MARINE BIOLOGICAL LABORATORY.
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THE
BIOLOGY OF THE PROTOZOA
BY
GARY N. CALKINS, Ph.D., Sc.D.
PROFESSOR OF PROTOZOOLOGY, COLUMBIA UNIVERSITY
SECOND EDITION, THOROVOHLY REVISED
ILLUSTRATED WITH 223 ENGRAVINGS AND 2 COLORED PLATES
LEA & FEBIGER
PHILADELPHIA
19 3 3
Copyright
LEA & FEBIGER
1933
PRINTED IN U. S. A.
TO
MY WIFE
WHOSE UNSELFISH DEVOTION HAS MADE THIS BOOK POSSIBLE
( L ! B f? A R %
PREFACE TO SECOND EDITION.
In writing' this volume the author has made no effort to give a
complete account of the Protozoa. As indicated by the title, it is
rather a study in biology illustrated by the unicellular animals.
The concept of a changing organization brought about by continued
metabolism was developed in the first edition. This conception
has been amplified in some respects, strengthened and condensed
in others, and furnishes the basis for an interpretation not only of
life histories but of the significant biological phenomena of cell
division, maturity, sex differentiation, fertilization and senescence
as well. To strengthen this conception a considerable change in
the order of presentation has been introduced. After the first intro-
ductory chapter we plunge at once in Chapter II into the sub-
stances and structures of the fundamental organization. This is
followed in Chapters III and IV by the development of these sub-
stances and structures into cytological derivatives (Chapter III)
and taxonomic structures (Chapter IV) of the derived organization.
In Chapter Y the general physiological activities are considered in
anticipation of Chapter VI on reproduction. The problem of gen-
eral vitality and its significance in fertilization and the accompany-
ing phenomena of sex differentiation, maturation, reorganization,
adaptation and variations are treated in Chapters VII, VIII and
IX. The special chapters on taxonomy, together with more elab-
orate keys to genera, are transferred from the middle of the book
to the end in Chapters XI, XII, XIII and XIV.
Parasitism and disease should be considered in any work on
general biology. These topics were omitted in the first edition
but are introduced here in Chapter X. Another innovation is the
elimination of all references to chlorophyll-forming flagellates, the
protozoan flagellates being limited to the Zoomastigophora.
Reorganization or de-differentiation of the derived taxonomic
structures at periods of division, endomixis and fertilization wherebv
vi PREFACE
the protoplasm is restored to the condition of the fundamental
organization with a renewed potential of vitality, is treated as a
special attribute of Protozoa and as an important distinction
between Protozoa and Metazoa. Through such reorganizations
either by division alone as in the Zoomastigophora and in occa-
sional forms here and there throughout the Protozoa, or by the more
drastic means of endomixis and fertilization, the protoplasm is able
to continue at an optimum of vitality. With this conclusion and
with the recognition of an internal self-regulating mechanism for
reorganization, resulting in the continuation of vitality, we are in
accord with the essence of Weismann's conclusion that protoplasm
of Protozoa is potentially immortal. On the other hand, we can-
not agree with Weismann in his further conclusions that natural
death is unknown in Protozoa, and that every individual is a
potential germ cell.
G. X. C.
New York City.
CONTENTS.
CHAPTER I.
Introduction
Size, Form and Appearance of Protozoa . ...'... 26
A. Form-relations of Protozoa 30
B. Protoplasmic Structure . 39
CHAPTEE II.
The Fundamental Organization.
I. Nuclear Substances and Structures of the Fundamental Organization 49
1. Chromatin . . 54
2. Other Substances of the Nucleus 57
Intranuclear Kinetic Elements 60
(a) Endobasal Bodies 60
1. Large Homogeneous Endobasal Bodies til
2. Endobasal Bodies With Centrioles 63
3. Nuclei With Pole Plates and Without Endo-
basal Bodies 65
II. Cytoplasmic Elements of the Fundamental Organization ... lis
1 . Chromidia 69
2. Volutin Grains 72
3. Mitochondria 73
1. ( iolgi Apparatus 77
5. Silver Line System so
CHAPTER III.
Derived Organization.
I. Cytological 83
A. Derived Nuclei and Derived Nuclear Structures .... 84
1. The Formation of a Nucleus 84
2. Multiple and Dimorphic Nuclei 84
3. Nuclear Derivatives During Division 88
(a) Origin of Chromosomes and of Intranuclear
Spindles at Division ... 88
lb Origin of Fertilization (Meiotic) Chromo-
somes 100
B. Derived Organization; Cytoplasmic Changes . . 104
1. Cytoplasmic Chromatin . ... 104
2. Cytoplasmic Kinetic Elements 104
.'••/."■ 7
CONTENTS
CHAPTER IV.
Derived Organization. Taxonomic Structures
I. Derived Structures of the Endoplasm.
II. Differentiations of the Cortex
Metaplastic
(a) Cortical Differentiations for Support and Protection
(b) Motile Organoids
1. Flagella ....
2. Pseudopodia ...
Rhizopodia
Filopodia
3. Cilia
4. Composite Motile Organs
Membranulae
Membranelles
Undulating Membrane;
Cirri . .
in ( )ther Organoids Adapted for Food-getting
(d) Oral and Anal Cortical Modifications
(e) Contractile Vacuoles
133
135
136
139
141
115
US
150
152
155
155
155
157
157
162
1(14
170
CHAPTER V.
General Physiology.
A. Respiration
B. Excretion of Metabolic Waste ....
('. Irritability
I). Nutrition
1. Food-getting
Secretions and Digestive Fluids
Digestion of Carbohydrates and Fats
Saprozoic Nutrition
2. Products of Assimilation
174
17(i
179
183
is:;
193
198
199
203
CHAPTER VI.
Reproduction.
I. Equal Division and Evidence of Reorganization
A. Division in Mastigophora
B. Division in the Sarcodina
C. Division in Infusoria
in) Evidence of Nuclear Reorganization .
(Id Evidence of Cytoplasmic Reorganization
II. Unequal Division (Budding or Gemmation)
A. Exogenous Budding
B. Endogenous Budding
III. Multiple Division (Spore-formation i
IV. Development
209
210
213
215
217
218
225
226
228
233
241
CHAPTER VII.
Vitality.
I. Isolation Cultures ....."
II. Organization and Differentiation
1. I nter-di visional Differentiations
2. Cyclical Differentiations
(a) Cyclical Differentiations Peculiar to Youth
(b) Cyclical Differentiations Peculiar to Old Age
(c) Cyclical Differentiations Peculiar to Maturity
2 1s
260
260
266
266
269
271
CONTENTS
IX
CHAPTER VIII.
Phenomena Accompanying Fertilization.
I. The Environmental Conditions of Fertilization
(a) Ancestry
(b) Environment
II. Internal Conditions at the Period of Fertilization .
III. The Process of Fertilization
A. Meiotic Phenomena
{<a Conjugant Meiosis .
(6) Gametic Meiosis
(c) Zygotic Meiosis
B. Disorganization and Reorganization
in) Phenomena of Disorganization
(h) Metagamic Activities and Reorganization
IV. Parthenogenesis
^4. Endomixis
B. Autogamy
285
285
286
290
292
294
294
307
309
311
311
312
316
317
322
CHAPTER IX.
Effects of Reorganization and the Origin of Variations in the Protozoa.
I. Effects of Reorganization on Vitality 328
1. Renewal of Vitality as a Result of Conjugation 334
2. Intensity of Vitality and Extent of Renewal 335
3. Relative Vitality of Different Series and Effect of Parents'
Age on Vitality of Offspring ... 339
4. Rejuvenescence After Parthenogenesis (Endomixis i 340
II. Heredity and Variations in Protozoa 342
A. Uniparental Inheritance 343
H. Biparental Inheritance 350
CHAPTER X.
General Ecology, Commensalism and Parasitism
1. Water-dwelling Protozoa ....
2. Semi-terrestrial Protozoa ....
3. Soil-dwelling Protozoa
4. The Sapropelic Flagellates ....
5. The Coprozoic Protozoa
Parasitic Protozoa
Ectoparasitic Protozoa
Endoparasitic Protozoa
Effects of Protozoan Parasites on the Host
Parasitic Flagellates ....
Trypanosoma in Mammals .
Trypanosomes of Birds .
Trypanosomes of Lizards
Trypanosomes in Snakes
Trypanosomes in Crocodiles
Trypanosomes in Turtles
Trypanosomes in Frogs, Toads and Salamanders
Trypanosomes in Fish
Parasitic Rhizopods. Dysentery
Early Taxonomic Observations
Early Etiological Observations
Period of Taxonomic Chaos
Other Amebae of the Human Intestine
Parasitic Ciliata ...
The More Important Sporozoan Parasites of Man
Hemosporidia ... ....
352
353
353
356
357
358
359
359
562
364
372
374
377
377
378
378
378
379
385
388
389
392
396
397
402
406
x CONTENTS
CHAPTER XI.
Special Morphology and Taxonomy of the Mastigophora.
Organization 412
Adaptations and Mode of Life .... 419
Specific Classification 121
The Water-dwelling Flagellates 421
Classification of the Animal Flagellates 421
Class I. Protomastigota 422
Order Protomonadida 422
Class II. Metamastigota 427
Order 1. Hyperinastigida Grassi 427
Order 2. Polymastigida ... 130
Sub-order 1. Monokaryomastigina 430
Sub-order 2. Dikaryomastigina 431
Sub-order 3. Polykaryomastigina ... .... 432
CHAPTER XII.
Special Morphology and Taxonomy of the Sarcodina.
Class I. Actinopoda Calkins
Sul>-class I. Heliozoa Haeckel
Si ili-class II. Radiolaria Haeckel .
Class II. Rhizopoda von Siebold
Sub-class I. Proteomyxa Lankester
Sub-class II. Mycetozoa de Bary
Order I. Acrasida van Tieghem
Order II. Phytomyxida Schroter
Order III. Euplasmodida Lister
Sub-class III. Foraminifera d'Orbigny
Sub-class IV. Amoebaea ....
Order 1. Amoebida (Gymnamoebida) Ehrenberg
Order 2. Testacea
Key to Actinopoda
Sub-class 1. Helizoa Haeckel .
Order I. Aphrothoraca Hertwig .
Order II. Clamydophora .
Order III. Chalarothoraca
Order IV. Desmothoraca
Sub-class 2. Radiolaria Joh. Midler .
Class II. Rhizopoda von Sieb
Sub-class I. Proteomyxa ....
Sub-class II. Mycetozoa de Bary
Order I. Acrasida van Tieghem .
Order II. Phytomyxida
Order III. Euplasmodida Lister .
Sub-order 1. Exosporea Rostaf
Sub-order 2. Myxogastres Fries
Sub-class^III. Foraminifera D'Orb. .
Sub-class IV. Amoebaea Btitschli
Order I. Amoebida Aut. .
Order II. Testacea M. Schultze
436
437
438
442
443
445
447
449
449
450
453
455
456
459
460
460
460
460
461
461
461
461
462
462
462
463
463
463
466
466
466
467
CHAPTER XIII.
Special Morphology and Taxonomy of the Infusoria.
Classification of the Infusoria
Infusoria
Class I. Ciliata Perty 1852; Btitschli 1889
186
488
CONTEXTS xi
Infusoria — Class I. — Continual.
Sub-class I. Holotricha Stein 1850 188
Order 1. Astomida IS'i
Order 2. Gymnostomida -490
Sub-order 1. Prostomina (Prostomata Schewiakoff) 490
Sub-order 2. Pleurostomina Schew. 1886; Em. Kahl 491
Sub-order 3. Hypostomina (Hypostomata Schewiakoff) 491
Key to Genera 491
Order 2. Gymnostomida 491
Sub-order 1. Prostomina 491
Sub-order 2. Pleurostomina (Tribe Pleurostomata Schewia-
koff; Kahl) 497
Sub-order 3. Hypostomina Schewiakoff 1896; Em. Kahl 498
Order 3. Trichostomida Butschli 1889 499
Order 4. Hymenostomida 503
Sub-class II. Spirotricha Butschli 1889; Em. Kahl 1931 ... 508
Order 1. Heterotrichida Stein 508
Order 2. Oligotrichida Butschli 1889 512
Order 3. Ctenostomida (Lauterborn) Kahl 1931 . . 516
Order 4. Hypotrichida Stein s. str 516
Sub-class III. Peritricha Stein 521
Sub-class IV. Chonotricha Wallengren 522
Class II. Suctoria Butschli 523
CHAPTER XIV.
Special Morphology and Taxonomy of the Sporozoa.
Class I. Telosporidia Schaudinn 533
Sub-class I. Gregarinina . . 534
Order 1. Eugregarinida Doflein Emend 540
Order 2. Schizogregarinida Leger (1892) 541
Sub-class II. Coccidiomorpha Doflein 541
Order 1. Coccidiida Leuckart, Em 541
Sub-order 1. Eimeriina 541
Sub-order 2. Hemosporidia Danilewsky, em. Doflein 542
Sub-order 3. Babesiina 543
Order 2. Adeleida 544
Class II. Cnidosporidia Doflein 515
Order 1. Myxosporidia Butschli 548
Order 2. Actinomyxida Stole 551
Order 3. Microsporidia Balbiani 552
Class III. Acnidosporidia Cepede 555
Key to Subdivisions and Genera of Sporozoa 558
Bibliography ... 571
\ ft 5
BIOLOGY OF THE PROTOZOA.
CHAPTER I.
INTRODUCTION.
A protozoon is a minute animal organism, usually consisting of
a single cell, which reproduces its like by division, by budding, or
by spore formation and whose protoplasm has passed, or will pass,
through various phases of vitality collectively known as the life
cycle.
The maze of microscopic life to which the scientific world was
first introduced by Anton von Leeuwenhoek in 1075 included a
heterogeneous collection of animals and plants. Crustacea, rotifers,
minute worms, diatoms and desmids, as well as the more minute
Protozoa, were all grouped together during the eighteenth and nine-
teenth centuries, first under the nondescript term animalcula and
later under the more ecological term Infusionsthiere of Ledenmiiller
(1763). The correct zoological position of the higher types was
recognized before the middle of the nineteenth century and the
group of strictly unicellular forms was first definitely outlined by
von Siebold in 1848 under the name Protozoa, a term substituted
by Goldfuss (1820) for Oken's suggestive Urthiere (1805), while the
old name Infusoria has been retained for one of the subdivisions of
the group.
The haziness in classification of the older zoologists has not
entirely disappeared in the light of modern knowledge and we are
confronted today by the difficulties of distinguishing between
Bacteria, unicellular Algae and unicellular animals or Protozoa.
It is no reflection on modern science that we are unable clearly to
differentiate between these three groups. To accept the problem
as insoluble at the present time is merely to admit and apply our
conviction that evolution is now, and has been in the past, the pri-
mary biological principle underlying the diversities of forms and
functions of living things. Few biologists today will refuse to
accept the view that higher types of animals — Metazoa— have been
derived from forms in the past which were more or less similar to
present-day Protozoa; or the view that higher plants have been
evolved from unicellular plants. The variations and adaptations
18 BIOLOGY OF THE PROTOZOA
which have been the stepping stones in this evolution have been
and are still in progress among all types of unicellular things, so
that no artificial definition of Bacteria, of Protozoa, or of Algae
will distinguish with strict accuracy either of these groups from the
others. Haeckel (1866) undertook to avoid the difficulty by com-
bining all unicellular forms under the common name Protista, but
this is, obviously, only another name for the aggregate and an
artifice for concealing the real difficulties which we should like to
overcome. Minchin (1912), on the ground of structural characters,
would distinguish Protozoa from Bacteria by the assumption that
the latter are not of " cellular grade" because of the absence in many
Bacteria of a typical cell nucleus. Here again, however, the old
difficulty shows its head, for in this sense, many well-recognized
Protozoa are not, while many Bacteria are, of cellular grade (see
Dobell, 1911). The problem after all has mainly an academic inter-
est, and the chief practical value to be gained by its solution would
be to set the limits of a text-book or monograph. We may reason-
ably expect to find therefore, in treatises on Protozoa, some types
which with equal right should be included in works on lower plants
and on Bacteria. In this connection the greatest difficulty lies in
the separation of one group of the flagellated Protozoa from the
unicellular algae. We are still tied firmly to the old tradition that
animals move and plants are quiescent, and a chlorophyll-bearing
organism, if actively moving, is ipse facto an animal. Were I to
advocate this as the main distinction between animals and plants,
there would be, undoubtedly, a storm of protests from all biologists.
And yet, what other characteristics do chlorophyll-forming organ-
isms have to justify us in claiming them as animals? At the present
time there is a double taxonomic system, one botanical, the other
zoological for these questionable forms, and these systems are
widely different. We can avoid the resulting confusion by adopting
one or the other system of classification. My own conviction is
that zoologists should follow the historical precedent furnished in
the last century by the elimination from Protozoa of filamentous
algae, desmids and diatoms, and now transfer to the botanists the
entire aggregate of so-called Protozoa in which the ability to form
chlorophyll is a characteristic. (See also p. 412.)
It is less difficult to distinguish between Metazoa and Protozoa;
the occurrence of a gastrula stage in the development of a question-
able form is sufficient to place it unmistakably with the higher
animals. Protozoa, indeed, are often associated in cell aggregates
called colonies, the individual cells being held in place by proto-
plasmic connections, by stalk attachments, or by fixation in a com-
mon gelatinous matrix. In some questionable cases, e. g., Mago-
sphaera, these colonial aggregates resemble tissues of Metazoa in
their structural appearance, but tissue cells are dependent upon
INTRODUCTION 19
other parts of the animal for fulfilment of their vital activities while
every cell of a colonial protozoon may be self-sufficient and inde-
pendent, and differentiation among them is limited, at most, to
reproductive and somatic cells (e. g., Epistylis, Zoothamnium and
other vorticellids) .
While the single protozoon is to be compared structurally with a
single isolated unit tissue cell of a metazoon as a bit of protoplasm
differentiated into cell body, or cytoplasm, and nucleus, it is a
very different unit physiologically. In its vital activities it should be
compared, not with the unit tissue cell, but with the entire organism
of which the tissue cell is a part. All animal organisms perform
the same fundamental vital activities of nutrition, excretion, irri-
tability with movement and reproduction, which are fundamental
attributes of living animal protoplasm. In the higher types of
Metazoa these primary activities are performed by complex organ
systems, nutrition for example, involving not only the digestive
system but the muscular, nervous, circulatory and respiratory
systems as well. Each organ has its particular part to play in the
economy of the whole and each cell is differentiated for the purpose
of its specialized function. Tissue cells, therefore, are physiologic-
ally unbalanced cells since they are preeminently specialized for
secretion, or contraction, or irritability, etc. Division of labor in
a physiological sense here reaches its highest expression.
In the lower Metazoa the organ systems are less highly special-
ized; fewer organs are present to perform the same fundamental
vital activities and the tissue cells have relatively more kinds of
work to do for the organism as a whole. Thus the supporting and
covering cells of a coelenterate combine the functions of respiration,
irritability, muscular contraction, excretion and circulation with
the primary functions of an epithelium. Each of them is more
nearly balanced physiologically than a single cell of the higher
types, but it still needs the activities of other cells, and the organism
is again the sum-total of all its cellular parts.
In the protozoon, finally, we find a cell which is physiologically
balanced ; it is still a cell and at the same time a complete organism
performing all of the fundamental vital activities within the con-
fines of that single cell. Whitman, in his essay on "The Inadequacy
of the Cell Theory" (1893), clearly expressed the inconsistencies in
the common use of the designation "cell" for this variety of struc-
tures, and later writers, notably Gurwitsch (1905) and Dobell (1911),
have followed in a similar vein.
As organisms the Protozoa are more significant than as cells. In
the same way that organisms of the metazoan grade are more and
more highly specialized as we ascend the scale of animal forms, so
in the Protozoa we find intracellular specializations which lead to
structural complexities difficult to harmonize with the ordinary
20
BIOLOGY OF THE PROTOZOA
conceptions of a cell. In perhaps the majority of the Protozoa the
fundamental vital activities are performed, as in the simpler Ameba
or simple flagellates, by the protoplasm as a whole and without other
visible specializations than nucleus and cell body. In other forms,
Mac.
Mic.--
C.V.-
Fig. 2. — Diplodinium ecaudatum, a parasitic ciliate in cattle. A, anal canal and
defecatory vacuole; C. V., one of the two contractile vacuoles; M, motorium with
fiber to circumpharyngeal ring; Mac., macro nucleus ; Mic, micronucleus ; S, skeletal
layer. (After Sharp.)
however, intracellular differentiations lead to intracellular division
of labor which in some types becomes as complicated as are many
of the organisms belonging to the Metazoa. Thus Diplodinium
ecaudatum, one of the Infusoria, according to Sharp (1914), has
intracellular differentiations of extraordinary complexity (Fig. 2).
INTRODUCTION 21
Bars of denser ehitinous substance form an internal skeleton;
special retractile fibers draw in a protrusible proboscis; similar
fibers closing a dorsal and a ventral operculum; other fibrils, func-
tioning as do nerves of Metazoa, form a complicated coordinating
system; cell mouth, cell anus and a fixed contractile vesicle or
excreting organ are also present. All of these are differentiated
parts of one cell for the performance of specific functions, and all
perform their functions for the good of the one-celled organism which
measures less than -jto mcn m length. Analogous, if not so com-
plete intracellular differentiations are present in the majority of
Infusoria, while many of the flagellates, notably the Hypermastigida,
have an almost equally elaborate make-up. In all such cases the
single cell is a complicated mechanism and the cooperating parts
have the same relation to the organism as a whole as do the organs
of a metazoon. Compared with an Amoeba proteus or other simple
rhizopod such complex organisms are highly specialized and show
the extent to which intracellular differentiation may be carried. As
Gurwitsch, Hartmann, Dobell and others have pointed out, the
application of the term cell which designates a structural unit with
specific physiological activity in Metazoa seems to be inappropriate,
and, as Whitman argued, inadequate.
A significant difference between Protozoa and Metazoa lies in
the phenomenon of reversibility. Differentiations in the protozoan
organism are reversible and the derived organization is restored to
the fundamental organization (see p. 83) at periods of division,
parthenogenesis and fertilization. This does not occur in Metazoa
where differentiated cells derived from the fundamental organiza-
tion of the egg are irreversible and the "somatic" individual dies.
Cell aggregates or colonies are likewise highly variable in their
functional specialization. AYhile many of them consist of fortuitous
groups of cells with dimensions varying with the number of indi-
viduals joined together {e.g., Ophrydium versatile, Poteriodendron
petiolatum, etc.), others are definite in form, number of cells and
in arrangement. Here the colony as such has a distinct individ-
uality and in some cases (e. g., Zoothamnium alternans) under-
goes a definite developmental cycle. Again some colonies com-
posed of otherwise independent cells do not react as separate
individuals but the colony reacts as a coordinated whole. Thus
Zoothamnium arbuscula, composed of many hundreds of individual
cells in a colony which may attain a diameter of 1 inch, reacts
as a unit organism if any one of the component cells is irritated.
The entire aggregate contracts into a small ball, so minute that
it is scarcely visible. The concerted action is due to the con-
traction of stalk myonemes which are continuous throughout the
entire aggregate, like the coenosarc of some hydroid colonies.
22
BIOLOGY OF THE PROTOZOA
For such colonies of protozoa, as for analogous colonies of hydroids,
the expression "individual of a second order" has been applied.
Between the limits of the simplest and the most complex of uni-
cellular organisms are the great majority of the (estimated) 15,000
or more known Protozoa. In each of the main subdivisions sim-
plicity as well as extreme complexity of organization is represented,
each subdivision including a series of representative forms ranging
from one extreme to the other. Differentiation in the different
subdivisions do not follow the same lines of development, however,
so that we are able to classify Protozoa according to a fairly natural
system. These diverse lines of development make it difficult to
treat this branch of the animal kingdom in any general way; the
wide range in habitat from the purest waters of lake or sea to the
Fig. 3. — Types of Protozoa. A, Amoeba proteus, a rhizopod; B, Peranema tricho-
phora, a flagellate; C, Stylonychia mytilis, a ciliate; D, a polycystic! gregarine; E,
Tokophrya quadripartita, a suctorian. (A, after Calkins, B, C, E, after Butsehli;
D, after Wasielewsky.)
foulest ditch, and adaptations to environments varying in charac-
ter from a mountain stream to the semifluid substance of an epithe-
lial, nerve or muscle cell, has brought about manifold varieties
of structure. To describe all of these modifications under a few
headings, or to attempt to formulate general laws from the different
and often highly complicated life histories, is out of the question.
The general trends of differentiation, however, permit of grouping
the different kinds of Protozoa in four types which were first out-
lined by the French microscopist Felix Dujardin in 1841. Three of
these types— Sarcodina, Mastigophora and Infusoria— are based
upon the nature of the locomotor organs— pseudopodia, flagella and
cilia respectively— while a fourth type— Sporozoa— includes organ-
isms which are invariably parasitic in mode of life and are essentially
without motile organs (Fig. 3).
INTRODUCTION
23
DISTRIBUTION OF PROTOZOA.
Protoplasm is an aggregate of fluid colloidal substances in which
water plays a conspicuous part; exposed to the air it dries and desic-
cation is fatal to the majority of Protozoa, although it is possible
that some forms, like certain rotifers, may reabsorb moisture and
again become active. If after losing its water the protoplasm is
surrounded by impervious membranes, further evaporation is pre-
vented and within such capsules the protoplasm remains alive. This
is the condition of encystment and many kinds of Protozoa, protected
by their cyst membranes, may live for long periods in a dried state
(Fig. 4). Because of their light weight these cysts may be carried
in the air and blown by the winds with dust, until surrounded
1 2 3
Fig. 4.— Types of cysts. Eughjpha alveolata, testate rhizopod; Podophrya fixa,
suctorian; and Chilomastix mesnili, a parasitic flagellate, urn, undulating mem-
brane. (First and second, original; third, after Kofoid and Swezy, University of
California Publications in Zoology, 1920.)
again by water the organisms emerge from their cysts and are
active once more for a few hours. Such encysted forms account
in part for the surprising protozoan fauna in uncovered sterilized
water in which food substances come from similarly protected germs
of Bacteria and minute plant forms. Similar encysted forms may
be present on the blades of dried grass, leaves and other vegeta-
tion. In the infusions formed by soaking such dried vegetation in
water various species of monads (Monas, Oicomonas, Bodo) and of
ciliates (Colpoda, Oxytricha, Stylonychia, Urostyla, Gastrostyla and
Vorticella) and the rhizopod Ameba make their appearance in the
order given (Woodruff, 1912). Puschkarew (1913) concluded that
air-borne cysts play only a minor role, however, in the spread of
Protozoa. It was found that, on the average, there are only 2|
protozoon cysts per cubic millimeter of air and that these are limited
24
BIOLOGY OF THE PROTOZOA
to 13 species and represent the same types for the most part as those
listed by Woodruff. Protozoa are very apt to stick to solid sub-
stances when they encyst and are carried, in the dried state, with
such substances, which accounts in part for the appearance of
Protozoa in all kinds of infusions. Similar adhering cysts may be
carried from place to place by birds and other flying creatures or
by land animals, thus helping to maintain a common type of proto-
zoan fauna in pools and casual waters. The commonest species of
Paramecium, viz., P. aurelia and P. caudatum, are widely distrib-
uted over the earth and are almost universally used in general
laboratory work as examples of ciliated Protozoa. Their mode of
distribution, however, has been a continued puzzle for their sup-
posed inability to form cysts has been generally recognized. Re-
cently, however, Cleveland (1927), upon injecting unknown species
of Paramecium in the rectum of a frog, found that a definite cyst
membrane is formed bv manv of the Paramecia. After a few
Fig. 5. — Paramecium caudatum, stages in encystment. The final product may
be easily mistaken for a sand grain. (After Michelson, Arch. f. Protistenkunde,
courtesy of G. Fischer.) .
days division within the cyst and ex-cystation were observed.
Michelson (1928), furthermore, has described encystment of Para-
mecium caudatum under conditions of slow desiccation entailing loss
of peristome, vacuoles and cilia. When fully dried the crumpled
cyst wall resembles a small sand grain and as such may be over-
looked (Fig. 5).
Some forms to which Lauterborn (1901) has applied the term
"sapropelic fauna" appear to be able to live without free oxygen.
Thus Frontonia leucas, Prorodon ovum, Spirostomum ambiguum,
Pehmyxa palustris, P. binucleata, etc., which usually live in rela-
tively clear waters, may also live in the sulphurous medium of
putrefying vegetable and animal matter, while certain species of
ciliates of fantastic form seem to require this peculiar habitat for
their vital activities (Dactylochlamys pisciformis, Lauterb., Saprodi-
nium dentatum, Lauterb., Discomorpha pectinata, Levand., Pelodt-
nium reniforme, Lauterb.). Doflein, following the suggestion made
earlier by Bunge, believed that the anaerobic parasitic forms of the
INTRODUCTION 25
digestive tract may have had their initial start toward parasitism
when living as such sapropelic forms.1
Protozoa are distributed over the entire world. Wherever there
is moisture, there will these unicellular animals be found unless
conditions of heat or of chemical composition are inimical to life.
Oceans and their tributaries, lakes, ponds, pools and ditches,
mountain streams and wells contain them, their numerical abund-
ance depending on the available food. They are present, not only
in permanent waters, but also in casual puddles of field and road,
in droplets caught in the axils of leaves or in hollows of rocks, in
rain wTater of roof or pail and in damp moss. In many cases they
are active for only an hour or more until their world dries up, when
they may be saved again by encystment, but some forms retain
their activity in ordinary garden earth where they are supposed to
play an important part in connection with Bacteria of the soil
(Cutler and Crump, 1920; Goodey, 1916). The majority of such
soil-dwelling forms belong to the Sarcodina and Mastigophora,
Gruber's Amoeba ierrieola being a typical case, while other genera
and species are discovered from time to time (Bodo, Prowazelcia,
Spironema, Oicomonas, Cercomonas, D hn a stig amoeba punctata and
many others (see Soil-dwelling Protozoa, Chapter X, p. 353).
While excessive heat kills them, excessive cold does little harm
beyond retarding vital activities and the melted ice of glaciers may
teem with them. They may live, not only in the exposed waters
of the earth's surface, but also as parasites in the fluids of other
living protoplasm or its products. They may be found in the warm
blood of birds and mammals, or in the cold blood of fishes, amphibia
and reptiles; in the digestive tract of every type of animal; in the
saliva and urine of different types and in the living protoplasm
itself of plants, other Protozoa and of tissue cells. No type of
animal life is free from the possibility of association with Protozoa
either as commensals, or svmbionts or parasites (see Chapter X,
p. 358).
The common Protozoa of our own ponds and pools are exactly
the same in genera and species as those found in similar places in
Europe, Asia, Siberia, Africa, South America and Australia; they
are cosmopolitan, and the temptation to describe new species because
they happen to have been found in some hitherto unexplored local-
itv has no justification from the facts of geographical distribution.
This is particularly applicable to the fresh water forms but does
1 The suggestive experiments and conclusions of Avery and Morgan (1924) give
reason for the belief that the inability of some organisms to live in free-oxygen hold-
ing media is due to the absence in such forms of a peroxidase capable of breaking
down hydrogen peroxide. The latter accumulates under ordinary aerobic conditions
and is detrimental to forms which are unable to provide the peroxidase. The limi-
tation of free oxygen may be the explanation of successful artificial cultivation of
forms — for example Spirostomum ambiguum — which grow best under partly anaero-
bic conditions (see Bishop, 1923).
26 BIOLOGY OF THE PROTOZOA
not apply equally to the deep sea types. The littoral fauna of salt
water, like the fresh water forms, appears to have a cosmopolitan
distribution according to the observations of Gourret and Roesser
(1886), of Levander and of Hamburger and Buddenbrock in Europe,
while in North America the brackish waters are particularly rich
in number and variety of Protozoa. The pelagic and deep sea forms
appear to be unequally distributed; some types are apparently
limited to the Indian Ocean; others to the Atlantic, while many
tropical genera and species, especially of Radiolaria and Foramini-
fera, are not found in the polar seas and vice versa. Some strictly
pelagic forms, on the other hand, notably Tintinnidae, are found
on or near the surface of sea water in all parts of the world.
Observations are sufficiently numerous to show that not only is
there a certain climatic distribution of salt water forms, but a ver-
tical distribution as well. Certain genera and species of Radiolaria
and Foraminifera are present in the surface waters but are rarely
found at the depth of from 600 to 3000 feet, while some families,
notably the Challengeridae and Tuscaroidae, are present only in
the extreme depths of the sea.
Many species are sufficiently adaptable to live either in fresh,
brackish or salt water; indeed most of the common forms of rhizo-
pods, flagellates and ciliates seem to be equally at home in either.
Many types, however, sometimes entire groups of Protozoa, are
not so ubiquitous; the sub-class Radiolaria for example, comprising
more species than any other entire class of Protozoa, is exclusively
marine, while another large sub-class of the Sarcodina, the Fora-
minifera, comprises only a few fresh water representative species.
Many more types of Choanoflagellates are present in salt than
in fresh water. Ciliates are poorly represented in the deep sea,
although one family— Tintinnidae— is wonderfully rich in salt water
forms while fresh water forms are uncommon. Heliozoa, another
sub-class of the Sarcodina, on the other hand, are typically fresh
water forms with relatively few salt water representatives.
The distribution of parasitic forms belonging to all groups of the
Protozoa obviously follows the distribution of their hosts, and we
know too little on this subject to generalize; where animals are
segregated the opportunities for parasitism are enhanced while
some climatic conditions are more advantageous than others for
the spreading of germs. Thus the blood-dwelling parasites are
more common in the tropics than elsewhere, the biological condi-
tions favorable to the intermediate transmitting hosts being largely
responsible for their numbers and variety.
SIZE, FORM AND APPEARANCE OF PROTOZOA.
Although Protozoa belong unquestionably to the microscopic
world their sizes vary within wide limits. Some are large enough
INTRODUCTION
27
to be picked up with forceps (Porospora gigantea, a gregarine, up to
16 mm.) and many of the larger ciliates are easily visible to the
unaided eye (Bursaria truncatella, Spirostomum ambiguum) while
many smaller types can be seen by the trained eye as mere white
specks which, in some cases, may be identified by their characteris-
tic movements (e. g., Paramecium, Frontonia, Dileptus, Amphileptus,
Loxophyllum, etc.). At the other extreme in size are types which
are barely visible even with the most powerful lenses of the micro-
scope. From 8 to 16 such forms have ample room for existence in
a red blood corpuscle (Babesia canis), or 200 to 300 may live simulta-
neously in a single infected liver or spleen cell of man (Leishmania
B
k
Fig. G. — Dileptus gigas, two sister cells. A, normal individual; B, individual starved
for several days. (From Calkins.)
donovani). Between these two extremes of size lie the majority of
Protozoa. Their measurements are usually expressed in terms of
" microns " or thousandth parts of a millimeter which are represented
by the symbol n, each micron being 2t|-oo- °^ an ^ncn- Thus Leish-
mania donovani measures from 2 n to 4 /x, Paramecium caudatum
upward of 200 //, Bursaria truncatella, 1500 /x, etc.
The same species frequently shows remarkable variations in size
due to environmental conditions or to different stages in the life
history. Thus normal specimens of Paramecium caudatum may
measure from 175 /j, to 250 /x when fully grown and similar variations
are characteristic of all species. Environmental factors, especially
28
BIOLOGY OF THE PROTOZOA
food conditions, are frequently responsible for changes in size and
character of a species, often rendering them difficult to recognize
and affording tempting opportunities for swelling the list of syn-
onyms by new names for the abnormal forms. Thus Dileptvs
gigas when starved has a very different size and character from
the normal form (Fig. 6). Again, different normal stages in the life
history of a given species are not infrequently mistaken for different
species, largely because of difference in size. Thus Uroleptus metritis
(see Fig. 1), in its adult vegetative condition, measures about
150 (J., but immediately after conjugation not only is it reduced
Fig. 7. — Uroleptus mobilis Engelm. Old age specimens showing degeneration of
macronneleus M and loss of micronuclei. See frontispiece. (After Calkins.)
by one-third in size, but its internal structure is entirely different
from that of the usual form, while during the period of old age it
frequently measures less than 75 // (Fig. 7), and has a different
appearance from the more youthful stages.
Even more striking examples of normal dimorphism are shown
by the rhizopod Dimastig amoeba and by the ciliate Glaucoma (Dalla-
sia) frontata. Species of the former usually appear as small earth-
dwelling ameboid rhizopods, but with the addition of water they
develop flagella and become actively moving ellipsoidal flagellates.
Glaucoma frontata in its usual vegetative state is a more or less
quiescent tailed form (Fig. 8), but under certain environmental
INTRODUCTION
29
conditions not yet fully understood it becomes an active tailless
navicular organism which divides repeatedly, giving rise to minute
M07
Fig. 8. — Glaucoma (Dallasia) frontata. Vegetative individual. A, anus; BC,
buccal cavity; CV, contractile vacuole; LS, "ladder" system; LU, left undulating
membrane; M, mouth of buccal cavity; MOT, region of motorium; RU, right undu-
lating membrane; T, "tongue" in buccal cavity. (After Calkins and Bowling,
Arch. f. Protistenkunde, courtesy of G. Fischer.)
30 BIOLOGY OF THE PROTOZOA
individuals one-sixteenth the original size (Fig. 200, p. 485). To
the uninitiated such variations in forms and habits offer great temp-
tation to swell the list of synonyms.
A. Form-relations of Protozoa. The forms of Protozoa are highly
varied and depend to some extent upon the mode of life, to some
extent upon the mode of reproduction and to some extent upon
their lifeless skeleton elements, but in the last analysis they depend
upon the physical consistency of the protoplasm. Fluid types, if
not confined by resistant cell membranes, readily change in form
according to environmental conditions, or by virtue of forces coming
from metabolic activities within. Amoeba proteus and other species
of Ameba are amorphous and are constantly changing in shape, a
characteristic phenomenon to which the term ameboid movement
is applied, and the same protoplasm may be spherical in form, or
flattened on the substratum, or extended in various ways. Many
forms, under certain pressure conditions in the surrounding medium
due to evaporation or reduced volume of water, will suddenly burst
and disappear leaving no trace whatsoever of their previous presence.
This phenomenon has been repeatedly mentioned by earlier observ-
ers in connection with types of Protozoa belonging to all classes,
and the term diffluence was applied to it by Dujardin. In such cases
the fluid protoplasm is usually confined by a resisting membrane
or cortex which remains intact during the ordinary phases of activ-
ity, but when the pressure from within becomes too great for the
resistance of the membrane the latter collapses, the cell disappear-
ing with all the characteristics of a miniature explosion.
Another evidence of the difference in density between different
species of Protozoa is the reaction after cutting with a scalpel.
Some species, for example Paramecium cavdatum, are extremely
difficult to cut successfully owing to the fluid character of the inner
protoplasm which, as soon as the cortex is cut, flows out and disin-
tegrates; in my experience not more than 20 per cent out of more
than 1000 operations on Paramecium caudatum have been success-
ful, but the percentage is greatly increased by preliminary treat-
ment with neutral red. Other forms of ciliates on the other hand
may be cut in any plane, Uronychia transfuga and Uroleptus mobilis
for example, reacting to such operations with all the physical
properties of a piece of cheese.
The more fluid Protozoa, when the form is not maintained by
resistant cortical differentiations, react to physical properties of
the surrounding medium. When forces on all sides are equal, as in
suspended water-dwelling types like Actinophrys sol, Actinosphae-
rium, many Radiolaria, etc., the form is spherical, or spherical also
in parasitic forms enclosed in the protoplasm of the host cell as is
the case with the majority of Coccidia. In all types, under certain
environmental conditions, or when continuously irritated, there is
INTRODUCTION
31
a tendency to become globular and this is the form assumed by
the great majority of Protozoa when they encyst. The spherical
or homaxonic type, furthermore, is characteristic, not only of free
floating forms, but also of the most generalized representatives of
all classes of Protozoa.
While density or consistency of the protoplasm is thus one of the
factors determining form in Protozoa, its effect in the majority of
types is offset by the presence of definite membranes, shells, tests
and skeletons; by specialized protoplasmic differentiations; or by
foreign bodies. Thus the density of the sluggish Pelomyxa palustris
Fig. 9. — Euglypha alveolala (A), and Cochlio podium, sp. (B). (After Calkins.)
is due to the enormous number of crystals of mud and sand, shells
of diatoms and peculiar refractile bodies resembling glycogen in
make up. Membranes of living substance, as in Cochlioyodium
(Fig. 9) and the majority of flagellates and ciliates, of lifeless chitin
as in Allogromia oviforme (Fig. 10) or the lifeless materials secreted
by the cell and deposited on it are responsible for the forms assumed
by many Protozoa. Even delicate types such as Clathrvlina elegans
and the majority of Heliozoa retain their forms by virtue of the
protecting shells of lifeless materials deposited on a chitinous mem-
brane. The protoplasmic bodies of many of the fresh water shelled
32
BIOLOGY OF THE PROTOZOA
rhizopods are relatively dense like that of the naked Amoeba verru-
cosa and are more or less globular or pyriform in shape. On such
a protoplasmic basis the shells of Dlfflugia species, Euglypha, Cyylw-
:
\ ,
Ik
' 1 i
•; n
D
Fig. 10. — Allogromia oviforme, foraminiferon with chitinous monothalamous shell
and reticulose pseudo podia. (£>) a recently captured diatom; OS) chitinous shell.
(From Calkins after M. Schultze.)
deria, Centropyxis, Arcella, etc., are deposited and these, once
formed, are never changed (Fig. 11). Only rarely are these shelled
rhizopods flattened or discoid as in Hyalodiscus (see Chapter XII).
The typical form in many shell-bearing or skeleton-forming rhizo-
INTRODUCTION
33
pods may be due in its last analysis to the finer structure of the pro-
toplasmic body in which the skeleton or shell parts are deposited.
Dreyer (1892) has given evidence to show that the form and size
- . \
4^1
&&*\ \ X
Fig. 11.
-Pseudodifflugia sp. circular mouth opening and mosaic shell (.4). B, division
stage. (Original.)
Fig. 12. — Schematic figure illustrating the modifications of skeletons according to
mechanical principles of deposition. (After Dreyer.)
of the elements making up the skeletal or shell parts depend upon
the alveolar make up of the protoplasm, the interalveolar deposits
of silica, etc., taking the form of spicules as in Heliozoa and many
3
34
BIOLOGY OF THE PROTOZOA
Radiolaria, of bars, hexagons, rings, fenestrated capsules, etc.
(Fig. 12).
Freely moving types are usually monaxonic. The type form of a
freely moving flagellate or holotrichous ciliate is ellipsoidal, the cell
being drawn out with its main axis extending in the direction of
movement. Attached forms are usually polyaxonic or radially sym-
metrical, the variations in form depending upon the nature of the
B
Fig. 13. — Diphasic rhizopods. A, B, C, heliozoa-like and flagellated stages of
Dimorpha mutans, (After Blochman.) D, E, F, Dimastigamoeba gruberi, ameboid
and flagellated stages; E, origin of blepharoplast (bl) from endosome; r, rhizoplast.
(After C. W. Wilson.)
attaching portion. Some for example are attached by the proto-
plasm of the posterior end of a cylindrical body (e. g., Cothurnia,
Vaginicolla, etc.); others by the more or less stalk-like attenuated
end of the body (e. g., Scyphidia, Podophrya, etc.); and others by
chitinous stalks of variable length (Vorticella species) which may be
more or less branched (Poteriodendron, Epistylis, Carchesium, Zooth-
amnium, etc.). In the same individual the form may change with
INTRODUCTION
35
change in mode of life, well illustrated by Bimorpha mutans (Fig. 13),
by Bimastigamoeba gruberi or Trimastigamoeba. Fantastic types
such as Biscomorpha pectinata or Tripalmaria dogieli (Fig. 14)
are not uncommon and no evident connection between such bizarre
forms and their mode of life is apparent.
Methods of food-getting and the nature of the food are also potent
factors in determining form. Many of the diatom- and desmid-
eating eiliates, whose food lies on the
bottom, are characteristically flattened
forms with the mouth on the under, or
physiological ventral, surface (holotrich-
ous eiliates belonging to the genera
Chilodon, Orthodon, Opisthodon, Chlamy-
dodon, Loxophyllum, etc., and the major-
ity of the hypotrichous eiliates) . Special
food-getting, or current-directing, organs
frequently modify the form as in the
collared flagellates (Choanoflagellates)
and in types like Folliculina ampulla
(Fig. 94, p. 169), Bursaria truncatella
(Fig. 94, p. 169), cephalont gregarines,
Pleuronema (Fig. 199, p. 482), etc. Shift-
ing of the position of the mouth in re-
sponse to different food requirements,
as Biitschli has shown, has undoubtedly
been the cause of some form changes.
Thus the proboscis-bearing species and
the asymmetrical Chilodon types may
owe their characteristic forms to such a
shifting of the oral region (Fig. 15).
The monaxonic types, while typically ellipsoidal in form, are
frequently characterized by a spiral twisting of the cell body, espe-
cially in the rapidly moving forms. In some cases, notably in the
flagellates Streblomastix, Spiromonas, Holomastigotes, etc., and in
the eiliates Aegyria, Paramecium, Metopus sigmoides, etc., the spiral
twist is highly characteristic (Fig. 16).
Bilateral symmetry is of rare occurrence among Protozoa; indeed
there seem to be few significant cases, that of Giardia being the
best known (Fig. 17). Here the two nuclei, the motor complex and
the eight flagella are arranged in the neatest bilateral manner. One
possible mode of origin of such bilaterally symmetrical types is
indicated by Uroleptus mobilis (Fig. 18). Here two individuals, after
conjugation, fused to form a single double and bilaterally symmetri-
cal individual which persisted through 367 generations (see also
Fig. 127, p. 245).
Form may be dependent also upon the mode of reproduction.
Fig. 14. — Tripalmaria" dogieli
(minor). Gut parasite of the
horse with three bundles of cilia
and internal skeleton. X 520.
(After Strelkow, Arch. f. Pro-
tistenkunde, courtesy of G.
Fischer.)
Fig. 15. — Diagrams illustrating shifting of the mouth in ciliates from terminal to
lateral or ventral surface (A, B, C, D). E, Prorodon griseus, corresponds with A;
F, Am.phileptus claparedi, corresponds with B or C; and G, Nassula microstoma, corre-
sponds with D. (E and F, after Butschli; G, after Calkins.)
A
Fig. 16.— Types of spirally wound Protozoa. A, Streblomastix strix. (After Kofoid
and Swezy.) B, Lacrymaria sp. (Original) ; C, Heteronema sp. (Original.)
(36)
INTRODUCTION
37
In this connection we have to do only with the multinucleated and
with the colonial forms of Protozoa, for in ordinary division the
daughter cells separate completely and reproduction has no effect
on the form assumed. Thus the foraminiferon Allogromia oviforme
gives rise by what is termed budding division to a free daughter
L-__/
M-—
*i — m
Fig. 17
Fig. 18
Fig. 17. — A bilaterally symmetrical flagellate, Giardia muris Grassi. AX, axostyle;
B, blepharoplast; BB, basal body; C, centriole; E, endosome; N, nucleus; PL,
parabasal body; RH, rhizoplast. (After Kofoid and Swezy.)
Fig. 18. — A bilaterally symmetrical ciliate from Uroleptus mobilis. A double
individual formed by fusion of two individuals after conjugating. With two mouths
and adoral zones (a. z.); two sets of cirri (/); and two sets of macronuclei (M) and
micronuclei (m). For structure of single individual see Frontispiece. (Original.)
cell which builds an independent test for itself while the other cell
remains in the old test. In other forms of Foraminifera, however,
the bud of protoplasm does not become separated from the parent
bulk of the cell but takes a position in relation to the other portion
which possibly depends upon the physical conditions of the proto-
38
BIOLOGY OF THE PROTOZOA
plasm. New shells are deposited about the buds and chambered
individuals result (Fig. 19). Repetition of the process gives rise to
distinct types of polythalamous or many-chambered Foraminifera,
depending upon the position assumed by the bud (Nodosarine,
Frondicularian, Rotaline types, etc.).
Dogiel (1929) interprets the duplication (polymerization) of
organelles such as contractile vacuoles, macro- and micronuclei,
flagella groups, particularly of Polymastigida, somatella formation
(see p. 233), multiple nuclei and kinetoplasts of Calonymphidae
(see p. 115), etc., as evidence of gradations in cellular differentia-
tions in Protozoa leading to a multicellular condition which is fully
established in Metazoa.
I D V
Fig. 19. — Types of shells of Foraminifera. A, B, side and ventral aspects of Cornu-
spira sp. ; C, and D, types of Nodosaria. (After Carpenter.)
In colonial types the form of the aggregate is determined by the
manner in which the individuals are held together after division.
The different types are described as spheroid, catenoid, arboroid
and gregaloid colonies. In the majority of spheroid colonies, the
associated cells are held together by a gelatinous matrix secreted
by the individual cells. The typical form of such colonies is spher-
ical as in the genus Proterospongia, among the flagellates, or Ophryd-
ium versatile among the ciliates. In catenoid colonies the individuals
are attached end to end as in some species of ciliates (e. g., Hapto-
phrya), or side by side as in the flagellate Rhipidodendron. In
arboroid colonies the individuals are attached by longer or shorter
stalks in a branching, often bush-like colony [Clathrulina elegans,
Poteriodendron petiolatum (Fig. 139, p. 418) , Codosiga eymosa (Fig. 20),
Epistylis umbellaria (Fig. 143, p. 280), Carchesium polypinum, Zooth-
amnium arbusctda, etc.] In the majority of these arboroid colonies
each individual is borne on its own stem which branches from a
common stalk. In some cases, however, especially amongst the
flagellates, each stalk bears a cluster of individuals as in Cladomonas
INTRODUCTION
39
fruticulosa, Anthophysa vegetans (Fig. 21) or Phalansterium digi-
iatum (Fig. 22). In Rhipidodendron splendidum the gelatinous
branches, colored brown or red by oxide of iron, are arranged in
parallel rows, spreading out fan-like as they increase with divi-
sion of the cells, the aggregate forming an organ-pipe-like arboroid
colony. Gregaloid colonies, finally, are fortuitous aggregates of
previously independent individuals found mainly amongst the rhizo-
pods and Heliozoa, or in parasitic flagellates under adverse envir-
onmental conditions (Spirochetes, Try panosomes) . The origin of
gregaloid colonies is not connected in any way with the manner of
reproduction.
Fig. 20.
-Type of flagellate colony. Codosiga cymosa Kent, an arboroid colony
of collared flagellates.
The combination of all of the above factors effective throughout
past ages has resulted in fixed, complex forms which, as in Metazoa,
are today associated with the germinal make-up of the protoplasm
or genotype, and are transmitted by inheritance.
B. Protoplasmic Structure.— All protoplasm contains the same
fundamental chemical elements — C, H, N, O and P— which are
necessary for the performance of vital activities. With these are
associated mineral elements of one kind or another— Na, K, Ca,
Mg, Fe, S, etc., usually as salts of different kinds, and water.
In its last analysis form depends upon the chemical and physical
combinations of these elements which indicate specific protoplasmic
40
BIOLOGY OF THE PROTOZOA
organizations and interactions of different protoplasmic substances
and which form the physical basis of inheritance. A minute frag-
ment of Uroleptus mobilis is difficult to distinguish from a similar
fragment of Dileptus gigas, yet the former develops into a perfect
Uroleptus, the latter into Dileptus. The encysted forms of many
types are impossible to identify until the cysts are opened and vital
processes begin again. These facts indicate that the finer or ulti-
mate composition of protoplasm is different in different forms and
4 A <?J%< ^V
c
'~llll
*&£%
^rt
Fig. 21. — Anthophysa vegetans. Colony of flagellates with iron encrusted gelatin-
ous stalks. X 1000. (After Doflein, Lehrbuch der Protozoenkunde, 1927, courtesy
of G. Fischer.)
specific for each species, and justify the view that there are as many
kinds of protoplasm as there are species of Protozoa, Metazoa or
living things generally. Considerations of this nature inevitably
lead us into the lines of thought followed by Whitman, Gurwitsch,
Dobell and many others and to question again the adequacy of the
cell theory in its application to Protozoa.
The specificity of protoplasm is not at all indicated by its appear-
ance, although obvious differences in many cases may be seen even
INTRODUCTION
41
with low powers of the microscope. In a living form what we
actually see under the microscope in most cases is the external zone
of protoplasm which, as the surface of contact between the organ-
ism and the outer world, has become modified in various ways.
Such outer differentiations are usually transparent so that the
nature of the internal protoplasm may be made out in more or less
detail. This is particularly true of the so-called "naked" forms
such as Amoeba proteus, etc., in which the surface protoplasm is
■■ WMv I \ Y V
-** ^
1 1
Fig. 22. — Phalansterium digitatum St. [ndividuals (/) in branched gelatinous colony.
(After Stein.)
only slightly different from the internal substance and is made up
of living material. Here the entire organism is living protoplasm
which appears as a drop of fluid substance, grayish-white in color,
viscid in physical character but tenuous and with no tendency to
mix with the surrounding water. In such living cells, internal
movement of the protoplasm is manifested by the streaming (cyclo-
sis) of distinct granules, some of which are more refractile than
others, but which are present in all cells, and invariably character-
42 BIOLOGY OF THE PROTOZOA
istic of the inner plasm. Spherical spaces or vacuoles are also visible
in the living forms, sometimes with solid, usually foreign, matter
within them (gastric vacuoles, defecatory vacuoles), sometimes
filled with clear watery fluid (contractile vacuoles) which is emptied
to the outside at regular intervals, or sometimes filled with fluids
which are not discharged (stationary vacuoles, or cavulae of Wetzell).
The same form, when fixed with a good killing agent, and properly
stained, gives a permanent picture of the granules, vacuoles and
other cell parts as they were at the instant of fixation. The nucleus
now stands out as the most conspicuous part of the cell, while the
granules are seen to be of different sizes and to react differently
after treatment with different stains.
In most cases the finer physical structure of the protoplasm can be
seen both in the living cell and after fixation. It is best described
as a foam structure similar to the bubbles of soap suds but with
"bubbles" or alveoli of microscopic size. Imagining an optical
section through soap suds in which granules of finely-powdered
carmine have been distributed by stirring, the picture presented
would be a network or meshwork of water, soap and carmine, and
with an accumulation of carmine granules where three planes of
contiguous bubbles come together, while the spaces within the
meshes would be filled with air. The apparent network, however,
is merely the optical section of continuous walls of bubbles enclosed
on all sides by the water and soap. The physical structure of the
protoplasm of a few Protozoa, called spumoid structure by Rhumbler,
may be accurately compared with such an emulsion of soap and
water. An analogous network, usually of exquisite fineness, repre-
sents the more solid substance of protoplasm; the apparent fibers
forming the meshwork in some cases at least are the optical sections
of continuous walls, which, like the soap bubbles, enclose materials
of lesser density. Butschli who, with Rhumbler, has studied the
finer structure of protoplasm of lower plants and animals as well
as that of higher forms, was the first to compare such structures
with the alveolar structure of emulsions like soap and water, oils
and water, etc. The granules of protoplasm, corresponding in posi-
tion with the carmine of the soap suds, lie in the substance of the
denser network of interalveolar material to which Doflein applied
the term stereoplasm. The alveolar substance, called rheoplasm by
Doflein, corresponds in position with the air of the soap bubbles.
All who have investigated protoplasm agree that it is not a homo-
geneous substance but a mixture of colloidal substances in the
physical state described by Ostwald as an emulsoid in which the
interalveolar materials act in the manner of a dispersing agent
while the more fluid intra-alveolar substances are dispersed, but all
arc subject to reversal of phase.
While the alveolar structure of protoplasm is convincingly demon-
INTRODUCTION 43
strated by a number of typical forms of living Protozoa, this struc-
ture is difficult to make out in other types. Thus in the endoplasm
of flagellates like Chilomonas, or the endoplasm of Actinophrys sol,
or Actinosphaerium eichhornii, the alveoli are easily discernible, but
in Paramecium caudatum, in many gregarines, and in many types
of flagellates and ciliates, the alveoli, if present, are too fine to be
seen with the usual powers of the microscope. Vonwiller (1918)
can find no evidence for upholding the alveolar theory of proto-
plasmic structure in general.
Certainly in many cases the protoplasm appears to be almost
homogeneous in structure, the granules alone being evidence of
structural configuration. Such forms are illustrations of the gran-
ula theory of Altmann, who held that protoplasm is made up of a
congeries of such granules or microsomes each of which is termed a
bioblast, each bioblast being regarded as a single unit performing
all of the functions of living matter including growth and reproduc-
tion. Here, however, theoretical considerations have been super-
imposed on the obvious structure and the physical appearances
become clouded in a mist of speculation. Other theories, such as
the reticular and fibrillar theories, associated with the names of
Heitzmann, Schafer, Flemming, etc., are based upon the actual
pictures of different types of protoplasm.
The larger vacuoles in different types of Protozoa to which the
names cavulae, gastric, and contractile vacuoles are given are inter-
preted according to the alveolar theory as due to the flowing together
and fusion of adjacent alveoli. This is certainly the case in the for-
mation of a contractile vacuole of Amoeba proteus where the begin-
nings of a vacuole may be watched under the microscope and the
coalescence of minute vesicles noted. In a similar way the relatively
huge cavulae or pseudo-alveolae characteristic of Actinosphaerium
eichhornii and of Radiolaria may be accounted for.
Physically, protoplasm is to be compared with an emulsion of
colloidal substances which, as Lord Rayleigh and others have
pointed out, as a polyphasic system can retain the emulsoid condi-
tion only as long as the limiting membranes between dispersed and
dispersing media are intact. In the activities of a living, moving
cell, there must be a continual disturbance of this physical equi-
librium and a constantly changing configuration of the protoplasm
due to the manifold chemical actions which are characteristic of
living matter.
Chemically, protoplasm is not a substance but a harmoniously
working aggregate of different interacting substances which have
been identified in general as nucleins, nucleo-albumins, nucleo-pro-
teins, lipoproteins, fats, carbohydrates, salts and the almost endless
variety of derivatives from these and from their combinations.
But the chemical make up of living substance is, as yet, in an
44 BIOLOGY OF THE PROTOZOA
uncertain and experimental stage. Beyond somewhat glaring gen-
eralizations of chemical groups as listed above, we know but little
that is definite concerning the chemistry of living matter. It is
freely admitted by those who are in the best position to know,
that many highly labile substances of active protoplasm are de-
stroyed or changed beyond recognition by the processes of modern
chemistry. Some of these are probably quite unaccounted for;
another group can be identified as chemically definable substances
which, however, we can only assume to be an integral and neces-
sary part of the protoplasmic make-up. Many qualitatively impor-
tant bodies are overlooked or hidden from observation; others are
materials in an absorbed condition or so enmeshed among the
colloidal stuffs that their clear demonstration is as yet scarcely
possible. The unavoidable destruction, physically and chemically,
of protoplasm during analysis must bring about mixtures, or chemi-
cal and physical changes amongst the substances originally present,
hence the position of different stuffs cannot be definitely ascertained
as fundamental or derived until methods are more refined and more
exact.
With the exception of the Mycetozoa which have been used
extensively for the purpose of protoplasmic analysis, protozoan
protoplasm, owing to the minute size of the individuals, has been
very little studied in connection with the chemistry of protoplasm,
and our present knowledge concerning it is based mainly on morpho-
logical considerations together with the results of chemical analysis
of protoplasm in higher types of animals and plants.1
The granules which invariably appear in protoplasm, and which
are probably intimately connected with the varied activities going
on during life are different in their chemical make-up although,
morphologically, they appear much the same. This is shown by
their reactions to micro-chemical tests of different kinds and it is
not unreasonable to infer that the specificity of protoplasm in dif-
ferent species of Protozoa is due in large part to the chemical and
physical composition of these granules and to interactions going on
amongst them.
The almost infinite variety of form and structure represented by
1 An example of one concrete case of chemical analysis may be cited. This is not
accepted without question, but it indicates the nature of the substances which enter
into the make up of protoplasm — in this case of the Plasmodium of the mycetozoon,
Fuligo varians, as analyzed by Lepeschkin (1923, 1926).
Per cent. Per cent.
Monosaccharid . . . . 14.2 Globulin 0.5
Albumin 2.2 Lipoproteid 4.8
Amino-acids ) Neutral fat 6.8
Purin bases > . . . . 24 . 3 Phytostearin 3.2
Asparagin J Phosphatids 1.3
Nucleoproteid 32 . 3 Other organic stuffs . . . 3.5
Free nucleic acid . . . . 2.5 Mineral stuffs 3.4
INTRODUCTION 45
the Protozoa must be traced back to the chemical nature of the
proteins and to their relations and interactions with other substances
in protoplasm. Types which have a similar chemical and physical
make up, with similar metaplastids and plastids, are practically
identical in form and structure and we recognize them as distinct
species. Variations in chemical composition, be they ever so little,
must result in different chemical reactions and products, and in
corresponding variations in form and structure of the organism,
and these variations furnish the basis for classification.
Under normal environmental conditions the reactions among the
varied substances in protoplasm of the same species, with their
products and arrangement of these products, are individual and
invariable. Furthermore, the entire organism partakes of this indi-
viduality. A fragment of Stentor obtained by cutting or by shaking
cannot be distinguished from a similar fragment of Dileptus, yet
the former regenerates into a perfect Stentor, the latter into a per-
fect Dileptus. Or an encysted Uroleptus mobilis is morphologically
identical with an encysted Didinium nasutum; both are apparently
homogeneous balls of undifferentiated protoplasm; the one emerges
from the cyst and develops with the characteristic differentiations
of Uroleptus, the other of Didinium. In short, the homogeneous
ball representing Uroleptus is as specific and different from the
homogeneous ball representing Didinium, as the adult Uroleptus is
different from the adult Didinium. We may speak of this undiffer-
entiated chemical and physical make-up as the fundamental organ-
ization of the species, in a sense similar to the architectonik of
Driesch. The adult characteristics result from the interactions of
the specific proteins, carbohydrates, salts, water, etc., among
themselves and with the environment, and represent what we may
call the derived organization.
Organization in the above sense is not only specific but is con-
tinuous from generation to generation, and has come down through
the ages subject, however, to modifications and changes through
interaction with the environment or through changes coming from
within as in amphimixis.
While organization is continuous the actions and reactions going
on within it are discontinuous. More or less prolonged periods of
rest are characteristic of all living things, best exemplified in the
case of spores, eggs, encysted Protozoa and seeds. At such times
the organization is static; the chemical substances making up the
specific organization are present but quiescent, or at least, in the
absence of water, relatively inactive. A striking illustration is
afforded by the phenomenon of desiccation in some types of animals,
e. g., rotifers, which has been known for decades. For some years
I had on my shelf a bottle of minute amorphous granules which
appeared like specks of dust under the microscope. After placing a
46 BIOLOGY OF THE PROTOZOA
few of these granules in water each of them would become an active,
living rotifer in an hour or so. Here organization was present
but inactive, and activity began with the absorption of water and
with oxidation. The rotifer in the active state is the same rotifer
that it was in the dried condition, so far as organization is concerned,
but it differs in that the organization is now in action. It is a
difference of the same nature as that between an automobile stand-
ing in the garage, and the same automobile travelling 30 miles an
hour. The organization is in action in both moving rotifer and mov-
ing automobile; is static in the dried rotifer and in the standing
machine.
The automobile simile, however, will not stand analysis. The
parts of the machine are little changed by activity and the organ-
ization remains the same throughout its period of usefulness. With
a living thing, on the other hand, the chemical and physical make up
changes with every activity and, as a result of such activities, the
protoplasmic organization itself will change. An encysted Uroleptus
is a motionless and apparently a homogeneous ball of protoplasm;
an hour later it is an elongate, cigar-shaped organism with special-
ized motile organs in the form of membranelles and cirri, and its
contractile vacuole pulsates with rhythmical regularity as it moves
actively about in the water. The organization has undergone a
change in this brief period; the first indication is the swelling and
enlargement of the cyst wall, evidently by the absorption of water;
oxidation probably occurs and substances already present, or new
substances formed as a result of this initial oxidation, are responsible
for the newly-developed structures or derived organization not
present before. Such structures, however, are the morphological
expression of the adult organization and their formation corresponds
to the development and differentiation of the metazoon egg.
Continued activity involves other and still more subtle changes in
organization; some of these are evident in individual life between
division periods; others are evident only in a long series of individuals
constituting a life cycle. These will be more fully treated in Chap-
ters VII and VIII.
Other changes in organization may be brought about by environ-
mental conditions; or they may be brought about by changes in
one or more of the substances constituting the protoplasm of the
species, as when amphimixis introduces a new combination of chro-
matin into the organization. These are undoubted factors in the
phenomena of adaptation and probably play a part in the orig-
ination of new species and types.
Consideration of these and of similar activities in living proto-
plasm lead to questions regarding the nature of life and the nature
of vitality. Should we use the two terms life and vitality as syno-
nyms? We are very apt to speak of life as activity, or to say that
INTRODUCTION 47
life is a series of reactions, integrations and disintegrations. These
may be manifestations of life but they are incomplete manifesta-
tions and do not tell the whole story. An encysted protozoon,
a spore, a seed, a resting egg, or a dried rotifer, shows no more evi-
dence of activity than does a parked car, yet each has life and in a
proper environment would manifest activity. An emulsion of oil,
salts and water manifests activity strikingly similar to the move-
ments of an Ameba, yet such an emulsion has no life. The encysted
protozoon or the dried rotifer has protoplasmic organization which
the oil emulsion has not, and with absorption of oxygen and water
becomes animated. Life thus is incontestably bound up with
organization of protoplasm and, for descriptive purposes at least,
we find a distinct advantage in a clear discrimination between this
concept and the concept vitality. Whatever name we give it,
however, brings us no nearer to a conception of what life actually is,
for it cannot be measured and endures until the organization is
disintegrated. With vitality the case is different; here we have to
do with protoplasm in motion and the activities can be measured
from beginning to end of a life cycle. While organization has evi-
dently been continuous from the first protoplasm, vitality has been
intermittent or discontinuous. Organization may exist without
vitality and has always the potential possibility of vitality, but
vitality is impossible without organization. I would define vitality,
therefore, as the sum total of actions, reactions and interactions between
and amongst the substance* making up the organization of protoplasm
and between these and the environment, while life may be defined as
protoplasmic organization manifesting vitality or with a potential of
vitality.
CHAPTER II.
THE FUNDAMENTAL ORGANIZATION.
Weismann's conception of a metazoon as made up of germinal
and somatic protoplasm is equally true of a protozoon. Here,
however, the two are combined in the make-up of a single cell, and
Weismann was not entirely right in considering all Protozoa as
equivalent to the germinal protoplasm only of Metazoa. In gen-
eral the derived organization of a protozoon is a combination of the
fundamental organization which retains its fundamental germinal
characteristics and the derivatives from it which characterize the
adult or fully differentiated individual. Like the metazoan somatic
plasm, these derivatives have a limited existence, and again like
somatic plasm, new ones are formed from the germinal protoplasm
with each successive act of reproduction. An essential difference
between the somatic structures of Protozoa and those of Metazoa,
is that such structures in Protozoa are reversible while in Metazoa
they are irreversible. It is important to make the attempt at least
to distinguish between the fundamental or germinal protoplasm
and the structures which are derived from it. The latter, as in
Metazoa, provide the structural features by which species are
differentiated and classified.
Although with our present knowledge it is impossible to analyze
protoplasm and to discover the nature of the ultimate fundamental
organization which involves the differences between species, it is
possible by experiment and upon a morphological basis to determine
what protoplasmic parts are necessary for perfect development.
Thus, in the experiment with fragments of Stentor or Dileptus
(see p. 45), we find that no development occurs if nuclei are not
included in the fragments, and nuclei without cytoplasm are equally
impotent. So, too, in all encysted Protozoa, we invariably find
a combination of nuclei and cytoplasm. The legitimate inference
is that both nucleus and cytoplasm are necessary for continued
vitality and that interactions between these two primary components
are necessary for the formation of the structures of the derived
organization. This is such a fundamental biological truth that it
seems hardly necessary to emphasize it here.
It is difficult to distinguish upon a morphological basis between
the visible differentiations of the fundamental organization and
structures of the cell which should be included more properly in
THE FUNDAMENTAL ORGANIZATION 49
the derived organization. Some substances are found in all Protozoa
and these may be considered the raw materials from which the
derived organization is manufactured.
Although they are intimately related, it is convenient to describe
the constituents of the nucleus and those of the cytoplasm under
separate headings.
I. NUCLEAR SUBSTANCES AND STRUCTURES OF THE
FUNDAMENTAL ORGANIZATION.
The term "nucleus" is ordinarily applied in a morphological rather
than a physiological sense. If the activities of the component parts
of the nucleus are absolutely necessary for the maintenance of life
of the cell, then, in some cases such as Holosticha, Trachelocerca,
or Vile phis, such activities must be performed by substances which
appear to be identical with chromatin but which are distrib-
uted throughout the cell. On the other hand, it is highly probable
that some functions are possible by virtue of the physical prop-
erties of a definite, but permeable, nuclear membrane, as in the
tissue cells of Metazoa. It is this type of membrane-bound nucleus
that we find in the vast majority of Protozoa.
Certain constantly recurring substances are characteristic of
protozoan as of metazoan nuclei, but some types of arrangement
and combination of these substances are typical of Protozoa and
are rarely found in Metazoa. The most universal of these nuclear
constituents are (1) chromatin, which is sometimes called nuclein
or identified as such; (2) nuclear sap or nuclear enchylema filling
the spaces of the linin reticulum; (3) nuclear membrane which
forms a permeable partition between cytoplasm and nucleoplasm;
(4) plastin, often so called without being specifically identified as
such; also termed paranuclein, or pyrenin. Plastin by itself forms
true nucleoli which are comparatively rare in Protozoa. In addition
to these, kinetic elements are characteristic of the majority of
protozoan nuclei, and these in the present work will be called
endobasal bodies.
It must be frankly admitted that very little is known in regard
to the chemical nature of these various constituents of the nuclei
in Protozoa and much confusion exists in the literature owing to
the promiscuous use of these terms in relation to structural elements
of the nucleus without knowledge of the actual chemical make up.
In their resting stages the nuclei of Protozoa present a bewildering
variety of forms and structures, differing in this respect from the
much less variable tissue nuclei of the Metazoa. Because of these
manifold differences students of the Protozoa have experienced great
difficulty in grouping nuclei for purposes of description. They
agree, however, in recognizing two primary nuclear types, the
4
50
BIOLOGY OF THE PROTOZOA
vesicular and the massive. Nuclei of the massive type more clearly
resemble the nuclei of spermatozoa being filled with small chromatin
granules, but they rarely present the homogeneous appearance of
a spermatozoon nucleus, the individual granules, although closely
packed, being recognizable (Fig. 23). In vesicular nuclei the
chromatin granules may be distributed more or less evenly through-
Fig. 23. — Types of vesicular and massive nuclei. A, vesicular type of Pelomyxa
binucleata; B, of Polystomcllina crispa; both with multiple endosomes; C, nucleus of
Actinosphacrium eichhornii with granular plastin (p); D, E, F, macro- and micro-
nuclei of Paramecium caudatum, the latter in different stages of vegetative mitosis.
(A, B, after Doflein; C, after Hertwig; D, E and F, original.)
out the nucleus, or they may be segregated in "net-knots" or either
alone or combined with other nuclear substances may be combined
in one large central globular mass to which Minchin gives the name
endosome as an equivalent for the term Binnenkdrper , or they may
be aggregated in several such globular masses or multiple endo-
somes distributed throughout the nucleus or plastered to the
nuclear membrane.
THE FUNDAMENTAL ORGANIZATION 51
Endosonies may consist entirely of chromatin as appears to be
the case in nuclei of some Microsporidia (Glugea and Thclohania),
or some flagellates (Prowazekia, Belar, 1920, etc.). Or they may
be composed of chromatin and plastin in various combinations.
Thus in Actinosphaerium eichhornii in some stages of nuclear activ-
ity, the chromatin component is in the form of an incomplete ring
which partially encloses the plastin portion (Fig. 23, C). In other
cases the plastin is entirely surrounded by a cortex of chromatin
which may be dense and compact as in the case of many types of
rhizopods and Sporozoa or loosely aggregated as in nuclei of End-
amoeba intestinalis (Fig. 24). The distributed granules of deeply
staining material which represent the substitute for a nucleus in
Dileptus gigas are similarly composed
of a plastin core and a chromatin cortex, / X
the former increasing enormously after / - '^. ; « ^
treatment of the animal with certain /• -'.'';;" I * ' 1
kinds of food such as beef broth. Here | « v ;, '■■
the term endosome is scarcely applicable " ^ ;-;|
since the bodies in question are not in- {'% ',-.* \;jM " :, '■". '
side a nuclear membrane, but they appear ( ^Nfe • 'c ■*'
to be morphologically equivalent to these
intranuclear structures. After treatment
with beef broth the body of Dileptus is
enormously distended due to the swelling xt v %,'<&
of these cytoendosomes (Fig. 25). \'% '*^-^^
The centrally placed intranuclear body ^4§ .
is generally described under the name
karyosome, a term which has been so rJjG\f:~E'ldamoch^intes-
. *. ' . , , „ ,, -r, hnahs; (e) endosome; (c) cor-
widely used by students or the rrotozoa tex of chromatin.
and for so many obviously different
structures that it is practically synonymous with endosome or
Binnenkorper. Thus Minchin describes it as a combination of chro-
matin and plastin; Doflein defines a karyosome as a centrally placed,
sharply outlined and constant constituent of the nucleus, which may
contain no chromatin or may be a combination of other substances
with chromatin and which divides during nuclear division, to form
two corresponding daughter structures. Hartmann's (1911) defini-
tion is more limited, a karyosome in his use of the term being an
endosome (Binnenkorper) containing a centriole. Belar (1921) finds
a "karyosome" in Chlamydophrys minor which breaks up and dis-
appears, forming neither chromatin nor kinetic elements. If we
attempt to combine these different views into a common definition
we find that a karyosome may be an intranuclear body which may
consist of plastin alone; or kinetic elements alone; or chromatin
together with plastin; or a combination of chromatin with kinetic
elements; or a combination of chromatin, plastin and kinetic ele-
,
52
BIOLOGY OF THE PROTOZOA
merits. Such a definition obviously would fail to specify any par-
ticularly nuclear structure, and so far as its practical value is
concerned the term karvosome is no more useful than the non-
Fig. 25. — Dileptus gigas: A, vegetative individual in culture with nucleus in the
form of scattered chromatin granules; B, individual showing the effect of treatment
with beef extract on the chromatin granules. (Original.)
committal term Binnenkorper or Minchin's equivalent term endo-
some. I would advocate, therefore, discarding altogether the term
karvosome which seemingly bears the earmarks of something
definite in the cell, using in its place the general non-committal
THE FUNDAMENTAL ORGANIZATION
06
expression Binnenkorper, or its equivalent term endosome, the
latter as yet, at least, having no specific significance, while for the
endosomes having functions characteristic of the kinetic complex
a specific term may well be applied. In the present work 1 shall
employ the term endosome in a general way to indicate all central
intranuclear structures including those of kinetic function, while
for those which are known to be of the nature of kinetic elements
I shall use the term endobasal body.
Fig. 26. — Division of amebae. A to /, successive stages in division (promitosis) of
Vahlkampfia Umax; J to L, mitosis in Endamoeba coli. (Original.)
The endosome-bearing vesicular nuclei present manifold variations
in the arrangement of chromatin. In some the entire chromatin
content is confined to the endosome which seems to rest in the center
of a colorless enchylema traversed by strands of linin radiating from
the endosome to the nuclear membrane (Arcella vulgaris, Cochlio-
podium bilimbosum and rhizopods generally, as well as in many
54 BIOLOGY OF THE PROTOZOA
Coccidia and Gregarinida). In other cases the endosome retains
only a little of the chromatin, the bulk of which is present as a
dense network in the zone between endosome and membrane
(Endavioeba intestinalis, A. crystalligera, etc.). In still other cases
the chromomeres are distributed more or less uniformly throughout
the nuclear reticulum (Euglypha alveolata, etc.).
In vesicular nuclei with endobasal bodies the chromatin may be
in the form of more or less regular chromomeres uniformly dis-
tributed in the nuclear space (Euglejia type), or more or less com-
pactly aggregated about the kinetic element (many species of
Endamoeba, various flagellates, Coccidia and Myxosporidia, etc.).
Or, finally, the chromatin may be in the form of relatively large
granules collected in a zone just within the nuclear membrane
(e. g., Pelomyxa), or in fine granular form may make up the chief
part of the nuclear membrane (Vahlkampfia Umax, Fig. 26).
1. Chromatin. — Chromatin has been more a conception than a
specific thing, the term being used to designate substances which
appear under different forms at different phases of cell life. It
appears normally in the form of minute granules or chromomeres
(chromidiosomes of Minchin) in the resting nucleus, but during
division of the nucleus these granules are massed together usually
to form characteristic solid and individualized structures, the
chromosomes. On a 'priori grounds chromosomes were early
regarded as intimately associated with the phenomena of inheritance
(Roux, Weismann, Boveri) and the more recent experimental work
in genetics has given substantial evidence of the soundness of this
early conclusion.
Our conception of chromatin is based largely upon investigations
upon the nuclear substances of Metazoa and the higher plants. In
ordinary descriptions, however, the term is often used in a vague
sense to include any substance or body which stains with the so-
called nuclear stains, i. e., the basic anilin dyes, while direct chem-
ical tests to determine the exact chemical composition of chromatin
have been made in very few cases. The best of these show it to
be composed mainly of nuclein, one of the most complex of protein
substances and rich in phosphorus.1
Vague as is the conception of chromatin in Metazoa it is even more
so in connection with the Protozoa, where little has been done in
a concrete way to throw light on the subject, although much has
been written about it.
Many of the granules found in the cell body of a protozoon as well
as those within the nucleus, stain with the usual nuclear dyes and
their identification as chromatin is a matter requiring knowledge
of their history and fate in the cell. It is only within recent years
1 For :i critical discussion of chromatin, see Wilson, 1925.
THE FUNDAMENTAL ORGANIZATION 55
that an effort has been made to discriminate between the various
granules in the Protozoa which stain intensely with the basic
stains, and to distinguish the chromatin granules which enter into the
make up of chromosomes from other chromatoid granules which are
distributed throughout the cell, particularly the chromidia and the
volutin grains. This is the more difficult in Protozoa because
chromatin granules are not necessarily confined to the nucleus.
Even in Metazoa and plants there are times during division when
the chromatin is not confined within a nuclear membrane. In
the Protozoa such a condition is permanent in many cases (e. g.,
in some flagellates; in Dileptus gigas, Holosticha, etc.). In other
cases the nuclear chromatin, by transfusion or by nuclear fragmen-
tation, spreads more or less widely throughout the cell protoplasm
(rhizopods, Actinosphaerium eichhornii, etc.). Here in different
species, the fate of the distributed chromatin varies. In some
cases this diffusion of chromatin indicates a degenerative change,
the chromatin ultimately losing its characteristic reactions. Thus
in Actinosphaerium eichhornii, Hertwig has shown that, under
adverse conditions such as starvation, or overfeeding, or during
periods of depression, such distribution of the nuclear chromatin
occurs, the granules ultimately becoming transformed into a
characteristic pigment of the cell. In other cases the distributed
granules retain their chromatin nature and according to numerous
observers are ultimately aggregated into minute secondary nuclei
which become the nuclei of conjugating gametes (see p. 69). In
these instances, other chromatin which is retained in the "primary
nucleus" takes no part in the germinal activities but degenerates
and disappears after the gametes are liberated. It must not be
inferred that germinal chromatin is thus distributed in the cyto-
plasm in all cases; on the contrary in the majority of Protozoa the
gamete nuclei are derived by division of the morphological nucleus
with its contained chromatin, and some authorities, notably Kofoid
(1921) deny in toto the origin of gamete nuclei from chromidia.
While chromatin thus has a definite germinal function there is
equally little doubt of the important participation of the nucleus
and presumably of chromatin in the ordinary metabolic activities
of the cell. Thus, if an Amoeba proteus or the ciliate Uronychia
transfuga (see Fig. 135, p. 262), be cut into two portions one of
which contains the nucleus while the other is enucleate, the former
portion only will digest and assimilate food, grow and regenerate
the lost part, while the enucleate portion will continue to move
and manifest various activities characteristic of destructive metab-
olism, but it will not take in food, nor digest what food may have
been taken in before cutting, and in the course of a week or ten
days it dies (Hofer, Verworn, Balbiani and many others).
It is evident that chromatin is directly associated with all of
50 BIOLOGY OF THE PROTOZOA
the important vital activities including reproduction, and the view
has been repeatedly advanced that, for these varied activities at
least, two different kinds of chromatin are responsible. One kind,
the so-called vegetative or trophochromatin, is active in the ordi-
nary metabolic functions of the cell, while the other, the germinal
or idiochromatin, has to do solely with perpetuation of the race.
While this view of the dual nature of chromatin would seem to be
sustained by the phenomena in rhizopods, gregarines, and by the
dimorphic nuclei in the ciliates, it is by no means assured that this
duality represents a fundamental difference in chromatins. On the
contrary it is much more probable, as Hertwig has maintained, that
there is only one chromatin and that its functional activity depends
upon different factors and conditions which may arise during the
life cycle; germinal chromatin in one cell-generation may become
vegetative chromatin in the next and vice versa. This is particularly
clear in the case of the ciliates where the macronucleus, a distinctly
vegetative nucleus, and the reproductive micronucleus, arise as
subdivisions of a fertilization nucleus after conjugation or its equiva-
lent parthenogenesis.
The importance of chromatin for life of the cell is indirectly indi-
cated by the extreme precision with which it is distributed to
daughter cells at the time of division. Like other granules of the
cell each chromomere grows and reproduces its exact duplicate by
division. Chemically it probably represents the pinnacle of complex
structures formed as a result of the activities of constructive meta-
bolism while its derivatives, likewise granular in form and difficult
to distinguish as chromatin, give rise to many more or less permanent
or temporary structures in the cell body, each of which may per-
form some cellular activity in its passage through the various stages
of chemical breakdown.
Few investigations of a purely chemical nature have been made
on protozoan chromatin. The usual procedure is to designate as
chromatin all structures of the nucleus which stain with the so-called
nuclear dyes, or to interpret chromatin mainly on a morphological
basis. Micro-chemical tests of all protoplasmic substances are made
primarily on the basis of solubility or insolubility with acids, alka-
lies, salts, etc., and the conclusion that certain structures are made
up of certain substances follows from the microscopic picture pre-
sented after such treatment. Such tests do not prove that a given
structure is composed of a definite substance and is not a mixture
of substances. Kossel, Miescher and others have shown that the
chromatin bodies composed mainly of the chemical substance
nuclein are not dissolved under the action of artificial gastric juice
(pepsin and trypsin in appropriate acid and alkaline media) while
other portions of the nucleus such as nucleoli and reticulum are
entirely dissolved. Chromatin bodies on the other hand are dis-
THE FUNDAMENTAL ORGANIZATION 57
solved in strong acids, dilute alkalies, calcium carbonate and
sodium phosphate.
There has been a tendency to regard chromatin as the most
important substance of the living cell, and the chromosome as the
most important nuclear structure. Important they doubtless are,
but in many cases chromatin is known as such only in the form of
chromosomes which belong to the derived and not to the funda-
mental organization (see p. 88). In other words, chromatin is
manufactured in the nucleus and the substances or substance from
which it is made are still more fundamental. There appears to be
little justification for Heidenhain's view of two kinds of chromatin,
one— oxy chromatin— unstainable with basic dyes, the other— basi-
chromatin — staining readily. A substance in the nucleus is either
chromatin or it is something else.
With the growing use of the Feulgen nucleal reaction there is
reason to believe that a more precise definition of chromatin will
be developed. This reaction finds its explanation in Steudel's (1912)
analysis of thymonucleic acid of which the empirical formula is:
C43H65P4X15O34.1 Under moderate hydrolysis with HC1 the purin
bodies are split off the molecule of thymonucleic acid and reducing
groups are freed. These behave like aldehydes and give the charac-
teristic red-violet color with Schiff's test (Magenta in the presence
of sulphuric acid).
The nuclei of various groups of Protozoa give positive chromatin
reactions with this test, and it is a useful method in tracing the
development of chromatin in ex-conjugants or in the chromosomes
of the maturation divisions. (See Feulgen and Rossenbeck, 1924;
Bresslau and Scremin, 1924; Robertson, 1927; Zuelzer, 1927;
Jirovec, 1927; Reichenow, 1928, and infra pp. 93 and 315.)
2. Other Substances of the Nucleus. — Belaf (1926) makes this state-
ment concerning nuclei of the Protozoa : " For the most part chro-
matin of the resting nucleus cannot be distinguished from the
ground substance of the nucleus (loc. cit., p. 241)." This refers to
the conditions of the living nucleus and not to fixed and stained
material. In the latter chromatin in the form of granules can be
1 This may be written:
(H20)2— P— CsHioOs— C5H4N6 (adenine)
/ \
O O
\ /
P— C6HI0O5— C6H4N5O (guanine)
/ \
O O
\ /
P— CeHioOs— C5H5N2O2 (thymine)
/ \
O O
\ /
(H20)2— P— C6Hio05— C4H4N3O (cystocine)
58
BIOLOGY OF THE PROTOZOA
distinguished from other substances of the resting nucleus by their
color reactions to basic and acidic dyes. Sometimes the chromo-
meres or chromioles are apparently suspended in a more or less
definite "linin" reticulum which is recognized as being a coagulation
product of the colloidal ground substance or karyolymph. In other
Fig. 27. — Origin of macronucleus after conjugation in Uroleptus mobilis. (1)
First metagamic mitosis of the amphinucleus; (2) one of the progeny of this division
dividing again; (3), (4), (5) telophase stages of second division of the amphinucleus
resulting in a new macronucleus (above) , and a degenerating nucleus (below) ; (6 to
10), stages in differentiation of the young macronucleus and disintegration and
absorption of the old macronucleus; in (10) two new micronuclei are in mitosis
preparatory to the first division of the ex-conjugant. (At) new macronucleus; (m) new
micronuclei; (d) degenerating old macronuclei. (After Calkins.)
cases they are combined with the substance "plastin" to form a
clearly-defined endosome (karyosome) which, depending apparently
on the relative proportions of plastin and chromatin, may or may
not be visible in life. Plastin appears to be a well-defined nuclear
substance and writers generally speak of it with familiar ease,
THE FUNDAMENTAL ORGANIZATION
59
despite the fact that very little definite information is at hand con-
cerning it. In pure form it is the nucleolus of tissue cells and stains
intensely with acid dyes. Such nucleoli are rare in Protozoa, but
the combination of plastin with chromatin in some degree is char-
acteristic of Protozoa, and the staining reaction with basic or acidic
dyes varies with the preponderance of one or the other.
The ground-substance of the nucleus or karyolymph (Lundegardh)
is difficult to define, a difficulty which Belar (1926) recognizes by
the statement: ". . . at best it can be defined as that part of
the nuclear space which is neither chromatin nor plastin" (loc. cit.,
p. 242). From this negative definition and from the fact that it
cannot be demonstrated by specific staining reactions or character-
ized by definite structures, it might seem that karyolymph is a
negligible part of the nuclear make-up. Such a conclusion, how-
ever, would be a mistake for some of the most important structures
of the active nucleus take their origin from this ground substance
(see pp. 88, 200).
Fig. 28. — Vahlkampfia Umax; chromatin forming the nuclear membrane and giving
rise to chromidia. (After Calkins.)
Membrane. Like other constituent parts of the protozoon nuclei,
the membranes are highly variable, sometimes presenting in optical
section only one contour on the outer side (e. g., Actinosphaerium) ;
sometimes showing contours both outside and inside (Amoeba pro-
teus) . In the former case the inner zone adjacent to the membrane
shows a decreasing density inwards, until the linin merges insen-
sibly into the intranuclear reticulum. In free-nuclei formation,
antecedent to gamete formation described above, the nuclear mem-
branes are probably formed from the cytoplasmic reticulum in
which the chromidiosomes are lying. Chromomeres also take part
in the formation of nuclear membranes in some cases, e. g., in
Vahlkampfia Umax, where the linin membrane is too delicate to be
seen, although the definite limitation of the chromomeres indicates
its presence (Fig. 28).
One peculiarity of the nuclear membranes of Protozoa which dis-
tinguishes them from nuclear membranes of tissue nuclei, is that in
the majority of cases they remain intact during all phases of cellular
activity and only rarely disappear, or disappear in part only, during
division processes of the cell. (For description of chromatin, mem-
branes, etc., during division, see p. 209.)
60 BIOLOGY OF THE PROTOZOA
Intranuclear Kinetic Elements. The kinetic elements, some of
which are intranuclear and a part of the fundamental organization,
are those structures of the cell which are closely connected with the
visible expression of the transformation of energy resulting from
destructive metabolism. Such expression may be in the form of
movement due to the activity of specific motile organs formed as a
rule from the substance of kinetic elements, or it may be in the form
of intracellular activities as indicated by the transformation and
movements of internal attraction centers, center of radiation, of
nuclear division, etc. The kinetic elements are justly regarded by
many observers as the most elusive and perplexing, but at the same
time amongst the most fascinating of all the organoids of Protozoa.
Kinetic elements appear in Protozoa in a multitude of structures,
sometimes intranuclear, sometimes cytoplasmic, and often both
inside and outside the nucleus. Whether or not they are permanent
organoids of the cell is subject to the same arguments pro and con
which have been raised for and against the permanency of the cen-
trosome in Metazoa. There is strong evidence, as the following
pages will show, that not only are many types of cytoplasmic kinetic
elements derived from the nucleus, but also that chromatin and
intranuclear endobasal bodies are closely related, while some types
that are confined to the cytoplasm are composed in part, or entirely,
of a substance which closely resembles chromatin (parabasal bodies).
Little is known of the chemical composition of the latter, but both
intranuclear and cytoplasmic kinetic elements stain intensely with
some of the nuclear dyes and divide by simple constriction at
periods of cell division.
In many cases it is impossible to tell from observations on ordi-
nary vegetative individuals, whether a given structure belongs to
the kinetic elements or to some other group of the many types of
protoplasmic granules. This is particularly true of the intranuclear
forms where incomplete extraction of a stain may give the appear-
ance of a granule in some chromatin or plastin mass. In such
cases the identity of the structure can be determined only by its
history during nuclear division. Cytoplasmic forms can be more
easily detected by reason of their relation to motile organs or to
more or less complex fibrillar structures.
(«) Endobasal Bodies. — Pmdobasal bodies in nuclei of different
Protozoa are highly variable and no general description is possible.
In some cases they stain intensely with nuclear dyes, especially
with iron hematoxylin; in other cases they stain feebly or not at
all with the same dyes that color the chromatin (e. g., Chilodon).
In some cases they are large and appear homogeneous throughout;
in other cases there is a definite, deeply-staining central granule
embedded in a more faintly staining plastin (?) matrix, or such a
granule may be present without the accompanying matrix; or,
THE FUNDAMENTAL ORGANIZATION
61
finally, there is no evidence at all of kinetic elements in resting
nuclei, but collections of homogeneous substance (karyolymph) are
present at the poles of the nucleus during division (pole plates).
1. Large Homogeneous Endobasal Bodies. — In this type the endo-
basal body is conspicuous by its large size and homogeneous struc-
ture. It was first described by Kenten (1895) in Euglena viridis
and was early recognized as a kinetic element connected with
nuclear division as attested by the names intranuclear centrosome,
Fig. 29. — Bodo ovatus Stein (edax, Belaf). (1) Vegetative individual with two
flagella; blepharoplast (bl) and nucleus with endosome. (2 to 6) Division of the
basal bodies, blepharoplast and nucleus; (7 to 10) completion of nuclear division and
division of cell body. (After Belaf, from Doflein.)
division center, etc., applied to it, while nuclei containing it were
included by Boveri in his "centronucleus" type. In Euglena viridis
and euglenoids generally, this endobasal body according to earlier
descriptions of Keuten, Tschenzoff (1916) and others is the most
conspicuous structure of the nucleus, where, in the resting nucleus,
it appears as a spherical or elongated ellipsoidal body with chromatin
granules of limited number suspended between it and the nuclear
membrane. It divides prior to division of the chromatin, first
elongating with a concentration of its material at the poles. The
G2
BIOLOGY OF THE PROTOZOA
m o.
e n d.
elongation continues until a thin fibril, called a centrodesmose,
alone connects the two halves. The centrodesmose ultimately
breaks and its substance is ab-
sorbed by the two daughter ele-
ments. [See also Baker, and Hall
(1923).] In the rhizopod Chlamy-
drophrys stercorea, as well as in
the flagellate Bodo ovatiis, the
endobasal body which is quite
similar to that of Euglena, divides
subsequently to division of the
chromatin (Schaudinn, Belaf,
Fig. 29), while in Amoeba crystal-
ligera (Schaudinn) there is no
centrodesmose formed during
division, a condition nof un-
common in the rhizopods (e. g.,
Arcella vulgaris according to
Swarczewsky ; Vahlkampfia Umax
[Fig. 28], and many species of
Endameba). Not only is this
simple type of endobasal body
found in rhizopods and flagel-
lates, but also in some cases in
the more complex ciliates, where,
in Chilodon cucullus, for example, the macronucleus contains a definite
endosome which behaves exactly like that of Euglena. It is highly
Fig. 30. — Chilodon sp. Macronucleus
with endosome and endobasal body (end) .
(mo) Mouth surrounded by pharyngeal
basket. (Original.)
B
Fig. 31. — Endamoeba dysenteriae (Councilman and Lafleur). Two stages in the
metamorphosis of endosome and endobasal body. (After Hartmann.)
probable that in all of these cases the endobasal body is em-
bedded in a core of plastin.
THE FUNDAMENTAL ORGANIZATION 63
2. Endobasal Bodies With Centrioles. — Centrioles are kinetic ele-
ments in the form of minute granules, which in Metazoa and in
some types of Protozoa, form the focal points of the mitotic spindle.
In many Protozoa minute granules may be embedded in a matrix
of chromatin or plastin, or in a combination of both. These in some
cases form the poles of typical spindles, but in the majority of cases,
apart from the polar granules and the connecting centrodesmose,
there is little evidence of a typical spindle.
In some forms this type of endosome undergoes changes in appear-
ance which Hartmann (1911) and his followers have interpreted as
periodic or cyclical in nature. Such variations have to do with
the concentration of the chromatin substance about the endobasal
body or centriole, being massive and dense in certain phases and
distributed in others. In Endamoeba dysenteriae the centriole in
the latter phase is distinct and definite but in the former phase it is
hidden by the dense chromatin (Fig. 31). From such conditions
Hartmann infers that all massive types contain hidden centrioles,
a conception applied by Naegler to all of the smaller amebae and
endamebae, but, according to Glaser, it is limited to comparatively
few types.
Typical endobasal bodies in the form of centrioles are contained
in the first maturation nuclei of Vroleptus mobilis. Here each
massive micronucleus fragments into chromatin granules which
remain in a dense reticulum at one pole of the enlarging nucleus until
the chromosomes are formed. A centriole, hidden in this mass,
divides and one-half traverses the nucleus to form the first pole of
the maturation spindle but remains connected by a centrodesmose
with the other centriole which, in turn, forms the other pole of the
spindle (Fig. 32, b-g). Similar centrioles are found in widely
separated groups of Protozoa. In Coccidivm schubergi, according
to Schaudinn (1900), the endobasal body divides with a long con-
necting centrodesmose. Here, however, part of the material of
the centrodesmose collects into two granules with a more densely
stained connecting thread, thus producing a structure which Doflein
interprets as analogous to the mid-body (Zwischenkorper) of
Metazoa and plant cells. The fate of the centrioles after division
differs in different cases. In some, e. g., Bodo lacertae (Belaf, 1921,
Figs. 33, 34), they come from the nucleus and re-enter the daughter
nuclei;1 in others they arise from basal bodies and become basal
bodies of the flagella after division (e. g., Chilomastix aulostomi,
Belaf, 1921; Spongomonas, Hartmann, etc.).
While the embedding matrix in most of the above cases is similar
to chromatin in its reaction, and forms an important part of the
endobasal body, there are other types (e. g., My.vobolus pfeifferi,
1 See, however, the earlier contradictory accounts of Prowazek (1904), Alexeieff
(1914), and Kuczynski (1918).
64
BIOLOGY OF THE PROTOZOA
Fig 32.-Uroleptus mobilis Eng. First and second meiotic divisions during con-
jugation. (A) Two conjugating individuals; (B to G) formation of the first spind e
pole by division of the endobasal body (with centrodesmose) ; (H to M) first meiotic
nuclear division; (.V to Q) second meiotic division. (After Calkins.)
THE FUNDAMENTAL ORGANIZATION
65
one of the Myxosporidia) in which the centriole emerges from an
enveloping plastin-like matrix, which, like a nucleolus, then degen-
erates and disappears.
3. Nuclei With Pole Plates and Without Endobasal Bodies. — This
type of nucleus is characterized by the entire absence of endobasal
bodies. A hyaline mass, which stains with difficulty, may, however,
be present at the spindle poles during nuclear division, but in
many cases it cannot be detected in the resting nucleus. During
division it occurs in characteristic forms known as pole plates.
Fig. 33. — Bodo lacertae Grassi. Early stages of division of the basal bodies, (l/b);
blepharoplast ring (bl); nucleus and parabasal body (p). (After Belaf.)
In the micronuclei of Paramecium caudatum such a mass forms a
hyaline cap at one pole of the otherwise chromatin-filled resting
nucleus. Observations are entirely lacking in regard to division
of this mass during reproduction, but similar aggregates of non-
staining substance are present at the distal ends of the daughter
nuclei during stages of division (Fig. 35). Similar pole plates appear
as broad, flat and hyaline ends of the spindles of Actinosphaerium
eichhornii according to Hertwig (1898), in the spindle of Tricho-
syhaeri urn sieboldi according to Schaudinn (1899), or in the macro-
5
66
BIOLOGY OF THE PROTOZOA
nucleus of Spirochona gemmipara (Hertwig). In this group, also,
we would include the peculiar hyaline globular bodies at the poles
of the nuclear spindles of Euglypha alveolata as described bv
Schewiakoff (1888).
It is quite possible, although direct evidence is lacking, that none
of these peculiar pole plate structures belongs to the group of
Fig. 34. — Bodo laccrtae Grassi; division stages continued. (E) Origin of centrioles
in the nucleus, and their retention in the daughter nuclei (F to G); (bb) basal bodies,
(c) centriole. (After Belar.)
kinetic elements. Indirect evidence favoring this possibility is
furnished by the entire absence of observations on the division of a
definite body, the substance of which forms the pole plates. Hertwig
(1898) and Doflein (1916) assume that they are formed from the
"limn" substance of the nucleus. On this assumption the pole plates
might be interpreted as hyaline aggregates of the ground substance
of the nucleus, indeed, the hyaline and homogeneous appearance of
THE FUNDAMENTAL ORGANIZATION 67
the pole plates is suggestive of ameba ectoplasm. With our present
knowledge I am inclined to agree with this interpretation of pole
plates and to regard Paramecium caudatum, with other species of
this genus, Actinosphaerium eichhornii and the other forms men-
c-.e.tv.
C.St
Fig. 35.— Paramecium caudatum. Section of a dividing individual; c. st., con-
necting strand of dividing micronuclei; e. tr., extruded trichocysts; a. v., gastric
vacuole; .1/, dividing macronucleus; m, m, divided micronuclei;^?-., trichocysts.
(Original.)
68 BIOLOGY OF THE PROTOZOA
tioned above, as containing no permanent intranuclear kinetic
elements. To such a group we would also assign forms like Aulo-
cantha scolymantha and Chilomonas paramedian, in which according
to observations of Borgert (1909) and Alexeieff (1911), not only
intranuclear kinetic elements but pole plates as well are entirely
absent.
On the whole I would interpret the intranuclear kinetic elements
of Protozoa as originating by condensation of the ground substance
or karyolymph of the nucleus. In Paramecium caudatum (Figs. 35,
147) both in vegetative and meiotic divisions, the ground substance
forming the pole plates shows but little condensation (Fig. 57),
but in the first meiotic division of Uroleptus halseyi the karyolymph
forms two irregular masses which condense to form the spindle
fibers and the two spindle poles which are more like pole plates
than like centrioles (Figs. 151, 153). In a similar stage of Uroleptus
mobilis, however, condensation results in the formation of a definite
centriole which divides with a connecting centrodesmose (Fig. 32).
In the flagellate type the endobasal body may well be a permanent
condition of such condensation. Whether or not such condensations
leading to endobasal body formation involve a specific chemical
make up, different from that of the karyolymph and from chroma-
tin, is an unsolved problem. The diffuse forms such as may be seen
in pole plates do not stain with iron hematoxylin or other nuclear
dyes nor do they give a positive Feulgen reaction. The centrioles
and permanent endobasal bodies stain with iron hematoxylin but
the Feulgen reaction is negative.
II. CYTOPLASMIC ELEMENTS OF THE FUNDAMENTAL
ORGANIZATION.
Very little work has been done on the finer structures of encysted
Protozoa, and we are relatively ignorant of the make-up of the
fundamental organization of the cytoplasm. It is difficult, and
often impossible, to distinguish between those elements which are
essential parts of the germinal protoplasm and those which are
formed as a result of metabolic activities. The latter, obviously,
would belong to the structures of the derived organization.
The great majority of the structural elements of the cytoplasm
are known only in the adult organism. Many of these are undoubt-
edly derived structures of the developing individual but some may
be essential parts of the germinal protoplasm. Until further knowl-
edge of the origin of such questionable elements is available we
may regard them tentatively as parts of the fundamental organiza-
tion and describe them as such. In most cases they are present in
the adult organism in the form of granules which, morphologically,
are almost indistinguishable from one another but which react
THE FUNDAMENTAL ORGANIZATION 69
characteristically with specific staining methods, thereby indi-
cating differences in their chemical composition. Amongst such
characteristic granular elements of the cytoplasm are (1) Chromidia,
found mainly in Sarcodina and Sporozoa; (2) Volutin grains, found
mainly in flagellates, but also present in Sarcodina and Sporozoa;
(3) Mitochondria, characteristic of all types; (4) Golgi apparatus,
probably universal; (5) Silver Line Si/stem of the Infusoria; (6)
Kinetic elements (for the latter see pages 88 and 104).
1. Chromidia.— The nature and the functions of chromidia have
been and still are matters of controversy in which there are wide
differences of opinion. Hertwig (1879) early called attention to
extra-nuclear chromatin in Radiolaria and later (1899) described
the zone of cytoplasmic, deeply staining substance which extends
from one nucleus to the other and characterizes the dorsal region of
Arcella vulgaris and related forms. Hertwig called this the chrom-
idial net and homologized it w ith the extranuclear chromatin which
he had found in Radiolaria. At about the same time (1898, 1902)
Hertwig described the breakdown of nuclei and the distribution of
chromatin into the cytoplasm of Actinosphaerium eichhornii. To
such chromatin granules in the cytoplasm he gave the name "Chro-
midien" and their appearance was regarded as a sure indication of
the approaching death of the organism.
These observations mark the commencement of a long controversy
over the question of chromidia duality which, so far as the Protozoa
are concerned, was first clearly announced by Schaudinn in connec-
tion with the life histories of the testate rhizopod Centropyxis
aculeata, the foraminiferon Polystomellina crispa, and some of the
endamoebidae.
The chromidia! net of Centropyxis is similar to that of Arcella
and according to Schaudinn is the seat of the formation of second-
ary nuclei by origin de novo from the chromatin of the chromidial
net. These secondary nuclei become the nuclei of gametes while
the primary nucleus degenerates. Similarly in Polystomellina, al-
though there is no chromidial net, the cytoplasm of mature indi-
viduals of the asexual generation becomes filled with minute chro-
matin granules— chromidia which arise by fragmentation of the
primary nuclei and ultimately become the nuclei of gametes (Fig. 123,
p. 235).
These findings by Schaudinn were subsequently confirmed by
Lister (1905) for Polystomellina crispa; by Elpatiewsky (1907) and
Swarczewsky (1908) for Arcella vulgaris; by Goldschmidt (1905)
for Mastigina and Mastigella belonging to the flagellate family
Rhizomastigidae; by Winter (1907) for Peneroplis pertusus, a fora-
miniferon; by Goette (1917) for Difflugia lobostoma. Similar obser-
vations were made in connection with Sporozoa of different kinds
by Leger and Duboscq for the gregarine Nina gracilis; by Swarc-
70 BIOLOGY OF THE PROTOZOA
zewsky (1910) for a species of Lankesteria a hemosporidian ; by
Kuschakewitsch (1907) for Gregarina cuneata; by Lebedew (1909)
for the ciliate Trachelocerca phoenicopterus. The findings and con-
clusions of these different observers have been criticized by Doflein
(Lehrbuch, Fourth Edition), by Kofoid (1921) and by others, as
unconvincing and not, as yet, adequately confirmed, while the
suggestion is repeatedly made that the "secondary" nuclei arising
thus de novo from chromidia may be intracellular parasites.
So far as the dualism of chromidia is concerned Schaudinn (1903)
was the first to suggest the idea by the term "somatochromidia"
for chromidia which are vegetative in function or the result, as in
Actinosphaerium, of degeneration, and by the term "gametochro-
midia" for chromidia which give rise to gamete nuclei. These
terms were turned into "trophochromidia" and "idiochromidia"
respectively by Mesnil (1905) with a slight difference in interpre-
tation of the former. Goldschmidt (1905) likewise indicated the
same interpretation by the terms "chromidia" and "sporetia"
respectively.
Before accepting interpretations . as above, particularly in con-
nection with chromidia of the testate rhizopods, it is necessary to
determine whether or not the granules in question are really chro-
matin. Khainsky (1910) came to the conclusion that the chromidial
net of Arcella has an active part to play in nourishment of the
organism, and Zuelzer (1904) maintained that the chromidial net
of Difflugia is the seat of formation of a carbohydrate nutritive
substance of the nature of glycogen. If these suggestions prove to
be correct it would indicate a different chemical make-up for chro-
midia and intranuclear chromatin, and a difference which should
be detectable by microchemical tests. In this field, however,
observations are few and results are discordant. The chromidial
net of Arcella vulgaris stains black with iron hematoxylin, green
with the Borrel mixture and, usually, gives a negative reaction
with the usual Feulgen treatment. These results confirm Hart-
mann's experiment with pepsin under the action of which the
chromidial net of Arcella is dissolved out while the secondary
nuclei are conspicuous after subsequent staining.
Belar (1926) and others apparently believe that Hartmann's
experiment gives a final answer in the negative to the question of
the chromatin nature of chromidia. This conclusion, however, is
somewhat premature for recent experiments with the Feulgen reac-
tion indicate that nucleic acid is certainly present at some stages.
With hydrolysis by strong hydrochloric acid at 60° F. followed
by the usual staining method the result is invariably negative, while
the primary nuclei show only a faint reaction. If, however, the
first part of the operation involving strong hydrolysis is omitted
and the Arcella material placed directly in the staining solution for
THE FUNDAMENTAL ORGANIZATION
71
from eight to fourteen hours, a positive reaction is obtained in all
forms in which the secondary nuclei are present (Fig. 3(3). Here
the nuclei and the embedding matrix of chromidia are intensely
stained. ( 'hromidia at other stages give varying shades of purple
depending apparently upon the condition of the organism. Nucleic
acid which is formed in the chromidia becomes concentrated in
the secondary nuclei; these obviously would resist the pepsin
digestion while the residue is dissolved.
Fig. 36.
-Arcella vulgaris. Growth of nucleic acid bodies in the chromidia! net.
(Original, X 500 and X 1000.)
The problem of extranuclear chromatin, or chromidia, assumed
a novel theoretical significance with the development of Hartmann's
so-called polyenergid theory. Hartmann (1909) suggested a mor-
phological interpretation of Sachs "energid" or nucleus with its
sphere of influence, by suggesting an energid as a nucleus consisting
of two components, one the chromatin or idiogenerative component,
the other a centrosome or homologous structure (kinetic or loco-
motor component). In 1911 he distinguished three main types of
nuclei of Protozoa, viz., monoenergid, meroenergid and polyenergid
types. Monoenergid types are in Protozoa having one kind of cell
division as in most flagellated Protozoa. Meroenergid types are
forms, originally with two nuclei, one of which has lost the idio-
72 BIOLOGY OF THE PROTOZOA
generative component (as in Heliozoa with central granule, or
Trypanosomes with "kinetonucleus"). Polyenergid types, finally,
involve nuclei containing an aggregate of monoenergid nuclei. Since
a monoenergid has but one kind of division Hartmann assumes
that this division may take place while in the aggregated condition;
or that the monoenergids are freed by rupture of the membrane
after which they may divide as monoenergids in the cytoplasm.
In all cases the monoenergids become the nuclei of gametes (as in
Radiolaria, Foraminifera and gregarines). The conception is inter-
esting, but apart from adding other somewhat unenlightening terms
meroenergid and polyenergid it leaves us practically where we were
before on the chromidia problem, and separates, without sufficient
justification, the chromidial net type from the gamete nuclei type.
In all probability the two types are not widely different. The
monoenergids which come from a polyenergid nucleus represent
chromatin which is formed in the nucleus (see p. 87) ; the gamete
nuclei which arise from the chromidial net represent chromatin
which is manufactured by a cytoplasmic substance of the same
nature as the karyolymph and a substance which, possibly, may
be derived from the nucleus.
2. Volutin Grains.— These are widely distributed in Protozoa with
the exception of the Infusoria, and are not difficult to distinguish
from chromidiosomes. They are usually spherical in form but may
be angular and irregular and stain intensely with the basic dyes,
retaining the stain even after the chromatin granules are completely
extracted. They were discovered by a pupil of A. Meyer in the
cells of Spirillum volutans from which the peculiar name is derived,
and, according to Guilliermond, they are identical with the "meta-
chromatic bodies" of Babes, and with the "red granules" discovered
by Biitschli. They take a yellow stain with iodine and a blue stain
with methylene blue and 1 per cent solution of sulphuric acid,
while their reaction to the usual chromatin stains makes them
difficult to distinguish from chromidia. They do not give a reaction
with the Feulgen method as usually employed, but Reichenow (1928)
found that if the preliminary acid hydrolysis is omitted a typical
Feulgen reaction follows upon treatment with the fuchsin-sulphuric
acid component alone. He infers from this that volutin substances
give a typical Feulgen reaction, which is much more rapid than
that of nuclear chromatin, and concludes that volutin consists of
free nucleic acid. The same conclusion was reached by Schumacher
(1926) on the basis of volutin reactions to his methylene blue phos-
phin method. Meyer himself regarded them as composed largely
of nucleic acid, a conclusion supported by the experiments of
Reichenow (1909) on Hematococcus in which it was shown that
volutin grains disappear in a medium free from phosphorus and
that, during the phases of active chromatin increase in the nucleus,
THE FUNDAMENTAL ORGANIZATION 73
they diminish perceptibly in size and increase in size when the
chromatin content becomes stationary. From these results, con-
firmed by van Herwerden (1917) on yeast cells, Reichenow con-
cluded that volutin grains play a most important part in the vital
activities of the cell and he regarded them as a reserve store of
nucleo-proteins for the purpose of chromatin growth in the nucleus.
They appear to be formed in the cytoplasm and, if these observa-
tions are well founded, are entirely different in origin and in function
from the other minute granules which they closely resemble. The
importance of these conclusions in problems connected with biology
of the cell warrants the demand for further and more complete
observations and experiments.
3. Mitochondria. — The chondriome of a cell consists of the aggre-
gate of cytoplasmic substances of lipoidal nature appearing in the
form of minute granules termed mitochondria, as strings of granules
termed chondriomites, or as smooth filaments termed chondrioconts
according to the terminology of Benda (1903) and Meves (1907).
The lipoidal make-up is shared with the Golgi apparatus, another
group of cytoplasmic substances which are equally well distributed
and similar in form and in reactions to mitochondria, but which
are regarded as distinct from the chondriome and with different
functions in the cell.
Some of the lipoidal substances making up the chondriome are
evidently autonomous bodies in the cell, while others, more transi-
tory in nature, probably result from metabolic activities. It is
quite probable, as Alexeieff suggests (1928), that different states or
stages of a common type of substance are represented in different
organisms and the terms mitochondria chondriomite, chondriocont,
etc., have merely a morphological significance. Of these the mito-
chondria appear to be the original neutral and most widely dis-
tributed of the lipoidal substances, and as such they belong to the
fundamental organization.
Mitochondria are minute inclusions in the cytoplasm, varying
in size from 0.5 ju to 1.5 ju. They may be spherical granules or
rod-shaped, resembling bacteria, or crescentic or sickle form.
(Fig. 37.) They have been identified in so many different types
of Protozoa that their universal distribution may be assumed with
assurance.
Except in a very general way the chemical make-up of mitochon-
dria is unknown. They become reduced in size or disappear after
treatment with alcohol or acetic acid, but there are wide differences
in the times required to bring this about. They blacken with
osmic acid, turn blue green with Janus green B, or red with Janus
red (Horning, 1926). Faure-Fremiet (1910) who was the first to
recognize mitochondria in Protozoa regarded them as a combination
of albumin and phosphates of fatty acids. Today there is no
74
BIOLOGY OF THE PROTOZOA
great advance beyond this original interpretation, the accepted view
being that mitochondria are combinations of a fat-like body (lipoid)
and protein, the variations in staining, in solubility, etc., depending
upon the relative amounts of protein in the combination, a small
proportion making them highly unstable, a large proportion making
them more resistant to heat, alcohol and fat solvents in general.
Fig. 37. — Urole-ptus halseyi. Difference in mitochondrial content of a cultural
individual (left) and an ex-conjugant (right). X 700. (After Calkins, Arch. f.
Protistenkunde, courtesy of G. Fischer.)
Opinions differ in regard to the autonomy and self-perpetuation
of mitochondria. Observations on the living protozoon cell con-
vinced Faure-Fremiet (1910) that the granules reproduce by spon-
taneous division and this observation has been confirmed by others
upon living and fixed material. Richardson and Horning (1931) in
particular, after a slight modification of the pH of the milieu,
obtained preparations of Oyalina showing practically every mito-
chondrial granule in division (Fig. 38). In other cases, however,
THE FUNDAMENTAL ORGANIZATION 75
particularly in the early sporozoites of Monocystis, Horning was
unable to demonstrate the presence of mitochondria and concluded
that they are absent in young forms but make their appearance in
the process of development. This was interpreted as evidence of
their origin de novo in the cytoplasm (Horning, 1929).
Suspicions have been aroused from time to time as to the nuclear
origin of mitochondria, although little positive evidence has been
forthcoming. Some has been obtained recently, however, in con-
nection with observations on the reorganization processes following
conjugation of Uroleptus halseyi (Calkins, 1930). Here the old
macronuclei, eight in number, break up, each into a group of minute
spherules. These spherules, at first, have a deeply staining cortex
* ft ." ■■ - » ft
IT:
m
• &f^ii *^r,*f
f. #•--* V- • A» ^>« 51
' *V.**YAk a' *« * *** •*
Fig. 38. — Dividing mitochondria in Opalina. (After Richardson and Horning, Jour.
Morph., courtesy of Wistar Institute.)
(with iron hematoxylin) and a more feebly staining medullary por-
tion, thus giving the appearance of black rings in optical section.
At a later stage the apparent rings break up into small crescents
and the latter ultimately become rod-like mitochondria filling the
cell of the ex-con jugant (Fig. 37) .
Opinions are equally divergent regarding the functions of mito-
chondria in the cell. The earliest suggestion was that of Faure-
Fremiet (1910), who believed that they play some part in connection
with the preparation of germ cells, and who was influenced no
doubt, by their conspicuous presence in germ cells of Metazoa.
Confirmation of this suggestion is furnished in part by observations
of Zweibaum (1922), who observed an increase in the fatty acid
content of Paramecium when ready to conjugate; and confirmed,
76 BIOLOGY OF THE PROTOZOA
in part, by the observations of Joyet-Lavergne (1927) on the differ-
ences in number, size, and staining capacity of the mitochondria in
the two individuals forming a syzygy in gregarines, thus indicating
what he interprets as male and female differentiation.
Numerous observers have maintained that mitochondria are
responsible for digestive processes in the cell. The best evidence
in support of this suggestion has been furnished by Horning (1928),
who, using dark-field illumination, observed mitochondria of hetero-
trich ciliates adhere to food particles which had been recently
ingested; the mitochondria were included in the gastric vacuoles,
where they disappeared pari passu with the breakdown of the food
substances. Horning concludes that, among other possible func-
tions, mitochondria are direct agents in food hydrolysis, playing
the part of zymogen granules in the preparation of proteolytic
digestive ferments. Causey (1925-1926, etc.) likewise associates
mitochondria with food digestion, but he distinguishes between
spherical and rod-like forms, the latter being found clustered about
the gastric vacuoles (Endomoeba gingivalis) while the former are
distributed about the cell, where they act as centers of katabolic
activity (?). The difficulty of distinguishing between mitochondria
and bacteria is obvious, particularly when inside a gastric vacuole,
and this has been the main criticism directed against Homing's
interpretation, who meets it by describing the stain used which
was specific for bacteria and did not stain the mitochondria.
Still other interpretations of the functions of mitochondria have
been advocated more or less vigorously by different observers. As
active centers they have been associated with the formation of
plastids (e. g., leucoplasts, pyrenoids, etc.) filamentous structures
of various kinds and with practically all of the cytoplasmic elements
of the derived organization. Cowdry (1924) states that more than
eighty substances have been claimed to come from mitochondria
(see especially Causey, 1926). Not only in cell activities have they
been regarded as direct causes, but also as latent or static centers
they have been interpreted as cytoplasmic transmitting agents in
heredity.
None of the suggested interpretations mentioned above seems to
be adequate to explain the purpose of mitochondria. Their universal
distribution in Protozoa and in Metazoa indicates some important,
possibly fundamental activity which is closely bound up with life
of the cell or protoplasm in action. Kingsbury (1912) long since
suggested that mitochondria might be associated with cell respira-
tion, a suggestion adopted and enlarged by Joyet-Lavergne (1927)
mainly from study of gregarines and coccidia. According to this
observer there is a close connection between mitochondria in
coccidia and the catalyst glutathion which is a powerful oxidase.
(See Needham and Needham, 1926; Tunnicliffe, 1926; etc.) He
THE FUNDAMENTAL ORGANIZATION 77
noted that glutathion is abundant where mitochondria are abun-
dant and vice versa. He has also shown that the oxidation-reduction
potential (indicated by the expression rH) varies with the distri-
bution of glutathion, low when glutathion is abundant, and high
when it is scarce.
While there is considerable evidence to indicate an association
between mitochondria and protoplasmic respiration, Joyet-Lavergne
himself finds that the association is not always demonstrable and
in some cases is highly improbable, and admits that there are
probably other functions of the mitochondria.
On the whole we are still in the air as regards the function or func-
tions of mitochondria. The variety of interpretations that have
been advanced, and often upon good evidence, suggests that we
may have to do here with cellular elements which have a general
enzymatic significance and functional both in constructive and in
destructive activities. As synthesizing enzymes they may be
agents in the selection of different materials from the cytoplasm
and in fashioning them into proteins, starch, fats, essential oils, etc.
(Cowdry, 1924, 1926; Regaud, 1909, etc.), or by metamorphosis
they may give rise directly to plastids of different kinds in the cell
(Guilliermond, et al.) ; or by degeneration giving rise to substances
like chromidia which Gatenby regards as badly damaged mito-
chondria. As catalytic enzymes they may act as oxidases in respira-
tion, or as hydrolyzing agents in protein and carbohydrate digestion.
It would seem that we are either demanding too much of one
type of protoplasmic substance or that the term mitochondria
embraces a large number of substances having different functions,
but with a common lipoidal composition in which the protein com-
ponent is the chief variable. Furthermore, it is not improbable
that the Golgi apparatus of the cell represents an extreme variation
of this type of substance.
4. Golgi Apparatus.— Another cytoplasmic substance which had
been identified as a phospholipin (Faure-Fremiet) or lipoproteid
(Bouin, Bowen, Hirschler, King, Horning, Joyet-Lavergne, etc.),
and known as the Golgi apparatus, Golgi bodies or (in part) dictyo-
somes, is also widely distributed in different groups of Protozoa.
There are many points of resemblance between this substance and
that of mitochondria, particularly in their lipoid composition and
consequently in their reactions to special stains. In many types
the Golgi bodies— dictyosomes— and mitochondria are apparently
indistinguishable (e. g., Gregarina blattarum, Spirostomum ambiguum
and Opalina ranarum according to Hirschler, 1924), but in cases
where, on morphological grounds, they are unmistakable, they
differ from mitochondria in their larger size and in their tendency
to clump together in masses, or to form a definite reticulum or net-
work (Metazoa) in the vicinity of the nucleus.
78
BIOLOGY OF THE PROTOZOA
In Metazoa the Golgi apparatus appears under two main aspects,
one diffused, the other localized. These may be converted one into
the other in different stages of cell activity and they should be
regarded as variations of the same substance in the cell or of the
same structural element. The localized phase was termed by Golgi
(1898) the "internal reticular apparatus" from the characteristic
net-like structure which it assumes in nerve cells. The granular
phase is derived, apparently, from the fragmentation of the fibrils
which make up the net structure.
In Protozoa the Golgi apparatus rarely appears in the form of a
network, although aggregates of lipoprotein^ which are found in
some cases are regarded as the equivalent of the localized phase
typical of metazoan cells. The granular phase, however, is widely
distributed in the form of spherules which are larger in size than
Fig.
39. — Golgi apparatus in Amoeba proteus. (After Brown, Biological Bulletin,
courtesy of the Marine Biological Laboratory.)
mitochondria and have an osmium blackening lipoidal cortex (osmi-
ophilic portion) and a gray-staining medullary part (osmiophobic
portion). This gives them the appearance of black rings or, if
imperfectly stained, of crescents or even of rods. In the latter
condition they are easily mistaken for mitochondria (Fig. 39).
Golgi bodies as distinct from mitochondria, were first recorded
by Hirschler (1914) in Monocystis ascidiae a gregarine and similar
parasitic forms seem to have been the favorite material for their
study. King and Gatenby (1923) and Joyet-Lavergne (1923)
described them again in Sporozoa. Since this time, however, descrip-
tions of Golgi bodies from many forms, including representatives
from all groups of Protozoa, have been published and various
attempts have been made to attach some specific function in the
cell to them.
Following the course of development of the subject in Metazoa,
THE FUNDAMENTAL ORGANIZATION
79
the function of Golgi bodies in Protozoa is generally associated
with the secretory activities of the cell. These activities, in turn,
fall into different categories but mainly in the group of enzymatic
functions. Thus Joyet-Lavergne describes a structure near the
tips of young forms (agametes, sporozoites) of coccidia, i. e., that
portion which first penetrates an epithelial cell, which he compares
with the acrosome of metazoon sperm cells (Fig. 40), the substance
of the Golgi body being the source of the cytolyzing agent. There
is some evidence also that the so-called parabasal bodies of the
Polymastigida and the Hypermastigida are made up of varying
proportions of lipoid and of proteid substances and have many
of the morphological attributes of Golgi bodies (Duboscq and
Grasse, 1925). Duboscq and Grasse hold that the parabasals here
have a secretory function in connection with the transformation of
energy underlying flagellar movements. This, however, has not
Fig. 40. — Golgi apparatus in reproductive cells. 1, 2 and 3, merozoites of Aggrc-
gata eberthi; 4, sporozoite of same; 5, microgametes of same; 6 and 7, sporozoites of
Gregarina polymor.pha. In all, the Golgi apparatus at anterior end recalls the acro-
some of spermatozoa. X 1000 U and 5), X 2000 (1, 2, 8, 6 and 7). (After Joyet-
Lavergne, Arch, d'anatomie microscopique, courtesy of Masson et Cie.)
been confirmed by later workers and there is high probability that
all of the structures which have been called parabasal bodies are
not identical in chemical composition (see Hall, 1931; V. E. Brown
et al, 1930.). Another type of secretory activity of Golgi bodies
in Protozoa is described by Nassonow in connection with the
lipoidal membranes, homologized as Golgi apparatus, about the
contractile vacuoles and canals of flagellates and ciliates. Nassonow
sees in this a special apparatus for the secretion of nitrogenous
waste into the vacuole whence it is excreted (see below, p. 170).
There is no satisfactory evidence of the origin of the Golgi bodies
in Protozoa. If the parabasals are to be included in this group of
substances and there is equal evidence for regarding them as chroma-
toid substances, then there is evidence that in some cases they arise
from the blepharoplast and the latter from the endobasal body of
the nucleus. Causey (1925), upon rather hazy evidence, concludes
that the Golgi bodies of Endamoeba gingivalis arise as thickenings
of the walls of gastric vacuoles.
so
BIOLOGY OF THE PROTOZOA
Further work on these different types of lipoidal elements of the
cytoplasm of Protozoa is much needed and a more critical classifi-
cation of the formed structures of the cell is greatly to be desired,
particularly in connection with chromidia, parabasals, mitochondria
and Golgi bodies.
5. Silver Line System.— Recent technical developments have led
to the discovery of a complex system of fibrils in the cortex of ciliates.
The way was paved for this by observations of Bresslau (1921) who
m
jMftf!!;
Fig. 41. Fig. 42.
Fig. 41. — The silver line system of Discomorpha pectinata. Right side. (After
Klein, Arch. f. Protistenkunde, courtesy of G. Fischer.)
Fig. 42. — The silver line system of Discomorpha pectinata. Left side. (After
Klein, Arch. f. Protistenkunde, courtesy of G. Fischer.)
endeavored to find some chemical (stain) which would cause imme-
diate coagulation of the colloidal structures, especially of the cortex.
He used a mixture of equal parts of a 10 per cent opal blue stain
and of 6.5 per cent phloxin-rhodamin stain. Ciliates were allowed
to dry in this mixture and were then mounted in balsam. Success-
ful preparations made in this way revealed specific types of cortical
markings of rectangular or rhomboidal shape. Here areas of
coagulation gave evidence of more or less definite boundaries.
B. Klein (1926) also used the method of drying, but drying with-
out coagulation. He argued that small organisms may lose their
THE FUNDAMENTAL ORGANIZATION 81
water without loss of organization and may re-establish vitality by
subsequent hydration (e. g., as in dried rotifers or protozoan cysts).
He maintained that normal structures are not disturbed by such
desiccation provided the latter process is correctly carried out.
Dried forms obtained in this way were treated with a 2 to 3 per
cent solution of silver nitrate, which was allowed to act for from
eight to ten minutes. The organisms were then submerged in
distilled water and exposed to sunlight. Blepharoplasts or basal
bodies of the cortex are apparently composed of a substance which
' ■
c >s
'.-.'.* ..... ■ .\ • ■
Fig. 43. — Podophrya fixa. Silver line system at the time of budding. A, budding
region of tentacle-bearing parent organism, aggregation and divisions of primary
blepharoplasts; B, later stage with final divisions of blepharoplasts; C, bud in which
the blepharoplasts have "satellites" which form the cilia. (After Chatton, Lwoff
and Tellier, Compt. rend. Soc. d. biol., 1929, courtesy of Masson et Cie.)
has an affinity for silver (argentophile substances). The silver is
reduced in sunlight and the basal bodies, their connectives and
associations are revealed in jet black lines and grannies against a
yellow background. Klein termed these structures the silver line
system and has shown that, specific systems characterize each
species of ciliate (Figs. 41 and 42).
Chatton and Lwoff (1929) have extended the silver nitrate method
for fixed material, thus avoiding the somewhat brutal desiccation.
Their results in general confirm Klein's.
6
82 BIOLOGY OF THE PROTOZOA
The silver line systems then are definite aggregates of granules
and fibrils which, in some pattern or other, form a part of the
cortex of every ciliate. It is present over large stretches of the
cell body, even where cilia are absent; for example, throughout the
surface of a Vorticella. In Suctoria and in some ciliates (e. </.,
Foettingeriidae) it persists after the embryonic cilia have entirely
disappeared, hence to Chatton and Lwoff (1929) the silver line
system may have a palingenetie significance, and they term it the
infraciliature.
The silver line system appears to be, like the nucleus, a definitely
organized part of the fundamental organization. It forms a con-
tinuum over the cell and persists from generation to generation by
division. Cortical structures are formed, apparently under its
influence (see Fig. 43) and it may well be a mechanism whereby
coordination is effected throughout the organism (see Klein, 1928,
1929, 1930).
CHAPTER III.
DERIVED ORGANIZATION.
I. CYTOLOGICAL.
PvVEKY protozoon, indeed every organism, has its own particular
fundamental organization. This is the specific aggregation of pro-
teins, carbohydrates and fats which, with the imbibition of water
containing salts of various kinds and oxygen, will undergo inter-
actions leading to the formation of substances and structures not
present before. The changes thus brought about furnish another
basic organization in which environmental stimuli, as well as stimuli
coming from within, cause interactions which result once more in
novel structures or substances. The organization thus is contin-
ually changing, each new organization on the basis of that laid
down before, until a structural stability results and further changes
cease. Such a series of changing organizations is what we usually
speak of as development or embryology or the transition through
varying phases from the fundamental to the derived organization.
Obviously with a given specific fundamental organization in the
same environment the successive changes will always be the same,
resulting in the same type of derived organization, and so a species
appears to be fixed in type. But different specific types of funda-
mental organizations have different potentials or possibilities of
development which result in different taxonomic types of organisms.
With Protozoa the potential of development is relatively low,
but is higher in some groups than in others. Thus the structures of
a Paramecium caudatum or the endoplasmic structures of a Giardia
indicate a higher potential in these organisms than in Amoeba proteus.
But even in the latter there is a vast difference between an encysted
ameba and its actively streaming developed stage, and this differ-
ence is brought about by changes in the fundamental organization.
The derived organization then includes the ordinarily invisible
structures which result from changes in the fundamental organiza-
tion, together with the ordinarily visible structures which furnish
the basis for classification. The latter for the most part are derived
from, or at least are intimately connected with, the former and
should not be separated from them. The former are included in
the present chapter under the caption Cytological characters', while
the latter are considered in the following chapter under the heading
Taxonom ic characters.
Changes of the fundamental organization into the derived, occur
84 BIOLOGY OF THE PROTOZOA
in all parts of the cell. The best known are those connected with
the nucleus— including its development and differentiation. The
changes in the nucleus, like changes in the cell, are brought about
through metabolic activity and the results of such changes belong
to the derived organization. The formation of nuclei, together
with chromatin changes, chromosome formation and spindle for-
mation, belong therefore to the derived and not to the fundamental
organization.
A. Derived Nuclei and Derived Nuclear Structures. — 1. The For-
mation of a Nucleus.— The formation of the massive type of nucleus
during reorganization after conjugation is clearly shown in the
case of Uroleptus mobilis (Fig. 1, Frontispiece). The young macro-
nucleus is formed by a second division of a fertilization nucleus
after conjugation when it appears as a vesicular nucleus with a
fine linin reticulum which has no staining capacity. In life it
appears like a large, highly refractile vacuole (the so-called "pla-
centa"). It remains in this ghost-like condition for a period of
three or four days, enlarging meanwhile and becoming ellipsoidal
in form. Chromatin ultimately makes its appearance in the form
of minute granules on the nuclear reticulum. These granules in-
crease in number and in size until the characteristic dense nucleus
with intense staining capacity results and the nucleus is no longer
visible in life1 (Fig. 27, p. 58). It then divides with the first post-
fertilization division of the cell, and each daughter nucleus divides
three times (see also p. 315).
2. Multiple and Dimorphic Nuclei.— While a single nucleus is
characteristic of the vast majority of Protozoa, multiple nuclei are
not uncommon and may be found in every group. In some forms,
as in many Mycetozoa, the multinucleate condition may be due,
not only to repeated nuclear divisions as in Uroleptus described
above, but to the plastogamic union of originally independent
cells, the aggregate being called a plasmodium. In other cases, as
in Foraminifera, Radiolaria and Myxosporidia, the multiple nuclei
are due to the incomplete division of the cell body after the nuclei
have "divided; or no attempt at all is made by the cell body to
divide. Analogous multinucleate stages are frequently found dur-
ing certain phases of the life history of many types such as the ante-
cedent stages of sporulation and gamete formation in Rhizopoda
and Sporozoa. In still other, and in the typical cases, multiple
nuclei are present throughout the entire vegetative life, the num-
ber ranging from two to several hundred (c. g., Actinosphaerium).
Characteristic and familiar examples of binucleate cells amongst
rhizopods are Arcella vulgaris, Pelomyxa binucleata, etc.; amongst
flagellates, Giardia intestinalis and other species of the same genus.
1 See also pp. 71 and 315 for development of nucleic acid.
DERIVED ORGANIZATION 85
Multiple nuclei are found in Pelomi/xa palustris, Actinosphaerium
eichhornii, Calonymphidae and in the majority of Infusoria.
Dimorphic nuclei are examples of multiple nuclei in which a differ-
ent function in the cell is associated with the different nuclei. Such
function may be of a sexual nature as in the Myxosporidia where
differences in size and structure indicate a differentiation which may
be expressed by the terms male and female nuclei since products
of two of them, one from each type, unite to form a fertilization
nucleus of the young cell (sporozoite) according to the observations
of Schroeder, Keysselitz, Naville and others (see p. o2C>). Or the
function may be of a metabolic nature in one type and reproductive
in the other, as in the Infusoria, where the two types show great
differences in form and size. Here the nucleus having to do with
metabolism makes up a large part of the volume of a cell and is
usually of relatively large size, hence is called the macronucleus,
while nuclei having to do with reproduction and fertilization are
always minute and are called micronuclei (Fig. 44). Usually the
micronucleus is closely attached to the macronucleus and, in some
cases, may be partially hidden in a depression or pit in the macro-
nucleus, or it may be entirely independent of the larger nucleus
and lie freely in the cytoplasm. A typical example of dimorphic-
nuclei is shown by Paramecium caudatum (Fig. 23, p. 50).
The derived forms assumed by macronuclei and the number in
a single cell vary within wide limits. The most generalized condi-
tion is a simple, spherical form; but ellipsoidal, rod-like, horse-shoe-
shape, beaded and branched macronuclei are not uncommon. The
beaded forms frequently appear like several separated nuclei but
the segments are usually enclosed in a common membrane con-
tracted at the nodal points, the entire aggregate forming a single
nucleus (Spirostomum, Stentor, Amphileptus, Uronychia, etc.). The
size of the macronucleus bears no constant relation to the size of
the organism (Fig. 44).
Micronuclei do not differ much in form but vary in structure
from typical vesicular to compact massive types. Their number in
the cell likewise varies from 1 to as many as 80 or more (Stentor).
They are never connected with one another, but are quite indepen-
dent and distributed at intervals along the sides of the macronuclei.
There is little or no evidence of the phylogenetic origin of these
dimorphic nuclei which are distinctive of the Infusoria. In onto-
genetic origin the nuclei are invariably derived after conjugation
from division products of the fertilization nucleus, the latter being
formed by the union of two micronuclear elements. Hence the
statement is usually made that macronuclei arise from micronuclei,
a statement which is not strictly accurate, since the fertilization
nucleus is neither one nor the other, but merely a cell nucleus of a
fundamental organization. In some cases macronuclei and micro-
86
BIOLOGY OF THE PROTOZOA
A
L -m o.
--M
C. V.
M-—
!
Fig 44 —Illustrating volume relations of macronuclei and cell body. A, in Spiro-
slomum amUguum; B, in Spirostomum teres; and C, Lionotus procerus; (A) anal pore ;
(CV) contractile vacuole; (M) macronucleus ; (mo.) mouth. In Lionotus the mouth
is a long slit, in Spirostomum a circular opening at the posterior end of the peristome.
(A and B, after Stein; C, original.)
DERIVED ORGANIZATION 87
nuclei are not differentiated until the third division of the fertiliza-
tion nucleus (e. g., in Cryptochilum nigricans, Paramecium caudatum,
Par. putrinum, Bursaria truncatella, Carchesium polypinum, Oper-
cularia coarctata, Ophrydium versatile, Vorticella monilata, V. nebu-
Ufera, etc.); in other cases differentiation occurs after the second
divisions (e. g., in Anoplophrya branchiarum, Colpidium colpoda,
Di<l in in hi nasutum, Glaucoma scintillans, Leucophrys patula, Lio-
notus fasciola, Paramecium aurelia, Par. bursaria, Blepharisma undu-
lans, Spirostomum teres, Euplotes patella and charon, Onychodromus
grand is, Stylonychia pustulata, Uroleptus mobilis, etc.); and in still
other cases the differentiation takes place after the first division
(e. g., Chilodon uncinatus). In all cases both macronucleus and
micronucleus are formed by metamorphosis of such products of
division of the original nucleus after conjugation, the former by a
remarkable increase in size and in quantity of chromatin, the lat-
ter by reduction in size and concentration of the chromatin; the
former becomes a metabolic organoid of the cell, the latter a germinal
organoid.
Mention may be made here of the vesicular nuclei which arise
by a process of so-called free-nuclei formation from chromidia, the
evidence for which is difficult to interpret otherwise. It rests, in the
main, on the observation of Hertwig as early as 1876, and again in
1899; of Schaudinn in 1903; of Lister, 1905; of Goldschmidt in 1907;
Elpatiewsky in 1907, and Swarczewski in 1908. In all cases the free
nuclei arise by the association of chromidia or chromidiosomes which
have been derived from the nucleus and distributed in the cyto-
plasm (see p. 69). Both Elpatiewsky and Swarczewski describe the
formation of the minute gametes of Arcella vulgaris by the fragmen-
tation of the cytoplasm into minute cells about these free nuclei.
These gametes move off as minute amebae leaving the parent with
its "primary" nuclei, which ultimately degenerate. Each of these
gametes contains at first a few scattered granules derived from the
chromidial mass which ultimately unite to form the gamete nucleus.
The process is more minutely described by Goldschmidt in connec-
tion with the mastigameba Mastigella vitrea. Here a chromidial
mass forms on the outside of the nuclear membrane by transfusion
of chromomeres (Fig. 45). After separation of this mass from the
nucleus, the chromatin granules come together in groups and form
nuclei about which minute gamete cells are cut out from the cyto-
plasm while the primary nucleus remains intact. The same thing
in principle is illustrated by the origin of the germ nucleus inside
the nucleus of Gregarina cuneata and other gregarincs as well (see
Fig. 55, p. 101). A somewhat similar mode of formation of the
microgamete nuclei of Coccidium schubergi was earlier described by
Schaudinn. This type of nucleus formation, according to Minchin,
represents the possible origin of Protozoa of "cellular grade" from
88 BIOLOGY OF THE PROTOZOA
bacteria-like organisms of non-cellular grade, in which the chroma-
tin is permanently distributed. Doflein (1916) remains skeptical
in regard to this type of free-nuclei formation and Kofoid (1921),
apparently without investigation of free-living forms, maintains
that such free nuclei are intracellular parasites. It is evident that
the burden of proof here rests with the critics. (See also p. 71.)'
Fig. 45. — Chromidia formation in Mastigella and Mastigina. A, B, young forms
of Mastigella vitrca prior to chromidia formation; C, chromidia arising from the
nucleus; D, young form of Mastigina sctosa with accumulation of chromidia; E, F,
mature stages of M. setosa; G, formation of gametic nuclei (a) from scattered chro-
midia. (After Goldschmidt.)
3. Nuclear Derivatives During Division.— The substances compos-
ing nuclei— karyolymph, plastin, chromatin and kinetic elements-
are apparently inert during vegetative life, inert at least so far as
demonstrable activity is concerned. Metabolic activities which
result in cell division, however, are manifested periodically by
characteristic changes in these substances, and structures not
present before — spindle elements and chromosomes — are formed
which, after a brief existence, pass again into the apparently inert
condition of the vegetative nucleus, that is, they are reversible.
Theoretically such transient phases are the most important of all
stages in the life history for they involve the formation and division
of chromosomes, which are regarded as the vehicle of hereditary
characteristics, and the kinetic elements, which are regarded as
instrumental in bringing about such formations and divisions.
(a) Origin of Chromosomes and of Intranuclear Spindles at Divi-
sion.— The nucleus is the most complex of the formed organoids
of the cell, and its reproduction involves growth and division of
DERIVED ORGANIZATION 89
its different elements. These may be more or less independent in
their division, or they may be united in various simple or complex
combinations during the division processes. Or the nuclear ele-
ments may be combined with extranuclear cytoplasmic elements to
form a characteristic division figure representing a most highly
perfected mechanism for the equal distribution of the more impor-
tant cell elements which are thus perpetuated from generation to
generation by equal division. Such a perfected mechanism, termed
a karyokinetic or mitotic figure, is characteristic of nuclear division
in cells of the Metazoa and of higher plants, the combination of
processes whereby the constituent parts are equally distributed to
daughter cells being known as indirect division, karyokinesis, or
mitosis. In Metazoa such processes involve division of centrioles
and centrosomes, formation of a fibrillar spindle figure, dissolution
of the nuclear membrane, aggregation of chromomeres into compact
chromosomes which are identical in size, shape and number in cor-
responding cells of all individuals of the same species, and the
longitudinal division of each chromosome in all somatic cells, sepa-
ration of the daughter chromosomes and reconstruction of the
daughter nuclei. In all Metazoa the processes of mitosis differ
only in minor details and mitosis is the characteristic type of nuclear
division, although direct division, whereby the nucleus divides
without the formality of centrosomes and spindle or chromosome
formation is known in a few cases.
In Protozoa, on the other hand, there is no one type of nuclear
diyision common to all forms. Here we find gradation, in the asso-
ciation of constituent nuclear and cytoplasmic kinetic elements
during division resulting in an enormous variety of division types.
These vary in complexity from a simple dividing granule to mitotic
figures as elaborate as in the tissue cells of higher animals and plants.
Some observers see in these diverse types a possible evolution of
the mitotic figure of Metazoa and use them as one would use the
separate pieces of a picture puzzle to reconstruct its past history
in development. Terms like "promitosis" (Naegler), "mesomito-
sis" (Chatton) and " metamitosis " (Chatton) may serve a useful
purpose to indicate general types of the association of nuclear and
cytoplasmic elements during division, but when an effort is made to
give a specific name to each step in an increasingly complex series
the result is a confusion of terms which defeats the useful purpose
intended. Thus Alexeieff proposes a large number of specific names,
not all his own, it is true, for protozoon division types which he
regards as sufficiently definite to permit of recognition.1
Because of the multitude of diverse types of division figures in the
1 These terms include Promitosis, Proteromitosis, Haplomitosis, Cryptohaplomi-
tosis, Eurypanmitosis, Cyclomitosis or Polymitosis, Polyrheomitosis, Metamitosis,
etc.
00 BIOLOGY OF THE PROTOZOA
Protozoa the difficulty of treating them in any general way has been
admitted by all students of cytology as well as by protozoologists.
1 shall endeavor here to convey an idea of this diversity and at the
same time to describe some of the more frequent types of division
figure without confusing the issue still more by my own views as to
their possible relations to one another or to any process of evolution.
The apparent object of the complex mechanism of a mitotic figure
is to ensure the exact bipartition of the hereditary complex repre-
sented by the chromosomes. These elements, and the chromatin of
which they are composed, are the most important, while the kinetic
elements with which they are associated in division, as agents in
the process, are of secondary importance.
The conception of chromosomes, as they appear in Metazoa, is
definite and consistent throughout. They are formed at certain
periods of cell activity (prophase of division) by the aggregation of
chromomeres into nuclear bodies of definite form and size, and the
number is constant for all somatic and germ cells in the same species.
Each chromosome is specific and retains its individuality from gen-
eration to generation by cell division. At the end of division it
resolves itself into an aggregate of chromomeres which, in some
cases, are found to be confined to a definite part of the nucleus
(chromosomal vesicle), at the prophase of the following division
these same chromomeres re-collect to form the chromosome which
divides into equal parts by longitudinal division. The chromo-
somes, furthermore, are qualitatively different, no two of them
being identical. During meiosis, finally, the number of chromo-
somes is reduced to one-half by the separation of half of them from
the other half, thus resulting in two types of nuclei which are quite
different in chromosomal make-up.
An analysis of the literature dealing with the so-called chromo-
somes of Protozoa shows that there has been little or no consistent
use of the term. To many observers the word is used to describe
any chromatin which happens to be in the center of a division figure
and without regard to other conditions which limit and define the
chromosome as a definite thing, viz. : A definite number in the
cell, longitudinal division, qualitative differences, reduction in num-
ber at maturation, etc. It is true that in only a few cases among
the Metazoa has it been demonstrated that chromosomes have a
specific individuality combined with qualitative differences, but
the striking similarity in dividing chromosomes of all Metazoa and
the same complicated mechanism in all cases for their equal distri-
bution to daughter cells, give a basis upon which the generalization
rests. We have no basis, however, for extending the generalization
to Protozoa, for here we have absolutely no evidence of qualitative
differences and but little evidence of individuality. In some cases
we have evidence that structures in the center of a division figure
DERIVED ORGANIZATION 91
are formed by the fusion of chromomeres, and some evidence that
such structures divide longitudinally. These two conditions, which
are relatively rare, are", the only conditions whereby many of the
so-called chromosomes of Protozoa resemble those of Metazoa, and
if we use the term chromosome at all it should be in a definite,
limited, morphological sense and only for those nuclear structures
of Protozoa which conform in origin and in fate to chromosomes of
Metazoa. I shall use the term chromosome, therefore, only for
those compact intranuclear aggregates of chromomeres which divide
as unit structures and which are resolved into chromomeres after
such division.
A brief review of some of the frequently recurring types of chro-
matin structure at the time of nuclear division will show how diffi-
cult it is to speak with assurance of chromosomes in Protozoa. The
series is not to be construed as an effort to establish a phylogenetic
chain of stages culminating in well-defined chromosomes, nor as a
means of pointing out that one is a "higher" type than another.
Certain vital functions are undoubtedly associated with the nucleus
and with the chromatin of the nucleus, and the fact that some types
of organisms with peculiar nuclei continue to live and reproduce is
evidence enough that such nuclei are adequate for their needs.
The variations in type arise through the association of chromatin
with other nuclear or cytoplasmic constituents, and this involves
more or less formality in preparation for its perpetuation by exact
bipartition to daughter cells. All traces of chromosome formality,
however, as well as reduction processes, appear to be absent in
gamete nuclei formed by rhizopod chromidia.
One group of types is represented by massive nuclei as found in
the macronuclei of the Infusoria. Here the resting nuclei are made
up of closely packed granules or chromomeres and there is little
formality or mechanism associated with their division during repro-
duction. Each granule elongates and divides into two parts, thus
doubling the number of chromomeres. The mass thus formed is
passively distributed to the daughter cells by division of the nucleus
through the center. It is a quantitative distribution, for the
daughter nuclei do not contain representative halves of the indi-
vidual chromomeres and the inference is that all of the chromo-
meres are qualitatively identical. To this type also I would assign
the peculiar chromatin granules of Dileptus gigas which are distrib-
uted throughout the protoplasm unconfined by a nuclear membrane.
Each granule divides where it happens to be and with the majority
of granules both halves remain in one daughter cell after division
(Fig. 46).
These macronuclei, however, particularly the band-form types of
the hypotrichous and peritrichous ciliates and the multinucleate
chain-form types of hypotrichs, may undergo characteristic pre-
92
BIOLOGY OF THE PROTOZOA
divisional changes which for lack of a better term may be called
"purification" processes. These are associated with the so-called
" Kernspalt" or nuclear cleft which for decades has been an enigma.
A simple case is that of Uroleptus halseyi, an hypotrichosis cihate
\f. , A
A^A
m m
Fig 46 -Division of Dileptus gigas. The longated chromatin granules (C) divide
where they happen to lie. (Original.)
DERIVED ORGANIZATION
93
with, normally, eight macronuclei which are separate and arise by
three consecutive divisions of the division nucleus (Fig. 47).
When first formed these eight nuclei are com-
posed of homogeneous chromatin granules simi-
lar in size and in staining capacity. After a
period of normal growth and activity, and
particularly at the approach of a division
period, a different type of granules appears in
each of the nuclei. These, which I have called
the "X granules" (Calkins, 1930), stain in-
tensely with iron hematoxylin but disappear
entirely, by hydrolysis of the Feulgen tech-
nique; furthermore, they stain green with the
acid component of the Borrel stain. One of
these X granules, usually more prominent than
the others, lies in the anterior third of each
nucleus. Its substance spreads out in a zone
or flat plate extending transversely through
the nucleus (Fig. 47, b, c). This plate reacts
to stains exactly like the X bodies and disap-
pears by hydrolysis in the same way. The
nuclear cleft forms just posterior to this plate
and the anterior third of each nucleus, viz.:
that portion anterior to the cleft is thrown off
and disappears in the cytoplasm. Other X
granules which may be present are similarly
discarded, leaving the bulk of each nucleus
with only one type of granule. The process
occurs in all eight nuclei at the same time,
and after it is completed, the residual " purified "
nuclei all fuse to form a single macronucleus
which, after condensation, becomes the division
macronucleus (Fig. 128, p. 246) . The substance
of the X granules thus appears to have a cyto-
lyzing effect on the nucleus and is the agent
in formation of the nuclear cleft.
Ivanic (1929) describes two deeply-staining
(iron hematoxylin) granules which appear at
the ends of the curved macronucleus of Ewplotes
yatella. These he interprets as centrosomes,
and argues for a premitotic division of the
macronucleus. It is more probable that these
are X granules marking the beginnings of two
nuclear clefts which pass from the extremities
of the nucleus to the center where they disappear, as shown by
Kidder (1932) in the case of Conchophthirius mytili. Turner (1930)
Fig. 47.— Uroleptus
halseyi. X bodies.
Chromatin elimina-
tion and nuclear cleft
in preparation for
division of the macro-
nucleus. (Original.)
94
BIOLOGY OF THE PROTOZOA
describes these as " reorganization bands," each band consisting of a
"reconstruction plane" (unstained) and a solution plane (Fig. 48).
Turner suggests that " The reorganization bands cause a phase reversal
of a colloidal system in which the chromatin changes from a continu-
ous (reticulum) to the dispersed (granular) phase." Certainly his
descriptions and figures indicate a marked change in the chromatin
after the "absorption bands" have passed by. A similar difference
is apparent in the chromatin granules anterior and posterior to the
nuclear cleft in Uroleptus halseyi, but here the portion with the
finer granules (reticulum?) is cast out. With this change in the
chromatin granules the macronucleus of Ewplotes is ready for
division.
0NB
■AZZ££
iff
I'-',
Fig. -is. — Euplotes patella, macronucleus with "absorption bands" which start at
the two ends and progress to the middle where they meet. At division, two small
granules are discarded in the cytoplasm. (After Turner, from University of Cali-
fornia Publications in Zoology, 1930.)
In another group of types we have to do with vesicular, endosome-
containing nuclei. The endosome may or may not contain an endo-
basal body. It is well represented by the nucleus of Spongomonas
splendida according to the observations of Hartmann and Chagas
(Fig. 49). Here, according to the description, the mass of chromatin
of the resting nucleus divides into two equal masses without frag-
mentation at any stage. Similar conditions are shown by the greg-
arine Gonospora varia according to Brasil (1905), by Sappinia dip-
loidea according to Hartmann and Xaegler (190S), by the simpler
amebaeand, in a striking way, by Haplosporidium ctenodrile according
to Granata (1915).
In another group of types the chromatin of the resting vesicular
nucleus is contained also in a definite endosome, but, in preparation
DERIVED ORGANIZATION
95
n b
A B
Fig. 49. — Division of Spongomonas splendida Hart, and Ch. The old flagella are
discarded and new ones form from the centrioles (C and D). (o.b.) old blepharo-
plasts; (n.b.) new blepharoplasts. (After Hartmann and Chagas.)
m
B
7§b
^
tAAitefa
•>
~5&
x<
."*.'■ ■*. i;
»■*»" „ ■•---*,"« V —
Fig. 50. — Nuclear division and budding in Heliozoa. A, Vegetative cell of Spfuu r-
astrum with axial filaments focussed in a central granule (centroblepharoplast) ;
B, C, D, division of central granule and spindle formation in Acanthocystis aculeata;
E, F, formation of buds of same; G, exit of central granule from the nucleus of young
cells. (After Schaudinn.)
£
96
BIOLOGY OF THE PROTOZOA
for division, the endosome fragments into minute chromomeres,
which may be strung out in lines through the nucleus, these strings
being divided transversely at division. Or the chromomeres may
be aggregated in a fairly homogeneous transverse plate in the center
of the dividing nucleus (Fig. 51). The former condition is illustrated
by the nucleus during vegetative division of Actinosphaerium eich-
hornii according to Hertwig, the latter condition by Sphaerastnnu
and Acanthocystis (Fig. 50), Collodictyum (Fig. 51), Paramoeba
chaetognathi, or the myxomycete Comatricha obtusata according to
Lister.
Fig. 51. — Nuclear division in Collodictyum tried latum. (After Belaf.)
A slight modification of this type is shown by nuclei containing
multiple endosomes as in Pelomyxa binucleata which fragment at
periods of division, giving rise to a granular nuclear plate (?) which
presumably divides to form the daughter plates as shown in Schau-
dinn's well-known figure or to division figures like that of Centwpyzis
aculeata.
Another widely distributed type of division figure is derived from
vesicular nuclei in which the chromatin is not contained in one or
more endosomes but is distributed peripherally about the nucleus
where it usually forms a distinct chromatin reticulum. Such nuclei
usually contain an endosome which may be the most conspicuous
structure of the nucleus. In . 1 moeba crystalligera the peripheral
chromatin appears to be passively divided without any appreciable
change in its make up. In Amoeba vespertilio the peripheral chro-
DERIVED ORGANIZATION
97
matin is similarly divided and distributed but the endosome appar-
ently contains some chromatin in addition for a complete division
figure is formed from its substances, chromatin-like granules form-
ing a nuclear plate (Fig. 52). In other cases, as for example End-
amoeba intestinalis and E. cobayae, the peripheral chromatin is
broken up into chromomeres, which collect in the center of a spindle
ife:
'■•.n't.
Fig. 52. — Amoeba vespertilio Dof. Origin of the spindle within the nucleus (1, 2),
nuclear division (5, 6, 7), and reconstruction of nuclei after division (3, 4, 8, 9).
(After Doflein.)
from the linin of the nucleus and with centrioles at the poles. In
Chlamydophrys the endosome apparently divides before it disap-
pears, the chromosomes being formed from the peripheral chromatin.
In still another general type, derived also from vesicular nuclei,
the chromatin in the form of chromomeres is suspended in a loose
reticulum. In Opalina chromatin appears to be aggregated in a
few larger granules, which divide where they happen to be without
7
98 BIOLOGY OF THE PROTOZOA
further formality, the nucleus meantime assuming an indefinite
division figure. More frequently, however, the chromomeres are
suspended between an endosome and the nuclear membrane, as in
Eimeria schubergi, or various species of Trypanosoma. In some of
these, at division the chromomeres appear to form a nuclear plate,
and are distributed in equal groups to the daughter nuclei (Fig. 51).
In a final group of types of nuclear division figures either from
massive or vesicular nuclei, the chromomeres are derived from the
fragmentation of endosomes or from a chromatin reticulum. The
common feature in this large group is the fact that these chromo-
meres unite secondarily to form definite chromatin bodies which
satisfy, in part at least, the definition of chromosomes as given above.
These chromosomes are divided equally, one-half going to each
pole of the division figure. In some cases it is obvious that their
'^^■W~'^M
Fig. 53. — Metaphase and anaphase of nuclear division in the radiolarian Aula-
cantha scolymantha. X 300. (After Borgert, Zoolog. Jahrbucher, courtesy of
G. Fischer.)]
division is longitudinal, but in the majority of cases it cannot be
ascertained with assurance whether their division is longitudinal
or transverse. Nuclear figures of this general type may be divided
into two groups, in one of which the chromosomes are too numerous
to permit of decision as to their constant number, and the second
comprising forms in which the chromosomes are constant in number
and in some of which this number is reduced to one-half at meiosis.
In the first of these groups we would include types like Euglypha
alveolata, the various species of Paramecium and some Radiolaria
(Fig. 53). In the second group we would place such forms as
Actinophrys sol, Aggregata eberthi, Trichomonas and allied flagellates,
Trichonympha and related forms, and the majority of filiates in
which the maturation processes are known.
In Euglypha alveolata the chromatin of the vesicular nucleus is
distributed throughout the resting nucleus. During the early divi-
DERIVED ORGANIZATION 99
sion stages the chromomeres are rearranged in rods or fibrils which
form a more or less definite skein within the nucleus; this skein
fragments into a large number of chromosomes which, according to
Schewiakoff, are longitudinally divided. A more aberrant history
is followed by the chromatin of the nuclei of various species of
Paramecium. In Paramecium caudatum the micronucleus belongs
to the massive type, and there is no satisfactory account of the
origin of chromosomes in vegetative division (Fig. 35, p. G7), but
the number is much smaller than in the meiotic divisions (see Fig.
147, p. 297).
A more definite metazoan type of chromosome formation is shown
by the organisms with a definite number of chromosomes which is
reduced to one-half at meiosis. Here the number of. chromosomes
is usually smaller and their individual history during nuclear divi-
sion is less difficult to make out. A good example, typical of the
more complex flagellates, is Trichonympha campanula, as described
by Kofoid and Swezy. Here the resting nucleus contains a large
granular endosome. In the prophase of division the granules of
this endosome give off chromatin along the walls of the linin
reticulum until a definite skein stage results (Fig. 54). Double
chromosomes, 2(1 in number, and formed by the splitting of the
spireme segments, make up a definite nuclear plate. They are
attached by intranuclear fibers to the daughter blepharoplasts and
are divided longitudinally with the division of the nucleus. The
original connecting fibrils between the separating halves of the
blepharoplast ('' centroblepharoplast ") remain at all times outside
the nuclear membrane, hence it is called a paradesmose by Kofoid
and Swezy. One of the chromosomes appears to be different from
the others, both in resting and division stages, and is called the
heterochromosome, although its function or significance is quite
unknown. Similar odd chromosomes are known in some Gregar-
inidae and Coccidiida where the vegetative stages are haploid, as
well as in other polymastigote flagellates. Except for the complica-
tions brought in by the extensive neuromotor apparatus of Trich-
onympha campanula, the division figures of other related flagellates
are quite similar, although the number of chromosomes is usually
smaller. Thus Kofoid and his collaborators found about 24 in
Leidyopsis sphaerica, 12 in- Trichomitus termitidis and 4 in Giardia
maris (Fig. 54, p. 100).
A smaller number of chromosomes is likewise found in a number
of the Gregarinida, and their history in division approaches that of
metazoan chromosomes. Thus in the case of Monocystis rostrata
Mulsow describes 8 definite chromosomes formed from a portion of
the nuclear chromatin, the number being reduced to 4 in the gamete-
forming divisions (Fig. 55). Shellack and Leger, also, have described
similar chromosomes in Monocystis ovata and in Stylorhynchus longi-
100
BIOLOGY OF THE PROTOZOA
roll is. In the latter case, also, there is a peculiar lagging hetero-
chromosome ("axial chromosome") of unknown significance.
(6) Origin of Fertilization (Meiotic) Chromosomes. — In practically
all Protozoa the sequence of stages leading to formation of chromo-
somes which enter into pronuclei is quite different from that of the
division nuclei. This phenomenon is one of the final acts of develop-
ment and in Protozoa represents a last stage of differentiation of
A
Fig. 54. — Triehonympha campanula in division. A, and B, prophase and anaphase
of nuclear division; the divided centroblepharoplast forms the poles of the spindle
and are connected by a paradesmose. C and D, breaking up of chromosome spireme
into chromosomes which show a tendency to unite in pairs. (After Kofoid and
Swezy.)
the derived organization of the nucleus. Here, as in Metazoa, there
are at least two maturation divisions, while in ciliates the number
is increased to three. As in Metazoa, one or the other of the matura-
tion divisions is a reducing division or reduction may be parcelled
out in both divisions, the end-result being that the number of
chromosomes is reduced by one-half, i. e., from the diploid to the
haploid number. As in Metazoa, the first of the meiotic divisions
DERIVED ORGANIZATION
101
is usually preceded by activity in the nucleus resulting in a skein-
like arrangement of the chromatin (spireme) from which definite
chromosomes emerge. This spireme, in Metazoa, is the stage of
pairing of homologous chromosomes, i. c, chromosomes representing
the same characteristics in the two parents. By such association
D
c
Fig. 55. — Monocystis rostrata; chromosome reduction. ^4, Formation of spindle
in pseudo-conjugant; B, C, nuclear plates of progamous divisions, 8 chromosomes;
D, anaphase of same; E, anaphase of last progamous division, the number of chromo-
somes is here reduced from 8 to 4. (After Mulsow.)
the chromosomes when fully formed are apparently reduced to the
haploid number, but each is double, and the actual reduction occurs
in the ensuing divisions.
In Protozoa the antecedent or prophase stages of the first meiotic
division rarely conform to the metazoan scheme, but in most cases
102
BIOLOGY OF THE PROTOZOA
there are stages which have some resemblance, at least, to spireme
formation of the metazoan type. For Actinophrys sol, Belaf (1922)
has described in great detail the transformations of the chromatin
of the vesicular nucleus in the first maturation division. A spireme,
bi>
d cf
B
d ri-
ff
G
si
X
%W
C
H
E
Fig. 56. — Chromosomes 1 if Aggregata eberthi. Letters a to /, or a' to /', "^designate
the haploid groups. .1, prophase of the first division (male); B, nuclearjplate of
same; C, anaphase groups at first division; E, chromosomes in macrogamete nucleus
before fertilization; F, chromosomes in zygote nucleus (diploid); G, paired chromo-
somes in nuclear plate of first zygote division; H, early anaphase groups of first zygote
division, and separation of homologous haploid groups. (After Dobell and Jameson.)
passing through bouquet, pachytene, strepsineme and synapsis
stages, into double chromosomes of the metaphase nuclear plate,
are strikingly similar to analogous stages in metazoan meiosis
(Fig. 157, p. 309). Here there is very little to suggest individuality
DERIVED ORGANIZATION
103
of the chromosomes, but in the coccidian Aggregate, eberthi where
reduction is zygotic (the vegetative stages being haploid) the twelve
chromosomes unite in six pairs of homologous chromosomes (Dobell)
(Fig. 56) and a modified spireme occurs in the progamous divisions.
Similar but less definite conditions are shown in the gregarine
Diplocystis schieideri as described by Jameson (1920) (Fig. 158,
p. 310). A somewhat simplified history of the chromatin was
given by Mulsow (1911) for the progamete nucleus of the gregarine
Monocystis rostrata (Fig. 55). Here, differing from Diplocystis, re-
duction is gametic and the vegetative stages are diploid. The
resting nucleus is vesicular and the chromatin granules join chain-
wise to form eight chromosomes. These split lengthwise in the
metaphase stage, a preliminary spireme stage, apparently, being
absent.
Fig. 57. — Micronucleus of Paramecium caudatum in the prophases of the first
meiotic division. .4, Early stage in the formation of chromosomes; B, elongation
of the nucleus prior to crescent formation ; C, metaphase of the first division. Dehorne
describes the entire chromatin aggregate as forming one highly convoluted chromo-
some. (After Dehorne.)
In the hypermastigida (Trichonympha, Dinenympha, Stauro-
joenina, etc.) flagellates, fertilization is unknown, but ordinary
nuclear division is preceded by formation of long chromosomes
which give the appearance of a spireme.
Quite a divergent type of spireme formation is found in the
ciliates where the chromatin is massed in homogeneous micronuclei.
In Paramecium caudatum the micronucleus elongates to form a bar
nearly equal in length to the macro nucleus (Fig. 57). The massed
chromatin becomes granular, and the granules stretch out in an
elongate network which, in the following crescent phase, breaks up
into a multitude of double chromosomes.
104 BIOLOGY OF THE PROTOZOA
In other ciliates the massive micro-nucleus gives rise to a group
of chromatin granules which form an umbrella shape mass at one
pole of the nucleus (Didinium, Oxytricha, Euplotes, Uroleptus, etc.).
This has been described as the "candelabra" stage by Collin (Ano-
plophrya) or the "parachute" stage by Calkins {Uroleptus). The
number of granules is much larger than the number of chromosomes
of the later reducing division, but this large number is halved at
the first meiotic division (Fig. 32, p. 64). With the second division
the remaining granules usually fuse to form the diploid number of
chromosomes and this number of chromosomes is finally reduced
to one-half. At the third division these resulting haploid chromo-
somes become granular and are divided transversely.
B. Derived Organization; Cytoplasmic Changes. — 1. Cytoplasmic
Chromatin. — During the metabolic activities of the cell, substances
which are undoubtedly derived from the nucleus are cast off into
the cytoplasm. The majority of these are not represented by
demonstrable structures of the cytological organization. Thus in
Uroleptus (mobilis and halseyi) fully one-third of the macronuclear
chromatin is shed into the cytoplasm at each division and disap-
pears as chromatin, while in ciliates generally the entire substance
of the macronuclei and a variable proportion of micronuclear
substance (fifteen-sixteenths in Uroleptus mobilis) is absorbed in
the cytoplasm at periods of conjugation. In the latter case, again,
this nuclear substance cannot be definitely traced into cytoplasmic
structures (see, however, the described origin of mitochondria in
Uroleptus halseyi, p. 75).
Secondary nuclei which are formed in the cytoplasm of Foramini-
fera, Radiolaria and some ameboid forms are traced directly back
to nuclear chromatin. Thus in Polystomellina crispa, Peneroplis and
other foraminifera the nuclei fragment distributing quantities of
chromatin granules (chromidia) in the cytoplasm. These granules
in groups of two or three form minute secondary nuclei, one such
nucleus in each swarm spore (amebula) which then develops into
a megalospheric generation with hundreds of small nuclei formed
by division (see p. 69). When mature the protoplasm breaks up
into swarms of flagellated gametes, each with one of these minute
nuclei (Schaudinn, Lister, Winter et at.).
The testate rhizopods secondary nuclei develop from chromidia
which form the nuclei of ameboid swarmers {Centropyxis Schaudinn,
Arcella). Similarly in pseudopodia-forming flagellates (Rhizomas-
tigidae) Goldschmidt (1905) describes the formation of secondarj'
nuclei in Mastigella and Mastigina (Fig. 45, p. 88) from the cyto-
plasmic chromidia.
2. Cytoplasmic Kinetic Elements. — It is in the cytoplasm that
kinetic elements are most highly differentiated, and the often
perplexing structures which appear in different types of Protozoa
DERIVED ORGANIZATION 105
have led to much confusion in terminology as well as in interpreta-
tion. Indeed the type of development of the kinetic elements in
flagellates is entirely different from that in ciliates and at the
present time, at least, they cannot be homologized. Any attempt,
therefore, to present a clear picture of the diverse elements and to
distinguish one type from another inevitably leads to contradictions
in interpretation. The facts may be marshalled, however, into
fairly logical series indicating increasing complexity in the organiza-
tion of the cell. Such series are presented in the following pages
with the understanding that they involve no claim of finality, nor
do they indicate phylogenetic relationships.
The kinetic structures most frequently found in the cytoplasm
of Protozoa are relatively simple, the more complex types which
have been revealed being found in comparatively few cases. In
considering Protozoa as a group, therefore, too much weight should
not be attributed to these more complicated forms. For purely
descriptive purposes they may be considered in the following order:
(1) Kinetic elements, which are morphologically and functionally
equivalent to intranuclear centrioles forming parts of endobasal
bodies and usually derived from them ; (2) blepharoplasts equivalent
to basal bodies, or independent of basal bodies, which lie at or near
the bases of motile organoids and give rise to the kinetic structures
in them ; (3) basal bodies derived from and independent of blepharo-
plasts; (4) parabasal bodies which are closely connected with the
blepharoplasts and probably derived from them ; (5) centrodesmoses
and paradesmoses, or connecting fibrils between kinetic elements at
the spindle poles; ((>) rhizoplasts, or fibrils originating as outgrowths
from the substance of specific kinetic elements and connecting two
such elements or ending blindly in the vicinity of the nucleus; (7)
astrospheres and centrosomes, similar to analogous structures in
the cells of Metazoa; (8) miscellaneous kinetic elements such as
centroblepharoplasts, axostyles, parastyles and the neuromotor
apparatus of flagellates. An entirely different series involves the
motorium, conductile fibrils, and myonemes of Infusoria together
with the silver line systems of the ciliates which we have included
in the structures of the fundamental organization (see p. 80).
Since many of these are characterized by their functional activi-
ties as well as by their specific structures, it is not illogical to find
that the same organoid performs generalized functions. Thus a
blepharoplast may be the same as a centriole, or as a basal body;
rhizoplasts may arise as a broken centrodesmose or paradesmose;
a myoneme as a conductile element, etc. The complexities of organi-
zation arise from the simultaneous presence of many of these differ-
ent kinetic elements in the cell where they may form a coordinating
system of organoids which Sharp and Kofoid have aptly designated
the neuromotor system.
10(1
BIOLOGY OF THE PROTOZOA
D
■9 Ci.r'^g,, — w.
.:-s^..
w
■- -'■;»#'
^
G
Fig 58.-Hartmannella klitzkei Arndt. Centrosome and centnole in a testate
rhizopod A, Animal with watch-glass-like shell; B to F origin of the centrosome
In the cytoplasm, its division, and position on the spindle; G, anaphase stage of nuclear
division. (After Arndt.)
DERIVED ORGANIZATION 107
1. Blepharoplast, Basal Body and Centriole.— In many of the
comparatively simple Protozoa which have no specialized motile
organoids, the cytoplasm apparently lacks all traces of specific
kinetic elements. Thus in the entire group of Sporozoa, in the
simpler Gymnamebida and in testate forms of rhizopods, kinetic
elements, if present at all, are in the form of endobasal bodies within
the nucleus or as centrosomes close to it. Arndt (1924), however,
described a centrosome, with centriole, which divides and forms
the poles of the mitotic figure in Hartmannella Mitzkei, a testate
rhizopod (Fig. 58). In some of the relatively simple rhizopods,
however, especially those belonging to the family which Doflein
has called the Bistadiidae, from the fact that two distinct phases
an ameboid and a flagellate phase— are interchangeable, we find
organisms which throw light on the origin of cytoplasmic- kinetic
elements. Such dimorphic types of rhizopods have been repeatedly
observed since Dujardin first called attention to them, but details
concerning the origin of kinetic elements and the flagellum have
been made out only through use of modern cytological methods.
In some Protozoa, e. g., Codosiga botrytis, the kinetic elements of
the flagellum grow directly out of an endobasal body of the nucleus,
indicating their origin from an intranuclear kinetic element (Fig.
59,^4), in other simple forms the flagellum arises from a kinetic
element situated in the cytoplasm but connected with the intra-
nuclear kinetic element by a rhizoplast at some stage (Fig. 59, B).
In the phytoflagellate Polytoma uvella, according to Geza Entz
(1918), the relation between intranuclear and cytoplasmic kinetic
elements varies with the age of the cell. The usual condition in
adult cells is two basal bodies, one at the base of each flagellum,
and neither of them is connected by a rhizoplast with the nucleus.
In young individuals, however, the original single blepharoplast
(= basal body) is connected by a rhizoplast with an intranuclear
endobasal body, or a larger rhizoplast from the blepharoplast may
break up into a calyx of fibrils which enter the nucleus at different
points. The inference might be drawn in all such cases that the
cytoplasmic body represents one of the daughter halves formed by
division of the nuclear endobasal body, while the connecting fibril
represents the rhizoplast formed during such division. Such stages
are well illustrated by the dimorphic forms of rhizopods during the
transition from the ameboid to the flagellated phase. Thus Whit-
more described a cytoplasmic kinetic element functioning as a basal
body which is connected by a fibril with the nucleus and which lies
at the base of the flagella in Trimastig amoeba philipijinensis , and
Puschkarew described a similar condition in Dimasiigamoeha bista-
dialis (Fig. 59, C). The most complete observations, however, were
made by Charlie Wilson in connection with the transition from ame-
boid to flagellated stage in a closely-related form, Dimastig amoeba
Fig. 59.— Flagellum insertion. A, Codosiga botrytis, with flagellum arising from
the nucleus. B, Dimastigamoeba bistadialis Pusch. with blepharoplast connected by
rhizoplasts with the nucleus, and with independent basal bodies. C, Dimastigamoeba
gruberi and origin of the blepharoplast from the endosome in the nucleus; (b) bleph-
aroplast; (w) nucleus; (r) rhizoplast. {A and B from Doflein, C from Wilson.)
(108)
DERIVED ORGANIZATION 109
gniberi, one of the soil amebae. She describes the nucleus of this
organism as containing a typical endosome within which an endobasal
body is embedded. At the period of flagellation this endobasal body
divides and one daughter element migrates through the substance of
the endosome and through the nucleus to the cytoplasm, retaining its
connection throughout with the intranuclear kinetic element (Fig.
59, C). In the cytoplasm it becomes a basal body which gives
rise to the kinetic elements of the flagella. In these cases the ex-
truded kinetic element combines the functional characteristics of a
blepharoplast and a basal body or group of basal bodies. In this
dual capacity it may be regarded as a blepharoplast— basal body.
In Dimasiigamoeba bistadialis according to Puschkarew it divides,
one part remaining as a blepharoplast, the other becoming a basal
body; the two parts, however, are connected by a rhizoplast and
rhizoplasts connect the blepharoplast with the endobasal body (Fig.
59, B).
In Bodo lacertae according" to Belaf the centrioles after division
are taken into the daughter nuclei. Here the kinetic elements,
although originating from an endobasal bod}7, are different in func-
tion from those described in the preceding paragraph. Forming
the poles of the mitotic spindle they are correctly described as
centrioles, but apparently they again become endobasal bodies
(Figs. 33, 34, p. 65).
While the flagella appear to emerge directly from the nucleus in
some cases, e. g., in Mastigamoeba invertens according to Prowazek,
or Codosiga botryiis according to Doflein, in many cases they take
their origin actually from kinetic elements in the form of centrioles
which lie on the outside of the nuclear membranes, as in Mastigina
setosa, Phialonema cyclostoma, Cercomonas longicauda, Oicomonas
termo, or Chilomastix gallinarum (Fig. 60). In such cases, illustrated
by Chilomastix aulostomi according to Belaf (1921), centrioles,
become the basal bodies, and the latter become centrioles. In
such cases the basal bodies are unquestionably blepharoplasts.
In other cases the blepharoplast does not remain connected with
the nucleus by any fibrillar process, but as an entirely separated
and independent kinetic element gives rise to the flagella at or near
the anterior end of the cell (Leptomonas jaculum) or Herpetomonas
gerridis (Fig. 169, p. 366). In Chilomastix mesnili Kofoid and Swezy
(1920) describe three blepharoplasts, one of which gives rise to two
flagella, another gives rise to one flagellum and the parastyle, the third
to the parabasal, peristomial fibril and the cytostomal flagellum
(Fig. 60, B). Boeck (1921) has confirmed these findings. Or, the
blepharoplast may migrate toward the posterior end of the cell
where with or without division to form blepharoplast and basal body
it gives rise to a flagellum, which becomes the vibratile margin of
an undulating membrane as in the majority of trypanosomes (Fig.
110
BIOLOGY OF THE PROTOZOA
61, E). In still other cases the blepharoplast also gives rise to one
endoplasmic fibril or rhizoplast, which extends deeply into the cell
as in Rhizomastix (Mackinnon), or a number of such rhizoplasts
may be formed as in Mastigella vitrea. In these cases the blepharo-
plast divides independently of the nucleus at periods of cell division.
2. Parabasal Body and Blepharoplast.— As a centriole may be
contained in an endobasal body which consists largely of chromatoid
substance, so may a basal body be enclosed in chromatoid substance
u.m
Fig. 60. — Flagellum insertion. A, Phialonema cyclostomwm; B, Chilomastix
nu snili; < ', the same, encysted, {u.m.) Margin of undulating membrane in cytostome.
(A, Original; B, C, after Kofoid and Swezy.)
of a blepharoplast, as shown by Goodey (1916) in the flagellate
Prowazekia (Bodo) saltans, or by Kofoid and Swezy (1915) in
Trichomonas augusta. Again, just as a centriole may be freed from
its enclosing chromatoid substance in an endosome, so may the
basal body be freed from the blepharoplast. In a similar way
the blepharoplast may be contained in an embedding chromatoid
mass of a cytoplasmic kinetic element, or it may be free from such
a mass. We may then have in the same cell a kinetic complex
consisting of one or more basal bodies, one or more blepharoplasts,
DERIVED ORGANIZATION
111
and a residual kinetic element in the form of a chromatoid mass.
To this residual chromatoid mass the name parabasal body is applied,
the term originating with Janicki (1915). Kofoid (1916) interprets
its function as a storage or feeding reservoir for the kinetic elements,
its substance in turn being derived from the nucleus.
/"
/.;/
*%>
D
Fig. 61. — Relation of parabasal to nucleus. A, Crithidia euryophthalmi endosome
of nucleus and parabasal connected by rhizoplast; B, origin of parabasal from endo-
some of nucleus; C and D, differentiation of parabasal and rhizoplasts; E, Trypano-
soma cruzi, and F, Crithidia leptocoridis, for comparison. (After MeCulloch.)
It is in connection with the parabasal body that most of the
difficulties have arisen concerning the interpretation of cytoplasmic
kinetic elements. It is still in the stage of polemics and contro-
versies continue over the chemical nature of its substance. The
difficulties began with Schaudinn's work (1904) on the trypanosome
112 BIOLOGY OF THE PROTOZOA
of the little owl (Glaucidium [Athene] noctuae). Schaudinn's descrip-
tion and figures of the history of the kinetic elements at the base
of the flagellum have been cited and copied in practically every
text-book dealing with the Protozoa and have had a wide influence
in theoretical protozoology. Other keen observers, however, have
sought in vain for evidence corroborating this history. In the
absence of such confirmation and in view of the multitude of differ-
ent observers who find a simpler explanation in many different
types of trypanosomes, including that of the little owl (see Minchin,
Robertson, Sergent, et al.), Schaudinn's interpretation and conclu-
sions can be accepted only with many reservations.
The essential point in Schaudinn's description was the origin by
heteropolar mitotic division of the nucleus of a recently " fertilized
cell," of a larger nucleus which becomes the nucleus of the cell,
and a smaller nucleus which forms the kinetic complex. This
smaller nucleus divides again by mitosis, also heteropolar, the smaller
portion becoming the basal granule which forms the flagellum and
the "myonemes" of the undulating membrane, while the larger
portion remains intact as a homogeneous deeply-staining granule.
The contested points in regard to this phase of Schaudinn's work
are, first, the "fertilized cell" of the trypanosome, which is now
generally regarded as a stage in the life history of an entirely differ-
ent parasite of the little owl (Minchin enumerates no less than five
different types of protozoon parasites which may live simultaneously
in the blood of this owl). A second contested point is the origin
of the kinetic elements of the cytoplasm by mitosis. Other con-
tested points and untenable conclusions drawn from them have to
do with sex differentiation and parthenogenesis which need not be
considered here.
It is not at all impossible that Schaudinn may have seen the emer-
gence of a kinetic element from the endosome of the nucleus as de-
scribed above in the case of Dimastigamoeba gruberi, and the similar
emergence of a basal granule or blepharoplast from a chromatoid
mass in the cytoplasm. The interpretation of such possible stages
as mitotic nuclear division, and the smaller products of such division
as nuclei, has led to numerous theoretical developments which have
only a narrow basis of fact. Two years after Schaudinn's paper
appeared, Woodcock translated it into English and conferred the
name " kinetonucleus " on the smaller body resulting from the
heteropolar mitotic division and the name " trophonucleus " on the
nucleus of the cell. Schaudinn himself was the first to announce
this binucleate character of the trypanosome body and the hypoth-
esis was taken up by his followers, Prowazek, and notably Hartmann
(1907). The latter developed the conception into an elaborate
view of original nuclear dualism upon the basis of which he created
a special group of the Protozoa including trypanosome-like flagel-
DERIVED ORGANIZATION 113
lates and hemosporidia, which he called the "Biiiucleata."1 As
Doflein points out, not only do the hemosporidia have no blepharo-
plasts as do the trypanosornes, but blepharoplasts in the latter are
not to be considered nuclei. In this use of the term blepharoplast
Doflein includes the structure to which Woodcock gave the name
kinetonucleus, but he employs the term in a special sense as a
kinetic element, while German writers generally use it for structures
of widely different significance. Thus Schaudinn, although con-
vinced of its nuclear character, nevertheless called it a blepharo-
plast. French writers, as a rule, speak of it as a centrosome (e. g.,
Mesnil, Laveran, etc.) as do some English observers (e. g., Moore
and Breinl) ; many of the latter, however, follow the original nuclear
interpretation, Bradford and Plimmer following Stassano, regarding
it as a " micronucleus " and comparing it with the smaller nucleus
of the ciliates, while Woodcock and Minchin considered it a "true
nucleus."
The essence of the problem indicated by the various usages of
these familiar terms comes down to a decision as to whether the
so-called kinetonucleus, by which is meant the relatively large
chromatoid body in the cytoplasm and closely connected with the
basal granule, is a nucleus, or a kinetic center of the cell, or neither.
Woodcock's term connotes a happy combination of both nuclear and
kinetic possibilities; the kinetic function evident from its relation to
basal granules or blepharoplasts, while its nuclear characteristic is
seen mainly in the deeply-staining chromatin-like substance of which
it is composed as well as by its frequent connection with the nucleus.
Some writers, notably Rosenbusch (1909), giving free play to the
imagination, and under the conviction that it is a nucleus, describe
it as such, with centriole, "karyosome," nuclear space which may
contain chromatin granules, and a nuclear membrane. The
extremely minute size of this organoid and the pranks which the
Romanowsky stain or any of its modifications may play with it, as
they do with structures of the actual nucleus, together with a fertile
imagination, are sufficient to account for the perfect nuclear type
which Rosenbusch, for example, described. Other observers, while
maintaining its nuclear character, do not accept this extreme inter-
pretation; Minchin, for example, describes it as a "mass of plastin
impregnated with chromatin staining very deeply, rounded, oval,
or even rod-like in shape" (Prot., p. 2SS).
If we bear in mind the many types of granules in the cell which
stain like chromatin with certain dyes, it seems unnecessary, to say
the least, to make the term nucleus, which stands for a well-known
and easily recognized organoid of the cell, elastic enough to embrace
cytoplasmic bodies in regard to which there is so little evidence of
nuclear structure or nuclear function. In well fixed and stained
1 For critiques of the Binucleata, see particularly Minchin (1912), Dobell (1911).
8
114 BIOLOGY OF THE PROTOZOA
material the so-called kinetonucleus affords little evidence of nuclear
make-up ; it appears as a homogeneous mass of chromatoid material
which divides into equal parts prior to division of the nucleus. Such
features do not make it a nucleus any more than similar features
make nuclei of pyrenoids, or of other plastids of the cell. Func-
tionally, and unlike the nucleus, it is not necessary for the vital
activities of the organism, as shown by the experiments of Werbitski
(1910), confirmed by others, in which by the use of certain chemicals
(e. g., pyronine) the "kinetonucleus" of Trypanosoma brucei disap-
pears without any effect upon the movements and reproduction of
the trypanosome, a race being formed in which this organoid is
absent. Nor can the " kinetonucleus " be regarded as a centrosome,
for although closely connected with basal granules, it never behaves
like an attraction center. With the exception of Schaudinn's account
and the overdrawn account by Rosenbusch there is no evidence that
it divides by mitosis; it never develops chromatin structures which
by any stretch of the imagination can be called chromosomes.
If the " kinetonucleus " is not a nucleus nor an active kinetic center
of the cell, then any misleading appellation such as kinetonucleus,
centrosome, or blepharoplast, which indicates co-partnership with
the actual cell nucleus or other easily recognizable organoid, should
be discarded together with the supplementary term trophonucleus.
Among names suggested to replace the term kinetonucleus is " kine-
toplast" used by Wenyon, Dobell, and Alexeieff, and "parabasal
body" (Janicki) as used by Kofoid.
The non-committal term parabasal body was first employed by
Janicki (1915) to designate an accessory structure in the kinetic
complex of Lophomonas (Fig. 105, p. 211). Analogous structures
have since been found in practically all of the parasitic flagellates
thus far described, although not found in free-living types generally.
It is present as a globular mass of deeply-staining substance close
to the blepharoplasts of types like Trypanosoma brucei, Bodo edax
or Bodo lacertae (Fig. 33, p. 65) ; as an elongate mass in most of the
Cryptobia species (Fig. 61, C) ; as a long basal filament in Trichomonas
augusta (Fig. 77, p. 145) ; or Chilomastix mesnili; as a spirally coiled
mass in Devescovina striata (Fig. 62, F), etc. It apparently differs
in size and form in different phases of the same organism as in Bodo
lacertae where, in addition to the globular form, it may be rod-like
or partly coiled or absent altogether. In Chilomastix mesnili an
homologous rod-like body, termed the parastyle, arises from a second
blepharoplast (Kofoid and Swezy, 1920) (Fig. 60).
The most extensive work on the parabasal body has been carried
out by Kofoid and his followers who regard this structure not as a
nucleus nor as a kinetic center, but as a "kinetic reservoir" or a
reservoir of substances which are used by the animal in its kinetic
activities under the conditions of its dense environmental medium.
DERIVED ORGANIZATION 115
This substance, according to Kofoid, appears to form at the expense
of the nuclear chromatin and increases or decreases— that is, the
parabasal body becomes larger or smaller apparently in relation to
metabolic demands. When the parabasal body is poor in chromatin
the blepharoplast and nucleus may be rich and vice versa. "Our
data are too incomplete to give a clear picture of the process, but
as far as they go they suggest the origin of the parabasal at the
expense of the chromatin of the nucleus, the movement of stain-
able substance on the rhizoplast, either to or from the blepharoplast
at the base of the flagella, and the wax and wane of the parabasal"
(Kofoid, 1916, p. 5). This interpretation is strengthened by the
positive reaction of the parabasal of some species to the Feulgen
nucleal test (see p. 57).
Kofoid's interesting and suggestive interpretation of the nature
of the parabasal is very well sustained by the morphological rela-
tions of blepharoplast, nucleus and parabasal body in widely diverg-
ent types of flagellates. Morphologically, a series representing a
gradually increasing complexity is illustrated by : (1) Dimastigamoeba
gruberi, in which the blepharoplast arises by division of the intra-
nuclear kinetic center and remains connected with it by a centro-
desmose or, in this case, a cytoplasmic rhizoplast; (2) Scytmnonas
subtilis in which the blepharoplast is not connected with the nucleus
and gives rise only to the flagella ; (3) Bodo edax, or species of Cryp-
tobia in which a large chromatoid mass, the parabasal body, is con-
nected by rhizoplasts with the blepharoplast, or may be indepen-
dent of it; (4) Bodo lacertae in which basal bodies (arising from the
blepharoplast), blepharoplast and parabasal body are all indepen-
dent; (5) Giardia augusta, in which the independent blepharoplast,
basal bodies and parabasal body are all double and arranged in
perfect bilateral symmetry; (6) Calonympha grassii (Fig. 63), in
which nuclei, parabasal bodies, blepharoplasts and basal bodies are
multiple and in which axial threads (rhizoplasts) unite to form a
central axial supporting rod; (7) Trichonympha campanula, in which
the blepharoplast (centroblepharoplast) acts as a centrosome in
mitosis while long rhizoplasts connecting distal basal bodies with
the blepharoplast form a complex radial system of astral rays (Figs.
61 to 65).
In many cases the blepharoplast, which is the central element of
the kinetic complex, remains connected with the nucleus by a rhizo-
plast as a permanent record of the intranuclear origin of the entire
complex (Fig. 62). In many cases the blepharoplast is double,
as in most biflagellated forms; in others it is triple as in Trimastig-
amoeba p)iilippinensis or Chilomastix mesnili (Fig. 60, B); in some
it is quadruple, or contains four basal bodies as in Trichomonas; in
others it is multiple, forming a ring of blepharoplasts about a
bundle of flagella as in Lophomonas blattarum (Fig. 105, p. 211).
116
BIOLOGY OF THE PROTOZOA
Finally in flagellates with multiple nuclei (family Calonymphidae) ,
in addition to a number of free blepharoplasts and parabasal bodies,
each nucleus is accompanied by a blepharoplast which gives rise
Fig. 62. — Types of parabasal body. A, Polymastix; B, Trypanosoma cruzi; C,
Cryptobia sp.; D, Bodo lacertae; E, Prowazekia sp.; F, Devescovina striata; G, Herpeto-
monas musca-dome.sticae. (b) Blepharoplast; (p) parabasal body; (n) nucleus; (x)
axostyle. (A, C, D, G, after iSwezy; B, after Chagas; E and F, after Doflein.)
to three uniform flagella and one longer, band-formed flagellum, by
a parabasal body, and by a rhizoplast (axial strand, Fig. 63).
Many of these aggregations of kinetic elements are sufficiently
DERIVED ORGANIZATION
117
complex to justify the term neuromotor system of Sharp and Kofoid
and appear to form a coordinated whole, as shown by the reaction
after maceration when they retain their connections and remain
together for some time after the supporting protoplasm has disap-
peared (Trichomonas, Kofoid). The term is certainly justified in
connection with the remarkable kinetic structures of flagellates
belonging to the family Trichonymphidae. In Trichonympha cam-
panula, Kofoid and Swezy (1919) describe the system as composed
of an external coating of cilia-like motile organs, three zones of
Fig. 63. — Calonympha grassii Foa. (From Doflein.)
flagella with their basal bodies, rhizoplasts connecting basal bodies
with a great anteriorly placed blepharoplast, and more deeply-lying
myonemes which apparently are not connected with the blepharo-
plast (Fig. 64). Kofoid and Swezy regard the central organoid as a
kind of superblepharoplast, calling it the "centroblepharoplast" since
it has the attributes of a centrosome. When it divides the entire
aggregate of kinetic elements of the cortical zone divides with it,
forming a mitotic figure with centrosomes, central spindle and astral
rays (Fig. 54). The connecting fibrils of the centrosomes, unlike
118
BIOLOGY OF THE PROTOZOA
the centrodesmose in Metazoa, remain outside of the nucleus (as
it does in many other flagellates) and is called the paradesmose by
Kofoid to distinguish it from the centrodesmose or central spindle.
From this review of the cytoplasmic kinetic elements in the flag-
ellates it is apparent that in endobasal bodies, basal bodies, and
parabasal bodies we have to do with structures closely connected
with the kinetic activities of the organism and closely related to
each other. The chromatoid substance of which they are composed
may or may not be chromatin, although the evidence adduced indi-
cates that it arises from the nucleus and in some cases is similar to
chromatin in its staining reactions. It does not behave like chro-
^V^' V^Vf -V-V^C"
" i, J, ^ ■*.**--. A« L.vJ '/
Fig. 64. — Trichonympha campanula Kof. and Swez. (After Kofoid and Swezy.)
matin during division of the cell, but like pyrenoids, or chromato-
phores, where each granule reproduces its like by division; nor
does it afford any evidence of constructive metabolic activities in
the cell. For these reasons I believe, with Kofoid, that the term
"parabasal body" expresses the relationships and functional activi-
ties of the so-called "kinetonucleus" much better than does the
latter term and should take its place in literature dealing with the
Protozoa. The interpretation of kinetonucleus and parabasals,
however, is still incomplete. In Trypanosoma, as stated above, the
kinetic element known as the "kinetonucleus" (aud.) or the "para-
basal" (Kofoid, Swezy, et al.) gives a positive Feulgen nucleal
reaction, indicating the presence of thymonucleic acid (Bresslau and
Scremin, 1924; Robertson, 1928; Jirovec, 1927; DaCunha and
DERIVED ORGANIZATION
119
m-
Muniz, 192S). Lwoff (1931) finds that this nucleal reaction is
confined to a cortical zone of the body in question, and holds that
probably in all cases the so-called kinetonucleus is composed of
two quite different substances, one of which, the medullary sub-
stance according to the observations of Grasse (1926), is apparently
of lipoid nature. Lwoff (1931) gives a new interpretation of para-
basals and kinetonuclei in the simpler parasitic flagellates such as
Leptomonas ctenocephali (Fig. 65). Here the so-called "parabasal
filament" (p.f.) does not originate from
the blepharoplast ("mastigosome" of Lwoff
= m) but from a flagellar ring (r) quite re-
moved from and not connected with the
blepharoplast. The latter, however, gives
rise to and is connected with what he terms
the "kinetonucleus," which he shows has
a chromatin cortex (k). The latter gives
rise to still another element which he calls
the "paranuclear" body (c.Bin). In this
case the "parabasal" is not derived from
the blepharoplast, but is of entirely differ-
ent origin from parabasals of other forms.
What Lwoff calls the "kinetonucleus" has
the same relation to the blepharoplast as
do the majority of parabasals (e. g.,
Crithidia, Trypanosoma cruzi, etc., Fig. 61).
Further study of these perplexing fibrils in
flagellates and particularly in the hyper-
mastigida, must be made before the puzzle
of exact homologies can be solved.
3. Other Cytoplasmic Kinetic Elements.—
A unique cytoplasmic kinetic element, ap-
parently homologous with the centrobleph-
aroplast of certain flagellates, is found
in some types of Heliozoa. The non-com-
mittal name central granule (Centralkorn)
was given to this structure by Grenadier
(1869), who was the first to observe it.
In some types it lies in the geometrical
center of the cell (Acanthocystis aculeata, Sphaerastrumfockei, Raphi-
diophrys pallida, etc.) ; in other types it is ex centric (Dimorpha m utans,
Wagnerella borealis) or absent altogether (Actinophrys sol, Actino-
sphaerium eichhornii, Camptonema nutans, etc.). In the ordinary
vegetative activities of the cell, radiating fibers starting from the
central grain extend through the protoplasm to the periphery, where
they form the axial filaments of the pseudopodia (Fig. 66) . In division
stages of the cell, the central grain first divides forming an amphi-
— I
— k
"c.Bm
-p.f.
Fig. 65. — Lepto m onas
ctenocephali. Parabasal ap-
paratus consisting of peri-
flagellar ring and posteriorly
directed filament; "kineto-
nucleus" and "mastigosome"
(basal body). (After A. and
M. Lwoff, Bull, biologique de
la France et de la Belgique,
courtesy of Prof. N. Caullery
and Les presses Universitaires
de France.)
120
BIOLOGY OF THE PROTOZOA
aster consisting of centrosomes, centrodesmose and astral rays made
up of the radiating fibrils (Fig. 50, p. 95 — see also Trichonympha cam-
panula) . Stern (1914) , however, found that mitotic spindles may arise
in Acanthocystis without any connection with the central granule (Fig.
67) . The central grain, however, takes no part in reproduction by bud-
ding, whereby ameboid or flagellated buds are formed which contain
a nucleus derived from the parent cell nucleus, but no central grain.
This nucleus, however, contains an endobasal body which divides
and one of the daughter granules emerges from the nucleus as it
does in Dimastigamoeba gruberi (p. 34), but retains its eentrodes-
mose for some time and ultimately forms the central grain of the
Fig. 66. — Relation of axial filaments to nuclei. Section of Actinophrys sol with
axial filaments arising from intranuclear granules in recently divided nuclei. (After
Schaudinn.)
adult organism (Schaudinn, 1896; Zuelzer, 1909; Acanthocystis acu-
leata, Wag nerd I a borealis, Fig. 50). Similarity with the centrobleph-
aroplast in flagellates is thus shown (1) by its origin from an
intranuclear centriole; (2) by its relation to axial filaments which are
homologous with rhizoplasts; (3) by its history during mitosis. The
analogy is further strengthened by its relation to the flagella and to
the axopodia which are simultaneously present in some of the Helio-
flagellida {Actinomonas mirabilis, Kent, Ciliophrys marina, Caullery,
and Dimorpha m titans, Gruber). In Dimorpha m utans (Fig. 13, p. 34),
the central grain lies near one pole of the cell where it forms the
basal body of the two flagella as well as the focal point for the axial
filaments; here flagella and axial filaments appear to be homologous
DERIVED ORGANIZATION
121
Fig. G7. — Acanthocystis aculeata; centroblepharoplasts disconnected from nuclear
spindle. (After Stern.)
122 BIOLOGY OF THE PROTOZOA
structures. According to Zuelzer the pseudopodia of Wagnerella
borealis are withdrawn at times, owing to the contraction of the
entire complex of radiating fibrils, and basal bodies lying at the
bases of the axopodia become grouped in a zone of granules about
the central grain. When the pseudopodia are again formed the
granules migrate centrifugally to the periphery and, as basal bodies,
give rise to the axial filaments.
In Heliozoa without a central granule the axial filaments in some
cases center in the nucleus in which there are many distinct and
definite granules of uniform size distributed about the outer zone,
from each of which an axial filament appears to rise (Fig. 66).
In Camptonema nutans the nuclei are multiple and, according to
Schaudinn, each one gives rise to a single pseudopodial element,
but in Actinosphaerium eichhornii, which is also multinucleate, the
axial filaments apparently have no connection with either nuclei or
central kinetic elements.
Apart from kinetic elements like centroblepharoplasts which, at
the same time, are centers of mitotic activity of the nucleus and of
kinetic activity of the motile organs, there are comparatively few
examples of kinetic elements comparable with centrosomes of Meta-
zoa. These are best represented in non-motile organisms such as
Sporozoa, whereas in freely-moving types there is always some pecu-
liar feature which makes the homology with centrosomes doubtful.
A frequently cited example of a centrosome in Protozoa was first
described by Hertwig in the case of Actinosphaerium eichhornii
(Fig. 6<S). Here, during the formation of the first maturation
spindle minute granules of chromatoid substance are cast out
of the nucleus and condensed into one or two minute centrioles from
which fibrillar structures radiate into the cytoplasm and throughout
the nucleus. This structure, however, has no permanent relation
to the cytoplasm or nucleus, but disappears after the first maturation
spindle is formed while subsequent maturation spindles and spindles
of division stages are characterized by pole plate formation (see
p. 65). Much more typical centrosomes are found by Arndt (1924)
in Hartmannella klitzkei (Fig. 58, p. 106) and in the Gregarinida,
especially in the Monocystis types, where they have been described
by Leger, Brasil, Mulsow, Doflein, and others. In Monocystis
rostrata, for example, a single centrosome with marked astral radi-
ations lies outside the nuclear membrane (Fig. 55, p. 101). An am-
phiaster is formed as in egg cells of Metazoa, and a complete mitotic
figure results. Similar centrosomes occur in Urospora lagidis, St.,
Gonospora varia, Leger, and Stylorhynchus longicollis, St.
In general we do not find the same types of kinetic elements in
Infusoria that are found in other forms of Protozoa. Blepharo-
plasts, parabasal bodies and centrosomes are still unknown in
filiates, although certain peculiar kinetic elements are present here
DERI VED ORG A NIZA TION
123
which may turn out to be homologous with one or more of these
structures. Endobasal bodies, however, are known in micronuclei
of a fewT types (e. g., Uroleptus mobilis, Oxytricha fallax) and in some
macro nuclei (e. g., Chilodon cucullw, Fig. 30, p. 62). On the other
hand, certain special types of cytoplasmic kinetic elements such as
myonemes, motorium, and conductile fibers, are characteristic of
the ciliates, some of which become highly complicated coordinated
neuromotor elements.
v ',1 :.-^..~~'J — '<•*■
D
!■■};
'■,'■ i
X
fflSfes
'.•■';-:/,. ;:^.?J 'l/'fc-'
7^
Fig. 68. — Actinosphaerium eichhornii; origin of centrosome from nucleus.
(After Hertwig.)
The most widely distributed of the kinetic elements are the basal
granules of the cilia, which are situated in the contractile zone of
the cortex and form a part of the silver line system (see p. 80).
The exact nature of these extremely minute bodies is unknown and
their origin or renewal is purely hypothetical. Collin (1909) and
Entz (1909) record some observations which suggest their derivation
from nuclei (Entz) or at least some connection with them (Collin).
A single basal body gives rise to a single cilium (Fig. 69) but groups
of them are found at the bases of the more complicated membranes,
124
BIOLOGY OF THE PROTOZOA
membranelles and cirri, the number varying with the species.
Thus Maier describes 2 in the membranelles of Nyctoiherus cordi-
formis and many of them arranged in a row in the membranelle of
Sientor niger; in undulating membranes of the vorticellids Maier
and Schroder describe 3 rows of basal granules while in the "par-
oral" and "endoral" membranes of Glaucoma scintillans there are
5 and 10 rows of basal granules respectively (Maier). In the cirri
of Stylonychia histrio which are circular in cross-section, according
to Maier, there is a discoidal plate of basal bodies. Alverdes (1922)
found that an isolated cilinm will beat if the basal body is attached,
not otherwise.
.;,••:; Uu l»ii
*&/$/$
a
a
Fig. 69. — Cilia and myonemes of Infusoria, a, Membrane and periplast of Sim-
tor coeruleus; b, c, and e, rows of cilia of same; d, myoneme of same: /, optical section
of membrane and myonemes of same, and g, optical section of cortex of Holoplirya
discolor; m, myoneme; t, myoneme canal, (a, b, e, after Johnson; c, d, f, and g, after
Butschli.)
A perplexing series of structures consisting of granules and con-
necting fibrils is found in some holotrichous ciliates. In Chla mydodon
mnemosyne, for example, a double row of granules with connectives
running around the body near the margin and visible in life as a
hyaline band, and a similar but more ladder-like structure is present
in the oral vestibule of Glaucoma frontata (Fig. 8, p. 29). It is
possible, but not demonstrated, that these structures belong to the
same category as the girdle around the posterior end of Yorticella
and represent the infraciliature (Chatton) or special tracts of the
silver line system.
Mi/on fines.— One of the most striking characteristics of certain
types of ciliates is their power of contraction. A fully-expanded
DERIVED ORGANIZATION 125
Spirostomum ambiguum may be 2 mm. in length but, on irritation,
it suddenly contracts to one-quarter that size, or a Trachelocerca
phoenicopterus contracts to one-twelfth its original length (Lebedew) ;
a Folliculina ampulla with its great peristomial lobes widely out-
spread quickly folds itself completely into its comparatively narrow
tube (Figs. 94, 206), or an entire colony of widely distended indi-
viduals of Zooihamnium arbuscula contracts instantly into a minute
ball. These varied movements which are quite independent of
movements of translation or rotation, are due to the contraction
of specialized muscle-like fibrils, the myonemes. These are long,
delicate, contractile threads, circular or band-like in cross-section
situated in the cortical zone and running throughout the entire
length of the body, either straight (Stentor) or spirally (Spiro-
stomum). In some cases a second set of myonemes run transversely
about the body as in the peristomial regions of Campanella umbellaria
or various species of Stentor. The myonemes of Stentor coeruleus
or Prorodon feres- lie in characteristic canals, which appear hyaline
in contrast with the granular adjacent "ribs" of the ectoplasm.
Their finer structure has been made out in only a few types, in
Stentor coeruleus perhaps better than in any other. Here Schroder
describes a typical cross-striping due to alternate rows of light and
dark substance (Fig. 69, d).
In the majority of cases the contractile effect of the activity of
myonemes is possible only by their intimate connection with the
firm membranous cortex which encloses the entire animal, a con-
nection which makes it possible for a coordinated contraction of the
whole animal at once. A retraction of special regions of the organ-
ism involves the attachment of one end of the contractile element
to some relatively fixed structure, as muscles in vertebrates are
attached to the endoskeleton (Fig. 70). In many cases the general
cortex serves this purpose as in the sphincter-like myonemes of the
Vorticellidse (Schroder), or the retractile elements of the "seizing
organ" or "tongue" of Didinium nasutum (Fig. 98, p. 187), or the
closing apparatus of the operculum-bearing types of ciliates. In
some cases, however, especially in parasitic ciliates like Ophryoscolex
or Diplodinium ecaudatum, there is a specialized differentiation of
the "cuticle" discovered by Gunther and well described by Sharp.
These peculiar differentiations function according to the latter
observer, as endoskeletal structures for the attachment of conspic-
uous band-form myonemes, which serve as retractor strands for
drawing into the body a characteristic gullet and adjacent organ-
oids. These skeletal elements are formed from the ectoplasm and
are hardened, according to Eberlein, by a deposit of silicic acid which,
as Sharp implies, may be the explanation of their rigid but brittle
nature.
Myonemes or analogous organoids are not confined to the ciliates
126
BIOLOGY OF THE PROTOZOA
but may be found in some types of Gregarinida (see p. 535) and in
one group of the Radiolaria. The so-called myonemes of the
Trypanosomidae, however, are very doubtful kinetic elements but,
more probably, are analogous to the cuticular markings which are
Fig. 70. — Epistylis plicatilis; longitudinal section showing myonemes (MY) from
membranelles to base of cell. (After Schroder.)
frequently found on the periplast of flagellates. In some of the
gregarines, myonemes form a thick layer of extremely fine fibrils in
the cortex, running longitudinally and circularly, or possibly spirally,
about the cell, their contractions giving rise to the peristaltic move-
ment so characteristic of these forms (see p. 535.)
DERIVED ORGANIZATION 127
Myophrisks of the Radiolaria are contractile strands which are
fastened by their distal ends to the extremities of the axial bars of
the Acantharia. The proximal ends fray out into fibrils which are
lost in the reticulum of the gelatinous mantle or calymma, of the
ectoplasm. By their contractions the calymma is drawn up to the
ends of the axial bars whereby the diameter of the organisms is
increased and its specific gravity decreased, the reverse occurring
with their relaxation. The myonemes thus seem to play a part in
the hydrostatic activities of these Radiolaria, although this func-
tion is difficult to understand, since the change in specific gravity
is usually interpreted as a means by which these motionless forms
escape from adverse conditions on the surface. We should expect,
however, that rough water or other surface conditions detrimental
to the organisms, would be sources of stimulation which should
cause the contractile elements to contract and thus to defeat their
apparent purpose by decreasing the specific gravity.
Coordinating Fibers. — If a single cilium of a resting Pleuronema
be touched the entire organism responds. Here and in similar cases
there appears to be a definite tactile function. In flagellates also
it is not improbable that certain flagella, as the anterior flagella of
Caduceia theobromae described by Franca (1918), or indeed possibly
all flagella have a more or less well-developed sensory function.
In ciliates, such as Paramecium caudatum, with a uniform coating
of cilia, the motile elements do not all beat simultaneously, but a
wave of contraction, beginning at the anterior end, passes down the
cell to the posterior end. Cilia in the same transverse row beat
synchronously, but each cilium in a longitudinal row begins its
beat shortly after the cilium anterior to it has started and before it
has ended its beat (Verworn). The cilia of transverse rows are thus
synchronous, those of longitudinal rows metachronous in their con-
tractions, a phenomenon which accounts for the wave-like movement
of undulating membranes which are formed of fused cilia of longi-
tudinal rows (well shown in the undulating membranes of the
Pleuronemidae). According to Alverdes (1922) isolated cilia with
basal body may act independently of a coordinating system but
they do not react to stimuli.
This regularity of cilia movement which may be easily seen in
the uniform ciliary coating of Nyctotherus ovalis from the cockroach,
indicates the transmission of impulses and the activity of some coor-
dinating mechanism in the cell which today we attribute to the
silver line system. Entz, Maier, Schuberg and many other observers
have found distinct fibers connecting the basal bodies of protozoon
cilia and have generally interpreted them as myonemes. Since
forms like Nyctotherus, Frontonia, Paramedium, etc., which do not
contract, show the same rhythmical action of the cilia, it is prob-
able that the threads connecting their basal bodies are not myo-
128
BIOLOGY OF THE PROTOZOA
nemes but coordinating fibrils. It is conceivable, moreover, that
myonemes in a generalized condition may be both coordinating
and contractile in function. In some cases, however, two distinct
sets of fibrils have been observed, one of which is interpreted as
contractile, the other as conductile. Thus Xeresheimer described
"myophanes" and "neurophanes" in Stentor coeruleus, and Clima-
costomum virens, the former extending the entire length of the
body, the latter only from the base to the center (Fig. 71). On
a priori grounds it would seem that, as Yocom points out, Neres-
,11'^i
%!-'-
Fig. 71.
■Climacosiomum sp. To show neurophanes (NE) and myophanes (MY).
(Original.)
heimer made an unfortunate application of his two terms, his
neurophane fibers, for example, to which lie ascribes a transmitting
function, being situated in the least advantageous position for the
functions of irritability or conductility, Jennings having shown that
the first and most strongly marked reactions to certain stimuli in
ciliates appear in the anterior region, a result confirmed by Alverdes
(1922).
The more recent observations of Sharp, Yocom, and Taylor, all
from Kofoid's laboratory, afford more striking evidence of specific
conducting or coordinating fibrils in ciliates, although not connected
DERIVED ORGANIZATION 129
with the silver line system. In connection with Dijplodinium
ecaudatum, Sharp described, for the first time in the literature, a
system of connected fibrils emanating from a common mass of
differentiated protoplasm, which he called a "motorium," the whole
system being termed the 'neuromotor apparatus." The motorium
is situated in the ectoplasm of the anterior end of the organism
between the two zones (adoral and dorsal) of membranelles (Fig. 2, M,
p. 20.) From it as a center a number of fibers pass to different regions
of contractile activity. These fibers are named and interpreted by
Sharp as: (1) A circiimesophageal ring strand running to a definite
ring of substance similar to that of the motorium encircling the gullet
(esophageal ring), from which other fibers apparently take their
origin and run posteriorly along the retractile gullet; (2) a dorsal
motor strand running to the bases of the adoral membranelles; (3)
opercular fibers or a group of fibers running to the operculum
(see Fig. 2).
The delicacy of structure and the position of this amazingly com-
plex aggregate are sufficient evidence to disprove any hypothesis of
a supporting function. Self-perpetuation of the elements by division
indicates no relationship to supporting structures such as trichites
(oral basket) in the mouth regions of forms belonging to the family
Chlamydodontidae. Their position in the cell and the attachments
of the several fibrils are arguments against their interpretation as
myonemes.
McDonald (1922) has recently described a somewhat similar
neuromotor system in Balantidium coli and B. mis. Here an ante-
rior motorium gives rise to (1) a ring-form fibril which passes around
the adoral cilia region and (2) a similar ring fibril passing around
the gullet. Other elements of the system consist of basal granules
of the cilia, from which rhizoplasts pass inward to the central region
of the cell. At the point where each rhizoplast enters the endoplasm
is a granular thickening from which a radial fibril passes toward
the periphery where it ends blindly.
Many other ciliates have been added to this list of motorium-
bearing forms, but we are still ignorant as to the origin and history
of the motorium during division. Amongst these forms are: Para-
mecium (Rees), Glaucoma frontata (Calkins and Bowling, 1929),
Uroleptus halseyi (Calkins, 1930), Concho phthiri us mytili (Kidder,
1933), and others. Until we have some positive evidence of its origin
and perpetuation by division, the interpretation of the motorium as a
definite organoid of the cell must be held in reserve (cf. Ilees, 1931;
Turner, 1933).
Evidence in favor of a conductile function of such a neuromotor
system is furnished by the observations of Yocom (1918) and the
micro-dissection experiments of Taylor (1920) on Ewplotes patella.
In Euplotidae, apart from the motile organs, contractility is un-
9
a- a.
-"'■■kg.
Fig. 72.— Micro-dissection of Euplotes patella. A, individual with lateral cut;
showing distribution of the cellular structures: B, neuromotor apparatus isolated; C,
an anal cirrus with accompanying structures; D, an isolated membranelle; F, the
five anal cirri; (a.c.) anal cirri fibers; (a.p.) basal plates of the anal cirri; (b.g.) basal
granules; (c) cirrus; (e.g.) ectoplasmic granules; (f.p.) fiber plate; (m.f.) membranelle
fiber; (m) motorium; (p.l.) membranelle plates. (After Taylor.)
(130)
DERIVED ORGANIZATION 131
known, nevertheless the literature contains many references to
myonemes in the several species. Distinct fibrils in these hypo-
trichs which Engelmann regarded as nerve-like in function, have
been interpreted in the main as supporting or contracting elements
(Maupas, Biitschli, Schuberg, Maier, etc.). Prowazek worked them
out in some detail in the case of Euplotes harpa and Griffin (1910)
in the case of E. worcesteri, both observers regarding them as con-
tractile in function. Yocom has studied them more recently in
Euplotes patella and a complex system, comparable with that of
Diplodinium ecaudatum is described. A definitely staining bilobed
mass of differentiated protoplasm which Yocom identifies as a
motorium is situated in the ectoplasm near the right anterior angle
of the triangular peristome (Fig. 72, m).
From one lobe of this mass a set of five prominent longitudinal
fibrils which seem to emerge as a single strand, run to the bases of
the five anal cirri near the posterior end (a. c); from the other lobe
a single fibril passes along the inner margin of the anterior lip and
down the left side of the peristome closely following the bases of the
frontal and peristomial membranelles. In the anterior lip it gives
rise to a simple network of branching fibrils (Yocom). The other
cirri of the ventral surface are not thus connected with the motorium,
and each appears to have an entirely independent set of fibers which
run into the endoplasm and disappear in different directions.
Yocom attempted, rather unsuccessfully, to homologize the
motorium with the blepharoplast of flagellates; until further obser-
vations are forthcoming in regard to the activities of this structure
at different periods of cell life it seems more expedient to regard the
motorium as a structure peculiar to the ciliates than to add it to
the already over-burdened conception of the blepharoplast.
The only direct evidence of the physiological nature of the neuro-
motor complex is furnished by Taylor's micro-dissection experi-
ments with the same organism, Euplotes patella (Fig. 72). Cutting
the fibers connecting the anal cirri with the motorium had a notice-
able effect on the normal reactions of creeping, swimming and
turning, while severing the membranelle fiber led to character-
istic irregularities in the usually coordinated activities of the mem-
branelles and to abnormal spiral revolutions while swimming.
Destruction of the motorium, finally, resulted in uncoordinated
movements of the membranelles and of the anal cirri. This evi-
dence, excellent as it is, rests upon an exceedingly delicate technique
and upon the personal interpretation or estimation of minute differ-
ences between normal and induced reactions. It is a line of work,
however, which invites further research and promises fruitful results.
CHAPTER IV.
DERIVED ORGANIZATION. TAXONOMIC STRUCTURES.
Although fundamentally important in vital functions, the
various granules and structures which have been described can
hardly be regarded as obvious or visible characteristics of Protozoa.
Careful study, involving elaborate technical methods, is necessary
to reveal the parts they play, and for some, at least, even this has
not yet yielded positive results.
The visible characteristics, those we see upon casual examination
with a microscope— form, color, movement, shells, tests, stalks, etc.
—are secondary in importance in respect to the ultimate vital activi-
ties. It is in connection with these, however, that the Protozoa
are best known and the peculiar fascination which they have for the
microscopist is mainly due to these obvious features. The outer
structures which please the eye, or the motile organoids which cause
the fascinating endless variety of movements, represent the out-
come or product of the activities going on between the various
constituent elements of the protoplasm. Some of them are neces-
sary for the continued life of the organism, some are useful in one
way or another, but not absolutely necessary, and some, e. g., the
scalloped cuirass of Entodinium or the fantastic forms of many
sapropelic types, have no obvious reason for being. These structures
represent the completed derived organization and furnish the obvious
characteristics upon the basis of which the Protozoa are classified.
In some types of Protozoa, even on superficial examination, it
is evident that the aggregate of substances making up the protoplasm
is differentiated into an external zone and an internal, medullary
part. The external portion is usually called ectoplasm, the inner
part endoplasm. The ectoplasm is that part of the protoplasm
which comes in direct contact with the environment. It is the
part through which food substances must pass into the organism
and through which the waste matters of destructive metabolism,
as well as undigested food, must be voided to the outside; it is the
part which first receives external stimuli of various kinds, and it is
the part which gives rise to the more easily visible portions of the
locomotor structures, and to the specializations for support and
protection.
Acting thus as a medium of exchange between the living proto-
plasm and the external world, the ectoplasm has become modified
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 133
in ways that would be impossible for the endoplasm. In simple
cases as, for example, in Amoeba proteus, it is not strikingly differ-
ent from the endoplasm, but in other cases it becomes a complex of
special adaptations and the seat of many important organoids of
the cell. The external zone of protoplasm thus becomes practically
an organ system with structures and functions quite different from
the inner protoplasm. In view of these distinctive features it is
frequently called the cortex.
I. DERIVED STRUCTURES OF THE ENDOPLASM.
METAPLASTIDS.
In the protoplasm of all Protozoa, in addition to the permanent
granules of one kind or another described in the preceding chapter,
there are many types of transitory or fixed products of cell activity
collectively known as metaplasmic granules or metaplastids. All
of these are formed during the vital activities of metabolism some
of them as reserve stores of food substance formed as products of
the building up or anabolic processes of metabolism, others by the
destructive or catabolic processes. In the former group are included
fats, glycogen, paraglycogen, oils, albumin spheres, etc. In the
latter group, as products of destructive metabolism, are included a
great variety of crystals, pigment granules, chitin and pseudo-
chitin, and other more or less widely distributed products. These
products of destructive metabolic activities are frequently so abun-
dant as to give the protoplasm a densely granular appearance.
The form and appearance of these various products of proto-
plasmic activities vary within wide limits and will be discussed more
fully in connection with the different classes of Protozoa. Many
of them serve a useful purpose as reserves in nutrition and other
physiological processes, while a number of them are used for pur-
poses of support, protection, or shell and skeleton building. Gly-
cogen-like bodies are found in a few types of flagellates; true glycogen
occurring in the protoplasm of Pelomyxa palustris according to
Stole (1900), and in the ciliates Paramecium, Opalina, Glaucoma and
Vorticella according to Barfurth. Paraglycogen, also called zooamy-
lum, which differs from glycogen in its solubility and in its color
reactions when subjected to sulphuric acid and iodine, is present in
many ciliates and flagellates as well as in some gregarines.
Oils and fats are widely distributed. Great oil globules are par-
ticularly characteristics of the Radiolaria where, in addition to
serving a useful purpose as reserves of nutriment, they also serve
a hydrostatic function in the activities of different organisms.
Globules of smaller size but conspicuous by their frequently brilliant
coloring are found in many types of flagellates and ciliates.
Protein derivatives in the form of chitin and pseudochitin are
134 BIOLOGY OF THE PROTOZOA
more widely distributed through the entire group of Protozoa,
forming the substratum upon which, or between layers of which,
shell materials are deposited, while cups, tests or "houses," cyst
membranes, stalks, etc., are formed directly from its substance.
Shell and skeleton materials such as calcium carbonate, silica,
strontium sulphate, etc., are likewise formed as results of metabolic
activity, sometimes continuously, as in the lime-stone shells of the
Foraminifera, and sometimes periodically at intervals of saturation
(dictyotic or lorication moment) as in the formation of the charac-
teristic silicious skeletons of the Radiolaria.
Pigments of various hues are also frequently found in Protozoa.
In some cases, as in Actinosphaerium eichhornU, they are formed as
a final product of degeneration of chromatin granules (chromidia) ;
in other cases they are products of metabolic activities following
the digestion of specific kinds of food, as melanin pigment, brown or
black in color, which follows the digestion of hemoglobin by malaria-
causing hemosporidia (Plasmodium species). Specific coloring
matters are found here and there, especially amongst the ciliates,
which have nothing to do with chlorophyll and which are named
according to the organism in which they are found. Thus the blue
coloring matter sometimes called stentorin, is characteristic of
Stentor coeruleus and some species of Folliculina; a red pigment of
Mesodinium rubrum; violet of Blepharisma undulans, etc. ; the colors
being due, probably, to the kind of food that is eaten, since the
pigmentation of the same species is not constant, some forms in the
same culture of Blepharisma undulans, for example, may be colorless
while others are more or less bright pink, or violet, or even purple
in color. The suggestion has been made that specific products of
hydrolysis of certain kinds of food act as intravitam stains on the
protoplasm, thus producing the characteristic colors. In many
cases the pigment is accumulated in masses of varying size repre-
senting excretory matters of one kind or other. Thus we find the
black pigment granules of Metopus sigmoid es and of Tillina magna,
or the brown pigmental masses (phaeodium), characteristic of the
tripylarian Radiolaria.
Other metaplastids that are useful for purposes of protection or
support, are the peculiar trichocysts and trichites found in the
ciliates and about which there is very little definite information
(Fig. 35, p. 67). They are usually embedded in the cortex when fully
formed but the trichocysts at least appear to be formed in the
vicinity of the nucleus as Mitrophanow has shown for Paramecium,
and as I have also observed in the case of Artinoboliiia radians. The
trichocysts at rest are capsules filled with a densely staining (with
iron hematoxylin) substance which is thrown out in the form of
long threads when the organisms are violently irritated as with
poisons of one kind or another. They appear to be connected with
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 135
the silver line system and, according to Bresslau, Kah'l and others,
are here represented by grannies when the trichocysts are undevel-
oped. In such granular form they are sometimes called "pro-
triehocysts" and Bresslau regards them as the source of the "tektin"
which forms artificially produced tests and houses (see p. 137).
The trichites are stiff, usually rod-like supporting structures and are
rarely discharged.
n. DIFFERENTIATIONS OF THE CORTEX.
It is quite probable that there is no such thing as an entirely
naked cell among the Protozoa. Even in Amoeba proteus, the class-
ical example of a naked cell, the ectoplasm is covered by a delicate,
viscous hyaline zone of modified protoplasm. Hofer, Verworn,
and others, have noted it in connection with food taking; Schaeffer
(1917), in connection with movement claiming that it is a third
kind of protoplasm in addition to ectoplasm and endoplasm and
Chambers (1915) came across it in connection with micro-dissection
experiments. Among Sporozoa and Infusoria it has been described
in many species, and in flagellates and ciliates it is not infrequently
characterized by definite markings or sculpturing. It is the most
external portion of the cell and is distinguished from the remainder
of the cortex by the special name periplast or pellicle.
The periplast always fits the body closely, dividing when the
body divides. In Paramecium caudatum during plasmolysis it is
extremely delicate, but may be seen when it becomes separated
from the rest of the cortex and distended by the accumulation of
fluids. In other cases it is much more definite and membrane-like
as in Cochliopodium bilimbosum (Fig. 9, p. 31), or in the loricate
ciliates such as Euplotes harpa, Uronychia setigera and their allies.
Periplasts are frequently delicate enough to give way to forces
generated within the body, but elastic enough not to break, a phe-
nomenon resulting in peristaltic movement which is not infrequent
in Gregarinida (e. g., Monocysti* agilis) and in some flagellates.
Such organisms are said to be "metabolic" and the peculiar motion
is sometimes called "euglenoid movement."
In many cases the periplast is ornamented by striations which
usually run obliquely down the cell; in some cases by ridges; by
furrows or by nodules as in the ciliate Vorticella monilata. In
Coleps hirtus the periplast is differentiated into definite plates of
characteristic form arranged in four girdles which compose an
armature for the organism (Fig. 73, A, C). The skeletal structures
of endoparasitic ciliates, e. g., Diplodinium ecaudatum are likewise
differentiations of the periplast (p. 21).
Not only the periplast, but the entire cortex has become differen-
tiated in a great variety of ways in response, apparently, to the
136
BIOLOGY OF THE PROTOZOA
many demands made upon it as a result of contact with the environ-
ment. These may be grouped as cortical differentiations for (a)
support and protection; (b) locomotion and irritability; and (c) food-
getting and defecation.
A b c
Fig. 73. — A, B, C, Form, structure of plates, and division of Coleps hirtus.
Maupas.)
(After
(a) Cortical Differentiations for Support and Protection.— Apart
from the thickening and hardening of the periplast which furnishes
sufficient protection and support for the great majority of flagellates
and ciliates, the cortex is the seat of precipitation of different
mineral substances; of secretion of gelatinous substances; or of
protoplasmic modifications into lifeless organic substances of various
kinds. These various products of cortical activity are moulded
into close-fitting, lifeless membranes of chitin, pseudochitin, and
cellulose, or into loosely-fitting shells, tests, skeletons, cups, tubes
and the like. These are not divided when the cell divides but are
either left as empty shells and tests, or one of the daughter indi-
viduals after reproduction remains in the old shell while the other
individual makes a new shell for itself.
Gelatinous mantles are common in flagellates and are occasionally
found in the ciliates (/>. g., Ophrydium versatile), but gelatinous
materials are secreted by all types of Protozoa. Usually, when the
secretion is abundant, daughter cells remain embedded in it as a
matrix after division, and the so-called spheroidal types of colony
result (see p. 38). The ability to secrete gelatinous mantles as a
reaction to unusual stimuli appears to be very widely distributed,
if not universal amongst Protozoa. Bresslau (1921), using a variety
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 137
of chemical stimuli, was able to demonstrate a voluminous gelatinous
envelope secreted by Colpidium campylum. Similar secretions were
also demonstrated in other filiates and in certain rhizopods and
flagellates as well. The secreted material, which he called "tektin,"
appears to be a combination of an albumin complex and a carbo-
hydrate complex and, according to Bresslau (see also Schneider,
1930) it is instrumental in forming shells and tests of Protozoa, as
well as trichocysts of many types.
The most characteristic shell-forming material manufactured by
Protozoa is chitin and pseudochitin. Chemically chitin is a modified
protein (C30H50O10N4 or multiple) and is undoubtedly polymorphic
in composition. Its mode of formation is still unproved, but condi-
tions in Protozoa support the view of Chatin that it arises by trans-
formation or differentiation of the peripheral cellular protoplasm.
Not only are cups, tests, "houses" of various kinds formed of
these substances, but cyst membranes, spore capsules of the Sporo-
zoa and "central capsules" of the Radiolaria as well, while impreg-
nated with calcium carbonate, silica, strontium sulphate, etc., or
covered by foreign bodies of different kinds, the chitinoid mem-
branes furnish the framework for the up-building of the most
complex shells and skeletons. In encysting ciliates the animal
becomes spherical, much condensed by loss of water and is sur-
rounded by an envelope of fluid-like material which condenses more
and more with exposure until the definite membrane, impervious
to moisture and resistant to all unfavorable conditions of the
environment, results. In Radiolaria the central capsule is a spherical
wall of chitin, separating the endoplasm from the external proto-
plasm and perforated in various ways to permit of communication
between the different regions of the cell (see p. 439).
In flagellates and ciliates the chitinous houses, tests, cups, etc.,
are usually colorless and very transparent, but in the rhizopods this
is unusual, the chitin shells being colored by oxides of iron usually
red or brown (Arcella sp., etc.). In the majority of fresh water
rhizopods the outer surface of the chitinoid shell is covered by foreign
particles of various kinds, such as sand crystals, diatom shells, or
even living algae, which are glued to the membranes by a chitinous
cement. Similar shells, which are generally known as arenaceous
shells, are found amongst the Foraminifera. In other cases, plates
of silica are deposited in the inner protoplasm and passed out during
reproduction to be cemented on the chitinous membrane in regular
patterns (Euglypha aheolata, Fig. 9, p. 31). Foreign bodies caught
up in the wrinkles of withdrawing pseudopodia are similarly stored
in the protoplasm to be used for shell-building purposes, Verworn,
for example, compelling Bifflugia to build its shell of differently
colored powdered glass.
138
BIOLOGY OF THE PROTOZOA
The lime shells of Foraminifera are formed in quite a different
manner. Here, calcium carbonate is precipitated between two lam-
ellae of chitin very much as a cement wall is made between board
surfaces. Except for a single mouth opening such limestone shells
may form an unbroken wall about the organism (imperforata) or
they may be perforated by myriads of minute pores (foramina)
through which the pseudopodia pass to the outside, a condition
which gave rise to the name Foraminifera. In the more compli-
cated types of these lime-stone shells, which may reach a diameter of
2 or 3 inches, the calcium carbonate may be deposited at successive
intervals of growth, thus giving rise to chambered structure of the
cells. Such polythalamous shells are complicated by the presence
of an intricate system of canals which, in life, are filled by moving
protoplasm (Fig. 74).
Fig. 74. — A complex polythalamous shell of Operculina (schematic). The shell is
represented as cut in different planes to show the distribution of the canals and the
arrangement of septa and chambers. (After Carpenter.)
Skeletons of Ileliozoa and Radiolaria, unlike the more clumsy
shells of the Foraminifera, are usually delicate in structure and
graceful in design. They are formed for. the most part by a deposit
of silica upon a chitinous base. Dreyer has given evidence to indi-
cate that such skeletons have their beginnings in spicules which
conform in shape and size with the nodal points in the alveolar walls
of the cytoplasmic reticulum (Fig. 12, p. 33). Isolated spicules are
characteristic of several Heliozoa and Radiolaria where they form a
loose or felted covering in the outer protoplasm. Such spicules
invariably grow by accretion, that is, by the addition of new sub-
stance to the outside of that already formed. If such added material
is formed in a limited region of the protoplasm, the result is a con-
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES L39
tinued accretion of silica to the end of a spicule which is pushed
farther out with each increment, thus giving rise to long bars and
spines which are radially arranged in forms like Acanthocystis
aculeata, etc. (Fig. 75). The silicious deposit, again, may be made
throughout a zone completely surrounding the center, resulting in
clathrate or latticed skeletons of varying grades of complexity
(Clathrulina elegans, Nassellaria).
While cellulose mantles and shells are more usually found in
A D
Fig. 75. — Types of spicules in Heliozoa. A, Raphidiophrys pallida with curved
silicious spicules; B, Pinaciophora rubiconda with tangential plates and forked spines;
C, Acanthocystis turfacea, with separated plates and forked spines: D, Pinaciophora
fluviatilis. (From Calkins after Penard.)
chlorophyll-forming organisms, there are some types in which inter-
nal skeleton elements are composed of this or a closely related sub-
stance. In the parasitic Ophryoseolecidae skeletal structures are
present which are made up of a substance resembling cellulose to
which Dogiel gave the name Ophryoscolecin.
(b) Motile Organoids.— The organoids by which Protozoa move
are to be considered as modifications of the cortex, although some
types, as shown in the preceding chapter, are derived in part
from internal kinetic elements (flagella and some pseudopodia).
Three main types are distinguishable flagella, pseudopodia and
cilia, each of which is sufficiently distinct from the others to furnish
a natural basis for classification of the Protozoa, a basis of classi-
140 BIOLOGY OF THE PROTOZOA
fication which Dujardin first em])loyed to create the three great
groups les flagelles, les rhizopodes, and les cilies. Each type is sub-
ject to many variations, due to inherent differences in the motile
organoids themselves, or to fusion in various ways leading to struc-
tures of considerable complexity.
It is extremely difficult to decide whether flagella or pseudopodia
are the more primitive in type. From most general text-books on
Zoology we learn that the matter admits of no question, and are
taught that the pseudopodium is the most primitive form of motile
organ in the animal kingdom. This certainly has been the most
widely accepted view. Many a generalization referring to Protozoa,
however, which has found its way into general works on Biology,
appears to have been drawn from the conditions in some one organ-
ism which is conspicuous by reason of its abundance and ease of
study. It would sometimes appear, indeed, that the common
species of Paramecium and Amoeba proteus, to many general writers
constitute the Protozoa. This seems to be the case with the problem
of pseudopodia and flagella, the argument being that a pseudopo-
dium of Amoeba proteus is certainly a less complex motile organ
than the flagellum of Euglena viridis, and therefore more primitive.
Had the comparison been made between the pseudopodia of Actino-
phri/s sol or Acanthocystis aculeata and a typical flagellum, the con-
clusion would not have been so obvious. There is a good deal of
evidence against the generalization as it is usually expressed. In
the first place, a pseudopodium of Amoeba proteus cannot be inter-
preted as a motile organ. It is not a definite structure in the cell,
nor does it cause the body of Amoeba proteus to move. On the con-
trary, it exists because of the movement of the body protoplasm
and the pseudopodium is merely the visible, physical expression of
this movement which, in turn, is due to the transformation of energy
in destructive metabolism. This energy finds its vent in that por-
tion of the ectoplasm which, for the time being offers the least resist-
ance; the ectoplasm gives way at this point, the endoplasm gushes
through and a pseudopodium results (see Chapter XII, p. 435).
Such pseudopodia are not the source of movements of the cell,
they are results, not causes, of movement. The pseudopodia of
some Heliozoa, on the other hand, are motile organs, and the axial
filaments which they contain are regarded as equivalent in struc-
ture and in mode of origin to the kinetic elements of flagella. The
pseudopodia of Foraminifera are intermediate between those of
Heliozoa and those of testate rhizopods. The problem, then, comes
down to a theoretical question of probabilities. Is it more probable
that pseudopodia of the type found in Amoeba proteus become pro-
gressively differentiated into motile organs through stages like the
finger-formed pseudopodia of the testate rhizopods, the reticulate
pseudopodia of Foraminifera and axopodia of Heliozoa and Radio-
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 141
laria, to the typical motile organ of the flagellate type? Or is it
more probable that a motile organ originating from a definite kinetic
center (basal body or blepharoplast) has become progressively indefi-
nite with loss of the kinetic elements through the same series of
forms, but in the opposite direction, and ending in types like Amoeba
proteus? To my mind, the pseudopodia of Amoeba proteus and its
immediate relations, have no place at all in such a series; they are
merely expressions of the physical conditions of the protoplasm and
of the forces operating within, and they may appear in any cell
having an appropriate physical make up. Thus we find them in
certain types of cell (leukocytes and phagocytes) widely distributed
throughout the animal kingdom, and we find them here and there,
in every group of the Protozoa.
An illuminating illustration in support of this conclusion is
afforded by the transitory flagellated stages of one group of ameboid
organisms, the Bistadiidae (see p. 108). Here, in Dimastigamoeba
gruberi, for example, the organism loses its pseudopodia under cer-
tain conditions, and develops flagella, not by metamorphosis of the
pseudopodia, but from blepharoplasts which, as centrioles, emerge
from the nucleus (Fig. 59, p. 108).
Although only a matter of academic interest, I believe that the
flagellum type of motile organs is the most primitive type we know
while axopodia and myxopodia, the former with kinetic elements of
weakened function, the latter with denser axial protoplasm which
Doflein also interprets as equivalent to axial filaments, represent
stages in the deterioration of the kinetic function coincident with
the absence of definite kinetic centers (see also p. 120). For these
reasons also, together with others which will be given later, we hold
with Doflein (1916), Klebs and many others, that the group of
flagellates furnishes more evidence of original ancestry than do the
rhizopods (see p. 411).
1. Flagella.— Flagella are widely distributed throughout the
animal and plant kingdoms, forming the motile elements of animal
spermatozoa and of plant zoospores, or current-producing organs of
many types of Metazoa. They are sometimes combined with
pseudopodia (Dimorpha mutans, Fig. 13, p. 34, Mastigamoeba inver-
tens, Ciliophrys infusionum, etc.), sometimes with cilia (Myriaphrys
paradoxa, Fig. 197, p. 478).
Flagella are usually excessively fine and delicate fibers extremely
difficult to see and to study in the living organism. In the great
majority of cases the finer structure has not been made out, but in
a few favorable types some progress has been made. In these cases
it is known that the flagellum is made up of two definite elements,
an axial, highly vibratile filament, which is formed as an outgrowth
from the basal body or blepharoplast, and an enveloping elastic
sheath which is formed from the periplastic substance of the cor-
142 BIOLOGY OF THE PROTOZOA
tex. In some cases the sheath is circular in cross-section (see
Plenge), in others ellipsoidal, while the contractile thread which is
usually attached firmly to the sheath may run in a straight line the
entire length of the sheath, or may follow a spiral course. In the
majority of flagellates the sheath undulates and vibrates in unison
with the contractile axial thread, but in a few types, such as Per-
anema trichophora or certain species of Bodo, the sheath remains
passive while the axial thread extends freely beyond the limits of
the sheath, where its activity in the surrounding medium results in
a steady progressive movement of the cell. Under the influence of
somewhat violent stimuli, however, the sheath itself may undergo
fibrations in such forms.
Owing to the nature of flagella and to their delicacy of structure,
there are not many possibilities of variation in type. In addition
to those which are circular or ellipsoidal in cross-section, there are
some which are band form. Such band-form flagella suggest the
possibility that vibratile membranes, which are not uncommon in
parasitic types of flagellates, may, morphologically, be regarded as
flagellum sheaths which remain attached throughout their length
to the cortex while the axial thread forms the contractile margin
(Fig. 169, p. 360). Such vibratile membranes are characteristic of
the genera Trypanosoma, Cryptobia, Trichomonas, Trichomastix, etc.,
all of which are parasites in the blood or digestive tract of different
animals.
There are, however, abundant variations in size, number and
position of flagella in the cell. When there is but one it usually
emerges from a pit or funnel-shaped opening at the anterior end of
the cell (flagellum fissure). When two are present they may be
equal in size and length (e. g., Spongomonas splendida, Fig. 49, p.
95), or one may be considerably thicker and longer than the other
(heteromastigote types). Both may be directed forward as in
Amphimonadidae or one may be directed forward, the other back-
ward, as in Bodo, Anisonema, etc. In such cases the posteriorly
directed flagellum (trailing flagellum or Schleppgeissel) appears to
act as a runner upon which the cell body glides, and has little to do
with the actual locomotion of the animal (Fig. 76).
Delage and Herouard have attempted to explain the dynamics of
flagellum action whereby the comparatively heavy body is moved
forward by reason of the vibrations of the exceeding^ delicate
thread. In the usual type the extremity of the flagellum describes
a rather wide circle so that it is in a certain focus of the microscope
for only an instant of time. With this circular movement, which
varies in different species, constant undulations pass from the base
to the tip. A forward pull results from the combination of such
movements and the cell either glides smoothly after its active pro-
peller or rotates more or less rapidly on its long axis while freely
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 143
swimming. When two flagella are present a curious shaking move-
ment may accompany rotation and translation.
With such energetic motile organs exerting a constant strain on
the body there would seem to be some danger of their being pulled
out, especially in those types with soft fluid bodies without firm
Fig 76.— Free-living flagellates with trailing flagella. A, C, D, Bodo caudatus St.
B, Bodo globosus St.; E, Ploeotia vitrea Duj. (After Calkins.)
144 BIOLOGY OF THE PROTOZOA
periplasts. This phenomenon has indeed been recorded by some
observers, the flagellum, freed from the body, moving off like a
spirochete (Klebs, Biitschli, Fischer, etc.). Such observations may
or may not be well founded, at any rate accidents of this char-
acter are guarded against by the manner of flagellum anchorage in
the cell. As described in Chapter III a flagellum is derived from
a blepharoplast which may be just below the periplast or deeper
in the protoplasm, or it may arise from the nucleus (Fig. 59, p. 108).
Its anchorage is further assured by rhizoplasts which sometimes run
to the posterior end of the cell as in Herpetomonas or species of
Rhizomastix (Fig. 62, p. 116), or which form a branching complex
deep in the body substance as in Dimastigamoeba (Fig. 59, p. 108).
In the various species of Giardia the basal bodies of the eight
flagella are connected by a complete system of rhizoplasts (Fig. 17,
p. 37).
Another type of structure which is regarded by some (e. g., Kofoid)
as a modified flagellum is represented by the axostyles or internal
motile organoids of the parasitic flagellates. In Trichomonas this
appears like a glassy, hyaline curved bar of considerable diameter,
extending from the nucleus to the posterior end of the cell where,
like a spine, it projects from the periphery (Fig. 77). It is usu-
ally interpreted as a supporting axial rod to give rigidity of form
to an otherwise soft and variable body (Doflein). Dobell regards
it as a remnant of the centrodesmose left in the cell after division
of the blepharoplast, a view supported by Hartmann and Chagas
(1910) who interpret it as a centrodesmose formed during division
of the intranuclear centriole. Martin and Robertson (1909), on the
other hand, found that axostyles arise after division quite inde-
pendently of the nucleus or of centrodesmose, and regarded them
as independent organoids of the cell. Kofoid and his associates
discard the assumption that axostyles are supporting or skeletal
structures and place them in the category of kinetic elements.
They are interpreted as intracellular organoids with a contractile
function characteristic of flagella and serve as organs of locomotion
in the dense media in which the parasites live and in which the
flagella would be ineffective. They are closely connected with the
blepharoplasts in all species of Giardia (Fig. 17, p. 37), and are
regarded as independent, self-perpetuating organoids which may be
the first to divide in the processes of reproduction (Giardia) or the
last to divide (Trichomonas). In all cases, according to these ob-
servers, but denied by others, the axostyle divides longitudinally
throughout its entire length, beginning with divisions of the anterior
end in which the blepharoplast may be embedded (Fig. 77).
In regard to the two opposing points of view as to the function
of axostyles the evidence rather supports the interpretation of
Kofoid and Swezy (1915). The necessity of a supporting struc-
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 145
ture, or a form-rectifying organ, in these parasitic types is difficult
to conceive. On the other hand, their intimate relation to the
blepharoplasts and their activity in reproduction indicate a common
function with the kinetic elements. The observations of Kofoid
and Swezy on the energetic movements of the axostyle while the
organism works its way through the mucus afford a more plausible
interpretation of the function of this organoid than the a priori
view of those who see in such movements only the efforts of an
elastic supporting structure to restore the form of a plastic cell.
Fig.
■Trichomonas augusta Alex. Two successive stages in division of the axo-
style. (After Kofoid and Swezy.)
2. Pseudopodia. — Pseudopodia are more or less temporary' pro-
jections of the cortex which may serve for purposes of locomotion
or, more often, as food-trapping or food-catching organoids. Four
types are recognized, axopodia, rhizopodia (myxopodia), filopodia
and lobopodia, which differ widely in their structural make up.
Of these only the first type can be regarded in a strict sense as
motile organs (see p. 140), the others functioning as food-catching
organoids, or mere protrusions of the semifluid body.
Axopodia.— Axopodia are different from other types of pseudo-
podia in possessing, like flagella, central axial fibers of specialized
protoplasm derived from endoplasmic kinetic elements. They are
found only in organisms belonging to the groups Heliozoa and
10
14G
BIOLOGY OF THE PROTOZOA
Radiolaria, in which they radiate out in all directions from a usually
spherical body (Fig. 78).
Unlike nagella, the outer coating of an axopodium is not a smooth
periplast-like sheath, but consists of fluid protoplasm in which the
movements of granules out on one side and back on the other are
c
'#£<*SW59?*«Wi^.w^»BO<s3(+*e*»*i,'3K#<"'.- .
.. *"■■ t--1*. ;J «-,--*•
D
Fig. 78. — Types of pseudopodia. ,4, B, Eruptive type of lobopodium; C, myxo-
podia type of Foraminifera ; D, axopodia type of Heliozoa. (After Calkins.)
clearly discernible. In this manner the outer protoplasm is con-
tinually changing about the central axial filament, which alone is
constant or fixed. Upon prolonged irritation, or in preparation for
division or encystment, the axial filaments themselves, together
with the enveloping protoplasm, are withdrawn.
Like flagella the axial filaments are formed as outgrowths from
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 147
endoplasmic kinetic elements. Gymnosphaera, Raphidiophrys,
Sphaerastrum, Acanthocystis, Dimorpha, etc., possess characteristic
"central grannies" which, from their activities in cell division, are
unmistakably centroblepharoplasts (see p. 117) from the substance
of which the axial filaments are formed (Fig. 50, p. 95). Wagner-
ella borealis, in addition to the central granule, possesses a zone of
basal bodies which give rise to the axial filaments and which at
times of retraction of the pseudopodia are drawn into the central
granule. In still other cases, as in Actinosphaerium eichhornii, the
axial filaments do not arise, apparently, either from central granules
or from nuclei, but appear to start indefinitely in the cytoplasmic
reticulum (Fig. 78, D).
While the more common forms of Heliozoa are quiescent, floating
types, some of the Heliozoa are freely motile. Acanthocystis acu-
leata, as well as other species of the same genus, turns slowly over
and over in a rolling movement; Camptonema nutans, according to
Schaudinn, bends and straightens its axopodia in food-getting and
in other activities. Actinosphaerium eichhornii and Actinophrys sol
are practically motionless. The active movements are due to the
axopodia and the structure of axopodia is strikingly like that of
flagella. That the contractile axial filament is the seat of this
movement, and not the enveloping protoplasm, is not open to
reasonable doubt. Structure, function and mode of origin thus
justify the inclusion of axopodia with the kinetic elements of the
cell.
On the other hand, in type-, with axopodia which are practically
motionless, the axial filaments have apparently lost the vibratile
function and now serve as supporting elements for the long radiating
pseudopodia. There is little reason to doubt that such elements are
homologous with the axopodia of motile types and that the latter
are homologous with flagella. This is well illustrated by the case
of Dimorpha mutatis where two flagella and many axial filaments
of axopodia originate from the same blepharoplast (Fig. 79.)
Speculations as to phylogeny on purely morphological grounds
are not profitable, but in this group of Heliozoa we have pretty good
evidence of a close relationship between flagellates and Sarcodina,
and equally good evidence of the transition from an active kinetic-
element to an inactive, supporting axial rod, as seen in the pseudo-
podia of Actinosphaerium eichhornii. This change in type is prob-
ably associated with the loss of specific kinetic centers for neither in
the cytoplasm nor in the nuclei are such elements to be found. In
some forms, finally, notably in Clathrulina elegans, the ends of the
axopodia are frequently branched, a condition which points the
way to pseudopodia of the rhizopodia type in which the supporting
element is not in the form of an axial rod, but in the form of stiff
stereoplasm (Fig. 78, C). The pseudopodia of Clathrulina, which
148
BIOLOGY OF THE PROTOZOA
have no axial filaments, appear to be transitional to those of the
testate rhizopods to which group Valkanov (1928) assigns them.
In this stalked form (Fig. 82), however, the stalk takes its origin
from the nucleus, as Valkanov clearly shows, and at some stages, at
least, has a fibrillar structure. This suggests the possibility that
the stalk of Clathrulina (and of Hedriocystis) may represent the con-
crescence of ancestral axial filaments.
B
Fig. 79. — Dimorpha mutans. Vegetative individual with two flagella and axopodia.
Axial filaments of axopodia and flagella meet in a common central granule. At
division the central granule divides and forms the poles of the mitotic figure, while
the axial filaments form astral rays. X 1950. (After Belaf, Allgemeine Biologie,
1927; B. Ergeb. u. Fortschritte d. Zoologie, courtesy of G. Fischer.)
Rhizopodia. — This type of pseudopodia differs from others, first,
in the tendency to branch and, second, in the tendency to fuse or
anastomose when such branches meet. From these characteristics
they are sometimes called reticulose pseudopodia and myxopodia.
So far as number of species is concerned, this type is the most
characteristic form of Sarcodina pseudopodia. They occur in all
forms of Foraminifera, Radiolaria and Mycetozoa which include the
great majority of Protozoa. As a result of their unlimited power
to branch and to anastomose, great meshworks of reticulated proto-
plasm are created which make ideal traps for the capture of food.
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 149
In many types, especially in Radiolaria, they may be long and ray-
like, with relatively little tendency to fuse; in other cases a main
trunk gives rise to so many branches that it is lost in the reticulum,
great accumulations of protoplasm collecting at the branching points
(Fig. 10, p. 32).
Doflein includes axopodia and these branching anastomosing
pseudopodia in the one type (rhizopodia), and sees in the axial fila-
ment of the former and the inner protoplasm of the latter only
Fig. 80. — Clathrulinaelcgans, stalk formation. (After Valkanow, Archiv f. Protisten-
kunde, 1928, courtesy of G. Fischer.)
different states of the same fundamental stereoplasm. Axial fila-
ments, however, derived from the substance of kinetic centers, are
quite different from structureless axial stereoplasm which has no
relation to kinetic elements. The enveloping protoplasm is appar-
ently the same in both types and granule streaming is a common
property, but the physical consistency is quite different. In rhizo-
podia the outer protoplasm is soft and miscible, leading to fusion
on contact with one another, while axopodia never anastomose.
The denser core of rhizopodia, while not condensed to a single fiber,
serves the same function of support as the axial filament of Actino-
sphaerium and gives stiffness and rigidity to long ray-like pseudo-
150 BIOLOGY OF THE PROTOZOA
podia of many Foraminifera and Radiolaria which stand out in all
directions from the cell.
Filopodia. — Structurally filopodia are entirely different from the
types described above, being formed of clear hyaline ectoplasm in
typical cases, or they contain a few granules indicative of endo-
plasm (Fig. 11, p. 33). They are usually long and slender and with
rounded ends giving the impression of slender glass rods. In some
forms there is a tendency to branch at the ends as in Euglypha
alveolata (Fig. 9, p. 31), but there is never anastomosis. Some-
times they sway back and forth like a filament of Oscillaria, but
usually they creep along the substratum where they serve mainly
for food capture.
Filopodia are characteristic of the fresh water testate rhizopods,
but are sometimes present in naked types like Amoeba radiosa.
Lobopodia. — Lobopodia are made up of granular endoplasm and
hyaline ectoplasm, and are temporarily projected portions of the
body protoplasm not to be compared with definite locomotor organs
of other Protozoa. The inner protoplasm of nearly all kinds of
Protozoa with granules of various kinds, food substances more or
less digested, and waste materials, is in constant movement called
cyclosis. In more highly differentiated forms, and in organisms with
a firm cell membrane, this movement is confined to the internal
protoplasm and the form of the cell is not affected by it. In the
shell-less rhizopods, however, there is no such outer covering, and
the peripheral protoplasm gives way at the weakest points, and an
outward flow of protoplasm with corresponding change in the form
of the body results (see Chapter V). If such a weak point is con-
stant in position, a constant flow in its direction is the outcome,
and the Ameba, consisting of practically one pseudopodium, as in
the Umax types, moves in one direction. In Amoeba verrucosa a
delicate periplast surrounds a somewhat dense protoplasm which,
accumulating on one side (according to Rhumbler, 1898), causes
the cell to roll over.
Withdrawal of pseudopodia is accomplished by their absorption
into the body substance, and is accompanied by a wrinkling of the
denser ectoplasm preparatory to its transformation into endoplasm
(see Schaeffer).
In pseudopodia generally it is evident that we have to do with
different types of structure which, in only a few instances, can
be regarded as motile organs. Axopodia, with their axial filaments
derived from kinetic elements, are closely related to flagella and may
be regarded as organs of locomotion, but the other types, which may
represent highly modified axopodia, have lost the kinetic elements,
if they ever had them, and are useful only as food-catching organs.
In most rhizopods the entire organism is the motile element, rhizo-
podia, filopodia and lobopodia being expressions of energy trans-
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 151
formations comparable with the rotation of protoplasm in Nitella
or circulation in Tradescantia. Axopodia of the motile Heliozoa,
axial filaments of the inactive species and stereoplasmic cor.s of
the rhizopodia may be regarded as successive phases in the modi-
fication of vibratile flagella. These types of pseudopodia have in
Fig. 81. — Types of Ciliata. A, Uroleptus pisces (after Stein); B, Cyclotrichium
gigas (after Faure-Fremiet) ; C, Stentor polymorpha (after Biitschli) ; D, Nyctotherus
ovalis (original).
common an enveloping layer of granular protoplasm, but filopodia
and lobopodia represent a different type, being made up in large
part, or entirely, of ectoplasm and without any evidence whatsoever
of kinetic elements. So-called "contractile elements" of this type
of pseudopodia are largely figments of the imagination.
152
BIOLOGY OF THE PROTOZOA
3. Cilia.— Cilia are the motile organs of Infusoria and accompany
the most highly differentiated types of cortex to be found in the
Protozoa. Individually they are shorter, more delicate and less
powerful than flagella and owe their importance as motile organs
to their large numbers and synchronous beating. Their action
may be compared with that of oars in rowing, while flagellum action
might be compared with sculling, and the results of cilia and flagella
activities bear a relation similar to that between a racing shell and
a gondola (Fig. 81).
Fig. 82. — Cilia structure. Axial filaments protruding from protoplasmic sheaths
in cilia of (1) Coleps hirtus, (2) Paramecium; (3) cilia make up of three lateral cirri
of Stylonychia. Silver line technique. (After Klein, Archiv f. Protistenkunde,
1929, courtesy of G. Fischer.)
According to the interpretation of several observers, mainly
Schuberg, Maier, Schubotz, Schroder, etc., the cortex of ciliates is a
composite of zones of differentiated protoplasm. In the majority of
cases such zones cannot be made out, for one shades into the other,
and the whole into the alveolar endoplasm. In favorable cases,
however, we can distinguish: (1) A superficial periplast perforated
for the exit of cilia and trichocysts when present; (2) an alveolar
DERIVED ORGANIZATION— TAX0N0M1C STRUCTURES 153
layer containing trichocysts if the latter are present; (3) a contrac-
tile zone containing the basal bodies of cilia, myonemes and coordin-
ating fibers; (4) a denser zone which shades off into the endoplasin
and supplies an anchorage for nuclei and contractile vacuoles.
A single cilium is constructed on much the same plan as a flagel-
lum, consisting of a central axial filament or fiber, and an elastic
sheath of protoplasm. Movement is due to the active contraction
Fig. 83. — Cyclidium glaucoma. Cilia with axial filaments protruding from plasmic
sheaths. Silver line technique. (After Klein, Archiv f. Protistenkunde, 1929,
courtesy of G. Fischer.)
in one plane of the axial fiber and recovery to the elasticity of the
enveloping sheath. The contractile element originates from a basal
body in the contractile zone. In many organisms local thickenings
occur at intervals along the axial filaments. These are similar to
basal bodies and are clearly demonstrated by silver nitrate impreg-
nations for bringing out the silver line system (Figs. 82 and 83).
The arrangement of cilia on the surface of the body varies in
154
BIOLOGY OF THE PROTOZOA
different species; sometimes they form a complete coating for the
organism as in the majority of Holotrichida (Fig. 84); sometimes
they are limited to certain zones as in Urocentrum turbo, Didinium
B
Fig. 84.— Types of Ciliata. A, Monodinium balbianii; B, Cyclotrichium sphaericum,
C, Dinophrya lieberkuhni; D, Askenasia elegans. (After Faure-Fremiet.)
nasutum, etc. (Fig. 205, p. 504) ; or sometimes to the ventral surface,
as in generalized Hypotrichida (Fig. 88, p. 159). In all cases they are
arranged in longer or shorter rows running straight or spirally, and
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 155
giving the striped appearance characteristic of the ciliates. Waves
of contraction pass from the anterior end posteriorly, cilia of the
same transverse rows beating synchronously, those of the same
longitudinal rows metachronously.
The periplast is variously sculptured in different species, giving
the appearance superficially of a different mode of origin of the
cilia. In some cases they appear to come from the centers of
minute cups or dimples as in Paramecium aurelia; in other cases
from longitudinal grooves or furrows between ridges of periplast
(Fig. 69, p. 124), and in some they appear to come from the ridges
themselves.
Rhizoplasts or endoplasmic prolongations from the basal bodies
are comparatively rare but occur in some cases as in Didinium
nasutum (Fig. 98, p. 187). Coordinating fibrils apart from the
silver line system have been described in a few types (En plaits,
Diplodinium, see p. 129), and center in a specialized neuromotor
body, the so-called motorium (Yocom, Taylor, Sharp).
In some cases cilia are uniform in length over the entire body
(Opalina); in other oases they are longer in the region of the mouth
or around the posterior end, but no sharp dividing point separates
short from long ones (Fig. 84). In some cases they are uniformly
long and vibrate like flagella (Actinobolus radians, Fig. 91, p. 163).
4. Composite Motile Organs.- A well-marked characteristic of cilia
is the ability of two or more to fuse into motile organs of vari-
able complexity. Such combinations give rise to membranulae,
membranelles, undulating membranes and cirri, each of which,
although composed of fused cilia, originates or grows as an inde-
pendent and complete organoid. In each case also the component
cilia may be demonstrated by use of dilute alkalies such as potas-
sium or sodium hydrate. It is often difficult to distinguish lines
of closely set cilia from fused cilia, and loosely bound cilia are
sometimes present, the aggregates being spoken of as "pseudo-
membranes."
Membranulae.— Membranulae are very long, delicate, finely-
pointed aggregates of cilia which differ from the somewhat similar
cirri in movement and in composition, while their basal granules,
in Didinium nasutum at least, are connected with the vicinity of
the nucleus by definite rhizoplasts (Fig. 98, p. 187). Similar mem-
branulae form the basal ring in Vorticellidae (Schroder, Schuberg,
etc.).
Membranelles. — Membranelles are formed by the fusion of cilia
in the region of the mouth. In many of the Holotrichida the cilia
are longer just posterior to the mouth than in other regions of the
body, frequently forming circlets about the mouth as in Lacrymaria
olor or L. lagenula (Fig. 85). In the other Orders of Ciliata oral
cilia are fused to form membranelles. In the oral regions the body
156
BIOLOGY OF THE PROTOZOA
is usually differentiated into a specialized food-collecting, frequently
funnel-like structure called the peristome. Cilia on the floor of the
peristome are usually longer than in other parts of the body, and in
I I
mm
' *J:
Fig. 85.— Types of Lacrymaria. A, Lacrymaria sp.; 5, and C, retracted and ex-
panded phases of Lacrymaria olor; D, Lacrymaria lagenula. (After Calkins.)
four of the five orders of ciliates some of these are invariably aggre-
gated in triangular, quadrilateral or ribbon-like membranelles and
membranes for producing food-bringing currents of water toward
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 157
the mouth. In every order except the Holotrichida a fringe of such
specialized motile organs, known as the adoral zone, lies on a margin
of the peristome (Fig. 88).
Membranelles are usually made up by the fusion of two rows of
cilia as shown by the double row of basal bodies (Maier) and their
flat or curved faces make powerful sweeps in the water. According
to Schuberg, Gruber, Maier and others, the anchorage of these
organoids is quite complex. The basal granules form a double row
immediately below the periplast; fibrils from these, analogous to
rhizoplasts, form a broad triangular basal plate and are then brought
together to form an end thread which connects the membranelle
with coordinating fibers (Fig. 72, p. 130).
While in most cases the membranelles represent the fusion of
comparatively few cilia in transverse rows of the peristome, making
them relatively narrow at the base, in other cases, notably in the
Tintinnidae, such fusion includes practically all of the cilia of the
transverse rows, making membranelles as broad as the peristome.
In the Vorticellidae there are two rows of membranelles, the double
adoral zone winding about the peristome usually in a direction
opposite to that of the Heterotrichida and Hypotrichida (Fig. 86.)
Undulating Membranes. — Undulating membranes are found in all
orders of the ciliates and range in size from delicate aggregates no
broader from base to tip than ordinary cilia to relatively enormous
balloon-like structures equal in width to more than half the diameter
of the body and in some cases, as Lembadion conchoides, almost equal
to length of the body (Fig. 87). In the simplest cases these mem-
branes are composed of a single row of longitudinally placed cilia, the
basal bodies of which form a single basal strand. Since cilia of the
longitudinal rows beat metachronously the result of their contrac-
tion when fused in these undulating membranes is a series of waves
passing from the anterior to the posterior end. In more complex
forms undulating membranes may be composed of 3 to 10 rows of
cilia, fused in longitudinal rows, the length varying from a few
microns to great waving sheets of protoplasm almost as long as
the entire cell (Fig. 87). They are usually found in the peristomial
area inside the adoral zone and are named preoral, endoral, paroral,
etc., according to their positions in relation to the mouth.
Pseudomembranes are present in numerous types. Here the
component cilia are not firmly united and the membrane is easily
disrupted. Such a membrane, which is rather easily disintegrated,
is characteristic of Blepharisma undulans. Chambers and Dawson
(1925) were able to hold down a portion of the pseudomembrane
with a needle whereupon the distal portion broke into fibrils which
later reunited after the obstruction was removed.
Cirri. — Cirri are the most highly specialized of all the motile
organs of ciliates, the most characteristic forms occurring in the
158
BIOLOGY OF THE PROTOZOA
Hypotrichida. They are placed more or less definitely on the
ventral surface, a group, variable in number, at the anterior end
being known as the frontal cirri, a similar group, also variable in
number, near the posterior end being known as the anal cirri, while
other groups may form caudal cirri, ventral cirri, marginal cirri, etc.
(Fig. 88).
Vj>
P.C.
Fig. 86
Fig. 87.
Fm. 86. — Structure of typical Vorticella showing the adoral membranes, AM'
I 1/ ,• vestibule, 1*.; contractile vacuole, C.V.; food vacuole, FA'., and posterior
circlet of cilia. (After Noland and Finley, from Trans. Am. Microscopical Sue,
1931.)
Fig. 87. — Lembadion conchoides F.'F. (After Faure-Fremiet.) .
( 'irri are always broader at the base and taper gracefully to a
fine point. In cross-section near the base they are either circular,
ellipsoidal, quadrilateral or irregular, and always have a basal plate
made up of the basal granules of the fused cilia. Under unfavorable
conditions of the medium in which the organisms live, and usually
after imperfect fixation, the constituent cilia become separated par-
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 159
'A
m
I
I
I
fllli
m
liiM
W
Fig. 88. — Types of Ciliata. A, Amphisia kessleri; B, Uroleptus pisces; C, Histrio
pellionella; D, Strongylidium sp. ; E, Oxytricha pellionella; F, Oxytricha fallax. (A,
after Calkins; B, C, D, E, after Biitschli ; F, after Stein. j
160
BIOLOGY OF THE PROTOZOA
ticularly near the tip, and the cirri then present a most frayed-out
or ragged appearance. They vary in size from extremely minute
cilia-like marginal and ventral cirri to great ventral brushes in
forms like Aspidisca (Fig. 90) or huge hooked structures as in
Uronychia, Diophrys and other Euplotidae (Fig. 89) (see also p. 221).
Fig. 89.— Types of ciliates. A, Perilromus i mmae; B, Kerona pediculus; C, Diophrys
appendiculatus; I), Euplotes charon. (A, C, D, after Calkins; B, after Stein.)
( !irri are preeminently organs of locomotion, but, unlike other
motile organs of the ciliates, their stroke is not confined to one
plane but may be in any direction. This gives to the Hypotrichida
an extreme variety of movements unparalleled by any other group
of Protozoa. Many of them walk or run on the tips of their frontal
and ventral cirri (Stylonychia) ; others swim with a peculiar jerky
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 161
movement (Aspidisca) ; others combine swimming due to the
adoral zone with sudden jumps or springs due to the anal or caudal
cirri (Uronychia, Euplotes, etc.). Such saltations are not limited
to the Hypotrichida, however, but are characteristic of organisms
in all groups where cirri are developed as in Halteria grandinella
among Oligotrichida, Mesodinium cinetum among Holotrichida, etc.
In some cases cirri are differentiated as tactile organs, especially
the more dorsal ones of certain Hypotrichida. It is probable that
such cirri are no different from other motile organs of the ciliates
in this respect, extreme irritability being a common characteristic.
Few observers can have failed to note the instantaneous effect of
a slight local irritation on a quietly resting Pleuronema chrysalis,
for example, with its long cilia radiating out in all directions, yet
there are no cirri here.
Fig. 90. — Two species of Aspidisca. (Original.)
The synchronous and metachronous vibrations of cilia and cilia
aggregates are probably regulated by coordinating fibers with
highly developed irritability. This is the interpretation given by
Schuberg to the basal fibrils in the contractile zone of Paramecium
caudatum; by Neresheimer (1903) to certain fibers distinct from
the myonemes in Stentor coerulens, and by Sharp, Yocom, Taylor
and others, to conspicuous fibers in Diplodinium ecaudatum and
Euplotes patella (see p. 127) ; others, however (e. g., Jollos, and Belaf ),
interpret them as supporting structures. In the latter organism
Yocom (1918) and Taylor (1920) found fibers running from the
posterior anal cirri and from the adoral zone of membranelles to a
common anteriorly placed structure termed the motorium, which
11
162 BIOLOGY OF THE PROTOZOA
they regard, with Sharp (1914), as a center of the neuromotor sys-
tem (see p. 129). The ventral and frontal cirri, however, are not
connected by similar fibrils with this motorium, but possess bundles
of fibrils, described earlier by Prowazek in Euplotes harya, and by
Griffin in E. ivorcesteri, which may run in any direction until lost
in the endoplasm. The inference is that these cirri are independent
of the coordinated system of fibrils which regulate the adoral zone
and the anal cirri, and that their movements, which are always
irregular, are not affected by cutting the coordinating fibrils of the
motor system (Fig. 72, p. 130, also see p. 131).
(c) Other Organoids Adapted for Food-getting.— Mention may
be made here of a few special types of cortical differentiation apart
from the cell mouths, which Infusoria use for purposes of food-
getting. The most striking of these are the tentacles of Actinobolina
radians, the "tongue" or "seizing organ" of Didinium nasutum and
the tentacles of the Suctoria.
Contractility due to myonemes is a widely-distributed phenome-
non in ciliated Protozoa and in most cases involves the activity of
the entire organism (see p. 124). When it is limited to restricted
portions of the body, such as the peristomial complex of Diplodi-
nium ecaudatum, or the "vestibule" of Vorticellidae, it acquires a
special interest. Even more remarkable than these, however, is
the power, possessed by Lacrymaria olor, of projecting its mouth-
bearing extremity any distance up to three times the length of the
flask-shaped body, or until the rubber-like neck is reduced to a
mere fibril. The "head" thus projected dashes here and there
with amazing rapidity, the body meantime remaining quiet and
unmoved, until finally the head and neck are withdrawn and the
cell swims off with no visible trace of contractile structures (Fig. 85,
p. 156). No special myonemes have been described in this form
and the projection and retraction of the "head" must be due to
the elasticity of the cortex of the "neck" region, combined with
activity of the oral circlet of cilia while the body cilia are at rest
or relatively quiet.
Another remarkable and special phenomenon, seen apparently
by few observers, is the method of- food-getting by Actinobolina
radian:-!. This organism, when at rest, protrudes a forest of radiat-
ing tentacles which stand out like axopodia, sometimes stretching
a distance equal to two or more times the body diameter. The
ends of these tentacles carry trichocysts (Entz, Calkins, Moody)
which upon penetrating an individual Halteria grandinella com-
pletely paralyze it. The tentacle, then, with prey attached, is
withdrawn entirely into the body, the Halteria is worked around
to the mouth and swallowed (Fig. 91). Actinobolina vorax (Wen-
rich) has a similar food-getting mechanism but is not as fastidious
about its food as is .1. radians.
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 163
In Didinium nasutum the proboscis bears a peculiar protrusible
plug or tongue of protoplasm termed the "seizing organ" by Thon
(1905) and Prandtl (1907) (Fig. 98, p. 187). A zoneof trichocyst-like
fibrils lies near the extremity of this plug and when certain types
of ciliates, preferably Paramecium, are struck by Didinium the
plug, with trichocysts penetrates the cortex of the prey, paralyzing
it. While this process takes place too rapidly to be seen, the
results show that it must have taken place for, after striking and
anchoring in the Paramecium, the seizing organ with prey attached
is retracted and the prey, often larger than the captor, is swallowed
whole (Fig. 98, p. 187). No satisfactory explanation of this phenom-
enon has yet been given.
Fig. 91. — Actinobolina radians St. (After Moody.)
Still another type of cortical organs is illustrated by the various
kinds of tentacles of the Suctoria. Some of these are constructed
for piercing, while others are hollow, forming sucking tubes through
which food is taken into the body. They are evidently provided
with some type of poison, for active ciliates, coming in contact with
these tentacles, become suddenly quiet and remain so while the
suctorial tentacles penetrate the cortex and suck out the endoplasm
of the prey which can be followed through the feeding tubes to the
endoplasm of the captor (Maupas, 1883). Like the tentacles of
Actinobolina radians, these suctorial tentacles are retractile, but
again there is no satisfactory explanation of their activity and no
description or mention of specialized motile apparatus.
164 BIOLOGY OF THE PROTOZOA
Like the majority of formed organoids of the cell, the more com-
plicated of the motile organs described above are formed anew at
each division of the cell. This does not apply to the majority of
pseudopodia nor has it been observed in the case of cilia, but is
well-established for flagella and for the aggregates of cilia, such as
membranelles, undulating membranes and cirri. In a few cases
the flagella themselves are said to divide, but this is questionable,
the flagella probably arising in all cases from the substance of
blepharoplasts or basal bodies which have divided. Young (1922)
has shown that a cirrus of Uronyckia transfuga if cut does not
regenerate, but if the protoplasm is partly included in the opera-
tion a new cirrus is regenerated. Demboska (1925) has shown that
if a single cirrus of Stylonychia is cut out all of the cirri are renewed.
(d) Oral and Anal Cortical Modifications. In all naked forms
of Protozoa and in corticate forms which, like Opalina, take in food
substances by osmosis through the general body surface, there are
no portions of the ectoplasm differentiated as cytostomes or cell
mouths. In such forms, furthermore, where there is no undigestible
matter, there is no modification as cytopyge (cytoproct, or cell
anus). In testate forms, obviously, there is only a limited region of
the body substance which is open for the reception of food. In
testate rhizopods the shell openings are due to the physical condi-
tions under which the lifeless shell materials are deposited and no
definite mouth parts as protoplasmic differentiations are present.
In all Protozoa, on the other hand, which take solid food and
which are covered by more or less highly differentiated cortical
plasm, there are permanent openings in the cortex serving for the
intake of solid bodies and for defecation of undigested remains.
In many cases such openings in the cortex merely expose a limited
region of soft receptive protoplasm as in Oikomonas termo (Fig.
97, B, p. 186), but in other cases complicated cortical differentia-
tions with supporting and food-procuring adaptations give rise to
complex and permanent cytostomes and cytoprocts.
In flagellates such an area of softer protoplasm is situated at or
near the base of the flagellum, or two such areas may be present,
each at the base of a flagellum or group of flagella, as in Trepomonas
and Ilexamitus. In one group, the Choanoflagellidae, a collar-like
membrane arises as a protoplasmic fold around the base of the
flagellum and forms a cuff or funnel surrounding the flagellum
for a distance equal to one-third or one-half its length (Fig. 92).
These are extremely delicate, the margins alone in many cases
indicating their presence and dimensions. According to France,
they are somewhat spirally rolled like a cornucopia, the free mar-
gin arising from the softer food receptive area and by its move-
ments directing food particles toward this area. This, according
to de Saedeleer (1929), is an erroneous interpretation, the appar-
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 165
ent spiral roll of the collar being due to the presence of two pre-
hensile tentacles. In some cases two such collars, one within
the other, are present as in Salpingoeca entzii or S. marinus (Fig.
92). The second, outer, collar in some types is regarded by Doflein
as a periplastic rigid structure which forms a part of the cup or
Fig. 92. — Types of choanoflagellates. A, Codosigapulcherrimus; B, Diplosigasocialis,
C, Salpingoeca marinus; D, collar type according to France. (After Calkins.)
house and is not morphologically equivalent to the inner collar,
which, like a pseudopodium, may be shortened or lengthened, or
drawn in and formed anew by the living cell. According to the
older interpretation these protoplasmic collars assist in food-taking
by forming a sticky directive course for particles down the inside
166 BIOLOGY OF THE PROTOZOA
to the receptive area at the base of the flagellum (Kent), but accord-
ing to France granules on the inside of the collar are moving away
from the cell as defecatory material while the food particles move
down the outside to a receptive area not included by the collar
base (Fig. 92, D).
In the majority of corticate flagellates the food-taking receptive
area is continued as a pit or groove known as the flagellum fissure,
or as the cytopharynx. The flagellum arises usually at or near the
base of such a pit and in many cases the contractile vacuole empties
into it.
It is in the ciliate group, however, that we find the most character-
istic and most complicated types of cytostome. Here they may be
mere pores in the cortex which remain closed except during the
process of ingestion and without accessory current-producing motile
organs, or they may be permanently open and provided with undu-
lating membranes or other vibratile elements. The former type,
known as the Gymnostomina, eats only occasionally and then by a
definite swallowing process, the soft mouth region widening into
a huge opening to receive the prey. Thus Didinium nasutum ordi-
narily swims about with little evidence of a mouth at the extremity
of the conical proboscis (Fig. 98, p. 187), but when swallowing a
Paramecium which may be larger than itself, the entire anterior
end appears to be nothing but mouth, the body wall of the Didinium
being reduced to a thin enveloping sheath about the Paramecium
(Figs. 98, 5). Similar, but not so spectacular cytostomes are present
in other types of Gymnostomina. Spathidium spathula may swal-
low smaller ciliates like Colpidium (Fig. 99, p. 188); Nassula aurea,
Chilodon cucullus, etc., still smaller forms. In all such forms
the protoplasmic region around the mouth is strengthened by
simple or complex metaplastic structures— the trichites (Fig. 195,
p. 475). The Trichostomina are always provided with food-getting
motile organs and a constant stream of water with suspended bac-
teria and other minute living things passes through the permanently
open mouths making these creatures, according to Maupas, gluttons
par excellence of the animal kingdom (see, however, p. 190).
The complications in regard to structure in these two types of
cytostome have to do with the support of the walls of the mouth
and of the gullet into which the mouth opens, and for the perfection
of the current-producing apparatus. Such support is obviously
important in preventing rupture of the soft protoplasmic bodies of
forms like Didinium nasutum, Enchelys farcimen, Prorodon tires
or Spathidium spathula (Fig. 99, p. 188). In all of these cases there
is an armature of elongated rods, trichites, formed of stereoplas-
mic substances, embedded in the walls of the mouth and gullet,
and these, like spiles in a ferry slip, take up the strain when the
mouth is opened. In many cases, however, the perfection and
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES U\i
strength of these cytostomial supports seem to be entirely out of
proportion to such hypothetical needs of the organism. Thus in
all of the Chlamydodontidae the trichites form a tubular armature,
the ends making a circumoral ring which may project beyond the
ventral surface (Chilodon cucullus). Such an aggregate, known as
an oral or pharyngeal basket, or pharyngeal armature, forms a more
or less definite cytopharynx. In some cases the trichites are re-
placed by a compact corneus tube which extends dee]) into the
endoplasm as in Nassula aurea, Orthodon hamatus, Trachelitis ovum,
etc. (Fig. 93).
mm >'
A
B
C
Fig. 93.-^4., Orthodon hamatus with oral tube; B, Frontonia leucas. with undulating
membrane on left margin of mouth; C, Trachelitis ovum. (A and C, after Biitschli; B,
after Calkins.)
In the Trichostomina the permanently open mouth always leads
into a more or less highly-developed gullet or cytopharynx, while
peristomial cortical differentiations of various kinds lead to it.
The cytopharynx is usually provided with one or more undulating
membranes, while membranelles, undulating membranes and cirri
may also be present in the peristome. These are well illustrated
bv the complex oral apparatus of Glaucoma {Dallasia) frontata
(Fig. 8, p. 29).
The mouth region of the ciliates appears to be the focal point of
the longitudinal rows of cilia. In the generalized forms, such as
Actinobolina radians, Prorodon teres, Holophrya discolor, etc., the
mouth is exactly terminal and the rows of cilia run symmetrically
168 BIOLOGY OF THE PROTOZOA
to the posterior end (Fig. 84, p. 154). In the majority of cases,
however, the mouth is not terminal but may be found at various
points on the side or upon the ventral surface. Thus it may be on
the side in forms like Nassula aurea, or Glaucoma (Dallasia) frontata
(Fig. 8, p. 29), on the ventral anterior surface in Frontonia leucas
(Fig. 93, B), or various species of Chilodon, or at the extreme pos-
terior end as in Opisthodon mnemiensis (Fig. 191, p. 472). Where-
ever the mouth is found the rows of cilia are correspondingly altered
from symmetrically placed lines as in the generalized forms, to all
kinds of asymmetrical arrangements. This has led to the view,
first elaborated by Biitschli, that the ancestral position of the mouth
in ciliates was terminal at the anterior end, and that by adaptation
to different modes of life, and to various types of food, the mouth
has shifted from the anterior end to the various positions as now
found in different types. With this shifting the focal points of the
ciliary rows have similarly shifted, and the positions of the lines of
cilia in some forms are used as evidence to indicate the path of this
shifting and the mode of evolution of the present-day cytostomes.
A familiar illustration of such shifting is the series of forms repre-
sented by the genera Holophrya, with terminal mouth, Spathidium,
with oblique mouth, Colpidium, Glaucoma (Dallasia) and many
others, with subterminal mouths, Amphileptus and Lionotus with
elongated slit-like mouths extending from the anterior end far down
the ventral surface, such types leading to the various proboscis-
bearing genera like Dileptus in which the mouth is limited to the
posterior end of such an ancestral slit-like aperture, now represented
for the most part by a row of trichocysts (Figs. 6, 13, 203).
In Chilodon there is an oblique line of cilia running from the
anterior left-hand margin of the ventral surface to the circular
mouth which in some species may be shifted well over on the right
side. The lines of ventral cilia begin at this line and not at the
mouth, while an oblique row of specialized cilia suggests the begin-
nings of adoral zone formations characteristic of the majority of
Trichostomina, while the line itself may well represent the positions
held by the mouth in ancestral forms.
In many types of ciliates, a special region of the body, not found
in the more generalized forms, is developed as a feeding surface.
Such regions, known as frontal fields, are characteristic of ciliates
which live permanently or temporarily as attached forms. There
is some evidence to indicate that such frontal fields as occur in
Stentor, and the Peritrichida, are derived from the anterior ventral
surface of more actively moving forms. In Pcritromus, for example,
the line of the peristome cuts out a definitely limited frontal region
of the ventral surface, which is provided with special motile organs,
the frontal cilia. Biitschli (1888) suggested that such a peristome,
if continued around the right side of the organism, would completely
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 169
separate an anterior frontal field from the remainder of the body,
as seems to be the case in Climacostommn virens (Fig. 71, p. 128).
With the development of an attaching portion of the body as in
Stentor, and in the interest of feeding, such a frontal field becomes
directed upward, reaching its most perfect development in types
like Vorticella and its allies (Fig. 86, p. 158).
Fig. 94. — A, Bursaria truncatella, frontal field deeply insunk; B^Folliculina
ampulla, with frontal field drawn out into two flexible arms. (.4, original; B, after
Doflein.)
Such frontal fields are flat in the various species of Stentor, or
they may be greatly invaginated as in Bursaria truncatella, or drawn
out into two ciliated food-getting arms as in Folliculina ampulla
(Fig. 94), or into a tripartite frontal field in Triloba paradoxa, or
rolled up in. spiral folds as in Spirochona gemmi para .and Bursalinus
synspiralis.
The cytoproct is rarely differentiated as a definite opening in the
cortex. In many cases, especially in the flagellate group, the cyto-
pharynx and anus are the same. In the majority of ciliates, on the
other hand, there is a constant opening or pore, usually in the pos-
170 BIOLOGY OF THE PROTOZOA
terior region of.the body, which is closed and invisible except during
the process of defecation (Fig. 44, C,p. 86). In some forms, notably
in Pycnothrix monocystoides and Diplodinium ecaudatum, a definite
anal apparatus is developed. In the latter case Sharp describes a
" rectum" with distinct walls opening to the outside by a permanent
cytopyge, while at the inner end there is a "cecum" which acts as
a collecting vacuole for the fecal matter (Fig. 2, p. 20).
(e) Contractile Vacuoles.— In the rhizopods and most of the soft-
bodied flagellates the contractile vacuole can scarcely be called a
cortical differentiation. In these cases they are more or less casual
organoids, moving freely with the endoplasmic granules. In the
corticate flagellates and ciliates, however, there is a permanent
spot in the cortex through which the contents of contractile vacuoles,
fixed in position, are emptied to the outside. As a rule, the salt water
forms of Protozoa do not have contractile vacuoles (see p. 176) and
the number in fresh water forms is variable, sometimes in the same
organism (testate rhizopods and Heliozoa). In many types, how-
ever, the number as well as the position is fixed; one, as a rule, in
Hypotrichida and Peritrichida, and variable numbers in the Holo-
trichida and Heterotrichida.
In rhizopods the roving vacuole adds to its volume by picking up
fluid substances from all parts of the endoplasm until it becomes too
heavy to be easily moved with the flowing endoplasm. The vacuole
is thus gradually left behind, so to speak, until it finally breaks
through the thinning wall of protoplasm and empties its contents
to the outside, usually at that part of the body which for the time
being is posterior. In the fixed forms of vacuoles the fluids to be
excreted are brought to the excretory organoid by more or less
definite routes or canals, through the endoplasm. Such canals are
highly characteristic of many types of ciliates. A familiar example
is afforded by the different species of Paramecium where the five
to ten radiating canals form a characteristic rosette about each of
the two contractile vacuoles (Fig. 95). In the Hypotrichida there
are usually two such canals leading to the dorsally placed vacuole,
and two in Stentor, one following the margin of the body to the
"foot," the other following the rim of the peristome in a circular
course around the body. In Ophryoglena flava there may be as many
as thirty fine feeding canals leading from all parts of the body to
the centrally placed vacuole, and in Fronton in leucas eight to twelve
such canals follow a tortuous course throughout the body substance.
In Pycnothrix the canals form a branching network through the
endoplasm. Such canals are replaced by a ring of feeding vacuoles
in many of the corticate flagellates.
In corticate Protozoa the contractile vacuole usually opens to
the outside in the vicinity of the anus when such a structure is
present. In many cases it opens into the cytopharynx as in the
majority of flagellates or in the vestibule of forms like Vorticella.
DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 171
In Campanella umbellata such a reservoir is replaced by two definitely
walled evacuation canals, while in Pycnothri.v the excretory canal
is said to be provided with special cilia.
c. v.
Fig. 95. — Golgi bodies in Chilomonas Paramecium (B) and Paramecium cau-
datum (A and C). c.v., Contractile vacuole; r, radial canals of Paramecium. (After
Nassonov.)
In some types of parasitic ciliates (Biitschliidae and Paraiso-
trichidae) a peculiar type of "concrement vacuole" has been de-
scribed by Dogiel (1929) which appears to be a normal part of the
derived organization. These are interpreted, not as excretory,
but as special structures with a statolith function.
CHAPTER V.
GENERAL PHYSIOLOGY.
There is no doubt that our knowledge of the structures of
Protozoa far outstrips our knowledge of their functions. The
minute size of the individuals and the inadequacy of micro-chemical
tests make it extremely difficult to follow out any physiological
process to its end. Furthermore, it must not be overlooked that
physiological problems here for the most part begin where similar
problems of the Metazoa leave off, namely in the ultimate processes
of the single cell. Here the functional activities have to do with the
action and interaction of different substances which enter into the
make-up of protoplasm and, for the most part, these are beyond
our powers of analysis. A few of these activities may be dupli-
cated individually and apart from correlated functions, in the
laboratory. Or specific reactions between specific chemical sub-
stances may be obtained as, for example, the digestion of fibrin by
fluids extracted from the protozoon protoplasm; or in a physical
sense the reversal of the sol and gel states in colloidal mixtures.
Such individualized processes, however, give little idea of the
infinite play of forces continually operating in living protoplasm,
all of which, harmoniously working together, make up the phe-
nomena of vitality and distinguish living from lifeless matter.
As Mathews points out, the essential differences in chemical
actions in protoplasm and in physical nature are: (1) The order-
liness with which they are carried on, and (2) the speed of the
reactions.
A starving Dileptus gigas will slowly decrease in size although its
form remains about the same (Fig. 6, p. 27). This is due to disinte-
gration through continued oxidation and other catalytic processes
which lead to the exhaustion of protoplasmic constituents unless new
food is added. If the process is continued the organism will ulti-
mately die in from one to three weeks. If a Dileptus is accidentally
crushed its protoplasm will completely disintegrate within a few sec-
onds. The process of disintegration in the first case is orderly, in the
latter completely disorganized. Other normal vital activities are
equally orderly; the orderliness dependent possibly on the regulation
of permeability by the colloidal membranes, the alveolar membranes,
nuclear membrane and investing membrane of the cell; and regula-
tion of permeability in turn is dependent upon the chemical make up
GENERAL PHYSIOLOGY 173
of the constituent parts, and salts or electrolytes and the continued
activity between them (cf. Clowes, Overton, Mathews).
The speed of specific chemical actions is a characteristic vital
phenomenon due to the participation of subtle and elusive, but
specific, catalytic agents, the enzymes.
This aggregate of colloidal substances forming polyphasic physical
systems in protoplasm is the seat of the multitude of activities
characteristic of life. Huxley's definition of protoplasm as the
physical Basis of Life does not carry us very far in the analysis of
living matter. In a moving protozoon there is a constant interaction
of the various substances making up its protoplasm— oxidation,
enzyme formation and action, amidization and deamidization, dis-
integration and regeneration, protein break-down and protein recon-
struction, all taking place simultaneously or seriatim. Substances
in this whirlpool of action may be regarded as living so long as
they are, or may be, drawn into the vortex of protoplasmic activi-
ties. The results of these multitudinous activities contribute to the
well-being of one organism. In another moving protozoon a similar
bewildering complex of activities likewise results in the well-being,
in this case of a distinctly different type of protozoon. The first
protozoon, let it be a Didinium nasutum, captures and swallows the
second, say a Paramecium caudatum. It is well known that a frag-
ment of a protozoon will regenerate into a perfect organism of its
type and we might well be perplexed by the problem why is it that
the Paramecium protoplasm in Didinium does not manifest itself as
Paramecium and not as Didinium. The answer to this apparently
simple problem is a matter of organization or the manner in which
the fundamental substances making up the protoplasm in the two
organisms are put together and interact. The architectonic of
Driesch, or protoplasmic architecture, is specific for each type of
organism and the form and structures of the organism are expres-
sions of this architecture. When this organization disintegrates,
life and the possibility of controlled reactions are lost and the
erstwhile living protoplasm becomes dead matter. This happens
when Paramecium is paralyzed by the seizing organ of Didinium
(see Fig. 98, p. 187). The vital activities of Paramecium are sud-
denly stopped, and disintegration of its organization, through
hydrolysis, continues with the digestive processes in Didinium.
The inert proteins, probably as amino-acids, are re-integrated in
the Didinium protoplasm, and what was living substance in Para-
mecium, now enters again, through a form of transmigration, into
the vortex of vital activities of quite another type of organism.
The sum total of the various physiological processes of the in-
dividual may be grouped for the Protozoa, as they are for the
Metazoa, inter aggregates of special activities which we call the
fundamental vital functions, and distinguish as respiration, nutri-
174 BIOLOGY OR THE PROTOZOA
tion, excretion, irritability and reproduction. In Metazoa these are
performed by specialized cells, grouped into tissues, organs and
organ systems, the complexity varying with the specialization of
the organism. In Protozoa they are all performed by the single
cell and all are more or less dependent on the activities of the diverse
substances and structures which compose it. All work together
in a harmonious cycle of matter and energy.
A. Respiration.— The scientific beginnings of the modern mech-
anistic conception of vital activities is traced to Lavoisier and his
comparison of animal heat with physical heat due to combustion
through oxidation. The utilization of chemical energy, or energy
of combination liberated by oxidation, is possibly the keynote to
the multiple vital harmonies of animal life (see Yerworn, 1907).
Oxygen necessary for such physiological combustion is obtained by
all protozoa without the aid of specialized respiratory organs. It
is readily absorbed through permeable membranes from the sur-
rounding water, or obtained by reduction from oxygen-holding
substances, as in anaerobic forms. In one way or another it is
ever present to initiate the round of vital functions.
Oxygen may be taken into the cell directly from the surrounding
medium as in the aerobic forms, or it may be obtained by breaking
down Oxygen-holding substances, in protoplasm, so-called reducing
processes of all types but especially of anaerobic forms. Through
the use of chemical indicators the degree of oxidizing power of a
cell, including both direct oxidation and reduction, may be deter-
mined and is expressed by the symbol rH in values from one to
forty. This factor, known as the "oxidation-reduction potential,"
varies from time to time and is used in much the same way as the
expression pH, indicating the hydrogen-ion concentration from
intense acidity (pll 1 or 2) to strong alkalinity (pll 10). It is «
highly probable that a definite rH is as important for cell activity
as a definite pH, and that this oxidation-reduction potential is
maintained by the 11 SI I compounds (cystine, cysteine and gluta-
thione) of the protoplasm (Krogh, 1916; Hopkins, 1921; Meverhof,
1924).
The intake of oxygen and the voiding of ( !02 constitute the essen-
tial needs of the cell in respiration. The relationship between the
oxygen taken in by an organism and the C02 produced by its
metabolic activities is indicated by the expression R. Q. (respiration
quotient). Daniel, 1931, found that the R. Q. of Balantidium coli
under aerobic (sic) conditions is 0.84, which is very nearly the same
as the usual R. Q. for man (0.85). For Amoeba proteus and Bleph-
arisma undulans Emerson (1929) found the R. Q. to be "about
unity."
To a certain extent the oxygen intake and ( X)2 output are measur-
able, but always with a large experimental error. Kalmus (1927),
GENERAL PHYSIOLOGY 17.")
for example, by an ingenious method, made out that a single Para-
mecium consumes 0.0052 c.mm. of 02 in one hour at 21° C, a
figure which Howland (1931), using the same method, slightly
modified, changed to 0.00049. Adolph (1929) made out a typical
rate of 0.55 cc. of oxygen intake per million individuals per hour
at 19.7° C,
In a similar way R. Emerson (1929) obtained results with Amoeba
proteus and Bkpharmna undulans; Peters (1921) with Colpidium
colpoda; Hulpieu (1930) with Amoeba proteus found that the rate
of movement is not noticeably affected by changes in the amount
of available oxygen from 0.005 to 100 per cent ; below or above these
limits the animals are slowly killed. He found, furthermore, that
amebae are able to move for some time in the absence of oxygen
#vhich indicates that its energy is not derived by direct oxidation.
Verworn (1896), on the other hand, found that Rhizoplasma kaiseri
in an oxygen-free medium ceases its centrifugal pseudopodial move-
ments while centripetal movements continue for some time but
ultimately stop. Addition of oxygen restores both types.
It is the function of catalytic enzymes to expedite chemical
processes which are under way and catalases of different kinds
result from metabolic activities going on in protoplasm. Amongst
these are the oxydases which aid in oxidation and reduction in
the cell. Indications of such agents as the "reducase" of Becker
(1926) and the extraction of glutathion have been obtained, while
Joyet-Lavergne (1929) adduces considerable evidence in support
of his view that glutathion is intimately associated with the mito-
chondria of the cell.
Correlated with the intake of oxygen is the output of C02 and
water. While these are perhaps more properly treated in connection
with the functions of excretion there is good evidence of a gaseous
exchange, but quantitative results are not altogether satisfactory.
The energy of combination, released by oxidation, is paid for by
loss in the chemical compound oxidized. Other compounds may
be formed with lessened energy of combination, and end-products,
notably C02 and urea ((NH2)2CO), are not only useless to the organ-
ism but positively harmful unless voided. Excretion, therefore,
must follow oxidation. To make good the loss of substance new
food materials must be taken in, digested and assimilated, but this
is possible only through movement, and movement in turn is an
expression of irritability. Excretion and irritability thus are funda-
mental vital functions, while a third, nutrition, is closely correlated.
Excess of food intake over waste by oxidation leads to growth of
the diverse protoplasmic substances and to their reduplication by
division, while the aggregate of such divisions, expressed visibly
by division of the cell, constitutes reproduction. The funda-
mental vital functions are intimately bound together; external con-
176 BIOLOGY OF THE PROTOZOA
ditions, such as decrease in temperature of the medium in which a
protozoon lives, means decreased oxidation, retarded movements,
less food and a lower division rate. Increase in temperature involves
a speeding up of all activities and, if food is abundant, a higher
division rate. External conditions involving absence of food lead
to starvation and death of the cell through uncompensated loss by
oxidation. In short, interference with any one of the fundamental
functions leads to disturbance of them all, and the various phases
of vitality of the protolasm during a typical life cycle may be due
to inadequate functioning of one or another or all of these activities.
B. Excretion of Metabolic Waste.— The waste matters of oxida-
tion and continued metabolism are frequently voided in the same
manner that water and oxygen are taken in, namely, by osmosis.
In such cases there is no physiological need of specialized excretory
organs. It is possible that all Protozoa excrete in this way, although
the majority of fresh water Protozoa possess contractile vacuoles
which are generally regarded as excretory organs. In marine forms
and in parasites they are generally absent. If the latter forms,
and these are in the majority of Protozoa, are able to dispose of
the products of destructive metabolism without definite organs for
the purpose, why are the latter necessary in fresh water forms?
Hartog (1888) has long maintained that contractile vacuoles are
not obligatory excretory organs, but are primarily hydrostatic
organs for the purpose of maintaining a pressure equilibrium between
the fluids within the cell and those in the surrounding water. Degen
(1905) interprets the vacuole in a similar way, its variations in size
and pulse depending upon permeability of the membrane which
varies with the environmental salts. Here difference in density of^
the surrounding medium is largely responsible for loss of the organ
characteristic of fresh water forms, but changes in permeability of
the cell membrane due to salts in the new medium undoubtedly
play an important part. Other experiments by different observers
bear out the same principle. Thus dilution of the normal neutral
salts in the medium causes enlargement of the contractile vacuoles
in ciliates according to Massart (1891), while increased concentra-
tion leads to reduction in size, retardation in rate of contraction,
or total disappearance of the vacuole.
While there is justification for Hartog's view of the purely physical
significance of the vacuole, there is every reason for believing that
water in protoplasm picks up any soluble waste matter that may
be present, and holds it in solution. Early experiments to prove
this, by Brandt (1885), Griffiths (1889) and others using chemical
indicators, or the murexid test for uric acid, were not convincing,
and the function of the contractile vacuole as a primitive type of
excretory organ remained an hypothesis.
Not only water, C02 (see Lund, 1918) and urea, but other prod-
GENERAL PHYSIOLOGY 177
nets of metabolism as well, are found in the protoplasm of differ-
ent Protozoa. These are usually present in crystalline form or in
amorphous heaps, which are rather loosely spoken of as "excretory
stuffs" without evidence as to their origin or significance. The
crystals often seen in Paramecium were identified by Schewiakoff
(1893) as calcium phosphate combined with some organic substance.
Similar crystals have been described by Schaudinn, Schubotz and
others from the protoplasm of different kinds of Protozoa. Schewia-
koff found that the crystals of Paramecium are not defecated as
are undigested food substances, but are first dissolved and then
disposed of— presumably with the water of the contractile vacuoles.
The function of the contractile vacuole in Protozoa thus has long
been a disputed problem. The views of the older students of the
group, with their conceptions of structural complexity of these uni-
cellular organisms, fantastic today, nevertheless have a certain his-
torical interest. The idea that a vacuole is a rudimentary beating
heart as interpreted by Lieberkuhn (1856), Claparede and Lachmann
(1854 and 1859), Siebold (1854) and Pritchard (1861) was no less
incongruous than the supposition of Ehrenberg (1838) that the
contractile vacuole is an organ connected with the gonadal system.
With development of knowledge of structure and function of the
Protozoa, and particularly of the mechanism of vitality, more
reasonable hypotheses of the function of the contractile vacuole
have been developed. There is, first, some ground for the belief of
Spallanzani (1770), Bossbach (1874) and Dujardin (1841) that it is
an organoid having to do with respiration of the organism, together
with other possible functions, a view supported in modern times by
Biitschli (1877, L888) and Degen (1905). There is, second, ground
for the belief held by Stein (1859), Gruber (1889) and the majority
of modern students of Protozoa, that it is an organoid for the excre-
tion of katabolic waste, despite the unconvincing experimental evi-
dence by Brandt (1885), and by Griffith (1889). Howland (1924),
however, by using a much more delicate test (the Benedict blood-
filtrate test) obtained unmistakable evidence of the presence of uric-
acid in cultures of Protozoa; in P. caudatum analyzed by Benedict,
a color reaction was obtained equivalent to 4 to 5 mg. of uric acid
per liter. There was no proof here, however, that the uric acid
came from Paramecium. Weatherby (1929) showed that the usual
ingredients of a culture medium contain measurable quantities of
uric acid. He found, however, that the extracted fluids of con-
tractile vacuoles of Paramecium and Spirostomum contain urea,
whereas the vacuole of Didinium nasutum contains ammonia, but
in no case does the nitrogenous waste of the vacuole represent all
of the nitrogenous output of the cell, much being voided by exosmosis.
There is, third, ground for the belief that the contractile vacuole is
an organoid for the regulation of osmotic pressure in the cell, a view
12
178 BIOLOGY OF THE PROTOZOA
first advanced by Hartog (1888) and supported by Degen (1905),
Stempell (1914), Khainsky (1910) and by Nassonov (1924).
These three beliefs are not necessarily exclusive and the possibil-
ity of all three functions is still open. The osmotic function is well
supported by evidence furnished by Gruber's (1889) experiments
in transferring fresh-water, vacuole-holding Actinophrys sol and
Amoeba crystalligera to salt water, and vice versa, or by Zuelzer's
similar experiment with Amoeba verrucosa, the protoplasm becom-
ing more condensed and the vacuole lost in salt water. Hogue
(1923) found that Vahlkampfia calkensi when transferred from salt
water to fresh water media developed 1, 2, 3, or even 4 contractile
vacuoles. More extensive experiments by Degen (1905) with salts
of different kinds and wTith varied conditions of the environment
show that the contraction of the vacuole is a function of osmotic
pressure, and irrespective of the type of salt or neutral solution
introduced. With Hartog, he concludes that protoplasm of fresh
water forms, with its salts in solution, has a higher osmotic pressure
than the surrounding medium, which leads to continued intake of
water. Such intake, if not balanced, would lead to inflation and
to diffluence, a conclusion strengthened by Botsford's (1926) mer-
otomy experiments with Amoeba proteus in which it was shown that
the size of the vacuole depends upon the size of the fragment cut
off. According to Degen and Hartog it is the function of the
contractile vacuole to establish this balance.
This hypothesis, with further evidence supplied by the absence
of contractile vacuoles in marine forms where osmotic relations of
protoplasm and environment are more evenly balanced, is theoreti-
cally correct. There is no reason to doubt, however, the further
possibility that the water expelled by the contraction of the vacuole
contains water-soluble, katabolic excretory substances such as C02
and nitrogenous waste, positive evidence for which is supplied by
several observers. This indeed was admitted by Degen although he
obtained no evidence of the nature of the substances excreted. He
saw in the membrane of the vacuole the possibility of an excretory
mechanism. The actual existence of such a membrane, however,
is still in dispute, indeed the majority of investigators deny its
existence (Biitschli, Khumbler, Schewiakoff, Taylor). Others,
however, give evidence to show that a true membrane, although
very delicate, is actually present. Howland (1924, 1) for example,
by micro-dissection methods has been able to remove the contractile
vacuoles of Amoeba verrucosa and of Paramecium caudatum after
which they retain their integrity for considerable periods as free
vacuoles in the surrounding water. She also has punctured the
vacuole with needles while in the endoplasm, causing the expulsion
of its contents into the surrounding endoplasm and resulting in the
wrinkling of the vacuole membrane. Nassonov (1924) also not
GENERAL PHYSIOLOGY 179
only demonstrates the presence of a membrane in various types
(Paramecium caudatum, Lionotus folium, Nassula lateritia, Cam-
panella umbellaria and other VorticelUdae) but, by use of fixation
methods employed for demonstrating the Golgi apparatus in meta-
zoan cells, comes to the conclusion that the membrane of the con-
tractile vacuole is a part of the Golgi apparatus. This, in Metazoa,
he had earlier (Nassonov, 1923) identified as an organoid intimately
bound up with secretory activities of the cell (see also Bowen). In
different Protozoa the contractile vacuole, which he unhesitatingly
calls an excretory apparatus with a definite lipoid membrane, is
variously complicated, from a simple vesicle with osmiophilic mem-
brane in forms like Chilomonas paramecium (Fig. 95, B, p. 171), to
complex aggregations of vesicle and canals as in Paramecium (Fig.
95, A, C). In the latter case the canals appear to contain the ma-
terial by activity of which substances are chemically differentiated
for secretion and these are passed on to the vesicle 1 >y which they are
excreted. According to Nassonov the lipoid-containing membrane
(confirmed by Chatton, 1925, and by Gelei, 1928) must be semi-
permeable and its contents must have a higher osmotic pressure than
the surrounding plasm. Hence fluids would flow into the vacuole
completely distending it until the pressure would burst the retaining
membrane and the fluid would be ejected. The highly viscous
membrane would mend but for a new flow into the vacuole a new
supply of osmotically active stuff would be necessary. This, Nas-
sonov assumes, is formed by secretion from the osmiophilic mem-
brane into the canals and vacuole. This secreting activity is com-
pared with the secretory activity of the Golgi apparatus in Metazoa.
Gelei holds, however, that the function here is to condense and to
conduct concentrates from the plasm into the canals, not a secre-
tory function, but excretory. (See also Lynch, 1930.) With this
work of recent investigators we have a very definite argument for
the excretory functions of the contractile vacuole and for the pres-
ence and function of the lipoid membrane. In quite a modern way
it brings us dangerously near to an Ehrenbergian conception of a
kidney and bladder in Protozoa.
C. Irritability. — In the absence of all knowledge as to the manner
in which protoplasmic particles respond to stimuli of different kinds,
we are constrained in speaking of irritability of Protozoa, to limit
descriptions to aggregates of such responses as manifested through
movement, as energy transformed by oxidation from the poten-
tial or stored chemical energy to the active or kinetic condition, or
as manifested by adaptations to changes in environment. But the
manner in which such kinetic energy is utilized in pseudopodia
formation or by the elements of rlagellum, cilium or myoneme, is
a matter of pure speculation. The reactions which characterize
the resulting movements, however, can be analyzed and measured
180 BIOLOGY OF THE PROTOZOA
and these form the chief basis of our knowledge of protozoan irri-
tability.
Attempts to explain pseudopodia formation and ameboid move-
ment have varied with the changes in our conceptions of the physical
make up of protoplasm. The protoplasm of Ameba regarded as
a fluid substance was supposed to follow the laws of surface tension
characteristic of all fluids. Pseudopodia formation, according to
the views of Berthold (1886), is the attempt of one fluid (proto-
plasm) to spread out between water and the substratum as Quincke's '
well-known experiments demonstrated for fluids. As physical con-
ditions on all sides of the Ameba are not equal, variations in tension
result in local diminution, and the tendency to spread is focussed in a
local area and the pseudopodium results. Biitschli's (1894) observa-
tions and experiments with emulsions of oil, salts and water, and
Rhumbler's (1898) analysis of the causes of movement in lobose
rhizopods led these observers also to interpret pseudopodia forma-
tion as a result of surface tension phenomena. With the more
modern conception of protoplasm as a colloidal aggregate in the
physical state of an emulsoid in which the external and internal
protoplasm of Ameba are in the relation of gel and sol, the difficulty
of applying the laws of fluids became apparent and the hypothesis
based upon surface tension has been generally abandoned. Rhum-
bler himself (1910 and 1914) recognized this difficulty and materi-
ally changed his conception of ameboid movement, while Hyman
(1917) greatly enlarged and perfected his later point of view.
According to Hyman the ectoplasm of Ameba, by virtue of its
relatively solid state, becomes tenuous but elastic, as demonstrated
by the experiments and observations of Jennings (1904), Kite (1913),
Schultz (1915) and Chambers (1915, 1917), and exerts an elastic
tension on the inner fluid protoplasm. Bancroft (1913) and Clowes
(1916) demonstrated the reversibility of phase in diphasic physical
systems through the agency of electrolytes, and the conclusion fol-
lowed that \he ectoplasm represents a reversal phase of the more
fluid inner protoplasm. Hyman argues that, owing to the tension
of the enveloping ectoplasm, if any local region of the more solid
ectoplasm becomes liquefied, the resistance gives way at such a
point and the fluid endoplasm is pressed out, thus forming a pseudo-
podium. The immediate cause of such liquefaction she traces to
a local increase of, or change in, metabolic activity resulting in the
production of hydrogen-ions which, with the surrounding medium,
form an acid appropriate for dissolution of the more solid ectoplasm.
By the use of Child's potassium cyanide test for metabolic gradients,
she was able to demonstrate that such local regions of greater meta-
bolic activity actually occur on the periphery of Amoeba proteus
before a pseudopodium breaks out, also that the extreme tip of the
advancing pseudopodium is the most actively metabolic part.
GENERAL PHYSIOLOGY 181
Whether changes in the nature of protoplasmic response or
changes in direction of movement after repeated shocks should be
interpreted on the basis of "memory" and "learning" or in some
other way is largely a matter of personal idiosyncrasy on the part
of the observer. Numerous writers have described processes of
food "selection" by Ameba (e.g., Gibbs and Dellinger, 1908;
Schaeffer, 1917 and elsewhere; Metalnikoff et al, 1910). Mast and
Pusch (1924) interpret an observed change in the protrusion of
pseudopodia of Amoeba proteus in respect to a beam of light as
evidence of something analogous to "learning" in higher animals,
etc. "Learning" involves "memory," and such terms connote
processes of an entirely different nature which we associate with the
highest types of animals. It is conceivable that fatigue, to use the
term in its broad sense implying total or partial exhaustion of pro-
toplasmic constituents necessary for a reaction, and therefore a
purely physical matter, is adequate for explanation without calling
upon any obscure pan-psychic interpretation. Similarly with Kep-
ner and Taliaferro's (1913) evidence of "purpose" in methods of
food-getting by Amoeba proteus.
Many of the reactions of Protozoa are bound up with the coor-
dinating mechanism of the cell through which the organism acts as
a unit. The specific response of an organism to a stimulus is the
result of its particular protoplasmic architecture expressed through
its coordinating mechanism and motile organs. This has been
elaborately worked out by Jennings (1904 to 1909) in connection
with the "motor response" of many different kinds of Protozoa.
The discussions and controversies over the matter of directive
stimuli or tropisms in Protozoa have evidently been due in large
part to a lack of common understanding of the definition. If by
"tropism" is meant the orientation of an organism in respect to the
path of a stimulus, then tropisms, as Jennings was the first to point
out, play little part in the activities of the Protozoa. If, however,
by "tropism" is meant "the direct motor response of an animal to
an external stimulus" (Washburn, 1908), then tropisms play a most
important part in such activities. The two definitions are not
compatible; the former conveys the idea of a directive stimula-
tion upon local motor organs or controlling elements; the latter
implies the complex reaction of a definite mechanism character-
istic of any specific protoplasm, and the same reaction follows upon
stimulation by any type of stimulus (Putter, 1903, Jennings, 1909).
It follows further that the reaction is called forth regardless of the
particular elements first to receive the stimulus.
We owe Jennings the credit for first clearly distinguishing between
these two conceptions, as well as for careful analyses of the move-
ments of lower organisms (1904 et seq.), and for demonstrating the
particular motor response distinctive of specific types of Protozoa.
182
BIOLOGY OF THE PROTOZOA
He also showed that the nature of the motor response in some
organisms, e. g., in Stentor, is correlated with the physiological
state of the organism, and adduced evidence which indicates that
phenomena of fatigue are involved. The classical example of a
Fig. 96,-Merotomy in Euplotes patella. (After Taylor.) >./., AnaUirri fibers; m.,
motorium; m. f., membranelle fiber. (See also Fig. 72.)
motor response, formerly interpreted as chemiotaxis, is the case of
Paramecium caudatum or aurelia in a drop of dilute acid. Casual
swimming brings the individual to the outer limit of the drop; the
transition from water to drop does not provide a stimulus strong
GENERAL PHYSIOLOGY 183
enough to bring about the motor response and the individual con-
tinues through the drop until it strikes the farther limit. Here the
stimulus is sufficiently strong to cause the motor response which
is manifested as a backward swimming, due to reversal of cilia,
turning on the long axis and recovery of normal forward swimming
movement. Repetition of this procedure keeps the individual in
the acid drop. Others enter in a similar way and are similarly
trapped until many are confined in the acid drop where they are
ultimately killed. Such motor responses unquestionably play an
important role in food-getting and in vital activities generally.
The stereotyped nature of the motor response in any specific
organism may be due in the main to the characteristic silver line
and neuromotor systems which the higher types of flagellates and
ciliates possess. The observations of Sharp (1914), Yocom (1916)
and McDonald (1922) on ciliates, of Kofoid on flagellates, and the
experiments of Taylor (1920) in cutting different regions of the
neuromotor complex of Euplotes, indicate that the motor response
of Protozoa is bound up with coordinating systems possessing some
of the attributes of coordinating systems in Metazoa (Fig. 96).
Knowledge of these complex systems and their reactions is quite
sufficient to dispel any lingering belief in tropisms as due to stimu-
lation of special motile elements acting independently in such a
way as to orient the organism in respect to the path of the stimulus.
Through coordinating fibrils all parts work together; cutting the
system at any point leads to inharmonious or uncoordinated move-
ments of the motile organs as Taylor has demonstrated. All reac-
tions depend upon the organism as a whole; enucleated fragments
are unable to react as do nucleated fragments (Hofer, 1890, Willis,
1916). Jennings' careful observations, which led him to the con-
clusion that the protozoon organism always acts as a whole is fully
confirmed by these later observations and experiments.1
D. Nutrition. — Under the heading nutrition are included all
physiological processes involved in the replacing of substances
exhausted by destructive metabolism. Groups of activities includ-
ing: (1) food-getting; (2) secretion and digestion; (3) assimilation;
(4) defecation, find their place here. Certain specialized structures
adapted for these various activities have been described for the
most part in the preceding chapters, and the following is supple-
mentary in nature dealing with the functions which these structures
perforin.
1. Food-getting.— The varied methods by which Protozoa acquire
the needed materials for replenishing protoplasmic substances
reduced by oxidation are all correlated with the phenomena of
1 For discussion of different types of stimuli and the resulting reactions by Pro-
tozoa see Minchin (1912), Khainsky (1910), Mast (1910-1918), Putter (1900, 1903),
Jennings (1904, 1909).
1S1 BIOLOGY OF THE PROTOZOA
irritability. The particular method employed by any one type of
organism is probably the result of many factors of organization and
adaptation combined with mode of life, all of which are traceable
to adaptations resulting from the effects of external stimuli and
response through irritability. It would indeed be remarkable,
considering the endless variety of endoplasmic and cortical differen-
tiations, were we to find a common method of food-getting amongst
the Protozoa. On the contrary, it is probable that no two types of
organism follow an identical method. Nevertheless it is possible,
and it is certainly convenient, to group these manifold activities
under a comparatively few main types which are designated:
(1) Holozoic nutrition; (2) saprozoic nutrition; (3) autotrophic or
holophytic nutrition; (4) heterotrophic nutrition. Many authori-
ties introduce a fifth type under the caption parasitic nutrition,
but as this does not differ in principle from saprozoic nutrition, it
is included with the latter type.
While these terms apparently indicate different modes of nutri-
tion they are more applicable to methods of food-getting, and the
differences have to do in the main with the nature of the raw
materials taken in and the subsequent processes necessary for
their elaboration. Thus holozoic nutrition in Protozoa as in Metazoa
involves the ingestion of raw materials in the form of proteins,
carbohydrates and fats which are usually combined in the proto-
plasm of some other living organism eaten as food. It is an expen-
sive method of acquiring raw materials for it necessitates capture
and killing of living prey, preparation and secretion of digestive
fluids and ferments necessary to make the proteins and carbo-
hydrates soluble, and disposal of the undigestible residue. On the
other hand, it assures the supply of capital in the form of chemical
energy without the labor of storing it up. Saprozoic nutrition is,
so to speak, a more economical method, for the organism does
away with the elaborate processes of secretion and digestion and
relies upon the activities of other organisms for the preparation
of its raw materials and the "storage of energy." Dissolved pro-
teins and carbohydrates made soluble through the agency of bac-
teria agjjj other organisms in infusions, or prepared by the digestive
processes of the host in the case of parasites and some commensals,
are absorbed directly through the body wall or through special
receptive regions, by endosmosis. This type of food-getting may
be regarded as a degeneration or adaptation of the holozoic method,
the specialized absorptive areas being reminiscent of former mouths,
while the pathogenic effects of some types of parasites are inter-
preted as due to the secretion by the parasite of digestive fluids
which cause cytolysis of the host cells. Holophytic or autotrophic
nutrition, characteristic of plants, is quite different in principle
from the other two. Digestive processes typical of the majority
GENERAL PHYSIOLOGY 185
of animals, as well as the intake of solid or dissolved food, are
absent. A highly labile substance, chlorophyll, is manufactured
in the presence of light and usually by specialized plastids— chromo-
plastids— of the cell. Chlorophyll is very sensitive to light and
in some way not yet understood is instrumental in utilizing the
radiant energy of the sun to form complex, energy-holding com-
pounds. Plants thus become the great banking house for animals
and their capital is the apparently inexhaustible energy of the sun.
Heterotrophic nutrition, finally, is characteristic of those Protozoa
which combine any two of the above methods of acquiring raw
materials.
The great majority of Protozoa are holozoic in their methods of
food-getting, and wTe may distinguish two main groups, the con-
tinuous feeders, and the occasional feeders. Continuous feeders
are those forms with permanently open mouths through which
a constant current of water is maintained by action of the peri-
stomial motile apparatus (see p. 164). Minute forms of life, espe-
cially Bacteria, are carried by these currents into the endoplasm
where they undergo digestion in improvised stomachs or gastric
vacuoles (see p. 193). Chejfec (1929) estimates that Paramecium
caudatum may thus ingest and digest from two to five million
Bacterium coll in twenty-four hours. The majority of ciliates,
including many of the holotrichous, hypotrichous, heterotrichous
and peritrichous ciliates, belong in this group.
The occasional feeders, like carnivorous types of Metazoa, feed
whenever chance brings prey within the radius of their activity, and
many of them, like cannibals, are guilty of feeding at times upon
their close relatives (Maupas, 1883, Joukowsky, 1898, Dawson,
1919, Lapage, 1922). In some cases balloon-like membranes are
unfolded and spread out like sails for the direction of food currents
to the mouth as in Pleuronema chrysalis (Fig. 199, p. 482). Such
forms are intermediate between the constant and occasional feeding
types. In other cases great net-like traps are spread for the capture
of unwary diatoms, desmids or smaller Protozoa, as in the Foramin-
ifera (Fig. 10, p. 32). In other cases the microscopic hunters, like
men in shooting boxes, lie in wait for their prey. Here long ten-
tacles usually radiate out from the body in the surrounding water
as in Actinobolina radians or in Suctoria, until a victim comes in
contact with one or more of the outstretched processes (Fig. 91,
p. 163) ; in the same way axopodia of the Heliozoa capture chance
organisms which serve as food (Fig. 97).
The most interesting of these holozoic types are the predatory
forms which hunt their prey and capture them, while in full motion.
The small but powerful ciliate, Didinium nasutum, belongs in this
group. It darts here and there with an erratic movement while
rotating at the same time on its long axis. In its sudden darts,
lSli
BIOLOGY OF THE PROTOZOA
it strikes a Paramecium or other ciliate purely at random; the
proboscis with seizing organ is buried in the victim which is then
swallowed whole (Fig. 98, 1-6). Lionotus fasciola, Spathidium
spathula and other gymnostomatous ciliates capture living organ-
isms in a similar way (Fig. 99) while less spectacular methods are
employed by Frontonia leucas, Ophryoglena flava, Prorodon niveus,
etc., in swallowing diatoms, desmids and other relatively stationary
organisms.
A special type of food-getting, illustrated by the Rhizopods, may
be interpreted in some cases as the result of physical properties of
semifluid bodies. Rhumbler has made the most exhaustive studies
>M
Fig. 97.— Types of food
getting. A, Acanthocystis (after Penard) ; B, Oicomonas
termo (after Biitschli).
of food ingestion in these forms and distinguishes four types, viz.:
Ingestion by (1) "circumvallation," (2) "circumfluence," (3) "invag-
ination" and (4) " importation." Food-taking by " circumvallation"
is illustrated by Amoeba yroteus and usually takes place at that por-
tion of the body which, for the time being, is posterior. According
to Hofer (1889), Schaeft'er (1917) and others, the body becomes
anchored to the substratum by the secretion of an ectoplasmic
gelatinous substance; then, through the physical stimulus (Schaeffer,
1917) produced by a moving object (even a moving needle point
according to Verworn, 1889), walls of protoplasm flow out on either
side of the object and meet around it, thus enclosing a rotifer, an
GENERAL PHYSIOLOGY
1ST
:■,-■
••
h
\^ *
Fig. 98. — Didinium nasutum O. F. M. capturing and swallowing Paramecium
caudatum. 1 to 6, Successive stages in the ingestion of Paramecium; 7, section of
conjugating form of Didinium with spindle-form gastric vacuoles (?), and two micro-
nuclei in mitosis; 8, section of Didinium just prior to encystment. The seizing organ
with zone of trichocysts is protruded from the mouth; and rhizoplasts run from the
membranulae (motile organs) deeply into the cell. (After Calkins.)
188
BIOLOGY OF THE PROTOZOA
Arcella, a diatom or other food body. Ingestion by "circumflu-
ence" appears to be due to a stimulus emanating from a living food
body, the effect of which through the motor response (Jennings,
1904) is to cause pseudopodia to flow toward the prey and to entrap
it while still at some distance from the body of the captor as in the
testate rhizopods, Foraminifera and Choanoflagellates where an
endoplasmic projection forms a pseudopodium which engulfs the
prey and then withdraws within the endoplasm where the prey is
Fig. 99. — Two types of ciliated carnivores. A, Spathidium spathula about to
ingest a Colpidium colpoda; B, Lionotus fasciola swallowing a Colpidium colpoda.
(Original.)
digested (De Saedeleer, 1927 and 1929; Ellis, 1929). "Invagina-
tion" occurs in forms having a somewhat resisting periplast-like
ectoplasm such as Amoeba terricola according to Grosse-Allermann
(1909). When a living organism comes in contact with the surface
at any point, the local ectoplasm with prey attached sinks into the
endoplasm as though " sucked "in, the ectoplasmic walls being trans-
formed into endoplasm, while the ectoplasm about the area of
ingestion comes together sphincter-like, and fuses again to a smooth
surface. So, too, in A. proteus where, according to Mast (1916 and
GENERAL PHYSIOLOGY 189
1923) and Beers (1924), the sphincter-like ingesting area is powerful
enough to cut in two organisms like Paramecium and Frontonia.
Ingestion by "importation" finally occurs where a food body, with-
out apparent movement on the part of the Ameba, merely sinks
into the protoplasm of the captor as in Amoeba dofieini according to
Neresheimer.
In most of these types, which grade more or less into one another,
the process of food ingestion may be interpreted as due to local
liquefaction in the more solid ectoplasm, and to special conditions
of capillarity in the more fluid endoplasm. Rhumbler has shown
that a filament of Oscillaria which enters Amoeba verrucosa by
" importation " and is too long to be entirely engulfed, becomes coiled
up as a result of the physical properties of the protoplasmic mass.
In a similar way a filament of shellac may be drawn from water
into a chloroform drop in which, by variations in surface tension,
it becomes rolled up in a strikingly similar manner.
Some of these methods of food-getting in holozoic types are sug-
gestive of "conscious" activities to a given end. Thus ingestion
by " circumfliience " suggests preliminary activities in anticipation of
a "square meal." Or traps formed by pseudopodia or by tentacles,
or the balloon sails of Pleuronema chrysalis, etc., might be regarded
as "set" by Protozoa for the purpose of catching food. Such inter-
pretations, however, are more probably evidences of a tempera-
mental imagination on the part of the observer than of purposeful
activities on the part of these minute organisms. "Sensing" at a
distance has been described for Ameba (Schaeffer, 1912), and for
Spathidium spathula (Woodruff and Spencer, 1922), and until these
phenomena are explained they will continue to serve as a basis for
such speculations. Losina-Losinsky (1931) gives good reasons for
interpreting all such phenomena as chemiotactic and dependent
upon the organizations of captor and prey.
The so-called "selective" activities of some Protozoa in their
apparent choice of food or of building materials for their shells are
likewise better interpreted as the outcome of physical conditions
of the protoplasm than as purposeful actions of the organisms.
Schaeffer (1917) attributes the power of discrimination in food-
taking to Ameba, as does Metalnikoff (1908) to Paramecium, a
conclusion vigorously opposed by Wladimirsky (1916), who inter-
prets negative reactions as a result of depression (fatigue?) in their
physiological condition. Actinobolina radians apparently chooses,
from a great number of miscellaneous forms, one particular species
to harpoon, paralyze and swallow. "This remarkable organism
possesses a coating of cilia and protractile tentacles which may be
elongated to a length equal to three times the diameter of the
body, or withdrawn completely into the body. The ends of the
tentacles are loaded with trichocysts. When at rest the mouth is
190 BIOLOGY OF THE PROTOZOA
directed downward and the tentacles are stretched out in all direc-
tions, forming a forest of plasmic processes among which smaller
ciliates, such as Urocentrum turbo, Gastrostyla steinii, etc., or flagel-
lates of all kinds may become entangled without injury to them-
selves and without disturbing the Actinobolina or drawing out its
fatal darts. When, however, an Halteria grandinella, with its quick,
jerky movements, approaches the spot, the carnivore is not so
peaceful. The tentacles are shot out with unerring aim and the
Halteria whirls around in a vigorous, but vain, effort to escape,
then becomes quiet, with cilia outstretched, perfectly paralyzed.
The tentacle with its prey fast attached is then slowly retracted
until the victim is brought to the body and swallowed with one gulp.
Within the short time of twenty minutes I have seen an Actinobolina
thus capture and swallow not less than ten Halterias." (Calkins.)
While these observations do not prove that Actinobolina radians
eats nothing else, it is certainly true that the usual food is Halteria
grandinella, a fact which may account for the rarity of Actinobolina.
That it thrives on Halteria is proved by the fact that isolation cul-
tures of Actinobolina have been maintained for a period of eight
months and through 375+ generations by division during which the
only food supplied was a daily ration of 1 to 3 dozen individuals
of Halteria, grandinella independent pure "mixed" cultures of which,
with bacteria, were maintained at the same time. In these cases
it is quite probable that the motor response brought about by
some specific chemotactic stimulus is responsible for the apparent
"choice" of food by Actinobolina, and chemotactic or thigmotactic
stimuli for food capture by "circumfluence," " circumvallation " and
"importation."
A certain degree of selection is forced upon some Protozoa by the
limitations of their mouth parts. Forms like Didinium, Spathidium,
Lionotus, etc., with distensible mouths, can handle organisms of
various sizes, but forms like Paramecium, Dileptus, Spirostomum,
etc., with small inelastic mouths are constrained to "select" small
objects for food. Here there is no apparent choice between nutri-
tious and innutritious particles, carmine or indigo granules being
taken in with the same initial avidity as bacteria or other useful
foods. A certain so-called "hunger-satisfaction," however, leads
to the cessation of ingestion in many organisms. Thus Actinobolina
radians often captures and paralyzes more Halterias than it actually
eats; on one occasion, for example, an individual was seen to catch
18 Halterias, 11 of which were swallowed while a small group of
7 were abandoned uneaten, when the Actinobolina swam away.
Amoeba proteus, after a period of eating no longer reacts to the
stimulus of living food substances, and apparently ignores types
which were previously engulfed (Schaeffer). So, too, in Paramecium
and Stent or, Metalnikoff and Schaeffer describe an apparent selection
GENERAL PHYSIOLOGY 191
of food as illustrated by the rejection of carmine granules after a
period during which such granules were actually taken in. It seems
probable that such phenomena indicate a type of fatigue involving
the temporary loss of irritability through which the organism
responds to stimuli produced by the chemical make-up of foreign
substances, a period of rest being necessary for the restoration of
this form of irritability. Selection in another sense, however, is
quite important. All kinds of food substances are not equally suit-
able for Protozoa any more than they are for individual men. This
may be due to the fact that digestive fluids of a given type of ciliate
or rhizopod are not adequate to dissolve all kinds of protein; or
it may be due to deleterious substances in the protoplasm of the
prey. All observers who have attempted to raise Protozoa in pure
cultures are familiar with the difficulty of providing the proper food
materials and excluding the harmful. Unsuccessful culture experi-
ments indicate that these conditions have not been met. Further-
more, a culture medium is suitable only when the organism under
cultivation continues to live during all phases of its life cycle.
Apparent selection of foreign objects used in shell-building may
be due to the physical consistency of the protoplasm and to its
ability to pick up foreign bodies like sand crystals, diatom shells,
etc., or in part to the size of the shell-opening through which such
objects must pass for storage in the protoplasm. Mud and other
fine particles of inorganic matter, like carmine granules, are engulfed
with bacteria and other microorganisms which produce the stimulus
necessary for the operation of food-taking. After the useful sub-
stances are digested the residue, like castings of worms, may be
voided to the outside or they may serve a useful purpose in the
construction of shells.
A special kind of holozoic food-getting is illustrated by the Suc-
toria which, instead of cilia, are provided with suctorial tentacles
(Fig. 100). The prey, usually some form of ciliated Protozoa, comes
in contact with one of these tentacles and is paralyzed through the
action of some kind of poison contained in it. The cortex of the
prey is perforated by the end of the tentacle and the fluid endoplasm
is sucked into the body of the captor, a stream of granules being
visible within the tentacle. In some cases it is said that the endo-
plasm of the captor flows through the tentacle and into the body
substance of the prey where the latter is digested (Maupas, 1883).
The body of the victim gradually collapses until nothing remains
but the denser walls and the insoluble parts.
Many of the Protozoa, while parasitic in the cavities and cells of
different animals, retain the holozoic method of food-getting, feed-
ing upon parts of the protoplasm of the host or upon other living
organisms such as bacteria of the digestive tract, or solid detritus
of one kind or another. Thus Endamoeba coll lives on intestinal
192
BIOLOGY OF THE PROTOZOA
Fig. 100.— Types of Suctoria. A, Trichophrya salparum on a gill filament of Salpa;
B, Acineta sp.; C, Podophrya sp. (Original.)
GENERAL PHYSIOLOGY 193
bacteria, while Endamoeba dysenteriae, Dientamoeba fragilis, etc.,
engulf, with other food substances, red blood corpuscles and digest
them. According to Haughwout (1919), the flagellate Pentatricho-
monas sp. likewise ingests red blood corpuscles. In the majority of
protozoan parasites, however, the organisms do not digest the food
necessary for the growth of their own protoplasm. They practically
live in a huge gastric vacuole and are surrounded by food already
digested or partly digested, which is absorbed by osmosis through
their body walls. Doflein thinks that such food substances, if not
appropriate for the up-building of protoplasm of the parasite, may
be made suitable by the secretion from the parasite of special diges-
tive substances and is ready for absorption after the action of such
secretions. He further suggests that the cytolytic action upon cells
and tissues of the host may be due to such secretions (for example
Endamoeba dysenteriae) and that other toxins of pathogenic Pro-
tozoa, probably enzymatic in their activity, may be similar digestive
secretions from the parasites (see p. 362).
Secretions and Digestive Fluids.— Products of metabolic activity
in the form of secretions and precipitations play most important roles
in structure and activities of all kinds of Protozoa. Skeletons, shells
and tests, gelatinous mantles, stalks, cyst and spore membranes,
and the like are all evidences of the secretory activity of the proto-
zoan protoplasm (see Chapter IV). There is evidence that these
activities, like secretory activity of the gland cells in Metazoa, are
dependent upon the general function of irritability and that specific
secretory response follows a specific stimulus. Thus Bresslau (1921)
finds that gelatinous mantles or tubes about Colpidium colpoda may
be called forth at will by the use of certain chemicals (iodine, fatty
acids). If fatty acids are used, the individuals, as in artificial
parthenogenesis, must be replaced in a suitable medium before the
membranes are formed. Enriques (1919) gives evidence to show
that the secretion of stalk material in Anthophysa vegetans depends
upon the quantity of food available. Stimulation, through the
agency of foreign proteins, is without much doubt responsible for
the secretion of digestive fluids and ferments in holozoic nutrition,
and considerable advance has been made in our knowledge of intra-
cellular digestion. This advance has been due mainly to the appli-
cation of the method first devised by Gleichen (1778) of introducing
into the body with food substances inorganic, usually colored par-
ticles which clearly outline the limits of the digestive cavities. These
cavities, early termed gastric vacuoles, were recognized as digesting
centers of the organisms, and Gleichen's method, employed by
Ehrenberg (1833-1838) led to his elaborate and at first widely
accepted, but erroneous, conception of the Polygastrica. Modern
applications of this method consist in the introduction with the
food of delicate chemical substances, or indicators, which change
13
194
BIOLOGY OF THE PROTOZOA
in color according to the acid or alkaline nature of the fluids in
which they lie. The observations of le Dantec (1890), Fabre-
Domergue (1888), Metschnikoff (1889), Greenwood (1887-1894),
Nirenstein (1905), Khainsky (1910) and Metalnikoff (1903, 1912),
together with the study of extractives by Mesnil (1903), Mouton
(1902), Metschnikoff '(1893), Krukenberg (1886), Hartog and
Dixon (1893), etc., have given a fairly comprehensive idea of the
processes of intracellular protein digestion in Protozoa. Another
group of observers including Meissner, Greenwood and Saunders,
Stole (1900), Wortmann (1884), Celakowski (1892), Nirenstein,
etc., have shown the digestive possibilities in relation to carbo-
hydrates and fats.
Fig. 101. — Colpidium colpoda and Paramecium aurelia after feeding with amylo-
dextrin and treatment with iodide. (After Cosmovici, courtesy of Annales Scien-
tifique de l'Universite de Jassy.)
An interesting conception of the gastric vacuoles in ciliates has
been given recently by Cosmovici (1932). Using an ingenious
method of dissolving rice starch with saliva and immersing ciliates
in the dextrin thus formed, he found, upon treating them at differ-
ent intervals with iodide, that a canal, colored blue, often con-
voluted or swollen into "gastric vacuoles," runs from mouth to
anus (Fig. 101). Further investigation of this remarkable canalic-
ular system is needed.
The majority of Protozoa which ingest "solid" food take in at
the same time more or less water, which forms the gastric vacuole.
Thus in trichostomatous ciliates a vacuole is formed at the base of
GENERAL PHYSIOLOGY 195
the cytopharynx which varies in size according to the abundance
of food particles present. In Paramecium caudatum the vacuole,
when formed, becomes spindle-shape as though pulled away from
the gullet by endoplasmic force, but it soon becomes spherical as it
moves about in the fluid endoplasm (Nirenstein, 1905). With the
ingestion of larger food bodies such as infusoria, flagellates of larger
size, diatoms, rotifers, etc., comparatively little water accompanies
the prey. Paramecium caudatum when eaten by Didinium na.su-
tum, for example, lies in close contact with the protoplasm of its
captor and no water at all can be made out (Fig. 98). In such cases
the ingested organism is paralyzed and therefore motionless when
swallowed, but it very often happens that resistant food bodies
continue to struggle after they have been taken into the protoplasm;
rotifers, for example, are usually not motionless when engulfed by
Amoeba proteus. In such cases a considerable volume of water
gives the prey ample room to move without danger to the make up
of the captor. In other cases in which water does not appear to
be taken in with the food, the latter becomes surrounded by fluids
secreted by the protoplasm.
With many types of Protozoa the process of digestion begins
before the living prey is taken into the protoplasm of the captor.
This is manifested in most cases by the paralysis of the victim when
it comes in contact with pseudopodia of many rhizopods and
Heliozoa, Ehrenberg (1833) for Actinophrys sol; F. E. Schultze
(1875-1876) for Allogromia and Polystomellina; Winter (1907) for
Peneroplis, etc. In some cases, at least, it is not improbable that
this paralyzing killing substance is analogous to, if not the same as,
the digestive fluids which kill bacteria and other prey after they
are taken into the body protoplasm. Thus bacteria become motion-
less in about thirty seconds after the gastric vacuole is detached
from the cytopharynx of Paramecium caudatum (Metalnikoff, 1903
and 1912). The color changes of chemical indicators, for example
alizarin sulphate, show that the killing agent is acid in nature;
this was early detected by Greenwood and Saunders (1894), who
interpreted it as a mineral acid without further specification. Later
observers have confirmed this suggestion, Nirenstein, Metalnikoff
and others showing that digestion in the vacuole is a process which
is divisible into two periods, in one of which the reaction of the
vacuole contents is acid, while in the other it is alkaline. The acid
reaction lasts for about fifteen minutes, according to Nirenstein
and Metalnikoff, in the gastric vacuoles of Paramecium, but Khain-
sky concluded that the acid reaction is maintained during the
entire period of digestion, becoming alkaline only after the dissolu-
tion of the protein substances is at an end. In other cases, however,
no acid reaction at all can be demonstrated. Thus, Metalnikoff,
also in the case of Paramecium, found that some vacuoles never give
an acid reaction; others much more rarely show an acid reaction
196
BIOLOGY OF THE PROTOZOA
throughout, while still others in the same organism are first acid
and then alkaline. Minchin (1912) suggests, in connection with
this diverse history of vacuoles in the same species, that different
food substances incite different responses on the part of the proto-
plasm much as different antibodies are formed from cells of the
Metazoa in response to toxins from different types of pathogenic
parasites. Shapiro (1927) followed the change in pH of the gastric
vacuole in Paramecium from an initial alkaline stage (7.6) which
quickly changed to a maximum acid stage (pH 4) from which it
slowly returned to the alkalinity of the surrounding water (pH 7).
In Heliozoa, Howland (1928) shows that the initial pH of a gastric
vacuole of Aciinosphacrium eichhornii is about neutral or slightly
acid (pH 7 to 6.6). This lasts
for a period of five or ten min-
utes but changes to pH 4.3 ±
0.1 in all vacuoles in which
active digestion is going on,
while old vacuoles containing
indigestible remains have a pH
range from 5.4 to 5.6.
In view of the number of
different ferments which have
been isolated from different
types of Protozoa, it is quite
probable that digestion does
not take the same course in
all types. Pepsin-like ferments,
which dissolve albumins in an
acid medium, were isolated by
Krukenberg (1886) from the
Mycetozoon Aethalium septi-
cum, and by Hartog and Dixon
(1893) from the ameba Pelo-
myxa pahisiris, while Metsch-
nikoff (1889) showed that
the food vacuoles in the Plas-
modia of Aethalium have an
acid reaction favorable to the activity of such ferments. Trypsin-
like ferments have likewise been isolated by Mouton (1902), from
soil amebae cultivated in large numbers on agar; also diastatic fer-
ments were easily obtained from Balautidium coli by Glaessner
(1908), and from Pelomyxa palustris by Hartog and Dixon (1893).
The typical course oi' a gastric vacuole through the endoplasm
of ciliates has been carefully worked out by Greenwood and by
Nirenstein for Carchesium and Paramecium caudatum (Fig. 102).
Prowazek (1897) staining with neutral red found a collection of red
granules about the gastric vacuole; similar granules were observed
Fig. 102. — Carchesium polypinum ?
History of food vacuole; (c) stage of stor-
age and little change; (b) stage of acid
reaction; (c) neutral reaction. (After
Greenwood.)
GENERAL PHYSIOLOGY 197
by him and by Nirenstein (1905) to pass into the gastric vacuole
and to mix with the food substances from which circumstance they
were regarded by both observers as the bearers of ferments (trypsin-
like according to Nirenstein). The so-called Excretperlen (excre-
tory granules) first described by Prowazek (1897) and interpreted
by him, by Nirenstein and by Doflein (1916) as furnishing evidence
of excretion through the general cell membrane, with equal justifi-
cation may be interpreted as secretory granules. If the neutral
red staining granules about the gastric vacuoles are bearers of
ferments as maintained by Prowazek, they certainly are secretory
in nature. There is some uncertainty, however, as to the identity of
these with the so-called excretory granules. The experiments of
Slonimski and Zweibaum (1922) show that there are two types
of these granules which they call A and B, and that the peripheral
granules (B) which exude from the membrane vary in number and
size according to external conditions of temperature and internal
conditions of vitality, being rare or absent prior to conjugation.
The nature of these varying granules and their function in metab-
olism are still unsolved problems.
In connection with secretions we may take into consideration
the various poisons produced by Protozoa either in the form of
toxins exuded by the individuals and soluble in the surrounding
medium, or in the form of endotoxins which are liberated only
when the individual is disintegrated. What little is known about
these secretions is mainly in connection with parasitic forms and
here knowledge is limited to the effects produced upon the host (see
Chapter X). In general it may be stated that, if we except the
toxins produced by the so-called Chlamydozoa (particularly small-
pox and rabies organisms), the poisons of protozoan origin are much
slower and indefinite in their action on the host than are bacterial
toxins, and the course of the specific diseases caused by pathogenic
protozoa is relatively much slower than diseases caused by bacteria.
Relatively few toxins of protozoan origin have been extracted and
used in experimentation. One such, called sarcocystin, was obtained
from sarcosporidia by Pfeiffer and Gasparck and by Laveran and
Mesnil (1899). The latter found that rabbits are soon killed by
the blood injection of sarcocystin in glycerin solution, also that
crushed cysts give rise to characteristic pathological effects in the
muscles, whereas no such reaction accompanies the presence of
uninjured cysts.
Filtered blood of malaria victims, if taken at the height of parox-
ysm and injected into a malaria-free individual, produces in the
individual a characteristic malarial paroxysm according to Rosenau
and his co-workers, and analogous "paroxysm toxins" have been
detected in connection with other blood parasites.
Toxins from organisms of amebic dysentery are more regional
in their action, causing local ulceration and abscess formation indi-
198 BIOLOGY OF THE PROTOZOA
eating a cytolytic process possibly due to secretions of digestive
fluids. There is still some uncertainty, however, in regard to this
matter, and the possibility of participation by bacteria in the
reactions is not excluded.
Notwithstanding the serious diseases in man and mammals
generally due to trypanosomes, there is very little positive evidence
that secretions are responsible for the effects produced. Experi-
ments with extractives from Trypanosoma brucei by Kanthak,
Durham and Blanford, and by Laveran and Mesnil, gave no indi-
cation of toxic effects. On the other hand, Novy and MacNeal,
injecting dead Trypanosoma brucei in guinea-pigs obtained definite
fever symptoms, loss of weight and local ulcerations which, however,
they did not trace to the effects of a specific toxin.
Somewhat more positive evidence is accumulating in regard to
the possibility of endoenzymes locked up in the trypanosome proto-
plasm and liberated on disintegration. Thus a number of observers,
among whom may be enumerated MacNeal, Plimmer, Leber,
Martin and others, have interpreted the rise in temperature of
organisms with trypanosomiasis as due to the presence of endotoxins,
freed in the blood upon death and disintegration of trypanosomes
resulting from treatment with medicaments. Also Uhlenhuth,
Woithe, Hiibener and others have concluded that endotoxins fatal
to rats are liberated if blood containing Trypanosoma equiperdum
is first dried, then dissolved again and injected into rats. Schilling,
Braun, Teichmann, on the other hand, got no reaction upon injecting
dead pathogenic trypanosomes into the peritoneum or subcutane-
ously (see pp. 363 and 384).
In all of these cases, with the exception of sarcocystin, the evi-
dence in favor of the secretion of exotoxins or the presence of
endotoxins is purely circumstantial and verification by chemical
and biological methods with exclusion of other possible contributing
factors has not yet appeared.
Digestion of Carbohydrates and Fats. — Specific ferments for the
transformation of starch into soluble sugar have not been isolated;
nevertheless, the evidence that such action takes place is convinc-
ing. Curiously enough, this evidence does not apply to the Infusoria
where very little digestion, beyond a slight corroding of starch
grains, occurs. In rhizopods, however, especially in the ameboid
Pelomyxa and in species of Ameba, starch grains are entirely dis-
solved, according to the observations of Stole (1900) who found
that the characteristic refringent granules of Pelomyxa palustris
have a very definite relation to carbohydrate nutrition. These
granules (Glanzkorper) are filled with glycogen, the volume of
which increases up to fourfold when the animals are fed with starch,
and decreases to entire disappearance when they are starved.
GENERAL PHYSIOLOGY 199
Even cellulose is said by Stole to be digested by this organism and
Schaudinn made the same observation on the Foraminiferon Cal-
cituba polymorpha. In Foraminifera generally, according to Jensen,
and in myxomycetes, according to Wortmann, Lister and Cela-
kowsky, starch may be similarly digested. The flagellates appar-
ently have in some cases, at least, the same power of dissolving
starch. Thus, Protomonas amyli and Phyllomitus augustatus eat
practically nothing but starch, a fact indicating the action of
appropriate digestive ferments. The Hypermastigidae which are
abundant in white ants (termites) are unusual in their ability to
digest cellulose. It has been shown that these flagellates live as
symbionts with their termite hosts digesting the wood eaten by
them. The termites die if deprived of their protozoan symbionts
by heating or by oxygenation; the protozoa die if the wood diet of
the termites is stopped (Cleveland, 1923).
In few Protozoa has the actual digestion of fat been observed.
Under experimental conditions, ingested fats are usually carried
along unchanged in the protoplasm. We cannot state arbitrarily,
however, that fats are not emulsified and used as food. On the
contrary, it is difficult to account for the presence of oils and fat
bodies in varying quantities in all groups of Protozoa under any
other assumption, despite the negative results of Stamiewicz (1910)
and of Nirenstein (1909). Positive results indeed have been ob-
tained by Dawson and Belkin (1928), who injected oils of different
kinds into Amoeba proteus; of these 8.3 per cent of cod-liver oil was
digested, 8.2 per cent of olive oil, 4 per cent of cotton-seed oil,
3.5 per cent of sperm oil and 1.4 per cent of peanut oil.
Saprozoic Nutrition. — In holozoic nutrition the food substances
are in the form of complex proteins, carbohydrates and fats, making
up the bodies of the various organisms ingested. In saprozoic
and saprophytic nutrition the food substances are less complex
chemically, consisting of materials dissolved out of the disintegra-
ting bodies of animals and plants. These are taken in, not through
the agency of specialized oral motile organs, nor through a definite
mouth, but are absorbed through the body wall. Many of the
smaller types of flagellates obtain their nutriment in this way,
extracts or infusions of animal or plant tissues containing various
salts and organic compounds forming excellent culture media for
such Protozoa. Little is known, however, of the chemical make-
up of such fluid substances, nor is it known whether they are
prepared for absorption by chemical processes due to the activity
of the receptive organism; nor is there any evidence to indicate
processes of digestion subsequent to their absorption. The general
assumption, based upon the thriving cultures in infusions of dis-
integrating animal and plant matter, has been that dissolved
200 BIOLOGY OF THE PROTOZOA
proteins are taken into the protoplasmic bodies of many kinds of
Protozoa by absorption through the general cortex or through some
specialized region for the purpose.
From experiments with the green alga, Euglena gracilis, by Zum-
stein (1900), Ternetz (1912), et al., it appears probable that some
saprozoic forms of Protozoa get their main nourishment from
amino-acids derived from disintegration of animal and plant matter
through the agency of bacteria, and from carbohydrates in solution.
The necessary mineral matters are obtained from the surrounding
alkaline medium.
Emery (1928), experimenting with Paramecium caudatum, found
that a measurable quantity of amino-acids is utilized in place of
the normal bacterial food. With a mixture of equal parts of ten
amino-acids he figured out that 100,000 Paramecium caudatum in
twelve hours would use 48.3 per cent of a 0.1 per cent solution,
while different amino-acids used singly gave differing results.1
In this connection, it is important to consider the possible inter-
action of excretion products of different Protozoa upon themselves
and upon each other, as well as the effects of products of bacterial
action. It has long been known that isolation cultures are fre-
quently threatened by the growth of detrimental bacteria. On
a 'priori grounds it is not improbable that excretion products of
Protozoa themselves may have such an effect. Woodruff (1912,
1913) has studied this problem in connection with Paramecium
aurelia and the hypotrichous ciliates, Stylonychia pustulata and
Pleurotricha lanceolata, and found that Paramecium, when placed
in filtered medium which had contained enormous numbers of
Paramecium in pure culture, were manifestly weakened in vitality.
Similarly the hypotrichs, when placed in filtered medium which had
swarmed with hypotrichs, showed a weakened vitality. When,
however, Paramecium was placed in filtered hypotrich culture
medium, the result was an increased vitality. Woodruff concluded
that excretion products from Paramecium are detrimental to
Paramecium, and hypotrich products to hypotrichs, while the
latter products have a somewhat stimulating effect on Paramecium.
This may be, as Woodruff suggests, of some importance in deter-
mining the sequence of protozoon forms in a limited environment
such as hay infusion.
1 The degree of absorption of specific amino-acids is as follows:
Per Per
cent. cent.
Mixture of different amino-acids Alanine 15.5
(except arginine) . 48 . 3 Glutamic acid 13.2
Glutamic acid hydrochloride . 45 . 6 Leucine 12.0
Cysteine hydrochloride 26.3 Glycocoll 9.6
Aspartic acid 25 . 1 Tryptophane 9.6
Tyrosin .17.7 Phenylalanine 7.7
Arginine 15.9
GENERAL PHYSIOLOGY
201
Specific structural adaptations, useful in methods of food-getting,
are characteristic. Haustoria-like processes, derived from the
epimerites of gregarines, in some cases extend deeply in the tissue
cell {Stylorhynchus longicollis, Echinomera hispida, Pyxinia moebiuszi,
etc., Fig. 103). The coccidian Caryotropha mesnili, according to
Siedlecki, shows a significant relation between the nucleus of the
host cell and that of the parasite. This organism is a parasite in
the spermatozoa of the annelid Polymnia nebvlosa where the sperm
cells are aggregated in bundles in the characteristic annelid fashion,
usually about a feeding mass or blastophore. The parasite gets
into such a cell as an agamete or sporozoite, one only of the bundle,
Fig. 103. — Food-getting adaptations of Sporozoa. 1, Pyxinia moebiuszi with epi-
merite deeply insunk in the epithelial host cell (after Leger and Dubosq) ; 2, Caryo-
tropha mesnili with an intracellular canal from the nucleus of the host cell (ti). (After
Siedlecki.)
as a rule, being infected, and as it grows the nucleus of the cell is
displaced to one side and the cell loses its characteristic structure,
becoming hypertrophied and distorted (Fig. 103, 2). Not only the
infected cell but all the other cells of the spermatogonia bundle are
affected, and none of them continues the normal development, but
they become arranged like epithelial cells about the hypertrophied
infected cell.
The specific effect of the young Caryotropha on the infected cell
consists not only of the enlargement of that cell, but of a definite
feeding mechanism by which the parasite is supplied with food.
That the nucleus is a center of constructive metabolic changes is
well assured at the present day, and the conditions in these para-
202
BIOLOGY OF THE PROTOZOA
sites suggest the peculiar relation which Shibata (1902) has described
in the intracellular mycorhiza, where a mycelium thread is grown
straight toward the nourishing cell nucleus of the host, causing
marked hypertrophy on the part of the cell. In Caryotropha,
the nucleus of the host cell is pushed to one side and the parasite
assumes such a form that the nucleus lies in a small bay (Fig. 103,
2n). In the cytoplasm of the cell an intranuclear canal is then
formed which runs from the host nucleus to the nucleus of the para-
site, and Siedlecki holds that the food of the parasite is all elab-
orated by the nucleus of the host cell, while the other spermatogonia
form a protective epithelial sheath around it. When the parasite
is full grown the cell is destroyed and the bundle degenerates.
_ O.
Fig. 104. — Ellobiophrya donacis, a peritrich with ring-form attaching organ which
passes around the gill bars of the lamellibranch. X 800 and 1350. (After Chatton
and Lwoff, Bull. biol. de la France et de la Belgique, 1929; courtesy of Prof. N.
Caullery and Les presses TJniversitaires de France.)
Other special adaptations in the interest of food-getting are fre-
quently spectacular. Thus Ellobiophrya branchiorum (Chatton and
Lwoff, 1928), a commensal ciliate on the gills of the lamellibranch
Donax sp., has developed a curious, posterior, ring-form process
whereby it is firmly anchored to the gill bars (Fig. 104).
It is difficult to draw the line between symbionts, commensals
and parasites. Symbionts are organisms living with a host in such
a relation that both are benefited ; commensals are organisms which
live with a host without benefit or injury to the latter but to their
own advantage, and parasites are organisms which, to their own
benefit, cause injury in one form or other to the host. Symbiosis
GENERAL PHYSIOLOGY 203
is well illustrated by the harmonious life of some chlorophyll-bearing
forms, Zoochlorella, Zooxanthella, etc., and Protozoa in which the
former live (Paramecium bursaria, "yellow cells of Radiolaria and
Foraminifera," Stentor viridis, Amoeba viridis, Vorticella viridis, etc.),
and it is conceivable that some gut-dwelling forms may perform a
useful activity for a host by disposing of pernicious bacteria, or by
preparing food substances for use by the host as do Hypermastigidae
in termites (Cleveland). Commensals, such as Endamoeba coll,
Endamoeba nana, Trichomonas species and other intestinal forms
may, on occasions, turn into parasites, as is the case with Tricho-
monas (Tritrichomonas, Kofoid), Giardia (Lamblia), etc.
2. Products of Assimilation. — With the majority of forms the
products of assimilation vary with the type of food used and are
frequently so abundant in the cell as to give a characteristic appear-
ance or color to the animal. Thus the refringent granules of Pehmyxa
palustris (Stole.) produce a peculiar refringent effect. The brown
granules of Plasmodium, species, characteristic of malaria, are
products of hemoglobin assimilation. Similarly the coccidin of
Coccidia; stentorin of Stentor coeruleus and Folliculina ampulla; the
pink of Holosticha; the lavender of Blepharisma undulans or the
red of Mesodinium rubrum, are examples of the great variety of
colored cellular substances dependent upon the food that is eaten.
In the absence of the specific kinds of food which yield these chromic
products the organisms are colorless, and colored or colorless indi-
viduals of the same species may appear in the same culture (see
p. 134).
CHAPTER VI.
REPRODUCTION.
Of all the marvels associated with the Protozoa there is nothing
more staggering to the imagination than the fixity of type which
their protoplasm manifests. The genotype, represented by the
derived organization, subject to minor variations of a fluctuating
character in the course of a normal life history, or subjected experi-
mentally to all kinds of unusual environmental conditions, remains
fundamentally unchanged. Types modified through amphimixis or
through permanent modifications of the environment may lead to
divergent types. This conservatism or fixity of type is a function
of the organization which has been continuous in the past and will
be continuous in the future. The activities which take place in
the organization, the sum total of which constitute vitality, are
discontinuous, they have been and will continue to be dependent
upon the interactions between organization and environment.
The single individual which we study under the microscope has
had no such history in the past and no promise for the future; its
span of life as an individual is measured by hours or days only. It
is the temporary trustee of a small portion of an organization which
has been parceled out among unknown myriads of similar trustees.
Its metabolic activities are the interactions within the organization
and as a result of these activities the fluctuating variations charac-
teristic of the genotype follow one after another in the form of
inevitable differentiations which may or may not be visibly indi-
cated by structural changes (see Chapter VII). Ultimately its possi-
bilities of further vitality as a single individual are exhausted and
it undergoes its final manifestation of vitality. The significance
of this final act is a function of all genotypes and of all organizations
whereby the organization is further parceled out to two or more
trustees. It is reproduction by division, which by reason of its
universal occurrence is one of the most characteristic properties of
protoplasm.
There is no doubt that division of the cell is a phenomenon of
deep-reaching significance; we shall endeavor to show that the
organization as parceled out to the descendants by division is not
a mere equal division of the protoplasm of the individual with its
load of metaplastids and other modifications of the organization,
but a renewed or purified organization such as the individual received
when it was formed. Unlike Metazoa, with the processes of division,
the old derived organizations of Protozoa are lost by absorption,
REPRODUCTION 205
the organization being de-differentiated, and the protoplasm has a
renewed potential of vitality.
In order to understand the relations of division to the chain of
metabolic activities we should know more about the conditions
under which division occurs, and the "causes" of division. There is
very little real evidence for conclusions in this matter but there
have been many theories. The latter for the most part are based
either upon analogies with physical phenomena or upon hypothetical
"spheres of influence" of morphological elements of the cell. They
have been developed in the main to interpret phenomena of division
in metazoan cells, particularly in egg cells, and fall completely to
the ground when applied to division of Protozoa. So it is with the
contractility hypothesis of Heidenhain, Driiner and others, who see
in the spindle fibers and astral rays a contractile system whereby
the nucleus and cell are divided in a strictly mechanical manner.
The intranuclear spindle and the absence of cytoplasmic rays in
the great majority of Protozoa are enough to show that such physical
interpretations do not reach to the root of the matter. The " spheres
of influence" hypotheses, based upon the kinetic center of the cell
and its influence on the cytoplasm, was developed by Boveri in the
attempt to associate cell growth and the causes of division. The
"energid" theory of Sachs and Strasburger was an analogous effort
to trace the causes of cell division to increasing volume of the cell
through growth, each nucleus having its sphere of influence in the
cytoplasm and dividing when the volume of the cell outgrows the
sphere of activity of the nucleus. The Kernplasmverhaltnis theory
of Hertwig was based upon somewhat similar grounds. Accord-
ing to this the volume of the nucleus bears a certain normal relation
or ratio to the volume of the cytoplasm in young actively func-
tioning cells, evidence of which in Fronionia was given by Popoff
(1909) and by Hegner (1920) in the equidistant distribution of nuclei
in various species of Arcella. With increasing age this ratio is
altered to the advantage of the cytoplasm until division of the cell
restores the normal ratio. With uninucleate forms such as Para-
mecium or Fronionia there is some evidence of change in relative
volumes, and careful measurements by Popoff (1909) and other
followers of Hertwig are adduced to support the hypothesis. In
these forms the volume of the nucleus is proportionally reduced
until just prior to division when the nucleus rapidly increases
in volume and divides. Looper (1928) more recently, by mech-
anical stimulation, caused Aciinophrys sol to fuse with enucleated
fragments from other individuals. This led to change in the nucleus-
cytoplasm ratio to the advantage of the cytoplasm. Such forms
divided from one-half to two times faster than the controls. If,
on the other hand, some cytoplasm is cut away, the reduced cells
(100 cases) divided on the average in eighty-eight hours, while
206 BIOLOGY OF THE PROTOZOA
the controls divided in twenty-four hours (see Hartmann's simi-
lar experiments with Ameba, p. 239). In Uroleptus, Uronychia
and similar forms, however, the many nuclei fuse to form one com-
pact and relatively small nucleus prior to division. It would seem
that such changes in relative volume of nucleus and cytoplasm are
better interpreted as the effects of underlying conditions which lead
to division rather than as the direct cause of division.
None of these theories is of much value in analyzing the antecedent
phenomena of division. These must be sought in the reactions of
different substances constituting protoplasm. Division of the cell
itself is a last step in a progressive series of reproductive changes
affecting the entire protoplasm, the constituents of which— micro-
somes, mitochondria, plastids, chromomeres, kinetic elements, etc.—
have already divided. It is in the division of these fundamental
granules in the make up of protoplasm that we must look for the
underlying causes of cell division. The dependence upon growth
and metabolism of the succession of division processes which char-
acterize reproduction is clearly evidenced by simple starvation exper-
iments, division ceasing with cessation of metabolic activities. There
is a possibility that environmental conditions play a more direct
part in reproduction than is indicated by their relations to metab-
olism. Thus Robertson (1921) concludes that a catalase (X sub-
stance) is secreted by the living cell which directly enhances division.
He found that two individuals, or more, of Enchelys farcimen in a
drop of culture medium would divide from four to sixteen times more
rapidly than a single individual in a similar drop, the result being
interpreted as due to contiguity of individuals. This, however, is a
direct contradiction of Woodruff's (1911) results with Paramecium
and Stylonychia, according to which the division rate is reduced
by accumulation of products of metabolism in the medium. Nor
is Robertson supported by other observers. Cutler (1924) for
example, found for Colpidium colpoda that the division rate depends
upon the number of bacteria present as food, and that increase in
number of individuals in a drop means a decrease in the individual
division rate. Greenleaf (1924) similarly found that solitary indi-
viduals of Paramecium caudatum, P. aurelia and Pleurotricha
lanceolata isolated in 2, 5, 20 and 40 drops of medium, gave a
highest division rate in five days in the 40-drop test, the lowest
in a 2-drop test. Also in Uroleptus mobilis, in a sixty-day test in
which 1 individual, 2, 3 and 4 individuals were isolated daily in
a single drop of medium the highest division rate was shown by
the solitary individual in a drop as shown in the following table
(see also table on next page) :
10 individuals, 1 to a drop, each divided in the sixty days . . 74. 1 times
20 individuals, 2 to a drop, each divided in the sixty days . 59 . 5
30 individuals, 3 to a drop, each divided in the sixty days . . 54 . 7
40 individuals, 4 to a drop, each divided in the sixty days . . 54 . 2
REPRODUCTION
207
Environmental conditions which alter the permeability of the
cell, thereby enhancing or retarding metabolic activities do, how-
ever, have a corresponding effect upon the division rate. Age of
individuals, or the protoplasmic organization at different periods of
the life cycle likewise has a determining effect on the rate of division,
the differences, as shown in the following table, being due to the
differences in the reactions of the protoplasm to the same medium
under different conditions of organization. Series 111 and 112, for
Uroleptus Mobilis Division Rate.
Experiment from September 2 1 to November 10, 1924.
t
Age.
Genera-
tion.
Divisions per individual.
Series.
No. in
drop.
First
ten
days.
Second
ten
days.
Third
ten
days.
Fourth
ten
days.
Fifth
ten
days.
Sixth
ten
days.
Total,
sixty
days.
f 1
12
7
10
13
9.
9
60
Ill
270
J 2
) 3
11
9
7
5
6
6
10
7
5
5
5
4
44
36
I 4
10
4
3
6
3
5
31
1
14
14
9
10
7
6
60
112
263
2
1 ;5
11
13
13
8
5
4
8
7
4
2
6
4
47
38
4
8
11
10
7
2
3
41
| 1
11
S
5
9
4
6
43
114
160
1 2
1 3
6
5
8
4
3
3
6
4
1
2
6
0
30
18
4
8
4
3
2
3
1
21
| 1
14
17
9
10
13
10
73
115
247
i 2
i 3
10
14
13
16
6
7
9
8
10
8
9
4
57
57
I 4
15
13
7
9
10
7
61
1
13
14
10
9
7
7
60
116
189
J 2
3
9
9
10
11
8
5
10
7
9
8
8
7
54
47
\ 4
7
7
3
7
6
4
34
1
16
18
11
10
14
12
81
117
133
l 3
14
14
17
17
7
8
10
9
8
10
9
9
65
67
4
13
17
6
8
10
8
62
f 1
IS
22
12
16
17
14
99
lis
140
J 2
IS
14
8
11
13
13
82
) 3
15
20
9
12
11
9
76
1 4
14
20
7
12
12
12
77 »
[ 1
15
19
10
10
10
8
72
11!)
110
J 2
] 3
15
11
14
14
7
7
7
8
7
6
9
6
59
52
4
10
14
6
8
7
5
50
1
18
19
11
13
13
12
S6
12 I
12
1 2
1 3
16
17
16
15
6
5
12
8
9
13
10
9
69
67
\ 1
16
15
9
9
13
11
73
18
23
13
16
18
19
107
121
10
J 2
14
24
9
8
15
18
88
3
15
23
10
11
14
16
89
I 4
19
21
10
11
14
17
92
208 BIOLOGY OF THE PROTOZOA
example, were 279 and 263 generations old at the beginning of the
experiment, the single individual isolated daily in a drop of medium
divided 60 times in sixty days; with 4 individuals in a drop, each
divided only 31 times. Series 120 and 121 were 12 and 10 genera-
tions old, and each solitary individual divided 86 and 107 times in
the same sixty days, and with the same medium freshly made each
day. From this table it is apparent that the division rate is reduced
by the presence of more than one individual to a drop. Furthermore,
the reduction of the division rate under such conditions is much less
for "y°ung" individuals than for old.
Substances making up the composition of living protoplasm are
constantly manufactured. Such substances, usually in the form of
granules, grow to a certain limit of size and each then divides. Evi-
dence for this is apparent only in the more obvious of the proto-
plasmic elements such as plastids, kinetic elements, chromomeres,
etc., the division of which has been mentioned in the preceding pages.
Finally the grand aggregate, the cell itself, divides as a last expres-
sion of the series of events that have taken place. It is evident
that such division of the cell as a whole constitutes only a small
part of the phenomena of reproduction and perhaps not the most
important part. While most of the elementary granules, apart
from those enumerated above, which make up the bulk of proto-
plasm, cannot be followed from their smallest stages to the stage
when they become visible, it is not inconsistent with the idea of
continuity from generation to generation to regard even the smallest
as retaining its integrity and reproducing itself by division. "For
my part I am disposed to accept the probability that many of
these particles, as if they were submicroscopical plastids, may have
a persistent identity, perpetuating themselves by growth and mul-
tiplication without loss of their specific individual type" (E. B.
Wilson, 1923).
While the division of a single granule results in the formation of
two probably identical granules of the same substance, the division
of aggregates of granules of different substance may or may not
result in identical daughter aggregates. The nucleus is such an
aggregate which, by ordinary equation division, is probably divided
into two identical halves, but in meiotic divisions the products of
the nucleus are different, visible evidence of which is shown by the
history of the sex chromosomes and by the results in modern
genetics. It is entirely possible that differentiations may arise from
such inequalities in nuclear division (see Chapter IX).
The cytoplasm of the cell, likewise, is such an aggregate, made up
of all the different substances variously distributed, which compose
living protoplasm. If all the granules were equally distributed at
division to the daughter cells, as are nuclei and many kinetic ele-
ments, then the products of cell division might be identical. Mor-
REPRODUCTION 209
phological evidence that all granules are not thus equally distributed
is furnished by all budding and spore-forming types, and by forms
like Dileptus gigas or Holosticha multinucleata, where the large
chromatin granules, while still in the process of division, are carried
bodily to one or the other daughter cell (Fig. 46, p. 92).
Reproduction whereby a type of organism is perpetuated and
distributed, is thus preeminently a process of division. In the last
analysis cell division is the only kind of reproduction known.
Potential individuals are contained in every germ cell, but germ
cells, like other cells, are formed by division and it follows that every
female reproduces as many potential offspring as eggs. Develop-
ment of such eggs, however, is usually dependent upon fertilization,
which is quite a distinct phenomenon, accessory to reproduction
and necessary in most animals, but not itself reproduction. In the
present chapter only a summary of the more obvious phenomena of
reproduction will be described, leaving the problems associated
with fertilization for treatment in a later section (see Chapter VIII).
It is division of the grand aggregate of protoplasmic substances,
/. e., division of the cell itself, that is usually described as reproduc-
tion of the Protozoa. Such reproductions are usually classified as
division, budding or gemmation, and sporulation, the inference
being that these are different modes of reproduction. In reality,
however, they arc different types of reproduction by division, and
such modifications would be expressed better by the terms equal
division, unequal division, and multiple division.
I. EQUAL DIVISION AND EVIDENCE OF REORGANIZATION.
In the ordinary metabolic processes of an active protozoon there
is evidence of a cumulative differentiation which indicates a differ-
ence in organization between a young cell immediately after division
by which it is formed and the same cell when it is mature and ready
itself to divide. Child (1916) mainly from experiments with cells
of the Metazoa, came to the conclusion that "senescence con-
sists in a decrease in metabolic-rate determined by the change
in, and the progressive accumulation of, the relatively stabile
components of the protoplasmic substratum during growth, develop-
ment and differentiation" (loc.cit. p. 333) . He further suggested that
in every cell division in unicellular animals, with the accompany-
ing processes of reorganization, there is some degree of rejuven-
escence and, if such rejuvenescence balances the cumulative differ-
entiation, continued life of the organisms by division alone may go
on indefinitely. By proper conditions of the environment it is ■
conceivable that such a balance may be established. On such an
hypothesis it is possible to account for the continued vitality of
animal flagellates in which fertilization processes are unknown, for
14
210 BIOLOGY OF THE PROTOZOA
the continued life of many of the higher plants, and for the con-
tinued life of the tissue cell cultures in the hands of Carrel and
others (see Chapter VII).
In many Protozoa there is unmistakable evidence of such reorgan-
ization processes which will be described in the following pages;
in many there is no visible evidence, but in such cases and in the
absence of other possibilities of reorganization, it is permissible to
assume that reorganization processes which escape the most vigilant
watchfulness of the observer, do actually occur.
A. Division in Mastigophora. — With very few exceptions cell
division in flagellates is longitudinal, beginning as a rule at the
anterior or flagellar end, the cleavage plane passing down through
the middle of the body. As the halves separate the two daughter
cells usually come to lie in one plane, so that final division appears
to be transverse. In the majority of forms the individuals divide
while freely motile, but this is by no means universal, variations
in this respect occurring in the same family and even in the same
genus.
As there are few details in the structure of a simple flagellate on
which to focus attention, descriptions of division processes are
practically limited to the history of the nucleus, kinetic elements
and the more conspicuous plastids. Here, in the main, are fairly
prominent granules of different kinds which divide as granules, and,
save for the chromatin elements of the nucleus, without obvious
mechanisms.
In the simpler cases there is little evidence that can be interpreted
as reorganization at the time of division, and the little we find is
limited to the motile organs. In the more complex forms, however,
there is marked evidence of deep-seated changes going on m the cell.
The earlier accounts of cell division in the simpler flagellates
described an equal division of all parts of the body including longi-
tudinal division of the flagellum, if there were but one, or equal dis-
tribution if there were two. One by one such accounts have been
checked up by use of modern technical methods until today there
is very little substantial evidence of the actual division of a flagel-
lum. The basal body and the blepharoplast usually divide, but
the flagellum either passes unchanged to one of the daughter cells
as in Crithidia, Trypanosoma, etc., or is absorbed in the cell. In
some doubtful cases it may be thrown off. If the old flagellum is
retained in uniflagellate forms the second flagellum develops by
outgrowth from the basal body or the blepharoplast. If the old
flagellum is absorbed, both halves of the divided kinetic element
give rise to flagella by outgrowths (Fig. 49, p. 95). Similarly,
if there are two or more flagella, one or more may be retained by
each daughter cell while the other, or full number, is regenerated.
In some cases, as in Herpetomonas musca-domesticae, the regenera-
REPRODUCTION
211
tion of a second flagellum occurs before division of the cell is evident,
a circumstance which evidently led Prowazek (1905) to conclude
that this organism is normally bi-flagellated (Fig. 170, p. 368).
E V\ F
Fig. 105.— Lophomonas blattarum. A, flagellar tuft and nucleus in calyx in pro-
phase of division; B, nucleus with chromosomes leaving calyx; paradesmose on side;
C-F, stages in nuclear division in the posterior part of the organism and formation
of new calyces and flagellar tufts. X 1850. (After Belaf, Erg. u. Fortschr. der
Zool., courtesy of G. Fischer.)
212
BIOLOGY OF THE PROTOZOA
Reorganization is indicated to some extent by these cases in which
the old flagellum is absorbed. It is still better indicated by a number
of flagellates in which the cytoplasmic kinetic elements, as well as
the flagella, are all absorbed and replaced by new combinations in
each of the daughter cells. Thus in Spongomonas splendida, accord-
ing to Hartmann and Chagas (1910) the old blepharoplasts and the
two flagella are absorbed and new ones are derived from centrioles
of the nuclear division figure (Fig. 49, p. 95). The phenomenon
cannot be regarded as typical of the simple flagellates, for in the
great majority the kinetic elements are self-perpetuating, even the
axostyles according to Kofoid and Swezy (1915) dividing in Tricho-
monas (Fig. 77, p. 145). This, however, has not been supported
by later workers.
Fig. 106.
-Vahlkampfia Umax. Nucleus in upper cell in full mitosis (promitosis).
(From Calkins.)
An extreme case of reorganization is apparent in the two species
of Lophomonas (L. blattae and L. striata) first described by Janicki
(1915). Here the parental calyx, basal bodies, blepharoplasts and
rhizoplasts all degenerate during division (Fig. 105). At division a
cytoplasmic centriole first divides with a connecting fibril which is
retained throughout as a parademose. The nucleus emerges from
the calyx in which it normally lies, and moves with the spindle to
the posterior end of the cell. The spindle takes a position at right
angles to the long axis of the cell; chromosomes, probably eight in
number, are formed and divided, and two daughter nuclei result,
each of which is enclosed by a new calyx while new basal bodies and
blepharoplasts apparently arise from the polar centrioles (Fig.
105). Thus the old kinetic complex, with the exception of the
cytoplasmic centriole, is discarded and entirely new_aggregates are
formed.
REPRODUCTION 213
B. Division in the Sarcodina. — It is questionable whether any
rhizopod divides in the very simple manner described by F. E.
Schultze for Amoeba polypodia. The "limax" types indeed approach
this simplicity (Fig. 106) but new discoveries are constantly at hand
to indicate that these are not as simple as they have been described.
Thus Arndt (1924) quite recently has given creditable evidence of
the existence in a simple ameba, Hartmannella klitzkei, of a definite
centrosome with centriole which is permanently extranuclear (Fig.
58, p. 106). At division of the cell the centrosome divides and the
daughter centers with their centrioles, take positions at the poles
of the nuclear spindle which originates within the nucleus. The
mitotic figure is thus made up of cytoplasmic elements, kinetic
elements derived from the nucleus, and chromatin. A similar
combination occurs in dividing Heliozoa. The original description
of division of Acanthocystis aculeata by Schaudinn, a form possessing
the characteristic central granule of the Heliozoa, has been consider-
ably modified by later observations. According to Schaudinn the
central granule or centroblepharoplast, which is the focal point in
the cell of the radiating axial filaments, divides to form an amphi-
aster (Fig. 50, p. 95) which becomes the central spindle of a typical
mitotic figure. The more recent observations of Stern (1924)
indicate that, as in the simpler ameba described above, the central
granule of Acanthocystis behaves as a cytoplasmic centrosome,
forming poles of a mitotic figure which is derived otherwise entirely
from the nucleus. Individuals which have been deprived of their
skeletons and membranes, which afford resistance to the activities
of the enclosed protoplasm, become "sprung," so to speak, and the
unusual freedom from restraint results in a separation of the eentro-
somes from the remainder of the spindle which completes its division
without further participation of the centrosomes (Fig. 0", p. 121).
Schaudinn's description of division in Heliozoa was confirmed in
the main by Zuelzer (1908) in connection with the aberrant form
Wagnerella boreal is. Here the axopodia-bearing portion of the cell
is free from the silicious mantle which covers the remainder of the
animal, the nucleus being in an enlarged pedal portion attached to
the substratum. The central granule is in the geometrical center
of the "head" and is the focal point of the axopodial filaments.
Each of the latter bears a granular enlargement similar to a basal
body. In preparation for division these move centripetally toward
the central granule forming a zone about it which divides with the
division of the central granule. In the meantime the nucleus
migrates from the other end of the body and with the spindle formed
by the divided central granule forms the mitotic figure.
Complications in the division process accompany the presence of
shells and tests. Where these are chitinous or pseudochitinous,
they may also divide with the cell body (Pseudodifflugia, Cochlio-
214
BIOLOGY OF THE PROTOZOA
podium). In other cases the individual divides within the shell,
after which one of the daughter individuals moves out and forms a
new shell, while the other one remains in the original test {Micro-
gromia socialis, Clathrulina elegans, etc, Fig. 107). In most cases,
however, a novel method of shell duplication found in no other divi-
sion of the Protozoa, has been developed. This process, known as
"budding division," occurs throughout the group of the testate
Fig. 107 '. — Microgromia socialis after Hertwig (A), and Microgromia sp. (B), original.
rhizopods and is well illustrated by the classical example of Euglypha
aheolata first described by Schewiakoff (188S). Here after full
growth following vegetative activity of the individual, the pseudo-
podia are drawn in; water is then absorbed whereby the protoplasmic
density is greatly reduced and the volume increased. This is fol-
lowed by a process resembling pseudopodia formation, the proto-
plasm emerging from the parent shell opening as a ball or dome which
REPRODUCTION 215
assumes the general form of the parent organism. A new membrane
of pseudochitin is formed about the extruded mass and on it the
silicious shell plates, preformed in the parent protoplasm, are now
cemented. In some forms, e. g., Arcella species, the chitinoid mem-
brane becomes the permanent shell of the organism, older shells
becoming brown or reddish by coloring due to oxides of iron ; in other
forms as in the Difflugiinae the chitinoid membrane is covered by
foreign objects picked up and stored by the parent organism. In
all cases of budding division after the budded individual is fully
molded, the nucleus divides and one-half passes into the protoplasm
of the new shell. The connecting zone of protoplasm between the
old and the new shell breaks out into pseudopodia and the two indi-
viduals separate (Fig. 11, p. 33).
The various types of foraminiferal shells, nodosarine, frondicular-
ine and rotaline— may be interpreted as due to a similar budding
division, but without actual separation of the parent and bud proto-
plasm, the type being dependent upon the density of the protoplasm
at the time of protrusion from the shell mouth (Fig. 19, p. 38).
There is very little evidence of reorganization of the protoplasm
at division in these rhizopods. The frequent withdrawal of pseudo-
podia and rounding of the body may be an indication of changes
going on within, as in Chlamydomyxa, Nuclearia, etc., but even such
questionable indications are absent in many cases of recent inves-
tigation (Belaf, Stern, et al.), where reorganization, if it occurs at
all, must be in the make-up of the protoplasmic and undifferentiated
elements.
C. Division in Infusoria.— Here in the most highly differentiated
forms of the Protozoa the processes of equal division are complex
and the protoplasmic changes far-reaching. With but few excep-
tions the division plane is through the center of the body and in a
plane at right angles to the long axis of the cell. The externals of
division are similar to division in other groups, with preliminary
division of the plastids and nuclei and final division of the cell body.
As in flagellates and some rhizopods the cup- or test-dwelling forms
divide within the parent cup, one of the daughter individuals migrat-
ing and forming a cup for itself. In some forms the daughter indi-
viduals may remain and share the old house (Cothurnia ingenita).
Where a tightly-fitting cell-covering is present as in Coleps hirtus,
it is divided transversely and the missing parts are regenerated by
the daughter organisms (Fig. 73, A, B, C, p. 136). In some Infusoria
as in the other groups, division in many cases is incomplete, the
daughter individuals remaining attached end to end as in Polyspira
delagei or Haptophrya gigantea. Or daughter individuals may
remain attached by incomplete division of their stalks, thus giving
rise to arboroid colonies of different types (Vorticellidae mainly).
In some forms, probably in the majority of ciliates, there appears
216
BIOLOGY OF THE PROTOZOA
^,
m
Fig. 108. — Paramecium caudatum, merotomy. 1, 2, and 3, different experiments,
the straight line indicating the plane of cutting; 3, the history of a monster; an original
cell, 3a, was cut as indicated; the posterior fragment (b) divided (c) into (d) and (e),
the latter formed a monster (3, f-o); enucleated individuals (h, k, and n) occasion-
ally separated from the parent mass. (After Calkins.)
REPRODUCTION 217
to be a definite and permanent division zone which indicates the
future plane of division and which is not displaced even after diverse
mutilations of the body. Thus if Paramecium caudatum is cut
across either the anterior or the posterior end, the cell ordinarily
does not regenerate more than a ciliated surface on the truncated
end. It divides like a normal form, but the division plane is not
in the geometrical center of the mutilated cell, but in the geomet-
rical center of the cell as it was before the cutting (Fig. 108). The
same is true of Uronychia transfuga or U. setigera (Fig. 113). In
daughter cells of dividing Paramecium the future division zones
appear to be formed at an early period, and if a daughter cell is
cut in such a manner that the geometrical center is destroyed
without, however, destroying the nuclei, monsters of various types
are produced indicating a complete upset of the organization (Fig.
ION, f-o). In some cases, e. g., Frontonia leucas, the geometrical
center, or division zone, has a different physical appearance from
the remainder of the cell (Popoff, 1908, also mentioned by Hance,
1917, as occurring in Paramecium), but in the majority of cases
there is no morphological evidence of the plane of division during
inter-divisional stages.
(a) Evidence of Nuclear Reorganization.— The two types of nuclei,
macronucleus and micronueleus, complicate the nuclear phenomena
at division. The macronucleus is more like a huge plastid of the
cell with active functions in metabolism, while the micronueleus is
generally interpreted as a germinal or racial nucleus, functioning
at division and particularly at conjugation.
Reproduction of the macronucleus in the majority of ciliates is
analogous to that of a plastid. Division is direct with only a few
isolated cases showing evidences of spindle formation or of indefinite
chromosomes. In preparation for division, however, there is evi-
dence in many forms of profound changes in the make-up of the
nucleus destined to divide and some of these afford evidence of a
clear-cut reorganization of this important element of the ciliate
(see p. 93).
In the less complicated types division of the macronucleus is
relatively simple. In Dileptus gigas, for example, the nuclear
material is in the form of many scattered chromatin and plastin
spheres, each of which divides prior to cell division (Fig. 46, p. 92).
There is no equal distribution of this chromatin to the daughter cells
but the daughter halves may go together to the daughter cell in
whose protoplasm they happen to lie. Some of the granules, how-
ever, those in the region of the division zone, may be represented in
each of the progeny.
In forms with a single ellipsoidal macronucleus as in many of the
commoner types (e. g., Paramecium, Colpoda, Frontonia, Glaucoma,
etc.), the macronucleus simply elongates and constricts to form
218 BIOLOGY OF THE PROTOZOA
two equal portions, one passing to each daughter cell (Fig. 35, p.
67). Band-form nuclei characteristic of Blepharisma, Spat Ind-
ium, Didinium, Vorticella, Euplotes, etc., condense into spheroidal
or ellipsoidal bodies before dividing. Where two macronuclei are
present in the usual vegetative cell, as in Oxytricha, Stylonychia,
Gastrostyla, etc., each divides independently of the other but syn-
chronously. As with band-form nuclei the beaded macronuclei
likewise form short rods as in Stentor, Spirostomum ambiguum,
etc., the beaded character in all cases being lost. Here the separate
beads are usually enclosed in a common nuclear membrane which
is constricted at intervals, the contained chromatin massing together
at the period of division. This is the condition in Uronychia trans-
fuga, also, the twelve to fourteen apparently separate macronuclei
are all connected, and the chromatin fuses prior to division to form
a relatively short ellipsoidal nucleus (Fig. 113).
In other types, however, the multiple macronuclei are independent
and entirely disconnected. They arise by division and retain their
independence during vegetative life. Thus in Urolepius mobihs
and U. halseyi the eight or more macronuclei are formed as a
result of a fourth division of the single parental nucleus from
which they came (cf. p. 93 and Fig. 110). In preparing for division
of the cell each of these eight nuclei of Uroleptus undergoes a
remarkable transformation. A nuclear cleft (Kernspalt) appears
in each, and in the cleft is a single large granule. The major part
of the nucleus lies below the cleft and is filled with densely-staining
chromatin; the other part lying above the cleft contains much less
chromatin in the form of fine granules (Fig. 47). This latter part,
together with the granules in the cleft, is thrown off and the
chromatin contents are distributed in the cytoplasm. When each
of the nuclei is thus freed from its distal portion the eight remaining
parts fuse, forming first a long banded nucleus, and later, by con-
densation, a relatively small ellipsoidal and single nucleus. This
divides twice or three times before the division of the cell is com-
pleted, the fourth division always occurring after the daughter
cells have separated (Fig. 110).
The micronuclei show no such complicated histories. If they are
multiple in the cell there is no fusion, nor is there any elimination
of micronuclear material. Each divides with the formation of an
unmistakable, but very minute, mitotic figure (Fig. 23, p. 50).
They are all represented furthermore by daughter halves in each
of the daughter cells.
(b) Evidence of Cytoplasmic Reorganization. — Not only is there
evidence of change in the cytoplasmic makeup at division through
the distribution and absorption of nuclear material as in Urolepius
mobilis, but the entire cytoplasm shows other evidence at this
period. In all eiliates there is a more or less clearly marked antero-
REPRODUCTION
219
posterior differentiation, the anterior part usually bearing the mouth
and the more or less specialized motile organs for the capture of food
Fig. 109.— Uroleptus mobilis. Stages in the fusion of the macronuclei prior to cell
division; rnicronuclei in mitosis. (After Calkins.)
or the directing of food currents, while the posterior part is usually
much less specialized. Should such a specialized ciliate be cut
through the center as Balbiani (1888) did for the first time, the two
220
BIOLOGY OF THE PROTOZOA
fragments would be different. The anterior fragment of a Stylo-
nychia or Uronychia, for example, would retain the highly differen-
tiated parts about the mouth while the posterior part would be
®
Fig. 110. — Uroleptus mobilis. Division stages after fusion of the macronuclei.
(After Calkins.)
relatively undifferentiated. The finer organization or genotype,
however, is represented by all of the protoplasm of the cell, and
that organization has the ability under proper stimulation, of form-
REPRODUCTION
221
ing all of the differentiated parts of the entire adult organism. By
regeneration, therefore, such a cut individual replaces the charac-
teristic structures of the posterior end by the anterior fragment and
the characteristic structures of the anterior end by the posterior
fragment (Fig. 113). By their usual method of transverse division
the ciliates have quite a different inheritance than do flagellates
which divide longitudinally. In the latter the highly differen-
tiated anterior ends and the less differentiated posterior ends are
equally divided so that the daughter cells have a like inheritance
(p. 95).
Fig.
111. — Uronychia Iransfuga with giant cirri, membranelles used in swimming,
ten macronuelear segments, and single micronucleus. (After Calkins.)
The processes through which the filiate cell passes during division
indicate that the organism is restored to a generalized condition
practically equivalent to an encysted cell. Except for the cyto-
stome the entire array of complex cortical organs is withdrawn and
a new set is formed from the cortical protoplasm. This significant
process first described by Wallengren (1900), later by Griffin (1910)
in hypotrichous ciliates, has been observed in many forms and is
probably characteristic of the entire group. It is most clearly
established in the Hypotrichida wThere the highly specialized and
conspicuous motile organs furnish suitable material for study.
According to Wallengren's description the membranelles of the
adoral zone slowly decrease in length as the process of absorption
222 BIOLOGY OF THE PROTOZOA
continues and at the same time minute buds of protoplasm appear
at the bases of these disappearing membranelles. These buds grow
pari passu with the dwindling motile organs until finally the latter
are entirely absorbed and the buds have developed into functional
membranelles. In the same way each cirrus is replaced by a new
growing bud quite regardless of the position in anterior or posterior
half. Undulating membranes are similarly withdrawn and replaced
by new ones so that the young cells formed by division of the meta-
morphosing parent cell receive a full set of new motile organs com-
mensurate with the size of the young organisms. The phenomenon
Fig. 112. — Chilodon uncinatus. New mouth and basket replacing the old ones
prior to cell division. (N.B.) New mouth and basket; (O.B.) old mouth and basket
before degeneration and disappearance; (P.B.) new mouth and basket for the pos-
terior individual after division. (After MacDougall.)
is very striking in forms with giant cirri such as the jumping types
of Euplotidae— Diophrys or Uronychia. In the latter genus the
great posterior cirri are the most conspicuous organs of the cell
(Fig. 111). The buds which are to grow and replace them are appar-
ent before there is other external evidence of the approaching
division and even before the nucleus has concentrated into its divi-
sion form. At the same time similar buds appear in the division
zone, that which is destined to form the giant-hooked cirrus appears
first and is always larger than the others which appear one after the
other according to ultimate size. Owing to their minute size it
has not been determined whether or not the individual cilium is
REPRODUCTION
223
withdrawn in like manner and replaced by new ones. In some, at
least, according to the observation of MacDougall on Chi lotion
uncinatus (1925) such substitution does take place and it is quite
probable that it is universal. The interesting experiments of
Dembowska (1925) show that removal of a single cirrus of Stylo-
Fig. 113.— Uronychia Iransfuga, merotomy and regeneration. 1, cell immediately
after division, cut as indicated; 2, fragment A of 1, three days after the operation;
no regeneration; 3, cell cut five hours after division; 4, fragment A of 3, three days
after operation, no regeneration; 5. cell cut at beginning of division as indicated into
fragments A, B, and C; A', B' , C", fragments A, B and C, twenty-four hours after
the operation; fragment A regenerated into a normal but amicronucleate individual
(A'); B, C divided in the original division plane forming a normal individual (<'') and
a minute but normal individual (B'). (After Calkins.)
nychia mytilus causes regeneration of the entire motile apparatus,
but no such result follows extirpation of any body region that is
free from cirri or cilia.
The phenomenon is obviously analogous to the absorption and
renewal of flagella in the flagellates. Whether or not there is a
224
BIOLOGY OF THE PROTOZOA
similar division of the basal bodies of the cilia and grannies of the
silver line system has not been fully established.
Other evidence of protoplasmic reorganization at division is
furnished by the history of some of the functional metaplastids of
the cell. Trichocysts are apparently handed down without change
Fig. 114. — Glaucoma scintillans. A, individual at beginning of division with
silver line system. The beginnings of the month of the posterior daughter cell are
seen on striation No. 1. B—F, successive stages in formation of the posterior mouth.
(After Chatton, A. and M. Lwoff and Monod, Compt. rend. Soc. biol., 1931, courtesy
of Masson et Cie.)
(Fig. 35, p. 67), but there is good evidence that the more compli-
cated aggregates of trichites are absorbed and replaced by new ones.
This is the case for example in the Chlamydodontidae, where the
complex oral baskets are replaced by new ones at each division
(Enriques, Nagler, MacDougall, et ah, Fig. 112).
REPRODUCTION 225
From this brief survey it is quite evident that far-reaching changes
of the protoplasmic organization take place at periods of division.
Both nuclei and cytoplasm are necessary but the micronucleus
apparently may be lost without destroying the power of the cell to
divide. Amicronucleate races of ciliates, arising possibly through
defective reorganization and division after conjugation (see Moore,
1924), have been maintained in culture for many generations by
division, although they are ultimately lost (see (Chapter VII). On
the other hand, the power to regenerate is connected in some manner
with the micronucleus. Thus young cells of Uronychia transfuga,
when transected with a scalpel, will regenerate only that fragment
which contains the micronucleus (Calkins, 1911, Fig. 113; Young,
1923). In old cells, however, both fragments regenerate regardless
of the presence or absence of a micronucleus, a fact indicating a
change in organization with advancing age (Fig. 113, 5).
The fate of the motorium and of the coordinating fibrils both
endoplasmic and those of the silver line system, at division is still
unknown. It is a significant fact that the peristome and the peri-
stomial organs appear first in the more specialized anterior half of
the ciliate cell, and from this position gradually shift to the region
immediately posterior to the division zone (Figs. 109, 110). The
relation of the posterior mouth to the silver line system in a dividing
form of Glaucoma scintillans is clearly shown by Chatton, Lwoff
(A. and M.) and Monod (1931). The complicated oral membranes
of this organism are formed as a result of division of the blepharo-
plasts at a localized region of certain lines of the silver line system
(Fig. 114). In Vorticella according to Biitschli (1888) after Fabre,
the peristome and adoral zones are reversed in the daughter cells.
II. UNEQUAL DIVISION (BUDDING OR GEMMATION).
In reproduction by budding or gemmation, one or more minute
fragments of the cell are produced by unequal division of the
organism. Parent and offspring are thus distinguished, their rela-
tive sizes varying in different cases. In many instances both parent
and offspring continue to live after such reproduction. In many
other instances the residual parental protoplasm is no longer able to
carry on metabolic activities and dies. Illustrations of both types
abound in all groups of the Protozoa, the buds being formed either
on the periphery of the parent in so-called exogenous budding, or
within the protoplasm of the parent in so-called endogenous budding.
The minute cells that are formed by budding always contain a por-
tion, sometimes one-half, of the nuclear structures of the parent
and may develop asexually into organisms similar to the parent, or
they may be differentiated as gametes requiring fertilization before
development.
15
226
BIOLOGY OF THE PROTOZOA
A. Exogenous Budding.— In Acanthocystis aculeata according to
Schaudinn (1896) and in Wagnerella borealis according to Zuelzer
(1909) the nucleus of the cell divides one or more times by simple
constriction and without the formality of mitosis or participation
of central granule. The minute nuclei thus formed wander to the
periphery of the cell where they are pinched off in minute cells.
In Acanthocystis these buds form minute amebae which after four
Fig. 115.
-Ephelota biitschliana, a suctorian. Budding individual with five exogen-
ous buds. N, branching macronucleus. (After Calkins.)
or five days of activity settle down and metamorphose into young
Heliozoa (Schaudinn). The buds have no central granule, but during
metamorphosis a kinetic element emerges from the nucleus and
this becomes the central granule of the adult Acanthocystis (Fig. 50,
p. 95). In Wagnerella borealis, according to Zuelzer, the buds which
are formed in a similar manner are flagellated, but her description in
other respects follows that of Schaudinn.
In Infusoria, particularly in Suctoria, exogenous budding is not
REPRODUCTlo.X
227
uncommon. In Ciliata it is comparatively rare and limited appar-
ently to the Conotrichida and some parasitic forms. In Spirochona
(ic mini para according to Hertwig a swelling appears at one side of
the base of the peculiar funnel-like peristome. The nucleus divides
equally, one-half passing into the swelling which, with only partial
peristomial development, breaks away from
the parent and then completes its peri-
stomial differentiations.
In Suctoria similar exogenous buds,
either single or multiple, are formed from
the oral extremity of the cell (Fig. 115).
Such buds are dissimilar to the parent
which they come to resemble only after a
period of metamorphosis and development.
In Sporozoa, with the exception of some
Cnidosporidia, exogenous budding is lim-
ited to unequal division in gamete-forming
processes. Thus, in Gregarinida and in
microgametocytes of Coccidiomorpha the
nucleus of the cell undergoes several divis-
ions, the final products arranging themselves
about the periphery from which they be-
come nuclei of variously formed gametes
budded out from the surface (Fig. 173,
p. 403). In all such cases the parent
protoplasm dies after giving rise to the
buds. In some ( 'nidosporidia, on the other
hand, budding processes appear to be
normal activities carried on during the
vegetative life of the organisms. Accord-
ing to Cohn (1895) large numbers of buds,
each containing several nuclei, may be
formed from the periphery of Myxidium
lieberkilhni. The phenomenon appears to
be an exaggeration of the peculiar process
of division termed plasmotomy by Doflein,
whereby a multinucleated cell divides
spontaneously into two more or less equal
parts as in Chloromyxum leydigi accord-
ing to Liihe and Doflein, or into several parts, as in the Coccidian
Caryotropha mesnili and Klossiella maris and termed "schizonto-
cytes," or "cytomeres" by Siedlecki (1902).
Terminal exogenous budding is characteristic of some parasitic
ciliates and a chain of posterior reproductive bodies is formed as
in Radiophrya limnodrili (Fig. 116).
Fig.
Radiop
limnodrili, astomatous fili-
ate with terminal budding.
(After Cheissin, Archiv f.
Protistenkunile, courtesy of
G. Fischer.)
228
BIOLOCY OF THE PROTOZOA
B. Endogenous Budding. — This type of unequal division is not
so widely distributed amongst Protozoa as is exogenous budding
and is apparently not represented at all in flagellated forms. It
does occur, however, in all of the other groups.
In Sarcodina endogenous budding has been described mainly in
connection with the testate rhizopods. In Centropyxis aeuhata
according to Schaudinn (1903) it leads to gamete formation, but
in Arcella vulgaris', according to Swarczewski (1908) and Elpatiewsky
(1909) it is a form of asexual reproduction.
In Infusoria internal budding is characteristic of many types of
Suctoria, but is apparently not represented in the Ciliata. In the
simplest cases the budding area at the anterior end becomes internal
by insinking of the anterior surface and constriction of the body
walls on all sides, so that the reproducing area is enclosed by living
■agjnpjp
Fig. 117. — Endogenous budding in Suctoria. A, B, two stages in the formation
of a bud (b) and (c), of Tokophrya quadri partita; C, Acincta tuberosa with endogenous
buds (e) and (d). (From Calkins after Butschli.)
protoplasm which thus becomes a potential brood chamber within
which the buds develop. Such buds may be single, as in Toko'phrya
quadripartita (Fig. 117, A, B), or multiple as in Metacineta (Fig.
117, C), and are always provided with cilia either as girdles or
otherwise. Through the activity of these cilia the buds swim freely
about in the brood chamber until they finally emerge through a
"birth-pore" and after a variable period as free swarmers or as
parasites in other Infusoria, they develop into adult forms of
Suctoria. Cilia in Suctoria are thus confined to the embryonic
stages and their various arrangements on the buds of different species
recall the types of ciliation in the other branch of the Infusoria.
A biologically interesting phenomenon of internal budding is
described by Collin (1911) in the case of Tokophrya qjchpum. Here
a brood pouch is formed by the cortical protoplasm within which
REPRODUCTION
229
the rest of the protoplasm becomes metamorphosed into a single
bud with cilia. When mature this bud leaves the parent membrane
on its old stalk and swims oft" as an embryo (Fig. 118).
In Sporozoa endogenous budding is manifested in a number of
different ways. In some it is apparently a method of multiplicative
reproduction, in others it is associated with gamete formation or
with sporulation. Asexual reproduction by internal budding is
illustrated by some of the Schizogregarinida where a typical brood
pouch is formed through which the internal buds escape through a
birth opening as in Suctoria. The Eleutheroschizon dubosqui, accord-
ing to Brasil (1906), the nucleus divides repeatedly until many are
formed (Fig. 119, A-D). Each is then surrounded by a small
portion of the parent protoplasm cut off from the rest of the cell.
A B C
Fig. 118. — Tokophrya cyclopum, the entire cell, except the membrane, is used in
the formation of a single bud which develops cilia (B) and swims off, leaving the old
membrane to shrivel up on its stalk (C). (After Collin.)
The central portion becomes vacuolated and opens to the outside,
the agamonts making their way through the opening, leaving the
remnants of the parental protoplasm to degenerate. Similarly in
Schizocy.stis sipunculi, Dogiel (1907) described the formation of a
brood pouch becoming filled with agamonts derived by internal
budding from the parent protoplasm (Fig. 119, E-G). Gametes
formed by internal budding are described by Leger (1907) in con-
nection with the life history of Ophryocystis mesnili. Here after
two ' 'maturation" divisions of the nucleus in each of the gamonts
united in pseudoconjugation, a single free cell is formed in each
gamont by internal budding (Fig. 120). Each bud here is a gamete
and the zygote is formed by union of the two in the parental brood
chamber.
230
BIOLOGY OF THE PROTOZOA
The phenomena of internal budding in the ameboid Myxosporidia
of the Cnidosporidia, are still different in character and fate of the
buds. Here in the endoplasm local islands of protoplasm are quite
Fig. 119.— Endogenous budding in Gregarinida. A to D, Eleutheroschizon dubosqui
and formation of endogenous agametes. (After Brasil.) E to G, Schizocystis
sipunculi and similar formation of agametes. (After Dogiel.)
separated from the surrounding protoplasm of the parent. Such
islands, called pansporoblasts by Gurley (1893) or internal "cells"
by Davis (1916), are specialized reproductive centers in each of
REPRODUCTION
281
K L M
Fig. 120. — Gamete formation and fertilization in Ophryocystis mesnili. A, two
individuals attached by processes to ciliated cells of a Malpighian tubule of Tenebrio
mollitor; B, union of gamonts in pseudoconj ligation; C, D, E, probable meiotie
divisions of nuclei of the two gamonts; G to K, formation of two gametes and their
union in fertilization; L to N, metagamic divisions resulting in eight sporozoites in
the single sporoblast. (After Leger.)
232
BIOLOGY OF THE PROTOZOA
which one or more sporoblasts are formed (see p. 545). In the same
living parent organism internal buds in various stages of maturity
may be present and in some cases the ameboid parent organism may
Fig. 121. — Internal buds or "gemmules," b, of Sphaerospora dimorpha,
a myxosporidian. (After Davis.)
REPRODUCTION 233
ultimately become a mere cyst wall containing large numbers of
encysted young. A quite different type of internal bud called a
"gemmule" is formed in Sphaerospora dimorpha according to Davis
(1916). These correspond to the agamont buds of the gregarines
(Fig. 121).
m. MULTIPLE DIVISION (SPORE FORMATION).
In reproduction by multiple division the entire protoplasm breaks
up simultaneously into a brood of minute young, a mere fragment
with perhaps a residual nucleus, may be left unused. Although the
end-product may be the same there is a difference in principle
between rapidly following divisions of cells within a cyst (as in
Colpoda cucullw) and the fragmentation of a cell into many minute
cells. There is less difference between sporulation and multiple
endogenous budding as in Schizocystis or Eleutheroschizon described
above.
Multiple division in many cases results in the formation of a
brood of smaller cells which develop directly into organisms similar
to the parent. In other cases the representatives of the brood are
differentiated as gametes, and fertilization is necessary before devel-
opment begins. We thus distinguish between sexual and asexual
generations of spores, a distinction mainly characteristic of parasitic
forms, but typical of many free-living types as well. In still other
cases multiple division may follow immediately after fertilization,
a phenomenon which is highly developed in the Sporozoa where the
ultimate products of division — sporozoites have a renewed poten-
tial of vitality.
Multiple division or spore formation thus may occur either in the
agamont (asexual) phase, or in the gamont and zygote phases
(sexual) of the life cycle. Division, budding or sporulation in the
asexual phase is called agamogony ( = schizogony) ; in the sexual
phase gamogony ( = sporogony). In the great majority of Protozoa
the two phases together in an alternation of generations, make up a
complete life history.
In Mastigophora sexual processes have in no case been safely
established, multiple division when it occurs being agamogony. In
animal flagellates, however, particularly the parasitic forms, a
highly characteristic method of multiple division is widely dis-
tributed. Here in certain phases or under conditions not yet well
understood, trypanosomes, trichomonads, lophomonads and other
parasitic flagellates undergo a process of asexual sporulation to
which the specific term "somatella formation" has been applied.
It is well described by Minchin and Thompson (1915) in the case
of Trypanosoma lewisi (Fig. 122) as follows:
"The parasites when taken up by the flea (Ceratophyllus fasciatus)
234
BIOLOGY OF THE PROTOZOA
pass with the ingested food into the stomach (mid-gut) of the insect.
In this part they multiply actively in a peculiar manner, not as yet
described in the case of any other trypanosome in its invertebrate
host; they penetrate into the cells of the epithelium, and in that
situation they grow to a very large size, retaining their flagellum
Fig. 122. — Trypanosoma lewisi. Cycle in the rat-flea Ceratophyllus fasciatus.
1, 2, blood trypanosomes entering the stomach; 3, 4, entering epithelial cells; 6-10,
intracellular somatella formation; 11, 12, adult trypanosomes leaving cell; N, young
trypanosomes repeating intracellular phase; C, Crithidial forms; H, haptomonads
reproducing by division. (After Minchin and Thompson.)
and undulating membrane, and exhibiting active metabolic changes
in the form of the body, which in early stages of the growth is
doubled on itself in the hinder region, thus becoming pear-shaped
or like a tadpole in form, but later is more block-like or rounded.
During growth the nuclei multiply, and the body when full-grown
approaches a spherical form, and becomes divided up within its
REPRODUCTION
235
own periplast into a number of daughter individuals, which writhe
and twist over each other like a bunch of eels within the thin
envelope enclosing them (Fig. 122, 11). When this stage is reached,
the flagellum, which hitherto had been performing active movements
and causing the organism to rotate irregularly within the cell,
u/Mdi^, i
w
imfm*1
Fig. 123. — Polystomellina crispa. A zygote (A) develops into an organism with a
microspherie type of shell (B) in which the nucleus divides by mitosis until many
nuclei are present which form chromidia. The protoplasm fragments into reproduc-
tive bodies or agametes, each having several granules of chromidia (C). Each agamete
develops into an adult with a macrospheric type of shell (D, E) : when adult these
fragment into hundreds of flagellated gametes (F) which fuse in fertilization and so
complete the cycle. (From Lang and Schaudinn.)
disappears altogether, and the metabolic movements cease; the
body becomes almost perfectly spherical, and consists of the peri-
plast envelope within which a number of daughter trypanosomes
are wriggling very actively; the envelope becomes more and more
tense, and finally bursts with explosive suddenness, setting free
236 BIOLOGY OF THE PROTOZOA
the flagellates, usually about eight in number, within the host cell
(Fig. 122, 12). The products of this method of multiplication are
full-sized trypanosomes, complete in their structure, and differing
but slightly in their characters from those found in the blood of the
rat. They escape from the host-cell into the lumen of the stomach."
(loc. cit., p. 290).
Similar multiple division phases have been described for Trypano-
soma cruzi (Chagas, Hartmann), for Eutrichomastix seryentis, and
Tetratrichomonas prowazeki (Kofoid and Swezy), Lophomonas blattae
(Janicki) and others. In these cases, as in Trypanosoma lewisi, the
number of individuals formed is usually eight.
In Sarcodina there is a typical alternation of generations combined
with multiple division best illustrated in the Foraminifera. Accord-
ing to the independent observations of Schaudinn (1903) and Lister
(1905) the zygote develops into an agamont characterized by an
initial central chamber of relatively minute size (microspheric shell,
Fig. 123, B). When fully grown the chromidia-laden protoplasm
breaks up by multiple division into a great number of ameboid
agametes (pseudopodiospores) each with a number of chromidial
granules which fuse to form a nucleus. Each agamete develops
into a gamont or individual of the sexual phase, characterized by a
large initial central shell-chamber (macrospheric shell, Fig. 123,
D, E). When these gamonts are mature, they also break up by
multiple division into myriads of flagellated gametes (flagellispores,
F). These are isogametes which fuse two-by-two forming zygotes,
and these zygotes repeat the cycle by developing into microspheric
individuals (Fig. 123, A). Similarly in Arcella vulgaris there is an
alternation of generations which is even more complicated than that
of the Foraminifera according to the descriptions of Swarczewsky
(1908) and Elpatiewsky (1909). A zygote (amebula) develops
into a typical adult Arcella agamont. This reproduces by agam-
ogony in no less than four ways if these observers are correct.
A first method is by exogenous budding whereby agametes
(amebulae) are liberated to develop again into agamont s. Another
method is by multiple endogenous budding whereby many agametes
are formed each of which develops into an agamont. A third
method involves the desertion of the parent shell and of the primary
nuclei by the bulk of the protoplasm and secondary nuclei formed
by chromidia, and breaking up of this mass into agametes which
likewise develop into agamonts. Ultimately these agametes develop
into gamonts which become either macrogametocytes or microgame-
tocytes, or gamonts which conjugate as do the ciliates with an
interchange of chromidia (chromidiogamy) . The macrogametocytes
by multiple division give rise to macrogametes, and microgameto-
cytes to microgametes. A macrogamete is fertilized by a micro-
gamete, and the resulting zygote repeats the cycle.
REPRODUCTION 237
Multiple division is safely established for a number of Radiolaria
although it is not yet determined whether the products are agametes
or gametes. In many cases the flagellated swarmers which are
thus formed by one individual are large, while those formed from
another individual are smaller. This has led to the view that the
swarmers are anisogametes, but actual fertilization has not been
safely established. They are formed from the materials of the cen-
tral capsular protoplasm which, at first uninucleate, becomes multi-
nucleate by repeated divisions of the nucleus. Comparatively
little cytological work has been done on these forms which offer a
promising field for further research. According to Brandt (1885)
the nuclear material is distributed about the endoplasm in the
form of many clumps of chromatin which later become vesicular
nuclei and undergo mitotic divisions. Hertwig (1.879) describes
the nucleus of Acanthometra as composed of a large endosome and
a massive peripheral zone of chromatin which metamorphoses into
a great number of small nuclei. In Aulacantha scolymantha accord-
ing to Borgert (1900) the great primary nucleus gives off minute
chromatin vesicles until the entire substance of the original nucleus
is thus distributed in the endocapsular plasm and these become
minute nuclei which now divide by mitosis. Ultimately the central
capsule is dissolved, the pheodium disappears and the proto-
plasm breaks up into many small spheres each with several nuclei.
Differences in these spheres indicate the later differences in the
resulting swarmers. A somewhat similar history has been described
for the giant nucleus of Thalassicola, but despite the observations
of Brandt (1885), Hartmann and Hammer (1909), Huth (1913),
Moroff (1910) and others, the significance of the peculiar processes
is not clear. A rather unusual phenomenon is described by Haecker
(1907) in Oroscena regalis. Here the huge single nucleus of the
central capsule divides into two nuclei of which one remains as a
functional nucleus of the organism, the other is interpreted as giving
rise to gametocyte nuclei. There is also some evidence, not con-
clusive indeed, that an alternation of generations occurs, somewhat
as in Foraminifera. Some types give rise by multiple division to
isospores, c. g., Aulacantha, which are biflagellated cells with charac-
teristic crystalloid structures interpreted by Brandt as the product
of an asexual generation. Other individuals of the same species give
rise to broods of anisospores which are interpreted as microgametes
and macrogametes representing the sexual generation.
In Mycetozoa multiple division is characteristic but complicated
by the typical plasmodium nature of the organisms. Such Plas-
modia are formed usually by the plastogamic union of amebae
arising from spores, the nuclei remaining separate and thus forming
a multinucleated protoplasmic aggregate. Many of these nuclei
degenerate (Kranzlin, Jahn); some become active agents in the
238 BIOLOGY OF THE PROTOZOA
formation of specialized structures of the fruiting bodies (elaters,
etc., Kranzlin, 1907); others divide by mitosis to form nuclei of the
spores contained with the elaters in the spaces of a meshwork formed
by a special protective and supporting part of the fruiting bodies
called the capillitium (Fig. 184, p. 447, see also p. 44(i).
Multiple division in the Sporozoa is characteristic of practically
all Coccidiomorpha, particularly in agamogony. The nuclei divide
repeatedly by mitosis until many are formed, after which the body
plasm breaks up into as many agametes as there are nuclei. In
many cases a portion of the old cells is left unused or not included
in the protoplasm of the offspring. Thus in Plasmodium vivax
and other malaria organisms, the pigmented granules (melanin) are
left behind when the agametes separate (Fig. 124) ; in many coccidia
the agametes are oriented in respect to such residual products.
Multiple division is also characteristic of the developing zygotes of
gregarines and hemamebidae, the eight sporozoites of gregarines
and the multitude of Sporozoites of Plasmodium being formed in
this manner.
A B C
Fig. 124. — Malaria organisms. .4, Plasmodium vivax in blood corpuscle; B, same
in agamete formation with distributed melanin (m). C, Plasmodium ?nalariae,
agamete formation with concentrated melanin, c, red blood corpuscle; m, melanin;
n, nuclei; /), parasite; v, vacuole. (After Calkins.)
In the above account of the reproductive activities of the Protozoa
no attempt has been made to give an exhaustive treatment, but
other examples will be given in the following chapters on classi-
fication.
In many cases in the above description there is evidence of
reorganization of the protoplasm and evidence that may be inter-
preted as supporting Child's view of de-differentiation as an offset
to the accumulation of products of metabolism which hamper
further metabolic activities. Some of this evidence is given
in connection with the phenomena of equal division, particularly
in division of the ciliated forms and the conclusions reached are
in agreement with Child's. Hartmann, also, comes to a similar
REPRODUCTION 239
conclusion in connection with merotomy experiments on Amoeba
polypodia (1924). In the latter an individual was cut in two frag-
ments; the nucleated part regenerated, but instead of permitting it
to divide it was cut again when fully grown. This process was
repeated until the original ameba had been cut 32 times in forty-
two days and without an intervening division. The control ame-
bae from the same clone divided 15 times in the same period. This
experiment would appear to confirm Child's argument that amputa-
tion of a part of the differentiated protoplasm would effect a partial
rejuvenescence, and Hartmann interprets it in this way: "Repro-
duction," he says, may rightly be interpreted as a process of reju-
venation. Our continued amputations in these experiments provide
a substitute for the rejuvenating effect of reproduction (1924,
p. 458). His further conclusion that his results "indicate experi-
mentally, a potential immortality of the protozoan individual"
(p. 456) can scarcely be allowed on the basis of forty-two days'
experience. A single individual of Urolcptus mobiJis has lived for
more than ninety days without dividing, and similar but younger
individuals have been cut as in Hartmann's experiments, to find out
if ciliates would sustain Child's conclusion. The results (not pub-
lished) were invariably negative, although Uroleptus is an excellent
type for this kind of work and invariably undergoes rejuvenescence
after conjugation and after endomixis (see Chapter VIII).
With unequal division by budding and multiple division there is
further evidence of reorganization with reproduction. The small
cells that are budded off contain none of the differentiated cellular
elements of the parent organism. The spores are likewise provided
with protoplasm whose activities are unhampered by accumulated
products. This is clearly evident in the asexual reproduction of
Plasmodium vivax (p. 238), and is well illustrated in forms where
specialized structural elements are indications of the differentiations
which the old protoplasm has undergone. Thus in Mycetozoa
some of the hundreds of nuclei degenerate and give rise to spiral
elaters which with their spiral walls are made up of microsomes and
kinetic elements (Strasburger, Kranzlin), while parts of the proto-
plasm become differentiated into encrusting peridia and supporting
capillitia. All of these differentiations are left behind when the
spores are formed and distributed. Analogous somatic structures
are also characteristic of the spore-forming stages of some types of
Gregarinida and Myxosporidia. In the former the spore-contain-
ing organs are either relatively simple spore cysts as in Monocystis
types (Fig. 213, p. 531) or more complicated structures— sporangia —
of some polycystid gregarines (e. g., Echinomera hispid a or Gre-
garina cuneata). In the former the spores are dispersed by the
formation of gas which bursts the cyst membranes. In the latter,
finger-formed tubes are developed from the peripheral protoplasm
240
BIOLOGY OF THE PROTOZOA
of the cyst. These are formed from residual "chromidia" which
collect in rings about the periphery and from which the finger-
formed tubes grow into the mass of developing zygotes (Fig. 125).
When the cysts are mature absorption of water causes the rupture
of the cyst walls, the tubes are forced out and evaginated as an
inturned glove finger may be blown out. The spores then are
distributed through these hollow tubes or sporoducts.
In Myxosporidia still more complicated structures recalling the
capillitia of Mycetozoa, are characteristic of the spore-forming
stages. In Syhaeromyxa sabrazesi according to Schroder (1907) and
in Myxobolus pfeifferi according to Keysselitz (1908) the internal
Fig. 125. — Gregarina cuneata. A, surface view of sporocyst with ripe sporoblasts
issuing from sporoducts (e). B, C, sections of sporocyst with ripening spores and
developing sporoduct (0- (From Calkins after Kuschakewitsch.)
bud (pansporoblast) which is destined to form the spores, contains
two nuclei, one of which is smaller than the other. These nuclei
increase by division until there are 14 altogether; 2 of these degen-
erate without further function, and the remaining 12 are divided
into two groups of 6 each, the protoplasm dividing with them to
form two protoplasmic multinucleated bodies which will develop
into sporoblasts (Fig. 164, p. 325). Of the 6 nuclei in each cell,
2 are "somatic" and take part in the formation of the shell or cap-
sule of the sporoblast; 2 others are also "somatic" and participate
in the formation of the polar capsules and threads characteristic
of the Cnidosporidia; the remaining 2 nuclei persist as germinal
REPRODUCTION 241
nuclei which, according to observations of several different authori-
ties, later fuse into one (p. 546).
In all of these cases the specialized structures accompanying
spore formation are formed only at one period in the life cycle and
a period which comes at the end of long-continued metabolic activ-
ity. They represent therefore, a differentiated protoplasm which is
not evident in the protoplasmic make up of the progeny. What
is true of these visible differentiations is also probably true of
analogous differentiations which are not visible, and we have reason
to believe that the products of unequal division and of multiple
division are not encumbered by protoplasmic conditions which
hamper vitality— in other words, that they have undergone reorgan-
ization. Such young forms have again the potential of vitality of
the genotype and are able to go through the series of differentia-
tions which are characteristic of the life of the genotype.
IV. DEVELOPMENT.
In Metazoa, development starts with the fertilized egg and con-
sists in the progressive formation of organs and organ systems by
differentiations, and grouping of differentiated cells. A strict com-
parison of Protozoa with Metazoa in development would involve the
history of a fertilized cell through all phases of asexual reproduction
(comparable with somatic cell division) to the gamont stage. Only
by a fanciful interpretation, however, can the entire progeny of a
single fertilized cell of Protozoa be regarded as an individual similar
to a metazoon, although there are similar phases of vitality which
may be indicated in common by the terms youth, maturity and age
(see Chapter VII). The protozoan "individual," however, is a single
cell and as usually seen is in the agamont stage. In the majority
of Protozoa little or no development is necessary, the daughter cells
being almost perfect individuals when formed and similar enough
to the parent to be mistaken for nothing else. Here the only pro-
cesses that can be regarded as development are those which have
to do with the formation of shell structures, as in Coleps hirtus,
etc., and the new development of anterior parts of posterior daughter
cells and posterior parts of anterior cells.
It is quite different, however, with the products of multiple bud-
ding or of multiple division. Here the young forms are unlike the
parent, and during growth undergo changes which may properly
fall under the heading of development. In some cases, for example
in Foraminifera, Mycetozoa, and Sporozoa, the small fragments
produced by a parent may or may not require fertilization in order to
develop. The zygote of Polystomellina crispa or of Trichosphaerium
sieboldi, formed by the fusion of flagellated gametes (flagellispores)
develops into the asexual generation by protoplasmic growth and
16
242
BIOLOGY OF THE PROTOZOA
nuclear division, but without cell division, development of the former
being indicated externally by the formation of a many-chambered
shell. Similarly in the Mycetozoa the zygote formed by ameboid
or flagellated gametes develops into a Plasmodium by cell fusions
and nuclear divisions.
In the Sporozoa the zygotes, formed by union of similar gametes
(isogametes) or of dissimilar gametes (anisogametes) undergo a
variable number of metagamic divisions, three in the majority of
Gregarinida and two or more in the Coccidiomorpha. The end-
result of such metagamic divisions is the formation of two or more
similar sporozoites which are entirely different from the adult indi-
viduals and undergo a more or less complex development. When
they are introduced into a new host the sporozoites are liberated
Fig. 126. — Development of a polycystic! gregarine (schematic) . n, nucleus of host cell ;
p, parasite. (After Wasielewsky.)
from their capsules, or introduced naked into the blood by some
intermediate host. They make their way to the definitive site of
parasitism, penetrate into cells and begin their development. In
the simpler gregarines only the young stages are passed in such host
cells and growth is not accompanied by any marked structural
differentiations. In the polycystid gregarines the parasite never
becomes entirely detached from its host cell until it is fully mature
and de-differentiation begun by the loss of the attaching organ
(epimerite). With its growth the body becomes differentiated into
an anterior chamber (protomerite) and a nucleus-holding posterior
chamber (deutomerite) and in the different species these three
portions of the cell become variously ornamented and specialized.
The epimerite particularly becomes modified in different ways that
are useful for purposes of anchorage (see p. 536). It may be a mere
REPRODUCTION 243
ball of protoplasm as in Gregarina longa; a spade-shaped structure
as in Pileocephalus hern'; a long knobbed proboscis either simple or
provided with spines as in Stylorhynchus longicollis or Gmiorhynchus
monnieri; or there may be many finger-form processes as in Echino-
mera hispida or thread-like processes as in Pterocephalus giardi.
In Corycella armata it becomes a single crown of hooks; in Beloides
firmus hooks combined with a lone spine. While these epimerites
serve primary for attachment, they also serve, in some cases at
least, as food-getting organs. In Pyxinia moebiuszi the epimerite
forms a long haustoria-like process which extends through the
epithelial cell of the gut and into the blood lacunae of the sub-
mucosa (Fig. 103, p. 201) and in Stylorhynchus longicollis a canal
is said to extend from the tip of the epimerite through the proto-
merite and into the deutomerite of the parasite serving for the
passage of food (Leger).
The buds of Suctoria have a rather complicated developmental
history, especially in forms whose "embryos" are parasitic in other
Protozoa (Sphaerophrya species). The buds possess cilia which are
arranged in different patterns in the various species, and by which
they swim actively about until they finally settle down for develop-
ment. They also possess, as a rule, some longer cilia at the anterior
end which have been homologized with the adoral zone of the ciliated
Infusoria, and at the posterior end they possess a sucking disc by
means of which the buds attach themselves to some solid object
either living or lifeless, and from which a stalk is developed. With
growth of the stalk the cilia are absorbed and tentacles— suctorial,
piercing or seizing— are developed. In the parasitic forms the cili-
ated embryos may develop tentacles while in the motile condition,
but on coming in contact with a quondam host, cilia and tentacles
are absorbed and as an ectoparasite the young form makes a pit
in the cortex of the host. It may then reproduce by cell division
in this pit until as many as 50 or more are produced, and these
escape through a slit-like birth opening of the improvised brood
pouch.
In some types of Protozoa finally, especially in the colonial
flagellated forms, the single cell undergoes a series of cleavage
stages the sequence of which is similar to that of many types of eggs
of Metazoa. This is particulary striking in forms like Epistylis,
Zoothamnium and other colonial filiates, which, as adults, consist
of more or less definite numbers of cells arranged in definite patterns.
CHAPTER VII.
VITALITY.
A normal active protozoon is a bit of protoplasm in which the
vital activities are perfectly balanced, correlated and coordinated
in response to internal and external stimuli. If the physiological
balance is disturbed by abnormal activity or inactivity in one or
other function the result is evident in the general vitality of the
organism. The organization, however, is not rigidly fixed and
undergoes adaptive changes in response to the newT conditions until
activities are again coordinated. The Protozoa thus agree with all
protoplasm in having the power of adaptation or ability of the pro-
toplasmic substances to react within limits to unusual stimuli in
such a way as to maintain perfect correlation and coordination under
the new conditions.
An interesting case of orderly response to unusual conditions
was the fusion of two conjugating individuals of Uroleptus mobilis
(Calkins, 1924). Instead of separating at the end of twenty-four
to twenty-six hours as in ordinary conjugation, these two individu-
als remained attached for six days during which time the usual
reorganization processes occurred in each. On the seventh day they
fused along the entire ventral side, forming a bilaterally symmetrical
individual with two oppositely placed mouths and peristomes, two
contractile vacuoles and two independent sets of macro- and micro-
nuclei (Fig. 127). On the eighth day this remarkable creature
divided three times, giving eight double individuals all similar to
the original bilaterally symmetrical one from which they came.
They continued to divide at the rate of approximately one division
per day on the average for a period of four hundred and five days
and through three hundred and sixty-seven divisions. The interest-
ing fact here is the correlation of two distinct sets of structures and
functions so as to act harmoniously and synchronously as one indi-
vidual, and the setting up of an entirely new organization. Had
the two individuals separated as in normal conjugation their meta-
bolic processes would not have been synchronous, the periods of
division would have been more or less similar but not identical. In
the double individuals the two sets of eight macronuclei behaved
differently in different individuals. In one case each set would fuse
prior to division to form a single ellipsoidal macronucleus (Fig. 128),
behaving thus like tw7o normal individuals when ready to divide
VITALITY
245
(p. 218). In the other case the sixteen macronuclei would all fuse
to form one single macronucleus which would divide and form two
groups of eight each (Fig. 129). In the latter case there was not
Fig. 127. — Uroleptus mobilis; origin of double individual. Above, two conju-
gating cells; below, the double individual which was formed by the fusion of two such
conjugating individuals. (Original.)
only a definite adaptation to the new conditions but a further
advance toward a composite animal of a new type and with a novel
organization. The synchronous activities indicate that common
246
BIOLOGY OF THE PROTOZOA
responses to common stimuli were operating and that a perfect
equilibrium was established throughout.
Vitality, as the sum total of all the protoplasmic activities set
up in response to internal and external stimuli, is variable. Varia-
tions due to external conditions may be readily seen in the effects of
heat and cold. Increased temperature increases oxidation leading
C
Fig. 128. — Uroleptus mobilis. Division of double individual; type with two divi-
sion nuclei. A, stages in the fusion of the two sets of macronuclei independently;
B, two division nuclei and two new peristomes; C, division of the cell, each half with
two sets of nuclei. (After Calkins.)
to more rapid movements including food-taking activities, more
active digestion, assimilation, growth and reproduction. It involves
more waste and more active pulsation of the contractile vacuole.
Conversely, decreased temperature slows up the entire series of
activities and vitality is reduced. In like manner any condition
of the environment which tends to quicken, to weaken, or to nullify
VITALITY
247
any one link in the chain of vital activities will have its effect on
the general vitality.
It is not improbable that internal reorganization, or disorganiza-
tion, with increase or decrease of activity in all or in some part of
the protoplasmic make-up may bring about similar variations in
vitality. Thus changes in organization may be effected by amphi-
mixis or by long-continued metabolic functioning with correspond-
;/
# i
Fig. 129. — Uroleptus mobilis. Division of double individual; type with one divi-
sion nucleus. D, the single nucleus formed by fusion of the two independent sets of
maeronuclei ; E, first division of the single nucleus; F, reconstruction after division
with a new type of macronucleus formed from the single division nucleus. (After
Calkins.)
ing effects upon the general vitality. The chemical and physical
make-up of the protoplasm of an individual may change with con-
tinued metabolic activities and lead to a change from what is termed
a labile condition when actions, reactions and interactions are per-
fectly balanced and at a maximum of activity, to a more stable
condition when these activities become increasingly unbalanced or
cease altogether.
248 BIOLOGY OF THE PROTOZOA
I. ISOLATION CULTURES.
The study of protozoon protoplasm by the isolation culture
methods has thrown considerable light on these problems of general
vitality. If a bit of such protoplasm in the form of a single indi-
vidual organism, and its progeny by division, is maintained under
conditions of food and temperature as constant and uniform as
possible, then variations in vitality may be measured and compared
in relation to phenomena in the life cycle which are suspected of
playing a role in connection with the lability of that protoplasm.
In order to study protoplasm in this manner it is necessary to
adopt some measure of vitality which will be an expression of the
sum-total of all vital activities. Since every function is a link in
the chain of vital activities any one function would do were it
possible to measure it accurately, but the difficulty comes with the
inability to measure excretion, or nutrition or irritability in any
complete and definite manner. Reproduction, however, can be
readily measured and being dependent upon the general functions
of metaJbolism, becomes an excellent measure of vitality in a relative
and comparative sense. In one way or another the division-rate
has been used^as a measure of vitality ever since Maupas, in 1888,
first attacked the problem of age and natural death in Protozoa by
the isolation culture method.
In practically any free-living form of Protozoa if proper condi-
tions of food and temperature are provided, the general vitality or
sum-total of functional activity as measured by the division-rate,
continues more or less uniformly for long periods. The single
individuals thus watched appear to be self-sufficient and able to
continue their vital activities indefinitely. The question may be
raised as it has been raised repeatedly, does the protoplasm of such
an individual retain this constant potential of vitality indefinitely,
or like a machine, does it wear out sooner or later, and will it ulti-
mately stop altogether?
The problem thus worded is only a partial restatement of the old
problem concerning life and death of unicellular organisms which
Weismann raised more than fifty years ago. He took the ground
that Protozoa do not grow old and do not die a natural death, both
of which are prevented by an individual dividing into two while in
full vigor. The two young ones thus formed by division leave no
parental corpse but share the old protoplasm between them and
they in turn grow and similarly divide, so that old age is impossible
and natural death inconceivable. Weismann further maintained
that these fateful phenomena— age and death are penalties which
the Metazoa must pay for their privilege of specialization and dif-
ferentiation into somatic and germinal protoplasm. Protozoa he
compared with the germinal protoplasm of Metazoa in common
VITALITY
249
with which they have the potential of an indefinitely continued
existence.
The experiments of Maupas (1888) to determine by isolation cul-
ture experiments whether Infusoria do actually grow old were not
convincing. He found, indeed, that a bit of protoplasm in the form
of a single infusorian cell if isolated in a suitable culture medium
would live, grow and divide. One individual cell formed by such
division, if similarly isolated, would repeat the process, and from
its progeny another representative bit of protoplasm would con-
tinue the race. Maupas found that, ultimately, such protoplasm
Fig. 1.30. — Stylonychia pustulata, senile degeneration. B, C, degenerated individuals
without micronuclei. (After Maupas.)
would lose its vitality and the race would die after morphological
and physiological evidences of degeneration (Fig. 130). In this
manner he followed the history of Stylonychia pustulata through
316 generations by division when the race died. Another species,
Stylonychia mytilus, died out after 319 generations; Leucophrys
patula after approximately 060 generations, etc. The single indi-
vidual was isolated in culture medium under a cover-glass and kept
in a moist chamber. Here it divided repeatedly during a period
of from two to six days until many individuals were present (in
one case 935) all descendants of the original ore. One of these was
then isolated and the process repeated. From these experiments
250 BIOLOGY OF THE PROTOZOA
he concluded that Infusoria die a natural death after a typical life
cycle and after a definite number of generations by division.
The criticism was soon advanced that adverse conditions and
bacterial products were responsible for death of his organisms, or,
that instead of dying from old age they were slowly killed. There
certainly was some justification for this criticism for not only was
the covered medium abnormal but the accumulation of bacterial
and protozoan products of metabolism might well have been detri-
mental, particularly if certain types of bacteria gained supremacy.
Woodruff (1911), furthermore, has shown that excretion products
of Paramecium are detrimental to Paramecium, and Stylonychia
products to Stylonychia, and the implication is that any type, if
continued for long intervals in an unchanged medium, will slowly
weaken in vitality and ultimately die.
Such criticisms, continued even to the present time in connection
with isolation culture work, do not minimize the value of the
splendid contribution of Maupas in these pioneer studies on vitality.
The present day scepticism in regard to his general conclusion is
based upon diverse results obtained by various experimenters with
mass cultures as compared with isolation cultures, the great majority
of the latter giving results which confirm Maupas. In these the
criticism that an unfit environment gradually killed the organisms
has been met by the use of carefully prepared culture media and by
daily transfers of the experimental organisms to freshly prepared
media. In this manner the undue accumulation of bacteria and
their products is prevented while the organisms under observation
are never present in large numbers.
By use of this method of study the life cycles of many different
kinds of ciliates have been established and with the exception of
the results obtained by Enriques (1913, 1915, 1916), Chatton
(1923) and of Woodruff (1908-1921), they all agree in demonstrating
a gradually waning vitality and ultimate death of the protoplasm
under observation. The method now generally employed is to start
with an ex-conjugant, or individual which has just emerged from
conjugation and allow it to reproduce by division three times. Four
(Woodruff) or five (Calkins) of the eight resulting individuals are
then isolated and continued in daily isolation cultures as "pure
lines," four or five pure lines to a " series." For vitality comparisons
the daily division-rates of all lines of a series are averaged for periods
of five days (Woodruff) or ten days (Calkins), and when the cycle
is completed the consecutive five- or ten-day division-rates may be
plotted to give a graph in which the ordinates represent the average
rates of division, the abscissas the consecutive periods. By this
method the history of the vitality of the protoplasm under obser-
vation is summarized in a graphic and effective manner (Figs. 131,
132, 133).
VITALITY
251
The above method was first used in connection with the life
history of Paramecium caudatum (Calkins, 1904), and many other
experiments of similar nature were made on this genus by later
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Fig. 131. — Composite graph of vitality of twenty-three series of Uroleptus mobilis,
each having vitality of more than 85 per rent (solid line). The ordinates represent
the average numbers of divisions in ten-day periods. The dotted line is the vitality
graph of the double organism. (After Calkins.)
observers. It turned out to be an unfavorable subject in some
respects for the study of this particular problem of vitality, for in
1914 Woodruff and Erdmann announced the discovery of a periodic
ao-
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reorganization process without conjugation or encystment in Para-
mecium aurelia which is exactly comparable with one type of
parthenogenesis occurring in Metazoa (see p. 316). The discovery
252
BIOLOGY OF THE PROTOZOA
of this reorganization process which they called "endomixis" was
the culmination of Woodruff's brilliant and long-continued study
of the life history of Paramecium aurelia which he began in 1907,
and which had been generally hailed as giving positive proof of
the correctness of Weismann's point of view. Parthogenesis, how-
ever, has the same effect upon organization and upon vitality
that conjugation has, and as Woodruff and Erdmann showed that
"endomixis" occurs approximately once in thirty days in Para-
mecium aurelia and about once in sixty days in Paramecium cau-
datum, any experiments and observations on vitality are valuable
only as they lie within these limits of time. For this reason many
of the conclusions of Hertwig (1889), of Joukowsky (1898), of
Calkins (1903, 1904, 1913) and of Jennings (1909, 1913) drawn from
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Fig. 133.— Vitality graph of Spathidium spathula. (After Woodruff and Spencer.)
observations on Paramecium are of questionable value, and should
be used cautiously in connection with the present problem. In
other forms, however, analogous reorganization processes occur
during encystment and are thus advertized in cultures whereas
Paramecium does not encyst under such conditions but continues
with low vitality to live and move during such periods of depression
when "endomixis" is taking place.
While the list of recent experimenters with the Infusoria is rather
a long one, the actual number of different organisms studied is
comparatively small, but different experimenters working with the
same species obtained strikingly similar results. Thus Pleurotricha
lanceolata has been studied by Joukowsky (1898) and by Woodruff
(1906), the former following out four series, three of which died out
after approximately 220, 250 and -142 generations without conjuga-
• VITALITY 2o3
tion while a fourth was abandoned after 458 generations. Woodruff,
using the daily isolation method, found a gradually waning vitality
with ultimate death. Baitsell (1914) also carried out isolation cul-
tures with this organism, obtaining a vitality curve similar to
that found by Woodruff (Fig. 132). Oxytricha fallax has been
similarly studied by Enriques (1905), by Woodruff (1906) and
by Baitsell (1914). The first gives no detailed account of his
cultures but makes the general statement that this and other
organisms cultivated by him are capable of multiplying asexually
ad infinitum. Woodruff, however, finds a definite curve of vitality
similar to that of Pleurotricha with a waning vitality and ultimate
death after 860 generations by division, and Baitsell followed the
history of three cultures all showing the typical life history, one
dying out in the 131st generation, a second in the 159th, a third
in the 150th, while a fourth culture in test-tubes lived for a longer
period but it also finally died, none of these cultures approaching
the long history of Woodruff's strain. Stylonychia pustulata also
has been cultivated by Enriques (1905) and by Baitsell (1912),
the former giving no statistical data but maintaining that division
can go on indefinitely without degeneration or conjugation if the
conditions are right. The latter follows out the history in isolation
cultures and finds a typical curve of vitality with waning vitality
ending in death, in the longest line after 572 generations. In other
organisms Woodruff (1905) found waning vitality and death in
Gastrostyla steinii after 288 generations, and Gregory (1909) a simi-
lar result with Tillina magna after 548 generations, and ( "alkins
(1912) a similar result with Blepharisma undulans after 224 gen-
erations.
In all the cases cited above the organisms under investigation
are bacteria feeders, and despite the daily change of medium and
care in maintaining the isolation cultures the old criticism of bac-
terial poisoning or deleterious effects of the medium has been
repeatedly advanced. Woodruff, however, has kept Paramecium
aurelia continuously living for seventeen years on the same bac-
teria diet, "endomixis" occurring at stated intervals and the same
observer using the same methods has followed other organisms
through periods of waning vitality and death. Metalnikov (1919)
similarly has continuously cultivated Paramecium caudatum with-
out conjugation. It seems highly probable, therefore, that the
prevention of death has little to do with the environment in these
experiments but lies in the organisms themselves— with Paramecium
in the phenomenon of "endomixis."
More direct evidence that bacteria contamination is not respon-
sible for the ultimate death in isolation cultures is afforded by
similar experiments with carnivorous ciliates. With these it is
possible to use bacteria-free culture media in which the food organ-
254 BIOLOGY OF THE PROTOZOA
isms are introduced with the experimental individual. Again in
the majority of cases the ultimate result has been the same as with
bacteria eaters. Thus Actinobolina radians was followed through
448 generations in isolation cultures in sterile spring water with
Halteria grandinella as food (Calkins, 1912) and Spathidium spathula
through 218 generations with Colpidium colpoda as food (Moody,
1912), the organisms finally dying in both cases.
Further and very complete evidence that environmental condi-
tions are not responsible in any direct way for waning vitality and
death is afforded by a long-continued study of the protoplasm of
Uroleptus mobilis, an hypotrichous ciliate (Calkins, 1918, 1919, 1920,
etc.). This rare organism found and isolated in 1917 is a bacteria
eater and was cultivated on a medium consisting of flour and
timothy hay boiled in spring water and allowed to stand for twenty-
four hours before using. Individuals were transferred daily to such
fresh medium in order to avoid an excess of bacteria. For each
series of five lines the division rates were figured in ten-day unit
periods which were then averaged for sixty-day periods at ten-day
intervals. The vitality history of twenty-three series averaged for
sixty-day periods and the history of the double Uroleptus are shown
in Fig. 131. The average division-rate here for the first sixty days
was 15.4 divisions per ten days from which it descended regularly
in successive sixty-day periods at ten-day intervals until death. A
single series by itself would be no evidence that slow killing had not
occurred. But when two of the progeny of a series are allowed to
conjugate with one another at any time after the first 75 genera-
tions, the ex-con jugants repeat the historv of the parent series but
do not die when the parent series dies. In this maimer the proto-
plasm of the original Uroleptus which was isolated November 17,
1917 was still under observation twelve years later, although any
single series lived from ten months to a year only. The life of the
progeny overlaps that of the parent; its progeny overlaps it, etc.;
the daily treatment of parents and offspring was identical through-
out; both were subject to the same deleterious conditions if present
but parents died and offspring lived, a history which was repeated
more than 140 times with as many series during a period of twelve
years.
From these clear-cut experimental results with Uroleptus mobilis
the fact is obvious that under these experimental conditions a fairly
uniform life cycle is the rule. The 140 completed life cycles upon
which this conclusion is based were all characterized by the same
phenomena, viz.: (1) A high initial vitality of the ex-conjugant
lasting for a limited period; (2) gradually waning vitality ending
in complete exhaustion and death; (3) a period of sexual "immatur-
ity" lasting from the first thirty to ninety days during which
encystment occurred if appropriate external conditions were pro-
VITALITY 255
vided but conjugation did not occur; (4) a period of maturity
beginning after the first thirty to ninety days approximately and
lasting until the ultimate depression when conjugation, under ap-
propriate external conditions did occur; and (5) a period of old
age indicated by morphological degeneration with accumulating
physiological depression which ended in death.
The many different series studied furnish ample opportunity for
the comparison of vitality in different series. In some there is a
greater intensity of vitality, i. e., the average division-rate is higher
throughout the cycle; in others the endurance factor is greater,
i. c, the individuals live for longer inter-divisional periods without
division and the cycle is correspondingly lengthened (see Chapter
VIII).
On the basis of such consistent experimental results one is tempted
to generalize and to hold that all Protozoa pass through a similar
life history. The temptation is increased by the confirmation of
the main results in connection with an entirely different ciliate,
Spathidium spat hula, in the hands of a no less competent observer
than Woodruff (Woodruff and Spencer, 1924). Spathidium is car-
nivorous and feeds normally on Colpidium colpoda. Woodruff and
Spencer's isolation cultures were carried on in a basic medium of
standardized beef extract to which a few individuals of Colpidium
were added . The individuals were transferred daily to fresh medium
and new food. Many complete series were followed from ex-con-
jugants, four lines to a series until the protoplasm died a natural
death. A typical example is illustrated in Fig. 133, representing
the division-rate averaged for five-day periods (solid line) and one
offspring series. "The data presented show that in the great
majority of cases the cultures died out sooner or later after a some-
what gradual decline in the division-rate" Qoc. cit. p. 178). Seventy-
nine series ran synchronously with their parent series for at least
fifteen days; some of these were then discarded but enough were
followed through to afford a justifiable basis for conclusions. Here
then we have again a large number of series carried on in isolation
cultures, all derived from the same ancestral single ex-conjugant,
and dying out "after a somewhat gradual decline in division-rate."
Woodruff, however (loc. cit.), does not grant that the decrease
in vitality is due to any intrinsic ageing tendency in the protoplasm,
but believes that both in Uroleptus and in Spathidium the proper
milieu for continued life was not provided in the culture methods
used, and implies that when a series dies in the absence of conjuga-
tion or of endomixis, it is ipso facto evidence of a faulty environment.
The matter is important for, if Woodruff's conclusion is correct, it
brings us to an impasse in the subject under discussion. He sup-
ports his argument with the citation of cases on record in which
there is no evident diminution in the division-rate under the condi-
256 BIOLOGY OF THE PROTOZOA
tions of culture, and in such cases he believes that natural environ-
mental conditions have been supplied. He obtained some cases of
greater longevity in a few series of Spathidium, and although the
methods and the culture medium supplied did not differ in any way
from those used in the series that showed decline and death, he
concludes that somehow the conditions were more suitable, and
that when suitable the ciliate has the ability or potential for an
indefinitely continued existence without the necessity of conjugation
(fertilization) or of an equivalent process.
Chatton (1921 ) shares this scepticism : " One may even conclude,"
he says, "that the more the facts accumulate, especially those of
an experimental nature, the more nebulous does this conception of
a life cycle (in filiates) become" (loc. cit. p. 128). The "facts"
thus mentioned include the exceptional results with experimental
culture methods by Woodruff as above, by Baitsell, Dawson,
Enriques, Mast and others, these being the most prominent, in
connection with the Infusoria. It is quite possible, as M. Robertson
(1929) brings out, that conditions of the milieu are such that stimuli
from the environment which ordinarily call forth adaptive changes
in the organization are not developed.
In a similar manner Dawson (1919) found that an amicronucleate
race of Oxytricha hymenostoma presents a typical cyclical curve
of vitality, and death follows a gradually decreasing vitality, if the
organisms are cultivated in isolation cultures. If maintained in
mass cultures they were found to live for a considerable period
longer than the isolated forms, and Dawson concludes that if a
suitable medium is provided an indefinite life is possible without
conjugation, endomixis or encystment. It is conceivable that
environmental media may induce different protoplasmic reactions
at different periods of the life cycle, as shown by Gregory's (1925)
experiments with Uroleptus, and that proper salts in the medium
at appropriate periods would enable the protoplasm to maintain its
youthful labile condition. Individuals might thus be "doctored"
at intervals with a resulting repression of cumulative differentiations
and a corresponding maintenance of youth. This was the under-
lying principle of Woodruff's cultivation of Paramecium aurelia on
a variable diet, the medium being changed at intervals but in this
case without difference in his results. Austin (1927) likewise, sub-
jecting Uroleptus mobilis to different media throughout entire cycles,
was unable to alter the usual history. It is possible that old pro-
toplasm might be reorganized by increasing the permeability and
with proper interaction between protoplasm and medium, restored
to its original labile condition.
In other groups than the ciliates, exceptions to the type of life
history shown by Uroleptus are true of the few cases known. In
the animal flagellates for example there is no case of indubitable
VITALITY
257
proof of fertilization in the entire group. On the other hand, there
have been no successful attempts to cultivate such flagellates by
the isolation culture method so that we are entirely uninformed as
to the relative vitality in a life cycle. It is possible that processes
analogous to endomixis in ciliates take place during encystment
stages but as to this we are also ignorant. With these exceptional
cases, therefore, we must wait for further information.
Exceptional cases are increased through Belaf's observations on
Actinoyhrys sol, a heliozoon (1924). A single line of his main
culture was followed through 1244 generations by division during
two years and eight months. Fertilizations were obtained from
time to time in mass cultures, but these were prevented in the
isolation cultures, the latter showing no indication of reduced
vitality with continued life (Fig. 134). Belaf also concludes that,
given proper conditions, the protoplasm of Act'vnophrys has the
possibility of indefinitely continued life and reproduction by division.
IJ
1 —
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1
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i
4
5
6
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8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
26
29
30
31
32
33
34
35
36
37
Fig. 134. — Vitality graph of Actinophrys sol. (After Belaf.)
In these exceptional cases we meet indeed with diverse experi-
mental results and diverse conclusions. Granted that the experi-
mental work in all cases is done with an equally conscientious
regard for controls and pitfalls of all kinds, it is necessary to accept
the conclusions on their merits and endeavor to find an explanation
which will bring them all into harmony. The first difficulty comes
in connection with the popular conception of an abnormal condition
of the environment. It is obviously impossible to study the life
history of an organism under normal environmental conditions in
Nature— in all probability there is no constant "natural" environ-
ment. To Enriques, Baitsell, Dawson, Belaf, Chatton, Jollos, and
Woodruff in part, the culture methods employed for ciliates are
"abnormal" and death is a result of these conditions. With Uro-
Irptus mobilis in mind it is difficult to understand by what process
of reasoning the conditions of the environment are responsible for
the decline of vitality and death when two individuals from such
cultural material are restored, upon conjugation, to full vitality
in the same medium. The conditions are identical for parent
protoplasm and offspring protoplasm and yet the former dies, the
17
258 BIOLOGY OF THE PROTOZOA
latter lives until a corresponding age, and dies in turn. The more
than one hundred and forty series that have followed one another
since 1917, in the same medium and under the same conditions, in
the same rhythmical cycles and with surprising uniformity, furnish
strong evidence that the environmental conditions have been suit-
able or " normal." For each series there has been the same sequence
of physiological conditions— high vitality and sexual immaturity,
encystment power, sexual maturity, decline in vigor and ultimate
death. If these phases of vitality are normal, if encystment and
reorganization, and conjugation are normal phenomena in the life
history of a ciliate then the conditions under which they occur must
likewise be normal. A hypercritical mind may deny the existence
of conjugation in Nature and maintain that conjugation occurs
only under the abnormal conditions introduced when the samples
are collected and transferred to small holders in the laboratory.
With such an individual convincing proof is apparently impossible
and we can only ignore the implication that conjugation is a phe-
nomenon which did not occur under " normal " conditions in Nature
but manifested itself only when man began to collect material.
I have no sympathy with such a point of view; I regard conjugation
as an entirely "normal" process in ciliates as gamete formation and
fertilization are "normal" processes in Sporozoa and Sarcodina.
When the conditions of the environment are such that this phe-
nomenon does not occur, then we may justly look for the unusual
at least. In a similar connection M. Robertson (1929) states:
" As the outcome of all the experimental work discussed above, the
American workers (i. e., the Woodruff school) deny the existence
of a life cycle in ciliates. To the present writer this seems an
erroneous attitude. . . . The result of this series of investiga-
tions is to show that the cycle is not a rigidly internally conditioned
sequence but is the response of an internally adaptable organism
to the external stimulus of the environment" (p. 163). The limits
of adaptation of protoplasm are unknown to us; it is quite con-
ceivable that conditions may be so arranged that for long periods
the normal sequence of phenomena in a life cycle are in abeyance
and the impression is gained that protoplasm under such conditions
has the possibility of indefinitely continued existence. But can this
be considered a normal environment? Here the conditions which
lead to conjugation are not offered and such conditions, if any,
might reasonably be regarded as abnormal; if conjugation is needed
the need is met by the artificial conditions and the organism is more
or less adapted to them. No one can maintain consistently that
Carrel's long-continued tissue cultures are normal, yet here we have
artificial conditions under which these vertebrate tissue cells con-
tinue, apparently indefinitely, to live and divide. Death of cells
occurs when the transfers are not made at appropriate intervals;
VITALITY 259
they have become adapted to the artificial conditions of cultivation
and continue to live and divide so long as these conditions are
maintained but they must divide.
The question of "normal" or "abnormal" environment after all
appears to me to be of an academic nature, and I cannot agree with
Woodruff and his followers in their belief that natural death is
not inherent in ciliates under natural, or, as he calls it, "normal"
conditions. Nor can I accept his further conclusion that the life
cycle of a ciliate is a "myth." It is quite evident that the cycle
may be greatly varied by reason of external conditions and it is
plainly obvious that it has no definite or fixed limits such as postu-
lated by Maupas. Chejfec (1929), for example, found that the life
of a single individual of Paramecium caudatum may be prolonged
up to one hundred and twenty days by appropriate regulation of
the number of Bacterium coli supplied. If fertilization is an almost
universal phenomenon we should be able to determine the conditions
both within the protoplasm and in the environment which bring it
about. If fertilization satisfies a protoplasmic need we should be
able to find out what the need is. When that explanation is forth-
coming we shall probably be able to understand why the animal
flagellates continue to live so successfully without it.
In regard to the life cycle of Protozoa we are apparently all
agreed on some cases. Since the classical work of Schaudinn (1900)
on Eimeria (Coccidium) schubergi no one doubts the general facts
of the life cycle in Sporozoa; his work has been confirmed by scores
of investigators and upon an enormous number of representative
species. A sequence of vital phenomena intervening from fertiliza-
tion to ultimate gamete formation and fertilization is characteristic
of all such cycles and in all cases the race comes to an end with
the formation of gametes, when without fertilization, the gametes
die. Similar cycles are characteristic of Foraminifera and wher-
ever gametes are formed the ultimate fate is the same. With
ciliates, except in rare instances, gametes are not formed but the
organization of the protoplasm undergoes changes at maturity when
fertilization processes (conjugation) occur, and in the great major-
ity of pedigreed cultures, the race, like unmated gametes, comes to
an end by natural death (see p. 282). The life cycle in all Protozoa
signifies the series of events between fertilization and fertilization
again or natural death. It involves characteristic changes in
organization of the protoplasm and equally characteristic manifes-
tations of vitality.
I have dwelt at some length upon these experimental results,
and on the diverse conclusions based upon them because I believe
that the principle of the life cycle in Protozoa is a fundamental
biological concept involving changes in protoplasmic organization
as a result of continued metabolism. I have reason to believe,
260 BIOLOGY OF THE PROTOZOA
furthermore, that such changes or differentiations from the funda-
mental organization underlie the phenomena of cell division, of
endomixis, of sex differentiations, fertilization and protoplasmic age
followed by natural death. In the following section an attempt is
made to correlate these characteristic phenomena in a life cycle
with progressive changes in the organization of the protoplasm.
II. ORGANIZATION AND DIFFERENTIATION.
It is evident to any one who has made a study of Protozoa that
forms and structures are practically unlimited. It is equally evi-
dent that these characteristics are specific for each species. Regen-
eration experiments show, furthermore, that these specific charac-
teristics are carried in all parts of the protoplasm of an individual,
a small part of a Stentor becomes a perfect Stentor, a small part
of a Uroleptus develops into a fully differentiated Uroleptus, etc.
The structure of the adult by which we recognize the species in
any particular case is the product of the finer make-up of the
protoplasm as it exists in a cyst for example or in a rounded-out
fragment cut from the body of an adult. What this finer make-up is
is purely conjectural, but the idea is carried by the non-committal
term "organization" as used in the preceding chapters. In this
term we include both the adult structures of the fully formed indi-
vidual and the undifferentiated protoplasm which has the ability to
produce them. There is reason to believe that the differentiations
which characterize the adult are brought about as a result of
metabolic activities constituting vitality, and these may be induced
by changes in environmental conditions as when an organism
emerges from a cyst, or regenerates at division periods (p. 221); or
they may require a longer period of metabolism and be combined
with growth; or they may appear only as a result of cumulative
differences representing a gradual change in organization. In gen-
eral the facts at hand warrant the statement that differentiations
always involve changes in organization, and for purposes of descrip-
tion it is convenient to describe them as: (1) Inter-divisional or
Ontogenetic Differentiations, and (2) Cyclical Differentiations.
1. Inter-divisional Differentiations.— In the development of a
Metazoon differentiated structures are never present in the initial
egg cell but appear in orderly sequence as a result of metabolism,
growth and division of cells. A protozoon about to emerge from its
cyst is comparable with such an egg cell. The cyst wall becomes
permeable, water and oxygen are admitted and metabolism begins.
Soon the characteristic motile organs make their appearance differ-
entiated from the apparently homogeneous protoplasm. The oral
apparatus, anal aperture and contractile vacuole appear and the
VITALITY 261
organism emerges apparently complete from its cyst. This is a
rapid differentiation accompanying the onset of metabolism.
Analogous processes of differentiation accompany the regenera-
tions associated with division of the cell. In ciliates a new oral
apparatus and specialized motile organs are formed at appropriate
positions by the dividing organism (see Chapter VI), and differ-
entiation is rapid and complete. The organization under which this
differentiation occurs is evidently a result of metabolic activities
prior to division (see below).
Differentiations accompanying growth of the cell are characteristic
of Protozoa which reproduce by unequal or by multiple division.
Here the protoplasm is parcelled out amongst many offspring and
each bit of protoplasm, like an encysted cell or a cut-out fragment,
possesses the fundamental organization characteristic of the species,
but undifferentiated. Thus a bud of Acanthocystis or of a Suctorian
has none of the adult characters but develops them gradually
during a period of some days. Or the sporozoite of a polycystid
gregarine slowly acquires, with growth, the particular epimerite,
protomerite and deutomerite of its species (Fig. 126). Differentia-
tion occurs here, but more slowly than in the case of a ciliate, and
is apparently more directly associated with metabolism. Arrested
stages in development are not uncommon and frequently lead to
puzzling complications in the life cycle. Trypanosoma lewisi, for
example, passes through stages resembling Leptomonas and Crithidia
(Fig. 122) or Leishmania donovani through a flagellated Leptomonas
stage to an adult quiescent intracellular phase. Similarly the
young ciliated bud of a Suctorian which may be either parasitic or
free-living gradually loses its cilia develops tentacles and a stalk
before it becomes the adult form of the specific description.
The changes in form and structure with growth are to be traced
to changes in the protoplasmic organization which in turn are
doubtless due to metabolic activities, and there is evidence that
analogous changes are responsible for the differentiations which
accompany regeneration in the more actively developing ciliates.
In this connection the merotomy experiments of Calkins (1911)
and Young (1922), patterned after the original merotomy experi-
ments of Balbiani (1891), are suggestive; in Chapter VI it is shown
that anticipatory changes in the cell precede the nuclear changes.
This was first demonstrated by Wallengren (1900) for Stylonychia
and Euplotes, and is clearly shown in Uronychia transfuga in which
the new posterior giant cirri are formed sometime prior to the
nuclear changes in preparation for division. The new cirri appear
in a region of the cell previously free from cirri, as well as at the
bases of the old cirri. Similarly there is a complete new formation
of the peristome with membranelles in the posterior half and a new
series of membranelles which replace the old ones in the anterior
262
BIOLOOY OF THE PROTOZOA
region. Except for mutilations these regenerations and replace-
ments occur only at periods antecedent to cell division and indicate
some far-reaching change in the constitution of the protoplasmic
make up. The ability to undergo such a change furthermore is
progressive as shown by experiments in cutting Uronychia (Calkins,
Fig. 135. — Uronychia transfuga, merotomy and regeneration. 1, cells immediately
after division, cut as indicated; 2, fragment A of 1, three days after the operation,
no regeneration; 3, cell cut five hours after division; 4, fragment A of 3, three days
after operation, no regeneration; 5, cell cut at beginning of division as indicated, into
fragments A and BC; A',B',C", fragments A, B, and C, twenty-four hours after the
operation; fragment A regenerated into a normal but amicronucleate individual
A'; B C divided in the original division plane forming a normal individual C,
and a minute but normal individual B'. (After Calkins.)
1911). In these experiments the cell if cut immediately after divi-
sion in a plane indicated by the section line (Fig. 135) is divided
into two fragments, one of which, the posterior with giant cirri,
contains the single micronucleus, while the anterior portion, with
peristome, contains a part of the macronucleus but no micronucleus.
VITALITY 263
In such cases the anterior portion may live for four or five days
as an amorphous fragment, but it never regenerates the giant cirri.
The posterior part, however, regenerates the missing anterior region
within a few hours and becomes a perfect cell. Exactly the same
result invariably follows if an individual is cut when five to eight or
ten hours old after division (Fig. 135, 3). At this time the normal
individual is fully grown and active. At the age of sixteen to eigh-
teen hours different results are obtained. If a number of individuals
are cut at this age a small percentage of the anterior parts without
micronuclei will regenerate into perfect individuals save for absence
of the micronuclei; the posterior parts always regenerate. This
percentage rises to 100 per cent of cases when individuals twenty-
four hours' old are cut. Under the conditions at the time the
experiments were made divisions occurred in normal animals at
intervals of twenty-six hours. Older cells, when cut, frequently
resulted in the formation of three perfect individuals; one from the
transected anterior portion without a micronucleus and two from
the normal division of the posterior portion. One of the latter, the
more anterior part, although perfect is of minute size owing to
the fact that division of the cell takes place through the original
geometrical center, or the "division zone" of the cell. This minute
cell grows to normal size and ultimately divides, although its divi-
sion is delayed. The original anterior fragment is perfect as far as
external appearances are concerned, but it has no micronucleus and
after seven or eight days it dies without dividing.
This experiment, fully confirmed in the essential points by
Young (1922), indicates a progressive change in the protoplasm in
the inter-divisional period. Except when a micronucleus is present,
young cells when cut are unable to regenerate the missing parts.
Fragments of old cells have the power to regenerate missing parts
even in the absence of a micronucleus. Such regeneration is char-
acteristic of cells in preparation for division and occurs with every
division. It follows, therefore, that the formation of cirri in these
regeneration experiments is due to some condition of the protoplasm
in old cells which is not apparent in young ones and illustrates one
type of inter-divisional differentiation.
These experiments also indicate another significant phenomenon,
viz.: the reorganization (de-differentiation) of the protoplasm with
every division of the organism, a phenomenon fully confirmed by
Taylor (1928). When division is nearly completed the power to
regenerate without a micronucleus which was possessed by the or-
ganism two hours before is entirely lost and fragments without a
micronucleus remain as they were when cut (Fig. 135). As stated
above a young cell is unable to regenerate unless the micronucleus
is present and this possibility does not appear in the protoplasm
until after some hours of metabolic activity. This strongly indicates
264 BIOLOGY OF THE PROTOZOA
the reorganization of the protoplasm or a restoration to a labile and
undifferentiated condition. Other evidences of de-differentiation
are shown by the loss through absorption of the old membranelles,
cirri, undulating membranes, oral baskets of the Chlamydodontidae
and kinetic elements of different kinds (see Chapter VI) while new
elements replacing them are developed from the protoplasm. In
this way there is a more or less complete reconstruction or reorgan-
ization of the organization at each division. (See also Herzfeld,
1925, and Schmahl, 1926.)
Another characteristic evidence of inter-divisional differentiation
is shown by the polarization of the cell immediately prior to divi-
sion whereby "division zones" are set up through which division of
the cell takes place. Such division zones first described by Popoff
(1907) are quite evident morphologically in Frontonia leucas and
physiologically in Paramecium caudatum or Uronychia transfuga
(Fig. 136). Paramecium caudatum when cut near the anterior or
posterior end, as indicated in Fig. 136, does not regenerate the lost
part (Calkins, 1911; Peebles, 1912). A membrane is formed over
the cut surface and cortical differentiations in the form of coordinat-
ing fibrils, basal bodies, cilia and trichocysts are produced. The
result is a characteristic truncated cell. When this divides, division
occurs in the geometrical center of the organism as it was before
cutting and not in the center of the truncated cell (Fig. 136, 3c).
Two diverse cells result from division; one is normal and full-sized,
the other small and truncated. It very often happens that cutting
in this manner induces deep-seated changes in the organization and
such that the precision of division phenomena in the truncated cell
is destroyed and incompletely divided cells or monsters result.
(Such a monster, one with 16 mouths, is illustrated in Fig. 136, o).
See also Herzfeld (1925) on the occurrence of abnormalities and
monsters in Paramecium. Similar monsters may be produced
experimentallv by use of drugs (e. q., KCN) as shown by de Garis
(1927).
Still further evidence of inter-divisional differentiation is shown
by the antecedent nuclear changes preparatory to division whereby,
in ciliates, macronuclear elements discard part of their substance
into the cytoplasm and fuse to form a single, usually ellipsoidal
macronucleus which then divides (Uronychia, Stentor, Uroleptus,
Spirostomum, etc.). Or in flagellates the entire kinetic complex is
absorbed in Lophomonas and several other types of flagellates (see
Chapter VI).
It thus appears that well-marked changes of the nature of differ-
entiations in the organization are taking place during the inter-
divisional metabolic period, and that transformations of the nature
of de-differentiations whereby the protoplasm is restored to the
labile condition of a young organism occur with each division of
VITALITY
2G5
#^4#jv
Fig. 136. — Paramecium caudatum, merotomy. 1, 2, and 3, different experiments,
the straight line indicating the plane of cutting; 3, the history of a monster: an
original cell (3a) was cut as indicated; the posterior fragment (b) divided (c) into (d)
and (e), the latter formed a monster (3, / to o); enucleated individuals (h, k and n)
occasionally separated from the parent mass. (After Calkins.)
266 BIOLOGY OF THE PROTOZOA
the cell. It is quite possible that this divisional reorganization
is adequate for the preservation of the protoplasm through long
periods of activity and may be the explanation of the long-continued
life in certain cultures of ciliates, or continued life of animal flagel-
lates in which fertilization processes are unknown.
Other differentiations occur in Protozoa which cannot be regarded
as inter-divisional in character. These are rather of a cumulative
nature and are not lost with the de-differentiation which occurs at
division.
2. Cyclical Differentations.— This second group of differentia-
tions is not manifested in every cell of a species but appears at
certain phases in the life history of the protoplasm composing any
series of individuals. They are racial, therefore, and correspond
roughly wTith periods in metazoon development such as youth, ado-
lescence and age. Some of these differentiations are characteristic
of very young forms, occurring immediately after fertilization and
at no other time in the life cycle. Others make their appearance
later in the cycle and often after many generations by division.
These lead to and accompany the phenomena of fertilization and
include maturation stages and gamete formation. Still others occur
only at the end phases of the life cycle and are specific characteristics
of age. We find justification, therefore, for purposes of description
at least, in presenting facts concerning differentiations of youth,
of maturity and of age, but we have no intention of setting limits
to these phases.
(a.) Cyclical Differentiations Peculiar to Youth. — Intensity of
metabolic activities is one of the characteristic features of young
organisms, but with Protozoa exact data are difficult to get except
from isolation cultures. In such cultures intensity is indicated by
the division-rate and the great majority of ciliates show a higher
division-rate in the early periods of vitality (see p. 250 and Figs.
131 to 133). In Urolcptus mobilis this intensity lasts for approxi-
mately sixty days (Fig. 131) and in Spathidium spathula for about
forty days (Fig. 133). The evidence is not consistent, however, if
all isolation cultures are considered, and in exceptional cases of
Uroleptus and of Spathidium there is no indication of this relative
intensity. Nor does Belaf give any evidence of it in his isolation
cultures of Actinophrys sol; nor does Hartmann (1921) for Eudorina
eUgans, nor E. and M. Chatton (1923-1925) for Glaucoma scintil-
lans. In such cases it is quite possible that the conditions of the
cultures are such that differentiations are offset and reorganization
at division periods is adequate for continued vitality. Y\ ith para-
sitic forms exact data in this matter are wanting and general
impressions are of little value.
Young organisms show the effects of abnormal conditions of the
environment more quickly and more intensely than do older ones.
VITALITY 267
Gregory (1925) for example has shown that salts and change of
medium are deleterious to very young forms of Uroleytus mobilis
while older forms are not affected. This is in line with Child's
results in connection with the action of potassium cyanide on many
kinds of organisms, those parts which have the highest metabolic
rate being first to succumb.
The differentiations indicated above are physiological in nature
and are rather intangible. Other differentiations characteristic of
youth while also physiological are indicated by morphological or
structural modifications. Of these the most noteworthy are the
different types of cysts which are secreted by all kinds of Protozoa.
Some are temporary cysts in which no endomictic phenomena occur
(e. g., division cysts of Colpoda, Tillina and many flagellates). Ex-
perimentally produced cysts are presumably of this kind (see
Lwoff, 1927; Wolff, 1927; Garnjobst, 1928; Bresslau, 1921, etc.).
Encystment has been generally regarded as a means of protection
for the organism against adverse conditions of the environment.
This is probably more traditional than accurate, for very few Pro-
tozoa are actually known to encyst when the external conditions
are unfavorable. Mast (1923) for example finds that food and
temperature have little effect in causing Didinium nasutum to
encyst, but encystment takes place under the best conditions. It
is more probable that organisms which have had the power to
encyst persist under such conditions while the great majority are
killed. Cutler (1919), however, gives evidence to show that skatol
induces encystment in Endamoeba dysenteriae, and Cleveland (1927)
that encystment of Paramecium occurs when injected into the rec-
tum of frogs. This power to form reorganizing and "permanent"
cysts appears to be a factor of young organisms induced possibly,
as Mast (1923) suggests, by the accumulation of waste materials.
The sporoblast capsules of all Sporozoa, with the exception of the
Cnidosporidia (p. 552), are formed as a result of the first activities
of the young fertilized cell and they do not occur again. The same
phenomenon is characteristic of zygotes in Sarcodina. With Infu-
soria where fertilization is accomplished through conjugation such
zygote cysts are practically unknown, but encystment, with reor-
ganization processes, is possible during the early period of the life
cycle until maturity, when it is apparently replaced by conjugation.
Thus in Uroleptus mobilis in connection with which this phenomenon
has been carefully studied, encystment may occur within three
days after fertilization but usually after a longer period has elapsed.
Such encystments occur under the same external conditions as do
conjugations later in the cycle. So-called "conjugation tests" arc
made every week or ten days. For these, all of the individual cells
of a series left over a daily isolation has been made are placed in a
large container with fresh medium. Here they are allowed to
268
BIOLOGY OF THE PROTOZOA
accumulate until thousands of individuals are present. The food
medium is not replenished and such mass cultures are watched daily
until the individuals die. After five or six days conjugations will
Sepies
88
_
25
~J !\~7
92
93
90
70
18
33
r—\
35
24
1
2
3
4 5
6
7 8
9
10
1112
13 14;15
161718
19 20 21
2223
24
25 2627
2629 30
3132 33
Fig. 137. — Vitality graphs showing the limited period of encystment (between
the two irregular vertical single lines), and the periods at which conjugation begins
(double line) in ten different series of Uroleptus mobilis. (Original.)
take place provided the organisms are mature; if they are not
mature encystment takes place and it frequently happens that
thousands of cysts are present in one container. From the records
VITALITY 269
made during the experiments it is possible to work out the inci-
dence of encystment and of conjugation for each series. Fig. 137
shows the vitality curve of ten different series. The periods of the
first encystments observed and the last encystments in the different
series are connected by vertical lines. The first appearance of con-
jugation is indicated in the same manner but with double lines.
In some series it happens that both encystments and conjugations
occur in the same container but tests of the same series made later
give only conjugations. With Uroleptus at least it appears, there-
fore, that encystment is a characteristic phenomenon of young
organisms comparable with the Dauersporen of phytoflagellates,
and lower plants generally, after fertilization; and that the power
to form reorganization cysts disappears with the advent of maturity.
It is highly desirable to have similar data for other types of ciliates
and to determine whether or not endomixis occurs in each case.
(b.) Cyclical Differentiations Peculiar to Old Age. Toward the
end of the life cycle even more characteristic differentiations occur
than at the outset. In many cases these are coincident with the
fertilization phenomena and will be discussed in connection with
differentiations at maturity. The most significant of these age
differentiations are: (1) Greatly reduced vitality; (2) structural
degeneration; (3) abnormal divisions leading to monster formation;
(4) special structures appearing at no other time in the life cycle.
The best evidence of reduced vitality toward the end of the
cycle is afforded by Uroleptus mobilis and Spathidium spathula. In
the former, series after series have been followed from high initial
vitality after fertilization until death occurred. In more than
one hundred and forty such series the history has been the same
but with variations in time and in number of generations well illus-
trated by the series selected from the records of different years
and shown in Fig. 131. The last individuals of such series may
show a remarkable tenacity in vitality but without the power to
reproduce. Of 283 such "last individuals " 1 lived more than ninety
days; 2 lived more than sixty days; 7 more than forty days; 15
more than thirty days; 26 more than twenty days; 88 more than
twelve days; while the remainder lived from one to ten days. In
all of these cases the old individuals were transferred daily to
fresh medium from the same source as that in which other, younger,
individuals were dividing from one to three times per day. In
most of the old specimens apart from the reduced division-rates,
there is little evidence of physiological weakness. They move with
the usual vigor and apparently maintain an equilibrium between
income and outgo for many days. This condition is the outcome
of a gradually waning vitality which in turn may be due to a slowly
increasing stability of substances in the protoplasmic organization,
or as Robertson (1921) suggests, to accumulation of substances
270 BIOLOGY OF THE PROTOZOA
which can no longer be discharged from the cell. This I interpret
as evidence of old age differentiation with the same fatal termina-
tion as that which follows highly differentiated gametes which fail
to unite in fertilization.
In many organisms this physiological deterioration is accompanied
and manifested by structural degenerations. Maupas (1888) noted
the loss of micronuclei in old age ciliates as well as other degenera-
tions involving the motile organs (Fig. 130). The observations
have been fully confirmed with Uroleptus mobilis, particularly in
regard to to the loss of micronuclei, but also noticeable in the extreme
vacuolization of the protoplasm (Fig. 7, p. 28). In Paramecium
caudatum and in individuals which have not conjugated for a long
period, old individuals are characterized by hypertrophy of the
micronucleus and by the loss of trichocvsts in the cortex.
Still another outcome of the physiological weakness is the ten-
dencv to divide abnormally, thus leading to monster formation.
Fig. 138. — Paramecium caudatum monster, a type common at periods of old age.
(After Calkins.)
This has been typical of all old age cultures which have come under
my observation. Such monsters are strikingly like those formed as
a result of cutting Paramecium (see supra p. 264), but they never
grow into large amorphous masses of protoplasm which frequently
develop from mutilated Paramecium individuals (Fig. 138).
The old age phenomena discussed above all involve a physiological
weakness or reduced vitality which may well be traced back to
increasing stability of protoplasmic substances, and lead to a
break-down in the protoplasmic organization. A fourth type has
to do with protoplasmic differentiations of a formative character
and involves structures which appear for the first time, and only,
when the protoplasm is old, probably as a result of the cumulative
differentiation which has taken place. The sporoducts of gregarines
furnish a good illustration of this phenomenon. Here in Gregarina
cuneata, according to Kuschakewitsch (1907), the old nucleus gives
rise to a minute germinal nucleus while the remainder is distributed
as chromidia throughout the cell. The characteristic sporoducts
VITALITY 271
grow into the brood cavity of the gametocyst in the form of tubules
at the bases of which the observer found collections of chromidia
(Fig. 125, p. 240). Similar observations have been made upon other
sporoduct-bearing forms (Clepsidrina, Gregarina ovata, etc.). These
are final products of protoplasmic activity with the prospective
function of sporoblast elimination and have nothing at all to do
with fertilization (see Chapter XIV). Also in the Cnidosporidia
some of the residual nuclei and protoplasm become differentiated
into sporoblast capsules while others give rise to the peculiar polar
capsules and the threads characteristic of these Sporozoa (p. 324).
In a number of Sarcodina, as in Gregarinida, there are special
morphological structures for the purpose of distributing the mature
products of multiple division. These are frequently quite complex,
the elaters and capillitia of Mycetozoa for example, recalling the
spore-disseminating elements of the higher plants. The life history
is varied, the complications being due mainly to the formation of
multinucleated plasmodia by fusion of numerous multinucleated
cells and to fruiting or spore structures which arise from the Plas-
modium. According to the later observations of Jahn (1911) the
Plasmodium begins as a single zygote in the form of an ameboid
cell with one nucleus. This nucleus divides repeatedly, resulting
in a multinucleated cell and plasmodia are formed by fusion of such
cells. When mature the plasmodium gives rise to the elaters through
the activity of nuclei which degenerate with the process. In some
forms the old plasmodium loses water, dries and forms a hard indu-
rated crust called a sclerotium. In the majority of forms the
protoplasm becomes transformed into a tough skin or membrane,
termed the peridium, which may be strengthened by deposits of
lime. Other parts of the protoplasm become modified into felted
spore capsules or capillitia through which the elaters ramify.
In all of these cases of old age protoplasm the evidence justifies
the conclusion that the organization has become profoundly changet I ,
the change often resulting in useful morphological and physiological
differentiations. The changes are of a character, however, which
prevents any recovery of vitality and death of the protoplasm
results unless gamete formation and fertilization supervene.
(c.) Cyclical Differentiations Peculiar to Maturity.— Sexual maturity
in^ Protozoa is not a theory but a fact demonstrated in many dif-
ferent kinds of Protozoa. In many cases the young form slowly
grows to its adult condition; differentiations appear with continued
metabolism until the individual becomes a gamont and gives rise
to gametes. Thus in polycystid gregarines the sporozoite slowly
grows to its definitive size and differentiations appear with that
growth. The protoplasmic conditions leading to gamete formation
may, with equal reason, be regarded as evidence of still further
differentiation in the protoplasmic organization. In Schizogre-
272 BIOLOGY OF THE PROTOZOA
garinida and in Ooccidiomorpha an asexual reproductive cycle
intervenes between the sporozoite and the gamont and the same is
true in the Foraminifera. In Infusoria, as Maupas long since
demonstrated, fertilization is possible only after a period of vege-
tative metabolism and reproduction. Sexual maturity in general
therefore, like other conditions of protoplasm, may well be inter-
preted as evidence of specific differentiations of the protoplasmic
organization.
Few problems in biology have attracted more attention than
those associated with sex, and attempts to interpret the phenom-
enon have been as varied as they are sometimes ingenuous. The
very definition varies with different interpreters, the usual defini-
tion involving association of the concept sex with peculiarities of
structure and function which enable an observer to distinguish
males from females. Others regard sex as evidence of a fundamental
difference in protoplasm, one type giving rise to males, another
type to females as in Weininger's arrhenoplasm (male-producing)
and thelyplasm (female-producing). Or the differences of sex,
according to Minot (1S82) and Schaudinn (1904), are due to specific
types of chromatin both of which are present in all individuals
derived from a fertilized cell, but male chromatin predominating
in males, female chromatin in females. Still others interpret sex
differences as originating through metabolic activities, segregation
of protoplasm thus differentiated, and distribution by inequalities
in division of the cell as Biitschli first suggested.
Not only somatic differentiations with their specific functions,
but products of such differentiation in the form of gametes together
with the causes which bring about the attraction and fusion of
gametes, are all bound up in the ultimate significance of sex. Som-
atic differentiations indicating male or female types are extremely
rare in Protozoa, but problems of gamete formation and fusion are
presented by Protozoa of all kinds and, so far as it applies to such
problems, the term sex and its connotations apply to the unicellular
animals.
There is little reason to doubt that a fundamental effect of sex
is the perpetuation of the species through union of gametes; and
there is equally little reason to doubt that the same function under-
lies conjugation and fertilization generally in Protozoa. It is
tacitly understood by biologists that the sum total of conditions
leading to the production of eggs or of spermatozoa is typical of
the female or of the male, hence egg-like gametes in Protozoa are
regarded as the result of female activities, while spermatozoa-like
gametes come from males. This line of thought has led to the wide-
spread custom of describing macrogametes in Protozoa as female
and microgametes as male organisms. A difficulty has arisen,
however, in connection with the entire absence of visible differences
VITALITY
between the gametes of many species distributed amongst all groups
of Protozoa, and here, obviously, the attempt to apply any defini-
tion of sex fails completely. Yet such fertilizations are as" fruitful
and as important for the species as are those in which gametic
differences are well-marked.
FIR5T MATURATION DIVISION OF MICRONUCLEUS
SECOND AND THIRD
DIVISION OF MICR0NUCLEU5
k \ m&\ Mm
THREE SOMATIC DIVISIONS OF FERTILIZED NUCLEUS
FERTILIZATION
TWO CONSECUTIVE DIVISIONS
GIVING FOUR NORMAL CELLS
Fig. 139.— Paramecium caudatum. Diagram of the fertilization processes.
(After Calkins.)
There are two fundamental biological problems associated with
the formation and fusion of gametes. These are: (1) The expla-
nation of the origin of gametic differences, and (2) explanation of
the phenomenon of attraction of gametes followed by their tem-
18
274 BIOLOGY OF THE PROTOZOA
porary or permanent fusion. It would be mere presumption to
claim that our present state of knowledge permits an explanation
of these phenomena, but there is an abundance of data from which
working hypotheses may be deduced.
Gametic Differences.— In Metazoa differences in gametes are
reduced to practically those between egg and spermatozoon. In
Protozoa there is no common type of difference but all gradations
may be found here, from apparently similar individuals to differ-
entiated eggs and spermatozoa. This has led to attempts to classify
gametes for purposes of description, into those which are similar
(isogametes) and those which are dissimilar (anisogametes). Similar
gametes, however, may be minute derivatives of adult individuals
— microgametes— or they may be adult individuals which cannot
be distinguished from ordinary asexual, vegetative individuals.
The latter type is represented by the vast majority of Infusoria,
and, as Minchin maintained, there is very little justification for
calling them gametes at all; yet they come together for purposes of
fertilization and to this extent at least resemble gametes. In the
majority of Protozoa fertilization involves the permanent fusion of
cell bodies as well as of cell nuclei and the term copulation is applied
to such cases. In the Infusoria fertilization involves the permanent
fusion of nuclei only, while the cell bodies, with few exceptions, are
incompletely fused and this is only temporary (Fig. 139). To this
phenomenon the term conjugation is given. A conjugating ciliate,
however, is physiologically different from a vegetative individual
and may be distinguished by the general designation gamont.
These considerations lead to the following classification:
(a) Conjugation.— Temporary cell fusion of gamonts; permanent
nuclear fusion.
(b) Copulation.— Permanent fusion of cell bodies and cell nuclei
of gametes.
(a) Similar macrogametes or gam-
A. Isogametes onts (hologametes) .
(b) Similar microgametes.
Gametes { J (a) Dissimilar microgametes.
i (b) Macrogametes and microgam-
B. Anisogametes -j etes.
(c) Egg and spermatozoa (oogam-
ogamy).
(a) Hologametes and Conjugates.— The nearest approach to
conjugation of the ciliates is to be found in the fertilization phe-
nomena (pseudo-conjugation) of the Sporozoa, particularly in the
Gregarinida. Here, two gamonts (gametocytes) come together but
do not fuse; after the formation of a common gametocyst each cell
VITALITY L>7:>
proceeds to form a number of gametes which may be isogamous
or anisogamous. After the gametes are formed the gametocytes
degenerate and disappear while the gametes fuse two by two in
copulation. In the coccidian Adelea the phenomena are more
nearly like those of the filiates. Here a microgametocyte and a
macrogamete become associated in conjugation and without the
formation of a cyst membrane (gametocyst). The former produces
four or more microgametes by division and one of these penetrates
the macrogamete and fuses with its nucleus (Fig. 140). One of the
conjugants thus resembles a ciliate while the other one, the micro-
gametocyte, resembles a gregarine in that it degenerates and dis-
appears. In ciliates there is a mutual formation of gametic nuclei,
a mutual interchange and a mutual fertilization. Here both indi-
viduals correspond to the macrogamete of Adelina and fertilization
is mutual.
B
Fig. 140. — Adelina dimidiata A. Schn. .1, association of macrogametocyte and
smaller microgametocyte. B, nuclear divisions in microgametocyte and formation
of gametic nuclei. X 1400. (From Doflein after Shellack, Arbeit, aus d. kaiserlichen
Gesundheitsamt, courtesy of J. Springer.)
It is possible that the peculiar conditions existing in present-day
ciliates may have resulted from conditions of pseudo-conjugation
as illustrated by the present-day gregarines, and that originally,
a group of gametes were formed which united to form zygotes
outside of the parent cells, or inside as in the case of Ophryocystis
mesnili1 (Fig. 120, p. 281). On this hypothesis which has been
very generally accepted by protozoologists, the fusing nuclei of
conjugating ciliates are interpreted as the nuclei without cell bodies
1 Some of the parasitic ciliates suggest the gregarines in their conjugation phe-
nomena. Thus in Balantidium coli, according to Brumpt (1909), two individuals
come together and form a common enveloping cyst membrane within which the
two cells now completely fuse.
27G BIOLOGY OF THE PROTOZOA
of gametes, such as those of Ophryocystis. An interesting observa-
tion by Dogiel (1923) on the parasitic ciliate (Cycloposthium bipal-
matum and in other Ophryoscolecidae as well (Dogiel, 1925) lends
some support to this theory. Here gametic nuclei are formed as in
other ciliates; one of these nuclei, the migrating nucleus, develops
a tail and, like a spermatozoon, makes its way through the mem-
brane of the peristomial region of the mother-cell, and into the
external chamber formed by the mode of fusion of the two gamonts
(Fig. 141). From this chamber it enters the other gamont by way
of the mouth and ultimately meets and fuses with the stationary
nucleus of this gamont.
(6) Isogametes and Anisogametes. — The term copulation as used
in connection with the Protozoa refers to total and permanent
--'J' /
Fig. 141. — Cycloposthium bipalmatum. Conjugating individuals with spermatozoon-
like wandering nucleus. (After Dogiel.)
fusion of gametes. Of these there is the greatest variety of struc-
tures and differences in different types of Protozoa. In very few
cases of isogametes do we find copulation between individuals
whose differentiations are not expressed by morphological char-
acteristics. In such types the individuals differ little if at all from
the ordinary vegetative forms except in a physiological sense.
Plastogamy or casual cell fusion is easily mistaken for such holo-
gamic copulation and descriptions of so-called fertilization proc-
esses in testate and in naked rhizopods, in Heliozoa and in different
types of flagellates are open to criticism on this ground. In the
case of Helkesimastix faecicola and H. major (Woodcock and Lapage,
1915, and Woodcock, 1921) the evidence, from observations on
living cells, seems to indicate that copulation of these flagellates
does occur, but even in these cases the interpretation is not above
criticism in the absence of cytological confirmation.
The majority of isogametes show morphological characteristics
VITALITY 277
which easily distinguish them from agametes or vegetative indi-
viduals. In many cases the physiological differences at maturity
are expressed by a change in the type of division whereby binary
fission is replaced by multiple division. Many daughter cells are
thus formed from one gametocyte and the term microgametes has
been applied to such a brood. The copulating gametes, however,
show no distinguishing morphological characteristics and the dif-
ferences between them if there are any must be of a chemical or
physical nature. In Foraminifera such isogametes are the rule and
their formation indicates a well-defined cyclical differentiation of
the parental protoplasm. Thus in Polystomellina crispa according to
Schaudinn (1903) and Lister (1905) ; in Peneroplis pertusus according
to Winter (1907) ; in Trichosphaerium sieboldi according to Schaudinn
(1899) and in Foraminifera generally, the young protoplasm after
fertilization forms one type of organism termed the microspheric
generation which after nuclear fragmentation and chromidia forma-
tion reproduces by agamete formation (Fig. 123, p. 235). Such
agametes develop without fertilization into organisms of a different
type, the difference being shown by the larger size of the initial
shell chamber, hence a macrospheric generation. After metabolic
activities and full growth the macrospheric organism breaks down
into a multitude of isogametes which have an entirely different
organization from that of the agametes. Whereas the latter are
pseudopodiospores, the isogametes are flagellispores, each bearing
two similar flagella, and copulation occurs by union of two of these
similar flagellispores (Fig. 123, A, C).
According to Schaudinn's interpretation of the fertilization proc-
esses in Actinophrys sol (1896) there is a permanent fusion of
similar adult cells (hologametes). But the recent investigations of
Belaf (1922) show that one of the apparent hologametes develops
a pseudopodial process which is the first to unite with the other
gamete and undergoes its meiotic divisions more quickly than does
its mate (Fig. 142). Similar minute differences in microgametes
are characteristic of Monocystis rostrata but the differences become
more pronounced in Pterocephalus nobilis, Schaudinella henleae, or
Stylorhynchus longicollis. In Sarcodina, apart from Actinophrys sol,
there are few cases in which the full development and fusion of
anisogametes have been convincingly demonstrated. Schaudinn
(1903) described the formation and union of anisogametes in Cen-
tropy.xis aculeata but the confirmation of his arcelliform gametes
has not yet appeared. Elpatiewsky (1909) described the fusion of
anisogametes in Arcella vulgaris as a part of a very complex life
cycle. In both of these testate rhizopods the nuclei of the gametes
are derived from chromidia formed in the gametocytes while the
cell bodies are formed by multiple division of the protoplasm. In
Radiolaria, according to Brandt (1885) and Borgert (1900), the
278
BIOLOGY OF THE PROTOZOA
same central capsular protoplasm gives rise to anisogametes in the
form of two types of flagellated swarmers, but fusion of gametes
was not observed. B«""eteb
Knowledge of the life cycle in Radiolaria, however, appears
■v a' » ' •••!■••.'•'.' -.»'
wm- -It p •-/ -'
-.-»■ ■•*■;. J*9 -° ' rkf
'V%-1 -J ° • • V'^L ■■•?*^ ■■
y?'.%J •/.©:*-•; W ::?a>/
;. «r»T ^#40 a®;,- <*>
ft?
9
10
ii
r.'Jr
a
. ,FlG- teZ.—Actinophrys sol, maturation and copulation of gametes. 1 section of
I-vt 4 ,Tn t0t fertili+Zati,0.ni 2' 3" d/™n of — leus and cell to form two gameto-
cytes, 4, 5 6 first meiotic division of the two gametocytes; 7, 8, 9, second meiotic
™ a,nd formation of gametes; 10, differentiation of the gametes; 11, 12 fusion
of cell bodies and nuclei. (After B&af.) ' ' IUSIon
VITALITY 279
to be inversely proportional to the numerical importance of the
group. Division of the complex organization occurs in some cases,
e. g., Aulacantha— the nucleus dividing first, then the central
capsule, after which the extracapsular plasm with the skeleton
divides, so that each daughter cell retains one-half the skeleton and
regenerates the other half. In species with a firmly-knit skeleton,
if a special mouth opening is present, one of the daughter cells
emerges and builds a new skeleton (see Gromia). In some cases
(Thalassicollidae and Tripylea) divisions of the nuclei and central
capsules outrun divisions of the extracapsular plasm so that indi-
viduals often remain for considerable time with two, four or eight
central capsules recalling the permanent condition of colonial
Radiolaria (Collozoum, etc.). In some species, representing Spu-
mellaria, Acantharia and Tripylea, multiple division occurs, result-
ing in broods of isospores (e. g., Polycyttaria) or in some cases aniso-
spores which may be formed by the same parent, or by different
parents. Isospores are generally regarded as agametes while aniso-
spores are usually interpreted as macrogametes and microgametes,
a conclusion confirmed by Hartmann's observation of their copu-
lation. Chatton (1923), however, holds that, in some cases at
least (Polycyttaria and Collodaria), these anisospores are derived
from intracellular dinoflagellate parasites (genus Merodinium).
Both Hartmann and Belaf contend that this is a case of parallelism
which may indicate some phylogenetic relation between Radiolaria
and Dinoflagellida, for isospores, which undoubtedly are normal
stages in Radiolaria life histories, have Dinoflagellate characters in
their nuclear division figures and in their body form. Further
information on the life history of Radiolaria is very much needed.
A further stage in the manifestation of differentiation at times of
maturity is shown by those Protozoa in which the form, character
and size of the fusing gametes are widely different. Here progres-
sive differentiation has followed two general directions resulting,
in one direction, in the formation of large, usually quiescent, food-
stored cells, the macrogametes, in the other direction, in minute
highly motile cells, the microgametes. In these cases furthermore
the differences in the gametes may be followed back through the
gametocytes for several generations so that cells destined to give
rise to macrogametes or to microgametes may be distinguished at
an early period.
Examples of this type of anisogamy are practically limited to the
Coccidiomorpha. In the Ciliata, however, there is a partial dif-
ferentiation in this direction in the Vorticellidae where a larger
and attached individual— the macrogamete— is scarcely distinguish-
able from vegetative agamonts, while the microgametes are one-
eighth as large and are formed by three successive divisions of the
microgametocytes (Fig. 143). The microgametes always become
280
BIOLOGY OF THE PROTOZOA
detached and swim about actively until they perish or meet and
fuse with a macrogamete.
A complete differentiation, or oogamy, is shown by the majority
of Coccidiomorpha amongst the Sporozoa. In some cases, how-
ever, notably in the genus Adelina, gamete differentiation is of the
same general type as in the Vorticellidae. In other cases a multi-
tude of minute sperm-like gametes are formed from the rnicro-
gametocyte while the macrogamete appears like a slightly modified
vegetative individual (Fig. 144). In Cyclospora karyolytica, Schau-
dinn (1905) maintained that differences shown by the mature garnet -
ocytes could be followed back to the sporozoites from which they
came.
Fig. 143.
Epistylis umbellaria; colony with mature macrogametes and micro-
gametes and their fusion (m) and (.1/). (After Greeff.)
In these various cases we find quite variable expressions of differ-
entiation in the protoplasm of a given species. This differentiation
appears to be cumulative in the life cycle and the same initial
protoplasm through differentiation in two directions may, at matur-
ity, give rise to both types of gametes. Anisogametes illustrate
not only the cyclical differentiation resulting in a different type of
reproduction from that of the usual vegetative type, but they also
illustrate the two divergent effects which such differentiations may
VITALITY
2S1
bring about, one leading to relatively greater stability, storage of
metabolic products and relative inactivity, the other leading to a
more kinetic organization with freedom from metabolic products.
As one would expect there is every gradation in the relative differen-
tiation of anisogametes, from hologametes to egg and spermatozoon.
If the differentiation in two directions is manifested at the very
outset of a life cycle in organisms developing from zygotes, one
y i :>■_/ jJ-y^\-i :.w Y-fr > ... • -. -l -A
Fig. 144. — Gametes of Gregarines and Coccidia. A, male and female gametes of
Stylorhynchus longicollis; B, Monocystis sp.; C, spermatozoid of Echinomera hispida,
to the left the two gametes of Pterocephalus ndbilis; D, gametes of Urospora lagidis;
E, of Gregarina ovata; /•'. of Schaudinella henleae; and G, of Eirru ria schubi rgi. (From
Shellack after Leger, Cut-not, Brasil, Schnitzler and Schaudinn.)
ultimately giving rise only to macrogametes, the other only to
microgametes, then we are dealing with a matter of inheritance
or fundamental organization and not with progressive or cumulative
differentiation through metabolic activities. In such instances,
particularly if the differentiations are manifested by structural
features whereby one type can be distinguished from the other
we are justified in using the term sex in the same sense as used for
Metazoa.
282 BIOLOGY OF THE PROTOZOA
Resume. — In the preceding pages an hypothesis has been devel-
oped for the purpose of bringing together a large array of discon-
nected facts in one comprehensive biological generalization. The
underlying principle is the irritability of protoplasm as manifested
by the phenomena of adaptation. The fundamental organization
or particular type and arrangement of the proteins, carbohydrates,
salts and other constituents of living substance is specific for each
kind of organism. Vitality is interpreted as the aggregate of chemi-
cal and physical reactions going on between and among the diverse
parts of the organization and between these and the environment.
Adaptation is the response of the organization to unusual condi-
tions. It involves somewhat changed reactions and these in turn
may involve new substances which may or may not be the basis
of new morphological elements, but the fundamental organization
becomes at least somewhat modified. The inciting causes of such
changes may be of environmental or of internal origin. Among
the latter are new combinations which occur with amphimixis.
Here, also, are the substances which are formed as a result of metab-
olism, particularly of oxidation. These may or may not be labile,
i. e., subject to reversal of phase in a physical sense, or to participa-
tion in the vortex of vital activities generally. If not labile they
become metaplastids and may or may not serve some useful purpose
for the organism. If such products of activity are labile, new com-
binations with other substances in the protoplasm are possible
and the results are manifested as differentiations.
On this basis we interpret the differentiations which appear
with the intake of water and oxygen by an encysted organism or
the various activities characteristic of Protozoa during the early
phases of the life history. On the basis of changes due to general
metabolic activities and due to the specific organization of any
particular form, we interpret the drastic alterations which accom-
pany and characterize cell division. These involve the changes in
physical condition of the various colloidal substances, such for
example, as the increase in permeability due possibly to the accumu-
lation of hydrogen ions, and the absorption of water. They also
involve cytolytic activities as indicated by the disintegration and
absorption of kinetic elements, of eliminated nuclear chromatin
and division of all the substances active in vitality. The conditions
under which these divisional activities are manifested represent
inter-divisional differentiations which are reduced or cast out
through protoplasmic activities at division, leaving the organization
in a labile state characteristic of the early inter-divisional period.
If the reorganizations effected by these divisional activities are
always the same generation after generation, then, on the hypoth-
esis, there is no a priori reason why under appropriate environ-
mental conditions, metabolic activities or vitality, should not
VITALITY
283
continue indefinitely (see Child, Hartmann, Belaf, Jollos, etc.).
Such is the explanation that I would give of continued life without
fertilization of animal flagellates, aided here possibly by changes
which may take place during the periods of encystment. On the
same basis we find an explanation of the long-continued isolation
cultures without fertilization of organisms which, under usual
conditions, undergo fertilization. Some types of organization are
evidently able under appropriate conditions of the environment to
return to the same labile organization after each division. Such
types would thus have a prolonged asexual cycle, possibly, as
Enriques asserts, as long as the observer cares to continue the
culture. In such cases it is not improbable, as M. Robertson (1929)
Fig. 145. — Paramecium caudatum in a period of depression and recovery by treat-
ment with salts. (After Calkins, i
concludes, that the environment is so stabilized that its stimuli do
not call out the cyclical changes which might be expected with an
irritable and adaptable protoplasmic organization.
If, however, reorganization as effected by division does not leave
the protoplasm in its original labile condition, then inter-divisional
activity of the progeny starts with a different organization than did
the previous generation and this, continued generation after genera-
tion produces an accumulative effect. This is manifested by physi-
ological activities and by structural modifications not shown before.
The decline in the division-rate for example may indicate that the
living substances are becoming relatively stabile and more and
more irreversible in phase, as was the case with one race of Para-
mecium caudatum in which the individuals became homogeneous
284 BIOLOGY OF THE PROTOZOA
and black in appearance with complete loss of the usual vesicular
character (Fig. 145). This particular condition was relieved by
the use of electrolytes (K2HP04, KC1, etc.) added to the usual
medium. In extreme old age in ciliates there is apparently a cessa-
tion of the intricate activities involved in cell division. Evidence of
this is the tendency to form monsters and the tendency of parts to
undergo degeneration, nuclei, motile organs, kinetic elements, etc.,
in particular.
Between the extremes of youth on the one hand and old age on
the other is a condition of cumulative differentiation termed sexual
maturity. In this condition phenomena occur which do not occur
earlier and the organization may become visibly altered. Thus
gregarines lose their attaching organs and become gamonts; the
physical condition of Paramecium changes to such an extent that two
individuals will fuse on contact at any part of the cortex (the author
has observed an amorphous group of nine such partially fused
individuals) ; or the phenomena of plastogamy in general are possible
under such conditions of differentiation.
With the protoplasm in this latter condition due to continued
metabolism further differentiations are possible and, carried out in
different directions, lead to specializations characteristic of gametes.
As Biitschli first suggested, inequalities in division may account for
the differences in gametes, a possibility indicated by the more irri-
table anterior region of the ciliates, or by the more active pulsations
of the anterior contractile vacuole in Paramecium caudatum, or
posterior vacuole in P. aurelia (Unger, 1926).
When such differentiation progresses to the point of isogamete
and anisogamete formation further constructive activities and repro-
duction are no longer possible, and if fusion is prevented, the
gametes die. With the ciliates this is true only of the Vorticellidae.
In other ciliates, differentiations at sexual maturity have not pro-
ceeded far enough to seriously affect the general metabolism and
power of reproduction. This is demonstrated by experiments with
"split" pairs, or separation of two individuals recently united in
conjugation, an experiment first performed by Hertwig (1S89) and
later by Calkins (1904, 1919) and by Jennings (1909). Here an
individual, thus separated, continues with the same division-rate
that it would have had had it not conjugated. Yet the history of
isolation cultures with exceptions noted above shows that ultimately
if conjugation and parthenogenesis are continually prevented, the
race, like anisogametes, will die.
CHAPTER VIII.
PHENOMENA ACCOMPANYING FERTILIZATION.
In the preceding chapters we have endeavored to show that
continued metabolism leads to changes in the organization of
Protozoa whereby phenomena of a cyclical nature in the life history
are possible. Among such changes are those which underlie activi-
ties at periods of sexual maturity including gamete formation. In
the present chapter we will consider the activities which take place
immediately before, during, and immediately after fertilization, phe-
nomena which are involved in any attempt to interpret the effects
of fertilization. Here we have to do both with protoplasm which
has become so changed in organization that further metabolism is
impossible, as in highly specialized gametes, and with protoplasm
which is so little changed that metabolic activities are still possible.
The special problems to be considered in this connection are:
(1) The protoplasmic and the environmental conditions under which
fertilization occurs; (2) fertilization types; (3) the internal phe-
nomena of maturation and reduction in number of chromosomes;
(4) the immediate metagamic internal activities involved in reor-
ganization; (5) parthenogenesis.
I. THE ENVIRONMENTAL CONDITIONS OF FERTILIZATION.
(a) Ancestry.— Attempts to analyze the conditions under which
fertilization by fusion of gametes, or by conjugation, takes place
have been made in relatively few cases. Since the first of such
attempts, and the majority of later ones, have to do with the
conditions of conjugation in ciliatcs we may consider these first.
Of the three conditions cited by Maupas (1889) as necessary for
fruitful conjugation— sexual maturity, diverse ancestry, and hunger
—the last one only has to do with environmental conditions. The
second condition, however— diverse ancestry— was considered so
important by Maupas and has been so frequently called upon in
explanation of results obtained by many subsequent investigators,
that it cannot be ignored. Maupas found that individuals of the
same ancestry either would not conjugate at all among themselves,
or if they did the ex-conjugants were weaklings and soon died.
He also found that, with other evidences of degeneration, closely
related individuals of extreme old age showed a tendency to con-
jugate and that such conjugations always lead to sterile results or
to abnormal ex-conjugants which quickly die.
Largely as a result of these conclusions of Maupas an unwarranted
286 BIOLOGY OF THE PROTOZOA
importance has been attached to the relationship of gametes, and
fertilizations have been described as exogamous, endogamous,
autogamous, or pedogamous. Of these the third refers to self-
fertilization and the second and fourth to union of closely related
individuals. Such terms serve a useful purpose for descriptions
but are without significance in the matter of effective fertilization.
It is quite possible, however, that a brood of gametes from the
same gametocyte will have a common physical and chemical make-up
and will not be attracted to one another but will meet and fuse with
apparently identical gametes from another gametocyte. This
appears to be the case with Polystomellina crista according to Schau-
dinn (1903) and also of gregarines. The significance of ancestry
however, appears to be in the matter of mating rather than in that
of effective fertilization and belongs to the same group of phenomena
as the fact that sperm cells do not unite with sperm cells or eggs with
eggs. With Infusoria Maupas' conclusion has not been supported
by later observers. Calkins (1904) found that fully as many
conjugations between closely related forms of Paramecium caudatum
were fruitful as between forms of diverse ancestry, and one such
ex-conjugant from a closely-related pair, was followed through 379
generations by division. Similar evidence has been furnished
by isolation cultures of Didinium nasutum, Paramecium aurelia,
Paramecium burs-aria, Stylonychia sp., Blepharisma undulans,
Spathidium spathula, Oxytricha fallax, and Chilodon cucullus.
With Uroleptus mob His the protoplasm of one individual gave rise
to progeny which would conjugate whenever the proper conditions
were provided, and the 140 series derived from ex-conjugants from
such unions furnish ample proof that the conjugations were fruitful.
Such results indicate that Maupas' conclusion regarding the neces-
sity of diverse ancestry was incorrect.
(b) Environment.^ One unmistakable conclusion can be drawn
from the many diverse observations and interpretations of the
conditions under which fertilization occurs in ciliates, viz., the pro-
toplasmic state with which conjugation is possible is induced in
large part, but not wholly, by environmental conditions.
In practice the simplest way to obtain conjugations in ciliates
is the method adopted by Maupas. A pure culture of the organism
to be tested is allowed to multiply freely in a rich culture medium ;
a large number of these are then transferred to a smaller container
with enough of the original medium in which they had developed
to make it unnecessary to add fresh medium. In this second con-
tainer, conjugations will appear in from twelve to thirty-six hours
provided a mixed population is present or if the organisms are
mature. In a similar way conjugation tests are made at regular
intervals in all complete isolation culture work. Such tests have
been made with Uroleptus mobilis approximately every ten days.
PHENOMENA 'ACCOMPANYING FERTILIZATION 287
The usual interpretation of this result is not very enlightening;
it runs somewhat as follows: After abundant feeding and active
division the large numbers of individuals produced soon exhaust
the food, and hunger follows; conditions thus due to hunger result
in conjugations provided the organisms are mature. Jennings
(1910) qualified this general statement by emphasizing the necessity
of a preliminary period of active multiplication in a rich food
medium. "The cause of conjugation," he states, "is a decline in
the nutritive conditions after a period of exceptional richness that
has induced rapid growth and multiplication" (he. cit., p. 292).
All experimenters since Maupas have used this method with more
or less success and it appears to be empirically sound. Some
observers, however, interpret the phenomenon as due exclusively
to such purely environmental conditions. Thus Chatton (1921)
argues that inanition is indeed an "internal condition" but the lack
of food which causes it is an external factor. " Inanition," he says,
"is a condition which is practically all that is needed for conjuga-
tion; it is an almost certain means of obtaining conjugations in no
matter what wild culture, and becomes the chosen technical means
of producing them. In current theories, however, conjugation is
regarded as independent of the external conditions, inanition playing
only an occasional role" (he. eit., p. 131). Yet, in a footnote
(p. 135), Chatton very properly calls attention to the fact that con-
ditions which call forth conjugations in nature do not cease after
conjugation is ended. Indeed it is an unwarranted assumption to
explain conjugations in nature as induced by a period of rich feeding
followed by a period of lack of food, and this in turn replaced by a
rich nutrient medium useful to the ex-conjugant. To this extent
the method employed in the laboratory to obtain conjugating
pairs is entirely artificial. Chatton's reflections and conclusions
supporting the view that external conditions are alone responsible
for conjugation are included in his excellent description of the struc-
tures, division, and conjugation of parasitic ciliates of the family
Nicollellidae, particularly Nicollella and Collinella. In the former
the conjugating individuals measure approximately one-fifth of the
vegetative forms; in the latter approximately one-half, in both types
the conjugating individuals differ in morphological details from the
vegetative forms. He interprets these changes as due to the
particular part of the digestive tract to which the parasites are
carried. Chatton's perplexity and call for further experimental
evidence in solving the raison d'etre of conjugation is justified and
the problem will probably remain perplexing so long as external
conditions alone are regarded as the controlling factors. In more
recent work (Chatton, E. and M., 1927) on Glaucoma scintillans,
both internal and external factors are regarded as necessary for
conjugation.
288 BIOLOGY OF THE PROTOZOA
Of these external conditions other factors than the supply of
food may, and apparently do, play a part. Enriques (1903, 1905,
1909, etc.) has long maintained that the phenomena of degeneration
and senescence are caused at bottom, not by internal conditions
but by external causes, apparently by the accumulation in the
medium of bacterial products which poison the organism. Hance
(1917) held that they are caused by the concentration of katabolic
products derived from the organism and accumulate in the medium.
Enriques also makes the statement that upon filtering the liquid
in which conjugating forms are present and adding non-conjugating
individuals to it, the latter will conjugate; on the other hand a
similar liquid with non-conjugating individuals if filtered and
used as medium for conjugating individuals, will act as a deterrent
to conjugation. Repeated attempts on our part with Didinium
nasutum, Paramecium eaudatum and Uroleptus mobilis have failed
utterly to confirm these results. There is more evidence for his
conclusion that salts in the medium are necessary for conjugation,
a conclusion based upon his experiments with NaCl, NaBr, and
Nal in certain concentrations, on the ciliate Cryptochilum nigricans.
These particular salts together with strong solutions (1 to 10,000)
of CaClo and FeoCls, produced epidemics of conjugations, while
weak solutions of the last two salts inhibited conjugations. Still
more extensive experiments along the same line were made by
Zweibaum (1912) on Paramecium eaudatum. Dilute salts, A1C1.3
in particular, added to the medium after a long period of rich feeding,
followed by a period of hunger of five to six weeks (sic) produced
almost complete epidemics. No salts at all, or very strong salts
added to the medium caused no conjugations. These results are
certainly suggestive but the experiments should be repeated with
carefully controlled material and with some other type than Para-
mecium. With this organism Hopkins (1921) failed to confirm
these results. Some rather incomplete and unconvincing experi-
ments by Baitsell (1912) may also be cited in this connection. Two
lines of Stylonychia from the same ancestral cell, were cultivated
on different media; one line on hay infusion, the other on beef
extract. Individuals of the former line refused to conjugate while
those of the latter line conjugated. From this Baitsell concluded
that the determining condition was the medium used. Chatton
(E. and M., 1931) concludes that certain types of food will induce
conjugation in Paramecium while other types will not. Calkins
and Gregory (1914) found that in the same medium some lines
would conjugate regularly while other lines from the same ancestral
cell would not conjugate at all or conjugate only after nine months
of continued culture (see also Hopkins, 1921).
A full consideration of the evidence that has accrued in support
of the thesis that external conditions are alone responsible for the
PHENOMENA ACCOMPANYING FERTILIZATION 289
onset of conjugation leaves one with the same perplexity that
troubles Chatton, Woodruff, and others and calls forth the same
demand for further experimental evidence. Indeed some embar-
rassing questions based upon what we already know must be
answered: If it is environment alone, what are the external condi-
tions responsible for the formation of the gametes in Coccidiomorpha,
Gregarinida, Foraminifera and Phytomonadida? Or in the ciliates
what is the explanation of the failure of external conditions to
induce conjugations in some lines and not in others? Or why will
the same external conditions fail with youthful forms when they
are successful with older (mature) forms?
In practically any epithelium deeply infected with coccidia
adjacent cells contain vegetative stages of the organism, agamont
stages in reproduction, gametocyte stages of both kinds, and nearby
are zygote stages. If conditions of the infected host cell are respon-
sible for the different phases it must be a very delicate difference
that calls out asexual reproduction in one and gamete formation
in another, and all within the radius of a single field of the micro-
scope. If products of degeneration of an infected host cell cause
gametocyte differentiation in one organism why do not the products
of the cell next to it produce a similar effect on its contained organism
instead of which we find the latter reproducing asexually? The
conception of external factors as the sole cause of protoplasmic
changes leading to fertilization must be very elastic to cover such
cases. Why are not all malaria parasites transformed into gameto-
cytes if the blood is the determining factor? Plasmodium vivax
taken into the gut of the mosquito should be transformed into
gametocytes producing gametes instead of which only gametocytes
already formed produce gametes while agamonts are apparently
digested; and in the blood of man or birds these gametocytes
circulate with the vegetative forms and with agamonts. Surely
in these parasitic forms, granted that external conditions may be
provocative, some internal condition of the organism nevertheless
predetermines the action of the environmental stimuli.
With ciliates every experimentalist knows that in pure line work
conjugation tests are sometimes successful, sometimes not. Jennings
(1913) noted this in different races of Paramecium; Woodruff for
several years was unable to obtain a single pair from his famous
culture of Paramecium aurelia, although ultimately they did
conjugate; Calkins and Gregory (1914), cultivating the first eight
individuals from an ex-conjugant of P. caudatum in pure lines,
found that conjugations were abundant in certain lines whenever
a test was made, while other lines remained negative at every test
until the race was many months old. Similar tests made with any
series of UrolejJhis mobilis, and by test we mean a period of rich
feeding followed by hunger, is negative if the organisms are young,
19
290 BIOLOGY OF THE PROTOZOA
positive if the organisms are mature (Fig. 137, p. 268). All of
these facts, and the literature contains many other similar cases,
indicate that environmental stimuli are without effect in producing
conjugations unless the protoplasm is in a condition where such
conjugations are possible. Indeed, when fully mature, i. e., when
the protoplasmic conditions are just right for conjugation, union
will take place in a rich food medium and without the transition
from full nourishment to hunger. This phenomenon is abundantly
illustrated in the records of Uroleptus mobilis and in my records
of Paramecium caudatum, Bhpharisma undulans, or of Didinium
nasntum. There is little information as to the exact nature of these
protoplasmic conditions prior to conjugation. Zweibaum (1922)
gives good evidence to show that the quantity of glycogen in the
cell is reduced to a minimum at this period, the large drops of
neutral fat disappear while small droplets of another type make
their appearance together with some cholesterine ester and large
quantities of what was interpreted as fatty acids. These are prob-
ably effects of inadequate food material, for the observer obtained
similar results with Paramecia under conditions of starvation which
were not followed by conjugation.
II. INTERNAL CONDITIONS AT THE PERIOD OF FERTILIZATION.
In the last analysis both internal and external conditions play
their respective parts in protoplasmic preparations for conjugation.
Without external stimuli, without oxygen and food, vitality would
soon cease; with them, vitality manifested by metabolism and
reproduction will continue. With metabolism, however, the pro-
toplasmic make up is constantly changing and these changes are
shown by the general reactions and by the organization (see Chap-
ter V). According to Hertwig (1908), Popoff (1908), and Rautmann
(1909), the changes thus brought about lead to disturbances of the
normal ratio of nucleus to cytoplasm (Kernplasmaverhaltnis)
and lead to conjugations whereby the normal relation of nucleus
to cytoplasm is regained. W'hatever the changes due to metabolism
are in a given case the conclusion is forced upon us by the mass of
evidence that given external conditions will provoke conjugations
at one period of the life cycle and will have no effect in producing
them at another period, while at the critical period of maturity
external conditions may be entirely negligible as they appear to be
in the Coccidiomorpha and in gamete-forming organisms generally.
Here protoplasmic and not external conditions control the issue.
There is some significance in the fact that encystment (with endo-
mixis) is induced by the same external conditions as is conjugation.
Mengheni (1913) found that Stylonychia will not encyst if food is
abundant but that hunger and low temperature are necessary con-
PHENOMENA ACCOMPANYING FERTILIZATION 291
ditions. With Urolejptus mobilis conjugation and encystment tests
are made in exactly the same way and in some tests conjugating
pairs and encysted forms are present simultaneously.
In the case of Uroleptus mobilis a mass culture of young indi-
viduals shows no tendency to agglomerate, the cells are distributed
more or less uniformly in the culture. In similar mass cultures of
individuals approaching maturity agglomeration in dense groups is
highly characteristic. Such cultures may show no conjugations,
but a mass culture made with the progeny of the same individuals
a week later will show not only the initial agglomerations but epi-
demics of conjugation as well (Calkins, 1919).
This phenomenon of agglomerations indicates something of the
nature of an attraction that increases in intensity as the organisms
approach maturity and have a bearing on the problem of mating.
What is it that brings two gametes together or two apparently simi-
lar ciliates? There is some evidence .that the attraction is of a
chemiotactic nature as illustrated by the often quoted experiment
of Pfeiffer with malic acid and fern spermatozoids. Two citations
from Engelmann (1876) illustrate this phenomenon with ciliates
of the genus Vorticella: "The buds, at the beginning, swarmed
about with constant and considerable rapidity rotating the while on
their axes but moving more or less in a straight line through the
drop. This lasted from five to ten minutes or even longer without
any special occurrence. Then the scene suddenly changed. Hap-
pening in the vicinity of an attached Vorticella a bud quickly
changed its direction with a jerk and approached the larger form,
fluttering about it like a butterfly over a flower and gliding over its
surface here and there as though tasting. After this play, repeated
upon several individuals, had gone on for several minutes, the bud
finally became firmly attached." Again: "I observed another per-
formance still more remarkable. A free-swimming bud crossed the
path of a large YorticeUa which had become free from its stalk in the
usual manner and was roaming about with great activity. At the
instant of the meeting, there was no trace of a pause, the bud sud-
denly changed its direction and followed the Vorticella with great
rapidity. It developed into a regular chase which lasted about five
seconds during which time the bud remained about jj of a milli-
meter behind the Vorticella although it did not become attached
for it was lost by a sudden side movement of the larger form"
(Inc. cit., p. 583). Another illustration taken from the observa-
tions of Schaudinn (1900) on the mating of gametes of Eimeria
schubergi, suggests an action analogous to that of attraxin as
described by F. R. Lillie in sea-urchin eggs. During the matura-
tion of the macrogamete of Eimeria schubergi, the "karyosome" is
cast out of the nucleus, breaks into fragments and the fragments
are extruded from the cell, remaining, however, attached to the
292 BIOLOGY OF THE PROTOZOA
periphery. The uiicrogametes swim aimlessly about and are not
attracted to the macrogamete until after these fragments are
eliminated, but as soon as the granules appear on the surface the
microgametes move toward them in the most direct path (loc. cit.,
p. 257), Zweibaum (1922) observed that the glycogen content is
fundamentally different in the two individuals of a conjugating pair
of Paramecium, which may be significant in this connection. Joyet-
Lavergne (1923, 1925) finds that mitochondria and lipoids in
gregarines are different in quantity and in distribution in the two
individuals of a pair (see p. 76).
While chemiotaxis may underlie the phenomena described above,
an equally intelligible interpretation might be drawn on the basis
of differences in potential of a magnetic nature. Two individuals
of Uroleptus mobilis, about to conjugate, circle about one another,
twist and turn but do not become separated; finally they become
lightly fused by the extreme anterior parts of their peristomes and
the zone of fusion ultimately extends about half way down the peris-
tomes. In the early stages, as with Paramecium, the two individ-
uals can be separated without injury to either ("split pairs") but
later the two protoplasms are welded into one, forming a proto-
plasmic bridge between the individuals. Experiments in cutting
apart the two fused individuals have shown that immediately
after contact and initial fusion the complete series of maturation
divisions proceeds as though the separated individuals were still in
conjugation (Calkins, 1921), and similar cutting at any time during the
period of conjugation does not alter the course of the internal and
consecutive processes (Fig. 155, p. 306). Ultimately reorganization
of the individual follows in due course and the subsequent happenings
are exactly like those of an ex-conjugant. These experiments
indicate that the phenomena of maturation and of reorganization
which characterize fertilization in Uroleptus mobilis are of the nature
of an "all or none" series of reactions and when once started they
go through to the end without deviation. It also appears that the
stimulus which sets in motion this chain of processes is received at
the time of initial contact and is mutually received by both con-
jugating individuals. It thus appears to be less of a chemical
reaction than a physical one and has many of the attributes of a
surface contact phenomenon between surfaces of different electrical
potential.
m. THE PROCESS OF FERTILIZATION.
The actual process of fusion, with the exception of fertilization by
conjugation, furnishes little material for descriptive purposes, two
cells come together and fuse, probably with cytolysis of the contig-
uous cell membranes. In hologamic forms of ciliates {e. g., in
Balantidium coli according to Brumpt) which are extremely rare,
PHENOMENA ACCOMPANYING FERTILIZATION 293
two individuals come together as in pseudo-conjugation of gre-
garines; they secrete a common cyst membrane and then fuse
completely.
In isogamic and often in anisogamic fertilization, fusion begins
as a rule with union of the flagellated ends, if the gametes are motile
A
B
Fig. 146. — Cycloposthium bipalmatum and Diplodinium triloricatum; conjugation.
.1, Cycloposthium with the two migrating pronuclei in the chamber formed by the
two peristomial spaces; B, same, the two migrating pronuclei have passed from the
peristomial chamber into the gullets; (', Diplodinium with migrating pronuclei in
the peristomial chamber in their passage from one individual to the other; p, pro-
nuclei. (After Dogiel.)
(PolystomeUina, gregarines, etc., Fig. 123, p. 235). In Adinophrys
sol (Fig. 142) according to Belaf , one of the fusing individuals devel-
ops a pseudopodium which unites first with the other cell.
With anisogamic fertilization the microgamete is usually motile,
the macrogamete is stationary and is sought by the microgamete
and the same is true also of oogamic fertilization. In some cases
294 BIOLOGY OF THE PROTOZOA
the macrogamete is smaller than the migrating mierogamete
(Fig. 144, p. 281). In the Vorticellidae the macrogamete remains
attached while the mierogamete is free-swimming.
In hologamous fertilization by conjugation there is no universal
mode of fusion. In the majority of ciliates with adoral zones the
fusion area is usually the anterior region of the peristomial furrow,
the mouth as a rule being involved (e. g., Fig. 146). In exceptional
cases the mouth itself is involved in the protoplasmic bridge between
the two conjugants (Paramecium sp. Didinium nasutum, Spathidium
spathula). In Stentor fusion is lateral. Dogiel (1923, 1925), describes
an interesting case of conjugation in Cycloposthium bipalmatum.
Here the two individuals are united end to end, fusion occurring
at the borders of the peristomes, leaving the membranelles of the
adoral zone intact in a common conjugation cavity (Fig. 146).
The wandering pronuclei are provided with tails and, sperma-
tozoa-like, break through the anterior wall and into the conjuga-
tion cavity from which each enters the other conjugant by way of
the mouth.
A. Meiotic Phenomena. The meiotic phenomena in many Pro-
tozoa are apparently started by stimuli resulting from contact and
partial fusion and may be divided into three types: (a) Conjugant
meiosis, or maturation processes occurring only after union of the
participating cells; (b) gametic meiosis (Wilson), or types in which
the maturation processes are antecedent to union; and (c) zygotic
meiosis (Wilson) characteristic of forms in which meiotic divisions
occur in the zygote subsequent to the fusion of the nuclei. The first
of these is illustrated by conjugating Infusoria; the second by the
great majority of types in which fertilization is accomplished by
permanent fusion of gametes; and the third by a few known cases
among the Sporozoa.
(a) Conjugant Meiosis. — In mature ciliates the protoplasmic
organization is such that the stimulus received on contact is appar-
ently all that is needed to start up the nuclear activities associated
with the phenomena of chromosome reduction and preparation of
the pronuclei. These activities furthermore, have to do almost
entirely with the micronuclei. Macronuclei take no part in the
process of fertilization but are important in the subsequent reor-
ganization.
With one or two exceptions (Trachelocerca phoenicopteriis, Spiro-
stomum ambiguum, etc.) all of the free-living ciliates thus far
described agree in the general course of their maturation phe-
nomena. Maupas (1889), the first to make a comparative study
of different ciliates during conjugation, described eight successive
phases of the process which are still applicable to practically all
ciliates. Of these, Phase A is characterized by the swelling and
early changes of the micronucleus; Phase B is the period of the
PHENOMENA ACCOMPANYING FERTILIZATION 295
first meiotic or maturation division; Phase C, the period of the
second meiotic division ; Phase D, the third nuclear division result-
ing in the formation of the pronuclei; Phase E, the period of in-
terchange and union of pronuclei; Phase F, the period of the first
metagamic nuclear division; Phase G, of the second metagamic
division, and Phase H, the period between the second metagamic
nuclear division and the first division of the reorganized cell.
The first four of these phases have to do with the phenomena of
maturation, the last four with the process of reorganization of
the individual. In Trachelocerca phoenicopterus this succession of
stages according to Lebedew (1908) is entirely absent and fertili-
zation follows quite a different course. Also in Euplotes charon
and Euplotes patella according to Maupas there is a slight varia-
tion in the usual sequence in that an anomalous, additional or
preliminary division of the micronucleus takes place in each con-
jugant prior to the first of the two maturation divisions. In the
Peritrichida also a similar preliminary division occurs but in these
cases it is limited to the microgamete, the macrogamete following
the usual history (Vorticella monilata, I . nebulifera Maupas;
Carchesium polypinum Maupas, and Popoff, 190S; Ophrydium
versatile Kaltenbach, 1915; and Opercularia coarctata Enriques,
1907). In the Ophryoscolecidae according to Dogiel (1925) similar
progamous nuclear divisions are followed by division of the cells
resulting in much smaller conjugating individuals.
If more than one micronucleus is normally present in the ciliate
the first meiotic division usually takes place in all of them and the
second division may occur in all, or one or more of the products
of the first division may be absorbed in the cell. Some multiple
micronuclei have been described in conjugating forms of Paramecium
aurelia (Hertwig, 1889), Onychodromus grandis (Maupas, 1889),
Stylonychia pustulata (Maupas, 1889; Prowazek, 1899) and Oxytricha
fallax (Gregory, 1923) each individual having 2 micronuclei. Two
or 3 micronuclei are present in conjugating Didinium nasutum
(Prandtl, 1906); 2 to 4 in Uroleptus mobilis (Calkins, 1919); 4 or 5
in Blepharisma unduians (Calkins, 1912) and 16 to 18 in Bursaria
truncatella (Prowazek, 1899).
1. Phase .1. The Prophase Stages of the First Meiotic Division.—
In many ciliates in which the history of maturation has been followed
there is very little to distinguish the first meiotic mitosis from the
usual vegetative divisions beyond a slight swelling of the micronu-
cleus, fragmentation of its homogeneous chromatin and formation
of its chromosomes. This appears to be the case in Loxophyllum
meleagris (Maupas, 1889), Spirostomum teres (Maupas, 1889),
Euplotes patella (Maupas, 1889), Colpidium colpoda (Hover, 1899),
and in Blepharisma unduians (Calkins, 1912). In the case of
Colpidium colpoda Iloycr (1899) described a typical tissue-cell
296 BIOLOGY OF THE PROTOZOA
spireme but this is so exceptional among eiliates that it cannot be
accepted without confirmation.
In the majority of eiliates this first meiotic mitosis is markedly
different from somatic mitoses. In different species of Paramecium
{caudatum, aurelia and bursaria) a typical prophase stage occurs
in the form of a crescent derived from the homogeneous micronucleus
which first draws out in the form of a long cylinder (Fig. 57, p. 103).
In Chilodon uncinatus the micronucleus draws out into a long comma-
shaped band and in Cryptochilum nigricans (Maupas, 1889), Vorti-
cella monilata and Vorticella nebulijera (Maupas) and in Opercularia
coarctata (Enriques, 1907) a similar chromatin rod extends in some
cases the entire length of the cell.
Still another type of prophase, the "candelabra" (Collin, 1909)
or "parachute" nucleus (Calkins, 1919) is found in Onychodromus
grandis (Maupas), Bursaria truncatella (Prowazek, 1899), Didinium
nusutum (Prandtl, 1906), Anoplophrya braucliiurum (Collin, 1909),
Oxytricha fallax (Gregory, 1923), Uroleptus mobilis and halscyi
(Fig. 32, p. 64), Euplotes, Turner (1930), Conchophthirius (Kidder,
1933). In these cases the nucleus swells to two or three times
the usual diameter with the compact chromatin at one pole
(Figs. 32, 162). In Uroleptus mobilis there is an endobasal body
within the nucleus; this divides, one-half passing to the periphery
of the nucleus at the pole opposite the chromatin mass while the
other half remains with the chromatin (Fig. 32, p. 64). The distal
centrosome is the focal point of the spindle fibers which spread out
from it to the fragmenting chromatin mass and forms one pole of
the mitotic spindle.
In the transformation of the crescent type of prophase Maupas,
Hertwig and Hamburger all agree that the spindle is formed by the
shortening of the long axis of the crescent. Calkins and Cull
(1907) and Dehorne (1920), however, find that the division center
or achromatinic substance which forms the poles of the spindle
migrates from its apical position in the crescent to the center of
the convex side, and that this new position marks one pole of the
spindle (Fig. 147).
In the parachute type the second pole is formed by the outgrowth
from the chromatin mass of a second pole similar to the first, the
chromatin granules thus being left in the nuclear plate position or
center of the spindle figure (Fig. 32, p. 64).
2. Phase B. The First Meiotic Division.— Exact knowledge of
the formation of chromosomes and their division is scanty, due in
part to the large number of chromosomes and to their small size.
Maupas (1889) made no attempt to enumerate the chromosomes;
nor did he describe their formation beyond the brief account of the
fragmentation of the homogeneous chromatin masses of the micro-
nuclei. Hertwig (1889) believed that there were S or 9 chromo-
PHENOMENA ACCOMPANYING FERTILIZATION 297
somes in Paramecium aurelia, basing his view not on the chromo-
somes but on the number of fibers which he could distinguish in
the connecting strand between the two daughter nuclei. Later
w*
iy
«
* 1
r
*
■
w *
1
.
'^SBaffll^
iMf
1
V
•
1
L w4 .
•**»
Fig. 147. — Paramecium caudatum; A, B, C, stages in the first meiotic division
during conjugation; A, shortening of the crescent and formation of pole-plate on
upper side; D, prophase of second meiotic division. (After Calkins and Cull.)
observers have found that the number in all species of Paramecium
is much greater than this, running up to more than one hundred.
Dehorne (1920), on the other hand, finds no chromosomes at all,
29S BIOLOGY OF THE PROTOZOA
the chromatin being in the form of a continuous single looped
thread which divides by transverse division (Fig. 57, p. 103. Cf.
Fig. 147).
• 4
|
P *
"'%
V
#
Fig. 148. — Didinium nasulum, section of conjugating individuals. Second meiotic
division of the nuclei (P). (Original.)
In more favorable types of ciliates than Paramecium the number
of chromosomes has been made out with some degree of accuracy.
Prandtl (1906) found 16 in Didinium nasutum (Fig. 14S). Prowazek
(1899) was a little in doubt whether there were 12 or 13 in the
nuclei of Bursaria truncatella (Poljansky, 192S, enumerates more
PHENOMENA ACCOMPANYING FERTILIZATION
299
than 100), but described 6 chromosomes in Stylonychia pustulata.
Stevens (1910) described 4 chromosomes in Boveria subcylindrica,
but gave no details of their formation or reduction. Enriques
(1908), confirmed by MacDougall (1925) found 4 in Chilodon
Fig. 149.
-Chilodon uncinatus. Third division and interchange of nuclei of diploid
(A) and tetraploid (B) stock. (After MacDougall.)
uncinatus; Popoff (1908) 16 in Carchesium polypinum; Enriques
(1907) the same number in Opercularia coarctata, and Collin (1909)
G chromosomes in Anoplophrya branchiarum.
Hamburger (1904) is a bit hazy in her account of the origin of
300 BIOLOGY OF THE PROTOZOA
the chromosomes In Paramecium bursar ia. The late stage in the
crescent is regarded by her as a spireme from which the chromosomes
are formed as short curved or V-shaped rods. Calkins and Cull
(1907) found that the chromosomes of Paramecium caudatum are
derived from a synezesis stage which precedes the crescent and that
the chromosomes are already divided at the stage which had gen-
erally been regarded as the metaphase. According to this account
the metaphase stage occurs during the metamorphosis of the
crescent into the spindle so that the latter when formed is in the
early anaphase stage (Fig. 147).
In other ciliates the chromosomes are formed by the union of
chromomeres which are derived by fragmentation of the homogene-
ous chromatin of the resting micronucleus. The process is com-
pleted at the parachute stage and the definitive number is present
by the time the second pole of the spindle is completed. In Urolep-
tus mobilis when diffusion of the granules has apparently reached
its limit, there are from 16 to 20 chromomeres (48 to 50 in U. halseyi)
i| i||| (Hi) lllf fl$
1 2 3 4 5
Fig. 150. — Euplotes patella, micronuclear chromosomes. 1, In vegetative mitosis;
2, 'A and 4, first, second and third meiotic divisions; 5, first division of the amphi-
nucleus. (After Turner, from University of California Publications in Zoology, 1930.)
(Fig. 32, p. 64). Prandtl's figures show that there are approximately
32 in Did i nium nasutum. Enriques (1908) and Collin (1909) have
described a similar fragmentation of the comma-shaped chromatin
rod <>f Chilodon uncinatus and of the homogeneous chromatin mass
of Anoplophrya branchiarum, the granules of chromatin collecting
in the center of the first maturation spindle. In Didinium, Chilodon
and Anoplophrya these granules fuse until a definite number of
chromosomes result— 16 in Didinium (Fig. 148), 4 in Chilodon (8 in
the tetraploid form found by MacDougall, 1925, Fig. 149), and 6 in
Anoplophrya and 8 in Euplotes patella where each is made up of
four previously separated chromomeres (Turner, 1930, Fig. 150).
In Uroleptus mobilis a similar fusion of granules results in 8 chromo-
somes (Fig. 32, p. 64). Urolejitus halseyi differs in many respects
from U. mobilis. Its micronucleus is larger and lacks an endobasal
body. The first pole of the first meiotic spindle is formed by con-
densation of the karyolymph which draws away from the peripheral
chromomeres. The second pole is formed by migration of part of
the condensing substance, and between the two poles the nuclear
PHENOMENA ACCOMPANYING FERTILIZATION 301
Fig. 151.— Uroleptus halseyi. Formation of chromosomes, spindle, and first
meiotic division of the micronucleus. X 1750. (After Calkins, Arch. f. Protisten-
kunde, courtesy of G. Fischer.)
302
BIOLOGY OF THE PROTOZOA
plate is formed with 48 to 50 chromosomes. With the first division
these separate into two groups, each with 24 chromosomes (Fig. 151).
3. Phase C. The Second Meiotic Division. — Prior to Prandtl's
work on Didinium there were no conclusive observations on the
reduction of chromosomes in ciliates. He found that the 1(3 chromo-
somes characteristic of the first maturation division become reduced
to 8 with the second division. Since his work appeared there has
been a number of authentic observations along the same line. Thus
Enriques (1907) found a reduction in number from 16 to 8 chromo-
somes in Opercularia coarctata and the same observer (1908) de-
scribed a reduction from 4 to 2 in Chilodon uncinatus (Fig. 149),
reduction occurring at the second division. Other cases of the same
type are Carchesium polypinum (Popoff, 1908) with reduction from
16 to 8; Anoplophrya branchiarum (( lollin), from 6 to 3; and Uroleptus
l!
c
Fig. 152.
■Uroleptus mobilis. The second meiotic division and reduction in number
of chromosomes during conjugation. (After Calkins.)
(Calkins, 1919) from 8 to 4 (Fig. 152). In all cases the second
meiotic division appears to be unaccompanied by any of the pre-
liminary activities which characterize the first division. In some
the nuclei do not return to a resting condition between the two
divisions, but in other cases, c. g., Chilodon (MacI)ougall, 1925),
the second spindle forms from a resting nucleus.
In ciliates with a multiple number of micronuclei the number par-
ticipating in the second division appears to bear no constant rela-
tion to the number derived from the first division. In cases having
but one micronucleus in the vegetative stages the numerical rela-
tions are fairly constant, two spindles in the second meiotic division
being the rule. There are, however, some exceptions. Thus in
Paramecium bursaria, according to Hamburger (1904), one of the
nuclei formed by the first division degenerates without forming a
spindle so that only one nucleus undergoes the second division.
PHENOMENA ACCOMPANYING FERTILIZATION 303
Other exceptions are found in Euplotes patella in all Vorticellidae
and Ophryoscolecidae examined up to the present time. Here the
micronucleus undergoes one or more preliminary mitoses prior to
the first meiotic division.
In eiliates with two micronuclei both undergo the first maturation
division. According to Prowazek (1899) the 4 resulting nuclei of
Stylonychia pustulata divide again, thus forming 8 products at the
second division. According to Maupas (1889), however, 2 of the
first 4 nuclei of Stylonychia pustulata, and of Onychodromus grandis
as well, degenerate so that only 2 second maturation nuclei are
formed. Gregory's (1923) observations indicate that a variable
number take part in the second division of Oxytricha fallax.
In forms with many micronuclei in the vegetative stage there
seems to be no general rule as to the number which undergo a
second division. Prandtl found a variable number in Didinium
nasutum, Prowazek a large number in Bursaria truncatella, and
Calkins a variable number in Uroleptus mobilis; while 1 and 4
nuclei are rarely found, 2 or 3 are characteristic.
In summing up the accumulating evidence on meiotic phenomena
in the eiliates the conclusion may be drawn that the history in the
main is similar to the history of meiosis in Metazoa. Chromo-
somes of definite number are characteristic of most species and this
number is reduced to one-half during one or the other of the two
divisions.
4. Phase!). The Third Division. Pronuclei Formation. — A third
division of the nuclei subsequent to reduction in number of chromo-
somes is characteristic of all eiliates in which fertilization has been
carefully studied. It is extremely difficult to interpret this final
division which gives rise to the pronuclei (see infra p. 319). In
the majority of cases it appears to be a transverse division which,
if judged by Metazoa, would make it a second reduction division.
One of the products is a wandering pronucleus which migrates,
the other is a stationary pronucleus which ultimately fuses with the
migratory pronucleus from the other individual. There is some
evidence that the migrating pronucleus is equivalent to a spermato-
zoon (Dogiel, 1925).
The third division spindles are always characteristic and different
from the spindles of the meiotic divisions. Not only are they fre-
quently heteropolar, but the late telophase state is characterized
by long connecting strands of nuclear substance (Fig. 153). There
is no uniformity in regard to the number of nuclei to undergo this
third division although only one of the dividing nuclei provides
the two functional pronuclei. Anoplophrya branchiarum, Para-
mecium caudatum, Chilodon uncinatus, Colpidium colpoda, Leuco-
phrys patula, Glaucoma scintillans, Loxophyllum meleagris, Spiro-
stomum teres, Bursaria truncatella, Blepharisma undulans, Boveria
304
BIOLOGY OF THE PROTOZOA
Fig. 153.— Uroleptus halseyi. Second and third meiotic divisions of the micro-
nucleus, approach of gametic nuclei, metaphase of first zygotic nuclear division
and second zygotic nuclear division. X 1750. (After Calkins, Arch. f. Protisten-
kunde, courtesy of G. Fischer.)
PHENOMENA ACCOMPANYING FERTILIZATION
i05
subcylindrica, Lionotus fasciola, and in the Vorticellidae, only 1
nucleus undergoes this third division. In Onychodromus grandis,
Stylonychia pustulata, and Euplotes patella, 2 nuclei; in Oxytricha
fa I lax (Gregory), 2 or 3, and in Uroleptus mobilis, 2, 3 or 4 nuclei,
undergo the third division.
Prandtl (190(5) was the first to note a difference in size between
the wandering and the stationary pronuclei (Didinium nasutum),
Calkins and Cull (1907) described a similar difference in pronuclei
of Paramecium caudatum and were able to trace this difference back
Fig.
154.— Uroleptus mobilis, conjugation. The interchange of pronuclei, each
preceded by a characteristic "attraction sphere." (After Calkins.)
to a heteropolar third division spindle. In other cases there seems
to be no characteristic difference in size between the two pronuclei
although other differences may be evident. Thus Maupas noted
the presence of a dense aggregate of cytoplasmic granules at the
forward pole of the advancing pronucleus of Euplotes patella and
Prandtl, more pronounced astral radiations about the wandering
pronucleus of Didinium nasutum. In Uroleptus mobilis such radi-
ations are absent, but a fairly homogeneous condensed "sphere"
of cytoplasmic substance precedes the wandering pronucleus in its
migration (Fig. 154).
20
306
BIOLOGY OF THE PROTOZOA
What is the significance of this third division? The answer can
be only speculative at the present time. The absence of definite
chromosomes in some cases, e. g., Paramecium, and the occurrence
of heteropolar mitotic figures lend some support to the view that it
is a differential division whereby male chromatin, as suggested
Fig. 155. — Uroleptus mobilis, cut during conjugation as indicated. In this case
the conjugants were in the prophase stage of the first meiotic division. PXI, history
of reorganization without fertilization. (After Calkins.)
by Schaudinn (1904) is separated from "female" chromatin, the
balance between the two being established by union of the wandering
and the stationary pronuclei. Such an hypothetical balance would
be maintained if there were no interchange of pronuclei and the
third division does not take place, a condition realized in what
PHENOMENA ACCOMPANYING FERTILIZATION 307
Woodruff and Erdmann (1914) called endomixis (see p. 317).
Experimental evidence leading to definite conclusions has not yet
been advanced. Calkins (1921) made an attempt in this direction
by cutting conjugating pairs of Uroleptus mobilis in such a way that
the two migrating pronuclei were removed while the two individ-
uals, now separated, possessed only the stationary pronuclei (Fig.
155). These individuals were then followed in cultures, the process
of reorganization was completed, the cells regenerated perfectly,
and in successful issues, normal rejuvenescence and a typical life
history resulted. The crucial point so far as the present matter
is concerned was not determined, viz., from what elements were the
new macro- and micronuclei derived? Did the stationary pro-
nucleus in its "unbalanced" condition give rise to the new nuclear
elements as it would have done were it an amphinucleus? Was
there a fusion prior to the degeneration of other pronuclei of the
stationary pronucleus with one of the "male" pronuclei of which
there may be as many as four in each conjugant? Or did the sta-
tionary pronucleus degenerate, its place being taken by one of the
other pairs of pronuclei? Some evidence that the last alternative
was the case is afforded by the fact that the conjugating pairs if cut
apart at an early period in conjugation may not undergo the third
division, some one of the products of the second division acting as
an amphinucleus, thus realizing the condition during "endomixis."
See also, in this connection, the merotomy experiments of Ilowaisky
(1926) on Stylonychia mytilus and Paramecium caudatum conjugants.
(6) Gametic Meiosis (Wilson, 1925). — In the preceding section
instances of meiotic divisions subsequent to cell fusion were inter-
preted as due to stimuli mutually imparted to the conjugating
individuals. For this the protoplasm must be in a mature condition,
that is, with an organization considerably modified from that of the
young or immature organisms. In a later section evidence will be
given which indicates that under proper conditions the stage is all
set for a similar all or none series of phenomena without, however, the
stimulus of contact (see p. 317, endomixis). An analogous condi-
tion termed here gametic meiosis if accompanied by subsequent cell
fusion of gametes, is characteristic of the majority of Protozoa
in which fertilization is accomplished by the fusion of cells. Unfor-
tunately the history of the chromosomes is known in but few cases
but there is scarcely a paper on the fertilization of Protozoa that
does not describe two rapidly-following divisions of the nuclei
prior to fusion, and these are called maturation divisions, and the
resulting nuclei "reduction nuclei." In Actinosphaerium eichhornii
according to Hertwig (1898) the first evidence of the process is
encystment of the adult organism and excretion of waste matters
contained in the protoplasm. The nuclei are reduced in number to
from 5 to 10 per cent of the original number by fusion and absorption
308
BIOLOGY OF THE PROTOZOA
in the protoplasm. The cell then divides into as many daughter
cysts as there are nuclei and these Hertwig calls cystospores No. 1,
each of which secretes a gelatinous envelope about itself. The
nucleus then divides by mitosis followed by division of the cell into
two daughter cells which he calls cytospores No. 2. The nuclei of
the latter undergo two successive "maturation" divisions resulting
in one pronucleus and two "polar bodies" in each (Fig. 156), the
latter degenerating and disappearing. The two cytospores of
the second order now unite again, reforming cytospores No. 1
and fertilization is completed by fusion of the pronuclei. Belaf
quite recently (1922) has given a more complete description of
Fig. 156. — Actinosphaerium eichhornii. A, two gametes ("cytospores No. 2")
resulting from the division of the same mother-cell; B, both "polar bodies" are
formed in the right gamete, the second one forming in the left gamete; C, the cell
bodies of the gametes have fused, and the nuclei are fusing; D, young organism leav-
ing cyst; p, p1, p2, " polar bodies. " (After Hertwig.)
the process in the allied form Actinophrys sol. The individuals
draw in their pseudopodia, ordinary vegetative division of the
nucleus follows, and the cell divides into two. By this division
which Belaf terms the "progarnous" division, the two gametes
are formed and after each of them has undergone two meiotic
divisions of the nuclei they reunite to form the zygote. One of
them anticipates the other in these divisions and develops a pseudo-
podial process which the other lacks. By this process the first
fusion of the two cells takes place. The original cell thus is a
gamont and the fusing gametes are sister cells, one of which shows
an incipient sex difference in its precocious activity and by its
pseudopodium-like process. (Fig. 142, p. 27S.) There are 44
PHENOMENA ACCOMPANYING FERTILIZATION 309
chromosomes in the vegetative mitoses of Actinophrys sol and after
the progamous division the gametic nuclei swell, chromosomes
arrange themselves in pairs (parasynapsis) oriented toward one pole
of the nucleus. These double chromosomes shorten and ultimately
form the nuclear plate of the first meiotic spindle (Fig. 157). Here
the two parts of the double chromosomes are separated and pass to
the resulting nuclei, each of which thus has 22 single chromosomes.
A second meiotic division results in the longitudinal splitting of these
22 chromosomes so that the pronuclei and the two "polar bodies"
in each gamete have 22. One of the products of each division
degenerates and is absorbed in the cytoplasm, and these are com-
pared with the polar bodies in Metazoa. The two gametes then
fuse, their nuclei fuse and the zygote becomes encysted (Fig. 142).
In this case the chromosome cycle is remarkably similar to that of
JK9H
sm5
am_
'Mm4m W!^W W&Wm
sassgs*- v
«i
A 5 C
Fig. 157. — Actinophrys sol. A, contraction of the double chromosomes of
strepsinine stage; B, metaphase of reduction division; C, anaphase of equation
division. X 1900. (After Belaf, Archiv f. Protistenkunde, 1926, courtesy of
G. Fischer.)
chromosomes of the metazoan egg and sperm in their maturation
divisions.
Analogous processes may take place in other types of Protozoa
in which fusion of gametes occurs, but the chromosome history is
known in but few cases. In Gregarinida there are several pro-
gamous divisions of the gamonts, the last of which, according to
Mulsow's (1911) observations of Monocystis rostrata, being a reduc-
ing division whereby the chromosomes are reduced in number from
8 to 4 (Fig. 55, p. 101). Mulsow's interpretation is confirmed for
Monocystis by Calkins and Bowling (1920).
(c) Zygotic Meiosis (Wilson).— Reduction in number of chromo-
somes subsequent to nuclear fusion of gametes occurs in rare
instances but the phenomenon may be more widely spread than is
at present admitted. Two well authenticated cases are the coccidian
310
BIOLOGY OF THE PROTOZOA
Aggregate eberthi and the gregarine Diplocystis schneideri. Dobell
(1915) describes 6 chromosomes in the vegetative divisions of
Aggregata eberthi, and Jameson (1915 and 1920) describes 3 in DipJo-
cystis schneideri (Fig. 56, p. 102, and Fig. 158). These numbers remain
constant in both organisms during gametogenesis, the mature
gametes have the same numbers while the diploid numbers 12 and
6 are present only in the zygotes (Figs. 56 and 158). With the
first division of the zygotes the two sets of chromosomes unite
in homologous pairs; in Aggregata 1 pair consists of long chromo-
somes, 1 pair is very short and 4 pairs are intermediate in length
(Fig. 56). The nuclei resulting from this first metagamic division
have 6 chromosomes each in Aggregata and 3 each in Diplocystis, and
these haploid numbers are retained throughout the vegetative
cycles.
ABC D
E
Fig. 158. — Diplocystis schneideri. Zygotic meiosis. A to E, nucleus of the zygote
forming 6 chromosomes (the diploid number), and the first metagamic division; F,
anaphase of the sixth progamous division preparatory to gamete formation, with
3 longitudinally split chromosomes, the haploid number. (After Jameson.)
The generalization made by Dobell and Jameson to the effect
that this method of reduction is probably universal among the
Telosporidia is hardly justified by these two cases. Few species
indeed have been studied with respect to the reduction of chromo-
some number and only one— Monocystis rostrata — by Mulsow (1911),
with sufficient care as to cytological detail to be admitted, and
here, as stated above, reduction occurs with the final progamous
division of the nuclei. Dobell and Jameson would explain this
divergent case as due to confusion by Mulsow of stages of two dif-
ferent gregarines, one with 8 the other with 4 chromosomes, but
PHENOMENA ACCOMPANYING FERTILIZATION 311
Mulsow's contention is proved by finding final progamous spindles
in the anaphase stage with 4 chromosomes in each daughter plate
(haploid) while other progamous spindles are present in the same
section with S chromosomes in each daughter plate (diploid) (Calkins
and Bowling, 1926). Evidence in support of Dobell and Jameson's
generalization is furnished by the fact of the frequent occurrence of
an odd number of chromosomes in nuclei of different gregarines.
Thus 5 chromosomes were found by Shellack (1907) in Echinomera
hispida and the same odd number by Leger and Duboscq (1909) in
Nina gracilis; while 3 were found by Shellack in Monocystis ovata
(1912). Such odd numbers are not difficult to interpret if reduction
takes place at the first metagamic division but they lead to question-
able hypotheses of "odd chromosomes" (Leger) "accessory chro-
mosomes," etc., if reduction is interpreted as taking place prior to
fertilization.
B. Disorganization and Reorganization. — (a) Phenomena of Dis-
organization.—While the meiotic processes are probably universal
accompaniments of fertilization they do not comprise all of the
phenomena taking place at this period. Evidences of disorganiza-
tion are apparent in the cell quite independent of the gametic
nuclei. Metagamic activities involving reorganization of the proto-
plasm are equally characteristic of the fertilized cell and lead to
the production of young organisms with full potential of vitality.
Disorganization and reorganization, although probably closely
related, are different in character and will be discussed separately.
The destruction of the old macronucleus in Infusoria is one of
the most significant of the phenomena attending conjugation
(Fig. 139, p. 273). Here is an organ of the cell which is generally
regarded as intimately connected with metabolic activities of the
organism; which has functioned throughout vegetative life of the
race and has divided with each division of the cell. Yet at con-
jugation the macronucleus degenerates through hypertrophy and
fragmentation and the fragments are ultimately absorbed in the
protoplasm. The process is fundamentally the same in all ciliates
differing only in details.
If the organization of a ciliate is dependent upon the specificity
of the proteins, carbohydrates, fats, salts and water which enter into
its make up, then this large bulk of nucleo-proteins distributed to
all parts of the cytoplasm must bring about a markedly different
matrix with which the new amphinucleus and its products are to
react. Zweibaum (1922) concluded that products of metabolism
during vegetative activity gradually poison the nuclear substances
so that both synthetic and oxidizing activities are weakened, but
at conjugation and with fragmentation of the macronucleus the
contained ferments are freed from their toxic bonds, and activity
is fully restored. The intake of oxygen is much greater after con-
312 BIOLOGY OF THE PROTOZOA
jugation than before, a fact which Zweibaum (1921) interprets as
due to reorganization and the freeing of oxidases by nuclear disor-
ganization. To this mass of nucleo-proteins is also added three-
quarters (c. g., Paramecium) to fifteen-sixteenths (Uroleptws) of the
substance of the old micronuclei, which is likewise absorbed in the
cytoplasm.
Not only is the old nuclear material broken down and distributed
but, in some instances at least, the formed metaplastids of the cell
are similarly destroyed and absorbed. This is well illustrated by
the disappearance of the old pharyngeal basket and some of the
cilia in Chilodon uncinatus (MacDougall, Fig. 112, p. 222). This
is perhaps relatively unimportant at conjugation since the same
thing happens at each division of the cell during vegetative life,
but it is evidence in support of the view that stabile substances of
the organism, substances that have accumulated with continued
vegetative life are reduced to labile substances at this significant
period of the life history.
In a similar manner the many nuclei of Actinosphaerium eichhornii
(300 or more) according to Hertwig (1898) are fused or absorbed
prior to fertilization. As there must be a limit to the number
that fuse (if any?) the great majority of nuclei must be absorbed
in the protoplasm, for only a few (up to 20) become nuclei of gamonts
(see p. 307).
In gregarines also there is a similar fragmentation of some of the
nuclei leading to collections of chromidia which appear to function
in the formation of sporoducts (see p. 239). In Mycetozoa and
Neosporidia also some of the nuclei are destroyed in connection
with the formation of accessory structures of the fruiting bodies
(elaters, sporoducts, spore capsules, etc.).
The conclusion is forced upon us that this period of fertilization
is marked by far-reaching changes in organization. Some of these,
as in ciliates, have a prospective value for the young organisms
while others are differentiations serving a useful purpose for the
limited period of fertilization in organisms whose individual meta-
bolic activities are approaching the end, and these are evidence of
extreme specialization.
(b) Metagamic Activities and Reorganization.— Under this heading
we include all changes which take place in the organism immediately
after formation of the amphinucleus. In ciliates the fragmentation
and absorption of the old macronucleus may continue for several
days after union of the gametic nuclei but the further activities
of the amphinucleus appear to be independent of the other happen-
ings in the cytoplasm. These activities have to do primarily with
the differentiation of the characteristic cell structures of the new
organism. Thus in Chilodon and other Chlamydodontidae a new
oral basket is formed and some if not all of the cilia are renewed;
PHENOMENA ACCOMPANYING FERTILIZATION 313
whether or not new cirri, membranelles, and undulating membranes
are formed and the old ones absorbed, has not been fully determined
by observation but this appears to be the case in Uroleptus mobilis.
The most important of the changes at this period have to do with
the formation of the new macro- and micronuclei. The inaccurate
statement is often made to the effect that the new macronucleus
is formed by the metamorphosis of a micronucleus. This is strictly
true only in cases of parthenogenesis. In fertilization both macro-
and micronucleus are formed from products of the amphinucleus,
Fig. 159. — Uroleptus mobilis; conjugation at the stage of nuclear fusion: g, n,
gametic nuclei about to fuse; B, same enlarged; C, elongation of amphinucleus
shortly after fusion. (After Calkins.)
and both types of nuclei are formed by metamorphosis of such
products. In the majority of cases the first metagamic division
of the amphinucleus results in two equivalent nuclei. In Uroleptus
mobilis this division occurs very soon after fusion and before com-
plete mixture of the two pronuclei is established (Fig. 159). This
is shown by the occasional finding of nuclei in which 4 of the 8
chromosomes are in the anaphase stage while the other 4 are in the
metaphase (Fig. 160). The two products of this division have
different fates. One of them divides again to form two nuclei
which lose their vesicular character and condense into minute and
314
BIOLOGY OF THE PROTOZOA
homogeneous bodies, the micronuclei. The other one forms a
heteropolar spindle and divides into two unequal products the larger
of which is vesicular and persists as the new macronucleus, the
smaller one is spheroidal and compact and ultimately disappears
Fig. 160. — Origin of macronucleus after conjugation in Uroleptus mobilis. (1)
first metagamie mitosis of the amphinucleus ; (2) one of the progeny of this division
dividing again; (3), (4), (5) telophase stages of second division of the amphinucleus
resulting in a new macronucleus (above), and a degenerating nucleus (below); (G to
10), stages in differentiation of the young macronucleus and disintegration and
absorption of the old macronucleus; in (10) two new micronuclei are in mitosis pre-
paratory to the first division of the ex-conjugant. (M) new macronuclei; (///) new
micronuclei; (d) degenerating old macronuclei. (After Calkins.)
by absorption (Fig. 160, 4). The young macronucleus sometimes
called the "placenta" becomes finely granular and loses its staining
capacity which is not regained for a period of from three to five or
more days. During this period the young macronucleus appears
like a vacuole in a center of a cell and is distinctly visible in the
PHENOMENA ACCOMPANYING FERTILIZATION 315
living cell. It is small at first but grows in size from day to day
while nucleic acid is formed and deposited in continually growing
chromomeres (Calkins, 1930; see p. 84), until finally the placenta
occupies fully two-thirds of the cell. It then condenses into a
compact homogeneous ellipsoidal nucleus, invisible in the living
cell, and now stains intensely with chromatin dyes (Fig. 160, 10). It
is now ready for the first macronuclear division and divides twice
prior to division of the cell. It is perhaps significant that a similar
dense ellipsoidal nucleus is formed by fusion of the 8 macronuclei
prior to cell division in vegetative life (see p. 220).
An essentially similar history of the amphinucleus occurs in
Colpidium colpoda (Hoyer, 1899), Stylonychia pustulata (Maupas,
1889) and Lionotus fasciola (Prowazek, 1909). In Paramecium
caudatum the amphinucleus divides twice without differentiation
and all 4 products divide a third time, 4 of the resulting 8 nuclei
become micronuclei and 4 become macronuclei (Calkins and Cull,
1907). Here there is no degeneration, but in Paramecium putrinum
according to Doflein (1916) and in Paramecium bursaria (Ham-
burger, 1904) 3 of the 8 nuclei degenerate. Three divisions of the
amphinucleus are also characteristic of Cryptochilum nigricans
(Maupas, 1889), Carchesium polypinum (Popoff, 1908), Vorticella
monilata and Vorticella nebulifera (Maupas, 1889) and Ophrydium
versatile (Kaltenbach, 1915). In these, 7 of the 8 resulting nuclei
form macronuclei while the eighth forms the micronucleus. All 7
fuse to form 1 maeronucleus in Cryptochilum (Maupas) but in the
others each forms a maeronucleus the 7 being separated by succes-
sive cell divisions until finally each cell has 1 (Popoff, Maupas,
Kaltenbach).
In Didinium nasutum (Prandtl, 1906), Paramecium bursaria
(Hamburger, 1904), Glaucoma scintillans, Leucophrys patula, Spiro-
stomum teres and Stylonychia pustulata (Maupas, 1889) differentia-
tion occurs with the second division; 2 of the 4 nuclei become macro-
nuclei and 2 micronuclei while none degenerates. A very exeeptional
history occurs in Bursaria truncatella according to Prowazek (1899).
Here no differentiation occurs until 10 nuclei are formed; 2 to 5 of
these become macronuclei; 3 or more become micronuclei and the
remainder degenerate. This history, however, is not confirmed by
Poljansky (1928) in a more critical examination of this phase of
Bursaria.
In Sporozoa metagamic activities take quite a different form.
The majority of gregarines become gamonts which form many
gametes (in Ophryocystis only two), which copulate within the
gametocyst (Fig. 120, p. 231). The amphinucleus of each zygote
divides, usually three times, to form eight products, each of which
becomes the nucleus of a sporozoite. In Diplocystis schneideri
the first of these divisions results in the reduction in number of
316 BIOLOGY OF THE PROTOZOA
chromosomes to one-half (Jameson, 1923; see p. 310). In the
Coccidia the number of metagamic divisions is still further increased.
Here the zygote as well as the amphinucleus divides to form from
two to many sporozoite-forming centers— the sporoblasts— each
of which becomes enclosed in a special sporoblast capsule (sporocyst)
where it divides, usually only once, to form sporozoites (see p. 530).
In Aggregata eberihi as in Diphcystis the first division of the zygote
results in halving the number of chromosomes (Dobell, 1916).
The Hemosporidia differ in that capsule-bearing sporoblasts are
not formed. Here the zygote grows to large size and the amphi-
nucleus divides repeatedly until myriads of sporozoites are formed.
In these types of Protozoa, therefore, metagamic activities involve
actual reproduction, and reproduction here is a sequel to fertilization.
Other groups of Protozoa differ widely in their metagamic activi-
ties and some types give unmistakable evidence of ontogenetic devel-
opment. Thus zygotes of Foraminifera grow directly into the more
or less complex asexual generation (microspheric) . Here the amphi-
nucleus divides repeatedly while the cell divisions are suppressed.
Other changes of a metagamic nature have to do with the clearing
up of accumulated substances in the cytoplasm. Zweibaum (1922)
finds that relatively large droplets of neutral fat which are charac-
teristic of vegetative phases of Paramecium are broken down prior
to conjugation while smaller droplets of another type accumulate.
Among these he was able to detect a larger amount of cholesterin
ester than normal and a great quantity of what he interpreted as
fatty acids. After conjugation these small drops disappear and
neutral fats reappear. A similar accumulation of fat-like droplets
and "lipoplasts" is described by Belaf (1922) in Actinophrys sol
as characteristic of the copulating gametes and of the zygote,
but the accumulation breaks down and disappears with germina-
tion of the latter. Macrogametes of Coccidia have an analogous
store of cytoplasmic substances of the nature of lecithin which also
disappears during metagamic activities.
There is some evidence, therefore, that specific products of
metabolism accumulate in cells of Protozoa prior to fertilization
and that these are utilized as are yolk substances of metazoon eggs
in the early metagamic activities. Their disappearance after fer-
tilization indicates that in this respect also, the general make up of
the cytoplasm is reorganized.
IV. PARTHENOGENESIS.
Parthenogenesis may be briefly defined as the development of
an organism from an egg cell (or its equivalent, e.g., a ciliate)
which has not been fertilized. The phenomenon occurs spontane-
ously in a few animal groups and may be induced artificially in
PHENOMENA ACCOMPANYING FERTILIZATION 317
eggs from animals of widely different phyla which usually undergo
fertilization before development.
The chief biological interest of parthenogenesis centers in the
nuclear phenomena. Under ordinary conditions of fertilization
two polar bodies are formed by the maturing egg and with their
formation the number of chromosomes is reduced to one-half so
that egg pronucleus and polar body nuclei are haploid. It follows,
therefore, that in artificial parthenogenesis all tissue cells of the
body are haploid. The same phenomenon occurs, naturally, in the
development of the drone honey bee, or of the male rotifer and may
be referred to hereafter as Type 1. In the great majority of par-
thenogenetic eggs, however, the second polar body is not formed
and the nucleus remains diploid as for example in parthenogenetic
aphids or female rotifers; this may be designated Type 2. A third
possibility, in theory, would be cases where two polar bodies are
formed which, with the pronucleus, are haploid but the egg becomes
diploid by later fusion of the pronucleus with one of the polar
body nuclei. This which may be called Type 3 has not been estab-
lished with certainty in any metazoon but was suggested as a possi-
bility by Boveri (1887) and described by Brauer (1893) as one type
of parthenogenesis in the eggs of Artemia.
In Protozoa many cases of so-called parthenogenesis have been
described some of which fall in line with one or another of the three
types in Metazoa as outlined above. These phenomena may be
grouped under two headings— so-called endomixis of Woodruff and
Erdmann (1914) and autogamy, a widely used term in connection
with Protozoa.
A. Endomixis.— Under this term Woodruff and Erdmann (1914)
described "a complete periodic nuclear reorganization without cell
fusion in a pedigreed race of Paramecium.'" At regular intervals
of approximately thirty days they found that the old macronucleus
of Paramecium aurelia gives rise to buds or fragments which are
absorbed in the cytoplasm. There appears to be some difference
in the details of macronucleus fragmentation between individuals
in 1914 and more recent individuals. Thus Woodruff and Spencer
(1922) find that ribbon or skein formation prior to fragmentation
and characteristic of conjugation, which was very rare in 1914,
had become much more common in 1921. Each of the two micro-
nuclei divides twice, forming S products some of which form new
micronuclei, some new macronuclei. The possible combinations of
nuclei and their relations are shown in Fig. 161. Later, Erdmann
and Woodruff (1916) demonstrated a similar periodic reorganiza-
tion at intervals of approximately sixty days in Paramecium cauda-
tum. In this case the single micronucleus divides three times,
forming 8 nuclei, 4 of which become macronuclei, 2 possibly degen-
erate and 2 persist as new micronuclei.
(318)
PHENOMENA ACCOMPANYING FERTILIZATION 319
In Paramecium, therefore, the first two divisions of the miero-
nuclei in endomixis correspond to the reducing divisions in conjuga-
tion, the third division as absent in aurelia but present in caudatum.
Ivanic (192S) described a similar nuclear history during the processes
of encystment of Chilodon uncinatus. If reduction occurs with the
first two divisions the four products in endomixis are equivalent to
haploid nuclei so far as the chromosomes are concerned, and corre-
spond, therefore, to the first type of parthenogenesis above. But
they are likewise equivalent to the fertilization nucleus and develop
with the diploid number of chromosomes. This number unfor-
tunately, is too large in Paramecium to permit of accurate counting,
while in ciliates with a small number of chromosomes, endomixis
takes place during encystment where cytological details have not
been made out in any case. Fermor (1912) indeed described the
union of the two macronuclei and of the two micronuclei in Stylo-
nychia pustulata during encystment, but the account of the phe-
nomenon is incomplete and on its face implies the fusion of diploid
nuclei. This is so improbable from the chromosome standpoint
that the result cannot be accepted without confirmation. Later
work by Ilowaisky (192(i) failed entirely to confirm Fermor's inter-
pretation of the happenings during encystment of Stylonychia.
As indicated above (p. 303) the difficulty over haploid and diploid
chromosome number reaches an extreme in connection with the
third division of the ciliate nucleus. If reduction in number occurs
during the first two meiotic divisions then the pronuclei are formed
by a third division of an haploid number of chromosomes. If
this division is transverse as appears to be the case with Para-
mecium, this third division might also be a reducing division, and
the amphinucleus coming from the union of such nuclei would
be haploid. If the third division, however, is equational the pro-
nuclei would still have the haploid number and their fusion would
result in a diploid amphinucleus. The latter appears to be the
correct solution. Gregory (1923) for example describes 24 dumb-
bell-shaped chromosomes in the nuclear plate of the first meiotic
division of Oxytricha fallax. This number is reduced to 12 dumb-
bell-shaped chromosomes with this first division and each dumb-
bell divides longitudinally. The equational halves are separated at
the second division and 12 dumb-bells form the equatorial plate
of the third division (Fig. 1()2). The two halves of the dumb-bell
are finally separated with this third division, 12 single chromosomes
passing to each pole. The pronuclei thus have 12 single chromo-
somes and the amphinucleus formed by their union has 24. An
equivalent process occurs in Uroleptus halseyi where there are 48
chromosomes in the first division reduced to 24. These 24 are
reduced to 12 in the second division and these 12 are divided trans-
versely in the third division (Figs. 151 , 153) . The interpretation here
320
BIOLOGY OF THE PROTOZOA
2 3
19
-'&B&'.
mm
3fe
20
Fig. 162. — Oxytricha fallax; conjugation and meiosis. 2 to 9, formation and divi-
sion of the first meiotic nuclear spindle and separation of the twenty-four dumb-bells
into two groups of twelve dumb-bells each; 10 to 12, the second meiotic division; 13
to 15, the third division; 1G, one of the pronuclei; 17 to 20, the first zygotic division.
(After Gregory.)
PHENOMENA ACCOMPANYING FERTILIZATION 321
depends upon the origin of the 24 or 48 chromosomes of the first
division. In Oxytricha the meiotic process begins with a spireme
which fragments into granules, approximately 48 in number.
Association of these granules, 2 by 2, results in 24 dumb-bells. If
the number of chromosomes were 48 this would be synapsis in the
usual sense. The reduced number, however, is 12 and only 24
chromosomes make up the amphinucleus. If the granules are
homologous and in pairs, and if like unites with like to form the
dumb-bells, then division of the 24 chromosomes of the first nuclear
plate in meiosis would be equivalent to equational division. The
latter interpretation satisfies the conditions in other ciliates (e. g.,
Chilodon, Uroleptus, Dddinium, etc.), and the anomalous condition
in ciliates generally may be cleared up by the assumption of two
equational and one reducing division per chromosome at meiosis, as
against one equational and one reducing division in Metazoa. With
all forms, furthermore, reduction occurs during the first two meiotic
divisions. The difficulties, however, cannot be cleared up by a priori,
reasoning in attempts to homologize protozoan and metazoan
meiosis. In Uroleptus halseyi all three meiotic divisions during
conjugation are transverse divisions and these chromosomes find
their place in the theory of the gene only on the assumption that
each chromosome represents one gene and one gene only (Calkins,
1930).
A further difficulty arises with parthenogenesis. Woodruff and
Erdmann regard the first two divisions of the nucleus at endomixis
as equivalent to the first two divisions in conjugation. If this is
true the chromosomes are presumably reduced in number by either
the first or the second division and the reorganization nucleus woidd
be haploid from which the normal number of chromosomes in endo-
mictic animals would have to be reestablished by division of each
of the chromosomes present. In the case of Oxytricha faUax cited
above, barring fusion of nuclei during endomixis, no evidence for
which has been advanced in any filiate, the functional nucleus would
have 12 dumb-bell-shaped chromosomes. If the chromosomes
remain double a race of haploid individuals would be formed. At
the next endomictic period these would again be halved, and so on.
This, however, is unbelievable. If on the other hand the parts
of the dumb-bell should separate, then the normal diploid number
would be restored with two sets of homologous chromosomes and
the 48 chromosomes wrould be formed by the further division of
the 24, and this would be intelligible on the above assumption of
a single gene per chromosome.
Still further difficulties are added by the merotomy experiments
with conjugating Uroleptus mobilis. A pair in conjugation at the
period of pronuclei interchange is cut across the angle as shown in
Fig. 155. The angular apex thus cut off and one of the arms are
21
322 BIOLOGY OF THE PROTOZOA
fixed and stained to determine the stage of maturation. The other
arm is cultivated. Since other pronuclei usually degenerate, it is
evident that only one pronucleus is present in the piece cultivated,
and this one contains the haploid number of chromosomes. The
possibility remains open, however, that this pronucleus may unite
with a sister pronucleus formed by sister nuclei, and which do not
degenerate, but for this there is no evidence. In this case it would
be parthenogenesis of the third type above. When such cutting
experiments are successful the resultant organisms regenerate per-
fectly and undergo typical life histories and each individual has the
normal number of chromosomes.
The most probable interpretation of such merotomy experiments
appears to be that the diploid number of chromosomes is restored
by chromosome division.
The conclusion follows that so far as chromosomes are concerned,
endomixis and amphimixis after prolonged in-breeding as in Urolep-
tus are similar in results. The cellular processes of reorganization
are identical in both and Woodruff is quite right in stating that
amphimixis is unnecessary for continued life of a ciliate. In respect
to vitality, endomixis and amphimixis are equivalent and so long as
one or the other occurs continued vitality is possible. Furthermore
it may be argued that if an equivalent reorganization is accomplished
in any other way then neither endomixis nor amphimixis by conjuga-
tion is necessary. Evidence of this third possibility is furnished by
observations on Actinophrys .sol (Belaf, 1922) and by the animal
flagellates. If this is a correct interpretation then there is a possi-
bility of harmonizing the many conflicting results and views
advanced in relation to the much discussed problem of indefinitely
continued vitality.
B. Autogamy.— Autogamy or self-fertilization in Protozoa is a
logical sequence of endogamy. If a gamont of Actinophrys sol
should not divide to form gametes which later fuse (see above, p.
308), and if the gamont's nucleus should divide and the two products
should undergo meiosis, and the two pronuclei should then unite,
all in the same one cell, then the process would be called autogamy.
Or if pronuclei from the same individual ciliate should unite, it
would be autogamy. In short autogamy is the realization of
Type 3 of parthenogenesis above.
The phenomena which have been described and interpreted as
autogamy, particularly as they occur in parasitic forms, are rather
cautiously interpreted today and many careful observers, perhaps
too careful, are inclined to regard the earlier descriptions of autog-
amy as dealing with degeneration phenomena rather than with
normal vital activities. One illustration, that of Sappinia diploidea,
appears to be well established. The organism has two nuclei which
lie closely together (Fig. 163). Both nuclei divide at cell division
PHENOMENA ACCOMPANYING FERTILIZATION 323
(Fig. 163, B). Two such amebae become enclosed in a common cyst
but do not fuse. According to Hartmann and Nagler, the two
amebae are products of division of one ameba, the apposed nuclei
of each organism then fuse into one. This fusion is followed by two
reduction divisions of the fused nuclei, three of the products degen-
erating. Two amebae then fuse again and their nuclei come
to lie side by side. The question of autogamy obviously depends
upon the origin of the two amebae in the common cyst. If they
Fig. 163. — Sappinia diploidea. The ordinary vegetative individual has two nuclei
which divide independently at cell division. With encystment these nuclei form
spindles (B) and the cells divide (C, D); the two pairs of nuclei then unite, forming
two fusion nuclei after which the cell bodies reunite, thus forming the vegetative
binucleated cell. (After Hartmann and Nagler.)
do not come from the same parent cell, the phenomenon is one of
delayed exogamy.
Autogamy appears to be characteristic of the Neosporidia among
the Sporozoa and the processes are fairly uniform in Myxosporidia,
Microsporidia and Actinomyxida. Multinucleate cells are typical
of the nutritive or vegetative stage and in some cases the nuclei are
dimorphic. Spores are formed endogenously and during the con-
tinued vegetative activity of the organism. The process was well
324 BIOLOGY OF THE PROTOZOA
described by Schroder (1907) for Sphaeromyxa sabrazesi, a parasite
of the sea horse, where the multinucleate ameboid body of the
parasite contains two kinds of nuclei distinguishable by size and
structure. Within the protoplasmic body small areas become differ-
entiated from the surrounding cytoplasm. These areas, character-
istic of the Myxosporidia, each contain 2 nuclei, 1 of each kind
(Fig. 164, K-Q). With the development of the pansporoblast,
each nucleus divides in such order that 7 daughter nuclei finally
result from each, the 14 nuclei behaving as follows: 2 are destined
to degenerate as "reduction nuclei;" 4 become the centers of capsule
and shell formation; 4 become centers of polar capsule formation;
and 4 remain as germinal nuclei. The protoplasm of the pansporo-
blast divides into two halves (M), the sporoblasts, and each contains
6 of the nuclei, while the 2 degenerating nuclei remain outside.
The 6 nuclei are thus differentiated into somatic and germinal
nuclei 4 in each case going into somatic differentiations of the spores
(shells, polar capsules and threads) and 2, presumably 1 of each of
the original two kinds, remain as pronuclei (N, 0, P).
Many different observers have noted this binucleated stage of the
young spore, and the problem of fertilization in Myxosporidia
appears to be bound up with their further fate. Schroder believes
that they unite later and so complete the fertilization, a belief
which he was able to prove in a later publication (1910). Keys-
selitz (1908), working on Myxobolus pfeifferi, likewise believed in
the union of an analogous pair of nuclei during either the final
stage of development of the spore or in the young animal immediately
after leaving the spore case (Fig. 164, A-T). Davis (1916) observed
the union of such nuclei in Sphaerophora dimorpha but was some-
what skeptical of his own observations, but Erdmann (1911 and
1917) confirmed Schroder in actually observing the fusion. Awer-
inzew (1909) on the other hand, working with Cer atomy xa drepano-
psettae, believed that fusion or fertilization does not occur in the
spore stage but after the initial development of the young animal
(see also Kudo, 1924). When the latter has reached the stage with
4 nuclei, 2 of the nuclei become trophic while the other 2 become
germinal giving rise by division to "microgametes" and macro-
gametes which fuse after "reduction." Mavor (1916) working with
an allied species {Cer atomy xa acadiensis) found uninucleate young
forms which, upon the first division of the nucleus, give rise to
dimorphic nuclei as described by Awerinzew. The fusion of "gam-
etes" which AwerinzewT described was confirmed in part by Keys-
selitz (1908) in connection with Myxobolus pfeifferi. Here the
pansporoblasts which Keysselitz names the "propagation" cells,
arise in the protoplasm of the adult organisms in the same manner
as in other Myxosporidia, but the nuclei, and writh them the cell
body of the germinal area, divide (Fig. 164, A, B, C). The prop-
PHENOMENA ACCOMPANYING FERTILIZATION 325
B
fe# .-<••■ \ -a -V,. _^e^s3!
Fig. 164. — Myxobolus pfeifferi (A to J) and Sphaeromyxa sabrazesi (K to Q) . See text,
(After Keysselitz and Schroder.)
326 BIOLOGY OF THE PROTOZOA
agative cells later unite 2 by 2 and are at first separated by a thin
cell wall, which later disappears. Within this united mass the
nuclei divide until there are 14 as in Sphaeromyxa. Such cases of
fusion are interpreted by Erdmann (1917) as plastogamous in
character.
A more complicated history is furnished by Naville (1931) for
Chhromyxum leydigi. Here the initial organism has a large number
of nuclei which divide by mitosis, each nucleus with 4 chromosomes.
These are succeeded by heteropolar mitoses with 2 chromosomes
at each pole. Two types of nuclei are thus formed, large and small,
each with 2 nuclei. Upon internal bud formation a large nucleus
unites with a small one. After fusion the fusion nucleus divides
several times, each time with 4 chromosomes. Later each undergoes
a reducing division and nuclei with 2 chromosomes again result.
Each of these haploids divides to form a group of 8 nuclei in the
sporogenous plasm and spores are formed as in other species, each
spore having 2 haploid nuclei which unite later.
These observations indicate that fertilization in Myxosporidia
belong in the group of autogamous phenomena. In the closely
related Microsporidia there is considerable difference of opinion in
connection with the time and place of fertilization if it occurs at
all. Stempell (1902, 1904, 1909) and Fantham and Porter (1912)
give evidence to indicate that union of nuclei occurs as in Myxo-
sporidia and after the spore leaves its capsule. Mercier (1909),
Swarczewsky (1914) and others believe that the formation of hetero-
gametes occurs prior to sporulation as described by Awerinzew
for Ceratomyxa; Debaisieux (1913, 1915, 1916) also believes in a
process of autogamy prior to sporulation in Glugea danilewskyi, G.
mulleri, G. anomala, and in microsporidian parasites of Simulium
larvae.
Similarly a process of autogamy occurs prior to sporulation in
Actinomyxida. Here, according to the observations of Caullery
and Mesnil (1905) on Sphaeractinomyxon, the youngest stages are
found as intestinal parasites of the tubificid worm Clitellio, and are
either uninucleated or binucleated. The observers were inclined
to believe that the uninucleated stage comes first and that it repre-
sents, possibly, a sporozoite. Whatever may be the origin of the
binucleated form, the 2 nuclei divide and 2 of the 4 resulting nuclei
become somatic nuclei connected wTith the formation of the cyst
wall. The remaining nuclei and cell body now divide until there
are 16 independent cells. These unite 2 by 2, fertilization thus
occurring endogamously, and 8 spores are finally formed.
In many of these cases so-called reduction nuclei have been de-
scribed as indicating processes comparable with chromosome reduc-
tion in meiosis. Up to the present time, however, while well-marked
chromosomes of definite number have been described by George-
PHENOMENA ACCOMPANYING FERTILIZATION 327
witsch (1915), by Davis (1916) and by Naville (1931), there is little
evidence of reduction in number either before or after nuclear
fusion, with the exception of Naville's account, and this is difficult
to harmonize with meiotic phenomena in either protozoa or metazoa.
Erdmann (1917) has shown that so-called reduction nuclei inside
the spore are masses of chromatin or perhaps glycogen, which serve
a purpose in the formation of the spore membrane. The extremely
minute size of the nuclei and the technical difficulties make the
general problem very difficult to solve in Cnidosporidia.
From the foregoing review it is apparent that the changes of a
cumulative character are taking place during the vegetative activi-
ties in all types of organization. Such changes are manifested by
structural or functional peculiarities at different stages, the most
marked of which are at periods of maturity and old age. Some of
these are peculiar to certain types only, e. g., the old age structural
differentiations of Mycetozoa and Sporozoa. Others, particularly
those occurring at maturity, are more universal but differ in degree
in different cases, the least evident being those of hologametes and
conjugating Infusoria, and the most evident are those in which
complete anisogamy occurs. One widely spread effect of such dif-
ferentiation is the phenomenon of meiosis or reduction in the number
of chromosomes. This also occurs at various periods, furnishing
a basis for the categories of conjugant meiosis, gametic meiosis and
zygotic meiosis.
Whatever may be the interpretation of the phenomenon, the fact
is obvious that all products of fertilization are labile, active organ-
isms quite different in character from the conjugants, hologametes,
or gametes which participated in their production. Apparently
the same protoplasm, however, is continuous from the old to the
young, and during transition certain processes, here described as
disorganization and reorganization, have taken place. These proc-
esses, as I believe, are responsible for the renewal of vitality and
for the inaguration of a new life cycle in a new organism, evidence
for which is given in the following chapter.
CHAPTER IX.
EFFECTS OF REORGANIZATION AND THE ORIGIN OF
VARIATIONS IN THE PROTOZOA.
In the preceding chapters we have developed the ideas that life
is organization plus its activity; that vitality is the sum total of
actions, reactions and interactions between and amongst the aggre-
gate of substances which make up protoplasm; that minute differ-
ences in the aggregate of substances constitute differences in organ-
ization; that no two organizations are identical; that with continued
metabolism the protoplasm of a given individual undergoes changes
in organization which are gradual but progressive; that such changes
may be manifested by structural differentiations and by physio-
logical activities which are characteristic of certain periods in the
life cycle; and that progressive differentiation leads to a condition
or protoplasmic stability such that metabolic activities weaken or
cease altogether.
We have no desire to belittle or ignore the fact that observations
are not all in accord with the conclusions outlined above or to under-
estimate the significance of data which apparently do not agree
with them. We are attempting however, to formulate a conception
of organization and vitality which will embrace as large a field of
observational results as possible and to give a rational interpretation
of them. An important part of such an interpretation is concerned
with the effects of fertilization and parthenogenesis which are
briefly considered in the present chapter.
I. EFFECTS OF REORGANIZATION ON VITALITY.
If our fundamental thesis that continued metabolism leads to
functional weakening and ultimate cessation of vitality is correct
it follows that for continued life some reconstructive or reorganizing
operation is necessary. The phenomena attending cell division,
together with experimental evidence (see Chapter VI), indicate that
such reorganization may occur with each division of the cell, and
that vitality of the protoplasm immediately after division is nor-
mally unhampered by accumulated products of activity in the form
of metaplastids or of substances which are becoming inert. The
deep-seated changes in organization which accompany fertilization
and parthenogenesis have a similar but even more profound effect,
for the protoplasm is entirely made over and new cell organs are
EFFECTS OF REORGANIZATION 329
present for activity in a renewed cytoplasmic body, the aggregate
resulting in a new organization and new vitality.
"Conjugation is a physiological necessity for maintenance of the
race" (Hartmann, 1921; p. 114). This indeed is one of the oldest
views as to the effect of conjugation of the ciliates. It is unfortunate
perhaps that the phenomena involved became labeled with fanciful
terms signifying renewal of youth (Verjiingung of Biitschli, 1876;
Rejuvenescence of Maupas, 1889), terms which many hard-headed
biologists find it difficult to accept. It might or might not have
made some difference if the phenomena had been interpreted as
a series of reactions whereby protoplasmic impedimenta are removed
leaving a renovated organism and a possibility of unhampered
vitality. It is in this sense that the term rejuvenescence is used
in these pages.
Another interpretation of the phenomena, however, was early
given in connection with theoretical biology. The union of two
individuals in conjugation, or in fertilization generally, involves
the fusion of two organizations represented either by nuclei alone
as in conjugation, or by nuclei and cell bodies as in merogamy.
The term amphimixis (Weismann) was applied to this phenomenon
and its significance was interpreted as a means of inaugurating
variations which would turn out to be useful or not in the grilling
process of natural selection.
Of the two interpretations the former appears to be the more
comprehensive and fundamental since it deals with vitality and
applies not only to phenomena of fertilization but to effects of
parthenogenesis as well, and may be still further extended to
include the effects of periodic reproduction by cell division. The
general truth of the latter interpretation is undeniable and has
been repeatedly confirmed in experimental zoology, but we avoid
the stigma of teleology by assuming that amphimixis arose in con-
nection with the satisfying of some fundamental protoplasmic need.
In other words and on this supposition, gametes were developed
not as a means of ensuring amphimixis but as a result of vital
activities and changes in organization which rendered them unable
to continue metabolic activities without fusion.
In would seem that the fundamental truth of this generalization
requires no argument insofar as it concerns merogamy. The fer-
tilized egg cell is a new organism with a new potential of vitality
having the possibility of development with differentiations leading
to the adult organism. It is the beginning of a new life cycle for
which the stimulus to development is furnished by the sperm cell.
The facts of parthenogenesis, however, show that this potential
is in the substance of the egg itself and that it, without participation
of the sperm cell, may likewise be the beginning of a life cycle.
The egg cell furthermore does not have the same organization as
330 BIOLOGY OF THE PROTOZOA
did the primordial germ cell, or endothelial cell, from which it
came. Reorganization of the protoplasm of that endothelial cell
has taken place in its metamorphosis to an egg cell and is brought
about by the often-described process of ovogenesis and matura-
tion. In this phenomenon of endothelial cell metamorphosis we find
the homologue in Metazoa of the reorganization processes of the
Protozoa.
The nearest approach to the metazoon egg and spermatozoon
condition amongst animal Protozoa is found in the group Coccidio-
morpha amongst Sporozoa. Here, no less than in Metazoa, the
fertilized egg is the beginning of a new life cycle or, by metagamic
divisions, gives rise to sporozoites, each of which is the beginning
of an independent life cycle with its characteristic phases and
differentiations. Few biologists would question the application to
Sporozoa of the term life cycle, and yet no single individual sporo-
zoon has ever been followed through the sequence of changes from
fertilization to fertilization. This cyclical history of Sporozoa is
forgotten by those who speak of a life cycle in Protozoa as a myth.
They have in mind only the ciliated Infusoria and the phenomena of
conjugation; indeed the controversy over the effects of fertilization
in Protozoa has been limited almost exclusively to the Infusoria.
Actual experiments to test the effects of conjugation on vitality
of the Infusoria have been few in number, the majority of investi-
gators stopping with experiments to determine the need of conjuga-
tion, i. e., whether or not vitality as measured by the division-
rate actually undergoes a diminution to a point where death ensues
if fertilization fails (see Chapter VII). Jennings (1921) has pointed
out that Maupas himself never claimed that the power to reproduce
is restored by conjugation, although his experiments did lead him to
the conclusion that ciliates undergo senile degeneration and natural
death. This inconsistency on Maupas' part requires some explana-
tion here for it is usually overlooked. His general conclusion is
carried in the statement: "In regard to Infusoria my culture
experiments have demonstrated that these Protozoa do not escape
the general law of senescence" (1888, p. 273). From this conclusion
we would naturally infer that senescence means a weakening of
the general physiological processes including the power to repro-
duce by division. But Maupas apparently had no such conception
of senescence for he adds: "The power of multiplication follows
no such diminishing and parallel course. It is maintained almost
intact even a long time after the other functions, and the entire
organism, are shown to be greatly reduced by senile degeneration"
(1888, p. 273).
The inconsistencies in Maupas' conclusions have been pointed
out in another place (Calkins, 1923); it is sufficient here to state
that exact data in the form of daily records of divisions were kept
EFFECTS OF REORGANIZATION
331
by Maupas for. only three series of individuals, and data for only
one series {Stylonychia pustulata) were published in full. The
graph shown in Fig. 165 was constructed from these published
data and it certainly appears to bear out his conclusion concerning
Stylonychia pustulata
36
30
25
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-
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20
-
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v
'i
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.
/
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23456789 10 11 12 li
Stylonychia mytilus
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Fig. 165. — Vitality graphs of Stylonychia pustulata and S. mytilus from records by
Maupas.
332 BIOLOGY OF THE PROTOZOA
multiplication. For another series, however {Stylonychia mytilus),
data were given for a different purpose and from these the graph
shown in Fig. 165 (below) was constructed. From this graph it
is apparent that his conclusions regarding multiplication and
vitality do not agree with his records. Maupas' experimental
evidence in connection with vitality after conjugation thus counts
for very little either for or against rejuvenescence.
A much more carefully planned and executed series of experiments
to test the effect of conjugation on the division-rate were carried
out on Paramecium by Jennings (1913) and later by his students
(Stocking, 1915; Raffel, 1930, et al). He found: (1) That ex-
conjugants in only a few exceptional cases have a higher division-
rate than do non-conjugants of the same strain; (2) that conjugation
causes a decrease in division-rate of the great majority of ex-con-
jugants; (3) that conjugation causes a high mortality among
ex-conjugants; (4) that it causes a marked increase of weak, sickly,
and abnormal individuals. From these results it would appear
that conjugation is a highly unprofitable habit of the Infusoria
which, if freely indulged in by Paramecium, would soon lead to
the extermination of the race. The annual crop of Paramecium,
however, remains about the same and we are forced to interpret
Jennings' results as due more probably to the conditions under
which the experiments were carried on than to the effects of con-
jugation (see infra p. 350, and Calkins, 1923).
The question of increased vitality after conjugation receives a
definitely affirmative answer with Woodruff and Spencer's experi-
ments with Spathidium spathula (1924). Conjugation tests fur-
nished material from pure lines for conjugation and ex-conjugants
were isolated and followed out in isolation cultures. The daily
division-rates for parent and offspring series were compared with
great exactness. Ninety-four different ex-conjugant series were
thus available for comparison with their respective parental series.
Of these the parent series died in 15 cases during the first fifteen
days of life of the ex-conjugants but the latter "all actually divided
more rapidly than their respective parents" (p. 187) during the
periods in which the parents were alive. In 67 cases both parents
and offspring continued to live and divide for more than fifteen
days, the offspring in all cases dividing more frequently than the
parents. Eighty-two cases therefore out of 94 ex-conjugant series
showed a definitely marked increase in vitality as measured by
the division-rate, as a result of conjugation: "it is evident that
conjugation directly induces an immediate acceleration of the
reproductive activity" (1924, p. 188). The same conclusion is
reached for the full life history of ex-conjugants in comparison
with the remaining life of the parental series after conjugations
have occurred. "Since conjugation is the sole variable involved
EFFECTS OF REORGANIZATION 333
in ex-conjugant and parental cultures it is evident that conjugation
directly induces not only an immediate acceleration of reproduction
but also an acceleration which persists at least as long as the life
of the parental cultures. These results are in opposition to all
results which indicate that conjugation is devoid of a profound
physiological stimulation of the metabolic activities of the cell
expressed in reproduction" {Joe. tit, p. 189). Thus in Spathidium
spathula not only are the division-rates of ex-conjugants higher
than those of the parental strains but the ex-conjugants actually
outlive the parent protoplasm, hence the authors further conclude:
''Conjugation typically has a high survival value in the life of the
organism" (p. 196).
It is significant that Woodruff and Spencer studiously avoid use
of the term "rejuvenescence" in their work. They speak of an
increased division-rate of ex-conjugants and of the "survival value"
of conjugation but not of renewal of vitality. As these are the two
essential factors which characterize the phenomena of rejuvenes-
cence we are justified in including Woodruff among the proponents
of rejuvenescence. The two factors were discussed in an earlier
analysis of rejuvenescence (Calkins, 1920) in which it was pointed
out that the division-rate expresses the "intensity" of vitality and
the length of life in division days the "endurance;" the latter is
evidently the same as Woodruff and Spencer's "survival value."
The experimental work on Spathidium spathula was a confirma-
tion of the work on Uroleptus mobilis which was begun in 1917.
A single ex-conjugant was the progenitor of all the material that
has formed the subject of the investigation. The method employed
throughout was the usual isolation culture method (see p. 248).
In the following account of the experiments the term "series"
always means an ex-conjugant with the progeny formed from it
by division; the progeny being represented by five pure lines which
are continued by isolation cultures until vitality is exhausted and
death ensues. Conjugation tests at regular intervals provide
material for filial series. Up to January 1, 1925, 125 different
series had been studied; 116 of them had followed the usual history
and had died out and 9 series were under culture. The last of
these 9 series represents the F 29 generation of successive conjuga-
tions since the original ex-conjugant was isolated. Abundant statis-
tical data were accumulated during these seven years and these
furnish valuable evidence in favor of the theory of rejuvenescence.
The analysis of this evidence has been the subject of many
papers by numerous writers (Calkins, Woodruff, Jennings, Robert-
son, et al.) from which the general conclusions may be drawn that
renewal of vitality follows conjugation, and that the extent of
renewed vitality as well as the continued vitality depend upon the
age of the parental protoplasm at the time of conjugation. The
:;:;i
BIOLOGY OF THE PROTOZOA
following synoptic table shows not only these facts but also that
for Uroleptus mobilis vitality may be maintained at an optimum
by conjugations during youthful periods of consecutive series (see
also Fig. 166). Experimental data show that parthenogenesis
(endomixis) also brings about a similar restoration to an optimum
vitality.
1. Renewal of Vitality as a Result of Conjugation.— In Chapter VII
it wTas shown that the life cycle of an ex-conjugant of Uroleptus
mobilis begins with high vitality; this gradually weakens during
a period of from nine to twelve months and ends with death of the
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Fig. 166. — Condensed vitality graphs showing the descent of Uroleptus mobilis from
November, 1917 to 1926. S = series; G = generation age of parents.
last individual representing that protoplasm if reorganization by
fertilization or parthenogenesis has been prevented. A full pedigree
of a late series (12S) is illustrated by the graphs shown in Fig.
166. Conjugation between the progeny of an ex-conjugant occurs
whenever a conjugation test is made after the series is mature
(see p. 271). An ex-conjugant from such a mating has a higher
vitality as expressed by the division-rate than the individuals
of the parent series which had not conjugated. The test for this
is shown by a comparison of the division-rate of the parent proto-
plasm which has not conjugated with the division-rate of the
protoplasm that had conjugated, both protoplasms running simul-
EFFECTS OF REORGANIZATION 335
taneonsly and under identical conditions in isolation cultures.
If such conjugations occur early in the life history of the parent
series both parent and offspring run simultaneously for some months;
if late in the life history of the parent the offspring series outlives
the parent, in some cases for many months. An arbitrary test
of the difference in vitality of parent and offspring is furnished by
a comparison of the division-rate of the ex-conjugant for its first
sixty days of life with the division-rate of the parent during the
same calendar sixty days. The difference between the two rates
indicates the difference in intensity of vitality between parent and
offspring. In the accompanying synoptic table data are listed for
all series from 1 to 120, including series number, relative vitality
(column 2), number of generations attained (column 3), number of
division days (column 4), parent series (column 5), age of parent
series at time of conjugation (column 6); number of divisions of
parent subsequent to conjugation (column 7); intensity of vitality
of parent and offspring and differences between these intensities
(columns 8, 9 and 10). The division-rates represent the numbers of
divisions which any individual of a series would undergo in ten days.
The last column of the table on pages 336, 337 and 338 gives an
emphatic affirmative to the question: Does conjugation effect a
renewal of vitality?
2. Intensity of Vitality and Extent of Renewal. — An important
matter which is usually overlooked in experiments of this nature
is the intensity of vitality of the parent protoplasm at the time of
offspring-forming conjugations. The metabolic activity, growth
and reproduction, of an organism are not unlimited, each species
having its limit of vitality. As more water cannot be forced into a
jug that is already filled, so it is impossible, under constant tempera-
ture conditions, to increase vitality in protoplasm that is already
functioning to its full capacity. In Uroleptus, however, conjugations
do not occur when the protoplasm is at its maximum of vitality
and the difference in intensity of vitality between parent and
offspring depends upon the age of the former at the time of con-
jugation. With offspring from young parents the parental vitality
is relatively high and the difference in intensity for the first sixty
days of life of the offspring between parent and offspring is fre-
quently so small as to fall within the limits of fluctuating variations
or of experimental error. This was the case for example in Series
2, 4, 64, 71, 78, 79, 85, 96, 97, 102, 104, and 111 where the difference
in intensity is less than two divisions in ten days. Reference to col-
umn 6 of the table shows that all of these series came from young
parents. Such slight differences afford little positive evidence of
rejuvenescence and failure to take into account the age of parents
explains a number of discordant results in the literature of this
subject. With advancing age of the parent protoplasm the differ-
336
BIOLOGY OF THE PROTOZOA
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EFFECTS OF REORGANIZATION 339
ence in intensity between parent and offspring becomes more pro-
nounced. The young ex-con jugant returns to the full capacity
of the species while the parent protoplasm shows the vitality
characteristic of its age. The difference between them is now
beyond the range of fluctuating variations or of experimental error
and furnishes unmistakable evidence of rejuvenescence. Series 7,
11, 24, 27, 28, 29, 30, 31, 36, 57, and 63, which exceed their parents
in rate of division by from 8 to 10 divisions per ten days, illustrate
this point, and reference to column 6 shows that these series came
from parents well along in age. With extremely old parents finally
the difference in intensity between parents and offspring reaches its
maximum and if parents have less than 35 divisions subsequent to
their age at the time of conjugation (column 7), the offspring have
an intensity of from 11 to 16 divisions per ten days more than the
parent protoplasm (Series 8, 15, 39, 63).
3. Relative Vitality of Different Series and Effect of Parents' Age
on Vitality of Offspring.— Do ex-conjugants from old parents have
as much vitality as do ex-conjugants from young parents? That is,
is the organization of offspring affected by the depleted vitality
of the parent? Except in extreme cases these questions cannot
be answered by comparison of the intensities of vitality of the two
series. For example a series living two hundred days and dividing
300 times would have an average intensity of vitality indicated
by 15 divisions in ten days; another series living only fifty days
and dividing only 75 times likewise has an intensity of 15 divisions
per ten days. It would be far from exact to say that the two series
have the same vitality; here the time factor or endurance is not
taken into account. Hence to compare vitalities of two different
series both intensity and endurance must be represented. The
method adopted (Calkins, 1920) rests on the principle of reference
to a common, ideal life cycle represented by a numerical constant.
The number of generations by division and the days of life of a
series have a definite relation expressed by a percentage of such
an ideal constant. Such percentages indicate the relative vitality
of the different series and are listed in column 2 of the table.
With these percentages expressing relative vitality it is possible
to compare different series in respect to the effect of age of parents
on the vitality of offspring. There is unmistakable evidence con-
tained in the table that offspring from old parents in the great
majority of cases have a much lower relative vitality than do the
parental series, or series from young parents. This is best illustrated
by instances where two or more offspring series are taken off at
different periods in the life history of the same parent. Such a
sequence is illustrated by Series 2,3,6 and 8, all of which came from
Series 1, and with a difference of 28.7 per cent in relative vitality
between the first (Series 2) and the last (Series 8) offspring. Another
340 BIOLOGY OF THE PROTOZOA
striking illustration is shown by Series 7 and its two offspring, Series
9 and 14; Series 9 came from Series 7 when the latter had lived more
than half of its life and its relative vitality was about 15 per cent
lower than its parent. Series 14 came from the same parent when
the latter had only 6 more divisions in its life history and the effect
of its old age is shown by the relative vitality of 5.4 per cent of
its offspring, Series 14. It is quite evident that the protoplasmic
organization of the parent is not the same at the beginning and at
the end of its life and that the effect of the change is indicated by
the organization and activities of its offspring. Some interesting
and perhaps significant surprises have turned up, however, from
such old age conjugations and it is possible that mutations may
arise at such times. Thus Series 19 came from parents that were
225 generations old and with only 32 more generations to live. The
expectation would be a low relative vitality for this old age offspring,
but on the contrary it had a relative vitality of 110.4 per cent, the
highest on record.
In our experience it has been impossible to restore an extremely
weak series to a vigorous condition by conjugation; all such attempts
result in still weaker series. It is possible, however, to restore com-
paratively weak series to full strength, a result which Woodruff and
Spencer also obtained with Spat Iridium spathula. This is well
shown by Series 60 and 62, in which the relative vitality is raised
from 70.3 to 96.4, or by Series (56 and 70, in which it is raised from
69.1 to 95.0, etc.
4. Rejuvenescence After Parthenogenesis (Endomixis).— Woodruff's
long culture of Paramecium aurslia furnishes an excellent illustration
of continued vitality through reorganization by parthenogenesis.
The fluctuations or waves in his graph (Woodruff, 1921) indicate
a series of depressions followed by increased vitality; reorganization
occurs during the periods of depression. Different culture media
have no effect in changing the frequency of endomixis in time but
may cause an increase or decrease in the number of interendomictic
generations by divisions (Woodruff, 1917). According to Jollos
(1916) external factors may call out parthenogenesis in Paramecium
at any stage in the life history, and according to Young (1917) sud-
den sharp changes of medium may bring on endomixis prematurely,
but the sequence always lapses to the regular routine and usually
by the next period. If endomixis does not occur the race invariably
dies. " This indicates strongly, if it does not prove that a periodic
occurrence of the definitive endomictic phenomena is a sine c/ua
rum for the continued life of the race" (Woodruff, 1917, p. 462).
With Uroleptus mobilis the evidence for rejuvenescence through
parthenogenesis is of the same kind as that from conjugations.
Reorganization without fertilization takes place during encystment
and the cysts are formed early in the life history of a series (see
EFFECTS OF REORGANIZATION 341
p. 268). On emerging from its cyst the organism is treated as
though it were an ex-eonjugant and the first five individuals are
maintained as five pure lines of the series. Such series are indicated
in the table, p. 336, by an asterisk. The vitality of the first sixty
days of a cyst series is compared with that of the parent series for
the sixty days following encystment and the results are practically
the same as with ex-conjugants. In some cases the cysts are kept
dried for a period of weeks or months but this has no effect upon
the vitality of the organism when it emerges. In all cases the
evidence of rejuvenescence is the same as for ex-conjugants from
young series.
The general results of these experiments with Uroleptus mobilis
leave little ground for reasonable doubt of the rejuvenating effect
of conjugation. The view of Woodruff and Spencer (1924) that
loss of vitality and death here are due to conditions of the milieu
seems rather far-fetched when we consider that series after series
with the similar sequence of renewed, waning, and exhausted
vitality pass by in apparently endless succession, and all in the
same milieu so far as it is possible to make it the same, from the
beginning of the experiments to the end. It is quite a different
question whether or not conditions of the medium can be so altered
as to bring about the same results as conjugation. The explanation
must be looked for in the protoplasmic happenings at the period of
conjugation or of endomixis (see Chapter VIII) . In both cases these
result in a rearrangement of the chromatin and cytoplasm which
according to Erdmann (1921) gives rise to new sets of autocatalyzers
and new cytoplasmic matrices for their activation.
The general and philosophical aspects of the phenomena described
above, particularly those pertaining to the so-called physical
immortality of the ciliates, are important or not according to the
individual point of view. To my mind the phenomena in these
forms lead to the conclusion that Protozoa and Metazoa are funda-
mentally alike in respect to protoplasmic continuity and proto-
plasmic death, the difference between them is bound up with our
definitions of the "individual." So far as immortality of Protozoa
is concerned, Hertwig's (1914) conclusions appear to sum up the
situation: "However these investigations may turn out, one may
say this now, that the doctrine of the immortality of the Protozoa
in the form established by Weismann at a time when we did not
know anything of the fertilization processes of the Protozoa, cannot
be retained. The beautiful investigations of Erdmann and Woodruff
do not detract from my conception based on former work and
repeated here, but furnish a new affirmation that death in many-
celled animals is the result of peculiarities which are present in
everything that is alive, and that the life process contains within
itself the germ of death and that the harm connected with it (death)
342
BIOLOGY OF THE PROTOZOA
may be postponed in Protozoa by reorganization processes. In
many-celled animals, however, these cannot be applied, the more
the life of the single cell depends on the total organization/'
(Hertwig, 1914, p. 580.)
II. HEREDITY AND VARIATIONS IN PROTOZOA.
Owing to the relative simplicity of the organisms with which we
are dealing there are few structural characteristics that can be used
in a study of variations. Variations in size are often noted but
3)0
Fig. 167. — Size variations in eight families of Paramecium. (After Jennings.)
these in themselves do not furnish reliable data, a Bileptiis gigas for
example may be 250 microns in length or only 25 microns (Fig. 6,
p. 27) according to the food it gets. Similar differences due to
temporary conditions are evident in all organisms that are studied
for a sufficient length of time. In a mixed population, however,
size differences may indicate fixed variations as was clearly shown
by Jennings (1909) for Paramecium (Fig. 167).
EFFECTS OF REORGANIZATION 343
It is difficult to distinguish between fluctuating or cyclical
variations and germinal variations and the distinction cannot be
realized where the germinal history is unknown. The difficulty
is increased by the fact that comparatively few life histories of
Protozoa are known. Many variations that have been recorded
may be cyclical in nature and repeated in all life histories of indi-
viduals of the species. These correspond to differentiations in
ontogeny of Metazoa and have been more fully discussed in Chapter
VII. The fact that such variations breed true by cell division is to
be expected for the organism could not do otherwise. The test
comes with amphimixis or parthenogenesis.
A. Uniparental Inheritance.— It is quite possible that changes in
the genotype or organization of Protozoa may occur and remain
permanently, and such changes may be due to environmental or
to internal causes. Changes due to environmental causes, to be
permanent, would have to so affect the germinal make-up that
reversions would not occur. Thus individuals formed by reversions
from the double Uroleptus described in Chapter VII (p. 245) never
regenerated the double organism but lived as single individuals of
Uroleptus mobilis (Series 91 of table, p. 338). Here the organi-
zation was unchanged although the new double type of organism
lived for four hundred and five days and divided 367 times.
Variations due to environmental changes should be retained as
long as such changes are maintained. Thus Zuelzer obtained a
very different type of organism by transferring Amoeba verrucosa
from fresh to salt water. The variation lasted as long as the organ-
isms were kept in salt water but reverted to the original form on
transference to fresh water again. Jennings (1921) cites a number
of cases of bacteria in which the organization appeared to be per-
manently changed by a temporary change of drastic character in
the medium. Similar results have been obtained with Protozoa
where adaptations or responses of the organism to solutions of
gradually increasing concentrations or to slowly increasing tem-
perature changes have apparently become permanent, or at least
endure for many generations by division. Among the first, and the
more extensive of such experiments, were those of Dallinger and
Drysdale (1873) in connection with the life histories of different
flagellates. Dallinger (1907) in particular, working with remark-
able patience and perseverance for seven years was able to accustom
three species of flagellates which are described as Tetramitus ros-
tratus, Monas dallingeri, and Dallingeria drysdali to temperatures
which are fatal to these organisms under normal conditions of 60° F.
At the beginning of the experiment all individuals were killed by
a sudden change to 78° F., but by accustoming them to slowly
increasing temperatures acting for long periods they became
adapted to this condition. Such adapted individuals were then
344 BIOLOGY OF TEE PROTOZOA
subjected to further increases in temperature, the change from
one degree of heat to another often requiring months of patient
waiting. Finally he obtained individuals which continued to live
vigorously in a temperature of 158° F. Here was a change in
organization or an adaptation to changed conditions which persisted
as long as the conditions were maintained and until an accident
brought the experiment to an end.
Similar but less extensive experiments have been carried on with
other Protozoa. Within the last few years Middleton (1918) and
Jollos (1918, 1923) have tested the effect of increased temperatures
on ciliates. Middleton (1918) separated progeny of an individual
of Stylonychia pustulaia into two groups, one of which was kept for
some thirty days at a relatively high temperature (about 30° C.)
the other at a low temperature (10° C). The set at 30° C. divided
more rapidly than those at 10° C. They were then transferred to
a common intermediate temperature in which the previously
warmed individuals continued to divide more actively than the
cooled set.
Experiments of this type and others to be described below show
that changes in organization can undoubtedly be produced in
Protozoa. If such changes are permanent they may be interpreted
as mutations; if not permanent they have little more value than
the fluctuating variations which accompany changes of metabolism.
The great majority of changes which have been described are cer-
tainly not mutations but illustrate the flexibility of protozoan
organizations and broaden the limits within which fluctuating varia-
tions are known to occur. Such variations ultimately revert to type
and although they may last for many generations by division, they
have no permanent effect upon the organization. Jollos (1913)
terms them "enduring modifications" (I)auermodificationen).
Other frequently-cited illustrations of this type of variations have
to do with the effects of minute doses of poison on the organi-
zation. Some races of Trypanosoma for example, may become
adapted and immune to weak doses of arsenic— the so-called
poison-fast, arsenic-fast, atoxyl-fast races first described by Ehrlich.
Bignami (1910) thus interprets malaria relapses as due to quinine-
fast organisms. Such modified types retain their immunity for
long periods and through many successive generations of trans-
plants but they apparently belong to this type of enduring modifica-
tions. Gonder (1912) has shown that poison-fast races of Trypano-
soma lewisi lose their acquired immunity by passing through the
rat flea. Also races of Trypanosoma without parabasal bodies
(Blepharoplastlose) first obtained by Werbitzski (1910) by injecting
pyronin into the host's blood, would live for many generations of
transplants without this kinetic element, but the parabasal body
ultimately reappears. Here too in all probability should be included
EFFECTS OF REORGANIZATION 345
the so-called mutations in Radiolaria described by Haecker (1909)
the observations in this case being somewhat casual and not followed
up experimentally so that the matter of permanency is in doubt.
The extensive experiments on Paramecium made by Jollos
(1913, 1923) offer many illustrations of change in organization and
subsequent return to normal, sometimes after many vegetative
divisions, sometimes after endomixis, and again only after conjuga-
tion. The effects of arsenic acid calcium compounds, and extreme
temperatures, were lasting through one or more periods of endomixis
and conjugation, but such effects were ultimately lost. A significant
fact, however, is the difference in effect produced by treatment with
arsenic or heat at critical periods. If treated during vegetative
life the results were as described above, i. r., temporary changes
or enduring modifications. If treated during the later phases of
conjugation, that is, during the period of reorganization of the
ex-conjugant (Jollos calls it the "sensitive" period) then the effects
were found to be permanent in a very small percentage of cases.
Such changes are evidence of a change in the organization itself,
or in the genotype, and were found to be lasting for generations
by conjugation. Jollos is apparently right in speaking of such cases
as mutations.
In this connection also we should include the numerous attempts
to perpetuate abnormalities in Protozoa. Popoff (1909) by centri-
fuging Stentor when about to divide, produced individuals in which
the original beaded nucleus was unequally distributed, one indi-
vidual receiving 16 beads, the other only 3. Both individuals
reorganized perfectly after fission, but the one with 3 beads was
about one-quarter the size of the individual with 10 beads. The
two types were persistent and divided normally for a short time,
the progeny of the smaller form regenerating the normal number of
beads. The cultures were then lost so that the further history
is unknown. In another case a dividing Stentor was suddenly
cooled so that the division processes ceased. The individual was
then placed under conditions of normal temperature, conditions
where it reorganized into a single but very large individual. From
it a race of giant Stentors was obtained by reproduction, the indi-
viduals breeding true for a period of about six wTeeks. An analogous
experiment by Chatton (1921) was made on the ciliate Glaucoma
scintillans, by treating individuals in the early phase of division
with a dilute solution of sodium bromide (16 to 1000) for ten minutes.
The division processes were hastened by the change in osmosis
and when nearly divided the individuals were restored to their
normal medium where the division planes were lost and the two
nearly divided halves were again resolved into one. In this maimer
Chatton obtained individuals with two mouths, several micronuclei
and only one macronucleus each. On reproduction some of the
346 BIOLOGY OF THE PROTOZOA
offspring were similarly distortions, while some, as with the Uroleptus
mobilis double individual, reverted to the single type. The double
individuals were maintained in culture for a period of five months
(sic) when they were abandoned, Chatton believing that they might
be continued indefinitely by division. Analogous double individuals
were obtained by Dawson (1920) by the fusion back to back of
amicro nucleate individuals of Oxytricha hymenostoma. The double
individuals reproduced double individuals for 102 generations by
division. Dawson's monsters ultimately died. The permanence
of Chatton's Glaucoma scintilla ns may well be questioned and it is
unfortunate that he discarded the race after only five months of
culture. The double Uroleptus at the age of five months was more
vigorous than at the outset, but like all other series of Uroleptus it
ultimately died. It lived and reproduced, however, for more than
fourteen months (see p. 244).
Similarly with mutilations. The mutilated portions are passively
handed down to progeny by division, but the organization is not
affected and in the course of a few divisions the normal type is
regenerated. This was demonstrated by Jennings (190S) and con-
firmed by Calkins and by Peebles (1911, 1912) in cutting off the
anterior or posterior end of Paramecium, leaving a truncated indi-
vidual which did not regenerate but divided to form a perfect
individual from the posterior end and a truncated individual from
the anterior end (Fig. 108, p. 216); after a few divisions both ante-
rior and posterior individuals were perfectly normal. Abnormal
projections such as spines or clefts in the cortex, etc., are likewise
passively transmitted to descendants by division for a limited time,
but no permanent change in organization is brought about.
In general the upshot of all experiments with poisons, heat, ab-
normalities, etc., is failure to modify the organization of Protozoa
in any permanent manner. The experiments of Jollos of treating
Paramecium at the time of reorganization are, however, possible
exceptions.
Modifications of the organization which arise from within the
organism itself, on the other hand, may be permanent. Such
modifications are possible through the sifting out of germinal
characteristics in the course of continued metabolic activity and
division. Some are manifested by morphological characters which
afford a basis for selection on the part of the investigator. Experi-
ments to this end have been carried out mainly by Jennings and his
associates. The underlying principle in such selection work is that
a single individual from a "wild" population is the result of a great
number of hereditary characteristics stored up in the past through
amphimixis and united now in the organization of the single indi-
vidual. Such an individual, if cultivated under uniform conditions,
gives rise to progency showing diversities in structure or function
EFFECTS OF REORGANIZATION 3-17
which are probably ancestral characters. The extreme individuals
showing such diversity are selected and bred independently.
Jennings has clearly shown that such differences are characteristic
of all the pure lines he has studied and his findings have been con-
firmed by Root (1918) for Centropyxis aculeata; by Hegner (1919)
for Arcella dentata; and by Reynolds (1923) for Arcella polypora.
While the fundamental character (genotype) of a race is maintained
there are minor differences in organization which may or may not
be manifested by structural peculiarities. This is strikingly shown
in Jennings' studies on Difflugia corona (1916), a favorable form since
the characteristics of the shell can be measured or counted and the
structure does not change after it is once formed. In such a study
Jennings says the method of evolution by slow and gradual change
rather than by sudden jumps or mutations becomes visible. " We
begin to exercise selection within the single family. On the one
hand we select all the long-spined individuals and place them
together; on the other hand we select all the short-spined ones and
place them together. In the long-spined group we continue to
save for generation after generation only the individuals that are
long-spined ; in the short-spined group only the offspring with short
spines. In the same way we select other sets for numerous spines
and for few spines; for large shells and for small shells; for many
teeth and for fewer teeth.
"And now as we keep this up for generation after generation we
find that the correspondence between parent and progeny becomes
more and more marked. We find that our single family is breaking
up into many different groups which differ from one another heredi-
tarily. We get finally what appears to be twTo diverse races—
one with long spines, the other with short spines— the difference
continuing for generation after generation. A third set has con-
stantly large shells, while others consistently produce small shells.
We also get stocks hereditarily different for numbers of spines; and
for numbers of teeth. Our single stock, derived by fission from a
single parent, has gradually diversified itself into many stocks that
are hereditarily different. If this is what we mean by evolution, we
have seen evolution occur" (Jennings, 1921, pp. 75-78).
In a similar manner Root (1918) and Hegner (1918) studied
uniparental inheritance in Centropyxis aculeata and in Arcella
dentata and obtained results of the same nature. External agents
(lack of food, salts, temperature, etc.) may bring about similar
variations in size of shell, numbers of spines, etc., which persist as
long as the conditions are maintained (Hegner, 1919). From this
it appears that external conditions may inhibit the expression of
germinal factors, but not permanently.
The interpretation as given by Jennings of these clear-cut results
appears to be fundamentally sound and its significance is not less-
348 BIOLOGY OF THE PROTOZOA
ened by the chromidia problems which are associated with all of
these testate rhizopoda. If, as generally believed, the chromidia
give rise to germ nuclei, there is some chance of this hereditarily
important chromatin being unequally distributed at cell division,
for the mass of chromidia is not halved with the same precision as
is the chromatin of the nucleus or nuclei. Whether or not chromidia
are responsible the interesting fact remains that demonstrable
variations in organization occur with continued reproduction. It
remains to be determined, however, whether the variations will
still breed true after endogamous fertilization and reorganization,
or will revert to the form of the original wild individual ; then only
will the matter of permanency of the changed organization be
settled. Jollos (1924), exercising selection in Arcella vulgaris,
Arcella discoides, and Arcella polypora obtained abnormalities in
parents and offspring which he interpreted as due to environmental
conditions, especially to the accumulations of metabolic waste.
With cultivation under better conditions of the medium such abnor-
malities gradually disappeared with reversion to the normal.
Further evidence of the sorting out of mixed characteristics was
given by Calkins and Gregory (1913). The first 4 of the individuals
formed by an ex-conjugant of Paramecium caudatum were individ-
ually isolated and the history of their progeny was followed out in
32 pure lines, S from each of the original 4 individuals. The history
of these 4 strains in one experiment is condensed in Fig. 168. Pure
lines that died are indicated by X and the 4 sets of 8 lines each
came from the 4 individuals A, B, 0, and I). Physiological differ-
ences in the progeny of these 4 are indicated by the division-rates
and by the ability to conjugate, the progeny of A for example giving
epidemics of conjugation at each test while similar tests gave no
conjugations in the progeny of B, C, and D until nine months of
culture, and then in very small numbers. Similar variations in size
were characteristic of the different quadrants. It is possible that
such results are due to the segregation of germinal materials during
three metagamic divisions of the amphinucleus, each of the original
four cells receiving a different combination of macro- and micro-
nuclei.
In general, all results that are based upon physiological differ-
ences must be cautiously interpreted. Thus with Uroleptus mobilis
individuals from the progeny of single ex-conjugants may be
selected at appropriate periods to show marked differences in divi-
sion-rates. One such individual may reproduce at the rate of 17
divisions in ten days; another individual from the same line will
reproduce at the rate of 8 divisions in ten days, and a third may
divide at the rate of only 2 divisions. One might erroneously
argue that these individuals represent the sifting out of an heredi-
tary complex and the argument would apparently be supported by
EFFECTS OF REORGANIZATION
349
results of conjugation between individuals of each set. In the first
set the high division-rate would appear to be inherited ; in the third
set the low division-rate in most cases would appear to be inherited
but such series invariably die. The real test is shown by conjugation
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the progeny of a single ex-eonjugant of Paramecium
in. (After Calkins and Gregory.)
in the second set which results in optimum division-rates. In such
sets of progeny, as shown above, the differences in vitality of the
offspring through conjugation are due to differences in vitality of
the parent. With low vitality of offspring from old parents it might
350 BIOLOGY OF THE PROTOZOA
be argued that here is an example of the inheritance of an acquired
characteristic, whereas it is merely a matter of general vitality.
B. Biparental Inheritance.— Through amphimixis there is a possi-
bility of introducing changes in the organization of a species from
within. The new amphinucleus is a new creation and its interac-
tion with the cytoplasm must differ from previous interactions. The
cytoplasm is also different in cases of merogamy and in cases of
conjugation. In merogamy there is a fusion of cell bodies as well
as of nuclei; in conjugation the old macronucleus, a product of the
old amphinucleus, is distributed throughout the cytoplasm and
absorbed. As a result of the interactions of new nucleus and new
cytoplasm, new structures and new activities or changed activities
may ensue.
While a priori such origination of variations in Protozoa is a
logical consequence, as a matter of fact it has been rarely observed
in Protozoa. Here genotypes as well as fixed and congenital varia-
tions usually vary little from the fluctuating variations of a species.
The remarkable fixity of the genotype is indicated by the world-wide
distribution of the common species, and is clearly demonstrated by
long-continued cultures of any given species. Vitality also is remark-
ably constant as illustrated by Woodruff's long culture of Para-
mecium aurelia, or by cultures of Uroleptus mobilis in which the
average relative vitality of the first 12 series representing the F to
F4 generations by conjugations was 83 per cent and the relative
vitality of a recent set of series representing the Fi8 to the F22
generation was 85.6 per cent. Here, although there wTas an interval
of six years between the two sets compared, the vitality remained
practically the same.
Despite this constancy there is some unmistakable evidence of
variations in the Protozoa. There is also considerable evidence
that has been misinterpreted as mutations. Among the latter,
abnormalities in reorganization may be responsible for apparent
mutations. Thus a bi-micro nucleated, short race of Paramecium
caudatum wTas obtained as a result of conjugation of two normal
individuals (Calkins, 1906). Its two micronuclei, shortened body
and rounded posterior end were characteristic of Paramecium
aurelia and the latter was erroneously interpreted as a mutation
of Paramecium caudatum. The aurelia characters persisted for 45
generations by division when they were lost, and reversion to the
caudatum type occurred, presumably during a period of endomixis.
In like manner we may account for the amicronucleate races of
many ciliates (Hance, Moody, Dawson, Woodruff, etc.), the amicro-
nucleate condition persisting for many generations, but ultimately
ending in death, since failure to conjugate is characteristic of such
races. These are evidently not cases of mutation but temporary
abnormalities resulting from imperfect reorganization.
EFFECTS OF REORGANIZATION 351
An exceptional case of mutation is that of Chilodon uncinatus
described by MacDougall (1925).
A single individual of Chilodon uncinatus was isolated by
MacDougall (1925) in December. Its progeny were maintained
in pure line cultures until lost in June. In May, larger forms
appeared in the cultures and these increased until they out-num-
bered the smaller forms, few of which could then be found. Cyto-
logical examination showed that the larger form was morphologically
identical with the smaller form, with the exception of the micro-
nuclei in which the chromosomes were eight in number as against
four in the smaller form. MacDougall worked out the meiotic divi-
sions for both types and found a similar history in both (Fig. 149,
p. 299) and correctly interprets the tetraploid form as a mutant
from the ordinary diploid type.
The entire matter of heredity in Protozoa, together with rejuven-
escence and related problems have been fully treated in a remark-
ably frank and impartial manner by Jennings (1929) in his excellent
monograph on the Genetics of the Protozoa, to which the reader is
referred.
The Protozoa, finally, cannot be regarded as simple organisms
which may be permanently changed in structure or function at will.
Each type has a remarkable tenacity of life which we believe is
organization and its activity, and which may be temporarily modi-
fied by environmental changes, but in which permanent changes
are rare, and when they occur must come apparently from within.
Organization, on the one hand, is continuous and has been handed
down from the indefinite past to the species which we know today.
Vitality, on the other hand, may be discontinuous and variable and
is manifested by the sum of activities which take place in the
organization at any time. Death is not of necessity the cessation
of vitality but the disintegration of the organization after which
vitality is impossible.
CHAPTER X.
GENERAL ECOLOGY, COMMENSALISM AND
PARASITISM.
As stated in the introductory chapter (p. 25), Protozoa may be
found wherever there is moisture. The general distribution is also
outlined, particularly with regard to deep sea forms. It is pointed
out, furthermore, that fresh water forms, both genera and species,
are for the most part cosmopolitan, so that a piece of research
begun in New York may be continued on similar forms in Siam,
China or Australia. Similar or identical species may be found in
both fresh and salt water or brackish water. There are, however,
a certain number of ecological centers which permit of a rough
classification into: (1) Water-dwelling forms; (2) semi-terrestrial
forms; (3) soil-dwelling forms; (4) sapropelic forms; (5) coprozoic
forms; and (6) parasitic forms.
1. Water-dwelling Protozoa.— Without too much exaggeration
this caption might well be applied to all Protozoa; here, however,
it is limited to those Protozoa which live in ordinary exposed waters,
where certain ecological conditions lend themselves to the vital
needs of some types and are fatal to others. These needs have to
do in the main with food requirements and oxygen pressure and a
rough classification, without taxonomic value, was suggested by
Kolkwitz in 1908. This was based upon the requirements of
water-dwelling forms in respect to the amounts and conditions of
organic matter present. Habitat groups were proposed under the
terms katharobic, oligosaprobic, mesosaprobic and polysaprobic.
Katharobic types are rare, for their environment is fresh water
springs, running rivers and streams which are free for the most part
of organic matter but rich in oxygen.
Oligosaprobic types are those which are able to live in waters
with little organic matter but rich in mineral matters. The chief
types here are the chlorophyll-bearing Protista, but some types of
Protozoa also are able to live (Amoeba proteus, Lacrymaria olor,
Trachelius sp., Frontonia sp., Ophrydium versatile, etc.).
Mesosaprobic types are numerically greater than those of other
habitat groups, for in this environment active oxidation is going
on and organic matter is decomposing. In addition to many
algal forms we find here flagellates such as Bodo, Tetramitus,
Anthophysa and Peranema, and many common ciliates including
Paramecium, Coleps, Spirostomum, Colpoda, Chilodon, Stenfor,
Stylonychia, Euplotes, Vorticella, etc. Heliozoa are represented by
Actinophrys and Actinosplaerium.
ECOLOGY, COMMENSALISM AND PARASITISM 353
Polysaprobic types finally live in waters with little free oxygen
but with sulphuretted hydrogen, carbonic acid and other products
of putrefaction advertized by their foul odors. In this group are
all of the open sewage Protozoa (see p. 357), as well as some of
the sapropelic fauna (Lauterborn) which live in a medium quite
free from oxygen at the bottom of ponds where ill-smelling gases
(methane, carbonic acid, sulphuretted hydrogen, etc.) accumulate.
These are anaerobic forms some of which, characterized by fan-
tastic shapes, are unable to live under aerobic conditions (see
p. 356).
2. Semi-terrestrial Protozoa.— Semi-terrestrial protozoa may be
found in moss, sphagnum, etc. (many types of testate rhizopods
and a few flagellates and ciliates).
Not only food and oxygen but relative alkalinity and acidity are
also determining factors in the life of given types. Acanthocystis
aculeata, for example, lives well with a hydrogen-ion concentration
(pH) of 8.1 but dies in a less alkaline medium with pH 7.4 (Stern,
1924). Other forms may live in a distinctly acid medium and
some may live in waters having a wide range of pH. In standing
waters with decomposed matter at the bottom, the pH at different
levels is variable which accounts in part for the sequence of forms
in a hay infusion (Woodruff, 1912; Bresslau, 1926, et al.) and the
segregation of specific types at different levels.
With the varying conditions to which Protozoa are adapted and
under which they live and thrive, it is probable that some types are
more readily adaptable to a parasitic mode of life than others.
Anaerobic forms, for example, are already partially adapted.
3. Soil-dwelling Protozoa.— It is to be expected that an occasional
water-dwelling form of Protozoa should be found in the soil, par-
ticularly where moisture abounds. It is also possible that coprozoic
forms under suitable conditions in the soil might have a more or
less extended life. The so-called soil Protozoa, therefore, might
well include representative genera and species of both water-dwelling
and coprozoic forms.
Modern studies of representative soils from all over the world,
including all types, have demonstrated, however, that the great
numbers of Protozoa found cannot be accounted for on any such
casual basis. In this connection Sandon (1927) states that soil
forms constitute a fairly well-defined group, with characteristic
functional needs and cannot well be regarded as an accidental
collection.1
Sandon's conclusion is supported by the facts of distribution which
he adduces. These apply to all groups of Protozoa of which he
1 Sandon, H.: The Composition and Distribution of the Protozoan Fauna of the
Soil, London, 1927, p. 63.
23
354 BIOLOGY OF THE PROTOZOA
describes no less than 250 species capable of living in the soil.
With arable soils the maximum numbers are found, as a rule, at a
depth of 4 to 5 inches while the sub-soil is generally free from
them. Such soil-dwelling types are able to live under partial
anaerobic conditions and are usually bacteria-eating holozoic forms.
As such they become important factors in all economic matters
concerning soil productiveness.
Of the flagellate group Sandon describes seven species which seem
to be limited to this habitat (Allantion trachyploon, Sandon; Alias
diplophysa, Sandon; Colponema symmetrica, Sandon; Phalansterium
solitarium, Sandon; Sainouron mikroteron, Sandon; Tetramitus spir-
alis, Goodey; Anisonema minus, Sandon; and Cercobodo vibrans,
Sandon). An eighth species, Parapolytoma satura, Jameson, is
questionably limited to the soil.
The relative frequency of animal flagellates found in 146 soils
from different parts of the world is shown in the table on p. 355,
condensed from Sandon's Chart II.
It is safe to say that the first 10 of these are characteristic of
flagellates of the soil and may be found practically anywhere, par-
ticularly in arable and garden soils. The last 10 may well be
regarded as chance specimens and without significance in soil
biology. The twenty-eight intermediate species may or may not
be present, depending upon environmental conditions of food
(bacterial), moisture, relative acidity, etc., the great majority being
species which are also found as water-dwelling or as coprozoic
forms. Furthermore, methods of examination are not sufficiently
perfected to determine whether a given form actually lives in the
soil or is dormant there and has developed in the artificial culture
medium subsequently used. It is quite possible that certain cysts
never develop in earth, and it is also quite possible that active
forms in the soil are killed by drying or by the conditions of
culture.
In addition to the list of flagellates described by Sandon other
workers have described different species from the soil, bringing the
total number of soil flagellates up to about 75 species. This esti-
mate, however, includes several forms which should be regarded as
rhizopods (particularly the Bistadiidae and flagellated swarmers of
the Mycetozoa) and plant flagellates. Amongst additional animal
flagellates we should include Codosiga botrytis, Ehr. (Goodey, 1911,
rare); Salpingoeca convallaria, Stein, and S. ampullacea, Braun
(Wolff, 1912); Rodo irrricolus (Martin, 1912); Pleuromonas jaculans,
Perty (Fellers and Allison, 1920; Fantham, 1922-1924; Wolff, 1912);
Phyllomonas contorta, Klebs (Wolff, 1912); Hexamitus inflatus, Duj.
(Fellers and Allison, 1920); Monas guttula, Ehr. (several observers);
Monas vivipara, Ehr. (several observers); Astasia sp. (Fellers and
Allison, 1920); Peranema trichophorum (various observers) ; Urceolus
ECOLOGY, COMMENSALISM AND PARASITISM 355
cyclostomum, Stein (Fantham and Paterson, 1923-1924); and Hetero-
nema acus, Stein (Fellers and Allison, 1920).
Flagellates of the Soil from 28 Stations in All Parts of the World,
in the Order of Frequency, Condensed from Sandon, 1927.
Per cent.
1. Heteromita globosa, Stein found in 143 soils, or 98.0
2. Cercomonas species found in 99 soils, or 67 . 8
3. Oikomonas termo, Elirbg found in 93 soils, or 64 . 3
4. Allantion mikroteron, Sandon .... found in 72 soils, or 50.0
5. Phalansterium solitarium, Sandon found in 56 soils, or 38.3
6. Tetramitus spiralis, Goodey .... found in 37 soils, or 25 . 3
7. Spongomonas sp found in 34 soils, or 23 . 1
8. Sainouron mikroteron, Sandon . . found in 32 soils, or 22 . 0
9. Cercomonas crassicauda, Alexeieff . found in 31 soils, or 21 .0
10. Cercobodo vibrans, Sandon .... found in 27 soils, or 19.0
11. Helkesimastix foecicola, W. and Lap. . found in 23 soils, or 16.0
12. Alias diplophysa, Sandon found in 21 soils, or 14.0
13. Anisonema minus, Sandon found in 17 soils, or 12.0
14. Proleptomonas foecicola, Woodcock found in 15 soils, or 10.0
15. Spiromonas angusta, Dujardin . . found in 13 soils, or 9.0
16. Scytomonas pusilla, Stein found in 12 soils, or 8.0
17. Actinomonas mirabilis, Kent .... found in 11 soils, or 8.0
18. Mastigella sp found in 10 soils, or 7.0
19. Heteromita sp. . ■ found in 8 soils, or 6.0
20. Cercobodo agilis, Moron' found in 6 soils, or 4.0
21. Tetramitus rostratus, Perty .... found in 6 soils, or 4.0
22. Monas sp found in 6 soils, or 4.0
23. Petalomonas angusta, Klebs . found in 6 soils, or 4.0
24. Entosiphon sulcatum, Dujardin found in 6 soils, or 4.0
25. Monosiga ovata, Kent found in 5 soils, or 3.0
26. Phyllomitus amylophagus, Klebs . found in 5 soils, or 3.0
27. Phyllomitus undulans, Stein .... found in 5 soils, or 3.0
28. Petalomonas sp found in 5 soils, or 3.0
29. Bodo celer, Klebs found in 4 soils, or 3.0
30. Bodo saltans, Ehr found in 4 soils, or 3.0
31. Colponema symmetrica, Sandon found in 4 soils, or 3.0
32. Heteromita obovata, Lemmermann found in 4 soils, or 3.0
33. Cephalothamnion cycloum, Stein . found in 4 soils, or 3.0
34. Polytoma sp Less than 3.0
35. Mastigamoeba limax, Moron" Less than 3 . 0
36. Heteromita ovata, Dujardin Less than 3.0
37. Menoidium sp Less than 3.0
38. Chlorogonium sp Less than 3.0
39. Bodo caudatus, Dujardin Less than 1 . 0
40. Bodo edax, Klebs Less than 1 . 0
41. Heteromita compressa, Lemmermann Less than 1.0
42. Phyllomitus sp Less than 1.0
43. Cladomonas fruticosa, Stein . Less than 1.0
44. Tetramitus pyriformis, Klebs Less than 1 . 0
45. Spironema multiciliata, Klebs Less than 1.0
46. Chilomonas sp Less than 1.0
47. Cryptomonas Less than 1 . 0
48. Petalomonas mediocanellata, Stein Less than 1.0
356 BIOLOGY OF THE PROTOZOA
Rhizopods and ciliates are represented by fewer genera and
species than are flagellates. Of the 250 species of Protozoa living
in the soil Sandon enumerates only 48 species of rhizopods and 35
species of ciliates; nor are they so widely distributed among the
146 soils from all parts of the world. Limax amebae were regis-
tered from 49.5 per cent of all sample soils examined ; HartmanneUa
hyalina, from 42 per cent; Nuclearia, from 27 per cent; Trinema
enchelys, from 22 per cent; Trinema lineare, 19 per cent; and Nagleria
gruberi, from 17.5 per cent. Of ciliates, Colpoda cucculus, Colpoda
steinii and Cyclidium glaucoma were present in 56, 47 and 23 per
cent respectively.
Few generalizations, however, can be made regarding soil-dwel-
ling forms as distinct from other Protozoa, and there is but little
evidence that morphological adaptations follow such a mode of
life. This phase of Protozoology, however, is still young and
further study will undoubtedly lead to important deductions as
well as to practical results.
4. The Sapropelic Flagellates.— Under the term "sapropelic
fauna" Lauterborn (1901) included Protozoa which are able to
live in media partly or wholly free from oxygen. Some of the soil
flagellates, particularly those living deep in the soil, are partially
anaerobic, and might well be included here. The majority of sapro-
pelic flagellates, however, live in sulphurous waters and in sewage,
especially in the deeper zones of sewage filtration tanks where
oxygen is entirely absent (polysaprobic forms, Kolkwitz, 1908).
The sapropelic fauna, according to Lauterborn, includes those
forms which live and multiply in the slime on the bottom of fresh
ponds or salt water pools and ditches. This slime consists, for the
most part, of plant debris and animal excrement and remains, while
inorganic mineral matters are reduced to a minimum. Necessary
conditions leading to the accumulation of the necessary ingredients
for building up this environment are: (1) A rich growth of vegeta-
tion in the surface water; (2) standing water free from currents;
(3) protection against intense sunlight. In still waters dead plants
and animals from the surface settle on the bottom where the protein
materials decompose rapidly, giving rise to foul-smelling gaseous
products such as sulphuretted hydrogen, marsh gas, carbonic acid
and the like. If direct sunlight is present there is an active pro-
duction of oxygen by green plants, and with the aid of aerobic
bacteria progressive oxidation causes the splitting up of organic
matters until stabile inorganic combinations result. Under such
conditions a slime suitable for sapropelic forms does not accumulate,
hence for a proper medium oxygen must be absent.
With the proper anaerobic conditions a fairly characteristic
sapropelic fauna develops. Many types are intermediate and may
live as semi-anaerobic forms, but others are obligatory anaerobes
ECOLOGY, COMMENSALISM AND PARASITISM
357
and die in the presence of oxygen. Amongst the animal flagellates,
Lauterborn (1916) includes as sapropelic forms: Mastigamoeba
trichophora, Lauterborn; Trepomonas agilis, Dnj.; Hexamitus infla-
tus, Duj. (also reported from sewage); Rhynchomonas nasuta, Stokes;
Pteridomonas pulex, Penard; Physomonas socialis, Kent; Heteronema
acus, Ehr.; //. spirale, Klebs, and Menoidium pelluddum, Perty.
Of rhizopod types he enumerates Pelomyxa palustris and Pamphagus
armatus as characteristic forms, while amongst the ciliates he finds
several types which are found nowhere else (Dactylochlamys pisci-
formis, Discomorpha pectinata, Legendrea bellerophon, Coenomorpha
medusula, Saprodinium dentatum and Pelodinium reniforme).
With these sapropelic forms should be added the anaerobic organ-
isms which live in sewage; a list of such forms found in Imhof tanks
by Lackey (1925) includes the following animal flagellates:
Common Forms.
Mastigophora:
Bodo caudatus1
Bodo mutabilis
Bodo ovatus
Cercomonas crassicauda1
Cercomonas longicauda
Cercomonas ovatus
Clautriavia parva
Dinomonas vorax
Hexamitus inflatus2
Mastigamoeba longifilum
Mastigamoeba reptans
Mastigella simplex
Monas amoebina
Monas minima
Notosolenus orbicularis
Oicomonas socialis
Pleuromonas jaculans
Tetramitus decissus
Trepomonas agilis2
Rhizopods:
Euglypha alveolata
Hartmannella hyalina1
Dimastigamoeba gruberi1
Vahlkampfia guttula
Vahlkampfia Umax
Infusoria:
Holophrya sp.
Metopus sigmoides
Saprodinium putrinum
Trimyema compressa
Rare Forms.
Anthophysa vegetans
Bodo angustus
Distigma proteus
Entosiphon sulcatus1
Heteronema sp.
Menoidium incurvum
Peranema trichophorum
Petalomonas carinata
Petalomonas mediocanellata1
Platytheca micropora
Salpingoeca Marssonii
Amoeba proteus
Chlamydophrys stercorea
Trinema lineare1
Vahlkampfia albida
Aspidisca costata
Colpoda inflata Chilodon sp.
Cinetochilum margaritaceum
Cy^lidium glaucoma
Glaucoma scintillans
5. The Coprozoic Protozoa.— Coprozoic Protozoa are forms which
pass through the digestive tracts of animals while encysted. Mixed
with water, dung containing such cysts forms a nutrient medium
1 Also reported as soil-dwelling.
2 Also reported in sapropelic fauna.
358 bio way of the protozoa
in which ex-cystment occurs and the freed organisms live and
multiply for a limited period. When their world dries up many of
the active organisms have encysted. Such cysts may be carried
with dust into food substances of man and other animals, and
through the agency of such contaminated food they are carried,
while remaining encysted, into the intestine where they do not
develop but which ultimately will provide a nutrient medium for
their development. In artificial cultures made up with feces of
different animals many such coprozoic Protozoa may be found,
and it is obvious that unwary observers may mistake them for
parasitic forms of the intestine.
At the present time at least, it is hardly feasible to speak of a
definite coprozoic fauna since many of the cysts which pass through
an intestine may contain organisms capable of living in stagnant
waters, or as parasites in the intestines of different types of animals.
There are several forms of flagellates, however, which develop from
cysts in dung and which in the unencysted condition are not known
as parasites. Amongst such coprozoic flagellates perhaps the most
common type is Bodo caudatus, Duj., which, as would be expected,
is also common in sewage; Rhynchomonas nasuta, Stokes, is copro-
zoic in cockroaches (Parisi), but seems to be widely distributed in
fresh (Stokes, Belaf) and in salt water (Griessmann). Cercomonas
longicauda, Duj., from human feces also occurs in sewage.
PARASITIC PROTOZOA.
By virtue of protoplasmic irritability there is a constant reaction
of the organization to environmental stimuli (see Chapter V).
The reaction may be manifested by morphological or physiological
changes which we interpret as adaptations. If the stimuli are too
drastic the protoplasmic response is too vigorous and disintegration
results. A given stimulus or set of stimuli may result in controlled
reactions by one type of organization, while similar stimuli may be
fatal to other types. This principle is well illustrated by the proto-
zoan parasites where complete adaptation to the environmental
stimuli within a given host has resulted in organizations which dis-
integrate upon exposure to the different stimuli of a free-living
existence, and, vice versa, free-living forms are killed by the drastic
change to the conditions of an animal host. Great numbers of
species of Protozoa have become adapted to the specific environ-
ments of different animal hosts and no type of animal is free from
the possibility of protozoan infection.
We can imagine a series of progressive adaptations whereby
free-living types may respond favorably to conditions of a partial
anaerobic medium (many such facultative aerobic forms are known).
Further adaptation to complete anaerobiosis is shown by the sapro-
ECOLOGY, COMMENSALISM AND PARASITISM 359
pelic and sewage-dwelling fauna. Such forms are partially prepared
for survival in the digestive tracts of animals, and these chances
are enhanced if their protoplasmic responses to stimuli provide a
resistance to the digestive fluids of the animal gut. We know of no
case amongst Protozoa where such resistance has been demonstrated
as a response to stimuli from the digestive tract, and must go as
far afield as the nematode worms for evidence. Here it has been
demonstrated that extracts from Ascaris lumbricoides contain anti-
ferments which neutralize the digestive ferments of the host (Wein-
land, 1902 and 1908).
Ectoparasitic Protozoa.— An ectoparasitic mode of life in most
cases is not sufficiently different from a free-living condition to call
for special morphological changes. Attached forms on algae or
detritus of different kinds may find an equally good anchorage on
shells of molluscs, carapace and appendages of arthropods, gill
structures of diverse types of fresh and salt water animals. Such
forms have the advantage of moving from place to place with their
hosts or of utilizing the food-bearing currents passing over their
gills. There is some evidence of adaptation to particular hosts even
in these ectoparasitic forms. Thus one can usually find Zooiham-
nium affine and Lagenophrys nassa on the legs of Gammarus pulex
and Spirochona gemmipara and Dendrocometes 2)arcld°>vus on the
gill lamellae while other species of the same genera are usually
found on Ascllus. In some cases special adaptations for such a
mode of life have been developed. Thus the suctorian Trichophrya
salparum adheres like a saddle to a gill bar of Salpa (Fig. 100, p. 192)
or the vorticellid ciliate Ellobiophrya donacis (Chatton and Lwoff,
1929, 1923) in which the usual adhesion disc (as in Scyphidia) is
drawn out in two arms which encircle a gill filament of the lamelli-
branch Donax vittatus (Fig. 104, p. 202). More frequently an attach-
ing organ ("scopula," Faure-Fremiet, 1910) is provided with spines
or hooks as in Trichodina species or Cyclochaeta on Hydra. A specific
thigmotactic reaction appears to keep Kerona pediculus on the ecto-
dermal surface of Hydra fusca.
Such forms, however, can scarcely be called parasites for they
apparently cause no ill-effects on the host. Schroder's term " Plank-
tonepibionten," or simply epibionts, appears to be more appropriate.
Ectoparasites in a strict sense are rare and appear to be limited to
fish hosts where the flagellate Costia necatrix grows to such numbers
that vitality, especially of young fish, is greatly impaired. Of the
ciliates, Chilodon cyprini furnishes a similar case, while Icthyoph-
thirius multifilvm, by boring into the skin of fish, becomes a more
deeply-lying parasite and the cause of distributed ulcerations.
Endoparasitic Protozoa.— In this group adaptations which are
often highly complex are mostly physiological and are directed
toward the preservation of the individual against the antagonistic
360 BIOLOGY OF THE PROTOZOA
reactions of the host, as well as toward the perpetuation of the
species. Many of them are obligatory parasites of specific animal
types and must find their appropriate environment to live. The
first question that arises is: How do they get into the body? As
a matter of fact the host, for example, the human body, is fairly
well protected and gateways to the insides are limited practically
to the mouth, nasal passages and the skin. The most obvious of
these is the mouth leading into the digestive tract, and infection may
follow the intake of contaminated food and drink. By far the
greatest number of protozoan parasites are introduced by this con-
taminative method. Minute germs and cysts may be taken in
with air currents through the nose and throat, but this method is
mainly limited to bacterial infections and if we exclude the ques-
tionable Chlamydozoa, protozoan infection by this method is prac-
tically unknown.
While probably the majority of endoparasitic Protozoa are
harmless, others are pathogenic and in each group with the probable
exception of the ciliates we find gradations between the two, while
with the Hvpermastigida and termites we find a perfect symbiosis
(p. 199).
The skin is a most effective barrier against infection and so long
as it is kept in good condition infection by this means is reduced
to a minimum. Abrasions, hang-nails, casual cuts, etc., however,
are portals of entry and bacteria, spirochetes or small flagellates
may gain access to the blood through such injuries. Or the skin
may be punctured by biting bugs, arachnids, flies, mosquitoes,
leeches and the like, and disease germs may be transmitted in this
way. Scratching the skin at points of irritation, thereby providing
entrance for possible parasites deposited with feces by ticks, mites
or other ectoparasites, is another means of inoculative infection.
Only rarely do Protozoa have invasive power of sufficient strength
to penetrate the unbroken skin and then only in the more delicate
coverings; such a disease is the so-called horse syphilis caused by
Trypanosoma equ i perdu m.
Obviously the most important of these modes of infection is that
by contaminated food and water taken into the digestive tract
through the mouth. Once adapted to the conditions of the gut,
intestinal parasites are prepared for further explorations and adap-
tations which may lead to parasitism in various organs of the host.
According to their seat of parasitism, internal parasites may be
grouped as entozoic (gut-dwelling), celozoic (lumen-dwelling),
hematozoic (blood-dwelling), cytozoic (intracellular), histozoic
(tissue-dwelling), karyozoic (intranuclear), etc.
In connection with the life history of trypanosomes Minchin
(1908) developed the thesis that hematozoic forms originate from
entozoic parasites in the same host. Support for this point of view,
ECOLOGY, COMMENSALISM AND PARASITISM 361
even if not acceptable for trypanosomes, is certainly given by the
life histories of several diverse types of the protozoan parasites.
Amongst flagellates, for example, the genus Trichomonas is one of
of the most widely distributed types in man. While there is some
question of the identity of species, representatives of the genus have
been recorded from the human mouth (many observers), from the
toe-nails (Wenyon), from sputum (many observers), from the
pleural cavity, from the vagina (many observers), in urine (many
observers), etc. Wenyon (1920) demonstrated the passage of forms
from the intestine into the surrounding tissue, and Pentimalli (1923)
found them in the blood. Similarly the widely distributed entozoic
genus Giardia and other flagellates — Eutrichomastix, Octomitus,
etc., are frequently present in great numbers in the blood (Reich-
enow). Even more striking instances of adaptation from entozoic
to hematozoic mode of life are shown by coccidimorpha amongst
the Sporozoa. Here in Shellackia, Lank ester ella, Hepatozoon, etc.,
infection is contaminative and blood parasitism is developed in
varying degrees. In all of these, infection is by the contaminative
method, the sporozoites of Shellackia and Hepatozoon develop and
reproduce like typical coccidia in epithelial cells of the gut. In
Hepatozoon (Miller) the gametocytes enter the blood where they
are engulfed by phagocytes. These are eaten by the mite Lelaps
echidninus, fertilization takes place in the gut and sporozoites are
formed in the body tissues of the mite— the latter when eaten by
a rat enter epithelial cells and repeat the cycle. In Shellackia
there is a similar history, but macrogametes penetrate the gut wall
of the host — a lizard— and are fertilized in the deeper tissues where
sporozoites are formed. These make their way into the blood where
they enter red blood cells or leukocytes. Here they remain dor-
mant until eaten by a mite and the mite eaten by a lizard. In the
lizard the cycle is repeated. Lankesterella, a blood parasite of the
frog, is a typical hematozoon. Here the initial sporozoite stage is
a gut parasite of the frog, eaten with infected leeches (Hemiclepsis
marginata). Unlike the other forms mentioned, no development
occurs in the frog's gut but the sporozoites penetrate the gut wall
and enter the blood where, as intracorpuscular parasites, they grow
and reproduce as hematozoa.
While the above cases illustrate the change from an entozoic to
a hematozoic mode of life in the same individual they do not
cover the whole story of the blood parasites. It is perfectly possible
for a gut parasite of one animal to become a blood parasite in an
entirely different type of animal. This indeed was regarded by
Leger (1904) as the mode of origin of mammalian trypanosomes.
Developing as entozoic parasites of insects they were inoculated
when the insect began to feed on mammalian blood and, finding a
suitable medium for growth and reproduction, they multiplied until
362 BIOLOGY OF THE PROTOZOA
each infected individual became a source of contamination for
other insects of the same type. The cycle thus established by
adaptation to the different kinds of host would continue indefinitely.
However this may be with trypanosomes, and it seems to be the
most probable hypothesis, there is little doubt about it in the case
of malaria parasites. Here the original host was the mosquito in
which fertilization and development take place in the gut and gut
wall while the sporozoites are liberated in the body cavity. In all
of these cases the protective cysts which all strictly gut parasites
form and which safeguard the germs against an unfavorable external
environment are quite unnecessary. The second host replaces the
cyst.
Effects of Protozoan Parasites on the Host. — Pernicious effects of
parasites depend largely upon the site of parasitism, cytozoic forms,
for example, being far more destructive than celozoic, coccidia
more often fatal than gregarines or Cnidosporidia or intestinal
flagellates. In general the more recent the association of host and
parasite the more serious are the effects upon the host, but with
physiological adaptive responses on the part of both host and
parasite, a balance is ultimately established which leads to com-
mensalism or even to symbiosis (as in the association of termites
and hypermastigida). South African cattle are little if at all
affected by Trypanosoma brucei, but European cattle succumb.
Domestic cattle and the wild animals of Africa thus become carriers
of the disease.
Functional derangement of the host may be brought about in
different ways some of which may be due to occlusion or massing
of parasites in bloodvessels, ducts or lymphatics, thus shutting off
the blood supply and food of vital organs. Thrombus formation
in capillaries of the brain or of other vital organs, due to massing
of parasites, makes tropical or pernicious malaria the most dreaded
of malarial diseases. The characteristic lethargy and accompanying
symptoms of African sleeping sickness are due to lack of nourish-
ment and atrophy of nerve cells in the base of the brain, caused by
the occlusion of smaller bloodvessels by accumulations of parasites
and lymphocytes in the perivascular spaces. Or impairment of
function may be due to the destruction of large numbers of secreting
cells— the coccidian Cyclospora karyolytica, for example, destroys so
many secreting cells of the intestine that the disease in ground
moles is fatal in 100 per cent of cases (Schaudinn). Secondary
organic complications may be due to the overactivity of vital
organs— thus in malaria so much hemoglobin is liberated that the
liver cannot take care of it all and the excess is passed on to the
kidneys, resulting in hemoglobinuria and functional impairment of
the excretory organs.
Secretions by parasites in many cases cause cytolysis of tissue
ECOLOGY, COMMENSALISM AND PARASITISM 363
cells and so lead to ulcers and to abscess formation, as in amebic
dysentery. The disintegrating proteins of such cells produce toxins
which by autointoxication impair the vitality of the host. Less
frequently there are specific toxins which poison the host but in
only a few cases have such products been determined— sarcocystine
from the sporozoan Sarcocystis is the one toxin which has been
extracted (Laveran and Mesnil, 1899).
Evidences of toxin action, both by direct poisoning and by
serological reactions of the host have been demonstrated in many
cases, rarely indicating direct secretion by the parasite (Sarcocystis
by Kasparek, 1895) but more often indicating a toxic compound
(endotoxin) which is liberated with death of the parasite or formed
as a chemical product from the breaking-down of substances com-
posing the body of the parasite (Endamoeba dysenteriae, Leishmania,
Trypanosoma, malaria organisms). In connection with host reac-
tions a great deal of work of serological nature has been done espe-
cially in reference to the detection of protozoan infections. Pre-
cipitation, agglutination, lysis and complement-fixation tests have
been developed to a high degree and are of the greatest importance
in detecting even mild infections (see Taliaferro, 1930, p. 411, for
serological methods). Craig (1926) has demonstrated two types of
toxin from Endamoeba dysenteriae: one, a hemolysin capable of
dissolving human red blood corpuscles; the other, a cytolysin cap-
able of breaking down the epithelial cells of the intestinal mucous
membrane of man and cats. Noguchi (1924) by serological methods
demonstrated the difference between morphologically identical
species of Leishmania (L. donovani, L. tropica and L. braziliense).
Parasiticidal reactions of the host to trypanosomes and malaria
organisms have been shown by Taliaferro (1926) and for trypano-
somes the parasite destroying agent was found, by experiments in
vitro, to be a lysin by Schilling (1902), Lingard (1904), Franke
(1905) and Rodet and Vallet (1906), and by Massaglia (1911-1912) ;
also by experiments in vivo by Diesing (1905), Klein and Mollers
(1906) and Johnson (1929). Similar reactions of the host cause a
diminution in rate of reproduction of the parasites, or even its
cessation (Taliaferro, 1924; Coventry, 1925).
It is evident from the few references given above to a vast field
of protozoan research that definite and often specific changes occur
in the blood of individuals infected with different kinds of protozoan
parasites. If the results of such changes, in the form of parasiticidal
lysins, agglutinins, etc., are retained in the blood, they would be
effective against reinfection. Active immunity thus established by
infection in a host may be of longer or shorter duration, but for
the most part it lasts only for a short time. It appears to be a
potent protection in some types of Leishmaniasis, particularly that
produced by Leishmania tropica, where a localized ulceration confers
364 BIOLOGY OF THE PROTOZOA
a general immunity. Advantage is said to be taken of this fact
by parents in countries bordering the Mediterranean who expose
children by inoculation of parasites of Oriental sore on arms or legs
and so prevent further infection with possible disfiguring scars on
more conspicuously exposed surfaces. Absolute immunity conferred
by a single infection of Tkeilcria parva, the cause of East Coast
fever of cattle, is another example; another case of relative immu-
nity is furnished by a single infection of rats with Trypanosoma
lewisi; further infections are harmless, although the parasites may
not be killed. In the majority of cases, however, the immunity
reactions have no permanent value. Here as with bacterial infec-
tions the blood may contain natural substances which are inimical
to specific parasites. Such individuals are said to be naturally
immune. In other individuals a gradual immunity is built up by
repeated infections— as in adult natives of a malarial country who
have been subject to repeated infections from childhood. Many
efforts also have been made to immunize by use of attenuated
strains but with dubious results. Some degree of success with
attenuated Trypanosoma brucei has been obtained (Ponselle, 1923)
and with Plasmodium praecox of bird malaria (Et. and Ed. Sergent,
1921).
Passive immunity, of transient nature, is established in many
types of protozoan disease by inoculation of blood serum from
actively or normally immunized individuals. Such serums may
act as alexins to stimulate phagocytosis (e. g., Laveran and Mesnil,
1901, with Trypanosoma lewisi) or to bring about agglomerations
and agglutinations resulting in swelling and disintegration (Trypano-
somes and Leishmanias).
Parasitic Flagellates. —The importance of the parasitic flagellates
of man centers mainly in the family Trypanosomidae. There is
strong evidence to show that these forms, originally, were parasites
of the digestive tract of invertebrates, mainly insects, which by
contaminative or inoculative methods transmitted their parasites
to vertebrates, especially to mammals, where they became adapted
to conditions in organ cells and in the blood. Reinfection of the
invertebrates follows from their blood-sucking habits and verte-
brate and invertebrate thus become mutual carriers of infection
which is often pathogenic to the former, but by mutual adaptation
apparently harmless to the latter.
Invertebrate forms which are known to harbor intestinal flagel-
lates and some of which have been proved to be, or suspected of
being, transmitting agents of vertebrate parasitic flagellates are
insects, arachnids and leeches. Of these the insects are by far the
most important, Wenyon listing no less than 25-i species containing
intestinal flagellates, while arachnids are limited to 5 species and
leeches to 11. Excluding insects which do not feed on vertebrates,
ECOLOGY, COMMENSAL ISM AND PARASITISM 365
the number of possible transmitting agents is considerably lessened.
There is, obviously, always a possibility of vertebrate infection,
either by contamination or by inoculation, from insects which feed
on vertebrates, but the transmission is always difficult to prove,
and the fact that pathogenic flagellates live and multiply in the
digestive tract of insects is no proof that the insect transmits them
to mammals, although the inference is highly plausible. So it is or
has been with the transmission of pathogenic Leishmanias by bed-
bugs, flies and fleas or of Trypanosoma by biting flies and bugs.
In some cases the transmission has been demonstrated without
question of doubt and these will be considered in the following
pages.
The family Trypanosomidae includes 7 genera which apparently
are genetically related and reveal an interesting series in progressive
parasitism. These are Leptomonas, Crithidia, Leishmania, Herpeto-
monas, Endotrypanum, Trypanosoma and Schizotrypanum of inver-
tebrates and vertebrates, and Phytomonas of invertebrates and
plants. These all have the same general type of structure and
represent the simplest forms of flagellates (Fig. 169). In all cases
the body in motile stages is elongate and ellipsoidal; the nucleus
is single and of the usual endosome-bearing type; the kinetic ele-
ments are more variable, but there is always a blepharoplast usually
connected by fibrils with a parabasal body. Rhizostyles, arising
from the blepharoplast are sometimes present but not invariably,
even in the same species. Axoplasts, analogous to axostyles, have
been reported for one species of Herpetomonas (II. drosophilae,
Chatton and Leger, 1911). The flagellum is of the usual type with
axoneme or axial filament originating from the blepharoplast and
periplastic sheath. In some forms (Herpetomonas, Leptomonas,
Crithidia, Leishmania and Phytomonas) the kinetic complex (kin-
etoplast) is anterior to the nucleus; in the fully-developed forms of
Trypanosoma, it is posterior (Fig. 169, D). In all cases a rhizoplast,
or endoplasmic portion of the axial filament is present. In forms
with the anteriorly placed blepharoplast this is relatively short,
but where the blepharoplast is posterior to the nucleus it may be
almost as long as the cell as in Crithidia forms and the trypanosome
form of Herpetomonas muscarum (Fig. 169, B), here it runs along
the margin of the cell restrained by the periplast. In Trypanosoma
the axial strand becomes the margin of a delicate periplastic ledge
to form an undulating membrane which vibrates with the activity
of the free axial filament of the flagellum.
Other structures of the cell are less constant and of less importance
— cytoplasmic granules of the nature of volutin (see p. 72) are
sometimes very abundant; mitochondria and Golgi bodies have
received scant attention and play no part in taxonomic or parasitic-
discussions.
366
BIOLOGY OF THE PROTOZOA
These parasites have no mouth, food-taking being osmotic or
saprozoic. They live, normally, in the dissolved food substances
of the gut or in the blood but may grow and multiply in the semi-
fluid protoplasm of different types of tissue cells. For the most
Fig. 169. — Trypanosomidae. A, Leptomonas ctenocephali; B, Herpetomonas mus-
carum, at left individual in division, at right trypanosoma form. C, Phytomonas
davidi; D, Trypanosoma gambiense; E, macrophage with intracellular phase of Leish-
manial donovani; F, Leishmania donovani, flagellated and division stages; G, Crith-
idia gerridis from water bugs; H, Endotrypanum schaudinni in blood of sloth; I,
Trypanosoma rhodesiense. X ca 2000. (After Wenyon, Protozoology, 1926; courtesy
of Bailliere, Tindall & Cox.)
part they grow readily in culture media which must be kept free
from bacteria. Novy and MacNeal (1904) were the first to culti-
vate Trypanosoma in the condensation fluid of solid blood agar,
their method being somewhat simplified by Nicolle and now gener-
ECOLOGY, COMMENSALISM AND PARASITISM 367
ally used under the designation NNN agar medium. In this medium
the same strains of Leishmania have been (1925) maintained for up-
ward of fourteen years with hundreds of sub-cultures (Nicolle, 1925).
In a nutrient medium— digestive tract, blood, cell or artificial
medium— the normal, fully-developed flagellates reproduce by longi-
tudinal division. Blepharoplast and parabasal body are the first to
divide, then the nucleus in which the endobasal body initiates divi-
sion (Fig. 1(39, B and F). In some cases the old flagellum is retained
by one of the daughter cells, a new flagellum growing out from the
blepharoplast in the other cell. Multiple division of -kinetic ele-
ments and nuclei, without accompanying cell division— so-called
somatella formation— is characteristic of some types, particularly
during intracellular stages, e.g., Trypanosoma lewisi (Fig. 122, p. 234).
Reproduction by division is not confined to the fully-developed
flagellates but may occur in any phase. Thus the " crithidia forms "
or haptomonads of Trypanosoma may divide while attached to
host cells as do the Leishmania forms within cells. " Leptomonas
forms" (nectomonads) likewise divide.
The genus Leptomonas is the simplest of this family of parasitic
flagellates. It is represented by many species which are widely
distributed amongst insects and by one species in nematode worms
(L. biitschlii, Kent, in Triloba gracilis). Encystment occurs in the
digestive tract, the cysts passing out with the feces and infection
is contaminative. Only one host— invertebrate— is known.
Structural changes are simple, from the fully-developed necto-
monad with kinetic complex anterior to the nucleus, and long
flagellum, it becomes progressively shorter and loses its flagellum.
In this condition it may become attached to epithelial cells of the
gut and Malpighian tubes (haptomonads) or it may become still
smaller, develop a protecting covering and pass out with the feces.
Crithidia is a second genus of the family with only one host
(invertebrate) and causing infection by contamination through the
agency of cysts. It also is widely distributed amongst the insects
and particularly in Diptera. Structurally it is similar to Lepto-
monas with the kinetic complex anterior to the nucleus. The endo-
plasmic portion of the axial filament, however, passes to the margin
of the body and continues along that margin until it leaves the
body at the anterior end, thus giving the impression of a rudimentary
undulating membrane (Fig. 170). As in Leptomonas the swimming
nectomonad becomes progressively shorter, attaches by the flagellar
end to epithelial cells where it may reproduce by longitudinal divi-
sion. Large areas of the exposed surface of epithelial cells may be
covered in this manner thus hampering the functional activity of
these cells (Fig. 170, F).
Leishmania shows an interesting and important step in progres-
sive parasitism leading to serious, often fatal, diseases of man and
368
BIOLOGY OF THE PROTOZOA
other vertebrated animals. Like the two preceding genera it has
two significant phases— a nectomonad, Leptomonas-Yike, swimming
phase in the invertebrate gut and in the vertebrate blood, and a
quiescent phase equivalent to the haptomonads of Leptomonas and
Crithidia. Unlike these haptomonads, however, the quiescent phase
is not passed as celozoic forms on the outer surfaces of cells but
as cytozoic forms within the cells, not only of the gut, but of prac-
tically all types of cells throughout the body. This leads to cell
hypertrophy and disintegration with a corresponding upset of
function. •
Fig. 170. — Protomonads. A, B, Herpetomonas musca-domesticce; C, resting
stage of same; D, Crithidia subulata, nectomonad; E, resting forms of same; F,
haptomonads of same attached to epithelial cells; (d) basal bodies; (k) parabasal
body; (/) nucleus. (From Calkins after Prowazek and Leger.)
The fully-developed organism is of the Leptomonas type (Fig.
169, F; 170, D). This stage occurs in the digestive tract of inverte-
brate hosts and in the blood of vertebrates, also in cultures. As
cytozoic parasites they appear primarily in macrophages and other
blood elements, and in cells of the liver and spleen, where they mul-
tiply by division, a single cell often containing 100 or more (Fig.
169, E).
Early reports of the parasite interpreted them as spores of peculiar
organisms (macrophages) in the blood (Cunningham, 1885) or as
Sporozoa furunculosa (Firth, 1891). Their correct interpretation
ECOLOGY, COMMENSALISM AND PARASITISM 369
was given in 1903, following a remarkable series of clear-cut observa-
tions which appeared in rapid succession. On May 30, 1903,
Leishman published some observations, which he had made a couple
of years before on peculiar intracellular bodies found in cases of
dum dum fever. These he interpreted as evidence of trypano-
somiasis in India. On July 11th, Donovan observed peculiar bodies
in the peripheral blood of cases of kala azar. Preparations were
sent to Laveran and Mesnil who regarded the "Leishman bodies"
as similar to parasites (Babesia) of mammalian erythrocytes and
on November 3rd named the organism Piroplasma donovani. On
November 14th and 28th Ross published his conclusions that the
" Leishman-Donovan bodies" are not Trypanosomes (Leishman)
but a new type of organism which he named Leishmania. The cor-
rect name of the peculiar organism of dum dum fever or kala azar
was thus established as Leishmania donovan i. The series of observa-
tions was not yet complete, however, for in December, 1903, Wright
published the results of his study of a case of tropical ulcer which
was treated in a Boston hospital, and he named the organism
Helcosoma tropica. Its resemblance to the Leishman-Donovan
bodies was soon recognized, but skeptics refused to admit that the
" Leishman-Donovan- Wright bodies" are organisms and held that
they might be the results but not the causes of these diseases.
All such doubts were dispelled, however, in 1904 when Rogers
cultivated in vitro material taken from infected blood and spleen
cells and demonstrated the transformation of the disputed " bodies "
into actively moving flagellated parasites.
Further discoveries followed. Nicolle, in 1908, found a similar
organism in cases of infantile ulcer which he named Leishmania
infantum, and Vianna (1911) discovered the cause of a South
American disease known as espundia, which he named Leishmania
braziliensis.
Clinically there appear to be two types of human leishmaniasis —
visceral and cutaneous. The former is characteristic of dum dum
fever, also called kala azar (black sickness), the latter of infantile
ulcer, tropical ulcer and Brazilian leishmaniasis. Structurally
the several species are indistinguishable, but serologically L. donovani
and L. infantum are apparently the same, both differing from L.
tropica and L. braziliensis. In regard to the specificity of the last
two there is considerable difference of opinion. Reichenow-Doflein
accepts them as independent species while Wenyon considers the
evidence inconclusive. L. tropica is the cause of localized cutaneous
diseases which are widely distributed geographically and known as
Oriental sore, Delhi sore, Aleppo boil, Bagdad sore, tropical ulcer,
Nile ulcer, etc. i. braziliensis causes a similar localized initial
cutaneous sore, which heals, but some time later, it may be months,
the parasites reappear in the mucous membrane of mouth, nose
24
370 BIOLOGY OF THE PROTOZOA
and throat, and cause a shocking disease resembling the effects of
syphilis except that only soft parts are eaten away.
Infantile ulcer is also a cutaneous disease and differs from kala
azar, which is distinctly a visceral disease, yet serologically the
organisms involved are one species only. L. donovani antiserum
will agglutinate not only L. donovani but L. infantum as well, while
it will not affect L. tropica or L. braziliensis.
The parasites of kala azar occur in all possible parts of the infected
human organism as intracellular forms (Fig. 169, E). These are
small (2 ll to 4 ll), round, oval or pyriform bodies, each with a rela-
tively large, dense nucleus and a round, ellipsoidal or rod-like body—
the blepharoplast— in the cytoplasm. Division stages, 4 ll to 5 ll in
diameter, and with double nucleus and blepharoplast, are frequent,
showing active multiplication in this non-flagellated stage. They
are most numerous in the spleen, liver and bone-marrow but are
also plentiful in lymph glands, mesenteries, endothelial cells of
bloodvessels, gut wall and skin, but are comparatively rare in the
circulating blood where they may be found in macrophages and
other cells derived from the endothelial vascular walls. Typical
symptoms are irregular fever, anemia, reduced vitality, enormous
enlargement of the spleen and frequently of the liver also. Acute
cases if untreated usually end in death in a few months, and chronic
cases in a year or more.
Diseases due to L. tropica are much less severe and do not involve
the entire human organism, the sores, up to 1 inch in diameter,
healing spontaneously within a few months, leaving a characteristic
scar. They are usually on exposed portions of the body, e. g.,
hands, wrists, legs and face, and one infection usually confers
immunity (see p. 363).
South American leishmaniasis is more severe and the clinical
symptoms are different, involving not only an initial cutaneous
sore, but later infections of the mucous membrane of mouth, nose
and throat. The skin lesions are deeper and more persistent than
with L. tropica and multiple lesions are more frequent; Torres (1920),
for example, reported one South American case in which 248 distinct
sores occurred on various parts of the bodv (quoted from Wen von,
p. 426).
Formerly the majority of cases of leishmaniasis ended fatally;
today the great majority recover. This is due to treatment with
tartar emetic (or the corresponding sodium salt) which was first
used with success by Vianno in South American leishmaniasis and
later in the same year for cases of kala azar by Di Cristina and
Caronia in 1913. Other compounds of antimony have proved
useful in combatting resistant forms of Leishmania in spleen, bone-
marrow, etc. (see Wenyon, p. 423).
The transmission of Leishmania is far from established. Experi-
ECOLOGY, C0MMENSAL1SM AND PARASITISM 371
ments have shown indeed that L. donovani lives and multiplies in
the digestive tracts of various kinds of blood-sucking arthropods-
mosquitoes, sand flies, fleas and bed-bugs, but no experiments
involving transmission to man have been successful. With L.
tropica the evidence is more positive and numerous successful
experiments in producing skin ulcers from leptomonas forms in
sand flies of the genus Phlebotomus have led to the general belief
that this type of insect at least is capable of transmitting not only
L. tropica but L. braziliensis as well.
The genus Herpetomonas, while not a parasite of vertebrates, is
interesting in having a stage in which it resembles a trypanosome.
In this stage the axial filament, as a rhizoplast, runs along the
margin of the cell, without however raising the periplast to form
an undulating membrane (Fig. 169, B).
Trypanosoma, in its fully-developed phase, differs from related
forms of protomonads in having an undulating membrane, the
margin of which is formed by the axial filament of the flagellum
which ends in a free whip or terminates at the anterior end (Fig.
169, D, I). The axial filament arises posterior to the nucleus. Near
it is a conspicuous granule, homologized by Kofoid and his school
as a parabasal body. This, by use of the Feulgen nucleal reaction,
has been shown to contain thymonucleic acid (see p. US). The
combination of blepharoplast and parabasal is termed the kineto-
plast by Wenyon. The nucleus is usually spherical, with the
usual protomonad endosome lying in a clear space within a nuclear
membrane. The cytoplasm is usually clear and homogeneous but
contains volutin granules, as a rule, and a small vacuole frequently
lies near the kinetoplast. Reproduction is always by longitudinal
division which begins with the kinetoplast. The cell divides first at
the flagellar end, the posterior end with the kinetoplast dividing last.
These few structural characters afford very little basis for divi-
sion of the genus into species, while the numerous changes which
the same species may undergo in the course of its life history make
it still more difficult. Size is some help, the largest forms occurring
in cold-blooded vertebrates. Other characters are relative length
of flagellum, distance from kinetoplast to posterior end, rounded
or pointed posterior end, position of the nucleus, etc. The ten-
dency is to name a trypanosome according to the host in which it
is found provided there are no specific structural characters by
which it can be identified — such methods may swell the synonyms
but they are relatively harmless until the full life history is worked
out in each case.
The following list of species,1 while not complete, gives some idea
of the distribution of trypanosomes and of the enormous literature
on the subject:
1 Compiled from Wenyon, Protozoology; Biological Abstracts; Zoological Record,
and miscellaneous sources.
372 BIOLOGY OF THE PROTOZOA
Trypanosoma in Mammals.
Trypanosoma aconsys, in spiny mouse, Wenyon, 1909.
Trypanosoma acouchii, in agouti, Brimont, 1909.
Trypanosoma akodoni, in vole mouse, Carini and Maciel, 1915.
Trypanosoma annamense, in dog, Blin, 1902; ox, Schein, 1907; horse,
Blanchard, 1888; mule, same.
Trypanosoma arvicanthi, in A. barbarus, striped mouse, Delanoe, 1915.
Trypanosoma asini, in donkey, Dschunkowsky and Luhs, 1909.
Trypanosoma, avicularis, in L. zebra, striped mouse, Wenyon, 1909.
Trypanosoma bandicotti, in Nesokia gigantea, Lingard, 1904.
Trypanosoma berberum, in horse, Sergent, et al., 1912.
Trypanosoma brucei, in buffalo, Bruce, 1913; Felis (cat), Bruce, 1895; gnu
(wildebeeste), Bruce, 1897; Cephalophus grimms (duiker), Bruce, 1913;
reed-buck, Bruce, 1903; water-buck, Bruce, 1913; dog, Bruce, 1915;
donkey, Bruce, 1905; goat, Bruce, 1915; horse, Bruce, et al., 1895; hyena,
Bruce, 1895; mule, Bruce, et al., 1895; oribi, Bruce, 1913; ox, Bruce, 1895;
wart-hog, Bruce, 1913; pig, Macfie, 1916; stein-buck, Bruce, 1903; koodoo,
Bruce, 1895; eland, Tante, 1913; bush-buck, Bruce, 1899; Speke's ante-
lope, Duke, 1921; mpala, Kinghorn and Yorke, 1912; hartebeest, Bruce,
1913.
Trypanosoma camelensis, in camel, Yakimoff, Schokker and Koselkine, 1917.
Trypanosoma caprae, in reed-buck, Bruce, 1913; water-buck, same; goat,
Kleine, 1910; oribi, Bruce, 1913; sheep, Fehlandt, 1911; koodoo, Bruce,
1914; eland, Bruce, 1913; bush-buck, same; mpala, Bruce, 1914.
Trypanosoma cazalboui (= T. vivax?), in reed-buck, Rodhain, et al., 1913;
puku, same; dog, same; donkey, Bouffard, 1907; goat, Bonet, 1908; roan
antelope, Rodhain, et al., 1913; ox, Cazalbou, 1904; sheep, Bonet, 1908;
koodoo, Rodhain, et al., 1913; bush-buck, same.
Trypanosoma cephalophi, duiker, Bruce, 1912.
Trypanosoma citelli, in Citellus richardsoni (ground squirrel), Watson, 1912.
Trypanosoma clevei, in Midas midas (vellow-banded marmoset), Leger and
Pettit, 1909.
Trypanosoma congolense, in buffalo, Bruce, 1913; camel, Broden, 1906;
duiker, Kinghorn and Yorke, 1912; reed-buck, Bruce, 1913; water-buck,
same; dog, Martin, et al., 1908; donkey, Broden, 1904; goat, Martin,
et al., 1909; puku, same; roan antelope, Kinghorn and Yorke, 1912; horse,
Bruce, 1914; hyena, Bruce, 1913; mule, Hornby, 1919; ox, Broden, 1906;
wart-hog, Bruee, 1913; pig, Bruce, 1914; eland, same; bush-buck,
Kinghorn and Yorke, 1912; mpala, Bruce, 1914.
Trypanosoma cricetuli, in Cricetulus griseus, Patton and Hindle, 1926.
Trypanosoma crocidurae, in Crocidura rursula, shrew, Brumpt, 1932.
Trypanosoma cruzi = Schizotrypanwn cruzi, in Chrvsothrix sciurcus,
Chagas, 1909; armadillo, Chagas, 1912; Torres, 1915.
Trypanosoma dendromysi, in Dendromys sp., Rodhain, 1915.
Trypanosoma denisi, in spiny-tailed flying squirrel, Rodhain, et al., 1912.
Trypanosoma dimorphon, in dog, Martin, 1906; donkey, Martin, 1906;
goat, same; horse, Dutton and Todd, 1903; mule (= T. congolense?),
Martin, 1906; ox, same; pig, same; sheep, same; bush-buck, Dutton,
et al, 1907.
Trypanosoma dutton i, in Rattus muris, Thiroux, 1905.
Trypanosoma eburneense, in Rattus chocha, Delanoe, 1915.
Trypanosoma elephantis (= T. brucei?), in elephant, Bruce, 1909.
Trypanosoma equinum, in donkey, Vital, 1907; horse, Voges, 1901; capybara,
Lutz, 1907.
ECOLOG Y, COMMENSALISM A ND PA RASI TISM 373
Trypanosoma equiperdum, in donkey, Schneider and Bouffard, 1899; horse,
Rouget, 1896.
Trypanosoma evansi, in dog, Lingard, 1894; donkey, Evans, 1880; elephant,
same; buffalo, Lingard, 1899; camel, Evans, 1880.
Trypanosoma evatomys, in Evatomys saturatus, Hadwen, 1912.
Trypanosoma gambiense, in Cercopithecus pygerythrus, Bruce, 1911 ; Cercop.
sp., Koch, 1909; goat, Klein and Eckard, 1913; ox, Bruce, 1911; sheep,
Klein and Eckard, 1913; Speke's antelope, Duke, 1912; Man, Dutton,
1902.
Trypanosoma grosi, in Mus sylvaticus (Apodermus svl.), Laveran and
Pettit, 1909.
Trypanosoma heybergi, in Nycteris hispida, Rodhain, 1932.
Trypanosoma hippicum, in horse, Darling, 1910; mule, same.
Trypanosoma indicum, in palm squirrel, Llihe, 1906.
Trypanosoma ingens, in duiker, Bruce, 1912; reed-buck, Bruce, 1909; water-
buck, Bruce, 1914; puku, Rodhain, et al., 1913; oribi, Bruce, 1913; ox,
Bruce, 1909; bush-buck, same; Speke's antelope, Duke, 1912.
Trypanosoma korssaki, in striped field mouse, Yakimoff, et al., 1910.
Trypanosoma legeri, in Tamandua triclactyla, Mesnil and Brimont, 1910.
Trypanosoma lesourdi, in spider monkey, Leger and Porry, 1918.
Trypanosoma lewisi, var. primatum, in monkey, Reichenow, 1917; gorilla,
same; chimpanzee, same; brown rat, Lewis, 1879; Rattus macleari,
Durham, 1908; R. maurus, Martin, et al., 1909; potts, Reichenow, 1917;
gerbil, Fantham, 1926.
Trypanosoma marocanum, in horse, Sergent, et al., 1915.
Trypanosoma megadermae, in Lavia frons (African bat), Wenyon, 1909.
Trypanosoma melophagium, in sheep, Woodcock, 1910.
Trypanosoma microti, in Microtus arvalis (field vole), Laveran and Pettit,
1909.
Trypanosoma minasense, Hapale penieillata, Dios Zuccarini and Werngren,
1925; marmoset, Chagas, 1908-1909.
Trypanosoma montgomeryi, in dog, Kinghorn and Yorke, 1912; ox, Mont-
gomery and Kinghorn, 1909.
Trypanosoma morinorum, in bat, Hipposidesus tridens, Leger and Baurv,
1923.
Trypanosoma morocanum, in dog, Delanoe, 1920.
Trypanosoma multiforme, in bush-buck, Kinghorn and Yorke, 1912.
Trypanosoma musculi, in Mus musculi, Pricoli, 1906.
Trypanosoma myoxi, in dormouse, Blanchard, 1903.
Trypanosoma nabiasi, in rabbit (Europe), Railliet, 1895.
Trypanosoma nicolleorum, in long-eared bat, Sergent, 1905.
Trypanosoma ninae, in camel, Yakimov, 1922.
Trypanosoma otospermophili, in ground squirrel, Wellman and Wherry, 1910.
Trypanosoma pecaudi (= T. brucei?), in dog, Bonet, 1908; donkey, Cazal-
bou, 1910; goat, Pecaud, 1909; horse, Cazalbou, 1900; mule, Bouffard,
1908; ox, Cazalbou, 1910; sheep, Pecaud, 1909; camel, Balfour, 1909;
pig, Bonet, 1908.
Trypanosoma peromysei, in American field mouse, Watson, 1912.
Trypanosoma pestani, in Meles meles (badger), Bettencourt and France,
1905.
Trypanosoma petrodromi, in elephant shrew, Bruce, 1915.
Trypanosoma phyllostomae, in So. American bat, Cartaya, 1910.
Trypanosoma proioazeki, in ouakari monkey, Gonder and B. Gossher, 1908.
Trypanosoma rabinowitschi, in common hamster, Cricetus cricetus, Brumpt,
1906.
Trypanosoma rhesii in Macacus rhesus, Terry, 1911.
374 BIOLOGY OF THE PROTOZOA
Trypanosoma rhodesiense (= T. brucei?), Stephens and Fantham, 1910.
Trypanosoma simiae, in wart-hog, Bruce, 1913.
Trypanosoma soricis, in shrew (Canada), Had wen, 1912.
Trypanosoma species, in Steatomys pratensis (fat mouse), Plimmer, 1912.
Trypanosoma species, in bush-buck, Dutton, et ah, 1906.
Trypanosoma species, in chevrotain, Dodd, 1912.
Trypanosoma species, in striped bat, Iturbe and Gonzalez, 1916.
Trypanosoma species, in howling monkey, Brimont, 1909.
Trypanosoma species, in hartebeest, Montgomery and Kinghorn, 1908.
Trypanosoma species, in hippopotamus, Kleine and Tante, 1911.
Trypanosoma species, in sable antelope, Week, 1914.
Trypanosoma species, in lion, Week, 1914; monkey, Mathis and Leger, 1911.
Trypanosoma species, in Cercopithecus schmidti, Dutton, Todd and Tobey,
1906.
Trypanosoma species, in serval, Week, 1914.
Trypanosoma species, in reed-buck, Kleine and Fischer, 1911; water-buck,
same.
Trypanosoma species, in little hamster, Cricetulus migratorius, Finkelstein,
1907.
Trypanosoma species, in Choloepus didactylus (two-toed sloth), Mesnil and
Brimont, 1908; also Endotrypanum schaudinni (Mesnil and Brimont,
1908).
Trypanosoma species, in gnu (Connochaetes gnu = wildebeeste), Week, 1914.
Trypanosoma species, in guinea-pig (Cavia porcellus), Kunstler, 1883.
Trypanosoma species, in Spermophilus evessmanni, Laveran, 1911.
Trypanosoma sudanense, in donkey, Roger and Greffulke, 1905; in horse,
Chauvrat, 1892.
Trypanosoma talpae, in mole, Franca, 1911.
Trypanosoma theileri, in duiker, Rodhain, Pons, et al., 1912; reed-buck,
Kleine and Fischer, 1911 ; roan antelope, Rodhain, et ah, 1913; ox, Theiler,
1902; bush-buck, Dutton, et al, 1906.
Trypanosoma togolense, in donkey, Schilling, 1901; horse, same; ox, same.
Trypanosoma tragelaphi, in Speke's antelope, Duke, 1912.
Trypanosoma uniforme, in buffalo, Duke, 1913; water-buck, same; ox, Bruce,
1911; bush-buck, Duke, 1912; Speke's antelope, Duke, 1912 and 1923.
Trypanosoma venezuelense, in dog, Rangel, 1905; donkey, Tejera, 1920;
capybara, Tejera, 1920; mule, same; howler monkey, same.
Trypanosoma vespertilionis, Miniopterus schreibersi (bat), Battaglia, 1904;
Dionisi, 1899; long-eared bat, Bettencourt and Franca, 1905; Sergent,
1905.
Trypanosoma vivax, in buffalo, Duke, 1913; duiker, Kinghorn and Yorke,
1912; reed-buck, Connal, 1917; water-buck, Kleine and Fischer, 1911;
donkey, Hornby, 1919; goat, Ziemann, 1905; roan antelope, Duke, 1923;
horse, Yorke and Blacklock, 1911; mule, Hornby, 1919; ox, Ziemann,
1905; sheep, same; bush-buck, Bruce, 1911; Speke's antelope, Duke, 1912.
Trypanosoma xeri, in Ethiopian ground squirrel, Leger and Baury, 1922.
Trypanosomes in Birds.
Trypanosoma anellobiae, in honey-sucker, Johnston, 1910; crow, oriole and
fly-catcher, Cleland and Johnston, 1911.
Trypanosoma ardeae, var. major, in Florida heron, Leger, 1918; goliath
heron, Rodhain, et al., 1913.
Trypanosoma asturinulae, in hawk, Stephens and Christophers, 1908.
Trypanosoma avium, in roller, Danilewsky, 1885; tawny owl, same; hang-
nest, Novy and MacNeal, 1905.
ECOLOGY, COMMENSALISM AND PARASITISM 375
Trypanosoma bicanistis, in hornbill, Stephens and Christophers, 1908.
Trypanosoma bouffardi, in weaver bird, Leger and Blanchard, 1911.
Trypanosoma bramae, in Indian little owl, Stephens and Christophers, 1908.
Trypanosoma brimonti, in bulbul, Mathis and Leger, 1910.
Trypanosoma calmdtei, in domestic fowl, Mathis and Leger, 1909.
Trypanosoma caprimulji, in nightjar, Kerandel, 1909.
Trypanosoma catharisti, in black vulture, Mesnil, 1912.
Trypanosoma chouqueti, in tiger bittern, Mathis and Leger, 1911.
Trypanosoma columbae, in pigeon, Stephens and Christophers, 1908.
Trypanosoma confusum, in hang-nest, Luhe, 1906; jay, robin and hang-nest,
Luhe, 1906; honey-sucker, Cleland and Johnston, 1911.
Trypanosoma corvi, in jackdaw, Stephens and Christophers, 1908.
Trypanosoma cotyli, in sand martin, Franchini, 1923.
Trypanosoma cypseli, in swift, Franchini, 1923.
Trypanosoma, dabbenei, in Chamaeza brevicauda, Mazza, et al., 1927.
Trypanosoma eurystomi, in roller, Kerandel, 1909, 1912.
Trypanosoma franchinii, in Xyphocolaptes major, Mazza and Fiora, 1930.
Trypanosoma francolini, in francolin, Kerandel, 1912.
Trypanosoma fringillinarum, in chaffinch, Woodcock, 1910; finch, same.
Trypanosoma gallinarum, in domestic fowl, Bruce and Coles, 1911.
Trypanosoma guyanense, in hawk, Mesnil, 1912.
Trypanosoma hannai, in rock pigeon, Pittaluga, 1904; pigeon, Mello and
Braz de Sa, 1916.
Trypanosoma johnstoni, in weaver finch, Dutton and Todd, 1903.
Trypanosoma lagonostictae, in weaver finch, Murallaz, 1914.
Trypanosoma langeroni, in Cerchneis spavesius, Mazza and Fiora, 1930.
Trypanosoma laverani, in American goldfinch, Novy and MacNeal, 1905;
rock sparrow, Leger, 1913.
Trypanosoma liothricis, in babbler, Laveran and Marullaz, 1914.
Trypanosoma loxiae, in crossbill, Noller, 1920.
Trypanosoma mathisi, in martin, Sergent, 1904, 1907.
Trypanosoma mayae, in house sparrow, Maya and David, 1912.
Trypanosoma mesnili, in American buzzard, Novy and MacXeal, 1905.
Trypanosoma milvi, in kite, Stephens and Christophers, 1908.
Trypanosoma moral, in Bubulcus ibis, da Silva, 1927.
Trypanosoma noctuae, in little owl, Schaudinn, 1904.
Trypanosoma numidae, in guinea fowl, Wenyon, 1909.
Trypanosoma nyctecoracis, in night heron, Stephens and Christophers, 190S.
Trypanosoma paddae, in weaver bird, Laveran and Mesnil, 1904.
Trypanosoma pedrozi, in Sclater's currasow, Carini and Botelho, 1914.
Trypanosoma palyplertri, in peacock pheasant, Vassal, 1905.
Trypanosoma pycnonoti, in bulbul, Kerandel, 1912.
Trypanosoma schistochlamydis, in tanager, Splendore, 1910.
Trypanosoma syrnii, in tawny owl, Noller, 1917.
Trypanosoma species, in crested lark, Sergent, Ed., et al., 1904.
Trypanosoma species, in weaver finch, Fantham, 1919.
Trypanosoma species, in waxwing, Ogawa, 1911.
Trypanosoma species, in bulbul, Zupitza, 1909.
Trypanosoma species, in meadow pipit, Nieschulz, 1921.
Trypanosoma species, in hang-nest, Carini and Maciel, 1916.
Trypanosoma species, in swift, Franchini, 1923.
Trypanosoma species, in green heron, Leger, A. and M., 1914.
Trypanosoma species, in buff-backed heron, Zupitza, 1909.
Trypanosoma species, in heron (Florida caerula), de Cerquiera, 1906.
Trypanosoma species, in egret, de Cerquiera, 1906.
Trypanosoma species, in Formosan birds, Ogawa and Uegaki, 1927.
376
BIOLOGY OF THE PROTOZOA
Trypanosoma
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in goliath heron, Rodham, el al., 1913.
in yellow bittern, Mathis and Leger, 1911.
in argus pheasant, Z. S., 1925.
in owl, Mathis and Leger, 1911.
in little owl, Franchini, 1924.
in ant-bird, Carini and Botelho, 1914.
in Siberian eagle owl, Boing, 1925.
in green heron, Rodhain, et al., 1913.
in hornbill, Ringenbach, 1914.
in hornbill, Ross, 1911.
in red-legged partridge, Plimmer, 1912.
in goldfinch, Sergent, 1910.
in kestrel, Boing, 1925.
in cuckoo, Martin, et al., 1909.
in bower bird, Breinl, 1913.
in golden cuckoo, Zupitza, 1909.
in bird of paradise, Plimmer, 1915.
in sun-bird, Leger, A. and M., 1914.
in marsh harrier, Boing, 1925.
in shama, Plimmer, 1914.
in hawfinch, Bettencourt and Franga, 1907.
in Japanese hawfinch, Ogawa, 1911.
in woodpecker, Novy and MacNeal, 1905.
in wood-pigeon, Boing, 1925.
in magpie, Plimmer, 1912.
in crow, Mine, 1914.
in house crow, Donovan.
in turaco, Minchin, 1910.
in quail, Franchini, 1924.
in hairy woodpecker, Novy and MacNeal, 1905.
in kite, Bettencourt and Franca, 1907.
in yellow hammer, Petrie, 1905.
in redstart, Nieschulz, 1921.
in robin, Bettencourt and Franga, 1907.
in weaver finch, Fantham, 1919.
in waxbill, Plimmer, 1912.
in falcon, Breinl, 1913.
in kestrel, Wasielewski, 1908.
in francolin, Plimmer, 1912.
in francolin, Ross, 1911.
in francolin, Todd and Wolbach, 1912.
in goldfinch, Sergent, 1904.
in linnet, Sergent, 1904.
in common jay, Bettencourt and Franga, 1907.
in jay, Ogawa, 1911.
in dove, Maya and David, 1912.
in owl, Leger, A. and M., 1914.
in ant-bird, Carini and Botelho, 1914.
in guinea fowl, Keysselitz and Mayer, 1909.
in kingfisher, Zupitza, 1909.
in kite, Breinl, 1913.
in mocking bird, Novy and MacNeal, 1905.
in swallow, Petrie, 1905.
in shrike, Neave, 1906.
in red-back shrike, Sj 6b ring, 1899.
in parrot, Plimmer, 1913.
ECOLOGY, COMMENSALISM AND PARASITISM 377
Trypanosoma species, in black game, Boing, 1925.
Trypanosoma species, in bee-eater, Zupitza, 1909.
Trypanosoma species, in American song sparrow, Novy and MacNeal, 1905.
Trypanosoma species, in bee eater, Minchin, 1910.
Trypanosoma species, in blackbird, Petrie, 1905.
Trypanosoma species, in wagtail, Bettencourt and Franga, 1907.
Trypanosoma species, in sunbird, Zupitza, 1909.
Trypanosoma species, in vulture, Neave, 1906.
Trypanosoma species, in house sparrow, Novy and MacNeal, 1905.
Trypanosoma species, in tree sparrow, Mine, 1914.
Trypanosoma species, in sparrow, Sergent, Ed. and Et., 1904.
Trypanosoma species, in warbler, Bettencourt and Franca, 1907.
Trypanosoma species, in warbler (willow), Nieschultz, 1921.
Trypanosoma species, in tyrant bird, Carini and Botelho, 1914.
Trypanosoma species, in wood-shrike, Rodhain, et al., 1913.
Trypanosoma species, in gray parrot, Zupitza, 1909.
Trypanosoma species, in fire-crested wren, Bettencourt and Franca, 1907.
Trypanosoma species, in black redstart, Bettencourt and Franca, 1907.
Trypanosoma species, in wheat ear, Nieschulz, 1921.
Trypanosoma species, in woodcock, Bettencourt and Franga, 1907.
Trypanosoma species, in barn owl, Bettencourt and Franga, 1907.
Trypanosoma species, in tanager, de Cerqueira, 1906.
Trypanosoma species, in stork, Migone, 1916.
Trypanosoma species, in ibis, Migone, 1916.
Trypanosoma species, in harpy, Iturbe and Bonzalez, 1916).
Trypanosoma species, in fruit pigeon, Wellman, 1905.
Trypanosoma species, in wren, Novy and MacNeal, 1905.
Trypanosoma species, in song thrush, Petrie, 1905.
Trypanosoma species, in ring ousel thrush, Nieschulz, 1921.
Trypanosoma species, in hoopu, Bettencourt and Franga, 1907.
Trypanosoma species, in weaver finch, Leger, A. and M., 1914.
Trypanosoma thiersi, in nightjar, Leger, 1913.
Trypanosoma tinami, in timamu, Mesnil, 1912.
Trypanosoma viduae, in weaver finch, Kerandel, 1909.
Trypanosoma zonotrichae, in finch, Splenclore, 1910.
Trypanosomes in Lizards.
Trypanosoma boueti, in Mabuia raddonii, Martin, 1907.
Trypanosoma chamaelonis, in Chamaeleon vulg., Wenyon, 1909.
Trypanosoma gallayi, in Psilodactylus caudacinctus, Bonet, 1909.
Trypanosoma hemidactyli, in Hemidactjdus gl., Mackie, et al., 1923.
Trypanosoma leschenaulti , in Hemidactylus leschen., Robertson, 190S.
Trypanosoma mabuiae, in Mabuia quinquetaeniata, Wenyon, 1909.
Trypanosoma martini, in Mabuia maculilabris, Bonet, 1909.
Trypanosoma pertenue, in Hemidactylus tri., Robertson, 1908.
Trypanosoma platydactyli, in Tarentola mauritanica, Catonillard, 1909;
= T. mauritanica, Chatton and Blanc, 1915.
Trypanosoma rudolphi, in Mabuia agilis, Carini, 1913.
Trypanosoma species, in Acanthosaura, Mathis and Leger, 1911.
Trypanosoma species, in Agama col., Todd and Wolbach, 1912.
Trypanosoma species, in Lvgosoma taeniolatum, Johnston and Cleland,
1910.
Trypanosomes ix Snakes.
Trypanosoma brazili, in Helicops modestus, Brumpt, 1914, 1915.
Trypanosoma clozeli, in Grayia smythii, Bonet, 1909; Tropidonotus ferox,
378 BIOLOGY OF THE PROTOZOA
Trypanosoma erythrolampris, in Erythrolamprus aeschulapii, Wenj'on, 1909.
Trypanosoma najae, in Naja nigricollis, Wenyon, 1909.
Trypanosoma phylodriasi, in Brazilian snake P. natteri, Pessoa, 1928.
Trypanosoma primati, in Hypsichina chinensis, Mathis and Leger, 1909;
Tropidonotus piscator, same, 1911.
Trypanosoma species, in Bitis aretans, Dutton, et al., 1907.
Trypanosoma species, in Diemenia textilis, quoted from Cleland and
Johnston, 1910.
Trypanosoma species, in Rhadinaea mersemii, Brumpt, 1914.
Trypanosomes in Crocodiles.
Trypanosoma kochi, in Crocodilus niloticus, Laveran and Mesnil, 1912.
Trypanosoma spermophili, in Crocodilus catophractus, Dutton, et al., 1907.
Trypanosomes in Turtles.
Trypanosoma chelodina, in Chelodina longicollis, Johnson, 1907.
Trypanosoma damoniae, in Damonise reevesii, Laveran and Mesnil, 1902.
Trypanosoma leroyi, in Cinixys homeana, Commes, 1919.
Trypanosoma pontyi, in Sternothaerus derbianus, Bonet, 1909.
Trypanosoma vittatae, in Emyda vittata, Robertson, 1908.
Trypanosomes in Frogs, Toads and Salamanders.
Trypanosoma borelli, in Hyla rubra, Marchoux and Salimbeni, 1907; also
in fish, species of Leuciscus, Keysselitz, 1906.
Trypanosoma diemyctili, in Xolge viridiscens, Tobey, 1906.
Trypanosoma hendersoni, in Rana tigrina, Patton, 1908.
Trypanosoma hylae, in Hyla arborea, Franca, 1908.
Trypanosoma inopinatum, in Rana esculenta, Sergent, 1904.
Trypanosoma karyozeukton, in Bufo regularis, Dutton and Todd, 1903; in
Rana sp., Martin, et al, 1909.
Trypanosoma leptodactyli, in Leptodactylus occelatus, Carini, 1907.
Trypanosoma mega, in Bufo regularis, Dutton and Todd, 1903; in Bufo sp.,
Minchin, 1910.
Trypanosoma nelsprutense in Rana sp., Laveran, 1904.
Trypanosoma neveu-lemairei, in Rana esculenta, Brumpt, 1928.
Trypanosoma parroti, in Discoglossus pictus, Brumpt, 1923, 1928.
Trypanosoma parvum, in Rana clamata, Kudo, 1922.
Trypanosoma rotatorium, in Bufo regularis, Balfour, 1909; in Hyla arborea,
Danilewsky, 1885, 1888; in Hyla lesueurii, Cleland and Johnston, 1911;
in Leptodactylus occelatus, Machado, 1911; in Rana clamata, Kudo,
1922; Rana tigrina, Patton, 1908.
Trypanosoma sergenti, in Discoglossus pictus, Brumpt, 1923.
Trypanosoma species, in Bufo melanostictus, Mathis and Leger, 1911.
Trypcmosoma species, in Bufo reticulatus, Brumpt, 1906.
Trypanosoma species, in Bufo sp., Stevenson, 1911.
Trypanosoma species, in Bufo vulgaris, Grassi, 1881, 1883.
Trypanosoma species, in Formosan frogs, Ogawa and Uegaki, 1927.
Trypanosoma species, in Hyla arborea, Wedl, 1850.
Trypanosoma species, in Hyla nasuta, Bancroft, 1890.
Trypanosoma species, in Hyla venulosa, Plimmer, 1912.
Trypanosoma species, in Limnodynastes omatus, Cleland and Johnston,
1911.
ECOLOGY, COMMENSALISM AND PARASITISM 379
Trypanosoma species, in Limnodynastes tasmaniensis. Cleland and John-
ston, 1911.
Trypanosoma species, in Microhyla pulchra, Mathis and Leger, 1911.
Trypanoso?na species, in Rana angolensis, Laveran, 1904.
Trypanosoma species, in Rana catesbiana, Hegner, 1920.
Trypanosoma species, in Rana clamata, Hegner, 1920.
Trypanosoma species, in Rana galamensis, Dutton, et al., VMM .
Trypanosoma species, in Rana guentheri, Mathis and Leger, 191 1 .
Trypanosoma species, in Rana hexadactyla, Dobell, 1910.
Trypanosoma species, in Rana limnocharis, Mathis and Leger, 1911.
Trypanosoma species, in Rana mascariensis. Dutton, et al., 1907.
Trypanosoma species, in Rana oxyrhynchus, Dutton, et al., 1907.
Trypanosoma species, in Rana rugosa, Koidzumi, 1911.
Trypanosoma species, in Rana temporaria, Danilewsky, 1885.
'Trypanosoma species, in Rana trinodis, Dutton and Todd, 1903.
Trypanosoma species, in Rappia marmorata, Dutton, et al., 1907.
Trypanosoma species, in Rhacophorus leucomystax. Mathis and Leger, 1911.
Trypanosoma tritonis, in Molge pyrrhogastra, Ogawa, 1914.
Trypanosoma tumida, in liana nutti, Awerinzew, 1918.
Trypanosomas in Fish.
Trypanosoma abramidis, in common bream, Laveran and Mesnil, 1904.
Trypanosoma acerinae, in ruff, Brumpt, 1906.
Trypanosoma aeglefini, in haddock, Henry, 1913.
Trypanosoma albopunctatus, in Plecostomus sp., da Fonseca and Vaz, 1928.
Trypanosoma anguillicola, in eels, Johnston and Cleland. 1910.
Trypanosoma bancrofti, in Copidoglanis tandanus, Johnston and Cleland,
1910.
Trypanosoma barbae, in Barbus barbus, Brumpt, 1900.
Trypanosoma barbatulae, in loach, Leger, 1904.
Trypanosoma blenniclini, in Blennius cornutus, Fantham, 1930.
Trypanosoma bliccae, in Blicca bjoerkna, Nixitan, 1929.
Trypanosoma bothi, in Bothus rhombus, Lebailly, 1905.
Trypanosoma callionymi, in Callionymus lyra, Brumpt and Lebailly, 1904.
Trypanosoma capigobii, in Gobius nudicep, Fantham, 1919.
Trypanosoma carassii, in Carassius carassius, Mitrophanov, Ins:;.
Trypanosoma carchariasi, in Carcharias sp., Laveran, 1908.
Trypanosoma catapracti, in pogge, Henry, 1913.
Trypanosoma chagasi, in Plecostomus punctatus, Horta, 1910.
Trypanosoma chetostomi, in Chetostoma sp., da Fonseca and Vaz, 1929.
Trypanosoma clarii, in Clarias macrocephalus, Montel, 1!)05.
Trypanosoma cobitis, in giant loach, Mitrophanov, 1883.
Trypanosoma cotti, in Cottus bubalis, Brumpt and Lebailly, 1904.
Trypanosoma danilewskyi, in common carp, Laveran and Mesnil, 1904.
Trypanosoma delagei, in Blennius pholis, Brumpt and Lebailly, 1904.
Trypanosoma dohrni, in Bolea monschir, Yakimoff, 1911.
Trypanosoma dorbignyi, in Rhinodorus dorbignii, da Fonseca and Vaz, 1928.
Trypanosoma elegans, in Gobio gobio, Brumpt, 1906.
Trypanosoma ferreirae, in Characinus sp., da Fonseca, et al., 1928.
Trypanosoma flesi, in Flesus vulgaris, Lebailly, 1904.
Trypanosoma francirochai ', in Otocinclus franciroehai, da Fonseca and Ymz,
1928.
Trypanosoma giganteum, in long-nosed skate, Neumann, 1909.
Trypanosoma gobii, in rock goby, Brumpt and Lebailly, 1904.
380 BIOLOGY OF THE PROTOZOA
Trypanosoma granulosum, in Anguilla sp., Franga, 1908; in A. vulgaris,
Laveran and Mesnil, 1902.
Trypanosoma hypostomi, in Plegostomus auroguttatus, Splendore, 1910.
Trypanosoma langeroni, in bullhead, Brumpt, 1906.
Trypanosoma larai, in Prochilodus sp., da Fonseca, 1929.
Trypanosoma laternae, in Platophryo laterna, Henry, 1913; in Arnoglossus,
Lebailly, 1904.
Trypanosoma leucisci, in roach, Coles, 1914; Brumpt, 1906.
Trypanosoma limandae, in dab, Brumpt and Lebailly, 1904.
Trypanosoma loricariae, in Loricaria sp., da Fonseca and Vaz, 1928.
Trypanosoma luciopercae, in Lucioperca volgensis, Nixitan, 1929.
Trypanosoma macrodonis, in Macrodon trahira, Bothelho, 1907.
Trypanosoma margaritiferi, in Plecostomus margaritifer, da Fonseca and
Vaz, 1928.
Trypanosoma murmanensis, in Gadus callarias, Nixitan, 1929.
Trypanosoma nudigobii, in Gobius nudiceps, Fantham, 1919.
Trypanosoma pelligrini, in paradise fish, Mathis and Leger, 1911.
Trypanosoma percae, in perch, Brumpt, 1906.
Trypanosoma phoxini, in minnow, Brumpt, 1906.
Trypanosoma piracicaboe, in Loricaria piracicaboe, da Fonseca, 1929.
Trypanosoma piavae, in Characinus sp., da Fonseca, 1928.
Trypanosoma platessae, in plaice, Lebailly, 1904.
Trypanosoma plecostomi, in Plecostomus sp., da Fonseca and Vaz, 1928.
Trypanosoma rajae, in skate, Coles, 1914; ray, Laveran and Mesnil, 1902.
Trypanosoma regani, in Plecostomus regani, da Fonseca, 1928.
Trypanosoma remaki, in pike, Laveran and Mesnil, 1901; pickerel, Kudo,
1921; Esox reticulatus, Kudo, 1921.
Trypanosoma rhamdiae, in Rhamdia queleni, Botelho, 1907.
Trypanosoma roulei, in Monopterus javanensis, Mathis and Leger, 1911.
Trypanosoma sacchobranchi, in Saccobranchus fossilis, Castellani and
Willey, 1905.
Trypanosoma scardinii, in rudd, Brumpt, 1906.
Trypanosoma scorpaenae, in Scorpaena ustulata, Neumann, 1909.
Trypanosoma simondi, in Auchenoglanis biscutatus, Leboeuf and Ringen-
bach, 1910.
Trypanosoma scylii, in Scy Ilium canicula, Laveran and Mesnil, 1902.
Trypanosoma solae, in common sole, Laveran and Mesnil, 1901.
Trypanosoma species, in climbing perch, Mathis and Leger, 1911.
Trypanosoma species, in Bagrus bayad, Neave, 1906.
Trypanosoma species, in Barbus carnaticus, Lingard, 1903.
Trypanosoma species, in Box salpa, Fantham, 1919.
Trypanosoma species, in Carassius auratus, Petrie, 1905.
Trypanosoma species, in Chrysichthys auratus, Wenyon, 1909.
Trypanosoma species, in Clarias angolensis, Dutton, et al., 1906.
Trypanosoma species, in Clarias sp., Zupitza, 1909.
Trypanosojna species, in Dentex argurozona, Fantham, 1919.
Trypanosoma species, in Etroplus maculatus, Patton, 1908.
Trypanosojna species, in Formosan fish, Ogawa and Uegaki, 1927.
Trypanosoma species, in Gobius giurus, Castellani and Willey, 1905.
Trypanosoma species, in Labio falcipinnis, Rodhain, 1907.
Trypanosoma species, in Lichia amia, Fantham, 1919.
Trypanosoma species, in Lota lota, Keysselitz, 1906.
Trypanosoma species, in Macrones cavasius, Castellani and Willey, 1905.
Trypanosoma species, in Macrones seenghala, Lingard, 1904.
Trypanosoma species, in electric eel, Rodhain, 1907.
Trypanosojna species, in Mugil sp., Neave, 1906.
ECOLOGY, COMMENSALISM AND PARASITISM 381
Trypanosoma species, in Polypterus sp., Neave, 1906.
Trypanosoma species, in serpent head, Mathis and Leger, 1911.
Trypanosoma species, in Siluris glanis, Keysselitz, 1906.
Trypanosoma squalii, in Squalus cephalus, Brumpt, 1906.
Trypanosoma strigaticeps, in Plecostomus strigaticeps, da Fonseca and Vaz,
1928.
Trypanosoma synodontis, in Synodontis notatus, Leboeuf and Ringenbach,
1910.
Trypanosoma tincae, in tench, Laveran and Mesnil, 1904.
Trypanosoma toddi, in Clarias anguillaris, Bonet, 1909.
Trypanosoma torpedinis, in torpedo, Sabarex and Muratet, 1908.
Trypanosoma triglae, in tubfish, Neumann, 1909.
Trypanosoma yakimovi, in pipefish, Wladimiroff, 1910.
Trypanosoma zungaroi, in Pseudopimelodus zungaro, da Fonseca and Vaz,
1928.
This formidable list of species of trypanosomes is not complete,
but zoologically more than nine-tenths of these are probably
synonyms. A useful purpose is served by the mere mention of a
species of trypanosome in a new host, and until the life history of
each is worked out the synonym may be ignored.
The term Trypanosoma was first used by Gruby (1843) as a
generic name for blood parasites which, earlier, were regarded as
amebae. Little attention was paid to the genus until mammalian
trypanosomes wrere discovered. Attention was particularly drawn
to these by Lewis, studying rats in Bombay as a possible means of
distributing the plague, when he found active organisms in the
blood. Smears were made and sent to Saville Kent for identifica-
tion. Still more important was the discovery of a mammalian
disease associated with trypanosomes in the following year by
Evans, who found peculiar organisms in the blood of horses and
mules in India with a disease called surra. Smears were likewise
sent to Kent who identified them as the same organism as that found
by Lewis, and he included them both in his genus Herpetomonas,
species leivisi. The correct interpretation of these as Trypanosomes
followed a few years later. A great advance was made by Bruce,
in 1893, who demonstrated the agency of tsetse flies (Glossina mor-
sltans) in transmitting the disease nagana to cattle, while human
trypanosomiasis and its transmission by tsetse flies (Glossina pal-
palis) was fully established by the observations on Gambia fever
of Forde (1901), Button (Tryp. gambiensi) (1902), of Castellani
who was the first to see trypanosomes in sleeping sickness; and of
Bruce (1903) who showed that Gambia fever is an initial stage of
sleeping sickness, and that, like nagana, the trypanosome is trans-
mitted by a tsetse fly. Later discoveries showed the presence of
trypanosomes in every group of vertebrates (see list, p. 372), many
of them producing fatal diseases, while transmission by various
kinds of invertebrate hosts— sand flies, biting bugs, mosquitoes,
fleas, lice, mites, ticks and leeches — has been established.
382 BIOLOGY OF THE PROTOZOA
Few stages of the life cycle are found in the vertebrate blood.
Here they may reproduce by longitudinal division until the blood
teems with them or a balance may be established whereby relatively
few forms can be found in the circulating blood. Such hosts become
carriers for many different species of trypanosomes, as appears to
be the case with African wild animals.
Developmental stages, on the other hand, are well known in the
invertebrate hosts, the most complete account being that of Minchin
and Thompson (1915) for Trypanosoma lewisi of the rat in the rat
flea, Ceratophyllus fasciatus. Here a most unusual somatella phase
occurs in the stomach cells of the flea which is described on page 233.
The young trypanosomes after leaving the stomach cell may
enter other stomach cells and repeat the process, or they may pass
down the intestine to the rectum where they, like Crithidia, become
attached to the epithelial cells (Fig. 122, p. 234). From here they
may swim off as Leptomonas forms or remain and divide as Crithidia
types. The rectum is, apparently, a site of multiplication, necto-
monad and haptomonad stages succeeding one another until finally
the metacyclic or transmitting types develop from haptomonads.
It is probable that intracellular stages occur in the invertebrate
hosts of other species of Trypanosoma but the life history is known
in relatively few cases. The method of infection of vertebrate hosts
depends largely upon the site of accumulation of the metacyclic
forms in the invertebrate host. If in the rectum, as is the case with
Trypanosoma lewisi in the rat flea, infection of the vertebrate is
brought about by the contaminative method, i. e., by ingesting the
feces of the invertebrate or eating it whole. If, on the other hand,
the metacyclic trypanosomes accumulate in the salivary glands,
hypopharynx or other mouth parts of the invertebrate host, infec-
tion is inoculative. Duke (1913) suggests that trypanosomes of
the latter type might be described as having an anterior station,
and Wenyon (192(5) attempted a rough classification of the patho-
genic trypanosomes into those having an anterior .station and those
having a posterior .station in the invertebrate host. Among the
former a further grouping is made by Wenyon according to the
knowm invertebrate host and the anatomical part in which the
trypanosome development occurs. Thus in tsetse flies development
in the stomach, proboscis and salivary glands is characteristic of
Trypanosoma brucei (cause of nagana in cattle and of human
sleeping sickness in Rhodesia); T. (jambicn.se (cause of human sleep-
ing sickness); development in stomach and proboscis: T. congolense
of cattle, horses and sheep; 7 . simiae of monkeys; development only
in proboscis: T. vivax of cattle, sheep and goats; T. caprae in cattle,
sheep and goats, also T. uniforme of the same hosts.
In tabanid flies and other blood-sucking arthropods development
in this anterior station is characteristic of Trypanosoma, evansi, the
ECOLOGY, COMMENSALISM AND PARASITISM 383
cause of surra in horses; T. hippicum in mules; T. venezuelensis in
horses and dogs; T. equinum of horses and others. In leeches also
with inoculative infection, the trypanosomes accumulate in the
mouth region.
Development in the posterior station of invertebrates, with con-
taminative infection, is characteristic not only of T. lewisi in the
rat flea but of the majority of small mammalian trypanosomes.
Trypanosoma equiperdum, the cause of dourine in horses, has no
invertebrate host, transmission occurring at coitus.
The genus Schizotrypanum chagas differs from Trypanosoma in
having an intracellular leishmania phase in tissues of the vertebrate
host. It was discovered in the form of crithidia by Chagas in Brazil
in 1907, in the posterior gut of the biting bug Triatoma megista.
When inoculated in a marmoset, they gave rise to typical trypano-
somes which Chagas called Schizotrypanum cruzi. Later Chagas
found them in cats and in children and associated them with a
widely-spread disease of unknown etiology now generally known as
Chagas' disease. The trypanosomes do not reproduce as free
flagellates but may enter nearly any type of cell of the body where,
as Leishmania forms, they reproduce by active division. Another
species, S. pipistrelli, was found by Chatton and Courrier (1921)
in the bat Vesperugo pipistrellus, in which it forms large (up to 200/1)
reproductive cysts in various organs of the bat.
Human trypanosomiasis, known as sleeping sickness in Africa, is
essentially a disease of the lymphatics. This, however, is a later
stage of the disease which, as Bruce demonstrated, begins as an
irregular fever which was known clinically as Gambia fever before
its relation to sleeping sickness was discovered. At this time the
flagellates are multiplying in the blood and may be detected by
direct examination more readily than at other times. Their accu-
mulation leads to antibody formation and the trypanosomes are
destroyed in large numbers, the irregular fever being due to the
liberation of endotoxins through disintegration of the parasites.
Search for living forms of trypanosomes during the febrile period is
thus almost invariably negative.
In this early period, which may last from one or two weeks to
several years, there is little or no evidence of glandular swelling
(Bruce, Kleine, Thiroux, et at.), indicating that the trypanosomes
have not yet become established in the lymphatic system. The use
of medicaments (atoxyl, urotropine, tartar emetic, etc.) at this
period is usually successful and a cure results, but when the try-
panosomes have become established in the lymphatics they are less
easily reached, and once established in the cerebrospinal fluid the
disease is incurable (Reichenow-I)oflein). Here the trypanosome
multiplication is rapid and at the same time the lymphocytes become
markedly increased in number. The peculiar nervous and psychic
.">M BIOLOGY OF THE PROTOZOA
symptoms (tremors of tongue and knee, shuffling gait, etc.) which
characterize sleeping sickness may be due, as Reichenow (p. 582)
believes, to the effect of an endotoxin upon the central nervous
system and liberated through destruction of the parasites by lymph-
ocytes. Others, notably Mott, Bruce, Wolbach and Binger, Star-
gardt, Stevenson, et ah, interpret these characteristic symptoms as
due to penetration of the brain substance by trypanosomes, their
accumulation, with lymphocytes, in the spaces about bloodvessels
causing occlusion of the smaller ones with accompanying lack of
nourishment followed by atrophy of the brain cells.
The Rhodesia n type of trypanosomiasis is not caused by Trypano-
soma gambiense but by T. rhodesiense (Stephens and Fantham),
which is closely related to T. brncei, the cause of nagana in cattle.
Like briicei, this human trypanosome is ordinarily transmitted by
the tsetse fly, Glossina morsitans. The disease is more rapid and more
severe than northern sleeping sickness. Trypanosomes may enter
the cerebrospinal fluid within a week after infection (Kudicke),
and untreated cases are usually fatal within a few months, so that
characteristic sleeping sickness symptoms, although they have been
observed, are not so pronounced as in the equatorial form of the
disease.
While sleeping sickness is essentially a disease of the lymphatics,
Chagas' disease or Brazilian trypanosomiasis is, according to
Chagas, essentially a disease of the endocrine organs. The para-
sites (Schizotrypanum cruzi) are abundant in the peripheral blood,
but unlike Trypanosoma they do not reproduce in the blood. They
penetrate organ cells and there, like Leishmania, they divide and
multiply until great groups of them are present in cross-striped
muscles of the body, in heart muscle and in the central nervous
system. Such groups may develop flagella simultaneously, so that
in acute cases the blood may be teeming with flagellates (Reichenow).
Children are most susceptible to infection, and the disease is most
severe with them; but adults are not immune. In acute forms it
is prevalent in very young children, but may assume a chronic type
in children up to fifteen years of age, in whom it is associated with
retarded development of mind and body. Chagas believes it to be
the cause, not only of retarded development, but of functional loss
of endocrine glands leading to goiter, cretinism and idiocy.
Other flagellated parasites common in man are found in the
intestine for the most part. These are: Embadomonas, MacKinnon
(1911); Chilomastix mesnili, AYenyon (1910); Tricercomonas intes-
tinalis, Wenyon and O'Connor (1917); Trichomonas hominis,
Davaine (I860); Trichomonas vaginalis, Donne (1837); Giardia
intestinalis , Lambl (1859). The etiological significance in each
case is doubtful, although the possibility is frequently admitted
that some of them may augment disorders of the digestive tract,
ECOLOGY, COMMENSALISM AND PARASITISM 385
but it is also possible that they may find under such conditions a
more suitable environment for growth and reproduction. Species
of Bodo which are amongst the commonest coprozoic flagellates
have been observed in the urine (Powell and Kohigar, 1920). The
intestinal flagellates, particularly Embadomonas intestinalis, Chilo-
mastix mesnili, Tricereomonas intestinalis, Trichomonas hominis and
Giardia intestinalis are usually present in large numbers in diarrheic
stools while only cysts, as a rule, are found in normal stools. This
certainly suggests an etiological connection, particularly with
Giardia infections in which periodic attacks of diarrhea occur with
passing of quantities of clear mucus in which the flagellates are
abundant.
Parasitic Rhizopods.- While Sarcodina are perhaps less striking in
their adaptations than are other groups of Protozoa, they are,
nevertheless, more or less specialized in conformity with their
habitats and modes of life. The fundamental type is spherical and
characteristic of suspended or floating forms (Heliozoa and Radio-
laria), but adaptations serving a hydrostatic purpose are numerous,
particularly in the great group of Radiolaria. Creeping forms are
found in superficial slime of ponds and sea or on stalks and leaves
of water. plants and are more or less segregated in localities where
appropriate food is abundant. Thus Amoeba vespertilio may be
found in fresh water where diatoms and algae are abundant:
A. proteus in waters with decomposing organic matter rich in bac-
teria, or Pelomyxa palustris in still fouler waters. Amoeba terricola,
many testate rhizopods and related forms are more terrestrial, living
in moss or damp earth and sand ; here also may be found the major-
ity of Mycetozoa, especially on damp and decaying wood. In
short, there are few damp places that are devoid of ameboid types.
The Sarcodina are never as spectacular as the Mastigophora or
Sporozoa in their adaptations for parasitism, but many types have
become adapted to the semifluid habitats of plant and animal hosts
or to the more fluid environments of animal digestive tracts. Copro-
zoic forms are not uncommon, many types, like coprozoic flagel-
lates, passing through the digestive tract while encysted to develop
later in the dejecta (e. g., Dimastigamrba, Sappinia species). Con-
versely the true parasites are active only in the lumina of the
alimentary tract and are able to withstand the rigors of an external
life only when protected by cysts. Such cysts, through contamina-
tive infection, germinate in the digestive tract where some types
of Endameba cause acute or chronic intestinal diseases.
Many amebae are ectoparasitic. One, Amoeba hydroxena (Entz,
1912), occurs on hydra (H. oligactis); another, A. pacdophora, Caul-
lery (1906), on the eggs of a crustacean Peltogaster curvatus; .1.
m/udcola, Chatton (1909), occurs on the gills of marine fish. Protista
are not exempt— species of Svhaerita parasitize Euglenoids, I olvox,
25
386 BIOLOGY OF THE PROTOZOA
Hematococcus as well as parasitic flagellates, particularly Tricho-
monas, and nuclei of amebae; ciliates of various kinds, and other
rhizopods are destroyed by Nucleophaga. Algae, diatoms, plant
and animal flagellates are all subject to infection by species of
Pseudospora.
The thick cellulose walls of various plant types may be dissolved
by amylolytic ferments formed by certain types. In such cases no
sharp line can be drawn between parasitism in a strict sense and
processes of holozoic nutrition. These are well illustrated by
Vampyrella spirogyrae which feeds on Spirogyra cells; V. lateritia,
Leidy, on algae of different kinds, and V. vorax, Klein, which lives
on diatoms.
# Serious and economically troublesome diseases of plants are
caused by parasites belonging to the Mycetozoa.
Plasmodiophora brassicae, Woronin, is the best known of this
group largely because of its economic importance. It attacks the
roots of cabbages and other Cruciferae and produces a character-
istic tumor disease known as "Club-root," "Hanberries," "Fingers
and Toes," " Kohlhernie," etc.
Minute flagellulae are formed from the cysts in an infected garden
and these, in some way, penetrate the root cells of the plant and
become myxamebae. The nuclei multiply and they grow in the
cells of the plant, different individuals fusing to form plasmodial
masses which fill the cell. With exhaustion of the cell contents the
process of reproduction begins and results in the formation of
great masses of uninucleate " spores."
Invertebrates have not been thoroughly investigated for ameboid
parasites, and a big field is open here for research. The earliest on
record is a parasite of cockroaches to which Leidy, in 1879, gave
the name Endamoeba blattae. Endamoeba minchini was described
by MacKinnon (1914) from the intestine of the crane-fly Tipula sp.;
Amoeba chironomi, Porter (1909), from larvae of Chironomus;
Endamoeba belostomi (Brug, 1922) from the water-bug Belostoma sp.
of Java and E. disparata, E. simulans and E. asbulosa, Kirby
(1927), from termites. A species from the gut of the oyster (Val-
kampfia paiuxent, Hogue) was described by Hogue (1921). End-
amebae from other insects include: E. apis, Fantham and Porter
(1911), in the honey bee; E. mesnili, Keilin (1917), in larvae of
Trichocera sp.; E. thompsoni in Blatta orientalis.
In entomostraca (Daphnia species) a curious sporulating ameboid
parasite was discovered by Chatton (1925) and named by him
Pansporella perplexa. Binucleated spores escape from thin-walled
cysts in the gut of Daplmia and give rise to uninucleate amebae,
whether by division or by fusion of nuclei was not determined.
These grow without dividing and finally encyst in which form they
are passed out of the intestine. A series of nuclear divisions occur
ECOLOGY, COMMENSALISM AND PARASITISM 387
in the encysted ameba followed by division of the body into
binucleated spores which repeat the cycle upon ingestion by Daphnia.
This history is so unusual for amebae that Chatton placed it in
a new family, the Sporoamoebidae.
Vertebrates, particularly mammals, have been more extensively
studied for parasitic amebae than have invertebrate animals.
Amoeba froschi was found by Hartmann (1907) in frogs' feces, and
Valkampfia (Epstein and Lovasky, 1914) from the frog intestine,
and A. laeertae, Hartmann, and A. dobelli, Hartmann, from the
intestinal contents of lizards. Other species described from reptiles
are: Endamoeba testudinis, Hartmann, in the land turtle Testudo
graeca; E. barreti, Hegner and Taliaferro, in Chelydon serpentina;
E. serpent is, Da Cunha and Fonseca (1917), in the snake Drimobius
bijossatus; E. varani, Lavier (1923), from Varanus viloticus. Few
amebae have been reported from fish. The genus Proctamoeba
salpae, named by AlexeiefT (1911) for an intestinal ameba discov-
ered by Leger and Duboscq (1904) in the marine fish Box boops,
is undoubtedly an Endameba, so Proctameba is a synonym.
Few parasitic amebae have been reported from birds. Fantham
(1912) described E. lagopodis from the intestine of the grouse, and
E. anatis from South African ducks (1924), and Tyzzer (1920) found
E. gallinarum, Tyzzer, in chickens and turkeys.
Amebae resembling the type of E. dysenteriae and E. colt
have been described from mammals of different kinds. Apart
from human intestinal forms they have been reported from the
mouse: E. muris, Grassi (1879), and E. decumani, Kessel (1924);
from the rat: E. ratti; from rabbits: E. cuniculi, Brug (1918);
from guinea-pigs: E. cobayae, Walker (1908) (E. caviae, Chatton,
1918); from swine: E. debliecki, Nieschultz (1925), E. polecki,
Prowazek (1912) (E. suis, Hartmann, 1913); from sheep: E. ovis,
Swt'llengrebel (1914), E. caprae, Fantham (1923); from cattle: E.
bovis, Liebetanz (1915); from horses: E. intestinalis, Fantham
(1920), and E. equi, Fantham (1921). In addition to these, suc-
cessful inoculations of human dysenteric amebae have been made,
particularly in cats and monkeys.
Parasitic amebae in man, naturally, have attracted most atten-
tion and have been extensively studied. Tropical dysentery is
such a dreaded malady that students over the entire world have
contributed until today there are few important gaps in the patho-
logical history of the disease or in our knowledge of the causative
agent.
Amebic dysentery has had a long and confusing history in which
taxonomic synonyms and etiological misfits have played a con-
spicuous part. The final chapter has not yet been written, but
much of the earlier confusion has been cleared and students of the
subject are working with a common understanding. In my opinion
388 BIOLOGY OF THE PROTOZOA
the best account of intestinal amebae is given by Dobell (1919).
For a clear comprehension of this modern point of view, I have found
it expedient and instructive in teaching to divide the history of
amebic dysentery into four arbitrary periods with the understand-
ing that no period is clearly marked but all grade into one another
in a slow, often backward, but nevertheless sure development. I
would designate these periods: (1) Early taxonomic observations;
(2) early etiological observations; (3) taxonomic chaos; and (4)
modern point of view.
1. Early Taxonomic Observations. —With our present knowledge of
the intestinal protozoan fauna of man it is difficult to decide whether
so-called amebae of the earlier observers were really rhizopods or
more or less abnormal forms of intestinal flagellates. The so-called
"amebae" mentioned by Lambl (1860), who is usually credited
with the discovery of human intestinal amebae, are regarded by
Dobell as degenerating individuals of Trichomonas, while the value
of his observations is further lessened by the fact which has been
frequently pointed out, that he also observed the free-living forms,
Diffkigia and Arcella, in the same intestinal material. Ten years
later (1870) Lewis, in India, whose investigations had already
yielded a new mammalian trypanosome, and Cunningham (1871),
working on cholera, discovered an intestinal ameba they believed
to be non-pathogenic and which may well have been some harmless
species of Endameba, possibly coli.
The first authentic association of an ameba and dysentery was
described by Losch (1875) in Russia. Upon autopsy of an indi-
vidual who had a well-developed hospital case of dysentery but
died of pneumonia, Losch found an abscess of the liver containing
amebae. Mainly negative results followed attempts to infect dogs
with material from fresh stools of the victim, and Losch concluded
that with only 1 dog showing dysentery symptoms while 3 were
negative his ameba, which he named A. coli, was a harmless com-
mensal living in the human intestine. There is little doubt in the
minds of modern students that he was really dealing with the active
agent of amebic dysentery, in which case, as Dobell, Wenyon,
Doflein-Reichenow and others have pointed out, the taxonomic
specific name of the dysentery ameba should be coli. Losch's
dictum, however, that his Amoeba coli was a harmless commensal
has influenced all subsequent investigators until the name coli is
so intimately associated with what has turned out to be a really
harmless ameba that it would involve needless confusion if an
attempt were made to apply rigorously the rules of scientific nomen-
clature.
While the specific name coli thus got oft' to a poor start, the generic
name Ameba for endoparasitic forms was destined to have a short
life. Leidy (1879), who was working on his classical monograph'on
ECOLOGY, COMMENSALISM AND PARASITISM 389
the "Fresh Water Rhizopods of North America," discovered a
parasitic ameba in the intestine of Blatta orientalis, which he first
named Amoeba blattae. Recognizing the impropriety of grouping
the relatively huge fresh water and free-living amebae, such as
A. proteus and the minute intestinal ameba of the cockroach in
the same genus, he changed the generic name of Amoeba blattae to
Endamoeba blattae. Sixteen years later Casagrandi and Barbagallo
(1895) studied an ameba from man which, apparently in ignorance
of Leidy's work, they named Entamoeba coll, changing it two years
later to Entamoeba hominis. Now in my opinion this is the exact
equivalent of Leidy's Endameba, for in this country we use the
form "endo" (witness endoplasm, endoderm, endothelium, etc.) in
the same sense that Europeans use the form "ento" (entoplasm,
entoderm, etc.). Endameba and Entameba thus are the same, the
form depending on the custom of the country where used, and there
is little justification for employing them, as Dobell, followed by
Wenyon, suggested, to represent two distinct genera. If there is a
generic difference between the intestinal amebae of the cockroach
and that of man, which is by no means established, then some at
least of the human forms should be included under Chatton and
Lalung-Bonnaire's name, Loschia (1912).
2. Early Etiological Observations. —This period marking the begin-
ning of a long controversy over the pathogenicity of intestinal
ameba may be arbitrarily fixed between the approximate dates
1880 and 1902. Leidy's generic name was little used until the late
'90's; indeed not until after Casagrandi and Barbagallo had intro-
duced the form Entameba. At the beginning of this period it was
generally believed that the human intestinal forms belong to one
species which, following Losch, was known as A. coli. The con-
troversy then was over the question whether or not A. coli is patho-
genic, and the cause of dysentery. Grassi (1879, 1882, 1883, 1888)
found amebae widely distributed in feces of normal individuals
as well as in those suffering from diarrhea, and when cysts of the
organism are swallowed by humans they give rise to amebae which
multiply in the intestine but cause no symptoms of dysentery or
other intestinal upset (1888). He was emphatic in concluding that
the ameba with which he worked and which he regarded, erro-
neously, as the same as Losch 's "A. coli," is altogether harmless
to man. The seed thus planted by Losch developed into a healthy
weed with Grassi, became a permanent plant with Schaudinn (1903)
and has never been uprooted. Entamoeba coli as a harmless parasite
had come to stay.
The pathogenic importance of the so-called A. coli was also well
supported at this early period. Losch started it and was supported
in the 'SO's by KartuHs in Egypt (1885, 1886, 1887, 1891), by Koch
(1883), Koch and Gaffky (1887) and others. Sections of intestinal
390 BIOLOGY OF THE PROTOZOA
ulcers (Koch) showed ameboid bodies but, according to Dobell,
while he evidently regarded these as amebae his observations were
not sufficiently definite to justify positive conclusions. The work of
Kartulis was more convincing and his evidence, including observa-
tions on some 150 cases of intestinal ulcer (1886) with the discovery
of amebae in all, together with amebae in liver abscesses, and
later (1904) of amebae in abscesses of the brain, went far to estab-
lish, clinically, the etiological connection between "Amoeba coli"
and dysentery.
What is probably the most thorough of the clinical works of this
period was the study of Councilman and Lafleur (1S91) of the
pathology of amebic dysentery and amebic abscess of the liver.
The possibility of two types of Amoeba coli in the human intes-
tine, one pathogenic, the other harmless, while evident now in the
conflicting observations of Grassi and Kartulis, does not seem to
have been considered by the earlier workers. It was fully considered,
however, by Councilman and Lafleur, who not only suggested the
possibility, from the evidence of their work, but went so far as to
name the innocuous form Amoeba coli, while to the pathogenic
form, capable of invading tissues and of causing liver abscesses,
they gave the new name Amoeba dysenteriae. This classical work
on the pathology of dysentery has received but scant attention from
later workers, particularly the more influential European parasitolo-
gists. There is absolutely no doubt that Councilman and Lafleur
recognized, gave adequate descriptions of, and named the cause of
amebic dysentery, which today is generally known as E. histolytica.
It is difficult to see any adequate reason why the specific name
dysenteriae should have been ignored save that histolytica is more
euphoneous and more descriptive of the havoc made by the ameba.
The reasons given by Dobell (1919) seem trivial and unworthy of
that astute critic, viz.: that Councilman and Lafleur in spelling
failed to capitalize the generic name Ameba and failed to italicize
the full name as a zoologist would have done. Dobell ignores the
ending iae which alone sets it apart from an ordinary descriptive
term. Again Dobell says (Ibid., p. 28): "I regard 'Amoeba dysen-
teriae,' Councilman and Lafleur, as ruled out because it is a syn-
onym of ' .1 moeba coli,' Losch." He accepts E. histolytica, however,
so this ruling does not seem to be forceful enough to set aside
Schaudinn's term which is equally well a synonym of A. coli, Losch.
When the subtleties of the legal profession are employed for scien-
tific ends and a matter settled on a post hoc technicality which
may be applied or not according to the whim of the individual, we
are rather close to unfair dealing. It may be too late to remedy the
injustice, for the name Endamoeba (or Entamoeba) histolytica is now
in general use, but it will never have a clear title. It is gratifying
to note that Chatton and Kofoid retain the name E. dysenteriae.
ECOLOGY, COMMENSALISM AND PARASITISM 391
Nor is the title clear for the generic name End(Ent)ameba
unless the arneba of the cockroach {E. blattae) and the dysentery
amebae of the human intestine are continued to be regarded as
cogeneric. If, and it may be true, these amebae are generically
different, then some other name must be used for the human para-
sites, for Endameba goes with E. blattae, Leidy. Dobell and Wen-
yon and Reichenow (1928) recognize this difficulty but are not sure
that these amebae belong to different genera. In case they do,
they agree in proposing Endameba for E. blattae and the form
Entameba for E. coll and the pathogenic species of man. This,
however, is a mere subterfuge, for they are only different spellings
of the same term. Dobell shows that in case Endamoeba coli is
shown to be generically different from E. blattae, then Chatton and
Lalung-Bonnaire's (1912) name Loschia would have priority.
Returning from this controversial digression to the host-parasite
relations of the intestinal amebae of man, we find that throughout
the decade 1890-1900 there was little recognition of two types of
amebae— one harmless, the other pathogenic. Quincke and Roos
(1893) and Roos (1894) indeed spoke of "harmless" and "patho-
genic" forms, the former being non-pathogenic to cats upon infec-
tion with amebae per os or per anum. Casagrandi and Barbagallo
(1895-1897), who introduced the generic name Entamoeba coli in
ignorance of Leidy's Endamoeba, returned to Grassi's contention
that there is only one form of ameba which they termed E. coli
(1895) but later changed to E. hominis.
Schaudinn (1903), also ignorant of Councilman and Lafleur's
work, was convinced by work of earlier observers and more so by
his own observations and experiments that there are two distinct
species of intestinal amebae, one harmless, the other pathogenic.
He had an excellent opportunity to rectify the mistake which was
then in its infancy of regarding Losch's E. coli as a harmless ameba,
but he failed. He accepted Casagrandi and Barbagallo 's generic
name Entameba but regarded their E. hominis as the same thing
as Losch's A. coli, and such was his great influence at that time that
this name E. coli was attached, firmly but erroneously, to the com-
mon non-pathogenic ameba of man. For the pathogenic species
he proposed the name Entamoeba histolytica.
With the establishment of two species of Ameba— one of which
is pathogenic, some of the old difficulties which were engendered by
Grassi's and similar work on the one hand, and by that of Kartulis
on the other, were cleared up. Throughout this period, however,
there were skeptics who could not be convinced that any ameba
is an etiological agent in human dysentery, for cases of dysentery
in which no evidence of amebae could be found were turning up
repeatedly. This difficulty was finally removed by the discovery
by Shiga (1898), confirmed by Flexner, of the Shiga-Flexner bacillus
392 BIOLOGY OF THE PROTOZOA
as the cause of bacillary dysentery. Thus by the end of our second
period two important points had been established, viz.: the occur-
rence of two types of amebae in the human intestine, and the
occurrence of at least two types of dysentery due to different kinds
or organisms.
3. Period of Taxonomic Chaos. — It is quite evident from the fore-
going that the term taxonomic chaos with propriety might be
applied to the entire history of dysentery. It is particularly applic-
able, however, to the first decade of the present century when,
owing to the prestige of Schaudinn, incorrect interpretation of the
life history of Endamoeba dysenteriae {histolytica) resulting from his
work stood in the way of progress for more than a decade. In his
paper on the reproduction of certain rhizopods Schaudinn (1903)
described the life histories of the foraminiferon Polystomellina crispa,
Lam., the testate rhizopods Centropyxis aculeata, Ehr., Stein, and
Chlamydophrys stercorea, Cienkowsky, and the parasitic amebae
of the human intestine. In connection with the first three he was
convinced that chromidia give rise to the nuclei of gametes (see
p. 69) and thus play an important role as germinal chromatin.
It is not surprising, therefore, that he ascribed an important part
to what he termed chromidia in the parasitic amebae. In respect
to these chromidia the life histories as he interpreted them in
Endamoeba coli and E. dysenteriae (histolytica) are complicated.1 In
this account emphasis was laid by Schaudinn on : (1) The structural
differences in nuclei of E. coli and E. histolytica; (2) formation of
encysted amebae with 8 nuclei, giving rise to 8 spores, in E. coli
but absence of all cysts in E. histolytica; (3) reproduction by periph-
eral, chromidia-holding buds in E. histolytica but not in E. coli; and
(4) infection by spores of E. coli and by "resistant buds" in E. his-
tolytica; (5) pathogenicity of E. histolytica and harmlessness of
E. coli.
In this same year (1903) Huber made observations and experi-
ments which, had they received the attention they merited (see
Dobell, 1919), would have saved subsequent confusion. From a
case of typical amebic dysentery he observed amebae and their
cysts, the former infecting cats when introduced per anum, the
latter infecting cats per mouth. The cysts were reported as con-
taining 1, 2 and 4 nuclei but never more than 4. In the glamor
of Schaudinn's prestige this latter important point was ignored.
Viereck (1907) and Hartmann (1907) found them and, since the
cysts had 4 nuclei and Schaudinn had stated that E. histolytica does
not form cysts, they regarded them as a new species of Endameba.
The former named it E. tetragena, the latter E. aj'ricana. Hartmann
recognized E. aj'ricana as the same as E. tetragena which had been
published somewhat earlier in the year. The observations were
1 See Calkins Protozoology, 1909, p. 296.
ECOLOGY, COMMENSALISM AND PARASITISM 393
quickly confirmed and, as was to be expected, E. tetragena was
reported as a much more widely spread dysenteric ameba than
E. histolytica. A small precystic phase of E. histolytica was regarded
as a distinct species to which Elmassian (1909) gave the name
E. minuta. Koidzumi (1909) created a new species, E. nipponica,
for a variety of amebae, some of which were probably E. dysenteriae
(histolytica). Other synonyms, originally suggested for the most
part as new species, were: Entamoeba schaudinni, Lesage (1908);
E. hartmanni, Prowazek (1912); E. braziliensis, Aragao (1912); and
several others since 1912. At this time (1912) suspicions as to the
identity of these suggested species began to appear in the works of
Darling (1912), Whitmore (1911) and James (1914) which turned
to certainty in the work of Walker (1911) and Walker and Sellards
(1913) who demonstrated the identity of E. histolytica, E. tetragena
and E. minuta and so brought to an end this particular period of
confusion, and, in addition, added many important points concern-
ing the distribution and transmission of the organisms of dysentery.
4. The Modern Period.— The general acceptance of the organism
now known as Endamoeba coli as a harmless commensal, together
with the proof that the organism End amoeba dysenteriae (histolytica)
is pathogenic to man, was the basis for a good start in the modern
period.
There is little doubt that Endamoeba dysenteriae (histolytica) is
a dimorphic species which, in one phase, is a tissue-penetrating
type which, presumably by secretion of a proteolytic ferment, causes
cytolysis of tissue cells leading to ulcerations and abscess formation.
Such a ferment has been extracted by Craig from cultures. The
other type is the minuta form which shows a more complete adap-
tation to the intestinal environment of man. This is the type
found in carriers and, were it not for the possibility of its trans-
formation into the pathogenic phase, might well take its place with
E. coli and other harmless amebae of the intestine. It reproduces
by division in the intestine, however, and is regarded as the typical
form of the dysentery -causing ameba (Mathis and Mercier,
Reichenow, etc.) which under certain conditions may revert to the
larger pathogenic form (Kuenen and Swellengrebel, 1913). Dobell,
on the other hand, maintains that it is a pre-cystic condition giving
rise only to the encysted form with from 1 to 4 nuclei. These cysts
are present in the formed stools while living minuta forms may be
found in fluid stools or after a purgative. The dysenteric forms are
not ordinarily found in stools, but may be present in the discharge
from ulcers. In artificial culture medium the pathogenic form
quickly passes into the minuta phase. Successful cultures were
made by Cutler (1918), by Boeck and Drbohlav (1925) and with
remarkable results by Cleveland and Sanders (1930). The latter
were able not only to cultivate the organisms indefinitely and in
394
BIOLOGY OF THE PROTOZOA
amazing numbers, but to bring about encystation and excystation
at will while, at any stage, dysentery in kittens could be produced.
The tissue-invading forms of E. dysenteriae are usually from 20 n to
30 n in size but variations above and below these limits may occur.
The organism quickly degenerates outside the body and becomes
quiet with a thick hyaline ectoplasm, but under normal conditions
it shows great activity, moving occasionally like a Umax type of
ameba or more frequently by the formation of large blunt pseudo-
Am
B
ij
V
/
cr-'
/
Fig. 171. — Endamotha dysenteriae. A, typical trophic ameba with red blood
corpuscle found in dysenteric stools; B and C, encysted individuals about ready for
excystment; D, cyst with eight nuclei and chromatoid bodies. (After Cleveland
and Sanders, Arch. f. Protistenkunde; courtesy of G. Fischer.)
podia which are suddenly formed and withdrawn with equal speed.
The endoplasm is densely granular and in addition to the nucleus
contains food vacuoles, "chromatoid" bodies and numerous small
granules which stain intra vitam with neutral red (Dobell).
The nucleus is difficult to see during life of the organism, owing
to the densely granular cytoplasm. In fixed preparations it may
be seen to have a delicate membrane studded internally by chroma-
tin granules, and with a minute homogeneous endosome (Fig. 171).
ECOLOGY, COMMENSALISM AND PARASITISM 395
Between the latter and the membrane there is a delicate linin
reticulum. Kofoid and Swezy (1924-1925) describe the division
of the endosome after migrating to the periphery of the nucleus,
and formation of a spindle figure with a centrodesmose on which
6 chromosomes divide.
Nutrition of the tissue invading form is primarily by endosmosis;
erythrocytes are frequently found in the food vacuoles sometimes
in large numbers, but just as often there are none at all. Bacteria
are present only exceptionally.
The minuta form is much smaller than the invasive form and
there is a greater variation in size— the variations being so consistent
that many authors (e. g., Wenyon and O'Connor, 1917; Dobell and
Jepps, 1917, 1918) regard them as distinct races. The sizes of the
cysts which they form likewise vary. Wenyon (1926) gives the
limit of size of the minuta amebae from 7 /x up to the size of the
invasive type while the cysts vary in size from 7 to 18 n-
Reproduction of the ameboid forms by simple division keeps up
the number of parasites in the intestine, and may continue indefi-
nitely in carriers. Conditions leading to the formation of minuta
types and precystic amebae in the intestine are only matters of
surmise, but with encystment multiple division into 4 small amebae
occurs. The cysts are usually spherical with smooth walls and from
5 fx to 20 it in diameter, and when fully developed contain 4 nuclei
(in some rare cases 8 may be present, Wenyon). In addition to
nuclei so-called chromatoid bodies are present in the cytoplasm.
These are of considerable diagnostic value for they are much more
rare in cysts of E. coll. They are usually in the form of rods with
rounded ends but may be filamentous, or irregularly shaped bodies
sometimes 2 or 3 in number, sometimes many. These appear to
be absorbed during the external life of the cyst. During the forma-
tion of the cyst the glycogen which is present at the commencement
of encystment disappears. Cleveland and Sanders have studied
ex-cystation. These cysts give rise to an ameba free from chro-
matoid bodies and with 4 cystic nuclei. So-called "metacystic
development" (Dobell) results in the formation of 8 young, uni-
nucleate amebae but not always by the same process. The 4 cystic
nuclei may all divide after which the cell divides into 8 uninucleate
forms. Or one of the 4 cystic nuclei may divide to form 2 meta-
cystic nuclei which with cytoplasmic division gives rise to an
ameba with 2 metacystic nuclei, and a sister cell but larger with
3 cystic nuclei. In other cases 2 or 3 of the 4 cystic nuclei may
divide and be cut off with some cytoplasm which ultimately result
in uninucleate forms. Hence metacystic amebae may be found
with any number of nuclei, from 1 to 8. Cleveland and Sanders
describe 24 such combinations.
While probable that E. dysenteriae (histolytica) may be carried
396 BIOLOGY OF THE PROTOZOA
by the blood to various sites in the body, it is only in rare cases that
organs apart from the digestive tract become infected. Brain ab-
scesses are very rare, and in these only the large tissue-invading
amebae are present and cysts are not found (Wenyon). Different
observers have reported similar amebae in urine, in ducts and tubules
of the male reproductive organs, in the lungs and even in the skin.
The so-called amebae described by Kofoid and Swezy (1922) from
the bone-marrow in cases of arthritis deformans and from degen-
erating lymphatic glands of Hodgkin's disease, and regarded by
them as End. dysenteriae, have not been taken seriously by the
majority of other students of the Protozoa.
Other Amebae of the Human Intestine.— Amebae of different
kinds are characteristic intestinal parasites of all kinds of animals.
In man, apart from E. dysenteriae (histolytica) and its many form
changes, they are not pathogenic. Mutual adaptation has made
them, for the most part, harmless guests of the alimentary tract,
while as stated above, even End. dysenteriae in "carriers" is a
harmless commensal.
Dientamoeba fragilis was discovered by Jepps and Dobell in 1918.
It is a minute ameba (3.5 /z to 12 /x) and very active with, charac-
teristically, 2 minute nuclei. It is very delicate and apparently
quite rare. The binucleate condition, together with the structure
of the nuclei and the rare occurrence of cysts (Kofoid, 1923), are
definite characters which distinguish it from Endameba. Opinions
differ as to its pathogenic character, but Dobell (1919) regards it
on the whole as a harmless type.
Endamoeba coll is a common but harmless commensal in the
digestive tract and never becomes a tissue-invading form. For the
casual observer it may be easily mistaken for E. dysenteriae but with
abundant material and with different stages of the organism there
is now no excuse for such a mistake. It is larger than E. dysenteriae
(15 y. to 30 n), has a more transparent protoplasm so that the nucleus
is visible in life and contains ingested food of different kinds but
rarely if ever does it ingest red blood corpuscles. The relative
scarcity of endoplasmic granules makes the difference between
endoplasm and ectoplasm less noticeable than in E. dysenteriae.
The nucleus is larger and the endosome more conspicuous than
in the dysentery causing ameba. The most characteristic feature,
however, is the cyst with its 8 nuclei (not infrequently with 16).
The pre-cystic forms are somewhat smaller than the active ameba
but the cysts are larger than in E. dysenteriae (10 /* to 30 n), usually
15 /* to 20 m-
The so-called Councilmania lafleuri of Kofoid and Swezy (1921)
is now generally regarded by protozoologists as referring to modified
or aberrant types of Endamoeba coli.
Other amebae of the digestive tract are E. gingival it found on
ECOLOGY, COMMENSALISM AND PARASITISM 397
the teeth and in the mouth; Endolimax nana (Wenyon and O'Con-
nor, 1917), one of the commonest amebae in man, and Iodoamoeba
butschlii (Prowazek, 1912).
Parasitic Ciliata.— A considerable volume could be written on
the parasitic ciliates. This is attested by the many great mono-
graphs on limited groups of this class of Protozoa, e. g., on Opal-
inidae, Astomida, Oxytrichida, Ophryoscolecida, etc. Highly
spectacular life histories, such as those of Leishmania, Trypanosoma
and Plasmodium, and economic importance in connection with
human affairs are absent here. Absent also are the pathogenic
effects of parasites of the Endameba type or of biologically sig-
nificant adaptations to complete symbiosis which characterize the
Hypermastigida. Nevertheless the parasitic ciliates represent a
group which illustrate in high degree the phenomenon of commen-
salism with morphological differentiations which place them with
the most complex types of Protozoa and the most highly organized
types of single cells.
Infection in all cases is contaminative and made possible by
protective cysts in which the fundamental organizations may
remain dormant for years. With the exception of Balantidium,
pathogenic effects in man are of little importance. By mere num-
bers, however, especially of ectocommensals, functional activity of
the host may be weakened or even suppressed as when gills, eyes
and skin are covered with cysts due to Ickthyophthirius multi-
filius. Entodiniomorpha, on the other hand, as commensals in
the forestomach of ruminants are interpreted as approaching the
symbiotic relationship of Hypermastigida in termites. Dogiel (1928)
estimates the number of ciliates in cattle as 50,000 in 1 cc. of rumen
contents and Ferber (1928) carries the number in sheep and goats
up to 900,000 in 1 cc. The ability of these ciliates to digest cellu-
lose and to build up albumin in their own cell bodies is indirectly
advantageous in the nutrition of their hosts through the added
supply of their body protein (Dogiel, Ferber, Reichenow-Doflein) .
Morphological evidences of adaptation to an endocommensal
mode of life are shown (1) by degenerative changes, and (2) by
specializations for protection, adhesion, movement and multiplica-
tion. Modifications of a degenerative character are shown by the
absence of mouth in Opalinidae and the Astomida in general and
the substitution of saprozoic food-getting methods for holozoic
methods which are characteristic of the free-living ciliates. Opal-
inidae are not only mouthless but they also lack the dimorphic
nuclei — macronuclei and micronuclei— which are distinctive diag-
nostic features of the Infusoria. The method of fertilization by
copulation of gametes and not by conjugation also distinguishes
the Opalinidae from the majority of other ciliates. On these grounds
Metcalf (1923) proposed a classification involving the separation of
398 BIOLOGY OF THE PROTOZOA
this group from other ciliates as a sub-class Protoeiliata, while the
remainder of the great group of ciliated Infusoria were grouped as
Kuciliata. In this he has been followed by Doflein, Reichenow-
Doflein, Wenyon and the majority of protozoologists. Personally,
however, I cannot subscribe to this point of view; I am second to
no one in recognizing the superlative work of Metcalf on represen-
tatives of this group, but I do not agree to the separation of 4 genera
of astomatous forms as Prociliata from the number of other astoma-
tous forms, which, together with the hundreds of genera of mouth-
bearing forms of ciliates are placed in an equivalent group, the
Euciliata. Nor can I regard the so-called Protoeiliata as primitive.
The most generalized forms of free-living ciliates, with which the
Opalinidae agree in ciliation, are mouth-bearing forms, and the
absence of a mouth in parasites is much more probably a degenera-
tive than a primitive character, and is to be regarded as a special
adaptation to the conditions of a limited but highly nutritive
environment.
Nor can the absence of dimorphic nuclei pass unquestioned.
The cell body of an opalinid is filled with discoidal structures which
were interpreted by Tonniges (1927) as representing a distributed
macronucleus similar in character to that of Dileptus gigas (Fig.25,
p. 52). The same point of view has been vigorously maintained
by Konsuloff (1922) but actual proof is still lacking. The history
of amicronucleate ciliates shows that dimorphic nuclei are not
essential for continued metabolism (see p. 225); here, however, the
diversity of chromatin in the opalinid nucleus suggests the correct-
ness of Tonniges' (1927) view that these nuclei possess both germ-
inal and somatic components.
Finally the absence of conjugation and the substitution of gametic
fertilization is not unique with the Opalinidae. Here by repeated
division without intervening growth, gametes of different size (aniso-
gametes) are formed and these fuse in copulation. The same
phenomenon occurs in Glaucoma (DaUasia) frontata, a free-living
ciliate, the only difference being that the gametes are isogamous
and derived from the same parent (Calkins and Bowling, 1928).
Here fertilization is pedogamous while in Ichthyophthirius multi-
filius the process has apparently gone one step farther into autogamy
according to Neresheimer (1908) and Biischkiel (1910).
The Opalinidae are parasites of frogs and toads primarily. Some
species occur in fish, and one, Protopalina nyanza, in a reptile.
They are represented, according to Metcalf, by 4 genera which
differ in form of the body and the number of nuclei. Protopalina,
Metcalf, and Zelleriella, Metcalf, have each 2 nuclei. Cepedea,
Metcalf, and Opalina, Purkinje, have many nuclei. Protopalina
and Cepedea are nearly circular in cross-section; Zelleriella and
Opalina are flat.
ECOLOGY, COMMENSALISM AND PARASITISM 399
The other representatives of the group Astomina are characteristic
parasites of invertebrates, particularly of the annelids, where they
may be found in the digestive tract, the coelom, or in the tissues
of diverse organs. Cepede (1910) has given the best monograph
on the group but his classification based on habitat has been much
improved by Cheissin (1930; see Key, p. 489). Adaptations for
attachment have been developed in the form of hook-like chitinous
organs which are deeply anchored in the body (Fig. 202, p. 492)
and of suckers with or without hooks (Steinella; Sieboldiellina from
Turbellaria). Chitinous skeletal bars are also widely distributed in
the group.
Astomida are also found as parasites in medusae (Kofoidella,
Cepede), in copepods (Perezella, Cepede), in amphipods and isopods
(Collinia, Cepede) and in the gonads of starfish (Orchitophrya,
Cepede).
Mouth-bearing forms of endoparasitic ciliates show great modi-
fications and specializations in structure. Taxonomically they are
distributed amongst Ilolotrichida and Spirotrichida, the latter
including Heterotricha, Oligotrichia (with Entodiniomorpha, Reich-
enow). (See Key, p. 508.)
The Holotrichida are subdivided into Gymnostomina, Hyposto-
mina, Trichostomina and Hymenostomina, all of which have para-
sitic genera and some groups in which parasites have not been
recorded. Among the Gymnostomida are the ectocommensal
Ichthyophthirius multifilius and the enterozoic forms Butschlia,
Schuberg (in ruminants) ; Bundleia, da Cunha and Muniz; Blepharo-
codon, Bundle, Blepharoconus, Gassovsky, Didesmis, Fiorentini,
and Blepharoprosthium, Bundle (all from the horse); Buissonella,
da Cunha and Muniz (from the tapir); and Protohallia, da Cunha
and Muniz (from the capybara).
Among the hypostomes we have some destructive ectocommen-
sals: Chilodon ci/prini, MorofY, for example, causes severe epidemics
amongst carp and goldfish. Less destructive, but biologically most
interesting, are the ectoparasites known as Foettingeriidae, where
the complicated life histories have been carefully followed by
Chatton and Lwoff. They appear to be primarily ectoparasites of
crabs, where they appear in the encysted condition on the gills.
When the exoskeleton of the crab is shed the ciliates leave their
cysts and grow apparently on the secretions of the skin. Ulti-
mately the fully-developed forms leave the old host and divide,
Polyspira in free-swimming condition, Gymnodinioides while en-
cysted.
Foettingeria actiniamm, Clap, lives in the gastral cavity of an
actinian; here it divides while encysted and the young forms after
emerging from the cyst cannot begin life again in the actinian
but become attached to Crustacea of different kinds where they
400
BIOLOGY OF THE PROTOZOA
form stalked cysts within which they undergo a metamorphosis.
If hosts and cysts are eaten by an actinian the metamorphosed
ciliates are liberated and these take up life again in the gastral
cavity of the coelenterate.
Of the endoparasitic forms the Pycnothricidae (Xicollelidae of
Chatton and Perard) are noteworthy because of the varying posi-
tions of the mouth, which is connected with an elongated furrow
ti m
Fig. 172. — Nicollellidae. Nicollella, Collinella, and Pycnothrix. (After Chatton
and Perard, Bull. Biol, de la France et de la Belgique, 1921; courtesy of Prof. X.
Caullery and Les Presses Universitaires de France.)
running from the mouth to the anterior end. In Xicollela, Chatton
and Perard, the furrow runs to the mouth which lies at the middle
of the ventral surface; in Collinella, Chatton and Perard, it runs
to the mouth at the posterior end; while in Pycnothrix, Schubotz,
which is by far the largest of the parasitic ciliates (2 to 3 mm.),
it runs down the ventral surface, around the posterior end and
back to near the anterior end on the dorsal surface where the
ECOLOGY, COMMENSALISM AND PARASITISM 401
mouth lies (Fig. 172). Here, also, in addition to the mouth open-
ing there are numerous pores opening into the endoplasm through-
out the course of the furrow. With this group also we include
provisionally Buxtonella, Jameson, a parasite of cattle.
Among the Trichostomina we have the families Conchoptheriidae
which are ectoparasites and endoparasites of molluscs; the Iso-
trichidae which are endoparasitic in ruminants; and Cyathodinidae,
endoparasites of Covin apersa (see Key, p. 503).
Amongst the HyfftenostominaT the Ancistridae include ecto-
parasites and endoparasiteSn^mussels (Ancistruma, Strand, and
Boveria, Stevens) and in holothurians (Boveria, Stevens).
These forms are all highly modified ciliates which in some cases
have acquired characteristics of the Suctoria. Thus Hypocoma
possesses a suctorial tentacle which functions as a mouth, and the
genera Pelecyophrya , Chatton and Lwoff, and Sphenophrya, Chat-
ton and Lwoff, have lost all cilia in the fully-developed condition,
their earlier presence indicated only by two zones of basal granules
of the infra-ciliature. As in Suctoria reproduction occurs by bud-
ding from the dorsal surface, the buds being ciliated, not as are the
Suctoria, but like the Ancistridae.
Amongst the heterotrichs we find the, only ciliated parasites of
man represented by species of the genera Xyctotherus and Balan-
tidium. Nyctotherus faba, Schaudinn, is a small form which, accord-
ing to Reichenow, has been safely identified as an intestinal parasite
of man only once (1899) and then in diarrheic stools. Balantidium
species are more frequently found in the human intestine; here,
particularly in B. coli, the ciliates may run a normal course in the
intestine without causing morbid symptoms, but under conditions
of the host which are not understood, they may cause an acute
enteritis of the same nature as dysentery. Like Endameba, these
ciliates may penetrate the gut wall and remain embedded in the
deeper tissues.
Balantidium species are widely distributed amongst the lower
vertebrates and mammals and B. coli is a characteristic parasite
of the pig, which is the main source of human infection. A second
species, B. minutum, was discovered by Schaudinn, together with
Xyctotherus, in one case; since then it has been observed only spora-
dically (Pinto in Mexico and Mathewossian in Armenia, according
to Reichenow-Dofiein, 1929).
The Oligotrichida are ciliates with greatly reduced filiation, the
adoral zone of membranelles and cirri alone representing the motile
organs. In the older systems of classification the Order was divided
into three families— Halteriidae, Tintinnidae and Ophryoscolecidae,
the last including all of the parasitic forms. These parasites are
quite different in organization and complexity from other Oligo-
trichida, but are of a common type amongst themselves and justify
26
402 BIOLOGY OF THE PROTOZOA
Reichenow in making them an independent order which he calls
the Entodiniomorpha. These are all peculiarly differentiated gut
parasites of mammals in which the cilia are reduced and represented
only by the adoral zone of membranelles which runs into a deep
vestibule at the anterior end of the body (Fig. 2, p. 20). The pos-
terior end is often drawn out into characteristic processes (Fig. 140,
]). 293). In Cycloposthium and related genera (see Key, p. 515)
there are bundles of cirrus-like motile organs in addition to the
adoral zone, the various arrangements of these groups of motile
organs furnishing the basis for generic distinctions (see Key, p. 513).
THE MORE IMPORTANT SPOROZOAN PARASITES OF MAN.
The Sporozoa comprise a most heterogeneous collection of animal
parasites with hosts in every branch of the animal kingdom, and
to limit their discussion here to the parasites of man is entirely a
matter of expediency.
We follow Doflein in giving a broader interpretation of Leuckart's
group Sporozoa than does Wenyon. The latter separates the
Cnidosporidia as a distinct Class from the Sporozoa in which he
includes only the Gregarinida and the Coccidiomorpha. These two
groups are united here as Orders in the Sub-class Telosporidia,
Schaudinn, while the Cnidosporidia (Schandinn's Neosporidia) con-
stitute an equivalent sub-class, but without any obvious relation-
ship to the Telosporidia. With the possible exception of Sarcocystis
which still has an uncertain taxonomic position, none of the Cnido-
sporidia are parasites of man.
In a discussion of human sporozoan parasites we are limited,
therefore, to the Telosporidia comprising the Gregarinida and the
Coccidiomorpha. The former are coelozoic parasites of inverte-
brates; the latter are parasites of both invertebrates and vertebrates
and are much more harmful to their hosts than are the gregarines.
This is due to their characteristic cytozoic mode of life which
involves the active destruction of tissue cells with corresponding
weakening of functions. These are the only forms of Sporozoa
which man has to fear and relatively few of them are known to
cause human disease.
According to the site of infection the Coccidiomorpha are divided
into Coccidia, or tissue-cell-dwelling forms, and Hemosporidia, or
blood-cell-dwelling forms. Notwithstanding the difference in habi-
tat and the special adaptations which are characteristic of blood
parasites, there is a remarkable uniformity in the life histories of
all coccidia and hemosporidia, and a common terminology has been
adopted for the different stages. The life cycle of Eimeria schubergi,
as given by Schaudinn for the parasite of the centipede, IAthobius
forftcatus, although thirty-two years old, is still the clearest and
ECOLOGY, C0MMENSAL1SM AND PARASITISM
403
the most instructive scheme for illustrating the stages in the life
history and the adopted terminology.
Eimeria schubergi is a common parasite of the centipede's intestine,
infection being brought about by contaminated food. In such food
substance the germs of Eimeria are protected against drying and
other adverse external conditions by cyst membranes, one of which,
Fig. 173. — Eimeria Schubergi. Sporozoites penetrate epithelial cells and grow
into adult intracellular parasites (a). When mature, the nucleus divides repeatedly
(6), and each of its subdivisions becomes the nucleus of an agamete (c). These enter
new epithelial cells and the cycle is repeated many times. After five or six days of
incubation, the agametes develop into gamonts; some are large and stored with yolk
material (d, e, /), others have nuclei which fragment into chromidia which become
the nuclei of microgametes (d, h, i, j). A macrogamete is fertilized by one micro-
gamete (g) and the zygote forms an oocyst (k) . This forms four sporoblasts, each
with two sporozoites (/). (After Schaudinn.)
the sporocyst membrane, encloses 2 germs termed sporozoites.
The second and outer membrane— oocyst— encloses a group of 4
sporocysts (Fig. 173) and 8 sporozoites.
Under the action of digestive fluids the double membrane about
the sporozoites are opened and the germs arc liberated. They make
their way to glandular cells of the intestine and get into the cyto-
plasm, usually 1 to a cell (Fig. 173, a). In the cytoplasm the sporo-
404 BIOLOGY OF THE PROTOZOA
zoite grows into an intracellular parasite termed the trophozoite,
which fills the greater part of the cell and forces the cell nucleus to
one side where it degenerates. The trophozoite grows at the
expense of the host cell, and when fully grown its nucleus divides
a number of times and the cell body divides into a number of
daughter cells. This process is termed schizogony or asexual repro-
duction and the products are called merozoites. These are liberated
into the lumen of the intestine, where they behave exactly like the
sporozoites entering epithelial cells which they, also, destroy and
grow into adult merozoite-forming trophozoites. The process is
repeated a number of times and in this way, by multiple progression,
great areas of normal cells are infected and destroyed. Ultimately
the merozoites give rise to trophozoites which have a different fate.
Some of them grow to full size and as macrogametocytes store up
reserve nutriment and become differentiated as macrogametes.
Others grow in like manner but instead of storing nutritive sub-
stances become free of granules and appear hyaline. The nucleus
ultimately begins to divide and its divisions are repeated until many
hundreds are present and distributed around the periphery of the
cell. These become the nuclei of microgametes which are delicate
hair-like cells, each with 2 flagella, distributed over the surface of
the mother cell or microgametocyte (Fig. 173, j).
Immediately after fertilization by union of a macrogamete and
a microgamete, a fertilization membrane is formed around the
zygote. This membrane becomes hardened into the oocyst or outer
protective covering. The zygote is then ready to undergo meta-
gamic divisions, first into 2 and then into 4 cells. Each of these is
a sporoblast which secretes a protective membrane about itself —
the sporocyst— and then divides into 2 daughter cells, each of which
is a sporozoite (Fig. 173, /). Each zygote thus gives rise to 4 sporo-
blasts with their sporocysts, and to 8 sporozoites, 2 to each sporoblast.
While details vary widely such a general outline of the life history
may be applied to all types of Coccidiomorpha. Variations occur
in all phases, particularly in the sporogony cycle, where we find
wide differences in the number of sporoblasts formed from the
zygote, and in the number of sporozoites formed from each sporo-
blast (see Key, p. 557). In the majority of cases the full life history
is completed within one host but in a few cases among Coccidia
and in all Ilemosporidia two different hosts are necessary, in one,
and presumably the original host, only sporogony or sexual phases
occur, in the other the usual asexual development and multiplica-
tions of the trophozoites. (See p. 406 for adaptations in Hemo-
sporidia) .
In general the effects produced by Coccidia are determined by
the extent of multiplicative reproduction and the area of devastated
cells. The centipede is little affected and so are the great majority
ECOLOGY, COMMENSALISM AND PARASITISM 405
of insects, worms, molluscs, Crustacea and lower vertebrates.
Severity also depends upon single or multiple infections and in the
ground mole, according to Schaudinn (1902), infection with Cyclo-
spora caryolytica is fatal in all cases. Similarly Eimeria necatrix,
.Johnson, is reported to be fatal to chickens in five days (Tyzzer,
1932). Here the sporozoites are liberated as early as one hour after
ingestion and penetrate the gland cells at once; this is followed by
rapid growth and multiplication with resulting destruction of great
numbers of epithelial cells and death of the host. Blood and mucus
containing sporocysts are passed out with the feces which becomes
infective material for other birds.
( 'occidia have been reported from the greatest variety of animals,
both cold-blooded and hot-blooded. In mammals, Cryptosporidium
niuris, Tyzzer (1907), parasitic in the peptic glands is noteworthy
because of its minute size and its coelozoic mode of life, no intra-
cellular stages characteristic of the coccidia generally are known.
Species of the genus Eimeria are parasites in horses, cattle, pigs,
sheep, goats, rats, mice, rabbits, cats, skunks, squirrels. They are
also found in fowls, geese, ducks, pigeons, pheasants, grouse and in
cold-blooded forms, in frogs, newts, salamanders, tortoises, snakes
and fish.
The genus Isospora (A. Schneider) differs from Eimeria chiefly
in the third mctagamic division, so that only 2 sporoblasts and 2
sporocysts are present in the oocyst. Each sporoblast gives rise to
2 sporozoites, the oocyst thus containing 4 instead of 8 sporozoites,
as in Eimeria. Like the latter genus representative species are
found in many different kinds of animals, both vertebrate and
invertebrate; here also are the only recognized pathogenic coccidia
of man.
It can be easily understood that sporocysts of different kinds of
Sporozoa may be eaten with contaminated food. If such cysts are
resistant to the digestive fluids of the stomach and intestine they
will pass out unchanged with the feces. Such cysts found in the
feces may easily be interpreted as the resistant cysts of coccidian
parasites of the human intestine. This appears to have been the
case with species of the genus Eimeria in which E. clupearum,
Thelohan (1892), and E. sardinae, Thelohan (1890), are known
intestinal parasites of different fish. The cysts of these species are
not infrequently found, although in small numbers, in human feces.
There seems to be little reason for doubt, however, that certain
species of Isospora are actually pathogenic to man. Isospora hom-
inis, Railliet and Lucet (190i), and I. belli, Wenyon (1923), are
fairly well established in this connection. Wenyon (p. 823) reports
an observation by Connal (1922) on a laboratory worker who
accidentally swallowed developed oocysts of Isospora belli; six days
later abdominal discomfort and diarrhea set in which lasted for
406 BIOLOGY OF THE PROTOZOA
about a month; toward the end of the time oocysts were found in
the feces and these lasted for several days, after which they disap-
peared and recovery was complete. Similar symptoms and similar
cysts have been found by a great number of observers in many
different parts of the world. The great wonder is that there are
not more cases of coccidian enteritis.
Hemosporidia.— The Hemosporidia are Coccidiomorpha which
have become adapted to life in the blood, and with this mode of
life the more common contaminative mode of infection is replaced
in general by the inoculative method. With this change, new and
far-reaching adaptations have been developed which modify to a
considerable extent the typical life history of the Coccidiomorpha.
One structural change of great importance is the entire loss of
protective capsules— oocyst and sporocyst— which, if present, would
make activity in the blood impossible.
Theoretical considerations as to the mode of origin of Hemospor-
idia and of blood parasites generally have already been considered
(see p. 361). Possibility of the origin from the gut of the same host
is indicated by some types of Coccidia where infection is contamina-
tive (Hepatozoon, Shellackia and Lankesterella, see Key, p. 566).
Here infection of the second host is also contaminative, in these
cases through infected blood. With Hemosporidia, fertilization
by union of gametes and development to the sporozoite take place
in the invertebrate host and the sporozoites are inoculated directly
into the blood of vertebrates.
So far as the hematozoic sporozoan parasites of man are con-
cerned the Plasmodiidae and the Piroplasmidae alone are important,
the former including the malaria-causing organisms of man and
birds.
The cause of malaria, although sporadically seen prior to 18S0,
was first recognized as a definite organism in that year by A. Laveran,
a French medical officer, when he discovered the phenomenon of
"flagellation" which we now know is microgamete formation. At
that time very little was known about blood-infesting Sporozoa,
although ten years before Lankester had observed parasites in
frog's blood which were later known as Lankesterella ranarum.
The generic name Plasmodium was given by Marchiafava and
Celli in 1SS5. Laveran had named the organism Oscillaria malariae,
but since the name Oscillaria was pre-occupied, the first-recognized
cause of malaria became Plasmodium malariae, Laveran. Golgi
(1886) showed that there are different types of life history in the
blood and suggested the possibility of different species. This was
made the basis of Grassi and Feletti's (1890) division of the malaria-
causing forms into Plasmodium vivax, Grassi and Feletti, P. malar i ae
and Laverania malariae. These observers believed, with some
justification, that the clinical features of pernicious malaria, also
ECOLOGY, COMMENSALISM AND PARASITISM 407
called tropical malaria, combined with the aberrant form of the
gametocytes, was sufficient justification for a different generic name.
That the point was well taken is shown by the fact that today there
are two camps: one, supported bv Reiehenow-Dofiein, maintains
the position of Grassi and Feletti, and recognizes the genus Laver-
ania; the other, supported by Welch, Schaudinn and Wenyon,
cannot see that the shape of the gametocytes with the somewhat
more virulent clinical history is sufficiently important to justify a
different generic name and, following Welch (1898), the third
species was named Plasmodium falciparum. A similar difference
of opinion concerns the generic name of the organisms causing bird
malaria. Some authorities, following Labbe (1894), use the generic
term Proteosoma; others cannot see that, other conditions being
the same, a difference in hosts is of sufficient zoological importance
to warrant a different generic name and the bird organisms are
also grouped under the generic name Plasmodium. Following the
example shown in connection with the genera Trypanosoma and
Endameba, it would seem that the weight of authority rests with
the advocates of the name Plasmodium.
Although Laveran's original discovery attracted much attention,
the organism was not immediately accepted by pathologists as the
cause of malaria, and it was only after careful work of the Italians,
Marchiafava, Celli, Grassi, Feletti and especially of Golgi (1886),
that the relationship was established. Golgi, beginning in 1885,
correlated the clinical picture of malaria with the developmental
stages in the intracorpuscular history of the parasite.
The transmission of malaria from individual to individual was
another story. R. Pfeiffer (1892) was struck by the resemblance
in their life histories, of Plasmodia and Coccidia, and, not finding
sporocysts and oocysts in the former, suggested that malaria organ-
isms might be transmitted from host to host by some blood-sucking
insect. Laveran in the same year and Manson in 1894 indepen-
dently advanced the same idea, and each suggested the mosquito
as the transmitting agent. These suggestions were brilliantly
proved, first in France, later in India by Ronald Ross and by
Grassi in Italy. Ross (1897), unable to finish his work on human
malaria in Paris, continued the work on bird malaria in India,
lie proved that mosquitoes of the genus Culex, and no other kind,
are capable of transmitting this type of malaria from bird to bird.
Grassi (f900) published a classical monograph on the life history
of the organism causing tropical malaria (P '. falciparum) , and with
beautiful figures of the developmental stages in the gut of the
mosquito. Supplementing Ross's observations on Culex, he showed
that mosquitoes of the genus Anopheles alone have the power to
transmit human malaria. Schaudinn (1902) confirmed these find-
ings by working out the life history of Plasmodium vivax, the cause
408 BIOLOGY OF THE PROTOZOA
of benign tertian malaria of man. He also added the last link to
the chain of evidence by watching the penetration of a human blood
corpuscle by a sporozoite fresh from a mosquito's proboscis.
The essential features by which the different types of malaria
organisms are distinguished are: (1) Length of time between suc-
cessive sporulating periods; (2) relative sizes of parasites and human
blood corpuscles; (3) effects of the parasites upon human corpuscles;
(4) relative numbers of merozoites formed at sporulation; (5) gen-
eral form of the sporulating organisms; (6) distribution of the
melanin ; (7) form of gametocytes.
1. The early history of the trophozoite is much the same in all
species. After an initial infection sporozoites enter erythrocytes
as minute rounded bodies (Plate I) which soon give rise to ring-
shape inclusions (signet-ring stage); these are characteristic of all
malaria organisms and, except for size, they are all alike (Plate I,
Figs. 1, 7, 13). When fully grown the nucleus divides from three to
five times, after which the parasite breaks up into as many merozo-
ites as there are nuclei (Plate I, Figs. 4, 10). Upon rupture of the
corpuscle the merozoites enter other normal corpuscles and the de-
velopmental cycle is repeated.
Invasion of corpuscles and their destruction thus increases by
geometrical progression until a stage is reached and enough toxic
substances are freed in the blood to give the first definite clinical
symptoms of the disease. Such a period of incubation, i. e., from
the time of inoculation to the first clinical symptoms, usually lasts
from ten to twelve days. A second convulsion (pyrexial attack)
occurs after the merozoites liberated at the time of the first attack
have grown to full size and again undergo sporulation. The time
required for this growth and reproduction differs with different
species and furnishes an important diagnostic character for the
identification of species. Thus P. vivax, the cause of so-called
benign tertian malaria, since it is rarely fatal, sporulates at forty-
eight -hour intervals (every third day); P. malariae, the cause of
quartan malaria, on every fourth day or at seventy-two-hour
intervals; and P. falciparum, at irregular intervals, from quotidian
to tertian. Fever charts of clear cases of tertian, quartan and sub-
tertian malaria are thus characteristically different.
2. While the phases of activity of all species of Plasmodium are
alike, there is a distinct difference in size of the parasites as shown
by the proportion of the corpuscle that is occupied. P. vivax rarely
exceeds three-quarters of the erythrocyte; P. malariae, the largest
of the Plasmodium species of man, may occupy as much as nine-
tenths; and P. falciparum, the smallest, rarely grows to more than
two-thirds the size of the corpuscle.
3. The effects of the parasites upon the infected corpuscles are
likewise different; P. civa.v causes a measurable enlargement
(Plate I), while in preparations stained by the Giemsa method
PLATE I
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12
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Plasmodium Species.
1. 2, trophozoite and schizogony; 5, female gametocyte and 6, male ■•
ax; 7. 8, 9 and 10, trophozoil hizogony; 11, !
gametocyte and 12, male gametocyte of I', malaria : 13-16, trophozoite and schizogony;
17, ga X 2000.
esy of B>
PLATE 1 1
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[
Plasmodium Falciparum.
Figures A F, development of the microgametocyte; G-L, develop]
macrogamete.
After Aragao, Memorias do Irtstiluto Oswaldo Cr
ECOLOGY, COMMENSALISM AND PARASITISM 400
infected corpuscles are uniformly stippled with pink spots, the
so-called Schuffner dots. The other 2 species cause no enlarge-
ment of the corpuscles, on the contrary there is a tendency to
reduce them; Sehiiffner's dots are absent, but irregularly scat-
tered larger dots (so-called Maurer's dots) are frequently present
in infections by P. falciparum.
4. While the numbers of merozoites formed by the sporulating
individual are not always the same but fluctuate about a given
mean, this mean or average is quite different in the 3 species. For
Plasmodium vivax it is 16; for P. malariae, about 8; for P. falciparum,
about 24.
5 and 6. During the growth of the parasite granules of dark
substance, known as melanin, malarial pigment, etc., and regarded
as products of hemoglobin breakdown, are stored up in the Plasmo-
dium protoplasm. At sporulation this melanin may be distributed
irregularly between the merozoites as it is in P. vivax, or clumped
in the center of the group as in P. malariae and P. falciparum.
In P. falciparum the merozoites are irregular as in P. vivax, but in
P. malarial' they are grouped rosette-like about the clump of
melanin (Fig. 12+, p. 2'-\S).
7. The gametocytes, finally, afford still another diagnostic
morphological character. It is limited, however, for there is not a
great difference between those of vivax and those of malariae. In
P. falciparum they are distinctly differentiated as crescents, the
female crescent with a slightly more definite capsule about it than
the male crescent (Plate II). All gametocytes are present in the
circulating blood with which they are taken into the stomach of a
female Anopheline mosquito.
The evolution of the gametocytes of P. falciparum has recently
been studied by Aragao (1930), who finds that there is a distinct
difference between the male and female gametocytes which may
be traced back to the merozoite stages. Merozoites destined to
form male gametocytes after entering a corpuscle are spherical,
with a distinct nucleus and without the vacuole typical of ring
forms (Plate II). The young female gametocyte, upon entering a
corpuscle stretches out across the corpuscle in the form of an
elongate bar. In all stages of its evolution the chromatin is more
definite than in the male gametocyte.
The sexual stages in the life history of Plasmodium, consisting
of maturation and fusion of the gametes, development of the zygote
and formation of sporozoites, all take place in the body of the
mosquito. In these processes there is no important difference in
the three species. The gametocytes of the circulating blood in
which no further development occurs, under the influence of the
changed conditions, are stimulated to undergo their maturation
processes whereby the female gametocyte becomes a macrogam-
ete and the male gametocyte gives rise to a small number of
410 BIOLOGY OF THE PROTOZOA
microgametes. After fusion of a macrogamete and a microga-
mete the zygote becomes a motile vermicule which makes its way
to the lining membrane of the gut, penetrates it and comes to
rest in the submucosa. Here the amphinucleus divides many
times and the cell body increases enormously in size, the delicate
fertilization membrane, unlike the resistant oocyst of the Coccidia,
enlarging with it. As growth progresses, the sporoplasm breaks
up in "islands" which suggest the sporoblasts of Coccidia, and
about each of them the nuclei are peripherally arranged. The
sporozoites are budded out from these islands, each with one of the
peripheral nuclei. These are ultimately liberated in the body
cavity of the mosquito; make their way to the salivary glands
which they penetrate, and come to rest in the lumen from which
they finally reach the proboscis.
(For genera of Hemosporidia and other Coccidiomorpha, see
Key, p. 566.)
CHAPTER XI.
SPECIAL MORPHOLOGY AND TAXONOMY OF THE
MASTIGOPHORA.
The classification of Protozoa was first put on a modern basis
by Biitschli (1882 L888). By this time larval forms of various
groups of invertebrates, worms, entomostraca, rotifers, desmids and
diatoms, all of which had been included in the Leeuwenhoek group
of Animalcula, were properly classified, and the Protozoa were
limited to the forms which we know today. For general purposes
there has not been much improvement over Biitschli 's system
whereby the Protozoa were divided into four main groups: (1)
The Sarcodina, in recognition of Dujardin's pioneer work on the
living substance of rhizopods; (2) the Mastigophora, a term sug-
gested by Diesing (1865) for Dujardin's group les flagelles; (3) the
Infusoria, a term connoting the original Infusionsthiere, and Leden-
miiller's term Infusoria, and Dujardin's les ciliees; and (4) the
Sporozoa, a term introduced by Leuckart (1879) for strictly parasitic-
types of gregarines, and coccidia.
The majority of recent workers have followed Doflein (1901) in
dividing the phylum Protozoa into two unequal groups or sub-
phyla: (1) The Plasmodroma, including Mastigophora, Sarcodina
and Sporozoa; and (2) the Ciliophora, including Ciliata and Suc-
toria. The writer fails to see any advantage in the creation of these
sub-phyla, although the Infusoria differ from other Protozoa, not
only in having dimorphic nuclei and fertilization by conjugation,
but also in the possession of the most highly differentiated cortex
to be found in the entire group of Protista. The absence of di-
morphic nuclei in some groups (Opalinidae), the occurrence of
fertilization by copulation of gametes (Glaucoma, Opalinidae) and
the interpretation of conjugation as evidence of an ancestral brood
of gametes indicate that in these respects the Infusoria fall in line
with other Protozoa.
A second change introduced by Doflein (1901) was to divide the
Sporozoa into two sub-phyla — Cnidosporidia and Sporozoa, s.str.,
the former including Myxosporidia, Microsporidia, Sarcosporidia
and Actinomyxida; the latter gregarines, coccidia and hemosporidia.
This change has much to recommend it and is adopted in the present
work. Other, but minor, changes from the classification as given
in the first edition of the present work will be found in each of the
412
BIOLOGY OF THE PROTOZOA
sub-phyla treated, while the keys to genera are entirely recast.
An important change is the omission here of all groups of chlorophyll-
hearing forms. Beginning with Pascher (1914) these were classified
as Algae, and they find a much more logical position as branches
of the botanical Stammbaum than they have in any protozoan rela-
tionship. As Protista or as Protophyta they have their unques-
tioned place, but as Protozoa they are anomalous (see also p. IS).
Diesing's term Mastigophora referred primarily to plant flagellates
and a new term should be provided for animal flagellates; I suggest
the sub-phylum Zoomastigophora.
Fig. 174. — Types of Rhizomastigidae. A, Mastigamoeba aspera. B, Actinomonas
mi nihil is; f, flagella; /), pseudopodia. (From Calkins after F. E. Schultze and Sav.
Kent.)
The only common characteristics of this group of Protozoa are
the possession of one or more vibratile motile elements in the form
of flagella, and reproduction by longitudinal division. In other
respects they differ widely in: (a) Complexity of organization,
axial relations, symmetry and body form; and (b) distribution and
mode of life.
Organization. — Many of the flagellates are simple ellipsoidal mon-
axonic organisms with a single flagellum at the anterior end (Pro-
tomonads); others are ameboid (Pantastomatida, Fig. 174); some
are bilaterally symmetrical (Diplozoic forms); some spherical
(Actinomonas, etc.) and some are spirally twisted (Holomastigo-
tidae, etc.).
While flagella are for the most part all similar in finer structure
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 41l>
(see p. 141), they vary widely in number, size and arrangement on
the organism. The most generalized types have 1 flagellum which
is directed forward (Herpetomonas, Leishmania, Crithidia, etc.).
When 2 are present they may be similar in length and in orienta-
tion (Amphimonadidae) or of dissimilar length and oriented in the
same direction (Monadidae) or they may be oriented in different
directions (Bodonidae, Embadomonadidae, Cercomonas, etc.).
One of the 2 may be adherent to the body (Cercomonas), or, re-
tained by the periplast, forms the margin of an undulating mem-
brane (see p. 142) as in Trypanoplasma, Cryptobia, Trypanophis,
etc. If 3 flagella are present, 1 is directed anteriorly while 2 are
trailing flagella (Trimastix, Dallingeria, Macromastix). When 4
are present, all may be directed anteriorly (Tetramitns, Copro-
mastix, Polymastix) ; or one may be trailing (Eutrichomastix,
Retortamonas) or retained within a buccal furrow or cytostome,
while 3 are directed forward (Chilomastix) . In some forms the
trailing flagellum may be attached to the periplast (Tricercomitus)
or it forms an undulating membrane (Trichomitns, some species of
Trichomonas). In some forms there are 4 or 5 anterior flagella
and an undulating membrane (Trichomonas). In another group
of forms the single flagellum forms an undulating membrane (Try-
panosoma, Myxomonas). Myxomonas (Dogiel) may even lose its
undulating membrane and turn into an ameboid wood-eating
form.
In one group of flagellates (diplozoic forms), including both
free-living and parasitic types., the organisms are bilaterally sym-
metrical. These interesting forms have two sets of flagella placed
symmetrically and 1 or 2 nuclei. They are supposed to have arisen
by reason of the suppression of cell division after the nucleus and
kinetic centers have divided. Similar double forms occur amongst
the ciliates where, by treatment with chemicals or ultra-violet rays
during division stages, cytoplasmic division is prevented (Glaucoma,
Chatton), or by union during conjugation double individuals result
(Uroleptus, see p. 245). Free-living diplozoic forms include Gyro-
monas, Trigonomonas, Trepomonas, Ilexamitus and Urophagus
and 2 genera of parasitic forms — Giardia and Octomitus. The
flagella are 4 in number in Gyromonas, 6 in Trigonomonas and 8 in
Hexamitus, Trepomonas, Urophagus, Octomitus and Giardia (Fig.
17, p. 37).
A multiple number of flagella is quite characteristic of parasitic
Mastigophora, particularly parasites of the white ants (Termites).
Such polymastigote forms may have a single nucleus (monozoic
Hypermastigidae) or many nuclei (polyzoic types). The latter,
like diplozoic forms above, are supposed to have arisen by multiple
division of the nucleus and kinetic complex without accompanying
cell division (somatella stage). According to Janicki (1915), each
414
BIOLOGY OF THE PROTOZOA
nucleus is accompanied by a blepharoplast, from which flagella
are developed, a parabasal body and an axial thread. Each such
group of cellular elements is a karyomastigont (Janicki) ; in some
groups the nucleus is lost but the kinetic complex remains, such
enucleate groups being akaryomastigonts. In all cases the axial
threads are united to form an axial strand which runs through to
the posterior end. Calonympha, Foa, and Stephanonympha,
Janicki, are compound individuals of karyomastigonts alone, or of
karyomastigonts and akaryomastigonts which are massed at the
anterior end of the cell and spirally arranged in Stephanonympha
Fig. 175. — Stephanonympha sylvestri; with many nuclei, kinetic groups, and flagella.
Rhizoplasts unite to form the inner axial strand. (After Janicki.)
(Fig. 175). Proboscidiella, Kofoid and Swezy, is likewise multi-
nucleate but differs in having a protrusible proboscis.
A large group of monozoic parasitic forms with from 4 to many
flagella leads into the highly complicated hypermastigotc flagellates.
Parabasal bodies, axostyles and axial strands may be single or
multiple in the cell. Polymastix, Biitschli, has 4 flagella and an
axostyle; Ilexamastix, Alexeieff (1912). has ('»; and there are 6 or
more also in Cochlosoma, Kotlan (1932). Oxymonas, Kofoid and
Swezy, has 6 flagella and, like Proboscidiella, bears a protrusible
proboscis. The 2 genera Pyrsonympha, Leidy, and Pinenympha,
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 415
Leidy, agree in that all of the flagella arise at the anterior end and,
like the trailing flagellum of Tricereomitus, adhere to the body to
form short free whips at the posterior end. The attached flagella
in some species form conspicuous spiral ribs down the body, and
these in some cases give an appearance of undulating membranes.
Axostyles are present which end freely in the endoplasm of
Pyrsonympha, but are attached at the
posterior end in Dinenympha (Fig. 176).
There is little doubt that the Hypermas-
tigida are the most highly differentiated of
all flagellate types. The differentiations,
however, have to do solely with the com-
plications of the kinetic elements or neuro-
motor system, for the nucleus is invariably
single. The group embraces only 1 genus—
Lophomonas (intestinal parasites of cock-
roaches) which is not found in termites.
Blepharoplasts and basal bodies are num-
erous while axial threads and so-called para-
basal bodies form variously complicated
internal structures. In the majority of
species the flagella are grouped at the
anterior end. Here they form a single
group or tuft of flagella in Lophomonas
(Fig. 105, p. 211) ; a spirally arranged group
of similar tufts (loricula) in Kofoidea, Light.
In Joenia, Grassi, the anterior flagella are
separated in two groups, one of which
forms an anteriorly-directed tuft, the re-
mainder, like trailing flagella, forming a
flagellar mantle about the body. A more
or less similar anterior grouping of flagella
is characteristic of Staurojoenia, Grassi,
Parajoenia, Janicki, Joenopsis, Cutler,
Joenina, Grassi, Gynmonympha, Dobell,
and Leidyonella, Frenzel. In Hoplonym-
pha, Light, they are arranged in two oppositely-directed tufts.
They are arranged in longitudinal rows, extending part way down
the body in Microjoenia, Grassi, and in Leidyopsis, Kofoid and
Swezy, and in spirally-wound rows from end to end in Holomas-
tigotoides, Grassi, Spirotrichonympha, Grassi, and Microspironym-
pha, Koidzumi. In Pseudotrichonympha, Hartmann, a covering of
flagella clothes the entire body, the flagella increasing slightly in
length toward the posterior end. This dissimilarity of flagella is
emphasized in Trichonympha, Leidy, where the flagella cover only
one-half to two-thirds of the body. The shorter, anterior flagella
Fig. 170. — Dinenympha
fimbriata — network of Golgi
apparatus at posterior end.
(After Brown, Arch. f. Pro-
tistenkunde; courtesy of G.
Fischer.)
416 BIOLOGY OF THE PROTOZOA
extend anteriorly or laterally while the longer ones extend posteriorly,
covering the entire hinder end of the organism.
With these enormously-developed external locomotor organs we
would expect to find more or less complicated internal structures
for attachment and support. In uniflagellate forms these are rela-
tively simple, the single flagellum originating from and attached to
a kinetic element in the nucleus or on its membrane (Salpingoeca,
J. Clark); or from a kinetic element (blepharoplast) in the cyto-
plasm (e. g., Oicomonas, Kent; Trypanosoma, Gruby, etc.). Com-
plications appear with the development of the parabasal body
(Herpetomonas, Crithidia, etc., see p. Ill) and with the axostyle
while parastyles and epistyles support the undulating membrane
and other motile organs. The nucleus is supported by axial threads
from the blepharoplasts in Lophomonas, by the axostyle in Tricho-
monas, Joenia and Parajoenia and Metadevescovina and by special
strands or membranes in Trichonymphidae.
Basal bodies are frequently united into apparently solid bars as
in the head organ of Triclionympha or plates as in Staurojoenia
assimilis, Kirby, the former acting as a complicated centrosphere
(centroblepharoplast, Kofoid) during division (Fig. 54, p. 100). In
Joenopsis polytricha, Cutler, this becomes a horseshoe-shape struc-
ture which bears the basal bodies for the anterior flagella.
With these intestinal forms bacteria are frequently found attached
to the body wall and may be mistaken for additional flagella. In
some cases they become a part of the organism, forming a fairly
complete armature (e. g., Lophomonas striata, Biitschli).
The protoplasmic body in all types of flagellates contains the usual
cytoplasmic substances. Mitochondria are probably universally
present (see p. 73), and volutin (see p. 72) is widely distributed,
if not universal. ( nromidia are only rarely present (Rhizomas-
tigidae).
The presence of Golgi bodies (see p. 77) is not demonstrated in
many forms, and some difference of opinion has arisen concerning
the chemical identity of certain characteristic structures, particu-
larly the parabasal body. Kofoid (1916) believed it to be of
chromatin (nucleic acid) nature, acting as a reservoir of substance
to maintain the activity of the kinetic elements. The chromatin
make up of the blepharoplast in Trypanosoma supports this view.
A similar purpose of the parabasal is advocated by Janicki (1915)
and by Duboscq and Grasse (1925), but they argue against its
chromatin nature and regard it as the homologue of the metazoan
Golgi apparatus and the product of the vacuome (Parat). This is
based on the fact that the colorable substance is often immediately
adjacent to a colorless vesicle. Janicki holds that the parabasals
present in large number in the Polymastigida and Ilypermastigidae
secrete substances of high potential energy which are used by the
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 417
complex motile organs for movement. Duboscq and Grasse hom-
ologize the parabasal with the idiosome of spermatozoa which is
regarded as a Golgi element, while Grasse (1925) interprets the
parabasals in Trichomonas batrachorum and Tetramastix bufonis as
secretory in function, forming minute droplets which break up into
smaller elements for distribution in the cytoplasm. Brown (1930),
more recently, dissents from this interpretation and finds no evi-
dence in Dinenympha or Pyrsonympha to support the view that
parabasals are homologous with the Golgi apparatus. The latter
is present, however, in the form of distributed spherical bodies,
which may appear as crescents or rings and which are believed to
be secretory in nature. When the granules are present, a Golgi
network is absent or much reduced, but a typical network appears
at times at the base of the axostyle (Fig. 176).
These diverse points of view leave us very much in the air in
regard to the chemical nature and function of the parabasal body
so conspicuous in the parasitic flagellates. Their variations in size
and shape in the same species certainly indicate their connection
with some urgent metabolic need, but for the present at least the
nature of this need is enigmatical.
Nuclei are not especially characteristic. In Protomonads it is
usually of the centronucleus type— with endosome and frequently
with endobasal body (see p. 60). In more complicated flagellates
(Polymastigida and Hypermastigida) the endosome becomes
greatly reduced or absent altogether and no longer contains the
centriole. The latter is either on the nuclear membrane or as a
blepharoplast near to it, and, during nuclear activity, it divides
with a connecting strand. This strand is homologous with the
intranuclear centrodesmose of simpler types, but remains outside the
nucleus as a paradesmose (Fig. 54, p. 100). Here, therefore, we have
evidence of a permanent separation of chromatic and kinetic com-
ponents of the nucleus, the latter now being permanent cytoplasmic
structures. A peculiarity of the chromosomes in some cases is the
apparent reduction to one-half the normal number during mitosis
(Giardia microti, Boeck, 1917; Trichonympha campanula, Kofoid
and Swezy, Fig. 54, p. 100), although with the possible exception of
Helkesimastix, Woodcock and Lapage (1915) no fertilization proc-
esses are safely established for any type of animal flagellate.
Contractile vacuoles are generally distributed in the free-living
forms, where they are invariably simple vesicles. In parasitic forms
they are generally absent.
Reproduction of flagellates is typically by simple longitudinal
division. In free-living forms the individual in many cases remains
connected by stalk-like processes (Poteriodendron, Fig. 177), or by
dichotomously branched gelatinous tubes (Cladomonas) or laterally
cemented tubes (Rhipidodendron). In some cases they are embed-
27
41S
BIOLOGY OF THE PROTOZOA
ded in masses of jelly (Spongomonas, Phalansterium). Amongst
parasitic forms many species show both simple division and multiple
division, during which nuclei and kinetic elements divide two or
Fig. 177. — Arboroid colony of protomonads, Poteriodendron petiolatum.
more times without division of the cell body (somatella formation).
In rare cases such phenomena are accompanied by the formation of
a cyst membrane and the process becomes a typical sporulation
(Fig. 122, p. 234).
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 419
Adaptations and Mode of Life.— Owing to their remarkable powers
of adaptation animal flagellates may be found in practically any
place with moisture. They are less abundant in clear drinking
waters, where plant flagellates may abound, than in ponds and pools,
where decaying vegetation is plentiful; some types of free-living
forms have become adapted to the conditions of the soil, others to
the putrefactive conditions of dung and feces in general.
Fig. 178. — Types of ehoanoflagellates. 1, Acanthoeca spectabilis; 2, Dicraspedella
stokesi, collar with short secondary collar; 3, Choanoeca perplexa, collar flattened;
4, Ste.phanoeca ampulla; 5, Pachyaoeca longicollis; (S, Diploeca placila; 7, Diaphanoeca
parva; 8, Choanoeca perplexa at division, young cell with flagellum leaving sister
cell in old house. (After Ellis, Ann. de la Soc. Royale Zoologique de Belgique, 1929;
courtesy of M. Forton.)
A favorite haunt for many of these types is in ponds or pools
where decomposition is active. Many of them are bottom forms
attached to debris or working their way about in the superficial
slime. Some are ameba-like (Rhizomastigidae) and in addition
to their flagella put out pseudopodia from any part of the body.
Others are like Ileliozoa and possess ray-like pseudopodia (Aetino-
420
BIOLOGY OF THE PROTOZOA
monas). Swimming types have a thickened periplast which may
be smooth as in Phialonema (Fig. 60, p. 110) or longitudinally
and spirally ribbed (Heteronema, Tropidoscyphus) . In one group
(Choanoflagellates) a protoplasmic collar surrounds the flagellum
(Fig. 178).
Fig. 179. — Flagellates with suckers, from the ruffed grouse. A, C, normal forms
of Cyathosoma striatum; B, dividing form of same; D, normal form of Ptyehostoma
bonasae; E, beginning of unequal division of same; F, slender individual, without
sucker, resulting from unequal division. X 2400. (After Tyzzer, 1930; courtesy of
Am. Jour. Hyg.)
The great majority of animal flagellates, however, have become
adapted to the anaerobic conditions accompanying a parasitic mode
of life and these flagellates have become a vital factor in the hygienic
and economic relations of man, other animals and some plants (see
Chapter X, p. 352). Some parasitic forms have developed suckers
for attachment (e. g., Cochlosomidae, Fig. 179),
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 421
SPECIFIC CLASSIFICATION.
1. The Water- dwelling Flagellates. — In separating the chloro-
phyll-bearing flagellates from Protozoa we encounter the difficulty
of border-line forms which, except for the absence of chlorophyll,
appear to be related to forms with chlorophyll. Euglena gracilis,
for example, ordinarily has chlorophyll, but upon cultivation in the
dark the chlorophyll is lost and the organisms live as saprophytes.
Such forms combine, therefore, holophytic and saprophytic modes
of food-getting, but it is obvious that they should not be included
with animal flagellates. By the same reasoning a number of
colorless forms should be retained with their structurally similar
colored relations so long as there is no question regarding their
homologous structures. Thus the colorless Chilomonas is so similar
to Cryptomonas in structure that it may be regarded as a descen-
dant of a chlorophyll-bearing form which has become permanently
adapted to a saprophytic mode of life. So, too, many of the Dino-
flagellates have lost their chlorophyll and live as animals do, either
by holozoic methods (Gymnodinium, Xoctiluca, etc.) or by parasitic
methods (Oodinium, Haplozoon, etc.). Here the characteristic
structures of the Dinoflagellates in swarm spores or adults are so
pronounced that the affinities are clearly indicated.
With other colorless flagellates, however, which have been
claimed by botanists, the affinities are obscure and there is no more
reason for regarding them as recently modified chlorophyll-bearing
types than as definitive animals. It may be true that all animal
groups should look back to the dim past for their plant ancestors,
but this does not mean that modern zoology should continue to
rest in the lap of botany.
Among such colorless forms which should be transferred to the
animal flagellates, Astasia, Menoidium, Englenopsis, Peranema,
Urceolus and Petalomonas would be classified as Protomonads;
Distigma, Sphenomonas as Monadidae; Heteronema, Tropido-
scyphus, Anisonema, Entosiphon and Marsupiogaster as Bodonidae.
These are all free-living holozoic or saprozoic forms living in fresh,
salt and brackish waters.
CLASSIFICATION OF THE ANIMAL FLAGELLATES.
Phylum Protozoa, Goldfuss, 1820.
Sub-phylum Zoomastigophora (Animal Flagellata).
Class I. Protomastigota.
Order 1. Protomonadida.
Family 1. Rhizomastigidae.
Family 2. Oicomonadidae.
422
BIOLOGY OF THE PROTOZOA
Class I. Protomastigota.
Order 1. Protomonadida.
Family
3.
Peranemidae.
Family
4.
Trypanosomidae.
Family
5.
Bicoecidae.
Family
6.
Craspedomonadidae
Family
7.
Amphimonadidae.
Family
8.
Monadidae.
Family
9.
Bodonidae.
Family
10.
Cercomonadidae.
Family
11.
Trimastigidae.
Class II. Metamastigota.
Order 1. Hypermastigida.
Family 1. Lophomonadidae, Grassi
Family 2.
Family 3.
Family 4.
Family 5.
Family 6.
Family 7.
Family 8.
Order 2. Polymastigida.
Sub-Order l.—Monokaryoma.stigina.
Family 1. Callimastigidae.
Family 2.
Family 3.
Family 4.
Family 5.
Family 6.
Family 7.
Family 8.
Family 9.
Sub-Order 2. Dikaryomastigina.
Sub-Order 3. Polykaryomastigina .
Family 1. Oxymonadidae.
Family 2. Calonymphidae
Hoplonymphidae, Light.
Kofoidiidae, Light.
Joeniidae, Grassi
Staurojoeniidae, Grassi.
Holomastigotidae, Grassi.
Trichonymphidae, Saville Kent.
Cyclonymphidae, Doflein.
Dinenymphidae.
Tetramitidae.
Trichomonadidae.
Devescovinidae.
Spironemidae.
Streblomastigidae.
Chilomastigidae.
Cochlosomidae.
Class I. PROTOMASTIGOTA.
Order PROTOMONADIDA.
Key to Families.
1. Flagellates always with pseudopodia in
addition to flagella 1 Family Rhizomastigidae
Flagellates without habitual pseudopodia 2
2. With one or more posteriorly-directed
flagella !*
Flagella directed anteriorly 3
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 423
Key to Families.
3. With one flagellum 4
With two flagella 8
4. Non-parasitic forms 5
Parasitic flagellates 4 Family Trypanosomidae
5. With protoplasmic collar about flagellum
6 Family Craspedomonadidae
Without protoplasmic collar (>
(3. Body wall distinct 3 Family Peranemidae
Body wall indistinct 7
7. With proboscis-like process. . . .5 Family Bicoecidae
Without proboscis 2 Family Oicomonadidae
8. Flagella of similar length 7 Family Amphimonadidae
Flagella of dissimilar length. . . .8 Family Monadidae
9. With one posteriori y directed flagellum. . 10
With two posteriorly directed flagella
11 Family Trimastigidae
10. Trailing flagellum leaves body at the
anterior end 9 Family Bodonidae
Trailing flagellum attached to full length
of body 10 Family Cforcomonadiuae
PROTOMONADS— Genera.
Family 1. Rhizomastigidae Butschli.
1. Flagella and pseudopodia distributed
around body
( lenus (incertae sedis)
.1/ ulticilia Cienkowsky
Flagella originate from anterior end of
body 2
2. Pseudopodia lobose 3
Pseudopodia ray-like 4
3. Flagellum arises from nucleus Genus Mastigamoeba F. E. Sch.
Flagellum independent of nucleus . . Genus Mastigella Frenzel
4. Stalked forms 5
Body not stalked; ray-like pseudopodia
with axial filaments
(? Genus Dimorphiella) Genus Dimorpha Gruber
5. Pseudopodia confined to circle about base
of flagellum Genus Pteridomonas Penard
Pseudopodia not limited to flagellum region
Genus Actinomonas S. Kent
Family 2. Oicomonadidae Senn.
1. Individuals not cup-dwelling 2
Individuals cup-dwelling 6
2. Form flattened, leaf-like Genus Ancyromonas S. Kent
Form spheroidal to ellipsoidal 3
3. Not parasitic ... . 4
Parasitic — cause of "blackhead" in turkeys
Genus Histomonas Tvzzer
4. Kinetoplast marginal 5
Kinetoplast not marginal Genus Proleptomonas Woodcock
5. Flagellum delicate, short, active. . . .Genus Oicomonas S. Kent
Flagellum heavy, long, sluggish .... Genus Rigidomastiz Alexeieff
6. Cup stalked Genus Codonoeca J. Clark
Cup without stalk Genus Platytheca Stein
424 BIOLOGY OF THE PROTOZOA
Family 3. Peranemidae Stein.
1 . Body metabolic 2
Body rigid 3
2. Body with endoplasmic rod ("Stab-"'
organ) Genus Peranema Dujardin
Body without endoplasmic rod Genus Euglenopsis Klebs
3. Endoplasm with rod apparatus .... Genus Urceolus Mereschkowsky
Endoplasm without rod apparatus 4
4. Periplast smooth 5
Periplast heavy, with 1-7 longitudinal fur-
rows or ridges Genus Petalomonas Stein
5. Periplast delicate Genus Scytomonas Stein
Thick and heavy Genus Thylacomonas Schewiakoff
Family 4. Trypanosomidae Doflein.
1. Undulating membrane absent 2
Undulating membrane present 6
2. Definitive hosts plants — cysts absent
Genus Phytomonas Donovan
Definitive hosts animals 3
3. Vertebrate and invertebrate hosts. .Genus Lei sh mania Ross
Invertebrate hosts only 4
4. Protoplasmic body extended around base
of flagellum Genus Crithidia Leger
Flagellum without protoplasmic extension . 5
5. Kinetoplast always anterior to nucleus
Genus Leptomonas S. Kent
Kinetoplast posterior to nucleus in some
phases Genus Herpetomonas S. Kent
6. Hematozoic forms only in vertebrate
Genus Trypanosoma Gruby
Hematozoic and cytozoic forms in verte-
brate 7
7. Cytozoic phases in erythrocytes .... Genus Endotrypanum
Mesnil et Brimont
Cytozoic phases in organ cells and tissues
Genus Schizotrypanum Chagas
Family 5. Bicoecidae Stein.
1. Cells with proboscis-like process at flagel-
lum base 2
Cells with thin periplastic process . . Genus Bicoeca Lauterborn
2. Cells without contractile thread; process
sail-like Genus Histiona Voigt
Cells with posterior contractile thread
Genus Poteriodendvon Stein
Family 6. Craspedomonadidae Stein.
1. Individuals with one collar 2
Individuals with two collars 17
2. Individuals without lorica or test 3
Individuals with lorica 10
3. Individuals solitary 4
Individuals colonial 5
4. Cells with very short stalks or none. .Genus Monosiga S. Kent
Cells with very long stalks Genus Codonosiga S. Kent
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 425
Family 6. Craspedomonadidae Stein.
5. Individuals not embedded in jelly 6
Individuals embedded in jelly 8
(3. Colonies umbellate, attached Genus Codonocladium Stein
Colonies free-swimming 7
7. Colonies with individuals attached radially
Genus Astrosiga S. Kent
Colonies band form; individuals side by
side Genus Desmarella S. Kent
8. Collars not enclosed by jelly 9
Collars enclosed by jelly Genus Phalansterium Cienkowsky
9. Individuals irregularly distributed in jelly
Genus Proterospongia S. Kent
Individuals radially distributed in jelly
Genus Sphaeroica Lauterborn
10. Lorica single 11
Lorica double Genus Diploeca Ellis
11. No circlet of marginal spines 12
With circlet of marginal spines Genus Acanthoeca Ellis
12. Lorica does not enclose collar and flagellum 13
Lorica encloses collar and flagellum 16
13. Individuals attached 14
Individuals free-swimming Genus Lagenoeca S. Kent
14. Lorica delicate, thin 15
Lorica thick with long neck Genus Pachyoecu Ellis
15. Collar huge, conspicuous, flagellum tran-
sient Genus Choanoeca Ellis
Collar small, inconspicuous Genus Salpingoeca Clark
16. Lorica with definite constriction above
collar Genus Diaphanoeca Ellis
Lorica with constriction below collar
Genus Stephanoeca Ellis
17. Individuals without lorica 18
Individuals with lorica Genus Diplosigopsis France
18. Both collars arise independently 19
Collars closely attached at base .... Genus Dicraspedella Ellis
19. Individuals sessile or with very short stalk
Genus Diplosiga Frenzel
Individuals with long stalks Genus Codonosigopsis Senn
Family 7. Amphimonadidae.
1. Individuals solitary 2
Individuals colonial, in jelly 7
2. Individuals naked 3
Individuals in cup Genus Diplomita S. Kent
3. Body not spirally twisted 4
Body spirally twisted Genus Spiromonas Perty
4. Form spherical, ovoid, or spindle-shape
Genus Amphimonas Dujardin
Form not spherical, ovoid, or spindle-shape 5
5. Form ear-shape, ectoparasitic on fish
Genus Costia Leclerque
Forms diverse — not ectoparasitic 6
6. Form horseshoe-shape Genus Furcilla Stokes
Form heart-shape Genus Streptomonas Klebs
7. Colonies irregular gelatinous masses. Genus Spongomonas Stein
Colonies branched or tubular 8
426 BIOLOGY OF THE PROTOZOA
Family 7. Amphimonadidae.
8. Colonies laterally associated tubes — organ-
pipe type Genus Rhipidodendron Stein
Colonies branched Genus Cladomonas Stein
Family 8. Monadidae Stein.
1. Individuals solitary 2
Colony-forming 5
2. Naked forms 3
Cup-dwelling Genus Stokesiella Lemmermann
3. Stalked; slime-covered; radial striations in
slime Genus Physomonas S. Kent
Free-swimming ; not stalked 4
4. Both flagella active Genus Monas Ehr.
Main flagellum stiff, anteriorly directed
Genus Sterromonas S. Kent
5. Monads in cups; colony branched. .Genus Stylobryon Fromentel
Monads not in cups 6
6. Single cells at ends of branched stems
Genus Dendromonas Stein
Groups of cells (corbels) at ends of
branched stems 7
7. Stalks colorless Genus Cephalothamnium Stein
Stalks colored yellow or brown Genus Anthophysa Bon-
Family 9. Bodonidae Blitschli.
1. Trailer not united with periplast to form
undulating membrane 2
Undulating membrane present — parasites . 18
2. One flagellum modified as a proboscis
Genus Rhynchomonas Klebs
Both flagella active 3
3. Individual metabolic 4
Individual rigid 12
4. With marginal bristles; occasional
branched pseudopodia Genus Thaumatomastix
Lauterborn
Without marginal bristles 5
5. With ventral furrow 0
No ventral furrow, cytostome apical or
absent 8
6. Flagella united at base by membrane
Genus Phyllomitus Stein
Flagella not united by membrane 7
7. Trailer short, rarely extending beyond fur-
row (parasitic) Genus Embadomonas Mackinnon
Trailer long, extending through furrow
beyond posterior end Genus Colponema Stein
8. Trailer used as gliding flagellum Genus Bodo (Ehr.) Stein
Trailer not a glider 9
9. Trailer used for attachment Genus Pleuromonas Perty
Trailer free 10
10. Parasitic Genus (Prowazekella) Proteromonas Kunstler
In stagnant waters — not parasitic 11
11. With apical cytostome Genus Heteronema Dujardin
Without cytostome Genus Dinomonas S. Kent
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 427
Family 9. Bodonidae Biitschli.
12. Body with keels or ridges 13
Bodv smooth — no ridges 15
13. With 1 to 4 ridges 14
With 8 ridges Genus Tropidosajphus Stein
14. Body flat Genus Sphenomonas Stein
Body ellipsoid Genus Notosolenus Stokes
15. Cytostome at end of internal protrusible
tube Genus Entosiphon Stein
Without internal or protrusible tube 16
16. With ventral furrow to posterior end. Genus Anisonema Dujardin
With pocket-like, deep cytostome 17
17. Mouth small; cell with rod or "Stab"-
organ Genus Dinema Perty
Mouth large; no "Stab "-organ. . . .Genus Marsupiogaster
Schewiakoff
IS. Without transverse bars Genus Cryptobia Leidy
With transverse bars Genus Trypanophis Keysselitz
Family 10. Cercomonadidae Kent.
1 . Without axoneme 2
With axoneme Genus Cercomastix Lemmermann
2. Primary flagellum single 3
Primary flagella two Genus Trimitus Alexeieff
3. Primary flagella very short, inconspicuous
Genus Helkesimastix
W< todcock and Lapage
Primary flagella conspicuous Genus Cercomonas Dujardin
Family 11. Trimastigidae Senn.
1. Secondary flagella arise from anterior end
Genus Macromastix Stokes
Secondary flagella arise below anterior end
Genus Dallingeria Kent
Class II. METAMASTIGOTA.
Order 1. HYPERMASTIGIDA Grassi.
1 . Organisms with segmented structure
Family 8. Cyclo nymphidae Dof.
Organisms without segmented structure . . 2
2. Flagella in bundles or tufts at anterior
end 3
Flagella not limited to anterior bundles ... 7
3. One bundle of flagella 6
Flagella in more than one anterior bundle. . 4
4. With two anterior bundles Family 2. Hoplonymphidae Light
With more than two bundles 5
5. With four bundles Family 5. Staurojoeniidae Grassi
With more than four bundles. . .Family 3. Kofoidiidae Light
6. Organisms without axostyle. . . .Family 1. Lophomonadidae Grassi
Organisms with axostyle Family 4. Joeniidae Grassi
7. All flagella insertion lines spirally wound
Family 6. Holomastigotidae
Grassi
Flagella insertion lines not spirally wound
Family 7. Trichonymphidae Kent
428 BIOLOGY OF THE PROTOZOA
Family 1. Lophomonadidae Grassi.
Flagella few (5-15) — termite parasite . . Genus Eulophomonas
Grassi and Foa
Flagella many (?) — cockroach parasite . Genus Lophomonas Stein
Family 2. Hoplonymphidae Light.
One genus Hoplonympha Light
Family 3. Kofoidiidae Light.
One genus Kofoidia Light
Family 4. Joeniidae Grassi.
1. Cell body with transverse furrow. . .Genus Joenopsis Cutler
Cell body without transverse furrow 2
2. Flagella inserted in longitudinal rows
Genus M icrojoenia Grassi
Flagella not in longitudinal rows 3
3. Flagella in one anterior bundle 4
Flagella arranged in circles or semi-circles . 5
4. Parabasal apparatus a single collar . . Genus Joenia Grassi
Parabasal apparatus double Genus Mesojoenia Grassi and Foa
5. Flagella in one circle — ring of parabasals
Genus Torquenympha Brown
Flagella arranged in semi-circles 6
6. Flagella in one semi-circle Genus Joenina Grassi
Flagella in two semi-circles; one trail-
ing flagellum Genus Para joenia Janicki
Family 5. Staurojoeniidae Grassi.
One genus with the family characters. .Genus Staurojoenia Grassi
Family 6. Holomastigotidae Grassi.
1 . With axostyle 2
Without axostyle 3
2. With 4 embedded, but conspicuous, flagel-
lar bands Genus Spirotrichonympha
Grassi and Foa
With many rows of flagella, no flagellar
bands Genus Holomastigotoides
Grassi and Foa
3. Periplast with conspicuous spiral folds
Genus Holomastigotes Grassi
Periplast without spiral folds Genus Spirotrichonymphella
Grassi
Family 7. Trichonymphidae (Kent) Grassi.
1. Flagella arising from anterior two-thirds
of body Genus Trichonympha Leicly
Flagella arising from most of body. .Genus Pseudotrichonympha
( I rassi and Foa
Family 8. Cyclonymphidae Doflein.
One genus Genus Cyclonympha Dogiel (Fig.
180) ( = Teratonympha
. Koidzumi)
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 429
Fig. 180.— Cyclonympha mirabilis, one of the Hypermastigida. (After Koidzumi.)
430 BIOLOGY OF THE PROTOZOA
Order 2. POLYMASTIGIDA.
Sub-order 1. Monokaryomastigina.
Key to Families.
1 . Bodj' not spirally wound (see exception in
Family 2) . . . *. 2
Body spirally wound or with spiral stripes . 8
2. Cy tostome, if present, not sucker-like .... 3
With sucker-like cytostome Family 9. Cochlosomidab
3. Without trailing flagellum 4
With trailing flagellum 6
4. Flagella six or more in number 5
Flagella less than six in number. .Family 3. Tetramitidae
5. Flagella grouped1 Family 1. Callimastigidae
Flagella distributed over body. Family 2. Dinenymphidae
6. With undulating membrane. . . .Family 4. Trichomonadidae
Without undulating membrane 7
7. Without cytostome Family 5. Devescovinidae
With definite cytostome Family 6. Chilomastigidae
8. Flagella four or more in number; anterior
Family 8. Streblomastigidae
Flagella twelve or more in number; lateral
Family 7. Spironemidae
Key to Genera.
Family 1. Callimastigidae da Fonseca.
Body spherical Genus Callimastix Weissenberg
Body watch-glass shape Genus Selenomonas Prowazek
Familv 2. Dinenymphidae Grassi.
1. With axostyle 2
Without axostyle. . . (Questionable) Genus Rhynchodinium
Da Cunha and Penido
2. Many flagella in spiral rows Genus Dinenympha Leidy
Four to eight flagella leaving body at pos-
terior end Genus Pyrsonympha Leidy
Family 3. Tetramitidae Biitschli.
1. Four flagella in one group 2
Four flagella in two groups 4
2. With axial fibril (coprozoic forms) ( lenus Copromastix Aragao
Without axial thread 3
3. With cytostome Genus Tetramitus Perty
Without cytostome, pseudopodial feci li ag
( renus Collodictyon Carter
4. Axostyle extends to posterior end . . .Genus Monocercomonas Grassi
Axostyle does not run to posterior end;
body ridged Genus Polymastix Biitschli
Familv 4. Trichomonadidae Wenyon(?)
1. With axostyle * 2
Without axostyle Genus Trichomitus
Kofoid and Swezy
1 Genus Hegneiia, Brumpt and Lavier, with 7 flagella; like Euglena bin color-
less and no stigma.
MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 431
Family 4. Trichomonadidae Wenyon(?)
2. Flagella less than five 3
Flagella six in number Genus Peniatrichomonoides Kirby
3. Parabasal wound around axostyle. .Genus Gigantomonas Dogiel
Parabasal not wound around axostyle
Genus Trichomonas Donne
Family 5. Devescovinidae.
1. With four flagella 2
With more than four flagella Genus Metadevescovina Light
2. Without axostyle 3
With axostyle _. . 4
3. Trailing flagellum leaves body at anterior
end Genus Retortomonas Grassi
Trailing flagellum leaves body at posterior
end Genus Tricercomonas
Wenyon and O'Connor
4. Parabasal wound around axostyle. .Genus Devescovina Foa
Parabasal rod-like 5
5. Parabasal a single rod 6
Parabasal double; two curved rods . . Genus Foaina Janicki
6. Parabasal closely applied to nucleus . Genus Janickiella
Duboscq and Grasse
Parabasal free from nucleus 7
7. Trailing flagellum leaves body near ante-
rior end Genus Paradevescovina Kirby
Trailing flagellum leaves body near poste-
rior end Genus Tricercomitus Kirby
Family 6. Spironemidae.
One genus Genus Spironema Klebs
Family 7. Streblomastigidae.
One genus Genus Streblomastix
Kofoid and Swezy
Family 8. Chilomastigidae.
1. With six flagella Genus Hexamastix Alexeieff
With four flagella 2
2. Trailing flagellum in cytostome; no axo-
style Genus Chilomastix Alexeieff
Trailing flagellum not in cytostome; with
axostyle Genus Eutrichomastix
Kofoid and Swezy
Family 9. Cochlosomidae Tyzzer,
1. Truncate anterior end with sucker 2
Anterior end not truncate ; cytostome large
Genus Cochlosoma Kotlan
2. Sucker flush with surface of body. . .Genus Cyathosoma Tyzzer
Sucker at end of tube-like prolongation
Genus Ptychosoma Tyzzer
Sub-order 2. Dikaryomastigina.
1. With more than four flagella 2
With four flagella (not parasitic). . .Genus Gyromonw Seligo
432 BIOLOGY OF THE PROTOZOA
2. With eight flagella 3
With six flagella (not parasitic) . . . .Genus Trigonomonas Klebs
3. Not parasitic 4
Parasitic 6
4. With two posterior cytostomal lobes
Genus Urophagus Klebs
Without cytostomal lobes 5
5. Flagella unequal in length Genus Trepomonas Dujardin
Flagella approximately equal (see also 7)
Genus Hexamitus Dujardin
(in part)
6. Cytostome present 7
Cytostome absent Genus Octomitus Prowazek
7. Cytostome single; anterior Genus Giardia Kunstler
(= Lamblia Blanchard)
Cytostome double (see also 5) Genus Hexamitus Dujardin
(in part)
Sub-order 3. Polykaryomastigina.
With proboscis Family Oxymonadidae
Without proboscis Family Calonymphidae
Family 1. Oxymonadidae Kirby.
1 . Said to be non-flagellated Genus Kirbyella Zeliff
Flag, anterior 2
2. Individual with single nucleus, double
kinetoplast Genus Oxymonas Janicki
Individual with one to several nuclei
Genus Proboscidiella
Kofoid and Swezy
Family 2. Calonymphidae Grassi.
1. Nuclei associated with kinetoplasts 2
Nuclei not associated with kinetoplasts
Genus Snyderella Kirby
2. Nuclei and kinetoplasts associated 3
Nuclei less numerous than kinetoplasts
Genus Calonympha Foa
(em. Grassi)
3. Nuclei in one anterior circle Genus Coronympha Kirby
Nuclei otherwise arranged 4
4. Each kinetoplast associated with one
nucleus 5
Each kinetoplast associated with more than
one nucleus Genus Diplonympha
5. Nuclei peripheral, spirally arranged . Genus Stephanonympha Janicki
Nuclei central, not spirally arranged . Genus Metastephanonympha
CHAPTER XII.
SPECIAL MORPHOLOGY AND TAXONOMY OF THE
SARCODINA.
The term Sarcodina was introduced by Biitschli in honor of
I )u jardin whose studies on the protoplasm of the Foraminifera led
him to believe that the living substance of these forms is simpler
than that of other living things and justifying his name for it —
sarcode. The peculiarity upon which Dujardin based his con-
clusion constitutes the essential difference between these types and
other groups of the Protozoa. A definite cell membrane is usually
absent and the body protoplasm in general is more fluid and more
tenuous than in other types. In the absence of confining mem-
branes and with the play of internal forces, protoplasmic processes
— pseudopodia are put forth so that the contour of the body
may be constantly changing, a phenomenon expressed by the term
ameboid movement.
The great majority of Sarcodina are suspended or floating forms
(Heliozoa, Radiolaria) and the ground type is homaxonic or spher-
ical, but creeping forms are characteristically flattened, while minor
variations of the spherical form lead to the greatest variety of radial
ellipsoidal and cylindrical types. They vary in size from a few
microns to many millimeters while some forms of fossil Foraminifera
are from 1 to 3 inches in diameter.
Unlike organisms in the three other great groups of Protozoa
the cortex of the Sarcodina rarely shows much structural differ-
entiation. In the majority of cases it is soft and highly vesicular
but shows a marked tendency to form an outer or inner lifeless
mantle of chitin. Such lifeless mantles or membranes may be
tightly fitting or may be in the nature of tests or houses. They
may be of pure chitin as in Coehliopodium, Gromia, etc., or, more
frequently, of chitin impregnated with iron oxides, or still more
frequently may serve as a substratum on which foreign particles
or plates and scales manufactured by the organism are cemented,
as in the majority of testate rhizopods. Or between lamellae of
chitin precipitation of calcium carbonate leads to the formation of
the limestone shells of the Foraminifera. Skeletons of silica or
strontium sulphate of varied patterns and often of exquisite design
are characteristic of the Radiolaria, while spicules, rods and plates
of silica are widely distributed amongst Heliozoa and Radiolaria.
28
434 BIOLOGY OF THE PROTOZOA
While many of the Sarcodina are typically uninucleate it may be
safely stated that this is exceptional in the group as a whole for
the vast majority of Mycetozoa, Foraminifera and Radiolaria are
multinucleate. Nuclear dimorphism, however, does not occur and
the multinucleate condition is brought about by fusion of cells to
form plasmodia as in the Mycetozoa, or by repeated division of
nuclei without accompanying division of the cell as in the Fora-
minifera and Radiolaria.
Contractile vacuoles are typical of fresh water forms and their
absence is equally typical of salt water and parasitic forms of
Sarcodina. When present they are invariably simple and burst
directly to the outside without reservoirs, canals or permanent
pores, and they furnish the best evidence for the view that contrac-
tile vacuoles here are primarily regulatory in a physical sense,
rather than excretory, in function.
The most characteristic feature of the Sarcodina as a group is the
ability of the individual cell to throw out protoplasmic processes
called pseudopodia, and movements of translation or in food-
getting are brought about by the protoplasm in the formation of
these processes. It was this ability which led Dujardin in 1841 to
distinguish these types as les rhizopodes from lesflagelles and les fibre*.
Pseudopodia, however, cannot be described by any one definition.
The most casual student of the Protozoa will not fail to recognize a
difference between the pseudopodia of Amoeba proteus and those of
an Arcella or Difflugia, while the difference is even more marked
between these types and the pseudopodia of any foraminiferon, or
between these and any heliozoon. These differences are so pro-
nounced that modern students of the Sarcodina beginning with
Lang have distinguished no less than four types of pseudopodia
under the names of axopodia, myxopodia, filopodia and lobopodia,
and there is some evidence that these four types and in the order
given represent adaptations of a degenerative nature from an ances-
tral flagellum-like type of motile organ.
Axopodia are homologous with the flagellum of Mastigophora
(p. 145). An axial filament extends from the endoplasm to the
tip of the pseudopodium. Many protozoologists, following Doflein,
regard this as essentially a supporting structure, but like the axial
filament of a flagellum in many cases it is derived from a kinetic
element in the endoplasm and as in the hypermastigote flagellates
the axial filaments in many forms form the astral rays of an amphi-
aster at division (c g., Dimorpha mutatis. Fig. 79, p. 148). In place of
the periplastic sheath of the flagellum an axopodium has an invest-
ing sheath of cortical plasm in which the protoplasmic granules
may be seen streaming back and forth. Many are elastic or mildly
vibratile and undoubtedly belong in the category of motile organs
since movement of the organism is dependent upon their activity.
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 435
Myxopodia are so called because of the tendency to fuse or
anastomose when two come in contact. The investing sheath of
protoplasm is highly miscible and upon fusion of many pseudopodia
a mesh or network, peculiarly characteristic of the Foraminifera, is
formed. In this type the axial filament of the axopodia is absent;
in its place there is a medullary core of denser substance termed
stereoplasmatic axis by Doflein, and interpreted by some as a
reminiscence of an earlier axial filament.
Filopodia are homogeneous hyaline pseudopodia possessing in
many cases a remarkable elasticity and power of independent move-
ment. It is possible that these pseudopodia do not represent the
clear ectoplasm of the Ameba type of pseudopodium, but may be
homologous with the stereoplasmatic part of a myxopodium, or the
highly modified representative of an axial filament.
Lobopodia finally cannot be interpreted properly as motile organs.
They are characterized by nothing that can be homologized with
structural parts of other types of pseudopodia. They are" depen-
dent upon the physical condition of the protoplasm from which
they are formed and are present in any type of cell and in any type
of animal in which such physical conditions prevail. They are by
no means limited to the rhizopods amongst Protozoa but, as shown
in Chapter XI, are characteristic of many types of flagellates as
well, and they are formed by one type of cell or another in the
majority of higher animals.
It is possible of course that the path of evolution has been exactly
the reverse of that outlined above and that progressive evolution
has resulted in the gradual differentiation of the more complex
types of pseudopodia until with Heliozoa we have a prototype of
the Mastigophora. Such an hypothesis makes it more difficult,
however, to account for such forms as the Bistadiidae or the flagel-
lated phase of different types of Sarcodina.
All types of reproduction are represented; simple division, budding
division, unequal division and multiple division (p. 209) and the
life histories of different types are so variable that a common or
generalized account would be inadequate. In general it is legiti-
mate to say that a two-phase, metagenetic life history is charac-
teristic although certainly not universal. Sexual processes are
widely distributed throughout the sub-phylum, but here again these
cannot be described as of any common type.
Encystment or resting stages are well known in fresh water forms
of Sarcodina, but are absent or have not been described in connec-
tion with representatives of the two great groups of marine forms —
the Foraminifera and Radiolaria.
Classification of the Sarcodina is fairly well established although
minor differences depending upon the individual judgment of rela-
tionship in special cases will be found. Division into main groups
430 BIOLOGY OF THE PROTOZOA
is made on the basis of pseudopodia types while minor groups are
based upon special structural or functional peculiarities. Thus one
great group is characterized by the possession of ray-like pseudo-
podia with axial filaments and is given here the taxonomic value of
Class I, the Actinopoda, and these show the nearest approach to the
Holomastigidae amongst the flagellates. A second group— Class II
—includes forms with myxopodia, filopodia and lobopodia and is
well termed, in recognition of Dujardin, the Rhizopoda. Possible
ancestral types for this group may be found in the Rhizomastigidae
amongst the Mastigophora.
Class I. ACTINOPODA Calkins.
These are usually homaxonic or spherical forms living for the
most part as suspended or floating organisms. Pseudopodia are
typically axopodia but lobose pseudopodia may also be formed,
mainly as food-taking organs. The protoplasm is highly alveolar,
becoming, in the ectoplasm particularly, vesicular or pseudo-
alveolar. A highly differentiated cortex is absent as well as the
denser cortical protoplasm which characterizes the Amebidae. In
fresh water forms (Heliozoa) one or more contractile vacuoles are
present in the vesicular ectoplasm. In the Radiolaria, ectoplasm
and endoplasm are sharply separated by a continuous chitinous
membrane— the central capsule— within which lie one or many
nuclei, while the extracapsular protoplasm is differentiated into
zones of more or less specialized ectoplasm.
While several types are naked, the great majority of Actinopoda
are provided with spicules, plates, spines or skeletons often of
elaborate design and exquisite delicacy. Some forms are covered
with a gelatinous mantle in which foreign particles— diatom shells,
sand grains, etc.— are embedded. For the most part the spicules
and skeletons are composed of silica but in one large group of
Radiolaria, the Acantharia, they are horn-like and composed of
strontium sulphate. According to Dreyer spicules and skeletons
depend upon the vesicular configuration of the protoplasm and upon
the quantitv of mineral matter precipitated between the alveoli
(Fig. 12, p. 33).
In Heliozoa a single vesicular nucleus is the rule, but there may
be from 200 to 300 in Actinosphaerium eichhornii and several nuclei
in Camptonema nutans. A multiple number is also characteristic of
the Radiolaria, or a single nucleus may become enormously enlarged.
Nutrition is invariably holozoic, living organisms being captured
through the agency of lobose pseudopodia (Fig. 97, p. 180). Few
observations have been made, however, upon digestive processes or
final history of the food (see Chapter V).
Reproduction occurs by division, either binary fission or unequal
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 437
division in the form of budding. Multiple division is frequent in
Etadiolaria where the endoplasm gives rise to a multiple number of
flagellated swarmers which may be of similar or dissimilar size
(isospores and anisospores). In some cases both kinds are formed
within the same central capsule. Whether these are gametes is a
matter which, while probable, has not been satisfactorily proved.
Among the Heliozoa sexual processes are fully described only
for Actinosphaerium and Actinophrys in which the peculiar type of
pedogamous isogamy is characteristic (see p. 277).
The Actinopoda are divided into two fairly well-defined sub-classes
— the Heliozoa of Haeckel and the Radiolaria of Joh. Muller.
Sub-class I. HELIOZOA Haeckel.
Heliozoa are typically fresh water forms although several species
of marine forms are known. They are homaxial and floating in
habitat for the most part but stalked and attached forms are occa-
sionally met with (Wagnerella borealis, Clathrulina elegans, etc.).
They are either naked (Aphrothoraca) or covered by a gelatinous
mantle without spicules (Chlamydophora), or with spicules (Chal-
arothoraca) or provided with a definite latticed shell (Desmo-
thoraca).
Pseudopodia are typically radial with central axial filaments which
penetrate the endoplasm. Here they end, or rather begin, either in
a nucleus (Actinophrys, Camptonema nutans, etc.), or in a central
kinetic granule called the Centralkorn by Grenadier (1869) (Acan-
thocystis, Sphaerastfum, Wagnerella, etc.). In such cases the nucleus
is excentric. In Camptonema nutans a single axial filament arises
from each of the many nuclei and there are as many pseudopodia
as there are nuclei. In Wagnerella borealis the nucleus is in the
basal plate, while the central granule, with radiating axial filaments,
is in an enlargement at the other end of the stalk.
The body protoplasm is alveolar and characterized by two zones
which in some cases are clearly differentiated as ectoplasm and
endoplasm (e.g., Actinosphaerium) but in most genera they are
rather indefinite. The ectoplasm is made up of relatively large
pseudo-alveoli in Actinophrys and Actinosphaerium and is very dif-
ferent from the dense ectoplasm of Ameba. The endoplasm is
more finely granular and contains one or more nuclei (up to two
hundred or more in Actinosphaerium). Symbiotic forms are not
infrequent in the endoplasm and are regarded as aflagellate forms
of algae.
Contractile vacuoles are present in fresh water species but are
generally absent in salt water forms. They are developed in the
cortex and resemble slightly enlarged ectoplasmic vesicles bursting
to the outside.
438 BIOLOGY OF THE PROTOZOA
Nutrition is holozoic, minute lobose pseudopodia being protruded
which capture and draw in minute organisms as food. In Campto-
nema, however, the axopodia are able to bend and several of them
may be directed toward the capture of living prey.
Reproduction is ordinarily by binary fission or by budding, while
incomplete division frequently leads to colony formation as in
Raphidiophrys. Sexual processes have been described for only a
few forms (see Chapter VIII) while flagellated swarm spores, which
may turn out to be gametes, are known for Acanthocystis, Claihrulina
and Wagner ell <i.
If doubtful forms resembling Heliozoa, but without axial filaments
(e. g., Nuclearia, Vampyrella, etc.), are transferred to the Rhizopoda
with which they have most affinities, then the classification of the
Heliozoa is simple. The division into orders following Hertwig
and Lesser (1874) is based upon the absence or upon the nature
of the skeleton elements.
Sub-class II. RADIOLARIA Haeckel.
Broadly stated the Radiolaria are pelagic organisms of the same
general type as the Heliozoa but offer many variations from the
homaxonic symmetry of the latter. They arc exclusively salt
water forms, surface-dwelling for the most part, but may be found
at great depths of the sea. Pseudo-alveoli are greatly elaborated
and form foam-like spheres with radiating axopodia or with soft
protoplasmic pseudopodia-like myxopodia, while complex skeletal
elements of silica or strontium sulphate afford the greatest variety
of structures and designs.
A typical radiolarian may be conceived by imagining a resistant
membrane of organic substance, presumably chitin or pseudo-
chitin, between the zones of ectoplasm and endoplasm of a heliozoon
like Actinosphaerium. Such a membrane is present in Radiolaria and
is called the " central capsule" (Fig. 181). It separates the intracap-
sular protoplasm (endoplasm) from the extracapsular protoplasm
(ectoplasm). Minute openings, the pylea, through which communi-
cation between the two main zones of protoplasm is possible, are
uniformly distributed, or arranged in lines and patterns, or limited
in number at definite polar positions. These serve as a basis of
classification for the main subdivisions of the group according to
the scheme early adopted by Hertwig.
The intracapsular protoplasm contains nuclei, fat particles and
plastids of one kind or another, and as Verworn showed, it can live
independently of the ectoplasm for a time but ultimately regener-
ates it. The outer or extracapsular plasm is composed of four parts
according to Haeckel. The outermost part is a zone of pseudopodia
which originate, however, in the more deeply lying fourth zone and
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 4^9
then extend through the gelatinous ectoplasm to the periphery.
A second zone — sarcodictyum — is in the form of a meshwork
which extends through the third zone of gelatinous material termed
the calymma which forms the greater bulk of the ectoplasm. A
fourth and most important zone, the sarcomatrix, lies close against
the central capsule and is the go-between for the intra- and extra-
capsular portions. The sarcomatrix is also the scat of digestion
Fig. 181.— Radiolarian central capsules. A, Thalassolampe, type of peripylea;
B, Acanthometron, type of actipylea; C, Aulographis, type of tripylea; I), Triptero-
calpis, type of monopylea ; c, central capsule: n, nucleus. (From Calkins after
Haeckel.)
and assimilation, the food coming to it by way of the pseudopodia
and the network of the sarcodictyum.
As the means of communication between the central protoplasm
and the sarcomatrix is of vital importance to the organism, the
arrangement of the apertures in the central capsule offers a good
character for the classification of the Radiolaria. Ilertwig (1879)
who first used this feature, divided the group into four legions as
follows: (1) Peripylea, in which the membrane of the capsule is
440
BIOLOGY OF THE PROTOZOA
perforated by pores arranged regularly around the entire surface.
(2) Actipylea, in which the pores are said to be arranged in groups
or lines over the surface. Schewiakoff (1926), however, in his mas-
terly monograph on the Acantharia, denies the presence of pylea
Fig. 182.^-Lichnaspis giltochii, one of the Actipylea. The spines of strontium
sulphate are arranged in accordance with the " Miillerian law" as follows: a, n, a, a,
northern polar; ft, ft, ft, ft, northern tropical; c, c, c, equatorial; '/. '/. </. </, southern
tropical; and c, r, c, southern polar. (After Haeckel.)
altogether. (3) Monopylea, in which there is only one such group
of pores. In these forms the perforated disc may be connected
with the center of the central capsule by a conical mass of endo-
plasm, the podoconus, rich in food particles and granules (Fig. 181).
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 441
(4) Cannopylea, in which the membrane around the pores is drawn
out into funnel-like projections termed astropyles of which one is
the primary, the other two secondary. In these forms, furthermore,
the central capsule is double. Haeckel found that certain types of
skeleton are characteristic of the different types of membrane per-
foration and gave corresponding names to the four legions of
Hertwig, viz.: (1) Spumellaria, or practically naked forms. (2)
Acantharia (Fig. 182), with spicules and bars supposed to be of horn
or acanthin, but later shown by Butschli to be composed of stron-
tium sulphate. — Schewiakoff (1926) separates this group as a distinct
sub-class because: (a) Of the chemical make-up and arrangement
of the skeletal bars ; (b) of the absence of a membranous and per-
forated central capsule which is replaced here by a more or less
thin plasmatic membrane without pylea; (c) of the presence of a
clearly-defined hydrostatic apparatus consisting of a gelatinous
layer which extends to the ends of the spines and is provided with
elastic fibers (myophrisks). — (3) Nassellaria, with skeletons and
spicules of silica. (4) Phaeodaria from the presence of a pigmented
mass or pheodium around the opening of the primary astropyle.
The Radiolaria are holozoic throughout, and feed upon flagel-
lates, diatoms, small copepods, etc. These are captured through
the agency of widespread pseudopodia. Nothing is known about
the digestive processes. Symbiotic "yellow cells" (Zooxanthellae)
which, with the exception of the Tripylea, are characteristic of the
group, may play a part in the nutritive processes.
Reproduction is primarily by binary division which begins with
division of the nucleus. This is followed by division of the central
capsule and of the extracapsular plasm. In many cases the skeletal
structures are also equally divided so that daughter cells must
regenerate the missing halves (e. g., Aulacantha) . Or one daughter
cell may leave the parent house and build a new one for itself.
Observations, however, are scanty on such phenomena. Repeated
divisions of the nuclei and central capsules without accompanying
divisions of the extracapsular plasm lead to temporary forms with
2, 4 or 8 central capsules (Thalassicollidae, Tripylea) while this
condition is permanent in the huge colony forms (Polycyttaria).
Multiple division leading to -the formation of minute bi-flagellated
swarmers is not uncommon and has been observed in Peripylea,
Actipylea and Tripylea. In some cases only one type— isospores—
is formed; in other cases what are termed microgametes are formed
by one individual, and macrogametes by another, a condition
which has led to the conclusion that such anisospores are gametes.
This is supported by Hartmann's observation of their fusion. On
the other hand, the formation of the two types in one and the
same individual throws some doubt on their gamete nature, (hat-
ton (1923) indeed regards them not as belonging to the life history
442 BIOLOGY OF THE PROTOZOA
of the radiolarian, but as swarmers of parasitic dinoflagellates
(Merodinium). Such problems remain unsolved until the full
development of the swarmers is observed.
We offer no apology for not attempting a special classification
of this group or a key to the genera. The enormous number of
genera of Radiolaria require monographic treatment which may be
found in Haeckel's three volumes of Challenger Reports and in
Schewiakoff's monograph of the Acantharia {Fauna and Flora,
Golfes von Xeapel, vol. 37, 1926).
Class II. RHIZOPODA von Siebold.
With the Rhizopoda we find types of derived organization that
are not found in the Actinopoda. Myxopodia, filopodia and lobo-
podia are characteristic, although rarely combined in the same indi-
vidual. The protoplasm is generally alveolar and may or may not
be differentiated into distinct ectoplasm and endoplasm but in gen-
eral shows less differentiation than in ciliates or flagellates or even
in Actinopoda. Protoplasmic inclusions, of the nature of metaplas-
tids, are highly varied while definite plastids are rare. A single
chloroplastid of unknown significance, in the form of a blue-green
so-called chromatophore, is present in the testate rhizopod Pauiin-
ella but these are not known elsewhere in the group. Pascher
(1929) finds that these " chromatophores " of Paulinella are able to
live independently of the rhizopod and he regards them as a distinct
genus of blue-green algae. Metaplastids such as " chromatoid bod-
ies" are characteristic of the parasitic amebae (Endamebidae),
while fat and glycogen-like bodies are widely distributed. These
are particularly abundant in the fresh water species Pelomyxa
palustris Green", the highly refringent bodies " Glanzkorper " found
here in abundance are interpreted by Stole and Bott as glycogen-
like in composition, by Veley (1905) as albuminous, and by Gold-
schmidt (1904) as the plastin remains of nuclei which have broken
down with the formation of chromidia. The function of these
inclusions and of the accompanying bacteria-like organisms (Clado-
thrix pelomyxae Veley) is still a matter of hypothesis. Chromidia,
or cytoplasmic chromatin granules, arc characteristic and may be
permanent or periodic constituents of the cytoplasm (see p. 69).
Living membranes equivalent to the cortical membranes of
flagellates, ciliates and gregarines are rarely found here. Transi-
tions toward the chitinous and pseudochitinous tests are present in
some forms {e. g., Cochliopodium bilimbosum) while the great
majority of Rhizopoda have tests of pseudochitin on which mineral
substances of quartz, silica or other types are cemented. In For-
aminifera, calcium carbonate is precipitated between two such
membranes of chitin, resulting in the highly complex and multiform
shells of lime stone.
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 443
Contractile vacuoles are present in fresh water forms but are
generally absent in marine types. They never have the complex
canal system such as found in some flagellates and ciliates and are
rarely fixed in position. Gas vacuoles are present in some of the
testate fresh water forms (Arcella).
The majority of Rhizopoda are multinucleate both in fresh water
and marine species, the multiple number due mainly to repeated
nuclear division aided, in Mycetozoa, by plasmodium formation
through fusion. The structure of nuclei is too varied for a general
description but the vesicular, endosome tvpe predominates (see
p. 50).
Nutrition is holozoic and some progress has been made in working
out processes of digestion, digestive ferments, etc. (see Chapter V).
Living organisms are captured by pseudopodia or entrapped in the
protoplasmic network where they are digested. Cyclosis is invar-
iable and the various protoplasmic granules, digested food sub-
stances, etc., are thoroughly mixed.
Reproduction occurs in a variety of ways by division which may
be either equal or binary division, budding division, unequal division
or budding, and multiple division or sporulation. So-called budding
division is the most characteristic and is a form of division appar-
ently limited to the Rhizopoda (see p. 225).
Sexual processes are well developed, microgametes being formed
in the majority of cases, which will be reviewed in connection with
the several classes.
The classification adopted is an extension of that used by Minchin
and includes as primitive forms those questionable Heliozoa-like
types which many authors (e.g., Reichenow-Doflein) include with
the Ileliozoa.
Sub-class I. PROTEOMYXA Laxkester.
There are but few common characteristics in this group of primi-
tive forms; the most widely spread feature apparently is the usual
occurrence of ray-like pseudopodia which recall the appearance of
Ileliozoa. These have no axial filaments however, and frequently
branch or partially anastomose. Flagellated swarm-spore stages are
common but the life history is known in few cases. An approach
to the Mycetozoa is seen in forms like Labyrinthula where the small
spindle-shape cells bear long filose pseudopodia which fuse to form
a net-like mesh. Most of them are parasites on lower algae and
Protozoa.
Family 1. Labyrinthulidae Ilaeekel. This family is composed of
different species of the genus Labyrinthula which may lie intracellu-
lar parasites in diatoms, Vaucheria, Spirogyra, etc. They frequently
become associated in groups or pseudoplasmodia and reproduce by
444
BIOLOGY OF THE PROTOZOA
division. Each individual or aggregate of individuals may encyst
to form permanent spore-like resting stages. Flagellated spores are
unknown (see Valkanov, 1929).
Family 2. Zobsporidae Zopf-Delage.— These forms are also endo-
parasitic in diatoms, algae and various Protozoa, and have filose,
Heliozoa-like pseudopodia without axial filaments. They are dis-
tinguished by the formation of swarm spores. Protomonas amyli
Cienkowsky apparently lives only on starch grains. Typical
genera: Pseudospora Cienkowsky, Protomonas Cienkowsky and
Protomyxa Haeckel.
Fig. 183. — Nuclcaria delicatula, quiescent and moving forms. (From Calkins.)
Family 3. Vampyrellidae Doflein.— Here also the pseudopodia
are very delicate and frequently branch and anastomose and may
proceed from all sides of the body or be limited in origin to certain
regions. They are frequently parasitic on algae and Protozoa, some
forms having the ability to dissolve the cellulose membranes of
plant cells, thus making holes through which the protoplast passes
into the body of the parasite (e. g., Vampyrella; see Lloyd, 1929)
or they may enter the plant cells. Products of chlorophyll nutrition
frequently form reddish-colored masses (karotin) in their proto-
MORPHOLOGY AND TAXONOMY OF THE SARC0D1NA 445
plasm. Encystment, with cellulose cyst walls, is common. Nuclei
are multiple as a rule; reproduction by plasmotomy or by division
into uninucleate amebae; flagellated swarmers unknown. Accepted
genera: Nuclearia Cienkowsky, Arachnula Cienkowsky and Vam-
pyrella Cienkowsky (Fig. 183).
Sub-class II. MYCETOZOA de Bary.
The Mycetozoa were formerly regarded as low types of fungi and
under the name of Myxomycetes or "slime molds" were included
among the lower plants. The investigations of de Bary, however,
revealed the rhizopod affinities, and the relationship with other
Sarcodina is now clearly recognized. There is little doubt, how-
ever, that Mycetozoa are borderline organisms and their semi-ter-
restrial habitat leads to modifications and adaptations not met with
elsewhere. Many of them are highly complex both as to organiza-
tion and as to life history and by no stretch of the imagination can
they be regarded as simple organisms.
A general idea of the essential characteristics of the Mycetozoa
may be gained by following through a typical life history beginning
with a recently germinated "spore." This is a small uninucleate
ameboid organism known as a "myxameba;" it is active, throwing
out pseudopodia and moving energetically about the field. It has
a contractile vacuole, and takes in solid food which is digested in a
gastric vacuole, or it may live upon dissolved proteins from decom-
posing organic matter. It may also reproduce by division while
in this ameboid condition.
The naked ameboid condition is usually temporary; sooner or
later the "myxameba" turns into a " myxoflagellate " by the devel-
opment of a flagellum. The contractile vacuole is retained and the
body, usually ellipsoidal, is highly metabolic and may even give
rise to pseudopodia, particularly at the posterior end where the
pseudopodia aid in the ingestion of solid food in the form of bacteria,
small Protozoa or bits of organic detritus; saprozoic nutrition, how-
ever, is also common. Like the "myxamebae" the "myxoflagel-
lates" may reproduce by longitudinal division, in which case the
centrioles of the mitotic figure become the basal bodies of the
flagella. Myxoflagellates are apparently rather sensitive and show
a ready tendency to encyst. Such "microcysts" are temporary
and the excysted organism again passes through myxameba and
myxoflagellate stages.
According to later investigations of Jahn these myxoflagellates
ultimately become gametes; the last division, prior to gamete
formation is a chromosome-reducing division, and the haploid
gametes fuse to form diploid zygotes. In Physarum didymoides the
gametes have 8, the zygotes 16 chromosomes.
446 BIOLOGY OF THE PROTOZOA
The zygotes thus formed are very miscible and fusion occurs when
two or more come in contact. In this way, and by multiplication
of the nuclei by mitosis, and growth, great multinucleated plasmodia
arise which may grow to be many inches in diameter and with
thousands of nuclei. All observers agree in describing the fascinat-
ing spectacle of these sheets of moving protoplasm, a phantas-
magoria of living and lifeless granules, nuclei, foreign particles
and pigment. The pseudopodia are myxopodia and by their anas-
tomosis great networks of flowing protoplasm form traps for minute
organisms utilized as food ; some forms, in addition, may be saprozoic
in nutrition.
Under conditions which are not entirely known, but some of
which are drought and scarcity of food, the entire mass may pass
into a resting condition. The fluid protoplasm hardens to form a
thick-walled "sclerotium" which is frequently impregnated with
calcium salts. The nuclei collect in groups and these become
encysted with cellulose walls. Such resting forms may retain life
for some years. Ultimately the hardened walls are liquefied and
the plasmodium condition is regained, the process requiring hours
or days according to the length of time in the dried state.
With maturity of the plasmodium the gametes, or gametocytes,
are formed by processes which are quite remarkable for their intri-
cacy and for the complexity of the specialized structures appearing
only at the time of fructification. The whole plasmodium may form
one "sporangium," but more often the plasmodium breaks up into
several "spore "-forming groups or "sporophores," each from a local
heaping of the substance of the plasmodium. Part of such a thick-
ening forms an outer investing wall termed the peridium which is
often further hardened by deposition of lime. Another portion
becomes differentiated into a thick network or feltwork, termed the
capillitium, which is continuous with the outer peridium (Fig. 184).
This network is made up of tubes and fibers; some of the latter,
termed elaters, have a spiral structure and are supposed to function
in the distribution of the spores. According to Kranzlin elaters
arise from the kinetic components of degenerating nuclei.
The formation of the spores varies in details but the essential
part of the process is the fragmentation of the residual mass into
uninucleate or multinucleate bits of protoplasm. If multinucleate
further fragmentation results in uninucleate bits, each of which
encysts independently. According to the later observations of
Jahn, the supposed fusion of nuclei leading to the uninucleate con-
dition, and interpreted as autogamic fertilization by Prowazek,
Kranzlin and earlier, by himself, is only a phase in the degeneration
of nuclei many of which are disposed of in this way at this period.
Fertilization is exogamic, the gametes being the myxamebae and
myxoflagellates which ultimately emerge from the spores.
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 447
Liberation of the spores is accomplished in different ways. In
some cases a lid is raised off the sporangium; in others the peridinm
dissolves in spots leaving a fenestrated capsule; in still others the
capsule splits longitudinally. The dry, powdery spores are distrib-
uted in various ways, air currents playing a conspicuous part, and
they finally germinate in the presence of moisture. Myxamebae
and myxoflagellates are formed and the cycle is completed.
Fig. 184. -Fruiting bodies of Comatricha nigra. A, five stalked spore capsules; B,
section of capsule with columella, capillitium, and spores. (After MacBride.)
Genera and species of Mycetozoa are distinguished according to
the nature of the plasmodia and by the form and organization of
the sporangia.
Order I. ACRASIDA van Tieghem.
(Pseudoplasmodidae of Zopf-Delage) Sorophora Lister (in part).
The individual ameboid organisms after a period of creeping by
active ameboid movement come together in clusters to form the
pseudoplasmodia, the amebae retaining their individuality. Indi-
viduals creep up over their fellows and form groups or sori which
in some cases are stalked, the stalks being formed by the dried
bodies of sacrificial Amebae. The sori are formed by other amebae
creeping over the stalk and accumulating in a mass at the top. Here
each encysts and when a suitable medium is assured the small
amebae again creep out, often, however, after a long period of
desiccation. Their characteristic habitat is animal dung.
While many competent authorities regard these organisms as
remotely related, if at all, to the more complex Mycetozoa, we
believe that their affinities are more probably here than with any
other group of Protozoa. The three families recognized show
different gradations in complexity.
Family 1. Sappiniidae Dangeard.— The single genus— Sappina
Dangeard — shows the characteristics of the family which differs
448
BIOLOGY OF THE PROTOZOA
from all other Mycetozoa in that not even a pseudoplasmodium is
formed, a single ameba going through all the motions of a Plas-
modium. Stalk and cyst are formed by one individual but the cysts
are frequently massed in sporangium-like groups (Fig. 185). The
species S. diploidea, originally named Amoeba diploidea by Hart-
C
D
Fig. 185. — Dictyoslelium, A, and Sappinia, B, C, D. (After Doflein.)
maim and Nagler, is much like Umax types of ameba. Both
S. diploidea and S. pedata Dangeard are binucleated, a condition
which arises as the result of the peculiar copulation process shown
by S. diploidea (see p. 323).
Family 2. Guttulinidae Cienkowsky.— These are small forms
which bear stalked or unstalked fruiting bodies covered with
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 449
"spores." The latter have either thin membranes or heavy cellu-
lose walls. The myxamebae foregather in clumps on which the
sori originate. Typical genera: Guttulina Cienkowsky, Gutlulin-
opsis Olive.
Family 3. Dictyostelidae Rostafinsky.— Here the fruiting bodies
are borne on simple or branched stalks formed by the hardened
bodies of amebae which have migrated from the pseudoplasmodium
mass. The polygonal bodies, covered with cellulose membranes,
form a sort of tissue over which other amebae migrate to form sori
at the top or at the ends of branches (Fig. 185). The myxamebae
are characterized by thin, pointed pseudopodia. Typical genera:
Dictyostelium Brefeldt and Polyspondylium Brefeldt.
Order II. PHYTOMYXIDA Schroter.
(Phy tomyxinae Schroter) .
Probably as a result of parasitism peridia and capillitia are absent
in the representatives of this group. Otherwise they agree with the
more complex Euplasmodida. They form true plasmodia and
myxoflagellates, but there are no closed sporangia, recalling in this
respect the simpler Acrasida. They are parasitic in plant cells and
in insects (beetles).
Plasmodiophora brassicac Woronin is the best known of this
group largely because of its economic importance. It attacks the
roots of cabbages and other Cruciferae and produces a character-
istic tumor disease known as "Club-root," "Hanberries," "Fingers
and Toes," "Kohlhernie," etc. (See p. 38(3.)
Other genera parasitic on plants are Tetramyxa Goebel (forming
galls on Ruppia rostellata) and Sorosphaera Schroter (causing tumors
in various species of Veronica).
The genera Sporomyxa Leger and Mycctosporidhnn Leger and
Hesse are parasites of beetles (Scaurus tristis and Otiorhynchus
uscipes) .
Order III. EUPLASMODIDA Lister.
(Mycetozoa s. str. Myxogastres).
This order includes the great majority of Mycetozoa which in
their life histories agree with the description given above (p. 445).
Myxamebae and myxoflagellates are invariable, so too are true
plasmodia and complex sporangia which with the exception of the
family Ceratiomyxidae (Exosporea) are invariably surrounded by
a peridium.
The "spores" are usually globular, rarely elliptical, and are often
compressed by pressure into polygonal forms. In the majority of
cases they are violet in color but colorless, white, yellow, brown and
29
450 BIOLOGY OF THE PROTOZOA
red sporangia are known. In most cases the "spores" are uninu-
cleate, but forms with two and with four nuclei are known.
In some cases the simultaneously formed sporangia unite to form
a common fruiting body in which the individual sporangia may still
be distinguished in some types. In other types, however, this inde-
pendence is lost and one common fruiting body results, with one
continuous capillitium. Such fruiting bodies are called aethalia.
(See Key for further classification.)
Sub-class III. FORAMINIFERA d'Orbigny.
(Reticulosa, Thalamophora.)
This group of the rhizopods includes a large number of bottom-
dwelling and marine Sarcodina with anastomosing pseudopodia
(myxopodia). A few forms live in fresh water (Allogromia species),
and some forms are pelagic in the sea (Globigerina, etc.). The great
majority are provided with tests composed for the most part of
calcium carbonate. In some, however, the test is purely organic,
consisting of substance of gelatinous or pseudochitinous character
(Allogromia); or foreign particles of sand, diatom shells and detri-
tus of one kind or another, may be cemented to the pseudochitinous
test by gelatinous or chitinous cement. Such tests are usually
described as arenaceous, in contrast with the clear lime shells or
porcellaneous types. The walls of the shells are either thick and
homogeneous or are perforated by minute pores (foramina) through
which single pseudopodia are protruded. The cavity of the shells
may be a single chamber, septa if present being incomplete (Mono-
thalamous). Or a multitude of chambers may be present, separated
by partitions or septa (polythalamous). The latter may be compli-
cated by secondary deposits of lime through which labyrinthine
canals and passages give occasion for intricate designs (Fig. 74,
p. 1-38). The surfaces of the shells are usually smooth but in some
forms, particularly the floating types of Globigerina, spines, ridges,
rays, etc., probably assist in floating.
The living substance is usually so fluid that it is rarely quiet and
protoplasmic streaming is so characteristic that the Foraminifera
have been favorite materials for the study of protoplasm. It is not
divided into zones, and the marine forms have no vacuoles. There
are numerous foreign bodies as a rule and aggregates of the residue
associated with food substances, form masses of fecal material
termed "stercome." In many forms living commensals are also
present in the form of small yellowish Cryptomonas-like forms
(Chrysidella) which are liberated with sporulation of the host
organism.
The living protoplasm fills more or less completely all chambers
of the organism. In polythalamous forms protoplasmic strands
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 111
passing through pores in the septa maintain all parts of the soft
body as a unit mass. In monothalamous and from the last-formed
chamber of polythalamous forms, a large mass of protoplasm gives
rise to the pseudopodial network which acts as a trap for the capture
of diatoms, Crustacea, rotifers and other smaller objects used as food.
In the perforate types pseudo-
podia are also, protruded through
the finer pores (foramina) of the
shell.
One large vesicular nucleus is
characteristic of both single and
many-chambered types. In the
latter the nucleus may be confined
to the first formed, or inner, cham-
bers, although it may wander
throughout the entire organism.
In many cases it is replaced by
several nuclei, and there is a gen-
eral tendency throughout the
group to form chromidia by
multiple division, or fragmenta-
tion of the primary nuclei.
Reproduction may or may not
be accompanied by fertilization
phenomena and throughout the
group there is a more or less reg-
ular alternation of sexual and
asexual processes, accompanied
in many cases by morphological
evidence of sexual or asexual
generation. In its simplest ease,
asexual reproduction consists of
so-called budding division. In
Allogromia, for example, the pro-
toplasm streams out of the shell
mouth and forms a ball of protoplasm of about the same size and
shape as the parent organism; on the extruded bud a daughter
cell is secreted and after division of the nucleus and migration
of one of the daughter nuclei, the bud becomes detached and
begins an independent existence. In the polythalamous forms,
an initial shell of one chamber contains an organism which grows
and buds in a similar manner, but the bud does not become
detached. According to the type of budding shell types known
as Xodosarian (Fig. 186), Frondicularian and Rotalian, are formed
(Fig. 187). A new shell is deposited about the naked bud and thus
a second chamber is added to the first, while the protoplasm by
Fig. 186. — Diagram to show the
mode of origin of the Nodosarine type
of Foraminifera shell.
452
BIOLOGY OF THE PROTOZOA
division of the nucleus, without complete cell division, becomes
binucleated or multinucleated. In a similar matter other cham-
bers are added to those already formed until complicated aggre-
gates measuring 3 or more inches in diameter in some cases result
(Nummulites, etc.). These, however, are to be regarded as single
individuals of syncytial nature illustrating growth and differentia-
tion rather than reproduction. With the formation of a brood of
reproductive bodies each of which produces a similar multinucleated
individual we can speak of asexual reproduction in a strict sense.
Thus in Polystomellina crispa (Fig. 123, p. 235), after multiplication
of the nuclei, the latter give rise by fragmentation to a large number
of minute nuclei having the significance of chromidia. The plasm
forms islands about each of these minute nuclei, or groups of them,
and is then broken up into as many minute cells as there are islands.
B
C
Fig. 187. — Types of polythalamous Foraminifera shells. A, nodosarine type; B,
frondicularian type; C, spiral type. (After Carpenter.)
These small cells, in the form of amebulae or amebospores leave
the parent shell by way of the foramina or by the mouth opening of
the last chamber and after a short period of ameboid movement
settle down and secrete the characteristic shell chamber. This
initial test (proloculum) is measurably larger than the initial cham-
ber of the organism which formed the amebulae and is called a
macrospheric chamber as opposed to the microspheric chamber of
the first generation. A new multi-chambered shell is then formed
according to the type of structure of the species. When fully grown
the protoplasm of this macrospheric generation breaks up into a
swarm of small biflagellate flagellispores which leave the parent
shell and swim about by means of their flagella. These flagellates
are gametes which ultimately unite two by two to form zygotes.
The flagella are absorbed and the young zygote secretes the shell
material of the first chamber about which other chambers are
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 453
formed with growth and budding division until the mature indi-
vidual again results. Thus there is a typical alternation of genera-
tions in the life history of a foraminif eron ; the microspheric indi-
vidual starting from a zygote, with its production of amebulae is
an asexual generation while the macrospheric individual starting
from an asexual spore is the sexual generation giving rise to gametes.
In Polystomellina the relative abundance of macrospheric and micro-
spheric shells is 38 to 40 of the former to 1 of the latter (Rhumbler,
1923).
Test dimorphism has led to much confusion in classification, and
this difficulty, as pointed out by Cushman (1928), is enhanced by
Hofker's (1927) discovery of trimorphic types amongst fossil
foraminif era.
Fossil forms are known from the paleozoic to recent times. These
have played a conspicuous part in geologic formations and are
useful today in economic ways. A complete classification must
take such forms into consideration. This is well done in Cushman's
system of classification in which 45 families and 411 genera, living
and fossil, are keyed and described. As with the Radiolaria it is
inexpedient to repeat such keys here and the reader is referred to
Cushman's excellent treatise (1928) for family and generic diagnoses.
Sub-class IV. AMOEBAEA.
When rhizopods are mentioned the mental picture in most cases
is Ameba or some of its close relations amongst the Amoebaea. It
is not the largest group of rhizopods but some of the forms included
here are amongst the most common types of Protozoa, while their
apparent simplicity and enigmatic movement have given them the
popular position of the lowest forms of animal life and the phrase
"from Ameba to man" is familiar to everyone. They are present
in all stagnant, fresh and brackish water; in damp moss or leaves;
abundant in the superficial soil, and also abundant as commensals
or parasites in all kinds of animals.
In all of the naked forms there is a well-marked differentiation of
the protoplasm into endoplasm and ectoplasm. The latter is more
dense, the former more fluid and with typical cyclosis. In the
shelled types there is frequently a characteristic zonal differentiation.
Pseudopodia are never myxopodia or axopodia. Naked forms
have blunt finger-form processes or lobopodia formed by an outflow
of ectoplasm and endoplasm. Shelled forms in the majority of
types have pseudopodia, composed apparently of ectoplasm only.
These have considerable power of movement apart from the usual
ameboid type of flowing substance, and may sway or move inde-
pendently with vigor. In the naked forms pseudopodia may be
thrown out from any part of the ceil, but in shelled types they are
454 BIOLOGY OF THE PROTOZOA
limited to the region adjacent to the orifice of the shell. In some
cases, as in the genus Cochliopodium, there is a firm ectoplasm which
has many of the features of a chitinous membrane. Pseudopodia
pass through it by way of permanent apertures (Fig. 9, p. 31),
and when the cell divides the membrane also divides. There arc
very few of such forms, however, the great majority of shelled forms
having a definite chitinous membrane on which foreign particles
are attached. In Arcellidae the membrane is clear chitin and in the
Euglyphidae the outer elements of the shell are secreted before divi-
sion and passed out to the daughter individual after the chitin
membrane is laid down. The variety of shells is due to the different
types of sand crystals, diatoms, detritus of various kinds and even
living plant cells.
The nucleus is vesicular and usually single although many types
of both naked and shelled forms are binucleated or multinucleated.
The entire group is further characterized by the distribution in the
cytoplasm of chromidia (see p. 09) which often takes the form
of a chromidial network.
With the exception of the parasitic forms, and some of these arc
also included, the Amoebaea are holozoic in nutrition and proteo-
lytic and amylolytic ferments have been isolated in some cases (see
Chapter V).
Notwithstanding the abundance and the wide distribution of
these forms of rhizopods there is very little agreement on the part
of different observers in regard to the life history. Few Protozoa
have been more frequently seen and studied than Amoeba proteus
and yet little is known accurately about the life cycle. Binary
division is characteristic of all the naked forms both free-living and
parasitic, and encystment stages are known in all forms. So-called
budding division is typical of the testate forms and differs materially
from binary fission (see p. 214). Acceptable accounts of sexual
processes are limited to the Testacea in which there is a general
resemblance to the type of gamete formation characteristic of the
Foraminifera (see Chapter VI).
Parasitic forms of the Amoebidae are widely distributed through-
out the animal kingdom. They are usually present in the diges-
tive tract but may be ectoparasites as well. The great majority
are of the nature of commensals and are harmless, some, however,
are pathogenic as Amoeba mucicola Chatton, a harmful ectoparasite
on the gills of Labridae, or Endamoeba dysenteriae, the cause of
dysentery in man (see p. 387).
The organisms included in the Amoebaea fall naturally in one of
two groups which have been generally recognized as Amoebida
(Gymnamoebida) and Testacea. Following the principle adopted
in classifying the Mastigophora where ameboid forms of animal
flagellates are retained as Mastigophora only when the flagellum or
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 455
flagella are permanent structures of the organism, we include as
rhizopods those forms with pseudopodia and temporary flagella;
flagella and pseudopodia being more or less interchangeable. These
are included here in the family Bistadiidae of Doflein.
Order 1. Amoebida (Gymnamoebida) Ehrenberg.
Naked forms of Amoebaea, either free-living or parasitic; with one
or more nuclei; with contractile vacuole (except in some of the para-
sitic forms); reproduction by binary fission, multiple division
occasional. Encystment widespread.
We recognize four families in this order, viz.: Bistadiidae, Amoe-
bidae, Endamoebidae and Paramoebidae. Separation of the para-
sitic forms of amebae from free-living forms is hardly justifiable
in a natural classification but is tolerated on grounds of expediency.
Family 1. Bistadiidae Doflein.— Organisms characterized by two
interchangeable phases — ameboid and flagellated. In the former
phase the body is ameboid with lobose pseudopodia. A single
nucleus with endobasal body is present; the basal body of the
flagellum is formed by division of the endobasal body (Wilson,
Puschkarew, et al.) and the flagellum grows out from the basal body.
(See Fig. 13, p. 34.) Transformation from the ameboid to the flagel-
lated condition involves loss of ameboid movement and change in
form to a monaxonic ellipsoidal form. Absorption of the flagellum
accompanies transformation again to the ameboid condition. These
changes are evidently induced by environmental conditions and, in
cultural forms, may be brought about at will. Genera with one,
two and three flagella in the flagellate phase are known. Repro-
duction by division is limited to the ameboid phase, sexual processes
unknown. The ameboid phase is represented by small creeping
amebae which have been generally included as Amoeba Umax, and
known as "limax" forms. These were separated from the genus
Ameba by Chatton and Lalung-Bonnaire (1912) under the name
Vahlkampfia. The forms with a single flagellum in the flagellated
stage are retained under the generic name Vahlkampfia, although
it is by no means assured that all "limax" amebae are thus di-
morphic. Forms with two flagella are grouped in the genus D'nnas-
tigamoeba Alexeieff and forms with three flagella in the genus
Trimastigamoeba Whitmore. Parasitic forms, regarded by Craig
(1906) as a cause of human dysentery and with a flagellated phase
with one flagellum, are included in the genus Craigia.
Family 2. Amoebidae (authors generally: em. Doflein, em.
Calkins).— The usual types of free-living amebae are grouped in
this family. Flagella, so far as known, are absent in all stages.
Nuclei single, double or multiple; contractile vacuole usually single,
present generally in fresh water forms. Reproduction is by simple
456 BIOLOGY OF THE PROTOZOA
division in vegetative forms, by multiple division during quiescent
phases. The great majority of forms are aquatic and developmental
phases of other types (e. g., mycetozoa) may be easily mistaken for
amebae. Others are semi-terrestrial, living in damp earth, moss,
etc., where they play a part in keeping down bacteria of the soil
(see Goodey).
Family 3. Endamoebidae.— These are parasitic amebae widely
distributed throughout the animal kingdom and with characteris-
tic vegetative phases during which the organisms live as harmless
commensals or, more rarely, as pathogenic parasites in the host,
and with permanent cyst stages by which infection is carried by
means of contaminative infection. The genus generally recognized,
Endamoeba, is represented by a vast number of species with ill-
defined diagnostic characters, while many questionable genera are
forms about which the taxonomic position is still in dispute (see
Chapter X). Nutrition is either holozoic, saprozoic or heterozoic.
Family 4. Paramoebidae. — Forms with single nucleus and pecu-
liar cytoplasmic structure (Nebenkern) variously interpreted as a
kinetic element, intracellular parasite, etc. Both free-living and
parasitic species. Genus: Paramoeba.
Order 2. Testacea.
These forms are generally described as amebae with shells; by
some they are grouped as a subdivision of the Foraminifera (Doflein).
The protoplasmic and test structure, as well as the pseudopodia
are so different from Foraminifera that little is gained by this pro-
cedure, while the association with naked forms has a long historical
backing. They are almost exclusively fresh water forms, although
some species are represented in brackish water as well. Many
species are semi-terrestrial and abound in moss and similar damp
places. The protoplasmic body differs from that of the Amoebidae
in having the ectoplasm concentrated at the region of the shell
opening, while many forms show a distinct zonal differentiation of
the protoplasm. Contractile vacuoles are always present.
Nuclei are either single, double or multiple and are usually accom-
panied by a zone of chromidia in the form of a dense reticulum
from which, according to the observations of numerous observers,
the nuclei of gametes are formed (Schaudinn, Zuelzer, Elpatiewsky,
el al.). It is rather the fashion to doubt this interpretation on the
ground that such nuclei are possible parasites, but we shall adhere
to it until the critics have a more probable explanation of the
nature of the chromidia (p. 69).
Pseudopodia are filopodia which in a few instances have the
tendency to branch (Fig. 18S). They lack the medullary endoplasm
of lobopodia and have a considerable power of independent move-
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 457
ment. In Chlamydophrys they form a network as in Allogromia
(Fig. 189).
The tests are simple, one-chambered structures of widely-varied
form, frequently ornamented with spines and processes. The basis
of all shells is a pseudochitinous membrane which, in some forms,
is greatly thickened and constitutes the test; in other cases foreign
particles are cemented to the outside of the chitinous membrane
(Difflugia, Centropyxis, etc.), and in still other cases silicious plates
are precipitated in the endoplasm in the vicinity of the nucleus, and
deposited on the chitinous membrane in definite patterns charac-
teristic of different genera (Euglypha, Quadrula).
Reproduction occurs by longitudinal binary division in forms with
a soft chitinous membrane, where membranes divide with the soft
*i
i
/
/ \ \ \\
-■■
Fig. 188. — A, Hyalosphenia? sp. (Original.) B, Pseudochlamys patella after Clap.
and Lachm.
body (Cochliopodium); in other cases it occurs by so-called " budding
division," whereby the protoplasm swells out of the shell mouth to
form a bud which assumes the size and shape of the parent (p. 214).
Multiple division also occurs in some types; many nuclei are formed
by division; these become the nuclei of small naked amebae which
after a short period of free movement and growth secrete the shell
characteristic of the species. Fertilization processes have been
described for several types (Centropyxis, Arcella, Trichosphaerium,
Difflugia, etc., Fig. 190), the gametes being either amebulse or
flagelluhe. A typical alternation of generations comparable with
that of the Foraminifera was described by Schaudinn for the peculiar
genus Trichosphaerium. Here asexual processes occur by irregular
plasmic divisions (plasmotomy) and by multiple division resulting
458 BIOLOGY OF THE PROTOZOA
in a swarm of minute naked amebae. These develop into an adult
form of different type which may likewise undergo plasmotomy
leading to the formation of gamonts and gametes. The latter, upon
fertilization, give rise to the initial type of organism. In this cycle,
the original asexual generation differs from the later sexual genera-
tion by the presence of a peculiar type of test consisting of radially-
arranged spicules of magnesium carbonate.
The forms included in this Order fall naturally into two families—
Arcellidae and Euglyphidae (see Key for genera).
F£ Oi
,'
;% % ' ,:^^rr-"--'^.-"--...
.-
.-"'
'.'.'^■"^^ ':<i?'% '?&.
• / '•-■'■;-. "--
; ■■■■■ ■ • •■.*.* \ " '
............
. - -y
>"■•* :-y Wi .
\i? I36*st "... \
i *£% ■'-.
"••'''' ji-
..'•■''
| v^ ; ' \\
--y
/ 7
Fig. 189. — Chlamydophrys utercorea. (From Doflein after Schaudinn.)
Family 1. Arcellidae.— Tests transparent or opaque by reason of
covering of foreign bodies picked up by the protoplasm and deposited
on the outside where they are cemented to the chitinous membrane.
Structure and materials of the shell afford a basis for further
classification of the family. They are either pyriform or shaped
like a watch-glass; the membrane may be rigid or flexible and the
aperture central or asymmetrically placed.
Family 2. Euglyphidae. — In members of this family the test is
covered by silicious plates or scales and the pseudopodia are of a
filose, branching type. The tests may be either symmetrical or
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 459
asymmetrical. In the former group the aperture is terminal, cir-
cular and provided with teeth in Euglypha formed from scales; or
the edge of the aperture is smooth or slightly serrated in Spheno-
deria. In asymmetrical forms the mouth is subterminal, and
oblique in Campascus. The test is retort-shape in Cyphoderia,
Campascus and Nadinella. It is pyriform but much compressed in
Placocista (without toothed membrane) and Assulina (with toothed
membrane about the aperture). In Paulinella the test is Euglypha-
like but the cell body possesses a band-form, blue-green, symbiotic
alga mistakenly called a chromatophore. In Trichosphaerium, fin-
ally, there is no definite test, but the body is enclosed in a gelatinous
mantle with radial rods in the asexual generation and without
these in the sexual generation.
Fig. 190. — Difflugia lobostoma; plastogamic stages, formerly interpreted as evidence
of conjugation. (From Calkins after Ethumbler.)
KEY TO ACTINOPODA.
Pseudopodia with axial filaments (axo-
podia) Class 1. Actinopoda
Pseudopodia without axial filaments (myx-
opodia, filopodia, lobopodia). . Class 2. Rhizopoda
Class 1. Marine forms; central capsule present
Sub-class 2. Radiolaria1
Salt or fresh water forms ; central cap-
suit absent Sub-class 1 . Heliozoa
1 For keys to 4 Legions, 21 Orders, 36+ Families and several hundred genera and
species, sec monographs by Hertwig (1879), Haeckel (1887) and Schewiakoff (1926).
460 BIOLOGY OF THE PROTOZOA
Sub-class I. HELIOZOA Haeckel.
1. Naked forms; no gelatinous mantle or
skeleton Order 1 . Aphrothoraca
2. Gelatinous mantle present; no spicules
or foreign bodies Order 2. Chlamydophora
3. With isolated or united spicules or plates
Order 3. Chalarothoraca
4. With fenestrated test Order 4. Desmothoraca
Order I. APHROTHORACA Hertwig.
1 . Individuals without stalks 2
Individuals with stalks 6
2. Ectoplasm and endoplasm clearly differ-
entiated— multinuclear 3
No clear differentiation between endoplasm
and ectoplasm 4
3. No central granule in which axial filaments
unite Genus Actinosphaerium Stein
With central granule Genus Gymnosphaera Sasaki
4. Axial filaments end in nuclei 5
Axial filaments end in central granule
Genus Oxnerelln Dobell
5. All axial filaments end in the single nucleus
Genus Actinophrys Ehrenberg
Multinucleate, each nucleus with one axial
filament Genus Camptonema Schaudinn
6. Stalk hollow Genus Actinolophus Schultze
Stalk solid Genus Haeckelina
Mereschkowsky
Order II. CHLAMYDOPHORA.
1. Flattened; with central granule; often col-
onial Genus Spkaerastrum
Central granule absent or not observed
Genus Astrodisculus
Order III. CHALAROTHORACA.
1 . Elements of test embedded in outer plas-
mic zone 2
Elements of test not embedded in outer
plasmic zone 4
2. Spicules chitinous, fine, radially arranged
Genus Heterophrys Archer
Spicules silicious, similar or dissimilar .... 3
3. Spicules loosely embedded ; all alike . Genus Raphidiophrys Archer
Spicules of diverse forms and sizes. .Genus Raphidiocystis Penard
4. Individuals without stalks 5
Individuals with stalks having silicious
membrane Genus Wagnerella
Mereschkowsky
5. Test of foreign bodies 6
Elements of test made by organism 7
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 461
6. Test close-fitting about organism. . .Genus Lithocolla Schultze
Test separated from plasm by fluid zone
Genus Eleorhanis Greeff
7. Test made up of colorless spherules . . Genus Pompholyzophrys Archer
Test made up of silicious discs or scales
with or without spines 8
8. Test of tangential scales and radial spines
Genus Acanthocystis Carter
Test of tangential, perforated discs; no
spines Genus Pinaciophora Greeff
Order IV. DESMOTHORACA.
1. Capsule spherical, with or without stalk. . 2
Capsule polyhedral, openings small, stalked
Genus Hedriocystis
Hertwig and Less.
2. Capsule with stalk, openings large. .Genus Clathrulina Cienkowsky
Capsules without stalks, openings small. . . 3
3. Openings with collars Genus Choanocystis Penard
Openings without collars Genus Elaster Grimm
Sub-class II. RADIOLARIA Joh. Muller.
The great number of genera of Radiolaria make it impossible to give
more than a superficial survey of this group. For keys to 4 legions, 21
orders and 36+ families and many hundred genera and species, see mono-
graphs by Hertwig, 1879; Haeckel, 1887, and Schewiakoff , 1926. (See p. 442).
Class II. RHIZOPODA von Sieb.
1. Naked; Heliozoa-like; radiating pseudo-
podia Sub-class 1. PRCtfEOMYXA
Naked or shelled; pseudopodia not Helio-
zoa-like 2
2. With myxopodia and Plasmodium forma-
tion Sub-class 2. Mycetozoa
No plasmodium formation 3
3. With calcareous shells ; marine . Sub-class 3. Foraminifera
Naked or with chitinous tests. .Sub-class 4. Amoebaea
Sub-class I. PROTEOMYXA.
1. Individuals Heliozoa-like; usually solitary. 2
Individuals fuse into thread-like plasmodia
Family 1. Labyrinthulidae
2. With flagellated swarmers Family 2. Zoosporidae
Without flagellated swarmers. . .Family 3. Vampyrellidae
Family 1. Labyrinthulidae Haeck.
Parasitic in algae Genus Labyrinthula Cienkowsky
Free-living in fresh water and earth . . . Genus Monobia Schneider
Family 2. Zoosporidae Zopf-Delage.
Intracellular parasites of Algae, Volvox, etc.
Genus Pseudospora Cienkowsky
Starch-eating ameboid forms Genus Protomonas Cienkowsky
Free-living; body red; marine Genus Protomyxa Haeckel
462 BIOLOGY OF THE PROTOZOA
Family 3. Vampyrellidae Doflein.
Form changeable; colorless; ray-like pseudo-
podia Genus A uclearia Cienkowsky
Body branched; naked; pseudopodia delicate
Genus Arachnula Cienkowsky
Color reddish; ectoparasitic on Algae. .Genus Vampyrella Cienkowsky
Color greenish; cysts of cellulose Genus Chlamydomyxa Archer
Body sharply pointed at base of pseudopodia
Genus Biomyxa Leidy
Protoplasm of body and pseudopodia yellow
Genus Rhizoplasma Verworn
Body yellow; pseudopodia colorless. . .Genus Dicitomyxa Monticelli
Sub-class II. MYCETOZOA de Bary.
Pseudoplasmodium in some; no peridia nor
capillitia; sporangium a mere mass of
spores Order 1 . Acrasida
Parasitic; no peridia nor capillitia. . .Order 2. Phytomyxida
Plasmodia; peridia and capillitia. . . Order 3. Euplasmodida
Order I. Acrasida van Tieghem.
Amebae solitary; stalked spore-case
Family 1. Sappiniidae
Amebae grouped ; sori from group . Family 2. Guttulinidae
Amebae grouped; stalks of sori hardened
amebae Family 3. Dictyostelidae
Family 1. Sappiniidae Uangeard.
One genus and species; dung of horse, cow,
dog, etc Genus Sappinia
Family 2. Guttulinidae Cienk.
Cells do not form stalks of sori Genus Copromyxa
Short stalks bearing sori Genus Guttulina
Family 3. Dictyostelidae Rostafinsky.
1. Stalks unbranched 2
Stalks branched Genus Polyspondylium
2. Spores without definite arrangement
Genus Dictyostelium
Spores in row like string of beads Genus Acrasis
Order II. Phytomyxida.
1 . Tissue parasites of plants 2
Celozoic parasites of animals 6
2. Tumor-causing parasites 3
Tumors not caused Genus Ligniera Maire and Tison
3. Cause of "club root" in cabbage family
Genus Plasmodiophora Woronin
Causing gall-like tumors 4
4. Spores in groups of four Genus Telramyxa Goebel
Spores massed in balls or plates 5
5. Spores massed as hollow balls Genus Sorosphaera Schroter
Spores in spongy masses Genus Sporospora Brunch
(i. Plasmodium forming in intestine of beetle
Genus Mycetosporidium
Leger and Hesse
Parasites of fat body and gonads or free in
cavity Genus Sporomyxa Leger
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 463
Order III. Euplasmodida Lister.
Spores exposed on surface of sporophores
Sub-order 1. Exosporea
Spores in sporangia Sub-order 2. Myxogastres
Sub-order 1. Exosporea Rostaf.
One genus; spores exposed; no sporangia
Genus Ceratiomyxa
Sub-order 2. Myxogastres Fries.
(Key to genera adapted from MacBride, 1022.)
Spore mass black or violaceous, rarely ferru-
ginous Series A
Spore mass never black; usually brown, yel-
low, etc Series B
Scries A
With delicate thread-like capillitium; spor-
angia more or less calcareous .... Legion 1 . Physarales
With capillitium and columella; rarely cal-
careous Legion 2. Stemonitales
Series B
Capillitium imperfect or none; spores brown,
rarely purple Legion 3. Cribrariales
Capillitium of interwoven plates or tubules;
spores pale or ashen Legion 4. Lycogalales
Capillitium of sculptured threads; spores yel-
low Legion 5. Trichiales
Legion 1. Physarales MacBr.
Fructification often calcareous throughout;
capillitium intricate Family 1. Physaridae
Lime in peridium only, or also in stipe; capil-
litium simple Family 2. Didymiidae
Family 1. Physaridae MacBr. em.
1 . Fructification an aethalium Genus Fuligo
Fructification an aggregate of sporangia . . 2
2. Peridium calcareous 3
Peridium apparently limeless, at least out-
side 6
3. Capillitium calcareous throughout . .Genus Badhamia
Capillitium largely hyaline 4
4. Sporangia globose; dehiscence irregular
( ienus Physarum
Sporangia vasiform or tubular 5
5. Dehiscence by lid-covered opening (ienus Craterium
Dehiscence irregular; peridium inverted
Genus Physarella
6. Sporangia sessile with irregular outlines
Genus Cienkowskia
Sporangia distinct Genus Leocarpus
Family 2. Didymiidae MacBr. em.
1 . Fructification an aethalium Genus Mucilago
Fructification not an aethalium 2
2. Peridium single 3
Peridium double; outer one gelatinous. ... 4
464 BIOLOGY OF THE PROTOZOA
Family 2. Didymiidae MacBr. em.
3. Calcareous deposits crystalline; stellate
Genus Didymium
Calcareous deposits in form of scattered
scales Genus Lepidoderma
4. Outermost peridium gelatinous Genus Colloderma
Outer peridium hardened Genus Diderma
Legion 2. Stemonitales MacBr.
1. Fructification aethalium4ike; columella
rudimentary or absent Family 1. Amourochaetidae
Fructification with distinct sporangia .... 2
2. Capillitium well-defined; columella prom-
inent, long Family 2. Stemonitidae
Capillitium developed from top of colum-
ella Family 3. Lamprodermidae
Family 1. Amourochaetidae MacBr. em.
A single genus Genus Amourochaeta
Family 2. Stemonitidae MacBr. em.
1. Sporangia grouped; capillitium with ves-
icles Genus Brefeldia
Sporangia distinct 2
2. Stipe and columella jet black 3
Stipe and columella whitish; calcareous
Genus Diachaea
3. Tips of capillitium branches free. . .Genus Comatricha
Tips united forming a surface network
Genus Stemonitis
Family 3. Lamprodermidae MacBr. em.
1. Columella through sporangium, capillitium
apical Genus Enerthenema
Columella only part way through sporan-
gium 2
2. Capillitium fully developed 3
Capillitium rudimentary ; minute forms
Genus Echinostellium
3. Capillitium does not form a net. . . .Genus Clastoderma
Capillitium forms an intricate net. . . Genus Lamj>roderma
Legion 3. Cribrariales MacBr.
1. Sporangia distinct and separated 2
Sporangia associated 3
2. Walls of sporangia perforate, especially
above Family 1. Cribuariidae
Walls not perforated; sporangia witli lid
Family 2. Oroadellidae
3. Sporangia irregularly grouped in delicate
membrane Family 3. Liceidae
Sporangia definitely grouped 4
4. Walls of sporangia not perforated; tubular
Family 4. Tubiferidae
Walls of sporangium perforated or frayed
Family 5. Reticulariidae
Family 1. Cribrariidae MacBr. em.
Peridium with meridional ribs or thickenings
Genus Dictydium
Peridium with apical thickenings only. .Genus Cribraria
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 405
Family 2. Orcadellidae MacBr. em.
A single genus Genus Orcadella
Family 3. Liceidae MacBr.
A single genus Genus Licea
Family 4. Tubiferidae MacBr. em.
1. Sporangia stipitate; clustered Genus Alwisia
Sporangia in linear series 2
2. Spores olivaceous < lenus Lindbladia
Spores umber Genus Tubifera
Family 5. Reticulariidae MacBr. em.
1. Spores brownish or umber 2
Spores yellowish Genus Dictydiaethalium
2. Sporangia bounded by broad perforated
plates Genus Enteridium
Sporangia wholly indeterminate. . . .Genus Reticularia
Legion 4. Lycogalales MacBr.
One genus only Genus Lycogala
Legion 5. Trichiales MacBr.
1. Capillitium a distinct net; no spiral bands
Family 1. Ahcyriidae
Capillitium threads fixed or free; no net. . . 2
2. Capillitium threads free; with spiral bands
Family 2. Trichiidae
Capillitium threads attached 3
3. Threads attached at both ends 4
Threads attached at one end if at all
Family 3. Perichaenidae
4. Threads plain or slightly roughened
Family 4. Dianemidae
Threads definitely sculptured. . .Family 5. Prototrichiidae
Family 1. Arcyriidae MacBr. em.
1 . Capillitium elastic 2
Capillitium non-elastic Genus Lachnobolus
2. Capillitium attached at base; no hamate
brandies Genus Arcyria
Capillitium centrally attached, with ham-
ate branches Genus Heterotrichia
Family 2. Trichiidae MacBr. em.
1. Capillitium threads long, centrally at-
tached 2
Capillitium threads short, free, sometimes
branched 3
2. Sculpture spiral Genus Hemitrichia
Sculpture reticulate Genus Calonema
3. Threads, elaters, marked by spiral' bands
Genus Trichia
Threads with irregular sculpture or none
Genus Oligonema
Family 3. Perichaenidae MacBr. em.
Sporangia more or less grouped; dehiscence
irregular Genus Ophiotheca
Sporangia grouped; polygonal; dehiscence by
lid Genus Perichaena
30
466 BIOLOGY OF THE PROTOZOA
Family 4. Dianemidae MacBr. em.
Capillitium threads attached at one end only
or free Genus Margarita
Capillitium threads attached at each end
Genus Dianema
Family 5. Prototrichiidae MacBr. em.
A single genus Genus Prototrichia
Sub-Class III. FORAMINIFERA D'Orb.
Cushman (1928) has published excellent keys to families and
genera of Foraminifera, including 45 families and -411 genera. It
is unnecessary to repeat these here.
Sub-class IV. AMOEBAEA Butschli.
Naked forms; pseudopodia lobopodia or 1am-
ellipodia Order 1. Amoebida
Testate or membraned forms Order 2. Testacea
Order I. Amoebida Aut.
1. Diphasic forms, ameboid and flagellated
stages Family 1 . Bistadiidae
Monophasic forms, amoeboid only 2
2. Free-living; water, earth, moss, etc 4
Parasites of cavities and tissues 3
3. Reproduction by binucleated spores
Family 4. Sporamoebidae
Reproduction by division and by uninucle-
ated spores Family 2. Endamoebidae
4. Without cytoplasmic '"Nebenkern"
Family 3. Amoebidae
With cytoplasmic "Nebenkern" . Family 5. Paramoebidae
Family 1. Bistadiidae Doflein.
Two flagella in flagellated phase Genus Dimastigamoeba Alexeieff
One flagellum in flagellated phase Genus Craigia Calkins
Three flagella in flagellated phase Genus Trvmastigamoeba
Whitmore
Family 2. Endamoebidae Calkins.
1. Vegetative forms with one nucleus 2
Vegetative forms with two nuclei. . .Genus Dientamoeba
Jepps and Dobell
2. Encysted stage with huge glycogen mass
Genus Iodamoeba Dobell
Encysted stage without large glycogen
mass 3
3. Individuals of "limax" type. .• Genus Endolimax Kuenen and
Swellengrebel
Individuals of ameba type Genus Endamoeba, Leidy
Family 3. Amoebidae Doflein.
1. Actively moving forms with lobose pseudo-
podia 2
Sluiiiiish forms; no definite pseudopodia
( ienus Pelomyxa
2. Large forms, several pseudopodia 3
Small forms moving as one pseud< ipodium . 4
MORPHOLOGY AX I) TAXONOMY OF THE SARCODINA 4<b
Family 3. Amoebidae Doflein.
3. Hody discoidal with short conical pseudo-
podia Genus Dactylosphaerium
Hertwig and Less.
Body ameboid with large lobose pseudo-
podia Genus Amoeba Ehr.
4. Endosome divides without fragmenting
Genus Vahlkampfia Chatton and
Lalung-Bonnaire
Endosome fragments forming typical
spindle ' Genus Hartmannella Alexeieff
Family 4. Sporamoebidae Chatton.
One genus and species Genus Pansporella Chatton
Family 5. Paramoebidae Doflein.
Free-living or parasitic, one genus . - .Genus Paramoeba Schaudinn
Order II. Testacea M. Schultze.
1. Testssimple; membranous, plastic or rigid . 2
Tests rigid, with foreign bodies, plates or
scales 3
2. Pseudopodia lobose or simply branched
Family 1 . Aecellidae
Pseudopodia reticulate, forming a network
Family 4. ( Iromiidae
3. Glutinous test covered by foreign bodies
Family 2. Difflugiidae
Chitinous test with plates made by organ-
ism family 3. EuGLYPHIDAE
Family 1. Arcellidae Schultze.
1. Tests membranous and flexible 2
Tests membranous; rigid; with or without
foreign bodies 9
2. Test like inverted watch-glass; aperture
full diameter 3
Test cup-like or sac-like 1
3. Test with hyaline margin (Fig. L88) ( lenus Pseudochlamys
Clap, and Lachm.
Tests completely hyaline Genus Pyxidicula Ehr.
4. Tests cup-like 5
Test bag or sac-like 7
.">. Margin of test aperture turned in •'•
Test aperture with diaphragm-like mem-
brane < ienus Diplochlamys < rreeff
6. Cell body uninucleate (Rhogostoma) (ienus Amphizonella Greeff
Body with more than one nucleus, .(ienus Zonomyxa Nusslin
7. Crown of test with circular and radial
ridges < Ienus Microcorycia Cockerel!
Crown of test simple; aperture an elastic
slit 8
8. Test non-encrusted ovoid sac; aperture
linear Genus Capsellina Penard
Test sac-like, covered with foreign bodies
( ienus Parmulina Penard
468 BIOLOGY OF THE PROTOZOA
Family 1 . Arcellidae Schultze.
9. Test rigid; chitinous; without foreign
bodies 10
Test more or less plastic ; one or more pores
Genus Cochliopodium
Hertwig and Less.
10. Test symmetrical 11
Test asymmetrical (one species encrusted)
Genus Lesquereusia Schlumberger
1 1. Tests circular in cross-section 12
Tests ellipsoidal in cross-section . . 15
12. Free-living forms 13
Parasitic form (Fig. 189) Genus Chlamydophrys
Cienkowsky
13. Pseudopodia lobose 14
Pseudopodia short lobose with aciculate tip
Genus Difflugiella Cash
14. Aperture of test with inturned margin
Genus Arcella Ehr.
Margin not inturned; one lobose pseudo-
podium Genus Leptochlamys West
15. Tests yellow or brown; minute; without
pits 16
Tests hyaline; transparent; usually with
pits Genus Hyalosphenia
1(3. Mouth oval placed obliquely to ventral
surface Genus Wailesella de Flandre
Test mouth slit-like, terminal Genus Cryptodifflugia Penard
Family 2. Difflugiidae.
1. Test circular in cross-section 2
Test ellipsoidal in cross-section (com-
pressed) 7
2. Aperture of test circular 3
Aperture of test ellipsoidal, linear, or tri-
radiate 6
3. Aperture without lobed external collar. ... 4
Aperture with three- or four-lobed external
collar Genus Cucurbitella Penard
4. Aperture excentric in position Genus Centropyxis Stein
Aperture central ; symmetrical 5
5. Test covered with diatom shells; pseudo-
podia pointed Genus Phryganella Penard
Test covered with sand, mud, detritus, etc.
( Fig. 190) Genus Difflugia Leclerc
6. Aperture triangular; inner shell about body
Genus Cystidina Volz
Aperture ellipsoidal Genus Plagiopyxis Penard
7. Test with constricted neck and internal
shelf Genus Pontigulasia Rhumbler
Test without internal shelf 8
8. Test with foreign particles on dome only. . 9
Test covered; aperture a long and narrow
slit Genus Bullinula Penard
9. Aperture of test convex Genus Heleopera Leidy
Aperture small, ellipsoidal, with thickened
margins Genus Awerintzia Schoutedon
MORPHOLOGY AND TAXONOMY OF THE SARCODINA 469
Family 3. Euglyphidae.
1 . Cells without symbiotic algae 2
Cells with one or two blue-green symbiotic
algae Genus Paulinella Lauterborn
2. Test curved, retort-shape 3
Test dome-shape; not curved 5
3. Aperture terminal oblique 4
Aperture terminal not oblique Genus Nadinella
4. Test with regular, small plates; no mem-
brane Genus Cyphoderia Schlumberger
Test with amorphous plates; aperture with
membrane Genus Campascus Leidy
5. Test circular in cross-section 6
Test ellipsoidal in cross-section (com-
pressed) S
(i. Dome with single long spine; plates fine
( lenus Pareuglypha
I )ome without spine 7
7. Shell-plates form teeth about aperture
( renus Euglypha Duj.
Aperture with fringed collarette, no teeth
( icnus Tracheleuglypha de Flandre
8. Test asymmetrical 9
Test symmetrical 10
9. Aperture circular; oblique; invaginated
Genus Trinerna Duj.
Aperture oval; oblique; not invaginated
Genus Corythion Taran
10. Test plates circular or oval 11
Test plates rectangular Genus Quadrula Schultze
1 1 . Test hyaline ; transparent ; plates numerous 1 2
Test brown or colorless; aperture oval
Genus Assulina Ehr.
12. Aperture as in Difflugia, circular. . .Genus Nebela Leidy
Aperture linear with undulate border
Genus Placocista Leidy
Family 4. Gromiidae.
1 . With one test aperture 2
With two or more test apertures
Sub-family 3. Amphistominae
2. Filose pseudopodia directly from plasm
Sub-family 1. Pseudogromiinae
Reticulate pseudopodia from peduncle
Sub-family 2. Allogromiinai;
Sub-family 1. Pseudogromiinae Wailes.
1 . Test of one piece 2
Test bivalved Genus Clypeolina Penard
2. Test smooth; no foreign particles. . .Genus Lecythium
Hertwig and Less.
Test covered with foreign particles 3
3. Test ovoid; no hair-like cirri Genus Pseudodifflugia
Schlumberger
Test ovoid; flexible; with hair-like cirri
Genus Diaphoropodon Archer
471) BIOLOGY OF THE PROTOZOA
Sub-family 2. Allogromiinae Rhumbler.
1 . Test ovoid; plastic, aperture lateral . Genus Lieberkiihnia
Clap, and Lachm.
Test rigid or plastic; aperture terminal. . . 2
2. Test oval or pyriform; not encrusted 3
Test cylindrical; encrusted with foreign
bodies Genus Rhynchogromia Rhumbler
3. Test and organism minute; often colonial
Genus Microgromia
Hertwig and Less.
Test large, oval, solitary Genus Allogromia Rhumbler
Sub-family 3. Amphistominae Cash.
1 . Test with two apertures 2
Test with from three to six apertures
Genus Microcometes
2. Test minute; hyaline; spheroidal; colored
globule ( renus Diplophrys
Test medium; oval; encrusted or not; with
symbionts Genus Amphitrema
CHAPTER XIII;
SPECIAL MORPHOLOGY AND TAXONOMY OE THE
INFUSORIA.
Since the first discovery of Vorticella and allied forms of Protozoa
by Leeuwenhoek in 1675, the Infusoria have been among the most
favored of living things studied through the microscope. The
designation Animalculae, given to include all forms of microscopic
life was changed by Ledenmiiller to Infusoria in 1760-1763, and the
entire phylum of Protozoa were included under this term by the
majority of writers down to Biitschli in 1882. Dujardin, 1841,
divided the "Infusoires" into rhizopods, flagellates and ciliates, a
classification adopted by Biitschli who, however, limited the use of
the term Infusoria to Protozoa bearing cilia at some period of the
life history. Two classes arc universally recognized today, the
Ciliata with permanent cilia, and Suctoria with cilia in the embry-
onic phases only. The classification of the Infusoria approaches
more closely to an ideal natural system than is possible at the
present time with any other group of Protozoa.
In size the Infusoria vary from minute forms, 12 /j. in length
(some species of Cinetochilum, Aspidisca, etc.), to giant ciliates, up
to 3 mm. (Bursaria, Lionotus proceros (Fig. 44, p. 86), Spirostomum
ambiguum. Size, however, has little taxonomic value.
The great majority of Infusoria are free-swimming but practically
all Suctoria and several minor groups of the Ciliata are attached,
while a few are parasitic. The majority of attached forms tend to
radial symmetry; free-swimming types show the greatest variety
of forms which in many cases may be traced to the effects of mode
of life, but the fantastic shapes of sapropelic and of many parasitic
types are difficult to reconcile with environmental conditions. The
ideal generalized form of Ciliata is a spherical or ellipsoidal organism
with the mouth at one end, contractile vacuole near the other, and
lines of cilia starting from the mouth and running in longitudinal
rows down the body. Shifting of the mouth with distortion of the
lines of cilia leads to various modifications of the generalized type
which is most closely represented by Holophrya or Prorodon species
(Fig. 191). A ventral surface bearing the mouth is established in the
Hypotrichida which includes some of the most highly specialized
forms of Protozoa.
Tests, cups or "houses" are found here and there throughout the
entire group. Gelatinous secretions forming tubes (Stichotricha,
472
BIOLOGY OF THE PROTOZOA
Ww
Fig. 191.— Types of Ciliata. A, Choenia teres, after Calkins; B, Cyclotrichium
ovatum, after Faure-Fremiet; C, Enchelys pupa, after Biltschli; D, Holophrya gar-
gamellae, after Faure-Fremiet; E, Holophrya discolor, and F, Opisthodon mnemiensis,
after Butsehli.
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 473
r-. .
nX*'
Fig. 192; Stentor, Calyptotricha, etc.) or spheroidal masses (Ophry-
il in in) are sometimes found, but cups or "houses" into which the
organisms withdraw (Cothurnia, Vaginicola, Folliculina, etc.) or by
which they are supported (Acinetidae, Discophryidae) are more
common. Tightly-fitting membranes with sculptured interlocking
plates of chitin or pseudochitin are present
in Cole})* and Tiarina (Fig. 73, p. 136).
The endoplasm is finely alveolar and much
more fluid than the more highly differentiated
cortex or ectoplasm. The endoplasm reveals
different types of refringent granules during
life, some of which have been identified as
excretory granules (Prowazek, Nirenstein),
others as mitochondria (Faure-Fremiet,
Cowdry) and others as belonging to the
Golgi apparatus (Nassonov). In addition to
these, reserves of food substances, kinetic
elements and metaplastids of different kinds,
with the nuclei make up the substance of the
endoplasm.
Metaplastids are numerous and widely dis-
tributed. Of these trichites, trichocysts and
"pharyngeal baskets" are the most charac-
teristic. Trichites are elongate, slender rods
usually surrounding the mouth in gymno-
stomes and are generally interpreted as organs
of support or protection. They are not lim-
ited to the oral region, however, and in some
forms provide a protective cuirass about the
posterior region (Strombidium) . The oral
trichites are numerous and closely applied and
in some cases form a continuous and smooth
tube extending deep in the endoplasm (some
Nassulas, Orihodon, etc.). Trichocysts are
shorter and more conspicuous; formed in the
endoplasm they assume a radial position
in the cortex and may cover the entire sur-
face (Paramccimn, Fig. 193; Frontonia, etc.)
or may be limited to certain regions (Dileptus
proboscis, Fig. 194). In a moving Actinobolina they are arranged
as in Paramecium, but in a quiescent individual each trichocyst is
carried out at the end of a long tentacle which this interesting ciliate
has the power to protrude for feeding purposes (Fig. 91, p. 163).
The function of the trichocysts is still in dispute (Visscher, 1923).
The substance of a trichocyst may be shot out in the form of a long
thread which hardens on contact with water. In such forms, repre-
fc&t
' I
Fig. 192.— Stichoiricha
secunda, a tube-dwelling
hypotrichous ciliate.
(Original, i
474
BIOLOGY OF THE PROTOZOA
_e.tr?
Fig. 193
Fig. 194
Fig. 193.— Paramecium caudatum. Section of a dividing individual, est. con-
necting strand of dividing micronuclei; e.tr., extruded trichocysts; g.v., gastric vacuole-
M, dividing macronucleus; m, m, divided micronuclei; tr., trichocysts. (Original )
Fig. 194.— Dileptus anser, with beaded macronucleus and 'twisted proboscis
(Original.)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 475
seated by Paramecium, Frontonia and other related forms, there
appears to be no toxic action connected with the trichocysts, the
threads affording protection by the formation of a net-like weft
about the organism. In other cases, however, there is considerable
evidence of toxic action and in such types the long threads are not
formed. Visscher (1923) has described such toxic action on the
part of the trichocysts of Dileptus, and the sudden paralysis of
Halteria grandinella upon coming in contact with a tentacle of
Actinobolina is interpreted as due to the toxic action of the minute
trichocyst at the extremity of the tentacle (Calkins, Moody). In
Didinium nasutum there is a zone of rods quite independent of the
Fro. 195. — Nassvla anna (C) and details of basket (.-1, B), after Butschli.
pharyngeal trichites and interpreted as trichocysts near the extrem-
ity of the seizing organ of this voracious animal (Fig. 98, p. 1ST).
A Paramecium jabbed by this proboscis in one of the vigorous
darts of Didinium is immediately paralyzed and the poisoning is
attributed to the trichocyst material. While this interpretation is
plausible it cannot be regarded as proved, and it must be admitted
that the protoplasm itself may carry the toxic substance. Thus
in the Suctoria a ciliate or other small organism is similarly par-
alyzed upon coming in contact with an outstretched tentacle in
which no trichocysts can be demonstrated.
Pharyngeal baskets are characteristic of the Chlamydodontidae
where they form conspicuous oral armatures (Fig. 195). The
476 BIOLOGY OF THE PROTOZOA
elements forming the basket are much larger than trichites and
are frequently combined in such a manner as to justify the term
basket. The rods are usually constant in number in a species and
may be united to form a tube at the posterior end of the basket
or in some cases may be united throughout. In Chilodon the
basket is protrusible and serves a useful purpose in food-getting.
According to MacDougall (1925) the basket is dissolved in artificial
gastric juice (pepsin) indicating a protein composition.
Metaplastic substances frequently appear in the form of pigments
which impart a characteristic color to a species. These are probably
connected with food metabolism and disappear in the absence of
appropriate food materials. Thus the bine pigment "stentorin''
of Stentor coeruleus, or Folliculina or the lavender of Blepharisma
undulans, the red of Mesodinium rubrum, the black spot of Tillina
magna, etc., are coloring matters of this type. Fats and oils also
are frequent inclusions and when brilliantly colored, as mNassula
aurea, give a striking and a pleasing picture as the organism rolls
through the water.
Symbionts are of frequent occurrence and give to Paramecium
bursaria, Stentor viridis, Ophrydium versatile and some Vorticella
species a bright green color.
Contractile vacuoles are practically universal among ciliates
and Suctoria. Held in place in the denser cortex they never move
about with cyclosis. They empty to the outside through a covered
but thinned orifice in the cortex, the covering being liquefied at
systole (Taylor, 1923). The vacuole system often includes canals
and reservoirs, reaching a high degree of specialization in some
forms, and ciliated excretory canals are said to be present in a few
parasitic types (Pycnothrix, Schubotz, 190S).
The Infusoria are unique in having an almost universal nuclear
apparatus in the form of dimorphic nuclei, macronucleus and micro-
nucleus. Of these the macronucleus is large and usually homo-
geneous in structure (granular) and is highly variable in shape in
different species. In some forms it is multiple and formed by
repeated division of an original single nucleus (Uroleptus); in other
cases attempted division results in a chain of nuclei connected by
a common nuclear membrane, giving rise to "beaded" nuclei
(Stentor, Spirostomum ambiguum, Uronychia transfuga, etc.). It
is frequently rod-shape as in Diplodinium (Fig. 2, p. 20), or horse-
shoe shape as in Vorticella, or very much branched as in Dendrosoma,
Ephelota and other Suctoria (Fig. 196).
Micronuclei are minute and are usually partially embedded in the
substance of the macronucleus. There is but little variation in
form of the micronucleus in different species, but there is a great
variation in the number present. In Paramecium caudatum and
P. bursaria there is but one, while in P. aurelia and P. calkinsi
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 477
there are two, in P. multimicronucleata there are many and two are
characteristic of the Oxytrichidae, etc. The number of micronuclei
runs up to eighty or ninety in Stentor and the number is intermediate
in several other genera.
Macronuclei are generally regarded as "somatic" nuclei with an
important part to play in general metabolism. They disappear by
absorption and are replaced by products of micronuclear division at
periods of reorganization by "endomixis," or by products of amphi-
nuclei after conjugation. Chromosome formation, with a definite
number of chromosomes, has been made out for a number of species
W &,; M&
Htm M wm^mSk i\f%A:
j m
'W n
Fig. 196. — Dendrosoma elegant; n, nucleus. (From Calkins after Kent.)
of ciliates, but no definite chromosomes have been described from
macronuclei. Evidence is accumulating to indicate that the micro-
nucleus is the essential element of the cell in conjugation but other
evidence is at hand to show that it is not essential for continued
vegetative life or for reproduction by cell division. Thus amicro-
nucleate races of Paramecium, Didinium, Spathidium, Oxytricha,
etc., have been maintained for long periods by Woodruff, Dawson
and others, while Maupas, Calkins and others have shown that the
micronucleus may disappear in long-continued cultures of hypo-
trichous forms, although the organisms are still able to divide
(p. 256). It is evident that different macronuclei represent different
478
BIOLOOY OF THE PROTOZOA
degrees of specialization and that some forms may carry on all
processes of asexual activity without a micronucleus and these may
represent transition stages to the condition in opalinids in which
there is no nuclear dimorphism at all and both sexual and asexual
processes are possible with only one type of nucleus. According to
McNally this is the condition in Nassula ornata or N. elegans.
The kinetic elements, including cilia and their derivatives and
coordinated systems of intracellular fibrils, represent a neuromotor
apparatus even more complex than that of the higher flagel-
lates. In but few cases are there combinations of other types of
motile organs with cilia. One such case is described by Penard
under the name Myriaphrys paradoxa, a form with axopodia and
cilia (Fig. 197); another is a combination of cilia with a flagellum,
Fig. 197. — Myriaphrys paradoxa (?), with cilia arid axopodia. (After Penard.
Monomastix (-Hiatus described by Schewiakoff. The possibility of
the derivation of ciliates from flagellates, in some cases through
Heliozoa-like forms, is suggested by such types, but origin of this
group involves far too much speculation for serious consideration.
Cilia, by fusion, form locomotor organs of complex nature (see
Chapter IV). Undulating membranes, meinbranelles and cirri are
present in the majority of ciliates. A fourth type of combination,
membranulae or pectinelles, combines several of the features of
flagella. Thus the powerful motile organs of Didinium are composed
of a few flagella-like, long cilia, while rhizoplasts run from their
basal bodies to the vicinity of the nucleus (Fig. 98, p. 187).
Undulating membranes are limited regionally, to the gullet,
margin of the mouth or to a circumscribed area called the peristome.
Meinbranelles are grouped usually in a curved row, the "adoral
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 479
zone," around the margin of the peristome, but a dorsal ring of
membranelles is present in some parasitic forms (e. g., Diplodinium,
Fig. 2, p. 20). Here also limited "arches" of apparent membran-
elles are variously distributed about the body (Fig. 1-4). Cirri
are combinations of cilia of usually the ventral surface, but they
may encroach on the dorsal surface (e. g., Uronychia); they form
groups, as a rule, named according to their position, frontal, ventral,
anal and caudal cirri, the number and arrangement forming a
basis for diagnosis of genera and species.
At the present time there is need of a more precise characterization
of cirri. The Order Hypotrichida, for example, is described by
Kahl (1931) as including forms which possess no cilia but only
membranelles, membranes and cirri. This distinction upsets the
classification, in use for half a century, as given by Stein. Having
no cirri, the former hypotrich family Peritromidae is removed to
the Heterotrichida while the accepted cilia of the Urostylidae (here
included in the Oxytrichidae) are now regarded as simple combina-
tions of cilia, i. e., cirri. Marginal cirri are more complex, frontals
and anals still more so, while the great steering and jumping organs
of Uronychia, Diophrys, etc., certainly call for more descriptive
terms than cirri. Temporarily the need may be met by use of the
expressions: simple cirri, caudal cirri, tactile cirri, frontal, anal
and marginal cirri and giant cirri.
The activities of the motile organs are coordinated through a
system of longitudinal and transverse fibrils connecting the basal
fibrillae coining from the cilia or groups of cilia (p. 152). A coor-
dinating center, termed the motorium, regarded by numerous
observers as an artefact (Rees, 1931; Turner, 1933, etc.) has been
demonstrated in some forms (Diplodinium Sharp, 1914; Euplotes
Yocom, 1918; Balantidium MacDonald, 1922; Kidder, 1932, ^ al.).
The "silver line" system, discovered by Klein, is a complex
meshwork of granules and fibrils in the cortex arranged in patterns
which appear to be characteristic of different species. This, appar-
ently, is a universal coordinating system of the Infusoria (see p. 80).
Myonemes also are widely distributed in the group. In Stentor
they lie in superficial canals within the cortex and in some cases
appear to be conducting as well as contractile elements. In Epis-
tylis Schroder has described myonemes running longitudinally from
the stalk to the peristome where they terminate in the basal plates
of the membranelles (Fig. 70, p. 120); distally they combine to form
the contractile strand of the stalk.
A well-defined mouth is present in almost all ciliates (absent in
an entire group, only in Astomida). In gymnostomida it is closed
save at times of food ingestion; in all other groups it is perma-
nently open. In these latter cases the form of the mouth varies
from circular to elliptical, crescentic or triangular openings and in
480
BIOLOOY OF THE PROTOZOA
the majority of cases the mouth leads into a ciliated gullet. Such
constant feeders are limited to a bacterial diet and other minute
food substances while the gymnostomes, by reason of the disten-
sibility of the oral region are able to take in living organisms even
larger than themselves (see p. 186 and Fig. 98).
C
£>
Fig. IDS. — Tentacles of Infusoria. .1, Mesodinium pulex, with four oral tentacles
for adhering; B, Podophrya fixa; C, I), tentacles of Ephelotidae. (A, C, D, from Cal-
kins; B, original.)
In Suctoria, food-taking is of an entirely different type. Mouths
are absent but food may be taken in through any one of the many
suctorial tentacles. The body wall of a captive organism is cyto-
lyzed at the point where the tentacle is in contact and the endoplasm
of the prey either passes in a stream through the lumen of the
tentacle, or the endoplasm of the captor enters the body of the
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 481
victim and digests its endoplasm in situ (Maupas, 1883). Ten-
tacles for adhesion are also present in Mesodinium (Fig. 198).
While the vast majority of Infusoria are holozoic in food -get ting,
parasitic types may be holozoic or saprozoic (Astomida). Proteins
are digested by all and carbohydrates in some (Balantidium Glaess-
ner, see p. 198).
Adaptations for food-getting, protection during ingestion and
other differentiations in the service of nutrition are responsible for
most of the cortical structures of the derived organization and
these for the most part determine the taxonomic position of genera.
Trichocysts, trichites, pharyngeal baskets, etc., have been described
(see p. 478). Adhesive discs (Lichnophoridae, Urceolariidae) ; thig-
motactic cilia or special cilia for attachment ("Thigmotricha" of
Chatton, Boveriidae, Aucistrumidae, Conchophthiriidae) and
suckers for attachment (some Astomida, Mesodinium, etc.) or for
food-getting (Hypocomidae, Suctoria) are widely distributed. The
most important, taxonomically, of all of these adaptations are those
associated with the filiate mouth. In the classification adopted
here we follow the recent trend (Poche, Kahl, Reichenow-Dorlein,
et id.) in filiate morphology in which the oral apparatus together
with position on the body are primary diagnostic characters. The
absence of an adoral zone of membranelles about the mouth (peri-
stome) distinguishes the' sub-class Holotricha from other ciliates.
The direction of curvature of the adoral zone, and spiral rows of
cilia in the sub-class Chonotricha distinguishes the sub-class Peri-
tricha. Here, however, sonic confusion results from use of the
terms left -wound and right-wound. Obviously a left-wound spiral
becomes a right-wound spiral if the start is made from the end
away from the mouth. Stein, Biitschli and others, until quite
recently, viewed the spiral as starting from the mouth and inter-
preted the adoral zones of Peritromus, Stentor, Stylonyehia, et <d.,
as wound to the left, whereas in the Peritricha it winds to the right.
Kahl, Reichenow-Doflein and other recent writers view the spiral
as starting from the end farthest away from the mouth with a
corresponding reversal in use of the descriptive terms left and
right. Since the stroke of the membranelles and the food currents
are toward the mouth, the modern point of view probably has more
justification than the older one and is adopted here. It makes a
difference furthermore whether the organism is viewed from the
ventral or dorsal aspect; for right and left as used above the organism
is viewed from the oral side.
The mouth proper may be provided with simple cilia or com-
binations of cilia, or void of cilia altogether. Those without motile
elements are grouped in the order Gymnostomida established by
Biitschli. These in turn are distributed in sub-orders according
to the position of the mouth. In the sub-order Prostomina the
31
482
BIOLOUY OF THE PROTOZOA
mouth is at the anterior end of the body and such forms are still
regarded as the most generalized types of eiliates. In the sub-order
Pleurostomina the mouth is no longer terminal but occurs as an
elongated slit (Amphileptus, Lionotus) or as a circular opening at
the base of a more or less pronounced proboscis (Dileptus, Trache-
lius, etc.). In the sub-order Hypostomina the mouth is on the
physiologically ventral side as in Nassula, ( nilodon, etc.
The orders Trichostomida and Hymenostomida include forms in
which the mouth is provided with cilia or with membranes, free
cilia in Trichostomida and undulating membranes in Hymenosto-
mida. There is no great difference between these two orders, and
it is frequently difficult to determine whether a particular form
belongs to one or the other. Lines of cilia in the gullet, as in Para-
mecium, often give the impression of an undulating membrane.
Fig. 199. — Types of eiliates. A, Cyclidium glaucoma; B, Lembadion bullinum;
C, Pleuronema chrysalis. (A, C, after Calkins; B, after Butsehli.)
In Hymenostomida the mouth, as a rule, is more complex than in
Trichostomida. Undulating membranes surrounding it (peristo-
mial) are frequently enormously developed (Pleuronemidae, Fig. 199),
forming sail-like traps for food bodies. In other cases the mem-
branes are inside an oral pit or vestibule and such mouth parts
are very complicated (Fig. 8, p. 29).
In the sub-class Spirotricha we find the most spectacular types of
eiliates; some are huge (Bursariidae, Condylostomidae, Stentoridae
of the order Heterotricha) ; some are spirally twisted (Metopidae) ;
some highly flexible (Lichnophoridae) .
Cilia, in additon to the adoral zone of membranelles, cover the
body in the majority of Heterotrichida — but are greatly reduced or
absent in the Oligotrichida and Hypotrichida, where in the latter
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 483
they are replaced in part or entirely by cirri. Here, also, particu-
larly in parasitic forms (Ophryoscolecidae and Cycloposthiidae), the
periplast is well developed and the organisms are frequently char-
acterized by fantastic sculpturing (Fig. 146, p. 293).
The sub-class Chonotricha includes a small number of forms
with highly exaggerated peristomial structures. These are spirally
wound (to the right) in Spirochonidae but are funnel-shape in
Chilodochonidae. The characteristic reproduction by budding in
these forms suggests a relationship to the Suctoria.
Parasitism in Infusoria, as in other great groups of Protozoa, is
widely spread and some of the adaptations to this end merit special
consideration. The majority are apparently harmless commensals
of digestive tract and body cavity; some, however, are more serious,
Balantidium coll for example, causing acute enteritis in man and
other mammals. Ectoparasitic forms may also be a source of
trouble. Amphileptus branchiarum gets under the gill mantles of
tadpoles and ingests groups of epithelial cells (Wenrich) ; others form
peculiar arms by which they are anchored to gill bars (Ellobiophrya
donacis Chatton, Fig. 104, p. 202). In the main, related forms are not
strictly parasitic but are attached in gill chambers where a constant
supply of food is assured. Special attaching organs, arising from
specially modified cilia, are characteristic of holotrichous and of
some peritrichous forms. These are best developed in Trichodina
(common on Hydra) where a special attaching organ termed the
scopula is characteristic, while the two arms of Ellobiophrya men-
tioned above are interpreted by Chatton as representing a split
scopula. Amongst the Holotrichida, ectoparasitism is character-
istic of the group which Chatton calls the Thigmotricha (1923).
Here a portion of the posterior ciliated region termed the " thigmo-
tactic area" becomes modified as an attaching organ. It is a sucking
disc in Ptychostomum, a protrusible tentacle in Hypocomidcs and
Hypocoma which Chatton, correctly, removes from the Suctoria to
the Holotrichida. It is rudimentary in Plagiospira and not at all
evident in Boveria. Two types of feeding adaptations are evident
in these forms. In one series the peristome and adoral zone become
greatly enlarged, forming a helicoid spiral in Boveria, Plagiospira,
Hemispira and Ancistruma, capable of drawing in food particles
from a distance. In another series the oral apparatus becomes
rudimentary or lost altogether, food substances being absorbed by
osmosis through the general body wall or by tentacles only as in
Hypocoma and Hypocomides.
Lumen-dwelling forms have apparently undergone less degenera-
tion than have ectoparasitic types. In the Astomida such degen-
eration has been the most extreme. Here mouth and other oral
structures are entirely wanting and nutrition is osmotic. In the
majority of cases, however, the peristome and mouth are retained
484 BIOLOGY OF THE PROTOZOA
while the cortex is often highly sculptured and fantastic as in the
Ophryoscolecidae.
The aberrant Opalinidae are parasitic in Amphibia. Not only
are they astomatous, but in certain characters they differ widely
from other ciliates so that they have been variously placed in
classification. Hartog (1906), for example, placed them with the
Hypermastigida of the flagellates. Met calf (1918, 1923) includes
them as Prociliata sharply marked oft' from the remaining ciliates.
In view of the adaptive changes brought about by a parasitic mode
of life, it seems more probable that they are degenerate rather than
primitive types. There are invariably two or more nuclei but the
nuclei are identical with no indication of dimorphism. In the
nuclei, however, there are two kinds of chromatin according to
Leger and Duboscq (1904) and Metcalf (1909 and 1923). The
latter distinguishes these types as " macrochromatin " and "micro-
chromatin," the former in mitosis giving rise to band-form "macro-
chromosomes," the latter to "microchromosomes" in apparently
even numbers (from two to ten). The "macrochromatin" is re-
garded as functional in vegetative life and, like the macronucleus
of other ciliates, gives rise to chromidia (Neresheimer) or otherwise
fragments preparatory to absorption in the cell. The "micro-
chromatin" on the other hand is functional during sexual phases.
From these considerations it would appear that the dimorphic
nuclear conditions of ciliates generally is here represented by each
nucleus, but the hypothesis is questionable.
In their sexual phenomena, also, the Opalinidae differ from the
majority of other ciliates. Individuals begin to divide rapidly with
decreasing size until minute forms result with one, two or more
nuclei according to species (Neresheimer, Metcalf). These encyst,
the cysts passing out with the feces. Tadpoles ingest the cysts
which open in the rectum, giving rise to the same type that had
previously encysted. These now multiply, ultimately forming mac-
rogametes and microgametes which fuse on contact. The zygote
has one nucleus at first which later gives rise to the binucleated or
multinucleated forms, although the exact manner has not been
described (Metcalf, 1923).
Reproduction in ciliates generally is typically by binary cross-
division and involves a renewal of motile organs, at least this is the
case in forms with cirri, and MacDougall (1925) gives evidence to
indicate that cilia also are similarly renewed. It thus results that
motile organs of both products of cell division are proportionate to
the size of the young individuals. Old metaplastids, as pharyngeal
baskets, are discarded and new ones are formed in both halves.
Nuclear changes during division are quite varied, each species having
its own peculiarities of macronuclear condensation and reformation.
Unequal division or budding, while uncommon among ciliates,
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 485
is the chief method of reproduction among the Suctoria but also
occurs in the Chonotricha (Spirochona, etc.). In Suctoria, budding
is either external or internal, in the latter case the budding area is
invaginated, the margins close over, and a brood chamber is formed
from which the embryos escape when formed.
Multiple division or sporulation is also uncommon in the Ciliata,
but occurs in some of the more generalized and in some parasitic
types. When it occurs it is usually under the protection of a
temporary cyst (Colpoda, Ichthyophthirius).
Sexual processes are practically universal in the group and the
main features of the process are similar throughout. In most cases
fusion is temporary and pronuclei are exchanged after which the
conjugants separate. In some cases, Vorticellidae, fusion is per-
manent and sexual dimorphism is the rule, in other cases such
dimorphism is expressed by the pronuclei, but in most cases there is
Fig. 200.-
-Glmicoma (DaUasia) frontata. Successive stages Leading to the formation
of copulating isogametes. (After Calkins and Bowling.)
no sex differentiation whatsoever (see Chapter VIII). In Trachelo-
cerca phoenicopterus, Ichthyophthirius multifilius, Glaucoma (Dal-
lasia) frontata and in Opalinidae the fertilization phenomena do not
follow the usual routine of other ciliates, microgametes being formed
and fusion being permanent.
Glaucoma (DaUasia) frontata illustrates a most unusual sexual
phenomenon. Here there are two types of fertilization, one by the
fusion of gametes, the other by typical conjugation (Figs. 200, 201 ).
Conjugation always results in physical reorganization of the pro-
toplasm, the old macronucleus is broken up and the fragments are
absorbed in the cytoplasm, while a new macronucleus and new micro-
nuclei are differentiated from products of the first or second division
of the amphinucleus after fertilization (see Chapter VIII) . A similar
reorganization takes place at regular intervals of thirty days (P.
aurelia) or sixty days (P. caudatum) according to Woodruff and
486
BIOLOGY OF THE PROTOZOA
Erdmann (1914) who termed the phenomena accompanying this
method of reorganization "endomixis" (p. 817). In other types of
^-.
\
v
Fig. 201. — Glaucoma (Dallasia) frontata. Normal conjugation occurring later in
the life history. (After Calkins and Bowling.)
ciliates similar asexual processes of reorganization take place under
the protection of a cyst (for significance of reorganization see
Chapter IX).
CLASSIFICATION OF THE INFUSORIA.
Sub-phylum. INFUSORIA Ledenmt'tller; em. Butkchli.
Class I. Ciliata Perty; em. Bi'itschli.
Sub-class I. Holotricha Stein
Order 1. Astomida Cepede
Family 1. Opalinidae Stein
Family 2. Anoplophryidae Cepede
Family 3. Chromodinidae Cheissin
Family 4. Haptophryidae Cepede
Family 5. Intoshellinidae Cepede
Family 6. Hoplitophryidae Cheissin
Order 2. Gymnostomida Biitschli
Sub-order 1. Prostomina (Prostomata Schowiakoff)
Family 1. Holophryidae Perty
Family 2. Actinobolinidae Kent
Family 3. Metacystidae Kahl
Family 4. Didiniidae Poche
Family 5. Colepidae Kent
Family 6. Spathidiidae Kahl
Family 7. Butschliidae Poche
Sub-order 2. Pleurostomina (Tribe Pleurostomata Schewiakoff)
Family 1. Amphileptidae Schoutedon
Family 2. Tracheliidae Ehr.
Family 3. Loxodidae Roux.
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 487
Class I. Ciliata Perty; em. Butschli.
Sub-class I. Holotricha Stein
Order 2. Gymnostomida Butschli
Sub-order 3. Hypostomina Schewiakoff
Family 1. Nassulidae Schoutedon
Family 2. Chlamydodontidae Claus.
Family 3. Dysteriidae Clap, and Lach.
Family 4. Pycnothricidae Poche (Nicollellidao Ch. and Pe.)
Family 5. Foettingeriidae Reichenow-Doflein.
Order 3. Trichostomida Butschli
Family 1. Sciadostomidae Kahl
Family 2. Spirozonidae Kahl
Family 3. Trichospiridae Kahl
Family 4. PlagiopyUdae Schewiakoff
Family 5. Clathrostomidae Kahl
Family 6. Colpodidae Poche
Family 7. Parameciidae Grobben
Family 8. Marynidae Poche
Family 9. Trichopelmidae Kahl
Family 10. Conchophthiriidae Reichenow-Doflein
Family 11. Hypocomidae Biitschli
Family 12. Boveriidae Pickard
Family 13. Ancistrumidae Issel
Family 14. Isotrichidae Butschli
Family 15. Paraisotrichidae da Cunha
Family 16. Blepharocoridae Hsiung
Family 17. Cyathodiniidae da Cunha
Order 4. Hymenostomida Hickson
Family 1. Frontoniidae Kahl
Family 2. Ophryoglenidae Kent
Family 3. Philasteridae Kahl
Family 4. Lembidae Kahl
Family 5. Pleuronemidae Kent
Family 6. Hemispeiridae (Hemispeirinae Konig)
Sub-class II. Spirotricha Butschli 1889; em. Kahl
Order 1. Heterotrichida Stein
Family 1. Metopidae Kahl
Family 2. Reichenowellidae Kahl
Family 3. Spirostomidae Kent
Family 4. Plagiotomidue Poche
Family 5. Condylostomidae Kahl
Family 6. Stentoridae Carus (Claus?)
Family 7. Folliculinidae Dons
Family 8. Bursariidae Perty
Family 9. Peritromidae Stein
Family 10. Lichnophoridae Stevens
Order 2. Oligotrichida Butschli 1889
Family 1. HaUeriidae Clap, and Lach.
Family 2. Strombilidiidae Kahl
Family 3. Tintinnidae Clap, and Lach.
Family 4. Ophryoscolecidae Claus. (?)
Family 5. Cycloposthiidae Poche
Order 3. Ctenostomida Lauterborn
Family 1. Epalcidae Wetzel
Family 2. Milestomidae Kahl
Family 3. Discomorphidae Poche
INS BIOLOGY OF THE PROTOZOA
( !lass I. Ciliata Perty; em. Butschli.
Sub-class II. Spirotricha Butschli 1889; em. Kalil
Order 4. Hypotrichida Stein
Family 1. Oxytrichidae Ehr.
Family 2. Ewphtidae Ehr.
Family 3. Aspidiscidae Stein
Sub-class III. Peritricha Stein
Family 1. Urceolariidae Stein
Family 2. Vorticellidae Ehr.
Sul i-class IV. Chonotricha Wallengren
Family 1. Spirochonidae Grobben
Family 2. Chilodochonidae Poche
Class II. Suctoria.
Family 1. Acinetidae Butschli
Family 2. Discophryidae Collin
Family 3. Dendrosomidae Butschli
Family 4. Dendrocometidae Stein
Family 5. Ophryodendridae Stein
Family 6. Podophryidae Butschli
Family 7. Ephelotidae Sand
INFUSORIA.
With simple cilia or combinations of cilia
throughout life Class Ciliata
Ciliated only in developmental stages ; derived
organization with tentacles bearing cup-
like sucking discs Class Suctoria
Class I. CILIATA Perty 1852; Butschli 1889.
Key to Sub-classes
1 . Body without adoral zone of membranelles
Sub-class 1. Holotricha
Body with left < ir right-wound adoral zone . 2
2. Adoral zone right-wound (towards the
mouth) 3
Adoral zone left-wound (towards the
mouth) Sub-class 3. Peritricha
3. Peristome not drawn out funnel-like
Sub-class 2. Spirotricha
Peristome drawn out like funnel
Sub-class 4. Chonotricha
Sub-class I. HOLOTRICHA Stein 1859.
Key to Orders
1. Mouthless parasitic forms Order 1. Astomida
Mouth-bearing forms; free-living or para-
sitic 2
2. Gullet opens on surface, or in a vestibule
without specialized cilia Order 2. Gymnostomida
Gullet opens in vestibule with special cilia
or membranes 3
3. Vestibule with rows of free cilia. . .Order 3. Trichostomida
Vestibule with membranes; with or with-
out additional cilia Order 4. Hymenostomida
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 489
Order 1. Astomida.
Key to Families
1. Without dimorphic nuclei Family 1. Opalinidae
With dimorphic nuclei 2
2. Skeleton organs or attaching structures
absent 3
Skeleton structures or attaching organs
present 4
3. Contractile vacuoles absent or scattered;
macronucleus spheroidal, elongate or
branched Family 2. Anoplophryidae
Contractile vacuole absent; macronucleus
fragmented Family 3. Chromidinidae
4. Vacuole a dorsal canal Family 4. Haptophryidae
Vacuoles in rows or distributed 5
5. Without supporting elements in cortex
Family 5. Ixtoshellinidae
With supporting elements in cortex
Family 6. Hoplitophryidae
Family 1. Opalinidae Claus.
1. Form cylindrical; circular in cross-section . 2
Form flattened ; ellipsoidal in cross-section . 3
2. With two similar nuclei Genus Protoopalina Metcalf
With many similar nuclei Genus Cepedea Metcalf
3. With two similar nuclei Genus Zelleriella Metcalf
With many similar nuclei Genus Opalina Purkinje
Family 2. Anoplophryidae Cepede 1910.
1. Body without anterior sucker 2
Body with anterior sucker 8
2. Without anterior protoplasmic process. ... 3
With anterior protoplasmic process 7
3. Cilia in longitudinal, not spiral, lines 4
Cilia in spiral lines Genus Orchitophrya Cepede
4. Contractile vacuoles present 5
Contractile vacuoles absent Genus Meta/phrya
5. Contractile vacuoles multiple, in rows
Genus Anoplophrya Dujardin
C. V. single, posterior 6
6. Body pyriform; C. V. sub-terminal . Genus Kofoidella Cepede
Body ellipsoid; C. V. terminal Genus Perezella Cepede
7. C. V. single; macronucleus spheroidal
Genus Herpetophrya Siedlecki
C. V. numerous, in one row; macronucleus
elongate Genus Biltschliella Awerinzew
8. Macronucleus spheroidal Genus Cepedella Poyarkoff
Macronucleus branched Genus Khizocaryum Caul, et Mes.
Family 3. Chromidinidae Cheissin 1930.
One genus only, Chromidina (including Opalinopsis)
Family 4. Haptophryidae Cepede 1923.
1. Body without sucker; with hook. . .Genus LachmaneUa Cepede
Body with sucker ; with or without hooks . 2
2. Body with sucker and two hooks. . .Genus Steinella Cepede
Highly developed sucker ; no hooks or skel-
eton Genus Haptophrya Stein
■490 BIOLOGY OF THE PROTOZOA
Family 5. Intoshellinidae Cepede 1910.
1. Skeleton elements in form of collar with
six spines Genus Intoshellina Cepede
2. Skeleton in form of circular disc with teeth
Genus Monodontophrya
Vejdowsky
Family 6. Hoplitophryidae Cheissin 1930.
1. Spine simple, projecting from anterior end . 2
Spine or skeleton entirely embedded 3
2. Spine extends beyond anterior end . .Genus Maupasella Cepede
Spine ends as an apical point Genus Protoradiophrya Rossolimo
3. Spine arrow-like, barbed; none in cortex. . 4
Body with spines in cortex 5
4. Spine with simple barb; one row of con-
tractile vacuoles Genus Mesnilella Cepede
Spine a tripartite spicule (Fig. 202) . . Genus Hoplitophrya Stein
5. Body vermiform, not swollen anteriorly
Genus Radiophrya Rossolimo
Body vermiform, much swollen anteriorly
with radiating spines Genus Mrazekiella Kijenskij
Order 2. Gymnostomida.
Key to Sub-orders and Families
1. Mouth at anterior pole or in immediate
vicinity Sub-order 1 . Prostomina
Mouth lateral or ventral 2
2. Mouth lateral; slit-like or round
Sub-order 2. Pleurostomina
Mouth on anterior half of flat-ventral
side Sub-order 3. Hypostomina
Sub-order 1. Prostomina (Prostomata Schewiakoff).
1 . Free-living forms 2
Parasitic forms Family 7. Butschliidae
2. Mouth region laterally compressed with
trichites Family 6. Spathidiidae
Mouth region not compressed, round cross-
section, no neck 3
3. Mouth opens into receptaculum in anterior
part of body (test-dwelling). . .Family 3. Metacystidae
Mouth without receptaculum (not test-
dwelling) 4
4. Mouth at tip of apical mound surrounded
by circlet of motile organs. . . .Family 4. Didiniidae
Mouth otherwise 5
5. Body covered by ectoplasmic, perforated
plates Family 5. Colepidae
Body surface otherwise 6
6. Body with radially arranged, retractile ten-
tacles (pseudop.) Family 2. Actinobolinidae
Bodv without tentacles Family 1. Holophryidae
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 491
Sub-Order 2. Pleurostomina Schew. 1886; em. Kahl.
1. Ventral side, with mouth, convex 2
Ventral side, with mouth, concave
Family 3. Loxodidae
2. Mouth an elongated slit Family 1. Amphileptidae
Mouth round, at base of trichocyst-bearing
neck Family 2. Tracheliidae
Sub-order 3. Hypostomina (Hypostomata Schewiakoff) .
1. Furrow from anterior end to mouth (gut
parasites) Family 4. Pycnothricidat
No furrow to mouth 2
2. Entire body ciliated, or cilia partly reduced 3
Cilia confined to ventral side; occasional
sensory bristles 4
3. Free-living forms; oral basket present
Family 1. Nassulidae
Invertebrate ectoparasites; no oral basket
Family 5. Foettingeriidak
4. Posterior spine on ventral side. .Family 3. Dysteriidae
No bristle or spine on ventral side
Family 2. Chlamydodontidae
KEY TO GENERA.
Order 2. Gymnostomida.
Sub-order 1. Prostomina.
Family 1. Holophryidae Perty 1852.
1 . Spheroidal to oval without definite mouth
and gullet 2
Anterior end with distinct mouth, often
surrounded by trichites 3
2. Globular, usually united in chains of four
Genus Sphaerobactrwn Schmidt
Oval, broadly truncate with bowl-like ante-
rior pit Genus Bursella Schmidt
3. Small; mouth polar; refractile; delicate,
armor-like pellicle 4
Pellicle not armor-like 6
4. Pellicle furrowed in spiral lines from ante-
rior right to posterior left Genus Plants Colm
Pellicle not spirally furrowed 5
5. Small, slightly bent ventrally; club-shape;
no tail cilia; mouth protruding. . .Genus Rhopalophrya Kahl
Very small, cylindrical, mouth not pro-
truding, one long tail cilium Genus Pithothorax Kahl
(>. Small; flattened laterally; anterior bent
ventrally 7
Small ; not flattened ; no anterior bend .... 8
7. No spiral furrows, mouth slit-like; at ante-
rior end surrounded by membrane ( Fig.
207) Genus Stephanopogon Entz
Spiral furrows posteriorly to right; mouth
sub-apical Genus Platyophrya Kahl
492
BIOLOGY OF THE PROTOZOA
C
IIII/0J
is,
!■- '^k'-.e,:-!
Y. ...if
Fig. 202. — Types of Ciliata. A, Hoplitophrya lumbrici; B, Trachelocerca phoeni-
copteris; C, Prorodon niveus; D, Prorodon far ebus; E, Urotricha /areata; F, Prorodon
teres; G, Prorodon armatus. (A, C, D, E, F, G, after Biitsrhli; B, after Calkins.)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 493
Family I. Holophryidae Perty 1852.
8. Body ovoidal to cylindrical with ventral
inclination; with snout-like oral process
Genus Lagenophrya Kahl
Body otherwise 0
9. Mouth a short slit, directed backwards
from pole; no trichocysts Genus Microregma Kahl
Mouth not a short, open slit 10
10. Mouth with 3 closely placed rows of small
bristles (dorsal brush), no oral papillae. 11
Mouth without 3 bristles, some with 1 ;
some with widely spread bristles 13
1 1 . Mouth polar ; slit-like ; usually closed ; outer
ends of gullet trichocysts not deeply sunk
Genus Pseudoprorodon Blackburn
Mouth slit-like; gullet surrounded by
double trichites which end deep in oral
ectoplasm 12
12. Ectoplasm surrounding the mouth flat
(Fig. 202) Genus Prorodon Ehr.
Ectoplasm surrounding the mouth slightly
raised Sub-genus Rhagadostoma Kahl
13. Ovoid or short cylindrical; neither elong-
ate nor flask shape; broad truncated an-
terior end absent 14
Elongate, lance-like cylindrical flask-shape ;
or worm-like; broad truncated oral end
in shorter forms 18
14. Gullet opening surrounded entirely or in
part by small papillae 15
Gullet opening not surrounded by papillae . 16
15. Posterior end with one or several caudal
tail cilia, otherwise not ciliated. . .Genus Urotricha C. and L.
Posterior end ciliated, no caudal cilia
Genus Spasmostoma Kahl
16. Small; oval; mouth with papillae on right
side, running into short ventral groove
Genus Plagiocanvpa Schew.
Mouth opening flush with body or slightly
raised 17
17. Mouth opening flush with body. . . .Genus Holophrya Ehr.
Mouth opening slightly raised. .Sub-genus Balanophrya Kahl
Ectoparasitic on fish Sub-genus Ichthyophthirius Fouquet
18. Elongate, lance-like or flask-shape; much
flattened, usually with 2 nuclei 19
Not flattened ; elongate to worm-like, nuclei
diverse 20
19. With long tentacle-like process from ter-
minal mouth Genus Ileonema Stokes
Without tentacle-like process Genus Trachelophyllum C. and L.
20. With annular furrow near anterior end,
making a head part with spiral rows of
cilia (Fig. 85) Genus Lacrymaria Ehr.
Without annular furrow and head part. . . 21
494 BIOLOGY OF THE PROTOZOA
Family 1. Holophryidae Perty 1852.
21. Elongate to worm-like species, usually
more or less distensible 22
Short or flask-shape species; little disten-
sible; ectoplasm without warts 24
22. Head region narrowed ; somewhat contrac-
tile, longitudinal or slightly spiral stripes 23
No spiral stripes; head region not nar-
rowed; no tuft of oral cilia, pellicle warty,
exclusively marine worm-like or flask-
shape usually very large Genus Trachelocerca Ehr.
23. Without caudal thread; tuft of cilia di-
rected forwards (Fig. 191) Genus Chaenea Quennerstedt
With two caudal threads Genus Urochaenea Savi
24. Gullet opens to outside with a distinct
dome-like process Genus Enchelydon C. and L.
Gullet mouth round to slit-form; with
cross or obliquely truncate anterior end . 25
25. Gullet mouth appears like long cross-cut
of anterior end; posterior end with tuft
of cilia Genus Crobylura Andre
Gullet mouth not clean-cut section in ap-
pearance; no anal tuft of cilia. . . .Genus Enchelys Hill
Family 2. Actinobolinidae Kent 1880.
Only 1 genus Actinobolina Strand 1926 (Actinobolus Stein pre-occupied)
Family 3. Metacystidae Kahl 1926.
1. Animals ovoid, without end vesicle; with
caudal cilia Genus Vasicola Tatem
Animals not ovoid 2
2. Spindle-form ; no caudal cilia ; closely annu-
late . Genus Pelatractus Kahl
Cylindrical; usually one, rarely more,
caudal cilia, with globular, swollen end
vesicle Genus Metacystis Cohn
Family 4. Didiniidae Poche 1913.
1 . No gullet; special polar area for food-taking
(Fig. 191) Genus Cyclotrichium Meunier
Distinct gullet, opening in center on a defi-
nite mound 2
2. Body with one or more circlets of cirri .... 3
Body with circlet of pectinelles 4
3. With circlet of pectinelles about oral
mound outside of which is circlet of cirri
Genus Askenasia Blochmann
With circlet of cirri around oral mound
Genus Mesodinium Stein
4. In addition to pectinelles, body uniformly
ciliated Genus Acropisthium Perty
With one to several circlets of pectinelles,
otherwise without cilia Genus Didinium Stein
Family 5. Colepidae Clap, and Lach. 1858.
1. Body rounded posteriorly; plates separate
on pressure Genus Coleps Nitsch
Body pointed posteriorly, plates firm
Genus Tiarina Bergh
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 495
Family 6. Spathidiidae Kahl 1930.
1. Mouth region not surrounded by tricho-
cyst-bearing swelling; nor with tricho-
cyst-bearing papillae nor tentacles 2
Mouth ventral, unciliated stripes, or papil-
lae or tentacles with trichocysts present . 9
2. Mouth without papilla on its dorsal end;
nor surrounded by three tentacle-like
arms ; occasional processes 3
Mouth dorsal, with three arms or with
trichocyst-bearing warts 8
3. Trichocysts of mouth region not heaped in
single bundle 4
Trichocysts in bundle on dorsal part of
mouth region Genus Cranotheridium Schew.
4. Body normally ciliated on both sides 5
Body long, worm-like; ciliated on right
side only Genus Homalozoon Stokes
5. Mouth area closed in front 6
Mouth area open Genus Enchelydium Kahl
6. Small, hyaline, with firm pellicle; with
snout-like process Sub-genus Spathidiella Kahl
Structures otherwise 7
7. From the mouth area to middle of body an
unciliated piece about which the cilia
run concentrically Genus Balantidiodes Penard
Ventral side without unciliated piece; cilia
meridional Genus Spathidium Dujardin
8. Mouth area with trichocyst-bearing warts
Genus Spathidiodes Brodsky
Mouth surrounded by 3 trichocyst-bearing
arms Genus Tmthophrys
Chatton and Beauchamp
9. No tentacles nor warts; mouth area ventral
with trichocysts 10
Body with trichocyst-bearing warts or ten-
tacles Genus Legendrea Faure-Fremiet
10. Body ridge runs spirally to posterior right . 1 1
Body ridge meridional Genus Penardiella Kahl
11. Anterior end with oblique ventral angle;
2 anterior horns absent Genus Perispira Stein
Anterior end drawn out into 2 horns . Genus Diceras Eberhard
Family 7. Biitschliidae Poche 1913.
1 . Entire body uniformly ciliated 2
Body not uniformly ciliated 5
2. Spiral groove from cytostome to posterior
end Genus Paraisotrichopsis
Gassowsky
No spiral groove 3
3. Cilia beat in uniform fashion 4
Cilia divided into 3 zones by 2 transverse
bands of cilia which beat at different
intervals Genus Blepharozoum Gassowsky
4. Cytopharynx at anterior end which is
slightly bent Genus Prorodonopsis Gassowsky
Anterior end straight, cytostome large
Genus Holophryoides Gassowsky
490
BIOLOGY OF THE PROTOZOA
Fig. 203. — Types of Ciliata. A, Lionotus wrzesniowskyi; B, Lionohis fasciola; C,
Loxodes rostrum; D, Loxophyllum meleagris; E and F, Loxophyllum seligera. (A
and C, after Biitschli, the others after Calkins.)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 4.97
Family 7. Biitschliidae Poche 1913.
5. Entire body ciliated 6
Parts of body naked 7
6. Body drawn out into long neck, covered
with, coarse, long cilia Genus Ampallacula Hsiung
Body ovoid, cytostome large and sur-
rounded by longer cilia Genus Butschlia Schuberg
7. Cilia over less than half the body 8
Cilia over all body except posterior end; a
few anal cilia present Genus Blepharosphaera Bundle
8. Body cilia divided into two zones 9
Body cilia divided into 3 zones by 2 trans-
verse naked bands Genus Alloiozona Hsiung
9. Anterior end drawn into long neck-like
process 10
Anterior end blunt or only slightly elevated 1 1
10. Macronucleus disk-shaped Genus Polymorphs Dogiel
Macronucleus sausage-shaped Genus Blepharoprosthium Bundle
11. Cystostome large at end of short elevation . 12
Cytostome small ; no elevation ; cilia about
cytostome and cytopyge Genus Bundleia
Cunha and Manix
12. Cytostome accompanied by supporting
rods Genus Blepharoconus ( rassowsky
No rod-like structures in gullet .... Genus Didesmis Fiorentini
Sub-order 2. Pleurostomina (Tribe Pleurostomata Schewiakoff;
Kahl).
Family 1. Amphileptidae Butschli; Schoutedon.
1. Normally ciliated on both surfaces of body . 2
Normally ciliated only on right side of body 3
2. Oral slit does not reach to middle of body;
no line of trichocysts Genus Amphileptus Ehr.
em. Butschli
Entire ventral surface surrounded by tri-
chocyst-bearing zone Genus Bryophyllum Kahl
3. Ventral surface with flat trichocyst zone;
dorsal same or with trichocyst warts
(Fig. 203) Genus Loxophyllum (Dujardin)
Wrzesniowsky
Trichocyst-bearing zones absent 4
4. Left side entirely without cilia Genus Lionotus Wrzesniowsky
Ciliated right side drawn over the dorsal
line to the left side so that almost half of
the left side is thereby ciliated . . . .Genus Acinerla (Dujardin)
Maupas
Family 2. Tracheliidae Ehr. 1838.
1. Anterior end drawn out into a snout or a
finger-like process; free-living 2
Ectoparasites on amphipods; anterior body
process lancet-like Genus Branchioecetes Kahl
2. With finger-like anterior proboscis; poste-
rior end tail-like (Fig. 194) Genus Dileptus Dujardin
Form oval or round; posterior rounded or
with barely evident point Genus Trachelitis Schrank
Family 3. Loxodidae Roux.
One genus only (Fig. 203) Genus Loxodes Ehr.
32
498 BIOLOGY OF THE PROTOZOA
Sub-order 3. Hypostomina Schewiakoff 1890; em. Kahl.
Family 1 . Nassulidae Blitschli.
1. Opening of oral basket deep in a vestibule
of which the external opening is nar-
rowed by a membrane Genus Nassula Ehr.
Opening of oral basket on surface or in a
shallow, uncovered depression 2
2. Basket opens in a deep depression with
cilia or membrane on anterior edge;
small, oval, slightly flattened infusoria,
with scattered trichocysts Genus Cyclogramma Perty
Basket opens on surface ; usually distinctly
flattened forms, no trichocysts 3
3. Basket opening, median; body margin with
slight or no snout formation Genus Chilodontopsis Blochmann
Basket strongly directed to right; right
margin of body shows a distinct snout-
like process in the mouth region. .Genus Orthodon Gruber
Family 2. Chlamydodontidae Clans 1874.
1. The ciliated surface is separated from the
unciliated surface by a narrow, hyaline,
cross-striped ring Genus Chlamydodon Ehr.
Cross-striped ring absent 2
2. Ciliated ventral surface limited to a V-
shaped median part and overlapped on
both sides by non-ciliated part. . .Genus Phascolodon Stein
Ciliated surface not thus limited 3
3. Mouth a transverse slit in first quarter of
body, with a clapper-like membrane
Genus Gastronauta Engelm.
Mouth opening circular 4
4. Gullet" with distinct basket; a cross row of
bristles on the anterior flattened part
Genus Chilodonella Strand
(= Chilodon Ehr.)
Basket indistinct; no cross row of bristles;
entire edge of body surrounded by dor-
sally directed spines Genus Cryptopharynz Kahl
Family 3. Dysteriidae Clap, and Lach. 1S5S.
1. Ventral side entirely ciliated; gullet with
short stout rods Genus Hartmannula Poche
( = Onychodactylus Entz)
Ventral surface with unciliated edge on at
least one side 2
2. Powerful end spine is continuation of tail
end ; ciliated area narrowed by unciliated
edges on both sides Genus Scaphidiodon Stein
Ventral ciliated area limited especially
from left 3
3. Ciliated on ventral right side, and in post-
oral area where rows shorten from right
to left Genus Twchilioides Kahl
Postoral cilia formed by extension of pre-
oral cilia to right of mouth and parallel
to right margin ; 1 or 2 adoral cross rows
may occur 4
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 499
Family 3. Dysteriidae Clap, and Lach. 1858.
4. Ciliated right area of ventral surface
entirely free Genus Trochilia Dujardin
Ciliated right area with mouth, in furrow by
overgrowth of right ventral surface
Genus Dysteria
(= Cypridium Kent;
Ervilia Duj.; Aegyria
C. and L.)
Family 4. Pycnothricidae Poche 1913 (= Nicollellidae Chatton and
Perard ) .
1. Mouth in mid-ventral surface Genus Nicollella Ch. and Per.
Mouth otherwise placed 2
2. Mouth at posterior end of body. . . .Genus Collinella Ch. and Per.
Mouth dorsal; furrow runs around poste-
rior end 3
3. Mouth near posterior end Genus Buxtonella Jameson
Mouth near anterior end Genus Pycnothrix Schubotz
Family 5. Foettingeriidae Chatton and Lwoff 1926.
1. Body with pigmented reserve mass 2
Body without pigmented reserve mass. ... 3
2. Chains of buds formed without encystment
Genus Polyspira Minkiewicz
Chains of buds formed while encysted
Genus Gymnodinioides Min.
3. Gastric parasites of Actinians; stalked
cysts in Crustacea Genus Foettingeria Clap.
No stalked cysts 4
4. Motile forms in Hydromedusae; cysts in
Copepods Genus Spirophrya
Clap, and Lach.
Motile forms and cysts in crabs. . . .Genus Synophrya
Chat, and Lwoff
Order 3. Trichostomida Butschli 1889.
Key to Fain Hies
1. Gelatinous test or cup absent 2
Gelatinous test present, animals swim
backwards Family 8. Marynidae
2. Small, mostly flattened laterally, with deli-
cate armor-like periplast; cilia sparse,
chiefly on right surface in 2-9 broken
rows on semicircular or crescentic keel;
mouth on compressed ventral surface
with obscure membrane-like structures
Family 9. Trichopelmidae
Structures and ciliation different 3
3. Small to very small ciliates with long cau-
dal cilium, cilia reduced to 3-4 cross
spiral rows about anterior half . Family 1 . Sciadostomidae
Ciliation otherwise; no caudal cilia 4
4. Zone of special cilia extends from mouth
to posterior end 5
Spiral zone of special cilia absent 6
500 BIOLOGY OF THE PROTOZOA
Key In Fmii Hies
5. Spiral zone extends from anterior right to
posterior left Family 2. Spirozonidae
Spiral zone extends from anterior left to
posterior right Family 3. Trichospiridae
6. Ciliated cross-furrow in anterior half of
body runs on ventral surface to mouth
Family 4. Plagiopylidae
Ciliated ventral cross-furrow absent 7
7. Mouth in flat oval longitudinal pit with
heavy ciliated walls, first quarter
Family 5. Clathrostomidae
Mouth deep, funnel-like 8
8. Mouth funnel with strong cilia; mouth
about central at base of diagonal peris-
tome Family 7. Parameciidae
Peristome from anterior end absent 9
0. Free living, many in moss ; oral funnel deep;
cilia at top and bottom Family 6. Colpodidae
Ecto-or endocommensals 10
10. Ectocommensals (on invertebrates) 11
Endocommensals in vertebrates (mam-
mals) 14
11. Attaching organs absent Family 10. Conchophthiriidae
Attaching organs present 12
12. Attaching organ tentacular. . . .Family 11. Hypocomidae
Attaching organs thigmotactic cilia 13
13. Thigmotactic cilia circumoral. .Family 12. Boveriidae
Thigmotactic cilia not circumoral
Family 13. Ancistrumidae
14. Entire body covered with cilia 15
Cilia in certain regions only 16
15. With "concretion" vacuole. . . .Family 15. Paraisotrichidae
Concretion vacuole absent Family 14. Isotrichidae
16. Mouth occupies entire anterior end; cilia
limited to mouth region Family 17. Cyathodiniidae
Mouth not terminal; tufts of cilia above
and below mouth and in posterior anal
region Family 16. Blepharocoridae
Key to Genera
Family 1. Schiadostomidae Kahl 1926.
Only one genus — S. difficile Kahl
Family 2. Spirozonidae Kahl 192(1
Only one genus — S. caudata Kahl
family 3. Trichospiridae Kahl 1926.
Only one genus — Trichospira Roux
Family 4. Plagiopylidae Schewiakoff 1896.
1. Peristome a distinctly ciliated groove or
pit ' 2
Peristome without groove or pit; with cres-
centic, protruding and stiff lip. . Genus Sonderiella Kahl
2. Gelatinous mantle present Genus Sonderia Kahl
Gelatinous mantle absent; peristome fur-
row near edge of dorsal side, forming dis-
tinct notch 3
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 501
Family 4. Plagiopylidae Schewiakoff 1896.
3. Free-living forms Genus Plagiopyla Stein
Parasitic in gut of sea-urchin Genus Lechriopyla Lynch
Family 5. Clathrostomidae Kahl 1926.
Only one genus — Clathrostoma Penard
Family 6. Colpodidae Poche 1913; em. Kahl,
* 192G
1. Mouth a funnel-shaped pit 2
Mouth a long tube, or a narrow diagonal
pit 4
2. Mouth funnel does not include almost half
of anterior end 3
Funnel deeply sunk; forms wide opening,
partly covered by cilia Genus Bresslaua Kahl
3. Mouth opens on the broad side; the right
edge is continued horse-shoe-shape
around posterior end of mouth and half
of left edge; group of posteriorly directed
cilia from anterior part of left edge
( tenus Bryophrya Kahl
Mouth opens more towards the left; its left
edge bears a cross-striped ciliated area,
but no membrane Genus Colpoda 0. F. M.
4. Mouth a long, bent, ciliated tube; form like
Colpoda Genus Tillina Gruber
Mouth a flat, diagonal pit; marine form,
like Chilodonella ( lenus Woodruffia Kahl
Family 7. Parameciidae Kent 1881 : em. Kahl 1931.
Only one genus — Paramecium Hill (Fig. 204)
Family 8. Marynidae Poche 1913.
1 . Peristome furrow describes a complete ring-
about anterior pole; colonial in branch-
ing gelatinous tubes ( renus Maryna < rruber
Peristome furrow confined to ventral sur-
face; in simple cups Genus Mycterothrix Lauterborn
Family 9. Trichopelmidae Kahl 1926.
1 . Oral funnel supported by delicate rodlets,
opening on anterior third or fourth of
body 2
Oral funnel without rodlets ; mouth opens in
middle or near posterior end .'!
2. Peristome extends over into right lateral
surface; small membrane in gullet. Genus Pseudomicrothorax
Mermod
Mouth area distinctly set off; gullet open-
ing directed to left; 2 or 3 cirri or mem-
branelle-like structures Genus Trichopelma Levander
3. Mouth opens to left in body center, in
membrane-bearing groove Genus Drepanomonas Fresenius
Mouth area in little pit near posterior end
of left edge Genus Microthorax Engelmann
Family 10. Conchophthiriidae Reichenow-Doflein 1920.
1. Dorsal lobe overhanging mouth. . . .Genus Entorhipidium Lynch
No dorsal lobe 2
502
BIOLOGY OF THE PROTOZOA
z>
sg=
Fig. 204. — Types of Ciliata. .4, Microthorax sulcatus; B, Paramecium putrinum;
(', Lembus pusillus; D, Paramecium bursaria. (.1, B, D, alter Biitschli; C, after
( lalkins.)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 503
Family 10. Conchophthiriidae Reichenow-Doflein 1929.
2. Body much flattened laterally 3
Body slightly flattened; mouth posterior;
oral groove narrow triangle; limpet par-
asite Genus Eupoterion MacLennon
3. Mouth in anterior third; oral groove S-like;
eehinoderm parasite Genus Cryptochilum Maupas
Mouth median ; oral groove straight . Genus Conchophthirius Stein
Family 11. Hypocomidae Butschli 1889.
1. Adoral cilia apart from attaching tentacle
Genus Hypocoun'des
Ch. and Lwoff
Adoral cilia absent; attaching and food-
taking tentacle Genus Hypocoma Gruber
Family 12. Boveriidae Pickard 1927.
1. Circum oral spiral begins part way up the
body Genus Plagiospira Issel
Circum oral cilia around oral end . . . Genus Boveria Stevens
Family 13. Ancistrumidae Issel 1903.
One gemts—Ancistruma Strand (Ancistrum Maupas pre-occupied)
Family 14. Isotrichidae Butschli 1889.
1. Protoplasmic strands from cortex support
the macronucleus Genus Isotricha Stein
Protoplasmic strands from cortex absent
Genus Dasytrieha Schuberg
Family 15. Paraisotrichidae da Cunha 1916.
One genus — Paraisotricha Fiorentini
Family 16. Blepharocoridae Hsiung 1929.
1. Anal cilia in a single group Genus Blepharocorys Bundle
Anal cilia in two groups ( icnus < 'haron Jameson
Family 17. Cyathodiniidae da Cunha 1916.
One genus — Cyathodinium da Cunha
Order 4. Hymenostomida.
Key to Families
1 . With aboral thigmotactic cilia (commen-
sals) Family 6. Hemispeiridae
Without attaching cilia 2
2. Oral pit not connected with a peristome
Family 1. Frontoniidae
Oral pit at end or at bottom of a peristome . 3
3. Mouth at bottom of sickle-shape, ciliated
peristome sunk at right angles to body
surface Family 2. Ophryoglenidae
Mouth at end of peristome running from
anterior pole on body surface 4
4. On right edge of peristome a one-layered
membrane which forms a pocket sur-
rounding posterior mouth, on left edge a
row of cilia or a membrane . . . Family 5. Pletjronematidae
Peristome otherwise 5
504
BIOLOGY OF THE PROTOZOA
Fig. 205. — Types of Ciliata. A, Ophryoglena flava; B, Glaucoma frontata; C, Fron-
tonia acuminata; D, Urocentrum turbo; E, Glaucoma sp.; F, Loxocephalus granulosus.
(A, C, D, and F, after Bi'itsohli; B, from Conn after Stokes; E, original.)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 505
Key to Families
5. On right edge of peristome are two simple
undulating membranes; a distinct pocket
is absent Family 4. Lembidae
Peristomial furrows with either a thick area
of cilia outside of which is an undulating
membrane, or a single thick undulating
membrane on the right edge; to right of
mouth and posteriorly a pocket with
small membrane is sunk below the ecto-
plasm Family 3. Philasteridae
Family 1. Frontoniidae Kahl 1926.
1. Except in Lembadion, no long caudal cilia;
never a single caudal bristle 2
With one or more caudal cilia, occasionally
fused in brush (Urocentrum) 22
2. Mouth opening pointed anteriorly 3
Mouth opening rounded or truncated ante-
riorly 10
3. Mouth at most one-third body length. ... 4
Mouth one-half to four-fifths of body
length 8
4. Mouth truncated posteriorly; undulating
membrane on left; partly fused mem-
brane-like cilia on right margin 5
Mouth not truncated posteriorly; but
sharp-pointed or rounded 7
5. Mouth without gullet-like, funnel-form
posterior prolongation G
Mouth with funnel-like gullet into which
membrane of left margin continues
Genus Frontoniella Wetzel
G. Gullet fibrils strong and numerous; poste-
rior to mouth, a distinct line runs to
posterior end ; form not triangularly nar-
rowed posteriorly Genus Fronton in Ehr.
Gullet fibrils delicate, sparse; ventral line
indefinite; narrows triangularly at pos-
terior region Genus Disemotostoma
Lauterborn
7. Mouth a small, sigmoid cleft; not at ante-
rior pole; with 2 membranes Genus Sigmostomum Gulati
Mouth elongate, from anterior pole; 2 mem-
branes; gullet with long fibrils. .Genus Leucoyhrydium Roux
8. Mouth about one-half body length 9
Mouth three-quarters to four-fifths body
length (with long caudal cilia) . . . .Genus Lembadion Perty
9. Anterior end pointed; body broadly oval
Genus Leucophrys Ehr.
Anterior end rounded, body slender . Genus Turania Brodsky
10. Mouth oblique (anterior right to posterior
left); ectoplasmic lip on right edge 11
No ectoplasmic lip on right margin of
mouth 13
506 BIOLOGY OF THE PROTOZOA
Family 1. Frontoniidae Kahl 1926.
1 1. Three ciliated structures on inside, left an
outer membrane; below it an inner mem-
brane and right, at bottom, a 3-row cilia
combination 12
Only one strong membrane from left edge
beats into ectoplasmic lip Genus Pseudoglaucoma Kahl
12. Mouth near middle of ventral surface; dor-
sal ciliated rows bent to right. . . .Genus Glaucoma Ehr.
Mouth on right edge of ventral surface;
dorsal rows bend sharply to right . Genus < 'olpidium Stein
13. Mouth with 2 or 3 membranes 14
Mouth with only 1 membrane 16
14. Slime dwelling; membranes surround
mouth at pole, forming pocket behind
Genus Cyrtolophosis Stokes
Naked forms; mouth without pocket 15
1 5. One free membrane on both sides of mouth ;
anterior rounded Genus Dichilum Schewiakoff
One free membrane on right side, 2 others
in oral pit; anterior sharply pointed
( !enus Paraglaucorna Kahl
1(3. Left and anterior membrane cover mouth
cap-like Genus Stegochihim Schewiakoff
Membrane not cap-like 17
17. Membrane inserted inside and continues
into posterior funnel IS
Mouth without funnel continuation 19
18. Form elongate-oval; slightly compressed
Genus Monochilum Schewiakoff
Small, flattened, kidney-shape Genus Chasmatostoma Engelmann
19. Mouth at or near anterior pole 20
Mouth distinctly separate from pole 21
20. Mouth a deep pit in the truncated end ; in
jelly of egg masses Genus Espejoia Burger
Mouth a narrow slit quite near anterior
pole Genus Malacophrys Kahl
2 1 . Spindle form ; delicate groove from pole to
small mouth Genus Bizone Lepsi
Mouth without groove; membrane on left
side ( ienus Aristerostoma Kahl
22. Cilia arranged in 1 or in 3 girdles 23
Cilia in longitudinal rows; not arranged in
girdle 24
23. Very small (20,u) ; only 1 median girdle;
1 caudal filament Genus Urozona Schewiakoff
Caudal cilia many, fused; 2 broad girdles,
1 anterior, 1 posterior to oral girdle
(Fig. 205) Genus Urocentrum Nitzsch
24. Mouth in center or anterior to center of
body 25
Mouth posterior to center of body 33
25. Body compressed laterally; small furrow
from anterior pole with membrane on
right side and thick cilia on left . . .Genus Rhinodisculus Mansfeld
Bodv not laterally flattened 26
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 507
Family 1. Frontoniidae Kahl 1926.
26. Slightly compressed; mouth depressed;
above middle of ventral surface 27
Body dorso-ventrally more or less com-
pressed 29
27. Anterior pole not ciliated ; indistinct turn >w
from pole to mouth Genus Uronema Dujardin
Anterior pole ciliated, no trace of furrow. . 28
28. C. V. terminal; no pocket formed by oral
membrane ( ienus Dexiotrichides Kahl
C. V. not terminal: oral membranes form
closed pocket ( ienus Uronemopsis Kahl
29. Body flattened; mouth near right edge;
form ovoid 30
Body not flattened, form ellipsoidal 31
30. Mouth with membranous pocket . .( ienus Saprophihis Stokes
Mouth small, kidney-shape; a membrane
on left concave edge Genus Platynema Kahl
31. Mouth with anterior and posterior truncate
processes Genus Balanonema Kahl
Mouth without such processes 32
.'!2. Form plump, worm-like; 4 to 5 caudal cilia ;
mouth small, heart-shaped in anterior
fifth of body Genus Cardiostoma Kahl
Not worm-like; anterior pole not ciliated:
cilia in longitudinal or oblique cross
rows; mouth with groove from right
(Fig. 205) Genus Loxocephalus Eberhard
33. Broad oval; ventrally flat and ciliated;
dorsal slightly flat or arched without
cilia Genus Cinetochilum Perty
Spindle-shape; not flattened: ciliated on
both sides 34
34. Very small salt water f< inns ; dancing move-
ment without pause Genus Uropedalium Kahl
Very small moss forms; gliding movement
< Ienus Homologastra Kahl
Family 2. Ophryoglenidae Kent 1882; em. Kahl 1931.
Only one genus — Ophryoglena Ehr. (Fig. 205)
Family 3. Philasteridae Kahl 1931.
1. Peristome with long rows of cilia; always a
tail filament, ectoplasm soft, with tricho-
cysts 2
Peristome ciliated only on right edge; ecto-
plasmic resistant heavy membrane on
right edge Genus Lemboides Kahl
2. Pocket from end to mouth, with small tri-
angular membrane, nucleus oval 3
Pocket winds spirally around oral pits;
nucleus elongate Genus Helicostoma Cohn
3. Large marine forms with terminal contrac-
tile vacuoles Genus Philaster Fabre-Dom.
Small; fresh water; contractile vacuole
near center Genus Philasterides Kahl
Here also Genus Anophrys Cohn 1866 — not confirmed
508 BIOLOGY OF THE PROTOZOA
Family 4. Lembidae Kahl 1931.
Only one genus— Lembus Cohn (Fig. 204)
Family 5. Pleuronematidae Kent 1882.
1. Small, test-building, fresh water species
Genus Calyptotricha Phillips
Not test-building 2
2. Marine; ectocommensal on Hydractinia
Genus Pleurocoptes Wallengren
Not ectocommensal 3
3. Undulating membrane without distinct
pocket; peristome oblique from anterior
right to posterior left Genus Ctedoctema Stokes
Undulating membrane pocket distinct;
hardly ever oblique 4
4. Body fiat; peristome continues as groove
posterior to mouth Genus Cristigera Roux
Peristome on right side, without groove
posterior to mouth 5
5. Large (70 to 180), striking forms (i
Small (up to 50); no semicircular swelling
of peristome Genus < 'yclidium ( >. F. Muller
0. Posterior sensory bristles; 1 contractile
vacuole; peristome begins at anterior
end; semicircular swelling to left at
mouth region Genus Pleuronema Dujardin
Sensory bristles distributed over body, 2
to 3 times longer than cilia; peristome
begins on first quarter, without oral
swelling^ C. V. numerous Genus Histiobalantium Stokes
Sub-class II. SPIROTRICHA Butschli 1889; km. Kahl 1931.
Key to Orders
1. Only free cilia present; exceptionally tufts
of cirrus-like aggregates 2
Ciliation exclusively cirri; dorsal rows of
short, delicate, slightly movable bristles
Order 4. Hypotrichida
2. Body uniformly ciliated; in flat forms no
cilia dorsally; in ectoparasitic Lichno-
phoridae cilia around edge only of at-
taching disc; frontal field ciliated
Order 1. Heterotrichida
Cilia much reduced or absent 3
3. Small, flattened, cara paced forms whose
peristome has only 8 membranelles
which lie in a ventral hollow. . .Order 3. Ctenostomida
Transverse section circular; cilia much
reduced; adoral zone encloses a non-cili-
ated frontal field Order 2. Oligotrichia
Order 1. Heterotrichida Stein.
Key to Finn i lies
1 . Ciliation complete, with uniform cilia .... 2
Ciliation absent or limited to ventral side . . !)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 509
Key to Families
2. Peristome almost free, leading to short and
narrow oral funnel which is absent in one
family 3
Peristome runs deeply into a funnel-like
hollow and is mostly covered. .Family 7. Bubsariidae
3. On right edge of peristomial membranelle
zone a narrow zone without cilia; on
right of this, in front of mouth, an undu-
lating membrane: between this and
membranelle zone a peristomial frontal
field difficult to see 4
Frontal hold surrounded wholly or in part
by spiral adoral zone 7
4. Adoral zone stretches diagonally to poste-
rior right on ventral side; many forms
have an elongated portion which twists
spirally around the body Family 1. Metopidae
Adoral zone runs for most part in direction
of long axis and, just before the mouth
opening, bends sharply to right 5
5. Gullet and undulating membranes absent:
mouth usually closed and difficult to
find; opens as a slit for food-taking
Family 2. Reichenowellidae
Oral funnel distinct; in typical forms an
undulating membrane or a double cili-
ated furrow before the mouth 6
6. Parasitic forms Family 4. Plagiotomidae
Free-living forms Family 3. Spirostomidae
7. Frontal field not ciliated; one large undu-
lating membrane on its right edge
Family 5. Condylostomidae
Frontal field ciliated; no undulating mem-
brane 8
8. Frontal field not drawn out in wings; free
or in jelly tests Family 6. Stentoridae
Frontal field drawn out in 2 wings, in flask-
shaped tests Family 6. Folliculinidae
9. Free-living, flat, marine forms; ciliated on
ventral side only; adoral zone surrounds
anterior ventral surface; mouth on left
edge near middle of body Family 9. Peritromidae
Ectoparasitic marine forms; both ends of
body discoid, in middle neck-like
Family 10. Lichnophoridae
Family 1. Metopidae Kahl 1927.
1. Ciliation of body uniform '-
Ciliation reduced ; body with "head" region 4
2. Ectoplasm soft, yielding 3
Ectoplasm stiff, carapace-like, spirally
keeled ( renus Tropidoatractus Levander
3. Flat oval to ovoid moss forms; C. V. on
ventral middle; broad, insunk stripings
Genus Bryometopus Kahl
Form diverse; free living in water; C. V.
terminal; peristome typical Genus Metopus Clap, and Lach.
510 BIOLOGY OF THE PROTOZOA
Family 1. Metopidae Kahl 1927.
4. Cilia of head reduced to lateral zone and
dorsal cirri 5
Cilia of head reduced to lateral zone and
about 8 fused cilia Genus Twchella Penard
5. One or two rows of dorsal cirri Genus Caenomorpha Perty
Two single, long cirri Genus Ludio Penard
Family 2. Reichenowellidae Kahl 1031.
1. Elongate, sapropelic, fresh water; C. V.
terminal; ciliation meridional. . . .Genus Reichenowella Kahl
Oval; moss dwelling; C. V. numerous; cili-
ation spiral Genus Balantidioides Penard
Family 3. Spirostomidae S. Kent, 1881.
1. No undulating membrane at mouth 2
An undulating membrane on right edge of
peristome 7
2. Worm-like; contractile 3
Not definitely contractile 4
3. Usually fresh water; greatly twisted on
contraction Genus Spirostomum Ehr.
Salt water forms; posterior tail-like; very
little torsion on contraction Genus Gruberia Kahl
4. Elongate fresh water forms; 2 rows of cilia
in place of undulating membrane . Genus Pseudoblepharisma Kahl
Fresh water forms ; not elongate 5
5. Oval; with marked ribs; in moss. . . .Genus Phacodinium Prowazek
Small, oval, marine forms; without notice-
able ribs 6
6. Adoral zone spirally rolled at mouth. Genus Spirostomina Gruber
Adoral zone runs directly to mouth. .Genus Protocrucia da Cunha
7. Peristome-bearing region not narrowed
neck-like; no gelatinous membrane
Genus Blepharisma Perty
Peristome narrowed neck-like; gelatinous
membrane; marine forms Genus Parablepharisma Kahl
Family 4. Plagiotomidae Poche 1913.
Elongate, oval; peristome begins at ante-
rior end; earthworm gut Genus Plagiotoma Dujardin
Oval to reniform; peristome beginning sub-
terminal; many hosts (Fig. 200) . Genus Nyctotherus Leidy
Family 5. Condylostomidae Kahl 1031.
Only one genus— Condylosloma Bory (Fig. 206)
Family 6. Stentoridae Cams 1863.
1. Adoral zone almost completely closed
circle; body contractile, "trumpet" ani-
mal Genus Stentor ( )ken
Adoral zone not complete ring; not con-
tractile 2
2. Right peristome edge drawn down ventral
surface Genus Climacostomum Stein
Right peristome edge continuous with
right anterior edge of body ( ionus Fabrea Henneguy
Family 7. Folliculinidae Dons 1*012.
1 . Neck of test not swollen 2
Neck has a basal swelling; tests fastened
laterally or on end Genus Parafolliculina Dons
Fni. 206.— Types of Ciliata. .1, Condylostoma patens; B, Metopus sigmoides;
C, Nyctotherus cordiformis. (A, after Calkins; B, c, after Biitschli.)
A B C
Fig. 207. — .4, Stephanopogon colpoda; B, Peritromus emmat ; < ', Onychodromus grandis;
c, cirri. (From Calkins after Biitschli.)
(511)
512 BIOLOGY OF THE PROTOZOA
Family 7. Folliculinidae Dons 11)12.
2. Posterior end and sides of test with sack-
like protuberances ( renus Mirofolliculina Dons
Tests without protuberances 3
3. Tests attached on broad surface; neck
oblique Genus Folliculina Lamarck
Tests attached at posterior end; tests up-
right 4
4. Test narrow, no central annular furrow
Genus Pseudofolliculina Dons
Test plump, with central furrow; neck
appears as a short collar Genus Pebrella Giard
Family 8. Bursariidae Perty 1852.
1. Posterior end of peristome straight; para-
sitic 2
Posterior end of peristome bends to right or
left; free-living 3
2. Peristome opening a narrow slit. . . .Genus Balantidiopsis Biitschli
Peristome opening medium wide. . .Genus Balantidium
Clap, and Lach.
3. Posterior end of peristome funnel bends to
left. 4
Posterior end of peristome funnel bends to
right Genus Bursaridium Lauterborn
4. Very large animals with longitudinal fold
(tongue) dividing peristomial space in
two sections Genus Bursaria 0. F. M.
Medium or small forms with simple peris-
tome Genus Thylacidium Schewiakoff
Family 9. Peritromidae Stein 1867.
1. Ventral surface flat; adoral zone semicir-
cular around anterior left margin. Genus Peritromus Stein
Flat surface bent dorsally; anterior to
mouth a peristome-like area with meri-
dional fibers to mouth Genus Pediostomum
Faure-Fremiet
Family 10. Lichnophoridae Stevens 1903.
One genus only — Lichnophora Claparede
Order 2. OLIGOTRICHIDA Butschli 1889.
Key to Families
1. Free-living forms 2
Endocommensal forms 4
2. Oral part of peristome lies free on ventral
surface Family 1. Halteriidae
Adoral zone encircles frontal field and
mouth region 3
3. No house or test Family 2. Strombilidiidae
House or test present Family 3. Tintinnidae
4. With one or two rings of membranelles
directed forwards Family 4. Ophryoscolecidae
With additional bundles of cirri directed
backwards Family 5. Cycloposthiidae
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 513
Key to Genera
Family 1. Halteriidae Clap, and Lach. 1859; mod. Kahl.
1. Posterior end without thick, dragging
process .
9
Posterior end with long, thick, retractile,
protoplasmic process Genus Tontonia Faure-Fremiet
2. Highly contractile; Sten tor-like; no pre-
oral adoral zone ?Genus Meseres Schewiakoff
Body not contractile 3
3. With equatorial circlet of long bristles or
cirri Genus Halter ia Dujardin
Without equatorial circlet of bristles 4
4. Adoral zone with distinct pre-oral section;
frontal part of zone surrounds an apical
projecting process Genus Strombidium
Clap, and Lach.
Adoral zone without special pre-oral sec-
tion Genus Metastrombidium
Faure-Fremiet
Family 2. Strombilidiidae Kahl 1032.
One safe genus Genus Strombilidium Schewiakoff
Family 3. Tintinnidae Clap, and Lach. 1859 (fresh water forms only).
Key to Genera of Fresh Water Forms
1. Tests gelatinous, delicate; more or less
covered by foreign bodies, etc 2
Tests firm; pseudochitin; may be covered
by nodules or by algae 3
2. Body with rows of distinct cilia; tests very
delicate Genus Strombidinopsis Kent
Body with cilia behind peristome only;
tests distinct .Genus Tintinnidium Stein
3. Tests cylindrical, without neck part . Genus Tintinnopsis Stein
Tests with definite neck part Genus Codonella* Haeckel
Family 4. Ophryoscolecidae Stein 1858.
1. Adoral zone of membranelles only; no
dorsal zone 2
Adoral and dorsal zone of membranelles . . 3
2. Adoral zone in spiral about cytostome;
macronucleus elongate Genus Entodinium Stein
Anterior end uniformly ciliated; macro-
nucleus spherical Genus Lauierella Buisson
3. Adoral and dorsal zones at about the same
level 4
Dorsal zone posterior to adoral zone 14
4. Dorsal zone at right angles to long axis of
the body 5
Dorsal zone nearly parallel to long axis of
the body Genus Cunhaia Hasselmann
5. Forms without skeletal plates 6
Forms with skeletal plates 7
fi. Macronucleus beneath dorsal surface of
the body; straight Genus Eodinium Kof. and MacL.
Macronucleus beneath right surface; ante-
rior third bent ventrally Genus Diplodinium Schuberg
* See Kofoid and Campbell (1929) for monographic treatment of Tintinnidae.
33
514
BIOLOGY OF THE PROTOZOA
Fig. 208. — Types of Ciliata. A and B, Epiclinles radiosa; C and F, species of
Tintinnopsis; D, Coenomorpha medusula; E, Blepharisma undulans. (A, B, C, E and
F, after Calkins; D, after Butschli.)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 515
Family 4. Ophryoscolecidae Stein 1858.
7. Forms with one skeletal plate S
Forms with more than one skeletal plate. . 10
8. Skeletal plate narrow 9
Skeletal plate very broad beneath the right
surface of the body Genus Ostracodinium Dogiel
9. Forms with triangular or rod-like macro-
nucleus; anterior end often bent ven-
trally Genus Eremoplastron
Kof. and MacL.
Rod-like macronucleus with anterior end
bent into a hook dorsally Genus Eudiplodinium Dogiel
10. Forms with 2 skeletal plates 11
Forms with more than 2 skeletal plates. . . 12
11. Macronucleus narrow and rod-like. .Genus Diploplastron
Kof. and MacL.
Macronucleus large with 2 or 3 dorsal lobes
Genus Metadinium Awerinzew
and Mutafowa
12. Three skeletal plates beneath right ventral
surface Genus Enoploplastron
Kof. and MacL.
More than 3 skeletal plates 13
13. Four skeletal plates; 2 right, 1 left and
1 ventral Genus Elyptroplastron
Kof. and MacL.
Five skeletal plates; 2 right and 3 left
Genus Poly plastron Dogiel
11. Dorsal zone short and far posterior. .Genus Opisthotrichum Buisson
Dorsal zone slightly below adoral zone. . . 15
15. Dorsal zone encircling less than half the
body Genus Epidinium Crawley
Dorsal zone encircling more than half the
body 16
16. Dorsal zone encircling four-fifths of the
body Genus Ophryoscolex Stein
Dorsal zone entirely encircling body . Genus Caloscolex Dogiel
Family 5. Cycloposthiidae Poche 1913.
1 . Posterior cirri in tufts (caudalia) 2
Posterior cirri in rows 6
2. Forms with 2 caudalia 3
Forms with more than 2 caudalia 5
3. Forms having a spherical macronucleus
Genus Bozasella Buisson
Forms having an elongate macronucleus . . 4
4. Body barrel-shaped ; caudalia posterior and
level Genus Cycloposthium Bundle
Body helmet-shaped ; caudalia at different
levels Genus Triadinium Fiorentini
5. Forms with 2 dorsal caudalia and 1 ventral
Genus Tripalmaria Gassowsky
Forms with 3 dorsal caudalia and 1 ventral
Genus Protoapirella Cunha
6. Forms with adoral zone and 2 rows of more
posterior membranelles 7
Forms with more than 2 rows of posterior
membranelles 8
516 BIOLOGY OF THE PROTOZOA
Family 5. Cycloposthiidae Poche 1913.
7. Forms with adoral zone and 2 long rows of
membranelles in spirals Genus Spirodinium Fiorentini
Forms with adoral zone and short dorsal
rows, 1 caudal and 1 occipital Genus Ditoxum Gassowsky
8. Adoral zone very reduced ; 2 rows of mem-
branelles anterior and 2 rows posterior
Genus Tetratoxum Gassowsky
Adoral zone prominent 9
9. Adoral zone and 3 rows of membranelles,
1 occipital and 2 caudal Genus Cochliatoxum Gassowsky
Adoral zone and row of membranelles mak-
ing at least 3 spirals about the body; the
row is broken at regular points by skel-
etal lappets Genus Troglodytella
Brumpt and Jouex
Order 3. CTENOSTOMIDA (Lauterborn) Kahl 1931.
Key to Families
1. Posterior carapace has 4 rows of cilia on
left, 2 on right— also 1 row of cilia on left
frontal edge Family Epalcidae
No frontal cilia; posterior row absent on
right side; on left side cilia are fused to
long cirrus-like groups 2
2. Broad, long, ciliated band extends over
both broad sides Family Discomorphidae
Ciliated band is short; extends equally on
both sides Family Milestomidae
Key to Genera
Family 1. Epalcidae Wetzel 1928.
1. Only 1 dorsal and 1 ventral row of cilia;
number of median teeth usually 4, often
indefinite 2
Right carapace with 2 median rows of cilia ;
its median teeth fused to one; 3 teeth in
all Genus Pelodinium Lauterborn
2. At least some anal teeth (left and right)
with spines Genus Saprodinium Lauterborn
Anal teeth all without spines Genus Epalxis Roux
Family 2. Mylestomidae Kahl 1931.
1. Right hind end with 2, left with 1 great
notch Genus Atopodinium Kahl
Notches absent, or very small one on right
Genus Mylestoma Kahl
Family 3. Discomorphidae Poche 1913.
Only one genus — Discomorpha Levander
Order 4. HYPOTRICHIDA Stein s. str.
Key tn Families
1. Adoral zone complete; dorsal bristles pres-
ent 2
Adoral zone reduced to small, encapsulated
pre-oral part; on anterior left is an incon-
spicuous remnant of membranelles which
are very small and cirrus-like. .Family 3. Aspidiscidae
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 517
Key to Families
2. Cirri essentially typical; ventrals may be
reduced; marginal rows present; dorsal
bristles present Family 1. Oxytrichidae
Marginal and ventral rows absent
Family 2. Euplotidae
Key to Genera
Family 1. Oxytrichidae Ehr. 1838.
1. Transverse cirri absent (not always easily
seen) 2
Transverse cirri present (not always easily
seen) 10
2. Ventral and marginal rows not distinctly
spiral 3
Ventral and marginal rows distinctly
spiral, overlapping dorsum 7
3. Long, band form, posterior pointed or
rounded (salt lakes) with only 2 feath-
ered frontal membranelles Genus Cladotricha Gajevskaja
Other types 4
4. Frontal cirri not limited to 3 to 6 but are
numerous, distributed in rows not dis-
tinct from ventral cirri 5
Frontal cirri reduced to 3; no other cirri. . 6
5. Small, oval (50 to 100/x) ; with long, widely
separated bristle-like cirri Genus Psiloiricha Stein
Frontal cirri arranged cross-wise over
frontal field Genus Eschaneustyla Stokes
6. Elongate, narrowed to tail-like end; usu-
ally 2 ventral rows Genus Uroleptus Engelm.
Ovoidal forms with 5 to 8 rows of long
ventral cirri not different from marginal
rows Genus Kahlia Horvath
7. Fresh water forms with broad peristome;
posterior end short spine-like. . . .Genus Hypotrichidium Ilowaisky
Slender forms with narrow peristome 8
8. Peristome only slightly narrowed; adoral
zone short Genus Strongylidium Sterki
Peristome neck-like, narrowed ; adoral zone
on left side 9
9. Peristome region little or not at all exten-
sible Genus Stichotricha Perty
Peristome region highly distensible. .Genus Chaetospira Lachmann
10. No specialized frontal cirri; ventral rows
run to anterior end without cirri special-
ization 11
Frontal cirri strongly developed; first 3
especially 16
11. Small, oval, marine forms with very large
peristome 12
Otherwise formed, or not marine 13
12. Transverse cirri small; not continued to
posterior end Genus Caryotricha Kahl
Transverse cirri long and stiff, reaching
well beyond posterior end Genus Stylocoma < '.ruber
518
BIOLOGY OF THE PROTOZOA
D
Fig. 209. — Types of Ciliata. A, Amphisia kessleri; B, Uroleptus pisces; C, Histrio
pellionella; D, Strong ylidium sp. ; E, Oxytricha pellionella; F, Oxytricha fallax. (A,
after Calkins; B, C, D, E, after Biltschli; F, after Stein.)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 519
Family 1. Oxytrichidae Ehr. 1838.
13. Small fresh water forms; long, separated
ventrals, no special frontal cirri; dorsal
bristles high Genus Ballad ina Kowalewski
Form and structure otherwise 14
14. With long tail, highly contractile marine
forms (Fig. 208) Genus Epiclintes Stein
Form different; if tailed, then moderately
contractile — fresh water 15
15. Commensal on different species of Hydra
Genus Kerona Ehr.
Free-living — not commensal 16
16. More than 2 ventral rows of cilia 17
One to 3 ventral rows of frontals not dis-
tinct Genus Holosticha (in part see 20)
Wrzesniowski
17. Three ventral rows; frontal rows not much
enlarged Sub-genus Trichotaxis Stokes
More than 3 ventral rows; 3 frontal cirri
strongly marked 18
18. Ventral cirri all in rows (1 to 6) 19
Ventral cirri united in groups 21
19. Ventral cirri in 4 or more rows Genus Urostyla Ehr.
Ventral cirri in 1 to 3 rows or absent 20
20. Ventral rows absent; marine form with
narrow neck-like peristome Genus Trachelostyla Kahl
Ventral rows 1 to 3 in number, 3 frontals
distinct Genus Holosticha (in part see 16)
21. Ventral cirri in 1 to 3 rows; post oral and
posterior groups of small cirri in addition 22
Complete ventral rows absent 26
22. Complete rows run parallel with long axis . . 23
Complete rows run diagonally from ante-
rior right to posterior left 25
23. One complete row on left, 2 on right; trans-
verse cirri in complete rows Genus Onychodromopsis Stokes
The 2 right transverse cirri well behind the
3 left 24
24. On each side, one complete ventral row
Genus Allotricha Sterki
Two complete ventral rows on right . Genus Pleurotricha Stein
25. One diagonal ventral row running close to
the transverse row (Fig. 210) .. . .Genus Gastrostyla Engelmann
Adoral zone placed laterally; ventral rows
short, within or just beyond peristome
Genus Gonostomum Sterki
26. Posterior end may be drawn out in long
thin stalk Genus Ancistropodium
Faure-Freinid
Posterior end never drawn out in long thin
stalk 27
27. 12 to 15 powerful frontal cirri, 4 macro-
nuclear parts Genus Onychodromus Stein
8 frontal cirri in 3 groups ; macronucleus in
2, rarely in 1 or 4 parts 28
520
BIOLOGY OF THE PROTOZOA
Fig. 210. — Types of Ciliata. A, Gastrostyla steinii; B, Euplotes vannus; C, Pleurotricha
lanceolala; D, Psilotricha acuminata. (A, B, after Calkins; C, D, after Stein.)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 521
Family 1. Oxytrichidae Ehr. 1838.
28. Posterior end tail-like or pointed. . .Genus Urosoma Kowalewsky
Posterior end not tail-like or pointed 29
29. Right peristome edge hook-like and turned
to left, spirally rolled anteriorly. .Genus Steinia Diesing
Peristome edge does not reach to adoral
zone 30
30. Body soft, plastic, occasionally contractile. 31
Body stiff 33
3 1 . Marginal rows continuous posteriorly
Genus Oxytricha Bon-
Marginal rows broken posteriorly 32
32. No caudal cirri Genus Tacky soma Stokes
With caudal cirri Genus Opisthotricha Kent
33. Marginal rows continuous posteriorly; no
caudal cirri Genus Histn'o Sterki
Marginal rows broken posteriorly; with
stiff caudal cirri Genus Stylonychia Ehrenberg
Family 2. Euplotidae Ehr. 1838.
Key to Genera
1 . Anterior third of body head-like because of
two lateral notches Genus Discocephalits Ehr.
Anterior third not head-like 2
2. No special steering cirri near posterior end . 3
Near posterior end 1 or 2 groups of power-
ful cirri 5
3. Left marginal cirri row continuous; 4 mac-
ronuclei, ellipsoid marine form. . .Genus Certesia Fabre-Dom.
Left marginal cirri absent, or isolated
single ones 4
4. Frontal part of adoral zone lies in flat
furrow Genus Euplotes Ehr.
Frontal part of adoral zone separated from
dorsum by deep funnel-like depression
Genus Crateromorpha
Perejaslawzewa
5. One group of 3 powerful cirri, on right
dorsal Genus Diophrys Dujardin
Powerful cirri in addition to 3 on right side,
dorsal Genus Uronychia Stein
Family 3. Aspidiscidae Stein 1859.
Only one genus — Aspidiscus Ehr.
Sub-class III. PERITRICHA Stein.
1. No peristomial trench; attaching disc
ciliated Family Urceolariidae
2. With peristomial trench; posterior cilia
temporary Family Vorticellidae
Family 1. Urceolariidae Stein.
1 . Forms with smooth attaching ring . . Genus Urceolaria Stein
Forms with toothed ring 2
2. With special tactile cilia Genus Trichodina Ehr.
Without special tactile cilia Genus Acyclochaeta Zick
522 BIOLOGY OF THE PROTOZOA
Family 2. Vorticellidae Ehr.
1. Cup or test-dwelling forms 2
Without test, with or without stalks, soli-
tary or colonial 5
2. Upright; attachment posterior, with or
without stalks 3
Recumbent ; attachment lateral 4
3. Cup delicate; peristome region cup-like
Genus Ophrydiopsis Penard
Cup thick with or without stalk. . . .Genus Cothurnia Ehr.
4. Peristome disc with neck; operculum-like
Genus Lagenophrys Stein
Peristome disc without neck Genus Vaghricola Lamarck
5. Forms with stalks 6
Forms without stalks, free-swimming or
attached 13
6. Stalks contractile 7
Stalks not contractile 9
7. Colonial forms 8
Solitary forms Genus Vortirelln Linn.
8. Entire colony contracts; stalk threads con-
nected Genus Zodtharnnium Ehr.
Individual stalks, only, contract. . .Genus Carchesium Ehr.
9. Colonial forms 10
Solitary forms 12
10. Great colonies of individuals embedded in
jelly Genus Ophrydium Bory
Feathery colonies, individuals not in jelly. 11
11. Peristome region raised on short neck
Genus Opercularia Stein
Peristome region without neck Genus Epistylis Ehr.
12. Adoral zone with greatly developed mem-
brane Genus Glossotella Biitschli
Adoral zone inconspicuous Genus Rhdbdostyla Kent
13. Free-swimming forms 14
Attached by posterior end 16
14. With digitiform protoplasmic processes
Genus Hastatella Erlanger
Without digitiform protoplasmic processes 15
15. With two caudal threads Genus Astylozoon Engelmann
Posterior ciliated girdle permanent . .Genus Opisthonecta F. Frem.
16. Posterior end with attaching disc. . Genus Scyphidia Lachm.
No attaching disc; organism rests on pos-
terior end or swims with posterior girdle
Genus Gerda Clap, and Lachm.
Sub-class IV. CHONOTRICHA Wallengren.
1. Peristome region funnel-like Family Spirochonidae
Peristome region drawn out as two lips
Family Chilodochonidae
Family 1. Spirochonidae Grobben.
1. Peristome spirally wound funnel. . .Genus Spirochona Stein
(On gill plates of Gammarus)
Peristome not spirally wound 2
2. Peristome margin with processes; 1 bud
formed (On gill plates of Nebalia) .Genus Kentrochona Keuten
Several buds formed Genus Kentrochonopsis Doflein
(On gill plates of Nebalia)
MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 523
Family 2. Chilodochonidae Poche.
One genus — Chilodochona Wallengren. On
mouth parts of crabs (Ebalia and Portunas)
Class II. SUCTORIA Butschli.
1 . Suctorial tentacles alone present 2
Prehensile tentacles in addition to suctorial
Family Ephelotidae
2. Body not bilaterally symmetrical; irregular
or branched 3
Body monaxial; more or less bilateral. ... 5
3. Without "proboscis" or special "arms"
Family Dexdrosomidae
With retractile proboscis or special "arms" 4
4. With retractile proboscis Family Ophkyodexdridae
With special, tentacle-bearing "arms"
Family Dendrocometidae
5. Reproduction by internal budding 6
Reproduction by external budding-
Family Podophryidae
G. Pellicle delicate Family Acinetidae
Pellicle tough, coriacious Family Discophryidae
Family 1. Acinetidae Butschli.
1 . Internal parasites 2
External parasites or free-living 3
2. In other Protozoa; no tentacles or suckers
Genus Endosphaera Engelm.
Horse parasites; with tentacles at opposite
ends of body Genus Allantozoon Gassovsky
3. Parasitic on other suctoria 4
Not parasitic on suctoria; or free-living. . . 5
4. Stalk embedded in Acineta or Paracineta
Genus Pseudogemma Collin
Parasitic on Ephelota Genus Tachyblaston Martin
5. Twelve to 15 finger-form processes, each
with sucker Genus Dactylophrya Collin
Without finger-form processes 6
(5. Test or cup absent; tentacles in fascicles. . 7
Test or cup present 8
7. Body pyramidal, with stalk (Fig. 117, p.
228) Genus Tokophrya Butschli
Form variable; no stalk Genus Halleziu Sand
8. Test without free margin, membrane-like
(Fig. 100, p. 192) Genus Acineta Ehr.
Test cup-like, with free rim or margin .... 9
9. Xo definite stalk; test attached by base. . . 10
Test attached by definite stalk 11
10. Cup attached by entire base Genus Solevophrya
Clap, and Lach.
Base of cup narrowed, almost stalk-like
Genus Periacineta Collin
11. Gup polyhedral; 1 to 6 central tentacles
Genus Acinetopsis Robin
( !up not polyhedral: distributed apical ten-
tacles Genus Tkecacineta Collin
524 BIOLOGY OF THE PROTOZOA
Family 2. Discophryidae Collin.
1. One primary tentacle; with or without
secondaries 2
With many tentacles 3
2. With stalk Genus Rhynchophrya Collin
No stalk; attachment by protoplasmic
body Genus Rhyncheta Zenker
3. Suctorial tentacles conical, with enlarged
bases Genus Thaumatophrya ( \>llin
Tentacles uniform in diameter 4
4. Tentacles expansile at extremities for food-
taking Genus Choanophrya Hartog
Tentacles not expansile Genus Discophrya Lachmann
Family 3. Dendrosomidae Butschli.
1. Forms with stalk 2
Forms without stalk 3
2. Body much branched, finger-like. . Genus Dendrosomides Collin
Body bar-like, not digitate Genus Rhabdophrya
Chat, and Collin
3. Body attached 4
Body free 6
4. Body bilateral or slightly asymmetrical
(Fig. 117, p. 228) .Genus Trichophrya
Clap, and Lach.
Body flat 5
5. With basal stolon; branches erect; often
second branches (Fig. 196, p. 477) Genus Dendrosomn Ehr.
No stolon; short unbranched processes,
fascicled tentacles Genus Lernaeophrya Perez
6. Body tetrahedral Genus Tetraedrophrya Zykoff
Body polyhedral 7
7. With 6 similar protuberances Genus Staurophrya Zacharias
With 8 radiate processes, each with a
fascicle Genus Astrophrya Awerinzew
Family 4. Dendrocometidae Stein.
1. Arms branched, each branch with one
sucker Genus Dendrocometes Stein
2. Arms not branched Genus Stylocomeles Stein
Family 5. Ophryodendridae Stein.
One genus only Genus Ophryodendron
Clap, and Lach.
Family 6. Podophryidae Butschli.
1 . Without test or cup 2
With test or cup 3
2. Normally with stalk, attached Genus Podophrya Ehr.
Free-swimming or parasitic Genus Sphaerophrya
Clap, and Lach.
3. Cup close-fitting, no visible rim. . . .Genus Parocineta Collin
Cup not close-fitting, rim visible 4
4. Tentacles numerous; in fascicles. . Genus Metacinata Butschli
Tentacles scarce; 1 to 3 Genus Urnvla Clap, and Lach.
Family 7. Ephelotidae Sand.
No test or cup; with or without stalk (Fig.
115, p. 226) Genus Ephelota Wright
With cup and stalk Genus Podoci/aUnis Kent
CHAPTER XIV.
SPECIAL MORPHOLOGY AND TAXONOMY OF THE
SPOROZOA.
Forms adapted to a parasitic mode of life are found in every main
group of the Protozoa and several highly pernicious human diseases
such as dysentery, Leishmaniasis and trypanosomiasis are due to
them. Such forms, however, may be regarded as having arisen as
casual parasites which owe their parasitic mode of life to their
original power to resist the digestive fluids and other conditions
of the animal body. Such adaptations are always possible in
normally free-living microorganisms subject to ingestion with food
and drink.
Sporozoa are obligatory parasites and free-living forms are
unknown. Practically all kinds of animals, even Protozoa, are
subject to invasion by one type or other and adaptations are mani-
fold and varied in response to the necessary and often highly special-
ized conditions of their existence.
In size the Sporozoa vary within wide limits; some are so small
that many of them may live together in a single mammalian erythro-
cyte (Theileria, Babesia) or in gland cells of different animals
(Microsporidia) . At the other extreme some forms of Gregarinida
(Porospora) grow to a length of 16 mm. In general they are larger
than flagellates, smaller than rhizopods and average about the
same size as the ciliates.
Form also is variable but fairly consistent within the major
groups. Ameboid forms are characteristic of the Myxosporidia
and of the Plasmodiidae of the Hemosporidia. Coccidia for the
most part are spheroidal to ellipsoidal and gregarines elongate
ellipsoidal or ovoidal. Fantastic shapes are not uncommon, par-
ticularly amongst the Gregarinida— star shape in Astrocystella,
dagger shape, or branched forms in Aikinetocystis, etc.
As with parasites generally, a necessary adaptation for the main-
tenance of species is the power of prolific multiplication. This is
realized by the universal method of reproduction by spore formation
to which the group owes its name. Such sporulation may occur
as multiple reproduction of vegetative individuals without sexual
processes or it may follow as a result of fertilization. Asexual and
sexual processes give rise to typical alternation of generations in
the majority of forms and complicated life histories result.
526 BIOLOGY OF THE PROTOZOA
Nuclei are single in number in Telosporidia and multiple in the
majority of Cnidosporidia. In structure they are highly charac-
teristic, particularly in Gregarinida. Here there is a great endosome
in vegetative stages of the organism which represents a combination
of somatic and germinal chromatin. When ready for sporulation
the germinal chromatin leaves the endosome as a small bud and
forms chromosomes on a relatively small spindle (Fig. 55, p. 101).
The residual mass of endosome and the remainder of the nucleus then
disintegrate and disappear. The small aggregate of germinal chro-
matin together with its division figure thus resembles a micronucleus
of the ciliates while the disintegrating portion is equivalent to the
macronucleus.
The chromosomes of Telosporidia give more evidence of indi-
viduality than do those of any other group of Protozoa. Meiotic
phenomena are of two general types— so-called gametic meiosis in
which reduction in number of chromosomes occurs during the
formation of gametes, and zygotic meiosis in which reduction
occurs during the first mitotic division of the amphinucleus. Both
types are found in Eugregarinida (Monocystis, Diplocystis, etc.)
and Coccidia (Aggregata). The number of chromosomes in gregar-
ines is often uneven (3, 5, 7, etc.) which indicates either zygotic
meiosis (Dobell, Jameson) or zygotic synapsis (Naville, see p. 309).
Asexual reproduction may occur by equal division (e. g., Ophryo-
cystis, Babesia, etc.), by budding which may be exogenous (Myxo-
sporidia) or endogenous (as in the gregarines Schizocystis and
Eleutheroschizon) , or by multiple division (Coccidiomorpha). Re-
production following fertilization always involves the formation
and the permanent fusion of gametes. These may be isogamous or
anisogamous and dimorphic gametes as different as are eggs and
spermatozoa of the Metazoa are characteristic of the Coccidia and
Hemosporidia. Sexual processes of peculiar type and regarded as
self fertilization or autogamy are characteristic of the Cnidosporidia
where such processes with resulting sporulation take place in endo-
genous buds.
Sporulation following fertilization in the majority of forms
involves adaptations for preservation of the species during exposure
to the conditions external to the definitive host. Such spores are
protected against drought and other external conditions by resistant
spore membranes or capsules which are opened or dissolved only in
the digestive tract of a new host. In the majority of cases such new
hosts are individuals of the same species and infection is brought
about by eating contaminated food. In many forms, however, the
life cycle involves a change of hosts, the metagamic spores develop-
ing in one type of animal and the sexual phases of the parasite
developing in another type belonging to an entirely different group
of the animal kingdom. Thus vegetative stages of the genus Aggre-
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 527
/
n
^ • ^?
Fig. 211. — Hepatozoon pemiciosa, a hemogregarine parasite of the rat. a to d.
development of the agamont in the liver cells of the rat; e, free parasites in the blood;
/, encysted parasites in the leukocytes; g to k, stages of fusion of the gametes in the
the surface; .
( lalkins after Miller.)
'±±U Ul \JIIV ilgtllllUllt Hi U1XC UVC1 UCllO Ui 111C 1 cL U , <: , ll^t puiuumu iiA ^"^ ^iwvv*,
1 parasites in the leukocytes; g to k, stages of fusion of the gametes in the
n, development of the zygote; o, sporocyst with sporo blast buds covering
e; p, section of the same; <?, older sporoblast with sporozoites. (From
ter Miller.!
528 BIOLOGY OF THE PROTOZOA
gain develop in the crab (Portunus depurator) and the sexual stages
in the cephalopod (Sepia officinalis); vegetative stages of the malaria
organisms, Plasmodium, develop in the blood of man or birds and
the sexual stages in the mosquito. In these blood-infesting Sporozoa
a further adaptation is noted in the loss of the characteristic cap-
sules of the metagamic spores which are inoculated with the bite
of the mosquito directly into the blood. In some cases parasites
reach the blood by way of the digestive tract and infection is con-
taminative. The rat parasite Haemogregarina (Hepatozoon) pemi-
ciosa (according to Miller, 1908) forms its metagamic spores in the
rat mite (Lelaps echidninus) . Such infected mites are eaten by
the rat and the spores develop in liver cells through some agametic
generations, the agamic spores finally entering the blood where
they are taken up by leukocytes in which the parasites encyst.
Such encysted spores are taken with the blood into the gut of the
mite where sexual phases take place and metagamic spores are
formed (Fig. 211).
For characterization of the homologous stages in the very diverse
life histories of Sporozoa a special and fairly definite terminology
has been adopted by all students of the group beginning with Schau-
dinn. These terms which are employed in classifications are as
follows :
Sporozoite. The final product of metagamic divisions and the
beginning of a new life history.
Trophozoite. A vegetative stage which develops from a sporo-
zoite or from a merozoite. (Also termed according to conditions,
agamont, gamont or schizont.)
Schizont. A mature trophozoite preparing for multiple or simple
division without fertilization. (Also termed agamont.)
Schizontocyte. A special type of schizont (or gamont) which by
multiple division breaks up into a number of germ-forming centers
as in Caryotropha and Klossiella.
Schizogony. The process of simple or multiple division of a
schizont.
Merozoite. A product of schizogony leading to spread of an
infection in the same host. (Also called Agamete.)
Sporont. A trophozoite destined to form copulating gametes.
This may be derived directly (i. c., without schizogony) from a
sporozoite as in Eugregarinida, or from a merozoite. (Also called
gamont)
Sporogony. The process or processes of reproduction leading to
the formation of gametocytes and gametes. (Also called gamogony.)
Gametocyte. A mother-cell which will produce gametes.
Macrogametocyte. A mother-cell which will produce macrogam-
etes (rare) or develops directlv into a macrogamete or female germ
cell.
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 529
Macrogamete. An inactive (female) cell ready for fertilization.
Microgametocyte. A mother-cell destined to form microgametes.
Microgamete. A motile element (male), equivalent to a sperma-
tozoon.
Gametes. Specialized cells destined to meet and fuse in fertili-
zation.
Gametocyst. A protective covering formed by two gregarines in
psendo-conj ligation; not equivalent to oocyst.
Zygote. A cell formed by the fusion of gametes.
Oocyst. The hardened fertilization membrane which surrounds
the zygote and its products.
Metagamic divisions. Divisions of the zygote leading to the
formation of sporoblasts and sporozoites.
Sporoblasts. First products of the division of a zygote. Sporo-
zoite mother-cells.
Sporocy.st. Hardened and resistant special capsule of a sporo-
blast.
Sporozoite. A final product of metagamic divisions.
The significance of these terms will be apparent by illustration
with a concrete example for which we may again use the classical
case of the life history of Eimeria (Coccidium) schubergi as worked
out by Schaudinn (1000) (Fig. 212). This is a common intestinal
parasite of the familiar centipede Lithobius, infection taking place
by feeding on contaminated food.
Under the action of the digestive fluids in the centipede the sporo-
zoites are liberated from their protective capsules (oocyst and
sporocyst). A sporozoite penetrates an epithelial cell and grows
at the expense of the cell into an agamont (Fig. 212, a). When
fully grown the nucleus of the parasite divides several times;
the protoplasm by multiple division breaks up into small cells
about the resulting nuclei the process of nuclear and cytoplasmic
division to form these cells being agamogony. The host cell is
destroyed and the young cells, known as agametes, are liberated.
These agametes make their way by independent gregariform move-
ment to other epithelial cells which they penetrate and in which they
repeat the entire agamic cycle, producing in turn new agametes.
After five or six days, during which this agamic cycle is repeated
resulting in multiple infection of the epithelium, the agametes
develop into gamonts or prosexual individuals. Some become
large, food-stored cells which, after "maturation" processes form
macrogametes directly (e,f, g). Others form large cells with clear
protoplasm — microgametocytes — which after repeated nuclear divi-
sions give rise to a multitude of microgametes, the process being a
form of gamogony. Each microgamete is provided with two
fiagella by means of which it moves about in the intestinal fluids
until it comes in contact with a macrogamete (//, i, j, s). The
34
530
BIOIJICY OF THE I'h'OToZOA
gametes fuse, a maeroganiete being fertilized by a single micro-
gamete (g). The fertilized cell resulting from this fusion is the
zygote in which the pronuclei fuse. The fertilization nucleus then
divides and the two products divide again before the protoplasm
divides into four parts, one about each of the nuclei. This process,
or metagamogony, results in the formation of four sporoblasts within
the sporocyst and each sporoblast has its own individual protective
Fig. 212. — Eimeria Schubergi. Sporozoites penetrate epithelial cells and grow
into adult intracellular parasites (a). When mature, the nucleus divides repeatedly
(b), and each of its subdivisions becomes the nucleus of an agamete (c). These enter
new epithelial cells and the cycle is repeated many times. After five or six days of
incubation, the agametes develop into gamonts; some are large and stored with yolk
material (d, e, ./'), others have nuclei which fragment into chromidia which become
the nuclei of mierogametes (d, h. i, j\. A maerogamete is fertilized by one micro-
gamete (g) and the zygote forms an oocyst (k). This forms four sporoblasts, each
with two sporozoites (/). (After Schaudinn.)
capsule (/). The nucleus of each sporoblast then divides and two
independent cells are formed in each sporoblast. These indepen-
dent cells arc the sporozoites. To recapitulate: Sporozoites come
from sporoblasts; sporoblasts from zygotes; zygotes from fusion of
gametes; gametes from gametoevtes, these from gamonts; gamonts
from agametes; agametes from agamonts, and agamonts, originally,
from sporozoites.
MORPHOLOGY AND TAXONOMY OF THE SPOliOZOA 531
There are thus two complete cycles in the life history of a typical
sporozoon, an asexual and a sexual cycle. There are many varia-
tions in different types and few life cycles conform exactly with
that of Eimeria. In the Eugregarines, for example, the asexual
cycle is entirely eliminated, the sporozoite developing directly into
a gametocyte. In Gregarines also we find a curious process which
recalls the phenomenon of conjugation in the Ciliata. It is termed
pseudo-conjugation. Two individuals come together side by side or
end to end and an envelope is secreted which encloses both indi-
Fig. 213. — Lankesteria ascidiae. Young sporozoites enter epithelial cells (A, B, C)
and grow directly into gamonts (D) ; two of these unite in pseudo-conjugation (E), and
each forms gametes after repeated nuclear divisions (F, G, H). The gametes fuse
two and two (/, ./, A"), and the zygotes undergo three metagamic divisions, forming
eight sporozoites (L to O). The parent cells degenerate and the sporocysts are filled
with sporoblasts, each with eight sporozoites. (After Siedlecki.)
viduals. This envelope is a gametocyst. Each individual now
forms a large number of gametes and those from one individual
fuse with the gametes from the other individual and a multitude
of zygotes is formed. The actual fertilization membrane becomes
the oocyst and sporocyst and the zygotes divide at once to form
sporozoites (Fig. 213).
Invariably parasitic, there is the greatest diversity in sites of
parasitism and modes of life of Sporozoa. Gregarines are found only
in invertebrates while Coecidiomorpha and Cnidosporidia are not
532 BIOLOGY OF THE PROTOZOA
restricted to any particular group. Comparatively harmless types
are lumen-dwelling parasites of different organs, particularly of the
digestive tract (Gregarinida, Actinomyxida, Cryptosporidium and
Eimeria mitraria among Coccidia, etc.); more pernicious types
are cytozoic (Coccidia, karyozoic in Cyclospora, and Microsporidia)
and hematozoic (Hemosporidia) for these involve the destruction
of cells and impairment of function. Histozoic forms (Myxospor-
idia, Sarcosporidia) are likewise pernicious through the formation
of great tumor-like cysts in muscles and skin. The massing of cysts
in celozoic types often impedes normal activities of the endothelial
cells as in the seminal reservoirs of earthworms wThich frequently
contain nothing but cysts, thus virtually effecting castration.
Transmission of Sporozoa from host to host for the most part is
by the contaminative method. Enteric parasites develop resistant
spores which are passed out with the feces and are ingested sooner
or later by other hosts of the same species. Or in some few cases
such enteric forms are ingested by hosts of an entirely different
animal type. Porospora, for example, is a quite harmless intestinal
gregarine of the lobster which forms so-called " gymnospores, "
either singly (P. gigantea) or during pseudo-conjugation (P. legeri).
These are taken into the digestive tract of the mussel (Mytilus
edulis) where fertilization occurs. This peculiar history involves
some difficulty in classification, for if these gymnospores are gametes
as is indicated by Porospora legeri then the genus belongs in the
Eugregarinida, as is advocated by Reichenow-Doflein; if, on the
other hand, they are equivalent to merozoites (agametes) as appears
to be the case in P. gigantea, then the genus should be classified
with the schizogregarines. Until further knowledge is forthcoming
we adopt the latter course.
When spores are formed in celomic or body cavities the mode of
transmission is less obvious. They may, indeed, be passed out
through nephridia or by way of sperm and oviducts or, like copro-
zoic forms, they may pass unaltered through the digestive tracts
of animals which feed upon the normal hosts, to be cast out ulti-
mately with the feces. Minchin suggested that birds may be the
main disseminating agent for spores of earthworm gregarines, but
it is also probable that dissemination occurs through death of the
host or by pinching off infected portions of the organism which then
disintegrate. In all such cases and in the great majority of all
Sporozoa infection is brought about by swallowing spores, the
resistant spore cases of which are dissolved by digestive juices and
the germs liberated. These spore coverings for gregarines, coccidia
and Cnidosporidia are special adaptations which are undoubtedly
useful for protection during the exposed periods in the life cycle.
With blood-dwelling parasites such capsules would be fatal, for
there is no chemical in the blood to dissolve off the coverings and
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 533
liberate the germs, nor would there be any normal way of eliminat-
ing such spores if formed in the blood. It is quite possible, of course,
that germs may make their way into the blood by way of the diges-
tive tract and this is realized in the Hemoproteidae and in Hemo-
gregarina where final stages in the life history chiefly gametocytes
(Hemoproteus) alone are blood-dwelling while other stages occur
in the intestinal cells or in the endothelial cells of bloodvessels
(Hemoproteus, Haplozoon, Karyolysis). In these cases transmis-
sion is brought about by other hosts (flies, mites and leeches) while
the definitive host becomes infected by the contaminative method
(see also p. 361).
In Plasmodiidae or malaria organisms the digestive tract of the
definitive host is not involved in the life history of the parasite.
Here the entire vegetative life is in the blood cells of birds or the
red blood corpuscles of mammals. Xo cysts of any kind are formed
but the blood, with parasites, is taken into the digestive tract of
mosquitoes where fertilization occurs and metagamic products are
formed. The final metagamic products— sporozoites— are inocu-
lated by the mosquito directly into the blood (see page 406).
Accompanying this type of life history is the formation from hemo-
globin of the characteristic pigment melanin (Plasmodium, Hemo-
proteus) which is absent in forms developing elsewhere than in
the blood. Here, also, we note the absence of resistant unchang-
ing membranes (oocyst, sporocyst) about the zygote which are
typical of the majority of Telosporidia. On the contrary, these
zygotes produce delicate fertilization membranes which enlarge
with growth and development of the zygote which, immediately
after fertilization, has the power of independent movement.
Other variations will appear in the discussion of the different
groups of Sporozoa as given in the following classification, in which,
following the majority of students of the Protozoa, we divide the
group into two classes— Telosporidia and Cnidosporidia. The two
groups have little in common besides the mode of life of parasites.
The Class Telosporidia includes those forms in which the life of
the individual comes to an end with sporulation. The Class Cnido-
sporidia includes those forms in which sporulation occurs in internal
buds during the vegetative activity of the individual, sporoblasts
being carried about by the still active parent cell.
Class I. TELOSPORIDIA Schaudinn.
Telosporidia are Sporozoa which, with very few exceptions, are
intracellular parasites during some phase of the life cycle. A new
host is infected by contamination or by inoculation and the young
germ— a sporozoite— enters some cell element, an epithelial cell if
the parasite is one of the Ooecidia, a blood element either blood
534 BIOLOGY OF THE PROTOZOA
corpuscle or Mood cell if it is one of the Hemosporidia. The adult
forms of Gregarinida are invariably extracellular or lumen-dwelling
parasites, young, growing stages alone being intracellular. Adult
forms of Coccidiomorpha are persistent intracellular parasites
throughout young, adult and reproductive phases. Although some
exceptional cases occur in both groups, these are essential differ-
ences between the two sub-classes Gregarinida and Coccidiomorpha.
All are typically uninucleate in the adult phase.
Reproduction occurs either by agamogony or gamogony, the
latter involving fertilization. In one order of the Gregarinida, the
• Eugregarinida, the sporozoite grows directly into a gamont and
asexual reproduction is unknown. In a second order, the Schizo-
gregarinida, agamogony occurs either by equal division, internal
budding, or by multiple division. In Coccidiomorpha alternation
of generations is the rule and change of hosts is frequent. Multiple
division is practically universal.
In both sub-classes the zygote undergoes metagamic divisions.
In Gregarinida and in Hemosporidia amongst the Coccidiomorpha,
the sporozoites are formed directly by divisions of the zygote; in
Coccidia the zygote divides into sporoblasts or sporozoite-forming
cells. In all cases except in Hemosporidia the sporozoites formed
in each such sporoblast are enclosed in a special capsule— Sporocyst
— by which the young organisms are protected against external
conditions. Hemosporidia are obligatory parasites in one host or
other throughout the entire life cycle otherwise they perish.
Sub-class I. GREGARININA.
The gregarines are typically celozoic or lumen-dwelling parasites
of the invertebrates, particularly of annelids and arthropods. They
vary in size from 10 /x to 16 mm. (Porospora gigantea) and are prone
to collect in masses in the intestine, a gregarious habit from which
the name of the group is derived. Saprozoic or osmotic in nutri-
tion they apparently do very little if any damage to the host organ-
ism, differing in this respect from the intracellular Coccidiomorpha.
The most frequent site of parasitism is the digestive tract and the
glands opening into it (e. g., Malpighian tubules) but the sporozoites
of some forms penetrate the wall of the gut and enter the body
cavity where they form cysts on the celomic side of the intestinal
wall or develop as free forms in the lumen of the seminal vesicles
(Monocystidae) or of other parts of the body cavity.
Gregarines are widely varied in form as well as in size but so far
as the present accounts go they are similar in their protoplasmic
make-up. A peripheral outer layer of lifeless material forms the
epicyte which is equivalent to the pellicle or periplast of other
Protozoa. This is secreted by the ectoplasm and is frequently
MORPHOLOGY AND TAXOXOM) OF THE SPOROZOA 535
drawn out into attaching organs in the form of filaments, hooks,
anchors and knobs. The outer surface is often definitely ribbed,
the ribs running longitudinally from end to end of the body. The
furrows between the ribs are filled with a gelatinous material derived
from a second layer, also lifeless, of the cortex and termed by
Schewiakoff the gelatinous layer. The third zone of the body
wall is formed by the living ectoplasm which, with the possible
exception of Stomatophora coronata described by Hesse (1909) as
possessing a mouth, peristome and cell anus, forms an unbroken,
living, protoplasmic membrane. The endoplasm, or fourth zone,
finally, forms the bulk of the organism and contains the single
nucleus, usually provided with a large endosome. Paraglycogen,
volutin granules and other products of living activity make the endo-
plasm dense and homogeneous so that it appears white by reflected
and black by transmitted light. Crystals of protein-like substance
are present in many cases, also crystals which have been identified
as calcium oxalate. Between endoplasm and ectoplasm, finally, a
system of myonemes may be found in some cases. These, accord-
ing to Roskin and Levinson (1929), lie in definite canals. The
presence of myonemes led to the view that a special myocyte zone
is present in addition to the other zones. It is found, however,
that in addition to these longitudinal myonemes a second set of
circular myonemes is present, lying between the sarcocyte and the
endoplasm. A definite myocyte zone, therefore, is absent and
myonemes may be found anywhere in the cortex. In Zygocystis
conspicuous myoneme-like threads originate in the cortex near the
anterior end, become free in the posterior third of the body and as
free threads trail out behind the posterior end in characteristic
manner.
The movement of gregarines has been variously interpreted. In
some cases, e. g., Clepsidrina munieri, the organism glides forward
without evident contraction of the body; in other cases, e. g., Mono-
cystis agilis, forward movement is accompanied by waves of peris-
taltic contraction and in still other forms there are more or less
spasmodic jerks from side to side. The smooth gliding motion,
according to Schewiakoff (1894), is due to the secretion of a gela-
tinous material from the sarcocyte which passes backward along the
grooves formed by the ridges of the epicyte. This gelatinous
material rapidly hardens on exposure to water, and fresh jelly
hardening in turn on this, forces the organism forward. On this
interpretation the myonemes play no part. Crawley (1902, 1905),
in connection with Stenophora juli and Echinomera hispida, holds
that the slime is not a cause but a result of movement and inter-
prets locomotion as due to the annular contraction of circular myo-
nemes, the organism moving in much the same manner as does a
snake. Sokoloff (1912) differs from both Schewiakoff and Crawley
536 BIOLOGY OF THE PROTOZOA
and maintains that the force generated by the secretion of slime is
sufficient to send the organism forward on the principle of a sky-
rocket.
The majority of observers (Leidy, Luhe, Paehler, Shellack, Dogiel,
Cognetti, Roskin and Levinson, etc.) maintain that myonemes
alone are responsible for the movements of various types of greg-
arines, the latest view (Roskin and Levinson, 1929) referring
them to the activities of the circular and longitudinal myonemes
in much the same way as an earthworm moves through contraction
of its longitudinal and circular musculature. The nature of the
remarkable threads in Zygocystis zonata is not clear. Bowling
(1931) observed the thickening of the threads both in living and in
fixed material, but whether this indicates a cause or a result of
movement is not evident.
Apart from changes in shape due to movements form changes
due to development and differentiation are highly characteristic,
particularly of the septate gregarines. In all gregarines the early
stages in the development of the sporozoite are cytozoic parasites.
After a period of growth the partly developed gregarine escapes
from the host cell and from that time on lives as a celozoic parasite
(Haplocyta). In septate gregarines, however, while the bulk of the
young parasite extends into the lumen of the organ, a small portion
remains as an anchor in the protoplasm of the host cell. This
anchoring part then develops into a specialized structure known as
the epimerite which is a characteristic morphological element of the
majority of Eugregarinida occurring here and there among the
Haplocyta (I)iplocystidae, Schaudinnellidae and Rhynchocystidae).
The character of the epimerite is a diagnostic feature of impor-
tance in the classification of gregarines. Its development into a
long intracellular filament is well shown in Leger and Duboscq's
illustration of Pyxinia moebiuszi (Fig. 103, p. 201). In other cases it
is a mere knob or button within the membrane of the host cell
(Stenophoridae), or a knob with recurved hooks as in Corycella,
Hoplorhynchus, Sciadophorus, etc. in short it is a morphological
feature of great diversity.
In these septate forms the body is further characterized by the
division into chambers (polycystid gregarines of earlier authors)
due to the ingrowth of the sarcocyte to form a posterior portion
bearing the nucleus and an anterior portion from which the epi-
merite arises. When the organism approaches maturity these cham-
bers separate from the epimerite, leaving it in the host cell, and
as gamonts become free in the lumen. In some rare cases the
anterior chamber is also cast off with the epimerite (Genus Schnei-
deria), and it frequently becomes a continuous part with the
epimerite.
Some forms, notably the Monocystidae, may be highly metabolic;
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 537
° o € X cf
oco0
O OQoo
O O ^ ° 4 J
c£)-a ° Q So
. t',1-1 ■■■
o O
o
others move steadily in one direction, a characteristic mode of pro-
gression which has given rise to the term gregariniform movement.
Motile forms are limited to the free types in the digestive tract
or body cavity. Quiescent forms are usually attached to some epi-
thelial cell by the epimerite.
The life history varies from a relatively simple and uncomplicated
progression from sporozoite to sporozoite to a complex alternation
of generations involving different hosts.
The simpler histories are found in the
Eugregarmida such as Monoeystis species
or in Lankesteria ascidiae (Fig. 213). The
latter is a parasite of the digestive tract
of the ascidian Ciona intestinalis which
becomes infected by eating contaminated
food. The sporozoites are liberated from
the sporocysts and enter epithelial cells
where they develop into gamonts. The
adult forms are free in the lumen of the
gut and are characterized by the possession
of a peculiar pseudopodium-like knob which
is regarded as a tactile organ. Two of these
adults which show evidence of sexual differ-
ences (Fig. 214) come together in "pseudo-
conjugation." A delicate membrane —
gametocyst — is formed and within this
membrane each of the individuals forms
a large number of gametes. From the
great nucleus a smaller nucleus is formed
and this divides repeatedly, its products
passing to the periphery where small buds,
each containing a nucleus, are pinched off
as gametes. A gamete from one individual
meets and fuses with a gamete from the
other. A fertilization membrane is formed
which becomes the capsule of the sporo-
blast. The synkaryon divides three times
and eight daughter nuclei are formed which
become the nuclei of eight sporozoites. In
each sporocyst, therefore, there is a possi-
bility of as many zygotes and sporoblasts
as there are gametes formed by one of the original gregarines. The
parasites are passed out of the intestine with the feces and further
development is inhibited until the sporoblasts are eaten by another
host.
A more complex, but still simple, life history involves a change
of hosts. The genus Porospora appears to be represented by several
ego* l
*o° "°o
Fie;. 214. — Nina gracilis
in pseudo-c onjug a t i o n,
above male, below female
roll. Lipoids (gray) and fats
(Mack) are more abundant
in the female than in the
male. X 500. (After Joyet-
Lavergne, Arch. d'Anatomie
Microscopique, courtesy of
Masson el < !ie. I
538
BIOLOGY OF THE PROTOZOA
species which pass their trophic stages in the digestive tract of
Crustacea and their sexual stages in mussels. Porospora gigantea
grows to an enormous size (up to 1(> mm.) in the lobster (Homarus
sp.) where it apparently lives for a long period. Ultimately, and
either in association or individually, it becomes spherical and forms
a cyst-like ball with a diameter of 3 to 4 mm. The ball then divides
into many gametocytes, each with a diameter of from 5 to 8 /x, and
Fig. 215.— Gametes of Gregarines and Coccidia. A, male and female gametes of
Stylorhynchus longicollis; B, Monocystis sp.; C, spermatozoid of Echinomera hispida,
to the left the two gametes of Pterocephalus nobilis; D, gametes of Urospora lagidis;
E, of Gregarina ovata; F, of Schaudinnella henleae; and G, of Eimeria schubergi. (From
Shellack after Leger, Cuenot, Brasil, Schnitzler and Schaudinn.)
each gametocyte forms gametes which are arranged radially about
a central residual body. The gametes are very small (3ju long by
1 ix in diameter) and pass out with the feces into the water with
which they enter the digestive tract of the mussel (Mytilus edulis)
where they unite to form zygotes. Each zygote forms a single
sporozoite which is liberated in the gut of the lobster.
The Schizogregarinida are more complicated through the intro-
duction of an asexual reproductive phase in the life history leading
Fig. 216. — Reproductive bodies in Sporozoa. .4, agametes of Barrouxia ornata;
B, C, sporocysts of same with exits of sporozoites; D, tailed sporocyst of Urospora
la'gidis; E, F, sporoblast of Ophryocystis mesnili with single and multiple spore cases;
G, spore of Ceratomyxa sp.; H, coccidian sporocyst with four sporozoites; J, spore
of Leptotheca agilis; K, type of Myxobolus spore; L, sporocyst of Crystallospora crys-
lalloides; M, N, coccidian sporocyst with two sporozoites. (After Schneider, Wasie-
Lewsky, Thelohan, Leger and Brasil.)
(539)
540 BIOLOGY OF THE PROTOZOA
to spread of the infection in the same host. Under the term " multi-
plicative reproduction" Doflein distinguishes this phase from the
reproduction following fertilization which he calls "propagative
reproduction." A relatively simple, but very interesting life cycle
is described by Leger in the case of Ophryocystis mesnili found in the
Malpighian tubules of the beetle Tenebrio molitor (Fig. 120, p. 231).
Here the asexual cycle is reduced to a process of equal division or
multiple division whereby a number of gamonts are formed. These
gamonts unite two by two in pseudo-conjugation. The nucleus of
each divides twice and one only of the resultant four nuclei becomes
the nucleus of a gamete. The two gametes become freed in a brood
chamber where they unite and in which the zygote gives rise to a
single sporoblast forming eight sporozoites.
In Schizocystis sipunculi and in Eleutheroschizon dubosqui the
asexual cycle is represented by a process of multiple unequal divi-
sion, the agametes being formed by a process of internal budding
(Fig. 119, p. 230).
In some cases, particularly in the cephalont gregarines, special-
ized sporoblast disseminating tubes known as sporoducts are formed
by the gametocysts. These are developed as ingrowths from the
cortical protoplasm which in the ripe gametocyst and under the
influence of moisture are evaginated as tubular processes through
which the sporocysts are emitted (Fig. 125, p. 240). In Gregarina
ovata they are quite short but reach a considerable length in other
species of Gregarina and in Clepsidrina.
Gamete dimorphism is highly variable in different species of greg-
arines. Isogametes are produced by some species of Monocystis,
anisogametes by others although here the differences are slight.
Well-marked anisogamy is found in Pterocephalis nobilis (Duboscq
and Leger) and in Schaudinnella henleae (Xusbaum), but in gen-
eral differences in gametes are much less pronounced than in the
Coccidiomorpha (Fig. 215).
The sporocysts in different species vary widely in form and in
sculpturing. The capsule is usually double, consisting of an inner
(endospore) and an outer (exospore) capsule, the latter sometimes
provided with short spines (Acanthospora) or long filaments (Cerato-
spora, Fig. 210). The typical number of sporozoites in a sporocyst
is eight, but this is not invariable. They are liberated by action of
gastric juices and emerge through preformed openings or by sepa-
ration of the two valves of the sporocyst. They creep out of the
endospore and make their way to epithelial cells within which the
first stages of their development occur.
Order 1. Eugregarinida Doflein Emend.
The great majority of known gregarines belong to this Order, the
agamous individuals living for long periods in the host before unit-
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 541
ing in couples to form isogamous or anisogamous gametes. Division
or asexual reproduction of any kind is unknown. Only exceptionally
are more, or less, than eight sporozoites formed in each sporocyst.
They are monocystid (single chambered) or polycystid in structure,
the former grouped in the Sub-order Haplocyta, the latter in the
Septata,
Order 2. Schizogregarinida Leger (1892).
The Schizogregarinida are parasites of the digestive tract and
appended organs of arthropods, annelids and tunicates. They
differ from the Eugregarinida in having an asexual or multiplicative
cycle, the sporozoite growing into an agamont either as an intra-
cellular or an extracellular parasite. Asexual reproduction occurs
by division, internal budding or by multiple division. The life
history, gamete formation and metagamic divisions of the zygote
vary widely and no characteristic difference marks the sporoblasts
from those of the Eugregarinida. Change of hosts is safely estab-
lished for only one type— the Porosporidae.
Sub-class II. COCCIDIOMORPHA Doflein.
While the Gregarinida are practically limited to invertebrate
hosts and are typically lumen-dwelling parasites, the Coccidio-
morpha are widely distributed in all groups of animals and are
typically intracellular parasites in all stages of growth and repro-
duction. Change of hosts with alternation of generations, while
by no means universal, is more common than in the Gregarinida.
Agamogony is characteristic of all types and leads to multiple
infection with frequently lethal results to the host due to the
destruction of multitudes of epithelial or blood cells, to thrombus
formation, or to the liberation of toxins. The life cycle varies
from relative simplicity to great complexity; gamonts become
differentiated into gametocytes which may be recognized as male
and female; gametes are anisogamous with rare exceptions; zygotes
give rise to sporoblasts which may (Coecidia) or may not (Herao-
sporidia) be protected by resistant membranes.
Order 1. Coccidiida Leuckart Em.
Sub-order 1. Eimeriina.
Typically epithelial-cell-dwelling parasites, with exceptions, how-
ever, in Cryptosporidium muris Tyzzer, Eimeria mitraria Laveran
and Mesnil and Orcheiobiiix herpobdellae Kunze, which are lumen-
dwelling coecidia.
Cellular differentiations are much less numerous than in the
gregarines; particularly is this true of the cortex. They are motion-
less forms without myonemes or other motile organs save flagella
542 BIOLOGY OF THE PROTOZOA
of the microgametes, and cellular processes are generally absent.
The endoplasm is usually well stored with products of metabolism,
some of which are so characteristic that they have received the name
of coccidin. They are all osmotic in nutrition, and infection is
always, so far as known, by the contaminative method through
the digestive tract. The sporozoite penetrates an epithelial or other
definitive cell, grows at the expense of the cell which it ultimately
destroys, and forms agametes while still intracellular. Cyclospora
karyolytica Schaudinn of the ground mole enters the nucleus of the
intestinal epithelial cell and as a karyozoic parasite completes its
life history.
Sub-order 2. Hemosporidia Danilewsky, em. Dofleix.
The Hemosporidia are Coccidia-like forms specifically adapted
for parasitic life in the blood, particularly of the erythrocytes,
although some forms become intracellular parasites of the inner
organs. Vertebrates of all classes— mammals, birds, reptiles,
amphibia and fish— are subject to infection by one type or other
and man is particularly susceptible, the malarial organisms causing
serious human diseases which in the tropics are frequently fatal.
Hemosporidia are minute forms, particularly in the agamous
stages during which they frequently show highly motile ameboid
stages, but in other cases they are more rigid and appear like the
hemogregarines. Contractile vacuoles are absent but cytoplasmic
non-contractile vacuoles, probably connected with nutrition, are
characteristic. Pigmented granules (Melanin) are also character-
istic and are formed as a product of hemoglobin break-down and
liberated only at periods of reproduction. Other products of
metabolism, in the form of toxins, may be liberated at the same
time.
Alternation of asexual and sexual generations is the rule, the
former taking place in the blood of vertebrates, the latter in the
digestive tract of some blood-sucking arthropod, insects in particu-
lar. The prevailing opinion is that arthropods were the primary
hosts and that parasitism in the blood is the result of adaptation.
One such adaptation, and a very essential one, is the absence of
protective capsules about the sporozoites. The latter are always
formed in the primary or invertebrate host and are transmitted to
the vertebrates at the time of drawing blood. A sporozoite pene-
trates an erythrocyte and grows to an agamont which forms mul-
tiple agametes after a definite interval; these agametes are liberated
into the blood where other erythrocytes are entered and the asexual
cycle is repeated. The parasites thus multiply rapidly by geometri-
cal progression until enough blood elements are destroyed to pro-
duce the first marked symptoms of the infection. Hegner and
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 543
Taliaferro (1924) estimate about 150,000,000 parasitized blood
elements at this time in the case of human malaria, all parasites, if
derived from a single infection, undergoing sporulation at practically
the same time and liberating their toxin simultaneously into the
blood. The pyrexia! attacks of chills and fever in human malaria
are thus accounted for. Ultimately the agametes develop into
gamonts which are usually easy to distinguish from the agamonts
and which are frequently differentiated into macrogametocytes and
microgametocytes. The gametocytes are taken with the blood
into the digestive tract of an invertebrate host (mosquitoes) where
the microgametes are formed and where union of gametes occurs.
The zygote, like that of some hemogregarines, is motile and makes
its way by gregariniform movement to the wall of the gut. These
motile zygotes, termed ookinets by Schaudinn, either enter the
epithelial cells of the gut or penetrate them and come to rest against
the inner membranes of the gut wall. Here a delicate sporocyst
membrane is formed and the amphinucleus divides repeatedly with-
out cytoplasmic division until a vast number of nuclei results. The
cytoplasm then divides to form as many naked sporozoites as there
are nuclei. The delicate sporocyst membrane is ruptured and the
sporozoites are liberated into the body cavity from which they are
passed into the blood of the vertebrate and the cycle repeated.
The life cycle of the hemosporidian thus has many points of
resemblance to that of the coccidian ; the same intracellular mode of
life, the same asexual generation and agamete formation, the same
formation of gametocytes and dimorphic, gametes. The micro-
gametes, however, have no flagella, as a rule, but move like spiro-
chetes and the zygote, as noted above, forms naked sporozoites.
In many cases, however, there is a reminiscence of sporoblast forma-
tion, when, after the amphinucleus has divided for a certain limited
number of times, the cytoplasm separates into a number of sporo-
zoite-forming centers. The resemblance to the coccidian would be
complete if such centers were provided with definite capsules.
The two families — Hemoproteidae and I'lasmodiidae — differ in
the site of asexual multiplication. In the former the schizogony
cycle occurs in endothelial cells, the merozoites ultimately entering
red blood cells of birds where they develop pigment and grow into
gametocytes. These are ingested by a biting fly (e. r/., Lynchia)
in which fertilization and sporozoite formation occur in the stomach
and body cavity. In Plasmodiidae schizogony occurs in the eryth-
rocytes of mammals and birds.
Sub-order 3. Babesiina.
These are parasites of red blood corpuscles of mammals which
differ from Hemosporidiina by the absence of melanin pigment.
544 BIOLOGY OF THE PROTOZOA
They cause epidemic diseases, particularly in cattle (e. (/., Texas
fever. East Coast fever, etc.). Here, as in Hemosporidiina, there
are two families— Babesiidae and Theileriidae, differing again in
the site of the asexual cycle. In Babesiidae the parasites reproduce
only in red blood corpuscles and only a limited number of division
products are formed. In Theileriidae schizogony occurs in endothe-
lial cells where a large number of merozoites are produced.
Order 2. Adeleida.
The members of this order differ from the Eimeriina in the
absence of flagellated gametes and fertilization of the Eimeria type.
A b
Fig. 217. Adelina dimidiata A. Schn. A, association of macrogametocyte and
smaller microgametoeyte. B, nuclear divisions in microgametoeyte and formation
< if gametic nuclei. X 1400. (From Dofiein after Shellack, Arbeit, aus d. kaiserlichen
Gesundheitsamt, courtesy of J. Springer.)
In place of this the sexual process resembles that of pseudo-conjuga-
tion in gregarines, without, however, the formation of a gametocyst
or a double set of gametes. Two gametocytes, one of which is
smaller, unite as in pseudo-conjugation. The microgametoeyte may
rest cap-like over one pole of the macrogamete (as in Adelea), or
laterally (as in Adelina, Fig. 217). The nucleus of the microgameto-
eyte divides one to three times and one of the products enters the
macrogamete and fuses with its nucleus. A rigid fertilization mem-
brane— oocyst- as in Eimeria, is formed in species of the sub-
order Adeleina, but in the sub-order Hemogregarina the oocyst is
delicate and like that of Plasmodium enlarges with growth and
development of the zygote. Species of Adeleina are intestinal para-
sites and infection is contaminative. Ilemogregarines are blood
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 545
parasites of vertebrates and are transmitted by leeches, ticks and
rnites (Fig. 218).
Fig. 218. — Type of Hemogregarines. A, Haemogregarina stepanowi; B and C,
Lankesterella ranarum. (Original.)
Class II. CNIDOSPORIDIA Doflein.
The Cnidosporidia form an independent stem of the Protozoa
with no recognizable affinities with other groups. They are ame-
boid and, in the adult stage, usually multinucleated, thus resembling
the Mycetozoa. Encapsulated sporoblasts and general mode of
life as parasites show some resemblance to the Telosporidia but the
life cycle is less complicated, sexual dimorphism and change of hosts
being absent. Unlike the Telosporidia reproduction does not
bring the life of an individual to an end but takes place more or
less continuously throughout the trophic stages, the sporoblasts
being carried about with the more or less active organism which
ultimately may become a relatively huge mass of spores.
Sporulation and sexual processes are entirely different from
analogous activities in the Telosporidia. In a typical form of
Myxosporidia in which the ameboid body is multinucleated and
the nuclei frequently dimorphic, sporulation begins with a peculiar
process of internal budding. An island of protoplasm is formed
about two of the nuclei, one of each kind if dimorphic, and this
island was termed a pansporoblast by Gurley. This gives rise to two
cells, each with 7 nuclei after the 2 nuclei have divided to form 14
nuclei which are now all alike. Two of these 7 nuclei disappear
with the formation of a bivalved capsule, 2 of them disappear
with the formation of peculiar nematocyst-like capsules termed
35
546 BIOLOGY OF THE PROTOZOA
polar capsules containing coiled threads, 1 is cast out of the1 cell
and 2 remain as the gametic nuclei which, sooner or later, unite to
form one, a process of fertilization frequently interpreted as autog-
amy (Fig. 164, p. 325).
Sexual processes in Cnidosporidia are so unlike analogous phe-
nomena in other Protozoa that they have long been a puzzle to
cytologists as well as matters of controversy to a long list of special-
ists (Debaisieux, Erdmann, Kudo, Parisi, Auerbach, Merrier,
Keysselitz, Schroder, Davis, et at.). Thanks to the splendid mono-
graph by Naville (1931) there is a fair prospect that the difficulties
will be solved and unanimity established although the phenomena
are quite diverse and, in comparison with other Protozoa, most
aberrant.
The cnidosporidian trophozoite is an ameboid organism with
multiple nuclei and may reproduce by division or by budding
(schizogony). There is no alternation of sexual and asexual cycles
but the sexual generation is contained in the protoplasm of the
trophozoite which develops from a sporozoite.
The activities of the sexual generation are confined to internal
buds or spore-forming centers termed pansporoblasts by Gurley
(1893). Two nuclei are present at the outset in these endogenous
buds and each undergoes division until 14 are present, 7 from
each of the original nuclei. The bud then divides into 2 cells,
each of which is a sporoblast and each contains 6 nuclei, 1 having
been cast out. Two of these 6 form capsules (sporocysts) , 2 form
nematocysts and 2 remain as pronuclei which subsequently fuse.
From this history it would appear that the endogenous bud
represents a zygote and the 2 original nuclei progamete nuclei.
Obviously the significance of these nuclei depends upon their pre-
vious history. The facts in such histories for different species have
been variously interpreted by earlier investigators and find a place
in Naville's interpretation. This is based upon his independent
study of five different species of Myxosporidia (Myxobolus guyenoti,
Chloromyxum leydigi, Myxidium incurvatum, Sphaeromyxa balbianii
and Sphaeromyxa sabrazesi). In all these species the early divisions
of the trophozoite nuclei indicate that there are two types as shown
by the mitotic figures. One type respresents germinal nuclei with
diploid number of chromosomes in the typical division figure. The
other type represents vegetative nuclei which divide by amitosis
(Naville) or by cryptomitosis (Reichenow). The germinal nuclei
after several divisions with the diploid number of chromosomes
undergo reducing divisions whereby the number of chromosomes is
reduced to one-half.
In Sphaeromyxa sabrazesi (Fig. 104, p. 325) the two original
nuclei of the pansporoblast are different in size. According to
Naville this results from two lines of germinal nuclei. In one line
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 547
which may be called male, the ultimate division gives rise to four
small nuclei, each with the reduced number of chromosomes. In
the other line — female — the last two divisions are heteropolar and
two so-called " polar bodies " are cast off as in metazoan eggs, leaving
one large nucleus with the haploid number. These two haploids,
large and small, do not fuse but each divides as stated above and
their products become equal in size. Finally the two germ nuclei
of the sporozoite unite and thus restore the diploid number charac-
teristic of the species (see also p. 324).
Fig. 219. — Types of Cnidosporidian spores. A, ATosema apis, after Fantham
and Porter; B, same, after Kudo; C, D, E, different Haplosporidia spores, after
Swellengrebel, Perrin, and Swarczewsky; F, Plistophora macrospora, after Loser
and Hesse; G, Plistophora longifilis, after Schuberg; H, Myxobolus toyamai, after
Kudo; ./, Stempellia magna, after Kudo: A', Mrazekia argoisi, after Leger and Hesse;
L, Nosema bombyces, after Stempel; M, Thelohania giardi, after Mercier. (From
Kudo.)
Essentially similar processes occur in Haplosporidia, in Actino-
myxida and in Microsporidia but in the latter the nuclei are small
and the chromosome history is indefinite.
Sporocysts are bivalved (Myxosporidia) or trivalved (Actino-
548 BIOLOGY OF THE PROTOZOA
myxida) or with a single valve (Microsporidia) and contain one or
more polar capsules which recall the stinging cells of the Coelenterata.
The threads of the capsules are probably hollow and are spirally
wound in the capsule from which they are evaginated under proper
conditions. Such threads, the function of which is entirely prob-
lematical, may be short or very long, reaching in some cases a length
many times that of the sporocyst. The germs can scarcely be called
sporozoites since they are not formed as a result of metagamic
divisions following fertilization. The term sporoplasm has been
used to distinguish the vital, living portion of the spore from the
other differentiated parts and will be used here to designate the
young germ up to the time of development into the trophic indi-
viduals. The spores are built on the same general plan of structure
(Fig. 219).
The form assumed by the trophozoites varies with the habitat.
Many of the Cnidosporidia are lumen-dwelling, and many are cell-
dwelling or tissue parasites. The free forms are characterized by
relatively complex organization with ectoplasm, endoplasm and
pseudopodia similar to amebae. The pseudopodia may be filiform,
lobose or lamellate and locomotion is frequently as active by ame-
boid movement as in many amebae. Tissue- or cell-dwelling forms
are active only in the young stages and according to Doflein may
appear in the following conditions: (1) Enclosed in cysts which are
formed for the most part by concentric layers of connective tissue
derived from the host, and an innermost layer formed by the
organism. Huge cysts resulting from association of parasites, and
easily visible to the naked eye, are formed in many cases. (2)
" Diffuse infiltration," a term used to indicate collections of parasites
between tissue cells where they may fill up cavities without doing
much or any harm to the host. (3) Intracellular parasites whereby
the usually minute organisms live at the expense of the cell host.
Order 1. Myxosporidia BCtschli.
The Myxosporida are the best known of the Neosporidia both
as to number of species and life histories. Of the 249 species listed
by Kudo (1919) all but 11 are parasitic in fishes, 5 have been found
in amphibia, 4 in reptiles, 1 in an insect and 1 in an annelid. They
are, therefore, characteristic fish parasites, where they occur both
as celozoic and as histozoic forms, never, according to Davis (1917),
in the digestive tract, but the free forms mainly in the gall and
urinary bladders, the tissue parasites mainly in the connective and
muscular tissues. The free forms produce no evident harmful effects
on the host but the tissue parasites are more disastrous, Myxobolus
pfeifferi, for example, causing costly epidemics amongst food fishes,
particularly in the barbel (Barbus barbus L.) of Europe.
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 549
The free or eelozoic forms are the most generalized in structure
and the tissue parasites are generally regarded as having been
derived from them by adaptation (Auerbach, 1910; Doflein, 1916;
Davis, 1917, et ah). They are somewhat more numerous than the
tissue-dwelling forms, Kudo enumerating 125 species of the former
and 1 14 of the latter while 3 species are apparently transitional and
7 of unknown habitat. The free forms often show a remarkable
resemblance to amebae; ectoplasm and endoplasm are usually
differentiated, the former, as in some amebae, forming a continuous
cortical zone about the organism or, as in other types of amebae,
evident in certain regions only. It is occasionally provided with
bristle-like processes and the pseudopodia of different types are
invariably derived from it (Davis).
The endoplasm is more fluid than the ectoplasm, contains many
nuclei and metaplasmic bodies in the form of fat globules, pigment
granules and crystalline bodies, in some cases embedded in struc-
tures which under the name of spherules (Davis) are sometimes so
abundant as to give a characteristic appearance to the organism
(Fig. 220).
Like other Sporozoa, the Myxosporidia are highly prolific and
adaptations to this end are well marked. Asexual reproduction
occurs by simple division or by multiple division (plasmotomy)
and by budding. Exogenous budding described by Cohn (1896) in
My.vidiiim lieberkuhni is regarded by Davis (1916) as abnormal and
without significance in reproduction but internal or endogenous
budding occurs in Sinuolinea dimorpha Davis, where free cells are
formed about nuclei in the endoplasm. These cells, called "gem-
mules" by Davis, escape from the parent organism and develop into
individuals (Fig. 121, p. 232).
Propagative reproduction involves the formation of spores and
the nearest approach to sexual processes to be found in the Cnido-
sporidia. The process has been described by various observers and
the general agreement of these descriptions indicates a common
plan throughout the group. Schroder's account of sporulation in
Sphaeromy.va sabrazesi Laveran and Mesnil may be selected as an
example for the entire Order. This form is parasitic in the sea-horse,
Siphonostoma rondeletii, and like many others has dimorphic nuclei
distinguishable by size and structure. Small areas become differ-
entiated within the endoplasm and contain two nuclei, one of each
type. These areas, the so-called pansporoblasts, are the mother-
cells of the spores. Each nucleus divides in such order that seven
nuclei arise from each; the mother-cell then divides into two cells
which are destined to form two spores. Each of these cells has
7 nuclei, 1 of which is cast out as a "reduction" nucleus; 2 are
involved in the formation of the two valves of the spore and ulti-
mately disappear; 2 are connected with the elaboration of the polar
550
BIOLOGY OF THE PROTOZOA
capsules and similarly disappear and 2 remain as germinal nuclei.
It is generally assumed that these 2 nuclei are descendants of the
original dimorphic nuclei of the trophozoite and observations by
Schroder (1910), Davis (1916), Erdmann (1911 and 1917), Naville
Fig. 220. — Leplotheca scissura, vegetative individuals with well-developed spherules.
(After Davis.)
(1931) leave little doubt that they ultimately fuse in autogamous
fertilization (p. 324).
The spores which differ from sporoblasts of the Telosporidia in
that, they are not formed as a result of fertilization are the most
characteristic structures of the Myxosporidia and are much more
highly differentiated than are sporoblasts of the former group. They
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 551
conform to the same general plan of structure throughout but differ
in axial relations and in sculpturing, as well as in number and time
of appearance. The spore capsule always consists of two valves
which are independently developed and come together with a med-
ian suture dividing the spore into right and left halves. In different
types the spores may be elongated in the plane of the suture or at
right angles to it. The polar capsules with their coiled threads
indicate what most authorities regard as the anterior end although
spores of the Myxidiidae have thread capsules at each end of the
elongated spore (Fig. 164, p. 325). Lateral processes, posterior spines
and external sculpturing of various types distinguish the different
genera and species and afford a means of classification.
Order 2. Actinomyxida Stolc.
These are Cnidosporidia about which little is known beyond the
process of sporulation. In its fully grown condition the entire
body may be interpreted as one pansporoblast which is surrounded
by a membrane, and which usually produces eight spores, the mem-
branes of which are usually triradiate and drawn out into elaborate
spines. Each spore has three polar capsules containing distinct
protrusible filaments.
The processes leading to the formation of spores involve fertil-
ization phenomena of a characteristic type. They are essentially
similar to those of the Myxosporidia but differ in some impor-
tant details. A plasmodial stage appears to be absent or rep-
resented by a binucleate amebula only, which develops into a
spore. The two nuclei divide and form 4 cells, 2 of which disappear
with the formation of a membrane within which the other 2 cells
lie. Each of these divides, forming 4, 2 of which continue to divide
rapidly until 8 are formed, while the other 2 remain large and
undivided the two-celled membrane now containing 8 small and
2 large cells. Ultimately the two large nuclei begin to divide in
turn until 8 products result and 16 cells, regarded by Caullery
and Mesnil (1905) and by Ikeda (1912) as gametes, lie free in the
cyst. The two sets of gametes differ slightly in nuclear size and in
staining capacity and unite 2 by 2 to form 8 zygotes. The nucleus
of each zygote now divides until 6 small nuclei and 1 large one result,
the large one destined to form a mass of sporozoites. The 6 small
ones arrange themselves in such a manner as to form 3 shell-forming
cells, while 3 of them lie within and form 3 polar capsules. The
germ-forming cell is not enclosed by the spore-forming cells but lies
outside of it and peripherally in the pansporoblast. It divides
repeatedly until 8, 32 or many sporozoites result (Fig. 221).
The Actinomyxida are parasites of annelids and sipunculids and
the spores are invariably triradiate. The anchor or star-form
552
BIOLOGY OF THE PROTOZOA
processes of the capsule are regarded by Doflein as supports in
floating, evidence for which is given by Kofoid's observation of
these spores in plankton.
Fig. 221. — Spores of Actinomyxida. ^4, Hexaetinomyxon psammoryctis, after
Stole.; B, Sphaeractinomyxon stolgi; C, Triactinomyxon ignotum; D, same, spore-bearing
part enlarged, after Leger; E, Synactinomyxon tubificis. (After Caullery and Mesnil.)
Order 3. Microsporidia Balbiani.
Probably because of their minute size the organisms included in
this Order are incompletely known and many points of structure
and of life history are still unknown or controversial. They are
practically all cell parasites which enter the host by way of the
digestive tract from which they may spread to all tissues of the
body, causing epidemics not only in fish but, economically more
important, costly epidemics in silkworms (Nosema bombyces Naeg.)
and honey bees (Nosema apis Zander). Pseudopodia and ameboid
movement are rarely observed (Nosema marionis Thel). Inter-
mediate hosts are unknown.
Agamous reproduction is well established through the observa-
tions of many investigators. The agametes are small, uninucleate,
and usually with indefinite outlines which scarcely delimit them
from the host cell protoplasm; they may have one or several nuclei,
and multiply actively by simple division resulting frequently in
chain formation through successive nuclear divisions and delayed
cell division (Fig. 222). As a result of such agamous reproduction
all of the tissues of the host may become infected and myriads of
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 553
tissue cells destroyed. In many species tumor-like masses are
formed in which the organisms are surrounded by a membrane
derived from the host and are thus encapsulated; in other species
such membranes are absent. In the majority of cases spread of
the infection in the same host comes to an end with sporulation,
Fig. 222. — Stempellia magna, life cycle. A, Developmental stages of young
amebula from spore S; B, stage of nuclear increase; C, formation of sporont; D,
formation of a single spore; E, formation of two spores; F, formation of four spores;
O, of eight spores; H, development of uninucleated spore with polar capsule. (After
Kudo.)
but in some species renewed infection is brought about by the
action of the digestive fluids on spores formed in the same organism
(Kudo).
Multiple endogenous budding, or fragmentation of the tropho-
zoite into numerous binucleate agametes, is described for some
forms (Debaisieux, 1920) and these, as in Telosporidia, ultimately
• ).)4
BIOLOGY OF THE PROTOZOA
give rise to the speculating individuals. .The phenomena of specula-
tion diti'er widely but there is still much uncertainty in the diff rent
accounts at hand. Id some cases the trophozoites are said to pro-
duce pansporoblasts as in Myxosporidia during the continued vege-
tative life of the individual (Polysporea). Such cases, included
formerly under the name Blastogenea, are regarded as very doubtful
Fig. 223. — Thelohania legeri, life cycle. A, Early stages of sporozoite after leaving
the spore S; B, formation of binucleated individuals; C, repeated binary division;
D, fusion of the two nuclei to form the sporont; E to H, nuclear and cell divisions
to form eight sporoblasts each of which forms one spore. (After Kudo.)
by Doflein. In other cases the trophozoite (pansporoblast?) breaks
up into numerous sporulating cells, each of which produces one or
more spores (Oligosporea) and in still other cases the entire indi-
vidual forms a single spore without pansporoblast formation (Mono-
sporea). The absence of pansporoblasts in such cases is regarded
as evidence of extreme adaptation on the part of the exclusively
cytozoic parasites (Nosema species).
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 555
The spores on the whole are less complex than those of the Myxo-
sporidia. They are small and ovoidal or bean-shape and rarely
(TelomyxahegeT and Hesse, 1910) with more than one polar capsule,
in some cases without any. The capsules and threads are invisible
or very difficult to see in the living spore (hence cryptocysts), but
are demonstrable upon treatment with alkalies. The spore capsule
is bivalved in some but consists of a single piece in other species.
The history of spore-formation agrees in the main with that of the
Myxosporidia but authorities disagree as to details and convincing
proof is yet to be demonstrated. Fertilization processes have been
described by Mercier (1908, 1909) whereby two isogametes of Thelo-
hania giardi fuse to form the pansporoblast. Autogamous union
of nuclei prior to spore formation and not, as in Myxosporidia, in
the later sporoplasm, has been described by Debaisieux (1913, 1915)
in species of Thelohania and Glugea.
The life history of Stempellia magna as given by Kudo (1924) is
typical of the Microsporidia (Fig. 222). The polar filament of the
spore (S) is extruded when the spore reaches the mid-gut of its
culicine host; the uninucleate sporoplasm creeps out of the opening
made by the cast-off filament, enters a fat cell and becomes an
agamont and reproduces by division (J). The products ultimately
become multinucleated with from four to eight nuclei (B); the
organisms then breaking up into binucleated cells, the nuclei of which
fuse after discarding some chromatin (0). This is identified as a
sporont which may become transformed into a single spore (D), or
it may divide into two (E), four (F) or eight (G) sporoblasts, each
of which forms a single spore after chromidia formation and recon-
struction of small nuclei (H, I), some of which take part in the
formation of the capsular thread. A more simple life history is
shown by Thelohania legeri according to Kudo (Fig. 223).
Class III. ACNIDOSPORIDIA Cepede.
The Sarcosporidia are parasites of vertebrates, particularly mam-
mals, in which the ultimate seat of parasitism is the muscular tissue.
There is but one genus — Sarcocystis— with several species in pigs
(S. miescheriaria Kiihn, 1S65, forming "Miescher's tubules"), in
sheep (S. tenella Railliet, 1886), in cattle (S. blanchardi Doflein,
1901), in mice (S. muris Blanchard, 1885), in opossums (S. darlingi
Brumpt, 1913), in monkeys (S. kortei Castellani and Chalmers,
1909) and in man (S. lindemanni Rivolta, 1878). A species from
birds was described by Stiles (1893) under the name of S. rileyi.
Sarcosporidia have been studied by a host of observers and an
almost equal number of interpretations has been the result. The
best-known species is S. maris from the mouse in which, beginning
with Th. Smith's (1901) inoculation experiments by feeding infected
556 BIOLOGY OF THE PROTOZOA
tissues to mice, the young stages and their development are now
known. Observations made by this method of study, particularly
by Erdmann (1910, a, b, c, and 1914), and by Crawley (1914 and
1916) and Marullaz (1920) permit of a tentative life history of
S. muris as follows:
Infection occurs by eating infected tissues, or, as Negre (1907)
showed, by eating contaminated feces. The germs, regarded by
Erdmann (1914) as sporozoites, enter the epithelial cells within an
hour to an hour and a half (Crawley and Marullaz). Here, accord-
ing to Crawley (1914 and 1916), they develop directly into gameto-
cytes which are sexually differentiated. The microgametocytes
become practically all nucleus the chromatin of which is distributed
in groups of granules about the periphery; each group forms a
single microgamete, the spermatozoids being arranged about the
periphery very much like the microgametes of a coccidian. The
macrogametocytes retain most of their cytoplasm and become
macrogametes. The latter are fertilized by a microgamete. The
zygotes then give rise to a large number of products (the sporoblasts
of Erdmann) which may enter the musculature, or may possibly
pass out with the feces (Crawley). Here there is a gap in the
accounts of the life history but ultimately the muscles are invaded
and asexual multiplication results in a number of sporozoites
(Erdmann) groups of which are massed together and kept in place
by membranes formed by the host. Upon reinfection these develop
again to gametocytes.
It is evident that if this account of the life cycle, the important
sexual phases of which are supplied by Crawley, is confirmed by
further studies, the Sarcosporidia should not be retained in the
Cnidosporidia but, as Crawley suggests, should be placed with the
Coccidiomorpha. Until such confirmation is forthcoming the older
arrangement is retained.
Sub-phylum SPOROZOA Letckart.
Class I. TELOSPORIDIA Schaudinn
Sub-class 1. Gregarinina (Gregarinae Doflein)
Order 1. Eugregarixida Doflein
Sub-order 1. Haplocyta Lankester
Family 1. Monocystidae Stein
Family 2. Zygocystidae Bhatia
Family 3. Diplocystidae Bhatia
Family 4. Schaudinnellidae Bhatia
Family 5. Rhynchocystidae Bhatia
Family 6. Stomatophoridae Bhatia
Family 7. Aikinetocystidae Bhatia
Family 8. Syncystidae Bhatia
Family 9. Ganymedidae J. Huxley
Family 10. Urosporidue Woodcock
Family 11. Lecvdinidae Kamm
Family 12. Allantocystidae Bhatia
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 55<
Class I. TELOSPORIDIA Schaud i \ \
Sub-class 1. Gregarinina (Gregarinae Doflein)
Order 1. Eugregarinida Doflein
Sub-order 2. Septata
Family 1. Stenophoridae Leger and Duboscq
Family 2. Gregarinidae Labbe
Family 3. Didymophyidae Leger
Family 4. Dactylophoridae Leger
Family 5. Actinocephalidae Leger
Family 6. Menosporidae Leger
Family 7. Stylocephalidae Ellis
Family S. AcantKosporidae Leger
Order 2. Schizogregarinida Leger
Sub-class 2. Coccidiomorpha Doflein
Order 1. Coccidiida Leuckart
Sub-order 1. Eimeriina
Crytosporidiidae Poche
Selenococcidiidae Poche
Eimeriidae Leger
Caryotrophidae Llihe
Aggregatidae Labbe
Lankesterellidae Reichenow
Ha emosporidiin a
Haemoproteidae Doflein
Plasmodiidae
Bahesiina
Babesiidae Poche
Theileriidae Wenyon
Family 1.
Family 2.
Family 3.
Family 4.
Family 5.
Family 6.
Sub-order 2.
Family 1.
Family 2.
Sub-order 3.
Family 1.
Family 2.
Order 2. Adeleida Leger
Sub-order 1. Adeleina
Family 1.
Family 2.
Family 3.
Family 4.
Sub-order 2.
Family 1.
Family 2.
Family 3.
Adeleidae Leger
Klossiellidae Wenyon
Dobellidae Wenyon
Legerellidae Wenyon
Haemogregarina
Haemogregarinidae
Hepatozoidae
Karyolysidae
Class II. CNIDOSPORIDIA Doflein
Order 1. Myxosporidia Blitschli
Sub-order 1. Eurysporina Kudo
Family Cer atomy xidae Doflein
Sub-order 2. Sphaerosporina Kudo
Family 1. Chloromyxidae Thelohan
Family 2. S phaerosporidae Davis
Sub-order 3. Platysporina Kudo
Family 1. Myxidiidae Thelohan
Family 2. Myxosomatidae Poche
Family 3. Myxobolidae Thelohan
Family 4. Coccomy xidae L£ger and Hesse
Order 2. Actinomyxida Stole
Family 1. Haploactinomyxidae Granata
Family 2. Euactinomy xidae Granata
558 BIOLOGY OF THE PROTOZOA
( 'lass II. CNIDOSPORIDIA Doflein
Order 3. Microsporidia Balbiani
Sub-order 1. Monocnidea Leger and Hesse
Family 1. Nosematidae Labbe
Family 2. Coccosjjoridae Kudo
Family 3. Mrazehiidae Leger and Hesse
Sub-order 2. Dicnidea Leger and Hesse
Family Telomyxidae Leger and Hesse
Class III. ACNIDOSPORIDIA Cepede
< >rder 1. Sarcosporidia Balbiani
Order 2. Haplosporidia Liihe
KEY TO SUBDIVISIONS AND GENERA OF SPOROZOA.
1. Spores with thread capsules Class 2. Cnidosporidia
Spores without thread capsules 2
2. Reproduction ends life of parent organism
Class 1. Telosporidia
Reproduction during continued vegetative
life Class 3. Acnidosporidia
Class I. TELOSPORIDIA Schaudinn
1. Typically celozoic parasites .. Sub-class I. Gregarinina
Typically cytozoic or hematozoic para-
sites Sub-class 2. Coccidiomorpha
(Exception in Cryptosporidium)
Sub-class 1. Gregarinina (Gregarinae Doflein).
1. Sporozoites develop into sporonts; no
asexual cycle Order 1 . Eugregarinida
Sporozoites develop into agamonts; with
asexual cycle Order 2. Schizogregarinida
Order 1. Eugregarinida Doflein
1. Typically with protomerite and deutomer-
ite Sub-order 2. Septata
Individuals of one chamber; no protomer-
ite Sub-order 1. Haplocyta
Sub-order 1. Haplocyta Lankester
Key to Families
1. Sporocysts alike at the two poles La
Sporocysts with dissimilar poles 8
la. Sporocysts without spines or processes. . . 2
Sporocysts with spines at each end
Family 8. Syncystidae
2. Trophozoites without attaching organs. . . 3
Attaching organs present 4
3. Trophozoites solitary without free myo-
neme threads Family 1. Monocystidae
Trophozoites always in pairs: often with
free myoneme threads or longitudinal
striations Family 2. Zygocystidae
1. Trophozoites with epimerites .">
Trophozoites with suckers <>
5. Individuals solitary 7
Individuals associated in masses . Family 3. Diplocystipae
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 559
Sub-order 1. Haplocyta Lankester
Key to Families
6. Trophozoites unbranehed — 1 terminal
sucker Family 6. Stomatophoridae
Trophozoites branched, each branch with
terminal sucker Family 7. Aikinetocystidae
7. Male and female gametes well differen-
tiated Family 4. Schaudinellidae
Gametes similar Family 5. Rhynchocystidae
8. Sporonts united by ball and socket joint
Family 9. Ganymedidae
Sporonts without ball and socket joint. . . 9
9. Sporocysts without funnel at one end .... 10
Sporocysts with funnel at one end
Family 10. Urosporidae
10. Sporocysts tetraedral Family 13. Tetraedrocystidae Baur
Sporocysts oval or spindle-shape 11
1 1 . Sporocysts oval, one pole thickened
Family 11. Lecudinidae
Sporocysts spindle-shape, one side thick-
ened Family 12. Allantocystidae
Si b-order Haplocyta Lank. Homopolaridea.
Family 1. Monocystidae Aut.
1 . Trophozoites spherical or oval 2
Trophozoites much elongated 3
2. Trophozoites ovoid, often with button at
anterior end Genus Monocystis Stein
Trophozoites spherical, no protuberances
Genus Apolocystis Cognetti
3. Trophozoite elongated; like nematode
worm Genus Xenmtocystis Hesse
Trophozoite elongated: one end swollen;
club-shape Genus Rhabdocystis Boldt
Family 2. Zygocystidae Bhatia 1930.
1 . Association tete-a-tete ; long posterior fila-
ments Genus Zygocystis Stein
Association otherwise 2
2. Association side by side; bod}' striations
distinct Genus Pleurocystis Hesse
Conjugants form cross; head of one at-
tached to center of the other. . . .Genus Enterocystis Zwetkov
Family 3. Diplocystidae Bhatia 1930.
1. Trophozoites spherical or oval Genus Diplocystis Kunstler
Trophozoites small, spatulate Genus Lankesteria Mingazzini
Family 4. Schaudinnellidae Bhatia.
One genus with epimerite or free as male and
female gamonts Genus Schatidinnella Nusbaum
Family 5. Rhynchocystidae Bhatia 1930.
One genus, with metabolic epimerite. .Genus Rhynchocystis Hesse
Family 6. Stomatophoridae Bhatia 1930.
1. Trophozoites round or oval 2
Trophozoites ellipsoid or star-shaped 6
2. Suckers; without filaments or pseudo-
podium 3
Suckers; with filaments or pseudopodium . 5
560 BIOLOGY OF THE PROTOZOA
Family 6. Stomatophoridae Bliatia 1930.
3. Trophozoites sub-spherical or cup-shape . . 4
Trophozoites spherical to ovoid; anterior
sucker with button Genus Stomatophora Drzewecki
4. Sucker with myonemes directed towards
convex side Genus Craterocystis Cognetti
Sucker with smooth walls Genus Alberticella Cognetti
5. Mobile sucker with pseudopoclium and fila-
ments Genus Choanocystis Cognetti
Mobile sucker with fringe of filaments, no
pseudopodium Genus Choanocystoid.es Cognetti
6. Trophozoites star-shape Genus Astrocystella Cognetti
Trophozoites ellipsoidal — suctorial depres-
sion anterior Genus Beccaricystis Cognetti
Family 7. Aikinetocystidae Bhatia 1930.
One genus in celomic cavities of Eutyphoeus
Genus Aikinetocystis Gates
Family 8. Syncystidae Bhatia 1930.
One genus, sp. S. mirabilis in body cavity of
Nepa cinerea Genus Syncystis A. Schn.
Family 9. Ganymedidae J. Huxley 1910.
One species G. anaspidis J. Huxley, in gut of
Ariaspis tasmaniae Genus Ganymedes J. Huxley
Family 10. Urosporidae (1) Woodcock, 1906.
1. Cross-section of epispore, circular 2
Cross-section of epispore, triangular
Genus Pterospora Rac. and Labbe
2. Sporocysts without caudal filaments 3
Sporocysts with 1 or 2 caudal filaments .... 4
3. Sporocysts with funnel at one pole,
rounded at other Genus Gonospora (2) A. Schn.
Sporocysts with funnel at one pole, flat-
tened at other Genus Lithocystis Giard
4. Sporocysts with funnel at one end, one
caudal filament Genus Urospora A. Schn.
Sporocysts with two rigid, diverging, cau-
dal filaments Genus Ceratospora L6ger
Family 11. Lecudinidae Kamm. (Doliocystidae Labbe).
One genus, species L. pellucida (Doliocystis) —
gut of Nereis Genus Lecudina Mingazzini
Family 12. Allantocystidae Bhatia 1930.
One genus, species A. dasyhelei, gut of larva
of Dasyhelea Genus Allantocystis Keilin
Synonyms
1. Urosporidae = Choanosporidae Dogiel
2. Gonospora = Cystobia Ming.; Diplodina \Yoodcock; Kalpidiorhynchus
Cunningham
3. Lecudina = Diliocystis Leger; Ophiodina Ming.
Sub-order 2. Septata.
1. Epimerite simple, no hooks or processes. . 2
Epimerite complex, on long necks or with
hooks and processes 4
MORPHOLOGY AXL) TAXONOMY OF THE SPOROZOA 56]
2. Epimerite a mere knob; sporocysts with
definite suture Family 1. Stenophoridae
Leger and Dub.
Epimerite variable; sporocysts without
suture 3
3. Satellites without septum Family 3. Didymophyidae Leger
Satellites with septum Family 2. Gregakinidae Labbe
4. Sporocysts without bristles or spines 5
Sporocysts with bristles at ends or equator
or both Family 8. Auanthosporidae Leger
5. Sporocysts brown or black; in chains
Family 7. Stylocephalidae Ellis
Sporocysts colorless 6
6. Sporocysts crescentic, smooth; epimerite
on long protrusible neck Family 6. Menosporidae Leger
Sporocysts elongate, biconical, cylindrical
or ellipsoidal 7
7. Epimerite asymmetrical, with linger form
processes Family 4. Dactylophoridae Leger
Epimerite symmetrical Family 5. Actinocephalidae Leger
Family 1. Stenophoridae Leger and Duboscq 1904.
Epimerite rudimentary Genus Stenophora Labbe
Epimerite a button on short conical neck
Genus Otocephalus Soli.
Epimerite a button on small spherical pro-
tomerite Genus Grenoblia Hasselmann
Family 2. Gregarinidae Labbe 1899.
1. Gametocysts with sporoducts 2
Gametocysts without sporoducts 4
2. Solitary individuals; epimerite a globular
knob
1. Epimerite on short neck Genus Leidyana Watson
2. Epimerite on long neck Genus Gryllotalpia Hasselmann
Individuals associated 3
3. Protomerite present in young stages only
Genus Gamocystis Leger
Protomerite in all stages; posterior half
yellow-green Genus Gregarina Dufour
4. Individuals solitary 5
Individuals associated 6
5. Protomerite temporary; body spherical,
gray Genus Sphaerocystis Leger
Protomerite in all stages; posterior half
yellow-green Genus Cnemidospora Schneider
(i. Individuals associated in pairs 7
Individuals associated in groups of 2 and
more 10
7. Endoplasm orange-yellow in color. .Genus Hyalospora Schneider
Endoplasm not colored 8
8. Sporocysts prismatic Genus Euspora Schneider
Sporocysts spherical or ovoidal 9
9. Sporocysts ovoid, with dark equatorial line
Genus Frenzelina Leg. and Dub.
Sporocysts spherical Genus Tettigonospora Smith
36
562 BIOLOGY OF THE PROTOZOA
Family 2. Gregarinidae Labbe 1899.
10. Individuals in groups of 2 or 3; epimerite
a forked style Genus Uradiophora Mercier
Individuals in groups of 2 to 12; epimerite
a small papilla Genus Hirmocystis Labbe
Family 3. Didymophyidae Leger 1892.
One genus— D. gigantea Stein Genus Didymophyes Stein
Family 4. Dactylophoridae Leger 1892.
1. Protomerite long, neck-like Genus Trichorhynchus Schneider
Pro torn erite flattened; epimerite long fila-
ments 2
2. Protomerite symmetrical ; drawn out in two
processes Genus Nina Grebnecki
Protomerite asymmetrical Genus Echinomera Labb6
Family 5. Actinocephalidae Leger.
1 . Sporonts with one or more septa 2
Sporonts without septum— protomerite
early lost, deutomerite alone Genus Schneideria
2. Sporonts with one septum 3
Sporonts with several septa
1. Epimerite lobed Genus Rhynchocystis Keilin
2. Epimerite simple Genus Taeniocystis Leger
3. Septum convex towards protomerite 4
Septum flat 6
4. Protomerite with small epimerite bearing
6 long filaments Genus Bothriopsides Strand
Epimerite without long filaments 5
5. Protomerite dilated anteriorly and massive
Genus Legeria Labbe
Protomerite a circular, shallow disc . Genus Coleorhynchus Labbe
6. Epimerite simple styliform process 7
Epimerite without style 13
7. Epimerite finger-form, conical or lance-
shape 8
Styliform process arises from epimerite
base 10
8. Epimerite finger-form changing to flat
button Genus Steinina
Leger and Duboscq
Epimerite conical or lance-shape 9
9. Epimerite a simple sharply-pointed cone
Genus Stylocystis Leger
Epimerite lance-shape Genus Pyocephalus Schneider
10. Epimerite a tuft of bristles on a long neck
Genus Geneiorhynchus Schneider
Epimerite without long bristles 11
11. Epimerite discoid with style from center. . 12
Epimerite spiny, globular with long apical
style Genus Beloides Labbe
12. Epimerite long thread-like Genus Pyxinia Hammerschmidt
Epimerite thick disc with milled border
Genus Asterophora
13. Epimerite on long neck-like process of pro-
tomerite 14
Epimerite on short neck, or sessile, usually
with hooks 15
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 563
Family 5. Actinocephalidae Leger.
r Genus Agrippina
14. Epimerite button-like with 8 to 10 I spores ellipsoid
finger-form processes | Genus Hoplorhynchus ^
{ spores biconical
Epimerite cushion-like with short teeth
Genus Phialoides Labbe
15. Epimerite flat sessile, with 8 to 10 short,
sharp spines Genus Actinocephalus Stein
Epimerite globular or swollen 16
16. Epimerite like half-open umbrella. . .Genus Sciadiophora Labbe
Epimerite globular, fluted, or with collar. . 17
17. Epimerite with collar, on short stalk
Genus Discorhynchus
Epimerite without collar; fluted or smooth . 18
18. Epimerite depressed anteriorly or flat. ... 19
Epimerite globular, not depressed. .Genus Amphoroides Labbe
19. Epimerite flat, fluted Genus Anthorhynchus Labbe
Epimerite spheroidal, depressed anterior. . 20
20. Fluting confined to concavity Genus Amphorocephalus Ellis
Fluting deep, on sides Genus Stictospora Leger
Family 6. Menosporidae Leger 1892.
One genus— M. polyacantha Leger .... Genus Menospora
Family 7. Stylocephalidae Ellis 1912 (Stylorhynchidae Labbe)
Includes Stylorhynchus pre-occup.; changed to
Stylocephalus Ellis
1. Epimerite on long slender neck 2
Epimerite sessile or on short neck 3
2. Spores oval Genus Sphaerocystis Labbe
Spores hat-shape Genus Stylocephalus Ellis
3. Epimerite a crateriform disc with club-
shaped processes Genus Lophocephalus Labbe
Epimerite a lance-shaped papilla on short
neck Genus Cystocephalus Schneider
Family 8. Acanthosporidae Leger 1892.
1. Sporocysts with polar but without equa-
torial spines Genus Corycella Leger
Sporocysts with both polar and equatorial
spines 2
2. Sporocysts with 2 rows of equatorial spines
Genus Cometoides Labbe
Sporocysts with 1 row of equatorial spines . 3
3. Epimerite a conical papilla without proc-
esses Genus Acanthospora Leger
Epimerite spheroidal with 5 to 10 finger-
form processes Genus Ancyrophora Leger
Order 2. Schizogregarinida Leger 1892.
1. Sporozoites in sporocysts less than 8 2
Sporozoites in sporocysts 8 4
2. Sporozoites in sporocysts 4; many sporo-
cysts Genus Selenidium Giard
Sporozoites in sporocysts 1 3
3. Trophozoite coiled in flat spiral .... Genus Spirocystis
Leger and Duboscq
Trophozoite not coiled; elongate (2 hosts)
Genus Porospora Schneider
564 BIOLOGY OF THE PROTOZOA
Order 2. Schizogregarinida Leger 1892.
4. Sporocysts less than 8 5
Sporocysts 8 or more 7
5. One sporocyst in gametocyst 6
Two sporocysts in gametocyst Genus Mattesia Naville
6. Schizogony in lumen Genus Ophryocystis Schneider
Schizogony, intracellular Genus Merogregarina Porter
7. Intracellular throughout most of cycle. ... 8
Celozoic throughout 9
8. With 16 sporocysts Genus Lipotropha Keilin
With more than 16 sporocysts Genus Mensbiera Bogolavlensky
9. Trophozoite elongate, worm-like. . Genus Schizocystis Leger
Trophozoite globular Genus Cdulleryella Keilin
FAcutheroschizon mesnili not known in sexual cycle.
Sub-class 2. COCCIDIOMORPHA.
1 . Gametocytes develop independently; many
microgametes Order 1 . Coccidiida
Gametocytes associated in pseudo-conju-
gation; few microgametes Order 2. Adeleida
Order 1. Coccidiida (Coccidia Leuckart).
1 . Zygote and sporoblasts protected by resis-
tant unchanging sporocyst capsules
Sub-order 1. Eimerilna
Zygote with delicate, growing sporocyst
Sub-order 2. Haemosporidhna
Order 2. Adeleida.
1. Zygotes with tough, resistant sporocyst;
non-motile Sub-order 1 . Adeleina
Zygotes ^ath delicate sporocysts; motile
Sub-order 2. Haemogregarinina
Sub-order 1. Eimeriina.
Key to Fmn i lies
1. Growing and multiplicative phases cy to-
zoic 2
Growing and multiplicative phases celo-
zoic _■ ■ • • 5
2. Trophozoite and microgametocyte divide
into secondary forms (Schizontocytes)
Family 4. Garyotrophidae
Trophozoite divides into agametes (mero-
zoites) . . . 3
3. Zygotes develop directly into sporozoites
(asporocystid) Family 6. Laxkesterellidae
Zygotes divide to form sporoblasts 4
4. Schizogony in one type of host, sporogony
in another Family 5. Aggregatidae
Schizogony and sporogony in the same host
Family 3. Eimeriidae
5. Schizonts and gametocytes intracellular
(cytozoic) Family 2. Selexococciidae
All stages celozoic Family 1. Gryptosporidiidae
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 565
Family 1. Cryptosporidiidae Poche 1913.
One genus — C. muris Tyzzer 1907. . . .Genus Cryptosporidium Tyzzer
Family 2. Selenococcidiidae Poche 1913.
One genus — S. intermedium Leger and Du-
boscq 1909 Genus Selenococcidium
Leger and 1 )uboscq
Family 3. Eimeriidae Poche 1913.
1. The zygote forms sporozoites directly (1
sporocyst) 2
The zygote forms more than 1 sporocyst . . 3
2. Sporocyst and oocyst without micropyle
Genus Pfeifferinella Wasielewski
Sporocyst and oocyst each with micropyle
Genus Caryospora L6ger
'■]. The zygote forms 2 sporocysts 4
The zygote forms more than 2 sporocysts . 6
4. Each sporocyst contains 2 sporozoites
Genus Cyclospora A. Schneider
Each sporocyst contains more than 2 sporo-
zoites 5
5. Each sporocyst has 8 sporozoites. . .Genus Dorisiella Ray
Each sporocyst has 4 sporozoites. . .Genus Isospora ( I ) A. Schneider
G. The zygote forms 4 sporocysts 7
The zygote forms many sporocysts 11
7. Each sporocyst has 2 sporozoites 8
Each sporocyst has ±30 sporozoites. Genus Angeiocystis Brasil
8. Sporocysts ellipsoidal or serrated at one
end Genus Eimeria (2) A. Schneider
Sporocj'sts not ellipsoidal 9
9. Sporocysts without neck at one end 10
Sporocysts with neck at one end. . Genus Jarrina Leger and Hesse
10. Sporocyst a double pyramid with short
spines Genus Crystallospora Thelohan
Sporocyst bivalved, opening like pea-pod
Genus Goussia Labbe
1 1 . Each sporocyst has 1 sporozoite 12
Each sporocyst has 2 or more sporozoites. 13
12. Sporocysts with radial markings or spines
Genus Echinospora Leger
Sporocysts smooth Genus Barrouxia Schneider
13. Each sporocyst has 2 sporozoites. . .Genus Pseudoklossin
Leger and Duboscq
Each sporocyst has main- sporozoites
Genus Merocystis Dakin
1. Synonyms of Isospora are: Diplospora Labbe, Klossia Lablx'\ Hyalo-
klossia Labbe and Lucertina Henri and La Blois 1925.
2. Synonyms of Eimeria— Mitrocystis Pinto 1927; Paracoccidium Lav.
and Mesnil; Orthospora A. Schn.
Family 4. Caryotrophidae Ltihe 1906.. .Genus Caryotropha Siedlecki
Family 5. Aggregatidae Labbe 1899.
One genus; type sp. A . eberthi Labbe 1895
Genus Agg regain (1)
566 BIOLOGY OF THE PROTOZOA
Family 6. Lankesterellidae Reichenow 1921.
Development takes place in gut cells of lizard;
sporozoites in blood cells .■ Genus Shellackia
Development takes place in endothelial cells
of bloodvessels; merozoites and gameto-
cy tes in blood cells of frog Genus LankestereUa
1. Synonyms of Aggregata: Klossia octopiana, Benedenia, L6geria,
Eucoccidium, Legerina, etc.
Sub-order 2. Haemosporidiina (Haemosporidia Danilewsky).
The entire asexual cycle occurs in the blood
(malaria) Family Plasmodiidae
Only gametocytes are present in the blood
Family Haemoproteidae
Family 1. Plasmodiidae Mesnil 1903.
One genus — Plasmodium Marchiafava and Celli
Family 2. Haemoproteidae Doflein 1916.
Melanin pigment produced ; gametocytes hal-
ter-shape Genus Haemoproteus Kruse
No melanin pigment produced; blood cells
much distorted Genus Leucocytozoon Danilewski
Sub-order 3. Babesima (Piroplasmodea).
Schizogony in red blood cells Family Babesiidae Poche
Schizogony in endothelial cells of bloodvessels
Family Theileriidae
Family Babesiidae Poche 1913.
One genus with several sub-genera .... Genus Babesia Starcovici
Family Theileriidae Franca and Borges 1907.
One genus with possible sub-genera . . . Genus Theileria Bettencourt,
Franca and Borges
Order 2. Adeleida.
Resistant, unchanging oocyst. . .Sub-order 1. Adeleina
With delicate oocyst, enlarging with growth
Sub-order 2. Haemogregarinina
Sub-order Adeleina (Adeleidae Leger 1911). Families.
1 . Zygote asponxystid 2
Zygote forms sporocysts 3
2. Microgametocyte produces many micro-
gametes Family 3. Dobelliidae
Microgametocyte produces only 4 micro-
gametes Family 4. Legerellidae
3. Each sporocyst has a small number (2, 4, 6)
of sporozoites Family 1. Adeleidae
Each sporocyst has many sporozoites
(±30) Family 2. Klossielidae
Family 1. Adeleidae.
1. Each sporocyst has 2 sporozoites 2
Each sporocyst has 4 or more sporozoites. . 3
2. Macrogametes with finger-form process—
sporocysts few, spherical Genus Adelina Hesse
Macrogametes spheroidal — sporocysts nu-
merous, discoid Genus Adelea Schneider
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 567
Family 1. Adeleidae.
3. Sporocysts few (3) ; 4 to 6 sporozoites
Genus Chagaselta Machado
Sporocysts numerous; 4 sporozoites 4
4. Macrogamete very long; 25 to 30 sporo-
cysts Genus Orcheobius
Schuberg and Kunze
Macrogamete spheroidal, many sporocysts 5
5. Microgametes 4 in number; 4 sporozoites
Genus Klossia A. Schneider
Microgametes 2 in number; sporocysts
with ±30 sporozoites Genus Klossiella
Smith and Johnson
Doubtful genus — Pneumocystis Delanoe' 1912.
Sub-order 2. Haemogregarinina.
Three families, each with a single genus.
1. Zygote forms sporozoites without forming
sporocysts Genus Haemogregarina
Danilewsky
Zygote forms several sporoblasts 2
2. Sporoblasts produce sporocysts and sporo-
zoites in oocyst Genus Hepatozoon Miller
Sporoblasts leave oocyst and develop spor-
ocysts and sporozoites independently
Genus Karyolysus Labbe
Class II. CNIDOSPORIDIA Doflein.
1. Spores large, with valves; polar capsules
visible in vivo 2
Spores small; membrane one piece; cap-
sules invisible in vivo Order 3. Microsporidia
2. Spore membrane bivalved; 1, 2 or 4 polar
capsules Order 1. Myxosporidia
Spore membrane trivalved; 3 polar cap-
sules Order 2. Actinomyxida
Order 1. Myxosporidia Butschli.
1. Spores elongated at right angles to sutural
plane Sub-order 1 . Eurysporina
Spores spheroidal, oval or elongated in
sutural plane 2
2. Spores spherical or sub-spherical; no iodin-
ophilus vacuole Sub-order 2. Sphaerosporina
Spores with sutural plane in long axis or
oblique to it Sub-order 3. Platysporina
Sub-order 1. Eurysporina (Eurysporea Kudo).
One family Family Ceratomyxidae
Family Ceratomyxidae Doflein.
1. Spore valves conical and hollow. . . .Genus Ceratomyxa Thelohan
Spore valves otherwise 2
568 BIOLOGY OF THE PROTOZOA
Family Ceratomyxidae Doflein.
2. Valves hemispherical or rounded. . .Genus Leptotheca Thelohan
Valves otherwise 3
3. Spores spheroidal or ovoidal in front view;
flattened in side view Genus Mitrospora Fujita
Spores otherwise 4
4. Spores pyramidal Genus Myxoproteus Doflein
Spores oval in side view; front view isos-
celes triangle with convex sides. . .Genus Wardia Kudo
Sub-order 2. Sphaerosporina (Sphaerosporea Kudo).
Spore with 4 polar capsules Family Chloromyxidae
Spores with 2 polar capsules Family Sphaerosporidae
Family 1. Chloromyxidae Thelohan.
One genus Genus Chloromyxum Mingazzini
Family 2. Sphaerosporidae Davis.
1. Spores with 1 polar capsule Genus Unicapsula Davis
Spores with 2 polar capsules 2
2. Spores with sinuous sutural line. . . .Genus Sinuolinea Davis
Sutural line not sinuous Genus Sphaerospora Thelohan
Sub-order 3. Platysporina (Platysporea Kudo).
1. Spores without iodinophilous vacuole 2
Spores with an iodinophilous vacuole
Family 3. Myxobolidae
2. Spores with 1 polar capsule Family 4. Coccomyxidae
Spores with 2 or 4 polar capsules 3
3. One polar capsule at each of 2 poles
Family 1. Myxidiidae
Two or 4 polar capsules all at one end
Family 2. Myxosomatidae
Family 1. Myxidiidae Thelohan.
1 . Polar filaments long and fine 2
Polar filaments short and thick. . . .Genus Sphaeromyxa Thelohan
2. Spores fusiform with pointed or rounded
ends; polar capsules oppositely directed
Genus Myxidium Butschli
Spores fusiform usually with truncated ends ;
polar capsules obliquely directed . Genus Zschokkela Auerbach
Family 2. Myxosomatidae Poche.
1 . Spores without posterior processes ; 2 polar
capsules 2
Four anterior polar capsules; with long
posterior processes Genus Agarelht Dunkerly
2. Spore ovoidal, flattened, somewhat elong-
ate Genus Myxosoma Thelohan
Spore circular to oval in front view . . Genus Lentospora Plehn
Family 3. Myxobolidae Thelohan.
1. Each valve of spore prolonged in long
process Genus Henneguya Thelohan
Valves without posterior processes. .Genus Myxobolus Butschli
MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 560
Order 2. Actinomyxida ST0L9.
With 2 spore membranes, outer trivalved,
inner one piece Family 1. Haploactinomyxidae
With only 1 membrane which is trivalved
Family 2. Etjactinomyxidae
Family 1. Haploactinomyxidae Granata.
One genus only Genus Tetractinomyxon Iked;i
Family 2. Euactinomyxidae Granata.
1 . Spore with posterior processes 2
Spore rounded, no posterior processes .... 4
2. Spores with 2 posterior processes. . .Genus Synactinomyxon Stole
Spores with 3 or 6 posterior processes .... 3
3. Anchor-shape, with 3 posterior processes
Genus Triactinomyxon Stole
Anchor-shape, with 6 posterior processes
Genus Hexactinomyxon Stole
4. Spores spherical Genus Sphaeractinomyxon
Caullery and Mesnil
Spore globular; each valve swollen to
hemisphere Genus Neoactinomyxon Granata
Order 3. Microsporidia Balbiani.
Spores with 1 polar capsule Sub-order 1. Monocnidea
Spores with 2 polar capsules. . . .Sub-order 2. Dicnidea
Sub-order 1. Monocnidea Leger and Hesse.
J . Spores elongate, tubular or cylindrical
Family 3. Mrazekiidak
Spores spheroidal or ovoidal 2
2. Spores oval to pyriform Family 1. Nosematidae
Spores spheroidal Family 2. Coccosporidae
Family 1. Nosematidae Labbe.
1 . Sporont becomes a single sporoblast 2
Sporont forms more than 1 sporoblast .... 3
2. The single sporoblast form a single spore
Genus Nosema Naegeli
The single sporoblast forms 2 spores . Genus Glugea Theloha n
3. Each sporont forms 16 or more sporoblasts 4
Each sporont forms less than 16 sporo-
blasts 5
4. Sixteen sporoblasts formed Genus Duboscqia Perez
More than 16 sporoblasts formed. . .Genus Plistophora ( turley
5. Sporonts produce 1, 2, 4 or 8 sporoblasts
Genus Stempellia Leger and Hesse
Sporonts produce 4 or 8 sporoblasts 6
6. Four sporoblasts produced Genus Gurleya Doflein
Eight sporoblasts produced Genus Thelohania Henneguy
Family 2. Coccosporidae Kudo.
One genus only Genus Coccoaponi Kudo
Family 3. Mrazekiidae Leger and Hesse.
1. Spores straight or slightly bent 2
Spores distinctly curved 3
570 BIOLOGY OF THE PROTOZOA
Family 3. Mrazekiidae L6ger and Hesse.
2. Spores straight, tubular; basal part of
thread runs through cell, thread coils
around it Genus Mrazekia Leger and Hesse
Spores slightly bent, no thickened basal
thread Genus Oosporea Flu
3. Spores spirally bent Genus Spiroglugea
Leger and Hesse
Spores bent U-shape Genus Toxospora Kudo
Sub-order 2. Dicnidea Leger and Hesse.
One family — Telomyxidae; one genus — Telormjxa Leger and Hesse
Class III. ACNIDOSPORIDIA Cepede.
Here (provisionally) are Sarcosporidia with one genus Sarcocystis and
Haplosporidia about which there is still some doubt as to their Sporo-
zoan nature and affinities. The following list of genera without definite
taxonomic position is given for completeness :
Amphiacantha Caullery and Mesnil, parasitic in Gregarine Lecudina.
Amphiamblis Caullery and Mesnil, parasite in gregarine of worm Capi-
tella.
Anurosporidium Caullery and Chappellier, parasite of Trematode in
Donax sp.
Bertramia Caullery and Mesnil, a body cavity parasite of worms and
rotifers.
Caulleryetta Dogiel, parasitic in the gregarine Selenidium in Travisia
forbesi.
Dermocystidium Perez, cyst-forming parasite in fish and amphibia.
Haplosporidium Caullery and Mesnil, different species parasitic in marine
annelids, fresh water oligochaetes, nemerteans and Chiton.
Helicosporidmm Keilin, spiral parasite in insects.
Icthyophonus Plehn and Mulsow, plasmodium-like, causes tumors in fish.
Ichthyosporidium Caullery and Mesnil, forms tumors in fish.
Lymphocystis Woodcock, forms globular masses in fish.
Lymphosporidium Calkins, in fish and oligochaete worms.
Metschnikovella Caullery and Mesnil, several species parasitic in greg-
arines.
Rhinosporidium Ridewood and Fantham, causes nasal tumors in man
(India).
Urosporidiwn Caullery and Mesnil, body cavity parasites of Syllis gracilis.
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586 BIOLOGY OF THE PROTOZOA
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INDEX.
Abnormalities, artificial production
of, 345
Acantharia, 440
Acanthocystis, Fig. 75, p. 139
budding, Fig. 50, p. 95
centroblepharoplast in division,
Fig. 50, p. 95
food-getting by Protozoa, Fig. 97,
p. 186
mitosis, 120; Fig. 67, p. 121
Acanthoeca spectabilis, Fig. 178, p. 419
Acanthosporidae, Key, 563
Acineta sp., Fig. 100, p. 192
tuberosa, endogenous budding, Fig.
117, p^228
Acinetidae, Key, 523
Acnidosporidia, 555
Key, 570
Acrasida, 447
Key, 462
Actinobolina radians, Fig. 91, p. 163
feeding, 189
isolation cultures, 254
Actinobolinidae, Key, 494, 562
Actinomonas mirabilis, Fig. 174, p. 412
Actinomyxida, 351
development, 551
Key, 569
Actinophrys sol, axial filaments, Fig. 66,
p. 120
fertilization, 277; Fig. 142, p.
27S
maturation, Fig. 157, p. 309
meiosis, 102
vitality graph, Fig. 134, p. 257
Actinopoda, 436
Actinosphaerium, centrosomes, 122;
Fig. 68, p. 123
eichhornii, axial filaments, 122
nucleus, Fig. 23, p. 50
Adelea, pseudo-conjugation, 275
Adeleida, 544
Key, p. 5(Hi
Adelina dimidiaia, pseudo-conjugation,
Fig. 140, p. 275; Fig. 217, p. 544
Adolph, oxygen consumption, 175
Adoral zone, 157
left and right wound, 181
Agamogony, 233
Age and differentiation, resume, 282
and division rate, table of, 207
of parents and vitality of offspring,
339
reduced vitality, 269
Aggregata eberthi, chromosomes, Fig.
56, p. 102
zygotic meiosis, Mill
Aggregatidae, Key, 566
Aikinetocystidae, Key, 560
Akaryomastigont, 414
Alexeieff, Chilomonas, 68
chondriome, 73
division types, 89
kinetoplast, 114
Allantocystidae, Key, 560
AUogromia, normal, Fig. 10, p. 32
Alternation of generations in Polysto-
mellina, 236
Altmann, structure of protoplasm, 43
Alverdes, isolated cilium, 124
seat of sensory reaction, 128
Amcba, rejuvenescence by merotomy,
239
.1 mebae, 453
Key, 466
Amebae of man, non-pathogenic, 396
Amebic dvsentery, MS7, MNS
history of, 38S
Amebida, 455
Key, 466
Amino-acid nutrition, 200
Amoeba crystalligera, division, 96
dysenteriae, 390
proteus, Fig. 3, p. 22
Golgi apparatus, Fig. 39, p. 78
R.Q., 174
vespertilio, division, 96; Fig. 52, p.
97
Amoebidae, 455
Key, 466
Amoeboid movement, 180
Aniphileptidae, Key, 497
Amphimixis, Weismann, 324
Ainphimonadidae, Key to genera, 425
Amphisia Iccssleri, Fig. 88, p. 159
Fig. 209, p. 518
Ancistrumidae, Key, 503
Animal cula, 17
Anisogametes, 274, 276
Anisospores in Radiolaria, 279
590
INDEX
Anoplophryidae, Key, 489
Anthophysa vegetans, colony, 39; Fig.
21, p. 40
Anti-digestive ferments, 359
Aphrothoraca, Key to genera, 460
Aragao, gametocyte formation in Plas-
modium, Plate II opp. p. 408
Arcella vulgaris, life cycle of, 236
origin of nucleic acid, Fig. 36,
p. 71
Arcellidae, 458
Key, 467
Arcyriidae, Key, 465
Armourochetidae, Key, 464
Arndt division in Hartmannella, 213
H artmannclla klitzkei, 106
Askenasia elegans, Fig. 84, p. 153
Aspidisca, Fig. 90, p. 161
Aspidiscidae, Key, 521
Assimilation, products of, 203
Astomida, Key, 489
Aulacantha scolymantha, chromosomes,
Fig. 53, p. 98
Austin, Uroleptus mobilis, 256
Autogamy, 322
in Cnidosporidia, 324
Awerinzew, autogamy, 324
Axopodia, 4 .' ! 1
Axopodium, 145; Fig. 78, p. 146
Axostyle, 144
division of, Fig. 77, p. 145
B
Babes, volutin, 72
Babesiidae, Key, 566
Babesiina, 543
Key, 566
Bacillary dysentery, 391
Baitsell, Pleurotricha lanceolata, graph,
( 251
Stylonychia pustulata, 253
Balantidium, 401
coli, copulation, 275
neuromotor system, 129
Balbiani, merotomy, 55, 219
Bancroft, reversibility of phase, 180
Basal body, 107
granules, ciliates, 123
Basichromatin, 57
Becker, reducase, 175
Beers, Ameba gastric vacuole, 189
Belaf, Actinophrys sol, maturation, 308
Bodo ovatus, Fig. 29, p. 62
division of Lophomonas, Fig. 105,
p. 211
fertilization in Actinophrys sol,
Fig. 142, p. 278
Karyosome, 51
lipoplasts in Actinophrys, 316
substances in nucleus, 57
vitality graph of Actinophrys sol,
Fig. 134, p. 257
Benda, chondriome, 73
Benedict, uric acid in Paramecium, 177
Berthold, ameboid movement, 180
Blepharisma undidans, Fig. 208, p. 514
pseudo-membrane, 157
R.Q., 174
Blcpharocoridae, Key, 503
Blepharoplast, 107
Blepharoplastless trypanosomes, 114
Bicoecidae, Key to genera, 424
Bignami, relapse in malaria, 344
Bilateral symmetry, Figs. 17, 18, pp.
35, 36
Binucleata, 113
Bioblast, 43
Biparental inheritance, 350
Bishop, Spirostomum, 25
Bistadiidae, 141, 455
Key, 466
Bodo lacertae centrioles, 63; Fig. 33, p.
65; Fig. 34, p. 66
parabasal, Fig. 62, p. 116
ovatus, kinetic elements, Fig. 29,
p. 61
species, Fig. 76, p. 143
Bodonidae, Key to genera, 426
Boeck, blepharoplast in Chilomastix,
109
and Drbohlav, Endameba cultures,
393
Bogert, Aulacantha, 68
scolymantha, Fig. 53, p. 98
Botsford, merotomy, 178
Boveri, centronucleus type, 61
"spheres of influence" and divi-
sion, 205
Boveriidae, Key, 503
Bowen, Golgi apparatus function, 179
Bowling, Zygocystis, 536
Brandt, function of contractile vacuole,
176
Brasil, budding in Eleutheroschizon,
229; Fig. 119, p. 230
Gonospora varia, 94
Brazilian trypanosomiasis, 384
Bresslau, artificial membranes, 193
silver line system, 80
temporary cysts, 267
Bresslau andScremin, Feulgen reaction,
57
parabasal Feulgen reaction,
118
Bresslau and Tektin, protrichocysts,
135, 137
Brown, Dinenympha, Fig. 176, p. 414
Brown and Golgi in Amoeba proteus, 78
Bruce, tsetse flies and trypanosomes,
381
Brumpt, copulation in Balantidium,
275
Budding, 225
division, 214
endogenous, 228
exogenous, 226
INDEX
591
Budding in Myxosporidia, 230
in Spirochona, 227
in Sporozoa, 229
terminal in ciliates, 227
Bunge, anaerobic forms, 24
Bursaria truncatella, Fig. 94, p. 169
Bursariidae, Key, 512
Biitschli, ameboid movement, 180
frontal field, 168
protoplasmic structure, 42; Fig.
15, p. 36
Verjungung, 329
Butschliidae, Key, 495
Buxtonella, 401
Calkins, Actinobolina feeding, 189
chondriome, 75
division of double Uroleptus, 246,
247
monster formation, Fig. 10S, p. 216
origin of double Uroleptus, 244
split conjugants, 284
Uroleptus halseyi motorium, 129
Calkins and Bowling, gametogamy in
Glaucoma, Fig. 200, p. 485
Glaucoma motorium, 129
Calkins and Gregory, selection in Para-
mecium, 348; Fig. 168, p. 349
Callimastigiidae, Key to genera, 430
Calonympha grassii, 115; Fig. 63, p. 117
Calonymphidae, Key to genera, p. 432
Calymma, 439
Campanella umbellaria, 125
Cam ptonema 'nutans, pseudopodia, 122
Canalicular system, Fig. 101, p. 194
Cannibalism, 185
Capillitium in Mycetozoa, 238
Carbohydrate digestion, 198
Carchesium polypinum, colony, 38
gastric vacuole history, Fig.
102, p. 196
Carrel, tissue culture, 210, 258
Caryotropha mesnili, food-getting, Fig.
103, p. 201
Caryotrophidae, Key, 565
Casagrandi and Barbagallo, 389
Castellani, human trypanosomiasis, 381
Catalase as stimulus to division, 20(5
Caullery and Mesnil, Actinomyxida
development, 551
autogamy in Actinomyxida,
326
Causey, chondriome, 76
origin of Golgi bodies, 79
Cavulae, 42
Cell division, 204
Cellulose digestion, 199
Central granule of Heliozoa, 119
Centrioles, 63, 107
Centroblepharoplast, 117
arising from nucleus, Fig. 50, p. 95
Centrodesmose, 62
Centronucleus type, 61
Centropyxis aculeata, chromidia, 69
fertilization, 277
Centrosomes, 122
Ceratomyxidae, Key, 567
Cercomonadidae, Key to genera, 427
Chagas, Schizotrypanum, 383
Chalarothoraca, Key to genera, 460
Chambered shells, Fig. 19, p. 38
Chambers, periplast, 135
physical conditions in Ameba, 180
Chambers and Dawson, pseudo-mem-
branes, 157
Chatin, chitin, 137
Chatton, abnormalities, 345
anisospores in Radiolaria as para-
sites, 279
contractile vacuole, 179
environment and conjugation, 287
Glaucoma sdntillans, 266
isolation cultures, 250
life cycle in ciliates, 256
mesomitosis, 89
Panspordla, 386
thigmotricha, 483
yellow cells, 441
Chatton and Courrier, Schizotrypanum,
383
Chatton and Lalung-Bonnaire, Loschia,
389
Chatton and Lwoff , Ellobiophrya dona-
cis, Fig. 104, p. 202
Foettingeria, 399
silver line system, 81
Chatton, Lwoff and Monod, origin of
mouth at division, Fig. 114, p. 224
Chatton and Perard, Pycnothricidae,
400
Chejfec, bacteria eaten by Paramecium
caudatum, 1 85
longevity of single Paramecium
individual, 259
Chemistry of protoplasm, 43
Child, senescence, 209
Chilodochonidae, Key, 523
Chilodon, mouth of, 168
sp., Fig. 30, p. 62
uncinatus, Fig. 112, p. 222
mutation, 351
Chile miastigidae, Key to genera, 431
Chilomastix centrioles, 63
mesnili, Fig. 60, p. 110
cyst, 23
Chilomonas Paramecium, contractile
vacuole, Fig. 95, p. 181
Chitin, 133-137
Chlamydodon mnemosyne, hyaline band,
124
Chlamydodontidae, Key, 498
Chlamydophrys stercorea, Fig. 189, p.
458
Chloromyxidae, Key, 568
Chlorophyll forms, 18
Choanocca perplexa, Fig. 178, p. 419
592
INDEX
Choanofiagellate collar, 104
Choanoflagellates, distribution of, 26
Choenia teres, Fig. 191, p. 472
Chondriochonts, 73
Chondriome, 73
Chondriomites, 73
Chonotricha, Key, 522
Chromatin, 54
Chromatoid bodies, 395
Chromidia, p. 69
Chromosomes in Uroleptus, 321
origin, 88
meiotic, 100
Cilia, 152
and membranes of Infusoria, Fig.
69, p. 124
composite, 155
replacement, 223
structure, Fig. 82, p. 152; Fig. 83,
p. 153
Ciliary beat, 127
Ciliata, anal modifications, Mil
cytostomes, 164
division zone, 215
myonemes, 124
oral modifications, 164
position of mouth of, 167
Ciliates, amicronucleate, 477
commensal, 397
distribution, 26
parasitic, 397
symbiotic, 397
Cirri, 157
anal, 158
caudal, 158
frontal, 158
marginal, 158
movement, 160
substitution, 223
tactile, 161
types, 479
ventral, 158
Cladomonas fruticulosa, colony, 38
Clathrostomidae, Key, 501
Clathrulina, colony, 38
elegans, stalk origin, 148; Fig. 80,
p. 139
Cleveland, Paramecium cysts, 24
symbiotic flagellates, 203
wood digestion by flagellates, 199
Cleveland and Sanders, excystation of
Endamoeba dysenteriae, 395
Climacostomum virens, frontal field, 169
myophanes, neurophanes, Fig.
71, p. 128
Clowes, permeability, 172
reversibility of phase, ISO
Club root in cabbages, 386
Cnidosporidia, 545
Key, p. 567
spore types, Fig. 219, p. 547
Coccidia, effects produced, 104
lumen-dwelling forms, 541
Coccidiida, 541
Coccidiida, Key, 564
Coccidiomorpha, 541
Key, 564
Coccidioses in chickens, 405
Coccidium (eimeria) schubergi, centriole,
63
Coccosporidae, Key, 569
Cochliopodium, normal, Fig. 9, p. 31
Cochlosomidae, Key to genera, 431
Codosiga botrytis, origin of flagelluin,
107; Fig. 59, p. 108
pulcherrimus, Fig. 92, p. 165
ramosum, colony, 38; Fig. 20, p. 3')
Coenomorphamedusula, Fig. 208, p. 514
Cohn, budding in Myxosporidia, 227
Colepidae, Key, 494
Colcps hirtus armature, Fig. 73, p. 136
cilia structure, Fig. 82, p. 152
division, 215
Collars in choanoflagellates, 165
Collin, origin of basal granules, 122
< 'oil null,,, Fig. 172, p. 400
Collodictyum triciliatum, nuclear divi-
sion, Fig. 51, p. 96
Colonies, 18, 21, 38
Colony types, 38
( 'olpidium colpodd, canalicular system,
194; Fig. 101, p. 194
Colpodidae, Key, 501
Comatricha nigra, Fig. 184, p. 447
Commensals, 202
Composite ciliary organs, 155
Concophthiriidae, Key, 501
Concrement vacuoles, 171
Condylostoma patens, Fig. 206, p. 511
Condylostomidae, Key, 510
Conjugation and encyst ment, graph,
Fig. 137, p. 268
and environment, 286
conditions for, 285
disorganization at, 311
effects of salts on, 288
endogamous, 286
reorganization after, 312
survival value of, 333
tests, 267
unfavorable effects on Para unci inn.
332
"Conscious" activities, 189
Contaminative infection, 360
Contractile vacuoles, 170
and Golgi apparatus, 7!)
function, 176
membrane of, 178
supposed functions, 177
Contraction in ciliates, 125
Coordinating fibers, 127
systems in protozoa, L83
Coprozoic protozoa, 357
Copulation and conjugation, 274
Cornuspira, type of shell, Fig. 19, p. 38
Cortex, 132
zonal differentiation, 152
Cortical differentiations, L35
INDEX
593
Cosmovici, canalicular system, Fig.
101, p. 194
Costia necatrix, ectoparasite, 359
Councilman and Lafleur, Amoeba dys-
enteriae, 390
Cowdry, functions of mitochondria, 76
Craig, toxins in endameba, 363
Craspedomonadidae, Key to genera,
424
Crawley, gregarine movement, 535
Sarcocystis, 556
Cribrariidae, Key, 464
Crithidia euryophihalmi, Fi^'. 61, p. Ill
gerridis, Fig. 169, G, p. 366
leptocoridis, Fig. 61, p. Ill
subulata, Fig. 170, p. 368
('ryjilobiasp., parabasal, Fig. 62, p. 116
Cryptocysts in Microsporidia, 555
Cryptosporidiidae, Key, 565
Crystalline excretory products, 177
Ctenostomida, Key, 516
Cups, houses, etc., 137
Cushman, Foraminifera, 452
Cutler, division-rate and food, 206
Endameba cultures, 303
Cutler and Crump, soil forms, 25
Cyathodiniidae, Key, 503
Cyathosoma striatum, Fig. 179, p. 120
Cyclidium glaucoma, Fig. 199, p. 482
cilia structure, Fig. 83, p. 183
Cyclonympha mirabilis, Fig. 180, p. 429
Cyclonymphidae, 428
Cycloposthiidae, Key, 515
Cycloposthiiim bipalmatum, conjuga-
tion, Fig. 141, p. 276
interchange of nuclei, Fig. 146, p.
293
Cyclosis, 150
< 'yclospora karyolytica, nuclear parasite,
542
Cyclotrichium gigas, Fig. si, p. 151
ovatum, Fig. 191, p. 472
sphericum, Fig. 84, p. 153
Cysts, air-borne, 23
endomixis, 267
Cytomeres, 227
Cytoplasmic elements of fundamental
organization, lis
kinetic elements, 104
list, 611
Cytostome in taxonomy, 4S1
da Cunha and Muniz, parabasal Feul-
gen reaction, 118
Dactylophoridae, Key, 562
Dallinger, adaptations to heat, 343
Dallinger and Drysdale, enduring mod-
ifications, 343
Daniel, respiration quotient, 174
Darling, dysentery, 393
Dauermodificationen, 344
38
Davis, autogamy, 321
Leptotheca, Fig. 220, p. 550
Sphaerospora dimorpha, Fig. 121,
p. 232
Dawson, abnormalities, 346
cannibalism, 185
isolation cultures, 256
Dawson and Belkin, oil digestion, 199
Debaisieux, fertilization in Cnidospor-
idia, 326
Microsporidia, 553, 555
Dedifferentiation with division, 263
de ( laris, monster production, 264
Degen, function of vacuole, 176, 178
Dehorne, Paramecium chromosomes,
Fig. 57, p. 103
Delage and Herouard, flagellum action,
142
Demboska, cirrus regeneration, 164
cirrus removal, 223
Dendrocometidae, Key, 524
Dendrosoma elegans, Fig. 196, p. 477
Dendrosomidae, Key, 524
Derived nuclear structures, 84
organization, cytoplasmic, 104
definition of, 45
Desmothoraca, Key to genera, 461
Development, 241
embryos of Suctoria, 243
Devescovina, parabasal, Fig. 62, p. 110
Devescovinidae, Key to genera, 431
I )ianemidae, Key, 466
Diastatic ferments, 196
Dicnidea, Key, 570
Dicraspedella stokesi, Fig. 178, p. 419
DictyosteUdae, 449; Key, 462
Dictyostelium, Fig. 185, p. 448
Dictyotic moment, 134
Didinium nasutum, food-getting, 185
rhizoplasts, 155
swallowing Paramecium, Fig.
98, p. 189
Didymiidae, Key, 463, 494
Didymophyidae, Key, 562
Dientamoeba fragilis, 396
Differentiation, age, 269
and organization, 260
cyclical, 26(5
gametic, 274
inter-divisional, 260
maturity, 271
youth, 266
Diffluence, 30
Difflugm lobostoma, Fig. 190, p. 459
Difflugiidae, Key, 468
Digestive fluids, 193
in gastric vacuoles, 1 95
use of indicators, 193
Dikaryomastigina, 422
Key to genera, 431
l)i,U plus, beef-fed, Fig. 25, p. 52
gigas, Fig. 6, p. 27; Fig. 194, p. 474
division, 91 ; Fig. 46, p. 92
nuclear division, 217
594
/.\ DEX
Dileptus gigas, starvation, 172
regeneration, 45
Dimastigamoeba bistadialis, kinetic ele-
ment, 107
gruberi, Fig. 13, p. 34
Dimorpha mutatis, Fig. 13, p. 34
Fig. 79, p. 148
Dimorphic nuclei, 84
origin after conjugation, 315
Dinenympha fimbriata, lug. 176, p. 415
Dinenymphidae, Key to genera, 430
Dinophrya lieberhiihni, Fig. 84, p. 153
Diophrys appendiculata, Fig. 89, p. 160
Diphasic forms, 34
Diplocystidae, Key, 559
Diplocystis schneideri, zygotic meiosis,
Fig. 158, p. 310
Diplodinium ecaudatum, Fig. 2, p. 20
motorium, 129
interchange of nuclei, Fig. 14(i, p.
293
Diploeca placita, Fig. 178, p. 149
Diplosiga socialis, Fig. 92, p. 165
Discomorpha pectinata, silver line sys-
tem, Fig. 41, p. 80; Fig. 42, p. 80
Discomorphidae, Key, 516
Discophryidae, Key, 524
Distribution of Protozoa, 23
Division and reorganization, 209
in Mastigophora, 210
in Sarcodina, 213
modes, 209
of protoplasmic granules, 208
Dobell, amebic dysentery, 388
axostyle function, 144
kinetoplast, 114
Protozoa as organisms, 18 19, 40
zygotic meiosis, 310
Dobell and Jameson, chromosome ag-
gregates, Fig. 56, p. 102
Dofiein, Amoeba vespertilio, 1 ig. 52, p.
97
anaerobic forms, 24
axostyle function, 144
chromidia, 70
< 'odosiga botrytis, 109
digestive fluids as toxins, 193
free nuclei formation, 88
Karyosome, 51
Plasmodroma and Ciliophora, 411
pole plates, 66
primitive form, 141
stereoplasm and rheoplasm, 42
stereoplasmatic axis, 435
Dogiel, concrement vacuoles, 171
gametic nuclei as spermatozoa, 276
ophryoscolecin, 139
polymerization, 38
Schizocystis sipunculi, 229
Donovan, organism of kala azar, 369
Dujardin, 22
classification, 140
diffluence, 30
sarcode, 433
Dreyer, skeleton formation, 138
skeletons, Fig. 12, p. 33
Driesch, architektonic, 173
Driiner, causes of division, 205
Duboscq and Grasse, Golgi apparatus,
79
Duke, sites of trypanosome develop-
ment, 382
Dutton, human trypanosomiasis, 381
Dysentery, amebic, 387
Dysteriidae, Key, 498
E
Eberlein, silica in ciliates, 125
Echinomera hispida, gametes, Fig. 144,
p. 281
Ectoparasites, 359
Ectoplasm, 132
Eimeria schubergi, cycle, Fig. 173, p.
403
gametes, Fig. 144, p. 281; Fig.
215, p. 538
Eimeriidae, Key, 565
Eimeriina, 541
Key, 564
Elaters in Mycetozoa, 239
Eleutheroschizon dubosqui, budding,
229; Fig. 119, p. 230
Ellis, choanoflagellates, Fig. 178, p. 419
food ingestion by Choanoflagel-
lates, 188
Ellobiophrya donacis, anchorage, Fig.
104, p. 202
Elpatiewsky, chromidia, 69
endogenous budding in A rcella, 22s
fertilization in Arcella, 277
life cycle of Arcella, '_':;» i
Emerson, respiration quotient, 174
Enchelys /'»/>", Fig. 191, p. 472
Encystment, 23
Endameba in insects, 386
in man, 387
in vertebrates, 387
Endamoeba coli, 396
nuclear division, Fig. 26, p. ").'>
cultures, 393
dysenteriae, Fig. 31, p. 62
cycle, 395
ex-cystation, 395
synonyms, 393
trophozoite and cvsts, Fig.
171, p. 394
gingivalis, 396
intestinalis, Fig. 24, p. 51
Endamoebidae, tori
Key, 466
Endobasal bodies, Hi
body, 53, 60
Endoenzymes and toxins, 198
Endomixis, 252, 317
Endoparasitic protozoa, 359
Endoplasm, 132
INDEX
595
Endosome, defined, 50
Endotoxins, 197
in protozoa, 363
Endotryanum schaudinni, Fig. 169 //,
p. 366
Energid theory, 205
Engelmann, chemiotaxis in fertiliza-
tion, 291
neural fibers, 131
Enriques, isolation cultures, 250
stalk formation, 193
Entamoeba coli, 391
histolytica, 391
Entodiniomorpha, 402
Entz, Actinobolina radians, 162
origin of basal granules, 123
polytoma, 107
Epalcidae, Key, 516
Ephelota, exogenous budding, Fig. 115,
p. 226
tentacles, Fig. 198, p. 480
Ephelotidae, Key, 524
Epiclintes, Fig. 208, p. 514
Epistylis, mvonemes, 125; Fig. 70, p.
126
luiibellaria, colony, 5S
fertilization, Fig. 14o, p. 280
Erdmann, reorganization, 341
Sareocystis, 556
Euactinomvxidae, Key, 569
Euciliata, Metcalf, 398
Evdorina elegans, 266
Euglypha alveolata, budding division,
214
cyst, Fig. 4, p. 23
normal, Fig. 9, p. 31
Euglyphidae, 45S; Key, 469
Eugregarinida, 540; Key, 558
Euplasmodida, 449; Key, 463
Euplotes charon, Fig. 89, p. 160
patella, absorption bands, Fig. 48,
p. 94
merotomv and reactions, Fig.
96, p. 182
microdissection, 129; Fig. 72,
p. 130
oannus, Fig. 210, p. 520
Euplotidae, Key, 521
Eurysporina, Key, 567
Evans, Trypanosoma, cause of Surra,
381
Excretion, 176
products, effects on Protozoa 200
Excretory granules, 197
Exosporea, Key, 463
Fantham, soil protozoa, 354
Kant ham and Porter, fertilization in
Cnidosporidia, 326
Fat and oil digestion, 199
Fatigue in protozoa, 181
Faure-Fremiet, chondriome, 7:>
ciliate types, Fig. 84, p. 153
Fellers and Allison, soil protozoa, 354
Fermor, endomixis in Stylonychia, 319
Fertilization, effect of initial contact,
292
phenomena, 285
processes of, 292
Feulgen and Rossenbeck, nucleal reac-
tion, 57
Kilo podia, 150, 435
Flagella, 140, 141
number and arrangement, 413
Flagellata, adaptations, 419
classification, 421
with suckers, Fig. 179, p. 420
Flagellates of soil, 354
list of, 355
parasitic, 364
Flagellum, insertion, Fig. 59, p. 108
Flemming, structure of protoplasm, 43
Flexner, bacillary dysentery, 391
Koettingeriidae, 399
Key, 499
Folliculina ampulla, Fig. 94, p. 169
contraction, 125
Folliculinidae, Key, 510
Food-catching by Protozoa, 185
Food-getting by Protozoa, 1 83
organoids, 162
Foraminifera, 450
alternation of generations, 452
arenaceous tests, 450
distribution, 26
porcellanous tests, 450
tests, types of, Fig. 187, p. 452
Forde, Gambia fever, 381
Franca, sensory flagella, 127
France, choanoflagellate collar, 164
Frontal fields, 168
Frontonia leucas, Fig. 93, p. 167
division zone, 217
Front oniidae, Key, 505
Fuligo varians, chemistry of, 44
Fundamental organization change.-, 83
definition of, 45
G
Gambia fever, 381
Gametes, defined, 529
of Gregarinida and Coccidia, Fig.
144, p. 281
Gametochromidia, 70
Gametocyte, defined, 528
Gamogony, 233
Ganymedidae, Key, 560
Garnjobst, temporary cysts, 267
Gastric vacuole formation, ]9.">
Gastrostyla steinii, Fig. 210, p. 520
< ratenby, function of mitochondria, 77
Gelei, contractile vacuole, 179
Gemmation, 225
596
INDEX
Giardia, bilateral symmetry, 36; Fig.
17, p. 37
Gibbs and Del linger, selection in Proto-
zoa, 181
Glaessner, diastatic ferments, 196
Glaser, centrioles, 63
Glaucoma, Fig. 205, p. 504
frontata, Fig. 8, p. 29
conjugation, Fig. 201, p. 486
(Dallasia) gametogamv, Fig.
200, p. 485
scintillans, basal bodies, 124
origin of posterior mouth at
division, Fig. 114, p. 224
Glutathion, 175
and mitochondria, 77
Glycogen, 133
at conjugation periods, 290
in Pelomyxa, 198
Goette, chromidia, 69
Goldfuss, Protozoa, 17
Goldschmidt, chromidia, 69, 87; Fig.
25, p. 88
Golgi apparatus, 69, 77
in flagellates, 416
bodies and contractile vacuole, 79
types of malaria organisms, 406
Gonder, enduring modification in Try-
panosoma, 344
Goodey, Prowazekia saltans, 110
soil forms, 25
protozoa, 354
Gourret and Roeser, distribution, 26
Granata, Haplosporidium, 94
Grasse, parabasal, 119
Grassi, dysentery, 389
malaria and mosquitoes, 407
Grassi and Feletti, genera of malaria
organisms, lot;
Greenleaf, effect of crowding on divi-
sion, 206
Greenwood and Saunders, digestion in
gastric vacuoles, 195
Gregarina cuneata, sporoducts, Fig. 125,
p. 240
ovata, gametes, Fig. 215, p. 538
Gregarinida, epimerite types of, 243
protomerite, 242
Gregarinina, 534
Key, 557
Gregarines, epicyte in, 534
epimerite, 536
movement, 535
myonemes in, 535
pseudo-conjugation, Fig. 213, p.
531
sex differences, Fig. 214, p. 537
Gregorv, chromosomes in Oxytricha,
319
Tillina magna, vitality, 253
Uroleptus response to chemicals at
different ages, 246, 257
Grenacher, central granule, 1 I'.t
Griffin, fibers in Euplotes, 131
Griffin, r 'ganization in ciliates, 221
Griffiths, function of contractile vac-
uole, 176
( Iromiidae, Key, 169
Grosse-Allerman, Amoeba terricola feed-
^ ing, 188
Gruber, environment effects, 178
Gruby, Trypanosoma, 381
Guilliermond, mitochondria, 77
volutin, 72
Gunther, skeleton, 125
Gurwitsch, inadequacy of term cell, 19,
40
Guttulinidae, 448
Key, 462
Gymnostomida, Key, 491
H
Habitat groups, 352
anaerobic types, 353
mesosaprobic types, 352
oligosaprobic types, 352
sapropelic types, 353
Haeckel, Protista, 18
Radiolaria classification, 438
Haemogregarina stepanowi, Fig. 218, p.
545
Haemoproteidae, Key, 566
Halteriidae, Key, 513
Hamburger and Buddenbrock, distri-
bution, 26
Haploactinomyxidae, Key, 569
Haplocvta, Key, 558
Haptophrya, colony, 38
Hartmann, Arcella, 70
Binucleata, 1 12
cell and protozoa, 21
centrioles in Endameba, 63
chromidia, 70
Endamoeba africans, 392
Eudorina, 266
Karyosome, 51
necessity of conjugation, 329
Polyenergid, 71
rejuvenescence by merotomy, 239
Hartmann and Chagas, Spongomonas,
94
Hartmann and Nagler, autogamy, 323
Sappinia, 94
Hartmannella klitzkei, Fig. 58, p. 106
division, 213
Hartog, function of vacuole, 176
Hartog and Dixon, pepsin-like fer-
ments, 196
Haughwout, Pentatrichomonas, food,
193
Hegner, selection in Arcella dentata, 347
Heidenhain, causes of division, 205
two kinds of chromatin, 57
Heitzmann, structure of protoplasm, 43
Heliozoa, 437
central granule, 119
INDEX
597
Heliozoa, distribution, 26
with centroblepharoplast, Fig. 50,
p. 95
Helkesimastix faedcola, copulation, 27G
Hematozoic parasites, 300
Hemosporidia, 406
Hepatozoon, cycle, big. 211, p. 527
hosts, 361
Heredity and variation, 342
Herpetomonas musca-domesticae, Fig.
170, p. 368
muscarum, Fig. 169 B, p. 366
parabasal, Fig. 62, p. 116
Hertwig, Actinosphaerium eichhornii,
centrosomes, 122; Fig. 68, p. 133
chromidia, 55
and chromidia] net, 69
duality of chromatin, 56
immortality, 341
Microgromia socialis, Fig. 107, p.
214
nucleoplasms relation, 205
pole plates, 65
Radiolaria, classification, 138
split conjugants, 284
Herzfeld, reorganization at division,
264
Heterochromosomes of Trichonympha
campanula, 99
Heterotrichida, Key, 508
Hexactinomyxon, Fig. 221, p. 552
Hirschler, Golgi and mitochondria, 77
llisirm pellionella, Fig. 88, p. 159; Fig.
209, p. 518
Hofer, Ameba anchorage at feeding,
186
merotomy, 55
periplast, 135
reaction of fragments, 183
Hogue, environment effects, 178
Hologametes, 274
Holomastigotidae, Key to genera, 42S
Holophrya, Fig. 191, p. 472
discolor and myonemes, Fig. 69, p.
124
Holophryidae, Key, 491
Holotricha, Key, 488
Holozoic nutrition, 184
Homogeneous endobasal bodies, 01
Hopkins, oxidation and reduction
potential, p. 171
Hoplitophrya, Fig. 202, p. 492
Iloplitophryidae, Key, 490
Hoplonymphidae, 428
Horning, chondriome, 73, 75, 7" t ">
I lowland, membrane of contractile vac-
uole, 178
oxygen consumption, 175
pH of gastric vacuoles, 190
test for uric acid, 177
Htibener, endotoxins in Trypanosoma,
198
Huber, cysts of Endamoeba dysenteriat,
3(12
Hulpieu, effect of oxygen on Ameba,
175
Hunger satisfaction and fatigue, 190
Huxley, nature of life, 173
Hyalosphenia, Fig. 188, p. 457
Hyman, pseudopodia formation, 180
Hymenostomida, Key, 503
Hypocomidae, Key, 503
Eypostomina, Key, 491, 498
Eypotrichidae, Key, 510
IcHTHYOPHTHiRirs, fish parasite, 359
Idiochromidia, 7(1
Ilowaisky, endomixis in Stylonychia,
319
Immaturity, 254
Immortality in Protozoa, 3 1 1
Immunity, 363
passive, 364
Indicators in digestion, 193
Infraciliature, 82
Infusionsthiere, 17
Infusoria, division in, 215
Key, 488
taxonomy, 471, 4S0
tentacles' in, 102, 103, 480
tests, 471
Inoculative infection, 360
Intestinal flagellates of man, 384
Intoshellinidae, Key, 490
Intranuclear kinetic elements, 00
Invertebrate hosts of parasitic forms,
304
Todamoeba, Prowazek, 397
Irritability, 179
Isogametes, 274, 276
Isolation cultures, 248
with carnivorous ciliated, 253
Isospora in man, 405
Isospores and anisospores as parasites,
279
in Radiolaria, 279
Isotrichidae, Key, 503
Ivanic, endomixis in Chilodon, 319
macronucleus, 93
Jahn, mycetozoa, 271
James, dysentery, 393
Jameson, Buxtonella, 401
zygotic meiosis, 310
Janicki, division of Lophomonas, 212
karyomastigont, Fig. 175, p. 414
parabasal, 111, 114
Jennings, conjugation and division
rate, 332
tests, 287
motor response in Protozoa, 181
physical conditions in Ameba, ISO
59S
INDEX
Jennings, scat of sensory reaction, 128
selection in Arcella, 348
split conjugants, 284
variations in Paramecium, Fig.
167, p. 342
Jepps and Dobell, Dientamoeba, 396
Jirovec, parabasal Feulgen reaction,HS
Joeniidae, Key to genera, 428
Jollos, endomixis and environment, 340
enduring modifications, 344
Joukowsky, cannibalism, 185
isolation cultures, 252
Joyet-Lavergne, chondriome and sex,
76
Golgi in metozoa, etc., 79
Glutathion and mitochondria, 175
Nina gracilis, sex, Fig. 214, p. 537
Kahl, protrichocysts, 135
Kalmus, respiration, 174
Kanthak, extractives from Trypano-
somes, 198
Kartulis, dysentery, 399
Karyomastigont, 414
Karyosome, endosome, 51
Kepner and Taliaferro, purpose in pro-
tozoan activity, 181
Kerona pediculus, Fig. 89, p. 160
Keuten, Euglena, 61
Key to genera of flagellates, 423
Keysselitz, Myxobolus autogamy, 324
somatic structures in Myxobolus,
240
Khainsky, chromidia, 70
digestion, 195
Kidder, Concophthirius, 98
motorium, 129
Kinetic elements in ciliates, 121
in cytoplasm, 105
Kinetonucleus, 112
Kinetoplast, 114
King and Gatenby, Golgi apparatus,
78
Kingsbury, mitochondria and respira-
tion, 7f>
Kite, physical conditions in Ameba,
180
Klebs, primitive form, 141
Klein, cilia structure, Fig. 82, p. 152;
Fig. 83, p. 183
silver line system, 80
Kofoid, axostyle function, 144
chromidia, 55, 70
free nuclei formation, 88
function of parabasal, 111, 115
neuromotor system, 105
Trichomonas, 1 17
Kofoid and Swezy, blepharoplast, 109
centroblepharoplast, 117
K mlo mix ha dysenteriae, nuclei,
394
Kofoid and Swezy, mitosis in Tricho-
nympha campanula, 99
parastyle, 1 14
Streblomastix, Fig. 16, p. 3
Trichomonas augusta, 110
Kofoidiidae, 428
Koidzumi (Teratonympha , Cyclo-
nympha, Fig. 180, p. 429
Kolkwitz, habitat groups, 352
kossel, chemistry of chromatin, 56
Kranzlin, origin of elaters, 44t>
Krogh, oxidation reduction potential,
174
Krukenberg, pepsin-like ferments, 196
Kudo, Myxosporidia distribution, 549
Stem /i< Ilia magna, cycle, Fig. 222,
p. 553
Thelohania cycle, Fig. 223, p. 554
Kuschakewitsch, chromidia, 70
I, ABYRINTHTJLIDAE, 443
Key, 461
Lackey, sewage protozoa, 357
Lacrymaria olor, elasticity, 162
types, Fig. 85, p. 156
Lamprodermidae, Key, 464
Lang, types of pseudopodia, 434
Lankesterella ranarum, Fig. 218, p. 545
Lankesterellidae, Key, 566
Lankesteria ascidiae, cvcle, Fig. 213, p.
531
Lapage, cannibalism, 185
Lauterborn, sapropelic forms, 24, 353
Laveran, kinetonucleus, 113
malaria., 106
transmission of malaria, 407
Laveran and Mesnil, sarcocystin, 197
Lavoisier, respiration, 174
Learning in Protozoa, 181
Lebedew, chromidia, 70
Leber, endotoxins in Trypanosoma, 198
Lecudinidae, Key, 560
Ledenmuller, Infusionsthiere, 17
Leger, Ophryocystis mesnili, 229; Fig.
120, p. 231
origin of mammalian trypano-
somes, 361
Leger and Duboscq, chromidia, 69
Leidy, Endamoeba, 386, 389
Leishman, organism of dam duin fever
369
Leishmania donovani, Fig. 169 E, F, p.
366
transmission, 371
Leishmaniases, 367
Leishmaniasis, types of, 369
Lembadion bullinum, Fig. 199, p. 182
conchoides, Fig. 87, p. 158
undulating membranes, 157;
Fig. 87, p. 15S
Lembidae, Key, 508
INDEX
599
Li minis pusillus, Fig. 204, p. 502
Lepeshkin, chemistry of Fuligo, 44
Leptomonas ctenocephali, Fig. 65, p.
119; Fig. 169.4, p. 366
Leptotheca scissura, Fig. 220, p. 550
Lewis, mammalian trypanosomes, 381
Levander, distribution, 26
Liceidae, Key, 465
Lichnaspis giltochii, Fig. 182, p. 440
Lichnophoridae, Key, 512
Life and Death, Weismann, 248
Lionotus fdsdola, Fig. 203, p. 496
'feeding, Fig. 99, p. 188
food-getting by, 186
procerus, 86
wrzesniowskyi, Fig. 203, p. 496
Lipoplasts in Actinophrys, 316
Lister, chromidia, 69
Lobopodia, 150, 435
eruptive type, Fig. 78, p. 146
Looper, nucleoplasmic relation, 205
Lophomonadidae, Key to genera, 428
Lophomonas blattarum, division, Fig.
105, p. 211
division, 212
Losch, Amoeba coli, 388
Loschia, 389
Losina-Losinsky, feeding reactions, 1 89
Loxocephalus granulosus. Fig. 205, p.
504
Loxodes rostrum, Fig. 203, p. 496
Loxodidae, Key, 497
Loxophyllum, Fig. 203, p. 496
Lund, function of contractile vacuole,
176
Lundgardh, karyolymph, 59
Lwoff, Leptomonas ctenocephali, 119
parabasal Feulgen reaction, 1 1 9
temporary cysts, 267
Lynch, contractile vacuole function,
'179
l.ysin, reaction of host, 363
M
McCullock, origin of parabasal, Fig.
61, p. Ill
McDonald, motoriuin, neuromotor ap-
paratus, 129
MacDougall, Chilodon uncinatus, Fig.
112, p. 222
mutation in Chilodon, 351
pharyngeal baskets, 476
MacNeal, endotoxins in Trypanosoma,
198
Macrochromatin and microchromatin,
484
Macrogametes, 272
Macronucleus, beaded, reorganization
of, 218
formation, 85
reorganization of, 217
Macrospheric and microspheric tests,
452
Maier, basal bodies of membranes, 124
Malaria organisms, sporulation, 238
types and reproduction, Plate
' I, p. 408
Mammalian trvpanosomes, origin of,
361
Manson, transmission of malaria, 407
Marchiafava and Celli, Plasmodium,
406
Martin, endotoxins in Trypanosoma,
198
soil protozoa, 354
Martin and Robertson, axostyle func-
tion, 144
Marullaz, Sarcocystis, 550
Marynidae, Key, 501
Massart, contractile vacuole, 176
Massive nuclei, 50
Mast, Ameba, gastric, vacuole, 189
Didinium cyst, 267
isolation cultures, 256
and Pusch, learning in Protozoa,
181
Mastigamoeba aspera, bis. 174, p. 412
Mastigella vitrea, chromidia, Fig. 45, p.
88
Mastigina, chromidia, Fig. 45, p. 88
Mathews, physiology, 172
Maturity, 255
Maupas, action of tentacles, 191
cannibalism, 185
conditions of conjugation, 285
isolation cultures, 249
rejuvenescence, 329
senility and division, 330
Suctoria feeding, 163
vitality graph of Stylonychia,
Fig. 165, p. 331
Mavor, autogamy, 324
Meiosis, gametic, 307
in Sporozoa, 526
zygotic, 309
Melanin, 134, 533
in malaria, 409
Membrane of nucleus, 59
Membranelles, 155
Membranulae, 155
Memory in Protozoa, 1S1
Mengheni, conditions of encyst ment,
290
Menosporidae, Key, 563
Mercier, fertilization in Cnidosporidia,
326
in Thelohania, 555
Merotomy and rejuvenescence in
Ameba, 239
Uronychia, Fig. 135, p. 262
Merozoite, defined, 528
with Golgi apparatus, Fig. 40, p.
79
Mesnil, chromidia, 70
kinetonucleus, 113
Mesodinium, tentacles, big. 198, p. 480
Mesomitosis, 89
600
INDEX
Metabolic gradient in Ameba, 180
types, 135
Metachromatic bodies, 72
Metacyclic trypanosomes, 382
Metacystidae, Key, 494
Metagamic divisions, defined, 529
Metalnikoff, choice of food, 189, 190
digestion in gastric vacuoles, 195
Paramecium, vitality, 253
selection in Protozoa, 181
Metamastigota, 422, 427
Metaplastids, 133
Metcalf, macrochromatin, 484
Opalinidae, 397
Metopidae, Key, 509
Metopus sigmoides, Fig. 206, p. 511
Metschnikoff, acid digestion, 196
Meves, chondriome, 73
Meyer, volutin, 72
Meyerhof, oxidation-reduction poten-
tial, 174
Michelson, Paramecium cysts, 24
Microdissection of Euplotes patella, 131
Microgametes, 272
Microgametocyte, defined, 529
Microgromia socialis colony, Fig. 107,
p. 214
division, 214
Micronucleus, 85
division, 218
Microsporidia, 552
Key, 569
Microihorax sulcata, Fig. 204, p. 502
Middleton, effect of increased tempera-
ture, 344
Miescher, chemistry of chromatin, 56
Miescher's tubules, 555
Miller, Hepatozoon cycle, Fig. 211, p.
527
history of Hepatozoon, 361
Minchin, cellular grade, 18
digestion, 195
endosome, 50, 51
kinetonucleus, 113
origin of cellular grade, 87
parabasal of little owl Trypano-
some, 112
source of blood parasites, 360
Minchin and Thompson, life history of
Trypanosoma leirisi, 233
Minot, chromatin and sex, 272
Mitochondria, 69, 73
and respiration, 76
of Opalina in division, Fig. 38, p.
75
Mitosis, 89
Monadidae, Key to genera, 426
Monocnidea, Key, 569
Monocystidae, Key, 559
Monocystis, meiosis, 309
rostrata, chromosomes, 99; Fig. 55,
p. 100
Monodinium balbianii, big. 84, p. 153
Monokaryomastigina, 422, 430
Monster formation, 264
Monsters and reduced vitality, Fig.
138, ]). 270
Moody, Actinobolina radians, 162
isolation culture of Spathidium,
254
Moore and Breinl, kinetonucleus, 113
Motile organoids, 139
organs, renewal, 221
Motor response in Protozoa, 181
Motorium in ciliates, 129
Mouth, origin at division, Fig. 114, p.
224
shifting, ciliates, Fig. 15, p. 36
Mouton, trypsin-like ferments, 196
Mrazekiidae, Key, 569
Mulsow, meiosis in Monocystis, 309
Monocystis rostrata, 99; Fig. 55, p.
102
Multiple nuclei, 84
Mutations, arising after treatment in
sensitive periods, 345
Mycetozoa, 445
aethalia, 450
capillitum in, 271, 446
elaters in, 446
Key, 462
life history, 445
microcysts, 445
peridium in, 271, 446
sclerotium in, 271
spore formation, 237
Mylestomidae, Key, 156
Myonemes of ciliates, 124
Myophanes, 128
Myophrisks of Radiolaria, 127
Myriaphrys paradoxa, Fig. 197, p. 478
Myxamebae, 445
Myxidiidae, Key, 568
Myxobolidae, Key, 568
Myxobolus pft ifferi, autogamy, Fig|.
164, p. 325
Myxoflagellates, 445
Myxogastres, Key, 463
Myxopodia, 435
stereoplasmatic axis, 435
Myxopodium, Fig. 78, p. 146
Myxosomatidae, Key, 56S
Myxosporidia, 54S
budding, 230
development , 55 1
Key, 567
N
Naegler, centrioles, 63
promitosis, 89
Nassonov, Golgi apparatus, 79
and contractile vacuole,
Fig. 95, p. 171
in contractile vacuole,
178
Nassula a urea, Fig. 195, p. 475
Nassulidae, Key, 498
IXhEX
601
Naville, autogamy in Cnidosporidia,
326
meiosis in Cnidosporidia, 546
Neresheimer, coordinating fibers, 1 (VI
myophanes and neurophanes, 128
Neuromotor apparatus, 129
system, 105
Neurophanes, 128
Nicolle, culture medium, 366
Leishmania infantum, 369
Nicollela, Fig. 172, p. 400
NicolleUidae, conjugation, 287
Nina gracilis, sex difference, Fig. 214,
p. 537
Xirenstein, digestion in gastric vacu-
oles, 195
gastric vacuole formation, 195
Nodosarine type of Foraminifera , ori-
gin, Fig. 186, p. 451
of shell, Fig. 19, p. 38
Xoguchi, serological work with L< ish-
mania, 363
Nosematidae, Key, 569
Novy and MacXeal, culture medium,
366
endotoxins in Trypanosomes,
198
Nuclear derivatives during division, SS
reorganization, 217
structure of fundamental organiza-
tion, 49
Nuclearia delicaiula, Fig. 183, p. 44 1
X'uclei with pole plates, (i."i
X'uclein, 65
X'ucleoplasmic relation, 205
Nucleus, J<»
cytoplasm changes at conjugation,
290
formation, 84
placenta, 84
Nutrition of Protozoa, 183
Nyctoth. rus, 401
cordiformis, Fig. 206, p. 51 1
basal hollies, 124
oralis, Fig. SI , ]). 151
Oicomonadidae, Key to genera, 423
Oicomonas, food-getting by Protozoa,
Fig. 97, p. 186
Oils and fats, 133
Oken, Frtiere, 17
Old age in I 'role pt us, 255
Ohgotrichida, Key, 512
Onychodromus grandis, Fig. 207, p. 511
Oocyst, defined, 529
Oogamy in Coccidiomorpha, 280
Opalinidae, fertilization, 484
Metcalf, 397
Operculina shell, Fig. 74, p. 138
Ophrydium, colony, 38
versatile, 21
Ophryocystis mesnili, gamete formation,
229; Fig. 120, p. 231
< )phryodendridae, Key, 524
Ophryoglena flava, Fig. 205, p. 504
Ophryoglenidae, Key, 507
Ophryoscolecidae, 401, 513
Ophryoscolecin, 139
Opisthodon mnemiensis, Fig. 191, p. 472
Oral baskets, 167
replacement at division, 222
Orcadellidae, Key, 465
Organization and differentiation, 260
defined, 47
Orthodon hamulus, Fig. 93, p. 167
Overton, permeability, 172
Oxidation-reduction potential, 174
Oxychromatin, 57
Oxygen, source of, 174
Oxvmonadidae, Key to genera, 432
Oxytricha, Fig. 209, p. 518
chromosomes, 319; Fig. 162, p. 320
fallax, Fig. 88, p. 159
pellioneUa, Fig. 88, p. 159
( )xytrichidae, Key, 517
Pachysoeca longicollis, Fig. 178, p. 419
Pansporella perplexa, 386
Pansporoblasts as endogenous buds,
232
Parabasal bodies, 60
body, 110, 111
types of, 416; Fig. 62, p. 116
Feulgen reaction, 118
Paradesmose, 1 1 8
in Trichonympha campanula, 99;
Fig. 54, p. 1()()
Paraglycogen, 133
Paramebidae, 456
Key, 467
Parameciidae, Key, 501
Paramecium aurelia, endomixis, Fig.
161, p. 318
bursaria, Fig. 204, p. 502
caudatum, fertilization in, Fig. 139,
p. 273
first meiotic, Fig. 57, p. 103
Golgi bodies and contractile
vacuole, Fig. 95, p. 171
in depression, Fig. 145, p. 283
in division, pole plates, Fig.
35, p. 67
nucleus, Fig. 23, p. 50
trichocysts, Fig. 193, p. 474
cilia structure, Fig. 82, p. 152
cyst, Fig. 5, p. 24
merotomy, Fig. 108, p. 216
monster formation, Fig. 108, p. 216
oxygen consumption, 175
putrinum, Fig. 204, p. 502
variations in size, Fig. 167, p. 342
Parasites, carriers of, 362
602
INDEX
Parasites, effect of, on hosts, 362
Parasitic flagellates, Haptomonad
stages, 367
Nectomonad stages, 31 17
Protozoa, 358
Parasitism, sites of, 360
Parastyle, 114
Parisotrichidae, Key, 503
Parthenogenesis, 316
and rejuvenescence, 340
in Paramecium, 251
Pascher, chromatophores of Paulinella,
442
Paulinella "chromatophores," 442
Peebles, merotomy, Paramecium, '-'til
Pelomyxa binucleata, nucleus, Fig. 23,
p. 50
Penard, types of Heliozoa, Fig. 75, p.
139
Pepsin-like ferments, 196
l'i rum mil trichophora, Fig. 3, p. 22
Peranemidae, Key to genera, 424
Perichenidae, Key, 465
Periplast, 135
Peristome, 156
Peritricha, Key, 521
Peritromidae, Key, 512
Peritromus emmae, fig. 89, p. 160; Fig.
207, p. 511
Peters, effect of oxygen on Colpidium,
175
Pfeiffer, sarcocystin, 197
transmission of malaria, 407
Pheodium, 134
Phalansterium digitatum, colony, 39;
Fig. 22, p. 41
Pharyngeal baskets, 167, 475
Phialonema cyclostoma, flagellum inser-
tion, 109; Fig. 60, p. Ill)
Philasteridae, Key, 507
Physaridae, Key, 463
Physiological balance, 19
Physiology, 172
Phytomonas davidi, Fig. 169 C, p. 366
Phytomyxida, 449
Key, 462
Pigments, 134
Pinaciopkora spicules, Fig. 75, p. 139
Plagiopylidae, Key, 500
Plagiotomidae, Key, 510
Plasmodiidae, Key, 566
Plasmodiophora brassicae, 386
Plasmodium falciparum, gametocytes,
Plate II, p. 409
formation, 271
malariae, sporulation, Fig. 124, p.
238 _
Marchiafava and Celli, 406
species, 406
vivax, sporulation, Fig. 124, p. 238
Plasmodroma, 411
Plastin, 58
Platysporina, Key, 568
Pleuronema chrysalis, Fig. 199, p. 482
Pleurostomina, Key, 491, 497
Pleurotricha lanceolata, fig. 210, p. 520
vitality graph, Fig. 132, p. 251
Plimmer, endotoxins in Trypanosoma,
198
Ploeotia vitrea, Fig. 76, p. 143
Podophrya cyst, Fig. 4, p. 23
li.ru, infraciliature, Fig. 43, p. 81
tentacles, Fig. 198, p. 480
sp., Fig. 100, p. 192
Podophryidae, Key, 524
Pole plates, 65
Poljansky, Bursaria conjugation, 315
Polycystid gregarine, development,
Fig. 126, p. 242
Polyenergid theory, 71
Polykaryomastigina, 422
Key to families, 432
Polymastix, parabasal, Fig. 62, p. 1 1 « >
Polystomellina crispa, alternation of
generations, Fig. 123, p. 235
chromidia, 69
nucleus. Fig. 23, p. 50
Ponselle, immunity, 364
Popoff, abnormalities, 345
division zones, 264
nucleoplasmic relation, 205
Porospora, cycle, 538
gymnospores, 532
taxonomy, 532
Poteriodetidron, 21
petiolatum, Fig. 177, p. 418
Predatory forms of protozoa, 185
Primitive forms, 141
Prociliata, Metcalf, 398
Promitosis, 89
Prorodon, Fig. 202, p. 492
Frost omina, Key, 490, 491
Proteomyxa, 443
Key, 461
Proterospongia, colonv, 38
Protista, 18
Protoplasm, death of, 227
Protoplasmic structure, 39
Prototrichiidae, Key, 466
Protozoa as organisms, 19
definition of, 17
distribution of, 23-25
form relations, 30
habitat of, 22
measurements of, 27
relation to other groups, 18
size, form and appearance, 26
the individual, 241
Protrichocysts, 135
Prowazek, division of Herpelomonas,
211
fibers in Euplotes, 131
granules in digestion, 196
lodamoeba, 307
Mastigamoeba invertens, 109
parabasal, Fig. 62, p. 116
Pseudochitin, 133-137
Pseudochlamys, Fig. 188, p. 457
INDEX
603
Pseudodifflugia, Fig. 11, p. 33
Pseudomembranes, 157
Pseudopodia, 145
as organs of locomotion, 150
formation, ISO
Pse idopodiospores, 236
Psilotricha acuminata, Fig. 210, p. 520
Pterocephalus nobilis, gametes, Fig. 144,
p. 281; Pig. 215, p. 538
Plychostoma bonasae, Fig. 179, p. 420
Pure lines and series, 250
Puschkarew, common air cysts, 23
Dimastigamoeba bistadialis, 107
Putter, reactions to stimuli, 1 SI
Pycnothricidae, 400
Key, 499
Pycnothrix, Fig. 172, p. 400
Pylea of central capsule, 438
Pyronine action on Trypanosoma bru-
cei, 114
Pyxinia moebiuszi, epimerite for food-
getting, Fig. 103, p. 201
R
Radiolaria, 438
central capsule of, 438
distribution of, 26
isospores and anisospores, 279
myophrisks, 127
spore formation, 237
types of, Fig. 181, p. 439
yellow cells of, 441
Radiophrya limnodrili, terminal bud-
ding, Fig. 116, p. 227
Raff el, conjugation and division rate,
332
Raphidiophrys pallida, Fig. 75, p. 139
Reducase and oxidation, 175
Rees, Paramecium motorium, 129
Regaud, function of mitochondria, 77
Regeneration of fragments without
micronuclei, 225
Reichenow, Feulgen reaction with volu-
tin, 72
nucleal reaction, 57
Reichenowellidae, Key, 510
Rejuvenescence after parthenogenesis,
340
by division, 209
by merotomy, 238
Maupas, 329
Reorganization and vitality, 328
bands of Euplotes, 94
cytoplasmic, 218
in Chilodon uncinatus, 222
in ciliates, 221
in Uronychia, 222
of cytoplasm at division, 218
Reproduction, 204
multiplicative, 540
propagative, 540
Respiration, 174
quotient, R.Q., 174
Reticulariidae, Key, 405
Reversibility of structures, 21, 4S
Reynolds, selection in Arcella polypora,
347
Rheoplasm, 42
Rhizomastigidae, Key to genera, 423
Rhizopoda, Kev, 461
Rhizopodia, 148, 442
Rhizopods, parasitic forms, 385
Rhodesian trypanosomiasis, 383
Rhumbler, ameboid movement, ISO
food ingestion by Protozoa, ISO
importation, 189
spumoid structure, 42
Rhynchocystidae, Key, 559
Richardson and Horning, chondriome,
74
Robertson, age and vitality, 269
catalase stimulating division, 200
environment and vitality, 256, 258
Feulgen reaction, 57
parabasal, US
Rogers, cultivation of Leishmania, 369
Root, selection in Centropyxis, 347
Rosenau, paroxysm toxins, 197
Rosenbusch, kinetonucleus, 113
Roskin and Levinson, gregarine myo-
nemes, 535
Ross, malaria and mosquitoes, 407
Rotifers, desiccation, 15
Sachs, energid theory, 205
Saedeleer, choanoflagellate collar, 104
food ingestion by Choanoflagel-
lates, 18S
Salpingoeca marinus, Fig. 92, p. 105
Sandon, soil Protozoa, 353
Sappinia, Fig. 185, p. 448
diploidea, 95
autogamy, Fig. 163, p. 323
Sappiniidae, 447
Key, 462
Sapropelic fauna, 24
flagellates, 356
Saprozoic nutrition, 199
Sarcocystin, 197
Sarcocystis muris, life history, 550
species, 555
Sarcode, 433
Sarcodictyum, 439
Sarcodina, chitin in, 433
nuclei in, 434
pseudopodia types of, 434
taxonomy, 433
Sarcomatrix, 439
Sehaeffer, Ameba anchorage at feeding,
ISO
choice of food, 189, 190
periplast, 135
pseudopodia, 150
selection in protozoa, 181
604
INDEX
Schaudinn, Actinophrys sol, Fig. 0(>, p.
120
Camptonema movement, 147
chemiotaxis in fertilization, 291
chromatin and sex, 272
chromidia, 69
cycle of Eimeria schubergi, Fig.
212, p. 530
division of Acanthocystis, 213
dysentery, 391
endobasal bodies, 62, 63
fertilization in Actinophrys, 277
in Centropyxis, 277
life cycle of Eimeria, 259
pole plates, 65
sex in Cyclospora, 280
Trichosphaerium, -457
Trypanosome of owl, 112
Schaudinnella he nit tit, gametes, Fig.
144, p. 281; Fig. 215, p. 538
Schaudinnellidae, Key, 559
Schewiakoff, Acantharia, 440, 441
budding division in Euglypha, 214
gregarine movement, 535
excretion, 177
mitosis in Euglypha, 98
Schizocystic sipunculi, budding, 229;
Fig. 119, p. 230
Schizogony, defined, p. 528
Schizogregarinida, 541
Key, 564
Schizont, denned, 52S
Schizontocyte, defined, 528
Schizontocytes, 227
Schizotrypanum cruzi, 383
Schmahl, reorganization at division,
264
Schroder, Epistylis, Fig. 70, p. 126
myonemes, 125
somatic structures in Actinom yxida,
, 240
Sphaeromyxa autogamy, 324
Schultz, physical conditions in Ameba,
180
Schultze, division of Ameba, 21:;
Schumacher, volutin, 72
Sciadostomidae, Key, 500
Sclerotium, 440
Scopula, 359, 483
Secretions as toxins, 193
Seizing organ, Didinium, 163
Selection and variations, 347
Selenococcidiidae, Key, 565
Senescence and division, 330
"Sensing" at a. distance by .1 meba, 1S9
Sensory cilia and flagella, 127
Septata, Key, 560
Sergent, immunity, 364
Serological work, 363
Sewage Protozoa, list of, 357
Sex, definition of, 272
in Cyclospora karyolytica, 280
Shapiro, pH of gastric vacuoles, 196
Sharp, Diplodinium, Fig. 2, p. 20
Sharp, motorium, neuromotor appa-
ratus, 129
skeletal structure, 125
Shellackia, hosts, 361
Shells and tests, 137
Shiga, bacillary dysentery, 391
Siebold, v., unicellular organisms, 17
Siedlecki, Lankesteria, Fig. 213, p. 531
schizontocyte formation, 227
Silver line system, 69, 80
origin of mouth at divi-
sion, Fig. 114, j). 224
Skin as barrier to infection, 300
Slime moulds, 445
Slonimski and Zweibaum, excretory
granules, 197
Smith, Sarcocystis muris, 555
Soil Protozoa, 353
Sokoloff, gregarine movement, 535
Somatella, formation of, 233, 418
Somatic structures and death, 239
Somatochromidia, 70
Spathidiidae, Key, 495
Spathidium spathula, feeding, Fig. 09,
188
food-getting by Protozoa, 186
increased vitality after con-
jugation, 332
vitality graph, Fig. 133, p. 252
Sphaeractinomyxon, Fig. 221, p. 552
autogamy, 326
Sphaerastrum with centroblepharo-
plast, Fig. 50, p. 95
Sphaeromyxa sabrazesi, autogamy, Fig.
164, p. 325
Sphaerospora dimorpha, endogenous
buds in, Fig. 121, p. 232
Sphaerosporidae, Key, 568
Sphaerosporina, Key, 568
Spicule formation and alveolar struc-
ture, Fig. 12, p. 33
types, Fig. 75, p. 138
Spiral types, Fig. 16, p. 36
Spirochonidae, Key, 522
Spironemidae, 431
Spirostomidae, Key, 510
Spirostomum ambiguum nuclei, si;
contraction, 125
teres nuclei, 86
Spirotricha, Key, 508
Spirozonidae, Key, 500
Split conjugants, 284
Spongomonas, centrioles, li."
splendida, division, 01; Fig. 49, p.
95
reorganization at division, 212
Sporamebidae, Key, 407
Spore formation, 233
in Myxobolus, 240
of Radiolaria, 237
Sporetia, 70
Sporoblast, defined, 529
Sporocyst, defined, 529
types, Fig. 216, p. 539
INDEX
605
Sporoducts, 240
age differentiations, 270
Sporogony, defined, 548
Sporont, defined, 528
Sporozoa, 525
form, 525
gametes in, Fig. 215, p. 538
nuclei, 526
parasites of man, 402
size, 525
Sporozoite, denned, 528, 529
Sporozoites with Golgi apparatus, Fig.
40, p. 79
Stamiewicz, fat digestion, 199
Staurojoeniidae, 428
Stemonitidae, Key, 464
Stempell, fertilization in Cnidosporidia,
326
Stempellia magna, life cycle, Fig. 222,
p. 553
Stenophoridae, Key, 561
Stentor coeruleus, myophanes, neuro-
phanes, 128
cilia and myonemes, Fig. 69,
p. 124
a i iji r, basal bodies, 124
polymorpha, Fig. 81, p. 151
regeneration, 45
Stentoridae, Key, 510
Stcntorin, 134
Stephanoeca ampulla, Fig. 178, p. 419
Stepkanonympha silvestri, Fig. 175, p.
114
Stephanopogon, Fig. 207, p. 511
Stephens and Fantham, trypanosomi-
asis, 384
Stercome, 450
Stereoplasm, 42
Stern, central granule of Heliozoa, 120;
Fig. 67, p. 121
division of Acanthocystis, 213
pH of medium, 353
Steudel, thymonucleic acid, 57
Stichotricha secunda, Pig. 192, p. 473
Stiles, Sarcocystis rileyi, 555
Stocking, conjugation and division-
rate, 332
Stole, glycogen in Pelomyxa, 133, 198
Stomatophoridae, Key, 559
Strasburger, energid theory, 205
St reblomastigidae, 431
Strelkow, Tripalmaria, Fig. 14, p. 35
Strombilidiidae, Key, 513
Strongylidium, Fig. 88, p. 158; Fig. 209,
p. 518
Stylocephalidae, Key, 563
Stylonychia, cirrus structure, Fig. 82,
p. 152
mi/lil us, Fig. 3, ]). 22
vitality graph, Fig. 165, p.
331
pustulata, vitality graph, Fig. 165,
p. 331
senescence, Fig. 130, p. 249
Stylorhynchus longicollis, gametes, Fig.
144, p. 281; Fig. 215, p. 538
Suckers in flagellates, 420
Suctoria, ciliated embryoes, 228
embryos, development of, 243
endogenous budding, Fig. 117, p.
228
food-taking in, 191
Key, 523
Surra, trypanosome disease of horses,
381
Swarczewski, chromidia, 69
endogenous budding in A reel In, 228
fertilization in Cnidosporidia, 326
Vahlkampfia, 62
Symbiohts, 202
in ciliates, 47(5
Synactinomyxon, Fig. 221, p. 552
Syncystidae, Key, 560
Taliaferro, serological work, 363
Taylor, dedifferentiation with division,
263
merotomy in Euplotes patella; Fig.
96, p. 182
microdissection, 129; Fig. 72, p.
130
Taxonomic structures, 132
Taxonomy of flagellates, -111
Tektin, 135
Telosporidia, 533
Key, 557
Ternetz, amino-acid nutrition, 200
Testacea, 456
Key, 467
Tetramitidae, Key to genera, 430
Theileriidae, Key, 566
Thelohania legeri, life cycle, Fig. 223,
^ p. 554
Thigmotricha, 483
Thon, seizing organ of Didinium, 163
Thymonucleic acid formula, 57
Tintinnidae, distribution, 26
Key, 513
Tintinnopsis, Fig. 208, p. 514
Tissue-cell culture, 210, 258
Tokophrya cyclopum, 228; Fig. IIS, p.
229
quadripartita, Pig. •'!, p. 22
endogenous budding, Fig. 107,
p. 228
Toxins, 197, 363
Tracheliidae, Key, 497
Trnihi lias ovum, Fig. 93, p. 167
Trachelocerca, Fig. 202, p. 492
contraction, 125
Trailing flagellum, 142
Triactinomyxon, Fig. 221, p. 552
Trichiidae, Key, 465
Trichites, 134, 166, 473
Trichocysts, 134, 473
606
INDEX
Trichomonadidae, Key to genera, 430
Trichomonas dugusta, division, Fig. 77,
I>. 145
distribution in man, 361
Trichonympha campanula, Fig. 64, p.
118
mitosis, Fig. 54, p. 100
Trichonymphidae, Key to genera, 428
Trichopelmidae, Key, 501
Trichophrya salparum, Fig. 100, p. 192
Trichosphaerium, alternation of genera-
tions, p. 457
Trichospiridae, Key, 500
Trichostomida, Key, 499
Trimastigamoeba philippinensis, kine-
tic element, 107
Trimastigidae, Key to genera, 427
Tripalmaria dogieli, Fig. 14, p. 35
Trophochromatin, 56
Trophonucleus, 112
Trophozoite, denned, 528
Tropisms, 181
Trypanosoma cruzi, origin of parabasal,
Fig. 61, p. Ill
parabasal, Fig. 62, p. 116
enduring modifications, 344
flagellum insertion, 109; Fig. 61,
p. Ill
gambiense, Fig. 169 D, p. 366
genus, 371
lewisi, somatella formation, 233;
Fig. 122, p. 234
life history, 382
list of species and hosts, 372-381
rhodesiensis, 383; Fig. 169 /, p. 366
stations in insects, 382
Trypanosomiasis, clinical history, 383
in man, 381, 383
Trypanosomidae, Fig. 169, p. 366
Key to genera, 424
Trypsin-like ferments, 196
Tschenzoff, Euglena viridis, 61
Tsetse flies and trypanosome transmis-
sion, 381
Tubiferidae, Key, 405
Turner, motorium, 129
reorganization bands, 93; Fig. 4S,
p. 94
Tyzzer, chicken coccidiosis, 405
Cochlosomidae, Fig. 179, p. 420
U
LIhlenhuth, endotoxins in Trypano-
soma, 198
Undulating membrane, 142
cilia t a, 157
Unequal division, 225
ITnger, vacuole activity, 284
Urceolariidae, Key, 521
Urocentrum turbo, Fig. 205, p. 504
Uroleptus, bilateral symmetry, 36; Fig.
18, p. 37
Uroleptus halseyi, chondriome, Fig. 37,
p. 74
nuclear cleft, 92; Fig. 47, p. 93
mobilis, Fig. 1 (Frontispiece)
centriole, 63; Fig. 32, p. 01
division of double individual,
Fig. 128, p. 246; Fig. 12(1,
]>. 247
division of macronucleus, Fig.
110, p. 220
encyst ment period, 267
formation of nuclei, 84
fusion of macronuclei, Fig.
109, p. 219
graph of vitality, Fig. 131, p.
251
isolation cultures, 254
metagamic divisions, Fig. 160,
]). 314
nuclear fusion, Fig. 159, p. 313
old age, Fig. 7, p. 28
optimum vitality for nine
years by conjugation, Fig.
166, p. 334
origin of double individual,
244; Fig. 127, p. 245
origin of Macronucleus, Fig.
27, p. 58
pisces, Fig. 81, p. 151; Fig. 20'.), p.
518
Uronychia transfuga, division zone, 217
merotomy, Fig. 113, p. 223;
Fig. 135, p. 262
structure, Fig. Ill, p. 221
Urospora lagidis, gametes, Fig. 144, p.
281; Fig. '215, p. 538
Urosporidae, Key, 560
Frthiere, 17
Vahlkampfia l/mas, chromidia, Fin 28,
' ]). 59
division, Fig. 106, p. 212
nuclear division, Fig. 26, p. 53
Valkanov, origin of Clathrulina stalk,
148
Vampyrellidae, 444
Key to genera, 462
van Herwerden, volutin, 73
Variation and heredity, 342
Verjiingung, Butschli, 329
Verworn, cilia beat, 127
effect of oxygen on Colpidium, 175
merotomy, 55
respiration, 174
Vesicular nuclei, 50
Vianna, cause of espundia, 309
Viereck, Endamoeba tetragena, 392
Visscher, trichocysts, 475
Vitality, 244
ami reorganization, 3-28
intensity and endurance of, 333
and renewal of, 335
INDEX
U0<
Vitality, measure of, 2 IN
of parent and offspring scries,
Table, p. 330
Volutin grains, 69, 72
von Leeuwenhoek, discovery of Proto-
zoa, 17
Vonwiller, protoplasmic structure, 43
Vorticella, frontal field, 169
structures, Fig. 86, p. 158
type, Fig. 86, p. 158
Vorticellidae, fertilization, 279; Fig.
143, p. 280
Key, 522
W
Wagnerella, axial filaments, 122
borealis, division, 213
Wailes, Pseudogromiinae, Key, 469
Walker and Sellards, dysentery, 393
Wallengren, reorganization in ciliates,
221
Washburn, tropisms, 181
Weatherby, uric acid, 177
Weininger, sex, 272
Weinland, anti-digestive ferments, 359
Weismann, amphimixis, 329
germ and soma, is
Life and Death, 24S
Wenrich, Actinobolina vorax, 162
Wenyon, grouping of trypanosomes
according to site in insect, 382
kinetoplast, 114
Wenyon and O'Connor, Endolimax
nana, 397
Werbitzski, enduring modification in
Trypanosoma, 344
trypanosomes without kinetonu-
cleus, 114
Wetzell, cavulae, 42
Whitman, inadequacy of term cell, 19,
40
Whitmore, dysentery, 393
Trimastigamoeba philippinensis,
107
Willis, reaction of fragments, 183
Wilson, division of granules, 208
Wilson, C, Dimastigamoeba gruberi,
107; Fig. 59, p. L08
Winter, chromidia, 69
Woithe, endotoxins in Trypanosoma,
198
Wolff, soil Protozoa, 354
temporary cysts, 267
Woodcock, kinetonucleus, 112
and Lapage, copulation in flagel-
lates, 276
Woodruff, effects of excretion products,
200
isolation cultures, 250
rejuvenescence after endomixis,
340
succession of Protozoa, 23
survival value of conjugation, 333
Woodruff and Erdmann, endomixis, 317
parthenogenesis, 251
Woodruff and Spencer, rejuvenescence
in Spathidium, 332
sensing, 189
Spathidium, vitality, 252, 255
Wortmann, cellulose digestion in Fora-
minifera, 199
Wright, organism of tropical ulcer, 369
Yocom, myophanes and neurophanes,
128
Young, cirrus regeneration, 164
endomixis and environment, 340
merotomy in Uronychia, 225, 263
ZOOMASTIGOPHORA, 412, 121
Zoosporidae, 444
Key to genera, 461
Zoothamnium alternans, 21
arbuscula, 21
colony, 38
contraction, 125
Zuelzer, chromidia, 70
division of Wagnerella, 213
enduring modification in Ameba,
343
environment effects, 1 78
Wagnerella, 122
Zumstein, amino-acid nutrition, 200
Zweibaum, chondriome, 75
disorganization significance, 31 1
protoplasmic make-up at conjuga-
tion, 290
Zygocystidae, Key, 559
Zygocystis zonula, caudal threads, 536
Zygote, defined, 529
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