, M. 

1910. Balantidium coli infection in man. Jour. Infect. Dis., 7, 609-624, 4 pis. 
BEZZENBERGER, E. 

1904. Ueber Infusorien aus asiatischen Anuren. Arch. f. Prot., 3, 138-174, 

pi. 1, 23 figs, in text. 
BOECK, W. C. 

1917o. Mitosis in Giardia microti. Univ. Calif. Publ. ZooL, 18, 1-26, pi. 1. 
1917&. A rapid method for the detection of protozoan cysts in mammalian 

faeces. Ibid., 18, 145-149. 
BRAUNE, E. 

1913. Untersuchungen iiber die im Wiederkauermagen vorkommenden Proto- 
zoan. Arch. f. Prot., 32, 5-63, pis. 3-6. 
BRUMPT, E. 

1909. Demonstration du role pathogene du Balantidium coli. C.-R. Soc. Biol., 
Paris, 67, 103. 

BtJTSCHLI, O. 

1889. "Ciliata" in "Protozoa" (1887-1889) in Bronn, Klass. und Ordn. des 

Thierreichs, 1, (3), 1228-1841, pis. 56-86. 
CHAGAS, C. 

1911. tiber die zyklischen Variationen des Caryosomes bei zwei Arten para- 
sitischer Cilia ten. Mem. Inst. Oswaldo Cruz, 3, 136-144, 2 pis. 

CLAPAREDE, E., and LACHMANN, J. 

1858. Etudes sur les infusoires et les rhizopodesi. (Geneve, Kossmann), 1, 

247-248, pi. 13. 
DELAGE, Y., and HEROUARD, E. 

1896. Traite de zoologie concrete. (Paris, Schleichter Freres), 1, 582, 870 

figs, in text. Eef. footnote, 404, fig. 692. 
DOBELL, C. C. 

1909. Researches on the intestinal Protozoa of frogs and toads. Quart. Jour. 

Micr. Sci, 53, 201-277, 4 pis. 

DOFLEIN, F. 

1911. Lehrbuch der Protozoenkunde. (Jena, Fischer), ed. 3, xii+1043, 951 

figs, in text. 
EHRENBERG, C. G. 

1838. Die Infusionsthierchen als volkommene Organismen. (Leipzig, Voss), 

xviii + 547 ; Atlas, pis. 1-64. 
ENGLEMANN, T. W. 

1880. Zur Anatomic und Physiologic der Flimmerzellen. Pfliiger's Arch. ges. 

Physiol., 23, 505-535, pL 5. 
GRIFFIN, L. E. 

1910. Euplotes worcesteri sp. nov., I, Structure. Philippine Jour. Sci., 5, 

291-312, pis. 1-3, 13 figs, in text. 
JENNINGS, H. S. 

1908. Heredity, variation and evolution in Protozoa. Proc. Am. Phil. Soc., 
47, 393-546. 



296 University of California Publications in Zoology IT OL - 20 

JOHNSON, H. P. 

1893. A contribution to the morphology and biology of the stentors. Jour. 

Morph., 8, 467-562, pis. 23-24. 
KOFOID, C. A., and CHRISTIANSEN, E. B. 

1915. On binary and multiple fission in Giardia muris (Grassi). Univ. Calif. 

Publ. Zool., 16, 30-54, pis. 5-8, 1 fig. in text. 
KOFOID, C. A., and McCuLLOCH, I. 

1916. On Trypanosoma triatomae, a new flagellate from a hemipteran bug 

from the nests of the wood rat Neotoma fuscipes. Ibid., 16, 113-126, 
pis. 14-15. 
KOFOID, C. A., and SWEZY, O. 

1915. Mitosis and multiple fission in triehomonad flagellates. Proc. Am. Acad. 

Arts and Sei., 51, 289-378, pis. 1-8, 7 figs, in text. 
1919. On Trichonympha campanula nov. sp. Univ. Calif. Publ. Zool., 20, 

41-98, pis. 5-12, 4 figs, in text. 
LEEUWENHOEK, A. VON. 

1708. "Animalcula e stercore ranarum." Opera omnia, 2, 49-64. 
LEUCKART, E. 

1861. Paramoecium ooli. Wiegemann's Archiv, 1, 80, pi. 5. 
LONG, J. A. 

1912. Studies on early stages of development in rats and mica Univ. Calif. 

Publ. Zool., 9, 105-136, pis. 13-17, 11 figs, in text, 
MAIER, H. N. 

1903. Ueber den feineren Bau der Wimperapparate der Infusorien. Arch. f. 

Prot, 2, 73-179, pis. 3-4. 
MALMSTEN, P. H. 

1857. Infusorien als Intestinaltiere beim Menschen. Virchow Arch. f. pathol. 

Anat., 12, 302-309, pi. 10. 
MAUPAS, E. 

1883. Contribution a 1 'etude morphologique et anatonlique des infusoires 

cilies. Arch. Zool. Exp. et Gen., (2), 1, 427-664, pis. 19-24. 
METCALF, M, M. 

1908. Opalina anatomy and reproduction. Arch. f. Prot., 13, 195-375, pis. 
14-28. 

MlNCHIN, E. A. 

1912. An introduction to the study of the Protozoa. (London, Arnold), 

xi + 520, 194 figs, in text. 
NERESHEIMER, E. E. 

1903. Die Hohe histologischer Differenzierung bei heterotrichen Ciliaten. 

Arch. f. Prot., 2, 305-324, pi. 7, 1 fig. in text. 
VON PROWAZEK, S. 

1903. Flagellatenstudien ; Anhang; fibrillare Strukturen der Vorticellen. 
Ibid., 2, 195-212, 2 pis. 

1913. Zur Kenntnis der Balantidiosis. Arch. f. Schiffs-u. Tropenhyg., 17, 

369-390, 2 pis., 9 figs, in text. 
PUTTER, A. 

1903. Die Flimmerbewegung. Ergebn. d. Physiol., 2, 1-102, 15 figs, in text. 
SAGTJCHI, S. 

1917. Studies on ciliated cells. Jour. Morph., 29, 217-268, pis. 1-4, 1 fig. in 

text. 



1922] McDonald: On Balantidium coU and Balantidium suis 297 

SGHAUDINN, F., and JAKOBY, M. 

1899. Ueber zwei neue Infusorien im Darm des Menschen. Centralbl. f. 

Bakt., Abt. I, 25, 487-494, 4 figs, in text. 

SCHUBEEG, A. 

1886. Ueber der Bau der Bursaria truncatella mit besonderer Berucksichti- 
gung der protoplasmatischen Structuren. Morph. Jahrb., 12, 333- 
365, pis. 19-20. 

1891. Ueber einige Organizationsverhaltnisse der Infusorien. des Wieder- 
kauermagens. Sitz.-ber. d. phys.-med. Ges. Wurzburg, 1891, 122-137. 

SCHWEIER, A. 

1900. Parasitische Wimperinfusorien (Endoparasiten). Arb. der St. Peters- 

burger naturf. Gesellsch., 29, 1-135, pis. 1-2. 

SHARP, E. G. 

1914. Diplodinium ecaudatum, with an account of its neuromotor apparatus. 
Univ. Calif. Publ. Zool., 13, 43-122, pis. 3-7, 4 figs, in text. 

SOLO JEW, N. S. 

1901. Das Balantidium ooli als Erreger chronischer Durchfalle. Centralbl. f. 

Bakt., 29, 321-830; 849-860, 8 figs, in text. 
STEIN, F. 

1867. Der Organismus der Infusionsthiere nach eigenen Forschungen in sys- 
tematischer Eeihenfolge bearbeitet. (2) Naturgeschichte der heter- 
otriehen Infusorien (Leipzig, Englemann), viii + 355, 16 pis. 

STRONG, E. P. 

1904. The clinical and pathological significance of Balantidium coll. Bureau 

Gov't. Labs. (Manila, P. I.), Bull. 26, 77, 10 pis. 
SWEZY, O. 

1916. The kinetonucleus of flagellates and the binuclear theory of Hartmann. 

Univ. Calif. Publ. Zool., 16, 185-240, 58 figs, in text. 
TAYLOR, C. V. 

1920. Demonstration of the function of the neuromotor apparatus in Euplotes 
by the method of microdissection. Ibid., 19, 403-470, pis. 29-33, 2 
figs, in text. 
THON, K. 

1904. Ueber den feineren Bau von Didinium nasutum O. F. M. Arch. f. Prot., 

5, 281-321, pis. 12-13, 3 figs, in text.. 
WALKER, E. L. 

1909. Sporulation in the parasitic Ciliata. Ibid., 17, 297-306, 2 pis. 

1913. Experimental balantidiasis. Philippine Jour. Sci., 8, (B), 333-349, 7 

pis. 
WILSON, C. W. v 

1916. On the life history of a soil amoeba. Univ. Calif. Publ. Zool., 16, 241- 

292, pis. 18-23. 
WISING, P. J. 

1871. Till kannedomen om Balantidium coli hos manniskan. Nordiskt Med. 

Ark., 3, 1-30, 1 pi. 
YOCOM, H. B. 

1918. The neuromotor apparatus of Euplotes patella. Univ. Calif. Publ. 
Zool., 18, 337-396, pis. 14-16, 1 fig. in text. 



EXPLANATION OF PLATES 

PLATE 27 

Camera lucida drawings of a series of transverse sections of Balantidium coli 
(Malmsten). The series begins at the anterior end and progresses posteriorly 
about one-third the length of the organism. X 1000. 

Fig. 1. This section shows dorsal portion only of peristome. The adoral cilia 
are removed showing their basal granules clearly. 

Fig. 2. A portion of the oral plug is shown with the circumoesophageal fiber 
and the connected oral plug fibers. The deeply-staining region between proto- 
plasm of oral plug and the surrounding ectoplasm, so marked in this individual, 
is rarely found. 

Fig. 3. The continuation of cilia over the ventral lip and down into the cyto- 
stome are to be noted particularly; the beginning of the motorium on the 
(reader's) left of the cytostome; and the connection of the adoral ciliary fiber 
with the motorium. 

Fig. 4. In this figure the cilia of the cytostome give the appearance of mem- 
branelles; the circumoesophageal fiber makes connection with the motorium. 

Fig. 5. This shows the beginnings of the enlargements of the adoral ciliary 
rootlets. 

Fig. 6. Here the oesophagus is completely surrounded by the enlargements 
and radial fibers may be seen arising from some of them. 

Fig. 7. The extreme posterior tip of the motorium appears within the circle 
of enlargements; the dorsal half of this section is through the endoplasm. 

Fig. 8. This section is posterior to the adoral apparatus with the exception of 
the rootlets of the adoral cilia which in cross-section can not be distinguished from 
the granules of the endoplasm. 



[298J 



UNIV. CALIF. PUBL. ZOOL. VOL. 20 



[ MCDONALD ] PLATE 27 




PLATE 28 

Figs. 9-12. Series of longitudinal sections through the anterior end of Balan- 
tidium ooli (Malmsten). X 1000. These sections are oblique, being more nearly 
frontal than sagittal, however. The section shown in figure 9 is tangential to the 
margin of the peristome some distance to the right of the most dorsal point of the 
latter (see fig. J in text). The remainder progress toward the left ventral lip. 
The oral plug fibers, the radial fibers, and the adoral ciliary rootlets are shown 
clearly in these sections. 

Fig. 13. A sagittal section through Balantidium suis (sp. nov.). X 1000. 
The specific characters, viz., elongate body and macronucleus, and oblique plane 
delimiting apical cone of ectoplasm, are shown in this section. The cytopyge is 
distinct and open to the exterior. A paramylum body of considerable size is 
present in the endoplasm. 

Fig. 14. An oblique longitudinal section through Balantidium coli (Malmsten) 
showing the protrusion of the oral plug. X 750. 



[300] 



UNIV. CALIF. PUBL. ZOOL. VOL. 20 



[ MCDONALD ] PLATE. 28 



lf --t- ; 

^--A'^.m'':^.* 







1 1 





UNIVERSITY OF CALIFORNIA PUBLICATIONS (Continued) 

16. The Subclavian Vein and Its Relations in Elasmobranch Fishes, by J. Frank 

Daniel. Pp. 479-484, 2 figures in text. August, 1918 . ......... ... .. ......... ----- ...... 1" 

17 The Cercaria of the Japanese Blood Fluke, Schistosoma japomcum Katsu- 

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Nos. 17 and 18 in one cover. January, 1919 ......................................... * 

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7. The Excretory System of a Stylet Cercaria, by William W. Cort. Pp. 275- 

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2. Studies on the Parasites of the Termites. II. On TricJwmitus termitidis, a 
Polymastigote Flagellate with a Highly Developed Neuromotor System, 
by Charles Atwood Kofoid and Olive Swezy. Pp. 21-40, plates 3-4, 2 
figures in text. July, 1919 ................. _ ......................................... -- ....... - ........... -- ? 

3 Studies on the Parasites of the Termites. III. On TrichonympTia campanula 
sp. nov., by Charles Atwood Kofoid and Olive Swezy. Pp. 41-98, plates 
5-12, 4 figures in text. July, 1919 ........ ..... ........... ...... 

4. Studies on the Parasites of the Termites. IV. On Leidyopsis sp en ? en / 

nov. sp. nov., by Charles Atwood Kofoid and Olive Swezy. Pp. 99-116, 
plates 13-14, 1 figure in text. July, 1919 ..... ............. 

5. On the Morphology and Mitosis of Cliilomastix meswh (Wenyon), a 

Flagellate of the Human Intestine, by Charles A. Kofoid and Olive Swezy. 

Pp. 117-144, plates 15-17, 2 figures in text. April, 1920 . ....... -35 

6. A Critical Review of the Nomenclature of Human Intestinal Flagella ;es, 

Cercomonas, CMornaistix, Trichomonas, and Giardia, by Charles A. Kofoid. 
Pp. 145-168, 9 figures in text. June, 1920 ..... ................................. ----- 

7. On the Free, Encysted, and Budding Stages of Councilmania la-fteun a Para- 

sitic Amoeba of the Human Intestine, by Charles Atwood Kofoid and 
Olive Swezy. Pp. 169-198, plates 18-22, 3 figures in text. June, 192 .60 

8. Mitosis and Fission in the Active and Encysted Phases of Giardia entenca 

(Grassi) of Man, with a Discussion of the Method of Origin of Bilateral 
Symmetry in the Polymastigote FlageUates, by Charles A. Kofoid and 
Olive Swezy. Pp. 199-234, plates 23-26, 11 figures in text. March, 
1922 ................................................................................................ 

9. The Micro-injection"of" "Paramaecium, by Chas. Wm. Rees. Pp. 235-242. 



10 Onaittttdm~wr^ and Balantidium suis (sp. nov.), wth 

an account of their neuromotor apparatus, by J. Daley McDonald. 
Pp 243-300, plates 27, 28, 15 figures in text. May, 1922 .............................. 1.00 



UNIVERSITY OF CALIFORNIA PUBLICATIONS (Continued) 

11. Mitosis in Endamoeba dysenteriae ia the Bone Marrow in Arthritis de- 

formans, by Charles Atwood Kofoid and Olive Swezy. Pp. 301-307, 
7 figures in text. 

12. Endamoeba dysenteriae in the Lymph Glands of Man in Hodgkin's Disease, 

by Charles A. Kofoid, Luther M. Boyers, M.D., and Olive Swezy. Pp. 309- 
312, 4 figures in text. 

Nos. 11 and 12 in one cover. April, 1922 .25 

VoL 21. 1. A Revision of the Microtus calif ornicus Group of Meadow Mice, by Reming- 
ton Kellogg. Pp. 1-42, 1 figure in text. December, 1918 50 

2. Five New Five-Toed Kangaroo Rats from California, by Joseph GrinneU. 

Pp. 43-47. March, 1919 05 

3. Notes on the Natural History of the Bushy-tailed Wood Rats of California, 

by Joseph Dixon. Pp. 49-74, plates 1-3, 3 figures in text. December, 1919 .25 

4. Revision of the Avian Genus Passerella, with Special Reference to the Dis- 

tribution and Migration of the Races in California, by H. S. Swarth. Pp. 
76-224, plates 4-7, 30 figures in text. September, 1920 $1.75 

5. A Study of the California Jumping Mice of the Genus Zapus, by A. Brazier 

HowelL Pp. 225-238, 1 figure in text. May, 1920 _ 15 

6. Two New Rodents (Genera Thomomys and Marmota) from the Eastern 

Border of California, by Joseph Grinnell. Pp. 239-244, 6 figures in text, 
November, 1921 15 

7. A Study of the Calif ornian Forms of the Microtus montanus Group of 

Meadow Mice, by Remington Kellogg. Pp. 245-274, 25 figures in text. 

8. A Synopsis of the Microtus mordax Group of Meadow Mice in California, 

by Remington Kellogg. Pp. 275-302, plate 8, 29 figures in text. 

Nos. 7 and 8 in one cover. April, 1922 75 

Vol. 22. 1. A Quantitative and Statistical Study of the Plankton of the San Joaquin 

River and Its Tributaries in and near Stockton, California, in 1913, by 

Winfred Emory Allen. Pp. 1-292, plates 1-12, 1 figure in text. June, 1920. $3.00 
Vol.23. The Marine Decapod Crustacea of California, by Waldo L. Schmitt. Pp. 

1-470, plates 1-50, 165 figures in text. May, 1921 5.00 



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