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Marine Biological Laboratory Library
Woods Hole, Mass.
Presented by
. 2. B. Harvey
Sept. 1, 1960
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/-
PROTOZOOLOGY
BY
GARY N. CALKINS, PH.D.
PROFESSOR OF PROTOZOOLOGY IN COLUMBIA UNIVERSITY, NEW YORK
TUlustratefc wttb 125 Engravings
anfc 4 Colored plates
LEA & FEBIGER
NEW YORK AND PHILADELPHIA
Entered according to Act of Congress, in the year 1909, by
LEA & FEBIGER
In the Office of the Librarian of Congress. All rights reserved
PREFACE,
IT is my purpose, in the present volume, to discuss some of the old
and some of the new problems in biology as illustrated by the lowest
forms of animal life, the protozoa, the subject matter being founded
on a course of Lowell Institute lectures given in the fall and winter of
1907. Interest in these organisms, of late, has centred mainly in the
practical side until, to many biologists and to most medical men,
protozoology implies the science dealing with pathogenic protozoa.
Protozoology has a broader scope than this, and it is one purpose of
this book to check, if possible, the limiting tendency and to point out
again the important part that the protozoa play in the problems of
modern biology. This is the more necessary because, in my opinion,
in the application of biological principles which underlie the vital
phenomena of free and parasitic forms alike, will be found the most
valuable data for the more practical sides of protozoology. Here in
these mere specks of animated jelly, which rarely measure more than
the hundredth part of an inch, we find, in their simplest forms, the
manifold processes of the living organism. Digestion and assimilation;
respiration, with its dual action of oxidation and renewal; excretion
and secretion; irritability and fatigue; reproduction, together with the
unfathomed mystery of fertilization and inheritance, all find expres-
sion in these simple animals and raise the lowest protozoon immeasur-
ably above the most complex of non-living substances. With such
vital processes reduced to their lowest terms in these protozoa, we
should expect to find a wealth of material for the study of life phenom-
ena which in the higher animals are masked under a cloak of differ-
entiated structures, and the study of these more general functions
should form the basis for explanations or interpretations of the more
specialized adaptations which are characteristic of pathogenic forms.
This more comprehensive field, as I understand it, is the scope of
modern protozoology.
The researches of Louis Pasteur, in connection with fermentation,
souring of wine, and the silkworm disease, led him to many reflections
and conclusions as to the nature of various contagious and hereditary
diseases. Perhaps more than any other single research, his investi-
gations, begun in 1865, on the cause and prevention of silkworm
epidemics (to which De Quatrefages had given the name of pebrine,
iv PREFACE
because of the characteristic black spots), led him to the belief that
many human ills are similarly due to minute and microscopic forms of
life, and so paved the way for the later generalization which now domi-
nates medicine — the germ theory of disease. Ahead of his times in
recognizing the present-day axiom that epidemics are ended by pre-
vention rather than by individual treatment, Pasteur patiently advised
and demonstrated, in connection with the silk industry, that perfect
silkworms and moths would not develop from eggs having pebrine
corpuscles on them. It is of no importance that these corpuscles were
not recognized by him as the spores of a protozoon, but the important
results which followed their discovery, and which led to increased
length of human life, and to the mitigation of human and of animal
suffering throughout the civilized world, make an increasingly sub-
stantial monument to the patience, courage, and virility of this man
of pure science, who, by the apotheosis of scientific method, proved
these unknown corpuscles to be the cause of this silkworm disease.
The recently opened chapter of the protozoan diseases of man
might have been earlier studied had these observations of Pasteur
upon the spores of Nosema bombycis been followed up. The parasitic
protozoa were known and the free-living forms had been brought into
prominence in scientific circles through the controversies over the cell
theory and the theory of spontaneous generation, but more than thirty
years were to elapse before general acceptance of the first human
disease attributable to protozoa.
The other minute organisms, bacteria and yeasts, whose presence
Pasteur had demonstrated in his experiments on fermentation and
spontaneous generation, were not neglected. In the hands of R.
Koch the means of studying bacteria were perfected, and "culture"
methods were introduced which soon raised bacterial research to the
dignity of an independent branch of biological science. The ease with
which bacteria could be studied, thanks to these methods, and the
rapidly increasing list of bacterial diseases, seemed to divert the atten-
tion of specialists from the pursuit of protozoan diseases and to confine
it to research on those of bacterial origin. Attempts were repeatedly
made, however, to cultivate protozoa as the bacteria are cultivated, on
artificial media, but until the present decade such efforts, for the most
part, were fruitless. The difficulties in applying the artificial culture
method to the protozoa are due, essentially, to the differences in their
mode of nutrition. Some of them, indeed, are similar to the bacteria in
being saprophytic or saprozoic (to use Blanchard's expressive term),
absorbing liquid or dissolved proteid matter through the body wall.
Such forms lend themselves to the culture method, and the success of
Novy andMacNeal and others with trypanosomes,herpetomonads, etc.,
in artificial liquid media follows from this nutritional characteristic.
Other forms of protozoa, as, for example, the parasitic amebse, may or
PREFACE V
may not lend themselves to the culture method, and then only upon
the condition of having other living things as food. Many observers
have found that intestinal aniebae, and others that feed on bacteria,
will thrive on solid culture media provided the latter are seeded with
bacteria, and this fact is of the greatest importance in obtaining
material for study. Other amebse cannot be cultivated in this way, and
it is quite probable, as Lithe maintains, that many parasitic protozoa,
especially the intracellular parasites, such as the coccidia, will never
be successfully cultivated.
There is need, furthermore, of caution in studying protozoa under
such artificial conditions, for they are extremely sensitive to variations
and are readily adapted to new conditions. The reactions, both
morphological and physiological, of protozoa under such conditions
of study require careful control.
The study of protozoa, therefore, even when it is possible to apply
bacteriological methods, is fundamentally different from the study of
bacteria as at present carried on. The latter, dependent upon growth
conditions, colony formation, reactions to media, etc., are essentially
physiological and based upon the functions of the organisms. The
study of protozoa, on the other hand, is essentially morphological, or
based upon the structures of the protozoan cell, and involves the
changes in cell structures which an individual undergoes during various
phases of vitality. Hence it becomes necessary, first of all, to know
the life history of the protozoon and the fundamental modifications
which its protoplasm assumes. Modern protozoology, therefore, has
demanded as a basis for genera and species of protozoa a knowledge
of the complete life cycle, and as a basis for classification not the struc-
tures of the single cells, but the structures which the protoplasm may
assume throughout its entire life history from fertilization to death or
until the next fertilization.
The present volume, finally, does not aim at being an exhaustive
treatise on the protozoa ; it aims, rather, to give an introduction to the
study of modern protozoology as seen from the author's point of view;
and for numerous omissions, incomplete references, etc., he can only
plead the excuse of a large subject crowded into a limited space.
G. N. C.
NEW YORK, 1909
CONTENTS.
CHAPTER I.
GENERAL ORGANIZATION OF THE PROTOZOA.
A. General Morphology IS
Protoplasmic Structure 21
Membranes, Shells, and Tests 22
Plastids 26
Vacuoles and their Functions 28
Nuclei, Chro matin, and Chromidia 28
Kinoplasm 29
B. Organs of Locomotion and Classification 34
Pseudopodia and Classification of the Sarcodina 35
Flagella and Classification of the Mastigophora ... 42
Cilia and Classification of the Infusoria 49
Parasites and Classification of the Sporozoa 56
CHAPTER II.
PHYSIOLOGICAL ACTIVITIES OP THE PROTOZOA.
Food-taking and Digestion 71
Excretion 83
Irritability 84
Growth and Reproduction 87
Division 88
Budding 92
Sporulation 96
CHAPTER III.
PROTOPLASMIC AGE OP PROTOZOA.
A Typical Life Cycle ... 104
Youth, Maturity, and Age 110
The Period of Youth . . Ill
Changes at Maturity 113
Idiochromidia 118
Sex Differentiation 126
Old Age . . . . 127
viii • CONTENTS
CHAPTER IV.
CONJUGATION, MATURATION, AND FERTILIZATION.
Fertilization by Autogamy 139
Fertilization by Endogamy 146
Fertilization by Exogamy 150
Parthenogenesis 161
Maturation in Protozoa 164
Significance of Conjugation 171
CHAPTER V.
PARASITISM.
Structural Modifications and Mode of Life of Protozoan Parasites . . . 175
Reproduction and the Life Cycle 178
Endogenous Cycle 181
Exogenous Cycle and its Variations 187
Sporulation in Gregarines 189
Sporulation in Coccidia 192
Sporulation in Myxosporidia 192
Exogenous Life of Protozoan Parasites 193
Air-borne Protozoa 195
Transmission by Inheritance 196
Transmission by Intermediate Hosts 198
Effects of Protozoan Parasites on Their Hosts 201
Protozoa and the Cancer Problem 204
CHAPTER VI.
THE PATHOGENIC FLAGELLATES.
The Genus Spirocheta and its Allies 217
Spirocheta Balbianii 220
The So-called Flagella of Spirochetes 223
The Spirochete Nucleus 225
Division of Spirochetes 226
Form Changes and Life History 228
Are Spirochetes Protozoa or Bacteria? . 231
CHAPTER VII.
THE PATHOGENIC FLAGELLATES (CONTINUED).
The Genera Herpetomonas and Crithidia 233
Herpetomonas Donovani and Kala Azar 238
The Genus Crithidia 241
CONTENTS ix
CHAPTER VIII.
THE PATHOGENIC FLAGELLATES (CONTINUED).
The Genus Trypanosoma 244
The Motile Apparatus of Trypanosoma 253
The Trypanosome Nuclei 255
Form Changes of Trypanosomes 257
Reproduction of Trypanosomes 260
Agglomeration 261
Invertebrate Hosts and Life Cycle 261
The Effects of Trypanosomes upon Vertebrate Hosts 267
CHAPTER IX.
THE PATHOGENIC HEMOSPORIDIA.
The Genus Babesia 270
Structural Characteristics 273
Transmission by Ticks and Life Cycle of Babesia 275
The Organisms of Malaria 279
CHAPTER X.
THE PATHOGENIC RHIZOPODA.
Entameba and the Dysentery Problem -. 294
Rabies and the Negri Bodies 300
Smallpox and the Guarnieri Bodies 302
Other Protozoan Diseases of Obscure Etiology 311
PROTOZOOLOGY
CHAPTER I.
GENERAL ORGANIZATION OF THE PROTOZOA.
A PROTOZOON is a primitive animal organism usually consisting of a
single cell, whose protoplasm becomes distributed among many free
living cells. These reproduce their kind by division, by budding, or by
spore formation, the race thus formed passing through different form
changes and the protoplasm through various stages of vitality collec-
tively known as the life cycle.1
FIG. 1
Types of protozoa. -4, Ameba proteus, a rhizopod (after Calkins'); B, Peranema trichoph-
orum, a flagellate (after Biitschli); C, Stylonychia mytilis, aciliate with specialized cilia (after
Biitschli); E, Tokophrya quadripartita, a suotorian (after Biitsohii); D, Pyxinia, sp., a poly-
cystid gregarine with primite and deutomerite (after Wasielewsky) ; c, contractile vacuole; e,
epithelial host cell; n, nucleus; v, food vacuole.
It is quite impossible within the limits of a small volume to give a
detailed or even adequate account of the many sides of interest of the
unicellular animals. The wide range in habitat, from the purest
waters of lake or sea to the foulest ditch, or the adaptation to environ-
ments varying in character from a mountain stream to the semifluid
substance of an epithelial nerve or muscle cell, has brought about
1 Definition by Calkins, 1906.
18 GENERAL ORGANIZATION OF THE PROTOZOA
manifold varieties of protozoon structure. To describe all of these
modifications under one or a few headings, and to attempt to formulate
general laws from the different and often highly complicated life
histories, is out of the question. Nevertheless, in spite of the struc-
tural modifications and special adaptations to particular modes of
life, it is possible to group the different kinds of protozoa in four defi-
nite types, first outlined by the French microscopist Felix Dujardin
in 1841. Three of these types — sarcodina, mastigophora, and infu-
soria— are based upon the form of the locomotor organs, pseudopodia,
flagella, and cilia respectively, while the fourth type — sporozoa—
including the gregarinida, first recognized as unicellular organisms
by Kolliker in 1845, are devoid of motile organs, and are invariably
parasitic in mode of life (Fig. 1).
A. GENERAL MORPHOLOGY.
While the different kinds of protozoa are undoubtedly the simplest
animals known to us, they comprise at the same time some of the most
complicated forms of cells, and the protoplasmic differentiations within
these cells are frequently highly developed. In some cases these
modifications are so highly evolved that we have little reason to regard
such cells as units of structure comparable with the tissue cells of
higher animals and plants, but should look upon them as composed
of still more elementary vital units, and to this extent the cell theory,
when applied to them, is inadequate.
The wride distribution of the protozoa and their varied modes of
life lead to the greatest possible differences between them and even
within the limits of the same class. No one form is characteristic of
any type, but in all cases where the body is plastic and subjected to an
even environmental pressure, as in floating, or in intracellular, quies-
cent forms, the body is spherical (homaxonic), readily changing, how-
ever, into an elongate or monaxonic form when the organism moves
or is subjected to a current. In all divisions, when for any reason the
surrounding medium becomes unsuitable, or in some cases for pur-
poses of digestion or reproduction, the organisms secrete a thick and
resistant covering of chitin, and they remain thus "encysted" until
conditions are again suitable, and such cysts are usually spherical.
The size of protozoa likewise varies within wide limits. Some of
them are on the very limits of vision, and some, apparently, are
invisible, even when the eyes are assisted by the highest powers of the
microscope. Thus, the organism causing yellow fever, and thought to
be a protozoon, is so minute that it has never been seen, although its
habitat and its general history are well known. Other protozoa, on the
other hand, are relatively enormous single cells, a Pelomyxa palustris
GENERAL MORPHOLOGY
19
or a Bursaria truncatella, reaching the size of 2 mm. (one-twelfth of an
inch), while the parasitic gregarine Porospora gigantea of the lobster's
gut attains the length of 16 mm., or two-thirds of an inch.
Unlike the majority of bacteria, the size of any given species of
protozoa often varies within wide limits, and this in the same environ-
ment. The reasons for this difference are numerous, sometimes it is
due to starvation, sometimes to developmental condition, and some-
times to the variations in vitality at different periods in the life history.
Thus, two cells from the same culture of dileptus species may be mis-
taken for different species, the difference between them being so great,
Dileptus, sp. Two sister cells. A, normal individual with macronucleus in form of
scattered chromatin granules (chromidia); B, individual starved for several days. From
photographs taken with same magnification.
and due solely to the lack of food in one case (Fig. 2). This
divergence in size is particularly noticeable in the parasitic forms,
where many factors influence the development of the cell.
Many forms of protozoa, especially the flagellated types, have
acquired the habit of association into colonies, and with such associa-
tion have gained the economy which conies from division of labor,
so that here in the colony forms may be found the first step in the
differentiation of cell aggregates and the nearest approach of protozoa
to the metazoa. Such colonies have been designated according to
their mode of formation, gregaloid, spheroid, arboroid, and catenoid
20
GENERAL ORGANIZATION OF THE PROTOZOA
colonies. A gregaloid colony arises by the adventitious union of
previously separated cells. Thus, many of the so-called "agglomera-
FIG. 3
Uroglena americana, Calkins, a spheroid colony, consisting of monads embedded
in a gelatinous matrix.
FIG. 4
Codosiga cymosa Sav. Kent, an arboroid colony of Choanoflagellates. (After Kent.)
tions" of spirochetes and trypanosomes are gregaloid colonies brought
about by some adverse condition of the environment. A spheroid.
GENERAL MORPHOLOGY 21
colony is a more perfect compound individual in which the cells are
embedded and held together in a common gelatinous matrix (Fig. 3).
An arboroid colony is one formed by continuous division of cells
which remain attached at some point, such colonies often being large
dendritic branched aggregates (dinobryon, epistylis, carchesium, etc.,
Fig. 4). A catenoid colony, finally, is formed by the union of two or
more cells end to end or side by side.
(a) Protoplasmic Structure. — The body of a protozoon is made
up of a somewhat gelatinous, diaphanous substance, to which Dujar-
din, in 1835, gave the name "sarcode," but which M. Schultze, in 1863,
showed to be identical with the substance "protoplasm" of higher
plants and animals, and named by von Mohl in 1846. The minute
structure of this protozoon protoplasm appears to be little more than
a fine network, the meshes of which are sometimes minute and narrow,
as though compressed, and sometimes large and open. The substance
of the walls of the meshwork appears to differ noticeably from that
within its spaces, the former more dense and made up of fine granules
(microsomes), the latter more fluid and containing granules of con-
siderable size. Microchemical reactions show that these granules
differ in chemical composition, and that some are reserve food par-
ticles, others reserve matters for one use or other, and that still others
are waste matters. This protoplasmic make-up, which Biitschli ('92)
compared with a foam structure (Schaumplasma), was described by
him as consisting of fine drops of a liquid alveolar substance, enclosed
within the meshes of a continuous interalveolar substance, also liquid
but of a different density. Each alveolus he compared with a bubble
in a foam structure; the air of the bubble corresponding to the alveolar,
the walls to interalveolar, substance.
While the inner protoplasm of all protozoa is probably alveolar in
nature, there is considerable variation in structure due to the great
variations in size of the alveoli and of the granules contained within
them. In some forms (e. g., in the heliozoon actinospherium) the
vacuoles are so large as to give a parenchymatous appearance to the
cell, but in others they are so minute as to give a uniformly dense
appearance; between these two typical cases fall the remainder of the
types of protozoa. The granules within the walls of the alveoli are
equally variable in size; in some cases they are very minute, corre-
sponding, apparently, to the fine elementary granules which Altmann
('94) regarded as the basis of all protoplasm, while in other cases they
are obviously of different kinds. There is reason to believe that some
of these interalveolar granules are endowed with a specific function,
and that some of them underlie the various motor activities of the cell
(" kinoplasm" of Strasburger; "ergastoplasm" of Prenant). It is
certain that the protoplasmic alveoli tend to condense toward the
periphery of the cell, the condensation due, apparently, to the loss of
22 GENERAL ORGANIZATION OF THE PROTOZOA
the more fluid alveolar substance, while the specific kinetic elements,
if present, are concentrated. Such an hypothesis might very well
account for the contractility of the ectoplasm of an ameba or for the
various locomotor appendages of flagellated and ciliated forms (see
page 29).
It is on the basis of these protoplasmic modifications that the pro-
tozoa are grouped into classes, orders, and finer subdivisions, and the
most important of these have to do with the changes undergone by the
outer protoplasm. This is the part of the cell that comes in contact
with the surrounding medium, and this is the part, therefore, if any,
which becomes changed by such contact. Being on the outside, it is
the region of the cell for food ingestion, and we find it differentiated
into mouth parts and into protoplasmic modifications for the procuring
and directing of food. It is also the seat of motion, and may be
differentiated into a great variety of motile organs which are so char-
acteristic that classification is based mainly upon them. These motile
organs, all of which may be traced back to a similar primitive type, may
become modified into complex organs of the cells, while the function
of locomotion is frequently changed into that of food getting, or into
a sensory function of touch. It is an interesting point in this connec-
tion that the sensory apparatus arises in the outer or cortical plasm as
a response of protoplasm to the surrounding medium, and it is signifi-
cant that in all higher animals the sensory and nervous systems arise
from the outermost layer of cells, the ectoderm.
In many protozoa, especially among the simpler rhizopods and
some of the sporozoa, there may be no distinction between the inner
and the outer protoplasm. Such cases, however, are exceptional, for
in the majority of protozoa a well-marked ectoplasm can be distin-
guished. In most cases the difference appears to be mainly in the
presence or absence of granules, their distribution depending upon
the density of the plasm. No great morphological value can be placed
upon this regional difference, for it appears to be only an index of the
physical condition of the protoplasm. In Ameba proteus, for example,
the outer layer is dense and the granules of the alveoli are forced into
the more fluid endoplasm, but in pelomyxa the protoplasm appears to
be everywhere the same in density and the granules penetrate to the
very periphery. In some of the rhizopods, especially the shelled forms,
the distribution of granules according to density is so marked that
several zones can be made out. In this connection it is significant
that in the artificial mixtures which Biitschli so successfully made to
imitate protoplasm, a similar regional differentiation into outer and
inner structures could be distinguished, a result due in this case to
surface tension.
(6) Membranes, Shells, and Tests.— It is possibly due to such a
tendency of protoplasm to stiffen under the influence of surface tension
GENERAL MORPHOLOGY
23
in water that we may turn for an explanation, first pointed out by
Gruber ('81), of the outer condensation of protoplasm resulting in the
numerous types of membranes and tests of the rhizopods or of the outer
coverings of the protozoa in general. The simplest form of membrane
is an almost invisible cuticle of extreme delicacy, and it would be
difficult to say whether such coverings are due to the physical change
of the protoplasm or to secretion of a covering material which gradu-
ally hardens in the water (as cysts are formed). In the ordinary forms
of ameba, at any rate, the pellicula is merely a hardening or condensa-
A, Englypha alveolata; B, Cochliopodium.
tion of the outer zone, and in the different species of ameba all grades
may be distinguished up to the relatively thick membranes of Ameba
tentacidata or Ameba actinophora. In other forms of protozoa there is
a gradual increase in density from within outward and the body of the
cell is covered by a living membrane which may become complicated
by the addition of muscular fibrils (myonemes), sensory or tactile
organs (cirri), or various protective structures like hooks, spines, and
tentacles (Figs. 5 and 6).
Like many of the cells which constitute the tissues of higher animals,
24
GENERAL ORGANIZATION OF THE PROTOZOA
the protozoon has the power of manufacturing by chemical processes,
over and above those which are devoted to nutrition, various products
which are secreted just within or outside the peripheral protoplasm,
where they may form a protective armor in the shape of shells, or tests.
The materials thus formed within the cell body may be chitin (as in
the case of Arcella vulgar ix or in any other shelled rhizopod where the
shell material is always laid down upon a chitin base); cellulose (as
FIG. 6
* x r ^T» **• 9 ° m t m ' i^-ViVifft*
?•* * > • \* :» • V °- ' ° . *3 ."fe^-^
^•.J^<ag.-it.j>^.^.«..^ga^A^[|j.^«yy
Ceratium tripos, a dinoflagellate. (After .Stein.)
in the dinoflagellates); calcium carbonate (as in the foraminif era) ;
or silica (as in the radiolaria). The secretions may take the form
of definite plates, as in dinoflagellates, of continuous deposits, or of
symmetrical skeletons which are often very complex. When the
deposit is regular and continuous the shell material is added to the
chitin membrane, the walls growing thicker with age of the organism;
but when the material is deposited at one time (dictyotic moment),
GENERAL MORPHOLOGY
25
as in the radiolaria, the deposit follows the contour of the protoplasmic
alveoli and gives rise to skeletons often of extreme beauty (Fig. 8).
In a number of fresh-water rhizopods the bulk of the shell material is
not secreted, but the test is composed of foreign particles, such as
FIG. 7
D
B
Types of marine rhizopod shells (Reticulariidce, Carpenter).
diatom shells, sand, mud, or detritus of any kind, all fused together and
to a chitinous substratum by means of a mucilaginous cement secreted
by the inner protoplasm.
These shells and skeletons after death of the organisms sink to the
bottom of ponds, lakes, or seas, where they may form thick beds of
FIG. 8
Schematic figure illustrating the modifications of skeletons according to mechanical
principles of deposition. (After Dreyer.)
calcium carbonate (as in globigerina ooze), or silica (as in radiolaria
ooze). Such beds have been thrown up from time to time in the past
by volcanic upheavals, forming more or less extensive areas of proto-
zoan land in which foraminifera or radiolaria may be easily identified.
26
GENERAL ORGANIZATION OF THE PROTOZOA
(c) Plastids. — In addition to the basic substances making up
the fluid protoplasm there are larger or smaller granules of different
kinds embedded in the alveolar or interalveolar material; these
granules may be food particles ready for assimilation, waste particles
waiting for excretion, metaplasmic particles like oil drops, pigment
grains, and the like, or foreign particles like sand grains, calcium,
silica, etc., to be used in building shells or stalks.
The plastids that are formed in a great many protozoa, especially
in those types which lie on the boundary line between the lower plants
and the protozoa, may have a considerable economic importance.
Many of them are starchy in nature, i. e., formed products to be used
FIG. 9
a-'
A complex polythalamous shell (schematic) of Operculina. (After Carpenter.) The shell
is represented as cut in different planes to show the distribution of the canals (a', a", a'");
c, c, c, the outer chambers with double walls (d, d, d), one of which is shown in section (g). The
chambers communicate by apertures at the inner ends of the septa (e), and by minute pores
(/). The outside (6) of the shell is marked by the radial septa.
as food; others are starch-forming centres or pyrenoids, which are
usually embedded in plastids of large size, called chromatophores from
the color they possess. These colors, due to some form of chlorophyl,
may be bright green like the foliage of higher plants, or red, orange,
yellow, brown, or black, according to the nature of the materials which
combine with the chlorophyl. When great numbers of these color-
bearing protozoa are massed together the result is a brilliantly colored
area; red snow, for example, being due to aggregates of hematococ-
cus, the red coming from the color of the minute chromatophore in
each small cell. Similarly, great patches on the sea may be colored
orange by the presence of noctiluca, or red by peridinium, while
GENERAL MORPHOLOGY 27
drinking waters are not infrequently made unsightly because of the
red coloring matters of Euglena sanguined, or of the yellow coloring
matters of dinobryon or uroglena.
In some cases the pigment is due to collections of waste materials
stored up in the cell, products of proteid metabolism held in reserve
for some useful purpose, or to be voided to the outside. The black
pigment of metopus or of tillina is a waste product of this nature,
while the yellow to brown pigment of some of the colony forms is
utilized in building the stalk.
The fats, oils, and other metaplasmic products, stored up in these
minute cells, minute as they are in the individual, are, collectively, a
great nuisance, or, in some parasitic forms, may be a menace to the
life of the host. Potable waters are frequently rendered unfit to drink
because of the odors and tastes due to these products of protozoan
vitality. Such odors are rarely due to putrefaction of the organisms,
but rather to the liberation of the minute drops of oil upon disintegra-
tion of the cell bodies. As crushing a geranium leaf causes minute
drops of oil to be thrown into the air, giving the fragrant perfume of
the plant, so disintegration of a uroglena colony, crushed by the
pressure in pumps and mains, liberates the minute oil drops stored
up in the inner protoplasm, but the cod-liver oil smell which they
give to the water is far from fragrant. Such water is harmless
so far as the health is concerned, but very offensive to the esthetic
sense. So characteristic are these metaplasmic products, that many
kinds of protozoa can be recognized in drinking waters simply by
the odors they impart.
The oils, which in the majority of cases, like fat, are probably a
reserve store of nutriment, may, in some cases, become useful for
purposes of protection. An interesting case of a possible protecting
function is that of noctiluca, where the particles of oily matter are
rapidly oxidized upon exposure to the air, resulting in a brilliant flash
of light, and giving one great source of the phosphorescence in the sea.
The possibility of a protective function comes from the fact that the
fatty material is thrown out of the body upon irritation, and the flash
of light may scare away small enemies.
Other plastids that are used for purposes of protection are tricho-
cysts and trichites. These are minute structures derived from
the nucleus (Mitrophanow, 1904) and arranged radially about the
entire periphery, as in paramecium, frontonia, etc., or in certain
regions only, as in dileptus or chilodon. When the organism is
irritated the contents of the capsules are thrown out with considerable
force, and the poison which they contain is strong enough to paralyze
any single-celled opponent, or, possibly, as Mast ('09) suggests, they
form, after their discharge, a dense protective envelope which cannot
be penetrated by small enemies. Sometimes they are used as weapons
28 GENERAL ORGANIZATION OF THE PROTOZOA
of offence as well as protective organs, and the minute hunters stalk
about with them in search of prey (see page 77).
(d) Vacuoles. — The other formed structures of the inner proto-
zoan body are the vacuoles. These for the most part are mere fluid-
filled spaces, but in many cases they possess a definite and permanent
form and are frequently complicated in structure.
The vacuoles are either storage or contractile vacuoles. The former
are minute improvised stomachs, and in them the food matters are
digested. The latter are the more complex structurally, varying from
simple spaces, which fill with fluid and empty to the outside in rhythmic
periods, to great branching canal systems with storage reservoirs and
contractile vesicles, the excretory system permeating the entire inner
protoplasm with a network of vessels.
(e) Nuclei, Chromatin, and Chromidia. — At the present time no
one who has made a careful study of protozoan cells accepts Haeckel's
view ('66) that some forms of unicellular animals are without nuclei
(Monera). It is, indeed, true that there are many forms in which nuclei,
in a morphological sense, are not permanently retained, but the essen-
tial part of the morphological nucleus — the chromatin — is invariably
present. Sometimes this chromatin is distributed uniformly through-
out the cell (the "distributed nucleus" of tetramitus, dileptus, etc.),
but usually it is concentrated about a central body (division centre)
having some of the attributes of a centrosome, or it is confined within
a firm nuclear membrane.
Within the last four years there has developed an ever-growing
tendency to recognize in protozoa two distinct types of nuclei. These
are distinguished from one another in the majority of cases not by
any structural characteristics, but by their functions in the cell. One
type, the trophonucleus, has to do with the ordinary vegetative func-
tions of metabolism. The other type, which may be designated the
karyoyonad, or simply the gonad nucleus, has no function in ordinary
metabolism, but is the source of chromatin forming the nuclei of con-
jugating gametes. In a broad sense, therefore, the karyogonad repre-
sents the germ plasm of protozoa.
The forms assumed by the chromatin in these two types of nuclei
vary within wide limits. In many cases both are included within one
common nuclear membrane, and are separated from one another only at
periods of maturation in preparation for fertilization (most gregarines,
coccidia, and many flagellates). In other cases the gonad nucleus
becomes separated from the trophonucleus at an earlier period in the
life history of the individual, and appears in the cytoplasm in the form
of distributed chromatin granules (idiochromidia of many different
genera, "chromidialnetz," etc.) or as compact and homogeneous
nuclei (micronuclei of infusoria, "secondary" or gametic nuclei of
sarcodina).
GENERAL MORPHOLOGY 29
The trophonuclei also may be permanently distributed in the form
of chromatin granules, or, under certain conditions of the environ-
ment, may assume this condition (chromidia formation). The former
is characteristic of the vegetative nucleus of some infusoria (e. g.,
dileptus, Fig. 2), the latter as a result of starvation or overfeeding,
or other abnormal environmental condition (e. g., "chromidia"
formation in actinospherium, Hertwig). (For further discussion of the
significance of chromidia formation, see page 115.)
In addition to the chromatin elements which enter into the make-up
of nuclei, there are specific materials of the cell which apparently
underlie the kinetic functions of protozoa. In some cases these are
aggregated into definite nucleus-like bodies to which the name kineto-
nucleus (Woodcock) has been applied (e. g., in trypanosoma and
other flagellates). Such organs of the cell will be considered at greater
length in the following section.
(/) Kinoplasm. — The question as to a specific motor or kinetic
substance in the cell has been repeatedly raised in general cytology
and is still unsettled. Strasburger has long maintained that the plant
cell possesses such a specific kinetic substance, which he termed
"kinoplasm" and which enters into the formation of mitotic figures,
flagella, cilia, and the peripheral zone of protoplasm. It is, according
to him, a substance which forms all of the motor organs and underlies
all of the physical activities of the cell. Similarly for animal cells,
Boveri ('88) early pointed out that the astrospheres and other parts
of the spindle figure are composed of a substance apparently quite
different from the rest of the protoplasm, and suggested the term
"archoplasm" for it. Subsequent observers have amplified this view
and some, notably Prenant, have endeavored to show that archo-
plasm, or, in a larger sense, kinoplasm, is not only specific, but a kind
of "superior" protoplasm, self-perpetuating and distinct. Wilson
('00), summing up the evidence for and against such a view in relation
to metazoan cells, comes to the conclusion that such substances, if they
exist in the cell, represent a more or less persistent but not permanent
phase, or product, of cellular metabolism. (The Cell, page 323.)
Prenant's point of view is probably the most satisfactory in con-
nection with the protozoan cell, for here the specific substances are
more persistent than in the higher animal cells, and in most cases they
assume the form of definite, active, kinetic bodies closely associated
with the mechanism of nuclear division and of locomotion. To this
body of the protozoan cell, whether within or without the nucleus,
the non-committal term "division centre" has been applied (Calkins,
1S9S).
In many different kinds of protozoa this division centre remains
inside the nucleus, giving rise to what Boveri has called the "centro-
nucleus" type. It is almost universally found among the represen-
30
GENERAL ORGANIZATION OF THE PROTOZOA
tatives of the flagellated and ciliated protozoa, and a characteristic
form is found in Euglena viridis and its allies (Fig. 10). Here a
definite intranuclear body is surrounded by chromatin granules, and
when the cell is ready to divide, this division centre, like a centrosome,
divides first and the chromatin elements are separated into two equal
groups, each half following one of the centres. In this case, and in some
of the infusoria (e. g., Paramecium aurelia [caudatutri\) the division
centre seems to be formed from a specific substance, and it appears
to be a permanent body in the cell, retaining its individuality from
generation to generation.
FIG. 10
Mitosis in Euglena. (From Wilson after Keuten.) A, preparing for division; the nucleus
contains a division centre surrounded by chromatin granules; B, formation of an intranuclear
"central spindle;" C, later anaphase, and D, telophase stage.
Much more enlightening, however, are the conditions in the heliozoa.
Here, in many cases, there is a central granule in the geometrical
centre of the cell, which was early noted by Grenadier ('69) and
Schultze and called by the former the "Centralkorn." The axial
filaments of the pseudopodia centre in this granule, which divides like
a centrosome prior to division of the cell, while the axial filaments
radiate out on all sides like the astral fibers of a mitotic figure. Biit-
schli ('92) was the first, to compare this body with a centrosome, and
the view was quickly accepted by cytologists, while the most complete
GENERAL MORPHOLOGY
31
observations regarding its history have been made by Schaudinn
('96) in the case of acanthocystis and spherastrum (Fig. 11).
This central granule or division centre, while thus apparently per-
manent in the adult forms of heliozoa, must be regarded as a product
of protoplasmic changes which have their seat in the nucleus. This
is clearly shown by the formation of the central body in small cells of
the above organisms that have been produced by budding. Schaudinn
has shown that in the formation of these buds the nucleus divides by
amitosis, after which the daughter nuclei migrate to the periphery of
the cell, where they are budded off with a small amount of cytoplasm.
FIG. 11
HSSSBMJ
ISO
3 ' ol/
^. ''^"'^ orGZTZ**.''. "-'.C' ^3^ y
^^»%-e
**.*« A ,'•>•. \ <: »;..-r-
HV"*?
/i(/np
-5
- '"» '••'•"-»» T
P.':?.* *Vv
|
*
Nuclear division and budding in Heliozoa. (After Schaudinn.) A, vegetative cell of
Spherastrum with the axial filaments focussed in a central granule (centrosome) ; B, D,
division of nucleus in Acanthocystis; E, F, flagellated and ameboid buds of Acanthocystis;
G, exit of the centrosome from the nucleus.
In some cases as many as twenty-four buds are thus formed by the
same animal, although this is an unusual number. The history of
these buds is somewhat different in different cases. In the simplest
ones the bud merely drops off of the parent and remains on the bottom
for some days, where it moves about by ameboid motion. These buds
contain no portion of the original division centre, nor does a new
division centre arise in them until about five days after their formation,
when in each bud a new division centre makes its appearance inside
the nucleus, from which it migrates to the cytoplasm, where it takes up
its position in the geometrical centre of the cell and gives rise to the
32
GENERAL ORGANIZATION OF THE PROTOZOA
axial filaments, and with their formation the young organism for the
first time assumes the appearance of a heliozoon (Fig. 11, F, 0).
These structures of the protozoa certainly justify, if any do, the use
of the term kinoplasm. Not only are they connected with the activity
of the cell in division, but they are also closely identified with the
motile organization of the cell. In heliozoa, as already pointed out,
they are the centres for the formation of the axial rays of the pseudo-
podia, which vary in motile power from practically quiescent append-
ages in forms like Actinophrys sol, through a slight elasticity in forms
like acanthocystis to vigorously vibratile appendages in artodiscus,
which cause the minute organism to dance about the field on the tips
FIG. 12
Dimorpha mutans. (After Schoutedan.) Two flagella and radiating axial filaments
centring in the extranuclear division centre.
of its pseudopodia. The similarity between these axial filaments and
flagella of the flagellated organisms is well shown in the case of Dimor-
pha mutans, in which the majority of the axial filaments are similar
to those of other heliozoa, but two of them remain uncovered by stream-
ing protoplasm and whip about in the surrounding water like the
vibratile lashes of the flagellates. One of these flagella, according to
Schoutedan ('07) serves to anchor the animal, while the other provides
a food current' (Fig. 12). In such cases the close connection of these
axiopodia with flagella is clearly shown and may well help to point
out the course of evolution of heliozoa and flagellates, perhaps the
former from the latter.
The actual participation of such division centres in the formation
GENERAL MORPHOLOGY 33
of the more active motile organs is well shown in the flagellated pro-
tozoa. In the majority of cases where the morphology has been
minutely studied, the flagellum has been traced either to such a basal
body or to the nucleus, while in some forms, notably in trypanosoma,
the materials of the vibratile or undulating membrane, of the flao-ellum,
O ^
which forms its edge and continues beyond the cell as a free whip, and
of the contractile myonemes are all derived from such a division centre
called by Woodcock the "kinetonucleus," which, in some cases at
least, has some of the attributes of a morphological nucleus.
In many cases this active substance of the division centre is confined
to the nucleus, where it may be in the form of a definite and permanent
body, as in euglena and its allies, or it may be diffused throughout
the nucleus as in actinophrys and actinospherium. The substance
of the axial filaments of such forms is derived from the nucleus by
a nuclear secretion, as Schaudinn has clearly shown in the case of
Camptonema nutans. All of these, however, are characteristically
quiet forms, and the activity of the division centre is shown only in
the process of nuclear division. In Actinophrys sol a typical spindle
with centrosomes and fibers is formed as in the metazoa and all from
the substance of the nucleus.
There seems to be unmistakable evidence, therefore, that the sub-
stance of the division centre is formed within the nucleus and that a
definite body, or condensation of this substance, occurs at certain
periods of vitality and has a more or less continuous existence as such.
This body makes its appearance in the bud of acanthocystis, during
mitosis of actinophrys and during reorganization of the cell after
fertilization in trypanosoma and its allies. It divides as do the nuclei,
and like a centrosome has a certain individualitv in the cell.
t
In certain other types of protozoa the substance of the division
centre may be permanently outside of the nucleus. This is the case
in the rhizopod parameba and in the flagellate noctiluca, while in the
latter there is good evidence to show that the material is diffused
throughout the cell body during vegetative phases. It is not too imagi-
native to think of a diffusion of this material throughout protozoan
cells generally, as it may be diffused through the nucleus, and it is
conceivable that the basal bodies of cilia, the substance of the con-
tractile centres of flagella and myonemes are, like the basal bodies of
flagella or the Centralkorn of the heliozoa, only local condensations of
such kinoplasm, which, in the long run, must be traced back to the
nucleus.
34 GENERAL ORGANIZATION OF THE PROTOZOA
B. ORGANS OF LOCOMOTION OF PROTOZOA, AND CLASSI-
FICATION.
As Dnjardin ( '41) early pointed out, the motile organs of protozoa
offer a natural basis for classification, which, with proper subdivisions,
is quite adequate to satisfy all of the requirements of a natural system.
AYithin the last year or so some confusion has arisen because of the
different forms an organism may assume at different periods of its
life history. Herpetomomis (Leishmanid) donovani, the cause of kala
azar, for example, has an intracellular non-motile phase in addition
to a free-living, flagellated phase, and in such a form it is conceivable
that some difficulty might arise as to whether the organism should be
classified as a sporozoon or as a flagellate. Such exceptions, however,
do not offer insuperable difficulties, and may, indeed, serve a useful
purpose in pointing out the path of evolution which the organisms in
question have undergone. They do not in any way destroy the value
of the motile apparatus as a basis for classification.
Dujardin outlined three of the four great divisions of the protozoa,
while the fourth, the Sporozoa, was named by Leuckart in 1S79. The
first group of protozoa was characterized by Dujardin as "animals
provided with variable processes" (pseudopodia); the second as
"animals provided with one or several flagelliform filaments" (flagella);
and the third as "ciliated animals." Gregarinida, belonging to the
fourth group, were the first protozoa to be regarded as single cells,
Kolliker ('45) regarding them as such.
The finer subdivisions of these several groups are made chiefly
according to the variations in the structure of the motile organs, the
Sarcodina, for example, are here subdivided into two classes, the
Rhizopoda and the Actinopoda, according as the pseudopodia are
amorphous or ray-like. These classes in turn are divided into sub-
classes, the former into Reticulosa, Mycetozoa, Foraminifera, and
Amebea, the latter into Heliozoa and Radiolaria.
Some subdivisions of the protozoa deserve especial mention because
the organisms included, occupy an anomalous position in the scale of
living things. One such group, the Mycetozoa, is sometimes placed
as a group of rhizopods, sometimes as fungi. In their simplest forms
these organisms are minute cells with lobose pseudopodia, which are
soft and miscible and fuse upon coming together. Such fusions result
in great accumulations of protoplasm known as plasmodia, which may
assume a variety of shapes and may become so highly differentiated
as to resemble higher metaphytes much more than single celled
protozoa. Another such group, the Phytoflagellida, have long been
the subject of academic wrangling as to the boundary line between
animals and plants. Similarly, the Spirilloflagellata are today the
ORGANS OF LOCOMOTION OF PROTOZOA 35
subjects of contention between bacteriologists and protozoologists.
Little satisfaction, however, comes from such wrangling, and there is
little practical value in connection with these hypothetical boundary
lines beyond setting the limits to text-book or monograph.
Pseudopodia, and Classification of the Sarcodina. — In many
respects pseudopodia are the simplest forms of motile organs. They
are merely prolongations or outflowings of the cell protoplasm, the
external expressions of internal physical forces which biologists have
tried in vain to analyze. In the inner protoplasm of nearly all kinds of
protozoa, the almost fluid cell contents with granules of various kinds,
food more or less digested, and with waste products, are in a constant
movement or cyclosis. In the more highly differentiated forms of
protozoa, this flow is quite confined to the inner protoplasm, the firm
cell membrane preventing an outward manifestation of the forces
which cause the flow. In the shell-less Sarcodina, however, there is no
firm outer covering, and the peripheral protoplasm gives way at the
points of least resistance and an outward flow of protoplasmic stuff
is the result, this flow ceasing with the exhaustion of the particular
force which caused it, while a new point of rupture gives rise to a new
pseudopodium. Thus the motile organs of these low types are incon-
stant, endlessly changing centres of protoplasmic energy, which have
defied the physicist, the chemist, and the biologist. Xot all pseudopodia
are of this simple type, however, and some of them have a permanent
form with supporting skeletal elements. The former, transitory kind,
are characteristic of the ordinary rhizopods such as ameba, arcella,
difflugia, etc., which are familiar to the novice as "the lowest forms
of animal life," and they appear and disappear again with an ever-
fascinating, inexplicable regularity. These are the so-called lobose,
"lobopodia," or finger-form pseudopodia.
The second, more permanent kind of pseudopodia, are sometimes
called axiopodia, because of the presence of a stiff axial filament, com-
posed of condensed protoplasm similar to acanthin or chitin, which
runs through the axis of the pseudopodium. These pseudopodia,
characteristic of the class Actinopoda, stand out, ray-like, from all
sides of the usually spherical animal, and give a peculiar radiating
appearance which led the early students of the group to call them the
sun-animals, a name which Haeckel, with characteristic felicity, turned
into Heliozoa. In these the protoplasmic flow leads to no change in
configuration of the motile organ, but courses outward on one side of
the pseudopodium and backward on another.
The central axis belonging, as shown above, to the category of kino-
plasmic substances, has a certain amount of elasticity, and may bend
and straighten again with considerable force, and thus the pseudo-
podium becomes a more or less vigorous organ of locomotion, an
acanthocystis rolling over and over with a slow vibration of the elastic
36
GENERAL ORGANIZATION OF THE PROTOZOA
filaments, while an artodiscus dances about the field with an energetic,
O
but erratic movement due to the springiness of the tips of its axiopodia.
FIG. 13
S
Lichnaspis giltochii, Haeek. One of the Actipylea. (After Haeckel.) The spines are
arranged in accordance with the Miilleriun law as follows: a, a, a, a, northern polar spines;
b, b, b, b, northern tropical spines; c, c, c, — equatorial spines; d, d, d, d, southern tropical
spines; and e, e, e, southern polar spines.
In some forms both flagella and these pseudopodia exist at the same
time, as in dimorpha or in myriophrys, while in the former the one
may change into the other. These axiopodia, therefore, are of con-
ORGANS OF LOCOMOTION OF PROTOZOA
37
siderable interest from a theoretical point of view, and indicate a
possible line of evolution which the protozoa may have followed in the
past (Fig. 14).
The Heliozoa possessing these axiopodia are not very numerous
nor are there many species; they are never parasitic and are mainly
confined to fresh water, only a few being found in the sea. Another
group, however, closely allied to the Heliozoa, the Radiolaria, are
exclusively marine. More than four thousand species of these marine
forms are known, and they are provided for the most part with the same
kind of pseudopodia as those of the Heliozoa, while the great majority
of them possess supporting skeletons of acanthin or silica, often
exquisitely designed (Fig. 13).
FIG. 14
Myriophrys paradoxa, Pfmard. (From Lang after Pcnar.l.)
axiopodia and flagelliform cilia.
Ilcliozoon with
Still another type of pseudopodia which may be considered inter-
mediate between the lobose and the filose types is the reticulose type,
so called from the side streams of protoplasm which start from the
central streams and fuse or anastomose with other pseudopodia form-
ing a network or reticulum of protoplasm. The calcareous shells of
these forms are usually perforated, so that their pseudopodia have
easy access to the surrounding medium. Such perforations gave rise
to the term foramen- or window-bearing, and under the name Fora-
minifera these rhizopods have been known ever since D'Orbigny gave
the name in 1828. In addition to the function of locomotion, the
pseudopodia of these forms become a trap for diatoms, other protozoa
or larval stages of higher forms, the sticky protoplasm making escape
very difficult, while the struggles of the prey stimulate an additional
flow of protoplasmic secretions by which digestion takes place.
38 GENERAL ORGANIZATION OF THE PROTOZOA
PHYLUM PROTOZOA.1
Subphylum SARCODINA. Protozoa showing no connections with the bacteria,
usually of simple structure and characterized mainly by motile organs in the
form of changeable protoplasmic processes — the pseudopodia.
Class I. RHIZOPODA. Sarcodina without axial filaments in the pseudopodia,
which may be lobose, filose, or reticulose.
Subclass 1. Proteomyxa. Minute organisms with soft, miscible pseudopodia,
which anastomose upon touching; the cells unite at times to form plasmodia;
frequently parasitic.
Typical genera: Gymnophrys, Cienkowsky, 1S76; Pontomyxa, Topsent, 1893;
Vampyrella, Cienkowsky, 1876; Pseudospora, Cienkowsky, 1876; Plasmo-
diophora, Woronin, 1878; Nuclearia, Cienkowsky, 1876.
Subclass 2. Mycetozoa. Pseudopodia-forming single cells which fuse to form
plasmodia, the latter often of great complexity. There are so many charac-
teristics of the fungi in the organisms of this group that their systematic posi-
tion is unsettled; botanists include them with the fungi as a primitive group
under the name Myxomycetes or slime moulds.
Order 1. ACRASLSE. The single cells unite to form a common mass, but the cells
do not fuse, hence a pseud oplasmodium is formed which is enclosed in a
gelatinous mantle.
Typical genera: Copromyxa, Zopf, 1885; Acrasis, Van Tieghem, 1880; Dic-
tyostelium, Brefeldt,'l869.
Order 2. FILOPLASMODIA. The aggregated cells are not firmly united, but
remain connected for the most part by delicate threads of protoplasm.
Typical genera: Labyrinthula, Cienkowsky, 1876; Chlamydomyxa, Archer, 1875.
Order 3. MYXOMYCETES. The aggregation of the cells is here complete and often
results in the formation of complex fructifications in which hygroscopic threads
play an important part in scattering the often flagellated spores.
Typical genera: Fuligo, Haller, 1768; Craterium, Trentepol, 1797; Stemonitis,
Gleditsch, 1753; Didymium, Schrader, 1797.
Subclass 3. Foraminifera. Rhizopoda with fine branching and anastomosing
pseudopodia which form an irregular network around the entire body or parts
of it. Shells, when present, are calcareous, provided with many pores (Per-
forina) or without pores (Imperforina), and consist of one chamber (Mono-
thalamous) or of many chambers (Polythalamous). Rigid diagnoses are here
impossible, for the limits of the orders are ill-defined, and in some cases it is
difficult to accurately place organisms which are sometimes grouped as fora-
minifera, sometimes as test-bearing amebse. The classification adopted here
is that of Lister, 1903.
Order 1. GROMIIDA. (Fresh-water test-bearing forms removed.) The cell cover-
ing is simple and for the most part without calcareous deposits; chitinous
and single chambered.
Typical genera: Grpmia, Dujardin, 1835; Microgromia, Hertwig, 1874; Diplo-
phrys, BarkeTTlSEepheardella, Siddall, 1880; Platoum, F. E. Sch., 1877.
Order 2. ASTRORHIZIDA. Lister recognizes four families^. Here the test is com-
posite, large, and monothalanious; the walls are formed of chitin with firmly
attached particles of sand, mud, sponge spicules, etc.
1 The classification adopted for a group of animals or plants in which life histories are but
little known and relationships obscure must be of a tentative nature, and the one here sug-
gested, while indicating relationships as they appear with our present knowledge, is only a.
snap shot, as it were, of a growing subject and makes no claim of finality.
PHYLUM PROTOZOA 39
Typical genera: Astrorhiza, Sandahl, 1857; Syringammina, Brady, 1884; Pilu-
lina. Carpenter, 1862; Saccammina, Sars, 1868; Rhabclammina, Sars, 1868;
Haliphysema, Bowerbk., 1862; Marsipella, Norman, 1878.
Order 3. LITUOLIDA. Lister recognizes four families. Here the test is arenaceous,
usually regular, mono- or polythalanious. Lister notes that it comprises
sandy isomorphs of certain types of hyaline or porcellanous forms.
Typical genera: Lituola, Lamarck, 1801; Rheophax, Montfort, 1808; Haplo-
phragrnium, Reuss, 1860; Hippocrepina, Parker, 1870; Polyphragma, Reuss,
1860; Cyclammina, Brady, 1884; Loftusia, Brady, 1884; Parkeria, Carpenter,
1862.
Order 4. MILIOLIDA. Lister recognizes six families. Here the test is typically
calcareous and hyaline, but may be covered with sand or detritus.
Typical genera: Cornuspira, M. Sch., 1854; Spiroloculina, D'Orb., 1826; Tri-
loculina D'Orb., 1826; Vertebralina, D'Orb., 1826; Articulina, D'Orb.,
1826; Peneroplis, Montfort, 1810; Orbiculina, Lamarck, 1801; Orbitolites,
Lamarck, 1801; Alveolina, D'Orb., 1826; Keramosphera, Brady, 1884;
Nubecularia, Defrance.
Order 5. TEXTULARIDA. Lister recognizes three families. Here the chambers
are arranged in one or two series, which may be alternate, spiral, or irregular;
arenaceous and with or without a perforated calcareous basis.
Typical genera: Textularia, Defrance, 1824; Valvulina, D'Orb., 1826; Virgulina,
D'Orb., 1826.
Order 6. CHILOSTOMELLIDA. Lister has three genera. The test is calcareous,
polythalamous and finely perforated.
Typical genera: Chilostomella, Reuss, 1860; Allomorphina, Reuss, 1860.
Order 7. LAGENIDA. Lister recognizes four families. Here the test is similar to
the last save for the monothalamous shell, which, however, may be compound
by the union of chambers end to end in a straight or curved series. Canals
and canalicular skeleton wanting.
Typical genera: Lagena, Walker, and Boys, 1784; Nodosaria, Lam., 1801; Poly-
morphina, D'Orb., 1826; Ramulina, R. Jones, 1875.
Order 8. GLOBIGERINIDA. Not divided into families. The test is perforated and
calcareous, with few chambers arranged in a spiral. Canals and canal
system absent.
Typical genera: Globigerina, D'Orb., 1826; Orbulina, D'Orb., 1826.
Order 9. ROTALIDA": Lister recognizes three families. The test is calcareous and
perforated, with all of the chambers visible from one aspect, and arranged in
a spiral ; some of the more highly developed forms with canal system.
Typical genera: Spirillina, Ehr., 1841; Discorbina, Parker and Jones, 1862;
Calcarina, D'Orb., 1826; Rotalia, Lamarck, 1801; Tinoporus, Carpenter,
1857; Carpentaria, Gray, 1858.
Order 10. NUMMULITIDA. Lister recognizes three families. Here the test is
calcareous, filled with tubules, and bilaterally symmetrical (except Amphis-
tegina), and with canal system in the higher forms.
Typical genera: Fusulina, Fischer, 1829; Polystomella, Lamarck, 1822; Oper-
culina, D'Orb., 1826; Nummulites, Lamarck," 1801; Orbitoides, D'Orb.,
1826 (Fig. 9, p. 26).
Subclass 4. Amebea. Here are included the more common forms of rhizopods
with blunt or lobose pseudopodia which do not anastomose on touching one
another, a physiological character which indicates a well-marked difference
in the different types of rhizopods. The protoplasmic body may bear shells
or not.
Order 1. GYMNAMEBIDA. Here the body is uncovered, although there is, in many
cases, a tendency of the peripheral plasm to harden into a denser, mem-
brane-like zone which approaches the simpler forms of tests.
40 GENERAL ORGANIZATION OF THE PROTOZOA
Typical genera: Ameba auct. Paraineba, Schaudinn, 1896; Trichospherium,
Schneider; Hyalodiscus, Hert. and Lesser, 1874; Chroniatella, Frenzel,
1S92; Pelomyxa, Greeff, 1874; Dactylosphera, Hert. and Lesser, 1874;
Xucleophaga, Dangeard, 1895.1
Order 2. TESTACEA. The ameboid organisms here are covered by definite mem-
branes or tests composed of different materials cemented to a chitinous base.
The pseudopodia are protruded through the single opening of the shell and
may be simply lobose or branched, but do not anastomose.
Typical genera: Arcella, Ehr., 1838; Cochliopodium, Hert. and Lesser, 1874;
Hyalospheria, Stein, 1857; Quadrula, F. E. Sch., 1875; Difflugja, Leclerc,
1815; Euglvpha, Dujardin, 1841; Trinema, Dujardin, 18367 Campascus,
Leidy, f87?:
Class 2. ACTINOPODA. Sarcodina provided with fine, ray-like pseudopodia
which are supported by a central axial filament corresponding to the kinetic
material of flagella.
/Subclass 1. Heliozoa. Typically fresh-water forms of actinate protozoa in which
there is no trace of a chitinous central capsule separating ectoplasm and
endoplasm.
Order 1. APHROTHORACA. Naked forms of heliozoa (except during encystment).
Typical genera: Actinophrys, Ehr., 1830; Myxastrurn, Haeckel, 1870; Actino-
spherium, Stein, 1857; Actinolophus, F. E. Sch., 1874.
Order 2. CHLAMYDOPHORA. Heliozoa with a soft gelatinous or felted fibrous
covering.
Typical genera: Heterophrys, Archer, 1865; Spherastrum, Greeff, 1873.
Order 3. CHALARATHORACA. Heliozoa with a silicious covering made up of
separate or loosely connected spicules.
Typical genera: Pompholyxophrys, Archer, 1869; Raphidiophrys, Archer, 1870;
Pinacocystis, Hert. and Lesser, 1874; Acanthocystis, Carter, 1863; Diplo-
cystis, P'enard, 1890.
Order 4. DESMOTHORACA. Heliozoa with a covering of one piece perforated by
numerous openings.
Typical genus: Clathrulina, Cienk., 1867.
/Subclass 2. Radiolaria. Actinopoda in which the inner protoplasm is separated
from the outer by a firm chitinous "central capsule" perforated in different
ways for the intercommunication of inner and outer parts. Exclusively salt-
water forms, living at the surface, suspended at various depths, or near the
bottom. Classification based upon Haeckel's magnificent monograph in the
Challenger reports.
Division A. Porulosa. Spherical (homaxonic) organisms with spherical central
capsule perforated by numerous scattered pores of minute size.
Legion 1. Peripylea (Spumellaria). The central capsule is perforated by evenly
scattered pores; a skeleton is usually present consisting of scattered silicious
spicules, fused spicules, or a latticed network.
Order 1. COLLIDA (following Brandt, 1902). Solitary forms with or without
skeletogenous spicules.
Typical genera: Thalassicolla, Huxley, 1851; Actissa, Haeckel, 1887.
Order 2. SPHEROZOEA (Brandt). Colony building forms with or without skele-
togenous spicules.
Typical genera: Collozoum, Haeckel, 1862; Collosphera, J. Miill, 1855.
Order 3. SPHEROIDA. Skeleton present as one or several concentric spherical
latticed or reticulate structures.
1 In this group I would place, provisionally, the organisms of smallpox (Cytoryctes
variolse), of rabies (Neuroryctes hydrophobise) , and the allied organisms which Prowazek
(1908) includes in his group Chlamydozoa.
PHYLUM PROTOZOA 41
Typical genera: Haliornma, Ehr., 1838; Actinomma, Haeckel, 1862.
Order 4. PRUNOIDA. Haeckel recognizes seven families. With spheroidal,
ellipsoidal to cylindrical skeleton, single or concentric, sometimes constricted.
Typical genera: Ellipsidium, Haeck., 1887; Druppula, Haeck., 1887.
Order 5. DISCOIDA. Haeckel recognizes six families. The skeleton and central
capsule are discoidal to lenticular.
Typical genera: Cenodiscus, Haeck., 1887; Heliodiscus, Haeck., 1887.
Order 6. LARCOIDA. Haeckel recognizes nine families. The skeleton is ellip-
soidal with asymmetrical axes, in some cases forming almost a spiral.
Typical genera: Larcarium, Haeck., 1887, Pylonium, Haeck., 1881.
Order 7. SPHEROPYLIDA (Dreyer). Peripylea having in addition to the distrib-
uted pores one basal or a basal and an apical opening to the central capsule.
Typical genus: Spheropyle, Dreyer, 1888.
Legion 2. Actipylea (Acantharia). Porulose forms in which the pores are aggre-
gated in definite areas; the skeleton usually consists of twenty spines of
acanthin radiating from the centre of the organism in a regular order (Miil-
lerian law). Branches from these spines may unite to form a latticed shell.
Order S. ACTINELLIDA. Haeckel recognizes three families. The radial spines are
more numerous than twenty.
Typical genus: Xiphacantha, Haeckel, 1862.
Order 9. ACANTHONIDA. Haeckel recognizes three families. The twenty spines
are arranged in regular order (four equatorial, eight tropical, and eight polar),
all are equal in size.
Typical genus: Acanthometron, Miiller, 1855.
Order 10. SPHEROPHRACTA. Haeckel recognizes three families. With twenty
equal, quadrangular spines and a complete fenestrated shell.
Typical genus: Dorataspis, Haeckel, I860.
Order 11. PRUNOPHRACTA. Haeckel recognizes three families. The twenty
radial spines are unequal, and an ellipsoidal, lenticular, or doubly conical shell
is present.
Typical genus: Thoracaspis, Haeck., 1860.
Division B. Osculosa. Radiolaria with monaxonic form and with the pores of the
central capsule limited to an area on the base, or to one such primary basal
area and two secondary, apical areas; these perforated areas of the central
capsule are termed oscula.
Legion 3. Monopylea (Nassellaria). The central capsule is subspherical to ovoid,
consists of a single layer of chitin, and is perforated only at one pole. The
skeleton is silicious.
Order 12. NASSOIDA. Haeckel recognizes only one family. Skeleton absent.
Typical genus: Nassella, Haeck., 1887.
Order 13. PLECTOIDA. Haeckel recognizes two families. A complete latticed
shell is never formed, the skeleton consisting of three or more spines radiating
from one point below the central capsule or from a central rod.
Typical genus: Triplecta, Haeck., 1881.
Order 14. STEPHOIDA. Haeckel recognizes four families. The skeleton consists
of fused spines forming one or more rings.
Typical genus: Lithocircus, Miiller, 1856.
Order 15. SPYROIDA. Haeckel recognizes four families. The skeleton consists of
a sagittal ring and a latticed shell furrowed in the sagittal plane; in some
cases a lower chamber is added to the shell.
Typical genus: Dictyospiris, Ehr., 1S47.
Order 16. BOTRYOIDA. Haeckel recognizes three families. Skeleton similar to
the preceding, but having in addition one more wing-like process or lobe
and one or more additional chambers.
Typical genus: Lithobotrys, Ehr., 1844.
42 GENERAL ORGANIZATION OF THE PROTOZOA
Order 17. CYRTOIDA. Haeckel recognizes twelve families. Skeleton similar to
the preceding, but minus lobes or furrows.
Typical genus: Theoconus, Haeckel, 1887.
Legion 4. Cannopylea (Pheodaria). The chitinous central capsule is double, with
a spout-like main opening at one pole and frequently with one or more
accessory openings at the opposite pole. The skeleton is silicious and the
spicules or bars are often hollow. The extracapsular protoplasm contains
an accumulation of dark pigment granules (pheodiurn).
Order 18. PHEOCYSTINA. Haeckel recognizes three families. The skeleton con-
sists of distinct spicules or is absent altogether; the central capsule is in the
centre of the spherical body.
Typical genus: Aulactinium, Haeckel, 1887.
Order 19. PHEOSPHERIA. Haeckel recognizes four families. The skeleton is a
simple or double latticed sphere, and the central capsule is in the geometrical
centre.
Typical genus: Oroscena, Haeck., 1887.
Order 20. PHEOGROMIA. Haeckel recognizes five families. The skeleton is a
simple latticed shell with a large opening at one pole; the central capsule is
excentric, lying in the aboral half of the cell.
Typical genera: Pharyngella, Haeckel, 1887; Tuscarora, Murray, 1876; Haeck-
eliana, Murray, 1879.
Order 21. PHEOCONCHIA. Haeckel recognizes three families. The skeleton
consists of two valves opening in the same plane as the three openings of the
central capsule.
Typical genus: Concharium, Haeck., 1879.
Flagella and Classification of the Mastigophora. — Flagella do
not present as many striking variations in form as do pseudopodia.
Nevertheless, several different types exist. The simplest form assumed
is a slight, tapering filament broadest at the base and ending in an
invisibly fine tip. It moves constantly, the tip forming a circle, while
undulations or waves pass from base to extremity. In other types of
flagella the tip alone moves, while the base is a conspicuous filament
without undulation, the whole flagellum resembling a whip stock with
lash. It is a remarkable sight to see a peranema, for example, with
its stiff whip base, dragged along by the propelling movement of the
tip end of the slender lash.
In some forms of mastigophora the flagellum appears to be flattened
out until it is quite band form. This is the case in some species of
peridmium, where the band is drawn out to a pointed end, or in other
cases it retains the same width throughout.
In many of the flagellates there is but one flagellum attached at one
end of the cell as in peranema or euglena. In other cases there are
two, and these may be of similar or dissimilar length. In bodo and
in most of the colony forming flagellates like dinobryon, synura,
uroglena, etc., one is much shorter than the other. In many forms of
bodo the longer flagellum trails along on the substratum so that the
cell has the appearance of sliding along on a runner (Fig. 15). In
some forms, especially the parasitic flagellates, this sliding flagellum
has apparently fused with the cell membrane, projecting outward from
PHYLUM PROTOZOA
43
one end as a trailing flagellum and forming a definite seam down one
side of the cell body (trypanoplasma). This seam in Trypanophis
grobbeni becomes an undulating membrane, while in trypanosoma
FIG. 15
Free-living flagellates with trailing flagellum. (After Calkins.) A, C, D, Bodo caudatus,
Stein; B, Bodo globosus, Stein; E, Anisonema vitrea, Duj.
44 GENERAL ORGANIZATION OF THE PROTOZOA
the anterior flagellum has disappeared apparently, leaving only the
undulating membrane and the distal flagellum as motile organs.
Finally, in spirocheta, especially in Spirocheta balbianii, both free
flagella have disappeared, leaving only the undulating membrane,
while in some species of spirocheta even this remnant of the motile
apparatus has disappeared, leaving the organism with no visible
means of locomotion. As such forms of spirocheta move with great
freedom, it is not incredible that the remnant of the contractile ele-
ment is still retained within the membrane of the cell.
In a number of forms the flagella are numerous and distributed
uniformly around the body. Many of these tvpes are of doubtful
K t/' V « i
systematic position and are placed by some students of the group in
the class ciliata while others regard them as flagellates. The nature
of the flagellum in such cases justifies the mastigophora affinities, for
they are long and undulating and have the characteristic flagellum
movement. Such is the case in multicilia, actinobolus, myriophrys,
etc., and in parasitic forms like trichonympha, pyrsonympha, etc.
Other features of the cell body, however, such as the nuclei, tricho-
cysts, etc., indicate relationship with the infusoria, and to classify
such questionable forms as one or the other type shows the artificial
character of even the best system of classification. The difficulty is
»/ «/
one that is constantly met with bv svstematists. and in this case it
V V' *
serves a useful purpose by indicating the very close connection between
the ciliated and the flagellated protozoa.
The single flagellum is usually inserted deep within the substance of
the body, sometimes, as in euglena, at the base of an opening at the end
of the body; this opening, known as the flagellum fissure, is the means
of exit of the waste matters of the cell, thrown out by the contraction
of the contractile vacuole. The flagellum originates deep within the
substances of the protoplasm and usually in the vicinity of the nuclear
membrane. The energy constantly freed by protoplasmic oxidation
is here concentrated, apparently, in the constantly moving material
of the flagella. The contractile material, formed within the nucleus
or at its periphery, as in the case of Camptonema mutans, is of similar
nature to the material of the heliozoon axial filaments as shown in the
case of dimorpha, and is associated in some way with the material
of the mitotic figure or division centre, as shown by its origin
from the blepharoplast in herpetonionas, crithidia, trypanosoma,
and trypanoplasma. The flagellum, therefore, is an element of the
cell formed from the active or kinetic substances that are intimately
associated with the nucleus. It is not merely a periplastic or mem-
brane prolongation which may arise at any point on the cell periphery,
but is much more deeply involved in the protoplasmic make-up. The
real flagellum is permanent, thrown off and reproduced again, only at
times of cell division. This point has importance in view of the ques-
PHYLUM PROTOZOA
45
tionable nature of the so-called flagella of certain parasites belonging
to the genus spirocheta, many of which are said to have flagella.
These so-called flagella are apparently variable structures, for in
Trypanosoma raite. (After Robertson.) Forms observed in the digestive tract of the leech
Pontobdella muricata. A, mature specimen from blood of skate; B to F, stages in the
development of the flagellum from the kinetonucleus, and change in position of the latter in
relation to the nucleus.
many cases as "diffuse flagella" they appear not only at the ends of the
cell, but at different points about the periphery, and there seems to be
no uniformity about their distribution. This is said to be the case in
46 GENERAL ORGANIZATION OF THE PROTOZOA
Spirocheta duttoni and in Spirocheta yallinarum. It is not improbable
that such diffuse and variable filaments, and with them perhaps the
so-called flagella of some bacteria, are mere transitory structures of
the cell, which, like the filaments sometimes seen on the outer side of a
diatom's shell, owe their origin not to any formed structural element
of the cell, but to some unformed exudation of a gelatinous nature, or
to disintegration of the cell membrane, or to some other fortuitous
cause. Whatever future research may show them to be, the so-called
flagella of these forms are as yet much too indefinite and too uncertain
to be taken as a basis for specific differences (see p. 223, and Fig. 88).
The various modes of origin of true flagella, as distinguished from
these transitory filaments, have recently been studied by Dobell ('08),
who makes out four distinct types, as follows: One, in which the
flagellum arises directly from the nucleus (cf. axiopodia of actino-
phrys or dimorpha); a second, in which the flagellum base is united
to the nucleus by a connecting filament, the "zygoplast," as in monas;
a third, in which the flagellum arises from a basal granule which is
independent of the nucleus, as in copromonas, herpetomonas, etc.;
and a fourth, in which the flagellum arises from a special "motor"
nucleus, the "kinetonucleus," as in trypanosoma (Fig. 16).
CLASSIFICATION OF THE MASTIGOPHORA.
Subphylurn. MASTIGOPHORA. Protozoa in which the kinoplasm is concentrated
in the form of one or more vibratile or undulating motile processes, called
flagella, or in a kinetonucleus which may lie inside or outside of the tropho-
nucleus. Simplest forms closely related to bacteria.
Class 1. ZOOMASTIGOPHORA. Flagellated forms in which animal characteris-
tics are predominant.
Subclass. Lissoflagellata. "Smooth" flagellates, i. e., without protoplasmic
collars.
Order 1. SPIROCHETIDA. Organisms, often pathogenic, of somewhat uncertain
position because of incomplete knowledge of flagella and life history; spiral
in form, the turns of the spiral more or less plastic; nuclei unknown or dis-
tributed as in bacteria; division either transverse or longitudinal, sometimes
both.
Typical genera: Spirocheta Ehr., 1833; (?) Treponema, Schaudinn, 1905; (?)
Spiroschaudinnia, Sambon, 1907.
Order 2. MONADIDA. Organisms of simple structure, the body being often plastic
or even ameboid and with one or more flagella at one end (so-called " anterior"
end) ; there is no distinct mouth opening, the food materials being ingested by
a soft area of protoplasm at the base of the flagellum; in some cases the
organisms are saprozoites.
Family Rhhomastigidce: Simple organisms with one or two flagella and with an
ameboid body capable of forming pseudopodia which may be lobose, as in
rhizopods, or axial, as in heliozoa; food taking is assisted by flagellum and
pseudopodia.
Typical genera: Mastigameba, Schultze, 1875; Dimorpha, Gruber, 1881: Actino-
monas, Kent, 1880; Mastigophrys, Frenzel, 1891.
CLASSIFICATION OF THE MASTIGOPHORA 47
Family Cercomonadidce: The organisms are frequently plastic and changeable in
form, but unable to form pseudopodia; there is but one flagellum with a
flagellum-fissure at the base ; nutrition is holozoic, saprozoic, or parasitic.
Typical genera: Cercomonas, Dujardin, 1841 (a very uncertain genus); Herpe-
tomonas, Kent, 1880, ("including Donovan-Leishman bodies"); Crithidia,
Leger, 1904; Oikomonas, Kent, 1880; Copromonas, Dobell, 1908.
Family Codonecidas: Small colorless monads which secrete and remain in gelati-
nous or membranous cups.
Typical genera: Codoneca, James-Clark, 1866; Platytheca, Stein, 1878.
Family Bikecidce: Minute organisms of peculiar shape, the basal broader portion
bearing a tentacle-like process; nutrition is holozoic; the individuals single
or colony forming.
Typical genera: Bicoseca, James-Clark, 1867; Poteriodendron, Stein, 1878.
Family Heteromonadidcc: Small colorless monads possessing one or more accessory
flagella in addition to the primary one; they frequently form large but delicate
colonies upon a common stalk.
Typical genera: Monas, Stein, 1878; Dendromonas, Stein, 1878; Anthophysa,
St. Vincent, 1824; Rhipidodendron, Stein, 1878.
Order 3. HETEROMASTIGIDA. A small group comprising various kinds of flagel-
lated forms which are sometimes naked and plastic, sometimes provided with
a highly differentiated membrane. The essential morphological characteristic
is the possession of two or more flagella, one or two of which are directed
downward and backward, while the other is directed forward and used in
locomotion.
Typical genera: Bodo, Stein, 1878; Phyllomitus, Stein, 1878; Oxyrrhus, Dujar-
din, 1841 ; Anisonema, Dujardin, 1841 ; Trimastix, Kent, 1881.
Order 4. TRYPAXOSOMATIDA. Organisms of elongate, usually pointed form, and
of parasitic mode of life; with one or two flagella arising from a special
"motor" nucleus, ami with an undulating membrane provided with myo-
nemes running from the kinetonucleus to the extremity of the cell; one of the
flagella is attached to the edge of this membrane throughout its length, and
may terminate with the membrane or be continued bevond the body as a free
lash.1
Typical genera: Trypanosoma, Gruby, 1841; Trypanoplasma, Lav. and Mesnil,
1904; Trypanophis, Keysselit/, 1904.
Order 5. POLYMASTIGIDA. ( >rganisms characterized by numerous flagella,
frequently arranged in groups, and with one or many mouth openings usually
at the bases of the flagella.
Tribe 1. Astomca. Organisms with many flagella uniformly distributed, and
without special mouth openings.
Typical genera: Multicilia, Cienk., 1SS1; Grassia, Fisch., 1885.
Tribe 2. Monostomea. Organisms with mouth opening at the base of the group
of from four to six flagella.
Typical genera: Collodictyon, Carter, 1865; Trichomonas, Donne, 1837; Megas-
toma, Grassi, 1881; Tetramitus, Perty,lW2.
Tribe 3. Distomea. Organisms with two mouth openings at the bases of the two
groups of flagella.
Typical genera: Hexamitus, Dujardin, 1838; Trepomonas, Dujardin, 1839; Spi-
ronerna, Klebs, 1893; Urophagus, Klebs, 1893.
!The conclusions of Novy, MacNeal, and Torrey (1907) that herpetomonas, crithidia,
and trypanosoma are synonyms cannot be accepted on the basis of cultural methods alone;
when the life history of these parasitic forms is known in detail will be time enough to speak
of synonyms, and as the important structural characteristic which the membrane represents
far outweighs the cultural characteristics, it is better to hold to the older view and thus to
prevent further complications in what is already almost a hopelessly complicated group.
48 GENERAL ORGANIZATION OF THE PROTOZOA
Tribe 4. Trichonymphinea. Parasitic forms of the digestive tract covered with a
coating of long flagella.
Typical genera: Trichonympha, Leidy, 1S77; Pyrsonympha, Leidy, 1877; Jenia,
Grassi, 1885.
Order 6. EUGLENIDA. Large forms of flagellates possessing one or two flagella, a
contractile often complicated body wall, a mouth and pharyngeal opening
at the base of the flagellum through which the contractile vacuole opens to
the outside; chromatophores are often present and colony forms are not
uncommon.
Family Euglenidas: The organisms are elongate with more or less pointed ends and
usually with one flagellum. The membrane is marked with spiral stripings
indicating the course of the myonemes. Red eye spots, and green chromato-
phores are usually present. Pyrenoids and paramylum granules usually
present in abundance.
Typical genera: Euglena, Ehr., 1830; Trachelomonas, Ehr., 1833; Phacus,
Nitsch, 1816.
Family Astasiidce: The body is elongate and usually provided with a striped
membrane and otherwise similar to Euglena, but there are no eye spots and
the body is always colorless.
Typical genera: Astasia, Ehr., 1838; Rhabdomonas, Fres., 1858.
Family Peranemidce: The body is either stiff or plastic, and is usually symmetrical.
Typical genera: Peranema, Dujardin, 1841; Petalomonas, Stein, 1859.
Order 7. SILICOFLAGELLIDA. Organisms with a peculiar lattice-like skeleton of
silica, one flagellum, and simple structure. Parasitic on radiolaria.
Typical genus: Distephanus, Stohr, 1881.
Subclass 2. Choanoflagellata. Simple flagellated protozoa with a well-defined and
characteristic protoplasmic collar surrounding the base of the flagellum.
They frequently form colonies in which the cells are embedded in a gelatinous
or a chitinous matrix.
Typical genera: Monosiga, Kent, 1880; Codosiga, James-Clark, 1867; Pro-
terospongia, Kent, 1880; Diplosiga (with two collars), Frenzel, 1891 ; Phalan-
sterium, Cienk., 1870.
Class II. PHYTOMASTIGOPHORA. Flagellated forms in which the plant char-
acteristics, if not predominant, are clearly marked. Here are classified the
majority of complex colony forming types, but the single cells are invariably
of simple structure, possessing eye spots, pyrenoids, and yellow, green, or
brown chromatophores.
Subclass 1. Phytoflagellata. In this group the organisms have yellow or green
chromatophores.
Order 1 . CHRYSOFLAGELLIDA. With yellow chromatophores.
Typical genera: Chromulina, Cienk., 1870; Dinobryon, Ehr., 1838; Hyalobryon,
Lauterborn, 1899; Mallomonas, Perty, 1876; Synura, Ehr., 1833; Uroglena,
Ehr., 1833; Chrysospherella, Lauterb., 1899; Cryptomonas, Ehr., 1831;
Chilomonas, Ehr., 1831 (without chromatophores).
Order 2. CHLOROFLAGELLIDA. With green chromatophores.
Typical genera: Chlorogonium, Ehr., 1835; Polytoma, Ehr., 1838; Hemato-
coccus, Agardh., 1828; Phacotus, Perty, 1852; Gonium, O. F. Miiller, 1773;
Pandorina, St. Vincent, 1824; Eudorina, Ehr., 1831; Pleodorina, Shaw,
1894; Platydorina, Kofoid, 1899.
Subclass 2. Dinoflagellata. Organisms with yellow or brown pigment, two or more
flagella, and an outer shell of cellulose secreted in the form of plates. The
body is usually cut by furrows, of which the transverse is the more important;
one flagellum lies in this furrow, while the other is extended in advance of the
organism. The two flagella combine to give a rotation and forward movement
at the same time.
CLASSIFICATION OF THE MASTIGOPHORA
49
Order 1. ADINIDA. Dinoflagellates without furrows, the two flagella free in the
water, the transverse with movement the same as though the furrow were
present.
Typical genera: Prorocentrum, Ehr., 1833; Exuviella, Oienk., 1882.
Order 2. DIXIFERIDA. Dinoflagellates with furrows, one transverse, the other
longitudinal.
Family 1. Peridinidce. The transverse furrow is without wide ledges and the
shell may be absent.
Typical genera: Peridinium, Ehr., 1832; Ceratium, Schrank, 1793; Gleno-'
dinium, Ehr., 1835; Gymnodinium, Stein, 1878.
Family 2. Dinophysidce. The borders of the cross furrow are developed into
great ledges, making a deep furrow for the flagellum.
Typical genera: Dinophysis, Ehr., 1839; Cithiristes, Stein, 1883; Amphidinium,
Clap, and Lach., 1859; Ceratocorys, Stein, 1883; Triposolenia, Kofoid, 1906.
Order 3. POLYDINIDA. The order consists of but one genus, Polykrikos, Biitschli,
1873, which is characterized by a naked body, by several transverse furrows
and flagella, by macro- and micronuclei, and nematocysts.
-Subclass 3. Cystoflagellata. Marine protozoa, which are plant-like in having a
highly parenchymatous body, a single nucleus and a firm membrane. The
young forms pass through a dinoflagellate stage in development.
Three genera: Noctiluca, Suriray, 1S36; Leptodiscus, Hertwig, 1877; Craspe-
dotella, Kofoid, 1905.
Cilia, and Classification of the Infusoria. — Cilia are quite differ-
ent from flagella, being shorter and moving with a sharp stroke in
one direction and with a slower, non-forceful recovery in the opposite
direction. Like the flagellum, the cilium is thicker at the base and
tapers to a fine point, while it owes its contractility to the presence of a
FIG. 17
Aspidisca hexeris, Quen. An hypotrichous ciliate with brushes of fused cilia.
(After Calkins.)
filament of kinetic granules placed along one edge of the cilium, the
contraction of this thread furnishing the power of the cilium, while
the synchronous contraction of thousands of similar cilia furnishes
-the motive power of the organism.
In some forms, as in dileptus or paramecium, and the majority of
4
50
GENERAL ORGANIZATION OF THE PROTOZOA
the largest forms of protozoa, the cilia are distributed evenly over the
entire cell body. But in some cases they are limited to one-half of
the body, as in halteria; in others to the ventral surface only, as in
gastrostyla, oxytricha, and the hypotrichida in general, while in others
they are reduced to a single girdle of cilia about the mouth, as in
vorticella and its allies.
An interesting feature in the comparative anatomy of infusoria is
the fusion of simple cilia into motile organs of a more complicated
type. Sometimes a bundle of cilia are grouped together in a small
brush-like organ, as in aspidisca, where the constituent elements of
the bundle can still be made out (Fig. 17). In other forms, as
oxytricha, the bundles are more tightly fused to form compact motile
organs, which are sometimes used for walking and running, or some-
times they are differentiated for feeling, and so constitute an elemen-
FIG. 18
Pleuronema chrysalis, Ehr., with well-developed undulating membrane. (After Calkins.)
tary sensory apparatus. Again, the cilia are fused into continuous
sheets, or membranes, which provide currents for bringing food toward
the mouth, as in pleuronema or lembus (Fig. IS).
Rows of small membranes, called membranelles, are found in three
of the four orders of ciliata. These are always placed around the oral
or peristomial cavity, and their synchronous beating brings a constant
food-bearing current toward the mouth. In some cases, as the vor-
ticella group, the cilia have quite disappeared, leaving, under ordinary
vegetative conditions, onlv this row of membranelles.
ti
In one subdivision of the infusoria, the suctoria, the cilia disappear
after a short embryonic life of the individual, and their place is taken
by protoplasmic prolongations called tentacles. Some of these ten-
tacles are hollow and provided with a suction cap, so that food may be
drawn through them into the inner protoplasm. Others are sharp
CLASSIFICATION OF THE MASTIGOPHORA
51
pointed and are used by the animal as piercing needles for pene-
trating the membranes of the victims that are caught for food.
The more than superficial resemblance of these suctoria to the
heliozoa gives a clue to the possible evolution of the infusoria from
sarcodina. We have seen that in forms like myriophrys, cilia and
pseudopodia are equally distributed around the body. We have also
seen that the central axis of such pseudopodia and flagella are of the
same type, and are probably homologous structures; furthermore,
we have seen that in actinobolus, projectile tentacles armed with
trichocysts can be thrown out at any point on the periphery. These
facts indicate the possibility of a common ancestry of the infusoria
FIG. 19
I
•"<
I
Cilia and myonemes of infusoria: a, b and e after Johnson; c, d, f and a after Biitschli.
The surface view of Stentor ceruleus (c, e) shows rows of cilia inserted on the borders of
canal-like markings, each of which contains a myoneme (rf). These are more clearly shown
in the optical section (/). In Holophyra discolor (g) the canals and myonemes are inserted
deeper in the cortical plasm, a, the membrane of Stentor ceruleus under pressure.
from a heliozoon-like ancestral race, represented in present-day forms
by types like myriophrys, hypocoma, ileonema, and mesodinium, which
have both tentacles and cilia. From such an ancestral group the
ciliata may have arisen by losing the tentacles and adapting the cilia
to the various needs of the cell, while the suctoria may have arisen by
loss of the cilia and development of the tentacles to meet all of the
needs of the cell, the cilia appearing in the embryos of the suctoria
as reminiscences of the earlier ciliated condition of the race.
These motile organs of the protozoa, with the exception of the
flagella, are products of the cortical protoplasm, the flagella retaining
52 GENERAL ORGANIZATION OF THE PROTOZOA
the same origin from the nucleus that the axial rays of the filose
pseudopodia have. Cilia, however, arise from small basal bodies
called microsomes, which have a nuclear origin and belong apparently
in the same category of kinetic stuffs as the substance of flagella. In
many of the infusoria these granules are arranged in definite lines or
rows, forming threads of contractile substance which lie immediately
below the cuticle. These threads, called rnyonemes, are in reality
primitive muscle elements, and their sudden contraction resembles
the action of the complicated muscle bundles of the metazoa
(Fig. 19).
Subphylum INFUSORIA. Protozoa in which the motor apparatus is in the form
of cilia, either simple or united into membranes, membranelles, or cirri. The
cilia may be permanent or limited to the young stages. With two kinds of
nuclei, macronucleus and rnicronucleus. Reproduction is effected by simple
transverse division or by budding. Nutrition is holozoic or parasitic.
Class I. CILIATA. Infusoria provided with cilia during all stages. Reproduction
is brought about typically by simple transverse division. Mouth and anus
are usually present. The contractile vacuole is often connected with a com-
plicated canal system.
Order 1. Holotrichida. Ciliata in which the cilia are similar and distributed all
over the body, with, however, a tendency to lengthen in the vicinity of the
mouth. Trichocysts are always present, either distributed about the body
or limited to a special region.
Suborder 1. GYMXOSTOMIXA. Holotrichida without an undulating membrane
about the mouth, which remains closed except during food-taking intervals.
Familv 1. Enchelinidce. The mouth is always terminal or subterminal, and is
usually round or oval in outline. Food taking is usually a process of swal-
lowing.
Typical genera: Holophrya, Ehr., 1831; Urotricha, Clap; and Lach., 1858;
Enchelys, Hill, 1752,' Ehr., 1838; Spathidium, Duj., 1841; Chenia, Quen-
nerstadt, 1868; Prorodon, Ehr., is:;:]; Dinophrya,' Butsehli, 1888; Lacrv-
niaria, Ehr., 1830; Trachelocerca, Ehr., 1833;' A<-tin<>bolus, Stein, TS67;
Ileonema, Stokes, 1884; Plagiopogon, Stein, 1859"; Coleps, Xitsch, 1827;
Tiarina, Bergh, 1879; Stephanopogon, Entz, 1884; Didiniuui, Stein, 1859;
Mesodinium, Stein, 1862; Btitschlia, Schuberg, 1886.
Family 2. Trachelinida'. The body is distinctly bilateral or asymmetrical, with
one side, the dorsal, slightly arched. The mouth may be terminal or sub-
terminal, or the entire mouth region may be drawn out into a long proboscis.
An esophagus or gullet may or may not be present; when present, it is usually
supported by a specialized framework.
Typical genera: Amphileptus, Ehr., 1830; Lionotus, Wrzesniowski, 1870; Loxo-
phyllum, Duj., 1841; Trachelius, Schrank, 1903; Dileptus, Duj., 1841;
Loxodes, Ehr., 1830.
Family 3. Chlamydodontidce. The general form is oval or kidney-shaped. The
mouth is almost always in the posterior region. The pharynx is supported
by a rod-apparatus or a smooth, firm tube.
Subfamily 1. Nassiilmce. Ciliation is complete.
Typical genera: Nassula, Ehr., 1833.
Subfamily 2. Chilodontmcp. The body is generally flattened, and the cilia are
stronger on the dorsal side, or are confined to that region.
Typical genera: Orthodon, Gruber, 1884; Chilodon, Ehr., 1833; Chlamydodon,
Ehi\, 1835; Opisthodon, Stein, 1859; Phascolodon, Stein, 1857; Scaphidio-
don, Stein, 1857.
CLASSIFICATION OF THE INFUSORIA 53
Subfamily 3. Erviliiiur. The cilia are confined to the ventral surface or to a por-
tion of it. The posterior end invariably possesses a movable style arising from
the posterior ventral surface.
Typical genera: .Ecjyria, Clap and Lach., 185S; Onychodactylus, Entz., 18S4;
Trochilia, Duj., 1841; Dysteria, Huxley, 1857.
Suborder 2. TRICHOSTO.MIXA. In addition to the general coating of cilia there is
an undulating membrane or membranes at the edge of the mouth or in the
pharynx. The mouth is always open.
Family 1. Chiliferidac. The mouth is in the anterior half of the body or close to
the middle. The pharynx when present is short. The so-called "peristorne
area" leading to the mouth is absent or only slightly developed.
Typical r/enera: Leucophrys, Ehr., 1830; Glaucoma, Ehr., 1830; Dallasia,
Stokes, 188(3; Frontonia, Ehr., 1838; Ophryoglena, Ehr., 1831; Colpjdiuni,
Stein, 1860; Chasmatostoma, Engelniann, 1S62; Uronema, Duj., 1841;
Urozona, Schewiakoff (Biitschli), 1888; Loxocephalus, Kent, 1881; Colpoda,
Miiller, 1773.
Family 2. Urocentridce. The mouth, with a long, tubular pharynx, is in the centre
of the ventral side. The cilia are confined to two broad zones around the
body at each end.
Typical genera: Urocentrum, Xitsch, 1827.
Family 3. Microthoracidce. Small asymmetrical forms, with the mouth invariably
in the hinder portion. The cilia are always more or less dispersed, sometimes
limited to the oral region. There may be one or two undulating membranes.
Typical genera: Cinetochilum, Perty, 1849; Microthorax, Engelmann, 1862;
Ptychostomum, Stein, 1X60; Ancistrum, Maupas, 1883; Drepanomonas,
Fresenius, 185s.
Family 4. Parammdtv. The mouth is sometimes in the anterior, sometimes in
the posterior, half of the body, and is accompanied by a large, triangular
"peristorne area," running from the left anterior edge of the body to the
mouth.
Typical genera: Paramecium, Stein, isiiO.
Family 5. Pleuraneinula:. The mouth is at the end of a long peristome, which
runs along the ventral side; the body is dorsoventrally or laterally com-
pressed. The entire left edge of the peristome is provided with an undulating
membrane which occasionally runs around the posterior end of the peristome
to form a pocket leading to the mouth. The right edge of the peristome is
provided with a less developed membrane. There may or may not be a well-
developed pharynx.
Typical genera: Lembadion, Perty, 1849; Pleuronema, Duj., 1841; Cyclidium,
Ehr., 1838, a subgenus of the preceding; Calyptotricha, Phillips, 1882;
Lembus, Colin, 1x66.
Family 6. Isotrickidce. The body is more or less plastic, but not contractile. The
cuticle is thick and provided with evenly distributed cilia. The mouth is
posterior and accompanied by a distinct pharynx. They are parasites in the
digestive tract of ruminants.
Typical (jenera: Isotricha, Stein, 1859; Dasytricha, Schuberg, 1888.
Family 7. Opalinida\ The form is oval, and the body may be short or drawn out
to resemble a worm. They are characterized mainly by the absence of mouth
and pharynx.
Typical genera: Anoplophrya, Stein, 1800; Hoplitophrya, Stein, I860; Disco-
phrya, Stein, I860; Opalinopsis, Foettinger, 1881; Qpalina, Purkinje and
Valentin, 1835; Monodontophrya, Vejdowsky, 1892.
Order 2. Heterotrichida. Ciliata characterized by the possession of a uniform
covering of cilia and an adoral zone, consisting of short cilia fused together into
membra nelles.
54 GENERAL ORGANIZATION OF THE PROTOZOA
Suborder 1. POLYTRICHIXA. Heterotrichous ciliates provided with a uniform
coating of cilia.
Family 1. Plagiotomidos. The peristome is a narrow furrow, which begins, as a
rule, close to the anterior end, and runs backward along the ventral side to the
mouth, which is usually placed between the middle of the body and the pos-
terior end. A well-developed adoral zone stretches along the left side of the
peristome, and it is usually straight.
Typical genera: Conchophthirus, Stein, 1861; Plagiotoma, Duj., 1841; Nycto-
therus, Leidy, 1849, a subgenus; Blepharisma, Perty, 1849; Metopus, Clap,
and Lach., 1858; Spirostomum, Ehr., 1835.
Family 2. Bursaridce. The body is usually short and pocket-like, but may be
elongate. The chief characteristic is the peristome, which is not a furrow,
but a broad triangular area, deeply insunk, and ending in a point at the
mouth. The adoral zone is usually confined to the left peristome edge, or it
may cross over to the right anterior edge.
Typical genera: Balantidium, Stein, 1867; Balantidiopsis, Biitschli, 1888; Con-
dylostoma, Duj., 1841; Bursaria, O. F. Miiller, 1773; Thylakidium, Sche-
wiakoff, 1892.
Family 3. Stentoridcc. The peristome is relatively short and limited to the front
end of the animal, so that its plane is nearly at right angles to that of the
longitudinal axis of the body. The adoral zone of cilia either passes entirely
around the peristome edge, or ends at the right-hand edge. The surface of the
peristome is spirally striated and provided with cilia. Undulating membranes
are absent.
Typical genera: Climacostomum, Stein, 1859; Stgntpr, Oken, 1815; Folliculina,
Lamarck, 1816. Genera •incrrttr si'di.v: Cenomorpha (Gyrocorys, Stein),
Perty, 1852; Maryna, Gruber, 187'.).
Suborder 2. OLIGOTRICHIXA. Heterotrichous ciliates characterized by the reduced
cilia, which are limited to certain localized areas.
Family 1. lAeberkuhnidoe. This name was given by Biitschli for certain little-
known forms, which were at first considered young Stentors.
Family 2. Haltcriidw. The peristome has no cilia, and only a few scattered ones
can be found on the ventral and dorsal surfaces.
Typical genera: Strombidium, Clap, and Lach., 1S5S; llaltcria, Duj., 1N41.
Family 3. Tintinnidae. The body is attached by a stalk tolTtheca. Inside of the
adoral zone of membranelles is a ring of cilia (paroral cilia ).
Typical genera: Tintinnus, Fol., 1889; Tintinnidium, Kent, 1881; Tintinnopsis,
Stein, 1867; Codonella, Haeckel, 1873; Dictyocysta, Ehr., 1854.
Family 4. Ophryoscolecidce. Heterotrichous ciliates characterized by a thick
cuticle and deep funnel-like peristome. The posterior end is provided with
distinct spine-like processes, while the terminal anus is provided with a well-
defined anal tube.
Typical genera: Ophryoscolex, Stein, 1859; Entodinium, Stein, 1859; Diplo-
dinium, Schuberg, 1888.
Order 3. Hypotrichida. Ciliata in which the cilia are limited to the ventral surface
of a dorsoventrally flattened body; they are frequently fused to form larger
appendages, the cirri, and an adoral zone of membranelles. The dorsal sur-
face is frequently provided with bristles. A pharynx may be absent or but
slightly developed.
Family 1. PeritromidcF. The peristome is but slightly marked off from the
remaining frontal area. The cilia on the ventral surface are uniform in size
and arrangement, and are not differentiated into cirri.
Typical genera: Peritromus, Stein, 1862.
Family 2. Oxyirichida'. The peristome is not always distinctly marked off from
the frontal area. In the most primitive forms the ciliation on the ventral sur-
CLASSIFICATION OF THE INFUSORIA 55
face is similar to that of the preceding family. Almost invariably in these primi-
tive forms some of the anterior and some'of the posterior cilia are fused into
large and more powerful appendages, the cirri, which are distinguished as the
frontal and anal cirri, respectively. In the majority of forms all of the cilia
are thus differentiated; strong marginal cirri are formed in perfect rows, and
ventral cirri in imperfect rows. In addition to the adoral zone of membra -
nelles, there is an undulating membrane on the right side of the peristome,
and, in some cases, a row of cilia between the membrane and the adoral zone.
These are the paroral cilia, and they form the paroral zone.
typical genera: Trichogaster, Sterki, 1878; Urostyla, Ehr., 1830; Kerona, Ehr.,
1838; Epiclintes, Stein, 1S62; Stichotricha,' Perty, 1849; Strongylidium,
Sterki, 1878; Amphisia, Sterki, 1878; Uroleptus, Stein, 1859; Sparotricha,
Entz, 1879; Onychodromus, Stein, 1859; Pleurotricha, Stein, 1859; (Jas-
trostvla, Engelmann, 1862; Gonostomum, Sterki, 1878; Urosoma, Kowalew-
sky, 1882; Oxytricha^ Ehr., 1830; Stvlonychia, Stein, 1859; Actinotricha,
Cohn, 1866; ~Galladina, Kowalewskyrl882; Psilotricha, Stein, 1859; Tetra-
styla, Schewiakoff, 1892; Holosticha, Wrzesniowski, 1877.
Family 3. Euplotidce. Hypotrichous ciliates, which are characterized mainly by
the considerable reduction of the cilia, frontal, marginal, and ventral cirri;
the anal cirri, on the other hand, are always present. The macronucleus is
band-formed.
Typical fji'ticra: Eupjotes, Stein, ]N5!l; Certesia, Fabre-Domergue, 1885; Dio-
phrys, Duj.,lS41; Uronychia, Stein, ls57; Aspidisca, Ehr., 1830.
Order 4. Peritrichida. Ciliata usually of cylindrical or cup-like form, in which the
cilia are reduced, as a rule, to those which form the adoral zone, but sec-
ondary rings of cilia mav be present.
Family 1. Spirochonidae. Peritrichous ciliates in which the peristome is drawn
out into a curious funnel-like process, either simple or rolled. They are
parasitic forms in which reproduction by budding is characteristic.
Typical genera: Spirochona, Stein, 1N51; Kentrocluma, Rompel, 1894; Kentro-
chonopsis, Dorlein, 1897.
Family 2. I/icknophoridoe. In addition to the adoral zone, there is a secondary
circlet of cilia around the opposite end. The adoral zone is a left-wound
spiral. A single genus Lichnophora, Claparede, 18()7, which is parasitic on
various marine arthropods.
Family 3. Vorticellidir. Attached or unattached forms of peritrichous ciliates, in
which the adoral zone, seen fmm above, forms a right-wound spiral (dexio-
tropic). A secondary circlet of cilia around the under end may be present
either permanently or periodically.
Subfamily 1. Urceolarinae. Yorticellid;e having a permanent secondary circlet of
cilia which incloses an adhesive disk, and without a peristome fold.
Typical genera: Trichodina, Stein, 1854; Cyclochseta, Jackson, 1875; Tricho-
dinopsis, Clajx and Lach., 185S.
Subfamily 2. Vorticellidince. Peritrichous forms without a permanent secondary
circlet of cilia, and provided with a peristome fold which can be contracted
sphincter-like to inclose the peristome.
Typical (/enera: Scyphidia, Lachmann, 185(>; Gerda, Clap, and Lach., 1858;
Astylozoon, Engelmann, 18(12; Vorticella, Ehr., 1838; Carchesium, Ehr.
1830; Zoothamnium, Stein, 1 854T" Glossatella, Biitschli, 1888; Ejjistylis,
Ehr., 1830; Rhabdostyla, Kent, 1882; Opercularia, Stein, 1854; Ophrydium,
Ehr., 1838; Cothurnia, Clap, and Lach., 1858; Vaginicola, Clap, and Lach.,
1858; Lagenophrys, Stein, 1851.
Subclass 2. Suctoria. Infusoria having no cilia during the adult stages, but
provided with them during the embryonic period. In a few cases the cilia are
retained. They have tentacles of various kinds, some adopted for sucking,
some for piercing.
56 GENERAL ORGANIZATION OF THE PROTOZOA
Family 1. Hypocomidce. These are unattached forms of Suctoria with a perma-
nently ciliated ventral surface, and with one suctorial tentacle. Reproduction
is effected by cross-division. A single genus, Hypocoma, Gruber, 1SS4.
Family 2. Urnulida\ A family of small attached forms, with or without a cup or
theca; with one or two, rarely more, simple tentacles. Swarm-spores holo-
trichous.
Typical genera: Rhyncheta, Zenker, 1866; Urnula, Clap, and Lach., 1858.
Family 3. Metacinetidce. Thecate forms; the base of the cup is drawn out into a
long stalk, and the walls are perforated for the exit of the tentacles. A single
genus, Mctarinrfn, Biitschli, 1888.
Family 4. Podopliryidcc. Stalked or unstalked forms of more or less globular
shape. The tentacles are numerous and distributed about the entire surface
or limited to the apical region; some of them are knobbed, others pointed and
have a prehensile function.
Typical genera: Spherophrya, Clap, and Lach., 1858; Endospha?ra, Engelmann,
1876; Podophrya, Ehr., 1838; Ephelota, Str. Wright, 1858; Podocyathus,
Kent, 1SS1.
Family 5. Acinetidce. The individuals are naked and stalked, or thecate and
stalked or unstalked. The tentacles are numerous, usually knobbed and all
alike. Reproduction is effected by inner or endogenous budding, which may
be simple or multiple. The swarm spores are usually peritrichous, but may
be holotrichous or hypotrichous.
Typical genera: Tokophrya, Biitschli, 1888; Acineta, Ehr., 1833; Solenophrya,
Clap, and Lach., 1S5S; Suctorella, Frenzel, 1891.
Family 6. Dendrosomidcr. Suctoria without stalks or theca. The tentacles are
numerous, all alike, and knobbed and grouped in distinct tufts; they may be
simple or branched. Reproduction by endogenous division; the swarm
spures are peritrichous.
Typical genera: Trichophrya, Clap, and Lach., 1858; Dendrosoma, Ehr., 1838;
Staurophrya, Zacharias, 1893.
Family 7. Dendrocometidcc. Sessile suctoria resting upon the entire basal surface
or upon a portion of it raised as a stalk. The numerous tentacles are short and
knobbed, and distributed over the entire apical surface or localized upon
branched arms. Spore formation is endogenous; the swarm spores peri-
trichous.
Typical genera: Dendrocometes, Stein, 1867; Stylocometes, Stein, 1867.
Family 8. Ophnjodendridce. Stalked or sessile forms possessing numerous long,
rarely knobbed tentacles, which are supported upon proboscis-like processes
of the apical side. Reproduction is brought about by endogenous budding.
The swarm spores are peritrichous.
Typical genera: Ophryodendron, Clap, and Lach., 1858.
PROTOZOA WITHOUT MOTILE ORGANS, AND CLASSIFICATION
OF THE SPOROZOA.
To state that the sporozoa are without motile organs is not strictly
accurate, for many of them have well-developed myonemes (gregarines)
and move with a vermiform motion. Others have, at times, the power
of progressing by means of pseudopodia (many of the neosporidia).
Nor is the method of reproduction (spore formation) any less equi-
vocal, for many forms reproduce by simple division as well as by spore
formation (schizogregarinida). This division, therefore, more than
PROTOZOA WITHOUT MOTILE ORGANS 57
any other of the unicellular animals must be regarded as provisional
only and comprising numerous heterogeneous groups of organisms
which can be more accurately classified only after the full life histories
are made out. Some of these groups are obviously related to the
mastigophora through the blood-dwelling flagellates, and others are
equally related to the sarcodina. Two divisions only, the gregarinida
and the coccidiidia. may be accepted as sufficiently definite to constitute
an acceptable division of the protozoa. At the present time, Schau-
clinn's grouping into telosporidia and neosporidia cannot be bettered,
although evidence is accumulating to show that the latter group is
entirely artificial.
SUBPHYLUM SPOROZOA. — Parasitic protozoa without motile
organs, but capable of moving from place to place by structural mod-
fications of one kind or other. Reproduction either simple or multiple,
but mainly by spore formation, which is either asexual (schizogony)
or sexual (sporogony).
The following classification of sporozoa is based upon Labbe's
"sporozoa," and upon "sporozoa" in Lankester's Treatise on Zoology,
Part I, Introduction and Protozoa. Second fascicle, with additions
and changes necessary for the present work and to bring the classifi-
cation up to date.
Suhphylurn SPOROZOA.
Class I. TELOSPORIDIA, Srliaiidinn. Sporozoa in which sporulation ends the
life of the individual.
Order 1. Gregarinida. Coelozoic telosporidia reproducing usually by spore forma-
tion alone, and after the fertilizing union of but slightly different gametes.
Suborder 1. SCHIZOGREGARIX.K. ( Jrcgarines reproducing by division or by
multiple budding in addition to spore formation.
This interesting group, which is continually being added to by various obser-
vers, was until finite recently represented by only those supposedly ameboid
forms known as the Amcbosporidia. The investigations begun by Leger
and carried on by Leger, Dubosq, Dogiel, Brasil, and others of recent date
have shown that the supposed ameboid processes are actually unchangeable,
serving more as attaching organs and for the purpose of absorbing food
than for the purposes of locomotion.
There is no question that these forms are gregarines, and from the very
characteristic types included here there is some hope of ultimately getting
light upon the closer relationships of the entire group of sporozoa to other
groups of protozoa.
Genus 1. Schizocystis, Leger, 1900. Type species S. gregarinoides, Leger, from
the intestine of larva of Ceratopogen sp. The trophozoites are somewhat
similar to Monocystis, but cliffer in reproducing by the formation of a group
of internal buds, which, as merozoites, leave the parent cell and grow into
new trophozoites; these finally couple up, fertilization and sporulation result,
and octozoic spores are finally formed, as in Monocystis (Fig. 76).
Genus 2. Ophryocystis, A. Sch., 1 SS4. Many species are known, most of which are
parasites hi tlie Malpighian tubules of beetles. The organisms have char-
acteristic pseudopodia-like processes for purposes of attachment, and the
trophozoites reproduce by simple division or by multiple division. Sporula-
tion ultimately takes place, the process differing in different cases (Fig. 801.
58 GENERAL ORGANIZATION OF THE PROTOZOA
Genus 3. Selenidium, Giard, 1884; emend Caullery et Mesnil, 1899. The body
is attenuated and worm-like, and marked externally by longitudinal stria- due
to the ectoplasmic myonemes. Epimerite conical and slender. Parasites of
polychetes and numerous species are recorded.
Suborder 2. EUGREGARIN^E, Leger. Reproduction here is limited apparently to
sporulation, division occurring, if at all, within the host cell and during the
young stages.
Tribe I. Acephalince, Kolliker. Eugregarines in which there is no division into
chambers and in which at no stage is there an epimerite.
Genus 4. Monocystis, Stein, 1848. The trophozoites are often highly contractile
owing to the peristalsis brought about by the contractions of ectoplasmic
myonemes. Spores boat-shaped and octozoic. Many species from worms and
entomostraca, a typical species, M. agilis may be found almost invariably in
the seminal reservoirs of the common earthworm, and excellent stages in
sporulation and fertilization may be easily obtained.
Genus 5. Zygocystis, Stein, 1848. The trophozoites are usually found in pairs or
groups of three. Typical species, Z. cometa, Stein, found in the seminal
vesicles and body cavity of the earthworm Lumbricus agricola.
Genus 6. Zygosoma, Labbe, 1899. The trophozoite has typical and characteristic
finger-like processes and is usually found in couples. Sporulation unknoivn.
Typical species, Z. gibbosum, Greeff, 1880, in the gut of Echiurus pallassii.
Genus 7. Pterospora, Racovitza and Labbe, 189(3. The piriform trophozoites
are always associated in couples. The spores have dissimilar poles and the
epispore is drawn out into lateral processes. One species, P. maldaneorum,
R. and L., from the celomic cavity of maldanid worms.
Genus 8. Cyxtobia, Mingazzini, 1891. The trophozoites are large and irregular
in form and usually have two nuclei due to the early fusion of two individuals.
The spores are heteropolar, and the epispore is drawn out into chimney-like
projections at one pole. One species, C. holothuriae, A. Sch., from the blood-
vessels and body cavity of holothurians.
Genus 9. Latkocysiis, Giard, 187(3. The trophozoite is characterized by an endo-
plasm filled with crystals of calcium oxalate. The epispore has long pro-
cesses. A single species from the ccelomic cavities of various echinids.
Genus 10. Ceratoxpora, Leger, 1892. The trophozoites fuse by their truncated
ends and give rise to spores without encysting. The spores are character-
ized by long spinous processes (Fig. 20). A single species, C. mirabilis,
Leger, from the body cavity of Glycera.
Genus 11. Urospora, A. Schn., 1875. The spores are characterized by the presence
of a long caudal filament at one pole. Several species from the body cavities
of oligochetes, nemertines, sipunculids, and other marine invertebrates.
Genus 12. Gonospora, A. Schn., 1875. The trophozoites are quite variable in
form and give rise to heteropolar spores bearing from one to several tooth-like
processes at one pole, and rounded at the other. Four species from the body
cavities of polychetous worms.
Genus 13. Syncystis, A. Schn., 1886. The spores are ovoid or boat-shaped, with
spines or processes at each extremity. One species, S. mirabilis, A. Schn.,
from fat body and ccelom of species of Xepa.
Genus 14. Diplocystis, Kunstler, 1887. The trophozoites fuse precociously to
form spherical masses of gregarines in the body cavity of crickets and cock-
roaches. The spores are either spherical or oblong.
Genus 15. Lnnkesteria, Mingazzini, 1891. The spores are more or less flattened
or spatulate, oval in outline, and octozoic. Type species, L. ascidite, Lank,
from the gut of Ciona intestinalis.
Genus 16. CaUyntroclilamyi*, Frenzel, 1885. The trophozoites have a central
constriction but no septum dividing the body into protomerite and deuto-
PROTOZOA WITHOUT MOTILE ORGAXS 59
merite; they are covered by a fur-like fringe of processes resembling cilia.
The spores are unknown. Type species, C. phronima?, Frenz., from the gut
of Phronima sedentaria.
Genus 17. Ancora, Labbe, 1899. The trophozoite has a peculiar anchor-like
form by reason of two lateral bulgings of the body. Spores unknown. Species,
A. sagittata, Leuck, from the gut of Capitella capitata.
Other genera provisionally placed here are: Pleurozyga, Mingazzini, 1891, from
ascidians; Ophioidina, Mingazzini, 1891, from Bonellia; Kollikerella,
Labbe, 1899, from Staurocephalus; Lobianchella, Mingazzini, 1891, from
Alciope.
Tribe II. Cephcdinoe, Delage. Eugregarines possessing an epimerite at some
stage of the life history, either in the adult phase or in the temporary young
phases. The body is usually divided by a septum into protomerite and
deutomerite, and the trophozoites are frequently associated in couples
arranged tandem, each couple consisting of primite and satellite. The tribe
consists mainly of parasites of the gut of various forms of arthropods.
Legion A. Gymnosporea, Leger. The sporoblast mother cells give rise directly
to sporozoites which do not form in sporocysts or specially protected sporo-
blasts.
Family 1. Aggregatidce, Labbe. With sporozoites grouped irregularly about a
number of residual masses.
Genus 18. Ayyreyafa, Frenzel, 1885. With the characteristics of the family.
Several species from various crustacean hosts.
Family 2. Porosporidce, Labbe. Special centres of sporozoite formation are
present (sporoblast centres), but they lack the protective sporocysts.
Genus 19. Porospora, A. Schn., 1875. Trophozoite with small button-like epi-
merite; cells very large (up to 1(5 mm.) and usually solitary. One species,
P. gigantea, Van Benedcn, from gut of the lobster.
Legion B. Any/ox/xir/a, Lcgvr. The sporocysts are well developed and usually
double coated to form endospore and epispore.
Family 3. GregarinidcB, Labbe. Trophozoites with simple epimerites; sporo-
cysts with or without sporoducts. Spores oval or barrel-shaped, and united in
strings in species with sporoducts.
Genus 20. Greyarina, Dufour, 1 si's. Cysts with spomducts; epimerite small,
conical, or knobbed (see Fig. 81, p. 191). Many species widely distributed in
digestive tracts of various insects.
Genus 21. Gamocystis, Leger, ls'.*2. The trophozoite has a temporary epimerite.
Cyst with sporoducts. Spores cylindrical and elongated. From gut of cock-
roach and other insects.
Genus 22. Eiermocyyfis, Leger, 1 892. The sporonts unite to form aggregates of
several individuals. The spores are ellipsoidal. Cysts without sporoducts.
One species, E. polymorpha, Leger, from the gut of insects.
Genus 23. Hycdospora, A. Schn., 1875. Cysts without sporoducts. Spores
pointed at each end and bulging in middle. Gut of Petrobius sp.
Genus 24. Euspora, A. Schn., 1875. Spores prismatic, cysts without sporoducts.
One species, E. fallax, from gut of Rhizotrogus estivus.
Genus 25. Spherocystis, Leger, 1892. Body spherical, protomerite temporary,
cysts without sporoducts, spores oval. One species, S. simplex, Leger, from
the gut of Xyphon pallidus larva.
Genus 26. Cnemidospora, A. Schn., 1882. The epimerite is large and lancet-
shaped; sporonts solitary with globular protomerites. No sporoducts.
Spores ellipsoidal, with thick spore cysts. One species, C. lutea, A. Schn.,
from the gut of Glomeris.
Genus 27. Stenophora, Labbe, 1899. Sporonts large, with small protomerite.
Cyst without sporoducts: spores fusiform with dark sutural line. One
species, S. juli, Franz, from gut of species of millipedes.
60 GENERAL ORGANIZATION OF THE PROTOZOA
Family 4. Didymophyidce, Leger. The sporunts always associated in pairs, the
protomerite of the satellite disappearing, thus giving the appearance of an
organism with three chambers and two nuclei.
Genus 28. Didymophyes, Stein, 1848. The epimerite has the form of a spike.
Cysts open by simple rupture liberating the oval spores. Four species.
Family 5. Dactylophoridoe, Leger. The epimerite is asymmetrical and irregular,
with digitiform processes. Sporocysts open by simple rupture or by the
swelling of a residual mass of plasm termed a " pseudocyst."
Genus 29. Rhopalonia, Leger, 1893. The epimerite is irregular and asymmet-
rical, bearing finger-formed prolongations. The trophozoite is solitary and
with traces only of a protomerite. One species, R. geophili, Leger, from gut
of geophilus sp.
Genus 30. Echinomera, Labbe, 1899. The trophozoite massive and oval in
outline; epimerite persistent and spiked, the point bearing small transitory
digitiform processes. Cysts open by simple rupture. One species, E. hispida,
A. Schn., from gut of Lithobius forficatus.
Genus 31. Trielwrlujnchus, A. Schn., 1882. Protomerite truncated with an
elongated and conical top. Cysts with oblong, wart-like protuberances.
Cysts open by the swelling of laterally placed pseudocysts. Spores not in
strings. One species, T. pulcher, A. Schn., from the gut of Scutigera.
Genus 32. Pteroccphalus A. Schn., 1887. Protomerite extends beyond the deuto-
merite on the two sides and is divided into two lobes by a constriction; the
two lobes are provided with sharp papillfe, and are united on one side and
so curved as to form a coiled horn. The spores are oval and associated
obliquely in strings. One species, P. nobilis, A. Schn., from gut of Scolo-
pendra.
Genus 33. DaciylopJtorus, Balb., 1889. The protomerite is dilated excentrically
and bears epimerite with digitiform processes. Sporonts are solitary and
elongated; cysts spherical and spores cylindrical; cysts open by swelling of
lateral pseudocyst. One species, D. robustus, Leger, from the gut of Cryp-
tops hortensis.
Family 6. AdinocepliaUda, Leger. Sporonts always solitary with simple, sym-
metrical, or irregular appendages. Cysts open by simple rupture. Spores
biconical, cylindrical, or navicular. Parasitic usually in the gut of carnivorous
arthropods.
Group A. Sdadiophorincp, Labbe, 1899. Protomerite umbrella-shaped, and with
radiating ridges. Spores biconical and with centra] swellings, the opening
at the equator by simple dehiscence, while the endospore opens terminally.
Genus 34. Stiadiophora, Labbe, 1899. The epimerite is large and flattened and
with the characteristics of the group. Three species from digestive tracts
of phalangidfe.
Group B. Anthorkynchince, Labbe, 1899. Spores ovoid with pointed ends;
joined in strings; equatorial opening.
Genus 35. Author hynchus, Labbe, 1899. Epimerite in form of a large grooved
knob or button. One species from gut of Phalangium opilio.
Group C. P'ileocephaliiKF, Labbe, 1899. Epimerite simple and regular; cysts
open by simple rupture; spores usually biconical.
Genus 36. Pilcocephalus, A. Schn., 1875. Epimerite simple and regular and
somewhat lance-like. Cysts open by simple rupture, spores biconical.
Genus 37. Amphoroides, Labbe, 1899. Epimerite spiked or rounded; proto-
merite very short and cup-like. Spores biconical. One species, A. polydesmi,
Leger, from the gut of Polydesmus.
Genus 38. Discorhynchus, Labbe, 1899. Epimerite large and discoid, with a
distinct rim; protomerite larger than the deutomerite, which is regularly
cylindrical and truncated posteriorly. Cysts spherical, spores biconical and
slightly bent. One species, D. truncatus, Leger, from gut of Sericostoma sp.
PROTOZOA WITHOUT MOTILE ORGANS 61
Group D. Stictosporince, Labbe, 1899. Spores biconical, with points slightly in-
curved and with papillae on the endospore.
Genus 39. Stictospora, Leger, 1S93. Epimerite with globular head depressed
ventrally, and covered with ribs which project posteriorly as spikes. Spores
biconical. One species, S. provincialis, Leger, from the gut of Melolontha and
Rhizotrogus larva?.
Group E. ActinocephalincB, Labbe, 1899. Epimerite always with appendages.
Spores regular, navicular or subnavicular, biconical or cylindrical.
Genus 40. Schneideria, Leger, 1892. Sporont has but one chamber; epimerite
a thick plate bordered by rib-like thickenings. Spores somewhat thickened
and biconical. Two species, S. mucronata, Leger, from gut of larvae of Bibio
marci, and S. caudata from gut of larva of Sciara nitidicollis.
Genus 41. Asterophora, Leger, 1892. The epimerite is a circular ridge with ribs
surrounding a prominent central papilla. The protomerite is as large or
larger than the deutomerite. Sporonts solitary; spores cylindrical with
conical extremities. Two species, A. mucronata, L., and A. elegans, L., from
the intestines of larvae of insects.
Genus 42. Stephanophara, Leger, 1892. Epimerite large and in form of a convex
disk with a crown of digitiform processes. Spores cylindrical with conical
ends. One species, S. lucani, Stein, from gut of Dorcus sp.
Genus 43. Bothriopsis, A. Schn., 1875. Epimerite in form of a large lens-shaped
knob with non-motile processes. Sporonts highly developed and very
motile. Spores biconical and thickened. One species, B. histrio, A. Schn.,
1875, from the gut of Hydaticus sp.
Genus 44. Coleorhynchus, Labbe, 1899. Sporont with sucker-like protomerite
extending over deutomerite. The convex septum projects into the proto-
merite. Cysts open by simple rupture; spores navicular. One species,
C. heros, A. Schn., from gut of Xepa cinerea.
Genus 45. Legcria, Labbe, 1899. Protomerite enlarged and club-like, with
invading septum, as above. Spores with thick sporocysts and subnavicular
in form. One species, L. agilis, A. Schn., from gut of Colyrnbetes sp.
Genus 46. Phialoides, Labbe, 1899. Complex epimerite consisting of a discoid
retractile cap surrounded by a circular ridge with collar-like membrane, with
ridges ending in triangular teeth. Sporonts solitary, massive ; spores biconical
and thickened. One species, P. ornata, Leger, from the gut of Hydrophilus
larvce.
Genus 47. Geniorhynrhiis, A. Schn., 1875. Epimerite in the form of a disk which
bears fine pointed teeth and is carried on a long neck. Spores subnavicular.
One species, G. monnieri, A. Schn., from intestines of nymphs of libellulidae.
Genus 48. Actinocephalus, Stein, 1S4S. Epimerite sessile or borne on neck-like
process, and is provided with hooks and spines. Spores biconical. Several
species from digestive tracts of beetles.
Genus 49. Pijxinia, Hammerschmidt, 1838. Epimerite in the form of a cup with
rim surrounding a central spine. Many species (Fig. 73).
Genus 50. Beloides, Labbe", 1899. Epimerite in the form of a disk or knob and
bearing about ten teeth in addition to a long spike. Spores navicular or oval.
Two species parasitic in the gut of species of Dermestes.
Genus 51. Styloci/stis, Leger, 1899. Trophozoite non-septate; epimerite in the
form of a long spine which is usually curved. Sporonts solitary with biconical
spores. One species, S. precox, Leger, from the intestine of the larva of
Tanypus sp.
Family 7. Acanthosporidcc, Leger, 1892. Sporonts always solitary; epimerite
simple or with appendages; cysts open by simple rupture; spores ornamented
with bristles at the poles or at the equator. Parasites of carnivorous insects.
Genus 52. Corycella, Leger, 1892. Protomerite spherical and somewhat dilated.
62 GENERAL ORGANIZATION OF THE PROTOZOA
Epimerite a knob with a crown of eight large and recurved hooks. One
species, C. armata, Leger, from the gut of Gyrinus natator.
Genus 53. Acanthospora, Leger, 1S92. Sporonts solitary and of elongate oval
form. Epimerite a conical obtuse knob; spores oval with four bristles at
each end and a circlet of spines about the equator. Three species, A. pileata,
Leger, from the gut of larva of Omoplus, a typical species.
Genus 54. Ancyrophora, Leger, 1S92. Sporonts solitary; posterior part pointed.
Epimerite a knob with appendages in the form of recurved hooks. Spores
biconical with polar tufts and six equatorial bristles. Two or more species
from carnivorous beetles.
Genus 55. Cometoides, Labbe, 1899. Epimerite a spherical knob flattened cen-
trally and bearing a circlet of flexible filaments. Spores with a bunch of
bristles at each pole and two circlets of bristles about the equator. Two or
more species from the larvre of beetles.
Family 8. Menosporidcc, Leger, 1892. Sporonts solitary, epimerite symmetrical,
with appendages and connected with the protomerite by a long neck. Cysts
spherical, opening by simple rupture. Spores in form of crescents more or
less curved.
Genus 56. Menospora, Leger, 1892. Epimerite cup-like and bordered by hooks.
One species, M. polyacantha, Leger, 1892, from gut of Agrion puella.
Genus 57. Hoplorhynchus, Cams, 1839. Epimerite in the form of a disk with
sharp teeth. One species, H. oligacanthus, Sieb., from the gut of Calopteryx
virgo, larva.
Family 9. Siylorhynchidcc, A. Schn., 1886. Epimerite symmetrical with or without
appendages. Cysts with two envelopes and pseudocyst. Brown or black-
colored spores in strings.
Genus 58. Lophocephalus, Labbe, 1899. Epimerite sessile, cup-like, with fringe
of vesicular appendages. Protomerite compressed. Cysts irregular, sub-
spherical. One species, L. insignis, A. Schn., in gut of Helops striatus.
Genus 59. Cysfocephalus, A. Schn., 1886. Epimerite vesicular, with short neck.
One species, C. algerianus, A. Schn., from gut of Pimelia sp.
Genus 60. Oocephalus, A. Schn., 1886. Epimerite a rounded knob on a short
neck. One species, O. hispanus, A. Schn., from the gut of Morica sp.
Genus 61. Spherorhynchus, Labbe, 1899. Epimerite small, spherical or oval, and
carried on a long cylindrical neck constricted deeply below the epimerite. One
species, S. ophioides, A. Schn., from the gut of Acis sp.
Genus 62. Stylorhynchus, Stein, 1848. Epimerite small and knob-like, borne on
an elongated neck of the protomerite. Deutomerite of the sporont much
elongated; protomerite rounded. Two or three species, the most typical being
S. longicollis, Stein, from the gut of Blaps mortisaga.
Family 10. Doliocystid<r, Labbe, 1899. Epimerite regular and simple; no trace
of a septum. Spores oval with a polar thickening. Marine annelids.
Genus 63. Doliocystis, Leger, 1893. Xo trace of septum; oval spores, and sporo-
cysts with polar thickenings. Two or three species, the most typical D.
pellucida, Kolliker, from the gut of Xereis sp.
Other genera referred to this division by Labbe. Alinchin, and other systematists
are: Xematoides, Mingazzini, 1891, from the gut of cirrhipedes; Ulivina,
Mingazzini, 1891. from the gut of Audouinia filigera: Sycia, Leger, 1892,
from gut of same.
Order 2. Coccidiidia. Cell-infesting sporozoa which usually reproduce by schizog-
ony and by sporogony, thus giving a life cycle with an alternation of asexual and
sexual generations. After fertilization the oosphere forms sporoblasts which
may or may not (asporocystea) be covered by a sporocyst membrane, and
which may each become transformed into one or several sporozoites.
Suborder 1. ASPOROCYSTINEA. Coccidiidia in which the sporoblasts have no
PROTOZOA WITHOUT MOTILE ORGANS 63
sporocysts. Here, if we were to be strictly consistent, we would advise,
with Minchin, the inclusion of the malaria-causing organisms, and group the
other hemosporidia with the genera included under the Sporocystinea. But it
does not seem opportune at the present time to give up the old group Hemo-
sporidia, at least not until the questionable "binucleate" forms have been
worked out in complete detail.
Following Minchin, in naming the families according to the more char-
acteristic of the contained genera, we have the following:
Family 1. Eimerldce (Asporocystida?, Leger). Sporocysts absent, the sporozoites
being naked in the parent cell (gymnospores).
Genus 1. Eimeria, A. Schn., 1875. (Syn., Legerella Mesnil.) With the characters
of the family. One species, E. nova, A. Schn., from the Malpighian tubules
of Glomeris.
Family 2. Isosparidce (Disporocystida?, Leger). The oosphere forms two sporo-
blasts each with sporocysts (chlamydospores).
Genus 2. Cyclospora, A. Sch., 1881. Each sporoblast forms two sporozoites. C.
glomericola, A. Schn., 1881, intestine of Glomeris sp., and C. caryolytica,
Schaudinn, from the intestine of moles.
Genus 3. Diploxpora, Labbe, 1893. Spores tetrazoic; many species occurring in
birds, snakes, lizards, and frogs.
Genus 4. Isoxpora, A. Schn., 1881 . Spores polyzoic ( ?). I. rara, A. Schn., from the
black slug, Limax cinereo niger.
Family 3. Cocci diidcc, (Tetrasporocystidae, Leger). The fertilized cell produces
four sporoblasts with sporocysts (chlamydospores).
Genus 5. Coccidium, Leuckart, 1879. The dizoic spores are spherical or oval.
Many species almost entirely limited to vertebrate hosts, and found in nearly
all orders. Here, also, belong some questionable forms, such as Paracoccidium
prevoti, Lav. and Mes., from the frog.
Genus 6. Cri/xftil/<>xpar(i, Labbe, iS'.Hi. The spores are dizoic and the sporocysts
in the form of a double pyramid placed base to base. ( hie species, Cr. crys-
talloides, Thel., from the intestine of Motella tricirrata of Uoscoh" (Fig. 20, L).
Family 4. A'Aw.s- /</«•, (Polysporocystidse, Leger). The fertilized cell contains
many sporoblasts (chlamydospores).
Genus 7. Barroussia, \. Schn., 1XX5. Spores spherical and monozoic; sporocyst
smooth. Manv species, a good type being B. ornata, A. Schn., from the gut of
Nepa cinerea (Fig. 20, C).
Genus 8. Echiu<i.^pnm, Leger, 1897. Spores monozoie, oval, and with spinous
sporocyst. Typical species, E. labbei, Leger. from gut of Lithobius mutabilis.
Genus 9. Diaspora, Leger, 1898. Spores, as above, but sporocysts not bivalve
and with micropyle at one end. L). hydatidea, Leger, from gut of Polydesmus.
Genus 10. Atlrlca, A. Schn., 1875. Spores dizoic with smooth, spherical or flattened
sporocyst. Many species, a typical one, A. ovata, A. Sch., from gut of Litho-
bius.
Genus 11. Minchinia, Labbe, 189(1. Spores dizoic, with oval sporocysts drawn
out into long polar filaments. M. chitonis, Lankester, 1896.
Genus 12. Eucoccidium ("Benedenia"), Liihe, 1902. Spores trizoic, schizogony
absent. E. eberthi, Labbe, from Sepia.
Genus 1 3. Klossia, A. Schn., 1 875. Spores tetrazoic or polyzoic, and with spherical
sporocysts.
Genus 14. Cari/otropha, Siedlecki, 1902. Twenty, more or less, sporoblasts, with
twelve sporozoites in each. Sporocysts spherical. One species, C. mesnili,
Sied., from the spermatogonia of Polvmnia nebulosa.
Genus 15. Klossicfla, Smith and Johnson, 1902.. Sporoblasts polyzoic, sporo-
cysts subspherical thirty to thirty-four sporozoites. One species, K. muris,
-S. and J., from the kidney of the mouse.
FIG. 20
Types of spores. (After Wasielewsky, A. Schneider, Thelohan.)
PROTOZOA WITHOUT MOTILE ORGANS 65
Questionable genera of coccidiida are the following:
Hyaloklossia, Labbe, 1896, from the frog.
Goussia, Labbe, 1896, from various species of fish. Usually classed as Coccidium
species (Fig. 20, M, X).
Bananella, Labbe, 1895, from the gut of Lithobius. Usually classed with Coc-
cidium.
Rhabdospora, Laguesse, 1895; Gonobia, Mingazzini, 1892; Pfeifferella, Labbe,
1899; Molybdis, Pachinger, 1886; Cretya, Mingazzini, 1892; Gymnospora,
Moniez, 1886, are all probably species of Coccidium.
Order 3. Hemosporidia, Danilewsky. Blood dwelling sporozoa cytozoic or celo-
zoic in mode of life in the blood constituents, and with or without alternation
of hosts. A somewhat heterogeneous collection of parasitic protozoa with
obscure affinities, pointing in part toward the flagellates, in part toward the
coccidia. For convenience, and purely as a temporary matter, we follow
Minchin in dividing the order into two suborders, Acytosporea and Hemo-
sporea, the former including those blood -dwelling forms which seem to bear
some relationship to Crithidia and Herpetomonas, the latter including the
more Coccidia-like forms.
Suborder A. ACYTOSPOREA. The trophozoite is an intracellular or intracorpus-
cular parasite which usually completes its schizogony within the host cell.
The sexual cycle is completed in the digestive tract or body cavity of some
intermediate host — in all known cases some species of blood-sucking arthro-
pod, usually an insect or arachnid.
Genus 1. Plasmodinm^ Marchiafava and Celli, 1885. The organisms of human
malaria are all referred to this genus. The characteristic morphological
features are the presence of melanin pigment, oval merozoites grouped around
a central residual body, and spherical or crescentic gametes. Sporogony in
the gut and body cavity of mosquitoes of the genus Anopheles. Three species
generally recognized P. vivax, Grassi and Fek'tt i, 1 N92, the cause of tertian
fever, with schizogony every forty-eight hours. P. malaria-, Lav., 1880, the
cause of quartan fever, with schizogony every seventy-two hours. P. immacu-
latum Gr. and Fel., 1892, the cause of pernicious malaria, with subspecies
according to Craig and others, exhibiting quartan and tertian characteristics.
This last species is generally held to be a distinct genus under the name
Laverania, Gr. and Fel., 1890, but Schaudinn's contention that crescentic
instead of spherical gametocytes is an insufficient distinction for generic
difference is rapidly gaining ground, and we follow it here. Minchin's
remark (footnote, p. 267, 1903), that the popular names given to the malaria-
causing parasites ("tertian," "quartan," and "pernicious") are more intel-
ligible and less misleading than the so-called scientific names, is confirmed
by Liihe, but it seems to us that such confusion is only further aggravated
by their retention of the generic name Laverania. In addition to the species of
Plasmodium causing human malaria, La veran described a species from the
blood of apes under the name of P. kochi, and Liihe places in the same
species the blood parasites of chimpanzees from Kamerun.
Subgenus. Hemoproteus, Kruse, 1890. The cause of bird malaria. Merozoites
and schizogony as in the preceding, sporogony in the digestive tract and body
cavity of mosquitoes of the genus Culex. Gametocytes bean-shaped. The
various species of this genus are now commonly referred to the genus Plas-
modium. Common in birds.
Genus 2. Babcsia, Starcovici, 1893. (Syn., Pyrosoma, Smith and Kilb.; Piro-
plasma, Patton.) An intracorpuscular parasite of mammalian blood. Tro-
phozoites usually piriform, without pigment, and reproducing by simple
division or by budding within the blood corpuscle. Transmission by ticks
and sporogony in the hitter's gut.
5
66 GENERAL ORGANIZATION OF THE PROTOZOA
Many species: In man, B. hominis, Manson, the disputed cause of Rocky
Mountain Spotted Fever; in cattle, B. bovis, Babes, 1888, and B. bigemina,
Smith and Kilbourne, 1893, and B. parvum, Theiler, 1904; in sheep, B. ovis,
Babes, 1892; in horses, asses, and mules, B. equi, Laveran, 1901; and in
dogs, B. canis, Piana and Galli- Valeric, 1895.
Some genera of questionable taxonomic value are referred to this suborder.
Among them Polychromophilus, Dionisi, 1900, and Achromaticus, Dionisi,
1900, from the blood of bats of the genera Vespertilio and Vesperugo, must be
temporarily placed. The former is characterized by the presence of pigment
similar to that of Plasmodium, while in the latter such pigment is absent.
Suborder B. HEMOSPOREA, Minchin, 1903. Intracellular blood parasites usually
called Hemogregarines, which become free in the blood. Alternation of hosts
in some cases, but apparently not in all. Parasites mainly in cold-blooded
animals.
Genus 3. Lankesicrclla, Labbe, 1899. (Syn., Drepanidium Lank., 1882.) The
parasite is not more than three-quarters of the length of the blood cell of the
frog in which it lives. Many species in many different species of frogs and
toads. Life history not yet satisfactorily worked out; according to Hintze,
it is completed in the frog's blood and digestive tract; according to Billet,
it involves a trypanosome phase analogous to that of Halteridium, as described
by Schaudinn (Hemoproteus). Further observations are much needed.
Genus 4. Hemogregarina, Danilewsky, 1885. The body of the parasite exceeds
the length of the blood cells of reptiles which it infests, and is bent in the form
of the letter V. Life history unknown, although varied observations have
been recorded in connection with the ten or more species that have been
described (see Liihe).
Genus 5. Hepatazoon, Miller, 1908. A liver cell, and blood parasite of rats.
Schizogony in liver cells, engulfing and encapsulation in leukocytes, dissolu-
tion of capsule and copulation of gametes in the digestive tract of the inter-
mediate host (a gamasid mite, Lelaps echidninus); sporulation in the body
cavity of the mite, ingestion of the mite and its parasites by rat, penetration
of gut wall by sporozoites and new infection of liver cells. One species, H.
perniciosum, Miller, 1908 (Fig. 106, p. 271).
Class II. NEOSPORIDIA, Schaudinn. Sporulation of the ameboid parasites takes
place during the activity of the parent cell and without interfering with the
vegetative processes. Celozoic, histozoic, or cytozoic parasites, mainly of
vertebrate hosts, and especially of fish.
Order 1 . Myxosporidia, Biitschli. Relatively large neosporidia reproducing by
pansporoblast formation, the spores provided with polar capsules containing
more or less easily seen threads.
Suborder 1. DISPOREA, Doflein, 1901. One pansporoblast containing two spores,
produced by each trophozoite. Spores wider than long. Trophozoites float-
ing freely in the fluids of various organs of fish hosts and frog hosts.
Family 1. Ceratomyxidce, Doflein. With the characters of the suborder.
Genus 1. Ccratomyxa, Thelohan, 1892. The two valves of the spore produced
into long attenuated processes. About nine species, mostly from the gall-
bladders of fishes (Fig. 20, G}.
Genus 2. Leptotheca, Thelohan, 1895. Valves of the spore not drawn out into long
processes. The sporoplasm completely fills the spore membranes. About
six species from the gall-bladders of fishes and the kidneys of frogs (Fig. 20, «7).
Suborder 2. POLYSPOREA, Doflein. More than two spores, usually a great num-
ber, produced in each pansporoblast. The spores are longer than wide.
PROTOZOA WITHOUT MOTILE ORGANS 67
(The characteristics distinguishing these two suborders are not very definite,
and some more natural system should be worked out with further knowledge
of the group. Under the polysporous forms, for example, the genus Sphero-
spora is exceptional in having at least one disporous species and in having
nearly spherical spores.)
Family 2. Mi/.ridiidcc, Thelohan, 1892. The trophozoites are typically free-living
parasites in the fluids of the internal organs of their hosts; the spore has two
polar capsules.
Genus 3. Sphcrottpora, Thelohan, 1892. With spherical spores. Four or five
species, mostly from fish kidneys.
Genus 4. Myxidium. Biitschli, 1882. Spores navicular, with polar capsules at
each end. Seven or more species from kidney and gall-bladder of fishes and
tortoises.
Genus 5. Spheromyxa, Thelohan, 1892. Spores navicular with truncated ends
and a polar capsule at each extremity. Polar filaments are short and thick,
and somewhat conical in form. Three species from the gall-bladder of
fishes.
Genus 6. Cystodiscus, Lutz, 1889. Trophozoites without ameboid movement or
changes of form; spores symmetrical with the sutural plane running obliquely
from one extremity to the other and with a polar capsule at the extremities of
the oblique suture. One species, C. inimersus, Lutz, from the gall-bladder of
toads and Cystignathus in Brazil.
Genus 7. Myxosoma, Thelohan, 1892. Spores flattened and ovoid in form and
with the polar capsules crowded together at the narrow extremity. One
species, M. dujardini, Thel., from the gills of Scardinius sp.
Genus 8. Myxoproteus, Doflein, 1898 (Myxosoma ambiguum of Thelohan and
Labbe). Spores somewhat pyramidal with spinous processes from the base of
the pyramid. One species, M. ambiguus, from the bladder of Lophius
piscatorius.
Family 3. Chloronnjxidoc, Thelohan, 1892. Spores with four polar capsules.
Genus 9. Chloromy.rtnn, Mingazzini, 1890. With the characters of the family.
Several species (six or seven) known and distinguished by presence of appen-
dages and distribution of polar capsules.
Family 4. My.robnlida', Thelohan, lS9o. Typical histozoic parasites rarely found
in the ameboid form but usually as cysts filled with spores. Usually poly-
sporous, the spores with one or two polar capsules. The sporoplasm contains
vacuoles which are stained a reddish brown by iodine.
Genus 10. MyxoboluSj Biitschli, 1882. Spores ovoid or flattened into an ellipse.
Polar capsules single or double. A great many species (about forty) known,
and found in some organ or other of various fishes, and usually in the connec-
tive tissue of such organs. The genus is usually split up into three divisions,
the first of which contains the aberrant forms M. piriformis and M. unicap-
sulatus from the tench, with a single polar capsule and with pear-shaped spores.
In the second are species with spores having polar capsules of dissimilar size.
In the third are the great majority of the species referred to this genus, all
with polar capsules of similar form and size (Fig. 20, K).
Genus 11. Hcnnccjuya, Thelohan, 1892. Ovoid spores with two polar capsules,
the sporocyst prolonged into two long caudal processes which are not pene-
trated by the sporoplasm. Four species from stickleback, pike, and perch.
Genus 12. Hoferella, Berg, 1898. Spores broad and compressed with two tail-
like processes at the posterior end. One species, H. cyprini, Dofl., from the
carp.
Order 2. Microsporidia, Balbiani, 1883. The trophozoites are more or less ame-
boid; the spores are very minute, piriform, and with only one polar capsule
which is invisible in the fresh state. They are typically parasites of inverte-
68 GENERAL ORGANIZATION OF THE PROTOZOA
brates and usually of Crustacea and other arthropods, where they are typically
cytozoic.
Family 5. Glugeidce, Thelohan, 1892. With the characters of the order.
Group A. Polysporogenea, Doflein, 1898. The trophozoite produces many
pansporoblasts, each of which gives rise to many spores.
Genus 13. Ghigea (Nosema), Thelohan, 1891. With the characters of the group.
Many species which are not satisfactorily worked out. The most famous
species is G. bombycis, which caused the destructive epidemic among silk-
worms from 1850 to 1865.
Group B. Oligoftporogenea, Doflein, 1898. The trophozoite produces but one
single pansporoblast.
Genus 14. Gurlcija, Doflein, 1898. The pansporoblast produces four spores.
One species, G. tetraspora, Dofl., from Daphnia maxima.
Genus 15. Thelohania, Henneguy, 1892. The pansporoblast produces eight
spores contained in small spherical or fusiform vesicles. Five species
recorded, all from the muscles of Crustacea.
Genus 16. Pleistopliora, Gurley, 1893. The pansporoblasts produce more than
eight spores. Many species, some of fish, but mostly of invertebrates.
Order 3. Actinomyxidia, Stole, 1890. Sporozoa consisting of a double cellular
envelope, three polar capsules, and eight spores arranged in ternary sym-
metry.
Genus 1 . Hexactinomyxon, Stole, 1899. Spores in anchor form, with six branches.
H. psammoryctis, Stole, 1899, in the intestinal epithelium of Psammoryctes
barbatus.
Genus 2. Triactinomyxon, Stole, 1899. Spore in anchor form, with three branches.
T. ignotum, Stole, 1899, in the intestinal epithelium of Tubifix t/ibifc.r,
Miiller.
Genus 3. Synactinamyxon, Stole, 1899. Spores associated in a common envelope.
S. tubijicix, Stole, 1899, in the intestinal epithelium of Tub/fc.r rivulorum,
Lam.
Genus 4. Spheractinomy.rou, Caull. and Mesnil, 1904. Spores spherical and
without wing-like prolongations. S. stolci, C. and M., 1904, in the body cavity
of marine oligochetes (CHicHis arenarius, O. F. M.), etc.
Order 4. Haplosporidia Caull. and Mesnil, 1899. A group of little-known para-
sites with obscure affinities and undetermined life histories. Caullery and
Mesnil, 1905, group them in three somewhat ill-defined subdivisions, as
follows:
Family 1. Hapfasporidiida', C. and M., 1905. Parasites of ameboid form, which
reproduce by encapsuled merozoites, Avhich may or may not be ornamented
by spines or processes. Genera Haplosporidium and Urosporidium, with
six species enumerated by C. and M., all parasites of annelids.
Family 2. Bcrtramhdce, C. and M., 1905. With two genera, Bertramia and
Ichtkyosporidium, and with four species parasitic in annelids, rotifers, and fish.
Family 3. Celosporidiidce, C. and M., 1905. With three genera, C'elosporidium,
Mesnil and Marchoux, 1898; Polycaryum, Stempell, 1901; and (?) Blastuli-
dium, Ch. Perez, 1903, mainly parasites of copepods. Doubtful forms, includ-
ing the genera Scheuriakowella, C. and M., 1905, parasite of Cyclops, etc.;
Chyiridiopsis, A. Schneider, 1884, parasite of Tenebrio mollitor and of Blaps;
Celosporidium, Crawley, of Blattella cjermanica; Lymphosporidium, Calkins,
1898; and Rhinosporidium, Minchin and Fantham, the cause of nasal tumors
in man.
Order 5. Sarcosporidia. Sporozoa in which the initial stage is passed in muscle
cells of vertebrates. Great sac-like spore cases are formed (Miescher's
tubules) with double membranes. Genus, Sarcocystis, Lankester, 1882 (Fig.
79, p. 186).
CHAPTER II.
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA.
EHREXBERG, in 1838, entitled his monumental work on the protozoa
Die Infusionsthierchen als vollkommene Organismen (The Infusoria
as Complete Organisms). Despite the great improvements that had
been made in the microscope, and the vast collection of facts that
had accumulated in connection with the structures of the protozoa,
Ehrenberg's point of view was but slightly advanced beyond that of
Leeuwenhoek one hundred and fifty years before. "Animalcula,"
said Leeuwenhoek, "which swim in stagnant waters, and which are no
longer than the tails of the spermatic animalcula, are provided with
organs similar to those of the highest animals. How marvellous
must be the visceral apparatus shut up in such animalcula!" Ehren-
berg sought to make out the various organs in this "visceral complex,"
and with great ingenuity managed to find digestive tract, kidney, brain,
heart, ovary, and other organs characteristic of raetazoa. The red,
so-called "eye spots" were regarded by him as eyes, and the colorless
lens upon which they frequently lie was interpreted as a cerebral
ganglion, or brain. The contractile vacuole became, for him, a beat-
ing heart, and the collecting canals formed the vessels. The macro-
nucleus was an ovary, the gastric vacuoles stomachs, while various
chance inclusions were regarded as organs of one kind or another.
While Leeuwenhoek's and Ehrenberg's interpretation made out
these primitive animals as marvels of creation in miniature, how much
more marvellous are the facts as we know them today and summed
up in the statement that the functions of all of these organs of the
highest animals are performed within the single cell! The protozoon
has no digestive tract, but it seizes food, digests and assimilates it, and
grows in size through the addition of such food. It has no heart or
circulatory system, and yet it distributes the digested food throughout
the bodv, takes in oxygen, and throws off carbon dioxide as does every
i/ •* v O «/
many celled animal. It has no kidney, but disposes of the waste
matters of oxidation none the less, and so every function of the highest
metazoa finds its counterpart in the vital activities of the primitive
forms. Nor is the importance of these simpler processes of the proto-
zoa any the less, in that they come very close to the ordinary physical
and chemical processes that we are familiar with in non-living matter.
As complete organisms, therefore, in a sense quite different from that
70
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
meant by Ehrenberg, the protozoa today offer a field of research in
physiology that is quite unique, for while they epitomize the vital
activities of the higher animals, these activities are of such simple
types that they may be more easily observed and correlated with the
ordinary reactions in physics and chemistry, reactions which we do
not associate with the vital processes of the higher animals.
The warning may not be out of place here that despite the simplicity
of function in the protozoon, and the analogy with reactions in the
inorganic world, there is, nevertheless, a power of acting as a whole,
a power of coordination combined with factors of adaptation and
FIG. 21
Food-taking. .4, after P^nard; B and C, after Biitschli. A, Raphidiophrys elegans, H. and L.;
B, Oikomonas terruo, Ehr.; C, Didinum nasutum, O. F. M.; /, food particles.
evolution, which permit of development into more and more com-
plicated structural units, which arises, per se, in all protoplasm, and
raises it immeasurably above the most complex of non-living sub-
stances; this power of adaptation is an inherent characteristic of
living matter, transcending physical or chemical analysis, and justify-
ing, perhaps, the often abused term vitalism. It must not be forgotten
that, notwithstanding the simplicity of the single functions, the proto-
zoa are units exhibiting a complex of these activities and an harmonious
working; of them all, no less surely than fish, bird, or mammal. In
^J V
studying these simple functions it is well not to forget that each belongs
in the same category of activities as the functions of much more highly
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 71
evolved organs. Consciousness, for example, an attribute of the brain
and central nervous system in general, is not seen as such in the
protozoa, but its prototype irritability, with the coordinated responses
to stimuli, is common to every protozoon, and such stimuli sometimes
lead to reactions on the part of the protozoon which are often appar-
ently directed toward a given end until we are tempted to interpret
them as conscious acts. While most of the actions of protozoa are
reactions to external stimuli, many are combinations of reactions that
do not lend themselves to analysis. Such, for example, is the apparent
choice of food or of building material for shells and tests, or the com-
plex reactions that are frequently involved in the avoidance of some
obstruction. Not infrequently such reactions have been interpreted
as evidence that the protozoon acts wilfully, or with a certain amount
of intelligence of the end to be accomplished, and they are frequently
cited as examples of conscious activity on the part of these primitive
forms. Many of these so-called conscious acts can be explained by
the ordinary physical laws of fluids, and while one cannot deny that
the protozoon's actions may be conscious, it seems much more prob-
able that these activities are the fundamental, often physical or chemi-
cal, reactions which serve in evolution as the starting point for the
infinitely more complex activities which we call our consciousness.
In all animals there is a certain amount of work clone in the daily
life, and the energy put into such work comes from the oxidation, or
physiological burning, of the body protoplasm. There is, therefore,
a constant waste of protoplasmic material which goes off as work
done, as heat, or as residual waste matters comparable with the smoke
and ashes of physical combustion. Such waste is made good by the
addition of new raw materials in the form of food, which is made over
into new protoplasm. The phenomena of waste and renewal are
usually spoken of together under the name of metabolism — waste as
destructive, repair as constructive, metabolism. Food getting, there-
fore, becomes the first necessity of the living thing, and the chief end
toward which the fundamental structures of the body are directed, and
this, whether in the highest mammal or the lowest protozoon, becomes
the chief economic problem to be solved (Fig. 21).
The methods employed by different kinds of living things are widely
varied, and the great problem is apparently well solved in many dif-
ferent ways. Green plants are the starting point for all living things,
for they manufacture not only their own food, but indirectly the food
for all other living things. This they are able to do because of the
chlorophyl or green colored matter which they possess and which has
the power to utilize the energy of sunlight in reducing CO2 and manu-
facturing starch out of water and carbon. The further changes of the
starch into more complex substances, and these into protoplasm of
the plant, are buried in the obscurity of unknown chemical processes
72
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
which take place in the plant's protoplasm. Animals solve the problem
of nutrition by living on plants, or by eating- other animals which,
either directly or indirectly, live on plants. Still other types live as
parasites upon other animals, some, like the intestinal worms, using
freely the foods that are prepared by, and for the use of, the host,
while others, like some insects, suck the blood, or, like trichina,
invade the cells and tissues, and live at the expense of the living-
protoplasm.
In the group of protozoa all of these methods of food getting are
found. Many forms possess chlorophyl, and like the green plants,
FIG. 22
Synura uvella, a colony of phytoflagellates, often a source of disagreeable odors and
tastes in drinking waters. (After Calkins.)
manufacture their food directly from simple elements. These protozoa
are of considerable theoretical interest, for they stand upon the border-
line between the animal and the plant kingdoms, and are sometimes
classed as one, sometimes as the other. They are thus involved in
what has been one of the most contested of biological problems, the
limits of the animal and plant kingdoms, and the problem is the more
difficult because some types of this intermediate group may on occa-
sions make their food, while at other times they eat like undoubted
animals and take in solid food (Chromulinaflavicans,a,i\d some forms
of dinoflagellata). The problem has but little significance in the present
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 73
day, for biologists recognize that it is only an academic matter after
all, and merely affords further evidence of the artificiality of classi-
fication.
It is to these intermediate forms that we must turn for the causes
of odors and tastes, which occasionally make potable waters unfit to
drink. As shown in the previous chapter, the metaplastic products of
vital activity are sometimes stored up in the cell as oils or fats, which,
when liberated in a water supply, give rise to offensive odors and tastes
(Fig. 2). Like all organisms which make their food, these sus-
pended protozoa require salts of different kinds. Many such salts are
normal to drinking waters, the nitrites and nitrates being almost
invariably present, and these are the very salts most needed for the
maintenance of these forms of life. Hence, it follows that if an
infected water supply can be freed from an excess of such nitrogen-
holding salts, the protozoa will disappear. If inlet and outlet of a
given water supply are closed, the organisms soon exhaust the avail-
able food elements and die.
While some forms of protozoa are thus holophytic, like the green
plants, others combine the holophytic with the animal, or holozoic
method, while still other protozoa, and, indeed, the great majority of
them, are entirelv holozoic. Thev seize their food in the form of other
tl t,
minute living things and digest it in much the same way that higher
animals do, all of the organs of the cell playing some part in the pro-
cess.. Food-getting, therefore, more than any other function of the
body, has been the most influential in leading to morphological
development.
Seizure of food is one of the most interesting of the protozoon pro-
cesses, and is frequently accompanied by such complicated reactions
on the part of the minute animal as to suggest wilful activity. In
other cases it is quite mechanical, as, for example, in choanoflagellates,
or in many ciliates. In these the motile organs, flagella, or cilia,
create a current in the surrounding water toward the mouth, and this
carries with it bacteria or minute pieces of disintegrated plant or animal
matter. In Vorticella campanula and its allies the apparatus is most
highly developed for this method of food taking. A powerful adoral
zone of membranelles creates a vortex current toward the oral or
vestibular opening, while within the vestibule a long, undulating
membrane carries the current to the mouth opening. The proto-
plasmic area around the mouth is furnished with contractile muscle
threads or myonemes, so that when any irritating object comes with
the food current, the entire vestibular area, adoral zone and all, con-
tracts into the cell body, while the myonemes of the distended stalk
contract at the same time and draw the body away from the offending
region. In other ciliates, like paramecium, colpidium, oxytricha,
etc., the process is essentially the same except that the animal is not
74 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
attached nor provided with contractile fibrils. In all of these ciliated
forms there is a definite and frequently very complicated mouth
opening, but in the flagellated forms, as a rule, there is no permanent
mouth, the entire anterior end of the cell forming a receptive area
for food products swept toward it in the current created by the flagel-
lum. This is a vortex current caused by the undulations of the long
flagellum, which, at the same time, moves in such a way as to describe
a cone whose apex is at the base of the flagellum and base at the tip.
In some cases, as in the collared flagellates or choanoflagellata, the
flagellum moves inside a protoplasmic, collar-like membrane, which,
like a pseudopodium, can be thrown out or retracted by the animal.
The surfaces of this collar are sticky, and small particles move down
it to the floor of the collar pit, where they are taken into the body.
As the flagella and cilia are in constant action, and as the mouth is
always open for more, these protozoa become, as Maupas pointed
out, the gluttons, par excellence, of the animal kingdom, while the oral
apparatus becomes strikingly modified and diversified.
Not all protozoa, however, are so persistent in food taking, and
many of them, while provided writh a mouth opening, keep the mouth
shut until a food particle is to be eaten. Such forms live upon larger
things than bacteria, and with them eating involves a regular swallow-
ing process. In some cases this is combined with the food-getting
activity of the flagella or cilia, and large particles of solid proteid
matter, either in the form of small organisms or of disintegrated
fragments of plant or animal brought with the current, are seized by
protoplasmic processes, as in Oikomonas termo, or the mouth opens
to swallow them, as in Didinium nasutum. There seems to be
a remarkable power of distention in these mouth openings, for a
didinium can take in an organism quite as large as itself (Fig. 21).
In those forms of protozoa belonging to the group suctoria there is
no mouth opening, nor flagella or cilia to create food currents, but the
animals are provided with tentacles, often twice as long as the diameter
of the body, with which they seize passing organisms. Once seized,
the victim struggles for a short time and then becomes quiet, as though
paralyzed. Its protoplasmic contents are then sucked into the body
of the captor, or, in some forms, the protoplasm of the captor passes
into the body of the victim and there digests its meal.
Many protozoa set a trap for their victims, so that they become
entangled as in a spider's web. This is the case with the majority of
the great group of rhizopods, especially the foraminifera and radio-
laria, where the pseudopodia form a network of branching protoplasm,
or a forest of protoplasmic spines, in which the streaming of granules
is constant, passing from the inner protoplasm of the shell outward
to the farthest tip of the pseudopodia. The sticky character of the
pseudopodia makes it difficult for any small animal to break away,
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 75
while its struggles furnish the stimulus for an accumulation of more
protoplasm about it, and this, armed with digestive fluids, soon kills
FIG. 23
\
\
-..^•j.,. , •>, ; --o. -x : '. j- \r-*3f \ f l-e- .(£&>
>^T*s Y\ ^\'- \1 J^^mr^
Allogromia, sp., with pseudopodial net and two diatoms. (After Calkins.)
76
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
the prey, which is then digested without even the formality of carriage
into the shell of the captor (Fig. 23).
Other rhizopods, as an ameba, throw out pseudopodia under the
stimulus of the touch of some other living animal or plant. These
FIG. 24
Actinobolus radians with tentacles partially retracted and with five ingested halterias;
swimming. (After Calkins.)
surround the victim, which frequently does not begin to struggle until
ensheathed in a wall of protoplasm, from which it rarely escapes.
Large animals like rotifers, and relatively large plants like the des-
mids are thus captured and digested.
While most of the protozoa thus far described wait until the prey
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 77
comes to them, and take what they can get, others are predatory and
go in search of food. These are the most interesting of all protozoa,
for they are occasionally too fastidious, apparently, to take the ordinary
run of the microscopic wilds, but seem to select their food with all the
care of a gourmand. They are usually armed with offensive weapons
in the form of trichocysts, which may be shot out from the surface
of the body, or carried javelin-like, at the extremities of projectile
tentacles. One of the most interesting of these types is Actinobolus
radians, one of the most primitive and one of the surest of hunters
(Fig. 24). "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
(Entz, 1883). When at rest, the mouth is directed downward, and
the tentacles are stretched out in all directions, forming a minute
forest of plasmic processes, among which smaller ciliates, such as
urocentrum, gastrostyla, etc., or flagellates of all kinds may become
entangled without injury to themselves and without disturbing the
actinobolus or drawing out the fatal darts. When, however, an
Halteria grandindla, with its quick and jerky movements, approaches
the spot, the carnivore is not so peaceful. The trichocysts are dis-
charged 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 contracted until the victim is brought to the
body, where by action of the cilia it is gradually worked around to the
mouth and swallowed with one gulp. Within the short time of twenty
minutes I have seen an actinobolus thus capture and swallow no less
than ten halterias." (Calkins, The Protozoa, p. 50.)
The complicated processes involved in this act of food-getting would
certainly justify an Ehrenberg in the belief that actinobolus is capable
of wilful actions to a certain end, and that in the apparent choice of
food, and skill in bringing it down, it shows a high order of intelligence.
It would be a natural tendency to interpret such activities in terms of
our own consciousness, but it is much more probable that simple
physical or chemical laws of attraction are at the bottom of it all,
halteria possessing an attraction for the darts of actinobolus analo-
gous to that between an iron filing and a magnet, or between various
chemical elements.
In all of the above cases solid food is taken into the body of the
protozoon and there disintegrated and digested. Many other protozoa
have no mouth opening nor chroma tophores to manufacture their
food, but absorb it through the general surface of the body, as does a
tapeworm. Such protozoa, like some of the lower plants, are sapro-
phytes and get their nutrition in the proteid matter from disintegrating
78
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
plant and animal tissues, dissolved in the water. Other saprophytes
live upon the juices in blood or other fluids of the animal body which
are similarly taken in by osmosis; these, however, belong to the group
of parasites or commensals, the difference between the two being
largely one of degree only, a parasite exerting some deleterious effect
upon the host, while a saprophyte and a commensal are harmless. In
all such cases the protozoa multiply in the region, such as a water
supply, or the fluids of the body, where food is most abundant and
\
FIG. 25
f
?Pr
V «' \.' -,
Digestion in a foraminiferon. (After Verworn.) A-E, successive stages in the disintegration
of a ciliate (Colpoda) in a pseudopodium of Lieberkiihnia.
where thev are least disturbed bv environmental factors. Thus, we
J i/
would account for the immeasurable swarms of chilomonas in a meat
infusion, or quantities of opalina in the frog's rectum, or the myriads
of cytoryctes and neuroryctes in skin and brain of victims of smallpox
and rabies.
In the higher animals solid food materials are taken into the food
receptacles of the body, where a secretion from the lining epithelial
cells is poured upon them, the food matter not coming in close contact
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 79
with the secreting cells. In the protozoa the solid food is taken directly
into the living cell, and the processes of digestion are all within the
living matter. Such a method is known as intracellular digestion, as
contrasted with intercellular digestion of the higher animals (Fig. 25).
When a rotifer or other small animal is enwrapped by the pseudo-
podia of an ameba, or swallowed by an actinobolus or other preda-
tory form, a certain amount of water is taken in with it so that the
victim moves freely within the body of its captor and in its normal
water environment. The water, with victim, forms a gastric vacuole
or an "improvised stomach," and is surrounded on all sides by a wall
of living protoplasm, and this soon begins to pour a secretion into the
vacuole. With the first changes in chemical nature of the surrounding
water the prey begins to struggle, and ceases its efforts to escape only
when killed by the secretion. This, according to the researches of
Fabre-Domergue, Meissner, le Dantec, and others, is acid in nature,
but, beyond the fact that it is some mineral acid probably hydrochloric
as in other animals, nothing is known as to the exact chemical nature
of this digestive fluid. Whatever it is, its manufacture is intimately
connected with the chromatin material of the nucleus, for Hofer and
Verworn have shown that digestion does not take place when the
nucleus is absent. This was determined by cutting an ameba into
two parts, one of which contained the nucleus, the other, a recently
ingested animal. The enucleated protoplasm retained its vitality for
from nine to fourteen days without any change in the gastric vacuole;
the nucleated fragment, on the other hand, soon recovered from the
operation and began to digest as usual. It is probable that the minute
particles of nucleoproteids that are constantly arising in the neighbor-
hood of the nucleus contain digestive ferments which stimulate the
formation of the mineral acid in the vicinity of the gastric vacuole.
In those protozoa in which the mouth is continually open, as in
paramecium, vorticella, dileptus, bursaria, etc., the food is usually
minute forms of unicellular algse, or, most often, bacteria. These are
collected in water in the protoplasm at the base of the vestibular
opening until a great number are massed together, or until the vacuole
has assumed a certain size. It is then caught up in the flow of proto-
plasm on the interior of the organism, and dragged away from the
mouth, while a new vacuole begins to form. The process of digestion
in one of the bacteria-eating vorticellids, carchesium, has been studied
by Greenwood, who found that the aggregate of bacteria passes into a
region of protoplasm in the immediate vicinity of the horseshoe-shaped
nucleus, where the water disappears, leaving the bacteria in close con-
tact with the protoplasm. This state of "storage" lasts for from one
to twenty hours, and during the time the many separate or individual
bacteria are massed together into a compact ball of food. This mass
is then again surrounded by fluid, this time having a decidedly acid
80 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
reaction. Through the action of this acid the compact mass of bac-
teria is broken into minute fragments, which ultimately mix with the
protoplasm as digested food. Although nothing further is definitely
known about it, it is quite probable that the product of this digestive
action is the formation of soluble peptones similar to the products of
proteid digestion in the higher animals. This is rendered the more
probable because of the extraction of a pepsin-like ferment from the
myxomycete Fulicjo varians by Krukenberg, and from the huge
ameboid rhizopod Pelomyxa palustris by Dixon and Hartog.
The problem of the nature of the digestive processes in protozoa
has an interest in connection with other questions of more vital impor-
tance. The nature of the digestive reaction in phagocytes in response
to the food matters supplied are involved in the general subject of
intracellular digestion. While the initial experiments of Engelmann,
Metchnikoff, Le Dantec, Greenwood, and others showed that there
is an acid reaction in the gastric vacuoles of certain forms of protozoa,
their conclusion that digestion here is entirely due to the action of some
ferment-like pepsin acting in an acid medium were apparently pre-
mature. The extraction by Krukenberg from fuligo, and by Dixon
and Hartog from pelomyxa, of a digestive ferment which dissolves
proteid in an acid medium, undoubtedly lends support to their view.
But, on the other hand, Mouton ('02) extracted a digestive ferment
from ameba which dissolves gelatin and fibrin in an alkaline medium,
while Mesnil and Mouton ('03) extracted a similar ferment from para-
mecium. These observers, therefore, insist that the digestive fluid is
more like trypsin than like pepsin.
An intermediate position was taken by Metalnikoff ('03), who,
on the basis of repeated observations, claimed that the reactions in
the paramecium vacuole are first acid and then alkaline. Feeding
paramecium with powdered alizarin, which is colored reddish violet
in an alkaline medium in which paramecium lives, he found that
the vacuoles are at first of this same color. In from five to fifteen
minutes the color changes from red to yellow, showing an acid reaction,
and this, after from ten to fifteen minutes more, is changed again to
the red, showing an alkaline reaction. Not all vacuoles are thus
colored, a few giving the alkaline reaction throughout. Metalnikoff
concluded, therefore, that proteid digestion in these protozoa follows
the same course as in higher animals, a ferment acting in an alkaline
medium following one which acts in an acid medium.
Nierenstein, repeating these experiments, confirmed MetalnikofFs
observations, but came to the conclusion that the acid medium plays
no part in the actual digestion of the food, serving merely to kill the
living organisms taken in. Metalnikoff, however, in a later publication
maintains that the bacteria swell in the acid medium and thus undergo
the first steps in the process of digestion. These results differ to some
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 81
extent from those obtained by Greenwood in the case of carchesium,
where the acid reaction is not forthcoming until after the "state of
storage," a state varying in length of time from one to twenty hours.
The chemical reactions in the later periods were not observed.
The protozoon, therefore, like phagocytes, evidently has the power
of secreting different kinds of ferments in response to the stimulus of
different kinds of living food particles. Not only proteolytic, but
other kinds of ferments as well are formed in the various types of
protozoa, although not by all kinds. Thus, some types of protozoa are
able to create starch dissolving ferments similar to the diastatic fer-
ments of higher animals, or fat emulsifying ferments similar to steap-
sin. In many forms, however, the starch grains, like other indigestible
parts, are thrown out of the body untouched (Greenwood, Fabre-
Domergue, Meissner).
The granules that are formed by the breaking down of food par-
ticles through the digestive process are ultimately distributed by means
of the protoplasm streaming to all parts of the protozoon. Some are
probably converted directly into protoplasm by an assimilative pro-
cess that is as little understood in these forms as in the metazoa, a
process involving synthetic changes whereby the relatively complex
food elements are built up into still more complex protoplasmic
molecules, thus leading to the repair of waste and to growth. Other
granules are not immediately assimilated, but are stored up in the
protoplasm as a reserve of nutriment. In these cases it is impossible
to say whether such granules are utilized directly as fuel for functional
activity through oxidation, or whether they are first built up into pro-
toplasm and the protoplasm itself, or its products, oxidized. In all
protozoa these reserve matters are present, giving the characteristic
granular appearance to the protoplasm of these forms, and their dis-
appearance may be easily followed by starving the individual. A
paramecium, for example, when normal and active, has a character-
istic granular appearance, while numerous gastric vacuoles are dis-
tributed throughout the inner protoplasm. When it is starved these
granules disappear first of all, and then, with continued starvation,
the protoplasmic network is used as a source of energy for the active
animal, and great vacuoles appear which increase in size with starva-
tion, while the size of the cell decreases to an eighth or a sixteenth
of the normal volume, the macronucleus alone, although frequently
fragmented, retaining its normal volume.
It often happens that some one of the many functions of metabolism
fails to act, and the organism suffers from the failure to assimilate or
from lack of oxidative ferments. I have frequently seen Paramecium
aurelia so filled with these reserve food granules that its protoplasm
appeared dense and black under the microscope (Fig. 26). In such
cases there are no gastric vacuoles, food taking and movement stop,
6
82
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
division stops, and the animal, unless treated, invariably dies. The
trouble seems to be due to the lack of oxidative processes, possibly
because the nucleus fails to provide the necessary ferments. The
tension is relieved and activity again started up by treating such an
organism with salts like potassium chloride or potassium phosphate,
or with the more complicated salts contained in an extract of pancreas.
It is possible that in the latter case the extracts from the pancreas have
some direct effect upon the granules in question, but such an explana-
tion cannot account for the successful results with the simple potassium
salts, and it seems more probable that the explanation lies in the fact that
the stimulants act directly upon the nucleus and cause it to resume
a neglected function. This conclusion is borne out by the fact that
the tension is first relieved in the immediate vicinity of the nucleus
(Fig. 26), and then progressively toward the ends of the organism.
FIG. 26
Paramecium aurelia in condition of protoplasmic "stability" (extreme left) and resumption
of normal "labile" condition as a result of treatment with salts.
The inner processes of digestion are entirely unknown in the sapro-
phytic forms of protozoa and in the parasitic forms, but there is reason
to believe that it is taken up at the point of granule formation in other,
holozoic, forms. In parasites like trypanosoma living in blood
lymph the nourishment is probably derived from the digested food
materials carried by the blood and upon which the organisms, pre-
sumably, live as saprophytes. Such forms are quite different, physio-
logically, from intracellular or intracorpuscular parasites, such as
coccidia, malaria organisms, etc., which live upon the substance of
the cells or blood corpuscles.
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA S3
The free-living forms of protozoa are almost constantly at work;
they are usually in motion, either in progressive movement, or, by
action of their flagella or cilia, are creating currents toward the
mouth. The energy for such work comes from the breaking down of
complex molecules of protoplasm or possibly of digested food, which
is accomplished by oxidation or physiological burning. The products
of such combustion, as in physical combustion, are kinetic energy,
heat, and residual matter, and the latter, like ashes, must be disposed
of, or by accumulation they hinder and ultimately prevent the normal
processes. The ordinary products of such physiological activity are
solid or fluid matters consisting mainly of water, some mineral sub-
stances, urea, and a gas, carbon dioxide. In higher animals the former
are disposed of through the medium of the skin in part, but mainly
through the activity of the kidney, while the latter are thrown out
through the skin and lungs, or gills. In protozoa, while there is the
same need of elimination of the waste materials, there is in manv
forms no especial organ for the purpose, elimination of urea and of
carbon dioxide taking place, as in some intestinal parasitic worms, by
osmosis through the general surface of the body. Such is the case in
all of the foraminifera and radiolaria, and in individual cases among
the other types of protozoa. In other forms of protozoa, however,
there may be special organs for the disposal of such waste matters.
These are the contractile vacuoles which fill with fluids from the
interior of the cell and then contract, emptying their contents to the
outside through a minute pore, as in the majority of infusoria, or
breaking through the outer wall of protoplasm at any point where the
vacuole may be at the time of contraction, as in amebea. The fluids
of these contractile vacuoles are supposed to hold urea in solution as
well as carbon dioxide, the experiments of Griffiths ('89) indicating
the presence of urea, while biologists generally agree that carbon
dioxide must also be present in the fluids discharged, although in no
case has this been proved. Another function of the contractile vacuole
may be, as Hartog early pointed out, the regulation of the tension in
protoplasm and surrounding water and the prevention of large dis-
ruptive vacuoles through the constant addition of water taken in by
the crystalloids of the cell. Whatever may be the function of the
vacuole, it becomes a very important element of the cell in the more
complicated forms of protozoa, and is frequently associated with long,
branching feeding canals, which to Ehrenberg were evidences of a vas-
cular system, since they ramify through the protoplasm, collecting fluid
which is emptied into the contractile vacuole. While the function of
such contractile vacuoles is elimination of waste or regulation of
density, they cannot be absolutely necessary to protozoa, nor the sole
means of disposing of waste materials, since great numbers of protozoa
are without them.
84 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
Oxygen, necessary for the various processes of oxidation, is taken
in through the general surface of the body and from the surrounding
water. Little or nothing is known regarding its action in the protozoan
cell.
Irritability.— 'This liberation of energy is the 'response' to an
action of itself inadequate to produce it, and has been compared not
inaptly to the discharge of a cannon, where foot-tons of energy are
liberated in consequence of the pull of a few inch-grains on the trigger,
or to an indefinitely small push which makes electric contact; the
energy set free is that which was stored up in the charge. This capa-
city for liberating energy stored up within, in response to a relatively
small impulse from without, is termed 'irritability;' the external
impulse is termed the 'stimulus." (Hartog, 1906, p. 8.) The sensi-
tiveness or irritability of protozoan protoplasm has been a favorite
branch of protozoon research, and is especially interesting in the light
of comparative psychology, for here is the prototype of higher animal
consciousness. It is manifested in a great variety of ways, and the
manifestations have been grouped into categories called taxes or
tropisms. Nearly all of these reactions take the form of motion in
some form or other, and are usually called out in response to stimuli,
which may be of various kinds. Mechanical stimuli, light and heat
rays, electricity, diffusing chemical substances, all exert some effect
on the movements of protozoa, sometimes toward the source of stimu-
lation (positive taxis), sometimes away from it (negative taxis). It is
this irritability of protoplasm that frequently saves the life of the small
organism, or provides it with food. Positive thigmotaxis is the name
given to that reaction of a paramecium, for example, when it
approaches and adheres to some larger object where its bacterial food
may be concentrated; positive chemiotaxis is the reaction shown in
the sudden extension of the tentacles of actinobolus; positive or nega-
tive aerotaxis is that reaction whereby the organism so places itself
in a medium that irritability is reduced to a minimum, and so on,
all movement probably being a response to stimuli which owe their
origin either to external or internal causes, the latter due, perhaps, to
the varying conditions of hunger, fatigue, and the like.
The most extensive and illuminating observations on this aspect of
protozoan physiological activity have been made by Jennings, and the
results of his long studies on the behavior of lower organisms are
well stated in his own words in the following theses (Jennings, 1906,
p. 261):
1. "First, we find that in organisms consisting of but a single cell,
and having no nervous system, the behavior is regulated by all the
different classes of conditions which regulate the behavior of higher
animals. In other words, unicellular organisms react to all classes
of stimuli to which higher animals react. All classes of stimuli which
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 85
may affect the nervous system or sense organs may likewise affect pro-
toplasm without these organs. Even the naked protoplasm of ameba
responds to all classes of stimuli to which any animal responds. The
nervous system and sense organs are, therefore, not necessary for the
reception of any particular classes of stimulations.
2. "The reactions produced in unicellular organisms by stimuli are
not the direct physical or chemical effects of the agents acting upon
them, but are indirect reactions, produced through the release of
certain forces already present in the organism. In this respect the
reactions are comparable with those of higher animals. It is true for
ameba as well as for more differentiated protozoa.
3. " In the protozoa, as in the metazoa, the structure of the organism
plays a large part in determining the nature of the behavior. There
are only certain acts which the organism can perform, and these are
conditioned by its organization; by one of these acts it must respond
to any stimulus. If the behavior of the metazoa is comparable in this
respect to the action of a machine, the same comparison can be made
for the behavior of the protozoa.
4. "Spontaneous action — that is, activity and changes in activity
induced without external stimulation — takes place in the protozoa as
well as in the metazoa. Both vorticella and hydra, as we have seen,
spontaneously contract at rather regular intervals, even when the
external conditions remain uniform. Continued activity is the normal
state of affairs in paramecium and most other infusoria. The idea
that spontaneous activity is found only in higher animals is a totally
erroneous one; action is as spontaneous in the protozoa as in man.
5. "In unicellular organisms, without a nervous system, certain
parts of the body may be more sensitive than the remainder, forming
thus a region comparable to a sense organ in a higher animal. Whether
such a part may become more sensitive to one form of stimulation
while insensitive to others, as in higher organisms, seems not to have
been determined.
6. "Conduction occurs in organisms without a nervous system.
This is, of course, seen in the fact that a stimulus limited to one part of
the body may cause a contraction of the entire body, or a reversal of
cilia over the entire body surface. A strongly marked case is the con-
traction of the stalk in vorticella, when only the margin of the bell is
stimulated.
7. "Summation of stimuli occurs in protozoa, as in metazoa. This
is shown most clearly in Statkewitsch's experiments with induction
shocks. Weak induction shocks have no effect until frequently
repeated.
8. "In the unicellular animal, as in that composed of many cells,
the reaction may change or become reversed as the intensity of the
stimulus increases, though the quality of the stimulus remains the
86 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
same. Such a change in reaction has sometimes been claimed as a
specific property of the nervous system. The protozoa ameba and
stentor, as well as the metazoan planaria, move toward sources of
weak mechanical stimulation, away from sources of strong stimulation.
9. "In the protozoa, as in the metazoa, the reaction may change
while the stimulus remains the same; that is, the animal may respond
at first by a certain reaction; later, while the stimulus remains the
same, by other reactions. This has been shown in detail in the account
of stentor. The change may consist in either a cessation of the reaction
or in a complete alteration of its character. These changes are, as a
rule, by no means due to fatigue, but are regulatory in character. The
behavior thus depends on the past history of the organism. For such
modifications of behavior a nervous system is then unnecessary.
10. "In the protozoa, as in the metazoa, the reactions are not
invariably reflexes, depending only on the external stimulus and the
anatomical structure of the organism. The reaction to a given stimulus
depends upon the physiological condition of the organism. In stentor
we could distinguish at least five different conditions, each with its
O
characteristic reaction to the given stimulus.
11. "In unicellular, as well as in multicellular, animals we find two
chief general classes of reactions, which may be designated as positive
and negative. The positive reaction tends to retain the organism in
contact with the stimulus, the negative to remove it from the stimulus.
In many classes of stimuli we can distinguish an optimum condition.
A change leading from the optimum produces a negative reaction,
while a change leading toward the optimum produces no reaction, or a
positive one. The optimum from this standpoint usually corresponds,
in a broad way, to the optimum for the general interests of the organ-
ism. These relations hold equally for protozoa and metazoa.
12. "In both the protozoa and the metazoa that we have studied,
the behavior is based to a considerable degree on a selection of certain
conditions through the production under stimulation of varied move-
ments. When the organism is subjected to an irritating condition, it
tries many different conditions or many different ways of ridding itself
of this condition, until one is found which is successful.
"Altogether, there is no evidence of the existence of differences of
fundamental character between the behavior of the protozoa and that
of the lower metazoa. The study of behavior lends no support to the
view that the life activities are of essentially different character in the
protozoa and metazoa. The behavior of the protozoa appears to be
no more and no less machine-like than that of the metazoa; similar
principles govern both."
Growth and Reproduction. — In all of the constructive pro-
cesses of the cell there is no doubt that the nucleus plays the most
important part, and that it is, in a sense, the directive centre of activi-
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 87
ties. This is shown by the behavior and history of enucleated frag-
ments, which, as we have seen, cannot digest food; other functions are
similarly crippled by removal of the nucleus, and movement itself is
greatly impaired. A contractile vacuole will reform and will contract
to a certain extent in enucleated protozoa, but it will not act normally
and soon ceases to contract, swelling then, with the continued addition
of fluids, until the cell bursts, as in the characteristic phenomenon of
diffluence.
When the constructive activities of the protozoan body exceed the
destructive, and when the addition of new raw material exceeds the
waste, new protoplasm is added to the old and growth results. The
dimensions of the cell are increased in all directions, the increase taking
place in the fluid protoplasm apparently throughout all parts of the
cell at the same time, a process of growth by intussusception. The
mere accumulation of reserve food granules plays no part in growth,
all growth ceasing when the cell becomes packed with them, but must
take place only after the necessary constructive changes have con-
verted such reserve stores into protoplasm. Growth continues until
the cell has attained to a more or less definite, optimum size, and then
it divides into two or more small cells according to the species.
The explanation of growth is one of the unsolved problems of
biology, and we get but little nearer the solution in the case of pro-
tozoan organisms than in the higher forms of life. We know, indeed,
that growth ceases with the elimination of the nucleus, hence, we
conclude that the nucleus is a necessary factor in the process. Growth
in the protozoa can be controlled in a variety of ways, and we know
that certain conditions of temperature, of density, and the like, are
necessary. While the explanation of the finer processes of growth is
far away, the solution of the problem of cell division is almost equally
remote, and no theory yet propounded satisfies the conditions as we
see them in the various forms of life. Spencer's theory of volume and
surface is very seductive; indeed, it may be a step toward the final
solution. Briefly stated it predicates that a normal relation exists
between the protoplasm and the nucleus of the cell, and, if the form
remains the same, this relation is disturbed by growth, for the surface
of the organism increases as the square of the diameter, while the
volume increases as the cube. Hence it results that the mass increases
faster than the surface which provides the means of interchange with
the environment (absorption and the like). The changed ratio of
surface to mass of protoplasm, according to Spencer and his followers,
brings about internal changes which result in cell division. But
after this theory is stated, we know nothing more about the ultimate
causes of cell division than we did before. When the nature of the
changes is understood, the reason for cell division will naturally follow.
Leaving aside the causes of cell division, and looking at the phenomena
88
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
alone, we find a far more satisfactory state of affairs, for the details of
the process are known in many different cases.
Whatever the causes of cell division may be, whether limits of
growth or sun spots, the fact is established that the first indications of
the process in the majority of cases are found in the nucleus. Here we
are dealing with a universal biological phenomenon, the division of
a cell, and the protozoa are interesting in this connection because of
the variations in the process which they present, and also because the
structures involved are less complicated than those of higher animal
and plant cells, and, therefore, more easily analyzed. In all tissue cells
of normal character, division is brought about through the medium of
a peculiar structure of the nucleus known as the mitotic or karyo-
kinetic figure. Under ordinary vegetative conditions of the cell, the
;. L'7
Gptew.
;
>t
A micronueleus of Paramecium aurelia in division.
nucleus contains chromatin substance in the form of granules arranged
in a more or less definite network or reticulum. Prior to cell division
these granules become rearranged in a much wound thread or spirenie,
and later the spireme thread is divided across into a number of short
chromatin elements known as the chromosomes, the number of such
chromosomes being constant for all of the cells of the same species of
animal or plant. The number of these chromosomes in no way
indicates the degree of differentiation of the organism, nor its position
in the animal or plant scale, some protozoa, for example, having a
larger number of chromosomes than does man. In the ordinary
process of mitosis these chromosomes are arranged in the centre of a
spindle-formed nuclear figure consisting of fibers of kinetic substance
focussed at two poles, these poles characterized by the presence of
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 89
small granules of deeply staining substance, the centrosomes. The
centrosomes, spindle fibers, and chromosomes, to which the spindle
fibers are attached, are collectively known as the mitotic figure, and
few cells that are known divide without the formation of this mitotic
figure, or some modification of it (Fig. 27). It represents, therefore,
the mechanism of cell division, and further, since the hereditary char-
acteristics are now known to be connected in some way with the
chromosomes, the mitotic figure becomes the mechanism of heredity.
The chromosomes, while in the equator of this mitotic figure, or in
some cases even before the mitotic figure is formed, are divided by a
cleft which passes from end to end through the centre, and the two
halves, as the daughter chromosomes, are apparently drawn apart by
the mechanism of the mitotic figure; the cell body is then divided
into two daughter cells by a constriction or cleft passing through the
middle; the nuclei reform their characteristic reticular condition, and
the two cells are then ready for further processes of digestion, assimi-
lation, and growth.
Ever since 1883, when Roux first called attention of biologists to
the extreme care with which the chromosomes were halved and dis-
tributed to the daughter cells, and especially since the publication of
Weismann's classical essays on the nature and constitution of the
germ plasm, these elements of the cell have been recognized as the
physical basis of inheritance, and their mode of origin and complete
history have been the chief subject for study by cytologists. Xot only
the chromosomes, but the entire spindle figure as the mechanism by
which they are divided, has also demanded the attention of biologists.
In this branch of biological research the protozoa have played an
important part, for in these cells we find the simplest types of the
division figure and the simplest forms of the chromosomes, while cell
division is found in every conceivable form, sometimes strikingly
similar to the division of a metazoan cell, as in some heliozoa, some-
times so highly modified as to be regarded as a type by itself, as in the
budding forms.
Cell division, therefore, which Spencer interpreted as marking the
limit of growth of a cell, is inaugurated through some change in the
relations of nucleus and cytoplasm, and some change which is entirely
unknown. In many protozoa the process is so different from tissue-
cell division that other names are given to it. We recognize : (1) Simple
binary division of the cell into equal parts, or simply cell division.
(2) Unequal division of the cell, the smaller part being pinched off
from the larger as a bud. This is known as budding or gemmation,
and is only a slight modification of cell division. (3) Spontaneous
division of the cell into four or more, frequently a great number of
daughter elements, each with a portion of the original cell nucleus, the
process being known as spore formation or sporulation.
90
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
These various modifications of the process of division or reproduc-
tion in its broadest sense may be conveniently summarized as follows:
Binary division
/-Cells dissociated (Protista).
J f Undifferentiated (Protozoa
Cells associated -j
Reproductio
.
f Simple -
I phyta).
[ Budding division (Euglypha, etc.).
I Exogenous.
( Gemmation • _
I , . i . - \ (_ Endogenous.
I Schizogony (without fertilization)
I. bporulation < a . . . ..
(. Sporogonv (after fertilization).
colonies).
Differentiated (Metazoa, Meta-
FIG. 28
Trypanosoma gambiense; stages in longitudinal division.
by F. W. Baeslack.
Original from a preparation
In a number of protozoa, the cell before division draws in or throws
off its motile organs, rounds out into a sphere, and then divides into two
equal parts. This is the case in some of the heliozoa, a nuclearia, for
example, which is very plastic with freely moving and often branching
pseuclopodia, becomes spherical and then divides through the middle,
the entire operation, as seen under the microscope, taking not more
than a minute.
The process becomes more complicated in those forms with com-
plex motile organs. In some cases, as in some forms of trypanosoma,
the flagellum is divided throughout the entire length, but in other
cases the basal body alone divides, a second flagellum being formed
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
91
from the free half, while in still other cases it is discarded before divi-
sion, and, as in copromonas, each daughter cell creates a new one
(Fig. 28). Similarly with the infusoria, some forms like paramecium,
colpidium, etc., have a cover of uniform cilia which are retained during
the act of division; indeed, the organisms swim vigorously throughout
the entire process, but in other forms, as Euplotes patella, oxytricha,
stylonychia, etc., the more complex motile organs are discarded and
formed anew by the daughter cells (Wallengren) (Fig. 29).
jln the flagellate Noctiluca miliaris (Fig. 30), the division is accom-
panied by very complicated nuclear changes, and a division figure is
formed which recalls the mitotic figure of the metazoan cells. The
chromatin in the ordinarv conditions of the cell is contained in a few
FIG. 29
Euplotes patella in division. The macronucleus is not quite divided, the daughter
nuclei being connected by a delicate strand.
large chromatin reservoirs or karyosomes; these disintegrate prior to
division, and the granules thus formed collect in lines, the chromo-
somes, which are oriented toward one pole of the nucleus. At this
pole, but on the outside of the nuclear membrane, lies a large centro-
some or division centre, which divides during the time of disintegra-
tion of the karyosomes and forms a central spindle between the two
halves. The nuclear membrane next disappears in the region between
the chromosomes and the spindle, but is retained elsewhere, and
special spindle fibres grow out from each of the division centres and
become attached to the ends of the chromosomes. The division
centres then move apart and the chromosomes are drawn asunder,
each having divided through the middle.
92
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
An entirely different mode of division is found in some of the more
simple flagellates. Euglena, for example, divides without any rupture
of the nuclear membrane and without any definite mitotic figure
(see Fig. 10, p. 30). The chromatin is in the form of granules
distributed throughout the nucleus, and surrounding a central, deeply
staining, larger granule, the division centre. When the cell divides
this granule first divides into two equal parts, about which the
chromatin granules are equally massed, and it corresponds to the
entire mitotic spindle of metazoan cells. This type of nucleus (the
centronucleus) is quite common among the protozoa, and from it we
can trace the evolution of the mitotic figure of higher animal cells
through forms like noctiluca and the heliozoa.
In some forms among the flagellates, and in some infusoria, there is
no definite nucleus, but the chromatin granules are distributed through-
out the cell unconfined by a nuclear membrane. This is the case with
some forms of tetramitus and with some ciliates like dileptus. In the
FIG. 30
Nucleus of Noctiluca miliaris in division. The light streak through the middle is the
groove in which the central spindle lies.
former, the chromatin granules collect about the division centre at the
time of cell division, and the nucleus then divides like one of the centro-
nucleus type. In the latter each of the separate granules divides,
although this does not mean that each granule is represented in
both daughter cells; on the contrary, only those granules pass into a
daughter cell that lie in the half of the parent organism represented
by that daughter cell. Division here is a means of keeping the
quantity of chromatin material and the active surface up to a
standard (Fig. 31).
Budding differs widely from simple division, in its external appear-
ance, at least, for, "in the majority of cases, the nucleus does not divide
until the daughter individual is nearly formed. In many rhizopods,
for example, the protoplasm swells out as a large protuberance from
the surface of the cell until it is quite as large as the parent cell, and
then the nucleus divides and the organisms move apart, each with a
nucleus and an equal portion of the protoplasm. This is the case in
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 93
forms like arcella, difflugia, or euglypha, where the cell is enclosed in
a test or shell. Here the protoplasm wells out of the mouth opening
of the shell until it forms a counterpart of the parent organism, then
the nucleus divides, as stated, and the two individuals separate. Such
a method is complicated, and to a certain extent anticipated, by the
organism, for long before the cell divides the shell plates of a euglypha
are formed and stored up in the protoplasm about the nucleus of the
parent organism, to be used only when the bud has reached a certain
size. They then flow into the bud with the protoplasmic streaming,
and arrange themselves on the outside of the bud protoplasm, where
they form a tightly fitting shell (Fig. 5, see A, p. 23). In other
cases the buds are much smaller than the cell which forms them, and
FIG. 31
Dileptus, sp., with distributed nucleus in process of division. Each of the chromatin
granules is drawn out in the form of a rod and divides (see Fig. 2, p. 19).
they first appear as mere protuberances on the surface of the parent
(Fig. 32, E). This is the case in forms like spherastruni, for example,
and several buds may form at one time. These are frequently dif-
ferent from the parent and are often provided with motile organs of a
different type. Thus, in the heliozoa the buds may have pseudopodia
of the lobose type and move around like small amebae, or they may
have flagella and move around like flagellates. The former are
called pseudopodiospores by Lang, and the latter flagellispores. In
all cases, however, the bud soon loses its larval motile organs and
develops into an organism similar to the parent (see Fig. 11, p. 31).
In the case of acanthocystis, the buds require five days for their com-
plete development, the characteristic centralkorn and the ray-like
pseudopodia appearing on the sixth day (Schaudinn).
94
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
Budding, in cases like the last, is very similar to spore formation,
and can scarcely be distinguished from it. Many instances of budding-
are presented by different groups of the protozoa, and in all of them the
process is characterized by the fact that the parent organism continues
to live as an individual after giving rise to these motile offspring. In
spore formation, on the other hand, the substance of the parent in the
majority of cases is used in the formation of the offspring, and it loses
its life as an individual.
In noctiluca the buds are formed after the nuclei divide, and appear
as minute swellings on the surface. The nuclei in these swellings
divide repeatedly until about five hundred buds are formed; these
FIG. 32
mm A
& f :i»** ^^W^^^lj
*;.T* -^
Entameba histolytica. (After Craig.) .4, organism showing rods and granules of chro-
matin in the nucleus, vacuole with some stained substance, and dense ectoplasm; B, the
chromatin of the nucleus passing into the cell plasm, where it is distributed as chromidia, shown
n C; D, aggregation of chromidia to form secondary nuclei (see Fig. 51, of Ameba limax); E,
"spore formation" by budding; F , spores of Entameba histolytica as seen in feces.
develop two flagella similar to those of the dinoflagellata, and swim
off. After a time one of the flagella turns into a tentacle, and the
. characteristic structures of the adult are then formed (Ishikawa).
Budding is the characteristic method of reproduction of the suctoria,
and is interesting from the fact that it may be either on the surface, as
in ephelota, or inside the body, as in acineta (Fig. 33). The latter
condition is derived from the former by the bud-forming area sinking
below the surface and being covered over by a membrane so that a
small brood pouch is created within which the buds swim about by
means of their embryonic cilia before making their escape (Fig. 34).
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
95
This so-called endogenous budding is perhaps the forerunner of the
curious method of spore formation, or, better, budding, which occurs
in one group of the sporozoa, the neosporidia. Here the individual
continues to live while forming buds, as in acineta, within its proto-
plasm. Such buds, known as pansporoblasts, then form peculiar
thread-bearing spores, the entire substance of the bud being used in
FIG. 33
Ephelota biitschliana, a budding individual with five daughter buds. Ar, maoronucleus, which
forms a branching organ connected throughout. (After Calkins.)
the formation of the spores, and these small bundles of spores are
carried about by the grandmother organism until its protoplasm is
loaded with them, and until it appears like a huge cyst filled with
spores (see Fig. 61, p. 145). These organisms are frequent parasites
on fish, where they may be the cause of costly epidemics.
Budding, furthermore, is frequently associated with the process of
conjugation; the mother cell, loaded with chromatin granules in the
96
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
chromidia form, gives rise to numerous buds, each of which is pro-
vided with chromidia, but with no part of the vegetative nucleus.
Such buds ultimately form the conjugating gametes in forms like
arcella, difflugia, centropyxis, etc. In parasitic forms like Entameba
histolytica, the cause of tropical dysentery, or Neuronjctcs hydrophobias,
the cause of rabies, there is a similar bud formation, the buds having
the characteristic chromidia; their further fate, however, is unknown,
the sexual processes of these organisms not having been made out
(see p. 303).
"A much more highly evolved method of division is found in some
ofjthe colony forms of protozoa, where, as in Gonium pectorale (Fig.
35), for example, each of the sixteen cells of the parent colony
forms simultaneously a daughter colony of sixteen cells. Here
FIG. 34
Endogenous budding in Suctoria. (After Biitschli.) A, B, two stages in the formation
of the bud in Tokophrya quadripartita, Cl. and Lach.; c, the bud liberated as a "swarmer;"
C, buds (e) in Acineta tuberosa, Ehr.; d, a bud liberated.
simple division is followed by association of the daughter cells, and
individuals result which have passed through an actual, although
primitive, ontogeny.
In spore formation, finally, we find one of the most prolific methods
of reproduction known. Here the organism breaks down simultane-
ously into great numbers of daughter elements, each dissimilar to the
parent in size if not in other characters. This process, involving as it
does the cessation of normal vegetative life with its ordinary processes
of digestion, assimilation, etc., usually takes place under the protection
of an outer covering or cyst, such encystment being a common phe-
nomenon among the protozoa, an outer covering of gelatinous material
being thrown out on the surface of the organism whenever the condi-
tions of the environment become unsuitable. This investment becomes
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
97
firm and membrane-like upon continued contact with the water, and,
finally, if conditions continue unsuitable, it turns into chitin, which
withstands drought or heat, and within it the reduced sphere of pro-
toplasm is protected until conditions are again favorable. The
chitin is then reduced or dissolved by enzymes from within the cell,
or by external agents acting on it, and the organism creeps out and
FIG. 35
h
Gonium pectorale in reproduction. Each of the sixteen cells of the colony is dividing
to form a daughter colony of sixteen cells. (After Calkins.)
resumes active life. Within such protecting cysts many different
types of protozoa go through the often complicated processes of spore
formation. In some cases the protection seems to be hardly neces-
sary, and spores are formed and liberated before the membrane has
had an opportunity to harden. This is the case in colpidium and in
Tillina magnet, for example; in colpidium, four or eight daughter cells
7
98 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
may be formed within the cyst, in tillina, only four, and these are all
alike, and, except for the smaller size, similar to the parent organism.
In many cases only two daughter individuals are formed within the
cyst, a fact showing that it is not a long step from the process of
simple division to that of such so-calltd spore formation, and tillina
and colpidium are examples illustrating the transition from the one
mode of reproduction into the other. Tillina rarely varies from the
formation of four spores, and then only to revert to the apparently
ancestral mode of simple division. Colpidium, on the other hand, has
progressed farther toward obligatory spore formation, and not infre-
quently forms eight spores within the temporary cyst. Other forms of
ciliate infusoria form a varying number of spores; in some, as in
Holophnja -multi filius, a great number of swarm spores are developed
in the cyst, each similar to the parent. It is a question whether such
reproductive elements are entitled to the name spore, for they are not
formed by the simultaneous fragmentation of the mother organism,
but by repeated division, the cleavages following one another in rapid
succession; in some cases, indeed, as in tillina, the divisions follow so
closely upon one another that the two planes of division are sometimes
seen at the same time, and this activity is followed by a period of rest
lasting for from twelve to twenty-four hours or longer, according to
the vitality of the individual. If this is not simultaneous, it is very
close to it, and the process in these ciliates must be due to the same, or at
least to similar, physiological causes that bring about spore formation
in other cases.
Spore formation, apart from the spores that are formed in prepa-
ration for fertilization, is uncommon among the protozoa and is found
chiefly in the one group — sporozoa — which gets its name from this
method of reproduction. In many of the flagellates, however, it
seems to be a method of reproduction which follows conjugation.
Thus, in Tdramitus restrains and Cercomonas longicauda a cyst is
formed immediately after conjugation of two similar cells, and within
the cyst the protoplasm fragments into hundreds of minute flagellated
organisms. In these cases the ordinary method of reproduction is by
cell division, the spore formation appearing to be a special method that
follows upon fertilization (Fig. 67, p. 155).
It is in the group of the sporozoa that we find the highest develop-
ment of the spore-forming power, and here it has been found necessary
to distinguish between the spores that are formed sexually, i. e., after
fertilization, and those that are formed asexually, for they differ both
in structure and in function. The spores that are formed after fer-
tilization are protected by firm and resisting coverings, and are able
to live outside of the body of the animal in which they are definitive
parasites; the other type of spores, formed asexually, have no such
coverings and cannot live apart from the host. With these various
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
99
differences to take into account, the use of the term spore has been
very ambiguous and misleading, and protozoologists have given it up
for two other terms, sporozoite and merozoite, now generally adopted.
The term sporozoite is used to designate those spores or germs that are
FIG. 36
$§& -/A - • " ® - ftl^*^
ill
Life cycle of Coccidium schubergi. (After Schaudinn.) Sporozoites penetrate epithelial
cells, and grow into adult intracelluhir paia-itrs (a). When mature, the nucleus divides re-
peatedly (b), and each of its subdivisions becomes the nucleus of a merozoite (c). These enter
new epithelial cells, and the cycle is repeated many times. After five or six days of incuba-
tion, the merozoites develop into sexually differentiated gametes; some are large and well
stored with yolk material (d, e, f); others have nuclei which fragment into many smaller par-
ticles ("Chromidien"). each granule becoming the nucleus of a microgamete or male cell (d),
h, i, j). The macrogamete is fertilized by one microgamete (g), and the copula immediately
secretes a fertilization membrane which hardens into a cyst. The cleavage nucleus divides
twice, and each of the four daughter nuclei form* a -poroblast (k) in which two sporozoites are
produced (?).
produced after fertilization, while merozoite is used for the asexually
produced germs. The protected sporozoites have the power to carry
the disease from one host to another, while the merozoites, as a rule,
carry the infection only from one part of the host to another part
(Fig. 36). Sporozoites, therefore, have the full potential of vitality
100 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA
of a new individual, while merozoites have a shorter life to run and a
lessened vitality (see Chapter III).
Merozoite formation is best illustrated by the coccidia, a group of
cell-infesting sporozoa, and the genus adelea is an interesting type,
because it combines asexual reproduction with sexually differentiated
organisms. A word here as to the significance of this fact. In the
sporozoa, both in the gregarinida and the coccidiidia, the cycle ends
with the formation of sexually differentiated reproductive bodies, one of
which is larger, corresponding to an egg cell, the other very minute and
similar to a spermatozoon; the former is called a macrogamete, the
latter a microgamete. The mother cells of these gametes are not
visibly different in many cases, and it is impossible to tell whether a
given cell will produce one or the other. In some cases there is a slight
difference either in size, or in possession or absence of granules, or in
the make-up of the nucleus. These differences do not go far back, as
a rule, and in the ordinary run, male and female cannot be distin-
guished. In adelea and a number of other forms, however, the sexual
differences do go back almost to the fertilized cell, and it is possible to
distinguish any given cell as female or male. The formation of
asexual reproductive elements, or merozoites, in these different
parents is the same, and begins with the division of the nucleus into
as many parts as there will be merozoites, in adelea usually twelve to
sixteen. After their formation they occupy a peculiar and character-
istic position, being rolled together like staves of a barrel, or like the
segments of an orange, a peculiar arrangement which has given rise
to the name corps en barillet, while the term eimerian cyst is also used
designate the parent membrane cyst where they are formed (Fig. 20, A].
The sporozoites differ but little from the merozoites when they are
deprived of their protecting cases. After fertilization of the macro-
gamete, which will be described in a later chapter, the nucleus of an
ordinary coccidian, such as Coccidium schubcrgi, for example, divides
twice and the protoplasm surrounds them in equal masses; these are
the sporoblasts. The nucleus of each sporoblast then divides again,
while the protoplasm secretes a sporoblast membrane, one of the pro-
tecting coats of the sporozoites. The second division of the nucleus
in each sporoblast provides the nuclei of the sporozoites, two develop-
ing in each sporoblast. The germs are then protected by the sporo-
blast membrane, and by a membrane which is secreted by the original
cell, and with this double safeguard the germs of the organism are
thrown to the outside, where no further development takes place until
the sporocysts are swallowed by some new host (Fig. 36, /).
The variations in these processes of merozoite and sporozoite forma-
tion are legion, and they are of great importance economically, as well
as interesting biologically, but their description belongs rather to the
special chapters dealing with protozoan diseases.
PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA 101
The protozoa are, then, complete living organisms, in which no
function found in the higher animals is lacking, and we have seen
enough of their structures and functions to show how the scope of
protozoology leads us into all fields of biological pursuits, from tax-
onomy, the description and classification of living things, through
morphology, physiology, cytology, psychology, and theoretical biology.
In the following chapters I wish to show how this scope widens out
and leads us into some of the most difficult, but at the same time
fascinating, problems of biology.
CHAPTER III.
PROTOPLASMIC AGE OF PROTOZOA.
UPON watching one of these simple organisms through the micro-
scope there is a certain fascination in the idea that this minute bit of
naked protoplasm has been continuously living since life appeared
upon the earth. As a matter of fact, the same sensations might be
experienced upon gazing at any of our fellow-beings, or, indeed, at any
other living thing; but somehow we do not think of the latter in this
way; we associate with them the ideas of age, of senile degeneration
and natural death, concepts which do not seem to be associated with
the free-living cell. It would appear, furthermore, that the ameba
protoplasm which we see under the microscope, and which has lived
continuously for all of these ages, might continue to live for an indefi-
nite time in the future. It would seem that this perfectly balanced
cell, with its powers of growth and reproduction, would be self-suffi-
cient, containing within itself the potential of an endless existence.
Such, however, is not the case, protozoa, like metazoa, may die of old
age-
In every higher animal we recognize certain more or less definite
periods of physiological activity, and according to these we roughly
divide the span of life into three stages, which are in no way sharply
outlined. These we call the stages of youth, adolescence, and old age.
Youth, characterized by a high degree of vitality, is the period of rapid
cell multiplication and growth; organs are formed and perfected,
functions are unimpaired and active and the body is a perfect living
thing. The second period is characterized by functional and sexual
maturity; the multiplication of tissue cells is less rapid; the organs
strengthen and their functions are more perfectly correlated; growth
comes to an end. In the perfected animal it is the period for per-
petuation of the race, and in conformity with this great function
sexual differentiation is fully established. The third period, old age,
brings a marked change, the potential of vitality wanes, cells atrophy,
and functions weaken; degenerations of all kinds appear; and cumu-
lative weakness ends in natural death.
These three periods are characteristic of all of the higher many-
celled animals, the last period being rarely seen in nature, because in
the wild animals a violent death follows the early functional weakening
and inability to fight off enemies. Do we find the same sequence of
PROTOPLASMIC AGE OF PROTOZOA 103
physiological changes in the unicellular animals, and can we distin-
guish periods of youth, maturity, and old age?
Since the fundamental biological laws are much the same, on
a priori grounds alone we should expect to find the same series of
changes in protozoa as in the metazoa. But while we do find them
in protozoa, they are manifested in a way that we would not at first
suspect. We have been accustomed to look upon the single-celled
ameba, or paramecium, or other protozoon, as a complete individual
in itself; but when we come to compare such an individual with a
metazoon we do not find the analogous periods of vitality which in
metazoa we recognize as youth, adolescence, and age. A protozoon
is a free-living cell, a complete organism indeed, but as such it has
no period of youth nor of sexual maturity, nor, by itself, old age. It
is formed by division or some modification of division; it regenerates
the normal form in a few hours, and then again divides; with division
its individuality is lost, to be merged into that of two new individuals,
these two into four and so on. Obviously such an individual cell
presents nothing comparable with the sequence of stages so char-
acteristic of the "individual" in higher forms of life.
Students of the protozoa and biologists generally (e. g., Btitschli,
Weismann, etc.) early called attention to the fact that not the single
cell of a protozoon, but the entire succession of cells that may be
formed from the period of one conjugation to that of the next, should
be compared with the metazoon. In the latter, the fertilized egg
cell gives rise to a multitude of body cells by repeated divisions;
the cells are bound together to form a uniform and differentiated
whole. In the former, the fertilized protozoon divides, but the cells
do not remain bound together; they separate and live as independent
units. If we could take such an entire succession of cells thus formed
from the repeated divisions of a fertilized protozoon, and if at any
given period could combine them in one mass of cells, we would have
the analogue of a metazoon and would find that the protoplasm
represented by the aggregate of cells would manifest the same suc-
cessive periods of vitality as those of youth, adolescence, and old age
in metazoa. We would find that the young cells divide more rapidly
than they do later in the cycle; we would find that after a certain
period they become sexually mature and able to conjugate and so to
perpetuate the race; and we would find that, ultimately, evidences of
weakened vitality and degeneration appear in the aggregate of cells,
and that they would finally die of old age.
Not only would such an aggregate show the characteristic periods
of vitality, but with the changes from one period to another there
would be, in a great number of cases, accompanying changes in the
form of the cell body; changes of so great a nature that a casual
observer would never regard such cells as belonging to the same
104 PROTOPLASMIC AGE OF PROTOZOA
species as those of the younger generations. It is for this reason,
mainly, that in recent years a number of biologists have strongly
advocated the use of the entire life cycle of a protozoon rather than the
cell, or many cells in the same stage of vitality, for the basis of species.
While Btitschli ('76) was the first to note the differences in vitality
in a race of protozoa, and Hertwig, Maupas, and a score of others
added many observations on different periods, it was Schaudinn
(1900) who first clearly perceived the importance of studying the com-
plete life history of every species. It is because of this importance that
the life cycle forms such a conspicuous part of the definition of protozoa
as given at the beginning of Chapter I.
Before outlining a typical protozoon's life history, it will be necessary
to understand clearly what is meant by age in protoplasm. It is quite
evident, broadly speaking, that there is some protoplasm that does not
die, the living things on the earth today testify to that, for they repre-
sent protoplasm that has been continuously living since the advent of
life on the earth, and which, through posterity, will continue for an
indefinite time in the future. Such protoplasm forms the substance
of the germ cells, and they alone of all cells have the potential of an
indefinite existence. But this capacity to live without finite end is
bound up with a biological phenomenon as little understood as life
itself, namely, fertilization. Without the union of two germ cells even
this endowed protoplasm would die no less surely than do tissue cells.
The protozoa are like both tissue cells and germ cells, and consist of
protoplasm which is differentiated into somatic and germinal parts,
and this protoplasm, like that in higher cells, will die of old age if
fertilization or its equivalent is prevented. The problem of age in
protozoa, then, has to do with vitality as apart from the union of germ
cells and as manifested in the ordinary processes of vegetative activity.
I. A TYPICAL LIFE CYCLE.
The manifestations of protoplasmic activity which occur in all cells
from monads to man, involving processes of digestion, growth, irri-
tability, etc., are easily studied in Paramecium aurelia, a very common
infusorian that may be found in any stagnant ditch or pool (Fig. 37).
To a trained eye it may be seen without the aid of a lens as a minute
white spot of protoplasm which moves from place to place in an irreg-
ular line of motion. When magnified it appears as an asymmetrical,
cigar-shaped organism, with a somewhat spirally wound depression or
"peristome" leading from one end toward the mouth near the centre
of the body. Within the protoplasm is a large nucleus, macronucleus,
usually ellipsoidal in form but subject to wide variations in size; and
a smaller nucleus, known as the micronucleus, which is embedded in
A TYPICAL LIFE CYCLE 105
the substance of the macronucleus. At each end of the infusorian is
a bright spot which appears and disappears with considerable regular-
ity; these are the contractile vacuoles, their function being to throw to
the outside of the body the waste matters that are formed during the
physiological activities of the cell. Each vacuole is supplied by a series
of canals from various parts of the body, the waste matters in fluid
form collecting in them to be emptied into the contractile vacuole and
thence disposed of. The peripheral protoplasm of paramecium is
filled with minute thread-like structures, the trichocysts, which are
thrown out when the cell is irritated. On the outside of the body,
finally, is a dense covering of minute lash-like whips which are con-
stantly in action during life, and by means of which the organism moves
about freely in the water, turning the while on its long axis. These are
the cilia which are arranged in spirally wound lines around the body,
while a somewhat more powerful set are located in the asymmetrical
peristome and are used to direct a food current toward the mouth.
FIG. 37
Paramecium aurelia. Macronucleus normal; micronucleus abnormally large.
The food consists of any proteid matter small enough to pass
through the mouth opening. The organism will take in bits of flesh,
or parts of vegetable matter, or bacteria or lifeless matter, such as
carmine or indigo granules, all with equal voracity. The process of
ingestion is hastened by the activity of an undulating membrane
situated in the small gullet, and the bacteria or other food matters are
collected in a vacuole which forms at the base of the gullet. Con-
siderable water is taken in with the food, and when the vacuole is
large enough it is caught up in the protoplasmic flow and carried away
from the mouth opening. Numerous gastric vacuoles are thus formed
and the food is digested in them.
When the organism is fully grown it reproduces by dividing into
two cells, each cell having the characters of the former one cell, which
has disappeared, indeed, although it has not died. Its protoplasm is
still living in the two daughter cells; these repeat the processes of
digesting and growing, and finally, each of them reproduces by trans-
verse division. The metabolic processes leading to reproduction by
division are thus repeated generation after generation, and, having all
that is necessary in the form of cellular organs for an indefinitely
106 PROTOPLASMIC AGE OF PROTOZOA
continued existence, they apparently offer some justification for the
older view that protozoa are practically deathless, so far as old age
is concerned.
The matter of physical immortality can be easily tested, however.
After a little practice, a single cell of parameeium can be isolated and
fed on the bacteria which develop in a previously sterilized hay infu-
sion made by boiling small pieces of hay in water. The organism is
placed in a small chamber filled with the hay infusion and made by
supporting a coverglass on pieces of glass. When it divides, which it
will do within twenty-four hours, the daughter cells can be similarly
isolated and fed on freshlv made hav infusion, and in this wav the
*/ */ «.
vitality of that originally minute bit of protoplasm can be watched
day after day and generation after generation of cell divisions, until
natural death from old age ensues. The writer successfully followed
the life history of such a culture of parameeium from an initial cell to
protoplasmic death from old age, giving fresh food medium and
isolating the single cells day after day and generation after generation
for a period of twenty-three months and 742 generations. The obser-
vations made during such a study deal with living protoplasm that
is growing old more rapidly than in nature, and with the ageing
process in an organism endowed with an initial potential of vitality.
A parameeium which is thus followed from generation to generation
shows surprisingly regular variations in vitality. Some of the more
minute variations are due to temperature changes, a warm day, for
example, increasing, a cold day diminishing, their vigor. In the
laboratory, however, such variations may be overlooked, for the
changes in temperature from day to day are of minor importance.
After much experimenting, a measure of vitality was finally found
which made it possible to compare the activity of the physiological
processes from time to time. This measure was represented in the
form of a curve, the points upon it being obtained by averaging the
number of divisions made by all of the organisms under observation
in periods of ten days, each average giving the ordinate for one period;
the abscissas represent the arbitrary ten-day periods (see Fig. 38).
Such a curve, representing the vitality of the parameeium proto-
. plasm, shows that in a period of six months under cultivation, if the
organisms are fed upon the same diet of hay infusion, there is a gradual
exhaustion of vitality, the curve falling from an average of about
twelve divisions in ten days in February to an average of one division
in ten days in July. As the curve shows, the average number of cell
divisions sinks more or less regularly during the six months, but
undergoes periodic rises and falls, until at the end of that time the
organisms are unable to digest and assimilate the bacterial food and
the cells begin to die, the minute cellular corpses being abundant at
such a period.
A TYPICAL LIFE CYCLE
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108 PROTOPLASMIC AGE OF PROTOZOA
This exhaustion of the power to digest and assimilate is an unmis-
takable phenomenon in the life history of a protozoon, and marks a
somewhat indefinite phase of the life history, which was designated
the "period of depression." Many other observers have noted it in
connection with protozoa of different kinds; the first, Biitschli, in 1876,
in relation to paramecium, without noting the sequence of stages lead-
ing to this depression period, observed that the organisms become
reduced in size and sluggish in movement, and that while in such
condition they conjugate, an observation which led him to his famous
suggestion that conjugation is not an act of reproduction, but a means
of renewing the vitality of the organisms, including the power to repro-
duce ; in other words, a Verjungung of the protoplasm. Later observers,
including Maupas and Hertwig, likewise studying the organisms en
masse, noted a similar stage of lowered vitality, the former concluding
that it indicates a senile degeneration of the nuclei, the latter, that it
indicates a changed relation between the volume of the nucleus and
that of the cell. Woodruff and Gregory, as graduate students in the
Columbia laboratory, have followed out, generation by generation,
the life history of different protozoa, the former in connection with
Oxytricha fallax, one of the hypotrichous infusoria, wThich he followed
for 860 generations of cell divisions, requiring twenty-one months,
the latter in connection with Tillina magnet, one of the holotrichous
infusoria, which was followed for thirteen months, dying out in the
548th generation. Periods of depression wrere observed in these
organisms as in paramecium, and the same physiological derange-
ments were noted by both observers, the first period of depression
carrying off all the cells of tillina.
What is the explanation of the depression period? The organisms
have abundant food; they are able to take in food up to a certain
time, but they appear abnormal in structure, and if left to themselves
they would die. The protoplasm at this period is markedly different
from that at other times; in paramecium the endoplasm lacks the
characteristic vacuoles of the ordinary organism and appears dense
and homogeneous (Fig. 39), an appearance due to the aggregation of
granules. The lack of vacuoles signifies a concentration of the cell
protoplasm and, therefore, a reduction in size of the organism; the
macronucleus, in the meantime, retains its full size, and it thus appears
that the volume of the latter is relatively greater than it is under normal
conditions. This is perhaps one reason why Hertwig, Popoff, and
others have concluded that the cause of depression is the change in
relative volume of nucleus and cytoplasm, but such a change in relative
volumes may be equally well an effect of the depression and not its
cause. Woodruff noted the same reduction in size of the cell in
oxytricha (his figures 1 and 9) during the period of depression and a
corresponding change in nature of the cytoplasm, which, in oxytricha,
A TYPICAL LIFE CYCLE
109
became vacuolated instead of granulated. There is no doubt, from
these daily observations on the same organisms, that there is a change
in physiological activity, which cannot be interpreted as due to the
difference in the relative sizes of nucleus and cytoplasm, but must be
traced to some more deeply lying cause.
After two similar periods of depression had been successfully offset
by artificial means, a fourth and final period, in which the protoplasmic
structures were quite different from previous conditions, carried off
the last generation of the race, 742d generation (see p. 129).
FIG. 39
Paramecium aurelia at period of depression, showing 'at left) the dense granular condition
of][the protoplasm, which, if not relieved art ilicially, invariably ends in death. The central
and right hand figures show the effects of >ndi artificial relief in the vicinity of the nucleus,
while the extremities are still
While these initial experiments would seem to indicate a certain
normal length of life (approximately 200 to 800 generations), it does
not follow that all parameeia have the same endowment. Different
races of paramecium, like different human individuals, vary in the
initial potential of vitality, and are capable of living for different
lengths of time upon the same medium. Thus, other cultures of para-
mecium, carried on at the same time as those described, yielded 376
and 379 generations before evidences of depression set in. A con-
stantly changing medium, furthermore, may tend to offset the cumula-
tive physiological weakness and so to prolong the life of the race.
Such an experiment on paramecium has recently been carried out by
Woodruff ('08), who, instead of constant hay infusion, used infusions
of leaves, grass, etc., from natural pond water, frequently changing
HO PROTOPLASMIC AGE OF PROTOZOA
the source of such food material. Upon such a continually changed
diet he carried on a race of Paramecium anrelia through several hun-
dred generations without the advent of a period of depression. It
appears, therefore, that in the constantly changing conditions of
nature a race of protozoa may live much longer than under the
conditions of laboratory experiments on a single diet. It is probable
that the salt contents of the medium rather than the food are of
importance in this connection, since the bacteria of the laboratory
air, with which all food media were inoculated, were presumably
the same.
II. MORE COMPLICATED LIFE CYCLES AND THE PERIODS OF
"YOUTH," "MATURITY," AND "AGE."
With different types of protozoa the three periods of vitality may be
recognized with quite the same facility as in any of the lower forms of
metazoa. There is no sharply defined difference between them, but,
as Maupas first pointed out, there is a fairly definite period of proto-
plasmic or "individual" maturity, which is preceded by a period that
may be designated "youth," and is followed by a period that may be
called "old age." The period of maturity is so frequently accom-
panied by well-marked cellular changes, which distinguish the organ-
isms at that period from the ancestral cells which gave rise to them,
that we are justified in the attempt to generalize, if only for descriptive
purposes, and to speak of periods of youth, maturity, and age in
protozoa.
In the life history of Paramecium anrelia the three periods, youth,
maturity, and age, of the life cycle are not so clearly marked by struc-
tural and functional manifestations as in some other forms of protozoa.
Nevertheless, there is a physiological difference which becomes appar-
ent when one follows out the complete history. The period of youth
is marked by a high rate of division energy and by the fact that con-
jugation does not occur if many of them are put together in a limited
space. After some time in culture, however, usually when the rate of
division has begun to decline, the protoplasm of the cell body
changes slightly in physical and chemical make-up, so that two or more
cells upon meeting fuse and conjugate. The entire race of para-
mecium in such a culture may become sexually mature at the same
time, and "epidemics" of conjugations may be thus obtained. At the
last period of depression, however, in the experiments cited, there were
no conjugations, a fact indicating, possibly, the exhaustion of the germ
plasm. Such a final period of old age may be easily identified, involv-
ing, as it does, the curious vacuolization and degeneration of the
protoplasm and exhaustion of the physiological energies.
MORE COMPLICATED LIFE CYCLES HI
A. The Period of Youth.— As with the fertilized egg of a metazoon,
this' first period of vitality of the copula or fertilized cell of a protozoon
is characterized by the distinct excess of constructive over destructive
metabolism, which indicates a high potential of vitality and great
powers of cell reproduction, which may take the form of division,
budding, or spore formation according to the difficulties successfully
overcome by the type in the struggle for existence. These young
forms show a well-marked conformity to type, and this feature, occur-
ring when the greatest numbers of representatives of the species are
in evidence, undoubtedly has given a false impression of the stability
of form of the protozoan species. The protoplasm, as a rule, is trans-
parent and without reserve matters, metaplasm products, and the like,
and the nucleus is often without the characteristic structures of the
later forms.
It is along physiological lines that the young forms are most promi-
nently marked. This is the period, for example, of the greatest resist-
ance to adverse conditions in the surrounding medium, and in patho-
genic forms it is the period of greatest malignancy. It is a well-
known fact that in many parasitic forms of protozoa attempts to
inoculate from animal to animal are either failures altogether or
result in a weakened infection, the failures being due, presumably, to
the inability of the organisms in a more or less weakened condition to
withstand the natural immunity of a new host. The matter of malig-
nancy is so intimately connected with restored vitality that in yellow
fever, for example, it is almost sufficient to indicate that fertilization
processes and renewal of vitality must have taken place in the body of
the intermediate mosquito host.
At this period, also, is the greatest power of self-preservation in other
ways than by resistance of a chemical nature; thus, the firm protective
cysts are formed at this period within which the fertilized cell may
resist heat, cold, and drought, as in many of the free forms of protozoa
when the organisms live thus through the winter, or in parasitic forms
like the sporozoa, when the organisms are protected in the interval of
changing hosts.
The difficulties in determining which are young and which older
cells of a life cycle are great, and much must be left for inference. It
may be accomplished, however, in one of several ways: (1) By culture
experiments for which cells are isolated immediately after conjugation,
a method that may be easily employed for the larger free protozoa.
(2) By inoculation of uninfected hosts with the spores of the form to
be studied, a method which may be employed with sporozoa or with
encysted ameba?. (3) By natural inoculation through the opera-
tion of intermediate hosts, such as insects, ticks, or leeches. Few
observations, however, have been made upon the young forms, prob-
ably because the morphological characteristics of the mature cells are
much more apparent than those of the young.
112
PROTOPLASMIC AGE OF PROTOZOA
The high grade of vitality of the young protozoan is undoubtedly
due to the perfection of the cellular structures and to their harmonious
working. This was very well illustrated in some observations on so-
called Paramecium caudatum (Calkins, 1906). This species has been
generally regarded as distinct from another very similar form, Para-
mecium aurelia, which is regarded as much more rare than the former.
The main difference between the supposed two species is the presence
FIG. 40
29
28
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25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
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6
5
4
3
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1
I «
1
MARCH
APRIL
MAY
JUNE
JULY
AUGUST
«
Diagram to show the relative vitality of the caudatum and aurelia forms of paramecium.
The dotted line represents the division rate (average for ten-day periods) of an ex-conjugant
from the same culture which reorganized normally, i. e., as a Paramecium "caudatum." The
solid line represents an ex-conjugant that reorganized abnormally, i. e,, as Paramecium
"aurelia," but which changed into a normal form during the month of June. Note the rise
in division rate with the assumption of the normal condition. (After Calkins.)
in the latter of two micronuclei as against one in the former, while
certain physiological differences, as indicated by the rate of division
and the rate of movement, were noted by Maupas ('89) and Simpson
('01). The observations mentioned were made upon some ex-con-
jugants from a culture of the more common "caudatum" form. The
two cells derived from such a union were isolated, and one of them
was maintained for months in culture, the other dying shortly after
MORE COMPLICATED LIFE CYCLES H3
isolation. In the reorganization of the cell following separation two
micronuclei instead of one were left in the cell. This abnormality for
the "caudatum" form was the "normal" condition for the "aurelia"
form, and was maintained for more than three months, the animals
showing every characteristic of form and function that have been
ascribed to Paramecium aurelia. The movement was sluggish and
the rate of division much lower than in the case of "caudatum" forms
which had been isolated at the same time and carried along as a con-
trol (see Fig. 40). At the expiration of three months in culture the
cells here and there showed the loss of one of the micronuclei, and ulti-
mately all of the so-called "aurelia" forms had become "caudatum"
forms and with the typical characteristics which mark this species.
The rate of division rose to a much higher average than before,
and the cells became much more animated and larger in size. The
average number of divisions in ten-day periods rose from 11.3 from
March 1 to June 10, to 19.3 in the time from June 10 to September 1,
that is, during the time when the nuclear relations were normal. It
is evident, therefore, that Paramecium caudatum and Paramecium
aurelia are not distinct species but merely variants of the same species,
and that the abnormal condition of the cell organs resulted in strongly
marked physiological derangement.
B. The Period of Maturity. — There is no definite limit to the
period of youth in protozoa, the changes which characterize the period
of maturity coming on slowly and imperceptibly as they do in higher
forms. The morphological characteristics of this period, when
arrived, are clearly marked, however, and unmistakable. Such
changes affect both the cell body and the nucleus, and may accom-
pany either vegetative or germinal activities, or both.
1. Protoplasmic Changes at Maturity. — While the most important
characteristic of the period of maturity is a general decrease in func-
tional activity, with decline in the rate of multiplication, these physio-
logical activities are accompanied by well-marked morphological
changes which may be of a sexual character. In a single cell or
specimen of a protozoan species there may be no clue to its position
in the life cycle unless it is in some phase of sexual activity, and where
sexual dimorphism does not exist it is quite impossible to tell from
morphology alone. Thus, in the mature paramecium the sexual
differences are so minute that unless one is following out the life his-
tory in culture the period of maturity passes unobserved. Nevertheless,
the cells of paramecium do undergo a physical change at this period;
the peripheral protoplasm becomes sticky and highly miscible, so that,
in some cultures, two organisms upon meeting will adhere at any
point, and groups of from six to nine cells may be seen whirling about
in aimless movement among the normally conjugating pairs. This
miscible state indicates a well-marked difference in the physical
114
PROTOPLASMIC AGE OF PROTOZOA
make-up of the protoplasm, for in the early periods of activity the body
wall, while plastic, always retains its firm contour and cortical density.
Pearl ('07), furthermore, has shown by biometric analysis that con-
jugating paramecia are markedly smaller and less variable than non-
conjugating forms.
Similar changes in density mark this period in other kinds of pro-
tozoa. Thus, among the flagellated forms like tetramitus or cerco-
monas the ordinarily firm contour of the cell becomes plastic and
highly changeable in form, and two of them upon meeting fuse in
conjugation. Here again a physical change is well illustrated.
FIG. 41
Polystomella crispa. Liberation of pseudopodiospores from the microspheric
individual. (Photo by J. J. Lister.)
Still more remarkable is the change in form which some types of
sarcodina undergo at this time. The rhizopods are especially note-
worthy in this connection, Schlumberger ('83) noting for the first time
a peculiar dimorphism in the shells of foraminifera (Fig. 42), a differ-
ence which Schaudinn ('03) and Lister ('05) were the first to explain.
These observers found that the young forms, immediately after fer-
tilization, give rise to what Schlumberger termed the "microspheric"
type of shell. Upon reproduction, such a cell ultimately gives rise to
pseudopodiospores which leave the old shell and secrete new ones of a
different type, termed the "megalospheric" type (Fig. 41). The
latter generation, when fully grown, gives rise to flagellispores which
conjugate and thus complete the cycle (see Fig. 52, p. 123).
MORE COMPLICATED LIFE CYCLES
115
Even more marked is the change in trichospherium where the
chemical composition of the skeleton parts changes with advancing
age. The young forms resulting from conjugation grow into an
adult characterized by a gelatinous membrane and radial spicules
of magnesium carbonate. This adult reproduces by the formation
of pseudopodiospores, which grow into organisms similar to the
parent, or after advanced age (presumably) to a second adult type
characterized by a firm membrane and entire absence of radial
spicules. This second type, as in the foraminifera, finally gives rise
to flagellispores, the progeny from different parents uniting and thus
FIG. 42
Megalospheric (A) and mierospheric (B) sli3lls of Biloculina depressa. Lam. (After
Schlumberger.) Dimorphism is shown by the central chamber c.
completing the cycle. Such secondary types are morphological
evidences of changed metabolic conditions characteristic of the second
period of vitality. The possibilities of similar alternations in the life
history of parasitic and pathogenic forms have hardly yet been realized.
2. Nuclear Changes at Maturity. — " Chromidia." — While changes in the
body form are often characteristic of the second period of vitality, there
are great numbers of protozoa in which the external structure gives
no clue to the state of affairs within. The nucleus, however, undergoes
changes at this period which are not only more widespread throughout
the phylum, but are of far more theoretical and practical importance.
These changes have to do with the formation of so-called "chromidia"
and with the maturation phenomena of the cell (Fig. 43) .
116
PROTOPLASMIC AGE OF PROTOZOA
The first definite observations upon chromidia formation were
made by Hertwig ('99) in connection with the minute structure of the
shelled rhizopod Arcella vulgaris. Previous observers had noted that
chromatin-like granules are distributed throughout the cell body in
many of these types, but Hertwig was the first to describe the origin of
this material from the nucleus in arcella and to show that it forms a
dense zone of granules in the protoplasm (Fig. 44). At that time
Hertwig described this material under the name of "chromatin net,"
but later, in 1902, he called it the "chromidialnetz," because of the
reticulate structure assumed by the granules en masse. The function
of this extranuclear chromatin was not made out, however, until the
following year, when Schaudinn ('03) worked out the origin and fate
of similar masses of granules in several different kinds of sarcodina
FIG. 43
"Chromidia" in rhizopods. Arcella vulgaris (on left) and Ameba proteus (on right).
dark granules are the idiochromidia distributed throughout the cytoplasm.
The
(Polystomella crispa, Centropyxis aculeata, Chlamydophrys siercorea,
and Entameba coli) and found that the nuclei of the conjugating
gametes were developed solely from this extranuclear chromatin. He
thus 'interpreted the material of the chromatin net of arcella and its
allies as sexual or racial chromatin and correctly compared it with the
micronuclei of the infusoria.
In the meantime the subject became more complicated by Hertwig's
further observations upon extranuclear chromatin in the heliozoon
Actinospherium eickhornii. These observations, first noted in 1897,
were confirmed and extended in 1904, when it was shown that in
starving forms and as well in forms that had been overfed, the nuclei
all disintegrate and the chromatin contents becomes distributed
throughout the cell body (Fig. 45). The distributed chromatin thus
MORE COMPLICATED LIFE CYCLES
117
formed was named by Hertwig, in 1902, "chromidien," from which
the term chromidia is derived, a term now universally employed by
protozoologists. According to Hertwig this latter material in actino-
spherium cytoplasm is prophetic of the death of the animal, for when
it is thus formed the renovation of the cell is impossible (1904).
Fir,. 44
Arcella vulgaris.
(After Calkins.) Three individuals in pla.-tngamic union.
P, idiochroinidia; X, nuclei.
FIG. 45
A^? *£ !<s
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Chromidia formation in Actinospherium eichhornii. (After Hertwig.) A, primary nuclei
and chromidia; B, complete transformation into chromidia.
It thus appears that we have to do with two kinds of chromatin
masses in the cell body and no little confusion has arisen in conse-
quence of the mixed terminology applied to this material, which is alike
in origin from the nucleus but very different in function. Chromidia,
in Hertwig's sense, is functionless extranuclear chromatin, but Schau-
dinn and others have used the term to designate the sexual chromatin
which is equivalent to the chromidialnetz in Hertwig's terminology.
118
PROTOPLASMIC AGE OF PROTOZOA
Subsequent observers have tried to straighten the tangle by giving new
terms for the different kinds of extranuclear material. Calkins ('04)
proposed the term protogonoplasm for the gamete-forming' substance;
Goldschmidt ('04) proposed the terms "chromidia" and "sporetia"
for chromidia and "chromidial net" respectively, and Mesnil ('05),
the terms "trophoehomidia" and "idiochromidia." Goldschmidt's
suggestion is a good one, but the term sporetia is not indicative of the
function, while Mesnil's term idiochromidia expresses the fate exactly
and will undoubtedly supplant the other names. In the present
instance the terms "chromidia" and "idiochromidia" will be used,
the former on grounds of priority, the latter on expediency.
FIG. 46
•
'.' A tf '•? v . -. . ^f.'ja • ' •
- ssB&ff
Arcella vulgaris. Secondary (gametic) nuclei (n) forming from the idiochromidia ch;
o, mouth opening of shell. (After Hertwig.)
(a) IDIOCHROMIDIA FORMATION. — As might be expected, the method
of formation of the idiochromidia differs widely in the different types
of protozoa, and frequently in the same type. Although all methods,
in their final analysis, may be traced back to the same physiological
causes arising during this period of maturity, the different types may
be separated for purposes of description into three groups, as follows :
(a) Idiochromidia formation by nuclear transfusion; (6) by dissolu-
tion of nuclear parts ; and (c) by nuclear fragmentation.
Nuclear Transfusion. — This method of idiochromidia formation is
most characteristic of the rhizopods, and has been worked out mainly
in connection with arcella, centropyxis, difflugia, and other mono-
MORE COMPLICATED LIFE CYCLES
119
thalamous forms. In arcella it has been described by Hertwig ('99)
and Elpetiewsky ('OS), and the process here may serve as a type for all.
The normal vegetative cell of arcella contains two nuclei which at
an early period begin to secrete chromatin materials, which collect
in masses about the nuclear periphery (Fig. 44). With continued
FIG. 47
c
Gametes and copulation of Arcella vulgaris. (', copula. (After Elpetiewsky).
FIG. 48
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Stages in development of Mastigella vitrea and Mastigina setusa. (After Goldschmidt.
X 1270. ^4, flagellate stage of M. vitrea; B, same, somewhat older and before chromidia
formation; C, same during chromidia formation; a, entire cell; b, nucleus only, showing
transfusion of chromatin to form chromidia; D, young Hagella stage of M. setosa, with heap
of chromidia; E, same, older form with pseudopodia, compact chromidia, and food vacuole;
F, same, young form with peripheral "bristles;" G, same, formation of gametic nuclei a,
from idiochromidia, b.
growth, and at maturity of the cycle, these masses become distributed
throughout the cell body in the form of deeply staining chromatin
granules (Fig. 43). When fully mature the protoplasm breaks down
into a number of pseuclopodiospores, each with distributed chromatin,
and these form new arcella shells in which the protoplasm ultimately
120
PROTOPLASMIC AGE OF PROTOZOA
breaks up into ameboid gametes, in which the nuclei are formed, as in
centropyxis, by fusion of the idiochromidia granules (Figs. 46 and 47).
Not only in rhizopods, but in flagellated protozoa as well, the idio-
chromidia arise in this manner. Thus, in the case of Mastigina
setosa, Goldschmidt ('07) has shown that the idiochromidia accumu-
late in heaps about the nuclear membrane, as in arcella or centropyxis,
before being scattered throughout the cytoplasm, where they ultimately
form the nuclei of gametes (Fig. 48).
Nuclear Dissolution.— -There is probably no great difference
between the above-described method of idiochromidia formation by
transfusion, whereby the chromatin materials percolate through the
nuclear membrane in fluid form, and that by nuclear dissolution,
whereby the peripheral portion of the nucleus becomes scattered in
granular form throughout the cell body. Nor is this second method
FIG. 49
''•
Ameba limax (group of five on left) and Chilomonas paramecium to show alveolar
structure of protoplasm prior to idiochromidia formation. Two of the amebsB are in process
of division.
different, save in degree, from the third, which I have called nuclear
fragmentation. The distinctions have, at best, only a descriptive
value.
Nuclear dissolution, in substance, was described more than thirty
years ago by Hertwig ('76) in connection with the radiolarian acan-
thometra. In this form there is a great increase in the thickness of
the chromatin at the periphery of the nucleus and at the expense of
the karyosome, and this cortex ultimately breaks down to form quan-
tities of minute secondary nuclei of the macro- and microgametes
(see Hertwig, 1907). Here, then, the peripheral rind of chromatin is
little more than a condensed zone of idiochromidia, and is closely
associated with the karyosome. In Ameba Umax (Fig. 49) there is no
MORE COMPLICATED LIFE CYCLES
121
such condensation, but the idiochromidia granules collect in a loose
shell or rind about the karyosome, and from it granules of chromatin
are discharged into the surrounding protoplasm prior to encystment
(Fig. 50). During encystment these distributed granules are abun-
dant in the cell while the karyosome becomes indistinct and ultimately
degenerates. Under proper environmental conditions (which may be
brought about artificially by changes in temperature) the idiochromidia
fuse into sixteen groups of secondary nuclei (Fig. 51). A similar
method of idiochromatin formation was described by Schaudinn
('03), and more recently by Craig ('08), in the case of Entameba
histolytica.
Not only idiochromidia, but chromidia as well, may be formed by
this method of nuclear dissolution. Thus, in some coccidia and grega-
rines according to the observations of Siedlecki ('07) and Leger ('07),
on caryotropha and ophryocystis, respectively, a similar disposal of
the peripheral rind of chromatin gives rise to degenerating granules
which, possibly, according to both observers, may have some vegeta-
Fic. .10
Ameba limax. Chromidia forming from nucleus and collecting in the cytoplasm
prior to encystment.
tive function in cell metabolism. The latter, therefore, apparently
agree with Hertwig's chromidia in actinospherium.
Nuclear Fragmentation. — Idiochromidia formation by fragmenta-
tion is widely scattered among protozoa, and has been described by
numerous observers, first by Schaudinn ('94), and by many others
since, in connection with various forms of foraminifera, rhizopods,
flagellates, and sporozoa. The most widely recognized example of this
mode of idiochromidia formation is the case of Polystomella crispa,
one of the foraminifera. Here, according to the independent obser-
vations of Schaudinn ('03) and Lister ('05), the nuclei of the micro-
spherical generation increase by division until a large number are
formed. The older ones then disintegrate, or fragment, into minute
chromatin granules, which are ultimately distributed throughout the
protoplasm. Later aggregations of these idiochromidial granules give
rise to the nuclei of the conjugating gametes (Fig. 52). Similarly in
the coccidian Klossia octopiana, according to the researches of Siedlecki
the nuclei of the microgametes, and in Gregarina cuneata, according
122
PROTOPLASMIC AGE OF PROTOZOA
to Kuschakewitsch ('07), the gametic nuclei, are formed by nuclear
fragmentation.
A slight modification of this method of idiochromidia formation is
found in Ameba proteus, where, according to Calkins ('07), the primary
nucleus divides repeatedly until about seventy nuclei are present in the
cell. These primary nuclei then give rise to secondary nuclei, which
form from the chromatin granules inside of the primary nuclei. The
chromatin substance of the primary nuclei is thus metamorphosed into
secondary gametic nuclei, and these conjugate two by two. Here the
process may be interpreted as a precocious development of the gametic
nuclei, a development taking place before the primary ones are com-
pletely fragmented (Fig. 53).
FIG. 51
•
*
•
Ameba limax. Aggregations of idiochromidia to form sixteen secondary nuclei, which
then unite to form eight.
The vegetative distributed chromatin granules or true chromidia,
as seen in Actinospherium eichhornii are formed by similar nuclear
fragmentation; it is quite obvious, therefore, that the method of
formation of these distributed chromatin granules has little or nothing
to do with the subsequent function.
(6) THE SIGNIFICANCE OF IDIOCHROMIDIA. — It is quite apparent
from even the few cases cited above that we cannot generalize as to the
function of the deeply staining granules of nuclear origin in the cyto-
plasm of protozoa. In some cases (e. g., actinospherium, ophryo-
cystis, caryotropha, etc.), whatever may be their significance in the
MORE COMPLICATED LIFE CYCLES
123
cell, they certainly are not connected with the formation of the gametic
nuclei. On the other hand, there can be no doubt of the propagative
nature of such distributed granules in the great majority of protozoa,
and in such cases we may, with reason, speak of a definitive germ
FIG. 52
a
-r^ 9
•- -•*, v^/.^ •.
D •// •'.
Life cycle of Polystomella crispa S. (Lang and Schaudinn). A young form derived from
the union of two flagellated gametes (A) develops into an organism with microspheric type
of shell. The nucleus increases by mitosis until many nuclei are present when they break
up into granules of chromatin (B). The protoplasm fragments into reproductive bodies,
equivalent to merozoites (C), each having several granules of the distributed chromatin
("Chromidien"). Each reproductive body (D) develops into an adult with a macrospheric
type of shell, and with nuclei in the form of small chromatin granules (-E). When mature
these forms fragment into hundreds of flagellate gametes (F) which conjugate, and so com-
plete the cycle. (See, also, Fig. 41, p. 114.)
plasm as contrasted with the somatic plasm. With such an assump-
tion we are brought in touch with a problem of high theoretical interest
in general cytology, and with the protozoa, as with the metazoa, we
have this question to consider: Are there two kinds of substances in
124 PROTOPLASMIC AGE OF PROTOZOA
the nucleus, the one superintending exclush7ely the processes having
to do with germinal life, heredity, and the race, the other having to do
only with the metabolic processes of the individual ?
In connection with higher animals and plants we meet with con-
flicting answers to such a question. ^^Teismann, Roux, and their
followers maintain — and their contention is strengthened by the con-
stantly increasing evidence as to individuality of the chromosomes
and their connection with specific characteristics of the adult organism-
thai a specific inheritable substance — idioplasm — is always present in
the cell from the start, and is gradually sifted out with growth as the
various organs are formed. Others, notably O. Hertwig, take the view
that nuclear materials are fundamentally the same, and that as growth
advances, environmental changes affect and alter the original homo-
geneous stuff. It is in connection with the latter point of view that
R. Hertwig approaches the problem of dualism in the protozoan
nucleus (1907). He believes that "functional degeneration" becomes
localized in certain substances of the cell nucleus, so that a dualism
is gradually brought about through such degenerative changes, and
indicated, morphologically, by the different chromatin elements
scattered throughout the cell. Chromidia, therefore, according to this
point of view, would be the same as idiochromidia save for a difference
in potential, the latter having the possibilities of continued existence,
the former not.
Neglecting, for the present, the question of original dualism in
nuclear substances in protozoa, we must accept the fact that there are,
at times, specific germ substances within the cell and localized in the
chromatin of the cell. In the higher animals the analogous germ
plasm becomes segregated and separated from the somatic plasm in
the form of germ cells or germinal epithelia. Differentiated from
somatic plasm during ontogeny, this racial protoplasm becomes
functional only after the period of maturity is reached. Similarly
with protozoa, there is, at periods of maturity, a definite germ plasm
distinct and separate from the somatic plasm. In some cases, like
the germ cells of higher animals, this specific racial substance is
early differentiated from the vegetative, functional, or somatic plasm.
Such is the case in infusoria, where, in Paramecium aurelia, for
example, germ nuclei and functional vegetative nuclei are differ-
entiated as micronuclei and macronuclei, respectively, after the third
division following conjugation; and such is the case in arcella and
allied forms where the germ plasm is not aggregated in a compact
micronucleus, but as idiochromidia is scattered throughout the cell.
In other cases the germinal and somatic parts are not separated
until later in the life history, or in some cases not until full maturity,
when for the first time chromatin of conjugation and of vegetative
function can be distinguished. Such is the case in Ameba proteus, in
MORE COMPLICATED LIFE CYCLES
FIG. 53
125
*
'
I
*. *
V
••**•
Idiochromidia formation in Ameba proteus. (After Calkins.)
126 PROTOPLASMIC AGE OF PROTOZOA
Polystomella crispa, in gregarines, and coccidia, where the residual
primary nucleus, or the Restkorperchen, may be interpreted as the
now functionless somatic chromatin.
Idiochromidia, or germ plasm, therefore, must be interpreted, in
some cases at least (infusoria), as a definite and distinct substance of
the cell. In other cases its segregation and separation from somatic
chromatin occurs only during the second period of the life cycle, and
its formation is the index of advancing age (sarcodina). It is, in point
of fact, the chief morphological feature characteristic of the period of
maturity in protozoa.
3. Sex Differentiation. — At the present time the hypothesis first
advanced by Montgomery ('01) is widely accepted, that during
maturation of the germ cells the reduced number of chromosomes is
brought about by union, two by two, of chromosomes representing the
same characteristics of the adult in maternal and paternal ancestors.
Of such characteristics, none are more marked than those primary and
secondary characters which distinguish the sexes. Wilson's obser-
vations, following and enlarging upon those of McClung, Stevens,
and others, on the structure of the germ nuclei in insects, have prac-
tically demonstrated that sex here, like other adult characteristics, is a
matter of inheritance.
In protozoa, sex differentiation, when present, is, apparently, the
final expression of the period of maturity. We have seen that, with
advancing age, the structure of the protozoan cell may become materi-
ally altered, and that these alterations may give rise to similar con-
jugating gametes, or, directed possibly by inheritance, may give rise
to male or female germ cells. In the former case (isogamy), conju-
gating elements may be similar in size to normal cells or only slightly
reduced, as in paramecium, didinium, and the majority of infusoria;
or both may be reduced to small-sized equal cells (isomicrogametes),
as in many gregarines and rhizopods. In the latter case (anisogamy)
one cell, macrogamete, may be similar to the ordinary vegetative cells
(as in vorticella, coccidium, etc.), or only slightly changed, while the
other cell (microgamete) may be relatively minute (vorticellidse,
coccidiidia, etc.) ; or both cells may be reduced and of dissimilar size
(as in polytoma, centropyxis, schaudinnella, stylorhynchus, and other
gregarines).
In sexually dimorphic gametes there is no difference between the
early cells in the majority of cases, differentiation coming only as a
last step in maturity (hemosporidia, coccidium, and coccidiidia gener-
ally); in some cases, however, notably in adelea (Siedlecki, 1899) and
cyclospora (Schaudinn, 1902) among coccidia, and in trypanosoma
(Schaudinn, 1904) among flagellates, the sex differences are said to
extend as far back as the schizont stage immediately after fertiliza-
tion; hence, if this is true, it is possible to speak in some cases of male
MORE COMPLICATED LIFE CYCLES 127
and female protozoan individuals. The evidence for this conclusion
is in every case somewhat inconclusive ; the differences seemingly are
not beyond the range of individual variation.
In the majority of free forms, gamete formation, with their libera-
tion, is accomplished in the ordinary medium in which the organisms
live, although these processes may be hastened or influenced by
artificial changes in the environment. Thus, Hertwig ('98) noted that
the quantity of food had much to do with these phenomena in the case
of actinospherium, and Klebs, Dangeard, Greeley, and others have
found that changes in temperature or in density of the medium may
induce gamete formation in different kinds of flagellates. Similar
changes in environment seem to be a sine qua non for sex differentia-
tion in many parasitic forms, the most notable and best-established
case being the malaria organisms where microgametes are formed only
in room temperature, in the mosquito's gut, or, in general, in a colder
(denser?) medium than the blood.
In the great majority of cases where gametic differentiation obtains,
if the gametes do not conjugate they die. This is invariably true of
the microgametes, and their fate is probably due to the extreme
specialization which they have undergone. In the female forms this
is not the invariable fate, for in some cases the cells undergo partheno-
genesis, a process of renewal which is accompanied by nuclear activi-
ties of a special kind. (See Chapter IV.)
C. The Period of Old Age.— Protozoa quickly die after the period
of maturity is passed, and old age, the final period of a life cycle, is
rarely seen or recognized. Maupas ('89), however, using the culture
method, gave a very graphic description of old age in certain forms
of infusoria. Thus, in Onychodromm yraudis the body of the cell
becomes much reduced in size, loses cilia and cirri, while other organs
both external and internal, atrophy, and the organisms die of senile
exhaustion. In Paramecium (turclia the circumstances accompanying
old age have been described above, but in this case the metabolic
processes had been restimulated, and apparently the cell organs were
suitable for a continued activity, but something was wrong and the
race died. This "something" had to do with the germ plasm, for,
as stated, the micronucleus was hypertrophied and divisions were
abnormal.
'The first clearly marked period of depression came in July, about
six months after the cultures were started. It was characterized
by a well-defined reduction in size (down to 109 microns) and by
vacuolization of the endoplasm, while the ectoplasm did not appear
to be much involved. Many of the individuals were characterized
«/
by great vacuoles similar to those in starved forms, which dis-
torted the body almost out of recognition; in others the nuclei were
fragmented into two or three parts, and in all there was a marked
128 PROTOPLASMIC AGE OF PROTOZOA
absence of the larger food granules and gastric vacuoles which
characterize the normal animals, and this, notwithstanding the fact
that bacterial food was present in abundance (see Studies I). As
stated in these Studies (HI), the organisms under these conditions
still take food, and in some cases the endoplasm appears opaque with
the undigested food balls, but the decrease in size continues and
the endoplasmic vacuolization is not prevented by the presence of the
food. It is the digestive function, apparently, which becomes ineffec-
tive at such periods, and if this is a correct assumption, this function
can be stimulated, as I have shown by the experiments.
''Identical results were obtained in the period of depression in
December, 1901, a depression which was again overcome by the use
of beef extract, while the individuals of the series which had been con-
tinued on the hay diet all died. These became smaller and smaller,
and again gave morphological indications of starvation, notwith-
standing the fact that the individuals which had been stimulated with
the beef extract were living and reproducing normally in the same food
medium. They became much reduced in size, the endoplasm became
distorted with vacuoles, and they died with absolutely no indication of
disease through parasites.
'These observations show, therefore, that starvation effects may
be produced, even though the animals are living in a medium rich in
food. It is trite to say that to prevent starvation we must have not
only food, but the ability to digest and assimilate it, yet common as
this observation is, it is important in the present connection, and
involves a factor which cannot be overlooked in any discussion on
old age.
"In the June period, as stated previously, the same conditions were
not observed, for the organisms, in part at least, had been treated with
the beef extract every week during the first three months, since the
previous period of depression. The division rate began to run down
in the case of the B series in April, in the A series in May, and in all of
the material that had been continued on the beef the characteristic
structure was a densely granular endoplasm (Fig. 26, p. 82). In the
specimens that had not been treated with the beef since the preceding
December this character of the endoplasm was not noted. These
unstimulated individuals died out in about the 508th generation (B
series) after becoming much emaciated and reduced in size, and with
reduced nuclei. . . . The unstimulated A series did not die out
until about two weeks later. At the time when the B individual
described above died (May 12) the unstimulated A series was char-
acterized by somewhat reduced size, a declining division rate, and
absence of the dense protoplasmic granules. In the stimulated A
series, on the other hand, (Al and A2) of about the 560th genera-
tion, the structures were normal, gastric vacuoles were numerous, and
MORE COMPLICATED LIFE CYCLES 129
divisions were frequent. Toward the end of June, however, when the
A series nearly died out in the 620th generation, the conditions were
very different. Fig. 26, left, is from a specimen in the 615th generation;
its size is below the normal; its endoplasm is choked up with granules,
and there is no trace of vacuoles save the contractile vacuole near one
end. The macronucleus is definitely granular, and its contour is
irregular, as though devoid of nuclear membrane. The micronucleus
is elongate and spindle-formed. The ectoplasm is not deformed, and
save for the absence of trichocysts it appears to be normal. This was
the condition of the protoplasm when the usual large number of culture
individuals was reduced to 6 A's and no B's, and a condition from
which the A series was rescued only with the greatest difficulty by the
use of pancreas extract.
"From this time until the race died out the division rate was slug-
gish. The conditions of the protoplasm in the latter individuals was
decidedly characteristic. Throughout the fall individuals would
appear with densely granular protoplasm, which is invariably the
FIG. 54
*
Paramecium aurelia from culture in 741st generation. The macronucleus and endoplasm
are normal, the micronucleus is abnormal, and the cortical plasm is filled with vacuoles.
(After Calkins.)
sign of death, unless the animals are stimulated in some way. In such
forms the macronucleus may or may not be normal, whereas the
micronucleus, as a rule, becomes hypertrophied and the ectoplasm
full of great vacuoles. Fig. 54 is a good representation of the condi-
tions at this time. The endoplasm is apparently normal; there are
food vacuoles and endoplasmic granules and vesicular structure, but
the micronucleus is spherical and vesicular, has lost its usual place
in a niche in the macronucleus, and shows evidence of granular
modification of the previously homogeneous chromatin.
"One of the two oldest of the A series (742 generations) showed
the following points while alive: 'A12 was alive this morning and was
picked out for examination. It had two contractile vacuoles situated
dorsally and close together. The astral canals were absent; in their
place wras a row of dorsal feeding canals, such as those characteristic
of the more generalized holotrichida (e.g., Chlamydodontidci). The
rest of the body contained eight or ten large vacuoles not contractile.
The macronucleus was slightly hypertrophied and visible, indicating
9
130 PROTOPLASMIC AGE OF PROTOZOA
the approach of disintegration. The papillae of the cuticle were plainly
visible, and what I have taken to be apertures of the trichocysts
were more or less numerous. (This is shown in the preserved cell,
Fig. 54.) A few trichocysts remained in the cortical plasm, but there
were many vacuoles in this layer, indicating that when the trichocysts
were discharged they were not reformed. The peristome was normal
and the mouth had a vigorous oral membrane. The size was large,
fully as great as any of the preparations that had been made at any
time during the 742 generations. Movements vigorous to slow, with
a tendency on the part of the animal to remain stationary.'1
'It was while the organisms were in this structural condition that
the many attempts to rejuvenate the race were made as described in
the previous pages, and it was in this condition of the protoplasm that
the race finally died out from exhaustion. Before dying, however, the
individuals, as indicated in the above paragraph from my notes, were
of full size and were filled with gastric vacuoles and partly digested
food, while the body form was normal.
"It must be admitted that these forms ivere capable of individual
growth at this period, and since the macronucleus was norm<d in the last
individuals, while the micronucleus was considerably changed, it must
be further admitted that the vegetative metabolic processes were presum-
ably re-invigorated; on the other hand, the functions of reproduction,
that is, of division, were degenerated possibly, if not probabhj, because
of the apparent degeneration of the micronucleus and of the cortical
plasm, whose functions were not reinvigorated by the artificial means
which were tried."
We are not in a position yet to demonstrate the nature of the cause
of the depression periods. It is probably to be sought in the chemical
make-up of the constituents of the cell, the chemical changes necessary
for the functions of digestion, such as the formation of proteolytic
ferments, oxidizing ferments, and the like, being no longer possible
with the same food. We may compare a paramecium or oxytricha
with a storage battery, the one having, at the outset, a certain potential
of physiological activity, comparable with the initial electric charge
of the battery. With the same food for a period of six months the
initial charge of vitality is drawn upon, as work done draws upon the
initial potential of the battery, until in a period of depression the
resources of the cell are exhausted and the organism dies by what
Hertwig calls "physiological" death.
The battery, however, to continue our analogy, can be recharged
and is good for another period of work. So can the paramecium pro-
toplasm. The six months of culture does not exhaust the germinal
possibilities of that protoplasm; in the cultures referred to, the organ-
1 From my notebook.
MORE COMPLICATED LIFE CYCLES 131
isms, or rather the race, were in the 200th generation at the time of the
first depression, but the vitality of the protoplasm was not exhausted
until the 742d. Woodruff's race of oxytricha protoplasm was in the
235th generation at the first depression period, but lived through SCO
generations. There is no doubt whatsoever that all of the cells of
paramecium would have died in the first period of depression had
nothing been done to revive them. Joukowsky, in 1898, followed
paramecium through 170 generations, when they all died during a
period of depression; Simpson, in 1901, noted the gradual loss of
vitality and death in his three to four months' cultures of paramecium.
My cultures would have disappeared in a similar manner had it not
been for a change of diet, by which it was found that beef extract, if
given to paramecium for several days during this depression period,
would restore the vitality and start the organisms off on another cycle
of cell generations. In this way the few surviving organisms of the
original culture were stimulated to new activity, or, to carry out the
analogy with the battery, were given a new potential of vitality and
a potential which again lasted through a period of six months, and
through approximately the same number of generations (actually, 198)
(see Fig. 3S, period, August, 1901).
How can the renewal be interpreted? Obviously the change in diet
gave the cells an entirely different assortment of chemical substances,
and it is to this fact that we may attribute the artificial rejuvenescence.
Woodruff found that the same expedient renewed the vitality of his
race of oxytricha, the effect being slower than in the case of para-
mecium. It was also found by Calkins that a change in the salt con-
tent of the usual food media would produce a similar stimulating effect,
and dilute solutions of potassium phosphate were used, the organisms
experimented with being allowed to swim in the solutions for half
an hour (a longer period being followed by death in a few days).
This simple salt, like the beef extract, was enough to renew the vitality,
and the stimulus thus given was sufficient to enable the organisms to
live again in the same medium for another cycle of 193 generations.
The effect of the change on the organism's structure is of interest,
and is represented by Fig. 39. The cell in a depressed condition is
shown on the left; a cell twenty-four hours after treatment is shown in
the centre, where a lighter area in the vicinity of the nucleus will be
noted, the ends meanwhile showing the same densely granular struc-
ture as that of the depressed condition, thus indicating that the organ-
ism is recovering from the disease, if we may so designate its trouble.
It is important, in this connection, to note that the reestablishing of
the normal structure occurs first in the neighborhood of the nucleus,
a fact that indicates that here is the region of greatest chemical activity
in the cell. A cell forty-eight hours after successful stimulation is
shown on the right. These show that the "labile" condition of the
132 PROTOPLASMIC AGE OF PROTOZOA
protoplasm is now extended nearly throughout the cell, the extremities
alone retaining the granular structure of the depressed condition.
After such successful stimulation the digestive processes recom-
mence, the organisms divide, and the division rate, as indicated by the
curve, rises to an average of more than one division per day (see
Fig. 38).
Three times in the history of this paramecium culture were the cells
stimulated to new activity by this artificial means. The first time,
as stated, was after the 200th generation, the stimulant being beef
extract; the second time was after 198 generations more (398th of the
race), the stimulant being beef extract and potassium phosphate; the
third was after about 193 generations more (about the GOOth of the
race). This third period of depression was most interesting, for it was
found that the same stimulants that had been previously used with
success were now without effect; beef and potassium salts of various
kinds were tried in vain, and the final extinction of the race was threat-
ened; indeed, one race, which was called the B series, died out entirely
in the 540th generation. Only six cells were left, finally, for experi-
mentation, but some of these were successfully stimulated by treatment
with an extract of pancreas, which contains many different salts in
solution. The effect of this last stimulation was a renewal of the
vitality, but the potential given to the protoplasm was not so great nor
so clearly defined as in the previous periods of depression, and after
another six months, in which the organisms showed great sluggishness,
the race died in the 742d generation. This fourth cycle is the most
important for our present purpose, since it represents the period of old
age in the protoplasm under observation. The cells divided only 123
times, and toward the end manifested curious and hitherto unobserved
degenerative phenomena, which deserve special attention.
The protoplasm of the cells in this final period of depression had
at first the same appearance as the protoplasm of the organisms at
previous periods of exhaustion; the cell body became granular, the
size decreased, and the general appearance was similar to that which
had been successfully met at previous periods. The same stimulants
were used; the diet was changed for short periods as before; and,
singularly enough, the same effect on the structures of the cell was
produced. The granules disappeared, the nucleus and cytoplasm
appeared perfectly normal, and the organisms were able to take in
food, digest, and assimilate it. The normal size was restored, and it
seemed, from morphological grounds, that the depression period had
been successfully overcome for a fourth time. Still, the cell divisions
were very infrequent and irregular, while the few that did take place
were mostly of a pathological nature, complete fission not taking place,
the result being monsters of different size and form (Fig. 55). The
macronucleus was perfectly normal in the last cells of the race, but the
MORE COMPLICATED LIFE CYCLES 133
micronucleus, which has but little part to play apparently in the
ordinary functions of vegetative life, now appeared enlarged and
vesicular, and entirely different in structure and size from the micro-
nucleus of the ordinary paramecium. The protoplasm was not granu-
lar nor chemically stable, and was apparently as active as ever. Still
the organisms died, and death was not due to infection or disease.
Something in the cells that had been operative before had given out,
and the only part of the cell which had not responded to treatment was
the micronucleus. Here, then, was a pathological condition which
could not be met, and the organisms died.
FIG. 55
A "monster" formed by incomplete division of Paramecium aurelia as an indication of the
exhaustion of division energy. (After Calkin-. >
Was it death from old age that carried off the race under obser-
vation? There seems to be no other alternative to consider, and by
old age we mean the wearing out of an organ and the cessation of a
function. If old age may be thus defined in a simple organism like
paramecium, it follows that three times previously had the race been
weakened by old age, since the organisms were unable to digest and
assimilate food. As soon as this power was restored by artificial means,
old age was overcome and cell division was resumed. The cells would
have died without any doubt had they not been stimulated, so that we
are justified, as I believe, in speaking of this condition of paramecium
as "physiological" old age, which leads to physiological death through
the cessation of one or more of the vegetative functions. It is
obviously death from a different cause that carried off the last cells of
the race, and since the ordinary vegetative functions were apparently
in perfect working condition at this final period, it follows that the cause
of death must be looked for in the cessation of some other than the
ordinary vegetative activities. The history of the micronucleus in
conjugation (see next chapter) shows that this is the organ of the
paramecium cell endowed with the characteristics of the race; in other
words, that it alone of all the structures of the cell, must contain the
134 PROTOPLASMIC AGE OF PROTOZOA
germinal elements. It is to be compared with the germ plasm con-
tained in the germ glands of the many-celled animals, while the macro-
nucleus and the cytoplasm are to be compared with the relatively
much more voluminous somatic tissue of the higher animals. Its
degeneration, therefore, indicates an exhaustion of the potential of
activity of the germinal functions, including the power to divide, and
with this exhaustion comes the death of the race, but death due to
"germinal" rather than physiological exhaustion. While physiological
death may be averted by stimulants of different kinds, germinal death,
at least in the experience of all investigators up to the present time,
cannot be offset, and with this comes the inevitable death of the race
of protoplasm or death from germinal old age. Still paramecium are
plentiful in ditches and ponds, a fact indicating that there is some
natural way in which germinal death can be averted. Here is where
the process of fertilization comes into play, and with fertilization the
protoplasm of an exhausted paramecium is made over into a new
"individual," in the same way that the protoplasm of a germ cell of a
bird, mammal, or man is made over into a new individual.
These various experiments indicate, therefore, that natural death
from old age under the conditions of the laboratory is actually inherent
in protoplasm as little differentiated as in these single-celled animals,
and they fail to confirm Weismann's claim that natural death is a
penalty which higher animals must pay for the privileges of differenti-
ation. They likewise fail to show that natural death by old age is due
to any malevolent action on the part of certain structures of the body,
as Metchnikoff would have us believe is one cause of old age in man.
It is a natural condition of all protoplasm to grow old, and if we find
the phenomenon in the generalized cells of the infusoria, how much
more probable is it in the highly specialized somatic cells of the body.
Each paramecium has a certain allotment of natural life and division.
I have called it the potential of vitality. When this is exhausted under
given conditions the protoplasm dies. It also has a certain allotment
of germ plasm, so that by exhaustion of the physiological potential
it still may retain a certain capacity for cell division, the germinal
potential not being exhausted. It may, therefore, be stimulated by
artificial means. In different kinds of animals and in different indi-
viduals of the same species it is probable that the initial potential
varies, in some representing a longer, in others a shorter, life. In
paramecium and. the protozoa generally we find the greatest relative
germinal potential, but as we go higher in the animal scale the ten-
dency is for the germinal plasm to concentrate in a definite tissue of
cells, the germinal epithelium, while the somatic cells have a corre-
spondingly low degree of germinal plasm. To illustrate, while in all
probability every cell of the paramecium race is capable of becoming
or of giving rise to a germ cell, the same is not true of the animals next
MORE COMPLICATED LIFE CYCLES 135
higher in the scale of animal forms, such as the hydroids and jelly fish.
A very small fragment, indeed, of a hydra will reproduce the entire
animal, but one cell of the hydra will not do so; each of the two germ
layers must be represented in the small piece. In worms and in still
higher forms of the invertebrated animals this power to regenerate
the entire animal decreases pari passu with the differentiation of the
animal, and although not absolutely true, it may be stated in general
that the higher the differentiation the less is the power to regenerate
lost parts. In other words, something is lost from the highly differ-
entiated somatic cells, something which is segregated in the germ cells
and something which we find in each cell of the lower forms of inver-
tebrates, but most widespread in the unicellular protozoa. It has to
do with the racial characters of the organism, that is, with the germ
plasm. In hydra and in some of the worms the cells retain enough of
this germ plasm to reproduce the entire organism, but in the mammals
the somatic cells have so nearly lost this germinal power that regen-
eration of an organ or limb is no longer possible, and is limited to the
mere repair of an injury. In this sense, therefore, Weismann's claim
that natural death is the penalty higher animals must pay for differ-
entiation is justified.
The so-called "noble" cells (Metchnikoff) of the body, that is, the
cells of brain, liver, kidney, and other important centres of physio-
logical activity, are somatic cells in which this regenerative power is
reduced to a minimum; the potential of germinal activity in them is
less than in connective-tissue cells, and after an injury their power of
repair is less than that in connective-tissue cells. This is seen in the
fact that a wounded epithelium is repaired less by the proliferation of
the neighboring epithelial cells than by the adjacent connective tissue,
and the "scar" tissue which results is composed of these "baser"
cells.
Like the physiological activities of paramecium, all somatic cells of
the body are endowed with a certain potential of physiological activity,
and like paramecium, when exhausted the particular function of those
cells ceases; they have reached the limit of their activity, and when
enough of them are so worn out a general impairment of the body
functions results. This condition of the exhausted cells mav be
t/
relieved by stimulants which, we imagine, may come from the general
body itself, or from artificial treatment, as in the case of paramecium.
But we have no reason to believe that in the human somatic cells this
stimulation can be repeated indefinitely. If in the generalized proto-
zoon there comes a time in which the potential of germinal activity
of the cell gives out, how much more probable would it be that the
somatic cells, with their low potential of germinal activity, likewise
fail to respond to the stimulants. Unable to reproduce by division,
with their potential of physiological activity reduced to a minimum,
136 PROTOPLASMIC AGE OF PROTOZOA
these "noble" cells atrophy, their positions being taken by the con-
nective-tissue cells.
Here, then, is the condition of old age; the somatic cells lose what
germinal power they possess through physiological usury; their
potential of physiological activity is greatly reduced; the function of
the organ is impaired and the entire organization correspondingly
weakened; the useless cells are attacked by phagocytes (?) (Metch-
nikoff), and they are replaced by the non-functional connective tissue.
Old age, therefore, is a biological condition of protoplasm, char-
acteristic alike of the lowest protozoon and the highest mammal.
Its progress is inexorable, its advent inevitable, while the only per-
manent plasm is that which has the highest power of germinal activity,
and this is contained in the germ cells. Here, however, that other
unfathomable mystery of life — fertilization, or its equivalent — is
essential for the proper stimulation of the latent developmental activity
and the distribution of the somatic and germinal cells in a new indi-
vidual organism. How this occurs in paramecium and other protozoa
will be shown in the following chapter.
While the experiments on the lowest animals show that old age is a
necessary condition of vitality and inherent in all protoplasm, it does
not follow that man or any other animal has made the best possible
use of the vital endowments. It may very well be, as Metchnikoff
maintains, that the traditional three score and ten is not an adequate
allowance for man, and it is conceivable that the normal length of life
may be increased by careful living to four or five score of years or
more. If there is a certain amount of vitality upon which one can
draw, it is obvious that the faster it is dra\vn the shorter will it last,
and conversely, the more saving one is by careful living, the longer will
it endure. Only one thing are we sure of, and this is that somatic
vitality, whether in protozoon or man, is a peau de chagrin which con-
stantly diminishes with use until finally nought is left.
CHAPTER IV.
CONJUGATION, MATURATION, AND FERTILIZATION.
IN the preceding chapter it was shown that the protoplasm of which
a protozoon is composed, as demonstrated by continual observation,
gives evidence of advancing age no less surely than does a many-
celled organism. It was shown further that the advance from youth
to age in such protoplasm is indicated by more or less well-marked
physiological and structural changes, the former being characterized
by the onset of a noticeable "period of depression," the latter by
morphological changes, of which the most important is the develop-
ment of a well-defined germ plasm. Experimental work on free-living
protozoa has shown that the cells die a natural death during such
periods of depression, but also, in some cases, that these periods may
be overcome by artificial stimulation. They show, also, that a final
depression, distinguished from ordinary physiological or metabolic
weakness, and characterized by loss of the germinal protoplasm, could
not be thus overcome. Apart from death by violence, therefore, the
free-living protozoon may lose its life by what Hertwig calls "physio-
logical death" at some period of physiological depression, or by
"germinal death" occurring with the exhaustion of the division energy
and degeneration of the germ plasm.
Notwithstanding the many natural enemies which a paramecium
or other protozoon has, and in spite of the fact that if it escapes such
enemies it may die from physiological or germinal "old age," it still
exists in more or less abundance in natural waters, and will probably
continue to exist in the future. In natural waters, salts, changes in
the local environment, and other external causes undoubtedly tend
to stimulate lagging physiological activities and to do on a large scale
what we have done in the laboratory; but in nature, as in the labor-
atory, such means of rejuvenation probably have their limits, and we
must turn to other vital activities for an explanation of the continued
existence of these living cells.
There is little reason to doubt that the explanation lies in the
secrets of the same mysterious and at present unfathomed phenomena
which underlie the newborn infant; which are repeated in all living
things with the creation of a new individual; and which are univer-
sally regarded as among the subtlest of vital activities. These
secrets are deeply hidden in the phenomena of fertilization, and
philosophers today, like the ancients, have only speculations to offer
138 CONJUGATION, MATURATION, AND FERTILIZATION
in explanation. The phenomena of conjugation and maturation of
the germ plasm which accompany fertilization are more easily inter-
preted, for they are largely matters of observation and deduction. In
protozoa we have a particularly rich field for investigation of these
problems, for the union of germ plasms is accompanied by phenomena
of such relative simplicity that they are more easily observed, con-
trolled, and interpreted than with metazoa.
In interpreting the phenomena of fertilization of protozoa we are
in accord with those naturalists who, since the time of Harvev, have
*/ 7
advocated some "dynamic" theory or other. (See Wilson, The Cell,
p. 178.) In recent times this explanation is usually based upon the
facts of decreasing vitality with advancing age, and, as expressed by
Hertwig, fertilization is the means of restoring to a labile condition
the protoplasm which, with continued physiological activity, has
become stable in physical and chemical equilibrium. It is, therefore,
essentially a process of rejuvenation.
Opposed to this point of view are those who, with Weismann and
his followers, maintain that protozoa do not die of old age, and that
conjugation with fertilization is an incidental occurrence in the life
of a race. Fertilization, in higher forms, is a means of bringing about
variation within the species, and at the same time a means of keeping
the species true to its structural type.
Weismann still maintained his contention in regard to the immor-
tality of infusoria after Maupas' classical experiments had demon-
strated old age, and held that conjugation does not alter the indi-
viduality of the cells, since that individuality is retained after con-
jugation. Such a point of view would seem to be, however, merely
an expedient to save the argument, for the essential part of the fer-
tilized protozoon, like the metazoon, results from the union of two
germ plasms, the protoplasm resulting from this union being a new
individual in both cases. Like the metazoon, the protozoon is physi-
cally immortal only in the same sense of continuity of the germ plasm,
for, with each fertilization there is a re-organization of the protoplasm,
new chemical and physical combinations, and new individuality.
There is no difference in kind in protozoa and metazoa, only a differ-
ence in degree.
The essential feature of fertilization appears to be the union of two
masses of chromatin. WTe can only conjecture as to the significance
of such union, but whatever hypotheses are framed to explain it, they
must take into consideration a great variety of conditions under which
the phenomenon is manifested. It is quite evident that complicated
processes in metazoa are the highest and last steps, so to speak, in the
elaboration of this universal biological phenomenon, and it is probable
that they differ only in degree from the lowest and most primitive
steps shown by the simple syngamic processes in protozoa.
FERTILIZATION BY AUTOGAMY
139
In this lowest group of animal forms we find every grade in com-
plexity in the sequence of syngamic processes, from those of undoubt-
edly primitive character to processes quite as complicated as in many
metazoa. We may pass from cases where only the one cell is involved,
fertilization taking place by union of two chromatin masses derived
from the same primary nucleus (autogamy) ; through cases where the
chromatin has had the same ancestry but is derived from different
cells (endogamy); to cases where sex differentiation and maturation
processes are quite as complicated as in higher animals and plants
(exogamy). With our present incomplete knowledge of the life his-
tory of lower forms, no great value is to be attached to such a classi-
fication, but its main purpose is served in providing a convenient
frame for attaching the manifold variations presented by the phe-
nomena of syngamy in protozoa.
A. FERTILIZATION BY AUTOGAMY (AUTOMYXIS, HARTMANN).
In the primitive forms of protozoa, as in those of plants, this method
of fertilization is widespread, and whatever may be the significance,
its wide distribution among the most diverse of these lower forms and
under the most varied conditions of life, indicates a natural and simple,
if not primitive, fertilization phenomenon. Even in these more primi-
tive cases, however, grades in complexity of the processes involved
are to be observed, and the transition from autogamy to endogamy
FIG. 50
. •••'•*.',
Ameba Umax budding, division, and idiochromidia forming stages.
may occur in the same group. So far as the protozoa are concerned,
the most primitive methods are to be found among the free and
parasitic amebse, but even here there are indications of a more
advanced process.
The main element that enters into the complexity of these more
primitive cases of autogamy is the formation of so-called secondary
nuclei from idiochromidia and the differentiation of somatic and
140 CONJUGATION, MATURATION, AND FERTILIZATION
germ nuclei. But in the simplest form such complication is not appar-
ent, for the idiochromidia becomes segregated in masses without
nuclear walls, and these masses fuse. This is the case in Ameba
Umax, a small free-living ameba common in ponds or decaying matter.
It may be easily cultivated on artificial culture media, such as agar,
in connection with various types of bacteria serving as food. Under
normal conditions of temperature, salt contents, etc., the amebse
reproduce by simple division and by budding (Figs. 56 and 57).
Under certain conditions of the cultures, conditions which have not
been thoroughly investigated, the organisms encyst and remain so until
transplanted to new culture media. Occasionally, and again under
conditions unknown, they form sexually mature cells, but this latter
condition may also be brought about by suitable temperature changes.
FIG. 57
''
•t
Ameba limax. Nucleus in upper cell in full mitosis; in lower cell (right) in
anaphase of the mitosis.
Syngarnic nuclear union is always preceded by idiochromidia
formation within the cyst, but the formation of this material does not
necessarily imply sexual maturity. In all cultures, after a time, the
nucleus, which consists of a central karyosome and peripheral chro-
matin, gives rise to idiochromidia by dissolution of the peripheral
portion. The idiochromidia become scattered throughout the cell,
and, under ordinary conditions of the culture, are evenly diffused. If
the cultures be subjected to rapid changes of temperature, the idio-
chromidia may be caused to accumulate in masses about the periphery
(Fig. 51, p. 122). Sixteen of these masses are usually formed, and
then by fusion two by two the number is reduced to eight. This
fusion possibly represents a sexual union, or, more strictly speaking,
takes the place of sexual union, being the fusion not of secondary
FERTILIZATION BY AUTOGAMY
141
nuclei, but of masses of idiochromidia which in other protozoa become
differentiated into such nuclei. The karyosome and some of the
peripheral chromatin form a degenerating "somatic" nucleus which
takes no part in the later processes.
The further fate of the encysted form thus brought about has not
been followed, but in Entameba histolytica, according to the observa-
tions of Schaudinn and. later, of Craig ('08), such a stage is followed
by spore formation. Schaudinn ('03) observed, and his observations
have been confirmed in every detail by Craig ('08) upon living and
fixed material, that in this ameba the nucleus fragments into idio-
FIG. 58
SsSfesk^...,, -
^'-K:&f ^
Entameba histolytica. (After Craig.) A, organism showing rods and granules of chro-
matin in the nucleus, vacuole with some stained substance, and dense ectoplasm; B, the
chromatin of the nucleus passing into the cell plasm, where it is distributed as chromidia, shown
in C; D, aggregation of chromidia to form secondary nuclei (see Fig. 51, of Ameba limax); E,
"spore formation" by budding; F, spores of Entameba histolytica as seen in feces.
chromidia (chromidia) which collect in masses at the periphery, and
these masses, with some cytoplasm, are protruded from the surface as
buds. The buds become covered with a hard and resistant membrane
which is so deeply colored by the intestinal fluids that further internal
processes could not be followed (Fig. 58). Neither Schaudinn nor
Craig observed union of these idiochromidia masses, and the resem-
blance to Ameba Umax can only be inferred from the similarity of
preliminary processes.
In the closely allied forms, Entameba coli, Entameba muris, and
Ameba proteus, the process of autogamy is somewhat more compli-
142 CONJUGATION, MATURATION, AND FERTILIZATION
cated because of the formation of definite nuclei from idiochromidia,
and because of so-called maturation divisions of these nuclei before
union (coli and muris').
Here, again, the early observations of Schaudinn ('03) upon Enta-
meba coli have been fully confirmed by Craig ('08) and their conclu-
sions have been fully supported by Wenyon ('07) in connection with
E. muris, a closely allied intestinal parasite of the mouse, and by
Hartmann ('07) upon Entameba tetragena in man. Schaudinn's
excellent description was not accompanied by illustrations, but the
FIG. 59
!
Autogamy in Entameba (ameba) muris. (After Wenyon.) A, ordinary ameboid form
with nucleus in process of division; B, ordinary individual encysted and with one nucleus;
C, nucleus divided; D, ehromatin has passed into cytoplasm, leaving no definite nuclei in
the cyst; E, two small nuclei reformed from the scattered ehromatin, other ehromatin
residue and food remains are being voided; F, two nuclei and so-called "reduction" bodies
remaining in cyst; G, a cyst with two spindles, food remains, and some waste ehromatin;
the two spindles give rise to four nuclei which conjugate two and two; H, cyst with two
recently conjugated nuclei which next divide to form four (/) and finally eight («7) spore
nuclei.
corresponding stages may be illustrated by Wenyon's figures of E.
muris. Here and in E. coli the organisms encyst after a period in the
intestine; the nucleus of the encysted cell divides (Fig. 59, A, B, C)
and the cell body indicates a corresponding division into two parts,
but the connections between these parts is never lost, and we are thus
dealing at the beginning of fertilization with a binucleated cell. The
nuclei next fragment, forming idiochromidia, from which two much
smaller nuclei (D, E) are formed by segregation of the scattered
granules. Each nucleus then divides twice, one-half of each division
forming nuclei which degenerate in the cell (reduction nuclei) and two
FERTILIZATION BY AUTOGAMY 143
fertilization nuclei finally result, each of which divides again, this time
with the long axes of the spindle parallel with one another; the final
daughter nuclei which are formed fuse two by two, the cleft in the
cell disappears, and an encysted ameba results with two fertilized
nuclei. Each of these nuclei divides twice, and eight spores are formed
about the eight resulting nuclei. Hartmann ('07) mentions a similar
process of autogamy in the case of an ameba from the frog and in one
of the free-living Umax forms, but describes a quite dissimilar process
in Entameba tetragemi.
In these cases, therefore, there is a concentration of the idiochro-
midia in secondary nuclei which then undergo so-called maturation
processes. A still greater complexity is shown by Ameba proteus,
where, according to the observations of Calkins ('07), there is no
formation of diffused idiochromidia, but the secondary conjugating
nuclei are formed directly from chromatin granules within the primary
nuclei, which, prior to this stage, had divided repeatedly until about
70 are present. These secondary nuclei next fuse two by two in the
cytoplasm and give rise to spore-mother cells (sporoblasts), of which
there may be as many as 250 within one parent organism (Fig. 60),
while at least one of the primary nuclei remains unused and finally
degenerates in the cell. In Ani-bn proteux, therefore, the organism
forms not one spore-mother cell, as in the parasitic amebse, but many
such spore-forming centres.
In all of the above cases of autogamy, we have to do with the fusion
of chromatin materials which at one time or another were parts of the
same nucleus of the same cell. In all of them, with the exception of
the free-living Ameba Umax and the parasitic Entameba histolijtica,
where further observations are much to be desired, the union of the
"gametic" nuclei does not take place until after two or more divisions
of the primary or secondary nuclei; that this fact has some signifi-
cance cannot be doubted, but there is no inkling as to what the
significance is, unless, indeed, it is evidence of an earlier gamete-
forming stage, autogamy thus being, as Hartmann ('09) suggests, a
degenerative rather than a primitive phenomenon.
With the myxosporidia the process is much more complicated,
involving the formation of vegetative and germinal nuclei. It is well
described by Schroder ('07) for the case of a parasite of the seahorse,
Spheromyxa labrazesi, where the multinucleate ameboid body of the
parasite appears to contain two kinds of nuclei distinguished by size
and structure. Within this protoplasmic body small areas become
differentiated from the surrounding matrix. These areas character-
istic of the myxosporidia, termed pansporoblasts (Gurley), contain
two nuclei, one of each kind (Fig. 61, K, Q). With development of
the pansporoblast each nucleus divides in such order that seven
daughter nuclei finally result from each, the fourteen nuclei being
144 CONJUGATION, MATURATION, AND FERTILIZATION
characterized as follows: Two are destined to degenerate as "reduc-
tion nuclei," four become the centres of shell formation of the spores,
four become centres of pole capsule formation, and four remain as
FIG. 60
< ~>
C ,'
* . *
*»•» '
0
«
I
* *
_
Autogamy in Ameba proteus. In upper figure secondary (gametic) nuclei are shown
emerging from the primary nuclei. In central figure is pictured the union of gametic nuclei
together with some undeveloped ones in a primary nucleus. In lower figure is shown the
mass of sporoblasts which develop from the fertilized gametes. (After Calkins.)
FIG. 61
G
"r*5
\ fi%YT
Conjugation in myxosporidia. .-1 to /, Myxobolus pfeifferi, Th. (after Keysselitz); K to <2,
Spheromyxa labrazesi, Lav. and Mes. (after Schroder); .4, B, formation of gametoblasts;
C to G, union of sporocysts and multiplication of nuclei; H, young sporoblast with polar
capsules forming and gametic nuclei not yet united; /, spore with capsules (not filled in) and
gametic nuclei united; K, young pansporoblast of spheromyxa, with dimorphic nuclei; L, pan-
sporoblast with fourteen nuclei; M , pansporoblast divided into sporoblasts, each with two
pole capsules (p), four globules present (x) and with two central reduction nuclei; N, sporo-
blasts having two shell nuclei (s), two polar capsules, each with a nucleus and two germ nuclei;
O, young spore, shell nuclei disappeared, capsule (p) and germ nuclei (g g) compact and lying
in a row; P, same, with union of gametic nuclei in the sporoplasm; Q, same, ripe spore with
T>r>loi- ,..i,,ii.loj onrl anni-nnlacm
146 CONJUGATION, MATURATION, AND FERTILIZATION
germinal nuclei. The sporoplasni of the pansporoblast divides into
two parts (A/), the sporoblasts each containing six of the fourteen
nuclei, while the reduction nuclei remain outside. The six nuclei in
each sporoblast are thus differentiated into somatic and germinal
nuclei, four in each case going into somatic modifications of the spores
(shells, pole capsules, and threads), and two, presumably one of each
of the original two kinds, remaining as pronuclei (AT, 0, P). After
the spores are mature and only traces of the somatic nuclei remain,
these germinal nuclei fuse, so that the spores, when taken into a new
host, are uninucleate (P, Q). If, as Schroder suspects, the multi-
nucleate ameboid adult is formed by fusion of two or more cells, then
such a process would be like that of the mycetozoa and exogamic
rather than autogamic (p. 150). Observations, however, are wanting
to confirm this supposition, the many obstacles in the way of observa-
tions to this end making confirmation extremely difficult, but the
other matters relating to number of nuclei formed, their fate, etc.,
are well corroborated (see actinomyxidee, and Myxobolus pfeifferi,
Fig. 61, A, /).
B. FERTILIZATION BY ENDOGAMY ( PEDOGAMY, PROWAZEK).
The transition from autogamy into endogamy, whereby the sexual
union is between descendants of the same original cell, is marked
by numerous intermediate stages which are sometimes described as
autogamous. The difference is largely one of degree only, and among
these intermediate forms, at least, to include them under one or the
other heading is mainly a matter of expediency. The principle under-
lying the distinction is, however, of considerable theoretical importance,
and the difference which exists between the partially divided cell in
Entameba coli (see above) and the union of separated parts within
the same parent cell (see myxobolus and other cases below) is a differ-
ence which becomes magnified in higher types into all of the differential
characteristics which distinguish exogamic processes.
The transition from autogamy to endogamy is well shown in myce-
tozoa and myxosporidia, wyhere, as may be seen, the difference is only
one of degree. There are numerous examples of the phenomenon,
from which we select a fewT showing different grades in complexity, and
it should be noted that the same arguments as to the possible exo-
gamic nature of. the processes apply here among the mycetozoa and
myxosporidia as well as in the cases cited above.
Keysselitz ('08) has quite recently described the process of pan-
sporoblast formation in a myxospore (My.robolus pfeifferi) which
differs in one important respect from the process in spheromyxa.
Here the pansporoblasts which Keysselitz names the " propagation
FERTILIZATION BY ENDOGAMY 147
cells" arise in the plasm of the adult organisms in the. same way as in
other myxosporidia, but the nuclei and with them the cell body of the
germinal area divide (Fig. 61, A, B, C). These propagative cells
later unite two by two, and are separated only by a thin cell wall,
which later disappears. Within this united mass the nuclei divide
until there are fourteen, as in spheromyxa; their formation differs in
some unessential details, but their fate is the same in both cases, two
germinal nuclei finally resulting which conjugate in the mature spore
(Fig. 61, D, /).
Caullery and Mesnil ('05) have carefully described the process of
spore formation in spheractinomyxon, one of the actinomyxidae, an
aberrant group of myxosporidia named by Stole ('90). Here the
process is a little more complex than in the case cited above, but it
agrees in essence with that described by Keysselitz. The youngest
stages are found as intestinal parasites of the tubificid worm clitellio,
and are either uninucleated or binucleated. The observers are inclined
to believe that the uninucleated stage comes first and that it repre-
sents, possibly, the youngest form, or sporozoite, and that the binu-
cleatecl stage represents the first division of this nucleus. If this pos-
sibility is not well founded the fertilization process here must be taken
out of the present category. Whatever may be the origin of these
nuclei in the binucleated stage, they divide, and two of the first four
nuclei formed become somatic nuclei and are connected with the
formation of the cyst wall, within which the further processes take
place. With the division of the nuclei the cell body also divides until
there are sixteen independent, nucleated subdivisions. These unite
two by two, the process of fertilization being thus affected, and eight
spores ultimately result. The interpretation of this interesting case,
as Caullery and Mesnil point out, depends entirely upon the mode of
origin of the early binucleated stage. If these two nuclei represent a
plastogamic union of gametes, as Leger ( '04) believed to be the case
in an allied form triactinomyxon, then the process might be one of
exogamy, but, as Caullery and Mesnil contend, this would involve two
sexual processes in the life cycle, which seems improbable. The
subject certainly needs further study.
The endogamous process in the mycetozoon Plasmodiophora
brassier is somewhat less complex than in the forms just described.
Here, as Prowazek ('05) has shown, the protoplasm breaks down
into many centres, each containing a sexual nucleus, and these centres
—gametes — fuse two by two, a spore wall being formed about each
copula (Fig. 62).
In the majority of parasites the probability of endogamous fertiliza-
tion is readily apparent, and the fusion of gregarines, for example,
two by two, may be a union of cells from the same sporocyst or dif-
ferent sporocysts. In such cases it is impossible to state definitely,
148 CONJUGATION, MATURATION, AND FERTILIZATION
therefore, whether the process is endogamous or exogamous, and the
same obscurity obtains in the union of free flagellated or ciliated
gametes. In some cases, on the other hand, there is no doubt about
the union of nearly related cells. Schaudinn ('94) described the
union of gametes of the same brood in Hyalopus dujardinii, and it is
proved in the case of Basidiobolus lacerto' by Loewenthal ('03); in
Actinospherium eichhornii by Hertwig ('98); in yeasts by Guillier-
mond ('02), and in cultures of free-living infusoria (Paramecium
aurelia^) by Calkins ('02).
FIG. 62
E
Endogamy in Plasmodiophora brassicse. (After Prowazek.) .4, portion of plasmodium
showing ordinary vegetative nuclei; B, reconstruction of the gametic nuclei; C, division of
same; D, union of gametes formed about gametic nuclei; E, F, stages in fusion of nuclei and
formation of the spore.
In basidiobolus, an intestinal fungoid parasite of the turtle, the
organism forms straight or branched hyphre composed of sister cells
lying end to end, and at maturity two adjacent sister cells conjugate,
a process recalling conjugation among the lower plants (conjugate,
diatoms, etc.). In actinospherium the phenomena of fertilization are
much more complex and have been made the subject of careful study
by Hertwig ('98). The first evidence of the process is the encystment
of the adult organism and excretion of waste matters contained in the
protoplasm. The many nuclei of the ordinary forms are here reduced
to about 5 per cent, of the total by a process of fusion and absorption
in the protoplasm, and after this has occurred the mother animal
fragments into as many daughter cysts (cytospores No. 1) as there are
FERTILIZATION BY ENDOGAMY
149
nuclei remaining (from one to twenty). Each of these daughter cysts
secretes a gelatinous envelope about itself, and the nucleus of each
divides by mitosis. This mitotic division is followed by division of
the cytospore into two daughter cells (cytospores No. 2), and in these
there are two successive nuclear divisions resulting in four nuclei.
Three of these nuclei degenerate ("polar bodies") and one remains as
a pronucleus. The cytospores of the second order next unite again,
reforming the cytospores No. 1, and the fertilization is completed by
FIG. 63
B
D
Endogamy in Actinospherium eichlumiii. (After Hertwig.) A, two gametes (cytospores
No. 2), resulting from the division of cytospore No. 1; B, both polar bodies are formed in
the right gamete, the second one forming in the left gamete; C, later fusion of the gametes,
the nuclei now uniting and the polar bodies being absorbed at p; D, young actinospherium
leaving cyst.
fusion of the pronuclei. Thus, by a process of union of sister cells
(endogamy) fertilization is brought about after complicated matura-
tion processes (Fig. 63).
Finally, in Paramecium auniia, Calkins ('02) found that cells
removed by not more than eight or nine divisions from a common
ancestral cell would conjugate normally, and that such fertilized cells
were able to live through an entire cycle of cell generations (379
actually). Conjugation between closely related forms, therefore, is
quite as potent as between those of diverse ancestry.
150 CONJUGATION, MATURATION, AXD FERTILIZATION
C. FERTILIZATION BY EXOGAMY.
It is not at all improbable that some of the cases that have been
described as autogamous may be in reality exogamous. In the multi-
nucleate forms, in order to decide such a matter it is necessary not only
to observe the union two bv two of such nuclei, but their mode of
*.•
origin must also be known. Thus, in the mycetozoa the plasmodium
from which the sexual nuclei are generated is formed by the fusion of
two or more ameboid cells at an early period of development, hence
the nuclei which later fuse may be derived from different ancestral
cells, and such fusions would not be examples of autogamy, but of
exogamy. In some cases of sexual reproduction among myxosporidia
(notably in the actinomyxida? and possibly in Spheromyxa labrazesi) a
similar derivation of the conjugating nuclei has been suspected. Such
cases of possible exogamy are well illustrated in almost any of the
higher types of mycetozoa, and one such has been well described by
Kranzlin ('07) for Arcyria cinerea and Trichia fallax, and by Olive
('07) and Jahn ('07) for Ceratiomyxa hydnoidcs. Without going into
the details the process may be summarized shortly as follows: The
young ameboid or flagellated spores, after assumption of the ameboid
state, fuse into plasmodia of considerable size. Cell boundaries are
entirely absent and the nuclei have an opportunity to become thor-
oughly mixed in the protoplasmic streaming. Fructification ensues
after a longer or shorter vegetative life and in these fruiting bodies,
or before their formation, the nuclei unite in pairs, the union being
followed by synapsis and double divisions and formation of the ripe
spores.
A somewhat similar union has been described by Hartmann and
Nagler in the case of Ameba diploidea, H. and N., where the organism
is binucleated throughout the ordinary vegetative stages and until the
period of maturity, when two cells place themselves side by side within
a common cyst. The two nuclei of each cell then unite, forming a
single synkaryon in each cell. The two adjacent cells finally unite
by dissolution of the cell walls that separate them, and the recently
fertilized nuclei, after some very questionable so-called maturation
processes, assume the characteristic position of the vegetative forms.
Here, then, if this observation is accurate, there is an exogamie fertili-
zation, but the end stage does not occur until the next following period
of maturity (Fig. 64).
In the majority of protozoa the germ of the new individual, as in
metazoa, is produced by the union of cells from different ancestors,
and these cells, for the most part, show characteristic evidences of the
period of maturity. In some cases there is but slight difference, if
any, between the conjugating cells and the normal ones, the conditions
FERTILIZATION BY EXOGAMY
151
of maturity manifesting themselves in other ways than by size changes.
In other cases the conjugating cells are reduced in size, but without
differences of a sexual character, and in still other cases there is a
C
FIG. 64
Ameba diploidea, Hartmann and Niigler. A and B, ordinary individuals at early and
mid-phases of division; C, D, E, union of two individuals within cyst, and fusion of the
double nuclei in each cell; F, ameba after fusion of cell bodies, now with two nuclei, creep-
ing out of cyst.
152 CONJUGATION, MATURATION, AND FERTILIZATION
marked sexual dimorphism, the manifestations of maturity showing in
greatly reduced size and relatively great kinetic energy on the one
part, and increased nutritive potential and relative sluggishness on
the other. For purposes of description these various conditions are
usually grouped under the headings isogamy (fusion of equal gametes)
and anisogamy (fusion of dissimilar gametes).
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FERTILIZATION BY EXOGAMY
153
1. Isogamy. — Not only may isogamous conjugation occur bet ween
full-sized and reduced-sized individuals, but among the former there
may be a further difference in that the conjugating cells do not fuse
to form a zygote, but separate after a few hours (copulation). This
process is particularly characteristic of the infusoria and is not met
with elsewhere.
FIG. 66
Copromonas subtilis. (After Dobell.) .1, normal adult cell before division, from life; B.
cells in conjugation, one flagellum being withdrawn; C, fusion, first stage in "nuclear reduc-
tion;" D, heteropolar division of nuclei for second "reducing division;" E, fusion of nuclei
and formation of cyst; F, fertilized cell in permanent cyst.
(«) The Union of Full-sized Cells. — With the exception of the lower
flagellates, there are few instances of conjugation among full-sized
individuals. It has been described by Schaudinn ('96) in the case of
the heliozoon Actinophrys sol (Fig. 65), where the two cells fuse after
a preliminary process of maturation. Here there is little change in the
normal aspect of the two conjugating cells beyond the withdrawal of
the pseudopodia and secretion of a protective cyst. So, too, among
some of the flagellates there is little difference in the gametes from the
normal. In Bodo saltans (Dallinger) they are all alike, while in Copro-
monas subtil is, according to Dobell ('08), one of the two cells is absorbed
in the other, and its flagellum is lost, while the flagellum of the other
154 CONJUGATION, MATURATION, AND FERTILIZATION
serves for locomotion (Fig. 66). So, too, in Dallingeria drysdali one
of the conjugating gametes has three flagella, while the other has only
one.
Analogous processes occur in Lamblia intestinalis (see Schaudinn,
1903), Hexamitus intestinalis, and among many of the phytoflagel-
lates, where size difference, however, appears to be facultative. In a
number of other cases, however, the adult form is lost during the
period of sexual maturity, the organisms becoming ameboid or losing
their characteristic motile organs. Thus, in Cercomonas dujardinii
and in Tetramitus restrains (Fig. 67) the ordinary firm contour of the
body is lost and it becomes highly plastic and changeable in shape,
although in the latter the anterior end with the four flagella does not
materially change in character until fusion of two cells is well advanced.
In Trichomonas intestinalis, on the other hand, the flagella are dis-
carded and the body becomes ameboid before fusion (Schaudinn,
1903), a condition in which, as Schaudinn observes, it is often difficult
to distinguish the flagellate from intestinal amebse.
(6) The Union of Diminutive Cells. — There appears to be no hard and
fast line between the phenomenon of union of adults and of smaller
cells, for there are cases, especially among the phytoflagellates, where
a larger cell may unite with one similar to itself, or with a smaller one,
or two smaller ones may unite, and these, in turn, may be similar or
dissimilar. Such facultative differences are rarely met with among
the animal flagellates, and one consistent rule is usually followed. The
union of reduced or diminutive cells is very rare among ciliates, but
an interesting exception is the case of Opalinaranarum, where, accord-
ing to Neresheimer ('07) the gametes are minute ciliated cells. On
the other hand, it is quite common among the rhizopods and seems
to be the rule among the foraminifera, but in many cases, as, for
example, among the radiolaria, the diminutive cells are at the same
time dissimilar, so that they do not properly come under the heading
of isogamy. These differences, however, are often so minute that no
great value can be placed upon such an artificial distinction.
Very frequently these diminutive gametes are totally different from
the parent cell in mode of locomotion, the rhizopods often forming
flagellated gametes which conjugate, the copula developing into the
ordinary form. This is the case in Polystomella crispa (see Fig. 52,
p. 123), and in Trickospherium sieboldi, Schaudinn ('03); in Pseudo-
spora volvocis, Robertson ('05), and in other sarcodina. In other cases
an ordinarily motionless form like Gregarina ovata (Schnitzler, '05)
and some species of monocystis produce ameboid isogametes. .
A very interesting case of isogamy has been recently described by
Leger ('07) in Ophryocystis mesnili, one of the schizogregarines.
Here two cells unite in accouplement, as Leger terms it, a characteristic
preliminary union of two gregarines (pseudoconjugation) before
FERTILIZATION BY EXOGAMY
155
formation of the gametes. So-called processes of reduction occur in
each of the nuclei, and a mature nucleus is formed in each cell which
becomes surrounded by protoplasm very much as in the case of
a myxospore pansporoblast (Fig. SO, p. 190). These two gametic
areas then fuse, forming a zygote or copula inside of the joined
gregarines, and within this copula the sporozoites are developed, while
the surrounding parent cells degenerate and die.
FIG. 67
D
\J
Different stages of the flagellate Tetramitus rostratus, Perty (Stein). Ordinary vegetative
individuals (A, B, from side and front) reproduce asexually by longitudinal division. They
ultimately become plastic (C) and miscible, and two individuals upon meeting (D) fuse.
The copula secretes a membrane, and its protoplasm fragments into hundreds of spores, (E)
which quickly grow into the parent type (F , G, H).
Such a condition is perhaps to be traced back to the process of
gamete formation in other types of gregarines, where, as in Monocystis
ascidioB, the two organisms unite in couples and give rise to numerous
minute gametes which move by ameboid movements through the liquid
156 CONJUGATION, MATURATION, AND FERTILIZATION
of the common parental cyst, the gametes from one cell ultimately
meeting and fusing with those of the other (Fig. 75, p. 181).
If, in cases like the preceding, the coupled cells should separate, the
process would be analogous to that characteristic of the infusoria, and
such processes may give a clue to the explanation of the highly enig-
matical processes in the latter group, where copulation, including
mutual fertilization, takes the place of gamete formation. A typical
example of this type of isogamy is that of Paramecium aurelia (cauda-
tum), which may be briefly outlined as follows:
A culture of Paramecium aurelia can be easily prepared in the
laboratory by seeding a hay infusion with a dozen or more cells from
pond water. After some weeks they will have accumulated in great
numbers, and quantities of conjugating forms may be obtained by
removing them to watch glasses. Pearl ('07) has shown biometrically
that the "conjugating population" consists of individuals of measur-
ably smaller size than those of the usual pond water. There is also a
difference in the physical and chemical make-up of the cells, by which
the protoplasm becomes much more sticky, so that two individuals
upon meeting frequently fuse at any point, but this extremely miscible
condition is probably evidence of physiological weakness indicative
of old age, and represents an excess of the conditions under which
conjugation is possible.
The union of the two paramecium cells is apparently the signal for the
beginning of the maturation processes of the nucleus (Fig. 68). In
many egg cells of metazoa, and in all spermatic cells, these processes
precede union, showing that they are more generally phenomena of the
ripening or maturity of a cell than phenomena induced by cell union, as
in paramecium. At the outset the two organisms are more loosely
attached, so that forceful ejection from a pipette is sufficient to separate
them. After twelve hours' union, however, the attachment is so firm
that no amount of force will break them apart without killing one or
both. Such forcibly separated conjugants are by no means without
vitality, five out of twelve which were followed in cultures continuing
to live and divide, one being followed through more than 158 genera-
tions before it was abandoned.
The normal course of conjugation requires from eighteen to thirty
hours, according to the temperature, and during the process the
micronucleus of each cell divides twice; one of the four cells in each
case then divides again into dimorphic nuclei. One of these nuclei is
smaller than the other and acts as a spermatic or wandering nucleus,
while the other remains in the parent cell. Each cell receives a wan-
dering smaller micronucleus from the other organism; this fuses with
the larger micronucleus to form the fertilization nucleus of the new
individuals. Each fertilization nucleus then divides three times in
quick succession, and eight micronuclei are formed. Four of these
FERTILIZATION BY EXOGAMY
FIG. 68
157
Conjugation of Paramecium aurelia.
158 CONJUGATION, MATURATION, AND FERTILIZATION
begin to swell and to metamorphose into four new macronuclei, while
four remain as micronuclei. In the meantime, the two conjugating
cells separate soon after the interchange of micronuclei, and the pro-
cesses of reorganization are carried out independently. The old
macronucleus begins to disintegrate by first forming a skein-like
structure and then breaking down into granules which are finally
absorbed in the cell protoplasm. The process of reorganization
requires from one to three days before the first division of the fertilized
cell, which, as we have seen, contains four micronuclei and four
macronuclei. The daughter cells after the first division each contain
two macronuclei and two micronuclei, and the normal nuclear rela-
tions are not reestablished until after the second division, when the
resultant four cells have each one macronucleus and one micronucleus.
This phenomenon may be interpreted in terms of the conjugation
in opalina, where minute ciliated cells conjugate, fuse, and form a
zygote (Neresheimer), if we assume that each of the daughter micro-
nuclei formed represents the nucleus of a microgamete in some phylo-
genetic ancestral stage, and if it is further assumed that in successive
phylogenetic stages (1) coupling of the adults occurred, as in grega-
rines; then (2) formation of endoplasmic gametes, as in ophryocystis;
and (3) interchange of micronuclei or gametic nuclei without the
formality of endoplasmic gamete formation. The vorticellidre show
an aberrant development in such a hypothetical history, for here one
of the conjugating cells is smaller than the other and fuses with it.
But here as many as eight micronuclei (Maupas) may be formed in
the preparatory stages, a number difficult to explain on any other
hypothesis. Copulation, therefore, as seen in the infusoria, involving-
temporary union of two similar cells, may be interpreted as a regression
of the gametes or a reminiscence of gamete formation in ancestral
cells, and as entirely different in its essential character from processes
of coition of the higher animals.
2. Anisogamy. — Under this term the greatest number of hetero-
geneous phenomena are usually collected, and in all probability there
is a wide physiological difference between them, involving in some of
the higher types all of the characteristics of sex differentiation. In
those cases where size differences are not obligatory, as in polytoma,
for example, it is hardly justifiable to speak of sex differentiation, by
which is usually meant the formation of definite somatic characters in
individuals destined to form either eggs or spermatozoa. So far as the
ultimate products are concerned, the protozoa give evidences of a
gradual evolution toward complete dimorphism of the conjugating
gametes. This is particularly well shown in the gregarinida, where a
series of forms shows the gradual development into gametes that
might well be interpreted as eggs and spermatozoa (Fig. 69). In
coccidia and in hemosporidia there are similar varieties of forms,
FERTILIZATION BY EXOGAMY
159
but not as complete as in the gregarines; one case, Adelea ovata, is
interesting in that one of the conjugants is a large form similar to the
ordinary vegetative individuals, while the other is much smaller and
is derived from an individual which forms four gametes while attached
to the other cell, one of these gametes penetrating the larger cell, while
the other three degenerate and disappear. In this form also we have
FIG. 69
.
$m , < Pf^.
'.;; IS&&5 :"' i
y
/
Different forms of gametes in gregarines and coceidiidia. (After Shellack.) A, Stylo-
rhynchus longicollis (after Leger) ; B, a species of monocystis from Lumbricus (Cuenot); C ,
spermatozoid of Echinomera hispida, to the left the two gametes of Pterocephalus nobilis;
D, the two gametes of Urospora lagidis (Brasil); E, the same of Gregarina ovata (after
Schnitzler); F, the same of Schaudinnella henleje (after Nusbaum); G, the same of Cocci-
diurn schubergi (after Schaudinn).
what may be regarded as complete sex differentiation, since the proto-
plasm of the race forms individuals of male or female character, never
both. Schaudinn and others have shown that the difference between
the two conjugating forms is present in potential throughout the
entire series ,of forms, the first division of the fertilized egg giving rise
to individuals which can be identified as male or female. In this case,
160 CONJUGATION, MATURATION, AND FERTILIZATION
and among the flagellates as well, this primitive sex differentiation can
be traced throughout the entire series, or the "individual" in the sense
used in the preceding chapter. In Coccidium schubergi (Fig. 74, p. 179)
a similar difference is demonstrable for a considerable number of
generations, but is not so marked apparently as in adelea. Here
fertilization is accomplished by union of a flagellated microgamete or
spermatozoid, and a food-stored macrogamete.
The flagellates, also, present wide variations in anisogamic conjuga-
tion, some of them, like Tnjpanosoma noctuce, being sexually differ-
entiated, according to Schaudinn, from the time of the first division of
the fertilized cell. In this form of trypanosome, and in other species
as well, Schaudinn and different observers have described three dis-
tinct types of the organism, females, males, and "indifferent" forms,
the latter, under appropriate circumstances, becoming either one or
the other sex.1
The female trypanosome of Trypanosoma noctuce is of relatively
large bulk, nearly spherical when mature, and somewhat inactive dur-
ing vegetative life. These are the most hardy of all forms of the para-
site, because of the reserve store of nutriment which they contain, and
these are the forms which, under certain conditions, may undergo
parthenogenesis (see p. 163). In order to undergo their full sexual
development, the parasites must be taken into the body of a mosquito
of the genus Culex, and here the male individuals are transformed into
microgametocytes and the females directly into macrogametes. In
the male gametocytes the kinetonucleus fuses with the vegetative
nucleus and the pigment granules are eliminated. The fused
nucleus next divides by a heteropolar mitosis into two nuclei, one
large, the other small. The larger nucleus degenerates, while the
smaller one divides repeatedly until eight nuclei are present.
Each of these divides still again to form a larger vegetative and a
smaller kinetonucleus of the future microgamete. The periphery
of the cell then draws out into eight projections, each containing
one pair of the recently formed nuclei, and these projections are
finally pinched off the parent cell as microgametes, each of which, in
the meantime, has formed its definite locomotor apparatus of the
typical character. The macrogamete, on the other hand, does not
form a locomotor apparatus, but after undergoing maturation pro-
cesses is sought out and fertilized by one of the microgametes.
Similar processes have been described by Prowazek, Keysselitz, and
1 Schaudinn's observations have been severely criticised and his conclusions denied by
numerous investigators, in particular by Novy and his collaborators; but while these criti-
cisms are of undoubted value, the fact remains that Schaudinn's description of the life history
of this parasite of the owl is entirely consistent and the most plausible of all that have been
presented in connection with trypanosomes, and I give it here as a type of fertilization in
trypanosomes in general.
PARTHENOGENESIS 161
others for different kinds of trypanosomes and for tjypanoplasma, a
closely allied form; none of the descriptions, however, are sufficiently
convincing to establish a life cycle, while numerous contradictory
accounts indicate the need of further careful and unprejudiced
research.
With the exception, therefore, of the case of Trypanosoma noctuce,
the flagellates present few well-defined instances of sex differentiation,
but other examples might be cited in which fertilization is accom-
plished by the union of anisogametes. In Mastigella vitrea, Gold-
schmidt ('07) has shown that a small non-motile gamete unites with a
larger flagellated gamete (Fig. 48, p. 1 19), a condition which reverses the
ordinary process, where the resting cell is usually larger and possesses
the attributes of an egg cell. Anisogamous conjugation occurs also
in Bodo caudatus, Bodo lacertae, and Monas dallingeri, and among
many of the phytoflagellates, where in Pandorina morum and Eudo-
rina elegans sex differentiation is well established, but in other forms,
as chlamydomonas, size differences are quite facultative.
Among the rhizopods the formation of anisogametes appears to
be widespread, especially among the fresh-water types. Schaudinn
('03) and Elpetiewsky ('08) showed that minute but anisogamous
gametes are formed in centropyxis and arcella, the gametes in all
cases having nuclei derived from the idiochromidia (Fig. 47, p. 119).
Fertilization by exogamy appears to be, therefore, the most wide-
spread and the most complicated of all methods of fertilization among
the protozoa, while in the higher types the process is accompanied
by well-marked maturation phases, approaching in complexity very
close to the reducing divisions and polar body formation of the higher
animals and plants.
D. PARTHENOGENESIS.
The processes of autogamy, as outlined above (p. 139), seem to have
many points in common with parthenogenesis or development of egg-
cells without fertilization. While the end result is undoubtedly the
same in both, a difference is implied from the fact that differentiated egg
cells, which normally develop after fertilization by a spermatozoon, in
parthenogenesis develop without such union. Parthenogenetic eggs,
therefore, are, in a sense, abnormal and may be interpreted as present-
ing a phenomenon of cenogenesis whereby the egg returns to a primi-
tive condition. Boveri ('87) suggested and Brauer ('93) confirmed
the suggestion in connection with the parthenogenetic eggs of Artemia,
that parthenogenesis is a result of the fertilization of the egg nucleus
by a polar body (Wilson, The Cell, p. 281). Such fertilization, as in the
case of autogamy, is brought about by the union of sister nuclei. In
11
102 CONJUGATION, MATURATION, AND FERTILIZATION
autogamy, however, we have to do, probably, with a much more
advanced cenogenetic process, and the cells at such periods of
activity cannot be regarded as egg cells, since there is no trace of
sexual differentiation.
Not only in different kinds of metazoa, but among some of the pro-
tozoa as well, the so-called "females," or egg cells, under certain con-
ditions, may develop by parthenogenesis, thus showing a first step in
degeneration leading to the method of fertilization by autogamy. Such
a possibility seems to have been first suggested by Grassi ('01) in con-
nection with the organisms of malaria, for he stated "the macrospores
(macrogametes) and possibly the microspores (microgametocytes) can
increase by parthenogenesis," but the process was first described for
the malaria organisms by Schaudinn ('02) in connection with Phis-
modium vivax, the cause of tertian fever. Here the macrogametocytes
(but not the microgametocytes) return to the condition of an ordinary
FIG. 70
c
Regression and merozoite formation (parthenogenesis) in Plasmodium vivax. (After
Schaudinn.) A, macrogametocyte in blood with nucleus differentiating into a denser and a
lighter part; B, the denser part of the nucleus now divides preparatory to schizogony, C, D,
while the paler portion with a part of the original cell degenerates; D, numerous merozoites
formed about the divided nucleus.
schizont after nuclear changes involving loss of a portion of the
chromatin. The cell partly divides, one portion containing a faintly
staining nucleus, and the majority of the pigment finally is cast off and
degenerates. The other portion, containing more intensely staining
chromatin, undergoes schizogony in the manner characteristic of an
ordinary blood parasite (Fig. 70).
A still more remarkable process of parthenogenesis was described
by the same author in the case of the flagellate Trypanosoma noctuce
(1904), where, as stated above, three kinds of cells were identified as
male, female, and indifferent. While the ordinary course is fertili-
zation of the female by a much more minute male cell, the macro-
gamete, or female, may, under certain conditions, undergo partheno-
genesis. The conditions of the environment at such times are such as
to bring about marked changes in the organisms. The male cells, or
microgametocytes, are too delicate to withstand the changed conditions
PARTHENOGENESIS
163
and are killed off; so, too, are the indifferent forms, but the female
cells, being much hardier, continue to live apparently upon the stored
up products of a nutritive character. The protoplasm finally becomes
vacuolar and the kinetonucleus migrates to a position alongside of
the trophonucleus (Fig. 71). Each nucleus then divides, the latter
equally, the former by a heteropolar mitosis, which gives rise to a much
smaller nucleus and a larger one (A, B). This smaller nucleus, like
the kinetonucleus, then divides, equally, one of the daughter nuclei of
this division degenerating while the other divides again. The result
of this second division is the formation of two nuclei, one of which
becomes attached to the larger trophonucleus, while the other degener-
ates. The same history is repeated by the products of the kineto-
nucleus. One degenerates, while the other divides a second time to
furnish a nucleus which similarly unites with the trophonucleus, and one
FIG. 71
Parthenogenesis in Trypanosoma noctusD, (After Sehaudinn.) .4, B, approach of the
kinetonucleus and division of both nuclei; C, D, division of the kinetonucleus and of the
"male" nucleus, degeneration of one-half of each, and union of one-quarter of each with
the trophonucleus; E, F, fusion of the two smaller nuclei in the trophonucleus to form the
karyosome of the fertilized cell.
which degenerates (C, D). The two smaller nuclei ("polar bodies")
then migrate into the trophonucleus and unite to form a new karyo-
some (E, F). With this fertilization the cell is again ready to form
other individuals of either male or female type.
In other trypanosomes similar but not identical processes of
parthenogenesis have been described by different observers. Moore
and Breinl ('07) describe the union of a portion of the kineto-
nucleus in Trijpanosoma gambiense with the trophonucleus, but
without any of the divisions, as described by Schaudinn. The
kinetonucleus (their "centrosome") grows out into a long rod which
reaches the trophonucleus, where a small part is taken into the
trophonucleus, uniting with the karyosome. A similar long rod
was observed by Prowazek ('05) in Trijpanosoma lewisi, but it was
described as arising from the trophonucleus and not from the kineto-
164 CONJUGATION, MATURATION, AND FERTILIZATION
nucleus, and interpreted as a characteristic of the male individual.
In this species, also, Prowazek described a union of portions of the
two nuclei, the process being much the same as that described by
Schaudinn. Phenomena which may be interpreted as parthenogenesis
seem to be, therefore, quite widespread among these parasitic flagel-
lates, and not only in species of this genus but in allied genera as well.
(See Keysselitz, 1906, for parthenogenesis in Trypanoplasma borreli).
In view of the possibility of confusing normal parthenogenetic pro-
cesses in these various forms of parasites, with involution and degen-
eration phases of the vegetative individuals, the various, and usually
conflicting, observations on parthenogenesis cannot be accepted as
established. On purely theoretical grounds, however, and in view of
the processes of autogamy in primitive protozoa and of partheno-
genesis in metazoa, it is not improbable that such methods of
fertilization may be found among the parasitic protozoa, where every
adaptation for preventing extinction of the species has apparently
been evolved.
E. THE PHENOMENA OF MATURATION IN PROTOZOA.
•
As Boveri ('90) long since pointed out, the numerical reduction of
chromosomes during the maturation of germ cells, first observed by
Van Beneden ('83), is no theory, but an accepted fact. Upon this fact,
however, a great superstructure of theories has been erected, and
around it some of the most fascinating and successful of modern
biological researches have been conceived and executed. In con-
nection with the higher animals and plants, the early view of Van
Beneden, that reduction is simply a process of eliminating one-half of
the chromosomes so that the number characteristic of the species may
be kept constant when the germ cells unite, has been given up. Sub-
sequent research has showTi that, in the maturation period of both
eggs and spermatozoa, after elimination in some cases of fully nine-
tenths of the nuclear material, the chromatin substance is redistributed
in such a way as to warrant the assumption of some deep-seated
purpose. In recent years biologists are coming more and more to
accept the hypothesis that this purpose has to do essentially with the
phenomena of inheritance, and that the orderly rearrangement of
chromatin with the ensuing maturation divisions is evidence of the
cellular mechanism by which the physical representatives of hereditary
characters are minutely halved and distributed.
While reducing divisions in highly differentiated forms of life,
according to this view, have their raison d'etre in the fact that the
great multiplicity of characters of an individual must have their physi-
cal representatives concentrated at some time in a single cell, reducing
THE PHENOMENA OF MATURATION IN PROTOZOA 165
divisions in protozoa, particularly in the simpler forms, bring such an
explanation almost to the limits of reductio ad absurdum. It is highly
probable that many of the so-called "reducing divisions" which dif-
ferent observers have noted in protozoa are not to be interpreted in
the same way as in metazoa. Indeed, there are but few instances
where chromosomes, using the term as applied to metazoan cells in
division, are formed, and too frequently suspicions are aroused that
the observer is influenced by what should be found according to
metazoan standards. The granules of chromatin, for example, appar-
ent after the technical processes which appear to be necessary in using
the Giemsa stain or any of its modifications, have been generally, but
erroneously, interpreted as chromosomes. Not only is there an entire
absence of the preliminary processes which characterize chromosome
formation in higher animals and plants, but these definite granules
cannot be demonstrated after use of the careful cytological methods
of fixing and staining that are used for tissue cells. Such "chromo-
somes," appearing only after use of what Moore and Breinl have
characterized as a "barbarous technique," can only be regarded as
artifacts, and the various descriptions of reduction in number of such
granules cannot be accepted until verified in every detail after the use
of methods whose reactions have been fully tested. On the other
hand, there is sufficient a priori reason for the belief, and numerous
observations to prove, that some process akin to reduction of chromo-
somes of higher types of germ cells occurs in protozoa, and these must
be taken into consideration in any attempt to explain the biological
significance of the phenomenon.
In higher animals and plants the number of fully formed chromo-
somes is primarily reduced to one-half, not by division of the nucleus,
but by fusion of the chromosomes two by two. Tetrads are then
usually formed by transverse division of the double chromosomes.
Separation of the tetrads and distribution of their four parts is then
accomplished by two divisions of the cell, resulting in four functional
spermatozoa in case of the male, and in three polar bodies and one egg
in case of the female. Two maturation divisions are thus character-
istic of all higher types.
It is quite remarkable, and not without significance, that two
rapidly following divisions of the nuclei characterize the preliminary
phases of fertilization in many different kinds of protozoa. They are
not necessarily connected with the two kinds of chromatin and do not
bring about an elimination of the chromidia from the idiochromidia
of the cell, for the double division not infrequently occurs after such
elimination has taken place. Thus, in cases of autogamy cited on
page 141 the nuclei formed from the idiochromidia in Entameba
coli and Entameba muris divide twice, one-half degenerating each
time, before the fertilization nuclei are mature (p. 142). In Adi-
166 CONJUGATION, MATURATION, AND FERTILIZATION
noplirys sol and Actinosphcriiim eichhornii (see Figs. 63, 65) the
former exogamic, the latter endogamie, similar divisions may occur,
two degenerating nuclei being formed in actinospherium, but only
one in actinophrys, a result which led Hertwig ('98) to believe that
Schaudinn ('96) had overlooked one of the division stages. In
gregarines there is evidence to indicate that the preliminary divisions
are not of the nature of reducing divisions, but are qualitative, whereby
idiochromidia or germinal chromatin is separated from vegetative.
Thus, in Leger's beautiful work on ophryocystis ('07), the nuclei
divide twice before the internal bud or gamete is formed, one of the
products of this division becoming a somatic or nutritive nucleus of
the parent cell, the other a "reduction" nucleus (Fig. 80).
In foraminifera and in fresh-water rhizopods reducing divisions do
not occur, but a "primary" vegetative nucleus remains unused and
degenerates in the residual body. Other instances of the elimination of
chromatin from all subdivisions of the protozoa might be cited, but
among them there are but few cases where the characteristic meta-
zoan conditions prevail. Certainly, the so-called reducing divisions of
the mxyosporidia are not analogous, for here, according to Schroder
('07) and Keysselitz ('08), fourteen nuclei are formed, ten of which
are "somatic," two of them degenerate, while two only remain to
conjugate (Fig. 61); nor are they in the actinomyxidae, where
Caullery and Mesnil ('05) found eighteen nuclei arising from the
single primary nucleus, two of them somatic and sixteen germinal,
the latter conjugating two by two.
Such a list might be further enlarged by the addition of case after
case of so-called reducing divisions, scarcely a paper being published
on the reproduction of protozoa that does not describe some such
process. But in none of them is there sufficient evidence of the forma-
tion and division of chromosomes, and until such evidence is forth-
coming we cannot draw accurate comparisons between the processes
of maturation in protozoa and in metazoa. In a few cases, however,
notably among the infusoria, definite maturation chromosomes are
formed and divided, and here we find the nearest approach to the
conditions in metazoa. They were first seen and correctly interpreted
by Biitschli ('76), while numerous observers (Balbiani, Maupas,
Hertwig, Hoyer, Hamburger, Prandtl, Popoff, and others) have since
added little by little, until, in some cases, notably in Paramecium
aurelia (caudatwri), the phenomena may be brought directly in line
with those of the metazoa.
In paramecium, as in other ciliates, the idiochromatin is separated
at an early stage from the vegetative chromatin, occurring with the
third division of the fertilized micronucleus when macronuclei and
micronuclei are differentiated.
The macronucleus of the cell plays absolutely no part in the conjuga-
THE PHENOMENA OF MATURATION IN PROTOZOA 167
tion process. Its work is done, and, like the somatic cells of the
metazoa, it dies. The micronucleus, on the other hand, after lying-
dormant so far as the vegetative functions of the cell are concerned,
now begins its germinal activity. It moves away from the macronu-
cleus, where it usually lies in a cleft in the substance of the macro-
nucleus, and begins to swell. It contains two substances: one, located
at one pole of the nucleus, is the substance of the division centre, and
gives rise to the fibers of the spindle figure, so that in it rests the poten-
tial energy which is later converted into the kinetic energy of division.
The other substance is chromatin, which is concentrated at this time
in a number of granules closely packed against the division centre.
The nucleus then elongates by fragmentation of the chromatin gran-
ules, the fragments arranging themselves in lines radiating out from
the division centre. They correspond to the idiochromidia of the
rhizopod cell, but are now assuming definite form, the irregular and
distributed idiochromidia of the more primitive organisms being-
replaced here by the more definite chromosomes. The elongation of
these lines of chromatin continues until the nucleus is an enlarged,
narrow structure many times longer than the resting nucleus. The
intranuclear division centre, which is concentrated at one end of the
nucleus, likewise increases in size (Fig. 72).
The micronucleus next becomes curved in such a way that the two
ends are brought close together, forming a distinct crescent, with the
long lines of chromatin uniting to make a branched network extending
from tip to tip, while the division centre, now much enlarged, moves
toward the centre of the crescent. The chromosomes of the first
division figure are formed by the transverse division of the elongated
lines of chromatin granules, but, owing to the net formation and
association side by side, these short fragments are each double, a
longitudinal split appearing in each. All of the chromatin is thus
utilized and an uncountable number of chromosomes are thus formed.
The substance of the division centre then diffuses through the nucleus
in a kind of flowing division and the two poles of the first maturation
spindle are formed by the accumulation of this material at the opposite
sides of the nucleus. With this flow the chromosomes are divided, so
that when the spindle is entirely formed the daughter halves of the
chromosomes are separated and now lie end to end in the so-called
anaphase stage of division (Fig. 72, C). (See Calkins and Cull ('08) for
the details of this spindle formation.)
The nucleus then divides by constriction through the middle and the
first two maturation nuclei are the result. Each of these next divides
again, the process of division being identical with that described
above and four maturation nuclei are formed. Two of these immedi-
ately begin to degenerate, while a third follows suit shortly after, the
fourth alone dividing a third time. Here the chromatin is not divided
168 CONJUGATION, MATURATION, AND FERTILIZATION
by longitudinal but by transverse division, and this division is hetero-
polar, so that the resulting nuclei are of different sizes. The smaller
FIG. 72
B
C
D
The micronucleus of Paramecium aurelia during conjugation. A, concentration of chro-
mosomes after the crescent phase. Accumulation of kinoplasm at upper pole; B, early
anaphase of first maturation division; C, late anaphase of first maturation division; D,
prophase of second maturation division. (After Calkins and Cull.)
is the migratory nucleus, the larger the stationary. Each migratory
nucleus wanders through the connecting bridge of protoplasm and
fuses with the opposite stationary nucleus, the fusion beginning at one
THE PHENOMENA OF MATURATION IN PROTOZOA
pole of the nuclei. The first division of the fertilization nucleus takes
place before the chromatin of the two nuclei is completely united.
The other two divisions of the fertilized nucleus follow in quick suc-
cession and the processes of reorganization bring the phenomena of
conjugation to an end (see Fig. 6S, p. 157).
The mere statement of the consecutive acts in maturation and
fertilization gives no clue to the significance of the processes whereby
the cell is reendowed with a potential of vitality which will again carry
it through the periods of a life cycle. We see that fully three-quarters
of the chromatin of the resting nucleus is eliminated to disintegrate in
the protoplasm of the cell, while still more is lost in the material of the
connecting strands of the daughter nuclei ; we see that there is a union
of this reduced ("purified") chromatin when the pronuclei come
together, and we see that the new macronucleus of the early genera-
tions of cells is derived from part of the fertilization nucleus.
It thus appears that the nuclear parts of the fertilized cell of para-
mecium are distinctly new creations, for they consist of the union of
chromatin material from two distinct organisms; the one, the macro-
nucleus, has from this period the essentials of vegetative activity,
while the micronucleus apparently enters into a "resting period,"
dividing, and possibly controlling, cell division, until the next period of
sexual activity. Not only is the nuclear apparatus new in the fertilized
cell, but the cytoplasm is also new, for it receives and changes over into
its own substance not only the remains of the old macronucleus, but
more than three-fourths of the entire quantity of chromatin possessed
by the maturation nuclei. There is no reason to doubt that this addi-
tion makes over the protoplasm of the cell in a manner analogous to
the reorganization of the nuclei, and presumably provides a physical
basis for the reinvigoration of the activities peculiar to the cytoplasm.
Except for the absence of a cellular corpse, therefore, there is no sup-
port for Weismann's contention that the old individual still persists;
it is a new individual, nucleus and cytoplasm, no less surely than a
fertilized ovum, or its progeny of cells, is a new individual.
The secret of development lies in this fertilization act, and if we
could work it out in paramecium and its allies, we would have a basis,
at least, for its discovery in the higher animals. The protozoon offers
a much more suitable organism for the study of this problem than any
manv-celled animal, for the conditions under which successful con-
j
jugation is brought about may be experimentally studied and con-
trolled. Not much has been done, as yet, in this direction, but numer-
ous observers are at work on the problem, and it thus presents one of
the most fascinating aspects of protozoology.
It is mainly in connection with such complicated phenomena of
chromosome formation and reduction that theories of inheritance and
of fertilization have been formulated.
170 CONJUGATION, MATURATION, AND FERTILIZATION
In simple division by mitosis each of the chromosomes divides
longitudinally, so that the daughter cells obtain the same number, and
an equal part of each chromosome. In 1883 Roux pointed out that
this wonderful mechanism in the cell, and the extreme care with which
each of the chromosomes is equally divided, must be connected in some
way with the phenomena of inheritance. Van Beneden, in the same
year, first showed that the number of chromosomes in the uniting
nuclei is just one-half that of ordinary tissue cells of the body, the
number characteristic of the species being restored by the union of the
two halves, half from one parent, half from the other. Weismann, in
his brilliant essays on heredity, suggested that each chromosome is
composed of a number of units, which he called biophores, each unit
representing some characteristic or group of characteristics to be
manifested in the prospective individual. These units are divided in
ordinary mitosis in such a way that each daughter cell would receive a
portion of each biophore, a result that could be reached only by longi-
tudinal division of the chromosome. To account for the differences in
characteristics of different offspring, he prophesied that in the forma-
tion of the germ cells the ordinary longitudinal division of the chromo-
somes would be replaced by a transverse division, and thus daughter
cells would result with different biophores. The apparent confirmation
of this prophecy a few years later was one of the great events in
the history of biology and a vast literature has accumulated since
1891 on this subject of "reduction." Today it is generally admitted
by cytologists that the reduced number of chromosomes is brought
about by association of the ordinary chromosomes in pairs (synapsis),
the union taking place by end to end or side to side association (telo-
synapsis and parasynapsis).1 In the preparation for fertilization such
double chromosomes are divided twice, so that four germinal elements
are produced from each primordial germinal cell. Furthermore, it
was suggested by Montgomery that the chromosomes representing
the same groups of characters are present in duplicate in the nucleus,
half coming from the male parent, half from the female, while synapsis
is the association of chromosomes representing the same groups of
characters but from different parents. This suggestion was rendered
more probable by the observations of Sutton, McClung, and others,
who showed that the chromosomes in insects have different forms and
that the different forms are present in pairs, and, further, that these
pairs unite in synapsis.
There is reason to believe, therefore, that Weismann's original
hypothesis of the make-up of the germinal chromosomes is as close as
1 These excellent terms were first used by Professor Wilson in lectures at Columbia Uni-
versity, and were used by the present author and Miss Cull with the mistaken impression
that Professor Wilson had already published them. For this breach I offer my tardy but
sincere apologies. — G. N. C.
THE SIGNIFICANCE OF FERTILIZATION 171
we can come at the present time to an explanation of the physical basis
of inheritance. The theoretical conclusions have been strengthened
and supported by morphological evidence upon the most widely
separated groups of animals and plants, and by experimental evidence
in connection with the principle of Mendelian inheritance.
Such, in brief, is the statement of the modern problem of inherit-
ance from the cytological standpoint. Now, what connection has this
problem with the protozoa ? The chromosome in a metazoon must be
a wonderfully complex element of the cell if there is anything in this
physical conception of its organization, for we find that the number of
chromosomes in the cells of metazoa does not increase with the hio-h
grade of differentiation which we find in the higher animals, and if
there is a physical basis for adult characteristics, the few chromosomes
of a man must be wonderfully more complex individually, than those
of invertebrates like a sea urchin or an earthworm which have approxi-
mately the same number. In protozoa the chromosomes, when present,
are of enormous numbers, in paramecium at maturation more than
200, and the only interpretation, on a purely physical basis, is that each
chromosome must represent a simple character, or, at least, a simpler
group of characters, than the chromosomes of higher animals. In the
more primitive protozoa the physical basis of inheritance (idiochro-
midia) is not moulded into definite chromosomes, but is uniformly
halved while in granule form. In other words, a study of protozoa
chromosomes leads to the theory that chromosomes, the characteristic
structures of the nucleus in mitosis, have had an evolution no less
surely than has the nervous system, digestive system, or supporting
system of the higher animals, and that the chromosomes of the pro-
tozoa have the same relation to chromosomes of the metazoa that the
organization of the protozoan body has to that of the rnetazoan, i. e.,
a unit structure.
F. THE SIGNIFICANCE OF FERTILIZATION.
It is perfectly obvious that whatever view is taken of the significance
of fertilization, it must be sufficiently general to account for the phe-
nomena of parthenogenesis, autogamy, and endogamy, as well as for
the more complicated processes of exogamy. Biitschli's ('76) early
view that conjugation is a process involving rejuvenation (Verjungung)
of the individual, while giving no idea as to what the nature of the
rejuvenating process actually is, has been but little improved upon by
the work of subsequent observers. Maupas' conclusion that nuclear
rejuvenescence is alone involved is not wholly consistent with the facts,
and his attempt to penetrate more deeply into the mysteries of the
matter by defining the conditions of conjugation has been only partly
172 CONJUGATION, MATURATION, AND FERTILIZATION
successful. The conditions, as he outlined them, are, briefly: (1)
diverse ancestry of the conjugating cells; (2) scarcity of food; and
(3) sexual maturity.
That diversity of ancestry has no great biological significance is
borne out by the facts of parthenogenesis, autogamy, and endogamy,
and on this ground alone might well be dismissed as a necessary con-
dition of fruitful conjugation. Not only in these instances, out in
exogamic fertilization as well, diverse ancestry is not essential. Thus,
in Paramedum aurelia (caudatum), which was one of the examples
cited by Maupas as an obligatory exogamous type, Calkins ('02)
showed that two cells removed by not more than eight or nine divisions
from the same ancestral cell, conjugated, and one of the exconjugants
gave rise to descendants through 379 generations of divisions. In
these experiments it was shown, furthermore, that fully as many con-
jugations between related forms were fruitful as between forms of
diverse ancestry.
The second of Maupas' conditions, scarcity of food, seems to have
some connection with the ability to conjugate, although in no case has
it been proved that such a condition is a necessary factor. Certainly
in cultures of paramecium, or of any other ciliate, dividing forms
indicate the presence of food, and in such cultures conjugating and
dividing individuals may be found side by side, and Maupas himself
states that conjugating forms may still actively take in food. It is not
improbable that surplus of food, followed by starvation, may assist
in bringing about the protoplasmic conditions where conjugation is
possible. Changes in the density of the surrounding medium, and
changes in temperature, certainly act to this end, but all of such
conditions seem to be dependent upon a third condition, sexual
maturity.
«/
Maupas' third condition of conjugation, sexual maturity, seems to
be quite probable, provided we mean by sexual maturity the appro-
priate chemical and physical condition of the protoplasm when con-
jugation is possible. The time element, which seems to be implied,
is not a necessary factor, however, for the proper conditions may
be induced by temperature and density changes in the surrounding
medium.
Finally, it appears to be not improbable that the interpretation of
fertilization rests in the obscure chemical relations and hypothetical
enzymatic action of idiochromatin elements whose potency depends
more or less upon the diversity of environment of the conjugating
forms. Culture experiments upon some of the larger forms of protozoa,
while not proving such a theory, nevertheless seem to point in this
direction. Thus, Cull ('07) found that out of a total of 186 para-
mecium individuals from pond water, 70 per cent, continued to live
after conjugation, ?. e., were fruitful. Calkins ('02), on the other
THE SIGNIFICANCE OF FERTILIZATION 173
hand, found that out of SO paramecium individuals that had been con-
tinuously on the same food for many months in culture, only 6 per
cent, continued to live, and this low percentage was the same whether
the conjugating forms were of the same or of diverse ancestry. It may
be as Stevens ('03) pointed out, that such low percentages were due to
the lowered vitality of the organisms in culture, but in all cases the
food medium was the same, and the explanation may lie in the fact
that the culture forms, having lived upon the same food material for
many months, were too similar to give rise to appropriate chemical
combinations upon fusing. The injurious effects of too close and too
prolonged inbreeding of higher forms may have their explanation in
such experiments, and similar experiments and observations on the
unicellular animals under culture may ultimately furnish the key to
the riddle of fertilization.
CHAPTER V.
PARASITISM.
IT is a well-recognized biological principle that degeneration is the
inevitable outcome of continued parasitism (Lankester Degeneration).
A certain crustacean parasite begins life with the same number of
appendages as other crustaceans, but when it becomes attached to a
crab host, its appendages atrophy, evidences of other structures dis-
appear, and it becomes a mere bag — sacculina — on the abdomen of
its victim. Ascaris, trichina, and their allies similarly have lost most
of the dermal musculature and the power to move as most worms do.
Tenia and other tapeworms in like manner have lost not only the
body musculature, but digestive organs as well. Such parasites, living
in the digestive tracts of their hosts, are surrounded by digested and
partly digested food which passes by osmosis through the body wall;
mouth and digestive organs are unnecessary, and their disappearance
is to be accounted for on the theory of disuse.
While degeneration of the usual vegetative organs is the inevitable
outcome of parasitism, the restricted mode of life of the parasite may
require certain accommodations which may lead to structural adapta-
tions on its part. The internal parasites of the digestive tract, for
example, might easily be dislodged and carried out of the intestine
with the muscular contraction and currents of that organ, while external
parasites would be readily detached and swept awray, were they not
provided with some means of holding on, hence sucking disks, hooks,
and spines are characteristic of internal and external parasites. In
addition to increased development of certain attaching organs and
degeneration of vegetative organs of digestion, etc., there is an enor-
mous increase in the power of reproduction. It is a biological fact that
the number of offspring of an animal is in inverse proportion to the
chances of reaching maturity, and the number is always great enough
to maintain the species. It is quite apparent that a parasite living in a
certain portion of a given host would experience no little difficulty in
reaching that spot, hence every parasite has acquired the power of
reproducing immense numbers of progeny; a tapeworm, for example,
produces many hundred thousands of eggs, and yet the frequency of
infection by tapeworms is not great enough to cause any apprehension
among people who live with ordinary decency.
With a ubiquitous group of organisms like the protozoa, it is to be
STRUCTURAL MODIFICATIONS OF PROTOZOAN PARASITES 175
expected that some of them, at least, would have acquired the parasitic
mode of life. The enormous literature which annually appears in
connection with the protozoan parasites, perhaps better than anything
else, shows that such an expectation is well founded (Liihe ('06)
points out that in connection with the blood-dwelling protozoan
parasites alone there are from 600 to 700 papers published every year),
and every division of the protozoa numbers among its genera some
that are wholly or in part parasitic.
I. STRUCTURAL MODIFICATIONS AND MODE OF LIFE OF
PROTOZOAN PARASITES.
It is not a too sweeping generalization to state that every living
thing, large enough to contain another living thing, is subject to inva-
sion by parasites. The protozoa, themselves single cells, often play
the part of host to smaller protozoan cells, and parasites often infect
even the nucleus of ameba, paramecium, vorticella, and other types.
If the imagination were allowed full play, it would not be very dif-
ficult to work out a logical hypothesis as to the transition of different
kinds of protozoa, from a free life in ponds and ditches to a parasitic
life in the digestive tract or other organs of various animals. It is
certainly true that representatives of all groups of protozoa have from
time to time in the past become adapted to life within some other
animal or plant, and it is equally true that in many cases their presence
is harmful to the host and may become fatal. Frequently such para-
sites have become so modified by their changed mode of life that their
structures furnish little or no hint as to the original or primary form.
Such is the case in the majority of sporozoa, where every member is a
parasite, the origin of the group, as a whole, whether from rhizopods
or flagellates, being purely conjectural. In some cases the method of
locomotion by pseudopodia formation, the presence of a contractile
yacuole, and the mode of reproduction indicate rhizopod affinities;
in other cases the evidence of degenerating structures, taking
place before our eyes, as it were, at the present time, is unmis-
takable, and such forms write their own phylogenetic history.
This is true of some members of the blood-dwelling parasites,
where, as in Herpeiomonas (Leishmania) donovani, the adult
organism is a flagellated protozoon in the gut of its definitive host
(bugs of the genus Cimex), but becomes an intra-cellular parasite
without motile organs of any kind in the intermediate host man;
or in Trypanosoma noctuce (H emoproteus noctuce), where a highly
differentiated free-swimming flagellate becomes an intra-cellular
blood parasite of the bird (Glaucidium (Athene} noctuce), and with
a much simpler structure (see page 244). From such evidence
176 PARASITISM
it is conceivable that the entire group of the hemosporidia may have
been thus evolved from the flagellated protozoa, as the majority of
protozoologists now suspect, the evidence, as Schaudinn, Minchin,
Liihe, Hartmann, and others admit, being supported by the casual
formation of flagella-like structures in different species of the malaria
organism and the peculiar thread or pseudopodium-like appendage
of Babesia canis [Nuttall and Graham-Smith ('06), Patton ('07),
Kinoshita ('07)]. This evidence, however, is not strong enough to
justify far-reaching changes as yet in the well-established system of
classification, and we cannot support Hartmann, Sambon, Manson,
and other recent contributors in their attempts to do away with the
old group of hemosporidia. Hartmann's ('07) group of " binucleata,"
including hemosporidia and the binucleated flagellates, is premature,
misleading, and demoralizing, and on the present evidence would be
no more justified than a zoologist would be justified in classifying
pisces and batrachia together in one group on the strength of the tad-
pole larva. In each case the vanishing structures show no more than a
suggestion of a possible relationship.
In other cases of parasitic protozoa the cellular structures are prac-
tically identical with those of the nearest allied free-living forms.
Balantidium, opalina, biitschlia, dasytricha, and other ciliated para-
sites show unmistakable resemblance to the infusoria; pyrsonympha,
trichonympha, and some others a less perfect resemblance. Ameboid
parasites like Eutameba histolytica, E. coll, or Chlamydophrys stercorea
are similarly related to the rhizopods.
Like parasitic worms and mollusks, these parasitic forms may
become highly modified by their parasitic mode of life, and suckers,
hooks, spines, and other attaching organs may be well developed.
Such changes in cell structure may be the outcome of the specific mode
of life of the parasite and their methods of nutrition. Some of them,
like the majority of motile forms in the fluids of the digestive or cir-
culatory system, absorb their food as saprophytes do, by osmosis;
others, like the gregarines, trichonympha, pyrsonympha, and others,
have especially adapted attaching or feeding organs which may
act as haustoria to absorb food from the fluids of the host (e. g.,
pyxinia, Fig. 73).
The parasitic forms may be divided for descriptive purposes into
unnatural groups, according to their modes of life. Some are purely
enterozoic, spending the entire life in the lumen of the digestive tract
(flagellates like copromonas, cercomonas, herpetomonas, crithidia,
etc.); others are coclozoic, dwelling in the coelomic cavities of the body
(many gregarines); others are ci/tozoic, living throughout the vegeta-
tive period of life as intracellular parasites (coccidiidia, in epithelial
cells; myxosporidia, in muscle cells; and intracorpuscular hemo-
sporidia) ; still others are caryozoic, passing into the cell body to find
STRUCTURAL MODIFICATIONS OF PROTOZOAN PARASITES 177
lodgement in the cell nucleus; such caryozoic forms are only specially
adapted cytozoic types, but their habitat is always the same (Cyclospora
caryolytica, Nucleophaga amebea, and in part Cytoryctes variola, and
others); others, finally, are hematozoic, living in the blood (trypano-
soma, plasmodium, hemoproteus, etc.). In many cases there may
be modifications of these modes of life, or combinations of two or
more. Thus, plasmodium may be hematozoic, cytozoic, enterozoic,
and coelozoic during some period of its life history in the mosquito or in
the blood, and the terms are too indefinite to be employed in any way
save for purposes of description. In many cases, as, for example, in
gregarines, the young phases are cytozoic, the adult coelozoic or entero-
Fio. 73
Pyxinia mobiuszi, from Liihe. (After Lfeger and Dubosq.)
zoic, and in such cases the young forms may have special organs
serving for attachment or for feeding, and as they grow to maturity
such processes may remain in the host cell, serving for attachment, or
as haustoria for the absorption of nutriment. Sometimes these are
great prolongations at one end of the cell, as in Pyxinia mobiuszi
(Fig. 73) ; again, many such processes may be present, as in Ptero-
cephalus yiardi, or in ophryocystis (Fig. 80). When the organism is
sexually mature or ready for reproduction the attaching processes are
discarded and left behind in the epithelial cell of the host, while the
freed parasite lies in the lumen of the organ. Such attached gregarines
are known as cephalonts, and the detached forms as sporonts. The
cephalonts may be variously ornamented, according as the attaching
12
178 PARASITISM
organ is produced into hooks, etc., the attaching portion being known
as the epimerite. The portion suspended from the cell in the lumen of
the organ may be further differentiated by septa of ectoplasmic origin
into an anterior and a posterior part, the former called the primitc,
the latter, usually containing the nucleus, the deutomerite (Fig. 1, D,
p. 17).
Other special adaptive structures brought about in the protozoan
cell, as a result of parasitism, are undoubtedly the protective capsules
which envelop the spores. When the parasite becomes sexually
mature it fuses with another cell in conjugation, and fertilization is
followed by spore formation. The spores thus formed do not reinfect
the same host, but, contained usually in the lumen of the digestive
tract or similar cavity of the body, they are finally carried to the outside
in one way or another with the waste matters. Here, were it not for
the protective coverings which they possess, they would soon be killed
by exposure, but, protected by resistant chitinous membranes, such
spores resist drying and retain their vitality until again taken into a
new host, usually by way of the digestive tract. Animals of gregarious
habits are particularly subject to protozoan infection, the spores
usually contaminating the food. In the intestine the germs of the
organisms are liberated from their coverings and make their way by
one means or another to the definitive locality where growth is possible.
The so-called "selection" of locality is a matter of mere passive
resistance on the part of the parasite, that part being "selected"
where they are not destroyed by the reactions of the host, and where
conditions of life are most satisfactory for nourishment and security.
If the young organism is a gregarine or. coccidian, it makes its way
to the epithelial cells lining the digestive tract and grows to adult size.
Some forms penetrate the walls of the gut and get into the celom where,
as celozoic parasites, they grow to maturity. Coccidia remain in the
first cell-host until it is destroyed, such destruction allowing the para-
site to fall into the lumen of the organ, where fertilization occurs.
Coccidian infection, for this reason, is much more severe than gre-
garine infection, and may give rise to acute enteritis (e. g., Cyclospora
caryolytica in moles).
II. REPRODUCTION AND THE LIFE CYCLE.
In common with the many-celled parasites, the protozoan forms
have acquired varied and prolific means of multiplication, which may
differ in type at different periods of the life cycle. In the majority of
cases such multiplication may involve sexual processes, or it may
be entirely asexual, the former occurring at the end of the vegetative
life of the parasite, the latter, during the vegetative life, in the host.
REPRODUCTION AND THE LIFE CYCLE
179
Sexual reproduction is bound up with spore formation, whereby germs
of the parasite are prepared to withstand various unsuitable conditions
of the external environment, such reproduction being termed sporo-
yony. Asexual reproduction, on the other hand, taking place writhin
the host, is a means of spreading the infection among different cells
FIG. 74
Life cycle of Coccidium schubergi. (After Schaudinn.) Sporozoites penetrate epithelial
cells, and grow into adult intracellular parasites (a). When mature, the nucleus divides re-
peatedly (6), and each of its subdivisions becomes the nucleus of a merozoite (c). These enter
new epithelial cells, and the cycle is repeated many times. After five or six days of incuba-
tion, the merozoites develop into sexually differentiated gametes; some are large and well
stored with yolk material (d, e, f); others have nuclei which fragment into many smaller par-
ticles ("Chromidien"), each granule becoming the nucleus of a microgamete or male cell (d,
h, i, j). The macrogamete is fertilized by one microgamete (g), and the copula immediately
secretes a fertilization membrane which hardens into a cyst. The cleavage nucleus divides
twice, and each of the four daughter nuclei forms a sporoblast (A:) in which two sporozoites are
produced (0-
and organs in the same host, or a means of auto-infection. This means
of asexual increase is termed schizogony, although, as a rule, the term
is restricted to multiple increase or asexual "spore" formation.
Similar alternations of sexual and asexual methods of reproduction
are invariably present in free forms of protozoa, but asexual increase
180 PARASITISM
is usually limited to simple division or budding, although spore forma-
tion is occasionally met with here (e. g., noctiluca, colpidium, etc.),
while after fertilization spore formation is quite common, especially
among the free flagellates. In parasitic forms, on the other hand,
and especially among sporozoa, simple division and budding are
extremely rare, being replaced here by the more prolific multiple
reproduction by asexual spore formation in response to the greater
need of numbers in maintaining the species. Two kinds of "spores,"
therefore, may be present in these parasitic protozoa, the one giving
rise to infection of new hosts (spores s. str.), the other to auto-infection
of the same host. No little confusion has arisen because of this dif-
ference, and various writers have sought to avoid it by giving different
terms to the "spores" of varied origin. Such efforts, instead of help-
ing, have, in the main, made "confusion more confused," and students
of the group have recognized the need of adopting some one standard
and acceptable terminology. At the present time there is a tendency
to eliminate the term "spore" as applying to any definite reproductive
body, and to reserve it for a general designation of any reproductive
body formed in brood. Specialists, however, especially those dealing
with the sporozoa, have generally applied the term in a still more
limited sense to the reproductive bodies in gregarinida and coccidiidia
within the sporocysts which give rise to the sporozoites or final repro-
ductive elements (Fig. 74). Such a young sporozoite as that of Cocci-
dium (Eimeria) schubergi grows into a vegetative organism termed a
trophozoite, which finally becomes a schizont and reproduces asexually,
forming spores known as merozoites (Fig. 74, c). These reproductive
bodies are naked and unable to withstand the unfavorable exigencies
of an external life, but are capable of developing within the same
host. They, too, grow into trophozoites, and the process of schizoyony
may be repeated many times; ultimately, however, vitality wanes and
the organisms become sexually mature. The trophozoites, at this
period, instead of forming schizonts, turn into gametocytes and give
rise to conjugating gametes, which may or may not be sexually dif-
ferentiated. The gametes conjugate and form a zygote or copula
which becomes a sporoblast or by division gives rise to sporoblasts.
The sporoblasts are enclosed in protective coatings termed sporocysts,
and within these they multiply again to form from two to many
germs, the sporozoites, or the sporoblast may, in some cases, become
the sporozoite directly without further division. The various forms
assumed by the sporozoan parasites and the many kinds of repro-
ductive bodies bring about great complexity in the life cycle, and
where only one phase of such a cycle is known, confusion is apt to
follow attempts at classification.
There is no doubt that the group of sporozoa which furnishes some
of the best and most complete examples of the life cycle of protozoa
REPRODUCTION AND THE LIFE CYCLE
is made up of heterogeneous and unrelated forms which may in time
be resolved into more natural groups than those of our present-day
classification. But notwithstanding the varieties in form, mode of life,
and diverse origin of these organisms, all seem to agree in the pos-
session of two distinct phases of activity, one, the endogenous cycle,
the other, the exogenous cycle, the former within the same host, the
latter outside of any definitive host and either free or temporari y
FIG. 75
1
.
•'
1 ; • ;-VL"
<
4^i|
-' #
'
Life cycle of Lankesteria (Monocystic ascidioe, Siedlecki). The young sporozoites enter epi-
thelial cells (A, B, C), and grow into adult gregarines, which leave the cells (D) and live as
"sporonts" in the cavity of the intestine. Two sporonts unite (E), their nuclei divide repeat-
edly (F), until many daughter nuclei are formed (GO. These become nuclei of ameboid
gametes (//), which move about inside of the cyst and -mm conjugate two by two (/), the
nuclei fusing to form cleavage nuclei of the sporoblusts (,/). The cleavage nuclei then
divide thrice to form eight daughter nuclei (A", L, .!/, Ar), which ultimately become nuclei
of the sporozoites (O) . The sporoblasts, meanwhile, secrete firm cysts within which the
sporozoites are protected.
parasitic in some other animal. The life history of Coccidium schu-
bergi, as outlined above, is neither the simplest nor the most compli-
cated of these histories, and may well serve as a starting point for a
description of the various modifications.
1. Variations in the Endogenous Cycle.— In some cases the life
history of parasitic protozoa is simplified to such an extent that no
reproductive processes take place during the endogenous cycle, the
young sporozoites developing directly into trophozoites and these into
182
PARASITISM
gametocytes (e. y., Lankesteria (Moriocystis) asddice, Sied. (Fig. 75)
Eucoccidium (Benedenia) octopiana, and E. eledone).
w
•i
^cy
*<M'
FIG. 76
/>'
•r *»;:1A
Hp^
/•• %gj*m •:£,
IWf
^H
7-
Intracellular sehizogony in gregarines. A to D, Eleutheroschizon dubosqui, Brasil, intes-
tinal parasite of Scoloplos armiger, showing multiplication of nuclei {A, B) and formation of
merozoites (C,D). (After Brasil.) E to G, Schizocystis sipunculi, Dogiel; E, adult organ-
ism; F, merozoite formation; G, mature merozoites in brood cavity. (After Dogiel.)
In other cases, processes of sehizogony in one form or other com-
plicate the endogenous cycle. The simplest of these processes of
REPRODUCTION AND THE LIFE CYCLE 183
multiplication is binary division of the trophozoite, as found among
the schizogregarines, where, as in ophryocystis, according to Leger
('07), vegetative increase may be by simple division, as in ameba. In
other cases, however, the nucleus of the organism divides repeatedly
until many are present, when the cell divides into as many schizozoites
or merozoites as there are nuclei (Fig. 76). Schizogony becomes
more complicated in other genera of schizogregarines, where, as in
Eleutheroschizon (Brasil, 1906) or in Schizocystis (Dogiel), a process
of internal budding similar to that in suctoria (acineta, tokophrya,
etc.) takes place. In the former, a parasite of the marine annelid
Scoloplos armiger, Brasil ('06), has shown that the nucleus multiplies
by mitosis until many are present, when each is surrounded by a small
part of the protoplasm and all remain in the trophozoite, which acts as
nurse (Fig. 76, A-D). Similarly, in Schizocystis sipunculi, a parasite
of Sipunculus nudus, Dogiel ('07), described the formation of a brood
pouch with many merozoites (Fig. 76, E-(ty, and, as in the preceding
form, the nurse cell or parent trophozoite is finally discarded as an
empty shell.
Processes like these would seem to be less primitive than simple
division, more primitive than merozoite formation in the coccidiidia,
where the entire cell is utilized in the formation of such asexual spores;
a further stage leading to full schizogony is illustrated by another
gregarine selenidium, in which, according to Brasil ('07), the entire
protoplasmic contents of the cell are used in merozoite formation.
These methods of increase have probably arisen from simple division
in response to the environmental conditions, and the resulting germs,
like sister cells from division, are produced by simultaneous division
of the entire cell. Such asexual spores are never protected by chitinous
coverings, and for this reason have been called yymuospores, as the
equivalent of merozoites and as distinctive from the covered spores or
chlamydospores , of the sexual generation. In some rare cases, e. g.,
in Legerella nova among the coccidiidia, the sporozoites, like mero-
zoites, are naked.
In still other cases among the coccidiidia endogenous multiplication
is further complicated by the division of the trophozoite into frag-
ments ("cytomeres" of Siedlecki), each of which becomes the centre
of merozoite formation. Such further complications are characteristic
of Klossiella muris (parasite of the mouse) and Caryotropha mesnili,
a parasite of the germinal cells of the annelid Polymnia nebulosa.
The highest type undoubtedly occurs in those forms of coccidiidia,
where merozoite formation accompanies the permanent differentiation
of the sexes, where, as in Cyclospora caryolytica (parasite of the mole),
Adelea ovata (parasite of the centipede), a series of male and female
merozoites are produced, which give rise to male and female tropho-
zoites, and these, finally, to sexually differentiated gametocytes.
184
PARASITISM
While most of the examples cited above are to be found among the
clearly defined forms of unquestioned systematic position, quite a
variety of endogenous variations have been described in the lesser
known parasites. Here, especially in the recently created group of
haplosporidia and in the sarcosporidia, the former, including parasites
mainly of annelids, Crustacea, and fish, the latter, mainly of mammals,
the method of asexual spore formation is much more primitive than in
the better-known parasites, and, as in selenidium, all of the cell con-
tents are used in the formation of the reproductive elements. Some
of these forms are cytozoic (Haplosporidium heterocirri, H. vejdow-
skii); some are coelozoic (H. inarchouxi}, and some combine the
Schewiakovella in the body cavity of cyelops. (From Minchin, after Schewiakoft.) A, free
ameboid form; B, encysted ameba; C, sporulation of ameboid stage; D, plasmodial stage;
E, sporulation stage of plasmodium.
intracellular with lumen dwelling life; but all agree, according to
Caullery and Mesnil ('05), in having an endogenous and an exoge-
nous cycle, although the full life history in no species is known. In
all cases the trophozoite begins as a uninucleated cell, similar to a
young form of Plasmodiophora brassicce, and develops into a multi-
nucleated ameboid form which fragments into as many germs (mero-
zoites ?) as there are nuclei. Conjugation processes are quite unknown ,
although Caullery and Mesnil suspected a fusion of nuclei (autogamy)
comparable with that in plasmodiophora or that in the more closely
allied group of actinomyxidae. The haplosporidia are forms of con-
siderable theoretical interest, as indicating a possible close connection
REPRODUCTION AXD THE LIFE CYCLE
185
with the mycetozoa, and through these a phylogenetic relationship
between the neosporidia and the rhizopocla. This is particularly
well illustrated in the case of SchewiakoveUa schmeili, a parasite of
copepods where there is not only a multinucleate trophozoite stage,
but the parasite differs from all other sporozoa in having a distinct
rhizopod characteristic in its contractile vacuole, while it agrees with
mycetozoa in that young forms come together and fuse to form plas-
modia. A further peculiarity of this organism is the binary division
of the spores (Fig. 77).
In this group of little-known forms, one case of human infection
has been reported by Minchin and Fantham ('05). The connective
tissue of nasal tumors in natives of India was found to contain quan-
FIG. 78
Rhinosporidium kinealyi, Minchin and Fnntliain. i After Mine-hill and Fantham.)
segment of a section through a cyst from a tumor of the human nasal septum. The ripe
pansporoblasts are accumulated in the centre of the cy.-t and gradually encroach upon the
peripheral plasm until all is utilized. One ripe ">pore-morula" is shown on the right.
tities of haplosporidian parasites — Rhinosporidium kinealyi — in all
stages of development, from young multinucleate organisms to adults
filled with pansporoblasts (Fig. 78). The pansporoblasts give rise to
sporoblasts (spores) which are formed successively until about a dozen
are developed. (As in other myxosporidian pansporoblast formation,
the possibility of sexual union of nuclei (autogamy) is not excluded
by the authors.) When mature, the cysts appear to burst, the mero-
zoites (?) thus being ([distributed to neighboring tissues, giving rise to
new tumors by auto-infection.
In sarcosporidia, including muscle parasites of birds, lower mam-
mals and man, the process of endogenous multiplication proceeds in
a manner quite similar to that described above. In its earliest stages
the parasite appears as a minute white body embedded in the material
186
PARASITISM
of a muscle fiber (Fig. 79), in which condition it is known as Miescher's
lube, a name applied to the vegetative forms of the mouse parasite
Sarcocystis muris. As the young trophozoites grow, the nuclei increase
in number, a definite sac-like membrane develops around the proto-
plasmic body, while in the centre groups of spores begin to form.
The ripening spores (merozoites, gymnospores) gradually encroach
upon the more peripheral unused protoplasm of the tube until the
ends only appear to be active, and capable of vegetative functioning,
and even these, finally, are used in spore formation. In Sarcocystis
tenella of sheep such cysts may grow to a length of two inches in the
muscle bundles, where they ultimately burst, the spores being scattered
or carried by blood to new regions, where development begins anew
(auto-infection). In some cases the entire body may be over-run by
such parasites, mice especially often being killed in this manner.
FIG. 79
Sarcocystis muris, a muscle parasite of the mouse. (After Minchin.)
Iii all cases there is everv reason to believe that this method of
i/
endogenous multiplication cannot be continued indefinitely any more
than a paramecium can continue to divide indefinitely, and there is
reason to suppose that the potential of vitality gives out at the end of a
more or less definite cycle of generations. In many cases, especially in
the disease-causing forms in man, the organisms seem to have devised
a means of counteracting this senile process and of being stimulated
to renewed activity in much the same way that paramecium was
stimulated by artificial means (see page 131). It is a recognized fact
that many of the blood diseases are characterized by relapses in which
the organisms reappear after having disappeared from the circulation.
REPRODUCTION AND THE LIFE CYCLE 187
It was shown in the last chapter that paramecium could be restimu-
lated, even during a well-advanced period of depression, by means of
salts of different kinds. Such stimulation, preventing natural physio-
logical death of the organism, is analogous to the artificial partheno-
genesis by use of salts in the case of eggs of sea urchins and star fish.
The researches of Morgan, Loeb, "Wilson, Delage, and others have
shown that fertilization is not necessary for development of the egg
of such forms. So in the case of paramecium and other ciliates in
which the life history has been followed out, the use of a new medium
with some appropriate salt effected the same reaction as salts do in
artificial parthenogenesis. The observations upon the lower organ-
isms went a step farther, however, by showing that in paramecium
such stimulation could not be continued indefinitely, a time coming
when the stimulants failed to produce the effect previously obtained.
So it may be with the blood parasites ; some of them, like the malaria
organisms, may be artificially stimulated by some minute change in
the constitution of the blood, and so bring about a relapse (see Calkins,
1906). Parthenogenesis, effecting the same end, has been described
by Schaudinn in the case of Plasmodium vivax, the cause of tertian
fever in man, and in the case of Trypanosoma noctuoe, a blood parasite
of the little owl (see p. 163).
Variations in the endogenous cycle of parasites thus have to do
mainly with the methods of asexual increase. The more primitive
forms of parasites, i. e., those which have most recently adopted the
parasitic mode of life, still reproduce as do the free-living or non-
parasitic types. In other forms simple division is replaced by more or
less prolific methods of brood formation, in response, probably, to the
needs of the race, and methods which culminate in fully developed
schizogony, usually serving as a means of auto-infection.
2. Variations in the Exogenous Cycle. — The exogenous cycle
begins with the fertilization of the cell and formation of the external
spore coverings within which the young organisms are protected from
adverse conditions. There is reason to believe that such protective
structures and adaptations of the exogenous cycle are distinctly
characteristic of the period of youth in the life history, and due in large
part to the high potential of vitality which distinguishes the fertilized
cell from all others. The reproductive processes involved are certainly
more complicated than those of the endogenous cycle, and are more
definitely correlated with the perpetuation of the race.
In the simplest cases the fertilized cell forms a chitinous spore
covering which, with desiccation, may become hard and resistant,
while no internal nuclear or cytoplasmic processes take place. When
taken again into a new host, where conditions are favorable for the
dissolution of the cyst, a single, young, and uninucleate parasite
emerges. Such is the condition in many of the parasitic flagellates
188 PARASITISM
and rhizopods of the digestive tract of different animals, and is well
illustrated by the case of Copromonus xubtilis, a parasite of the frog
(Fig. 66, p. 153). Here two complete individuals are fused into one, the
copula forms a chitinous cyst and passes with the feces to the outside.
No multiplication takes place within the cyst, and infection of a new
host is brought about by feeding. A somewhat more complicated
history is presented by the intestinal amebre, wyhere encystment and
fertilization (in these cases autogamous) is followed by the formation
of spores, usually in small numbers, which are not liberated until the
definitive seat of parasitism is reached. Here, again, although several
young may be formed at the period of fertilization, there is apparently
little reason to imagine any great difficulties to be overcome by the
parasites in finding a new host.
Since, in flagellates, ameba?, and sporozoa, encystment is thus bound
up with fertilization, it would not be unreasonable to argue that where
such cysts are found, previous fertilization may, at least, be suspected.
Too much importance must not be attached to encystment, however,
for in many forms, especially in the free flagellates, ciliates, and rhizo-
pods, encystment may be brought about by the temporary adverse
condition of the surrounding medium, or even for purposes of diges-
tion. The encysted trypanosome, Tri/panosoma yntyi, which Minchin
('07) discovered in the rectum of the tsetse fly, Glossina pal pal is,
may be due to such change in the medium, or, which is less probable,
may be interpreted as a result of fertilization. This is the only case
among trypanosomes in which an encysted stage has been noted,
although Moore and Breinl ('07) have described small reproductive
bodies in Trypanosoma gambiense, which may have a like significance.
In this case, however, they are found in the blood and belong obviously
to the endogenous cycle (see p. 267). Metcalf ('07) has shown that
encystment of Opalina intestinalis and dimidiata which occurs in the
rectum of the frog, has nothing to do with conjugation. The cysts
pass out with the feces and after a longer or shorter period may again
be taken into a tadpole's digestive tract, where, after dissolution of the
cyst, a larger macrogamete fuses with a smaller "tailed" gamete, so
that fertilization in this case follows encystment. (Metcalf does not
find conjugation between two " tailed" forms, as Neresheimer describes,
see p. 158.)
It is among the sporozoa that the most remarkable and best-
illustrated phenomena of exogenous sporulation are to be found, and
here there is almost every conceivable grade of complexity. Owing
to the heterogeneous nature of the sporozoa and the wide variations
in the processes of sporogony, confusion must follow any attempt to
describe them all in one category. Generalizations can be made only
in connection with the more homogeneous groups of gregarinida and
coccidiidia, while the hemosporidia and other parasitic forms will
REPRODUCTION AND THE LIFE CYCLE 189
be considered more appropriately in connection with the diseases due
to them.
(a) Sporulation in Gregarinida. — As shown in the preceding chapter,
the number of gametes formed by the conjugating gregarines varies
within wide limits. In ophryocystis, according to Leger ('07), there is
but one gamete formed in each cell, while only one sporoblast results
from the fusion of the gametes (see Fig. 80). In other gregarines there
are many gametes, which, as previously shown, may be sexually
differentiated. In most cases these gametes arise from the parent
gametocytes, which are enclosed together within one common cyst
wall (pseudoconjugation), but in the remarkable case of Schaudin-
nclla hcnlece, described by Xusbaum ('03), the organisms are sexually
differentiated even before the gametocytes are formed, and pseudo-
conjugation of the gametocytes does not occur, each organism forming
its microgametes or macrogametes, as the case may be, independently
of one another, the gametes then meeting and fusing in the lumen of
the digestive tract.
At the other extreme we may place the two species of diplocystis,
where the organisms pair immediately after entering the celom of
their hosts and continue to live in couples, while any individual
remaining solitary dies without further growth (Cuenot, 1901).
Here, therefore, pseudoconjugation appears to be a necessity for the
organisms.
In all cases when the coupled gregarines are mature, the nucleus of
each divides bv mitosis to form a residual nucleus and a so-called
t/
" micronucleus" (Cufenot). The latter undergoes successive mitotic
divisions, and the resulting nuclei finally reach the periphery of the
cell, where the gametes are formed as buds.
Development of the fertilized egg is essentially the same in all of
the gregarines. The fertilization nucleus (synkaryon) divides by a
primitive mitosis three successive times, and the sporoplasm separates
into eight parts, one around each of the nuclei. Eight sporozoites
are thus formed in the typical case, only one exception, that of seleni-
dium, where there are but four sporozoites, being known.
The arrangement of the sporozoites in the sporocysts presents the
greatest variety, but has no importance from a systematic point of
view (Fig. 20). More important are the surrounding envelopes of the
bundle of sporozoites. In the majority of cases the sporocyst consists
of one (monocystis forms) or two tough, resistant membranes which
may become greatly hardened. \Yhen two are present, the inner or
cndospore is smooth and relatively thin, forming a closely investing
sheath about the sporozoites. The second or outer covering, the
episporc, is more resistant and may consist of several layers (ophryo-
cystis), while it is frequently drawn out into spines, lateral processes, or
long filaments (Fig. 20, D, F). Under the proper conditions the
190
PARASITISM
FIG. 80
Gamete formation and sporulation in Ophryoeystis mesnili, Leger. (After Leger.) X 2000.
A, two individuals attached by processes to ciliated epithelial cells of Malpighian tubule of
Tenebro mollitor; B, union of "gamonts;" C, D, E, first division of nuclei to form ger-
minal and somatic (s) nuclei; F, division of germinal nuclei to form first reduction nucleus
(r); G, segregation of protoplasm to form gametes (g); H,I,J, fusion of mature gametes;
K, L, M, first division of zygote; N, normal sporoblast with eight sporozoites.
REPRODUCTION AND THE LIFE CYCLE
191
epispores open either by dehiscence (Fig. 20, B, JV,) or by dissolution at
certain points, and the sporozoites emerge by typical contractile move-
ments. In the majority of cases there is a residual mass of sporoplasm,
which has received various names (reliquat sporal, sporenrest, sporal
residuum, etc.), and about which the sporozoites may be grouped in
characteristic manner. In some cases this residual protoplasm is more
than a mere degenerating mass, but is provided with special nuclei and
plays a definite purpose in the reproductive process. Thus, in
Ophryocystis mesnili it is nucleated, and functions as a nurse cell or
cells for the developing sporoblast (Fig. 80). In Monocystis and other
FIG. 81
?T^-W'Sa$£S
-fK>Vv/.;-:*^\
c
Cysts and siioroducts of Ciregarina cuneata. (After Kuschakewitsch.) A, surface view
of cyst with ripe spores (s) issuing fnnu spcirodurt.-. (e); B, section with ripening spores and
points on wall where sporoducts will form; C, section showing ingrowth of finger-like sporo-
duct (i), which finally evaginates to form the emission ducts (e).
gregarines the residual mass is gradually absorbed as food during the
formation of the sporozoites.
In some cases the residual mass of protoplasm plays an important
part in the dissemination of the mature sporozoites; in Gregarina
cuneata and probably in allied forms, according to the recent observa-
tions of Kuschakewitsch ('07), the residuum takes the form of a hollow
brood chamber (Bndraum, of Kuschakewitsch), and its protoplasm
retains a quantity of the residual chromatin from which as "amphi-
chromidia" the gametic nuclei had previously been formed. This
residual "chromidial net" collects in rings at the periphery and around
192 PARASITISM
the borders of the brood chamber, which is connected by broad spaces
with the peripheral rings of chromatin. From the walls of these rings
tubular ingrowths next develop and grow down into the brood chamber
among the sporocysts (Fig. 81). When mature, and under proper
environmental conditions, not as yet . recognized, these tubular
ingrowths are evaginated and the sporocysts ejected through them.
(6) Sporulation in Coccidiidia. — In coccidiidia the processes of con-
jugation and sporulation are involved with complex sex differences,
pseudoconjugation, as observed in gregarines, being unknown. Here
a spermatozoid and an egg cell are formed and fusion is complete.
The fertilized cells, furthermore, have a somewhat different history
from those of the gregarines, where the zygote becomes at once the
sporoblast and secretes a single or double sporocyst. In the coccidian
forms, on the other hand, the fertilization nucleus of the zygote or
copula only rarely (Legerella, Mesnil) divides to form sporozoites
directly, but in the remaining genera the primary divisions give rise
to nuclei of two or more independent sporozoite-forming centres.
Thus, in Coccidium schubergi the zygote nucleus divides twice, form-
ing four daughter nuclei, about which the protoplasm of the zygote
forms four sporoblasts. Each sporoblast secretes its own covering or
sporocyst, and each gives rise to two sporozoites (Fig. 74, p. 179). The
final mature germs are thus inclosed within two membranes, their own
sporocysts and the oocyst which forms as a fertilization membrane,
Legerella alone being protected by the latter only. Classification of
the coccidiidia is frequently based upon the number of sporocysts
thus formed. Cryslullospora crystalloides, like coccidium, has four
such sporocysts, but the great majority of the tetrasporocyst forms
belong to the latter genus. Others, notably cyclospora, diplospora,
and isospora, have only two sporocysts; still others, and perhaps the
most common forms, have more than four sporocysts, adelea, caryo-
tropha, and klossiella belonging to this category.
In these forms, as in the gregarines, the number of sporozoites is
independent of the number of sporocysts; in barrousia, echinospora,
and diaspora (Fig. 20, p. 64) the sporocysts are monozoic; in adelea and
minchinia, dizoic; in benedenia, trizoic; in klossia, tetrazoic; and in
caryotropha, polyzoic. It is significant that in the malaria organisms
there are several centres of sporozoite formation, each of which, if
covered by a membrane, would be homologous with the polysporo-
cystid sporocyst. This may be merely a parallel development, or it
may have some phylogenetic significance, showing descent from coc-
cidium-like forms, with loss of the now useless protective sporoblast
membranes.
(c) Sporulation in Myxosporidia. — Little more need be added to what
has already been given in connection with spore formation in this group
(see p. 143), for it is closely connected with the phenomena of fertiliza-
REPRODUCTION AXD THE LIFE CYCLE
193
tion considered in the preceding chapter. The spores are usually pro-
tected by thick and tough membranes, and are distinguished from all
other sporozoan spores by the presence of spirally wound threads con-
tained in two to four polar capsules. They are often ornamented in
some way and are always in the form of two valves, which meet in a
suture representing the line of splitting when the spores germinate
(Fig. 20, G, K, p. 64). The polar capsules are variously arranged in
the spore, and the usual interpretation of the thread is that originally
given by Thelohan ('92), that they are for the purpose of anchoring
the spore in the lumen of the digestive tract. The most curiously
FIG. 82
Spores of actinomyxidae. (After Caullery and Mesnil.) A, Hexactinomyxon psarn-
moryctis (after Stole), X 450; B, Spheractinomyxon stolci (after Caullery and Mesnil), X 900;
C, Triactinomyxon ignotum, Stole, X 250; D, Triactinomyxon ignotum, spore-bearing part of
same enlarged (after Leger), X 900; E, Synactiuomyxon tubificis, Stol6, X 900. In A, B, D,
and E, the evaginated spiral filaments are shown.
ornamented of all spores are those of the actinomyxidae, where long-
processes and curiously placed polar capsules and sporozoites are
characteristic (Fig. 82).
3. Exogenous Life of Protozoan Parasites.— By exogenous life of
parasites is meant here the life outside of the usual host, whether this
is the primary or " intermediate" host. It is the most critical period in
the entire life history of a parasite, and a successful outcome is depen-
dent upon several factors, the most important being: (a) dissemination
of the spores, and (6) infection of new hosts, the latter factor in
particular having given rise to the most diverse adaptations.
13
194 PARASITISM
The environmental conditions which parasites have to meet and
overcome are well stated in principle by Manson in the following
excerpt: "The pathogenic protozoa are responsible probably for a
very large number of diseases. Many appear to be able to pass directly
from host to host, unaffected apparently by the atmospheric conditions
they encounter on the passage; that of smallpox and of most of the
exanthematous fevers probably belong to this category. Others, on
the contrary, demand special climatic conditions. Such are the germ
of scarlet fever, which does not spread in the tropics, and the germ of
dengue which, conversely, does not spread in cold climates. That of
the first is killed or paralyzed by heat; that of the latter by cold. Or,
it may be, they do not find appropriate transmitters except in special
climatic conditions. Many of the protozoa acquire the power of suc-
cessfully invading the human body only after certain developmental
changes, which take place after they leave their first host. Thus,
according to Schaudinn, the germ of amebic dysentery has to pass
through a sporulating stage before it becomes infective, and this stage
is accomplished outside the body and in conditions of tropical heat.
Hence, amebic dysentery is a tropical disease. Other protozoan dis-
ease germs, notably those of malaria, yellow fever, trypanosomiasis,
and relapsing fever, require an animal intermediary to remove them
from the body of their original host, foster them during a necessary
stage of development, and reimplant them in the human host. These
animal intermediaries being tropical, the diseases they disseminate
are also necessarily tropical." (Introduction to Vol. II, Part II, of
Allbutt and Rolleston's System of Medicine, 1907.)
The majority of facultative parasites (some species of entameba,
cercomonas, copromonas, etc.), and many obligatory parasites, find
their best environment for further development in the digestive tract
of different animals, and the spores, when formed, are discharged with
the feces. Protected by their tough sporocysts, they may resist drying
for long periods or until taken again into some digestive tract, infection
being due to the more or less gregarious mode of life of the hosts and
to their indiscriminate feeding. An essentially similar result is
obtained in the case of cannibalistic animals, where, as in centipedes,
the weaker forms are eaten by the stronger and with them whatever
parasites they happen to harbor; it is in large part for this reason
probably that centipedes are rarely found without sporozoan para-
sites of some kind. In wTater-dwelling animals the spores of mvxo-
sporidia are usually disseminated through the water, so that infection
is brought about in the same way through the digestive system. In
land-dwelling or air-breathing animals of clean habits such sources
of infection are rare, and comparatively few protozoan parasites
occasionally found in them acquire a new host in this way. Other
means, however, especially in the higher animals and man, are effective
REPRODUCTION AND THE LIFE CYCLE 195
in keeping up the various races of parasites, and infection of new hosts
may be brought about by (a) breathing; (6) by direct transmission or
contact; (c) by inheritance; or (d) by indirect transmission through
the agency of intermediate hosts.
(a) Air-borne Protozoan Parasites. — So far as the protozoa are con-
cerned, this method of infection plays but little part, and then only in
cases of certain diseases, such as scarlet fever, smallpox, and a few
others which are not yet accepted by all as due to protozoan parasites.
The great majority of protozoa capable of withstanding the condition
necessary for this mode of infection are too large and heavy to be
conveyed as dust. In trachoma, smallpox, and scarlet fever, which no
one would question as being germ diseases, the spores of the organ-
ism causing: them are so minute as to be readilv disseminated with
o «.
cutaneous debris, or as Fltigge ('97) has shown in experiments with
bacteria of different kinds, they may be spread in minute droplets of
mucus or sputum. So far as known, the seat of invasion of these
spores or minute organisms is the respiratory tract, where the nasal
lining may harbor the spores of trachoma, or the corrugated surface
and imperfect epithelium of the tonsils may give lodgement for the
spores of smallpox and scarlet fever. It is possible that the organism
found by Minchin and Fantham ('05) in nasal tumors (Rhinospori-
dium kinealyi) is transmitted in this way, although nothing is known
as to the exact method of its dissemination.
(6) Transmission of Protozoan Parasites by Contact. — A large number
of protozoan diseases are due to the transmission of the parasites by
direct transmission through contact which may be brought about in
various ways. Wherever external lesions occur this means of infection
is possible. In the case of rabies, where contact is brought about
usually by the bite of some infected animal, the parasites are intro-
duced with the saliva and gradually make their way into the central
nervous system, although, as Pasteur first showed, the entire nervous
system from periphery to centre may contain the virus. Not only by
biting, but by other ways as well, may the organism of hydrophobia
(Neuroryctes hydrophobici) get into the human organism; infection
may follow from carelessness in the operating room, or, a particularly
potent way, from the licking of infected animals on abraded or chapped
surfaces of hands or face.
Usually the organisms thus transmitted by contact have the power of
spontaneous motion, the passive sporozoa being rarely spread in this
way. A possible exception, however, appears to be the case of the
so-called Coccidioides immitis, described by Rixford and Gilchrist
('97), in Argentina and the Southern States. The disease first mani-
fests itself in the human skin, and may pass by way of the lymphatics
to liver, spleen, peritoneum, and other organs of the body, ultimately
causing death. The organisms first form small granulation tumors in
196 PARASITISM
the corium and give rise to minute papilla-like protuberances, which
may run together, continually increasing by peripheral growth. Blan-
chard considers these parasites to be sporozoa, but doubts their affinity
with the coccidiidia (Liihe, Minchin).
The genitalia are frequently the seat of infection for several kinds
of protozoan parasites; Trypanosoma equiperdum, Dofl., for example,
the cause of dourine in horses, is transmitted solely by coition, the
flagellates getting into the blood by penetrating the epithelium. Simi-
larly, with Trypanosoma gambiense, the cause of sleeping sickness in
man, the organisms are said to pass from person to person in this
way (Koch), while the organism of syphilis in man — Treponema palli-
dum — is readily transmitted from person to person by coition. Rest-
ing or encysted stages' of the latter organism are unknown, but vitality
is apparently retained for long periods, for infection may be brought
about by contact with places contaminated by infected persons; abra-
sions and chapped surfaces are particularly dangerous.
(c) Transmission by Inheritance. — The transmission of protozoan
parasites by inheritance is only a modified form of contact trans-
mission, and might well be expected in the case of such parasites as
are capable of independent motion. It is satisfactorily established
at the present time that bacteria are not transmitted from mother to
child and that bacterial infection in utero is practically nil. With
protozoa, on the other hand, infection in utero by way of the placenta
and umbilical cord is fullv established in some cases, while in the
«i
lower animals, such as invertebrates and aplacentalia among verte-
brates, inheritance of such disease-causing forms is much more
common.
Pasteur ('58) early discovered that the only successful means of
combating the silkworm disease, due to Glugea (Nosema) bombyces,
was to carefully examine the eggs of the insect for cysts and to destroy
all that were found to be infected. Careful prophylaxis of this kind,
together with proper scrutiny of food, finally put an end to the inheri-
tance of the disease from generation to generation and brought to a
close a long-continued epidemic which had cost nearly one thousand
millions of francs. The later observers have placed such inheritance
among insects and arachnids upon a much safer basis, and in many
cases the transmission of protozoa from parent to offspring is fully
established. Smith and Kilbourne ('91) discovered that ticks belong-
ing to the genus Rhipicephahis (Boophilus) draw blood from cattle
infected with Babesia bovis (Piroplasma bovis), and convey the infec-
tion in time to some new host. Koch observed that the ova of ticks
were actually infected, and that the young, in addition, feed upon the
infected blood, so that the second generation transmits the disease,
and Christophers ('07) showed that reproductive bodies of Babesia
(Piroplasma) canis penetrate the ova, either in the ovary or during the
REPRODUCTION AND THE LIFE CYCLE 197
passage of the eggs down the oviduct, develop in the yolk of the egg,
and become disseminated throughout the embryonic cells, reproducing
the while, and finally lodging in the salivary glands of nymphs and
images. Similarly, with ticks of the genus Argas, which are known to
transmit spirochetes of different species infecting birds and fowls,
Levaditi has shown that the spirochete of relapsing fever or spirillosis
in chicks penetrates the ova of Arc/as miniatus, and in this way infects
the young chickens. Relapsing fever in man due to Spirocheta dnitoni
is conveyed by ticks of the genus ornithodorus, in the eggs of which
Carter ('06) and others have shown that the ova are frequently the
seat of multiplication of the parasites derived from the infected parent.
FIG. 83
V (' -4- 'VVT
'
Section of lung infested by Treponema pallidum; congenital syphilis. X 800.
A final stage in the development of this means of transmission is sug-
gested by Ward ('08), in connection with the parasites of the intestine
of the housefly, which, no longer drawing blood, transmit the para-
sites from generation to generation only through the embryos. This
suggestion, however, loses weight from the fact made out by Patton
('08) that direct infection follows ingestion of encysted forms of the
intestinal parasites.
With man and mammals transmission by inheritance is much more
difficult, if for none but mechanical reasons. The parasites must
penetrate the placenta and the solid tissue of the umbilical cord, and
it is conceivable that only minute and highly motile forms can do so.
It is a well-established fact, however, that certain kinds of parasites
198 PARASITISM
belonging chiefly to the trypanosome and spirochete group are capable
of passing through the finest filters, and such forms of protozoa, if any,
might be expected to infect an embryo in utero. This is certainly
true of the organism of human syphilis, congenital cases not infre-
quently occurring in which the parasites are transmitted either with
the spermatozoa or with the egg, or through the placenta from the
mother infected during pregnancy. Such congenital cases are often
highly virulent; all organs and tissues of the unfortunate infant may
be over-run with the malignant spirals (Fig. 83).
With transmission by contact or by inheritance, there is, strictly
speaking, no free or external life of the parasite, the organisms passing
directly from one living host into another, and this form of infection is
often bound up with one of the most interesting and important of the
protozoan vital phenomena, the transmission by intermediate hosts.
(rf) Transmission by Intermediate Hosts. — Direct infection by way
of the digestive tract by ingestion of spores of the parasites with food
may become complicated by passive carriage through intermediate
hosts often of a quondam character. While not proved, this appears
to be a highly probable means of infection. Thus, as Minchin points
out, in the case of the monocystis parasites of the earthworm, where
the organisms are parasitic in the seminal vesicles of the worm, there
is but slight possibility of the parasite spores passing to the outside
with the spermatozoa or through the dorsal pores of the worm, and
there is little doubt that the animals are infected by way of the diges-
tive tract. It is suggested by Minchin that the infected worms are
eaten by birds, and that the spores of the gregarine, protected by their
resistant coatings, pass undissolved through the avian digestive tract,
to be disseminated with the bird's feces about the ground, where in
time they may be again eaten by a worm. Similar conjectures might
be made for other animals whose habits, life histories, and parasites
are known.
A mode of transmission such as this would involve only a passive
phase in the life history of the protozoan parasite; in the majority of
cases where the relation of parasites to intermediate hosts are fully
made out the period in such a host involves some of the most impor-
tant activities in the life of the parasite. Here are to be found some of
the most perfect adaptations of means to ends that are known in
biology; those forms which are not protected by resistant coverings
and where infection is brought about through the aid of an obligatory
intermediate host are the most remarkable. The malaria organisms,
for example, if sucked with the blood into the digestive tract of a
mosquito of the genus anopheles, are all digested save the conjugating
forms, which are apparently endowed with some greater power of
resistance than are the vegetative forms. But if the same parasites are
taken into the stomach of a mosquito of the genus culex, gametes, and
REPRODUCTION AND THE LIFE CYCLE 1Q9
other stages as well are alike digested; hence the various species of
culex cannot transmit malaria to man. Similarly with other forms of
blood-dwelling parasites, each is apparently restricted to certain types
of hosts, although in some cases a certain latitude in this direction is
noted (Trypanosoma brucei, some species of Babesia, etc., may be
carried by different hosts). The ultimate explanation of this resist-
ance lies in the domain of physiological chemistry, and until this branch
of biological science is more fully worked up the full significance of
these adaptations will not be known.
The same powers of adaptation that underlie the transmission of
malaria by mosquitoes apply to other cases of parasite transmission.
Mosquitoes carry trypanosomes from owl to owl; others (stegomyia)
carry the organism of yellow fever; tsetse flies (giossina) transmit
sleeping sickness in man or Nagano, in cattle; other insects and ticks
carry different kinds of disease-causing organisms in lower domesti-
cated and wild animals; bedbugs transmit kala azar and relapsing
fever; while leeches are intermediate hosts for some parasites of fish
and amphibia.
In many of these cases the parasites undergo a definite develop-
mental cycle in the body of the intermediate host, although in relatively
few cases have the happenings in such cases been fully determined.
In the case of malaria organisms, of Herpetomonas (Leish mania)
donovani and some trypanosomes, the most important phases in the
life history of the parasites, sexual reproduction whereby the vitality
is restored, are known to take place. In other cases, including the
majority of trypanosomes and spirochetes, and most other protozoan
disease-causing forms, little more than asexual multiplication within
the intermediate hosts is known to occur.
It makes a very pretty subject for an academic debate whether
anopheles first gave malaria to man, or whether man gave acute
enteritis to the mosquito. There is some reason to believe that these
blood parasites, or at least some of them, have descended from the
coccidiidia, and that they have become specifically adapted for life
in the blood instead of in the epithelial cells of intestine or ccelom.
The evidence for this is based partly upon the intracellular mode of
life characteristic of the majority of the hemosporidia and partly upon
Hintze's (questioned by Liihe on the ground of confusion with some
form of coccidiidia) observations upon the life history of the common
blood parasite of the frog, Lankesterella. While his observations have
been questioned, they have not yet been refuted, and his conclusions
are still possible, especially in consideration of the recent findings
of Miller ('OS) in the case of Hepatozoon perniciosum (see p. 269).
Fertilization, according to Hintze, takes place in the intestine of the
frog, and the zygote moves like a gregarine through the fluids of the
digestive tract until it enters an epithelial cell, where it encysts. As
200 PARASITISM
Minchin suggests, it is possible that the organism is taken into the
digestive tract and the sporozoites liberated there to pass through the
epithelial cells into the blood, where asexual reproduction occurs. If
this questionable life history is true, it is conceivable that the ancestral
forms of the blood-dwelling hemosporidia were similar to coccidiidia
and made their way into the blood spaces from the digestive tract.
On the same hypothesis it is further conceivable that the blood-sucking
insects or leeches, while usually able to digest such forms taken in
with the food, in some cases provided a suitable environment for their
further development. Spore cases, characteristic of the supposed
ancestral forms, would be unnecessary with the substitution of the
insect-dwelling mode of life for the former exposed life, and, on
the other hand, would be of marked disadvantage to the young forms
upon reinoculation in the blood of a newr host. According to such an
hypothesis, the first or original primary host of such hemosporidia
would be man or other vertebrate type, while the secondary or "inter-
mediate" host would be the insect or leech. On such an hypothesis it
might be further assumed that in earlier times the intermediate host
acted as a mere carrier, the organisms remaining passive during the
interim.
The above is the opinion concerning intermediate hosts held by
Minchin ('07) and other protozoologists whose dicta carry much
weight, but opposed to them are other students of the group, including
Laveran, Mesnil, Grassi, Liihe, and others whose conclusions, based
upon the recent observations on the blood-dwrelling forms, are more
convincing. Such conclusions are based largely upon the fact that the
most important phases in the parasite's life history occur in the diges-
tive tract of the invertebrate host, and that sporozoites, not merozoites,
are transmitted by them to man. Recent observations on blood-
dwelling forms in man indicate that the ancestral forms were not
coccidiidia but mastigophora. Schaudinn was the first to note the
relation between a free-swimming Trypanosoma noctuce in the blood
of the little owl, Glaucidium (Athene) noctuce, and the intracorpus-
cular parasite of birds which had been known as halteridium (hemo-
proteus); also, he was the first to see the transformation of the intra-
cellular into the flagellated form. Since then his observations have
been confirmed by various observers, the brothers Sergent ('C5) find-
ing most of the details as he had described them. In a number of
other forms as well the relation of a flagellated type to intracellular
types has been established. Rogers, Christophers, Leishman,
Patton, and others have noted the transformation of the intracellular
Leishman-Donovan bodies into flagellated parasites similar to the
genus herpetomonas, such transformation taking place both in the
digestive tract of the invertebrate host (Cimex rotundatus) and in
artificial culture media. From these observations there is reason for
EFFECTS OF PROTOZOAN PARASITES UPON THEIR HOSTS 201
the belief of Liihe, Mesnil, and others, that the original forms of some
at least of these organisms were flagellated protozoa which have lost
their motile organs and assumed an intracorpuscular or cytozoic mode
of life with the accession of parasitism in man. Also, it appears from
such cases that the original hosts were insects and not man, so that
here at least man wTould appear to play the part of intermediate or
secondary host.
The further deductions which some recent observers have made
(notably Hartmann and Kisskalt, and others), that all hemosporidia
are to be traced to flagellated ancestral forms, and that the group as a
division of the sporozoa should, therefore, be abandoned, does not
follow from the evidence and cannot be sustained at the present time
(see p. 269).
III. EFFECTS OF PROTOZOAN PARASITES UPON THEIR
HOSTS.
The malevolent effects of various kinds of protozoan parasites on
their hosts may be either chemical or physical in nature, and due to
products of their own metabolism, or to mechanical destruction of
cells and tissues. The majority of the former type give rise to anti-
bodies which may persist for varying periods, thus setting up an active
or a passive immunity.
Beyond the fact that they differ in different cases, little is known
about the chemical effects produced by protozoan parasites. Nor is
the definite action known in many instances. In the case of malaria
the pyrexial attacks are supposed, by the majority of authorities, to
be due to the liberation of a toxin contained in the pigment melanin
which is elaborated by the parasites. The sudden precipitation of this
pigment in the blood upon dissociation of the merozoites causes intoxi-
cation and convulsions. Celli, Gualdo, Montesano, and others have
produced similar convulsions by inoculation with the serum of malarial
blood without the organisms, while, as Thayer points out, the coinci-
dence of the convulsions with the schizogony of the parasites and the
liberation of these pigmented substances, when taken together with
the degenerative changes often found in the brain, nerves, liver, and
kidney, all point to the conclusion that some toxic substance or sub-
stances are present.
A widespread effect of protozoa is the lysis set up by their presence
in cells and tissues. This was clearly worked out by Councilman and
Lafleur ('91) in the case of amebic dysentery, where the parasites
penetrate the submucosa, where they cause the cells to jellify and
degenerate. Similar destructive changes are brought about by the
organisms of trachoma, of rabies, and of smallpox. Neurorydes-
202
PARASITISM
hydrophobia, presumably by the secretion of some toxic substance,
causes the destruction of brain and nerve cells, while Cytorydes
variolce produces a like destruction of the generative cells of the skin.
A much more subtle action is shown by those parasites which
cause hypertrophy or multiplication of the infected cells. The great
tumors often found in the cruciferee arising from the root cells owe
their origin to some chemical effect produced by the intracellular
parasites Plasmodiophora brassicce, and numerous observers have
sought to explain human cancer and other tumors in like manner.
FIG. 84
n
^sK^^v^s^. * /^«u) / x
^li^^^^m^fe^^
^M "*§KfeC5»' ^J? ;?»^ /(*&'»?,,*<$-,
*c/. V j-Tr t — uj rS^-^ !io»i '4.TOTs^> *• _• i ?? ^ ^Jt-r
Caryotropha mesnili, Sied. 4, coecidian parasite of spermatogonium cell which is much
hypertrophied while the remaining spermatogonia of the bundle form an epitheliod layer about
it. An intracellular canal in the parasite connects the nucleus (n) of the host cell and the
nucleus of the parasite while a stream of foodstuff proceeds from the former to the latter.
(After Siedlecki, combination of drawing and photograph.) X 760.
The demoralizing effect which an intracellular parasite has upon
an animal cell is well shown by Siedlecki in the case of the sporozoon
Caryotropha mesnili. The organism is a parasite in the spermato-
gonia of the annelid Polymnia nebulosa, 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 a merozoite or sporozoite, one only of the bundle, 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 germinal structure, becom-
ing hypertrophied and distorted (Fig. 84). Not only the infected cell,
but all of the other cells of the spermatogonia bundle are affected,
and none of them continue the normal development, but become
arranged like epithelial cells about the hypertrophied infected cell.
EFFECTS OF PROTOZOAN PARASITES UPON THEIR HOSTS 203
Here, then, is a change which, as Siedlecki points out, recalls the con-
dition which Hertwig ('04) shows is characteristic of degenerating
cells, the simplification of the cell type from a more complex "organo-
type" into a simple "cytotype," or a return to the embryonic condition.
The specific effect of the young caryotropha on the infected cell
consists not only in the enlargement of that cell, but of a definite feed-
ing mechanism by which the parasite is supplied with food. That
the nucleus is the seat of constructive metabolic changes is well assured
at the present day, and the conditions in these parasites suggest the
peculiar relation which Shibata ('02) has described in the intracel-
lular 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. 84). In the cytoplasm of the cell an
intracellular canal is then formed which runs from the host nucleus to
the nucleus of the parasite, and Siedlecki holds that the food of the
parasite is all elaborated 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.
Not only hypertrophy of the cell, but of the nucleus as well, may be
caused by the presence of protozoan parasites. Doflein ('07) has
shown that the nucleus of Ameba vespertilio becomes greatly enlarged
through the action of intranuclear parasites, and similar enlargement
is characteristic of the skin cells in smallpox lesions. Leger and
Duboscq ('04) noted that gregarines may cause the formation of
multinucleated cells, while in some forms (Stylorhynchus oblongatus
and >S/. longicollis) the epimerite penetrates the cell and rests in
the vicinity of the host nucleus. In these cases the French observers
state that the parasites attached to the epithelial cells prevent the
normal nourishment of the latter and also prevent the cells from
secreting properly, so that they do not develop but remain of embryonic
type, and may even divide. Where the parasites are abundant in an
organ the destruction of cells is too rapid for regenerative processes to
keep up. Thus, Schaudinn ('02) has shown that Cyclospora caryolytica
may be so abundant as to cause acute enteritis and death of the mole,
its host, within a few days. Here the effects are purely mechanical,
and in this category belong the great majority of protozoan parasites,
especially those forms which are intracellular during part or the whole
of their life. Liver cells, muscle cells, even heart cells, may all be
destroyed by some form or other of protozoan parasite, usually a
sporozoan, and these cytozoic forms rarely confer immunity on the
host organism.
204 PARASITISM
IV. PROTOZOA AND THE CANCER PROBLEM.
Before describing, in the following chapters, the well-defined and
accepted pathogenic protozoa, it may be well to consider first some
pseudoprotozoa that have been brought forward from time to time as
the cause of cancer. This disease, more than any other human ail-
ment, has been a fruitful field for such forms, and the many struc-
tures that have been described as protozoa must be regarded only as
monuments to innumerable well-meant but immature efforts to dis-
cover the cause of this subtle malady.
Of the many varieties of tumor occurring in man, carcinoma, or
"cancer," is the one offering the most striking biological phe-
nomena, although there is reason to believe that other tumors, espe-
cially sarcomata and epitheliomata, are manifestations of the same or
of similar causes. In all cases, whether benign tumor or malignant
growth, the one common characteristic is the power of cell prolifera-
tion, and the "cancer problem" which today engages the best effort
of many pathologists, chemists, biologists, and medical men in general
in every civilized country is to ascertain the cause or causes under-
lying such proliferation. Many believe that the secret is bound up
with the problem of life itself, and will be solved only when the latter
is an open secret; but the great majority of investigators fortunately
take the more hopeful view that cancer, being an abnormal growth,
has some specific and demonstrable cause.
In every type of animal, including even the protozoa, there is a
more or less well-defined power or "potential" of division energy of its
cells, a power which gradually diminishes with advancing age and
ultimately gives out (see p. 134). The individual cells then cease to
multiply, and in the higher animals their activities are directed toward
the one physiological object for which they are specialized, and divi-
sion is resumed only when some external and unforeseen cause, such
as a wound, starts up the inhibited development. Even this power of
regeneration is lost to some types of physiologically unbalanced tissue
cells.
In the higher animals the cells of the epithelial group retain the
physiologically balanced condition longer than any other type. This
is the group to which the germ cells and the endothelial and secreting
cells belong, the so-called "noble" cells of the body, some of them,
like the skin cells, retaining their division energy throughout life,
while others, the germ cells, possess the potential of endless existence.
Even among the cells of the epithelial type the potential of division
energy varies, and in the highly specialized and physiologically unbal-
anced tissue cells it is early exhausted. It is in connection with these
cells that we must look for the cause of carcinoma; in their vital
PROTOZOA AXD THE CANCER PROBLEM 205
manifestations and in the reanimation of their latent division energy
lies the cause of from five to six deaths from cancer in every hundred
deaths from all causes.
The carcinoma cell biologically is a perfect vital mechanism
endowed with far greater power of resistance than normal cells, a
resistance which enables it to withstand long exposure to liquid
air, or long periods apart from the sources of nourishment. In
reality it is no longer an epithelial cell; something has changed it
from such a physiologically unbalanced unit, subject to the coordi-
nating control and regulation of the organism, into a physiologically
balanced cell, uncontrolled and unregulated. Functionally, it is a
more perfect type than its orderly associates of the epithelium from
whence it springs; it takes in and assimilates abundance of food,
grows rapidly, especially when near the source of food, and repro-
duces its like by means of the same complicated processes of mitosis
that characterize normal cells, although it does not become differen-
tiated into organs, as do embryonic cells. "In short, it is a complete
organism in itself, simulating in many ways the parasitic protozoon,
but differing in some of the most important respects connected with
the continued life of the latter." (Calkins, 1908, p. 286.)
By this continued cell division masses of tissue are formed which
grow out into lymph channels, pressing into spaces wherever found,
mechanically obstructing the normal activities of surrounding tissues
and organs, or breaking through such tissues, and ever giving off small
groups of free cells which may be carried by the blood to various parts
of the body, there to set up independent growths (metastases) and to
become new centres of malignant activity. "With the local disturb-
ances caused by such abnormal growths, many normal cells are killed
for lack of nourishment, or by poisonous degenerative matters of one
kind or other, while the cancer cells themselves undergo hyperplasia
and hypertrophy through lack of food, pressure, or natural resistance
of the victim. The march of cancer, therefore, is invariably accom-
panied by multitudes of degenerating cells, leukocytes of all kinds,
blood platelets, and the like, and these different structures are the
things which, in various stages of involution and degeneration, have
been interpreted as "coccidia," "amebo?," "X-bodies," or, more
specifically, as "strombodes" (Sjobring), "Rhopalocephalus car-
cinomatosus" (Korotneff, '93), "Cancriameba macroglossa" (Eisen,
'00), "Histosporidium carcinomatosum" (Feinberg, '03), or as other
"organisms" with resounding names, the "cause" of cancer.
Little interest is excited at the present time by description of such
cell inclusions in cancer, and investigators, on the whole, are content to
regard all such structures as degenerations or products of the disease
rather than its cause, and with this change in attitude the problem of
cancer has passed from the descriptive into the much more fruitful
stage of experimental research.
206 PARASITISM
The early history of animal cancer has a certain historical interest
in medical circles, but the present-day activity dates back only to 1902,
when Jensen, of Copenhagen, discovered that mouse cancer (adeno-
carcinoma) can be transplanted from one mouse to another. With
more than usual breadth of view and scientific generosity, Jensen
distributed his cancer material to all who wished it, and the result is
that the "Jensen strain" of mouse cancer is being studied and trans-
planted in all parts of the civilized world, while special laboratories
for the exclusive study of cancer have been established in Buffalo, in
London, Heidelberg, and other places. Investigation has brought
out the fact that this mouse tumor differs but little from human car-
cinoma, while similar primary tumors are now known to occur in one
mouse in every 2500 (Bashford). Hundreds of such primary cancers
have been transplantable, so that today many in addition to the Jensen
strain are being studied. Malignant growths in other animals (rats
and dogs especially) have been discovered, and are all contributing
data for the ultimate control of human cancer. This dreaded disease,
therefore, which is still impossible to control and the cause of which is
still unknown, is at present in the full swing of experimental study.
It was early shown by Jensen and his followers that a tumor induced
in a normal animal by inoculation is derived not by the abnormal
division of cells of the normal animal, but by proliferation of the
transplanted cancer cells of the diseased mouse. The induced tumor,
therefore, is not equivalent to a primary tumor, but may be regarded
as equivalent to a metastasis from such a primary growth. Further-
more, it was early shown that human cancer when similarly trans-
planted in mice, or any other lower animal, will not grow; nor will
the mouse or rat tumor grow in any other animal than the definitive
species. Cancer in lower animals, therefore, need not cause appre-
hension, although it is always possible that the unknown cause or
causes may be the same or similar in all cases.
The Jensen tumor, to take only one example, has now been trans-
planted through nearly 100 generations, or possibly more, counting
as a generation the successive tumors produced by inoculation. The
average length of time required by the Jensen strain to develop into
a cancer fatal to the inoculated mouse varies from three to four weeks,
but it may be reduced to ten days or two weeks, or increased to three
or four months or longer.
This long-continued transplantation and the fact that each new
transplantation results in the formation of a mass of cancer cells
derived from the transplanted cells, yielding a growth which, up to
the present time, amounts to a small mountain of mouse tissue, indi-
cates that the cancer cells are somehow endowed with the possibility
of an indefinitely continued division energy. The cancer cell, there-
fore, is different from any animal organism that we know, for in all
PROTOZOA AND THE CANCER PROBLEM 207
cases indefinitely continued protoplasmic existence is bound up with
the phenomena of fertilization and inheritance. The cancer cell, so
far as we know, undergoes no process analogous to fertilization.
Farmer, Moore, and Walker ('03) have described "hetero typical"
mitosis in cancer cells, and claim that, as in germ cells, this is evidence
of the preparation for fertilization, but numberless critics have shown
that it indicates only the degenerative changes which the majority
of the cancer cells that are formed must undergo, since all that are
formed cannot find nourishment, or escape the protective reactions
of the host organism. Cytologists, also, are constantly demonstrating
that heterotypical mitosis is a form which the mitotic figure may
assume under almost any abnormal condition ; Haecker ('04) obtained
them in embryonic cells treated with ether and other poisons, while
Bonnevie ('07) has shown that they are common enough in normally
developing cells of different animals and plants. The further obser-
vations of the English observers as to a reduced number of chromo-
somes in cancer cells are more safely explained upon the lines early
laid down by Hansemann ('93), as due to abnormalities brought about
by deranged mitotic figures in degenerating cells.
It is beyond the scope of the present volume to discuss the various
theories that have been advanced to explain the source of the stimu-
lus to cancer-cell proliferation. Ewing ('08), in an excellent summary
of the present status of the cancer problems, broadly divides all theories
into two categories, which he designates the parasitic theory and the
cell-autonomy theory. The former, held by von Leyden, Behla,
Borrel, Gaylord, and a host of others, interprets cancer as due to the
action of some foreign living organism stimulating the cell to divide,
and so to produce the primary tumor, and by its continued presence
maintaining the stimulus to proliferation. The other theory, held by
the great majority of pathologists and medical men in some form or
other, and taking concrete form in the theories of Cohnheim, Ribbert,
Ehrlich, Ewing, and others, interprets cancer as due to the breaking
loose of some cell or cells from the regulating control of the organism
and starting off on an independent career of lawless development.
Against the former theory must be charged the fact that no specific
parasite has been continuously found in human or animal cancer,
nor does the clinical history of the disease furnish anything similar to
that of known infectious diseases. Against the latter must be raised
the important objection that in no form which the theory assumes is
there a satisfactory explanation either of the cause of cancer or of the
power of continued proliferation. It is true that normal vital processes
are not yet sufficiently known to enable us to predict what might
happen under abnormal conditions, and with those who are pessimistic
enough to believe that the problems of cancer and of life itself are all
one, we may assume that only in time will further knowledge show
208 PARASITISM
how the power of regulation may be lost to these specialized tissue
cells, and the power of endless proliferation gained. To say, as
Adami ('01) does, that in cancer cells the "habit of growth" has
replaced the "habit of work," or to admit with Oertel ('07) that if
a gland cell can be induced to excessive secretion we might with equal
right expect it to be induced to divide excessively, is simply to say
with Hertwig ('04) that the cells of carcinoma have changed from an
"organotype" into a "cytotype." Such statements, forming the real
substance of many polemical writings on cancer, merely state the
problem and are perfectly true, for cancer, or malignant growth of
cells, does exist. These truths do not furnish any clue to the cause
which underlies the abnormal growth, nor do they in any way explain
the apparent power of endless growth which the cancer cell, unlike
any other mammalian cell, possesses. The phenomena of normal
regeneration cannot be invoked; a begonia plant or hydra animal may
be cut into small pieces and each will grow into a perfect organism, but
here in these generalized forms, apparently, the all-important germ
plasm is present in all cells, and they are widely different from the
highly specialized, physiologically unbalanced, tissue cells of mammals,
and are always subject to the coordination and regulation of the organ-
ism, as a whole.
On the other hand, the parasitic theory of cancer in its naked form
is altogether too simple an explanation, and the clinical symptoms of
the disease differ so widely from those of different germ diseases, as to
weigh heavily against it. Nevertheless, there is some positive evi-
dence, as shown by the frequently localized distribution of cancer, by
cancer a deux, by the facts of cancer immunity (Gaylord, Clowes, and
Baeslack, Ehrlich, "athreptic" immunity), by cage infection (Gaylord,
Borrel, Lignieres, etc.), and by the " infectivity" of cancer cells, as
contrasted with cells of benign or embryonic tumors, of vegetable
galls, or with normal transplanted tissue cells.
While there is little doubt that the morbid symptoms of cancer are
due to the autonomous activity of these malignant growths, the problem
is deeper than mere descriptions of the symptoms caused by the onrush
of the anarchistic cells, and is resolved into the biological inquiry as to
what was the initial cause of the loss of organic regulation and what
underlies the secret of their inexhaustible division energy. The advo-
cates of the cell-autonomy theory have no satisfactory explanation for
the first, but throw the burden of proof upon the biologist and look for
enlightenment. to the school of experimental embryology and zoology.
Nor are their explanations of the continued power of proliferation
more successful, for they call upon the mysteries of fertilization, find-
ing, with Klebs ('89), Farmer, Moore, and Walker ('03), that epi-
thelial cells conjugate with leukocytes, or with Recklinghausen ('96),
that they are "fertilized" by fibroblasts, or with Waldeyer ('87), that
PROTOZOA AND THE CANCER PROBLEM 209
vitality is renewed by parthenogenesis, and they fail for the most part
to see that their supposed applications of this biological phenomenon
are far more improbable than the parasitic theory which they deride.
Many advocates of the theory of cell autonomy go so far into the
other camp as to believe that the cancer cell is itself a parasite. This
parasitism is shown by the fact that when placed in a suitable medium
it reproduces cells similar to itself and continues to multiply in this
way, without showing signs of differentiation into organs, a phenom-
enon which has given rise to the term " infectivity" of cancer cells, and
it certainly is an attribute which parasites possess. Bashford, Murray,
and Bowen ('06), confirmed later by Hertwig and Poll ('07), made the
observation, based upon statistical data, that the growth energy in
these cancer cells in mice undergoes rhythmical variations in vigor and
depression. Calkins ('08) found similar rhythms, based upon the
records of the New York State Cancer Laboratory, but showed that
the rhythmical variations were not in the growth energy of the cancer
cells, but in the infectivity of these cells, the growth energy and infec-
tivity showing no relationship after the tumor is established in trans-
plantation.
The advocates of the parasite theory believe that the cancer cell
became a parasite in the above sense, not from any derangement of
metabolic processes, nor from any vague, hypothetical, inherent
tendency to cellular anarchy, but because of the susceptibility to the
poisonous stimulus of some parasite. In this they are supported by
the facts of gall formation in plants, where a known poison, secreted
by insects, stimulates the latent division energy of the plant cells, and
a tumor is produced. The counter argument, so often made, that such
abnormal growths are nothing like cancer, is certainly true; the
analogy, however, is not with the form which the growth assumes, but
with the cell which is stimulated to divide by the activity of a parasite.
Among other things, the gall differs from the cancer cell in having
no infectivity, the stimulus not being continuous.
Another analogy is drawn from the great tumor-like growths in
•certain vegetables (cruciferse), due to the presence in the root cells
of a protozoon parasite, Plasmodiophora brassicce. These growths,
known as club root, hanburies, fingers and toes, etc., are highly
infectious and are frequently a serious menace to market gardens.
The organism causing the tumors penetrates the root hairs of the
cabbage or other allied vegetables, in the form of a minute ameboid
flagellate (Woronin, 1878, Prowazek, WQP>}. Two or more may
enter the same cell, where, immersed in the fluid cytoplasm, they lose
their flagella and grow into larger ameboid organisms (Fig. 62, p. 148).
Later, these ameboid cells fuse, forming, as in all myxomycetes, a
syncytium or plasmodium. The infected cells are caused to divide
i>y the presence of the parasite, the infected cells thus carrying the
14
210 PARASITISM
disease-causing germ, which apparently has no power of migrating
from cell to cell (Prowazek, '05). After a number of such divisions
the infected cells undergo hyperplasia and hypertrophy; the pressure
and possibly the toxins from the organism cause neighboring cells to
proliferate until large abnormal growths result. The parasites, in
the meanwhile, having exhausted the nutriment of the host cells,
form permanent spores, the spore formation being preceded by endo-
gamous fertilization processes, as described on p. 147. These spores
are stored up in the plant cells until the latter decompose and disin-
tegrate in the soil.
In club root, therefore, we find an analogy not in the form or type
of the tumor produced, but in the renewed division energy of tissue
cells through the presence of an intracellular parasite. Here, again,
infectivity is entirely independent of growth energy of the tissue cell,
and dependent upon the parasite alone. The vegetable cell cannot
long withstand the inroads of the relatively large parasites, and ulti-
mately dies because of them. It is conceivable that a cancer parasite
may exist within a cancer cell and serve as a source of continued
stimulus to the division energy without causing more harm to the cell
than anaplasia or hyperplasia. Such an aspect of the cancer problem
was stated as follows in an earlier publication: "It is certainly con-
ceivable that a parasite of cancer may be too minute to be seen with the
technique at our disposal. At the present time we know a great deal
about the yellow fever organism; we know the period of incubation
it requires in the human blood; we know that it requires from twelve
to fourteen days to develop in the -body of the mosquito before the
latter is able to transmit the disease; we know that the disease (apart
from blood inoculation) cannot be transmitted in any other way, and
yet, knowing all these things, the organism of yellow fever has never
been seen. It will pass through the finest filters, and belongs, there-
fore, to a group which, until they are actually seen, we must perforce
consider as ultramicroscopic organisms. Such parasites might be
adapted to life within the epithelial cell as well as the organisms of
club root are, and there in the protoplasm might easily be overlooked.
It has been suggested that a species of spirocheta is responsible for
yellow fever, and spirochetes have actually been found in the kidney
of yellow fever victims. But they apparently do not exist as such in
the blood or in the mosquito. We know nothing about the life history
of the spirochetes as a group; if it is analogous to the life history of
most protozoa, we might well look for stages in which the organism
is of ultramicroscopic size."
Many so-called parasites from human tumors have been described.
Protozoa representing all groups of these unicellular animals have
1 Calkins, The So-called Rhythms of Growth-energy in Mouse Cancer, Jour, of Exper. Med.,_
1908, vol. x, No. 3, p. 304.
PROTOZOA AND THE CANCER PROBLEM 211
been held responsible by one or more investigators, but in no case
have the claims been made good. Not only protozoa, but yeasts and
bacteria, and still other forms of living things, have been drawn into
the vortex of a discussion over the parasite theory when that discussion
was more spirited than it is today. Many of the structures thus inter-
preted as organisms are characterized by surrounding shells or cap-
sules which some investigators have interpreted as parts of an invading
organism (Fig. 85 2, 3). Cell invasions, however, are common in cancer
tissue, leukocytes, or even cancer cells themselves, invading other cells
and there degenerating or causing degeneration, while the capsules are
only condensations of the invaded protoplasm. This is the view
adopted by Sjobring ('02), Sawtschenko ('95), Ruffer and Walker
('93), and many others, while numerous observers have described the
successive changes in the degeneration of the contained, leukocytes
and interpreted the various "organisms" that had been described as
merely one form or other of such degenerating cells (Fig. 85). One
type of these inclusions, on account of its minute size, characteristic
structure, and occurrence, was designated the "X-body" by Behla
('03), and was regarded as different from other cell inclusions which
were due to degeneration. This "body" occurs under many different
forms and has been variously interpreted (Fig. 85, 12, 14, 15, 18).
It is known in literature as the "Plimmer body," as the "bird's-eye
inclusion," as the astrosphere or centrosphere of Borrel ('01), as the
"cancer parasite" of Bosc ('98), the "plasmodiophora-like bodies" of
Gaylord, as "Histosporidium carcinomatosum" of Feinberg ('03), as
the "intracellular secretions" of Nosske ('02) and Greenough ('01),
as "chytridire" of Behla ('03), as the "yeast cells" of San Felice ('98)
and others. Pianese ('96), Sawtschenko ('95), Soudakewitsch ('92),
Ruffer ('92), and others observed similar bodies inside the nuclei of
cancer cells, and interpreted both these and the cytoplasmic forms as
colloidal degenerations of the chromatin and cytoplasm, Sawtschenko
regarding them as masses of food material for the real parasite.
Calkins ('05) described stages leading to the conclusion that all of
such bodies are derived from the degenerating nucleoli of the cancer
cells, these nucleoli first becoming clathrate, irregular in outline, and
surrounded by local thickenings of chromatin or cytoplasm. Other
forms, however, might better be interpreted as blood platelets or
portions of leukocytes having the power to move from cell to cell
(Fig. 85, 13, 17), but in no case is there evidence to regard them as
specific organisms.
While these cell inclusions in human cancer cannot be interpreted
as organisms, it does not follow that real organisms are not present.
Later stages of the disease are particularly suitable for secondary
infection, and exposed surface lesions form a suitable medium for the
growth of bacteria, yeasts, or protozoa, while in one case of epithe-
212
PARASITISM
lioma spores of the fern lycopodium, which were probably introduced
with a face powder, were found. All such organisms, finding a favor-
FIG. 85
15
ar>Sla
e WL
^^ rv-£v
18^ji&t
/li*-. '-v.J**C.>»-ST.
^i^w
WfcSfif*
Types of the cell inclusions found in human cancer. (After Calkins.)
PROTOZOA AND THE CANCER PROBLEM
213
able medium for growth in the degenerating masses accompanying
cancer, cannot be regarded as the causes of the disease, and as such
saprophytic organisms we must include the ameba Leydenia gemmi-
para of Schaudinn ('96), which was found by E. von Leyden ('96)
in the peritoneal fluids of ascitic dropsy and associated with cancer.
This organism is a definite ameboid rhizopod measuring about 25 PL
in diameter. It moves rapidly in body temperatures, by forming
flat and lamellose pseudopodia. Structurally it differs from most
parasitic rhizopods in having a pulsatile vacuole which contracts
ordinarily every fifteen minutes. It reproduces by simple binary
division and also by bud formation, the buds often being very minute
(3 n to 4 fi] cf. intestinal amebre). Schaudinn considered it possible
that these organisms may have been the cause of the cancers in the
two patients in which they were found, and even compared the buds
with the small cell inclusions described by Sawtschenko ('95). He
was never inclined to push the suggestion in subsequent work, how-
FIG. 86
Spirocheta microgyrata (Low.) var. gaylordi, in cancer tissue of mice. (After Calkins.)
ever, and later (1903) regarded Leydenia gemmipara as only a phase
in the life history of an intestinal rhizopod Chlamijdophrys stercorea
(see p. 294). The general belief now is that they had nothing to do
with the cause of the disease.
The organisms of epithelioma contagiosum of fowls and of mol-
luscum contagiosum of man are not to be included with such sapro-
phytic forms, nor with these degeneration products, but are protozoa
directly connected with the disease (see p. 312).
Similar degenerative products have not been found in mouse cancer,
and there is less chance here for secondary infection. One organism,
however, discovered by Gaylord ('07), Spirocheta microgyrata gay-
lordi, occasionally found in the blood of mice, is invariably found in
the stroma of mouse cancer, both in primary and transplanted tumors,
and is present in enormous numbers in the more malignant strains
214 PARASITISM
(Fig. 86). It is sometimes found inside the cancer cells and very often
in the detritus of degenerating centres. The dimensions and general
character of this spirochete agree with the one which Lowenthal ('06)
described from ulcerating human cancer, dog tumors, and in feces,
and which he named Spirocheta microgyrata, because of the minute size
of the nodes and abruptness of the turns (Fig. 86, left). The ends of
the organism are blunt and rounded and there is no evidence of undu-
lating membrane or flagellum (as to the nature of spirocheta flagella,
see p. 223). Reproduction is evidently by transverse division, but
nothing is known in regard to the life history. Similar but not the
same species of spirochetes have been found by Borrel ('05) and by
Wenyon ('06) in the blood and tissues of mice, and Tyzzer ('07) has
found it in tissues of so-called normal mice. It can hardly be claimed
that these spirochetes are the cause of mouse cancer, at least not in
the form as ordinarily seen. Gaylord and Clowes have found that
they are much reduced in number in the tissues after the material for
inoculation had been treated with potassium cyanide, although they
reappear later. There is reason to believe that, as with Trypano-
soma gambiense, under treatment with atoxyl, the ordinary form of the
organism may be lost, and that the poison does not kill, but causes
them to encyst. The absence of all evidence of similar organisms in
human cancer, however, makes it probable that these mouse spiro-
chetes, like Leydenia gemmipara, are only commensals finding here a
suitable soil for life and multiplication. On the other hand, the
possibility that they are inciting or aggravating agents must not be
overlooked.
The cancer problem or problems, finally, must be regarded as still
in the stage of working hypotheses, of which no one points out with
unmistakable clearness the path for future research. That the field
of parasites thus far has been harrowed in vain is no reason for aban-
doning this particular working hypothesis, at least not until we know
more about the still invisible organisms of yellow fever, or those of
foot and mouth disease, or until we know more about the minute forms
of the organisms of "fixed virus" of rabies, or the stages which pass
the filters in clavelee, molluscum contagiosum, dengue, and similar
diseases.
CHAPTER VI.
THE PATHOGENIC FLAGELLATES.
IT is a well-recognized zoological principle that some groups of
animals, families, orders, classes, or even phyla, may be stationary,
so far as evolution is concerned, and not easily adapted to new environ-
mental conditions. Other groups, on the other hand, are remarkable
for the variety of structures, for ready adaptability to new conditions,
and, in general, for their high "potential of evolution."
Similarly with the protozoa we meet with the same variations; the
infusoria, for example, both ciliates and suctoria, are highly differ-
entiated, and, as shown by the well-defined orders and families, are
fairly stable in evolution, while the mastigophora, on the contrary,
possess a remarkable power of variation and a high potential of evolu-
tion. It is among these latter forms that we meet with all methods
of nutrition and with all grades of organization connecting animals
with plants, while it is here, also, that we look, especially among the
colony forms, for cellular division of labor or developmental processes,
that may throw light on the origin of multicellular from unicellular
animals.
With their great power of adaptation combined with the variety of
available modes of life, it is to be expected that many types of flagel-
lated unicellular parasites should be known, and among them, that
we should find numerous cases of incomplete adaptation. This is
particularly probable in organisms like the hematozoic flagellates,
where the uncertain conditions of the definitive invertebrate and
secondary vertebrate hosts make stability of form and life cycle
difficult to work out. There is reason to believe, with R. Koch, that
certain types of trypanosomes are established, or are "good" species
(e. g., Trypanosoma lewis i, T. t heller i), while others are undoubtedly
in that phase of adaptability which De Vries calls the period of muta-
tion. While such an hypothesis probably contains an element of truth,
it is just as well to keep it for the present as a generality, and not to
apply it as the famous bacteriologist does, to specific cases until after
the life histories of such cases are known. "Good" or "bad" species of
protozoa, especially in this group, have no scientific standing until the
life cycle is accurately established, and "degrees of virulence" or
''promiscuity of secondary (vertebrate) hosts" have no more to do with
establishing a protozoan species than the salt- or fresh-water habitat
has to do with actinophrys, chilodon, or colpoda, and whether there is
216 THE PATHOGENIC FLAGELLATES
one species of trypanosoma with many varieties, or seventy different
ones, cannot be determined on the basis of physiological effects alone,
or by the nature of the habitat.
The uncertainties and the many contradictions which characterize
our present knowledge of the parasitic flagellates make the group very
difficult to handle from a zoological point of view, and deductions and
generalizations made upon the strength of slender lines of evidence are
not only premature but very confusing to those who are seriously
concerned with protozoology, and distracting to medical men whose
energies are directed toward the cure and extinction of diseases due to
these organisms. The attempt to classify hemosporidia and flagellates
in one group, as certain recent writers have done (Hartmann, Sambon,
etc.), rests upon a very shaky foundation of fact, and until that founda-
tion is better built, we would do much better to adhere to the older
system, which, even if not entirely accurate, at least has the advantage
of established familiarity and of accepted limits, while those forms in
which the life history is now known can be safely placed. To illus-
trate, the Donovan-Leishman bodies were first seen as intracellular
parasites, and were classified as aberrant forms of hemosporidia similar
to babesia. But with the discovery of the flagellated phase in culture
and in the definitive host cirnex, the enigmatical "bodies" were found
to be only intracellular phases of a flagellated protozoon similar to
herpetomonas, and, under the name Herpetomonas (Leishmania)
donovani (Mesnil), are today classified as flagellates. Similarly the
hematozoic parasite of the little owl, halteridium, was found to be a
phase of the life cycle of Trypanosoma noctuae, and should be removed
from the hemosporidia and placed with the flagellates.
These two instances, while safely established, do not justify a zoolo-
gist or a medical man in jumping to the conclusion that all hemo-
sporidia have a flagellate stage, and should, therefore, be classed with
the mastigophora (Hartmann), or that all trypanosomes have an intra-
cellular stage, or that the hemosporidia, as a group, should be aban-
doned (Hartmann). An intracellular stage of herpetomonas or of
trypanosoma does not make a sporozoon of either one; nor does a
flagellated stage of Plasmodium vivax (if such a stage exists, which
is extremely doubtful) or of proteosoma, make flagellates of these
any more than the tailed tadpole makes a fish of a frog. The old
group hemosporidia should not be given up until each species it now
contains is proved to be only a phase of some flagellate. To give it up,
or to classify these protozoa under the caption of "blood-dwelling
forms" (Sambon, Manson), save for purely physiological or thera-
peutic reasons, is misleading and unnecessary.
With these parasitic flagellates the condition of affairs at present
is analogous to that in the group hydrozoa among celenterates.
Here many species are characterized by two distinct phases : one, the
THE GENUS SPIROCHETA AND ALLIES 217
sexual generation, is a free-swimming medusa or jelly fish, the other,
an attached and often branched asexual hydroid. The greatest con-
fusion grew out of the fact that each of these generations received a
distinct name and were supposed to be different forms of animal life.
The medusa phialidium, for example, was regarded as independent
at first, but later was shown to be only the sexual generation of the
hydroid clytia ; the genus eucope also was proved to be only the medusa
of the hydroid obelia. With the increased knowledge of the life history
of these forms of coelenterates the confusion was gradually cleared,
and the group is now well understood. It was found that some
medusas have no hydroid generation, and that some hydroids have no
medusae, and such forms were classified in appropriate subdivisions.
So it will be, probably, with the hemosporidia; some others, like the
Leishman-Donovan bodies, may be found to have a flagellated stage;
babesia, for example, is said to have such a stage by some observers
(Kinoshita), while certain others have labored hard to make out a
flagellum in one form of plasmodium. Others, like Plasmodium
malaricB and P. vivax, are certainly obligatory cytozoic forms.
Some forms of parasitic flagellates are of sucn doubtful structure
that the taxonomic position must be left in abeyance. The much-
discussed spirochetes, for example, when all is said, cannot be dis-
tinguished from certain spiral forms usually classed with the bacteria,
and transitional forms bridge the gap between the protozoon Spiro-
cheta balbianii and Spirocheta plicatilis, and the bacterial form
Spirillum gigantea and Spirillum recurrentis. It is possible that some
morphological or developmental feature may be found ultimately
which will permit of a definite limitation of the two types, but it is
equally possible that future research will demonstrate the close affinity
of the supposedly different types, and to my mind the present con-
ditions of facts indicate the latter and not the former alternative, and
justify the non-committal term spirillochetidse as a family name for
the contested forms. Certainly, the spirochetes are so close to the
spirillse that hard and fast lines cannot now be drawn, and, like the
phytoflagellates and the lowest plants, the questionable forms indicate
once more the high mutability of the group.
THE GENUS SPIROCHETA AND ALLIES.
C. G. Ehrenberg, in his masterly treatise on the Infusionsthier-
schen, published in 1838, described spirocheta and spirillum as
follows :
28th Genus. Spirocheta: Animal e familia Vibrioniorum, divisione
spontanea imperfecta in catenam tortuosam S. cochleam filiformen
flexibilem elongatum.
218 THE PATHOGENIC FLAGELLATES
29th Genus. Spirillum : Animal e familia Vibrioniorum divisione
spontanea imperfecta (et obliqua ?) in catenam tortuosam S. cochleam
rigidam et in cylindri fornaam extensam abk ns.1
This first description of the organism which Ehrenberg named
spirocheta is certainly very meagre and not much more enlightening
for present-day purposes than the spirilliform figures of Kohler,
published in 1777, or the crude descriptions and figures of similar
forms by O. F. Miiller, in 1786. The essential point of difference
between the genus spirocheta and the genus spirillum was the rigidity
or inflexibility of the latter as against the flexibility of the former.
Schaudinn, in 1905, added another point to the diagnostic character-
ization of the genus by describing a definite undulating membrane.
Spirocheta thus characterized as an organism with flexible, spirally
twisted body with laterally placed undulating membrane, would seem
to be definitely distinguished from the genus spirillum with rigid cork-
screw-like body and no membrane; but, unfortunately, the problem is
not so simple, for we have to do with exquisitely minute things which
offer extreme difficulties in technical treatment and require carefully
trained eyes. Statements as to structure and activities of certain
species, even though made by equally eminent authorities, are fre-
quently directly contradictory, and only too often the individual
prejudices are so strong as to weaken the scientific value of the obser-
vations.
Schaudinn's discovery, in 1905, of the organism of syphilis, Trepo-
nema (Spirocheta) pallidum, was the direct inspiration to thousands
of investigators to study anew the old forms and to penetrate unknown
fields of pathology in the hope of finding and describing new forms.
As a consequence of this activity, the systematist today is confronted
with a most heterogeneous collection of spirilliform organisms, and is
forced to wade through a most conflicting tangle of observations and
deductions. The descriptions of organisms which have been classified
as spirocheta are often obviously far from the original type of Ehren-
berg, so far, indeed, as to justify new generic names. Some of them
differ in having flagella (of the spirilla type) at one or at both ends;
others have multiple flagella so called; and still others have neither
membrane nor flagella. These discrepancies have been widely recog-
nized and new generic names have been proposed and, in some cases,
accepted. Some observers, on the other hand, have made the mistake
of basing genera on physiological lines alone, and these, like the genus
spiroschaudinnia of Sambon, based upon the fact of change of hosts,
will not be accepted.
Observations are too incomplete and too often contradictory to
justify a safe grouping at the present time, and in making groups of
1 Ehrenberg, Die Infu?ionsthierschen, etc., 1838, p. 83, 84
THE GENUS SPIRQCHETA AND ALLIES 219
spirochetes a given species will be placed in one division or another,
according to the discretion of the present author in following one or
another authority. With this preliminary caution the following table
of the different kinds of spirochetes, classified according to the pres-
ence or absence of so-called flagella and undulating membrane, is
based.
A. TYPE GENUS SPIROCHETA.
With undulating membrane; without flagella.
Spirocheta plicatilis. Ehrenberg, 1838. Free living. Length up to 200 //.
Sp. balbianii. Certes, 1882. In oysters, clams, etc. Length up to 150 ft.
Sp. anodontse. Keysselitz, 1906. Mussell (anodon). Length up to 60 /*.
Sp. vincenti. Blanchard, 1906. Human ulcers.
Sp. pyogenes. Mezincescu, 1904. Tuberculous cattle.
Sp. refringens. Schaudinn, 1905. Human syphilitic lesions (external).
Sp. pseudopallida. Kiolemenoglou and von Cube. Ulcerating carcinoma.
Sp. eberthi. Kent, 1880. Bird intestine.
Sp. gigantea. Warming, 1874.
Sp. buccalis. Steinberg, 1862. Probably same as dentium. Same habitat.
B. GENUS TREPONEMA.
Without undulating membrane; with flagella.
Treponema pallidum. Schaudinn, 1905. In human and ape syphilitic lesions.
Tr. pertenuis. Castellani, 1905. In lesions of frambesia or yaws.
Tr. anserinum. Sacharoff, 1890. Blood of geese.
Tr. gallinarum. March, and Salimbeni, 1903. Blood of chickens.
Tr. theileri. Laver. and Valle'e, 1904. Blood of cattle.
Tr. muris. Wenyon (Tr. Laverani, Breinl and Kinghorn). Blood of mice.
C. UNDETERMINED FORMS REFERRED TO GENERA SPIROCHETA AND
SPIRILLUM.
Spirocheta dentium. Koch, 1877. Human mouth and teeth.
Sp. vaccinse. Bonhof, 1905. Pustules of calf.
Sp. recurrentis (Sp. obermeieri). Lebert, 1874. Cause of relapsing fever.
Sp. duttoni. . Novy and Knapp, 1906. Cause of tick fever in man.
Sp. microgyrata. Lowenthal, 1906. Ulcerating human carcinoma.
Sp. microgyrata. Low. var. Gaylordi. In non-ulcerating mouse tumors.
Sp. of dysentery. Le Dantec.
Sp. ovis. Novy and Knapp. Blood of sheep.
Sp. equi. Novy and Knapp, 1906. Blood of horses.
Sp. vespertilionis. Novy and Knapp, 1906. Blood of bat.
Sp. muris, variety Virginiana. MacNeal, 1907. Blood of rat.
So far as the morphology is concerned, the best known of these forms
are the giant spirochetes Sp. balbianii and anodontce, which have been
described by Certes, Laveran and Mesnil, Perrin, Swellengrebel,
Keysselitz, and Fantham (Fig. 88). The large size and definite struc-
220
THE PATHOGENIC FLAGELLATES
tures make them relatively easy to study, and the conclusions that
have been drawn are comparatively free from imaginative diversions,
and for this reason they are the best representatives of the group for
descriptive purposes.
FIG. 87
Spirocheta anodontse. X 1500. (After Fantham.) The membrane winds around the body
in right-handed spiral; chromatin rodlets and basal granules shown.
A. Structures of Spirocheta Balbianii, Certes, 1882. — This
organism, first studied by Certes as a trypanosome, may be found in
the anterior part of the oyster's digestive tract, where, if present at all,
it is usually in the crystalline style. Both Perrin ('06) and Fantham
('08) note that the organisms soon disappear after the oysters are
removed from sea water.
The spirochete is a spirally wound thread from 50 to 150 // long
and about 2 to 3 fj. wide. The inner protoplasm contains a number
of transverse bands of chromatin, about 60 in all, which Perrin,
erroneously, calls "chromosomes," and which constitute the sole
nuclear apparatus of the organism. Sometimes these bands run
together to form a more or less complete helix of chromatin; again,
they are completely divided in preparation for longitudinal division
of the cell; but at no time do they come together to form a definite
THE GENUS SPIROCHETA AND ALLIES 221
nucleus like that of most protozoa and higher types of cell. Nor do
the granules collect in spore aggregates, such as Schaudinn ('02)
described in Bacillus biitschlii and Guilliermond ('08) in different
endosporous bacteria. The nuclear apparatus is of the "diffuse"
type, therefore, and represents an intermediate condition between the
"distributed nucleus" of bacteria and the morphological nucleus of
higher cells.
The protoplasmic body is covered by a distinct sheath or periplast,
which is twisted in a characteristic manner and which gives rise to a
lateral undulating membrane likewise spirally wound and running
from end to end of the organism (Figs. 87, 88). Laveran and Mesnil
regard this membrane as a mere fold of the periplast (gaine) and of an
accidental nature, but both Perrin and Fantham give sufficient evi-
dence to show that it is a definite organoid of the cell, while Fantham
has demonstrated the presence of numerous fibrils which he describes
as myonemes and correctly interprets as the seat of movement of
the cell (Fig. 88, A,C}. Under abnormal conditions, the membrane,
like that of the ciliated infusoria, may disintegrate, and the several
myonemes then may assume the appearance of numerous flagella,
a phenomenon which may account for the presence of many flagella
occasionally found on Spirocheta gallinarum and Spirocheta duttoni.
The movements brought about by this membrane are characteristic
of spirochetes in general, and consist of rotation about the long axis,
forward or backward translation, and bending movements at different
levels of the body, all of which may occur simultaneously or inde-
pendently.
Reproduction occurs by either longitudinal or transverse division.
There is some difference of opinion in regard to the mode of division,
however. Laveran, Mesnil, and Swellengrebel maintain that it is
always transverse; Perrin, that it is always longitudinal; while Certes,
Lustrac, and especially Fantham, whose account is the most con-
vincing, found both types, cross-division more rarely than lengthwise.
Transverse division, according to Swellengrebel, occurs, as in bacteria,
by the preliminary division of internal granules and by the forma-
tion of a "cloison transversal," but he also figures and describes the
double chromatin granules which can be interpreted only as a prepa-
ration for longitudinal division. Longitudinal division, according to
Fantham, begins with division of the membrane, being first noted in
the division of what he terms the basal granules (Fig. 88, E). The
granules at one end separate while the others remain together, and with
the separation the membrane, chromatin granules, and cell divide, the
daughter cells remaining attached at the one end for a considerable
time; ultimately a vacuole appears in the common terminal proto-
plasm and final separation takes place.
Perrin describes a number of different types of Spirocheta balbi-
222
THE PATHOGENIC FLAGELLATES
anii as representing "male," "female," and "indifferent" forms of the
organism; but there is little that is convincing in his descriptions, and
FIG. 88
Spirocheta balbianii. (After Fantham.) A, parasite showing myonemes in membrane,
rounded ends and transverse bars of chromatin, X 3000; B, a so-called "flagellated" form,
the apparent flagella being myonemes from the dissociated undulating membrane, X 2000;
C, beginning of division, the undulating membrane being entirely divided and the chromatin
arranged in characteristic spiral form; basal granules also divided, X 1500; D, separation
of longitudinally divided form, basal granules divided, X 1000; E, daughter cells attached
at one end, X 1000.
THE GENUS SPI ROCHET A AND ALLIES
223
he himself is not altogether certain of his ground in some cases.
Fantham was unable to confirm these observations, while Swellen-
grebel interprets these structures, probably correctly, as involution or
degeneration forms. All evidence of so-called conjugation described
by Perrin is unconvincing, and the sexual processes of these interesting
forms, as with all other spirochetes, remain undetermined.
While Spirocheta bolbianii is the best known of the spirochetes,
it is quite evident, from the accounts of the various observers, that
much yet remains to be done before its life history is known. But we
know still less about the other forms of the group, especially those
which appear to be the causes of specific diseases. Nevertheless,
some problems connected with them have been solved, many careful
experiments have been planned and successfully executed, and many
FIG. 89
•sSas&&&Mi* 2" > * >X; •' v- • ; f^7'>W*-q?Z&%^ ~r- tf^^Z
Types of flagellum insertion in bacteria. (After Butschli.)
structures and functions faithfully described. The literature is enor-
mous, and in the limited space of this chapter only the general trend of
observations and experiments can be given.
B. The So-called Flagella of Spirochetes. — As stated on page
45, there is good reason to doubt the specific flagellum nature of the
attenuated ends of many of the spirochetes, and, owing to the extremely
small size of most of these organisms, it is hardly probable that the
question will be definitely settled one way or another very soon. Sev-
eral factors, however, combine to show that these organoids lack the
specific kinetic accompaniments characterizing flagellated protozoa.
In the latter, wherever carefully studied, and in plant and animal
flagellates alike, the flagella are deeply inserted in the protoplasm and
arise as outgrowths from the nucleus or from special basal bodies
(Fig. 100, p. 249). In spirillum the so-called flagella are of an entirely
224 THE PATHOGENIC FLAGELLATES
different type, Butschli ('02) finding only one case, and this not wholly
satisfactory, where the flagellum appeared to be prolonged into the cell
body of Spirillum giganteum (volutans) (Fig. 89). Swellengrebel ('07)
described an occasional thickening at the lower end of the flagellum of
this same species which he regarded as a basal granule, but as it lies
outside of the protoplasmic body it is more probably a local thick-
ening or condensation rather than a kinetic body similar to those of
animal flagella. Furthermore, numerous observers (Fischer, Kutscher,
Ellis, and others) affirm that the flagellum is not single, but consists,
at times at least, of a bundle or tuft of "cilia." Zettnow, Fischer, and
Butschli give evidence to show that the flagellum arises as a prolonga-
tion of the periplast, the latter, with Ellis and Swellengrebel ('07),
showing that it comes from an apical thickening (calotte) of the
periplast.
In the spirillum group the flagellum thus appears to arise from the
enveloping periplast, and is not, as in protozoa, of endoplasmic origin.
In spirocheta the conditions have recently been carefully studied by
Siebert ('08), who finds that the so-called flagellum of different forms
arises in the same manner as in the spirillacese, and is morphologically
different from the flagella of mastigophora. As processes of the peri-
plast arising as the attenuated ends after division of the cells, e. g.,
in Sp. recurrentis (Sp. obermeieri), the flagella have an entirely dif-
ferent significance from those of the monads and other mastigophora.
Furthermore, the rare occurrence of "ciliated" forms — sometimes
double (Schaudinn), sometimes single and variously placed (Levaditi)
—of Treponema pallidum, or of Sp. microgyrata, may be interpreted, as
Krzysztalowicz and Siedlecki ('05-'08) assert, as the attenuated ends
which remain after division.
The myonemes characteristic of the undulating membrane of Sp.
balbianii, indicate, however, a higher development of kinetoplasm
than is to be found among the bacteria, and it is reasonable to
assume that all spirochetes with undulating membranes have similar
contractile fibrils. Furthermore, the energetic movements of spiro-
chetes without flagella may be accounted for upon the hypothesis
that the periplast or membrane is similarly provided with muscular
elements. Siebert has shown that under the action of certain digestive
fluids spirochetes break up into fibrillae similar to those which have
been described in peritrichous forms. Borrel ('06), Zettnow ('06),
the former for Tr. gallinarum, the latter for Sp. duttoni, and Levaditi
and Mclntosh ('07), for a species of treponema similar to, if not
identical with, Treponema pallidum, have described so-called diffuse
flagella appearing at various parts of the cell, sometimes terminal,
sometimes lateral, while oftentimes they are multiple and irregularly
placed. Whatever these chance peritrichous appendages may be,
they are certainly not flagella in any strict morphological sense, and
THE GENUS SPIROCHETA AND ALLIES 225
Siebert's conclusion that they are products of periplastic dissociation,
or Prowazek's ('06), that they are dissociated myonemes, appears to
be the more probable explanation.
C. The Spirochete Nucleus. — As already shown for Spirocheta
balbianii and Sp. anodontce, there is no definite morphological nucleus
in these forms, and the distribution of chromatin granules recalls the
condition of bacteria. Nevertheless, the occasional aggregation of
these granules into a heliform cord or the permanent rod form, as
in Sp. plicatilis (Schaudinn), indicates a higher organization than in
bacteria and a step toward the condition in protozoa, where, as in
tetramitus, there may be only granules which come together at periods
of division to form a loose but nucleus-like aggregate (Calkins, 1898).
The view expressed by MacWeeney, that spirochetes are all nucleus,
or chromatin only, brings back the controversy over the nature of
bacteria which has now been definitely settled, and it is unnecessary
to go over the matter again for these spirilliform types.
In the great majority of spirochetes that have been described more
or less minutely, no nucleus of any kind has been mentioned. In the
better-known forms, however, chromatin granules of one form or
another have been described somewhat fully. Bonhoff describes a
single brightly staining central granule in his Sp. vaccines. In Sp.
recurrentis, the cause of relapsing fever, Novy and Knapp ('06) made
out no internal structures; the organisms "invariably gave a solid
stain, exactly as in the case of ordinary spirilla or bacilli" (p. 300).
But ordinary bacilli and spirilla do show internal structures, many of
them analogous to chromatin and interpreted as such by different obser-
vers (Biitschli, Schaudinn, etc.). So, too, the organism of relapsing
fever possesses granules which may be chromatin and may correspond
with the chromatin granules of Sp. balbianii. In the closely allied
Trep. gallinarum Prowazek ('06) finds local condensations which stain
like chromatin and which he interprets as such (his Fig. 6). Similar but
more numerous granules were observed by Dutton, Todd, and Tobey
('06) in Spirillum (Spirochefa) duttoni, and by Carter ('06) in the same
species from the eggs of Ornithodorus moubata. Finally, in Treponema
pallidum, Krzysztalowicz and Siedlecki ('05-'OS) have observed small
deeply staining granules which they regard as condensed chromatin
surrounding a clear space of "achromatin." (It might be pointed
out, however, that this observation might be used equally well in sup-
port of Swellengrebel's view of transverse division through the medium
of a cloison transversal.} Wechselmann and Lowenthal (1900) have
observed similar granules by aid of the ultraviolet light. Summing
up the evidence as to nuclei of spirochetes, it may be safely affirmed
that these primitive types of organisms possess nuclei in the form of
scattered chromatin granules which may come together at times to
form rod-like or sphere-like aggregates, a condition duplicated by the
15
226
THE PATHOGENIC FLAGELLATES
bacteria on the one hand, and by unquestioned flagellates on the
other.
D. Division of Spirochetes. — In regard to the mode of division of
spirochetes the greatest diversity of opinion prevails, and every species
whose reproduction is known is interpreted by some as dividing trans-
versely, by others longitudinally. As in the case of Spirocheta bal-
bianii, it is possible that both methods occur. The greatest number of
FIG. 90
Different forms assumed by Treponema pallidum, the organism of syphilis. (After
Krzysztalowicz and Siedlecki.) A, three ordinary forms with "nuclear space" from primary
lesion; B, six contracted and ring forms from initial lesion; C, D, E, late stages in condensa-
tion of organism from papule; F, minute forms from initial lesion, G to M, successive stages in
longitudinal division; N, "enigmatical" bodies from an eruptive papule (similar to "cytoryctes
luis").
observers and the liveliest disputes on this point have been in con-
nection with Treponema pallidum, the organism of syphilis (Fig. 90).
Without entering into an extensive review of the literature, it may be
stated that Krzysztalowicz and Siedlecki ('05) were among the first to
describe longitudinal division, which Schaudinn in the same year con-
firmed by observations on the living organisms. Herxheimer, Hoffman,
Siebert, and others agree with this view. Many others, on the other
THE GENUS SP I ROCHET A AND ALLIES
227
hand, are equally positive that division here is transverse, Borrel,
Laveran, Zettnow, Koch, Novy and Knapp, Levaditi, Goldhorn, and
many others taking this view. Schaudinn and the Hungarian ob-
servers note that the greater part of the organism divides with great
rapidity, and that, as in Spirocheta balbianii, the partly separated
daughter cells remain attached for a long period, and finally pull
apart as though dividing transversely (Fig. 90, G, H, I, J, Af). The
advocates of transverse division, on the other hand, explain the
apparent longitudinal splitting as an illusion caused by the dividing
cells turning and twisting upon one another. No final decision can be
made at present; it is certainly difficult, on the basis of longitudinal
division only, to account for the strings of cells that are often found
with thinned regions, and skepticism regarding the schematic course
of events as given by Krzysztalowicz and Siedlecki cannot be wholly
FIG. 91
D
Spirocheta duttoni (Novy and Knapp). A,B,C, after Breinl, X 4500; D, after Carter;
A,B, spiroehetes reproducing by transverse division; C, by longitudinal division; D, para-
sites from egg of Omit hod orus moubata with chromatoid granules divided equally and cell
bodies partly split.
dispelled by their explanation of these strings as "colonies." If, like
Spirocheta balbianii, the organism of syphilis divides both longitu-
dinally and transversely, the catenoid colonies are easily interpreted.
Similarly with Treponema gallinarum, Sp. recurrentis, and Sp.
duttoni, equally competent observers take diametrically opposite
sides regarding the plane of division. It is highly probable that
Sp. recurrentis of relapsing fever divides usually by cross-division, but
Carter's and Prowazek's observations on Sp. duttoni and Sp. galli-
narum certainly show that lengthwise division occurs in these forms,
Carter ('07) especially showing that the granules of chromatoid matter
within the cell are placed opposite one another in the divided daughter
halves (Fig. 91, D).
228 THE PATHOGENIC FLAGELLATES
E. Form Changes and Life History. — Stability of form, due to
the firm body wall, is one of the characteristics of bacteria, while
polymorphism is equally distinctive of protozoa (p. 19). With the
spirochetes, some appear to be remarkably stable in form (e. g., Sp.
microgyrata, Sp. recurrentis, etc.), while others are highly variable
(e. g., Tr. pallidum). All seem to have a greater or less power of
agglomeration comparable with the agglutination of bacteria, and
indicating some physical change in the cell analogous, perhaps, with
the "miscible state" at certain periods of the life history of infusoria.
Another matter of considerable importance in the structure of the
spirochetes is colony formation and the question as to the "unit"
individual. The number of nodes often varies within such wide limits
that the problem as to what constitutes a single spirochete cell has
a more than theoretical interest. Migula ('00) and Fischer ('03)
suggested that spirochetes may be composed of many units, a point of
view supported by the effect of abnormal conditions upon the spiro-
chete strings. Warming ('75) and Zopf ('82) described the fragmenta-
tion of the spirochete body after death in the cases of Sp. plicatilis and
Sp. giganteum, while Laptschinsky ('SO) claimed to have made out
such segmentation in the living cells of the former. These early obser-
vers may have been misled by the segmented appearance due to the
bands of chromatin in these forms. Similar observations, however,
have been made upon other forms, and under such different condi-
tions by competent observers that there is some justification for the
view that the " unit" consists of one node. Wechselmann and Lowen-
thal ('05) showed that long forms of Tr. pallidum, upon treatment
with mercury, break up into short forms with from one to four nodes.
Karlinsky ('90) found very short forms of Sp. recurrentis in the blood
of patients having previously had malaria, and these short forms, when
placed in normal blood, developed into normal spirals. In connection
with the same organism Afanassiew ('99) observed comma- and S-
shaped forms in addition to the usual spirals, while Novy and Knapp
('06) described the fragmentation of the long forms into such comma-
and S-shaped types under the action of phagocytes. Lowenthal ('05),
Krzysztalowicz and Siedlecki ('05), and others described minute types
of Tr. pallidum somewhat similar to those of the organism of relapsing
fever.
In view of these facts, and in connection with the apparent disap-
pearance of spirochetes from the blood and organs of the body, the
possibility of .the unit organism being much more minute than that
usually seen should not be overlooked. The actual life history,
furthermore, of no form has been satisfactorily worked out, and it is
quite within the bounds of probability that excessively minute stages
occur. Fertilization and the sexual phenomena, if they exist, are
unknown at the present time, and most of the attempts to formulate a
THE GENUS SPIROCHETA AND ALLIES 229
sexual cycle have been too fantastic for belief. Prowazek ('06)
observed curious local swellings in Treponema gattinarum and Sp.
buccalis, which he regarded as similar to those seen by Heydenreich
in Sp. recurrentis, by Perrin in Sp. balbianii, and by Keysselitz in
Sp. anodontce, all of which he interpreted as possibly indicating a
sexual process. Swellengrebel's and Fantham's observations on Sp.
balbianii leave little reason to doubt that in this form, at least, the
structures in question are the results of abnormal or degenerative
processes. Krzysztalowicz and Siedlecki ('05) described a complex
cycle of Treponema pallidum, involving many form changes, including
a so-called trypanosome stage, and sexually differentiated gametes.
In their more extended and very valuable paper of 1908 they express
doubt as to this earlier interpretation,1 but give most convincing evi-
dence of the manifold form changes which these organisms may assume
under normal conditions. Muhlens ('07) and many others have noted
the same polymorphism, enough, indeed, to show that no one standard
of form or size can be depended upon in identifying Tr. pallidum.
The most marked and characteristic of these varieties are the short and
thick forms with from two to four nodes (noted also by Muhlens and
Hartmann in Sp. dentium and buccalis). The other variations shown
in Fig. 90 are sufficient to indicate the difficulty in distinguishing this
spirochete from other harmless ones and the danger of basing diagnosis
upon structures alone. Krzysztalowicz and Siedlecki, who have
studied this species for years, admit that they cannot distinguish some
stages in its life history from other spirochetes. They conclude that
the ring forms (Fig. 90, B) are resting stages, the baguette forms
stages during the "period of depression," while the oblong or granu-
lar forms are involution or degeneration types. The curious and
interesting structures called Cijtorydes luis by Siegel ('05) may well be
stages of unknown significance in the life history of Tr. pallidum;
they certainly have no resemblance to the bodies described by
Guarnieri ('92) under the generic name of cytorvctes (see p. 307),
but do recall the "spindle-formed bacilli" found by Seitz and inter-
preted by Silberschmidt, Wechselmann, Lowenthal, and others as
stages in the life history of Spirocheta mncenti.
So-called encysted forms of spirochetes have been mentioned from
time to time. Breinl and Kinghorn ('06) suggest that Sp. duttoni,
which they found occasionally coiled up within a definite membrane,
represent the encysted state of this organism, while "resting stages"
have been noted by many different observers in different species of
spirochetes without, however, their significance being known.
F. Mode of Life and Change of Hosts. — Many of the spirochetes
are undoubtedly intracellular parasites, although differences of opinion
1 A vrai dire, nos dtudes ulteriures nous ont inspire beaucoup de doutes a cet egard, p. 221.
230 THE PATHOGENIC FLAGELLATES
exist in regard to this. Many are lymph or blood-dwelling forms,
while some are neither parasitic nor commensal in their mode of life.
Some forms may be both coslozoic and cytozoic. Tr. pallidum, for
example, is considered by some observers (e. g., Bandi and Simonella,
1905) to be a typical intracellular parasite, although usually found in
the lymph. Treponema gallinarum frequently leaves the blood serum
and penetrates the blood cells of chicks (Prowazek, Marchoux, and
Salimbeni). Sp. duttoni penetrates the egg of the tick Ornithodorus
moubata and multiplies there (Koch, Carter), while Sp. microgyrata
var. Gaylordi is frequently found in the cancer cells of mice (Fig. 86,
p. 213).
Closely connected with their habitat and mode of life in the host
is the possibility of transmission by insects, which, according to Liihe
('06), are the definitive hosts of these forms. It is generally believed,
upon the basis of experiments made by Nuttall, that bedbugs convey
Sp. recurrentis from man to man, while Schaudinn found that the
organisms multiply within the body of this insect. Similarly, the
closely allied spirochete Sp. duttoni of tick fever was found by Button
and Todd ('07) to be conveyed by the bite of a tick Ornithodorus
moubata; they also showed that the larvae were capable of transmitting
the disease with the first feeding operation, while Koch ('05) described
spirochetes on the surfaces of ovaries and eggs of the insect and gave
strong evidence to indicate that they multiply there. This evidence
wras fully confirmed by Carter ('07), who found the organism dividing
rapidly in the protoplasm and yolk of the egg (Fig. 91). Here, there-
fore, is a case of direct inheritance, in insects, of disease-causing organ-
isms. Treponema gallinarum and Sp. theileri are similarly trans-
mitted by ticks, the former by Argas miniatis, the latter by Rhipi-
cephalus decoloratus. Borrel and Marchoux, for the former, and
Theiler, for the latter, showed that multiplication likewise occurs here
in the bodies of the insects, and that the eggs may be infected and may
carry the organisms.
Beyond simple division there seems to be no important life phase
in the bodies of insects; but this fact of multiplication is of consider-
able importance, as showing that the insect hosts are not merely
passive carriers, but are active agents in the transmission and distri-
bution of the parasites, and therefore are important agents in spread-
ing these spirochete diseases among vertebrates. Further research
will probably bring to light some conjugation process, but as yet nothing
of the kind is known.
Schaudinn ('04), on the strength of his observations on the reduction
in size until almost invisible of Leukocytozodn ziemanni, after repeated
divisions, suggested that yellow fever might well be a disease due to
spirochetes. The now well-known agent of transmission, Stegomyia
fasciata, requires a period of twelve days before it is capable of giving
THE GENUS SPIROCHETA AND ALLIES 231
the disease to man; after infection, the human victim is first pros-
trated in from three to five days; after the onset, the blood is capable of
infecting a mosquito again only for a period of three days. These facts
indicate that the organism undergoes some cycle of activity in the
mosquito; that it has a period of incubation in man, and that it dis-
appears from the blood after three days (see Reports of Yellow Fever
Commission, 1900, 1901; also Goldberger, 1900). In spite of all that
is known about yellow fever, the organism causing it has never been
seen; it passes readily through the finest filters, and must, therefore, be
extremely minute, possibly justifying a position in Borrel's group of
the ultramicroscopic or invisible organisms. It may be pointed
out, however, as Schaudinn does, that known forms of spirochetes
become progressively smaller with successive divisions, and it is con-
ceivable that spirochetes consisting of a single unmeasurable node
may exist and multiply without forming catenoid colonies in the blood,
and, because so minute, remain unseen. Stimpson's ('06) discovery
of spirochetes in the kidney of a yellow fever victim is interesting and
suggestive in this connection, but they must be found more often
before much importance can be attached to them.
G. Are Spirochetes Protozoa or Bacteria? — From the foregoing
review of the structures and life histories of the spirochetes there is
little that is definite to determine the natural affinities of these spirilli-
form organisms. The plastic nature of the body and polymorphism
are protozoan characters. The structure of the so-called flagellum is a
point in favor of the bacterial nature, but the highly kinetic membrane
is an equally strong point in favor of the protozoa. The nucleus or
its equivalent is more like that of the bacteria than like the mor-
phological nucleus of the protozoa; but there are protozoa with dis-
tributed nuclei (p. 29), so that this character is not distinctive. The
physiological characteristics are quite as typical of protozoa as they
are of bacteria; division, so often a subject of acrimonious and con-
tradictory statements, is not decisive, for many protozoa divide trans-
versely (all ciliates and Oxyrrhis and Polykrikos among flagellates),
while some bacteria are said to divide longitudinally. Cultivation on
artificial media, thus far unsuccessful with spirochetes, is now, thanks
to the excellent work of Novy and MacNeal and their followers, no
longer a distinctive feature, for trypanosomes, like most bacteria, may
be so cultivated. The results of plasmolysis, urged by Novy and
Knapp ('06) as an argument in favor of the bacterial nature of spiro-
chetes, have but little value, for the time factor necessary to plasmolyse
is a purely relative matter dependent upon the nature and resistance
of the cell membrane. Differences among the bacteria themselves,
in this respect, as Prowazek, Siebert, and many others have pointed
out, are quite as marked as the differences between undoubted pro-
tozoa and spirochetes. The periodicity of symptoms in the hosts of
232 THE PATHOGENIC FLAGELLATES
disease-causing forms is more characteristic of protozoa than of bac-
teria, but the formation of toxins and the installation of immunity
give no light on either side. So, too, the passive carriage or active
multiplication within the insect host, which Stiles ('06) regarded as a
sufficient test of the plant or animal nature of spirochetes, only pushes
the problem a step farther back, for some spirochetes, at least, multiply
in the insect host and some trypanosomes are apparently carried and
transmitted in a passive state.
On the whole, therefore, while again repeating that the controversy
now has only an academic importance, the weight of evidence favors
the view that spirochetes as a group are structurally (ectoplasmic)
more complex and more plastic and variable in form than bacteria,
while functionally they have a more complicated life history. On the
other hand, their structures (endoplasmic especially) are much less
complex than in protozoa, and their life history, so far as it is known,
more simple than that of the known protozoa. Until further obser-
vations on the life histories of different species are made we are justi-
fied in doing no more than to place the spirochetes as an intermediate
group between the bacteria and the protozoa, but leaning more toward
the latter, and in this sense they are included under the name spiro-
chetida in our classification.
CHAPTEE VII.
THE PATHOGENIC FLAGELLATES— (CONTINUED).
THE GENERA HERPETOMONAS (INCLUDING "LEISHMANIA")
AND CRITHIDIA.
WITH these genera belonging to some of the more primitive forms
of the mastigophora, there is no question as to the animal nature, and
from the biological standpoint they form an extremely interesting-
series of protozoa. Among them may be found all of the stages
leading from a free, flagellated, and celozoic mode of life to a non-
motile, intracellular, or cytozoic life, while some of them (H. donovani)
during the latter phase may give rise to fatal diseases in man. Again,
they are interesting in a zoological sense, in that here (crithidia) may be
found variations in cellular structure pointing toward that compli-
cated kinetic structure of the trypanosomes, the undulating mem-
brane. On the other hand, they show, through herpetomonas, a
close relation to free-living forms in stagnant water and belonging to
the family cercomonadidre. Undulating membranes are uncommon
among flagellated protozoa, but are frequently found among ciliated
forms. Here, however, they represent quite different morphological
structures (Fig. 92).
Novy, MacNeal, and Torrey ('07) hold that all forms of herpeto-
monas and crithidia are in reality trypanosomes, basing their conclu-
sion upon the fact that cultural forms of trypanosoma lack the undu-
lating membrane and appear in no wise different from these ordinary
flagellates of the insects' digestive tracts. Such a conclusion cannot be
allowed in any zoological sense, for at no time in the life history of any
species of herpetomonas or crithidia are stages present with char-
acteristic structures specific to the genus trypanosoma.1
The point of view held by Leger, Caullery and Mesnil, and some
others is quite different. According to this the trypanosomes are
1 If species admittedly do not conform to a generic diagnosis, there is no possible reason
for enrolling them in such a genus where they obviously do not belong. What would a
zoologist say to a naturalist who claims that necturus and other perennibranchiate amphibia
are only species of amblystoma, on the ground that the larval form of the latter has gills?
And yet it is exactly this, in effect, that Novy, MacNeal, and Torrey claim for herpetomonas
and crithidia, and the high position which these investigators occupy in medical circles makes
an error like this particularly unfortunate. The group of trypanosomes is quite complicated
enough as it is, without the added difficulties of other genera.
234
THE PATHOGENIC FLAGELLATES
regarded as developed herpetomonas forms which have become
specially adapted for life in the blood, the undulating membrane
being a special reaction on the part of the organism to the conditions
in the blood.
FIG. 92
M—
Types of undulating membranes. A/, membrane. (After Calkins.)
It is quite otherwise with the supposed genus leishmania in regard
to which every new observation tends to strengthen Rogers' ('05) view
that this organism of kala azar agrees with herpetomonas in all of
its generic diagnostic characters. Crithidia also rests upon differ-
ences of a very slight nature, but the primitive type of membrane at
the base of the flagellum is of positive diagnostic value and in most
cases it is sufficient to distinguish this genus from herpetomonas.
In all forms the flagellum is well defined and of the characteristic
THE GENERA HERPETOMONAS AND CRITHIDIA
235
flagellate type (Fig. 93), arising from a distinct kinetic body, the
blepharoplast. The nucleus is not of the diffuse type so characteristic
of the bacteria and spirochetes, but is compact and cytologically
similar to the nucleus of tissue or of typical protozoa cells, while in
primitive mitosis it passes through more or less complicated form
changes.
All are parasites, and all are apparently typical intestinal forms of
definitive insect hosts. Herpetomonas is found chiefly in the stomach
FIG. 93
A, B, C, Herpetomonas muscse domestic®; A, ordinary form with double flagellum; B,
dividing form; C, form encysted in slime coat; D to F, Crithidia subulata Leger, from gut of
Tabanus glaucopis Meig; D, free monad form; E, gregarine-like resting forms showing with-
drawal of flagellum; F, the same fixed to an epithelial cell in great numbers; k, kinetonucleus;
t, trophonucleus; d, diplosome; A to B, after Prowazek, D to F, after Leger. X 1800.
and intestine of various kinds of insects, H. donovani in the digestive
tract of the bedbug Cimex rotundahis, while crithidia has a wide
range among diptera and hemiptera. With development of the blood-
sucking habit these various insects have furnished the opportunity
for their parasites to adapt themselves to man and other intermediate
hosts.
Non-flagellated, quiescent, and encysted stages are known in all
cases, the quiescent forms remaining passive in the digestive tract
(herpetomonas), or actively migrating ("gregarine" forms) to the
236 THE PATHOGENIC FLAGELLATES
epithelial cells, to which they attach themselves often in large num-
bers (crithidia), or they may migrate into the cells, multiply there,
and cause serious trouble (Herpetomonas donovani). Because of
these dual motile and quiescent phases, they have quite upset the
taxonomic balance of many recent writers and have caused some of
the latter to sacrifice the well-known group, hemosporidia, while some
have gone, prematurely, to the length of entirely giving up the estab-
lished subphylum sporozoa as a group, although, indeed, even the
most conservative of systematists must admit that this group is not a
natural one.
A. The Genus Herpetomonas. — The most primitive and the least
changed from the free-living forms of cercomonadine flagellates is the
genus which Kent, in 1881, named herpetomonas, characterizing it as
follows :
"Animalcules free-swimming, elongate or vermicular, highly
flexible; the posterior extremity often the most attenuate, but not
constituting a distinct caudal appendage; flagellum single, terminal;
contractile vesicle conspicuous." To this he added the following
note: "This new genus is instituted for the reception of the form
figured by Stein, 'Infusionsthiere/ Abth. Ill, 1878, under the title of
Cercomonas muscce domesticce, and identified by that authority with
the Bodo muscce domesticce of Burnett, and the Cercomonas mus-
carum of Leidy. The entire absence of a distinct caudal filament
«/
serves, however, at once to distinguish it from the typical representa-
tives of either of the two last-named genera and approximates it the
more nearly to leptomonas or ophidomonas. A second minute form
recently discovered by Mr. T. R. Lewis in the blood of rats (Trypano-
soma lewisi) is provisionally referred to this generic group." Kent
Manual, p. 245.
The contractile vacuole seems to have been more or less imaginative,
certainly subsequent observers have not described it and it is quite
possible that Kent and others mistook the vacuole about the blepharo-
plast for a contractile organ. Among the species that are now recog-
nized are the following:
H. muscce domesticce, found in the intestine of the housefly.
II . sarcophagce, Prow. Intestine of meat flies.
H. lesnei, Leger. Malpighian tubules of Dasyphora pratorum.
H. gradlis, Leger. Malpighian tubules of the sucking fly tanypus sp.
H. campanvlata, Leger. Intestine of larva of a sucking fly.
H. jaculum, Leger. Intestine of 'the water bug Napa cinerea.
H. donovani, Lav. and Mes. Intestine of cimex and cause of kala
azar.
H . lygei, Patton. Intestine of the water bug lygseus.
Herpetomonas of culex sp., Patton.
The most primitive and least changed from the free-living forms of
THE GENERA HERPETOMONAS AND CRITHIDIA 237
flagellated intestinal parasites is the genus which Kent named herpeto-
monas. It is a widely distributed parasite of flies; that of the common
housefly, Herpetomonas muscce domesticos, Burnett, is among the best
known of these species, largely through the observations of Prowa-
zek ('04). This organism is elongate and somewhat flattened at one
end, which gives rise to the single, long, vibratile flagellum (Fig. 93).
Apart from the nucleus and blepharoplast, the inner protoplasm has
no characteristic structures and the nucleus is of the characteristic
mastigophora type, with chromatin granules (often erroneously called
chromosomes) of more or less definite number. The blepharoplast
(fc) lies between the nucleus and the flagellum, and is frequently of
large size, while from it the base of the flagellum (rhizoblast) takes its
origin. Prowazek describes the flagellum as double, the two parts
being connected by a delicate membrane. If this were true, then, as
Minchin ('07) remarks, this organism would have to be enrolled in
some other genus than herpetomonas, but it is more than probable
that Prowazek described an early phase of division in which the
flagellum is precociously divided, as the typical form of the adult,
an interpretation supported by his own figure (B) of a dividing form.
Patton ('08), furthermore, has been unable to confirm Prowazek's
observation, and finds that the flagellum is single both in H. muscce
domesticce and H. sarcophagce, but that it with the blepharoplast
divides first in reproduction. At the base of the flagellum, just outside
of the body, is a small basal granule ((/), which in the cells with a
double flagellum was called the diplosome by Prowazek.
Reproduction occurs by longitudinal division (Fig. 93, 5). The
nucleus divides by a primitive process of mitosis, the granules being
equally distributed. This nuclear division is preceded by division
of the blepharoplast and of the flagellum, which in this case appears
to divide throughout its entire length instead of one being formed, as
in some trypanosomes, by outgrowth from the blepharoplast.
Conjugation has been described by Prowazek as taking place
between forms which are not sexually differentiated beyond the fact
that one appears to be denser and larger than the other. During
conjugation the flagella are withdrawn and the nuclei undergo so-
called reducing divisions, similar in character to those occurring in
Tnjpanosoma noctuce (see p. 255). After conjugation a permanent
resting cyst is formed by the fertilized cell, and in this condition the
parasite passes from the intestine with the feces of the host.
According to Prowazek, infection of new hosts takes place usually
by ingestion of these permanent cysts with the food ; but he also finds
that 5 per cent, of the flies examined and known to contain the allied
form H. sarcophagce had parasites in the body cavity and in the
ovaries as well as in the intestine. It is probable, therefore, that the
organism may be transmitted by inheritance. In H. lygei, on the
238 THE PATHOGENIC FLAGELLATES
other hand, there is no evidence, according to Patton, of parasites
in the body cavity, nor in the nymphs and larvae reared from the
egg. In this form, therefore, inheritance appears to be out of the
question, the insects becoming infected solely by the ingestion of
encysted forms of the parasite.
As in trypanosoma, the various species of herpetomonas are char-
acterized by the habit of forming rosettes or agglomerations through
the union of individuals by the flagellated ends. Also, in common
with trypanosomes and with the merozoites of malaria organisms, they
manifest a well-marked rheotropism or reaction against a current, a
property, especially in the latter case, which enables the organism to
make headway against a blood flow or intestinal current.
In all forms of herpetomonas there are free-moving monadiform
parasites, or motile gregariform parasites, which move with a worm-
like motion and finally aggregate about the epithelial cells, where they
often form masses of considerable size. In both of these conditions
the organisms may reproduce by longitudinal division. The gregari-
form phase may also encyst by secreting a slimy covering, which
becomes more or less hardened, and in this cyst the organisms pass out
of the digestive tract with the feces, thus serving to spread the infection.
The history of Herpetomonas donovani, Lav. and Mes., is par-
ticularly interesting from both the medical and the biological points
of view, and shows the devious paths which an organism may follow
before reaching its definitive place in a zoological system. The etiology
of a number of peculiar diseases of India, characterized by well-
marked splenomegaly (dum dum fever, kala azar "black sickness"),
by irregularly recurrent fevers, anemia, and emaciation, resulting
finally in profound cachexia and usually in death, has been only
recently established. Leishman ('03) found peculiar bodies in cells
obtained in films from a postmortem, and considered them degenerated
forms of trypanosomes ; from this they were given the name of "Leish-
man bodies." Donovan ('03) found peculiar bodies in the peripheral
blood of cases of kala azar, and sent his preparations to Laveran and
Mesnil, who, in November, 1903, described the peculiar bodies as
similar to the blood parasites of Texas fever (babesia "piroplasma")
and named the organism accordingly Piroplasma donovani. From
this the bodies became known as the " Leishman-Donovan bodies,"
although considerable difference of opinion existed as to the identity
of the forms in the spleen and in the blood. In December, 1903,
Wright described peculiar structures, which he interpreted as organ-
isms belonging to the microsporidia, in a case of tropical ulcer, and
named the organism Helcosoma tropicum. Having a well-marked
resemblance to the bodies found in kala azar, these new structures
added a third term to the series, and they became known as the
"Leishman-Donovan- Wright bodies" (Woodcock). In the meantime,
THE GENERA HERPETOMONAS AND CRITHIDIA 239
however, R. Ross, examining the Leishman-Donovan bodies, came
to the conclusion (November 14, 1903) that they were distinct forms
of protozoa, and named the organism causing kala azar Leishmania
donovani, but Rogers ('05), on the basis of culture experiments, found
no perceptible difference between the flagellated phase and herpeto-
monas, while Patton ('08) has demonstrated that the non-flagellated
phases are likewise identical. The genus leishmania, therefore,
cannot hold. If the organisms discovered by Wright are found to
belong to the same genus, but are specifically different, then the name
for Wright's organism must be Herpetomonas tropica, Wr.
Rogers' discovery of the flagellated stage was quickly confirmed
by Christophers and by Leishman, the latter finding in this dis-
covery a confirmation of his earlier belief that the organisms were
trypanosomes, basing his view on the fact that some trypanosomes
under culture have no undulating membrane. Rogers gave many
reasons for considering the bedbug the means of transmitting the
disease from individual to individual, and his surmise was not only
confirmed, but the transformation of the intracellular bodies into
flagellates within the intestine of Cimex rotundatus was fully worked
out by Patton in 1907. With this discovery Leishman's conclusions
regarding the trypanosome relation cannot hold, the organism finding
its nearest relative, as stated above, in the genus herpetomonas.
The Leishman-Donovan bodies, as the intracellular forms have been
called, are present in large numbers in the cells of liver, spleen, and
bone marrow, while, according to Christophers, leukocytes and great
macrophages of endothelial origin may become crowded with them,
100 to 200 in a single cell (Leishman). They are taken into the
stomach of the bedbug still as intracellular forms, and are liberated
there by degeneration and digestion of the human cells. When first
liberated, and during the early changes in the gut, the parasites
measure from 4 to 7 /£ (Patton); they may be oval or spherical in
shape, but they soon divide and may form small "rosettes" of six to
eight cells.
No sexual differences and no conjugation processes have been made
out, although Leishman described the formation of very slender forms
from larger ones (Fig. 94) in organisms under culture; such conjuga-
tion processes are to be sought in the intestine of the bedbug, and it
may be predicted that within a very short time they will be found there.
Herpetomonas donovani, in its quiescent phase, is undoubtedly an
endothelial cell parasite which multiplies in human tissue cells until
the normal histological relations of such cells are broken down and
the cells are liberated as macrophages in the general circulation. Here
many of the parasites become free, only to be captured and ingested
by leukocytes, so that toward the end of the disease the peripheral
blood contains great numbers of parasite-filled leukocytes and endo-
240
THE PATHOGENIC FLAGELLATES
thelial cells. When such blood is sucked into the digestive tract of
a bedbug the cell bodies of leukocytes and macrophages are broken
down and their contained parasites liberated. Patton found that the
parasites thus introduced into male or female bugs could remain in the
mid-gut for at least five days before beginning to develop, although
the majority of them are well under process of development by the
second or third day.
Development of the parasite begins with a well-marked increase in
volume, and the cell nucleus (trophonucleus) early divides. This
process of division is not described in great detail by Patton, but it is
evidently similar to the process of mitosis of the euglena type. The
cell then rapidly undergoes flagellation, a pink staining (with Giemsa)
area being the seat of flagellum formation. This area was noted by
other observers and called the "flagellar vacuole" (Leishman, Patton),
the " vacuole-like area" (Christophers), and the "eosin body"
Fir,. P4
Herpetomonas donovani, unequal division to form slender flagellated individuals.
(After Leishman.)
(Rogers), and is probably the same organoid of the cell that Kent
('81) described as the contractile vacuole in his characterization of
the genus herpetomonas. This enlarged flagellar vacuole passes to the
cell periphery, where it bursts and a small "brush" of pink-staining
fibers protrudes from the cell, and these, later, by coalescence, form
the definitive flagellum. In other cases the parasites do not undergo
division in this manner, but the nucleus divides and the blepharoplast
divides two or three times, and eight flagella are formed at various
points on the cell periphery. These so-called "rosettes" divide to
form elongated flagellates as many in number as there are flagella
and blepharoplasts. The size of the flagellates varies considerably from
relatively long ones (up to 20 microns), by continued division, to
minute spirilla-like forms.
THE GENERA HERPETOMONAS AND CRITHIDIA
241
Pattern finds no evidence of encystment and no evidence of infection
of the bedbugs other than from human victims. Nor is there any
evidence to support the idea of direct inheritance from female bugs to
their offspring, but Patton suggests in a later paper (1908) that nymphs
of blood-sucking forms of such bugs may take in the infection with
their food. The method of reentry into a human host is likewise
unknown.
B. The Genus Crithidia, Leger, 1902.— The genus crithidia, by
reason of its non-kinetic prolongation of protoplasm at the base of the
flagellum, forms an interesting link in the evolution of the trypano-
somes. It is quite true, as Novy, MacNeal, and Torrey ('07) point
out, that the distinctions between these several genera are extremely
"fragile," and that the points of difference are so minute as not to
FIG. 95
A
D
Crithidia melophagia, Flu, from the gut of Melophagus ovinus. (After Flu.) A, fully
developed parasite with myoneraes; B, individual with degenerated trophonucleus; C,
encysted form (see herpetomonas) ; D, division form.
count for much. It must not be overlooked, however, that minute
differences must be utilized in connection with organisms that are
themselves minute, and a definite structural feature which Liihe
points out as the most characteristic of the genus crithidia, since it
exists in all of the parasites regardless of their size, is a perfectly
satisfactory differential characteristic, and unlike Leger's original
basis of distinction (smaller size of crithidia and truncated ends),
has morphological value.
The type species is Crithidia subulata, Leger, a parasite of the
intestinal tract of a tabanid fly. The body is elongate and slender and
drawn out upon the base of the flagellum in a typical manner (Fig. 93,
p. 235). The nucleus and blepharoplast are distinct and persistent after
16
242
THE PATHOGENIC FLAGELLATES
withdrawal of the flagelltim. This gradually shortens and disappears, a
rhizoblast remaining for some time; but this too is ultimately absorbed,
and as a "gregarine" form the minute organism makes its way to
epithelial cells, where it becomes attached (Fig. 93).
Since Leger's original observations several others have worked upon
different species of crithidia, the most recent results being obtained by
Patton ('08) in connection with a species (Cr. gerridis, Patton) from
a water bug, Gerris fossarum, and by Flu ('08) in connection with a
species (Cr. melophagia, Flu) from Melophagus ovinus, an ectoparasite
of sheep. In each of these there are well-defined, non-flagellated con-
ditions of the organisms similar to those of H. donovani. A nucleus
and blepharoplast are present, and the flagellum develops from the
latter by the apparent outgrowth of its substance (Fig. 95). In
Stages in the development of Crithidia gerridis, Patton. (After Patton.) A, group of
young forms from mid-gut of nymph of Gerris fossarum, Fabr.; blepharoplast and origin of
flagellum; B, development of the flagellum inside the periphery of parasite; C, further develop-
ment and division of flagellum; D, E, adult forms, flagellum dividing in E; F, two stages in
withdrawal of flagellum to form resting stages; G, cyst.
Cr. gerridis the flagellum forms as a ridge upon the surface, and often
divides as it grows, the basal bodies first dividing into two. By con-
tinued division rosettes of many individuals may be formed before
the fully developed flagellated adults break away. Division occurs as
in herpetomonas (Fig. 96).
Encysted forms similar to those described by Prowazek for her-
petomonas were observed by Flu in the case of Cr. melophagia, but
not in Cr. gerridis. Cr. melophagia further differs from other forms in
possessing definite myonemes which run the length of the body, unit-
ing in the anterior end with the rhizoblast of the flagellum (Fig. 95).
THE GENERA HERPETOMONAS AND CRITHIDIA 243
Neither conjugation nor mode of infection has been observed
in connection with these parasites, and the caution which Novy,
MacNeal, and Torrey express in regard to the possible confusion of
such flagellates of insects, with developmental stages of human or
other vertebrate blood parasites, is certainly well grounded, but we
cannot indorse their view that all such parasites are to be looked
upon as developmental stages in the life history of trypanosomes.
CHAPTER VIII.
THE PATHOGENIC FLAGELLATES- -(CONTINUED).
THE GENUS TRYPANOSOMA, GRUBY.
AT the present day more than sixty species of trypanosoma have
been described from different types of vertebrates, and although the
greatest difference of opinion exists here, as with spirochetes, it is not
in connection with the animal or plant characteristics, but rather with
the relationships and life history. Various students of the group,
beginning with Leger ('04), have attempted to separate all of the dif-
ferent varieties known into distinct groups, according to the morpho-
logically "anterior" end. In some the flagellum issues from the cell
at the supposedly posterior end, in others at the supposedly anterior
end. The former, including all of the piscine trypanosomes, are
grouped by Liihe ('00) in a distinct genus, to which he applies Mitro-
phanow's name, hematomonas; the latter includes all of the mam-
malian trypanosomes to which Lithe gives the distinct generic name
trypanozoon, while a third generic name, hemoproteus, is given for
the trypanosome of the owl, having a dual life in the serum and in the
blood cells, as described by Schaudinn. Woodcock ('06) likewise
separates the latter from all other trypanosomes, under the generic
name of trypanomorpha.
The scientific value of these divisions of the trypanosomes stands or
falls with their phylogeny and with the terminal homologies of the
different species. A typical trypanosome, for example, T. theilerl,
Bruce, found exclusively in the blood of cattle, consists of an elongate,
more or less serpentine cell body, from one end of which projects a
vibratile flagellum (Fig. 97). The flagellum is continued toward the
opposite end of the cell as a well-marked marginal cord, and takes its
origin from a minute granule (blepharoplast) not shown in Liihe's
figure. Near this terminal granule lies a large, deeply staining body
of chromatin (&), which in some species is larger than the nucleus, and
in others has a typical reticulate nucleus character. In agreement with
the views of Schaudinn, Woodcock, Liihe, Minchin, and others, this
chromatin or nucleus-like body will be designated the " kinetonucleus,"
a term suggested by Woodcock ('06) because of its close connection
with the motile elements of the cell (see p. 33). Between the attached
part of the flagellum and the body is a delicate protoplasmic mem-
THE GENUS TRYPANOSOMA
245
brane, which, as in Spirocheta balbianii, is frequently, if not always,
provided with contractile myonemes. The non-flagellated end of the
cell may be pointed, as in T. thelleri, or rounded or blunt. The endo-
plasm frequently contains granules of chromatoid material, and may
have a vacuolated appearance; little importance, however, has been
attached to these structural details of the endoplasm. The nucleus of
the cell, the element, that is, which superintends the vegetative pro-
cesses and sometimes called the " trophonucleus," is a clearly defined
morphological nucleus in which a nuclear membrane may be made
out in some cases, again not. The chromatin is usually in the form
of granules (miscalled chromosomes) of usually a definite number;
but there is reason to believe that under satisfactory cytological
methods the chromatin is finely granular, surrounding a central
division centre, as in the majority of free flagellates (see p. 30).
Reproduction of the cell is by longitudinal division preceded by divi-
sion of the blepharoplast, kinetonucleus, and vegetative nucleus.
FIG. 97
Trypanosoma "Trypanozoon" theileri (Bruce), blood of cattle Tran^caiica<ia. X 3000.
(After Liihe.) k, kinetonucleus; t, trophonucleus; u, undulating membrane.
There are two different theories as to the phylogenetic history of
this well-marked and highly characteristic type of organism: one
deriving it from heteromonad forms like bodo or anisonema (Fig. 1 5
p. 43), the other from forms like herpetomonas and crithidia. According
to the first hypothesis, the trypanosome condition is brought about by
the union of the trailing runner, flagellum, or Schleppgeissel with the
cell body. If this were the case, then the flagellum end of the organism
would be posterior. A certain amount of evidence in favor of this point
of view is given by two interesting types of blood-dwelling parasites
of fishes, trypanoplasma and trypanophis, in both of which there are
two flagella, one directed in advance at the anterior end, the other
attached to the body throughout its length and terminating as a
246
THE PATHOGENIC FLAGELLATES
free flagellum at the posterior end (Fig. 98). Such forms may be
readily conceived as coming from bodo-like types in which the pos-
terior or trailer flagellum becomes attached to the cell, while the
trypanosome type may arise from such forms by the suppression of the
FIG. 98
C
Trypanoplasma borreli. (After Keysselitz.) A, B, old, developmental stages; C, a so-called
"male" form; D, E, so-called "female" forms; G, H, the "copula."
THE GENUS TRYPANOSOMA
247
anterior flagellum and elaboration of the lateral protoplasm into an
undulating membrane. According to such a derivation, the flagellated
end of a trypanosome would be posterior, and this is the view taken by
a number of authorities. As Minchin ('08) points out, however, the
developmental history of no trypanosome points to this mode of origin,
but tends rather to support the second hypothesis of the origin of
trypanosomes from herpetomonas and crithidia-like forms by the
posterior migration of the kinetonucleus and blepharoplast, whereby
these structures become secondarily posterior, while the flagellum
FIG. 99
Trypanosoma noctuse. (After Schaudinn.) Schematic representation of the metamor-
phosis of a fertilized cell into an "indifferent" type of Trypanosoma. F, G, H, formation
of the undulating membrane and flagellum from kinetoplasmic material.
would be attached to the cell, as in herpetomonas, at the anterior end.
Schaudinn has shown that the flagellum in Trypanosoma noctuce has
this mode of origin, and grows out from the anterior end, while the
kinetonucleus and blepharoplast (Fig. 99) remain anterior to the
nucleus. In other species, however, the developmental history shows
that young forms and culture forms are similar to crithidia with
rudimentary membrane and anterior blepharoplast and kinetonucleus.
This is well described in the case of a trypanosome of the ray, Try-
panosome mice (?), by Robertson ('07). Here in young forms, after
division in the gut of the leech Pontobdclla muricata, the kinetonucleus
248 THE PATHOGENIC FLAGELLATES
is anterior to the nucleus, but becomes posterior to the nucleus as
development progresses (Fig. 100) until the adult posterior position is
attained. Novy has laid great stress upon the fact that in trypano-
somes in culture the form is similar to that of herpetomonas and cri-
thidia, and for this reason regards the species of these genera as true
trypanosomes. It will hardly be allowed by anyone familiar with the
morphological changes of protozoa that trypanosomes under culture
in artificial media are in any way normal, either structurally or physio-
logically, and his purely hypothetical conclusion that herpetomonas
and crithidia "really represent cultural forms of true trypanosomes"
(1907), zoologically speaking, is far-fetched. The herpetomonad
form assumed by some types may be evidence of a phylogenetic
ancestral state, but it certainly cannot be accepted as evidence that the
more primitive, ancestral organisms are themselves trypanosomes.
In the present state of knowledge of trypanosomes it is extremely
uncertain as to where lines should be drawn between species; mor-
phology is no aid in this, for the same species in the same animal may
present so many form changes that were they found in different
animals they would be assigned to different species without hesitation.
No safe limitations can be established until the life histories are known,
and as these have been worked out in only a few cases the difficulties
are not much relieved. Physiological grounds, culture relations, etc.,
are equally unsatisfactory, but there is reason to believe that differ-
ences in such respects are indications of different specific relationships.
For the present, therefore, it is expedient to consider each new form
described in a new host as a distinct species until its affinities are
established by the full life history, and until then, furthermore, it
seems better not to break the genus trypanosoma into other genera as
Liihe ('06) has done on the basis of supposed different ancestry. This
supposition is purely hypothetical, and it is quite possible that we have
not yet found the true explanation of the anterior and posterior ends
of trypanosomes.
Trypanosomes are present in all kinds of vertebrates, where they are
normally parasites of the blood system; they are also found in the
intestines of different blood-sucking insects. Liihe, with Leger,
believes the latter to be the definitive hosts, the trypanosomes coming
from ancestors like herpetomonas and crithidia, which are typical
intestinal parasites. Novy also takes this point of view, holding, with
Leger, that the trypanosome structures are special adaptations which
the organisms have developed as a response to conditions in the blood.
Minchin ('OS) regards the trypanosomes as originally parasitic in the
vertebrate intestine, basing his conclusion largely upon the observa-
tions of Hintze ('02) and upon theoretical considerations of the fact
that trypanosomes may be transmitted by leeches as well as by insects.
There is much to be said in favor of his point of view, and Leger 's
THE GENUS TRYPANOSOMA
249
criticism that no sexual phases have as yet been found in the blood of
vertebrates is not wholly unanswerable, since we do not yet know
FIG. 100
Trypanosoma raia. (After Robertson.) Forms observed in the digestive tract of the leech,
Pontobdella muricata. ^1, mature specimen from blood of skate; B to F, stages in the
development of the flagellum from the kinetonucleus, and change in position of the latter in
relation to the nucleus.
much about the conjugation processes in any species, while Hintze's
view is conceivable, viz., that the organisms migrate from the blood
back into the intestine, where they conjugate, while in blood-sucking
250
THE PATHOGENIC FLAGELLATES
forms the stomach and intestine of the invertebrate is substituted for
that of the vertebrate. Minchin holds that trypanosomes are never
found in the alimentary tract of insects which do not draw blood, and
finds in this a further support for his hypothesis.
All such speculations, while interesting and stimulating to further
research, are, however, unsubstantial, and generalizations cannot yet
be drawn with any safety. The following list of species, founded in
large part upon the species enumerated in Lube's excellent paper on
these forms, shows what a large field for research this group presents,
and that "material" is at hand for investigators everywhere.
The most plausible hypothesis concerning the origin of the trypano-
somes interprets them as more highly evolved organisms of the her-
petomonas or crithidia type. Like the latter they are characteristically
fluid-dwelling parasites either in the denser fluids of the digestive tract
of invertebrates (Trypanoplasma borreli in the leech) or in the less
dense fluids of the blood. As crithidia and herpetomonas may lose
their motile organs and pass into a quiescent phase, or in the case of
H. donovani into a cell invading phase, so trypanosomes may assume
resting or encysted phases (e. g., T. grayi in the rectum of the tsetse)
or even the cell-invading phase (T. noctuse) in the blood.
LIST OF SPECIES OF TRYPANOSOMA.
Name of species.
T. remaki , Lav. and
Mes.
T. danilewskyi,
Lav. and Mes
T. tincae, Lav. and
Mes.
T carassii, Mitrop.
Vertebrate host.
Esox lucius, L.
Cyprinus carpio
Tinea tinea, L.
Carassius caras-
sius, L.
Abramis abramis
T abramis, Lav.
and Mes.
T. granulosum, Lav. Anguilla anguilla
and Mes.
T. cobitidis, Mitr.
T. barbatulse, Leg.
Cobitis fossilis
Cobitis barbatula.
L.
Brazilian fish
Brazilian fish
T. rhamdise, Botello
T. macrodonis, Bo-
tello.
T. solese, Lav. and Solea solea, L.
Mes.
T. platessae, Leb.
T. flesi, Lebailly
T. laternae, Leb.
Platessa platessa
Flesus flesus
Arnoglossus later-
nus, Walb.
Limanda limanda
T. limandffi, Br. and
Leb.
T. gobii, Brump. Gobius niger
and Leb.
T. callionymi, Br. Callionymus dra-
and Leb. cunculus, L.
Serum or cell
parasite.
Serum
Invertebrate host
known or suspected
Size.
THE GENUS TRYPANOSOMA
251
Name of species.
Vertebrate host.
Serum or cell
parasite.
Invertebrate host
known or suspected
Size.
T. cotti, Br. & Leb
Cottusbubalis, Eu.
Serum
T. delagei, Br. and
Blennius pholis
44
Leb.
T. scyllii, Lav. and
Scyllium canicula
"
Mes.
and S. stellare
T. raise, Lav. and
Raja punctata
11
Mes.
R. macrorhyncha
44
R. mosaica
44
R. clavata
44
T. rotatorium,
Rana esculenta
11
Mayer
R. temporaria
41
Hyla arborea
T. mega, Dutton
Rana sp. (Africa)
4 •
and Todd
T. karyozeukton,
Rana sp. (Africa)
44
40-SO/J
Dutt. and Todd
T. mopinatum,
Rana esculenta
44
60-72^
Sergent
T. nelsprutense,
Rana sp.
i*
82. 4 «
Lav.
T. borrelli, March.
Hyla sp.
«»
Leech Helobdella al-
25-30/Z
and Salimbeni
gira, Moq.
T. clamatae, Steb.
Rana clamata
it
24-35/4,
T. damonise, Lav.
Damonia reevesi
it
with flagellum
and Mes.
T. boueti, Martin
Lizard
it
T. noctuae, Celli
Glaucidium
Both Leech (probable)
32^,
and San Felice
noctua
with flagellum
T. danilewsky, iCorvus cornix
Kruse
T. columbse, Celli
Columba livia
Culex pipiens
and San Felice
T. passeris, Celli
Passer (many sp.)
and San Felice
T. alaudse, Celli and
Alauda arvensis
San Felice
T. fringillse, Lab. JFringilla celebs
T. aluci, Celli and
Syrnium aluco
San Felice
T. bubonis, Celli
Bubo buba
and San Felice
T. maccallumi,
Zenaidura carol i-
Novy & MacNeal
nensis
T. sacharovi, Novy
Passer domesticus
and MacNeal
T. rouxii, Novy and
Syrnium aluco
MacNeal
T. avium, Lav.
Syrnium aluco
T. confusum, Lu he Common Ameii-
(T. avium, Novy) can birds
T. laverani, Novy
Astragalinsis tris-
and MacNeal
tis
T. mesnili, Novy
Buteo lineatus
and MacNeal
T. paddse, Lav. and
Padda orizzivora
Mes.
T. johnstoni, Dut-
Estrilda astrild
ton and Todd
T. mathisi, Serg.
Common swallow
252
THE PATHOGENIC FLAGELLATES
Name of species.
Vertebrate host.
Serum or cell
parasite.
Invertebrate host
known or suspected.
Size
Includ'g flagellum
T. lewisi, Kent
Blood of rats
Serum
Louse Hsmatopinus
7-30/1
spinulosus Bur.
T. criceti, Liihe
Cricetus cricetus
"
Flea? Pulex fascia-
?
tus Bur.
T. cuniculi, R. Bl.
Lepus cuniculus
"
Hematopinus ven-
?
tricosus. Denny?
or Pulex sp?
T. duttoni, Thiroux
Mice in Senegal
"
?
25-30/Z
T. indicum, Liihe.
Funambulus pal-
"
?
18-20U.
marum (Mad-
ras)
T. blanchardi, Br.
Myoxus glis, L.
"
?
T. vespertilionis,
Vespertilio noc-
41
?
12-15JJ.
Battaglia
tula
T. nicolleorum, Ser-
Myotis myotis,
**
?
20-24/t
gent
Vespertili >kulili
T. gambiense, Dut.
Man
Serum, sleeping
Glossina palpalis
17-28 fi
sickness
T. brucei, Plimmer
Horse and other
Serum, nagana
Tsetse flies.especially
25-35/t
and Bradford
domestic ani-
Glossina morsi-
mals
tans, W.
T. equiperdum,
Horses, asses
Serum, dourine
(Transmitted by
2.5-28/<
Dofl.
coitus)
T. dimorphon, Lav.
Horses
Serum
?
13-30 fi
and Mes.
T. nan um, Lav.
Cattle
"
?
10-14f{
T. vivax, Ziemann.
Sheep and deer
••
Tabanid flies?
18-20/f
T. congolense, Bro-
Sheep
"
?
10.5-15.5fi
den
T. suis, Ochmann
Swine
"
9
?
T. evansi, Steel
Horse, cattle, buf- Serum, surra
Stomoxys calci-
22-30/i
falo, camel, etc.
trans? Tabanus
lineola '.'
T. equinum, Voges
Horse, cattle Mai de Caderas
?
22-24^
T. theileri,1 Bruce
Cattle Gall sickness
Hippobosca rufi|>cs
6Q-70JJ.
T. mustesari, Ling.
Cattle '
Serum
7
T. pecaudi, Lav.
Sheep
"
?
T. soudananse,
Dromedary
"
?
Lav.
So perfectly have trypanosoraes become adapted to mammalian
blood and mammalian temperature, that in the majority of species
removal from the circulation, even if the blood be kept sterile, results
in loss of virulence or activity, and in death. In some cases, e. c/.,
T. lewisi, different observers have kept infected blood for considerable
periods (Francis, eighty-one days), but in the majority of cases the
organisms do not remain alive for so long a time (T. brucei or T.
rcansi only two to three days). Even when successful such experi-
ments involve no multiplication processes, the organisms being merely
preserved alive, and with a few exceptions such appears to be the case
1 Includes T. transvaaliensis, Lav., and T. lingardi, R. Bl.
THE GENUS TRYPANOSOMA 253
when mammalian blood and organisms are taken into the digestive
tracts of different insects (T. brucei disappears from the tsetse in from
two to three days).
It is quite otherwise with cultivation on artificial media first suc-
cessfully accomplished by Novy and MacNeal, in 1903, with T.
lewisi. These keen investigators opened a new era by this application
of bacteriological culture methods with pathogenic protozoa, the
method, as we have seen (p. 239), giving excellent results with seem-
ingly obligatory cytozoic forms ( Leishman-Donovan bodies). The
culture medium is made up of nutrient agar and defibrinated rabbit's
blood. When desired for use the agar is melted and cooled to about
50° C., the blood added and thoroughly mixed. The organisms collect
and multiply in the water of condensation or even on the agar directly.
It was found that the organisms gradually lose their virulence and die
as a result of the exhaustion of the food medium, but that renewed
virulence and vitality could be established by transplanting to fresh
culture tubes. In this way Novy and his associates have maintained
trypanosomes in pure culture for several years. While T. lewivi
appears to be an especially favorable subject for this method of re-
search, other forms as well have been studied in this way, Novy and
MacNeal being successful with T. brucei, T. evansi, and with several
bird trypanosomes, while Laveran and Mesnil have succeeded with
T. brucei, dimorphon, T. f/amb/'ense, and others.
A. The Motile Apparatus of Trypanosomes. — In fresh blood
the presence of trypanosomes, when abundant, may be easily noted by
the agitation of the blood corpuscles, which are whipped about by the
lashings of the ever-active flagellum. This movement of the trypano-
somes may be analyzed as a combination of snake-like undulations,
active bending, rotation, and translation. In some, notably in T.
r/rax, the peculiar writhing movements without progression, which
are characteristic of a great many species, are replaced by an active,
business-like forward movement in straight lines across the field of the
microscope. In such movement the flagellum, as with free-living
flagellates, is always in advance.
As shown in Chapter I, the flagellum of a typical mastigo-
phoran is formed by the outgrowth of substance from the kinetic
centre, which may be in the form of a basal granule or blepharoplast,
or in the kinetic material within the nucleus. Such kinetic centres
have the appearance and often the functions of centrosomes, so that
the term centrosome sometimes used for the basal granule has some
significance.
In trypanosomes, the flagellum has the same mode of origin as in
other flagellates, coming from a basal granule or blepharoplast which
may or may not be included in the kinetonucleus. In some cases,
during division of the cell, it appears to divide longitudinally as it does
254 THE PATHOGENIC FLAGELLATES
in herpetomonas, but in other cases, and apparently in the best authen-
ticated cases, the flagella are always formed by newgrowth from the
basal body.
The flagella are always accompanied by a protoplasmic membrane,
to which they are attached as a lateral cord. This membrane, if
drawn out straight, is often longer than the body whence it is attached
in folds or undulations, while by its movements, directed by the
attached flagellum, the organism moves through a liquid medium
with a peculiar auger-like movement, and gave the reason for Gruby's
name, trypanosoma. In the majority of forms the flagellum is con-
tinued beyond this membrane as a free "whip" in the surrounding
medium, but in other cases, as in Tryp. dimorphon, it terminates with
the membrane.
As to the minutiae of flagellum and membrane formation the best
and most complete account has been given by Schaudinn in the case
of Tryp. noctuce, the blood parasite of the little owl Glaucidium noctuce.
The kinetonucleus divides by heteropolar mitosis, the smaller part
becoming the blepharoplast, the larger remaining as the kinetonu-
cleus. The smaller then divides again and a spindle figure is formed
which, except that it is heteropolar, resembles that of free flagellates,
having a central spindle formed by the division centre, and eight
"mantle fibers" corresponding to the chromosomes. The central
spindle forms the flagellum at the edge of the undulating membrane
which now grows out from the anterior end of the organism, while
the eight fibers form the myonemes of this membrane (Fig. 99, p. 247).
There is reason to believe that if this account of the formation of the
membrane is accurate, the so-called chromatin of the kinetonucleus
is in reality kinetic substance. Schaudinn's figures were acknowl-
edged by himself to be schematic, and it is quite probable that the
formation of flagellum and membrane does not follow such a clean-
cut scheme ; it illustrates the fact of widespread occurrence, however,
that the flagellum does not emerge from the kinetonucleus direct. A
similar granule is formed from the division centre of the kinetonucleus
(Prowazek, 1905) of Tryp. lewisi, and the flagellum is held by
Prowazek to arise in the same way as in Tryp. noctuce, while the
mantle fibers become eight longitudinal but ill-defined lines running
the length of the cell. Similar myonemes were observed by Prowazek
in Tryp. brucei, while Button, Todd, and Tobey ('07) found striations
(myonemes) in every trypanosome examined by them in Africa;
neither Moore and Breinl nor Minchin could find myonemes in Tryp.
gambiense, although the basal granules (which Moore and Breinl
laboriously call the "bead," in order to save their very strained nomen-
clature) are found. Eight myonemes, furthermore, were found by
Keysselitz ('06) in Trypanoplasma borreli. It is quite probable,
therefore, that the ectoplasm of a trypanosome cell is provided with
myonemes or elementary muscular fibers of kinetoplasm.
THE GENUS TRYPANOSOMA 255
B. The Trypanosome Nuclei.— The terms micronucleus and
macronucleus are frequently used to designate the trophonuclei and
kinetonuclei of these flagellates, but this use of the term micronucleus
is greatly to be deplored, since the kinetonucleus has absolutely no
analogy with the micronucleus of infusoria, and the binucleate con-
dition of the trypanosomes is to be explained upon other grounds than
that of the ciliates.
The nucleus of an ordinary trypanosome is constructed upon the
same plan as that of simpler flagellates, and consists of a spherical
body of chromatin with a more or less well-defined nuclear membrane,
and a central division centre similar to that originally described by
Keuten in euglena. The nucleus, therefore, belongs to the category
of centronuclei, as described by Boveri ('01). Many observers have
been careless in describing the chromatin in such nuclei under the
term "chromosomes," the custom originating with Schaudinn's
description of the structure of Tryp. noctuce. Cytologists have repeat-
edly pointed out the impossibility of getting accurate cytological
demonstrations from poorly fixed material, and the ordinary technique
recommended in connection with the Giemsa staining fluid gives
unreliable preparations. The nucleus in particular undergoes modi-
fications of a well-marked character; the chromatin here appears to
be a fluid substance which when dried, as in a smear, coagulates in
irregular masses without definite structure. Moore and Breinl have
made similar criticisms of the so-called chromosomes of various
authors, and in Tryp. gambiense, Tryp. leivisi, and other forms have
observed nuclei of the same type as those pictured in Fig. 102, p. 2(;0.
The descriptions of "chromosomes" in different accounts, therefore,
must be taken with reserve.
Nearly all of the subsequent observers have followed Schaudinn's
description of the happenings in Trypanosoma noctuce, and there is a
certain ground for the suspicion that the multiple and confusing
forms assumed by these nuclei, especially when the usual methods are
employed, are more easy to interpret along the lines of a path already
made than to be described as involution or degeneration types. Hence
we find in the literature all kinds of nuclei arranged in definite series as
illustrating "reducing divisions," or "karyogamy," or "partheno-
genesis," where it is more than likely that the structures thus inter-
preted are artefacts, or evidences of hyperplasy and degeneration.
The schematic figures and categorical descriptions of Schaudinn's
original contribution are still the most convincing of all such attempts
to describe the nuclear changes, and may well serve as a type,
although the terminology employed by this gifted and careful ob-
server, borrowed from the nomenclature of animal cytology, cannot
be employed in the same sense for these flagellates.
The nuclear structures of Trypanosoma noctuoe is shown in Fig.
256
THE PATHOGENIC FLAGELLATES
99, p. 247, of a so-called indifferent form. Here, after elimination
of waste material from the fertilized cell (A) the nucleus divides by
heteropolar mitosis to form a trophonucleus and a kinetonucleus. The
former consists of a central division centre (karyosome) and chromatin
which is arranged in eight groups; the latter, as described above,
divides to form the substance of the motile apparatus and the perma-
nent kinetonucleus, in which, again, Schaudinn finds eight chromatin
masses and a central division centre. The nucleus of the "female"
type of organism differs from that of the "indifferent" form in that a
large part of the "achromatic" portion of the nucleus is eliminated
before the first division of the copula. This eliminated part divides
FIG. 101
^3f&®
Trypanosoma noctuee. (After Schaudinn.) A, elimination of the "male" part of the
nuclear material; B, division of the so-called "male" part; f , heteropolar division of the
female nucleus and degeneration of the daughter nuclei of the "male" part; D, formation of
adult female cell.
three times, forming eight minute nuclear masses, which finally
degenerate and disappear (Fig. 101), while the nucleus now divides
by heteropolar mitosis, as in the previous case. The nucleus of the
"male," on the other hand, eliminates the larger part of the nuclear
material which ordinarily goes to form the nucleus (trophonucleus) of
the cell, and this degenerates, while the smaller denser nucleus result-
ing from the first division now divides three times to form the nuclei
of the eight microgametes and a fourth time to form the tropho-
nucleus and kinetonucleus of these gametes.
The nuclei are thus sexually differentiated, according to Schaudinn,
a statement which, if true, gives the first complete confirmation of
THE GENUS TRYPANOSOMA 257
the early hypothesis of Balfour and Minot that the nucleus of the
primordial egg or sperm cell contains both kinds of sex chromatin,
the opposite kind being eliminated by the reducing divisions of each
sex. It may be noted in this connection that while modern cytology
has brilliantly confirmed the essence of this theory, it is not at all in
the way supposed by the early speculators, nor at all in the way out-
lined by Schaudinn in this trypanosome (see Wilson, Stevens, and
others on sex chromosomes in insects).
The kinetonucleus varies greatly in size, from a mere granule, as in
Tryp. gambiense, to a large body equal to, or larger than, the nucleus
(as in Trypanoplasma borreli)', the great majority of forms present no
such structures as described by Schaudinn, the kinetonucleus usually
being homogeneous and dense in appearance; Robertson ('07), how-
ever, finds "chromatic" thickenings in Try p. raice which she interprets
as equivalent to the chromatin of Schaudinn's form.
The relative positions of kinetonucleus and nucleus are used by
many observers as of sufficient importance to justify specific distinc-
tions; this was considered of more importance formerly than it is
today; indeed, at the present time no conclusions as to taxonomy can
be drawn from such relations. Novy, Minchin, Robertson, and a
host of others have shown that in the same species the kinetonucleus
may be anterior, lateral, or posterior to the nucleus (Fig. 100, p. 249).
C. Form Changes of Trypanosomes. — The variations in the
relative position and sizes of the nuclei accompany the greatest variety
of form changes in the body as a whole and next to the ameboid
forms, which after all have a certain constancy in their form changes,
these trypanosomes are perhaps the most variable of protozoa. They
seem to be highly susceptible to the conditions surrounding them.
" I am convinced," says Minchin, " that the appearance, and even the
structure, of trypanosomes may be greatly affected by the condition of
their hosts" (1908, p. 178). If slight changes in the blood of verte-
brates can bring about such marked changes in structure of the para-
sites, it is obvious that the much greater change in external conditions,
when transferred from the vascular system, especially of mammals,
to the relatively cold environment of an insect's digestive tract, should
be the cause of even greater changes. The modifications brought
about by these several different conditions have been variously inter-
preted as sexual differences, as resting phases, degeneration phases,
and the like, while so-called latent bodies and encysted forms have
been found in some cases.
Size differences were first brought into prominence by Schaudinn
in connection with the rapid multiplication of Tryp. ziemanni of the
owl, where, he states, "as a result of the rapid multiplication the indif-
ferent spirochetes (trypanosomes) become remarkably small; indeed,
I have found forms which are so immeasurably fine that they can be
17
258 THE PATHOGENIC FLAGELLATES
recognized only when agglomerated or when in motion" (1904, p.
432). The majority of observers have confirmed this observation,
although in no form are the extremes so far apart as in this case.
Minchin ('08) finds the greatest variety of form changes in Tryp.
gambiense in the body of the tsetse fly, Glossina palpal is. Here, during
the first twenty-four hours, the trypanosomes multiply by division in
the fly's digestive tract, two distinct types being formed, one stout, the
other slender. During the next twenty-four hours the two types are
connected by all kinds of intermediate forms, which in the third day
become thinned out and presenting some degeneration forms, and
many trypanosomes of great length, both stout and slender; while
after the fourth day no organisms were found at all. Similarly Tryp.
grayi was found in the digestive tract of the same fly to manifest the
most "bewildering variety of forms and sizes," while in different flies
the run of organisms might be much larger than in others. Division,
also, is responsible for variation in size, Minchin finding that smaller
daughter trypanosomes are formed by unequal division of the parent
cell.
Following Schaudinn, many, indeed the majority of, observers have
attempted to distinguish these manifold form changes as male, female,
and indifferent types. While some of their descriptions are mani-
festly labored and far-fetched, others are supported by more or less con-
vincing evidence. In the type form Tryp. noctuce the chief differences
are found in the nuclei, where, as described above, the male and female
organisms are freed from female and male chromatin respectively
(Figs. 99 and 101 ). In addition to this difference, Schaudinn noted that
the male cells were hyaline and more free from granules of one kind
or another than the female, while the indifferent forms were dis-
tinguished from both of the other types by the complete nucleus
and by minor cytoplasmic differences. It must be confessed that,
despite the scientific acumen of this observer, one's credulity is greatly
stretched by these findings, and in view of the fact that so much of the
subsequent work has been interpreted in terms of these descriptions,
it is much to be regretted that Schaudinn's figures were wholly
schematic. Prowazek ('05) found only a slight difference between
the sexes in Tryp. lewisi while in the gut of the louse, the male
being smaller and more fragile than the female and much more
liable to degenerate, while the nucleus assumes an elongate band
form or rod form in the male. These might be identified as
degeneration forms were one inclined to be skeptical, especially as
fertilization stages were rarely seen; the "rod" form of nucleus, as
Doflein ('09) points out, may be interpreted as an abnormally devel-
oped flagellum.
Moore and Breinl ('07) question the advisability of designating
arbitrarily chosen extremes in a series of varying forms as male and
THE GENUS TRYPANOSOMA 259
female, while Minchin ('08) states, in connection with Tryp. gamblense,
that only the extremes remain after twenty-four hours in the diges-
tive tract of the fly, thus indicating that such extremes are physiologi-
cally adapted to resist unfavorable conditions, while the intermediate
forms are killed off. It is intimated that such resistance may be inter-
preted as indicating two physiological grades, which may be identified
as male and female. This conclusion, however, is weakened by the
fact that intermediate forms reappear during the second day. Dof-
lein's ('09) criticism that such size differences may represent young
and old individuals is certainly to be considered. Moore and Breinl
describe very remarkable forms of Tryp. yambiense, in which the
kinetonucleus grows out into a long rod reaching to the nucleus. Such
forms recall Prowazek's "male" of Tryp. lewisi, but the English
observers hold that it indicates the preparation for union of a part of
the rod with the nucleus, i. e., a type of autogamy.
While it is quite obvious that the last word has not yet been written
in regard to such trimorphism in trypanosomes, there is no doubt at all
of the form changes, and it is highly probable that some of them, at
least, are characteristic of different periods in the life history and that
some, at least, are gametes. Further than this, the evidence at the
present time does not warrant generalizations.
The encysted stages of trypanosomes are particularly interesting
as an important phase in the life history whereby the organisms are
able to withstand unfavorable conditions. The first observations
were made by Minchin ('07) in connection with Tryp. grai/i in the
posterior region of the gut of Glossina palpalis. The flagellum is
retracted and a slime cyst similar to that described by Prowazek in
Herpctomonas muacce domesticce secreted. The last trace of the flagel-
lum disappears and the nucleus fragments into chromidia, while the
kinetonucleus is no longer demonstrable. The cyst wall becomes
more definite and resistant, changing the while from an ellipsoidal to
a spherical form. Internal changes were not seen beyond evidences
of division observed in a few cases. It may be suggested here that
chromidia formation and disappearance of nuclei and subsequent
division of a nucleus in the cyst may indicate a method of autogamous
fertilization similar to that occurring in entameba.
The "latent bodies" described by Moore and Breinl ('07) are
entirely different from encysted forms such as Minchin describes,
and different from the encysted forms of Tryp. c/amlnense which they
themselves describe as being formed after the action of atoxyl in the
blood. These cysts are much larger than the latent bodies and similar
to ordinary cysts which free flagellates secrete under abnormal con-
ditions. These " latent bodies," which Moore and Breinl regard as the
same things seen by Rodet and Vallet, Plimmer and Bradford in
infections with Tryp. brucei, and by Lingard in the blood of cattle
260
THE PATHOGENIC FLAGELLATES
infected with Try p. indicwn, or Holmes in connection with Tryp.
cvansi, are regarded as normal stages in the life history of the
organism. From the meagre account of the English observers these
appear to be nothing more than the nucleus of the cell with a very
small layer of protoplasm about it; in rats they become stored up
in the spleen and bone marrow, and the authors believe that they
ultimately give rise to adult organisms in much the same way
that crithidia or herpetomonas is metamorphosed from the resting
stage into a flagellate. Without further evidence such phases may be
interpreted as special reactions to abnormal conditions rather than
stages in the ordinary life history.
FIG. 102
Trypanosoma gambiense; stages in longitudinal division. Original from a
preparation by F. W. Baeslack.
D. Reproduction. — Reproduction by division is easily observed
in all types of trypanosomes, and seems to follow a similar method
throughout, the details varying in some cases. As in herpetomonas,
it is inaugurated by the division of the kinetic elements of the cell, the
flagellum dividing first, according to some observers (e. g., T. gam-
biense, according to Minchin), the kinetonucleus dividing before the
nucleus, the latter dividing as does the centronucleus of free flagellates.
Abnormal division figures are frequently observed, due to the division
of nuclei and the formation of new flagella before the cell body splits.
As in spirochetes, the daughter cells in the last stage of division are
connected only at one end — in this case the anterior or kinetonucleus
THE GENUS TRYPANOSOMA 261
end — and, seen alone, such a stage might be wrongly interpreted as
transverse division (Fig. 102). Very often the cells divide without
becoming entirely separated, repeated divisions following one another
until rosettes are formed. A very remarkable process of multiple
division was described by Dutton, Todd, and Tobey ('07) in Tryp.
loricatum, a parasite of African toads and frogs; here the organism,
by repeated binary division, gave rise to more than forty cells, "all
apparently inside the outer covering of the original trypanosome"
(op. cit., p. 312). Such a process of multiplication is quite novel for
trypanosomes, and needs confirmation.
E. Agglomeration. — Rosettes due to incomplete division are
quite different from the aggregations of trypanosomes known as
agglomerations, which are due to abnormal conditions of the environ-
ment, or, as Laveran and Mesnil first observed, may be phenomena
due to decreasing vitality. It may be brought about in the blood by
mixing immune serum with the normal infected blood, by addition of
weak chemicals (e. g., acetic acid), by lowering the temperature, or by
conditions arising in artificial culture media, Novy and MacNeal
finding agglomerations of more than a thousand cells at times.
F. The Invertebrate Hosts and Life Cycle of Trypanosomes.—
At the present time nothing can be farther from settled than the
happenings within the bodies of invertebrate hosts of trypanosomes,
and much unfortunate controversy of an entirely unnecessary char-
acter has been filling the pages of medical and scientific journals.
Although mammalian trypanosomes were . first observed and
described by Lewis, in 1877, for Tryp. lewisi of trie rat and in 1880 for
Tryp. evansi, the cause of surra in horses, little importance was
attached to them as the causes of disease until Bruce, in 1894, demon-
strated the connection between the disease nagana of horses in Africa
of unknown etiology, and the tsetse fly diseases of horses. The history
of this discovery is best given in his own modest account, while at the
same time it reveals the modus operandi in establishing the connection
between invertebrate host and protozoan parasite. "In October,
1894," says Bruce, "when serving in Natal, South Africa, the governor
of that colony, the Hon. Sir Walter Hely-Hutchinson, G.C.M.G.,
asked me to go to Zululand to report on a disease which was causing a
severe loss among the native cattle. The native name of the disease
was nagana. At this time no suspicion that nagana and the tsetse fly
disease were identical was entertained. The writer at once proceeded
to Zululand, and after a month's travelling by ox wagon from Eshowe,
the capital of the country, arrived in the infected area. A small
laboratory having been set up and some of the affected cattle obtained
from the surrounding natives, examination by the ordinary bacterio-
logical methods was begun. The animals were emaciated, with staring
hair, some fever, and sometimes edema of the subcutaneous tissues of
202 THE PATHOGENIC FLAGELLATES
the neck. Examination of the blood and organs for bacteria by micro-
scopic and cultural methods produced no result. At this time it was
my custom, when starting on a study of a new disease, to make a care-
ful daily examination of the blood of the living animal, enumerating
the number of the red and white blood corpuscles and estimating the
percentage of the various varieties of leukocytes. After a few days of
this blood examination it was noted that there were sometimes to be
seen a peculiar stained body, having something of the appearance of
an artistic dolphin, lying among the red blood corpuscles. It must be
remembered that the trypanosomes are usually found in very small
numbers in cattle, so that it is only after a long search that a single
one can be found. It was thought at first that this small, peculiarly
shaped object was an accidental appearance due to the stain, but
thinking that if the body was a parasite, it might show motion, several
specimens of fresh blood were examined. A long search was rewarded
by finding a very active body wriggling and twisting about with great
energy and dashing in and out among the red. blood corpuscles. It
was the first time the writer had seen a trypanosome, and, as then
there was little or no literature on the subject of these parasites, it was
•difficult to know how to place it. It seemed it must be a filaria, but
having compared the description and drawing of the rat trypanosome
in Lewis' book with my parasite, it was concluded it was a trypano-
some. But there was no proof that the parasite was the cause of
nagana; it occurred only in small numbers in the blood of the cattle,
and the rat trypanosome lives as a harmless guest in healthy animals.
Therefore the blood of infected cattle was inoculated into horses and
dogs. The disease in the horse and dog is much more acute than in
the ox.
"In a few days the blood, especially of the dog, was found to be teem-
ing with thousands of trypanosomes. It therefore began to appear
probable that this parasite might be the cause of nagana. At that time
there was no suspicion that this disease among the native cattle, occur-
ring in kraals situated many miles from the 'fly country/ was the same
disease as that known to travellers as the tsetse-fly disease. The
work at this time was being done on the summit of a mountain called
Ubombo, some 2000 feet above the surrounding low country. The
low country to the east of the mountain was known to be infected with
the tsetse fly, and having often read, in Livingstone's and other books
of travel and hunting, about this disease, it was determined to take a
few animals into this 'fly country' and see what the disease was like.
Two young oxen, a horse, and several dogs were taken into the heart
of the 'fly country.' After being there a fortnight the animals were
brought back to the top of the mountain and examined in the usual
way — their temperature taken, their blood examined, and any symp-
toms that might occur noted. It was found that the blood of these
THE GENUS TRYPANOSOMA 263
animals affected with the tsetse-fly disease contained the same parasite
as that found in nagana. In this way, after many experiments and
many observations, it was forced upon me that the two diseases,
nagana and tsetse fly, were one and the same. It is a characteristic
of this species of tsetse fly, Glossina morsitans, that at rare intervals,
probably due to long-continued drought, it overspreads its usual
bounds to a distance sometimes fifty or sixty miles, and so sets up an
epidemic among the native cattle in a previously healthy district.
This was the case in 1894; the disease had overspread its natural
bounds and given rise to a widespreading epidemic among the cattle
to a distance of sixty miles.
"When it was once established that the two diseases were the
same, experiments were made to find out how the animals became
infected, whether the fly was the carrier or the mere concomitant of the
low-lying, unhealthy district, and, if a carrier, if it was the only carrier
of the disease from sick to healthy animals. Horses taken down into
V
the 'fly country,' and not allowed to feed or drink there, took the
disease. Bundles of grass and supplies of water, brought from the
most deadly parts of the 'fly country' to the top of Ubombo and there
used for fodder for healthy horses failed to convey the disease. Tsetse
flies caught in the low country and kept in cages on top of the
mountain, when fed on affected animals, were capable of giving rise
to the disease in healthy animals up to forty-eight hours after feeding.
Tsetse flies brought up from the low country and placed straightway
upon healthy animals were also found to give rise to the disease. The
flies were never found to retain the power of infection for more than
forty-eight hours after they had fed upon a sick animal, so that if wild
tsetse flies were brought up from the low country, kept without food
for three days, and then fed on a healthy dog, they never gave rise to
the disease. In this way it was proved that the tsetse fly, and it alone,
was the carrier of nagana. Then the question arose as to where the
tsetse flies obtained the trypanosomes. The flies lived among the wild
animals, such as buffaloes, koodoos, and other species of antelopes, and,
naturally, fed on them. It seemed that, in all probability, the reser-
voir of the disease was to be found in the wild animals. Therefore, all
the different species of wild animals obtainable were examined both
by the injection of their blood into healthy susceptible animals, and
also by direct microscopic examination of the blood itself. In this way
it was discovered that many of the wild animals harbored this try-
panosome in their blood. The parasites were never numerous, so that
it was only after a long search that they could be discovered by the
microscope alone. The wild animals did not seem to be affected by the
trypanosomes in any way; they showed no signs or symptoms of the
disease, and it, therefore, appeared probable that the trypanosomes
264
THE PATHOGENIC FLAGELLATES
lived in their blood as harmless guests, just as the trypanosome of the
rat lives in the blood of that animal."1
In a very similar way the cause of human trypanosomiasis, Tnj-
paiwsoma (jambiense, was shown to be transmitted by another tsetse fly,
Glossina palpalis (Fig. 103). Button, whose own life was the first to
be martyred in the cause of sleeping sickness, gave the name to this
trypanosome, which was first seen by Forde, in 1891, in the blood of
victims of gambia fever. Castellani ('03), later, found trypanosornes
in five cases of sleeping sickness in the cerebrospinal fluid, and in one
of these cases, also, in the blood. This organism was regarded by
FIG. 103
Glossina palpalis, Rob. X 3%.
Castellani as different from air others and named by him Tryp.
ugandense. Bruce, in the same year, confirmed these observations of
Castellani, and also those of Dutton and Todd on gambia fever, and
succeeded in demonstrating that the latter is only the first phase of
sleeping sickness, and that the trypanosome is conveyed to man by
only one agent, a species of tsetse fly.
Confirmatory observations followed rapidly, English, German,
French investigators risking their lives in scientific rivalry to get at the
life history of this protozoan pest and its insect carrier. Tulloch's
1 Bruce, Trypanosomiasis, Osier's Modern Medicine, pp. 462 to 464.
THE GENUS TRYPANOSOMA
265
life was a second English sacrifice to this end, and his own obser-
vations, together with those of Todd, Koch, Brumpt, Greig, Gray,
Minchin, Nabarro, and a host of others, have made Trypanosoma
gamhiense one of the best known of all mammalian trypanosornes.
In the meantime other students of the protozoa were showing the
connections between different species of vertebrate trypanosomes and
invertebrate transmitting forms, so that today not only biting flies, but
mosquitoes, lice, and leeches are known to carry trypanosomes from
one vertebrate host to another, while only one case of direct trans-
mission from animal to animal has been demonstrated. This is of
considerable interest, as showing the power of trypanosomes to pene-
trate membranes, the organism Trypanosoma equiperdum being trans-
FIG. 104
A tsetse fly (Glossina longipennis, Corti, from Somalilancl) in resting attitude, showinir
position of wings. (X3}.)
mitted by coitus, and thus giving rise to the disease dourine or mal
de coit. Koch and Doflein ('09) suggest that sleeping sickness may
be transmitted in the same way.
Very great importance attaches to the happenings within the body
of the blood-sucking host, and here the matter is still in the whirl of
controversy. Bruce states that in the hundreds of tsetse flies examined
by him he has never found different stages of the parasite in the diges-
tive tract and no indication whatsoever of migration into the body
cavity of the fly. He regards the fly as a mere passive carrier of the
protozoon, transmitting the disease during a limited period, by inocu-
lating the victim with trypanosomes adhering to the proboscis either
inside or out. In this he is supported by Koch, Moore and Breinl,
Novy, Roubaud, and a host of others, who note that the organisms
266 THE PATHOGENIC FLAGELLATES
disappear from the digestive tract of the fly within three or four days
after feeding. Others, on the other hand, notably Gray, Minchin,
Tulloch, have found abundant multiplicative forms in the anterior
part of the digestive tract, and encysted forms in the posterior part
(proctodeum). These observers hold, and many others on a priori
grounds alone support them, that important developmental stages of
Tryp. gambiense will yet be found outside of the human body. That
such an external life is obligatory for trypanosomes in general is
disproved by the fact of direct transmission in the case of Tryp.
equiperdum, where all of the developmental phases must take place
in the mammal.
A very strong argument in favor of the advocates of an external
cycle are the observations, by different investigators, of the life history
of trypanosomes infecting other than mammalian hosts. Keysselitz
('06), for example, found both multiplicative and propagative (terms
used in Doflein's sense) development of Trypanoplasma borreli in the
digestive tract of the leech Piscicola geometra; Prowazek ('05) found
similar phases of Tryp. lewisi in the gut of the louse Hematopinus
spinulosus; but these, and all of the subsequent observers, go back to
the classical work of Schaudinn ('04) upon Tryp. noctuce of the owl
for their models, a work fully confirmed by the brothers, Et. and Ed.
Sergent ('05).
The mosquitoes used by Schaudinn and by the Sergents were raised
from eggs and larvre, so that previous infection was thereby excluded,
the chances of their being infected by inheritance, which Novy, Mac-
Neal, and Torrey ('07) claim in criticism, being so remote that the
results are by no means vitiated by this possibility.1
Mosquitoes which are allowed to feed upon owls (Glaucidium
noctuce) infected with Tryp. noctuos take male and female trypano-
somes into the gut with the blood. Here fertilization takes place in the
manner described by MacCallum ('99), in connection with the para-
site Hemoproteus (H alter idium) of the American crow. The so-called
halteridium, therefore, of the owl is only a stage in the life history of a
trypanosome, the microgametes being formed in response, apparently,
to the changed conditions of temperature and chemical composition
in the new environment. The fertilized gamete, called ookinete, or
copula, by Schaudinn, develops into a trypanosome which may be
male, female, or indifferent, according to the changes undergone by
1 Schaudinn (loc. cit., p. 390) states: Die Zucht der Miicken, die Art der Infection, die
Blutuntersuchungen usw. erfolgte in derselben Weise wie bei meinen Malariastudien. For the
latter work he made use of carefully watched mosquitoes bred from the egg. Knowing from
personal experience Schaudinn's keen zoological sense, quickness of vision, and remarkable
talent in handling protozoa of various kinds, I personally do not share in the skepticism
which has grown up in regard to his observations, and, although not always agreeing with
his interpretations, I find much more reason for accepting his conclusions than those of his
many critics which are based mainly on a priori arguments or upon negative results with
artificial culture methods, which, at best, are unnatural media for protozoa.
THE GENUS TRYPANOSOMA 267
the nucleus and cytoplasm (see above p. 256). The males and females
appear to lose the power of division, but, like indifferent forms, have
the power of penetrating epithelial cells of the gut and making their
way to various parts of the insect's body, including even the ovaries.
Under conditions of extreme cold and starvation of the insect, all
stages of the trypanosome die save these females, which appear to have
a remarkable power of resistance, and Schaudinn suggests that they
may be retained in the ovaries of the hibernating mosquitoes until
spring, when they may develop and infect the new generation. It is
in these forms that parthenogenesis occurs (see p. 168). The power
of changing, as crithidia does, from a free, flagellated, into a quiescent
parasite, not only in the gut of the mosquito, but also in the blood of
the bird, is a feature known to occur in no other trypanosome. Accord-
ing to Schaudinn and Sergent the intracellular parasite is the typical
form of the organism during the day, while it leaves the blood cell,
changes into a typical trypanosome, and grows during the night,
the change being induced, as Schaudinn believed, by the lowered
temperature of the bird at night.
Although "latent bodies," encysted forms, and other non-flagellated
stages of trypanosomes have been observed by Moore and Breinl,
Minchin, Robertson, Laveran and Mesnil, and others, this is the only
case of trypanosomes known where, as in Herpetomonas donovani,
the flagellated organism becomes an intracellular parasite. The
phenomenon must be interpreted zoologically, as an indication of the
more evolved phylogenetic state of Tryp. noctuoe and leading to the
group hemosporidia of permanently intracellular blood parasites.
In our opinion these facts do not justify the use of a different generic
name for Trypanosoma noctuce as Liihe proposes, but are only further
evidence of the tendency to polymorphism exhibited by the group as a
whole.
The Effects of Trypanosomes on Vertebrate Hosts. — The
great majority of trypanosomes, especially the parasites of cold-
blooded forms, have no evident effect upon their hosts. But among
warm-blooded animals they rank with the most deadly parasites
known. The horse, mule, and dog always succumb to infections of
Tryp. evansi, the cause of surra, while cattle, camels, etc., are less
affected (Liihe). The organism of nagana, Tryp. brucei, is fatal to
horses, dogs, and cattle, and that of mal de caderas (hip sickness) is
fatal to horses, rats, and mice. On the other hand, the rat try-
panosome, Tryp. lewisi, and the cause of galziekte (gall-sickness) in
cattle, Tryp. theileri, are relatively harmless. Immunity, in some
cases, is set up by one invasion of the parasites, wild animals, as
Bruce has shown, being immune to Tryp. brucei, which quickly kills
imported animals. Laveran and Mesnil ('02) showed that immunity
was conferred on rats by one infection with Tryp. lewisi.
Human trypanosomiasis is particularly malignant, having a fatality
_>liS THE PATHOGENIC FLAGELLATES
of 100 per cent. According to Bruce ('05) the disease is rapidly spread-
ing, now that Africa is being opened up. In regard to this he says:
'This sleeping sickness, which occurs on the west coast of Africa,
particularly in the basin of the Congo, has within the last few years
spread eastward into Uganda, has already swept off some hundreds
of thousands of victims, is spreading down the Nile, has spread all
around the shores of Lake Victoria, and is still spreading southward
around lakes Albert and Albert Edward." (Science, 1905, vol. xxii,
p. 298.)
Just how the ill effects are produced is not known. There is evi-
dence, supported by the facts of acquired immunity in other forms,
that a toxin is produced causing more or less chronic inflammation,
or rapid destruction of erythrocytes. In man it produces a gradually
increasing lethargy, with mental and physical degeneration, rapid pulse,
increasing emaciation, all finally resulting in marked drowsiness, which
passes into a state of coma ending with death (Fig. 105). Mott ('99)
FIG. 105
Sleeping sickness; shortly before death.
explained the lethargy as due to the action of some toxin, probably
of microorganism derivation, in the cerebrospinal fluid and acting
on the neurons. Bruce regards the disease as essentially "a disease of
the lymphatic system, and the irritation and proliferation of the lym-
phocytes is probably due to a toxin secreted by, or contained in, the
bodies of the trypanosomes. The characteristic symptoms of the
disease are, no doubt, due to the accumulations of these lymphocytes
in the perivascular spaces of the brain, compressing the arteries and
so interfering \vith the normal nutrition of the brain cells." (Bruce,
1907, p. 4S3.)
It is still too early to speak of a cure for human trypanosomiasis,
and it is outside the limits of this work to enter into a discussion of the
various attempts that have been made to cure. The preliminary
success with atoxyl, alone or in combination with other salts, gives
reason to expect an ultimate control over the disease.
CHAPTER IX.
THE PATHOGENIC HEMOSPORIDIA.
MANY recent students of the protozoa (e. g., Hartmann, Liihe) are
inclined to place the group of parasites which Danilewsky ('85) named
hemosporidia with the mastigophora rather than with the sporozoa.
It is possible that future research will justify this step, and that the
large, relatively immobile blood parasites, like lankesterella of the
frog, hemogregarina of turtles and tortoises, karyolysis of lizards,
hemoproteus of birds, and plasmodium of man, are, like the Leish-
man-Donovan bodies, only passing phases of some flagellated proto-
zoan, but at the present time the evidence is not weighty enough to
warrant such a step even as a working hypothesis. The weakness of
the evidence, apparent as soon as reviewed, may be briefly summarized
as follows: Trypanosoma noctuce has an intracorpuscular cytozoic
phase; Herpetomonas donovani has an intracorpuscular cytozoic
phase; babesia (Piroplasma) a genus whose several species infect
erythrocytes of various mammals, at certain periods possesses a
blepharoplast (?) and gives rise to so-called "flagella;" merozoites of
Plasmodium vivux and of hemoproteus are said to show at times
rudimentary flagella (Hartmann).
Evidence is constantly accumulating, on the other hand, to show
that the full life history of hemosporidia may be completed without
any sign of a flagellated stage. Such is the case, for example, in
Hintze's account of the life history of Lankesterella ronarum, while the
incomplete accounts in cases of other hemosporidia give no ground
for assuming the occurrence of such a stage. The carefully studied
life history of a new genus and species of hemogregarinidse, Hepato-
zoon perniciosum, Miller, of the rat, gives the best evidence of the
independent position in classification of these forms. This organism,
discovered by W. W. Miller,1 somewhat resembles Leukocytozoun
canis, Bentley, of Indian dogs. In the majority of cases it causes
death of the infected rat, the disease being normally transmitted by
mites of the species Lelaps echidniiuis. The sporocysts are taken into
the digestive tract of the rat together with its mite host, and the sporo-
zoites (16/.« long) are liberated by the action of the digestive juices
(Fig. 106). The young forms penetrate the intestinal walls and enter
lThe premature death of this giftei young observer, his life a sacrifice to duty, was a sad
blow to the cause of protozoology in America.
270 THE PATHOGENIC HEMOSPORIDIA
the blood stream, which conveys them to the liver (Fig. 106, a to (/).
Here they enter the liver cells and undergo schizogony, about 10
merozoites being formed. These may enter other liver cells or pass
into the blood stream, where they are taken up by large mononuclear
leukocytes in which they remain protected by a distinct membrane or
cyst (Fig. 106, /'). If such infected blood is taken by a mite, the encysted
parasite is set free in the insect's digestive tract. Two similar ones con-
jugate in the lumen of the gut (Fig. 108, g to A*) and a motile ookinete
penetrates the stomach wall and gets into the body cavity. In the body
tissues the fertilized cell rapidly increases in size, the fertilization
nucleus divides a number of times, and the daughter nuclei migrate to
the periphery of the cell, where they lie in minute papillae on the sur-
face. The papillae enlarge and grow into sporoblasts, each of which
ultimately gives rise to about sixteen sporozoites (Fig. 106, o, p).
Mature parent cysts contain from 50 to 100 of such sporocysts.
When such an infected mite is swallowed by a rat the sporozoites are
liberated and the cycle completed.
Trypanosoma and Leishman-Donovan bodies (herpetomonas
donovani) are acknowledged flagellates, but babesia and a fortiori
plasmodium, and other hemosporidia, stand very far removed from
such more primitive forms, and although there is good reason to believe
that hemosporidia and, through them, coccidiidia have been derived
from mastigophora, to classify them as such would be unwarranted.
The so-called "flagella" of babesia have little in common with this
characteristic motile organ of the flagellates, and Doflein's, Nuttall
and Graham-Smith's, and Kinoshita's view that they may be micro-
gametes, although not demonstrated in any case, seems much more
plausible and will remain so until the process of fertilization is fully
known. The method of microgamete formation in plasmodium gives
rise to reproductive bodies which are strikingly similar to the so-called
flagella of Babesia canis, as described by Bowhill and Le Doux ('04),
Nuttall and Graham-Smith ('04- '07), and especially by Breinl and
Hinclle ('08), who find two "flagella" appearing successively. The
long history of the "polymitus" form of plasmodium should be a
warning against premature conclusions regarding these structures.
The process of sporulation in plasmodium and in Babesia cants,
according to Christophers ('04), in the bodies of the invertebrate hosts
is entirely different from reproduction in pathogenic flagellates, while
save for the absence of spore cases, it conforms exactly with the sporo-
zoan type. For these reasons, therefore, I believe it premature to
separate the hemosporidia from sporozoa, but recognize the phylo-
genetic possibilities indicated by such a series as herpetomonas,
crithidia, trypanosoma, babesia, hemoproteus, and plasmodium.
A. The Genus Babesia. — Smith and Kilborne ('93) found
peculiar minute parasites in the red blood corpuscles of cattle sick
THE PATHOGENIC HEMOSPORIDIA
271
Hepatozoon perniciosum, Miller, a hemosporidian parasite of the rat. (After Miller.)
a to d, development of the schizont in the liver cells of the rat; e, free parasites in the blood;
f, encysted parasites in lymphocytes; g to k, stages in conjugation of isogametes; I, m, n,
growth of the ookinet into sporont; o, sporocyst derived from the ookinet, with sporoblast
buds covering the surface; p, section of same; q, older sporoblast with sporozoites; r, a
single sporozoite. Stages g to r are formed in the tissues of the intermediate host, a mite,
Lelaps echidninus.
272
THE PATHOGENIC HEMOSPORIDIA
with "Texas fever." These were so often found in pairs that the
specific name biaeminum was given to them, while the new genus was
named pyrosoma. The latter name, however, having been long
used for a genus of tunicates, was changed to piroplasma by Patton
('95), and is still widely used. Starcovici, however, in 1893, gave the
name babesia to a blood parasite of European cattle which Babes
first described in 1888 under the name of Hematococcus bovis. This
organism appears to be the same as that found by Smith and Kilborne,
and if proved so by the full life history the organism of Texas fever
must have the specific name bovis, while, since hematococcus is the
generic name of a phytoflagellate, Starcovici's name babesia must
supplant Patton's piroplasma.
FIG. 107
/
.
/ . -v\ 1 >.
Stages in the development of Babesia canis. (After Kinoshita.) A, round discoid parasite
in a blood corpuscle; B, ameboid form with long processes; C, a pair of " mature gametes";
D, a mature "female" gamete; E, a mature "male" gamete; F, a budding form in blood
corpuscle; G, a group of sixteen young "gametes."
Subsequent observers have found babesia in many different animals.
R. Koch ('03) was sent by the German Government to investigate
a cattle disease which he called East Coast fever, in German East
Africa, and the organism causing it was named (piroplasma) Babesia
parvum by Theiler, in 1904. Babes ('92) discovered a blood parasite
in Roumanian sheep which he named Babesia ovis; Piana and Galli
Valeric ('95) discovered a similar parasite in the blood of dogs, naming
it (piroplasma) Babesia canis; Gugliemi ('99) found a blood parasite
in horses, Laveran ('01) naming it (piroplasma) Babesia equi; Fan-
tham ('05) discovered one in the blood of rats and called it (piro-
plasma) Babesia muris. Similar parasites have been found in monkeys
THE PATHOGENIC HEMOSPORIDIA 273
(Ross, 1905), in goats, horses, and asses (Ziemann), and in man
(Wilson and Chowning, 1901 ; Anderson, 1903).
In all cases the medium of transmission, where known, is some
species of tick, and with their discovery of this important function of
tracheates, Smith and Kilborne ('93) opened up a new era in the his-
tory of preventive medicine, a discovery followed by the brilliant work
of Bruce with trypanosomes and flies; of Ross and Grassi with malaria
organisms and mosquitoes; and of a host of other investigators upon
blood parasites in all kinds of animals.
Structural Characteristics. — Unlike Herpetomonas donovani an endo-
thelial parasite, or unlike the serum-dwelling forms of flagellates gen-
erally, the various species of babesia are intracorpuscular parasites,
although at periods they may become free in the serum. The general
form is spherical or pear-like (whence the names piroplasma and piro-
plasmosis), the size varying from 0.5/* (Smith and Kilborne for B. bovis)
to 5 fi (occasionally in B. canis, according to Nuttall and Graham-
Smith). As a rule, they are single in the blood corpuscles in peripheral
blood (50 to 76 per cent., according to Graham-Smith, in dogs with
B. canis), although double infection, arising usually by division of the
parasite, occurs in from 20 to 30 per cent. Such double ones were
regarded as characteristic by Smith and Kilborne, who suggested the
name "bigemina" for the organism of Texas fever (Babesia bovis).
The parasite of dogs, Babesia canis, has been more thoroughly
studied than any other form, and furnishes a good object for general
description. It has been monographed by Nuttall and Graham-
Smith ('05-'07), by Kinoshita ('07), by Bowhill and Le Doux ('04),
by Christophers ('07), and by Breinl and Hindle ('08), so that,
although the various observers are not always in agreement, nor
the life history in any case complete, there is a good basis of facts
for others to work on.
According to all observers, the living parasite is very active, thro wing-
out processes of pseudopodial nature at various points of the periphery,
and with such vigor " as sometimes to move the corpuscle in which the
parasite is situated" (Christophers). Sometimes these protoplasmic
processes are drawn out into long filaments resembling flagella (Fig.
107), while crescents, ring forms, triangles, etc., are forms assumed at
one time or another, the greatest activity being shown during the
febrile state (Nocard and Motas).
The nucleus of the cell, like that of plasmodium, is of indefinite
shape, consisting of chromatin granules arranged in rod, ring, or semi-
circular form, the size and form of the aggregate giving an indication
of the developmental period (Kinoshita). The nucleus is usually
excentric in position, becoming flattened at times against the periphery
of the cell, but in free forms it usually lies in the centre of the para-
site (Christophers).
" 18
274
THE PATHOGENIC HEMOSPOR1DIA
In addition to the nucleus there appears to be a second brightly
staining structure in the cell, which Schaudinn ('04) first drew atten-
tion to from blood smears made by Kossel and Weber from cattle
with Texas fever, and regarded as a blepharoplast by Liihe, Nuttall
and Graham-Smith, Christophers, and others who have worked with
these forms. Nuttall and Graham-Smith, in addition, described a
third chromatin structure as a reticulate and faintly staining mass of
chromatin lying close to the nucleus, but Christophers and Kinoshita
give evidence to show that this is but a part of the nucleus (Fig. 108).
FIG. 108
D
B
C
Babesia (Piroplasma) canis. (After Christophers.) Different stages in the erythrocyte
culture media, and, /, in embryonic salivary cell of tick Rhipicephalus sanguineus.
A number of investigators have attempted to cultivate babesia on
artificial culture media, a limited success only being obtained, the chief
result being merely the prolongation of life of the parasites in the
infected blood kept under proper conditions. In this way Chris-
tophers and others obtained various morphological changes in the
organisms, but no developmental processes. Kleine ('06) and Miya-
jima ('07), on the other hand, claim to have produced many develop-
mental stages in vitro, the former with Babesia canis in young dog's
THE PATHOGENIC HEMOSPORIDIA 275
blood, the latter with B. parvum in blood bouillon. In each of these
experimental cultures the forms assumed were highly different from
those in the blood. Kleine noted long protoplasmic filaments similar
to those seen by Koch ('06) in developmental stages in the tick, while
Miyajima gives descriptions and photographs of crithidia-like flagel-
lates, "five times the diameter of an erythrocyte" in length, which he
found in cultures and subcultures of Babesia parvum. Schaudinn
('04) apparently found similar flagellated forms in smears of fresh
blood from cattle infected with Texas fever. The significance of these
flagellates, which, according to Miyajima, reproduce by longitudinal
division, cannot be interpreted until further observations and con-
firmations are made.
The parasites reproduce by division while in the erythrocytes, and
thus form the typical twin forms characteristic of babesia, or larger
groups of from four to eight cells. Kinoshita describes an irregular
division or budding process which he regards as equivalent to schizogony
and merozoite formation in plasmodium (Fig. 107, F). Christophers,
however, does not confirm these findings, but describes the nucleus as
dividing by a modified mitosis (Fig. 108, D), or in some cases the blepha-
roplasts divide and the chromatin flows about the daughter halves,
which then push out from the periphery of the cell as buds. The buds
thus formed are not pinched off, as Kinoshita describes, but the pro-
toplasm of the cell flows into them in equal parts and the cell divides
by fission. In some cases further division of the daughter cells begins
before complete separation. The relative infrequency of multiple
forms in erythrocytes1 is an argument against Kinoshita's view that
this represents schizogony.
B. Transmission by Ticks and the Life Cycle of Babesia.-
Since Smith and Kilborne's epoch-making discovery of the tick as the
sole agent in the transmission of babesia, observations have accumu-
lated in regard to intermediate hosts and developmental changes of
the parasites in them, but, notwithstanding the number of observations
made, the life history of no form is yet known.
The mechanism of transmission by ticks is often very complicated ;
according to Smith and Kilborne and Curtice, the insect becomes sex-
ually mature at its last moult while hanging to the skin of the ox. In
this condition the females are fertilized, gorge themselves with infected
blood, and drop to the ground, where they lay an enormous number of
eggs (up to 2000). Each egg case is supplied with a small quantity
of ox blood, which serves as food for the larva. The latter, very much
undeveloped, crawls upon a blade of grass, and if it manages to attach
itself to the hair of another ox it will live; if not, it dies of starvation.
1 Erythrocytes with four parasites number from 2 to 5 per cent, of all infected corpuscles;
with eight, less than 0.05 per cent., and with sixteen, from 0.004 to 0.01 per cent., according
to Graham-Smith and Christophers (1907).
276 THE PATHOGENIC HEMOSPORIDIA
The larva changes into the adult form on the ox and transmits the
disease with its first feeding.
Lounsbury ('04), after three years of experimentation and obser-
vation in South Africa, proved that Babesia canis of the dog is con-
veyed by the tick Hemophysalis leachi, and not, as in Texas fever, by
the larva from infected ticks, but only by adult ticks reared from the
eggs of infected ticks. Later, Christophers ('05-'07) demonstrated
that another tick, Rhipicephalus sanguineus, Latr., is also capable of
transmitting the disease, and he believes this to be the primary agent
in transmitting European dog piroplasmosis. According to Chris-
tophers, the larvae or the nymphs, as well as eggs, may become infected
directly from the dog, and so may carry the disease into the later
developmental stages of the insect. The latter means of transmission
seems to be the only one in the case of East Coast fever, where, accord-
ing to Lounsbury ('04) and Theiler('Oo), the parasite (Babesia parvuni)
can be conveyed only by the larva which becomes infected, the infec-
tion being carried to and transmitted by the nymph, while infected
nymphs convey the infection to adults. The variations in regard to
the mechanism of transmission, especially the time factor, indicate that
obligatory changes in the life history take place in the insect's body.
What these changes are must be very difficult to ascertain, because of
the minute size of the parasite. The first observations to this end were
made by Koch ('05) upon the organism of East Coast fever in the
digestive tracts of different ticks (Rhipicephalus australis, B. evertsi,
and Hcmaphysalis egyptium). Here they become stellate in form
and often appear in couples, a circumstance leading Koch to surmise
some type of conjugation. Globular and peculiar club-shaped forms
were also observed, but their significance was not made out (Fig.
108, E).
Evidence is accumulating to show that, as in the case of Plas-
modium malarias, a sexual cycle takes place in the tick, and it is not
oversanguine to state that the various conflicting observations on
"flagella" and other structures formed by the parasite at different
stages will shortly be straightened out in a consistent life history.
First, as to the so-called "flagella." Leaving out of account Miya-
jima's unconfirmed observations on a crithidia-like stage of Babesia
parvum, there are repeated references to flagella formation, especially
in the case of the dog parasite Babesia canis. Here the descriptions
by Bowhill and Le Doux ('04), Nuttall and Graham-Smith ('06),
Kinoshita ('07), and Breinl and Hindle ('08) are in agreement with
the observations of Lignieres ('03) on Babesia parvum, and with
Fantham ('05) on Babesia muris. According to Kinoshita, the flagellum
which he, with Doflein and many others, interprets as a microgamete
invariably takes its origin from the blepharoplast (Fig. 107, C, E). It
is not smooth and uniform, like a flagellum, but possesses granular
THE PATHOGENIC HEMOSPORIDIA 277
thickenings. He did not find more than one of these processes from
the same cell, but Breinl and Hindle ('OS) describe typical flagella,
which appear to have no definite or constant place in reference to one
another or with the cell. The latter observers, while stating that these
"flagella" are formed only during a very transient phase in the life
history, do not offer any interpretation in regard to them. Christo-
phers ('07) failed to find flagellated forms either in vivo or in vitro.
Second, as to the so-called "club-shaped bodies" first observed by
Xuttall and Graham-Smith ('03) and recently followed out by Chris-
tophers in Babesia canis in the tick Rhipicephalus sanguineus. These
characteristic bodies have been found only in the insect's body where
they give rise by direct metamorphosis to what Christophers does not
hesitate to call "zygotes" or fertilized cells, although nothing in the
nature of fertilization and nothing resembling gametes were described
by him. Two varieties of this club-shaped body are described, one
being "rigid, thorn-like," and relatively inactive; the other more
"leech-like" and active. Curious disks, with or without short spines,
and with the appearance of boring organs, are present at one end.
Christophers states that these bodies may reproduce by longitudinal
division, the daughter cells remaining attached so as to give the
appearance of conjugation. They are found not only in the gut of
infected ticks, but also in oviducts, ovaries, and ova of the adult,
while in nymphs they may be spread throughout the tissues of the
body. The "zygotes" formed by metamorphosis of these club-shaped
bodies are intracellular parasites of oval or spherical form, and may
grow to the size of 25 /«. The chromatin becomes diffused throughout
the cell prior to the formation of reproductive centres which Christo-
phers regards as sporoblasts, and the zygote ultimately gives rise to
" sporozoites" similar to the intracorpuscular forms in dog's blood.
Nuttall and Graham-Smith interpreted these club-shaped bodies
as gametocytes, a view confirmed by Christophers, whose account
certainly suggests a sexual cycle in the tick. If this account is con-
firmed, the life history of Buhrx'nt en nix is very similar to that of plas-
modium. The rarity of "flagellated" stages and their occurrence
only at late stages of infection certainly point toward Doflein's original
view that the "flagella" are microgametes, a view which the majority
of subsequent investigators have accepted. Doflein and, later, Kino-
shita maintained that there is a cvclical difference between the ame-
«/
boid forms and the pyriform bodies, the former representing the
schizogonous cycle, the latter the sexual. The prevalence of the
piriform bodies at the end of the disease in infected animals, and the
formation of "flagella" from them, lends support to this hypothesis.
Babesia in man gives rise to an acute disease variously designated
as "blue fever," "black fever," "tick fever," "spotted fever," "piro-
plasmosis hominis," and the like. It appears to be local in distribu-
278 THE PATHOGENIC HEMOSPOR1DIA
tion, occurring during the spring and early summer in the high valleys
in the mountains of Montana and Idaho. The disease is conveyed
V
to man by the bite of ticks (Dermacentor reticulatus occidentalis), and
may be transmitted by them to rabbits, guinea-pigs, and monkeys as
well (King, 1906; Ricketts, 1906), while the experimental animals
show a high degree of immunity after one attack of the disease.
Unfortunately, authorities do not agree as to the cause of the disease.
The transmission and general course of the disease, enlargement of
the spleen, immunity, etc., are not against the facts of piroplasmosis,
and this was the view taken by Wilson and Chowning ('02), who dis-
covered minute bodies in the erythrocytes of infected blood, both
fresh and stained. They named the organism Pyroplasma (Piro-
plasma) Babesia hominis, and were the first to suggest that ticks were
the agents of transmission, while the gopher (Spermophilus colum-
bianus) was regarded as the natural host or reservoir of the parasite.
Anderson ('03) confirmed the observations of Wilson and Chowning,
and noted with them the characteristic ameboid movements of the
parasites within the erythrocytes, and the frequent occurrence of twins
so characteristic of babesia. Their observations, descriptions, and
figures were not convincing, however, and others, notably Stiles ('05),
Ricketts ('06), and King ('06), failed completely to find the bodies
either in fresh or postmortem blood. Boggs ('07) states that some of
Wilson's and Chowning's descriptions and figures resemble blood
platelets, while others appear like the "navicular body of Arnold,"
and like endothelial degenerations of various kinds.
None of Wilson and Chowning's critics have been able to demon-
strate any other disease-causing organism, either by bacteriological,
pathological, or cytological methods, and their negations or compari-
sons with previously known bodies, or with structures from that
unlimited field of ill-defined possibilities, degeneration forms, cannot
offset Wilson and Chowning's positive findings and the collateral
evidence, and their "organism" must receive the benefit of the doubt
until more definite observations on the cause of Rocky Mountain
spotted fever are made. It is certainly interesting, in this connection,
that Gotschlich ('03) and other investigators have noted the presence
of protozoa in the blood of victims of Egyptian typhus fever, the
former describing an " apiosoma " (babesia) in the erythrocytes.
Darling ('08) has recently described similar structures, under the
name Histoplasma capsulatum, in the blood of natives of tropical
America, and in endothelial cells lining blood and lymph vessels,
spleen, liver, lungs, and bone-marrow. The symptoms are spleno-
megaly, emaciation, and irregular remittent temperature. The organ-
isms are characterized by irregular masses of chromatin and an occa-
sional small deeply staining dot which may be a blepharoplast. If
the author's surmise is correct, that the organism has a flagellated
THE PATHOGENIC HEMOSPORIDIA 279
phase, his evidence for which is scarcely convincing, then it should be
classed with the organism of kala azar (Herpetomonas donovani)
rather than with babesia.
C. The Organisms of Malaria.— As late as 1896 the cause of
malaria and of its mode of transmission were equally little known,
while the idea of bad air, from which malaria gets its name, has a
long traditional history reaching back to the time of Morton, in 1692
(Craig). The irregularity of infection, the curious sporadic nature of
new cases, and the general history of the disease in damp and swampy
localities, made malaria, in its several forms, a most uncertain and
puzzling disease, the actual cause of which was entirely unknown
until 1881, when a French military doctor in Algiers, Dr. Laveran,
discovered a new and curious organism in the blood of malaria victims,
which he characterized at once and without any misgivings as the cause
V f~J O
of the disease. At that time the blood-infesting sporozoa were very
little known, Lankester, indeed, having discovered, ten years before,
in 1871, a sporozoon in the blood of frogs and a form which he named
in 1882, calling it Drepanidium (Lankesterella) ranarum. Laveran
did not recognize the possible relationship between the blood parasites
of the frog and man, parasites which, in 1885, Danilewsky grouped
together under the general name of hematozoa, which finally took the
form of the name hemosporidia, but regarded it as a plant organism
belonging to the genus oscillaria, and he named it OsciUaria malarias.
The curious interpretation of the organism as a vegetable possibly
owed its origin to the fact that the bacteria were being vigorously
studied at this period, for we find not only Laveran, but Metchni-
koff and Marchiafava and Celli, likewise giving to it a plant name.
The latter, in 1885, from its supposed resemblance to some of the
plasmodia-forming fungi, gave the malaria organisms the name of
Plasmodium malar ice, while the former, two years later, named them
hematophyllum. Laveran's name being untenable, on the grounds
of mistaken genus, the next name suggested in chronological order
had to be accepted in conformity with the rules of zoological nomen-
clature, and thus it happens that a name which should be used only
to designate a condition assumed by certain kinds of organisms (fungi
and mycetozoa) has become a generic name.
Laveran's discovery did not attract much attention; indeed, the
new organism as the cause of the disease was scarcely accepted by
pathologists, and it was not until after 1896 that the real nature of the
disease was recognized. Laveran ('91) in France, and Manson ('94)
in England, quite independently suggested that the organism is trans-
mitted from man to man by some blood-sucking insect, suggestions
which were brilliantly proved, from 1897 to 1899, by Major Ross, an
English army surgeon in the India service, and by Prof. Grassi, in
1899, who showed that mosquitoes belonging to the genera culex
280
THE PATHOGENIC HEMOSPORIDIA
(for bird malaria) and anopheles (for human malaria) are alone capable
of transmitting the disease from host to host. Little by little new facts
and discoveries were added, until by 1901 malaria was as thoroughly
understood as perhaps any other germ disease, Grassi, in Italy, working
out the complete life history of the pernicious type, and Schaudinn,
in 1901, the life history of the parasite causing the tertian form of the
disease; the latter adding the last link in the chain of evidence by
watching the penetration of the sporozoite fresh from a mosquito's
FIG. 109
Temperature variations in tertian malarial fever.
FIG. 110
Temperature variations in quartan malarial fever.
proboscis in his own red blood corpuscles. Malaria was thus the first
of the human diseases in which it was proved that a protozoon is the
direct cause.
Authorities differ as to the number of kinds of these protozoan para-
sites responsible for malaria. On the clinical side, also, there seems
to be some difficulty in the classification of the fevers due to the dif-
ferent kinds of parasites. Grassi and Laveran have reduced the large
number of species that have been described to three, and they believe,
THE PATHOGENIC HEMOSPORIDIA
281
also, that the cause of the pernicious type belongs to a different genus
from the others. There seems to be little justification for this increase
in number of genera, and I am inclined to follow Schaudinn, Craig,
and others in grouping all of the malarial parasites under the one
generic name of plasmodium. Associated with these different forms
of the organism there are three well-marked types of malaria, while
some observers, notably Craig and the majority of the Italian authori-
FIG. m
Temperature variations in tertian estivo-autumnal fever.
FIG. 112
Temperature variations in quotidian estivo-autumnal fever.
ties, distinguish four such types. The essential features by which they
are distinguished are the differences in the rate of development as
measured by the time between successive pyrexial attacks. Tertian
fever, caused by Plasmodium vivax, is characterized by an attack every
forty-eight hours ; quartan fever, by an attack every seventy-two hours ;
estivo-autumnal or pernicious fever, by daily or more or less constant
fever. The significance of these attacks, first made out by Golgi in
1SS6, is that they coincide and are caused, therefore, by the sporulation
282 THE PATHOGENIC HEMOSPORIDIA
(schizogony) of the parasites in the blood. Coming from the same
original brood, the parasites in the blood all sporulate at the same
time; this results in a constantly increasing number of reproductive
bodies being liberated at stated intervals. At first the young forms
are too few to cause any serious trouble, and there is no reaction on the
part of the host. This is the period of incubation (ten to twelve days)
of the disease, but with the increase in numbers of merozoites there is
a continuous army of invaders, increasing in geometrical progression
and entering the blood corpuscles until finally the numbers are incredi-
bly large. With each invasion occurring every day or every three days
or every four days, according to the nature of the parasite, there is a
marked anemia and poisoning, which tend to produce cachexia and
sometimes death. Fever coincides with the liberation of new swarms
of merozoites, as shown in the accompanying charts or fever curves
(Figs. 109 to 1 12) . At the time of merozoite formation waste matters that
have accrued as products of the parasite's metabolism and kept stored
up in the body of the parasite are liberated and help in the general
intoxication of the victim. These are modified products of hemoglobin
digestion on the part of the parasite, and, known as the melanin
granules, they are collected from the blood and stored in the liver,
kidney, or spleen, or even in the lungs and brain, leading to pigmenta-
tion of these organs and frequently to hypertrophy, more especially of
the spleen and liver.
The essential differences between the parasites of tertian, quartan,
and estivo-autumnal fevers mav be brieflv summarized as follows :
«/ %/
1. Tertian Parasite (Plasmodium vivax) (Plate I, Fig. 1).
Young schizonts from 1 to 3 a up to the size of normal blood
corpuscles.
Melanin granules distributed throughout protoplasm or (at
schizogony) collected at one point on periphery.
Merozoites, 12 to 24, formed every forty-eight hours. Peripheral
circulation (see also Fig. 109).
Ameboid activity very pronounced.
Macrogametes spherical. "
Effects slight enlargement of corpuscle.
Incubation period about fourteen days.
2. Quartan Parasite (Plasmodium malariae) (Plate I, Fig. 2).
Size as above, but never as large as normal corpuscle.
Melanin granules not distributed; collected in zone on periphery.
Merozoites, 6 .to 12, formed every seventy-two hours. Frequent
in circulation (see Fig. 110).
Relatively quiescent in the corpuscle.
Macrogametes spherical; less numerous than in vivax.
Effects no enlargement, frequently shrinkage of corpuscle.
Incubation period about three weeks.
20
FIG. 2
«
<u
.
10
/ ^-
f
;•;•
O
13
11
-v
0
«
i
12
k">N
8
Fig. 1. Tertian Malarial Plasrnoclium. Staiiied by Oliver''s
Modification of Wright's Stain. (After Craig.)
I to 4. Ring forms of tertian parasite.
5. Ring form. (Conjugation form of Ewing.)
0 to 10. Pigmented organisms.
II to 14. Nearly full-grown forms, showing
diffusion of the chromatin.
15 to 17. Segmenting forms within red corpuscle.
18. Segmenting forms after destruction of red
corpuscle.
19- Microgamete.
20. Sporozoite.
Fig. 2. — Quartan Malarial Plasmodium. Stained by Oliver's
Modification of Wright's Stain. (After Craig.)
1 to 4. Ring forms of quartan parasite. 10 to 12. Segmenting forms of quartan parasite.
5, 6, 7, 8, 9. Pigmented parasites. 13. Segmenting stage after destruction of red corpuscle.
NOTE.— Chromatin of nucleus stained red; protoplasm stained blue; vesicular portion of
nucleus unstained.
THE PATHOGENIC HEMOSPORIDIA 283
3. Estivo-autumnal Parasite (Plasmodium falciparum) (Plate II).
Young forms alone found in peripheral circulation; very small,
occupying from one-fourth to one-half the corpuscle.
Melanin scarce, a few (2 to 3) granules usually central in position.
Merozoites, 6 to 15, formed at twenty-four to forty-eight hour
intervals (see Figs. Ill and 112).
Ameboid activity marked, but less than that of vivax.
Macrogamete at first crescentic in form.
Effects slight shrinkage and often crenulation of corpuscles.
Incubation period usually from ten to twelve days.
As an example of the asexual reproduction of the malaria organisms
we may select the cause of tertian fever, Plasmodium vivax, which has
been carefully worked out and described by Schaudinn. The young
sporozoite from the mosquito was studied in the living state and every
stage confirmed in preparations. With characteristic ingenuity he
succeeded in getting his own blood in sufficiently dilute condition to
follow the movements of the young sporozoite in life. This he did by
raising a blister on his hand and then teasing the contents of an infected
mosquito's salivary gland into the fluid obtained from the blister; the
blood corpuscles were thus relatively few in number, and with a warm
stage he was able to follow the history of the parasites for hours. The
young forms grow into a large organism which may nearly fill the
erythrocyte. In the course of its growth a vacuole appears in the
vicinity of the nucleus, probably due, as Schaudinn believed, to the
active processes going on in the vicinity of the parasite's nucleus.
In this way the ring-forms of the parasite are formed, the vacuole
increasing relatively in size. Ewing ('98) interpreted these ring-
forms as due to the coalescence of two horn-like pseudopodia, the
vacuole thus arising in a purely fortuitous manner, and Argutinsky
interpreted them as artefacts. Schaudinn's observations on the living-
organisms and his seeing this vacuole appear and disappear indicate
that the vacuole and the ring forms are only evidences of physiological
stages of the parasite, the vacuole serving only to increase the surface
of absorption in relation to volume. It is not without significance,
either, that he did not observe the formation of the vaucole in the
sexual cycle. The nucleus of the young form consists of a relatively
large karyosome and a minute vesicular part, the karyosome finally
becoming granular and then dividing, the division being of a very primi-
tive type of mitosis. At this period, which marks the full growth of the
schizont, the organism becomes extremely motile within the blood cor-
puscle (Plate I, Fig. 1). Schaudinn graphically describes it as follows:
'This period of the highest development of its vegetative activity is
characterized by an important increase of its ameboid motion. It
assumes the most unusual forms and is not for a moment at rest. The
pigment becomes distributed throughout the body, long pseudopodia are
284 THE PATHOGENIC HEMOSPORIDIA
thrown out from all sides of the body and again drawn in, great vacuoles
appear and disappear, deep incisions cut into the periphery, to be filled
in immediately with the restless protoplasm. In short, this living
organism is a most changing and fascinating spectacle to watch, and
leaves the impression that the parasite is well-named 'vivax.' 'n
Shortly after this period of activity the organism becomes quiet,
spherical, and rapidly undergoes the changes preparatory to rnero-
zoite formation. The nucleus divides, as stated, by a primitive method
of mitosis, but with the continued division all traces of a mitotic pro-
cess are lost, and at the end of the second division the process is little
more than multiple fragmentation, division being so irregular that a
definite plan is excluded. The end result is a number of daughter
nuclei, each a small spherical granule of chromatin about which the
protoplasm of the parasite divides to form a small reproductive element
—the merozoite — while an unused residue containing the pigment and
crystals remains behind to be dissolved in the blood plasma and carried
to all parts of the system. The many merozoites thus liberated make
their way to fresh corpuscles and the simultaneous attack leads to the
characteristic symptoms of the disease.
The young quartan parasite cannot safely be distinguished from
that causing tertian fever, save, perhaps, in regard to its relative
inactivity, a function which decreases with growth of the merozoite.
Its form, therefore, is more regularly spherical than that of Plasmodium
vivax (Plate I, Fig. 2). After about ten hours of growth (Ziemann,
1906) it contains fine dark brown granules of pigment. At the sixteenth
hour it occupies about one-quarter of the volume of the corpuscle,
the pigment granules being unevenly distributed about the periphery,
while the chromatin is less readily stained than that of the tertian
parasite. At the end of two days the containing blood corpuscle
remains only as a rim of material about the enlarged parasite, and this
shortly afterward disappears, the freed organism being the size of the
corpuscle. Characteristic merozoite formation follows, giving rise
to what Golgi described as the "marguerite form," due to the regular
segmentation of the cell body into from six to twelve merozoites
(Plate I, Fig. 2, 12}.
The merozoite of the organism of pernicious malaria is a very
minute (1.5 to 2 microns) ring-formed parasite, the rings, according to
Nocht, being optical illusions, due to discoid bodies with thickened
rims. The chromatin is in the form of a small spherical granule which
not infrequently elongates to a rod form and then fragments to form
two or three similar chromatin granules (Plate II). Double or multiple
infection of blood corpuscles is not infrequent, but union of these
separate individuals never takes place, according to Ziemann (how-
1 Schaudinn Plasmodium vivax G. and F. der Erreger des Tertianfiebers beim Menschen.
Arb. a. d. Kais. Gesundh., 19:1902:216.
PLATE II
•
2 4?
10
17
14
20
25
*'••/
^V#
30
11
.*•
• •
18
21
31
35
36
15
ft/
22
13
12
>
»
23
27
32
19
/•
29
^
'&•
34
f
Tertian Estivo-autumnal Malarial Plasmodium. Oliver's
Modification of Wright's Stain. (After Craig.)
22. Macrogamete.
1, 3, 4, 5, 6, 7, 8. 9, 10, and 15. Ring forms of
tertian estivo-autumnal plasmodium.
2. Intracellular form.
11, 13, 14, 16, and 17. Pigmented ring forms.
12. Red corpuscle, showing infection with two
" ring forms."
18 and 19. Pigmented forms, just prior to seg-
mentation.
20, 21, 23, and 24. Round and ovoid forms
developed from crescent *.
25 to 36. Crescentic forms of estivo-autumnal
plasmodium (tertian).
29. Ovoid form.
37. Segmenting form.
38. Sporozoites.
n. Segmenting form of quotidian estivo-autumnal
plasmodium.
THE PATHOGENIC HEMOSPORID1A 285
ever, see p. 287). After some twenty-four hours the plasm of- the
ring form collects at one point, giving the effect of a signet ring, and the
pigment granules first appear in the thickened portion. After about
thirty hours the majority of the parasites have disappeared from the
peripheral circulation, although a few may be found, especially in the
Italian forms of the disease. In such cases the parasites, after thirty-
six hours, appear round or oval and very sharply contoured, occupying
from one-fifth to one-fourth of the whole volume of the corpuscle, which
now begins to shrink. The chromatin divides (Plate II, 17 to 20, a)
and the body of the parasite breaks up into from 12 to 16 merozoites,
although the number of these may vary anywhere from 8 to 24
(Ziemann).
By analogy with other parasitic protozoa this process of asexual
multiplication may continue for a longer or shorter time, or until the
vitality is exhausted. A period finally ensues, the conditions being
unknown, in which the merozoites develop into the sexual phases of the
organism. These are the macrogametocytes and microgametocytes,
the former female organisms, the latter mother cells of the male
organisms. The stages in this development in the case of Plasmodiu m
vivax are shown in Plate III, Fig. 1. The female organism is a large
cell with reserve granules and a well-developed nucleus. The male
mother cell is less granular and its nucleus divides by a multiple divi-
sion into a number of daughter nuclei which migrate to the periphery
and there become the long-drawn-out nuclei of the flagelliform micro-
gametes. The female nucleus, before fertilization, divides to form a
small nucleus, which is extruded from the cell, this corresponding to
the polar body equivalent of other protozoa and metazoa (Schaudinn).
The processes thus briefly outlined do not all occur in the human
blood. The early stages of gametocyte formation occur there while
the remaining stages, viz., gamete formation and maturation processes,
occur in the gut of a mosquito. Schaudinn had reason to believe that
these sexual reproductive stages, especially of the microgametocytes,
degenerate in the blood and come to nothing unless stimulated to
development by the action of a cooler medium, such as room tempera-
ture or the cool medium of an insect's body. The organisms ready for
this further development are constantly in the blood after the first few
paroxysms, and when sucked up by the mosquito, the further changes
take place rapidly in the latter's stomach and fertilization is brought
about by the penetration of one of the slender microgametes into a
macrogamete. The fertilized cell, called by Schaudinn the ookinet,
now makes its way by a peculiar vermiform movement (giving rise to
the name vermicule) to the epithelial cells lining the gut; it penetrates
the mucous membrane and comes to rest in the submucosa. Here it
rapidly grows into an organism of the size of a coccidium, the nucleus
divides, and the cell body, at about the third or fourth day, forms
286 THE PATHOGENIC HEMOSPORIDIA
a permeable outer membrane and by the sixth day divides into as
many portions as there are nuclei. These are special reproductive
centres corresponding to the sporoblasts of the coccidia, and, as in the
coccidia, each sporoblast forms by division a number of germs, the
sporozoites. Unlike the sporoblasts of the coccidia, however, there is
no protecting membrane or capsule about these plasmodium sporo-
blasts; the sporozoites are naked and unfitted by this very fact for a
free existence outside the body of some host. When mature, after a
period of about fourteen days in the mosquito, they are liberated from
the sporoblasts into the body cavity of the insect where, by the cir-
culation of the body fluids, they are carried to all parts of the body,
collecting, however, in the region of the head. Here they make their
way into the salivary glands in the thorax and pass into the proboscis
of the insect and thence into the human blood at the time of the
first meal subsequent to their maturity.
There is, perhaps, no better instance in the realm of biology of the
delicate relationship existing between these intestinal parasites and
the infected host. If the human blood of a malaria victim is taken by
a mosquito belonging to the genus culex, the blood and its parasites
are alike digested by this mosquito's digestive fluids; no stage of the
organism remains alive. But it is quite different with the species of
mosquito belonging to the genus anopheles. Here the digestive fluids
kill the ordinary asexual forms of the parasite, but the gametocytes
have in some manner acquired immunity to the digestive ferments of
these mosquitoes and continue to live in the gut and to reproduce in
the tissues lining it. Ross, in India, showed that this very phenomenon
occurs in the case of bird malaria, in which the organism Plasmodium
precox is digested by the fluids of anopheles, but immune to those of
culex or stegomyia (Newmann), so that species of culex and stegomyia
are the carriers of bird malaria, but harmless to man, for the organisms
of bird malaria do not live in human blood. It is generally supposed,
also, that mosquitoes may become immune to all kinds of blood para-
sites, that is, capable of digesting all of the organisms, gametocytes
and schizonts alike, and thus become quite harmless to man. This is
the interpretation given to the fact that, although anopheles is common
in England, there is no malaria.
The phenomena of sporogony in connection with other forms of
malaria are not essentially different from those of the tertian organism
(Plate III, Figs. 2, 3, 4). The macrogamete of pernicious malaria is,
however, distinguishable from those of other forms of malaria by its
sausage or crescent form (Plate III, Fig. 3). A number of observers
(Grassi and Felletti, Mannaberg, Ziemann, et al.) have observed the
binary division of such macrogametes, a method of reproduction which
recalls the multiplication of the female organisms in trypanosomes.
Schizogony and sporogony in the case of Plasmodium precox, the
EXPLANATIONS OF FIGURES IN PLATE III.
Fig. 1.— Tertian Malarial Plasmodium. (After Craig.)
1. Hyaline form. 8. Flagellate form. (Microgametocyte.)
2. Pigmented ring form. 9. Non-flagellate form. (Macrogamete.)
3 to 6. Pigmented forms. 10. Segmenting form after destruction of red
7. Segmenting forms. corpuscle.
Fig. 2. — Quartan Malarial Plasmodium. (After Craig.)
1. Hyaline forms. 8. Segmenting forms after the destruction of the
red corpuscle.
2 to 5. Pigmented forms. ,,. .. , ,-.
9. I'lagellate form. (Microgametocyte.)
6 and 7. Segmenting forms. 10 Non-flagellate form. (Macrogamete.)
Fig. 3. — Tertian Estivo-autumnal Malarial Plasmodium.
(After Craig.)
1 and 4. Hyaline ring form. 9. Segmenting forms.
2,3, and 7. Pigmented ring form. 10 Flagellate form. (Microgametocyi.-. i
5 and G. Pigmented forms.
II i<> 14. Creseentic forms.
8. Young intracorpuscular crescent.
Fig. 4. — Quotidian Estivo-autumnal Malarial Plasmodium.
(After Craig.)
1 to 4. Hyaline ring forms. Some cells show 9. Flagellate form. (Microgametocyte.)
infection with more than one organism. .
10, 11, 13, and 15. Creseentic forms.
,"> to , Pigmented forms. In 6 one hyaline form.
12. Ovoid form.
8. Segmenting forms. Segmentation complete
\\ithin infected red blood corpuscle. 14. Non-flagellate forms. (Macrogamete.)
0
•-
10
FIG. 1
FIG. 3
PLATE III
.3,
7
v^
•
.
*
10
FIG. 2
«l
'.'V
' 1
A i»
-">
FIG. 4
9
12
11
G "
' V *
**+* ,
8 W
15
10
13
14
13
14
12
9
THE PATHOGENIC HEMOSPORIDIA
287
cause of bird malaria, are not different in essentials from similar
phenomena in human parasitic forms.
Of great importance in the malaria problem is the fact of latent
and recurrent malaria. In many cases, months after the first attack
and apparent cure, the victim suffers anew from the parasites, and
this without new infection. The matter has been studied carefully by
many observers, among others by Craig and by Schaudinn, and it has
been found that parasites, even after apparent cure, are stored up in
the spleen and the bone marrow, where they live a comparatively pas-
sive existence, getting into the peripheral blood when the conditions for
their further development are favorable. What these conditions are
is the one remaining obscure point in our knowledge of the malaria
organisms. Schaudinn claims that certain of the forms of Plasmodium
vivax, which under ordinary conditions would form the macrogameto-
FIG. 113
B
C
Regression and merozoite formation (parthenogenesis) in Plasmodium vivax. (After
Schaudinn.) A, macrogarnetocyte in blood with nucleus differentiating into a denser and a
lighter part; B, the denser part of the nucleus now divides preparatory to schizogony, C, D,
while the paler portion with a part of the original cell degenerates; D, numerous merozoites
formed about the divided nucleus.
cytes, undergo a process of parthenogenesis (Fig. 113), whereby the
vitality is again renewed and with this the ability to withstand the
natural or acquired immunity of the host. Craig, on the other hand,
describes the conjugation of two schizonts within the human blood
cell, an observation which Ewing ('01) and Wright ('01) had also made,
although in the last two cases in connection with the normal infection
and not with recurrence, while the occurrence was stated as rare and
exceptional. Craig ('05 and '07), however, claims that the union of
schizonts is a normal process in every infection, and sees in this fact a
means by which the organisms renew their vitality and thus bring
about recurrence. Minchin doubts the interpretation of this fusion as
given by Wright and by Ewing, and regards it as a process of plasto-
gamy without sexual significance. Craig's view is certainly enticing,
but we must not forget that plastogamy is a very common phenom-
enon throughout the group of protozoa and occurs frequently when
288 THE PATHOGENIC HEMOSPORIDIA
there is no subsequent reproduction. It happens in most of the
common rhizopods, for example, and has been described for cases of
arcella, difflugia, centropyxis, ameba, etc., and it has been shown that
these unions have nothing to do with the actual process of fertilization.
It is impossible to state that no stimulation whatsoever results from
such a plastogamic union, especially if it is followed by nuclear union
or karyogamy, according to the account given by Craig; but it is diffi-
cult to believe that two widely different processes of fertilization should
exist in the same organism. My experiences with the free living para-
mecium in cases of depression where the organisms were stimulated
to new activity and new reproduction by purely artificial means
opens the possibility, at least, that some analogous stimulation in the
human system may start up the flagging energies of the malarial
parasites. It is not inconceivable that minute changes in the con-
stitution of the blood, especially of the salt contents, act upon the
parasites in the same manner that potassium phosphate acts upon the
weakened paramecium.
Apart from the clinical effects of the different malaria parasites
there is not much difference between them. The cause of quartan
fever, Plasmodium malarice, for example, agrees in all of its phases
with Plasmodium vivax, the most important difference being the period
elapsing between successive sporulating phases, requiring seventy-two
hours as against forty-eight. The forms assumed by the gametocytes
agree in all essential features, and fertilization in the mosquito follows
the same history as in Plasmodium vivax.
There is evidence that at least two kinds of parasites causing
pernicious malaria exist, one giving rise to a daily and the other to
a forty-eight-hour recurrence. The difference in form of the macro-
gametocyte was considered evidence of sufficient morphological value
to justify a different generic name, and Grassi, therefore, gave it the
name Laverania malarice. The grounds seem hardly sufficient for
this, however, and the name Plasmodium falciparum, as given by
Welch, is the one we adopt. (PL irnmaculatum, accepted by Schaudinn,
was shown by Blanchard to be the name given by Grassi and Felletti
to parasites occurring in birds.) In this parasite the macrogamete
assumes the form of a crescent before maturity, but rounds out into
a perfect sphere before fertilization.
The action of quinine on the malaria organisms is particularly
interesting, since it is one of the best-known specifics against any
of the protozoan diseases. Introduced into Europe, in 1640, by del
Cinchon, it was immediately recognized as a specific and was used as
a diagnostic therapeutic test for malaria. Just how it acts upon the
malaria organism was, of course, unknown until more or less of the
life history of the parasites was known. Marchiafava and Celli,
Schaudinn, and, in short, all who have studied the matter carefully
THE PATHOGENIC HEMOSPORIDIA
289
have come to the same conclusion, that the drug acts directly upon the
parasite, killing it with more or less distinct evidences of disintegra-
tion of the organism. Marchiafava and Celli conclude that the treat-
ment is most effective during the period of sporulation and upon the
young stages of the organism, and practically without effect during
the period of pigment formation and full growth of the schizonts.
f
19
CHAPTEK X.
THE PATHOGENIC RHIZOPODA.
THE biological conditions which underlie parasitism are but little
known, but, as with free-living protozoa, the dominant factor is the
problem of food-getting. The causes which lead an organism to
invade a specific organ or tissue must, in the final analysis, be traced
to this function, and reproduction leading to complete annihilation
a cell or group of cells follows a parasite's life in a suitable food
medium. There is a limit also to the kinds of parasites that can become
cell-infesting forms, for the organism must have either the mechanical
or cytolytical power of breaking down the barriers of a cell, and
physical force enough and of a certain kind, to enable it to penetrate
the cell membranes and cytoplasm. For such a function cilia are not
useful, nor flagella, and we find that ciliates and ordinary flagellates
rarely become intracellular parasites, and then only after losing their
motile organs; unless, as in trichonympha, pyrsonympha, etc., they
are provided with special anterior boring organs, by which they pene-
trate the cell membranes, or unless, as in spirocheta, they possess the
power of undulatory motion independent of flagella action (Fig. 114).
Spirochetes may thus become cell-dwelling as well as fluid-dwelling
forms, and some, like Sp. microgyrata or Treponema pallidum, work
their way through the tissues of an infected host and not infrequently
bore into the cells themselves. The ciliated and flagellated protozoa,
however, are typically fluid-dwelling forms, and when they attack the
epithelial cells of an organ it is usually only for purposes of attach-
ment, as in trichonympha and pyrsonympha. There is considerable
evidence, however, to indicate that one of the ciliates, balantidium, is
occasionally found inside the mucosa of the intestine, and even within
*/
the muscular coating of the colon, while collections often appear in the
epithelial cells and, apparently, cause the ulcers that are found there.
Two kinds of these ciliated parasites are common in man, Balantidium
coli, frequent in the rectum, and Bal. minutum, and, according to Strong,
Brooks, and Stengel, with others, the parasite becomes an important
etiological factor in catarrhal inflammation of the intestine (Fig. 115).
Other observers, including Malmsten, Opie, Doflein, and others, hold
that these forms are quite harmless, increasing in number with dis-
orders of the digestive tract, and for this reason are not uncommon in
the intestinal tract of victims of cholera, typhoid, dysentery, or diar-
THE PATHOGENIC RHIZOPODA
FIG. 114
291
/I , Mult-icilia lacustris, Lauterb. (After Lauterborn.) B, Pyrsonympha vertens, Leidy, with
attaching organ. (After Porter.) x, vibrating band in the inner protoplasm.
FIG. 115
Flagellated and ciliated intestinal parasites. A,B, Megastoma (Lamblia) entericum.
Grassi; C, Balantidium entozoon, Ehr.
2<)2 THE PATHOGENIC RHIZOPODA
rhea. Brooks has given strong evidence to show that Bed. coli was the
cause of a fatal disease resembling dysentery, in some valuable apes
belonging to the New York Zoological Society, and from his observa-
tions it is evident that these ciliates must be taken into account in
searching for the causes of certain types of intestinal trouble, for, if
not themselves the direct causative agent, they may be the bearers of
some more pernicious organism.
While ciliates and flagellates are not adapted morphologically for
an intracellular parasitic life, the rhizopods have no such disadvan-
tage, and by virtue of their ameboid movements, and of the cytolytic
ferment which they are apparently able to secrete, they make their
way into tissues and cells and then live upon the fluid elements of
the living protoplasm. Thus, Plasmodiophora brassiccs, while in the
young amebula stage, works its way into the root cells of a cabbage
or turnip plant, absorbs and grows upon the fluid protoplasm of the
plant cells, forms a plasmodium, and reproduces within these cells
(see p. 209). Certain human diseases, notably dysentery, hydro-
phobia, and smallpox, are characterized by the destruction of tissue
cells, the agent being minute ameboid forms which we interpret as
protozoa. In dysentery the organism causes the destruction of the
epithelial cells of the digestive system; in hydrophobia, the nerve cells
of the brain are destroyed, and in smallpox, the epithelial cells of the
skin.
In none of these cases is it generally agreed that the structures
found within the diseased cells are the causes of the several diseases,
and, indeed, in the last two, hydrophobia and smallpox, pathologists
do not agree that the structures found within the diseased cells are
organisms at all, much less the causes of the troubles. Unfortunately,
cultivation of such organisms upon artificial media, and in pure cul-
tures, has never succeeded. Indeed, up to the present time no one
has succeeded in cultivating a cell-infesting rhizopod, and Liihe goes
so far as to state that it will never be done, although success with forms
like the Leishman-Donovan bodies makes such sweeping generaliza-
tions unsafe. The only means of determining whether such things are
organisms rests upon morphological evidence, and lacking cultural
possibilities the only proof that they are the cause of disease is to find
them in every case of the disease. The morphological evidence, to
most pathologists, is insufficient, and to most of them these organisms
are more probably artefacts or degeneration products of the human
cells caused by the disease, than etiological factors. To a proto-
zoologist, however, the morphological evidence of organic structures
of these protozoa is far more convincing, for he is familiar with the
many variations in size and structure, in the different phases of the
life history, of hundreds of different kinds of protozoa, and the struc-
tures seen in these questionable inclusions become to him convincing
THE PATHOGENIC RHIZOPODA 293
evidence of their protozoan nature. Such is the situation at the pres-
ent time in regard to the inclusions found in trachoma, molluscum
contagiosum, hydrophobia, and smallpox, while those in dysentery
(although still in dispute as to etiology) are universally recognized as
ameboid organisms. In the present chapter, I purpose to give some
of the evidence upon which the protozoologist bases his conclusions
that the more questionable inclusions referred to are actually organ-
isms of the rhizopod type, and if, thereby, I am able to impart some of
my personal convictions in regard to them, the matter of etiology will
take care of itself.
In order to provide a basis for comparison of these disputed organ-
isms it is necessary to consider first the variations in structure that
occur during the life histories of widely different types of rhizopods,
and then to show that, despite the minor differences, they all conform
to a common type. The full life histories of many different kinds of
rhizopods have been worked out on free living material, so that there
is no ground for cavil as to whether such types are living organisms
or artefacts.
As fully shown in Chapter III, the life histories of free living
rhizopods, involving many form changes, are characterized, at certain
periods of maturity, by diffusion of the nuclear material throughout
the cell and by the formation of exceedingly minute gametes.
The curious diffuse idiochromidia are known to be no artefacts, nor
abnormal features of the cell, but specific and highly important
elements whose chief function is in sexual reproduction. It may be
expected, therefore, and reasonably so, that similar structures should
be characteristic of parasitic as well as of free living rhizopods, and the
idiochromidia of chlamydophrys, of entameba, of neuroryctes, and
cvtoryctes, features of these organisms which many observers are
reluctant to regard as evidences of organic structure, have the same
importance as elsewhere. It is upon this feature of these organisms
that we may reasonably depend for the assurance of the protozoa
nature of the cell inclusions in trachoma, molluscum contagiosum,
rabies, and smallpox.
There is no reason to believe that the life cycle of a parasitic
rhizopod should be essentially different from that of a free living
form, unless, indeed, there may be an acquisition of some special
means of overcoming the unfavorable condition of parasitic life, such
as exposure to antibodies, acids, alkalies, etc., in the body fluids of the
host, or to difficulties in transmission from one host to another. These
are, in the main, provided for by the phenomenon of encystment, the
organism within its cyst being amply protected against unfavorable
conditions. Such a function, however, is shared with the free living
rhizopods, encystment playing an important part in the life history
of both shelled and shell-less forms.
294 THE PATHOGENIC RHIZOPODA
A transition from the free living to the cell infesting rhizopods is
afforded by one species of shelled forms — Chlamydophrys stercorea—
and by different species of ameba — Entameba coli and Entameba
histolytica — the life activities in all being singularly in conformity with
the examples given above.
Chlamydophrys stercorea, first described by Cienkowsky in 1876, is
a rhizopod provided with a transparent glass shell of silica, found in
animal feces. From its type of pseudopodia it would be classed with
the reticulosa rather than with the lobosa or ameba type, and comes
closer, therefore, to polystomella than to arcella or centropyxis.
Schaudinn (loc. cit) found it in the feces of many different mammals,
including cow, guinea-pig, turtles, and man, and was able to follow its
life history by infecting his own digestive tract with encysted forms
of the organism.
The protoplasm of the cell contains one nucleus, many fine par-
ticles, which are destined to form the shell of the daughter individual,
contractile vacuoles (one or more), and idiochromidia in the form of
a densely packed mass of granules about the cell nucleus. Like
arcella, centropyxis, euglypha, and other shelled rhizopods, the organ-
ism reproduces asexually by budding division, the plasm flowing out
of the shell opening until a daughter mass is formed equal in size to the
parent ; the nucleus then divides by mitosis, one-half passing into the
bud organism. The idiochromidia do not flow into the daughter
protoplasm with the protoplasmic streaming, as in euglypha and
centropyxis, but adhere to the nuclear membrane, so that when the
nucleus divides, the germ plasm is likewise divided into two parts, the
daughter organism thus getting its proportion of the important idio-
chromidia. The sexual development is quite different from that of
centropyxis. There is no dimorphism, and whereas in centropyxis
the idiochromidia-bearing swarmers move out of the shell, leaving
the disintegrating primary nucleus and residual protoplasm in control
of the parental abode, here the residual parts are thrown out of the
shell opening and the idiochromidia remain in the shell. The idio-
chromidia next give rise to a small number of secondary nuclei, usually
eight, by segregation of the chromatin granules, and the protoplasm
then divides into as many parts as there are nuclei. Each part assumes
an oval form, develops two flagella at the pole, and swims out of the
shell and away. Two swarmers (flagellispores) from different ances-
tors fuse, form a hard, protecting cyst which becomes brown in color
and irregular in contour, and within these the fertilized cells with a
high potential of vitality, live until conditions are again suitable for
development. With characteristic patience and ingenuity Schaudinn
kept these cysts in damp chambers for a period of many months
without observing any change, and finally inoculated himself: "I
swallowed on November 17, 1899, for the first time, the contents of
THE PATHOGENIC RHIZOPODA 295
eight moist chambers, in which were innumerable permanent cysts of
chlamydophrys, which had lain unchanged for two or three months,
and found on the 20th two typical chlamydophrys in an infusion made
from solid feces of the 18th, while by the 24th they were so numerous
that every preparation contained from one to two individuals."
(Schaudinn, loc. cit., p. 562). When he found that the organism would
live in other digestive tracts, he gave up experimenting upon himself
and used mice. One phase in the life history of this organism was
earlier (1896) interpreted as a distinct species and named Leydenia
gemmipara. (Schaudinn, 1903, p. 563).
Chlamydophrys, therefore, behaves like centropyxis and arcella in
its vegetative activities, but resembles polystomella more closely in
its formation of isogamous gametes. The chromidia are the same
in all, being the substance of the nuclei of the conjugating cells.
A transition from the lumen dwelling to the intracellular rhizopods
is afforded by the intestinal amebae, which, since the time of Losch,
in 1875, have been closely associated with the problem of dysentery.
These are minute amebse which penetrate the tissues by forcing the
cells apart, and although they apparently do not enter the cells, they
cause destruction of the cells by cutting off the food supply, exposing
them to the materials of the intestine, or disturbing the ordinary pres-
sure relations by infiltration with round cells and edema. Different
observers have described many kinds of ameba in the human intestine,
both during health and disease, and while some of these observations
warrant careful consideration, the majority of them are not zoologi-
cally satisfactory. There are few points of structure in the parasitic
amebse upon which to base species, and all attempts to create new
species on account of size differences, nature of the pseudopodia,
vacuoles, and the like, are insufficient; the only safe taxonomic basis
is the life history, or the "individual" in the larger sense. At the present
time very few of the many described amebse have been followed in
their life history, and, although there are probably more, we recognize
only two species of intestinal amebse, the one, Entameba coli, regarded
by Casagrandi and Barbagallo, Schaudinn, Craig, and others as a
harmless commensal in the human intestine, and Entameba histo-
lytica (dysenierice, Councilman and Lafleur), regarded by pathologists
generally as the cause of amebic dysentery. A third form, Entameba
buccalis, is found in carious teeth (Prowazek). The life history in
both of the intestinal species was worked out by Schaudinn, and the
specific features were established by his demonstration of the char-
acteristic differences in mode of reproduction.
Losch, in 1875, was the first to describe the simple structures of
these amebse, which he also was the first to regard as an additional
irritant, if not the cause, of dysentery. He named it Ameba coli.
Later observers, finding the organism in so many cases of the normal
296 THE PATHOGENIC RHIZOPODA
intestine, denied the pathogenic character of "Ameba coll," claiming
that it is an organism of wide distribution and quite harmless. Casa-
grandi and Barbagallo were the first to prove, although not the first
to suggest, that the ordinary form of the ameba is harmless, a proof
which was confirmed by Schaudinn, who inoculated himself with
Entameba coli and without any disturbance, a result which he also
repeatedly obtained with young cats. From the medical side Council-
man and Lafleur, in 1891, first demonstrated that dysentery is not all
one type of disease, and that amebic dysentery is both clinically and
etiologically different from other kinds. They suggested the name
Ameba dysenteric for the organism causing the intestinal ulcerations,
and Ameba coli, Losch, for the harmless form ; but their suggestion was
not followed by enough morphological data to warrant the creation of
a new species, and zoologists did not accept the new terms. Casagrandi
and Barbagallo, working on A. coli, came to the conclusion that the
generic name ameba should not be stretched to include forms like
Ameba proteus, on the one hand, and these small intestinal parasites
on the other, and so called the latter entameba, while the specific name
hominis was substituted, without justification, for Losch's term coli,
Schaudinn, finally, overlooking Councilman and Lafleur's observa-
tions, adopted Casagrandi and Barbagallo's name entameba for the
genus, and named the harmless form Entameba coli, and the patho-
genic form Entameba histohjtica, a better name, but not prior to
Councilman's "dysenteries."
Entameba coli is widely distributed in the human intestine, this
distribution varying with the locality and with the people. Schaudinn
found it in about 20 per cent, of the feces investigated by him in Berlin,
while in the region about Rovigno, in Istria, he found it in 256 cases
out of 385, and other observers have noted a like variation in the per-
centage of healthy persons infected. It is an organism to be obtained
without much difficulty, and is more prevalent in persons suffering
from intestinal disturbances. During the ordinary inactive phases
there is little or no differentiation into cortical plasm (ectosarc, ecto-
plasm) and endoplasm, but when it moves, a hyaline sheet of proto-
plasm moves out from the body, and this is similar to the cortical plasm
of fresh water ameba?. This ectoplasm is only momentary, however,
for the endoplasm quickly flows into the advanced part. The nucleus
is vesicular, with a distinct membrane and with one or more karyo-
somes of chromatin and plastin, while the numerous chromatin
granules are distributed throughout the space of the nucleus, with a
tendency — of frequent occurrence among the protozoa — to collect at
the periphery. The abundance of chromatin makes the nucleus stand
out prominently in stained preparations.
Multiplication of the parasite is accomplished asexually by simple
division and by multiple division or spore formation into eight daughter
THE PATHOGENIC RHIZOPODA 297
organisms. The centronucleus, with its single division centre divides,
according to Schaudinn, by amitosis, but, as in the flagellates it is a
primitive mitosis. Spore formation is accomplished after a peculiar
fragmentation of the nuclear chromatin into minute granules which
collect in a rim around the inside of the nuclear membrane, the cell
body, in the meantime, throwing out all foreign matter and ceasing its
movements. The peripheral chromatin next collects in eight centres,
the nuclear membrane is ruptured, and the eight small nuclei pass
into the cell body. The protoplasm divides into eight parts around
the nuclei, and eight small amebae finally creep out.
As with all protozoa that have been carefully investigated, the
reproduction by asexual means, in this case leading to auto-infection of
the host, cannot be maintained indefinitely, and there comes a period
when the organisms encyst, the conditions under which encystment
takes place being somewhat indefinite in Schaudinn's account. The
cell throws out foreign matter and products of its own metabolism,
and becomes more compact, smaller, and spherical, and then secretes
a thick and slightly refractive gelatinous membrane. The nucleus then
divides by primitive mitosis into two nuclei, which are separated from
one another by the entire diameter of the spherical cell. The idiochro-
midia characteristic of the rhizopods is then formed by disintegration
of the two nuclei, the protoplasm of the cell in the meantime dividing
into two incompletely separated parts around the two nuclei. In some
cases the entire nucleus disappears in a mass of chromidial granules,
in other cases there appears to be a secretion of chromidial substance
as in arcella, but in all cases a part of the nuclear material is thrown
out of the nucleus to degenerate, and this portion represents the
eliminated and unused nuclear parts of the free living rhizopods.
The fertilization process, following this preliminary division of the
nucleus, is autogamous and similar to that in Ameba protcus and in
the heliozoon actinospherium, as observed by Hertwig. The organism
fertilizes itself in the following remarkable manner, the processes of
maturation recalling those of the ciliate paramecium:
From the disintegrated chromatin or idiochromida of the divided
cell within its cyst membrane a new and a smaller nucleus is formed
t/ f
in each of the halves. This divides by a primitive mitotic process into
two nuclei, one of which immediately degenerates, the shrunken
nucleus remaining as a highly refractive irregular mass in the cell body;
the other daughter nucleus then divides again, so that three nuclei lie
in each half of the double organism, or six altogether, two of these
undergoing degeneration. Two of the remaining four nuclei then
begin to shrink and to degenerate like the first one, until there are only
two functional nuclei left. After this process, which Schaudinn inter-
prets as equivalent to the reduction and polar body formation of
metazoan cells, the final encvstment takes place. The gelatinous
298 THE PATHOGENIC RH1ZOPODA
membrane disappears, and in its place is secreted a thin but much more
refractive membrane, the definitive cyst membrane. The contents of
the cyst become again closely united, and the two remaining nuclei
are brought closely together. Then follows a third division by mitosis,
characterized by long connecting strands which lie parallel with one
another in the centre of the cell, so that the daughter nuclei of the two
parent nuclei lie side by side in pairs. These nuclei then fuse, an
eighth part of one of the original nuclei uniting with an eighth part of
the other, while the outer membrane hardens and thickens. Each
cyst thus contains two fertilized nuclei, the process recalling the
phenomenon in paramecium where, from the same primary nucleus, a
wandering and a stationary nucleus is formed. In the fertilized
Entameba coll each of the two nuclei divides, forming four nuclei;
then each of these divides again, making eight nuclei in the cyst, and
in this condition the encysted parasite passes into the intestine of a
new host, where the protoplasm of the cell divides into eight parts
around the eight nuclei, the cyst membrane is dissolved off and eight
small amebse start a new infection with a new potential of vitality.
This complicated life history has been confirmed in part by other
observers, Wenyon ('07) and Craig following out the sexual history
in E. muris and E. coll respectively (see p. 142). The possibility of
union of two amebas before encystment is not excluded, nor is the
possibility of pseudoconjugation, as seen in the gregarines, beyond
question. Autoconjugation, while recognized in many different kinds
of animals, is too unusual to be granted without the surest proof,
and further research on the life history of these parasites is urgently
needed.
The structure of Entameba histolytica, according to Schaudinn, is
somewhat different from that of E. coll, and makes it better adapted
for its cell destroying function. This is shown by its definite cortical
plasm, a layer of firm protoplasm with distinctly higher refractive
index than the internal protoplasm, which gives a more rigid character
to the pseudopodia, by which the organism is able to force its way
between the epithelial cells of the intestine and into the more deeply
lying tissues. Schaudinn has watched the organism thus make its
way into the epithelial tissue of a freshly extirpated, infected cat
intestine, its active movements often lasting an hour, while its own
body assumed the greatest variety of forms. The nucleus is difficult
to see during life of the organism, a feature in marked contrast to the
nucleus of Entameba coll, which Schaudinn recommends as a par-
ticularly favorable object for the study of the changes of the living
nucleus. The nucleus of E. histolytica has very little chromatin matter
as compared with the nucleus of the other species, but there is a single
central karyosome and a slight collection of chromatin around the
periphery. While the nucleus of Entameba coli is only slightly vari-
THE PATHOGENIC RHIZOPODA 299
able, usually spherical, and without much change in position during
the activities of the body, that of E. histolytica is highly variable, bend-
ing and turning with contact with objects in the cell, or flattening into
a disk in the cortical plasm.
The ordinary vegetative increase of Entameba histolytica takes
place by simple division or by budding on the periphery, the formation
of eight spores never being seen. Division takes place while the
organisms are lying between the cells of the gut tissues, and may be
either equal or unequal, the unequal division passing by imperceptible
grades into bud formation. The buds are apparently similar in their
mode of formation to those of acanthocystis (see p. 31), the nuclei
arising, according to Schaudinn, by amitosis (Fig. 32, p. 94.)
Permanent cysts are not formed during the height of the disease, but
are first found during periods of healing, and after the organisms have
reproduced again and again by division. The beginnings of the
preparations for spore formation are first manifested in the nucleus.
Here the peripheral zone of chromatin granules becomes thicker, the
membrane of the nucleus disappears and the granules are ultimately
disseminated throughout the protoplasm in a typical chromidium
form similar to that of centropyxis (see p. 150), while the residual
nuclear parts, with some protoplasm, degenerate. Spores are formed
by the protrusion on the surface of the cell of small buds containing
chromidia, and these buds are transformed into spores by secretion
about themselves of a definite resisting membrane, while the central
protoplasm, with the residual nucleus, degenerates. The further his-
tory of these buds was not ascertained by Schaudinn beyond the fact
that they were capable of infecting normal cats with amebic dysentery,
so that the processes of conjugation are still unknown. It will be an
interesting study for some student of the group to see if conjugation
follows the pattern of Entameba coll or that of centropyxis, where the
idiochromidia bearing spores are gametes which unite after leaving the
parent cells.
It is not the place here to discuss the question whether or not these
parasites of the human intestine are the causes, or the sole causes, of
acute enteritis in man.1 Pathologists, in the main, are in accord that
one type, at least, of dysentery is traceable to these rhizopods, but
there is a difference in opinion as to whether the rhizopods create an
enzyme or poisonous product which acts as a direct agent on the tissues,
or whether they are passive in this respect, but cause mischief by the
mechanical irritation of their movements between the cells. Shiga
and Flexner have shown that one type of dysentery is to be traced to a
bacillus, and Prowazek suggests that these parasitic ameba? may play
an important part as carriers of bacteria into the deeply lying tissues
1 Prowazek has recently given evidence to support the view that flagellates of the genus
Lamblia megastoma (Fig. 115) are capable of causing acute intestinal trouble of like nature.
300 THE PATHOGENIC RHIZOPODA
of the intestine which they are incapable of reaching by their own
movement. On the other hand, the nearly pure cultures of the ameba
which Strong, Musgrave and Clegg, and others have succeeded in
raising and in causing the disease in normal animals, and Schaudinn's
experiments on kittens with dried spores of E. histolytica, speak for
their specific pathogenic nature. Musgrave and Clegg ('04), indeed,
are so positive of the pernicious effect that they maintain the patho-
genic nature of all intestinal amebse, and claim that ordinary pond or
soil dwelling amebee may become pathogenic on entering the intestine.
Taking all into consideration, there is no doubt that the intestinal
rhizopods are dangerous, and are either the causes of certain types
of the disease, or pernicious accessories of the cause.
If skepticism exists as to the pathogenic nature of entameba and the
causes of dysentery in general, what can be said as to neuroryctes and
cytoryctes and the causes of hydrophobia and smallpox? With
entameba, skepticism never reaches the level of denial of the organism,
but with these other organisms not only does doubt exist as to their
connection with disease, but their claims to relationship with living
forms are widely denied. The problems are certainly very difficult,
and with the immense numbers of degenerations, secretions, and the
like which may be imagined in tissues under diseased conditions, it is
easily possible to be mistaken when morphology is the sole criterion.
But it is not inconceivable that these difficulties are overestimated,
and that the questionable structures in diseased tissues are actual
organisms.
Certainly no one doubts that rabies and smallpox are germ diseases,
and it is equally certain that no other cause, apart from these cell
inclusions, is known. There is a strong a priori reason, therefore, for
believing: that these intracellular structures in cells which are known
O
to be the seat of the disease are the actual causes and not the product
of the diseases. Thus, the Negri bodies (Neuroryctes hydrophobia;)
are constant inclusions in the brain cells of victims of rabies, and the
Guarnieri bodies (Cytoryctes variola:^ are equally constant inclusions
in the skin cells of man and apes infected with smallpox. So strong-
is the morphological evidence of the nature of these inclusions that
there is no doubt whatsoever in my own mind as to their protozoan
nature and to their affinities with entameba and other rhizopods.
The transition from the intercellular to these intracellular para-
sites of the rhizopod type is shown by such unquestionable ameboid
forms as Plasmodiophora brassicce, while recently a number of other
forms of similar nature have been described. Among these the
genus which Prandtl ('07) describes under the name of allogromia is
very instructive. This is a parasite of free-living protozoa, such as
Ameba proteus, arcella, nuclearia, or even paramecium, unicellular
hosts which become infected with the sexual generation of the allo-
THE PATHOGENIC RHIZOPODA
301
gromia. These grow to maturity and form gametes which escape
and conjugate in the surrounding water, the resulting copula devel-
oping into a biflagellated organism which subsequently becomes
ameboid and grows into an adult allogromia (Fig. 116). While
there is reason to doubt some of the developmental stages of this life
history, the essential fact remains that here is a clearly defined rhizopod
D
"Allogromia," sp. (After Prandtl.) A, an individual from Ameba proteus with nucleus
undergoing fragmentation to form chromidia; B, aggregation of distributed chromatin into
secondary nuclei; C, A, Vampyrella, sp., infected with Allogromia, sp.; D, allogromia from
Ameba proteus shortly before ripening of the gametes.
FIG. 117
Single and multiple infection of ameba nuclei by Nucleophaga amebse. (After Penard.)
one stage of whose life history is passed as an intracellular parasite.
The history of its nucleus is important as furnishing a possible interpre-
tation of the distributed condition of the chromatin in neuroryctes and
cytoryctes. The cell plasm of this so-called allogromia becomes filled
with idiochromidia which are derived from the nucleus (Fig. 1 16, A, 5).
It is probable, as Doflein points out, that this organism is not an
302
THE PATHOGENIC RHIZOPODA
allogromia in the sense of Rhumbler's organism of that name, but that
it is a species of a still more striking intracellular rhizopod first
described by Dangeard in 1895, under the name of Nucleophaga
amebce and subsequently identified by Gruber, Penard, and Doflein.
It is a fairly common parasite of Ameba proteus and similar fresh-
water forms, penetrating the nuclei and forming relatively large
spherical reproductive bodies within the nuclear membrane (see
Fig. 117). The nucleus becomes more and more hypertrophied with
growth of the parasite, until finally the membrane gives way and the
mass of spores is left in the enucleated body of the host. Under
the name of Karyorydes cytorydoides the author described a similar
FIG. 118
*&&&«&&
• im
•-A ,-•'
Nucleophaga, sp., an intranuclear parasite in the macronucleus of Paramecium aurelia.
(After Calkins.)
intranuclear parasite of Paramecium aurelia in 1904 (Fig. 118).
Being unfamiliar at the time with Dangeard's work, I was under the
impression that the parasite in question was a new organism, and
described it as such, pointing out its close resemblance to the intra-
nuclear forms of the smallpox organism. There is no doubt, however,
that the parasite is a species of nucleophaga, and the name karyoryctes
must go. The striking similarity between the smallpox organisms and
these intranuclear parasites leaves little room to doubt the close rela-
tions of the two, while the structures and life phases, also, of neuroryctes
are almost identical with those of nucleophaga (Fig. 120). We are
justified, therefore, at least until more convincing evidence to the con-
trary is forthcoming, in regarding the Guarnieri bodies of vaccinia and
THE PATHOGENIC RHIZOPODA 303
smallpox, and the Negri bodies of rabies, as protozoan organisms of the
nucleophaga type.
Neuroryctes hydrophobia, Williams, the "Negri body," offers the
best evidence of the rhizopod affinities of these intracellular inclu-
sions, the mammalian brain cells, better than the skin cells, lending
themselves to rapid fixation and study.
When Pasteur and his immediate followers were working on the
antirabic serum in connection with the cure of hydrophobia, they
were obliged to wait from two to three weeks to tell whether the treat-
ment they were giving a supposed victim was necessary or not. This
was due to the fact that many days were required for the disease to
develop in laboratory animals inoculated with the virus of the sus-
pected animal, and, as may be imagined, it was a period of great
suspense for all concerned. In 1898 the inoculation period was
shortened to about nine days by Wilson's substitution of guinea-pigs
for rabbits, these animals taking the disease more quickly than rabbits
as used by Pasteur. Still, the time was far too long for diagnosis.
Today it is possible to determine rabies in "mad" animals off the
street in one-half hour. This wonderful practical advance in technical
methods of the laboratory is due to the discovery by Negri, in 1903,
of minute, characteristic inclusions in nerve cells of brain and spinal
cord of animals with rabies, and by a special "smear" method of
demonstrating them devised by A. W. Williams in 1904. The value
of the Negri bodies in diagnosis was quickly recognized by pathologists
throughout the wrorld, and contributions confirming and extending
Negri's discovery poured into the press. At the present time it is
recognized that these characteristic structures occur in 100 per cent,
of definite cases of street rabies, and that they are found nowhere else
in diseased tissues. WThat claims have these specific structures to be
regarded as organisms, and if organisms, where do they belong?
Negri regarded them as protozoa belonging to the class sporozoa, but
was not particularly clear as to their classification. Previous observers,
notably Di Vestea, in 1894, and Grigoriew, in 1897, had mentioned
structures in the nervous system of rabic animals and had described
them as protozoa, but the things observed were apparently quite unlike
the Negri bodies. Others, notably Volpino, in 1904, followed Foa,
Schaudinn, and Prowazek in their interpretation of the Guarnieri
bodies in smallpox, in believing that the real organism of hydrophobia
is the granule, more often multiple, found in the substance of the
"body," while the bulk of the "body" consists of material secreted by
the cell (hence Prowazek's term " chlamydozoa") about the parasite.
Williams' and Lowden's work, in 1906, and Negri's later papers leave
no grounds for such an interpretation, the former believing that the
granules represent distributed chromatin so characteristic of many
forms of protozoa, and placing the Negri bodies as protozoa in the
304 THE PATHOGENIC RHIZOPODA
suborder microsporidia, while Williams later gave the name Neuro-
ryctes hydrophobia to the Negri body.
The life history of Neuroryctes hydrophobias, despite the admirable
researches of Williams and Lowden, cannot yet be regarded as estab-
lished, nor do I think the stages observed by Negri, Williams, and
others justify us in assigning the organism to the sporozoa. The
variable form, the uninucleate condition leading to the condition of
distributed chromatin, and the budding phenomena are not charac-
teristic of sporozoa, but are common to parasitic rhizopods, and the
distributed chromatin is, in all probability, the idiochromidia, which,
we have seen, is a characteristic phenomenon of all rhizopods.
FIG. 119
I
.V
» •
6
9.
"Negri bodies," or Neuroryctes hydrophobise, in different stages of chromatin distribution.
(After Negri.)
The organism is most abundant in the region of Ammon's horn,
less abundant in the nerve cells of the cerebral cortex, cerebellum,
medulla, and cord. In many cases, especially in street rabies, the
organisms are large and ameboid in form, measuring up to 18 [J. (Wil-
liams) (to 23 fji, Negri), while minute forms, one-half a micron and less
in diameter, are characteristic of the organism after the virus has been
THE PATHOGENIC RHIZOPODA 305
repeatedly inoculated in animals of the same kind, and, owing to their
very minute size, such organisms are easily overlooked in this "fixed"
virus. It has been found by Remlinger, Schiider, Bertarelli, and
others that the virus is still effective after filtration through a Berkefeld
filter, a fact used as an argument against the specific pathogenicity of
these structures ; but the well-known variations in size of ameboid
protozoa and the small size of some stages of the organism, combined
with plasticity, which suggests ameboid movements, explains the
ability to pass a filter. Other protozoa, notably spirocheta and
trypanosoma, likewise pass through the Berkefeld. It is probable,
therefore, that an organism as variable as neuroryctes in size would
have some stages minute enough to escape filtration.
Negri was the first to make out the typical nucleus of the organism
and to call attention to the distributed granules, although he didjiot
FIG. 120
Form and size changes of the organism of rabies, with evidence of budding in
some cases. (After Williams and Lowden.)
interpret these correctly, Williams and Lowden, in 1906, being the
first to interpret them as granules of distributed chromatin. Negri,
in 1905, found that the nucleus has either a solid or reticular structure,
according to the success in staining (Fig. 119), while the cell body
contains a variable number of chromatin granules.
Reproduction of Neuroryctes hydrophobia, according to Williams
and Lowden, occurs by simple division and by budding. The division
is either an equal binary fission, in which nucleus and chromatoid
material are distributed to the two cells, although nothing like mitosis
was observed. In budding, small buds are pinched off, these buds
being single or multiple in number and containing granules of chro-
matin. The possibility of conjugation was suggested by Williams and
Lowden, and illustrated by figures, but it is equally possible, and more
probable, that the cases cited and illustrated were cells in division.
Finally, what appears to be a spore-containing cyst (Fig. 120) was also
described.
20
306
THE PATHOGENIC RH1ZOPODA
With the exception of the rhizopods, the entire range of protozoa
offers no analogies to these stages of neuroryctes. The series of forms,
following more or less closely the clinical history, agrees with the his-
tory of the parasitic amebse so far as the general outline goes, while
further details and careful study are necessary before the life history
can be stated. With our present knowledge it appears that the organ-
ism, as seen in its smallest forms, is uninucleate; that as it develops
into a larger ameboid form, the nucleus, either by fragmentation
(as in polystomella) or by diffusion (as in centropyxis or Entameba
histolyticci), gives rise to the diffused chromatin or idiochromidia. In
its mode of asexual reproduction it apparently follows Entameba
histolytica in binary fission and in budding. Its sexual reproduction
FIG. 121
"Negri bodies in nerve cells." (After Wolbach.) A X 2000; B X 1000.
is as yet unknown, the union of two cells, as pictured by Williams and
Lowden, being quite unlike any authentic account of conjugation in
rhizopods or sporozoa. The nature of the "fixed" form, also, is
enigmatical, but may be looked upon as a biological response on the
part of a highly variable organism to long-continued conditions of the
same nature.
Further work is needed on Neurorydes hydrophobias in respect to
the mode of division and budding, and with especial reference to the
nuclear phenomena; further, in respect to the nature of the permanent
forms, encysted or otherwise, which might be expected to exist in
animals shortly after recovery from rabies; and finally, work is needed
in connection with the sexual phenomena whereby the potential of
vitality of the parasite, and with it its capacity for further mischief,
is restored.
The early illustrations published by Negri, Luzzani, and others of
the organism of rabies showred an irregular body with numerous
THE PATHOGENIC RHIZOPODA 307
vacuoles (Fig. 121), and sections of infected tissue not properly fixed
and stained give no satisfactory pictures of the organism, the place of
chromatoid granules and nuclei being taken by the vacuoles. Such
a picture is duplicated by improperly fixed parasites of dysentery
vacuoles appearing in the place of the formed parts of the cell.
These, again, are duplicated by the ordinary appearance of the
smallpox organism as it appears in sections of the skin (Fig. 123).
This structure has been, and is still, next to the so-called protozoan
inclusions in cancer, the most widely discredited cause of any malig-
nant contagious disease. The reason for the skepticism on the part of
pathologists generally is that the organism presents no appearance
that can be identified with the ordinary cell, its lack of a vesicular
nucleus, its highly vacuolated appearance, and its development in
cells that are unquestionably pathological and degenerate, being, to
them, evidence against its protozoan or parasitic nature.
While a great deal of the skepticism is due to traditional conserva-
tism on the part of medical men and disinclination on their part to
accept any but conclusively demonstrable evidence, it must be stated,
with all respect, that there is among them a strong tendency to ignore
such evidence as we do have in regard to the nature of these structures,
and disinclination to accept such evidence as similar to structures in
other protozoa. The difficulties attending the observations on the
organism of smallpox are aggravated by the fact that it is apparently
an exclusively human disease, and further, that the organism is an
intracellular parasite which quickly disintegrates upon leaving its
normal environment. One phase of the disease, however — vaccinia-
is suitable for experimental study, but at best this is but a mild disorder
when compared with variola inoculata of apes or with variola vera of
man. Until some means of studying it on an experimental basis is
established, we must make the best of the morphological evidence
afforded by imperfectly fixed tissues from human beings, or from
material in experimental animals with variola inoculata and vaccinia.
The cell inclusions in the Malpighian layer of the skin were early
seen, interpreted as protozoa, and named Monocystis epithelialis
by Pfeiffer, in 1887, but as he found so-called protozoa in all kinds of
diseased tissue, his observation did not create much comment nor
stimulate research. It was quite otherwise with Guarnieri, in 1892;
this skilful investigator inoculated the corneal cells of guinea-pigs and
rabbits with vaccine virus and with pustule contents, and found that
the peculiar cell inclusions characteristic of smallpox and vaccinia
reappeared in each new epithelium inoculated. He found that the
structures appear with the greatest regularity in the vicinity of the
nucleus, the largest forms appearing around the point of inoculation,
while the most distant forms were the smallest. He regarded them as
protozoa, naming the form as observed in vaccinia, Cytorydes vac-
308 THE PATHOGENIC RHIZOPODA
cinicB, and in smallpox, Cytorydes variolas, but they were much more
often referred to in subsequent investigations as the Guarnieri bodies.
To Guarnieri, therefore, belongs the credit of placing smallpox and
vaccinia among the experimental diseases, and the stimulus given by
his work had an immediate effect. The majority of later investigators
wrere opposed to his conclusions, although many, including Pfeiffer,
Ruffer, and Plimmer, Clark, Monti, Wasielewsky, and others, believed
that the parasitic nature of the inclusions had been demonstrated.
The opponents based their criticisms upon the facts that no ameboid
movement could be observed, nor division phases, nor cellular struc-
tures (Hiickel, Foa, Mann, etc.), and they interpreted the Guarnieri
bodies as special secretions or degenerations resulting from a peculiar
transformation of a portion of the cell plasm under the stimulus of
the vaccine virus. Wasielewsky, in 1901, brought new support to the
view of Guarnieri by passing vaccine virus through forty-eight suc-
cessive transplantations, the thirty-sixth giving a successful vaccination
against smallpox. In each case the same inclusions were present in
the epithelial cells and in approximately the same number, indicating
that reproduction must have taken place. In 1903 Councilman, in
cooperation with seven other investigators, published an exhaustive
monograph on the pathology and etiology of smallpox, covering all
phases of the pathology of the disease, Brinckerhoff and Tyzzer
extending the experimental investigations of Guarnieri and Wasie-
lewsky to apes, and Calkins working out a tentative life history of
the parasite. Howard, in 1905, confirmed, independently, all of the
findings of Councilman and co-workers, and identified every stage of
life history of the organism.
So far as the organism is concerned, the most important discovery
of these investigators was made by Councilman, Magrath, and
Brinckerhoff, who found that in variola the inclusions are present both
in the cell bodies and in the nuclei, while in vaccinia they are present
only in the cell bodies. Councilman concluded that the intranuclear
position indicates a phase in the life history of the parasite which is
absent in the vaccinia cycle, and that this phase is responsible for the
greater malignancy of smallpox.
Calkins interpreted the parasite as a sporozoan belonging to the group
of microsporidia, and, as it now appears, gave an unnecessarily compli-.
cated account of the life history. Minchin('OG) regards it as more closely
related to the haplosporidia, because of the absence of polar capsules
and threads. The tentative life history worked out by Calkins was
formulated before the observations on the chromidia of rhizopods
were made and before the importance of this material of the cell was
established. In the light of our present knowledge it is much more
probable that the Guarnieri bodies are rhizopods, and that the com-
plicated changes which were earlier interpreted as pansporoblast
THE PATHOGENIC RHIZOPODA
309
formations are phases in the development of the idiochromidia.
Without going into the controversy again as to whether or not these
bodies are organisms, a matter, I may add, which is not yet settled to
the satisfaction of either pathologists or biologists, I will here give only
an interpretation of the questionable structures on the basis of their
probable relationship to neuroryctes and the other parasitic rhizopods
like nucleophaga, a relationship of which I am fully convinced.
The youngest forms of the parasite are small, spherical, and appar-
ently homogeneous granules measuring about half a micron. In
slightly larger forms a central granule can be detected more easily in
the cornea cells of inoculated rabbits than in the human skin. Dif-
ferentiation of the organism follows with growth, two substances of
the cell indicating differentiation. One of these is distinctly chroma-
FIG. 122
m
Section of the lower part of the epidermis, showing the cytoplasmic stage of cytoryctes
in the epithelial cells. X 1000.
toid, and becomes diffused throughout the body of the parasite at first
in irregular clumps (Fig. 122), later in a fine network (Fig. 123). Such
a structure is to be compared with the chromidiennetz of the rhizopods.
As with the chromidia material of the free forms, small, spherical,
deeply staining nuclei are formed out of this chromidial substance,
the organism then assuming an appearance strikingly like the figure
of arcella as given by Hertwig, in 1899 (compare Figs. 46 [p. 118] and
123). These granules are not artefacts, but developmental stages of
the organism. The proof of this is given by the fact that they may be
distinguished after any of the ordinary differential nuclear stains, but
more surely by the fact that their presence is indicated by photographs
made with the ultraviolet rays from unfixed and unstained living
tissue of the inoculated cornea. These granules were interpreted as
gemmules in 1904, and as vegetative spores or merozoites I would
310
THE PATHOGENIC RHIZOPODA
similarly interpret them today. The body ruptures and the spores are
liberated, to be carried by the blood into new regions of the skin, where
the cytoplasmic cycle is repeated.
In vaccinia it is apparent that this vegetative cycle is the only phase
of the life history, and this, in the same host at least, is limited in
extent. In variola, however, the vegetative cycle is repeated many
times, but finally the nucleus becomes infected and the parasites,
FIG. 123
Cytoryctes variolse in different stages of multiplication, outside first three figures and
outside last two figures of the nucleus. (Alter Calkins.)
FIG. 124
Two of the larger cytoplasmic forms of cytoryctes in the epithelium. The two dark bodies
in the middle showing reticular structure are the parasites. X1000.
like nucleophaga, develop in a more definite manner. Chromidial
fragments are formed, varying in size and character, while a residual
portion of the chromatin, analogous to the residual nucleus of free
living rhizopods, remains unformed and apparently useless (Fig.
123). The many rings, vacuolated structures, etc., which earlier were
interpreted as developmental phases of sporoblast and spores, I now
believe to be degeneration forms assumed by the parasite, possibly due
EXPLANATION OF FIGURES IN PLATE IV. (After Mallory.)
The drawings wore made with the Abbe camera lucida; projection on to table.
Zeiss apochromatic homogeneous immersion 2.0 mm., apert. 130, compensation
ocular 6.
FIGS. 1 and 2 show numerous large and small scarlet fever bodies (stained light
blue) in and between the epithelial cells of the rete mueosum. In Fig. 1 is a
large body in a lymph space of the curium just underneath the epidermis.
Several of the bodies suggest fixation while in amceboid motion.
FIGS. 3, "), and G are coarsely reticulated forms which may he degenerated
forms of the scarlet fever bodies, or stages in sporogony.
Fins. 4, S, and 9 probably represent stages preceding the radiate bodies. In
Fig. 0 I he bodies lie in a lymph space. It shows also four small forms which
have just got free from a rosette.
FIGS. 7, 10, 11, 12, 13, 14, and 1~> show different stages in the development of
the radiate bodies.
Fig. 10 is the earliest stage: there is a distinct central body and a definite,
regular arrangement of granules at the periphery. Figs. 7, 11, and 12 show a
little later stage of development; 11 and 12 are optical sections, while 7 is a
surface view. Moreover, in Fig. 7 the body lies free in a lymph space in the
curium. The segments begin to show a certain amount of lateral separation
from each other. Fig. 13 is a still later stage: the segments are increasing in
size and are more or less free from each other, although most of them arc still
attached to the central body. In Fig. 14 the segments are all free and enlarging,
although still grouped around the central body. In Fig. 15 the bodies are still
grouped around the central body, which is free and stains deeply with eosin.
PLA'i IV
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r •'
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ill
i
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.
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It
v
J-S
THE PATHOGENIC RHIZOPODA
311
to the toxins, infective material, etc., of the developing pustule, or pos-
sibly to ill preservation of the tissues. They are characteristic of the
later pustules, and their vacuolated appearance may be ascribed to the
same causes as that which produces poorly fixed and stained amebse,
or poorly stained Negri bodies. In the latter the better technique
of recent methods has shown that what appear as vacuoles in the
photographs are actually chromatin fragments (see Fig. 125), and by
analogy I would prophesy that when better methods of fixing and
staining the intranuclear form of cytoryctes are devised, a similar
chromatin distribution will be discovered. The tissues, such as we
worked upon four years ago, show many cellular structures like those of
the well-fixed and stained Negri body (compare Figs. 121, 122, 124 and
125), and although these were regarded formerly as aberrant forms of
the sporoblast structures, many of them were figured and described.
FIG. 125
A large cytoplasmic form of Cytoryctes variolse.
As with neuroryctes, further study with better methods must be
undertaken to complete the life history of cytoryctes; the important
sexual stages must be found, a hint to this end being given by the
changed nuclear phenomena of the intranuclear form (see difference
in nuclear processes of vegetative and sexual phases of entameba).
In this same category, finally, must be placed the interesting organ-
isms discovered by Mallory ('04) in the skin cells of scarlet fever
victims, and named by him Cyclasterion scarlatinalis (Plate IV). Also
the curious structures described by Prowazek in trachoma, forms
312 THE PATHOGENIC RHIZOPODA
similar to cytoryctes and neuroryctes, and all of which, together with
the cell inclusions of molluscum contagiosum, Prowazek includes
under the name of chlamydozoa or "mantle-covered" organisms.
This name represents a point of view held by many protozoologists
that the real organisms are the chromatin granules, while the material
about them is only coagulated nuclear material. The entire absence
of fortuitous strands of such nuclear material in the cell, apart from the
enclosed granules, together with the definite history which corresponds
exactly with the idiochromidia formation in other rhizopods, renders
this interpretation improbable.
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M. J. Morphologisches Jahrbuch.
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Z. A. Zoologischer Anzeiger.
Z. u\ Z. Zeitschrift fiir wissenschaftliche Zoologie.
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INDEX OF AUTHORS.
ADAMI, the cancer problem, 208
Afanassiew, structure of spirochetes. 228
Anderson, Rocky Mountain spotted
fever, 278
Argutinsky, ring forms in malaria organ-
isms, 283
BABES, Hematococcus bovis, 272
Baeslack, immunity to cancer in mice,
208
Bandi and Simonella, mode of life of
spirochetes, 230
Barker, classification, 38
Bashford, Murray, and Bowen, rhythms
of growth energy in cancer, 209
Behla, the cause of cancer, 207
the X-body, 211
Bertarelli, rabies problem, 305
Blanchard, Coccidioides inn nil is. 196
Boggs, Rocky Mountain spotted fever,
278
Bonhoff, spirochete nuclei, 225
Bonnevie, heterotvpical mitosis, 207
Borrel, cancer cell-inclusions, 211
division of spirochetes, 227
parasite theory of cancer, 207
spirochetes in cancer mice, 214
Borrel and Marchoux, transmission of
spirochetes, 250
Bosc, cancer parasites, 211
Boveri, centronuclei, 255
kinoplasmic structures, 29
parthenogenesis, 161
Bowhill and Le Doux, structure of
babesia, 270
Brady, classification, 39
Brasil, budding in gregarines, 183
Brauer, parthenogenesis, 161
Brefeldt, classification, 38
Breinl and Hindle, structure of babesia,
270
Breinl and Kinghorn, polymorphism in
spirochetes, 229
Brinckerhoff, cytoryctes and smallpox,
308
Brooks, Balantidium coli, 290, 292
22
Bruce, trypanosomes and disease, 261
Butschli, centrosomes in heliozoa, 30
flagella of spirochetes, 224
protoplasmic structure, 21
reducing divisions in infusoria, 166
significance of fertilization, 171
vitality in protozoa, 104
(' \UPEXTER, classification, 39
Carter, division of spirochetes, 227
nuclei in spirochetes, 225
transmission by ticks, 230
Cassagrandi and Barbagallo, dysentery
problems, 295
Castdlani, sleeping sickness, 264
('aiillery and Mesnil, cycle, 184
endogamy in actinomyxidse.
147
origin of trypanosomes, 233
Celli, melanin and malaria, 201
Certes, Spirocheta balbianii, 219
Christophers, form changes in Leish-
man-Donovan bodies, 200
infection of ova in babesia canis,
196
structures and life history of
babesia, 270
Clowes, immunity to cancer in mice, 208
Cohnheim, the cause of cancer, 207
Councilman and Lafleur, dysentery, 295
lysis in dysentery, 201
Craig, autogamy in ameba, 141
dysentery problems, 295
malaria problems, 287
Cuenot, conjugation of diplocystis, 189
Cull, conjugation of paramecium, 167
significance of fertilization, 172
DANGEARD, classification, 40
gamete formation, 127
nucleophaga amebre, 302
Danilewsky, the hemosporidia, 269
Darling, Histoplasma capsulatum, 278
Defrance, classification, 39
338
INDEX OF AUTHORS
Del Cinchon, introduction of quinine,
288
Di Vestea, negri bodies, 303
Dobell, exogamy in copromonas, 153
insertion of flagella, 46
Doflein, Balantidium coli, 290
effect of parasites on nuclei, 203
structure of babesia, 270
of trypanosomes, 258
Dogiel, budding in gregarines, 183
Donovan, organism of kala azar, 238
D'Orbignv, foraminifera, 37
Dujardin, F., classification, 18, 34
sarcode, 21
Dutton, Trypanosoma gambiense, 264
Dutton and Todd, transmission of
spirochetes, 230
Dutton, Todd, and Tobey, nuclei in
spirochetes, 225
structure of trypano-
somes, 254
EHRENBERG, spirocheta and spirillum,
217
Ehrlich, the cause of cancer, 207
Ellis, flagella of spirochetes, 224
Elpetiewsky, exogamy in arcella, 161
Ewing, cancer problems, 207
ring forms in malaria organisms,
283
F
FANTHAM, Babesia muris, 272
Spirocheta balbianii, 219
Farmer, Moore, and Walker, cause of
cancer, 207
fertilization of epithelial
cells, 208
Feinberg, cancer cell inclusions, 211
Fischer, classification, 39
flagella of spirochetes, 224
Flexner, dysentery, 299
Flu, types and structures of crithidia,
242'
Fliigge, transmission of germs, 195
Foa, negri bodies, 303
Forde, sleeping sickness, 264
Frenzel, classification, 40
GAYLORD, the parasite theory of cancer,
207
Spirocheta microgyrata gay lord i,
213
Gleditsch, classification, 38
Goldhorn, division in spirochetes, 227
Goldschmidt, anisogamy, 161
chromidia and sporetia, 118
Mastigina setosa, 120
Gotschlich, typhus fever and protozoa,
278
Grassi, malaria and mosquitoes, 279
origin of hemosporidia, 200
parthenogenesis in malaria, 162
Gray, classification, 39
Greeley, gamete formation, 127
Greenough, cancer cell inclusions, 211
Greenwood, digestion in infusoria. 80
Gregoriew, negri bodies, 303
Gregory, depression periods, 108
Grenadier, centrosome in heliozoa, 30
Griffiths, excretion and urea in infusoria,
83
Gualdo, melanin and malaria, 201
Guarnieri, cytorvctes, 229
variola, 300
Gugliemi, Babesia equi, 272
Guilliermond, fertilization in yeasts, 148
nuclei in bacteria, 221
HAECKEL, monera, 28
heliozoa, 35
Haecker, mitosis in cancer cells, 207
Haller, classification, 38
Hansemann, heterotypical mitosis in
cancer cells, 207
Hartmann, autogamy in entameba, 142
Hartmann and Kisskalt, origin of
hemosporidia, 201
Hartmann and Nagler, exogamy in
Ameba diploidea, 150
binucleata, 176
Hartog, function of vacuoles, 83
Hertwig and Poll, rhythms of growth
energy in cancer, 209
Hertwig, (.)., fertilization, 138
idioplasm, 124
Hertwig, R., chromidia in arcella, 119
classification, 38
depression periods, 108
dualism in nuclear materials, 124
fertilization of actinospherium, 148
organotype and cytotype, 203, 208
use of term chromidia, 116
Herxheimer, division of spirochetes, 226
Hintze, Lankesterella, 199, 248
Hoffmann, division of spirochetes, 226
Howard, cytorvctes and smallpox, 308
JAHN, exogamy in mycetozoa, 150
Jennings, on irritability, 84
INDEX OF AUTHORS
Jensen, transplantable mouse tumor,
206
Joukowsky, physiological death, 131
Jones, R., classification, 39
KARLINSKY, structure of spirochetes,
228
Keysselitz, endogamy in mvxosporidia,
146
exogamy in trypanoplasma, 160
parthenogenesis, 164
reducing divisions, 166
spirochete structure, 219
structure and history of trypano-
somes, 254
King, Rocky Mountain spotted fever/
278
Kinoshita, structure and life history of
babesia, 270
Klebs, fertilization as explanation of
cancer, 208
gamete formation, 127
Kleine, cultivation of babesia, 274
Koch, division in spirochetes, 227
East Coast fever, 272
infection of ova of ticks, 196
species of trypanosomes, 215
transmission of ticks, 230
Kolliker, classification, 18, 34
Kossel and Weber, babesia, 274
Kriinzlin, exogamy in mycetozoa, 150
Krzysztalowicz and Siedlecki, cycle
of Treponema pallidum, 229
flagella in spirochetes, 224
Kuschakewitsch, sporoducts in Gre-
garina cuneata, 191
Kutscher, flagella of spirochetes, 224
LABBK, classification, 57
Lamarck, classification, 39
Lankester, drepanidium (Lankesterella),
279
Laptschinsky, structure of spirochetes,
228
Laveran, division of spirochetes, 227
the malaria problems, 279
origin of hemosporidia, 200
Laveran and Mesnil, organism of kala
azar, 238
spirochetes, 219
Leger, chromidia formation in gre-
garines, 121
crithidia, 242
divison in gregarines, 183
endogamy in aetinomyxidse, 147
exogamy in ophryocystis, 154
Leger, genus trypanosoma, 244
origin of trypanosomes, 233
sporulation in gregarines, 189
Leger and Dubosq, eflect of parasites
on nuclei, 203
Leishman, form changes in Leishman-
Donovan bodies, 200
organism of kala azar, 238
Leuckart, classification, 34
Levaditi, division of spirochetes, 227
spirochetes in relapsing fever and
spirillosis of chicks, 197
Lewis, trypanosomes, 261
Lignieres, structure of babesia, 276
Lister, chromidia in polvstomella, 121
Loesch, ameba coli and dysentery, 295
Lowenthal, endogamy in n^cetozoa,
148
Spirocheta microgyrata, 214
Lounsbury, transmission of babesia, 276
Liihe, mode of life of spirochetes, 230
origin of hemosporidia, 199
structures, history, etc., of try-
panosomes, 248
trypanosomes, 244
M
McCLUNG, sex differentiation, 126
significance of synapsis, 170
Mclntosh, flagella in spirochetes, 224
MacCallum, life history of trypano-
somes, 266
MacNeal, structure and history of try-
panosomes, 253
MacWeeney, nuclei of spirochetes, 225
Mallory, scarlet fever organisms, 311
Malmsten, Balantidium coli, 290
Manson, environmental effects on pro-
tozoa, 194
the malaria problems, 279
Marchiafava and Celli, the malaria
problems, 279
Mast, function of trichocysts, 27
Maupas, conditions of conjugation, 172
depression periods, 108
Mesnil, origin of hemosporidia, 200
Metcalf, opalina encystment, 188
Metchnikoff, age, 135
digestion in infusoria, 80
organism of malaria, 279
Migula, units of spirochetes, 228
Miller, Hepatozoon perniciosum, 199,
269
Minchin, conjugation in plasmodium,
287
cytoryctes and smallpox, 308
encystment of trypanosoma, 188
origin of trypanosomes, 247
position of' Herpetomonas muscse
domestics?, 237
340
INDEX OF AUTHORS
Minchin, structures, life history, encyst-
ment of trypanosomes, 248
transmission of monocystis, 198
Minchin and Fantham, Rhinosporidium
kinealyi, 185, 195
Miyajima, cultivation of babesia, 274
Montesano, melanin and malaria, 201
Montfort, classification, 39
Montgomery, sex differentiation, 126
Moore and Breinl, fertilization in Try-
panosoma gambiense, 163
reproduction in Trypanosoma
gambiense, 188
structure of trypanosomes, 254
Mott, trypanosomiasis, 268
Muhlens, polymorphism in treponema,
229
Musgrave and Clegg, dysentery, 300
N
NAGLER. See Hartmann and, 150
Negri, hydrophobia, 300
Neresheimer, exogamy in opalina, 154
Nierenstein, digestion in infusoria, 80
Nocard and Motas, babesia and fever,
273
Nocht, malaria organisms, 284
Norman, classification, 39
Nosske, cancer cell inclusions, 211
Novy, life history of trypanosomes,
structures, cultivation, etc., 248
Novy and Knapp, structure of spiro-
chetes, 225
division, 227
Novy, MacNeal, and Torrey, relation
of herpetomonas and trypanosoma,
233
Nusbaum, Schaudinella henlea?, 189
Nuttall, mode of life of spirochetes, 230
Nuttall and Graham-Smith, structure
and life history of babesia, 270
OERTEL, the cancer problem, 208
Olive, exogamy in mycetozoa, 150
Opie, Balantidium coli, 290
PASTEUR, silkworm' disease, 196. See
Preface.
Patton, form-changes in Leishman-
Donovan bodies, 200
organism of kala azar, 239
structures and history of babesia,
272
transmission of protozoa, 197
Patton, types and structures of crithi-
dia, 242
Perrin, Spirocheta balbianii, 219
Pfeiffer, Monocystis epithelialis, 307
Piana and Galli Yalerio, Eabesia canis,
272
Pianese, cancer cell inclusions, 211
Prandtl, allogromia, 300
Prenant, kinoplasmic structures, 29
Prowazek, chlamydoza, 312
dysentery, 299
endogamy in plasmodiophora, 147
exogamy in trypanosomes, 160
flagella in spirochetes, 255
Herpetomonas muscse domesticse,
237
male trypanosomes, 163
negri bodies, 303
structure of spirochetes, 229
structures and life history of try-
panosomes, 254
RECKLINGHAUSEN, fertilization of epi-
thelial cells, 208
Remlinger, rabies problem, 305
Reuss, classification, 39
Ribbert, the "cause" of cancer, 207
Ricketts, Rocky Mountain spotted
fever, 278
Rixford and Gilchrist, Coccidioides
immitis, 195
Robertson, exogamy in pseudospora,
154
structure and history of trypano-
somes, 247
Rogers, form, changes in Leishman-
Donovan bodies, 200
systematic position of Leishmania,
' 234
Ross, malaria and mosquitoes, 279
organism of kala azar, 239
Roux, idioplasm, 124
Ruffer and Walker, cell inclusions in
cancer, 211
S
SAN FELICE, cancer cell inclusions, 211
Sandahl, classification, 39
Sars, classification, 39
Sawtschenko, cell inclusions in cancer,
211
Schaudinn, acute enteritis in moles, 203
autogamy in rhizopods, 141
centrosomes in heliozoa, 31
chromidia function, 116
classification, 40
dysentery problems, 294
INDEX OF AUTHORS
341
Schaudinn, endogamy, 148
exogamy in actinophrys, 153
in rhizopods, 154
idiochromidia in rhizopods, 121
Leydenia gemmipara, 213
malaria problems, 280
origin of hemosporidia, 200
parthenogenesis in malaria, 162
in trypanosoma, 162
sex in protozoa, 126
structure of babesia, 274
the syphilis organism, 218
trypanosomes, structure and life
history, 254
yellow fever, 230
Schlumberger, dimorphism in forami-
nifera, 114
Schneider, classification, 39
Schoutedan, structure of dimorpha, 30
Schrader, classification, 38
Schroder, fertilization in myxosporidia,
143
reducing divisions in same, 166
Schuder, rabies problem, 305
Schultze, F. E., centrosomes in helio-
zoa, 30
classification, 38
Schultze, M., protoplasm, 21
Sergent, life history of trypanosomes,
266
Trypanosoma nocture, cycle, 200
Shibata, intracellular mycorhizse, 203
Shiga, dysentery, 299
Siddall, classification, 38
Siebert, flagella in spirochetes, 224
Siedlecki, Caryotropha mesnili, 202
chromidia formation in coccidiiclia,
121
Siegel, "cytoryctes luis," 229
Silberschmidt, structure of spirochetes,
229
Simpson, physiological death, 131
species of paramecium, 112
Sjobring, cell inclusions in cancer, 211
Smith and Kilbourne, life cycle of
babesia, 270
transmission by ticks, 196
Soudakewitsch, cancer cell inclusions,
211
Spencer on growth, 87
Starcovici, the name babesia, 272
Stengel, Balantidium coli, 290
Stevens, sex differentiation, 126
Stiles, Rocky Mountain spotted fever,
278
spirochetes and bacteria, 232
Stimpson, spirochetes and vellow fever,
231
Stole, actinomyxidae, 147
Strasburger, kinoplasm, 29
Strong, Balantidium coli, 290
Sutton, significance of synapsis, 170
Swellengrebel, spirochete structure, 219
THEILER, Balx-sin. parvum, 272
transmission of spirochetes, 230
Thelohan, function of threads in polar
capsules, 193
Topsent, classification, 38
Trentepol, classification, 38
Tullock, sleeping sickness, 264
Tyzzer, cytoryctes and smallpox, 308
spirochetes in cancer mice, 214
VAN BENEDEN, reduction of chromo-
somes, 164
Van Tieghem, classification, 38
Volpino, negri bodies, 303
Von Leyden, the cancer problems, 207
Leydenia gemmipara, 213
Von Mohl, protoplasm, 21
W
WALDEYER, parthenogenesis of cancer
cells, 208
Walker and Boys, classification, 39
Ward, transmission of protozoa, 197
Warming, "units" of spirochete struc-
ture, 228
Wasielewsky, cytoryctes and smallpox,
308
Wechselmann and Lowenthal, nuclei
in spirochetes, 225
unit structure, 228
Weismann, idioplasm, 124
natural death, 134
constitution of chromosomes, 170
Welch, Plasmodium falciparum, 288
Wenyon, autogamy in ameba, 142
entameba, 298
spirochetes in cancer mice, 214
Williams, Neuroryctes hydrophobise, 303
Williams and Lowden, negri bodies, 303
Wilson, kinoplasmic structures, 29
sex and inheritance, 126
Wilson and Chowning, Rocky Mountain
spotted fever, 278
Woodcock, kinetonucleus, 29
trypanosomes, 244
Woodruff, depression periods, 108
renewal of vitality, 131
Woronin, classification, 38
malaria problems, 287
organism of kala azar, 238
ZETTNOW, flagella of spirochetes, 224
division of spirochetes, 227
Ziemann, malaria, 284
Zopf, classification, 38
structure of spirochetes, 228
GENERAL INDEX,
A
ACANTHOCYSTIS, budding and centro-
some formation, 31
Acanthonida, classification, 41
Acanthosporida?, classification. 61
Acephalimr, classification, 58
Acinetid«, classification, 56
Acrasise, classification, 38
Acrasis, classification, 38
Actinellida, classification, 41
Actinobolus radians, 76
apparent choice of food, 77
Actinocephalida>, classification, 60
Actinocephalinu1, classification, 60
Actinomyxidia, classification, 68
Actinomyxid;i\ spores, 193
Actinophrys sol, conjugation, 152
kinetic structures, 32
Actinopoda, classification, 40
Actinospherium eichhornii, chromidia,
116, 117
fertilization, 149
Actipylea, classification, 11
Acytosporea, classification, 65
Adelea ovata, exogamy, 159, 183
Adinida, classification, 49
Aggregatid:e, classification, 59
Allogromia sp., 75, 301
Alveolina, classification. :>'.»
Ameba actinophora, 23
autogamy, 122
budding and chromidia, 139
diploidea, exogamy, 151
idiochromidia, 121
protoplasmic structure and division,
120
pro tens, 17
autogamy, 141, 144
idiochromidia formation, 122,
125
tentaculata, 23
vespertilio, 203
Amebea, classification, 39
Angiosporea, classification, 59
Animals and plants, 72
Anisogamy, 126
Anisonema vitrea, 43
Anthorhynchinae, classification, 60
Aphrothoraca, classification, 40
Arcella vulgaris, copulation, 119
gametic nuclei, 118
plastogamy, 117
shell material, 24
Arcyria cinerea, exogamy, 150
Articulina, classification, 39
Aspidisca hexeris, 49
Asporscystinea, classification, 62
Assimilation in protozoa, 81
Astasiidse, classification, 48
Astomea, classification, 47
Astrorhiza, classification, 39
Astrorhizida, classification, 38
Atoxyl, use in sleeping sickness, 268
Autogamy, 139
in A. limax, 141
in A. proteus, 141
in myxosporidia, 143
Auto-infection, definition, 179
Axiopodia in heliozoa, 32
in classification, 35
BABESIA and transmission, 196
canis, flagellum, 176, 272
genera, species and life histories,
270
Balantidium coli, 290
entozoon, 291
Bedbugs and kala azar, 199
Bertramiidse, classification, 68
Bikecidse, classification, 47
Binucleata, 176
Bird malaria, 287
Black fever, 277
sickness, 238
Blepharoplast in babesia, 277
Blue fever, 277
Bodo caudatus, 43
saltans, exogamy, 153
Botryoida, classification, 41
Budding, a form of division, 89
in entameba histolytica, 94
in rhizopods, 92
in spherastrum, 92
in suctoria, 95
Bursaria truncatella, size, 19
Bursaridn?, classification, 54
344
GENERAL INDEX
( ' \GE infection in mouse cancer, 208
Camptonema nutans, origin of axio-
poclia, 33
Cancer and protozoa, 204
cell inclusions, 212
Cannopylea, classification, 42
Caryotropha mesnili, 202
schizogony, 183
Caryozoic parasites, 176
Cell autonomy, theory of cancer, 208
division, causes, 87, 88
in paramecium, 88
Centralkorn, centrosome in heliozoa, 30
Centronucleus, see kinoplasmic struc-
tures, 29
Centropyxis aculeata, chromidia, 116
( Vphalinse, classification, 59
Cephalont, definition, 177
Ceratiomyxa hydnoides, exogamy, 150
Ceratium tripos, 24
Ceratomyxidse, classification, 66
Cercomonadidse, classification, 47
Cercomonas dujardinii, exogamy, 154
Chalarathoraca, classification, 40
Chiliferidse, classification, 53
Chilomonas paramecium, protoplasmic
structure, 120
Chilostomellida, 141
Chitin, basis of shells and tests, 24
Chlamydodontidse, classification, 52
( 'hlamydomyxa, classification, 38
Chlamydophora, classification, 40
Chlamj-dophrys stercorea, chromidia,
116, 213
life history, 294
( 'lilamydospore, definition, 183
Chlamydozoa, 303
Chloroflagellida, classification, 48
Chloromyxida^, classification, 67
Choanoflagellata, classification, 48
Chromatophores, protoplasmic struc-
ture, 26
Chromidia at period of maturity, 115
in rhizopods, 116
Chromosomes and inheritance, 89
in trypanosoma, 255
( 'liromulina flavicans food-getting, 72
( 'hrvsoflagellida, classification, 48
Cilia and classification of infusoria, 49
Ciliata, classification, 52
Cirri, protoplasmic structure, 23
Club-root and cancer, 210
Club-shaped bodies in babesia, 277
Coccidiidse, classification, 63
Coccidiidia, classification, 62
Coccidioides immitis, 195
Coccidium schubergi, exogamy, 160
life cycle, 180
life history, 99
Cochliopodium, 23
Codonecidse, classification, 47
Codosiga cymosa, 20
Coelosporiidae, classification, 68
Coelozoic parasites, 176
Coitus, mode of transmission of try-
panosomes, 265
Collida, classification, 40
Colony formation, 19
Colors in -water due to protozoa, 26
Conjugation, 137
Consciousness, 71
Contractile vacuoles, function, 83
Griffiths, Hartog interpreta-
tion, 83
Copromonas subtilis, cycle, 188
exogamy, 153
Copromyxa, classification, 38
Cornuspira, classification, 39
Craterium, classification, 38
Crithidia, genus, 241
gerridis, 242
melophagia, 241
subulata, 233
Cyclammina, classification, 39
Cyclospora caryolytica, 183
cause of acute enteritis in moles,
203
Cyrtoida, classification, 42
Cystoflagellata, classification, 49
Cytomere, definition, 183
Cytoryctes variola-, 202, 309, 310, 311
Cytozoic parasites, 176
DACTYLOPHORID.E, classification, 60
Dallingeria drysdali, exogamy, 154
Death in protozoa physiological and
germinal, 130
Dendrocometidsc-, classification, 56
Dendrosomidsp, classification, 56
Depression periods in protozoa, 108
action of salts and renewed vitality,
131
Desmothoraca, classification, 40
Deutomerite, definition, 178
I >ict yostelium, classification, 38
Dictyotic moment in shell formation, 24
Didinium nasutum, food-getting, 74
Didymium, classification, 38
Didymophyidae, classification, 60
Diffuse flagella, 45
Digestion in foraminifera, 78
in infusoria, 79
MetaJnikoff on acid and alkaline, 80
in mycetozoa, 80
Dileptus, division of distributed nucleus,
92, 93
effects of starvation, 19
Dimorpha mutans, 32
GENERAL INDEX
345
Diniferida, classification, 49
Dinoflagellata, classification, 48
Dinophysidae, classification, 49
Diplophrys, classification, 38
Discoida, classification, 41
Disporea, classification, 66
Distomea, classification, 47
Division centre. See Kinoplasmic
structures, 29
in protozoa, 87
pathological, in paramecium, 133
Doliocystidse, classification, 62
Dourine in horses, 196
Dum dum fever, 238
Dysentery in apes, 292
in man, 295
EAST Coast fever, 272
Ectoplasm, cortical modifications, 22
Effects of protozoan parasites on host,
201
Eimeridse, classification, 63
Eleutheroschizon dubosqui, 182
Enchelinidse, classification, 52
Encystment and fertilization, 188
general statement, 18
Endogamy in actinospherium, 149
in myxosporidia, 146
in paramecium, 149
in plasmodiophora, 147
in protozoa, 146
Endogenous cycle of parasites, 181
Endospore, definition, 189
Entameba and dysentery, 295
autogamy, 141
coli, chromidia, 116
muris, 141, 142
Enterozoic parasites, 176
Ephelota biitschliana, budding, 95
Epimerite, definition, 178
Estivo-autumnal fever and plasmodium
falciparum, 283, 286
Euglena, division, 92
sanguinea, cause of red color in
water, 27
viridis, centronucleus type, 30
Euglenida, classification, 48
Euglypha alveolata, 23
Eugregarince, classification, 58
Euplotes patella, division, 91
Euplotidse, classification, 55
Excretion in protozoa, 83
Exogenous cycle of parasites, 181
Exospore, definition, 189
F
FERTILIZATION by autogamy, 139
by endogamy, 146
by exogamy, 150
Fertilization in protozoa, 137
significance of, 171
Fever charts, malaria, 280, 281
Filoplasmodia, classification, 38
Flagella of babesia, 270
of bacteria, 223
in classification, 42
of spirochetes, 223
Food-getting methods, 71
Foraminifera, classification, 38
Fuligo, classification, 38
GAMETOCYTE, definition, 180
Globigerinida, classification, 39
Glossina palpalis, 264
longipennis, 265
Glugeida?, classification, 68
Gonium pectorale, ontogeny, 97
Gregarina cuneata, gamete formation,
121, 191
Gregarinida, classification, 57
Gromia, classification, 38
Gromiida, classification, 38
Growth and reproduction, 86
Spencer on, 87
Guarnieri bodies in smallpox, 300
Gymnamebida, classification, 39
Gymnophrys, classification, 38
Gymnospore, definition, 183
Gymnosporea, classification, 59
Gymnostomina, classification, 52
HALIPHYSEMA, classification, 39
Halteria grandinella, food of Actino-
bolus radians, 77
Halteriidee, classification, 54
Haplophragmium, classification, 39
Haplosporidia, classification, 68
Haplosporidiidse, classification, 68
Haustoria in parasites, 176
Helcosoma tropicum, 238
Heliozoa, classification, 40
Hematozoic parasites, 177
Hemosporea, classification, 65
Hepatozoon perniciosum, 199, 269, 271
Herpetomonas, 233, 236
donovani, 238
variations in habitat, 175, 199,
240
(Leishmania) donovani, the cause
of kala azar, 34
muscse domesticse, 235
species of, 236
Heteromastigida, classification, 47
Heteromonadidae, classification, 47
Heterotrichida, classification, 53
346
GENERAL INDEX
Heterotypical mitosis in cancer, 207
Hexamitus intestinalis, exogamy, 154
Hippocrepina, classification, 39
Histoplasma capsulatuni, 278
Holophyra multifilius, sporulation, 98
Holotrichida, classification, 52
Hyalopus dujardinii, endogamy, 148
Hydrophobia and protozoa, 293
Hypocomidse, classification, 56
Hypotrichida, classification, 54
IDIOCHROMIDIA, methods of formation.
118
significance, 122
Idioplasm in metazoa and protozoa, 124
Immortality in protozoa, 106
Indigestion in Paramecium aurelia, 81
Int'usoria, classification, 52
Irritability, 84
Hartog on, 84
Isogamy, 126, 153
Isosporida?, classification, 63
Isotrichidse, classification, 53
KALA azar, 238
Karyogonad or gonad nucleus, 28
Karyoryctes cytoryctoides, 302
Keramosphera, classification, 39
Kinetonucleus, centre of cell activity,
29, 33
Kinoplasm, kinetic substance of the
cell, 29
Klossidie, classification, 63
Klossiella muris, schizogony, 183
LABYRINTHULA, classification, 38
Lagenida, classification, 39
Lamblia (megastoma) entericum, 291
intestinalis, exogamy, 154
Lankesteria ascidise, 181
Larcoida, classification, 41
Latent bodies in trypanosomes, 259
malaria, 2s 7
Leishmania, 233
Leukocytozoon ziemanni, 230
Leydenia gemmipara in cancer, 213
a stage of chlamydophrys, 295
Licknaspis giltochii, 36
Lichnophoridae, classification, 55
Lieberkuhnidse, classification, 54
Life cycle of parasites, 178
Lissoflagellata, classification, 46
Lituola, classification, 39
Lituolida, classification, 39
Lobopodia, in classification, 35
Loftusia, classification, 39
Lysis produced by protozoa, 201
M
MACROSPHERIC and microspheric shells,
114, 115
Malaria and its causes, 279
problems, 279
Marsipella, classification, 39
Mastigella vitrea, chromidia formation,
119
Mastigina setosa, chromidia formation,
119
Mastigophora, classification, 46
Maturation in protozoa, 137
phenomena, 164
Maturity in protozoa, 113
Melanin and malaria, 201
Membranes, cirri, etc., 50
protoplasmic structure, 22
Menosporidse, classification, (\'2
Merozoite, definition, 99, 180
Metacinetidse, classification, 56
Microgromia, classification, 38
Micronucleus of trypanosomes, 255
Microsporidia, classification, 67
Microthoracidae, classification, 53
Miescher's tubules, cvsts of sarco-
cystis, 186
Miliolida, classification, 39
Mitrophanow, origin of trichocysts, 27
Molluscum contagiosum and protozoa,
293
Monadida, classification, 46
Monera, 28
Monocystis ascidia*, exogamy, 155
Monopylea, classification, 41
Monostomea, classification, 17
Mosquitoes and malaria, 198,
and yellow fever, 199
Multicilia lacustris, 291
Mycetozoa, classification, 38
Myonemes and contractile substance, 52
protoplasmic structure, 23
Myriophrys paradoxa, 37
Myxidiidse, classification, 67
Myxobolidse, classification, 67
Myxobolus pfeifferi, 145
.Myxomycetes, classification, 38
M}-xosporidia, classification, 66
spore formation, 192
N
NAGANA, tsetse fly disease, 261
Nassoida, classification, 41
Negri bodies, 300, 304, 305, 306
GENERAL INDEX
347
Neosporidia, classification, 66
Neuroryctes hydrophobias, 202, 304
Noctiluca miliaris, division, 91
nucleus in mitosis, 92
Nubecularia, classification, 39
Nuclearia, classification, 38
Nuclei, chromatin and chromidia, 28
in digestion, 82
Nucleophaga amebse, 301
Nummulitida, classification, 39
ODORS and taste in drinking water, 27,
73
Oikomonas termo, 70
food-getting, 74
Old age, in Onychodromus grandis, 127
in Paramecium aurelia, 127
in protozoa, 127
Oligosporogenea, classification, 68
( >ligotrichina, classification, 54
Opalina intestinalis, encystment, 188
ranarum, exogamy, 154
Opalinida?, classification, 53
Operculina. schematic shell structure,
26
Ophryocystis mesnili, 190
exogamy, 154
Ophryodendridae, classification, 56
Ophryoscolecidae, classification, 54
Orbiculina, classification, 39
Qrbitolites, classification, 39
"Organisms" of cancer, 205
Osculosa, classification, 41
Oxytrichidae, classification, 54
PANSPOROBLAST, definition, 143
Paramecidse, classification, 53
Paramecium aurelia, life cycle, 104
105
curve of vitality, 107
at depression period, 109
caudatum, a variety, 112
old age, 127
first generation, 129
conjugation, 156
reduction, 166, 168
parasites, 302
Parasite theory of cancer, 209
Parasitism, 174
Parthenogenesis, 161
Parkeria, classification, 39
Pathogenic flagellates, 215
Pedogamy in protozoa, 146
Pelomyxa palustris, size, 18
Peneroplis, classification, 39
Peranema trichophorum, 17
Peronemidae, classification, 47
Peredinidse, classification, 49
Peripylea, classification, 40
Peritrichida, classification, 55
Peritromidae, classification, 54
Pheoconchia, classification, 42
Pheocystina, classification, 42
Pheogromia, classification, 42
Pheospheria, classification, 42
Phosphorescence in sea water, 27
Phytoflagellata, classification, 48
Phytomastigophora, classification, 48
Physiology of protozoa, 69
Pileocephalinie, classification, 60
Pilulina, classification, 39
Piroplasmosis hominis, 277
Plagiotomida?, classification, 54
Plasmodiophora brassicse, classifica-
tion, 38
endogamy, 147, 148
plant tumors, 202, 209
Plasmodium malaria-, vivax, falciparum.
279
vivax, parthenogenesis, 162
Plastids, protoplasmic structure, 26
Platoum, classification, 38
Plectoida, classification, 41
Pleuronema chrysalis, 50
Pleuronemidse, classification, 53
Podophyridse, classification, 56
Polydinida, classification, 49
Polymastigida, classification, 47
I'olyphragma, classification, 39
Polysporea, classification, 66
Polysporogenea, classification, 68
Polystomella crispa, sporulation, 114,
life cycle, 123
Polytrichina, classification, 54
Pontomyxa, classification, 38
Porospora gigantea, size, 19
Porulosa, classification, 40
Primite, definition, 178
Proteomyxa, in classification, 38
Protogonoplasm, 118
Protoplasmic age of protozoa, 102
definition, 104
Protozoa, classification, 34
definition of, 17
protoplasmic structure of, 21
size of, 18
Primoida, classification, 41
Primophracta, classification, 41
Pseudopodia, in classification, 35
Pseudospora, classification, 38
volvocis, exogamy, 154
Pyrsonympha vertens, 291
Pyxinia mobiuszi, 177
sp., 17
Q
QUARTAN fever and Plasmodium
malaria-, 282, 284
34S
GENERAL INDEX
Quinine, effects on malaria organisms,
288
RADIOLARIA, classification, 40
Raphidiophrys elegans, 70
Reducing divisions in metazoa and
protozoa, 164
in entameba, 165
in heliozoa, 166
Reproduction, kinds of, 90
Rhabdammina, classification, 39
Rheophax, classification, 39
Rhinosporidium kinealyi, 185
Rhizomastigidse, classification, 46
Rhizopoda, in classification, 38
Rotalida, classification, 39
S
SACCAMMINA, classification, 39
Sarcocystis muris, 186
Sarcode, 21
Sarcodina, in classification, 38
Sarcosporidia, classification, 68
Scarlet fever, 311
organisms of, 311
Schaudinnella henlese, 189
Schewiakovella schmeili, 184
Schizocystis sipunculi, 182
budding, 183
Schizogony, definition, 179
Schizogregarinse, classification, 57
Sciadiophorinfe, classification, 60
Sex differentiation in protozoa, 126
Shells and tests, protoplasmic struc-
ture, 22
Shepheardella, classification, 38
Silicoflagellida, classification, 48
Smallpox and protozoa, 293
organisms, 300
Spherastrum, nuclear division, 31
Spheroida, classification, 40
Spheromyxa labrazesi, fertilization, 143,
145
Spherophracta, classification, 41
Spheropylida, classification, 41
Spherozoea, classification, 40
Spirocheta anodontce, 220
balbianii, 222
structure, 220, 22
division, 226
duttoni and transmission by ticks,
197
gallinarum and duttoni, 221, 227
genus, 217
flagella, 223
life history, 228
microgyrata gaylordi, 213
Spirocheta, mode of life and change of
hosts, 229
nuclei, 225
relation to bacteria, 231
species, 219
Spirochetida, classification, 46
Spirochonidse, classification, 55
Spiroloculina, classification, 39
Spores, misuse of term, 99
Sporetia. See Idiochromidia, 118.
Sporoducts, formation and function, 192
Sporogony definition, 179
Sporont, definition, 177
Sporozoa, classification, 56
Sporozoite, definition, 99, ISO
Sporulation, a form of division, 89, 96
in Tillina magna, 97
in flagellates, 98
in sporozoa, 98
Spotted fever, 277
Spyroida, classification, 41
Stemonitis, classification, 38
StentoridiP, classification, 54
Stephoida, classification, 41
Stictosporina>, classification, 60
Stimuli, effects of, 85
Stylonvchia mytilis, 17
Stylorhynchidse, classification, 62
Suctoria, classification, 55
food-getting, 74
Surra, disease of horses, 267
Synapsis in protozoa, 170
Syiiura uvella, 72
S\ | ihilis organism, Treponema pallidum,
'226
Syringammina, classification, 39
TELOSPORIDIA, classification, 57
Tentacles and the suctoria, 50, 51
Tertian fever and plasmodium vivax,
281, 282
Testacea, classification, 39
Tetramitus rostratus, exogamy, 154,
155
Texas fever, 272
Textularia, classification, 39
Ticks and the transmission of babesia,
275
Tintinnidae, classification, 54
Tokophrya quadripartita, 17
Trachelinidse, classification, 52
Trachoma and protozoa, 293
Transmission of protozoa by air, 195
by coition, 196
by contact, 195
by inheritance, 196
by intermediate hosts, 198
Treponema pallidum and syphilis, 197,
226
GENERAL INDEX
349
Trichia fallax, exogamy, 150
Trichocysts and trichites, 27
Trichomonas intestinalis, exogamy, 154
Trichonymphinea, classification, 48
Trichospherium sieboldi, exogamy, 154
Trichostomina, classification, 53
Triloculina, classification, 39
Trophonucleus, vegetative function, 28
Trypanophis grobbini, origin of undu-
lating membrane, 43
Trypanosoma agglomeration, 2G1
borreli, 246
changes in habitat, 175
effects on host in sleeping sickness,
267
equiperdum, cause of dourine, 196
form changes, 257
gambiense, 264
stages in division, 90
genus, 244
grayi, encystment, 1SS
lewisi, male forms, 163
life cycle, 261
list of species, 250
motile apparatus, 253
noctuac*, 247
exogamy, 160
nuclei, 255
parthenogenesis, 162, 163
raise, 45, 247
reproduction, 260
thcileri, 245
Trypanosomatida, classification, 47
T rypanosomiasis, 267
Tsetse flies, 264, 26.~>
fly and nagana, 199
Tsetse fly and sleeping sickness, 199
Typhus fever and protozoa, 278
ULTRAMICROSCOPIC protozoa, 210, 231
Undulating membranes, 234
Urceolinidse, classification, 55
Urea in infusoria, 83
experiments of Griffiths, 83
Urocentridte, classification, 53
Uroglena Americana, 20
Urnulinidse, classification, 56
VACUOLES, protoplasmic structure, 28
Valvulina, classification, 39
Vampyrella, classification, 38
Vertebralina, classification, 39
Virgulina, classification, 39
Vorticella campanula, food-getting, 73
Vorticellidse, classification, 55
Yorticellidinse, classification, 55
YELLOW fever, 231
Youth, maturity, and age in protozoa,
110
ZOOMASTIGOPHORA, classification, 46
Zygoplast, 46
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