The Cytology and Binary Fission of Peranema.
By
Virginius E. Brown,
Zoological Laboratory, University of California.
With Plates 19-21
and 1 Text-figure.
CONTENTS.
INTRODUCTION
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MATERIAL AND
TECHNIQUE
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MORPHOLOGY
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MITOSIS
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Prophase
Metaphase .
Anaphase .
Telophase
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Staborgan .
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Kinetic Elements
Cytoplasmic Inclusions
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DISCUSSION
GENERAL
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SUMMARY
REFERENCES
EXPLANATION
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411
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412
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413
415
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O FPLATES
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I N T R O D U C T I O N .
THE Peranemidae are animals of a primitive type and they
show rather close phylogenetic relationships to the lower protistan forms. P e r a n e m a affords good cytological material.
They have a clear cytoplasm and therefore their kinetic elements
are easily determined. Likewise they are easy to culture.
Thereby they can be obtained in quantities large enough to
allow of good cytological investigation. Also the study of their
cytology is of interest, for the conception of the Protozoa as
a primitive type has led to various studies which may bring to
light a better interpretation of the riddles of protozoan morphology.
404
VIRGINIUS B. BEOWN
The divergence of opinion among those who have written on
the various flagellates belonging to the Euglenoidina has presented many interesting problems. The kinetic elements, the
gullet, and the reservoir system of P e r a n e m a are subjects of
controversy. The purpose of this paper is to clear up the various
interpretations that have been made on the morphology and
mitosis of this protozoon. It is also my aim to point out the
phylogenetic relationships of the neuromotor system.
This work was done in the laboratory of Dr. Eobert C. Ehodes
at Emory University. I wish to express to Dr. Rhodes many
thanks for his valuable criticisms and general co-operation.
Thanks are due also to the University of California for supplying
the optical equipment used in completing this investigation.
MATERIAL AND TECHNIQUE.
I have successfully cultured P e r a n e m a t r i c h o p h o r u m
in the following manner: A 200 c.c. culture of E u g l e n a
p r o x i m a was centrifuged and the material thus obtained was
washed in distilled water and crushed between two glass slides.
To this crushed E u g l e n a I added 100 c.c. of tap-water and
allowed the culture to stand for a day before I inoculated with
P e r a n e m a t r i c h o p h o r u m . After eight days division
forms were observed in abundance.
For fixation, the centrifuge method of killing was found to be
the best process as it ensured large quantities of the material.
Various fixing reagents were used, but the best for general purposes were found to be hot Schaudinn's and strong Plemming's
fixatives. I used the fixatives of Champy and Mann-Kopsch for
demonstrating mitochondria. The most satisfactory nuclear
stain was found to be Heidenhein's iron-alum-hematoxylin.
Counter stains of eosin or Bordeaux red were used to demonstrate
the axial filaments of the flagellum. ' Licht Griin ' was used to
show the spiral striations of the cuticle. The mitochondria were
stained with fuchsin and toluidin blue after Champy's fixative,
or they were impregnated with Bowen's modification of the
Mann-Kopsch procedure. Then I stained with safranin to bring
PERANEMA
405
out the nuclear structures. The method of Bowen likewise
brought out the Golgi apparatus.
The plates were sketched by the aid of a camera lucida from
a Busch and Lomb binocular microscope with 2 mm. aprochromatic objective and x 12-5 oculars.
MORPHOLOGY.
The genus P e r a n e m a is characterized by the lack of an eyespot. It is spindle or cigar-shaped, and it tapers anteriorly to
a point. Its broad posterior end is truncate or retuse.
The size of P e r a n e m a t r i c h o p h o r u m is 60 /x to 72 yx in
length and 28 /x to 32 /x in breadth. It has a thinflexiblecuticle of
a metabolic nature. A single flagellum occurs, and it possesses
two axial filaments which arise from basal granules situated at
the base of the reservoir. The length of the flagellum varies
from one-fourth to almost body length.
The genus is likewise characterized by a ' crawling' method of
locomotion. Here the contour of the animal assumes various
protean forms by means of a series of wave-like contractions and
contortions of a fugacious character which run along the cuticular surface. These are clearly apparent when the animal
doubles on itself by an abrupt retrogressive motion, which is
similar to that described by Mast, 1922. The flagellum is usually
kept straight forward and rigid, except the tip, which is bent into
the form of a hook. This bent portion vibrates in a continuous
whirl. The point of the flagellum when in motion describes an
ellipse. P e r a n e m a g r a n u l o s a often swims by whirling the
entire flagellum around and hurls itself backward.
The vacuole system is complex ; it consists of a large flaskshaped vesicle ( = Hauptvacuole of Klebs, 1863) ; also a small
contractile vacuole is situated at the base of this structure, which
I prefer to call the reservoir after Ehodes, 1926 ; Baker, 1926 ;
Calkins, 1926. At each systole the contents of this adjacent
contractile vacuole ( = Neben vacuole of Klebs, 1863) is emptied
into the main reservoir. A slight contraction of this main reservoir seems to aid the flagellate to reach the substratum ; so
we suggest that its function is not only an organelle for the
406
VIBGINIUS B. BROWN
storage of waste materials, &c, but also that it is of a hydrostatic
nature.
I believe that the old family Peranemidae (Stein) should stand,
because all of the group, with the exception of E u g l e n o p s i s ,
TEXT-FIG. 1.
neck of reservoir
cytostomz
rodorganor
Siaborgan
ayiaL FiLament
centrobLepharoplast
reservoir
contractile vacuoLe
GoLgi bodies
endosome
mitochondrium
FLac/eLLum
Food vacuole
siriations
cuticLe
on
I- GoLgi network
A diagrammatic sketch of Peranema trichophorum.
(Note that the crescent-shaped Golgi bodies shown around the reservoir
are not present when the Golgi network occurs.)
possess a rod-organ, or ' Staborgan '. Hall and Powell were unfortunately not informed of this fact. The rod-organ of P e 1 a t oruonas is small and the lateral rods are quite short. Also
PERANEMA
407
Scytomonas, Tropidoscyphus, Marsupiogaster,
and Dinema have well-developed rod-organs. In U r c e o l u s
the rod-organ is spread out into an urn-like structure ; whereas
the rod-organs of A n i s o n e m a and E n t o s i p h o n extend
posteriorad, as an internal' siphon ', almost the entire length of
the body. I see no reason, therefore, to split up an old family
of Peranemidae into several families which have one or more
flagella. Shaeffer (1916) stated that the Peranemidae are holozoic
and ingest solid organic matter which is composed of pieces of
plant or animal tissues. I wish to add that they exhibit great
selectivity with relation to their food.
P e r a n e m a t r i c h o p h o r u m lives almost entirely on dead
E u g l e n a p r o x i m a , and has been observed to engulf E n t o s i p h o n and C h i l o m o n a s . The animal rarely if ever attacks
immotile forms, but it is content to tear encysted or dead
E u g l e n a to bits. On the other hand, P e r a n e m a g r a n u l i fera eats living Z o o c h l o r e l l a . This type of food selection
is not uncommon among protozoa; for example, D i d i n i u m
feeds almost entirely upon P a r a m e c i u m (Calkins, 1926). It
is quite reasonable to believe that P e r a n e m a is almost entirely
holozoic, because a culture will not live unless it is inoculated with
some Euglenoid. For this reason as well as the one mentioned above, I do not think it advisable to place P e r a n e m a
in the same family with the saprozoic Astasidae of Calkins (1926),
but I prefer to accept the classification of Doflein and place the
genus in the old family Peranemidae (Stein).
Wager (1900) was the first to describe the insertion of a
Euglenoid flagellum. He stated that the flagellum of E u g l e n a
v i r i d i s bifurcated on entering the main vacuole (= reservoir),
and that each of these strands was anchored at the base of this
vesicle to a basal granule. Later writers (Rhodes, 1926 ; Baker,
1926; Eatcliffe, 1928) have suggested that these strands be
called axial filaments.
Hartman and Chagas (1909) believed that the flagellum of
P e r a n e m a was single and that it was anchored at the base of
the main vacuole (= reservoir) by a basal granule.
They also stated that another short flagellum arose within
408
VIRGINIUS B. BROWN
this vesicle from a basal granule adjacent to the other one and
traversed the vesicle to become anchored to another granule on
its upper surface.
Hall and Powell (1928) believed that the flagellum remained
single after entering the reservoir and that a new flagellum
started to grow out of the reservoir early in mitosis.
Doflein figures P e r a n e m a with a singleflagellumwhich has
two axial filaments similar to those described by Wager (1900)
for E u g l e n a v i r i d i s .
It is possible that Hartman and Chagas (1909), as well as
Hall and Powell (1928), misinterpreted the second axial
filament as a new flagellum of the daughter individual. I find
that P e r a n e m a has a flagellum which is formed by the union
of two axial filaments which arise from basal granules situated
at the side of the reservoir.
P e r a n e m a does not possess the granule which has been
described to occur on one of the axial filaments by Wager,
1900 ; Baker, 1926 ; and Eatcliffe, 1927 ; however, in all other
respects its flagellum is similar to that of E u g l e n a . It is
possible that this granule is absent in P e r a n e m a because it
does not possess an eye-spot. Wager (1900) believed this granule
was associated with the eye-spot of E u g l e n a and that it
aided in orienting the animal to light. Since this granule
is absent in P e r a n e m a it is possible that this statement is
correct.
The occurrence of a cytostome has been detected by Carter,
Clarepede, and James-Clark, but Klebs (1883) gave the first
description of its organization. He believed that the mouth
opening was ventrally placed and that it was separated from
the ' Hauptvacuole ' or reservoir. However, he failed to consider
the pharynx as a tubular structure, and he believed it was composed of two adjacent rods on the ventral side of the cuticle.
These he termed the ' Stabapparat '.
Ehodes (1926) has shown that the reservoir of H e t e r o n e m a
acus is a separate structure from the ' staborgan ' (Stabapparat
of Klebs), and that it consists of three rods. The outer lip of the
cytostome is bounded by a falcate rod, which he terms ' trichite '.
PERANEMA
409
He stated that the tube which leads from the mouth is bounded
on each side by lateral rods.
I agree with Klebs (1883) and Bhodes (1926) that the
' staborgan ' and the gullet of P e r a n e m a are not connected in
any way with the reservoir, but that the cytostome is a separate
opening on the ventral side of the body. The cytostome is
capable of great distension and its outer lip is reinforced with
a heavy falcate rod. The inner or proximal' lip ' is protoplasmic.
These rods of the ' staborgan ' probably act as a support to
strengthen the sides of the gullet and to prevent the prey from
tearing its own cuticle. The third rod ( = falcate rod or trichite
of Bhodes, 1926) seems to act not only as a support to the lower
lip, but also as a trigger or valve which prevents the cytostome
from opening except when the protozoan is feeding. It also aids
in holding its prey so that it can be pinched off by the aid of the
other two rods which border the gullet (=Cytoesophagus of
Ehodes).
I agree with Ehodes, 1926, that the rod-organ is displaced
during the early prophase and that it later disintegrates in the
cytoplasm. New rod-organs are formed in the early anaphase.
The new cytostomes are formed by an inpitting of the cuticle.
At the base of this pit a granule is formed and out from it grow
two rows of granules. These condense to form the lateral rods
of the gullet. (I prefer to use this term because it has been used
extensively in protozoology; however, it should not be confused
with any part of the reservoir.) During the telophase the third
or the falcate rod forms by an outgrowth from the top of the
medial lateral rod (fig. 11, PI. 20 ; fig. 12, PI. 21).
The mitochondria of P e r a n e m a vary from a small round
form to a large disc-shaped type with a clear centre. The small
spherical forms range from | ^ to \ fj., whereas the disc-shaped
types vary from \p to lfi in width and are £ju to J/M in breadth.
They are usually grouped around the nucleus and the base of
the reservoir. When the protozoan divides most of the mitochondria move anteriorly along with the nucleus and group
themselves about the reservoir. The ovoid mitochondria seem
to be capable of becoming the disc-shaped types by growth.
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VIRGINIUS E. BROWN
These disc-shaped types show a differential staining with the
toluidin blue and fuchsin method. The core is magenta, whereas
the cortex is dark blue. The small mitochondria often show
connexion^ or form dumb-bell structures. These are in all
probability division stages. The mitochondria are straw-coloured
when stained by the Mann-Kopsch method, whereas the Golgi
apparatus is black.
The Golgi apparatus of P e r a n e m a is a network of long interwoven fibres which are concentrated in the posterior portion of
the animal (fig. 15, PI. 21). This network is not as dense in the
later division stages of P e r a n e m a as it is during the early
prophase. Neither the reservoir nor the contractile vacuole takes
an osmic impregnation. However, the Golgi apparatus forms
spheres around the reservoir during the early prophase.
MITOSIS.
Prophase.—During the early prophase the nucleus of
P e r a n e m a t r i c h o p h o r u m migrates anteriorly to the base
of the reservoir. The nucleus at this time is of a vesicular nature ;
its centre contains a large dark staining body of chromatin.
This body may be single or fragmented (Hall, 1926). This
endosome ( = Binnenkorper) is filled with vacuoles of various
sizes. No centriole occurs within their centre, as some writers
have believed. Therefore I agree with Hall and Powell (1928)
that these vacuoles are of no significance. In the early prophase
the dispersed chromatin comes together to form very thin
chromomeres. These chromomeres are formed from 'spherules'
which are connected together to form loops. Within these
chromatic structures one can easily discern basophilic granules
of variable sizes. During the growth of chromatin these loops
thicken and the nucleus moves anteriorly and comes to lie on
the edge or the base of the reservoir. By continued anterior
migration it comes in contact with the largest basal granule
(fig. 4, PI. 19). This granule or centroblepharoplast seems to pull
the nucleus upward and strands can be traced from it into the
endosome. The endosome begins at once to elongate and the
nucleus swings around on its axis until the other portion of
PEKANEMA
411
the elongated endosome is connected by similar lines to the other
basal granule. The chromatin loops then thicken and arrange
themselves parallel to the elongated endosome. At this period
the longitudinal splitting of the metaphase occurs. The chromosomes separate from only one end to form V-shaped structures
(fig. 5, PL 19).
At this stage a polarity is established between the opposite
centroblepharoplasts at each end of the nucleus. Also fibres are
noticed connecting each centroblepharoplast with the end of the
elongated endosome (fig. 6, PL 19). The nucleus then pushes
up against the reservoir. This not only distorts the vesicle but
also it pushes the rod-organ out of position (figs. 5, 6, PL 19).
The rod-organ is thus cast out into the plasma of the animal,
where it disintegrates before the end of the anaphase (figs. 5,
6, PL 19, and fig. 7, PL 20). This disintegration of the rod-organ
has been described in H e t e r o n e m a a c u s by Rhodes, 1926.
During the prophase the basal granules divide twice to form
new basal granules ; out from these grow axial filaments. Each
of these filaments unites with one of the old axial filaments to
produce a new flagellum. A part of the nagelluni thus persists
to form one of the newflagellar filaments of a daughter individual.
The chromosome count at this time has been estimated to be
thirty-two.
Metaphase.—The longitudinal splitting of the chromosomes
takes place during the prophase when the chromatin is arranged
in a group of granular chromosomes. These pull apart to form
V-shaped chromosomes (fig. 4, PL 19). These V-shaped structures widen and contract into chromosomes which come to lie
parallel to the endosome (fig. 5, PL 19). Such a situation is
usually termed the equatorial plate. The nuclear membrane
remains intact.
Anaphase.—The endosome continues to elongate and often
vacuolates or splits longitudinally (figs. 8, 9, 10, PL 20). The
chromosomes during the early anaphase separate or pull apart
from the last end which splits during the metaphase, and thereby
an appearance of a pseudo-transverse splitting is noticed. The
chromosomes become more granular and group themselves at
412
VIRGINIUS E. BROWN
the ends of the endosonie ; the nucleus then shows a constriction
in the central portion (figs. 8, 9, 10, PI. 20). The attachment
between the endosome and the centroblepharoplasts persists.
During the anaphase the new cytostomes are formed by
invagination of the anterior cuticular surface. On the edge of
this newly formed cytostome a group of four granules grows in
size and later they collect into two distinct rod-like structures
(fig. 9, PI. 20). These form the lateral rods of the rod-organ.
The daughter reservoirs pull farther apart, and a partition begins
to form between them. This division of the daughter reservoirs
is produced by an outgrowth from the base of the old reservoir.
Telophase.—The telophase begins by a constriction of the
anterior end of the animal. This deepens and the animal begins
to split from the anterior end so that the animal divides by
binary fission. The continued constriction of the nucleus causes
the central portion to break apart. The chromosomes form
granular loops around the endosome (fig. 12, PI. 21). The third
rod of the staborgan forms by an outgrowth from the top of
the median rod. This connexion persists after the rod is formed;
the same condition is found in H e t e r o n e m a (Bhodes, 1926).
Division is completed by the daughter individuals pulling
apart (fig. 13, PI. 21). This action is very violent and the entire
protoplasm is kept in motion. The flagella grow out, and they
are kept in violent motion until the division is completed.
DISCUSSION.
R o d - o r g a n or ' S t a b o r g a n ' . — T h e Staborgan of P e r a n e m a consists of the rods which I have described above. There
is no evidence that these rod-organelles are parabasals, as Calkins
(1926) and Hall (1926) believed.
In fact P e r a n e m a seemstouse them in feeding, and they are
used just as a ciliate uses its trichites. The falcate rod opens
and closes the cytostome when the animal feeds. Hall (1926)
believed the parabasal to lie adjacent to the gullet and that the
parabasal body doubled during division. Hall and Powell (1927)
stated that they believed the parabasal body to be the equivalent
of the 'Staborgan'. Later (1928) they ignore this statement
PERANEMA
418
(Hall, 1926) and refer to it as the pharyngeal rod apparatus.
I object to the use of this term since the cytostome is not connected with the reservoir, hence it cannot be of a pharyngeal
nature. I suggest that the term 'Staborgan' or rod-organ ( = rod
organelle) be applied to this structure since this term is found in
all of the literature (Doflein, 1912; Ehodes, 1926). Also I have
not been able to find a parabasal in P e r a n e m a , and I see no
reason to believe that the 'Staborgan' is either analogous or
homologous to the parabasal body. Let us consider this question
from a phylogenetic view-point. In the primitive protist,
E u g 1 e n a, we find a homology between the parabasal body and
the kinetic complex (Baker, 1926). This kinetic complex is derived
from the endosome. Now in a higher form like P e r a n e m a it
is reasonable to believe that such a body is either lost during the
evolution of this protozoon or that it still remains within the
endosome. Obviously the endosome is part of the kinetic mass ;
I do not believe that P e r a n e m a has any homologue of the
parabasal body, but I do believe that the endosome is the
kinetic reserve mass.
Hall and Powell (1928) state that P e r a n e m a has only one
' pharyngeal' rod element in the early stages of binary fission.
This they believe suggests that one of the two original rods
passes to each of the daughter organisms. I have not noticed
anything like this and I suggest that Hall and Powell studied
the 'Staborgan' from a lateral view so that one would be above
the other, and unless care is used this structure may appear
as only one. The 'Staborgan' does not split during binary fission,
but the old 'Staborgan' disintegrates and new ones form from
granules on either side of the new daughter cytostomes. These
granules are possibly of mitochondrial origin.
K i n e t i c Elements.—Theblepharoplast-rhizoplast-centrosome complex is of a primitive type and has been described to
occur in many of the lower flagellates. Likewise we find such
a complex in most of the Polymastigotes and the Hypermastigotes. Associated with this centroblepharoplast-rhizoplastcentrosome complex, in the Polymastigotes and the Hypermastigotes, is a dark staining paradesmose. This structure
NO. 291
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414
VIRGINIUS E. BROWN
connects the daughter centrosomes during fission (Kofoid and
Swezy, 1915). I do not find such a paradesmose in P e r a n e m a .
The kinetic elements of P e r a n e m a are of a type like that of
O c h r o m o n a s (Doflein, 1912). Here we have the centrohlepharoplast, but no paradesmose occurs. During mitosis
centroblepharoplasts are connected to the ends of the endosome
by numerous spindle-fibres. No permanent rhizoplast exists.
In fact I see no reason to believe that the ' blepharoplastrhizoplast-centrosome ' complex occurs in P e r a n e m a ; thousands of granules occur around the nucleus, but these do not
function as a centrosome.
Although the paradesmose is known to occur in the Hypermastigotes and in the Polymastigotes, I suggest that it does not
occur in any of the Euglenoid flagellates, because it has not
been demonstrated by any of the recent workers on the Euglenoid
group (Baker, 1926 ; Katcliffe, 1928).
After a due consideration of the behaviour of the centroblepharoplast of P e r a n e m a during mitosis, I have decided that
there is a relationship between the centroblepharoplast and the
endosome. In other words, the action of the centrosome, or
better, the centroblepharoplast, does not initiate mitosis alone ;
but that this kinetic force is an interaction of both the centroblepharoplast and the endosome as well as intranuclear physiological forces. If such a kinetic mass as the endosome is charged
by a type of ' mitokinetism ' or any type of electrostatic force,
and if that force is associated with other forces which are of
a physiological nature, there will be balance between all the
forces which may initiate mitosis. Now if this balance is upset
and a change in polarity occurs and the endosome is elongated,
then this structure will split (fig. 8, PI. 20). In all probability
the same interacting forces cause the chromosomes to split
longitudinally and to ' flow ' apart. If the endosome is the centre
of this kinetic force, then it is quite reasonable to expect that
a division centre (or even a kinetic reserve complex) is given off
in some of the lower protistan forms. Otherwise it would be
hard to establish a phylogenetic line between P e r a n e m a and
the lower flagellates. Such division centres or kinetic reserve
PERANBMA
415
masses have been described by various workers (Kater, 1925 ;
Baker, 1926).
The C y t o p l a s m i c I n c l u s i o n s . — H a l l (1928) describes
certain cytoplasmic inclusions which he believes are mitochondria and Golgi elements. The mitochondria he states are small
elongated structures in P e r a n e m a and they lie in spiral rows.
Likewise he noted numerous spherical inclusions similar in structure to the ' Golgi' elements of higher animals. I find that the
mitochondria are rarely in spiral rows and that they assume this
position for only a short while during the early prophase. It is
possible that Hall (1928) has confused the Golgi network with
the mitochondria, because at this time the Golgi apparatus is
a network of long fibres. These fibres of the Golgi network are
grouped in spirals round the nucleus and round the base of the
reservoir (fig. 15, PL 21). When P e r a n e m a is not in division,
the Golgi apparatus is a network of long fibres arranged in
a tangled mass. During the early prophase these fibres condense
into a tangled network which lies in the posterior portion of the
animal. This mass breaks up into small irregular bodies which
group themselves round the nucleus during the metaphase. But
the typical network of long fibres form again during the anaphase and persist as such during the interkinetic phase. The
mitochondria are spherical and disc-shaped (fig. 14, PI. 21).
The large disc-shaped types are grouped heavily round the
nucleus and the base of the reservoir. They lie deep within the
cytoplasm, whereas the spherical forms are more superficial and
often take dumb-bell or rod-like shapes. The spherical forms
are almost evenly distributed throughout the cytoplasm, whereas
the large disc-types are grouped together. These disc-shaped
types quite often show a clear centre. Earely these discshaped types form ' roulettes '.
In the same slides with the P e r a n e m a material I found
E u g l e n a p r o x i m a and E u g l e n a g r a c i l i s . The mitochondria are similar in shape and distribution to those I have
described in P e r a n e m a . This leads me to believe that the
mitochondria of E u g l e n a described by Causey (1926) are only
a part of the chromatophores and possibly the pyrenoids of this
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VIRGINIUS E. BROWN
protist; however, I shall discuss the behaviour of the cytoplasmic inclusions of E u g l e n a during binary fission in
another paper.
GENERAL SUMMARY.
1. P e r a n e m a t r i c h o p h o r u m is holozoic in nature and
selective in its food, but not predaceous. It feeds usually on
dead and encysted E u g l e n a p r o x i m a , E u g l e n a g r a c i l i s ,
and rarely upon C h i l o m o n a s and E n t o s i p h o n .
2. The 'Staborgan' or rod-organ is not connected with the
reservoir, but it opens into the cytostome which lies ventrally
to this vesicle. Therefore the term gullet should not be applied
to the neck of the reservoir.
3. The chromosome count of P e r a n e m a t r i c h o p h o r u m
is estimated to be thirty-two in number.
4. The 'Staborgan' is thrown out of its position during mitosis
and it disintegrates in the cytoplasm. New rod-organs grow out
from granules which form at the base of the new daughter
cytostomes. These granules may be of mitochondrial origin.
5. A centroblepharoplast is described. No paradesmose is
present.
6. A theory is suggested which supposes that an interaction
between the centroblepharoplast and the endosome occurs.
The centroblepharoplast acts as a kinetic attraction sphere
which carries the nucleus anteriorly in order that the blepharoplasts can function as extra-nuclear division centres ; thereby
a co-ordinated interaction is brought about between both intranuclear kinetic elements and all of its cellular components. Such
a reaction or interrelation of parts is necessary to initiate
cellular division.
7. The mitochondria of P e r a n e m a were found to be
spherical; these may grow into large disc-shaped types with
clear centres. The latter have a tendency to group themselves
round the nucleus and the reservoir.
8. The Golgi apparatus was found to be a network of long
fibres. These Golgi bodies seem to be concentrated in the
posterior end and round the reservoir. Neither the contractile
PEEANBMA
417
vacuole nor the reservoir was impregnated by osmic acid
methods.
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EXPLANATION OF PLATES 19-21.
Pigs. 1-15 inclusive are of Peranema trichophorum.
All figures were drawn with the aid of an Abbe camera
lucida. Figs. 2-4, 6-13, from preparationsfixedin Schaudinn's